Sep 21, 2010
Super-aligned CNTs replace metal in supercapacitor upgrade
Super-aligned CNTs (SACNTs) can be fabricated into highly conductive, flexible and nanoporous sheets to replace metal current collectors in oxide-based supercapacitors. The specific capacitance (SC) of the SACNT/oxide composites, as both active material and current collector, is close to that of pure oxides as active materials and the substance offers much better rate capability.
SACNTs were first reported by researchers from Tsinghua-Foxconn Nanotechnology Research Center, Tsinghua University, Beijing, China, in 2003. SACNTs are a type of CNT array that can be drawn out directly in sheets. Because of the superior length of the CNTs and their direct arrangement, the SACNT sheet shows higher conductivity (40,000 S m–1) than normal CNT-based macroscopic materials. In addition, the SACNT sheet shows excellent mechanical strength with a free-standing areal density of just 1 µg cm–2.
The outstanding physical properties and better chemical stability make the SACNT sheet an ideal substitute for metal foil current collectors in electrochemical power sources. Scientists have demonstrated this by cross-stacking the SACNT sheets and decomposing metal nitrate on the structure. The SACNT/oxide nanoparticle composite films perform outstandingly as supercapacitor electrodes. The SC is as high as 500 F g–1, taking into account the mass of both the SACNT and oxides. The SC remains at more than 50% when current is increased 60 times, and after 2500 cycles it remains more than 95%.
SACNT sheet has also been applied to another electrochemical device, the Li-ion battery. The researchers are now trying to utilize the material to fabricate novel dye-sensitized solar cells.
The group published its work in the journal Nanotechnology.
About the author
Ruifeng Zhou MSc is a member of Prof. Kaili Jiang's group. Zhou's research focuses on the application of CNT-based composites in electrochemical power sources – for example, supercapacitors, fuel cells and dye-sensitized solar cells, as well as other branches of nanoscience and nanotechnology. Prof. Jiang's research covers growth mechanisms, controlled synthesis, physical properties and applications of CNTs, especially SACNT.