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 Li2S6 is significantly improved while surface oxidation of FeS2 is inhibited: iron oxide and sulfate, thus avoiding FeS2 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 FeS2 electrocatalytic activity can be improved when Co‐doped FeS2 suppresses surface oxidation and provides a reference for low‐cost separator coating design in pouch batteries.