Thermal shock resistant alumina fiber / glass fiber composite battery separator assembly and preparation method thereof

Abstract

The present invention belongs to the field of battery separators, and in particular relates to a thermal shock resistant alumina fiber / glass fiber composite battery separator assembly and a preparation method thereof. The method comprises the following steps: mixing alumina powder, polyvinyl alcohol and a solvent, and ball milling to form a ceramic matrix slurry; subjecting glass fiber cloth and alumina fiber cloth to a high-temperature degumming treatment; negative pressure impregnation: placing the glass fiber cloth and alumina fiber cloth in a vacuum impregnation device respectively, evacuating the device, injecting the ceramic matrix slurry, and allowing the ceramic matrix slurry to immerse the glass fiber cloth and alumina fiber, and continuously evacuating the device for 3-8 hours to fully impregnate the fiber cloth with the ceramic matrix slurry; laying the treated glass fiber cloth and alumina fiber cloth; then, adding a mold for hot pressing and forming; then, heating at a constant temperature to fully volatilize the solvent in the ceramic matrix slurry to obtain a green body; sintering the green body, and then naturally cooling the green body to obtain a thermal shock resistant alumina fiber / glass fiber composite battery separator assembly.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery separators, and in particular relates to a thermal shock resistant alumina fiber / glass fiber composite battery separator assembly and a preparation method thereof. Background Art

[0002] As one of the core components of lithium-ion batteries, the separator is located between the positive and negative electrodes, preventing battery short circuits caused by contact between the positive and negative electrodes, while allowing lithium ions to pass freely, providing a transmission channel for lithium ions between the two electrodes. The performance of the separator directly affects the electrochemical performance, safety, and cycle life of lithium-ion batteries. Therefore, the battery separator is required to have appropriate porosity, excellent mechanical properties, chemical stability, and thermal stability. At present, the lithium-ion battery separators commonly used in the market are polyolefin microporous films, represented by polyethylene (PE) and polypropylene (PP). They have the advantages of good chemical stability, low production cost, and simple process. However, polyolefin microporous films have poor heat resistance and are prone to deformation and shrinkage at high temperatures, causing safety accidents such as battery short circuits and explosions, posing a great safety hazard. Therefore, the research and development of safe, stable, and high-performance lithium-ion battery separators is of great significance to the development of lithium-ion batteries. Summary of the Invention

[0003] Technical issues:

[0004] Provided is a method for preparing a battery separator assembly to obtain a battery separator assembly having the properties of impact resistance, high heat resistance and low thermal conductivity.

[0005] Technical solution:

[0006] On the one hand, a method for preparing a thermal shock resistant alumina fiber / glass fiber composite battery separator assembly is provided, comprising the following steps:

[0007] (1) Preparing a ceramic matrix slurry: mixing alumina powder, polyvinyl alcohol, and a solvent, and ball milling to form a ceramic matrix slurry; wherein: the average particle size of the alumina powder is 0.1-0.3 μm; the mass concentration of polyvinyl alcohol in the ceramic matrix slurry is 0.5-2 wt %, and the solid content of alumina is 40-60 wt %;

[0008] (2) Fiber cloth degumming: The glass fiber cloth and the alumina fiber cloth are subjected to a high-temperature degumming treatment at 500-800°C for 1-2 hours respectively; the alumina fibers in the alumina fiber cloth are continuous alumina fibers; the fineness of the fibers in the glass fiber cloth and the alumina fiber cloth is 55-400 Tex;

[0009] (3) Negative pressure impregnation: The glass fiber cloth and alumina fiber cloth treated in step (2) are placed in a vacuum impregnation device respectively, vacuumed, and the ceramic matrix slurry is injected so that the ceramic matrix slurry immerses the glass fiber cloth and alumina fiber. The vacuum is continuously applied for 3-8 hours to allow the ceramic matrix slurry to fully impregnate the fiber cloth;

[0010] (4) Lamination + Hot Pressing: Lay the glass fiber cloth and alumina fiber cloth treated in step (3) and then add a mold for hot pressing. Then, heat at a constant temperature to fully volatilize the solvent in the ceramic matrix slurry to obtain a green body.

[0011] (5) Sintering: The green body is sintered and then cooled naturally to obtain a thermal shock resistant alumina fiber / glass fiber composite battery separator assembly.

[0012] In some embodiments, the glass fibers in the glass fiber cloth are E-grade glass fibers.

[0013] In some embodiments, in step (4), the glass fiber cloth and alumina fiber cloth treated in step (3) are layered in sequence in the order of one layer of glass fiber cloth, n layers of alumina fiber cloth, and one layer of glass fiber cloth, where n is an odd number greater than or equal to 3; the n layers of alumina fiber cloth are obtained by alternately layering according to different weaving angles.

[0014] In some embodiments, n is equal to 3, and a layer of glass fiber cloth, three layers of alumina fiber cloth, and a layer of glass fiber cloth are laid in such a manner that the braiding angles are 0° / 90° / 0° / 90° / 0° or 0° / -45° / 45° / -45° / 0°.

[0015] In some embodiments, the alumina fiber cloth and the glass fiber cloth are both two-dimensional woven fabrics, and the weaving method of the alumina fiber cloth and the glass fiber cloth is one of plain weave, twill weave or satin weave.

[0016] In some embodiments, the lamination method in step (4) is one of unidirectional lamination, orthogonal lamination or symmetrical lamination.

[0017] In some embodiments, in step (1), the ball milling treatment time is 2-3 hours.

[0018] In some embodiments, in step (5), the sintering parameters are: sintering temperature is 1000-1200° C., and sintering time is 1-3 hours.

[0019] In some embodiments, in step (3), the vacuum degree of the vacuum is -0.1 MPa.

[0020] In some embodiments, in step (4), the parameters of the mold hot pressing molding are: pressure of 4-10 MPa, hot pressing program of 50-80°C for 5 hours, and 120°C for 1-2 hours.

[0021] On the other hand, a thermal shock resistant alumina fiber / glass fiber composite battery separator assembly prepared by the aforementioned method is provided.

[0022] Beneficial effects:

[0023] (1) The alumina fiber / glass fiber composite battery separator assembly prepared by the present invention has the characteristics of impact resistance, high heat resistance, low thermal conductivity and good heat dissipation: according to the ASTM C1341 standard, the bending strength test was carried out on it and it was found that the bending strength can reach 634MPa; according to the ASTM C1421 standard, the fracture toughness test of the separator assembly was found to be 16.1MPa·m 1 / 2 According to ASTM E831-06 standard, the thermal expansion coefficient of the diaphragm assembly was tested and found to be as low as 6.8*10 -6 / ℃; according to ASTM C518 standard, the thermal conductivity of the diaphragm assembly was analyzed and found to be as low as 0.11W / (m·K);

[0024] (2) Compared with traditional polyolefin microporous films, the alumina fiber / glass fiber composite battery separator assembly prepared by the present invention can effectively reduce the risk of safety accidents such as battery short circuit and explosion caused by the denaturation and shrinkage of the battery separator due to high temperature;

[0025] (3) The alumina fiber / glass fiber composite battery diaphragm assembly of the present invention adopts a glass fiber / alumina fiber / glass fiber composite sandwich structure. Based on a specific process, the battery diaphragm assembly is endowed with excellent comprehensive properties such as impact resistance, low thermal conductivity, high heat resistance, and heat dissipation. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic structural diagram of the thermal shock resistant alumina fiber / glass fiber composite battery separator assembly in Example 1, wherein the direction perpendicular to the warp direction is the weft direction. DETAILED DESCRIPTION

[0027] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0028] On the one hand, a method for preparing a thermal shock resistant alumina fiber / glass fiber composite battery separator assembly is provided, comprising the following steps:

[0029] (1) Preparing a ceramic matrix slurry: mixing alumina powder, polyvinyl alcohol, and a solvent, and ball milling to form a ceramic matrix slurry; wherein: the average particle size of the alumina powder is 0.1-0.3 μm; the mass concentration of polyvinyl alcohol in the ceramic matrix slurry is 0.5-2 wt %, and the solid content of alumina is 40-60 wt %;

[0030] (2) Fiber cloth degumming: The glass fiber cloth and the alumina fiber cloth are subjected to a high-temperature degumming treatment at 500-800°C for 1-2 hours respectively; the alumina fibers in the alumina fiber cloth are continuous alumina fibers; the fineness of the fibers in the glass fiber cloth and the alumina fiber cloth is 55-400 Tex;

[0031] (3) Negative pressure impregnation: The glass fiber cloth and alumina fiber cloth treated in step (2) are placed in a vacuum impregnation device respectively, vacuumed, and the ceramic matrix slurry is injected so that the ceramic matrix slurry immerses the glass fiber cloth and alumina fiber. The vacuum is continuously applied for 3-8 hours to allow the ceramic matrix slurry to fully impregnate the fiber cloth;

[0032] (4) Lamination + Hot Pressing: Lay the glass fiber cloth and alumina fiber cloth treated in step (3) and then add a mold for hot pressing. Then, heat at a constant temperature to fully volatilize the solvent in the ceramic matrix slurry to obtain a green body.

[0033] (5) Sintering: The green body is sintered and then cooled naturally to obtain a thermal shock resistant alumina fiber / glass fiber composite battery separator assembly.

[0034] In some embodiments, the glass fibers in the glass fiber cloth are E-grade glass fibers.

[0035] In some embodiments, in step (4), the glass fiber cloth and alumina fiber cloth treated in step (3) are layered in sequence in the order of one layer of glass fiber cloth, n layers of alumina fiber cloth, and one layer of glass fiber cloth, where n is an odd number greater than or equal to 3; the n layers of alumina fiber cloth are obtained by alternately layering according to different weaving angles.

[0036] In some embodiments, n is equal to 3, and a layer of glass fiber cloth, three layers of alumina fiber cloth, and a layer of glass fiber cloth are laid in such a manner that the braiding angles are 0° / 90° / 0° / 90° / 0° or 0° / -45° / 45° / -45° / 0°.

[0037] In some embodiments, the alumina fiber cloth and the glass fiber cloth are both two-dimensional woven fabrics, and the weaving method of the alumina fiber cloth and the glass fiber cloth is one of plain weave, twill weave or satin weave.

[0038] In some embodiments, the lamination method in step (4) is one of unidirectional lamination, orthogonal lamination or symmetrical lamination.

[0039] In some embodiments, in step (1), the ball milling treatment time is 2-3 hours.

[0040] In some embodiments, in step (5), the sintering parameters are: sintering temperature is 1000-1200° C., and sintering time is 1-3 hours.

[0041] In some embodiments, in step (3), the vacuum degree of the vacuum is -0.1 MPa.

[0042] In some embodiments, in step (4), the parameters of the mold hot pressing molding are: pressure of 4-10 MPa, hot pressing program of 50-80°C for 5 hours, and 120°C for 1-2 hours.

[0043] On the other hand, a thermal shock resistant alumina fiber / glass fiber composite battery separator assembly prepared by the aforementioned method is provided.

[0044] Test method:

[0045] Bending strength test: According to ASTM C1341 standard, the diaphragm assembly is subjected to bending strength test.

[0046] Fracture toughness test: According to ASTM C1421 standard, the fracture toughness test of the diaphragm assembly is carried out.

[0047] Thermal expansion coefficient test: According to ASTM E831-06 standard, the thermal expansion coefficient of the diaphragm assembly is tested.

[0048] Thermal conductivity test: According to ASTM C518 standard, the thermal conductivity of the diaphragm assembly is analyzed.

[0049] Example 1

[0050] A method for preparing a thermal shock resistant alumina fiber / glass fiber composite battery separator assembly comprises the following steps:

[0051] (1) Preparing a ceramic matrix slurry: Alumina powder, polyvinyl alcohol, and a solvent were mixed and ball-milled for 2 h to form a ceramic matrix slurry; wherein: the average particle size of the alumina powder was 0.2 μm; the mass concentration of polyvinyl alcohol in the ceramic matrix slurry was 1 wt %, and the solid content of alumina was 50 wt %;

[0052] (2) Fiber cloth degumming: The glass fiber cloth and the alumina fiber cloth were placed in a muffle furnace and subjected to a high-temperature degumming treatment at 600°C for 2 h; wherein: the weaving method of the glass fiber cloth and the alumina fiber cloth were both plain weave; the weaving angle of the glass fiber cloth was 0°; the weaving angle of the alumina fiber cloth was 0° or 90°; the glass fiber in the glass fiber cloth was E-grade glass fiber; the alumina fiber in the alumina fiber cloth was alumina continuous fiber (e.g., Akabane alumina continuous fiber), purchased from Shanghai Rongrong New Materials Co., Ltd.; the fineness of the glass fiber and alumina fiber was 200 tex respectively;

[0053] (3) Negative pressure impregnation: The glass fiber cloth and alumina fiber cloth treated in step (2) are placed in a vacuum impregnation device respectively, and the vacuum is evacuated to a vacuum degree of -0.1 MPa. The ceramic matrix slurry prepared in step (1) is injected, and the ceramic matrix slurry is immersed in the glass fiber cloth and the alumina fiber. During the process of injecting the ceramic matrix slurry, the vacuum is continuously drawn to maintain a negative pressure environment. After the injection of the ceramic matrix slurry is completed, the vacuum is continuously drawn for 5 hours to ensure that the ceramic matrix slurry fully impregnates the fiber cloth;

[0054] (4) Lamination + hot pressing: Figure 1 As shown, the glass fiber cloth and alumina fiber cloth treated in step (3) are layered in the order of one layer of glass fiber cloth 1, three layers of alumina fiber cloth 2, and one layer of glass fiber cloth 1, with the weaving angles being 0° / 90° / 0° / 90° / 0° in sequence; then, a mold is added for hot pressing (pressure is 8 MPa, hot pressing procedure: 60°C for 5 hours, then 120°C for 2 hours); then, the mold is placed in a blast dryer at a constant temperature of 80°C to fully evaporate the solvent in the ceramic matrix slurry for 2 hours to obtain a green body;

[0055] (5) Sintering: The green body obtained in step (4) is sintered in a muffle furnace at 1000° C. for 2 h, and then cooled naturally to obtain a thermal shock resistant alumina fiber / glass fiber composite battery separator assembly.

[0056] Comparative Example 1

[0057] A method for preparing a battery separator assembly, referring to Example 1, except that the weaving methods of the glass fiber cloth and the alumina fiber cloth in step (2) are replaced with twill weaving to obtain an alumina fiber / glass fiber composite battery separator assembly.

[0058] Comparative Example 2

[0059] A method for preparing a battery separator assembly, referring to Example 1, except that the weaving methods of the glass fiber cloth and the alumina fiber cloth in step (2) are replaced with satin weaving to obtain an alumina fiber / glass fiber composite battery separator assembly.

[0060] Comparative Example 3

[0061] A method for preparing a battery separator assembly, referring to Example 1, except that the braiding angle of the alumina fiber cloth in step (2) is adjusted to 45° or -45°; and the laying method in step (4) is adjusted to: the braiding angles are 0° / -45° / 45° / -45° / 0° in sequence, to obtain an alumina fiber / glass fiber composite battery separator assembly.

[0062] Comparative Example 4

[0063] A method for preparing a battery diaphragm assembly, referring to Example 1, differs only in that, in steps (2) to (4), only glass fiber cloth is used, and alumina fiber cloth is not used, that is, the alumina fiber cloth is replaced by glass fiber cloth, and the braiding angle of the glass fiber cloth is 0° or 90°; in the laying process of step (4), the glass fiber cloth treated in step (3) is laid in the order of one layer of glass fiber cloth, three layers of glass fiber cloth and one layer of glass fiber cloth, and the laying method is: the braiding angles are 0° / 90° / 0° / 90° / 0° in sequence, and the other steps and parameters remain unchanged, thereby obtaining a battery diaphragm assembly.

[0064] Comparative Example 5

[0065] The invention discloses a battery separator assembly, which adopts a commercially available polyethylene separator.

[0066] The battery separator assemblies obtained in Example 1 and Comparative Examples 1-3 were subjected to performance tests, and the test results are shown in Table 1 below.

[0067] Table 1 Test results of Example 1 and Comparative Examples 1-5

[0068]

[0069]

[0070] The embodiments provided above are not intended to limit the scope of the present invention, nor are the steps described to limit their execution order. Any obvious improvements to the present invention made by those skilled in the art in combination with existing common knowledge shall fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing a thermal shock resistant alumina fiber / glass fiber composite battery separator assembly, characterized in that: The following steps are involved: (1) Preparing a ceramic matrix slurry: mixing alumina powder, polyvinyl alcohol, and a solvent, and ball milling to form a ceramic matrix slurry; wherein: the average particle size of the alumina powder is 0.1-0.3 μm; the mass concentration of polyvinyl alcohol in the ceramic matrix slurry is 0.5-2 wt %, and the solid content of alumina is 40-60 wt %; (2) Fiber cloth degumming: The glass fiber cloth and the alumina fiber cloth are subjected to a high-temperature degumming treatment at 500-800°C for 1-2 hours respectively; the alumina fibers in the alumina fiber cloth are continuous alumina fibers; the fineness of the fibers in the glass fiber cloth and the alumina fiber cloth is 55-400 Tex; (3) Negative pressure impregnation: The glass fiber cloth and alumina fiber cloth treated in step (2) are placed in a vacuum impregnation device respectively, vacuumed, and the ceramic matrix slurry is injected so that the ceramic matrix slurry immerses the glass fiber cloth and alumina fiber. The vacuum is continuously applied for 3-8 hours to allow the ceramic matrix slurry to fully impregnate the fiber cloth; (4) Lamination + Hot Pressing: The glass fiber cloth and alumina fiber cloth treated in step (3) are laid in the order of one layer of glass fiber cloth, n layers of alumina fiber cloth, and one layer of glass fiber cloth, wherein n is an odd number greater than or equal to 3; the n layers of alumina fiber cloth are alternately laid in layers according to different braiding angles; then, a mold is added for hot pressing; and then constant temperature heating is performed to fully volatilize the solvent in the ceramic matrix slurry to obtain a green body; (5) Sintering: The green body is sintered and then cooled naturally to obtain a thermal shock resistant alumina fiber / glass fiber composite battery separator assembly.

2. The method according to claim 1, characterized in that The glass fibers in the glass fiber cloth are E-grade glass fibers.

3. The method according to claim 2, characterized in that n is equal to 3. The laying method of one layer of glass fiber cloth, three layers of alumina fiber cloth and one layer of glass fiber cloth is: the weaving angles are 0° / 90° / 0° / 90° / 0° or 0° / -45° / 45° / -45° / 0°.

4. The method according to claim 1, wherein The alumina fiber cloth and the glass fiber cloth are both two-dimensional woven fabrics, and the weaving method of the alumina fiber cloth and the glass fiber cloth is one of plain weave, twill weave or satin weave.

5. The method according to claim 1, characterized in that The laying method in step (4) is one of unidirectional laying, orthogonal laying or symmetrical laying.

6. The method according to claim 1, characterized in that In step (1), the ball milling treatment time is 2-3 hours.

7. The method according to claim 1, characterized in that In step (5), the sintering parameters are: sintering temperature is 1000-1200° C., and sintering time is 1-3 hours.

8. The method according to claim 1, characterized in that In step (4), the parameters of the mold hot pressing molding are: pressure of 4-10 MPa, hot pressing program of 50-80°C for 5 hours, and 120°C for 1-2 hours.

9. A thermal shock resistant alumina fiber / glass fiber composite battery separator assembly prepared by the method according to any one of claims 1 to 8.

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