Gradient Interphase Engineering Enables Crystallographically Aligned Zinc Anodes for Dendrite-Free Electrochemistry

Rechargeable aqueous zinc-ion batteries (AZIBs) represent promising candidates for sustainable energy storage; yet, their development is fundamentally hindered by irreversible zinc anode degradation stemming from corrosion and sluggish Zn²⁺ deposition kinetics. Herein, to address these challenges, we pioneer zinc hexafluorosilicate hexahydrate (ZnSiF₆·6H₂O, ZSF) as a low-cost, multifunctional electrolyte additive through ion coordination chemistry and interfacial engineering. Comprehensive analyses reveal that ZSF simultaneously reconstructs hydrogen-bond networks to suppress free-water activity and forms a gradient ZnF₂/SiO₂-rich solid electrolyte interphase (SEI). This SEI architecture inhibits parasitic reactions while accelerating [Zn(H₂O)₆]²⁺ desolvation kinetics, reduces nucleation barriers by 46.0%, and enhances Zn²⁺ migration by 115.6%. Consequently, the synergistic effects enable symmetric cells to achieve exceptional cycling stability exceeding 2500 h at 4 mA cm^-2/4 mAh cm^-2, a 23-fold enhancement over baseline electrolytes. Paired with α-MnO₂ cathodes, full cells retain 73.4% capacity after 2000 cycles at 2 A g^-1, significantly outperforming control cells (25.1% retention). This work establishes an atomic-level electrolyte engineering paradigm through functional inorganic additives, paving the way for grid-scale deployable AZIBs.