New Imaging Technique Enhances Lithium-Ion Battery Performance

A research team at the University of Oxford has developed an innovative imaging technique that allows for the precise visualization of polymer binders within lithium-ion battery electrodes. This advancement, detailed in a study published on February 17 in *Nature Communications*, focuses on the binders used in the negative electrodes (anodes) of lithium-ion batteries, which, despite comprising less than 5% of the electrode's weight, play a crucial role in determining the battery's mechanical strength, electrical and ionic conductivity, and overall lifespan.

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Polymer binders serve as adhesives that hold electrode materials together. Their distribution within the electrode significantly influences battery performance, yet their small quantity and lack of distinct visual signatures have historically made it challenging for scientists to analyze their placement. The new staining technique developed by the Oxford team employs traceable silver and bromine markers that can be attached to commonly used cellulose- and latex-based binders. This allows for the detection of these binders through energy-dispersive X-ray spectroscopy and energy-selective backscattered electron imaging, providing detailed maps of their distribution.

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The application of this imaging tool has revealed that even minor variations in binder distribution can substantially affect battery charging efficiency and longevity. In experimental tests, modifications to the slurry mixing and drying processes led to a reduction in internal ionic resistance by up to 40%, addressing a significant barrier to fast charging. The researchers were able to visualize extremely thin layers of carboxymethyl cellulose (CMC) binder, detecting layers as thin as 10 nanometers and observing how uniform coatings can become uneven during processing, potentially compromising battery performance.

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Lead author Dr. Stanislaw Zankowski emphasized the significance of this technique, stating, "This staining technique opens up an entirely new toolbox for understanding how modern binders behave during electrode manufacturing." Co-author Professor Patrick Grant noted the multidisciplinary nature of the research, highlighting its potential to drive advancements across various battery applications.

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The research, supported by the Faraday Institution's Nextrode project, has garnered considerable interest from industry stakeholders, including major battery manufacturers and electric vehicle producers. The findings are expected to facilitate improvements in battery manufacturing processes, ultimately leading to faster charging times and longer-lasting batteries.

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While the research presents promising advancements, some experts caution that the practical implementation of this technique in large-scale battery production may face challenges. Concerns include the scalability of the staining process and the potential costs associated with integrating new materials and methods into existing manufacturing workflows.

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• “Stanislaw Zankowski (Department of Materials, University of Oxford) said: "This staining technique opens up an entirely new toolbox for understanding how modern binders behave during electrode manufacturing.” — Dr. Stanislaw Zankowski, Lead Author

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