PPy-encapsulated hydrangea-type 1T MoS2 microspheres as catalytic sulfur hosts for long-life and high-rate lithium-sulfur batteries

Abstract

Lithium-sulfur batteries are regarded as promising candidates for next-generation energy storage applications owing to their high theoretical specific capacity, low cost, and eco-friendliness. However, the poor conductivity, large volume variation of sulfur species during the charging/discharging process, complicated conversion reactions of sulfur species, shuttle effect of lithium polysulfide, and low sulfur loading greatly hinder the practical application of lithium-sulfur batteries. In this study, we propose an efficient approach to design polypyrrole (PPy)-encapsulated 1T-MoS2 microspheres with a hydrangea-like structure as catalytic sulfur hosts for lithium-sulfur batteries. The catalytic effect of 1T-MoS2 and the high conductivity of the PPy layer accelerated the adsorption/conversion of lithium polysulfides. The hydrangea-like structure of the 1T-MoS2 microspheres provided adequate number of active sites and sufficient space for sulfur loading. Meanwhile, the specific inter-porous/outer-coating layer structure could also restrain the expansion of sulfur electrode during the electrochemical reaction process. The obtained 1T-MoS2-S@PPy cathode material exhibited outstanding electrochemical performance with an excellent reversible capacity of 1434 mAh g−1 at 0.1C rate, a considerable capacity of 1023 mAh g−1 at 1C rate, and excellent cycling stability for over 800 cycles with a low cycling decay rate of 0.051% per cycle.