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

Abstract 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 mA h 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).