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Quest for better battery

Page history last edited by PBworks 16 years ago

 

MIT Builds Efficient Nanowire Storage to Replace Car Batteries

Could the ultracapacitor replace lithium ion in hybrids and plug-in vehicles? Our senior automotive editor already thinks the science adds up, but it’s in a tiny box at a messy lab that the future of automotive efficiency is taking a surprising turn toward extending range and battery life.

Published on: February 29, 2008

CAMBRIDGE, Mass. — Sometimes the cliché fits: It looks like a bomb went off—not necessarily in this lab, but somewhere, with the aftermath seemingly carted here. The gutted remains of a sedan, its engine exposed, the seats ripped out of the frame, sits encased in cables. At other workstations the focus is a single part—an isolated camshaft, an alternator hooked up to test apparatus. It would be easy to misinterpret this place and think that researchers at MIT’s Lab for Electromagnetic and Electronic Systems (LEES) are either piecing back together some shattered car or entering the Automotive X Prize. In fact, each of these experiments has different methodologies, but many have the same goal: automotive efficiency, by any means necessary.

The wired car, for example, is an effort to test more detailed diagnostic systems, with sensors that detect changes in the system’s electrical signature—and maybe even warn you before the starter motor fails. And the modifications made to the alternator would let it run at 30 percent greater efficiency, with a smoother electrical system translating to about 1 mpg in improved mileage. Researchers estimate that the increased cost for the manufacturer would be about $5.

One of the most promising experiments here is tucked away in what appears to be the messiest part of the entire lab, a small room littered with hand tools and testing gear. Joel Schindall, the associate director of LEES, pulls a tray out of a cabinet and flips it open. Inside are four black squares, like overturned tiles from a Magnetic Poetry set. If my job was to clean out this lab, I would probably take one look at these unassuming little things and fling the entire tray into the nearest trash can. Because unless they’re under an electron microscope, vertically aligned carbon nanotube arrays don’t look like much.

The point of these particular arrays is to capture ions and eventually give traditional rechargeable batteries a run for their money. The focus of Schindall’s research is ultracapacitors, which store drastically less energy than a battery but have essentially none of the drawbacks. In any capacitor, there’s no battery memory caused by partial discharging and no reduction in capacity with each recharge. “They never wear out, they have no electrolyte, they don’t have any chemistry taking place in them,” Schindall says. “It’s just an electric field that stores the energy. So you can recharge a capacitor a gazillion times. It’s very efficient—just the internal resistance of the wires.” The ions cling electrostatically to materials in a capacitor, which also allows for much quicker charge times. And by avoiding the chemical reaction that drives traditional batteries, there’s no real danger of a capacitor suddenly overloading—or exploding like a laptop’s lithium-ion battery pack. (For more on how this technology works, read senior automotive editor Mike Allen’s new take on why ultracapacitors could replace batteries in hybrid cars.)

The problem with capacitors—and the reason they’ve taken such a back seat to batteries since they were first stumbled upon in the ’60s—is capacity. Even ultracapacitors can manage only a fraction of the power of a lead-acid or lithium-ion battery. So the recipe for a better ultracapacitor is more surface area. Researchers have already expanded capacity with the addition of activated carbon coatings, which are porous enough to provide an effective surface area that’s 10,000 times greater than the materials previously used to gather ions. Around four years ago, Schindall was reading about various experiments that utilized nanowire arrays, when he experienced—though no scientist, Schindall included, would ever actually put it this way—the proverbial “eureka” moment.

By replacing the porous activated carbon used in ultracapacitors with tightly bunched nanotubes, Schindall believed that the ion-collecting surface area could be increased by as much as five. Since current ultracapacitors can store around 5 percent of the energy in an equivalent-size battery, the addition of nanowires could bring this up to 25 percent. “And you can also operate [the ultracapacitor] at a higher voltage with the nanotubes, and that’s about another factor of two in energy,” he says. “We are hopeful—we haven’t proven it—that we can get up somewhere between 25 and 50 percent of a battery’s energy. At that point, it becomes a compelling device for many applications.”

Those applications could include not only electric vehicles, where the benefits of unlimited charge cycles and less overload-prone storage are clear, but in hybrid cars as well. The math gets a little complicated here, but Schindall says that even standard ultracapacitors, with their relatively paltry 5 percent storage, are potential competitors for the pack in his Toyota Prius. “In order to prolong the life of the battery in my car, they only use it over the middle 10 to 15 percent of its range,” he says. “So actually I’m only using perhaps 15 percent of the capacity. With an ultracapacitor you can use it all, or almost all. So the difference between 5 percent and 15 percent is not nearly as severe.”

According to Schindall, ultracapacitors would also outlive the car, possibly solving the complicated warranty issues surrounding hybrids and, whenever they’re finally released commercially, plug-in hybrids. If nanotube ultracapacitors can reach that 25 or 50 percent mark, then they could not only compete with the batteries currently used by Toyota, but thanks to their ability to discharge without risk, they could provide even longer ranges. “I try to contain myself, because it hasn’t been proven yet, but it could be a real paradigm change,” Schindall says.

The process of creating the nanowire arrays is relatively straightforward—a tiny piece of conductive substrate is coated with a catalyst, and then placed in a vacuum chamber. The chamber is then filled with carbon gas, and the square is heated until a black, sootlike coating appears. After about 10 minutes, the tile is complete, and the nanowires are fully grown. The challenge has been in reaching the theoretical capacity that Schindall’s team originally calculated. So far, the nanotubes can match the energy storage of standard ultracapacitors, but the goal remains to boost that capacity by a factor of five or even 10. “A couple of years ago, we thought we were six months to a year away. And that time has come and gone,” he says.

The next step for this project is to create test cells about the size of watch batteries to be distributed to existing ultracapacitor manufacturers. The team will also release its latest results, but by allowing companies to independently verify that data, Schindall believes it could demonstrate the commercial viability of the nanotube approach. He hopes to have those test cells ready within a year, or possibly as soon as a few months. Still, it could take years for ultracapacitors of any kind to reach the kind of production volume and capacity necessary to rival batteries in the marketplace. So for now, these nano-dusted squares are going back in their tray and back on the shelf to fight for energy storage supremacy another day.

 

In Quest for Better Battery,

Keep an Ion Nationalism

By NORIHIKO SHIROUZU

April 13, 2007; Page B1

 

In 2005, General Motors Corp. executives -- blue over their company's less-than-green reputation and envious of eco-darling Toyota Prius -- began searching the world for advanced batteries they hoped would power a new generation of gas-electric hybrid cars.

 

Most roads led them to Japan, the leader in battery technology and Toyota Motor Corp.'s home turf. Several GM engineers and executives describe their experience at Panasonic EV Energy Co. Ltd., one of the top makers of hybrid-car batteries, as typical of the reception they received there: When GM team members asked for detailed information about the company's most sophisticated automotive lithium-ion batteries, Panasonic EV refused.

 

A Panasonic EV spokesman says that as a matter of company policy it only discloses that kind of information to its parent company, Toyota.

 

Toyota Prius fitted with A123 Systems' lithium-ion batteries

 

The car business may have gone global, but the rush to develop new technology to reliably and inexpensively electrify 21st-century cars has rekindled some 20th-century-style economic nationalism. Facing growing pressure to curtail greenhouse-gas emissions, U.S. auto makers are increasingly worried that the critical battery technology they'll need to compete is getting locked up by Japanese rivals who moved more quickly to develop gas-electric hybrid vehicles.

 

"It's important to have the knowledge base on advanced automotive battery technology and manufacturing capacity right here locally in the U.S." says Beth Lowery, GM vice president of Environment and Energy.

 

So now, GM, which sells more than half its vehicles outside the U.S. and has an aggressive strategy to shift more purchasing and engineering to Asia, is talking up the importance of an American solution to the problem of building longer-lasting, more-reliable, less-costly automotive batteries, and looking for help from the federal government to subsidize those efforts.

 

One beneficiary of this battery war is a small Watertown, Mass., start-up called A123 Systems, which has developed a small pack of lithium-ion batteries that can be retrofitted into the spare-tire well of a Toyota Prius. The batteries turn the Prius into a "plug-in hybrid," which can be recharged through an electrical outlet and run almost exclusively on electricity in the first 40 miles of driving. During a test drive around Watertown, near Boston, there is nothing noticeably different about how the converted black Prius drives, except for a screen in the center of the car's dashboard that flashes its eye-popping fuel economy, sometimes 100 miles to the gallon and at other points 150 miles to the gallon.

 

This is the kind of technology GM wants to use, to develop, among other future vehicles, a Saturn Vue Green Line plug-in hybrid SUV and a real-world version of the Chevrolet Volt show car the company has been promoting to demonstrate its seriousness about clean technology.

 

Nearly all hybrid vehicles sold today, including the Toyota Prius, are equipped with a less sophisticated kind of technology, nickel metal hydride batteries. But these batteries and the accompanying technology are heavy and expensive -- adding $2,000 or more to the cost of a car. Moreover, nickel metal hydride battery systems can't power the car very far on electricity alone, which means the fuel savings are relatively modest, especially if the car is driven mainly at highway speeds.

 

Auto makers are looking to lithium-ion batteries to take hybrid vehicles to the next level by allowing them to be recharged from the electrical grid, theoretically reducing total carbon emissions. The batteries would be able to pack more electricity in the same space and weight as the current generation, enabling them to power the vehicle for longer distances on electricity alone.

 

Toyota, considered the industry's hybrid leader, is looking to adopt lithium-ion technology in the redesigned Prius, due to be launched as early as the second half of 2008. Rivals, from GM to Honda Motor Co. to Ford Motor Co. to DaimlerChrysler AG, are fighting to match Toyota and are expected to come out with their own lithium-ion hybrids by the end of the decade.

 

As with many other technology wars -- from computer operating systems to video recorders to music players -- each of the combatants wants to be the winner that sets the industry standard, giving it an edge as the market moves from old technology to new. The key will be finding the chemical recipe that makes lithium-ion technology safe, durable and reliable enough to power cars under a wide range of road and temperature conditions without breaking down.

 

"There's a global economic challenge for our competitiveness" with lithium-ion batteries, said Alexander Karsner, assistant secretary of energy efficiency and renewable energy of the U.S. Department of Energy. He believes it's critical for the government and the private sector to invest in the technology because U.S. companies are falling behind Japanese rivals in commercializing high-powered, lightweight automotive batteries.

 

The U.S. Department of Energy, in collaboration with the U.S. Advanced Battery Consortium, which is made up of Detroit's three auto makers, last year awarded A123 a $15 million contract to develop its version of lithium-ion technology for hybrid-electric vehicle applications. In addition to the A123 contract, the Energy Department has requested $41 million this year to continue advanced battery research. There are also broad energy programs under which that could provide loan guarantees to battery companies.

 

Meanwhile, in Japan, the Ministry of Economy, Trade and Industry last year moved to consolidate various state-sponsored battery projects into a single national battery project with a focus on automotive use and a first-year budget of 4.9 billion yen ($42 million).

 

Haruhiko Ando, the Japanese trade ministry official who spearheaded the move, believes the global leadership positions of Sanyo Electric Co. and Panasonic EV in advanced automotive battery technology happened in part because of Japan's long-standing strategy to make batteries a top research priority.

 

"Detroit is belatedly realizing the true importance of having an edge in electrification of vehicles," Mr. Ando said.

 

South Korea, China and the European Union also have government-supported advanced battery projects, according to U.S. and Japanese government officials and documents. And a joint venture between Johnson Controls and French battery cell producer SAFT, a €560 million ($751.9 million) a year maker of batteries for industrial and electronics uses, also is vying to supply GM.

 

A123 was founded in 2002 by Massachusetts Institute of Technology professor Yet-Ming Chiang, former American Superconductor executive Bart Riley and entrepreneur Ric Fulop. The company, which has 250 workers compared with about 1,000 at Panasonic EV, has raised $100 million in capital from investors, including Sequoia Capital, a Menlo Park, Calif., venture capital firm, and General Electric Co.'s commercial-finance unit. It already has more than $150 million of orders for its breed of lithium-ion batteries, which Black & Decker Corp. now uses in its popular power tools.

 

"We feel pretty good about the company, as well as a few others in the market today," says Joe LoGrasso, engineer group manager of GM's hybrid energy storage systems, of A123.

 

Prof. Chiang says "a key differentiator" for A123's technology is a design that makes it less likely the batteries will overheat and catch on fire -- a problem that has bedeviled computer makers and a concern if an auto maker tries to apply lithium-ion battery technology to vehicles.

 

While blessed with strong private backing and the benefit of Prof. Chiang's technology, A123 Chief Executive David Vieau believes the company couldn't have accomplished the progress it has made without financial assistance from the U.S. government.

 

"Every bit of government assistance helps," Mr. Vieau says.

 

Write to Norihiko Shirouzu at norihiko.shirouzu@wsj.com

 

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