H. Lin, F.Y. Liu, Y.P. Xie, Z.-S. Wu*

Liaoning Chemical Industry, 2023, Accepted.

To overcome the issue that commercial lithium hexafluorophosphate (LiPF6)-based electrolytes can’t operate properly at -20 °C, the development of low-temperature lithium-ion battery electrolytes has become a key research priority. Among them, lithium tetrafluoroborate (LiBF4)-based electrolytes show their low charge transfer impedance at low temperatures, and lithium difluoroborate (LiDFOB)-based electrolytes present their good film-forming properties. In this work, a new LiBF4 and LiDFOB dual salt electrolyte was developed to provide excellent electrochemical performance of hard carbon anode at both room temperature and low temperature through optimization and modulation. The effects of lithium tetrafluoroborate (LiBF4), lithium difluoroxalate borate (LiDFOB) and their mixed LiBF4 + LiDFOB double salt electrolytes on the electrochemical performance of hard carbon anodes at room temperature and low temperature were systematically compared by cyclic voltammetry, multiplicity and cycling performance tests. The results show that the LiBF4 + LiDFOB double salt electrolytes can achieve excellent low temperature cycling performance of hard carbon, showing a reversible capacity of 134 mAh g-1 after 100 cycles, which is significantly better than the cycling performance of hard carbon in commercial lithium hexafluorophosphate (LiPF6)-based electrolytes (reversible capacity after 100 cycles is only 2 mAh g-1).