A Metal–Organic Framework as a Multifunctional Ionic Sieve Membrane for Long‐Life Aqueous Zinc–Iodide Batteries

Abstract The introduction of the redox couple of triiodide/iodide (I 3 − /I − ) into aqueous rechargeable zinc batteries is a promising energy‐storage resource owing to its safety and cost‐effectiveness. Nevertheless, the limited lifespan of zinc–iodine (Zn–I 2 ) batteries is currently far from satisfactory owing to the uncontrolled shuttling of triiodide and unfavorable side‐reactions on the Zn anode. Herein, space‐resolution Raman and micro‐IR spectroscopies reveal that the Zn anode suffers from corrosion induced by both water and iodine species. Then, a metal–organic framework (MOF) is exploited as an ionic sieve membrane to simultaneously resolve these problems for Zn–I 2 batteries. The multifunctional MOF membrane, first, suppresses the shuttling of I 3 − and restrains related parasitic side‐reaction on the Zn anode. Furthermore, by regulating the electrolyte solvation structure, the MOF channels construct a unique electrolyte structure (more aggregative ion associations than in saturated electrolyte). With the concurrent improvement on both the iodine cathode and the Zn anode, Zn–I 2 batteries achieve an ultralong lifespan (>6000 cycles), high capacity retention (84.6%), and high reversibility (Coulombic efficiency: 99.65%). This work not only systematically reveals the parasitic influence of free water and iodine species to the Zn anode, but also provides an efficient strategy to develop long‐life aqueous Zn–I 2 batteries.