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To design better rechargeable ion batteries, engineers and chemists at the University of Illinois Urbana-Champaign collaborated to combine a powerful new electron microscopy technique and data mining to visually pinpoint areas of weathering. chemical and physical in ion batteries.

From left to right, professors Paul Braun, Hong Yang, Jian-Min Zuo, Qian Chen and postdoctoral researcher Wenxiang Chen.

Photo by Fred Zwicky

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A study by materials science and engineering professors Qian Chen and Jian-Min Zuo is the first to map altered domains inside nanoscale rechargeable ion batteries – a 10-fold increase or more resolution compared to current X-ray and optical methods.

The results are published in the journal Nature Materials.

The team said that previous efforts to understand the functioning and failure mechanisms of battery materials have mainly focused on the chemical effect of recharge cycles, namely changes in the chemical composition of battery electrodes. .

A new electron microscopy technique, called four-dimensional scanning transmission electron microscopy, allows the team to use a highly focused probe to collect images of the inner workings of batteries.

“During the operation of rechargeable ion batteries, ions diffuse in and out of the electrodes, causing mechanical stress and sometimes cracking,” said postdoctoral researcher and first author Wenxiang Chen. “Using the new method of electron microscopy, we can capture for the first time the nanoscale domains caused by stresses inside battery materials.”

Qian Chen said these types of microstructural heterogeneity transformations have been widely studied in ceramics and metallurgy, but have not been used in energy storage materials until this study.

“The 4D-STEM method is essential for mapping otherwise inaccessible variations in crystallinity and domain orientations within materials,” Zuo said.

The team compared their 4D-STEM observations to computer modeling led by mechanical science and engineering professor Elif Ertekin to spot these variations.

“Combined data mining and 4D-STEM data show a pattern of nucleation, growth, and coalescence processes inside batteries as nanoscale domains grow,” said said Qian Chen. “These models were further verified using X-ray diffraction data collected by materials science and engineering professor and study co-author Daniel Shoemaker.”

Qian Chen plans to take this research further by creating movies of this process – something his lab is well known for.

“The impact of this research may go beyond the multivalent ion battery system studied here,” said Paul Braun, professor of materials science and engineering, director of the Materials Research Laboratory and co-author. of the study. “The concept, principles and enabling characterization framework apply to electrodes in a variety of Li-ion and post-Li-ion batteries and other electrochemical systems, including fuel cells, synaptic transistors and electrochromes.”

Illinois researchers Andrew Gewirth, of chemistry; Hong Yang, of chemical and biomolecular engineering; and Shell researcher Ryan Stephens also participated in this study.

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