Improved performance of lithium–sulfur battery with a free-standing cobalt-doped vanadium nitride carbon nanofiber interlayer

Abstract

Lithium–sulfur batteries (LSBs) are considered promising devices for next-generation secondary battery owing to their low cost and high energy density. However, the practical application of LSB is hindered by the sluggish redox kinetics of sulfur and the shuttling effect of polysulfide. To address the above problems, cobalt-doped vanadium nitride/three-dimensional carbon nanofiber (Co-VN/3DNC) composites were synthesized based on non-woven fabrics. The Co-VN/3DNC interlayer can serve as a physical barrier directly for the shuttle effect alleviating in LSBs. The introduction of the Co atom can enrich the d-electron number of VN, improving the catalysis of LSBs redox reaction. The growth of curved carbon nanotubes (CNTs) on the surface of the intermediate layer can expose active adsorption-catalytic sites, accelerating polysulfide redox kinetics for LSBs. The electrochemical performance of the LSB is greatly enhanced by the synergistic effect of Co, VN, and 3DNC. The LSB with Co-VN/3DNC interlayer demonstrate a capacity of 1207.7 mAh g−1 at a current density of 0.1C, and retain a specific capacity of 918.2 mAh g−1 even after 250 cycles. This work provides an effective strategy for the intermediate layers design to improve the electrochemical performance of LSBs.