In lithium-ion battery electrodes, especially anode materials, three lithium-storage mechanisms dominate: insertion, alloying and conversion reactions. Although transition metal oxides including Fe2O3 and Fe3O4 have a high storage capacity by the lithium conversion reaction, they suffer from poor capacity sustainability on cycling that prohibits practical applications. Recently, state-of-the-art nanostructuring of hybrid transition metal oxides has opened up great opportunities for high-energy and high-power lithium-ion batteries.

Researchers at Ajou University, Korea, have successfully demonstrated core-shell heterostructured Fe/Fe3O4 nanocomposites formed by a simple and efficient thermochemical reduction process, which offer a high-capacity anode with excellent capacity retention for lithium-ion batteries. As reported recently in Nanotechnology, highlights of the work include: 1) the formation of core/shell (Fe3O4/Fe) nanorod electrodes by the controlled thermochemical reduction of Fe2O3 nanobundles and 2) the realization of high capacity without significant fading (~540 mAh/g even after 100 cycles at a rate of 185 mA/g, larger than the theoretical capacity of the carbon-based electrodes currently used in commercial lithium-ion batteries).

This approach will allow other conversion reaction electrodes to be tailored with superior cycling performance. In the near future, the team will be exploring the design of vertically aligned architecture of heterostructured nanorods/nanowires/nanotubes for tiny microbatteries as well as 3D, high-energy and high-power batteries for plug-in hybrid electric vehicles.