全固态电池硅基负极

Silicon is anticipated to be a next-generation anode active material with a high theoretical capacity density of ∼3600 mAh g-1 around room temperature. However, the volume expansion and contraction derived from lithiation (charging) and delithiation (discharging) are understood to be significant challenges. Particularly in all-solid-state batteries, not only does cracking of the silicon particles themselves occur, but also the disruption of contact between silicon and the solid electrolyte, leading to difficulties in maintaining battery performance, which requires a certain level of mechanical restraint for effective battery operation. Therefore, accurately understanding the internal nanometer-order structure of the silicon/solid electrolyte composite electrode under restrained conditions is crucial for improving the performance of all-solid-state batteries by using silicon anodes. In this study, an all-solid-state battery with a composite anode consisting of silicon and the sulfide solid electrolyte Li6PS5Cl was charged and discharged under constrained conditions, and the internal structure during battery operation was observed using in situ computed tomography measurements. As a result of the observation, different cracking modes were identified during charging and discharging. The modes of cracking and subsequent reattachment were observed during the charging process, whereas anisotropic void formation became evident during the discharge process.

Polyethylene oxide (PEO)-based solid electrolytes have been widely studied in all-solid-state lithium (Li) metal batteries due to their favorable interfacial contact with electrodes, facile fabrication, and low cost, but their inferior Li dendrite suppression capability renders low actual areal capacities of Li metal anodes. Here, we develop a high-capacity all-solid-state battery using a metal-organic framework hosted silicon (Si@MOF) anode and a fiber-supported PEO/garnet composite electrolyte. Si nanoparticles are embedded in the micro-sized MOF-derived carbon host, which efficiently accommodates the repeated deformation of Si over cycles while providing sufficient charge transfer pathways. As a result, the Si@MOF anode shows excellent interfacial stability toward the composite polymer electrolyte for over 1000 h and achieves a high reversible areal capacity of 3 mAh cm-2. The full cell using the LiFePO4 (LFP) cathode is able to deliver 135 mAh g-1 initially and maintains 73.1% of the capacity after 500 cycles at 0.5 C and 60 °C. More remarkably, the full cells with high LFP loadings achieve areal capacities of more than 2 mAh cm-2, exceeding most PEO-based ASSBs using metallic Li. Finally, the pouch cell using the proposed design exhibits decent electrochemical performance and high safety.

Applying high stack pressure (often up to tens of megapascals) to solid-state Li-ion batteries is primarily done to address the issues of internal voids formation and subsequent Li-ion transport blockage within the solid electrode due to volume changes. Whereas, redundant pressurizing devices lower the energy density of batteries and raise the cost. Herein, a mechanical optimization strategy involving elastic electrolyte is proposed for SSBs operating without external pressurizing, but relying solely on the built-in pressure of cells. We combine soft-rigid dual monomer copolymer with deep eutectic mixture to design an elastic solid electrolyte, which exhibits not only high stretchability and deformation recovery capability but also high room-temperature Li-ion conductivity of 2×10−3 S cm−1 and nonflammability. The micron-sized Si anode without additional stack pressure, paired with the elastic electrolyte, exhibits exceptional stability for 300 cycles with 90.8% capacity retention. Furthermore, the solid Li/elastic electrolyte/LiFePO4 battery delivers 143.3 mAh g−1 after 400 cycles. Finally, the micron-sized Si/elastic electrolyte/LiFePO4 full cell operates stably for 100 cycles in the absence of any additional pressure, maintaining a capacity retention rate of 98.3%. This significantly advances the practical applications of solid-state batteries. Applying high stack pressure is primarily done to address the mechanical failure issue of solid-state batteries. Here, the authors propose a mechanical optimization strategy involving elastic electrolyte to realize solid-state batteries operating without external pressurizing.

No abstract available

Sulfide‐based all‐solid‐state lithium‐sulfur batteries (ASSLSBs) hold immense promise for next‐generation energy‐storage due to their high theoretical energy density and enhanced safety. However, fatigue issues such as electrolyte cracking and interfacial damage caused by big volume changes of both electrodes and mechanical stress remain critical challenges. Herein, the distinct alternative against monotonical stress evolution is first analyzed in ASSLSBs employing pre‐lithiated silicon‐based anodes versus conventional lithium metal by using in‐situ pressure‐detection techniques. Notably, the pre‐lithiated silicon‐based system demonstrates an alternating stress dominance pattern that effectively stabilizes mechanical responses through stress cancellation effects. Moreover, the investigation shows that the stress‐buffering effect of pre‐lithiated silicon‐based stems from the phase transition dynamics of intermediate Li21Si5 during lithiation. The finite element modeling and micro‐structural morphology analysis is employed to link phase transformation kinetics directly to mechanical stress modulation. This unique characteristic proves crucial in suppressing crack propagation within electrolytes while maintaining stable electrode/electrolyte interfaces. Consequently, the full‐cell using pre‐lithiated silicon‐based achieves stable cycling performance with high S loading (4.5 mg cm−2) at 0.5C (∼3.6 mA cm−2), which outperforms conventional solid‐state lithium‐sulfur batteries. The discovered chemo‐mechanical coupling principles provide new insights for developing high‐stability ASSLSBs, particularly in mitigating interfacial degradation induced by large volume changes.

No abstract available

As a next-generation rechargeable battery, all-solid-state battery is expected for used in practical applications, in which electrolyte solution of the current lithium-ion battery is replaced with a solid electrolyte. To further increase the capacity of all-solid-state batteries, silicon is used as the anode active material forming an alloy with lithium. However, in the charge and discharge reaction using silicon anode, poor cycle capability due to the volume change of the silicon alloying reaction has been known. Many reports are limited to the analysis of the volume change of the whole electrode, and there are few reports on the quantitative analysis of the volume change of the silicon active material itself. In this study, X-ray computed tomography (X-ray CT) was used to analyze the expansion and contraction of silicon-active materials in all-solid-state battery. X-ray CT analysis can provide the contacted state information between electrode active materials and solid electrolytes [1]. By operando X-ray CT analysis, the expansion and contraction behavior of silicon particles during charging and discharging on the electrode was studied. Nb-coated LiNi1/3Co1/3Mn1/3O2(NCM), Li10GeP2S12(LGPS), acetylene black (AB) mixed at a weight ratio of 1:1:0.2 were used as the cathode composite. Silicon, LGPS, AB mixed at a weight ratio of 1:1:0.1 were used as the anode composite. All-solid-state battery, Si | LGPS | NCM was assembled in a cylinder with an inner diameter 1 mm. The cell was brought into SPring-8 BL20XU beamline, and the operando X-ray CT measurement was carried out. From the obtained X-ray CT images, the three-dimensional analysis of silicon particles was performed. Mean expansion coefficients of silicon‐particles traced during charging and discharging were calculated. The expansion of silicon particles by charging (lithiation) and the contraction of silicon particles by discharging (delithiation) are confirmed. Furthermore, the volume expansion rate of the silicon particles after the charging is average exceeded 300%. After discharge, silicon shrinkage is observed with delithiation, but the solid electrolyte cannot follow the volume change, and the silicon/solid electrolyte interface is broken. However, the contact is not completely failed, maintaining the partial contact between silicon and the electrolyte. [1] Y. Sakka, H. Yamashige, A. Watanabe, A. Takeuchi, M. Uesugi, K. Uesugi and Y. Orikasa, J. Mater. Chem. A, 10 16602–16609 (2022). Acknowledgement: This work was partially supported by the New Energy and Industrial Technology Development Organization (NEDO), JPNP20004.

Sulfide all-solid-state batteries (ASSBs) using high-capacity silicon (Si) anodes and high‑nickel ternary cathodes offer a promising route to realize high energy density and safety simultaneously. However, the low inherent electronic conductivity of Si constrains its further application in ASSBs. Importing element doping is an available strategy to improve intrinsic electronic conductivity of raw Si anodes. Herein, the effects of N-type (phosphorus doped) and P-type (boron doped) Si anodes were systematically studied in ASSBs. The doping type and doping contents determined the anodic performances. It is unraveled that the doping element with low content will migrate away from the Si matrices during the initial lithiation and amorphization process of the Si anode, forming low conductivity elemental phases. These low conductivity doping elements hinder internal Li+ migration through Si particles and deteriorate the electrochemical performance. In contrast, the high content element doping remains stable conductive ionic network inside the Si particles. In addition, the N-type Si with phosphorus formed conductive Li3P help to increase the lithium utilizations. Therefore, after prelithiation, matching with Li(Ni0.83Co0.11Mn0.06)O2 (NCM811) cathode, the capacity retention of the high content doped N-type Si ASSBs is 76.24 % after 100 cycles at 0.5C, whereas the capacity retention of the raw Si ASSBs is only 70.61 %.

Understanding the electrochemical reactions at the interface between a Si anode and a solid sulfide electrolyte is essential in improving the cycle stabilities of Si anodes in all-solid-state batteries (ASSBs). Highly dense Si films with very low roughnesses of <1 nm were fabricated at room temperature via cathodic arc plasma deposition, which led to the formation of a Si/sulfide electrolyte model interface. Li (de)alloying through the model interface hardly occurred during the first cycle, whereas it proceeded stably in subsequent cycles. Hard X-ray photoelectron spectroscopy and neutron reflectometry directly revealed that the reduction or oxidation of the interfacial component or Li3PS4 electrolyte occurred during the first cycle. Consequently, an interfacial layer with a thickness of 13 nm and primarily composed of Li2S, SiS2, and P2S5 glasses was formed during the first cycle. The interfacial layer acted as a Li-conductive, electron-insulating solid electrolyte interphase (SEI) that provided reversible (de)lithiation. Our model interface directly demonstrates the electrochemical reaction processes at the Si/Li3PS4 interface and provides insights into the structures and electrochemical properties of SEIs to activate the (de)lithiation of Si anodes using a sulfide electrolyte.

Silicon has a theoretical capacity about 10 times that of graphite, so it is expected to be one of the next-generation anode materials to further increase the capacity of batteries. However, silicon has a large volume change during charging and discharging, which result in poor cyclability. Although morphological change of silicon has been shown in a lot of previous studies, most of them are ex-situ observations using electron microscopes such as SEM and are two-dimensional observations1). Moreover, many previous studies target liquid battery. It is necessary to understand the expansion and shrinkage mechanism of silicon to improve all-solid-state battery performance using silicon anode. Synchrotron X-ray computed tomography (X-ray CT) is a technique that can measure the internal structure of a battery in three dimensions with micrometer-order spatial resolution in a short time. In addition, operando X-ray CT measurement is possible under charging and discharging in an all-solid-state battery2). In this study, we analyzed that morphological changes of silicon during charging and discharging by operando X-ray CT measurements. We used LiNi1/3Co1/3Mn1/3O2 (NCM), Li6PS5Cl (LPSCl) and acetylene black (AB), which were mortar-mixed in a mass ratio of 1:1:0.1 as the cathode composite material, and Si, LPSCl and AB in a mass ratio of 1:2.78:0.42 as anode composite material. Si｜LPSCl｜NCM all-solid-state cells were assembled. X-ray CT measurements at SPring-8 BL20XU using 20 keV X-rays while performing constant current charge/discharge measurement at 2.3×10-3 A cm-2. The pixel resolution was 0.5 µm. A silicon particle was extracted from the X-ray CT images obtained from X-ray CT measurements to observe the morphological changes of silicon during charging and discharging reaction. Then, change of the silicon volume and the contact area fraction of silicon particle and LPSCl solid electrolyte were calculated. Volume expansion was observed with lithiation of silicon and volume shrinkage with delithiation of silicon. As the lithiation process, silicon density decreased, and silicon was observed to be darker. As the delithiation process, cracks appeared in the silicon particle as the expanded silicon shrank. In addition, the silicon/solid electrolyte interface changed so that the silicon formed shell voids at the surface of silicon particles. This indicates that the plasticity of the LPSCl solid electrolyte cannot follow the form change of the interface. However, shell voids in the interface were formed for all directions, but some parts remained in contact area between the silicon particle and the solid electrolyte. After the second cycle of lithiation, cracks in the particle and the voids in the interface between the silicon particle and the solid electrolyte that had been formed due to the shrinkage of silicon as the delithiation disappeared by the re-lithiation. However, the re-delithiation caused cracks in the particle in the same area and formed shell voids in the interface again. Moreover, as the second delithiation process, the number of cracks in the particle increased compared with that as the first delithiation. This suggests that the number of cracks in the particle increases as silicon repeated lithiation and delithiation, and so silicon is miniaturized. In addition, a correlation was confirmed between the silicon volume change and the contact area fraction change. After the first cycle, the volume didn’t return to pristine silicon volume and the contact area fraction was reduced compared to pristine silicon. The isolation of the silicon particle from the solid electrolyte interface is suggested to be one of the factors causing the poor cycle performance because of the lithium ion reaction path is limited. 1) T. Li, J. Y. Yang, S.G. Lu, H. Wang and H. Y. Ding, Rare Metals, 32, 299-304 (2013). 2) Y. Sakka, H. Yamashige, A. Watanabe, A. Takeuchi, M. Uesugi, K. Uesugi and Y. Orikasa, J. Mater. Chem. A, 10, 16602–16609 (2022).

The intermittent nature of renewable energy generation can be tackled by integrating them with electrochemical energy storage, which can also close the gap between supply and demand effectively. It has recently been demonstrated that Si3N4‐based negative electrodes are a promising option for lithium‐ion batteries due to their large theoretical capacity and appropriate working potential with extremely low polarization. In the present work, Si3N4 was utilized as anode material in all‐solid‐state lithium‐ion battery with lithium borohydride as a solid electrolyte and Li foil placed as a counter electrode. The electrochemical properties were investigated using galvanostatic charge/discharge profiling whereas the mechanism of lithiation delithiation was investigated in detail using x‐ray diffraction (XRD). The highest capacity of the composite materials was obtained as 1700 mAhg−1 at 0.05 C current rate in the first cycle, which is reduced to 370 in 5 cycles. However, a stability in the capacity was observed in subsequent cycles and a retention of almost 88% could be achieved in 150 cycles. The interfacial resistance before and after the electrochemical cycling was observed as 326 Ω and 13 kΩ, respectively which is also supported by the microstructural investigations where the cracks are observed because of thermochemical reactions.

No abstract available

Silicon (Si) is anticipated to become one of the most promising anode materials for high‐energy‐density solid‐state battery (SSB) applications owing to its high theoretical specific capacity and low working potential. This work compares the electrochemical behavior of slurry‐cast electrodes in Si|Li6PS5Cl|In/InLi cells, with micron‐sized Si particles (≥99% active electrode material content) and polyacrylic acid (PAA) or polyvinylidene fluoride (PVDF) serving as active material and aqueous/nonaqueous model binder, respectively. The cycling stability of Si‐PVDF cells is found to decrease with increasing binder content (accelerated capacity fade), whereas the Si‐PAA cells show more or less the opposite trend. However, they exhibit a similar performance when using 0.5 wt% binder, with specific capacities of ≈850 mAh g−1 (for −0.51–0.11 V vs In/InLi) and high capacity retention depending on the cutoff potentials. This result suggests that PVDF can be substituted for by PAA in Si anodes for SSBs, thereby potentially decreasing cost and environmental impact.

Silicon (Si) anodes possess remarkable theoretical capacity in Li-ion batteries; however, they are facing challenges including huge volume-expansion leading to structural failure and performance decay. Conventional coatings commonly exhibit poor adhesion to Si, resulting in interfacial degradation and non-ideal electron/ion transport. Here, a heterojunction-induced Si@FeSe@C anode, composing of a robust Fe-Se-Si bonding at the heterointerface followed by an external carbon coating is developed. This design enables both structural stability and highly efficient ion and electron transport. The Si@FeSe@C anode delivers a high capacity of 1092.8 mAh g-1 after 100 cycles at 0.2 A g-1, and maintains a Coulombic efficiency exceeding 99.6% over 500 cycles at 1.0 A g-1. The electrochemical performance of full-cell configurations assembled with both conventional liquid and all-solid-state electrolytes, also revealing remarkable cycling performances. In situ X-ray diffraction and in situ Raman analysis confirm reversible phase- and species-change, and density functional theory (DFT) calculations reveal that the heterojunction significantly reduces the energy barrier for Li+ diffusion. These findings present a general design strategy that synergistically enhances electrochemical performance, which will find a broad set of applications in developing high-performance secondary battery systems.

Silicon has a theoretical capacity about 10 times that of graphite is expected to be one of the next-generation anode materials to further increase the capacity of batteries. However, silicon has a large volume change during charging and discharging, which result in poor cyclability. Although morphological change of silicon has been shown in a lot of previous studies, most of them are ex-situ observations using electron microscopes such as SEM and are two-dimensional observations1). Previous studies have shown that silicon may fulfill its potential as an all-solid-state battery anode material with the garnet oxide-based solid electrolyte2). Further understanding of the expansion and shrinkage mechanism of silicon is needed to improve battery performance using silicon anode. Synchrotron X-ray computed tomography (X-ray CT) is a technique that can measure the internal structure of a battery in three dimensions with micrometer-order spatial resolution in a short time. In addition, operando X-ray CT measurement is possible under charging and discharging in an all-solid-state battery3). In this study, we analyzed that morphological changes of silicon during charging and discharging by operando X-ray CT measurements. We used LiNi1/3Co1/3Mn1/3O2 (NCM), Li6PS5Cl (LPSCl) and acetylene black (AB), which were mortar-mixed in a mass ratio of 1:1:0.1 as the cathode composite material, and Si, LPSCl and AB in a mass ratio of 1:2.78:0.42 as anode composite material. Si｜LPSCl｜NCM all-solid-state cells were assembled. X-ray CT measurements at SPring-8 BL20XU using 20 keV X-rays while performing constant current charge/discharge measurement at 2.3×10-3 A cm-2. The pixel resolution was 0.5 µm. A silicon particle was extracted from the X-ray CT images obtained from X-ray CT measurements to observe the morphological changes of silicon during the charging and discharging reaction. Cracks were observed in the silicon particle due to silicon shrinkage during the delithiation process. In addition, the silicon/solid electrolyte interface changed so that the silicon formed shell voids at the surface of silicon particles. This indicates that the plasticity of the LPSCl solid electrolyte cannot follow the form change of the interface. However, shell voids in the interface were formed for all directions, but some parts remained in contact area between the silicon particles and the solid electrolyte. The isolation of silicon particles from the solid electrolyte interface is suggested to be one of the factors causing the poor cycle performance because of the lithium ion reaction path is limited. 1) T. Li, J. Y. Yang, S.G. Lu, H. Wang and H. Y. Ding, Rare Metals, 32, 299-304 (2013). 2) W. Ping, C. Yang, Y. Bao, C. Wang, H. Xie, E. Hitz, J. Cheng, T. Li and L. Hu, Energy Storage Materials, 21, 246-252 (2019). 3) Y. Sakka, H. Yamashige, A. Watanabe, A. Takeuchi, M. Uesugi, K. Uesugi and Y. Orikasa, J. Mater. Chem. A, 10, 16602–16609 (2022).

Nano-Si (n-Si) encapsulated with SiOx shells and anchored onto reduced graphene oxide (rGO) via hydrothermal self-assembly is demonstrated as a promising solid-state battery anode. Compared to simple n-Si, this composite anode exhibited improved rate capability and cycle life, enabled by robust Si-O-C bonding, mechanical reinforcement, and rapid electron transport.

Silicon is one of the most promising anode active materials for future high‐energy lithium‐ion‐batteries (LIB). Due to limitations related to volume changes during de‐/lithiation, implementation of this material in commonly used liquid electrolyte‐based LIB needs to be accompanied by material enhancement strategies such as particle structure engineering. In this work, we showcase the possibility to utilize pure silicon as anode active material in a sulfide electrolyte‐based all‐solid‐state battery (ASSB) using a thin separator layer and LiNi0.6Mn0.2Co0.2O2 cathode. We investigate the integration of both solid electrolyte blended anodes and solid electrolyte free anodes and explore the usage of non‐toxic and economically viable solvents suitable for standard atmospheric conditions for the latter. To give an insight into the microstructural changes as well as the lithiation path inside the anode soft X‐ray emission and X‐ray photoelectron spectroscopy were performed after the initial lithiation. Using standard electrochemical analysis methods like galvanostatic cycling and impedance spectroscopy, we demonstrate that both anode types exhibit commendable performance as structural distinctions between two‐dimensional and three‐dimensional interfaces became evident only at high charge rates (8 C).

The silicon (Si) is one of the most promising anodes for next‐generation lithium‐ion batteries, but addressing the interfacial side reactions caused by volume expansion remains a key challenge. In this study, a composite of nano‐Si with covered and interstitial LaF3 (Si@LaF3) is synthesized via a low‐cost and scaleable ball milling process. Upon lithiation, the LaF3 layer on the nano‐Si surface in situ reconstructs into an interface containing LiF and La. The LiF interface promotes the uniform formation of LiF‐rich solid electrolyte interphase (SEI), and La grains can block the penetration of electrolyte anions into an electrode, inducing the stable and thin SEI on the Si@LaF3 anode. Additionally, the interstitial LaF3 particles facilitate the migration of Li+ into Si and reduce local expansion stress in the Si anode by alleviated electrochemical sintering. Compared to micron‐ and nano‐Si anodes, the Si@LaF3 anode demonstrates higher specific capacity and superior cycling stability. The Si@LaF3||‐LiFePO4 full battery retains a specific capacity of 125.1 mAh g−1 after 200 cycles at 0.35 C, while the Si@LaF3/graphite anode in all‐solid‐state battery maintains a capacity of 491 mAh g−1 after 100 cycles at 0.1 A g−1. This study provides new insights on the commercialization of Si‐based anodes and solid‐state batteries.

All-Solid-State Batteries (ASSB) are a promising technology to replace conventional Lithium-Ion Batteries (LIB) since the energy density and fast charging capability of LIBs are projected to reach a physical limit soon. In this regard, the ASSB technology is considered superior, especially if the incorporation of the lithium metal anode, or other high-capacity anode materials like silicon is achieved. However, these systems still require intensive research as many physical effects, especially those concerning the interaction of electrochemistry and solid mechanics, are to date not well understood [1]. Most experimental investigations on ASSB cells are performed on laboratory scale and are usually operated at elevated mechanical pre-stress to obtain satisfactory system performance. The delamination of active materials and solid electrolyte during cycling is expected to be one of the key effects for the required mechanical pre-stress. Furthermore, a lot of experimental research focuses on the development of new material classes and their stability in the cell compound, while a systematic optimization of the cell setup is missing. Comprehensive computational models can help to generate insights in these regards as they allow for detailed investigations of local effects, which is often not possible in experimental setups. Another advantage of computational models compared to experiments is the ability to change input parameters in a fast and systematic way to quantify their influence on the battery cell performance and thereby help to speed up the optimization of battery designs. Since the multitude of physical effects that are relevant in ASSB are computationally challenging, a lot of modeling approaches rely on numerous simplifications like spatial homogenization or neglect of mechanical effects to name just two. However, such assumptions can significantly limit the validity of the model. We propose a novel computational model for ASSB [2] to thoroughly investigate the interdependence of electrochemistry and solid mechanics on resolved microstructures that vastly influence the behavior and the performance of an ASSB cell. It is based on nonlinear continuum mechanics and accounts for large deformations due to lithiation dependent volume changes of the active materials. The mass and charge conservations are consistently formulated to also ensure the conservation property in large deformation scenarios. Furthermore, the model is extended by interaction effects of electrochemistry and solid mechanics like a nonlinear contact formulation at the electrode-electrolyte interfaces to account for delamination phenomena and the subsequent absence of charge transfer reaction (see Fig. 1). We thereby show how delamination phenomena drastically change available percolation paths in the microstructure. The efficient parallel implementation of the computational model allows to investigate realistic three-dimensionally resolved microstructures of ASSB cells while accounting for the coupling effects of electrochemistry and solid mechanics. A combination of elaborate physical models and probabilistic methods enables to gain further understanding and to quantify main influencing factors on the cell performance. To showcase these capabilities and how they can be exploited to increase system understanding, we analyze how statistical values like the porosity, or the composition of the electrode microstructure influence the capacity of an ASSB cell and thereby contribute to find optimal electrode designs. References: [1]: J. Janek, W.G. Zeier, Challenges in speeding up solid-state battery development, Nature Energy 8, 230–240 (2023) https://doi.org/10.1038/s41560-023-01208-9 [2]: C.P. Schmidt, S. Sinzig, V. Gravemeier, W.A. Wall, A Three-Dimensional Finite Element Formulation Coupling Electrochemistry and Solid Mechanics on Resolved Microstructures of All-Solid-State Lithium-Ion Batteries, 2022, preprint: https://ssrn.com/abstract=4189627. Figure 1

Silicon-based anodes, composed of micrometric Si, graphite (MAG), LiI-Li3PS4 solid electrolyte (LPSI), and carbon nanofiber (CNF), which can be prepared by straightforward manual grinding, are proposed in this study. The relation between composition and performance of the anodes is investigated through the mixture design approach, which allows to discriminate the effect of each component and also the combined effect of the components on the end-performance. By increasing the fraction of LSPI in the anode, the capacity of the electrode is improved, and the best performance is obtained when the ratio of Si:MAG:LPSI is 15:15:70. This composite integrated with 5 wt% CNF exhibits the capacity above 1200 mAh g-1 throughout 50 cycles in bulk-type all-solid-state battery with LPSI as the electrolyte. From scanning electron microscope (SEM) analysis, it is confirmed that the presence of LPSI suppresses the aggregation of Si and improves the ratio of Si available for lithiation/delithiation.

To address the ever-growing demands for battery-driven electrification, successful solid-state batteries (SSBs) are expected to deliver a higher energy density than lithium-ion batteries (LIBs). One of the drastic pathways to realize this is utilizing a high-capacity anode active material such as silicon and lithium metal. In particular, silicon electrodes can be made via a roll-to-roll process that has been used in producing LIB electrodes without worrying about the ambient moisture level and, therefore, their use in SSBs will be more cost-competitive and safer than those using lithium metal if the incorporation of solid electrolytes into the electrode layer can be achieved easily. In this respect, we previously developed an incorporation method of emergent soft solid electrolytes, i.e., Li+-containing organic ionic plastic crystals (OIPCs), into a silicon electrode and demonstrated their excellent applicability to doctor-blade coating, which can be scaled up to the roll-to-roll process.1 OIPCs, which are composed of organic cations and organic/inorganic anions, are unique ion-conduction media and have been actively employed in research of SSBs, especially since the discovery of a significant improvement of ionic conductivity by the addition of a Li+ salt to OIPCs.2 Incorporating additional components into OIPC structures alters their ion-conduction behaviors and the resulting ionic conductivities of the composites depend on various factors such as the chemical nature,3 particle size,4 and concentration of dopants.5 In the case of Li+ addition, it has been known that the physical states (i.e., softness) of Li+-containing OIPCs also depend on Li+ concentration.1 Therefore, both the electrochemical and mechanical properties of Li+-containing OIPCs need to be tailored to achieve the long-term cyclability of OIPC-containing electrodes for SSBs, but this has yet to be fully explored. In the present study, we made solid-state silicon composite electrodes with Li+- containing triethylmethylphosphonium bis(fluorosulfonyl)imide (Li x [P1222]1−x [FSI]) of various Li+ concentrations (x = 0.05, 0.10, 0.30, 0.50, 0.70, or 0.90) via the “all-in-one” method1 and evaluated their electrochemical performances in CR2032 half cells with Li0.50[P1222]0.50[FSI]-containing poly(diallyl dimethylammonium) bis(fluorosulfonyl)imide (PDADMA-FSI) interlayers at 50 °C, where the silicon electrode’s composition was 70 : 15 : 15 wt% and the weight ratio of the electrode to Li x [P1222]1−x [FSI] was 85 : 15 wt%. The mechanical properties of Li x [P1222]1−x [FSI] were evaluated by rheometry. We also performed cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic intermittent titration technique (GITT) to decipher the electrochemical properties of the electrodes with different Li+ concentrations. These results allowed a discussion about how the properties of Li x [P1222]1−x [FSI] influenced the half-cell cyclability. Fig. 1 shows the delithiation capacities of silicon–OIPC composite electrodes with different Li+ concentrations over the first ten cycles. From the first cycle, the delithiation capacity of the electrode with a relatively low or high Li+ concentration (i.e., 5, 70, or 90 mol%) was lower than those of the other electrodes with middle Li+ concentrations. As the cycle number increased, the dependence of the delithiation capacity on the Li+ concentration became obvious and, at the 10th cycle, the electrode with 50 mol% Li+ showed the highest delithiation capacity. The potential difference (ΔE) between dQ/dV peaks for the redox couple involving amorphous silicon (a-Si) also showed the same trend (Fig. 2), i.e., the 50 mol% sample provided the prolonged observation of the redox couple over the cycle test as well as the lowest ΔE value among various Li+ concentrations. This highlights the importance of controlling the interfacial Li+ concentration at a silicon surface to a middle range. In the presentation, we will show the results of other electrochemical and mechanical analyses to clarify the benefit of using the middle concentration further. Acknowledgment The authors acknowledge the Australian Research Council (ARC) for the financial support under the Linkage Project scheme [grant number: LP180100674]. H. Ueda would like to thank Deakin University for providing an Alfred Deakin Postdoctoral Research Fellowship. References H. Ueda, F. Mizuno, M. Forsyth and P. C. Howlett, J. Electrochem. Soc., 171, 020556 (2024). D. R. Macfarlane, J. Huang and M. Forsyth, Nature, 402, 792 (1999). J. M. Pringle, Y. Shekibi, D. R. MacFarlane and M. Forsyth, Electrochim. Acta, 55, 8847 (2010). Y. Zhou, X. Wang, H. Zhu, M. Armand, M. Forsyth, G. W. Greene, J. M. Pringle and P. C. Howlett, Energy Storage Mater., 15, 407 (2018). H. Ueda, N. Saito, A. Nakanishi, H. Zhu, R. Kerr, F. Mizuno, P. C. Howlett and M. Forsyth, Mater. Today Phys., 43, 101395 (2024). Figure 1

All-Solid-State Batteries (ASSBs) are increasingly perceived as a viable substitute to Li-ion batteries, primarily due to their enhanced safety and energy density. ASSBs utilize a non-flammable solid electrolyte, significantly reducing the risk of fire hazards. Furthermore, they can operate under a broader temperature and voltage spectrum. This research aims to optimize the composition of anode electrode materials, comprised of a particle mixture of Active Material (AM), Solid Electrolyte (SE), and conductive additive. Graphite, a frequently used AM, is favored for its low voltage characteristics and its low volume expansion during charge cycling. Additionally, graphite's low Young Modulus is beneficial in preventing the build-up of substantial stresses within the battery cell. Silicon (Si) is another appealing material due to its high gravimetric capacity, which is up to ten times greater than that of graphite. However, during Li insertion, the crystalline structure transitions to an amorphous state, resulting in a substantial expansion of up to 300%, which triggers a significant accumulation of stress. Numerous strategies have been explored to alleviate the stress build-up resulting from expansion by adding graphite or carbon nanotubes (CNTs). The latter provides void spaces which can accommodate the volumetric expansion. Furthermore, the CNTs possess the capacity to retain the electrode's structure during volume expansion, which is advantageous for maintaining structural integrity, preserving solid-solid contacts, and enhancing the electrical conduction network. Owing to these factors, ASSBs with the addition of CNTs have demonstrated improved cycling performance. 1 Simulating Si composite solid-state anodes presents a significant challenge due to the stress induced by localized Si particles. The substantial expansion of Si can lead to the formation of shell voids in minute localized regions surrounding the microscopic Si particles. This complexity makes it difficult to simulate the dynamics using traditional finite element (FE) based mechanical models. An alternative solution is to employ the Discrete Element Method (DEM) which is a type of particle-based models that solve for Newton's laws of motion for each particle. While continuum models are instrumental in deterministically calculating the properties of bulk materials, DEMs can be utilized to compute particle slippage and the evolution of void regions between individual particles, which influence the local contact area of solid-solid interactions. In our previous research,2 we developed a multiscale chemo-mechanical DEM model for Si anode solid-state batteries. This model encompasses two stages: fabrication and cell operation. During the fabrication stage, particles were simulated within a high-pressure mold, for which we devised an elasto-plastic contact model. Throughout the cell operation stage, we simulated Li insertion and AM volume expansion. However, in current study it was observed that during charge cycling in confined cell volume, the pressure exceeded levels that are acceptable for practical applications. Furthermore, during discharge, the contact areas between particles declined and AM progressively lost its ability to form an electronic percolative chain, reducing the discharge capacity. We successfully incorporated CNTs into the DEM model by linking particles into elongated fibers, each with robust adhesive fusion bonds. The electronic percolation network and interface contact areas saw significant improvement with the addition of CNTs. By further implementing this model, we can determine the optimal composition of Si, graphite and CNTs based on several performance indicators, including the electrode's power density and capacity fade. The study will be broadened to simulate various geometrical configurations, such as a particle mixture of Si and graphite, and coated Si and SE particles on CNT structures. Acknowledgements We gratefully acknowledge the support of the Japan Science and Technology Agency (JST) through the JST-Mirai Program, Grant number JPMJMI24G1. References L. Hu, X. Yan, Z. Fu, J. Zhang, Y. Xia, W. Zhang, Y. Gan, X. He, and H. Huang, ACS Appl. Energy Mater., 5, 14353–14360 (2022). M. So, S. Yano, A. Permatasari, T. D. Pham, K. Park,. and G. Inoue, Journal of Power Sources, 546, 231956 (2022).

Silicon-graphite composites are among the most widely used anode materials in conventional lithium-ion batteries and recently have been considered as promising candidates in lithium-ion solid-state batteries. In this work, we investigate the influence of the silicon content on the electrochemical and chemo-mechanical behaviors of different Si/graphite composites in solid-state batteries. All anode composites show that an increase of Si presence in the composite enhances the cyclability at a high current density. Using direct-current (DC) polarization and temperature-dependent electrochemical impedance spectroscopy, we observe that both electronic and ionic conductivities are sufficient across the composition series. Operando stress measurements demonstrate how the internal pressure of the anode in a solid-state battery changes as a function of the Si content. Less Si (e.g., ≤10 wt %) in the blended matrix offers smaller internal stress, while it is significantly increased at 20 wt % of Si. This study emphasizes the importance of optimizing the silicon/graphite ratio in the anode composites to balance high battery performance with stable chemo-mechanical properties.

All-solid-state thin-film secondary battery (TFB) has come to recognized as one of the key enabling technologies for stand-alone MEMS/sensor devices which are indispensable for internet-of-things (IoT) solution. This paper presents on anode material development for TFB. Silicon is promising candidate to replace metallic lithium due to high heat-resistant and even high theoretical specific capacity. In this work, the effect of titanium addition on sputtered silicon electrode performance was investigated in order to improve not only mechanical damage but also resistivity.

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Silicon (Si) has attracted much attention as an emerging negative electrode material for all-solid-state lithium-ion batteries (ASSLIBs) because of the considerably high theoretical energy-density. However, its notorious volume changes during charge/discharge cycles often cause the rapid capacity fading. Thus, investigations into physicochemical and mechanical phenomena in Si electrodes during electrochemical lithiation/delithiation under ASSLIB configurations are of great importance. Single-crystal Si ( sc -Si) is an excellent subject of research to understand the anisotropic lithiation/delithiation characteristics by using different face orientations. Nevertheless, the available studies to date are mainly focused on the conventional-type LIB systems, which employ liquid organic-compounds as the main electrolyte components 1,2 . We have previously revealed the nanomechanical phenomena in a thin-film amorphous Si ( a -Si) electrode assembled in an ASSLIB configuration during the first electrochemical lithiation/delithiation using our newly constructed operando bimodal atomic force microscopy (AFM) system for solid-state batteries 3 . A steep elastic modulus decrease was observed at the initial stage of the lithiation, due to the formation of lithium silicide (Li x Si), followed by a gradual modulus reduction up to the completion of the first lithiation 3 . Likewise, operando X-ray photoelectron spectroscopy (XPS) analysis of the a -Si electrode indicated a steep binding energy shift of the bulk Si 0 peak to form Li x Si in the initial stage of lithiation, followed by the monotonic shift in response to the increase of Li content x in Li x Si 4-6 . Interestingly, a drastic peak shift associated with the phase transformation from crystalline Li 15 Si 4 ( c -Li 15 Si 4 ) into a -Li x Si was detected at Li content x = 1.6 – 2.0 in Li x Si during the subsequent delithiation, which caused the significant capacity loss probably due to the mechanical phenomena 4-6 . Electrochemical lithiation of sc -Si electrodes is known to be anisotropic 1,2 , and thus, a guideline to mitigate the rapid capacity fading due to the mechanical phenomena can be obtained by understanding the lithiation/delithiation mechanism of sc -Si electrodes, leading to the development of the long-lived Si-based negative electrode materials. In this study, we investigate the anisotropic electrochemical lithiation behaviors in sc -Si electrodes with different surfaces of (110), (100), and (111), evaluated using a variety of techniques including transmission electron microscopy (TEM), scanning electron microscopy (SEM), and XPS. ASSLIB half-cells with a configuration of sc -Si working electrode/lithium phosphorous oxynitride (LiPON) solid-electrolyte/Li metal counter electrode ( sc -Si/LiPON/Li) were fabricated from commercially available sc -Si wafers by sputter-deposition of a LiPON layer, followed by incorporation of a piece of Li metal foil. After the electrochemical lithiation, the sc -Si/LiPON/Li cells were cleaved to expose their cross-sections in an inert Ar-filled glove box, transported via a sealed transfer vessel, and analyzed by the above-mentioned techniques. At all the surface orientations (110), (100) and (111), the formation of a -Li x Si layer was clearly observed between the LiPON layer and sc -Si electrode. However, the Li content x in a -Li x Si layer was significantly different depending on the surface orientations, confirming the anisotropic lithiation reaction and Li-ion diffusion. The details including chemical species and nanomechanical properties will be discussed at the meeting as well as the anisotropic reaction mechanism. References (1) Aoki, N.; Omachi, A.; Uosaki, K.; Kondo, T., ChemElectroChem 2016, 3 (6), 959. (2) Omachi, A.; Aoki, N.; Uosaki, K.; Kondo, T., ECS Trans. 2017, 75 (52), 67. (3) Putra, R. P.; Matsushita, K.; Ohnishi, T.; Masuda, T., J. Phys. Chem. Lett. 2024, 15 (2), 490. (4) Endo, R.; Ohnishi, T.; Takada, K.; Masuda, T., J. Phys. Chem. Lett. 2020, 11 (16), 6649. (5) Endo, R.; Ohnishi, T.; Takada, K.; Masuda, T., J. Phys. Commun. 2021, 5 (1), 015001. (6) Endo, R.; Ohnishi, T.; Takada, K.; Masuda, T., J. Phys. Chem. Lett. 2022, 13 (31), 7363.

Investigating local strain distributions is essential for developing long‐life all‐solid‐state batteries (ASSBs) because capacity fading primarily results from cracks and contact loss caused by volume changes in electrode active materials during battery operation. Digital image correlation (DIC) analysis can be used to create strain distribution maps from continuous images of materials under applied pressure. In this study, DIC analysis of operando confocal microscopy images of an ASSB cross‐section was conducted to elucidate the mechanical degradation mechanism in ASSBs with Si electrodes exhibiting ~300 % volume change. The Si electrode layer exhibited irreversible strain changes, whereas the solid electrolyte (SE) layer exhibited no significant strain changes. Furthermore, DIC analysis was performed using in situ SEM images focused on the Si electrode layer to investigate detailed strain distribution maps for individual Si particles. Higher strain changes were observed in the vertical direction within the SE layer, which led to cracks forming in relatively large Si particles at the beginning of the lithiation process. Visualizing local strain distribution in the electrode layer through DIC analysis of operando/in situ images is a powerful approach for understanding how and where cracks form.

All-solid-state lithium-ion batteries (ASSLBs) have garnered considerable attention as the next-generation electrochemical energy storage systems due to their high chemical safety and wide electrochemical potential windows1. Among the available candidates for ASSLB negative electrodes, silicon is a promising material because of its extremely high theoretical capacity and low lithiation/delithiation potential2. However, Si is known to undergo severe structural changes during electrochemical lithiation/delithiation, as revealed by our previous operando studies using a laboratory-based X-ray photoelectron spectroscopy setup3,4. These dramatic structural changes may result in a significant volume expansion/contraction, leading to particle cracking, pulverization, and electrode failure. Hence, the understanding and control of such physicochemical phenomena are critical to prevent nanomechanical and electrochemical degradation of the electrode. In this talk, we will introduce our newly developed operando bimodal atomic force microscopy (AFM) system which enables real-time nanomechanical monitoring of an amorphous Si thin film electrode during electrochemical lithiation/delithiation, simultaneously with cross-sectional topography imaging5. An ASSLB cell composed of 3 µm-thick Si thin film/500 µm-thick Li6.6La3Zr1.6Ta0.4O12 (LLZT) solid electrolyte/50 µm-thick Li foil (Si/LLZT/Li) was fabricated, and its cross-section was smoothened by an Ar-ion beam prior to carrying out the nanomechanical mapping on the Si/LLZT interface. The nanomechanical mapping was performed during the first electrochemical lithiation and delithiation within a potential window of 0.01-1.20 V vs. Li+/Li under Ar atmosphere (H2O < 0.1 ppm, O2 < 0.1 ppm). Nanomechanical property maps of the Si electrode, in the form of Young’s modulus maps, were successfully acquired as a function of apparent Li content x in lithium silicide (Li x Si), together with real-time topography images. At the first lithiation, the average Young’s modulus drastically decreased due to the formation of Li x Si from pristine Si, followed by a moderate modulus reduction up to a capacity of 3300 mAh g-1 (x = 3.46 in Li x Si). Throughout the successive delithiation up to 1467 mAh g-1 (x = 1.54 in Li x Si), the average modulus was gradually recovered. The Li x Si moduli obtained from this study are consistent with the values from the first-principles calculations, showing the sensitivity and reliability of the technique6. The demonstrated technique can be implemented for a wide range of battery materials for both solid-state and liquid-electrolyte lithium battery systems. References: K. Takada. J. Power Sources. 2018, 394, 74. J. Sakabe, N. Ohta, and T. Ohnishi. Commun. Chem. 2018, 1, 1, 24. R. Endo, T. Ohnishi, K. Takada, and T. Masuda. J. Phys. Chem. Lett. 2020, 11, 16, 6649. R. Endo, T. Ohnishi, K. Takada, and T. Masuda. J. Phys. Chem. Lett. 2022, 13, 31, 7363. R.P. Putra, K. Matsushita, T. Ohnishi, T. Masuda. J. Phys. Chem. Lett. 2024, 15, 2, 490. V.B. Shenoy, P. Johari, Y. Qi. J. Power Sources. 2010, 195, 19, 6825.

For the first time, we demonstrate a silicon solid‐state battery (SSB) architecture that achieves >400 Wh kg−1, approaching the theoretical limit for silicon‐based SSBs. This configuration features a 99.9 wt% micro‐Si, a thin sulfide solid electrolyte (SSE), and a high‐loading NMC811. Key to these results is strategically selecting and evaluating the processing techniques, whether wet or dry, for the negative electrode, positive electrode and thin sheet‐type SSE. Excessive lithium incorporation into the silicon host, beyond the Li3.75+Si phase to form a LiSi composite, is essential to match the high capacity of the positive electrode. This SSB achieves over 1000 cycles for a 2 mAh cm−2 with ≈80% capacity retention and 94% capacity retention for 3 mAh cm−2 over 500 cycles at 25 °C. Post analysis identifies the primary capacity decay mechanisms as oxidation at the NMC/SSE interface and structural disruptions within NMC. Meanwhile, the Si electrode maintains a robust solid‐electrolyte interphase layer, minimizing capacity decay. This study highlights the necessity for improved NMC coatings, lattice oxygen stabilization, and a durable positive electrode‐electrolyte interface to improve the long‐term stability of SSBs. Strategies leading to a single‐layer pouch cell SSB exceeding 400 Wh kg−1 are developed.

Interfaces are the critical components of all-solid-state batteries, and it is generally believed that high interfacial impedance is the major culprits of battery failure. In this study, the interface impedance has been found not to be a major issue in the batteries comprising Si negative electrode, Li10GeP2S12 and Li10Si0.3PS6.7Cl1.8 electrolytes and LiNi0.8Mn0.1Co0.1O2 positive electrode. Instead, it is the sustainable interfacial reaction that depletes the active lithium source, causing continuous capacity decay. The interphase layer at the Si/Li10Si0.3PS6.7Cl1.8 interface comprising nanocrystalline Li2S dispersed in an amorphous matrix is thin (with a thickness < 200 nm) and stable, and the battery maintains a good cyclability. In contrast, the interphase layer at the Si/Li10GeP2S12 interface is thick with a thickness of 10 μm. Couter-intuitively, despite the thick interfacial layer comprising mainly needle shaped Li2S, the interfacial impedance does not increase dramatically, suggesting that interfacial impedance is not the main issue, rather, it is the chemically/electrochemically continuous reaction of negative electrode with Li10GeP2S12 that consumes the active lithium source from positive electrode and causes the capacity decay. This study provides atomic-scale interface structures of sulfide based batteries, which have important implications for the design of stable interfaces for high performance batteries. Here, authors use Cryo-FIB and Cryo-TEM to reveal the atomic structures of the sulfide electrolyte/Si electrode interfaces, showing that the continuous lithium-ion consumption during interfacial reaction rather than interface impedance leads to capacity fade and battery failure.

The direct observation of the morphological changes in silicon-based negative electrode (Si-based negative electrode) materials during battery charging and discharging is useful for handling such materials and in electrode plate design. We developed an operando scanning electron microscopy (operando SEM) technique to quantitatively evaluate the expansion and contraction of Si-based negative electrode materials. A small all-solid-state lithium-ion battery was charged and discharged, and the expansion/contraction of particles while harnessing capacity was observed using SEM. We found that in a silicon monosilicate (SiO)/graphite negative electrode, SiO expanded first during charging, and graphite contracted first during discharging. Our study provides insights into the relationship between capacity and expansion and contraction coefficient of Si-based negative electrode materials.

Solid-state batteries (SSBs) are promising alternatives to the incumbent lithium-ion technology; however, they face a unique set of challenges that must be overcome to enable their widespread adoption. These challenges include solid–solid interfaces that are highly resistive, with slow kinetics, and a tendency to form interfacial voids causing diminished cycle life due to fracture and delamination. This modeling study probes the evolution of stresses at the solid electrolyte (SE) solid–solid interfaces, by linking the chemical and mechanical material properties to their electrochemical response, which can be used as a guide to optimize the design and manufacture of silicon (Si) based SSBs. A thin-film solid-state battery consisting of an amorphous Si negative electrode (NE) is studied, which exerts compressive stress on the SE, caused by the lithiation-induced expansion of the Si. By using a 2D chemo–mechanical model, continuum scale simulations are used to probe the effect of applied pressure and C-rate on the stress–strain response of the cell and their impacts on the overall cell capacity. A complex concentration gradient is generated within the Si electrode due to slow diffusion of Li through Si, which leads to localized strains. To reduce the interfacial stress and strain at 100% SOC, operation at moderate C-rates with low applied pressure is desirable. Alternatively, the mechanical properties of the SE could be tailored to optimize cell performance. To reduce Si stress, a SE with a moderate Young’s modulus similar to that of lithium phosphorous oxynitride (∼77 GPa) with a low yield strength comparable to sulfides (∼0.67 GPa) should be selected. However, if the reduction in SE stress is of greater concern, then a compliant Young’s modulus (∼29 GPa) with a moderate yield strength (1–3 GPa) should be targeted. This study emphasizes the need for SE material selection and the consideration of other cell components in order to optimize the performance of thin film solid-state batteries.

While solid electrolyte-excluded Si electrodes can form in situ lithiated monolithic structures with minimal side reactions, their poor performance at low operating pressures remains a formidable challenge for all-solid-state batteries. Herein, we propose an electrically conductive binder—poly(3,4-ethylenedioxythiophene):poly((styrene sulfonic acid)x-co-(maleic acid)y) (PEDOT:P(SSx-co-MAy))—that is scalable, fluorine-free, and water-processable. This binder offers sufficient e−-conductivity to eliminate carbon additives, while ensuring strong adhesion and electrochemical stability in contrast to conventional liquid electrolyte systems. Ex situ measurements reveal disrupted e-connectivity during delithiation at 5 MPa, resolved by employing PEDOT:P(SSx-co-MAy). The improved electrochemical performance of Si electrodes comprising PEDOT:P(SSx-co-MAy), compared with those using conventional polyvinylidene fluoride, is validated in (Li-In) | Li6PS5Cl | Si half cells and Si | Li6PS5Cl | LiNi0.70Co0.15Mn0.15O2 full cells at 30 °C and 5 MPa, achieving 134 mAh g−1 at 0.5 C with 86% capacity retention after 100 cycles. Finally, 233 mAh pouch-type Si || LiNi0.83Co0.12Mn0.05O2 ASSBs are demonstrated, highlighting the potential of PEDOT:P(SSx-co-MAy) as a practical binder platform for high-energy ASSBs. Silicon negative electrode in all-solid-state batteries can lose electrical contact at low stack pressure, reducing performance. Here, the authors introduce a conductive, water-processable polymer binder that preserves contact and supports stable operation at low stack pressure.

The graphite/silicon‐based diffusion‐dependent electrodes (DDEs) are one of the promising electrode designs to realize high energy density for all‐solid‐state batteries (ASSBs) beyond conventional composite electrode design. However, the graphite/silicon‐based electrode also suffers from large initial irreversible capacity loss and capacity fade caused by significant volume change during cycling, which offsets the advantages of the DDEs in ful‐cell configuration. Herein, a new concept is presented for DDEs, dry pre‐lithiated DDEs (PL‐DDEs) by introducing Li metal powder. Since Li metal powder provides Li ions to graphite and silicon even in a dry state, the lithiation states of active materials is increased. Moreover, the residual Li within PL‐DDE further serves as an activator and a reservoir for promoting the lithiation reaction of the active materials and compensating for the active Li loss upon cycling, respectively. Based on these merits, ASSBs with PL‐DDE exhibit excellent cycling performance with higher columbic efficiency (85.2% retention with 99.6% CE at the 200th cycle) compared to bare DDE. Therefore, this dry lithiation process must be a simple but effective design concept for DDEs for high‐energy‐density ASSBs.

State-of-the-art lithium-ion batteries incorporating silicon negative electrodes face significant challenges due to the volume fluctuations that occurs during cycling, leading to enormous internal stress and eventual battery failure. Notably, existing research predominantly focuses on material-level solutions, with limited exploration of effective cell design strategies. Herein, we present a systematic implementation of a Stress-Neutralized Si-S full cell design that leverages the natural volume change dynamics of silicon and sulfur electrodes. Our approach goes beyond inherent stress compensation by employing a dynamic volume compensation strategy. This strategy involves real-time stress monitoring and precise structural optimization to achieve full utilization of the active mass (100%) and to mitigate the residual stresses and heterogeneity that naturally arise during cycling. A quantitative analysis proved the effectiveness of this approach, showcasing high specific energy (525 Wh kg−1) based on total battery mass, long cycling stability (500 cycles), large areal current density (25.12 mA cm−2), and high capacity (1.24 Ah) in Si-S system. This approach systematically enhances the naturally occurring stress-compensation phenomenon, addressing the residual stresses and optimizing electrode behavior for high-performance solid-state batteries. Silicon electrodes in lithium-ion batteries are severely limited by the stress that arises from large volume changes during cycling. Here, authors exploit the inherent volume change dynamics of silicon and sulfur electrodes and design a stress-neutralized solid-state battery.

Silicon is a promising negative electrode material for solid‐state batteries (SSBs) due to its high specific capacity and ability to prevent lithium dendrite formation. However, SSBs with silicon electrodes currently suffer from poor cycling stability, despite chemical engineering efforts. This study investigates the cycling failure mechanism of composite Si/Li6PS5Cl electrodes by decoupling the effects of interface chemical degradation and mechanical cracking. Chlorine‐rich Li5.5PS4.5Cl1.5 suppresses interface chemical degradation when paired with silicon, while small‐grained Li6PS5Cl shows 4.3‐fold increase of interface resistance due to large Si/Li6PS5Cl contact area for interface degradation. Despite this, small‐grained Li6PS5Cl improves the microstructure homogeneity of the electrode composites, effectively alleviating the stress accumulation caused by the expansion/shrinkage of silicon particles. This minimizes bulk cracks in Li6PS5Cl during the lithiation processes and interface delamination during the delithiation processes. Mechanical cracking shows a dominant role in increasing interface resistance than interface chemical degradation. Therefore, electrodes with small‐grained Li6PS5Cl show better cycling stability than those with Li5.5PS4.5Cl1.5. This work not only provides an approach to decouple the complex effects for cycling failure analysis but also provides a guideline for better use of silicon in negative electrodes of SSBs.

Next-generation solid-state batteries are expected to offer improved capacity and safety. The increase in capacity depends on the negative electrode material, and high-capacity materials such as Si, which can absorb large amounts of Li, are the subject of research. The amount of Li transferred can be measured electrically. However, it has not been possible to visualize where Li is distributed within the anode particles or to analyze the chemical state of the anode particles in real-time. Therefore, we installed a system on the SEM that enables real-time observation and analysis during charging and discharging (in-situ), which is an important technology in research and development. This system has the following three features. 1) A tool that can maintain confining pressure and transport the battery from cross-section processing to SEM observation 2) Live imaging to visualize Li behavior during charging and discharging 3) Chemical state analysis of materials such as Si negative electrodes The above three features are possible by combining the following devices and detectors; 1) a holder that maintains stack pressure and can be used together with processing and observation instruments, 2) a Windowless EDS detector “Gather-X” that can detect low characteristic X-ray energies like Li (54eV), and 3) a soft X-ray spectrometer (SXES) that enables local chemical state analysis. Using this system, we were able to visualize the behavior and distribution of Li intercalating into Si particles during charging and discharging and analyze the transformation of anode particles into crystals, alloys, and amorphous states. The Si anode composite was made by mixing Si particles and polyimide and applying a slurry. The cathode composite was made by mortar mixing the ternary oxide cathode material LiNi1/3Mn1/3Co1/3O2 (NMC), argyrodite sulfide solid electrolyte (SSE) and acetylene black (AB). Each component was put into a pelletizer, stacked, and pressurized at about 500 MPa to produce a full cell pellet. The pellet was cut into 4.8 mm squares using a precision punching tool for highly brittle materials (NOGAMIGIKEN, NC-CE-SS) and placed on a constrained charge/discharge holder, where a constraining pressure of 25 MPa was applied. The cross-sections were prepared with an Ar ion beam (acceleration voltage: 5 kV, cooling temperature: -120 °C, processing time: 5 hr) using a cross-section preparation system (JEOL, Cooling Cross Section PolisherTM, IB-19520CCP). To minimize sample deterioration due to exposure to the atmosphere, glove boxes and transfer vessels that can be closed to the atmosphere were used for the entire process from pretreatment to processing to observation. A Schottky FE-SEM (JEOL, JSM-IT800) equipped with a Windowless EDS (JEOL, DrySDTM Gather-X) and a soft X-ray spectrometer (JEOL, SS-94000SXES) was used for observation and analysis. SEM- EDS-SXES analysis was performed while charging and discharging at a C rate of 0.2 C (vs. NMC standard) using a battery charge/discharge device (HOKUTO DENKO, Hz-Pro) and a restrained charge-discharge holder in the SEM. The result of SEM-Windowless EDS analysis (backscattered electron (BSE) and EDS MAP images) at SOC 0% to 10% is shown in Fig.1(a). Expansion of Si particles and changes in composition contrast were observed in the BSE composition image. From the EDS MAP, it was confirmed not only from contrast changes but also from characteristic X-ray information that Li was gradually inserted and alloyed toward the anode end of the solid electrolyte side of the Si particles in contact with the solid electrolyte interface. It was observed that Li was selectively inserted into some of the Si particles that were in contact with the solid electrolyte interface. The results of SXES analysis of specific Si particles, when the sample was charged to 0%, 10%, 20%, and 40% SOC and then discharged, are shown in Fig.1(b). The peak intensity of Li-K gradually changed as the charge rate changed. The peak position of Li K is about 53.4 eV, suggesting that Li-Si alloying is in progress. On the other hand, the half-width and peak shape of Si-L also gradually changed with the change in charge rate. After discharge, the Li-K peak intensity became lower, and the Si-L peak shape was like that of amorphous silicon, indicating that the chemical state of the Si particles changed due to the desorption of Li. These results show the continuous change of Si particle shape with Li insertion/extraction in the process of charging/discharging a single Si particle and the change of Si chemical state from crystalline silicon to amorphous state due to Li-Si alloying and discharge. Acknowledgments We would like to thank Professor Nobuya Machida of Konan University for cooperation in some of the battery sample preparation. Figure 1

In all-solid-state batteries (ASSBs), silicon-based negative electrodes have the advantages of high theoretical specific capacity, low lithiation potential, and lower susceptibility to lithium dendrites. However, their significant volume variation presents persistent interfacial challenges. A promising solution lies in finding a material that combines ionic-electronic conductivity, stable physicochemical properties, and adhesive characteristics. Poly(acrylic acid) (PAA) is widely used in liquid-state batteries due to its superior properties compared to polyvinylidene fluoride (PVDF). In this study, silicon particles were coated with varying concentrations of PAA and LiPAA using an in situ liquid-phase coating method to form electrode sheets. The experimental and analytical results revealed significant trends in the impact of different additive concentrations on the electrochemical performance, with 1.0 wt % LiPAA showing notable improvements in Coulombic efficiency, rate capability, and long-term cycling stability. The assembled all-solid-state batteries exhibited a high initial discharge capacity of 3200 mAh/g, with a capacity retention of 81.9% after 300 cycles at 0.3 C, and a stable discharge capacity of 1300 mAh/g at a 2 C rate. A rapid and efficient in situ liquid-phase coating method for LiPAA was developed and confirmed through FTIR, XRD, and TEM characterization. SEM and XPS analyses demonstrated that LiPAA encapsulation effectively alleviates interfacial issues. This study demonstrated for the first time that an appropriate amount of LiPAA coating on silicon particles can mitigate the interfacial challenges caused by the volume expansion of silicon-based negative electrodes. These findings improve electrochemical performance and promote the application of silicon-based negative electrodes in all-solid-state batteries.

Silicon-based solid-state batteries are promising next-generation high-energy-density technologies. However, poor (electro)chemical compatibility between silicon negative electrodes and solid electrolytes (e.g., Li6PS5Cl) plus sluggish interfacial kinetics severely limits their reversibility and Coulombic efficiency. Here, we propose a surface halogenation strategy that transforms the native amorphous SiO2 passivation layer on silicon particles into a functional Al(Si)OCl composite surface via controlled reaction with AlCl3. This artificial interphase reconciles interfacial incompatibility and enables fast ionic/electronic transport, suppressing irreversible lithium loss. The optimized negative electrode achieves a high initial Coulombic efficiency of 94.3% in half-cells and 85.6% initial Coulombic efficiency (86.6% with pre-lithiation) in full cells paired with LiNi0.88Co0.09Mn0.03O2. Enhanced reversibility further delivers long-term cyclability. The optimized negative electrode delivers 86% capacity retention and 99.998% average Coulombic efficiency over 200 cycles. Even at high-loading ( > 10 mAh cm-2, and no adhesives/conductive carbon/electrolyte), it retains 72% capacity after 500 cycles. The full cells maintain 80% capacity after 200 cycles at 1 C, with an average Coulombic efficiency exceeding 99.95%. The versatility of this halogenation strategy underscores halide chemistry’s broad potential in advancing high-performance, reversible silicon-based solid-state batteries. Silicon negative electrodes in solid-state batteries exhibit poor reversibility. Here, the authors demonstrate surface halogenation engineering that suppresses irreversible lithium loss, achieving 94.3% initial Coulombic efficiency and 72% capacity retention over 500 cycles at 25°C.

No abstract available

Graphite, a lithium intercalaion-type host, is considered as the most commercially available anode material for secondary batteries. However, mojor issues on poor kinetics, a low capacity, and interfacial reaction with sulfide solid electrolytes hinders the introduction of graphite to all solid-state batteries (ASSBs). Here we propose a rational material design on graphite/Si-based anodes for high capacity and long-cycle-life ASSBs. A mechano-fusion process is used to synthesize hetero-aggregates with a core-shell structure, where (sub-)micron SiOx particles are anchord on the surface of graphite host particles (10-20 µm). As-prepared SiO x /graphite composite (SGC) is covered with a carbon layer (~10nm) by pitch conating and thermal treatment (C@SGC). The ASSB is fabricated with Li-metal as a counter electrode and an anode with the C@SGC and Li6PS5Cl in a weigh ratio of 8 : 2. When tested at 25℃ and undr 25 MPa, it delivers a initial discharge capacity of 706 mAh g− 1 and a high capacity retention of 89% over 200 cycles. Monitoring of a swelling behavior shows 2% of a negligible volume change after charge/discharge, in contrast to 33% for a LIB system, leads to a good interfacial solid-solid contacts and electrode integrity. We further reveals that the pitch carbon coating largely suppress the side reaction between the SGC and the Li6PS5Cl. Our design strategy on materials opens up new possibility for the graphite/Si-based anode for room-terperature all-solid-state battery.

No abstract available

The utilization of Si anode in sulfide‐based all‐solid‐state batteries (ASSBs) has gained more research attention in recent years to overcome the interface challenges associated with ASSB‐containing Li metal anode. However, the volume expansion feature of the Si, stress/strain evolution inside the electrode, and the parasitic side reaction at the Si/sulfide SE interface are the most predominant limiting factors for practical device applications. It is necessary to investigate and understand the interface challenges through in‐depth analysis in real‐time battery operation to design highly efficient ASSBs for commercial device applications. Hence, this perspective paper provides a summary of the characterization tools and the analysis results related to the Si/sulfide SE interface. Moreover, in this perspective, we emphasize the importance of further investigation of the interface through more advanced in‐depth/operando analysis tools to gain insightful information about the anodic interface, which could be useful for the researchers to design efficient research strategies for solving the challenging issues associated with the anodic interface.

All-solid-state batteries (ASSBs) are promising next-generation batteries owing to their improved safety compared with lithium-ion batteries using flammable liquid electrolytes. Among various solid electrolytes, sulfide-based electrolytes exhibit high ionic conductivities, and their ductile properties allow them to be easily processed without high-temperature sintering. In sulfide-based ASSBs, a polymer binder is essential for achieving a good cycling performance by maintaining strong interfacial contacts in the composite electrodes during cycling. In this study, we prepared a composite Si-C anode and a LiNi0.82Co0.1Mn0.08O2 cathode using a nitrile-butadiene rubber binder for ASSB applications, and investigated the effect of the binder content on the mechanical properties and electrochemical performance. The binder content significantly influenced the physical and electrochemical characteristics of the composite electrodes, and the ASSB prepared with 1.5 wt.% binder showed the best cycling performance considering capacity retention and rate capability. Furthermore, we investigated how the excess binder adversely affected the cycling performance through time-of-flight secondary ion mass spectrometry analysis.

In recent years, all-solid-state batteries (ASSBs) have attracted considerable attention within the scientific community owing to their potential for achieving high energy density, enhanced safety characteristics, and a broader operational temperature window. Specifically, sulfide-based solid-state electrolytes (SSEs) demonstrated the most promising ASSB chemistry with their room-temperature Li+ ionic conductivity comparable or exceeding to that of conventional liquid electrolytes (~10 mS cm-1). Our previous works showcased the superior cyclability of ASSB implementing sulfide-SSEs and carbon-free silicon anode with phenomenal stable cycling for 500 cycles1. Recently, we further demonstrated the scalability of carbon-free Si anode at the pouch cell level with cell capacity reaching 100 mAh under significantly low stacking pressure of 5 MPa2-3, showing promise to accelerate the development and commercialization of ASSBs. Characterizing ASSBs during and after operation is critical for their further development. Crucially, scaling up ASSBs to pouch-cell level introduces new challenges as characterizing the internal microstructure and morphological evolution at a larger scale becomes difficult and time-consuming. Previous works using destructive focus-ion beam-scanning electron microscope (FIB-SEM) can only visualize several tens of micrometers with long imaging times for 3D reconstruction up to hours. Thus, techniques with larger field of view (FOV) and shorter imaging time are inevitably needed to have a better statistical analysis. This study leverages the non-destructive nature of synchrotron X-ray micro-computed tomography (CT) to visualize the morphology and microstructure of each component within an ASSB pouch cell. Leveraging the large FOV of X-ray micro-CT, up to several millimeters and shorter imaging time, we are able to perform a quantitative analysis of the extracted microstructural information, including porosity, loss of contact, and tortuosity. These findings will provide a broader understanding of the structural evolution in ASSB pouch cells, bridging the gap between lab-level research and application-level production. Reference: Tan, D. H. S.; Chen, Y. T.; Yang, H.; Bao, W.; Sreenarayanan, B.; Doux, J. M.; Li, W.; Lu, B.; Ham, S. Y.; Sayahpour, B.; Scharf, J.; Wu, E. A.; Deysher, G.; Han, H. E.; Hah, H. J.; Jeong, H.; Lee, J. B.; Chen, Z.; Meng, Y. S., Carbon-free high-loading silicon anodes enabled by sulfide solid electrolytes. Science 2021, 373(6562), 1494-1499. Tan, D. H. S.; Meng, Y. S.; Jang, J., Scaling up high-energy-density sulfidic solid-state batteries: A lab-to-pilot perspective. Joule 2022, 6 (8), 1755-1769. Chen, Y.-T.; Jang, J.; Oh, J. A. S.; Ham, S.-Y.; Yang, H.; Lee, D.-J.; Vicencio, M.; Lee, J. B.; Tan, D. H. S.; Chouchane, M.; Cronk, A.; Song, M.-S.; Yin, Y.; Qian, J.; Chen, Z.; Meng, Y. S., Enabling Uniform and Accurate Control of Cycling Pressure for All-Solid-State Batteries. 2023.

All‐solid‐state batteries (ASSBs) are emerging as a promising alternative to conventional lithium‐ion batteries, offering improved safety and potential for energy density. However, the substantial volume fluctuations of high‐capacity anodes such as lithium and silicon induce interfacial degradation, impeding practical applications. Herein, an aluminum–silicon (Al–Si) alloy anode is introduced that effectively mitigates these challenges by stabilizing volume variation after initial volume expansion and maintaining stable interfacial integrity with the solid electrolyte (SE). By employing a SE‐free wet anode and leveraging advanced characterization techniques, including three‐dimensional X‐ray nanoimaging and digital twin‐based particle‐to‐electrode volume expansion simulations, the structural evolution and electrochemical behavior of Al–Si are elucidated. Furthermore, the integration of an elastic‐recoverable anolyte enables the formation of a robust Al–Si composite anode, effectively suppressing contact loss and enhancing reversibility. ASSBs integrating this Al–Si composite anode and a high‐areal‐capacity LiNi0.8Co0.1Mn0.1O2 cathode (6 mAh·cm−2) achieve a capacity retention of 81.6% after 300 cycles, offering a viable pathway toward high‐energy‐density and durable ASSBs.

All-solid-state lithium-ion batteries (ASSLBs) are attractive energy storage devices because of their excellent gravimetric and volumetric capacity and ability to supply high power rates. Porous silicon (Si) is a promising material for an anode in lithium-ion batteries due to its high capacity and low discharge potential. However, Si anodes cause significant problems due to strong volume growth during the lithiation and delithiation processes, which results in rapid capacity fading and poor cycle stability. To overcome this problem, we developed mesoporous silica (SiO2) aerogels into porous silicon (Si) anodes using a magnesiothermic reduction (MTR) process. By effectively preserving the porous structure, this approach enables the material to endure volume fluctuations while maintaining its structural integrity during cycling. In our study, we demonstrated a feasible approach to fabricate the porous silicon (Si) from hydrophobic and hydrophilic silica (SiO2) aerogel and magnesium powder (Mg) through the MTR process at 600~900 °C. The sample obtained after the reduction process was treated with hydrochloric acid (HCl) to remove byproducts. As prepared, Si was characterized using various techniques, including XRD, XRF, FT-IR, XPS, SEM, and BET, which confirmed the successful production, chemical purity, and structural retention of Si. Furthermore, the coin cell was fabricated using Si as an anode, and the electrochemical performance was analyzed. The charge/discharge cycling tests at 1 C and 0.02~2 V (vs. the Li condition) revealed the effects of silicon content, wettability, and interfacial compatibility on electrode performance. Conversely, for better understanding, a long-term cycling test was conducted at 1 C rate, 0–1.5 V (vs. Li) to evaluate capacity retention. Our findings highlight the potential application of silicon (Si) aerogels produced from silica (SiO2) aerogels by magnesiothermic reduction to improve lithium-ion battery performance.

Sulfide all solid‐state batteries (ASSBs) with Si‐based anode offers a promising route to high energy density of Energy Storage Devices. Nevertheless, the unstable interface of ASSBs remains a critical challenge, especially causing issues such as decomposition of sulfide solid electrolyte (SSE). Thus, a composite porous CuAg‐Si (PCuAg‐Si) anode with a coherent interface of multi‐phase (Ag, Cu and Cu 15 Si 4 ) is designed. The Si epitaxial grown Cu and Ag form a coherent interface with the sulfide electrolyte, which provides enhanced Li + diffusion pathways. Furthermore, this coherent interface creates an “electron shielding effect” that lowers the rate of reduction reactions in the SSE, further stabilizing the interface and reducing unnecessary degradation of the electrolyte. Additionally, the porous structure can effectively inhibit volume expansion during Li + insertion/disinsertion, ensuring stable interfacial stress and further reducing the electron leakage path caused by mechanical cracks in the SSE. Consequently, the PCuAg‐Si anode exhibits a reversible specific capacity of 420 mAh g −1 after 1500 cycles at 1 A g −1 (capacity degradation rate per cycle is as low as 0.02%). Meanwhile, PCuAg‐Si || LNO@NCM811 demonstrates a high specific capacity of 77 mAh g −1 after 720 cycles at 1C. Engineering coherent interfaces charts a compelling pathway toward next‑generation, high‑performance ASSBs.

Silicon (Si) has long captured the spotlight as an anode candidate for lithium‐ion batteries (LIBs) due to its exceptionally high theoretical capacity and abundant availability. However, chemomechanical failure of larger‐sized Si has plagued its electrochemical performance. Herein the presence of a stack pressure‐dependent size effect of Si particles in sulfide‐based all‐solid‐state batteries (ASSBs) is unveiled that can be harnessed to overcome the chemomechanical failure of Si. Remarkably, the application of stack pressure, necessary to enhance interface contact and charge transfer in ASSBs, shifts the size threshold from nanometer scale observed in liquid electrolyte batteries to the microscale in ASSBs. The essence of the stack pressure‐dependent size effect is the suppression of the Hoop stress that causes the fracture of Si particles during lithiation by the applied external stress. This revelation offers an effective strategy to optimize the size of Si for the desired electrochemical performance in ASSBs. These findings provide invaluable insights that offer indispensable guidance for mitigating Si anode failure in ASSBs, ultimately advancing the next‐generation high‐performance Si‐based ASSBs.

No abstract available

No abstract available

Micron-sized Si anodes garner renewed attention due to their advantages of low cost, small specific surface area, and high energy density. However, micron-sized Si anodes undergo significant volume changes during lithiation/delithiation, leading to particle cracking and pulverization. This study employs the tape casting method and ultrafast high-temperature sintering technology to construct a porous sheet, within which a solid framework constrains the Si particles. In rate performance tests, when the current density rises to 1 A g-1, the micron-sized Si in the porous sheet demonstrates a delithiation capacity of 2145 mAh g-1, compared to 113 mAh g-1 for the pristine Si, showing efficient ion and electron conductive pathways in the framework. When cycled at 0.3 A g-1, the delithiation capacity of the ball-milled micron-sized Si in the porous sheet is 1496 mAh g-1 after 100 cycles, in contrast to 95 mAh g-1 for the pristine Si. The enhanced cycling stability of Si in the porous sheet results from the strong mechanical constraint imposed by the solid framework, which suppresses volume changes, inhibits particle cracking, and reduces solid electrolyte interphase growth. This strategy of constructing porous sheets and utilizing solid-solid bonding to constrain Si particles represents a novel approach for Si anode modification.

Despite the high theoretical capacity, silicon (Si) anode suffers from dramatical capacity loss, due to its massive volume swings (up to 300%) during cycling. Hence, thorough understanding of the structural evolution mechanism is necessary and essential for performance optimization of Si anode. Herein, a multi-scale three-dimensional (3D) image reconstruction technique is firstly applied to visualize the structural evolution process of Si anodes. Three key components (Si particles, inactive components, and voids) in the electrode are quantitatively analyzed by focused ion beam and scanning electron microscope (FIB-SEM) technology. Furthermore, the average sizes of Si particles were run statistics during the cycling. By combining the componential observation within the electrode (macroscopic information) and the 3D models of the particle with solid electrolyte interphase (SEI) layer (microscopic information), the failure mechanism of Si anode is vividly demonstrated. This work establishes a new methodology to quantitatively analyze the structural and compositional evolution of Si anode, which could be further applied for the studies of many other electrode materials with similar issues.

No abstract available

An operando bimodal atomic force microscopy system was constructed to perform nanomechanical mapping of an amorphous Si thin film electrode deposited on a Li6.6La3Zr1.6Ta0.4O12 solid electrolyte sheet during electrochemical lithiation/delithiation. The evolution of Young’s modulus maps of the Si electrode was successfully tracked as a function of apparent Li content x in lithium silicide (LixSi) simultaneously with real-time surface topography observation. At the initial stage of lithiation, the average modulus steeply decreased due to the generation of LixSi from intrinsic Si, followed by a moderate modulus reduction until the electrode capacity reached 3300 mAh g–1 (Li content x = 3.46). In the following delithiation, the gradual recovery of the average modulus of LixSi was observed up to 1467 mAh g–1 (Li content x = 1.54) at which delithiation stopped due to the significant volume change induced by phase transformation of LixSi.

In the past decades, due to an always more electrification and the research of a greener environment, Li-ion Batteries (LIB) have taken an important place in worldwide research. Solid-state batteries (SSBs) have the potential to revolutionize the energy storage industry, offering superior safety and energy density in comparison to traditional LIBs[1, 2]. Our research aims to enhance the performance and safety of solid-state batteries at ambient temperature by incorporating electrodes with high specific capacity with a lithium lanthanum zirconate (LLZO) solid electrolyte. The integration of SiNW electrodes into the solid-state battery architecture offers several advantages. SiNWs are known for their large surface area and superior electrical conductivity and offer a strong platform for efficient lithium-ion transport and cell energy density optimization, theoretically almost 10 times the capacity of graphite[3, 4]. Furthermore, LLZO solid electrolytes are a stable and non-flammable alternative to conventional liquid electrolytes[2, 5], significantly improving battery safety. The main objectives of this study are to investigate the combined effects of silicon nanowires (SiNWs) electrodes and LLZO solid electrolyte and to determine the optimal amount of liquid electrolytes to improve cell safety. In this work, an LLZO thin solid electrolyte tape has been manufactured by casting technique. Precise volumes of liquid electrolyte have been added to the LLZO tape to improve surface contact and ion conductivity. Furthermore, the study will provide a view of the relationship between the quantity of liquid electrolytes introduced and their impact on cell stability and safety. Preliminary results show the preparation of a mechanically stable LLZO tape with high ionic conductivity (>10-4 S cm-1) through an easy and up-scalable procedure. Improvements have been reported in the electrochemical performance of SiNW-LLZO solid-state batteries compared to the relative Li-ion liquid cell. In conclusion, here we developed a new thin solid electrolyte tape with high ionic conductivity, used in solid-state LIBs with silicon nanowires as anode material. Moreover, we standardized a procedure to optimize the use of organic liquid electrolytes as an additive, without omitting the volume or using any excess that could lead to safety issues. This optimization process can contribute to the development of solid-state batteries that are not only high-performance but also safe and reliable for various applications, including electric vehicles and portable electronics. References Wu, F., J. Maier, and Y. Yu, Guidelines and trends for next-generation rechargeable lithium and lithium-ion batteries. Chem Soc Rev, 2020. 49(5): p. 1569-1614. Wang, C., et al., Garnet-Type Solid-State Electrolytes: Materials, Interfaces, and Batteries. Chem Rev, 2020. 120(10): p. 4257-4300. Chan, C.K., et al., High-performance lithium battery anodes using silicon nanowires. Nat Nanotechnol, 2008. 3(1): p. 31-5. Kennedy, T., M. Brandon, and K.M. Ryan, Advances in the Application of Silicon and Germanium Nanowires for High-Performance Lithium-Ion Batteries. Adv Mater, 2016. 28(27): p. 5696-704. Xu, L., et al., Garnet Solid Electrolyte for Advanced All ‐Solid ‐State Li Batteries. Advanced Energy Materials, 2020. 11(2).

Silicon is one of the highest-capacity anode active materials and, therefore, its use in solid-state batteries (SSBs) is expected to provide both high energy density and safety. Although the creation of solid-state Si electrodes via a scalable method is important from the perspective of battery production, its effect on electrochemical performance has yet to be clarified for the electrodes containing Li+-doped organic ionic plastic crystals (OIPCs) as solid electrolytes. Here, we made various Si−OIPC composite electrodes using four electrode-preparation methods and measured their electrochemical performances to decipher the method−structure−property relationship for high-performing SSBs. The Si−OIPC composite electrode containing 50 mol% LiFSI in N-ethyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide ([C2mpyr][FSI]) showed the highest initial Coulombic efficiency and cyclability. Three out of four methods provided the Si−Li0.50[C2mpyr]0.50[FSI] electrodes with relatively large capacity retentions that were close to that of the Si electrode in a liquid electrolyte. Elemental analysis for the electrode cross-sections resolved the homogeneous distribution of Li0.50[C2mpyr]0.50[FSI], except for the one made by the drop-casting method, suggesting that three methods can establish the long-range ion-conduction network in the electrode to improve the electrochemical stability of Si during cycling. This study clarifies the importance of the OIPC-incorporation method in fabricating highly functional OIPC-based electrodes for SSBs.

Solid-state lithium batteries (SSBs) have the potential to achieve high energy and power densities due to the use of solid electrolytes (SEs) that are compatible with lithium metal or silicon-based anodes. However, fabrication of SEs with good ionic conductivity, mechanical strength, electrochemical stability, and interfacial contact with solid electrodes have been challenging. One promising approach is to combine ceramic lithium conductors that is expected to show a relatively high room-temperature Li-ion conductivity and a soft polymer matrix that facilitates mechanical integrity at the electrode-electrolyte interface during charge-discharge cycling. In this study, we report a scalable synthesis of Al0.25Li6.25La3Zr2O12 (LLZO) nanofibers and polyethylene oxide (PEO) composite SEs using roll-to-roll manufacturing. Our LLZO fibers showed 0.3 mS/cm conductivity at room temperature and the LLZO-PEO composites showed three times higher critical current density than a single PEO polymer electrolyte. Microstructural and electrochemical properties of the composite electrolytes will be discussed.

Electrode binders are critical components for the successful engineering and large-scale manufacturing of modern lithium-ion rechargeable batteries. They provide cohesion among the micro- and nano-sized electrode particles and ensure adhesion between these particles and the current collectors. Binders also modulate the significant volume changes that particles undergo during charging and discharging. This seminar will delve into the fundamentals of electrode binders and recent advancements in multifunctional conductive polymers. We will specifically focus on their application as materials for dual ion and electron transport in silicon (Si) and tin (Sn) alloy electrodes for advanced lithium-ion, sodium-ion, and solid-state batteries, as well as for battery recycling. As an example, Si's high theoretical specific capacity (4200 mAh/g) presents a promising alternative to traditional graphite anodes (370 mAh/g). However, the substantial volume changes associated with lithium insertion and extraction pose significant challenges to electrode integrity and performance. This presentation will explore how conductive polymer binders can address these challenges by providing improved adhesion, connectivity, ion compensation, enhanced conductivity, and surface/interface modification. Leveraging our recent materials advancements, I will discuss the molecular design principles and synthetic strategies employed to tailor binder structures and functionalities. Furthermore, we will examine the interaction of these binders with various alloy materials and the resulting electrochemical performance of the composite electrodes. This seminar aims to provide insights into the crucial role of multifunctional electrode binders in enabling the next generation of high-performance energy storage systems.

Electrode binder is a critical component for the successful engineering of modern lithium-ion rechargeable batteries. Electrode binder provides cohesion among the micron and nano size electrode particles, adhesion between particles and current collectors, and modulates particles volume changes during charge and discharge. The alloy material-based anode such as Si and Sn, is an attractive candidate for lithium-ion batteries and solid-state battery because it delivers much greater theoretical (e.g. Si at 4200 mAh/g) specific capacity than that of a traditional graphite anode material (∼370 mAh/g). However, the widespread application of silicon materials has remained a significant challenge because of the large volume change during lithium insertion and extraction processes, disrupting the electrode surface, electrode mechanical formation and cell integrity. The instabilities of the alloy materials lead to loss of the electrical contact in the electrode and increased parasitic reactions with electrolyte, causing the battery failure and significantly shorten the battery life. To address those challenges, multifunctional conductive polymers have been re-designed. In the conventional design of conductive polymers, organic functionalities are introduced via bottom-up synthetic approaches to enhance specific properties by modification of the individual polymers. Unfortunately, the addition of functional groups leads to conflicting effects, limiting their scaled synthesis and broad applications. Here we show a conductive polymer coating with simple primary building blocks that can be thermally processed to develop hierarchically ordered structures (HOS) with well-defined ordered morphologies. Our approach to constructing permanent HOS in conductive polymers leads to substantial enhancement of charge transport properties and mechanical robustness, which are critical for alloy material-based electrode and overall cell integrity.

Green processing of lithium rechargeable battery electrode without NMP solvent and PFAs materials is highly desired for battery manufacturing. The properties of electrode binder play a critical function to achieve green manufacturing process. Electrode binder has been recognized as an important component for the successful engineering of modern lithium-ion rechargeable batteries. Electrode binder provides cohesion among the micron and nano-size electrode particles, adhesion between particles and current collectors, and modulates particles volume changes during charge and discharge. The alloy material-based anode such as Si and Sn, is an attractive candidate for lithium-ion batteries and solid-state battery because it delivers much greater theoretical (e.g. Si at 4200 mAh/g) specific capacity than that of a traditional graphite anode material (∼370 mAh/g). However, the widespread application of silicon materials has remained a significant challenge because of the large volume change during lithium insertion and extraction processes, disrupting the electrode surface, electrode mechanical formation and cell integrity. The instabilities of the alloy materials lead to loss of the electrical contact in the electrode and increased parasitic reactions with electrolyte, causing the battery failure and significantly shorten the battery life. To address those challenges, multifunctional conductive polymers have been re-designed. In the design of conductive polymers, organic functionalities that has strong interaction with environmentally benign solvents are introduced via bottom-up synthetic approaches to achieve green processability. Here, we are reporting a functional electrode binder that enables green processing and has the full functions of conductivity, adhesion and surface protection for the Si materials.

No abstract available

All-solid-state lithium-ion batteries (ASSLBs) employing silicon (Si) anode and sulfide electrolyte attract much attention, since they can achieve both high energy density and safety. For large-scale application, sheet-type Si anode matching sulfide based ASSLBs is preferred. Here, a LiAlO2 layer coated Si (Si@LiAlO2 ) is reported for sheet-type electrode. This electrode employs conventional slurry coating methods without adding any sulfide electrolyte. The effect of LiAlO2 coating on the electrochemical performance and morphology evolution of Si electrode is investigated. Since the high mechanical strength and ionic conductivity of LiAlO2 layer can sufficiently relieve the huge expansion of Si and promote the Li+ diffusion, the electrochemical performance is significantly enhanced. The Si@LiAlO2 electrodes deliver high coulombic efficiency exceeding 80% and hold considerable specific capacity of 1205 mAh g-1 (150 cycles, 0.33 C). The Si@LiAlO2 | LiNi0.83 Co0.11 Mn0.06 O2 full-cells exhibit a high reversible capacity of 147 mAh g-1 (0.28 mA cm-2 ) and a considerable capacity retention of 80.2% (62 cycles, 2.8 mA cm-2 ). This work demonstrates promising practicability and provides a new route for the scalable preparation of Si electrode sheets for ASSLBs with extended lifespan.

No abstract available

The demand for high-energy-density and safe energy storage has accelerated the development of all-solid-state batteries (ASSBs), especially those employing sulfide solid electrolytes (SSEs). Silicon (Si) is a promising anode material for ASSBs due to its exceptional theoretical capacity (3579 mAh·g⁻¹). However, its application is limited by severe chemo-mechanical challenges, such as >300% volume expansion during lithiation and subsequent interfacial instability with SSEs. To address these limitations, we propose an aluminum-silicon (Al-Si) alloy anode architecture. The Al phase not only enhances electrical conductivity and mechanical compliance but also forms the β-LiAl phase upon lithiation, offering moderate capacity (990 mAh·g⁻¹) and minimal volume change (~96%). The Al-Si wet anode, composed of 99 wt% active material, exhibits early expansion saturation ( ~SOC 30%) followed by stable volumetric behavior. Using operando stress monitoring, synchrotron X-ray nanoimaging, and digital twin simulations, we elucidate the unique electro-chemo-mechanical evolution of the Al-Si anode during cycling. To take advantage of this behavior, an electrochemical prelithiation process is introduced. The process pre-expands the anode and forms lithiated Al-Si phases before full-cell assembly, significantly reducing stress accumulation. The resulting prelithiated Al-Si (Li-Al-Si) anode shows only ~37.5% volume change in the first cycle—substantially lower than untreated Si or Al-Si. Paired with a high-loading NCM811 cathode (8.2 mg·cm⁻²), full cells deliver >100 mAh·g⁻¹ over 250 cycles. However, notable capacity fade is observed over extended cycling, revealing the limitations of planar (2D) interfacial contact between SSEs and wet-processed anodes. In response, we design a composite anode incorporating a hydride-based SE, 3LiBH₄–LiI (LBHI), as a compliant anolyte. This enables the formation of a 3D percolated interface with the active material. Compared to the conventional argyrodite-type SE, Li₆PS₅Cl (LPSCl), LBHI exhibits superior mechanical resilience and electrochemical compatibility with Al-Si, tolerating volume fluctuations and suppressing interfacial degradation. In contrast, LPSCl systems undergo plastic deformation and undesirable reactions with Si, leading to capacity loss. The optimized LBHI-integrated Al-Si composite anode is validated in ASSBs using an NCM811 cathode with a high areal capacity of 6 mAh·cm⁻². This configuration delivers a remarkable capacity retention of 81.6% after 300 cycles and approximately 70% after 500 cycles at a high rate of 1C/-1C. This represents an outstanding performance compared to previous studies using Si-based anodes paired with NCM cathodes in ASSBs. This work identifies elastic recovery of LBHI as the dominant factor enabling long-term cycling stability, by maintaining robust interfacial contact and suppressing mechanical disconnection. These findings demonstrate the potential of Si-based ductile active material-the elastic resilient anolyte strategies to resolve interfacial and mechanical degradation modes common to high-capacity Si-based anodes in solid-state systems. This work represents the first demonstration of a practical Al-Si alloy anode for high-loading sulfide-based ASSBs, addressing key failure mechanisms. Beyond offering an effective route toward stable long-term cycling of Si-based anodes, the framework developed here provides a broader insight into how tailored anode–electrolyte compatibility and mechanical compliance can unlock the performance limits of next-generation ASSBs.

The construction of a continuous ionic/electronic pathway is critical for Si‐based sulfide all‐solid‐state batteries (ASSBs) with the advantages of high‐energy density and high‐cycle stability. However, a significant impediment arises from the parasitic reaction occurring between the ionic sulfide solid‐state electrolyte and electronic carbon additive, posing a formidable challenge. Additionally, the fabrication of electrodes necessitates stringent operational conditions, further limiting practical applicability. Herein, an ionic–electronic dual conductive binder for the fabrication of robust silicon anode under ambient air conditions in the absence of high‐cost and air‐sensitive sulfide solid‐state electrolyte for ASSBs is reported. This binder incorporates in situ reduced silver nanoparticles into a high‐strength polymer rich in ether bonds, establishing a conductive pathway for lithium ions and electrons. With the binder‐composited Si anode, the half‐cell exhibits a remarkable capacity of 1906.9 mAh g−1 and stable cycling for 500 cycles at a current density of 2 C (4.4 mA cm−2) under a low stack pressure of 5 MPa. The full cell using Ni0.9Co0.075Mn0.025O2 (NCM90) exhibits a remark cycling stability within 2000 cycles at 5 C (8 mA cm−2). This work presents an inspired design of functional binders for large‐scale manufacture and mild operation in a low‐cost way for Si anodes in ASSBs.

A critical challenge facing silicon-based anodes in all-solid-state lithium-ion batteries (ASSLBs) is the need for high stack pressure to maintain good interfacial contact (often up to tens of megapascals). However, bulky pressurization systems degrade the energy density and increase the cost of ASSLBs. Herein, a modified silicon anode is proposed to achieve stable operation of sulfide ASSLBs without extra external pressure. LiBO2 and LiF phases are in situ constructed on the surface of nano silicon by a simple solid phase reaction. Chemical analysis, theoretical calculations, and simulations all demonstrate that the uniformly distributed LiBO2 improves lithium storage kinetics, while LiF acts as a mechanical buffer phase. Its high Young's modulus not only restrains the large volume expansion of silicon but also preserves the structural integrity of the electrode-electrolyte interface by dispersing lithiation stress. This ingenious interface architecture eliminates bulky external pressurization and enables high energy density ASSLBs.

Silicon (Si) is a competitive anode material owing to its high theoretical capacity and low electrochemical potential. Recently, the prospect of Si anodes in solid-state batteries (SSBs) has been proposed due to less solid electrolyte interphase (SEI) formation and particle pulverization. However, major challenges arise for Si anodes in SSBs at elevated temperatures. In this work, the failure mechanisms of Si-Li6PS5Cl (LPSC) composite anodes above 80 °C are thoroughly investigated from the perspectives of interface stability and (electro)chemo-mechanical effect. The chemistry and growth kinetics of LixSi|LPSC interphase are demonstrated by combining electrochemical, chemical and computational characterizations. Si and/or Si–P compound formed at LixSi|LPSC interface prove to be detrimental to interface stability at high temperatures. On the other hand, excessive volume expansion and local stress caused by Si lithiation at high temperatures damage the mechanical structure of Si-LPSC composite anodes. This work elucidates the behavior and failure mechanisms of Si-based anodes in SSBs at high temperatures and provides insights into upgrading Si-based anodes for application in SSBs.

Silicon is widely recognized as a promising anode material for all-solid-state batteries (ASSBs) due to exceptional specific capacity, abundant availability, and environmental sustainability. However, the considerable volume expansion and particle fragmentation of Si during cycling lead to significant performance degradation, limiting its practical application. Herein, the development of a pre-lithiated Si-based composite anode (c-Li1Si) is presented, designed to address the key challenges faced by Si-based anodes, namely severe volume changes and low electrochemical stability. The c-Li1Si anodes are prepared by incorporating Li₁Si powders with Li6PS5Cl (LPSCl) sulfide solid electrolyte (SSE), forming a dense structure that enhances conductivity and mitigates structural degradation. The ASSBs with c-Li1Si-60 anode exhibit outstanding electrochemical performance, including excellent rate capability and capacity retention of 84.4% after 1000 cycles at 1 C and exceptional performance even at low anode-to-cathode capacity ratios (N/P ratio) of 1.68. EIS and pressure measurements reveal improved reaction kinetics and reduced volume expansion. X-ray micro-CT and SEM further confirmed the introduction of LPSCl effectively alleviated volume changes and maintained electrode structural integrity, contributing to enhanced electrochemical performance. These results underscore the potential of the c-Li1Si anode to overcome the intrinsic limitations of Si-based anodes, offering a promising pathway toward high-energy-density ASSBs.

Silicon (Si) has been considered as one of the most promising anode materials because of its high theoretical capacity of 4200 mAh g− 1. However, the huge volume change and side reactions upon cycling cause poor cycle performance and limit a use of Si for the commercialization. Recently all solid-state batteries (ASSBs) open up new possibilities for an introduction of high capacity electrode materials due to their ability to operate under compression, which can mitigate electrode volume expansion. Herein, we study an effect of multifunctional polymeric binders on silicon anode for all solid-state batteries enabled by a sulfide Li6PS5Cl electrolyte. The Si electrode manufactured by a single rigid polymer shows stable electrochemical properties because of applied external pressure and potential hydrogen bonds between carboxyl groups and Si particles, resulting in a mitigation of a volume change. In addition, an introduction of multifunctional network binders to the Si-based electrode leads to a high discharge capacity of 3000 mAh g− 1 and stable cycle performances at room temperature.

Silicon (Si) has been considered as one of the most promising anode materials because of its high theoretical capacity of 4200 mAh g−1. However, the huge volume change and side reactions upon cycling cause poor cycle performance and limit a use of Si for the commercialization. Recently all solid-state batteries open up new possibilities for an introduction of high capacity electrode materials due to their ability to operate under compression, which can mitigate electrode volume expansion. Herein, we study an effect of multifunctional polymeric binders on silicon anode for all solid-state batteries enabled by a sulfide Li6PS5Cl electrolyte. The Si electrode manufactured by a single rigid polymer shows stable electrochemical properties because of applied external pressure and potential hydrogen bonds between carboxyl groups and Si particles, resulting in a mitigation of a volume change. In addition, an introduction of multifunctional network binders to the Si-based electrode leads to a high discharge capacity of 3000 mAh g−1 and stable cycle performances at room temperature.

Silicon is the preferred choice for lithium-ion battery anodes due to its high theoretical capacity and low lithiation potential. However, achieving high areal capacity with silicon anodes in solid-state batteries (SSBs) is challenging because of poor electronic and ionic conductivity, as well as chemo-mechanical instability at the silicon|solid electrolyte (Si|SE) interfaces. Here, we propose fabricating and testing composite anodes made of nanosized Si powder embedded in partially fluorinated graphene (Si-FG) and Li6PS5Cl (LPSCl) sulfide SE. X-ray photoelectron spectroscopy revealed that the in situ formation of LiF-rich SEI can protect against SE decomposition at the interface in the Si-FG-LPSCl composite anode. FIB-SEM and EIS analyses also indicate a stable structure and low interfacial resistance after one cycle for a composite anode containing FG. The incorporation of partially FG enhances both electronic (through heterojunction formation with Si) and ionic conductivities, buffers significant volume changes, and ensures chemo-mechanical stability in the composite anode. The Si-FG-LPSCl composite anode in SSBs delivered high discharge/charge capacities of 3499/2994 mAh g–1 at a C-rate of C/20 and an ICE of 85.6% in a half cell. This work provides valuable insights for advancing high-capacity Si composite anodes to meet future energy needs.

Silicon (Si) anode is a promising anode material for all-solid-state lithium batteries with ultra-high theoretical specific capacity and low lithium dendrite risk. However, the inevitable vast volume expansion of Si anode during charge/discharge is recognized as a major limitation preventing its commercial application. Herein, an N, S self-doped amorphous carbon layer coated on porous micron-sized Si (p-mSi@C) is designed to construct an electron/ion conducting network while ensuring structural and interfacial stability. Uneven distribution of von mises stresses during p-mSi lithiation leads to irregular volume expansion and even fragmentation. Meanwhile, the growth of by-products at the interface between p-mSi and electrolyte contact leads to a rapid capacity decay. Compared to p-mSi anode, p-mSi@C reduces the risk of fragmentation thanks to the stress-absorbing effect of amorphous carbon, delivering excellent electrochemical performance (2679.65 mAh g-1 at 0.2 mA cm-2 with initial coulombic efficiency of 84%). More importantly, the chemical failure mechanisms of p-mSi and p-mSi@C composite anodes are revealed through structural characterization, chemical analysis, and simulation, which provides the necessary theoretical guidance for practicalization.

All-solid-state lithium batteries (ASSLBs) with sulfide-based solid electrolytes offer improved safety compared to conventional lithium-ion batteries. Silicon-based anode materials enable an increase in the energy density of ASSLBs. However, the substantial volume change during cycling induces interfacial degradation, leading to significant capacity loss. In this study, the composite silicon-graphite (Si-C) anodes were fabricated via an in situ cross-linking reaction between polybutadiene (PBD) and n-butyl acrylate monomer. The resulting three-dimensional cross-linked polymer binder significantly improved interfacial adhesion and cycling stability of the composite anode. Furthermore, the influence of PBD isomeric structure on cross-linking selectivity was investigated to optimize the electrochemical performance and mechanical properties of the composite anode. As a result, the composite anode employing solid electrolyte (Li6PS5Cl0.5Br0.5) and highly cross-linked binder based on cis-PBD delivered a high initial discharge capacity of 1056.3 mAh g-1 (areal capacity: 3.8 mAh cm-2) and exhibited superior capacity retention at 0.3 C and 30 °C.

The anode plays a critical role relating to the energy density in all‐solid‐state lithium batteries (ASLBs). Silicon (Si) and lithium (Li) metal are two of the most attractive anodes because of their ultrahigh theoretical capacities. However, most investigations focus on Li metal, leaving the great potential of Si underrated. This work investigates the stability, processability, and cost of Si anodes in ASLBs and compares them with Li metal. Moreover, single‐crystal LiNi0.8Mn0.1Co0.1O2 is stabilized with lithium silicate (Li2SiOx) through a scalable sol–gel method. ASLBs with a cell‐level energy density of 285 Wh kg−1 are obtained by sandwiching the Si anode, the thin sulfide solid‐state electrolyte membrane, and the interface stabilized LiNi0.8Mn0.1Co0.1O2. The full cell delivers a high capacity of 145 mAh g−1 at C/3 and maintains stability for 1000 cycles. This work inspires commercialization of ASLBs on a large scale with exciting manufacturing lines for large‐scale, safe, and economical energy storage.

All-Solid-State Batteries (ASSBs) have emerged as a highly promising post-lithium-ion battery technology, offering notable advancements in safety and energy density. However, an intrinsic disadvantage arises from the usually higher density of inorganic solid electrolyte materials compared to their liquid counterparts, constituting a drawback that hinders gains in overall energy density. To overcome this limitation, the imperative is to transition towards higher specific capacity materials, thereby unlocking the full potential for enhancing the energy density of ASSBs. On the cathode front, research predominantly centers around layered transition metal oxide materials like NMC, already widely employed in traditional lithium-ion batteries (LIBs). Simultaneously, on the anode side, there is a progressive shift from conventional graphite to silicon, which boasts an almost tenfold higher specific capacity, offering a compelling avenue to elevate the overall performance of ASSBs. Contemplating the potential upscaling of ASSBs, the most mature technology currently revolves around sulfide-based materials. Despite the considerable progress in research, only a limited number of studies have explored the cycling stability of ASSB full-cells at this stage.[1,2,3,4,5] This critical evaluation is essential, as it serves as the foundational evidence for the viability of a potentially commercial application. In this work, we studied the cycling stability of full-cell ASSBs, composed of an Li6PS5Cl solid electrolyte separator sheet, and NMC622-Li6PS5Cl composite cathode, and a microcrystalline-silicon-rich (>94 wt. %) anode. Emphasizing the foundational role of uniaxial pressure during both assembly and operation, we aimed to elucidate its crucial impact on cell performance. It became evident that, beyond just the magnitude, the in-plane distribution of pressure plays a pivotal role in achieving and sustaining effective contacts across multiple solid-solid interfaces. Significantly elevated pressures, reaching up to 500 MPa, proved necessary for the complete densification of the composite cathode and for establishing optimal contact within the 2D area between the anode and the separator. Furthermore, maintaining a homogeneous operational pressure of at least 20 MPa emerged as a key factor in ensuring a stable cycle-life at a C/3 current rate for over 400 cycles until 20% capacity loss, as exemplary showed in Figure 1. This promising cycle life was observed for cells with an areal capacity of 2.9 mAh/cm², highlighting the critical interplay between pressure and overall cycling performance in full-cell ASSBs. The second part of our investigation focused on determining the primary factors that contribute to the capacity fading observed in the here-examined ASSB full-cells. We endeavored to categorize these factors into two main groups, related to either increasing kinetic overpotentials or to active material losses. Within the first group, kinetic limitations could originate from either the anode or the cathode side, potentially due to ineffective/unstable solid electrolyte interphases at the anode (SEI) and/or at the cathode (CEI). These interphases are known to conduct ions less effectively than the Li6PS5Cl itself. Additionally, contact resistance arising from void formation and diffusion resistance due to a more tortuous lithium diffusion pathway in the active material, possibly caused by cracking, were identified as potential contributors to kinetic overpotential. In the material losses group, scenarios were explored where the active material could undergo chemical inactivity, such as the NMC crystalline transformation from a layered to a rock-salt structure at high potential. Mechanical inactivity might also occur when a portion of the active material becomes ionically and/or electrically disconnected from the rest of the cell stack. Finally, a critical focus was placed on lithium inventory loss, a phenomenon where lithium undergoes electrochemical consumption in parasitic reactions like the reduction of Li6PS5Cl to LiCl, Li3P, and Li2S during SEI growth. Upon thorough examination, it became evident that a homogeneously applied compressive force is able to render the kinetic overpotential negligible during cycling by maintaining the contact between the several components of the cells. Therefore, the lithium inventory loss emerged as the predominant factor contributing to the observed capacity fading in the studied ASSB full-cells. References: Cangaz, Hippauf, Reuter, Doerfler, Abendroth, Althues, Kaskel; Adv. Energy Mater., 10, 2001320 (2020) Tan, Chen, Yang, Bao, Sreenarayanan, Doux, Li, Lu, Ham, Sayahpour, Scharf, Wu, Deysher, Han, Hah, Jeong, Lee, Chen, Meng; Science 373, 1494–1499 (2021) Kim, Jung, Kang, Park, Lee, Jin, Shin, Lee, Lee; Adv. Energy Mater., 12, 2103108 (2022) Zhou, Zuo, Li, Zhang, Janek, Nazar; ACS Energy Lett., 8, 3102−3111 (2023) Fan, Ding, Li, Chang, Hu, Xu, Zhang, Dou, Zhang; eTransportation, 18, 100277 (2023) Figure 1

Silicon has attracted extensive research attention in lithium-ion battery (LIB) field due to its high theoretical specific capacity (~3600 mAh/g) and cost-effectiveness. In recent years, silicon has emerged as a viable candidate for anode material for solid-state battery (SSB) technology. Similar to its application in LIBs, silicon utilizing in SSBs encounters challenges, such as significant volume variation (~300%) during cycling and poor cycling performance. In addition, the utilization of silicon in SSB faces another critical bottleneck in ionic conductivity due to the absence of liquid electrolyte. To address these challenges, various pioneering studies have explored potential solutions, including controlling the thickness of silicon anode to be below 150 nm,(1) fabricating electrodes with a combination of silicon and solid-state electrolyte (e.g, Garnet-type electrolyte(2) and sulfide electrolyte(3)), subjecting SSBs to a high pressure (10-50 MPa)(4). Here, we introduced an alternative approach to mitigate these challenges by designing anodes through incorporating silicon with mixed electronic-ionic conductive (MEIC) hierarchically ordered structure (HOS) polymer binders. These multifunctional HOS polymer binders effectively preserve the structural integrity of electrode materials, even when silicon materials experiences significant volume expansion and shrinkage during the charging-discharging process. Owing to establishments of covalent bonds between silicon surface and the polymer binders, the resulting SSBs exhibited excellent resilience and only required hand-tightening force (<1 ton) for operation. These polymer binders effectively maintained continuous electronic and ionic pathways within silicon-based anodes without the need of additional additives, such as carbon material and solid-state electrolytes. Utilizing these versatile polymer binders, the resultant SSBs featured an outstanding cycling performance over 100 cycles in full cells, with an average Coulombic efficiency exceeding 97%. Reference A. Song, W. Zhang, H. Guo, L. Dong, T. Jin, C. Shen and K. Xie, Advanced Energy Materials, 13, 2301464 (2023). W. Ping, C. Yang, Y. Bao, C. Wang, H. Xie, E. Hitz, J. Cheng, T. Li and L. Hu, Energy Storage Materials, 21, 246 (2019). M. Rana, Y. Rudel, P. Heuer, E. Schlautmann, C. Rosenbach, M. Y. Ali, H. Wiggers, A. Bielefeld and W. G. Zeier, ACS Energy Letters, 8, 3196 (2023). D. H. Tan, Y.-T. Chen, H. Yang, W. Bao, B. Sreenarayanan, J.-M. Doux, W. Li, B. Lu, S.-Y. Ham and B. Sayahpour, Science, 373, 1494 (2021).

Sulfide all-solid-state batteries (ASSBs) have become an essential development direction for next-generation energy storage and automotive applications due to their potentially high energy density and safety. Compared with lithium (Li) metal anode, silicon (Si) anode not only mitigates the risk of dendrite growth and suppresses interfacial reactions in sulfide ASSBs, but also possesses significant advantages in cost and processability. The micro-Si anode without any electrolyte or conductive carbon introduced by Meng’s group has attracted widespread attention. Building on this progress, numerous studies have focused on the innovative structural design of Si anode in sulfide ASSBs. However, these works primarily aim to achieve high loading and long life, with a lack of attention on the rate performance of Si anode. Silicon is well known to be a semiconductor material with low electronic conductivity and lithium diffusivity, especially compared to graphite, thus potentially contributing to the limited rate performance in sulfide ASSBs. Our study systematically evaluates the rate performance of the micro-Si anode in sulfide ASSBs, and indicates the constrained delithiation capability and significant lithiation overpotential associated with kinetic limitations. A combination of kinetic parameter tests and electrochemical model simulations later confirms the existence of “lithiation activation” characteristic in the micro-Si anode, and further clarifies the relationship between the "lithiation activation" characteristic and the limited rate performance. Based on the mechanism analysis and model simulations, a precise pre-lithiation amount is designed to activate the micro-Si anode. And it is verified by the simplified pre-lithiation wet process, finally breaking through the rate performance limits. The activated micro-Si anode exhibits 82% capacity retention at 2C, even with a thick SE layer of 580 μm. As Si anode is gradually becoming a hotspot in the field of ASSBs, it is particularly important to comprehensively improve its overall performance. The insights of this work help to understand the rate performance limits of micro-Si anode, and promote researchers to reconsider the design strategy of Si anode for sulfide ASSBs. In addition, our study proposes a rapid and accurate model-based method to design the pre-lithiation amount according to various operating conditions, such as temperature, charge/discharge rate, and areal capacity, which could finally break through the rate performance limits of micro-Si ASSBs.

Lithium sulfide (Li2S) is a promising electrode material with high specific capacity and can be paired with commercial anode materials such as graphite. However, bulk Li2S requires a high activation energy during the initial charge due to its inert electrochemical activity, resulting in high charge overpotential. Here, lithium phenyl selenide (PhSeLi) is proposed as a mediator that can effectively activate Li2S by altering the oxidation pathway in the initial charge process. It enables Li2S to release normal capacity over the general voltage range (1.5–3 V). The composite cathode with the Li2S:PhSeLi molar ratio of 4:1 exhibits a high reversible capacity of 615.9 mAh g−1 at 0.2 A g−1 after 400 cycles in all‐solid‐state batteries with Li7P3S11 sulfide electrolyte and In–Li anode (the corresponding capacity based on Li2S is 1016.6 mAh g−1). In a full cell with a partially pre‐lithiated silicon anode, it can still provide an average discharge capacity of 524 mAh g−1 at 0.1 A g−1 (the capacity based on Li2S is 844.2 mAh g−1). This work will contribute to the further development of Li2S‐based all‐solid‐state Li–S batteries.

No abstract available

The commercialization of all-solid-state Li batteries (ASSLBs) demands solid electrolytes with strong cost-competitiveness, low density (for enabling satisfactory energy densities), and decent anode compatibility (the need for cathode compatibility can be circumvented by the cathode coating techniques that are widely applied in sulfide-based ASSLBs). However, none of the reported oxide, sulfide, or chloride solid electrolytes meets these requirements simultaneously. Here, we design a Li7P3S7.5O3.5 (LPSO) solid electrolyte, which shows a combination of all the aforementioned characteristics. The synthesis of this material does not need the expensive Li2S, so the raw materials cost is only $14.42/kg, which, unlike most solid electrolytes, lies below the $50/kg threshold for commercialization. The density of LPSO is 1.70 g cm-3, considerably lower than those of the oxide (typically above 5 g cm-3) and chloride (around 2.5 g cm-3) solid electrolytes. Besides, LPSO also shows excellent anode compatibility. The Li | LPSO | Li cell cycles stably with a potential of ~50 mV under 0.1 mA cm-2 for over 4200 h at 25 °C, and the all-solid-state pouch cell with the Si anode shows a capacity retention of 89.29% after 200 cycles under 88.6 mA g-1 at 60 °C.

No abstract available

Silicon is widely recognized as an ideal anode material due to its high specific capacity, low lithiation potential, high abundance, and environmental friendliness. Nevertheless, the immense volume expansion during the lithiation leads to pulverization of silicon particles, which causes electrode failure with a rapid capacity decay. Herein, the polymerized 1, 3‐dioxolane (PDOL) electrolyte is used to stabilize the micro‐silicon Si anode via in situ polymerization route. The conformality of the quasi‐solid electrolyte suppresses the pulverization of the Si microparticles (SiMPs) effectively and thus alleviates the capacity decay. The SiMPs/PDOL anode shows an excellent initial CE of 97.5% and maintains a reversible capacity of 1837.1 mAh g−1 at 500 mA g−1 after 100 cycles. The Si/PDOL/LiFePO4 full cells also exhibit a stable cycling performance with a capacity retention of 76.3% after 300 cycles. This work provides a new and easy path for the practical application of silicon anode at low cost.

The commercialization of silicon anode for lithium-ion batteries has been hindered by severe structure fracture and continuous interfacial reaction against liquid electrolytes, which can be mitigated by solid-state electrolytes. However, rigid ceramic electrolyte suffers from large electrolyte/electrode interfacial resistance, and polymer electrolyte undergoes poor ionic conductivity, both of which are worsened by volume expansion of silicon. Herein, by dispersing Li1.3 Al0.3 Ti1.7 (PO4 )3 (LATP) into poly(vinylidene fluoride)-hexafluoropropylene (PVDF-HFP) and poly(ethylene oxide) (PEO) matrix, the PVDF-HFP/PEO/LATP (PHP-L) solid-state electrolyte with high ionic conductivity (1.40 × 10-3  S cm-1 ), high tensile strength and flexibility is designed, achieving brilliant compatibility with silicon nanosheets. The chemical interactions between PVDF-HFP and PEO, LATP increase amorphous degree of polymer, accelerating Li+ transfer. Good flexibility of the PHP-L contributes to adaptive structure variation of electrolyte with silicon expansion/shrinkage, ensuring swift interfacial ions transfer. Moreover, the solid membrane with high tensile limits electrode structural degradation and eliminates continuous interfacial growth to form stable 2D solid electrolyte interface (SEI) film, achieving superior cyclic performance to liquid electrolytes. The Si//PHP-L15//LiFePO4 solid-state full-cell exhibits stable lithium storage with 81% capacity retention after 100 cycles. This work demonstrates the effectiveness of composite solid electrolyte in addressing fundamental interfacial and performance challenges of silicon anodes.

Silicon-based anodes show great potential in solid-state batteries due to their high theoretical density, low cost, and resistance to lithium dendrite formation. However, the severe interfacial degradation caused by the large volume expansion of silicon remains a critical challenge. To address these interfacial problems, this study innovatively employs mechanical blending to rapidly achieve solid-phase coating, encapsulating nanosilicon particles on the surface of sulfide electrolytes. The reliability of this coating method was verified through SEM and TEM characterization. The coated silicon anode demonstrated stable operation under ultralow stack pressure and showed significantly enhanced rate capability and long-term cycling performance. These improvements were attributed to the enlarged interfacial contact area, the formation of a more robust electrode structure, and the creation of fast ion/electron transport pathways. The proposed mechanical blending strategy significantly improves the efficiency of solid-state coating and facilitates the practical application of silicon-based anodes in ASSBs.

Silicon offers great promise as a potential anode active material and the optimum alternative to lithium metal in all‐solid‐state lithium‐ion batteries. However, its practical application is limited by severe volume expansion (≈300%) during lithiation, leading to cracking upon delithiation. In this study, the microstructural evolution of microcrystalline silicon electrodes in a solid‐electrolyte‐free environment is investigated using cryogenic scanning transmission electron microscopy (STEM) after electrochemical cycling. A controlled workflow prevents ambient exposure, and cryo‐TEM ensures structural integrity. After the first lithiation, the electrode shows a heterogeneous mix of crystalline Li15Si4, various amorphous LixSi phases, and residual crystalline silicon. After the first delithiation, the silicon becomes largely amorphous, showing a heterogeneous texture with pronounced thread‐like features and only traces of crystallinity. By the tenth delithiation, the bulk microstructure is far more uniform, with thread‐like features largely eliminated and persisting only in small regions near grain boundaries. These results indicate that, although silicon begins in a crystalline state, a more homogeneous bulk silicon amorphous microstructure develops only after several cycles. These findings highlight that stabilizing the microstructure and minimizing cracking during cycling requires not only optimization of electrode architecture but also careful selection of the silicon phase.

Silicon (Si) anodes have attracted significant attention for all-solid-state batteries (ASSBs) due to their high theoretical capacity (~3500 mAh g⁻¹), which is nearly ten times that of conventional graphite (~370 mAh g⁻¹). Additionally, Si is earth-abundant and environmentally benign, making it a highly attractive candidate for sustainable energy storage. However, the practical deployment of Si anodes in ASSBs remains challenging, primarily due to severe volume expansion (>300%) during lithiation/de-lithiation, which leads to particle pulverization, interfacial degradation, and substantial irreversible capacity loss, especially under low stack pressure. In this work, we investigate a Si composite anode architecture that addresses these limitations by embedding Si particles within a Li x PS y Cl z (LPSCl) solid electrolyte (SE) matrix. The SE not only functions as an ion-conducting medium but also serves as a mechanical buffer to mitigate stress-induced degradation. Electrochemical analysis reveals that the Si–LPSCl composite delivers significantly enhanced performance, particularly under low operating pressure. Under high operating pressure (75 MPa), the composite achieves an initial Coulombic efficiency (ICE) of ~95% in a full cell with an NCM811 cathode, approaching the theoretical maximum and far surpassing the 80% ICE observed for a pure Si anode. Notably, the Si composite also retains high performance under low operating pressure (~5 MPa), with an ICE of 81%, compared to only 55% for the pure Si anode. Morphological characterization confirms that the Si–LPSCl anode maintains structural integrity during cycling, exhibiting minimal cracking and allowing for 3D ionic and electronic transport throughout the electrode layer. In contrast, the pure Si anode exhibits pronounced kinetic and mechanical degradation, particularly under low operating pressure, where lithium trapping and poor reversibility dominate. These findings highlight the critical role of kinetic–mechanical coupling in the design of solid-state electrodes and demonstrate that embedding a solid electrolyte matrix within silicon anodes effectively mitigates pressure-induced limitations. This approach enables stable and reversible electrochemical cycling, even under practical low-pressure conditions, thereby advancing the viability of ASSB systems for real-world applications. Figure 1

Silicon is one of the promising anode materials for next-generation all-solid-state batteries (ASSBs). With a high theoretical capacity of 3590 mAh∙g−1, it is an alloy-type anode active material (AAM) that is both non-toxic and widely available in nature.1 However, its practical application is hindered by severe volume changes taking place during cycling and the formation of an unstable solid-electrolyte interphase (SEI). These issues lead to mechanical degradation, loss of contact, and poor long-term cycling stability, thus novel approaches are needed. Silicon is often used combined with argyrodite solid electrolytes which have good ionic partial conductivity (σion ≈ 10−3 S cm−1) and their softness facilitates the adaptation to volume changes taking place during cycling.2 Silicon nitrides (SiN x ) are promising AAMs that could overcome these limitations. By forming silicon clusters in a matrix phase consisting of silicon, lithium, and nitrogen, SiN x offers enhanced chemical stability, potentially mitigating the volume expansion and SEI instability.3 However, the electrochemical investigation of SiN x in ASSBs remains in its early stages, with the matrix formation in the first cycle impacting the initial Coulomb efficiency (ICE). This work investigates the electrochemical performances of SiN x in ASSBs and the parameters affecting capacity decay during cycling. The electrochemical test performed (e.g., long-term cycling and c-rate tests) revealed the enhanced performance of SiN x -based anodes. We investigate the role of SEI and its formation in contact with an argyrodite solid electrolyte. Further analytical methods (e.g., FIB-SEM and EDX) are performed to examine the impact of the nitrogen incorporation. References 1 Huo, H.; Janek, J. Silicon as Emerging Anode in Solid-State Batteries. ACS Energy Lett. 2022, 7 (11), 4005–4016. DOI:10.1021/acsenergylett.2c01950. 2 Zheng, F.; Kotobuki, M.; Song, S.; Lai, M. O.; Lu, L. Review on Solid Electrolytes for All-Solid-State Lithium-Ion Batteries. Journal of Power Sources 2018, 389, 198–213. DOI:10.1016/j.jpowsour.2018.04.022. 3 Kilian, S. O.; Wankmiller, B.; Sybrecht, A. M.; Twellmann, J.; Hansen, M. R.; Wiggers, H. Active Buffer Matrix in Nanoparticle-Based Silicon-Rich Silicon Nitride Anodes Enables High Stability and Fast Charging of Lithium-Ion Batteries. Advanced Materials Interfaces 2022, 9 (26), 2201389. DOI:10.1002/admi.202201389.

The demand for next generation secondary batteries with high energy density and safety has increased significantly with the rapid adoption of electric vehicles and energy storage systems. Among the various candidates, all-solid-state lithium batteries (ASSLBs) have attracted significant interest due to their potential to replace flammable organic electrolytes with solid-state electrolytes, thereby enhancing thermal stability and safety during operation. Silicon (Si), with its high theoretical capacity of 3,579 mAh g -1 , is a strong candidate for high-capacity anodes in ASSLBs. However, its practical application remains challenging due to severe volume expansion during cycling, mechanical degradation, unstable interfaces, and poor intrinsic electronic conductivity. These issues become more critical in solid-state systems, where interfacial resistance can dominate overall performance. In order to address these issues, strategies for doping silicon so as to tailor its electrical properties have been proposed. In contrast to the existing range of methods for using conductive materials, the deposition method through doping has the potential to enhance the electrical conductivity of the active material itself, thus avoiding the need for additional conductive materials and improving the energy density more effectively. In this study, phosphorus-doped silicon anodes were fabricated via thin-film deposition and integrated into ASSLBs with sulfide-based solid electrolytes. A systematic analysis was conducted to investigate the impact of doping on electronic conductivity and interfacial characteristics, through rate capability and long-term cycling tests. The findings of this study are expected to provide insight into the design of doped silicon-based anodes and contribute to the development of practical ASSLBs with high capacity and durability.

Lithium-ion batteries (LIBs) have nearly reached their physicochemical theoretical energy density limit, necessitating innovative strategies to achieve further advancements. One of the most promising approaches involves replacing graphite, which has a specific capacity of 350 mAh/g, with silicon, capable of achieving up to 3579 mAh/g when fully lithiated. However, silicon's inherent limitations present significant challenges, especially its substantial volume expansion (~300%) during lithiation, which leads to mechanical cracking and severe degradation of the active material. This results in rapid capacity fading, mainly because the progressive cracking of silicon particles leads to a loss of electronic contact and to freshly exposed surface area accompanied by solid electrolyte interphase growth.[1] The development of all-solid-state batteries (ASSBs) provides a potential pathway to overcome these challenges. For example, some ASSB architectures utilize an anode almost exclusively composed of microcrystalline silicon where the contact available for SEI growth is limited to the 2D geometrical surface area of the electrode with the solid-electrolyte separator.[2] In addition, this type of cell architecture could constitute an advantageous model system to try to answer some remaining open questions regarding the intrinsic electronic and ionic conductivities of silicon; if sufficiently high, this would enable electrode designs with minimum amounts of conductive carbon additives and without added solid electrolyte, which would minimize SEI formation. In this work, the electrochemical performance of Si-based electrodes with an areal capacity of approximately 3 mAh/cm² was systematically investigated in a half-cell ASSB configuration, employing InLi as the counter and reference electrode. Particular emphasis was placed on identifying the limitation due to electrons and lithium-ion transport in the electrode during rapid delithiation. In the first phase of the study, the impact of lamination pressure, operational pressure, electrode thickness, and conductive carbon (C65) content on the electronic resistance of pristine silicon electrodes was analyzed using impedance spectroscopy. Subsequently, the intrinsic variations in the electronic properties of crystalline silicon during lithiation and consequent amorphization were monitored.[3] The influence of conductive carbon additives was evaluated during a rate capability test at delithiation rates of up to 14C. These experiments demonstrated that, once silicon was lithiated beyond a minimal threshold, its electrical resistance became negligible. As a consequence, the addition of up to 10 wt% carbon showed no measurable influence on the rate capability of the investigated Si-based anodes. In the second phase of this study, the role of lithium solid-state diffusion through the Si-Li alloy was assessed, with a focus on the influence of temperature on this process. The delithiation rate test was interpreted within the framework of solid-state diffusion theory, as described by Fick’s laws, and the apparent diffusion coefficient was determined using Sand’s equation.[4,5] These findings were corroborated through chronoamperometry experiments initiated from different states of charge (SOCs), enabling the application of the Cottrell equation in its semi-infinite diffusion regime.[4,6] Additionally, the calculated values for the apparent solid-state diffusion coefficient were further validated through GITT-PEIS experiments, where potential relaxation and low-frequency impedance responses were fitted using established models from the literature.[7,8] Finally, the combination of these four experimental approaches, conducted over a temperature range of 5 to 80 °C, facilitated a comprehensive comparison of the diffusion coefficient values. These data were represented on an Arrhenius plot to calculate the activation energy for lithium solid-state diffusion within the Si-Li alloy at various SOCs. Our analysis indicates the dominance of lithium solid-state diffusion over electronic resistance in this Si-based electrode architecture, providing critical insights to understand and predict its rate capability at different loadings and operating temperatures, as reported in Figure 1. References: Jantke, Bernhard, Hanelt, Buhrmester, Pfeiffer, Haufe; Journal of The Electrochemical Society, 166 (16) A3881-A3885 (2019) Tan, Chen, Yang, Bao, Sreenarayanan, Doux, Li, Lu, Ham, Sayahpour, Scharf, Wu, Deysher, Han, Jeong, Lee, Chen, Meng; Science 373, 1494–1499 (2021) Pollak, Salitra, Baranchugov, Aurbach; J. Phys. Chem. C, 111, 11437-11444 (2007) Bard, Faulkner; Electrochemical methods: fundamentals and applications (1980) Krauskopf, Mogwitz, Rosenbach, Zeier, Janek; Adv. Energy Mater., 9, 1902568 (2019) Levi, Markevich, Aurbach; J. Phys. Chem. B, Vol. 109, No. 15 (2005) Ruess, Schweidler, Hemmelmann, Conforto, Bielefeld, Weber, Sann, Elm, Janek ; Journal of The Electrochemical Society, 167 100532 (2020) Lvovich ; Impedance Spectroscopy (2012) Sedlmeier, Kutsch, Schuster, Hartmann, Bublitz, Tominac, Bohn, Gasteiger; J. Electrochem. Soc. 169, 070508 (2022) Acknowledgements: This work was carried out as part of the research project "Industrialisierbarkeit Festkörperelektrolyte", funded by the Bavarian Ministry of Economic Affairs, Regional Development and Energy. The work was also supported by Wacker Chemie AG which provided the microcrystalline silicon.

Si anodes in all-solid-state batteries are expected to achieve high energy density and durability because large volume changes in Si can be mechanically suppressed by the hardness of solid electrolytes. However, the effects of volume changes on the mechanical interface between Si and solid electrolytes during charge/discharge reactions have not been investigated. In this study, operando X-ray computed tomography was used to determine the microstructure of an all-solid-state battery comprising Si active materials and a solid sulfide electrolyte, Li10GeP2S12, during charge/discharge reactions. To evaluate the volume expansion/contraction effects on the charge/discharge properties, the tortuosity of the ion conduction path and the contact area fraction between Si and the solid electrolyte during the charge/discharge reactions were quantitatively estimated. Shell-shaped voids around the Si particles were observed after Si shrinkage owing to the plastic deformation of the solid electrolyte. This characteristic resulted in poor charge/discharge efficiency and incomplete delithiation in the battery. These results will facilitate the design optimization of Si composite electrodes, which will be highly beneficial to the development of effective all-solid-state batteries.

The growing demand for vehicle electrification and sophisticated energy storage systems is driving research into lithium-ion batteries (LIBs) with high energy density. Employing inorganic materials as solid electrolytes (SEs) presents a compelling strategy to enhance the energy density and safety profile of these batteries. Nonetheless, the integration of Li metal anodes (LMAs) in all-solid-state batteries (ASSBs) still presents dendrite issues, and without specific protective layers like C-Ag, cycle stability remains a challenge. In contrast, Si anodes, which are not subject to these limitations, may offer a viable alternative. However, Si anodes in LIBs are prone to extreme volume expansion (> 300%) during charge-discharge cycles, causing fractures and loss of electrical contact. Si ASSBs can have electrodes in the form of pure Si and a composite with the SEs. Recent studies suggest that each exhibits different failure mechanisms. Specifically, in the case of pure Si, numerous vertical cracks in the electrode and delamination with SE layer have been reported. In low-operating pressure, the resistance to electronic conduction in Si anode is further exacerbated. ASSBs present significant environmental concerns related to their manufacturing and recycling processes, which frequently incorporate hazardous substances such as NMP solvent and fluorinated polymers, including PVDF and PTFE. To commercialize ASSBs, two issues must be resolved. In our study, we designed an aqueous-process-based binder for eco-friendly strategies and utilized it for low pressure operating Si ASSBs. Additionally, the binder significantly contributes improving electrical conductivity during the delithiation process with adhesion properties, as observed by an electrical conductivity measurement cell. The NCM/Si full cell exhibited high discharge capacity at 30°C and 5 MPa with high rates. Our design demonstrates enhanced performance of ASSBs under reduced pressure conditions, addressing a critical aspect of practical applicability. [1] H. S. Tan Darren et al., Science 2021, 373, 1494. [2] H. Huo et al., Nat. Mater. 2024, 23, 543.

All-solid-state batteries comprising Si anodes are promising materials for energy storage in electronic vehicles because their energy density is approximately 1.7 times higher than that of graphite anodes. However, Si undergoes severe volume changes during cycling, resulting in the loss of electronic and ionic conduction pathways and rapid capacity fading. To address this challenge, we developed composite anodes with a nanoporous Si fiber network structure in sulfide-based solid electrolytes (SEs) and conductive additives. Nanoporous Si fibers were fabricated by electrospinning, followed by magnesiothermic reduction. The total pore volume of the fibers allowed pore shrinkage to compensate for the volumetric expansion of Li_12Si_7, thereby suppressing outward expansion and preserving the Si-SE (or conductive additive) interface. The network structure of the lithiated Si fibers compensates for electronic and ionic conduction pathways even to the partially delaminated areas, leading to increased Si utilization. The anodes exhibited superior performance, achieving an initial Coulombic efficiency of 71%, a reversible capacity of 1474 mAh g^−1, and capacity retention of 85% after 40 cycles with an industrially acceptable areal capacity of 1.3 mAh cm^−2. The proposed approach can reduce the constraint pressure during charging/discharging and may have practical applications in large-area all-solid-state batteries.

All-solid-state lithium–silicon (Li–Si) batteries (ASSLSBs) promise high energy density due to the high capacity of silicon (3580 mAh/g) and the safety benefits of solid electrolytes. However, their practical deployment is hindered by several key challenges: (i) poor interfacial compatibility between silicon and sulfide-based solid electrolytes, leading to interfacial degradation and impedance buildup; (ii) severe mechanical failure stemming from silicon’s ~300% volume expansion during cycling; and (iii) sluggish ion and electron transport for the pure Si anode. Integrating hard carbon to stable Si has been proven as a useful strategy to improve the stability of the Li-Si anode to over 10,000 cycles. 1 However, the significantly improved electron conductivity increases the risk of lithium dendrite formation and internal short circuits at high rates. A better low-voltage stable hydride-based SE (3LiBH 4 -LiI, LBHI) also shows great potential to improve the stability of the composite Si anode, but the low ion-conductivity (≈0.1 mS/cm) cannot satisfy the fast charge request. 2 Herein, this work utilizes a multifunctional low-voltage stable β-Li 3 N anolyte, which serves as the ion-transport channel, structure-stable matrix, lithium dendrite suppressor, and additional lithium replenishment source for the composite Si anode. Combined with manipulating the balance of the electron and ion conductivities by inducing carbon nanotubes (CNTs), the composite Si-β-Li 3 N-CNT anode shows significant improvement in the rate and cycling stability, which paves the way for the commercialization of ASSLSBs. The work focuses on understanding the functions of the β-Li 3 N anolyte in the composite Si anode. The vacancy-rich β-Li 3 N was synthesized by a high-speed ball milling process, resulting in an ion conductivity of over 2 mS/cm. 3 The composite Si anode was synthesized by further ball-milling micro-Si, β-Li 3 N, and CNT under different parameters. During the ball-milling process, Li 3 N reacts with Si to form a Li-Si-N interlayer on the Si particle with in-situ lithiation of Si. By optimizing the composition of the Si, Li 3 N, and CNT, composite Si anodes show improved initial columbic efficiencies (ICEs) of 88.5% and 96.7% compared with the ICE of 74.5% of the pure Si anode. The composite anode demonstrated a superior high critical current density (CCD) over 25 mA/cm² without dendrite formation or a sudden increase in delithiation impedance. For the LCO-Si full cell, a superior high-rate capacity was demonstrated, with around 50% capacity retention at the rate of 19C (25.5 mA/cm 2 ) compared with the capacity obtained at C/5. Over 500 cycles at a rate of 5C, the ASSLSB provides a high capacity retention (>93%) with ultra-high average columbic efficiency (>99.95%). By developing a high-performance composite Si anode with high rate capacity and cycle life, with the fundamental understanding of the functionality of Li 3 N anolyte in volume-expansion anode materials, this work inspired researchers and industry for the strategies of development of solid-state anolyte and volume-expansion anode materials and provided a scalable integration methodology for next-generation batteries. Reference Yan, W.; Mu, Z.; Wang, Z.; Huang, Y.; Wu, D.; Lu, P.; Lu, J.; Xu, J.; Wu, Y.; Ma, T.; Yang, M.; Zhu, X.; Xia, Y.; Shi, S.; Chen, L.; Li, H.; Wu, F., Hard-carbon-stabilized Li–Si anodes for high-performance all-solid-state Li-ion batteries. Nature Energy 2023, 8 (8), 800-813. Huang, Y.; Shao, B.; Wang, Y.; Han, F., Solid-state silicon anode with extremely high initial coulombic efficiency. Energy & Environmental Science 2023, 16 (4), 1569-1580. Li, W.; Li, M.; Wang, S.; Chien, P.-H.; Luo, J.; Fu, J.; Lin, X.; King, G.; Feng, R.; Wang, J.; Zhou, J.; Li, R.; Liu, J.; Mo, Y.; Sham, T.-K.; Sun, X., Superionic conducting vacancy-rich β-Li3N electrolyte for stable cycling of all-solid-state lithium metal batteries. Nature Nanotechnology 2025, 20 (2), 265-275.

Silicon is expected to be one of the next-generation anode materials to further increase the energy density of batteries because of its high theoretical capacity. However, silicon undergoes a large volume change during charge-discharge, which results in poor cyclability. Although all-solid-state batteries are expected to mitigate the disadvantage of volume expansion and shrinkage of silicon1, the volume change of silicon can affect the mechanical interface between the silicon particle and the solid electrolyte. However, despite its importance, direct observation of the silicon particle/solid electrolyte contact interface has not yet been reported. In this study, morphological changes of silicon particles during charge-discharge were tracked by operando X-ray computed tomography (CT) measurements, and the change of the silicon particle/solid electrolyte contact interface affected by expansion and shrinkage of silicon was analyzed. LiNi1/3Co1/3Mn1/3O2 (NCM), Li6PS5Cl (LPSC) and acetylene black (AB) were mixed in a mass ratio of 1:1:0.1 as a cathode composite, and Si, LPSC and AB were mixed in a mass ratio of 1:4.4:0.6 as an anode composite. Si | LPSC | NCM all-solid-state cell for operando X-ray CT were assembled. X-ray CT measurements were performed at the beamline BL20XU on SPring-8 using 20 keV of X-rays. Galvanostatic charge-discharge was conducted at 0.07C rate during X-ray CT measurements. The pixel resolution was 85 nm. A silicon particle was extracted from the X-ray CT images and the silicon particle/LPSC solid electrolyte contact interface was analyzed. X-ray CT images reveal the structural changes in silicon particles by charge-discharge cycles. As the lithiation of silicon, cracks appear at the silicon particle/LPSC solid electrolyte contact interface. This indicates that due to the stress on the contact interface caused by the volume expansion of the silicon. However, these cracks are reduced by the removal of stress due to the volume shrinkage of the lithiated silicon. The elasticity of the LPSC may have contributed to this. Figure 1 shows X-ray CT image of a silicon particle after charging and discharging. As the lithiated silicon shrinks, the silicon particle/LPSC solid electrolyte contact interface undergoes significant alterations, leading to the formation of shell voids on the surface of the silicon particle. This indicates that the plasticity of the LPSC solid electrolyte is insufficient to accommodate the changes at the interface. Despite the formation of shell voids across various directions, certain areas remain in contact, ensuring a connection between the silicon particle and the solid electrolyte. This imply that silicon particles are not entirely detached from the solid electrolyte interface, partially preserving the ionic conduction pathway. The appearance of cracks at the silicon particle/LPSC solid electrolyte contact interface and the formation of shell voids on the surface of the silicon particle lead to increase in tortuosity and limitation of the reaction path, which results in poor battery performance. However, these change of silicon particle/solid electrolyte contact interface is reversible and has little effect on cycle properties after the second cycle, so these observations suggesting that silicon may be able to fulfill its potential in all-solid-state batteries. 1) W. Ping, C. Yang, Y. Bao, C. Wang, H. Xie, E. Hitz, J. Cheng, T. Li and L. Hu, Energy Stor. Mater., 21, 246-252 (2019). Acknowledgement: This work was partially supported by the New Energy and Industrial Technology Development Organization (NEDO), JPNP20004. Figure 1

The utilization of silicon (Si) anodes in all-solid-state lithium batteries (ASLBs) provides the potential for high energy density. However, the compatibility of sulfide solid-state electrolytes (SEs) with Si and carbon is often questioned due to potential decomposition. To investigate this, operando X-ray absorption near-edge structure (XANES) spectroscopy, ex-situ scanning electron microscopy (SEM) and ex-situ X-ray nano-tomography (XnT) were utilized to study the chemistry and structure evolution of nano Si composite anodes. Results from XANES demonstrated a partial decomposition of SEs during the first lithiation stage, which was further accelerated by the presence of carbon. But the performance of first three cycles in Si-SE-C was stable, which proved the generated media is ionically conductive. XnT and SEM results showed that the addition of SEs and carbon improved the structural stability of the anode with fewer pores and voids. A chemo-elasto-plastic model revealed that SEs and carbon buffered the volume expansion of Si, thus enhancing mechanical stability. The balance between the pros and cons of SEs and carbon in enhancing reaction kinetics and structural stability enabled the Si composite anode to demonstrate the highest Si utilization with higher specific capacities and better rate than pure Si and Si composite anodes with only SEs.

Solid state batteries (SSBs) are promising next generation propulsion for electric vehicles due to their improved safety, high gravimetric and volumetric energy densities, and increased reliability. Silicon is one of the limited choices for the anode material for the SSBs due to its high applicable capacity, low operating potential and natural abundance. However, significant challenges remain for the commercialization of Si anode based SSBs, including the insufficient operational and calendar life, requirement of high stack pressure for operation, and inadequate fast charge capability. Almost each of the technical challenges associated with Si anode is entangled with the volume change of Si during charging and discharging. Si possesses high lithium storage capacity because it can form various LixSiy compounds upon lithiation. For example, when 3.75 moles of Li+ is added to 1 mole of Si, the compound Li15Si4 is formed, which gives a capacity of 3578 mAh/gSi. What accompanies this is a considerable volume expansion (e.g., 280% increase for Li15Si4), resulting from the reorganization of the compound crystals. Assuming an anode that initially composes of perfectly compacted Si particles, this volume expansion translates to a 56% increase in the thickness of the Si anode. In a practical SSB, the real thickness variation in the Si anode is expected to be smaller because of the architecture design of the anode. Nonetheless, this volume change in Si creates many problems, including the Si particle pulverization, delamination of electrode from the current collector and electrolyte separator, loss of electronic and ion conductions in the electrode, among others. To maintain the electric contact in Si anode based SSBs, high stack pressures, from several MPa to several tens of MPa, are normally applied. In this work, we carefully measure the real-time stack pressure in a specially designed setup. The stress-strain characteristics of Si anode based SSBs during operation, including the stack pressure spike and the degradation of the average stack pressure, is studied and correlated with the Si anode structure changes. Furthermore, different measures, including external and internal ones, are explored to improve the cell pressure control. The external measures include selecting an appropriate spring and using a mechanical buffer layer, while the internal measure refers to an elastic current collector design. As a result, a better SSB pressure control is obtained. More importantly, a reduction of the stack pressure significantly below 10 MPa without compromising the cell performance is achieved.

All‐solid‐state batteries (ASSBs) with silicon‐based anodes are emerging as a viable energy storage system compared to conventional lithium‐ion batteries (LIBs) due to 1) the use of nonflammable solid electrolytes that not only suppress solvent‐induced parasitic reactions and volume expansion of silicon (Si) but also enhance overall safety and energy density. 2) a solid‐state charge–discharge pathway with solvent‐free interphases that reduces concentration polarization and enhances the interfacial stability. However, substantial research limitations impede their extensive application in fast‐charging devices, especially in balancing the energy and power density of ASSBs. Although strategies such as nanostructured Si, composite designs, and interfacial engineering have improved energy density and cycle life, achieving high power density remains a challenge, limiting the fast‐charging capability of Si‐based ASSBs. In this perspective article, the specific challenges are aimed to address, which are related to the limiting factors at both material and electrode levels for achieving high power density in Si‐based ASSBs. It is anticipated that this perspective will offer valuable insights into the various influencing factors, failure mechanisms, and advanced optimization strategies for achieving high‐rate retention and power density in next‐generation Si‐based ASSBs operating under low stack pressure, thus helping to bridge the gap between fundamental research and practical applications.

Silicon is considered a promising next-generation anode material for lithium-ion batteries because of its high theoretical capacity. However, significant challenges remain, particularly its poor cycle stability. The volume change of silicon active materials leads to surface cracking and continuous exposure of fresh surfaces to the liquid electrolyte, resulting to repeated electrolyte decomposition. When solid electrolytes are used instead of liquid electrolytes, the rigid structure of the electrolyte prevents its infiltration into newly formed cracks, potentially mitigating surface film growth and improving cycle stability. Despite these advantages, direct, high-resolution observation of how the silicon/electrolyte interface evolves during charge-discharge in all-solid-state batteries has not yet been reported. In particular, operando imaging at sub-micrometer scales of the interface phenomena between silicon particles and a solid electrolyte remains largely unexplored. In this study, we employed operando phase-contrast nano X-ray computed tomography (CT). Building on our previously developed operando X-ray CT measurement cell and interface observation methods1,2), we tracked the morphological changes of silicon particles and their contact interfaces with a Li6PS5Cl (LPSC) solid electrolyte during charge-discharge. We discuss how the volumetric expansion and contraction of silicon affects the mechanical interface and the resulting electrochemical performance in all-solid-state batteries. Si|LPSC|NCM cells were prepared comprising a cathode composite (Nb-coated LiNi1/3Co1/3Mn1/3O2 (NCM), LPSC, and acetylene black at a weight ratio of 1:1:0.1), a solid electrolyte layer (LPSC), and an anode composite (Si microparticles, LPSC, and acetylene black at a weight ratio of 1:4.4:0.6). The pelletized assembly was placed in a 1 mm diameter acrylic cylinder. Synchrotron X-ray CT measurements were performed at beamline BL20XU in SPring-8. CT measurements were conducted intermittently during galvanostatic charge-discharge. From the X-ray CT images, we observed that during lithiation (Si expansion), cracks formed in the solid electrolyte surrounding the silicon particles. These cracks likely emerge due to tensile stress imposed on the rigid LPSC by the volumetric growth of silicon. Upon delithiation, when silicon contracts, the silicon particles partially delaminate from the surrounding solid electrolyte. This interfacial delamination correlates with the large irreversible capacity loss observed in the first cycle. The voltage drop during the initial discharge corresponds to the delamination. Although these interfacial voids emerge, the silicon particles remain partially connected to the electrolyte, essentially “bridging” rather than becoming completely isolated. We also found that delamination preferentially initiates along the horizontal sides of the silicon particles, rather than directly along the vertical direction. This anisotropy in delamination behavior may be explained by differing mechanical constraints. Vertically, the cell stack applies significant pressure, whereas horizontally there is less constraint. Consequently, the horizontal surfaces are more prone to interfacial separation. Moreover, the electrolyte side tends to undergo more pronounced reactions due to easier charge-discharge processes, influencing the progression of delamination. Acknowledgement: This work was supported by JST-Mirai Program Grant Number JPMJMI24G1, Japan. [1] Y. Sakka, H. Yamashige, A. Watanabe, A. Takeuchi, M. Uesugi, K. Uesugi and Y. Orikasa, J. Mater. Chem. A, 10, 16602–16609 (2022). [2] Y. Sakka, M. Matsumoto, H. Yamashige, A. Takeuchi, M. Uesugi, K. Uesugi, C. Zhong, K. Shimoda, K. Okazaki and Y. Orikasa, J. Electrochem. Soc, 171, 070536 (2024).

All-solid-state batteries (ASSBs) with silicon anodes offer high energy density and mitigate issues such as continuous solid–electrolyte interphase (SEI) formation in lithium-ion batteries with liquid electrolytes. However, the evolution of the mechanical contact interface between silicon (Si) and the rigid solid electrolyte during cycling remains poorly understood. This study utilized operando synchrotron X-ray micro-computed tomography (micro-CT) and nano-computed tomography (nano-CT) to achieve high-resolution, 3D visualization of the silicon–electrolyte interface during lithiation and delithiation. Micro-CT revealed that silicon particles retain partial contact with the solid electrolyte as they delithiate and shrink to form shell voids, preserving ionic conduction pathways. High-resolution nano-CT further revealed a thin, previously undetectable solid electrolyte layer that adheres to the surfaces of the silicon particles and helps maintain these contact points. Additionally, interfacial delamination of the silicon was found to be highly anisotropic, initiating from sides that were laterally unconstrained due to uneven mechanical pressure and reaction inhomogeneity. Meanwhile, the vertically compressed interface remained largely intact. These findings elucidate the morphological evolution of the Si/electrolyte interface in ASSBs and demonstrate that continuous ion transport can be partially maintained despite significant volume changes.

No abstract available

All‐solid‐state (ASS) Li‐metal batteries are regarded as promising energy‐storage devices due to their high energy density and improved safety. Recently, the interface thermal runaway issues between reactive Li‐metal and solid‐state electrolytes (SSEs) have attracted increasing attention, but it has been less studied. Here, using in situ high‐resolution thermal imaging, a significant stress‐release period before the interface catches fire and burns between Li metal and Li1.5Al0.5Ge1.5(PO4)3 (LAGP) SSE is found that can provide opportunities for early thermal runaway warning for the batteries. Further, a highly safe ASS Li‐metal battery without external pressure package is reported by constructing a stable heterogeneous interface layer (HIL) consisting of ALD‐coated aluminum oxide and PECVD‐deposited amorphous silicon (a‐Si), which significantly reduces the interface exothermic reaction and suppresses the interface thermal runaway both theoretically and experimentally. The ASS Li‐metal symmetric battery shows a long cycling stability both at RT and high temperature over 150 °C being at least 8‐times higher than that of the one without HIL. The assembled Li‐CO2 battery is capable of 100 stable cycles with <3.2 V low charge potential at 500 mAg−1 at 150 °C. This work paves a way for the development of the next‐generation safe and high‐energy lithium batteries.

No abstract available

Silicon (Si) anode with high theoretical specific capacity (3579 mAh g−1) offers great promise for realizing high-energy solid-state batteries (SSBs). However, given Si’s huge volume variations during cycling, sluggish kinetics...

Silicon anodes are promising for all‐solid‐state batteries (ASSBs) due to their high specific capacity and dendrite‐free safety. However, its practical application is hindered by a fundamental trade‐off: pure silicon anodes suffer from poor transport kinetics, while composite silicon anodes, designed to improve transport, face severe interfacial passivation from the decomposition of solid electrolytes. Here, we introduce a local electrochemical co‐sintering (LECS) strategy to resolve this dilemma. This is achieved through a counter‐intuitive positive silicon gradient architecture, which harnesses (de)alloying stress to trigger localized silicon sintering toward the critical silicon/electrolyte interface. This in situ process encapsulates conductive additives within newly formed, densified silicon phases, simultaneously minimizing the reactive interface to suppress electrolyte decomposition and creating robust electronic pathways. As a result, the LECS anode demonstrates significantly enhanced kinetics and reversibility under high areal loading (over 4 mAh cm−2). This work establishes a paradigm of proactively engineering the electrode microstructure to achieve stable high‐energy ASSBs.

Silicon is a promising anode material due to its high theoretical specific capacity, low lithiation potential and low lithium dendrite risk. Yet, the electrochemical performance of silicon anodes in solid-state batteries is still poor (for example, low actual specific capacity and fast capacity decay), hindering practical applications. Here the chemo-mechanical failure mechanisms of composite Si/Li6PS5Cl and solid-electrolyte-free silicon anodes are revealed by combining structural and chemical characterizations with theoretical simulations. The growth of the solid electrolyte interphase at the Si|Li6PS5Cl interface causes severe resistance increase in composite anodes, explaining their fast capacity decay. Solid-electrolyte-free silicon anodes show sufficient ionic and electronic conductivities, enabling a high specific capacity. However, microscale void formation during delithiation causes larger mechanical stress at the two-dimensional interfaces of these anodes than in composite anodes. Understanding these chemo-mechanical failure mechanisms of different anode architectures and the role of interphase formation helps to provide guidelines for the design of improved electrode materials. Although silicon anodes are promising for solid-state batteries, they still suffer from poor electrochemical performance. Chemo-mechanical failure mechanisms of composite Si|Li6PS5Cl and solid-electrolyte-free silicon anodes are now revealed and should help in designing improved electrodes.

Although a high stack pressure (≥50 MPa) enhances solid-solid contacts in solid-state batteries (SSBs), it poses impracticality for commercialization. This work proposes a self-pressure silicon (Si)-carbon composite anode that enables stable operation under reduced external pressure (≤2 MPa). The self-pressure anode features a prestress structure that can effectively alleviate the internal and external stress simultaneously, which is fabricated with ionic-conductive poly(ethylene oxide) (PEO)/lithium salt-coated carbon nanotubes (CNTs) being compressed by shrinking graphene hydrogel. The capillary-driven hydrogel shrinkage generates internal pressure, compensating for the volumetric expansion (up to 300%) of Si. This creates dynamic solid-solid interfaces between compressed CNTs/PEO and expanding Si, ensuring both mechanical stability and ion/electron transport. The SSBs with this self-pressure anode have a long cycle life of 700 cycles and a high capacity retention of 79.2% in an organic/inorganic composite electrolyte without external pressure (0 MPa). The half-cell using a sulfide solid-state electrolyte reached 700 cycles and was able to achieve a stable cycle life at the lowest 2 MPa stack pressure. This design resolves interfacial challenges by prestress in SSBs.

Silicon-based anode solid‑state batteries are among the most promising systems for simultaneously achieving high energy density and enhanced safety. However, silicon anodes suffer from severe loss of electronic contact in low–electrolyte or electrolyte‑free environments due to their substantial volume changes, which significantly hinders their integration into solid‑state systems. In this work, we introduce single-walled long carbon nanotubes (SWCNTL) into micron-sized silicon (MSi) anodes to reinforce the three‑dimensional conductive network and thus optimize electrochemical performance in a solid‑state system based on poly(vinylidene fluoride)@lithium lanthanum zirconium tantalum oxide (PVDF@LLZTO)composite solid electrolyte. We demonstrate that SWCNTL promote deeper lithiation of MSi particles at elevated current densities, while simultaneously enhancing electron‑ion transport kinetics and mechanical integrity during cycling under solid-state conditions. Thus, MSi electrodes incorporating SWCNTL deliver markedly improved electrochemical performance and cycling stability in both PVDF@LLZTO-based solid-state half-cells and solid-state full cells countered with LiFePO₄(LFP)cathode. Our findings provide a viable strategy to enhance the practical application of silicon anodes in next-generation solid-state battery systems.

Despite the advantages of nanostructure design with a balance of capacity and cycle life, the low tap density (<1 g cm-3) and high swelling properties make nanostructured silicon far from practical in applications. Here, we design a free-standing silicon graphite composite integrated anode through facile one-pot sintering with pitch under pressure. The thermomechanical effect during compression carbonization enables the integrated electrode to achieve a high tap density of 1.51 g cm-3, >2 times that of typical free-standing electrodes. In situ expansion measurements demonstrate that the longitudinal expansion of integrated electrodes is <20% of that of conventional electrodes. A rational conductive framework enables integrated electrodes to exhibit remarkable cycling stability in both liquid lithium-ion batteries (77.6% capacity retention after 500 cycles) and all-solid-state lithium-ion batteries (98.5% capacity retention after 1000 cycles). In particular, integrated electrodes remain stable even with a high areal capacity of 12.6 mAh cm-2.

The high gravimetric and volumetric capacity of silicon makes it an attractive anode material for lithium-ion solid-state batteries (SSBs). [1,2] However, silicon suffers from high volume changes during cycling and requires high stack pressures to stabilize the interfaces. [3-5] Herein, we present different approaches to minimize the breathing of silicon-based anodes leading to stabilized cycling. Silicon carbon void structures (Si-C) obtain a void between the silicon nanoparticle and the surrounding carbon matrix to compensate the volume changes already within the anode structure. As a result, excellent cycling performance in solid-state cells with areal loadings as high as 7.4 mAh cm-2 can be demonstrated. Thereby, Si-C composite electrodes show higher lithiation capacities, better rate stability and higher capacity retentions than pristine silicon nanoparticles (SiNPs), which rapidly degrade due to the immense mechanical stress upon charging and discharging. Hence, the volume changes of the SiNPs are well compensated by the carbon matrix, which also stabilizes the entire electrode. In full cells with nickel-rich NCM (LiNi0.9Co0.05Mn0.05O2, 210 mAh g-1) as cathode, higher initial discharge capacities and coulombic efficiencies (72.7 % vs. 31.0 %) can be achieved compared to the liquid system. The solid electrolyte (Li6PS5Cl, 3 mS cm-1) does not penetrate the whole carbon matrix of the Si-C particles resulting in less side reactions. Consequently, prelithiation of the Si-C anodes is not required in SSBs. By applying either a low (1.1) or rather high n/p ratio (2.0) capacity retentions of up to 87.7 % after 50 cycles can be reached. [6] Especially for industrial fabrication of SSB anodes other procedures than the complex multi-step synthesis of e.g. Si-C composites are needed. [7] Consequently, we evaluated low-cost silicon microparticles (µm-Si) as partially lithiated electrode material (800 mAh g-1) in SSB half- and full cells. By reducing the utilized fraction of silicon, the breathing during cycling is reduced from 300 % to 66 %, which reduces the armorphization of the active material. In addition, the grain boundaries of silicon are connected by a matrix of solid electrolyte and carbon additive, which drastically reduces the need for a high stack pressure. After limiting the charge cut-off potential of NCM|SE|µm-Si full cells, significant increased capacity retentions from 32 % to 71 % after 50 cycles can be reached. In addition, similar performance compared to the Si-C electrodes can be demonstrated making it to an auspicious alternative. [8] Overall, the herein presented silicon materials achieved decent electrochemical performance without active pressure control on the cells being beneficial for electric vehicle and other applications. Hence, both Si-C and µm-Si particles are promising concepts for stable, high-capacity SSB anodes. Literature: [1] A. Mukanova, A. Jetybayeva, S.-T. Myung, S.-S. Kim, Z. Bakenov, Mater. Today Energy 2018, 9, 49. [2] N. Nitta, G. Yushin, Part. Part. Syst. Charact. 2014, 31, 317. [3] X. Su, Q. Wu, J. Li, X. Xiao, A. Lott, W. Lu, B. W. Sheldon, J. Wu, Adv. Energy Mater. 2014, 4, 1300882. [4] D. H. S. Tan, Y.-T. Chen, H. Yang, W. Bao, B. Sreenarayanan, J.-M. Doux, W. Li, B. Lu, S.-Y. Ham, B. Sayahpour et al., Science (N.Y.) 2021, 373, 1494. [5] S. Cangaz, F. Hippauf, F. S. Reuter, S. Doerfler, T. Abendroth, H. Althues, S. Kaskel, Adv. Energy Mater. 2020, 3, 2001320. [6] S. Poetke, F. Hippauf, A. Baasner, S. Dörfler, H. Althues, S. Kaskel, Batteries Supercaps 2021, 4, 1323. [7] D. Jantke, R. Bernhard, E. Hanelt, T. Buhrmester, J. Pfeiffer, S. Haufe, J. Electrochem. Soc. 2019, 166, A3881. [8] S. Poetke, S. Cangaz, F. Hippauf, S. Haufe, S. Dörfler, H. Althues, S. Kaskel, Energy Technol. 2022 submitted.

Silicon (Si) anodes, free from the dendritic growth concerns found in lithium (Li) metal anodes, offer a promising alternative for high-energy all-solid-state batteries (ASSBs). However, most advancements in Si anodes have been achieved under impractical high operating pressures, which can mask detrimental electrochemo-mechanical issues. Herein, we effectively address the challenges related to the low-pressure operation of Si anodes in ASSBs by introducing an silver (Ag) interlayer between the solid electrolyte layer (Li6 PS5 Cl) and anode and prelithiating the anodes. The Si composite electrodes, consisting of Si/polyvinylidene fluoride/carbon nanotubes, are optimized for suitable mechanical properties and electrical connectivity. Although the impact of the Ag interlayer is insignificant at an exceedingly high operating pressure of 70 MPa, it substantially enhances the interfacial contacts under a practical low operating pressure of 15 MPa. Thus, Ag-coated Si anodes outperform bare Si anodes (discharge capacity: 2430 vs 1560 mA h g-1 ). The robust interfacial contact is attributed to the deformable, adhesive properties and protective role of the in situ lithiated Ag interlayer, as evidenced by comprehensive ex situ analyses. Operando electrochemical pressiometry is used effectively to probe the strong interface for Ag-coated Si anodes. Furthermore, prelithiation through the thermal evaporation deposition of Li metal significantly improves the cycling performance.

Silicon (Si) shows excellent potential as an anode material for sulfide‐based all‐solid‐state lithium batteries (ASSLBs). However, Si anodes face inherent challenges such as low electron conductivity and large volume changes during cycling, ultimately resulting in a short cycle life. Herein, to address these challenges, In2O3/C derived from an indium‐based metal‐organic framework (In‐MOF) is utilized to encapsulate Si particles in situ. The Li‐In alloy and Li2O formed in situ after the lithiation of In2O3/C provide rapid Li+ transportation properties, and the existence of In2O3/C efficiently relieves the significant volume changes of Si. Consequently, the Si anode exhibits improved cyclic stability. The composite Si@In2O3/C anode prepared with a high loading of 7.64 mg cm−2 maintains a high specific capacity of 1093.2 mAh g−1 (8.36 mAh cm−2) after 500 cycles at 2.74 mA cm−2, maintaining 84.3% of the initial capacity. Furthermore, a full cell prepared with a Si@In2O3/C composite anode and a LiNbO3‐coated LiNi0.7Co0.2Mn0.1O2 (LNO@NCM) cathode shows excellent cyclic stability, with 74.3% of the capacity retained after cycling 1000 times at 0.2C (0.51 mA cm−2) and an average Coulomb efficiency of 99.94%. This study offers a compelling idea for the design of sulfide‐based ASSLB anode materials.

Alloy‐based anodes featuring high capacity and moderate operating potentials hold great promise for high‐energy‐density all‐solid‐state batteries (ASSBs). However, the significant volume fluctuations during cycling often lead to solid–solid interfacial failure, compromising reversibility and cycling stability. Multilevel architectural designs of composite alloy anodes have proven effective in enhancing electronic conductivity, ion transport, and interfacial stability. Herein, the influence of stacking sequence on the structural evolution and electrochemical performance of electrodes composed of silicon (Si) and aluminum (Al) is investigated. The results reveal that the plastic deformability of the upper layer active material (directly interfacing with the solid‐state electrolyte) and its electrochemical potential window critically influence the reversibility, rate capability, and failure mechanism of the composite anode. Notably, when Si is employed as the upper layer, the anode delivers an initial Coulombic efficiency of 87.3% at 0.25 mA cm−2, significantly exceeding that of the Al‐upper configuration (59.3%). These results provide mechanistic understanding for the rational design of composite alloy anodes, highlighting the importance of component stacking for mitigating kinetic limitations and enhancing the performance of ASSBs.