Halfway between capacitors and batteries, supercapacitors offer ultra-fast charge and discharge times. Their market is expanding despite the cap on stored electrical power. One way to overcome this hurdle is to use new electrode materials based on vertically aligned carbon nanotubes impregnated with conductive polymers. The challenge is to lower the temperature of the manufacturing processes for these nanotubes so that they can be grown on aluminum foil, permitting continuous production.

This step has just been successfully completed. A simple, inexpensive and scalable process has been optimized to produce a mat of pure (99.5%), dense nanotubes on aluminum foil. Specifically, the process, which is assisted by aerosols, is based on the Catalytic Chemical Vapor Deposition technique. The reactor is fed continuously and simultaneously with carbon precursors (acetylene) and a metal catalyst (ferrocene). Growth on an aluminum substrate requires a temperature below the melting point of this metal (660°C), which results in a slower growth of the nanotubes. This slowdown is compensated for by the choice of acetylene as a source of carbon, since it is more reactive at low temperatures. However, its output must be adjusted in order to optimize the growth of the nanotube mat, whose thickness can reach 200 µm.