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"gewg_" writes:

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.