Dynamic phase evolution of MoS3 accompanied by organodiselenide mediation enables enhanced performance rechargeable lithium battery

Abstract

Considerable efforts have been devoted to Li-S batteries, typically the soluble polysulfides shuttling effect. As a typical transition metal sulfide, MoS2 is a magic bullet for addressing the issues of Li-S batteries, drawing increasing attention. In this study, we introduce amorphous MoS3 as analogous sulfur cathode material and elucidate the dynamic phase evolution in the electrochemical reaction. The metallic 1T phase incorporated 2H phase MoS2 with sulfur vacancies (SVs-1T/2H-MoS2) decomposed from amorphous MoS3 achieves refined mixing with the "newborn" sulfur at the molecular level and supplies continuous conduction pathways and controllable physical confinement. Meanwhile, the insitu-generated SVs-1T/2H-MoS2 allows lithium intercalation in advance at high discharge voltage (≥1.8 V) and enables fast electron transfer. Moreover, aiming at the unbonded sulfur, diphenyl diselenide (PDSe), as a model redox mediator is applied, which can covalently bond sulfur atoms to form conversion-type organoselenosulfides, changing the original redox pathway of "newborn" sulfur in MoS3, and suppressing the polysulfides shuttling effect. It also significantly lowers the activation energy and thus accelerates the sulfur reduction kinetics. Thus, the insitu-formed intercalation-conversion hybrid electrode of SVs-1T/2H-MoS2 and organoselenosulfides realizes enhanced rate capability and superior cycling stability. This work provides a novel concept for designing high-energy-density electrode materials.