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Analytical Chemistry

Imaging lithium dendrite growth via cryo-electron microscopy

Method preserves and reveals structure and composition details obscured by standard microscopy methods

by Mitch Jacoby
November 6, 2017 | A version of this story appeared in Volume 95, Issue 44

This pair of images shows that microscopy details lost by using standard TEM methods are preserved by the cryo-TEM method.
Credit: Science
Standard microscopy methods corrode lithium dendrites and cause substantial electron-beam damage (left). In contrast, cryo-TEM preserves dendrites’ native structures and composition (right).

An analytical technique famous for imaging biological structures in exquisite detail can do a heck of a job when adapted to energy storage materials, according to a study. A research team led by Stanford University materials scientists Yuzhang Li, Yanbin Li, and Yi Cui applied cryo-transmission electron microscopy (cryo-TEM), the subject of the 2017 Nobel Prize in Chemistry, to study formation of needlelike lithium dendrites inside lithium-ion batteries (Science 2017, DOI: 10.1126/science.aam6014). Deposition of lithium during charging cycles can lead to dendrites that grow large enough to pierce a battery’s insulating separator and make contact with both of its electrodes. That process short-circuits the battery, causing it to fail and occasionally burst into flames. Standard methods for loading a specimen into a microscope for TEM analysis expose the sample to air. In the case of room-temperature lithium dendrites, that process causes corrosion, which irreversibly changes their structure and composition. To preserve the dendrites, in an effort to understand and ultimately prevent their growth, the Stanford team assembled coin-type lithium-ion batteries in an inert atmosphere, applied electrical current to cause dendrite growth, and then used customized techniques and equipment to do TEM analysis on pristine, cryogenically cooled samples. The study shows that dendrites grow along select lattice directions as faceted, single-crystalline nanowires and that the nanostructure details depend on the type of liquid electrolyte used in the battery.


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