Unveiling the Coupled Electric Field–Diffusion Mechanism in Redox‐Active Electrochromic Microsupercapacitors

Electrochromic microsupercapacitors (EC‐MSCs) featuring in‐plane interdigital electrodes are multifunctional energy storage devices capable of real‐time visualization of their charge state within a compact footprint. In particular, redox‐active organic EC molecules possess high optical modulation and high structural tunability, enabling diverse color expression and electrochemical properties. Despite these advantages, the correlation between the diffusive flux behavior of redox species and the resulting electrochemical performance within interdigitated electrode architectures remains unclear. In this study, we systematically elucidate the correlation between key factors governing diffusive flux, namely, electric field distribution and concentration gradient, and energy storage performance. The electrode gap size and redox species concentration were systematically varied, and the ionic motion and redox species transport during device operation were decoupled for separate analysis. Our results suggest that energy storage performance, while linearly dependent on the concentration gradient, can exhibit nonlinear behavior depending on the electric field distribution, highlighting the dominance of electric field configuration in diffusion‐controlled EC‐MSCs. This work provides a design framework for future development of compact and multifunctional energy storage systems.