High-performance solution-combustion synthesized V2O5/NiO nanocomposites for supercapacitor applications: comparative electrochemical evaluation

Abstract

Vanadium pentoxide (V₂O₅), nickel oxide (NiO), and V₂O₅/NiO nanocomposites (NCs) with molar ratios of 1 : 0.5, 1 : 1, and 1 : 1.5 were synthesized by a solution-combustion (SC) method and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and X-ray photoelectron spectroscopy (XPS). Electrochemical properties were examined in a 1 M KOH electrolyte through cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge–discharge (GCD) using two electrode types: a carbon-paste electrode (CPE) and a nickel-foam electrode (NFE). Among all compositions, the V₂O₅/NiO (1 : 1) NC delivered the highest specific capacitance, achieving 2367 F g⁻¹ on the CPE and 1177 F g⁻¹ on the NFE at 10 mV s⁻¹, with low charge-transfer resistance and excellent cycling stability. The CPE, prepared with 70% graphite powder, 15% V₂O₅/NiO nanocomposite powder and 15% silicone oil, provides a three-dimensional porous architecture that allows a greater fraction of electrochemically active material to participate compared to the NFE. This architecture enhances ion diffusion, electron transport, and rate capability, demonstrating that V₂O₅/NiO NCs on a CPE offer a practical pathway to high-energy-density supercapacitors.