High-Strength and Conductive Starch/Poly(vinyl Alcohol) Hydrogel Electrolytes via Synergistic Salting-Out and Solvent Effects for Supercapacitor Applications

Conventional hydrogel electrolytes generally suffer from insufficient mechanical properties, poor low-temperature tolerance, and unsatisfactory recyclability. In this work, a starch-based hydrogel electrolyte (PS-SS) was fabricated by a simple freeze-thaw method using starch, poly(vinyl alcohol), dimethyl sulfoxide (DMSO), and sodium chloride (NaCl) as raw materials via the synergy of salting-out and solvent effect. Benefiting from the synergistic effect of the DMSO/H2O binary solvent and the salting-out effect of NaCl, the obtained PS-SS organohydrogel exhibited excellent overall performance, including elongation at break of 1009.3%, tensile strength of 1.1 MPa, toughness of 5.86 MJ/m3, and ionic conductivity of 5.49 S/m. To evaluate its practical applicability, flexible supercapacitors were assembled using the original and recycled PS-SS hydrogels as electrolytes and activated carbon as electrodes. The device based on the original hydrogel delivered an areal capacitance of 231.96 mF/cm2 at a current density of 1 mA/cm2 and retained 87.8% of its initial capacitance after 5000 charge−discharge cycles. The utilization of the recycled hydrogel electrolyte enables the supercapacitor to exhibit a superior areal capacitance of 181.34 mF/cm2 and a Coulombic efficiency of 81.96% at 1 mA/cm2. In summary, this work presents a generalizable strategy for preparing high-performance starch-based organohydrogels via the synergistic integration of salting-out and solvent effects.