For use in commercial electric vehicles, lithium battery electrodes need to last through at least 300 charge cycles. In this respect, the nanowires could face stiff competition. In December 2008, a team from Hanyang University in Ansan, South Korea, unveiled nanoporous silicon anodes that lasted for more than 100 charging cycles and could store more charge than the nanowires. Chemist Jaephil Cho, who led the work, says that the nanoporous material has more silicon-per-unit volume than nanowires, so it can hold more charge per unit volume. However, he says, "carbon fiber [manufacturing] is easy to scale up and therefore [Cui's] method for making carbon-silicon nanowires is believed to be very practical."

General Motors and Applied Sciences, meanwhile, are developing nanowire anodes that are very similar to those of the Stanford team. The companies coat carbon nanofibers with silicon particles, as opposed to amorphous silicon, resulting in anodes that can store charge of 1,000 to 1,500 milliamp hours per gram. Gholam-Abbas Nazri, who is leading the work at the GM Research and Development Center in Warren, MI, says that the anode capacity can be increased by making the silicon layer thicker, but right now it's best to stabilize the capacity at 1,000 milliamp hours per gram. Anodes that store more charge need cathodes that can supply higher charge, Nazri says, and "at the moment, there is no cathode [material] with enough capacity to match carbon-silicon anode."

Cui is confident in the success of silicon as an anode material for lithium batteries. "In the next five years or less, we'll see a battery with silicon anodes," he says. However, cost will be the deciding factor. In the end, he says, it all depends on "whoever can come up with a low-cost, large-scale manufacturing process, produce the best performance, and put out products."