Ammonium Iodide Doped Methylcellulose-Polyacrylonitrile Blend Based Solid Polymer Electrolytes with Application in Electrochemical Double Layer Capacitor

Solid polymer electrolytes (SPEs) are considered promising candidates for all-solid-state energy storage devices. Despite ongoing advancements, achieving optimal electrochemical performance in SPE-based devices continues to be a critical hurdle. This study investigates the viability of an eco-friendly SPE system using methylcellulose–polyacrylonitrile (MC–PAN) blend host matrix and ammonium iodide (NH4 I) as the doping salt for use in an electrochemical double layer capacitor (EDLC). MC–PAN–NH4 I electrolytes were successfully synthesized using the solution casting technique in which different concentrations of NH4 I were introduced into a MC–PAN blend with a weight ratio of 1:1. Fourier transform infrared spectroscopy (FTIR) analysis demonstrated the interaction between polymer host and NH4I through changes in peak intensities and shifts in peak positions. The semi-crystalline nature of the SPEs was revealed by X- ray diffraction (XRD) analysis. Results from electrochemical impedance spectroscopy (EIS) showed that the maximum conductivity of 1.18 × 10−3 S cm−1 was achieved upon incorporation of 20 wt.% NH4 I. Using the highest conducting electrolyte, an EDLC was assembled, and its performance was analysed using impedance technique. A specific capacitance of 59.70 F g−1 was obtained.