Flexible\nHigh-Energy-Density Hybrid Supercapacitors\nwith Alkaline Hydrogel Electrolytes

Abstract

Ionic\nhydrogel electrolyte supercapacitors are the next-generation\nflexible wearable devices for energy storage, which have superb conductivity\nand mechanical performance, thus arousing great attention. However,\nexisting hydrogel electrolyte supercapacitors exhibit obvious limitations\nin electrochemical performance (e.g., narrow working voltage range,\nlow power density and energy density, and unstable cycle life at high\ncurrent density). In this work, an alkaline ionic conductive hydrogel\n(PEGMA) was prepared by copolymerization of acrylamide (AM), ethylene\nglycol methyl ether acrylate (MEA), and poly­(ethylene glycol) methyl\nether acrylate (PEGA), and potassium hydroxide (KOH) was selected\nas a conductive substance to form hydrogel electrolytes that could\nbe used in flexible hybrid supercapacitors. The assembled supercapacitor\n(PEGMA-ZHS) exhibited superb electrochemical properties, such as a\nhigh energy density (356.6 Wh kg^–1) at 2647.4 W\nkg^–1 powder density and a wide (0.2–2.0 V)\noperating voltage range and high stability with a capacity retention\nof nearly 100% after charging/discharging for 10,000 cycles at 10\nA g^–1 current density. The strategy would make progress\nin exploring hydrogel-based flexible supercapacitors with excellent\nelectrochemical performance for electronic devices.