Cellulose Acetate-based magnesium ion conducting plasticized polymer membranes for EDLC application: Advancement in biopolymer energy storage devices

Abstract

The growing demand for environmentally friendly materials in energy storage has led to a significant focus on using biopolymer membranes derived from renewable resources. This study focuses on creating eco-friendly biopolymer electrolytes for Electric Double Layer Capacitors (EDLC) by blending Magnesium trifluoromethanesulfonate (Mg(CF3SO3)2) with Cellulose Acetate (CA) through a solution casting method. To enhance performance, plasticized membranes were developed using nontoxic Poly(ethylene glycol) (PEG) as a plasticizer. The addition of PEG reduced membrane crystallinity, as shown by X-ray diffraction (XRD). Fourier Transform Infrared (FTIR) spectroscopy indicated complexation among electrolyte constituents. The optimal composition, containing 25 wt% PEG, exhibited the highest ion conductivity (3.76 × 10−4 S/cm) according to Electrochemical Impedance Spectroscopy (EIS). EIS data allowed determination of important ion transport parameters, such as Diffusion Coefficient, Ionic Mobility, and Carrier Density. The EDLC device showed a Specific Capacitance (Csp) of 13.14 F/g at a scan rate of 5 mV/s, with excellent stability (3.2 V) in Linear Sweep Voltammetry (LSV). Cyclic Voltammetry (CV) and Galvanostatic Charge Discharge (GCD) tests confirmed no redox processes, yielding a Csp of 12.94 F/g at 0.1 A/g. The EDLC device demonstrated exceptional cyclic stability, high coulombic efficiency, and maintained consistent results in terms of Power Density (Pd) and Energy Density (Ed) over 1000 cycles. Incorporating PEG into biopolymer membranes enhances the electrochemical energy storage of EDLC devices, contributing to sustainable energy storage solutions.