Improving Electrochemical Performance and Structural Stability of LiNi0.6Co0.2Mn0.2O2 via Nanoscale Coating with LiTiO2

LiNi0.6Co0.2Mn0.2O2 (NCM622) has been coated with rock-salt-type LiTiO2 by ball milling and tempering to improve its electrochemical properties and structural stability. The rock-salt-type LiTiO2 was synthesized by a solvothermal method using tetrabutyl titanate as raw material. The optimal molar ratio of LiTiO2 to NCM was identified as 0.5 mol.%, and the thickness of the cladding layer was observed to be approximately 5 nm to 14 nm by high-resolution transmission electron microscopy. Compared with pristine NCM, modified samples exhibited higher capacity of 20 mAh g(-1) after 200 cycles under 1C at 2.7 V to 4.3 V, corresponding to capacity retention of 88.03%, while that of pristine NCM was only 80.01%. The best LiTiO2-coated sample exhibited a superior rate capability at 5C (152.90 mAh g(-1)) compared with the BNCM sample (113.75 mAh g(-1)). The improvement in these properties occurs because the coating layer protects the NCM material from direct contact with the electrolyte, thereby reducing undesirable side reactions, which is helpful to extend the lifetime of lithium-ion batteries. These new discoveries are beneficial for the development of nickel-based cathode materials for lithium-ion batteries with stabilized structure.