Interfacial Sodiopobicity Regulating for Dendrite-Free Solid-State Sodium Metal Batteries

High interfacial thermodynamic and contact stabilities are two key factors to suppress dendrite growth in solid-state sodium metal batteries (SSSBs). However, a thermodynamical stable interface often features with sodiophobic character to aggravate interfacial contact affinity, thus making the two key factors paradox with each other. Herein, a new strategy is reported to resolve the intrinsic contradictions between high sodiophobicity and interfacial contacts with a “kinetic-driven alloy sinking” process. Specifically, the sodiophilic and electronic conductive alloy (e.g., KNa₂) is spontaneously “sunk” into bulk Na metal, thus remaining a sodiophobic/ionic conductive but intimately contacted interface (e.g., NaF). Unlike conventional concept of sodiophilic interface, this work demonstrates the advantage of sodiophobic modification with an in situ formed ionic conductive interphase, which establishes a foundational distinction from prior literatures. Consequently, an ultrahigh time-constant mode critical current density (CCD) of 4.0 mA cm⁻² is achieved, surpassing the state-of-the-art values in existing literature. The fundamental understanding on interfacial sodiophobicity and conduction types of interphases will provide new insight for designing high-performance SSSBs.