Cyano-functionalized electrolyte additive enables the coupled solvation chemistry and interfacial regulation for...

For large-scale energy storage applications, zinc‑iodine (ZnI₂) batteries stand out as viable options, primarily due to their high safety, plentiful resources, and low cost. Nonetheless, their practical application is impeded by the migration of soluble iodine-based substances at the cathode, alongside dendrite formation and unintended chemical reactions occurring at the zinc anode. Herein, ethylene glycol dipropionitrile ether (EDPN) serves as an effective additive that enables comprehensive regulation from the cathode to the anode through electrolyte optimization. EDPN simultaneously modulates the Zn²⁺ solvation structure and competitively adsorbs on the zinc surface, forming a stable hybrid solid-electrolyte interphase that suppresses the zinc dendrites and enhances the anode reversibility. At the same time, the highly polar cyano moieties (-C ≡ N) within it bind polyiodide species, alleviating the shuttle phenomenon and enhancing the redox reaction dynamics at the cathode side. Thus, Zn||Zn symmetric cells stable cycling for more than 1800 h (1 mA cm^-2, 1 mAh cm^-2) and 1000 h (10 mA cm^-2, 1 mAh cm^-2). Moreover, the ZnI₂ battery system shows 89.3% capacity remaining even after 32,000 cycles under 5 A g^-1, with an average Coulombic efficiency of 99.9%, while the pouch-type battery provides a high areal capacity of 33.4 mAh. This work presents a practical electrolyte preparation method to create high-efficiency and long-lasting aqueous ZnI₂ batteries.