[Press Release] Beyond the Paddle-Wheel Mechanism: Elucidating the Microscopic Lithium Ion Transport in Solid-State Electrolytes for Next-Generation Batteries

An international collaborative research group led by Professor Bong June Sung of the Department of Chemistry at Sogang University and Professor Shinji Saito of the Institute for Molecular Science (IMS), National Institutes of Natural Sciences (NINS), and the Graduate University for Advanced Studies, SOKENDAI has elucidated, at the molecular level, how lithium ions move within organic ionic plastic crystals (OIPCs)--which are attracting attention as solid electrolytes for next-generation batteries.

In OIPCs, although the material is solid, molecules and ions within the crystal rotate actively in situ; consequently, the "paddlewheel mechanism"--in which this rotational motion pushes lithium ions forward--has long been considered the primary mechanism of ion conduction. In this study, the researchers theoretically re-examined this hypothesis using molecular dynamics simulations on a supercomputer and hop-function analysis, which precisely extracts individual ion jumps. The results revealed that the movement of lithium ions is not directly driven by the surrounding rotational motion, but rather occurs through the cooperative rearrangement of an ion cage formed by the surrounding anions. In particular, we theoretically demonstrated that when the number of anions surrounding a lithium ion temporarily decreases--causing the cage to "open"--the movement of the lithium ion increases significantly.

This study was published online in the Journal of the American Chemical Society (JACS) on June 1, 2026.

For Details (Eurekalert!)

• Title: Beyond the Paddle-Wheel Mechanism: Hop Function Analysis of Ion Transport in Organic Ionic Plastic Crystals
• Authors: Hyungshick Park, Shinji Saito, and Bong June Sung
• Journal: Journal of the American Chemical Society
• DOI: 10.1021/jacs.6c04713

• Institute for Molecular Science
• Molecular Science