Electrochemical performances for preferred oriented PLD thin-film electrodes of LiNi 0.8Co 0.2O 2, LiFePO 4 and LiMn 2O 4

Abstract

The charge–discharge performances for lithium ion batteries using the PLD thin-film cathodes of LiNi 0.8Co 0.2O 2, LiFePO 4 and LiMn 2O 4 were investigated. LiMn 2O 4 and LiFePO 4, which have a 3-D frame work crystal structure, showed smooth charging and discharging. On the contrary, LiNi 0.8Co 0.2O 2, which consists of a 2-D layered crystal structure, exhibited a poor discharge capacity. The differences in electro-chemical behaviors might be related to characteristics of PLD thin-film such as high crystallinity or high degree of preferred orientation. Furthermore, the surface roughness and film thickness of LiMn 2O 4 thin-film were varied by using SPT and PLD method, and their structures were clarified by XRD and SEM. The SPT method gave the film with rough and large surface area, while the PLD method provided a flat and high crystalline film. Their rate performances of charge and discharge were independent of the deposition method but depended on the film thickness. Optimum performance was obtained with the PLD film deposited for 30 min, which showed almost the same shape of the discharge curve between 36 C and 720 C.