Development of a Novel Metal-Gelatine-Infused Polyaniline Solid Electrolyte for Room-Temperature Na-S Batteries

Solid-state sodium batteries are promising candidates for next-generation energy storage systems due to their safety, sustainability, and cost-effectiveness. However, developing efficient and eco-friendly polymer electrolytes remains challenging. In this study, a novel composite solid polymer electrolyte (SPE) composed of polyaniline (PANI), gelatin, and NaTFSI was synthesized using four different solvents (NMP, toluene, hexane, and THF) to investigate the solvent effect on electrochemical performance. Among them, the toluene-based electrolyte exhibited the highest ionic conductivity (4.64 × 10 −4 S·cm −1 ) and the lowest interfacial resistance (∼260 Ω) at room temperature. The materials were characterized using FTIR, XRD, SEM, EDX, and TGA to analyze their structural, morphological, and thermal properties. Thermal analysis confirmed enhanced stability upon salt incorporation, while structural and morphological studies revealed improved polymer chain interaction and uniform ion dispersion. Moreover, the sodium symmetric cell (Na/SPE/Na) demonstrated stable cycling at 1 mA cm −2 without dendrite formation, and the full Na–S cell exhibited high and stable specific capacities ranging from 591 to 778 mAh g −1 over multiple cycles at 0.1 C. These findings highlight the critical role of solvent evaporation rate in tuning polymer morphology, crystallinity, and ionic transport, and demonstrate that the proposed PANI–gelatin–NaTFSI system provides a sustainable and cost-effective route for room-temperature solid polymer electrolytes in sodium-based energy storage applications.