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

Lithium-sulfur (Li-S) batteries receive great attentiondue to their high theoretical energy density and low cost. However, thesulfur-carbon cathode suffers from the polysulfide dissolution duringcycling, and the severe shuttle effect limits the practical application ofLi-S batteries. In this work, a carbon material (XU76 carbon) derivedfrom 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 showthat the interconnected micromesopores in XU76 could act as areservoir and trap polysulfide intermediates efficiently. The XU76carbon with high surface area (similar to 1005 m2g-1), good electricconductivity, good ion transport, and optimized distribution ofinterconnected micromesopores is used as the sulfur host for trappingpolysulfide intermediates and advancing sulfur redox kinetics. The Li-S battery with the sulfur-XU76 carbon cathode gives aninitial discharge capacity of similar to 1200 mAh g-1in the initial cycle and reversible capacity of similar to 700 mAh g-1after 100 cycles at a C rateof 0.1 C while the Li-S battery with the sulfur-KB carbon cathode only delivers a discharge capacity of 400 mAh g-1after 100cycles. Also, a discharge capacity of 462 mAh g-1is obtained after 200 cycles at a high C rate (1 C). The detailed reactionmechanism of sulfur-carbon cathodes is systematically studied at high C rates usingoperandoRaman and SK-edge X-ray absorptionspectroscopy.