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CN-122011477-A - Functionalized diaphragm, preparation method thereof and lithium ion battery

CN122011477ACN 122011477 ACN122011477 ACN 122011477ACN-122011477-A

Abstract

The invention belongs to the technical field of battery diaphragms, and particularly relates to a functional diaphragm, a preparation method thereof and a lithium ion battery, wherein the preparation method comprises the following steps of immersing a diaphragm base film in an aqueous solution of alcohol for pretreatment, immersing the diaphragm base film in a mixed aqueous solution of 2, 5-diamino-1, 4-dihydroxybenzene dihydrochloride Pa-OH and a surfactant, immersing the obtained 2, 5-diamino-1, 4-dihydroxybenzene dihydrochloride modified base film in an organic solution of 1,3, 5-tricarboxyl phloroglucinol TP, wherein the TP and the Pa-OH can undergo Schiff base reaction at a two-phase interface to obtain a base film for generating TP-COF in situ; immersing the membrane in succinic anhydride or a derivative solution thereof for reaction, introducing carboxyl, and immersing the obtained TP-COF-COOH modified base membrane in an alcohol solution of lithium salt to obtain the TP-COF-COOLi functionalized membrane. The modified-COOLi group can provide a lithium ion specific transmission path, the migration number and the ion conductivity of lithium ions are obviously improved, the wettability of the electrolyte is enhanced by carboxyl, the affinity of the electrolyte to Li + is enhanced, the internal resistance of the battery can be reduced, and the rate capability is improved.

Inventors

  • Xiang Jinxuan
  • SU HANG

Assignees

  • 安徽得壹能源科技有限公司

Dates

Publication Date
20260512
Application Date
20260410

Claims (10)

  1. 1. A preparation method of a functional diaphragm is characterized by comprising the following steps: immersing the diaphragm base film in an aqueous solution of alcohol for pretreatment; Dipping the pretreated base film in a mixed aqueous solution of 2, 5-diamino-1, 4-dihydroxybenzene dihydrochloride Pa-OH and a surfactant to obtain a2, 5-diamino-1, 4-dihydroxybenzene dihydrochloride modified base film; Dipping the 2, 5-diamino-1, 4-dihydroxybenzene dihydrochloride modified base film in an organic solution of 1,3, 5-tricarboxyl phloroglucinol TP, and allowing TP and Pa-OH to undergo Schiff base reaction at a two-phase interface to obtain a base film for generating TP-COF in situ; Immersing the in-situ generated TP-COF base film in succinic anhydride or a derivative solution thereof for reaction, and introducing carboxyl to obtain a TP-COF-COOH modified base film; And (3) dipping the TP-COF-COOH modified base film in an alcohol solution of lithium salt to obtain the TP-COF-COOLi functionalized membrane.
  2. 2. The method of claim 1, wherein the base film is a polypropylene base film or a polyethylene base film.
  3. 3. The method for preparing a functionalized membrane according to claim 1, wherein the volume fraction of the alcohol in the aqueous solution of the alcohol is 50% -90%; or, in the aqueous solution of the alcohol, the alcohol is ethanol, isopropanol, n-propanol, n-butanol or trifluoroethanol; or, the base film is immersed in an aqueous solution of alcohol for pretreatment for 10min-60min.
  4. 4. The method for preparing a functionalized membrane according to claim 1, wherein the concentration of 2, 5-diamino-1, 4-dihydroxybenzene dihydrochloride is 0.01wt% to 0.2wt% and the concentration of surfactant is 0.01wt% to 1wt% in the mixed aqueous solution of 2, 5-diamino-1, 4-dihydroxybenzene dihydrochloride and surfactant; Or, the surfactant is cetyl pyridinium bromide, cetyl pyridinium chloride, dodecyl pyridinium bromide, sodium dodecyl sulfate or sodium alpha-alkenyl sulfonate; Or, the pretreated base film is immersed in the mixed aqueous solution of 2, 5-diamino-1, 4-dihydroxybenzene dihydrochloride and a surfactant for 30min-120min.
  5. 5. The method for preparing the functionalized membrane according to claim 1, wherein the solvent of the organic solution of 1,3, 5-tricarboxyl phloroglucinol is a mixed solvent of 1, 4-dioxane and metaxylene, and the volume ratio of 1, 4-dioxane to metaxylene is 1:0.5-1.5; or, in an organic solution of 1,3, 5-tricarboxyl phloroglucinol, the concentration of TP is 0.01wt% to 0.2wt%; Or, immersing the 2, 5-diamino-1, 4-dihydroxybenzene dihydrochloride modified base film in an organic solution of 1,3, 5-tricarboxyl phloroglucinol for 30-120 min; or after the impregnation reaction is finished, washing the surface of the diaphragm by methanol, removing unreacted monomers, and then drying to obtain the base film of the in-situ generated TP-COF.
  6. 6. The method for preparing a functionalized membrane according to claim 1, wherein the in-situ generated TP-COF base film is immersed in a succinic anhydride or a derivative solution thereof at a reaction temperature of 60-100 ℃ for 24-48 hours; Or, the solvent of the succinic anhydride or the derivative solution thereof is anhydrous N, N-dimethylformamide; or after the reaction is finished, washing the membrane by adopting methanol, removing redundant reagents, and drying to obtain the TP-COF-COOH modified base membrane.
  7. 7. The method for preparing the functional membrane according to claim 1, wherein in the alcoholic solution of the lithium salt, the alcohol is absolute methanol or absolute ethanol, and the lithium salt is lithium bis (trifluoromethanesulfonyl imide), lithium hexafluorophosphate, lithium difluorooxalato borate or lithium tetrafluoroborate; Or, in the alcohol solution of the lithium salt, the concentration of the lithium salt is 0.5mol/L to 1.5mol/L.
  8. 8. The method for producing a functionalized membrane according to claim 7, wherein the time for immersing the TP-COF-COOH modified base film in an alcoholic solution of lithium salt is 6 hours to 24 hours.
  9. 9. A functionalized membrane is characterized by being prepared by the preparation method of the functionalized membrane according to any one of claims 1-8.
  10. 10. A lithium ion battery, characterized in that the lithium ion battery comprises a positive electrode, a negative electrode and a diaphragm, wherein the diaphragm is the functional diaphragm according to claim 9.

Description

Functionalized diaphragm, preparation method thereof and lithium ion battery Technical Field The invention belongs to the technical field of battery diaphragms, and particularly relates to a functional diaphragm, a preparation method thereof and a lithium ion battery. Background The primary function of the battery separator is to physically isolate the positive and negative electrodes to prevent shorting while allowing free passage of lithium ions. Compared with inorganic nano materials and conventional organic materials, the organic frame material has a more ordered and uniform pore structure, and the pore diameter can be accurately regulated and controlled. The nanoscale pores and the higher specific surface area increase the contact area with electrolyte, enhance the liquid absorption, are favorable for improving the rate performance and the cycle life, and the COF covalent bond skeleton has excellent thermal stability and can bear higher temperature. However, the existing COF material is coated on the surface of the diaphragm in a surface coating mode, the binding force between the coating and the base film is weak, physical adhesion is realized by means of a binder, local short circuit is possibly caused by falling of the coating, partial pore channels are possibly blocked by the binder, the porosity is reduced, the ion transmission resistance is increased, and the problems of agglomeration, cracking or uneven thickness and the like are easily caused when slurry is coated on the base film, so that the cycle stability and the service life of the battery are influenced. Disclosure of Invention Aiming at the defects existing in the prior art, the invention aims to provide a functional diaphragm, a preparation method thereof and a lithium ion battery. In order to achieve the above object, the present invention is realized by the following technical scheme: In a first aspect, the present invention provides a method for preparing a functionalized membrane, comprising the steps of: immersing the diaphragm base film in an aqueous solution of alcohol for pretreatment; immersing the pretreated base film in a mixed aqueous solution of 2, 5-diamino-1, 4-dihydroxybenzene dihydrochloride (Pa-OH) and a surfactant to obtain a 2, 5-diamino-1, 4-dihydroxybenzene dihydrochloride modified base film; Dipping the 2, 5-diamino-1, 4-dihydroxybenzene dihydrochloride modified base film in an organic solution of 1,3, 5-Tricarboxyl Phloroglucinol (TP), and allowing TP and Pa-OH to undergo Schiff base reaction at a two-phase interface to obtain a base film for generating TP-COF in situ; Immersing the in-situ generated TP-COF base film in succinic anhydride or a derivative solution thereof for reaction, and introducing carboxyl to obtain a TP-COF-COOH modified base film; And (3) dipping the TP-COF-COOH modified base film in an alcohol solution of lithium salt to obtain the TP-COF-COOLi functionalized membrane. In a second aspect, the present invention provides a functionalized membrane prepared by the method for preparing a functionalized membrane according to the first aspect. In a third aspect, the present invention provides a lithium ion battery comprising a positive electrode, a negative electrode, and a separator, the separator being the functionalized separator of the second aspect. The beneficial effects achieved by one or more embodiments of the present invention described above are as follows: According to the invention, 2, 5-diamino-1, 4-dihydroxybenzene dihydrochloride (Pa-OH) and 1,3, 5-Tricarboxyl Phloroglucinol (TP) are introduced on an activated base film to generate a beta-ketoenamine bond connected TP-COF coating diaphragm in situ, then succinic anhydride or derivatives thereof are subjected to ring opening reaction to introduce carboxyl groups to obtain TP-COF-COOH, and finally the TP-COF-COOH diaphragm is immersed in an alcohol solution of lithium salt to generate ion exchange, so that the TP-COF-COOLi functional diaphragm is formed. The in-situ modification not only can retain the porous structure of the COF material and realize the surface wettability equivalent to that of surface coating, but also can enhance the adhesive force between the coating and the base film and reduce the peeling defect. The surface coating is generally only covered on the outer surface of the base film, the coating formed by in-situ modification can permeate the inner and outer surfaces of the diaphragm, in-situ synthesis enables COF to grow on the surface and in the pores of the base film to form an integrated structure, the coating and the base film are combined without an adhesive, the COF forms a continuous and uniform film on the base film from bottom to top, the interfacial resistance is obviously reduced due to strong binding force and uniformity, the uniform distribution of Li + is promoted, the wettability of the diaphragm is effectively improved, the rapid transmission and uniform deposition of lithium ions are facilitated,