Fluorinated Carboxylate‐Based Electrolyte Facilitates Interfacial Film Formation and Desolvation of Low‐Temperature Lithium Metal Batteries

The electrochemical performance of lithium metal batteries hinges on interfacial desolvation and ion transport kinetics, particularly in low‐temperature environments. Herein, we design a fluorinated carboxylate electrolyte that facilitates desolvation and promotes the formation of interfacial films for low‐temperature lithium metal batteries. By employing lithium bis(fluorosulfonyl)imide (LiFSI) as the lithium salt and using methyl trifluoroacetate (MTFA) and fluoroethylene carbonate (FEC) as solvents, an MTFA‐FEC fluorinated carboxylate‐based electrolyte is formulated. MTFA effectively reduces the freezing point of the electrolyte, while FEC enhances the dissociation of LiFSI and improves the film‐forming ability of the electrolyte. The relatively weak binding force between Li + and MTFA is conducive to the desolvation process. By adjusting the ratio of MTFA and FEC solvents, we effectively enhance the stability of the electrode–electrolyte interface. The results demonstrate that when the volume ratio of MTFA to FEC is 8:2, the Li||Cu cell using this electrolyte can stably cycle for 80 cycles at 0°C. At −20°C, the Li||LFP cell can stably cycle for 200 cycles at 0.2 C, with an initial discharge specific capacity of 100.2 mAh g −1 . Notably, even at 1 C, the discharge specific capacity remains at 53.0 mAh g −1 .