An Electrospun Nanofiber Membrane as Gel-Based Electrolyte for Room-Temperature Sodium–Sulfur Batteries

We report on the synthesis and characterization of an electrospun gel polymer electrolyte (GPE) membrane based on polyacrylonitrile nanofibers (PAN) swollen in a polyethylene glycol dimethyl ether/Na-salt electrolyte solution, for application in room temperature sodium–sulfur (Na–S) batteries. The membranes show a high ionic conductivity, wide electrochemical stability window, and good thermal stability. We demonstrate the performance of the membrane in an Na–S cell using a sulfur–carbon nanotubes composite cathode and Na metal as anode. Our results show that the GPE membrane stabilizes the Na metal anode resulting in stable cycling behavior. The capacity of the Na–S cell, using the GPE membrane and operating at room temperature, is approximately 500 mAh g⁻¹ over 40 cycles. The selected electrolyte configuration also provides improved safety by replacing the highly reactive sodium perchlorate (NaClO₄) salt previously used in literature. All these benefits make the gel-polymer electrolyte membrane a very promising system for application in room-temperature sodium and sodium–sulfur batteries.