Electrochemical behaviour of sputtered c-V 2O 5 and LiCoO 2 thin films for solid state lithium microbatteries

Abstract

Here are reported for the first time electrochemical data on all-solid-state lithium microbatteries using crystalline sputtered V 2O 5 thin films as cathode materials and LiPON as solid electrolyte. The stable specific capacity of 30 µAh/cm 2 found with a 2.4 µm thick film competes very well with the best values obtained for solid state microbatteries using amorphous films. With the challenge of decreasing the temperature of heat treatment for sputtered LiCoO 2 thin films, we show that a temperature of 500 °C combined with an optimized bias sputtering (-50 V) allows to get highly crystalline deposits, to minimize the presence of Co 3O 4 and to suppress any trace of the cubic phase. At the same time the theoretical specific capacity is reached in the 4.2 V-3 V range and a good cycling behaviour is achieved with a high capacity of 50 µAh/cm 2/µm after 140 cycles at 10 µA.cm 2.