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A Super Material for Batteries and Other Energy Conversion Devices

Unplanned discoveries can lead to vital discoveries in the future, such as batteries, fuel cells, and devices for converting heat to electricity.

Scientists usually conduct research by carefully selecting a research problem, devising an appropriate plan to solve it, and implementing that plan. However, unplanned discoveries can occur along the way.

Mercouri Kanatzidis, Professor Northwestern University Co-appointed at the US Department of Energy’s (DOE) Argonne National Laboratory, he was looking for a new superconductor with unconventional behavior when he made an unexpected discovery. With a thickness of only 4 atoms, it was a material that could study the motion of charged particles in two dimensions. Such research could spur the invention of new materials for a variety of energy conversion devices.

“Our analysis reveals that prior to this transition, silver ions were fixed in a confined space within the two dimensions of our material, but after this transition they shook. Did.” – Co-appointed with Mercouri Kanatzidis, Argonne and Northwestern University

Kanatzidis’s target material is a combination of silver, potassium and selenium (a-KAg)3Se2) 4-layer structure like a wedding cake. These 2D materials have lengths and widths, but they have very little thickness because they are only 4 atoms high.

Superconducting materials lose all resistance to electron movement when cooled to very low temperatures. “Very unfortunately, this material was not a superconductor and could not be made into a superconductor,” said Kanatzidis, a senior scientist at Argonne’s Department of Materials Science (MSD). “But to my surprise, it turned out to be a great example of a superionic conductor.”

In superionic conductors, charged ions in solid materials move freely, much like the liquid electrolytes found in batteries. This results in a solid with unusually high ionic conductivity, a measure of its ability to conduct electricity. This high ionic conductivity results in low thermal conductivity. In other words, it is difficult for heat to pass through. Both of these properties make superionic conductors supermaterials for energy storage and conversion devices.

4-layer atomic structure 2D superionic conductor

4-layer atomic structure of α-KAg3Se2, a 2D superionic conductor. The color of the atom is in harmony with the color of the name.Credits: Images by Mercouri Kanatzidis / Northwestern University and Argonne National Laboratory

The first clue that the team discovered a material with special properties was when it was heated from 450 degrees to 600 degrees. Fahrenheit.. It has moved to a more symmetrical layered structure. The team also found that this transition was reversible when the temperature was lowered and then raised again in the hot zone.

“Our analysis reveals that prior to this transition, silver ions were anchored in a confined space within the two dimensions of our material,” Kanatzidis said. “But after this transition, they wiggle around.” Much is known about how ions move in three dimensions, but only in two dimensions. Little is known.

Scientists have been looking for some time to find exemplary materials for investigating the movement of ions in 2D materials. This layered potassium-silver-selenium material appears to be one. The team measured how the ions diffused within this solid and found that they were comparable to one of the fastest known ionic conductors, the highly salted water electrolyte.

It is premature to determine if this particular superionic material will be put to practical use, but it will soon serve as an important platform for designing other 2D materials with high ionic conductivity and low thermal conductivity. There is a possibility.

“These properties are very important to anyone designing new 2D solid electrolytes for batteries and fuel cells,” said Duck Young Chung, MSD’s leading materials scientist.

Research using this superionic material could also help in the design of new thermoelectric elements that convert heat into electricity in power plants, industrial processes, and even the exhaust from automobile emissions. And such studies can be used to design membranes for purification of the environment and desalination of water.

This study appeared in Nature Materials A paper entitled “Two-dimensional type I superionic conductor”. In addition to Kanatzidis and Chung, authors include Alexander JE Rettie, Jingxuan Ding, Xiuquan Zhou, Michael J. Johnson, Christos D. Malliakas, Naresh C. Osti, Raymond Osborn, Olivier Delaire and Stephan Rosenkranz. The team includes researchers from Argonne, Northwest, Oak Ridge National Laboratory at DOE, University College London, and Duke University.

See also: “2D Type I Superion Conductor” by Alexander JE Rettie, Jingxuan Ding, Xiuquan Zhou, Michael J. Johnson, Christos D. Malliakas, Naresh C. Osti, Duck Young Chung, Raymond Osborn, Olivier Delaire, Stephan Rosenkranz Mercouri G. Kanatzidis, July 22, 2021 Nature Materials..
DOI: 10.1038 / s41563-021-01053-9

The team’s experimental measurements show the Spalling Neutron Source at Oak Ridge National Laboratory, the Center for Integrated Molecular Structure Education and Research in the northwest, and the beamline 17-BM-B at Argonne National Laboratory, a user facility at Argonne National Laboratory. Was used. Their computer simulations used the computing resources provided by Bebop, Argonne’s high-performance computing cluster.

This research was mainly supported by the DOE Science Department and the Basic Energy Science Department.



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