Synergistic Ion Transport and Spatial Confinement in Sb‐Embedded Hollow Carbon Nanofibers for Stable Na Metal Anodes

ABSTRACT Sodium metal anodes (SMAs) are pivotal for developing high‐energy‐density sodium metal batteries (SMBs) but are plagued by uncontrollable dendrite growth and unstable solid‐electrolyte interphases (SEI). While 3D core‐shell hosts can mitigate these issues, these conventional designs often lack active control over ion transport and involve complex syntheses. Herein, we develop an sodiophilic 3D Sb‐embedded hollow carbon nanofiber (Sb@HCF) host via electrospinning and wet etching approach. Combining in situ characterizations and theoretical simulations, it was clearly verified that the in situ formed Na‐Sb alloy not only guides uniform Na deposition but also serves as Na + transport highways, thereby significantly suppressing Na dendrite and promoting the formation of a robust NaF‐rich SEI. As a result, the Na||Sb@HCF delivers an exceptional Coulombic efficiency of 99.88% over 1400 cycles at 4 mA cm −2 /4 mAh cm −2 , and the symmetric cells simultaneously operate steadily over 1200 h at 10 mA cm −2 /2 mAh cm −2 , achieving a superior cumulative plating capacity of 6 Ah cm −2 . Moreover, the Na@HCF||Na 3 V 2 (PO 4 ) 3 @C full cell retains a capacity of 84.10 mAh g −1 with a Coulombic efficiency of 98.05% even after 1000 cycles. Our strategy paves a promising way for for stabilizing SMA and developing high‐energy‐density SMBs.