Gurpreet Singh, Kansas State University associate professor of mechanical and nuclear engineering, and his research team have developed a paperlike battery electrode using silicon oxycarbide glass and graphene. Credit: Kansas State University
It may improve tools for space exploration or unmanned aerial vehicles. A/Prof Gurpreet Singh of mechanical and nuclear engineering, and his research team created the battery electrode using silicon oxycarbide-glass and graphene.
The battery electrode has all the right characteristics. It is >10% lighter than other battery electrodes. It has close to 100% cycling efficiency for >1000 charge discharge cycles. It is made of low-cost materials that are byproducts of the silicone industry. And it functions at temperatures as low as -15C, which gives it numerous aerial and space applications.
It has been difficult to incorporate graphene and silicon into practical batteries because of challenges that arise at high mass loadings – such as low capacity per volume, poor cycling efficiency and chemical-mechanical instability. Singh’s team has addressed these challenges by manufacturing a self-supporting and ready-to-go electrode that consists of a glassy ceramic called silicon oxycarbide sandwiched between large platelets of chemically modified graphene, or CMG. The electrode has a high capacity of ~600 miliamp-hrs/g – 400 miliamp-hrs/cu cm- that is derived from silicon oxycarbide. The paperlike design is made of 20% chemically modified graphene platelets.
“The paperlike design is markedly different from the electrodes used in present day batteries because it eliminates the metal foil support and polymeric glue – both of which do not contribute toward capacity of the battery,” Singh said.
The silicon oxycarbide material itself is quite special. It is prepared by heating a liquid resin to the point where it decomposes and transforms into sharp glasslike particles. The silicon, carbon and oxygen atoms get rearranged into random 3D structure and any excess carbon precipitates out into cellular regions. Such an open 3D structure creates large sites for reversible lithium storage and smooth channels for lithium-ion transportation. This structure and mechanism of lithium storage is different than crystalline silicon electrodes. Silicon oxycarbide electrodes are expected to be low cost as the raw material – liquid resin – is a byproduct of the silicone industry.
Moving forward, Singh and his team want to address practical challenges. Singh’s goal is to produce this electrode material at even larger dimensions. For example, present-day pencil-cell batteries use graphite-coated copper foil electrodes that are more than 1 foot in length. The team also would like to perform mechanical bending tests to see how they affect performance parameters.
“Ultimately, we would like to work with industry to explore production of lithium-ion battery fuel-cells,” Singh said. “Silicon oxycarbide can also be prepared by 3-D printing, which is another area of interest to us.” http://www.k-state.edu/media/newsreleases/mar16/singh33116.html
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