Lignosulfonate sodium assisted PEDOT-based all-gel supercapacitors with enhanced supercapacitance and wide temperature tolerance

Conducting polymer hydrogels are typically employed in all-gel supercapacitors; however, Poly[3,4-ethylene-dioxythiophene] (PEDOT)-based hydrogel supercapacitors still suffer from low capacitance because of the low packing density of PEDOT in the electrodes. Here, we demonstrate lignosulfonate sodium (LS) as an excellent template to synthesize various LS-PEDOT conductive nanofillers for high mass-loading LS-PEDOT/PAAM hydrogel electrodes. Then, the optimum LS-PEDOT/PAAM electrode was assembled with a redox-active LS/PAAM/Fe hydrogel electrolyte to form sandwich-structured all-gel supercapacitors, which could deliver a high specific capacitance of 672.5 mF/cm and an energy efficiency of 60 μWh/cm , which are three times higher than the 220 mF/cm and 19.5 μWh/cm of the device without Fe at the same condition. Such a device shows excellent temperature tolerance from -30 to 100 °C. Besides, the LS-PEDOT/PAAM electrode has excellent photothermal conversion effects under simulated solar illumination. The sluggish electrochemical performance of the SC under low temperatures could be significantly boosted by ~50 % under simulated solar light. All of these findings demonstrate that the capacitance performance of the PEDOT-based hydrogel device is successfully improved not only at room temperature but also under subzero conditions.