Water-based binder and preparation method therefor, and carbon-coated aluminum foil

Abstract

The present application relates to the technical field of battery binders, in particular to a water-based binder and a preparation method therefor, and a carbon-coated aluminum foil. The water-based binder comprises a water-soluble monomer, an oil-soluble monomer, an amphiphilic monomer, a functional monomer, an initiator and a neutralizing agent, wherein the amphiphilic monomer comprises at least one of sodium vinylsulfonate, sodium styrene sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, and N-vinylpyrrolidone; and the functional monomer comprises at least one of divinylbenzene, pyrrole, phenylacetylene, and 3,4-ethylenedioxythiophene. The water-based binder of the present application is formulated by compounding the water-soluble monomer, the oil-soluble monomer, the amphiphilic monomer and the functional monomer in proportion, thereby simultaneously improving the electrical conductivity of the binder, the wettability toward conductive carbon materials and aluminum foils, the adhesion to aluminum foils, etc.; and the water-based binder makes a battery prepared therefrom exhibit a good cycling stability, and is conducive to prolonging the service life of the battery.

Description

Water-based adhesives and their preparation methods and carbon-coated aluminum foil Technical Field

[0001] This application relates to the field of battery binder technology, and in particular to an aqueous binder, its preparation method, and carbon-coated aluminum foil. Background Technology

[0002] With the rapid development of electric vehicles, the requirements for power batteries are also increasing. Coating the surface of aluminum foil with a layer of conductive carbon material can not only increase the wetting performance and peel strength between the positive electrode material and the aluminum foil, reduce the internal resistance of battery polarization, improve battery consistency, and improve rate performance, but also alleviate the corrosion of the aluminum foil surface by electrolyte oxidation products.

[0003] Typically, conductive carbon material is dispersed using a binder and then coated onto the surface of aluminum foil to form carbon-coated aluminum foil. However, current carbon-coated aluminum foil has the following problems: on the one hand, conductive carbon material is highly hydrophobic, making it difficult for ordinary binders to disperse and wet it, often resulting in pitting and missed coating during the coating process; on the other hand, existing binders have low adhesion to the positive electrode sheet, leading to minimal improvement in battery performance.

[0004] Chinese patent application CN114957522A discloses a modified acrylic resin that can be used to prepare carbon coatings for secondary batteries. However, the synthesis process of this modified acrylic resin is complex and lengthy, resulting in low production efficiency. Chinese patent application CN116285785A discloses an adhesive for carbon-coated aluminum foil, which improves adhesion by introducing phosphate ester monomers. However, this adhesive requires grinding when mixed and dispersed with conductive carbon materials; and the adhesive's conductivity is insufficient. Chinese patent application CN117777898A discloses an internally cross-linking adhesive that ensures electron transport efficiency, has strong adhesion, reduces coating internal resistance, and improves peel strength. However, this adhesive has insufficient dispersibility for conductive carbon materials, requiring the addition of a certain amount of dispersant during use.

[0005] In view of the above, this application is hereby submitted. Summary of the Invention

[0006] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of the claims.

[0007] One objective of this application is to provide an aqueous binder that exhibits excellent dispersibility to conductive carbon materials, excellent adhesion properties, and improved conductivity.

[0008] Another objective of this application is to provide a method for preparing a water-based adhesive.

[0009] Another object of this application is to provide a carbon coating paste, including the above-mentioned water-based binder.

[0010] Another object of this application is to provide a carbon-coated aluminum foil, which is made from the above-mentioned carbon coating paste.

[0011] To achieve the above objectives, this application provides an aqueous adhesive comprising the following components in parts by weight:

[0012] 30-70 parts of water-soluble monomer, 10-40 parts of oil-soluble monomer, 10-30 parts of amphiphilic monomer, 2-20 parts of functional monomer, 0.1-3 parts of initiator and 3-40 parts of neutralizer;

[0013] The amphiphilic monomers include at least one of sodium vinyl sulfonate, sodium styrene sulfonate, 2-acrylamide-2-methylpropanesulfonic acid, and N-vinylpyrrolidone;

[0014] The functional monomers include at least one of divinylbenzene, pyrrole, phenylacetylene, and 3,4-ethylenedioxythiophene.

[0015] In specific embodiments of this application, the water-soluble monomer includes at least one of maleic acid, acrylonitrile sulfonic acid, vinyl sulfonic acid, acrylic acid, methacrylic acid, and acrylamide.

[0016] In specific embodiments of this application, the oil-soluble monomer includes at least one of isooctyl acrylate, lauryl acrylate, acrylonitrile, methacrylonitrile, and styrene.

[0017] In a specific embodiment of this application, the initiator includes at least one of sodium persulfate, ammonium persulfate, and benzoyl peroxide.

[0018] In a specific embodiment of this application, the neutralizing agent includes at least one of lithium hydroxide, sodium hydroxide, calcium hydroxide, and ammonia water.

[0019] In a specific embodiment of this application, the water-based adhesive further includes water.

[0020] This application also provides a method for preparing any of the above-described water-based adhesives, comprising the following steps:

[0021] (a) Dissolve the water-soluble monomer in water, add a neutralizing agent to adjust the pH, and then add the amphiphilic monomer, oil-soluble monomer and functional monomer to obtain a monomer solution;

[0022] (b) Dissolve the initiator in water to obtain an initiator solution;

[0023] (c) The monomer solution and the initiator solution are added to water and reacted at 40-80°C to obtain the water-based binder.

[0024] In a specific embodiment of this application, in step (c), the monomer solution and the initiator solution are added at a time of 1 to 5 hours.

[0025] In a specific embodiment of this application, in step (c), the reaction time is 1 to 3 hours.

[0026] In a specific embodiment of this application, the ratio of water used in steps (a), (b), and (c) is (5-20):3:(20-35).

[0027] In another aspect, this application provides a carbon coating paste, including any of the above-described water-based binders.

[0028] In a specific embodiment of this application, the carbon coating slurry further includes water, a co-solvent, and a conductive carbon material. Further, the carbon coating slurry comprises the following components by weight: 75-79 parts water, 8-12 parts co-solvent, 2-4 parts conductive carbon material, and 6-10 parts water-based binder.

[0029] In another aspect, this application provides a carbon-coated aluminum foil, comprising an aluminum foil substrate and a carbon coating layer disposed on the surface of the aluminum foil substrate, wherein the carbon coating layer is made from any of the carbon coating pastes described above.

[0030] Compared with the prior art, the beneficial effects of this application are as follows:

[0031] (1) The aqueous binder of this application achieves excellent adhesion to aluminum foil by controlling the monomer composition, using polar groups to increase the conductivity of the binder, and introducing amphiphilic monomers to reduce the surface tension of the binder, improve the dispersibility of conductive carbon materials and wettability of aluminum foil, thereby improving the adhesion of the coating to aluminum foil and improving the conductivity of the coating, so that the prepared battery has excellent cycle stability and helps to extend the battery life.

[0032] (2) The preparation method of the water-based adhesive of this application is simple to operate, has high production efficiency, and can be industrialized.

[0033] After reading and understanding the accompanying diagrams and detailed descriptions, the other aspects can be understood. Attached Figure Description

[0034] The accompanying drawings are used to provide a further understanding of the technical solutions in this paper and form part of the specification. They are used together with the embodiments of this application to explain the technical solutions in this paper and do not constitute a limitation on the technical solutions in this paper.

[0035] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0036] Figure 1 shows the carbon-coated aluminum foil prepared using the adhesive of Example 1 in this application;

[0037] Figure 2 is a photograph of the 180° peel force test of this application;

[0038] Figure 3 shows a photograph of the carbon-coated aluminum foil and 3M tape after a peel strength test, obtained by using the adhesive of Example 1 in this application. Detailed Implementation

[0039] The technical solution of this application will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are only some embodiments of this application, not all embodiments, and are only used to illustrate this application, and should not be regarded as limiting the scope of this application. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0040] This application provides an aqueous adhesive comprising the following components in parts by weight:

[0041] 30-70 parts of water-soluble monomer, 10-40 parts of oil-soluble monomer, 10-30 parts of amphiphilic monomer, 2-20 parts of functional monomer, 0.1-3 parts of initiator and 3-40 parts of neutralizer;

[0042] The amphiphilic monomers include at least one of sodium vinyl sulfonate, sodium styrene sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, and N-vinylpyrrolidone;

[0043] The functional monomers include at least one of divinylbenzene, pyrrole, phenylacetylene and 3,4-ethylenedioxythiophene.

[0044] The aqueous binder of this application utilizes the polar groups in water-soluble monomers to ensure the binder's adhesive properties and improve its NMP resistance; it utilizes the affinity between oil-soluble monomers and conductive carbon materials to improve the dispersion properties of the conductive carbon materials; the introduction of amphiphilic monomers, with their lipophilic groups having a strong affinity for the conductive carbon materials and their hydrophilic groups ensuring water solubility, improves the binder's wettability to the conductive carbon materials and reduces surface tension, improving wettability to the aluminum foil and enhancing coating performance. Even in thin coatings, it ensures the consistency of the carbon coating layer, avoiding problems such as missed coating and pinholes; the introduction of functional monomers increases the conductivity of the binder and improves the conductivity of the carbon coating layer. Therefore, the aqueous binder of this application uses a mixture of water-soluble monomers, oil-soluble monomers, amphiphilic monomers, and functional monomers in a specific ratio, which comprehensively improves the binder's conductivity, wettability to conductive carbon materials and aluminum foil, and adhesion to the aluminum foil, resulting in batteries with excellent cycle stability and contributing to extended battery life.

[0045] This application adjusts the dosage ratio of various monomers to fully utilize their effects, thereby achieving a balance of improved conductivity, wettability, and adhesion. In the water-based adhesive of this application, the dosage of each component, by weight, can be as follows:

[0046] The amount of water-soluble monomer can be 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, or any combination thereof.

[0047] The amount of oil-soluble monomer can be 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 40 parts, or any combination thereof;

[0048] The amount of the amphiphilic monomer can be 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, or any combination thereof;

[0049] The amount of functional monomer can be 2 parts, 5 parts, 8 parts, 10 parts, 12 parts, 15 parts, 20 parts, or any combination thereof. An appropriate amount of functional monomer helps to improve conductivity. When there is too little functional monomer, the improvement in conductivity is not obvious. When there is too much functional monomer, it will affect the wettability of the adhesive to the conductive carbon material and the adhesion performance of the adhesive to the aluminum foil, resulting in insufficient peel strength and a sharp increase in resistance.

[0050] The amount of initiator can be 0.1 parts, 0.5 parts, 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, or any combination thereof;

[0051] The amount of neutralizing agent can be 3 parts, 5 parts, 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, or any combination thereof.

[0052] In a specific embodiment of this application, the water-based adhesive comprises the following components by weight: 50-60 parts of water-soluble monomer, 20-25 parts of oil-soluble monomer, 10-15 parts of amphiphilic monomer, 5-15 parts of functional monomer, 0.1-3 parts of initiator, and 3-40 parts of neutralizer.

[0053] In specific embodiments of this application, the water-soluble monomer includes at least one selected from maleic acid, acrylamide, vinyl sulfonic acid, acrylic acid, methacrylic acid, and acrylamide. Further, the water-soluble monomer is at least one selected from acrylic acid, vinyl sulfonic acid, and acrylamide.

[0054] The water-soluble monomers in this application contain strongly polar groups, such as carboxylic acid groups, amide groups, cyano groups, ester groups, etc., which ensure the adhesion between the carbon coating layer and the aluminum foil and the positive electrode active material. Furthermore, the ionization of some groups further improves the water solubility of the binder.

[0055] In specific embodiments of this application, the oil-soluble monomer includes at least one selected from isooctyl acrylate, lauryl acrylate, acrylonitrile, methacrylonitrile, and styrene. Further, the oil-soluble monomer includes at least one selected from isooctyl acrylate and acrylonitrile.

[0056] The lipophilic monomer exhibits good affinity with conductive carbon materials, which facilitates their dispersion. The resulting binder demonstrates good dispersibility for conductive carbon materials even without the addition of a dispersant. This application controls the amount of the lipophilic monomer within a certain range, balancing dispersibility with the binder's NMP resistance.

[0057] In specific embodiments of this application, the functional monomer includes at least one of pyrrole and phenylacetylene. Using pyrrole and / or phenylacetylene as the functional monomer is more advantageous in balancing improved conductivity and peel strength.

[0058] In a specific embodiment of this application, the initiator includes at least one selected from sodium persulfate, ammonium persulfate, and benzoyl peroxide. Further, the initiator includes at least one selected from ammonium persulfate and benzoyl peroxide.

[0059] In specific embodiments of this application, the neutralizing agent includes at least one of lithium hydroxide, sodium hydroxide, calcium hydroxide, and ammonia water, and may further be sodium hydroxide.

[0060] In a specific embodiment of this application, the water-based adhesive further includes water. More specifically, the amount of water used is 280 to 580 parts.

[0061] In different embodiments, the amount of water used can be a range of 280 parts, 300 parts, 350 parts, 400 parts, 450 parts, 500 parts, 550 parts, 580 parts, or any combination thereof.

[0062] This application also provides a method for preparing any of the above-mentioned water-based adhesives, comprising the following steps:

[0063] (a) Dissolve the water-soluble monomer in water, add a neutralizing agent, and then add an amphiphilic monomer, an oil-soluble monomer, and a functional monomer to obtain a monomer solution;

[0064] (b) Dissolve the initiator in water to obtain an initiator solution;

[0065] (c) Add the monomer solution and the initiator solution to water and react at 40-80°C to obtain an aqueous binder.

[0066] In step (c), the reaction temperature can be 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃ or any combination thereof, for example 70~75℃. The specific reaction temperature can be conventionally adjusted according to the type of initiator to initiate the polymerization reaction and ensure the stable progress of the reaction.

[0067] In practice, the monomer solution in step (a), the initiator solution in step (b), and the water used as the reaction substrate in step (c) can be deoxygenated, for example, by removing dissolved oxygen from the liquid under a nitrogen atmosphere, in order to ensure the smooth progress of the reaction and improve the degree of reaction.

[0068] In step (c), water, which serves as the reaction substrate, can be added to the reactor beforehand, and then the monomer solution and initiator solution are simultaneously added to the reactor dropwise. In a specific embodiment of this application, the addition time of the monomer solution and initiator solution in step (c) is 1 to 5 hours.

[0069] In different embodiments, the addition time of the monomer solution and the initiator solution can be 1 h, 2 h, 3 h, 4 h, 5 h, or any combination thereof.

[0070] In a specific embodiment of this application, the reaction time in step (c) is 1 to 3 hours. Here, "reaction time" refers to the duration of the reaction after the monomer solution and initiator solution have been completely added; it can be 1 hour, 2 hours, 3 hours, etc., but is not limited to this.

[0071] In the specific embodiments of this application, the pH is adjusted to 2-7. In actual operation, the amount of neutralizing agent added is adjusted according to the specific pH of the solution.

[0072] In a specific embodiment of this application, the ratio of water used in steps (a), (b), and (c) is (5-20):3:(20-35).

[0073] In different embodiments, the water ratio in steps (a) and (b) can be a range of 5:3, 8:3, 10:3, 14:3, 17:3, 20:3, or any two of these; the water ratio in steps (c) and (b) can be a range of 20:3, 23:3, 26:3, 30:3, 32:3, 35:3, or any two of these.

[0074] In another aspect, this application provides a carbon coating paste, including any of the above-mentioned water-based binders.

[0075] In a specific embodiment of this application, the carbon coating slurry further includes water, a co-solvent, and a conductive carbon material. Further, the carbon coating slurry comprises the following components by weight: 75-79 parts water, 8-12 parts co-solvent, 2-4 parts conductive carbon material, and 6-10 parts water-based binder.

[0076] In specific embodiments of this application, the carbon coating paste may not include a dispersant. When the binder of this application is used in the carbon coating paste, it can ensure good dispersibility of the conductive carbon material without adding a dispersant. Furthermore, the preparation of the carbon coating paste of this application does not require grinding.

[0077] In specific embodiments of this application, the co-solvent includes alcohol or ether solvents. More specifically, the co-solvent is ethanol. The addition of the co-solvent can improve the coating drying rate and promote film formation, further enhancing the coating's water and solvent resistance.

[0078] This application also provides a carbon-coated aluminum foil, comprising an aluminum foil substrate and a carbon coating layer disposed on the surface of the aluminum foil substrate, wherein the carbon coating layer is made from any of the aforementioned carbon coating pastes.

[0079] Example 1

[0080] This embodiment provides a method for preparing an aqueous adhesive, comprising the following steps:

[0081] (1) Weigh out 45 parts of acrylic acid, 10 parts of acrylamide, 25 parts of isooctyl acrylate, 15 parts of sodium styrene sulfonate, 5 parts of 3,4-ethylenedioxythiophene, 0.5 parts of ammonium persulfate, 3 parts of sodium hydroxide, and 400 parts of water by weight.

[0082] (2) Dissolve acrylic acid and acrylamide in 70 parts of water, then add sodium hydroxide, then add isooctyl acrylate, sodium styrene sulfonate and 3,4-ethylenedioxythiophene, remove dissolved oxygen in the solution under a nitrogen atmosphere to obtain a mixed monomer solution;

[0083] (3) Dissolve ammonium persulfate in 30 parts of water, remove dissolved oxygen from the solution under a nitrogen atmosphere, and obtain an initiator solution;

[0084] (4) Add 300 parts of water to the reactor and remove dissolved oxygen in the nitrogen atmosphere. Then, add the mixed monomer solution obtained in step (2) and the initiator solution obtained in step (3) to the reactor simultaneously. Control the dripping time to 2h and then keep the reaction at 70℃ for 2h to obtain the water-based binder.

[0085] Example 2

[0086] This embodiment provides a method for preparing an aqueous adhesive, comprising the following steps:

[0087] (1) Weigh out 45 parts of acrylic acid, 10 parts of acrylamide, 20 parts of isooctyl acrylate, 15 parts of sodium vinyl sulfonate, 10 parts of 3,4-ethylenedioxythiophene, 0.5 parts of ammonium persulfate, 3 parts of sodium hydroxide, and 400 parts of water by weight.

[0088] (2) Dissolve acrylic acid and acrylamide in 70 parts of water, then add sodium hydroxide, then add isooctyl acrylate, sodium vinyl sulfonate and 3,4-ethylenedioxythiophene, remove dissolved oxygen in the solution under nitrogen atmosphere to obtain a mixed monomer solution;

[0089] (3) Dissolve ammonium persulfate in 30 parts of water, remove dissolved oxygen from the solution under a nitrogen atmosphere, and obtain an initiator solution;

[0090] (4) Add 300 parts of water to the reactor and remove dissolved oxygen in the nitrogen atmosphere. Then, add the mixed monomer solution obtained in step (2) and the initiator solution obtained in step (3) to the reactor simultaneously. Control the dripping time to 2h and then keep the reaction at 70℃ for 2h to obtain the water-based binder.

[0091] Example 3

[0092] This embodiment provides a method for preparing an aqueous adhesive, comprising the following steps:

[0093] (1) Weigh out 45 parts of acrylic acid, 10 parts of acrylamide, 20 parts of acrylonitrile, 10 parts of sodium vinyl sulfonate, 15 parts of pyrrole, 0.5 parts of ammonium persulfate, 3 parts of calcium hydroxide, and 400 parts of water by weight.

[0094] (2) Dissolve acrylic acid and acrylamide in 70 parts of water, then add calcium hydroxide, then add acrylonitrile, sodium vinyl sulfonate and pyrrole, remove dissolved oxygen in the solution under nitrogen atmosphere to obtain a mixed monomer solution;

[0095] (3) Dissolve ammonium persulfate in 30 parts of water, remove dissolved oxygen from the solution under a nitrogen atmosphere, and obtain an initiator solution;

[0096] (4) Add 300 parts of water to the reactor and remove dissolved oxygen in the nitrogen atmosphere. Then, add the mixed monomer solution obtained in step (2) and the initiator solution obtained in step (3) to the reactor simultaneously. Control the dripping time to 2h and then keep the reaction at 70℃ for 2h to obtain the water-based binder.

[0097] Example 4

[0098] This embodiment provides a method for preparing an aqueous adhesive, comprising the following steps:

[0099] (1) Weigh out 45 parts of maleic acid, 10 parts of acrylamide sulfonic acid, 25 parts of methacrylonitrile, 15 parts of N-vinylpyrrolidone, 5 parts of pyrrole, 0.5 parts of ammonium persulfate, 3 parts of calcium hydroxide, and 400 parts of water by weight.

[0100] (2) Dissolve maleic acid and acrylamide in 70 parts of water, then add calcium hydroxide, then add methacrylonitrile, N-vinylpyrrolidone and pyrrole, remove dissolved oxygen in the solution under a nitrogen atmosphere to obtain a mixed monomer solution.

[0101] (3) Dissolve ammonium persulfate in 30 parts of water, remove dissolved oxygen from the solution under a nitrogen atmosphere, and obtain an initiator solution;

[0102] (4) Add 300 parts of water to the reactor and remove dissolved oxygen in the nitrogen atmosphere. Then, add the mixed monomer solution obtained in step (2) and the initiator solution obtained in step (3) to the reactor simultaneously. Control the dripping time to 2h and then keep the reaction at 70℃ for 2h to obtain the water-based binder.

[0103] Example 5

[0104] This embodiment provides a method for preparing an aqueous adhesive, comprising the following steps:

[0105] (1) Weigh out 45 parts of maleic acid, 10 parts of acrylamide, 20 parts of lauryl acrylate, 15 parts of N-vinylpyrrolidone, 10 parts of phenylacetylene, 0.5 parts of benzoyl peroxide, 3 parts of lithium hydroxide, and 400 parts of water by weight.

[0106] (2) Dissolve maleic acid and acrylamide in 70 parts of water, then add lithium hydroxide, then add lauryl acrylate, N-vinylpyrrolidone and phenylacetylene, remove dissolved oxygen in the solution under nitrogen atmosphere to obtain a mixed monomer solution;

[0107] (3) Dissolve benzoyl peroxide in 30 parts of water, remove dissolved oxygen in the solution under a nitrogen atmosphere, and obtain an initiator solution;

[0108] (4) Add 300 parts of water to the reactor and remove dissolved oxygen in the nitrogen atmosphere. Then, add the mixed monomer solution obtained in step (2) and the initiator solution obtained in step (3) to the reactor simultaneously. Control the dripping time to 2h and then keep the reaction at 70℃ for 2h to obtain the water-based binder.

[0109] Example 6

[0110] This embodiment provides a method for preparing an aqueous adhesive, comprising the following steps:

[0111] (1) Weigh out 45 parts of maleic acid, 10 parts of acrylamide, 20 parts of styrene, 10 parts of 2-acrylamide-2-methylpropanesulfonic acid, 15 parts of phenylacetylene, 0.5 parts of benzoyl peroxide, 5 parts of lithium hydroxide, and 400 parts of water by weight.

[0112] (2) Dissolve maleic acid and acrylamide in 70 parts of water, then add lithium hydroxide, then add styrene, 2-acrylamide-2-methylpropanesulfonic acid and phenylacetylene, remove dissolved oxygen in the solution under a nitrogen atmosphere to obtain a mixed monomer solution;

[0113] (3) Dissolve benzoyl peroxide in 30 parts of water, remove dissolved oxygen in the solution under a nitrogen atmosphere, and obtain an initiator solution;

[0114] (4) Add 300 parts of water to the reactor and remove dissolved oxygen in the nitrogen atmosphere. Then, add the mixed monomer solution obtained in step (2) and the initiator solution obtained in step (3) to the reactor simultaneously. Control the dripping time to 2h and then keep the reaction at 70℃ for 2h to obtain the water-based binder.

[0115] Example 7

[0116] This embodiment provides a method for preparing an aqueous adhesive, comprising the following steps:

[0117] (1) Weigh out 45 parts of methacrylic acid, 10 parts of acrylamide, 25 parts of styrene, 15 parts of sodium styrene sulfonate, 5 parts of divinylbenzene, 0.5 parts of benzoyl peroxide, 5 parts of sodium hydroxide, and 400 parts of water by weight.

[0118] (2) Dissolve methacrylic acid and acrylamide in 70 parts of water, then add sodium hydroxide, then add styrene, sodium styrene sulfonate and divinylbenzene, remove dissolved oxygen in the solution under nitrogen atmosphere to obtain a mixed monomer solution;

[0119] (3) Dissolve benzoyl peroxide in 30 parts of water, remove dissolved oxygen in the solution under a nitrogen atmosphere, and obtain an initiator solution;

[0120] (4) Add 300 parts of water to the reactor and remove dissolved oxygen in the nitrogen atmosphere. Then, add the mixed monomer solution obtained in step (2) and the initiator solution obtained in step (3) to the reactor simultaneously. Control the dripping time to 2h and then keep the reaction at 70℃ for 2h to obtain the water-based binder.

[0121] Example 8

[0122] This embodiment provides a method for preparing an aqueous adhesive, comprising the following steps:

[0123] (1) Weigh out 45 parts of methacrylic acid, 10 parts of acrylamide, 20 parts of acrylonitrile, 15 parts of N-vinylpyrrolidone, 10 parts of divinylbenzene, 0.5 parts of benzoyl peroxide, 5 parts of sodium hydroxide, and 400 parts of water by weight.

[0124] (2) Dissolve methacrylic acid and acrylamide in 70 parts of water, then add sodium hydroxide, then add acrylonitrile, N-vinylpyrrolidone and divinylbenzene, remove dissolved oxygen in the solution under a nitrogen atmosphere to obtain a mixed monomer solution;

[0125] (3) Dissolve benzoyl peroxide in 30 parts of water, remove dissolved oxygen in the solution under a nitrogen atmosphere, and obtain an initiator solution;

[0126] (4) Add 300 parts of water to the reactor and remove dissolved oxygen in the nitrogen atmosphere. Then, add the mixed monomer solution obtained in step (2) and the initiator solution obtained in step (3) to the reactor simultaneously. Control the dripping time to 2h and then keep the reaction at 70℃ for 2h to obtain the water-based binder.

[0127] Comparative Example 1

[0128] Comparative Example 1 provides a commercially available polyacrylic acid adhesive (manufactured by Sumitomo Corporation of Japan).

[0129] Comparative Example 2

[0130] Comparative Example 2 provides a method for preparing an aqueous adhesive, comprising the following steps:

[0131] (1) Weigh out 55 parts of acrylic acid, 15 parts of acrylamide, 25 parts of isooctyl acrylate, 5 parts of pyrrole, 0.5 parts of ammonium persulfate, 3 parts of sodium hydroxide, and 400 parts of water by weight.

[0132] (2) Dissolve acrylic acid and acrylamide in 70 parts of water, then add sodium hydroxide, then add isooctyl acrylate and pyrrole, remove dissolved oxygen in the solution under a nitrogen atmosphere to obtain a mixed monomer solution;

[0133] (3) Dissolve ammonium persulfate in 30 parts of water, remove dissolved oxygen from the solution under a nitrogen atmosphere, and obtain an initiator solution;

[0134] (4) Add 300 parts of water to the reactor and remove dissolved oxygen in the nitrogen atmosphere. Then, add the mixed monomer solution obtained in step (2) and the initiator solution obtained in step (3) to the reactor simultaneously. Control the dripping time to 2h and then keep the reaction at 70℃ for 2h to obtain the water-based binder.

[0135] Comparative Example 3

[0136] Comparative Example 3 provides a method for preparing an aqueous adhesive, comprising the following steps:

[0137] (1) Weigh out 50 parts of acrylic acid, 15 parts of acrylamide, 20 parts of acrylonitrile, 15 parts of sodium vinyl sulfonate, 0.5 parts of ammonium persulfate, 3 parts of calcium hydroxide, and 400 parts of water by weight.

[0138] (2) Dissolve acrylic acid and acrylamide in 70 parts of water, then add calcium hydroxide, then add acrylonitrile and sodium vinyl sulfonate, remove dissolved oxygen in the solution under a nitrogen atmosphere to obtain a mixed monomer solution;

[0139] (3) Dissolve ammonium persulfate in 30 parts of water, remove dissolved oxygen from the solution under a nitrogen atmosphere, and obtain an initiator solution;

[0140] (4) Add 300 parts of water to the reactor and remove dissolved oxygen in the nitrogen atmosphere. Then, add the mixed monomer solution obtained in step (2) and the initiator solution obtained in step (3) to the reactor simultaneously. Control the dripping time to 2h and then keep the reaction at 70℃ for 2h to obtain the water-based binder.

[0141] Comparative Example 4

[0142] Comparative Example 4 provides a method for preparing an aqueous adhesive, comprising the following steps:

[0143] (1) Weigh out 42 parts of acrylic acid, 9 parts of acrylamide, 18 parts of acrylonitrile, 9 parts of sodium vinyl sulfonate, 22 parts of pyrrole, 0.5 parts of ammonium persulfate, 3 parts of calcium hydroxide, and 400 parts of water by weight.

[0144] (2) Dissolve acrylic acid and acrylamide in 70 parts of water, then add calcium hydroxide, then add acrylonitrile, sodium vinyl sulfonate and pyrrole, remove dissolved oxygen in the solution under nitrogen atmosphere to obtain a mixed monomer solution;

[0145] (3) Dissolve ammonium persulfate in 30 parts of water, remove dissolved oxygen from the solution under a nitrogen atmosphere, and obtain an initiator solution;

[0146] (4) Add 300 parts of water to the reactor and remove dissolved oxygen in the nitrogen atmosphere. Then, add the mixed monomer solution obtained in step (2) and the initiator solution obtained in step (3) to the reactor simultaneously. Control the dripping time to 2h and then keep the reaction at 70℃ for 2h to obtain the water-based binder.

[0147] Comparative Example 5

[0148] Comparative Example 5 provides a method for preparing an aqueous adhesive, comprising the following steps:

[0149] (1) Weigh out 40 parts of acrylic acid, 10 parts of acrylamide, 10 parts of isooctyl acrylate, 40 parts of sodium styrene sulfonate, 5 parts of 3,4-ethylenedioxythiophene, 0.5 parts of ammonium persulfate, 3 parts of sodium hydroxide, and 400 parts of water by weight.

[0150] (2) Dissolve acrylic acid and acrylamide in 70 parts of water, then add sodium hydroxide, then add isooctyl acrylate, sodium styrene sulfonate and 3,4-ethylenedioxythiophene, remove dissolved oxygen in the solution under a nitrogen atmosphere to obtain a mixed monomer solution;

[0151] (3) Dissolve ammonium persulfate in 30 parts of water, remove dissolved oxygen from the solution under a nitrogen atmosphere, and obtain an initiator solution;

[0152] (4) Add 300 parts of water to the reactor and remove dissolved oxygen in the nitrogen atmosphere. Then, add the mixed monomer solution obtained in step (2) and the initiator solution obtained in step (3) to the reactor simultaneously. Control the dripping time to 2h and then keep the reaction at 70℃ for 2h to obtain the water-based binder.

[0153] Experimental Example

[0154] The binders of different embodiments and comparative examples are made into carbon-coated slurry, then carbon-coated aluminum foil is prepared, and then positive electrode slurry is coated on the carbon-coated aluminum foil to prepare positive electrode sheet. The specific preparation method is as follows.

[0155] Preparation of carbon coating slurry: Weigh 8 parts of the corresponding binder, 3 parts of conductive carbon black Super-P, 77 parts of water and 10 parts of ethanol by weight, stir at 2500 r / min for 6 hours to mix evenly, and filter through a 150 mesh sieve to obtain carbon coating slurry.

[0156] Preparation of carbon-coated aluminum foil: Carbon coating slurry was coated onto aluminum foil using a coating machine and dried at 110°C to obtain carbon-coated aluminum foil. The thickness of the carbon coating layer was controlled at 0.5 μm. Figure 1 shows the carbon-coated aluminum foil prepared using the binder of Example 1.

[0157] The properties of different carbon-coated aluminum foils were tested. The test methods are as follows, and the test results are shown in Table 1.

[0158] Peel strength test: The carbon-coated aluminum foil was cut into strips of 12cm × 2.5cm. A 12.5cm × 5cm stainless steel plate was selected, and a 2.5cm wide strip of 3M double-sided tape was applied to the stainless steel plate. The aluminum foil was then adhered to the double-sided tape with the coating facing towards the tape. Another 2.5cm wide strip of 3M tape was applied to the other side of the aluminum foil. The prepared test sample was rolled back and forth three times under a pressure of 1kg. After 1 hour, the peel strength of the carbon coating layer was tested using a tensile testing machine. The 180° peel strength was tested using a tensile testing machine according to the method shown in GB / T 2792-2014. Figure 2 shows a photograph of the 180° peel strength test. Figure 3 shows a photograph of the carbon-coated aluminum foil prepared using the adhesive of Example 1 after the peel strength test and the 3M tape. There was no residual carbon coating layer on the 3M tape.

[0159] NMP resistance test: Dip a cotton swab in NMP and rub it back and forth on the same position on the carbon coating layer of the carbon-coated aluminum foil. One back and forth is counted as 1 time. Continue until the carbon coating layer is scratched and the substrate is exposed. Record the number of times you rub at this point.

[0160] Surface contact resistance: The carbon-coated aluminum foil sample to be tested is cut into a rectangle of about 5cm×10cm and placed on the sample stage of the electrode resistance meter. The test pressure is set to 25MPa and the holding time is 15s. The surface contact resistance of the carbon-coated aluminum foil is then measured.

[0161] Carbon coating defects and pitting: Visually inspect the surface of the carbon coating layer of the carbon-coated aluminum foil for pitting or defects. Record the presence of pitting or defects as ×, and the absence of pitting or defects as √.

[0162] Table 1 Performance test results of carbon-coated aluminum foil prepared with different binders

[0163] The test results above show that the water-based binder of this application is formulated by blending water-soluble monomers, oil-soluble monomers, amphiphilic monomers and functional monomers in proportion, which takes into account the improvement of the binder's conductivity, wettability to conductive carbon materials and aluminum foil, and adhesion to aluminum foil, so that the prepared battery has excellent cycle stability and helps to extend battery life.

[0164] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A water-based adhesive comprising the following components in parts by weight: 30-70 parts of water-soluble monomer, 10-40 parts of oil-soluble monomer, 10-30 parts of amphiphilic monomer, 2-20 parts of functional monomer, 0.1-3 parts of initiator and 3-40 parts of neutralizer; The amphiphilic monomer includes at least one of sodium vinyl sulfonate, sodium styrene sulfonate, 2-acrylamide-2-methylpropanesulfonic acid, and N-vinylpyrrolidone; The functional monomers include at least one of divinylbenzene, pyrrole, phenylacetylene, and 3,4-ethylenedioxythiophene.

2. The water-based adhesive according to claim 1, wherein, The water-soluble monomers include at least one of maleic acid, acrylamide, vinyl sulfonic acid, acrylic acid, methacrylic acid, and acrylamide.

3. The water-based adhesive according to claim 1, wherein, The oil-soluble monomers include at least one of isooctyl acrylate, lauryl acrylate, acrylonitrile, methacrylonitrile, and styrene.

4. The water-based adhesive according to claim 1, wherein it has at least one of the following characteristics: (1) The initiator includes at least one of sodium persulfate, ammonium persulfate and benzoyl peroxide; (2) The neutralizing agent includes at least one of lithium hydroxide, sodium hydroxide, calcium hydroxide and ammonia water; (3) The water-based adhesive also includes water.

5. A method for preparing a water-based adhesive, comprising the following steps: (a) The water-based adhesive according to any one of claims 1 to 4 is formulated by dissolving a water-soluble monomer in water, adding a neutralizing agent to adjust the pH, and then adding an amphiphilic monomer, an oil-soluble monomer and a functional monomer to obtain a monomer solution. (b) Dissolve the initiator in water to obtain an initiator solution; (c) The monomer solution and the initiator solution are added to water and reacted at 40-80°C to obtain the water-based binder.

6. The preparation method according to claim 5, wherein it has at least one of the following characteristics: (1) In step (c), the monomer solution and the initiator solution are added at a time of 1 to 5 hours; (2) In step (c), the reaction time is 1 to 3 hours; (3) The ratio of water used in steps (a), (b) and (c) is (5-20):3:(20-35).

7. A carbon coating paste comprising the water-based adhesive according to any one of claims 1 to 4 or the water-based adhesive prepared by the preparation method according to any one of claims 5 to 6.

8. The carbon coating slurry according to claim 7, wherein, The carbon coating slurry also includes water, a co-solvent, and a conductive carbon material.

9. The carbon coating paste according to claim 8, wherein, The carbon coating slurry comprises the following components by weight: 75-79 parts water, 8-12 parts co-solvent, 2-4 parts conductive carbon material, and 6-10 parts water-based binder.

10. A carbon-coated aluminum foil comprising an aluminum foil substrate and a carbon coating layer disposed on the surface of the aluminum foil substrate, wherein, The carbon coating layer is prepared from the carbon coating slurry according to any one of claims 7 to 9.

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