Hierarchical V₃S₄/C nanofibers with fast kinetics for superior alkali metal batteries

Owing to the numerous benefits, including low cost and great theoretical capacity, V₃S₄ has been a research hotspot for Li⁺/Na⁺/K⁺ storage. Nonetheless, the V₃S₄ electrode with long cycling stability and high specific capacities continues to pose significant challenges. In this work, vacuum vulcanization is combined with electrospinning to synthesize V₃S₄/C composite nanofibers (V₃S₄@CNF). The study finds out that many nanosheets attach to the surface of the nanofibers following vulcanization, and the surface becomes rougher. This allows V₃S₄@CNF to create exterior defects, which improves Li⁺/Na⁺/K⁺ transport and increased electrochemical active sites. The result shows that the V₃S₄@CNF electrode can retain the capacities of 291.3 mAh·g⁻¹ (at the 1000th cycle) and 241.9 mAh·g⁻¹ (at the 2400th cycle) at 5 A·g⁻¹ for Li⁺/Na⁺ storage, respectively, indicating exceptional cyclic stability. A great potential in practical application is also exhibited, where the full cell based on Na₃V₂(PO₄)₃/C(NVP/C)//V₃S₄@CNF can maintain a reversible capacity of 114 mAh·g⁻¹ after 200 cycles at 1 A·g⁻¹. Furthermore, the V₃S₄@CNF electrode has a discharge specific capacity of 270.7 mAh·g⁻¹ at the 600th cycle at 1 A·g⁻¹ for potassium-ion batteries. This research can serve as a solid foundation for the ultimate development of alternative sulfide-treated electrode materials for high-performance Li⁺/Na⁺/K⁺ storage.