Construction of hierarchical NiCo2S4 nanotube@NiMoO4 nanosheet hybrid arrays as advanced battery-type electrodes for hybrid supercapacitors

Abstract

Design and construction of hybrid nanostructures with the desired structure and composition is a promising approach for the development of high-performance hybrid supercapacitors (HSCs). Here, we report the fabrication of NiCo₂S₄@NiMoO₄ nanotube/nanosheet arrays on Ni foam through multi-step hydrothermal processes. Ultrathin and mesoporous NiMoO₄ nanosheets are controllably grown on the surface of NiCo₂S₄ nanotubes. By taking advantage of the good electrical conductivity, high porosity and interconnected features of NiMoO₄ shell nanosheets and the tubular structure of the NiCo₂S₄ core, the optimized hybrid electrode can achieve favourable fast electron transport and ion diffusion kinetics, and delivers a high areal capacity of 673.3 μA h cm⁻² at 5 mA cm⁻² with excellent rate capability (94.6% retention at 100 mA cm⁻²), superior to many reported values of Ni–Co sulfide based electrodes. Furthermore, the HSC devices fabricated by employing NiCo₂S₄@NiMoO₄ and activated carbon (AC) as the cathode and anode, respectively, exhibit a maximum energy density of 33.1 W h kg⁻¹ at a power density of 219 W kg⁻¹, as well as good cycling stability, retaining 83.5% of the initial capacity over 2000 cycles at 20 mA cm⁻². These results imply the great potential of such core–shell hybrid nanostructures as advanced battery-type electrodes for applications in energy storage devices.