A team of Rice University and Lockheed Martin scientists has discovered a way to use simple silicon to radically increase the capacity of lithium-ion batteries. Watch this one, Rice University in Houston is famed for the ‘buckyball’ discovery now 25 years on for nanotechnology development and Lockheed Martin is deep into lots of high tech as a military contractor and sometimes Eestor insider.

Rice is celebrating the buckyball this week and is using that forum to introduce the new silicon battery building work, which could become a key component for electric car batteries, small electronics on up to large-capacity energy storage.

Sibani Lisa Biswal, an assistant professor in chemical and biomolecular engineering, revealed how she, colleague Michael Wong, a professor in chemical and biomolecular engineering and in chemistry, and Steven Sinsabaugh, a Lockheed Martin fellow, are enhancing the inherent ability of silicon to absorb lithium ions.  Here’s the story.

Wong explains, “The anode, or negative, side of today’s batteries is made of graphite, which works. It’s everywhere (in the lithium-ion build business), but it’s maxed out. You can’t stuff any more lithium into graphite than we already have.”

Silicon has the highest theoretical capacity of any material for storing lithium, but there’s a serious drawback to its use. “It can sop up a lot of lithium, about 10 times more than carbon, which seems fantastic,” Wong said. “But after a couple of cycles of swelling and shrinking, it’s going to crack.” That makes it near useless.

Other labs have tried to solve the problem with carpets of silicon nanowires that absorb lithium as a mop soaks up water, but the Rice team took a different tack.

Together with Mahduri Thakur, a postdoctoral researcher in Rice’s chemical and biomolecular engineering department, and Mark Isaacson of Lockheed Martin, Biswal, Wong and Sinsabaugh found that putting micron-sized pores into the surface of a silicon wafer gives the material sufficient room to expand. While common lithium-ion batteries hold about 300 milliamp hours per gram of carbon-based anode material, the researchers determined the treated silicon could theoretically store more than 10 times that amount.

Right on the common theoretical target.

Sinsabaugh described the breakthrough as one of the first fruits of the Lockheed Martin Advanced Nanotechnology Center of Excellence at Rice. He said the project began three years ago when he met Biswal at Rice and compared notes. “She was working on porous silicon, and I knew silicon nanostructures were being looked at for battery anodes. We put two and two together,” he said.

Top and Side View of Etched Silicon Battery Material from Rice University. Click image for more info.

Nanopores are simpler to create than silicon nanowire structures, Biswal said. The pores, a micron wide and 10-50 microns deep, form when positive and negative charge is applied to the sides of a silicon wafer, which is then bathed in a hydrofluoric solvent. “The hydrogen and fluoride atoms separate,” she said. “The fluorine attacks one side of the silicon, forming the pores. They form vertically because of the positive and negative bias.”

She said the treated silicon “looks like Swiss cheese.”

The straightforward process makes it highly adaptable for manufacturing, she said. “We don’t require some of the difficult processing steps they do – the high vacuums and having to wash the nanotubes. Bulk etching is much simpler to process.

“The other advantage is that we’ve seen fairly long lifetimes. Our current batteries have 200-250 cycles, much longer than nanowire structure batteries,” Biswal said.

But the researchers said putting pores in silicon requires a real balancing act, as the more space is dedicated to the holes, the less material is available to store lithium. And if the silicon expands to the point where the pore walls touch, the material could degrade.  So it isn’t a simple slam-dunk, as at these sizes nothing can be.

The researchers are confident that cheap, plentiful silicon combined with ease of manufacture could help push their idea into the mainstream.  The team does need to work on total cycles a bit more in the meantime.

“We are very excited about the potential of this work,” Sinsabaugh said. “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.”

Biswal and Wong plan to study the mechanism by which silicon absorbs lithium and how and why it breaks down. “Our goal is to develop a model of the strain that silicon undergoes in cycling lithium,” Wong said. “Once we understand that, we’ll have a much better idea of how to maximize its potential.”

Wong is right about the need for understanding, yet serendipity has gotten the Rice and Lockheed team way out in front.  It’s not real clear just how the balancing act while building might play out, but every manufacturer on the planet has to be seeking more information.

The consumer view also has strong motives.  A major increase in battery performance such as this reduces the amount of raw materials needed to get the desired capacity.  It also reduces weight.

Congratulations to the Rice Lockheed group.  It’s been 25 years for the buckyball and that set off a huge run of nanotechnology research.  Perhaps the etched silicon for lithium-ion batteries will too.  We consumers sure hope so.


2 Comments so far

  1. amadee Bender on February 4, 2011 11:14 AM

    who should press releases be sent to?

  2. Mackenzie Perrino on March 22, 2011 6:21 PM

    Thanks for the very good resources listed within your site, this is a little test for your weblog viewers. Who stated the following quote? . . . .If life were measured by accomplishments, most of us would die in infancy.

Name (required)

Email (required)


Speak your mind