Impact of 2D layered VS 2 on the electrochemical properties of gel polymer electrolytes for sodium-ion battery applications

In the present investigation, we report the synthesis of composite gel polymer electrolytes (CGPEs) based on a poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)/poly(methyl methacrylate) (PMMA) blend incorporated with 2D layered vanadium disulfide (VS2). The incorporation of VS2 significantly enhances the ionic conductivity (3.6 × 10-3 S cm-1) compared with that of the pristine GPE (2.5 × 10-3 S cm-1). The optimized CGPE achieves a high ionic conductivity of 3.6 × 10-3 S cm-1, a good sodium-ion transference number of 0.44, a wide electrochemical stability window (ESW) of ∼4.1 V vs. Na+/Na, and excellent thermal stability up to ∼125 °C. Structural analyses confirmed uniform polymer-filler interactions, contributing to efficient ion transport. The fabricated sodium-ion battery using the CGPE as the electrolyte delivered a high reversible capacity of 195 mA h g-1 after 30 cycles at 50 mA g-1, with stable cycling performance up to 100 cycles. The enhanced electrochemical performance of the CGPE demonstrates the potential of VS2-incorporated systems as promising electrolytes for flexible, high-energy sodium-ion batteries (SIBs) and highlights the suitability of 2D materials as effective fillers in GPEs.