Amorphous Vanadium Oxide Nanoparticle-Impregnated Three-Dimensional Reduced Graphene Oxide and Nitrogen-Doped Carbon Nanotubes Composite Microspheres as Functional Interlayers for Lithium–Sulfur Batteries

Herein, amorphous vanadium oxide (a-VO_x) nanoparticle-impregnated three-dimensional (3D) microspheres comprising highly conductive and porous reduced graphene oxide (rGO) and nitrogen-doped carbon nanotubes (N-CNTs) framework (a-VO_x@rGO-N-CNTs) were designed as functional interlayers for lithium–sulfur batteries (LSBs). N-CNTs were successfully formed on the rGO sheet surfaces, uniformly distributed between rGO and mesopores, via the catalytic effect of metallic Co–Fe. The rGO and N-CNTs framework not only provided an additional pathway for electron transport but also improved structural durability of the electrode materials. Moreover, polar a-VO_x nanoparticles involved within the conduction pathway offered numerous chemisorption sites for anchoring polysulfides, thereby improving the utilization of active materials. The cell employing a-VO_x@rGO-N-CNTs-coated separator as a functional interlayer exhibited excellent rate capabilities (473 mA h g⁻¹ at 1.5 C) and cycling performance (800 cycles at 1.0 C and an average decay rate of 0.09% per cycle) at high C-rate. This outstanding performance was mainly ascribed to the synergistic effects of rGO, N-CNTs framework, and polar a-VO_x nanoparticles. The design strategy proposed in this study offers insights into the development of porous and conductive nanostructures for extensive energy storage applications including LSBs.