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

Hong, Xu-Jia; Song, Chun-Lei; Yang, Yan; Tan, Hao-Chong; Li, Guo-Hui; Cai, Yue-Peng; Wang, Hongxia · ACS Nano · 2019

basic_science · Level V

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Abstract

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/cm<sup>2</sup>, 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/cm<sup>2</sup>, 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 Li<sub>2</sub>S<sub>6</sub> species and its catalytic effect toward conversion of polysulfides, resulting in suppressed shuttle effect of polysulfides in the Li-S batteries.