Hierarchical NiCoO2@Ni3S2 core/shell nanoflakes arrays with superior capacitive performances for energy storage

Herein, it reports the design and synthesis of NiCoO2@Ni3S2 core/shell arrays on Ni foam using a two-step method of hydrothermal method and electrodeposition. The hetero-structures are composed of NiCoO2 flakes as the core-material and Ni3S2 ultrathin nanosheets as the shell-material. Due to the unique core/shell heterostructure and positive synergistic effect of two components, hierarchical NiCoO2@Ni3S2 arrays exhibit excellent capacitive performance as energy storage materials. The mass specific capacity of NiCoO2@Ni3S2 is as high as 1599.5C g(-1) at 1.0 A g(-1), which is higher than the sum of the capacity of the two samples NiCoO2/NF(640.0C g(-1)) and Ni3S2/NF(695.3C g(-1)). NiCoO2@Ni3S2/NF also shows a very high areal specific capacity of 4.06 C cm(-2). Therefore, NiCoO2@Ni3S2 arrays greatly releases the energy storage potential of the NiCoO2 and Ni3S2 materials in supercapacitors. Furthermore, a hybrid supercapacitor device fabricated using NiCoO2@Ni3S2/NF as positive electrode and the graphene as negative electrode possesses a high energy density of 73.97 Wh kg(-1) at a power density of 800 W kg(-1) , and maintain 22.01 Wh kg(-1) at a high power density of 12.8 kW kg( -1). These results demonstrate that hierarchical NiCoO2@Ni3S2 core/shell arrays have great potential as a positive electrode in supercapacitor with high energy density.