Anchoring Antimony Single Atoms into Carbon Shells via Vacuum Pyrolysis as Advanced Sodium Host

The sodium (Na) metal anode suffers from uncontrolled dendrite growth and an unstable solid-electrolyte interphase (SEI), especially when high areal capacity is required. Herein, we have developed a multifunctional Na host, nitrogen-doped carbon shells anchored with antimony single atoms (SbSA-NC). The host is prepared via vacuum pyrolysis of polypyrrole-coated Sb₂O₃, during which sublimated Sb₂O₃ is partially captured by the carbonized polymer shells in the form of single atoms. During multiscale monitoring and electrochemical measurements, SbSA-NC demonstrates the ability of inhibiting dendrite growth, reducing nucleation overpotential, and enabling the half-cells to achieve an average Coulombic efficiency above 99.9% for over 2000 cycles. The excellent performance of SbSA-NC, as revealed by Cryo-TEM analysis, is correlated with the conformal and uniform SEI with abundant NaF or the rather good mechanical and chemical stability of the SEI. When paired with Na₃V₂(PO₄)₃ cathodes, full cells achieve 84% capacity retention after 5000 cycles at 5 C.