Rice University researchers refine silicon-based lithium-ion batteries

Rice University professor Sibani Lisa Biswal holds two vials — one of crushed silicon and the other of her lab's porous silicon powder. The treated silicon may lead to robust, powerful lithium-ion batteries.

Researchers at Rice University have refined the silicon-based lithium-ion battery by creating a material with commercial potential for rechargeable lithium batteries.

Let by engineer Sibani Lisa Biswal and research scientist Madhuri Thakur, the team created a silicon-based anode, which is the negative electrode of a battery, that achieves 600 charge-discharge cycles at 1,000 milliamp hours per gram. This marks a large improvement over the current capacity of graphite anodes, which is 350 milliamp hours per gram.

"We previously reported on making porous silicon films," Biswal said in the press release. "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."

According to the release, silicon holds 10 times more lithium ions than graphite, which is commonly used in anodes. However, silicon more than triples its volume when totally lithiated, and the swelling and shrinking that occurs when repeated causes it to quickly break down.

As such, scientists have created nanostructured silicon, which has a high surface-to-volume ratio allowing the material to accommodate larger volume expansion. But the team at Rice tried an opposite approach and etched pores into silicon wafers to give it room to expand. This led to an advancement in making silicon films that are sponge-like.

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