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

Low temperatures (< −20 °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 °C, enabling stable cycling of Li/NCM811 cells at −50 °C, and further allows 0.75 Ah graphite(Gr)/LiNi_0.8Co_0.1Mn_0.1O₂(NCM811) batteries dischargeable at −40 °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.