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

Three-dimensional (3D) interwoven nitrogen -doped carbon nanotubes (N-CNTs)/CoxNii,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 CoxNii_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/NCNTs/Coo 5Nio 5-LDHs nanosheets electrode displays a remarkable maximum capacitance (2170 F g (1) at 1 Ag I and 1.62 F cm (2) at 1 mAcm (2)), excellent rate capability (80.9% specific capacitance retention at 20 A g (1) and 75.8% areal capacitance retention at 30 mAcm 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/Co-x N1-x-LDHs nanosheets electrode with remarkable electrochemical properties, which can be used in energy storage and conversion. (C) 2016 Published by Elsevier Ltd.