Boosted Durability and Diffusion Kinetics of High‐Potential Azopyridines for Aqueous Organic Flow Batteries

Abstract

ABSTRACT High‐potential organic redox‐active molecules are crucial for high‐energy‐density aqueous organic flow batteries (AOFBs). Azopyridine (AZO) derivatives with high redox potential (0.86 V vs. SHE) suffer from structural rearrangement instability and slow redox kinetics during the oxidation process. Herein, we achieve dual‐target modulation of the electronic structure and dynamic steric hindrance, which increases the bond energy of the azo bond and buffers the drastic change of redox‐induced molecular structure. Thus, the azo bond cleavage and nucleophilic side reactions were suppressed, thereby simultaneously promoting the redox potential (0.9 V vs. SHE) and stability. Further modulation of the solvation shell anions also alleviates molecular aggregation and minimizes solvation reorganization energy, thereby markedly increasing the cell energy efficiency by ∼60%. The AZO‐based AOFB demonstrated robust durability for 7000 cycles (>1400 h). Impressively, the cell sustained over 1250 cycles at high electron concentrations of 2.4 M, achieving an energy density of 70.4 Wh L catholyte  −1 . This work establishes an integrated molecular and solvation‐structure design paradigm for realizing durable and high‐energy‐density AOFBs.