Zinc Single-Atom Catalysts Encapsulated in Hierarchical Porous Bio-Carbon Synergistically Enhances Fast Iodine Conversion and Efficient Polyiodide Confinement for Zn-I2 Batteries

Abstract

Aqueous zinc iodine (Zn-I₂) batteries have attracted attention due to their low cost, environmental compatibility, and high specific capacity. However, their development is hindered by the severe shuttle effect of polyiodides and the slow redox conversion kinetics of the iodine (I₂) cathode. Herein, a long-life Zn-I₂ battery is developed by anchoring iodine within an edible fungus slag-derived carbon matrix encapsulated with Zn single-atom catalysts (SAZn@C_FS). The high N content and microporous structure of SAZn@C_FS provide a strong iodine confinement, while the Zn-N₄-C sites chemical interact with polyiodides effectively mitigating the iodine dissolution and the polyiodide shuttle effect. Additionally, the uniformly distributed SAZn sites significantly enhance the redox conversion efficiency of I⁻/I₃⁻/I₅⁻/I₂, leading to improved capacity. At a high current density of 10 A g⁻¹, the designed Zn-I₂ battery delivers an excellent capacity of 147.2 mAh g⁻¹ and a long lifespan of over 80 000 cycles with 93.6% capacity retention. Furthermore, the battery exhibits stable operation for 3500 times even at 50 °C, demonstrating significant advances in iodine reversible storage. This synergistic strategy optimizes composite structure, offering a practical approach to meet the requirements of high-performance Zn-I₂ batteries.