Novel Low-Temperature Electrolyte Using Isoxazole as the Main Solvent for Lithium-Ion Batteries

A novel electrolyte system with an excellent low-temperature performance for lithium-ion batteries (LIBs) has been developed and studied. It was discovered for the first time, in this work, that when isoxazole (IZ) was used as the main solvent, the ionic conductivity of the electrolyte for LIBs is more than doubled in a temperature range between −20 and 20 °C compared to the baseline electrolyte using ethylene carbonate–ethyl methyl carbonate as solvents. To solve the problem of solvent co-intercalation into the graphite anode and/or electrolyte decomposition, the lithium difluoro­(oxalato)­borate (LiDFOB) salt and fluoroethylene carbonate (FEC) additive were used to form a stable solid electrolyte interphase on the surface of the graphite anode. Benefitting from the high ionic conductivity at low temperature, cells using a new electrolyte with 1 M LiDFOB in FEC/IZ (1:10, vol %) solvents demonstrated a very high reversible capacity of 187.5 mAh g–1 at −20 °C, while the baseline electrolyte only delivered a reversible capacity of 23.1 mAh g–1.