MOF-Derived Nickel-Cobalt Sulfide Nanoflakes Wrapped Carbon Nanotubes for Hybrid Supercapacitors

Transition metal sulfide has been regarded as an ideal electrode material for supercapacitors due to its high energy density. However, the poor cyclic stability caused by low electroconductivity seriously limits its practical application. Herein, carbon nanotubes and nickel-cobalt bimetallic organic framework composites were prepared by the in situ growth method and used as precursors to prepare carbon nanotubes/nickel-cobalt bimetallic sulfide (CNTs/ Ni-Co-S-3) composites. Benefits from the synergy between the components, CNTs/Ni-Co-S-3, as a positive electrode material, presented an extremely high specific capacity of 734 C g-1 at 1 A g-1 and an improved rate capability. Furthermore, when CNTs/Ni- Co-S served as the positive electrode of the hybrid supercapacitor (CNTs/Ni-Co-S-3//AC HSC), the device provided a competitive energy density of 42.15 Wh kg-1 at the power density of 852 W kg-1 and long-term stability (88.46% of specific capacitance retention for 10000 cycles at 8 A g-1). This synthesis strategy provides a new pathway for further improving the energy density and cyclic stability of metallic sulfide group composite electrodes.