Effects of physical properties of N-doped carbon on carbon/N-doped carbon/sulfur composite cathodes

Non-polar porous carbon/doped polar carbon composite hosts have been proved effective for sulfur in lithium–sulfur (Li–S) battery. Pores in carbon can adsorb sulfur and Li 2 S, and nitrogen–doped surface shows a stronger affinity for polysulfides through additional chemisorptions. However, how the physical properties of doped carbon, e.g., surface area and porosity, affect the performance of the non-polar carbon/doped polar carbon composite hosts is unknown. Herein, we reported the cotton-derived carbon/porous 1-ethyl-3-methylimidazolium dicyanamide (Emim-dca) derived N-doped carbon, named C/PNC, and the cotton-derived carbon/imporous Emim-dca derived N-doped carbon, named C/NC. The surface area and porosity of the doped polar carbon in C/PNC and C/NC are controlled. The higher surface area of N-doped carbon makes more surface of cotton-derived carbon coated and more sulfur located on the surface of composite hosts. The micro-mesopores in the N-doped carbon can restrain sulfur but shows slow reactive kinetics at a higher current rate. The C/PNC cathode showed a higher discharge capacity of 1100 mAh g −1 than that of 1027 mAh g −1 for the C/NC cathode at 0.1 C and a lower capacity of 208.1 mAh g −1 than that of 349.2 mAh g −1 for C/NC cathode at 2 C.