NiCo₂S₄ nanocone arrays on three-dimensional graphene with small hole diameters for asymmetric supercapacitor

Chemical vapor deposition (CVD) is utilized to fabricate 3D graphene (3D Gr) with small hole diameters using nickel nanoparticles sintered at high temperatures as the sacrificial template. NiCo₂S₄ nanocone arrays (NiCo₂S₄ NCAs) are vertically grown in situ on the 3D Gr by a seeding layer and hydrothermal synthesis process. The results show the hole diameters of 3D Gr are ∼ 3 µm. The small hole diameters of 3D Gr not only enhances the high electrical conductivity but also increases the contact area to the solution. Moreover, NiCo₂S₄ NCAs on the 3D Gr can provide more electrochemical redox activities and shorter channels for ion transport. NiCo₂S₄ NCAs/3D Gr is applied as a supercapacitor electrode, showing a specific capacitance of 948.9 F/g at 1 A/g. In addition, an asymmetric supercapacitor is assembled with the NiCo₂S₄ NCAs/3D Gr as the cathode material and the activated carbon as the anode material. The supercapacitor has an energy density of 64.1 Wh/kg at the power density of 1153.8 W/kg. It exhibits 90 % capacitance retention under 10, 000 charge and discharge cycles at 10 A/g.