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Hybrid ribbons a gift for powerful batteries

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Graphene-coated ribbons of vanadium oxide, seen in a scanning electron microscope image, might be the best electrode for lithium-ion batteries yet tested, according to researchers at Rice University. (Credit: Ajayan Group/Rice University)

Hybrid ribbons of vanadium oxide (VO2) and graphene may accelerate the development of high-power lithium-ion batteries suitable for electric cars and other demanding applications. The Rice University lab of materials scientist Pulickel Ajayan determined that the well-studied material is a superior cathode for batteries that could supply both high energy density and significant power density. The ribbons created at Rice are thousands of times thinner than a sheet of paper, yet have potential that far outweighs current materials for their ability to charge and discharge very quickly. Cathodes built into half-cells for testing at Rice fully charged and discharged in 20 seconds and retained more than 90 percent of their initial capacity after more than 1,000 cycles. “This is the direction battery research is going, not only for something with high energy density but also high power density,” Ajayan said. “It’s somewhere between a battery and a supercapacitor.” The ribbons also have the advantage of using relatively abundant and cheap materials. “This is done through a very simple hydrothermal process, and I think it would be easily scalable to large quantities,” he said.