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Graphene/carbon nanotube mix to spawn low-cost ultracapacitors

Posted: 25 Apr 2014     Print Version  Bookmark and Share

Keywords:George Washington University  ultracapacitor  graphene  carbon nanotube 

A group of researchers at the George Washington University's Micro-propulsion and Nanotechnology Laboratory has created a mixture of graphene flakes with single-walled carbon nanotubes to develop what they claim is an ultracapacitor that boasts high performance and low cost. The device capitalises on the synergy brought about by using two carbon nanostructures with complementary properties, the scientists noted.

Single-walled carbon nanotubes and graphene have excellent electronic, thermal and mechanical properties that make them attractive materials for designing new ultracapacitors, said Jian Li, first author on the paper. Many groups had explored the use of the two materials separately, but few had looked at combining them.

"In our lab we developed an approach by which we can obtain both single-walled carbon nanotubes and graphene, so we came up with the idea to take advantage of the two promising carbon nanomaterials together," added Michael Keidar, a professor in the department of mechanical and aerospace engineering in the School of Engineering and Applied Science at GW, and director of the Micro-propulsion and Nanotechnology Laboratory.

The researchers synthesised the graphene flakes and nanotubes by vaporising a hollow graphite rod filled with metallic catalyst powder with an electric arc.

They then mixed the two nanostructures together to form an ink that they rolled onto paper, a common separator for current commercial capacitors.

The combination device's specific capacitance, a measurement of the performance of a capacitor per unit of weight, was three times higher than the specific capacitance of a device made from carbon nanotubes alone.

The advantage of the hybrid structure, Li explained, is that the graphene flakes provide high surface area and good in-plane conductivity, while the carbon nanotubes connect all of the structures to form a uniform network.

While other types of ultracapacitors have also achieved the high specific capacitance of the graphene/nanotube hybrid, the researchers said, the main advantage of the combination approach is its low costs, since the team has developed a simple way to manufacture large amounts of the desirable mix of carbon nanostructures.

The hybrid ultracapacitor is also small and light, an advantage as electronic devices get ever smaller.

- Paul Buckley
  EE Times Europe

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