Bond Exchange-Driven Interfacial Relay Redox Enables Ultrahigh-Rate Zn Batteries With High Iodine Utilization

Aqueous Zn || iodine batteries are promising for multiple application scenarios but suffer from severe "dead iodine" issues, leading to limited iodine utilization and areal capacity, especially at high rates. Here, we design an interfacial relay redox strategy driven by halogen-bond exchange to address this challenge. Using electrochemically generated polyiodides (e.g., I₃ ^-) from sulfonium iodides on the current collector as redox anchors, our approach enables iodine relay conversion at the electrolyte-electrode interface with uniform polyiodide deposition/dissolution. The formed hydrophobic organic cation-polyiodide pairs suppress shuttling, while halogen-bond exchange promotes rapid ion/electron transport and further conversion from I₃ ^- to I₅ ^-, effectively eliminating "dead iodine." Consequently, the Zn || iodine battery demonstrates exceptional rate capability (up to 100 mA cm^-2), high iodine utilization (51%-80% at 1-40 mA cm^-2), and long-term cyclability (> 1,200 cycles at 7.04 mA h cm^-2), far beyond most of the state-of-the-art systems. A pouch cell validates its practicality. This work establishes a new paradigm for designing static halogen batteries with high energy/power density and extended lifespan, offering broader insights for energy storage systems.