Rational Construction of Br/N Active-Site Covalent-Organic Frameworks as a Dual-Functional Host for High-Performance...

The shuttle effect and sluggish redox kinetics of lithium polysulfides (LiPS) at the cathode, along with uncontrolled lithium dendrite growth at the anode, hinder the practical application of lithium-sulfur (Li-S) batteries. To address the aforementioned challenges, a covalent organic framework (COFs) material, TAPB-TaBr₂, is elaborately designed in this study. The electron-rich Br/N dual active sites are evenly distributed in the TAPB-TaBr₂ skeleton, serving as efficient LiPS anchoring and lithium deposition regulation sites. DFT calculations and experiments reveal that the TAPB-TaBr₂ exhibits strong electrostatic affinity and catalytic activity through the Br/N sites, promoting efficient anchoring and reversible conversion of LiPS to alleviate the shuttle effect at the cathode side. Meanwhile, its ordered porous structure and lithiophilic nature facilitate uniform lithium nucleation and deposition, effectively suppressing dendrite growth and stabilizing the electrode interface at the anode side. The full battery with a TAPB-TaBr₂ dual-functional host delivers a high initial capacity of 1261.6 mAh·g^-1 at 0.5C, with an ultra-low capacity decay rate of 0.24% per cycle over 200 cycles. This study presents a dual-function COFs platform that integrates LiPS regulation and lithium deposition control, offering a new strategy for optimizing practical Li-S full batteries.