Tuesday, August 05, 2008

Better Batteries Charge Up

A startup reports progress on a battery that stores more energy than lithium-ion ones.

By Tyler Hamilton

Electric power: ZENN Motor, which makes this low-speed electric car, plans to use EEStor's energy-storage device for its next vehicles. Credit: ZENN Motor

A Texas startup says that it has taken a big step toward high-volume production of an ultracapacitor-based energy-storage system that, if claims hold true, would far outperform the best lithium-ion batteries on the market.

Dick Weir, founder and chief executive of EEStor, a startup based in Cedar Park, TX, says that the company has manufactured materials that have met all certification milestones for crystallization, chemical purity, and particle-size consistency. The results suggest that the materials can be made at a high-enough grade to meet the company's performance goals. The company also said a key component of the material can withstand the extreme voltages needed for high energy storage.

"These advancements provide the pathway to meeting our present requirements," Weir says. "This data says we hit the home run."

EEStor claims that its system, called an electrical energy storage unit (EESU), will have more than three times the energy density of the top lithium-ion batteries today. The company also says that the solid-state device will be safer and longer lasting, and will have the ability to recharge in less than five minutes. Toronto-based ZENN Motor, an EEStor investor and customer, says that it's developing an EESU-powered car with a top speed of 80 miles per hour and a 250-mile range. It hopes to launch the vehicle, which the company says will be inexpensive, in the fall of 2009.

But skepticism in the research community is high. At the EESU's core is a ceramic material consisting of a barium titanate powder that is coated with aluminum oxide and a type of glass material. At a materials-research conference earlier this year in San Francisco, it was asked whether such an energy-storage device was possible. "The response was not very positive," said one engineering professor who attended the conference.

Many have questioned EEStor's claims, pointing out that the high voltages needed to approach the targeted energy storage would cause the material to break down and the storage device to short out. There would be little tolerance for impurities or imprecision--something difficult to achieve in a high-volume manufacturing setting, skeptics say.

But Weir is dismissive of such reactions. "EEStor is not hyping," he says. Representatives of the company said in a press release that certification data proves that voltage breakdown of the aluminum oxide occurs at 1,100 volts per micron--nearly three times higher than EEStor's target of 350 volts. "This provides the potential for excellent protection from voltage breakdown," the company said.

Jeff Dahn, a professor of advanced materials in the chemistry and physics departments at Dalhousie University, in Nova Scotia, Canada, says the data suggests that EEStor has developed an "amazingly robust" material. "If you're going to have a one-micron dielectric, it's got to be pretty pure," he says.