Activation of Bulk Li₂S as Cathode Material for Lithium‐Sulfur Batteries through Organochalcogenide‐Based Redox Mediation Chemistry

Abstract

Lithium sulfide (Li₂ S) is considered as a promising cathode material for sulfur-based batteries. However, its activation remains to be one of the key challenges against its commercialization. The extraction of Li⁺ from bulk Li₂ S has a high activation energy (E_a ) barrier, which is fundamentally responsible for the initial large overpotential. Herein, a systematic investigation of accelerated bulk Li₂ S oxidation reaction kinetics was studied by using organochalcogenide-based redox mediators, in which phenyl ditelluride (PDTe) can significantly reduce the E_a of Li₂ S and lower the initial charge potential. Simultaneously, it can alleviate the polysulfides shuttling effect by covalently anchoring the soluble polysulfides and converting them into insoluble lithium phenyl tellusulfides (PhTe-S_x Li, x>1). This alters the redox pathway and accelerates the reaction kinetics of Li₂ S cathode. Consequently, the Li||Li₂ S-PDTe cell shows excellent rate capability and enhanced cycling stability. The Si||Li₂ S-PDTe full cell delivers a considerable capacity of 953.5 mAh g^-1 at 0.2 C.