Suppressing Polysulfide Shuttle and Boosting Reaction Kinetics via UiO-66-SH-Functionalized Separators for Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries represent promising energy storage devices by virtue of their ultrahigh theoretical energy density, yet their practical deployment is severely impeded by the polysulfide shuttle, sluggish sulfur redox kinetics, and progressive degradation of lithium anodes. Herein, we design a thiol-functionalized UiO-66 (UiO-66-SH)-coated polypropylene separator that addresses these challenges simultaneously. The UiO-66-SH combines abundant coordinatively unsaturated Zr sites and -SH groups, enabling both strong chemical anchoring of lithium polysulfides and catalytic acceleration of their conversion to Li₂S. The modified separator exhibits superior electrolyte wettability, a high Li⁺ transference number (0.76), and enhanced ionic conductivity. Furthermore, it regulates lithium deposition to achieve a dendrite-free anode and mitigates polysulfide-induced corrosion. Consequently, Li–S cells incorporating UiO-66-SH/PP separator deliver an initial discharge capacity of 821.3 mAh g⁻¹ at 1 C, retain 521 mAh g⁻¹ after 500 cycles, and achieve a high-rate capacity of 590.9 mAh g⁻¹ at 5 C. Even under a high sulfur loading of 5.05 mg cm⁻², a reversible capacity of 620.1 mAh g⁻¹ is maintained after 200 cycles. This work offers a rational design of a multifunctional MOF-based separator that integrates polysulfide entrapment, catalytic conversion, and anode protection, paving the way toward high-performance, long-life Li–S batteries.