Nanowire Battery Holds Ten Times The Charge

Stanford researchers have found a way to use silicon nanowires to reinvent the rechargeable lithium-ion batteries. The new version, developed through research led by Yi Cui, assistant professor of materials science and engineering, produces ten times the amount of electricity of existing lithium-ion batteries. A laptop that now runs on battery for two hours could operate for 20 hours.

The electrical storage capacity of a Li-ion is limited by how much lithium can be held in the battery’s anode, which is typically made of carbon. Silicon has a much higher capacity than carbon. However, Silicon placed in a battery swells as it absorbs positively charged lithium atoms during charging, then shrinks during use as the lithium is drawn out of the silicon. This expand/shrink cycle typically causes the silicon (often in the form of particles or a thin film) to pulverize, degrading the performance of the battery.

Cui’s battery gets around this problem with nanotechnology. The lithium is stored in a forest of tiny silicon nanowires, each with a diameter one-thousandth the thickness of a sheet of paper. The nanowires inflate four times their normal size as they soak up lithium. But, unlike other silicon shapes, they do not fracture. For their experiments, graduate student Candace Chan grew the nanowires on a stainless steel substrate, providing an excellent electrical connection.

Cui says that a patent application has been filed. He is considering forming a company or an agreement with a battery manufacturer. Manufacturing the nanowire batteries would require “one or two different steps, but the process can certainly be scaled up,” he added.