Three-dimensional hierarchical interwoven nitrogen-doped carbon nanotubes/CoxNi1-x-layered double hydroxides ultrathin nanosheets for high-performance supercapacitors

• A facile, low-cost and scalable route has been developed to design and fabricate 3D hierarchical Ni foam/N-CNTs/CoxNi1-x-LDHs NSs electrodes.
• The Ni foam/N-CNTs/Co0.5Ni0.5-LDHs NSs electrode possesses the maximum specific capacitance of 2170 F g−1 (1 A g−1) and areal capacitance of 1.62 F cm−2 (1 mA cm−2).
• First-principles calculations further reveal that the Co doping can effectively reduce the band gap of Ni(OH)2 and increase the conductivity.

Three-dimensional (3D) interwoven nitrogen-doped carbon nanotubes (N-CNTs)/CoxNi1-x-layered double hydroxides (CoxNi1-x-LDHs) ultrathin nanosheets on Ni foam have been rationally designed via the combination of chemical vapor deposition and electrochemical deposition approaches. The CoxNi1-x-LDHs nanosheets are uniformly distributed on the N-CNTs, which can not only serve as the stable frame to improve the specific surface area, but also can enhance the conductivity. The Ni foam/N-CNTs/Co0.5Ni0.5-LDHs nanosheets electrode displays a remarkable maximum capacitance (2170 F g−1 at 1 A g−1 and 1.62 F cm−2 at 1 mA cm−2), excellent rate capability (80.9% specific capacitance retention at 20 A g−1 and 75.8% areal capacitance retention at 30 mA cm−2) and good cycling stability. First-principles calculations further reveal that the Co doping can effectively reduce the band gap of Ni(OH)2 and increase the conductivity. This work demonstrates a facile synthesis strategy of 3D hierarchical Ni foam/N-CNTs/CoxNi1-x-LDHs nanosheets electrode with remarkable electrochemical properties, which can be used in energy storage and conversion.