These images demonstrate the structure of a new paper-like battery electrode made from silicon oxycarbide glass and graphene. Images: Kansas State University.A paper-like battery electrode developed by engineers at Kansas State University could prove ideal for use in space exploration or unmanned aerial vehicles. Gurpreet Singh, associate professor of mechanical and nuclear engineering, and his research team produced the electrode from silicon oxycarbide-glass and graphene.
This new battery electrode possesses a combination of useful characteristics. It is more than 10% lighter than other battery electrodes. It has close to 100% cycling efficiency for more than 1000 charge-discharge cycles. It is made of low-cost materials that are by-products of the silicone industry. And it functions at temperatures as low as -15°C, giving it numerous aerial and space applications. It is described in a paper in Nature Communications.
Singh's research team has been actively exploring new material combinations for batteries and electrodes. However, they found it 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 addressed these challenges by manufacturing a paper-like electrode that consists of a glassy ceramic called silicon oxycarbide sandwiched between large platelets of chemically modified graphene (CMG), which account for 20% of the electrode. The silicon oxycarbide gives the electrode a high capacity of approximately 600 miliampere-hours per gram – 400 miliampere-hours per cubic centimeter.
"The paper-like 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 design that Singh's team developed saves approximately 10% in the total weight of the cell. The result is a lightweight electrode capable of storing lithium-ion and electrons with near 100% cycling efficiency for more than 1000 charge-discharge cycles. The most important aspect is that the material is able to demonstrate such performance at practical levels, Singh said.
The paper electrode cells are still able to deliver a capacity of 200 miliampere-hour per gram when kept at -15°C for about a month, which is quite remarkable considering that most batteries fail to perform at such low temperatures, Singh said. "This suggests that rechargeable batteries from silicon-glass and graphene electrodes may also be suitable for unmanned aerial vehicles flying at high altitudes, or maybe even space applications," he proposed.
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 glass-like particles. The silicon, carbon and oxygen atoms get rearranged into random three dimensional (3D) structures 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. These silicon oxycarbide electrodes are expected to be low cost because the raw material – liquid resin – is a by-product 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 one foot in length. The team would also like to perform mechanical tests to see how bending affects battery performance.
"Ultimately, we would like to work with industry to explore production of lithium-ion battery full-cells," Singh said. "Silicon oxycarbide can also be prepared by 3D printing, which is another area of interest to us."
This story is adapted from material from Kansas State University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.