A redox-active dual-network hydrogel electrolyte for flexible supercapacitor

In recent years, the research focus of flexible supercapacitor is to improve its energy density. The recently reported improved energy storage method is to introducing suitable redox-additive in gel electrolytes to enhance their redox-activity. Herein, a novel stretchable, redox-active and double-network 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxy-containing polyacrylamide/alginate/H2SO4 (PAM/SA/H2SO4/TEMPOL) hydrogel electrolyte is prepared by radical cross-linking polymerization and solvent displacement process. The PAM/SA/H2SO4/TEMPOL hydrogel possesses superior stretchability (750 %) because of the electrostatic interactions between the -NH3+ groups of the PAM and the -COO− groups of SA. In addition, the introduction of the TEMPOL additive into PAM/SA/H2SO4/TEMPOL hydrogel electrolyte of flexible EDLC can gain a high specific capacitance (386 F g−1) and high energy density of 24.5 Wh kg−1, which is due to dual redox reactions both positive/negative electrode. This study provides a new strategy for designing a multifunctional redox hydrogel electrolyte. [Display omitted] •A novel redox-active double-network hydrogel electrolyte (PAM/SA/H2SO4/TEMPOL) is designed.•The double-network hydrogel had better tensile properties than the single-network hydrogel.•Excellent capacity retention rate under severe bending deformation.•Flexible supercapacitor with redox-active hydrogel electrolyte has good electrochemical performance.