Spectroelectrochemical studies on highly polarized LiCoO2 electrode in organic solutions

In situ Raman spectroscopy was conducted on thin film electrodes of pure Li CoO2 in order to observe the nature of the changes in interfacial structure between LiCoO2 and organic solutions (propylene carbonate and ethylene car bonate containing 1 M LiClO4) when LiCoO2 is scanned up to highly anodic po tentials (similar to 5.0VLi(+)/Li). Raman spectra and cyclic voltammograms were recorded simultaneously during the potential scan. We observed a sudde n increase in the background signals of the Raman spectra at potentials mor e positive than 4.7 V. The increased background did not change after potent ial cycling. The change was irreversible, indicating that surface film form ation occurred at positive potentials. As organic compounds fluoresce by vi sible light, the increased background is ascribed to the formation of a fil m On the LiCoO2 electrode surface in organic solutions. (C) 2000 Published by Elsevier Science S.A.