• Number 329  |
• January 24, 2011

Argonne battery technology helps power Chevy Volt

This month, thousands of new Chevy Volt owners will begin the real road tests of the first mass-produced plug-in hybrid electric car. While much of the car's engineering is unique, consumers may be unaware that some of its most extraordinary technology is inside the nearly 400-lb. battery that powers the vehicle in electric mode.

The battery's chemistry is based in part on a revolutionary breakthrough pioneered by scientists at the U.S. Department of Energy's Argonne National Laboratory.  The new development helps the Volt's battery—a lithium-ion design similar to those in your cell phone or laptop—last longer, run more safely and perform better than batteries currently on the market.

"To me this cuts right to the heart of green energy," said Jeff Chamberlain, who heads Argonne's battery research and development. "This battery technology is a step towards energy independence for the U.S.; it helps create jobs; and it can have a positive impact on the environment."

The story begins in the late 1990s, when the DOE's Office of Basic Energy Sciences funded an intensive study of lithium-ion batteries. “Existing materials weren't good enough for a high-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 for an electric vehicle."

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. 

At its most basic level, a lithium battery is composed of a negatively charged anode and a positively charged cathode. Between them is a thin membrane that allows only tiny, positively charged lithium ions to pass through. When a battery is fully charged, all of the lithium ions are contained in the anode. When you unplug the battery from the charger and begin to use it, the lithium ions flow from the anode through the membrane to react with the cathode—creating an electrical current.

The team wanted to improve the cathode, the positively charged material. They began by using incredibly intense X-rays from Argonne's Advanced Photon Source synchrotron to monitor and understand reactions that occur in lithium batteries—in real time. Next, 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 existing designs.

Because manganese-rich 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 upped 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.

Submitted by DOE's Argonne National Laboratory