Lithium-ion batteries power everything from smartphones to electric cars, yet scientists are still learning how the tiny parts inside them affect performance.
Researchers at the University of Oxford have now developed a new way to see one of the most important — and previously invisible — components inside battery electrodes.
Their discovery could help manufacturers build batteries that charge faster and last longer.
The study focused on polymer binders, a type of “glue” used in the negative electrode, or anode, of lithium-ion batteries.
These binders hold the active materials together and help maintain the electrode’s structure during repeated charging and discharging.
Although they make up less than five percent of the electrode’s weight, they play a crucial role in how well a battery works, influencing stability, conductivity, and lifespan.
Despite their importance, binders have been extremely difficult to study because they blend into the surrounding materials and lack distinctive features.
Scientists could not easily see where the binder was located or how evenly it was spread. Without this information, improving battery design has been challenging, since the placement of binder affects how electricity and lithium ions move through the electrode.
To solve this problem, the Oxford team created a new staining technique that makes the binders visible under powerful microscopes.
They tagged the binders with tiny amounts of silver and bromine, elements that can be detected using advanced imaging methods. When examined with an electron microscope, these tagged binders produce signals that reveal their location and structure in remarkable detail.
Using this technique, researchers could see the binder distribution throughout the electrode for the first time, from large areas down to nanoscale layers only billionths of a meter thick. The method worked not only on traditional graphite-based electrodes but also on newer materials such as silicon, which are being explored for next-generation batteries.
The images revealed that even small changes in how binders are distributed can have a major impact on battery performance. By adjusting how the electrode mixture was prepared and dried during manufacturing, the team was able to reduce internal resistance by up to 40 percent in test samples. Lower resistance means electricity and ions can move more easily, which is essential for faster charging.
The researchers also discovered extremely thin layers of a common binder material called carboxymethyl cellulose coating graphite particles. These layers, only about 10 nanometers thick, were shown to break apart into uneven patches during processing. Such fragmentation may weaken the electrode and reduce battery life, offering a new explanation for performance losses that had puzzled scientists.
This breakthrough imaging method provides a powerful new tool for understanding what happens inside batteries as they are made and used. By revealing details that were previously hidden, it could help engineers design electrodes that are more efficient and durable.
As demand for better batteries continues to grow, advances like this could lead to devices that charge more quickly, run longer, and perform more reliably. Sometimes, improving technology depends not on inventing entirely new materials, but on finally seeing the tiny ones that were there all along.
Source: University of Oxford.
