Inside lithium ion
Nickel-metal hydride batteries are hydrogen-based and require more expensive metals than lithium ion. When lithium-ion battery packs replace nickel-metal hydride packs in hybrids, they will be about the same size but half the weight. The implications are numerous.
A lighter battery pack would improve performance and increase fuel economy. Lithium-ion batteries also could enable plug-in hybrids to become a reality, says Al Mumby, general manager of Johnson Controls' hybrid-battery business unit.
Ford's Watson sees lithium ion as the battery of the future for his company's growing fleet of hybrids: the Ford Escape Hybrid and Mercury Mariner Hybrid and the upcoming Ford Fusion, Edge and Five Hundred, Mercury Milan and Montego and Lincoln MKZ.
Watson says lithium ion is expected to play a large role in Ford making a profit selling hybrids.
"We are not making money on hybrids today," he says. "Our goal would be to design an equivalent power level in the lithium-ion battery pack to provide an equivalent level of performance to the nickel-metal hydride. That way we could take advantage of the weight and cost efficiencies that come with lithium ion."
Before lithium-ion batteries replace nickel-metal hydride batteries in hybrids, battery manufacturers have a few hurdles to clear, says Dave Hermance, Toyota's executive engineer for environmental engineering.
"The challenge is to increase durability and learn how to manufacture lithium-ion batteries more efficiently," Hermance says.
Lithium-ion batteries are extremely sensitive to temperature and must be kept cool and well-ventilated. That means that before they can work in a hybrid, engineers must perfect a way to keep the batteries cool. If the batteries overheat, they could burst into flames.
Here's another obstacle: Not all lithium-ion batteries can be recharged quickly. Hybrid vehicles have regenerative braking systems, which create electricity when the driver applies the brakes. Nickel-metal batteries absorb that electricity quickly. Lithium-ion batteries need to be improved.
But Toshiba Corp. said last year that it had developed a lithium-ion battery that can be 80 percent recharged in less than a minute.
Hermance says lithium-ion battery technology is developing quickly. "A year ago, battery experts said lithium-ion batteries were 10 years away," he says. "Now they are saying two to four years from today for high-volume applications."
Hermance would not say when a Toyota hybrid would have lithium-ion batteries. Toyota does offer a car in Japan that uses the batteries to power a stop-start system, he said. A stop-start system turns off a vehicle's gasoline or diesel engine when the vehicle comes to a stop. The engine restarts immediately when the driver lifts his or her foot off the brake pedal.
Johnson Controls formed its partnership with Saft last year and is gearing up for production of lithium-ion batteries, possibly in North America.
Mumby, who leads that effort, says researchers and engineers are overcoming temperature, safety and durability issues.
Meanwhile, officials at another battery supplier -- Cobasys LLC, which makes nickel-metal hydride batteries for the Saturn Vue Greenline -- say it's too early to anoint lithium ion as the replacement for nickel-metal hydride. Cobasys is a joint venture in suburban Detroit between Chevron Corp. and Energy Conversion Devices Inc.
Scott Lindholm, Cobasys' vice president of systems engineering, says cost and weight reductions and power increases are still possible with nickel metal, as are improvements to performance and long-term durability.
Suppliers ready to build
Cobasys, which already is producing nickel-metal hydride batteries at its Ohio factory, could switch to lithium ion or make both batteries.
Johnson Controls is drawing up plans for a lithium-ion plant to supply hybrids sold in North America. No decision has been made where to build the plant, but North America is being considered, Mumby says.
"Our intent is to supply full battery systems ready to install in the vehicle," Mumby says. "That includes cell manufacturing all the way up through electronics and controls on the battery. We would deliver a system ready to be installed."
Ford signed a contract with Delphi Corp. to provide battery packs for the next generation of hybrids due around 2008. The batteries, made by Sanyo Electric Co., still would come from Japan.
General Motors plans to use Japan-made batteries from Panasonic EV for its upcoming Two-Mode hybrid powertrain that will be used in large SUVs. Toyota and Honda also use batteries made in Japan by Sanyo or Panasonic.
You may e-mail Richard Truett at [email protected]