Green Optimistic: LightScribe-Etched Graphene DVDs Making Supercapacitors Better Than Batteries
I never found a true application to those LightScribe-enabled DVD writers, and although I have one in my laptop, I don’t remember using it more than one or two times. UCLA researchers, on the other hand, may have discovered the ultimate way to store energy by using this technology to create world’s most efficient supercapacitors.
To make a long story short, they coated a thin plastic film (PET) with graphite oxide, designed a model on a computer, stuck the plastic sheet on a DVD and put it into the recorder. There, the LightScribe technology, using an infrared laser, turned the graphite oxide into graphene.
The most interesting part, though, is that this technique offers the most precise etching available. Also, the graphene layer is resistant to mechanical stress, and enables supercapacitors made with it to have much higher energy densities (the energy density tells us how far the car can go a single charge whereas the power density tells us how fast the car can go).
Maher El-Kady, a UCLA professor, says that “the devices can be charged and discharged for more than 10,000 cycles without losing much in performance,” unlike the average battery, which can only stand about 1,000 charge/discharge cycles.
The ultracapacitor LSG (Laser Scribed Graphene) electrodes made with this technology can also brag conductivities of 1738 S/m (compared to 10 to 100 S/m for activated carbon, currently used in making the capacitors) and a huge surface area of 1520 sq.meters/g. Some activated carbon variants can nevertheless do better, but they’re mostly expensive and hard to obtain. Controlling the pore size and structure on activated carbon has been proved to be rather difficult, which is why they failed to obtain high energy densities.
THE LSG-EC CAN EXHIBIT ENERGY DENSITIES OF UP TO 1.36 MWH/CM3, A VALUE THAT IS APPROXIMATELY TWO TIMES HIGHER THAN THAT OF THE AC-EC. ADDITIONALLY, LSG-ECS CAN DELIVER A POWER DENSITY OF ~20W/CM3, WHICH IS 20 TIMES HIGHER THAN THAT OF THE AC-EC AND THREE-ORDERS OF MAGNITUDE HIGHER THAN THAT OF THE 500-MAH THIN-FILM LITHIUM BATTERY. ALTHOUGH THE ELECTROLYTIC CAPACITOR DELIVERS ULTRAHIGH POWER, IT HAS AN ENERGY DENSITY THAT IS THREE ORDERS OF MAGNITUDE LOWER THAN THE LSGEC. (SCIENCEMAG.ORG)
The LSG devices are also flexible, being able to bend extremely, without any loss in its capacity. A slight 1% loss in electrical resistance has been observed after 1,000 bending cycles.
A way more complete version of this information, with thorough graphs, measurements, analyses and comparisons has been published in the journal Science, Vol. 335.
You can view UCLA chemist Richard Kaner speaking about the LSG supercapacitor and making a demonstration so you can picture yourself better how they’re made. Watch the video below (requires Flash):
[via UCLA/Sciencemag.org, thanks to Jennifer Marcus (UCLA) for the extra clarifications]