All-natural hydrogel electrolytes prepared by a universal strategy for supercapacitors

Abstract

A traditional method for preparing a gel electrode membrane is generally free radical polymerization or chemical cross-linking, which inevitably introduces toxic substances. In this work, an all-natural gel electrolyte membrane is prepared by condensing chitosan, sodium carboxymethyl cellulose, and tannic acid through a simple two-step method to achieve physical cross-linking through hydrogen bonding interactions. The hydrogel electrolyte membrane displays excellent mechanical properties with a strength of 2.8 MPa and an elongation of 35%, and a high ionic conductivity of 1.43 × 10⁻² S cm⁻¹; the flexible supercapacitor shows good electrochemical performance with a capacitance retention of 84% and an energy density of 14.29 Wh kg⁻¹. Interestingly, based on the principle of sol–gel interaction, the electrochemical performance of the regenerated hydrogel electrolyte membrane remains stable, and the preparation method has also been proved to be a strategy universal to other natural polymer materials that contain the same functional groups.