For lithium-sulfur batteries (Li-S batteries), a high-content electrolyte typically can exacerbate the shuttle effect, while a lean electrolyte may lead to decreased Li-ion conductivity and reduced catalytic conversion efficiency, so achieving an appropriate electrolyte-to-sulfur ratio (E/S ratio) is essential for improving the battery cycling efficiency. A quasi-solid electrolyte (COF-SH@PVDF-HFP) with strong adsorption and high catalytic conversion was constructed for in situ covalent organic framework (COF) growth on highly polarized polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) fibers. COF-SH@PVDF-HFP enables efficient Li-ion conductivity with low-content liquid electrolyte and effectively suppresses the shuttle effect. The results based on in situ Fourier-transform infrared, in situ Raman, UV–Vis, X-ray photoelectron, and density functional theory calculations confirmed the high catalytic conversion of COF-SH layer containing sulfhydryl and imine groups for the lithium polysulfides. Lithium plating/stripping tests based on Li/COF-SH@PVDF-HFP/Li show excellent lithium compatibility (5 mAh cm⁻² for 1400 h). The assembled Li-S battery exhibits excellent rate (2 C 688.7 mAh g⁻¹) and cycle performance (at 2 C of 568.8 mAh g⁻¹ with a capacity retention of 77.3% after 800 cycles). This is the first report to improve the cycling stability of quasi-solid-state Li-S batteries by reducing both the E/S ratio and the designing strategy of sulfhydryl-functionalized COF for quasi-solid electrolytes. This process opens up the possibility of the high performance of solid-state Li-S batteries.

中文翻译：

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巯基功能化的 COF 基电解质增强了准固态锂硫电池中多硫化物的化学亲和力

对于锂硫电池（Li-S电池）来说，高含量的电解液通常会加剧穿梭效应，而稀薄的电解液可能会导致锂离子电导率下降和催化转化效率降低，因此要实现适当的电解液到-硫比（E/S比）对于提高电池循环效率至关重要。构建了一种具有强吸附性和高催化转化率的准固体电解质（COF-SH@PVDF-HFP），用于在高极化聚偏二氟乙烯-六氟丙烯（PVDF-HFP）纤维上原位共价有机骨架（COF）生长。 COF-SH@PVDF-HFP能够在低含量液体电解质的情况下实现高效的锂离子传导性，并有效抑制穿梭效应。基于原位傅里叶变换红外、原位拉曼、紫外-可见光、X射线光电子和密度泛函理论计算的结果证实了含有巯基和亚胺基团的COF-SH层对多硫化锂的高催化转化率。基于Li/COF-SH@PVDF-HFP/Li的镀锂/剥离测试显示出优异的锂兼容性（5 mAh cm ^-2 1400小时）。组装的Li-S电池表现出优异的倍率（2 C 688.7 mAh g ^-1）和循环性能（2 C 568.8 mAh g ^-1，800次循环后容量保持率为77.3%）。这是第一篇通过降低E/S比和准固态电解质的巯基功能化COF的设计策略来提高准固态锂硫电池循环稳定性的报告。这一过程开启了固态锂硫电池高性能的可能性。