Researchers working on next generation batteries rely heavily on electron microscopes to examine materials at extremely small scales. Transmission electron microscopy, commonly referred to as TEM, allows scientists to observe the atomic structure of battery materials and interfaces that determine how well a battery performs. However, new research led by the University of Chicago’s Pritzker School of Molecular Engineering suggests that the very process used to study these materials may unintentionally alter them. The findings highlight the need for more consistent methods when imaging highly reactive battery components.
Bai, S., Liu, Z., Cheng, D., Lu, B., Zaluzec, N. J., Raghavendran, G., Wang, S., Marchese, T. S., van Leer, B., Li, L., Jiang, L., Stokes, A., Cline, J. P., Osmundsen, R., Chen, M., Barends, P., Bright, A., Zhang, M., & Meng, Y. S. (2026). Guidelines for correlative imaging and analysis of reactive alkali metal battery materials. Joule, 102311. https://doi.org/10.1016/j.joule.2025.102311
The study, was led by Professor Shirley Meng and carried out through a collaboration involving the Energy Storage Research Alliance, the University of Chicago Pritzker School of Molecular Engineering, Argonne National Laboratory, and Thermo Fisher Scientific. Researchers involved in the work include Shuang Bai of Argonne National Laboratory and the University of Chicago, and Zhao Liu of Thermo Fisher Scientific. The team examined how different methods of preparing and transferring battery materials for microscopy can influence the structures that scientists ultimately observe.
Professor Shirley Meng from University of Chicago Pritzker School of Molecular Engineering stated,
“This will be getting more and more critical once you go to next-generation batteries like sodium, because the materials we use will be more and more air- and beam- sensitive, imposing a higher challenge for proper characterization.”
Lithium and sodium based materials are central to many emerging battery designs, particularly those intended for electric vehicles and large scale energy storage. These metals are highly reactive and can quickly degrade when exposed to air or moisture. To prevent contamination, samples are usually prepared in sealed laboratory gloveboxes that maintain an inert atmosphere. The challenge arises when those samples need to be moved to imaging equipment such as an electron microscope. Even short exposures during transfer can change the chemical or structural state of the material.
The research team found that sample handling procedures vary widely across laboratories, which can lead to inconsistent experimental results. Different groups often use their own methods for storing samples, transporting them to microscopes, and controlling imaging conditions. As a result, identical materials studied in different labs can appear to have different structures or properties simply because of variations in the imaging process.
To investigate the problem, the researchers prepared multiple identical samples of several lithium and sodium based battery compounds. Each sample had the same particle size and composition. The only variable was how the sample was transferred to the microscope and how imaging was performed. By isolating these variables, the team was able to determine how each step in the process could affect the final images.
One of the most widely used transfer approaches involves cryogenic cooling. In this method, samples are rapidly frozen using liquid nitrogen before being moved into the microscope. The idea is that freezing stabilizes the material and prevents reactions with air. However, the team found that this approach introduces its own complications. When a cryogenic sample is exposed to ambient air during transfer, moisture from the air can condense and freeze on the surface. This effect is similar to the condensation that forms on a cold glass of water and can damage the delicate surface structure of lithium and sodium samples.
Another commonly used method involves placing the sample inside a cooling holder and transferring it using a protective glovebag filled with inert gas. Although this approach reduces exposure to oxygen and moisture, the team found that even very brief air exposure during insertion into the microscope can alter lithium metal. In some experiments, structural changes were observed after only a few seconds of contact with air.
The researchers also tested a third method in which samples are transferred at room temperature within a sealed inert gas holder. This approach had often been dismissed in previous studies because many researchers believed lithium metal could only be safely imaged at cryogenic temperatures. The new experiments showed that this assumption may not be correct. According to the study, pure lithium metal can be imaged at room temperature if it is properly protected from air during transfer.
The confusion appears to stem from a thin layer that forms on lithium surfaces during battery operation. When lithium metal is deposited during electrochemical processes, it develops what is known as a solid electrolyte interphase, or SEI. This layer is extremely sensitive to the electron beam used in microscopy. Earlier studies interpreted damage to this layer as evidence that lithium itself required cryogenic imaging. The new findings suggest that the SEI is the component that is most sensitive, not the underlying lithium metal.
The researchers also examined what happens once samples are inside the electron microscope. They found that the intensity of the electron beam can influence the structure of certain compounds. For example, lithium fluoride particles exposed to a high electron beam dose can decompose and form lithium metal. That lithium metal can then react with residues inside the microscope column and form lithium oxide. These reactions can occur during imaging, which means the microscope itself may unintentionally change the material being studied.
One of the concerns highlighted by the study is that many published research papers do not report the electron beam dose used during imaging. Without this information, it becomes difficult to determine whether the observed structures represent the original material or artifacts introduced during the experiment. The authors suggest that more detailed reporting standards would allow researchers to compare results more reliably across different laboratories.
To address these challenges, the team proposes a set of guidelines for imaging reactive battery materials. The framework covers the entire workflow, including sample storage, preparation, transfer to the microscope, imaging conditions, and data reporting. By standardizing these steps, the researchers hope to reduce inconsistencies in the way lithium and sodium battery materials are studied.
The issue is likely to become more important as battery technologies evolve. Future battery designs are expected to incorporate materials that are even more sensitive to air and electron beams than those used in current lithium ion systems. Sodium based batteries and other emerging chemistries are already attracting attention for grid scale energy storage and other applications. Accurately characterizing these materials will be essential for improving performance and reliability.
The researchers describe their work as an effort to bring greater consistency to a critical experimental technique. Electron microscopy remains one of the most powerful tools available for studying battery materials at the atomic level. By clarifying how imaging conditions influence the results, the study provides a framework that could help laboratories produce more reliable data and better understand how next generation batteries function.
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).
