Oil-based separator and manufacturing method therefor, and secondary battery

Abstract

An oil-based separator and a manufacturing method therefor, and a secondary battery. The oil-based separator comprises a base membrane and a coating disposed on at least one surface of the base membrane, and the coating comprises a first binder, a second binder, and an inorganic filler; the mass percentage of the first binder is A, and the mass percentage of the second binder is B, wherein A and B satisfy the relationship: 0.25≤A / B≤4; the particle size D50 of the first binder is RA, and the particle size D50 of the second binder is RB, wherein RA and RB satisfy the relationship: 0<RA / RB≤0.6. In the oil-based separator provided by the present invention, by controlling the relationships of the particle sizes and the mass percentages of the two binders, the binding power can be effectively improved, and the pores of the separator are not easily blocked, thereby accelerating ion transfer, and improving charging and discharging speed.

Description

Oil-based separator, preparation method thereof and secondary battery TECHNICAL FIELD

[0001] The present application relates to the field of secondary batteries, in particular to an oil-based separator, a preparation method thereof and a secondary battery. BACKGROUND

[0002] Lithium ion batteries have been widely used in modern electronic devices due to their excellent performance, such as high specific energy, high specific power, high voltage platform, low self-discharge rate, long cycle life, small environmental impact, and no memory effect. They have become an indispensable energy solution for mobile phones, computers, electric vehicles, military and space technology, and other fields. The chemical and physical properties of these batteries provide energy-dense and long-life power sources for portable devices, greatly promoting the development of mobile technology and electric vehicle industry. Therefore, for the future development of lithium ion batteries, it is necessary to comprehensively improve the energy density, cycle life and safety performance of lithium ion batteries, which requires the development of higher performance separators that match them.

[0003] In recent years, oil-based functional slurry has been widely used, and its coating adhesion is good. Conventional oil-based slurry often adds N-methyl pyrrolidone, dimethyl acetamide, etc. as organic solvent. The organic functional polymer coated separator has good wettability and liquid retention for electrolyte, can effectively bond the separator and the pole piece, increase the cycle performance of the battery, and significantly improve the safety of the battery. However, the oil-based separator coating with strong adhesion generally has poor pore-forming property and has the risk of blocking pores, and vice versa, the coating with good pore-forming property has insufficient adhesion.

[0004] Therefore, it is urgent to develop an oil-based separator that can effectively improve the adhesion while solving the problems of separator blocking and poor air permeability.

[0005] SUMMARY

[0006] The purpose of the present application is to provide an oil-based separator that can effectively improve the adhesion while solving the problems of separator blocking and poor air permeability in view of the deficiencies of the prior art.

[0007] In order to achieve the above purpose, the present application adopts the following technical solutions:

[0008] An oil-based separator, comprising a base film and a coating layer provided on at least one surface of the base film, the coating layer comprising a first binder, a second binder and an inorganic filler; the mass fraction of the first binder is A, and the mass fraction of the second binder is B, wherein A and B satisfy the relationship: 0.25≤A / B≤4; the particle size D50 of the first binder is R A , and the particle size D50 of the second binder is R B , wherein R A and RB Satisfy the relationship: 0 < R A / R B ≤0.6.

[0009] Wherein, the first binder mainly controls the pore forming degree, and the second binder mainly controls the bonding force, if A / B < 0.25, the coating slurry has poor pore forming property, which will cause the risk of pore blocking; if A / B > 4, the bonding force of the coating slurry is weak. Therefore, the two should be set in a certain range to effectively improve the bonding force while solving the problems of coating pore blocking and poor air permeability.

[0010] Preferably, the mass fraction of the inorganic filler is C, wherein A, B and C satisfy the relationship: 0.2 ≤ C / (A+B) ≤ 0.55.

[0011] The addition of ceramic not only reduces the cost, but also meets the heat shrinkage performance of the separator. When C / (A+B) is controlled within the preset range, the heat shrinkage performance of the coating is good. If C / (A+B) < 0.2, the heat shrinkage of the oil-based separator is poor; if C / (A+B) > 0.55, the pore forming property of the oil-based separator is poor.

[0012] Preferably, the particle size R of the first binder is 1-120 μm, and the particle size R of the second binder is 2-200 μm. A B

[0013] Preferably, the molecular weight of the first binder is 300000-600000 g / mol, and the molecular weight of the second binder is 600000-1000000 g / mol.

[0014] Preferably, the first binder and the second binder are selected from one or more of polyvinylidene fluoride, vinylidene fluoride-trifluorochloroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether copolymer, vinylidene fluoride-vinylidene propylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer.

[0015] Preferably, the inorganic filler is selected from one or more of alumina, magnesium oxide, calcium oxide, barium oxide, zinc oxide, silicon dioxide, titanium dioxide, zirconium dioxide, magnesium hydroxide, aluminum hydroxide, boehmite and ceramic fiber.

[0016] In addition, the application also provides a preparation method of the oil-based separator of the secondary battery, comprising the following steps:

[0017] S1, uniformly dispersing the inorganic filler in the organic solvent; ​​

[0018] S2, dispersing and dissolving the first binder in the organic solvent in step S1 to obtain a first slurry;

[0019] S3, adding a second binder to the first slurry to obtain a separator coating slurry after being dispersed and dissolved;

[0020] S4, coating the separator coating slurry on at least one surface of the base film, and performing solidification and drying to obtain the oil-based separator of the secondary battery.

[0021] In addition, the application also provides a secondary battery, which comprises a positive electrode sheet, a separator, a negative electrode sheet and an electrolyte, and the separator is the above-mentioned oil-based separator.

[0022] Preferably, the oil-based separator is connected with the positive electrode sheet, and the peeling strength between the coating of the oil-based separator and the positive electrode sheet is 10-20 N / m.

[0023] Compared with the prior art, the application has at least the following beneficial effects:

[0024] (1) The application sets the mass ratio of the first binder and the second binder in the coating of the oil-based separator to satisfy the relationship 0.25≤A / B≤4, and the particle size R A of the first binder and the particle size R B of the second binder satisfy the relationship 0 A / R B ≤0.6, which can effectively improve the adhesion while not easily blocking the pores of the separator, and is conducive to accelerating ion transfer and improving the charging and discharging speed.

[0025] (2) The application sets the mass fraction C of the inorganic filler to satisfy the relationship 0.2≤C / (A+B)≤0.55, which ensures that the oil-based separator coating has good pore-forming property while having heat shrinkage performance. BRIEF DESCRIPTION OF DRAWINGS

[0026] Fig. 1 is an SEM image of the oil-based separator prepared in Example 2 of the application.

[0027] Fig. 2 is an SEM image of the oil-based separator prepared in Comparative Example 1 of the application.

[0028] Fig. 3 is an SEM image of the oil-based separator prepared in Comparative Example 2 of the application.

[0029] Fig. 4 is an SEM image of the oil-based separator prepared in Comparative Example 3 of the application.

[0030] Fig. 5 is an SEM image of the oil-based separator prepared in Comparative Example 5 of the application. DETAILED DESCRIPTION

[0031] In order to make the technical solutions and advantages of the present application clearer, the technical solutions of the present application will be described clearly and completely below in conjunction with specific embodiments. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts fall within the scope of the present application.

[0032] According to a first aspect of the present application, the present application aims to provide an oil-based separator, comprising a base film and a coating layer provided on at least one surface of the base film, the coating layer comprising a first binder, a second binder and an inorganic filler; the mass fraction of the first binder is A, and the mass fraction of the second binder is B, wherein A and B satisfy the relationship: 0.25≤A / B≤4, for example, can be 0.25, 0.3, 0.5, 0.7, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4. The particle size D50 of the first binder is R A , and the particle size D50 of the second binder is R B , wherein R A and R B satisfy the relationship: 0 A < R B / R B ≤0.6, for example, can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6.

[0033] In some embodiments, the base film is one or more of PE, PP, PE / PP composite film, PET, PI.

[0034] In some embodiments, the mass fraction of the inorganic filler is C, wherein A, B and C satisfy the relationship: 0.2≤C / (A+B)≤0.55, for example, can be 0.2, 0.3, 0.4, 0.5, 0.55.

[0035] In some embodiments, the particle size R A of the first binder is 1-120 μm, for example, can be 1 μm, 20 μm, 40 μm, 60 μm, 80 μm, 100 μm, 120 μm; and the particle size R B of the second binder is 2-200 μm, for example, can be 2 μm, 20 μm, 40 μm, 60 μm, 80 μm, 100 μm, 120 μm, 140 μm, 160 μm, 180 μm, 200 μm.

[0036] In some embodiments, the first binder has a molecular weight of 300000-600000 g / mol, for example, it can be 300000 g / mol, 500000 g / mol, 510000 g / mol, 520000 g / mol, 530000 g / mol, 540000 g / mol, 550000 g / mol, 560000 g / mol, 570000 g / mol, 580000 g / mol, 590000 g / mol, 600000 g / mol; the second binder has a molecular weight of 600000-1000000 g / mol, for example, it can be 600000 g / mol, 800000 g / mol, 810000 g / mol, 820000 g / mol, 830000 g / mol, 840000 g / mol, 850000 g / mol, 1000000 g / mol.

[0037] In some embodiments, the first binder and the second binder are each selected from one or more of polyvinylidene fluoride, vinylidene fluoride-trifluorochloroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether copolymer, vinylidene fluoride-vinylidene propylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer.

[0038] In some embodiments, the inorganic filler is selected from one or more of aluminum oxide, magnesium oxide, calcium oxide, barium oxide, zinc oxide, silicon dioxide, titanium dioxide, zirconium dioxide, magnesium hydroxide, aluminum hydroxide, boehmite, and ceramic fiber.

[0039] According to a second aspect of the present application, the present application aims to provide a preparation method of an oil-based separator of a secondary battery, comprising the following steps:

[0040] S1, uniformly dispersing an inorganic filler in an organic solvent;

[0041] S2, dispersing and dissolving a first binder in the organic solvent in step S1 to obtain a first slurry;

[0042] S3, adding a second binder to the first slurry, and obtaining a separator coating slurry after dispersion and dissolution;

[0043] S4, coating the separator coating slurry on at least one surface of a base film, and then performing solidification and drying to obtain the oil-based separator of the secondary battery.

[0044] According to a third aspect of the present application, the present application provides a secondary battery, which comprises a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte, and the separator is the above-mentioned oil-based separator.

[0045] In some embodiments, the oil-based separator is connected to the positive electrode sheet, and the peeling strength between the coating of the oil-based separator and the positive electrode sheet is 10-20 N / m.

[0046] wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, the positive electrode active material layer comprising a positive electrode active material, which can be one or more of a combination of compounds represented by the formulae Li a Ni x Co y M z O 2-b N b LiCoO2, LiNiO2, LiVO2, LiCrO2, LiMn2O4, LiCoMnO4, Li2NiMn3O8, LiNi 0.5 Mn 1.5 LiCoPO4, LiMnPO4, LiFePO4, LiNiPO4, LiCoFSO4, CuS2, FeS2, MoS2, NiS, TiS2, etc. The positive electrode active material can also be modified, and methods for modifying the positive electrode active material will be known to those skilled in the art, for example, the positive electrode active material can be modified by coating, doping, etc., and the materials used for modification can be one or more of a combination of Al, B, P, Zr, Si, Ti, Ge, Sn, Mg, Ce, W, etc. The positive electrode current collector is typically a structure or part that collects current, and can be any of various materials suitable for use as a positive electrode current collector in a lithium ion battery, for example, the positive electrode current collector can be one or more of a combination of Al, Cu, Ni, Fe, etc.

[0047] The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer coated on at least one surface of the negative electrode current collector, and the negative electrode active material layer can be one or more of a combination of graphite, soft carbon, hard carbon, carbon fiber, mesocarbon microbeads, silicon-based materials, tin-based materials, lithium titanate, or other metals that can form alloys with lithium, etc.

[0048] The graphite can be selected from one or more of artificial graphite, natural graphite, and modified graphite; the silicon-based material can be selected from one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, and silicon alloys; the tin-based material can be selected from one or more of elemental tin, tin oxide compounds, and tin alloys. The negative electrode current collector is typically a structure or component that collects current. The negative electrode current collector can be any material suitable for use as a negative electrode current collector in lithium-ion batteries, for example, it can be, but is not limited to, metal foil, and more specifically, it can be, but is not limited to, copper foil. The secondary battery also includes an electrolyte, which comprises an organic solvent, an electrolyte lithium salt, and additives. The electrolyte lithium salt can be LiPF6 and / or LiBOB used in high-temperature electrolytes; it can also be at least one of LiBF4, LiBOB, and LiPF6 used in low-temperature electrolytes; it can also be at least one of LiBF4, LiBOB, LiPF6, and LiTFSI used in overcharge-resistant electrolytes; or it can be at least one of LiClO4, LiAsF6, LiCF3SO3, and LiN(CF3SO2)2. The organic solvent can be cyclic carbonates, including PC and EC; it can also be chain carbonates, including DFC, DMC, or EMC; or it can be carboxylic acid esters, including MF, MA, EA, and MP. Additives include, but are not limited to, at least one of film-forming additives, conductive additives, flame-retardant additives, overcharge-resistant additives, additives for controlling H2O and HF content in the electrolyte, additives for improving low-temperature performance, and multifunctional additives.

[0049] To make the technical solution and advantages of the present invention clearer, the present invention and its beneficial effects will be described in further detail below in conjunction with specific embodiments, but the embodiments of the present invention are not limited thereto.

[0050] Example 1

[0051] Oil-based diaphragm coating slurry

[0052] The coating slurry for the oil-based diaphragm includes a first binder, a second binder, and inorganic fillers; the mass fraction of the first binder is A, and the mass fraction of the second binder is B, wherein A and B satisfy the relationship: 0.25 ≤ A / B ≤ 4; the particle size D50 of the first binder is R. A The particle size D50 of the second binder is R B , where R A With R B Satisfying the relation: 0 < R A / R B ≤0.6.

[0053] The first binder is polyvinylidene fluoride-hexafluoropropylene copolymer (molecular weight 600000 g / mol), the mass fraction A of the first binder is 34 parts, the particle size R of the first binder is 7.1 μm; the second binder is polyvinylidene fluoride-hexafluoropropylene copolymer (molecular weight 800000 g / mol), the mass fraction B of the second binder is 136 parts, the particle size R of the second binder is 14.5 μm; and the inorganic filler is bormite, the mass fraction C of the inorganic filler is 40 parts. A The first binder is polyvinylidene fluoride-hexafluoropropylene copolymer (molecular weight 600000 g / mol), the mass fraction A of the first binder is 34 parts, the particle size R of the first binder is 7.1 μm; the second binder is polyvinylidene fluoride-hexafluoropropylene copolymer (molecular weight 800000 g / mol), the mass fraction B of the second binder is 136 parts, the particle size R of the second binder is 14.5 μm; and the inorganic filler is bormite, the mass fraction C of the inorganic filler is 40 parts. B The first binder is polyvinylidene fluoride-hexafluoropropylene copolymer (molecular weight 600000 g / mol), the mass fraction A of the first binder is 34 parts, the particle size R of the first binder is 7.1 μm; the second binder is polyvinylidene fluoride-hexafluoropropylene copolymer (molecular weight 800000 g / mol), the mass fraction B of the second binder is 136 parts, the particle size R of the second binder is 14.5 μm; and the inorganic filler is bormite, the mass fraction C of the inorganic filler is 40 parts.

[0054] Preparation of the separator

[0055] S1, uniformly dispersing 2.6 kg of inorganic filler in 133 kg of NMP;

[0056] S2, dispersing and dissolving 2.21 kg of the first binder in the NMP in step S1 to obtain a first slurry;

[0057] S3, adding 8.84 kg of the second binder to the first slurry, and obtaining a separator coating slurry after dispersion and dissolution;

[0058] S4, coating the oil-based separator coating slurry on the surface of the PE base film, and obtaining the oil-based separator of the secondary battery after solidification and drying.

[0059] Example 2

[0060] Different from example 1, the mass fraction A of the first binder in this example is 85 parts; the mass fraction B of the second binder is 85 parts; and the mass fraction C of the inorganic filler is 40 parts.

[0061] The rest is the same as example 1, which will not be repeated here.

[0062] Example 3

[0063] Different from example 1, the mass fraction A of the first binder in this example is 136 parts; the mass fraction B of the second binder is 34 parts; and the mass fraction C of the inorganic filler is 40 parts.

[0064] The rest is the same as example 1, which will not be repeated here.

[0065] Example 4

[0066] Different from example 1, the mass fraction A of the first binder in this example is 34 parts; the mass fraction B of the second binder is 136 parts; and the mass fraction C of the inorganic filler in this example is 34 parts.

[0067] The rest is the same as example 1, which will not be repeated here.

[0068] Example 5

[0069] Different from example 1, in this example, the mass fraction A of the first binder is 115 parts; the mass fraction B of the second binder is 30 parts; the mass fraction C of the inorganic filler is 80 parts.

[0070] The rest is the same as example 1, which will not be repeated here.

[0071] Example 6

[0072] Different from example 1, in this example, the first binder is polyvinylidene fluoride-hexafluoropropylene copolymer (molecular weight is 600000 g / mol), the particle size R A of the first binder is 8.1 μm; the second binder is polyvinylidene fluoride-hexafluoropropylene copolymer (molecular weight is 850000 g / mol), the particle size R B of the second binder is 16 μm.

[0073] The rest is the same as example 1, which will not be repeated here.

[0074] Example 7

[0075] Different from example 1, in this example, the first binder is polyvinylidene fluoride-hexafluoropropylene copolymer (molecular weight is 600000 g / mol); the second binder is polyvinylidene fluoride-hexafluoropropylene copolymer (molecular weight is 800000 g / mol); the inorganic filler is aluminum oxide, and the mass fraction C of the inorganic filler is 40 parts.

[0076] The rest is the same as example 1, which will not be repeated here.

[0077] Example 8

[0078] Different from example 1, in this example, the first binder is polyvinylidene fluoride-hexafluoropropylene copolymer (molecular weight is 500000 g / mol), the particle size R A of the first binder is 9.0 μm; the second binder is polyvinylidene fluoride-hexafluoropropylene copolymer (molecular weight is 800000 g / mol), the particle size R B of the second binder is 15.0 μm.

[0079] The rest is the same as example 1, which will not be repeated here.

[0080] Example 9

[0081] Different from example 2, in this example, the mass fraction C of the inorganic filler is 20 parts.

[0082] The rest is the same as example 2, which will not be repeated here.

[0083] Example 10

[0084] Different from example 2, the mass fraction C of the inorganic filler in this example is 120 parts.

[0085] The rest is the same as example 2, which will not be repeated here.

[0086] Comparative example 1

[0087] Different from example 1, this comparative example only contains the first binder, and does not contain the second binder. The first binder is polyvinylidene fluoride-hexafluoropropylene copolymer (molecular weight is 600000 g / mol), the mass fraction A of the first binder is 170 parts, and the particle size R of the first binder is 7.1 μm. A

[0088] The rest is the same as example 1, which will not be repeated here.

[0089] Comparative example 2

[0090] Different from example 1, this comparative example only contains the second binder, and does not contain the first binder. The second binder is polyvinylidene fluoride-hexafluoropropylene copolymer (molecular weight is 800000 g / mol), the mass fraction B of the second binder is 170 parts, and the particle size R of the second binder is 14.5 μm. B

[0091] The rest is the same as example 1, which will not be repeated here.

[0092] Comparative example 3

[0093] Different from example 1, the mass fraction A of the first binder in this comparative example is 30 parts; the mass fraction B of the second binder is 170 parts; and the mass fraction C of the inorganic filler is 50 parts.

[0094] The rest is the same as example 1, which will not be repeated here.

[0095] Comparative example 4

[0096] Different from example 1, the mass fraction A of the first binder in this comparative example is 170 parts; the mass fraction B of the second binder is 30 parts; and the mass fraction C of the inorganic filler is 50 parts.

[0097] The rest is the same as example 1, which will not be repeated here.

[0098] Comparative example 5

[0099] Different from example 1, the first binder in this comparative example is polyvinylidene fluoride (molecular weight is 1000000 g / mol), the particle size R of the first binder is 7.1 μm. A ​​The first binder was polyvinylidene fluoride (molecular weight 1000000 g / mol), and the particle size R B was 107 μm.

[0100] The rest was the same as Example 1, which will not be repeated here.

[0101] The specific parameters of Examples 1-10 and Comparative Examples 1-5 are shown in Table 1 below.

[0102] Table 1

[0103] The following performance tests were conducted on the separators of the secondary batteries prepared in the examples and comparative examples, respectively:

[0104] 1. The separators prepared in Example 2, Comparative Examples 1, 2, 3, and 5 were subjected to SEM tests, and the test results are shown in Figures 1-5.

[0105] Peeling strength test: 1) First, the adhesive separator and the positive electrode sheet were hot-pressed at 1 MPa and 95°C; 2) The 180° peeling strength of the separator and the electrode sheet was tested.

[0106] 2. Separator heat shrinkage test: The oven temperature was set to 110°C, and when the temperature was stable at 110°C, the oily separator was placed in the oven and kept for 1 h before stopping, and the shrinkage size ratio of the oily separator before and after baking was tested.

[0107] The results of the above performance tests are shown in Table 2 below.

[0108] Table 2

[0109] As can be seen from the experimental data of Examples 1-10 and Comparative Examples 1-5 in Table 2, when the mass fraction A of the first binder and the mass fraction B of the second binder satisfy the relationship: 0.25≤A / B≤4, the particle size R A of the first binder and the particle size R B of the second binder satisfy the relationship: 0 A < R B ≤0.6, the pore-forming property of the separator coating can be effectively improved, the pore uniformity is good, the ion transmission can be accelerated, and the adhesion can be improved.

[0110] As can be seen from FIGS. 1-5, the coating of Example 2 has good porosity and high porosity. When only the first binder is used without the second binder, as shown in Comparative Example 1, the porosity is good but the adhesion is poor. When only the second binder is used without the first binder, as shown in Comparative Example 2, the porosity of the separator is poor and the pores are easily blocked. When the value of A / B is too small, as shown in Comparative Example 3, the pore structure of the separator is small and the porosity is poor and the pores are easily blocked. When the value of A / B is too large, as shown in Comparative Example 4, the adhesion of the separator is poor. When the value of R A B is too large, as shown in Comparative Example 5, the porosity of the separator is poor and the pores are easily blocked.

[0111] According to the disclosure and teachings of the above specification, those skilled in the art will be able to make changes and modifications to the above embodiments. Therefore, the present application is not limited to the above specific embodiments, and any obvious improvements, replacements or modifications made by those skilled in the art based on the present application shall fall within the scope of the present application. In addition, although some specific terms are used in the specification, these terms are only for convenience of explanation and do not constitute any limitation on the present application.​

Claims

1. An oil-based separator, characterized by, The oil-based separator comprises a base film and a coating layer provided on at least one surface of the base film, wherein the coating layer comprises a first binder, a second binder and an inorganic filler. The mass fraction of the first binder is A, the mass fraction of the second binder is B, and A and B satisfy the relationship: 0.25≤A / B≤4. The particle size D50 of the first binder is R A The particle size D50 of the second binder is R B wherein R A and R B satisfy the relationship: 0 < R A / R B ≤ 0.

6.

2. The oil-based separator according to claim 1, characterized by The mass fraction of the inorganic filler is C, and A, B and C satisfy the relationship: 0.2≤C / (A+B)≤0.

55.

3. The oil-based separator according to claim 1, characterized by The particle size R of the first adhesive A The particle size R of the second binder is 1-120 μm. B It ranges from 2 to 200 μm.

4. The oil-based separator according to claim 3, characterized by The molecular weight of the first binder is 300000-600000 g / mol.

5. The oil-based separator according to claim 3, characterized by The molecular weight of the second binder is 600000-1000000 g / mol.

6. The oil-based separator according to any one of claims 1 to 5, characterized by The first binder and the second binder are selected from one or more of polyvinylidene fluoride, vinylidene fluoride-trifluorochloroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether copolymer, vinylidene fluoride-vinylidene propylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, and vinylidene fluoride-tetrafluoroethylene copolymer.

7. The oil-based separator according to any one of claims 1 to 5, characterized by The inorganic filler is selected from one or more of alumina, magnesia, calcia, baryta, zinc oxide, silica, titania, zirconia, magnesium hydroxide, aluminum hydroxide, boehmite and ceramic fiber.

8. A method for producing the oil-based separator of the secondary battery according to any one of claims 1 to 7, characterized by, The method comprises the following steps: S1, uniformly dispersing the inorganic filler in an organic solvent; S2, dispersing and dissolving the first binder in the organic solvent in step S1 to obtain a first slurry; S3, adding the second binder to the first slurry, and obtaining a separator coating slurry after dispersion and dissolution; S4, coating the separator coating slurry on at least one surface of the base film, and then performing solidification and drying to obtain the oil-based separator of the secondary battery.

9. A secondary battery characterized by comprising: The oil-based separator as claimed in any one of claims 1-7.

10. The secondary battery according to claim 9, wherein The oil-based separator is further connected with a positive electrode sheet, and the peeling strength between the coating layer of the oil-based separator and the positive electrode sheet is 10-20 N / m.

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