Synthetic porous material promises ‘new-age’ supercaps, batteries

Technology News | December 9, 2019

By Rich Pell

University of Oregon scientists who analyzed the material, which was synthesized by a research group at the Massachusetts Institute of Technology, say they have discovered that electrical charges flow through it in an unexpected but potentially advantageous way. The material acts as metal in one direction and a semiconductor in other directions – properties that allow the electrical charges to flow between atoms.

Such materials, say the researchers, could eventually lead to new-age supercapacitors and batteries that deliver fast and precise pulsed power.

“This is an important result, because it means that charges are flowing through material in a direction where things are not technically touching,” says Christopher Hendon, a professor in the UO’s Department of Chemistry and Biochemistry and member of the Materials Science Institute. “As a design principle, doing that is something we’ve been working on a long time.”

The research builds on efforts that began 20 years ago by numerous labs to produce electrically conductive metal organic frameworks – sponge-like material with extremely high surface areas. If a couple of grams of the material were flattened, says Hendon, the material would cover a space about the size of the University of Oregon’s Autzen Stadium.

“We’ve taken a type of material that we have conventionally thought of as simply a sponge and demonstrated that you can conduct electricity through it in different directions,” says Hendon. “As a result, these types of materials now have broadened their applications to energy storage devices.”

Research on materials using a variety of other charged elements is rapidly evolving, say the scientists. For example, a similar material is part of a new joint MIT-Lamborghini project to produce supercapacitors for use in the automaker’s efforts to build an electric supercar.

A challenge in making such conductive metal organic frameworks, says Hendon, is that charges traditionally are expected to flow in the direction of the points of connectivity.

“In this case, however, we noticed that the material was conducting and suspected that the current was flowing in the non-connected direction,” he says. “Our theory led us to find that the conductivity was flowing perpendicular to the connectivity.”

That means, say the scientists, that conductivity can be driven by how stacked two-dimensional sheets are fitted above and below the new spongy organic-lanthanide material. The researchers reported their findings in a paper in the journal Nature Chemistry.

“This paper lays a foundation that says it is possible to make a tunable electrical conductor that does not feature physical bonds in the direction of conductivity,” says Hendon. “There has been a lot of work where researchers have been hypothesizing about molecules stacking and conducting. In this case, what we observed has been highly evasive.”

Such research, say the scientists, could lead to devices that rapidly charge and discharge pulses of high voltage without generating high current and associated heat – such as, for example, a supercapacitor that would charge as a car brakes and then discharge during rapid acceleration, or a sunlight-powered jet pack like the one used in the first “Iron Man” movie.

For more, see “Efficient and tunable one-dimensional charge transport in layered lanthanide metal–organic frameworks.”