Lithium-ion batteries have changed everyday life — nearly everyone owns a smartphone, we see more electric cars on the road, and they keep generators running in emergencies. As more and more portable electronic devices, electric vehicles and large-scale power grids come online, the demand for safe and affordable batteries with high energy density continues to grow.

Now, a team of researchers at the University of Houston, in collaboration with researchers at Pacific Northwest National Laboratory and the U.S. Army Research Laboratory, have developed an in situ reflection interferometric microscope (RIM) to better understand how batteries work, which has the potential to Significant implications for next-generation batteries.

“For the first time, we have achieved real-time visualization of solid-electrolyte interface (SEI) dynamics,” said Xiaonan Shan, assistant professor of electrical and computer engineering at UH’s Cullen School of Engineering and corresponding author of a study published in Nature. nanotechnology. “This provides key insights into the rational design of the interphase, a battery component that is the least understood and most challenging obstacle to developing electrolytes for future batteries.”

High-sensitivity microscopy allowed the researchers to study the SEI layer, the extremely thin and fragile layer on the surface of a battery electrode that determines the battery’s performance. Its chemical composition and form are constantly changing—making research challenging.

“Understanding SEI formation and evolution requires a dynamic, non-invasive and highly sensitive in situ imaging tool. Such a technique capable of directly probing SEI is rare and highly desirable,” said Yan Yao, Hugh Roy and Lillie Cranz . Cullen Distinguished Professor of Electrical and Computer Engineering and co-corresponding author, has worked with Shan on this project for the past four years.

“We have now shown that RIM is the first of its kind to provide important insights into the working mechanism of the SEI layer and help design better high-performance batteries,” said Yao, who is also a principal investigator at the Texas Center for Superconductivity . at the University of Houston.

The researchers say the new technology platform allows them to image the dynamic activity of the battery at the mesoscopic scale in real time, which is difficult but important to do. With this technology, they have the ability to analyze the changes in particle chemical composition and current density in real time, study the charging and discharging process of batteries, and image the electrochemical reactions inside individual battery particles, which is of great help to better understand the charging mechanism of batteries. And optimizing battery performance is helpful.

how it works

In this project, the research team applied the principle of interferometric reflection microscopy, in which a light beam – centered at 600 nanometers with a spectral width of about 10 nanometers – is directed towards the electrodes and the SEI layer and reflected. The collected light intensity contains interference signals between different layers, carrying important information about the evolution process of SEI, allowing researchers to observe the entire reaction process.

“RIM is very sensitive to surface changes, which allows us to monitor the same location at large scales with high spatial and temporal resolution,” said UH graduate student Guangxia Feng, who conducted much of the experimental work on the project.

The researchers point out that most battery researchers currently use cryo-electron microscopes, which can only take a picture at a specific time and cannot continuously track changes in the same location.

“I want to approach energy research from a different perspective by adapting and developing new characterization and imaging methods that provide new information to understand reaction mechanisms during energy conversion,” said Shan, who specializes in developing imaging and spectroscopy techniques to study reactions in electrochemical energy storage and conversion. This new imaging technique could also be applied to other state-of-the-art energy storage systems.

New microscope developed for designing better, high-performance batteries

Feng received his Ph.D. Earn a Ph.D. in Electrical Engineering from UH in 2022 with plans to pursue further research in the evolving field of battery technology.

“To realize the next generation of batteries, understanding the reaction mechanism and novel materials are crucial,” she said, adding that developing higher energy batteries would also benefit the environment. “I’ve always wanted to be a scientist because they can make great things happen to people and make the world a better place.”