Ultracapacitors, a.k.a. supercapacitors, have the advantage of allowing us to create more efficient electronic products. Essentially, they are a combination of conventional batteries and capacitors, possessing some features of both. In addition, they are currently an area of extensive research due to the increasing amount of electronics in our daily lives. Electric vehicles can greatly benefit from ultracapacitors, as well as small handheld consumer electronics.
I have used them in several projects to replace batteries. When you are at the 100 Farad level, you have some serious Joules at your disposal!
However, one of the difficulties with ultracapacitors is creating a product that is high performance and low cost. Researchers at George Washington University's Micro-propulsion and Nanotechnology Laboratory have been working to develop a new structural make-up for ultracapacitors. By combining the power of carbon nanotubes and graphene, the researchers have successfully created a unique ultracapacitor. The researchers mentioned that many groups have looked at using carbon nanotubes and graphene to create devices separately; however, none have thought of combining the technologies to create an ultracapacitor.
Carbon nanotube structure can reinforce the graphene sheets and increase surface area to boot.
It is well known now that graphene and carbon nanotubes possess excellent electrical, mechanical, and thermal properties. There have been many different ways of isolating these structures, but the researchers used a method that involves using an electric arc to vaporize a hollow graphite rod filled with a metallic catalyst powder. The ultracapacitor is then created by combing the two structures in ink and rolling them onto a paper. The carbon nanotubes create a uniform structure, while the graphene offers good plane conductivity and a high surface area.
It has been shown many times over that graphene has lots of super properties. Nevertheless, manufacturing this material presents a challenge. Current methods involve growing the graphene on a metal and then dissolving away the metal. However, before the metal is dissolved a polymer must be put on top of the graphene to reinforce it. Now the polymer must be dissolved. The end result is graphene with residues and impurities that will limit its potential.
The carbon nanotube and graphene combination has proved to provide a much more simple way of synthesizing the end product. The carbon nanotubes reinforce the graphene in a way that is similar to steel rebar reinforcing concrete. Additionally, the carbon nanotubes can improve the overall mechanical and electrical properties. Since the hybrid material now has a more rigid structure, the polymer step can be taken out of the manufacturing process, eliminating many of the impurities that would normally be included. The new manufacturing process can be beneficial for ultracapacitors as well as many other graphene made devices.