Influence of irreversible reactions at non-graphitizable carbon electrodes on their thermal stability in Li-ion batteries

The thermal stability of four kinds of non-graphitizable carbon negative-electrodes was studied quantitatively by differential scanning calorimetry (DSC). Charged non-graphitizable carbon electrode powder gave exothermic peaks at around 300 °C. The heat values increased with both the charge capacity and the amount of charged electrode powder sealed in a hermetic pan. Based on the present and previous results, the heat values increase with an increase in the charge capacity, the irreversible capacity, and the amount of charged electrode powder. Exothermic peaks were seen at around 290 °C even for discharged non-graphitizable carbon electrode powder. The heat values increased with the irreversible capacity. The amount of Li-ions remaining in the carbon as well as the amount of surface film should increase with the irreversible capacity, and therefore the heat values increased for discharged non-graphitizable carbon.