Thermal studies of charged cathode material (LixCoO2) with temperature-programmed decomposition-mass spectrometry

Thermal reactions of charged LixCoO(2) and electrolyte are investigated by means of temperature-programmed decomposition-mass spectrometry (TPD-MS), DSC, TGA, and XRD. The electrolyte is composed of ethylene carbonate, propylene carbonate, and dimethyl carbonate. Direct observation of gas species resulting from the reactions is beneficial in understanding the reaction mechanisms. From 02 peaks in the TPD-MS spectra with weight loss in TGA and XRD results, it is obvious that the reduction of LixCoO(2) to LiCoO2 and Co3O4 is triggered at 190 degrees C and completed at 400 degrees C. The initial stages of electrolyte combustion and decomposition are confirmed by H2O and CO2 peaks in the TPD-MS spectra along with exothermic peaks in DSC plots. The reaction of electrolyte with O-2 released from the reduction of LixCoO(2) begins at 240 degrees C; the decomposition starts at 290 degrees C. (C) 2010 Elsevier B.V. All rights reserved.