ABSTRACTIncreasing the operation voltage of LiCoO2 (LCO) is a direct way to enhance the energy density of the Li-ion batteries. However, at high voltages, the cycling stability degrades very fast due to the irreversible changes in the electrode structure, and formation of an unstable solid electrolyte interface layer. In this work, Ag thin film was prepared on commercial LCO cathode by using magnetron sputtering technique. Ag coated electrode enabled an improved electrochemical performance with a better cycling capability. After 100 cycles, Ag coated LCO delivers a discharge capacity of 106.3 mAh g-1 within 3 - 4.5 V at C/5, which is increased by 45 % compared to that of the uncoated LCO. Coating the electrode surface with Ag thin film also delivered an improved Coulombic efficiency, which is believed to be an indication of suppressed parasitic reactions at the electrode interface. This work may lead to new methods on surface modifications of LCO and other cathode materials to achieve high-capacity Li-ion batteries for high-voltage operations.
Sensitive in-operando observation of Li and O transport in thin film Li ion batteries