Non-aqueous quasi-solid electrolyte for use in supercapacitors

Gel electrolytes have attracted increasing attention for use in supercapacitors. An ideal gel electrolyte usually solves several problems, including electrolyte leakage, corrosion of the liquid electrolyte, and electrolyte packing. In this study, to address these issues, tetraethylammonium tetrafluoroborate in propylene carbonate was integrated into a poly(ethylene glycol) dimethacrylate polymer matrix with azobisisobutyronitrile as a thermal initiator. The specific capacitance of this quasi-solid electrolyte was 22% higher than that of the corresponding liquid-based electrolyte at 1 mA cm⁻². Further, a supercapacitor wrapped with the quasi-solid electrolyte exhibited energy and power densities of 39 Wh kg⁻¹ and 2.5 kW kg⁻¹, respectively. Notably, the quasi-solid-electrolyte-based supercapacitor was very stable when cycled at a high current density (5 mA cm⁻²), with only 31% of its initial capacitance lost after 10,000 cycles. Wrapping the supercapacitor with the non-aqueous quasi-solid electrolyte provided a solidified surface, which reduced contact with moisture and oxygen in the air, thereby solving the evaporation problem encountered with liquid electrolytes.