RICHLAND, Wash. -- A study that examines a new type of silicon-carbon nanocomposite electrode reveals details of how they function and how repeated use could wear them down. The study also provides clues to why this material performs better than silicon alone. With an electrical capacity five times higher than conventional lithium battery electrodes, silicon-carbon nanocomposite electrodes could lead to longer-lasting, cheaper rechargeable batteries for electric vehicles.
Published online in the journal Nano Letters last week, the study includes videos of the electrodes being charged at nanometer-scale resolution. Watching them in use can help researchers understand the strengths and weaknesses of the material.
"The electrodes expand as they get charged, and that shortens the lifespan of the battery," said lead researcher Chongmin Wang at the Department of Energy's Pacific Northwest National Laboratory. "We want to learn how to improve their lifespan, because silicon-carbon nanofiber electrodes have great potential for rechargeable batteries."
Plus & Minus
Silicon has both advantages and disadvantages for use as a battery material. It has a high capacity for energy storage, so it can take on a hefty charge. Silicon's problem, though, is that it swells up when charged, expanding up to 3 times its discharged size. If silicon electrodes are packed tightly into a battery, this expansion can cause the batteries to burst. Some researchers are exploring nano-sized electrodes that perform better in such tight confines (http://www.pnl.gov/news/release.aspx?id=832).
A multi-institution group led by PNNL's Wang decided to test nano-sized electrodes consisting of carbon nanofibers coated with silicon. The carbon's high conductivity, which lets electricity flow, nicely complements silicon's high capacity, which stores it.
Researchers at DOE's Oak Rid
|Contact: Mary Beckman|
DOE/Pacific Northwest National Laboratory