Significance of Redox Additive Electrolyte over Energy and Power Densities of Mixed Metal Vanadate-Based Supercapattery Device

The energy demand of the current era suggests the need for the advancement of smart and efficient energy conversion/storage technologies. Thereby, a BiVO4/FeVO4:rGO nanocomposite-based supercapattery device was fabricated, and its electrochemical performances were reported. A BiVO4/FeVO4:rGO nanocomposite was synthesized through a hydrothermal route. The synthesized samples were characterized using XRD, FT-IR, Raman, UV, SEM, and HR-TEM analyses to study their structural, functional, optical, and morphological characteristics, respectively. In a three-electrode setup, the electrochemical properties of the produced samples were investigated using 1 M KOH and 0.1 M K4[Fe(CN)6] mixed with 1 M KOH redox additive electrolytes, respectively. With the redox additive electrolyte, a maximum specific capacitance of 1343.6 F g-1 was achieved for the BiVO4/ FeVO4:rGO nanocomposite-modified working electrode. Further, the supercapattery device was fabricated by assembling a BiVO4/FeVO4:rGO-modified working electrode as the cathode and rGO deposited Ni foam as an anode in an asymmetrical cell configuration. The supercapattery device performance was also tested in pure and redox-additive-based KOH electrolytes, similar to the three-electrode system. The fabricated device exhibited a maximum energy density and power density of 29.7 W h kg-1 and 3780 W kg-1, respectively, in 1 M KOH electrolyte. The energy and power densities were improved to 70.5 W h kg-1 and 6300 W kg-1, respectively, by the inclusion of 0.1 M K4[Fe(CN)6] in 1 M KOH.