Improvement of electrochemical properties in LiCoO2 cathode films grown on Pt/TiO2/SiO2/Si substrates by liquid-delivery metalorganic chemical vapor deposition

The structural and electrochemical properties of LiCoO2 cathode films grown on Pt/TiO2/SiO2/Si substrates at 500degreesC by liquid-delivery metalorganic chemical vapor deposition (LDMOCVD) were investigated as a function of Li/Co mol ratio. The electrochemical properties such as initial discharge capacity and cyclic retention were improved through the study of Raman spectra of as-grown and annealed LiCoO2 films. The deposition temperature of 500degreesC was chosen to characterize the films because films grown at 500degreesC showed a typical high temperature hexagonal phase without Co3O4 impurities in the films. The optimum annealing condition of as-grown samples with Li/Co = 2.0 and 3.0 was at 700degreesC for 30 min in an oxygen ambient. The highest initial discharge capacity and capacity retention were obtained in Liparallel toLiCoO(2) cells grown with Li/Co = 3.0 and 2.0, respectively, and were approximately 38 muA h cm(-2) mum and 77%, respectively. The compositional window for an optimum electrochemical property exists in the range of Li/Co = 2.0 to 3.0 in an as-grown temperature of 500degreesC and annealing temperature of 700degreesC for 30 min in O-2. (C) 2004 American Vacuum Society.