Controllable Synthesis And Electrochemical Performance Study Of LiNi_0.5Mn_1.5O₄ Cathode Materials For Lithium Batteries

LiNi_0.5Mn_1.5O₄ material is a promising cathode material for lithium-ion batteries due to its high operating voltage and high energy density.However,LiNi_0.5Mn_1.5O₄ material has the problem of poor cycle stability and rate performance,which limits the commercial application of this material.In order to improve the cycle performance and high rate performance of LiNi_0.5Mn_1.5O₄ material,this paper prepared sphere-rod hybrid morphological LiNi_0.5Mn_1.5O₄ material by hydrothermal-high temperature sintering method,and coating and doping research were conducted to improve the material's high rate performance to meet the needs of high power density lithium-ion batteries.In this paper,a sphere-rod hybrid morphology LiNi_0.5Mn_1.5O₄ material was prepared by hydrothermal-high temperature sintering method.The phase structure and morphology of the material were characterized by X-ray diffraction,Raman spectroscopy,scanning electron microscopy and other test methods,and the electrochemical properties of the materials under different preparation conditions were tested.The results show that the LiNi_0.5Mn_1.5O₄ material sintered at 750°C for10 h with basic nickel carbonate as nickel source has good performance.The material has a sphere-rod hybrid morphology and high crystallinity;the discharge specific capacity reached 119 mAh/g at 0.1 C,and the cycle performance was good that the capacity retention is 94%after 100 cycles.Graphene Oxide?GO?and Reduced Graphene Oxide?RGO?coated GO/LiNi_0.5Mn_1.5O₄ and RGO/LiNi_0.5Mn_1.5O₄ composites were prepared by electrostatic self-assembly method.The structure and electrochemical properties of the composites were tested and characterized.The results show that the performance of RGO/LiNi_0.5Mn_1.5O₄ composite is better.The material was Fd3m space group structure.Compared with LiNi_0.5Mn_1.5O₄ material,the material has lower impedance and higher specific discharge capacity.For example,after 1000 cycles at a high rate of 10 C,the specific discharge capacity was 108.6 mAh/g,and the cycle stability was good.Li_1+x+x Ni_0.5Mn_1.5-x.5-x Al_xO₄ and LiNi_0.5Mn_1.5-x.5-x Sn_xO₄ composites were prepared by doping Al element and Sn element into LiNi_0.5Mn_1.5O₄ material.The structure and electrochemical properties of the composites were tested and characterized.The results show that all the Al-doped composites were Fd3m space group structure and the impedance was small,but the discharge specific capacity of the material was lower than that of the undoped LiNi_0.5Mn_1.5O₄ material.The prepared composite material has the best performance with the Sn doping amount x is 0.01.This material was mainly P4332 space group structure,which was sphere-rod hybrid morphology and has high crystallinity.The material has good high rate performance and excellent cycle stability.After 1000 cycles at 10 C,the discharge specific capacity was 102.7 mAh/g and the capacity retention was 97.8%.