2012-03-06

Lithium Air: The Quest To Build The Electric Vehicle Battery That Will Make Gas Guzzlers Irrelevant

The same kind of battery that’s powering your laptop is what powers electric cars. That doesn’t make much sense, so scientists are hard at work on next-gen batteries that will make fears of running out of charge a thing of the past.

Despite the rising cost of gasoline, electric vehicles still remain outside the mainstream. There are a number of reasons for this—people can’t afford to buy a new car every year, there are still far more gasoline-powered options, et cetera—but chief among them is range anxiety, or the fear that the EV battery will peter out while driving. It’s not an unreasonable fear; electric cars today have an average range of 100 to 200 miles, which isn’t enough for long trips. And an EV highway charging infrastructure is still years away from really taking off.

These are all problems with the lithium ion batteries found in today’s vehicles. Lithium air batteries, which have an energy density 1,000 times that of lithium ion batteries, are a different story. They can provide enough juice for a car to go 500 miles at a time before a battery recharge is necessary. With that kind of range, there’s no need for an extensive charging infrastructure. Most people can just wait until they get to their final destination to charge up. When that happens, EVs will truly be competitive with gasoline-powered cars.

Lithium air batteries aren’t on the road today, but a group of researchers at IBM and a handful of national labs have been working on bringing them to market since 2009. I visited Winfried Wilcke, principle investigator of the Battery 500 Project, to learn more about the project that could overhaul the EV landscape.

In essence, lithium air batteries work by "breathing air"—they use air while driving, and release it while charging. Where lithium ion batteries use metal oxides in the positive electrode, lithium air batteries use carbon, which is significantly lighter. Lithium air batteries also have a much higher energy density because they use an open system—carbon reacts to the oxygen in the air—while lithium ion batteries use a closed system that makes them easier to build (you don’t have to worry about external contamination) but limited in energy density.

"[Lithium air batteries] are like burning lithium, except the energy shows up as an electron current that can drive a motor," explains Wilcke.

IBM’s lithium air battery lab.

While promising, lithium air batteries aren’t quite ready for commercial production. Wilcke estimates that they will be viable sometimes between 2020 and 2030—if all the kinks can be worked out. That includes ensuring that the price is right. "It’s not clear that this will succeed in an economically viable way," admits Wilcke.

Researchers also need to improve stability. So far, labs haven’t been able to create a lithium air battery that has both high capacity and many charge cycles. For some perspective, lithium air batteries need about 500 charge cycles to last 200,000 miles (a good battery life). Researchers have only been able to create batteries with 25 charge cycles.

Says Wilcke: "We know the the electrochemical reaction underlying lithium air batteries works, but this is still basic bleeding-edge research."

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