Evolution of α-V2O5 into electrochemically transformed NaV3O8 structure: Structural changes and supercapacitor application

Abstract

Nowadays, cost-effective and environmentally friendly supercapacitors (SCs) with high energy and power densities are gaining significant research attention since they could broaden the application of capacitors. The present study demonstrates a low-cost green synthesis technique to prepare the α-V2O5 phase using Aloe Vera leaf extract. X-ray diffraction technique confirmed the formation of the orthorhombic α-V2O5 phase. The prepared α-V2O5 was employed as an electrode material for SC application. During an electrochemical cyclic voltammetry test in Na2SO4 electrolyte, Na+ ions intercalation and de-intercalation processes resulted in a phase transformation of α-V2O5 to NaV3O8. Structural transformation (i.e., orthorhombic to monoclinic crystal structure) and morphological changes were also observed during the electrochemical phase conversion process. This electrochemical phase transformation process improved the overall supercapacitive performance of the α-V2O5 material. Such electrochemically converted NaV3O8 displayed a maximum specific capacitance of 640.1 F g−1 at 0.5 A g−1 with a long cyclic stability. Furthermore, the AC // NaV3O8 asymmetric SC coin cell device delivered a maximum energy density of 62.6 Wh kg−1 and a power density of 7.3 kW kg−1 along with an excellent cycling stability of ∼81 % over 5000 GCD cycles.