Propelling Polysulfide Conversion by Defect-Rich MoS Nanosheets for High-Performance Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries have tremendous energy density and are cost effective and environmentally compatible, thereby deemed one of the most promising secondary energy storage systems. However, Li-S batteries present sluggish polysulfide intermediate redox kinetics due to the unavoidable "shuttle effect", thus hindering their industrialization and resulting in low sulfur utilization, rapid capacity fading, poor Coulombic efficiency, and anode corrosion. Herein, the present study updates a one-step hydrothermal method to synthesize a highly efficient sulfur host integrating three-dimensional porous graphene aerogel (GA) with uniformly dispersed defect-rich MoS nanosheets (200-300 nm) (GA-DR-MoS). The electrochemical studies reveal that these MoS nanosheets with abundant defects could provide strong chemical adsorption for polysulfides, as well as act as an electrocatalyst to markedly accelerate polysulfide redox reactions during the charge/discharge process. The resultant GA-DR-MoS composites (70 wt % of sulfur loading) present a high initial discharge capacity of 1429 mAh g at 0.2C, an outstanding cycling stability with a low capacity decay rate of 0.085% per cycle over 500 cycles at 0.2C, and a superior rate performance with an improved capacity from 290 to 581 mAh g at 5C. The presented strategy is effective in achieving high-energy-density Li-S batteries from the point of electrocatalysis and facilitating their practical applications.