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Friday, September 6, 2013

Hybrid Materials on Nanostructured Templates to Improve Lithium-ion Batteries

By using hybrid materials assembled on a vertical brush-like nanostructured template, a university-industrial collaboration has developed novel anode materials for lithium-ion batteries with eight-fold improvement in storage capacity and five-fold improvement in charge-discharge rate.

Jun Li, professor of chemistry at Kansas State University, and Judy Wu, University Distinguished Professor of Physics at The University of Kansas, worked together to develop these materials with their collaborators at NASA Ames Center for Nanotechnology and Catalyst Power Techologies Inc. both in California.

Lithium-ion batteries are critical energy sources for portable electronics. Improving the energy capacity, the charge-discharge rate (i.e. power), and lifetime can significantly enhance these devices. It is particularly important for new renewable energy applications such as electric cars and storage of intermittent electrical energy generated by solar cells and wind turbines.

Silicon has been known as a good Lithium-ion anode material which can theoretically provide about 10 times higher Li storage capacity than the current commercial anode material (i.e. graphite). However, the pulverization caused by the large volume changes during charge-discharge cycles has limited its usable lifetime. Coating silicon as thin shells around vertically aligned carbon nanotubes allows it to freely expand and contract but remain in good electrical contact with the highly conductive and stable carbon core. The hybrid material has shown dramatically improved performance.

The core-shell hybrid nanostructure (see the TEM image at the center) allows the reversible volume change during cycling between the charged (right) and discharged (left) states.

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