Anion-endowed high-dielectric water-deficient interface towards ultrastable Zn metal batteries

To achieve reversible metallic Zn anodes for aqueous rechargeable zinc batteries, regulating the electrolyte-Zn interface is the key to addressing the side reactions on Zn. Beyond water-deficiency, design rules for constructing the highly efficient electrochemical interface are still vague. Anions, as primary electrolyte constituents, not only play a role in solvation structure, but also influence the electrolyte-Zn interface. Here, the characteristics of representative anions in current aqueous zinc electrolytes are surveyed. A candidate combining polarizability, H-bond tuning ability and high solubility is proposed to construct a high-dielectric water-deficient electrolyte-Zn interface to regulate the interfacial chemistry on Zn. The anion-dominated electrochemical interface promotes the Zn deposition kinetics and achieves uniform Zn deposition with high stability, which further enables the in situ formation of an SEI for highly stable Zn stripping/plating, e.g., at 20 mA cm^-2 and 20 mA h cm^-2. Furthermore, this built-in interface exhibits an effect in stabilizing the V₂O₅ cathode, endowing the V₂O₅/Zn cell with ultra-stable long-term cycling, e.g., 10 000 cycles at 10 A g^-1 with a high retention rate of 89.7%. Our design offers insight into guidelines for the development of novel electrolytes towards rationally designed electrochemical interfaces.