Ultrathin high-heat-resistance high-wettability lithium battery diaphragm as well as preparation method and application thereof

Abstract

The invention discloses an ultra-thin high-heat-resistance high-wettability lithium battery diaphragm and a preparation method and application thereof, the ultra-thin high-heat-resistance high-wettability lithium battery diaphragm comprises a base membrane and a coating on the base membrane, and the coating comprises nano aluminum oxide and micron aluminum oxide. According to the preparation method disclosed by the invention, the slurry is prepared from the nanoscale aluminum oxide and the micron-sized aluminum oxide so as to modify the diaphragm, more pores can be generated in the presence of the micron-sized aluminum oxide with a relatively large particle size, and the electrolyte wettability of the diaphragm is improved by virtue of the more pores, so that the electrochemical performance of the diaphragm is effectively improved. In addition, a framework of the micron-sized aluminum oxide also plays a good supporting role, and pores of the micron-sized aluminum oxide are filled with the nano-sized aluminum oxide, so that the coating is more compact, and the thermal stability of the diaphragm is further improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery separators, and in particular relates to an ultra-thin, highly heat-resistant and highly wettable lithium battery separator, and a preparation method and application thereof. Background Art

[0002] With the rapid development of modern society and the improvement of living standards, people have higher and higher requirements for lithium batteries, especially for the fast charging performance, cycle performance and safety performance of lithium-ion batteries. + Under the action of electrode potential, the electrolyte passes through the diaphragm and goes back and forth between the positive and negative electrodes to complete a charge and discharge. + If the amount of transport carrier is too small, it will seriously affect the wetting of positive and negative electrodes and the separator, making Li + The process of escaping from the positive electrode through the separator to the negative electrode is very slow, which ultimately affects the performance of the battery.

[0003] The traditional polyolefin separator is limited by the surface energy, resulting in poor wettability of the electrolyte. In addition, when the battery operating temperature is too high, the separator is damaged and causes a short circuit in the battery, which can cause the lithium-ion battery to explode.

[0004] This shows that improving the wettability and heat resistance of the separator is of great significance to the electrical performance and safety of lithium-ion batteries. Summary of the invention

[0005] In view of the deficiencies of the prior art, the object of the present invention is to provide an ultra-thin lithium battery separator with high heat resistance and high wettability.

[0006] Another object of the present invention is to provide a method for preparing the above-mentioned ultra-thin, highly heat-resistant and highly wettable lithium battery separator.

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

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

[0009] An ultra-thin, highly heat-resistant and highly wettable lithium battery separator comprises: a base film and a coating on the base film, wherein the coating comprises: nano-alumina and micro-alumina, and the ratio of nano-alumina to micro-alumina is (5-15) by weight:

[0010] (20~30).

[0011] In the above technical solution, the particle size of nano-alumina is D50=0.1-0.25 nm, D90=0.5-0.6 nm; the particle size of micron-alumina is D50=0.6-0.8 μm, D90=1.2-1.7 μm.

[0012] In the above technical solution, the ratio of nano-alumina to micron-alumina is preferably (5-6): (28-30) by mass.

[0013] The method for preparing the above-mentioned ultra-thin, highly heat-resistant and highly wettable lithium battery separator comprises: coating the slurry on the base film, drying, obtaining a coating on the base film, and obtaining the lithium battery separator, wherein the slurry comprises: nano-alumina, micro-alumina, water, adhesive and dispersant.

[0014] In the above technical solution, the coating speed is 20 to 50 m / min.

[0015] In the above technical solution, the drying temperature is 50-80° C., and the drying time is 1-3 minutes.

[0016] In the above technical solution, the coating thickness is 1 to 3 μm.

[0017] A slurry comprises: nano alumina, micron alumina, water, adhesive and dispersant. The ratio of nano alumina, micron alumina, water, adhesive and dispersant is (5-15): (20-30): (52.4-70.8): (4-7): (0.2-0.6) by weight.

[0018] In the above technical solution, the particle size of the slurry is D50: 0.450-0.525 microns, D90: 1.569-2.088 microns.

[0019] In the above technical solution, the adhesive is an acrylic copolymer solution.

[0020] In the above technical solution, the dispersant is ammonium polyacrylate.

[0021] The preparation method of the above-mentioned slurry includes: mixing nano alumina, micron alumina, water, adhesive and dispersant until uniform to obtain slurry, wherein the ratio of nano alumina, micron alumina, water, adhesive and dispersant is (5-15): (20-30): (52.4-70.8): (4-7): (0.2-0.6) by mass.

[0022] In the above technical solution, the method for preparing the slurry comprises the following steps:

[0023] Step 1, mixing a dispersant, water, nano-alumina and micro-alumina until uniform to obtain a first solution;

[0024] In step 1, a dispersant, water, nano-alumina and micro-alumina are mixed, and stirred at a rotation speed of 1400 to 3000 r / min and a revolution speed of 30 to 50 r / min for 10 to 20 minutes until the mixture is uniform, to obtain a first solution.

[0025] Step 2: Mix the first solution and the adhesive until they are uniform to obtain a slurry.

[0026] In step 2, the first solution and the adhesive are mixed, and stirred and ultrasonicated for 10 to 20 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.

[0027] The application of nano-alumina and micro-alumina in synergistically improving the wettability (liquid absorption rate / liquid retention rate) of diaphragms.

[0028] The application of nano-alumina and micro-alumina in synergistically improving the heat resistance of diaphragms.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The present invention uses nano-alumina (powder) and micron-alumina (powder) to prepare slurry to modify the diaphragm, and the micron-alumina plays a "skeleton" role in the coating. Compared with the pure ultrafine alumina (nano-alumina) coating, the presence of micron-alumina with a larger particle size can produce more pores, and more pores are conducive to improving the electrolyte wettability of the diaphragm, thereby effectively improving the electrochemical performance of the diaphragm. The "skeleton" of micron-alumina also plays a good supporting role. Nano-alumina is filled into the pores of micron-alumina, making the coating denser and further improving the thermal stability of the diaphragm. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is an electron microscope image of the ultra-thin, highly heat-resistant and highly wettable lithium battery separator prepared in Example 5. DETAILED DESCRIPTION

[0032] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0033] The raw material information involved in the following examples is as follows:

[0034] Nano-alumina and micro-alumina: Shanghai Baitu High-tech Materials 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] In the following examples, water is pure water.

[0038] In the following examples, the base film is a PE film, and the thickness of the base film is 7 μm.

[0039] Embodiments 1 to 4

[0040] A method for preparing a slurry comprises the following steps:

[0041] Step 1, mixing a dispersant, water, nano-alumina and micro-alumina, and stirring in a double planetary mixer at a rotation speed of A1 r / min and a revolution speed of A2 r / min for B1 min until the mixture is uniform, to obtain a first solution;

[0042] Step 2, mixing the first solution and the adhesive, in a double planetary mixer, in a vacuum environment with ultrasonic oscillation function, stirring and ultrasonic (high-speed dispersion) for B2 min until uniform, the vacuum degree is C KPA, the stirring rotation speed is A3 r / min, the revolution speed is A4 r / min, the ultrasonic frequency is D kHz, and a slurry is obtained. The ratio of nano alumina, micron alumina, water, adhesive and dispersant is E by mass, the adhesive is an acrylate copolymer solution (acrylate copolymer is copolymerized by acrylic acid and ammonium acrylate), the dispersant is ammonium polyacrylate, the particle size of nano alumina is D50=0.2~0.25nm, D90=0.52~0.6nm, the particle size of micron alumina is D50=0.7~0.8μm, D90=1.25-1.4μm. The values ​​of A1, A2, A3, A4, B1, B2, C, D and E are shown in Table 1.

[0043] Table 1

[0044]

[0045]

[0046] The particle size of the slurry prepared in Example 1 is D50: 0.487 microns, D90: 1.876 microns; the particle size of the slurry prepared in Example 2 is D50: 0.498 microns, D90: 1.901 microns; the particle size of the slurry prepared in Example 3 is D50: 0.487 microns, D90: 2.076 microns; the particle size of the slurry prepared in Example 4 is D50: 0.467 microns, D90: 1.908 microns.

[0047] Comparative Example 1

[0048] A method for preparing a slurry comprises: mixing 30 parts by mass of aluminum oxide (particles), 63.8 parts by mass of pure water and 0.2 parts by mass of a dispersant in a double planetary mixer, stirring for 30 minutes at a rotation speed of 3500 r / min and a revolution speed of 30 r / min, ultrasonicating for 10 minutes at a frequency of 5 kHz, adding 6 parts by mass of an adhesive, and simultaneously ultrasonically oscillating for 15 minutes under stirring conditions (the stirring rotation speed is 1000 r / min, the revolution speed is 45 r / min, and the ultrasonic frequency of the ultrasonic oscillation is 5 kHz) to obtain a slurry, wherein the adhesive is an acrylate copolymer solution (the acrylate copolymer is copolymerized by acrylic acid and ammonium acrylate), the dispersant is ammonium polyacrylate, and the particle size of the aluminum oxide (particles) is D50: 0.501 microns and D90: 1.389 microns.

[0049] Comparative Example 2

[0050] A method for preparing a slurry comprises: mixing 10 parts by mass of nano-boehmite (D50=0.23nm, D90=0.762nm), 20 parts by mass of micron-boehmite (D50=0.76μm, D90=0.1.32μm), 63.8 parts by mass of pure water and 0.2 parts by mass of a dispersant in a double planetary mixer, stirring for 20 minutes at a rotation speed of 3000r / min and a revolution speed of 40r / min, then ultrasonicating for 10 minutes at a frequency of 5kHz, adding 6 parts by mass of an adhesive, and simultaneously ultrasonically oscillating for 20 minutes under stirring conditions (the stirring rotation speed is 1000r / min, the revolution speed is 45r / min, and the ultrasonic frequency of the ultrasonic oscillation is 5kHz) to obtain the slurry, wherein the adhesive is an acrylate copolymer solution (the acrylate copolymer is copolymerized by acrylic acid and ammonium acrylate), and the dispersant is ammonium polyacrylate.

[0051] Examples 5 to 8 and Comparative Examples 3 to 4

[0052] A method for preparing a diaphragm, comprising: placing a base film on a coating machine filled with slurry, coating the slurry on one side of the base film at a coating speed of X m / min, pulling the base film into a drying device through a traction roller, drying at Y°C for Z min, obtaining a coating on the base film, and obtaining a diaphragm (the diaphragm prepared by the slurry of Examples 1 to 4 is an ultra-thin, highly heat-resistant and highly wettable lithium battery diaphragm).

[0053] Table 2

[0054] Diaphragm Slurry for preparing diaphragm X(m / min) Y(℃) Z(min) Example 5 Example 1 20 50 3 Example 6 Example 2 30 70 2 Example 7 Example 3 50 80 2 Example 8 Example 4 50 80 2 Comparative Example 3 Comparative Example 1 30 50 3 Comparative Example 4 Comparative Example 2 30 50 3

[0055] The test data of the diaphragm prepared in Example 5 are as follows:

[0056]

[0057] The test data of the diaphragm prepared in Example 6 are as follows:

[0058]

[0059]

[0060] The test data of the diaphragm prepared in Example 7 are as follows:

[0061]

[0062] The test data of the diaphragm prepared in Example 8 are as follows:

[0063]

[0064] The test data of the diaphragm prepared in Comparative Example 3 are as follows:

[0065]

[0066] The test data of the diaphragm prepared in Comparative Example 4 are as follows:

[0067]

[0068] Figure 1 This is an electron microscope image of the ultra-thin, highly heat-resistant, and highly wettable lithium battery separator prepared in Example 5. Figure 1 It can be seen that there is a lot of nano-sized aluminum oxide in the gaps between the micron-sized aluminum oxide.

[0069] 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. An ultra-thin, highly heat-resistant and highly wettable lithium battery separator, characterized in that: include: The base film and the coating on the base film include: nano-alumina and micro-alumina, and the ratio of nano-alumina to micro-alumina is (5-15): (20-30) by weight.

2. The ultra-thin, highly heat-resistant and highly wettable lithium battery separator according to claim 1, characterized in that: The particle size of nano-alumina is D50 = 0.1 ~ 0.25nm, D90 = 0.5 ~ 0.6nm; The particle size of micron alumina is D50=0.6~0.8μm, D90=1.2~1.7μm.

3. A method for preparing the ultra-thin, highly heat-resistant and highly wettable lithium battery separator according to any one of claims 1 to 2, 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: nano alumina, micron alumina, water, adhesive and dispersant.

4. The method according to claim 3, characterized in that The coating thickness is 1 to 3 μm.

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

6. A slurry, characterized in that: include: The ratio of nano-alumina, micron-alumina, water, adhesive and dispersant is (5-15): (20-30): (52.4-70.8): (4-7): (0.2-0.6) by mass.

7. The slurry according to claim 6, characterized in that The particle size of the slurry is D50: 0.4-0.6 microns, D90: 1.5-2.2 microns.

8. The method for preparing the slurry according to claim 7, characterized in that: include: The nano-alumina, micron-alumina, water, adhesive and dispersant are mixed until uniform to obtain a slurry. The ratio of the nano-alumina, micron-alumina, water, adhesive and dispersant is (5-15): (20-30): (52.4-70.8): (4-7): (0.2-0.6) by mass.

9. Application of nano-alumina and micro-alumina to synergistically improve the wettability of diaphragms.

10. The application of nano-alumina and micron-alumina in synergistically improving the heat resistance of diaphragms.

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