Institute of Clean Energy, Yangtze River Delta Research Institute, Northwestern Polytechnical University, Taicang215400, People's Republic of China.
Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore117543.
ACS Nano. 2023 Feb 14;17(3):2901-2911. doi: 10.1021/acsnano.2c11300. Epub 2023 Jan 13.
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 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. 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 at 10 C, and an areal capacity of 7.60 mA h cm with a high sulfur loading (∼9 mg cm). This work demonstrates that functionalizing nanochannels in COFs can impart permselectivity for energy storage applications.
为了实现锂硫（Li-S）电池的实际应用，需要通过促进锂离子迁移来抑制不受控制的锂沉积，并通过阻止多硫化物穿梭来抑制阴极的不可逆消耗。然而，具有快速离子传输但多硫化物交叉率低的选择性人工膜或中间层仍然难以实现。在这里，我们报告了一种基于氟化共价有机框架（4F-COF）的膜的设计和合成，该膜具有高选择性和增加的电池寿命。通过密度泛函理论计算、分子动力学模拟和拉曼分析相结合，我们证明了氟化 COF 消除了多硫化物穿梭和枝晶锂的形成。因此，Li 对称电池在 1 mA cm 下经过 2000 小时的 1 mA cm 循环后表现出 Li 电镀/剥离行为。更重要的是，基于 4F-COF/PP 分离器的 Li-S 电池在 2 C 下经过 1000 次循环后具有 82.3%的循环保持率，在 10 C 下具有 568.0 mA h g 的倍率性能，在高硫载量（~9 mg cm）下具有 7.60 mA h cm 的面积容量。这项工作表明，在 COFs 中功能化纳米通道可以赋予储能应用的选择性。
