Synergistic Effect of Bimetallic MOF Modified Separator for Long Cycle Life Lithium‐Sulfur Batteries

Abstract

AbstractSevere polysulfide dissolution and shuttling are the main challenges that plague the long cycle life and capacity retention of lithium‐sulfur (Li‐S) batteries. To address these challenges, efficient separators are designed and modified with a dual functional bimetallic metal‐organic framework (MOF). Flower‐shaped bimetallic MOFs (i.e., Fe‐ZIF‐8) with nanostructured pores are synthesized at 35 °C in water by introducing dopant metal sites (Fe), which are then coated on a polypropylene (PP) separator to provide selective channels, thereby effectively inhibiting the migration of lithium polysulfides while allowing homogeneous transport of Li‐ions. The active sites of the Fe‐ZIF‐8 enable electrocatalytic conversion, facilitating the conversion of lithium polysulfides. Moreover, the developed separator can prevent dendrite formation due to the uniform pore size and hence the even Li‐ion transport and deposition. A coin cell using a Fe‐ZIF‐8/PP separator with S‐loaded carbon cathode displayed a high cycle life of 1000 cycles with a high initial discharge capacity of 863 mAh g−1 at 0.5 C and a discharge capacity of 746 mAh g−1 at a high rate of 3 C. Promising specific capacity has been documented even under high sulfur loading of 5.0 mg cm−2 and electrolyte to the sulfur ratio (E/S) of 5 µL mg−1.