Suppressing Surface Oxidation of Pyrite FeS2 by Cobalt Doping in Lithium Sulfur Batteries

Abstract Lithium–sulfur batteries have emerged as a promising energy storage device due to ultra‐high theoretical capacity, but the slow kinetics of sulfur and polysulfide shuttle hinder the batteries' further development. Here, the 10% cobalt‐doped pyrite iron disulfide electrocatalyst deposited on acetylene black as a separator coating in lithium‐sulfur batteries is reported. The adsorption rate to the intermediate Li 2 S 6 is significantly improved while surface oxidation of FeS 2 is inhibited: iron oxide and sulfate, thus avoiding FeS 2 electrocatalyst deactivation. The electrocatalytic activity has been evaluated in terms of electronic resistivity, lithium‐ion diffusion, liquid‐liquid, and liquid‐solid conversion kinetics. The coin batteries exhibit ultra‐long cycle life at 1 C with an initial capacity of 854.7 mAh g −1 and maintained at 440.8 mAh g −1 after 920 cycles. Furthermore, the separator is applied to a laminated pouch battery with a sulfur mass of 326 mg (3.7 mg cm −2 ) and retained the capacity of 590 mAh g −1 at 0.1 C after 50 cycles. This work demonstrates that FeS 2 electrocatalytic activity can be improved when Co‐doped FeS 2 suppresses surface oxidation and provides a reference for low‐cost separator coating design in pouch batteries.