In situ surface modification with solid-state reaction enabling long cycle performance of 4.5 V LiCoO2

Surface modification is a highly effective strategy to suppress side reactions between electrode materials and electrolytes. The preparation of coated electrode materials generally involves two steps: the synthesis of electrode materials and subsequent surface coating, which is a long and costly process. Here, we report a novel solid-state reaction method to prepare Li 2 ZrO 3 -coated LiCoO 2 in a single step. By controlling the cooling rate, the solid solubility of Zr in LiCoO 2 decreases, resulting in the precipitation of Zr 4+ on the surface and the formation of a Li 2 ZrO 3 coating layer. X-ray photoelectron spectroscopy, combined with a focused ion beam and high-resolution transmission electron microscopy, confirms the uniform Li 2 ZrO 3 coating on the surface of LiCoO 2 . Electrochemical performance testing shows that Li 2 ZrO 3 -coated LiCoO 2 exhibits enhanced cycle stability, even when charged to 4.5 V. After cycling at 1C for 200 cycles, Li 2 ZrO 3 -coated LiCoO 2 maintains a capacity of about 180 mAh  g −1 , which is 94 % of the initial 193 mAh  g −1 .