Flexible\nWood Enhanced\nPoly(acrylic acid-co-acrylamide)/Quaternized\nGelatin Hydrogel Electrolytes for High-Energy-Density Supercapacitors

Abstract

Hydrogels with good flexibility and\nstrong hydrophilicity\ncan be\ncandidates for excellent flexible electrolyte materials. However,\nthe poor structural stability, uncontrollable swelling, and lower\npotential window of hydrogel electrolytes need to be improved. This\nwork combined quaternized gelatin with cross-linked poly­(acrylic acid-co-acrylamide)\nto form a semi-interpenetrating network and gelatinized in situ in\na flexible porous wood skeleton. The flexible wood (FW) skeleton enhances\nthe hydrogel and limits the swelling of the hydrogel. In addition,\nquaternary ammonium groups and FW act synergistically to provide the\ncomposite hydrogel electrolyte with a high ionic conductivity of 5.57\n× 10^–2 S cm^–1. The composite\nhydrogel electrolyte can enable the flexible supercapacitor to operate\nsafely in a potential window of 0–2 V. The optimized supercapacitor\nhas a high specific capacitance of 286.74 F g^–1 and\nprovides an outstanding energy density of 39.09 W h kg^–1. The flexible supercapacitor shows a capacitance retention of up\nto 94.6% after 10,000 charge–discharge cycles, indicating dramatic\ncycling stability. Simultaneously, a capacitance retention of nearly\n90% can be maintained by the flexible supercapacitor after 180°\nbends for 1000 times. A viable idea for developing high-performance\nhydrogel electrolytes and flexible supercapacitors is provided in\nthis research.