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

Abstract

The invention relates to the technical field of battery binders, in particular to a water-based binder, a preparation method of the water-based binder 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 neutralizer, the amphiphilic monomer is prepared from at least one of sodium vinyl sulfonate, sodium p-styrenesulfonate, 2-acrylamide-2-methylpropanesulfonic acid and N-vinyl pyrrolidone; the functional monomer comprises at least one of divinylbenzene, pyrrole, phenylacetylene and 3, 4-ethylenedioxythiophene. According to the water-based binder, the water-soluble monomer, the oil-soluble monomer, the amphiphilic monomer and the functional monomer are compounded in proportion, the conductivity of the binder, the wettability to a conductive carbon material and an aluminum foil, the adhesion to the aluminum foil and the like are improved, the prepared battery has excellent cycle stability, and the service life of the battery is prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of battery binders, in particular to a water-based binder and a preparation method thereof, and a carbon-coated aluminum foil. Background Art

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

[0003] Conductive carbon materials are usually dispersed with a binder and then coated on the surface of aluminum foil to form carbon-coated aluminum foil. However, the current carbon-coated aluminum foil has the following problems: on the one hand, the conductive carbon material has strong hydrophobicity, and it is difficult for ordinary binders to disperse and wet it, and pitting and missing coating often occur during the coating process; on the other hand, the existing binder has low bonding strength with the positive electrode sheet, resulting in no obvious improvement in battery performance.

[0004] A modified acrylic resin that can be used to prepare secondary battery carbon coating is recorded in the Chinese patent application with publication number CN114957522A. However, the synthesis process of the modified acrylic resin is complicated and the process is long, resulting in low production efficiency. The Chinese patent application with publication number CN116285785A records a binder for carbon-coated aluminum foil, which improves the bonding performance by introducing a phosphate monomer. However, when the binder is mixed and dispersed with a conductive carbon material, it needs to be ground; and the conductivity of the binder is insufficient. The Chinese patent application with publication number CN117777898A records an internally cross-linked binder that can ensure electron transfer efficiency, has strong bonding properties, reduces the internal resistance of the coating, and improves the peeling force. However, the binder is not sufficiently dispersible for the conductive carbon material, and a certain amount of dispersant needs to be added during use.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] One object of the present invention is to provide an aqueous binder that has excellent dispersibility for conductive carbon materials, excellent bonding properties, and can also improve conductive properties.

[0007] Another object of the present invention is to provide a method for preparing the aqueous binder.

[0008] Another object of the present invention is to provide a carbon coating slurry comprising the above-mentioned aqueous binder.

[0009] Another object of the present invention is to provide a carbon-coated aluminum foil made from the above-mentioned carbon-coated slurry.

[0010] In order to achieve the above-mentioned object of the present invention, the present invention provides an aqueous binder on the one hand, comprising the following components in parts by weight:

[0011] 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;

[0012] The amphiphilic monomer includes at least one of sodium vinyl sulfonate, sodium styrene sulfonate, 2-acrylamide-2-methylpropane sulfonic acid and N-vinyl pyrrolidone;

[0013] The functional monomer includes at least one of divinylbenzene, pyrrole, phenylacetylene and 3,4-ethylenedioxythiophene.

[0014] In a specific embodiment of the present invention, the water-soluble monomer includes at least one of maleic acid, propylene sulfonic acid, vinyl sulfonic acid, acrylic acid, methacrylic acid and acrylamide.

[0015] In a specific embodiment of the present invention, the oil-soluble monomer includes at least one of isooctyl acrylate, lauryl acrylate, acrylonitrile, methacrylonitrile and styrene.

[0016] In a specific embodiment of the present invention, the initiator includes at least one of sodium persulfate, ammonium persulfate and dibenzoyl peroxide.

[0017] In a specific embodiment of the present invention, the neutralizing agent includes at least one of lithium hydroxide, sodium hydroxide, calcium hydroxide and ammonia water.

[0018] In a specific embodiment of the present invention, the aqueous binder further comprises water.

[0019] Another aspect of the present invention provides a method for preparing any of the above-mentioned aqueous binders, comprising the following steps:

[0020] (a) dissolving a water-soluble monomer in water, adding a neutralizer to adjust the pH, and then adding an amphiphilic monomer, an oil-soluble monomer and a functional monomer to obtain a monomer solution;

[0021] (b) dissolving an initiator in water to obtain an initiator solution;

[0022] (c) adding the monomer solution and the initiator solution into water and reacting them at 40-80° C. to obtain the water-based binder.

[0023] In a specific embodiment of the present invention, in step (c), the monomer solution and the initiator solution are added for 1 to 5 hours.

[0024] In a specific embodiment of the present invention, in step (c), the reaction time is 1 to 3 hours.

[0025] In a specific embodiment of the present invention, the usage ratio of water in step (a), step (b) and step (c) is (5-20) : 3 : (20-35).

[0026] Another aspect of the present invention provides a carbon coating slurry comprising any one of the above-mentioned aqueous binders.

[0027] In a specific embodiment of the present invention, the carbon coating slurry further comprises water, a cosolvent and a conductive carbon material. Further, the carbon coating slurry comprises the following components by weight: 75-79 parts of water, 8-12 parts of a cosolvent, 2-4 parts of a conductive carbon material and 6-10 parts of an aqueous binder.

[0028] Another aspect of the present invention 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 one of the above-mentioned carbon coating slurries.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The aqueous binder of the present invention achieves excellent adhesion to aluminum foil by regulating the monomer composition, utilizing polar groups, increasing the conductivity of the binder by utilizing functional monomers, and introducing amphiphilic monomers to reduce the surface tension of the binder, thereby improving the dispersibility of the conductive carbon material and the wettability to the aluminum foil, thereby improving the adhesion of the coating to the aluminum foil and improving the conductivity of the coating, so that the prepared battery has excellent cycle stability, which helps to extend the battery life;

[0031] (2) The preparation method of the water-based binder of the present invention is simple to operate, has high production efficiency, and can be industrialized. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 The carbon-coated aluminum foil is prepared by using the binder of Example 1 of the present invention;

[0034] Figure 2 This is a photo of the 180° peel force test of the present invention;

[0035] Figure 3This is a photo of the carbon-coated aluminum foil prepared by the adhesive of Example 1 of the present invention and the 3M tape after the peeling force test. DETAILED DESCRIPTION

[0036] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0037] In one aspect, the present invention provides an aqueous binder comprising the following components in parts by weight:

[0038] 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;

[0039] The amphiphilic monomer includes at least one of sodium vinyl sulfonate, sodium styrene sulfonate, 2-acrylamide-2-methylpropane sulfonic acid and N-vinyl pyrrolidone;

[0040] The functional monomer includes at least one of divinylbenzene, pyrrole, phenylacetylene and 3,4-ethylenedioxythiophene.

[0041] The water-based binder of the present invention utilizes the polar groups in the water-soluble monomers to ensure the adhesive properties of the binder and improve the NMP resistance of the binder; utilizes the affinity between the oil-soluble monomers and the conductive carbon material to improve the dispersion properties of the conductive carbon material; the introduction of the amphiphilic monomers, the lipophilic groups and the conductive carbon material have strong affinity, and the hydrophilic groups ensure water solubility, which can improve the wettability of the binder to the conductive carbon material on the one hand, and reduce the surface tension on the other hand, improve the wettability to the aluminum foil, improve the coating performance, and ensure the consistency of the carbon coating layer even when thinly coated, avoiding the problems of missing coating and holes; the introduction of the functional monomers can increase the conductivity of the binder and improve the conductivity of the carbon coating layer. Therefore, the water-based binder of the present invention adopts water-soluble monomers, oil-soluble monomers, amphiphilic monomers and functional monomers to be compounded in proportion, taking into account the improvement of the conductivity of the binder, the wettability to the conductive carbon material and the aluminum foil, the adhesion to the aluminum foil, etc., so that the prepared battery has excellent cycle stability and helps to extend the battery life.

[0042] The present invention regulates the dosage ratio of various monomers to give full play to the role of the monomers, so as to achieve the improvement of conductivity, wettability, adhesion and other properties. In the water-based binder of the present invention, the dosage of each component can be as follows by weight:

[0043] The amount of the water-soluble monomer can be 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, 65 parts, 70 parts or a range consisting of any two of them;

[0044] The amount of the oil-soluble monomer can be 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 40 parts or a range consisting of any two of them;

[0045] The amount of the amphiphilic monomer can be 10 parts, 15 parts, 20 parts, 25 parts, 30 parts or a range consisting of any two of them;

[0046] The amount of the functional monomer can be 2 parts, 5 parts, 8 parts, 10 parts, 12 parts, 15 parts, 20 parts or any two of them; an appropriate amount of the functional monomer helps to improve the conductive properties; when the functional monomer is too little, the conductive properties are not significantly improved; when the functional monomer is too much, it will affect the wettability of the binder to the conductive carbon material and the bonding performance of the binder to the aluminum foil, the peeling force is insufficient and the resistance will increase sharply;

[0047] The amount of the initiator can be 0.1 part, 0.5 part, 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts or a range consisting of any two of them;

[0048] The amount of the neutralizer can be 3 parts, 5 parts, 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts or a range consisting of any two of them.

[0049] In a specific embodiment of the present invention, the aqueous binder includes the following components in parts by weight: 50-60 parts of water-soluble monomers, 20-25 parts of oil-soluble monomers, 10-15 parts of amphiphilic monomers, 5-15 parts of functional monomers, 0.1-3 parts of initiators and 3-40 parts of neutralizers.

[0050] In a specific embodiment of the present invention, the water-soluble monomer includes at least one of maleic acid, propylene sulfonic acid, vinyl sulfonic acid, acrylic acid, methacrylic acid and acrylamide. Further, the water-soluble monomer is at least one of acrylic acid, vinyl sulfonic acid and acrylamide.

[0051] The water-soluble monomer of the present invention contains strong 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, and after some groups are ionized, the water solubility of the binder is further improved.

[0052] In a specific embodiment of the present invention, the oil-soluble monomer includes at least one of isooctyl acrylate, lauryl acrylate, acrylonitrile, methacrylonitrile and styrene. Further, the oil-soluble monomer includes at least one of isooctyl acrylate and acrylonitrile.

[0053] The lipophilic monomer has good affinity with the conductive carbon material, which helps to disperse the conductive carbon material. The prepared binder has good dispersibility for the conductive carbon material even without the addition of an additional dispersant. The present invention regulates the amount of the lipophilic monomer within a certain range, taking into account both the dispersibility and the NMP resistance of the binder.

[0054] In a specific embodiment of the present invention, the functional monomer includes at least one of pyrrole and phenylacetylene. When pyrrole and / or phenylacetylene are used as the functional monomer, it is more conducive to improving both the conductivity and the peel strength.

[0055] In a specific embodiment of the present invention, the initiator includes at least one of sodium persulfate, ammonium persulfate and dibenzoyl peroxide. Further, the initiator includes at least one of ammonium persulfate and dibenzoyl peroxide.

[0056] In a specific embodiment of the present invention, the neutralizing agent includes at least one of lithium hydroxide, sodium hydroxide, calcium hydroxide and ammonia water, preferably sodium hydroxide.

[0057] In a specific embodiment of the present invention, the aqueous binder further comprises water. Further, the amount of water used is 280 to 580 parts.

[0058] For example, in different embodiments, the amount of water can be 280 parts, 300 parts, 350 parts, 400 parts, 450 parts, 500 parts, 550 parts, 580 parts, or a range consisting of any two of them.

[0059] Another aspect of the present invention provides a method for preparing any one of the above-mentioned aqueous binders, comprising the following steps:

[0060] (a) dissolving a water-soluble monomer in water, adding a neutralizing agent, and then adding an amphiphilic monomer, an oil-soluble monomer and a functional monomer to obtain a monomer solution;

[0061] (b) dissolving an initiator in water to obtain an initiator solution;

[0062] (c) The monomer solution and the initiator solution are added into water and reacted at 40-80° C. to obtain a water-based adhesive.

[0063] In step (c), the reaction temperature can be 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C or a range consisting of any two of them, for example, 70-75°C. 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.

[0064] In actual operation, the monomer solution in step (a), the initiator solution in step (b) and the water used as the reaction base liquid in step (c) can be deoxygenated, for example, by removing dissolved oxygen in the liquid under a nitrogen atmosphere, to ensure smooth reaction and improve the degree of reaction.

[0065] In step (c), water as a reaction base liquid can be added to the reactor in advance, and then the monomer solution and the initiator solution are added to the reactor simultaneously in a dropwise manner. In a specific embodiment of the present invention, in step (c), the monomer solution and the initiator solution are added for 1 to 5 hours.

[0066] For example, 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 a range consisting of any two thereof.

[0067] In a specific embodiment of the present invention, in step (c), the reaction time is 1 to 3 hours. The reaction time here refers to the length of time for the reaction after the monomer solution and the initiator solution are added, such as 1 hour, 2 hours, 3 hours, etc., but is not limited thereto.

[0068] In a specific embodiment of the present invention, in adjusting the pH, the pH is adjusted to 2 to 7. In actual operation, the amount of the neutralizer added is adjusted according to the specific pH of the solution.

[0069] In a specific embodiment of the present invention, the usage ratio of water in step (a), step (b) and step (c) is (5-20) : 3 : (20-35).

[0070] For example, in different embodiments, the usage ratio of water in step (a) and step (b) can be 5:3, 8:3, 10:3, 14:3, 17:3, 20:3 or a range consisting of any two thereof; the usage ratio of water in step (c) and step (b) can be 20:3, 23:3, 26:3, 30:3, 32:3, 35:3 or a range consisting of any two thereof.

[0071] Another aspect of the present invention provides a carbon coating slurry comprising any one of the above-mentioned aqueous binders.

[0072] In a specific embodiment of the present invention, the carbon coating slurry further comprises water, a cosolvent and a conductive carbon material. Further, the carbon coating slurry comprises the following components by weight: 75-79 parts of water, 8-12 parts of a cosolvent, 2-4 parts of a conductive carbon material and 6-10 parts of an aqueous binder.

[0073] In a specific embodiment of the present invention, the carbon coating slurry may not include a dispersant. When the binder of the present invention is used in the carbon coating slurry, it can ensure good dispersibility of the conductive carbon material without adding a dispersant. In addition, in the preparation of the carbon coating slurry of the present invention, grinding treatment is not required.

[0074] In a specific embodiment of the present invention, the cosolvent includes an alcohol or ether solvent. Further, the cosolvent is ethanol. By adding the cosolvent, the coating drying rate can be increased and the coating film formation can be promoted, and the water resistance and solvent resistance of the coating can be further improved.

[0075] Another aspect of the present invention 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 of any one of the above-mentioned carbon coating slurries.

[0076] Example 1

[0077] This embodiment provides a method for preparing a water-based binder, comprising the following steps:

[0078] (1) Weigh 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, respectively, by weight;

[0079] (2) dissolving acrylic acid and acrylamide in 70 parts of water, then adding sodium hydroxide, and then adding isooctyl acrylate, sodium styrene sulfonate, and 3,4-ethylenedioxythiophene, and removing dissolved oxygen in the solution under a nitrogen atmosphere to obtain a mixed monomer solution;

[0080] (3) dissolving ammonium persulfate in 30 parts of water, and removing dissolved oxygen in the solution under a nitrogen atmosphere to obtain an initiator solution;

[0081] (4) 300 parts of water were added into the reaction kettle, and the dissolved oxygen therein was removed under a nitrogen atmosphere. Then, the mixed monomer solution obtained in step (2) and the initiator solution obtained in step (3) were simultaneously added into the reaction kettle, and the dropping time was controlled to be 2 hours. Then, the mixture was kept warm at 70° C. for 2 hours to obtain a water-based adhesive.

[0082] Example 2

[0083] This embodiment provides a method for preparing a water-based binder, comprising the following steps:

[0084] (1) Weigh 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, respectively, by weight;

[0085] (2) dissolving acrylic acid and acrylamide in 70 parts of water, then adding sodium hydroxide, and then adding isooctyl acrylate, sodium vinyl sulfonate, and 3,4-ethylenedioxythiophene, and removing dissolved oxygen in the solution under a nitrogen atmosphere to obtain a mixed monomer solution;

[0086] (3) dissolving ammonium persulfate in 30 parts of water, and removing dissolved oxygen in the solution under a nitrogen atmosphere to obtain an initiator solution;

[0087] (4) 300 parts of water were added into the reaction kettle, and the dissolved oxygen therein was removed under a nitrogen atmosphere. Then, the mixed monomer solution obtained in step (2) and the initiator solution obtained in step (3) were simultaneously added into the reaction kettle, and the dropping time was controlled to be 2 hours. Then, the mixture was kept warm at 70° C. for 2 hours to obtain a water-based adhesive.

[0088] Example 3

[0089] This embodiment provides a method for preparing a water-based binder, comprising the following steps:

[0090] (1) Weigh 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, respectively, by weight;

[0091] (2) dissolving acrylic acid and acrylamide in 70 parts of water, then adding calcium hydroxide, and then adding acrylonitrile, sodium vinyl sulfonate, and pyrrole, and removing dissolved oxygen in the solution under a nitrogen atmosphere to obtain a mixed monomer solution;

[0092] (3) dissolving ammonium persulfate in 30 parts of water, and removing dissolved oxygen in the solution under a nitrogen atmosphere to obtain an initiator solution;

[0093] (4) 300 parts of water were added into the reaction kettle, and the dissolved oxygen therein was removed under a nitrogen atmosphere. Then, the mixed monomer solution obtained in step (2) and the initiator solution obtained in step (3) were simultaneously added into the reaction kettle, and the dropping time was controlled to be 2 hours. Then, the mixture was kept warm at 70° C. for 2 hours to obtain a water-based adhesive.

[0094] Example 4

[0095] This embodiment provides a method for preparing a water-based binder, comprising the following steps:

[0096] (1) Weigh 45 parts of maleic acid, 10 parts of propylene sulfonic acid, 25 parts of methacrylonitrile, 15 parts of N-vinyl pyrrolidone, 5 parts of pyrrole, 0.5 parts of ammonium persulfate, 3 parts of calcium hydroxide, and 400 parts of water, respectively, by weight;

[0097] (2) dissolving maleic acid and propylene sulfonic acid in 70 parts of water, then adding calcium hydroxide, and then adding methacrylonitrile, N-vinyl pyrrolidone, and pyrrole, and removing dissolved oxygen in the solution under a nitrogen atmosphere to obtain a mixed monomer solution;

[0098] (3) dissolving ammonium persulfate in 30 parts of water, and removing dissolved oxygen in the solution under a nitrogen atmosphere to obtain an initiator solution;

[0099] (4) 300 parts of water were added into the reaction kettle, and the dissolved oxygen therein was removed under a nitrogen atmosphere. Then, the mixed monomer solution obtained in step (2) and the initiator solution obtained in step (3) were simultaneously added into the reaction kettle, and the dropping time was controlled to be 2 hours. Then, the mixture was kept warm at 70° C. for 2 hours to obtain a water-based adhesive.

[0100] Example 5

[0101] This embodiment provides a method for preparing a water-based binder, comprising the following steps:

[0102] (1) Weigh 45 parts of maleic acid, 10 parts of acrylamide, 20 parts of lauryl acrylate, 15 parts of N-vinyl pyrrolidone, 10 parts of phenylacetylene, 0.5 parts of dibenzoyl peroxide, 3 parts of lithium hydroxide, and 400 parts of water, respectively, by weight;

[0103] (2) dissolving maleic acid and acrylamide in 70 parts of water, then adding lithium hydroxide, and then adding lauryl acrylate, N-vinyl pyrrolidone, and phenylacetylene, and removing dissolved oxygen in the solution under a nitrogen atmosphere to obtain a mixed monomer solution;

[0104] (3) dissolving dibenzoyl peroxide in 30 parts of water, and removing dissolved oxygen in the solution under a nitrogen atmosphere to obtain an initiator solution;

[0105] (4) 300 parts of water were added into the reaction kettle, and the dissolved oxygen therein was removed under a nitrogen atmosphere. Then, the mixed monomer solution obtained in step (2) and the initiator solution obtained in step (3) were simultaneously added into the reaction kettle, and the dropping time was controlled to be 2 hours. Then, the mixture was kept warm at 70° C. for 2 hours to obtain a water-based adhesive.

[0106] Example 6

[0107] This embodiment provides a method for preparing a water-based binder, comprising the following steps:

[0108] (1) Weigh 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 dibenzoyl peroxide, 5 parts of lithium hydroxide, and 400 parts of water respectively by weight;

[0109] (2) dissolving maleic acid and acrylamide in 70 parts of water, then adding lithium hydroxide, and then adding styrene, 2-acrylamide-2-methylpropanesulfonic acid, and phenylacetylene, and removing dissolved oxygen in the solution under a nitrogen atmosphere to obtain a mixed monomer solution;

[0110] (3) dissolving dibenzoyl peroxide in 30 parts of water, and removing dissolved oxygen in the solution under a nitrogen atmosphere to obtain an initiator solution;

[0111] (4) 300 parts of water were added into the reaction kettle, and the dissolved oxygen therein was removed under a nitrogen atmosphere. Then, the mixed monomer solution obtained in step (2) and the initiator solution obtained in step (3) were simultaneously added into the reaction kettle, and the dropping time was controlled to be 2 hours. Then, the mixture was kept warm at 70° C. for 2 hours to obtain a water-based adhesive.

[0112] Example 7

[0113] This embodiment provides a method for preparing a water-based binder, comprising the following steps:

[0114] (1) Weigh 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 dibenzoyl peroxide, 5 parts of sodium hydroxide, and 400 parts of water, respectively, by weight;

[0115] (2) dissolving methacrylic acid and acrylamide in 70 parts of water, then adding sodium hydroxide, and then adding styrene, sodium styrene sulfonate, and divinylbenzene, and removing dissolved oxygen in the solution under a nitrogen atmosphere to obtain a mixed monomer solution;

[0116] (3) dissolving dibenzoyl peroxide in 30 parts of water, and removing dissolved oxygen in the solution under a nitrogen atmosphere to obtain an initiator solution;

[0117] (4) 300 parts of water were added into the reaction kettle, and the dissolved oxygen therein was removed under a nitrogen atmosphere. Then, the mixed monomer solution obtained in step (2) and the initiator solution obtained in step (3) were simultaneously added into the reaction kettle, and the dropping time was controlled to be 2 hours. Then, the mixture was kept warm at 70° C. for 2 hours to obtain a water-based adhesive.

[0118] Example 8

[0119] This embodiment provides a method for preparing a water-based binder, comprising the following steps:

[0120] (1) Weigh 45 parts of methacrylic acid, 10 parts of acrylamide, 20 parts of acrylonitrile, 15 parts of N-vinyl pyrrolidone, 10 parts of divinylbenzene, 0.5 parts of dibenzoyl peroxide, 5 parts of sodium hydroxide, and 400 parts of water, respectively, by weight;

[0121] (2) dissolving methacrylic acid and acrylamide in 70 parts of water, then adding sodium hydroxide, and then adding acrylonitrile, N-vinyl pyrrolidone, and divinylbenzene, and removing dissolved oxygen in the solution under a nitrogen atmosphere to obtain a mixed monomer solution;

[0122] (3) dissolving dibenzoyl peroxide in 30 parts of water, and removing dissolved oxygen in the solution under a nitrogen atmosphere to obtain an initiator solution;

[0123] (4) 300 parts of water were added into the reaction kettle, and the dissolved oxygen therein was removed under a nitrogen atmosphere. Then, the mixed monomer solution obtained in step (2) and the initiator solution obtained in step (3) were simultaneously added into the reaction kettle, and the dropping time was controlled to be 2 hours. Then, the mixture was kept warm at 70° C. for 2 hours to obtain a water-based adhesive.

[0124] Comparative Example 1

[0125] Comparative Example 1 provides a commercially available polyacrylic acid adhesive (produced by Sumitomo, Japan).

[0126] Comparative Example 2

[0127] Comparative Example 2 provides a method for preparing a water-based binder, comprising the following steps:

[0128] (1) Weigh 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, respectively, by weight;

[0129] (2) dissolving acrylic acid and acrylamide in 70 parts of water, then adding sodium hydroxide, and then adding isooctyl acrylate and pyrrole, and removing dissolved oxygen in the solution under a nitrogen atmosphere to obtain a mixed monomer solution;

[0130] (3) dissolving ammonium persulfate in 30 parts of water, and removing dissolved oxygen in the solution under a nitrogen atmosphere to obtain an initiator solution;

[0131] (4) 300 parts of water were added into the reaction kettle, and the dissolved oxygen therein was removed under a nitrogen atmosphere. Then, the mixed monomer solution obtained in step (2) and the initiator solution obtained in step (3) were simultaneously added into the reaction kettle, and the dropping time was controlled to be 2 hours. Then, the mixture was kept warm at 70° C. for 2 hours to obtain a water-based adhesive.

[0132] Comparative Example 3

[0133] Comparative Example 3 provides a method for preparing a water-based binder, comprising the following steps:

[0134] (1) Weigh 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, respectively, by weight;

[0135] (2) dissolving acrylic acid and acrylamide in 70 parts of water, then adding calcium hydroxide, and then adding acrylonitrile and sodium vinyl sulfonate, and removing dissolved oxygen in the solution under a nitrogen atmosphere to obtain a mixed monomer solution;

[0136] (3) dissolving ammonium persulfate in 30 parts of water, and removing dissolved oxygen in the solution under a nitrogen atmosphere to obtain an initiator solution;

[0137] (4) 300 parts of water were added into the reaction kettle, and the dissolved oxygen therein was removed under a nitrogen atmosphere. Then, the mixed monomer solution obtained in step (2) and the initiator solution obtained in step (3) were simultaneously added into the reaction kettle, and the dropping time was controlled to be 2 hours. Then, the mixture was kept warm at 70° C. for 2 hours to obtain a water-based adhesive.

[0138] Comparative Example 4

[0139] Comparative Example 4 provides a method for preparing a water-based binder, comprising the following steps:

[0140] (1) Weigh 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, respectively, by weight;

[0141] (2) dissolving acrylic acid and acrylamide in 70 parts of water, then adding calcium hydroxide, and then adding acrylonitrile, sodium vinyl sulfonate, and pyrrole, and removing dissolved oxygen in the solution under a nitrogen atmosphere to obtain a mixed monomer solution;

[0142] (3) dissolving ammonium persulfate in 30 parts of water, and removing dissolved oxygen in the solution under a nitrogen atmosphere to obtain an initiator solution;

[0143] (4) 300 parts of water were added into the reaction kettle, and the dissolved oxygen therein was removed under a nitrogen atmosphere. Then, the mixed monomer solution obtained in step (2) and the initiator solution obtained in step (3) were simultaneously added into the reaction kettle, and the dropping time was controlled to be 2 hours. Then, the mixture was kept warm at 70° C. for 2 hours to obtain a water-based adhesive.

[0144] Comparative Example 5

[0145] Comparative Example 5 provides a method for preparing a water-based binder, comprising the following steps:

[0146] (1) Weigh 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, respectively, by weight;

[0147] (2) dissolving acrylic acid and acrylamide in 70 parts of water, then adding sodium hydroxide, and then adding isooctyl acrylate, sodium styrene sulfonate, and 3,4-ethylenedioxythiophene, and removing dissolved oxygen in the solution under a nitrogen atmosphere to obtain a mixed monomer solution;

[0148] (3) dissolving ammonium persulfate in 30 parts of water, and removing dissolved oxygen in the solution under a nitrogen atmosphere to obtain an initiator solution;

[0149] (4) 300 parts of water were added into the reaction kettle, and the dissolved oxygen therein was removed under a nitrogen atmosphere. Then, the mixed monomer solution obtained in step (2) and the initiator solution obtained in step (3) were simultaneously added into the reaction kettle, and the dropping time was controlled to be 2 hours. Then, the mixture was kept warm at 70° C. for 2 hours to obtain a water-based adhesive.

[0150] Experimental example

[0151] The binders of different embodiments and comparative examples are made into carbon-coated slurries, and then carbon-coated aluminum foil is prepared. The positive electrode slurry is then coated on the carbon-coated aluminum foil to prepare a positive electrode sheet. The specific preparation method is as follows.

[0152] Preparation of carbon coating slurry: According to weight, weigh 8 parts of corresponding binder, 3 parts of conductive carbon black Super-P, 77 parts of water, and 10 parts of ethanol, stir at 2500r / min for 6h to mix evenly, and filter with a 150-mesh sieve to obtain carbon coating slurry.

[0153] Preparation of carbon-coated aluminum foil: The carbon-coated slurry is coated on the aluminum foil by a coating machine, and dried at 110°C to obtain the carbon-coated aluminum foil. The thickness of the carbon-coated layer is controlled at 0.5 μm. Figure 1 The carbon-coated aluminum foil is prepared using the adhesive of Example 1.

[0154] The performance of different carbon-coated aluminum foils was tested. The test methods are as follows and the test results are shown in Table 1.

[0155] Peel force test: Cut the carbon-coated aluminum foil into 12cm×2.5cm strips. Select a 12.5cm×5cm stainless steel plate, stick a 2.5cm wide 3M double-sided tape on the stainless steel plate, and then stick it on the double-sided tape with the coating facing the double-sided tape. Then stick a 2.5cm wide 3M tape on the other side of the aluminum foil. Roll the prepared test sample back and forth 3 times with a pressure of 1Kg. After leaving it for 1 hour, use a tensile tester to test the peel force of the carbon coating layer. Use a tensile tester to test the 180° peel force according to the method shown in GB / T 2792-2014. Figure 2 This is a photo of the 180° peel force test. Figure 3 The carbon-coated aluminum foil prepared by the adhesive of Example 1 and the 3M tape are photographed after the peeling force test. No carbon coating layer remains on the 3M tape.

[0156] NMP resistance test: Dip a cotton swab in NMP and wipe back and forth on the same position on the carbon-coated layer of the carbon-coated aluminum foil. One back and forth is counted as one time. When the carbon-coated layer is scratched and the substrate is exposed, the number of wipes at this time is recorded.

[0157] Surface contact resistance: Cut the carbon-coated aluminum foil sample to be tested into a rectangular size of about 5 cm × 10 cm, place it on the sample table of the electrode resistor meter, set the test pressure to 25 MPa and the pressure holding time to 15 s, and measure the surface contact resistance of the carbon-coated aluminum foil.

[0158] Carbon coating missing and pitting: Observe the carbon coating surface of the carbon-coated aluminum foil by visual method to see if there are pitting or missing coating. If there are pitting or missing coating, record it as ×, and if there are no pitting or missing coating, record it as √.

[0159] Table 1 Performance test results of carbon-coated aluminum foil made with different binders

[0160]

[0161]

[0162] It can be seen from the above test results that the aqueous binder of the present invention adopts water-soluble monomers, oil-soluble monomers, amphiphilic monomers and functional monomers compounded in proportion, taking into account the improvement of the conductivity of the binder, the wettability to conductive carbon materials and aluminum foil, the adhesion to aluminum foil, etc., so that the prepared battery has excellent cycle stability, which helps to extend the battery life.

[0163] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A water-based adhesive, characterized in that: It includes the following components 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-methylpropane sulfonic acid and N-vinyl pyrrolidone; The functional monomer includes at least one of divinylbenzene, pyrrole, phenylacetylene and 3,4-ethylenedioxythiophene.

2. The aqueous adhesive according to claim 1, characterized in that The water-soluble monomer includes at least one of maleic acid, propylene sulfonic acid, vinyl sulfonic acid, acrylic acid, methacrylic acid and acrylamide.

3. The aqueous adhesive according to claim 1, characterized in that: The oil-soluble monomer includes at least one of isooctyl acrylate, lauryl acrylate, acrylonitrile, methacrylonitrile and styrene.

4. The aqueous adhesive according to claim 1, characterized in that: Having at least one of the following characteristics: (1) The initiator comprises at least one of sodium persulfate, ammonium persulfate and dibenzoyl peroxide; (2) The neutralizing agent includes at least one of lithium hydroxide, sodium hydroxide, calcium hydroxide and ammonia water; (3) The aqueous binder also includes water.

5. A method for preparing a water-based binder, characterized in that: The steps include: (a) preparing the components of the aqueous binder according to any one of claims 1 to 4, dissolving a water-soluble monomer in water, adding a neutralizer to adjust the pH, and then adding an amphiphilic monomer, an oil-soluble monomer and a functional monomer to obtain a monomer solution; (b) dissolving an initiator in water to obtain an initiator solution; (c) adding the monomer solution and the initiator solution into water and reacting them at 40-80° C. to obtain the water-based binder.

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

7. A carbon coating slurry, characterized in that: The invention comprises the aqueous binder according to any one of claims 1 to 4 or the aqueous binder prepared by the preparation method according to any one of claims 5 to 6.

8. The carbon coating slurry according to claim 7, characterized in that: The carbon coating slurry also includes water, a solvent and a conductive carbon material.

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

10. A carbon-coated aluminum foil, characterized in that: It comprises an aluminum foil substrate and a carbon coating layer arranged on the surface of the aluminum foil substrate, wherein the carbon coating layer is made of the carbon coating slurry according to any one of claims 7 to 9.

Images