Enhancing electrochemical conversion of lithium polysulfide by 1T-rich MoSe2 nanosheets for high performance lithium–sulfur batteries

Abstract

The sluggish conversion kinetics and shuttle effect of lithium polysulfides (LiPSs) severely hamper the commercialization of lithium–sulfur batteries. Numerous electrocatalysts have been used to address these issues, amongst which, transition metal dichalcogenides have shown excellent catalytic performance in the study of lithium–sulfur batteries. Note that dichalcogenides in different phases have different catalytic properties, and such catalytic materials in different phases have a prominent impact on the performance of lithium–sulfur batteries. Herein, 1T-phase rich MoSe2 (T-MoSe2) nanosheets are synthesized and used to catalyze the conversion of LiPSs. Compared with the 2H-phase rich MoSe2 (H-MoSe2) nanosheets, the T-MoSe2 nanosheets significantly accelerate the liquid phase transformation of LiPSs and the nucleation process of Li2S. In-situ Raman and X-ray photoelectron spectroscopy (XPS) find that T-MoSe2 effectively captures LiPSs through the formation of Mo-S and Li-Se bonds, and simultaneously achieves fast catalytic conversion of LiPSs. The lithium–sulfur batteries with T-MoSe2 functionalized separators display a fantastic rate performance of 770.1 mAh/g at 3 C and wonderful cycling stability, with a capacity decay rate as low as 0.065% during 400 cycles at 1 C. This work offers a novel perspective for the rational design of selenide electrocatalysts in lithium–sulfur chemistry.