Suitable polysulfides adsorption and conversion on MoSe2@g-C3N4 interlayer for advanced lithium-sulfur batteries

The shuttle effect of lithium polysulfides (LiPS) and sluggish redox kinetic still restrict the commercial application of lithium-sulfur batteries (LSBs). Developing the modified functional separators that block the migration of LiPS and accelerate the LiPS conversion is an effective method to solve both problems. Here we report a MoSe2@g-C3N4 composite material with the merits of strong adsorption in g-C3N4 and appropriate migration in MoSe2 for LiPS simultaneously achieved on the surface. g-C3N4 has strong adsorption for LiPS while MoSe2 with a low migration barrier of LiPS and improves their conversion into solid-state Li2S. The excellent wettability of MoSe2@g-C3N4 facilitates electrolyte migration and improves the electrochemical performance. With a MoSe2@g-C3N4 interlayer delivered 2.2 times increase initial capacity than that with a conventional polypropylene (PP) separator at 0.5C, and a low-capacity decay per cycle of 0.09 % was achieved at 0.5C after 500 cycles. It showed the best rate capability of 564.2 mA h g(-1) at 3C. Even under the high sulfur loadings of 3.2 and 4.0 mg cm(-2), showing high initial capacity and decent capacity retention. This project provides a novel insight into designing the functional separators with the g-C3N4 substrate composites for stable LSBs.

Automated summary

A MoSe2@g-C3N4 composite material with strong adsorption capability and appropriate migration behavior for lithium polysulfides was developed as a functional separator, effectively solving the shuttle effect and sluggish redox kinetic issues in lithium-sulfur batteries.