Difficulties, strategies, and recent research and development of layered sodium transition metal oxide cathode materials for high-energy sodium-ion batteries

Energy-storage systems and their production have attracted significant interest for practical applications.Batteries are the foundation of sustainable energy sources for electric vehicles(EVs),portable electronic devices(PEDs),etc.In recent decades,Lithium-ion batteries(LIBs) have been extensively utilized in largescale energy storage devices owing to their long cycle life and high energy density.However,the high cost and limited availability of Li are the two main obstacles for LIBs.In this regard,sodium-ion batteries(SIBs) are attractive alternatives to LIBs for large-scale energy storage systems because of the abundance and low cost of sodium materials.Cathode is one of the most important components in the battery,which limits cost and performance of a battery.Among the classified cathode structures,layered structure materials have attracted attention because of their high ionic conductivity,fast diffusion rate,and high specific capacity.Here,we present a comprehensive review of the classification of layered structures and the preparation of layered materials.Furthermore,the review article discusses extensively about the issues of the layered materials,namely(1) electrochemical degradation,(2) irreversible structural changes,and(3) structural instability,and also it provides strategies to overcome the issues such as elemental phase composition,a small amount of elemental doping,structural design,and surface alteration for emerging SIBs.In addition,the article discusses about the recent research development on layered unary,binary,ternary,quaternary,quinary,and senary-based O3-and P2-type cathode materials for high-energy SIBs.This review article provides useful information for the development of high-energy layered sodium transition metal oxide P2 and O3-cathode materials for practical SIBs.

Modification strategies improving the electrochemical and structural stability of high-Ni cathode materials

With the increasing spotlight in electric vehicles,there is a growing demand for high-energy-density batteries to enhance driving range.Consequently,several studies have been conducted on high-energy-density LiNi_(x)Co_(y)Mn_(z)O_(2)cathodes.However,there is a limit to permanent performance deterioration because of side reactions caused by moisture in the atmosphere and continuous microcracks during cycling as the Ni content to express high energy increases and the content of Mn and Co that maintain structural and electrochemical stabilization decreases.The direct modification of the surface and bulk regions aims to enhance the capacity and long-term performance of high-Ni cathode materials.Therefore,an efficient modification requires a study based on a thorough understanding of the degradation mechanisms in the surface and bulk region.In this review,a comprehensive analysis of various modifications,including doping,coating,concentration gradient,and single crystals,is conducted to solve degradation issues along with an analysis of the overall degradation mechanism occurring in high-Ni cathode materials.It also summarizes recent research developments related to the following modifications,aims to provide notable points and directions for post-studies,and provides valuable references for the commercialization of stable high-energy-density cathode materials.

Research progresses on cathode materials of aqueous zinc-ion batteries

Electrochemical energy storage and conversion techniques that exhibit the merits such as high energy density,rapid response kinetics,economical maintenance requirements and expedient installation procedures will hold a pivotal role in the forthcoming energy storage technologies revolution.In recent years,aqueous zinc-ion batteries(AZIBs)have garnered substantial attention as a compelling candidate for large-scale energy storage systems,primarily attributable to their advantageous featu res encompassing cost-effectiveness,environmental sustainability,and robust safety profiles.Currently,one of the primary factors hindering the further development of AZIBs originates from the challenge of cathode materials.Specifically,the three mainstream types of mainstream cathode materials,in terms of manganese-based compounds,vanadium-based compounds and Prussian blue analogues,surfer from the dissolution of Mn~(2+),in the low discharge voltage,and the low specific capacity,respectively.Several strategies have been developed to compensation the above intrinsic defects for these cathode materials,including the ionic doping,defect engineering,and materials match.Accordingly,this review first provides a systematic summarization of the zinc storage mechanism in AZIBs,following by the inherent merit and demerit of three kind of cathode materials during zinc storage analyzed from their structure characteristic,and then the recent development of critical strategies towards the intrinsic insufficiency of these cathode materials.In this review,the methodologies aimed at enhancing the efficacy of manganese-based and vanadium-based compounds are emphasis emphasized.Additionally,the article outlines the future prospective directions as well as strategic proposal for cathode materials in AZIBs.

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.

Recent Progress and Regulation Strategies of Layered Materials as Cathode of Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries(ZIBs)have shown great potential in the fields of wearable devices,consumer electronics,and electric vehicles due to their high level of safety,low cost,and multiple electron transfer.The layered cathode materials of ZIBs hold a stable structure during charge and discharge reactions owing to the ultrafast and straightforward(de)intercalation-type storage mechanism of Zn^(2+)ions in their tunable interlayer spacing and their abilities to accommodate other guest ions or molecules.Nevertheless,the challenges of inadequate energy density,dissolution of active materials,uncontrollable byproducts,increased internal pressure,and a large de-solvation penalty have been deemed an obstacle to the development of ZIBs.In this review,recent strategies on the structure regulation of layered materials for aqueous zinc-ion energy storage devices are systematically summarized.Finally,critical science challenges and future outlooks are proposed to guide and promote the development of advanced cathode materials for ZIBs.

Enhancing thermodynamic stability of single-crystal Ni-rich cathode material via a synergistic dual-substitution strategy

Nickel(Ni)-rich cathode materials have become promising candidates for the next-generation electrical vehicles due to their high specific capacity.However,the poor thermodynamic stability(including cyclic performance and safety performance or thermal stability)will restrain their wide commercial application.Herein,a single-crystal Ni-rich Li Ni_(0.83)Co_(0.12)Mn_(0.05)O_(2) cathode material is synthesized and modified by a dual-substitution strategy in which the high-valence doping element improves the structural stability by forming strong metal–oxygen binding forces,while the low-valence doping element eliminates high Li^(+)/Ni^(2+)mixing.As a result,this synergistic dual substitution can effectively suppress H2-H3 phase transition and generation of microcracks,thereby ultimately improving the thermodynamic stability of Ni-rich cathode material.Notably,the dual-doped Ni-rich cathode delivers an extremely high capacity retention of 81%after 250 cycles(vs.Li/Li+)in coin-type half cells and 87%after 1000 cycles(vs.graphite/Li^(+))in pouch-type full cells at a high temperature of 55℃.More impressively,the dual-doped sample exhibits excellent thermal stability,which demonstrates a higher thermal runaway temperature and a lower calorific value.The synergetic effects of this dual-substitution strategy pave a new pathway for addressing the critical challenges of Ni-rich cathode at high temperatures,which will significantly advance the high-energy-density and high-safety cathodes to the subsequent commercialization.

Optimization Strategies of Na_(3)V_(2)(PO_(4))_(3) Cathode Materials for Sodium‑Ion Batteries

Na_(3)V_(2)(PO_(4))_(3)(NVP)has garnered great attentions as a prospective cathode material for sodium-ion batteries(SIBs)by virtue of its decent theoretical capacity,superior ion conductivity and high structural stability.However,the inherently poor electronic conductivity and sluggish sodium-ion diffusion kinetics of NVP material give rise to inferior rate performance and unsatisfactory energy density,which strictly confine its further application in SIBs.Thus,it is of significance to boost the sodium storage performance of NVP cathode material.Up to now,many methods have been developed to optimize the electrochemical performance of NVP cathode material.In this review,the latest advances in optimization strategies for improving the electrochemical performance of NVP cathode material are well summarized and discussed,including carbon coating or modification,foreign-ion doping or substitution and nanostructure and morphology design.The foreign-ion doping or substitution is highlighted,involving Na,V,and PO_(4)^(3−)sites,which include single-site doping,multiple-site doping,single-ion doping,multiple-ion doping and so on.Furthermore,the challenges and prospects of high-performance NVP cathode material are also put forward.It is believed that this review can provide a useful reference for designing and developing high-performance NVP cathode material toward the large-scale application in SIBs.

Research on Preparation and Electrochemical Performance of the High Compacted Density Ni-Co-Mn Ternary Cathode Materials

The high compacted density LiNi0.5-xCo0.2Mn0.3MgxO2 cathode material for lithium-ion batteries was synthesized by high temperature solid-state method, taking the Mg element as a doping element and the spherical Ni0.5Co0.2Mn0.3 (OH)2, Li2CO3 as raw materials. The effects of calcination temperature on the structure and properties of the products were investigated. The structure and morphology of cathode materials powder were analyzed by X-ray diffraction spectroscopy (XRD) and scanning electronmicroscopy (SEM). The electrochemical properties of the cathode materials were studied by charge-discharge test and cyclic properties test. The results show that LiNi0.4985Co0.2Mn0.3 Mg0.0015O2 cathode material prepared at calcination temperature 930°C has a good layered structure, and the compacted density of the electrode sheet is above 3.68 g/cm3. The discharge capacity retention rate is more than 97.5% after 100 cycles at a charge-discharge rate of 1C, displaying a good cyclic performance.

Corrigendum to“Anthraquinone derivatives supported by Ti_(3)C_(2)(MXene)as cathode materials for aluminum-organic batteries”[J.Energy Chem.74(2022)174–183]

The authors regret that the printed version of the above article contained an error reference.We hope to correct it here.[14]B.J.M.Christophe Legein,Franck Fayon,Angew.Chem.Int.Ed.,132(2020)19409–19415.

Impact of Transition Metal Layer Vacancy on the Structure and Performance of P2 Type Layered Sodium Cathode Material

This study explores the impact of introducing vacancy in the transition metal layer of rationally designed Na_(0.6)[Ni_(0.3)Ru_(0.3)Mn_(0.4)]O_(2)(NRM)cathode material.The incorporation of Ru,Ni,and vacancy enhances the structural stability during extensive cycling,increases the operation voltage,and induces a capacity increase while also activating oxygen redox,respectively,in Na_(0.7)[Ni_(0.2)V_(Ni0.1)Ru_(0.3)Mn_(0.4)]O_(2)(V-NRM)compound.Various analytical techniques including transmission electron microscopy,X-ray absorption near edge spectroscopy,operando X-ray diffraction,and operando differential electrochemical mass spectrometry are employed to assess changes in the average oxidation states and structural distortions.The results demonstrate that V-NRM exhibits higher capacity than NRM and maintains a moderate capacity retention of 81%after 100 cycles.Furthermore,the formation of additional lone-pair electrons in the O 2p orbital enables V-NRM to utilize more capacity from the oxygen redox validated by density functional calculation,leading to a widened dominance of the OP4 phase without releasing O_(2) gas.These findings offer valuable insights for the design of advanced high-capacity cathode materials with improved performance and sustainability in sodium-ion batteries.

Effect of crystal morphology of ultrahigh-nickel cathode materials on high temperature electrochemical stability of lithium ion batteries

Higher nickel content endows Ni-rich cathode materials LiNi_(x)Co_yMn_(1-x-y)O_(2)(x>0.6)with higher specific capacity and high energy density,which is regarded as the most promising cathode materials for Li-ion batteries.However,the deterioration of structural stability hinders its practical application,especially under harsh working conditions such as high-temperature cycling.Given these circumstances,it becomes particularly critical to clarify the impact of the crystal morphology on the structure and high-temperature performance as for the ultrahigh-nickel cathodes.Herein,we conducted a comprehensive comparison in terms of microstructure,high-temperature long-cycle phase evolution,and high-temperature electrochemical stability,revealing the differences and the working mechanisms among polycrystalline(PC),single-crystalline(SC)and Al doped SC ultrahigh-nickel materials.The results show that the PC sample suffers a severe irreversible phase transition along with the appearance of microcracks,resulting a serious decay of both average voltage and the energy density.While the Al doped SC sample exhibits superior cycling stability with intact layered structure.In-situ XRD and intraparticle structural evolution characterization reveal that Al doping can significantly alleviate the irreversible phase transition,thus inhibiting microcracks generation and enabling enhanced structure.Specifically,it exhibits excellent cycling performance in pouch-type full-cell with a high capacity retention of 91.8%after 500 cycles at 55℃.This work promotes the fundamental understanding on the correlation between the crystalline morphology and high-temperature electrochemical stability and provides a guide for optimization the Ni-rich cathode materials.

Advances in cathode materials for Li-O_(2)batteries

Lithium-oxygen(Li-O_(2))batteries have attracted significant attention due to their ultra-high theoretical energy density.However,serious challenges,such as potential lag,low-rate capability,round-trip efficiency,and poor cycle stability,greatly limit their practical application.This review provides a comprehensive account of the development of Li-O_(2)batteries,elucidates the current discharge/charge mechanism,and highlights both the advantages and bottlenecks of this technology.In particular,recent research progress on various cathode materials,such as carbon-based materials,noble metals,and non-noble metals,for Li-O_(2)batteries is deeply reviewed,emphasizing the impact of design strategies,material structures,chemical compositions,and microphysical parameters on oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)kinetics,as well as discharge products and overall battery performance.This review will also shed light on future research directions for oxygen electrode catalysts and material construction to facilitate the development of Li-O_(2)batteries with maximized electrochemical performance.

Ab Initio Design of Ni-Rich Cathode Material with Assistance of Machine Learning for High Energy Lithium-Ion Batteries

With the widespread use of lithium-ion batteries in electric vehicles,energy storage,and mobile terminals,there is an urgent need to develop cathode materials with specific properties.However,existing material control synthesis routes based on repetitive experiments are often costly and inefficient,which is unsuitable for the broader application of novel materials.The development of machine learning and its combination with materials design offers a potential pathway for optimizing materials.Here,we present a design synthesis paradigm for developing high energy Ni-rich cathodes with thermal/kinetic simulation and propose a coupled image-morphology machine learning model.The paradigm can accurately predict the reaction conditions required for synthesizing cathode precursors with specific morphologies,helping to shorten the experimental duration and costs.After the model-guided design synthesis,cathode materials with different morphological characteristics can be obtained,and the best shows a high discharge capacity of 206 mAh g^(−1)at 0.1C and 83%capacity retention after 200 cycles.This work provides guidance for designing cathode materials for lithium-ion batteries,which may point the way to a fast and cost-effective direction for controlling the morphology of all types of particles.

Suppress oxygen evolution of lithium-rich manganese-based cathode materials via an integrated strategy

Improving the reversibility of anionic redox and inhibiting irreversible oxygen evolution are the main challenges in the application of high reversible capacity Li-rich Mn-based cathode materials.A facile synchronous lithiation strategy combining the advantages of yttrium doping and LiYO_(2) surface coating is proposed.Yttrium doping effectively suppresses the oxygen evolution during the delithiation process by increasing the energy barrier of oxygen evolution reaction through strong Y–O bond energy.LiYO_(2) nanocoating has the function of structural constraint and protection,that protecting the lattice oxygen exposed to the surface,thus avoiding irreversible oxidation.As an Li^(+) conductor,LiYO_(2) nano-coating can provide a fast Li^(+) transfer channel,which enables the sample to have excellent rate performance.The synergistic effect of Y doping and nano-LiYO_(2) coating integration suppresses the oxygen release from the surface,accelerates the diffusion of Li^(+)from electrolyte to electrode and decreases the interfacial side reactions,enabling the lithium ion batteries to obtain good electrochemical performance.The lithium-ion full cell employing the Y-1 sample(cathode)and commercial graphite(anode)exhibit an excellent specific energy density of 442.9 Wh kg^(-1) at a current density of 0.1C,with very stable safety performance,which can be used in a wide temperature range(60 to-15℃)stable operation.This result illustrates a new integration strategy for advanced cathode materials to achieve high specific energy density.

Preparation of lithium-ion battery anode materials from graphitized spent carbon cathode derived from aluminum electrolysis

Graphitized spent carbon cathode(SCC)is a hazardous solid waste generated in the aluminum electrolysis process.In this study,a flotation-acid leaching process is proposed for the purification of graphitized SCC,and the use of the purified SCC as an anode material for lithium-ion batteries is explored.The flotation and acid leaching processes were separately optimized through one-way experiments.The maximum SCC carbon content(93wt%)was achieved at a 90%proportion of−200-mesh flotation particle size,a slurry concentration of 10wt%,a rotation speed of 1600 r/min,and an inflatable capacity of 0.2 m^(3)/h(referred to as FSCC).In the subsequent acid leaching process,the SCC carbon content reached 99.58wt%at a leaching concentration of 5 mol/L,a leaching time of 100 min,a leaching temperature of 85°C,and an HCl/FSCC volume ratio of 5:1.The purified graphitized SCC(referred to as FSCC-CL)was utilized as an anode material,and it exhibited an initial capacity of 348.2 mAh/g at 0.1 C and a reversible capacity of 347.8 mAh/g after 100 cycles.Moreover,compared with commercial graphite,FSCC-CL exhibited better reversibility and cycle stability.Thus,purified SCC is an important candidate for anode material,and the flotation-acid leaching purification method is suitable for the resourceful recycling of SCC.

Alleviating the anisotropic microstructural change and boosting the lithium ions diffusion by grain orientation regulation for Ni-rich cathode materials

Generally,layered Ni-rich cathode materials exhibit the morphology of polycrystalline secondary sphere composed of numerous primary particles.While the arrangement of primary particles plays a very important role in the properties of Ni-rich cathodes.The disordered particle arrangement is harmful to the cyclic performance and structural stability,yet the fundamental understanding of disordered structure on the structural degradation behavior is unclarified.Herein,we have designed three kinds of LiNi_(0.83)Co_(0.06)Mn_(0.11)O_(2) cathode materials with different primary particle orientations by regulating the precursor coprecipitation process.Combining finite element simulation and in-situ characterization,the Li^(+)transport and structure evolution behaviors of different materials are unraveled.Specifically,the smooth Li^(+)diffusion minimizes the reaction heterogeneity,homogenizes the phase transition within grains,and mitigates the anisotropic microstructural change,thereby modulating the crack evolution behavior.Meanwhile,the optimized structure evolution ensures radial tight junctions of the primary particles,enabling enhanced Li^(+)diffusion during dynamic processes.Closed-loop bidirectional enhancement mechanism becomes critical for grain orientation regulation to stabilize the cyclic performance.This precursor engineering with particle orientation regulation provides the useful guidance for the structural design and feature enhancement of Ni-rich layered cathodes.

Boosting rate performance of layered lithium-rich cathode materials by oxygen vacancy induced surface multicomponent integration

The rapid development of electric vehicles and portable energy storage systems demands improvements in the energy density and cost-effectiveness of lithium-ion batteries,a domain in which Lithium-rich layered cathode(LLO)materials inherently excel.However,these materials face practical challenges,such as low initial Coulombic efficiency,inferior cycle/rate performance,and voltage decline during cycling,which limit practical application.Our study introduces a surface multi-component integration strategy that incorporates oxygen vacancies into the pristine LLO material Li1.2Mn_(0.6)Ni_(0.2)O_(2).This process involves a brief citric acid treatment followed by calcination,aiming to explore rate-dependent degradation behavior.The induced surface oxygen vacancies can reduce surface oxygen partial pressure and diminish the generation of O_(2)and other highly reactive oxygen species on the surface,thereby facilitating the activation of Li ions trapped in tetrahedral sites while overcoming transport barriers.Additionally,the formation of a spinel-like phase with 3D Li+diffusion channels significantly improves Li^(+)diffusion kinetics and stabilizes the surface structure.The optimally modified sample boasts a discharge capacity of 299.5 mA h g^(-1)at a 0.1 C and 251.6 mA h g^(-1)at a 1 C during the initial activation cycle,with an impressive capacity of 222.1 mA h g^(-1)at a 5 C.Most notably,it retained nearly 70%of its capacity after 300 cycles at this elevated rate.This straightforward,effective,and highly viable modification strategy provides a crucial resolution for overcoming challenges associated with LLO materials,making them more suitable for practical application.

Proof of Aerobically Autoxidized Self-Charge Concept Based on Single Catechol-Enriched Carbon Cathode Material

The self-charging concept has drawn considerable attention due to its excellent ability to achieve environmental energy harvesting,conversion and storage without an external power supply.However,most self-charging designs assembled by multiple energy harvesting,conversion and storage materials increase the energy transfer loss;the environmental energy supply is generally limited by climate and meteorological conditions,hindering the potential application of these selfpowered devices to be available at all times.Based on aerobic autoxidation of catechol,which is similar to the electrochemical oxidation of the catechol groups on the carbon materials under an electrical charge,we proposed an air-breathing chemical self-charge concept based on the aerobic autoxidation of catechol groups on oxygen-enriched carbon materials to ortho-quinone groups.Energy harvesting,conversion and storage functions could be integrated on a single carbon material to avoid the energy transfer loss among the different materials.Moreover,the assembled Cu/oxygen-enriched carbon battery confirmed the feasibility of the air-oxidation self-charging/electrical discharging mechanism for potential applications.This air-breathing chemical self-charge concept could facilitate the exploration of high-efficiency sustainable air self-charging devices.

Accurate estimation of Li/Ni mixing degree of lithium nickel oxide cathode materials

Li/Ni mixing negatively influences the discharge capacity of lithium nickel oxide and high-nickel ternary cathode materials.However,accurately measuring the Li/Ni mixing degree is difficult due to the preferred orientation of labbased XRD measurements using Bragg–Brentano geometry.Here,we find that employing spherical harmonics in Rietveld refinement to eliminate the preferred orientation can significantly decrease the measurement error of the Li/Ni mixing ratio.The Li/Ni mixing ratio obtained from Rietveld refinement with spherical harmonics shows a strong correlation with discharge capacity,which means the electrochemical capacity of lithium nickel oxide and high-nickel ternary cathode can be estimated by the Li/Ni mixing degree.Our findings provide a simple and accurate method to estimate the Li/Ni mixing degree,which is valuable to the structural analysis and screening of the synthesis conditions of lithium nickel oxide and high-nickel ternary cathode materials.

Cycling performance of layered oxide cathode materials for sodium-ion batteries

Layered oxide is a promising cathode material for sodium-ion batteries because of its high-capacity,high operating voltage,and simple synthesis.Cycling performance is an important criterion for evaluating the application prospects of batteries.However,facing challenges,including phase transitions,ambient stability,side reactions,and irreversible anionic oxygen activity,the cycling performance of layered oxide cathode materials still cannot meet the application requirements.Therefore,this review proposes several strategies to address these challenges.First,bulk doping is introduced from three aspects:cationic single doping,anionic single doping,and multi-ion doping.Second,homogeneous surface coating and concentration gradient modification are reviewed.In addition,methods such as mixed structure design,particle engineering,high-entropy material construction,and integrated modification are proposed.Finally,a summary and outlook provide a new horizon for developing and modifying layered oxide cathode materials.