Electrospun electroactive polyvinylidene fluoride-based fibrous polymer electrolyte for sodium ion batteries

Electrospinning is an efficient technique to produce ultrafine electroactive mat, diameters ranging from few nanometers to micrometers to use as a separator in sodium ion battery. The polyvinylidene fluoride (PVDF) polymer solution was optimized to 19 wt%, applied voltage 25 kV and flow rate of 0.5 ml h^-1 to get a bead free ultrafine electroactive structure. The electroactive β-phase is confirmed by x-ray diffractometer (XRD). Ionic conductivities, electrolyte uptake, wettability, linear sweep voltammetry (LSV) and thermal stability of the electroactive fibrous polymer electrolyte (EFPE) were studied by soaking the separator with a liquid electrolyte of 1 M sodium hexafluorophosphate (NaPF₆) dissolved in ethylene carbonate (EC)/propylene carbonate (PC) (1:1 vol%). The EFPE exhibits high ionic conductivity of 1.08 mS cm^-1 and electrochemical stability window of 5.0 V versus Na/Na⁺ under ambient condition. The half-cell containing Na_0.66Fe_0.5Mn_0.5O₂ as cathode and EFPE as the separator cum electrolyte showed a stable cycling performance at a current rate of 0.1C.