Contradictory to the conventional understanding of solid-state ionics, we find that some organic crystals are highly ion conducting (>10-4 S/cm at room temperature). Through the microparticles of charge-transfer (CT) complexes, dissociated lithium ions move readily. Fast conduction is observed for a wide variety of compounds that form CT complexes, irrespective of the functional groups. Automatic relationship analysis via machine learning indicates the importance of polarization of the CT complexes for the ionic conduction. The decoupling system, where ion transport is not dominated by the segmental motion of media molecules, paves the way for achieving superionic properties in organic monomeric and polymeric conductors.
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