In Situ Analysis of Solid Electrolyte Interface over Si Based Anodes Using Diffuse Reflectance Infrared Fourier Transform Spectroscopy

In this work the formation and evolution of solid electrolyte interphase (SEI) layer on a Silicon based electrode in electrolytes containing 1 M LiPF6/EC:EMC (1:2):VC (2 % wt) and 1 M LiPF6/EC:EMC (1:2):VC (2 % wt) + FEC (10 % wt) was investigated by in-situ DRIFT spectroscopy. Electrolyte without FEC is composed primarily of poly (VC), polycarbonates and lithium carbonate. Incorporation of 10 % wt FEC results with the formation of poly (VC/FEC), polycarbonates, lithium carbonate species, alkoxy species and alkyl phosphates. Incorporation of FEC also result with the increase in the formation of poly (VC/FEC). Moreover in the course of 2nd discharging, incorporation of FEC impedes the decomposition of both solvent and salt anion reduction.