A sodium ion conducting gel polymer electrolyte

• A sodium ion conducting gel polymer electrolyte is prepared through a simple phase separation process.
• It is a porous membrane based on poly(vinylidene difluoride-co-hexafluoropropylene).
• The gel polymer electrolyte provides the sodium ionic conductivity of 0.60 mS cm− 1 at ambient temperature.
• Its ionic transference number of sodium ion (tNa +) is 0.30, higher than that (0.17) in the commercial separator.

A sodium ion conducting gel polymer electrolyte based on poly(vinylidene difluoride-co-hexafluoropropylene) porous membrane is reported, which is prepared through a simple phase separation process. It exhibits high safety, good mechanical properties and good electrochemical stability. The gel polymer electrolyte provides the sodium ionic conductivity of 0.60 mS cm− 1 at ambient temperature, while the commercial separator (Celgard 2730) offers only 0.16 mS cm− 1. The temperature dependence of the ionic conductivity from 25 to 75 °C is consistent with an Arrhenius-behavior. The ionic transference number of sodium ion (tNa+) in the gel polymer electrolyte is 0.30, higher than that (0.17) in the commercial separator. This provides a new direction to improve the safety of sodium ion batteries.