Lithium difluoro(sulfato)borate as a novel electrolyte salt for high-temperature lithium-ion batteries

• LiBF2SO4 was investigated as a novel electrolyte salt for advanced high-temperature LIBs.
• At 80 °C, LiBF2SO4-EC/DMC electrolyte favourably facilitates the formation of a thermal stable, effective and conductive interface film on the surface of carbonaceous anode.
• At 80 °C, LiBF2SO4-EC/DMC electrolyte exerts several advantages, such as stable cycling performance, low polarization resistance, and good rate performance in LiFePO4/Li cells.

High-temperature electrochemical behaviors of the novel salt named lithium difluoro(sulfato)borate (LiBF2SO4) were studied by employment of ethylene carbonate (EC) and dimethyl carbonate (DMC) as mixed solvents. In Li/MCMB (mesophase carbon microbeads) cells at 80 °C, LiBF2SO4-EC/DMC electrolyte favourably facilitates the formation of a thermal stable, effective and conductive interface film on the surface of carbonaceous anode. Besides, in LiFePO4/Li cells at 80 °C, LiBF2SO4-EC/DMC electrolyte exerts several advantages, such as stable cycling performance, low polarization resistance, and good rate performance. It suggests that LiBF2SO4 is an excellent candidate salt for advanced high-temperature lithium-ion batteries.