Binder for spraying lithium ion battery separator, preparation method therefor and use thereof

Abstract

The present invention relates to a binder for spraying a lithium ion battery separator, a preparation method therefor and the use thereof, and belongs to the technical field of lithium ion battery binders. The technical problem to be solved by the present invention is to provide a binder for spraying a lithium ion battery separator. The binder for spraying a lithium ion battery separator of the present invention comprises an acrylonitrile polymer, a hydrophilic polymer and a surfactant, wherein the weight ratio of the acrylonitrile polymer, the hydrophilic polymer and an auxiliary agent is 80-98:1-20:1-5. Said binder is sprayed on a battery separator, and can improve the bonding strength between same and a substrate and electrode sheets and achieve a good cold-pressing bonding performance between the sprayed separator and positive and negative electrodes of a battery while maintaining a good hollowed-out structure. The preparation method for said binder is simple and uses water as a preparation solvent, thereby being green and environmentally-friendly, involving a low cost, and being applicable to industrial production.

Description

Adhesives for Lithium-ion Battery Separator Spraying, Preparation Methods and Applications

[0001] Cross-references to related applications

[0002] This application claims the benefit and priority of Chinese patent application CN2025101165086, filed on January 24, 2025, which is incorporated herein by reference and for all other purposes. Technical Field

[0003] This invention relates to adhesives for spraying lithium-ion battery separators, their preparation methods, and applications, belonging to the field of lithium-ion battery adhesive technology. Background Technology

[0004] As a key material in lithium-ion batteries, the separator is typically coated with one or more functional layers with adhesive properties on one or both sides of a microporous base membrane. This allows for bonding of the positive and negative electrode plates, improving the interface between the separator and the positive and negative electrode plates, enhancing lithium-ion permeability, increasing cell hardness, and improving battery safety and cycle life. Currently, commonly used coating materials include polyvinylidene fluoride homopolymer or copolymer (PVDF), polymethyl methacrylate polymer (PMMA), and acrylate polymers. Common coating processes include micro-gravure roller coating and high-speed rotary spraying. High-speed rotary spraying is widely used in lithium-ion power battery systems because it effectively controls coating coverage and reduces battery internal resistance. The slurry used for coating the separator generally includes polymer particles such as PVDF / PMMA, binders, dispersants, and wetting agents. After spraying, the slurry creates a hollow structure on the ceramic layer surface: formed by protrusions, with the interior of the protrusions being hollow areas. The binder is crucial in ensuring polymer dispersion, the formation of the hollow structure, and bonding to the ceramic layer and the positive and negative electrode plates.

[0005] Currently, these adhesives are mainly based on acrylonitrile multi-polymer systems. This system has high polymer polarity, enabling the formation of good perforated structures, but its adhesion to the electrode is relatively weak and needs improvement. Therefore, it is necessary to improve the adhesion strength between the adhesive and the substrate and the electrode while maintaining a good perforated structure. Summary of the Invention

[0006] To address the above deficiencies, the technical problem solved by this invention is to provide an adhesive for spraying lithium-ion battery separators.

[0007] This invention relates to an adhesive for spraying lithium-ion battery separators, comprising an acrylonitrile polymer, a hydrophilic polymer, and additives. The acrylonitrile polymer comprises monomers of acrylonitrile, acrylic acid, and acrylamide. The hydrophilic polymer comprises at least one of polyvinyl alcohol, methoxy polyethylene glycol methacrylate, β-cyclodextrin, gum arabic, polyvinylpyrrolidone, sodium alginate, gelatin, methylcellulose, polyethyleneimine, polyethylene glycol, and polyethylene oxide. The additives comprise fatty alcohol polyoxyethylene ether, and the HLB value of the fatty alcohol polyoxyethylene ether is 16–19. The weight ratio of the acrylonitrile polymer, the hydrophilic polymer, and the additives is 80–98 : 1–20 : 1–5.

[0008] In one specific embodiment of the present invention, the acrylonitrile monomer includes at least one of acrylonitrile and methacrylonitrile;

[0009] Acrylic monomers include at least one of acrylic acid, methacrylic acid, allyloxyhydroxypropylsulfonic acid, vinylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, propylene sulfonic acid, methpropylene sulfonic acid, itaconic acid, maleic acid, and β-acryloyloxypropionic acid; acrylamide monomers include at least one of acrylamide, methacrylamide, N-ethylacrylamide, N-hydroxymethylacrylamide, N-hydroxyethylacrylamide, and N-hydroxypropylacrylamide; fatty alcohol polyoxyethylene ethers include at least one of MOA-20, MOA-23, O-30, ZetaSperse179, and ZetaSperse182.

[0010] In one embodiment of the present invention, the weight ratio of acrylonitrile monomers, acrylic monomers, and acrylamide monomers is 30–60 : 10–40 : 8–20. In a specific embodiment, the weight ratio of acrylonitrile monomers, acrylic monomers, and acrylamide monomers is 50 : 35 : 15.

[0011] In some specific embodiments, the molecular weight of the hydrophilic polymer is 10,000 to 1,000,000, and the weight-average molecular weight of the acrylonitrile polymer is 10,000 to 1,000,000.

[0012] In one embodiment of the present invention, the weight of the hydrophilic polymer is 1-20% of the total weight of the acrylonitrile polymer, the hydrophilic polymer, and the additives. In some specific embodiments, the hydrophilic polymer accounts for 5-15%. In some specific embodiments, the hydrophilic polymer accounts for 5%, 6%, 6.5%, 7%, 8%, 8.5%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, etc.

[0013] The adhesive for spraying lithium-ion battery separators of the present invention further includes a solvent, wherein the solvent is water.

[0014] In one specific embodiment of the present invention, based on a solid content of 15%, the viscosity of the adhesive for spraying the lithium-ion battery separator is 2000 to 200000 cp when measured at 25°C.

[0015] The second technical problem solved by the present invention is to provide a method for preparing an adhesive for spraying lithium-ion battery separators.

[0016] The present invention discloses a method for preparing an adhesive for spraying lithium-ion battery separators, comprising the following steps:

[0017] The monomers of acrylonitrile polymers are mixed with a solvent, the pH is adjusted to 7-9, an initiator is added to initiate the reaction, and after 8-20 h of reaction, a hydrophilic polymer is added and the reaction continues until the reaction is completed. After neutralization, an additive is added to obtain an adhesive for spraying lithium-ion battery separators.

[0018] The initiator can be a commonly used initiator in the art, such as ammonium persulfate or potassium persulfate, and the reaction temperature can also be a conventional temperature in the art.

[0019] The present invention also provides the application of the adhesive for spraying lithium-ion battery separators described herein in the spraying of lithium-ion battery separators.

[0020] The present invention relates to an adhesive for spraying lithium-ion battery separators. The adhesive is prepared by mixing PVDF / PMMA and other polymer particles with water to form a slurry, which can be sprayed onto the surface of the battery separator to improve battery performance.

[0021] In one specific embodiment of the present invention, the battery separator is a PP separator or a PE separator.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention relates to an adhesive for spraying lithium-ion battery separators. When sprayed onto the battery separator, it improves the adhesion strength between the separator and the substrate and the electrode while maintaining a good hollow structure. The coated separator exhibits good cold-pressing adhesion performance to the positive and negative electrodes of the battery.

[0024] The preparation method of the spray adhesive for battery separators of the present invention is simple, uses water as a solvent, is green and environmentally friendly, has low cost, and can be industrialized. Detailed Implementation

[0025] This invention relates to an adhesive for spraying lithium-ion battery separators, comprising an acrylonitrile polymer, a hydrophilic polymer, and additives. The acrylonitrile polymer comprises monomers of acrylonitrile, acrylic acid, and acrylamide. The hydrophilic polymer comprises at least one of polyethyleneimine, polyvinyl alcohol, methoxy polyethylene glycol methacrylate, β-cyclodextrin, gum arabic, polyvinylpyrrolidone, sodium alginate, gelatin, methylcellulose, polyethylene glycol, and polyethylene oxide. The additives comprise fatty alcohol polyoxyethylene ether, and the HLB value of the fatty alcohol polyoxyethylene ether is 16–19. The weight ratio of the acrylonitrile polymer, the hydrophilic polymer, and the additives is 80–98 : 1–20 : 1–5.

[0026] The present invention relates to an adhesive for spraying lithium-ion battery separators. Based on acrylonitrile polymers, it mixes hydrophilic polymers and additives, which can improve the phenomenon of easy powder shedding of existing acrylonitrile multi-component copolymers, and can improve the adhesion strength between the adhesive and the substrate and the electrode while maintaining a good hollow structure.

[0027] The fatty alcohol polyoxyethylene ether is a nonionic surfactant. HLB (Hydrophilic Lipophilic Balance) is an indicator of the hydrophilicity and lipophilicity of a surfactant. The higher the HLB value, the stronger the hydrophilicity of the surfactant; the lower the HLB value, the stronger its lipophilicity. The fatty alcohol polyoxyethylene ether of this invention has an HLB value of 16-19.

[0028] Commonly used fatty alcohol polyoxyethylene ethers with HLB=16 to 19 are applicable to this invention, including but not limited to MOA-20 (fatty alcohol polyoxyethylene ether-20), MOA-23 (fatty alcohol polyoxyethylene ether-23), O-30 (fatty alcohol polyoxyethylene ether O-30), ZetaSperse179, and ZetaSperse182.

[0029] The acrylonitrile polymers of the present invention can be acrylonitrile multi-component copolymers commonly used in the art, which are polymerized from acrylonitrile and other monomers containing double bonds. In one specific embodiment of the present invention, the polymerizing monomers of the acrylonitrile polymer include acrylonitrile monomers, acrylic monomers and acrylamide monomers.

[0030] Acrylonitrile monomers are substances containing double bonds and nitrile groups, such as, but not limited to, at least one of acrylonitrile and methacrylonitrile.

[0031] Acrylic monomers are substances containing double bonds and carboxyl groups, including but not limited to at least one of acrylic acid, methacrylic acid, allyloxyhydroxypropyl sulfonic acid, vinyl sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, propylene sulfonic acid, methpropylene sulfonic acid, itaconic acid, maleic acid, and β-acryloyloxypropionic acid.

[0032] Acrylamide monomers are substances containing double bonds and amide groups, including at least one of acrylamide, methacrylamide, N-ethylacrylamide, N-hydroxymethylacrylamide, N-hydroxyethylacrylamide, and N-hydroxypropylacrylamide.

[0033] The ratio of acrylonitrile monomers, acrylic monomers, and acrylamide monomers can adopt conventional ratios in the art. In one embodiment of the present invention, the weight ratio of acrylonitrile monomers, acrylic monomers, and acrylamide monomers is 30-60 : 10-40 : 8-20. In a specific embodiment, the weight ratio of acrylonitrile monomers, acrylic monomers, and acrylamide monomers is 50 : 35 : 15.

[0034] Hydrophilic polymers are high molecular materials with excellent hydrophilic properties. In this invention, the hydrophilic polymers include at least one of polyvinyl alcohol, methoxy polyethylene glycol methacrylate, β-cyclodextrin, gum arabic, polyvinylpyrrolidone, sodium alginate, gelatin, methylcellulose, polyethyleneimine, polyethylene glycol, and polyethylene oxide.

[0035] In some specific embodiments, the molecular weight of the hydrophilic polymer is 10,000 to 1,000,000. Unless otherwise specified, all molecular weights mentioned in this invention are weight-average molecular weights. The weight-average molecular weight of acrylonitrile polymers is 10,000 to 1,000,000.

[0036] In one embodiment of the present invention, the weight of the hydrophilic polymer is 1-20% of the total weight of the acrylonitrile polymer, the hydrophilic polymer, and the additives. In some specific embodiments, the hydrophilic polymer accounts for 5-15%. In some specific embodiments, the hydrophilic polymer accounts for 5%, 6%, 6.5%, 7%, 8%, 8.5%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, etc.

[0037] The adhesive for spraying lithium-ion battery separators of the present invention further includes a solvent, wherein the solvent is water.

[0038] In some embodiments, the adhesive for spraying lithium-ion battery separators of the present invention also includes dispersants, wetting agents, antioxidants, defoamers, and other substances.

[0039] In one specific embodiment of the present invention, based on a solid content of 15%, the viscosity of the adhesive for spraying the lithium-ion battery separator is 2000 to 200000 cp when measured at 25°C.

[0040] The viscosity measurement method of this invention is as follows: the DV2T viscometer (DV2TLV, Bollefeld, USA) is used for measurement at a temperature of 25°C, the rotor model is No. 64#, the rotation speed is 12 RPM, the test conditions are: test time = 3 min, data acquisition duration = 2 min, and the data acquisition method is: single-point averaging.

[0041] The second technical problem solved by the present invention is to provide a method for preparing an adhesive for spraying lithium-ion battery separators.

[0042] The present invention discloses a method for preparing an adhesive for spraying lithium-ion battery separators, comprising the following steps:

[0043] The monomers of acrylonitrile polymers are mixed with a solvent, the pH is adjusted to 7-9, an initiator is added to initiate the reaction, and after 8-20 h of reaction, a hydrophilic polymer is added and the reaction continues until the reaction is completed. After neutralization, an additive is added to obtain an adhesive for spraying lithium-ion battery separators.

[0044] In one embodiment of the present invention, the solvent is water.

[0045] The initiator can be a commonly used initiator in the art, such as ammonium persulfate or potassium persulfate, and the reaction temperature can also be a conventional temperature in the art.

[0046] Neutralization can be achieved using commonly used alkaline substances in this field, such as hydroxides like lithium hydroxide, sodium hydroxide, potassium hydroxide, and calcium hydroxide, or lithium salts, sodium salts, potassium salts, calcium salts, ammonium salts, organic amines, etc.

[0047] The present invention also provides the application of the adhesive for spraying lithium-ion battery separators described herein in the spraying of lithium-ion battery separators.

[0048] The present invention relates to an adhesive for spraying lithium-ion battery separators. The adhesive is prepared by mixing PVDF / PMMA and other polymer particles with water to form a slurry, which can be sprayed onto the surface of the battery separator to improve battery performance.

[0049] In one specific embodiment of the present invention, the battery separator is a PP separator or a PE separator.

[0050] The specific embodiments of the present invention will be further described below with reference to examples, but the present invention is not limited to the scope of the embodiments described herein. Example

[0051] Examples 1-16, Comparative Examples 1-6

[0052] Add 300 g of distilled water, acrylic monomers, and acrylamide monomers to a 500 mL four-necked flask. Then add neutralizing salt to adjust the pH to 9.0, add acrylonitrile monomers, and heat the reaction to the reaction temperature. Add ammonium persulfate initiator to initiate the reaction. After reacting for 15 h, add hydrophilic polymers. After reacting for 30 h, add neutralizing salt and water to the reaction flask to neutralize, and then add fatty alcohol polyoxyethylene ether additives in the HLB range of 16 to 19 to obtain an adhesive for spraying lithium-ion battery separators.

[0053] The types and amounts of polymeric monomers used in each embodiment and comparative example are shown in Table 1.

[0054] Table 1

[0055] Number Neutralizing Salt Acrylic Acid Monomer Acrylamide Monomer Acrylonitrile Monomer Hydrophilic Polymer Auxiliary Agent Initiator Reaction Temperature °C Example 1 Sodium Salt Acrylic Acid 33g Acrylic Acid 16g Acrylonitrile 51g 9.0g PEI20000+ 9.0g PVA0599O-30 2.0g Ammonium Persulfate 3g 72 Example 2 Lithium Salt Acrylic Acid 42g Methacrylamide 9g Methacrylonitrile 49g 9.0g MPEG600MMA+ 4.5g PVA2499MOA-20 2.0g Ammonium Persulfate 3g 65 Example 3 Salt Acrylic Acid 40g N-Ethyl Acrylamide 10g Acrylonitrile 50g 4.5g PVA1788+ 4.5g MPEG600MMAZetaSperse 182 3.0g Ammonium Persulfate 3g 65 Example 4 Organic Amine Acrylic Acid 46g Methacrylamide 16g Methacrylonitrile 38g 4.5g β-Cyclodextrin+ 4.5g PVA1788+ Example 5: Sodium salt methacrylic acid 34g, acrylamide 14g, methacrylonitrile 52g 2.5g, sodium alginate + 2.5g, PVA2499MOA-20 4.0g, ammonium persulfate 3g 65. Example 6: Lithium salt methacrylic acid 34g, N-hydroxymethylacrylamide 10g, methacrylonitrile 52g 2.5g, gum arabic + 2.0g, PVA2499MOA-23 5.0g, ammonium persulfate 2.5g 80. Example 7: Sodium salt allyloxyhydroxypropyl sulfonic acid 49g, acrylamide 13g, acrylonitrile 38g 4.5g, PVA2499 + 2.5g, MPEG600MMAMOA-23 4.5g, potassium persulfate 3g 75. Example 8: Lithium salt vinyl sulfonic acid 42g, acrylamide 17g, acrylonitrile 41g 4.5g, polyethylene oxide + 2.5g. Example 9: Potassium salt 2-acrylamide-2-methylpropanesulfonic acid 41g, N-hydroxyethylacrylamide 19g, methacrylonitrile 40g 3.5g, Sodium alginate + 2.5g, β-cyclodextrin + 7.0g, MPEG600MMAZetaSperse 182 2.5g, Potassium persulfate 4g 65. Example 10: Calcium salt propylene sulfonic acid 45g, acrylamide 15g, acrylonitrile 40g 2.0g, PVA2499 + 4.5g, MPEG800MMAZetaSperse 179 1.5g, Potassium persulfate 4g 65. Example 11: Sodium salt methylpropanesulfonic acid 30g, acrylamide 20g, acrylonitrile 50g 2.0g, PVA1799 + 2.5g, gum arabic + 2.5g, Sodium alginate MOA-20 2.0g. Example 1: Potassium persulfate 3g 70g, 2-ammonium salt itaconic acid 38g, N-hydroxypropyl acrylamide 14g, acrylonitrile 48g 9.0g, polyethylene oxide + 4.5g, sodium alginate + 2g.Example 13: Sodium salt methacrylic acid 35g, acrylamide 15g, acrylonitrile 50g, 5.5g, PVA2499+ 5.5g, MPEG600MMZetaSperse 179 3.0g, ammonium persulfate 3g, 70g. Example 14: Potassium salt acrylic acid 48g, acrylamide 10g, acrylonitrile 42g, 2.5g, β-cyclodextrin+ 2.5g, polyvinylpyrrolidone ZetaSperse 182 2.0g, potassium persulfate 6g, 65g. Example 15: Organic amine acrylic acid 35g, methacrylamide 14g, acrylonitrile 51g, 3.0g, PVA2499+ 2.0g, polyethylene glycol ZetaSperse 179 1.5g, potassium persulfate 4g, 75g. Example 16: Sodium salt β-acryloyloxypropionic acid 47g, acrylamide 13g, acrylonitrile 40g, 5.0g. β-Cyclodextrin +2.0 g PVA2499 +2.0 g MPEG600MMAMOA-23 2.5 g Potassium persulfate 3 g 65 Comparative Example 1 Lithium salt methacrylic acid 35 g Methacrylamide 15 g Acrylonitrile 50 g None MOA-23 3.0 g 1.5 g Ammonium persulfate 70 Comparative Example 2 None None None None 50 g PVA2499 +50 g MPEG600MMAZetaSperse 179 3.0 g Ammonium persulfate 3 g 70 Comparative Example 3 Sodium salt methacrylic acid 35 g Acrylamide 15 g Acrylonitrile 50 g 5.5 g PVA2499 +5.5 g MPEG600MMAM0 Ammonium persulfate 3 g 70 Comparative Example 4 Sodium salt methacrylic acid 35 g Acrylamide 15 g Acrylonitrile 50 g 5.5 g PVA2499 +5.5 g MPEG600MMA 3.0g, Sodium Dodecylbenzenesulfonate, Ammonium Persulfate 3g, 70g; Comparative Example 5: Sodium Salt, Methacrylic Acid 35g, Acrylamide 15g, Acrylonitrile 50g, 5.5g; PVA2499+ 5.5g; MPEG600MMA PEG6000MO 3.0g, Ammonium Persulfate 3g, 70g; Comparative Example 6: Sodium Salt, Methacrylic Acid 35g, Acrylamide 15g, Acrylonitrile 50g, 5.5g; PVA2499+ 5.5g; MPEG600MMAO-20 3.0g, Ammonium Persulfate 3g, 70g.

[0056] In the table above, O-30 is fatty alcohol polyoxyethylene ether-30, HLB=16-17; MOA-20 is fatty alcohol polyoxyethylene ether-20, HLB=16-17; MOA-23 is fatty alcohol polyoxyethylene ether-23, HLB=17-18; and O-20 is fatty alcohol polyoxyethylene ether-20, HLB=15-16. All of these were purchased from Haian Petrochemical Plant, Jiangsu Province. ZetaSperse179 has an HLB of 17.9, and ZetaSperse182 has an HLB of 18.2; both were purchased from Evonik Chemicals. PEG6000MO is polyethylene glycol (6000) oleate, HLB=19.

[0057] PEI20000 is polyethyleneimine (molecular weight 20000), PEI70000 is polyethyleneimine (molecular weight 70000), PEI750000 is polyethyleneimine (molecular weight 750000), PVA0599 is polyvinyl alcohol 0599, PVA1788 is polyvinyl alcohol 1799, PVA2499 is polyvinyl alcohol 2499, MPEG400MMA is methoxy polyethylene glycol (400) methacrylate, MPEG600MMA is methoxy polyethylene glycol (600) methacrylate, MPEG800MMA is methoxy polyethylene glycol (800) methacrylate, sodium salt is sodium hydroxide, and lithium salt is lithium hydroxide.

[0058] The performance of the adhesives for spraying lithium-ion battery separators obtained in the above examples and comparative examples was measured, and the results are shown in Table 2.

[0059] Table 2

[0060] Example 1: 15.12 1593 37.54; Example 2: 15.05 1295 07.60; Example 3: 15.03 1072 97.55; Example 4: 15.18 152 267.48; Example 5: 14.98 1142 27.49; Example 6: 15.05 1180 77.40; Example 7: 14.88 1383 17.51; Example 8: 15.10 1055 77.58; Example 9: 14.95 141 107.50; Example 10: 14.92 142 747.46; Example 11: 14.96 Example 115487.53 Example 12 15.04 128567.49 Example 13 15.11 128227.54 Example 14 15.04 141667.54 Example 15 15.08 106857.53 Example 16 15.15 130097.58 Comparative Example 1 15.14 105407.41 Comparative Example 2 14.95 122417.40 Comparative Example 3 14.92 138697.51 Comparative Example 4 15.11 10207.43 Comparative Example 5 15.04 152 157.47 Comparative Example 6 15.02 115807.53

[0061] The testing method is as follows:

[0062] Solid content test: The moisture content was measured using a moisture analyzer (LHS16-A, accuracy: 0.1 g, Shanghai Tianmei Balance Instrument Co., Ltd.). The moisture analyzer was set to a heating temperature of 115℃; the heating method was standard; and the end method was automatic stop after 70 seconds.

[0063] pH test: The pH value of the sample was measured and the test results were recorded using a pH meter (Mettler S400K) calibrated with an alkaline slope.

[0064] Viscosity test: The solid content of the sprayed adhesive was adjusted to 12%, and the viscosity was measured using a DV2T viscometer (DV2TLV, Bollefeld, USA). The measurement temperature was 25℃, the rotor model was No. 63#, and the rotation speed was 12 RPM. The test conditions were: test time = 3 min, data acquisition duration = 2 min, and data acquisition method: single point averaging.

[0065] Experimental Example 1

[0066] The adhesives for lithium-ion battery separator spraying obtained in the above embodiments and comparative examples are used in separator spraying.

[0067] Slurry preparation process and formula: Add 240.33 g of water and 46.67 g of lithium-ion battery separator coating adhesive (12%) to a 1000 mL beaker. Stir with a high-speed disperser at 500 r / min for 5 min, then slowly add 63 g of PVDF / PMMA powder. After the powder is added, increase the speed to 2000 r / min and disperse for 120 min. Then add 350 g of water and reduce the speed to 1000 r / min and disperse for 10 min to obtain the slurry.

[0068] Slurry particle size testing method: The particle size of the well dispersed slurry sample is tested using a laser particle size analyzer (for specific operation methods, refer to the SOP-MAStersizer 3000 operating procedure). Test parameter settings: Analysis mode: general; Particle type: spherical; Opacity: 4-10%; Material name: PAN; Refractive index: 1.52; Absorption rate: 0.01; Medium: water.

[0069] Spraying method: The prepared slurry is sprayed onto the PP / PE film using a spray gun, controlling the spray density to 0.5 g / m². 2 Spraying parameters: spraying pressure 0.2 MPa, feeding speed 50 Hz, diaphragm conveyor speed 3~5 m / min.

[0070] Adhesion test: In an environment with a humidity of 0.5%RH, cut the sprayed diaphragm into strips of 4 cm * 20 cm; take a 5 cm * 20 cm positive or negative electrode sheet, attach the sprayed surface of the diaphragm to the positive or negative electrode sheet, and roll it onto a 3 cm wide PP sheet to form a 3 cm wide and 5 cm long sample to be cold-pressed. Prepare at least three samples. Place the samples to be cold-pressed on a cold press with the following parameters: temperature 25℃, pressure 3 MPa, duration 5 min. Perform the adhesion test according to GB / T 2790-1995 Adhesives 180° Peel Strength Test Method. Apply double-sided tape to the tensile testing panel of the tensile testing machine, unfold the sample, and attach the electrode surface to the double-sided tape. Connect the diaphragm and the tensile testing machine with tape, turn on the tensile testing machine, and read the value T. Take multiple measurements and average the result. Adhesive force = ∆T / 0.04 (N / m) (∆T is the average value of multiple measurements). The value indicates the strength of the adhesive force.

[0071] The test results are shown in Table 3.

[0072] Table 3

[0073] Number Solid content % Particle size of dispersed slurry D 50μm positive electrode cold pressing bonding N / m negative electrode cold pressing bonding N / m Example 1 109.1 11 1.25 9.5 Example 2 109.8 2 10.5 9.5 Example 3 109.5 11 28.5 Example 4 109.5 9 12.5 10.0 Example 5 109.5 6 12.2 5 9.5 Example 6 109.5 2 11.5 9.25 Example 7 108.9 8 11.0 10.5 Example 8 109.1 2 11.7 5 7.5 Example 9 109.9 8 12.0 10.5 Example 10 109.4 6 12.0 10.25 Example Example 11: 109.55 11.5 7.75 Example 12: 109.33 11.25 8.5 Example 13: 109.18 12.25 10.5 Example 14: 109.32 10.75 9.0 Example 15: 109.24 9.25 9.5 Example 16: 109.52 9.7 9.5 Comparative Example 1: 109.36 5.0 4.0 Comparative Example 2: 109.27 1.2 0.3 Comparative Example 3: 10 10.18 5.5 4.6 Comparative Example 4: 10 Powder Agglomeration -- Comparative Example 5: 109.87 5.2 3.8 Comparative Example 6: 109.99 7.0 4.8

[0074] It can be seen that the adhesive for lithium-ion battery separator spraying of the present invention, when sprayed onto the battery separator, can improve the bonding strength between the separator and the substrate and the electrode, and the cold pressing bonding performance of the coated separator to the positive and negative electrodes of the battery is good.

Claims

1. An adhesive for spraying lithium-ion battery separators, characterized in that: The invention includes acrylonitrile polymers, hydrophilic polymers, and additives, wherein the monomers of the acrylonitrile polymers include acrylonitrile monomers, acrylic monomers, and acrylamide monomers; and the hydrophilic polymers include at least one of polyvinyl alcohol, methoxy polyethylene glycol methacrylate, β-cyclodextrin, gum arabic, polyvinylpyrrolidone, sodium alginate, gelatin, methylcellulose, polyethyleneimine, polyethylene glycol, and polyethylene oxide. The additives include fatty alcohol polyoxyethylene ether, and the HLB of the fatty alcohol polyoxyethylene ether is 16 to 19. The weight ratio of acrylonitrile polymers, hydrophilic polymers, and additives is 80–98 : 1–20 : 1–5.

2. The adhesive for spraying lithium-ion battery separators according to claim 1, characterized in that: Acrylonitrile monomers include at least one of acrylonitrile and methacrylonitrile; Acrylic monomers include at least one of acrylic acid, methacrylic acid, allyloxyhydroxypropyl sulfonic acid, vinyl sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, propylene sulfonic acid, methpropylene sulfonic acid, itaconic acid, maleic acid, and β-acryloyloxypropionic acid; Acrylamide monomers include at least one of acrylamide, methacrylamide, N-ethylacrylamide, N-hydroxymethylacrylamide, N-hydroxyethylacrylamide, and N-hydroxypropylacrylamide; Fatty alcohol polyoxyethylene ethers include at least one of MOA-20, MOA-23, O-30, ZetaSperse179, and ZetaSperse182.

3. The adhesive for spraying lithium-ion battery separators according to claim 1, characterized in that: The weight ratio of acrylonitrile monomers, acrylic monomers, and acrylamide monomers is 30–60 : 10–40 : 8–20.

4. The adhesive for spraying lithium-ion battery separators according to claim 3, characterized in that: The weight ratio of acrylonitrile monomers, acrylic monomers, and acrylamide monomers is 50:35:

15.

5. The adhesive for spraying lithium-ion battery separators according to claim 1, characterized in that: The weight-average molecular weight of hydrophilic polymers is 10,000 to 1,000,000; the weight-average molecular weight of acrylonitrile polymers is 10,000 to 1,000,000.

6. The adhesive for spraying lithium-ion battery separators according to claim 1, characterized in that: The weight of the hydrophilic polymer is 1 to 20% of the total weight of the acrylonitrile polymer, the hydrophilic polymer, and the additives.

7. The adhesive for spraying lithium-ion battery separators according to claim 6, characterized in that: The weight of the hydrophilic polymer is 5 to 15% of the total weight of the acrylonitrile polymer, the hydrophilic polymer, and the additives.

8. The adhesive for spraying lithium-ion battery separators according to claim 1, characterized in that: It also includes a solvent, wherein the solvent is water.

9. The adhesive for spraying lithium-ion battery separators according to claim 8, characterized in that: With a solid content of 15%, its viscosity is 2000-200000 cp when measured at 25°C.

10. A method for preparing the adhesive for spraying lithium-ion battery separators according to any one of claims 1 to 9, characterized in that: Includes the following steps: The monomers of acrylonitrile polymers are mixed with a solvent, the pH is adjusted to 7-9, an initiator is added to initiate the reaction, and after 8-20 h of reaction, a hydrophilic polymer is added and the reaction continues until the reaction is completed. After neutralization, an additive is added to obtain an adhesive for spraying lithium-ion battery separators.

11. The use of the adhesive for spraying lithium-ion battery separators according to any one of claims 1 to 9 in the preparation of lithium-ion battery separators.