Lithium-ion battery separator spray adhesive, method of making and use thereof

Abstract

The present application relates to lithium ion battery separator spraying adhesive and its preparation method and application, belong to lithium ion battery adhesive technical field.The technical problem solved by the present application is to provide a kind of lithium ion battery separator spraying adhesive.The present application lithium ion battery separator spraying adhesive includes acrylonitrile polymer, hydrophilic polymer and surfactant;The weight ratio of acrylonitrile polymer, hydrophilic polymer and additive is 80-98:1-20:1-5.The present application lithium ion battery separator spraying adhesive is sprayed on battery separator, improves the adhesion strength between substrate and pole piece under the premise of maintaining better hollow structure, and the cold-pressed adhesion performance of the sprayed separator and battery positive and negative pole is good.The preparation method of the present application battery separator spraying adhesive is simple, prepared with water as solvent, green and environmental protection, cost is lower, and can be industrialized production.

Description

Technical Field

[0001] 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

[0002] As a key material in lithium-ion batteries, the separator typically consists of one or more functional layers with adhesive properties coated on one or both sides of a microporous base membrane. These layers bond the positive and negative electrode plates, improve the interface between the separator and the plates, enhance lithium-ion permeability, increase cell hardness, and improve battery safety and cycle life. Commonly used coating materials include polyvinylidene fluoride homopolymer or copolymer (PVDF), polymethyl methacrylate (PMMA), and acrylate polymers. Common coating processes include 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 separator coating 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 these protrusions being hollow areas. The binder is crucial in ensuring polymer dispersion, hollow structure formation, and adhesion to the ceramic layer and the positive and negative electrode plates.

[0003] 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

[0004] To address the above deficiencies, the technical problem solved by this invention is to provide an adhesive for spraying lithium-ion battery separators.

[0005] This invention relates to an adhesive for spraying lithium-ion battery separators, comprising an acrylonitrile polymer, a hydrophilic polymer, and an additive. 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 additive comprises fatty alcohol polyoxyethylene ether, wherein the HLB value of the fatty alcohol polyoxyethylene ether is 16–19. The weight ratio of the acrylonitrile polymer, the hydrophilic polymer, and the additive is 80–98:1–20:1–5.

[0006] In one specific embodiment of the present invention, the acrylonitrile monomer includes at least one of acrylonitrile and methacrylonitrile;

[0007] 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.

[0008] 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.

[0009] 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.

[0010] 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.

[0011] The adhesive for spraying lithium-ion battery separators of the present invention further includes a solvent, wherein the solvent is water.

[0012] 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.

[0013] The second technical problem solved by the present invention is to provide a method for preparing an adhesive for spraying lithium-ion battery separators.

[0014] The present invention discloses a method for preparing an adhesive for spraying lithium-ion battery separators, comprising the following steps:

[0015] 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 hours of reaction, a hydrophilic polymer is added and the reaction continues until the reaction is completed. After neutralization, an auxiliary agent is added to obtain an adhesive for spraying lithium-ion battery separators.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] In one specific embodiment of the present invention, the battery separator is a PP separator or a PE separator.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 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.

[0022] 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

[0023] 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, 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, wherein 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] Acrylonitrile monomers are substances containing double bonds and nitrile groups, such as, but not limited to, at least one of acrylonitrile and methacrylonitrile.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] The adhesive for spraying lithium-ion battery separators of the present invention further includes a solvent, wherein the solvent is water.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] The second technical problem solved by the present invention is to provide a method for preparing an adhesive for spraying lithium-ion battery separators.

[0040] The present invention discloses a method for preparing an adhesive for spraying lithium-ion battery separators, comprising the following steps:

[0041] 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 hours of reaction, a hydrophilic polymer is added and the reaction continues until the reaction is completed. After neutralization, an auxiliary agent is added to obtain an adhesive for spraying lithium-ion battery separators.

[0042] In one embodiment of the present invention, the solvent is water.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] In one specific embodiment of the present invention, the battery separator is a PP separator or a PE separator.

[0048] 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.

[0049] Example

[0050] Add 300g of distilled water, acrylic monomers, and acrylamide monomers to a 500mL 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 hours, add hydrophilic polymers. After reacting for 30 hours, add neutralizing salt and water to the reaction flask to neutralize, and then add fatty alcohol polyoxyethylene ether additives in the HLB range of 16-19 to obtain an adhesive for spraying lithium-ion battery separators.

[0051] The types and amounts of polymeric monomers used in each embodiment and comparative example are shown in Table 1.

[0052] Table 1

[0053]

[0054]

[0055] 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.

[0056] 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.

[0057] 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.

[0058] Table 2

[0059] serial number Solid content % Viscosity mPa·S@25℃ pH Example 1 15.12 15933 7.54 Example 2 15.05 12950 7.60 Example 3 15.03 10729 7.55 Example 4 15.18 15226 7.48 Example 5 14.98 11422 7.49 Example 6 15.05 11807 7.40 Example 7 14.88 13831 7.51 Example 8 15.10 10557 7.58 Example 9 14.95 14110 7.50 Example 10 14.92 14274 7.46 Example 11 14.96 11548 7.53 Example 12 15.04 12856 7.49 Example 13 15.11 12822 7.54 Example 14 15.04 14166 7.54 Example 15 15.08 10685 7.53 Example 16 15.15 13009 7.58 Comparative Example 1 15.14 10540 7.41 Comparative Example 2 14.95 12241 7.40 Comparative Example 3 14.92 13869 7.51 Comparative Example 4 15.11 1020 7.43 Comparative Example 5 15.04 15215 7.47 Comparative Example 6 15.02 11580 7.53

[0060] The testing method is as follows:

[0061] 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.

[0062] 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.

[0063] 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.

[0064] Experimental Example 1

[0065] The adhesives for lithium-ion battery separator spraying obtained in the above embodiments and comparative examples are used in separator spraying.

[0066] Slurry preparation process and formula: Add 240.33g of water and 46.67g of lithium-ion battery separator spraying adhesive (12%) to a 1000mL beaker. Stir with a high-speed disperser at 500r / min for 5min, then slowly add 63g of PVDF / PMMA powder. After the powder is added, increase the speed to 2000r / min and disperse for 120min. Then add 350g of water and reduce the speed to 1000r / min and disperse for 10min to obtain the slurry.

[0067] 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.

[0068] 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 0.2MPa, feeding speed 50Hz, diaphragm conveyor speed 3~5m / min.

[0069] Adhesion test: In an environment with a humidity of 0.5% RH, cut the sprayed diaphragm into strips of 4cm*20cm; take a 5cm*20cm positive or negative electrode sheet, attach the sprayed surface of the diaphragm to the positive or negative electrode sheet, and roll it onto a 3cm wide PP sheet to form a 3cm wide and 5cm 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 3MPa, duration 5min. 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 = ΔT / 0.04 (N / m) (ΔT is the average of multiple measurements). The value indicates the strength of the adhesive force.

[0070] The test results are shown in Table 3.

[0071] Table 3

[0072]

[0073]

[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; preferably, the weight ratio of acrylonitrile monomers, acrylic monomers and acrylamide monomers is 50:35:

15.

4. 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.

5. The adhesive for spraying lithium-ion battery separators according to claim 1, characterized in that: The weight of the hydrophilic polymer is 1-20% of the total weight of the acrylonitrile polymer, the hydrophilic polymer, and the additives; preferably, the weight of the hydrophilic polymer is 5-15% of the total weight of the acrylonitrile polymer, the hydrophilic polymer, and the additives.

6. 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.

7. The adhesive for spraying lithium-ion battery separators according to claim 6, characterized in that: With a solid content of 15%, its viscosity is 2000-200000cp when measured at 25°C.

8. The method for preparing the adhesive for spraying lithium-ion battery separators according to any one of claims 1 to 7, 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 hours of reaction, a hydrophilic polymer is added and the reaction continues until the reaction is completed. After neutralization, an auxiliary agent is added to obtain an adhesive for spraying lithium-ion battery separators.

9. The use of the adhesive for spraying lithium-ion battery separators according to any one of claims 1 to 7 in the preparation of lithium-ion battery separators.

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