Synergistically accelerating capture and catalytic conversion of polysulfides by Co@NCNT-MoSe2 nanocomposite modified separator for advanced Lithium-Sulfur batteries

Abstract

Lithium-sulfur (Li-S) battery with a high theoretical energy density (2600 Wh·kg−1) is considered as a promising energy storage system. However, the shuttle effect and the sluggish redox kinetics of lithium polysulfides (LiPSs) lead to low sulfur utilization. A multifunctional layer modified on separator, as a collaborator of capturer-catalyst-conductor, is be regarded as an effective strategy to solve these problems. Herein, the Co@NCNT-MoSe2 nanocomposite as a modified layer is synthesized with a mesoporous structure by the hydrothermal reaction, in which a large number of transparent MoSe2 nanosheets grow outside NCNT embedded with Co nanoparticles, forming a flower-like outer walls of tube. The modified layer displays the significant features of capturing and catalytic conversion toward LiPSs, attributing to strong adsorption abilities, abundant catalytic active sites, and efficient transferring pathway of electron/Li+. Benefitting from these alluring properties, the results demonstrate that the modified separator offers a high discharge capacity of 983.2 mAh·g−1 at 0.2C after 200 cycles. Even at 2C, after long-term 1000 cycles, it still shows a superb capacity of 725 mAh·g−1 accompanied by a low capacity fading of 0.042 % per cycle. More notably, at 0.2C, the modified separator can realize an ideal areal capacity of 5.24 mAh·cm−2 under high S load (5 mg·cm−2) and poor electrolyte (7.5 μL·mg−1). Therefore, this work will provide a new insight on the development of multifunctional separators to achieve a long-life battery with high sulfur utilization by restraining shuttle effect and accelerate redox kinetics of LiPSs.