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

Abstract In this paper, hierarchical NiCo 2 S 4 @Co(OH) 2 nanotube arrays supported on Ni foam have been synthesised though a facile and commendable method. The smart combination of NiCo 2 S 4 nanotubes and Co(OH) 2 nanosheets exhibits brilliant synergistic effect for supercapacitors with significantly enhanced performances. The NiCo 2 S 4 @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 NiCo 2 S 4 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 NiCo 2 S 4 @Co(OH) 2 nanotubes as the positive electrode and active carbon (AC) as the negative electrode. The NiCo 2 S 4 @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 NiCo 2 S 4 @Co(OH) 2 nanotube arrays not only demonstrate promising applications in energy storage but also remind researchers of the unlimited potential of heterostructured materials.