Multi-Site Co-Doped Hierarchical Porous Carbon for Efficient Iodine Conversion and Uniform Zinc Deposition in Zinc-Iodine Batteries.

Aqueous zinc-iodine (Zn─I2) batteries demonstrate immense potential for energy storage owing to their inherent safety, stable voltage plateau, and environmental friendliness. However, the slow iodine conversion, polyiodide shuttle effect, and uncontrollable Zn dendrites impede the improvement of their performance. Herein, we successfully designed a bifunctional core-shell host derived from BiHCF@ZIF-8, which consists of a porous carbon matrix encapsulating abundant metal catalytic sites and trace N-doping (BZPC). This superior multi-site co-doped hierarchical porous structure can serve as a high-efficiency iodine carrier to effectively confine iodine species and enhance their conversion kinetics. Simultaneously, the BZPC can also be applied as a functional modification layer to induce uniform Zn deposition, thereby achieving a dendrite-free Zn anode. The assembled Zn//BZPC@I2 batteries and BZPC@Zn symmetric cells can operate stably at ultrahigh current densities of 50 C and 100 mA cm-2, respectively. Through a synergistic optimization strategy of "one host for dual purposes", the BZPC@Zn//BZPC@I2 batteries achieve an ultralong lifespan of 28 000 stable cycles even at an ultrahigh current density of 50 C. This study not only pioneers the difunctional BZPC for both iodine host design and zinc interface engineering but also establishes an innovative and scalable strategy for developing long-life and high-rate Zn─I2 batteries.