Acrylate copolymer wetting agent and electrode sheet comprising wetting agent

Abstract

The present invention relates to the technical field of new energy battery auxiliaries. Disclosed are an acrylate copolymer wetting agent and an electrode sheet comprising the wetting agent. The acrylate copolymer wetting agent is obtained by means of a copolymerization reaction of an acrylic acid and / or acrylate monomer and an ether monomer. The electrode sheet is obtained by applying a slurry comprising a conductive additive, a binder, a dispersant, an acrylate copolymer wetting agent, an active material, and water onto a current collector and then drying, cutting, and rolling the current collector. The high-swelling acrylate copolymer wetting agent obtained in the present invention can be used in a homogenization process for manufacturing an electrode sheet and can significantly improve the wetting rate of the electrode sheet in an electrolyte solution while ensuring the performance of the electrode sheet.

Description

An acrylate copolymer infiltrant and an electrode sheet containing the same

[0001] Priority information

[0002] The present application claims priority to and the benefit of the filing date of Chinese Patent Application No. 202410871061.9, filed on July 1, 2024, and is hereby incorporated by reference in its entirety. TECHNICAL FIELD

[0003] The present application belongs to the technical field of new energy battery additives, and specifically relates to an acrylate copolymer infiltrant and an electrode sheet containing the same. BACKGROUND

[0004] The production and manufacturing process of existing lithium ion batteries mostly adopts flow production. The process flow is first to fully disperse the electrode active material, conductive agent and adhesive additives in the solvent, then to coat the slurry on the foil to make the electrode sheet, and finally to assemble the battery cell. The battery cell then needs to go through the liquid injection step, which usually takes a long time to completely infiltrate the electrode sheet. After the liquid injection operation, the battery cell is usually sealed and allowed to stand for full infiltration. If the electrolyte does not fully infiltrate the electrode sheet, it will cause a series of problems such as high battery resistance and short service life. Therefore, the infiltration time is extended to ensure that the battery cell is fully infiltrated, which directly affects the time cost of battery cell production.

[0005] In addition, high energy density batteries are the focus of research in recent years. High energy density lithium ion batteries often require high compaction density. The better the compaction of the electrode sheet, the higher the battery capacity. However, high compaction density will result in small porosity in the electrode sheet, which not only reduces the amount of electrolyte that can be absorbed by the electrode sheet, but also greatly reduces the infiltration efficiency of the electrolyte. Therefore, the liquid injection and infiltration step of high energy density batteries often requires a longer time, and there is still a situation where the electrode sheet is not fully infiltrated. These problems hinder the development of high energy density batteries to some extent.

[0006] In summary, accelerating the infiltration speed of the battery electrode sheet in the electrode sheet and fully infiltrating the electrode sheet in a shorter time is a very valuable research topic. SUMMARY

[0007] In view of the shortcomings and deficiencies of the prior art, the primary purpose of the present application is to provide an acrylate copolymer infiltrant.

[0008] Another purpose of the present application is to provide a preparation method of the above-mentioned acrylate copolymer infiltrant.

[0009] The present application further provides an electrode plate containing the above-mentioned impregnating agent.

[0010] The object of the present application is achieved by the following technical solutions.

[0011] An acrylate copolymer impregnating agent is obtained by copolymerization of acrylate monomers and ether monomers; the ether monomers are at least one of C1-C8 alkyl vinyl ether (molecular formula CH2=CH-OR, R is C1-C8 alkyl; such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, isobutyl vinyl ether, octyl vinyl ether, etc.) and polyethylene glycol allyl methyl ether (molecular formula CH2=CHCH2O(CH2CH2O) n CH3, n is an integer of 1-10).

[0012] Further, the acrylate monomers are at least one of (meth)acrylic acid, C1-C8 alkyl (meth)acrylate (such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl methacrylate, isooctyl acrylate, etc.), 2-methoxyethyl acrylate, 3-methacryloyloxypropyl methyl dimethoxy silane and 2-(dimethylamino)ethyl acrylate.

[0013] Further preferably, the acrylate monomers are at least one of C1-C8 alkyl (meth)acrylate, 3-methacryloyloxypropyl methyl dimethoxy silane and 2-(dimethylamino)ethyl acrylate.

[0014] More preferably, the acrylate monomers are a mixture of isooctyl acrylate, 3-methacryloyloxypropyl methyl dimethoxy silane and 2-(dimethylamino)ethyl acrylate; and the ether monomers are a mixture of butyl vinyl ether and isobutyl vinyl ether.

[0015] Further, the mass percentage content ratio of the acrylate monomers and the ether monomers is 57-76 wt.% of the acrylate monomers and 24-43 wt.% of the ether monomers. Specifically, the acrylate monomers can be 76 wt.%, 70 wt.%, 67 wt.%, 62 wt.%, 57 wt.% and the like; and the ether monomers can be 24 wt.%, 30 wt.%, 33 wt.%, 38 wt.%, 43 wt.% and the like. The copolymer impregnating agent obtained within the above-mentioned ratio range has better impregnating performance.

[0016] The preparation method of the above-mentioned acrylate copolymer impregnating agent comprises the following preparation steps:

[0017] (1) adding emulsifier into water and dispersing uniformly, then adding acrylic acid and / or acrylate monomer, ether monomer and crosslinking agent and mixing uniformly to obtain monomer pre-emulsion;

[0018] (2) adding initiator into water and dispersing uniformly to obtain initiator solution; under nitrogen protection, the initiator solution is heated to 60-80℃, then the monomer pre-emulsion is added dropwise to carry out polymerization reaction to obtain acrylate copolymer infiltrant.

[0019] Further, the emulsifier in step (1) is at least one of sodium dodecyl sulfate (K12), sodium lauryl alcohol polyoxyethylene ether sulfate (AES) and fatty alcohol polyoxyethylene ether (AEO), and the amount of the emulsifier added is 0.1-0.5wt.% of the total mass of the reaction monomers.

[0020] Further, the crosslinking agent in step (1) is a trifunctional acrylate compound, commonly used such as pentaerythritol triacrylate, trimethylolpropane triacrylate, propoxylated glycerol triacrylate, ethoxylated trimethylolpropane triacrylate, etc. The amount of the crosslinking agent added is 1-2wt.% of the total mass of the reaction monomers.

[0021] Further, the initiator in step (2) is potassium persulfate or ammonium persulfate, and the amount of the initiator added is 0.05-0.1wt.% of the total mass of the reaction monomers.

[0022] Further, the amount of water used in step (1) and step (2) is in the ratio of 1:3-5.

[0023] Further, the dropping time of the monomer pre-emulsion in step (2) is 1-2h, and the total time of the polymerization reaction is 2-8h (including the dropping time of the monomer pre-emulsion); after the completion of the polymerization reaction, the PH of the system is adjusted to 6-8, and deionized water is added to dilute and adjust the viscosity and solid content to 8-15wt.%.

[0024] The above preparation method is a semi-batch emulsion polymerization, and different viscosities of the final product can be obtained by controlling the dropping speed during the dropping process of the monomer pre-emulsion. If the dropping speed is too fast, it will lead to reaction gel, and water can be added to solve the gel problem during the reaction process. The obtained low-viscosity colorless transparent aqueous solution is convenient to use, and can be quickly dispersed during homogenization.

[0025] An electrode sheet containing the above acrylate copolymer infiltrant is prepared by the following method:

[0026] A slurry including a conductive additive, a binder, a dispersant, an acrylate copolymer infiltrant, an active material and water is coated on a current collector, and then an electrode sheet is obtained after drying, cutting and rolling.

[0027] Further preferably, the conductive additive is conductive carbon black; the binder is styrene-butadiene rubber (SBR); the dispersant is carboxymethyl cellulose (CMC); and the active material is graphite.

[0028] Further preferably, the content of the conductive additive in the slurry is 1.5 wt.% of the total mass of solid ingredients, the content of the acrylate copolymer infiltrant is 0.3-1.2 wt.% of the total mass of solid ingredients, and the total amount of the binder, the dispersant and the acrylate copolymer infiltrant added is not more than 3.5% of the total mass of solid ingredients. In the above-mentioned adding amount, the performance of the pole piece can be better ensured.

[0029] Compared with the prior art, the present application has the following advantages:

[0030] (1) The acrylate copolymer infiltrant of the present application can significantly improve the infiltration speed of the pole piece in the electrolyte while ensuring the performance of the pole piece. Specifically, the acrylate copolymer infiltrant can regulate the surface energy and enhance the wetting, and the "polar groups" (such as hydroxyl, carboxyl, ether bond) in the infiltrant molecules can improve the spreading of the electrolyte in the microporous structure by reducing the interfacial tension between the electrolyte and the electrode / separator, forming a monolayer adsorption film, thereby improving the infiltration speed of the pole piece in the electrolyte.

[0031] (2) The acrylate copolymer infiltrant of the present application is a low-viscosity colorless transparent aqueous solution, which can be quickly dispersed during the homogenization process. The microstructure of the copolymer infiltrant is reticular, and a colorless transparent elastic film is obtained after drying to remove water. The mass swelling rate of the film in the electrolyte can be up to 3120%.

[0032] (3) The existing infiltrant is added to the electrolyte, while the high-swelling acrylate copolymer infiltrant obtained by the present application can be applied during the homogenization process and used for pole piece production. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is a contact angle test result graph of the pole pieces of the experimental group and the control group in Example 1;

[0034] Figure 2 is a liquid absorption test result graph of the pole pieces of the experimental group and the control group in Example 1. DETAILED DESCRIPTION

[0035] The present application will be further described in detail below in conjunction with the embodiments and the drawings, but the embodiments of the present application are not limited thereto.

[0036] Example 1

[0037] (1) Take 0.5 g of emulsifier K12 (sodium dodecyl sulfate) and disperse it in 50 g of water. Add 1 g of propoxylated glycerol triacrylate to the dispersion. Add 80 g of a mixture of isooctyl acrylate, 3-methacryloxypropyl methyldimethoxysilane, and 2-(dimethylamino)ethyl acrylate (mass ratio of isooctyl acrylate, 3-methacryloxypropyl methyldimethoxysilane, and 2-(dimethylamino)ethyl acrylate is 1:2:1) to the dispersion. Add 25 g of a mixture of butyl vinyl ether and isobutyl vinyl ether (mass ratio of the two monomers is 1:1) to the dispersion and disperse thoroughly to obtain a monomer pre-emulsion.

[0038] (2) Take 0.1 g of potassium persulfate as an initiator and disperse it in 200 g of deionized water. Under stirring, introduce nitrogen gas at the bottom for 30 min to obtain an initiator aqueous solution. Under nitrogen protection, heat to 70°C, then add the monomer pre-emulsion to the initiator aqueous solution. The monomer pre-emulsion is added at a constant rate, the dropping time is 2 h, and the total reaction time is 6 h. Then cool to room temperature and add appropriate amount of glacial acetic acid to adjust the pH to 6-8. Dilute with 500 g of deionized water to adjust the viscosity, and obtain a colorless transparent high-swelling acrylate copolymer infiltrant (YY36-P).

[0039] The infiltrant obtained in this example is dried overnight at 80°C to obtain a colorless transparent elastic film. The film is then soaked in excess electrolyte (mass ratio of lithium hexafluorophosphate is 40%, mass ratio of EC+DMC+EMC three carbonates is 60%) at 70°C for 24 h. Record the mass of the polymer before and after soaking and calculate the swelling rate of the infiltrant, which is 3150%.

[0040] The infiltrant obtained in this example is prepared into a negative electrode sheet by homogenization. The homogenized negative electrode slurry of 1.5% conductive carbon black SP, 2% SBR, 0.8% CMC, 0.7% acrylate copolymer infiltrant (YY36-P), 95% graphite, and water is coated on a current collector. During the homogenization process, first disperse CMC and infiltrant YY36-P, then disperse conductive carbon black SP, then disperse graphite, and finally disperse SBR. The solid content of the negative electrode slurry is 50%. The current collector is a copper foil. Then after drying, cutting, and rolling, the negative electrode sheet (experimental group) is obtained. The negative electrode slurry composition of the control group is 1.5% CMC + 2% SBR + 1.5% SP + 95% graphite.

[0041] Electrode sheet contact angle test: The rolled electrode sheet was placed on a glass slide, and the contact angle of 10 μL electrolyte at the instant of contact with the electrode sheet and the time required for complete absorption of 10 μL electrolyte were recorded. The contact angle test results of the experimental group and the control group electrode sheets of this example are shown in Figure 1. As can be seen from Figure 1, the average contact angle of the experimental group was 23.3°, and the average contact angle of the control group was 28.3°. It was observed that the contact angle of the electrolyte with the electrode sheet of the experimental group was significantly smaller than that of the control group, with a difference of 5°. The time required for complete absorption of 10 μL electrolyte by the electrode sheet of the experimental group was 18.7 s, and the time required for complete absorption of 10 μL electrolyte by the electrode sheet of the control group was 32.2 s, with a difference of 13.5 s.

[0042] Electrode sheet liquid absorption test: The electrode sheets of the experimental group and the control group were cut to the same length, width and height, and then fixed to the bottom of a glass slide so as to hang vertically as much as possible. The top of the glass slide was fixed to the top of an expansion cylinder, and the bottom of the electrode sheet was made to just contact the bottom of the expansion cylinder. Electrolyte was added so as to just soak the bottom of the electrode sheet, and then the rate of electrolyte absorption by the electrode sheets of the two groups was recorded over the same period of time (20 min). The test method and test results are shown in Figure 2. It was observed that the rate of electrolyte absorption by the electrode sheet of the experimental group was significantly faster than that of the control group. After 25 minutes, the height of the electrolyte absorbed by the negative electrode sheet of the experimental group was 9 cm, and the height of the electrolyte absorbed by the negative electrode sheet of the control group was 6 cm.

[0043] Battery pack liquid absorption test: The battery packs composed of the electrode sheets of the experimental group and the control group were placed in an expansion cylinder, and electrolyte was added. After soaking for the same period of time, the battery packs were removed, and the electrode sheets were observed for the rate of electrolyte absorption. It was observed that the rate of electrolyte absorption by the negative electrode sheet of the experimental group was significantly faster than that of the control group.

[0044] Comparative Example 1 and Examples 2 to 15

[0045] An acrylate copolymer impregnant was prepared according to the raw material composition of Table 1 below, and the remaining conditions were the same as in Example 1.

[0046] Table 1

[0047] Example 16

[0048] Prepared according to the method described in Example 1, except that the amount of emulsifier K12 added was 0.105 g.

[0049] Example 17

[0050] Prepared according to the method described in Example 1, except that the amount of potassium persulfate added was 0.0525 g.

[0051] Example 18

[0052] Prepared according to the method described in Example 1, except that the ratio of water used in step (1) to step (2) was 60 g: 180 g.

[0053] Example 19

[0054] Prepared according to the method described in Example 1, except that the ratio of water used in step (1) to step (2) was 40 g: 200 g.

[0055] Example 20

[0056] Prepared according to the method described in Example 1, except that the length of time for dropping in step (2) was 1 h, and the total reaction time was 2 h.

[0057] The swelling rate of the infiltrating agent obtained in Examples 2-20 and the prepared negative electrode sheet were tested according to the method of Example 1, and the contact angle and liquid absorption were tested, and the test results are shown in Table 2.

[0058] Table 2

[0059] As can be seen from the results in Table 2, the acrylate copolymer infiltrating agent of the present application can significantly improve the infiltration speed of the electrode sheet in the electrolyte. As can be seen from the comparison results of Comparative Example 1 and Example 1, if no ether monomer is added, the affinity of the polymer to the electrolyte may be reduced, and the swelling of the polymer in the electrolyte is reduced. The electrolyte is mainly composed of lithium salt and various carbonic acid compounds, and therefore contains a large amount of carbonic acid groups. The acrylate and ether substances together provide similar functional groups to the carbonic acid, and the lipids and ether substances are beneficial to the transmission of lithium ions, so the polymer copolymerized from the two has high affinity to the electrolyte, and can improve the infiltration performance. At the same time, as can be seen from the results of Example 6 and Example 9, the polymer obtained by selecting the combination of acrylic acid or 2-propenoic acid-2-methoxy ethyl ester and ether monomer has slightly poorer infiltration performance than the combination of other acrylate monomers and ether monomers, and the reason is also due to the difference in the affinity of the polymer copolymerized from different monomers to the electrolyte. As can be seen from the comparison results of Table 2 and Example 1, when the acrylate monomer is selected as a mixture of isooctyl acrylate, 3-methyl acryloyl oxy propyl methyl dimethoxy silane and 2-(dimethyl amino) ethyl acrylate, and the ether monomer is selected as a mixture of butyl vinyl ether and isobutyl vinyl ether, the infiltration performance of the obtained copolymer infiltrating agent is the best.

[0060] Examples 21-26

[0061] The negative electrode sheets were prepared according to the formulations in Table 3 using the infiltrating agent obtained in Example 1, and the remaining conditions not listed were the same as in Example 1.

[0062] Table 3

[0063] The negative electrode sheets prepared in Examples 21 to 26 were subjected to contact angle test and liquid absorption test, respectively, according to the method of Example 1, and the test results are shown in Table 4 below.

[0064] Table 4

[0065] As can be seen from the results in Table 4, the acrylate copolymer impregnant of the present application can significantly improve the impregnation speed of the electrode sheet in electrolyte, and the improvement effect is more significant when the content of the acrylate copolymer impregnant is in the range of 0.3 to 1.2 wt.% of the total mass of solid components.

[0066] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited to the above examples, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application should be equivalent replacement methods, and are all included in the protection scope of the present application.

Claims

1. An acrylate copolymer impregnant characterized in that, obtained by a copolymerization reaction of an acrylic acid and / or an acrylic ester monomer and an ether monomer; the ether monomer is at least one of C1-C8 alkyl vinyl ether and polyethylene glycol allyl methyl ether.

2. The acrylate copolymer impregnant according to claim 1, characterized in that, The acrylic acid and / or acrylic ester monomer is at least one of (meth)acrylic acid, C1-C8 alkyl (meth)acrylate, 2-methoxyethyl acrylate, 3-methacryloxypropyl methyldimethoxysilane, and 2-(dimethylamino)ethyl acrylate.

3. The acrylate copolymer impregnant according to claim 1 or 2, characterized in that, The acrylic acid and / or acrylic ester monomer is at least one of C1-C8 alkyl (meth)acrylate, 3-methacryloxypropyl methyldimethoxysilane, and 2-(dimethylamino)ethyl acrylate.

4. The acrylate copolymer impregnant according to any one of claims 1 to 3, characterized in that, The acrylic acid and / or acrylic ester monomer and the ether monomer have a mass percentage ratio of 57-76 wt.% of the acrylic acid and / or acrylic ester monomer and 24-43 wt.% of the ether monomer.

5. The method of producing the acrylate-based copolymer sizing agent according to any one of claims 1 to 4, characterized by, The preparation steps include: (1) uniformly dispersing an emulsifier in water, and then uniformly mixing an acrylic acid and / or an acrylic ester monomer, an ether monomer, and a crosslinking agent to obtain a monomer pre-emulsion; (2) uniformly dispersing an initiator in water to obtain an initiator solution; under nitrogen protection, the initiator solution is heated to 60-80°C, and then the monomer pre-emulsion is added dropwise to perform a polymerization reaction to obtain an acrylic ester copolymer infiltrant.

6. The method for preparing an acrylate copolymer wetting agent according to claim 5, characterized in that, The emulsifier in step (1) is sodium dodecyl sulfate, and the emulsifier is added in an amount of 0.1-0.5 wt.% of the total mass of the reaction monomers.

7. The method of preparing an acrylate copolymer impregnant according to claim 5 or 6, characterized in that, The crosslinking agent in step (1) is a trifunctional acrylic ester compound, and the crosslinking agent is added in an amount of 1-2 wt.% of the total mass of the reaction monomers.

8. The method of preparing an acrylate copolymer impregnant according to any one of claims 5 to 7, characterized in that, The initiator in step (2) is potassium persulfate or ammonium persulfate, and the initiator is added in an amount of 0.05-0.1 wt.% of the total mass of the reaction monomers.

9. The method of preparing an acrylate copolymer impregnant according to any one of claims 5 to 8, characterized in that, The water in steps (1) and (2) is used in a ratio of 1:3-5.

10. The method of preparing an acrylate copolymer impregnant according to any one of claims 5 to 9, characterized in that, The monomer pre-emulsion in step (2) is added dropwise for 1-2 h, and the total polymerization reaction time is 2-8 h; after the polymerization reaction is completed, the system PH is adjusted to 6-8, and deionized water is added to dilute and adjust the viscosity and the solid content to 8-15 wt.%.

11. An electrode sheet containing the acrylic acid ester-based copolymer impregnant according to any one of claims 1 to 4, characterized by The slurry including a conductive additive, a binder, a dispersant, the acrylic ester copolymer infiltrant, an active material, and water is coated on a current collector, and then dried, cut, and rolled to obtain an electrode sheet. The conductive additive is conductive carbon black; the binder is styrene-butadiene rubber; the dispersant is carboxymethyl cellulose; and the active material is graphite.

12. The electrode pad of claim 11, wherein The content of the conductive additive in the slurry is 1.5 wt.% of the total mass of the solid components, the content of the acrylic ester copolymer infiltrant is 0.3-1.2 wt.% of the total mass of the solid components, and the total amount of the binder, the dispersant, and the acrylic ester copolymer infiltrant does not exceed 3.5% of the total mass of the solid components.

13. The electrode pad according to claim 11 or 12, characterized in that ​

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