Towards realistic electrical double layer capacitor device with elevated energy and power densities designed from plasticized nanocomposite PVA-based electrolyte

Abstract The current work establishes a breakthrough for the electrical double-layer capacitor (EDLC) device, utilizing biodegradable polymer and non-toxic salt. In this project, polymer electrolytes (PEs) comprising polyvinyl alcohol (PVA), sodium thiocyanate (NaSCN), glycerol (Gly), and various amounts of TiO2 nanofillers were prepared by solution casting. The electrolyte inserted with 3 wt% TiO2 showed the maximum DC conductivity, reaching 1.86 × 10–3 S/cm. Dielectric analysis revealed a high dielectric constant (8.5 × 106), indicating efficient charge storage. The AC conductivity pattern demonstrated a low-frequency spike and a flat region, emphasizing the direct current (DC) component. Additional tests on the highset conducting electrolyte verified that ion transport was the primary mechanism (tion = 0.976) and that the electrolyte maintained good electrochemical stability around 2.5 V. This electrolyte was subsequently employed in the construction of an EDLC device. The cyclic voltammetry (CV) results revealed a non-Faradaic charge storage process characterized by an almost leaf-like profile. Galvanostatic charge–discharge curves close enough to the ideal shape with minimal voltage drop, reinforcing the device’s excellent performance. The constructed EDLC exhibited strong performance, delivering 138 F/g in capacitance, with an output power of 4000 W/kg and an energy storage capacity of 17.3 Wh/kg. The Ragone plot showed high power and energy densities comparable to lead-acid and Ni–Cd batteries, highlighting its potential for rapid charge–discharge performance. Finally, the limitations of EDLC devices have been discussed.