Rapid microwave-assisted fabrication of 3D cauliflower-like NiCo2S4 architectures for asymmetric supercapacitors

Abstract

In this study, 3D cauliflower-like NiCo₂S₄ architectures have been synthesized through a facile, one-step and template-free microwave method. The cauliflower-like NiCo₂S₄ materials are made up of 3D microstructures with an average diameter of around 600 nm and each nanostructure is found to be constructed of many intertwined nanoparticles. The NiCo₂S₄-modified electrode was successfully applied to a pseudocapacitor. The electrochemical performance of the NiCo₂S₄ material was studied by cyclic voltammetry, galvanostatic charge–discharge and electrical impedance spectroscopy. The 3D cauliflower-like NiCo₂S₄ materials exhibit a maximum capacitance of 1471 F g⁻¹ at 1 A g⁻¹ and also show remarkable rate capability and prominent cycling stability. To improve the energy density of the supercapacitor, a NiCo₂S₄-modified electrode and activated carbon-modified electrode were used to assemble an asymmetric capacitor. The asymmetric capacitor demonstrates remarkable properties with a maximum energy density of 44.8 W h kg⁻¹ and a maximum power density of 16.0 kW kg⁻¹. Furthermore, two capacitors assembled together can successfully light up a red light-emitting diode (LED) and last for more than 10 min. The excellent capacitance performance demonstrates that the cauliflower-like NiCo₂S₄ has potential applications in supercapacitors.