Surface structure regulation toward anionic redox activation of Li1.20Mn0.533Ni0.133Co0.133O2 cathodes with high initial coulombic efficiency

Abstract

Li-rich layered oxides cathodes (LLOs) as the promising next-generation cathode materials can provide ultrahigh capacity and energy density due to their distinctive anionic redox chemistry. Unfortunately, severe interfacial side reactions, surface structural degradation and sluggish Li+ kinetics have resulted in low initial coulombic efficiency (ICE), capacity decay and poor rate performance, restricting their practical applications for high-energy–density lithium-ion batteries. Herein, Surface structure regulation strategy used as surface modified agent is proposed to activate the anionic redox chemistry via ammonium tungstate treatment. Experimental results showcase that dual coating layer spinel-like structure LiMn2O4 and Li2WO4 have been successfully constructed on the surface of LLOs. The surface spinel-like structure providing 3 D Li+ diffusion channels together with fast-ion conductive layer decrease the interfacial Li+ diffusion barrier and boost the fasting Li+ kinetics. In addition, the in-situ reconstruction layer can further alleviate the interfacial side reactions and reinforce the surface structural stability. As a result, the ICE of modified LLOs can be precisely increased from 74.71 % to 107.42 % with the adjustment of ammonium tungstate usage. Moreover, it delivers a high reversible capacity of 279.5 mAh/g at 0.1 C, as well as excellent rate capability with capacity of 147.2 mAh/g at 5 C. This work provides a significant reference for designing high-energy–density LLOs via surface structure regulation strategy.