Ionic conductivity, Na plating-stripping, and battery performance of solid polymer Na ion electrolyte based on poly(vinylidene fluoride) and poly(vinyl pyrrolidone)

Solid-state sodium-ion batteries (ss-SIBs) are a promising alternative to commercially available lithium-ion batteries for next-generation energy storage applications due to the abundance and cost-effectiveness of sodium over lithium. Herein, using a facile solution casting process, a high sodium-ion conductive, filler-less composite solid polymer electrolyte (SPE) film based on poly(vinylidene fluoride) polymer, poly(vinyl pyrrolidone) (PVP) binder, and NaPF₆salt for ss-SIB has been successfully fabricated. Total conductivities of 8.51 × 10^-4and 8.36 × 10^-3S cm^-1at 23 and 83 °C, respectively, were observed from the SPE. A hybrid symmetric half-cell assembly using Na electrode and 1 M NaClO₄in ethylene carbonate (EC) and propylene carbonate (PC) (EC/PC = 1:1 wt %) electrolyte showed excellent Na plating-stripping performance at 10 mA cm^-2at 23 °C. The study showed that PVP binder played an important role in achieving good Na ion conductivity and excellent Na plating-stripping performance, highlighting the applicability of the as-prepared SPE in next-generation high-power rechargeable SIBs. A full cell with an SPE, a Na anode, and a Na₃V₂(PO₄)₃cathode showed a discharge capacity of 93.2 mAh g^-1at 0.1 C with 86% capacity retention and 99.68% Coulombic efficiency for 100 cycles.