March 16, 2009
Nano holes make fast electricity
Start with closely spaced microscopic
holes, line them with layers of metal only a few nanometers thick
and you have a superfast electricity storage device.
The device is an array of nanoscale electrostatic capacitors
formed in close, regularly spaced holes in a thin film of aluminum
oxide. The holes are lined with metal, insulator and metal layers
totaling 25 nanometers.
The electrostatic capacitor holds 0.7 watt hours per kilogram
-- 10 times as much as other nanostructured electrostatic capacitors
and almost as much as the widely used but slower electric double layer
Electrostatic capacitors store electricity as charges on the
surfaces of metal electrodes. This makes them the fastest type of
capacitor. The densely-packed nanotube structure gives the device
it's greater capacity.
The electrostatic capacitor could be a lower-cost alternative
to electric double layer capacitors for electric vehicles. Capacitors
are paired with high-capacity batteries in electric vehicles. The
battery provides bulk storage and the capacitor burst power for quick
acceleration and a way to capture braking energy.
Metal-Insulator-Metal Capacitor Arrays for Energy Storage
Nature Nanotechnology, published online March 15, 2009
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