Regulating the interfacial chemistry of graphite in ethyl acetate-based electrolyte for low-temperature Li-ion batteries

Abstract

Lithium-ion batteries suffer from severe capacity loss and even fail to work under subzero temperatures, which is mainly due to the sluggish Li+ transportation in the solid electrolyte interphase (SEI) and desolvation process. Ethyl acetate (EA) is a highly promising solvent for low-temperature electrolytes, yet it has poor compatibility with graphite (Gr) anode. Here, we tuned the interfacial chemistry of EA-based electrolytes via synergies of anions. ODFB- with low solvation numbers, participates in the solvation sheath, significantly reducing the desolvation energy. Meanwhile, combined with the high dissociation of FSI-, the reduction of both anions constructs an inorganic-rich SEI to improve interfacial stability. The electrolyte enables Gr anode to deliver a capacity of 293 mA h g(-1) and 2.5 Ah LiFePO4 Gr pouch cell to exhibit 96.85% capacity retention at -20 degrees C. Remarkably, LiFePO4 Gr pouch cell with the designed electrolyte can still retain 66.28% of its room-temperature capacity even at -40 degrees C.