Thermal reactions of a lithiated graphite anode in 1M LiPF6-ethylene carbonate (EC)/dimethyl carbonate (DMC) (50:50 vol.%) in the temperature range 40–320°C were investigated by TG–MS analysis. Studies by TG–MS during thermal reactions detected a small exothermic peak around 140°C due to CO2 (m/z =44) evolution, which suggests partial destruction of the SEI formed on the graphite and/or decomposition of the electrolyte through the SEI. In addition, the main exothermic reaction above 280°C, which is associated with simultaneous evolution of C2H4O (m/z =44), is caused by direct reaction of the lithiated graphite with solvent.