Polysulfides anchoring and enhanced electrochemical kinetics of 3D flower-like FeS/carbon assembly materials for lithium-sulfur battery

To suppress the shuttle effect in lithium sulfur battery (Li-S battery), carbon materials are often used to encapsulate sulfur to avoid sulfur and polysulfides dissolution. Meanwhile metal oxide and sulfide are usually used to modify the cathode performance due to the strong chemical interaction with sulfur. In this work, three-dimensional (3D) flower-like carbon assembly materials with FeS decorated are synthesized by a facile solvothermal method. Despite a lower specific surface area, 3D flower-like FeS/carbon assembly materials (FeS/C) show enhanced electrochemical properties than flower-like porous carbon used for lithium-sulfur batteries. Compared with the capacity retention (25.6%) of C-S electrode, the FeS/C-S electrode delivers obvious higher capacity retention of 66.2% after 100 cycles at 0.1 C. Moreover, the electrode shows higher capacity retention when current density is increased. Owing to the strong chemical interactions between FeS and sulfur or polysulfides, polysulfides dissolution is depressed during electrochemical process, causing an enhancement of sulfur utilization. Except as polysulfides anchor, FeS also acts as electrocatalytic active site to promote the conversions of intermediate polysulfides during electrode reactions, thus causing superior rate performance. This study reveals the roles of ferrous sulfide on improving Li-S battery properties, further enriching the research on Li-S battery cathode materials.