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

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. (C) 2016 Elsevier B.V. All rights reserved.