Triple-Site Integrated Redox-Active Metal-Organic Cages Enable Complementary Acceleration Mechanisms for Serially Enhancing Sulfur Redox Kinetics.
basic_science · Level V
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- Record sourced from PubMed, PMID 40987577.
- Also identified by DOI 10.1021/acsnano.5c10684.
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Abstract
The development of lithium-sulfur batteries (LSBs) is hindered by the shuttle effect of lithium polysulfides (LiPSs) and sluggish sulfur redox reaction (SRR) kinetics. Herein, we integrate multiple functional units (-SH, -NH<sub>2</sub>, Zr) into metal-organic cages (MOCs) to construct a triple-site integrated MOC (TSI-MOC), synergistically suppress the shuttle effect, and promote the SRR. The -SH-decorated ligand forms a sulfur oligomer with LiPSs, promoting faster reaction pathways. The exposed Zr-based clusters catalyze the conversion of LiPSs, while the -NH<sub>2</sub>-functionalized ligand adjacent to the metal clusters aids in aggregating LiPSs, further enhancing the catalytic and confinement effects. LSBs with TSI-MOCs deliver a higher discharge capacity (949.7 mAh g<sup>-1</sup>) and a lower capacity decay rate (only 0.018% at 1 C) compared to those with single-site MOCs (S-MOCs) and dual-site integrated MOCs (DSI-MOCs). The TSI-MOC also enables LSBs with a high areal capacity of 9.08 mAh cm<sup>-2</sup> under a high sulfur loading of 9.1 mg cm<sup>-2</sup>, as well as the stable operation of Li-S pouch cells with a high energy density of 307 Wh kg<sup>-1</sup>. This work demonstrated the importance of integrating multiple functional sites to improve the chemical interactions between hosts and redox-active intermediates, facilitating the thoughtful design of MOCs for high-performance LSBs.