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

Abstract

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 m2 g–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–1 in the initial cycle and reversible capacity of ∼700 mAh g–1 after 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–1 after 100 cycles. Also, a discharge capacity of 462 mAh g–1 is 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.