NiCo2S4@Co(OH)2 core-shell nanotube arrays in situ grown on Ni foam for high performances asymmetric supercapacitors

• Hierarchical NiCo2S4@Co(OH)2 nanotube arrays supported on Ni foam.
• The NiCo2S4@Co(OH)2 electrode shows a relatively high area capacitance.
• An asymmetric supercapacitor with high energy density was successfully assembled.

In this paper, hierarchical NiCo2S4@Co(OH)2 nanotube arrays supported on Ni foam have been synthesised though a facile and commendable method. The smart combination of NiCo2S4 nanotubes and Co(OH)2 nanosheets exhibits brilliant synergistic effect for supercapacitors with significantly enhanced performances. The NiCo2S4@Co(OH)2 electrode shows a relatively high area capacitance of 9.6 F cm−2 at 2 mA cm−2 (almost 2 times as high as that of bare NiCo2S4 electrode), even at 32 mA cm−2, the area capacitance is maintained at 6.4 F cm−2. Moreover, an asymmetric supercapacitor is successfully assembled by using NiCo2S4@Co(OH)2 nanotubes as the positive electrode and active carbon (AC) as the negative electrode. The NiCo2S4@Co(OH)2//AC device achieves a relatively high energy density of 35.89 Wh kg−1 at a power density of 0.4 kW kg−1 with excellent cycling performance(70.01% capacitance retention over 5000 cycles). Such unique NiCo2S4@Co(OH)2 nanotube arrays not only demonstrate promising applications in energy storage but also remind researchers of the unlimited potential of heterostructured materials.

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