Metal-Organic Xerogel Binder Enables Strong Chemisorption and Fast Conversion Kinetics towards Shuttle-Suppressed Zn–I 2 Batteries

Abstract

The loss and incomplete conversion of soluble polyiodide intermediates limit the long-term cycling stability of aqueous Zn–I2 batteries. Conventional functional binders can restrict polyiodide migration but generally do not promote the conversion of the retained species. Here, an amorphous iron-benzene-1,3,5-tricarboxylate (Fe–BTC) metal–organic xerogel (MOX) is used as a redox-responsive binder to couple polyiodide capture with interfacial redox conversion. Its heterogeneous electrostatic environment retains iodine species near the cathode, while the mixed-valence Fe centers electronically interact with the adsorbed intermediates and are proposed to assist interfacial electron transfer. This capture-conversion coupling suppresses polyiodide accumulation and migration, reduces interfacial polarization, and preserves electrochemically accessible iodine during cycling. Consequently, the MOX-based cell retains 122.8 mAh g−1 after 20,000 cycles at 10 C. Its robustness is further demonstrated at a high iodine loading of 7 mg cm−2, at temperatures of −10 and 60 °C, and in pouch cells. These results demonstrate that redox-responsive metal coordination within the binder phase provides an effective strategy for regulating both the location and reactivity of soluble intermediates in aqueous Zn–I2 batteries.