Posted: February 9, 2009 |
Researchers create hybrid nanocables to improve lithium battery technology |
(Nanowerk News) Need to store electricity more efficiently? Put it behind bars.
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That's essentially the finding of a team of Rice University researchers who have created hybrid carbon nanotube metal oxide arrays as electrode material that may improve the performance of lithium-ion batteries.
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With battery technology high on the list of priorities in a world demanding electric cars and gadgets that last longer between charges, such innovations are key to the future. Electrochemical capacitors and fuel cells would also benefit, the researchers said.
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The team from Pulickel Ajayan's research group published a paper this week describing the proof-of-concept research in which nanotubes are grown to look – and act – like the coaxial conducting lines used in cables. The coax tubes consist of a manganese oxide shell and a highly conductive nanotube core.
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"It's a nice bit of nanoscale engineering," said Ajayan, Rice's Benjamin M. and Mary Greenwood Anderson Professor in Mechanical Engineering and Materials Science.
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"We've put in two materials – the nanotube, which is highly electrically conducting and can also absorb lithium, and the manganese oxide, which has very high capacity but poor electrical conductivity," said Arava Leela Mohana Reddy, a Rice postdoc researcher. "But when you combine them, you get something interesting."
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That would be the ability to hold a lot of juice and transmit it efficiently. The researchers expect the number of charge/discharge cycles such batteries can handle will be greatly enhanced, even with a larger capacity.
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"Although the combination of these materials has been studied as a composite electrode by several research groups, it's the coaxial cable design of these materials that offers improved performance as electrodes for lithium batteries," said Ajayan.
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"At this point, we're trying to engineer and modify the structures to get the best performance," said Manikoth Shaijumon, also a Rice postdoc. The microscopic nanotubes, only a few nanometers across, can be bundled into any number of configurations. Future batteries may be thin and flexible. "And the whole idea can be transferred to a large scale as well. It is very manufacturable," Shaijumon said.
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The hybrid nanocables grown in a Rice-developed process could also eliminate the need for binders, materials used in current batteries that hold the elements together but hinder their conductivity.
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The paper was written by Reddy, Shaijumon, doctoral student Sanketh Gowda and Ajayan. It appears in the online version of the American Chemical Society's Nano Letters (Coaxial MnO2/Carbon Nanotube Array Electrodes for High-Performance Lithium Batteries).
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