Perfluoroaryl‐Elemental Sulfur SNAr Chemistry in Covalent Triazine Frameworks with High Sulfur Contents for Lithium–Sulfur Batteries

• Published in: Advanced functional materials Vol. 27; no. 47
• Main Authors: Je, Sang Hyun, Kim, Hyeon Jin, Kim, Jiheon, Choi, Jang Wook, Coskun, Ali
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc 15-12-2017
• Subjects: Chemical synthesis; Chemistry; elemental sulfur; Lithium; Lithium sulfur batteries; lithium–sulfur battery; Materials science; Nitrogen atoms; nucleophilic aromatic substitution; porous organic polymer; Separators; Sulfur content; trimerization
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201703947

In order to address the challenges associated with lithium–sulfur batteries with high energy densities, various approaches, including advanced designs of sulfur composites, electrolyte engineering, and functional separators, are lately introduced. However, most approaches are effective for sulfur cathodes with limited sulfur contents, i.e., <80 wt%, imposing a significant barrier in realizing high energy densities in practical cell settings. Here, elemental sulfur‐mediated synthesis of a perfluorinated covalent triazine framework (CTF) and its simultaneous chemical impregnation with elemental sulfur via SNAr chemistry are demonstrated. SNAr chemistry facilitates the dehalogenation and nucleophilic addition reactions of perfluoroaryl units with nucleophilic sulfur chains, achieving a high sulfur content of 86 wt% in the resulting CTF. The given sulfur‐impregnated CTF, named SF‐CTF, exhibits a specific capacity of 1138.2 mAh g−1 at 0.05C, initial Coulombic efficiency of 93.1%, and capacity retention of 81.6% after 300 cycles, by utilizing homogeneously distributed sulfur within the micropores and nitrogen atoms of triazine units offering high binding affinity toward lithium polysulfides.
Elemental sulfur‐mediated trimerization of aromatic nitriles along with perfluoroaryl‐elemental sulfur SNAr chemistry leads to preparation of sulfur‐embedded covalent triazine frameworks with a high sulfur content of 86 wt% and exceptional electrochemical performance when tested as a cathode material in lithium–sulfur batteries, 93.1% initial Coulombic efficiency, and a specific capacity of 1138.2 mAh g−1.