Sputter-Deposited Amorphous LiCuPO4 Thin Film as Cathode Material for Li-ion Microbatteries

We report the electrochemical performance of amorphous LiCuPO4 thin films obtained by radio frequency sputtering as a cathode material for Li-ion microbatteries. The thin films were characterized by X-ray diffraction, scanning electron microscopy, profilometry and electrochemical techniques. Charge/discharge profiles and cycling performance were evaluated in lithium electrochemical test cells. Cyclic voltammogram of the LiCuPO4 film shows the typical redox reaction peak at approximate to 1.9V vs. Li/Li+. A discharge capacity of 160mAhg(-1) (50Ahcm(-2)) is attained for the first cycle at C/10 to reach a stable capacity of 70mAhg(-1) (22Ahcm(-2)) with good stability over 160 cycles. For comparison, the electrochemical performance of a crystalline LiCuPO4 film was investigated. The first discharge could deliver a high capacity of around 375mAhg(-1) at C/10, but the capacity decayed quickly to a low capacity of 11mAhg(-1) over 50 cycles. The results show that the LiCuPO4 amorphous materials can be considered as the exciting cathode candidate for Li-ion microbatteries.