Functional binders toward zinc–iodine batteries: From mechanism to design

Aqueous zinc‑iodine (Zn-I 2 ) batteries have emerged as a promising alternative for grid energy storage, yet their practical application is critically plagued by the polyiodide shuttle effect, sluggish iodine redox kinetics, and unstable zinc anode interfaces. Although extensive advances have been achieved in cathode host design, electrolyte engineering, and anode modification, binders, a minor yet decisive component in cathodes, have long been underappreciated in current research. Unlike existing reviews that primarily focus on electrode materials and electrolyte systems, this review systematically summarizes the rational design and mechanistic understanding of advanced functional binders for high-performance Zn-I 2 batteries. We comprehensively categorize and elaborate the mainstream regulation mechanisms of state-of-the-art binders based on the interactions with iodine species, namely spatial confinement, hydrogen bonding, chemisorption, electrostatic interaction, and cross-mechanism. For each category, the structural taxonomy of functional binders, the engineering of binders, and the electrochemical performance, as well as advantages and limitations are discussed in detail, highlighting their crucial roles in polyiodide immobilization, interfacial stabilization, and four-electron activation. Finally, the existing challenges and future perspectives on binder engineering are prospected, aiming to provide insightful guidelines for the development of high-efficiency and durable aqueous Zn-I 2 batteries.