Electrolyte solvents for electrochemical devices have been dominated by oxygen (O)-based and nitrogen (N)-based ligands over the past decades1–5, for which the dipole–ion (Li+, Na+ and so on) interaction usually lays the foundations of ion dissociation and transport but frustrates the charge transfer process at the electrolyte–electrode interface6–9. Here, by synthesizing alkanes with monofluorinated structures, we show that fluorine (F)-based ligands with designed steric hindrance and Lewis basicity enable salt dissolution of more than 2 mol l−1. Among them, 1,3-difluoro-propane (DFP)-based Li-ion electrolyte is endowed with all merits for energy-dense and low-temperature batteries, including low viscosity (0.95 cp), high oxidation stability (>4.9 V) and ionic conductivity of 0.29 mS cm−1 at −70 °C. By incorporating F atoms in the first solvation shell, the weak F–Li+ coordination facilitates the Li plating/stripping process with Coulombic efficiency (CE) up to 99.7% and exchange current density one magnitude larger than O–Li+ coordination at −50 °C. The electrolytes further enable the operation of lithium-metal pouch cells under an electrolyte amount of less than 0.5 g Ah−1, achieving energy densities greater than 700 Wh kg−1 at room temperature and about 400 Wh kg−1 at −50 °C. The hydrofluorocarbon (HFC) electrolytes in this work provide a feasible approach to building electrochemical systems beyond traditional coordination chemistry.
