COBALT DISSOLUTION IN LICOO2-BASED NONAQUEOUS RECHARGEABLE BATTERIES

Rechargeable lithium batteries using a variety of differently prepared LiCoO2 samples were cycled to 4.5 V versus Li and the negative electr ode was investigated for Co deposits after the cell was cycled over 25 times. Qualitative analysis revealed evidence of cobalt dissolution f or samples showing high capacity loss with cycle number. A direct corr elation between the percentage capacity loss and percentage cobalt los s was established. Cycling LiCoO2-based cells to voltages ranging from 4.1 to 4.5 was found to result in an increase in the capacity fade fo r voltages greater than 4.2 V, consistent with the traditional limit o f reversibility of 4.2 V for LiCoO2. For voltages greater than 4.2 V, the capacity fading scaled with the measured amount of cobalt dissolut ion which was found to correlate with structural changes observed by i n-situ X-ray diffraction.