Breakthrough In Use of Graphene For Ultracapacitors

Hugh Pickens writes "Researchers at the University of Texas at Austin have achieved a breakthrough in the use of a one-atom thick graphene for storing electrical charge in ultracapacitors. They believe their development shows promise that graphene could eventually double the capacity of existing ultracapacitors. 'Through such a device, electrical charge can be rapidly stored on the graphene sheets, and released from them as well for the delivery of electrical current and, thus, electrical power,' says one of the researchers. Two main methods exist to store electrical energy: in rechargeable batteries and in ultracapacitors, which are becoming increasingly commercialized but are not yet well known to the public. Some advantages of ultracapacitors over traditional energy storage devices such as batteries include: higher power capability, longer life, a wider thermal operating range, lighter, more flexible packaging and lower maintenance. Graphene has a surface area of 2,630 square meters, almost the area of a football field, per gram of material."

Comments

Re:How?

[Paradigm_Complex]

2D area vs mass. What that statement was trying to get across was that graphene is so thin that you could almost cover a football field with only a gram of it. Think of spreading cream cheese on a bagel. You only have a gram of cream cheese, though, so you have to spread very, very thin. Except the bagel is the size of a football field, so you have to spread it even more ridiculously thin: only an atom thick. Now instead of cream cheese it's carbon atoms.

graphene surface area

[metalcup]

I found this image from Nature magazine useful in imagining how 1 gm of graphene can have such a large surface area..

http://www.nature.com/nature/journal/v427/n6974/fig_tab/nature02311_F1.html

Re:How?

[m.dillon]

Yes, massively folded. Similar technology has been in used for many years to produce multi-Farad 'dime' capacitors, whos surface areas start around the size of a tennis court and go up from there.

These sorts of capacitors have very high capacitances (in the multiples, even tens of Farads) and a 20-50 year life span (or longer depending on how they are built), but also tend to only be able to be charged to fairly low voltages (3v, 5v, etc), and also have fairly high internal resistances (though this might be different for the newer Graphene-based caps), limiting the discharge rate.

This means they won't be replacing batteries any time soon, but the advances we're seeing are pretty cool.

We mostly use these things to run real time clock chips and provide backup power for static ram... i.e. very low current applications.

-Matt

Re:Safety ?

[Eivind]

More energy, true, but slower release-rate.

A battery has significant internal resistance, even if you short-circuit it the power-levels are limited. (high, but limited)

A capacitator can recharge significantly faster.

Put differently, the thing may only hold 10% of the energy in a battery. But if that energy is released a hundred times quicker, you're still looking at hell of a bang.

Re:Safety ?

[LehiNephi]

The flywheel has embedded permanent magnets. Coils surround it in the case, and spin up/down the flywheel in order to inject or extract energy. It's a brushless DC motor, essentially. Once you include magnetic bearings, you end up with something that can be encased in a near-perfect vacuum, eliminating all friction and giving rather impressive efficiency.

Large-scale systems of this sort are actually in use, just not inside vehicles. There are some electric train systems that use it to recapture energy from trains arriving in the station, and then assist trains as they accelerate out of the station.