Reducible, recyclable and reusable (3R) hydrogel electrolyte membrane based on Physical&Chemical Bi-networks and reversible sol-gel transition

Hydrogel electrolytes are attracting growing interest in the various fields, and tremendous efforts have been widely made for enhancing the hydrogel electrolyte of flexible devices. However, conventional hydrogel electrolytes generally contain non-degradable and non-renewable polymer matrix materials, inevitably causing waste of resources and environmental pollution, which fundamentally restricts the utilization of hydrogel electrolyte in the aspect of energy storage device during daily use. In this work, a novel flexible hydrogel electrolyte, that can be reducible, recyclable, and reusable (3R), is fabricated through physical and chemistry double crosslinking among carboxylated chitosan, N-methylol acrylamide, N, N′-methylene bisacrylamide, and potassium persulfate, followed by intense uptake of Li2SO4 electrolyte. The hydrogel electrolyte membrane displays high ionic conductivity of 3.52 × 10−2 S cm−1, and exhibits 348.92% electrolyte uptake., The flexible quasi-solid supercapacitor assembled with the hydrogel electrolyte shows remarkable electrochemical performance like high capacitance retention of 83% and outstanding energy density of 8.74 Wh kg−1. Interestingly, the renewable performance of hydrogel electrolyte membrane is observed when the hydrogel electrolyte membrane suffered from heating to cooling cycle, which allows to easily realize multiple regeneration of electrolyte membrane based on the reversible sol-gel transition. This work provides a promising route to design a hydrogel electrolyte membrane with infinite regeneration times for flexible energy storage devices in the future.