High-performance metal oxide nanoparticle materials synthesised using polar aprotic solvents for advanced supercapacitor applications

Abstract

We report on a newly developed, surfactant free and scalable methodology for the synthesis of spherical nanoparticles of nickel hydroxide [Ni(OH)₂] and nickel oxide (NiO), employing the polar, aprotic solvent, dimethylformamide (DMF), and evaluate their potential for electrochemical battery-type supercapacitor applications. The material synthesis methodology was extended to the hybrid nanomaterial nickel hydroxide-manganese dioxide [Ni(OH)₂–MnO₂] and, with the addition of SDBS, manganese dioxide (MnO₂) nanoparticles. The resulting nanostructured materials were comprehensively characterised by various structural, morphological, and thermal techniques. Of all electrode materials investigated in three-electrode configuration, surfactant free NiO and α-Ni(OH)₂–MnO₂ exhibit the highest specific capacities with values of 312.42 mAh g⁻¹ and 348.61 mAh g⁻¹ at a current density of 1 A g⁻¹, respectively. In symmetric devices, where surfactant free NiO and α-Ni(OH)₂–MnO₂ were employed as the active layers, specific capacities of 94.31 mAh g⁻¹ and 139.43 mAh g⁻¹ at a current density of 1 A g⁻¹ and energy densities of 47.21 Wh kg⁻¹ and 69.72 Wh kg⁻¹ at a power density of 1 kW kg⁻¹ respectively have been measured. The devices have a maximum capacity retention of 86.50% and 90.18% after 5000 charge–discharge cycles at 3 A g⁻¹ demonstrating that they also possess high cycle stability. These results confirm the viability of the rational design methodology employed here for the surfactant free synthesis of electrode materials for deployment in energy storage applications.