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Search for a better battery keeps going and going

Lithium-ion batteries may eventually give way to tiny fuel cells.

By Staff writer of The Christian Science Monitor / September 18, 2006



Cellphones and laptop computers are so useful because they've cut the cord. Powered by tiny, lightweight batteries, they operate for hours far away from any power outlet.

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Today these and other portable devices largely run on lithium-ion batteries, which pack more electrical punch per pound and square inch than earlier nickel-based rechargeables did. But the dangers and limits of this technology were exposed last month when Dell and Apple asked customers to return nearly 6 million lithium-ion laptop batteries made by Sony Corp. that could overheat and start a fire. In a much smaller recall, Matsushita Electric Industrial Co. also said last month that it would recall 6,000 similar batteries used in its Panasonic laptops sold in Japan because of concerns that they might overheat.

While the recalls embarrassed some of high-technology's biggest brand names, they aren't likely to change the way portable devices are powered – at least in the short term, say industry observers. Lithium-ion (li-ion) battery technology, introduced to consumers in 1991, still has plenty of room to improve in both safety and performance, while better alternatives using different chemistries, including long-touted fuel cells, still aren't ready for prime time.

Last week, a consortium of battery manufacturers met to hammer out new design specifications for li-ion batteries, including improved safety standards. The hope is that the standards will be accepted and adopted in a matter of months, says Kimberly Sterling, a spokeswoman for IPC, the electronics standards association in Bannockburn, Ill., that sponsored the meeting.

The rechargeable li-ion batteries found in nearly all laptops, cellphones, and other portable devices can overheat or even catch fire if tiny metal fragments, left over from the manufacturing process, get into the electrolyte, the medium through which charged particles flow between a battery's positive and negative sides.

The metal fragments lodge in tiny pores in the plastic separator between the battery's positive and negative sides. That causes short circuits that may lead to dangerous overheating. These concerns were the apparent cause of the recent recalls.

"The only thing that should move in a lithium battery are the lithium ions," the electrically charged atoms, says Steve Carlson, president and CEO of Optodot Corp., in Boston, which is developing a new battery separator. "You don't want to have any tiny particles in the electrolyte moving around."

Optodot hopes to make batteries safer in two ways, he says. The company's separators are made of an inorganic material that, unlike plastic, can't melt or shrink. And, using nanotechnology, the separator's pores are about five times smaller than those in other separators, too small for the metal fragments to lodge in them. His company's product, not yet on the market, is being evaluated by a number of manufacturers, Mr. Carlson says.

"There's a need now for second-generation designs. And I think that's what these [recall] events bring out," Carlson says. "We need a better separator, we need a better electrolyte. It's all open for better design." He expects li-ion batteries to be even more powerful in the future and able to be recharged many more times before wearing out.

Other chemistries could be used to create safer batteries, but so far they don't provide as much power or operating time in such a small, light package. That makes li-ion attractive, despite safety concerns.

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