A new ultracapacitor or electric double-layer capacitor (DLC) design has been announced in the journal Science this week, and could pave the way for smaller and lighter portable electronics devices.
Ultracapacitors are capable of charging and discharging in only seconds and this gives them an advantage over batteries, which take much longer, and make them extremely useful in applications such as regenerative braking. However, for some applications even a few seconds is too long, and this is where a new nanoscale ultracapacitor comes in. Researchers in the US have built an ultracapacitor from nanometer-scale fins of graphene, and this design gives them a device that can charge/discharge in under 200 microseconds.
Ultracapacitors store charge in electric fields between conducting surfaces, so a larger surface area of conducting surfaces enables the device to hold more charge. A larger amount of stored charge enables ultracapacitors to work in devices needing more energy than ordinary capacitors can provide, and they can deliver the energy much faster than a battery.
A team of researchers led by John Miller, president of JME, an electrochemical capacitor company based in Shaker Heights, Ohio has been able to increase the speed of the ultracapacitor by redesigning the electrodes to give more surface area. The new electrode, developed by Ron Outlaw, a team member from the College of William and Mary, in Williamsburg, Virginia, consists of sheets of graphene sticking up vertically from a graphite base. The graphene sheets are made of carbon one atom thick, and grown by a plasma-assisted chemical vapor deposition process. The graphite base is 10 nanometers thick. Miller described the design as resembling "rows of 600-nanometer tall potato chips standing on edge."
via New ultracapacitor recharges in under a millisecond.
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