Titanium-Containing Metal–Organic Framework Modified Separator for Advanced Lithium–Sulfur Batteries

The shuttling of polysulfide intermediates (Li2Sn, 2 < n ≤ 8) and the dendrite growth on the Li-metal surface have blocked the practical applications of lithium–sulfur (Li–S) batteries. Functionalizing the separator provides a straightforward approach to address these issues. Herein, we demonstrate a multifunctional MIL-125(Ti)-modified polypropylene/polyethylene separator for advanced Li–S batteries. The MIL-125(Ti), a Ti-containing metal–organic framework (MOF), features an open-skeleton construction, a high intrinsic microporosity and a Lewis acid characteristic. Compared with pristine separator, that with MIL-125(Ti) coating shows better electrolyte wettability and less resistance. The unique coating layer acts as an effective physical and chemical barrier region to capture polysulfide species without affecting the smooth transport of Li+. Meanwhile, the highly ordered micropores with a diameter of ∼1.5 nm in the MOFs guide in a homogeneous Li+ plating and thereby inhibit lithium dendrites. Consequently, the MOF-modified separator enables a significantly improved cycling stability and rate capability of the Li–S battery. The capacity retention of over 60% at 0.2 C (1 C = 1675 mA g–1) upon 200 cycles and a specific capacity of 612 mAh g–1 at 2 C is realized. The facile approach offers an effective pathway toward high-performance Li–S batteries.