Via the MIT Technology Review, today I learned that some guys in Korea claim they have a new type of graphene supercapacitor design or material or something that allows you to charge an EV-sized pack in about 16 seconds. Huh.
In the spirit of propagating information that I have no way to verify, here you go, from the MIT source:
Santhakumar Kannappan at the Gwangju Institute of Science and Technology in Korea and a few pals say they have a solution based on the wonder material of the moment–graphene. These guys have built high-performance supercapacitors out of graphene that store almost as much energy as a lithium-ion battery, can charge and discharge in seconds and maintain all this over many tens of thousands of charging cycles.
The trick these guys have perfected is to make a highly porous form of graphene that has a huge internal surface area. They create this graphene by reducing graphene oxide particles with hydrazine in water agitated with ultrasound.
The graphene powder is then packed into a coin-shaped cell, and dried at 140 degrees C and at a pressure of 300/kg/cm for five hours.
The resulting graphene electrode is highly porous. A single gram of this stuff has a surface area bigger than a basketball court. That’s important because it allows the electrode to accomodate much more electrolyte (an ionic liquid called EBIMF 1 M). And this ultimately determines the amount of charge the supercapacitor can hold.
Kannappan and co have measured the performance of their supercapacitor and are clearly impressed with the results. They say it has a specific capacitance of over 150 Farrads per gram can store energy at a density of more than 64 Watt hours per kilogram at a current density of 5 Amps per gram.
That’s almost comparable with lithium-ion batteries which have an energy density of between 100 and 200 Watt hours per kilogram.
If you want to see the original paper, it’s here. It’s got all sorts of cool graphs and stuff I don’t understand. Here’s a summary from it:
The key of graphene synthesis for high performance supercapacitors is to have a high surface area and good electrical activation.
There are several methods to synthesis graphene such as Hummer’s method, dispersion method, microwave method, and electrochemical method. But, the graphene synthesized from the above mentioned methods still delivered low capacitance performance, which cannot be adopted for practical applications.
It is well known that the electrochemical performance of graphene could be enhanced by improving their surface
and morphological properties. Graphene synthesis method has to be improved on the oxidiation, exfoliation and reduction process.
In this work we synthesized graphene using tip sonication for exfoliation based on the modified Hummer’s method.
Using ionic liquid a superior capacitance value with an operating voltage of 3.5 V was achieved with energy density 83.36 Whkg-1 at a current density of 2.5 Ag-1at room temperature. Several cells were assembled to check the
repeatability of the performance and all cells exhibited similar results with plus or minus 15 %
variation in specific capacitance
I can’t decide which I’d like to see first. This, or my jetpack. Or this in my jetpack.
If you want to make this stuff at home, using simple things around the kitchen, see my post How to make a Graphene Supercapacitor, here.