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

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.