Ultracapacitors, energy-storage devices that absorb and release
charge in minutes, could be a rapid-charging, cheaper, and safer
alternative to batteries for electric cars. But commercial
ultracapacitors can hold just 5 percent of the energy of lithium-ion
batteries, providing short power bursts that limit them to uses such as
acceleration in hybrid buses.
Researchers at
Nanotek Instruments in Dayton, Ohio, have now made graphene electrodes that could lead to
ultracapacitors with more than five times the energy density of
commercial devices. By using graphene--atom-thick sheets of
carbon--Nanotek increases the surface area of the electrodes in the
ultracapacitors, boosting the amount of charge that they can store. "We
are trying to bridge the performance gap between an ultracapacitor and a
lithium-ion battery," says Nanotek's Bor Jang, the lead author of a
paper published in the online version of the journal
Nano Letters.