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/H 2 SO 4 (PAM/SA/H 2 SO 4 /TEMPOL) hydrogel electrolyte is prepared by radical cross-linking polymerization and solvent displacement process. The PAM/SA/H 2 SO 4 /TEMPOL hydrogel possesses superior stretchability (750 %) because of the electrostatic interactions between the -NH 3+ groups of the PAM and the -COO − groups of SA . In addition, the introduction of the TEMPOL additive into PAM/SA/H 2 SO 4 /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.