Reactivity of the Solid Electrolyte Interface on Carbon Electrodes at Elevated Temperatures

Lithium-ion rechargeable cells, which use carbons in the negative electrode and lithium transition metal oxides in the positive electrode, show excellent cycle life at room temperature, but their charge capacity decreases and internal resistance increases during cycling and storage at elevated temperatures. To determine the locus and mechanism of such degradation, it is essential to study the active materials. However, at present, few data have been published on the behavior of carbon electrodes at elevated temperatures. 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.