Details

Autor(en) / Beteiligte

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

Titel

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

Ist Teil von

• Nano letters, 2016-05, Vol.16 (5), p.3292-3300

Ort / Verlag

United States: American Chemical Society

Erscheinungsjahr

2016

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• 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 (Li2S x ) 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 Li2S x adsorption phenomena are theoretically investigated through density functional theory calculations. Benefiting from the chemical/structural uniqueness, the NN interlayers effectively capture Li2S x 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.