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.

NiCl_(2)作为添加剂对热电池NiF_(2)正极材料倍率性能的影响

与硫化物相比,氟化物作为热电池正极材料,具有较高的理论放电电压和放电比容量。其中,NiF_(2)正极材料的理论放电电压为2.96 V,理论放电比容量为554 mAh/g。然而,由于NiF_(2)本征的离子电导率较低,导致其作为热电池正极材料时倍率性能较差,在1 A/cm^(2)电流密度下出现明显的容量衰减现象;另外,NiF_(2)的实际放电电压也远低于理论值。NiCl2正极材料的倍率性能较为优异,将其作为添加剂与NiF_(2)正极材料进行复合,可以显著改善NiF_(2)正极材料在大电流密度下的极化现象,延长热电池的放电时间。

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.

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.

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.

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.

Hydrothermal synthesis of spindle-like Li_2FeSiO_4-C composite as cathode materials for lithium-ion batteries

In this paper,we report on the preparation of Li2FeSiO4,sintered Li2FeSiO4,and Li2FeSiO4-C composite with spindle-like morphologies and their application as cathode materials of lithium-ion batteries.Spindle-like Li2FeSi04 was synthesized by a facile hydrothermal method with（NH4）2Fe（SO4）2 as the iron source.The spindle-like Li2FeSiO4 was sintered at 600 ℃ for 6 h in Ar atmosphere.Li2FeSiO4-C composite was obtained by the hydrothermal treatment of spindle-like Li2FeSiO4 in glucose solution at 190 ℃ for 3 h.Electrochemical measurements show that after carbon coating,the electrode performances such as discharge capacity and high-rate capability are greatly enhanced.In particular.Li2FeSiO4-C with carbon content of 7.21 wt%delivers the discharge capacities of 160.9 mAh·g-1 at room temperature and 213 mAh·g-1 at45℃（0.1 C）,revealing the potential application in lithium-ion batteries.

Enhancing Direct Electrochemical CO_(2)Electrolysis by Introducing A-Site Deficiency for the Dual-Phase Pr(Ca)Fe(Ni)O_(3-δ)Cathode

High-temperature CO_(2)electrolysis via solid oxide electrolysis cells(CO_(2)-SOECs)has drawn special attention due to the high energy convention efficiency,fast electrode kinetics,and great potential in carbon cycling.However,the development of cathode materials with high catalytic activity and chemical stability for pure CO_(2)electrolysis is still a great challenge.In this work,A-site cation deficient dual-phase material,namely(Pr_(0.4)Ca_(0.6))_(x)Fe_(0.8)Ni_(0.2)O_(3-δ)(PCFN,x=1,0.95,and 0.9),has been designed as the fuel electrode for a pure CO_(2)-SOEC,which presents superior electrochemical performance.Among all these compositions,(Pr_(0.4)Ca_(0.6))_(0.95)Fe_(0.8)Ni_(0.2)O_(3-δ)(PCFN95)exhibited the lowest polarization resistance of 0.458Ωcm^(2)at open-circuit voltage and 800℃.The application of PCFN95 as the cathode in a single cell yields an impressive electrolysis current density of 1.76 A cm^(-2)at 1.5 V and 800℃,which is 76%higher than that of single cells with stoichiometric Pr_(0.4)Ca_(0.6)Fe_(0.8)Ni_(0.2)O_(3-δ)(PCFN100)cathode.The effects of A-site deficiency on materials'phase structure and physicochemical properties are also systematically investigated.Such an enhancement in electrochemical performance is attributed to the promotion of effective CO_(2)adsorption,as well as the improved electrode kinetics resulting from the A-site deficiency.

Electrochemical performance of Al-substituted Li_3V_2(PO_4)_3 cathode materials synthesized by sol-gel method

The effect of Al-substitution on the electrochemical performances of Li3V2(PO4)3 cathode materials was studied.Samples with stoichiometric proportion of Li3AlxV2-x(PO4)3(x=0,0.05,0.10)were prepared by adding Al(NO3)3 in the raw materials of Li3V2(PO4)3.The XRD analysis shows that the Al-substituted Li3V2(PO4)3 has the same monoclinic structure as the un-substituted Li3V2(PO4)3.The SEM images show that Al-substituted Li3V2(PO4)3 has regular and uniform particles.The electrochemical measurements show that Al-substitution can improve the rate capability of cathode materials.The Li3Al0.05V1.95(PO4)3 sample shows the best high-rate performance.The discharge capacity at 1C rate is 119 mA·h/g with 30th capacity retention rate about 92.97%.The electrode reaction reversibility and electronic conductivity are enhanced,and the charge transfer resistance decreases through Al-substitution.The improved electrochemical performances of Al-substituted Li3V2(PO4)3 cathode materials offer some favorable properties for their commercial application.

Synthesis and Characterization of LiCo_xMn_(2-x)O_4 Cathode Materials

LiCoxMn2.04 cathode materials for lithium ion batteries were synthesized by mechanical activation-solid state reaction at 750 ℃ for 24 h in air atmosphere, and their crystal structure, morphology, element composition and electrochemical performance were characterized with XRD, SEM, ICP-AES and charge-discharge test. The experimental results show that all samples have a single spinel structure, well formed crystal shape and uniformly particle size distribution. The lattice parameters of LiCo Mn2-xO4 decrease and the average oxidation states of manganese ions increase with an increase in Co content. Compared with pure LiMn2O4, the LiCo Mn2xO4 （x=0.03-0.12） samples show a lower special capacity, but their cycling life are improved. The capacity loss of LiCo009Mn191O4 and LiCo0.1Mn1.88O4 is only 1.85% and 0.95%, respectively, after the 20th cycle. The improvement of the cycle performance is attributed to the substitution of Co at the Mn sites in the spinel structure, which suppresses the Jahn-Teller distortion and improves the structural stability.

Optimum Preparation Conditions of LiNi_(0.8)Co_(0.2)O_2 and LiNi_(0.95)Ce_(0.05)O_2 as Lithium-Ion Battery Cathode Materials

The preparation of LiNi_(0.8)Co_(0.2)O_2 was discussed by the multiply sintering method for solid reaction, in which the sintered material was smashed, ground and pelletted between two successive sintering steps. The optimum technological condition was obtained through orthogonal experiments by L_9(3~4) and DTA analysis. The result indicates that the factors of effecting the electrochemical properties of synthesized LiNi_(0.8)Co_(0.2)O_2 are molar ratio of Li/Ni/Co, oxygen pressure, homothermal time, the final sintering temperature in turn according to its importance. The oxygen pressure is reviewed independently and the technological condition is further optimized. With the same method, rare earth element Ce was studied as substitute element of Co and the cathode material of LiNi_(0.95)Ce_(0.05)O_2 with excellent electrochemical properties was prepared. The electrochemical testing results of LiNi_(0.8)Co_(0.2)O_2 and LiNi_(0.95)Ce_(0.05)O_2 experimental batteries show that discharge capacities of them reach 165 and 148 mAh·g^(-1) respectively and the persistence is more than 9 h at 3.7 V.

Direct Synthesis of Al_2O_3-modified Li(Ni_(0.5)Co_(0.2)Mn_(0.3))O_2 Cathode Materials for Lithium Ion Batteries

To improve the cyclic stability at high temperature and thermal stability, the spherical Al2O3-modified Li（Ni0.5Co0.2Mn0.3）O2 was synthesized by a modified co-precipitation method, and the physical and electrochemical properties were studied. The TEM images showed that Li（Ni0.5Co0.2Mn0.3）O2 was modified successfully with nano-Al2O3. The discharge capacity retention of Al2O3-modified Li（Ni0.5Co0.2Mn0.3）O2 maintained about 99% after 200 cycles at high temperature（55 ℃）, while that of the bare one was only 86%. Also, unlike bare Li（Ni0.5Co0.2Mn0.3）O2, the Al2O3-modified material cathode exhibited good thermal stability.

Two-Dimensional Graphitic Carbon-Nitride(g-C_(3)N_(4))-Coated LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2) Cathodes for High-Energy-Density and Long-Life Lithium Batteries

High-capacity nickel-rich layered oxides are promising cathode materials for high-energy-density lithium batteries.However,the poor structural stability and severe side reactions at the electrode/electrolyte interface result in unsatisfactory cycle performance.Herein,the thin layer of two-dimensional(2D)graphitic carbon-nitride(g-C_(3)N_(4))is uniformly coated on the LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(denoted as NCM811@CN)using a facile chemical vaporization-assisted synthesis method.As an ideal protective layer,the g-C_(3)N_(4)layer effectively avoids direct contact between the NCM811 cathode and the electrolyte,preventing harmful side reactions and inhibiting secondary crystal cracking.Moreover,the unique nanopore structure and abundant nitrogen vacancy edges in g-C_(3)N_(4)facilitate the adsorption and diffusion of lithium ions,which enhances the lithium deintercalation/intercalation kinetics of the NCM811 cathode.As a result,the NCM811@CN-3wt%cathode exhibits 161.3 mAh g^(−1)and capacity retention of 84.6%at 0.5 C and 55°C after 400 cycles and 95.7 mAh g^(−1)at 10 C,which is greatly superior to the uncoated NCM811(i.e.129.3 mAh g^(−1)and capacity retention of 67.4%at 0.5 C and 55°C after 220 cycles and 28.8 mAh g^(−1)at 10 C).The improved cycle performance of the NCM811@CN-3wt%cathode is also applicable to solid–liquid-hybrid cells composed of PVDF:LLZTO electrolyte membranes,which show 163.8 mAh g^(−1)and the capacity retention of 88.1%at 0.1 C and 30°C after 200 cycles and 95.3 mAh g^(−1)at 1 C.

Synthesis and Electrochemical Properties of Cr-doped Li_3V_2(PO_4)_3 Cathode Materials for Lithium-ion Batteries

Cr-doped Li3V2（PO4）3 cathode materials Li3V2-xCr（PO4）3 were prepared by a carbothermal reduction（CTR） process. The properties of the Cr-doped Li3V2（PO4）3 were investigated by X-ray diffraction （XRD）, scanning electron microscopic （SEM）, and electrochemical measurements Results show that the Cr-doped Li3V2（PO4）3 has the same monoclinic structure as the undoped Li3V2（PO4）3, and the particle size of Cr-doped Li3V2（PO4）3 is smaller than that of the undoped Li3V2（PO4）3 and the smallest particle size is only about 1 1μm. The Cr-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 Cr was that x=0.04 in the Li3V2-xCrx（PO4）3 samples to achieve high discharge capacity and good cyclic stability. The electrode reaction reversibility was enhanced, and the charge transfer resistance was decreased through the Cr-doping. The improved electrochemical performances of the Cr-doped Li3V2（PO4）3 cathode materials are attributed to the addition of Cr^3＋ ion by stabilizing the monoclinic structure.

Effect of lithium content on electrochemical property of Li_(1+x)(Mn_(0.6)Ni_(0.2)Co_(0.2))_(1-x)O_2(0≤x≤0.3) composite cathode materials for rechargeable lithium-ion batteries

In order to confirm the optimal Li content of Li-rich Mn-based cathode materials(a fixed mole ratio of Mn to Ni to Co is0.6:0.2:0.2),Li1+x(Mn0.6Ni0.2Co0.2)1-xO2(x=0,0.1,0.2,0.3)composites were obtained,which had a typical layered structure with R3m and C2/m space group observed from X-ray powder diffraction(XRD).Electron microscopy micrograph(SEM)reveals that the particle sizes in the range of0.4-1.1μm increase with an increase of x value.Li1.2(Mn0.6Ni0.2Co0.2)0.8O2sample delivers a larger initial discharge capacity of275.7mA·h/g at the current density of20mA/g in the potential range of2.0-4.8V,while Li1.1(Mn0.6Ni0.2Co0.2)0.9O2shows a better cycle performance with a capacity retention of93.8%at0.2C after50cycles,showing better reaction kinetics of lithium ion insertion and extraction.

Synthesis and Characterization of LiNi_(0.85)Co_(0.15-x)Al_xO_2 as Cathode Materials for Lithium-ion Batteries

LiNi0.85CO0.15-xAlxO2 samples （x=0.025, 0.05 and 0.10） were prepared by solid state reaction at 725℃ for 24 h from LiOH-H2O, Ni2O3, Co2O3 and Al（OH）3 under oxygen flow. Layered LiNiO2 simultaneously doped by Co-Al has been tried to improve the cathode performance. The results showed that substitution of optimum amount Al and Co for the Ni in LiNiO2 definitely had some beneficial effect on increasing the capacity and cycling behavior. When increasing x in LiNio.85CO0.15-xAlxO2, the initial discharge capacity decreased and its cyclability increased. Compromising high specific capacity and good cyclability, the optimum x in LiNi0.85Co0.15-xAlxO2 was x=0.05. As a consequence, LiNi0.85Co0.15-xAlxO2 had the first discharge capacity of 186.2 mAh/g and a capacity of 180.1 mAh/g after 10 cycles. Differential capacity vs voltage curves indicated that the co-doped LiNiO2 showed suppression of the phase transitions as compared with LiNiO2.

Orthorhombic 3-LiV2O5 as Cathode Materials in Lithium Ion Batteries： Synthesis and Property

The rod-like and bundle-like v-LiV205 were synthesized via a simple solvothermal process- ing. The rod-like 7-LiV205 with diameter of 500-800 nm and the bundle-like architectures are composed of several of order-attached rods with diameter of 100-600 nm. ＂y-LiV205 were synthesized using LiOH.H20, NH4VO3, HNO3, C2H5OH without and with PVP as raw materials. At the same time, the actual formation mechanism of Y-LiV205 was also investigated. As the cathode materials for lithium ion batteries, the bundle-like Y-LiV205 prepared with PVP delivers a better electrochemical performance, which has an initial dis charge capacity of 269.3 mAh/g at a current density of 30 mA/g and is still able to achieve 228 mAh/g after the 20th cycle. The good electrochemical properties of the as-synthesized Y-LiV205 coupled with the simple, relatively low temperature, and low cost of the prepara tion method may make this material a promising candidate as a cathode material for lithium ion batteries.

Electrochemical Properties of Spinel LiMn_2O_(4-δ)F_δ for Cathode Materials of Secondary Lithium-ion Battery

The spinel LiMn_2O_(4-δ)Fδ cathode materials were synthesized by solid-state reaction, With calculated amounts of LiOH·H_2O, MnO_2(EMD). LiF. The results of electrochemical test demonstrated that these new materials exhibited excellent electrochemical properties.Its initial capacity reached -115 mAb·g^(-1) and reversible efficiency is about 100%. After 60 cycles. its capacity was still around 110 mAh· g^(-1), with nearly 100% reversible efficiency,

Summary of the Performance of V_(2)O_(5)Materials as Lithium Battery Cathode

Lithium battery has recently gained more and more attention worldwide.It has wide usage that range from toys to electric cars.Choosing a suitable material that best fits the overall performance as electrode for the battery is very essential.For cathode material,apart from the traditional and widely-used LiCoCO_(2),LiFePO_(4)and so on,there are innovations that include the use of V_(2)O_(5).Researches have been done focusing on how to further improve the performance for V_(2)O_(5)cathode in terms of different structure,forms or combination with other chemical molecules.This research paper will make a summary of the materials derived from traditional V_(2)O_(5)as well as their performances.