Unlocking Anode‐Free Sodium Metal Batteries Via Solvent Co‐Insertion Mediated In Situ Sodiophilic Interface Engineering

Anode‐free sodium metal batteries hold significant promise for high‐energy‐density storage but face critical challenges related to sodium deposition dynamics and interfacial instability. Traditional approaches, such as alloy‐based current collectors or fluorinated interfaces, often suffer from irreversible volume expansion or corrosive fabrication processes. This study introduces a solvent co‐intercalation‐mediated in situ sodiophilic interface engineering strategy to overcome these limitations. A graphitized carbon‐modified aluminum current collector dynamically regulates interfacial evolution through solvated sodium‐ion co‐intercalation during initial cycling, prompting the formation of a C‐NaF interface with ultralow Na + adsorption energy. This sodiophilic interface not only facilitates uniform sodium nucleation by providing abundant sodium‐philic sites but also encourages the preferential decomposition of anions in the electrolyte, leading to the creation of a robust and NaF‐rich solid electrolyte interphase. Consequently, the asymmetric half‐cell delivers an ultralow nucleation overpotential (9.7 mV at 0.5 mA cm −2 ) and maintains an average coulombic efficiency of 99.8% over 400 cycles at 1 mA cm −2 . When combined with a Na 3 V 2 (PO 4 ) 2 O 2 F (NVPOF) cathode, the full cell achieves an energy density of 363 Wh kg −1 with 80% capacity retention after 250 cycles at 0.5 C. This work integrates molecular‐level dynamic interfacial engineering with macroscopic electrochemical stability, providing a scalable industrial solution for next‐generation battery systems.