Cation-anion synergy enables Zn(002) oriented growth in aqueous zinc ion batteries

The practical application of aqueous zinc-ion batteries (AZIBs) is significantly hindered by the unregulated growth of dendrites and the instability at the interface of Zn anodes. Here, we report an interfacial engineering strategy using ionic liquid modified electrolytes to achieve uniform Zn deposition and long-term stability. Two imidazolium-based ionic liquids, 1-butyl-3-methylimidazolium chloride (BmCl) and 1-butyl-3-methylimidazolium bromide (BmBr), were incorporated to regulate Zn²⁺ solvation structure and interfacial behavior. The imidazolium cation (Bm⁺) exhibits preferential adsorption on the Zn(002) facet, forming a compact protective layer, while halide anions (Cl^-/Br^-) tune Zn²⁺ desolvation and migration kinetics. Combined spectroscopic and theoretical analyses reveal that BmBr possesses a higher desolvation energy and stronger interfacial regulation capability, which effectively promote selective Zn(002) oriented growth and suppress dendrite formation. As a result, Zn||Zn symmetric cells using the BmBr/ZnSO₄ (BmBr/ZSO) electrolyte demonstrate exceptional cycling stability, maintaining performance for over 5000 h at 0.5 mA cm^-2 and 0.5 mAh cm^-2. Furthermore, Zn||NVO full cells exhibit a remarkable specific capacity of 401 mAh g^-1 at 0.1 A g^-1, along with excellent cycling stability. The BmBr/ZSO electrolyte also effectively suppresses self-discharge. This study elucidates the underlying mechanisms of cation-anion driven regulation and presents a broadly applicable approach for developing high-performance, dendrite-free AZIBs.