Chloroethylene carbonate, a solvent for lithium-ion cells, evolving CO2 during reduction

We have investigated the role of chloroethylene carbonate (CIEC) on the formation of the solid-electrolyte interfacial film on graphite electrodes for rechargeable lithium-ion cells. In situ infrared spectroelectrochemical experiments have been correlated with galvanostatic charge/discharge measurements. During the first reduction of graphite in a CIEC-based electrolyte, a sloping potential plateau from similar to 1.7 to similar to 1.4 V vs Li/Li+ appears, which we relate to the generation of CO2. We assume that the CO2 generated from CIEC is an intermediate reduction product that undergoes further reactions that contribute to the formation of the protective-film.