The “polysulfide shuttle,” a process initiated by the dissolution of polysulfides, is recognized to be one of the major failure mechanisms of lithium–sulfur (Li–S) batteries. Much research effort has been dedicated toward efficient cathode additives and host materials to suppress the leaching of polysulfide species. Herein, we report a new 2D metal–organic framework constituted by a tritopic ligand, boron imidazolate ([BH(Im)₃]⁻, Im = imidazole), and Co²⁺ ions for lithium polysulfide adsorption. The cobalt imidazolate framework (CoN₆-BIF) contains octahedrally coordinated Co centers that form two-dimensional layers in the a,b plane. Composite cathodes containing CoN₆-BIF exhibited high sulfur utilization and capacity retention, resulting in improved specific capacity and cycle life compared to sulfur/carbon controls. Density functional theory (DFT) calculations suggest that CoN₆-BIF linkers are rotationally flexible, allowing the framework to accommodate polysulfide in the expanded pores. This unusual property of BIFs opens up new avenues for exploring flexible metal–organic frameworks (MOFs) and their applications to energy storage.

中文翻译：

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用于锂硫电池中多硫化物吸附的柔性二维硼咪唑骨架

“多硫化物穿梭”是由多硫化物溶解引发的过程，被认为是锂硫（Li-S）电池的主要失效机制之一。许多研究工作都致力于高效的阴极添加剂和主体材料，以抑制多硫化物物质的浸出。_{在此，我们报道了一种由三位配体、咪唑硼（[BH(Im) 3} ] ^- , Im = 咪唑）和 Co ²⁺离子构成的新型二维金属有机框架，用于吸附多硫化锂。咪唑酸钴骨架 (CoN _{6 -BIF) 包含八面体配位的 Co 中心，在}a和b平面中形成二维层。_{含CoN 6}的复合阴极-BIF 表现出高硫利用率和容量保持率，与硫/碳控制相比，可提高比容量和循环寿命。密度泛函理论 (DFT) 计算表明 CoN ₆ -BIF 接头具有旋转柔性，允许框架在膨胀的孔隙中容纳多硫化物。BIF 的这种不寻常特性为探索柔性金属有机骨架 (MOF) 及其在储能方面的应用开辟了新途径。