Design of plasticized proton conducting Chitosan:Dextran based biopolymer blend electrolytes for EDLC application: Structural, impedance and electrochemical studies

Abstract

In this work, for the use of an electrical double-layer capacitor (EDLC) device applications, the fabrication and characterization of solid polymer electrolytes (SPEs) based on chitosan-dextran (CS-DN) blended polymer doped and plasticized with ammonium thiocyanate (NH 4 SCN) and glycerol are studied, respectively. The Fourier transform infrared (FTIR) spectroscopy method has been used to investigate the structural behavior of electrolytes. It was observed that the FTIR bands are shifted and decreased in their intensities with the increased glycerol plasticizer content and it results in the complex formation. According to the electrical impedance spectra (EIS), the electrolyte incorporated with high contents of plasticizer (42 wt%) revealed the highest ionic conductivity of (3.08 × 10 −4 S/cm). The electrical equivalent circuits (EEC) were used to investigate the circuit elements of the electrolytes further. Increasing glycerol plasticizers verified an improvement in ions density number (n), mobility (μ), and diffusion coefficient (D). The transference number measurements (TNM) indicated that the predominant charge carriers in the conduction process are ions where the ( t ion ) is 0.95. According to the linear sweep voltammetry (LSV) study, the uppermost conducting sample was found to have sufficient anode stability with a breakdown voltage of 1.9 V that can be used in electrochemical devices. The absence of peaks in the cyclic voltammetry (CV) demonstrated that the charge storage mechanism within the constructed EDLC is fully capacitive. Based on this finding, the starting specific capacitance ( C s ), energy density ( E d ), and power density ( P d ) have been identified to be 118F/g, 13.2 Wh/kg, and 1560 W/kg, respectively. Throughout its 100 cycles, the equivalence series resistance ESR value was between 53 and 117 Ω.