Covalent triazine framework polymer nanosheets for cathode materials in lithium-sulfur batteries

A preparation method for covalent triazine framework polymer nanosheets for cathode materials in lithium-sulfur batteries, comprising the following steps:

• step 1:
• adding cyclohexanehexone and diaminomaleonitrile into acetic acid;
• heating under reflux for a first reaction;
• after the reaction, washing with hot acetic acid to obtain a crude product containing hexaazatriphenylenehexacarbonitrile (HATCN);
• ultrasonically dispersing the crude product in nitric acid solution, and continuing heating under reflux for a second reaction;
• after the second reaction, adding ice water for refrigerating and standing;
• obtaining a primarily purified HATCN by washing the obtained product with deionized water and vacuum drying;
• step 2:
• ultrasonically dissolving the primarily purified HATCN in an acetonitrile solution, heating under reflux for a third reaction;
• after the third reaction, obtaining a secondarily purified HATCN by washing with acetonitrile and vacuum drying;
• step 3:
• adding the secondarily purified HATCN into acetonitrile and magnetically stirring until dissolved, then adding sodium chloride and stirring until obtaining a uniformly dispersed mixture;
• drying the obtained uniformly dispersed mixture to fully evaporate acetonitrile, thereby obtaining a solid mixture of HATCN and sodium chloride;
• step 4:
• in a liquid nitrogen cryogenic environment, adding trifluoromethanesulfonic acid into a glass tube, then adding the solid mixture obtained in step 3, vacuumizing the system and flame-sealing;
• transferring the system to a tube furnace and calcining under an inert atmosphere to enable triazine polymerization of HATCN on the surface of sodium chloride crystals, thereby obtaining CTF-HATCN;
• wherein a dosage ratio of the trifluoromethanesulfonic acid to the secondarily purified HATCN in step 3 is 20-30 μL:0.1 g, the inert atmosphere is argon or nitrogen, and a calcination temperature is 400-600° C. with a holding time of 16-20 h;
• and
• step 5:
• removing sodium chloride particles, collecting the product and freeze-drying, then ultrasonically dispersing and exfoliating the obtained CTF-HATCN to obtain covalent triazine framework polymer nanosheets for cathode materials in lithium-sulfur batteries, wherein the triazine framework polymer nanosheets are CTF-HATCN nanosheets.