Research shows metal catalysts play important role in improving efficiency
CAMBRIDGE, Mass. — A team of researchers at MIT has made significant
progress on a technology that could lead to batteries with up to three
times the energy density of any battery that currently exists.
Why it matters: Lightweight batteries that can deliver lots of energy are crucial for a variety of applications — for example, improving the range of electric cars. For that reason, even modest increases in a battery's energy-density rating — a measure of the amount of energy that can be delivered for a given weight — are important advances.
Next Steps: One issue to be dealt with in developing a battery system that could be widely commercialized is safety. Lithium in metallic form, which is used in lithium-air batteries, is highly reactive in the presence of even minuscule amounts of water. This is not an issue in current lithium-ion batteries because carbon-based materials are used for the negative electrode. Shao-Horn says the same battery principle can be applied without the need to use metallic lithium; graphite or some other more stable negative electrode materials could be used instead, she says, leading to a safer system.
A number of issues must be addressed before lithium-air batteries can become a practical commercial product, she says. The biggest issue is developing a system that keeps its power through a sufficient number of charging and discharging cycles for it to be useful in vehicles or electronic devices.
Researchers also need to look into details of the chemistry of the charging and discharging processes, to see what compounds are produced and where, and how they react with other compounds in the system. "We're at the very beginning" of understanding exactly how these reactions occur, Shao-Horn says.
Gholam-Abbas Nazri, a researcher at the GM Research & Development Center in Michigan, calls this research "interesting and important," and says this addresses a significant bottleneck in the development of this technology: the need find an efficient catalyst. This work is "in the right direction for further understanding of the role of catalysts," and it "may significantly contribute to the further understanding and future development of lithium-air systems," he says.
While some companies working on lithium-air batteries have said they see it as a 10-year development program, Shao-Horn says it is too early to predict how long it may take to reach commercialization. "It's a very promising area, but there are many science and engineering challenges to be overcome," she says. "If it truly demonstrates two to three times the energy density" of today's lithium-ion batteries, she says, the likely first applications will be in portable electronics such as computers and cell phones, which are high-value items, and only later would be applied to vehicles once the costs are reduced.
Source: "The Influence of Catalysts on Discharge and Charge Voltages of Rechargeable Li–Oxygen Batteries," Yi-Chun Lu, Hubert A. Gasteiger, Michael C. Parent, Vazrik Chiloyan, Yang Shao-Horn. Electrochemical and Solid-State Letters, 1 April 2010 (Vol.13, No.6).
Funding: Department of Energy, with additional support from the Martin
Family Society of Fellows for Sustainability and the National Science Foundation.