A self-healable and easily recyclable supramolecular hydrogel electrolyte for flexible supercapacitors

Abstract

Although research on polymer hydrogel electrolytes has achieved great progress, their practical application is restricted due to their vulnerability and non-recyclability problems caused by covalent cross-linking effects. Herein, we report a ferric ion cross-linked supramolecular PAA hydrogel electrolyte (KCl–Fe³⁺/PAA), in which the ionic bond and hydrogen bond endow the KCl–Fe³⁺/PAA hydrogel electrolyte with favorable self-healing ability and easy-recyclability. In addition, considering the eco-friendly and cost effective properties of both ferric ion and polyacrylic acid, there would be great potential for this KCl–Fe³⁺/PAA hydrogel electrolyte to be broadly applied. Meanwhile, the hydrogel electrolyte maintained good mechanical performance (extensibility > 700%, and stress > 400 kPa) and excellent conductivity (0.09 S cm⁻¹), which completely satisfy the demands of flexible supercapacitors. After being assembled with graphene foam supported polypyrrole electrodes, the electrochemical performance of this flexible supercapacitor is comparable to that of its liquid electrolyte counterpart.