A highly conductive Ni(OH)2 nano-sheet wrapped CuCo2S4 nano-tube electrode with a core–shell structure for high performance supercapacitors

Abstract

The design of microstructures and the optimum selection of electrode materials have substantial effects on the electrochemical performances of supercapacitors. A core–shell structured CuCo₂S₄@Ni(OH)₂ electrode material was designed, with CuCo₂S₄ nanotubes as the core wrapped by interlaced Ni(OH)₂ nano-sheets as the shell. The hydrothermal and electro-deposition processes were adopted to synthesize CuCo₂S₄@Ni(OH)₂ materials. The CuCo₂S₄ nanotubes can both provide specific capacitance and act as a “superhighway” for electrons due to their highly conductive skeleton structure. The Ni(OH)₂ nano-sheets will boost the electrochemically active sites and enhance the specific surface area. Meanwhile, the mutually restricted core–shell CuCo₂S₄@Ni(OH)₂ electrode could regulate the volume deformation to improve its stability. The CuCo₂S₄@Ni(OH)₂ electrode had a maximum specific capacitance of 2668.4 F g⁻¹ at a current density of 1 A g⁻¹ and a superior cycling stability of 90.3% after 10 000 cycles. Moreover, a CuCo₂S₄@Ni(OH)₂//active carbon asymmetric supercapacitor with a maximum energy density of 44 W h kg⁻¹ was assembled, suggesting that CuCo₂S₄@Ni(OH)₂ is a successful binder-free electrode material for high performance supercapacitors.