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

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 ZnSO4 electrolyte enables precise modulation of the distribution and conversion of H2O, SO4 2- and Zn2+ at the Zn interface. This resulting composite interface (ZnF2, ZnS, ZnO, and C─N species) improves Zn2+ 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.