|Capacity limited cycling of a graphite-core/silicon-shell electrode. Source: Fuchsbichler et al. Click to enlarge.|
Researchers at the Institute for Chemistry and Technology of Materials at the Graz (Austria) University of Technology have a new method to utilize silicon in lithium-ion anode materials.
Silicon is a promising anode material for Li-ion batteries, as it offers about 10x the theoretical capacity of graphite; it also suffers from structural challenges—specifically changes in volume upon lithiation and delithiation that quickly degrade the structural integrity of the material—resulting in short lifecyles. As a result, numerous studies have and are exploring ways to methods the cycle life Li-ion cells with a silicon anode material.
The new findings—which came to light in the “” EU project—have been recently submitted to the patent office by researchers together with their co-operation partner Varta Microbattery.
In the newly developed process, researchers utilize a new graphite-core/ silicon-shell composite material that appears to offer an excellent cycling stability and coulometric efficiency.
In this way the graphite works as a buffer, cushioning the big changes in volume of the silicon during the uptake and transfer of lithium ions.
—Dr. Stefan Koller
For the fabrication of the graphite-core/silicon-shell composite a gelatinous silicon compound was thermal decomposed under an argon flow on natural graphite. This decomposition leads to the silicon-shell on the graphite.
This method is far cheaper than the previous methods in which silicon is separated in the gas phase, the researchers said.
Fuchsbichler B., Stangl C., Kren H., Sternad M., Hohl R., Koller S. (2009) (ECS 216)