Led in part by James Kaduk, Research Professor of Chemistry at the Illinois Institute of Technology, an international research team has identified where lithium ions reside inside a newly developed solid-state electrolyte, a finding that helps explain why the material conducts ions efficiently even at low temperatures. The work contributes to a broader effort to design solid-state batteries that are safer and more reliable than conventional lithium-ion systems, particularly in applications where performance drops in cold environments.
Zhao, F., Zhang, S., Wang, S., Reid, J. W., Xia, W., Liu, J., King, G., Kaduk, J. A., Liang, J., Luo, J., Gao, Y., Yang, F., Zhao, Y., Li, W., Alahakoon, S. H., Guo, J., Huang, Y., Sham, T.-K., Mo, Y., & Sun, X. (2025). Anion sublattice design enables superionic conductivity in crystalline oxyhalides. Science, 390(6769), 199–204. https://doi.org/10.1126/science.adt9678
The study focuses on a crystalline material known as lithium tantalum oxychloride, or LTOC, which was recently reported to exhibit unusually high lithium-ion conductivity combined with low activation energy. These properties are central to the performance of solid-state batteries, where ions must move through a solid lattice rather than a liquid electrolyte. Understanding how lithium ions navigate that lattice is essential for explaining why certain materials outperform others.
James Kaduk, Research Professor of Chemistry at the Illinois Institute of Technology stated,
“Being able to complete the job just based on some pretty simple ideas, that’s very satisfying. Especially when you do the quantum mechanics calculations and see that they’re pretty happy with where these lithiums were, it gives you extra confidence.”
Lithium is well suited for energy storage because its ions are small and mobile, but those same qualities make them difficult to observe experimentally. In crystalline materials that contain heavier elements such as tantalum and chlorine, conventional X-ray diffraction struggles to detect lithium directly. X-rays interact with electrons, and lithium’s low electron count means its signal is often overwhelmed by surrounding atoms.
Rather than attempting to locate lithium ions directly, Kaduk approached the problem indirectly by first determining the positions of the heavier atoms in the structure. Once those atoms were mapped, the remaining open spaces within the crystal lattice could be analyzed to identify sites large enough to host lithium ions. By progressively narrowing these regions, the team identified a network of closely spaced sites that would allow lithium ions to move through the material by hopping from one position to the next.
This structural arrangement revealed a defining feature of LTOC. Rigid chains formed by tantalum, oxygen, and chlorine create open channels that run through the crystal. Lithium ions diffuse along these pathways with relatively low resistance, which helps explain the material’s high ionic conductivity. Because ion transport occurs efficiently along these channels, the material maintains strong performance even at temperatures where conventional electrolytes begin to fail.
To validate the proposed lithium positions, the researchers applied quantum mechanical modeling based on density functional theory. These calculations showed that the refined structure remained stable after optimization, providing additional confidence that the identified lithium sites accurately represent how the material behaves at the atomic level.
The findings help clarify why LTOC stands out among emerging solid-state electrolytes. Many materials exhibit good conductivity only under narrow temperature ranges or require complex processing to achieve acceptable performance. In contrast, the structural features revealed in this study suggest that ion transport in LTOC is an inherent consequence of its crystal architecture rather than a fragile or incidental property.
While the work represents only one component of a larger international collaboration, identifying the lithium substructure was critical to connecting measured performance with atomic-scale mechanisms. For battery researchers, this kind of insight is essential for moving beyond trial-and-error materials discovery toward more predictive design strategies.
For engineers working on next-generation batteries, the work underscores a central lesson: improving macroscopic performance often depends on resolving microscopic questions that are easy to overlook, such as where the smallest atoms reside and how they move through a solid.
Adrian graduated with a Masters Degree (1st Class Honours) in Chemical Engineering from Chester University along with Harris. His master’s research aimed to develop a standardadised clean water oxygenation transfer procedure to test bubble diffusers that are currently used in the wastewater industry commercial market. He has also undergone placments in both US and China primarely focused within the R&D department and is an associate member of the Institute of Chemical Engineers (IChemE).
