Sulfur-infiltrated yeast-derived nitrogen-rich porous carbon microspheres @ reduced graphene cathode for high-performance lithium-sulfur batteries

The defects of polysulfide dissolution and sulfur insulating causes in Li-sulfur batteries have effectively diminished by immobilizing sulfur in porous carbon microspheres via the interactions of doping-nitrogen and encapsulating-reduced graphene. The nitrogen-rich porous carbon microspheres were prepared by using yeast as natural precursor and high content of nitrogen (up to 8.52%) doped carbon microspheres was confirmed by the elemental analysis. As cathode for lithium-sulfur batteries, the rGO@HYC/S composite exhibits a high retention capacity of 921 mA h g−1 at 0.2 C and 675 mA h g−1 at 1 C over 200 cycles. The battery delivers low capacity decay rate of 0.09% and stable coulombic efficiency about 98% at 1 C during the 200 cycles. Further, we reveal that the enhanced electrochemical performance is ascribed to a hollow porous structure of carbon framework for sulfur storage, carbon matrix exerted by nitrogen-doping for polysulfide adsorption, rGO wrapper for polysulfide interception and conductivity improvement.