Study On Preparation Of Cathode Material Li LiNi_0.8Co_0.15Al_0.05O₂ For High Performance Of Lithium Ion Batteries

The ternary material LiNi_0.8Co_0.15Al_0.05O₂ is a kind of cathode material with high capacity(up to 180 m Ah g^-1),low cost,good compatibility with electrolyte and wide market prospect.However,due to serious mixing of cations and poor cycling stability,the development and application of it are severely restricted.This paper improved its electrochemical properties through the preparation method.Similar rose-shaped spherical structure precursor was prepared by hydrothermal method,then the LiNi_0.8Co_0.15Al_0.05O₂ was obtained after calcining with lithium and aluminum hydroxide.This method studied on the influence of hydrothermal time on the electrochemical properties.The results show that wh en the hydrothermal times 12 h,the initial discharge capacity and rate performance of the material are the highest,but the capacity decline is the most serious.The specific discharge capacity at current density of 1 C is 208.33 m Ah g^-1,and the capacity retention is 52.40%after 100 cycles.The discharge capacity is 136.71 m Ah g^-1at 10 C.The poor cycle performance can be attributed to the value of diffraction peak I?003?/I?104?that less than 1.2.It means a large degree of mixing of the cation and hinder the embedding of lithium ions,leading to its capacity decay seriously.In order to solve the above problems,PVP was used to assist hy drothermal reaction that added into the hydrothermal reaction to obtain a precursor.The experimental results show that adding PVP can effectively inhibit the cationic mixing and improve the cycling performance.Among them,the sample with t he molecular weight of 58000 has the best cycling performance which the capacity retention is 96.42%after cycling 100 cycles at 1 C?52.40%for the sample without PVP?.The columnar Li Ni0.8Co0.15Al0.05O2 was successfully prepared by oxalic acid template method.And the influence of different synthesis process on its electrochemical performance was studied.The study find that synthesizing LiNi_0.8Co_0.15Al_0.05O₂O₄ samples firstly has the best performance.The specific discharge capacities at 2 C rate is 139.73 m Ah g^-1,and the capacity retention is84.89%after 100 cycles.The specific discharge capacity at 10 C rate is 74.05 m Ah g^-1.In addition,based on the synthesis of LiNi_0.8Co_0.15Al_0.05C₂O₄ precursors,the influence of different solvents on their electrochemical properties was studied.The experimental results show that the samples prepared with water has the best electrochemical performance.The specific discharge capacities at 1C and 2C rates are 183.47 m Ah g^-1and 150.64 m Ah g^-1,respectively,which increase by 20 mAh g^-1and 10 m Ah g^-1compared with the samples that prepared with alcohol.After 100 cycles,the capacity retention rates are 96.72%and 97.33%,which up 8.38%and12.44%,respectively.Based on the preparation method,the effects of reaction time,additives,synthesis process and solvent type on the crystal structure,morphology and electrochemical properties of the material were studied in this paper.High cycle performance is obtained and it is expected that this material will be further developed in the market application.