Wenxiang Chen in the laboratory. Photo: Fred Zwicky.
Wenxiang Chen in the laboratory. Photo: Fred Zwicky.

With the aim of designing better rechargeable ion batteries, engineers and chemists from the University of Illinois at Urbana-Champaign combined a powerful new electron microscopy technique with data mining to visually pinpoint areas of chemical and physical alteration within ion batteries.

This study, led by materials science and engineering professors Qian Chen and Jian-Min Zuo, is the first to map out altered domains inside rechargeable ion batteries at the nanoscale – a 10-fold or more increase in resolution over current X-ray and optical methods. The researchers report their findings in a paper in Nature Materials.

Previous efforts to understand the workings and failure mechanisms of battery materials have primarily focused on the chemical effect of charging and recharging, especially on the chemical composition of the battery electrodes. With this new electron microscopy technique, called four-dimensional scanning transmission electron microscopy (4D-STEM), the researchers were able 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 strain and sometimes cracking failures,” explained Wenxiang Chen, a postdoctoral researcher and first author of the paper. “Using the new electron microscopy method, we can capture the strain-caused nanoscale domains inside battery materials for the first time.”

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

“The 4D-STEM method is critical to map otherwise inaccessible variations of crystallinity and domain orientations inside the materials,” said Zuo.

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

“The combined data mining and 4D-STEM data show a pattern of nucleation, growth and coalescence process inside the batteries as the strained nanoscale domains develop,” said Qian Chen. “These patterns 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 further this research by creating movies of this process – something for which her lab is well known.

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

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