Sodium-ion–conducting natural resin–based flexible electrolyte membranes for energy applications

Sodium-ion–based solid electrolyte membranes for energy storage devices are gaining importance as a potential replacement for lithium-ion batteries. The limitations of synthetic and biopolymer-based solid electrolyte materials have led to the development of biomaterial-based polymer electrolytes for sustainable electrochemical energy storage applications. Recently, plant exudates (e.g., gums) have demonstrated excellent properties, including film-forming ability, polar coordination sites, biocompatibility, electrochemical stability, and eco-friendliness. Moringa oleifera gum (MG) comprises D-galactose, D-glucuronic acid, L-arabinose, L-mannose, and L-rhamnose, which contribute to its abundance of polar functional groups. Herein, MG-CF₃NaO₃S-based sodium-ion–conducting electrolyte membranes have been developed in different weight percentages by solution casting method. The X-ray diffraction analysis (XRD) confirms the increased amorphous nature of 1 g MG + 0.5 wt.% CF₃NaO₃S (MGNA-3). The MGNA-3 membrane exhibits a low glass transition temperature of 78.52 °C. MGNA-3 demonstrates the highest ionic conductivity of 2.42 ± 0.04 × 10⁻² S cm⁻¹ at room temperature. The MGNA-3 membrane demonstrated an electrochemical stability window of 3.61 V and steady redox behavior over 20 cycles. A primary sodium-ion battery with the configuration Na|MGNA-3|V₂O₅-graphite exhibited a good open-circuit potential of 3.72 V. The battery showed excellent load discharge characteristics, sustaining stable performance under a 100 KΩ load for 120 h and operating effectively under other loads (10 KΩ and 1 KΩ). Furthermore, it successfully powered 20 LED lights connected in series, emitting bright light for 10 min, underscoring its robust electrochemical performance.