The impact of Co2+ ions in solutions on the performance of LiCoO2, Li, and lithiated graphite electrodes

We report herein on the impact of the presence of CO2+ ions in solutions, on the performance of LiCoO2, lithium, and graphite electrodes. X-ray diffraction for bulk structural measurements and X-ray photoelectron spectroscopy for surface studies were applied together with standard electrochemical techniques. It was found that the presence of CO2+ ions in solutions stabilizes the behavior of LiCoO2 electrodes in repeated Li insertion-reinsertion cycles and exacerbates the performance of Li anodes. The initial performance of graphite electrodes in cobalt ions containing solutions is inferior compared to that measured in standard solutions. However, during prolonged cycling, the behavior of graphite electrodes in solutions containing cobalt ions improves and becomes similar to that of electrodes in standard solutions. The effect of the CO2+ ions in solution on the performance of the above three electrodes relates to surface phenomena, namely, the involvement of precipitation of cobalt salts in the electrodes' surface chemistry. (C) 2004 The Electrochemical Society.