Fig. 5. Aqueous supercapacitor composed of AC electrodes and three-layered hydrogel electrolyte.

a Schematic of fabricating three-layered hydrogel electrolyte. b Photograph and cross-sectional SEM image of the three-layered hydrogel. c Cyclic voltammetry (CV) curves at different scan rates. d Galvanostatic charge-discharge (GCD) curves at different current densities. e Capacitance retention during 1000 charge-discharge cycles at a current density of 1 mA cm⁻², showing stable cycle performance.