Decreasing the initial irreversible capacity loss by addition of cyclic sulfate as electrolyte additives

Initial irreversible capacity loss in graphite electrodes was suppressed by 1,3,2-dioxathiolane-2,2-dioxide and its derivatives (cyclic sulfates) in propylene carbonate (PC) containing electrolyte. Cyclic voltammetry (CV) showed that cyclic sulfates were decomposed at higher potentials than that for electrolyte solvents. In galvanostatic charge and discharge measurement, first cycle efficiency was increased from 58.2% to 90.5% by the addition of 1,3,2-dioxathiolane-2,2-dioxide. Passivation films formed by cyclic sulfates were observed by X-ray photoelectron spectroscopy (XPS), FT-IR, and pyrolysis/GC/MS (pyro/GC/MS). These results indicate that the surface was covered by a PEO like polymer with the inner layer comprised of Li2S like compounds.