Three dimensional carbon nanotube/nickel hydroxide gels for advanced supercapacitors

Abstract

In this work, we have successfully developed three-dimensional (3D) nickel hydroxide (Ni(OH)₂)/single-walled carbon nanotube (SWNT) gel composites for supercapacitor applications. The composites are prepared using a facile coating-aging method followed by an electrochemical deposition. The obtained SWNT gels and their derived Ni(OH)₂/SWNT composites present 3D network structures composed of randomly orientated nanotube bundles. It is found that the sizes of these bundles can be easily tuned using two different drying techniques. The directly dried Ni(OH)₂/SWNT composites with seriously bundled nanotubes are capable of maintaining an excellent discharge performance as well as a satisfactory cycling stability. The improved electrochemical performance of the Ni(OH)₂/SWNT xerogel composite comes from a 3D SWNT conductive highway and a stronger Ni(OH)₂/SWNT interface bonding. In contrast, the hydrogel composite prepared in the absence of a drying process, despite achieving both high areal and mass-based capacitance, suffers a severe cycling drop. Compared with 3D graphene and its derived composites, our composite design with the employment of 1D SWNTs has the merit of shorter ion diffusion distances which offers a distinctive opportunity for the future development of 3D electrodes.