Battery technology: Better batteries will save the world. Too bad they're impossible to make.

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June 21 2011 10:39 AM

Better Batteries Will Save the World

Too bad they're impossible to make.

Nissan Leaf. Click image to expand.
Will batteries ever be able to compete with the stored power of gasoline?

In the early 1970s, the research arm of Exxon hired a promising young engineer named Michael Stanley Whittingham and asked him to invent something—anything—that could reduce the company's dependence on crude oil. Whittingham and a team holed up at an Exxon R & D lab in New Jersey, and, as engineers are wont to do, started mixing together chemicals to see what would happen. When they injected potassium into the rare metal tantalum, they noticed something extraordinary—the resulting mixture had an extremely high capacity to store energy.

Over the next few months they continued tinkering with various metals. Whittingham's team replaced tantalum with titanium, and because potassium was hazardous to work with, they switched it for lithium. When they were done, Whittingham raced to Exxon's headquarters to report to the board that they'd created something amazing. It was the first lithium-based battery that worked at room temperature, and it had the potential to upend the entire energy business.

Of course, that didn't happen. Soon came a recession, an oil glut, and the election of Ronald Reagan, which ended a great deal of government funding for research into advanced energy projects. Exxon licensed Whittingham's battery technology and closed off the division. And for a while, the dream of a perfect battery that could replace gasoline was, once again, dead.

This is how it goes in the battery business. As Seth Fletcher, a senior editor at Popular Science, recounts in his engaging new book Bottled Lightning: Superbatteries, Electric Cars, and the New Lithium Economy, scientists have been trying to build a better battery since before the days of Thomas Edison (who was a major battery tinkerer himself). (Disclosure: Fletcher and I share the same literary agent.) If we had batteries that matched the price and performance of fossil fuels, we would not only have cleaner cars, but we might be able to remake much of the rest of the nation's energy infrastructure, too. Wind and solar power are generated intermittently—sometimes the wind doesn't blow and the sun doesn't shine—and batteries can moderate that volatility. Stores of batteries placed in the electric grid could collect energy when the sun shines or when the wind blows and then discharge it when we need it. Not to put too fine a point on it, but you might say that the future of the world depends on better batteries—a better battery would alter geopolitics, mitigate the disasters of climate change, and spur a new economic boom.

But a better battery doesn't seem to be in the offing anytime soon. As Fletcher explains, physics, politics, and the price of gasoline have always conspired against the improvement of battery technology. Fletcher's book is hopeful—he investigates a number of promising technologies that might theoretically challenge the dominance of fossil fuels. But many of them are a long way from fruition, and the history of failure in the battery industry doesn't inspire confidence. We might get a better battery someday, and if we do it will probably come from China, which has become the hub of advanced energy production. But don't hold your breath.

The fundamental problem with batteries is the existence of gasoline. Oil is cheap, abundant, and relatively easy to transport. Most importantly, it has a high "energy density"—meaning that it's phenomenally good at storing energy for its weight. Today's best lithium-ion batteries can hold about 200 watt-hours per kilogram—a measure of energy density—and they might theoretically be able to store about 400 watt-hours per kilogram. Gasoline has a density equivalent of around 13,000 watt-hours per kilogram.

The only reason electric cars might one day compete with cars that rely on internal combustion is that gasoline engines are highly inefficient; nearly all of the energy stored in gasoline is lost to heat. But gasoline makes up for that flaw with another advantage: When your car's out of gas, you can refill it in a few minutes. With today's electrical infrastructure, batteries need many hours to recharge. There's some hope that we might one day install fast-charging stations across the country, but the researchers Fletcher interviews point out that this is a daunting challenge. The battery in today's Tesla roadster needs about four hours to charge. If you wanted to charge that battery in 15 minutes, you'd need a 200-kilowatt electric substation feeding the charging station. "Your house takes 1 kilowatt," one expert tells Fletcher. "If you want to have something like a gasoline fuel station that is all electrical, you're talking about multimegawatts of power at that station. And I just don't see that happening."

Neither do I. So what's the answer? Fletcher's book ends with a look at the most far-out research in the battery world—the lithium-air battery. In this design, lithium and carbon combine with oxygen from the air to form a system with a staggering potential to store energy. In theory, the lithium-air battery could store 11,000 watt-hours per kilogram, which makes it, Fletcher says, "the best chance battery scientists have to beat gasoline." A lithium-air battery could allow a car to drive 500 miles before recharging. With that range, you wouldn't need a nationwide system of quick-charging stations. You could drive pretty much wherever you wanted all day, and then recharge your car at night.

But lithium-air is the cold fusion of the battery world—a would-be game-changer that has the unfortunate downside of being impossible to achieve (probably). Researchers have been working at lithium-air for decades, but there are a number of challenges to overcome before such a battery might be commercially viable. For one thing, the system uses lithium metal, which is highly, explosively reactive with water. (In a lithium-ion battery, lithium is combined with another element in the cathode, and it is also present as a salt that's dissolved in a solution.) * Water, of course, is present in the air, so the very idea of a battery that mixes lithium metal with air has always seemed little more than a fantasy. Fletcher reports that the fantasy has become slightly more real lately. A company called PolyPlus has developed a way to coat lithium metal to protect it from moisture, and IBM has launched a research project aimed at building a lithium-air battery.

But with every advance, there's another hurdle. PolyPlus's innovation makes the lithium metal in a lithium-air battery easy to recharge, but nobody knows, yet, how to recharge such a battery. Figuring that out seems destined to take many more years. The chief technology officer of PolyPlus tells Fletcher that it will be "a long time before you see battery packs that are large enough and proven and tested enough that you would start thinking about transportation."

That's the paradox of battery research. Advanced batteries could well solve many of the problems that dog us today. But they'll only come about many, many years from now—and by then, it could be too late.

Correction, June 22, 2011: This article originally included an incorrect description of the components of lithium-ion batteries. The batteries include lithium both in the cathode and as part of a salt solution. (Return to the corrected sentence.)

Farhad Manjoo is a technology columnist for the New York Times and the author of True Enough.