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CN-122025992-A - Composite diaphragm for high-performance lithium ion battery and preparation method thereof

CN122025992ACN 122025992 ACN122025992 ACN 122025992ACN-122025992-A

Abstract

The invention discloses a composite diaphragm for a high-performance lithium ion battery and a preparation method thereof, belonging to the technical field of battery diaphragms; the composite diaphragm for the high-performance lithium ion battery comprises a diaphragm base film and ceramic slurry coated on the surface of the diaphragm base film, wherein raw material components of the ceramic slurry comprise alumina composite aerogel, deionized water, a dispersing agent, a defoaming agent, a surfactant, a binder, a plasticizer and a flame retardant, wherein the composite diaphragm for the high-performance lithium ion battery is prepared by ageing alumina sol in an ethyl orthosilicate alcohol solution by adopting a sol-gel method, then carrying out surface modification and acetylation by adopting triethoxy-2-pyridine silane, the dispersing agent adopts lithium polyacrylate, the defoaming agent adopts n-octanoic acid, the surfactant adopts fatty alcohol polyoxyethylene ether, the binder adopts polyvinyl alcohol, the plasticizer adopts polyethylene glycol, and the flame retardant adopts hexa-p-aldehyde phenoxy cyclotriphosphazene.

Inventors

  • ZHOU FEIFEI
  • ZHANG LIBIN
  • MENG XIANWEI
  • ZHAO HAIYU
  • ZHOU XIAOXIA
  • WENG XINGXING
  • MAO YUAN

Assignees

  • 重庆厚生新材料科技有限公司

Dates

Publication Date
20260512
Application Date
20260128

Claims (10)

  1. 1. The composite diaphragm for the high-performance lithium ion battery comprises a base film and a ceramic layer on the surface of the base film, and is characterized in that the ceramic layer is obtained by coating ceramic slurry on the surface of the base film, and raw material components of the ceramic slurry comprise aluminum oxide composite aerogel, deionized water, a dispersing agent, a defoaming agent, a surfactant, a binder, a plasticizer and a flame retardant.
  2. 2. The composite separator for high-performance lithium ion batteries according to claim 1, wherein the base film is a polyolefin-based film, and the base film thickness is 7 μm.
  3. 3. The composite diaphragm for the high-performance lithium ion battery, according to claim 1, is characterized in that the mass ratio of the aluminum oxide composite aerogel, deionized water, a dispersing agent, a defoaming agent, a surfactant, a binder, a plasticizer and a flame retardant is (80-100): (100-120): (2-4): (1.2-1.8): (0.2-2): (30-50): (8-12): (5-15).
  4. 4. The composite separator for high-performance lithium ion batteries according to claim 1, wherein the alumina composite aerogel is obtained by aging an alumina sol in an ethyl orthosilicate alcohol solution by a sol-gel method, and then performing surface modification and acetylation by triethoxy-2-pyridine silane.
  5. 5. The composite separator for a high-performance lithium ion battery according to claim 1, wherein the dispersing agent comprises lithium polyacrylate, the defoaming agent comprises n-octanoic acid, the surfactant comprises fatty alcohol polyoxyethylene ether, the binder comprises polyvinyl alcohol, and the plasticizer comprises polyethylene glycol.
  6. 6. The composite separator for high-performance lithium ion batteries according to claim 1, wherein said flame retardant is hexa-p-aldehyde phenoxy cyclotriphosphazene.
  7. 7. A method for preparing the composite separator for a high-performance lithium ion battery according to any one of claims 1 to 6, characterized in that the preparation steps include: (1) Dispersing the alumina composite aerogel in absolute ethyl alcohol, adding a flame retardant and sodium hydroxide, stirring for 4-6 hours at room temperature, adding concentrated ammonia water, refluxing for 11-13 hours, cooling to room temperature, and performing suction filtration, washing and drying to obtain a premix; (2) Mixing and ball milling premix, water, a dispersing agent, a 2/3 defoaming agent and a surfactant for 11-13 hours, then adding a binder, a plasticizer and the rest defoaming agent, continuing ball milling for 11-13 hours, and performing vacuum defoaming after ball milling to obtain ceramic slurry; (3) And uniformly coating the ceramic slurry on the surface of the base film by using a coating machine to form a ceramic layer.
  8. 8. The preparation method of the composite diaphragm for the high-performance lithium ion battery, which is disclosed in claim 7, is characterized in that the mass ratio of the aluminum oxide composite aerogel to the absolute ethyl alcohol to the sodium hydroxide to the concentrated ammonia water is (18-21): 80-100): 4.5-5.5): 53-55.
  9. 9. The method for preparing a composite separator for a high-performance lithium ion battery according to claim 7, wherein the preparation steps of the alumina composite aerogel are as follows: A1. Mixing aluminum trichloride hexahydrate, deionized water and absolute ethyl alcohol, stirring at room temperature for 4-6 hours to form sol, then sequentially adding formamide and propylene oxide, continuously stirring for 10 minutes, and accelerating sol-gel conversion to obtain aluminum sol; A2. Pouring an ethanol solution of tetraethoxysilane into a centrifuge tube containing aluminum sol, enabling the liquid level to reach 2/3 of the height of the centrifuge tube, standing and aging for 23-25 h at 43-47 ℃, and then replacing the centrifuge tube with absolute ethanol for 4 times within 48 hours to obtain wet gel; A3. Dissolving triethoxy-2-pyridine silane in absolute ethyl alcohol, adding the absolute ethyl alcohol into wet gel, reacting for 23-24 hours at 55-65 ℃, washing with absolute ethyl alcohol, drying, grinding and sieving to obtain a composite aerogel blank; A4. dispersing the composite aerogel blank in acetonitrile, then adding paraldehyde, ferrous sulfate heptahydrate, trifluoroacetic acid and tert-butyl peroxide, heating and refluxing for 3-5 hours, then cooling to room temperature, suction filtering, washing and drying to obtain the aluminum oxide composite aerogel.
  10. 10. The preparation method of the composite membrane for the high-performance lithium ion battery is characterized in that in the step A1, the mole ratio of aluminum trichloride hexahydrate, deionized water, absolute ethyl alcohol, formamide and propylene oxide is 1:20:7-9:0.7-0.9:7-9, the mole ratio of triethoxy-2-pyridine silane to absolute ethyl alcohol and aluminum trichloride hexahydrate in the step A3 is 1.5-1.6:15-16:3, the mole ratio of triethoxy-2-pyridine silane, paraldehyde, ferrous sulfate heptahydrate, trifluoroacetic acid and tert-butyl peroxide is 127:610-630:2.1-2:120-140:250-254, and the mass ratio of the composite aerogel blank to acetonitrile is 1:8-10.

Description

Composite diaphragm for high-performance lithium ion battery and preparation method thereof Technical Field The invention relates to the technical field of battery diaphragms, in particular to a composite diaphragm for a high-performance lithium ion battery and a preparation method thereof. Background With the rapid development of new energy automobiles, energy storage systems and portable electronic devices, higher requirements are put on the energy density, cycle life, safety performance and the like of lithium ion batteries. As one of the key components of the lithium ion battery, the separator has good electrolyte wettability, excellent ion transmission capability and structural stability under high temperature or abnormal working conditions while isolating the positive electrode from the negative electrode and preventing short circuit in the battery. The traditional polyolefin diaphragm has the advantages of low cost, good mechanical strength, controllable pore structure and the like, but the inherent defects are increasingly remarkable, namely, on one hand, the polyolefin material has a low melting point, is easy to thermally shrink or even melt and close pores under the high-temperature condition to cause short circuit in a battery to cause thermal runaway, on the other hand, the surface of the polyolefin material has strong hydrophobicity, has poor wettability to polar electrolyte, limits the rapid migration of lithium ions to influence the rate performance of the battery, and in addition, the polyolefin material has no flame retardant property and is difficult to effectively inhibit fire risks under the abuse condition of the battery. In order to overcome the above problems, a strategy of forming a composite separator by coating inorganic ceramic particles on the surface of a base film has been widely used by researchers in recent years. The ceramic layer can not only remarkably improve the thermal dimensional stability of the diaphragm and inhibit the shrinkage deformation of the high Wen Xiaji film, but also enhance the affinity to electrolyte through abundant surface hydroxyl groups, thereby improving the ionic conductivity. Meanwhile, part of the functional ceramic material also has the characteristics of intrinsic flame retardance or endothermic decomposition, and can absorb heat and release nonflammable gas or form a compact protective layer in the initial stage of thermal runaway, thereby effectively delaying or preventing flame propagation. However, existing ceramic coated membranes still face a number of challenges, such as the severe agglomeration of particles in the ceramic slurry can reduce the uniformity of the coating, affecting the continuity of the ion transport channels, and furthermore, relying solely on physical coating can be difficult to balance between high porosity, high thermal stability and high ionic conductivity. Therefore, development of a composite separator for a high-performance lithium ion battery and a high-efficiency and controllable preparation method thereof are needed to comprehensively improve the safety and electrochemical performance of the lithium ion battery. Disclosure of Invention The invention aims to provide a composite diaphragm for a high-performance lithium ion battery and a preparation method thereof, so as to solve the technical problems in the background art. The technical scheme for realizing the aim of the invention is as follows: The invention provides a composite diaphragm for a high-performance lithium ion battery, which comprises a base film and a ceramic layer on the surface of the base film, wherein the ceramic layer is formed by coating ceramic slurry on the surface of the base film, and raw material components of the ceramic slurry comprise aluminum oxide composite aerogel, deionized water, a dispersing agent, a defoaming agent, a surfactant, a binder, a plasticizer and a flame retardant. Further, the base film is a polyolefin-based film, and the base film thickness is 7 μm. The alumina composite aerogel comprises, by mass, 80-100 parts of aluminum oxide composite aerogel, 100-120 parts of deionized water, 2-4 parts of dispersant, 1.2-1.8 parts of plasticizer and 5-15 parts of flame retardant, 30-50 parts of plasticizer, 8-12 parts of surfactant and 5-15 parts of plasticizer. Further, the alumina composite aerogel is obtained by ageing alumina sol in an ethyl orthosilicate alcohol solution by adopting a sol-gel method, and then carrying out surface modification and acetylation by adopting triethoxy-2-pyridine silane. Further, the dispersing agent comprises lithium polyacrylate, the defoaming agent comprises n-octanoic acid, the surfactant comprises fatty alcohol polyoxyethylene ether, the binder comprises polyvinyl alcohol, and the plasticizer comprises polyethylene glycol. Further, the flame retardant adopts hexa-para-aldehyde phenoxy cyclotriphosphazene. In a second aspect, the present invention provides a method for preparing the comp