Rate dependent structural transition and cycling stability of a lithium-rich layered oxide material

Abstract

Lithium-rich layered oxide materials, xLi₂MnO₃·(1 − x)LiMO₂ (M = Mn, Fe, Co, Ni, etc.), are a promising candidate for use as cathode materials in the batteries of electric vehicles (EVs). This is due to their high energy density (∼900 W h kg⁻¹), which is larger than those of the currently used commercial cathode materials. Moreover, EV technologies require lithium ion batteries with a high rate performance to achieve short charging times. The high rate property largely depends on the electrochemical properties of the electrodes in these batteries. However, the correlation between the cycling rate, structural stability and electrochemical properties of cathode materials is not clearly understood. In this work, the influence of cycling rate on structural transition behaviors and cycling stability of a 0.5Li₂MnO₃·0.5LiCoO₂ composite-based material was investigated. The experimental results reveal that cycling rates significantly affect the activation of the Li₂MnO₃ component. A high cycling rate retards Li₂MnO₃ activation, leading to a smaller spinel phase transition and a higher cycling stability.