Influence of the Vinylene Carbonate on the Wetting and Interface Chemical Structure of Doped Ionic Liquid Electrolyte at Porous Graphite Surface

Adding organic carbonates (e.g., vinylene carbonate, VC) into ionic liquid (IL)-based electrolytes generally improves the electrochemical performance of graphite electrode (Cgr)-based Li-ion batteries. The impact of VC on the wettability at open-circuit voltage and the interface chemical structure change between pristine Cgr and the ionic liquid-based electrolyte have been investigated by electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS). The XPS results show a change in the surface dipole and a better impregnation of the IL-based electrolyte when the VC is added to the electrolytic media. The Cgr dipole change and the better impregnation of IL-based electrolyte induce a change in the electrical series resistance and double-layer capacitance as deduced by EIS measurements.