Programming Ion‐Engineered Interphase for Practical Zinc Batteries Through Exogenous Cation‐Anion Synergy Chemistry

ABSTRACT A stable anode‐electrolyte interface is vital for battery cycling. Translating the successful anion‐derived interphase paradigm from Li‐ion to aqueous Zn‐ion batteries (ZIBs) is hindered by narrow electrochemical windows and chaotic interfacial reactions. Here we overcome this by programming interphase formation via exogenous cation–anion synergy. Hydrolysable anions drive the rapid formation of an inorganic‐rich interphase, while weakly hydrated bulky cations with low ionic potential ( φ ) dually function as noncorrosive electrostatic shields and field‐driven anion receptors to dynamically regulate the interfacial environment without parasitic reactions. As a proof of concept, importing tetramethylfluorourea hexafluorophosphate into ZnSO 4 electrolyte enables precise modulation of the distribution and conversion of H 2 O, SO 4 2− and Zn 2+ at the Zn interface. This resulting composite interface (ZnF 2 , ZnS, ZnO, and C─N species) improves Zn 2+ transport, and promotes uniform deep Zn deposition. As a result, Zn//Zn cells operate for 3400 h at 1 mA cm −2 and 1 mAh cm −2 , for 1800 h at 5 mA cm −2 and 5 mAh cm −2 , and for 410 h at a depth of discharge of 42.7%. Zn//KVO full cells and pouch cells also show improved cycling stability. These results establish exogenous cation‐anion pairing as a practical route for ZIB interphase engineering.