We report a bio-inspired design strategy for constructing anin situpolymeric SEI in aqueous Zn chemistry. This SEI can restrain interfacial side reactions, facilitate a uniform Zn²⁺flux, and consequently endow a highly stable Zn metal anode.

Aqueous Zn-ion batteries have attracted increasing research interest; however, the development of these batteries has been hindered by several challenges, including dendrite growth, Zn corrosion, cathode material degradation, limited temperature adaptability and electrochemical stability window, which are associated with water activity and the solvation structure of electrolytes. Here we report that water activity is suppressed by increasing the electron density of the water protons through interactions with highly polar dimethylacetamide and trimethyl phosphate molecules. Meanwhile, the Zn corrosion in the hybrid electrolyte is mitigated, and the electrochemical stability window and the operating temperature of the electrolyte are extended. The dimethylacetamide alters the surface energy of Zn, guiding the (002) plane dominated deposition of Zn. Molecular dynamics simulation evidences Zn²⁺ions are solvated with fewer water molecules, resulting in lower lattice strain in the NaV₃O₈·1.5H₂O cathode during the insertion of hydrated Zn²⁺ions, boosting the lifespan of Zn|| NaV₃O₈·1.5H₂O cell to 3000 cycles.