A redox additive gel-polymer electrolyte and vanadium oxide hydrate electrode material for quasi-solid state...

Herein, we prepared layered vanadium oxide hydrate (VOH), a vanadium pentoxide-based electrode material for supercapacitor applications. The VOH electrode showed a specific capacity of 77.6 C g^-1 at 4 A g^-1 in a 3 M KOH electrolyte solution. Furthermore, the enhancement of the electrochemical performance of the VOH was achieved by adding K₃[Fe(CN)₆] to the electrolyte as a redox additive. Among the various concentrations, the VOH electrode showed a specific capacity of 1085.9 C g^-1 at 4 A g^-1 in a 3 M KOH containing 75 mM K₃[Fe(CN)₆] electrolyte. The performance enhancement was attributed to the eased diffusion of ferricyanide species into the hydrated, enlarged interlayer structure of the active material. Additionally, the [Fe(CN)₆]^3-/[Fe(CN)₆]^4- redox pair contributed to the charge-storing process through reversible redox reactions in the electrolyte. Moreover, a quasi-solid-state asymmetric supercapacitor was constructed by employing VOH as positive electrode, activated charcoal (AC) as negative electrode, and PVA/KOH/K₃[Fe(CN)₆] as gel-polymer electrolyte (GPE). The constructed device displayed a specific capacity of 105.2 C g^-1 at 1 A g^-1 and delivered a maximum energy density of 24.8 Wh kg^-1 at 850 W kg^-1 power density with a cell voltage of 1.7 V. The outcomes of this work suggest a viable strategy for the rational design of next-generation high-performance energy storage systems.