From left, students Betar Gallant and Seung Woo Lee and professors Yang Shao-Horn and Paula Hammond, in one of the labs where they did research on the use of carbon nanotubes in lithium batteries. (Credit: MIT.)
According to an MIT press release, researchers claim to have created electrodes from carbon nanotubes that can make lithium-ion batteries ten times more powerful than conventional models. Such batteries, they say, could one day be used for power-hungry applications, such as hybrid vehicles and renewable energy sources.
Yang Shao-Horn and colleagues have created electrodes made of multi-walled carbon nanotubes that could be the first to bridge the gap between capacitors and batteries. Carbon nanotubes have very high electronic conductivities to help charge flow, and their long, thin dimensions mean they can form porous electrodes, which provide fast transport for lithium ions.
Redox of surface oxygen-containing functional groups on the layered carbon nanotube electrodes by lithium ions in organic electrolytes is responsible for the electrodes' high energy and power capabilities. (Credit: Nature Nanotechnology.)
The researchers make their new electrodes with a layer-by-layer technique, which gives them high control of electrode thickness and other properties. It involves dipping a substrate alternately into solutions of positively and negatively charged carbon nanotubes, so that they self-assemble onto the surface without the help of any binding compounds.
To test the electrode, Shao-Horn and colleagues incorporated it as the positive electrode in a conventional battery assembly, with either lithium metal or lithium titanium-oxide functioning as the negative electrode. They found that the battery could store five times the energy of a normal capacitor, and could deliver ten times the power of a Li-ion battery with standard electrodes. Moreover, they found the energy capacity did not fade over more than a thousand recharge and discharge cycles.
Seung Woo Lee, one of the lead authors, says that while carbon nanotubes have been produced in limited quantities so far, a number of companies are currently gearing up for mass production of the material, which could help to make it a viable material for large-scale battery manufacturing.
The findings were published in the June 20 issue of Nature Nanotechnology.