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

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 2 , 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 2 , 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 2 S 6 species and its catalytic effect toward conversion of polysulfides, resulting in suppressed shuttle effect of polysulfides in the Li−S batteries.

Multilayer Nanofiber Composite Separator for Lithium-Ion Batteries with High Safety

“…Electrospinning is a simple and straightforward way to prepare a nanofiber membrane with high porosity [5]. Many polymers, such as PAN (Polyacrylonitrile) [6,7,8,9], PVDF (Polyvinylidene fluoride) [7,10,11], PVDF-HFP (Polyvinylidene fluoride-hexafluoropropylene) [12,13,14], and PI (Polyimide) [2,9], are used to prepare LIB membranes by electrospinning. Inorganic nanoparticles, such as TiO 2 [15,16,17], SiO 2 [18], Al 2 O 3 [19], and ZrO 2 [20], have been used to prepare composite lithium-ion battery separators, which can enhance the mechanical and electrochemical properties of the separator.…”

Mechanistic understanding of the role separators playing in advanced lithium‐sulfur batteries

“…After being physically/chemically absorbed, polysulfides will be further reduced to insoluble sulfides and fixed in the trapping layer. On the basis of the physical/chemical adsorption effect, some trapping materials also exhibit good catalytic activity for the polysulfide reduction reaction . Metal sulfides like Co 9 S 8 , MoS 2 , VS 4, and WS 2 were used in lithium‐sulfur batteries as catalytic trapping materials.…”

Multifunctional MOF‐Based Separator Materials for Advanced Lithium–Sulfur Batteries

“…A kind of Ce‐based MOF was used to catalyze the transformation of the lithium polysulfide reported by Hong et al. [ 115 ] The Ce‐MOFs‐1,2/CNT was prepared by a solvothermal method. Ce‐MOFs‐2 is the alternative name of Ce‐UiO‐66‐BPDC and the Ce‐MOF‐1 is another name of Ce‐MOF‐808.…”