Binder-free supercapacitive of ultrathin Co(OH)2 nanosheets-decorated nitrogen-doped carbon nanotubes core-shell nanostructures

Abstract

Three-dimensional (3D) nitrogen-doped carbon nanotubes (N-CNTs)/Co(OH)2 core-shell nanostructures as binder-free supercapacitor electrode have been synthesized via electrodeposition and chemical vapour deposition. The ultrathin Co(OH)2 nanosheets are uniformly coated on the surface of N-CNTs. Such unique well-designed binder-free electrode exhibits a high areal capacitance (0.46 F cm−2 at a current density of 1 mA cm−2) and good cycling stability (81.2% capacitance retention after 2000 cycles). In the electrode, the cable-like N-CNTs around Ni foam with close contact act as current collector, facilitating the electrical transport, while two-dimensional Co(OH)2 nanosheets grown on external surface increase the surface area and provide good contact with ions at electrode/electrolyte interface, exhibiting low charge transfer resistance (Rct) and better charge storage performance. As a result, such combined synthetic strategy may provide design guidelines for constructing advanced binder-free supercapacitors electrode.