Carbon nanotube electrodes dramatically increase lithium battery capacity
Researchers at MIT have found that using specially treated thin layers of carbon nanotubes in batteries can boost the amount of power delivered per unit of weight by up to ten times. While the technology still needs improving, its full development and large-scale employment would certainly revolutionize the way we use any electronic devices, from an iPod to an electric car.
The electrode was fabricated with a layer-by-layer technique in which a base material is alternately dipped in solutions containing specially treated carbon nanotubes to either have a slightly positive or a slightly negative charge: when layers of the two kinds are put together, the opposite magnetic forces pull the parts tightly together, self-assembling an electrode that is porous at the nanometric scale and doesn't seem to deteriorate at all as the battery is subjected to over a thousand charge-discharge cycles.
The electrodes produced by the team were a few microns thick, making the technology potentially useful for small portable electronics. With time, the researchers hope to be able to develop much thicker electrodes that could be used for more power-demanding applications like electric cars.
The news is an important step building on the findings made by Stanford researchers regarding silicon nanotube electrodes not too long ago, and looks particularly promising. However, before we start daydreaming about a Tesla Roadster that can go up to 2,400 miles between charges, a couple of problems still need to be tackled.
The first issue is that, while there isn't a real limit on the potential thickness of the electrode, the time that it would take to actually build a powerful electrode from layers only a few nanometers thick would be substantial, to the point where the process would simply become impractical. The researchers are making some steps toward solving this issue by advancing a new manufacturing strategy that would involve spraying the layers with a conductive solution rather than dipping them, which could speed up the process by up to 100 times.
But perhaps the major hurdle to the widespread use of this technology is the scarce availability of carbon nanotubes. A number of companies have been working on this issue for some time, but there is no telling when truly affordable and high-quality carbon nanotubes might become a reality.
The MIT team's findings were reported in a paper published in the journal Nature Technology. The research was funded by Dupont-MIT Alliance, Office of Naval Research and the MRSEC Program of the National Science Foundation.