Anodes in lithium ion batteries have traditionally been made up of layers of carbon atoms (graphite), 6 of which hold onto each individual lithium ion; lithium ions provide the power for a device by unloading the extra electrons they grabbed during the charging process. Because each silicon atom is capable of holding 4 lithium ions, it's long been thought that silicon would work much better than carbon in extending batteries' longevity.Past attempts to use silicon films or particles in batteries had failed, however, because the large number of lithium atoms had destroyed the silicon, breaking its contact with the metal substrate and drastically reducing the batteries' longevity. Cui and his colleagues were able to resolve this issue by growing a bunch of flexible silicon nanowires directly bonded to a stainless steel base - ensuring they wouldn't break away under the stress of the lithium atoms. To relieve the strain, the nanowires were able to contract and expand radially as needed.
Gerbrand Ceder, a materials scientist at MIT, said that for the technology to move past the concept stage, Cui's team would first need to find a way to get the cathode to hold 10 times the charge as well. If they are successful in accomplishing this, we may all soon be looking at much longer battery lives.
Via ::ScienceNOW: A 40-Hour Laptop Battery? (news website)