2007 Chevrolet Volt ConceptEnlarge Photo
What’s the deal with lithium-ion batteries for electric vehicles? Are they really coming as soon as Chevy’s Volt would seem to indicate — or are they still too pie-in-the-sky to gamble on?
GM is racing full-speed ahead with suppliers to develop them for volume production of the Chevy Volt plug-in hybrid in about three years.
“The card we have up our sleeve in terms of advanced technology and propulsion,” GM Global Product Vice Chairman Bob Lutz told a large audience of auto executives, engineers, and media at the Center for Automotive Research Management Briefing Seminars, held this August, “is our E-Flex architecture and electric propulsion system. But before we get to play that card, we need further advancement in battery technology. And we’re making great progress there.”
Then he announced a new agreement with A123Systems to “co-develop” A123’s nanophosphate Lithium-ion chemistry for a long-lasting, safe, and powerful battery for plug-in hybrid and other E-Flex variants.
“This is a great strategic agreement,” Lutz said, “and it will help us get E-Flex, and vehicles like the Volt, on the road sooner. Breakthrough battery technology will drive future automotive propulsion, and the company that aligns with the best strategic partners will win.”
No two are alike
The hugely important message here is that not all Li-ion battery chemistries are alike, and this one is looking so promising that GM believes it may well emerge the winner in the race to market with auto-capable Li-ion cells. And the fact that GM and A123 are co-developing the cells hints that a production-ready pack may be fairly close. The contract calls for delivery of vehicle-size battery packs in running test vehicles by early 2008, and Lutz says he expects plug-in Volts in Chevy showrooms by late 2010. “Believe me,” he concluded, “electrically driven vehicles represent the next great paradigm shift in the automotive industry.”
"We're talking today about the Volt and implications that it will have on the electrification of passenger vehicles,” said A123Systems CEO Dave Vieau, “but the technology goes a lot further than that. The weight, size, safety, and performance of these batteries have implications on all transportation, including hybrid buses, trucks, and aircraft.” He added that A123’s batteries will also be less expensive than others, since they use no precious metals or rare materials, and they will degrade more slowly over time.
“We start with the premise that not all Li-ion batteries are created equal,” Vieau told us in an exclusive interview. “They’re all different. The flow of ions back and forth between the anode and cathode, the tremendous energy density with light weight and small size, the design of the batteries and the manufacturing processes are essentially the same. But there are a variety of chemistries, the actual ingredients. In our case, [the major difference] is on the cathode side, which is a dominant element of the performance of a battery.”
A typical Li-ion laptop or cell phone battery uses a cobalt oxide or lithium cobalt oxide cathode material based on particles between five and ten microns in diameter. A123 uses a nanophosphate less than 100 nanometers in diameter. For perspective, a typical human hair is about 75 microns in diameter, and a nano is one-thousandth of a micron.
“There are mechanical expansions and contractions as the battery cycles, and larger particles can fracture over time,” Vieau continued. “With a traditional Li-ion battery, you might expect to get 500 full charges and discharges before it begins to lose its capacity. With our technology, we’ve experienced 7000 full charges and discharges. Our system has less mechanical strain for longer life, and its greater thermal stability over a broader temperature range improves the safety of the cell and predicts much longer calendar life – how many years it will last – which is different from cycle life. We’ve done accelerated life testing that predicts more than ten years.”
Li-ion on the charge?
Hedging its bets, GM also has contracts with Continental Automotive Systems, which will integrate A123's cells into vehicle-size packs for vehicle-level testing, and with Troy-based Compact Power, Inc. (CPI), which will make competing packs with cells developed by its Korean parent, LG Chem. "A123Systems and LG Chem are both top-tier battery suppliers with proven technologies," said Denise Gray, GM’s Director of Energy Storage Devices and Strategies. "We're confident one or possibly both of these companies' solutions will meet our battery requirements for the E-Flex system."
Said A123’s Vieau of his claim of lower Li-ion battery cost: “We looked at the price of the Prius battery system over the last few years, compared it to the system we’re developing, and found we’d be favorable. We also believe that by investing in research in the core ingredients over the next five to ten years, we’ll be driving cost out of these systems. Volume drives cost, and continuously increasing the volume will bring its cost down.”
As we have learned over decades of on-again, off-again industry EV effort, there are no guarantees in the vehicle battery business. But at this point, GM just may have a solid leg up.
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