Heteroatom dopings and hierarchical pores of graphene for synergistic improvement of lithium–sulfur battery performance

Lithium–sulfur batteries have attracted wide research interest due to their high specific capacity (1675 mA h g⁻¹) and high specific energy (2500 W h kg⁻¹). Herein, the two-dimensional nitrogen/sulfur synchronous-doped few-layer graphene (N,S-FLG) was prepared by a simple calcination route at 900 °C under an argon atmosphere with g-C₃N₄ as a structural template. The calcination temperature favorably adjusted the doping levels and surface texture of the as-obtained samples. Relying on the synergistic interaction of the structural traits, as the reservoir of sulfur, NS-FLG-900 (calcination temperature 900 °C) can maintain a reversible capacity of 602 mA h g⁻¹ after 300 cycles at a current density of 0.8 A g⁻¹ and 506.4 mA h g⁻¹ after 500 cycles at a current density of 1.6 A g⁻¹. The outstanding performance is obtained due to the synergistic effect of the introduction of N and S into the carbon lattice, the high pore volume (1.31 cm³ g⁻¹) and large specific surface area (460.9 m² g⁻¹).