A two-stage, self-aligned vertical densification process for as-grown CNT forests in supercapacitor applications

The method of a two-stage, self-aligned liquid densification process for carbon nanotube (CNT) forests has been demonstrated for supercapacitor electrode applications with enhanced energy density. By combining processes of mechanical bending and liquid densification, the vertical height of a 10 mm x 5 mm in size, as-grown CNT forest on top of a silicon substrate was reduced from 320 mu m to 21 mu m in our prototype experiments. It was found that densified CNTs maintained the film continuity and the self-alignment configuration but the alignment changed into the lateral direction of the growth substrate while the CNT-silicon bottom contacts were preserved. After immersing in a liquid electrolyte, the system capacitances were measured by extracting data from the recorded cyclic voltammetry curves. Results show that, even though densified CNT forest samples had slightly reduced total capacitances as compared with samples from as-grown CNT forests, volumetric specific capacitance increased from 1.07 F/cm(3) to 10.7 F/cm(3) for densified CNT samples. As such, this two-stage, self-aligned vertical densification process could be scaled up to produce highly densified, large area, porous and conductive CNT films for potential energy storage applications. (C) 2012 Elsevier B.V. All rights reserved.