3D hierarchical self-supported NiO/Co 3 O 4 @C/CoS 2 nanocomposites as electrode materials for high-performance supercapacitors.

Multi-dimensional nanomaterials have drawn great interest for application in supercapacitors due to their large accessible surface area. However, the achievements of superior rate capability and cycle stability are hindered by their intrinsic poor electronic/ionic conductivity and the erratic structure. Herein, we develop a three-dimensional hierarchical self-supported NiO/Co 3 O 4 @C/CoS 2 hybrid electrode, in which NiO/Co 3 O 4 nanosheets are in situ grown on a nickel foam substrate and combined with CoS 2 nanospheres through a carbon medium. The hybrid electrode has a high specific capacity of ∼1025 C g -1 at 1 A g -1 with a superior rate performance of ∼74% capacity retention even at a current density of 30 A g -1 . Moreover, the assembled NiO/Co 3 O 4 @C/CoS 2 //AC hybrid supercapacitor achieves excellent performance with a maximum voltage of 1.64 V and a high energy density of 62.83 W h kg -1 at a power density of 824.99 W kg -1 and excellent cycle stability performance with a capacity retention of ∼92% after 5000 cycles. The high electrochemical performance of the hybrid supercapacitor is mainly attributed to the porous structure of the NiO/Co 3 O 4 @C nanosheets and CoS 2 nanospheres and intimate integration of active species. The rational strategy for the combination of various earth-abundant nanomaterials paves a new way for energy storage materials.