Multifunctional separator modified with catalytic multishelled structural CoS2 enables a stable lithium–sulfur battery†

Abstract

Lithium–sulfur batteries have been considered as promising next-generation energy storage devices due to their ultrahigh theoretical energy density and natural abundance of sulfur. However, the shuttle effect and sluggish redox kinetics of polysulfides hinder their commercial applications. Herein, by combining smart material design and structure engineering, a CoS₂ hollow multishelled structure (HoMS) has been developed to modify the separator and establish a “vice electrode”, which effectively hinders the shuttle effect and catalyzes redox reactions. CoS₂ HoMS can not only obstruct polysulfides through multiple shell barriers but also provide a large available polar surface to effectively capture polysulfides. Additionally, CoS₂ HoMS, with good conductivity, could greatly accelerate the redox conversion of polysulfides and enhance the decomposition of Li₂S. Moreover, CoS₂ HoMS can buffer the large volume change of sulfur during cycling, ensuring good contact and stability of the electrodes. As a result, the lithium–sulfur battery with the CoS₂ HoMS-modified separator exhibited a high discharge capacity of 873.1 mA h g⁻¹ at a high rate of 1 C, with only 0.054% capacity decay per cycle during 350 cycles.