Three-dimensional NiCo2O4@NiCo2O4 core–shell nanocones arrays for high-performance supercapacitors

Abstract The highly ordered three-dimensional hierarchical NiCo 2 O 4 @NiCo 2 O 4 core–shell nanocones arrays on nickel foams are synthesized by stepwise hydrothermal synthesis. The unique nanoarchitectures consist of a layer of NiCo 2 O 4 nanosheets well coated on the surface of NiCo 2 O 4 nanocones. When used in supercapacitors, the NiCo 2 O 4 @NiCo 2 O 4 core–shell hierarchical nanostructures exhibit a remarkable capacitance of 2045.2 F g −1 at a current density of 1 A g −1 , which are better than that of the individual components of NiCo 2 O 4 nanosheets and NiCo 2 O 4 nanocones. Furthermore, the predominant diffusion-controlled storage is revealed by theoretical analysis. An asymmetric supercapacitor device based on the hierarchical NiCo 2 O 4 @NiCo 2 O 4 core–shell nanostructure and activated carbon is fabricated and exhibits a desirable high energy densities with a value of 82.95 Wh kg −1 at power density of 0.35 kW kg −1 . These results indicate that the as-prepared NiCo 2 O 4 @NiCo 2 O 4 are outstanding candidate for electrochemical supercapacitors.