Innovative Design of a Double‐Layer Gradient Coating for Dendrite‐Free and Ultrastable Zinc Anodes

Abstract The rampant “top‐growth” dendrites, hydrogen evolution reaction (HER), and zinc (Zn) self‐corrosion severely impede the further development of rechargeable aqueous zinc ion batteries. To address these challenges, a novel double‐layer gradient coating consisting of a zincophilic Sn inner layer and an organic polymer outer layer (OSA/PAM@Sn) is constructed on the surface of the Zn anode. The organic outer layer, composed of cross‐linked oxidized sodium alginate and polyacrylamide (OSA/PAM), not only serves as a physical barrier to isolate active water but also accelerates Zn 2+ diffusion by facilitating the desolvation process of [Zn(H 2 O) 6 ] 2+ due to its plentiful polar functional groups, thereby effectively suppressing the detrimental HER and Zn self‐corrosion. Simultaneously, the loose Sn inner layer can offer abundant nucleation sites to induce uniform “bottom‐to‐top” Zn deposition with low overpotential. Benefiting from the synergistic effect of the designed double‐layer gradient coating, the OSA/PAM@Sn‐Zn anode exhibits remarkable reversibility, with lifespans of over 5000 and 1200 h at 1 mA cm −2 –1 mAh cm −2 and 5 mA cm −2 –5 mAh cm −2 in symmetric cells, respectively. Additionally, the MnO 2 ||OSA/PAM@Sn‐Zn full battery also displays an improved rate performance and cycle stability. This work emphasizes the importance of synergistic effects in interface design to achieve side reaction‐free and dendrite‐free Zn anodes.