Pulsed Laser Deposition and Characterization of Crystalline Lithium Cobalt Dioxide (LiCoO2) Thin Films

The pulsed laser deposition of LiCoO₂ and LiCo_0.5Al_0.5O₂ thin films was investigated as a function of deposition conditions. The initial growth process optimization focused on films grown on (200)-textured SnO₂-coated glass substrates. Film growth was also investigated on ZnO and indium-tin oxide (ITO) coated substrates. For both LiCoO₂ and LiCo_0.5Al_0.5O₂, dense uniaxially textured (003)-oriented films of the layered LiCoO₂ phase were grown on the SnO₂ 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 LiCoO₂ films, grown at T, = 700°C, Po₂ = 2000 mTorr, had an initial discharge capacity of ∼118 mAh/g (0.43 Li/Co) which decreased ∼0.5% per cycle. For LiCo_0.5Al_0.5O₂, although, as predicted, the films did have a higher cathode potential, the charge capacity was significantly lower than that for LiCoO₂ films. Finally, functional LiCoO₂ thin film cathodes were grown on flexible ITO-coated Upilex polymer substrates at T₈ = 300°C.