Rational design of an Allyl-rich Triazine-based covalent organic framework host used as efficient cathode materials for Li-S batteries

To overcome the loss of soluble lithium polysulfides (LiPSs) generated during the discharge process of lithiumsulfur (Li-S) batteries, a lot of efforts have been devoted to the design of novel micro- or nano-structured host materials, aiming to trap soluble polysulfide within the network. Covalent organic framework (COF) as porous materials have been receiving a great deal of attention. Herein, an allyl-rich triazine covalent organic framework (ART-COF) synthesized by 5-(allyloxy) isophthalaldehyde and 4,4',4 ''-(1,3,5-triazine-2,4,6-triyl) trianiline (TAPT) is used as cathode host material for Li-S batteries. Owning to the synergistic effect of physical force (through microporous channel) and chemical force (through C-S covalent bond and dipole-dipole interaction between nitrogen and lithium), the shuttle action of LiPSs to anode electrode can be effectively limited. ART-COF shows a high initial specific capacity of 1270 mAh g(-1) which retains 1220 mAh g(-1) after 100 charge-discharge cycles at 0.2C, and even at 1C it also demonstrates an initial specific capacity of 993 mAh g(-1) which retains 818 mAh g(-1) after 500 cycles with a low fading rate of 0.035% per cycle. This work represents a sustainable approach for developing highly stable and long-lived Li-S batteries.