Ultrafine Sb nanoparticles embedded in nitrogen-doped carbon nanofibers as ultralong cycle durability and high-rate anode materials for reversible sodium storage

Sodium ion batteries (SIBs) have achieved much attention and actively developed. Among possible anode materials of SIBs, nanosized metallic antimony is one of the most promising ones. However, the large volume changes of Sb and insufficient cyclability still remain a huge challenge for the large-scale applications. Herein, the effect of different Sb contents (named as C@Sb, C@Sb-L and C@Sb-H) on electrode performance, morphology, stability, and sodium storage mechanism has been systematically evaluated for the first time by a feasible electrospinning technique. As a result, the as-prepared C@Sb nanofibers exhibit excellent sodium storage performance with high-rate performance of 272.1 mAh g−1 at 20 A g−1, large reversible discharge capacity of 437.6 mAh g−1 after 300 cycles at 1 A g−1 and ultralong cycling life of 4000 cycles at 5 A g−1, such a cycling performance and high-rate capability for the C@Sb anode has rarely been reported. The significantly enhanced performance is ascribed to the synergetic effects between the well-dispersed ultrafine Sb nanoparticles and the N-rich 3D conductive carbon network structure. This homogeneously dispersed structure of ultrafine Sb nanoparticles encapsulated in the carbon network can dramatically improve the volume change and particle aggregation of Sb during ultralong charge/discharge process, thus solving the major problems of pulverization, loss of electrical contact and low utilization rate facing Sb anode. In addition, the full cell of Na3V2(PO4)3@C//C@Sb shows a high output potential of about 2.75 V and a discharge capacity of 264.3 mAh g−1 after 500 cycles at 1 A g−1. Those promising results should provide the basis for the potential large-scale application of Sb-based materials as high-performance anode for SIBs.