Preparation Of High Voltage（5 V）spinel Li Ni_0.5Mn_1.5O₄ Cathode Material

Lithium-ion batteries are currently one of the most promising battery energy sources.In the composition of lithium-ion batteries,the cathode materials are closely related to the performance of lithium-ion batteries.Among them,LiNi_0.5Mn_1.5O₄cathode materials have attracted much attention due to its advantages of high working voltage,high energy density,abundant resources,and low cost.However,the capacity decay during cycling has always been a major problem in LiNi_0.5Mn_1.5O₄ cathode materials.This article discussed different synthesis processes and metal ion doping in order to improve the electrochemical performance of LiNi_0.5Mn_1.5O₄ cathode materials.In this paper,CH₃COOLi·2H₂O,Ni（CH₃COO）₂·4H₂O,and Mn（CH₃COO）₂·4H₂O were used as metal raw materials,and H₂C₂O₄·2H₂O was used as the precipitant.The LiNi_0.5Mn_1.5O₄ cathode materials was prepared by the freezing-precipitation method,and the effects of calcination temperature and calcination time on the properties of the material were studied.The study found that the material obtained by calcination at800°C for 16 h had a complete crystal form,stable structure,and no Li_xNi_1-xO impurity peak.The initial discharge specific capacity of the material at 0.1 C was 110.4 m Ah·g^-1;The LiNi_0.5Mn_1.5O₄ cathode material was doped and modified,and the effect of different Na⁺content on the material performance was studied.The results showed that when the amount of Na⁺added x was 0.05,the material had high crystallinity,stable structure,and uniform particle size.Compared with the original phase LiNi_0.5Mn_1.5O₄,the initial discharge specific capacity of the material was greatly improved,reaching128.7 m Ah·g^-1 at 0.1 C.After 50 cycles,the capacity decreased by only about 3%.The problem of rapid capacity decay of LiNi_0.5Mn_1.5O₄ cathode material during cycling was improved.The LiNi_0.5Mn_1.5O₄ cathode material was doped with Mo⁶⁺,and the changes in the material properties under different doping levels were discussed.The results showed that when the Mo⁶⁺doping amount was 0.01,there was no impurity peak in the samples,and the particle size was small;Discharged at high rate（10.0 C）,the capacity was 31.0m Ah·g^-1,which was more than 3 times that of undoped.Through the EIS test,the lithium ion diffusion coefficient of the material is calculated,D_Li+was 2.0×10^-14 cm²·s^-1,which was an order of magnitude higher than the undoped 1.0×10^-15 cm²·s^-1.This is because Mo⁶⁺replaced Mn³⁺in the material,reduced the generation of Mn³⁺disproportionation reaction,prevented the reaction of Mn²⁺with electrolyte,promoted the transmission of electrons and lithium ions on the surface of the material,improved the lithium ion diffusion coefficient,and increased the capacity...