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Aqueous zinc (Zn) battery with remarkable advantages of high safety, low cost, and high reversibility is highly applauded in next‐generation low‐speed electric vehicles and large‐scale energy storage applications. However, Zn anode suffers from a series of unfavorable reactions, hindering its progress toward industrialization. Herein, a functionalized hydrogel film is designed using polydopamine and polyacrylamide crosslinking (PDAM) as the Zn protective layer to stabilize the Zn anode. Benefiting from the strong interaction of Zn2+ with PDAM, the primary solvation shell of Zn2+ is regulated by PDAM into the form of PDAM–Zn2+‐5H2O. This remodeling prevents Zn dendrite growth and inhibits water‐induced side reactions. As a result, the Zn–MnO2 battery using PDAM‐coated Zn anode exhibits excellent cycling stability, demonstrating over 1150 cycles at an areal capacity of 5 mAh cm−2 with an average Coulombic efficiency (CE) of 96.5%. For a scaled‐up PDAM@Zn–MnO2 pouch cell with a capacity of 80 mAh, stable cycling of over 200 cycles with an average CE of 91.9% is achieved. The superior Zn–MnO2 battery enabled by the functionalized hydrogel protective film enlightens an arena toward next‐generation energy storage applications. [ABSTRACT FROM AUTHOR]

The commercialization of electrolytic MnO2–Zn batteries is highly applauded owing to the advantages of cost‐effectiveness, high safety, high energy density, and durable working performance. However, due to the low reversibility of the cathode MnO2/Mn2+ chemistry at high areal capacities and the severe Zn anode corrosion, the practical application of MnO2–Zn batteries is hampered by inadequate lifespan. Leveraging the full advantage of an iodine redox mediator, here we design a highly rechargeable electrolytic MnO2–Zn battery with a high areal capacity. The MnO2–Zn battery coupled with an iodine mediator in a mild electrolyte shows a high discharge voltage of 1.85 V and a robust areal capacity of 10 mAh cm−2 under a substantial discharge current density of 160 mA cm−2. The MnO2/I2–Zn battery with an areal capacity of 10 mAh cm−2 exhibits prolonged stability of over 950 cycles under a high‐capacity retention of ~94%. The scaled‐up MnO2/I2–Zn battery reveals a stable cycle life under a cell capacity of ~600 mAh. Moreover, our constructed MnO2/I2–Zn battery demonstrates a practical energy density of ~37 Wh kg−1 and a competitive energy cost of <18 US$ kWh−1 by taking into account the cathode, anode, and electrolyte. The MnO2/I2–Zn battery, with its remarkable reversibility and reasonable energy density, enlightens a new arena of large‐scale energy storage devices. [ABSTRACT FROM AUTHOR]