Lithium battery diaphragm as well as preparation method and application thereof

Abstract

The invention discloses a lithium battery diaphragm and a preparation method and application thereof, the lithium battery diaphragm comprises a base membrane and a coating on the base membrane, and the coating comprises gamma-phase superfine porous alumina. The method for preparing the lithium battery diaphragm comprises the steps that a base membrane is coated with slurry, drying is conducted, a coating is obtained on the base membrane, the lithium battery diaphragm is obtained, and the slurry comprises water, gamma-phase superfine porous aluminum oxide, an adhesive and a dispersing agent. The gamma-phase superfine porous aluminum oxide has a rich powder pore structure, so that the weight of the diaphragm is reduced, and the lithium battery diaphragm disclosed by the invention has high ion conductivity and high wettability while having high temperature resistance. The high-safety lithium ion battery diaphragm is an important way for improving the safety and the cycling stability of a lithium battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery separators, and in particular relates to a lithium battery separator and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries are developing towards high energy density, high power density and long life. As an important component, the diaphragm is developing towards lighter and more functional. The coating material is the main component of the diaphragm, which is responsible for absorbing and storing electrolyte and preventing thermal shrinkage. It can be found that the use of ultrafine ceramic particles at the same thickness can make the coating denser and increase the heat resistance of the diaphragm, but compared with conventional ceramic particle coatings (larger gaps between ceramic particles), the gaps between ultrafine ceramic particles are smaller, which affects the liquid absorption and retention rate and ionic conductivity of the diaphragm.

[0003] How to make the diaphragm maintain a high liquid absorption and retention rate under high temperature conditions will become a direction worthy of our attention. Summary of the invention

[0004] In view of the deficiencies in the prior art, an object of the present invention is to provide a lithium battery separator.

[0005] Another object of the present invention is to provide a method for preparing the above-mentioned lithium battery separator.

[0006] Another object of the present invention is to provide a slurry.

[0007] Another object of the present invention is to provide a method for preparing the slurry.

[0008] The purpose of the present invention is achieved through the following technical solutions.

[0009] A lithium battery separator comprises: a base film and a coating on the base film, wherein the coating comprises: a γ-phase ultrafine porous alumina, wherein the particle size of the γ-phase ultrafine porous alumina is D10: 0.220-0.260 μm, D50: 0.429-0.512 μm, D90: 0.678-0.873 μm, and the specific surface area of ​​the γ-phase ultrafine porous alumina is 18.25-20.07 m 2 / g, and the average pore size of γ-phase ultrafine porous alumina is 11nm.

[0010] The method for preparing the above-mentioned lithium battery diaphragm includes: coating the slurry on the base film, drying, obtaining a coating on the base film, and obtaining the lithium battery diaphragm, wherein the slurry includes: water, γ-phase ultrafine porous alumina, an adhesive and a dispersant.

[0011] In the above technical solution, the adhesive is an acrylic copolymer solution.

[0012] In the above technical solution, the dispersant is ammonium polyacrylate.

[0013] In the above technical solution, the coating thickness is 2 to 3 μm.

[0014] In the above technical solution, the coating speed is 20 to 40 m / min.

[0015] In the above technical solution, the drying temperature is 40-60° C., and the drying time is 1-2 minutes.

[0016] A slurry comprises: water, gamma-phase ultrafine porous alumina, adhesive and dispersant, wherein the ratio of water, gamma-phase ultrafine porous alumina, adhesive and dispersant is (50-70): (20-30): (5-8): (0.2-0.5) by weight.

[0017] In the above technical solution, the ratio of water, γ-phase ultrafine porous alumina, adhesive and dispersant is preferably (50-70): (20-22): (6-8): (0.3-0.4) by mass.

[0018] In the above technical solution, the particle size of the slurry is D50: 0.420-0.500 microns, D90: 0.70-0.93 microns.

[0019] The preparation method of the above-mentioned slurry comprises: mixing water, γ-phase ultrafine porous alumina, adhesive and dispersant until uniform to obtain slurry, wherein the ratio of water, γ-phase ultrafine porous alumina, adhesive and dispersant is (50-70): (20-30): (5-8): (0.2-0.5) by mass.

[0020] In the above technical solution, the method for preparing the slurry comprises the following steps:

[0021] Step 1, mixing a dispersant, water and γ-phase ultrafine porous alumina until uniform to obtain a first solution;

[0022] In step 1, a dispersant, water and γ-phase ultrafine porous alumina are mixed, and stirred at a rotation speed of 1400 to 2500 r / min and a revolution speed of 40 to 60 r / min for 15 to 20 minutes until the mixture is uniform, to obtain the first solution.

[0023] Step 2: Mix the first solution and the adhesive until they are uniform to obtain a slurry.

[0024] In step 2, the first solution and the adhesive are mixed, and stirred and ultrasonicated for 15 to 25 minutes in a vacuum environment until they are uniform. The vacuum degree of the vacuum environment is 0.06 to 0.08 KPA, the stirring rotation speed is 1200 to 4000 r / min, the revolution speed is 30 to 50 r / min, and the ultrasonic frequency is 5 to 8 kHz.

[0025] Application of γ-phase ultrafine porous alumina in improving the wettability, ionic conductivity and / or heat resistance of separators.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The γ-phase ultrafine porous alumina has a rich powder pore structure, which reduces the weight of the diaphragm. The lithium battery diaphragm of the present invention has high temperature resistance while taking into account high ion conductivity and high wettability. High-safety lithium-ion battery diaphragms are an important way to improve the safety and cycle stability of lithium batteries.

[0028] 2. The rich pore structure of the γ-phase ultrafine porous alumina increases the absorption and storage of the electrolyte by the coating. The high porosity of the diaphragm enables Li + The shuttle path becomes shorter, which improves the liquid absorption rate, liquid retention rate and ion conductivity of the separator, thereby reducing the internal resistance of the lithium-ion battery and improving the power density of the battery.

[0029] 3. Compared with conventional ultrafine alumina-coated diaphragms, under the condition of the same coating thickness, since the γ-phase ultrafine porous alumina has more pores, the coating obtained by using a slurry containing γ-phase ultrafine porous alumina can reduce the weight of the coating obtained by conventional ultrafine alumina by about 10%. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is an electron microscope image of the diaphragm prepared in Example 4. DETAILED DESCRIPTION

[0031] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0032] The raw material information involved in the following examples is as follows:

[0033] γ-phase ultrafine porous alumina (powder): Suzhou Jinyi New Material Technology Co., Ltd., γ-phase ultrafine porous alumina powder has D10 = 0.260 μm, D50 = 0.429 μm, D90 = 0.678 μm, and a specific surface area of ​​20.07 m 2 / g, and the average pore size is 11nm. Due to the small particle size of the powder, the coating part has a higher density, which can improve the heat resistance of the diaphragm.

[0034] Acrylate copolymer solution: Baoding Lucky Imaging Material Technology Co., Ltd.;

[0035] Ammonium polyacrylate: Shanghai Sanrui Polymer Materials Technology Co., Ltd.

[0036] The instruments and models involved in the tests in the following embodiments are:

[0037] Double planetary mixer: XFZH-30L.

[0038] In the following examples, water is pure water.

[0039] In the following examples, the base film is a PE film, and the thickness of the base film is 7 μm.

[0040] Ionic conductivity: The test temperature is 25°C and the relative humidity is 50-60%.

[0041] Examples 1 to 3

[0042] A method for preparing a slurry comprises the following steps:

[0043] Step 1, mixing a dispersant, water and γ-phase ultrafine porous alumina in a double planetary mixer, stirring for B min at a rotation speed of A1 r / min and a revolution speed of A2 r / min until uniform, to obtain a first solution;

[0044] Step 2, the first solution and the adhesive are mixed, and in a double planetary mixer, in a vacuum environment with an ultrasonic oscillation function, stirred and ultrasonicated (high-speed dispersion) for 15 minutes until uniform, the vacuum degree of the vacuum environment is 0.06KPA, the stirring rotation speed is A3 r / min, the revolution speed is A4 r / min, and the ultrasonic frequency is 5kHz, to obtain a slurry, in which the ratio of water, γ-phase ultrafine porous alumina, adhesive and dispersant is X by mass, the adhesive is an acrylate copolymer solution (acrylate copolymer is copolymerized by acrylic acid and acrylamide), and the dispersant is ammonium polyacrylate. The values ​​of X, A1, A2, A3, A4 and B are shown in Table 1.

[0045] Table 1

[0046]

[0047] The particle size of the slurry prepared in Example 1 is D50: 0.478 microns, D90: 0.863 microns; the particle size of the slurry prepared in Example 2 is D50: 0.468 microns, D90: 0.752 microns; the particle size of the slurry prepared in Example 3 is D50: 0.450 microns, D90: 0.871 microns.

[0048] Comparative Example 1

[0049] A method for preparing a slurry, comprising: preparing an α-phase alumina (D10=0.472 μm, D50=0.864 μm, D90=1.589 μm, and a specific surface area of ​​5.31 m 2 / g), pure water and dispersant are mixed in a double planetary mixer, first stirred at a rotation speed of 2000r / min and a revolution speed of 45r / min for 30min, and then ultrasonicated at a frequency of 5KHZ for 20min. Add the adhesive, and ultrasonically vibrate for 15min under stirring conditions (the stirring rotation speed is 1500r / min, the revolution speed is 45r / min, and the ultrasonic frequency of ultrasonic vibration is 5kHz) to obtain a slurry. In terms of mass fractions, the ratio of α-phase alumina, pure water, dispersant and adhesive is 25:68.5:0.5:6, the adhesive is an acrylate copolymer solution (acrylate copolymer is copolymerized by acrylic acid and acrylamide), and the dispersant is ammonium polyacrylate.

[0050] Comparative Example 2

[0051] A method for preparing a slurry comprises: mixing conventional ultrafine alumina (α phase) (D10=0.256μm, D50: 0.465 micron, D90: 0.901 micron), pure water and a dispersant in a double planetary mixer, first stirring at a rotation speed of 2500r / min and a revolution speed of 40r / min for 30min, then ultrasonicating at a frequency of 5kHz for 15min, adding an adhesive, and ultrasonically oscillating for 15min under stirring conditions (the stirring rotation speed is 1500r / min, the revolution speed is 40r / min, and the ultrasonic frequency of the ultrasonic oscillation is 5kHz) to obtain a slurry, wherein the ratio of conventional ultrafine alumina (α phase), pure water, dispersant and adhesive is 30:63.5:0.5:6 by mass, the adhesive is an acrylate copolymer solution (the acrylate copolymer is copolymerized by acrylic acid and acrylamide), and the dispersant is ammonium polyacrylate.

[0052] Comparative Example 3

[0053] A method for preparing a slurry comprises: mixing γ-phase porous alumina (D10=0.364μm, D50: 0.865 micrometer, D90: 1.542 micrometer), pure water and a dispersant in a double planetary mixer, first stirring at a rotation speed of 2500r / min and a revolution speed of 40r / min for 30min, then ultrasonicating at a frequency of 5kHz for 15min, adding an adhesive, and ultrasonically oscillating for 15min under stirring conditions (the stirring rotation speed is 1500r / min, the revolution speed is 40r / min, and the ultrasonic frequency of the ultrasonic oscillation is 5kHz) to obtain a slurry, wherein the ratio of the γ-phase porous alumina, pure water, dispersant and adhesive is 25:68.5:0.5:6 by mass, the adhesive is an acrylate copolymer solution (the acrylate copolymer is copolymerized by acrylic acid and acrylamide), and the dispersant is ammonium polyacrylate.

[0054] Examples 4 to 6 and Comparative Examples 4 to 6

[0055] A method for preparing a diaphragm, comprising: placing a base film on a coating machine equipped with a slurry, coating the slurry on one side of the base film at a coating speed of E m / min, pulling the base film into a drying device through a traction roller, drying the base film at F°C for G min, obtaining a coating on the base film, and obtaining a lithium battery diaphragm. The slurry is one of the slurries prepared in Examples 1 to 3 and Comparative Examples 1 to 3.

[0056] Table 2

[0057] Diaphragm Slurry for preparing diaphragm E(m / min) F(℃) G(min) Example 4 Example 1 20 40 2 Example 5 Example 2 30 50 2 Example 6 Example 3 40 60 2 Comparative Example 4 Comparative Example 1 20 50 3 Comparative Example 5 Comparative Example 2 30 50 3 Comparative Example 6 Comparative Example 3 30 50 3

[0058] The test data of the diaphragm prepared in Example 4 are as follows:

[0059]

[0060] The test data of the diaphragm prepared in Example 5 are as follows:

[0061]

[0062] The test data of the diaphragm prepared in Example 6 are as follows:

[0063]

[0064] The test data of the diaphragm prepared in Comparative Example 4 are as follows:

[0065]

[0066]

[0067] The test data of the diaphragm prepared in Comparative Example 5 are as follows:

[0068]

[0069] The test data of the diaphragm prepared in Comparative Example 6 are as follows:

[0070]

[0071] Figure 1 This is an electron microscope image of the diaphragm prepared in Example 4.

[0072] The phase transition sequence of alumina is AlOOH-γ-δ-θ-α. In the process of AlOOH transforming to the γ phase, water molecules escape to form pores to form porous alumina. Compared with conventional ultrafine alumina (α phase), the γ phase ultrafine porous alumina has an extremely rich pore structure, which can effectively reduce the weight of the coating film and make the diaphragm thinner. It also has good electrochemical and chemical stability, and can better bear the electrolyte infiltration and absorption while maintaining a certain thermal shrinkage, thereby improving the liquid absorption rate, liquid retention rate and ionic conductivity of the diaphragm.

[0073] The present invention is described above by way of example. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacement that can be made by those skilled in the art without inventive effort falls within the protection scope of the present invention.

Claims

1. A lithium battery separator, comprising: The base film and the coating on the base film, the coating comprising: gamma phase ultrafine porous alumina, the particle size of the gamma phase ultrafine porous alumina is D10: 0.22-0.27 μm, D50: 0.40-0.52 μm, D90: 0.60-0.90 μm, and the specific surface area of ​​the gamma phase ultrafine porous alumina is 18-21 m 2 / g.

2. The method for preparing the lithium battery separator according to claim 1, characterized in that: include: The slurry is coated on the base film and dried to obtain a coating on the base film to obtain a lithium battery separator. The slurry includes: water, gamma-phase ultrafine porous alumina, an adhesive and a dispersant.

3. The method according to claim 2, characterized in that The adhesive is an acrylate copolymer solution, and the dispersant is polyacrylate ammonium salt.

4. The method according to claim 2, characterized in that: The coating thickness is 2 to 3 μm.

5. A slurry, characterized in that: include: The ratio of water, gamma-phase ultrafine porous alumina, adhesive and dispersant is (50-70): (20-30): (5-8): (0.2-0.5) by weight.

6. The slurry according to claim 5, characterized in that The particle size of the slurry is D50: 0.420-0.500 micron, D90: 0.701-0.922 micron.

7. The method for preparing the slurry according to claim 5, characterized in that: include: Water, γ-phase ultrafine porous alumina, adhesive and dispersant are mixed until uniform to obtain a slurry, wherein the ratio of water, γ-phase ultrafine porous alumina, adhesive and dispersant is (50-70): (20-30): (5-8): (0.2-0.5) by mass.

8. Application of γ-phase ultrafine porous alumina in improving the ionic conductivity of diaphragms.

9. Application of γ-phase ultrafine porous alumina in improving the heat resistance of diaphragms.

10. Application of γ-phase ultrafine porous alumina in improving the liquid absorption rate and / or liquid retention rate of diaphragms.

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