Self‐Assembled Molecular Capsule via Metastable Soft Interface for Stable Aqueous Batteries

ABSTRACT Organic redox materials hold great promise for sustainable energy storage due to their structural tunability and elemental abundance. However, their practical application remains hindered by rapid degradation during repeated electrochemical reactions, primarily caused by side processes involving water and unstable redox intermediates. Here, we report a metastable, rehydration‐stable molecular capsule formed through the interfacial self‐assembly of amphiphilic Pluronic F127 on hydrophobic 2‐ethyl‐anthraquinone (2‐E‐AQ) particles. The hydrophobic polypropylene oxide segments anchor onto the 2‐E‐AQ surface, while the hydrophilic polyethylene oxide chains form a soft, ion‐permeable shell that endures drying and reconstructs a gel‐like interface upon rehydration, bridging solid‐liquid boundaries. Integrated into an aqueous 2‐E‐AQ||Li ₂ SO ₄ ||NaI battery, this soft‐interface design stabilizes ion transport and suppresses redox degradation, achieving 99.7% Coulombic efficiency and 85.4% capacity retention after 300 cycles. This work introduces an interface‐induced self‐assembly paradigm for stabilizing hydrophobic organic redox materials and provides a general framework for constructing adaptive soft interfaces in aqueous electrochemical systems.