Preparation And Modification Of Nickel-rich Cathode Material LiNi_0.9Co_0.05Mn_0.05O₂ For Lithium-ion Batteries

At present,lithium-ion battery is widely used because of its high energy density.Lithium-ion battery is mainly composed of cathode material,electrolyte,membrane and anode material.Among them,the cathode material plays a great decisive role in the battery performance,so it is of great significance to study the cathode material.The ternary nickel-cobalt-manganese material is one of the important cathode materials,which has been widely studied because of its environment-friendly,high energy density and good thermal stability.The nickel-rich LiNi_0.9Co_0.05Mn_0.05O₂（NCM9055）ternary has a higher energy density than other low-nickel ternary materials,and it is considered to be one of the positive electrode materials for lithium ion battery with great potential.However,with the increase of Ni content,the cyclic and discharging properties of the material decrease.Therefore,it is of great significance to study the nickel-rich NCM9055 material.In this work,in order to improve the NCM9055 material performance,we studied the effects of La doping and Li_1.3Al_0.3Ti_1.7（PO₄）₃（LATP）coating modification on NCM9055.The specific research contents and results are as follows:1.The high nickel ternary cathode material LiNi_0.9Co_0.05Mn_0.05O₂（NCM9055）doped with rare earth element La was prepared by high temperature solid phase synthesis method.The phase structure and morphology of the materials were studied by XRD and SEM.The analysis of XRD results show that the crystal structure of NCM9055 is not changed by La doping.The effect of La doping on the electrochemical performance of the button battery made of the La-doped cathode was studied.When the doping amount is 0.1wt%,the initial specific discharging capacity is 180.1m Ah·g^-1,and the capacity retention rate reaches 93.34%for 100 cycles.The results show that La-doping leads to the reduction of the charge transfer impedance of NCM9055 surface film,the increase of the Li⁺diffusion coefficient,the stabilization of the structure of NCM9055.Therefore,the specific discharge capacity and cycle performance of NCM9055 have been improved.2.NCM9055 was coated with solid electrolyte LATP by using sol-gel method,and the structure and electrochemical properties of the coated material were tested and analyzed.The results show that the material structure of NCM9055 is not changed by LATP coating.When the coating amount is 1 wt%,the capacity retention rate of 100 cycles is 74.74%.When the coating amount is 0.5 wt%,the attenuation of the middle plateau voltage is the slowest,and the attenuation rate of 100 charge-discharge cycles is only 2.39%.The results show that the LATP coating of NCM9055can suppress the side reaction between the cathode material and the electrolyte,reduce the damage to the cathode material caused by HF generated in the cycle process,stabilize the structure of the cathode material and reduce the Li⁺migration impedance in the material,so as to improve the recycling performance of the material and extend the lifetime of lithium battery.In conclusion,this study provides valuable experimental data and research basis for improving the properties of NCM9055 cathode materials by La-doping and LATP coating method.