Highly porous carbonaceous aerogel for symmetric supercapacitor with dual-redox active electrolyte revealing high performance pseudo-capacitance

Abstract

Due to the increasing global energy demand, there is an urgent need for more efficient energy storage systems. Redox-active electrolytes offer a promising, long-term solution for high-energy-density supercapacitors, as they enhance energy density and pseudo-capacitance through redox reactions. This study introduces a symmetric supercapacitor utilizing a dual redox-active electrolyte, achieving the highest levels of pseudo-capacitance and energy density with a biomass-derived carbonaceous aerogel (BCA) electrode. The BCA electrode's unique flower-like cubic-sphere structure, partially graphitized edges, and high specific surface area of around 1299 m²g⁻¹ enable efficient access for electrolyte ions, enhancing charge storage. The dual-redox electrolyte, comprising KBr and methyl Viologen dichloride (MVCl2), enhances the performance of both electrodes through redox reactions, resulting in a maximum half-cell specific capacitance of about 887 Fg⁻¹ at 1 Ag⁻¹ current density. When incorporated into a supercapacitor device, this dual-redox-electrolyte system achieves a maximum specific capacitance of 560 Fg⁻¹ and an energy density of approximately 77 WhKg⁻¹ at the same 1 Ag⁻¹ current density, with outstanding capacitance retention of approximately 93% over 10,000 charge-discharge cycles. Thus, the combination of KBr and MVCl2 in the KOH electrolyte, as demonstrated in this work, enhances redox behaviour, leading to significantly more efficient energy storage solutions.