Pulsed Laser Deposition and Characterization of Crystalline Lithium Cobalt Dioxide (LiCoO[sub 2]) Thin Films

Abstract

The pulsed laser deposition of LiCoO2LiCoO2 and LiCo0.5Al0.5O2LiCo0.5Al0.5O2 thin films was investigated as a function of deposition conditions. The initial growth process optimization focused on films grown on (200)-textured SnO2SnO2 -coated glass substrates. Film growth was also investigated on ZnO and indium-tin oxide (ITO) coated substrates. For both LiCoO2LiCoO2 and LiCo0.5Al0.5O2,LiCo0.5Al0.5O2, dense uniaxially textured (003)-oriented films of the layered LiCoO2LiCoO2 phase were grown on the SnO2SnO2 coated substrates. The grain size increased substantially with increased substrate temperature in the range from 400 to 700°C. For constant current cycling between 3.5 and 4.4 V vs. Li, the best crystalline LiCoO2LiCoO2 films, grown at Ts=700°C,Ts=700°C, pO2=2000 mTorr,pO2=2000 mTorr, had an initial discharge capacity of ∼118 mAh/g (0.43 Li/Co) which decreased ∼0.5% per cycle. For LiCo0.5Al0.5O2,LiCo0.5Al0.5O2, although, as predicted, the films did have a higher cathode potential, the charge capacity was significantly lower than that for LiCoO2LiCoO2 films. Finally, functional LiCoO2LiCoO2 thin film cathodes were grown on flexible ITO-coated Upilex polymer substrates at Ts=300°C.Ts=300°C. © 2001 The...