In-Situ Spectro-electrochemical Insight Revealing Distinctive Silicon Anode Solid Electrolyte Interphase Formation in a Lithium-ion Battery

The formation and evolution of solid electrolyte interphase (SEI) layer on a silicon electrode in 1 M LiPF6 in EC/DMC electrolyte is investigated by in-situ FTIR spectroscopy. The results point that lithium alkyl carbonates formation is initiated during a lithiation process via a one-electron reduction of EC/DMC, followed by a free radical reaction. Interesting enough, the studies indicate that most of the SEI material is actually formed in the delithiation process. Carbon dioxide (CO2) generated at low potentials during the shallow lithiation process is consumed during a deeper lithiation process and also during subsequent delithiation processes, resulting in the formation of lithium carbonate.