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: 3, Informative) by subs on Monday April 06 2015, @10:11PM
1) Extremely fast charging not limited by internal resistance (and thus heat generation).
2) Insensitivity to temperature.
3) Insensitivity to deep discharge.
4) Extremely long life span since no chemical reactions take place which would erode an electrode or consume/pollute an electrolyte.
In short, if they boost the energy density to about lithium-ion or at least NiHM battery levels, that'd make EVs a practical replacement for ICEs, since you could pretty much hold equally as much charge, not make the vehicle too heavy and recharge in a couple of minutes at any service station along your route (no need to wait for hours to recharge). It would also allow making the battery pack last far beyond the lifespan of the mechanical parts of the vehicle.
In short, it takes all of the drawbacks of chemical batteries and removes them, assuming they can boost the capacity a bit more.
(Score: 2) by VLM on Tuesday April 07 2015, @11:51AM
Extremely fast charging not limited by internal resistance (and thus heat generation).
I can assure you that there is no such thing as a capacitor of any sort without series resistance (other than superconductor caps) and no such thing as a cap without series inductance. And square/cube law issues means "big batteries" of whatever sort are usually in thermal limit unless you play energy expensive games with liquid coolant.
I guess one way to phrase it, is with old small "normal" capacitors the capacity is so small that the thermal effects aren't a big deal beyond some weird corner cases with high power switching power supplies and some high power RF radio transmitter stuff.
(Score: 2) by subs on Tuesday April 07 2015, @02:38PM
I wanted to keep it simple. Fact is, caps react quite differently, since there's no chemical reaction going on inside which has a reaction rate limit (which is what gives rise to internal resistance as you try and pump more energy into it over a shorter period of time). Of course, it's still a real circuit and it still has some resistive component, but it's far less of an issue in the storage medium itself. You can still very well overheat in wires, contacts, connectors, etc. but the numbers are far prettier than for batteries. Of course, this has the converse effect that the far lower internal resistance can result in inadvertent discharge currents far higher than from batteries.