Rechargable and disposable batteries use a chemical reaction to produce energy. “That’s an effective way to store a large amount of energy,” he says, “but the problem is that after many charges and discharges … the battery loses capacity to the point where the user has to discard it.”

But capacitors contain energy as an electric field of charged particles created by two metal electrodes. Capacitors charge faster and last longer than normal batteries. The problem is that storage capacity is proportional to the surface area of the battery’s electrodes, so even today’s most powerful capacitors hold 25 times less energy than similarly sized standard chemical batteries.

The researchers solved this by covering the electrodes with millions of tiny filaments called nanotubes.
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This technology has broad practical possibilities, affecting any device that requires a battery. Schindall says, “Small devices such as hearing aids that could be more quickly recharged where the batteries wouldn’t wear out; up to larger devices such as automobiles where you could regeneratively re-use the energy of motion and therefore improve the energy efficiency and fuel economy.”