Lightweight, Cheap Ultracapacitor Built Using Graphene, Carbon Nanotubes

Scientists have now created an ultracapacitor using graphene and carbon nanotubes. The supercapacitor is both light and inexpensive and could advance hybrid vehicles and electronic devices.

Ultracapacitors can charge electronic devices in seconds and electric cars in minutes. These storage devices are safe but expensive.  A new study shows that supercapacitors can be made small and cheap by combining the wonder-material graphene with carbon nanotubes. The research could pave way for smaller electronics and better still, cheaper hybrid cars.

Capacitors are kind of like a battery in that they store energy. However, capacitors don't produce new electrons, but only store them. Super or Ultracapacitors can store a high amount of electric charge, which is why they are considered a replacement for conventional chemical batteries.

Previous research has shown that ultracapacitors can be made using graphene flakes. In the present study, scientists at George Washington University combined graphene flakes along with single-walled carbon nanotubes to make a high-energy and low-cost ultracapacitor.

"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.

How did they make the Ultracapacitor

Researchers obtained graphene and carbon nanotubes by using an electric arc to vaporize a hollow graphite rod. The rod was filled with metallic crystal powder. The two nanoparticles, graphene and carbon, were then mixed to form an ink, which was rolled onto a paper.  

The specific capacitance of the resultant device was three times higher than the specific capacitance of a structure made of carbon nanotubes alone. Specific capacitance is a measurement of the ability of the capacitor to store electric charge per unit of weight, according to a news release from the American Institute of Physics

 According to the researchers, in the combination capacitor, graphene flakes provide in-plane conductivity and a high surface area. The carbon nanotubes create a good network, making combination capacitors better than single material capacitor.

Another major advantage of the graphene- carbon capacitor is its low-cost. Researchers said that the device is easy to make and can be produced on a larger scale. Also, the hybrid device is small and light, meaning that size of electronic devices could shrink in the future.  

The study is published in the Journal of Applied Physics and was supported by NSF/DOE Partnership in Plasma Science and Technology.

Both graphene and carbon nanotubes have shown the potential to create ultracapcitors that could advance hybrid cars. However, graphene is expensive to produce on a large scale, which has limited its use in the industry. A recent research by Trinity College Dublin scientists showed that high-quality graphene can be produced using a  kitchen blender and dishwashing soap.