Carbon Nanotube Ultracapacitors
Supercapacitors or ultracapacitors use electrodes with very high surface area (e.g. porous activated carbon) and are currently used in niche application such as hybrid vehicles.
Among the advantages over electrochemical batteries are the high charge/discharge rate and stability. However, energy densities are relatively low compared to traditional batteries.
New electrode materials with increased surface area have the potential to make hypercapacitors attractive for a wider range of mobile applications.
The approach developed at MIT’s Laboratory of Electromagnetic and Electronic Systems (LEES), uses vertically-aligned single-walled carbon nanotubes.
From the MIT Technology Review:
Ultracapacitors could allow laptops and cell phones to be charged in a minute. And unlike laptop batteries, which start losing their ability to hold a charge after a year or two, they could still be going strong long after the device is obsolete. “Theoretically, there’s no process that would cause the [ultracapacitor] to need to be replaced,” says professor John Kassakian, another of the researchers.
The main hurdle the new technology is likely to face is not technical but economic. “The nanomaterials are probably a hundred or a thousand times more expensive, today, than the materials that we use,”
Other large surface area materials for ultracapacitors include carbon aerogels and barium titanate.