Double-state pressure-sensitive adhesive lithium battery diaphragm coating slurry as well as preparation method and application of double-state pressure-sensitive adhesive lithium battery diaphragm coating slurry

Abstract

The invention relates to the technical field of battery diaphragms, and provides dual-state pressure-sensitive adhesive lithium battery diaphragm coating slurry and a preparation method and application thereof.The dual-state pressure-sensitive adhesive lithium battery diaphragm coating slurry is prepared from porous ceramic powder, a dual-state pressure-sensitive adhesive and deionized water; the double-state pressure-sensitive adhesive is prepared from the following raw materials: a monomer A, an organic solvent, a monomer B, a monomer C and an initiator, the monomer A comprises one or two of sym-tribenzoyl chloride and acryloyl chloride; the monomer B comprises 1, 4-bis (4-aminophenoxy) benzene; the monomer C comprises styrene, lithium methacrylate and butyl methacrylate. According to the technical scheme, the problem that the dry-state and wet-state bonding performance of the lithium battery diaphragm formed by the lithium battery diaphragm coating slurry in the prior art is poor is solved.

Description

Technical Field

[0001] This invention relates to the field of battery separator technology, specifically to a dual-state pressure-sensitive adhesive lithium battery separator coating slurry, its preparation method, and its application. Background Technology

[0002] In the current lithium battery manufacturing field, polyvinylidene fluoride (PVDF) has relatively good electrochemical stability and adhesive strength, and is widely used in separator coatings. However, with the significantly accelerated pace of cell production and the ever-increasing demands for performance, PVDF is unable to form sufficient adhesive force in a short period of time. This ultimately results in weak bonding between the separator and the electrode, making it prone to delamination, reducing cell production efficiency, and shortening battery life.

[0003] To address the current issues with PVDF in separator applications, researchers considered increasing the amount of PVDF used in separators. However, excessive addition reduces the ionic conductivity of the lithium-ion battery separator, affecting its performance. It also leads to poor compatibility between PVDF and other components in the separator. More importantly, even if the dry adhesion of the PVDF coating with increased PVDF content meets the standards, the wet adhesion between the separator and the electrode weakens after the battery cell is injected into the electrolyte. In other words, increasing the amount or thickness of the PVDF coating fails to provide the lithium-ion battery separator with good dual-state adhesion, ultimately affecting cell quality and battery production yield.

[0004] The dual-state adhesion of lithium-ion battery separators specifically refers to dry-state adhesion and wet-state adhesion. Dry-state adhesion is the traditional adhesion between the lithium-ion battery separator and the electrode. Good wet-state adhesion mainly refers to the ability of the separator coating and the base film (separator and electrode) to maintain sufficient adhesion strength after the cell absorbs electrolyte. If the dual-state adhesion performance of the lithium-ion battery separator is insufficient, the coating on the separator will peel off, causing blockage of the separator pores, increasing internal resistance, and affecting battery performance and safety. It will also cause the adhesion between the separator and the electrode to fail, resulting in increased battery internal resistance, shortened cycle life, and even short circuits under abuse conditions. Traditional conventional PVDF base film spraying or roller coating products are difficult to guarantee dual-state adhesion of lithium-ion battery separators. The pressure sensitivity of the separator allows the product to be adapted to various battery cell production lines, resulting in high adaptability and higher production efficiency. Therefore, a lithium battery separator coating slurry is proposed. When used in lithium battery separators, it can give them good dual-state adhesion properties, which is of great significance for improving the overall performance and production efficiency of the battery and extending its service life. Summary of the Invention

[0005] This invention proposes a dual-state pressure-sensitive adhesive lithium battery separator coating slurry, its preparation method, and its application, which solves the problem of poor dry and wet dual-state adhesive performance of lithium battery separator coating slurries in related technologies.

[0006] The technical solution of the present invention is as follows: This invention proposes a dual-state pressure-sensitive adhesive lithium battery separator coating slurry, the raw materials of which include porous ceramic powder, dual-state pressure-sensitive adhesive and deionized water; The raw materials of the dual-state pressure-sensitive adhesive include the following components: Monomer A, organic solvent, monomer B, monomer C, initiator; The monomer A includes one or both of benzoyl chloride and acryloyl chloride; The monomer B includes 1,4-bis(4-aminophenoxy)benzene; The monomer C includes styrene, lithium methacrylate, and butyl methacrylate.

[0007] As a further technical solution, monomer A includes benzoyl chloride and acryloyl chloride; The initiator includes tert-butyl peroxyvalerate and benzoyl peroxide.

[0008] As a further technical solution, the mass ratio of the tribenzoyl chloride and acryloyl chloride is 0.5~0.6:0.45~0.55.

[0009] As a further technical solution, the mass ratio of tert-butyl peroxyvalerate to benzoyl peroxide is 0.05~0.08:0.05~0.08.

[0010] As a further technical solution, the mass ratio of styrene, lithium methacrylate and butyl methacrylate is 2~3:1~2:1~2.

[0011] As a further technical solution, the preparation method of the dual-state pressure-sensitive adhesive includes the following steps: A1. Under a first gas atmosphere, monomer A is added, and after cooling to -10~-5℃, the organic solvent and monomer B are added to carry out a first polymerization reaction. Then, monomer C and tert-butyl peroxyvalerate are added to carry out a second polymerization reaction to obtain the first product. A2. Under a second gas atmosphere, the first product and the benzoyl peroxide are mixed evenly and subjected to a third polymerization reaction to obtain the dual-state pressure-sensitive adhesive. The first gas is a protective gas; The second gas is a fluorinated olefin gas.

[0012] As a further technical solution, the degree of polymerization of the dual-state pressure-sensitive adhesive is 153~259, and the number-average molecular weight is 443802~751274.

[0013] As a further technical solution, the temperature of the first polymerization reaction is -10~-5℃, and the time is 6~8h; The second polymerization reaction is carried out at a temperature of 120~130℃ for 6~8 hours. The third polymerization reaction is carried out at a temperature of 120-130°C for 4-6 hours.

[0014] As a further technical solution, the mass ratio of monomer A, monomer B, monomer C, and initiator is 0.95~1.15:1:4~7:0.1~0.16; The amount of organic solvent added is 10 to 15 times the mass of monomer B; The amount of the fluorinated olefin gas added is 4 to 6 times the mass of monomer B.

[0015] As a further technical solution, the protective gas includes one or more of argon, helium, and nitrogen, preferably argon; The fluorinated olefin gases include hexafluoropropylene and vinylidene fluoride.

[0016] As a further technical solution, the mass ratio of hexafluoropropylene to vinylidene fluoride is 2~3:2~3.

[0017] As a further technical solution, the raw materials of the coating slurry also include polyvinyl alcohol and dispersant; The mass ratio of the porous ceramic powder, the dual-state pressure-sensitive adhesive, the polyvinyl alcohol, the dispersant, and the deionized water is 1:2~5:1~2:0.05:10.

[0018] As a further technical solution, the organic solvent includes one of N,N-dimethylacetamide, N-methylpyrrolidone, hexamethylphosphoramide, 1,4-dioxane, diethylene glycol dimethyl ether, and N,N-dimethylformamide, preferably N-methylpyrrolidone, wherein the water content of N-methylpyrrolidone is 49 ppm.

[0019] As a further technical solution, the porous ceramic powder includes one or more of porous alumina, porous calcium carbonate, and porous boehmite, preferably porous alumina.

[0020] As a further technical solution, the dispersant includes one or two of polyvinylpyrrolidone and sodium polyacrylate, preferably polyvinylpyrrolidone.

[0021] This invention proposes a method for preparing a dual-state varistor adhesive lithium-ion battery separator coating slurry, which includes the following steps: S1. After the dispersant and deionized water are mixed evenly, the mixture is emulsified for the first time to obtain the first substance; S2. Add the porous ceramic powder to the first substance, and emulsify it a second time to obtain the second substance; S3. Add the dual-state pressure-sensitive adhesive and the polyvinyl alcohol to the second substance, and emulsify for the third time to obtain the dual-state pressure-sensitive adhesive lithium battery separator coating slurry.

[0022] In this invention, the polyamide segments in the dual-state pressure-sensitive adhesive can increase the heat resistance of the lithium-ion battery separator, while the addition of polyvinyl alcohol can improve the adhesion of the coating slurry, thus enhancing the overall stability of the coating slurry. The synergistic effect of the polyamide segments and polyvinyl alcohol can effectively improve the heat resistance and mechanical strength of the lithium-ion battery separator, inhibit the formation of lithium dendrites, and reduce the risk of lithium dendrites directly piercing the lithium-ion battery separator. Furthermore, the rough surface and multiple pores of the porous ceramic powder can provide active sites for the adhesive. The addition of porous ceramic powder can improve the adhesion between the coating formed by the dual-state pressure-sensitive adhesive lithium-ion battery separator coating slurry and the positive and negative electrode sheets. Finally, through the stepwise emulsification of porous ceramic powder, dual-state pressure-sensitive adhesive, polyvinyl alcohol, and dispersant, a dual-state pressure-sensitive adhesive lithium-ion battery separator coating slurry with a uniform and stable internal structure is obtained. After coating this slurry onto a polyolefin-based film, the dual-state pressure-sensitive adhesion performance of the lithium-ion battery separator can be increased.

[0023] As a further technical solution, the stirring speed for the first emulsification is 20~50 r / min, the dispersion speed is 1800~2000 r / min, and the time is 20~30 min; The stirring speed for the second emulsification is 30-50 r / min, the dispersion speed is 2000-2200 r / min, and the time is 50-60 min; The stirring speed for the third emulsification is 30~50 r / min, the dispersion speed is 1600~1800 r / min, and the time is 60~70 min.

[0024] This invention also proposes the application of the dual-state pressure-sensitive adhesive lithium battery separator coating slurry or the dual-state pressure-sensitive adhesive lithium battery separator coating slurry prepared by the aforementioned preparation method in the preparation of lithium battery separators. The preparation method of the lithium battery separator includes the following steps: The dual-state pressure-sensitive adhesive lithium battery separator coating slurry is applied to at least one side of the base film by dot coating or roller coating, and then dried to obtain the lithium battery separator.

[0025] In preparing the lithium-ion battery separator according to the present invention, a dual-state pressure-sensitive adhesive lithium-ion battery separator coating slurry is applied to at least one side of the base film by dot coating or roller coating, preferably by dot coating. Through matrix dot coating, the dual-state pressure-sensitive adhesive lithium-ion battery separator formed has a more reasonable matrix arrangement morphology on its surface, which can not only increase the ionic conductivity of the lithium-ion battery separator, but also facilitate the flow of electrolyte from the structural gaps of the dot arrangement, further improving the dual-state pressure-sensitive adhesive performance of the lithium-ion battery separator.

[0026] In this invention, in accordance with GB / T 36363 The method in 2018 "Polyolefin Separator for Lithium-ion Batteries" tests the thickness of lithium-ion battery separators. The thickness increment of the lithium-ion battery separator is calculated as: thickness increment = lithium-ion battery separator thickness - base film thickness. In this invention, the thickness increment of the battery separator is 0.5~4μm, for example, it can be 0.5μm, 0.8μm, 1μm, 1.2μm, 1.5μm, 1.8μm, 2μm, 2.2μm, 2.5μm, 2.8μm, 3μm, 3.2μm, 3.5μm, 3.8μm, 4μm, preferably 0.5μm, 1μm, 4μm.

[0027] In this invention, the base film comprises a wet-process polyethylene base film or a wet-process polypropylene base film, preferably a wet-process polyethylene base film, with a base film thickness of 5.1 μm and an areal density of 3.56 g / m³. 2 Other thicknesses and areal densities of base films are also applicable.

[0028] The working principle and beneficial effects of this invention are as follows: 1. In this invention, a dual-state pressure-sensitive adhesive is used as the main material, combined with porous ceramic powder. The multiple pores of the porous ceramic powder can increase the overall heat resistance and electrolyte wettability of the separator. In this system, it works synergistically with the dual-state pressure-sensitive adhesive to obtain a dual-state pressure-sensitive adhesive lithium battery separator coating slurry. When used in lithium battery separators, it can effectively improve the adhesion performance between the lithium battery separator and the positive and negative electrode sheets, giving it good dry-state adhesion performance as well as good wet-state adhesion performance, thus achieving dual-state adhesion.

[0029] This invention utilizes hexafluoropropylene, vinylidene fluoride, 1,4-bis(4-aminophenoxy)benzene, styrene, lithium methacrylate, butyl methacrylate, and tribenzoyl chloride and / or acryloyl chloride as monomers. Under the action of an initiator, a controllable polymerization reaction is achieved through precise raw material ratios. This process prepares a multi-segment dual-state pressure-sensitive functional adhesive that simultaneously possesses segments of polyvinylidene fluoride-hexafluoropropylene, polybutyl methacrylate, and polystyrene. It combines the adhesive properties of polyvinylidene fluoride-hexafluoropropylene, polybutyl methacrylate, and polystyrene with the heat resistance of polyamide. Yes, the highly electronegative fluorine atoms in the polyvinylidene fluoride-hexafluoropropylene segment can interact with the active groups on the electrode surface under external pressure, increasing the adsorption force between the dual-state pressure-sensitive adhesive and the electrode. The total number of adsorption sites varies with pressure. Lithium methacrylate, as a monomer, increases the number of active carboxyl lithium groups, thereby improving the deionized water-oil amphoteric solubility of the synthesized dual-state pressure-sensitive adhesive polymer and lowering the glass transition temperature of the polymer. Butyl methacrylate also lowers the glass transition temperature of the synthesized polymer. The addition of butyl methacrylate and styrene monomers with rigid supporting properties can effectively enhance the hydrogen bonding between the bi-state pressure-sensitive adhesive and the electrode under external force, thereby increasing the pressure sensitivity of the bi-state pressure-sensitive adhesive. Tribenzoyl chloride, due to the presence of three condensation reaction sites, undergoes a condensation reaction with 1,4-bis(4-aminophenoxy)benzene, increasing the number of segments in the bi-state pressure-sensitive adhesive. Acryloyl chloride can act as a "bridge," connecting the upstream free radical reaction segment and the condensation polyamide segment, linking the chemical bonds of the two segments together. It possesses carbon-carbon double bonds, which can... Free radical reactions link chain segments, resulting in a unified three-dimensional network structure for the bi-state pressure-sensitive adhesive polymer. The presence of butyl methacrylate, its ester and alkyl butyl groups, increases the distance between polymer chains, increasing polymer disorder and steric hindrance. This further enhances the pressure-sensitive properties of the disordered segments. Simultaneously, the increased inter-chain spacing facilitates electrolyte desorption, reducing polymer swelling, avoiding internal conflicts between segments, and enhancing the adhesive's dual-state adhesion in both dry and wet states. In summary, a bi-state pressure-sensitive adhesive with extremely strong bi-state pressure-sensitive properties was prepared through controlled polymerization using hexafluoropropylene, vinylidene fluoride, 1,4-bis(4-aminophenoxy)benzene, styrene, lithium methacrylate, butyl methacrylate, and tribenzoyl chloride and / or acryloyl chloride as monomers under the action of an initiator. Attached Figure Description

[0030] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0031] Figure 1This is a polymerization reaction diagram of the dual-state pressure-sensitive adhesive lithium battery separator coating slurry in Example 2 of the present invention; Figure 2 This is a Keyence microscope image of the lithium-ion battery separator obtained by the dot coating method in Example 2 of the present invention; Figure 3 This is a scanning electron microscope image of the lithium battery separator in Embodiment 2 of the present invention; Figure 4 This is a scanning electron microscope image of the lithium battery separator in Embodiment 6 of the present invention. Detailed Implementation

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0033] In the following embodiments and comparative examples: 1,4-Bis(4-aminophenoxy)benzene, CAS No. 3491-12-1, is a light yellow powder; Benzoyl chloride, CAS number 4422-95-1, is a white crystalline powder; Acryloyl chloride, CAS number 814-68-6, is a slightly yellow transparent liquid; Styrene, CAS number 100-42-5, is a colorless, transparent, oily liquid; Lithium methacrylate, CAS number 13234-23-6, is a yellow powder. Butyl methacrylate, CAS number 97-88-1, is a colorless and transparent liquid. Hexafluoropropylene, CAS number 116-15-4; Vinylidene fluoride, CAS number 75-38-7; tert-butyl peroxyvalerate, CAS number 927-07-1; Benzoyl peroxide, CAS number 94-36-0, is a pale yellow powder with a density of 1.33 g / cm³. 3 Its molecular weight is 242.23; The porous alumina has an average particle size of 0.259 μm and a specific surface area of ​​59.12 m². 2 / g, porosity is 50.23%; PVDF powder is a copolymer of vinylidene fluoride and hexafluoropropylene, with an average particle size of 6.3 μm. PMMA powder is polymethyl methacrylate powder with a number average molecular weight of 551208 and an average particle size of 2.0 μm. Polyvinyl alcohol has a density of 1.29 g / cm³ at 25°C. 3 The solid content is 15%~20%, and the number average molecular weight is 100967; Polyvinylpyrrolidone (PVP), a light yellow powder with a density of 1.144 g / cm³. 3 It has a boiling point of 217.6℃, a melting point of 130℃, a flash point of 93.9℃, and a number-average molecular weight of 8971.

[0034] Example 1 The preparation method of the dual-state pressure-sensitive adhesive includes the following steps: A1. Open the gas microchannel reaction controller one to introduce argon gas into the organic ceramic polymerization reactor to complete the first gas replacement and continue to introduce argon gas. Open the feeding microchannel one and add tribenzoyl chloride. Open the feeding microchannel two and add acryloyl chloride. After cooling to -10℃, start stirring (stirring speed is 30r / min). Open the solvent microchannel reactor and add N-methylpyrrolidone. Open the feeding microchannel three and add 1,4-bis(4-aminophenoxy)benzene. After the polymerization reaction is carried out at -10℃ for 8 hours, close the gas microchannel reaction controller one. Then open the feeding microchannel four and add styrene. Open the feeding microchannel five and add lithium methacrylate. Open the feeding microchannel six and add butyl methacrylate. Open the initiator microchannel one and add tert-butyl peroxyvalerate. Raise the temperature to 130℃ and carry out the polymerization reaction at 130℃ for 8 hours to obtain the first product. A2. Open the second gas microchannel reaction controller and introduce hexafluoropropylene into the organoceramic polymerization reactor containing the first product. Open the third gas microchannel reaction controller and introduce vinylidene fluoride for a second gas replacement. Open the second initiator microchannel and add benzoyl peroxide. After mixing evenly, carry out the polymerization reaction at 130°C for 6 hours to obtain a bi-state pressure-sensitive adhesive (degree of polymerization of 259, number average molecular weight of 751274). The mass ratio of 1,4-bis(4-aminophenoxy)benzene, benzoyl chloride, acryloyl chloride, styrene, lithium methacrylate, butyl methacrylate, hexafluoropropylene, vinylidene fluoride, tert-butyl peroxyvalerate, benzoyl peroxide, and N-methylpyrrolidone is 1:0.6:0.45:3:2:2:3:3:0.08:0.08:15. A method for preparing a dual-state pressure-sensitive adhesive lithium battery separator coating slurry includes the following steps: S1. After mixing polyvinylpyrrolidone and deionized water evenly, emulsify for 20 minutes at a stirring speed of 50 r / min and a dispersion speed of 2000 r / min to obtain the first substance; S2. Add porous alumina to the first substance above, and emulsify for 60 min at a stirring speed of 50 r / min and a dispersion speed of 2200 r / min to obtain the second substance; S3. Add a dual-state pressure-sensitive adhesive and polyvinyl alcohol to the second substance mentioned above, and emulsify for 70 min at a stirring speed of 50 r / min and a dispersion speed of 1800 r / min to obtain a dual-state pressure-sensitive adhesive lithium battery separator coating slurry. The mass ratio of porous alumina, dual-state pressure-sensitive adhesive, polyvinyl alcohol, polyvinylpyrrolidone, and deionized water is 1:5:2:0.05:10. The preparation method of lithium battery separator includes the following steps: The above-mentioned dual-state pressure-sensitive adhesive lithium battery separator coating slurry was applied to one side of a wet-process polyethylene film by dot coating and dried to obtain the lithium battery separator; wherein the wet-process polyethylene film has a thickness of 5.1 μm and an areal density of 3.56 g / m³. 2 The thickness increase is 1.0 μm, and the coating amount per micrometer is 1.0 g / m. 2 .

[0035] Example 2 The preparation method of the dual-state pressure-sensitive adhesive includes the following steps: A1. Open the gas microchannel reaction controller one to introduce argon gas into the organic ceramic polymerization reactor to complete the first gas replacement and continue to introduce it. Open the feeding microchannel one and add tribenzoyl chloride. Open the feeding microchannel two and add acryloyl chloride. After cooling to -8℃, start stirring (stirring speed is 25r / min). Open the solvent microchannel reactor and add N-methylpyrrolidone. Open the feeding microchannel three and add 1,4-bis(4-aminophenoxy)benzene. After the polymerization reaction is carried out at -8℃ for 7h, close the gas microchannel reaction controller one. Then open the feeding microchannel four and add styrene. Open the feeding microchannel five and add lithium methacrylate. Open the feeding microchannel six and add butyl methacrylate. Open the initiator microchannel one and add tert-butyl peroxyvalerate. Raise the temperature to 125℃ and carry out the polymerization reaction at 125℃ for 7h to obtain the first product. A2. Open the second gas microchannel reaction controller and introduce hexafluoropropylene into the organoceramic polymerization reactor containing the first product. Open the third gas microchannel reaction controller and introduce vinylidene fluoride for a second gas replacement. Open the second initiator microchannel and add benzoyl peroxide. After mixing evenly, carry out the polymerization reaction at 125°C for 5 hours to obtain a bi-state pressure-sensitive adhesive (degree of polymerization of 208, number average molecular weight of 603340). The mass ratio of 1,4-bis(4-aminophenoxy)benzene, benzoyl chloride, acryloyl chloride, styrene, lithium methacrylate, butyl methacrylate, hexafluoropropylene, vinylidene fluoride, tert-butyl peroxyvalerate, benzoyl peroxide, and N-methylpyrrolidone is 1:0.55:0.5:2.5:1.5:1.5:2.5:2.5:0.065:0.065:12. A method for preparing a dual-state pressure-sensitive adhesive lithium battery separator coating slurry includes the following steps: S1. After mixing polyvinylpyrrolidone and deionized water evenly, emulsify for 30 min at a stirring speed of 30 r / min and a dispersion speed of 1800 r / min to obtain the first substance; S2. Add porous alumina to the first substance above, and emulsify for 50 min at a stirring speed of 30 r / min and a dispersion speed of 2000 r / min to obtain the second substance; S3. Add a dual-state pressure-sensitive adhesive and polyvinyl alcohol to the second substance mentioned above, and emulsify for 60 minutes at a stirring speed of 30 r / min and a dispersion speed of 1600 r / min to obtain a dual-state pressure-sensitive adhesive lithium battery separator coating slurry. The mass ratio of porous alumina, dual-state pressure-sensitive adhesive, polyvinyl alcohol, polyvinylpyrrolidone, and deionized water is 1:2:1:0.05:10. The preparation method of lithium battery separator includes the following steps: The above-mentioned dual-state pressure-sensitive adhesive lithium battery separator coating slurry was applied to one side of a wet-process polyethylene film by dot coating and dried to obtain the lithium battery separator; wherein the wet-process polyethylene film has a thickness of 5.1 μm and an areal density of 3.56 g / m³. 2 The thickness increase is 1.0 μm, and the coating amount per micrometer is 1.0 g / m. 2 ; The polymerization reaction diagram of the dual-state pressure-sensitive adhesive lithium battery separator coating slurry in Example 2 is shown below. Figure 1 As shown; Keyence microscope image of the lithium battery separator obtained by the dot coating method in Example 2 is shown below. Figure 2 As shown; The scanning electron microscope image of the lithium battery separator in Example 2 is shown below. Figure 3 As shown.

[0036] Example 3 The preparation method of the dual-state pressure-sensitive adhesive includes the following steps: A1. Open the gas microchannel reaction controller one to introduce argon gas into the organic ceramic polymerization reactor to complete the first gas replacement and continue to introduce argon gas. Open the feeding microchannel one and add tribenzoyl chloride. Open the feeding microchannel two and add acryloyl chloride. After cooling to -5℃, start stirring (stirring speed is 20r / min). Open the solvent microchannel reactor and add N-methylpyrrolidone. Open the feeding microchannel three and add 1,4-bis(4-aminophenoxy)benzene. After the polymerization reaction is carried out at -5℃ for 6 hours, close the gas microchannel reaction controller one. Then open the feeding microchannel four and add styrene. Open the feeding microchannel five and add lithium methacrylate. Open the feeding microchannel six and add butyl methacrylate. Open the initiator microchannel one and add tert-butyl peroxyvalerate. Heat to 120℃ and carry out the polymerization reaction at 120℃ for 6 hours to obtain the first product. A2. Open the second gas microchannel reaction controller and introduce hexafluoropropylene into the organoceramic polymerization reactor containing the first product. Open the third gas microchannel reaction controller and introduce vinylidene fluoride for a second gas replacement. Open the second initiator microchannel and add benzoyl peroxide. After mixing evenly, carry out the polymerization reaction at 120°C for 4 hours to obtain a bi-state pressure-sensitive adhesive (degree of polymerization of 153, number average molecular weight of 443802). The mass ratio of 1,4-bis(4-aminophenoxy)benzene, benzoyl chloride, acryloyl chloride, styrene, lithium methacrylate, butyl methacrylate, hexafluoropropylene, vinylidene fluoride, tert-butyl peroxyvalerate, benzoyl peroxide, and N-methylpyrrolidone is 1:0.5:0.55:2:1:1:2:2:0.05:0.05:10. A method for preparing a dual-state pressure-sensitive adhesive lithium battery separator coating slurry includes the following steps: S1. After mixing polyvinylpyrrolidone and deionized water evenly, emulsify for 30 min at a stirring speed of 30 r / min and a dispersion speed of 1800 r / min to obtain the first substance; S2. Add porous alumina to the first substance above, and emulsify for 50 min at a stirring speed of 30 r / min and a dispersion speed of 2000 r / min to obtain the second substance; S3. Add a dual-state pressure-sensitive adhesive and polyvinyl alcohol to the second substance mentioned above, and emulsify for 60 minutes at a stirring speed of 30 r / min and a dispersion speed of 1600 r / min to obtain a dual-state pressure-sensitive adhesive lithium battery separator coating slurry. The mass ratio of porous alumina, dual-state pressure-sensitive adhesive, polyvinyl alcohol, polyvinylpyrrolidone, and deionized water is 1:2:1:0.05:10. The preparation method of lithium battery separator includes the following steps: The above-mentioned dual-state pressure-sensitive adhesive lithium battery separator coating slurry was applied to one side of a wet-process polyethylene film by dot coating and dried to obtain the lithium battery separator; wherein the wet-process polyethylene film has a thickness of 5.1 μm and an areal density of 3.56 g / m³. 2 The thickness increase is 1.0 μm, and the coating amount per micrometer is 1.0 g / m. 2 .

[0037] Example 4 The only difference between this embodiment and Embodiment 2 is that, in this embodiment, the thickness increase in the lithium battery separator preparation method is 4.0 μm, and the coating amount per micrometer is 2.0 g / m. 2 .

[0038] Example 5 The only difference between this embodiment and Embodiment 2 is that, in this embodiment, the thickness increase in the lithium battery separator preparation method is 0.5 μm, and the coating amount per micrometer is 0.5 g / m. 2 .

[0039] Example 6 The only difference between this embodiment and Embodiment 2 is that the preparation method of the lithium battery separator is different in this embodiment, specifically: The above-mentioned dual-state pressure-sensitive adhesive lithium battery separator coating slurry was coated onto one side of a wet polyethylene base film by roller coating and dried to obtain a lithium battery separator. The scanning electron microscope image of the lithium battery separator in Example 6 is shown below. Figure 4 As shown.

[0040] Example 7 The only difference between this embodiment and Embodiment 1 is that the preparation method of the lithium battery separator is different in this embodiment, specifically: The above-mentioned dual-state pressure-sensitive adhesive lithium battery separator coating slurry was coated onto one side of a wet-process polyethylene base film by roller coating and dried to obtain a lithium battery separator.

[0041] Example 8 The only difference between this embodiment and Embodiment 3 is that the preparation method of the lithium battery separator is different in this embodiment, specifically: The above-mentioned dual-state pressure-sensitive adhesive lithium battery separator coating slurry was coated onto one side of a wet-process polyethylene base film by roller coating and dried to obtain a lithium battery separator.

[0042] Example 9 The difference between this embodiment and Embodiment 2 lies only in that, in the preparation method of the dual-state pressure-sensitive adhesive in this embodiment, the mass ratio of 1,4-bis(4-aminophenoxy)benzene, tribenzoyl chloride, acryloyl chloride, styrene, lithium methacrylate, butyl methacrylate, hexafluoropropylene, vinylidene fluoride, tert-butyl peroxyvalerate, benzoyl peroxide, and N-methylpyrrolidone is 1:0.8:0.71:5:2.5:2.5:4:4:0.065:0.065:18.

[0043] Example 10 The only difference between this embodiment and Example 2 is that in the preparation method of the dual-state pressure-sensitive adhesive in this embodiment, the mass ratio of 1,4-bis(4-aminophenoxy)benzene, tribenzoyl chloride, acryloyl chloride, styrene, lithium methacrylate, butyl methacrylate, hexafluoropropylene, vinylidene fluoride, tert-butyl peroxyvalerate, benzoyl peroxide, and N-methylpyrrolidone is 1:0.6:0.2:1.5:0.75:0.75:1.5:1.5:0.065:0.065:8.

[0044] Example 11 The only difference between this embodiment and Embodiment 2 is that in the preparation method of the dual-state pressure-sensitive adhesive lithium battery separator coating slurry in this embodiment, the mass ratio of porous alumina, dual-state pressure-sensitive adhesive, polyvinyl alcohol, polyvinylpyrrolidone, and deionized water is 1:7:3:0.05:10.

[0045] Example 12 The only difference between this embodiment and Embodiment 2 is that in the preparation method of the dual-state pressure-sensitive adhesive lithium battery separator coating slurry in this embodiment, the mass ratio of porous alumina, dual-state pressure-sensitive adhesive, polyvinyl alcohol, polyvinylpyrrolidone, and deionized water is 1:1:0.2:0.05:10.

[0046] Comparative Example 1 The only difference between this comparative example and Example 2 is that in the preparation method of the dual-state pressure-sensitive adhesive lithium battery separator coating slurry in this comparative example, the dual-state pressure-sensitive adhesive is replaced with an equal amount of PVDF powder.

[0047] Comparative Example 2 The only difference between this comparative example and Example 2 is that in the preparation method of the dual-state pressure-sensitive adhesive lithium battery separator coating slurry in this comparative example, the dual-state pressure-sensitive adhesive is replaced with an equal amount of PMMA powder.

[0048] Comparative Example 3 The only difference between this comparative example and Example 2 is that in the preparation method of the dual-state pressure-sensitive adhesive lithium battery separator coating slurry in this comparative example, the dual-state pressure-sensitive adhesive is replaced with PVDF powder and PMMA powder in a mass ratio of 1:1, wherein the mass of PVDF powder and PMMA powder is equal to the mass of the dual-state pressure-sensitive adhesive.

[0049] Comparative Example 4 The only difference between this comparative example and Example 2 is that porous alumina is not added in the preparation method of the dual-state pressure-sensitive adhesive lithium battery separator coating slurry in this comparative example.

[0050] Comparative Example 5 The only difference between this comparative example and Example 2 is that, in the preparation method of the dual-state pressure-sensitive adhesive lithium battery separator coating slurry in this comparative example, porous alumina and dual-state pressure-sensitive adhesive are replaced with equal masses of PVDF powder.

[0051] Comparative Example 6 The only difference between this comparative example and Example 2 is that, in the preparation method of the dual-state pressure-sensitive adhesive lithium battery separator coating slurry in this comparative example, porous alumina and dual-state pressure-sensitive adhesive are replaced with equal masses of PVDF powder, and polyvinyl alcohol is replaced with equal masses of sodium carboxymethyl cellulose.

[0052] Comparative Example 7 The only difference between this comparative example and Example 2 is that in the preparation method of the dual-state pressure-sensitive adhesive lithium battery separator coating slurry in this comparative example, polyvinyl alcohol is replaced with an equal amount of sodium carboxymethyl cellulose, and the dual-state pressure-sensitive adhesive is replaced with an equal amount of PVDF powder.

[0053] Experimental Example 1 The lithium-ion battery separators prepared in Examples 1-12 and Comparative Examples 1-7 were subjected to the following basic performance tests: (1) Liquid absorption rate and liquid retention rate test: The liquid absorption rate and liquid retention rate of the lithium battery separator sample were tested according to the test method in QB / T 2303-2024 "Pulp Paper for Primary Batteries"; (2) Wetting test: Wetting characterizes the affinity between the separator and the electrolyte. The higher the wettability value, the better the wettability and the stronger the liquid absorption and retention, which can reduce the internal resistance of the battery. The formula for calculating wettability v is: v = h / t, where h is the wetting height (the height of the electrolyte penetrating the lithium battery separator in the vertical direction), in mm, and t is the wetting time, in min; the electrolyte used in the wettability test is a mixture of electrolyte and solvent, wherein the electrolyte is lithium hexafluorophosphate, and the solvent is a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) (the volume ratio of EC to DEC is 1:1), and the concentration of electrolyte in the electrolyte is 1 mol / L; (3) Ionic conductivity test: The ionic conductivity of the lithium battery separator sample was tested according to the method in GB / T 36363-2018 "Polyolefin separator for lithium-ion batteries". The temperature during the test was 40℃ and the relative humidity was 45%~50%. (4) Heat shrinkage performance test: The transverse (TD) heat shrinkage rate and longitudinal (MD) heat shrinkage rate were determined according to the test method in GB / T 36363-2018 "Polyolefin separator for lithium-ion batteries". The test results are the average values ​​of three samples. The test results are shown in Table 1.

[0054] Table 1. Basic performance test results of lithium battery separators in Examples 1-12 and Comparative Examples 1-7

[0055] Compared with Comparative Examples 1-7, the lithium battery separators prepared in Examples 1-8 showed improved liquid absorption rate, liquid retention rate, wettability, and ionic conductivity, and reduced thermal shrinkage rate. This indicates that the dual-state pressure-sensitive adhesive prepared in this invention, when used in the lithium battery separator slurry containing the dual-state pressure-sensitive adhesive and porous ceramic powder, can effectively improve the overall performance of the lithium battery separator, including wettability, ionic conductivity, and heat resistance.

[0056] Furthermore, compared with Examples 9-10, the lithium-ion battery separators prepared in Examples 1-3 showed improved liquid absorption rate, liquid retention rate, wettability, and ionic conductivity, and reduced thermal shrinkage rate. This indicates that during the preparation of the lithium-ion battery separator in this invention, the mass ratio of each raw material in the dual-state pressure-sensitive adhesive was reasonably controlled. When the mass ratio of monomer A, monomer B, monomer C, and initiator was 0.95-1.15:1:4-7:0.1-0.16, the amount of organic solvent added was 10-15 times the mass of monomer B, and the amount of fluorinated olefin gas added was 4-6 times the mass of monomer B, the mass ratio of each raw material in the dual-state pressure-sensitive adhesive was reasonable, which helped to improve the overall performance of the lithium-ion battery separator.

[0057] Compared with Examples 11-12, the lithium battery separators prepared in Examples 1-3 showed improved liquid absorption rate, liquid retention rate, wettability, and ionic conductivity, and reduced thermal shrinkage rate. This indicates that during the preparation of the lithium battery separator in this invention, the mass ratio of each raw material in the dual-state pressure-sensitive adhesive lithium battery separator coating slurry was reasonably controlled. When the mass ratio of porous ceramic powder, dual-state pressure-sensitive adhesive, polyvinyl alcohol, dispersant, and deionized water was 1:2~5:1~2:0.05:10, the mass ratio of each component in the coating slurry was reasonable, which helped to improve the overall performance of the lithium battery separator.

[0058] Experiment Example 2 The lithium-ion battery separators prepared in Examples 1-12 and Comparative Examples 1-7 were subjected to dual-state adhesion tests: (1) Dry electrode adhesion test: The electrode is either a positive electrode or a negative electrode. The adhesion strength of the positive electrode is obtained when the electrode is a positive electrode, and the adhesion strength of the negative electrode is obtained when the electrode is a negative electrode. Cold-pressed positive electrode adhesion strength: The lithium battery separator is cut to a size of 25mm×150mm, and the positive electrode is cut to a size of 25mm×150mm; the temperature of the cold press is adjusted to 25℃, and the pressure is set to the set value (100kg, 500kg, 1000kg, 2000kg, 5000kg, 8000kg). The lithium battery separator and the positive electrode are preheated for 1s and cold-pressed for 1s using the cold press; the adhesion strength of the cold-pressed positive electrode is tested using an electronic tensile testing machine. The lithium battery separator and the positive electrode are peeled off until the tensile distance of the electronic tensile testing machine is 50mm. The electronic tensile testing machine operates at a speed of 300 mm / min and a peel angle of 180°. The cold-pressed positive electrode bonding strength is calculated as: peel force / tensile distance of the electronic tensile testing machine. Peel force is the average force collected by the electronic tensile testing machine during the peeling process of the lithium battery separator and positive electrode. The cold-pressed positive electrode bonding strength is calculated based on data with a tensile distance between 10 and 40 mm, i.e., cold-pressed positive electrode bonding strength = peel force between 10 and 40 mm / 30 mm. The positive electrode is a ternary lithium nickel cobalt aluminum oxide electrode with the chemical formula LiNi. 0.8 Co 0.15 Al 0.05 O2, the negative electrode is a carbon-based graphite electrode (91% carbon content), and the average value of 10 test groups is taken; the test results are shown in Table 2. (2) Wet electrode adhesion test: Following the method in the dry electrode adhesion test, the cold-pressed electrode / lithium battery separator was placed in a 50mm×200mm aluminum foil plastic bag, and 3mL of electrolyte (the electrolyte is a mixture of electrolyte and solvent, wherein the electrolyte is lithium hexafluorophosphate, and the solvent is a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) (the volume ratio of EC and DEC is 1:1), and the concentration of electrolyte in the electrolyte is 1mol / L) was injected and sealed. After soaking at 25℃ for 64h, it was taken out and the surface of the free electrolyte was gently pressed and wiped with industrial wiping paper for testing. The bonding strength of the cold-pressed positive electrode sheet was tested using an electronic tensile testing machine. The lithium battery separator and positive electrode sheet were peeled until the tensile distance measured by the electronic tensile testing machine reached 50 mm. The speed of the electronic tensile testing machine was 300 mm / min, and the peel angle was 180°. The bonding strength of the cold-pressed positive electrode sheet was calculated as: peel force / tensile distance measured by the electronic tensile testing machine. Peel force: the average force collected by the electronic tensile testing machine during the peeling process. The bonding strength of the cold-pressed positive electrode sheet was calculated based on data with tensile distances between 10 and 40 mm, i.e., bonding force between 10 and 40 mm / 30 mm. The positive electrode sheet was a ternary lithium nickel cobalt aluminum oxide electrode sheet with the chemical formula LiNi. 0.8 Co 0.15 Al 0.05 O2, the negative electrode is a carbon-based graphite electrode (containing 91% carbon); 10 groups were tested and the average value was taken; the test results are shown in Table 3.

[0059] Table 2. Test results of dry electrode adhesion in Examples 1-12 and Comparative Examples 1-7

[0060] Table 3. Test results of wet electrode adhesion in Examples 1-12 and Comparative Examples 1-7

[0061] As can be seen from Tables 2 and 3, compared with Comparative Examples 1-3 and 5-7, the lithium-ion battery separators prepared in Examples 1-8 showed improved adhesion to both the dry and wet states of the positive and negative electrodes at 100 kg, 500 kg, 1000 kg, 2000 kg, 5000 kg, and 8000 kg. This indicates that the dual-state pressure-sensitive adhesive prepared in this invention can effectively improve the dual-state adhesion performance of lithium-ion battery separators when used in lithium-ion battery separator slurry containing the dual-state pressure-sensitive adhesive and porous ceramic powder.

[0062] Experimental Example 3 The swelling rate of the dual-state pressure-sensitive adhesives prepared in Examples 1-3, the PVDF powder in Comparative Example 1, the PMMA powder in Comparative Example 2, and the mixed polymer of PVDF powder and PMMA powder in Comparative Example 3 (mass ratio of PVDF powder to PMMA powder is 1:1) was tested. During the test, the polymers were dried in a vacuum drying oven at 80°C and -0.095 MPa for 64 hours, and their mass was weighed in a beaker and recorded as M1. Electrolyte (M1:electrolyte mass = 1:15, the electrolyte being a mixture of electrolyte and solvent) was added to each beaker. The polymer was tested using lithium hexafluorophosphate as the electrolyte and a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) as the solvent (EC to DEC volume ratio 1:1, electrolyte concentration 1 mol / L). The mixture was placed in a glove box at 25°C for 64 hours. After the electrolyte was poured out, the polymer was removed and the surface of the polymer in the beaker was gently pressed and wiped with industrial wiping paper to remove the free electrolyte. The mass was weighed and recorded as M2. The swelling rate was calculated according to the following formula: Swelling rate = (M2-M1) / M1×100%. The swelling rate is the average value of 10 test groups. The test results are shown in Table 4.

[0063] Table 4. Swelling rate test results for Examples 1-3 and Comparative Examples 1-3

[0064] As can be seen from Table 4, the swelling rates of the dual-state pressure-sensitive adhesives prepared in Examples 1-3 are all lower than those of the PVDF powder, PMMA powder, or mixed polymer of PVDF powder and PMMA powder in Comparative Examples 1-3. This indicates that the dual-state pressure-sensitive adhesives prepared in this invention are beneficial for electrolyte desorption and can reduce the swelling rate of the dual-state pressure-sensitive adhesive polymer in the electrolyte, exhibiting good stability.

[0065] Furthermore, the swelling ratio of the dual-state pressure-sensitive adhesive is smaller compared to PVDF powder, indicating better electrolyte tolerance. The dual-state pressure-sensitive adhesive is more stable than PVDF in the battery cell after electrolyte injection, and its wet adhesion is superior to both PVDF and PMMA. Simultaneously, the dual-state pressure-sensitive adhesive and porous ceramic powder (with pores allowing electrolyte flow and negligible swelling) exhibit good synergistic stability in the system, enhancing the dual-state adhesion performance of the separator.

[0066] Experiment Example 4 The lithium-ion battery separators prepared in Examples 1-12 and Comparative Examples 1-7 were encapsulated in CR2032 button cells. After the button cells were subjected to 500 charge-discharge cycles at 0.5C, the cell capacity retention rate was tested. The electrolyte was a 1 mol / L LiPF6 / EC (ethylene carbonate) / DEC (diethyl carbonate) solution. The test results are shown in Table 5.

[0067] Table 5. Cell capacity retention test results for Examples 1-12 and Comparative Examples 1-7

[0068] As can be seen from Table 5, compared with Comparative Examples 1-7, the battery cell capacity retention rate of the lithium battery separator prepared in Examples 1-8 is improved after being used in the battery, reaching more than 96.38%. This indicates that the dual-state pressure-sensitive adhesive prepared in this invention, when used in the lithium battery separator slurry containing the dual-state pressure-sensitive adhesive and porous ceramic powder, can improve the cycle life of the battery using this lithium battery separator.

[0069] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A dual-state pressure-sensitive adhesive lithium battery separator coating slurry, characterized in that, The raw materials include porous ceramic powder, dual-state pressure-sensitive adhesive, and deionized water; The raw materials of the dual-state pressure-sensitive adhesive include the following components: Monomer A, organic solvent, monomer B, monomer C, initiator; The monomer A includes one or both of benzoyl chloride and acryloyl chloride; The monomer B includes 1,4-bis(4-aminophenoxy)benzene; The monomer C includes styrene, lithium methacrylate, and butyl methacrylate.

2. The dual-state pressure-sensitive adhesive lithium battery separator coating slurry according to claim 1, characterized in that, The monomer A includes similar tribenzoyl chloride and acryloyl chloride; The initiator includes tert-butyl peroxyvalerate and benzoyl peroxide.

3. The dual-state pressure-sensitive adhesive lithium battery separator coating slurry according to claim 2, characterized in that, The preparation method of the dual-state pressure-sensitive adhesive includes the following steps: A1. Under a first gas atmosphere, monomer A is added, and after cooling to -10~-5℃, the organic solvent and monomer B are added to carry out a first polymerization reaction. Then, monomer C and tert-butyl peroxyvalerate are added to carry out a second polymerization reaction to obtain the first product. A2. Under a second gas atmosphere, the first product and the benzoyl peroxide are mixed evenly and subjected to a third polymerization reaction to obtain the dual-state pressure-sensitive adhesive. The first gas is a protective gas; The second gas is a fluorinated olefin gas.

4. The dual-state pressure-sensitive adhesive lithium battery separator coating slurry according to claim 3, characterized in that, The degree of polymerization of the dual-state pressure-sensitive adhesive is 153~259, and the number-average molecular weight is 443802~751274.

5. The dual-state pressure-sensitive adhesive lithium battery separator coating slurry according to claim 3, characterized in that, The first polymerization reaction is carried out at a temperature of -10 to -5°C for 6 to 8 hours. The second polymerization reaction is carried out at a temperature of 120~130℃ for 6~8 hours. The third polymerization reaction is carried out at a temperature of 120-130°C for 4-6 hours.

6. The dual-state pressure-sensitive adhesive lithium battery separator coating slurry according to claim 3, characterized in that, The mass ratio of monomer A, monomer B, monomer C, and initiator is 0.95~1.15:1:4~7:0.1~0.16; The amount of organic solvent added is 10 to 15 times the mass of monomer B; The amount of the fluorinated olefin gas added is 4 to 6 times the mass of monomer B.

7. The dual-state pressure-sensitive adhesive lithium battery separator coating slurry according to claim 3, characterized in that, The protective gas includes one or more of argon, helium, and nitrogen. The fluorinated olefin gases include hexafluoropropylene and vinylidene fluoride.

8. The dual-state pressure-sensitive adhesive lithium battery separator coating slurry according to claim 1, characterized in that, The raw materials for the coating slurry also include polyvinyl alcohol and dispersants; The mass ratio of the porous ceramic powder, the dual-state pressure-sensitive adhesive, the polyvinyl alcohol, the dispersant, and the deionized water is 1:2~5:1~2:0.05:

10.

9. A method for preparing a dual-state varistor adhesive lithium-ion battery separator coating slurry, used to prepare the dual-state varistor adhesive lithium-ion battery separator coating slurry as described in claim 8, characterized in that, Includes the following steps: S1. After the dispersant and deionized water are mixed evenly, the mixture is emulsified for the first time to obtain the first substance; S2. Add the porous ceramic powder to the first substance, and emulsify it a second time to obtain the second substance; S3. Add the dual-state pressure-sensitive adhesive and the polyvinyl alcohol to the second substance, and emulsify for the third time to obtain the dual-state pressure-sensitive adhesive lithium battery separator coating slurry.

10. The application of the dual-state pressure-sensitive adhesive lithium-ion battery separator coating slurry according to any one of claims 1 to 8 or the dual-state pressure-sensitive adhesive lithium-ion battery separator coating slurry prepared by the preparation method according to claim 9 in the preparation of lithium-ion battery separators, characterized in that, The method for preparing the lithium battery separator includes the following steps: The dual-state pressure-sensitive adhesive lithium battery separator coating slurry is applied to at least one side of the base film by dot coating or roller coating, and then dried to obtain the lithium battery separator.

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