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The Search for Cheaper, Lighter Car Batteries

Electric cars are all the rage, but we still need lighter, cheaper batteries. Lithium-air may be the answer.

A lithium-water battery from PolyPlus, a first step toward a lithium-air battery. The lithium is protected from water by a ceramic membrane that lets ions pass but not water molecules. They will first be used to power underwater robots.

The Nissan Leaf, an electric car that will go on sale this fall, is priced at $33,000. It’s a $16,500 subcompact car that costs double that thanks to a battery estimated to cost $16,500. The eStar, an electric truck being developed by Navistar, will sell for $150,000 because it will tote a battery that costs at least $75,000. Cost isn’t the only problem. Both the Leaf and the eStar will be limited to 100 miles of driving on a charge.

Both vehicles are powered by the same kind of batteries that power your laptop, ones that shuttle lithium ions back and forth between two electrodes. The unattractiveness of electric vehicles boils down to two facts: Rechargeable batteries cost a lot and weigh a lot. A lithium-ion battery, at its best, packs 110 watt-hours of energy per pound. Gasoline has 6,000 watt-hours per pound. Now, a gasoline motor is inefficient, discarding 85% of the fuel’s energy–losing it to the transmission, wasting it on idling and discharging it as heat. Electric motors waste just 10%, but it still leaves gas with a 9-to-1 weight advantage.

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Yahoo! BuzzWhile battery makers are making impressive progress beating down the cost of lithium-ion batteries and improving their performance for cars, battery makers and electric vehicle builders agree that the world needs something new for electric vehicles.

“No one expects the lithium-ion battery to even double [in energy density],” says Winfried Wilcke, a nanoscale-science manager at IBM Research. “And we need to do much better even than that.”

Wilcke is the senior scientist in an IBM group that is trying to develop a battery that can do much better–more than seven times better, he hopes, or 800 watt-hours per pound. This would mean that a 125-pound battery would be competing with a 100-pound full gas tank.

The trick is to make use of something light and easily available: air. IBM and others, including carmakers like Toyota ( TM – news – people ) and the tiny 20-year-old PolyPlus of Berkeley, Calif., are working on what are known as metal-air batteries. One electrode is a metal (lithium is the most promising), but the other is air. This type of battery would be lighter for the simple fact that it doesn’t have to carry around one of its electrodes. The concept is, says Wilcke, a lot like burning gasoline, which is a dense energy source precisely because the oxygen it marries doesn’t have to be schlepped around.

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Too bad most of the batteries will be charged by coal fired, mercury spewing generators. 10% charged by non-renewable, undependable solar or wind. Only a small portion will be charged with non-bree….

Post a CommentThe benefits of metal-air batteries have been known for decades, and zinc-air batteries are made by the millions to power small devices like hearing aids. But no one has figured out how to make them bigger and rechargeable–that’s why this is still a bit of a science project. Hope now rests with improvements in materials science, computer modeling and techniques used to observe the behavior of materials at the atomic scale.

The goal is a car battery that can push a family of four 500 miles down the road. IBM calls its program the Battery 500 Project. A bill introduced in the Senate recently would pay a $10 million prize to the developer of a commercially viable electrical car battery that can go 500 miles on a charge.

Most batteries are packaged with both the positive electrode (called the cathode during discharge) and the negative electrode (the anode). For a lithium-ion battery the anode, often made of graphite, stores lithium ions when charged. The battery also includes a cathode made from some mixture of lithium and cobalt, iron, oxygen or phosphorus that collects the ions the way a parking garage stores cars. That’s the problem: “The weight of the cars is much less than the weight of the building,” says Wilcke. “The useful ions are dwarfed by the cathode material.”



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