Electrolyte engineering enables high-energy Li‖CFx battery operation at ultralow temperatures

A lithium metal‖carbon fluoride (Li‖CF_x) primary battery offers high energy density and long shelf-life but suffers from poor performance at low temperatures. We report a linear ester-based electrolyte comprising ethyl acetate (EA) and ethyl trifluoroacetate (ET) with LiBF₄ salt to address this challenge. EA served as the primary solvent, while ET acted as an anti-solvent, weakening Li⁺ coordination due to its strong electron-withdrawing fluorine atoms. This unique solvation structure enhanced Li⁺ transport for an Li‖CF_x battery, delivering a high discharge capacity of 706 mA h g^-1 at -40 °C and 395 mA h g^-1 at -60 °C.