Redox Active Lignosulfonate Functionalized Polyaniline-Based Hydrogel Electrodes for Wide Temperature Tolerant Flexible Supercapacitors

Electrically conductive hydrogel electrodes with high electrochemical activity are crucial for flexible supercapacitors. However, the sluggish electrochemical performance caused by the cold temperature still hinders their practical applications. Herein, we use ligninsulfonate sodium (LS) as a template to prepare a highly conductive polyaniline (PANI)-based electrode material, which is then incorporated into a chitosan (CS)/PAAM double-network scaffold to form an LS-PANI/CS/PAAM hydrogel. The as-prepared hydrogel not only exhibits excellent mechanical flexibility but also possesses antifreezing and antidrying properties due to the participation of the H3PO4 electrolyte. As a proof, the assembled LS-PANI/CS/PAAM supercapacitor achieves a superb-specific capacitance of 891 mF/cm2, an outstanding energy density of 65.9 μWh/cm2, and a wide working temperature window from −30 to 90 °C. In addition, the device showed efficient photothermal-stimulated self-heating ability, which could realize solar-thermal conversion capacitance enhancement. In the presence of 0.8 W/cm2 solar illumination, the device exhibits a considerable specific capacitance of 681 mF/cm2 at −30 °C, corresponding to a 30.2% improvement over the capacitance without solar illumination. In addition, the energy density of 60.5 μWh/cm2 is delivered at −30 °C, which is superior to that of most hydrogel SCs. Therefore, by developing a photothermal supercapacitor using solar energy sources, it is possible to mitigate the capacitance decay under low-temperature environmental conditions.