A sulfur–carbon composite for lithium/sulfur battery based on activated vapor-grown carbon fiber

► Longitudinally opened VGCF with a porous structure was prepared by KOH activation.
► The interconnected fibrous composites construct a network-like structure by nature.
► Fibrous VGCF contributes to the enhancement of active material utilization.
► Pores in a VGCF matrix help to disperse sulfur and absorb polysulfides.

A sulfur–carbon composite based on vapor-grown carbon fiber (VGCF) is synthesized for lithium/sulfur batteries by potassium hydroxide (KOH) activation and melt-diffusion strategy. The sulfur-activated VGCF (S–aVGCF) composites were characterized by field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and N2 adsorption/desorption measurements. It is found that VGCF treated by KOH activation is longitudinally opened and presents a porous structure, and sulfur is embedded into the pores of an aVGCF network-like matrix after a melt-diffusion process. The S–aVGCF composite cathode exhibits better electrochemical reversibility, higher active material utilization and less severe polysulfide shuttle than both a pristine sulfur cathode and a S–raw VGCF composite cathode because of excellent conductivity, and the fibrous and porous structure of the aVGCF matrix.