The newly developed devices were also found to be three orders of magnitude faster than conventional supercapacitors, which are used in backup power supplies, wind power generators and other machinery. These new devices have been dubbed “micro-supercapacitors” because they are only a few micrometers (0.000001 meters) thick. A paper on their work was published online in the journal Nature Nanotechnology on 15 August.

The microsupercapacitors are produced by the electrophoretic deposition of a several-micrometer-thick layer of nanostructured carbon onions with diameters of 6–7 nm. Integration of these nanoparticles in a microdevice with a high surface-to-volume ratio, without the use of organic binders and polymer separators, improves performance because of the ease with which ions can access the active material. Increasing the energy density and discharge rates of supercapacitors will enable them to compete with batteries and conventional electrolytic capacitors in a number of applications.

—Pech et al.

This is the first time a material with very small spherical particles has been studied for this purpose. Previously investigated materials include activated carbon, nanotubes, and carbide-derived carbon (CDC).

The surface of the onion-like carbons is fully accessible to ions, whereas with some other materials, the size or shape of the pores or of the particles themselves would slow down the charging or discharging process. Furthermore, we used a process to assemble the devices that did not require a polymer binder material to hold the electrodes together, which further improved the electrode conductivity and the charge/discharge rate. Therefore, our supercapacitors can deliver power in milliseconds, much faster than any battery or supercapacitor used today.

—Vadym Mochalin, research assistant professor of materials science and engineering at Drexel and co-author

Resources

• David Pech, Magali Brunet, Hugo Durou, Peihua Huang, Vadym Mochalin, Yury Gogotsi, Pierre-Louis Taberna, Patrice Simon (2010) Ultrahigh-power micrometre-sized supercapacitors based on onion-like carbon. Nature Nanotechnology doi: 10.1038/nnano.2010.162