Visualizing and Understanding the Reaction‐Coupled Ion Grotthuss Transport in Single‐Crystal Organic Battery

Abstract Tracking dynamic ion diffusion in electrode materials has long posed a significant challenge in battery performance research. The development of facile visualization techniques to reveal ion transport dynamics enables more intuitive and in‐depth understanding of degradation mechanisms. In this study, we introduce an in situ optical electrochemical characterization method for organic single‐crystal electrode materials. By leveraging the electrochemical‐responsive optical properties of these materials, we successfully visualized the dynamic ion diffusion process within organic single‐crystal electrodes. Using this approach, we identified a reaction‐coupled ion diffusion mechanism governed by Fick's first law. Our results reveal strong crystal‐plane‐dependent diffusion characteristics and demonstrate that reaction‐induced conductivity enhancement is a key factor enabling high‐rate performance. Furthermore, the method vividly captures ion‐intercalation‐induced volume expansion and active material dissolution/shuttling phenomena. This methodology provides fundamental insights into the kinetic behavior and degradation mechanisms of organic electrode systems and demonstrates broad applicability to other material systems.