Interconnected Microporous and Mesoporous Carbon Derived from Pitch for Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries receive great attention due to their high theoretical energy density and low cost. However, the sulfur-carbon cathode suffers from the polysulfide dissolution during cycling, and the severe shuttle effect limits the practical application of Li-S batteries. In this work, a carbon material (XU76 carbon) derived from industry-residual petroleum was synthesized with a simple and low-cost method. Nitrogen adsorption, small-angle neutron scattering (SANS), adsorption kinetics, and UV-vis spectroscopy results show that the interconnected micromesopores in XU76 could act as a reservoir and trap polysulfide intermediates efficiently. The XU76 carbon with high surface area (∼1005 m²g^-1), good electric conductivity, good ion transport, and optimized distribution of interconnected micromesopores is used as the sulfur host for trapping polysulfide intermediates and advancing sulfur redox kinetics. The Li-S battery with the sulfur-XU76 carbon cathode gives an initial discharge capacity of ∼1200 mAh g^-1in the initial cycle and reversible capacity of ∼700 mAh g^-1after 100 cycles at a C rate of 0.1 C while the Li-S battery with the sulfur-KB carbon cathode only delivers a discharge capacity of 400 mAh g^-1after 100 cycles. Also, a discharge capacity of 462 mAh g^-1is obtained after 200 cycles at a high C rate (1 C). The detailed reaction mechanism of sulfur-carbon cathodes is systematically studied at high C rates using operando Raman and S K-edge X-ray absorption spectroscopy.