Green and Low‐Cost Interfacial Protection: Natural Polymer Gel‐Coated Zinc Anodes for Aqueous Zinc‐Ion Batteries

ABSTRACT Aqueous zinc‐ion batteries (AZIBs) hold great promise for large‐scale energy storage but suffer from uncontrollable dendrite growth, hydrogen evolution, and severe interfacial corrosion. Here, we report a scalable doctor‐blading strategy to construct an in situ formed multifunctional gel protective layer using natural sodium alginate (SA) and sodium lignosulfonate (SLS). SA provides ordered “egg‐box” coordination sites for Zn 2+ while SLS modulates the Zn 2+ solvation structure through strong sulfonate‐Zn 2+ interactions. The SA‐SLS coated Zn (Zn‐SS) effectively homogenizes the interfacial electric field, accelerates Zn 2+ transport, suppresses parasitic reactions, and guides uniform Zn deposition. Benefiting from this coordinated interfacial regulation, the Zn‐SS symmetric cell delivers an ultralong cyclic life exceeding 2200 h at 0.5 mA cm −2 , while the Zn‐SS||Cu half cell exhibits highly reversible plating and stripping with an average Coulombic efficiency of 99.5% over 500 cycles. When paired with a V 2 O 5 cathode, the full cell maintains a high capacity of 265 mAh g −1 after 600 cycles at 3 A g −1 . This work offers a green, cost‐effective and highly effective interfacial protection strategy, providing new insights toward practical, safe and durable AZIBs.