You are thisclose to the breakthrough energy storage technology of the next millennium if you a) have a computer, b) buy a blank DVD, c) own or have access to a DVD label-burning device and d) pre-treat your DVD with a thin film of graphite oxide. Well, there might be an extra step or two involved, but that’s the basic idea behind a new method for making high-efficiency energy storage devices called supercapacitors. Researchers at UCLA headed by graduate student Maher F. El-Kadyh have demonstrated that an ordinary DVD pre-treated with graphite oxide can be inscribed by laser into components for a graphene-based supercapacitor using a commercially available CD/DVD label burning drive, in this case from the company LightScribe.
What’s so great about a supercapacitor?
Supercapacitors store energy like batteries, but they charge up and discharge far more quickly, giving them the potential to pack more power into a smaller, lighter space.
However, until now the conventional technology has been based on activated carbon electrodes, which are characterized by tiny pores that result in a relatively low ability to store energy. Activated carbon also fares poorly when it comes to discharging at a high level of power.
Graphene makes a better supercapacitor
By using graphene instead of activated carbon, the electrodes in El-Kadyh’s supercapacitor achieve a high degree of conductivity while providing a greater surface area, enabling it to store more energy. The research is being supervised by Richard B. Kaner, a professor of chemistry and materials science and engineering at UCLA, who has stated that the graphene supercapacitor can “store as much charge as conventional batteries, but can be charged and discharged a hundred to a thousand times faster.”
With this degree of storage and discharge efficiency, combined with light weight and extreme flexibility, the new supercapacitor could enable a new generation of high-performance portable electronics and solar cells.
A new way to work with graphene
According to Jon Cartwright of Chemistry World, the laser process enables the UCLA team to circumvent the fabrication difficulties that usually bedevils work with graphene, a sheet of carbon that is only one atom thick.
Despite (or because of) its extraordinary thinness, graphene possess extraordinary strength and unique electrical properties.
Graphite oxide is a yellowish substance that has been the subject of previous research into graphene manufacture, since it can yield a form of graphene under a variety of treatments including pulses of light. The problem is to achieve the precise, uniform structure of natural graphene, in bulk quantities.
The LightScribe laser works around that by reducing and stripping a thin layer of graphite oxide to form graphene on the spot. The result is a flat surface without the performance-inhibiting pores that characterize activated carbon.
Peel-away electrodes for your DIY supercapacitor
The graphite oxide coating is preceded onto the blank DVD by a layer of plastic. When the LightScribe operation is finished, the plastic can simply be peeled off the DVD with its atom-thick layer of graphene intact, and cut into shape literally with a pair of scissors (check out YouTube for a video of the process). Two of the sheets, with an electrolyte in between, form the supercapacitor.
If this whole thing rings a bell, you might be thinking of the “Shrinky Dinks” process developed by researcher Michelle Khane, who developed a new method for fabricating nanoscale circuits by printing them on plastic, shrinking them (literally, in a toaster oven, just like Shrinky Dinks), and transferring the pattern to flexible polymer sheets.
A new road to low cost alternative energy
Supercapacitors and other high efficiency energy storage solutions are key to the growth of the market for solar power and other forms of alternative energy, and laser scribed graphene electrodes could have a potentially significant role to play due to their potential for low-cost production, compared to activated carbon. The graphene process involves just one integrated layer rather than the complicated structure of a typical activated carbon electrode, and it uses a gel-based electrolyte that eliminates the flexibility issues and risk of leakage posed by liquid electrolytes.
In any case the UCLA team is confident that they are on to something. As described in a published abstract of their study:
“Devices made with these electrodes exhibit ultrahigh energy density values in different electrolytes while maintaining the high power density and excellent cycle stability of ECs.* Moreover, these ECs maintain excellent electrochemical attributes under high mechanical stress and thus hold promise for high-power, flexible electronics.”
Image: Courtesy of UCLA. Follow Tina Casey on Twitter: @TinaMCasey.
*Note: UCLA press materials refer to supercapacitors and electrochemical capacitors (ECs) interchangeably.
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