Batteries that Breathe
With the launch of the Nissan Leaf and Chevy Volt, it's been a big year for electric vehicles, but their batteries still have a fairly limited range without a recharge. For a car running on today's lithium-ion batteries to match the range provided by a tank of gasoline, you'd need a lot more batteries, which would weigh down the car and take up too much space.
But what if you could take away one of the electrodes in a battery and replace it with air? Researchers estimate that a lithium-air battery could hold 5 to 10 times as much energy as a lithium-ion battery of the same weight and double the amount for the same volume. In theory, the energy density could be comparable to that of gasoline.
"No other battery has that kind of energy density, so far as we know," says Ming Au, principal scientist at Savannah River National Laboratory (SRNL), in Aiken, S.C. Au was one of several scientists who reported new research into rechargeable lithium-air batteries during the fall meeting of the Materials Research Society, in Boston.
In such a battery, the anode is made of lithium. The cathode is oxygen, drawn from the surrounding air. As the lithium oxidizes, it releases energy. Pumping electricity into the device reverses the process, expelling the oxygen and leaving pure lithium.