Lithium Cobalt Oxide (LiCoO2) Nanocoatings by Sol−Gel Methods

Lithium cobalt oxide (LiCoO2) was synthesized using two different sol−gel processes. The first method used stoichiometric molar ratios of cobalt 2-methoxyethoxide and lithium nitrate in alcoholic solutions; the second method used aqueous equimolar ratios of precursors of lithium nitrate and cobalt acetate with poly(ethylene glycol) (PEG) 200 as the chelating agent. Lithium cobalt oxide films were deposited on Si wafers and silica−soda−lime glass using a dipping technique. Based on differential thermal analysis/thermogravimetric analysis results, densification of the films was achieved by thermal treatment at both 500 and 800 °C in the case of silicon wafer substrates and at 500 °C for the silica−soda−lime glass. X-ray diffraction, spectroellipsometry, and atomic force microscopy were used to characterize the films. The correlation between the preparation procedure and the type of support on the structure and morphology of LiCoO2 compound films is discussed. Uniform ultrathin films were obtained on the glass (heat treated at 500 °C) and Si wafer (heat treated at 800 °C). The alcoholic synthetic procedure was also used to coat particles of LiMn2O4 with films of LiCoO2. The sol−gel method resulted in partial coverage of LiMn2O4 by LiCoO2 as determined by elemental mapping with scanning electron microscopy.