Tohoku University researchers used MRI to observe metal ion dissolution in lithium-ion batteries, providing real-time insights into battery degradation.
Many modern devices depend on rechargeable batteries for convenience and efficiency. Among them, lithium-ion batteries are widely used due to their affordability and high operating voltage, making them well-suited for electronic devices and electric vehicles.
However, these batteries experience performance degradation over time, and safety concerns increase as they age.
One key factor contributing to this decline is the dissolution of metal ions from the cathode into the electrolyte. Studying this process has been challenging because the dissolved amounts are extremely small. To effectively address the issue, researchers must first determine where, when, and how much dissolution occurs within the battery.
Researchers at Tohoku University have been working on a method to detect and investigate the dissolution of the metal ion in the cathode. Using nuclear magnetic resonance imaging (MRI), they were able to directly observe the dissolution in real time.
The results of their research were published in Communications Materials on February 13, 2025.
MRI Technology Sheds Light on Metal Ion Dissolution
According to Nithya Hellar, a researcher at the Institute of Multidisciplinary Research for Advanced Materials (IMRAM) at Tohoku University, “the results of the present study show that the dissolution of a very small amount of manganese (Mn) can be detected with high sensitivity by MRI and visualized in real-time, which can greatly accelerate the speed of research.”
An MRI is a medical imaging technology that uses magnetic fields and radio waves to produce imaging scans. To enhance the visibility of areas of interest in an MRI image, contrast agents such as gadolinium are used. Gadolinium is paramagnetic, and it can alter the magnetic properties of targeted areas, thereby increasing their visibility to the MRI.
The Tohoku University group was able to use this principle of MRI as the Mn dissoluted from the cathode is paramagnetic. Specifically, they looked at the dissolution of Mn2+ from spinel-type LiMn2O4 cathode, in a commercial battery electrolyte LiPF6 EC:DMC. So, if dissolution is occurring it would show up as an increase in signal intensity in the MRI images, and that is exactly what they saw. Using the MRI gave them the ability to directly observe the dissolution as it occurred in real time.
Implications for Battery Design and Future Research
The researchers used this technique to investigate whether an alternative electrolyte system could suppress the dissolution. Using the MRI, they could observe the dissolution of the metal ion. It also follows that if there was no increase in signal, that dissolution was not occurring.
They tested the electrolyte system LiTFSI MCP developed by researchers from MEET (Munster Electrochemical Energy Technology) Battery Research Center, University of Munster, Germany, which they believed would suppress the dissolution of the metal ion. There was no significant increase in signal intensity on the MRI. From this, they concluded that there was no dissolution occurring.
Using this testing method gives researchers invaluable help in “exploring the metal ion dissolution in any electrochemical systems under different electrochemical conditions, such as changing the electrolyte solution, salt, electrodes, and additives. This identification method may help design lithium battery materials and improve their performance,” said Junichi Kawamura, Emeritus Professor at Tohoku University.
Looking to the future, there is enormous promise in how this technique can increase the ability of researchers to understand how reactions within these batteries work and how to test alternate battery technology. “We believe the method developed here can answer the long-time unanswered question of when, where, and how the metal ion dissolution occurs in the lithium-ion battery electrode and can be extended to other electrochemical systems,” said Hellar.
Reference: “Direct observation of Mn-ion dissolution from LiMn2O4 lithium battery cathode to electrolyte” by Nithya Hellar, Yoshiki Iwai, Masato Ohzu, Sebastian Brox, Arunkumar Dorai, Reiji Takekawa, Naoaki Kuwata, Junichi Kawamura and Martin Winter, 13 February 2025, Communications Materials.
DOI: 10.1038/s43246-025-00733-2
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