Unrevealed Performance of NH4VO3 as a Redox-Additive for Augmenting the Energy Density of a Supercapacitor

Herein, we have used ammonium vanadate (NH4VO3) as a redox-additive for the first time to boost the energy density of a flexible supercapacitor. Surprisingly, a significant enhancement in the specific capacitance (Csp) is attained after the addition of NH4VO3 with H2SO4 (658 F g–1) when compared with H2SO4 (375 F g–1). In addition, the energy density conquered with NH4VO3/H2SO4 (32 Wh kg–1) is 4.5-fold greater than H2SO4 electrolyte at 3 A g–1 (7 Wh kg–1). Moreover, the flexible solid-state supercapacitor (FSSC) device with ammonium vanadate/poly(vinyl alcohol)/sulfuric acid (NH4VO3/PVA/H2SO4) gel electrolyte shows a better electrochemical performance while compared with PVA/H2SO4. The electrochemical performance of the working electrode enhanced after the addition of NH4VO3 with conventional H2SO4 due to the redox reaction between the VO3– and H+ ions.