Design of advanced separators for high performance Li-S batteries using natural minerals with 1D to 3D microstructures

Lithium-sulfur (Li-S) batteries are of great interest due to their high energy density. However, polysulfides shuttle and low S loading severely impede their practical applications. Here, we report design of advanced separators for Li-S batteries using natural minerals with 1D to 3D microstructures. Four natural minerals with different microstructures including 1D halloysite nanotubes, 1D attapulgite nanorods, 2D Li+-montmorillonite (Mmt) nanosheets and 3D porous diatomite were used together with carbon black (CB) for preparation of the mineral/CB-Celgard separators. The Si-OH groups of the minerals act as Lewis acid sites, which could effectively absorb polysulfides by forming LiO and OS bonds with polysulfides. Among all the separators, the Mmt/CB-Celgard separator endowed the Li-S battery with the highest upper plateau discharge capacity (369 mA h g-1), initial reversible capacity (1496 mA h g-1 at 0.1 C), rate performance and cycling stability (666 mA h g-1 after 500 cycles at 1.0 C with 0.046% capacity decay per cycle). The Mmt/CB-Celgard separator also enabled stable cycling of the Li-S battery with high S loading (8.3 mg cm-2) cathode. This work will provide inspiration for future development of advanced separators for high-energy-density Li-S batteries.