rGO/g-C3N4 and rGO/g-C3N4/CNT microspheres are synthesized through the simple ethanol-assisted spray-drying method. The ethanol, as the additive, changes the structure of the rGO/g-C3N4 or rGO/g-C3N4/CNT composite from sheet clusters to regular microspheres. In the microspheres, the pores formed by reduced graphene oxide (rGO), g-C3N4, and carbon nanotube (CNT) stacking provide physical confinement for lithium polysulfides (LiPSs). In addition, enriched nitrogen (N) atoms of g-C3N4 offer strong chemical adhesion to anchor LiPSs. The dual immobilization mechanism can effectively alleviate the notorious "shuttle effect" of the lithium-sulfur battery. Meanwhile, the cathode with high cyclic stability can be achieved. The rGO/g-C3N4/CNT/S cathode delivers a discharge capacity of 620 mA h g-1 after 500 cycles with a low capacity fading rate of only 0.03% per cycle at 1 C. Even, the cathode shows a retained capacity of 712 mA h g-1 over 300 cycles with a high sulfur loading (4.2 mg cm-2) at 0.2 C.
Keywords: ethanol-assisted spray drying; high nitrogen content; lithium−sulfur battery; rGO/g-C3N4/CNT microspheres.