Methyl tetrafluoro-2-(methoxy) propionate as co-solvent for propylene carbonate-based electrolytes for lithium-ion batteries

Methyl tetrafluoro-2-(methoxy) propionate (MTFMP) was evaluated as co-solvent for PC-based electrolytes in combination with graphite electrodes. Already 10 wt% (5.6 mol%) of MTFMP in PC were sufficient to form an effective and stable SEI on graphite as confirmed by battery tests. In the first cycle, the formation of an effective SEI via the decomposition of MTFMP was observed before PC co-intercalation thus preventing the subsequent exfoliation of the graphite. The stability of this SEI was verified by long term cycling tests, which showed that the capacity loss of the graphite-based cell was only 1.3% after 300 cycles at 1 C. The electrolyte, 1 M LiPF6 in PC:MTFMP (9:1 wt%), showed also a good rate capability up to 5 C on graphite. Therefore, MTFMP can be considered as a new, very promising co-solvent for PC-based electrolytes for use in lithium-ion batteries with graphite anodes.

► MTFMP is a new co-solvent for PC-based electrolytes with LiPF6 as lithium salt. ► MTFMP is able to suppress graphite exfoliation in PC-based electrolytes. ► MTFMP does not affect conductivity and increases the oxidative stability. ► Capacity retention of graphite-based cells is 99% after 300 cycles.