Vacuum Pyrolysis Engineered CoSb/C Scaffold for Sodium Metal Anodes with Sodiophilic and Superionic Interphase

Sodium metal anodes are plagued by uncontrolled dendrite growth and electrolyte depletion due to sluggish interfacial ion transport and nonuniform nucleation. Scaffold materials that combine sodiophilic sites with fast lateral diffusion pathways can potentially resolve both issues, yet integrating these two functions into a single architecture remains challenging. Herein, we develop a vacuum pyrolysis strategy to fabricate a hollow CoSb/C scaffold that, upon electrochemical activation, produces sodiophilic Co nanoparticles and a Na₃Sb superionic conductor, effectively suppressing local aggregation and enhancing kinetic reversibility. Cryogenic transmission electron microscopy (Cryo-TEM) observations reveal that the resulting bifunctional interface facilitates the formation of a thin, amorphous, and mechanically robust solid electrolyte interphase (SEI), which remains stable and suppresses electrolyte degradation throughout prolonged cycling. The scaffold delivers a Coulombic efficiency of 99.7% and stable cycling over 1200 h, and Na₃V₂(PO₄)₃-based full cells retain 84% capacity after 1000 cycles at 5 C.