The research team led by Professor Lee Jihoon from the Department of Materials Science and Engineering at Kyungpook National University has identified the key factors that determine the performance and lifespan of all-solid-state batteries (ASSBs), which are attracting attention as next-generation batteries.
All-solid-state batteries use a solid electrolyte instead of a liquid electrolyte, which reduces the risk of fire and increases energy density, making them a promising next-generation technology for electric vehicles and energy storage systems (ESS).
However, in actual operation, reactions within the cathode layer do not occur uniformly, leading to reduced performance and persistent concerns about the battery degrading faster than expected.
Professor Lee's team identified that the most critical factor determining the performance and lifespan of all-solid-state batteries is how uniformly the active cathode material and the solid electrolyte are distributed and in contact within the cathode layer-in other words, the "microstructural homogeneity between the cathode layer and the electrolyte." The team also proposed a new design principle to control this factor.
To investigate how the internal microstructure of the cathode layer affects battery reactions, the research team designed several composite cathodes with varying mixing and arrangement methods of the active cathode material and solid electrolyte, and comparatively analyzed changes in electrochemical performance. They also used synchrotron-based multi-scale X-ray analysis techniques to observe the actual reactions occurring within the cathode layer from multiple perspectives.
As a result, the team experimentally demonstrated that the more uniform the interfacial contact between the active cathode material and the solid electrolyte within the cathode layer, the more consistently the state-of-charge (SoC) of individual active cathode material particles is maintained. This, in turn, effectively suppresses the oxidative decomposition of the solid electrolyte that otherwise occurs only in specific areas.
In particular, by visualizing charge inhomogeneity at the level of individual active cathode material particles using transmission X-ray microscopy and X-ray absorption analysis, the research team systematically presented the so-called "microstructural causality chain," showing that microscopic inhomogeneity leads to battery performance degradation, which they highlighted as a significant achievement.
Professor Lee Jihoon stated, "This study goes beyond simply attributing the causes of performance degradation in all-solid-state batteries to material issues, and instead clarifies them from the perspective of structural and chemical uniformity within the electrode's microenvironment. In the future, it will provide design guidelines to ensure stable battery reactions even in real-world operating environments, such as large-area pouch cells for electric vehicles."
This research was supported by the Mid-Career Research Program and the Doctoral Research Fellowship Program funded by the Ministry of Science and ICT and the National Research Foundation of Korea.
The corresponding author is Professor Lee Jihoon, and the first author is Lee Juhyun, a doctoral student in the same department.
The research results were published online on December 23 in "Materials Horizons," a leading international journal in the field of materials science published by the Royal Society of Chemistry, and, in recognition of their significance, will be featured as a cover article in the February 2026 issue.
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