Green Design

Silicon Strategy Shows Promise for Lithium-ion Batteries

Scientists from Rice University and Lockheed Martin have discovered a way to use simple silicon to radically increase the capacity of lithium-ion batteries. The researchers are confident that cheap, plentiful silicon combined with ease of manufacture could help push their idea into the mainstream.

Sibani Lisa Biswal, an assistant professor of chemical and biomolecular engineering; Michael Wong, a professor of chemical and biomolecular engineering and of chemistry; and Steven Sinsabaugh, a Lockheed Martin Fellow, contributed to the research.

"The anode, or negative, side of today's batteries is made of graphite, which works. It's everywhere," Wong said. "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 is a 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."

The team 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, they determined the treated silicon could theoretically store more than 10 times that amount.