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

Abstract

A core-shell structured LiNi0.5Mn1.5O4@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 LiNi0.5Mn1.5O4-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 LiNi0.5Mn1.5O4@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 LiNi0.5Mn1.5O4@LiCoO2 electrode with 1% LiCoO2 is much higher than that for the bare LiNi0.5Mn1.5O4 (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.