A team of researchers at the University of Texas at Dallas and their colleagues have made a discovery that could aid in the development of lithium-ion batteries that are safer and more powerful.

The discovery is an emerging technology using solid rather than liquid electrolytes, the materials that make it possible for ions to move through the device to generate power, UTD said.

‘Space charge layer’

The team discovered that mixing small particles between two solid electrolytes can generate an effect called a “space charge layer,” an accumulation of electric charge at the interface between the two materials.

“Solid-state battery technology is part of our next-gen battery chemistries research at the BEACONS center, and it is expected to enable advanced battery systems to improve the performance of drones for defense applications,” said Kyeongjae Cho, professor of materials science and engineering, director of BEACONS, and a co-corresponding author of the study.

UTD said the finding could aid the development of batteries with solid electrolytes, called solid-state batteries, for applications including mobile devices and electric vehicles. The researchers published their study in ACS Energy Letters, where it is featured on the cover of the March issue.

How it works

When the separate solid electrolyte materials make physical contact, a layer forms at their boundary where charged particles, or ions, accumulate because of differences in each material’s chemical potential, Laisuo Su, assistant professor of materials science and engineering in the Erik Jonsson School of Engineering and Computer Science, and a co-corresponding author of the study, said in a statement.

Su said the layer helps create pathways that make it easier for ions to move across the interface.

“Imagine mixing two ingredients in a recipe and unexpectedly getting a result that is better than either ingredient alone,” Su said. “This effect boosted the movement of ions beyond what either material could achieve by itself.”

“This discovery suggests a new way to design better solid electrolytes by carefully choosing materials that interact in a way that enhances ionic movement, potentially leading to better-performing solid-state batteries,” Su added.

UTD said the research is a project of its Batteries and Energy to Advance Commercialization and National Security (BEACONS) initiative. The initiative launched in 2023 with $30 million from the U.S. Department of Defense to develop and commercialize new battery technology and manufacturing processes, enhance the domestic availability of critical raw materials, and train high-quality workers for industry.

Showing promise

UTD said that most lithium-ion batteries currently used in consumer products contain liquid electrolytes, which are flammable and can present safety issues.

Su said that although conventional lithium-ion batteries are reaching the theoretical limit of how much energy they can store, solid-state batteries show promise for generating and storing more than twice as much power as batteries with liquid electrolytes and are safer because they are not flammable.

Developing solid-state batteries faces challenges, however, because it is more difficult to move ions through solid materials, UTD said. The university’s researchers studied the performance of the solid-state electrolyte compounds lithium zirconium chloride and lithium yttrium chloride, and they proposed a theory to explain why mixing the materials increased ionic activity.

“The interface formed unique channels for ion transport,” Su said.

UTD said that Su and the other researchers plan to continue to study how the composition and structure of the interface leads to greater ionic conductivity.

The UTD team collaborated with two researchers from Texas Tech University: Zeeshan Ahmad, assistant professor of mechanical engineering and a co-corresponding author; and Md Salman Rabbi Limon, a doctoral candidate in mechanical engineering.

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