A review:Modification strategies of nickel-rich layer structure cathode(Ni≥0.8)materials for lithium ion power batteries

Lithium ion power batteries have undoubtedly become one of the most promising rechargeable batteries at present;nonetheless,they still suffer from the challenges such as requirement of even higher energy density and capacity retention.Nickel-rich layer oxides(Ni≥0.8)become ideal cathode materials to achieve the high specific capacity.Integration of optimization of synthesis process and modification of crystal structure to suppress the capacity fading can obviously improve the performance of the lithium ion batteries.This review presents the recent modification strategies of the nickel-rich layered oxide materials.Unlike in previous reviews and related papers,the specific mechanism about each type of the modification strategies is specially discussed in detail,which is mainly about inhibiting the anisotropic lattice strain and adjusting the cation mixing degree to maintain crystal structure.Based on the recent progress,the prospects and challenges of the modified nickel-rich layer cathodes to upgrade the property of lithium ion batteries are also comprehensively analyzed,and the potential applications in the field of plug-in hybrid vehicles and electric vehicles are further discussed.

The nature of irreversible phase transformation propagation in nickel-rich layered cathode for lithium-ion batteries

Ni-rich layered cathode is regarded as one of the most promising candidates to achieve lithium-ion batteries (LIBs) with high energy density. However, due to the irreversible phase transformation (IPT) and its eventual propagation from surface to the bulk of the material, Ni-rich layered cathode typically suffers from severe capacity fading, structure failure, and thermal instability, which greatly hinders its mass adoption. Hence, achieving an in-depth understanding of the IPT propagation mechanism in Ni-rich layered cathode is crucial in addressing these issues. Herein, the triggering factor of IPT propagation in Ni-rich cathode is verified to be the initial surface disordered cation mixing domain covered by a thin rock-salt phase, instead of the rock-salt phase itself. According to the density functional theory (DFT) results, it is further illustrated that the metastable cation mixing domain possesses a lower Ni migration energy barrier, which facilitates the migration of Ni ions towards the Li slab, and thus driving the propagation of IPT from surface to the bulk of the material. This finding clarifies a prevailing debate regarding the surface impurity phases of Ni-rich cathode material and reveals the origin of IPT propagation, which implies the principle and its effectiveness of tuning the surface microstructure to address the structural and thermal instability issue of Ni-rich layered cathode materials.

Spray pyrolysis synthesis of nickel-rich layered cathodes LiNi_(1-2x)Co_xMn_xO_2(x = 0.075, 0.05, 0.025) for lithium-ion batteries

In this study we report a series of nickel-rich layered cathodes LiNi1-2xCoxMnxO2（x = 0.075, 0.05,0.025） prepared from chlorides solution via ultrasonic spray pyrolysis. SEM images illustrate that the samples are submicron-sized particles and the particle sizes increase with the increase of Ni content.LiNi0.85Co0.075Mn0.075O2 delivers a discharge capacity of 174.9 mAh g-1 with holding 93% reversible capacity at 1 C after 80 cycles, and can maintain a discharge capacity of 175.3 mAh g-1 at 5 C rate. With increasing Ni content, the initial specific capacity increases while the cycling and rate performance degrades in some extent. These satisfying results demonstrate that spray pyrolysis is a powerful and efficient synthesis technology for producing Ni-rich layered cathode（Ni content 〉 80%）.

Recent progress on electrolyte functional additives for protection of nickel-rich layered oxide cathode materials

In advantages of their high capacity and high operating voltage,the nickel(Ni)-rich layered transition metal oxide cathode materials(LiNi_(x)Co_(y)Mn_(z)O_(2)(NCMxyz,x+y+z=1,x≥0.5)and LiNi_(0.8)Co_(0.15)Al_(0.05)O_(2)(NCA))have been arousing great interests to improve the energy density of LIBs.However,these Nirich cathodes always suffer from rapid capacity degradation induced by unstable cathode-electrolyte interphase(CEI)layer and destruction of bulk crystal structure.Therefore,varied electrode/electrolyte interface engineering strategies(such as electrolyte formulation,material coating or doping)have been developed for Ni-rich cathodes protection.Among them,developing electrolyte functional additives has been proven to be a simple,effective,and economic method to improve the cycling stability of Nirich cathodes.This is achieved by removing unfavorable species(such as HF,H_(2)O)or constructing a stable and protective CEI layer against unfavorable reactive species(such as HF,H_(2)O).Herein,this review mainly introduces the varied classes of electrolyte functional additives and their working mechanism for interfacial engineering of Ni-rich cathodes.Especially,key favorable species for stabilizing CEI layer are summarized.More importantly,we put forward perspectives for screening and customizing ideal functional additives for high performance Ni-rich cathodes based LIBs.

Recent progress in synthesis and surface modification of nickel-rich layered oxide cathode materials for lithium-ion batteries

Nickel-rich layered oxides have been identified as the most promising commercial cathode materials for lithium-ion batteries(LIBs)for their high theoretical specific capacity.However,the poor cycling stability of nickel-rich cathode materials is one of the major barriers for the large-scale usage of LIBs.The existing obstructions that suppress the capacity degradation of nickel-rich cathode materials are as a result of phase transition,mechanical instability,intergranular cracks,side reaction,oxygen loss,and thermal instability during cycling.Core–shell structures,oxidating precursors,electrolyte additives,doping/coating and synthesizing single crystals have been identified as effective methods to improve cycling stability of nickel-rich cathode materials.Herein,recent progress of surface modification,e.g.coating and doping,in nickel-rich cathode materials are summarized based on Periodic table to provide a clear understanding.Electrochemical performances and mechanisms of modified structure are discussed in detail.It is hoped that an overview of synthesis and surface modification can be presented and a perspective of nickel-rich materials in LIBs can be given.

Functional copolymer binder for nickel-rich cathode with exceptional cycling stability at high temperature through coordination interaction

Nickel-rich layered oxide LiNi_(1-x-y)Co_(x)Al_yO_(2)(NCA) with high theoretical capacity is a promising cathode material for the next-generation high-energy batteries.However,it undergoes a rapid capacity fading when operating at high temperature due to the accelerated cathode/electrolyte interfacial reactions and adhesive efficacy loss of conventional polyvinylideneffuoride(PVdF) binder.Herein,poly(acrylonitrile-co-methyl acrylate) copolymer is designed with electron-rich-C≡N groups as a novel binder for LiNi_(0.8)Co_(0.1)Al_(0.1)O_(2) cathode at high temperature.The electron-rich-C≡N groups are able to coordinate with the active Ni^(3+) on the surface of NCA,alleviating electrolyte decomposition and cathode structure degradation.Moreover,the strong adhesive ability is conducive to maintain integrity of electrodes upon cycling at 55℃.In consequence,the NCA electrodes with this functional binder display improved cycling stability(81.5% capacity retention after 100 cycles) and rate performance at 55℃.

Surface-targeted functionalization of nickel-rich cathodes through synergistic slurry additive approach with multi-level impact using minimal quantity

LiNi0.8Co0.1Mn0.1O_(2)(NCM811),a Ni-rich layered oxide,is a promising cathode material for high-energy density lithium-ion batteries(LIBs).However,its structural instability,caused by adverse phase transitions and continuous oxygen release,as well as deteriorated interfacial stability due to excessive electrolyte oxidative decomposition,limits its widespread application.To address these issues,a new concept is proposed that surface targeted precise functionalization(STPF)of the NCM811 cathode using a synergistic slurry additive(SSA)approach.This approach involves coating the NCM811 particle surface with 3-aminopropyl dimethoxy methyl silane(3-ADMS),followed by the precise deposition of ascorbic acid via an acid-base interaction.The slurry additives induce the formation of an ultra-thin spinel surface layer and a stable cathode–electrolyte interface(CEI),which enhances the electrochemical kinetics and inhibits crack propagation.The STPF strategy implemented by the SSA approach significantly improves the cyclic stability and rate performance of the NCM811 cathode in both half-cell and full-cell configurations.This work establishes a promising strategy to enhance the structural stability and electrochemical performance of nickel-rich cathodes and provides a feasible route to promote practical applications of high-energy density lithium-ion battery technology.

Research progress in failure mechanisms and electrolyte modification of high-voltage nickel-rich layered oxide-based lithium metal batteries

High-voltage nickel(Ni)-rich layered oxide-based lithium metal batteries(LMBs)exhibit a great potential in advanced batteries due to the ultra-high energy density.However,it is still necessary to deal with the challenges in poor cyclic and thermal stability before realizing practical application where cycling life is considered.Among many improved strategies,mechanical and chemical stability for the electrode electrolyte interface plays a key role in addressing these challenges.Therefore,extensive effort has been made to address the challenges of electrode-electrolyte interface.In this progress,the failure mechanism of Ni-rich cathode,lithium metal anode and electrolytes are reviewed,and the latest breakthrough in stabilizing electrode-electrolyte interface is also summarized.Finally,the challenges and future research directions of Ni-rich LMBs are put forward.

Surface cobaltization for boosted kinetics and excellent stability of nickel-rich layered cathodes

The feasibility of LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2) as a primary cathode material has decreased due to the fragile cobalt(Co)supply chain and its undesirable effects on structural degradation.LiNi_(0.6)Mn_(0.4)O_(2) deserves greater attention because of its high thermal and cyclic stability,coupled with low raw material and production costs.However,this material suffers from low reversible capacity and poor rate performance.Herein,we rationally design a high-performance cathode structure composed of a robust conductive protective layer,gradient Li^(+)ions conductive layer and stable bulk phase of LiNi_(0.6)Mn_(0.4)O_(2) through surface cobaltization,which not only boosts the reaction kinetics of the electrode but also suppresses particle cracking and mitigates surface structural degradation.As a result,a dramatically improved rate capacity(118.7 vs 53.5 mAh g^(-1) at 5 C)and impressive capacity retention after 300 cycles(90.4% in a full cell)at a high cutoff voltage(4.4 V)are obtained.Co-modified Li-Ni_(0.6)Mn_(0.4)O_(2) is promising to challenge commercial position of LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2) attributed to the accessible capacity,superior rate capacity,excellent cycle performance,good thermal stability and low cost.Our results open a door for optimizing the use of Co and the structural design of high-nickel cathodes.

Beneficial impact of lithium bis(oxalato)borate as electrolyte additive for high-voltage nickel-rich lithium-battery cathodes

High-voltage nickel-rich layered cathodes possess the requisite,such as excellent discharge capacity and high energy density,to realize lithium batteries with higher energy density.However,such materials suffer from structural and interfacial instability at high voltages(>4.3 V).To reinforce the stability of these cathode materials at elevated voltages,lithium borate salts are investigated as electrolyte additives to generate a superior cathode-electrolyte interphase.Specifically,the use of lithium bis(oxalato)borate(LiBOB)leads to an enhanced cycling stability with a capacity retention of 81.7%.Importantly,almost no voltage hysteresis is detected after 200 cycles at 1C.This outstanding electrochemical performance is attributed to an enhanced structural and interfacial stability,which is attained by suppressing the generation of micro-cracks and the superficial structural degradation upon cycling.The improved stability stems from the formation of a fortified borate-containing interphase which protects the highly reactive cathode from parasitic reactions with the electrolyte.Finally,the decomposition process of LiBOB and the possible adsorption routes to the cathode surface are deduced and elucidated.

Multi-scale boron penetration toward stabilizing nickel-rich cathode

Nickel-rich layered oxides LiNi_(x)Co_(y)Mn_(1-x-y)O_(2)(x≥0.8)have been recognized as the preferred cathode materials to develop lithium-ion batteries with high energy density(>300 Wh kg^(−1)).However,the poor cycling stability and rate capability stemming from intergranular cracks and sluggish kinetics hinder their commercialization.To address such issues,a multi-scale boron penetration strategy is designed and applied on the polycrystalline LiNi_(0.83)Co_(0.11)Mn_(0.06)O_(2)particles that are pre-treated with pore construction.The lithium-ion conductive lithium borate in grain gaps functions as the grain binder that can bear the strain/stress from anisotropic contraction/expansion,and provides more pathways for lithium-ion diffusion.As a result,the intergranular cracks are ameliorated and the lithium-ion diffusion kinetics is improved.Moreover,the coating layer separates the sensitive cathode surface and electrolyte,helping to suppress the parasitic reactions and related gas evolution.In addition,the enhanced structural stability is acquired by strong B-O bonds with trace boron doping.As a result,the boron-modified sample with an optimized boron content of 0.5%(B5-NCM)exhibits a higher initial discharge capacity of 205.5 mAh g^(−1)at 0.1C(1C=200 mA g^(−1))and improved capacity retention of 81.7%after 100 cycles at 1C.Furthermore,the rate performance is distinctly enhanced by high lithium-ion conductive LBO(175.6 mAh g^(−1)for B5-NCM and 154.6 mAh g^(−1)for B0-NCM at 5C)

黄铜集流体在无负极锂金属电池中的应用研究

虽然无负极锂金属电池(AF-LMBs)具有能量密度高、结构简单等优势,但是金属锂在负极集流体界面不可逆的沉积/剥离过程以及与电解液之间的副反应会大量消耗电池中有限的活性锂,导致电池容量迅速衰减。开发高性能的负极集流体是提升AF-LMBs循环寿命的有效策略之一。因此,本文研究了商业黄铜箔(F-Cu-Zn)作为负极集流体在AF-LMBs中的电化学性能,并且结合多种表征技术揭示了F-Cu-Zn电极在循环过程中的结构演变。结果表明:与商业铜箔(F-Cu)相比,F-Cu-Zn含有丰富的亲锂位点,诱导金属锂均匀成核与生长,所组装的Cu-Zn||NCM712软包全电池的室温循环寿命从75次增加至117次。此外,F-Cu-Zn电极中的Zn元素会在循环过程中不断溶解,最终在电极表层形成三维多孔结构。

Residual alkali-evoked cross-linked polymer layer for anti-air-sensitivity LiNi_(0.89)Co_(0.06)Mn_(0.05)O_(2)cathode

High-energy density lithium-ion batteries(LIBs)with layered high-nickel oxide cathodes(LiNi_(x)Co_(y)Mn_(1-x-y)O_(2),x≥0.8)show great promise in consumer electronics and vehicular applications.However,LiNi_(x)Co_(y)Mn_(1-x-y)O_(2)faces challenges related to capacity decay caused by residual alkalis owing to high sensitivity to air.To address this issue,we propose a hazardous substances upcycling method that fundamentally mitigates alkali content and concurrently induces the emergence of an anti-air-sensitive layer on the cathode surface.Through the neutralization of polyacrylic acid(PAA)with residual alkalis and then coupling it with 3-aminopropyl triethoxysilane(KH550),a stable and ion-conductive cross-linked polymer layer is in situ integrated into the LiNi_(0.89)Co_(0.06)Mn_(0.05)O_(2)(NCM)cathode.Our characterization and measurements demonstrate its effectiveness.The NCM material exhibits impressive cycling performance,retaining 88.4%of its capacity after 200 cycles at 5 C and achieving an extraordinary specific capacity of 170.0 mA h g^(-1) at 10 C.Importantly,this layer on the NCM efficiently suppresses unfavorable phase transitions,severe electrolyte degradation,and CO_(2)gas evolution,while maintaining commendable resistance to air exposure.This surface modification strategy shows widespread potential for creating air-stable LiNi_(x)Co_(y)Mn_(1-x-y)O_(2)cathodes,thereby advancing high-performance LIBs.

Recent progress in Ni-rich layered oxides and related cathode materials for Li-ion cells

Undoubtedly,the enormous progress observed in recent years in the Ni-rich layered cathode materials has been crucial in terms of pushing boundaries of the Li-ion battery(LIB)technology.The achieved improvements in the energy density,cyclability,charging speed,reduced costs,as well as safety and stability,already contribute to the wider adoption of LIBs,which extends nowadays beyond mobile electronics,power tools,and electric vehicles,to the new range of applications,including grid storage solutions.With numerous published papers and broad reviews already available on the subject of Ni-rich oxides,this review focuses more on the most recent progress and new ideas presented in the literature references.The covered topics include doping and composition optimization,advanced coating,concentration gradient and single crystal materials,as well as innovations concerning new electrolytes and their modification,with the application of Ni-rich cathodes in solid-state batteries also discussed.Related cathode materials are briefly mentioned,with the high-entropy approach and zero-strain concept presented as well.A critical overview of the still unresolved issues is given,with perspectives on the further directions of studies and the expected gains provided.

Stabilizing High-Nickel Cathodes via Interfacial Hydrogen Bonding Effects Using a Hydrofluoric Acid-Scavenging Separator

Nickel-rich layered Li transition metal oxides are the most promising cathode materials for high-energydensity Li-ion batteries.However,they exhibit rapid capacity degradation induced by transition metal dissolution and structural reconstruction,which are associated with hydrofluoric acid(HF)generation from lithium hexafluorophosphate decomposition.The potential for thermal runaway during the working process poses another challenge.Separators are promising components to alleviate the aforementioned obstacles.Herein,an ultrathin double-layered separator with a 10 lm polyimide(PI)basement and a 2 lm polyvinylidene difluoride(PVDF)coating layer is designed and fabricated by combining a nonsolvent induced phase inversion process and coating method.The PI skeleton provides good stability against potential thermal shrinkage,and the strong PI-PVDF bonding endows the composite separator with robust structural integrity;these characteristics jointly contribute to the extraordinary mechanical tolerance of the separator at elevated temperatures.Additionally,unique HF-scavenging effects are achieved with the formation of-CO…H-F hydrogen bonds for the abundant HF coordination sites provided by the imide ring;hence,the layered Ni-rich cathodes are protected from HF attack,which ultimately reduces transition metal dissolution and facilitates long-term cyclability of the Ni-rich cathodes.Li||NCM811 batteries(where“NCM”indicates LiNi_(x)Co_(y)Mn_(1-x-y)O_(2))with the proposed composite separator exhibit a 90.6%capacity retention after 400 cycles at room temperature and remain sustainable at 60℃with a 91.4%capacity retention after 200 cycles.By adopting a new perspective on separators,this study presents a feasible and promising strategy for suppressing capacity degradation and enabling the safe operation of Ni-rich cathode materials.

Early-stage latent thermal failure of single-crystal Ni-rich layered cathode

High nickel content worsens the thermal stability of layered cathodes for lithium-ion batteries,raising safety concerns for their applications.Thoroughly understanding the thermal failure process can offer valuable guidance for material optimization on thermal stability and new opportunities in monitoring battery thermal runaway(TR).Herein,this work comprehensively investigates the thermal failure process of a single-crystal nickel-rich layered cathode and finds that the latent thermal failure starts at∼120℃far below the TR temperature(225℃).During this stage of heat accumulation,sequential structure transition is revealed by atomic resolution electron microscopy,which follows the layered→cation mixing layered→LiMn_(2)O_(4)-type spinel→disordered spinel→rock salt.This progression occurs as a result of the continuous migration and densification of transition metal cations.Phase transition generates gaseous oxygen,initially confined within the isolated closed pores,thereby not showing any thermal failure phenomena at the macro-level.Increasing temperature leads to pore growth and coalescence,and eventually to the formation of open pores,causing oxygen gas release and weight loss,which are the typical TR features.We highlight that latent thermal instability occurs before the macro-level TR,suggesting that suppressing phase transitions caused by early thermal instability is a crucial direction for material optimization.Our findings can also be used for early warning of battery thermal runaway.

Approaching Ultimate Synthesis Reaction Rate of Ni-Rich Layered Cathodes for Lithium-Ion Batteries

Nickel-rich layered oxide LiNi_(x)Co_(y)MnzO_(2)(NCM,x+y+z=1)is the most promising cathode material for high-energy lithium-ion batteries.However,conventional synthesis methods are limited by the slow heating rate,sluggish reaction dynamics,high energy consumption,and long reaction time.To overcome these chal-lenges,we first employed a high-temperature shock(HTS)strategy for fast synthesis of the NCM,and the approaching ultimate reaction rate of solid phase transition is deeply investigated for the first time.In the HTS process,ultrafast average reaction rate of phase transition from Ni_(0.6)Co_(0.2)Mn_(0.2)(OH)_(2) to Li-containing oxides is 66.7(%s^(-1)),that is,taking only 1.5 s.An ultrahigh heating rate leads to fast reaction kinetics,which induces the rapid phase transition of NCM cathodes.The HTS-synthesized nickel-rich layered oxides perform good cycling performances(94%for NCM523,94%for NCM622,and 80%for NCM811 after 200 cycles at 4.3 V).These findings might also assist to pave the way for preparing effectively Ni-rich layered oxides for lithium-ion batteries.

富镍LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)正极材料改性研究进展

锂离子电池用富镍正极材料LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)具有高能量密度、高安全性等优点。受容量衰减、循环寿命和热稳定性等方面的限制,该材料进一步的改性成为当前研究的热点。针对LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)材料的改性研究主要集中在离子掺杂、表面包覆和结构设计等方面。离子掺杂能改善结构稳定性和电化学性能,特别是过渡金属离子的掺杂有助于延长循环寿命和提高结构稳定性;表面包覆改性可增强电化学稳定性和抗氧化性能,延长循环寿命和提高抗极化能力;结构设计可优化晶体结构、提高传导性能和缓解应力,提高循环稳定性、容量保持率和功率密度。

碳钢表面电镀锌镍/有机富铝复合涂层的制备与性能

为提高碳钢表面电镀锌镍的防护性能和应用限制,采用电镀锌镍层作为底层,有机富铝涂层作为顶层,设计出一种复合涂层防护体系。采用扫描电镜(SEM)、能谱(EDS)、中性盐雾试验、电化学测试等手段对电镀锌镍/有机富铝复合涂层的表面/截面形貌及耐蚀性进行表征与分析。结果表明:电镀锌镍/有机富铝复合涂层表面光滑平整,无明显缺陷,复合涂层体系界面结合良好,无分层现象,经1500 h中性盐雾试验后复合涂层无红锈。复合涂层较单独的电镀锌镍合金层腐蚀电流密度降低了2个数量级,表现出受控的牺牲阳级作用,并实现了在海洋防护领域的应用。复合涂层有效提升了电镀锌镍层的耐腐蚀性能,拓宽了电镀锌镍层在腐蚀防护领域的应用范围。

一步法实现Rb^(+)/Cl^(-)双位点共掺杂高性能锂离子电池正极材料LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)

针对LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM)正极材料在循环过程中结构不稳定的问题,提出了Rb^(+)/Cl^(-)双位点共掺杂NCM材料的策略。NCM晶格中Rb^(+)/Cl^(-)双位点共掺杂的协同效应提高了Li^(+)扩散速率,缓解了内部应变,抑制了高截止电压循环时Li^(+)/Ni^(2+)的混排。电化学测试结果表明,Li_(0.99)Rb_(0.01)(Ni_(0.8)Co_(0.1)Mn_(0.1))O_(1.99)Cl_(0.01)(RbCl-NCM)材料在电流密度10C下放电容量高达176.9 mAh/g;RbCl-NCM材料在电流密度1C下首次放电容量203.5 mAh/g,且具有优异的循环性能,经200个循环后,容量保持率高达87.8%,而NCM材料在相同测试条件下的容量保持率仅57.3%。