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Sustainable Energy

Designer Carbon Provides Longer Battery Life

Energ2’s nanostructured carbon anodes can boost lithium-ion battery capacity by 30 percent.

Battery capacity limits the potential of mobile devices and electric vehicles.

A Seattle-based startup, EnerG2, has developed a carbon anode that significantly improves the storage capacity of lithium-ion batteries without requiring a new battery design or a different manufacturing process.

Batteries with more energy density could allow electric vehicles to travel longer on a charge. They could also enable lighter, thinner electronic gadgets. Because of this, many advanced battery makers are pursuing a jump in storage capacity with novel chemistries and materials.

EnerG2 said last week that its synthetic carbon anode increases the storage capacity of lithium-ion batteries by up to 30 percent. An anode is the negatively charged electrode in a battery, which attracts electrons as it discharges. The company has started production of its anode, which it hopes will appeal to lithium-ion battery makers.

The company’s technology, originally developed at the University of Washington, is a process for creating carbon with desired properties. Its first products were lead-acid batteries and components for ultracapacitors, two relatively small markets compared to the one for lithium-ion batteries.

EnerG2’s new lithium-ion battery anode is made of a form of carbon in which the atoms have a disorganized, amorphous structure, compared to the crystalline structure of graphite, the material normally used for anodes. EnerG2’s “hard carbon,” as the material is called, can store 50 percent more energy per area on its surface than graphite.

Hard carbon anodes tend to lose storage capacity when batteries are first charged. EnerG2 has been able to engineer an anode with a level of loss that is acceptable for battery makers, says CEO Rick Luebbe.

The company’s process controls the chemical reactions that occur as raw carbon is converted into a finished product. That means it can optimize the surface area, pore size, and pore density of carbon for different applications.

Engineering synthetic materials rather than working from organic sources is typically more expensive, but Luebbe says manufacturing the new anode is relatively simple, so it costs about the same as existing ones.

Hard carbon costs about 20 percent more than graphite, says Luebbe. This means EnerG2’s anode material is unlikely to appeal to companies that make lithium-ion batteries for electric vehicles, says Cosmin Laslau, an analyst at Lux Research. But companies that make batteries for consumer electronics may be willing to pay a premium to save battery space in a tablet or smart phone.

Several other companies are focusing on better battery electrodes for rechargeable lithium-ion batteries. Two venture-backed battery companies—Envia Systems and Amprius—are developing anodes made with silicon, which also boosts storage capacity. But the cycle life of new materials can be lower than graphite or hard carbon. Furthermore, EnerG2’s material is essentially a drop-in replacement for an existing graphite anode. “You don’t have to do a lot of battery design to use this material,” says Luebbe.

EnerG2 has also demonstrated that it can manufacture at scale. It received a $21 million federal grant in 2010 to build a factory in Albany, Oregon, which has been operating since early last year. “There’s no shortage of fantastic materials for anodes,” Laslau says. “The key question is whether you can scale from a couple of grams to metric tons or thousands of tons.”

EnerG2 is seeking other uses for its hard carbon. One could be storing natural gas at lower pressure, a technology called absorbed natural gas. This could make fueling up gas-powered vehicles safer and more energy-efficient, says Luebbe.

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