A core-shell structured LiNiMnO@LiCoO cathode material with superior rate capability and cycling performance.

A core-shell structured LiNiMnO@LiCoO cathode material has been successfully synthesized by the combination of sol-gel and solid state methods. The coating of LiCoO has a significant effect on the electrochemical performance of the spinel LiNiMnO-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 LiCoO. The LiNiMnO@LiCoO with 1% LiCoO presents the optimal rate capability and delivers a relatively high discharge capacity of 122 mA h g at 10C. On the other hand, the surface coating of LiCoO 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 LiNiMnO@LiCoO electrode with 1% LiCoO is much higher than that for the bare LiNiMnO (74.93%) after 100 cycles at elevated temperature. Our study confirms that the core-shell structure construction caused by the coating of LiCoO plays a critical role in the improvement of the electrochemical cycling stability at elevated temperatures and rate capability.