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Supercapacitors: carbon nanotube “mats” on aluminum foil

A new electrode material for supercapacitors has been developed by the Iramis and its partners: composed of carbon nanotube "mats" aligned on aluminum foil, it should significantly increase the amount of stored electrical power. This is an essential result for their industrialization by the startup company NawaTechnologies.
Published on 20 February 2020

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.

NawaTechnologies and NawaLab

The Iramis and its partners developed a process for manufacturing aligned carbon nanotubes that led to the creation of the startup NawaTechnologies in 2013. This was followed by NawaLab, a joint research laboratory between the Iramis, CY Cergy Paris University and the University of Tours.

NawaLab has co-developed a new concept in electrodes in which excess carbon is inserted into the layer of aligned nanotubes. This has given rise to high-power devices that are currently being developed by NawaTechnologies. For optimal energy management, hybrid devices are also being studied that combine batteries, with their high energy storage capacity, and supercapacitors that allow rapid charging and discharging.

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