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The Register reports
In a paper published at [Proceedings of the National Academy of Sciences] (abstract), the researchers claim capacitance of more than 1,100 Farads per cubic centimetre--or around 1,145 Farads per gram, which is about as much as they reckon you could get out of the manganese dioxide (MnO2) in the cap.
Using a combination of graphene and MnO2, the researchers say the energy density they can achieve can be as high as 42 Watt-hours per litre, which is getting close to that of a lead acid battery.
It's not much yet: the demonstrator pictured below from the UCLA California NanoSystems Institute is one-fifth the thickness of paper, however it can hold charge long enough to power the demo LED overnight.
That, the university claims, beats a thin-film lithium battery on a pound-for-pound (or rather gram-for-gram) basis.
Manganese dioxide is cheap and plentiful, and is good at storing charge--which is why it's popular in dry-cell batteries and alkaline batteries.
The combination of the MnO2 and laser-etched graphene--the secret sauce in all of this--can be produced without dry rooms or extreme temperatures.
(Score: 2) by frojack on Monday April 06 2015, @10:02PM
Another question is the safety factor of large capacitors.
LiPoly batteries are dangerous enough all by themselves, because the high current capability.
But Capacitors can usually dump their entire charge in a split second.
No, you are mistaken. I've always had this sig.
(Score: 2) by kaszz on Monday April 06 2015, @11:57PM
So what happens if a fully charged capacitor with 306 MJ is smashed or crushed?
(Capacitor energy in joule = 1/2 * (Capacitance [F]) * (Voltage [V])^2)
For a comparison A Tesla Model S Review [autoevolution.com] specify the battery to 2.450 x 2.440 x 0.102 meters = 0.6098 m³. Tesla Model S [roperld.com] battery has a voltage of 402 V. The weight is 544 kg.