CoSe2@C-N/CNT-modified separator for highly efficient lithium-sulphur battery

Abstract Lithium-sulfur battery has been seen as one of the most promising energy storage devices because of its peculiar features such as high energy density, low cost, and environment friendliness. However, the relatively poor cycle stability caused by the shuttle effect of polysulfides (PS) severely limits its further application. The functional modification of separator has been proved to be a meaningful method to improve its cycle stability. Herein, CoSe2@C-N/CNT is synthesized by in-situ growth of carbon nanotubes (CNTs) using metal-organic framework (MOF) as a catalyst and followed by further selenization reaction. Due to its high specific surface area, porous structure and abundant bonding sites, the PS can be effectively captured and also be reversibly released owing to the cross-electron transport network composed of CNTs. Therefore, the lithium-sulfur battery exhibits an excellent performance after its separator is coated and modified by CoSe2@C-N/CNT. The initial discharge capacity of 1224 mA h g−1 can be obtained at 0.5 C current density and the capacity of 975 mA h g−1 after 150 measuring cycles, and furthermore the capacity retention rate can reach 79.7%. Even at 3.0 C high current density, it can still exhibit 798 mA h g−1 initial discharge capacity.