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

Abstract

The structural and electrochemical properties of LiCoO2 cathode films grown on Pt∕TiO2∕SiO2∕Si substrates at 500°C 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 500°C was chosen to characterize the films because films grown at 500°C 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 700°C for 30min in an oxygen ambient. The highest initial discharge capacity and capacity retention were obtained in Li‖LiCoO2 cells grown with Li∕Co=3.0 and 2.0, respectively, and were approximately 38μAhcm−2μm and 77%, respectively. The compositional window for an optimum electrochemical property exists in the range of Li∕Co=2.0to3.0 in an as-grown temperature of 500°C and annealing temperature of 700°C for 30min in O2.