Well‐Defined Redox‐Active Hyperbranched Polymers for Flow Batteries: Harnessing Self‐Condensing Vinyl Copolymerization by Flow Chemistry

Abstract The increased adoption of renewable power necessitates the development of grid‐scale storage solutions, with aqueous redox flow batteries (RFBs) at the forefront. Despite their potential, performance limitations arising from high solution viscosity at high concentrations of active material and rapid degradation due to active material crossover continue to pose challenges. Here, we use flow chemistry to create redox‐active hyperbranched copolymers (HBCs), which exhibited substantially improved suppression of crossover and enhanced rheology behaviors. The distinct reaction dynamics of flow chemistry facilitated the efficient and monomer‐independent control over self‐condensing vinyl polymerization, yielding well‐defined HBCs with remarkably low dispersity. This strategy effectively enhanced the uniformity of the redox‐active HBCs, leading to significantly reduced crossover and accelerated diffusion rates. The RFBs equipped with our redox‐active HBCs exhibited long‐term stability, mapping a pathway towards practical application of polymer‐based technologies as well as highlighting the unique advantages of the flow chemistry techniques in high‐precision electrolyte design.