Improving the Performance of Frozen 'Jeongoche Battery'

Crystal structure of sulfide solid electrolyte (Li6.5P0.5Ge0.5S5I) observed by conventional transmission electron microscopy (TEM) and cryogenic transmission electron microscopy

[Asia Economy Reporter Junho Hwang] Domestic researchers have developed a technology that can improve the performance of all-solid-state batteries by utilizing a technique that rapidly freezes materials at minus 170°C to observe high-resolution images. In addition to all-solid-state batteries, this technology can be applied in various fields such as lithium-ion batteries, and is expected to be used as a research technology for developing safe batteries.

Ulsan National Institute of Science and Technology (UNIST) announced on the 14th the joint research results of Professor Hyunwook Lee’s team from the Department of Energy and Chemical Engineering and Professor Yunseok Jeong’s team from Hanyang University’s Department of Energy Engineering.

Sample Preparation Process for Cryo-Transmission Electron Microscopy Analysis under Non-Vacuum Conditions

The research team succeeded in analyzing the structure of sulfide solid electrolytes at the atomic level. The team developed a new method to rapidly freeze the material and observe it while blocking contact with air.

Sulfide compounds are highly likely to be used as electrolytes in next-generation batteries called "solid electrolyte batteries." To use them in batteries, research is needed to increase ion conductivity in the solid state. However, these materials are vulnerable to electron beams in conventional electron microscopes. Observing the internal structure for explosion risk or performance improvement was only possible indirectly.

The research team introduced cryogenic transmission electron microscopy (cryo-TEM) analysis, which freezes biomolecules without damage to obtain high-resolution images, and observed sulfide compounds composed of various components. As a result, they confirmed the crystal structure (hexagonal shape) of the material with the highest ion conductivity within the sulfide compound.

Schematic Diagram of Crystal Structure Formation According to Heat Treatment Temperature of Sulfide Solid Electrolyte

Professor Hyunwook Lee said, "The air-isolated cryogenic transmission electron microscopy analysis method is a technique that blocks contact with air and prevents damage to materials, so it will be actively applied to observe other components of highly reactive lithium-ion batteries." He added, "This will serve as a bridgehead for the secondary battery industry nearby and contribute to the development of the bio and materials science industries in the long term."

Meanwhile, all-solid-state batteries replace the electrolyte between the battery’s cathode and anode from liquid to solid. They have no risk of explosion or fire and can realize high-capacity batteries. The research results were introduced on the 5th in the academic journal Nano Letters.

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