Researchers at the University of Oxford have developed a powerful new method to visualise an essential lithium-ion battery electrode component that had been extremely difficult to trace before. The discovery, published today (17 February) in Nature Communications , could lead to increased manufacturing efficiency of battery electrodes and ultimately help improve the charging rate and lifetime of Li-ion batteries.
The study focused on modern polymer binders used in negative lithium-ion battery electrodes (anodes). These binders play a critical role in holding battery electrodes together, affecting their mechanical stability, electrical and ionic conductivity, and cycle life. However, because they make up less than 5% of the electrode by weight and lack distinct features, their distribution in anodes has been nearly impossible to image or control. This has hindered efforts to improve battery performance, as binder placement directly influences electrode conductivity, stability, and long-term durability.
To address this, the researchers developed a novel, patent-pending staining technique that uses traceable markers of silver and bromine to tag commercial cellulose- and latex-derived binders in graphite- and silicon-based anodes. These tags make the binders visible by producing characteristic X-rays (measured with energy-dispersive X-ray spectroscopy) or by reflecting high-energy electrons from the sample surface (measured with energy-selective backscattered electron imaging). When detected using an electron microscope, these methods give precise information about the distribution of elements and the surface topography.
Lead author Dr 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. For the first time, we can accurately see the distribution of these binders not only generally (i.e., their thickness throughout the electrode), but also locally, as nanoscale binder layers and clusters, and correlate them with anode performance."
Importantly, the imaging method works not only on graphite-based electrodes but also on more advanced materials such as silicon or SiOx, making it applicable across next-generation battery designs.
Using the method, the team found that small changes in how binders are distributed could dramatically affect how efficiently a battery charges and how long it lasts. For example, by adjusting slurry mixing and drying protocols, the researchers reduced the internal ionic resistance of test electrodes by up to 40% - a key bottleneck in fast charging.
The study also captured elusive nanoscopic layers of carboxymethyl cellulose (CMC) binder that coats graphite particle surfaces. The imaging provided unparalleled detection of 10 nm-thick CMC layers, resolving feature sizes across four orders of magnitude in single images. This revealed how the thin CMC layers fragment from an initially complete coating into broken, inhomogeneous patches during electrode processing, potentially impairing battery performance and stability.
Co-author Professor Patrick Grant (Department of Materials, University of Oxford) said: "This multidisciplinary effort-spanning chemistry, electron microscopy, electrochemical testing, and modelling- has resulted in an innovative imaging approach that will help us to understand key surface processes that affect battery longevity and performance. This will drive forward advancements across a wide range of battery applications."
The research, funded through the Faraday Institution's Nextrode project , has already attracted strong industrial interest, including from major battery and electric vehicle manufacturers.
