Cubic FeS2 enabling robust polysulfide adsorption and catalysis in lithium/sulfur batteries

Lithium/sulfur batteries are considered to have great prospects in advanced energy storage devices in the future. However, the shuttling of polysulfides in electrolytes and sluggish electrochemical kinetics of polysulfides hinder the development of lithium/sulfur batteries. To address these stumbling blocks, we introduced cubic pyrite FeS2 modification of Ketjen black@sulfur (FeS2/KB@S) composite that adsorb and provide sufficient sites with polysulfides interaction. The cubic pyrite FeS2 has a pivotal effect on the adsorption and catalysis performance of the polysulfides, which further accelerates the redox kinetics. Consequently, the FeS2/KB@S cathode with 3.1 mg/cm2 sulfur loading attained a high discharge capacity of 0.5 C current density and reversible capacity was 446 mAh/g after 500 cycles. Meanwhile, it also shows excellent rate capability and still maintains a high capacity of 508 mAh/g at 2 C current density. Even at high sulfur loading of 5.1 mg/cm2, the FeS2/KB@S electrode still delivers a high initial area capacity of 4.03 mAh/cm2 at 0.2 C. The cyclic and rate properties of FeS2/KB@S were greatly improved over that of KB@S. The results suggest the multifunction cubic pyrite FeS2 that anchors effectively and catalysis is beneficial to realize the goal of large-scale application for lithium/sulfur batteries.