A high-density flame-retardant battery film and preparation method thereof

Abstract

The present invention relates to the field of battery technology, and in particular to a high-density flame-retardant battery membrane and a preparation method thereof, wherein the high-density flame-retardant battery membrane comprises a polypropylene diaphragm body and a modified flame-retardant coating coated on the polypropylene diaphragm body. The preparation method of the high-density flame-retardant battery membrane comprises the following steps: S1: preparing a modified flame-retardant coating; S2: uniformly coating the modified flame-retardant coating on the surface of a polypropylene diaphragm body base film, placing it at 55-65°C and drying it for 10-12h to obtain a high-density flame-retardant battery membrane. The present invention relates to a high-density flame-retardant battery membrane and a preparation method thereof, wherein the obtained battery membrane has excellent flame retardant properties.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a high-density flame-retardant battery film and a preparation method thereof. Background Art

[0002] Lithium-ion batteries have the characteristics of high operating voltage, high energy density, wide operating temperature, long cycle life, no memory effect, and environmental friendliness. They have become one of the main choices for green batteries in the 21st century. Lithium-ion batteries are now widely used in power battery fields such as automobiles and electric bicycles, energy storage fields such as power grids, industrial energy storage, household energy storage, and communication energy storage, and 3C digital fields such as smart phones, laptops, smart wearable devices, and mobile power supplies. In the structure of lithium batteries, the diaphragm is one of the key inner components. The performance of the diaphragm determines the interface structure and internal resistance of the battery, which directly affects the battery's capacity, cycle, and safety performance. The diaphragm with excellent performance plays an important role in improving the comprehensive performance of the battery. The main function of the diaphragm is to separate the positive and negative electrodes of the battery to prevent the two electrodes from contacting and short-circuiting. In addition, it also has the function of allowing electrolyte ions to pass through. The safety of the diaphragm will have a great impact on the safety of the battery. High-safety diaphragms must have excellent heat resistance, but the flame retardant efficiency of the diaphragm in the prior art is low, and a good flame retardant effect cannot be achieved. Summary of the invention

[0003] In view of this, an object of the present invention is to provide a high-density flame-retardant battery membrane and a preparation method thereof, wherein the obtained battery membrane has excellent flame-retardant properties.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] A high-density flame-retardant battery membrane comprises a polypropylene diaphragm body and a modified flame-retardant coating coated on the polypropylene diaphragm body.

[0006] A method for preparing a high-density flame-retardant battery film comprises the following steps:

[0007] S1: preparing modified flame retardant coating;

[0008] S2: The modified flame retardant coating is evenly coated on the surface of the polypropylene diaphragm body base film, and dried at 55-65°C for 10-12 hours to obtain a high-density flame retardant battery film.

[0009] Preferably, the modified flame retardant coating in step S1 comprises the following raw materials in parts by weight: 80-100 parts of modified melamine emulsion, 20-40 parts of modified crosslinking agent and 5-10 parts of silica sol.

[0010] Preferably, the preparation method of the modified melamine emulsion is:

[0011] Ammonium persulfate, acrylic acid monomer and isopropanol are mixed and stirred at 65-75°C for 0.5-1h, then sodium dodecyl sulfate is added, stirring is continued for 0.5-1h, allowed to stand for 10-12h, cooled to room temperature, melamine is added, stirring is continued for 1-2h, and modified melamine emulsion is obtained.

[0012] Preferably, the weight ratio of the ammonium persulfate, the monomer acrylic acid, the isopropyl alcohol, the sodium lauryl sulfate and the melamine is 1:2:4:1:2.

[0013] Preferably, the preparation method of the modified cross-linking agent is:

[0014] 1-Butyl-3-methylimidazole dihydrogen phosphate, 50% by mass sodium hydroxymethyl cellulose solution and polyethylene glycol are mixed, stirred for 1-2 hours, and dried to obtain a modified cross-linking agent.

[0015] Preferably, the weight ratio of the 1-butyl-3-methylimidazole dihydrogen phosphate, the sodium hydroxymethylcellulose solution and the polyethylene glycol is 1:2:1.

[0016] Preferably, the preparation method of the silica sol is: mix hexadecyltrimethylammonium bromide, cyclohexane, methyl orthosilicate, urea and 75% ethanol solution by volume, adjust the pH to 4-5 with hydrochloric acid, and stir the mixture at 45-55° C. for 6-8 hours;

[0017] Then add 50% by mass of polyvinyl alcohol and glutaraldehyde, stir at 30-40° C. for 1-2 hours to obtain silica sol.

[0018] Preferably, the weight ratio of the hexadecyltrimethylammonium bromide, cyclohexane, methyl orthosilicate, urea, ethanol solution, polyvinyl alcohol and glutaraldehyde is 2:1:1:2:5:3:1.

[0019] Preferably, the modified flame retardant coating is prepared by mixing a modified melamine emulsion, a modified crosslinking agent and a silica sol, stirring for 1-2 hours, and standing to obtain the modified flame retardant coating.

[0020] The emulsion of the present invention is condensed on the surface of the polypropylene diaphragm body, thereby improving the packing density of the polypropylene diaphragm body. By modifying melamine, a long-chain high molecular polymer is grafted on its surface to form a cross-linked point-surface core-shell network flame-retardant structure. At the same time, the modified silicon dioxide can be adsorbed and diffused into the gaps in the network flame-retardant structure to increase the flame-retardant effect, thereby forming a dense surface structure, so that a "firewall" is formed between the polypropylene diaphragm body and the external oxygen to hinder the flow between the diaphragm and the external gas, thereby exerting the flame-retardant effect for a long time. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention. In addition, it is specifically stated that the raw materials and equipment of the present invention can be obtained from commercial sources, and no longer listed one by one. Among them, the raw materials of the present invention can be obtained from commercial sources and are well known to those skilled in the art. Embodiment 1:

[0022] A high-density flame-retardant battery membrane comprises a polypropylene diaphragm body and a modified flame-retardant coating coated on the polypropylene diaphragm body.

[0023] A method for preparing a high-density flame-retardant battery film comprises the following steps:

[0024] S1: preparing a modified flame retardant coating: mixing 80 parts by weight of a modified melamine emulsion, 20 parts by weight of a modified crosslinking agent and 5 parts by weight of a silica sol, stirring for 1 hour, and standing to obtain a modified flame retardant coating;

[0025] Wherein, the preparation method of modified melamine emulsion is:

[0026] ammonium persulfate, acrylic acid monomer and isopropanol are mixed, and stirred at 65°C for 0.5h, and then sodium dodecyl sulfate is added, and the mixture is stirred for 0.5h, left to stand for 10h, cooled to room temperature, and then melamine is added, and stirred for 1h to obtain a modified melamine emulsion, wherein the weight ratio of ammonium persulfate, acrylic acid monomer, isopropanol, sodium dodecyl sulfate and melamine is 1:2:4:1:2;

[0027] The preparation method of the modified cross-linking agent is:

[0028] 1-butyl-3-methylimidazole dihydrogen phosphate, 50% sodium hydroxymethyl cellulose solution by weight and polyethylene glycol were mixed in a ratio of 1:2:1 by weight, stirred for 1 hour, and dried to obtain a modified cross-linking agent;

[0029] The preparation method of silica sol is:

[0030] Mix hexadecyltrimethylammonium bromide, cyclohexane, methyl orthosilicate, urea and 75% ethanol solution by volume, adjust the pH to 4-5 with hydrochloric acid, and stir and react at 45°C for 6 hours;

[0031] Then, 50% by weight of polyvinyl alcohol and glutaraldehyde were added, and the mixture was stirred at 30° C. for 1 hour to obtain a silica sol; wherein the weight ratio of hexadecyltrimethylammonium bromide, cyclohexane, methyl orthosilicate, urea, ethanol solution, polyvinyl alcohol and glutaraldehyde was 2:1:1:2:5:3:1;

[0032] S2: The modified flame retardant coating is evenly coated on the surface of the polypropylene diaphragm body base film, and dried at 55° C. for 10 hours to obtain a high-density flame retardant battery film. Embodiment 2:

[0033] A high-density flame-retardant battery membrane comprises a polypropylene diaphragm body and a modified flame-retardant coating coated on the polypropylene diaphragm body.

[0034] A method for preparing a high-density flame-retardant battery film comprises the following steps:

[0035] S1: preparing a modified flame retardant coating: mixing 100 parts by weight of a modified melamine emulsion, 40 parts by weight of a modified crosslinking agent and 10 parts by weight of a silica sol, stirring for 2 hours, and standing to obtain a modified flame retardant coating;

[0036] Wherein, the preparation method of modified melamine emulsion is:

[0037] ammonium persulfate, acrylic acid monomer and isopropanol are mixed, stirred at 75°C for 1 hour, sodium dodecyl sulfate is added, stirring is continued for 1 hour, standing for 12 hours, cooled to room temperature, melamine is added, and stirring is continued for 2 hours to obtain a modified melamine emulsion, wherein the weight ratio of ammonium persulfate, acrylic acid monomer, isopropanol, sodium dodecyl sulfate and melamine is 1:2:4:1:2;

[0038] The preparation method of the modified cross-linking agent is:

[0039] 1-butyl-3-methylimidazole dihydrogen phosphate, 50% sodium hydroxymethyl cellulose solution by weight, and polyethylene glycol were mixed in a weight ratio of 1:2:1, stirred for 2 hours, and dried to obtain a modified crosslinking agent;

[0040] The preparation method of silica sol is:

[0041] Mix hexadecyltrimethylammonium bromide, cyclohexane, methyl orthosilicate, urea and 75% ethanol solution by volume, adjust the pH to 4-5 with hydrochloric acid, and stir and react at 55°C for 8 hours;

[0042] Then, 50% by weight of polyvinyl alcohol and glutaraldehyde were added, and the mixture was stirred at 40° C. for 2 hours to obtain a silica sol; wherein the weight ratio of hexadecyltrimethylammonium bromide, cyclohexane, methyl orthosilicate, urea, ethanol solution, polyvinyl alcohol and glutaraldehyde was 2:1:1:2:5:3:1;

[0043] S2: The modified flame retardant coating is evenly coated on the surface of the polypropylene diaphragm body base film, and dried at 65° C. for 12 hours to obtain a high-density flame retardant battery film. Embodiment 3:

[0044] A high-density flame-retardant battery membrane comprises a polypropylene diaphragm body and a modified flame-retardant coating coated on the polypropylene diaphragm body.

[0045] A method for preparing a high-density flame-retardant battery film comprises the following steps:

[0046] S1: preparing a modified flame retardant coating: mixing 90 parts by weight of a modified melamine emulsion, 30 parts by weight of a modified crosslinking agent and 8 parts by weight of a silica sol, stirring for 1.5 hours, and standing to obtain a modified flame retardant coating;

[0047] Wherein, the preparation method of modified melamine emulsion is:

[0048] ammonium persulfate, monomer acrylic acid and isopropanol are mixed, and stirred at 70°C for 0.8h, and then sodium dodecyl sulfate is added, and the mixture is stirred for 0.8h. The mixture is allowed to stand for 11h, cooled to room temperature, and then melamine is added, and the mixture is stirred for 1.5h to obtain a modified melamine emulsion, wherein the weight ratio of ammonium persulfate, monomer acrylic acid, isopropanol, sodium dodecyl sulfate and melamine is 1:2:4:1:2;

[0049] The preparation method of the modified cross-linking agent is:

[0050] 1-butyl-3-methylimidazole dihydrogen phosphate, 50% sodium hydroxymethyl cellulose solution by weight, and polyethylene glycol were mixed in a ratio of 1:2:1 by weight, stirred for 1.5 hours, and dried to obtain a modified cross-linking agent;

[0051] The preparation method of silica sol is:

[0052] Mix hexadecyltrimethylammonium bromide, cyclohexane, methyl orthosilicate, urea and 75% ethanol solution by volume, adjust the pH to 4-5 with hydrochloric acid, and stir and react at 50°C for 7 hours;

[0053] Then, 50% by weight of polyvinyl alcohol and glutaraldehyde were added, and the mixture was stirred at 35° C. for 1.5 h to obtain a silica sol; wherein the weight ratio of hexadecyltrimethylammonium bromide, cyclohexane, methyl orthosilicate, urea, ethanol solution, polyvinyl alcohol and glutaraldehyde was 2:1:1:2:5:3:1;

[0054] S2: The modified flame retardant coating is evenly coated on the surface of the polypropylene diaphragm body base film, and dried at 60° C. for 11 hours to obtain a high-density flame retardant battery film.

[0055] The performance of Examples 1-3, the commercially available battery membranes of Taizhou Yajun Battery Materials Co., Ltd., and the polypropylene bulk battery membrane were tested. Test method:

[0056] Membrane rupture temperature: The membrane rupture temperature is measured by the resistance mutation method. The point where the resistance suddenly increases is the membrane rupture temperature.

[0057] LOI test: According to ASTM D2863-23 test standard, the standard size of the sample is 130 × 6.5 × 3.2 mm 3 .

[0058] Limiting oxygen index: According to GB / T8924-2005 test standard, the standard size of the sample is 130×6.5×3.2mm 3 .

[0059] The test results are shown in Table 1.

[0060] Table 1 Test data of Examples 1-3, commercially available battery membranes and polypropylene bulk battery membranes

[0061]

[0062] It can be seen from the above table that the flame retardant effects of Examples 1-3 are improved compared with the polypropylene bulk battery membrane and the commercially available battery membrane.

[0063] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a high-density flame-retardant battery film, characterized in that: The following steps are involved: S1: preparing modified flame retardant coating; S2: The modified flame retardant coating is evenly coated on the surface of the polypropylene diaphragm body base film, and dried at 55-65° C. for 10-12 hours to obtain a high-density flame retardant battery film; The modified flame retardant coating in step S1 comprises the following raw materials in parts by weight: 80-100 parts of modified melamine emulsion, 20-40 parts of modified crosslinking agent and 5-10 parts of silica sol; The preparation method of the modified melamine emulsion is: Mix ammonium persulfate, monomer acrylic acid and isopropanol, stir at 65-75°C for 0.5-1h, then add sodium dodecyl sulfate, continue stirring for 0.5-1h, let stand for 10-12h, cool to room temperature, then add melamine, continue stirring for 1-2h to obtain modified melamine emulsion; The preparation method of the modified cross-linking agent is: 1-Butyl-3-methylimidazole dihydrogen phosphate, 50% by mass sodium hydroxymethyl cellulose solution and polyethylene glycol are mixed, stirred for 1-2 hours, and dried to obtain a modified cross-linking agent.

2. The method for preparing a high-density flame-retardant battery film according to claim 1, characterized in that: The weight ratio of the ammonium persulfate, monomer acrylic acid, isopropyl alcohol, sodium lauryl sulfate and melamine is 1:2:4:1:

2.

3. The method for preparing a high-density flame-retardant battery film according to claim 1, characterized in that: The weight ratio of the 1-butyl-3-methylimidazole dihydrogen phosphate, the sodium hydroxymethylcellulose solution and the polyethylene glycol is 1:2:

1.

4. The method for preparing a high-density flame-retardant battery film according to claim 1, characterized in that: The preparation method of the silica sol is as follows: hexadecyltrimethylammonium bromide, cyclohexane, methyl orthosilicate, urea and 75% ethanol solution are mixed, the pH is adjusted to 4-5 with hydrochloric acid, and the reaction is stirred at 45-55° C. for 6-8 hours; Then add 50% by mass of polyvinyl alcohol and glutaraldehyde, stir at 30-40° C. for 1-2 hours to obtain silica sol.

5. The method for preparing a high-density flame-retardant battery film according to claim 4, characterized in that: The weight ratio of the hexadecyltrimethylammonium bromide, cyclohexane, methyl orthosilicate, urea, ethanol solution, polyvinyl alcohol and glutaraldehyde is 2:1:1:2:5:3:

1.

6. The method for preparing a high-density flame-retardant battery film according to claim 1, characterized in that: The preparation method of the modified flame retardant coating is as follows: the modified melamine emulsion, the modified crosslinking agent and the silica sol are mixed, stirred for 1-2 hours, and allowed to stand to obtain the modified flame retardant coating.

7. A high-density flame-retardant battery membrane, made by the preparation method of claim 1, characterized in that: The invention comprises a polypropylene diaphragm body and a modified flame retardant coating coated on the polypropylene diaphragm body.

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