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New Graphite-Core/Silicon-Shell Composite Material for Enhanced Li-ion Performance

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.

Resources

  • Fuchsbichler B., Stangl C., Kren H., Sternad M., Hohl R., Koller S. (2009) (ECS 216)

Comments

HarveyD

Is this another method to use silicon composite in anodes to increase energy flow and density?

Didn't MIT to the same some times back?

Carlos Fandango

I think its something similar. Didn't MIT use nano rods to absorb the volume change of the silicon? Where this is using a composite structure.

I think 10X increase in Anode capacity can only lead to ~2X increase in overall battery capacity as the anode is only XX% of the total capacity.

Interesting that this is patented with Varta. I hope it could actually lead to commercialisation in the next 5 years. No sign of commercialisation from the MIT disclosure thus far.

arnold

Carlos,
The graph shows coulometric capacity rising by 2/3 - nearly double.
But the best news is efficiency increase from 80% to over 95% - 98?.
(every graph and reader can be interpreted differently, I prefer the simplest and more obvious)

I know graphs are often deliberately misleading or try to exaggerate certain aspects or in some other way. Any class of twenty will have six different opinions. Only half are likely to grasp the meaning.

From this little black duck's interpretation of the graph - This should equate to massive efficiency improvements properly rivaling capacitors. That's the "excellent coulometric efficiency."
Benefit by cooler running cells so huge reduction in battery cooling requirement.Hence weight savings and cycling stability as mentioned.

Suggest look at the graph again and refer to the link provided.

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