Rechargeable aqueous zinc iodine (Zn-I2) batteries offer benefits such as low cost and high safety. Nevertheless, their commercial application is hindered by hydrogen evolution reaction (HER) and polyiodide shuttle, which result in a short lifespan. In this study, 1-(2-hydroxyethyl)imidazole (HEI) organic molecules featuring pyrrole-N groups are introduced as dually-functional electrolyte additives to simultaneously stabilize Zn anode and confine polyiodide through ion-dipole interactions. The pyrrole-N groups in HEI can preserve the interfacial pH equilibrium at Zn anode by reversibly capturing H+ ions and dynamically neutralizing OH- ions, thereby suppressing the HER. Notably, the H2 evolution rate at the Zn anode is reduced to a mere 2.20 μmol h-1 cm-2. Furthermore, the pyrrole-N moieties in HEI effectively curtail the polyiodide shuttle at I2 cathode, which show adsorption energies of -0.174 eV for I2, -0.521 eV for I3 -, and -0.768 eV for I-, as indicated by density functional theory calculations. Electrochemical testing demonstrates that the Zn//Zn symmetric cell maintains stable cycling for up to 4,200 hours at 1 mA cm-2. Most strikingly, at a high I2 mass loading of 9.7 mg cm-2, the Zn-I2 battery achieves an extraordinary cycle life of 50,000 cycles.
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