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

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.