▎ 摘　　要

NOVELTY - Preparation of polyvinylidene fluoride (PVDF)-chlorotrifluoroethylene (CTFE)-based composite diaphragm involves activating carbon material using 68% concentrated nitric acid, washing activated carbon material several times until the pH of the washing solution is 7, filtering, washing, drying to obtain activated carbon material, adding activated carbon material to anhydrous ethanol, ultrasonically processing to obtain precursor solution (P1), adding predetermined amount metal compound to deionized water to form a suspension, adding the suspension to the precursor solution (P1), ultrasonically processing, stirring to obtain precursor solution (P2), filtering, washing several times, collecting precipitated metal compound, drying, mixing precipitated metal compound, binder and organic solvent, stirring to obtain coating slurry, uniformly coating the coating slurry on a PVDF-CTFE base film, and vacuum-drying. USE - Preparation of polyvinylidene fluoride-chlorotrifluoroethylene-based composite diaphragm send in for lithium-sulfur battery for portable electronic device and electric automobile. ADVANTAGE - The prepared diaphragm has good lithium ion selective permeability and high safety performance, which can effectively improve the cycle performance and coulomb efficiency of the lithium sulphur battery. DETAILED DESCRIPTION - Preparation of polyvinylidene fluoride (PVDF)-chlorotrifluoroethylene (CTFE)-based composite diaphragm involves activating carbon material using 68% concentrated nitric acid for 6 hours, washing activated carbon material several times until the pH of the washing solution is 7, filtering, washing, drying to obtain activated carbon material, adding predetermined amount activated carbon material to anhydrous ethanol, ultrasonically processing for 2 hours to obtain precursor solution (P1), adding predetermined amount metal compound to deionized water to form a suspension, adding the suspension to the precursor solution (P1), ultrasonically processing for 1 hour, stirring for 4 hours to obtain precursor solution (P2), filtering, washing several times, collecting precipitated metal compound, drying in a vacuum oven at 70℃ for 12 hours, placing dried precipitated metal compound in a desiccator, mixing precipitated metal compound, binder and organic solvent, stirring at 65℃ for 10 hours to obtain coating slurry, uniformly coating the coating slurry on a PVDF-CTFE base film with a doctor blade, and vacuum-drying at 60℃ for 12 hours. The mass ratio of activated carbon material and anhydrous alcohol is 1:4-5. The mass ratio of metal compound and deionized water is 1:0.5-0.7. The mass ratio of activated carbon material and metal compound is 1:5-8. The mass ratio of precipitated metal compound, binder and organic solvent is 2-3:1:7-8. The PVDF-CTFE base film is prepared by drying PVDF-CTFE at 80℃ for 24 hours, dissolving dried PVDF-CTFE in an organic solvent to form solution (D) containing 20-30 %mass PVDF-CTFE, mechanically stirring the solution (D) at 60℃ for 12 hours to obtain a homogeneous solution, adding metal oxide-coated covalent organic framework (MxOy-COF, where x and y are not defined) powder, ball-milling for 3 hours, aging at 60-80℃ for 12-24 hours, ultrasonically stirring for 24-36 hours, aging for 24-48 hours to form a spinning solution, spinning at voltage of 10-15 kV, solution injection rate of 0.5-1.5 ml/hour, and receiving distance of 15-25 cm, and drying obtained fiber film in a vacuum drying oven at 60℃ for 12-18 hours. The metal oxide-coated covalent organic framework (MxOy-COF) powder is prepared by adding predetermined amount oxide nanoparticles and 2,5-dihydroxyterephthalaldehyde to a mixed solution of mesitylene and organic solvent, ultrasonically processing for 15 minutes to obtain a solution (A), adding predetermined amount sulfonated polymer to the mixed solution of mesitylene and organic solvent, ultrasonically processing for 15 minutes to obtain a solution (B), mixing the solution (A) and solution (B) in a Pyrex(RTM: glass tube), adding predetermined amount acetic acid to obtain a solution (C), ultrasonically processing the solution (C) for 10 minutes, rapidly freezing with liquid nitrogen, degassing through three freeze-thaw cycles, sealing the Pyrex(RTM: glass tube), heating at 110℃ for 72 hours, vacuum-filtering to obtain precipitate, washing the precipitate with acetone, deionized water and ethanol, and vacuum-drying at 120℃ overnight. The mass ratio of oxide nanoparticles, 2,5-dihydroxyterephthalaldehyde, mesitylene and organic solvent is 7-8:1:0.8-0.9:0.5-0.7. The mass ratio of sulfonated polymer, mesitylene, organic solvent, and the oxide nanoparticles in solution (A) is 13-16:1:1.2-1.5:6-7. The mass ratio of acetic acid, and sulfonated polymer in solution (B) is 1:35-45. The mass ratio of metal oxide-coated covalent organic framework powder and PVDF-CTFE is 1:10-15.