The stability and reformation of solid electrolyte interfaces (SEIs) on carbon electrodes during storage at elevated temperatures were studied. The capacity change observed for carbon samples after storage at elevated temperatures is attributed to the instability of the SEI layer in the liquid electrolyte. The capacity change was found to correlate well with the specific surface area of graphite. (C) Telcordia Technologies. The Electrochemical Society. S0013-4651(99)04-006-9.