Synergy of Dual-Salt and Fluorinated Electrolyte Enables a Low-Solvation Structure and LiF-Rich Solid Electrolyte Interphase for Cryogenic Lithium-Ion Batteries

Amid the global drive toward clean and cost-effective energy development, lithium-ion batteries (LIBs) have emerged as a cornerstone technology due to their high energy density and long cycle life, underpinning applications ranging from electric vehicles to portable electronic devices. However, the detrimental effect of low temperatures on lithium-ion battery performance remains a critical challenge, which demands urgent solutions at present. In this work, we designed a low-temperature fluorinated electrolyte, denoted LTDFM, by incorporating methyl difluoroacetate (MDFA), a fluorinated cosolvent with an ultralow melting point, into a dimethyl carbonate (DMC)/fluoroethylene carbonate (FEC) (8:2 v/v) base. This formulation was further enhanced with a dual-salt system of LiPF 6 and bis(trifluoromethanesulfonyl)imide (LiTFSI) at a 6:4 molar ratio (1.0 M total salt concentration). The resulting LTDFM electrolyte enables not only stable long-term cycling performance at room temperature but also excellent electrochemical performance at a low temperature of −30 °C. This low temperature tolerance is attributed to the formation of a denser and mechanically robust solid electrolyte interphase (SEI) film rich in LiF, which effectively suppresses the growth of lithium dendrites and parasitic side reactions. This work provides valuable mechanistic insights and a practical strategy for designing high-performance low-temperature electrolyte for LIBs in extreme environments.