最新高镍文献与国际高水平期刊发表的创新想法

Abstract Ni-rich layered oxides, LiNixCoyMnzO2 (NCM) and LiNixCoyAlzO2 (NCA) with x ​+ ​y ​+ ​z ​= ​1 and x ​≥ ​0.8, are regarded to be the best choice for the cathode material of high energy Li-ion batteries due to their combined advantages in capacity, working potential and manufacture cost. However, their application in practical Li-ion batteries is hindered by two essential problems of (1) performance degradation and (2) safety hazard over the whole life of battery. Performance degradation behaves as declines in battery's capacity and working voltage as well as the battery's swelling and impedance growth; Safety hazard arises from thermal runaway under abuse conditions such as overcharging, overheating, and electric shorting. It appears that nearly all problems can be ultimately attributed to the loss of oxygen, especially caused by the oxidation of lattice oxygen in H3 phase where the capacities are contributed by both of the Ni and O redox couples. In this review, the problems and their origins of Ni-rich layered oxides are overviewed, and the solutions attempted to mitigate these problems are outlined.

Ni-rich layered oxide cathode materials hold great promise for enhancing the energy density of lithium-ion batteries (LIBs) due to their impressive specific capacity. However, the chemical and structural stability issues associated with the materials containing a high Ni content have emerged as a primary safety concern, particularly in the context of traction batteries for electric vehicles. Typically, when these materials are in a highly charged state, their metastable layered structure and highly oxidized transition metal ions can trigger detrimental phase transitions. This leads to the generation of oxygen gas and the degradation of the material’s microstructure, including the formation of cracks, which can promote the interactions between Ni-rich materials and electrolytes, further generating flammable gases. Consequently, various strategies have been devised at the material level to mitigate potential safety hazards. This review begins by providing an in-depth exploration of the sources of instability in Ni-rich layered oxides, drawing from their crystal and electronic structures, and subsequently outlines the safety issues that arise as a result. Subsequently, it delves into recent advancements and approaches aiming at modifying Ni-rich cathode materials and electrolytes to enhance safety. The primary objective of this review is to offer a concise and comprehensive understanding of why Ni-rich cathode materials are susceptible to safety incidents and to present potential methods for improving the safety of Ni-rich cathode materials in high-density LIBs. Graphical Abstract Safety risk origin of Ni-rich cathode materials, potential safety issues, and possible measures to improve safety are summarized.

… Due to the potential in enhancing energy density and cyclic life of LIBs, Ni-rich layered NCM (NCM, x ≥ 0.6) have garnered significant research attention. However, improved specific …

A critical challenge in the commercialization of layer‐structured Ni‐rich materials is the fast capacity drop and voltage fading due to the interfacial instability and bulk structural degradation of the cathodes during battery operation. Herein, with the guidance of theoretical calculations of migration energy difference between La and Ti from the surface to the inside of LiNi0.8Co0.1Mn0.1O2, for the first time, Ti‐doped and La4NiLiO8‐coated LiNi0.8Co0.1Mn0.1O2 cathodes are rationally designed and prepared, via a simple and convenient dual‐modification strategy of synchronous synthesis and in situ modification. Impressively, the dual modified materials show remarkably improved electrochemical performance and largely suppressed voltage fading, even under exertive operational conditions at elevated temperature and under extended cutoff voltage. Further studies reveal that the nanoscale structural degradation on material surfaces and the appearance of intergranular cracks associated with the inconsistent evolution of structural degradation at the particle level can be effectively suppressed by the synergetic effect of the conductive La4NiLiO8 coating layer and the strong TiO bond. The present work demonstrates that our strategy can simultaneously address the two issues with respect to interfacial instability and bulk structural degradation, and it represents a significant progress in the development of advanced cathode materials for high‐performance lithium‐ion batteries.

Ni‐rich layered LiNixCoyMn1−x−yO2 (LNCM) with Ni content over >90% is considered as a promising lithium ion battery (LIB) cathode, attributed by its low cost and high practical capacity. However, Ni‐rich LNCM inevitably suffers rapid capacity fading at a high state of charge due to the mechanochemical breakdown; in particular, the microcrack formation has been regarded as one of the main culprits for Ni‐rich layered cathode failure. To address these issues, Ni‐rich layered cathodes with a textured microstructure are developed by phosphorous and boron doping. Attributed by the textured morphology, both phosphorous‐ and boron‐doped cathodes suppress microcrack formation and show enhanced cycle stability compared to the undoped cathode. However, there exists a meaningful capacity retention difference between the doped cathodes. By adapting the various analysis techniques, it is shown that the boron‐doped Ni‐rich layered cathode displays better cycle stability not only by its ability to suppress microcracks during cycling but also by its primary particle morphology that is reluctant to oxygen evolution. The present work reveals that not only restraint of particle cracks but also suppression of oxygen release by developing the oxygen stable facets is important for further improvements in state‐of‐the‐art Li ion battery Ni‐rich layered cathode materials.

… , 0.20, and 0.30) cathode materials, combining the advantages of the high specific capacity of the Ni-rich layered phase and the surface chemical stability of the Li-rich layered phase. X-…

Nickel‐rich layered transition‐metal oxides with high‐capacity and high‐power capabilities are established as the principal cathode candidates for next‐generation lithium‐ion batteries. However, several intractable issues such as the poor thermal stability and rapid capacity fade as well as the air‐sensitivity particularly for the Ni content over 80% have seriously restricted their broadly practical applications. The properties and nature of the stable surface/interface, where the Li+ shuttles back and forth between the cathode and electrolyte, play a significant role in their ultimate lithium‐storage performance and industrial processability. Thus, tremendous efforts are made to in‐depth understanding of the essential origins of surface/interface structure degradation and efficient surface modification methodologies are intensively explored. The purpose of the contribution is first to provide a comprehensive review of the up‐to‐date mechanisms proposed to rationally elucidate the surface/interface behaviors, and then, focus on recent developed strategies to optimize the surface/interface structure and chemistry including synthetic condition regulation, surface doping, surface coating, dual doping‐coating modification, and concentration‐gradient structure as well as electrolyte additives. Finally, the perspective on future research trends and feasible approaches toward advanced Ni‐rich cathodes with stable surface/interface is presented briefly.

… Ni-rich layered oxides and Li-rich layered oxides are topics of much research interest as cathodes for Li-ion … However, Ni-rich layered oxides have several pitfalls, including difficulty in …

Abstract Ni-rich layered oxides with chemical formula of LiNixCoyMnzO2 or LiNixCoyAlzO2 (x + y + z = 1, x ≥ 0.6) have been considered as promising cathode materials for lithium-ion batteries (LIBs) because of their high specific capacity (≥180 mAh g–1) and acceptable manufacture cost. However, the problems associated with high Ni content severely restrict their large-scale applications. In this review, we summarize the recent advances in Ni-rich layered oxide particle materials for LIBs. We begin with the introduction of the structure, redox mechanism, and problems of Ni-rich layered oxides, mainly including residual lithium compounds, gas evolution, rock-salt phase formation, microcrack of particles, dissolution of transition-metal ions, and thermal runaway. Then, four strategies (primary particle engineering, surface coating, doping, concentration gradient design) toward solving the problems of Ni-rich layered oxides will be systematically discussed with the emphasis on structure-performance relationships. To achieve satisfied comprehensive performance and accelerate large-scale applications of Ni-rich layered oxides, the combination of two or more strategies (particle engineering and surface/bulk stabilization techniques) with synergistic effects is necessary in future works. This review would promote further research and application of high-performance Ni-rich layered oxide particle materials for LIBs.

Abstract Ni-rich layered oxides (LiNi1-x-yCoxMnyO2, 1-x-y ≥ 0.5) are attracting great attention due to their high capacity and operating voltage. However, Ni-rich layered oxides still face long-standing challenges, such as incomplete capacity release and fast capacity fade, especially at high C rates. Herein, we implement a wet chemical method to dope Ti into LiNi0.8Co0.1Mn0.1O2 (NCM811). We discover that NCM811 with the homogeneously distributed Ti can effectively enhance ion transfer kinetics and thus greatly improve capacity delivery at high C rates. The Ti-doped NCM811 exhibits a capacity of 196 mAh/g and 157 mAh/g at 0.5C and 2C in voltage range of 2.8–4.6 V, 5% higher (188 mAh/g at 0.5C) and 15% higher (136 mAh/g at 2C) than the pristine NCM811. Ti-doped NCM811 cathodes also exhibit enhanced cycling stability with capacity retention of 84% after 100 cycles at 1C, which shows that our methodology for Ti doping is potentially competitive for a practical production of Ni-rich layered oxides.

… The findings shed light on designing high performance Ni-rich layered oxide cathodes … The findings shed light on designing high performance Ni-rich layered oxide cathodes through …

Surface engineering is sought to stabilize nickel-rich layered oxide cathodes in high-energy-density lithium-ion batteries, which suffer from severe surface oxygen loss and rapid structure degradation, especially during deep delithiation at high voltages or high temperatures. Here, we propose a well-designed oxygen-constraining strategy to address the crisis of oxygen evolution. By integrating a La, Fe gradient diffusion layer and a LaFeO3 coating into the Ni-rich layered particles, along with incorporating an antioxidant binder into the electrodes, three progressive lines of defense are constructed: immobilizing the lattice oxygen at the subsurface, blocking the released oxygen at the interface, and capturing the residual singlet oxygen on the external surface. As a result, effective surface passivation, mitigated bulk and surface degradation, suppressed side reactions, and enhanced electrochemical performance are achieved, far beyond conventional single surface modification. The Ni-rich layered oxide cathodes with integrated oxygen-constraining modifications demonstrate impressive cycling stability in both half-cells and full cells, achieving stable long-term cycling even at a high cutoff voltage of 4.7 V and a high temperature of 45 °C. This work provides a multilevel oxygen-constraining strategy, which can be extended to various layered oxide cathodes involving oxygen release challenges, providing an effective path for the development of high-energy-density lithium-ion batteries.

… the structural transformations in the Ni-rich layered oxides. These will spur new strategies to enhance the performance of the cathode materials for the next-generation Li-ion batteries. …

… the crystal growth during the synthesis of highly Ni-rich cathode materials, leading to a reduced Li … This study provides valuable insights for the design of cobalt-free Ni-rich cathodes and …

Abstract Ni-rich layered transition metal oxide is one of the most promising cathode materials for the next generation lithium-based automotive batteries due to its excellent electrochemical performances. Nevertheless, its further applications are capped by the structural/interfacial instability during the prolonged charging/discharging, leading to severe performance fading and serious safety concerns. Here, we provide a comprehensive review about challenges and solutions to modify Ni-rich layered cathodes specifically for microcrack failure. Firstly, the mechanism of microcrack formation and evolution are concluded thoroughly. Secondly, recent advances in stabilizing the structure/interface of Ni-rich cathodes are summarized such as surface coating, cation/anion doping, composition tailoring, morphology engineering and electrolytes optimization. Furthermore, strategies to mitigate the microcrack and then boost the electrochemical performance of Ni-rich cathodes at the chemical & mechanical engineering level are presented. More importantly, outlook and perspectives to facilitate the practical application of Ni-rich layered cathodes toward electrical vehicle application are provided as well.

Abstract Ni-rich layered lithium transition metal oxides (LTMO) are regarded as one of the most potential candidates to usher in a new stage of the ultra-high available energy density lithium-ion batteries (LIBs). However, the severe capacity and voltage fading remain a big challenge on the practical application, while lacking of atomic scale evidence makes the performance degradation mechanism of Ni-rich LTMO essentially ambiguous. Here we report a more accurate study on the detailed structural transformation and chemical evolution processes upon cycling to shed light on the performance decay from the perspective of variation on the nature of the stoichiometric Ni-rich LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode. A novel continuous structural evolution mechanism at atomic scale based on the migration of transition metal cations into lithium ion diffusion channels has been proposed to acquire a new insight into the energy decay behaviour of Ni-rich cathode. It is demonstrated that Ni would migrate from bulk to surface along with the irreversible reduction by virtue of the low diffusion barrier and the Ni concerntration gradient in lattice, resulting in the growth of structural restruction layer (SRL) throughout the whole charge/discharge processes and the ongoing performance decay. Thus, the future works on achieving higher available energy and longer cycle life for Ni-rich layered cathodes should focus on how to prevent the migration of transition metal ions.

Ni‐rich layered oxides are promising cathode material for high‐energy‐density lithium‐ion batteries (LIBs). However, they suffer from poor capacity retention due to unstable structures. Herein, a strategy of high‐valence W doping is put forward to tune the nanometer‐sized crystal domains and reshape the primary particle textures, which can stabilize the structure against the formation of microcracks to improve the electrochemical performance. The Ni‐rich layered oxide with 0.5 mol% doped W delivers a high‐capacity retention of 91.6% up to 300 cycles under 1 C. Such an improved performance is ascribed to the pre‐introduced nanometer‐sized spinel and rock‐salt crystal domains, which remarkably improve the structure stability, and the radially alignment of primary particles, and effectively reduce the anisotropic mechanical strain in deep charge states. This study sheds light on the design of high‐performance Co‐less Ni‐rich cathode materials through the adjustment of microstructures via a small amount of suitable dopants.

Nickel-rich layered oxides are envisaged as key near-future cathode materials for high-energy lithium-ion batteries. However, their practical application has been hindered by their …

… Here, we investigate the dominant mechanism of nonlinear capacity fading of Ni-rich electrode materials under different charge-discharge rates. Despite the high initial discharge …

Abstract Ni-rich layered oxide (LiNixMnyCozO2 (NMC), x > 60%), one of the most promising cathode materials for high-energy lithium ion batteries (LIBs), still suffers from surface instability even with the state-of-art protective coatings, which normally are limited to ≤10 nm to maintain the required kinetics. Here we demonstrate a highly conductive protective layer with bio-tissue structure that can enable high-rate operation of NMC cathodes even with a thickness exceeding 40 nm. With this thick protection layer, the modified LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode retains 90.1% and 88.3% of its initial capacity after 1000 cycles in coin cells and pouch cells, respectively. This novel membrane is composed of crystalline nano-domains surrounded by ~1 nm amorphous phase, which is an effective distance to enable tunneling of electrons and Li+ ions between these domains. The coated NMC811 cathode releases ~55.3% less heat under thermal abuse and largely enhances his safety feature during puncture test. The coating also enables excellent electrochemical stability of NMC811 even after it was exposed to a moist environment for four weeks at 55 °C, which is critical for large-scale production of high-energy-density LIBs.

… various micrometer-scale pristine NCM-811 powders via a solid-… the NCM-811 cathode material to highlight the importance of the size effect. The results showed that NCM-811 cathode …

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...

Abstract High nickel LiNi0·8Co0·1Mn0·1O2 (NCM811) cathode materials have advantages of high specific energy and relatively low-cost, so that it has a very broad application prospect in the future power lithium ion batteries. In this paper, the issues and challenges of NCM811 materials are overviewed, including the disadvantages of mixed cation discharge, weak thermal stability, poor cycle performance and storage characteristics, and safety hazard. The modification strategies for NCM811 materials, including ion doping modification, coating modification, structure design optimization are summarized and analyzed with emphasis on the future development trend and perspectives of high nickel NCM811 materials.

The utilization of high nickel content NCM cathode material is now viewed as the promising strategy to alleviate the gap between the demand and supply in the commercialized Li-ion …

High nickel (Ni ≥ 80%) lithium‐ion batteries (LIBs) with high specific energy are one of the most important technical routes to resolve the growing endurance anxieties. However, because of their extremely aggressive chemistries, high‐Ni (Ni ≥ 80%) LIBs suffer from poor cycle life and safety performance, which hinder their large‐scale commercial applications. Among varied strategies, electrolyte engineering is very powerful to simultaneously enhance the cycle life and safety of high‐Ni (Ni ≥ 80%) LIBs. In this review, the pivotal challenges faced by high‐Ni oxide cathodes and conventional LiPF6‐carbonate‐based electrolytes are comprehensively summarized. Then, the functional additives design guidelines for LiPF6‐carbonate ‐based electrolytes and the design principles of high voltage resistance/high safety novel electrolytes are systematically elaborated to resolve these pivotal challenges. Moreover, the proposed thermal runaway mechanisms of high‐Ni (Ni ≥ 80%) LIBs are also reviewed to provide useful perspectives for the design of high‐safety electrolytes. Finally, the potential research directions of electrolyte engineering toward high‐performance high‐Ni (Ni ≥ 80%) LIBs are provided. This review will have an important impact on electrolyte innovation as well as the commercial evolution of high‐Ni (Ni ≥ 80%) LIBs, and also will be significant to breakthrough the energy density ceiling of LIBs.

… ternary LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) cathode … However, many problems still exist in high-nickel materials: (1) … In this paper, a high-nickel ternary NCM811 cathode material …

The aim of this article is to examine the progress achieved in the recent years on two advanced cathode materials for EV Li-ion batteries, namely Ni-rich layered oxides LiNi0.8Co0.15Al0.05O2 (NCA) and LiNi0.8Co0.1Mn0.1O2 (NCM811). Both materials have the common layered (two-dimensional) crystal network isostructural with LiCoO2. The performance of these electrode materials are examined, the mitigation of their drawbacks (i.e., antisite defects, microcracks, surface side reactions) are discussed, together with the prospect on a next generation of Li-ion batteries with Co-free Ni-rich Li-ion batteries.

… 2 (NCM811) cathode combining sol–gel method and heat treatment. The capacity retention and operating voltage stability of the cathode … The modified NCM811 exhibited a high cycling …

With the rapid increase in demand for high-energy-density lithium-ion batteries in electric vehicles, smart homes, electric-powered tools, intelligent transportation, and other markets, high-nickel multi-element materials are considered to be one of the most promising cathode candidates for large-scale industrial applications due to their advantages of high capacity, low cost, and good cycle performance. In response to the competitive pressure of the low-cost lithium iron phosphate battery, high-nickel multi-element cathode materials need to continuously increase their nickel content and reduce their cobalt content or even be cobalt-free and also need to solve a series of problems, such as crystal structure stability, particle microcracks and breakage, cycle life, thermal stability, and safety. In this regard, the research progress of high-nickel multi-element cathode materials in recent years is reviewed and analyzed, and the progress of performance optimization is summarized from the aspects of precursor orientational growth, bulk phase doping, surface coating, interface modification, crystal morphology optimization, composite structure design, etc. Finally, according to the industrialization demand of high-energy-density lithium-ion batteries and the challenges faced by high-nickel multi-element cathode materials, the performance optimization direction of high-nickel multi-element cathode materials in the future is proposed.

The commonly used polycrystalline Ni-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode materials suffer from the electrochemical degradation such as rapid impedance growth and capacity decay due to their intrinsically vulnerable grain-boundary fracture during...

… High-nickel layered oxides, like LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811), are promising cathode … However, the serious cathode-electrolyte interface reactions and cathode degradation …

… instability in high-nickel layered LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) cathodes caused by … Electrochemical characterization demonstrates that the optimized NCM811@3Cr sample …

… Those limitations of LIBs incorporating Ni-rich NCM cathode materials are mainly attributed … coin-type cells incorporating the pristine NCM811 and the BTJ-L@NCM811 cathodes. …

… of sintering temperature on the crystal structure of NCM 811. The XRD peaks of all the samples … In high-nickel cathode materials, the extent of cation mixing is assessed by the intensity …

… As a result, the NCM811 modified with the rare earth composite … 117 mAh g −1 ) at 5 C than the NCM811. Even the designed full … storage performance of high-nickel NCM811 cathodes. …

Doping of Ni-rich cathode active materials with boron is a promising way to improve their cycling stability and mitigate their degradation, but it is still not understood how this effect is achieved and where the boron is located. To receive deeper insights into the impact of doping on atomic and microscale properties, B-doped Li[Ni0.8Co0.1Mn0.1]O2 (NCM811) cathode materials were synthesized by a hydroxide coprecipitation as a model compound to verify the presence and location of boron in B-doped, Ni-rich NCM, as well as its impact on the microstructure and electrochemical properties, by a combined experimental and theoretical approach. Besides X-ray diffraction and Rietveld refinement, DFT calculation was used to find the preferred site of boron absorption and its effect on the NCM lattice parameters. It is found that boron shows a trigonal planar and tetrahedral coordination to oxygen in the Ni layers, leading to a slight increase in lattice parameter c through an electrostatic interaction with Li ions. Therefore, B-doping of NCM811 affects the crystal structure and cation disorder and leads to a change in primary particle size and shape. To experimentally prove that the observations are caused by boron incorporated into the NCM lattice, we detected, quantified, and localized boron in 2 mol % B-doped NCM811 by ion beam analysis and TOF-SIMS. It was possible to quantify boron by NRA with a depth resolution of 2 μm. We found a boron enrichment on the agglomerate surface but also, more importantly, a significant high and constant boron concentration in the interior of the primary particles near the surface, which experimentally verifies that boron is incorporated into the NCM811 lattice.

As two typical layered nickel-rich ternary cathode materials, NCA and NCM are expected to be commercialized in lithium-ion batteries. However, NCA is more stable than NCM, because the structural stability of Al doped in the nickel-rich layered oxide is stronger than Mn.

… the NCA cathode is stable with excellent cycling stability at … cycling stability degradation of the nickel-rich NCA cathode via … of the cycling stability degradation of the nickel-rich cathode is …

… Nickel-rich layered oxide cathodes offer high reversible … structural stability compared to polycrystalline (PC) cathodes. In … 2 (PC- and SC-NCA) layered oxide cathodes are obtained after …

With increasing demands for high energy lithium-ion batteries, layered nickel-rich cathode materials have been considered as the most promising candidate due to their high reversible capacity and low cost. Although some of the materials with nickel contents %60% were commercialized, there are tremendous obstacles for further improvement of electrochemical performance, which is strongly related to the unstable cathode surface and interfacial properties. In this regard, a specific review on the interfacial chemistry between the cathode and electrolyte during electrochemical testing is provided. We highlight the underpinning interfacial chemistry and degradation mechanisms of the cathode materials. Finally, light is shed on the recent efforts for enhancing the interfacial stability of the nickel-rich cathode materials.

Nickel-rich LiNi0.8Co0.15Al0.015O2 (NCA) with excellent energy density is considered one of the most promising cathodes for lithium-ion batteries. Nevertheless, the stress concentration caused by Li+/Ni2+ mixing and oxygen vacancies leads to the structural collapse and obvious capacity degradation of NCA. Herein, a facile codoping of anion (F-)-cation (Mg2+) strategy is proposed to address these problems. Benefiting from the synergistic effect of F- and Mg2+, the codoped material exhibits alleviated Li+/Ni2+ mixing and demonstrates enhanced electrochemical performance at high voltage (≥4.5 V), outperformed the pristine and F-/Mg2+ single-doped counterparts. Combined experimental and theoretical studies reveal that Mg2+ and F- codoping decreases the Li+ diffusion energy barrier and enhances the Li+ transport kinetics. In particular, the codoping synergistically suppresses the Li+/Ni2+ mixing and lattice oxygen escape, and alleviates the stress-strain accumulation, thereby inhibiting crack propagation and improving the electrochemical performance of the NCA. As a consequence, the designed Li0.99Mg0.01Ni0.8Co0.15Al0.05O0.98F0.02 (Mg1+F2) demonstrates a much higher capacity retention of 82.65% than NCA (55.69%) even after 200 cycles at 2.8-4.5 V under 1 C. Furthermore, the capacity retention rate of the Mg1+F2||graphite pouch cell after 500 cycles is 89.6% compared to that of the NCA (only 79.4%).

… are ultrafine, monodisperse, and exhibit high thermal stability. This method is widely used to develop nickel-rich NCA cathode materials. Because of the shorter reaction and sintering …

… is presented to restore the structural stability and electrochemical performances of degraded … stability both at room and elevated temperatures compared with degraded NCA cathodes. …

Ni-rich Li[Ni1–x–yCoxAly]O2 (NCA) cathodes (1 – x – y = 0.8, 0.88, and 0.95) are synthesized to investigate the capacity fading mechanism of Ni-rich NCA cathodes. The capacity retention and thermal property of the cathodes deteriorate as their discharge capacity increases when the Ni fraction is increased. The capacity fading correlates well with the anisotropic volume variations caused by the H2–H3 phase transition and the resulting extent of microcracking. Although all three cathodes start to develop microcracks after being charged to 3.9 V, the potential at which microcracks propagated to the outer surface of the particle decreases with increasing Ni content. These microcracks undermine the mechanical integrity of the cathode and facilitate electrolyte penetration into the particle core, which accelerates surface degradation of the internal primary particles. Therefore, mitigating or delaying the H2–H3 phase transition is key to improving the cycling performance of Ni-rich NCA cathodes.

… Ta-doped nickel-rich cathode material in our case displays better cycling stability in terms of single ion doping when compared to the other results reported for Ta-doped NCA cathodes. …

… We prepared nickel-rich LiNi 0.84 Co 0.14 Al 0.02 O 2 cathode (NCA) with an average diameter of ≈14 µm by using traditional coprecipitation method (Figure S1, Supporting …

Layered, nickel-rich lithium transition metal oxides have emerged as leading candidates for lithium-ion battery (LIB) cathode materials. High-performance applications for nickel-rich cathodes, such as electric vehicles and grid-level energy storage, demand electrodes that deliver high power without compromising cell lifetimes or impedance. Nanoparticle-based nickel-rich cathodes seemingly present a solution to this challenge due to shorter lithium-ion diffusion lengths compared to incumbent micrometer-scale active material particles. However, since smaller particle sizes imply that surface effects become increasingly important, particle surface chemistry must be well characterized and controlled to achieve robust electrochemical properties. Moreover, residual surface impurities can disrupt commonly used carbon coating schemes, which result in compromised cell performance. Using x-ray photoelectron spectroscopy, here we present a detailed characterization of the surface chemistry of LiNi0.8Al0.15Co0.05O2 (NCA) nanoparticles, ultimately identifying surface impurities that limit LIB performance. With this chemical insight, annealing procedures are developed that minimize these surface impurities, thus improving electrochemical properties and enabling conformal graphene coatings that reduce cell impedance, maximize electrode packing density, and enhance cell lifetime fourfold. Overall, this work demonstrates that controlling and stabilizing surface chemistry enables the full potential of nanostructured nickel-rich cathodes to be realized in high-performance LIB technology.

Ni-rich LiNi1–x–yMnxCoyO2 (NMC) cathode materials are being aggressively developed for high-voltage applications such as electric vehicles. These materials are desirable because of their high volum...

This Perspective discusses the prospective strategies for overcoming the stability and capacity trade-off associated with increased Ni content in layered Ni-rich Li[NixCoyMnz]O2 (NCM) and Li[NixCoy...

… recent and promising results concerning NCA and NCM cathode materials. Published results … Thus, if the cathode materials are covered with stable metal fluoride layers such as AlF 3 , …

… material, Li 1.5 Ni 0.25 Mn 0.75 O 2.5 (LNMO, synthesized by a co-precipitation method) with commercially available nickel-rich cathode material, LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC 811). …

Driven by the increasing plea for greener transportation and efficient integration of renewable energy sources, Ni-rich metal layered oxides, namely NMC, Li [Ni1−x−yCoyMnz] O2 (x + y ≤ 0.4), and NCA, Li [Ni1−x−yCoxAly] O2, cathode materials have garnered huge attention for the development of Next-Generation lithium-ion batteries (LIBs). The impetus behind such huge celebrity includes their higher capacity and cost effectiveness when compared to the-state-of-the-art LiCoO2 (LCO) and other low Ni content NMC versions. However, despite all the beneficial attributes, the large-scale deployment of Ni-rich NMC based LIBs poses a technical challenge due to less stability of the cathode/electrolyte interphase (CEI) and diverse degradation processes that are associated with electrolyte decomposition, transition metal cation dissolution, cation–mixing, oxygen release reaction etc. Here, the potential degradation routes, recent efforts and enabling strategies for mitigating the core challenges of Ni-rich NMC cathode materials are presented and assessed. In the end, the review shed light on the perspectives for the future research directions of Ni-rich cathode materials.

Residual impurities such as lithium carbonate and hydroxide are a major concern for accelerating parasitic reactions at the cathode electrolyte interface of lithium‐ion batteries. Removal of these lithium‐bearing species becomes a necessity for high‐performance nickel‐rich cathode materials. Instead of directly removing these impurities through washing steps, a wet impregnation process is employed to convert these detrimental surface impurities into beneficial surface coating on nickel‐rich cathode materials. Specifically, the pristine cathode material is treated with Al(H2PO4)3 solution to convert undesired compounds into Li3PO4 and AlPO4, both of which are considered positive surface coating materials for high‐voltage cathodes. It is found that the introduced modification greatly suppresses the interfacial impedance hike and improves the capacity retention of the cathode material after repeating charging/discharging. It is believed that these benefits are realized through the modification of the surface chemistry of the cathode material, which helps to slow down the parasitic reactions and reduce the damage to the cathode material.

… layer with high stability instead of Li 2 CO 3 on the outer surface of NCA. … stable phosphate skim improves the electrochemical stability of NCA effectively, and the modified cathode …

High energy density Ni‐rich layered oxide cathodes LiNi0.83Co0.12Mn0.05−xAlxO2 (x = 0 [NMC], 0.025 [NMCA], 0.05 [NCA]) are fabricated in two different microstructural forms: (i) nanoparticles (NP) and (ii) nanofibers (NF), to evaluate the morphology and compositional effect on the electrochemical properties using same precursors, with the latter fabricated by electrospinning process. Although all the cathodes exhibit a similar crystal structure as confirmed using X‐ray diffraction and Raman spectroscopy, the contrasting difference is observed in their electrochemical properties. XRD and XPS analyses indicate a higher amount of cationic disorder for the NP cathodes compared to their NF counterparts. Nanofibrous Ni‐rich layered oxide cathodes exhibit higher discharge capacities at all C‐rates in comparison to NP cathodes. When cycled at 1C‐rate for 100 cycles, capacity retention of 81% is observed for NCA‐NF, which is superior to all cathodes. Voltage decay as a function of the charge–discharge cycle is found to be low (0.2 mV/cycle) for nanofibrous cathodes compared to 1.5 mV/cycle for NP cathodes. The good rate capability and cyclic stability of nanofibrous Ni‐rich layered oxide cathodes are attributed to a shorter pathway of Li+ diffusion and a large proportion of the active surface area.

Single‐crystal nickel‐rich cathode materials (SC‐NRCMs) are the most promising candidates for next‐generation power batteries which enable longer driving range and reliable safety. In this review, the outstanding advantages of SC‐NRCMs are discussed systematically in aspects of structural and thermal stabilities. Particularly, the intergranular‐crack‐free morphology exhibits superior cycling performance and negligible parasitic reactions even under severe conditions. Besides, various synthetic methods are summarized and the relation between precursor, sintering process, and final single‐crystal products are revealed, providing a full view of synthetic methods. Then, challenges of SC‐NRCMs in fields of kinetics of lithium diffusion and the one particularly occurred at high voltage (intragranular cracks and aggravated parasitic reactions) are discussed. The corresponding mechanism and modifications are also referred. Through this review, it is aimed to highlight the magical morphology of SC‐NRCMs for application perspective and provide a reference for following researchers.

Single-crystal nickel-rich materials are considered promising cathode materials for high-energy lithium-ion batteries. The reduction in grain boundaries reduces the initiation and propagation of microcracks, thereby improving cycling stability and thermal resistance. However, the dense structure of single-crystal particles restricts lithium-ion diffusion and weakens interfacial stability, leading to poor rate performance. Therefore, further advancements are necessary to meet the performance requirements of next-generation lithium-ion batteries. This review summarizes current synthesis strategies-including co-precipitation combined with solid-state sintering, molten salt flux, sol-gel, spray pyrolysis, and solid-state methods-with an emphasis on their influence on particle morphology and crystallinity. Various modification techniques, such as element doping, surface coating, and interfacial engineering, are also discussed for their roles in enhancing lithium-ion transport and mitigating structural degradation. Comparative electrochemical analysis shows that single-crystal nickel-rich materials exhibit higher capacity retention and slower capacity fading than polycrystalline counterparts under high-rate and elevated-temperature conditions. However, issues such as sluggish lithium-ion diffusion kinetics, cation mixing, and intragranular cracking remain to be addressed. Future research should integrate a deeper understanding of failure mechanisms with scalable synthesis techniques and cost-effective processing to facilitate the commercial application of single-crystal nickel-rich cathodes.

… of single-crystal nickel-rich layered cathode materials from the … design of single-crystal nickel-rich cathode materials should … development of single-crystal nickel-rich cathode materials, …

Abstract Electro-mechanical degradation is commonly observed in various battery electrode materials, which are often prepared as polycrystalline particles consisting of nanoscale primary grains. The anisotropic volume change during lithium extraction/insertion makes these materials intrinsically vulnerable to grain-boundary (inter-granular) fracture that leads to rapid impedance growth and capacity decay. Here, guided by fracture mechanics analysis, we synthesize microsized single-crystal Ni-rich layered-oxide (NMC) cathode materials via an industrially-applicable molten-salt approach. Using single-crystal LiNi0.6Mn0.2Co0.2O2 as a model material, we show that the cycle performance of the Ni-rich NMC can be significantly improved by eliminating the internal grain boundaries and inter-granular fracture. The single-crystal LiNi0.6Mn0.2Co0.2O2 cathodes show high specific capacity (183 ​mAh g−1 ​at 0.1 ​C rate, 4.3–2.8 ​V) and excellent capacity retention (94% after 300 cycles at 1C/1C cycling). Further, it is confirmed for the first time that the single-crystal LiNi0.6Mn0.2Co0.2O2 particles are stable against intra-granular fracture as well under normal operating conditions but do crack if severely overcharged. Electrochemical-shock resistant single-crystal NMC reveals an alternative path towards developing better battery cathode materials, beyond the traditional one built upon polycrystalline NMC.

… In this study, single-crystal NCM811 (SNCM811) was … LiPF 6 , a Ni-rich single-crystal NCM811 modified by both Al bulk … And the capacity retention of the single-crystal cathode materials …

Nickel‐rich layered oxides are a class of promising cathodes for high‐energy‐density lithium‐ion batteries (LIBs). However, their structural instability derived from crystallographic planar gliding and microcracking under high voltages has significantly hindered their practical applications. Herein, resurfacing engineering for single‐crystalline LiNi0.83Co0.07Mn0.1O2 (SNCM) cathode is undertaken. A passivation shell, comprising a surface fast ion conductor Li1.25Al0.25Ti1.5O4 (LATO) layer and a near‐surface confined cation hybridization region, is established through co‐infiltrating Al and Ti into SNCM, which can profoundly improve structural stability. Compelling evidences show that high‐conductivity LATO‐overcoat facilitates Li+ conduction and resists electrolyte attack. The introduction of strong Al─O bonds and resurfacing regions stabilize bulk and near‐surface lattice oxygen respectively during cycling, thus hindering the formation of oxygen vacancies and the occurrence of detrimental phase transformations, ultimately suppressing the crystallographic planar gliding and nanocracking. Subsequently, the modified SNCM drastically outperforms the baseline SNCM, exhibiting an ultrahigh 88.9% retention rate of original capacity at 1.0C after 400 cycles, and a discharge capacity of 146.8 mAh g−1 with a 92.6% capacity retention rate after 200 cycles at 5.0C within a voltage window of 2.7–4.3 V. The promising performance demonstrated by the multifunctional surface coating highlights a new way to stabilize Ni‐rich cathodes for LIBs.

For conventional polycrystalline Ni-rich cathode material consisting of numerous primary particles in disordered orientation, the crystal anisotropy in charge/discharge process results in the poor rate capability and rapid capacity degradation. In this work, highly-dispersed submicron single-crystal LiNi0.8 Co0.15 Al0.05 O2 (SC-NCA) cathode is efficiently prepared by spray pyrolysis (SP) technique followed by a simple solid-state lithiation reaction. Porous Ni0.8 Co0.15 Al0.05 Ox precursor prepared via SP exhibits high chemical activity for lithiation reaction, enabling the fabrication of single-crystal cathode at a relatively low temperature. In this way, the contradiction between high crystallinity and cation disordering is well balanced. The resulted optimized SC-NCA shows polyhedral single-crystal morphology with moderate grain size (≈1 μm), which are beneficial to shortening the Li+ diffusion path and improving the structural stability. As cathode for lithium ion batteries, SC-NCA delivers a high discharge capacity of 202 and 140 mAh g-1 at 0.1 and 10 C, respectively, and maintains superior capacity retention of 161 mAh g-1 after 200 cycles at 1C. No micro-crack is observed in the cycled SC-NCA particles, indicating such single-crystal morphology can greatly relieve the anisotropic micro-strain. This effective, continuous and adaptable strategy for preparing single-crystal Ni-rich cathode without any additive may accelerate their practical application.

With the continuous development and progress of new energy electric vehicles, high-capacity nickel-rich layered oxides are widely used in lithium-ion battery cathode materials, and their cycle performance and safety performance have also attracted more and more attention.

… rate capability of single crystal nickel-rich cathode materials (… precursors to synthesize single crystal nickel-rich cathode at lower … single crystal LiNi 0.9 Co 0.055 Mn 0.045 O 2 (NCM90) …

Lithium-ion batteries (LIBs) represent the most promising choice for meeting the ever-growing demand of society for various electric applications, such as electric transportation, portable electronics, and grid storage. Nickel-rich layered oxides have largely replaced LiCoO2 in commercial batteries because of their low cost, high energy density, and good reliability. Traditional nickel-based oxide particles, usually called polycrystal materials, are composed of microsized primary particles. However, polycrystal particles tend to suffer from pulverization and severe side reactions along grain boundaries during cycling. These phenomena accelerate cell degradation. Single-crystal materials, which exhibit robust mechanical strength and a high surface area, have great potential to address the challenges that hinder their polycrystal counterparts. A comprehensive understanding of the growing body of research related to single-crystal materials is imperative to improve the performance of cathodes in LIBs. This review highlights origins, recent developments, challenges, and opportunities for single-crystal layered oxide cathodes. The synthesis science behind single-crystal materials and comparative studies between single-crystal and polycrystal materials are discussed in detail. Industrial techniques and facilities are also reviewed in combination with our group’s experiences in single-crystal research. Future development should focus on facile production with strong control of the particle size and distribution, structural defects, and impurities to fully reap the benefits of single-crystal materials.

… Nickel-rich layered oxide cathodes are promising candidates … to fabricate single-crystal nickel-rich layered oxide cathodes (… crystallographic control on the cathode performance. These …

… LiNi 0.8 Co 0.1 Mn 0.1 O 2 (SC-NCM811 cathode material) … performance of nickel-rich cathode materials coated with … for modifying the nickel-rich cathode of a lithium-ion battery. …

… , the quasi-single crystal Ni90 materials with moderate PPS … and single-crystal Nickel-rich cathode materials for LIBs. … reflect the cycling stability of Nickel-rich cathode material,33 which …

The capacity degredation in layered Ni-rich LiNixCoyMnzO2 (x ≥ 0.8) cathode largely originated from drastic surface reactions and intergranular cracks in polycrystalline particles. Herein, we report a highly stable single-crystal LiNi0.83Co0.12Mn0.05O2 cathode material, which can deliver a high specific capacity (∼209 mAh g-1 at 0.1 C, 2.8-4.3 V) and meanwhile display excellent cycling stability (>96% retention for 100 cycles and >93% for 200 cycles). By a combination of in situ X-ray diffraction and in situ pair distribution function analysis, an intermediate monoclinic distortion and irregular H3 stack are revealed in the single crystals upon charging-discharging processes. These structural changes might be driven by unique Li-intercalation kinetics in single crystals, which enables an additional strain buffer to reduce the cracks and thereby ensure the high cycling stability.

Nickel-rich layered electrode material has been attracting significant attention owing to its high specific capacity as a cathode for lithium-ion batteries. Generally, the high-nickel ternary precursors obtained by traditional coprecipitation methods are micron-scale. In this work, the submicrometer single-crystal LiNi0.8Co0.1Mn0.1O2 (NCM) cathode is efficiently prepared by electrochemically anodic oxidation followed by a molten-salt-assisted reaction without the need of extreme alkaline environments and complex processes. More importantly, when prepared under optimal voltage (10 V), single-crystal NCM exhibits a moderate particle size (∼250 nm) and strong metal-oxygen bonds due to reasonable and balanced crystal nucleation/growth rate, which are conducive to greatly enhancing the Li+ diffusion kinetics and structure stability. Given that a good discharge capacity of 205.7 mAh g-1 at 0.1 C (1 C = 200 mAh g-1) and a superior capacity retention of 87.7% after 180 cycles at 1 C are obtained based on the NCM electrode, this strategy is effective and flexible for developing a submicrometer single-crystal nickel-rich layered cathode. Besides, it can be adopted to elevate the performance and utilization of nickel-rich cathode materials.

Single-crystal (SC) Ni-rich cathode materials have attracted great attention for Li-ion battery applications due to their outstanding cyclability. However, the high temperature required for synthesizing SC also causes damage to temperature-sensitive Ni-rich cathode materials. Severe surface damage can result, even without notable bulk property degradation. Fortunately, we reveal that the surface damage can be mitigated by applying molten salt as an in situ protection agent to the particle surface during the high-temperature calcination. Detailed morphology evolution and near-surface features captured by in situ and ex situ techniques demonstrate that even a small amount of molten salt can effectively enclose particles during calcination. As a result, a solid-liquid-gas interface is built to replace the solid-gas interface, inhibiting the irreversible loss of lithium and oxygen to the high-temperature environment. Overall, SC particles synthesized with a suitable amount of molten salt addition show fewer surface defects and impurities than those without molten salt, leading to an enhanced electrochemical performance. This study highlights the importance of controlling surface damage in the production of high-performance SC Ni-rich cathode materials.

Single-crystal nickel-rich cathode materials are considered ones of the most promising candidates for automobile Li-ion batteries due to their high compacted density and superior cycling stability. Herein this work, we...

Singe-crystal (SC) nickel-rich layered oxide cathodes, composed of boundary-free particles with high tap density, offer significant advantages in volumetric energy density and mechanical strength compared with polycrystalline (PC) cathode materials. However, as the nickel content increases (≥80%), SC Ni-rich cathodes often suffer from faster performance degradation than PC cathodes of the same composition, and the underlying causes of this discrepancy remain poorly understood. Herein, we reveal the distinct Ni redox behaviors that govern the electrochemical performance of SC and PC Ni-rich cathodes using multiscale and operando characterization techniques. Our results indicate that the increasingly heterogeneous Ni oxidation process in SC cathodes leads to the additional irreversible oxygen redox activity that deteriorates both the mechanical and chemical structures. In contrast, PC cathodes, despite with more pronounced surface reconstruction, exhibit greater chemomechanical stability due to homogeneous redox reactions during charging. Consequently, we find that bulk degradation, more than surface reactions, ultimately leads to fast capacity decay of SC Ni-rich cathodes during cycling. This work offers a comprehensive view on the impact of Ni redox evolutions on the chemomechanical stability in Ni-rich layered oxide cathodes, providing new insights into the longstanding performance gap between SC and PC cathodes, and guiding the rational design of Ni-rich cathode architectures.

ABSTRACT High energy density and high safety are incompatible with each other in a lithium battery, which challenges today's energy storage and power applications. Ni-rich layered transition metal oxides (NMCs) have been identified as the primary cathode candidate for powering next-generation electric vehicles and have been extensively studied in the last two decades, leading to the fast growth of their market share, including both polycrystalline and single-crystal NMC cathodes. Single-crystal NMCs appear to be superior to polycrystalline NMCs, especially at low Ni content (≤60%). However, Ni-rich single-crystal NMC cathodes experience even faster capacity decay than polycrystalline NMC cathodes, rendering them unsuitable for practical application. Accordingly, this work will systematically review the attenuation mechanism of single-crystal NMCs and generate fresh insights into valuable research pathways. This perspective will provide a direction for the development of Ni-rich single-crystal NMC cathodes.

Nickel‐rich (Ni‐rich) layered oxides are considered as the most promising cathode candidates for lithium‐ion cells owing to their high theoretical specific capacity. However, the higher nickel content endows structural deformation through unwanted phase transitions and parasitic side reactions that lead to capacity fading upon prolonged cycling. Hence, a deep understanding of the chemistry and structural behaviour is essential for developing Ni‐rich Lithium Nickel Cobalt Manganese oxide (NCM) cathode‐based high‐energy batteries. The present review focuses on the different challenges associated with Ni‐rich NCM materials and surface modification as a strategy to solve the issues associated with NCM materials, assessment of several coating materials, and the recent developments in the surface modification of Ni‐rich NCMs, with an in‐depth discussion on the impact of coating on the degradation mechanism.

… Many studies of wet coating on nickel-rich … the surface reconstruction of the cathode materials but cannot eliminate these phenomena. [ 141 ] This study suggests that nickel-rich cathode …

Ni-rich layered ternary cathodes (i.e., LiNixCoyMzO2, M = Mn or Al, x + y + z = 1 and x ≥ 0.8) are promising candidates for the power supply of portable electronic devices and electric vehicles. However, the relatively high content of Ni4+ in the charged state shortens their lifespan due to inevitable capacity and voltage deteriorations during cycling. Therefore, the dilemma between high output energy and long cycle life needs to be addressed to facilitate more widespread commercialization of Ni-rich cathodes in modern lithium-ion batteries (LIBs). This work presents a facile surface modification approach with defect-rich strontium titanate (SrTiO3-x) coating on a typical Ni-rich cathode: LiNi0.8Co0.15Al0.05O2 (NCA). The defect-rich SrTiO3-x-modified NCA exhibits enhanced electrochemical performance compared to its pristine counterpart. In particular, the optimized sample delivers a high discharge capacity of ∼170 mA h/g after 200 cycles under 1C with capacity retention over 81.1%. The postmortem analysis provides new insight into the improved electrochemical properties which are ascribed to the SrTiO3-x coating layer. This layer appears to not only alleviate the internal resistance growth, from uncontrollable cathode-electrolyte interface evolution, but also acts as a lithium diffusion channel during prolonged cycling. Therefore, this work offers a feasible strategy to improve the electrochemical performance of layered cathodes with high nickel content for next-generation LIBs.

… stability of the integrated cathode. The surface engineering strategy proposed herein is generally effective for the electrochemical improvement of nickel-rich ternary cathode materials. …

… Nickel-rich layered oxides with high capacity and acceptable cost have established their critical status as cathode … drives the research on surface protective coating techniques in both …

… Lithium-ion conductors are also broadly applied as coating matrixes for nickel-rich cathode surfaces. Li 2 ZrO 3 as a superior Li + conductor with a high conductivity of 3.3 × 10 −5 S m −…

Nickel (Ni)‐rich cathodes are among the most promising cathode materials of lithium batteries, ascribed to their high‐power density, cost‐effectiveness, and eco‐friendliness, having extensive applications from portable electronics to electric vehicles and national grids. They can boost the wide implementation of renewable energies and thereby contribute to carbon neutrality and achieving sustainable prosperity in the modern society. Nevertheless, these cathodes suffer from significant technical challenges, leading to poor cycling performance and safety risks. The underlying mechanisms are residual lithium compounds, uncontrolled lithium/nickel cation mixing, severe interface reactions, irreversible phase transition, anisotropic internal stress, and microcracking. Notably, they have become more serious with increasing Ni content and have been impeding the widespread commercial applications of Ni‐rich cathodes. Various strategies have been developed to tackle these issues, such as elemental doping, adding electrolyte additives, and surface coating. Surface coating has been a facile and effective route and has been investigated widely among them. Of numerous surface coating materials, have recently emerged as highly attractive options due to their high lithium‐ion conductivity. In this review, a thorough and comprehensive review of lithium‐ion conductive coatings (LCCs) are made, aimed at probing their underlying mechanisms for improved cell performance and stimulating new research efforts.

Abstract Nowadays, lithium-ion batteries (LIBs) are widely applied in many fields, in order to reduce the material cost, increase volumetric/gravimetric energy density, raise safety performance and so on, nickel-rich cathode materials have gained much attention. Besides the technique for preparation of precursors and corresponding cathode materials, bulk doping and surface coating are very important to strengthen the performance of nickel-rich cathode materials. However, the intrinsic mechanism of doping and coating for cathode materials is not fully understood, further extensive and intensive investigation is needed. In this article, the varieties of doping and coating are reviewed, and research status, recent progresses and their underlying mechanism are presented. The paper suggests that combination of coating and doping at the same time is crucial to effectively improve the internal and external structure as well as electrochemical performance of nickel-rich cathode materials. Moreover, the present problems and challenges to nickel-rich cathode materials are put forward, the issues of safety and capacity fade of nickel-rich cathode materials are urgently need to resolve, which are closely related to the interface damage, volumetric change, lattice internal strain and gas release during cycling process.

Abstract Controllable uniformity and thickness of the coating layer of oxides on the nickel-rich materials are extremely crucial for optimization of the performance of the materials, due to the poor electronic and ionic conductivity of oxides. In this work, an efficient coating approach is developed based on organic/water two-phase system. The Al2O3-coated LiNi0.8Co0.1Mn0.1O2 with uniform and controlled thickness of the coating layer can be prepared by adjusting the amount of water used in the organic/water mixture, where aluminum isopropoxide is hydrolyzed in water phase on the surface of the LiNi0.8Co0.1Mn0.1O2 spheres. It is demonstrated that the electrochemical performance of LiNi0.8Co0.1Mn0.1O2 strongly correlates to the thickness of the Al2O3 coating layer. With optimized thickness of the coating layer, the Al2O3-coated LiNi0.8Co0.1Mn0.1O2 can deliver a good initial discharge capacity of 191.3 mAh g−1, although the coated Al2O3 is electrochemically inactive. Importantly, a capacity retention of 95.42% can be achieved for the Al2O3-coated LiNi0.8Co0.1Mn0.1O2 upon 200 cycles at 1C, superior to that of 82.73% for the pristine counterpart. Those are ascribed to the protection effect of the coating layer to LiNi0.8Co0.1Mn0.1O2, to alleviate the side reactions at the electrode/electrolyte interface.

… coating process… surface modification strategies for nickel-rich cathode active materials. In this study we will examine the reactions that occur during the washing of the nickel-rich cathode …

… Advanced surface engineering of nickel-rich cathode … the nickel-rich cathode. Considering that the parasitic redox reaction occurs at the cathode/electrolyte interface, surface coating is a …

… method to effectively coat LLZO on the NMC particle surface. The coated cathode demonstrates superior electrochemical performance compared with the pristine NMC cathode. …

… (1, 2) Among a large number of candidates, LiCoO 2 has been widely used as a cathode … high Ni contents, in the battery industry, the surface coatings with various materials of Al 2 O 3 , (…

… We also share our perspectives on key doping principles and future cathode designs. This … the cathode doping strategies from doping mechanisms to valence states of doping elements, …

… doping in a Ni-rich layered oxide cathode. The experimental methods and dopant selection rules are briefly introduced. Then we discuss here the effects of the elemental doping from …

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.

… these elements into the lattice notably strengthens the oxygen bonding and structural integrity of nickel-rich cathodes… capability to stabilize the cathode structure through reinforced metal-…

Nickel-rich layered transition metal oxides are considered as promising cathode candidate to construct next-generation lithium ion batteries to satisfy the demands of electrical vehicles, because of the high energy density, low cost and environment friendliness. However, some problems related with rate capability, structure stability and safety still hamper the commercial application. In this review, beginning with the relations between the physicochemical properties and electrochemical performance, the behind mechanisms of the capacity/voltage fade and the unstable structure of Ni-rich cathodes are deeply analyzed. Furthermore, the recently research progress of Ni-rich oxide cathode materials via element doping, surface modification and structure tuning are summarizeNickel-rich layered transition metal oxides are considered as promising cathode candidate to construct next-generation lithium ion batteries to satisfy the demands of electrical vehicles, because of the high energy density, low cost, and environment friendliness. However, some problems related to rate capability, structure stability, and safety still hamper the commercial application. In this review, beginning with the relations between the physicochemical properties and electrochemical performance, the behind mechanisms of the capacity/voltage fade and the unstable structure of Ni-rich cathodes are deeply analyzed. Furthermore, the recent research progress of Ni-rich oxide cathode materials via element doping, surface modification and structure tuning are summarized. And this review ends up by discussing new insights to expand the field of Ni-rich oxides and promote practical applications.d. And this review is end up by discussing new insights to expand field of Ni-rich oxides and promote the practical applications.

… diffusion into the cathode, thereby … doped elements with their dynamic modification on cathode structure, providing mechanistic insights into the design of nickel-rich cobalt-free cathodes…

Elemental doping represents a prominent strategy to improve interfacial chemistry in battery materials. Manipulating the dopant spatial distribution and understanding the dynamic evolution of the dopants at the atomic scale can inform better design of the doping chemistry for batteries. In this work, we create a targeted hierarchical distribution of Ti4+, a popular doping element for oxide cathode materials, in LiNi0.8Mn0.1Co0.1O2 primary particles. We apply multiscale synchrotron/electron spectroscopy and imaging techniques as well as theoretical calculations to investigate the dynamic evolution of the doping chemical environment. The Ti4+ dopant is fully incorporated into the TMO6 octahedral coordination and is targeted to be enriched at the surface. Ti4+ in the TMO6 octahedral coordination increases the TM-O bond length and reduces the covalency between (Ni, Mn, Co) and O. The excellent reversibility of Ti4+ chemical environment gives rise to superior oxygen reversibility at the cathode-electrolyte interphase and in the bulk particles, leading to improved stability in capacity, energy, and voltage. Our work directly probes the chemical environment of doping elements and helps rationalize the doping strategy for high-voltage layered cathodes.

To develop Co-free LiNiO2-based layered cathode materials is crucial for meeting the demands of the lithium-ion batteries with high energy density, long cycling life, and low cost. Herein, the LiNi1-x-yAlxMgyO2 materials are synthesized by the solid-solid interface elemental interdiffusion strategy. It is elucidated that the Mg2+ and Al3+ ions are mainly doped in the Li slabs and transition metal slabs, respectively, leading to the alteration of the crystal lattice. Furthermore, the incorporation of the Mg2+ ions may induce more Ni2+ ions formed in the transition metal slabs, which would have great impact on the electrochemical performance of the materials. The LiNi1-x-yAlxMgyO2 materials with optimized Mg/Al co-doping exhibit much better electrochemical performance than the pristine LiNiO2 and Al-doped LiNiO2 materials, including cycling stability and rate capability. The in-situ XRD characterization and structural analysis show that stabilization of the crystal structure, preservation of the integrity of the secondary particles, and enlargement of the interlayer spacing by the Mg/Al co-doping are the main factors responsible for the superior performance of the materials. The Mg/Al co-doping strategy might be the promising approach for the design of the cobalt-free nickel-rich materials.

With the rapid development of plug-in hybrid electric vehicles (PHEVs) and electric vehicles (EVs), high-energy layered lithium nickel-rich oxides have received much attention, but there are still many challenges due to the inherent properties of materials. The poor cycling performance and initial capacity loss of the nickel-rich layered oxide are associated with structural stability of the material and Li+/Ni2+ cation disorder. Moreover, the synergistic effect of the vacancy of Li and Ni in the delithiation process aggravates the instability of oxygen, eventually resulting in the release of oxygen. It can cause damage to the stability of the structure and even cause safety issues. In this work, we report that Ce0.8Dy0.2O1.9 solid electrolyte inhibits the release of oxygen and improves the structural stability and safety of the Ni-rich cathode material, which is rich in oxygen vacancies. Besides, Ni2+ could be oxidized to Ni3+ along with the strong oxidation of Ce4+ doping into the bulk structure, which suppress the Li+/Ni2+ cation disorder and improves the initial coulombic efficiency of the material. This study successfully designed a novel cathode material structure to provide a basis for the future development of layered lithium nickel-rich oxides, which can be used to improve initial coulombic efficiency and cycle life.

… radius, a strategy of nickel-rich material modified by niobium-doping is proposed. The … of nickel-rich cathode (LiNi 0.8 Co 0.1 Mn 0.1 O 2 ). Accordingly, the niobium-doping cathode …

Capacity fading and safety concerns accompanied other deep‐rooted challenges have severely hindered commercial development of Ni‐rich layered cathodes. Herein, a robust Sr‐doped Ni‐rich cathode is structurally designed by the reconstruction of the crystal lattice and electronic distribution. Notably, the orbital hybridization between Ni 3d (t2g) and O 2p is remarkably reinforced owing to the shortened NiO bond enabled by the electrostatic interaction between Ni and Sr atoms, giving rise to the enhanced crystal structure. Theoretically, the formation energy of oxygen vacancies is greatly increased due to the intensified electronic polarization between Ni and O states evoked by the weak electronegativity of Sr, resulting in the alleviation of lattice oxygen loss. More impressively, the distances of LiO bonds and the OLiO slab are also extended on account of the electrochemically inactive Sr ion functioning as a pillar, further promoting the transmission of lithium ions. Therefore, the as‐designed Sr‐modified NCM delivers an ultrahigh capacity retention of 98.5% after 150 cycles. This work provides a powerful mechanistic incentive to increase the stability of the crystal phase and electrochemical performance for Ni‐rich layered cathodes through appropriate chemical and mechanical engineering, facilitating the practical applications of Ni‐rich cathodes in high‐performance electric vehicles.

… Nickel-rich layered oxides are attracting extensive interest as cathode materials to build high-… Herein, we report concentration-gradient Mg and Al doped LiNi 0.95 Co 0.03 Al 0.01 Mg …

… -valent doping is an effective strategy for stabilizing ultrahigh-Ni layered cathodes through … slight Li enrichment with high-valent element doping. This approach aims to precisely regulate …

… demonstrated that W/Mg co-doping can tune H2−H3 phase transition… doping strategic guidelines for the use of high energy efficiency and robust stability high-nickel low-cobalt cathodes …

Nickel‐rich layered oxides have attracted many attentions for their superior specific capacity and low cost, but they are subjected to fast structural degradation during cycling. Herein, the Al and Sm co‐doped LiNi0.83Co0.07Mn0.10O2 (SC‐NCM‐AS) single‐crystal is demonstrated to overcome their cycling instability issue, and its mechanistic origin for improved structural stability is investigated. It is found that soluble Al ions are homogenously incorporated in the LiNi0.83Co0.07Mn0.10O2 (SC‐NCM) lattice, while Sm ions tends to aggregate in the SC‐NCM outer surface layer. The Li/Ni cation disordering is greatly suppressed through the pillaring effect of stronger AlO bond in SC‐NCM single crystals. Sm‐concentrated outer surface layer can effectively prevent the dissolution of transition metals from SC‐NCM‐AS and inhibit undesirable side reactions induced by the organic electrolyte. This synergistic effect facilitates to suppress the formation of LiOH/Li2CO3 and oxygen vacancies, resulting in released the internal strain, decreased in‐plane transition metals migration and gliding, and eventually preventing formation of nanocracks in SC‐NCM‐AS single crystals upon cycling at high cut‐off voltage. Consequently, Al and Sm co‐doped SC‐NCM exhibits a high specific capacity of 222.4 mAh g−1 and remarkable cycling performance with a capacity retention of 91.1% for 100 cycles.

Abstract The demand for lithium-ion batteries (LIBs) with high mass-specific capacities, high rate capabilities and long-term cyclabilities is driving the research and development of LIBs with nickel-rich NMC (LiNi x Mn y Co 1− x − y O 2 , $$x \geqslant 0.5$$ x ⩾ 0.5 ) cathodes and graphite (Li x C 6 ) anodes. Based on this, this review will summarize recently reported and widely recognized studies of the degradation mechanisms of Ni-rich NMC cathodes and graphite anodes. And with a broad collection of proposed mechanisms on both atomic and micrometer scales, this review can supplement previous degradation studies of Ni-rich NMC batteries. In addition, this review will categorize advanced mitigation strategies for both electrodes based on different modifications in which Ni-rich NMC cathode improvement strategies involve dopants, gradient layers, surface coatings, carbon matrixes and advanced synthesis methods, whereas graphite anode improvement strategies involve surface coatings, charge/discharge protocols and electrolyte volume estimations. Electrolyte components that can facilitate the stabilization of anodic solid electrolyte interfaces are also reviewed, and trade-offs between modification techniques as well as controversies are discussed for a deeper understanding of the mitigation strategies of Ni-rich NMC/graphite LIBs. Furthermore, this review will present various physical and electrochemical diagnostic tools that are vital in the elucidation of degradation mechanisms during operation to supplement future degradation studies. Finally, this review will summarize current research focuses and propose future research directions. Graphic Abstract The demand for lithium-ion batteries (LIBs) with high mass specific capacities, high rate capabilities and longterm cyclabilities is driving the research and development of LIBs with nickel-rich NMC (LiNi x Mn y Co 1− x − y O 2 , x  ≥ 0.5) cathodes and graphite (Li x C 6 ) anodes. Based on this, this review will summarize recently reported and widely recognized studies of the degradation mechanisms of Ni-rich NMC cathodes and graphite anodes. And with a broad collection of proposed mechanisms on both atomic and micrometer scales, this review can supplement previous degradation studies of Ni-rich NMC batteries. In addition, this review will categorize advanced mitigation strategies for both electrodes based on different modifications in which Ni-rich NMC cathode improvement strategies involve dopants, gradient layers, surface coatings, carbon matrixes and advanced synthesis methods, whereas graphite anode improvement strategies involve surface coatings, charge/discharge protocols and electrolyte volume estimations. Electrolyte components that can facilitate the stabilization of anodic solid-electrolyte interfaces (SEIs) are also reviewed and tradeoffs between modification techniques as well as controversies are discussed for a deeper understanding of the mitigation strategies of Ni-rich NMC/graphite LIBs. Furthermore, this review will present various physical and electrochemical diagnostic tools that are vital in the elucidation of degradation mechanisms during operation to supplement future degradation studies. Finally, this review will summarize current research focuses and propose future research directions.

… Nickel-rich NCM cathodes have garnered significant … of the degradation mechanisms that afflict these Ni-rich cathodes. … of the intricate factors responsible for degradation, including Li/Ni …

… Layered nickel-rich materials (LiNi 1-yz Co y Mn z O 2 , 1–y–z ≥ 0.8) are regarded as promising cathode candidates for all-solid-state batteries (ASSBs); however, nickel-rich cathodes …

… based on Ni-rich NCM cathodes. Herein, we studied the structural degradation of Ni-rich NCM/… causes the battery performance to suddenly degrade at a certain value. We found that the …

… mechanisms and effective modification strategies for next-generation nickel-rich cathodes is … latest findings on microstructural degradation mechanisms in Ni-rich cathodes, delve into …

… However, due to the high sensitivity of materials to air, structural degradation occurs during … The degradation of the structure will weaken the comprehensive properties of Ni-rich cathode …

Layered Cobalt (Co)-free Nickel (Ni)-rich cathode materials have attracted much attention due to their high energy density and low cost. Still, their further development is hampered by material instability caused by the chemical/mechanical degradation of the material. Although there are numerous doping and modification approaches to improve the stability of layered cathode materials, these approaches are still in the laboratory stage and require further research before commercial application. To fully exploit the potential of layered cathode materials, a more comprehensive theoretical understanding of the underlying issues is necessary, along with active exploration of previously unrevealed mechanisms. This paper presents the phase transition mechanism of Co-free Ni-rich cathode materials, the existing problems, and the state-of-the-art characterization tools employed to study the phase transition. The causes of crystal structure degradation, interfacial instability, and mechanical degradation are elaborated, from the material's crystal structure to its phase transition and atomic orbital splitting. By organizing and summarizing these mechanisms, this paper aims to establish connections among common research problems and to identify future research priorities, thereby facilitating the rapid development of Co-free Ni-rich materials.

Fast charging technology for electric vehicles (EVs), offering rapid charging times similar to conventional vehicle refueling, holds promise but faces obstacles owing to kinetic issues within lithium-ion batteries (LIBs). Specifically, the significance of cathode materials in fast charging has grown because Ni-rich cathodes are employed to enhance the energy density of LIBs. Herein, the mechanism behind the loss of fast charging capability of Ni-rich cathodes during extended cycling is investigated through a comparative analysis of Ni-rich cathodes with different microstructures. The results revealed that microcracks and the resultant cathode deterioration significantly compromised the fast charging capability over extended cycling. When thick rocksalt impurity phases form throughout the particles owing to electrolyte infiltration via microcracks, the limited kinetics of Li+ ions create electrochemically unreactive areas under high-current conditions, resulting in the loss of fast charging capability. Hence, preventing microcrack formation by tailoring microstructures is essential to ensure stability in fast charging capability. Understanding the relationship between microcracks and the loss of fast charging capability is essential for developing Ni-rich cathodes that facilitate stable fast charging upon extended cycling, thereby promoting widespread EV adoption.

Preventing the decomposition reactions of electrolyte solutions is essential for extending the lifetime of lithium-ion batteries. However, the exact mechanism(s) for electrolyte decomposition at the positive electrode, and particularly the soluble decomposition products that form and initiate further reactions at the negative electrode, are still largely unknown. In this work, a combination of operando gas measurements and solution NMR was used to study decomposition reactions of the electrolyte solution at NMC (LiNixMnyCo1−x−yO2) and LCO (LiCoO2) electrodes. A partially delithiated LFP (LixFePO4) counter electrode was used to selectively identify the products formed through processes at the positive electrodes. Based on the detected soluble and gaseous products, two distinct routes with different onset potentials are proposed for the decomposition of the electrolyte solution at NMC electrodes. At low potentials (<80% state-of-charge, SOC), ethylene carbonate (EC) is dehydrogenated to form vinylene carbonate (VC) at the NMC surface, whereas at high potentials (>80% SOC), 1O2 released from the transition metal oxide chemically oxidises the electrolyte solvent (EC) to form CO2, CO and H2O. The formation of water via this mechanism was confirmed by reacting 17O-labelled 1O2 with EC and characterising the reaction products via1H and 17O NMR spectroscopy. The water that is produced initiates secondary reactions, leading to the formation of the various products identified by NMR spectroscopy. Noticeably fewer decomposition products were detected in NMC/graphite cells compared to NMC/LixFePO4 cells, which is ascribed to the consumption of water (from the reaction of 1O2 and EC) at the graphite electrode, preventing secondary decomposition reactions. The insights on electrolyte decomposition mechanisms at the positive electrode, and the consumption of decomposition products at the negative electrode contribute to understanding the origin of capacity loss in NMC/graphite cells, and are hoped to support the development of strategies to mitigate the degradation of NMC-based cells.

A series of Ni-rich Li[NixCo(1-x)/2Mn(1-x)/2]O2 (x = 0.9, 0.92, 0.94, 0.96, 0.98, and 1.0) (NCM) cathodes are prepared to study their capacity fading behaviors. The intrinsic tradeoff between the capacity gain and compromised cycling stability is observed for layered cathodes with x ≥ 0.9. The initial specific capacities of LiNiO2 and Li[Ni0.9Co0.05Mn0.05]O2 are 245 mAh g-1 (91% of the theoretical capacity) and 230 mAh g-1, and their corresponding capacity retentions are 72.5% and 88.4%. However, the capacity retention characteristic deteriorates at an increasingly faster rate for x > 0.95, in contrast with the nearly linear increase of specific capacity. The fast capacity fading stems from the chemical attack of the cathode by the electrolyte infiltrated through the microcracks, resulting from the mechanical instability inflicted by the anisotropic internal strain caused by the H2 = H3 phase transition. Thus, the capacity fading of the NCM cathodes for x > 0.9 critically depends on the extent of the H2 → H3 phase transition. Retardation or protraction of the H2 = H3 phase transition by engineering the microstructure should improve the cycle life of these highly Ni-enriched NCM cathodes.

Ni-rich layered oxides have received significant attention as promising cathode materials for Li-ion batteries due to their high reversible capacity. However, intergranular and intragranular cracks form at high state-of-charge (SOC) levels exceeding 4.2 V (vs. Li/Li+), representing a prominent failure mechanism of Ni-rich layered oxides. The nanoscale crack formation at high SOC levels is attributed to a significant volume change resulting from a phase transition between the H2 and H3 phases. Herein, in contrast to the electrochemical crack formation at high SOC levels, another mechanism of chemical crack and pit formation on a nanoscale is directly evidenced in fully lithiated Ni-rich layered oxides (low SOC levels). This mechanism is associated with intergranular stress corrosion cracking, driven by chemical corrosion at elevated temperatures. The nanoscopic chemical corrosion behavior of Ni-rich layered oxides during aging at elevated temperatures is investigated using high-resolution transmission electron microscopy, revealing that microcracks can develop through two distinct mechanisms: electrochemical cycling and chemical corrosion. Notably, chemical corrosion cracks can occur even in a fully discharged state (low SOC levels), whereas electrochemical cracks are observed only at high SOC levels. This finding provides a comprehensive understanding of the complex failure mechanisms of Ni-rich layered oxides and provides an opportunity to improve their electrochemical performance.

… of its heterogeneous degradation mechanism. This contribution … degradation mechanisms at each length scale are analyzed, and corresponding strategies to alleviate the degradation …

Among the existing commercial cathodes, Ni-rich NCM are the most promising candidates for next-generation LIBs because of their high energy density, relatively good rate capability, and reasonable cycling performance. However, the surface degradation, mechanical failure and thermal instability of these materials are the major causes of cell performance decay and rapid capacity fading. This is a huge challenge to commercializing these materials widely for use in LIBs. In particular, the thermal instability of Ni-rich NCM cathode active materials is the main issue of LIBs safety hazards. Hence, this review will recapitulate the current progress in this research direction by including widely recognized research outputs and recent findings. Moreover, with an extensive collection of detailed mechanisms on atomic, molecular and micrometer scales, this review work can complement the previous failure, degradation and thermal instability studies of Ni-rich NMC. Finally, this review will summarize recent research focus and recommend future research directions for nickel-rich NCM cathodes.

… Therefore, improving the cycle stability of high-nickel cathode materials at … cycle stability at 45 C. Its capacity retention exceeds 88.4% after 100 cycles at 1.0 C, while the bare cathode …

This study investigates the degradation mechanisms of high-nickel (Ni) layered oxide (LiNi0.83Co0.11Mn0.06O2) under varying discharge C-rates at a high cut-off voltage (4.3 V) during long-term cycling. Contradictory to conventional knowledge, a low discharge rate (0.1C) results in worse cycle performance than a high discharge rate (1C) at a high cut-off voltage. In-depth transmission electron microscopy analysis reveals that at a high C-rate discharge condition, more Ni ions are reduced from +3 to +2, yet the layered structure is maintained. In contrast, at a low C-rate, more Ni ions retain their +3 valence but the phase transition to the periodically ordered spinel occurs at some portion. The prolonged dwell time at high voltage forces Ni ions in Li layers to be locally ordered, and this phase transition more critically affects the cycling. Therefore, this study underscores that setting a proper cut-off voltage can be more significant to the cycle performance than the discharge C-rate.

Lithium‐ion batteries are extensively employed in electric vehicles and energy storage systems due to their exceptional energy density and operational voltage. However, with the swift expansion of the electric vehicle market, batteries are now confronted with increasingly stringent demands concerning energy density, driving range, and charging efficiency. As the pivotal and determinant component of a battery, the cathode material has a direct impact on the overall performance of the battery. Ultra‐high nickel cathodes have emerged as a research focus owing to their superior high capacity and voltage. Despite efforts to reduce or even completely replace cobalt in the pursuit of low‐cost and high‐performance cathodes, its indispensable role in structural stabilization and charge compensation cannot be overlooked, rendering complete cobalt substitution a formidable challenge. To gain a more profound understanding of the role of cobalt in ultra‐high nickel cathodes, this paper delves into the structural characteristics of these cathodes by analyzing their failure mechanisms by means of structural characterization and electrochemical performance evaluation, and comprehensively discussing the role of cobalt in ultra‐high nickel cathodes. This comprehensive study aims to provide a reliable theoretical basis for the industrialization of ultra‐high nickel cathode materials.

… cathode materials exhibit critical drawbacks such as voltage fade in association with voltage hysteresis, low first-cycle efficiency… the energy efficiency and cyclability of such cathodes. [12…

Abstract Titanium doping is employed to enhance the structural strength of a high-Ni layered cathode material in lithium ion batteries during high temperature cycling. After Ti-doping, the external morphology remains similar, but the lattice parameters of the layered structure are slightly shifted toward larger values. With application of the prepared materials as cathodes in lithium-ion batteries, the initial capacities are similar but the cycling performance at 25 °C is enhanced by Ti-doping. During high temperature cycling at 60 °C, furthermore, highly improved capacity retention is achieved with the Ti-doped material (95% of initial capacity at 50th cycles), while cycle fading is accelerated with the bare electrode. This enhancement is attributed to better retention of the compressive strength of the particles and retarded crack formation within the particles. In addition, impedance increase is reduced in the Ti-doped electrode, which is attributed to an improvement in the structural strength of the high-Ni cathode material with Ti-doping.

Abstract Improving capacity retention during cycling and the thermal–abuse tolerance of layered high–nickel cathode material, LiNi0.8Mn0.1Co0.1O2 (NMC811), is a significant challenge. A series of core–shell structured cathode materials with the overall composition of LiNi0.8Mn0.1Co0.1O2 was prepared via a coprecipitation method in which the nickel–rich composition (LiNi0.9Mn0.05Co0.05O2) is the core and the manganese–rich composition (LiNi0.33Mn0.33Co0.33O2) is the shell. In terms of achieving a higher nickel content (more than 80%) of heterogeneous material, this core–shell structured material is a more practical approach because it has a larger nickel–rich core region and a thicker manganese–rich shell than the full–concentration gradient material, not to mention being more feasible for continuous mass production. Analysis of mechanical strength through nanoindentation shows that the core–shell structured NMC811 has higher stiffness and compressive stress–strain than the commercial homogeneous NMC811 and retains the mechanical strength and the binding force strong enough to prevent crack formation even after 200 cycles. The prepared core–shell structure NMC811 exhibits a greatly improved capacity retention of 76.6% compared to the commercial homogeneous NMC811 with a capacity retention of 39.6% after 200 cycles. This material also exhibits significantly improved thermal stability over the commercial homogeneous NMC811.

Abstract The high-nickel cathode material of LiNi0.8Co0.15Al0.05O2 (LNCA) has a prospective application for lithium-ion batteries due to the high capacity and low cost. However, the side reaction between the electrolyte and the electrode seriously affects the cycling stability of lithium-ion batteries. In this work, Ni2+ preoxidation and the optimization of calcination temperature were carried out to reduce the cation mixing of LNCA, and solid-phase Al-doping improved the uniformity of element distribution and the orderliness of the layered structure. In addition, the surface of LNCA was homogeneously modified with ZnO coating by a facile wet-chemical route. Compared to the pristine LNCA, the optimized ZnO-coated LNCA showed excellent electrochemical performance with the first discharge-specific capacity of 187.5 mA h g−1, and the capacity retention of 91.3% at 0.2C after 100 cycles. The experiment demonstrated that the improved electrochemical performance of ZnO-coated LNCA is assigned to the surface coating of ZnO which protects LNCA from being corroded by the electrolyte during cycling. Graphical abstract

The high nickel layered oxide cathode is considered to be one of the most promising cathode materials for lithium-ion batteries because of its higher specific capacity and lower cost. However, due to the increased Ni content, residual lithium compounds inevitably exist on the surface of the cathode material, such as LiOH, Li2CO3, etc. At the same time, the intrinsic instability of the high nickel cathode material leads to the structural destruction and serious capacity degradation, which hinder practical applications. Here, we report a simple and scalable strategy using hydrolysis and lithiation process of aluminum isopropoxide (C9H21AlO3) and isopropyl titanate (C12H28O4Ti) to prepare a novel α-LiAlO2 and Li2TiO3 double-coated and Al3+ and Ti4+ co-doped cathode material (NCAT15). The Al and Ti doping stabilizes the layered structure due to the strong Al-O and Ti-O covalent bonds and relieves the Li+/Ni2+ cation disorder. Besides, the capacity of the cathode material for 100 cycles reaches 163.5 mA h g-1 and the capacity retention rate increases from 51.2% to 90.6% (at 1C). The microscopic characterization results show that the unique structure can significantly suppress side reactions at the cathode/electrolyte interface as well as the deterioration of structure and microcracks. This innovative design strategy combining elemental doping and construction of dual coating layers can be extended to other high nickel layered cathode materials and help improve their electrochemical performance.

Abstract LiNixCoyAl1-x-yO2 (NCA), as high nickel cathode material, has a high capacity and is one of the most promising cathode materials for lithium-ion batteries. However, the disadvantages such as more residual lithium compounds and serious capacity decay have hindered the industrial application of this material. In order to reduce the residual lithium compound on the surface of the material and restrain the capacity degradation, we designed and prepared a high nickel cathode material by pretreatment washing and subsequent spray drying, which has high cycle life and high discharge specific capacity. Compared to the first discharge specific capacity of 196.6 mAh•g-1(0.2 C) for the raw material and 131.4 mAh•g-1 after 100 cycles of 1 C, the discharge specific capacity of the modified sample 2V2O5@NCA was increased to 210.4 and 163.8 mAh•g-1, respectively. Microstructure observation revealed that V2O5 not only uniformly covers the surface of the secondary particles, but also the presence of electrochemically active LiV3O8, which avoids the direct contact between the active material and electrolyte, thus significantly suppressing the interfacial side reactions between the cathode material and electrolyte and improving the structural stability of the material. Our exploration may pave a way for developing high cycle stability of high nickel cathode materials.

Abstract The degradation of interface and crystal structure during the cycle seriously hinders the further development and application of high-nickel cathode materials. In order to solve this problem, we synthesize a Al2O3 modified coating on LiNi0.88Co0.09Al0.03O2 (NCA) cathode material particles. However, further research discovers that the coating is not composed of a single Al2O3 as previously reported. On the contrary, a part of Al2O3 in the inner layer of the coating near the host material may be induced to form a thin layer of LiAlO2 on the surface of the NCA, while the outer layer of the coating is still composed of Al2O3. This LiAlO2@Al2O3 dual-modified coating reveals a new surface coating structure. And the results show that the NCA material coated with the appropriate thickness of the coating has a first charge/discharge capacity of 242.1/210.3 mAh g−1 at a current density of 0.1 C (20 mA g−1). When the current density is increased to 1.0 C (200 mA g−1), the capacity retention rate is still 82.8% (62.6% of the pristine material) after 100 cycles. Even at a current density of 2.0 C, the discharge capacity is still 189.2 mAh g−1, which shows its better rate performance. The cycle performance and the capacity retention of materials at high currents are significantly improved. The study finds that LiAlO2@Al2O3 dual-modified coating has a positive effect on stabilizing the particle surface, resisting attacks from the electrolyte and improving the diffusion performance of Li+, which may be the reasons for the enhanced cycle stability and capacity retention of the material.

It is well understood that cathode‐to‐anode crossover, especially of transition‐metal ions, can significantly impact the long‐term cycling of lithium‐ion batteries. The dissolved transition‐metal ions in lithium‐ion cells deposit on the graphite anode, disrupt the solid‐electrolyte interphase (SEI), and catalyze further side reactions. Meanwhile, crossover effects in lithium‐metal batteries have rarely been studied. This study is the first to investigate crossover effects in lithium‐metal batteries with high‐nickel layered‐oxide cathodes. It is shown that the crossover of transition‐metal ions from LiNi0.9Mn0.05Co0.05O2 has minimal effect on the lithium‐metal anode (LMA) due to the following reasons. The catalytic transition metals 1) have less effect on an inherently reactive LMA, 2) are diluted in a thicker SEI, and 3) are produced in overall lower quantity due to the limited cycle life of the LMA. Conversely, the LMA generates soluble decomposition products that cross over to the cathode even during early cycling. This crossover accelerates impedance growth and capacity fade at the cathode and is partially responsible for the mismatch between the performance of half and full‐cells with layered‐oxide cathodes. This study highlights the need for better battery design with LMA, potentially including electrolyte or cell modifications.

… during cycling. Nevertheless, recent reports suggest that certain electrolytes might reduce microcracks in NMC cathodes during deep cycling… on the cycle life of high-Ni cathodes is more …

… For the cathode materials in LIBs, lithium transition metal (Co, Ni, Mn) oxides have been employed because of their high operating potential, good cycle performance, and high material …

Nickel-rich layered transition metal oxides are leading cathode candidates for lithium-ion batteries due to their increased capacity, low cost and enhanced environmental sustainability compared to cobalt formulations. However, the nickel enrichment comes with larger volume change during cycling as well as reduced oxygen stability, which can both incur performance degradation. Here we show an ultrahigh-nickel cathode, LiNi0.94Co0.05Te0.01O2, that addresses all of these critical issues by introducing high valent tellurium cations (Te6+). The as-prepared material exhibits an initial capacity of up to 239 milliampere-hours (mAh) per gram and an impressive capacity retention of 94.5% after 200 cycles. The resulting Ah-level lithium metal battery with silicon-carbon anode achieves an extraordinary monomer energy density of 404 watt-hours (Wh) per kilogram with retention of 91.2% after 300 cycles. Advanced characterizations and theoretical calculations show that the introduction of tellurium serves to engineer the particle morphology for a microstructure to better accommodate the lattice strain and enable an intralayer Te–Ni–Ni–Te ordered superstructure, which effectively tunes the ligand energy-level structure and suppresses lattice oxygen loss. This work not only advances the energy density of nickel-based lithium-ion batteries into the realm of 400 Wh kg−1 but suggests new opportunities in structure design for cathode materials without trade-off between performance and sustainability. Increasing the Ni content to replace Co can increase the capacity and sustainability of cathode for batteries but leads to performance degradation issues. Here the authors address the structural and oxygen instabilities of Ni-rich cathodes by doping with tellurium.

Electrolytes connect the two electrodes in a lithium battery by providing Li+ transport channels between them. Advanced electrolytes are being explored with high‐nickel cathodes and the lithium‐metal anode to meet the high energy density and cycle life goals, but the origin of the performance differences with different electrolytes is not fully understood. Here, the mechanisms involved in protecting the high‐capacity, cobalt‐free cathode LiNiO2 with a model high‐voltage electrolyte (HVE) are delineated. The kinetic barrier posed by a thick surface degradation layer with poor Li+‐ion transport is found to be the major contributor to the fast capacity fade of LiNiO2 with the conventional carbonate electrolyte. In contrast, HVE reduces the side reactions between the electrolyte and the electrodes, leading to a thinner nano‐interphase layer comprised of more beneficial species. Crucially, the HVE leads to a different surface reorganization pathway involving the formation of a thinner nanoscale LiNi2O4 spinel phase on the LiNiO2 surface. With a high 3D Li+‐ion and electronic conductivity, the spinel LiNi2O4 reorganization nanolayer preserves fast Li+ transport across the cathode–electrolyte interface, reduces reaction heterogeneity in the electrode and alleviates intergranular cracking within secondary particles, resulting in superior long‐term cycle life.

High-Ni cathodes promise high energy density but suffer from interfacial degradation. Here, a dual-additive electrolyte-trimethylsilyl phosphate to scavenge HF and adiponitrile to tailor Li+ solvation-enables a robust, LiF-rich CEI, boosting NCM811's stability. This strategy achieves 90.16% capacity retention at 5C, offering a pathway to durable, high-performance batteries.

High-nickel (Ni ≥ 90%) cathodes which have a high specific capacity hold great potential for next-generation lithium-ion batteries (LIBs). However, their practical application is restricted by their high interfacial reactivity because of the presence of residual lithium (Li) compounds on the surface. Herein, the LiNi0.9Co0.06Mn0.04O2 (NCM90) cathode is surface-modified with sulfur (S) via a simple and feasible dry mixing and low-temperature heat treatment, converting the residual lithium compound on the surface into inactive lithium sulfate (Li2SO4). This induces the formation of a stable inorganic enriched electrode-electrolyte interface on the cathode surface and inhibits the occurrence of side reactions, ultimately inhibiting lattice collapse and the dissolution of transition metal ions. After modifying, the capacity retention rates of NCM90/Li and NCM90/graphite cells are both greatly enhanced after long cycling. This work provides a new idea for the rational design of the electrode-electrolyte interface of high-nickel cathodes.

High‐nickel (Ni ≥ 90%) cathodes with high specific capacity hold great potential for next‐generation lithium‐ion batteries (LIBs). However, their practical application is restricted by the high interfacial reactivity under continuous air erosion and electrolyte assault. Herein, a stable high‐nickel cathode is rationally designed via in situ induction of a dense amorphous Li2CO3 on the particle surface by a preemptive atmosphere control. Among the residual lithium compounds, Li2CO3 is the most thermodynamically stable one, so a dense Li2CO3 coating layer can serve as a physical protection layer to isolate the cathode from contact with moist air. Furthermore, amorphous Li2CO3 can be transformed into a robust F‐rich cathode electrolyte interphase (CEI) during cycling, which reinforces the cathode's interfacial stability and improves the electrochemical performance. The assembled coin cell with this modified cathode delivers a high discharge capacity of 232.4 mAh g–1 with a superior initial Coulombic efficiency (CE) of 95.1%, and considerable capacity retention of 90.4% after 100 cycles. Furthermore, no slurry gelation occurs during the large‐scale electrode fabrication process. This work opens a valuable perspective on the evolution of amorphous Li2CO3 in LIBs and provides guidance on protecting unstable high‐capacity cathodes for energy‐storage devices.

Considering the high price and scarcity of cobalt resource, zero-cobalt, high-nickel layered cathode material (LNM) have been considered as the most promising material for next-generation high-energy-density lithium-ion batteries (LIBs). However,...