Spatially confined dual-alloy components SnBi@SbBi nanofibers for fast-charging and stable sodium-ion batteries

Alloy-type anodes with high theoretical capacity are attractive for sodium-ion batteries (SIBs), yet their practical application is still severely hindered by drastic volume variation and sluggish reaction kinetics, especially under fast-charging condition. Herein, we report a coaxial binary nanofiber architecture (BiSn@BiSb @CNFs) fabricated via coaxial electrospinning followed by carbothermic reduction. This unique structure establishes a radially differentiated dual-alloy configuration, featuring Sn- and Sb-regions bridged by a continuous Bi bridge within a one-dimensional conductive carbon matrix. Benefiting from the Bi-regulated binary dual-alloy system, the fabricated BiSn@BiSb@CNFs electrodes exhibit pseudocapacitive-dominated sodium storage property with reduced polarization and accelerated Na + diffusion kinetics. Subsequently, the fabricated BiSn@BiSb@CNFs electrodes deliver prominent rate capability and ultralong cycling stability, retaining specific capacity of 306.9 mAh g −1 after 6000 cycles at 5 A g −1 , significantly outperforming Bi-free Sn@Sb@CNFs counterparts. Moreover, a full cell paired with a Na 3 V 2 (PO 4 ) 3 cathode demonstrates promising fast-charging performance, highlighting the potential of dual binary alloy engineering for advanced SIB anodes.