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Boeing announced late today that it's postponing deliveries of its new 787 Dreamliner because of problems with the aircraft's big batteries. Aviation authorities in the U.S. and abroad grounded the new plane this week after those batteries failed, possibly overheating, on two planes operated by Japanese airlines. One battery burned while the plane was on the ground. These lithium-ion batteries are new to jetliners.
As NPR's Christopher Joyce reports, they are powerful, lightweight and fragile.
CHRISTOPHER JOYCE, BYLINE: Lithium-ion batteries are all around us.
VINCE BATTAGLIA: Everyone's carrying a lithium ion battery in their pocket today and there's not a big issue.
JOYCE: Vince Battaglia is a chemical engineer at Lawrence Berkeley Lab in California. The batteries are in cell phones, laptops, cameras. They produce twice the voltage traditional batteries do. And when they go bad, that power turns into heat. Battaglia says this is not a big issue because the batteries usually are smaller than your pinkie.
BATTAGLIA: The energy is small. It's easy to get the heat out of that little battery.
JOYCE: A small battery loses its heat quickly. But if you supersize that battery, up to, say, the size of a big suitcase...
BATTAGLIA: When you go to these bigger cells, you've got all the heat in one cell. You've got to get it out.
JOYCE: You do that with fans or circulating a coolant around the battery. That works fine so long as the battery is intact. But chemical engineers know that lithium-ion batteries have an Achilles' heel. Well, more like an Achilles' ankle than heel, two weak spots. One is the fluid inside the battery called the electrolyte. Positive and negative ions flow back and forth through the electrolyte, creating electricity. In normal batteries, the electrolyte is an acidic water. In lithium-ion batteries, it's a flammable organic compound. Donald Sadoway is an engineer with MIT.
DONALD SADOWAY: And so if you do get up to temperature, you've got fuel there. It'll burn.
JOYCE: And you can get high temperature because of the second weakness. It's a thin membrane inside the battery. It regulates the flow of ions in that electrolyte fluid. But if that membrane breaks, the fluid heats up.
SADOWAY: You breach that membrane and now you've got two compounds that want to react with each other violently, and there's nothing to prevent them from doing so.
JOYCE: If it gets hot enough, the electrolyte fluid vaporizes and escapes. Think of that brandy you pour into a hot skillet and light up for a little flambe. Laptop batteries sometimes burn like this. And one of Chevrolet's Volt electric cars did. After a controlled crash test, the battery's electrolyte got loose and burned the car to a crisp. Berkeley's Vince Battaglia says these batteries are pretty delicate. He says he'd drive a car with a lithium-ion battery, but he worries about what happens when the internal membrane gets damaged.
BATTAGLIA: If I got in an accident, I wouldn't take it into my garage and plug it in.
JOYCE: But Sadoway at MIT says these batteries certainly can be used safely.
SADOWAY: You know, we know what the possible failure modes are, and they are defendable. You can make these lithium-ion batteries absolutely bulletproof, safe and everything else. But, you know, the question is what's your price point?
JOYCE: That price point may be too high for the auto industry. John Hanson, Toyota's environment and safety manager, says the company uses them in its all-electric vehicles and trusts them. But Toyota is looking for alternatives.
JOHN HANSON: The only thing that we have against lithium is that in order to go to the next step in developing vehicles that the mass market will buy, they have to be less expensive and they have to deliver more range. And we can't get that from lithium.
JOYCE: Their future in airplanes, however, likely hangs on what engineers learn from the two incidents on the Dreamliner. Christopher Joyce, NPR News.
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