A cheaper, lighter version of the lithium batteries used in laptop computers and cellular phones may soon become available. Researchers have found a way to replace cobalt--the most expensive component of these batteries--with aluminum. The new material, described in today's issue of Nature, is the first of its kind to be designed using theoretical calculations rather than simply by trial and error.
Batteries discharge electricity by sending a stream of electrons from a positive to a negative electrode, thus powering any device that dips into that stream. In lithium batteries, the negative electrodes are made up of an oxide of lithium and cobalt. Cobalt is expensive, but scientists thought that only metals like cobalt could satisfactorily discharge the current. One strategy for finding a replacement electrode would be to fabricate and test countless combinations of lithium-metal oxides. Gerd Ceder and his colleagues at the Massachusetts Institute of Technology wanted to search in a more directed way.
Armed with the basic laws of quantum mechanics, they developed a computer simulation that predicted the properties of different materials. The calculations identified a promising replacement: an oxide made primarily of lithium and aluminum. The team synthesized this new material and experimentally confirmed their predictions. That aluminum works supports a previous finding of theirs that oxygen is more important than cobalt in accepting electrons from the positive electrode.
The work is a "marvelous" example of how theory can point to an experiment, says Didier de Fontaine, a materials scientist at the University of California, Berkeley, who has done pioneering work in calculating the properties of complicated materials from the ground up. Ceder and his colleagues say they have already developed a different material, based on the same approach, that could be ready to use in a battery in less than a year.