A genipin-crosslinked chitosan hydrogel as a quasi-solid-state electrolyte for sustainable electrochemical capacitors

Abstract

Genipin, a naturally occurring bicyclic molecule, was utilized as a non-toxic alternative to dialdehyde-based crosslinkers for synthesizing a chitosan-based quasi-solid-state electrolyte (QSSE) tailored for supercapacitors. The crosslinking process resulted in a uniform matrix, which, upon immersion in a 2 M Li₂SO₄ aqueous solution, formed a long-lasting (up to 96 h) chitosan/genipin (CS/GEN)-QSSE. Electrochemical analysis of an electric double-layer capacitor incorporating CS/GEN-QSSE showed excellent performance, with a specific capacitance of 26 F g⁻¹ for the device (at 1 A g⁻¹, 0–0.8 V), a low series resistance (1.1 Ω), and high energy density (2.19 W h kg⁻¹ at 5 A g⁻¹), surpassing non-crosslinked chitosan gel electrolyte in terms of specific capacitance and rivaling a commercial glass fiber separator in energy density, rate capability, and capacitance retention. These results establish genipin-crosslinked chitosan as a viable alternative to conventional polysaccharide-based materials in electrochemical applications.