The Power of Carbon Nano Spaghetti
By Bill Moore
Carbon nanotubes are revolutionizing how we make things from lighter, stronger aircraft, to solar panels, to LED lighting, but have you any idea how? I can't say with any confidence that I do, that's why I agreed to talk with Dave Arthur, the CEO of SouthWest Nano Technologies, or SWeNT for short, about how these incredibly tiny tubes will dramatically increase the life of tomorrow's electric car batteries.
What I didn't expect was for him to liken them to a bowl of spaghetti, complete with tomato sauce and meat balls.
Arthur's company is a spin-off of the University of Oklahoma in Norman. It was in the university that researchers discovered how to precisely control the formation of these nano-scale (one nanometer equals one-millionth of a millimeter) strings, right down to the arrangement of the carbon atoms from which they are formed. As he explains in this EV World 'Future in Motion' podcast for August 5, 2010, what SWeNT has done is perfect the way carbon nanotubes are formed, which enables them to be either highly conductive or semi-conductive.
They have taken this ability and adapted it to two broad applications: ink for printed electronics and paste for lithium battery cathodes. It is the latter application that EV World wanted to better understand and from this came the spaghetti analogy.
Arthur explained that most cathodes include carbon black, along with lithium and a binder material known as PVDF (polyvinylidene fluoride) as part of the cathode of the battery. Discharged energy from a battery always flows from the anode to the cathode. While the carbon black is a wonderful conductor of electric current, it is like a string of pearls, he explained. While it is highly stable thermally, meaning it is not unduly impacted by heat, carbon black is affected by the minute mechanical stresses that occur inside the cell. Once the pearls in necklace begin to separate over time with multiple recharges, the battery's potential to hold a charge begins to degrade.
"That new laptop that could stay running on a coast-to-coast flight, will not last nearly as long one year later," Arthur noted. A large part of the reason has to do with the breakdown of the carbon black in the cathode. What carbon nanotubes offer is a way to prevent that breakdown.
"Think of all those nanotubes as a bowl of spaghetti with all the noodles randomly arranged in a dense network of multiple connections," he told me. They are as thermally stable as the carbon black spheres, but far stronger mechanically. As a result, he thinks battery cathodes that utilize the company's paste someday will see the life expectancy of their lithium batteries as much as double.
At present, SWeNT is working with Rensselaer Polytechnic Institute in New York State to collect hard test data on batteries using the Oklahoma company's carbon nanotube paste. Arthur stated that so far the tests are very encouraging.
In the meantime, Southwest Nano Technologies are focusing their sales efforts on the ink product. But Arthur foresees in a few years time that the battery paste side of the business will be very large.