The application prospects of lithium–sulfur (Li–S) batteries are constrained by many challenges, especially the shuttle effect of lithium polysulfides (Li₂S_x). Recently, microporous covalent organic framework (COF) materials have been used to anchor electrodes in Li–S batteries, because of their preferable characteristics, such as self-design ability, suitable pore size, and various active groups. To identify the ideal anchoring materials that can effectively restrain the shuttle of Li₂S_x species, the anchoring mechanism between COF materials and Li₂S_x species should be investigated in depth. Therefore, we systematically investigated the anchoring mechanism between specific COF nanomaterials (consisting of boron and oxygen atoms and benzene group) and Li₂S_x (x = 1, 2, 4, 6, or 8) species on the surface and inside the pore using density functional theory methods with van der Waals interactions. The detailed analysis of the adsorption energy, difference charge density, charge transfer, and atomic density of states can be used to determine that the COF nanomaterials, with the structure of boroxine connecting to benzene groups and boroxine groups not constructed at the corner of the structure, can effectively anchor the Li₂S_x series. Accordingly, this study provides the theoretical basis for the molecular-scale design of ideal anchoring materials, which can be useful to improve the performance of the Li–S batteries.

中文翻译：

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锂硫电池纳米多孔共价有机骨架内多硫化物锚固机理的新见解

锂硫（Li–S）电池的应用前景受到许多挑战的限制，特别是多硫化锂（Li ₂ S _x）的穿梭效应。最近，由于微孔共价有机骨架（COF）材料具有较好的特性，例如自我设计能力，合适的孔径和各种活性基团，已被用于锚定Li-S电池中的电极。为了确定可以有效抑制Li ₂ S _x物种穿梭的理想锚固材料，COF材料和Li ₂ S _x之间的锚固机理物种应进行深入调查。因此，我们系统地研究了特定的COF纳米材料（由硼和氧原子以及苯基组成）与孔表面和孔内部的Li ₂ S _x（x = 1、2、4、6或8）物种之间的锚固机制。使用具有范德华相互作用的密度泛函理论方法。吸附能，电荷密度差，电荷转移和原子态密度的详细分析可用于确定COF纳米材料，其环硼氧烷的结构与苯基相连，而环硼氧烷的结构未构造在结构的一角，可以有效地锚定Li ₂ S _x系列。因此，这项研究为理想的锚固材料的分子尺度设计提供了理论基础，这对改善Li-S电池的性能很有用。