Hydrogel‐Engineered Interface Suppressing Water Activity by Hydrogen Bonds and Regulated Solvation for Stable Zn Metal Anodes

ABSTRACT The instability of zinc metal anodes in aqueous electrolytes, primarily caused by water‐induced side reactions such as hydrogen evolution and corrosion, severely limits the lifespan of aqueous zinc‐ion batteries. Herein, we propose an in situ polymerized hydrogel coating strategy to engineer the Zn/electrolyte interface. A robust polyacrylamide (PAM)‐based hydrogel layer incorporating polyethylene glycol (PEG) and concentrated ZnCl 2 is constructed directly on the Zn surface (Zn‐PAM/PEG/ZnCl 2 ). This multifunctional layer simultaneously suppresses water activity and regulates Zn 2+ solvation structure. Specifically, the abundant hydrophilic groups in the PAM/PEG networks immobilize free water molecules via strong hydrogen bonding, while Cl − ions partially replace the water molecules in the primary solvation sheath of Zn 2+ , effectively mitigating hydrogen evolution. Furthermore, PEG enhances the mechanical strength and water‐retention capability of the hydrogel, ensuring exceptional interfacial stability. Consequently, the Zn‐PAM/PEG/ZnCl 2 electrode achieves an extraordinary cycling lifespan exceeding 6600 h (> 9 months) in symmetric cells at 1 mA cm −2 and 1 mAh cm −2 . When paired with activated carbon and MnO 2 electrodes, respectively, the full cells also demonstrate remarkable electrochemical performance and cycling durability. This work provides a profound insight into interfacial chemistry manipulation and offers a feasible approach to developing highly reversible zinc metal anodes for practical energy‐storage applications.