A high performance spray diaphragm for cryogenic pressure medium and a method of making the same

Abstract

The application provides a high-performance spray diaphragm treated by cold gas pressure medium and a preparation method thereof, and the preparation method comprises the following steps: (1) placing a base film in a cold gas pressure medium treatment device, treating one side or two sides of the base film by the cold gas pressure medium, then cleaning the base film by pure water, and drying the surface of the base film to obtain a base film treated by the cold gas pressure medium; (2) dispersing and homogenizing a water-based polymer raw material to obtain a water-based polymer slurry which is uniformly dispersed and stable; (3) coating the water-based polymer slurry on the base film treated in the step (1) by a spraying process to form a coating layer, and drying to obtain the high-performance spray diaphragm. The high-performance diaphragm of the application not only improves the phenomenon of spraying powder, but also significantly improves the cycle performance and thermal stability of the lithium ion battery.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery separator technology, specifically to a high-performance spray-coated separator treated with cold air pressure medium and its preparation method. Background Technology

[0002] With the rapid development of modern technology, lithium-ion batteries, as efficient and rechargeable energy storage devices, have been widely used in many fields, such as portable electronic devices (smartphones, tablets, etc.), electric vehicles, and energy storage systems. In the structure of a lithium-ion battery, the separator is a crucial component. Located between the positive and negative electrodes, it prevents direct contact between the electrodes, thus preventing short circuits, while also allowing lithium ions to pass freely during charging and discharging, thereby ensuring the normal operation of the battery. Therefore, the performance of the separator has a significant impact on the safety, cycle life, and charge / discharge performance of lithium-ion batteries.

[0003] Traditional spray-coated separators experience stress during battery charging and discharging due to the expansion and contraction between electrodes, leading to coating detachment. In high-temperature or high-humidity environments, the adhesive strength may decrease, increasing the risk of powder shedding. Powder shedding not only affects battery performance but also reduces capacity and cycle life, and can even cause internal short circuits, resulting in safety accidents. Therefore, a new and effective method is needed to address the powder shedding problem associated with spray-coated separators. Summary of the Invention

[0004] To address the shortcomings of the existing technology, this invention provides a high-performance spray-coated diaphragm with cold air pressure medium treatment and its preparation method, which not only improves the powder shedding phenomenon during spraying but also significantly enhances the cycle performance and thermal stability of lithium-ion batteries.

[0005] The technical solution provided by this invention: A method for preparing a high-performance spray-coated diaphragm for cold air pressure medium treatment, comprising the following steps:

[0006] (1) The base film is placed in a cold air pressure medium treatment device and the base film is treated on one or both sides by cold air pressure medium. After that, it is cleaned with pure water and dried on the surface to obtain the base film treated by cold air pressure medium.

[0007] (2) The aqueous polymer raw materials are dispersed and homogenized to obtain a uniformly dispersed and stable aqueous polymer slurry;

[0008] (3) The aqueous polymer slurry is coated onto the base film after step (1) by spraying to form a coating. After drying, a high-performance sprayed diaphragm is obtained.

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

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

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

[0012] Furthermore, the cold gas pressure medium is nitrogen or a mixture of nitrogen and 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 readily available and inexpensive.

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

[0014] Furthermore, by 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 remainder is pure water.

[0015] Furthermore, the 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, glycerin, polyethylene glycol ether, and stearyl alcohol.

[0017] Furthermore, the dispersion and homogenization treatment described in step (2) includes, but is not limited to, mechanical dispersion, ultrasonic dispersion, chemical dispersion, high-pressure homogenization, alternating milling homogenization, and ultrasonic homogenization. Dispersing and homogenizing the slurry effectively prevents slurry agglomeration and sedimentation, reducing pore blockage. 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] The beneficial effects of this invention are:

[0020] (1) After being treated with cold air pressure medium, the surface energy and roughness of the base film are effectively improved, and the interaction force between the spraying material and the base film surface is enhanced; this is conducive to the better adhesion of the spraying material to the base film surface, thereby solving the problem of powder shedding in the spraying diaphragm.

[0021] (2) The binder in the aqueous polymer slurry is a combination of sericin and aqueous binder. The sericin contains abundant hydrophilic groups, which improves the bonding strength between the polymer material and the base film, reduces the powder shedding problem of the sprayed separator, and significantly improves the electrolyte compatibility of the separator, effectively shortens the battery electrolyte injection time, and reduces the battery manufacturing cost.

[0022] The high-performance separator of this invention not only improves the powder shedding phenomenon of spray coating, but also significantly enhances the cycle performance and thermal stability of lithium-ion batteries. Detailed Implementation

[0023] To make the objectives, features, and advantages of this invention more apparent and understandable, the invention will be further described in detail below with reference to specific embodiments.

[0024] Example 1

[0025] A method for preparing a high-performance spray-coated diaphragm for cold air pressure medium treatment includes the following steps:

[0026] (1) A 9µm thick polyethylene film is placed in a cold pressurized medium treatment device. The film is treated on one side using a cold pressurized medium, resulting in increased surface roughness and surface energy. The cold pressurized medium is nitrogen gas with a pressure range of 150 Pa, a treatment temperature of 10°C, and a treatment time of 20 seconds. The film is then washed with pure water and dried to obtain the cold pressurized medium-treated film.

[0027] (2) The aqueous PVDF polymer slurry is dispersed and homogenized (mechanical dispersion) to obtain a uniformly dispersed and stable sprayable aqueous PVDF polymer slurry.

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

[0029] In Example 1, the aqueous PVDF slurry contained 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 was a compound system of sericin and LA133, with a mass ratio of sericin to LA133 of 1:4.

[0030] Example 2

[0031] A method for preparing a high-performance spray-coated diaphragm for cold air pressure medium treatment includes the following steps:

[0032] (1) A 12µm thick polypropylene base film is placed in a cold pressure medium treatment device. The base film is treated on one side using a cold pressure medium, resulting in increased surface roughness and surface energy. The cold pressure medium is argon gas with a pressure range of 120 Pa, a treatment temperature of 15°C, and a treatment time of 30 seconds. The base film treated with the cold pressure medium is then washed with pure water and dried to obtain the cold pressure medium-treated base film.

[0033] (2) The aqueous PVDF polymer slurry is dispersed and homogenized (mechanical dispersion) to obtain a uniformly dispersed and stable sprayable aqueous PVDF polymer slurry.

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

[0035] In Example 2, the aqueous PVDF slurry contained 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 was a compound system of sericin and LA132, with a mass ratio of sericin to LA132 of 1:5.

[0036] Example 3

[0037] A method for preparing a high-performance spray-coated diaphragm for cold air pressure medium treatment includes the following steps:

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

[0039] (2) The aqueous PMMA polymer slurry is dispersed and homogenized (ultrasonic dispersion) to obtain a uniformly dispersed and stable sprayable aqueous PMMA polymer slurry.

[0040] (3) The aqueous PMMA polymer slurry is coated onto the base film treated in step (1) by spraying process to form a coating. After drying, a high-performance sprayed PE diaphragm with cold air pressure medium treatment is obtained.

[0041] In Example 3, the aqueous PMMA slurry contained 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 was a compound system of sericin and acrylonitrile binder, with a mass ratio of sericin to acrylonitrile binder of 1:3.

[0042] Example 4

[0043] A method for preparing a high-performance spray-coated diaphragm for cold air pressure medium treatment includes the following steps:

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

[0045] (2) The aqueous PMMA polymer slurry is dispersed and homogenized (ultrasonic dispersion) to obtain a uniformly dispersed and stable sprayable aqueous PMMA polymer slurry.

[0046] (3) The aqueous PMMA polymer slurry is coated onto the base film treated in step (1) by spraying to form a coating. After drying, a high-performance sprayed PP / PE / PP diaphragm with cold air pressure medium treatment is obtained.

[0047] In Example 3, the aqueous PMMA slurry contained 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 was a compound system of sericin and polyvinylpyrrolidone, with a mass ratio of sericin to polyvinylpyrrolidone of 1:6.

[0048] Comparative Example 1

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

[0050] Comparative Example 2

[0051] PVDF-coated PE membrane without cold pressurized medium treatment (the binder is a compound system of sericin and LA133, with a mass ratio of sericin to LA133 of 1:4).

[0052] Comparative Example 3

[0053] PVDF-coated PE diaphragm (adhesive LA133) without cold pressurized medium treatment. Performance testing:

[0054] The contact angle and powder shedding amount of the diaphragms obtained in the embodiments and comparative examples of the present invention were tested as follows:

[0055] (1) Contact angle test: The diaphragm was cut into a 5cm×5cm square and a dynamic contact angle tester was used. The data acquisition interval was 10000 milliseconds / frame, and 10 sets of data were tested. The test results are shown in Table 1.

[0056] (2) Powder shedding test: The diaphragm was cut into strips of 3cm × 22cm and subjected to a friction test using a color fastness tester; a 2N weight was used for the test, and the test was repeated 5 times. The difference between the weight of the diaphragm before and after the test is the powder shedding 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. Test data on powder loss

[0060]

[0061] The test results above show that the high-performance spray-coated separator prepared by the present invention, subjected to cold pressure medium treatment, is superior to other comparative cases in terms of powder shedding and wettability. The high-performance separator of the present invention not only improves the powder shedding phenomenon during spraying but also significantly enhances the cycle performance and thermal stability of lithium-ion batteries.

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

Claims

1. A method for preparing a high-performance spray-coated diaphragm for cold air pressure medium treatment, characterized in that, Includes the following steps: (1) The base film is placed in a cold air pressure medium treatment device and the base film is treated on one or both sides by cold air pressure medium. After that, it is washed with pure water and dried to obtain a base film treated by cold air pressure medium. (2) The aqueous polymer raw materials are dispersed and homogenized to obtain a uniformly dispersed and stable aqueous polymer slurry; (3) The water-based polymer slurry is coated onto the base film after step (1) by spraying to form a coating. After drying, a high-performance sprayed diaphragm is obtained. The aqueous polymer slurry comprises a polymer, a solvent, a binder, and a wetting agent. The binder is a composite binder of sericin and an aqueous binder, with a mass ratio of sericin to aqueous binder of 1:(3-10). The aqueous binder is selected from any one of LA133 binder, LA132 binder, acrylonitrile binder, acrylic resin binder, and polyvinylpyrrolidone. The cold gas pressure medium mentioned in step (1) includes one of inert gas, compressed air, or treated low-temperature gas; The pressure range of the cold air pressure medium treatment in step (1) is 100-1000Pa, the treatment temperature is -50-50℃, and the treatment time is 1-300s.

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

3. The method for preparing a high-performance spray-coated diaphragm for cold air pressure medium treatment according to claim 1, characterized in that, The cold air pressure medium is nitrogen or a mixture of nitrogen and an inert gas.

4. The method for preparing a high-performance spray-coated diaphragm for cold air pressure medium treatment according to claim 1, characterized in that, By 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 remainder is pure water.

5. The method for preparing a high-performance spray-coated diaphragm for cold air pressure medium treatment according to claim 4, characterized in that, The polymer is selected from any one of PVDF, PMMA, and PAA.

6. The method for preparing a high-performance spray-coated diaphragm for cold air pressure medium treatment according to claim 4, characterized in that, The wetting agent is selected from any one of polyoxyethylene ethyl ether, propylene glycol, glycerin, polyethylene glycol ether, and stearyl alcohol.

7. The method for preparing a high-performance spray-coated diaphragm for cold air pressure medium treatment according to claim 1, characterized in that, The dispersion and homogenization process described in step (2) includes mechanical dispersion, ultrasonic dispersion, chemical dispersion, high-pressure homogenization, alternating milling homogenization, and ultrasonic homogenization.

8. The method for preparing a high-performance spray-coated diaphragm for cold air pressure medium treatment 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 10-100m / min, the coating thickness is 0.1-5um, and the coating method is single-sided coating or double-sided coating.

9. A high-performance spray-coated diaphragm for cold air pressure medium treatment prepared by the method according to any one of claims 1-8.

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