Eco-Friendly Mof-199/Phytagel Composite Solid Polymer Electrolytes for Supercapacitors

Conventional liquid electrolytes in energy storage devices pose leakage and safety risks, driving interest in solid polymer electrolytes as safer alternatives. In this work, a flexible composite solid polymer electrolyte (CSPE) was developed using MOF-199 and the natural biopolymer phytagel, with NaCl as the Na⁺ source and glycerol as a plasticizer to enhance ionic mobility. Fourier transform infrared confirmed chemical interactions within the composite, while PXRD verified its crystallinity and structural integrity. Field-emission scanning electron microscopy images showed a uniform dispersion of metal-organic framework particles throughout the polymer matrix. The optimized CSPE achieved an ionic conductivity of 2.31 × 10^-4 S cm^-1 at room temperature. Electrochemical testing demonstrated excellent performance: cyclic voltammetry yielded specific capacitances of 139 F g^-1 at 1 mV s^-1 and 69 F g^-1 at 5 mV s^-1, indicating efficient ion transport and charge storage. Galvanostatic charge-discharge measurements further confirmed a stable capacitance of 38 F g^-1 at 0.1 A g^-1. The CSPE also exhibited good cycling durability, maintaining ∼89% coulombic efficiency over 1000 cycles, with a low equivalent series resistance (∼70 Ω) even at the final cycle. Overall, these findings highlight the CSPE as a promising, eco-friendly, and scalable electrolyte platform for next-generation energy storage technologies, including batteries, supercapacitors, and fuel cells.