MMaterialsgateNEWS 2012/11/05

Energy: Rice team boosts silicon-based batteries

'Crushed' porous silicon anodes show dramatic increase in charge-discharge cycles

Researchers at Rice University have refined silicon-based lithium-ion technology by literally crushing their previous work to make a high-capacity, long-lived and low-cost anode material with serious commercial potential for rechargeable lithium batteries.

The team led by Rice engineer Sibani Lisa Biswal and research scientist Madhuri Thakur reported in Nature's open access journal Scientific Reports on the creation of a silicon-based anode, the negative electrode of a battery, that easily achieves 600 charge-discharge cycles at 1,000 milliamp hours per gram (mAh/g). This is a significant improvement over the 350 mAh/g capacity of current graphite anodes.

That puts it squarely in the realm of next-generation battery technology competing to lower the cost and extend the range of electric vehicles.

The new work by Rice through the long-running Lockheed Martin Advanced Nanotechnology Center of Excellence at Rice (LANCER) is the next and biggest logical step since the partners began investigating batteries four years ago.

"We previously reported on making porous silicon films," said Biswal, an assistant professor of chemical and biomolecular engineering. "We have been looking to move away from the film geometry to something that can be easily transferred into the current battery manufacturing process. Madhuri crushed the porous silicon film to form porous silicon particulates, a powder that can be easily adopted by battery manufacturers."

Silicon can hold 10 times more lithium ions than the graphite commonly used in anodes today. But there's a problem: Silicon more than triples its volume when completely lithiated. When repeated, this swelling and shrinking causes silicon to quickly break down.

Many researchers have been working on strategies to make silicon more suitable for battery use. Scientists at Rice and elsewhere have created nanostructured silicon with a high surface-to-volume ratio, which allows the silicon to accommodate a larger volume expansion. Biswal, lead author Thakur and co-author Michael Wong, a professor of chemical and biomolecular engineering and of chemistry, tried the opposite approach; they etched pores into silicon wafers to give the material room to expand. By earlier this year, they had advanced to making sponge-like silicon films that showed even more promise.

But even those films presented a problem for manufacturers, Thakur said. "They're not easy to handle and would be difficult to scale up." But by crushing the sponges into porous grains, the material gains far more surface area to soak up lithium ions.

Biswal held up two vials, one holding 50 milligrams of crushed silicon, the other 50 milligrams of porous silicon powder. The difference between them was obvious. "The surface area of our material is 46 square meters per gram," she said. "Crushed silicon is 0.71 square meters per gram. So our particles have more than 50 times the surface area, which gives us a larger surface area for lithiation, with plenty of void space to accommodate expansion." The porous silicon powder is mixed with a binder, pyrolyzed polyacrylonitrile (PAN), which offers conductive and structural support.

"As a powder, they can be used in large-scale roll-to-roll processing by industry," Thakur said. "The material is very simple to synthesize, cost-effective and gives high energy capacity over a large number of cycles."

"This work shows just how important and useful it is to be able to control the internal pores and the external size of the silicon particles," Wong said.

In recent experiments, Thakur designed a half-cell battery with lithium metal as the counter electrode and fixed the capacity of the anode to 1,000 mAh/g. That was only about a third of its theoretical capacity, but three times better than current batteries. The anodes lasted 600 charge-discharge cycles at a C/2 rate (two hours to charge and two hours to discharge). Another anode continues to cycle at a C/5 rate (five-hour charge and five-hour discharge) and is expected to remain at 1,000 mAh/g for more than 700 cycles.

"This successful endeavor between Rice University and Lockheed Martin Mission Systems and Sensors will provide a significant improvement in battery technology by the development of this inexpensive manufacturing technique for silicon anode material," said Steven Sinsabaugh, a Lockheed Martin Fellow who works with LANCER and a co-author of the paper along with Lockheed Martin researcher Mark Isaacson. "We're truly excited about this breakthrough and are looking forward to transitioning this technology to the commercial marketplace."

"The next step will be to test this porous silicon powder as an anode in a full battery," Biswal said. "Our preliminary results with cobalt oxide as the cathode appear very promising, and there are new cathode materials that we'd like to investigate."

Source: Rice University - 01.11.2012.

Investigated and edited by:

Dr.-Ing. Christoph Konetschny, Inhaber und Gründer von Materialsgate
Büro für Material- und Technologieberatung
The investigation and editing of this document was performed with best care and attention.
For the accuracy, validity, availability and applicability of the given information, we take no liability.
Please discuss the suitability concerning your specific application with the experts of the named company or organization.

You want additional material or technology investigations concerning this subject?

Materialsgate is leading in material consulting and material investigation.
Feel free to use our established consulting services

MMore on this topic

Researchers at Rice University and the Université catholique de Louvain, Belgium, have developed a way to make flexible components for rechargeable lithium-ion (LI) batteries from discarded silicon.

The Rice lab of materials scientist Pulickel Ajayan created forests of nanowires from high-value but hard-to-recycle silicon. Silicon absorbs 10 times more lithium than the carbon commonly used in LI batteries, but because it expands and contracts as it charges and discharges, it breaks down quickly. The Ajayan lab reports this week in the journal Proceedings of the National Academy of Science on its technique to make carefully arrayed nanowires encased in electrically conducting copper and ion-conducting polymer electrolyte into an anode. The material gives nanowires the space to grow and shrink as needed, which prolongs their usefulness. The electrolyte also serves as an efficient spacer... more read more

Engineering Researchers at Rensselaer Polytechnic Institute Use Intentionally Blemished Graphene Paper To Create Easy-To-Make, Quick-Charging Lithium-ion Battery With High Power Density

Engineering researchers at Rensselaer Polytechnic Institute made a sheet of paper from the world’s thinnest material, graphene, and then zapped the paper with a laser or camera flash to blemish it with countless cracks, pores, and other imperfections. The result is a graphene anode material that can be charged or discharged 10 times faster than conventional graphite anodes used in today’s lithium (Li)-ion batteries. Rechargeable Li-ion batteries are the industry standard for mobile phones, laptop and tablet computers, electric cars, and a range of other devices. While Li-ion batteries have a high energy density and can store large amounts of energy, they suffer from a low power density... more read more

Rice University, Lockheed Martin researchers extract multiple anodes from a single wafer for lithium-ion batteries

Researchers at Rice University and Lockheed Martin reported this month that they’ve found a way to make multiple high-performance anodes from a single silicon wafer. The process uses simple silicon to replace graphite as an element in rechargeable lithium-ion batteries, laying the groundwork for longer-lasting, more powerful batteries for such applications as commercial electronics and electric vehicles. The work led by Sibani Lisa Biswal, an assistant professor of chemical and biomolecular engineering at Rice, and lead author Madhuri Thakur, a Rice research scientist, details the process by which Swiss cheese-like silicon “sponges” that store more than four times their weight in lithium... more read more


Partner of the Week

Search in MaterialsgateNEWS