December 18, 2007

Silicon nanowires for 10 times the amount of electricity of existing lithium-ion

New batteries using silicon nanowire, developed through research led by Yi Cui, assistant professor of materials science and engineering, produces 10 times the amount of electricity of existing lithium-ion, known as Li-ion, batteries. If these batteries are produced in high volume at a reasonable cost this will enable high performance all electric cars and plug in hybrid vehicles. The researchers do believe that they can commercialize quickly.

The breakthrough is described in a paper, "High-performance lithium battery anodes using silicon nanowires," published online Dec. 16 in Nature Nanotechnology, written by Cui, his graduate chemistry student Candace Chan and five others.

The greatly expanded storage capacity could make Li-ion batteries attractive to electric car manufacturers. Cui suggested that they could also be used in homes or offices to store electricity generated by rooftop solar panels.

"Given the mature infrastructure behind silicon, this new technology can be pushed to real life quickly," Cui said.

The electrical storage capacity of a Li-ion battery 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, but also has a drawback.

Silicon placed in a battery swells as it absorbs positively charged lithium atoms during charging, then shrinks during use (i.e., when playing your iPod) 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.

Chan grew the nanowires on a stainless steel substrate, providing an excellent electrical connection.

Cui said that a patent application has been filed. He is considering formation of 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. "It's a well understood process."

Publications from Cui research group


Jonathan said...

Would these new bateries let you charge them up faster? That is a critical issue wrt the automotive industry.

Snake Oil Baron said...

That is a good question. Even though there would be lots of applications for them even if they were slow, the automotive and mobile robot applications would really get a boost if these were faster to charge. But then I have heard of the idea of hybrid systems where you could have ultra capacitors to give you the speed of charge and discharge while using batteries for holding charges longer. You might charge up the batteries at night and use the capacitors when you need to "top-up" while on the road.

I would guess that they would be since there is a much larger surface area to reabsorb the lithium but that is just an uneducated guess.

I was wondering whether it is easier or harder to grow these tubes than the carbon ones and whether there have been similar improvements to the silicon tube production methods as have been seen recently in carbon ones.

roid said...

Looking for an update on this silicon nanowire lithium ion battery technology, came across this article suggesting that the research has an ongoing stable source of funding.

Also there is a 40 minute google-talk by Lu Cui (Sept 2006) about nanowires, on youtube.