Molecular Protonation Gating of Lewis Base Monolayers Stabilizes Aqueous Zinc Metal Batteries

Aqueous zinc–metal batteries offer safe, low-cost grid storage but suffer from nonuniform Zn plating and parasitic water reduction. Adsorption-type additives offer interfacial regulation but often lose functionality due to protonation under practical aqueous conditions. Here, we propose a protonation-tolerant molecular design integrating electronic modulation with a planar, zincophilic adsorption scaffold. By introducing an electron-withdrawing cyano substituent into an aromatic amine, the basicity is reduced while preserving the NH2 lone-pair anchoring, enabling 4-aminobenzonitrile (ABN) to maintain stable horizontal adsorption and high surface coverage. The resulting molecular layer reconstructs the electric double layer, suppresses water-induced side reactions, and promotes uniform (002)-oriented Zn plating/stripping through facet-selective interactions. With 3.3 mM ABN, symmetric Zn//Zn cells cycle for >700 h at 4 mAh cm–2. Zn//β-MnO2 cells deliver 4.4 mAh cm–2 after 250 cycles at 0.25 A g–1 with zinc utilization ratio of 21.4% and retain 4.28 mAh cm–2 for 150 cycles at ZUR of 46.2%.