Construction of flexible V3S4@CNF films as long-term stable anodes for sodium-ion batteries

Abstract The vanadium sulfides draw comprehensive attention as alternative anode materials for sodium ion batteries (SIBs) owing to their layered structural features and high theoretical capacities, but the unsatisfactory cycle life and rate performance caused by the huge volume change hinder their commercial application. Herein, we fabricate a flexible film with layered V3S4 embedded in carbon nanofiber (V3S4@CNF) via a facile and scalable industrialized electrospinning method followed by the thermal sulfuration. When evaluated as anodes for SIBs, V3S4@CNF delivers brilliant sodium storage performance (400 mAh g−1 at 0.1 A g−1; 185 mAh g−1 at 10 A g−1; capacity retention of 98% after 3500 cycles). Moreover, the assembled full cell performs remarkable capacity of 265 mAh g−1 and superior energy density of 400 Wh kg−1 at 0.1 A g−1. The carbon nanofibers-constructed film supported the integrity of the structure and constructed the cross-linked conductive skeleton to boost the electron transfer and reaction kinetic, and the layered V3S4 in the carbon nanofibers gave the mostly capacity, endowing the excellent sodium storage performance. This work not only provides a casual engineering to devise flexible freestanding electrode, but also designs a high energy density anode with great potential for practical application in SIBs.