Dual‐Domain Coupling‐Driven Interface Remodeling Enables Ultra‐Dilute Flame‐Retardant Electrolytes for High‐Voltage, Wide‐Temperature Batteries

ABSTRACT

The paradigm shift in electrolyte research is a critical driver for performance breakthroughs in sustainable batteries under extreme conditions. Ultra‐dilute electrolytes (UDEs) have attracted extensive attention due to their remarkable cost advantages and broad application prospects, yet excess free solvents cause trade‐offs among high‐voltage stability, wide‐temperature adaptability, longevity, and safety. In this work, we propose a dual‐domain coupling‐driven interface remodeling strategy to tailor bulk solvation and interfacial microenvironments via integrating hierarchically‐solvated carbonate ester, ether, and fluorinated cyclophosphazene. The designed UDE (0.05 M) features a more flexible solvation configuration with less restricted ion transport; concurrently, electric double layers on both electrode surfaces are regulated through molecular competitive adsorption and decomposition under electric field induction. Consequently, cross‐scale microenvironment remodeling is realized to essentially overcome the existing performance limitations. The UDE not only exhibits intrinsic flame retardancy but also significantly improves electrode compatibility (phosphate and oxide cathodes, metal anode) through a bidirectional interface stabilization mechanism. Remarkably, Na _0.67 Ni _0.33 Mn _0.67 O ₂ cathode achieves desirable durability over a wide temperature range (−40∼70°C). Furthermore, this strategy is extended to potassium‐ion batteries, enabling stable operation of KVPO ₄ F cathode at 4.95 V. This work establishes a universal framework for multi‐scale interfacial molecular engineering, offering a promising advancement in extreme energy storage technologies.