Toyota Motor Corp. and Ford Motor Co. intend to migrate away from nickel-metal hydride battery technology to range-extending lithium-ion chemistries in their future electric vehicles, the auto maker's leading engineers say.

But the changeover from NiMH-assisted hybrids will not happen overnight, says Scott Ankeney, an engineer at Toyota's Ann Arbor, MI-based Toyota Motor Engineering & Mfg. North America unit.

“We continue to find it a very important technology we want to see on our future platforms,” Ankeney says at the recent Automotive Energy Storage Systems conference, which brings together suppliers, OEMs, power companies and regulatory organizations to examine technology and advancements in batteries, hydrogen and biomass-derived fuels.

The current-generation Toyota Prius and Camry and Lexus 600h sedans and RX 450h cross/utility vehicle are among the 2 million NiMH-assisted hybrid-electric vehicles sold by the Japanese auto maker in the U.S.

The upcoming Prius plug-in HEV, unveiled at this year's Detroit auto show, will mark Toyota's first application of Li-ion technology to its hybrid lineup.

Modeled after the just-released, third-generation Prius, the PHEV version adds the Li-ion battery, as well as a charging unit for the plug-in system, and the pack moves from behind the rear seating area to along the base of the vehicle due to its larger size.

Software controls also receive some tweaks, but otherwise the plug-in model is a near duplicate of its HEV platform mate.

Ankeney says although Toyota recognizes the advantages of Li-ion, such as higher energy density, a longer lifecycle and sound safety, the auto maker's years of research on NiMH chemistry simply makes the old-school approach more cost-effective.

“It provides us the power we need for our customers at the right cost,” he says. “However, when we go to plug-in hybrid or electric vehicles, where we need more energy density, the lithium-ion then comes in with stellar performance.”

Dawn Bernardi, a research engineer at Ford, confirms a switch to Li-ion batteries with the auto maker's next-generation HEVs and the prototype Ford Escape PHEV, which promises 30 miles (48 km) of electric-only range and fuel economy of 120 mpg (2.0 L/100 km).

A future Ford EV also will use Li-ion, Bernardi says. But like Toyota, the Dearborn auto maker has concerns over cost.

“Lithium is cheap right now compared with nickel,” she says, lamenting how costs skyrocket with Li-ion battery production.

The Environmental Protection Agency estimates the 16kWh battery in the upcoming Chevrolet Volt extended-range EV will cost about $8,000 — even at large volumes.

The EPA believes $2,000 represents a more realistic cost for such a battery. Its goal is to bring down the per-kWh cost of a battery to $300 by 2014, targeting improvements in material costs, cell counts and cell-pack hardware.

NiMH batteries offer less potential for advancement than Li-ion, Bernardi says, noting “all the low-hanging fruit” with old technology has been picked. “When you start getting interested in more all-electric range, we start looking at lithium-ion.”

General Motors Co. tells conference attendees the national energy policy must embrace a number of alternative propulsion technologies to reach the U.S. government's stated goals for reducing greenhouse-gas emissions.

The U.S. wants to slash GHG emissions 80% over the next 40 years. But Ian Sutherland, an engineer on GM's global-energy systems team, says the government will not achieve that goal unless it embraces renewable fuels, electrification and hydrogen, as well.

“It's not just pulling out one propulsion system and putting another in, or swapping fuels,” he says. “It's a systems approach.”

Sutherland says GM research shows advances to the internal-combustion engine, alone, would require a fuel-economy improvement from an average of 21 mpg (11 L/100 km) today to 240 mpg (1.0 L/100 km) in 2050 to meet the GHG goal.

GM considers cellulosic biomass the single-best, near-term solution to trimming GHG emissions, as EVs would require a much cleaner grid currently powered mostly by coal-fired plants. Hydrogen-powered vehicles remain a long-term solution.

Also at the conference, the California Air Resources Board admits a new national fuel-economy target has taken some of the teeth out of its rules.

The U.S. government, CARB and auto makers agreed last year on a corporate average fuel economy standard of 35.5 mpg (6.6 L/100 km) by 2016, equal to emissions of about 250 grams of carbon dioxide per mile.

CARB's Pavley 1 mandate called for fuel economy of more than 40 mpg (5.8 L/100 km) in the same timeframe, and 13 other states were set to make the same rules before last year's deal was brokered with the Obama Admin.

“We had to roll back some of the requirements, so we are a little less strict,” says Sharon Lemieux, manager-emissions research at CARB. But because CAFE is nationwide, CARB believes the GHG reduction will be greater than Pavley 1 anticipated.