Halogen-doping in LiCoO2 cathode materials for Li-ion batteries: insights from ab initio calculations

Abstract

Lithium cobalt oxide is one of the most commonly used cathode materials for Li ion batteries. However, the electrochemical cycling performance is limited by the structural instability of LiCoO₂ during the charging/discharging processes. Using density functional theory calculations, we investigate the effects of halogen doping on the structural stability, electronic state, electrode potential, and Li diffusion behavior of LiCoO₂ systems. Fluorine, chlorine, and bromine substitutions of oxygen species suppress the lattice changes upon Li deintercalation, enhance the structural stability, electronic conductivity and Li mobility, as well as retain the electrode potential of the undoped system. Thus, halogen doping opens an effective route to improve the structural and electrochemical properties of LiCoO₂ cathodes for Li ion batteries with better rate capacities and longer lifetimes.