Fluorinated Covalent Organic Framework-Based Nanofluidic Interface for Robust Lithium-Sulfur Batteries.

Zhang, Kun; Li, Xing; Ma, Li; Chen, Fangzheng; Chen, Zhongxin; Yuan, Yijia; Zhao, Yaohua; Yang, Jinlin et al. · ACS Nano · 2023

basic_science · Level V

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Abstract

To realize the practical application of lithium-sulfur (Li-S) batteries, there is a need to inhibit uncontrolled Li deposition by facilitating Li-ion migration, and suppress the irreversible consumption of cathodes by preventing polysulfide shuttling. However, a permselective artifical membrane or interlayer which features fast ion transport but low polysulfide crossover is elusive. Here, we report the design and synthesis of a fluorinated covalent organic framework (4F-COF)-based membrane with a high permselectivity and increased battery lifespan. Combining density functional theory calculation, molecular dynamic simulation, and <i>in situ</i> Raman analysis, we demonstrate that fluorinated COF eliminates polysulfides shutting and dendritic lithium formation. Consequently, Li symmetrical cells demonstrate Li plating/stripping behaviors for 2000 h under 1 mA cm<sup>-2</sup>. More importantly, Li-S batteries based on the 4F-COF/PP separator achieve cycling retention of 82.3% over 1000 cycles at 2 C, rate performance of 568.0 mA h g<sup>-1</sup> at 10 C, and an areal capacity of 7.60 mA h cm<sup>-2</sup> with a high sulfur loading (∼9 mg cm<sup>-2</sup>). This work demonstrates that functionalizing nanochannels in COFs can impart permselectivity for energy storage applications.