Design of high‐performance flexible symmetric supercapacitors energized by redox‐mediated hydrogels including metal‐doped acidic polyelectrolyte

The fabrication of flexible supercapacitors was achieved by employing the novel redox-activated polymer electrolytes comprising poly(vinylphosphonic acid) (PVPA) and nickel nitrate Ni(NO3)2, Ni. The hydrogels, PVPA/NiX, were produced in various contents, in which X denotes the doping fraction of Ni in PVPA. The structure, thermal, and morphology of the materials were characterized, and then they were applied for construction of supercapacitors. The performance evaluations of the fabricated devices were carried out by electrochemical impedance spectroscopy, galvanostatic charge-discharge, and cyclic voltammetry experiments. Flexible supercapacitor devices assembled with activated carbon (AC) electrodes and PVPA/NiX hydrogels produced 793 F g−1 specific capacitance with 30 times enhanced capacitance compared with Ni-free system. The energy density of 103.1 Wh kg−1 was yielded from the device at a power density of 500 W kg−1. The supercapacitor demonstrated an excellent performance during 5.000 charge-discharge cycles, while preserving 84% of its initial capacitance. The supercapacitor constructed of 1 × 5 cm dimension, successfully operates the LED after charging at 3 V.