Nov 3 2026
Understanding how ions move through solid materials is key to advancing technologies such as batteries, fuel cells and sensors. A team of scientists led by the U.S. Department of Energy's (DOE) Argonne National Laboratory has demonstrated a cutting-edge method for gauging the activity of ions, revealing a new level of detail about how they move and interact.
The team tested the technique, which they have called 4D quasielastic neutron scattering (4D-QENS), at the Spallation Neutron Source, a DOE Office of Science user facility at DOE's Oak Ridge National Laboratory (ORNL). The results show that 4D-QENS provides critical insights that will help improve the theoretical models needed to design next-generation solid-state batteries and related technologies.
Some materials allow charged atoms or molecules - called ions - to move quickly. This property makes them suitable as electrolytes in solid-state batteries, which could store more energy and offer greater safety compared to conventional batteries - most of which use liquid electrolytes to move ions during charging and discharging.
But a clearer understanding of the mechanisms underlying ionic conduction would help scientists optimize solid-state battery performance. Historically, researchers generally believed that ionic motion in solids was essentially an independent, diffusion-based process. Researchers are now exploring the idea that correlated motion - movement driven by interactions between ions - is key to ultrafast conductivity. However, direct experimental observation remains elusive.
Ionic motion is best studied by quasielastic neutron scattering (QENS), which involves directing neutrons at a material sample and measuring the changes in direction and energy as they scatter off the sample. Those changes reveal movements of atoms or molecules within the material.
Such studies have provided important insight into the independent, diffusion-based dispersion of ions. The 4D-QENS technique involves rotating a single-crystal sample as it is exposed to the neutrons. This results in data that allows the researchers to generate a complete picture not only of how ions are moving but also of interactions that drive correlated motion.
"The idea of doing these sample rotations has been around at pulsed neutron sources for about 15 years, but it has not been applied to QENS before," said Raymond Osborn, senior physicist at Argonne and lead author of a study unveiling this new method. "With 4D-QENS, we show new effects that we would never have seen without such large, contiguous volumes of data."
To test the method's potential, the researchers performed 4D-QENS on single-crystal samples of strontium chloride, a salt that becomes a fast-ion conductor at temperatures above 1,200 degrees Fahrenheit. Though strontium chloride is not a candidate for future applications, its well-studied properties made it an ideal model crystal on which to test the technique.
The study delivered a refined understanding of ion movement from one site to another within the crystal lattice structure - hopping - that agreed with previous studies. But it also revealed direct evidence of correlated motion among ions that can either facilitate movement through the material or lead to traffic jams that would be detrimental in a battery. A deeper understanding of such correlated motion through 4D-QENS is crucial to help improve solid-state electrolytes.
The unique properties of neutrons, which are electrically neutral with a mass similar to the atoms and ions, are key for this technique. Minute changes in neutron velocity, accompanied by significant changes in direction, allow researchers to chart ion movements in considerable detail. That led researchers to the Spallation Neutron Source at ORNL, the world's most powerful pulsed neutron source.
The volume of data from such measurements further increased with the recent power upgrade of the Spallation Neutron Source, along with ever more powerful DOE computing resources such as the Argonne Leadership Computing Facility (ALCF), also a DOE Office of Science user facility.
"The questions that we were able to ask about ion conductivity even a few years ago were much more limited in scope. Now we're measuring 3D volumes plus energy transfer, making it 4D," said Stephan Rosenkranz, Argonne Distinguished Fellow and group leader in the Materials Science division. "These comprehensive datasets are allowing new modes of data analysis. Those modes demand computing resources that can match the quality of the data."
This type of analysis would be appropriate in future applications of 4D-QENS to more complex materials that are directly relevant to solid-state electrolytes and other energy technologies, the researchers said.
The work, supported by DOE's Office of Basic Energy Sciences, is detailed in the journal PRX Energy. In addition to Osborn and Rosenkranz, Argonne authors include Jared Coles, Omar Chmaissem, Matthew Krogstad, Daniel Pajerowski, Feng Ye, Duck Young Chung and Mercouri Kanatzidis. Along with Argonne and ORNL, the team's affiliations include Northern Illinois University and Northwestern University.
Christina Nunez is a freelance writer and editor who covers science, technology, and innovation at Argonne and other research facilities under the U.S. Department of Energy. Her work also appears at National Geographic and other publications. She has been writing for Argonne since 2018.
The Argonne Leadership Computing Facility provides supercomputing and AI capabilities to the scientific and engineering community to advance fundamental discovery and understanding in a broad range of disciplines. Supported by the U.S. Department of Energy's (DOE's) Office of Science, Advanced Scientific Computing Research (ASCR) program, the ALCF is one of two DOE Leadership Computing Facilities in the nation dedicated to open science.
Argonne National Laboratory seeks solutions to pressing national problems in science and technology by conducting leading-edge basic and applied research in virtually every scientific discipline. Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy's Office of Science.