1-Ethyl-3-Methyl-Imidazolium Bis (Trifluoromethane-sulfonyl) Imide as an Electrolyte Additive in LiFePO4-Based Batteries for Suppressing Aluminum Corrosion

Lithium bis (trifluoromethanesulfonyl) imide (LiTFSI) is a potentially useful electrolyte salt for use in Li-ion batteries. LiTFSI, however, is associated with severe corrosion of Al current collectors. This study investigates the ionic liquid 1-ethyl-3-methyl-imidazolium bis (trifluoromethanesulfonyl) imide (EMITFSI) as an Al corrosion inhibitor in LiTFSI electrolytes. Different concentrations of EMITFSI are used as additives in 1 m LiTFSI-based electrolytes to systematically assess the performance of lithium iron phosphate (LiFePO4) cathodes. The results from electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Cyclic voltammetry (CV) indicate that adding EMITFSI into LiTFSI-based electrolytes can effectively prevent severe corrosion of Al caused by LiTFSI-based electrolytes. The LiFePO4 cells that use 1 m LiTFSI + 11% EMITFSI-based electrolytes demonstrate a superior rate capability and cycling stability when compared to cells that use the LiTFSI-based electrolyte.