Unraveling the multiple effects of Li 2 ZrO 3 coating on the structural and electrochemical performances of LiCoO 2 as high-voltage cathode materials

The poor cycle performance, low rate capability and thermo-instability limit the practical application of LiCoO2 as high-voltage cathode materials for lithium-ion batteries. Herein, we propose an integrated modification strategy which combines the advantages of elements doping, surface modifications and even the high Li+-diffusion of the coating layer. In this study, Li+-conductive Li2ZrO3 has been successfully coated on the surface of LiCoO2 (Li2ZrO3@LCO) through a synchronous lithiation strategy and the multiple effects of Li2ZrO3 coating on the structural and electrochemical performances of LiCoO2 as high-voltage cathode materials for Li-ion batteries have been discovered. In compared to bare LiCoO2, the cycle performance, polarization, rate capability and thermo-stability of Li2ZrO3@LZO have been significantly improved. Li2ZrO3@LCO shows a much higher capacity retention than bare LiCoO2 both at 25 °C (85.2% vs.32.6% at 5 C, 1 C = 200 mA g−1) and 55 °C (71.3% vs.13.9% at 5 C), and the specific capacity at 10 C has also been largely increased from 33.9 mAh g−1 to 103.4 mAh g−1. The enhancement of the electrochemical performances can be largely attributed to the multiple effects of Li+-conductive Li2ZrO3 coating: the alleviation of side reactions and transition metal dissolution, the enhancement of Li-ion diffusion coefficient and electronic conductivity, Zr4+ migration and doping, the resulting interplanar spacing expansion and the improvement of the layered structure stability.