Understanding the role of TiO2 coating for stabilizing 4.6V high-voltage LiCoO2 cathode materials

Abstract

TiO2 surface coating is considered to be an effective strategy for improving the cycling performance of commercially available high voltage LiCoO2 (HV-LCO) batteries. However, the mechanism underlying the TiO2 coating remains ambiguous due to the synergy of solid-state coating and annealing processes. In this work, the effects of TiO2 were systematically studied for 4.6 V HV-LCO batteries. The results showed that the coated TiO2 can be transformed into LiTiO2-rich layer, which can reduce surface residual lithium (SRL), lower the formation of Co3O4 and LiF-rich cathode electrolyte interphase (CEI) layer. Moreover, the annealed sample delivered improved surface texture, reduced specific surface area, and lower SRL, which was beneficial to improve the rate capability and cyclic performance. However, the LCO after annealing and coating exhibited weak static oxygen stability at high voltage due to the change in bulk Li/Co stoichiometry, leading to higher gas production. This work provides new insights into the effects of metal oxide coating and sheds light on the commercial process for HV-LCO.