Quantum Size Effect Synergizes Space-Limited Domain Action for Advanced Aqueous Zinc-Iodine Batteries

Rechargeable aqueous zinc-iodine batteries (AZIBs) demonstrate immense potential for large-scale energy storage owing to their high theoretical capacity, resource abundance, and low cost. However, their practical deployment is hampered by the notorious polyiodide shuttle effect and sluggish redox kinetics. Herein, an Al-TCPP(Fe) metal-organic framework (MOF) is designed and synthesized with specific functional sites as an advanced iodine host. The unique microporous structure of this MOF provides significant spatial confinement, which effectively suppresses the dissolution and migration of polyiodide intermediates, thereby mitigating the shuttle effect. Furthermore, precisely engineered Fe-N₄ catalytic sites embedded within the MOF framework induce a quantum size effect under nanoscale confinement, which significantly modulates the electronic structure of the Fe sites, dramatically accelerating the iodine redox kinetics. Benefiting from these structural merits, the resulting I₂@Al-TCPP(Fe) cathode delivers a high specific capacity of 210.95 mAh g^-1 at 1C, achieves an ultralong cycling lifespan of over 54 000 cycles at a high rate of 50C, and enables the fabrication of an ampere-hour-level pouch cell. This work highlights a synergistic strategy of coupling the quantum size effect with spatial confinement to engineer advanced MOF-based hosts, paving the way for developing high-performance, long-lifespan aqueous zinc-iodine batteries.