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Lithium–sulfur (Li–S) batteries have great potential as next generation energy storage devices. However, the redox chemistry mechanism involves the generation of solubilized lithium polysulfides, which can lead to leaching of the active material and, consequently, passivated electrodes and diminished capacities. Chemical tethering of lithium polysulfides to materials in the sulfur cathode is a promising approach for resolving this issue in Li–S batteries. Borrowing from the field of synthetic chemistry, we utilize maleimide functional groups in a Zr-based metal–organic framework to chemically interact with polysulfides through the Michael Addition reaction. A combination of molecular and solid-state spectroscopies confirms covalent attachment of Li 2 S x to the maleimide functionality. When integrated into Li–S cathodes, the maleimide-functionalized framework exhibits notable performance enhancements over that of the unfunctionalized material, revealing the promise of polysulfide anchors for Li–S battery cycling.
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Phosphate‐functionalized Zirconium Metal–Organic Frameworks for Enhancing Lithium–Sulfur Battery Cycling
Abstract Lithium–sulfur batteries are promising candidates for next‐generation energy storage devices due to their outstanding theoretical energy density. However, they suffer from low sulfur utilization and poor cyclability, greatly limiting their practical implementation. Herein, we adopted a phosphate‐functionalized zirconium metal–organic framework (Zr‐MOF) as a sulfur host. With their porous structure, remarkable electrochemical stability, and synthetic versatility, Zr‐MOFs present great potential in preventing soluble polysulfides from leaching. Phosphate groups were introduced to the framework post‐synthetically since they have shown a strong affinity towards lithium polysulfides and an ability to facilitate Li ion transport. The successful incorporation of phosphate in MOF‐808 was demonstrated by a series of techniques including infrared spectroscopy, solid‐state nuclear magnetic resonance spectroscopy, and X‐ray pair distribution function analysis. When employed in batteries, phosphate‐functionalized Zr‐MOF (MOF‐808‐PO4) exhibits significantly enhanced sulfur utilization and ion diffusion compared to the parent framework, leading to higher capacity and rate capability. The improved capacity retention and inhibited self‐discharge rate also demonstrate effective polysulfide encapsulation utilizing MOF‐808‐PO4. Furthermore, we explored their potential towards high‐density batteries by examining the cycling performance at various sulfur loadings. Our approach to correlate structure with function using hybrid inorganic–organic materials offers new chemical design strategies for advancing battery materials.
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- PAR ID:
- 10462208
- Date Published:
- Journal Name:
- Chemistry – A European Journal
- Volume:
- 29
- Issue:
- 40
- ISSN:
- 0947-6539
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1002/chem.202300821
