Chevrel Phase Mo6 S8 Nanosheets Featuring Reversible Electrochemical Li-Ion Intercalation as Effective Dynamic-Phase Promoter for Advanced Lithium-Sulfur Batteries.

Abstract

Modifying sulfur cathodes with lithium polysulfides (LiPSs) adsorptive and electrocatalytic host materials is regarded as one of the most effective approaches to address the challenging problems in lithium-sulfur (Li-S) batteries. However, because of the high operating voltage window of Li-S batteries from 1.7 to 2.8V, most of the host materials cannot participate in the sulfur redox reactions within the same potential region, which exhibit fixed or single functional property, hardly fulfilling the requirement of the complex and multiphase process. Herein, Chevrel phase Mo6 S8 nanosheets with high electronic conductivity, fast ion transport capability, and strong polysulfide affinity are introduced to sulfur cathode. Unlike most previous inactive hosts with a fixed affinity or catalytic ability toward LiPSs, the reaction involving Mo6 S8 is intercalative and the adsorbability for LiPSs as well as the ionic conductivity can be dynamically enhanced via reversible electrochemical lithiation of Mo6 S8 to Li-ion intercalated Lix Mo6 S8 , thereby suppressing the shuttling effect and accelerating the conversion kinetics. Consequently, the Mo6 S8 nanosheets act as an effective dynamic-phase promoter in Li-S batteries and exhibit superior cycling stability, high-rate capability, and low-temperature performance. This study opens a new avenue for the development of advanced hosts with dynamic regulation activity for high performance Li-S batteries.