High-performance spraying diaphragm treated by cold air pressure medium and preparation method of high-performance spraying diaphragm

Abstract

The invention provides a high-performance spraying diaphragm treated by a cold air pressure medium and a preparation method thereof, and the preparation method comprises the following steps: (1) placing a base membrane in a cold air pressure medium treatment device, treating the single surface or double surfaces of the base membrane through the cold air pressure medium, then cleaning with pure water, drying the surface, and drying to obtain a high-performance spraying diaphragm; obtaining a base film treated by a cold air pressure medium; (2) dispersing and homogenizing the water-based polymer raw material to obtain uniformly dispersed and stable water-based polymer slurry; and (3) coating aqueous polymer slurry on the base membrane treated in the step (1) by adopting a spraying process to form a coating, and drying to obtain the high-performance spraying diaphragm. The high-performance diaphragm provided by the invention not only improves the phenomenon of powder falling during spraying, but also remarkably improves the cycle performance and thermal stability of the lithium ion battery.

Description

Technical Field

[0001] The invention relates to the technical field of lithium ion battery diaphragms, and in particular to a high-performance spray diaphragm treated with a cold air pressure medium and a preparation method thereof. Background Art

[0002] With the rapid development of modern science and technology, lithium-ion batteries, as an efficient and rechargeable energy storage device, have been widely used in many fields, such as portable electronic devices (smartphones, tablets, etc.), electric vehicles, and energy storage systems. In the structural composition of lithium-ion batteries, the diaphragm is a crucial component. It is located between the positive and negative electrodes, and it prevents the positive and negative electrodes from directly contacting and short-circuiting. At the same time, it also allows lithium ions to pass freely during the charging and discharging process to ensure the normal operation of the battery. Therefore, the performance of the diaphragm has a very significant impact on the safety, cycle life, and charging and discharging performance of lithium-ion batteries.

[0003] During the charge and discharge process of the battery, the expansion and contraction between the electrodes of the traditional spray diaphragm will produce certain stress on the diaphragm, causing the coating to fall off. In a high temperature or high humidity environment, the bonding strength of the binder may decrease, thereby increasing the risk of powder loss. Powder loss not only affects the performance of the battery, but also reduces the battery capacity and cycle life. It may also cause internal short circuits in the battery and cause safety accidents. Therefore, a new and effective method is needed to solve the problem of powder loss in spray diaphragms. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the present invention provides a high-performance spray diaphragm treated with cold air pressure medium and a preparation method thereof, which not only improves the spray powder shedding phenomenon, but also significantly improves the cycle performance and thermal stability of lithium-ion batteries.

[0005] The technical solution provided by the present invention is a method for preparing a high-performance spray diaphragm treated with cold air pressure medium, comprising the following steps:

[0006] (1) placing the base film in a cold air pressure medium treatment device, treating one or both sides of the base film with the cold air pressure medium, and then washing with pure water and drying the surface to obtain a base film treated with the cold air pressure medium;

[0007] (2) dispersing and homogenizing the water-based polymer raw material to obtain a uniformly dispersed and stable water-based polymer slurry;

[0008] (3) applying the water-based polymer slurry onto the base film treated in step (1) by a spraying process to form a coating, and drying to obtain a high-performance sprayed diaphragm;

[0009] The aqueous polymer slurry includes a high molecular polymer, a solvent, a binder and a wetting agent. The binder is a composite binder of sericin and an aqueous binder. The mass ratio of the sericin to the aqueous binder is 1:(3-10). The aqueous binder is selected from any one of LA133 binder, LA132 binder, acrylonitrile binder, acrylic resin binder and polyvinyl pyrrolidone.

[0010] Furthermore, the base film in step (1) is selected from one of PP, PE, PP / PE / PP, PE / PP / PE, and the thickness of the base film is between 3-50 um.

[0011] Furthermore, the cold air pressure medium in step (1) includes but is not limited to an inert gas, compressed air or a specially treated low-temperature gas.

[0012] Furthermore, the cold air pressure medium is nitrogen or a mixture thereof with an inert gas; wherein nitrogen can increase the surface roughness of the base film, improve the surface energy and coating adhesion without introducing functional groups, and nitrogen is easy to obtain and low in cost.

[0013] The air pressure range of the cold air pressure medium treatment described in step (1) is 100-1000Pa, the treatment temperature is -50-50°C, and the treatment time is 1-300s. The cold air pressure medium treatment temperature is low, the treatment process is gentler, and has less impact on the performance of the base film itself. It can improve its surface performance without damaging the performance of the base film itself.

[0014] Furthermore, in terms of weight, the aqueous polymer slurry contains 10-30 parts of high molecular weight polymer, 3-10 parts of binder, 0.1-5 parts of wetting agent, and the balance is pure water.

[0015] Furthermore, the high molecular polymer is selected from any one of PVDF, PMMA and PAA.

[0016] Furthermore, the wetting agent is selected from any one of polyoxyethylene ethyl ether, propylene glycol, glycerol, polyethylene glycol ether, and stearyl alcohol.

[0017] Furthermore, the dispersion and homogenization treatment in step (2) includes but is not limited to mechanical dispersion, ultrasonic dispersion, chemical dispersion, high pressure homogenization, alternating grinding homogenization and ultrasonic homogenization. The slurry is dispersed and homogenized to effectively avoid slurry agglomeration and precipitation and reduce pore blocking. This improves production efficiency while ensuring product quality and stability.

[0018] Furthermore, the spraying process in step (3) is selected from one of high-pressure mist spraying, air-assisted spraying, and electrostatic spraying, the spraying speed is 10-100m / min, the coating thickness is 0.1-5um, and the coating method is single-sided coating or double-sided coating.

[0019] Beneficial effects of the present invention:

[0020] (1) The surface energy and roughness of the base film are effectively improved after the cold air pressure medium treatment, and the interaction force between the spraying material and the base film surface is enhanced; it is conducive to better adhesion of the spraying material to the base film surface, thereby solving the problem of powder loss in the spray diaphragm.

[0021] (2) The binder in the aqueous polymer slurry is a compound of sericin and an aqueous binder. The sericin contains abundant hydrophilic groups, which can enhance the bonding strength between the polymer material and the base film, reduce the problem of powder shedding during spraying of the diaphragm, and significantly enhance the compatibility of the electrolyte with the diaphragm, effectively shorten the battery filling time, and reduce the battery manufacturing cost.

[0022] The high-performance diaphragm of the present invention not only improves the spray powder shedding phenomenon, but also significantly improves the cycle performance and thermal stability of the lithium-ion battery. DETAILED DESCRIPTION

[0023] In order to make the objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below in conjunction with specific embodiments.

[0024] Example 1

[0025] A method for preparing a high-performance spray diaphragm treated with cold air pressure medium comprises the following steps:

[0026] (1) A polyethylene base film with a thickness of 9 μm is placed in a cold air pressure medium treatment device, and the base film is treated on one side by the cold air pressure medium. After the cold air pressure medium treatment, the surface roughness of the base film increases and the surface energy is improved. The cold air pressure medium is nitrogen, the air pressure range is 150 Pa, the treatment temperature is 10° C., and the treatment time is 20 s. The base film treated with the cold air pressure medium is then washed with pure water and the surface is dried to obtain a base film treated with the cold air pressure medium.

[0027] (2) The water-based PVDF polymer slurry is dispersed and homogenized (mechanically dispersed) to obtain a uniformly dispersed and stable spray-coated water-based PVDF polymer slurry.

[0028] (3) The water-based PVDF polymer slurry is coated on the base film treated in step (1) by a spraying process to form a coating, and then dried to obtain a high-performance sprayed PE diaphragm treated with a cold air pressure medium.

[0029] In Example 1, the aqueous PVDF slurry contains 19 parts of high molecular weight PVDF polymer, 3 parts of binder, 0.5 parts of propylene glycol, and 77.5 parts of pure water. The binder is a compound system of sericin and LA133, and the mass ratio of sericin to LA133 is 1:4.

[0030] Example 2

[0031] A method for preparing a high-performance spray diaphragm treated with cold air pressure medium comprises the following steps:

[0032] (1) The surface of a polypropylene base film with a thickness of 12 μm is placed in a cold air pressure medium treatment device, and the base film is treated on one side by the cold air pressure medium. After the cold air pressure medium treatment, the surface roughness of the base film increases and the surface energy is improved. The cold air pressure medium is argon gas, the air pressure range is 120 Pa, the treatment temperature is 15° C., and the treatment time is 30 seconds. Subsequently, the base film treated with the cold air pressure medium is cleaned with pure water and the surface is dried to obtain a base film treated with the cold air pressure medium.

[0033] (2) The water-based PVDF polymer slurry is dispersed and homogenized (mechanically dispersed) to obtain a uniformly dispersed and stable spray-coated water-based PVDF polymer slurry.

[0034] (3) The water-based PVDF polymer slurry is coated on the base film treated in step (1) by a spraying process to form a coating, and then dried to obtain a high-performance sprayed PP diaphragm treated with a cold air pressure medium.

[0035] In Example 2, the aqueous PVDF slurry contains 20 parts of high molecular weight PVDF polymer, 4 parts of binder, 0.6 parts of glycerol, and 75.4 parts of pure water. The binder is a compound system of sericin and LA132, and the mass ratio of sericin to LA132 is 1:5.

[0036] Example 3

[0037] A method for preparing a high-performance spray diaphragm treated with cold air pressure medium comprises the following steps:

[0038] (1) The surface of a PE base film with a thickness of 12 μm is placed in a cold air pressure medium treatment device, and the base film is treated on both sides by the cold air pressure medium. After the cold air pressure medium treatment, the surface roughness of the base film increases and the surface energy is improved. The cold air pressure medium is nitrogen, the air pressure range is 150 Pa, the treatment temperature is 5° C., and the treatment time is 10 s. Then, the base film treated with the cold air pressure medium is cleaned with pure water and the surface is dried to obtain a base film treated with the cold air pressure medium.

[0039] (2) The water-based PMMA polymer slurry is dispersed and homogenized (ultrasonic dispersion) to obtain a uniformly dispersed and stable spray-coated water-based PMMA polymer slurry.

[0040] (3) The water-based PMMA polymer slurry is coated on the base film treated in step (1) by a spraying process to form a coating, and then dried to obtain a high-performance sprayed PE diaphragm treated with a cold air pressure medium.

[0041] In Example 3, the aqueous PMMA slurry contains 22 parts of high molecular weight PMMA polymer, 3 parts of binder, 0.4 parts of polyethylene glycol ether, and 74.6 parts of pure water. The binder is a compound system of sericin and acrylonitrile binder, and the mass ratio of sericin to acrylonitrile binder is 1:3.

[0042] Example 4

[0043] A method for preparing a high-performance spray diaphragm treated with cold air pressure medium comprises the following steps:

[0044] (1) The surface of a PP / PE / PP base film with a thickness of 12 μm is placed in a cold air pressure medium treatment device, and the base film is treated on both sides by the cold air pressure medium. After the cold air pressure medium treatment, the surface roughness of the base film increases and the surface energy is improved. The cold air pressure medium is oxygen, the air pressure range is 180 Pa, the treatment temperature is 20° C., and the treatment time is 5 s. Subsequently, the base film treated with the cold air pressure medium is cleaned with pure water and the surface is dried to obtain a base film treated with the cold air pressure medium.

[0045] (2) The water-based PMMA polymer slurry is dispersed and homogenized (ultrasonic dispersion) to obtain a uniformly dispersed and stable spray-coated water-based PMMA polymer slurry.

[0046] (3) The water-based PMMA polymer slurry is coated on the base film treated in step (1) by a spraying process to form a coating, and then dried to obtain a high-performance sprayed PP / PE / PP diaphragm treated with a cold air pressure medium.

[0047] In Example 3, the aqueous PMMA slurry contains 20 parts of high molecular weight PMMA polymer, 3 parts of binder, 0.5 parts of polyoxyethylene ethyl ether, and 76.5 parts of pure water. The binder is a compound system of sericin and polyvinyl pyrrolidone, and the mass ratio of sericin to polyvinyl pyrrolidone is 1:6.

[0048] Comparative Example 1

[0049] A PE-based film treated with a cold air pressure medium, wherein the specific embodiment is the same as that of embodiment 1, except that no spraying treatment is performed.

[0050] Comparative Example 2

[0051] PVDF spray-coated PE diaphragm without cold air pressure medium treatment (wherein the binder is a compound system of sericin and LA133, and the mass ratio of sericin to LA133 is 1:4).

[0052] Comparative Example 3

[0053] PVDF sprayed PE diaphragm (binder is LA133) without cold air pressure medium treatment. Performance test:

[0054] The contact angle and powder loss test of the diaphragms obtained in the examples of the present invention and the comparative examples were performed as follows:

[0055] (1) Contact angle test: The membrane was cut into 5 cm × 5 cm squares and a contact angle tester was used to perform a dynamic contact angle test. The acquisition interval was 10,000 milliseconds per frame, and 10 sets of data were tested. The test results are shown in Table 1.

[0056] (2) Powder loss test: The diaphragm was cut into 3 cm × 22 cm strips and subjected to friction test using a color fastness tester. The test used a 2N weight and was repeated 5 times. The difference between the weight of the diaphragm before and after the test was the powder loss value. The test results are shown in Table 2. Two sets of data were tested for each sample.

[0057] Table 1 Contact angle test data

[0058]

[0059] Table 2 Powder loss test data

[0060]

[0061] From the above test results, it can be seen that the high-performance spray diaphragm treated with cold air pressure medium prepared by the present invention is superior to other comparative cases in terms of powder loss, wettability, etc. The high-performance diaphragm of the present invention not only improves the spray powder loss phenomenon, but also significantly improves the cycle performance and thermal stability of lithium-ion batteries.

[0062] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a high-performance spray diaphragm treated with cold air pressure medium, characterized in that: The steps include: (1) placing the base film in a cold air pressure medium treatment device, treating one or both sides of the base film with the cold air pressure medium, and then washing with pure water and drying the surface to obtain a base film treated with the cold air pressure medium; (2) dispersing and homogenizing the water-based polymer raw material to obtain a uniformly dispersed and stable water-based polymer slurry; (3) applying the water-based polymer slurry onto the base film treated in step (1) by a spraying process to form a coating, and drying to obtain a high-performance sprayed diaphragm; The aqueous polymer slurry includes a high molecular polymer, a solvent, a binder and a wetting agent. The binder is a composite binder of sericin and an aqueous binder. The mass ratio of the sericin to the aqueous binder is 1:(3-10). The aqueous binder is selected from any one of LA133 binder, LA132 binder, acrylonitrile binder, acrylic resin binder and polyvinyl pyrrolidone.

2. The method for preparing a high-performance spray diaphragm treated with cold air pressure medium according to claim 1, characterized in that: The base film described in step (1) is selected from one of PP, PE, PP / PE / PP, PE / PP / PE, and the thickness of the base film is between 3-50um.

3. The method for preparing a high-performance spray diaphragm treated with cold air pressure medium according to claim 1, characterized in that: It is characterized in that The cold air pressure medium described in step (1) includes but is not limited to one of inert gas, compressed air or specially treated low-temperature gas.

4. The method for preparing a high-performance spray diaphragm treated with cold air pressure medium according to claim 3, characterized in that: The cold air pressure medium is nitrogen or a mixture thereof with an inert gas; the air pressure range of the cold air pressure medium treatment in step (1) is 100-1000 Pa, the treatment temperature is -50-50°C, and the treatment time is 1-300s.

5. The method for preparing a high-performance spray diaphragm treated with cold air pressure medium according to claim 1, characterized in that: In terms of weight, the aqueous polymer slurry contains 10-30 parts of high molecular polymer, 3-10 parts of binder, 0.1-5 parts of wetting agent, and the balance is pure water.

6. The method for preparing a high-performance spray diaphragm treated with cold air pressure medium according to claim 5, characterized in that: The high molecular polymer is selected from any one of PVDF, PMMA and PAA.

7. The method for preparing a high-performance spray diaphragm treated with cold air pressure medium according to claim 5, characterized in that: The wetting agent is selected from any one of polyoxyethylene ethyl ether, propylene glycol, glycerin, polyethylene glycol ether, and stearyl alcohol.

8. The method for preparing a high-performance spray diaphragm treated with cold air pressure medium according to claim 1, characterized in that: The dispersion and homogenization treatment in step (2) includes, but is not limited to, mechanical dispersion, ultrasonic dispersion, chemical dispersion, high-pressure homogenization, alternating grinding homogenization and ultrasonic homogenization.

9. The method for preparing a high-performance spray diaphragm treated with cold air pressure medium according to claim 1, characterized in that: The spraying process in step (3) is selected from one of high-pressure mist spraying, air-assisted spraying, and electrostatic spraying. The spraying speed is 10-100 m / min, the coating thickness is 0.1-5 um, and the coating method is single-sided coating or double-sided coating.

10. A high performance spray diaphragm treated with cold air pressure medium prepared by the method according to any one of claims 1 to 9.

Images