Transmission electron microscopes (TEMs) allow researchers at the forefront of energy technology to study next-generation battery materials down to the atom.
But new research from the Energy Storage Research Alliance (ESRA), University of Chicago Pritzker School of Molecular Engineering (UChicago PME), Argonne National Laboratory and Thermo Fisher Scientific discovered that the very act of microscoping damages both lithium and sodium battery samples more severely than previously thought, highlighting a need for a standard framework for how labs image these important materials.
“People use many different tools for characterizing samples and people have their own ways to run their experiments,” said co-first author Shuang Bai, a postdoctoral researcher at Argonne and research associate with UChicago PME. “We are trying to resolve what is the best way to store samples of reactive metals like lithium or sodium, transfer them from one piece of equipment to another and image them for the best data analysis.”
In a paper published today in Joule , the team brings the issues with electron microscopy into focus, showing how both transferring samples to electron microscopes and the microscopes themselves can damage reactive samples. The research also overturns a longstanding assumption in battery research, showing that samples of pure lithium do not need to be preserved at cryogenic temperatures to be imaged.
“With our inert gas transfer method, we confirm we can actually image high resolution pure lithium metal at room temperature,” Bai said.
This new transfer method coupled with recommendations for data reporting outlined in the paper promises better standards for studying battery samples safely, efficiently and with a minimum of damage.
"This is a milestone for both our lab and the research teams who are in search for better batteries to power the planet sustainably,” said ESRA Director and UChicago PME Liew Family Professor Shirley Meng, the lead corresponding author of the new work. “By adopting the guidelines we outline in this paper, labs across the world can ensure consistent, reliable data will inform every step of our R&D efforts, which accelerate science into impact in real world.”
'You use your way... I use my way’
Removing samples from the protective environment of a laboratory glovebox, even for a quick peek under a microscope, can contaminate them. As many smaller labs do not have high-powered electron microscopes, preparing and sending samples off for characterization increases the potential for contamination.
“There is no standard framework or format for different researchers to use," said co-first author Zhao Liu of Thermo Fisher Scientific. “It's more like you use your way to transfer sample image materials and I use my way, so even in exactly the same materials, people may get a very different result.”
In the new work, the team prepared multiple identical samples of common battery compounds, then prepared and imaged them with electron microscopes. The particle sizes were identical for each compound. The only differences were how they moved them to the microscope and how they imaged under the microscope.
They repeated this process with the most significant sodium- and lithium-based inorganic compounds commonly recognized in battery work. They plan to extend the work scope to organic compounds as well, Bai said.
‘Lithium metal doesn't need cryo’
The three most common methods for transporting samples are cryo-transfer holders, cooling holders with glovebag transfer, and inert gas transfer holders.
Cryo-transfer flash-freezes the sample with liquid nitrogen before transport. This preserves the sample, but frozen water inevitably forms while transferring the sample from glovebox to holder and holder to microscope. It’s similar to how beads of “sweat” form on a cool glass of water left outside in summer, and can damage lithium and sodium samples.
Cooling holders with glovebag transfer keep the sample in an inert atmosphere, but air exposure while inserting the sample into the TEM is unavoidable. The team found significant structural changes in lithium metal after just 15 seconds of exposure to air.
Previous researchers had long rejected the third method – transferring the sample at room temperature under an inert gas – for battery work under the assumptions that all lithium metal required cryo temperatures imaging. Instead, the team found, the problem was not with the lithium metal itself but with a layer that forms on the lithium’s surface after electrochemical deposition.
“Electrochemically deposited lithium has a solid electrolyte interface, or SEI. That SEI is very beam sensitive and that SEI – not the lithium itself – is why samples need cryo temperatures,” Bai said. “Lithium metal doesn't need cryo.”
A glovebag protected by O-ring and retractable tip keeps the sample under an inert argon gas until it is transferred to the vacuum conditions of the electron microscope.
“Lithium and sodium react with air or water very easily,” Bai said. “But with our transfer method, our sample is well-protected, either under the glovebag’s argon environment or in the vacuum of the TEM.”
'All kinds of different results’
The complications don’t stop once the sample is in the microscope. The team found TEM image may result in misleading conclusion if the electron beam dose is not carefully controlled, even under cryogenic temperature.
For example, lithium fluoride can be decomposed into lithium metal at high electron beam exposure, and lithium metal will react with the residue inside the column and be oxidized to lithium oxide eventually. Therefore, to avoid the variance caused by different equipment and operation preference, careful control and recording of electron beam imposed on samples is very critical.
Most papers don’t include this information, so there’s no way to know which past research presented damaged samples as accurate and comparable.
“When we did the literature review, we actually found very few people even reported dose,” Liu said. “That’s part of why a lot of people with similar samples are coming out with all kinds of different results.”
The new imaging guidelines and disclosure standards should help prevent these issues with future research, but the issue is increasingly pressing.
“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 higher challenge for proper characterization,” Liu said.
Funding for the study was provided by ESRA, an Energy Innovation Hub funded by the U.S. Department of Energy Office of Science. Comprising researchers across three national laboratories and eleven universities (including UChicago), ESRA aims to enable next-generation battery materials discovery.
Citation: “Guidelines for Correlative Imaging and Analysis of Reactive Alkali Metal Battery Materials,” Bai et al, Joule , March 2, 2026. DOI: 10.1016/j.joule.2025.102311
Joule
Guidelines for correlative imaging and analysis of reactive alkali metal battery materials
2-Mar-2026