[Technology Report]
Li-ion Suppliers Try To Find The Right Chemistry With Car Buyers
Li-ion technology has seen some significant advances since its introduction nearly two decades ago, but these improvements still require economies of scale before the topology breaks out of its niche.
Since Sony introduced them in 1991, lithium-ion (Li-ion) batteries have transformed portable electronic products. Now, carmakers and would-be automotive battery suppliers are looking for a similar transformation to redefine automotive propulsion.
Currently, well over 2 billion Li-ion battery cells are sold annually for consumer electronic applications, most notably cell phones and laptop computers. If cars become a significant market for Li-ion batteries, this number will rise dramatically. However, any similarities to Li-ion batteries residing in consumer products could be in name only.
The Li-ion technology (lithium cobalt oxide) used in portable electronics, which requires precise control, has encountered some well-publicized problems, including explosions. Much higher current and voltage levels and the rigorous requirements of the harsh automotive environment dictate unique and more complex battery management and control systems.
The competing nickel-metal-hydride (NiMH) battery chemistry, successfully used in hybrid vehicles for more than a decade, has several shortcomings compared to Li-ion technology. For example, Li-ion batteries are 20% to 30% smaller and 50% lighter than NiMH. Li-ion technology also promises:
• Two to three times the power for the same mass for greater acceleration and fuel efficiency • Three to four times the energy for the same mass for greater electric-only vehicle range and fuel efficiency • Two to three times faster recharge • Enhanced cycle life for longer battery operating life
DRIVING LI-ION TECHNOLOGY Essentially all carmakers in the established industry, as well as several new players such as Aptera, Fisker Automotive, Tesla Motors, and Think, are vying for a piece of the electric propulsion business. Hybrids, plug-in hybrids, and extended-range vehicles like the Chevy Volt with various engine combinations and degrees of hybridicity (such as mild hybrids), in addition to full electric vehicles, also use battery-powered propulsion.
Though vehicles with Li-ion batteries are just starting to emerge, carmakers have explored their capabilities for many years. In fact, Nissan has been on the case since 1992, a year after the technology was first applied to cell phones.
Initially investigating a cylindrical cobalt-based technology, Nissan switched to a manganese-based laminated design. The company will implement this technology in the Leaf EV, slated for production in 2010. Through the Automotive Energy Supply Corp. established in 2007 by Nissan, NEC, and NEC Tokin, Nissan and Renault will obtain battery-cell module and battery management system technology.
While research has been ongoing for years, the first company to supply a production vehicle with a Li-ion battery was startup vehicle manufacturer Tesla Motors. Tesla introduced its Roadster electric vehicle in 2008. Out of necessity, when it started to develop the Roadster earlier this decade, Tesla engineers chose existing commodity Li-ion cells with the 18650 form factor commonly used in portable computers.
As other carmakers joined the hunt for an improved chemistry, the cell quantities became significant enough to attract volume suppliers of batteries as well as several startups. Companies developing Li-ion batteries and battery systems include LG Chem and its subsidiary Compact Power Inc. (CPI), A123Systems, Atieva, Altairnano, Continental, EnerDel, JCI-Saft, Sakti3, and Valence.
In the dynamic world of Li-ion batteries, the close working relationship between carmaker and battery supplier doesn’t preclude exploring alternatives. General Motors chose LG Chem to supply Li-ion batteries for its Chevy Volt extended-range vehicle, which will be launched in 2010. However, GM is keeping its options open.
“The guy that seems to be the best battery supplier today may not be the best one tomorrow,” says Ronn Jamieson, director of global battery systems engineering at General Motors. “So, we are constantly monitoring the supplier base and the technologies. At any particular time, we could have some number of different battery suppliers’ cells in our test lab to characterize and understand.”
With its battery lab facility, the largest in North America, GM can perform extensive evaluations both at the pack level for validating in-process production programs such as the Chevy Volt and at the cell level and groupings of cells level (Fig. 1). The lab can characterize and qualify cells for production.
In some cases, carmakers have established their own battery technology. Toyota took this approach for NiMH batteries for the Prius, and Nissan did the same for its Leaf EV.
CELL DESIGN While Li-ion describes the nominal electrochemistry of the cell, variations on the Li-ion theme continue to grow. As Mohamed Alamgir of Compact Power and Ann Marie Sastry of the University of Michigan concluded in “Efficient Batteries for Transportation Applications,” which won the best paper award at the Convergence 2008 biennial conference on automotive electronics, “Not all Li-ion battery systems are equal. Choice of chemistry, separator, and packaging can provide significant advantages to one system compared to another.”
I know the Ford EV's built in the 1990's (electric Ranger) were very capable of being immersed in salt water with no damage or functional impact..
Walter Klosnick -November 17, 2009
Recently, someone swerved off the road near Houston and drove a million dollar+ sports car into a salt marsh. What would happen if you drove an electric Tesla sports car into salt water? Isn't the battery voltage seveal hundred volts? What protection is there?
Bob Fischer -November 16, 2009
The "two to three times faster recharge" is an illusion when you consider the capacity of normal electrical outlets. A 115V/15A outlet provides about 1.5kW and a 230V/30A dryer outlet about 6kW. Sounds like plenty but if the vehicle has say 20kW of batteries it would take several hours regardless of battery chemistry. A new infrastructure with outlets of vastly higher capacity would be necessary to put EV recharging times on a par with gasoline/diesel vehicles.
Mark Spellman -November 16, 2009
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