Defect Engineering:Can it Mitigate Strong Coulomb Effect of Mg^(2+)in Cathode Materials for Rechargeable Magnesium Batteries?

Rechargeable magnesium batteries(RMBs)have been considered a promising“post lithium-ion battery”system to meet the rapidly increasing demand of the emerging electric vehicle and grid energy storage market.However,the sluggish diffusion kinetics of bivalent Mg^(2+)in the host material,related to the strong Coulomb effect between Mg^(2+)and host anion lattices,hinders their further development toward practical applications.Defect engineering,regarded as an effective strategy to break through the slow migration puzzle,has been validated in various cathode materials for RMBs.In this review,we first thoroughly understand the intrinsic mechanism of Mg^(2+)diffusion in cathode materials,from which the key factors affecting ion diffusion are further presented.Then,the positive effects of purposely introduced defects,including vacancy and doping,and the corresponding strategies for introducing various defects are discussed.The applications of defect engineering in cathode materials for RMBs with advanced electrochemical properties are also summarized.Finally,the existing challenges and future perspectives of defect engineering in cathode materials for the overall high-performance RMBs are described.

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.

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.

Influences of transition metal on structural and electrochemical properties of Li[Ni_xCo_yMn_z]O_2(0.6≤x≤0.8) cathode materials for lithium-ion batteries

Li[NixCoyMn2]O2（0.6≤x≤0.8） cathode materials with a typical hexagonal α-NaFeO2 structure were prepared utilizing a co-precipitation method.It is found that the ratio of peak intensities of（003） to（104） observed from X-ray diffraction（XRD）increases with decreasing the Ni content or increasing the Co content.The scanning electron microscopy（SEM） images reveal that the small primary particles are agglomerated to form the secondary ones.As the Mn content increases,the primary and secondary particles become larger and the resulted particle size for the Li[Ni（0.6）Co（0.2）Mn（0.2）]O2 is uniformly distributed in the range of100-300 nm.Although the initial discharge capacity of the Li/Li[NixCoyMn2]O2 cells reduces with decreasing the Ni content,the cyclic performance and rate capability are improved with higher Mn or Co content.The Li[Ni（0.6）Co（0.2）Mn（0.2）]O2 can deliver excellent cyclability with a capacity retention of 97.1%after 50 cycles.

Grinding sol gel synthesis and electrochemical performance of mesoporous Li_3V_2(PO_4)_3 cathode materials

Li3V2（PO4）3 precursor was obtained with V2Os.nH2O , LiOH＇H2O, NH4H2PO4 and sucrose as starting materials by grinding-sol-gel method, and then the monoclinic-typed Li3Vz（PO4）3 cathode material was prepared by sintering the amorphous Li3V2（PO4）3. The as-sintered samples were investigated by X-ray diffraction （XRD）, transmission electron microscopy （TEM）, N2 adsorption-desorption and electrochemical measurement. It is found that Li3Vz（PO4）3 sintered at 700 ℃ possesses good wormhole-like mesoporous structure with the largest specific surface area of 188 cmZ/g, and the smallest pore size of 9.3 nm. Electrochemical test reveals that the initial discharge capacity of the 700 ℃ sintered sample is 155.9 mA.h/g at the rate of 0.2C, and the capacity retains 154 mA.h/g after 50 cycles, exhibiting a stable discharge capacity at room temperature.

Synthesis and electrochemical properties of LiNi_(0.87)Co_(0.10)Mg_(0.03)O_2 cathode materials

A Co-Mg co-substituted LiNi0.87Co0.10Mg0.03O2 cathode material was prepared by a co-precipitation method. The prepared LiNi0.87Co0.10Mg0.03O2 exhibits excellent electrochemical properties, such as initial discharge capacities of 202.6 mA.h/g and 190.5 mA.h/g at 0.2C and 1C rate, respectively, in operating voltage range of 3.0-4.3 V （versus Li^＋/Li）. The capacity retentions are 96.1% and 93.4% at 0.2C and 1C, respectively, after 50 cycles. Moreover, the cycle performance of the sample was investigated in a 053048-type square Li ion battery. This type of battery can keep 81.7% of initial capacity after 500 charge-discharge cycles at 1C rate, which is close to that of commercial LiCoO2 battery. Therefore, the as-prepared material is capable of such high energy applications as portable product power.

Synthesis of porous nano/micro structured LiFePO_4/C cathode materials for lithium-ion batteries by spray-drying method

In order to enhance electrochemical properties of LiFePO4 （LFP） cathode materials, spherical porous nano/micro structured LFP/C cathode materials were synthesized by spray drying, followed by calcination. The results show that the spherical precursors with the sizes of 0.5-5 μm can be completely converted to LFP/C when the calcination temperature is higher than 500 ℃. The LFP/C microspheres obtained at calcination temperature of 700 ℃ are composed of numerous particles with sizes of -20 nm, and have well-developed interconnected pore structure and large specific surface area of 28.77 mE/g. The specific discharge capacities of the LFP/C obtained at 700 ℃ are 162.43, 154.35 and 144.03 mA.h/g at 0.5C, 1C and 2C, respectively. Meanwhile, the capacity retentions can reach up to 100% after 50 cycles. The improved electrochemical properties of the materials are ascribed to a small Li＋ diffusion resistance and special structure of LFP/C microspheres.

Microwave synthesis of Li_2FeSiO_4 cathode materials for lithium-ion batteries

A novel synthetic method of microwave processing to prepare Li2FeSiO4 cathode materials is adopted. The Li2FeSiO4 cathode material is prepared by mechanical ball-milling and subsequent microwave processing. Olivin-type Li2FeSiO4 sample with uniform and fine particle sizes is successfully and fast synthesized by microwave heating at 700 ℃ in 12 rain. And the obtained Li2FeSiO4 materials show better electrochemical performance and microstructure than those of Li2FeSiO4 sample by the conventional solidstate reaction. ？2009 Yan Bing Cao. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Electrochemical performance of sulfur composite cathode materials for rechargeable lithium batteries

The structure and characteristic of carbon materials have a direct influence on the electrochemical performance of sulfur-carbon composite electrode materials for lithium-sulfur battery. In this paper, sulfur composite has been synthesized by heating a mixture of elemental sulfur and activated carbon, which is characterized as high specific surface area and microporous structure. The composite, contained 70% sulfur, as cathode in a lithium cell based on organic liquid electrolyte was tested at room temperature. It showed two reduction peaks at 2.05 V and 2.35 V, one oxidation peak at 2.4 V during cyclic voltammogram test. The initial discharge specific capacity was 1180.8 mAh g-1 and the utilization of electrochemically active sulfur was about 70.6% assuming a complete reaction to the product of Li2S. The specific capacity still kept as high as 720.4 mAh g^-1 after 60 cycles retaining 61% of the initial discharge capacity.

A closed-loop process for recycling LiNi_xCo_yMn_((1-x-y))O_2 from mixed cathode materials of lithium-ion batteries

With the rapid development of consumer electronics and electric vehicles(EV), a large number of spent lithium-ion batteries(LIBs) have been generated worldwide. Thus, effective recycling technologies to recapture a significant amount of valuable metals contained in spent LIBs are highly desirable to prevent the environmental pollution and resource depletion. In this work, a novel recycling technology to regenerate a LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2 cathode material from spent LIBs with different cathode chemistries has been developed. By dismantling, crushing,leaching and impurity removing, the LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2(selected as an example of LiNi_xCo_yMn_(1-x-y)O_2) powder can be directly prepared from the purified leaching solution via co-precipitation followed by solid-state synthesis. For comparison purposes, a fresh-synthesized sample with the same composition has also been prepared using the commercial raw materials via the same method. X-ray diffraction(XRD), scanning electron microscopy(SEM) and electrochemical measurements have been carried out to characterize these samples. The electrochemical test result suggests that the re-synthesized sample delivers cycle performance and low rate capability which are comparable to those of the freshsynthesized sample. This novel recycling technique can be of great value to the regeneration of a pure and marketable LiNi_xCo_yMn_(1-x-y)O_2 cathode material with low secondary pollution.

Influence of Doping Rare Earth on Performance of Lithium Manganese Oxide Spinels as Cathode Materials for Lithium-Ion Batteries

Some rare earth doping spinel LiMn_(2-x)RE_xO_4 (RE=La, Ce, Nd) cathode materials for lithium ion batteries were synthesized by the solid-state reaction method. The structure characteristics of these produced samples were investigated by XRD, SEM, and particle size distribution analysis. According to the microstructure and charge-discharge testing, the effect of doping rare earth on stabilizing the spinel structure was analyzed. Through a series of doping experiments, it is shown that when the doping content x within the range of 0.01～0.02 the cycle performance of the materials is greatly improved. The discharge capacity of the sample LiMn_(1.98)La_(0.02)O_4, LiMn_(1.98)Ce_(0.02)O_4 and LiMn_(1.98)Nd_(0.02)O_4 remain 119.1, 114.2 and 117.5 mAh·g^(-1) after 50 cycles.

Study on Preparation of Cathode Material of Lithium Iron Phosphate Battery by Self-Craning Thermal Method

The cathode material of carbon-coated lithium iron phosphate(LiFePO4/C)lithium-ion battery was synthesized by a self-winding thermal method.The material was characterized by X-ray diffraction(XRD)and scanning electron microscope(SEM).The electrochemical properties of LiFePO4/C materials were measured by the constant current charge-discharge method and cyclic voltammetry.The results showed that the LiFePO4/C material prepared by the self-propagating heat method has a typical olivine crystal structure,and the product had fine grains and good electrochemical properties.The optimal sintering temperature is 700℃,the sintering time is 24 h,the particle size of the lithium iron phosphate material is about 300 nm,and the maximum discharge capacity is 121 mAh/g at 0.1 C rate.

Overcharge-to-thermal-runaway behavior and safety assessment of commercial lithium-ion cells with different cathode materials:A comparison study

In this paper,overcharge behaviors and thermal runaway(TR)features of large format lithium-ion(Liion)cells with different cathode materials(LiFePO4(LFP),Li[Ni_(1/3)Co_(1/3)Mn_(1/3)]O_(2)(NCM111),Li[Ni_(0.6)Co_(0.2)Mn_(0.2)]O_(2)(NCM622)and Li[Ni_(0.8)Co_(0.1)Mn_(0.1)]O_(2)(NCM811))were investigated.The results showed that,under the same overcharge condition,the TR of LFP Li-ion cell occurred earlier compared with the NCM Li-ion cells,indicating its poor overcharge tolerance and high TR risk.However,when TR occurred,LFP Li-ion cell exhibited lower maximum temperature and mild TR response.All NCM Liion cells caught fire or exploded during TR,while the LFP Li-ion cell only released a large amount of smoke without fire.According to the overcharge behaviors and TR features,a safety assessment score system was proposed to evaluate the safety of the cells.In short,NCM Li-ion cells have better performance in energy density and overcharge tolerance(or low TR risk),while LFP Li-ion cell showed less severe response to overcharging(or less TR hazards).For NCM Li-ion cells,as the ratio of nickel in cathode material increases,the thermal stability of the cathode materials becomes poorer,and the TR hazards increase.Such a comparison study on large format Li-ion cells with different cathode materials can provide deeper insights into the overcharge behaviors and TR features,and provide guidance for engineers to reasonably choose battery materials in automotive applications.

Synthesis and characterization of phosphate-modified LiMn_2O_4 cathode materials for Li-ion battery

LiMn2O4 spinel cathode materials were modified with 2 wt.%Li-M-PO4（M=Co,Ni,Mn） by polyol synthesis method.The phosphate surface-modified LiMn2O4 cathode materials were physically characterized by X-ray diffraction（XRD）,scanning electron microscopy（SEM） and energy dispersive X-ray spectroscopy（EDS）.The charge-discharge test showed that the cycling and rate capacities of LiMn2O4 cathode materials were significantly enhanced by stabilizing the electrode surface with phosphate.

Synthesis and electrochemical properties of Al-doped LiVPO_4F cathode materials for lithium-ion batteries

Al-doped LiVPO4F cathode materials LiAlxV1-xPO4F were prepared by two-step reactions based on a car-bothermal reduction （CTR） process. The properties of the Al-doped LiVPO4F were investigated by X-ray diffraction （XRD）,scanning electron microscopy （SEM）,and electrochemical measurements. XRD studies show that the Al-doped LiVPO4F has the same triclinic structure （space group p-↑1 ） as the undoped LiVPO4F. The SEM images exhibit that the particle size of Al-doped LiVPO4F is smaller than that of the undoped LiVPO4F and that the smallest particle size is only about 1 μm. The Al-doped LiVPO4F was evaluated as a cathode material for secondary lithium batteries,and exhibited an improved reversibility and cycleability,which may be attributed to the addition of Al^3＋ ion by stabilizing the triclinic structure.

Preparation and electrochemical properties of Y-doped Li_3V_2(PO_4)_3 cathode materials for lithium batteries

Y-doped Li3V2（PO4）3 cathode materials were prepared by a carbothermal reduction（CTR） process.The properties of the Y-doped Li3V2（PO4）3 were investigated by X-ray diffraction（XRD） and electrochemical measurements.XRD studies showed that the Y-doped Li3V2（PO4）3 had the same monoclinic structure as the undoped Li3V2（PO4）3.The Y-doped Li3V2（PO4）3 samples were investigated on the Li extraction/insertion performances through charge/discharge, cyclic voltammogram（CV）, and electrochemical impedance spectra（EIS）.The optimal doping content of Y was x=0.03 in Li3V2-xYx（PO4）3 system.The Y-doped Li3V2（PO4）3 samples showed a better cyclic ability.The electrode reaction reversibility was enhanced, and the charge transfer resistance was decreased through the Y-doping.The improved electrochemical perormances of the Y-doped Li3V2（PO4）3 cathode materials were attributed to the addition of Y3＋ ion by stabilizing the monoclinic structure.