Could you try to be a little more specific.
I suppose that you are not looking for Zinc-air batteries for your hearing aid. Because they are high energy density but only primary and probably not really up to the task of driving a car.
But try to put some numbers on what you are looking for, and also a if todays available Lipo is high energy enough, then you have multiple choice.
If Your looking for over 200wh/kg then you might get a hard time finding something to buy yet.
I think the most commercial technology is lithium-based. A good exaple I know of, are Kokam cells, they are higher than TS-cells, but not as commercial as TS.
The technology should be litium-based, but other high-densitys are also welcome as well.
Of course, the energy density should be as high as possible along with high cacle life as well.
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