最近发表的高镍文献及其在国际高水平期刊发表的创新想法

Abstract Mo doped Ni-rich LiNi0.8Co0.1Mn0.1O2 cathode materials have been synthesized via coprecipitation followed by high-temperature solid state method. The effect of Mo doping on the structure, morphology, and electrochemical performances of Ni-rich cathode material has been investigated. The results reveal that Mo doping may promote the formation of surface rock salt phase and expand the Li+ diffusion channels for Ni-rich material. Benefit from which, the further transition of layered to rock salt structure during cycling has been alleviated. As a result, the optimal Mo doped material, with 1 wt% doping, exhibits enhanced cycling stability with superior electrochemistry performances, that is high reversible capacity of 215.7 mAh g−1 at 0.1C, and 184.1 mAh g−1 at 1C with an excellent 100th capacity retention of 92.4%. Even the cut-off voltage raises to 4.5 V, the 100th capacity retention of Mo-doped material still reaches as high as 85.2%. The results indicate that fabricating the Ni-rich materials with a surface rock salt phase is an effective strategy towards better structure stability and electrochemical performances.

Ni-rich layered oxides LiNixCoyMn1-x-yO2 (NCMs, x > 0.8) are the most promising cathode candidates for Li-ion batteries because of their superior specific capacity and cost affordability. Unfortunately, NCMs suffer from a series of formidable challenges such as structural instability and incompatibility with commonly used electrolytes, which seriously hamper their practical applications on a large scale. Herein, the Al/Ta codoping modification strategy is proposed to improve the performance of the LiNi0.83Co0.1Mn0.07O2 cathode, and the as-prepared Al/Ta-modified LiNi0.83Co0.1Mn0.07O2 delivers exceptional cycling stability with a capacity retention of 97.4% after 150 cycles at 1C and an excellent rate performance with a high capacity of 143.2 mAh g-1 even at 3C. Based on the experimental study, it is found that the structural stability of NCM is strengthened due to the regulated coordination of oxygen by introducing a robust Ta-O covalent bond, which prevents the layered structure from collapsing. Moreover, the reconstructed rock-salt-like surface is capable of effectively inhibiting interfacial side reactions as well as the overgrowth of the cathode-electrolyte interface. Theoretically, the energy of Li/Ni mixing is significantly increased with the introduction of Al and Ta elements in Al/Ta codoped NCM, leading to inhibited adverse phase transition during cycling. A feasible pathway for designing and developing advanced Ni-rich cathode materials for Li-ion batteries is provided in this work.

Overall structural modification, integrating coating and doping, was developed to enhance the structural stability and Li+ transport kinetics in a layered Ni-rich cathode, which significantly improves the electrochemical performance at high voltage.

In situ XRD examinations demonstrate significant effects of a Li2MnO3 coating on suppressing structural degradation during charging/discharging of Ni-rich cathode materials for enhanced cycling stability.

Abstract Ni-rich cathodes have been considered as promising cathodes for Li-ion batteries (LIBs) because their high electrochemical capacities and low costs. However, fast capacity fading caused by interfacial instability and bulk structural degradation of Ni-rich cathodes during charge-discharge processes severely hinders their development and application. To address these challenges, we report a one-step dual-modification strategy to in-situ synthesize complex In2O3&LiInO2 co-coating layer on the surface of LiNi0.8Co0.1Mn0.1O2, which can cooperate collaboratively to stabilize layered structure and deplete lithium impurity. The dual-modified LiNi0.8Co0.1Mn0.1O2 materials not only show distinguished cycling stability at 1 C with a capacity retention of ca. 90%, but also exhibit a discharge capacity of 177.1 mAh g−1 at a high rate of 5 C with a capacity retention of 86.4% after 300 cycles. Further studies confirm structural degradation and intergranular cracks at the particle level can be effectively mitigated by uniformly adherent bi-functional coating layer even after long-term cycling. The results shed light on the feasibility of dual-modified strategy for improving the performance of Ni-rich cathode materials, which can also be applied to other oxide cathode materials.

Significance In order to support the growth of electrochemical energy storage applications, improved cathode materials of Li-ion batteries are required to unlock a longer lifespan in combination with enhanced energy density. Developing micro-sized single-crystalline Ni-rich cathodes (SCN) has emerged as the mainstream to improve the volumetric energy density and safety. However, uneven Li-ion distribution and stress concentration result in intragranular crack generation with a limited cycle life. Herein, an optimal particle size is predicted by simulating the stress distributions and a unique strategy is proposed to synthesize the target-sized SCN (m-NCM83). Accordingly, the m-NCM83 exhibits superior cycling stability with high structural integrity. This work provides crucial guidance for the design and synthesis of high-energy density SCN with superior cycling stability.

… , in which a poor capacity retention of 51.8% after 250 cycles at 5C is observed for single-… Ni-rich cathodes, and highlighted the trade-off between the energy density and cycling …

Compared with the polycrystal (PC) Ni-rich cathode materials, the single-crystal (SC) counterpart displayed excellent structural stability, high reversible capacity and limited voltage decay during cycling, which received great attention from academic and industry. However, the origin of fascinating high-voltage stability within SC is poorly understood yet. Herein, we tracked the evolution of phase transitions, in which the destructive volume change and H3 phase formation presented in PC, are effectively suppressed in SC when cycling at a high cut-off voltage of 4.6 V, further clarifying the origin of high-voltage stability in SC cathode. Moreover, SC electrode displayed crack-free morphology, and excellent electrochemical stability during long-term cycling, whereas PC suffered severe capacity and voltage fade because of the spinel-like phase, decoding the failure mechanisms of PC and SC during cycling at high cut-off voltages. This finding provides universal insights into high-voltage stability and failure mechanisms of layered Ni-rich cathode materials.

… Li + /Li with 83.4% retention for up to 500 cycles, significantly superior to that of the bare … enables the effective stabilization of the Ni-rich cathode materials for long-term cycling at high …

Abstract Ni-rich layered lithium transition metal oxides are promising cathode materials for the next generation high energy density lithium ion batteries. However, high Ni content leads to severe side reactions at cathode/electrolyte interface, coupled with mechanical disintegration significantly degrading the electrochemical performance and safety. Surface coating and grain boundary (GB) engineering can respectively protect surface layer and suppress cracking issue, but direct comparisons of the individual effect of the two methods at different cycling conditions has not been fully explored. Moreover, the two methods have never been coupled together previously, let alone their coupling effect. Herein, we take LiNi0·8Mn0·1Co0·1O2 as a model material and utilize atomic layer deposition coating and annealing protocol to demonstrate the individual and coupling effects of surface coating and GB engineering on cycling stability. GB engineering is found to be more effective than surface coating in enhancing cycling stability due to suppressed intergranular cracks. Promisingly, coupling GB engineering and surface coating, we can achieve superior cycle stability even upon high voltage cycling (91% retention after 200 cycles at 2.7–4.7 V), which demonstrates the importance to simultaneously alleviate surface degradation and bulk disintegration in design of advanced cathode materials.

Ni-rich layered oxide cathode materials are promising candidates for high-specific-energy battery systems owing to their high reversible capacity. However, their widespread application is still severely impeded by severe capacity loss upon long-term cycling. It has been proven that the cyclic stability of Ni-rich cathode materials is closely related to their microstructure and morphology. Despite this, the influence of the microstructure of primary particles on the fatigue mechanism of Ni-rich cathode materials during prolonged cycling has not been fully understood. Here, two Ni-rich layered spherical agglomerate oxides consisting of the primary particle with different length/width ratios are successfully synthesized. It is found that the long-term structural stability of both materials strongly depends on the microstructure of primary crystallites, although there is no significant difference between the electrochemical and crystalline characteristics during the initial cycle. A higher primary particle length/width ratio could effectively inhibit the accumulation of microcracks and chemical degradation during long-term cycling, thereby promoting the electrochemical performance of the cathode materials (80% capacity retention after 200 cycles at 1 C compared to the 55% of the counterpart with a lower primary particle length/width ratio). This study highlights the structure-activity relationship between the primary particle microstructure and fatigue mechanisms during long-term cycling, thereby advancing the development of Ni-rich cathode materials.

A multi-functional coating with high electronic and ionic conductivity is constructed on the surface of LiNi0.8Co0.1Mn0.1O2 (NCM) to boost the battery stability upon cycling and during storage as well. Phosphoric acid reacts with residual lithium species on the pristine NCM to form Li3PO4 coating with extra CNTs penetrating through, which shows high ionic and electronic conductivity. NCM, Li3PO4, CNTs, and the electrolyte jointly form a four-phase cathode electrolyte interface, which plays a key role in the great enhancement of capacity retention, from 50.3% for pristine NCM to 84.8% for modified one after 500 cycles at 0.5C at room temperature. The modified NCM also deliveries superior electrochemical performances at high cut-off voltage (4.5 V), high temperature (55 ℃) and high rate (10C). Furthermore, it can deliver 154.2 mA h g-1 at the 500th cycle after exposed to air with high humidity for two weeks. These results demonstrate that the well-constructed multi-functional coating can remarkably enhance the chemical and electrochemical performances of NCM. The improved cycling, storage and rate performance are attributed to the four-phase cathode electrolyte interface delivering high electron and ionic conductivity, and securing the cathode against attack. This work broadens the horizon of constructing effective electrode/electrolyte interface for electrochemical energy storage and conversion.

Abstract The cationic ordering of Ni-rich cathode materials at original state and in lithiation/delithiation process is the key factor in obtaining high discharge capacity and excellent cycle performance. However, it is still one of the greatest challenges to synthesize Ni-rich cathodes with low cationic disordering and maintain the well-ordered layered structure with no phase degradation during cycling. Herein, cationic ordering tuned Ni-rich cathodes with well-ordered layered structure at as-prepared state and suppressed cationic mixing during cycling are synthesized by synchronous dual-site doping of Zn2+ at transition metal (TM) and lithium sites. The proper amount of Zn2+ ions doped at TM sites reduce the content of Ni2+, thus promoting the ordering of layered structure in as-prepared state and ensuring high capacity. Meanwhile, a part of Zn2+ ions substituted for Li+ ions act as pillaring ions, inhibiting the migration of TM ions from TM slabs to Li slabs and maintaining the integrity of crystal structure during lithiation, especially at highly delithiated state. The first principle calculations demonstrate that the dual-site doping of Zn2+ in Ni-rich cathode is thermodynamically favorable and the modified cathodes have excellent structure and phase stability during electrochemical reaction. With the tuned cationic ordering, Zn modified cathode shows high capacity and stable cyclability, with significantly improved capacity retention of 86% at 5 C over 200 cycles and excellent high-temperature performance.

… by per-cycling of the layered Ni-rich oxide cathode at high … the layered Ni-rich oxide LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathode by … The as-prepared LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathode coated …

… High-nickel layered oxides, LiNi x Co y Mn z O 2 (0.6 ≤ x < 1), are promising cathode … Herein, an integrated surface coating/doping strategy is developed to significantly improve the …

… Therefore, improving the cycle stability of high-nickel cathode materials at elevated temperature … All these indicates that the LiAlO 2 @Al 2 O 3 coating significantly improves the capacity …

Atomic layer deposition (ALD) derived ultrathin conformal Al2O3 coating has been identified as an effective strategy for enhancing the electrochemical performance of Ni-rich LiNixCoyMnzO2 (NCM; 0 ≤ x, y, z < 1) based cathode active materials (CAM) in Li-ion batteries. However, there is still a need to better understand the beneficial effect of ALD derived surface coatings on the performance of NCM based composite cathodes. In this work, we applied and optimized a low-temperature ALD derived Al2O3 coating on a series of Ni-rich NCM-based (NCM622, NCM71.51.5 and NCM811) ready-to-use composite cathodes and investigated the effect of coating on the surface conductivity of the electrode as well as its electrochemical performance. A highly uniform and conformal coating was successfully achieved on all three different cathode compositions under the same ALD deposition conditions. All the coated cathodes were found to exhibit an improved electrochemical performance during long-term cycling under moderate cycling conditions. The improvement in the electrochemical performance after Al2O3 coating is attributed to the suppression of parasitic side reactions between the electrode and the electrolyte during cycling. Furthermore, conductive atomic force microscopy (C-AFM) was performed on the electrode surface as a non-destructive technique to determine the difference in surface morphology and conductivity between uncoated and coated electrodes before and after cycling. C-AFM measurements on pristine cathodes before cycling allow clear separation between the conductive carbon additives and the embedded NCM secondary particles, which show an electrically insulating behavior. More importantly, the measurements reveal that the ALD-derived Al2O3 coating with an optimized thickness is thin enough to retain the original conduction properties of the coated electrodes, while thicker coating layers are insulating resulting in a worse cycling performance. After cycling, the surface conductivity of the coated electrodes is maintained, while in the case of uncoated electrodes the surface conductivity is completely suppressed confirming the formation of an insulating cathode electrolyte interface due to the parasitic side reactions. The results not only show the possibilities of C-AFM as a non-destructive evaluation of the surface properties, but also reveal that an optimized coating, which preserves the conductive properties of the electrode surface, is a crucial factor for stabilising the long-term battery performance.

… of LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) cathode combining sol–gel method and heat treatment. The … In high nickel cathode coating modification, LCP as the thinnest phosphate coating …

… More importantly, B 2 O 3 coated NCM811 cathode exhibits the low interfacial reaction … surface treatment of Ni-rich cathode materials, and deepens the understanding of surface …

… a coating layer. By utilizing conventional solid-state mixing and sintering process, a novel LATP-coated single-crystal high-nickel … not only functions as a coating layer but also acts as a …

… /capacity degradation and thermal instability of the high-nickel cathode material (Ni > 0.8), the … contaminations and builds a homogeneous TiO 2 coating on the surface of SC-NCM. The …

Despite the advantage of reduced cobalt content, widely proposed Ni-rich cathode candidates face significant challenges related to thermal instability and structural deterioration under high-voltage conditions. In particular, when the Ni...

… Then, surface coating and surface doping are deployed on NCM … 2 surface coating and Zr 4+ surface doping can significantly inhibit the formation of LiOH and Li 2 CO 3 on NCM surface …

… LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) high-nickel lithium layered oxide material has gained … However, the presence of high nickel content leads to capacity fading resulting from surface …

High-nickel layered oxides, such as LiNi0.8Co0.1Mn0.1O2 (NCM-811), offer higher energy density than their low-nickel counterparts at a given voltage and are gaining major traction in automotive lit...

… Here, we report on the facile surface modification of nickel-rich layered oxide by chemical vapor deposition with methane which yields a conductive and protective artificial solid …

Introducing additional elements into Ni‐rich cathodes is an essential strategy for addressing the instability of the cathode material. Conventionally, this doping strategy considers only the incorporation of additional elements into the bulk structure of the cathode in terms of fortifying the crystal structure. However, high‐valence elements such as Nb5+, Ta5+, and Mo6+ are likely to be insoluble in the crystal structure, resulting in accumulation along the interparticle boundaries. Herein, a new mechanism for doping high‐valence elements into Ni‐rich cathodes and their effects on the morphology and crystal structure are investigated by calcining LiNiO2 (LNO) and X‐doped LNO cathodes (X = Al, Nb, Ta, and Mo) at various temperatures. Operando X‐ray diffraction analysis reveals that the temperature at which the content of Li‐X‐O compounds declines is higher for the dopants with high oxidation states, reinforcing segregation at the grain boundary and widening the calcination temperature range. Thus, the highly aligned microstructure and high crystallinity of the LNO cathode are maintained over a wide calcination temperature range after doping with high‐valence elements, enhancing the electrochemical performance. As next‐generation dopants, high‐valence elements can fortify not only the crystal structure, but also the microstructure, to maximize the electrochemical performance of Ni‐rich cathodes.

Ni-rich cathode materials have garnered significant attention attributable to the high reversible capacity and superior rate performance, particularly in the electric vehicle industry. However, the structural degradation experienced during cycling results in rapid capacity decay and deterioration of the rate performance, thereby impeding the widespread application of Ni-rich cathodes. Herein, a Mg/Ti co-doping strategy was developed to boost the structure stability and Li-ion transport kinetics of the Ni-rich cathode material LiNi0.90Co0.05Mn0.05O2 (NCM9055) under long cycle. It is demonstrated that the Mg2+ ions inserted into the lithium layer could serve as pillars, enhancing the stability of the delithiated layer structure. The introduction of robust Ti-O bonding mitigated the detrimental H2-H3 phase transition (∼4.2 V) during cycling. In addition, despite the fact that Mg/Ti co-doping slightly reduces Li+ diffusion coefficient in the modified cathode material (NCM9055-MT), it effectively stabilized the robustness of the layered structure and maintained the Li+ diffusion channel while charging and discharging, thereby improving the Li+ diffusion coefficient after a long cycle. Therefore, the Mg/Ti co-doped cathode materials exhibited an exceptional capacity retention rate of 99.9% (100 cycles, 1 C). Additionally, the Li+ diffusion coefficient of the co-doped NCM9055-MT (2.924 × 10-10 cm2 s-1) after 100 cycles was effectively enhanced compared with the case of undoped NCM9055 (4.806 × 10-11 cm2 s-1). This work demonstrates that the Mg/Ti co-doping approach effectively enhanced the stability of layered Ni-rich cathode materials.

A high fraction of reactive Ni4+ ions at the cathode–electrolyte interfaces lead to capacity fading of Ni‐rich cathodes. Therefore, a core–shell (CS) design encapsulating the Ni‐rich region by a Ni‐less shell is an effective approach for improving the cycling stability of the cathodes. However, with increasing average Ni content to increase the capacity, the thickness of the shell should be reduced or the Ni fraction of the shell will be inevitably higher, making it susceptible to interdiffusion, which flattens the concentration gradient during the lithiation process. Herein, the limit of the average Ni composition in the CS‐type cathode is pushed to 94% via Ta doping, which suppresses interdiffusion by segregating the Ta‐rich phases at the particle boundaries. Ta doping allows the maintenance of the highly aligned microstructure and the ordered intermixing structure of Li and transition metal ions, as well as the concentration gradient, over a wide lithiation temperature range. The Ta‐doped CS‐type cathode retains 92.6% of its initial capacity after 1000 cycles and exhibits resistance to damage from fast charging. Multifunctional Ta doping in the CS‐type cathode provides a simple and all‐around solution to maximize the electrochemical performance of Ni‐rich cathodes, providing flexibility in the lithiation process.

… of Ni-rich cathode has … Ni-rich cathode has been successfully achieved by altering Mn content. It is found that single bulk W-doping has been obtained in LiNi 0.8 Mn 0.2 O 2 cathode. …

The suppression of oxygen oxidation is proposed as the critical origin of Zr doping on LiNi0.92Co0.04Mn0.04O2 layered oxide LIB cathode material.

… elemental doping in a Ni-rich layered oxide cathode. The experimental methods and dopant … tried to clarify the particle refinement mechanism caused by the doping strategy. Similar …

… At 50% SOC, the dopant and Co atoms synergistically … doped atom significantly contributes to the prediction of ΔNi–O and ΔCo–O. In this study, the energy gap regulation mechanisms …

Layered ultra-high-nickel oxides are promising cathodes for high-energy-density lithium-ion batteries but suffer from severe structural degradation. Although high-valence doping is widely employed to enhance stability, the underlying mechanism—whether dominated by morphological alignment or cation ordering—remains contested. Through systematic investigation of W6+-doped LiNi0.92Co0.04Mn0.04O2 across varied doping concentrations and sintering temperatures, this work demonstrates that cation ordering, rather than morphological alignment, plays the decisive role in electrochemical enhancement. Although W-doping refines primary particles and sustains a radial microstructure even under extreme sintering conditions (up to 850 °C), correlation analysis reveals that cycling stability and specific capacity depend strongly on the suppression of Li+/Ni2+ cation mixing, while showing only weak correlation with grain morphology. The 0.75 mol% W doped cathode calcined at 800 °C delivered a high specific capacity of 244.3 mAh g−1 and exceptional long-term cyclability, retaining 91.53% capacity after 1000 cycles in full cells. These findings clarify that high-valence dopants enhance performance primarily via lattice stabilization through cation ordering and highlight the necessity of co-optimizing doping content with synthesis temperature. This work revises the conventional understanding of high-valence doping mechanisms by establishing cation ordering as the primary factor for stability, providing a generalizable principle for designing next-generation ultra-high-nickel cathodes.

Abstract Chemical modification of electrode materials by heteroatom dopants is crucial for improving storage performance in rechargeable batteries. Electron configurations of different dopants significantly influence the chemical interactions inbetween and the chemical bonding with the host material, yet the underlying mechanism remains unclear. We revealed competitive doping chemistry of Group IIIA elements (boron and aluminum) taking nickel‐rich cathode materials as a model. A notable difference between the atomic radii of B and Al accounts for different spatial configurations of the hybridized orbital in bonding with lattice oxygen. Density functional theory calculations reveal, Al is preferentially bonded to oxygen and vice versa, and shows a much lower diffusion barrier than B III . In the case of Al‐preoccupation, the bulk diffusion of B III is hindered. In this way, a B‐rich surface and Al‐rich bulk is formed, which helps to synergistically stabilize the structural evolution and surface chemistry of the cathode.

High nickel content in LiNixCoyMnzO2 (NCM, x ≥ 0.8, x + y + z = 1) layered cathode material allows high specific energy density in lithium-ion batteries (LIBs). However, Ni-rich NCM cathodes suffer from performance degradation, mechanical and structural instability upon prolonged cell cycling. Although the use of single-crystal Ni-rich NCM can mitigate these drawbacks, the ion-diffusion in large single-crystal particles hamper its rate capability. Herein, we report a strategy to construct an in situ Li1.4Y0.4Ti1.6(PO4)3 (LYTP) ion/electron conductive network which interconnects single-crystal LiNi0.88Co0.09Mn0.03O2 (SC-NCM88) particles. The LYTP network facilitates the lithium-ion transport between SC-NCM88 particles, mitigates mechanical instability and prevents detrimental crystalline phase transformation. When used in combination with a Li metal anode, the LYTP-containing SC-NCM88-based cathode enables a coin cell capacity of 130 mAh g−1 after 500 cycles at 5 C rate in the 2.75-4.4 V range at 25 °C. Tests in Li-ion pouch cell configuration (i.e., graphite used as negative electrode active material) demonstrate capacity retention of 85% after 1000 cycles at 0.5 C in the 2.75-4.4 V range at 25 °C for the LYTP-containing SC-NCM88-based positive electrode. Single-crystal Ni-rich cathodes suffer from side reactions with the electrolyte and slow Li-ion transport during high-voltage cycling. Herein, a Li1.4Y0.4Ti1.6(PO4)3 coating is applied to facilitate the Li-ion transport and improve the cycling life of the cell.

High-capacity Ni-rich layered oxides are promising cathode materials for secondary lithium-based battery systems. However, their structural instability detrimentally affects the battery performance during cell cycling. Here, we report an Al/Zr co-doped single-crystalline LiNi0.88Co0.09Mn0.03O2 (SNCM) cathode material to circumvent the instability issue. We found that soluble Al ions are adequately incorporated in the SNCM lattice while the less soluble Zr ions are prone to aggregate in the outer SNCM surface layer. The synergistic effect of Al/Zr co-doping in SNCM lattice improve the Li-ion mobility, relief the internal strain, and suppress the Li/Ni cation mixing upon cycling at high cut-off voltage. These features improve the cathode rate capability and structural stabilization during prolonged cell cycling. In particular, the Zr-rich surface enables the formation of stable cathode-electrolyte interphase, which prevent SNCM from unwanted reactions with the non-aqueous fluorinated liquid electrolyte solution and avoid Ni dissolution. To prove the practical application of the Al/Zr co-doped SNCM, we assembled a 10.8 Ah pouch cell (using a 100 μm thick Li metal anode) capable of delivering initial specific energy of 504.5 Wh kg−1 at 0.1 C and 25 °C. Li-ion cathode active materials are transitioning from poly- to single-crystal structures. However, the performance of high Ni-content single-crystal cathodes remains below expectations. Here, via Al/Zr co-doping, the authors propose a strategy to mitigate structural degradation in this class of materials.

Interface fusion plays a key role in constructing Ni-based single-crystal cathodes, and is governed by the atomic migration related to kinetics. However, the interfacial atom migration path and its control factors are lack of clearly understanding. Herein, we systematically probe the solid-state synthesis mechanism of single-crystal LiNi0.92Co0.04Mn0.04O2, including the effects of precursor size, Li/transition metal (TM) ratio and sintering temperature on the structure. Multi-dimensional analysis unravels that thermodynamics drives interface atoms migration through intermediate state (i.e., cation mixing phase) to induce grain boundary fusion. Moreover, we demonstrate that smaller precursor size (< 6 μm), lager Li/TM ratio (> 1.0) and higher temperature (≥ 810 ℃) are conducive to promote the growth of the intermediate state due to reaction kinetics enhancement, and ultimately strengthen the atomic migration-induced interface fusion.

… for the promising single-crystal (SC) Ni-rich cathode material, has not … Ni-rich material is elaborately diagnosed from surface to bulk phase and compared with polycrystalline (PC) Ni-rich …

… NMC (LiNi x Mn y Co 1-xy O 2 , x ≥ 0.6) is a very promising cathode material in Li-ion … commercialization of Ni-rich NMC cathode materials. Micron-sized single crystal Ni-rich NMC has …

Ultra-high nickel layered cathodes suffer accelerated degradation through a mechanically and chemically coupled cycle, highlighting the need to concurrently enhance durability and …

… in situ doping strategy for single-crystal Ni-rich cathode by the … both in surface and bulk of single-crystal LiNi 0.83 Co 0.11 Mn … high structural stability of single-crystal Ni-rich cathodes. …

Single-crystal LiNi1-x-yCoxMnyO2 (NCM) are a promising cathode material featuring with improved structural integrity, suppressed particle cracking and enhanced capacity retention during cycling. Herein, well-informed single crystalline NCM cathode materials are...

Single‐crystal high‐nickel oxide with an integral structure can prevent intergranular cracks and the associated detrimental reactions. Yet, its low surface‐to‐volume ratio makes surficial degradation a more critical factor in electrochemical performance. Herein, artificial proton‐rich (ammonium bicarbonate) shell is successfully introduced on the nickel‐rich LiNi0.92Co0.06Mn0.02O2 single crystals for in situ electrochemically conversing into inorganic maskant to enhance stability of cathode. The process is that the surficial enriched proton, once released from the ammonium bicarbonate shell (proton reservoir) during 1st charge, is immediately captured by LiPF6, in situ electrochemically conversing to LiF and Li3PO4 sub‐nano particle dense maskant (sub‐nano F‐&P‐maskant). The in situ formed compact nano F‐&P‐maskant significantly resists the cathode against electrolyte attack and improves the surface stability of particles during long‐term cycling. Consequently, this surface modification enables 95% capacity retention after 100 cycles at a high voltage of 4.5 V in the half cell and 83% capacity retention after 800 cycles in the full cell. This work demonstrates a strategy for reconstructing the protective layer using the rational design of surficial enriched proton shells for advanced lithium batteries.

Abstract Non‐equilibrium kinetic intermediates are usually preferentially generated instead of thermodynamic stable phases in the solid‐state synthesis of layered oxides. Understanding the inherent complexity between thermodynamics and kinetics is important for designing high cationic ordering cathodes. Single‐crystal strategy is an effective way to solve the intrinsic chemo‐mechanical problems of Ni‐rich cathodes. However, the synthesis of high‐performance single‐crystal is very challenging. Herein, the kinetic reaction path and the formation mechanism of non‐equilibrium intermediates in the synthesis of single‐crystal Co‐free Ni‐rich were explored. We demonstrate that the formation of non‐equilibrium intermediate and the electrochemical‐thermo‐mechanical failure can be effectively inhibited by driving low‐temperature topotactic lithiation. This work provides a basis for designing high‐performance single‐crystal Ni‐rich layered oxides by regulating the defective structures.

Ni‐rich cathode material possesses a considerable theoretical capacity, yet achieving their full capacity potential remains challenging. Elevating its operation voltage is an effective approach, while the stability of Ni‐rich cathode material is relatively poor, which is limited by Li+/Ni2+ mixing. Herein, a strategy of cation/anion co‐doping is proposed for single‐crystal ultrahigh‐nickel cathode LiNi0.92Co0.04Mn0.04O2 operated at 4.5 V. The enhancement mechanism is explicitly revealed by in situ/ex situ tests and theory calculations. Specifically, Mo6+ and F− are introduced to construct an appropriate Li+/Ni2+ antisite defects structure at the particle surface, which can maintain the low‐defect Li+ layered channel inside the bulk simultaneously, inducing a stable access portal for Li+ transport from the cathode/electrolyte interface. More importantly, the Li+/Ni2+ antisite passivation layer on the surface can uphold the stability of Li‐layer and optimize the reactive behavior of Ni2+, thus boosting the interfacial stability and reducing the lattice mismatch. As a result, it can achieve high capacity (204 mAh g−1 at 1 C) and stable retention during long‐term high‐voltage measurements both in half‐cell (87.1% after 200 cycles) and full‐cell (91.9% after 400 cycles). This facile strategy provides a feasible technical reference for further exploiting the ultrahigh‐capacity of Ni‐rich cathode for commercial application.

… Ni-rich NMC811, NMC80155, and NMC85105 single-crystal … the intrinsic reactivities of Ni-rich NMCs and the specific role … -induced particle cracking in single-crystal Ni-rich NMCs, we …

… , especially at the single-crystal architecture. … cathode. These findings are beneficial for understanding the fundamental reaction mechanism of single-crystal Ni-rich Co-free cathode …

It is crucial to minimize cobalt content in Ni‐rich layered single‐crystal cathodes due to their high price and limited availability, yet it will inevitably lead to cation disordering, capacity degradation, and thermal issues. Herein, to overcome the intrinsic trade‐off between performance and composition of Ni‐rich Co‐less single‐crystal cathodes, a precursor engineering strategy with an epitaxially grown cobalt enrichment on the surface is innovatively proposed. In contrast to traditional coating modifications with random orientation and rigid surface‐bulk boundary, the epitaxially enriched surface cobalt layer on the precursor undergoes rapid interdiffusion with the internal Ni3+ during the optimized sintering process. This interdiffusion eliminates the surface‐bulk boundary, promoting the uniform distribution of cobalt and synergistically addressing the Li/Ni intermixing. Moreover, an enhanced surface Li+ diffusion is obtained, thereby suppressing the Li+ concentration gradient and intragranular cracks generation. Consequently, the modified LiNi0.7Co0.07Mn0.23O2 exhibits impressive cycling stability with increased capacity retention in both coin‐type half‐cells and pouch‐type full‐cells (91% after 1000 cycles), even under the harsh condition of high‐temperature, surpassing the majority of previously reported Ni‐rich cathodes. This work opens new avenues toward the low cost, high energy density, thermal stability, and long cyclic life for Ni‐rich Co‐less cathodes and sheds light on large‐scale commercial production.

… cathodes with high Ni content promise high energy density and competitive cost for Li-ion batteries (LIBs). However, Ni-rich cathodes suffer from irreversible interface … of Ni-rich cathodes …

The degradation of Ni‐rich cathodes during long‐term operation at high voltage has garnered significant attention from both academia and industry. Despite many post‐mortem qualitative structural analyses, precise quantification of their individual and coupling contributions to the overall capacity degradation remains challenging. Here, by leveraging multiscale synchrotron X‐ray probes, electron microscopy, and post‐galvanostatic intermittent titration technique, the thermodynamically irreversible and kinetically reversible capacity loss is successfully deconvoluted in a polycrystalline LiNi0.83Mn0.1Co0.07O2 cathode during long‐term charge/discharge cycling in full cell configuration. Contradicting the dramatic capacity loss, the layered structure remains highly alive even after 1000 cycles at 4.6 V while undergoing a three‐order of magnitude reduction in the mass transfer kinetics, leading to almost fully recoverable capacity under kinetic‐free conditions. Such kinetic dormant behavior after cycling is not simply ascribed to poor chemical diffusion by reconstructed cathode surface but highly synchronizes with the lattice strain evolution stemming from the structural heterogeneity between deeply delithiated layered and degraded rock‐salt phases at high voltage. These findings deepen the degradation mechanism of high‐voltage cathodes to achieve long‐cycling and fast‐charging performance.

Ni-rich layered oxide cathodes LiNixCoyMn1-x-yO2 (NCM, x ≥ 0.8) suffer from concurrent structural instability, interfacial degradation caused by residual lithium, and sluggish Li+ diffusion kinetics, which severely limit their application in high-energy lithium-ion batteries. Although extensive efforts have been devoted to addressing these issues, strategies capable of concurrently regulating the bulk structure, surface chemistry, and Li+ diffusion kinetics in a simple and scalable manner remain limited. Herein, a simple Ti and Nb comodification strategy via secondary calcination is proposed to synergistically regulate bulk structure, surface chemistry, and Li+ transport in Ni-rich cathodes. The incorporation of high valence Ti and Nb induces controlled Li/Ni antisite defects, which enhance the lattice and thermal stability of the cathodes. Meanwhile, the comodification reduces surface residual lithium, suppresses interfacial side reactions, and introduces oxygen vacancies, thereby enhancing Li+ diffusion kinetics. Benefiting from this synergistic regulation, the modified cathode delivers a high rate capacity of 174 mAh g-1 at 5 C and retains 94% capacity after 100 cycles at 1 C. This work provides an effective strategy for constructing Ni-rich cathodes with high structural stability and excellent performance for next-generation high-energy LIBs.

The sluggish kinetics in Ni-rich cathodes at subzero temperatures causes decreased specific capacity and poor rate capability, resulting in slow and unstable charge storage. So far, the driving force of this phenomenon remains a mystery. Herein, with the help of in-situ X-ray diffraction and time of flight secondary ion mass spectrometry techniques, the continuous accumulation of both the cathode electrolyte interphase (CEI) film formation and the incomplete structure evolution during cycling under subzero temperature are proposed. It is presented that excessively uniform and thick CEI film generated at subzero temperatures would block the diffusion of Li+ -ions, resulting in incomplete phase evolution and clear charge potential delay. The incomplete phase evolution throughout the Li+ -ion intercalation/de-intercalation processes would further cause low depth of discharge and poor electrochemical reversibility with low initial Coulombic efficiency, as well. In addition, the formation of the thick and uniform CEI film would also consume Li+ -ions during the charging process. This discovery highlights the effects of the CEI film formation behavior and incomplete phase evolution in restricting electrochemical kinetics under subzero temperatures, which the authors believe would promote the further application of the Ni-rich cathodes.

… We propose a mechanism for the interplay between the kinetics and thermodynamics on the morphological evolution of nickel-rich NCM during the solid-state synthesis, as illustrated in …

Slow lithium diffusion kinetics of H1 phase during discharge determines the initial irreversible capacity loss of NCM-based materials. By controlling lithium diffusion rate in the discharge process, extra capacity is obtained in the materials.

Ni-rich (Ni content ≥ 80%) layered oxide (NRLO) cathode is a promising candidate for boosting the energy density of Li-ion batteries due to its high discharge voltage and capacities over...

Sulfide‐based all‐solid‐state lithium batteries (ASSLBs) featuring Ni‐rich layered oxide cathodes are emerging as the leading contenders for the next generation of rechargeable batteries with outstanding safety and energy density characteristics. However, the composites of Ni‐rich oxides and sulfide electrolytes continue to grapple with persistent challenges encompassing structural deterioration, adverse interfacial parasitic reactions, and sluggish kinetics within the carbon‐free cathodes. Here, a synergistic design to circumvent these issues via the coupling of Zr/F co‐doping and conductive cyclized polyacrylonitrile (cPAN) coating to tailor both the bulk and surface chemistry of the Ni‐rich layered oxide LiNi0.83Co0.12Mn0.05O2 (NCM83125) cathode is proposed. The cathode subjected to this coordinated modification strategy showcases exceptional performance in sulfide‐based ASSLBs. It demonstrates robust cycling performance, with a capacity retention of 95% observed after 300 cycles at a rate of 0.2 C, alongside satisfactory rate performance, achieving a capacity of 109 mAh g‒1 at a high rate of 3 C.

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.

Further commercialization of Ni‐rich layered cathodes is hindered by severe structure/interface degradation and kinetic hindrance that occur during electrochemical operation, which leads to safety risks and reduced range in electric vehicles (EVs). Herein, by selecting elements with different solubility properties, a multifunctional strategy that synchronously fabricates perovskite‐type SrZrO3 coating and Sr/Zr co‐doping is employed to strengthen the structure/interface stability and the Li+ transport mobility of LiNi0.85Co0.10Mn0.05O2 (NCM). Perovskite‐type SrZrO3 protective layers formed on the particle surface can substantially mitigate the unexpected interfacial side reactions and surface phase transitions. In addition, a robust crystal framework is constructed by optimizing local O coordination through the introduction of strong Zr−O bonds. Notably, Li+ diffusion kinetics is effectively improved due to expanded cell parameters and O‐Li‐O slab spacing with the incorporation of large‐diameter Sr pillar ions, as revealed by X‐ray diffraction. As a result, the Sr/Zr‐modified NCM achieves a remarkable capacity retention of 99.4% after 200 cycles at 1 C, and a high rate capacity of 168.9 mAh g−1 at 10 C. This work opens new avenues to develop high‐performance NCM cathodes with high energy and high power for EVs with long calendar life.

… of Ni-rich layered oxide (NRLO) cathodes by quantitatively establishing their dynamic structure–kinetics … Contrary to conventional views, we discovered electrode kinetic properties …

Although layered lithium nickel‐rich oxides have become the state‐of‐the‐art cathode materials for lithium‐ion batteries in electric vehicle (EV) applications, they can suffer from rapid performance failure—particularly when operated under conditions of stress (temperature, high voltage)‐the underlying mechanisms of which are not fully understood. This essay aims to connect electrochemical performance with changes in structure during cycling. First, structural properties of LiNiO2 are compared to the substituted Ni‐rich compounds NMCs (LiNixMnyCo1−x−yO2) and NCAs (LiNixCoyAl1−x−yO2). Particular emphasis is placed on decoupling intrinsic behavior and extrinsic “two‐phase” reactions observed during initial cycles, as well as after extensive cycling for NMC and NCA cathodes. The need to revisit the various high‐voltage structural changes that occur in LiNiO2 with modern characterization tools is highlighted to aid the understanding of the accelerated degradation for Ni‐rich cathodes at high voltages.

… could work as an artificial cathode electrolyte interphase (CEI) to greatly enhance the cycle stability, moisture tolerance and even kinetics performance of Ni-rich layered oxides (NROs). …

Abstract In order to improve the performance of Ni-rich cathode materials for lithium-ion batteries at high cut-off voltage, a highly effective TiO2 nano-coating is constructed on the surface of LiNi0.8Co0.1Mn0.1O2 by precisely controlling the hydrolytic dynamics of Ti4+, and the effect of this coating layer is systematically studied, especially at high upper cut-off voltage. The continuous TiO2 nano-coating layer provides a complete protection for LiNi0.8Co0.1Mn0.1O2 particles and enhances the reversibility of the phase transition between hexagonal and hexagonal (H2→H3) during cycling, which guarantees an excellent cycling stability under high upper cut-off voltage up to 4.5 V. Electrochemical impedance spectroscopy results confirm a stable interface between electrolyte and electrode and the fast kinetics at the surface of the modified sample. High Resolution Transmission Electron Microscopy (HR-TEM) measurement for the cycled electrodes further verifies the slight structure decay of the coated sample comparing with the pristine one. Thus, the modified sample presents excellent cycling stability with capacity retention of 72.2% after 500 cycles and 63.4% after 1000 cycles with the upper cut-off voltage of 4.5 V and 4.3 V, respectively. This work provides a universal method to prepare conformal TiO2 nano-coating and also offer guidance to properly evaluate the function of a coating.

… Here, we report that infusing the grain boundaries of cathode secondary particles with a … stability of the cathode. We find that the solid electrolyte infused in the boundaries not only acts …

The wide applications of Ni-rich LiNi1- x-y Cox Mny O2 cathodes are severely limited by capacity fading and voltage fading during the cycling process resulting from the pulverization of particles, interfacial side reactions, and phase transformation. The canonical surface modification approach can improve the stability to a certain extent; however, it fails to resolve the key bottlenecks. The preparation of Li(Ni0.4 Co0.2 Mn0.4 )1- x Tix O2 on the surface of LiNi0.8 Co0.1 Mn0.1 O2 particles with a coprecipitation method is reported. After sintering, Ti diffuses into the interior and mainly distributes along surface and grain boundaries. A strong surface and grain boundary strengthening are simultaneously achieved. The pristine particles are fully pulverized into first particles due to mechanical instability and high strains, which results in serious capacity fading. In contrast, the strong surface and the grain boundary strengthening can maintain the structural integrity, and therefore significantly improve the cycle stability. A general and simple strategy for the design of high-performance Ni-rich LiNi1- x - y Cox Mny O2 cathode is provided and is applicable to surface modification and grain-boundary regulation of other advanced cathodes for batteries.

… Herein, we propose a lattice engineering and grain boundary … grain boundaries are preferentially passivated via the formed surface LiF coating, effectively shielding the cathode from …

… of the secondary particles and at the grain boundaries between the primary particles. From the OK … bonding environment within the grains is different from the one of grain boundaries. …

… and failure at grain boundaries. To address this, we propose a grain boundary engineering strategy … This phase reinforces grain boundaries by creating strong chemical bonds, buffering …

The rapidly growing demand of electrical vehicles (EVs) requires high-energy-density lithium-ion batteries (LIBs) with excellent cycling stability and safety performance. However, conventional polycrystalline high-Ni cathodes severely suffer from intrinsic chemomechanical degradation and fast capacity fade. The emerging single-crystallization strategy offers a promising pathway to improve the cathode's chemomechanical stability; however, the single-crystallinity of the cathode is not always guaranteed, and residual grain boundaries (GBs) could persist in nonideal synthesis conditions, leading to the formation of "quasi-single-crystalline" (QSC) cathodes. So far, there has been a lack of understanding of the influence of these residual GBs on the electrochemical performance and structural stability. Herein, we investigate the degradation pathway of a QSC high-Ni cathode through transmission electron microscopy and X-ray techniques. The residual GBs caused by insufficient calcination time dramatically exacerbate the cathode's chemomechanical instability and cycling performance. Our work offers important guidance for next-generation cathodes for long-life LIBs.

Grain boundary engineering, achieved by combining annealing and surface coating, is an effective strategy for modifying high-nickel-layered oxide cathode materials. However, high-temperature annealing can induce irreversible phase transformations in high-nickel materials, which significantly hinder lithiation/delithiation and degrade their electrochemical performance. In this study, we propose a grain boundary engineering approach for LiNi0.83Mn0.05Co0.12O2, combining rapid heating to the annealing temperature with atomic layer deposition (ALD) to enhance its electrochemical properties. Compared to conventional heating, the rapid heating process minimizes Li/O loss and prevents the formation of a disordered phase. More importantly, grain boundary modification and bulk gradient doping effectively reduce large cracks and the erosion of the cathode, which slows down the capacity decay during long cycles. The direct heating sample exhibits a significant improvement in capacity retention, and after stable cycling for 300 times at C/3, the capacity retention rate remained at 84.7%. This approach offers a promising low-cost strategy for the development of advanced cathode materials with enhanced cycling stability.

Nanometer-thick reconstruction layers on layered cathode surfaces have been widely observed on both pristine and cycled materials. However, the mechanisms of reconstruction and the role that these ...

The electrochemical–mechanical degradation of ultrahigh Ni cathode for lithium‐ion batteries is a crucial aspect that limits the cycle life and safety of devices. Herein, the study reports a facile strategy involving rational design of primary grain crystallographic orientation within polycrystalline cathode, which well enhanced its electro‐mechanical strength and Li+ transfer kinetics. Ex situ and in situ experiments/simulations including cross‐sectional particle electron backscatter diffraction (EBSD), single‐particle micro‐compression, thermogravimetric analysis combined with mass spectrometry (TGA‐MS), and finite element modeling reveal that, the primary‐grain‐alignment strategy effectively mitigates the particle pulverization, lattice oxygen release thereby enhances battery cycle life and safety. Besides the preexisting doping and coating methodologies to improve the stability of Ni‐rich cathode, the primary‐grain‐alignment strategy, with no foreign elements or heterophase layers, is unprecedently proposed here. The results shed new light on the study of electrochemical–mechanical strain alleviation for electrode materials.

… transition motifs at complex phase boundaries in high-Ni cathodes. We reveal that an O3 → … shear-induced phase transformations and phase boundaries in high-Ni layered cathodes. …

Further popularization of ultrahigh-Ni layered cathodes for high-energy lithium-ion batteries (LIBs) is hampered by their grievous structural and interfacial degeneration upon cycling. Herein, by leveraging the strong electronegativity and low solubility properties of Sb element, a multifunctional modification that couples atomic/microstructural reconstruction with interfacial shielding is well designed to improve the LiNi0.94Co0.04Al0.02O2 (NCA) cathode by combining Sb5+ doping and Li7SbO6 coating. Notably, a robust O framework is established by regulating local O coordination owing to the incorporation of a strong Sb-O covalence bond, leading to the inhibited lattice O evolution at high voltage, as revealed by synchrotron X-ray absorption spectroscopy. Moreover, the radially aligned primary particles with (003) crystallographic texture and refined/elongated sizes are achieved by the pinning of Sb on grain boundaries and are confirmed by scanning transmission electron microscopy, resulting in the fast Li+ diffusion and mitigated particle cracking. Additionally, in situ construction of the Li7SbO6 ionic conductive layer on grain boundaries can effectively boost interfacial stability and Li+ kinetics. As a result, the optimal Sb-modified NCA delivers a high capacity retention of 94.6% after 200 cycles at 1 C and a good rate capacity of 183.9 mAh g-1 at 10 C, which is expected to be applied to next-generation advanced LIBs.

… morphology and GB modifications of the NMC811 cathode, realizing a radial alignment of the columnar grains in the secondary particle. More cross-sectional SEM images are shown in …

Nickel adds to the capacity of layered oxide cathodes of lithium-ion batteries but comprises their stability. We report a petal-grained Li[Ni0.89Co0.10Sb0.01]O2 cathode that is, nevertheless, stable. The stability originates from the ordering of the nanosized grains in a dense, flower-petal-like array, where the elongated and nearly parallel grains radiate from the center to the surface. The ordering of the grains prevents microcrack generation from abrupt lattice changes of the stressful H2-H3 phase transition. The tight packing of the nanograins is conserved upon cycling, preventing destructive seepage of the electrolytic solution into the particles. The half-cell, cycling between 2.7-4.3 V versus Li/Li+ at a 0.5 C rate retains 95.0% of its initial capacity of 220 mAh g-1 after 100 cycles. The full-cell, cycling with a graphite anode and between 3.0-4.2 V at a 1 C rate, retains 83.9% of its initial capacity after 1000 cycles.

… ≥ 5) cathode materials, even if microcracks occur, numerous triple junctions and tortuous grain boundaries … In addition, improving the electrochemical performance of high-Ni cathodes …

Ni-rich layered cathodes have been used in commercial Li-ion batteries because of their high capacity and low cost. However, they suffer from crack formation at the grain boundaries owing to heterogeneous large volume changes during the reactions. To improve their performance, a comprehensive understanding of the grain architecture, Li transport pathways, and phase transitions is essential. Here, we show the correlations between these factors using in situ transmission electron microscopy. The results show that Li ions are extracted through tortuous paths connecting the Li-containing a-b planes in the crystals. Moreover, the grain boundary resistance depends not only on the misorientations of the neighboring grains. Even twins with misorientation angles of 70° are not decisive factors in Li movement. We also show the existence of two-phase separation in single crystals between two hexagonal phases during fast charging. These results provide valuable information for determining the optimal grain architecture and for material design, helping enhance high capacity and high stability.

… cycle life of high-Ni cathodes is more pronounced … grain boundary separation is an inherent consequence of high lithium utilization, and the natural “breathing” phenomenon of high-Ni …

… temperature is required for high Ni-content cathodes. This can be … grain boundaries and intergranular fractures during cycling. The high specific capacity, stable cyclability, high cathode …

The ever‐growing demand for high‐energy lithium‐ion batteries in portable electronics and electric vehicles has triggered intensive research efforts over the past decade. An efficient strategy to boost the energy and power density of lithium‐ion batteries is to increase the Ni content in the cathode materials. However, a higher Ni content in the cathode materials gives rise to safety issues. Herein, thermal expansion and oxygen vacancies are proposed as new critical factors that affect the thermal stability of charged Ni‐rich cathode materials based on a systematic synchrotron‐based X‐ray study of Li0.33Ni0.5+xCo0.2Mn0.3‐xO2 (x = 0, 0.1, 0.2) cathode materials during a heating process. Charged cathode materials with higher Ni contents show larger thermal expansion, which accelerates transition metal migration to the Li layers. Oxygen vacancies are formed and accumulate mainly around Ni ions until the layered‐to‐spinel phase transition begins. The oxygen vacancies also facilitate transition metal migration to the Li layers. Thermal expansion and the presence of oxygen vacancies decrease the energy barrier for cation migration and facilitate the phase transitions in charged cathode materials during the heating process. These results provide valuable guidance for developing new cathode materials with improved safety characteristics.

Abstract Despite increasing demands for higher energy density cathode materials, they can be bigger threats unless thermal stability is guaranteed. Herein, the thermal stability of LixNi0.835Co0.15Al0.015O2 (NCA83) and LixNi0.8Co0.15Al0.05O2 (NCA80) is compared by using in-situ transmission electron microscopy. Analysis demonstrates that NCA83 and NCA80 degrade thermally by distinct mechanisms. Al prevents the transition to CoO2-type O1 phase by suppressing O-slab gliding by residual Li. At 67% SOC, in the sub-surface area, thermal degradation of NCA80 is mainly due to reduction of Ni, whereas thermal degradation of NCA83 is a result of concurrent reduction of Ni and Co. The difference indicates that NCA83 has both earlier transition to the rock-salt structure and poorer thermal stability than NCA80. This study presents a protocol to properly evaluate new high energy density cathode materials, and provides important insights into the thermal degradation mechanism of Ni-based layered oxides.

… that cycling stability relies solely on Mn stability. Unraveling the … collective contributions impact the cathode's overall performance. … cycling stability of Ni-rich layered cathode materials. …

… and poor thermal stability, … Ni-rich LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathodes with Al(OH) 3 nanoparticles are selected as the model case to reveal the distinct chemical evolution on cathode …

Thermal runaway is a major safety concern hindering the large‐scale application of Ni‐rich lithium ion batteries. In this paper, the thermal runaway behaviors of lithium ion batteries with LiNi0.6Co0.2Mn0.2O2 and LiNi0.8Co0.1Mn0.1O2 cathode materials are investigated using accelerating rate calorimetry. The onset temperature of thermal runaway for the battery with LiNi0.8Co0.1Mn0.1O2 cathode is 20°C lower than that with LiNi0.6Co0.2Mn0.2O2 cathode, demonstrating that battery thermal runaway is highly correlated with cathode chemistry. In situ X‐ray diffraction and thermogravimetry tests further reveal that the LiNi0.8Co0.1Mn0.1O2 exhibits more severe structural change and oxygen generation compared to LiNi0.6Co0.2Mn0.2O2, leading to worsen of battery thermal runaway behavior. Based on the correlation between cathode thermal stability and battery thermal runaway, an approach by changing cathode morphology from polycrystal to single crystal is proposed to mitigate the thermal runaway of battery with LiNi0.8Co0.1Mn0.1O2 cathode. The single crystal LiNi0.8Co0.1Mn0.1O2 can reduce cationic distribution and enhance cathode thermal stability, and thus improve the safety performance of large format Ni‐rich battery by postponing thermal runaway by 13°C and reducing temperature rate.

Abstract LiNi0.8Co0.1Mn0.1O2 (NCM811) is demonstrated as potential cathode material for next-generation lithium-ion batteries. However, the electrochemical performance of this material is severely inhibited by structural degradation and capacity decay, especially at elevated temperatures. Herein, we try to design an ultra-thin CaF2 coating on the surface of NCM811 and examine the electrochemical performance. Physicochemical characterization results show that a CaF2 layer with a thickness of 5–12 nm was successfully attached to the surface of microspheres, without significant changes in structure or morphology. Electrochemical tests indicate that calcium fluoride modified samples especially 3 wt% exhibit a surprising cycle capability and rate performance. What's more, Calcium fluoride coating can also improve the high temperature stability of cathode material, sample with 3 wt% CaF2-coated shows an initial discharge specific capacity of 149.6 mAhg−1 and a capacity loss of 20.32% after 50 cycles at 55 °C, whereas the pristine material is 150.4 mAhg−1 and a severely capacity loss of 40.68%. The cyclic voltammograms (CV) and electrochemical impedance spectra (EIS) tests show that coated samples deliver a smaller potential difference (ΔV) and impedance after cycles, further confirming that CaF2 coating can enhance the electrochemical performance of NCM811 material.

In this study we use N,N′-bismaleimide-4,4′-diphenylmethane (BMI), trithiocyanuric acid (TCA), and Jeffamine®-M1000 (molar ratio: 2:1:1; BTJ211) as a novel hybrid oligomer …

… thermal stability of these Co-free Ni-rich cathodes remain notably scarce. In this work, … thermal degradation behavior of the Co-free Ni-rich layered LiNi 0.9 Mn 0.1 O 2 (NM91) cathode …

… Ni-rich cathode materials may offer improved safety while maintaining high performance. Herein, we show that enhanced thermal stability in NCM811 Ni-rich cathodes … cathode material …

The intrinsic poor thermal stability of layered LiNixCoyMn1-x-yO2 (NCM) cathodes and the exothermic side reactions triggered by the associated oxygen release are the main safety threats for their large-scale implantation. In the NCM family, it is widely accepted that Ni is the stability troublemaker, while Mn has long been considered as a structure stabilizer, whereas the role of Co remains elusive. Here, via Co/Mn exchange in a Ni-rich LiNi0.83Co0.11Mn0.06O2 cathode, we demonstrate that the chemical and structural stability of the deep delithiated NCM cathodes are significantly dominated by Co rather than the widely reported Mn. Operando synchrotron X-ray characterization coupling with in situ mass spectrometry reveal that the Co4+ reduces prior to the reduction of Ni4+ and could thus prolong the Ni migration by occupying the tetrahedra sites and, hence, postpone the oxygen release and thermal failure. In contrast, the Mn itself is stable, but barely stabilizes the Ni4+. Our results highlight the importance of evaluating the intrinsic role of compositional tuning on the Ni-rich/Co-free layered oxide cathode materials to guarantee the safe operation of high-energy Li-ion batteries.

Mechanical integrity issues such as particle cracking are considered one of the leading causes of structural deterioration and limited long-term cycle stability for Ni-rich cathode materials of Li-ion batteries. Indeed, the detrimental effects generated from the crack formation are not yet entirely addressed. Here, applying physicochemical and electrochemical ex situ and in situ characterizations, the effect of Co and Mn on the mechanical properties of the Ni-rich material are thoroughly investigated. As a result, we successfully mitigate the particle cracking issue in Ni-rich cathodes via rational concentration gradient design without sacrificing the electrode capacity. Our result reveals that the Co-enriched surface design in Ni-rich particles benefits from its low stiffness, which can effectively suppress the formation of particle cracking. Meanwhile, the Mn-enriched core limits internal expansion and improve structural integrity. The concentration gradient design also promotes morphological stability and cycling performances in Li metal coin cell configuration. Mechanical integrity issues are one of the main causes of limited long-term cycle stability for Ni-rich cathode materials. Here the authors analyse the roles of cobalt and manganese and utilise a concentration gradient design to mitigate these issues.

The irreversible deterioration of electrochemical performance in Ni‐rich cathode materials, attributed to crack propagation and undesired side reactions, poses a critical barrier to the further development of high‐energy power batteries for electrical vehicles (EVs). Herein, a concentration gradient strategy is proposed for synthesizing a Ni‐rich cathode with enhanced mechanical and electrochemical stability to address the issues related to the irreversible structural deterioration. Notably, the concentration gradient structure contributes to superior mechanical strength in secondary particles due to the radially orientated primary particles resulted from Mn composition grading, which effectively alleviate the internal strain caused by structural changes and fatigue destruction during successive cycling. Moreover, the Mn‐rich surface minimizes the parasitic side reactions at the electrode–electrolyte interface. Benefitting from the above, the concentration gradient sample can deliver ≈180.1 mA h g−1 at 1 C and retain 96.2% of its initial discharge capacity after 100 cycles. This work demonstrates that the concentration gradient structure can simultaneously improve the mechanical and chemical stabilities of Ni‐rich cathode and offers a feasible way for designing stable lithium‐ion batteries with high energy density.

Abstract Structural instability and inferior storage property are bottlenecks of the Ni-rich cathodes. Herein, a coating and doping co-modified Ni-rich cathode, in which La and Al is homogeneously doped in the inner and an epitaxial layer is distributed in the outer surface region of secondary particle, is constructed. The outer surface layer tightly integrates a La2O3 coating layer, an epitaxial grown La Al doped atomic structure and a Ni concentration gradient into the bulk phase. The La and Al act as a pillar ion enlarging c axis spacing and a positively charged center, enhancing Li+ transportation and suppressing the phase transition. The outer surface region with La-enriched layer and decreased Ni concentration suppresses the side reactions between organic electrolyte and oxidizing Ni4+ and improves the storage stability in air. During cycling, the modified material exhibits enhanced rate capability and cycling stability with capacity retention of 80.0% after 480 cycles at 10C in the cell potential range of 2.7–4.3 V.

Nickel-rich (Ni > 90 %) cathodes are regarded as one of the most attractive because of their high energy density, despite their poor stability and cycle life. To improve their performance, in this study we synthesized a double concentration-gradient layered Li[Ni0.90Co0.04Mn0.03Al0.03]O2 oxide (CG-NCMA) using a continuous co-precipitation Taylor-Couette cylindrical reactor (TCCR) with a Ni-rich-core, an Mn-rich surface, and Al on top. The concentration-gradient morphology was confirmed through cross-sectional EDX line scanning. The as-synthesized sample exhibited excellent electrochemical performance at high rates (5C/10C), as well as cyclability (91.5 % after 100 cycles and 70.3 % after 500 cycles at 1C), superior to that (83.4 % and 47.6 %) of its non-concentration-gradient counterpart (UC-NCMA). The Mn-rich surface and presence of Al helped the material stay structurally robust, even after 500 cycles, while also suppressing side reactions between the electrode and electrolyte, resulting in better overall electrochemical performance. These enhancements in performance were studied using TEM, SEM, in-situ-XRD, XPS, CV, EIS and post-mortem analyses. This synthetic method enables the highly scalable production of CG-NCMA samples with two concentration-gradient structures for practical applications in Li-ion batteries.

… a concentration gradient, specifically through Sr–Zr co-modification. We synthesized Ni-rich … It demonstrates a depth-dependent concentration gradient at the secondary particle level …

… novel Ni-rich cathode materials with concentration-gradient … leads to flattening of the gradient and weakens the surface … constructed a concentration-gradient nickel-rich cathode with an …

Nickel‐rich layered oxide cathode material LiNixCoyMnzO2 (NCM) has emerged as a promising candidate for next‐generation lithium‐ion batteries (LIBs). These cathode materials possess high theoretical specific capacity, fast electron/ion transfer rate, and high output voltage. However, their potential is impeded by interface instability, irreversible phase transition, and the resultant significant capacity loss, limiting their practical application in LIBs. In this work, a simple and scalable approach is proposed to prepare gradient cathode material (M‐NCM) with excellent structural stability and rate performance. Taking advantage of the strong coordination of Ni2+ with ammonia and the reduction reaction of KMnO4, the elemental compositions of the Ni‐rich cathode are reasonably adjusted. The resulted gradient compositional design plays a crucial role in stabilizing the crystal structure, which effectively mitigates Li/Ni mixing and suppresses unwanted surficial parasitic reactions. As a result, the M‐NCM cathode maintains 98.6% capacity after 200 cycles, and a rapid charging ability of 107.5 mAh g−1 at 15 C. Furthermore, a 1.2 Ah pouch cell configurated with graphite anode demonstrates a lifespan of over 500 cycles with only 8% capacity loss. This work provides a simple and scalable approach for the in situ construction of gradient cathode materials via cooperative coordination and deposition reactions.

… To overcome the aforementioned inherent shortcomings of Ni-rich layered cathodes, we … NCM cathodes, we used a similar approach to prepare a gradient Ni-rich NCA cathode with an …

A novel progressive concentration gradient cathode material, LiNi0.7Co0.13Mn0.17O2, with superior capacity and cycling stability is reported for the first time.

Abstract The construction of Nickel-rich layered oxide cathodes with concentration gradient structure (FCG) is still a tough challenge due to the adverse thermal-induced diffusion of the transition metal ions (TM) during sintering process. Here a series of full concentration gradient Li[Ni0.8Co0.1Mn0.1]O2 (FCG811) cathode materials with TiO2-regulation is constructed and studied. The introduction of TiO2 could effectively block the interdiffusion of TM in FCG811, and thus a large evolution of the composition from the central Li[Ni0.91Co0.06Mn0.03]O2 to the surficial Li[Ni0.55Co0.16Mn0.29]O2 is achieved. The larger gradient enables the FCG cathodes with higher electrochemical stability and smaller internal strain at highly charged state. In addition, the Ti4+ doping is also acquired, which is favorable for the structural durability of the NCM cathodes. As a result, the FCG811 with TiO2 incorporation displays high capacity of 169 mAh g−1, with 96% retention after 150 cycles, which is 18% higher than that of the conventional FCG811. Structural and compositional characterizations (i.e., in-situ XRD, EIS, XPS and HRTEM) further reveal the electrochemical mechanism and kinetics of the designed FCG811-TiO2 cathode.

… we successfully design and fabricate the layered oxide cathode material Li[(Ni 0.90 Co 0.10 … NC90 cathode will increase from 0.472 nm to 0.491 nm due to the concentration gradient Te…

… Ni-rich layered cathode materials (LiNi x Co y Mn 1-xy O 2 ) … the commercialization of high nickel cathodes. In this paper, … -NCM5) with Mn concentration gradient, which the Ni content is …

Major challenge hindering the large-scale applications of Ni-rich cathode materials (CAMs) lies on the poor cycle (especially under elevated temperature or high cutoff voltage) and …

… cathode surface remains susceptible to electrolyte attack due to its high Ni content. When designing the Ni-rich cathode with concentration-gradient … -free Ni-rich cathodes with superior …

Developing cost-effective high-voltage Ni-rich cathodes has reached a consensus to replace conventional ultrahigh Ni counterparts for high-energy Li-ion batteries, but more rigorous requirements are put forward for their mechanical and chemical stability. Herein, we report the design and synthesis of a full concentration gradient LiNi0.75Mn0.20Co0.05O2 cathode with a Mn-rich Ni-poor surface, which has been realized by in situ forming a PO43- gradient distribution to retard the transition-metal ions' interdiffusion during the high-temperature lithiation process. This design mitigates the mechanical stress concentration at the source with high morphological integrity and refrains the lattice oxygen loss under 4.5 V high-voltage operation. After Li0.1B0.967PO4 is coated, the surface parasitic reactions are further ameliorated with stable interface chemistry. The resultant Ni-rich cathodes deliver a reversible capacity as high as 212.6 mAh g-1 at 2.7-4.5 V with an energy density of >800 Wh kg-1cathode, almost equivalent to the state-of-the-art Ni-content 90% cathodes at 2.7-4.3 V. In commercial-grade full cells, a superior cycle life of 80.5% capacity retention is achieved at 1C within 2.7-4.5 V after 1700 cycles, exhibiting promising opportunities in compositional gradient design for Ni-rich cathodes.

… performance of FCG Ni-rich layered cathode materials. In this … of FCG Ni-rich layered LiNi 0.80 Co 0.05 Mn 0.15 O 2 (FNCM) … improve the cycle stability of FCG Ni-rich cathode materials. …