The technology that almost buried the electric vehicle (EV) a decade ago is back under the microscope again, as automakers try to develop new batteries for a new breed of EVs.
This time, though, it’s a whole new ballgame.
Instead of having to do the nearly impossible task of lugging around a 2,500-lb electric automobile for 200 to 300 miles between re-charges, the new breed of battery faces a much simpler challenge: Travel 40 miles — or less — on a single charge. Then, if necessary, get a recharge from an on-board internal combustion engine. Makers of the Chevy Volt, a concept vehicle that debuted in January, claim they can get a stunning 640 miles of range using this scheme.
For battery engineers, the resulting technical task has become a less daunting one. With engine-generator backup, the new breed of batteries needn’t be world-beaters. Shorter range means less energy and fewer batteries. Fewer batteries mean less cost. And while there is work to be done, especially with regard to safety, experts say this new electric vehicle mission is a doable one, especially by the targeted 2012 time frame.
“The Chevy Volt is a radical departure from the electric vehicles of the past,” says Donald Sadoway, the John P. Elliott Professor of Materials Chemistry at MIT, a nationally renowned battery expert. “If we’re talking about making a battery that can send a car 40 miles and then be charged by an internal combustion engine, then, yes, that can be done.”
Indeed, battery makers are again lining up in hopes of being the designated providers of such new technology. In June, GM awarded contracts to Compact Power Inc., a subsidiary of the Korean battery manufacturer LG Chem and Continental Automotive, a subsidiary of Continental AG, to develop electric vehicle batteries and electrical systems. The giant automaker had also previously announced in January it is doing similar work with A123 Systems, Johnson Controls Inc. and French battery maker Saft, on rechargeable batteries.
To be sure, however, battery makers have anxiously taken on such electric vehicle tasks previously. But this time, experts say, the outlook appears rosier.
“We’re testing the batteries in-situ, on vehicles and on chassis dynamometers,” says Donald Hillebrand, director of the Center for Transportation Research at Argonne National Lab., which has run extensive tests on the new breed of electric vehicle batteries. “And the batteries are performing pretty close to the way the battery companies are saying they’ll perform.”
It wasn’t always so, however. Nearly a decade ago, the bottom dropped out of the industry’s EV effort amid a flurry of complaints and finger-pointing. Chrysler, Ford, GM, Honda, Nissan and Toyota all abandoned their programs, believing so-called “pure electrics” (vehicles powered solely by batteries) were not practical in the marketplace.
Even hybrid proponents came down on the pure battery-powered models. The late David Hermance, executive engineer of environmental engineering for Toyota and the man widely known as the “American Father of the Prius,” proclaimed in 2000, “pure electric vehicles are hideously expensive and consumers don’t want them unless someone else subsidizes them.”
The inability to find a practical EV battery may change now, however, mainly because the new breed of EVs are, in a sense, hybrids. GM’s Volt, for example, is called an “extended-range electric vehicle” by the giant automaker, but it uses an internal combustion engine to boost its ultimate range from 40 to 640 miles. Similarly, GM is looking at another hybrid variant called the Saturn Aura Green Line, which would travel a scant 10 miles on battery power before engaging an internal combustion engine.
Such vehicles change everything for battery makers. Because they have different energy and cost requirements than the pure electric vehicles of a decade ago, they nudge the battery requirements into a realm of reality.
Specific energy requirements, for example, have been relaxed. Whereas the domestic auto industry’s U.S. Advanced Battery Consortium called for specific energies of 200W-hr/kg a decade ago, they’re now calling for 150W-hr/kg. That’s a big difference, say experts, because battery makers were creeping over the 100 mark a decade ago, with hopes of reaching 150. Now, they say, 150W-hr/kg is within sight.
“What we’re doing leverages off prior electric vehicle experience,” says Mark Verbrugge, director of the Materials and Process Labs. at GM Research Labs. and former chief engineer of GM’s ill-fated EV1. “We’re coming down mid-way between where we were with the old electric vehicle batteries of 10 years ago and the charge-sustaining hybrid vehicle batteries of today, like the ones used in the Prius.”
Moreover, battery makers say they’re close to reaching the desired specific energy requirement of 150W-hr/kg now. A123 Systems, which is building cells for the Volt project, says its batteries have achieved 110-120W-hr/kg in power tool applications.
“We’re talking only a 30 percent improvement, so, yes, we think it’s possible,” says Yet-Ming Chiang, co-founder of A123 and a professor of ceramics at the Massachusetts Institute of Technology.
Experts say lithium-ion shows promise, not only because its chemistry produces high energy, but because lithium is the third lightest element in the Periodic Table. That combination creates high specific energy (energy per unit mass) and even higher expectations, they say.
“If you look at the performance curves, the line for lithium-ion is very steep,” says Hillebrand of Argonne National Labs. “It’s getting better fast and it’s going to continue.”
Safety and Cost Challenges
Still, questions remain, especially in the areas of safety and cost. Moreover, many experts believe the two may be tied inextricably together.
Safety concerns stem from fire-related incidents involving lithium-ion batteries. The presence of cobalt in the cathode of such batteries reportedly makes the likelihood of runaway temperatures more likely.
“We know about charger malfunctions, where cell phones and laptops catch fire, but that’s peanuts (compared to a car) because those are such tiny batteries,” says one expert who declined to be named. “The question is: What kind of thermal management will the automakers have in place? What kind of shutdown procedures will they have so that a car barreling down a highway doesn’t turn into a flaming chariot?”
Automakers and battery manufacturers say they are working together on solutions to such potential problems. The goal, they say, is to keep the core temperature of the batteries below 35C. They plan to do that with liquid cooling, using a physical configuration resembling a water jacket, or by air cooling, using large plenums and chambers to re-circulate air around the battery pack. Compact Power Inc., in particular, has worked with GM on development of electronic battery management systems incorporating sensors to monitor voltage, current and temperature of the battery cells.
Moreover, battery makers say new lithium-ion chemistries make fires less likely. Compact Power, for example, has replaced the cobalt in the cathode with manganese, which is reportedly more abundant, less costly and more stable.
“With manganese, you get greater thermal stability than with the cobalt that goes into laptop and cell phone batteries,” says Mohamed Alamgir, director of research for Compact Power.
Similarly, A123 Systems has replaced the cobalt in lithium-ion with lead phosphate. By doing so, A123 engineers say they’ve reduced the possibility of thermal runaway. (See nail penetration test video of A123 battery).
Still, concerns remain. Because lithium-ion has enormous charge capabilities and enormous power, experts say it needs to be carefully controlled. And while the new chemistries offer a promising alternative to cobalt, no battery maker has extensive experience with large-format lithium-ion batteries.
Most observers believe battery makers will find a solution, but wonder whether they’ll be able to do it at the costs automakers ultimately need. “The question is not, 'Can they do it?’” says Sadoway of MIT. “The question is, 'Can they do it and meet the price point?’”
There, too, there’s hope. Given that the new breed of electric vehicles are backed by internal combustion engines (and therefore need smaller battery packs), the U.S. Advanced Battery Consortium has relaxed its cost targets. Whereas electric vehicle batteries were targeted to hit a long-term cost of $100/kW-hr a decade ago, they’re now targeted to hit $200/kW-hr in the long term and $300 in the short term.
“Looking at the technology and knowing we can relax some of the requirements on the plug-in hybrid side, I’m optimistic,” says Chiang of A123. “But time will tell. We’re definitely not there yet.”