CoS2@montmorillonite as an efficient separator coating for high-performance lithium–sulfur batteries

Abstract

The shuttle effect and sluggish redox kinetic of polysulfides still hinder the large-scale application of lithium–sulfur (Li–S) batteries. Herein, we adopt a CoS₂-intercalated/coated-montmorillonite (CoS₂@montmorillonite) composite to work as an efficient separator coating for improving the performance of Li–S batteries. The polar montmorillonite aluminosilicate sheets can efficiently anchor polysulfides and the well-dispersed nano-micron CoS₂ particles can act as electrocatalysts to propel the polysulfide conversion. Furthermore, the modified separator possesses high electrolyte affinity and excellent Li ion transport performance. Consequently, the Li–S cell with the modified separator achieves an outstanding rate performance of up to 7 C (∼446 mA h g⁻¹) and a high initial specific capacity of 1348 mA h g⁻¹ at 0.2 C. It also maintains excellent long-term cycling stability for a reversible capacity of 676 mA h g⁻¹ after 1000 cycles at 2 C with an extremely low decay rate of only 0.025% per cycle. Even with a high sulfur loading of 4.0 mg cm⁻², the cell with the modified separator still delivers satisfactory cycling performance with an areal capacity of 3.41 mA h cm⁻² after 100 cycles at 0.2 C.