High performance sulfur/nitrogen-doped graphene cathode for lithium/sulfur batteries

A sulfur/nitrogen-doped graphene (S/N-G) composite was synthesized by simple sonicated mixing of nanosized sulfur suspension and nitrogen-doped graphene suspension followed by heat treatment. Scanning electron microscopy and energy dispersive spectroscopy mapping showed the formation of a porous structure with uniform distribution of sulfur and nitrogen-doped graphene. Electrochemical performance reveals that the resultant S/N-G composite exhibits a high reversible capacity of 1355 mAh g−1 at the initial cycle, with 823 mAh g−1 remaining after 80 cycles at 0.1 C. Moreover, a reversible capacity of 475 mAh g−1 could still be obtained at 2.5 C. Such an electrochemical performance of S/N-G composite is superior to the graphene counterpart. The enhanced electrochemical performance can be attributed to the introduction of nitrogen-doped graphene with the N functionalization, which provides both a more effective electron conduction path and a stronger physical and chemical confinement setting for elemental sulfur and resident polysulfides.