Solvation-programmed hybrid interphase enables durable aqueous zinc-metal batteries

Aqueous zinc-metal batteries (AZMBs) are promising candidates for next-generation energy storage because of their low cost, environmental compatibility, and intrinsic safety. However, their practical application is constrained by the limited reversibility of Zn metal anodes, which arises from parasitic hydrogen evolution, interfacial alkalization, corrosion, and nonuniform Zn deposition. Here, diammonium succinate ((NH₄)₂C₄H₄O₄, denoted as DS) is introduced as a multifunctional additive into a zinc acetate electrolyte to establish a coupled solvation-pH-interphase regulation strategy. Distinct from previously reported succinate-based additives mainly investigated in sulfate-containing electrolytes, DS exhibits complementary ionic functions in the acetate-based electrolyte. Succinate anions (C₄H₄O₄^2-) weakly participate in the near-range coordination environment of Zn²⁺, reorganizing the surrounding hydrogen-bond network, and preferentially adsorb at the Zn surface, thereby moderately redistributing the solvation structure and regulating interfacial Zn deposition. Meanwhile, NH₄⁺ neutralizes OH^- generated by parasitic water reduction and helps maintain the electrolyte pH near 5.68 during polarization, mitigating local alkalization and associated side reactions. Molecular dynamics simulations and interfacial characterizations further indicate that the cooperative action of DS and the zinc acetate electrolyte promotes the in situ formation of an inorganic/organic hybrid interphase containing ZnCO₃, ZnO, Zn(CN)₂, and amorphous organic species. This chemically heterogeneous interphase regulates Zn²⁺ transport, suppresses interfacial parasitic reactions, and facilitates more uniform Zn deposition, although progressive interfacial evolution is not completely eliminated during extended cycling. Consequently, Zn||Zn symmetric cells operate stably for over 1200 h, while Zn||I₂ full cells retain stable cycling for 6000 cycles at 2 A g^-1. This work reveals the distinct yet complementary roles of NH₄⁺ and succinate anions in a zinc acetate electrolyte and provides an electrolyte-specific route for constructing hybrid interphases toward highly reversible aqueous Zn anodes.