A battery separator and method of making the same

Abstract

The application relates to the technical field of battery separators, and discloses a battery separator and a preparation method thereof. The battery separator comprises a polyolefin base film and a UV curing coating layer coated on at least one surface of the polyolefin base film; the UV curing coating layer comprises the following raw materials in parts by weight: 0.1-0.3 parts of a photoinitiator and 100 parts of a solvent; the photoinitiator comprises one or a mixture of several of 2-ethylanthraquinone, 4-chlorobenzophenone, 2,2-dimethoxy-1,2-diphenylalk-1-ketone, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, 2-hydroxy-2-methyl-1-phenyl-1-propanone and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide. The above technical scheme solves the problem of poor high-temperature strength of the polyolefin base battery separator in the related art.

Description

Technical Field

[0001] This invention relates to the field of battery separator technology, specifically to a battery separator and its preparation method. Background Technology

[0002] Lithium-ion batteries, as the mainstream energy storage devices, are widely used in electric vehicles, portable electronic devices, and many other fields. Among these, the separator, as one of the key components of the battery, directly affects the overall performance and safety of the battery. Polyolefin-based membranes, due to their excellent chemical stability, good insulation, and certain mechanical strength, have become one of the main materials for lithium-ion battery separators. However, with the continuous development of battery technology, higher requirements are being placed on the mechanical strength of the separator, especially in the face of challenges in extreme operating environments, such as high temperatures, where the mechanical strength of existing polyolefin-based membranes is no longer sufficient. Summary of the Invention

[0003] This invention proposes a battery separator and its preparation method, which solves the problem of poor strength of polyolefin-based battery separators at high temperatures in related technologies.

[0004] The technical solution of the present invention is as follows:

[0005] This invention provides a battery separator, comprising a polyolefin-based film and a UV-curable coating applied to at least one surface of the polyolefin-based film;

[0006] The UV-curable coating comprises the following raw materials in parts by weight: 0.1-0.3 parts photoinitiator and 100 parts solvent;

[0007] The photoinitiator includes one or more of 2-ethylanthraquinone, 4-chlorobenzophenone, 2,2-dimethoxy-1,2-diphenylalkyl-1-one, 2,4-diethylthioxanthraquinone, 2-isopropylthioxanthraquinone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

[0008] As a further technical solution, the solvent includes one or more of diethyl ether, ethanol, isopropanol, acetone, and ethyl acetate;

[0009] The polyolefin-based film comprises the following raw materials in parts by weight: 15-30 parts of polyolefin and 70-85 parts of diluent;

[0010] The polyolefin includes polyethylene with a molecular weight of 600,000 to 1,200,000.

[0011] As a further technical solution, the diluent is mineral oil.

[0012] As a further technical solution, the photoinitiator includes 2-ethylanthraquinone, 4-chlorobenzophenone, and 2,2-dimethoxy-1,2-diphenylalkyl-1-one in a mass ratio of 1:2:2 to 3:1:1.

[0013] In this invention, when the photoinitiator is 2-ethylanthraquinone, 4-chlorobenzophenone, or 2,2-dimethoxy-1,2-diphenylalkyl-1-one in a mass ratio of 1:2:2 to 3:1:1, the strength of the polyolefin-based battery separator at high temperatures is further improved.

[0014] As a further technical solution, the UV-curable coating further includes the following raw materials in parts by weight: 0.05~0.2 parts of nano-zirconia;

[0015] The polyolefin-based film also includes the following raw materials in parts by weight: 5-10 parts of filler.

[0016] As a further technical solution, the filler comprises nano-silica and nano-zirconia in a mass ratio of 1:5 to 7:1.

[0017] In this invention, nano-silica and nano-zirconia with a mass ratio of 1:5 to 7:1 are added to the polyolefin-based membrane as fillers, and work synergistically with the zirconium dioxide in the UV-cured coating to further improve the strength of the polyolefin-based battery separator at high temperatures.

[0018] As a further technical solution, the filler is a vinyl bis-stearamide modified filler.

[0019] In this invention, by using vinyl bis-stearamide to modify the filler in the polyolefin-based membrane, the agglomeration between fillers is reduced, the compatibility with the polyolefin-based membrane is improved, and the strength of the polyolefin-based battery separator at high temperature is further improved.

[0020] As a further technical solution, the preparation method of the vinyl bis-stearamide modified filler includes the following steps: mixing vinyl bis-stearamide and filler to obtain vinyl bis-stearamide modified filler.

[0021] As a further technical solution, the mass ratio of the vinyl bis-stearamide to the filler is 0.4~0.5:2.

[0022] The present invention also proposes a method for preparing a battery separator, comprising the following steps:

[0023] S1. Mix the raw materials of the UV-curable coating to obtain a coating slurry;

[0024] S2. The raw materials of the polyolefin-based film are mixed, extruded into a film, heat-set, coated with the coating slurry online, UV cured, and heat-set to obtain the battery separator.

[0025] As a further technical solution, the thickness of the UV-cured coating of the battery separator is 0.01~1.5μm.

[0026] As a further technical solution, the online coating includes one of dip coating, microgravure coating, and bar coating.

[0027] A combination of online coating and UV curing is employed, where the prepared coating material is uniformly applied to the surface of a continuously operating polyolefin-based film using precision coating equipment. Subsequently, a high-efficiency UV light source is used to rapidly cure the coating. The ultraviolet light emitted by the UV source penetrates the coating, activating the photoinitiator and triggering a series of cross-linking reactions, allowing the coating to cure rapidly within a short time. During this process, a strong chemical bond is formed between the coating and the base film, significantly enhancing their bonding strength.

[0028] The working principle and beneficial effects of this invention are as follows:

[0029] This invention achieves a high-strength bond between the coating and the base film through a unique coating formulation and UV curing, effectively addressing the shortcomings of traditional coating technologies in improving mechanical strength. This provides a new solution for enhancing the safety, durability, and performance of lithium-ion batteries. The polyolefin base film coated online with UV-cured coating technology exhibits significant improvements in hot needle penetration strength, film rupture temperature, and thermal shrinkage performance. Specifically, compared to uncoated polyolefin base films, its hot needle penetration strength is increased by more than 30%, its film rupture temperature is increased by more than 20%, and its thermal shrinkage performance is also significantly improved. Furthermore, due to the high efficiency of the UV-cured coating, this invention also boasts advantages such as short production cycles and low energy consumption, making it highly valuable for widespread application. Detailed Implementation

[0030] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0031] In the following examples and comparative examples, the particle size of nano-zirconia is 10 nm; the particle size of nano-silica is 10 nm.

[0032] Example 1

[0033] The battery separator includes a polyolefin-based membrane and a UV-curable coating with a thickness of 0.05 μm applied to the upper surface of the polyolefin-based membrane.

[0034] The UV-curable coating comprises the following raw materials in parts by weight: 0.3 parts photoinitiator and 100 parts acetone; the photoinitiator is 2-ethylanthraquinone;

[0035] The polyolefin-based film comprises the following raw materials in parts by weight: 30 parts of polyethylene with a molecular weight of 600,000 and 70 parts of white oil;

[0036] The method for preparing a battery separator includes the following steps:

[0037] S1. Mix the raw materials for UV-curable coating to obtain a coating slurry;

[0038] S2. Mix the raw materials of the polyolefin-based membrane, extrude them into a film, heat set them, coat the above coating slurry online at a running speed of 40m / min, UV cure it, heat set it, and obtain the battery separator.

[0039] Example 2

[0040] The battery separator includes a polyolefin-based membrane and a UV-curable coating with a thickness of 0.03 μm coated on the upper surface of the polyolefin-based membrane;

[0041] The UV-curable coating comprises the following raw materials in parts by weight: 0.2 parts photoinitiator and 100 parts acetone; the photoinitiator is 4-chlorobenzophenone.

[0042] The polyolefin-based film comprises the following raw materials in parts by weight: 20 parts of polyethylene with a molecular weight of 900,000 and 80 parts of white oil;

[0043] The method for preparing a battery separator includes the following steps:

[0044] S1. Mix the raw materials for UV-curable coating to obtain a coating slurry;

[0045] S2. Mix the raw materials of the polyolefin-based membrane, extrude them into a film, heat set them, coat the above coating slurry online at a running speed of 50m / min, UV cure it, heat set it, and obtain the battery separator.

[0046] Example 3

[0047] The battery separator includes a polyolefin-based membrane and a UV-curable coating with a thickness of 0.01 μm applied to the upper and lower surfaces of the polyolefin-based membrane.

[0048] The UV-curable coating comprises the following raw materials in parts by weight: 0.1 parts photoinitiator and 100 parts acetone; the photoinitiator is 2,2-dimethoxy-1,2-diphenylalkyl-1-one;

[0049] The polyolefin-based film comprises the following raw materials in parts by weight: 15 parts of polyethylene with a molecular weight of 1.2 million and 85 parts of white oil;

[0050] The method for preparing a battery separator includes the following steps:

[0051] S1. Mix the raw materials for UV-curable coating to obtain a coating slurry;

[0052] S2. Mix the raw materials of the polyolefin-based membrane, extrude them into a film, heat set them, coat the above coating slurry online at a running speed of 60m / min, UV cure it, heat set it, and obtain the battery separator.

[0053] Example 4

[0054] The only difference between this embodiment and Example 1 is that the photoinitiator is 4-chlorobenzophenone and 2,2-dimethoxy-1,2-diphenylalan-1-one in a mass ratio of 1:1.

[0055] Example 5

[0056] The only difference between this embodiment and Example 1 is that the photoinitiator is 2-ethylanthraquinone and 2,2-dimethoxy-1,2-diphenylalkyl-1-one in a mass ratio of 3:1.

[0057] Example 6

[0058] The only difference between this embodiment and Example 1 is that the photoinitiator is 2-ethylanthraquinone and 4-chlorobenzophenone in a mass ratio of 3:1.

[0059] Example 7

[0060] The only difference between this embodiment and Example 1 is that the photoinitiator is 2-ethylanthraquinone, 4-chlorobenzophenone, and 2,2-dimethoxy-1,2-diphenylalkyl-1-one in a mass ratio of 3:1:1.

[0061] Example 8

[0062] The only difference between this embodiment and Example 1 is that the photoinitiator is 2-ethylanthraquinone, 4-chlorobenzophenone, and 2,2-dimethoxy-1,2-diphenylalkyl-1-one in a mass ratio of 1:2:2.

[0063] Example 9

[0064] The only difference between this embodiment and embodiment 8 is that the UV-cured coating also includes the following raw materials in parts by weight: 0.05 parts of nano-zirconia.

[0065] Example 10

[0066] The only difference between this embodiment and embodiment 8 is that the UV-cured coating also includes the following raw materials in parts by weight: 0.2 parts of nano-zirconia.

[0067] Example 11

[0068] The difference between this embodiment and embodiment 8 is that the polyolefin-based film also includes the following raw materials in parts by weight: 5 parts of filler, which are nano-silica and nano-zirconia in a mass ratio of 1:5.

[0069] Example 12

[0070] The difference between this embodiment and Example 10 is that the polyolefin-based film also includes the following raw materials in parts by weight: 5 parts of filler, which are nano-silica and nano-zirconia in a mass ratio of 1:5.

[0071] Example 13

[0072] The difference between this embodiment and Example 10 is that the polyolefin-based film also includes the following raw materials in parts by weight: 5 parts of filler, which are nano-silica and nano-zirconia in a mass ratio of 7:1.

[0073] Example 14

[0074] The difference between this embodiment and Example 13 is that the filler has also undergone vinyl bis-stearamide modification treatment. The preparation method of vinyl bis-stearamide modified filler includes the following steps: mixing vinyl bis-stearamide, filler and chloroform, drying to obtain vinyl bis-stearamide modified filler; the mass ratio of vinyl bis-stearamide to filler is 0.2:1, and the mass-volume ratio of vinyl bis-stearamide to chloroform is 1:30mL.

[0075] Example 15

[0076] The only difference between this embodiment and Example 13 is that the filler is a vinyl bis-stearamide modified filler. The preparation method of the vinyl bis-stearamide modified filler includes the following steps: mixing vinyl bis-stearamide, filler and chloroform, drying to obtain vinyl bis-stearamide modified filler; the mass ratio of vinyl bis-stearamide to filler is 0.5:2, and the mass-volume ratio of vinyl bis-stearamide to chloroform is 1:30mL.

[0077] Example 16

[0078] The only difference between this embodiment and Embodiment 15 is that the thickness of the UV-cured coating is 1.5 μm; and the filler in the polyolefin-based film is 10 parts by weight.

[0079] Comparative Example 1

[0080] The only difference between this comparative example and Example 1 is that the battery separator does not include a UV-curable coating.

[0081] Comparative Example 2

[0082] The only difference between this comparative example and Example 2 is that the battery separator does not include a UV-cured coating.

[0083] Comparative Example 3

[0084] The only difference between this comparative example and Example 3 is that the battery separator does not include a UV-cured coating.

[0085] The battery separators prepared in Examples 1-16 and Comparative Examples 1-3 were subjected to the following performance tests:

[0086] Thermal needle penetration strength: Using a needle with a diameter of 1 mm and a tip bending radius of 0.5 mm, the battery separator is needled at a speed of 2 mm / sec, and the thermal needle penetration strength of the maximum load value during needle penetration at different temperatures is measured.

[0087] Membrane breakage test: The membrane breakage temperature and time were tested using the TMA method;

[0088] Shrinkage rate: The battery separator was placed in an oven at 130°C for 1 hour in its natural state, and then the transverse (TD) shrinkage rate and longitudinal (MD) shrinkage rate of the battery separator were measured.

[0089] The results are shown in Tables 1 and 2 below.

[0090] Table 1. Battery separator performance test results

[0091]

[0092] By comparing Examples 1-3 and Comparative Examples 1-3, it was found that the battery separators prepared in Examples 1-3 had higher thermal needle penetration strength, ink splashing temperature, and lower shrinkage rate compared with Comparative Examples 1-3. This indicates that by using a combination of online coating and UV curing, and utilizing a high-efficiency UV light source to rapidly cure the coating, a strong chemical bond is formed between the coating and the base film, which significantly improves the performance of the battery separator at high temperatures.

[0093] Table 2 Battery separator performance test results

[0094]

[0095] By comparing the data from Examples 1 and 4-8, it was found that the battery separators prepared in Examples 7-8 had higher thermal needle penetration strength compared to Examples 1 and 4-6. This indicates that when the photoinitiator is 2-ethylanthraquinone, 4-chlorobenzophenone, and 2,2-dimethoxy-1,2-diphenylalkyl-1-one in a mass ratio of 1:2:2 to 3:1:1, the strength of the polyolefin-based battery separator at high temperatures can be further improved.

[0096] Comparing the data from Examples 8 to 13, it was found that the battery separators prepared in Examples 12 to 13 had higher thermal needle penetration strength compared to Examples 8 to 11. This indicates that the addition of nano-silica and nano-zirconia in a mass ratio of 1:5 to 7:1 as fillers to the polyolefin-based membrane, and their synergistic effect with the zirconium dioxide in the UV-cured coating, further improved the strength of the polyolefin-based battery separator at high temperatures.

[0097] By comparing the data of Examples 13-16, it was found that the battery separators prepared in Examples 14-16 had higher thermal needle penetration strength than those in Example 13, indicating that by using vinyl bis-stearamide to modify the filler in the polyolefin-based membrane, the strength of the polyolefin-based battery separator at high temperature was further improved.

[0098] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A battery separator, characterized in that, Includes a polyolefin-based film and a UV-curable coating applied to at least one surface of the polyolefin-based film; The UV-curable coating comprises the following raw materials in parts by weight: 0.1-0.3 parts photoinitiator and 100 parts solvent; The photoinitiator comprises 2-ethylanthraquinone, 4-chlorobenzophenone, and 2,2-dimethoxy-1,2-diphenylalkyl-1-one in a mass ratio of 1:2:2 to 3:1:

1. The polyolefin-based film also includes the following raw materials in parts by weight: 5-10 parts of filler; The filler is a vinyl bis-stearamide modified filler; The preparation method of the vinyl bis-stearamide modified filler includes the following steps: mixing vinyl bis-stearamide and filler to obtain vinyl bis-stearamide modified filler.

2. The battery separator according to claim 1, characterized in that, The solvent includes one or more of diethyl ether, ethanol, isopropanol, acetone, and ethyl acetate; The polyolefin-based film comprises the following raw materials in parts by weight: 15-30 parts of polyolefin and 70-85 parts of diluent; The polyolefin includes polyethylene with a molecular weight of 600,000 to 1,200,000.

3. The battery separator according to claim 1, characterized in that, The UV-curable coating also includes the following raw materials in parts by weight: 0.05 to 0.2 parts of nano-zirconia.

4. A battery separator according to claim 1, characterized in that, The filler comprises nano-silica and nano-zirconia in a mass ratio of 1:5 to 7:

1.

5. A battery separator according to claim 1, characterized in that, The mass ratio of the vinyl bis-stearamide to the filler is 0.4~0.5:

2.

6. A method for preparing a battery separator according to any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Mix the raw materials of the UV-curable coating to obtain a coating slurry; S2. The raw materials of the polyolefin-based film are mixed, extruded into a film, heat-set, coated with the coating slurry online, UV cured, and heat-set to obtain the battery separator.

7. The method for preparing a battery separator according to claim 6, characterized in that, The thickness of the UV-cured coating on the battery separator is 0.01~1.5μm.

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