Suppressing Zinc Metal Corrosion by an Effective and Durable Corrosion Inhibitor for Stable Aqueous Zinc Batteries

Abstract The development of aqueous zinc‐ion batteries (AZIBs) for large‐scale industrial applications is substantially constrained by the persistent issue of zinc anode corrosion. This study introduces fucoidan (FCD), a corrosion inhibitor, to effectively mitigate the corrosion‐related challenges in zinc metal anodes. FCD forms a robust, covalently bonded layer on the zinc surface at a low concentration of 25 m m through interactions between the lone pairs on its polar atoms and the d orbitals of zinc. This layer is ultrathin, which does not deteriorate ion transfer but effectively shields the zinc from corrosive electrolytes and promotes uniform zinc deposition, resulting in suppressed corrosion, passivation, and dendrite formation. Consequently, the Zn||Zn cells exhibit excellent reversibility, stably operating for 2700 h at 1 mA cm −2 under 1 mAh cm −2 and 400 h at 10 mA cm −2 under 10 mAh cm −2 . Furthermore, a large‐sized Zn||I 2 pouch cell with a high iodine loading of 2 g and a discharge capacity of ≈300 mAh is demonstrated, which shows minimal capacity degradation—<3% after 300 cycles—and maintains a high Coulombic efficiency of ≈99.5%. The corrosion inhibition strategy proposed in this study provides crucial insights for enhancing the durability and practicability of AZIBs.