Facilitating efficient catalytic conversion of polysulfides in lithium-sulfur batteries via self-assembled hydrogen-bond-rich covalent organic frameworks.

The widespread commercialization of lithium-sulfur (Li-S) batteries is hindered by two critical challenges: sluggish redox kinetics and the detrimental polysulfide shuttle effect. In this study, we present a novel approach utilizing hydrogen-bond-rich covalent organic frameworks (TTP@PVDF50), synthesized through an in situ self-assembly process incorporating polymeric guest species. These covalent organic frameworks (COFs), when integrated into the separators of Li-S batteries, preserve their intrinsic porosity and crystallinity, while the abundant fluorine-rich sites and well-defined pore structures enhance lithium-ion (Li⁺) transport kinetics. The hydrogen-bond-rich nature of the COFs provides an effective strategy to mitigate the polysulfide shuttle, leveraging both spatial hindrance and strong polar interactions for enhanced adsorption. Density functional theory (DFT) calculations and in situ Raman spectroscopy reveal that the F∙∙∙OH hydrogen bonding network in the TTP@PVDF50 composite significantly accelerates Li⁺ migration and catalyzes the conversion of LiPSs. The modified separator demonstrates a high discharge capacity of 1420.2 mAh g^-1 at 0.2 C (1 C=1675 mAh g^-1), alongside remarkable anti-self-discharge performance with only 9.0% capacity loss. Notably, the Li-S battery with a high sulfur loading (4.59 mg cm^-2) and a lean electrolyte (6 µL mg^-1) retains over 83% of its capacity, underscoring the effectiveness of this strategy in advancing the performance and longevity of Li-S batteries.