Graphite Carbon-Coated Nicop/Nicoo Heterostructure with 3d Hierarchical Network Structure for High-Performance Supercapacitors

Abstract

Rate capability and cycling stability are vital aspects for high-performance electrode materials in the application of supercapacitors. This study reports a new approach for constructing a carbon-coated NiCoP/NiCoO heterostructure on nickel foam (NiCoP/NiCoO-CHT), which graphite carbon nanosheets were in-situ coated on the surface of the NiCoP/NiCoO precursor surface to form a unique 3D hierarchical network structure via simple hydrothermal-calcination route. The NiCoP/NiCoO-CHT exhibited a high specific charge (1427.8 C g−1 at 1 A g−1), satisfactory rate capability (74.6% capacity retention at 15 A g−1) and desired cycling stability (90.4% capacity retention after 5 000 cycles), owing to the synergy of the high specific capacitance of the NiCoP/NiCoO, the mechanical stability of graphite carbon nanosheets and the 3D porous network structure. Especially, the graphite carbon not only prevented the NiCoP/NiCoO volume expansion for enhancing cycling durability, but also improved the electrical conductivity and provided sufficient electron/ion channels for accelerating Faradaic reaction. As a result, the assembled NiCoP/NiCoO-C//AC device gave a high energy density of 85.6 Wh kg−1 at 850 W kg−1 and retained 79.9% capacity after 10 000 cycles. This work offers some guidance for designing and constructing desirable electrode materials for supercapacitors.

Keywords: Nickel-cobalt phosphide, Graphite carbon, NiCoP/NiCoO heterostructure, Supercapacitors