A high heat-resistant lithium battery separator and preparation method thereof

Abstract

The present invention relates to the technical field of lithium battery separators and proposes a highly heat-resistant lithium battery separator and a method for preparing the same. The separator comprises a coating film and a base film, arranged sequentially from top to bottom. The coating film comprises the following components by weight: 30-50 parts inorganic particles, 0.4-1.2 parts dispersant, 0.2-1 parts thickener, 2-6 parts binder, 0.02-0.1 parts wetting agent, and 35-55 parts water; the inorganic particles include silica aerogel. This technical solution addresses the poor heat resistance and air permeability of lithium battery separators in related technologies.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery separators, and in particular to a high-heat-resistant lithium battery separator and a preparation method thereof. Background Art

[0002] Lithium batteries are widely used rechargeable batteries, playing a vital role in consumer electronics, electric vehicles, and large-scale energy storage systems. With their widespread use, their safety performance has become a major concern. As one of the four main components of lithium batteries, the separator is crucial to their safety. However, existing lithium battery separators suffer from poor heat resistance and air permeability, which indirectly affects the safe use of lithium batteries. Therefore, developing a new type of lithium battery separator to improve its heat resistance and air permeability is of great significance. Summary of the Invention

[0003] The present invention provides a high-heat-resistant lithium battery separator and a preparation method thereof, which solves the problems of poor heat resistance and air permeability of lithium battery separators in the related art.

[0004] The technical solutions of the present invention are as follows:

[0005] The present invention provides a high-heat-resistant lithium battery separator, comprising a coating film and a base film arranged sequentially from top to bottom, wherein the raw materials of the coating film include the following components in parts by weight: 30-50 parts of inorganic particles, 0.4-1.2 parts of a dispersant, 0.2-1 parts of a thickener, 2-6 parts of a binder, 0.02-0.1 parts of a wetting agent, and 35-55 parts of water;

[0006] The inorganic particles include silica aerogel.

[0007] As a further technical solution, the base film is a polyolefin film, preferably a polyethylene film.

[0008] As a further technical solution, the thickness of the base film is 8-10 μm, preferably 9 μm.

[0009] As a further technical solution, the coating film has a thickness of 2-4 μm, preferably 3 μm.

[0010] As a further technical solution, the preparation method of the silica aerogel comprises the following steps:

[0011] S1, adding ammonia water to the first solvent to obtain solution A;

[0012] S2, adding tetramethoxysilane to the second solvent to obtain solution B;

[0013] S3. Adding the solution B to the solution A, reacting, curing, soaking, and drying to obtain silica aerogel.

[0014] As a further technical solution, in step S3, the soaking is carried out in alcohol, preferably methanol.

[0015] As a further technical solution, the volume ratio of the ammonia water to the first solvent is 1:2~3.

[0016] As a further technical solution, the mass fraction of the ammonia water is 0.15%~0.16%.

[0017] As a further technical solution, the volume ratio of the tetramethoxysilane to the second solvent is 1:1~2.

[0018] As a further technical solution, the volume ratio of the solution A to the solution B is 0.75:1.

[0019] As a further technical solution, the first solvent and the second solvent are each independently methanol or ethanol.

[0020] As a further technical solution, the silica aerogel is a modified silica aerogel, and the components of the modified silica aerogel include silica aerogel, p-hydroxycinnamic acid and sodium dodecylsulfonate.

[0021] In the present invention, the silica aerogel is modified by p-hydroxycinnamic acid and sodium dodecylsulfonate, which can enhance the dispersion ability of the silica aerogel in the coating slurry, thereby promoting the uniform distribution of the silica aerogel in the coating film, and further improving the air permeability and heat resistance of the lithium battery separator.

[0022] As a further technical solution, in the modified silica aerogel, the weight ratio of the silica aerogel to the p-hydroxycinnamic acid and the sodium dodecylsulfonate is 18-23:1:1.

[0023] In the present invention, when the weight ratio of silica aerogel to p-hydroxycinnamic acid and sodium dodecylsulfonate in the modified silica aerogel is 18-23:1:1, it helps to further improve the air permeability and heat resistance of the lithium battery separator.

[0024] As a further technical solution, the preparation method of the modified silica aerogel comprises the following steps: dissolving p-hydroxycinnamic acid and sodium dodecylsulfonate in ethanol, adding silica aerogel, dispersing evenly, and drying to obtain the modified silica aerogel.

[0025] As a further technical solution, the inorganic particles further include aluminum oxide.

[0026] In the present invention, when the inorganic particles further include aluminum oxide, it can be ensured that the lithium battery separator has good thermal stability and good puncture strength.

[0027] As a further technical solution, the weight ratio of the silica aerogel to the inorganic particles is 1-25:100.

[0028] As a further technical solution, the dispersant is polyacrylate ammonium salt, which can be selected from Solpro-AN33, Orotan-1124, Ecodis-P90, etc., preferably Orotan-1124.

[0029] As a further technical solution, the thickener includes one or more of sodium carboxymethyl cellulose, sodium starch phosphate, and polyvinyl pyrrolidone, preferably sodium carboxymethyl cellulose.

[0030] As a further technical solution, the adhesive is a polyacrylate adhesive, which can be selected from VOK-5112, VOK-5115, VOK-5108, etc., preferably VOK-5112.

[0031] As a further technical solution, the wetting agent is an alkyl polyoxyethylene ether, which can be selected from Trideceth-E1312, Emulsogen-LCN-407, SK1, etc., preferably Emulsogen-LCN-407.

[0032] The present invention also proposes a method for preparing the high-heat-resistant lithium battery separator, comprising the following steps: uniformly mixing the raw materials of the coating film to obtain a coating slurry, and applying the coating slurry on the upper surface of the base film to obtain a lithium battery separator.

[0033] The working principle and beneficial effects of the present invention are:

[0034] In the present invention, the coating film of the lithium battery separator contains silica aerogel. The addition of silica aerogel can increase the overall air permeability and heat resistance of the lithium battery separator, reduce the air permeability of the lithium battery separator to below 168 s / 100mL, and reduce the thermal shrinkage rate at 150°C and 1h to below 2.3%, which is more advantageous than conventional ceramic coating films. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] Figure 1 This is the SEM image of the coating film in the lithium battery separator of Example 1. DETAILED DESCRIPTION

[0037] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0038] In the following examples and comparative examples, unless otherwise specified, the dispersant is polyacrylate ammonium salt, model No. Orotan-1124; the thickener is sodium carboxymethyl cellulose, CAS No. 9004-32-4; ​​the binder is a polyacrylate binder, model No. VOK-5112; and the wetting agent is an alkyl polyoxyethylene ether, model No. Emulsogen-LCN-407.

[0039] Example 1

[0040] A high-heat-resistant lithium battery separator comprises a coating film and a polyethylene base film arranged in sequence from top to bottom. The preparation method comprises the following steps: by weight, 30 parts of silica aerogel, 0.4 parts of a dispersant, 0.2 parts of a thickener, 2 parts of a binder, 0.02 parts of a wetting agent, and 35 parts of water are mixed uniformly to obtain a coating slurry, and the coating slurry is micro-gravure coated on the upper surface of the polyethylene base film to obtain a lithium battery separator. In the lithium battery separator, the thickness of the polyethylene base film is 9 μm, the thickness of the coating film is 3 μm, and the SEM image of the coating film is as follows: Figure 1 As shown;

[0041] The preparation method of silica aerogel comprises the following steps:

[0042] S1. Add 0.15% ammonia water to methanol (the volume ratio of ammonia water to methanol is 1:2) to obtain solution A.

[0043] S2. Add tetramethoxysilane to methanol (the volume ratio of tetramethoxysilane to methanol is 1:1) to obtain solution B;

[0044] S3. Solution B was added to solution A (the volume ratio of solution A to solution B was 0.75:1), reacted, allowed to stand and solidify for 0.5 h, soaked in methanol for one week, dried, and ground to obtain silica aerogel.

[0045] Example 2

[0046] A high-heat-resistant lithium battery separator comprises a coating film and a polyethylene-based film sequentially arranged from top to bottom. The preparation method comprises the following steps: uniformly mixing, by weight, 50 parts of silica aerogel, 1.2 parts of a dispersant, 1 part of a thickener, 6 parts of a binder, 0.1 part of a wetting agent, and 55 parts of water to obtain a coating slurry; micro-gravure coating the coating slurry on the upper surface of the polyethylene-based film to obtain a lithium battery separator, wherein the polyethylene-based film in the lithium battery separator has a thickness of 9 μm and the coating film has a thickness of 3 μm;

[0047] The preparation method of silica aerogel comprises the following steps:

[0048] S1. Add 0.16% ammonia water to methanol (the volume ratio of ammonia water to methanol is 1:3) to obtain solution A.

[0049] S2. Add tetramethoxysilane to methanol (the volume ratio of tetramethoxysilane to methanol is 1:2) to obtain solution B;

[0050] S3. Solution B was added to solution A (the volume ratio of solution A to solution B was 0.75:1), reacted, allowed to stand and solidify for 0.5 h, soaked in methanol for one week, dried, and ground to obtain silica aerogel.

[0051] Example 3

[0052] The only difference between this embodiment and Example 2 is that in this embodiment, the silica aerogel is modified silica aerogel, and the preparation method of the modified silica aerogel comprises the following steps: dissolving 6 parts of p-hydroxycinnamic acid in 50 parts of ethanol, adding 44 parts of silica aerogel, dispersing evenly, and drying to obtain the modified silica aerogel.

[0053] Example 4

[0054] The only difference between this embodiment and embodiment 3 is that, in this embodiment, p-hydroxycinnamic acid is replaced by an equal amount of sodium lauryl sulfonate.

[0055] Example 5

[0056] The only difference between this embodiment and Example 2 is that in this embodiment, the silica aerogel is modified silica aerogel, and the preparation method of the modified silica aerogel comprises the following steps: dissolving 3 parts of p-hydroxycinnamic acid and 3 parts of sodium dodecylsulfonate in 50 parts of ethanol, adding 44 parts of silica aerogel, dispersing evenly, and drying to obtain the modified silica aerogel.

[0057] Example 6

[0058] The only difference between this embodiment and embodiment 5 is that, in this embodiment, when preparing the modified silica aerogel, the weight parts of p-hydroxycinnamic acid are 1 part, the weight parts of sodium lauryl sulfate are 1 part, and the weight parts of silica aerogel are 48 parts.

[0059] Example 7

[0060] The only difference between this embodiment and embodiment 5 is that, in this embodiment, when preparing the modified silica aerogel, the weight parts of p-hydroxycinnamic acid are 2.5 parts, the weight parts of sodium lauryl sulfate are 2.5 parts, and the weight parts of silica aerogel are 45 parts.

[0061] Example 8

[0062] The only difference between this embodiment and embodiment 5 is that, in this embodiment, when preparing the modified silica aerogel, the weight parts of p-hydroxycinnamic acid are 2 parts, the weight parts of sodium lauryl sulfate are 2 parts, and the weight parts of silica aerogel are 46 parts.

[0063] Example 9

[0064] A high-heat-resistant lithium battery separator comprises a coating film and a polyethylene-based film sequentially arranged from top to bottom. The preparation method comprises the following steps: uniformly mixing, by weight, 3 parts of silica aerogel, 27 parts of aluminum oxide, 0.4 parts of a dispersant, 0.2 parts of a thickener, 2 parts of a binder, 0.02 parts of a wetting agent, and 35 parts of water to obtain a coating slurry; micro-gravure coating the coating slurry on the upper surface of the polyethylene-based film to obtain a lithium battery separator, wherein the polyethylene-based film in the lithium battery separator has a thickness of 9 μm and the coating film has a thickness of 3 μm;

[0065] The preparation method of silica aerogel comprises the following steps:

[0066] S1. Add 0.16% ammonia water to methanol (the volume ratio of ammonia water to methanol is 1:2) to obtain solution A.

[0067] S2. Add tetramethoxysilane to methanol (the volume ratio of tetramethoxysilane to methanol is 1:1) to obtain solution B;

[0068] S3. Solution B was added to solution A (the volume ratio of solution A to solution B was 0.75:1), reacted, allowed to stand and solidify for 0.5 h, soaked in methanol for one week, dried, and ground to obtain silica aerogel.

[0069] Example 10

[0070] The only difference between this embodiment and embodiment 9 is that, in this embodiment, the weight portion of silica aerogel is 7.5 parts, and the weight portion of aluminum oxide is 22.5 parts.

[0071] Comparative Example 1

[0072] The only difference between this comparative example and Example 1 is that in this comparative example, the silica aerogel is replaced by an equal amount of alumina.

[0073] Experimental Example 1 Effect of Silica Aerogel on Lithium Battery Separator

[0074] The lithium battery separators prepared in Examples 1 to 8 and Comparative Example 1 were subjected to the following performance tests:

[0075] ① Air permeability: Test the air permeability of lithium battery separators according to GB / T 36363-2018 "Polyolefin separators for lithium-ion batteries";

[0076] ② Thermal shrinkage rate: Refer to GB / T 36363-2018 "Polyolefin separators for lithium-ion batteries" to test the thermal shrinkage rate of lithium battery separators at 150°C for 1 hour.

[0077] The test results are shown in Table 1 below.

[0078] Table 1 Test results

[0079]

[0080] Comparison of Example 1 and Comparative Example 1 shows that compared with conventional ceramic coating films, the coating film containing silica aerogel can significantly increase the air permeability and heat resistance of the lithium battery separator. Comparison of Example 2 and Examples 3 to 8 shows that by modifying the silica aerogel, the air permeability and heat resistance of the lithium battery separator can be further increased. Comparison of Examples 3 to 4 and Example 5 shows that modification of the silica aerogel with p-hydroxycinnamic acid and sodium dodecyl sulfonate is more conducive to further increasing the air permeability and heat resistance of the lithium battery separator. Comparison of Examples 5 to 6 and Examples 7 to 8 shows that in the modified silica aerogel, when the weight ratio of silica aerogel to p-hydroxycinnamic acid and sodium dodecyl sulfonate is 18 to 23:1:1, it helps to further increase the air permeability and heat resistance of the lithium battery separator.

[0081] Experimental Example 2 Effects of Silica Aerogel and Alumina on Lithium Battery Separators

[0082] The lithium battery separators prepared in Example 1, Examples 9-10 and Comparative Example 1 were subjected to the following performance tests:

[0083] ① Thermal shrinkage: Refer to GB / T 36363-2018 "Polyolefin separators for lithium-ion batteries" to test the thermal shrinkage of lithium battery separators at 150°C for 1 hour;

[0084] ② Puncture strength: The puncture strength of lithium battery separators is tested according to GB / T 36363-2018 "Polyolefin separators for lithium-ion batteries" at a test speed of 100 mm / min.

[0085] The test results are shown in Table 2 below.

[0086] Table 2 Test results

[0087]

[0088] It can be seen from Table 2 that when the lithium battery separator contains silica aerogel and alumina, it can ensure that the lithium battery separator has good thermal stability and good puncture strength.

[0089] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A high heat-resistant lithium battery separator, characterized in that: The coating film comprises a coating film and a base film arranged in sequence from top to bottom, wherein the raw materials of the coating film include the following components in parts by weight: 30-50 parts of inorganic particles, 0.4-1.2 parts of a dispersant, 0.2-1 parts of a thickener, 2-6 parts of a binder, 0.02-0.1 parts of a wetting agent, and 35-55 parts of water; The inorganic particles include modified silica aerogel, and the components of the modified silica aerogel include silica aerogel, p-hydroxycinnamic acid and sodium lauryl sulfonate; The weight ratio of the silica aerogel, the p-hydroxycinnamic acid, and the sodium lauryl sulfate is 18-23:1:1; The preparation method of the modified silica aerogel comprises the following steps: dissolving p-hydroxycinnamic acid and sodium dodecylsulfonate in ethanol, adding silica aerogel, dispersing uniformly, and drying to obtain the modified silica aerogel.

2. A high heat-resistant lithium battery separator according to claim 1, characterized in that: The preparation method of the silica aerogel comprises the following steps: S1, adding ammonia water to the first solvent to obtain solution A; S2, adding tetramethoxysilane to the second solvent to obtain solution B; S3. Adding the solution B to the solution A, reacting, curing, soaking, and drying to obtain the silica aerogel.

3. A high heat-resistant lithium battery separator according to claim 2, characterized in that: The volume ratio of the ammonia water to the first solvent is 1:2~3.

4. A high heat-resistant lithium battery separator according to claim 3, characterized in that: The mass fraction of the ammonia water is 0.15% to 0.16%.

5. A high heat-resistant lithium battery separator according to claim 2, characterized in that: The volume ratio of the tetramethoxysilane to the second solvent is 1:1-2.

6. A high heat-resistant lithium battery separator according to claim 2, characterized in that: The volume ratio of the solution A to the solution B is 0.75:

1.

7. A high heat-resistant lithium battery separator according to claim 6, characterized in that: The first solvent and the second solvent are each independently methanol or ethanol.

8. The high heat-resistant lithium battery separator according to claim 1, characterized in that: The inorganic particles also include aluminum oxide.

9. A high heat-resistant lithium battery separator according to claim 8, characterized in that: The weight ratio of the modified silica aerogel to the inorganic particles is 1-25:

100.

10. A method for preparing a high heat-resistant lithium battery separator according to any one of claims 1 to 9, characterized in that: The following steps are involved: The raw materials of the coating film are mixed evenly to obtain a coating slurry, and the coating slurry is coated on the upper surface of the base film to obtain a lithium battery separator.

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