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 in situ-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 in situ-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.