Without doubt the day of the
super battery is fast approaching. Here
is some more research news. Look at the
implied complexity achieved. There is a
lot of wow factor here.
As we have reported there is plenty of work underway and it is profoundly difficult but we are also learning to work with atomic layering which is the ultimate source of all our core future technology.
Everything we use is presently hopelessly
obsolete in terms of our current present knowledge. Remember that.
Hybrid ribbons a gift for powerful batteries
Rice lab finds vanadium oxide/graphene material works well for
lithium-ion storage
David
Ruth
713-348-6327
david@rice.edu
713-348-6327
david@rice.edu
Mike Williams
The Rice University
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.
Ajayan said vanadium oxide has long been considered a material with great potential, and in fact vanadium pentoxide has been used in lithium-ion batteries for its special structure and high capacity. But oxides are slow to charge and discharge, due to their low electrical conductivity. The high-conductivity graphene lattice that is literally baked in solves that problem nicely, he said, by serving as a speedy conduit for electrons and channels for ions.
The atom-thin graphene sheets bound to the crystals take up very little
bulk. In the best samples made at Rice, fully 84 percent of the cathode’s
weight was the lithium-slurping VO2, which held 204 milliamp hours of energy
per gram. The researchers, led by Rice graduate student Yongji Gong and
lead author Shubin Yang, said they believe that to be among the best overall
performance ever seen for lithium-ion battery electrodes.
“One challenge to production was controlling the conditions for the
co-synthesis of VO2 ribbons with graphene,” Yang said. The process involved
suspending graphene oxide nanosheets with powdered vanadium pentoxide (layered
vanadium oxide, with two atoms of vanadium and five of oxygen) in water and
heating it in an autoclave for hours. The vanadium pentoxide was completely
reduced to VO2, which crystallized into ribbons, while the graphene oxide was
reduced to graphene, Yang said. The ribbons, with a web-like coating of
graphene, were only about 10 nanometers thick, up to 600 nanometers wide and
tens of micrometers in length.
“These ribbons were the building blocks of the three-dimensional
architecture,” Yang said. “This unique structure was favorable for the
ultrafast diffusion of both lithium ions and electrons during charge and
discharge processes. It was the key to the achievement of excellent
electrochemical performance.”
In testing the new material, Yang and Gong found its capacity for
lithium storage remained stable after 200 cycles even at high temperatures (167
degrees Fahrenheit) at which other cathodes commonly decay, even at low
charge-discharge rates.
“We think this is real progress in the development of cathode materials for high-power lithium-ion batteries,” Ajayan said, suggesting the ribbons’ ability to be dispersed in a solvent might make them suitable as a component in the paintable
batteries developed in his lab.
Co-authors of the new paper are Rice graduate students Daniel Hashim and Lulu Ma; research scientist Zheng Liu; former Rice visiting researcher Liang Zhan, now an associate professor at East China University of Science and Technology in Shanghai; and faculty fellow Robert Vajtai. Ajayan is the Benjamin M. and Mary Greenwood Anderson Professor in Engineering and a professor of mechanical engineering and materials science, chemistry, and chemical and biomolecular engineering.
The work was funded by the U.S. Army Research Office and the Office of
Naval Research through a Multidisciplinary University Research Initiative grant
and a National Science Foundation Graduate Research Fellowship grant.
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Read the abstract at http://pubs.acs.org/doi/abs/10.1021/nl400001u
This news release can be found online at http://news.rice.edu/2013/03/25/hybrid-ribbons-a-gift-for-powerful-batteries/
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