Tough, Freeze-Resistant, Pressure-Response Gel Polymer Electrolytes with Redox Pairs for Flexible Supercapacitors

Gel polymer electrolytes are an indispensable part of flexible supercapacitors, since their various characteristics determine the device performance. Here, a composite gel electrolyte (FLPS) mainly consisting of polyvinyl alcohol (PVA), sodium alginate (SA), K₃Fe(CN)₆/K₄Fe(CN)₆, and LiCl is rationally designed, in which PVA and SA form a robust three-dimensional network, the redox pair of K₃Fe(CN)₆/K₄Fe(CN)₆ serves as a cross-linking agent with SA and even donates the oxidation-reduction reaction from the Fe³⁺/Fe²⁺ couple with additional capacitance for the device, and LiCl functions as an ion carrier and a water-retaining salt to improve the long-term stability of FLPS. Thus, the FLPS-based supercapacitor exhibits superior electrochemical characteristics, displaying impressive pseudocapacitance across all current densities and excellent cycling stability (∼99.07% of capacitance retention after 10,000 cycles). Moreover, the FLPS-based supercapacitor demonstrates great low-temperature working ability and pressure responsiveness, suggesting its freeze-resistance, flexibility, and pressure sensing potential. This work provides a promising strategy for preparing tough gel polymer electrolytes with both ion transfer and charge storage ability.