Cations Mediate Lithium Polysulfide Adsorption in Metal–Organic Frameworks for Lithium–Sulfur Batteries
Cations Mediate Lithium Polysulfide Adsorption in Metal–Organic Frameworks for Lithium–Sulfur Batteries
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DOI：
10.1021/acs.jpcc.3c05539
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发表时间：
2023-10
期刊：
影响因子：
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通讯作者：
Roberto A. Jarrín;Kevin J Bennett;V. S. Thoi;Brandon C. Bukowski
中科院分区：
文献类型：
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作者：
Roberto A. Jarrín;Kevin J Bennett;V. S. Thoi;Brandon C. Bukowski
锂硫（Li-S）电池由于其较高的理论比容量和能量密度而成为锂离子电池的一种有前途的替代品。然而，仍然存在一些技术挑战，例如多硫化物穿梭。由于液体多硫化物扩散到电解质中导致容量损失，因此已经探索了不同的材料类别以锚多硫化锂并减少活性材料损失。金属有机骨架（MOF）UiO-66因其孔隙率、高表面积和可以锚定液体多硫化物的氧化锆节点而被确定为一种候选材料。MOFs还允许合成后修饰，这可以增加它们对液体多硫化物的吸附特异性并减少穿梭。在这项工作中，我们结合原子模拟和实验表征，以探测多硫化锂和功能化UiO-66节点之间的分子相互作用。我们探讨了多硫化锂如何吸附到由缺失的连接体缺陷引起的开放位点以及用碱金属阳离子官能化的位点。我们的研究结果表明，锂多硫化物吸附有利于UiO-66通过Li-O静电相互作用。此外，我们发现用碱金属官能化的节点通过促进电荷转移到节点而表现出对长链多硫化锂（Li 2S 4 -8）的更强吸附。实验紫外-可见光和7 Li NMR测量锆聚氧乙烯酸盐和UiO-66提供了进一步的证据，锂化有利于长链多硫化物的吸附。我们的研究结果表明，UiO-66功能化在多硫化物吸附中起着重要作用，这可能对控制穿梭效应有影响。这里所示的多硫化物吸附的基本见解提供了定量的原则，设计官能化的部分，并进一步抑制多硫化物穿梭。
Lithium–sulfur (Li–S) batteries are one promising alternative to Li-ion batteries due to their higher theoretical specific capacity and energy density. However, several technical challenges such as polysulfide shuttling remain. As liquid polysulfide diffusion into the electrolyte causes a loss of capacity, different material classes have been explored to anchor lithium polysulfides and reduce the active material loss. The metal–organic framework (MOF) UiO-66 has been identified as one candidate material due to its porosity, high surface area, and zirconium oxide nodes that could anchor liquid polysulfides. MOFs also allow for postsynthetic modifications that can increase their adsorption specificity toward liquid polysulfides and reduce shuttling. In this work, we combined atomistic simulations and experimental characterization to probe the molecular interactions between lithium polysulfides and functionalized UiO-66 nodes. We explored how lithium polysulfides adsorb to open sites caused by missing linker defects as well as sites functionalized with alkali cations. Our results demonstrate that lithium polysulfides adsorb favorably to UiO-66 through Li–O electrostatic interactions. In addition, we found that nodes functionalized with alkali metals demonstrated stronger adsorption of long-chain lithium polysulfides (Li2S4–8) by facilitating charge transfer to the nodes. Experimental ultraviolet-visible and7Li NMR measurements on Zr polyoxometalates and UiO-66 provided further evidence that lithiation favors adsorption of long-chain polysulfides. Our findings indicate that UiO-66 functionalization plays an important role in polysulfide adsorption, which may have implications in controlling the shuttle effect. The fundamental insights into polysulfide adsorption shown here provide quantitative principles to design functionalized moieties and further inhibit polysulfide shuttling.