Building Better Batteries for Electric Cars


TO reduce our vast appetite for oil, the government and auto industry are working together to encourage car buyers to think electric when they go car shopping.

Peter Wynn Thompson for The New York Times

POWER Researchers at Argonne National Laboratory are working on an aluminum-coated battery, top, with a film of lithium metal oxide powder and two flexible cells made from pieces of coated aluminum.

More fuel-efficient gasoline engines, electric cars, energy sources in North and South America and other means of breaking the nation’s dependency on Mideast oil.While industry watchers may debate how quickly consumers will make the transition to electric vehicles, they generally agree this transition will require big improvements to the batteries that power these cars.

Even the White House agrees, acknowledging in a recent blog post, “The lack of affordable, highly functional batteries has been a particularly high barrier to the widespread adoption of electric vehicles.”

In the near term, reducing the cost of the battery — and with it, the price of the vehicle — will come mostly from better manufacturing techniques and building more batteries. Improving durability and range will largely be the domain of researchers and scientists.

The Italian scientist Alessandro Volta built the original battery in 1800. Volta filled a container with alternating pairs of zinc and copper plates, and separated each pair with a cardboard disk soaked in salt water. His battery produced a steady flow of electrical current through a chemical reaction that forced the zinc disk (negative anode) to release an electron and the copper disk (positive cathode) to catch it.

Today’s electric car batteries no longer resemble Volta’s container, but they work on the same basic principles. And two centuries of gradual improvements in the overall chemistry, design and materials have led to the lithium-based battery that relies on a lithium ion to shuttle back and forth from the anode and cathode.

Simply put, the lithium-ion battery offers a higher energy density than other previous battery systems, according to Venkat Srinivasan, manager of the Battery for Automotive Transportation Technologies Program, an Energy Department-supported program managed by Lawrence Berkeley National Laboratory at the University of California, Berkeley.

 Compared with the nickel-metal hydride battery used in the Toyota Prius, for example, a lithium-ion battery of the same weight and volume would increase energy density two to three times, said Dr. Srinivasan.

All the vehicles available with electricity as their primary power source, like the Nissan Leaf or Chevy Volt, use some form of lithium-ion chemistry in their batteries. And these batteries will be prevalent for at least the next decade or two with plenty of room for innovation, said Jeffrey P. Chamberlain, head of the Electrochemical Energy Storage group at the Argonne National Laboratory, a lab near Chicago sponsored by the Energy Department.

Lithium is blended with other materials in the battery’s cathode. The materials used dictate the voltage of the cell and the amount of lithium the cathode can hold; raising both increases energy density, said Dr. Srinivasan.

At Argonne, researchers are working with new mixes of nickel, manganese and cobalt for the cathode. Blending these in varying amounts and assembling them in different structures has been shown to double the cathode’s energy capacity. Argonne has begun to license patents for this material to different battery makers. The result, Mr. Chamberlain said, would be batteries “that squeeze more energy into a smaller package, are less expensive to make and last longer.”

Similarly, researchers at Argonne and elsewhere are experimenting with silicon for the anode, replacing the carbon anode commonly used today. During the charging cycle, the anode collects lithium ions, then releases them during discharge when the battery is providing power to the electric motor. A pure silicon anode theoretically has the potential to increase the amount of energy it can hold tenfold.

But efforts to reach this maximum have been thwarted by silicon’s tendency to expand as it collects the lithium ions. So researchers are blending silicon with materials like graphite, looking for a balance that will solve the physical challenges but still increase energy density, said Mr. Chamberlain.

Even as these new advances move from the lab to the production line in coming decade, in the near term most cost reductions for the battery pack will come from lowering manufacturing costs, according to Alex A. Molinaroli, president of the Power Solutions group at Johnson Controls, a company building lithium-ion batteries for BMW, Daimler and Ford.

Because lithium-ion is a relatively new technology for powering cars, “it will take time to understand how these batteries will perform with years of use,” said Mr. Molinaroli. And because the electric car battery is now part of the drive train, “these will have much higher performance and durability requirements compared to lead-acid starter batteries or the battery in your laptop,” he said.

Lacking decades of road-test data from primarily electric cars, manufacturers must overbuild the batteries, adding in materials and safety features to ensure they meet the demands of the drive-train warranty, said Mr. Molinaroli. He estimated that this overcompensation accounts for 50 percent of the material used in the current battery packs. A common measure of the battery’s energy density is the number of kilowatt-hours of electricity it can produce given its weight.

With the battery the costliest component of the car, automakers tend to be tight-lipped about actual prices, considering it competitive information. Even so, Mike Omotoso, an automotive power train forecaster for J. D. Power & Associates, estimated today’s cost at around $750 to $800 per kilowatt-hour. For electric vehicles to achieve parity with gasoline-powered cars, from a cost perspective, most analysts estimate that battery cost must come closer to $200 per kilowatt-hour.

At Johnson Controls, the company expects price parity when battery costs achieve $200 per kilowatt-hour combined with gasoline prices that are consistently at or above $4 a gallon. Once you get to these levels, “you have a good business case, and as energy prices go up, this becomes a much more relevant conversation,” said Mary Ann Wright, vice president for global technology and innovation in the company’s Power Solutions group.

Ms. Wright further estimates that this parity point is a decade away, but offers two caveats. “You have to consider that the gasoline engine will also become more fuel-efficient during this time,” she said. “This technology is not standing still.” And parity must be considered as the total cost of ownership over the life of the car. “So while the sticker price may always be higher, the electric vehicle will be less expensive to maintain and operate over the life of the car compared to a gasoline-powered car,” she said.

Alessandro Volta’s invention earned him a royal title and a place on the 10,000-lire note, and set the stage for the modern electrical age. As continuing improvements enable electric cars to match price and performance with their gasoline-powered competitors, the impact could be no less profound.


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: