A core–shell structured LiNi0.5Mn1.5O4@LiCoO2 cathode material with superior rate capability and cycling performance

Abstract

A core–shell structured LiNi_0.5Mn_1.5O₄@LiCoO₂ cathode material has been successfully synthesized by the combination of sol–gel and solid state methods. The coating of LiCoO₂ has a significant effect on the electrochemical performance of the spinel LiNi_0.5Mn_1.5O₄-based cathode material, especially the cycling stability at high temperature and rate capability. After modification, the ionic conductivity of the material is greatly improved due to the high ion conductivity of LiCoO₂. The LiNi_0.5Mn_1.5O₄@LiCoO₂ with 1% LiCoO₂ presents the optimal rate capability and delivers a relatively high discharge capacity of 122 mA h g⁻¹ at 10C. On the other hand, the surface coating of LiCoO₂ can effectively facilitate Li⁺ interfacial diffusion, and alleviate the side reactions between the active material and the electrolyte; as a result, the capacity retention of 96.17% for the LiNi_0.5Mn_1.5O₄@LiCoO₂ electrode with 1% LiCoO₂ is much higher than that for the bare LiNi_0.5Mn_1.5O₄ (74.93%) after 100 cycles at elevated temperature. Our study confirms that the core–shell structure construction caused by the coating of LiCoO₂ plays a critical role in the improvement of the electrochemical cycling stability at elevated temperatures and rate capability.