Low-water-absorption high-temperature-resistant lithium battery diaphragm and preparation method thereof

Abstract

The invention discloses a low-water-absorptivity high-temperature-resistant lithium battery diaphragm and a preparation method thereof, the low-water-absorptivity high-temperature-resistant lithium battery diaphragm comprises a base membrane and a coating on the base membrane, and the coating comprises porous ceramic and nano ceramic. The nano-ceramics are well filled among the porous ceramics, so that the permeation path of moisture is reduced, and the water absorption of the diaphragm is reduced, thereby improving the safety and cycling stability of the lithium battery; the diaphragm has good high-temperature resistance due to good compactness of the coating, so that the diaphragm can be kept stable in a high-temperature environment, and risks of diaphragm shrinkage, melting and even combustion caused by temperature rise are reduced, so that the overall safety of the battery is improved, and the service life of the battery is prolonged.

Description

Technical Field

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

[0002] Lithium-ion batteries are developing towards high energy density, high power density and long life. As a key component, the diaphragm is also evolving towards being thinner and more functionalized to improve battery performance and safety. In order to improve the liquid absorption and retention rate and ion conductivity of the diaphragm, researchers used porous ceramics to modify the PE diaphragm. Porous ceramics, due to their rich pore structure, can not only reduce the weight of the diaphragm, but also improve its liquid absorption and retention rate and ion conductivity. However, porous ceramics have a large specific surface area and are prone to water absorption, which may eventually cause the water content of the diaphragm to exceed the standard, especially in a high humidity environment. Therefore, reducing the water absorption of porous ceramic coated diaphragms becomes a key issue.

[0003] In addition, when the battery operating temperature is too high, the diaphragm is easily damaged, causing the battery to short-circuit, thereby causing the lithium-ion battery to explode. How to effectively improve the heat resistance of the diaphragm is also a crucial issue. Summary of the invention

[0004] In view of the deficiencies in the prior art, an object of the present invention is to provide a low water absorption and high temperature resistant lithium battery separator.

[0005] Another object of the present invention is to provide a method for preparing the above-mentioned low water absorption and high temperature resistant lithium battery separator.

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

[0007] The purpose of the present invention is achieved through the following technical solutions.

[0008] A low-water-absorption, high-temperature-resistant lithium battery separator comprises a base film and a coating on the base film, wherein the coating comprises porous ceramics and nano-ceramics, and the ratio of the porous ceramics to the nano-ceramics is (20-30): (10-18) by mass.

[0009] In the above technical solution, the porous ceramic is porous alumina.

[0010] In the above technical solution, the particle size of the porous ceramic is: D10 = 0.225 ~ 0.301 μm, D50 = 0.552 ~ 0.651 μm, D90 = 1.543 ~ 1.793 μm, and the specific surface area of ​​the porous ceramic is 15.342 ~ 17.553 m 2 / g.

[0011] In the above technical solution, the nano-ceramic is one of nano-alumina, nano-boehmite and nano-silicon oxide, and the particle size of the nano-ceramic is: D10=50-100nm, D50=210-323nm, D90=703-832nm.

[0012] The method for preparing the above-mentioned low water absorption and high temperature resistant lithium battery separator comprises: coating the slurry on the base film, drying, obtaining a coating on the base film, and obtaining the low water absorption and high temperature resistant lithium battery separator.

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

[0014] In the above technical solution, the coating speed is 20 to 30 m / min.

[0015] A slurry comprises: porous ceramics, nano ceramics, water, adhesive and dispersant. The ratio of porous ceramics, nano ceramics, water, adhesive and dispersant is (20-30): (10-18): (50-65): (4-7): (0.2-0.5) by weight.

[0016] In the above technical solution, the particle size of the slurry is D50: 0.505-0.725 microns, D90: 1.282-1.524 microns.

[0017] In the above technical solution, the adhesive is an acrylic copolymer solution.

[0018] In the above technical solution, the dispersant is ammonium polyacrylate.

[0019] The method for preparing the slurry comprises: mixing porous ceramics, nano-ceramics, water, adhesive and dispersant until they are uniform to obtain slurry.

[0020] In the above technical solution, the method for preparing the slurry is specifically as follows:

[0021] Step 1, mixing a dispersant, water, porous ceramics and nano-ceramics until uniform to obtain a first solution;

[0022] In step 1, a dispersant, water, porous ceramics and nano-ceramics are mixed, and stirred at a rotation speed of 2000 to 4000 r / min and a revolution speed of 40 to 60 r / min for 20 to 25 minutes until the mixture is uniform, thereby obtaining a 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 20 to 30 minutes in a vacuum environment until they are uniform to obtain a slurry, wherein the stirring rotation speed is 2000 to 3000 r / min, the revolution speed is 40 to 50 r / min, the ultrasonic frequency is 5 to 8 kHz, and the vacuum degree of the vacuum environment is 0.06 to 0.08 KPA.

[0025] Application of porous ceramics and nanoceramics in synergistically reducing the water content of separators.

[0026] The application of porous ceramics and nanoceramics in synergistically improving the heat resistance of separators.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. Nanoceramics are well filled between porous ceramics. The interfacial interaction between nanoceramics and porous ceramics can enhance the density and stability of the coating, reduce the water penetration path, and thus reduce the water absorption of the diaphragm. In a high humidity environment, the lower water absorption can ensure that the water content of the diaphragm is not easy to exceed the standard, thereby improving the safety and cycle stability of lithium batteries; the good density of the coating gives the diaphragm good high temperature resistance, allowing the diaphragm to remain stable in a high temperature environment, reducing the risk of diaphragm shrinkage, melting, or even burning due to increased temperature, thereby improving the overall safety of the battery and extending the battery life.

[0029] 2. The synergistic effect of porous ceramics and nanoceramics helps to improve the transmission efficiency of lithium ions, making the diaphragm have good electrolyte wettability, the electrolyte is evenly distributed in the diaphragm, reducing the internal resistance of the battery, thereby improving the battery's charge and discharge rate and cycle stability. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0031] Porous ceramics (powder): Shanghai Baitu New Materials Technology Co., Ltd.;

[0032] Acrylate copolymer solution: Baoding Lucky Imaging Material Technology Co., Ltd.;

[0033] Ammonium polyacrylate: Shanghai Sanrui Polymer Materials Technology Co., Ltd.;

[0034] Nanoceramics (powder): Shanghai Baitu New Materials Technology Co., Ltd.;

[0035] In the following examples, the base film is a PE film, and the thickness of the PE film is 7 μm.

[0036] In the following examples, water is pure water.

[0037] Water content: tested at dew point temperature -40°C.

[0038] Water content in clean room after 12 hours of static condition: tested at dew point temperature of 40℃.

[0039] Ionic conductivity: The test temperature is 25°C and the relative humidity is 60%.

[0040] Examples 1 to 3 and Comparative Example 1

[0041] A method for preparing a slurry, comprising:

[0042] Step 1: Mix the dispersant, water, porous ceramic and nanoceramic in a double planetary mixer, and stir for 20 minutes at a rotation speed of 2000 r / min and a revolution speed of 40 r / min until uniform, to obtain a first solution, wherein the dispersant is ammonium polyacrylate, the porous ceramic is porous alumina, the particle size of the porous alumina is: D10=0.225 μm, D50=0.553 μm, D90=1.543 μm, and the specific surface area is 16.342 m 2 / g; the nano ceramic is nano alumina, and the particle size of nano alumina is: D10 = 75nm, D50 = 235nm, D90 = 710nm;

[0043] Step 2, mixing the first solution and the adhesive, stirring and ultrasonicating for 30 minutes in a vacuum environment with an ultrasonic oscillation function until uniform, to obtain a slurry, wherein the stirring rotation speed is 2000r / min, the revolution speed is 50r / min, the ultrasonic frequency of the ultrasonic wave is A kHz, the vacuum degree of the vacuum environment is B KPA, the adhesive is an acrylate copolymer solution (acrylate copolymer is polymerized from acrylic acid and acrylamide), and the ratio of porous ceramics, nanoceramics, water, adhesive and dispersant is X in parts by mass. X, A and B are shown in Table 1.

[0044] Table 1

[0045]

[0046]

[0047] The particle size of the slurry prepared in Example 1 is D50: 0.605 microns, D90: 1.452 microns; the particle size of the slurry prepared in Example 2 is D50: 0.583 microns, D90: 1.312 microns; the particle size of the slurry prepared in Example 3 is D50: 0.592 microns, D90: 1.305 microns. The particle size of the slurry prepared in Comparative Example 1 is D50: 0.524 microns, D90: 1.465 microns.

[0048] Comparative Example 2

[0049] A method for preparing a slurry comprises: preparing a porous ceramic (the porous ceramic is porous alumina, the particle size of the porous alumina is: D10 = 0.225 μm, D50 = 0.553 μm, D90 = 1.543 μm, and the specific surface area is 16.342 m 2 / g), water and dispersant are mixed, stirred for 20 minutes at a rotation speed of 2000r / min and a revolution speed of 40r / min in a double planetary mixer, and then ultrasonicated for 15 minutes at a frequency of 5kHz until uniform, and then an adhesive is added, and stirred and ultrasonicated for 30 minutes at the same time in a vacuum environment with an ultrasonic oscillation function (the stirring rotation speed is 2000r / min, the revolution speed is 50r / min, the ultrasonic frequency of the ultrasonic is 5kHz, and the vacuum degree of the vacuum environment is 0.06KPA) to obtain a slurry, wherein the adhesive is an acrylate copolymer solution (the acrylate copolymer is polymerized by acrylic acid and acrylamide), the dispersant is ammonium polyacrylate, and the ratio of porous ceramics, water, dispersant and adhesive is 30:63.5:0.5:6 by mass.

[0050] The particle size of the slurry prepared in Comparative Example 2 is D50: 0.565 microns, D90: 1.413 microns.

[0051] Comparative Example 3

[0052] A method for preparing a slurry, comprising: mixing micron alumina (D50: 0.425 micron, D90: 1.123 micron), porous ceramic (porous ceramic is porous alumina, the particle size of the porous alumina is: D10 = 0.225 μm, D50 = 0.553 μm, D90 = 1.543 μm, and the specific surface area is 16.342 m 2 / g), water and dispersant are mixed, stirred for 20 minutes at a rotation speed of 2000r / min and an orbital speed of 40r / min in a double planetary mixer, and then ultrasonicated for 15 minutes at a frequency of 5kHz until uniform, and then an adhesive is added, and stirred and ultrasonicated for 30 minutes at the same time in a vacuum environment with an ultrasonic oscillation function (the stirring rotation speed is 2000r / min, the orbital speed is 50r / min, the ultrasonic frequency of the ultrasonic wave is 5kHz, and the vacuum degree of the vacuum environment is 0.06KPA) to obtain a slurry, wherein the adhesive is an acrylate copolymer solution (the acrylate copolymer is polymerized by acrylic acid and acrylamide), the dispersant is ammonium polyacrylate, and the ratio of micron alumina, porous ceramics, water, dispersant and adhesive is 10:20:63.5:0.5:6 by mass.

[0053] The particle sizes of the slurry prepared in Comparative Example 3 are D50: 0.615 μm, D90: 1.673 μm.

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

[0055] A method for preparing a diaphragm comprises: placing a base film on a coating machine equipped with a slurry, coating the slurry on one side of the base film, pulling the base film into a drying device through a pulling roller, drying the base film at C (℃) for D (min), obtaining a coating on the base film, and obtaining a diaphragm, wherein the coating speed is 30 m / min. The slurry is one of Examples 1 to 3 and Comparative Examples 1 to 3.

[0056] Table 2

[0057] Diaphragm Slurry for preparing diaphragm C(℃) D(min) Example 4 Example 1 55 3 Example 5 Example 2 55 3 Example 6 Example 3 55 3 Comparative Example 4 Comparative Example 1 55 3 Comparative Example 5 Comparative Example 2 50 2 Comparative Example 6 Comparative Example 3 50 2

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

[0059]

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

[0061]

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

[0063]

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

[0065]

[0066] The test parameters of the diaphragm prepared in Comparative Example 5 are as follows:

[0067]

[0068] The test parameters of the diaphragm prepared in Comparative Example 6 are as follows:

[0069]

[0070] 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 low water absorption and high temperature resistant lithium battery separator, characterized in that: include: The base film and the coating on the base film include porous ceramics and nano ceramics. The ratio of porous ceramics to nano ceramics is (20-30): (10-18) by weight. The particle size of the nano ceramics is D50=210-323nm.

2. The low water absorption and high temperature resistant lithium battery separator according to claim 1, characterized in that: The particle size of porous ceramics is: D10 = 0.2 ~ 0.4μm, D50 = 0.5 ~ 0.7μm, D90 = 1.5 ~ 1.8μm, and the specific surface area of ​​porous ceramics is 15 ~ 18m 2 / g.

3. The low water absorption and high temperature resistant lithium battery separator according to claim 1, characterized in that: The particle size of nano-ceramics is: D10=50~100nm, D90=703~832nm.

4. The low water absorption and high temperature resistant lithium battery separator according to claim 1, characterized in that: The thickness of the coating is 2 to 3 μm.

5. The method for preparing a low water absorption and high temperature resistant lithium battery separator according to any one of claims 1 to 4, 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 low water absorption and high temperature resistant lithium battery separator.

6. A slurry, characterized in that: include: The porous ceramics, nano-ceramics, water, adhesive and dispersant are in the following ratios by mass: (20-30): (10-18): (50-65): (4-7): (0.2-0.5).

7. The slurry according to claim 6, characterized in that The particle size of the slurry is D50: 0.5-0.8 microns, D90: 1.2-1.6 microns.

8. A method for preparing the slurry according to any one of claims 6 to 7, characterized in that: include: The porous ceramic, nano-ceramic, water, adhesive and dispersant are mixed until uniform to obtain slurry.

9. Application of porous ceramics and nanoceramics in synergistically reducing the water content of diaphragms.

10. The application of porous ceramics and nanoceramics in synergistically improving the heat resistance of diaphragms.

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