Charge transport and electrochemical enhancement in fish skin gelatin–chitosan polymer blend electrolytes for biocompatible energy storage applications

Abstract This study presents the development of a novel solid polymer electrolyte system based on fish skin gelatin (FG) and chitosan (CS) as polymer hosts, impregnated with ammonium nitrate (NH 4 NO 3 ) using the solvent casting method. The incorporation of NH 4 NO 3 significantly enhances ion dissociation and facilitates proton conduction within the polymer matrix. Fourier transform infrared spectroscopy confirms strong interactions between NH 4 + ions and functional groups of the polymer blend, indicating successful complexation. The optimized composition, CHFs_40 (40 wt. % NH 4 NO 3 ), exhibits a high ionic conductivity of (1.62 ± 0.33) × 10 −3 S cm −1 , along with the lowest degree of crystallinity (10.03%) and a dominant ionic transference number of 0.96. Morphological analysis reveals an increase in amorphous regions, which promotes efficient ion transport. The temperature-dependent conductivity follows Arrhenius behavior, proving a thermally activated hopping mechanism. Linear sweep voltammetry establishes a stable electrochemical window of 2.5 V for CHFs_40. The fabricated electrical double layer capacitor utilizing the CHFs_40 electrolyte delivers outstanding specific capacitances ( C sp ) values of 76.28 F g −1 (cyclic voltammetry) and 112.77 F g −1 (galvanostatic charge discharge), along with stable cycling stability. These findings highlight the potential of the FG-CS-NH 4 NO 3 system, as a sustainable and efficient electrolyte for next-generation energy storage applications.