The reactions of Li0.5CoO2 with nonaqueous solvents at elevated temperatures

Differential scanning calorimetry (DSC), accelerating rate calorimetry (ARC), and X-ray diffraction experiments on the reaction of Li0.5CoO2 in various solvents have been performed. In the presence of sufficient solvent the reaction proceeds in a clear stepwise manner through solid phases as a function of temperature as Li0.5CoO2 --> 1/2 LiCoO2 + 1/6 Co3O4 --> 1/2 LiCoO2 + 1/2 CoO --> Co+ 1/4 Li2CO3. Accompanying these changes are solvent combustion reactions due to the evolved oxygen that realease large amounts of heat. If there is only a small amount of solvent present relative to the amount of Li0.5CoO2, the last step of the reaction does not occur, at least at temperatures below 450degrees C. A kinetic description for the stepwise reaction of Li0.5CoO2 in ethylene carbonate (EC)/propylene carbonate (PC) was developed using successive Avrami-Erofeev reaction models. The kinetic triplets obtained from DSC experiments were then used to accurately predict a number of ARC experiments of Li0.5CoO2 in EC/PC, giving confidence in the determined kinetic triplet. (C) 2002 The Electrochemical Society.