One-pot method for in situ synthesis of triple cross-linked hydrogel electrolytes for flexible supercapacitors with high mechanical and electrochemical properties

Hydrogel electrolytes are widely used in quasi-solid-state supercapacitors due to their unique flexibility and safety. However, achieving high stretchability and ionic conductivity simultaneously by a simple and effective method remains a great challenge. Herein, triple cross-linked hydrogel electrolytes are prepared by a feasible and maneuverable one-pot in situ synthesis method. This strategy forms a polyacrylamide-hydroxypropyl chitosan hydrogel electrolyte with excellent mechanical and electrochemical properties through chemical cross-linking, hydrogen bonding cross-linking and electrostatic interactions. The optimal hydrogel electrolyte exhibits high tensile strength (0.494 MPa) and ionic conductivity (65 mS/cm). The assembled supercapacitor possesses a high specific capacitance of 224.67 F/g at 1 mA/cm2. Remarkably, after 10,000 cycles of charge and discharge tests, the supercapacitor retains capacitance at a rate of 84.85 %. Moreover, the prepared supercapacitors still maintain good electrochemical properties under a certain degree of folding and pressure, indicating that polyacrylamide-hydroxypropyl chitosan hydrogels show superior prospects as electrolytes in flexible supercapacitors. This work has certain guiding significance for the simple design and development of one-pot method for in situ synthesis of triple cross-linked hydrogels, and further lays the foundation for the application of hydrogel electrolytes in flexible energy storage devices.