Anion-Dominated Conventional-Concentrations Electrolyte to Improve Low-Temperature Performance of Lithium-Ion Batteries

Low temperatures (< -20 degrees C) significantly diminish lithium-ion battery performance due to freezing issues within commercial electrolytes and the high energy barrier for Li+ desolvation at the interface. Although high-concentration electrolytes and localized high-concentration electrolytes enhance Li+ desolvation kinetics featuring anion-participated solvation structures, their high viscosity and propensity for Li salt precipitation render them unsuitable for low-temperature environments. This study introduces an anion-dominated conventional-concentrations electrolyte (ACCE) created by incorporating Lithium difluorophosphate(LiPO2F2)into a 1 M Lithium bis((trifluoromethyl)sulfonyl)azanide(LiTFSI) Dimethyl carbonate(DMC)/Fluoroethylene carbonate(FEC)/Methyl acetate(MA) electrolyte solution. LiPO2F2, characterized by its poor solubility and strong binding with Li+, demonstrates a pronounced tendency to integrate into the primary solvation sheath of Li+. Moreover, the synergy between LiTFSI and LiPO2F2 establishes a dual anion configuration, unveiling a dual anion-driven mechanism. This mechanism significantly diminishes the interaction between Li+ and solvent molecules, resulting in reduced desolvation energy under low temperatures. The ACCE exhibits high ionic conductivity of 1.3 mS cm(-1) at -50 degrees C, enabling stable cycling of Li/NCM811 cells at -50 degrees C, and further allows 0.75 Ah graphite(Gr)/LiNi0.8Co0.1Mn0.1O2(NCM811) batteries dischargeable at -40 degrees C. This study presents a practical application potential for poorly soluble lithium salts and provides a new avenue for designing electrolytes suitable for low-temperature applications.