Surfactant‐Mediated “ Oil‐in‐Water ” Electrolyte Design via Sonochemical Assembly: Low‐Dielectric Interfacial Regulation for Ultrastable Aqueous Zinc Batteries

Aqueous zinc‐metal batteries are plagued by severe performance degradation originating from the Zn anode's instability. Although electrolyte engineering has been widely established as a primary strategy to address this challenge, the utility of numerous promising species is intrinsically limited by their poor aqueous solubility. Herein, a surfactant‐mediated “ oil‐in‐water ” (denoted as SMOW) electrolyte design is proposed to unlock the potential of hydrophobic species. A long‐term stable micellar electrolyte is developed via sonochemically engineered self‐assembly, in which hydrophobic species are encapsulated within the surfactant micelles. Driven by interfacial electrostatic repulsion, these micelles release the hydrophobic species on the zinc anode surface. The enriched interfacial layer acts as an effective low‐dielectric shield, intrinsically accelerating Zn 2+ desolvation while physically isolating the Zn anode from reactive water molecules. Owing to the synergistic effect between the hydrophobic species and the surfactant, highly compact and dendrite‐free Zn deposition with suppressed parasitic side reactions is realized, enabling an ultralong cycling lifespan of over 3900 h for the Zn anode at 10 mA cm −2 . Furthermore, the assembled Zn||I 2 full cells deliver cycling for over 10000 cycles at 5 A g −1 with negligible capacity fading. This work provides a universal paradigm to break through the design constraints of aqueous electrolytes.