Ultra-Stable Aqueous Zinc-Ion Batteries Enabled by Trace Ionic Liquid–Polar Solvent Synergistic Induction of Vertically Oriented (101) Facet Epitaxial Growth

Aqueous zinc-ion batteries (AZIBs) are promising for grid-scale storage due to their safety, low cost, and environmental benignity. However, water-dipole enrichment in the inner Helmholtz plane (IHP) of Zn anodes triggers hydrogen evolution, corrosion, and dendrites, limiting cycle life. We report a trace “ionic liquid–polar solvent coupling” strategy: adding only 0.01 M EMIMBF4 and 0.03 M DMSO to 2 M ZnSO4 electrolyte. Hydrophobic EMIM+ adsorbs on the IHP to expel interfacial water, while BF4− enters the primary solvation shell and DMSO penetrates both first and second shells of Zn2+, forming a water-deficient coordination environment. This interfacial–solvation synergy suppresses parasitic reactions and directs preferentially oriented Zn deposition exclusively along the (101) facet, enabling dense vertical plating and in situ formation of a compact, inorganic-rich SEI (ZnCO3–ZnSO3–Zn(OH)2). Consequently, Zn||Zn cells cycle stably for >5362 h at 1 mA cm−2/1 mAh cm−2; Zn||Cu cells achieve 1300 cycles with 99.8% average Coulombic efficiency; and Zn||V2O5 full cells retain 326.4 mAh g−1 after 500 cycles. This work shows that minimal additive loading can simultaneously engineer the electrode–electrolyte interface and crystallographic deposition pathway, offering a simple yet robust design for ultra-stable AZIBs.