New microscope offers new understanding on battery interphase

Xiaonan Shan observes Guangxia Feng working on the operando reflection interference microscope inside a glove box. Photo: University of Houston.

Lithium-ion batteries have transformed everyday lives – being used for everything from smartphones to electric vehicles to energy storage. As more portable electronic devices, electric vehicles and large-scale grid implementations come online, the demand for higher-energy-density batteries that are safe and affordable continues to grow.

Now, a research team at the University of Houston (UH), in collaboration with researchers from the Pacific Northwest National Laboratory and the US Army Research Laboratory, has developed an operando reflection interference microscope (RIM) that provides a better understanding of how batteries work. This understanding could have significant implications for the next generation of batteries.

“We have achieved real-time visualization of solid electrolyte interphase (SEI) dynamics for the first time,” said Xiaonan Shan, assistant professor of electrical and computer engineering at UH’s Cullen College of Engineering and corresponding author of a paper on this work in Nature Nanotechnology. “This provides key insight into the rational design of interphases, a battery component that has been the least understood and most challenging barrier to developing electrolytes for future batteries.”

The highly sensitive microscope allows researchers to study the SEI layer, which is an extremely thin and fragile layer on the surface of battery electrodes that determines battery performance. Its chemical composition and morphology are continuously changing – making it a challenge to study.

“A dynamic, non-invasive and high sensitivity operando imaging tool is required to understand the formation and evolution of SEI. Such a technique, capable of direct probing SEI, has been rare and highly desirable,” said Yan Yao, professor of electrical and computer engineering at UH and a co-corresponding author who has worked with Shan on this project for the past four years.

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

The research team applied the principle of interference reflection microscopy to this project, in which the light beam – centered at 600nm with a spectrum width of about 10nm – was directed towards the electrodes and SEI layers, and reflected. The collected optical intensity contains interference signals between the different layers, which carry important information about the evolution process of SEI and allow the researchers to observe the entire reaction process.

“The RIM is very sensitive to surface variations, which enables us to monitor the same location with large-scale high spatial and temporal resolution,” said UH graduate student Guangxia Feng, who performed much of the experimental work on the project.

The researchers note that most battery researchers currently study the SEI using cryo-electron microscopes, which can only take one picture at a certain time and cannot continuously track changes at the same location.

“I wanted to approach energy research from a different angle by adapting and developing new characterization and imaging methods which provide new information to understand the reaction mechanism in energy-conversion processes,” said Shan, who specializes in developing imaging techniques and spectrometry techniques to study electrochemical reactions in energy storage and conversions. This new imaging technique could also be applied to other state-of-the-art energy-storage systems.

Feng, who earned a PhD in electrical engineering from UH in 2022, plans to pursue further research in the growing field of battery technology. “To realize the next generation of batteries, it is essential to understand the reaction mechanisms and novel materials,” she said, adding that developing higher-energy batteries also benefits the environment. “I have always wanted to be a scientist because they can make great things happen for people and change the world for the better.”

This story is adapted from material from the University of Houston, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.