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Argonne Battery Technology Helps Power Chevy Volt

The 2011 Chevy Volt's 16 kWh battery can be recharged using a 120V or 240V outlet. Image courtesy of General Motors. View larger image.

When General Motors recently introduced the Chevy Volt as the first mass-produced, plug-in hybrid electric car, it was widely viewed as a technological marvel.

In addition to the car's unique engineering, it has a battery that lasts longer, runs more safely and performs better than other batteries currently on the market. This novel battery chemistry is based in part on a revolutionary breakthrough pioneered by scientists at Argonne National Laboratory.

"Existing materials weren't good enough for a long-range vehicle," explained Michael Thackeray, an Argonne Distinguished Fellow who is one of the holders of the original patent. "The Argonne materials take a big step forward in extending the range of an electric vehicle."

The Argonne-developed technology offers the longest-lasting energy available in the smallest, lightest package: a 50–100 percent increase in energy storage capacity over conventional cathode materials. Further, its unique lithium- and manganese-rich mixed-metal oxide combination extends the operating time between charges, lengthens the calendar life and improves the inherent safety of lithium-ion cells.

A Decade of Research

But this potential game-changing technology is not brand new; it's the culmination of nearly a decade of research. The story begins in the late 1990s, when the U.S. Department of Energy's Office of Basic Energy Sciences funded an intensive study of lithium-ion batteries.

In order to improve the design, scientists had to know how batteries worked at the atomic level.

"What we really needed to do was understand the molecular structure of the material," said Argonne chemist Chris Johnson.

The Argonne research team wanted to improve the battery's cathode, the positively charged material. They began by using incredibly intense X-rays from Argonne's Advanced Photon Source synchrotron to watch chemical reactions while they were occurring in the lithium battery. Once these reactions were understood, they set out to modify and optimize the cathode materials. Using new synthesis methods, they created lithium- and manganese-rich materials that proved remarkably more stable than those found in existing designs.

Because these cathodes are more stable than those used in today's batteries, the new batteries are safer and less likely to overheat. Manganese is cheap, so the battery will cost less to manufacture. The researchers also increased the upper charging voltage limit to 4.6 volts—higher than the usual operating voltage—and saw a tremendous jump in the battery's energy capacity.

The Argonne battery design became, in a radical leap forward, cheaper, safer, and longer-lasting.

"To me, that's exceptional," said Jeff Chamberlain, who heads Argonne's battery research and development. "New advances often sacrifice cost or safety for performance; it's a rare breakthrough that improves all three."

The Next Generation

Batteries for electric and plug-in hybrid cars are much larger—and thus far more expensive—than laptop batteries, and they make up a large percentage of the car's price. Lowering the cost of the battery will lower the cost of all-electric and hybrid cars, according to Khalil Amine, an Argonne senior materials scientist, and subsequent improvements will improve battery performance even further.

"Based on our data, the next generation of batteries will last twice as long as current models," Amine said.

Furthermore, Chamberlain said that the new battery technology pioneered by Argonne can boost American manufacturing and create new jobs.

"Batteries are a large, heavy component of electric and hybrid cars, and so it's best to manufacture them near the factory where the cars are assembled," Chamberlain explained. "This means cars assembled in U.S. factories will also need battery factories nearby—creating more American jobs."

A total of $1.5 billion in stimulus grants went to several companies last year—including A123 Systems, Johnson Controls and Compact Power, an LG-Chem subsidiary—to build battery plants in the United States.

Chamberlain, who worked in private industry for 13 years before joining Argonne in 2006, says the national laboratories play a crucial role in developing these kinds of breakthrough technologies. "The labs perform basic research," he said. "In the U.S., businesses tend to invest in research that will pay off in the short term; in this field of research, the national laboratories are filling a gap by conducting the essential research that will change the game ten to 20 years down the road."

When companies show interest in the technology, he said, the labs collaborate with them to help adopt the method for large-scale production.

LG Chem licensed the technology from Argonne and used the materials to create the battery supplied for the 2011 Volt. GM has also licensed the technology for its own tests.

"Seeing this play out is absolutely gratifying," Chamberlain said. "We're developing technology that I'm highly confident will help make plug-in hybrid cars more economical. The work at Argonne ends up in the hands of taxpayers who paid for research. This is a fulcrum, a key component to moving away from fossil fuels."

Funding for this work was provided by the U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy, Vehicle Technologies Program and the Office of Basic Energy Sciences.

May 2011

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