“…Ionic liquids (ILs) with favorable properties such as low vapor pressure, low flammability, wide electrochemical stability windows, and high ionic conductivities have been extensively investigated as electrolytes for electric energy storage applications, mainly with lithium‐ion batteries (LIBs) and sodium‐ion batteries (SIBs). [ 1–6 ] The successful operation of LIBs and SIBs, particularly their long term cycling stability, depends on the quality of solid electrolyte interphases (SEIs) formed on the surfaces of both anode and cathode electrodes (or cathode electrolyte interphase (CEI), in the case of the cathode). Both the SEI and CEI are ionically conductive but electronically insulative and mainly formed during the initial battery formation cycles.…”