Design of Gel Electrolyte Bearing Redox Additive for High-Performance Functional Supercapacitors

In advanced supercapacitor applications, redox-based electrolyte systems, particularly the synergistic potential of benzoquinone, glycerol, and phosphoric acid, plays a crucial role. However, the poor electrochemical stability of these systems limits their practical use. Benzoquinone, known for its high redox activity, was incorporated into glycerol as a stable host-gel matrix and combined with phosphoric acid to produce a high-ion-conductivity electrolyte. In this study high electrochemical stability and improved charge–discharge kinetics of redox-mediated supercapacitors were systematically addressed. The findings highlight the potential of this unique electrolyte system to contribute to the development of high-performance and environmentally friendly energy storage devices for diverse applications. In this regard, a comparative study was conducted on aqueous and nonaqueous glycerol (Gly)/phosphoric acid (P) systems, where benzoquinone (BQ) was introduced as a redox mediator in varying fractions. This research provides valuable insights into the design and optimization of electrolyte compositions for next-generation supercapacitors with enhanced efficiency and sustainability. Furthermore, the devices assembled with Gly3P50BQ exhibited a high specific energy of 48 Wh kg⁻¹ at 150 W kg⁻¹ and demonstrated a superior capacitance retention rate of 95% after 10,000 charge–discharge cycles.