A hydroxyl fluoralkyl arene derivative modified adhesive, its preparation method and application

Abstract

The application discloses a kind of hydroxyl fluorine alkyl aromatic hydrocarbon derivatives modified binder and its preparation method and application, the binder is prepared by crosslinking of acrylic acid, epoxide chloropropane and p-hydroxy trifluoroalkyl styrene.The lipophilic group trifluoroalkyl and hydrophilic group hydroxyl (can form hydrogen bond between slurry) in the binder of the application, so that the hydrophobicity of polymer to slurry is regulated, can significantly improve the adhesion between binder and active material.The branched chain of the binder of the application enhances the structural stability of molecule, and increases the viscosity and suspensibility of slurry, so that when it is applied as binder in lithium battery negative electrode, electrode structure becomes more stable.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of high polymer materials, and particularly relates to a hydroxyl fluorine alkyl aromatic hydrocarbon derivative modified adhesive as well as a preparation method and application thereof. BACKGROUND

[0002] Lithium ion batteries are widely used in new energy vehicles, energy storage devices, consumer electronics and other fields due to their high energy density, long cycle life, flexible size design, and clean and pollution-free characteristics, and are one of the most competitive chemical batteries at present.

[0003] With the continuous development of the lithium ion battery industry, the performance requirements of the adhesive are also continuously improved. The adhesive is a key auxiliary material for lithium ion batteries, and its amount accounts for 5-8% of the positive and negative active materials. Its main function is to connect the active material, the conductive agent and the current collector, so that the active material, the conductive agent and the current collector have connectivity. In the charging and discharging process, it can provide sufficient adhesive strength to ensure that the active material does not fall off and fail during battery production, use (storage, cycle) process.

[0004] At present, the widely used adhesives mainly include polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC). In addition, polyacrylic acid (PAA), polyacrylonitrile (PAN) and polyacrylate and other water-based adhesives also occupy a certain market. The adhesives have limited bonding strength, wear resistance and low temperature resistance, and further improvement is needed to improve their chemical stability and thermal stability during battery cycle.

[0005] The application of lithium ion batteries is continuously developing towards high energy density, high output and wider temperature range, and therefore, it is urgent to develop an adhesive with more excellent performance. SUMMARY

[0006] One of the purposes of the present application is to provide a preparation method of a hydroxyl trifluoroalkyl aromatic hydrocarbon modified adhesive. The hydroxyl fluorine alkyl aromatic hydrocarbon modified adhesive contains lipophilic and hydrophilic groups and branched structures, so that it has excellent adhesion.

[0007] Another purpose of the present application is to provide the hydroxyl trifluoroalkyl aromatic hydrocarbon modified adhesive and its application.

[0008] To achieve the above-mentioned purposes of the application, the present application provides the following technical solutions.

[0009] A preparation method of a hydroxyl trifluoroalkyl aromatic hydrocarbon derivative modified adhesive, comprising the following steps:

[0010] 1) a first mixed solution is prepared by cross-linking carboxyl-containing monomer A, epichlorohydrin monomer B and hydroxyl-containing trifluoroalkyl aromatic monomer C under the action of an initiator;

[0011] 2) the first mixed solution is subjected to a neutralization reaction under the action of a neutralizing agent, the pH value and the content of non-volatile matter are adjusted, and finally the adhesive is obtained.

[0012] In a specific embodiment, the carboxyl-containing monomer A comprises one or more of acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid and fumaric acid, preferably acrylic acid.

[0013] In a specific embodiment, the hydroxyl-containing fluorine alkyl aromatic monomer C comprises one or more of p-hydroxy trifluoroalkyl styrene, o-hydroxy trifluoroalkyl styrene, p-hydroxy trifluoroalkyl phenyl acrylate and p-hydroxy trifluoroalkyl phenyl methacrylate, preferably p-hydroxy trifluoroalkyl styrene.

[0014] In a specific embodiment, the carboxyl-containing monomer A is added in an amount of 10-30 wt%, for example 15 wt%, 17 wt%, 20 wt%, 23 wt%, 25 wt%, 28 wt% and the like, based on the total mass of all monomers, the epichlorohydrin monomer B is added in an amount of 20-40 wt%, for example 20 wt%, 23 wt%, 25 wt%, 28 wt%, 30 wt%, 35 wt%, 37 wt%, 39 wt% and the like, and the hydroxyl-containing fluorine alkyl styrene monomer C is added in an amount of 40-50 wt%, for example 41 wt%, 43 wt%, 45 wt%, 46 wt%, 48 wt%, 49 wt% and the like.

[0015] In a specific embodiment, the initiator is a thermal initiator and / or an oxidation-reduction initiator; preferably, the initiator is one or more of di-tert-butyl peroxide, ammonium sulfate, sodium persulfate, potassium persulfate, sodium metabisulfite and sodium bisulfite.

[0016] In a specific embodiment, the carboxyl-containing monomer A, the epichlorohydrin monomer B and the hydroxyl-containing trifluoroalkyl aromatic monomer C and water are mixed, and a polymerization reaction is carried out under the catalysis of an aqueous solution of an initiator to obtain a first mixed solution.

[0017] In a specific embodiment, the mass ratio of all monomers and the initiator is (100-2000):(1-15), for example 100:1, 1200:10, 2000:15, 100:15, 2000:1, 1500:5 and the like.

[0018] In one specific implementation, the initiator aqueous solution is added dropwise over a period of 1-2 hours, such as 1.1 hours, 1.3 hours, 1.5 hours, 1.6 hours, 1.8 hours, or 1.9 hours. The reaction temperature during addition is 30-70°C, such as 40°C, 50°C, 60°C, or 65°C. The concentration of the initiator aqueous solution is not particularly limited; it is sufficient to dissolve the initiator in an appropriate amount of water to prepare a solution for easy dropwise addition.

[0019] In one specific implementation, in step 2), the temperature of the first mixture is raised to 50-90°C before neutralization, for example, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 82°C, 85°C, 90°C, etc.

[0020] In one specific embodiment, the neutralizing agent is an inorganic alkali metal compound, preferably one or more of sodium carbonate, sodium hydroxide, potassium carbonate, potassium hydroxide, lithium carbonate, and lithium hydroxide; preferably, the pH of the neutralized solution is 6-9, for example, 7 or 8.

[0021] In one specific implementation, the pH value and the content of non-volatile components are adjusted, and after neutralization, the solution is cooled to 20-25°C to finally obtain the modified binder. The modified binder has a solid content of 2-10 wt%, such as 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, etc.; and the number average molecular weight of the modified binder is 400,000-500,000, such as 410,000, 420,000, 430,000, 440,000, 450,000, 460,000, 470,000, 480,000, 490,000, 500,000, etc.

[0022] On the other hand, the binder modified with hydroxytrifluoroalkyl aromatic hydrocarbon derivatives prepared by the aforementioned preparation method.

[0023] On another aspect, the application of the hydroxytrifluoroalkyl aromatic derivative modified binder prepared by the aforementioned preparation method or the aforementioned modified binder in the lithium-ion battery anode, preferably, the modified binder accounts for 0.3 to 2 wt% of the total dry powder slurry, and is used in the lithium-ion battery anode.

[0024] Compared with the prior art, the modified binder of the present invention has the following beneficial effects:

[0025] The hydroxyl fluorine alkyl aromatic hydrocarbon modified binder provided by the present application is a styrene derivative containing a hydroxyl fluorine alkyl group, wherein the fluorine alkyl group is a lipophilic group, and the hydroxyl group is a hydrophilic group, so that the polymer controls the hydrophilic and hydrophobic properties of the slurry. In the preparation of the slurry, strong intermolecular forces are formed between the active material (graphite, silicon-carbon, silicon, etc.) and the conductive agent, which can significantly improve the adhesion between the negative electrode materials. At the same time, the binder contains abundant carboxyl, hydroxyl and carboxylate groups, which not only enhances the strength of the slurry itself, but also improves the interaction between the slurry and the current collector. The epoxy chloropropane mainly plays a role in connecting the small molecule monomer A and the macromolecular monomer C. The branched chain on the molecular chain of the binder makes the structure of the binder more stable, and also leaves more space for the negative electrode to flow more smoothly in the process of lithium intercalation / deintercalation, thereby improving the battery performance. DETAILED DESCRIPTION

[0026] In order to better understand the technical solutions of the present application, the following examples will further illustrate the method provided by the present application, but the present application is not limited to the listed examples, and any other known changes within the scope of the claims of the present application should also be included.

[0027] The main raw materials involved in the following examples are as follows in Table 1:

[0028]

[0029]

[0030] Unless otherwise specified, other chemical reagents used in each example are purchased from the market, and the purity is analytical pure.

[0031] Example 1

[0032] (1) 1.2 Kg of deionized water was added to a 3L round-bottom flask, and the temperature was raised to 50℃;

[0033] (2) 60g of acrylic acid, 40g of epoxy chloropropane, 100g of p-hydroxy trifluoromethyl styrene and 200g of water were mixed and stirred until dissolved;

[0034] (3) Nitrogen was passed for half an hour to reduce the oxygen content of the solution to below 5%, to avoid the inhibitory effect of oxygen on the early stage of the reaction;

[0035] (4) Prepare an aqueous solution of ammonium persulfate (0.3g of ammonium persulfate dissolved in 25g of deionized water) and an aqueous solution of sodium pyrosulfite (0.2g of ammonium persulfate dissolved in 25g of deionized water);

[0036] (5) The solutions prepared in steps (2) and (4) were added to the round-bottom flask simultaneously, and the dropping time was 1h;

[0037] (6) After the end of dropping, the temperature is increased to 70°C, sodium carbonate aqueous solution is added to adjust the pH of the solution to 7.0, after neutralization, the temperature is decreased to 25°C, and the solid content of the solution is adjusted to 5wt% to obtain the target modified binder.

[0038] Example 2

[0039] Similar to the method of Example 1, except that the types and amounts of the three monomers are 50g crotonic acid, 60g epichlorohydrin, and 90g p-hydroxy trifluoromethyl styrene, the polymerization reaction dropping time is 2h, and the pH is adjusted to 9.

[0040] Example 3

[0041] Similar to the method of Example 1, except that the types and amounts of the two monomers are 20g maleic acid and 80g epichlorohydrin, the initiator is a thermal initiation system (ammonium persulfate aqueous solution, 0.3g dissolved in 25g deionized water), the reaction temperature is increased to 70°C, and the solid content of the target binder is adjusted to 10wt%.

[0042] Example 4

[0043] Similar to the method of Example 1, except that the types and amounts of the three monomers are 60g acrylic acid, 60g epichlorohydrin, and 80g p-hydroxy trifluoroalkyl styrene, the initiator is adjusted to ammonium persulfate aqueous solution (0.9g ammonium persulfate dissolved in 25g deionized water) and sodium metabisulfite aqueous solution (0.6g ammonium persulfate dissolved in 25g deionized water), the neutralization temperature is increased to 90°C, and the neutralizing agent is sodium hydroxide.

[0044] Comparative Example 1

[0045] Similar to the method of Example 1, monomer B is adjusted to vinyl chloride.

[0046] Comparative Example 2

[0047] Similar to the method of Example 1, monomer C is adjusted to styrene.

[0048] Test Method

[0049] The binder prepared by the above method is applied to the lithium battery negative electrode sheet, and the steps are as follows:

[0050] First, the negative active material graphite: conductive carbon black sp: thickener CMC: binder = 97.0:1.2:0.3:1.5 ratio according to the formula, CMC is added to 120 parts of deionized water, high speed stirring for 15 minutes, then sp, graphite and binder are added in turn, and high speed stirring is needed after each material is added to ensure mixing. After sieving through a 200 mesh nylon screen, the negative electrode slurry is obtained. Then, the prepared negative electrode slurry is uniformly coated on the current collector (copper foil) using a coating machine, the coating thickness is 100 μm, then dried in a 110°C oven for 5 minutes, and then rolled three times by a roller to obtain a negative electrode sheet with a thickness of 70 μm. Finally, the electrode sheet is cut into a length of 200 mm and a width of 20 mm using a cutting knife, and the peel strength test is performed.

[0051] Peel strength evaluation: the cut electrode sheet is tested for peel strength using a Jianjia tensile testing machine. The specific operation is as follows: in a constant temperature and humidity chamber, the cut electrode sheet is fixed on a smooth and clean stainless steel plate using a 150 mm wide 20 mm 3M double-sided tape, then the steel plate is fixed on the base of the tensile testing machine, the copper foil without tape is clamped using the probe of the tensile testing machine, then the base of the tensile testing machine is pulled at a speed of 5 cm / min, and the sensor measures the peel force during the whole process. The average value of 5 parallel samples is the final peel strength. Peel force = computer reading / 0.015, unit: N / m.

[0052] Product viscosity test: Brookfield DV2T model viscosity tester, 64# rotor, 12 rpm, constant temperature (25±0.5°C), rotor groove and liquid surface level, read after the reading is stable (no climbing phenomenon), if there is a climbing phenomenon, record the data before climbing, test each sample 3 times, take the average value.

[0053] Slurry stability test: the prepared slurry is placed at room temperature for 5 days, the solid content at the top and bottom of the slurry is tested, the stratification of the slurry is observed, and the stability of the slurry is determined.

[0054] The application performance test of the modified binder of the examples and comparative examples in the lithium battery negative electrode sheet is as follows:

[0055]

[0056] As can be seen from the results in the table, examples 1-4, due to containing hydroxyl group, trifluoromethyl group and branched chain, exhibit excellent viscosity and superior adhesion. Comparative example 1 reduces the amount of hydroxyl group contained in the polymer, and comparative example 2 eliminates trifluoromethyl group and branched chain, both of which operations reduce the viscosity of the adhesive and the peel force performance is also poor. From the preparation of the slurry, the slurry dispersibility of examples 1-4 and comparative examples 1-2 is normal, but after three days of static storage, the solid content difference between the upper and lower layers of comparative examples 1-2 is obvious, the appearance shows stratification, and the stability is poor, while the hydroxyl group and trifluoromethyl group contained in examples 1-4 have a strong hydrophobicity control ability on the slurry, forming effective hydrophobic association, enhancing the suspension of the slurry.

[0057] The applicant declares that the above description is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and it should be understood by those skilled in the art that any changes or replacements within the technical scope disclosed by the present application can be easily thought of by those skilled in the art, and all fall within the protection scope and disclosure scope of the present application.

Claims

1. A method for producing a binder modified with a hydroxytrifluoroalkylarene derivative, characterized by, The method comprises the following steps: 1) preparing a first mixed solution by cross-linking carboxyl-containing monomer A, epichlorohydrin monomer B and hydroxyl-containing trifluoroalkyl aromatic monomer C under the action of an initiator; 2) adjusting the pH value and the content of non-volatile matter by neutralizing the first mixed solution under the action of a neutralizing agent, and finally obtaining the adhesive.

2. The production method according to claim 1, characterized by, The carboxyl-containing monomer A comprises one or more of acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid and fumaric acid.

3. The production method according to claim 2, characterized by, The carboxyl-containing monomer A is acrylic acid.

4. The production method according to claim 1, characterized by, The hydroxyl-containing fluorine alkyl aromatic monomer C comprises one or more of p-hydroxytrifluoroalkylstyrene, o-hydroxytrifluoroalkylstyrene, p-hydroxytrifluoroalkyl phenyl acrylate and p-hydroxytrifluoroalkyl phenyl methacrylate.

5. The preparation method according to claim 4, characterized in that, The hydroxyl-containing fluorine alkyl aromatic monomer C is p-hydroxytrifluoroalkylstyrene.

6. The method of any one of claims 1 to 5, wherein, The carboxyl-containing monomer A accounts for 10-30 wt% of the total mass of all monomers, the epichlorohydrin monomer B accounts for 20-40 wt%, and the hydroxyl-containing fluorine alkyl styrene monomer C accounts for 40-50 wt%.

7. The method of any one of claims 1 to 5, wherein the method further comprises the step of: The initiator is a thermal initiator and / or an oxidation-reduction initiator.

8. The production method according to claim 7, characterized by, The initiator is one or more of di-tert-butyl peroxide, ammonium sulfate, sodium persulfate, potassium persulfate, sodium metabisulfite and sodium bisulfite.

9. The method of claim 1, wherein, The method comprises mixing carboxyl-containing monomer A, epichlorohydrin monomer B and hydroxyl-containing trifluoroalkyl aromatic monomer C with water, and performing a polymerization reaction under the catalytic action of an aqueous solution of an initiator to obtain a first mixed solution.

10. The method of claim 9, wherein, The mass ratio of all monomers and the initiator is (100-2000):(1-15).

11. The method of claim 10, wherein, The aqueous solution of the initiator is added dropwise.

12. The method of claim 11, wherein, The dropwise addition time is 1-2 h, and the reaction temperature during dropwise addition is 30-70°C.

13. The method of claim 1, wherein, In step 2), the temperature of the first mixed solution is increased to 50-90°C before neutralization.

14. The method of claim 13, wherein, The neutralizing agent is an inorganic alkali metal compound.

15. The preparation method according to claim 14, characterized in that, The neutralizing agent is selected from one or more of sodium carbonate, sodium hydroxide, potassium carbonate, potassium hydroxide, lithium carbonate and lithium hydroxide.

16. The method of claim 14, wherein, The pH value of the solution after neutralization is 6-9; and / or The solid content of the modified adhesive is 2-10 wt%.

17. A hydroxytrifluoroalkyl aromatic derivative modified adhesive prepared by the preparation method of any one of claims 1-16.

18. Use of the hydroxytrifluoroalkyl aromatic derivative modified adhesive prepared by the preparation method of any one of claims 1-16 or the modified adhesive of claim 17 in a lithium ion battery anode.

19. Use according to claim 18, characterized in that, The modified adhesive accounts for 0.3-2 wt% of the total dry powder slurry for a lithium ion battery anode.

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