Sandia LabNews

Hybrid cars coming: Sandia's lithium-ion battery research paves way toward American electric hybrids

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BATTERY TESTING — Pete Roth examines a battery cell before testing it in an Accelerating Rate Calorimeter (ARC) that raises the temperature around the cell at the same rate as the cell naturally heats up. (Photo by Randy Montoya)

In 15 years Americans will be routinely driving hybrid electric cars performing at 80 miles per gallon. Today’s internal-combustion-engine-only vehicle will become an artifact of history.

That’s the future Dan Doughty, Manager of Sandia’s Lithium Battery Research and Development Dept. 2521, envisions for this country.

If the US achieves this, Sandia will have played a key role in the success through its lithium-ion battery research. The lithium-ion battery is expected to be the "battery of choice" for hybrid electric vehicles — vehicles that combine a gasoline- or diesel-powered engine with an electric motor to increase fuel economy. The internal combustion engine would be used for constant-speed highway travel while the electric motor would operate during stop-and-go city traffic.

The Labs is a participant in the Partnership for a New Generation of Vehicles (PNGV), a research collaboration involving the federal government and the US automotive industry. PNGV’s goal: by 2004 produce a "production prototype" — the last stage before a car goes into production — of a full-size electric hybrid sedan that will get three times the mileage of today’s models with no sacrifice in safety, performance, affordability, or compliance with emission standards.

PNGV partners — including seven agencies, 19 federal laboratories, and USCAR, a consortium representing DaimlerChrysler, Ford, and General Motors — each research different areas of building a better hybrid electric car. Sandia focuses on energy storage — batteries.

"Batteries for electric and hybrid electric cars have come a long way in performance," Dan says. "But they still lag behind in calendar life and safety. We at Sandia’s Power Sources Technology Group work on both safety and life as part of the PNGV."

Sandia emphasizes the rechargeable lithium-ion battery, which combines high energy with the potential for power and cycle-life needed to make hybrid electric vehicles a reality.

The lithium-ion battery has four times the energy density of lead-acid batteries and two to three times the energy density of nickel-cadmium and nickel-metal hydride batteries. It also has the potential to be one of the lowest-cost battery systems. In a hybrid car it would be recharged by electricity generated by the engine as well as by energy recovered during vehicle deceleration.

As part of early PNGV activities, Sandia successfully developed new electrode materials using synthetic carbons and lithiated manganese oxides for lithium-ion batteries. The result is enhanced battery safety and improved cycle life. The materials displayed stability over the wide operating temperature range needed for vehicle applications.

More recently two Sandia researchers, Chris Crafts and Pete Roth (both 2521), have been characterizing lithium-ion cells to determine how and why they fail and to identify ways to correct the problems. The thermal safety of these cells must be assured before commercial use.

Lithium-ion batteries are currently used in smaller electronics such as camcorders, which have battery safety controls in place. These same controls may not work in the larger batteries needed for a hybrid electric vehicles.

Argonne National Laboratory, also a PNGV participant, developed the battery cells Chris and Pete have been testing. They spent 15 months testing "Gen 1," the first generation of cells for the PNGV research. They expect to receive "Gen 2," the second and improved generation of cells for testing, this month.

"For Gen 1 we had to develop testing procedures and figure out what to measure and how to measure it. Now, with all that in place, Gen 2 testing will go much quicker," Pete says. (See "From parts to the whole: Battery researchers work together," above.)

Last modified: August 28, 2000