Rationally designed spider web-like trivanadium heptaoxide nanowires on carbon cloth as a new class of pseudocapacitive electrode for symmetric supercapacitors with high energy density and ultra-long cyclic stability

The design and construction of one-dimensional (1D) nanostructures on flexible electrodes without the use of polymer binders/conductive additives has shown great potential for engineering improved electrochemical properties in supercapacitors. Herein, a facile in situ hydrothermal technique was adopted for the growth of trivanadium heptaoxide nanowires on carbon fiber cloth (V₃O₇/CFC). The resultant V₃O₇ sample displayed the self-accumulated growth of nanowires on CFC after 48 h with a spider web-like morphology. The specially designed binder-free V₃O₇/CFC was used to fabricate a symmetric supercapacitor in aqueous 1 M Na₂SO₄ electrolyte, which showed excellent electrochemical performance. Specifically, in the half-cell configuration, the device exhibited a maximum specific capacitance (C_sp) of 198 F g^-1 at 1 A g^-1 and in full-cell configuration, it showed a C_sp of 151 F g^-1 at the same current density with ultra-high cycling stability of ∼97% (after 100000 cycles). In addition, the performance of the symmetric device in 1 M 1-ethyl-3-methylimidazolium trifluoromethanesulfonate electrolyte was studied and it showed a wide potential window of 2 V with a maximum C_sp of 178 F g^-1. Furthermore, the device exhibited high energy and power densities of 24.7 W h kg^-1 (48.5 mW h cm^-2) and 5.13 kW kg^-1 (10.05 W cm^-2), representing as a viable electrode in ionic liquid electrolyte.