Cold-pressed adhesives, their preparation methods and applications

Abstract

This invention discloses a cold-pressing adhesive, its preparation method, and its application. The cold-pressing adhesive comprises: polybutyl acrylate, polyvinyl acetate, and styrene-butadiene rubber, wherein, by mass parts, the ratio of polybutyl acrylate, polyvinyl acetate, and styrene-butadiene rubber is (100-150):(70-110):(20-40). The preparation method of the cold-pressing adhesive includes: mixing polybutyl acrylate, polyvinyl acetate, and styrene-butadiene rubber, and stirring until homogeneous to obtain the cold-pressing adhesive. The battery separator obtained by coating the cold-pressed lithium battery slurry of this invention can reduce the hot-pressing temperature during battery assembly, reduce the deformation of the battery separator caused by thermal expansion and contraction, reduce the risk of battery degradation during charging and discharging, improve the adhesion between the battery separator and the electrode at room temperature, and increase the battery's service life and safety.

Description

Technical Field

[0001] This invention belongs to the field of battery separator technology, specifically relating to a cold-pressed adhesive, its preparation method, and its application. Background Technology

[0002] With the development of the lithium battery industry, lithium-ion batteries are being used more and more widely in various aspects of life, and more and more new energy projects are attracting social attention, among which electric vehicles are particularly popular. As the power source for electric vehicles, the safety and range of lithium-ion batteries are key research areas.

[0003] As a key component of lithium-ion batteries, the separator separates the positive and negative electrodes to prevent short circuits. The pores in the separator allow selective and free passage of cations and anions in the electrolyte, enabling the internal reactions of the battery to continue cyclically. The performance of the separator determines the battery's interface structure, internal resistance, and other characteristics, directly affecting the battery's capacity, cycle performance, and other properties.

[0004] However, due to the characteristics of the separator, the hot-pressing process remains an indispensable part of the existing lithium-ion battery assembly technology. However, during the hot-pressing process, the separator undergoes slight deformation, reducing the contact area between the separator and the electrode, affecting the adhesion between them. Long-term cycling can impact the battery's lifespan and safety. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a cold-pressed adhesive.

[0006] Another object of the present invention is to provide a method for preparing the above-mentioned cold-pressed adhesive.

[0007] Another object of the present invention is to provide a cold-pressed lithium battery slurry.

[0008] Another object of the present invention is to provide a method for preparing the above-mentioned cold-pressed lithium battery slurry.

[0009] Another object of the present invention is to provide a battery separator.

[0010] The objective of this invention is achieved through the following technical solution.

[0011] A cold-pressed adhesive comprises: polybutyl acrylate, polyvinyl acetate and styrene-butadiene rubber, wherein, by mass parts, the ratio of polybutyl acrylate, polyvinyl acetate and styrene-butadiene rubber is (100-150):(70-110):(20-40).

[0012] The preparation method of the above-mentioned cold-pressed adhesive includes: mixing polybutyl acrylate, polyvinyl acetate and styrene-butadiene rubber, stirring until uniform, to obtain the cold-pressed adhesive.

[0013] In the above technical solution, the stirring time is 150-180 min, the rotation speed of the stirring is 800-1200 r / min, and the revolution speed is 20-40 r / min.

[0014] A cold-pressed lithium battery slurry includes: a dispersant, PVDF, water, a thickener, and the cold-pressed binder, wherein, by mass parts, the ratio of the dispersant, PVDF, water, thickener, and cold-pressed binder is (0.6-1.2):(10-15):(58-70):(9-15):(10-20).

[0015] In the above technical solution, the dispersant is ammonium polyacrylate and the thickener is hydroxymethyl cellulose.

[0016] The method for preparing the above-mentioned cold-pressed lithium battery slurry includes: mixing a dispersant, water and PVDF, stirring for at least 70 minutes, then adding a thickener and a cold-pressing binder, and mixing for 30 to 60 minutes to obtain the cold-pressed lithium battery slurry.

[0017] In the above technical solution, the dispersant, water and PVDF are mixed and stirred for 70 to 90 minutes.

[0018] In the above technical solution, the rotation speed of the stirring for 70-90 minutes is 1800-2200 r / min, and the revolution speed is 30-60 r / min.

[0019] In the above technical solution, the rotation speed of the blending process for 30-60 minutes is 600-900 r / min, and the revolution speed is 20-40 r / min.

[0020] A battery separator includes: a base film and a coating applied to the base film, said coating being obtained by cold-pressing lithium battery slurry.

[0021] In the above technical solution, the thickness of the coating is 2 to 5 μm.

[0022] The method for preparing the above-mentioned battery separator includes: coating the cold-pressed lithium battery slurry onto a base film and drying it to obtain the battery separator.

[0023] In the above technical solution, the base film is a PE film.

[0024] In the above technical solution, the drying time is 1 to 5 minutes and the drying temperature is 50 to 70°C.

[0025] In the above technical solution, the coating speed is 40-60 m / min.

[0026] Cold-pressed adhesives are used in battery separators to improve the adhesion of electrode sheets.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] The battery separator obtained by cold-pressing lithium battery slurry coating of the present invention can reduce the temperature of hot pressing during battery assembly, reduce the deformation of the battery separator caused by thermal expansion and contraction, reduce the risk of battery degradation during charging and discharging, improve the adhesion between the battery separator and the electrode at room temperature, and increase the battery's service life and safety. Attached Figure Description

[0029] Figure 1 SEM image of the cold-pressed adhesive in Example 1;

[0030] Figure 2 The image shows the battery separator obtained from the cold-pressed lithium battery slurry preparation in Example 1 after hot pressing.

[0031] Figure 3 The image shows the battery separator obtained from the cold-pressed lithium battery slurry preparation in Example 1 after cold pressing.

[0032] Figure 4 Image of the battery separator obtained from the lithium battery slurry preparation of Comparative Example 1 after hot pressing;

[0033] Figure 5 This is an image of the battery separator obtained from the lithium battery slurry preparation of Comparative Example 1 after cold pressing. Detailed Implementation

[0034] The raw materials and their manufacturers involved in the following examples are as follows:

[0035] Ammonium polyacrylate was purchased from Tianjin Ceprui.

[0036] PVDF was purchased from Guangzhou Jiejin;

[0037] The electrodes (positive and negative) were purchased from Hunan Binbin Technology.

[0038] The instruments and their model information involved in the following embodiments are as follows:

[0039] Dual planetary mixer: Haojiete 30L model;

[0040] In the following examples, the water used was ultrapure water prepared by an ultrapure water system: Qianjing Q-200XF;

[0041] Imaging system: Shanghai Benpeng VMA4030;

[0042] Press: QMESYS QM-940AS;

[0043] Electronic tensile testing machine: Jinan Sike TSL-1002.

[0044] In the following examples, the base film is a PE film with a thickness of 12 μm.

[0045] Test method for hot-press adhesion: The electrode size is 25*60mm, and the battery separator size is 25*150mm. The coated surface of the battery separator is placed in contact with the electrode, and two A4 sheets of paper are used to hold it (the holding order is A4 paper / electrode / battery separator / A4 paper) to prevent the separator from being damaged by temperature during hot pressing. A press is used to perform hot pressing at a pressure of 1000kgf, a preheating temperature of 80℃, a preheating time of 1s, and a hot pressing time of 1s. After hot pressing, the adhesion of the battery separator is tested using an electronic tensile testing machine at a speed of 300mm / min and a peel angle of 180°. The adhesion force is recorded after the test.

[0046] Test method for cold-press adhesion: The electrode size is 25*60mm, and the battery separator size is 25*150mm. The coated surface of the battery separator is placed in contact with the electrode, and two A4 sheets of paper are used to hold it (the holding order is A4 paper / electrode / battery separator / A4 paper). A press is used to perform cold pressing at a pressure of 1000kgf, a preheating temperature of 25℃, a preheating time of 1s, and a cold pressing time of 1s. After cold pressing, the adhesion of the battery separator is tested using an electronic tensile testing machine at a speed of 300mm / min and a peel angle of 180°. The adhesion force is recorded after the test.

[0047] In the following embodiments, the battery separator hot-pressing image was obtained by hot-pressing at 1000 kgf and 80°C for 1 second.

[0048] In the following embodiments, the method for obtaining the cold-pressed image of the battery separator is: cold pressing at 1000 kgf and 25°C for 1 second.

[0049] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0050] Examples 1-3

[0051] A cold-pressed lithium battery slurry includes: a dispersant, PVDF, water, a thickener, and a cold-pressed binder. The ratio of the dispersant, PVDF, water, thickener, and cold-pressed binder by mass is X (Table 1). The cold-pressed binder is a mixture of polybutyl acrylate, polyvinyl acetate, and styrene-butadiene rubber. The cold-pressed binder is obtained by mixing polybutyl acrylate, polyvinyl acetate, and styrene-butadiene rubber and stirring at a rotation speed of 1000 r / min and a revolution speed of 25 r / min for 160 min. The ratio of polybutyl acrylate, polyvinyl acetate, and styrene-butadiene rubber by mass is 125:90:28. The dispersant is ammonium polyacrylate, and the thickener is hydroxymethyl cellulose.

[0052] Table 1

[0053] Example X Example 1 1.2:12:65:11.8:10 Example 2 1:11:63:12:13 Example 3 0.8:10:60:9.2:20

[0054] The method for preparing the above-mentioned cold-pressed lithium battery slurry includes: mixing a dispersant, water and PVDF, stirring in a double planetary mixer under vacuum conditions at a rotation speed of 2000 r / min and a revolution speed of 40 r / min for 70 min, then adding a thickener and a cold-pressing binder, and mixing at a rotation speed of 600 r / min and a revolution speed of 30 r / min for 40 min to obtain the cold-pressed lithium battery slurry.

[0055] Comparative Example 1

[0056] A method for preparing a lithium battery slurry is basically the same as the method for preparing the cold-pressed lithium battery slurry in Example 1, except that the cold-pressed binder in Example 1 is replaced with "methyl methacrylate".

[0057] Comparative Example 2

[0058] A method for preparing a lithium battery slurry is basically the same as the method for preparing the cold-pressed lithium battery slurry in Example 2, except that the cold-pressed binder in Example 2 is replaced with "methyl methacrylate".

[0059] Comparative Example 3

[0060] A method for preparing a lithium battery slurry is basically the same as the method for preparing the cold-pressed lithium battery slurry in Example 3, except that the cold-pressed binder in Example 3 is replaced with "methyl methacrylate".

[0061] Comparative Example 4

[0062] A method for preparing a lithium battery slurry is basically the same as the method for preparing the cold-pressed lithium battery slurry in Example 1, the only difference being that the cold-pressed binder in Example 1 is replaced with a "binder". The binder is a mixture of polybutyl acrylate and polyvinyl acetate, with a mass ratio of 100:80. The binder is obtained by mixing polybutyl acrylate and polyvinyl acetate and stirring at a rotation speed of 1000 r / min and a revolution speed of 25 r / min for 160 min.

[0063] Comparative Example 5

[0064] A method for preparing a lithium battery slurry is basically the same as the method for preparing the cold-pressed lithium battery slurry in Example 1, the only difference being that the cold-pressed binder in Example 1 is replaced with a "binder". The binder is a mixture of polybutyl acrylate and styrene-butadiene rubber, with a mass ratio of 110:35. The binder is obtained by mixing polybutyl acrylate and styrene-butadiene rubber and stirring at a rotation speed of 1000 r / min and a revolution speed of 25 r / min for 160 min.

[0065] Comparative Example 6

[0066] A method for preparing a lithium battery slurry is basically the same as the method for preparing the cold-pressed lithium battery slurry in Example 1, the only difference being that the cold-pressed binder in Example 1 is replaced with a "binder". The binder is a mixture of polyvinyl acetate and styrene-butadiene rubber, with a mass ratio of 75:25. The binder is obtained by mixing polyvinyl acetate and styrene-butadiene rubber and stirring at a rotation speed of 1000 r / min and a revolution speed of 25 r / min for 160 min.

[0067] Examples 4-6 and Comparative Examples 7-12

[0068] The method for preparing a battery separator includes: applying a slurry onto a base film using a coating machine at a coating speed of 40 m / min on one side; drawing the slurry into a drying device via a traction roller; drying at 50°C for 3 min; and obtaining a coating layer on the base film to obtain a battery separator. The slurry is one of the cold-pressed lithium battery slurries prepared in Examples 1-3 and the lithium battery slurries prepared in Comparative Examples 1-6. Battery separators of Examples 4-6 and Comparative Examples 7-12 are prepared sequentially. The thickness of the battery separator is shown in Table 2.

[0069] Table 2 (The positive electrode material is LiFePO4, and the negative electrode material is graphite)

[0070]

[0071]

[0072] The data in Table 2 show that, without affecting the basic properties of the battery separator such as thickness, air permeability, and areal density, the battery separator made with cold-pressed lithium battery slurry not only has a significantly improved hot-pressing adhesion, but also an even more significant improvement in cold-pressing adhesion, which is 2 to 10 times that of the battery separators prepared in Comparative Examples 7 to 12.

[0073] pass Figure 1 It can be observed that the cold-pressed adhesive exhibits a uniform particle distribution and no pore blockage under its microstructure.

[0074] pass Figure 2 and Figure 4 It can be observed that, through imaging tests, the battery separator obtained by coating with cold-pressed lithium battery slurry after hot pressing has smaller deformation than the battery separator obtained by coating with conventional lithium battery slurry.

[0075] pass Figure 3 and Figure 5 It can be observed that, through imaging tests, the cold-pressed lithium-ion battery slurry coated battery separator exhibits less deformation than the conventional lithium-ion battery slurry coated battery separator.

[0076] 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 battery separator, characterized in that, include: The base film and the coating applied to the base film, the coating including a cold-pressed adhesive, the cold-pressed adhesive including: polybutyl acrylate, polyvinyl acetate and styrene-butadiene rubber, wherein, by mass parts, the ratio of polybutyl acrylate, polyvinyl acetate and styrene-butadiene rubber is (100~150):(70~110):(20~40).

2. The battery separator according to claim 1, characterized in that, The preparation method of cold-pressed adhesive includes: mixing polybutyl acrylate, polyvinyl acetate and styrene-butadiene rubber, stirring until uniform, to obtain cold-pressed adhesive.

3. The battery separator according to claim 2, characterized in that, The stirring time is 150~180min, the rotation speed of the stirring is 800~1200r / min, and the revolution speed is 20~40r / min.

4. A cold-pressed lithium battery slurry, characterized in that, Cold-pressed lithium battery slurry is used in battery separators. The cold-pressed lithium battery slurry includes: dispersant, PVDF, water, thickener and cold-pressing binder. The ratio of the dispersant, PVDF, water, thickener and cold-pressing binder by mass parts is (0.6~1.2):(10~15):(58~70):(9~15):(10~20). The cold-pressing binder includes: polybutyl acrylate, polyvinyl acetate and styrene-butadiene rubber. The ratio of the polybutyl acrylate, polyvinyl acetate and styrene-butadiene rubber by mass parts is (100~150):(70~110):(20~40). The dispersant is ammonium polyacrylate and the thickener is hydroxymethyl cellulose.

5. A method for preparing the cold-pressed lithium battery slurry according to claim 4, characterized in that, include: Mix the dispersant, water and PVDF, stir for at least 70 minutes, then add the thickener and cold-pressing binder, and mix for 30-60 minutes to obtain the cold-pressed lithium battery slurry.

6. The method according to claim 5, characterized in that, The dispersant, water and PVDF are mixed and stirred for 70-90 minutes; the rotation speed of the mixture during the 30-60 minutes is 600-900 r / min and the revolution speed is 20-40 r / min.

7. The method according to claim 6, characterized in that, The rotation speed during the stirring process for 70-90 minutes is 1800-2200 r / min, and the revolution speed is 30-60 r / min.

Images