Solid-State\nDouble-Network Hydrogel Redox Electrolytes\nfor High-Performance Flexible Supercapacitors

Abstract

Flexible\nsupercapacitors have great potential applications in wearable\nand portable electronics, but their practical applications were limited\ndue to the low energy density and mechanical flexibility of solid-state\nelectrolytes used for the construction of flexible supercapacitors.\nIn this study, we first report the solid-state double-network (DN)\nhydrogel electrolytes (HEs) incorporated with Na₂MoO₄ redox additives. It is found that the solid-state DN HEs\nwith Na₂MoO₄ redox additives exhibit high electrochemical\nperformance, excellent mechanical properties, and fast self-recovery\nfeatures. We then demonstrate novel symmetric supercapacitors (SSCs)\nincorporated with the solid-state Na₂MoO₄ DN\nHEs and the active carbon cloths as the electrodes. The SSCs exhibit\na specific capacitance of 84 mF/cm² at a current density\nof 1 mA/cm² and an energy density of 70 μWh/cm² at a power density of 3800 μWh/cm². Moreover,\nthe SSCs retain approximately 80% capacitance retention after 7000\ncharge/discharge cycles, which indicates that the SSCs possess excellent\nflexibility and stability. All of these results demonstrate that the\nSSCs incorporated with the solid-state Na₂MoO₄ DN HEs as energy-storage devices have great practical applications\nin wearable and portable electronics.