A bifunctional strategy enabling 4.55 V LiCoO2 with improved electrochemical performance

Abstract

LiCoO2 (LCO) has been functionally modified with electronic conductor of Al doped ZnO (AZO) and ionic conductor of Li3PO4 (LPO). The physicochemical characterization results demonstrated that the hexagonal structured AZO small crystal particles epitaxial growth formed island-like structures on the surface of LCO particles and LPO filled on the surface of remaining exposed LCO particles. Due to the unique composite coating layer with excellent electronic conductivity and Li ion conductivity, the AZO and LPO coated LCO exhibits outstanding rate capability and cycle stability in the voltage range of 2.75–4.55 V. The modified LCO delivered a specific capacity 206 mA h g−1 at 0.5C rate (100 mA g−1), and the capacity retention was 91.7 % after 50 cycles, which was a remarkable improvement comparing with uncoated LCO (34.8 %). Moreover, it exhibited an outstanding rate property, maintaining a discharge capacity of 161.4 mA h g−1 at 4C. This bifunctional strategy with AZO and Li3PO4 is an efficient approach to improve the electrochemical performance of LCO at high cut-off voltage (>4.5 V).