Three-dimensional nitrogen-doped graphene/sulfur composite for lithium-sulfur battery

A three-dimensional nitrogen-doped graphene/sulfur composite (NGS3) was synthesized by a simple hydrothermal method using urea as the nitrogen source and subsequent thermal treatment. The structure and electrochemical performance of the prepared nitrogen-doped graphene/sulfur composite (NGS3) were confirmed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), Energy dispersive spectroscopy mapping (EDS), and galvanostatic charge/discharge measurements. SEM and EDS mapping show that NGS3 exhibits a porous structure with uniform distribution of sulfur. Compared with the graphene/sulfur composite (NGS1), NGS3 delivers an outstanding rate capability with 1501, 1278, 1136, and 1024 mAh g−1 at 200, 400, 800, and 1000 mA g−1, respectively, and the cycle stability of NGS3 is also wonderful, a reversible discharge capacity of 1330 mAh g−1 is obtained after 80 cycles under the current rate of 200 mA g−1. The wonderful electrochemical performance could be attributed to the special three-dimensional conductive structure with the help of nitrogen atom.