Cerium Based Metal–Organic Frameworks as an Efficient Separator Coating Catalyzing the Conversion of Polysulfides for High Performance Lithium–Sulfur Batteries

In this work, we demonstrate cerium (Ce) based metal-organic frameworks (MOFs) combined with carbon nanotubes (CNTs) to form Ce-MOF/CNT composites as separator coating material in the Li-S battery system, which showed excellent electrochemical performance even under high sulfur loading and much better capacity retention. At the sulfur loading of 2.5 mg/cm², initial specific capacity of 1021.8 mAh/g at 1C was achieved in the Li-S cell with the Ce-MOF-2/CNT coated separator, which was slowly reduced to 838.8 mAh/g after 800 cycles with a decay rate of only 0.022% and the Coulombic efficiency of nearly 100%. Even at a higher sulfur loading of 6 mg/cm², the cell based on Ce-MOF-2/CNT separator coating still exhibited excellent performance with initial specific capacity of 993.5 mAh/g at 0.1 C. After 200 cycles, the specific capacity of 886.4 mAh/g was still retained. The excellent performance is ascribed to the efficient adsorption of the Ce-MOF-2 to Li₂S₆ species and its catalytic effect toward conversion of polysulfides, resulting in suppressed shuttle effect of polysulfides in the Li-S batteries.