Fluorinated Covalent Organic Polymers for High Performance Sulfur Cathodes in Lithium−Sulfur Batteries
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초록
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Lithium-sulfur (Li-S) batteries offer far higher theoretical energy density than that of the commercial lithium-ion battery counterparts, but suffer predominantly from an irreversible shuttling process involving lithium polysulfides. Here we report a fluorinated covalent organic polymer (F-COP) as a template for high performance sulfur cathodes in Li-S batteries. Fluorination allows facile covalent anchoring of sulfur to a porous polymer framework via nucleophilic aromatic substitution reaction (SNAr), leading to high sulfur contents, e.g. over 70 wt%. The F-COP framework is microporous with 72% of pores being confined to three well-defined pore sizes, 0.58, 1.19, and 1.68 nm, effectively suppressing polysulfide dissolution via steric and electrostatic hindrance. Our findings suggest the F-COP family with the adaptability of SNAr chemistry and well-defined micropore structures as useful frameworks for highly sustainable sulfur electrodes in Li–S batteries.