COF-Net on CNT-Net as a Molecularly Designed, Hierarchical Porous Chemical Trap for Polysulfides in Lithium-Sulfur Batteries

Jongtae Yoo, Sung Ju Cho, Gwan Yeong Jung, Su Hwan Kim, Keun Ho Choi, Jeong Hoon Kim, Chang Kee Lee, Sang Kyu Kwak, Sang Young Lee

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107 Citations (Scopus)

Abstract

The hierarchical porous structure has garnered considerable attention as a multiscale engineering strategy to bring unforeseen synergistic effects in a vast variety of functional materials. Here, we demonstrate a "microporous covalent organic framework (COF) net on mesoporous carbon nanotube (CNT) net" hybrid architecture as a new class of molecularly designed, hierarchical porous chemical trap for lithium polysulfides (Li2Sx) in Li-S batteries. As a proof of concept for the hybrid architecture, self-standing COF-net on CNT-net interlayers (called "NN interlayers") are fabricated through CNT-templated in situ COF synthesis and then inserted between sulfur cathodes and separators. Two COFs with different micropore sizes (COF-1 (0.7 nm) and COF-5 (2.7 nm)) are chosen as model systems. The effects of the pore size and (boron-mediated) chemical affinity of microporous COF nets on Li2Sx adsorption phenomena are theoretically investigated through density functional theory calculations. Benefiting from the chemical/structural uniqueness, the NN interlayers effectively capture Li2Sx without impairing their ion/electron conduction. Notably, the COF-1 NN interlayer, driven by the well-designed microporous structure, allows for the selective deposition/dissolution (i.e., facile solid-liquid conversion) of electrically inert Li2S. As a consequence, the COF-1 NN interlayer provides a significant improvement in the electrochemical performance of Li-S cells (capacity retention after 300 cycles (at charge/discharge rate = 2.0 C/2.0 C) = 84% versus 15% for a control cell with no interlayer) that lies far beyond those accessible with conventional Li-S technologies.

Original languageEnglish
Pages (from-to)3292-3300
Number of pages9
JournalNano letters
Volume16
Issue number5
DOIs
Publication statusPublished - 2016 May 11

All Science Journal Classification (ASJC) codes

  • Bioengineering
  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanical Engineering

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    Yoo, J., Cho, S. J., Jung, G. Y., Kim, S. H., Choi, K. H., Kim, J. H., Lee, C. K., Kwak, S. K., & Lee, S. Y. (2016). COF-Net on CNT-Net as a Molecularly Designed, Hierarchical Porous Chemical Trap for Polysulfides in Lithium-Sulfur Batteries. Nano letters, 16(5), 3292-3300. https://doi.org/10.1021/acs.nanolett.6b00870