Redox Active\nLignosulfonate Functionalized Polyaniline-Based\nHydrogel Electrodes for Wide Temperature Tolerant Flexible Supercapacitors

Electrically conductive hydrogel electrodes with high\nelectrochemical\nactivity are crucial for flexible supercapacitors. However, the sluggish\nelectrochemical performance caused by the cold temperature still hinders\ntheir practical applications. Herein, we use ligninsulfonate sodium\n(LS) as a template to prepare a highly conductive polyaniline (PANI)-based\nelectrode material, which is then incorporated into a chitosan (CS)/PAAM\ndouble-network scaffold to form an LS-PANI/CS/PAAM hydrogel. The as-prepared\nhydrogel not only exhibits excellent mechanical flexibility but also\npossesses antifreezing and antidrying properties due to the participation\nof the H<sub>3</sub>PO<sub>4</sub> electrolyte. As a proof, the assembled\nLS-PANI/CS/PAAM supercapacitor achieves a superb-specific capacitance\nof 891 mF/cm<sup>2</sup>, an outstanding energy density of 65.9 μWh/cm<sup>2</sup>, and a wide working temperature window from −30 to\n90 °C. In addition, the device showed efficient photothermal-stimulated\nself-heating ability, which could realize solar-thermal conversion\ncapacitance enhancement. In the presence of 0.8 W/cm<sup>2</sup> solar\nillumination, the device exhibits a considerable specific capacitance\nof 681 mF/cm<sup>2</sup> at −30 °C, corresponding to a\n30.2% improvement over the capacitance without solar illumination.\nIn addition, the energy density of 60.5 μWh/cm<sup>2</sup> is\ndelivered at −30 °C, which is superior to that of most\nhydrogel SCs. Therefore, by developing a photothermal supercapacitor\nusing solar energy sources, it is possible to mitigate the capacitance\ndecay under low-temperature environmental conditions.