Co₉S₈ nanoparticles encapsulated in nitrogen-doped mesoporous carbon networks with improved lithium storage properties

We report the designed synthesis of unique Co₉S₈ nanoparticles encapsulated in nitrogen-doped mesoporous carbon networks (Co₉S₈@NMCN nanocomposites). Uniform zeolitic imidazolate framework-67 was first synthesized and then transformed into Co₉S₈@NMCN nanocomposites by thermal annealing with sulfur powders in an Ar atmosphere. The structural and compositional analysis were conducted by employing X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), which show that each Co₉S₈ nanoparticle is well encapsulated in nitrogen-doped carbon layers. When evaluated as an anode material for LIBs, the as-prepared composite electrodes delivered superior capacity, excellent cycling stability and rate capability, which are attributed to the advantageous structural features.