NEWS OF THE W EEK
A123 TOUTS A BATTERY ADVANCE TECHNOLOGY: Improvement in battery chemistry promises higher performance
A123 SYSTEMS
A123 Systems’ current startup battery for microhybrid cars could benefit from its improved lithium iron phosphate technology.
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123 SYSTEMS, a troubled lithium-ion battery
maker, says it has tweaked the chemistry of its lithium iron phosphate battery in a way that optimizes performance in extreme temperature conditions without requiring costly heating or cooling systems. The firm’s latest battery, the Nanophosphate EXT, is “a game-changing breakthrough,” CEO David P. Vieau says. “By delivering high power, energy, and cycle life capabilities over a wider temperature range,” he says, the battery overcomes limitations of competing batteries such as lead-acid and lithium nickel manganese cobalt oxide batteries. Although A123 won’t provide details on the battery’s electrochemistry, the company does say it will retain more than 90% of its initial capacity after 2,000 full charge-discharge
LONG-LIFE LITHIUMAIR BATTERY ELECTROCHEMISTRY: Unusually stable
electrolyte advances promising energy-storage technology
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Semicrystalline Li2O2 particles, like the one shown in this TEM image, form on the oxygen electrode during discharge of a Liair battery.
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N UNCOMMON and highly stable electrolyte
endows lithium-air batteries with long operating life and other attractive performance traits, according to a study in Nature Chemistry by researchers in Italy and South Korea (DOI: 10.1038/nchem.1376). Because of the large quantity of energy released in the oxidation of lithium, these devices have the potential to pack a lot more energy into a small, lightweight cell than other batteries—possibly 10 times more than lithium-ion batteries (C&EN, Nov. 22, 2010, page 29). That high theoretical energy density has made Li-air batteries heavily studied systems for powering electric vehicles over acceptably long driving ranges. Yet several technical challenges, such as short lifetimes, low numbers of charging cycles, and sluggish discharge rates, have prevented these batteries from fulfilling their promise. Researchers beWWW.CEN-ONLIN E .ORG
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cycles at 45 °C and deliver 20% more power at –30 °C than A123’s standard battery. A123 says the improved low-temperature performance of the Nanophosphate EXT eliminates the cold-cranking power advantage of a Pb-acid battery in a microhybrid passenger car—a new type of gas-powered vehicle with an engine that turns off at stoplights. The development could herald a turnaround for A123, which has been plagued by a $52 million defective battery recall and slower than expected demand for its electric-vehicle batteries. In a document filed late last month with the Securities & Exchange Commission, A123 acknowledged financing difficulties and said it expects to continue operating at a loss, raising “substantial doubt on the company’s ability to continue as a going concern.” “These are smart guys with good technology, but will it be enough to save them?” asks Kevin See, an analyst at consulting firm Lux Research. Quoting Lux figures, A123 says the worldwide microhybrid market could reach 39 million vehicles by 2017, creating a $6.9 billion battery market. But See says price-sensitive automakers are more likely to go with Pb-acid batteries, except in highend vehicles. And although A123 is first to market with an advanced lithium iron phosphate battery, other firms, such as LG Chem, are poised to come out with similar models, See says. Raw material producers such as BASF and Clariant are ready to supply them, he adds.—MARC REISCH
lieve those problems are connected to lithium oxidation products and intermediates, which include Li2O2 and an anionic oxygen radical, O2·–, a highly reactive species. O2·– decomposes typical electrolytes such as organic carbonate solutions of lithium compounds. Until now, scientists have had little success finding stable alternatives. Bruno Scrosati and Jusef Hassoun of Sapienza University of Rome, Yang-Kook Sun of Hanyang University, Seoul, and coworkers find that tetraethylene glycol dimethyl ether (TEGDME)-lithium triflate serves as a highly stable Li-air battery electrolyte. On the basis of microscopy and various types of analyses, the group reports that its “preliminary” data provide evidence of reversible formation of Li2O2, fast kinetics, and almost no deterioration in battery performance during more than 100 charging cycles.They propose that the enhanced battery stability may be partly attributed to a fleeting oxygen radical lifetime in the selected electrolyte. “This contribution is significant in that it demonstrates that Li-air batteries are capable of long cycle life,” says Li-air battery inventor Kuzhikalail M. Abraham, a Northeastern University research professor and battery consultant. Last year, Abraham published a study pointing to the potential of TEGDME-lithium hexafluorophosphate as an electrolyte, but he noted that his test cells exhibited high resistance and charge-capacity loss with continued cycling. The improvement reported now may be related to the design of the carbon-based oxygen diffusion electrode, he says.—MITCH JACOBY
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