Tracking Hidden Imperfections Inside Operating Lithium-ion Batteries

Penetrating x-rays can image defects and phase changes during battery charging and discharging.

X-rays can characterize the motion of atomic-scale defects (for example, dislocations) relative to the morphology of a nanoparticle in the electrode of an operating lithium-ion battery. The dislocations are extra planes of atoms inserted into the atomic lattice. — Image courtesy of *Science*. Reprinted with permission from AAAS.

The Science

After rapid charging and discharging of a lithium-ion battery, defects of incomplete atomic planes, called dislocations, developed in the tiny particles that make up the electrode. The defects were revealed with a new x-ray imaging technique that coupled high penetration x-ray spectroscopy and image reconstruction. The dislocations moved as the battery charges and discharges, and structural changes occurred at those locations upon further charging.

The Impact

With penetrating x-rays, the ability to image dislocations and structural transformations in operating nanoparticle-based electrodes gives battery researchers an important tool to understand electrode degradation and enables effective engineering of more reliable electrodes, and batteries.

Summary

Researchers, working to limit battery degradation and improve performance lifetimes, need a firm understanding of the damage mechanisms in real configurations and under operating conditions. Coherent x-ray imaging at a synchrotron x-ray light source can penetrate into and sort through the complex battery architecture that often includes liquid or polymer electrolytes and composite electrodes composed of metal and ceramic nanoparticles. A new technique that uses high- energy x-rays and lensless image reconstruction is sufficiently sensitive to image dislocation defects and track their motion in a single electrode nanoparticle during battery charging and discharging. Scientists used the technique to locate a dislocation and subsequent structural reorganization of the atoms relative to the imaged nanoparticle morphology. Dislocations are a key type of defect in the mechanical behavior of the electrode. The ability of this technique to characterize dislocations could provide additional insights on how to improve the plasticity and increase the toughness of the electrode, which may lead to improved battery lifetimes.

Contact

Oleg Shpyrko
University of California, San Diego
oshpyrko@physics.ucsd.edu

Funding

This work was supported by the DOE Office of Science, Office of Basic Energy Sciences (x-ray scattering), the Northeast Center for Chemical Energy Storage (battery expertise), Energy Frontier Research Centers (EFRC) Program, the Advanced Photon Source (synchrotron x-rays), a DOE Office of Science User Facility; University of California, San Diego; and the Volkswagen Foundation.

Publications

A. Ulvestad, A. Singer, J. N. Clark, H. M. Cho, J. W. Kim, R. Harder, J. Maser, Y. S. Meng, and O. G. Shpyrko, “Topological defect dynamics in operando battery nanoparticles.” Science 348, 1344 (2015). [DOI: 10.1126/science.aaa1313]