Cooperative chemisorption of polysulfides via 2D hexagonal WS₂-rimmed Co₉S₈ heterostructures for lithium–sulfur batteries

Many heterostructures containing two types of strong polar bonds were often designed to synergistically increase the chemical confining for soluble lithium polysulfide in lithium-sulfur batteries (LSBs). To make maximum use of the two chemical interactions on confining the polysulfides, a novel structure of 2D hexagonal WS₂-rimmed Co₉S₈ heterostructure nanoflakes was designed on the surface of carbon nanofiber (CNF) skeletons via a simple technique. The composite nanoflakes are ~50 nm in diameter and ~5 nm in thickness, and comprised of a ~40-nm Co₉S₈ core and a 3–4 WS₂ edge. In this design, the Co₉S₈ core and WS₂ edge can confine the polysulfides and catalyze the electrochemical progresses at the same time. Electrochemical tests indicated that the CNF@WS₂@Co₉S₈-S cathodes show a high capacity (1175 mAh g⁻¹ at 0.1 C), an excellent rate capability (keep 77.85% at 2.0 C), and a superior cycling stability (a low decay rate of 0.061% per cycle at 2.0 C, even lower at 7.0 C and 12.0 C).