This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: A signal that appears to show ions moving inside a battery may, in fact, be an illusion caused by an uneven surface. A KAIST research team has identified the origin of this type of artifact, which can lead researchers to misinterpret what is happening inside a battery, and has developed a method to reduce it.
The findings are expected to enable more accurate analysis of ion movement and improve the reliability of next-generation battery-material development, including that of solid-state and sodium-ion batteries. A research team led by professor Seungbum Hong from the Department of Materials Science and Engineering, in collaboration with the research groups of professor Jong Min Yuk from the same department and professor Nam-Soon Choi from the Department of Chemical and Biomolecular Engineering, has identified the cause of a measurement artifact in nanoscale battery analysis that can be mistaken for actual ion transport. The team also proposed a method for effectively reducing this artifact.
The paper is published in the journal Small Methods. During charging and discharging, lithium or sodium ions move back and forth within a battery. The speed and ease with which these ions move affect the battery's performance and lifespan.
Developing better batteries therefore requires researchers to precisely determine where ions can move freely and where their movement is hindered. One technique used for this type of analysis is electrochemical strain microscopy (ESM), which is based on atomic force microscopy (AFM). ESM scans the surface of a battery material with an extremely fine tip and measures nanoscale changes in the material associated with ion movement, allowing researchers to indirectly track ion transport.
The problem is that when the surface of a battery material is rough, similar signals can appear even in the absence of actual ion movement. If these signals are interpreted as evidence of ion transport, researchers may incorrectly identify where ions are moving within the material. To investigate the origin of these artifacts, the team created fine trenches on the surface of an ionically inactive single-crystal silicon sample.
This provided an experimental environment in which no ions were moving while the sample surface remained uneven. The results quantitatively demonstrated that variations in surface height alone can alter the degree of contact between the microscope tip and the sample, producing signals similar to those generated by actual ion movement. The same phenomenon was also observed in actual battery materials.
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