Tailoring Water-Shielding Electric Double Layer and Hydrophobic Solid Electrolyte Interphase for Parasitic Reaction-Free Zinc Metal Anode

Aqueous zinc-ion batteries (AZIBs) have attracted considerable interest due to their intrinsic merits, such as excellent safety, affordability, and eco-friendliness. However, the practical deployment is greatly limited by H2O-induced parasitic reactions at the zinc metal anode (ZMA), such as the hydrogen evolution reaction (HER) and interfacial passivation. Herein, we propose a synergistic interfacial-regulation strategy to mitigate these parasitic reactions. By leveraging the zincophilic carboxyl groups and hydrophobic alkyl chains of straight-chain fatty acid (SFA) molecules, a H2O-shielding electric double layer (EDL) and a hydrophobic solid electrolyte interphase (SEI) are simultaneously constructed in situ at the ZMA|electrolyte interface. This integrated H2O-shielding EDL and hydrophobic SEI framework effectively suppresses H2O-induced parasitic reactions and enhances the stability of Zn2+ deposition, highlighting the critical role of coordinated regulation. Under optimal conditions using lauric acid (a C12-based SFA), the Zn||Zn symmetric cell delivers an exceptional reversible cycle life exceeding 5785 h at 1 mA cm−2 and 1 mA h cm−2. Furthermore, the full cell exhibits excellent cycling stability, retaining 75.4% of its initial capacity after 1500 stable cycles at 5 A g−1. This work provides a promising strategy for achieving stable, high-performance ZMA and opens avenues for advancing AZIBs technology.