Preparation method of high-infiltration and high-adhesion lithium battery diaphragm

Abstract

This invention discloses a method for preparing a high-wetting-strength, high-adhesion lithium-ion battery separator. The high-wetting-strength, high-adhesion coating slurry comprises: polyethylene wax powder, alumina, adhesive, dispersant, and isopropanol. This invention modifies the separator surface with a mixture of polyethylene wax powder and alumina, giving the separator good heat resistance. The polyethylene wax powder solution coats the alumina surface and penetrates into the pores between the alumina particles, weakening the cohesive force and making the alumina easier to open under applied shear force. This makes the combined coating powder easier to wet with electrolyte, increasing the separator's liquid absorption and cycle rate. Simultaneously, the high-wetting-strength, high-adhesion coating slurry made from polyethylene wax powder provides more uniform coating, reduces slurry viscosity, improves surface tension, and enhances material adsorption, increasing the adhesion between the separator and the electrode.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, and specifically relates to a method for preparing a lithium battery separator with high wettability and high adhesion. Background Technology

[0002] With the rapid development of modern society and the improvement of living standards, people have increasingly higher requirements for lithium batteries, especially for the fast charging performance, cycle performance, and safety performance of lithium-ion batteries. As we know from the working principle of lithium batteries, Li+ in the electrolyte passes through the separator under the influence of electrode potential, traveling back and forth between the positive and negative electrodes to complete one charge-discharge cycle. The electrolyte acts as a transport carrier for Li+; if the amount is too small, it will severely affect the wetting of the positive and negative electrodes and the separator, making the process of Li+ detaching from the positive electrode, passing through the separator, and reaching the negative electrode very slow. This ultimately affects the battery's fast charging and cycle performance. Under overcharge and over-discharge conditions, the internal temperature of a lithium-ion battery becomes excessively high. At this point, the separator, which acts as a barrier, will shrink laterally and longitudinally. This causes the positive and negative electrodes to come into contact, resulting in a short circuit. The reaction releases a large amount of heat, and the electrolyte decomposes in large quantities. The internal pressure of the battery increases sharply, ultimately leading to battery failure and explosion.

[0003] Meanwhile, lithium-ion batteries are naked cells assembled from positive and negative electrode sheets and separators through winding or stacking. In traditional coating methods, a single adhesive polymer coating cannot maintain sufficient adhesion to both the positive and negative electrodes at the same time. After being soaked in electrolyte, the coated separator has almost no adhesion to the negative electrode sheet, which affects the cycle life of the lithium battery and may even cause a short circuit and safety accident in severe cases.

[0004] Therefore, improving the liquid absorption capacity of lithium batteries and enhancing the adhesion of the separator to the electrodes are of great significance to the performance and safety of lithium-ion batteries. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a coating slurry with high wettability and high adhesion.

[0006] Another object of the present invention is to provide a method for preparing the above-mentioned high wettability and high adhesion coating slurry.

[0007] Another object of the present invention is to provide a lithium battery separator with high wettability and high adhesion.

[0008] Another object of the present invention is to provide a method for preparing the above-mentioned high wettability and high adhesion lithium battery separator.

[0009] The objective of this invention is achieved through the following technical solution.

[0010] A highly wettable and highly adhesive coating slurry comprises: polyethylene wax powder, alumina, adhesive, dispersant and isopropanol, wherein the ratio of polyethylene wax powder, alumina, adhesive and dispersant and isopropanol by mass parts is (1-2):(7-10):(5-8):(0.1-0.5):(74-92).

[0011] In the above technical solution, the adhesive is an acrylate copolymer solution and the dispersant is ammonium polyacrylate.

[0012] The preparation method of the above-mentioned high wettability and high adhesion coating slurry includes the following steps: adding the isopropanol in two parts, a first isopropanol and a second isopropanol, wherein the dispersant, the first isopropanol and alumina are mixed, stirred and ultrasonicated to obtain solution A; adding polyethylene wax powder solution and adhesive to solution A, and simultaneously dispersing at high speed in a vacuum environment with ultrasonic oscillation function to obtain high wettability and high adhesion coating slurry, wherein the polyethylene wax powder solution is obtained by mixing polyethylene wax powder and the second isopropanol and stirring.

[0013] In the above technical solution, the ratio of the first isopropanol to the second isopropanol by mass parts is (1-2):(5-10).

[0014] In the above technical solution, polyethylene wax powder and second isopropanol are mixed and stirred at a rotation speed of 1000-1500 rpm and a revolution speed of 20-50 rpm for 10-20 minutes.

[0015] In the above technical solution, the dispersant, first isopropanol and alumina are mixed and stirred at a rotation speed of 1500-3100 rpm and a revolution speed of 20-50 rpm for 10-20 minutes.

[0016] In the above technical solution, the dispersant, first isopropanol and alumina are mixed, stirred and ultrasonicated at a frequency of 10-50KHZ for 10-20 minutes.

[0017] In the above technical solution, polyethylene wax powder solution and adhesive are added to solution A, and simultaneously dispersed at a high speed of 1000-3800 rpm rotation speed and 20-40 rpm revolution speed for 10-20 minutes.

[0018] In the above technical solution, the frequency of the ultrasound is 5 to 8 kHz, and the pressure of the vacuum environment is 0.06 to 0.08 kPa.

[0019] A high wettability and high adhesion lithium battery separator includes: a base film and a coating covering one or both sides of the base film, the coating being formed by applying a high wettability and high adhesion coating slurry.

[0020] In the above technical solution, the particle size of the high wettability and high adhesion coating slurry is: D50 is 0.583-0.869 micrometers; D90 is 1.449-2.078 micrometers.

[0021] The preparation method of the above-mentioned high wettability and high adhesion lithium battery separator includes the following steps:

[0022] Step 1: Apply a highly wettable and highly adhesive coating slurry to the base film to obtain a coating layer on the base film;

[0023] In step 1, the coating method is roller coating, and the coating speed is 30-50 m / min.

[0024] In step 1, the thickness of the coating is 2 to 3 μm.

[0025] Step 2: Drying to obtain a lithium battery separator with high wettability and high adhesion.

[0026] In step 2, the drying temperature is 50-70°C and the drying time is 1-3 minutes.

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

[0028] 1. The present invention modifies the surface of the diaphragm by mixing polyethylene wax powder and alumina, thereby giving the diaphragm good heat resistance;

[0029] 2. The polyethylene wax powder solution coats the surface of alumina and penetrates into the pores between alumina particles, weakening the cohesive force and making the alumina easier to open under the action of external shear force. This makes the combined coating powder easier to wet with electrolyte, increases the liquid absorption of the separator, and increases the cycle rate of the lithium battery separator.

[0030] 3. At the same time, the coating slurry made of polyethylene wax powder has high wettability and high adhesion, resulting in more uniform coating. It can reduce the viscosity of the slurry, improve its surface tension, and increase the adhesion between the diaphragm and the electrode by improving the material's adsorption properties. Attached Figure Description

[0031] Figure 1 This is a SEM image of the high wettability and high adhesion lithium battery separator of Embodiment 1 of the present invention. Detailed Implementation

[0032] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0033] The raw materials involved in this invention and their manufacturers are as follows:

[0034] Polyethylene wax powder: Guangzhou Xinxi Metallurgical Chemical Co., Ltd.;

[0035] In the following examples, the adhesives are all acrylate copolymer solutions. The acrylate copolymer solution is from Tianjin Sepre Co., Ltd. (model: N318).

[0036] In the following examples, the dispersant is ammonium polyacrylate, which is from Shanghai Sanrui Polymer Materials Technology Co., Ltd. (model: BASF).

[0037] In the following examples, the base film is a 9μm thick PE film.

[0038] The instruments involved in this invention and their model information are as follows:

[0039] Mixer: XFZH-30L dual planetary mixer.

[0040] Example 1

[0041] A high-wetting and high-adhesion coating slurry comprises: polyethylene wax powder, alumina, adhesive, dispersant and isopropanol, wherein the ratio of polyethylene wax powder, alumina, adhesive, dispersant and isopropanol by mass parts is 1:7:5:0.1:86.9.

[0042] The preparation method of the above-mentioned high wettability and high adhesion coating slurry includes the following steps: isopropanol is added in two parts, a first isopropanol and a second isopropanol, with a mass ratio of 1:5. The dispersant, the first isopropanol, and alumina are mixed and stirred for 10 minutes at a rotation speed of 3100 rpm and a revolution speed of 20 rpm. The mixture is then sonicated at 50 kHz for 15 minutes to obtain solution A. Polyethylene wax powder solution and adhesive are added to solution A, and simultaneously dispersed at high speed for 15 minutes at a rotation speed of 1000 rpm and a revolution speed of 40 rpm in a vacuum environment with ultrasonic oscillation function (5 kHz, 0.06 kPa) to obtain the high wettability and high adhesion coating slurry. The particle size of this high wettability and high adhesion coating slurry is: D50 is 0.688 micrometers, and D90 is 1.556 micrometers. The method for obtaining the aforementioned polyethylene wax powder solution is as follows: polyethylene wax powder and second isopropanol are mixed and stirred for 10 minutes at a rotation speed of 1300 rpm and a revolution speed of 40 rpm to obtain a polyethylene wax powder solution.

[0043] A high wettability and high adhesion lithium battery separator includes: a base film and a coating covering one side of the base film, the coating being formed by applying a high wettability and high adhesion coating slurry.

[0044] The preparation method of the above-mentioned high wettability and high adhesion lithium battery separator includes the following steps:

[0045] Step 1: A high wettability and high adhesion coating slurry is applied to the base film by roller coating using a coating machine to obtain a 3μm thick coating on the base film. The coating speed is 30m / min.

[0046] Step 2: The membrane is drawn into the drying equipment by the traction roller and dried at 50°C for 3 minutes to obtain a lithium battery separator with high wettability and high adhesion.

[0047] The high wettability and high adhesion lithium battery separator obtained in Example 1 was subjected to performance testing, and the data are as follows:

[0048]

[0049] The viscosity of the high wettability and high adhesion coating slurry prepared in Example 1 was tested to be 50 mPa·s.

[0050] Example 2

[0051] A high-wetting and high-adhesion coating slurry comprises: polyethylene wax powder, alumina, adhesive, dispersant and isopropanol, wherein the ratio of polyethylene wax powder, alumina, adhesive, dispersant and isopropanol by mass parts is 1.5:7:5:0.2:86.3.

[0052] The preparation method of the above-mentioned high wettability and high adhesion coating slurry includes the following steps: isopropanol is added in two parts, a first isopropanol and a second isopropanol, with a mass ratio of 1:7. The dispersant, the first isopropanol, and alumina are mixed and stirred for 15 minutes at a rotation speed of 2000 rpm and a revolution speed of 30 rpm. The mixture is then sonicated at 50 kHz for 15 minutes to obtain solution A. Polyethylene wax powder solution and adhesive are added to solution A, and simultaneously dispersed at high speed for 15 minutes at a rotation speed of 2800 rpm and a revolution speed of 30 rpm in a vacuum environment with ultrasonic oscillation function (6 kHz, 0.07 kPa) for 15 minutes to obtain the high wettability and high adhesion coating slurry. The particle size of this high wettability and high adhesion coating slurry is: D50 is 0.743 μm and D90 is 1.608 μm. The method for obtaining the aforementioned polyethylene wax powder solution is as follows: polyethylene wax powder and second isopropanol are mixed and stirred for 10 minutes at a rotation speed of 1300 rpm and a revolution speed of 40 rpm to obtain a polyethylene wax powder solution.

[0053] A high wettability and high adhesion lithium battery separator includes: a base film and a coating covering one side of the base film, the coating being formed by applying a high wettability and high adhesion coating slurry.

[0054] The preparation method of the above-mentioned high wettability and high adhesion lithium battery separator includes the following steps:

[0055] Step 1: A high wettability and high adhesion coating slurry is applied to the base film by roller coating using a coating machine to obtain a 3μm thick coating on the base film. The coating speed is 40m / min.

[0056] Step 2: The membrane is drawn into the drying equipment by the traction roller and dried at 60°C for 2 minutes to obtain a lithium battery separator with high wettability and high adhesion.

[0057] The performance of the high wettability and high adhesion lithium battery separator obtained in Example 2 was tested, and the data are as follows:

[0058]

[0059]

[0060] Example 3

[0061] A high-wetting and high-adhesion coating slurry comprises: polyethylene wax powder, alumina, adhesive, dispersant and isopropanol, wherein the ratio of polyethylene wax powder, alumina, adhesive, dispersant and isopropanol by mass parts is 2:7:5:0.2:85.8.

[0062] The preparation method of the above-mentioned high wettability and high adhesion coating slurry includes the following steps: isopropanol is added in two parts, a first isopropanol and a second isopropanol, with a mass ratio of 1:10. The dispersant, the first isopropanol, and alumina are mixed and stirred for 20 minutes at a rotation speed of 1500 rpm and a revolution speed of 50 rpm. The mixture is then sonicated at 50 kHz for 15 minutes to obtain solution A. Polyethylene wax powder solution and adhesive are added to solution A, and simultaneously dispersed at high speed for 15 minutes at a rotation speed of 3800 rpm and a revolution speed of 20 rpm in a vacuum environment with ultrasonic oscillation function (8 kHz, 0.08 kPa) for 15 minutes to obtain the high wettability and high adhesion coating slurry. The particle size of this high wettability and high adhesion coating slurry is: D50 is 0.623 micrometers, and D90 is 1.698 micrometers. The method for obtaining the aforementioned polyethylene wax powder solution is as follows: polyethylene wax powder and second isopropanol are mixed and stirred for 15 minutes at a rotation speed of 1500 rpm and a revolution speed of 50 rpm to obtain a polyethylene wax powder solution.

[0063] A high wettability and high adhesion lithium battery separator includes: a base film and a coating covering one side of the base film, the coating being formed by applying a high wettability and high adhesion coating slurry.

[0064] The preparation method of the above-mentioned high wettability and high adhesion lithium battery separator includes the following steps:

[0065] Step 1: A high wettability and high adhesion coating slurry is applied to the base film by roller coating using a coating machine to obtain a 3μm thick coating on the base film. The coating speed is 50m / min.

[0066] Step 2: The membrane is drawn into the drying equipment by the traction roller and dried at 70°C for 1 minute to obtain a lithium battery separator with high wettability and high adhesion.

[0067] The performance of the high wettability and high adhesion lithium battery separator obtained in Example 3 was tested, and the data are as follows:

[0068]

[0069]

[0070] Comparative Example 1

[0071] A conventional alumina coating slurry comprises: alumina, pure water, dispersant and adhesive, wherein the ratio of alumina, pure water, dispersant and adhesive by mass parts is 7:87.8:0.2:5.

[0072] In this comparative example, the adhesive is an acrylate copolymer solution and the dispersant is ammonium polyacrylate.

[0073] The preparation method of the above-mentioned conventional alumina coating slurry includes the following steps: mixing alumina, pure water, and a dispersant, stirring at a rotation speed of 3100 rpm and a revolution speed of 20 rpm for 10 min, and ultrasonicating at 50 kHz for 15 min to obtain a first solution; adding an adhesive to the first solution, and simultaneously ultrasonically oscillating at a rotation speed of 1000 rpm and a revolution speed of 40 rpm for 15 min (frequency of 5 kHz) to obtain the conventional alumina coating slurry. The particle size of this conventional alumina coating slurry is: D50 is 0.599 μm; D90 is 1.473 μm.

[0074] An alumina lithium battery separator includes: a base film and a coating covering one side of the base film, the coating being formed by applying a conventional alumina coating slurry.

[0075] The above-mentioned method for preparing the alumina lithium battery separator includes the following steps:

[0076] Step 1: A conventional alumina coating slurry is applied to the base film using a coating machine by roller coating to obtain a coating with a thickness of 3μm on the base film. The coating speed is 30m / min.

[0077] Step 2: The material is pulled into the drying equipment by the traction roller and dried at 50°C for 3 minutes to obtain an alumina lithium battery separator.

[0078] The performance of the alumina lithium battery separator obtained in the comparative example was tested, and the data are as follows:

[0079]

[0080]

[0081] The viscosity of the conventional alumina coating slurry prepared in Comparative Example 1 was tested to be 30 mPa·s.

[0082] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. A lithium battery separator with high wettability and high adhesion, characterized in that, include: A base film and a coating covering one or both sides of the base film, the coating being formed by applying a highly wettable and highly adhesive coating slurry, the highly wettable and highly adhesive coating slurry comprising: polyethylene wax powder, alumina, adhesive, dispersant and isopropanol, wherein the ratio of polyethylene wax powder, alumina, adhesive and dispersant and isopropanol by mass parts is (1~2):(7~10):(5~8):(0.1~0.5):(74~92); the polyethylene wax powder coats the surface of the alumina and penetrates into the pores between the alumina particles; The preparation method of the high wettability and high adhesion coating slurry includes the following steps: the isopropanol is added in two parts, a first isopropanol and a second isopropanol, wherein the dispersant, the first isopropanol and alumina are mixed, stirred and ultrasonicated to obtain solution A, a polyethylene wax powder solution and an adhesive are added to solution A, and simultaneously dispersed at high speed in a vacuum environment with ultrasonic oscillation function to obtain the high wettability and high adhesion coating slurry, wherein the polyethylene wax powder solution is obtained by mixing polyethylene wax powder and the second isopropanol and stirring.

2. The high wettability and high adhesion lithium battery separator according to claim 1, characterized in that, The adhesive is an acrylate copolymer solution, and the dispersant is ammonium polyacrylate.

3. The high wettability and high adhesion lithium battery separator according to claim 2, characterized in that, The ratio of the first isopropanol to the second isopropanol by mass parts is (1~2):(5~10).

4. The high wettability and high adhesion lithium battery separator according to claim 3, characterized in that, The frequency of ultrasound is 5~8kHz, and the pressure of the vacuum environment is 0.06~0.08KPa.

5. The high wettability and high adhesion lithium battery separator according to claim 4, characterized in that, After mixing polyethylene wax powder and second isopropanol, stir at a rotation speed of 1000~1500 rpm and a revolution speed of 20~50 rpm for 10~20 minutes. Mix the dispersant, isopropanol, and alumina, and stir at a rotation speed of 1500-3100 rpm and a revolution speed of 20-50 rpm for 10-20 minutes.

6. The high wettability and high adhesion lithium battery separator according to claim 5, characterized in that, The dispersant, first isopropanol and alumina are mixed and stirred, and then sonicated at a frequency of 10~50KHz for 10~20min.

7. The high wettability and high adhesion lithium battery separator according to claim 6, characterized in that, Add polyethylene wax powder solution and adhesive to solution A, and disperse at high speed for 10-20 minutes with a rotation speed of 1000-3800 rpm and a revolution speed of 20-40 rpm.

8. The high wettability and high adhesion lithium battery separator according to claim 1, characterized in that, The particle size of the high wettability and high adhesion coating slurry is: D50 is 0.583~0.869 micrometers; D90 is 1.449~2.078 micrometers.

9. The high wettability and high adhesion lithium battery separator according to claim 1, characterized in that, A method for preparing a lithium-ion battery separator with high wettability and high adhesion includes the following steps: Step 1: Apply a highly wettable and highly adhesive coating slurry to the base film to obtain a coating layer on the base film; Step 2: Drying to obtain a lithium battery separator with high wettability and high adhesion.

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