Feb 232013

A brief video describing recent work on graphene-based supercapacitors. The end result might be metal-free capacitors that can store as much energy as modern batteries, but would be able to charge up a hundred or a thousand times faster. A cell phone that charges in 2 seconds; an electric car that charges in a minute, rather than the multiple-hours currently required.

As well as getting rid of the toxic and expensive metals current batteries require, the graphene batteries could, it seems, be produced by virtually anyone: their prototypes were made by coating blank DVDs with graphite oxide and zapping it with the standard DVD-burner laser. If this can be made truly functional and distributable to the public, imagine the possibilities: anyone with a DVD burner could just crank out thin sheets of supercapacitor, and these could be use to built up capacitors or perhaps arbitrary size and storage capacity, and perhaps of arbitrary shape. Batteries of large storage and vast power that can be shaped to fit within – oh, let’s say a Gauss gun the design of which is simply downloaded off the web, and printed on your home 3D printer.

Heck: make long, thin graphene capacitors in the shape of RC helicopter blades, then mount them to RC helicopters.  Given the strength of graphene, this would seem a  good structural choice. Replace other structures with graphene-capacitor structures, and you might be able to produce an RC helicopter with, effectively, *no* weight penalty for the battery. Automobile skin panels. Aircraft skin panels. Aircraft spars. Flexible sheets that form portions of clothes; integrate them with some sort of piezo electric cloth that charges up the capacitor cloth from motions such as walking. Integrate the graphene capacitor directly with photovoltaic cells, then mount directly to your roof.


 Posted by at 3:37 pm
  • B Lewis

    Sounds great! But, boy, I’d sure hate to be standing nearby if a sheet of dielectric in one of those superbatteries were to give way. Zap!

  • Doug

    Holy crap an actual supercapacitor?

    • Christopher James Huff

      Supercapacitors aren’t at all new, they’re actually quite widespread as RTC backup batteries. This is just another way to build them, hopefully cheaper and better than other methods.

  • Christopher James Huff

    Keep in mind that the graphene produced by this process may not be as mechanically strong as large sheets of high-quality graphene. Given the talk about high surface area, I rather suspect it’s something like many small flakes of graphene, or a highly wrinkled form. Also, the electrical properties might vary strongly with strain and a charged capacitor may fail rather energetically when damaged, so combining structure and energy storage may not be a good idea.

    You could probably get some of the same benefit from the flexibility in form factor, but resistive losses across large sheets are likely to be significant, so more conventional form factors might be preferable. And a piece of plastic with an array of these “micro supercapacitors” is a long way from an actual supercapacitor. However, the process could allow capacitors to more easily be printed on a PCB, something that can be done now but requires large board areas for anything but tiny capacitance values.

    As for the storage density, in the end, batteries store energy in chemical bonds while capacitors store it in charged plates and distortions of existing chemical bonds in the dielectric. That’s why capacitors charge and discharge faster, and why batteries achieve such higher energy densities. And the same high surface area means graphene materials make good electrodes for even higher-performance batteries. I don’t think this is going to replace batteries.

    • Anonymous

      > may fail rather energetically when damaged, so combining structure and energy storage may not be a good idea.

      Oh, come now. I can think of times when that would be a *bonus.* A drone, say, heavily charged. That crashes into a powerplant or electronics factory. I wonder if it might be useful as an EMP generator.. make a sphere or cylinder out of this stuff, charge, then detonate with explosives. At the very least, there should be a good ZAP out of it.

    • Roberta X

      Christipher, it’s an essentially two-dimensional substance. If the laser process does fully fuse it, “wrinkled” is not really an applicable notion. How do you bend an hexagonal matrix?

      • Christopher James Huff

        The bonds aren’t perfectly rigid. It’ll wrinkle just fine, especially if there’s defects in the crystal structure.

        Their paper has some SEM images that appear to show the film produced with the LightScribe technique as essentially a deep pile of interlinked flakes of graphene, which is where it gets its surface area: https://www.sciencemag.org/content/suppl/2012/03/14/335.6074.1326.DC1/El-Kady-SOM.pdf

  • Anonymous

    This is probably more expensive and difficult to produce, but it reminds me of Poul Anderson’s “Capacitite” from his short story _Snowball_. If you haven’t read it, I highly recommend it. A scientist husband-wife team invent a material that can be made in a home oven and can store electricity at energy densities that are almost arbitrarily high. The recipe gets out, and the world changes as *everyone* starts making the stuff and running cars and airplanes and guns off it. Great story.

  • Roberta X

    My nose tells me they’re leaving some steps out.

    Can’t be sure but the dieletcric of the capacitor shown appears to be kapton,* which has fabulous electrical properties but — as Scott probably knows better than I do — has mechanical limits: abrasion, puncture and bending are real weak points. (The deposited-silver capacitors used for bypassing in VHF/UHF electron-tube tuned-cavity amplifiers required very careful handling — a bit of grit trapped during assembly, or a crease, and they’d fail soon after high voltage was applied). Polyethylene film is way more flexible, but it’s fragile and has a much lower high-temp limit.

    Commenters here and on other articles I have found (trying to decide to what extent GE is blowing smoke up, as they are wont to do) appear to think graphene has the same conductivity as ordinary carbon. This seems to be far from the truth; it’s heavy going but if the various articles are saying what I think they’re saying, the stuff is highly conductive in addition to having insanely high electron velocity. Electron behavior in graphene is plain strange.

    All that said, it’s also a bit of a dark mirror at present: researchers see vast possibilities but are only beginning to figure out which are achievable and useful, and which are wishful thinking. What they dream and what we eventually get are likely to be as different as a Hugo Gernsback radio magazine from the 1910s is to your cell phone and microwave oven.
    * The orange-gold color is a bit of a giveaway.

    • Christopher James Huff

      Kapton might easily be the substrate, but isn’t the dielectric…they need something that follows the surface of the graphene to give a high surface area, and which is much thinner. Supercapacitors use electrolytes that produce a dielectric layer electrochemically. More info: http://www.photonics.com/Article.aspx?AID=50784

      The LightScribe-produced graphene has a conductivity of 1738 S/m. Copper is 5.96e7 S/m. It might be better than other forms of carbon used for supercapacitors, but nichrome (an alloy used in resistive heating elements and wire-wound resistors) is a better conductor.

  • Christopher James Huff

    As for rapid-charging your car, there’s issues with just handling the amounts of electrical power required. Say your car can put out 50 kW (67 hp) for 4 hours. Recharging in 10 minutes takes 1.2 megawatts plus losses. (At the EPA limit of 10 gal/minute, a gasoline pump handles the equivalent of 16.4 MW.) With constant-power charging, that’s something like 1.2 kA at 1 kV. If the total resistance through the whole circuit is 0.1 ohm, you’re producing 144 kW of heat for those 10 minutes. Toasty. High voltages help keep current down but also increase leakage and risk of arcing and insulation failure.

    Also note that graphene is a “good” conductor but not a great one, copper being about 30 thousand times better than the LightScribe stuff. So this doesn’t get rid of the need for metal: you’ll want lots of copper (or aluminum, etc) in those capacitors so you can use high power charging/discharging without setting them on fire. This doesn’t seem difficult though, I bet you could burn the graphene layer right on top of a conductive metallized layer.

  • Rick

    best hardware hack in a long time, using a DVD burner to make such items.