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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]

Mg batteries utilizing divalent Mg2+ as charge carriers have been attracting significant attention for energy storage owing to their uniqueness in terms of low cost, high safety, and high energy density. However, the short cycling life arising from the accumulation of a passivation layer on the Mg anode prohibits their further development. Here, a new strategy to suppress the accumulation of the passivation layer is presented, thus stabilizing the Mg anode by constructing a robust interfacial layer using organic solvent‐in‐water electrolytes. The organic solvents decompose on the Mg anode to form a MgO, polyether Mg enriched organic‐inorganic hybrid interfacial layer, preventing free water attack to the Mg anode. In addition, the organic solvent forms an H‐bond with H2O to suppress the water activity and therefore protecting the Mg anode. As an illustration to benefits of the solvent‐in‐water electrolytes, a Mg‐MnO2 battery that is coupled by a MnO2 cathode in Mn2+/MnO2 chemistry with the Mg anode is developed. The Mg‐MnO2 battery exhibits a well‐maintained discharge plateau at ≈2.5 V and a discharging capacity of ≈500 mAh g−1 over 1000 cycles. This result highlights the feasibility to stabilize the Mg anode by interface engineering through the solvent‐in‐water electrolyte design. [ABSTRACT FROM AUTHOR]