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? Over the past several years, researchers have been working on an alternative battery called a lithium-air battery. These batteries could significantly increase the range of electric vehicles due to their high energy density, which could theoretically be equal to the energy density of gasoline. Lithium-air batteries have an anode made of lithium and an ‘air cathode’ made of a porous material that draws in oxygen from the surrounding air. When the lithium combines with the oxygen, it forms lithium oxide and releases energy. Since the oxygen doesn’t need to be stored in the battery, the cathode is much lighter than that of a lithium-ion battery, which gives lithium-air batteries their high energy density. But one of the biggest challenges facing lithium-air batteries is their limited number of charge/discharge cycles. Whereas lithium-ion batteries can be recharged more than 100,000 times, the lithium-air battery can be recharged only about 50 times. Although single-use lithium-air batteries are already being used, for example to power hearing aids, electric vehicles require batteries that can be recharged thousands of times. The biggest problem with recharging lithium-air batteries is that it’s very difficult to convert the lithium oxide back into lithium. Currently, researchers can do this only by using catalysts, and even then some of the lithium oxide cannot be converted because it builds up in the battery. Researchers also face challenges in speeding up the recharging process and in keeping water vapor out of the oxygen, since lithium reacts violently with water. Scientists agree that it will be a few years before the battery reaches the commercial market, and for that to happen, will require significant funding,
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