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

Abstract Thermal reactions of charged Li x CoO 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 O 2 peaks in the TPD–MS spectra with weight loss in TGA and XRD results, it is obvious that the reduction of Li x CoO 2 to LiCoO 2 and Co 3 O 4 is triggered at 190 °C and completed at 400 °C. The initial stages of electrolyte combustion and decomposition are confirmed by H 2 O and CO 2 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 Li x CoO 2 begins at 240 °C; the decomposition starts at 290 °C.