Comparative Performance of Aqueous and Ionic Liquid-Based Gel Electrolytes in Co(OH)2/rGO-Based Supercapacitor

Abstract

Supercapacitors are known for their highpower density and excellent cycling stability, but their practicality is often hindered by limited energy density and a narrow potential window. Herein, the energy density can be enhanced by modifying the electrode material and the potential window can be expanded through the use of ionic liquid (IL) electrolytes. In the present study, Co(OH)₂/reduced graphene oxide (rGO) (Co-G) nanocomposite electrodes was synthesized using a simple hydrothermal method while IL-based electrolyte was used as an electrolyte for supercapacitor device fabrication. Morphological analysis reveals a porous honeycomb-like nanostructure with a vertical orientation on the rGO sheet. Electrochemical analysis of the samples is conducted to assess electrode performance, with the Co-G electrode achieving a capacitance of 2156 F g⁻¹ at 1 A g⁻¹. This electrode exhibits lower electrochemical resistance than pure Co(OH)₂. The synthesized material's practicality evaluated in an asymmetric device Co-G/C//AC/C using ionic gel and aqueous gel-based electrolytes. IL-based gel electrolyte device demonstrated superior performance, delivering an energy density of 130 Wh kg⁻¹ and a power density of 3860 W kg⁻¹, maintaining 91% capacitance after 5000 charge–discharge cycles, and outperforming the KOH/PVA gel-based device, highlighting the advantages of ionic gel electrolytes.