Study On The Coating Modification Of LiNi_0.6Co_0.2Mn_0.2O₂ And LiNi_0.8Co_0.1Mn_0.1O₂ Cathode Materials For Lithium Ion Batteries

Ni-Co-Mn ternary layered materials are considered to be one of the most promising cathode materials in the field of power batteries due to their high energy density,low cost and environmental protection.However,due to the poor thermal stability,high cation mixing degree,unstable surface structure and excessively high surface alkali content of Ni--Co-Mn ternary laminated materials,such problems as poor cycling performance and low safety performance seriously limit their commercial application in the field of power batteries.A large number of studies have shown that many problems of Ni-Co-Mn ternary layered materials originate from the material/electrolyte interface,or the stability of the interface is destroyed in some way.In order to solve the above problems,LiNi_0.6Co_0.2Mn_0.2O2（NCM622）and LiNi_0.8Co_0.1Mn_0.1O₂（NCM811）ternary layered materials were modified by coating materials of Li₄SiO₄ fast ion conductor.The results are as follows:（1）In this study,Li₄SiO₄ fast ion conductor material was successfully coated on the surface of LiNi_0.6Co_0.2Mn_0.2O2（NCM622）material by hydrolyzation-high temperature solid phase method.XRD,SEM,TEM and other physical characterization showed that the intrinsic structure of the coated material did not change.The electrochemical data showed that the cycle capacity retention rate of LiNi_0.6Co_0.2Mn_0.2O2 at 1C current density increased from 61.89%to84.78%,and the cycle stability was significantly improved.The capacity retention rate is increased by 7%at 5C magnification,and the high magnification performance is improved to a certain extent.（2）In this study,Li₄SiO₄fast ionic material was coated on the surface of LiNi_0.8Co_0.1Mn_0.1O₂cathode material by hydrolyzation-high temperature solid phase method.The physical characterization results of SEM,TEM and XRD confirmed that the coating had no obvious effect on the structure and morphology of the material.Electrochemical test results show that the cyclic stability and structural stability are improved obviously after modification.（3）After modification by Li₄SiO₄ coating,the electrochemical properties of the two ternary materials are improved.The coating material can inhibit the corrosion of cathode materials LiNi_0.6Co_0.2Mn_0.2O₂（NCM622）and LiNi_0.8Co_0.1Mn_0.1O₂（NCM811）by the electrolyte.It avoids the dissolution of transition metal ions,reduces the occurrence of side reactions and the exposure of the material in the air,and improves the structural stability of the material.