Synthesis of S/CoS2 Nanoparticles-Embedded N-doped Carbon Polyhedrons from Polyhedrons ZIF-67 and their Properties in Lithium-Sulfur Batteries

S/CoS2 nanoparticles-embedded N-doped carbon polyhedrons (S/CoS2-NC) as the cathode of lithium-sulfur battery are prepared. The synthesis is via the carbonization of metal organic frameworks polyhedron ZIF-67, followed by the heat treatment with sulfur. XRD confirms the existence of CoS2 and S, TEM shows the polyhedrons morphology and EDX mapping analysis displays the uniform distribution of Co, S and N in the carbon polyhedrons. As cathode for lithium-sulfur battery, S/CoS2-NC exhibit the enhanced cycling stability with the capacity of 702 mA h g−1 at 0.5C after 250 cycles and rate performance, which is superior to S/Co nanoparticles-embedded N-doped carbon polyhedrons composites (S/Co-NC), S/N-doped carbon polyhedrons composites (S-NC) and the bare sulfur. When coupled with the Ge anode, the discharge capacity of 502 mA h g−1 is obtained after 75 cycles at 0.5C. The enhanced property is mainly attributed to the synergistic effects of N-doped carbon polyhedrons and embedded CoS2.