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CHAMPAIGN, Fig – Solid-state batteries pack a lot of energy in a small space, but their electrodes are not good at staying in contact with their electrolytes. Liquid electrolytes reach every corner of an electrode to generate energy, but liquids take up space without storing energy and fail over time. Researchers are now bringing solid electrolytes into contact with electrodes made from strategically placed materials – at the atomic level – and the results are helping to advance better solid-state battery technologies.

A new study led by Paul Braun, professor of materials science and engineering at the University of Illinois at Urbana-Champaign, postdoctoral fellow Beniamin Zahiri, and Xerion Advanced Battery Corp.’s director of research and development, John Cook, shows how Controlling the atomic alignment of solid materials can improve the interface between cathode and solid electrolyte and the stability in solid-state batteries. The results are published in the journal Nature Materials.

“When it comes to batteries, not only are materials important, but also the arrangement of the atoms on the surfaces of these materials,” said Zahiri. “Currently, solid state battery electrodes contain materials with a wide variety of surface atomic arrangements. This leads to a seemingly infinite number of possible interfaces between the electrode and the solid electrolyte, all of which have different chemical reactivities. We are interested in finding out what precautions will lead to practical improvements in battery life, energy density and performance. “

The researchers said that the stability of an electrolyte controls how many charge and discharge cycles a battery can handle before it begins to lose power. Because of this, scientists are in a race to find the most stable electrolyte materials.

“In the rush to find stable solid electrolyte materials, developers have lost sight of the importance of what happens in this very thin electrolyte-electrode interface,” said Zahiri. “However, the stability of the electrolyte does not matter if the connection between it and the electrodes cannot be evaluated efficiently.”

Illustration of a traditional solid-state battery and the team’s new high-performance design incorporating bespoke electrode-electrolyte interfaces.

Courtesy of Beniamin Zahiri and Paul Braun

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In the laboratory, the team built electrodes containing sodium and lithium ions with specific atomic arrangements. They found correlations between battery performance and the atomic arrangement of the interfaces in both lithium and sodium-based solid-state batteries. They also discovered that minimizing the interface surface area and controlling the atomic alignment of the electrodes is key to understanding the nature of the interface instabilities and improving cell performance.

“This is a new paradigm for evaluating all of the major solid electrolytes available today,” said Cook. “In the past, we mostly only guessed which interface structures between the electrode and the solid electrolyte performed best. Now we can test this and find the best combination of materials and atomic orientations.”

As co-author of mechanics and engineering professor Elif Ertekin and her group have shown, with this level of control the researchers have obtained the information necessary to conduct atomic simulations that they believe will lead to even better electrolyte materials in the future the researchers said.

“We believe this will teach us a lot about how to study emerging solid electronics,” said Braun. “We’re not trying to invent new solid electrolytes. The material world is already doing a great job. Our methodology will allow others to accurately measure the interfacial properties of their new materials, which was otherwise very difficult to determine. “

Braun is director of the Materials Research Laboratory and a member of Mechanical and Engineering, Chemistry, Beckman Institute of Advanced Science and Technology, and the Holonyak Micro and Nanotechnology Laboratory in Illinois. Ertekin is the director of mechanical programs in the mechanical and engineering sectors and is also a member of the Materials Research Laboratory and the National Center for Supercomputing Applications.

The Department of Defense, the US Army, and the Army Corps of Engineers supported this study.

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