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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 captain normal on Tuesday April 07 2015, @06:43AM
Aren't batteries just a capacitor? So maybe this is a better battery.
When life isn't going right, go left.
(Score: 5, Informative) by Anonymous Coward on Tuesday April 07 2015, @10:04AM
No, batteries are not just capacitors. This is most evident in the non-rechargeable batteries (there is no such thing as a non-rechargeable capacitor!), but also a rechargeable battery has very different characteristics from a capacitor.
Basically, a battery converts chemical energy into electrical energy. A rechargeable battery also allows the reverse process, converting electrical energy into chemical energy. A capacitor on the other hand stores electrical energy directly. This results in a different behaviour: For a battery, the voltage is mainly determined by the chemistry, and only slightly changes during discharge. On the other hand, the voltage of a capacitor is proportional to its charge. Since you usually need a fairly constant voltage for your circuits, this means you need some extra circuit between a capacitor and the circuit to provide the correct voltage, while a battery can often be connected directly. On the other hand, since a battery has to use chemical reactions to provide the charge, it can only provide a limited current (and in reverse, recharging a rechargeable battery also has a limited rate), while the charge/discharge rate of a capacitor is in practice only limited by the attached circuit.
Now a supercapacitor actually also uses chemical processes to increase the apparent capacity (that's also called "pseudocapacity", because strictly speaking it's not a capacity), but its characteristics are still mainly those of capacitors (that's why you call them supercapacitors, not batteries).