Small pouch cells containing Si/graphite electrodes were systematically charged to 100, 120, 140, 160, 180 and 250% state of charge. Characterization of the Si/graphite electrode after the overcharge showed some features similar to those found in a pure graphite electrode. Since the amount of silicon in the electrode was similar to 15 wt%, this was not unexpected. The effect of silicon was seen in the composition of the SEI layer and the trends in two components of the SEI layer.