Functional coating material for lithium ion battery diaphragm, preparation method of functional coating material and battery diaphragm

Abstract

The invention discloses a functional coating material for a lithium ion battery diaphragm, a preparation method of the functional coating material and the battery diaphragm, and belongs to the technical field of diaphragm materials. The functional coating material for the lithium ion battery diaphragm comprises the following raw materials in parts by weight: 30-40 parts of an MOF (Zn) porous ceramic material; 1 to 1.5 parts of sodium hexametaphosphate modified bentonite; 1 to 2 parts of sodium carboxymethyl cellulose; 4-6 parts of a binder; 0.5-2 parts of a defoaming agent; 45 to 50 parts of water; the organic ligand of the MOF (Zn) is 3-amino-1, 2, 4-triazole and 4-(trifluoromethyl)-1H-imidazole, and the organic ligand of the MOF (Zn) is 3-amino-1, 2, 4-triazole and 4-(trifluoromethyl)-1H-imidazole. The preparation method comprises the following steps: (1) performing primary mixing on sodium carboxymethyl cellulose and water to obtain a sodium carboxymethyl cellulose solution, and then performing secondary mixing on the sodium carboxymethyl cellulose solution, sodium hexametaphosphate modified bentonite, water and a defoaming agent to obtain mixed slurry; and (2) mixing the mixed slurry obtained in the step (1) with the MOF (Zn) porous ceramic material and a binder to obtain the functional coating material. After a diaphragm is coated with the prepared slurry, the heat resistance and flame retardance of the diaphragm can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of diaphragm materials, and in particular to a functional coating material for lithium-ion battery diaphragms, a preparation method thereof, and a battery diaphragm. Background Art

[0002] Lithium-ion batteries, a crucial component of electric vehicles, are experiencing increasing demand. Separators, a key component of lithium-ion batteries, have a performance that directly impacts their capacity, cycle life, and safety. Therefore, the development and research of high-performance separators is imperative, with safety performance being particularly crucial.

[0003] Currently, the heat resistance of ceramic separators for lithium-ion batteries on the market is limited. With the gradual development of the lithium-ion battery field, the energy density of the battery increases, the charge and discharge current becomes larger, and the temperature inside the battery rises. This has placed increasing demands on the heat resistance of ceramic separators. Therefore, it is of great significance to prepare ceramic separators for lithium-ion batteries that can withstand higher temperatures.

[0004] Patent publication number CN106519742B discloses a flame-retardant ceramic modified slurry and a lithium-ion battery separator coated with the slurry. This patent utilizes a silane coupling agent to pre-treat the surface of inorganic particles and a flame retardant to form a flame-retardant ceramic modified powder. The powder is then stirred and ball-milled in a solvent, followed by the addition of a binder and a thickener, followed by high-speed stirring to form a flame-retardant ceramic modified slurry. The flame-retardant ceramic modified slurry is then coated onto a polyolefin microporous membrane that has been surface-modified with low-temperature plasma to form a lithium-ion battery separator. While this solves the problem of the separator's poor flame retardancy, the dispersion of the ceramic particles needs to be improved to further enhance the separator's overall performance. Summary of the Invention

[0005] The present invention provides a functional coating material for lithium ion battery separator and a preparation method thereof, and a battery separator, which can solve the problem in the prior art that the dispersibility of ceramic particles needs to be improved.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A functional coating material for lithium-ion battery separators, comprising the following raw materials in parts by weight:

[0008] MOF(Zn)@porous ceramic material 30-40 parts;

[0009] 1-1.5 parts of sodium hexametaphosphate modified bentonite;

[0010] 1-2 parts of sodium carboxymethyl cellulose;

[0011] 4-6 parts of adhesive

[0012] 0.5-2 parts of defoaming agent;

[0013] 45-50 parts water;

[0014] The organic ligands of the MOF (Zn) are 3-amino-1,2,4-triazole and 4-(trifluoromethyl)-1H-imidazole.

[0015] Furthermore, the binder includes at least one of styrene-butadiene rubber, polyacrylate, polyacrylamide, polystyrene, and polyvinyl alcohol.

[0016] Furthermore, the defoaming agent includes at least one of GPES defoaming agent, higher alcohol, tributyl phosphate or dimethyl silicone oil.

[0017] Furthermore, the preparation method of the MOF(Zn)@porous ceramic material is:

[0018] S1: soaking the porous ceramic in anhydrous ethylenediamine and placing it at 150° C. for 24-48 hours. After the reaction is completed, washing it with deionized water 3-5 times until it is neutral, and drying it to obtain a pretreated porous ceramic;

[0019] The usage ratio of the porous ceramic and anhydrous ethylenediamine is 8g:50-60mL.

[0020] Surface modification by ethylenediamine adds active groups such as hydroxyl and amino groups to the surface of porous ceramics, activating the inherently inert porous ceramic surface, which will be beneficial to the loading and growth of MOFs on the ceramic surface.

[0021] S2: Dissolve zinc formate dihydrate, 3-amino-1,2,4-triazole, and 4-(trifluoromethyl)-1H-imidazole in DMF to obtain a MOF (Zn) precursor solution at room temperature; then add the pretreated porous ceramics and crystallize them at 100-120°C for 12-24 hours. After the reaction is completed, take them out and wash them with DMF and anhydrous ethanol for 3-5 times, and dry them at 120°C under vacuum for 24 hours to obtain MOF (Zn) @ porous ceramic material.

[0022] The usage ratio of zinc formate dihydrate, 3-amino-1,2,4-triazole, 4-(trifluoromethyl)-1H-imidazole, DMF, and pretreated porous ceramics is 1.9 g: 0.8-1.3 g: 1.4-2.7 g: 50-80 mL: 6 g.

[0023] Furthermore, in step S1, the porous ceramic particles include at least one of porous alumina, porous barium titanate, porous silica, porous titanium dioxide, porous silicon nitride, and porous silicon carbide.

[0024] Furthermore, the specific steps of modifying bentonite with sodium hexametaphosphate are:

[0025] The calcium-based bentonite is crushed and mixed with water, and then sodium hexametaphosphate is added. The mixed solution is shaken and dispersed to obtain sodium hexametaphosphate modified bentonite.

[0026] The dosage ratio of calcium bentonite, water and sodium hexametaphosphate is 10g:40-50mL:0.1-0.3g.

[0027] A method for preparing a functional coating material for a lithium-ion battery separator comprises the following steps:

[0028] (1) mixing sodium carboxymethyl cellulose and water to obtain a sodium carboxymethyl cellulose solution, and then mixing the sodium carboxymethyl cellulose solution with sodium hexametaphosphate-modified bentonite, water, and a defoaming agent to obtain a mixed slurry;

[0029] (2) Mixing the mixed slurry obtained in step (1) with the MOF(Zn)@porous ceramic material and a binder to obtain the functional coating material.

[0030] A battery separator comprises a base film and a ceramic coating formed on at least one side of the base film; the ceramic coating is made of the functional coating material described above or the functional coating material prepared by the preparation method described above.

[0031] Furthermore, the base film is a PE film or a PP film; the thickness of the base film is 2-5 μm.

[0032] Furthermore, the thickness of the ceramic coating is 0.5-3 μm.

[0033] Beneficial effects of the present invention:

[0034] 1. The present invention utilizes MOF(Zn)@porous ceramic materials and sodium hexametaphosphate-modified bentonite in the preparation of functional coating materials. In the MOF(Zn)@porous ceramic material, the MOF(Zn) grows on the ceramic surface, addressing the poor dispersibility of the ceramic and improving the overall performance of the diaphragm. The sodium hexametaphosphate-modified bentonite reduces the tendency of bentonite particles to agglomerate by complexing the dissociated phosphate ions with the metal ions in the bentonite. Simultaneously, its anionic groups ionize in the aqueous slurry, imparting a negative charge to the surface. This creates a stable network through electrostatic repulsion and hydration expansion, preventing ceramic particle sedimentation and improving the overall performance of the diaphragm.

[0035] 2. The organic ligands of MOF(Zn) in the MOF(Zn)@ porous ceramic material are 3-amino-1,2,4-triazole and 4-(trifluoromethyl)-1H-imidazole. 3-amino-1,2,4-triazole exhibits flame retardancy, while the -CF3 group in 4-(trifluoromethyl)-1H-imidazole is thermally stable, inhibiting the high-temperature decomposition of the MOF ligand. Together with the triazole ring, it enhances the thermal stability of the MOF framework, thereby improving the heat resistance of the separator. Sodium hexametaphosphate-modified bentonite contains phosphorus, which also enhances the flame retardancy of the separator.

[0036] 3. Negative charge on the surface of sodium hexametaphosphate-modified bentonite and Zn at the defective sites of MOF 2+ Electrostatic adsorption occurs, promoting the uniform dispersion of the two in the matrix, and forming a stable network structure through physical cross-linking, thereby optimizing the mechanical strength of the separator and the electrolyte wettability DETAILED DESCRIPTION

[0037] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

[0038] Preparation Example 1

[0039] The preparation method of MOF(Zn)@ porous ceramic material is as follows:

[0040] S1: 8 g of porous alumina was immersed in 50 mL of anhydrous ethylenediamine and placed at 150 ° C for 24 h. After the reaction, it was washed with deionized water three times until neutral and dried to obtain pretreated porous ceramics;

[0041] S2: 1.9 g of zinc formate dihydrate, 0.8 g of 3-amino-1,2,4-triazole, and 1.4 g of 4-(trifluoromethyl)-1H-imidazole were dissolved in 50 mL of DMF to obtain a MOF(Zn) precursor solution at room temperature; then 6 g of pretreated porous ceramics were added and crystallized at 120°C for 24 h. After the reaction, the solution was taken out and washed with DMF and anhydrous ethanol 5 times, and dried at 120°C under vacuum for 24 h to obtain MOF(Zn)@porous ceramic material.

[0042] Preparation Example 2

[0043] The preparation method of MOF(Zn)@ porous ceramic material is as follows:

[0044] S1: 8 g of porous alumina was immersed in 60 mL of anhydrous ethylenediamine and placed at 150 ° C for 48 h. After the reaction, it was washed with deionized water five times until neutral and dried to obtain pretreated porous ceramics;

[0045] S2: 1.9 g of zinc formate dihydrate, 1.3 g of 3-amino-1,2,4-triazole, and 2.7 g of 4-(trifluoromethyl)-1H-imidazole were dissolved in 80 mL of DMF to obtain a MOF(Zn) precursor solution at room temperature; then 6 g of pretreated porous ceramics were added and crystallized at 120°C for 24 h. After the reaction, the solution was taken out and washed with DMF and anhydrous ethanol five times, and dried at 120°C under vacuum for 24 h to obtain MOF(Zn)@porous ceramic material.

[0046] Comparative Example 1

[0047] This comparative example differs from Preparation Example 1 only in that 4-(trifluoromethyl)-1H-imidazole is omitted. The specific steps are as follows:

[0048] S1: 8 g of porous alumina was immersed in 50 mL of anhydrous ethylenediamine and placed at 150 ° C for 24 h. After the reaction, it was washed with deionized water three times until neutral and dried to obtain pretreated porous ceramics;

[0049] S2: 1.9 g of zinc formate dihydrate and 0.8 g of 3-amino-1,2,4-triazole were dissolved in 50 mL of DMF to obtain a MOF(Zn) precursor solution at room temperature. 6 g of pretreated porous ceramics were then added and crystallized at 120°C for 24 h. After the reaction, the solution was taken out and washed with DMF and anhydrous ethanol five times, and dried at 120°C under vacuum for 24 h to obtain a MOF(Zn)@porous ceramic material.

[0050] Comparative Example 2

[0051] The only difference between this comparative example and Preparation Example 1 is that the MOF(Zn)@porous ceramic material is replaced by porous alumina.

[0052] Preparation Example 3

[0053] The specific steps of sodium hexametaphosphate modified bentonite are:

[0054] 10 g of calcium-based bentonite was crushed and mixed with 50 mL of water, and then 0.1 g of sodium hexametaphosphate was added. The mixed solution was shaken and dispersed to obtain sodium hexametaphosphate-modified bentonite.

[0055] Preparation Example 4

[0056] The specific steps of sodium hexametaphosphate modified bentonite are:

[0057] 10 g of calcium-based bentonite was crushed and mixed with 50 mL of water, and then 0.3 g of sodium hexametaphosphate was added. The mixed solution was shaken and dispersed to obtain sodium hexametaphosphate-modified bentonite.

[0058] Comparative Example 3

[0059] The only difference between this comparative example and Preparation Example 3 is that bentonite is used instead of sodium hexametaphosphate modified bentonite.

[0060] Example 1

[0061] A functional coating material for lithium-ion battery separators, comprising the following raw materials in parts by weight:

[0062] 30 parts of MOF(Zn)@porous ceramic material prepared in Preparation Example 1;

[0063] 1 part of sodium hexametaphosphate-modified bentonite prepared in Preparation Example 3;

[0064] 1 part of sodium carboxymethyl cellulose;

[0065] 4 parts of styrene-butadiene rubber

[0066] 0.5 parts of GPES defoamer;

[0067] 45 parts water.

[0068] Its preparation method is:

[0069] (1) mixing sodium carboxymethyl cellulose and water to obtain a sodium carboxymethyl cellulose solution, and then mixing the sodium carboxymethyl cellulose solution with sodium hexametaphosphate-modified bentonite, water, and a defoaming agent to obtain a mixed slurry;

[0070] (2) Mixing the mixed slurry obtained in step (1) with the MOF(Zn)@porous ceramic material and a binder to obtain the functional coating material.

[0071] The functional coating material is coated on one side of the PE film, and after drying, a battery separator is obtained. The thickness of the base film is 5 μm, and the thickness of the ceramic coating is 1 μm.

[0072] Example 2

[0073] A functional coating material for lithium-ion battery separators, comprising the following raw materials in parts by weight:

[0074] 35 parts of MOF(Zn)@porous ceramic material prepared in Preparation Example 1;

[0075] 1.3 parts of sodium hexametaphosphate-modified bentonite prepared in Preparation Example 3;

[0076] 1.5 parts of sodium carboxymethyl cellulose;

[0077] 5 parts of styrene-butadiene rubber

[0078] 1.5 parts of GPES defoamer;

[0079] 47 parts water.

[0080] Its preparation method is:

[0081] (1) mixing sodium carboxymethyl cellulose and water to obtain a sodium carboxymethyl cellulose solution, and then mixing the sodium carboxymethyl cellulose solution with sodium hexametaphosphate-modified bentonite, water, and a defoaming agent to obtain a mixed slurry;

[0082] (2) Mixing the mixed slurry obtained in step (1) with the MOF(Zn)@porous ceramic material and a binder to obtain the functional coating material.

[0083] The functional coating material is coated on one side of the PE film, and after drying, a battery separator is obtained. The thickness of the base film is 5 μm, and the thickness of the ceramic coating is 1 μm.

[0084] Example 3

[0085] A functional coating material for lithium-ion battery separators, comprising the following raw materials in parts by weight:

[0086] 40 parts of MOF(Zn)@porous ceramic material prepared in Preparation Example 1;

[0087] 1.5 parts of sodium hexametaphosphate-modified bentonite prepared in Preparation Example 3;

[0088] 2 parts of sodium carboxymethyl cellulose;

[0089] 6 parts of styrene-butadiene rubber

[0090] 2 parts of GPES defoamer;

[0091] 50 parts water.

[0092] Its preparation method is:

[0093] (1) mixing sodium carboxymethyl cellulose and water to obtain a sodium carboxymethyl cellulose solution, and then mixing the sodium carboxymethyl cellulose solution with sodium hexametaphosphate-modified bentonite, water, and a defoaming agent to obtain a mixed slurry;

[0094] (2) Mixing the mixed slurry obtained in step (1) with the MOF(Zn)@porous ceramic material and a binder to obtain the functional coating material.

[0095] The functional coating material is coated on one side of the PE film, and after drying, a battery separator is obtained. The thickness of the base film is 5 μm, and the thickness of the ceramic coating is 1 μm.

[0096] Example 4

[0097] The only difference between this embodiment and Example 3 is that the MOF(Zn)@porous ceramic material in Example 3 is replaced by the product prepared in Preparation Example 2.

[0098] Example 5

[0099] The only difference between this embodiment and embodiment 3 is that the sodium hexametaphosphate-modified bentonite in embodiment 3 is replaced by the product prepared in preparation example 4.

[0100] Comparative Example 1

[0101] The only difference between this comparative example and Example 1 is that the MOF(Zn)@porous ceramic material in Example 1 is replaced by the product prepared in Control Example 1.

[0102] Comparative Example 2

[0103] The only difference between this comparative example and Example 1 is that the MOF(Zn)@porous ceramic material in Example 1 is replaced by the product prepared in Control Example 2.

[0104] Comparative Example 3

[0105] The only difference between this comparative example and Example 1 is that the sodium hexametaphosphate-modified bentonite in Example 1 is replaced by the product prepared in Control Example 3.

[0106] Comparative Example 4

[0107] The only difference between this comparative example and Example 1 is that the MOF(Zn)@porous ceramic material in Example 1 is replaced by the product prepared in Control Example 2, and the sodium hexametaphosphate-modified bentonite in Example 1 is replaced by the product prepared in Control Example 3.

[0108] The ceramic diaphragms prepared in Examples 1 to 5 and Comparative Examples 1 to 4 were tested using the following test methods. The test results are shown in Table 1.

[0109] (1) Heat shrinkage: First cut 50×50mm 2 A ceramic diaphragm with a regular shape is placed in an oven and baked at 130°C for 1 hour. The length L and width W of the diaphragm are immediately taken out and measured. The shrinkage rate is calculated using the formula: η = (So-S1) / So = (1-LW / 2500) × 100%, where S1 is the area of ​​the diaphragm after baking and So is the area of ​​the cut diaphragm.

[0110] (2) Flame retardant performance: The limiting oxygen index is tested in accordance with the GBT / 2406.3-2022 test standard.

[0111] Table 1

[0112]

[0113]

[0114] As can be seen from Table 1, the heat resistance and flame retardancy of the diaphragms prepared in Examples 1 to 5 are better than those in Comparative Examples 1 to 4.

[0115] Compared with Example 1, Comparative Example 1 does not contain -CF3. From the results, it can be seen that the heat resistance and flame retardancy are reduced, indicating that -CF3 has thermal stability and -CF3 can cooperate with the flame retardant group to improve the flame retardancy of the diaphragm.

[0116] Compared with Example 1, Comparative Example 2 replaces MOF (Zn) @ porous ceramic material with porous alumina. The dispersibility of the porous ceramic material is reduced, the comprehensive performance is reduced, and 3-amino-1,2,4-triazole is lacking. 3-amino-1,2,4-triazole has flame retardant properties. The lack of MOF (Zn) causes the heat resistance and flame retardant properties of the diaphragm prepared in Comparative Example 2 to decrease.

[0117] Comparative Example 3 Compared with Example 1, the sodium hexametaphosphate modified bentonite is replaced by bentonite, and the comprehensive performance decreases, indicating that the sodium hexametaphosphate modified bentonite chelates with the metal ions in the bentonite through the dissociated phosphate ions, reduces the agglomeration tendency of the bentonite particles, and at the same time, its anionic groups are ionized in the aqueous slurry to make the surface negatively charged, and form a stable network through electrostatic repulsion and hydration expansion, preventing the ceramic particles from settling and improving the overall performance of the diaphragm. And the sodium hexametaphosphate modified bentonite contains phosphorus, which can also improve the flame retardant properties of the diaphragm. The sodium hexametaphosphate modified bentonite has a negative charge and has an adsorption effect on the metal ions in the MOF (Zn)@ porous ceramic material, which is conducive to the two being evenly dispersed in the matrix to form a cross-linked network, thereby improving the comprehensive performance of the diaphragm.

[0118] The porous ceramic material of Comparative Example 4 has the worst dispersibility and the worst overall performance.

[0119] The above disclosures are only a few specific embodiments of the present invention. However, the embodiments of the present invention are not limited thereto. Any changes that can be conceived by those skilled in the art should fall within the scope of protection of the present invention.

Claims

1. A functional coating material for lithium-ion battery separator, characterized in that: It includes the following raw materials in parts by weight: MOF(Zn)@porous ceramic material 30-40 parts; 1-1.5 parts of sodium hexametaphosphate modified bentonite; 1-2 parts of sodium carboxymethyl cellulose; 4-6 parts of adhesive 0.5-2 parts of defoaming agent; 45-50 parts water; The organic ligands of the MOF (Zn) are 3-amino-1,2,4-triazole and 4-(trifluoromethyl)-1H-imidazole.

2. The functional coating material for lithium-ion battery separator according to claim 1, characterized in that: The binder includes at least one of styrene-butadiene rubber, polyacrylate, polyacrylamide, polystyrene, and polyvinyl alcohol; the defoamer includes at least one of GPES defoamer, higher alcohol, tributyl phosphate, or dimethyl silicone oil.

3. The functional coating material for lithium-ion battery separator according to claim 1, characterized in that: The preparation method of the MOF(Zn)@porous ceramic material is as follows: S1: soaking the porous ceramic in anhydrous ethylenediamine and placing it at 150° C. for 24-48 hours. After the reaction is completed, washing it with deionized water 3-5 times until it is neutral, and drying it to obtain a pretreated porous ceramic; S2: Dissolve zinc formate dihydrate, 3-amino-1,2,4-triazole, and 4-(trifluoromethyl)-1H-imidazole in DMF to obtain a MOF (Zn) precursor solution at room temperature; then add the pretreated porous ceramics and crystallize them at 100-120°C for 12-24 hours. After the reaction is completed, take them out and wash them with DMF and anhydrous ethanol for 3-5 times, and dry them at 120°C under vacuum for 24 hours to obtain MOF (Zn) @ porous ceramic material.

4. The functional coating material for lithium-ion battery separator according to claim 3, characterized in that: In step S1, the usage ratio of the porous ceramic and anhydrous ethylenediamine is 8 g:50-60 mL.

5. The functional coating material for lithium-ion battery separator according to claim 3, characterized in that: In step S2, the usage ratio of zinc formate dihydrate, 3-amino-1,2,4-triazole, 4-(trifluoromethyl)-1H-imidazole, DMF, and pretreated porous ceramic is 1.9 g: 0.8-1.3 g: 1.4-2.7 g: 50-80 mL: 6 g.

6. The functional coating material for lithium-ion battery separator according to claim 3, characterized in that: In step S1, the porous ceramic particles include at least one of porous alumina, porous barium titanate, porous silica, porous titanium dioxide, porous silicon nitride, and porous silicon carbide.

7. The functional coating material for lithium-ion battery separator according to claim 1, characterized in that: The specific steps of modifying bentonite with sodium hexametaphosphate are: The calcium-based bentonite is crushed and mixed with water, and then sodium hexametaphosphate is added. The mixed solution is shaken and dispersed to obtain sodium hexametaphosphate modified bentonite.

8. The functional coating material for lithium-ion battery separator according to claim 7, characterized in that: The dosage ratio of calcium bentonite, water and sodium hexametaphosphate is 10g:40-50mL:0.1-0.3g.

9. A method for preparing a functional coating material for lithium-ion battery separator, for preparing the functional coating material according to any one of claims 1 to 8, characterized in that: The following steps are involved: (1) mixing sodium carboxymethyl cellulose and water to obtain a sodium carboxymethyl cellulose solution, and then mixing the sodium carboxymethyl cellulose solution with sodium hexametaphosphate-modified bentonite, water, and a defoaming agent to obtain a mixed slurry; (2) Mixing the mixed slurry obtained in step (1) with the MOF(Zn)@porous ceramic material and a binder to obtain the functional coating material.

10. A battery separator, characterized in that: The invention comprises a base film and a ceramic coating formed on at least one side of the base film; the ceramic coating is made of the functional coating material according to any one of claims 1 to 8, or the functional coating material prepared by the preparation method according to claim 9; The base film is a PE film or a PP film; the thickness of the base film is 2-5 μm; The thickness of the ceramic coating is 1-3 μm.

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