14 DAY TRIAL // A group of investigators in the United States has developed a method of improving silicon's ability to absorb lithium ions, an achievement that may lead to the development of higher-capacity lithium-ion batteries.
The team, made up of researchers at the Rice University and Lockheed Martin, says that it has developed a method of using simple silicon for this job.
The work was conducted by Rice assistant professor of chemical and biomolecular engineering Sibani Lisa Biswal, Rice professor of chemical and biomolecular engineering and of chemistry Michael Wong, and Lockheed Fellow Steven Sinsabaugh.
Using silicon to improve batteries may result in creating advanced electric car batteries, as well as large-capacity energy storage devices, for a wide variety of applications.
The announcement of the new method was made at the Rice Buckyball Discovery Conference, which was organized to celebrate the 25th anniversary of the discovery of the buckminsterfullerene.
This finding, which ended up winning the Nobel Prize, represented the first time the carbon-60 molecule was developed. Celebrations of the event will take place throughout 2010.
“The anode, or negative, side of today's batteries is made of graphite, which works. It's everywhere. But it's maxed out. You can't stuff any more lithium into graphite than we already have,” Wong said.
Experts have known for many years that silicon is the best theoretical candidate for anodes, but the material has some properties that made it unfeasible to use.
Silicon “can sop up a lot of lithium, about 10 times more than carbon, which seems fantastic. But after a couple of cycles of swelling and shrinking, it's going to crack,” Wong explained.
So the Rice group started to investigate methods of modifying silicon so that it would resist more cycles. The team discovered that creating pores into the surface of a silicon wafer is the best approach.
The holes are only the size of a few microns, but this leaves the chemical with ample room to expand, thus reducing the risk of developing cracks after prolonged use.
“The other advantage is that we've seen fairly long lifetimes. Our current batteries have 200-250 cycles, much longer than nanowire batteries,” Biswal explains.
“We are very excited about the potential of this work. This material has the potential to significantly increase the performance of lithium-ion batteries, which are used in a wide range of commercial, military and aerospace applications,” Sinsabaugh concludes.