Trans-interfacial distribution of Se vacancies in Bi2Se3 core and carbon nanofiber matrix enables long-lifespan and ultra-stable sodium storage

Abstract

Despite the high capacity of metal selenides (MSes) anode materials for sodium-ion batteries (SIBs), they still face significant challenges, including rapid capacity degradation and slow reaction kinetics. Herein, a novel structure of Bi₂Se₃ nanospheres uniformly embedded in a nitrogen-doped carbon nanofiber matrix (denoted as Bi₂Se_3−x@CNFs) was constructed through a facile fabrication approach involving electrospinning, followed by one-step selenization, demonstrating exceptional performance as an SIB anode. The extremely high mechanical strength and consecutive fibrous structure of carbon fibers effectively alleviate the agglomeration and volume expansion of Bi₂Se₃ particles and ultimately improve stability and service life. Furthermore, the engineered selenium vacancy distribution in both Bi₂Se₃ nanospheres and carbon fiber substrates produces synergistic effects, significantly improves bulk electronic conductivity, and expedites redox reaction kinetics. As expected, the Bi₂Se_3−x@CNFs-600 electrode demonstrates high capacity and exceptional durability (327.8 mAh g⁻¹ after 1000 cycles at 3.0 A g⁻¹ and 284.0 mAh g⁻¹ over 3000 cycles at 5.0 A g⁻¹). It is noteworthy that the assembled Bi₂Se_3−x@CNFs//Na₃V₂(PO₄)₃ full cells demonstrate good rate capability and stability, rendering them a viable option for SIBs.