固态电池空间电荷层随高低温变化

Hybrid solid electrolytes (HSEs) have attracted much attention due to their advantages as both inorganic and organic polymer electrolytes. However, the organic/inorganic interfacial space charge layer has a great barrier to the transport of Li+ in the HSE. Here, an in situ polymerization layer is proposed on garnet‐type particles, working as the coherent region to eliminate the space charge layer at the organic/inorganic interfaces by inhibiting electron localization. The conjugate hybridization of fillers weakens the aggregation of particles, induces the dissociation of Li salt, and provides high‐throughput Li+ transport pathways at the ceramics/polymer interface. Furthermore, the continuous Li+ conduction networks are connected by the coherent region between inorganic fillers and polymer chains. The fabricated HSE exhibits a high ionic conductivity of 0.47 mS cm−1 and ion migration numbers of 0.78 at room temperature. The 3D Li//Li systematic battery assembled with the HSE delivers a high critical current density (CCD) of 2.0 mA cm−2. Meanwhile, the 4.5 V NCM811//Li batteries achieve a prolonged operation of 500 cycles at 0.5 C. The Li//LiFePO4 batteries demonstrate superior capacity retention of 96.4% at 1 C after 500 cycles.

The poor structural stability of polymer electrolytes and sluggish ion transport kinetics of interfaces with cathode limit the fundamental performance improvements of polymer all‐solid‐state lithium metal batteries under high voltages. Herein, it is revealed that by introducing dielectric BaTiO3 in an in‐situ polymerized composite solid‐state electrolyte, the generated interaction between the ether group of polymer electrolyte and dielectric material could effectively regulate the lithium‐ion (Li+) coordination structure to achieve an oxidative potential higher than 5.2 V. The dielectric BaTiO3 with spontaneous polarization also weakens the space charge layer effect between the cathode and electrolyte, facilitating fast Li+ transport kinetics across the cathode/electrolyte interfaces. The all‐solid‐state LiNi0.8Co0.1Mn0.1O2/Li batteries with the dielectric composite solid‐state electrolyte exhibit an ultra‐long cycling life of 1800 and 1300 cycles at room temperature under high cut‐off voltages of 4.6 and 4.7 V, respectively. This work highlights the critical role of dielectric materials in high‐performance solid‐state electrolytes and provides a promising strategy to realize high‐voltage long‐life all‐solid‐state lithium metal batteries.

The current controversies about the role of space charge layers hinder the development of better solid–solid interfaces and, thus, the improvement of solid-state batteries (ASSBs). To overcome this, we have combined high spatial resolution and nondestructive techniques, operando heterodyne Kelvin probe force microscopy (KPFM), and operando nuclear reaction analysis (NRA) to conduct a study of space charge layers in ASSBs. A model thin-film ASSB was fabricated from lithium (Li)|Li3PO4 (LPO)|LiCoO2 (LCO) for this study. This battery excels due to negligible interfacial defects and side reactions. For a working battery voltage range from 3.0 to 4.3 V vs Li/Li+, a space charge layer mainly exists at the LPO|LCO interface. This space charge layer with a width <50 nm arises from the redistribution of Li-ions at the interface. We clarified controversial views on the role of space charge layers in ASSBs by quantitatively determining the interfacial space charge layer resistance and found a maximum value between 18.4 and 19.1 Ω cm2 at 4.3 V vs Li/Li+. The absolute value of interfacial resistance from space charge layer formation is much smaller compared with the bulk solid electrolyte resistance in the fabricated thin-film ASSB. By employing KPFM and NRA techniques in ASSB research, our knowledge of space charge layer evolution at the solid electrolyte electrode interface is more comprehensive, even beyond the investigation of space charge layers.

The electrochemical performance of all‐solid‐state lithium batteries (ASSLBs) can be significantly improved by addressing the challenges posed by space charge layer (SCL) effect, which plays a crucial role in determining Li+ ions transport kinetic at cathodic interface. Therefore, it is critical to realize the in situ inspection and visualization of SCL behaviors for solving sluggish Li+ ions transport issues, despite remaining grant challenges. Therewith, the well‐defined model of LiNbO3‐coated NCM (NCM@LNO) cathode is constructed and assembled for the representative Li6PS5Cl‐based ASSLBs, which not only ensures excellent cathodic compatibility, but also preferably enables the better monitoring of Li+ ions transport kinetics. Combining ex situ analysis with DFT calculation, the formation and evolution mechanism of SCL are comprehensively understood, and the relationship between well‐controlled SCL configuration and Li+ electrochemical behavior has been also further illustrated and established through the operando Raman spectroscopy. On these grounds, the preferred NCM@LNO cathodes acquire the enhanced discharge capacity of 90.6% (144.8 mAh g−1) after 100 cycles and it can still deliver the exceptional capacity of 136.2 mAh g−1 after 800 cycles in ASSLBs. Hence, the research will pave up a new perspective for fundamental scientific insight of the SCL and reasonable tailoring of cathodic interface for high‐efficiency ASSLBs.

The application of nickel-rich layered oxide cathodes to sulfide all-solid-state batteries (SASSBs) is the most promising way to achieve high capacity, high energy density, and high safety. However, the disadvantages of the space charge layer, elemental diffusion, and poor interfacial contact lead to excessive interfacial impedance. Herein, a hybrid coating of LPO and LBO is designed for NCM cathode with 95% Ni content. The hybrid coating not only improves the ionic conductivity and Li+ migration efficiency of the surface layer, but also improves the mechanical strength and effectively mitigates the stress-strain effect of the cathode during long-term cycling. SC-NCM92@LPO+LBO||Li6PS5Cl||Li-In SASSB delivers a high specific discharge capacity of 220.5 mAh g-1 with excellent high-rate performance. SC-NCM95@LPO+LBO||Li6PS5Cl||Li-In SASSB presents a high specific capacity of 253.3 mAh g-1 excellent high-rate performance (137.9 mAh g-1 at 10C) and cycling stability, maintaining its electrochemical performance under various conditions. This work provides a valuable reference for the application of ultrahigh nickel-layered oxide cathodes in SASSBs.

Understanding the degradation mechanisms in solid-state lithium-ion batteries at interfaces is fundamental for improving battery performance and for designing recycling methodologies for batteries. A key source of battery degradation is the presence of the space charge layer at the solid-state electrolyte-electrode interface and the impact that this layer has on the thermodynamics of the electrolyte structure. Currently, Li10GeP2S12 in its pristine form has one of the highest lithium conductivities and has been used as a template for designing even higher conductivity derived structures. However, being an ionic material with mostly linear diffusion, it is prone to path-blocker defects, which we show here to be especially prevalent in the space charge layer. We analyze the thermodynamic properties of a number of path-blocker defects using density functional theory and their potential crystal decomposition and find that the presence of an electrostatic potential in the space charge layer elevates the likelihood of existence of these defects, which otherwise would not be likely to form in the bulk of the electrolyte away from electrodes. We use ab initio molecular dynamics to assess the impact of these defects on the diffusivity of the crystal and find that they all reduce the lithium diffusivity. While our work focuses on Li10GeP2S12, it is relevant to any solid-state electrolyte with mainly linear diffusion.

All-solid-state batteries (ASSBs) are poised to transform electrochemical energy storage, yet their performance remains critically limited by high interfacial impedance. A central origin of this bottleneck is the space charge...

All-solid-state batteries (ASSBs) working at room and mild temperature have demonstrated inspiring performances over recent years. However, the kinetic attributes of the interface applicable to the subzero temperatures are still unidentified, restricting the low-temperature interface design and operation. Herein, a host of cathode interfaces are constructed and investigated to unlock the critical interface features required for cryogenic temperatures. The unstable interface between LiNi0.90Co0.05Mn0.05O2 (Ni90) and Li6PS5Cl (LPSC) sulfide solid electrolyte (SE) results in unfavorable cathode-electrolyte interphase (CEI) and sluggish lithium-ion transport across the CEI. After inserting a Li2ZrO3 (LZO) coating layer, the activation energy of the Ni90@LZO/sulfide SE interface can be reduced from 60.19 kJ mol-1 to 41.39 kJ mol-1 owing to the suppressed interfacial reactions. Through replacing the LPSC SE and LZO coating layer by the Li3InCl6 (LIC) halide SE, both a highly stable interface and low activation energy (25.79 kJ mol-1) can be achieved, thus realizing an improved capacity retention (26.9%) at -30 °C for the Ni90/LIC/LPSC/Li-In ASSB. Moreover, theoretical evaluation clarifies that cathode/SE interfaces with high ionic conductivity and low energy barrier are favorable to the Li+ conduction through the interphase and the Li+ transfer across the cathode/interphase interface. These critical understandings may provide guidance for low-temperature interface design in ASSBs.

To understand the electrochemistry of all-solid-state batteries (ASSBs), the use of electrochemical equivalent circuits with a physical meaning is essential. A model battery is needed whose characterization is independent of the influence of the complex battery assembly. Therefore, LICGC©, a model solid electrolyte is chosen that shows stability in air, but on the other hand is also well-known for its instability against metallic lithium upon direct contact. As a first step towards a model ASSB, the interface between lithium and the solid electrolyte (SE) is stabilized with thin (5 nm and 10 nm) coatings of titanium oxide (TO). Impedance data shows that symmetric cells with the TO coatings are protected from rapid SE surface degradation due to reducing lithium. Titanium oxide nano-interlayers can hence serve as a protective interlayer on the anode side of a model ASSB. Additionally, the formation of space charge layers (SCLs), which have been already documented for LICGC alone, appear once again at the interface between metal oxide interlayer and the solid electrolyte. The observed SCL thickness can reach up to ∼ 5 µm (cf. figure). Figure 1

In an all solid state Li-ion battery, it is crucial to reduce ionic resistivity at the interface between the electrode and the electrolyte in order to enhance Li+ mobility across the interface. Recent first principles calculations predict the presence of a space-charge layer (SCL) at the interface due to the difference in the Li+ chemical potential at the interface between two different materials, as in the metal-semiconductor junction in electronic devices. However, the presence of SCL has never been experimentally observed. Our first attempt in a fresh multilayer sample, Cu(10 nm)/Li3PO4(50 nm)/LiCoO2(100 nm) on a sapphire substrate, with low-energy µ +SR (LE µ +SR) revealed a gradual change in the nuclear magnetic field distribution width as a function of implantation depth even across the interface between Li3PO4 and LiCoO2. This implies that the change in the field distribution width at SCL of the sample is too small to be detected by LE µ +SR.

Coupling with high‐voltage oxide cathode is the key to achieve high‐energy density sulfide‐based all‐solid‐state lithium batteries. However, the complex interfacial issues including the space charge layer effect and undesirable side reaction between sulfide solid‐state electrolytes and oxide cathode materials are the main constraints on the development of high‐performance all‐solid‐state lithium batteries, which lead to the continuous decay of electrochemical performance. Herein, different from the complicated coating procedure, a LiPO2F2 additive engineering was proposed to achieve high‐performance all‐solid‐state lithium batteries. With the introduction of LiPO2F2 additive, a protective cathode–electrolyte interphase consisting of LiPxOyFz, LiF, and Li3PO4 could be in situ formed to improve the interfacial stability between LiNi0.8Co0.1Mn0.1O2 (NCM811) and Li5.5PS4.5Cl1.5 (LPSC). Benefiting from this, the NCM811/LPSC/Li all‐solid‐state lithium battery exhibited impressive cyclic stability with a capacity retention of 85.5% after 600 cycles (at 0.5 C). Diverse and comprehensive characterization, combined with finite element simulation and density functional theory calculation fully demonstrated the effective component, interfacial stabilization function and enhanced kinetic of LiPO2F2‐derived cathode–electrolyte interphase. This work provides not only a feasible and effective method to stabilize the cathodic interface but also worthy insight into interfacial design for high‐performance all‐solid‐state lithium batteries.

The high interfacial resistance between an electrode and a solid electrolyte remains a critical problem needed to be addressed for the practical application of all-solid-state batteries (ASSBs). While introducing an interlayer is a promising strategy to mitigate this resistance, the unclear action mechanism of the interlayer on the interfacial Li+ transport impedes further development. Herein, employing a first-principles-informed thermodynamic model, we demonstrate an effective approach for modulating the space–charge layers and electrostatic barriers for Li+ transport at the β-Li3PS4/LixCoO2 interfaces by incorporating a LiAlO2 interlayer in Li/β-Li3PS4/LixCoO2 ASSBs. The potential profile calculations reveal a high discharge barrier for Li-ion migration at the β-Li3PS4/LiCoO2 cathode interface, hindering the discharge process. By contrast, at the β-Li3PS4/LiAlO2/LiCoO2 interface, a lower interface potential drop is achieved to assist Li+ transport for fast discharging. Further analysis of the charge transfer and the band alignment reveals that the reduced interface potential drop stems from the synergistic effects of LiAlO2's Fermi level, chemical potential, and ionization potential. This work enhances the understanding of the interlayer's impact on interfacial Li+ transport and provides design principles for interlayer materials in ASSBs.

No abstract available

Differences in the chemical potential of ions and electrons/holes at solid-state interfaces drive the transfer of charged species upon heterogeneous boundary formation. This leads to the accumulation of a space-charge layer, which in turn produces an electrostatic potential drop at the interface. Quantifying the interfacial potential drop and its impact on both ionic and electronic transport across the interface is critically important for the performance and reliability of solid-state batteries (SSBs) and electrochemical random-access memory (ECRAM) devices. LiPON/Li x V 2 O 5 (0<x<2) interfaces are of particular interest, due to the large Li stoichiometry range that is possible in α-V 2 O 5 , which translates to large capacities for SSB and allows for numerous accessible states in ECRAM. Here, we predict the formation of space charge layers, interface band alignments, and electrostatic potential drops for the Li/LiPON/Li x V 2 O 5 (0<x<2) and Li 1-x V 2 O 5 /LiPON/Li 1+x V 2 O 5 (0<x<1) systems, based on density functional theory (DFT) calculations of electronic structures and point defect formation energies. Bcc-Li and orthorhombic α-V 2 O 5 , δ-LiV 2 O 5 , and γ-Li 2 V 2 O 5 were used as model structures for DFT calculations, while LiPON was represented by two structures: crystalline Li 2 PO 2 N was used to describe ALD-grown LiPON, whereas Li 3 PO 4 was used to represent PVD-grown LiPON. We found that square pyramidal d -orbital splitting, instead of distorted octahedral splitting used in previous works, faithfully reproduces the range of DOS peaks of V in Li x V 2 O 5. This is more consistent with the crystalline structure of layered V 2 O 5 with VO 5 square pyramids alternating between corner and edge-sharing. We also predicted the Fermi level in Li x V 2 O 5 , by plotting the formation energy of the dominant defects as a function of Fermi level and solving for the Fermi level that enforces charge neutrality. Through a systematic screening of charged point defects and requiring charge neutrality, we determined the dominant defects to be Li + interstitials and O + vacancies for each phase of Li x V 2 O 5. To determine the driving force for space charge layer formation, we calculated the energy difference for all possible defect exchange reactions involving Li and O across the interfaces. These calculations predict that transferring Li + interstitials from LiPON to each Li x V 2 O 5 phase is thermodynamically favorable. Following expectations, the transfer of Li + becomes less thermodynamically favorable as x increases. These defect calculations also revealed that O + vacancies will transfer from LiPON to Li x V 2 O 5 for each phase, therefore, oxygen will transfer from Li x V 2 O 5 to LiPON. Both ionic transfers will build a positive potential on the Li x V 2 O 5 side. By requiring the electrochemical potential of Li-ions to reach a constant at equilibrium, the electronic and ionic degrees of freedom are connected and give rise to band-bending and electrostatic potential drops in both the Li/LiPON/Li x V 2 O 5 (0<x<2) and Li 1-x V 2 O 5 /LiPON/Li 1+x V 2 O 5 (0<x<1) systems. These findings are compared with measurements of depth-resolved cathodoluminescence spectroscopy (DRCLS), which is an electron microscopy technique that can nondestructively probe the electronic state of a device in operando. This work is supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, under Grant No. DE-SC0025452.

The significant interfacial resistance between solid electrolyte‐electrode interfaces is a major bottleneck for the practical application of solid‐state lithium batteries. This resistance is primarily caused by the formation of space charge layers (SCLs), resulting from the redistribution of ionic carriers at the interface between dissimilar materials with varying chemical potentials, which lead to insufficient carriers and sluggish lithium‐ion transport. In this study, a conjugated structure polymer is constructed through in situ polymerization onto the oxide electrolyte, forming charge‐rich SCLs on the organic/inorganic interface, and enabling the interfacial layer to maintain superior ion transfer and contact. The Li solid NMR spectra and computational study suggest that optimized SCLs offer effective pathways for Li+ conduction in the electrolyte, thereby enhancing the interfacial conduction. Furthermore, the designed electrolyte induces the formation of an inorganic‐rich interphase layer on the lithium anode, enabling rapid lithium‐ion transport and uniform Li deposition. Consequently, the lithium symmetric cell with this electrolyte operates for more than 5100 h, while LiFePO4/Li solid‐state batteries can stably cycle up to 800 times at 5 C. This interfacial modification strategy provides a new perspective for the rational design of the charge‐rich SCLs and advances the understanding of the SCLs inside the electrolyte.

All-solid-state lithium batteries (ASSLBs) with high volumetric energy density and enhanced safety are considered one of the most promising next-generation batteries. Elucidating the capacity-fading mechanism caused by the space-charge layer (SCL) and the interfacial side reaction (ISR) is crucial for the future development of high-energy-density ASSLBs with a longer cycle life. Here, a systematic study to probe the electrochemical performance of Li10GeP2S12-based ASSLBs with stoichiometric-controlled LixCoO2 was performed with the aid of density functional theory (DFT) calculations, X-ray photoelectron spectroscopy (XPS), focused ion beam-field emission scanning electron microscopy (FIB-SEM), and solid-state nuclear magnetic resonance (NMR) spectroscopy. We discovered that the overstoichiometric Li1.042CoO2 shows a high capacity at first cycle with the smallest overpotential, but the capacity gradually decreases, which is ascribed to the weak SCL effect and strong interfacial side reactions. On the contrary, the lithium-deficient Li0.945CoO2 achieves the best cycling stability with a very low capacity associated with the strongest SCL effect and weak interfacial side reactions. The SCL effect is indeed coupled with ISR, which eventually leads to capacity fading in long-term operation. We believe that the new insights gained from this work will accelerate the future development of LiCoO2/LGPS-based ASSLBs with both a mitigated SCL effect and a longer cycle life.

The space charge layer (SCL) is generally considered one of the origins of the sluggish interfacial lithium-ion transport in all-solid-state lithium-ion batteries (ASSLIBs). However, in-situ visualization of the SCL effect on the interfacial lithium-ion transport in sulfide-based ASSLIBs is still a great challenge. Here, we directly observe the electrode/electrolyte interface lithium-ion accumulation resulting from the SCL by investigating the net-charge-density distribution across the high-voltage LiCoO2/argyrodite Li6PS5Cl interface using the in-situ differential phase contrast scanning transmission electron microscopy (DPC-STEM) technique. Moreover, we further demonstrate a built-in electric field and chemical potential coupling strategy to reduce the SCL formation and boost lithium-ion transport across the electrode/electrolyte interface by the in-situ DPC-STEM technique and finite element method simulations. Our findings will strikingly advance the fundamental scientific understanding of the SCL mechanism in ASSLIBs and shed light on rational electrode/electrolyte interface design for high-rate performance ASSLIBs. Understanding the effect of the space charge layer (SCL) in all-solid-state lithium-ion batteries is challenging due to lack of direct experimental observations. Here the authors visualize the SCL using an in-situ DPC-STEM imaging technique, based on which they further introduce a built-in electric field to suppress its formation.

Understanding the interfacial impedance between the solid electrolyte and the electrode is a critical issue for the design of solid-state batteries. We propose a new equivalent circuit model that treats the interface not only as a capacitor but also includes the space charge layer resistance and the resultant polarization resistance. Moreover, the elements of the circuit model are quantified by the physical quantities based on the recently proposed modified Planck-Nernst-Poisson (MPNP) model, which includes the effect of the unoccupied regular lattice sites (vacancies) in the electro-diffusion problem and takes both the ion and electron contributions into the account. We provide a new analytical solution for the space charge layer capacitance. Comparative numerical results demonstrate that our proposed model with additional polarization resistance can explain well the real impedance tail at the low-frequency region, for which the pure capacitor interface model fails. The model is verified against the experimental impedance spectra of LiPON.

ABSTRACT Space charge layer (SCL) formation at cathode–electrolyte interfaces severely limits the performance of sulfide-based all-solid-state Li batteries (ASSLBs). While conventional strategies focus on cathode modifications, we propose a novel electrolyte-centric approach by incorporating WO3 into argyrodite electrolyte (Li5.49P0.99W0.01S4.47O0.03Cl1.5). This design achieves a record-high ionic conductivity of 13.5 mS cm−1 (at 25°C) among O-substituted argyrodites. When paired with a LiNi0.92Co0.05Mn0.03O2 cathode, the full cell delivers 217 mAh g−1 at 0.1C, and retains 92% capacity after 1000 cycles (1C) and 80% capacity after 5000 cycles (5C), far outperforming the cells with frequently-used Li5.5PS4.5Cl1.5 argyrodite electrolytes (200 mAh g−1 at 0.1C; failure at 408 cycles at 1C). Mechanistic studies reveal that WO3 substitution modulates the electrolyte’s chemical potential to align with the cathode, reducing interfacial energy barriers and inhibiting Li+ depletion, and then significantly suppresses SCL effects. This work pioneers an electrolyte engineering strategy to mitigate SCL issues, enabling high-energy-density, ultra-stable ASSLBs.

The formation of space charge layers in solid-state ion conductors has been investigated as early as the 1980s. With the advent of all-solid-state batteries as an alternative to traditional Li-ion batteries, possibly improving performance and safety, the phenomenon of space charge formation caught the attention of researchers as a possible origin for the observed high interfacial resistance. Following classical space charge theory, such high resistances result from the formation of the depletion layers. These layers of up to hundreds of nanometers in thickness are almost free of mobile cations. With the prediction of a Debye-like screening effect, the thickness of the depletion layer is expected to scale with the square root of the absolute temperature. In this work, we studied the temperature dependence of the depletion layer properties in model solid Ohara LICGC Li+ conducting electrolytes using electrochemical impedance spectroscopy. We show that the activation energy inside the depletion layer increases to ca 0.42 eV compared to ca 0.39 eV in the bulk electrolyte. Moreover, the proportionality between temperature and depletion layer thickness, correlating to the Debye length, is tested and validated.

Introduction Oxide-based all-solid-state batteries (Ox-ASSBs) have been attracting attention as next-generation secondary batteries because of their high safety and high energy density. Recently, Ox-ASSBs have been reported by use of LISICON-type Li3.5Ge0.5V0.5O4(LGVO) as a solid electrolyte and layered NaCl-type LiCoO2 and LiNi1/3Mn1/3Co1/3O2 as positive electrodes. We have focused on Li2MnO3-based positive electrodes without Co, as shown in Li4/3-2/3x Mn2/3-1/3x NixO2 (0<x<1/2). LiNi0.5Mn0.5O2(x=1/2, LNMO) combines high capacity and thermal stability. It is well known that disordering of Li and Ni in the layered NaCl-type structure occurs during sintering and that oxide ions involve in charge compensation at higher voltages. Accordingly, the electrochemical properties vary depending on the amount of Ni substitution and excess Li relative to the transition metal in conventional Li-ion battery. Therefore, we have investigated an Ox-ASSB battery using LNMOs as a positive electrode, specifically focusing on effects of both Li, Ni-disordering and their sintering temperatures on the performance while controlling chemical compositions precisely. Experimental LNMO were prepared by co-precipitation method. The precursor Ni and Mn hydroxides ware prepared from Ni(NO3)2･6H2O and Mn(NO3)2･6H2O. The precursor and LiOH･H2O were mixed to a specified chemical composition ratio, formed under pressure, and calcined at 1073, 1173, 1273 K to obtain LNMO. The solid electrolyte LGVO was synthesized by sintering a mixture of Li4GeO4 and Li3VO4 at 973 K. The LNMO composite cathode layer on LGVO was prepared by applying a composite LNMO cathode slurry, drying, and sintering at 1023K for 6 hours The solid electrolyte LGVO and cathode material LNMO contain 5 % Li3BO3 as a sintering aid. The crystalline phase was identified by powder X-ray diffraction measurement by CuKα radiation. The chemical bonding state was analyzed by X-ray photoelectron spectroscopy Electrochemical testing was performed by LNMO/ LGVO / sulfide solid electrolyte Li10GeP2S12 / In-Li cell (Φ10mm) at 323 K. The rate of constant current was 1/100 C in the 2.0-(3.6~4.0) V. Results and discussion The samples sintered at 1073, 1173, and 1273 K showed a single phase of LiNi0.5Mn0.5O2. The I (003)/I (104) intensity ratio of Bragg peak, which is an index of the degree of disordering of Li and Ni, increased with increasing sintering temperature. The disordering of Li and Ni in the layered NaCl-type structure occurred with increasing sintering temperature. Fig. 1 shows the charge-discharge measurement results of Ox-ASSB using LNMO (x=1/2) sintered at 1173 K. Followed by a single phasic reaction, a plateau is observed around 3.9 V, the discharge capacities are 175 mAhg-1 at the end-of-charge voltage of 3.6 V and more than 250 mAhg-1 at 4.0 V. Compared to conventional LiB using a liquid electrolyte, this LNMO shows a higher specific capacity, suggesting a possibility to have stable charge-discharge behaviors with LGVO solid electrolyte. These results will be discussed based on the analysis of the cell resistance and the chemical bonding states by XPS measurements before and after charging and discharging. We will present results of other Li-rich positive electrodes in Ox-ASSBs while focusing on a role of oxide ions during and charging-discharging. Figure 1

As a new type of Lithium-ion batteries technology, all-solid-state Lithium-ion battery is regarded as one of the cutting-edge directions for new-generation battery technology. The biggest challenge of solid-state Li battery technology is that interface compatibility and stability problems must be solved urgently. In this paper, we specialize in the overall design of solid electrolyte interfacial compatibility and study the interfacial compatibility and stability by calculating the interfacial region interactions, charge transfer, adhesion energy, adsorption energy, interface formation energy, diffusion barrier, and density of states changes through the first nature principle. We conclude that LLZO solid-state electrolytes exhibit excellent interfacial properties, and interfacial compatibility and stability are further improved after doping. This paper shows a theoretical framework for exploiting novel electrolyte materials in all-solid-state battery.

Rapid electric vehicle adoption has elevated battery safety and high energy density from desirable attributes to core requirements, bringing all-solid-state batteries (ASSBs) employing sulfide solid electrolytes (SEs) to the forefront as credible next-generation candidates. Yet, in practice, the composite cathode remains the principal bottleneck. In Ni-rich high-capacity cathode active materials (CAMs) paired with sulfide SEs, parasitic interfacial reactions and contact degradation during charge–discharge are recognized sources of performance loss. In addition, the spatial distribution and percolation characteristics of CAM and SE complicate the ionic and electronic pathways, hindering uniform electrochemical reactions throughout the electrode. These issues are exacerbated in thick electrodes, where ionic transport resistance, electronic transport resistance, and contact resistance—collectively termed “electrode resistance”—become markedly larger than in conventional lithium-ion batteries. In impedance measurements, the electrode resistance contribution rarely manifests as an isolated feature; instead, it overlaps with signals arising from interfacial processes, including charge-transfer resistance (R ct ) and film resistance (R film ), thereby complicating mechanistic interpretation. The thicker the electrode, the stronger this overlap becomes, and the more uncertain the assignment of spectral features to purely interfacial or purely transport origins. Despite this reality, prior studies have largely emphasized half-cell-based impedance analyses focused on interfacial reaction resistances. Under conditions where electrode resistance and interfacial resistance coexist and co-evolve, such a narrow focus limits the reliability of impedance interpretation and can lead to ambiguous or even misleading conclusions. To enable trustworthy assessment of interfacial behavior in ASSBs and to guide high-energy designs, it is therefore essential to systematically separate and quantify electrode resistance components from genuine interfacial contributions, and to clarify their relative weights under practically relevant electrode conditions. In this study, we investigate the impedance of composite ASSB cathodes with the goal of improving the reliability of interpretation by explicitly decoupling electrode and interface contributions. Using electrochemical impedance spectroscopy (EIS) coupled with Distribution of Relaxation Times (DRT) analysis on composite-cathode half cells, we examine how the impedance response varies with state of charge (SoC) and areal loading—the latter determining electrode thickness. By scanning SoC and areal loading in a systematic manner, we construct a frequency-resolved picture in which processes can be separated by their SoC sensitivity and their evolution with thickness. This approach enables identification of distinct features associated with electrode resistance, charge transfer at the CAM/SE interface, and the formation of interfacial films that arise during cycling. Across SoC and areal-loading conditions, three dominant DRT peaks emerge, labeled P1, P2, and P3. P1 remains essentially invariant with SoC and occupies the high-frequency region of the spectrum, indicating an origin in electrode resistance that reflects through-plane ionic/electronic pathways and contacts within the composite network. P2 exhibits a U-shaped dependence on SoC, with larger values at Li-poor and Li-rich extremes and a minimum at intermediate states, a hallmark of R ct governed by composition-dependent kinetics at the CAM/SE interface. P3 gradually stabilizes as cycling proceeds, consistent with the growth and subsequent stabilization of a cathode–electrolyte interphase (CEI) that contributes a film-resistance component. The concurrent presence of these features explains why interfacial analysis alone can be unreliable in thick electrodes: as electrode resistance rises, its high-frequency signature can extend into the mid-frequency range and partially obscure or distort interfacial signals. Areal-loading-dependent measurements further reveal a critical loading that separates two regimes of behavior. Below this threshold, increasing electrode thickness leads to a pronounced growth in P1, reflecting the amplification of electrode resistance with extended transport pathways. In the same regime, P2 and P3 decrease with increasing areal loading, a trend attributed to the effective increase in electrochemically active area and improvements in local CAM–SE contact as the composite volume increases. Above the critical loading, however, spectral separation deteriorates: signals associated with electrode resistance and R ct begin to overlap. Taken together, these results quantitatively map how electrode and interfacial resistances contribute to the overall impedance as a function of areal loading and SoC. They show that electrode resistance can significantly bias the mid- and low-frequency response and thereby distort conclusions about interfacial reactions if it is not first isolated and properly accounted for in the analysis. On this basis, we advocate an analysis sequence in which high-frequency features associated with electrode resistance are identified and considered before interpreting the mid- and low-frequency regime associated with R ct and CEI-related film resistance. The study strengthens the foundation for accurate interfacial analysis in thick ASSB electrodes and supports rational strategies for energy-density enhancement and performance optimization.

Sulfide all‐solid‐state battery (SASSB) with ultrahigh‐nickel layered oxide cathode (LiNixCoyMn1‐x‐yO2, NCM, x ≥ 0.9) offers the potential of high energy density and safety for superior energy storage systems. However, stable cycling is difficult to realize due to adverse interfacial reactions, space charge layer (SCL), and elemental diffusion. Herein, a straightforward solid‐phase coating strategy is exploited to synthesize Ni90‐S cathode, which greatly improves the charge transmission capability of the composite cathode and suppresses interfacial reactions in SASSB. The consequent SC‐Ni90‐0.2%S/Li6PS5Cl/Li4Ti5O12 SASSB exhibits enhanced electrochemical performance, including a long life of 500 cycles with 87% capacity retention at 1C, high areal capacity of 11.44 mAh cm−2, and excellent rate performance at 20 C. These results promise an efficient strategy for designing cathode materials for SASSBs.

As all-solid-state batteries (SSBs) develop as an alternative to traditional cells, a thorough theoretical understanding of driving forces behind battery operation is needed. We present a fully first-principles-informed model of potential profiles in SSBs and apply the model to the Li/LiPON/Li_{x}CoO_{2} system. The model predicts interfacial potential drops driven by both electron transfer and Li^{+} space-charge layers that vary with the SSB's state of charge. The results suggest a lower electronic ionization potential in the solid electrolyte favors Li^{+} transport, leading to higher discharge power.

All‐solid‐state lithium batteries (ASSLBs) can overcome many problems in cathode and lithium anode, and it is a very promising safe secondary battery. However, unstable interface problems between electrolyte and electrode and within the electrolyte still restrict its commercial development. Herein, the interface problems are first revealed in ASSLBs and highlight the need to deeply explore the intrinsic failure mechanisms to solve these problems. Subsequently, the three failure mechanisms of ASSLBs: chemical, electrical, and electrochemical failure are broken down, and focus on the impact of the space charge layer problem on the cathode‐electrolyte interface. The effect of the anode physical contact problem on the anode‐electrolyte interface is discussed. Then, recent advances in ASSLBs, cathode and anode interface optimization strategies, and their corresponding electrochemical properties are discussed. Finally, the interface challenges faced by ASSLBs and feasible interface modification strategies are summarized, which provide references for subsequent studies and insights into the design of interface structures for the new generation of high‐performance ASSLBs.

Nickel-rich layered oxide with high reversible capacity and high working potentials is a prevailing cathode for high-energy-density all-solid-state lithium batteries (ASSLBs). However, compared to the liquid battery system, ASSLBs suffer from poor Li-ion migration kinetics, severe side reactions, and undesired formation of space charge layers, which result in restricted capacity release and limited rate capability. In this work, we reveal that the capacity loss lies in the H2-H3 phase transition period, and we propose that the inconsistent interfacial Li-ion migration is the arch-criminal. We introduce Si doping to stabilize the bulk structure and Li4SiO4 fast ionic conductor coating to regulate the interfacial behaviors between the Ni-rich cathode and sulfide-based solid electrolyte Li6PS5Cl. The modified NCM@LSO-2||LPSCl||Li-In ASSLBs deliver a high reversible capacity of 183.5 mA h g-1 at 0.1C, 30.3% higher than the bare NCM811 electrode. Besides, the interfacial regulation strategy enables the operation at a high rate of 5.0C and achieves a high capacity retention ratio of ∼85.8% after 500 cycles at 1.0C. Furthermore, the underlying mechanisms are well investigated through kinetic analyses and theoretical simulations. This work provides an in-depth understanding on the interfacial degradations between Ni-rich cathodes and sulfide-based all-solid-state electrolytes from the view of kinetic limitations and offers potential solutions.

Abstract It is still unclear which role space charge layers (SCLs) play within an all‐solid‐state battery during operation with high current densities, as well as to which extent they form. Herein, we use a solid electrolyte with a known SCL formation and investigate it in a symmetric cell under non‐blocking conditions with Li metal electrodes. Since the used LICGC™ electrolyte is known for its instability against lithium, it is protected from rapid degradation by nanometer‐thin layers of TiOx deployed by atomic layer deposition. Close attention is given to the interfacial properties, as now additional Li+ can traverse through the interface depending on the applied bias potential. The interlayer‘s impedance response shows efficient lithium‐ion conduction for low bias potentials and a diffusion‐limiting effect towards high positive and negative potentials. SCLs grow up to a thickness of 5.1 μm. Additionally, estimating the apparent rate constant of the charge transfer across the interface indicates that the potentials where kinetics are hindered coincide with the widest SCLs. In conclusion, the investigation under higher steady‐state currents was only possible because of the improved stability due to the interlayer. No chemo‐physical failure could be observed after 800+ hours of cycling. However, an ex‐situ SEM study shows a new phase at the interface, which grows into the electrolyte.

In this study, we fabricated a Li-metal all-solid-state battery (ASSB) with a low mass loading of NMC111 cathode electrode, enabling a sensitive evaluation of interfacial electrochemical reactions and their impact on battery performance, using Li1.3Al0.3Ti1.7(PO4)3 (LATP) as the solid electrolyte. The electrochemical behavior of the battery was analyzed to understand how the solid electrolyte influences charge storage mechanisms and Li-ion transport at the electrolyte/electrode interface. Cyclic voltammetry (CV) measurements revealed the b-values of 0.76 and 0.58, indicating asymmetry in the charge storage process. A diffusion coefficient of 1.5 × 10−9 cm2⋅s−1 (oxidation) was significantly lower compared to Li-NMC111 batteries with liquid electrolytes, 1.6 × 10−8cm2⋅s−1 (oxidation), suggesting that the asymmetric charge storage mechanisms are closely linked to reduced ionic transport and increased interfacial resistance in the solid electrolyte. This reduced Li-ion diffusivity, along with the formation of space charge layers at the electrode/electrolyte interface, contributes to the observed asymmetry in charge and discharge processes and limits the rate capability of the solid-state battery, particularly at high charging rates, compared to its liquid electrolyte counterpart.

Solid electrolyte materials have improved the safety and stability of quasi‐solid‐state lithium‐ion batteries, making them highly desirable. Through mesoporous confinement regulation of anodic aluminum oxide (AAO) membranes and optimization of lithium bis (trifluoromethanesulfonyl) imide (LiTFSI) concentration, a low‐crystallinity polyethylene oxide (PEO) based solid electrolyte membrane, 18PEO/LiTFSI‐160, was prepared. This electrolyte shows that when the molar ratio of ethylene oxide to lithium ion (EO: Li) is 18 and the AAO pore size is 160–200 nm, the electrolyte membrane exhibits a crystallinity as low as 13%, a room‐temperature ionic conductivity of 9.78 × 10−5 S cm−1, a Li+ transference number increased to 0.4, and an electrochemical window broadened to 5.1 V. In Li/Li symmetric cell tests, the interfacial impedance remained stable at 180 Ω after 160 h of cycling, with a smooth interface and no dendrite formation observed. Full‐cell performance tests further verified the optimization effects: the cell assembled with LiFePO4 delivered a discharge capacity of 142 mAh/g at a 0.1 C rate and retained 95% of its capacity after 100 cycles. The 18PEO/LiTFSI‐160 solid polymer electrolyte demonstrates promising performance and is a viable material for all‐solid‐state lithium metal secondary batteries. The AAO membrane plays a crucial role in enhancing its performance.

The application of solid-state electrolytes (SSEs) is anticipated to enhance the safety performance of lithium metal batteries (LMBs). However, the progress of SSEs has been hindered by the unstable electrode-electrolyte interfaces (EEIs). In this study, in-situ polymerization of 1,3-dioxolane (DOL) is employed for the preparation of SSEs, with the addition of tributyl borate (TBB) to establish stable EEIs, particularly under high-voltage conditions. On one hand, the addition of TBB promotes the dissociation of lithium salts and increases the concentration of free Li+, resulting in an increase in room temperature ionic conductivity to 1.13 × 10-4 S cm-1 and an improvement in the Li+ transference number to 0.69 for the prepared poly-DOL electrolytes (PDE-TBB). Benefiting from the enhanced Li+ transport, the Li/PDE-TBB/Li symmetric cell exhibits a cycle life exceeding 1,000 h with a low polarization voltage as low as 12 mV, and the Li/PDE-TBB/LiFePO4 cell demonstrates exceptional cyclic stability over 800 cycles at 1C, with a coulombic efficiency exceeding 99.8 % and a capacity retention of 89.6 %. On the other hand, PDE-TBB exhibits improved stability under high-voltage conditions and the capacity to establish robust boron-rich cathode electrolyte interphase (CEI) on the LiNi0.8Co0.1Mn0.1O2 (NCM811) surface, thereby enhancing the structural stability of cathode materials and ensuring exceptional cycling performance of Li/PDE-TBB/NCM811cell. This work presents a promising strategy for developing novel ether-based SSEs suitable for high-voltage lithium metal batteries.

The kinetics of the electrochemically driven lithium ion (Li+) transfer from a liquid Li+ electrolyte to a solid (ceramic) Li+ electrolyte is investigated. A DC polarisation is applied to measure the current density i vs. the drop in the electrochemical potential ΔLi+ of Li+ ions at the interface. LLZO:Ta and LATP were chosen in this study as the two most promising oxide-ceramic electrolytes and combined with LiPF6 in EC/DMC (1 : 1) and LiBOB in THF/DME (1 : 1) as the most relevant liquid electrolytes. To determine the rate-limiting step of the Li+ transfer across the interface, the results were modelled using a combination of a constant ohmic resistance and a current-dependent, thermally activated Butler-Volmer-like ion transfer process. At low Li+ concentrations in the liquid electrolyte, the Butler-Volmer-like transfer process is rate limiting, while at high Li+ concentrations, the low-conductive surface layer on the solid electrolyte is rate limiting. The areal resistance of the low-conductivity surface layer is in the order of 600 Ω cm2 (25 °C) for LLZO:Ta, and thus about three times higher compared to that for LATP. The activation energy of the ionic transport in the low-conductivity surface layer is about twice that of the solid electrolytes LLZO:Ta and LATP. The exchange current density of the Butler-Volmer-like transfer process is in the order of 100-300 μA cm-2 (25 °C, 1 mol l-1 Li+). There is a symmetric transition state (α ≈ 1/2).

The prediction of electrochemical performance is the basis for long-term service of all-solid-state-battery (ASSB) regarding the time-aging of solid polymer electrolytes. To get insight into the influence mechanism of electrolyte aging on cell fading, we have established a continuum model for quantitatively analyzing the capacity evolution of the lithium battery during the time-aging process. The simulations have unveiled the phenomenon of electrolyte-aging-induced capacity degradation. The effects of discharge rate, operating temperature, and lithium-salt concentration in the electrolyte, as well as the electrolyte thickness, have also been explored in detail. The results have shown that capacity loss of ASSB is controlled by the decrease in the contact area of the electrolyte/electrode interface at the initial aging stage and is subsequently dominated by the mobilities of lithium-ion across the aging electrolyte. Moreover, reducing the discharge rate or increasing the operating temperature can weaken this cell deterioration. Besides, the thinner electrolyte film with acceptable lithium salt content benefits the durability of the ASSB. It has also been found that the negative effect of the aging electrolytes can be relieved if the electrolyte conductivity is kept being above a critical value under the storage and using conditions.

The demand for high-energy-density and fast-charging solid-state lithium metal batteries (SSLMBs) often subjects practical devices to internal thermal loads, making high-temperature operation a common operational condition rather than an isolated scenario. To address the interfacial degradation and dendrite growth accelerated by such thermomechanical stresses, we developed a composite gel electrolyte (CGE) by incorporating an optimal concentration of active Li6.4La3Zr1.4Ta0.6O12 (LLZTO) into a fluoropolymer network. The abundant Lewis acidic sites on the LLZTO surfaces promote competitive solvation decoupling by interacting with anions, thereby modulating the primary solvation sheath of Li+. This localized modulation lowers the lithium-ion migration activation energy to 0.248 eV and facilitates a dual-interfacial passivation mechanism. Specifically, a rigid, inorganic-rich solid electrolyte interphase (SEI) forms to suppress morphological instability at the lithium anode, while an organic-dominated cathode electrolyte interphase (CEI) enhances the oxidative stability up to 4.3 V. As a result, symmetric cells demonstrate stable electrodeposition for over 450 h at 80 °C and 0.5 mA cm−2. Furthermore, NCM811/Li full cells utilizing this CGEs exhibit significantly improved thermal resilience and cycling stability.

The spatial distribution of charge carriers in lithium ion batteries during current flow is of fundamental interest for a detailed understanding of transport properties and the development of strategies for future improvements of the electrolyte-electrode interface behaviour. In this work we explored the potential of (7)Li 1D in situ NMR imaging for the identification of concentration gradients under constant current load in a battery cell. An electrochemical cell based on PTFE body and a stack of glass microfiber discs that are soaked with a technically relevant electrolyte suitable for high-temperature application and squeezed between a Li metal and a nano-Si-graphite composite electrode was assembled to acquire (7)Li 1D in situ NMR profiles with an improved NMR pulse sequence as function of time and state of charge, thereby visualizing the course of ion concentration during charge and discharge. Surface localized changes of Li concentration were attributed to processes such as solid electrolyte interphase formation or full lithiation of the composite electrode. The method allows the extraction of lithium ion transport properties.

No abstract available

The quality of Li–solid electrolyte interface is crucial for the performance of solid-state lithium metal batteries, particularly at low stack pressure, but its dynamics during cell operation remain poorly understood due to a lack of reliable operando characterization techniques. Here, we report the evolution of Li–electrolyte interface with high spatial resolution using operando scanning electron microscopy under realistic operating conditions. By tracking the stripping process of both Li and Li-rich Li-Mg alloy anodes, we show that multiple voids coalesce into a single gap and eventually delaminate the interface in Li, whereas the voids split and collapse to partially recover interfacial contact in Li-Mg. Density functional theory calculations show that the stronger Mg-S interaction at the metal–electrolyte interface attracts Mg toward the interface and repels Li-vacancies into the bulk, resulting in a reduced number of voids. The pressure-dependent voltage profiles of Li and Li-Mg stripping suggest that loss of contact due to void formation, rather than Mg accumulation at the interface, is the origin of high overpotential that limits the utilization of metal anodes. Improved interfacial contact enables stable cycling of all-solid-state lithium full cell at low stack pressure (1 MPa) and moderate rate (2 mA cm−2) simultaneously. The real-time visualization of Li–electrolyte interface dynamics provides critical insights into the rational design of solid-state battery interfaces. The quality of the Li–electrolyte interface is key to solid-state battery performance, especially at low pressure. Here, authors use operando electron microscopy to reveal how Li-Mg alloy anodes improve interfacial contact and low-pressure cycling stability by suppressing void formation.

All‐solid‐state lithium batteries (ASSLBs) are considered a promising technology for next‐generation energy storage systems due to their inherent safety. However, the conventional laboratory‐scale ASSLBs reported to date are based on pellet‐type structures with thick solid electrolyte layers, leading to challenges related to low energy densities and poor electrochemical performance. In this study, porous adhesive poly(ethylene vinyl acetate) (PEVA) scaffolds and polytetrafluoroethylene (PTFE) binders are utilized to interweave sulfide solid electrolytes into freestanding films with an ultra‐low thickness of 40 µm, high ionic conductivity of 1.1 mS cm−1, and a high tensile strength of 74 MPa. To mitigate the reduction reaction between the PTFE binder and the lithium metal anode, a Li3N‐rich solid electrolyte interphase (SEI) in situ on lithium metal is formed, and the assembled symmetric cell shows excellent cycling stability within 800 h at the current density of 0.2 mA cm−2 and room temperature. Additionally, the ASSLBs using oxidatively stable Li2ZrCl5F in the composite cathode and the prepared solid electrolyte film demonstrate exceptional cycling performance and fast‐charging capability, with a high cell‐level energy density of 354.4 Wh kg−1. The ASSLBs prepared by coupling E‐LPSCl film and stable interface design exhibit excellent electrochemical performance and a high cell‐level energy density.

Benefiting from the significantly improved energy density and safety, all-solid-state lithium batteries (ASSLBs) are considered to be one of the most promising next-generation energy technologies. Their practical applications, however, are strongly impeded by Li dendrite formation. Despite this recognized challenge, a comprehensive understanding of the Li dendrite nucleation and formation mechanism remains elusive. In particular, the initial locations of Li dendrite formation are still ambiguous: do Li clusters form directly at the Li anode surface, inside the bulk solid electrolyte (SE), or within the solid-electrolyte interphase (SEI)? Here, based on the deep-potential molecular dynamics simulations combined with enhanced sampling techniques, we investigate the atomic-level mechanism of Li cluster nucleation and formation at the Li anode/SE interface. We observe that an isolated Li cluster initially forms inside the SEI between the Li6PS5Cl SE and the Li metal anode, located ∼1 nm away from the Li anode/SEI boundary. The local electronic structure of the spontaneously formed SEI is found to be a key factor enabling the Li cluster formation within the SEI, in which a significantly decreased band gap could facilitate electronic conduction through the SEI and reduce Li+ ions to metallic Li atoms therein. Our work provides atomic-level insights into Li-dendrite nucleation at anode/SE interfaces in ASSLBs and could guide future design for developing Li-dendrite-inhibiting strategies.

Thermal transport across cathode–electrolyte stacks critically affects temperature rise and thermal safety in all-solid-state lithium-ion batteries, but quantitative benchmarks for Li(Ni,Mn,Co)O2 (NMC)/Li7La3Zr2O12 (LLZO) remain scarce. Here, we perform nonequilibrium molecular dynamics simulations to evaluate the lattice thermal conductivity of layered NMC with varying transition-metal ratios and random cation distributions, compare representative NMC polymorphs (R3m, C2/m, and Fm-3m), and quantify grain-boundary as well as NMC/LLZO interfacial thermal resistance. At 300 K, the thermal conductivity of NMC ranges from 1.3 to 7.5 W·m−1·K−1 depending on composition and phase, whereas tetragonal LLZO and cubic doped LLZO exhibit weak temperature dependence, ∼1.3–1.5 W·m−1·K−1. Layered NMC phases are strongly anisotropic, while the rock-salt phase is nearly isotropic. The interfacial thermal resistance between different NMC phases is 1.3–17.6 × 10−11 m2·K·W−1, and the NMC/LLZO interfacial resistance is ∼3.05 × 10−10 m2·K·W−1. Analysis of the overlap of phonon density-of-states indicates that improved vibrational matching reduces the interfacial resistance. These results provide atomistic inputs for continuum thermal models and guide interface engineering for solid-state batteries.

The speculation concerning the presence of interfacial states in the BaTiO3‐based positive temperature coefficient of resistance (PTCR) model originating from the formation of the grain boundary barrier in semiconductor is argued to be unsuitable. This communication provides new insights into the formation of the grain boundary barrier without the grain boundary phase of the BaTiO3‐based PTCR model. New insights into the temperature and voltage dependences of the resistance or resistivity with and without grain boundary phase of the BaTiO3‐based PTCR model are proposed. Concerning the absence of the grain boundary phase, two new plausible models are proposed: the net dipolar polarization field due to the applied voltage and effective permittivity owing to the net dipole charges accumulated near the grain boundary. As for the presence of the grain boundary phase, a new thinking concerning the field emission tunneling with the conduction band conduction mechanism for the occurrence of low resistance at low applied voltage is posited.

This study investigates the electrical properties of piezomagnetic Ni0.5Co0.5Fe2O4 nanoparticles (NPs), emphasizing the effects of magnetic fields and temperature. Ni0.5Co0.5Fe2O4 NPs were synthesized using the chemical pyrophoric reaction method, yielding nanocrystalline powders confirmed through XRD, field emission scanning electron microscopy (FE‐SEM), and energy‐dispersive X‐ray (EDX) analyses. Alternating current (AC) and direct current (DC) electrical measurements reveal significant nonlinear current–voltage behavior influenced by oxygen vacancies, interfacial polarization, and magnetic domain alignment. The application of applied magnetic field enhances electrical conductivity, increasing the magnetocurrent percentage up to 526%, while the temperature variations reveal a metal‐to‐insulator transition. Dielectric studies indicate a strong dependence of dielectric constant and dielectric loss on frequency and applied magnetic field. At low frequencies, the dielectric constant is significantly high due to space charge polarization, which diminishes at higher frequencies as polarization mechanisms lag. The application of a magnetic field increases the dielectric constant, with magnetodielectric and magnetoloss effects reaching up to 27% and 10%, respectively. Impedance spectroscopy further elucidates the interplay between grain and grain boundary conduction mechanisms, with resistance decreasing and capacitance increasing under an applied magnetic field. Temperature‐dependent measurements reveal a peak in impedance near 323 K, corresponding to a phase transition, with a shift in impedance peaks to higher frequencies as temperature rises due to enhanced charge carrier mobility. The findings underscore the dynamic interplay of magnetic, electrical, and thermal properties in Ni0.5Co0.5Fe2O4 NPs, demonstrating their potential for advanced applications. This comprehensive analysis provides insights into the behavior of magnetic nanomaterials under varying environmental conditions, paving the way for innovative materials with multifunctional properties.

Introduction All-solid-state sodium batteries (ASSSBs) have attracted large attentions as one of the alternatives to lithium-ion batteries from the viewpoint of the relative abundance and low cost of sodium and safety. Oxide-based inorganic solid electrolytes have been proposed as a promising candidate among various solid electrolytes because of their high ionic conductivity and electrochemical stability, but their hardness causes increased charge transfer resistance at the interface between electrode and solid electrolyte. A major key to the practical application of ASSSBs is to enhance the interfacial contact between active materials and electrolytes. In contrast, polymer electrolytes are relatively soft and easy to contact at the interface, although their ionic conductivity is inferior. Therefore, composite electrolytes that appropriately mix inorganic solid electrolytes and polymer electrolytes have been proposed, and many studies have been conducted, but the ionic conduction paths are so complex that there is no clarity regarding the effect of the polymer electrolyte on the resistance at the interface. In this study, we introduced a softer polymer electrolyte than inorganic solid materials between Na3V2(PO4)3 positive electrode / Na-β"-Al2O3 solid electrolyte to reduce the interfacial resistance by the enhancement of the solid | solid contact. This allows a detailed analysis of the resistive components of composite electrolyte systems with complex ionic conduction paths. Experimental Na3V2(PO4)3 (NVP), which has been reported to exhibit sodium-ion insertion/de-insertion at relatively high 3.4 V (vs. Na+/Na) when used with liquid electrolyte and good cycle characteristics, was used as the positive electrode material. [1] Acetylene black was added as conductive material and polyvinylidene fluoride (PVdF) as binder to form composite electrode. The polymer electrolyte was prepared as the dry polymer film by casting an acetonitrile solution containing sodium bis(fluorosulfonyl)amide (NaFSA) and polyethylene oxide (PEO), followed by completely volatilizing the solvent. [2] The polymer electrolyte membrane was introduced between the oxide solid electrolyte Na-β"-Al2O3 and positive electrode, and Na metal was used as a negative electrode to construct a two-electrode cell. Electrochemical impedance spectroscopy (EIS) was performed with an AC amplitude of 10 mV in a frequency range of 1.0 MHz–10 mHz, after constant current charge-discharge measurements (measurement temperature: 50°C, current density: 5.9 mA g−1, voltage range: 2.7~3.7 V) to investigate the effect of the polymer electrolyte membrane on the junction interface between positive electrode and solid electrolyte. Results and discussions The charge-discharge curves without and with PEO dry polymer electrolyte membrane are shown in Fig. 1(a)(b), respectively. The reversible reaction did not occur in the cell without the polymer electrolyte, whereas a reversible capacity of more than 70 mAh g−1 with a coulombic efficiency of more than 99% was obtained in the cell with the polymer electrolyte. The Nyquist plots of the potential dependence are shown in Fig. 1(c)(d). In the cell without polymer electrolyte, the very large semicircle with potential dependence is observed. Since the bulk and grain boundary resistance of Na-β"-Al2O3 and the charge transfer resistance at Na-β"-Al2O3 / Na interface was very small, this semicircular component was attributed to the charge transfer resistance at Na-β"-Al2O3 / NVP interface. This result suggests that the frequency factor is very small because Na-β"-Al2O3 / NVP interface is the solid | solid contact. On the other hand, in the cell with polymer electrolyte, the overall resistance is greatly reduced. The main components of the semicircles observed in the high frequency up to 5 kHz, the medium frequency from 5 kHz to 1 Hz, and the low frequency region from 1 Hz were attributed to the bulk resistance of the polymer electrolyte, the ion transfer resistance at the polymer electrolyte / Na-β"-Al2O3 interface, and the charge transfer resistance at the polymer electrolyte / NVP interface, respectively. The results suggest that the introduction of the polymer electrolyte increases the frequency factor by the enhancement of the solid | solid contact at Na-β"-Al2O3 / NVP composite electrode junction interface. Conclusion The effect of polymer electrolytes on Na3V2(PO4)3 positive electrode / Na-β"-Al2O3 junction interface of ASSSBs was investigated. In a composite electrolyte system with complex ionic conduction paths, the introduction of a polymer electrolyte as a membrane allows us to analyze the effect of the polymer electrolyte on the junction interface. References [1] Zelang Jian, Liang Zhao, Huilin Pan, Yong-Sheng Hu, Hong Li, Wen Chen, Liquan Chen, Electrochem. Commun. 14 (2012) 86-89. [2] Xingguo Qi, Qiang Ma, Lilu Liu, Yong-Sheng Hu, Hong Li, Zhibin Zhou, Xuejie Huang, and Liquan Chen, ChemElectroChem 3 (2016) 1741-1745. Figure 1

Solid-state batteries based on lithium-stuffed oxides ceramics promise to improve the safety and energy density over current commercial batteries. Li7La3Zr2O12 (LLZO) is one of the most promising of these solid electrolytes as it has high ionic conductivity and low reactivity with Li metal. The major challenge of this material is its high interfacial resistance with commonly used cathodes such as LiCoO2 (LCO) and particularly Li2NixMnyCozO2 (NMC) due to the solid-solid nature of the contact and the thermochemical instability of these materials when mixed at high temperatures. This work experimentally elucidates the nature of the thermochemical instability between LLZO and NMC by providing experimental validation of computational work performed by collaborators and exploring various parameters such as sintering atmosphere, Li content, and processing temperature. Improving our understanding of these two compounds in sintering environments will allow for minimizing the interfacial resistance between LLZO and NMC to provide a pathway for producing a solid-state ceramic Li metal battery that can achieve theoretical capacities at commercially applicable charge rates at room temperature. Preliminary results have already determined several trends in NMC/LLZO thermochemical instability. XRD and TGA/DSC results have shown a heavy dependence on the composition of NMC used. Namely, the higher the nickel content of the NMC, the more it will react with LLZO at high temperature. However, the theoretical capacity of NMC increases with increasing nickel content such that NMC622 appears to be the optimal composition because of its higher theoretical capacity compared to NMC111 while reacting less than NMC811. The atmosphere during sintering has been shown to also be important with pure O2 gas providing better stability at temperatures above 1000°C compared to argon gas. Furthermore, increasing the Li concentration in the LLZO has been shown to increase the decomposition reaction of NMC and LLZO, leading to the formation of new phases.

A major dilemma faced by Zn anodes at high zinc utilization rate (ZUR) is the insufficient supply of ionic carriers that initiate the space charge layer (SCL) subject to rampant growth of Zn dendrites. Herein, an 'anion-cation co-regulation' strategy, associated with a fundamental principle for screening potential electrolyte additives coupling the Zn2+ ferrying effect with anion-retention capability, are put forward to construct dendrite-free, high-ZUR Zn anode. Taking ninhydrin-modified ZnSO4 system as a proof-of-concept, the multiple zincophilic polar groups of ninhydrin facilitate the transport of Zn2+ ions while its electron-deficient aromatic ring retains SO42- counterions via anion-π interaction, constructing an ion-rich interface that minimizes the SCL-driven Zn deterioration. Consequently, the Zn anode can endure ~240 h continuous cycling at an ultrahigh ZUR of 87.3%. The superiority brought by ninhydrin is further reflected by the ultralong cycling durability of Zn-I2 batteries (over 100000 cycles at 10 A g-1, ~20-fold lifespan extension). Even at an ultralow N/P ratio of 1.1 (~90.6% ZUR), the battery with a capacity of ~5.27 mAh cm-2 can still sustain for 350 cycles, which has been hardly achieved in aqueous Zn batteries. Furthermore, the effectiveness of this strategy is fully validated by a series of additives sharing similar fundamentals.

The increasing demand for energy in portable electronics and electric vehicles has highlighted the necessity for lithium‐ion batteries that offer high energy density, safety, and long cycle life. To address this challenge, this study introduces a novel gel polymer electrolyte (GPE) based on a poly(vinylidene fluoride‐co‐hexafluoropropylene)‐perfluoropolyether methacrylate (PH‐PFPE) 3D network structure, integrated with lithium oxide (Li₂O) fillers that form a space charge layer (SCL). Lithium metal batteries (LMBs) utilizing this new gel electrolyte demonstrate exceptional rate performance across a broad current density range (0.2 to 4 C) and retain 95.64% of their capacity after 1500 cycles at 3 C. This paper provides a comprehensive analysis of the microstructure and interfacial properties of both the electrode materials and gel electrolytes. Furthermore, molecular dynamics simulations reveal the molecular‐level synergistic effect between the polymer and fillers, which significantly enhances lithium‐ion transport.

The space charge layer (SCL) dilemma, caused by mobile anion concentration gradient and the rapid consumption of cations, is the fundamental reason for the generation of zinc dendrites, especially under high‐rate discharge conditions. To address the issue, a physical (PbTiO3)/chemical (AMPS‐Zn) barrier is designed to construct stable zinc ion flow and disrupt the gradient of anion concentration by coupling the ferroelectric effect with tethered anion electrolyte. The ferroelectric materials PbTiO3 with extreme‐high piezoelectric constant can spontaneously generate an internal electric field to accelerate the movement of zinc ions, and the polyanionic polymer AMPS‐Zn can repel mobile anions and disrupt the anions concentration gradient by tethering anions. Through numerical simulations and analyses, it is discovered that a high Zn2+ transference number can effectively weaken the SCL, thus suppressing the occurrence of zinc dendrites and parasitic side reactions. Consequently, an asymmetric cell using the PbTiO3@Zn demonstrates a reversible plating/stripping performance for 2900 h, and an asymmetric cell reaches a state‐of‐the‐art runtime of 3450 h with a high average Coulombic efficiency of 99.98%. Furthermore, the PbTiO3@Zn/I2 battery demonstrated an impressive capacity retention rate of 84.0% over 65000 cycles by employing a slender Zn anode.

Space-charge layers are frequently believed responsible for the large resistance of different interfaces in all-solid-state Li batteries. However, such propositions are based on the presumed existence of a Li-deficient space-charge layer with insufficient charge carriers, instead of a comprehensive investigation on the atomic configuration and its ion transport behavior. Consequently, the real influence of space-charge layers remains elusive. Here, we clarify the role of space-charge layers in Li_0.33La_0.56TiO_3, a prototype solid electrolyte with large grain-boundary resistance, through a combined experimental and computational study at the atomic scale. In contrast to previous speculations, we do not observe the Li-deficient space-charge layers commonly believed to result in large resistance. Instead, the actual space-charge layers are Li-excess; accommodating the additional Li^+ at the 3c interstitials, such space-charge layers allow for rather efficient ion transport. With the space-charge layers excluded from the potential bottlenecks, we identify the Li-depleted grain-boundary cores as the major cause for the large grain-boundary resistance in Li_0.33La_0.56TiO_3. Space-charge layers are believed to profoundly influence the interfaces in all-solid-state Li batteries. Here, the authors provide atomic scale insights into this phenomenon, and discover that its impact could be fundamentally different from commonly believed.

No abstract available

The space charge layer (SCL) effects were initially developed to explain the anomalous conductivity enhancement in composite ionic conductors. They were further extended to qualitatively as well as quantitatively understand the interfacial phenomena in many other ionic-conducting systems. Especially in nanometre-scale systems, the SCL effects could be used to manipulate the conductivity and construct artificial conductors. Recently, existence of such effects either at the electrolyte/cathode interface or at the interfaces inside the composite electrode in all solid state lithium batteries (ASSLB) has attracted attention. Therefore, in this article, the principle of SCL on basis of defect chemistry is first presented. The SCL effects on the carrier transport and storage in typical conducting systems are reviewed. For ASSLB, the relevant effects reported so far are also reviewed. Finally, the perspective of interface engineer related to SCL in ASSLB is addressed.

MoS2 is widely reported as anode material for sodium‐ion batteries (SIBs). However, its ability to operate effectively across a wide temperature range and at high rates continues to pose fundamental challenges, limiting its further development. Herein, a monolayer Fe‐doped MoS2/N,O‐codoped C overlapping structure is designed and employed as an anode for wide‐temperature‐range SIBs. Fe doping imparts MoS2 electrode with zero bandgap characteristics, an increased interlayer spacing, and low sodium‐ion diffusion energy barriers across wide operation temperatures. Impressively, Fe atoms doped into the MoS2 lattice can be reduced to superparamagnetic Fe0 nanocrystals of ≈2 nm during conversion reactions. In situ magnetometry reveals that these Fe0 nanocrystals can be used as electron acceptor in the formation of space charge zones with Na+, thereby triggering strong spin‐polarized surface capacitance that facilitates fast sodium‐ion storage over a wide temperature range. Consequently, the designed MoS2 electrode demonstrates exceptional fast‐charging capability in half/full cells operating at −40–60 °C. This study provides novel perspectives on the utilization of heteroatom doping strategies in conversion‐type electrode material design and proves the effectiveness of spin‐polarized surface capacitance effect on enhancing sodium‐ion storage over a wide temperature range.

Uncontrolled transport of anions leads to many issues, including concentration polarization, excessive interface side reactions, and space charge‐induced lithium dendrites at the anode/electrolyte interface, which severely deteriorates the cycling stability of lithium metal batteries. Herein, an asymmetrical polymer electrolyte modified by a boron‐containing single‐ion conductor (LiPVAOB), is designed to inhibit the nonuniform aggregation of free anions in the vicinity of the lithium anode through the repulsion effect improving the lithium‐ion transference number to 0.63. This LiPVAOB exerts a repulsion interaction with free anions even at a long distance and a selective effect for free anions transport, which diminishes uneven aggregation of free anions at the interface and suppresses space charges‐induced lithium dendrites growth. Consequently, the assembled Li||Li cell delivers an ultra‐long cycle for over 5400 h. The Li||LiFePO4 cell exhibits outstanding cycle performance with a capacity retention of 93% over 4500 cycles. In particular, the assembled high‐voltage Li||Li1.2Ni0.2Mn0.6O2 cell (charged to 4.8 V) exhibits good cycle stability with a high specific capacity of 245 mAh g−1. This designed polymer electrolyte provides a promising strategy for regulating ion transport to inhibit space charge‐induced lithium dendrite growth for high‐performance lithium metal batteries.

When two different materials come into contact, mobile carriers redistribute at the interface according to their potential difference. Such a charge redistribution is also expected at the interface between electrodes and solid electrolytes. The redistributed ions significantly affect the ion conduction through the interface. Thus, it is essential to determine the actual distribution of the ionic carriers and their potential to improve ion conduction. We succeeded in visualizing the ionic and potential profiles in the charge redistribution layer, or space-charge layer (SCL), formed at the interface between a Cu electrode and Li-conductive solid electrolyte using phase-shifting electron holography and spatially resolved electron energy-loss spectroscopy. These electron microscopy techniques clearly showed the Li-ionic SCL, which dropped by 1.3 V within a distance of 10 nm from the interface. These techniques could contribute to the development of next-generation electrochemical devices.

Lithium metal deposition is strongly affected by the intrinsic properties of the solid-electrolyte interphase (SEI) and working electrolyte, but a relevant understanding is far from complete. Here, by employing multiple electrochemical techniques and the design of SEI and electrolyte, we elucidate the electrochemistry of Li deposition under mass transport control. It is discovered that SEIs with a lower Li ion transference number and/or conductivity induce a distinctive current transition even under moderate potentiostatic polarization, which is associated with the control regime transition of Li ion transport from the SEI to the electrolyte. Furthermore, our findings help reveal the creation of a space-charge layer at the electrode/SEI interface due to the involvement of the diffusion process of Li ions through the SEI, which promotes the formation of dendrite embryos that develop and eventually trigger SEI breakage and the control regime transition of Li ion transport. Our insight into the very initial dendritic growth mechanism offers a bridge toward design and control for superior SEIs.

For years, the space charge layer formation in Li-conducting solid electrolytes and its relevance to so-called all solid-state batteries have been controversially discussed from experimental and theoretical perspectives. In this work, we observe the phenomenon of space charge layer formation using impedance spectroscopy at different electrode polarizations. We analyze the properties of these space charge layers using a physical equivalent circuit describing the response of the solid electrolytes and solid/solid electrified interfaces under blocking conditions. The elements corresponding to the interfacial layers are identified and analyzed with different electrode metals and applied biases. The effective thickness of the space charge layer was calculated to be ∼60 nm at a bias potential of 1 V. In addition, it was possible to estimate the relative permittivity of the electrolytes, specific resistance of the space charge layer, and the effective thickness of the electric double layer (∼0.7 nm).

No abstract available

Heterogeneous interfaces exhibit the unique phenomena by the redistribution of charged species to equilibrate the chemical potentials. Despite recent studies on the electronic charge accumulation across chemically inert interfaces, the systematic research to investigate massive reconfiguration of charged ions has been limited in heterostructures with chemically reacting interfaces so far. Here, we demonstrate that a chemical potential mismatch controls oxygen ionic transport across TiO2/VO2 interfaces, and that this directional transport unprecedentedly stabilizes high-quality rutile TiO2 epitaxial films at the lowest temperature (≤ 150 °C) ever reported, at which rutile phase is difficult to be crystallized. Comprehensive characterizations reveal that this unconventional low-temperature epitaxy of rutile TiO2 phase is achieved by lowering the activation barrier by increasing the “effective” oxygen pressure through a facile ionic pathway from VO2-δ sacrificial templates. This discovery shows a robust control of defect-induced properties at oxide interfaces by the mismatch of thermodynamic driving force, and also suggests a strategy to overcome a kinetic barrier to phase stabilization at exceptionally low temperature. The research to utilize chemical potential mismatch for materials synthesis has been limited across the oxide interface. Here, the authors show that directional ionic transport from the VO2 layers stabilizes the rutile TiO2 phase at extremely low temperatures, at which epitaxy is difficult, by effectively lowering the activation barrier for crystallization.

Interfacial space charges significantly influence transport and recombination of charge carriers in optoelectronic devices. Due to the mixed ionic‐electronic conducting properties of halide perovskites, not only electronic effects, but also ionic interactions at their interfaces need to be considered in the analysis of space charges. Understanding of these interactions and their control is currently missing. This study elucidates the ionic effects on space charge formation at the interface between methylammonium lead iodide (MAPI) and alumina, and its modulation through surface modification using organic molecules. Embedding insulating alumina nanoparticles within MAPI films leads to enhancement of the electronic conductivity. This effect is consistent with the formation of an interfacial inversion layer in MAPI and can only be explained on the basis of ionic interactions. Such an effect is attenuated by surface modification of the oxide via the chemisorption of organic molecules. Finally, the same trend is observed in solar cells, where reducing the potential of the distributed space charges within the composite active layer improves device performance. These findings emphasize the necessity of taking into account ionic interactions to control the space charge formation at interfaces involving mixed ionic‐electronic conductors, an essential aspect in the performance optimization of halide perovskite‐based devices.

The progress in the research of metal-ion batteries, including lithium-ion batteries and sodium-ion batteries, has accelerated the development of mobile electronics and electric vehicles. However, metal-ion batteries with liquid electrolytes are facing safety concerns associated with flammability, leakage, thermal runaway, and so forth. This has led to the development of all-solid-state batteries with solid state electrolytes. There are reports on the existence of a space-charge zone at the interface between electrode material and electrolyte and its effect on the charge accumulation in all-solid-state batteries. Most analyses of the electric field in the space charge zone are based on the Boltzmann distribution with electric potential as the state energy. In this talk, we present a multi-field model, taking into account the contributions of strain energy and electric energy to the Gibbs free energy for binary solid electrolyte with cations as mobile species, which can occupy interstitial sites. A nonlinear and coupling system is established for the field determination. Numerical results for a solid electrolyte sandwiched between two parallel electrodes reveal the presence of a space charge zone with a layer of charges adjacent to the electrodes. The size of the space charge zone is dependent on the thickness of the solid electrolyte. This work is supported by the NSF through the grant CBET-2438033 as part of the NSF-DFG Lead Agency Activity in Measurements of Interfacial Systems at Scale with In-situ and Operando Analysis (NSF-DFG MISSION initiative).

No abstract available

The current–voltage characteristics (IVCs) of anodic TiO2 films in a thin-film structure (Carbon paste/TiO2/Ti/Al) were investigated in the temperature range of T = 80–300 K with bias voltages from −0.5 V to +0.5 V. Anodic oxide film, with a thickness of 14 nm, was obtained by electrochemical oxidation of Ti at a voltage of 10 V. The obtained data for various temperatures showed that the IVCs in the forward (negative on the Ti electrode) and reverse (positive on the Ti electrode) bias of the thin film structure are not symmetrical. Based on the analysis, three temperature ranges (sections) were identified in which the IVCs differ in their behavior. Examination of the IVCs revealed that the conductivity mechanism in Section I (temperature range from 298 to 263 K) is determined by the Space Charge Limited Current (SCLC). Section II, in the temperature range from 243 to 203 K, is characterized by the onset of conductivity involving donor centers, in the case where the concentration of electrons on traps is significantly higher than the concentration of electrons in the conduction band. In Section III, within the temperature range from 183 to 90 K, the conduction mechanism is the Poole–Frenkel process involving donor centers. These donor centers are located below the level of traps in the forbidden band. The results obtained indicate that anodic TiO2 is an n-type semiconductor, in the bandgap of which there are both electron traps and donor centers formed by anionic (oxygen) vacancies. The different behavior of the characteristic energy with different sample biasing in the case of the Poole–Frenkel mechanism indicates a two-layer structure of anodic TiO2.

The interface between a solid electrolyte and an electrode plays an important role in determining the physical processes controlling the electrochemical performance of metal-ion batteries. In this work, we developed an electrochemical-mechanical model for the determination of net charge density, stress and electric fields in a solid electrolyte, which is in contact with an electrode, under the framework of thermodynamics and linear elasticity. Mobile species are cations, which occupy interstitial sites through the formation of Frenkel defects. Analytical solutions of net charge density, stress and electric fields are derived using the linear coupling model, which is a simplification of the nonlinear coupling system under low stress and electric fields. For a solid electrolyte sandwiched between two parallel electrodes, numerical results predict that there exists an accumulation/adsorption of a layer of charges (interstitial ions) onto the electrode, i.e., the presence of a space charge zone whose size is dependent on the electric potential and elastic constants of the solid electrolyte. Such behavior is similar to the Stern layer of a liquid electrolyte and allows for the storage of energy in a capacitive form, similar to an electrical double layer. The ratio of the nominal size of the space charge zone to the thickness of a solid electrolyte decreases as the thickness of the solid electrolyte increases. The nonlinear and coupling system developed in this work lays a foundation to analyze the interface behavior of heterogeneous structures and the effects of the space charge zone on the energy storage of multilayer structures. The approach presented in this work can be extended to investigate the multi-field coupling problems in solid oxide fuel cells, mixed halide quantum dots and transducers.

No abstract available

No abstract available

Solid electrolyte is a key component to high temperature solid oxide cells, ensuring gas-tight electrode separation while allowing ion transport and blocking electrons. In practice, polycrystalline electrolytes are used. Though considered homogeneous, they consist of bulk grains and grain boundaries (GBs). GBs hinder oxygen transport due to segregation of additives, impurities, and space-charge layer formation, reducing ionic conductivity compared to monocrystalline electrolytes. However, the role of GBs in oxygen ion incorporation/release at the three-phase boundary (active site, simultaneous contact of electrolyte, electrode and pore) remains debated, with studies supporting both enhancement and inhibition [1,2]. These conflicting results rely on isotope penetration experiments rather than direct electrochemical observations. Additionally, the effect of electrolyte lattice orientation is poorly understood. This study aims to address these gaps in the knowledge and discrepancies through extensive experiments and an innovative distribution of relaxation times (DRT) analysis method. Commercially available monocrystalline 13YSZ substrates with <100> , <110> , and <111> orientations (1 mm thick, 25 mm diameter) were used as model cases. A polycrystalline counterpart ( ) of the same dimensions was fabricated in-house by uniaxial compression of combustion-synthesized electrolyte powder [3]. LSM suspension was screen-printed to form all electrodes. First, a circular counter electrode (CE, 12 mm diameter) and a concentric reference electrode (RE, 3 mm gap, 1 mm width) were deposited and sintered at 1150 °C for 3 h. Then, a circular working electrode (WE, 12 mm diameter) was precisely aligned with the CE on the opposite side and sintered under the same conditions. The resulting cells ( <100> , <110> , <111> , and ) were tested in an alumina housing placed inside a tubular furnace. Electrochemical testing was performed in three-electrode arrangement and involved electrochemical impedance spectroscopy (EIS) at various potentials for oxygen evolution (OER, 0 to +1 V vs. RE) and reduction (ORR, 0 to -1 V vs. RE) reactions. Measurements were conducted at 700–850 °C with varying O 2 concentrations in the WE feed gas, while pure O 2 was supplied to the CE+RE compartment to stabilize the RE potential. EIS data were corrected for stray inductance and deconvolved using in-house implementation of the DRT method [4] using Gold deconvolution algorithm [5]. DRT deconvolution of the EIS data revealed up to six processes at 800 °C with characteristic frequencies around 8×10 4 , 6×10 3 , 500, 200, 20, and 1 Hz, varying with experimental conditions. Most were linked to charge transfer and oxygen sorption/desorption, primarily related to the LSM electrode and thus not relevant for this study. The 8×10 4 Hz process ( GB ) was clearly attributed to GBs effects based on EIS data measured for at 700 °C. Surprisingly, a similar contribution appeared in monocrystalline samples, likely due to the space-charge layer at the electrolyte surface, acting as a “grain boundary” ( “GB” ). This step corresponded to oxygen transport in the electrolyte domain near the surface, i.e. from the surface to the bulk in ORR regime and from the bulk to the electrolyte surface in OER regime, analogous to transport across GBs in polycrystalline electrolyte. A second electrolyte-related process was identified at 6 kHz based on the results of our previous work [6]. In the ORR regime, this step corresponds to oxygen anion incorporation ( I ) into the YSZ lattice. Conversely, in the OER regime, it represents oxygen anion release ( R ) to the electrolyte surface. Thus, the effect of electrolyte structure and GBs can be assessed through the polarization resistance the identified processes: GB and I / R for polycrystalline electrolytes, and “GB” and I / R for monocrystalline electrolytes. As expected, the GB contribution in polycrystalline electrolyte was significantly higher than “GB” in monocrystalline ones due to the high occurrence of GBs in the volume of the polycrystalline electrolyte. However, showed no major differences in I / R steps compared to <100> and <110> , indicating that GBs mainly hinder oxygen anion transport but have little impact on oxygen incorporation/release to/from the electrolyte crystalline lattice. While “GB” and I / R followed similar trends across all monocrystalline electrolytes, their absolute values varied. <111> exhibited the lowest polarization resistances for “GB” and I in ORR but the highest for “GB” and R in OER. The opposite was true for <100> , which showed the highest resistances in ORR and the lowest in OER. This suggests that <100> hinders oxygen ion incorporation but facilitates its release, whereas <111> promotes incorporation but impedes its release. This findings align with the lattice geometry of the monocrystalline place, as <111> has a more open configuration than <100> . The DRT method allowed for examining electrolyte contributions to OER and ORR. The results show that, as expected, GBs in polycrystalline electrolytes hinder oxygen transport in the bulk of the electrolyte component body. The surface of monocrystalline electrolytes behaves similarly to GBs due to the space-charge layer. GB presence does not significantly affect oxygen anion release or incorporation from/to electrolyte crystalline lattice. Additionally, the orientation of monocrystalline electrolytes notably influences both oxygen incorporation/release and transport in the electrolyte domain. These findings highlight a significant role of electrolyte lattice orientation in oxygen transport dynamics, directly influencing the performance of solid oxide cells in various operating modes. This publication was supported by the project "The Energy Conversion and Storage", funded as project No. CZ.02.01.01/00/22_008/0004617 by Programme Johannes Amos Commenius, call Excellent Research. [1] Shim, J.H.; Park, J.S.; Holme, T.P.; Crabb, K.; Lee, W.; Kim, Y.B.; Tian, X.; Gür, T.M.; Prinz, F.B., Enhanced oxygen exchange and incorporation at surface grain boundaries on an oxide ion conductor, Acta Mater. 60(1) ( 2012 ) 1-7. https://doi.org/10.1016/j.actamat.2011.09.050. [2] De Souza, R.A.; Pietrowski, M.J.; Anselmi-Tamburini, U.; Kim, S.; Munir, Z.A.; Martin, M., Oxygen diffusion in nanocrystalline yttria-stabilized zirconia: the effect of grain boundaries, Physical Chemistry Chemical Physics 10(15) ( 2008 ) 2067-2072. https://doi.org/10.1039/B719363G. [3] Carda, M.; Adamová, N.; Budáč, D.; Rečková, V.; Paidar, M.; Bouzek, K., Impact of Preparation Method and Y 2 O 3 Content on the Properties of the YSZ Electrolyte, Energies 15(7) ( 2022 ) 2565. https://doi.org/10.3390/en15072565. [4] Masicko, Masicko/ElChemTools: Basic functionality verified, v0.0.1 ed., Zenodo2023. https://doi.org/10.5281/zenodo.8176605. [5] Bergmann, T.G.; Schlüter, N., Introducing Alternative Algorithms for the Determination of the Distribution of Relaxation Times, ChemPhysChem 23(13) ( 2022 ) e202200012. https://doi.org/10.1002/cphc.202200012. [6] Miloš, V.; Vágner, P.; Budáč, D.; Carda, M.; Paidar, M.; Fuhrmann, J.; Bouzek, K., Generalized Poisson-Nernst-Planck-Based Physical Model of the O 2 |LSM|YSZ Electrode, J. Electrochem. Soc. ( 2022 ) https://doi.org/10.1149/1945-7111/ac4a51.

Mechanical contact loss at the solid electrolyte/electrode interface in all-solid-state batteries, a type of next-generation battery, has been reported as a major issue for ion transport in all-solid-state batteries[1]. To improve this contact problem, it has been proposed to add a small amount of liquid electrolyte to the solid electrolyte/electrode interface[2]. However, the reported ion transport analysis at the solid electrolyte/liquid electrolyte interface is limited in semi-solid-state system using symmetrical cells with lithium metal as the working electrode[3]. In this study, charge transfer reactions at the solid electrolyte/liquid electrolyte interface were analyzed by impedance (EIS) measurements in a three-electrode cell with a solid/liquid electrolyte interface using a composite electrode containing a cathode active material as the working electrode. A composite electrode prepared by mixing LiCoO2:acetylene black:polyvinylidene fluoride in a weight ratio of 8:1:1, coating Al foil, drying and pressing was used as the working electrode, while lithium metal was used as the counter and reference electrodes. A NASICON-type solid electrolyte Li1+x+y Al x (Ti2−y Ge y )P3−z Si z O12 was constructed between the working electrode and the counter electrode, and a three-electrode cell prepared by filling the liquid electrolyte 1 M LiClO4/PC between the solid electrolyte and both electrodes. The reference electrode was placed between the solid electrolyte and the counter electrode, as the solid electrolyte/liquid electrolyte interface charge transfer is not observed in EIS measurements when the reference electrode is placed between the working electrode and the solid electrolyte. After two cycles of constant current charge/discharge measurements (current rate: 0.1 C rate, cut-off potential: 3.2 V - 4.2 V vs. Li/Li+), the solid electrolyte/liquid electrolyte interface charge transfer was analyzed by performing EIS measurements. To identify the semicircle associated with the solid electrolyte/liquid electrolyte interface resistance, measurements were also performed in a cell without a solid electrolyte and the resistance components corresponding to each semicircle were assigned. The temperature dependence of the observed semicircles was analyzed. A comparison of the activation energies calculated from the slopes of the Arrhenius plots confirmed a particularly large activation barrier at the solid electrolyte/liquid electrolyte interface and the working electrode/liquid electrolyte interface charge transfer. [1] R. Koerver, I. Aygun, T. Leichtweiss, C. Dietrich, W. Zhang, J.O. Binder, P. Hartmann, W.G. Zeier and J. Janek, Chem. Mater., 29, 5574-5582 (2017). [2] C. Wanga, Q. Suna, Y. Liua, Y. Zhaoa, X. Lia, X. Lina, M.N. Banisa, M. Lia, W. Lia, K.R. Adaira, D. Wanga, J. Lianga, R. Lia, L. Zhangb, R. Yangb, S. Lub and X. Suna, Nano Energy, 48, 35-43 (2018). [3] T. Abe, H. Fukuda, Y. Iriyama, Z. Ogumi, J. Electrochem. Soc., 151, A1120-A1123 (2004).

Solid-state batteries potentially offer increased lithium-ion battery energy density and safety as required for large-scale production of electrical vehicles. One of the key challenges toward high-performance solid-state batteries is the large impedance posed by the electrode–electrolyte interface. However, direct assessment of the lithium-ion transport across realistic electrode–electrolyte interfaces is tedious. Here we report two-dimensional lithium-ion exchange NMR accessing the spontaneous lithium-ion transport, providing insight on the influence of electrode preparation and battery cycling on the lithium-ion transport over the interface between an argyrodite solid-electrolyte and a sulfide electrode. Interfacial conductivity is shown to depend strongly on the preparation method and demonstrated to drop dramatically after a few electrochemical (dis)charge cycles due to both losses in interfacial contact and increased diffusional barriers. The reported exchange NMR facilitates non-invasive and selective measurement of lithium-ion interfacial transport, providing insight that can guide the electrolyte–electrode interface design for future all-solid-state batteries. The large impedance at the interface between electrode and electrolyte poses a challenge to the development of solid-state batteries. Here the authors utilize two-dimensional lithium-ion exchange-NMR to monitor the spontaneous lithium-ion transport, providing insight into the interface design.

No abstract available

All-solid state batteries have the promise to increase the safety of Li-ion batteries. A prerequisite for high-performance all-solid-state batteries is a high Li-ion conductivity through the solid electrolyte. In recent decades, several solid electrolytes have been developed which have an ionic conductivity comparable to that of common liquid electrolytes. However, fast charging and discharging of all-solid-state batteries remains challenging. This is generally attributed to poor kinetics over the electrode-solid electrolyte interface because of poorly conducting decomposition products, small contact areas, or space-charge layers. To understand and quantify the role of space-charge layers in all-solid-state batteries a simple model is presented which allows to asses the interface capacitance and resistance caused by the space-charge layer. The model is applied to LCO (LiCoO2) and graphite electrodes in contact with an LLZO (Li7La3Zr2O12) and LATP (Li1.2Al0.2Ti1.8(PO4)3) solid electrolyte at several voltages. The predictions demonstrate that the space-charge layer for typical electrode–electrolyte combinations is about a nanometer in thickness, and the consequential resistance for Li-ion transport through the space-charge layer is negligible, except when layers completely depleted of Li-ions are formed in the solid electrolyte. This suggests that space-charge layers have a negligible impact on the performance of all-solid-state batteries.

No abstract available

Research for All-Solid-State Battery (ASSB) aimed at EVs have attracted the attention around the world, and Solid Electrolytes (SE) have been actively developed to improve performance [1,2]. While higher ionic conductivity is required, another key issue in electrode design for ASSB is how to form and maintain the active material (AM)/solid electrolyte (SE) interface. Therefore, we have been working on developing a quantitative evaluation method for AM/SE interface of ASSB. The state of surface-charge at the AM/SE interface of the electrode mixture in the initial state was evaluated by utilizing the Alternating-Current-impedance (AC impedance) test of a symmetrical cell composed of an electrode mixture layer/SE layer/electrode mixture layer. As a result, we found that it was possible to quantify the contact state at the AM/SE interface [3]. Li3PS4-LiBH4 (LPS-LBH) solid electrolyte has the argyrodite-type structure, is promising SE that has both high ionic conductivity of approximately 10-2 mS/cm and high formability [4]. Comparison of LPS-LBH and a general argyrodite SE (ex. LixPS6-xClx, LPSCl) solid electrolyte, LPS-LBH shows superior formability properties. When used as a solid electrolyte in an electrode mixture using NCM 523 and LPS-LBH similarly exhibits superior formability properties. When used as SE in the electrode mixture for example NCM 523 similarly exhibits superior formability properties. This is due to the excellent formability of LPS-LBH. To analysis more detailed of the excellent formability of LPS-LBH, the amount of surface charge at the AM/SE interface in LPS-LBH and LPSCl was evaluated using the AC impedance method described above. Comparing each solid electrolyte at the same volume fraction, LPS-LBH shows about 1.2 to 1.3 times higher surface charge to LPSCl. LPS-LBH has lower charge transfer resistance than LPSCl in the cathode half-cell, and we confirmed that there is a clear proportional correlation between this surface charge of AM/SE interface and charge transfer resistance. From these results, we revealed that LPS-LBH is promising SE that has great material properties. In this research, we quantitatively evaluated the contact state at the AM/SE interface in ASSB using the AC impedance method and verified its correlation with electrochemical performances. We also examine how the contact state at AM/SE interface changes with changes in pressure, and discuss design direction for SE used in electrode composites. 【Acknowledgments】 This study was supported by the SOLiD-NEXT project (JPNP23005) commissioned by the New Energy and Industrial Technology Development Organization (NEDO). 【References】 [1] Y. Kato, S. Hori, T. Saito, K. Suzuki, M. Hirayama, A. Mitsui, M. Yonemura, H. Iba, R. Kanno, Nat. Energy, 1 (2016), 16030. [2] Y. Morino, H. Sano, S. Kawaguchi, S. Hori, A. Sakuda, T. Takahashi, N. Miyashita, A. Hayashi, and R. Kanno J. Phys. Chem, 127 (2023) 18678 [3] H. Iden, A. Ohma, Journal of Electroanalytical Chemistry 693 (2013) 34 [4] Daiwei Wang, Li-Ji Jhang, Rong Kou, Meng Liao, Shiyao Zheng, Heng Jiang, Pei Shi, Guo-Xing Li, Kui Meng & Donghai Wang, Nat. Com, 14 (2023) 1895

Lithium-metal batteries employing solid electrolytes (ceramics or polymers) could surpass the energy and power densities of current state-of-the-art lithium-ion batteries. Unfortunately, ceramic electrolyte/electrode interfaces suffer from poor interfacial contact, and polymer electrolytes show insufficient ionic conductivities for practical uses. Composite solid electrolytes, comprised of mixtures of ceramic and polymer electrolytes, could mitigate these challenges by combining high ionic conductivity with good interfacial contact. However, it is imperative to understand the kinetics of charge transfer at interfaces in composite solid electrolytes, as these can drastically affect the overall ion transport properties of such electrolytes. Here, we design a systematic study of charge transfer kinetics using multilayer LLZO/PEO (tantalum-doped lithium lanthanum zirconium oxide and poly(ethylene oxide)) solid electrolyte architectures as model systems for composite electrolytes. Electrochemical impedance spectroscopy and DC polarization measurements highlight the nonlinear charge transfer kinetics at Li/PEO as well as PEO/LLZO interfaces and show that charge transfer kinetics at each of these interfaces is limited by ion transfer in accordance with a Butler-Volmer model that incorporates a film resistance term. In addition, slow ion transport through the solid electrolyte interphase at Li/PEO interfaces and through contamination layers at LLZO/PEO interfaces are dominant sources of impedance, the latter of which can be significantly mitigated by decreasing interfacial contaminants through a high-temperature (700 °C) heat treatment of LLZO prior to battery assembly. These results provide new insights into the charge transfer kinetics at interfaces in multilayer and composite solid-state batteries and support the future design thereof.

Lithium metal batteries (LMBs) are in the spotlight as a next‐generation battery due to their high theoretical capacity. However, LMBs still suffer from inferior cycle stability owing to dendritic lithium (Li) growth during Li plating and stripping, leading to battery explosion. To solve this problem, solid electrolytes have emerged as a promising candidate by suppressing the dendritic Li growth. Despite numerous efforts, however, many challenges, such as low ionic conductivity, air stability, space charge layer, and contact loss issues, have been encountered. This review aims to provide the current challenges and new insights of solid electrolytes and then explore optimal solutions for next‐generation solid electrolytes.

Recent advances in high-voltage all-solid-state batteries (ASSBs) have demonstrated the potential of high-ion-conducting solid electrolytes (SEs) to achieve higher energy density, longer cycle life, and improved safety. However, electrochemical and chemical compatibility issues at the SE/electrode interface remain a critical challenge, often leading to high interfacial resistance and degraded performance. Addressing this requires a fundamental understanding of interfacial reactivity and stability. In this study, we employed first-principles density functional theory calculations of chemical mixing energies/interface reaction energy to investigate the thermodynamics of interface formation and structural evolution between LiPON (Li14P2O3N6) SE and a range of potential Li cathode chemistries. Our analysis identified disordered rocksalt cubic structured Li2Mn0.5Ti0.5O2F as a promising cathode material and β-Li3PO4 as an effective buffer layer to further stabilize the interface. To complement the thermodynamic insights, ab-initio molecular dynamics (AIMD) simulation was conducted to assess the kinetic effects on interfacial evolution. The AIMD results revealed decomposition products distinct from those predicted by static thermodynamic models, underscoring the crucial role of kinetics in determining interfacial structure and its impact on charge transfer processes. These findings provide valuable guidance for designing stable, high-performance interfaces in next-generation ASSBs.