Proton conducting Cicer arietinum L starch electrolyte doped with NH4SCN for electrochemical double layer capacitors

Abstract A chickpea starch–agar biopolymer electrolyte plasticized with glycerol and doped with NH 4 SCN was successfully developed for symmetric electrochemical double-layer capacitor (EDLC) applications. FTIR confirmed the interaction between NH 4 SCN and the biopolymer matrix, while XRD revealed increasing amorphous character with salt addition. The optimized CSA5 electrolyte exhibited a maximum ionic conductivity of 1.1 × 10 − 3 S cm −1 , a low bulk resistance of 43.60 Ω, an ionic transference number of 0.89, an electrochemical stability window of 1.8 V, and good thermal stability. The EDLC exhibited a specific capacitance of 40.0 F g −1 at 5 mV s −1 from CV, decreasing to 3.9 F g −1 at 70 mV s −1 . From GCD measurements, the specific capacitance decreased from 42.14 F g −1 at 0.15 mA to 21.28 F g −1 at 0.25 mA. The corresponding energy density decreased from 5.85 to 2.95 Wh kg −1 , while the power density increased from approximately 375–625 W kg −1 . The rate-dependent capacitance indicates limitations in ion transport and electrode/electrolyte interfacial accessibility at higher scan and current rates. Overall, the CSA5 electrolyte demonstrates the basic electrochemical functionality required for solid-state EDLC applications and provides a preliminary assessment of its energy-storage potential.