Nanotubular Ni-supported graphene @ hierarchical NiCo-LDH with ultrahigh volumetric capacitance for supercapacitors

Abstract

The design of the electrode materials for supercapacitors with high volumetric utilization and excellent capacitance is in high demand. In this study, the three dimensional porous hierarchical nickel cobalt layered double hydroxides (NiCo-LDH) grown on the nanotubular Ni supported N-doped graphene (ntN-NG) matrix are fabricated via chemical vapor deposition process combined with hydrothermal method. The ntN-NG substrate with low void content, high specific surface area, appropriated pore size and a hydrophilic surface facilitates the effective nucleation and robust growth of hierarchical NiCo-LDH, and thus, ensures high material loading in a limited space and the structure stability of the composite. The hybrid exhibits a record high volumetric capacitance of 867 F/cm3 at 1 mA/cm2 and remarkable cycling stability of 89.4% retention after 10,000 cycles, which holds great promising application as the miniaturized energy storage and conversion devices in the future.