A separator and its preparation method and application

Abstract

The present invention provides a separator and its preparation method and application. The preparation method includes the following steps: S1: Double-sidedly coat a substrate to obtain a first film; S2: Subject the first film to phase inversion to obtain the separator; wherein, the double-sided coating is carried out by two slit dies arranged oppositely. When the substrate is double-sidedly coated by the double slit dies, the distances between the substrate and the two slit dies are the same; denote the die lip opening of the slit die as S, the thickness of the substrate as T, and the sum of the distances between the two slit dies and the substrate as D. S, T, and D satisfy the following relationship: 3S ≤ D - T ≤ 55S. The present invention adopts double slit dies to coat face to face, and limits the relationship among the die lip opening of the slit die, the thickness of the substrate, and the sum of the distances between the two slit dies and the substrate, ensuring the consistency of the thickness on both sides of the separator and making the thickness deviation of the coatings on both sides of the obtained separator small.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion batteries, and relates to a separator and a preparation method and application thereof. Background Art

[0002] Due to the particularity of the alkaline electrolytic cell separator, at present, only the "pad film method" process route is available, and the pad film method process path is as follows: pad film unwinding -- coating slurry on the pad film -- substrate unwinding -- laminating the substrate with the pad film coated with slurry -- coating again -- phase separation -- after the coating is cured, the pad film is peeled off from the formed separator -- the pad film and the formed separator are respectively wound up.

[0003] The pad film method process has the following disadvantages: (1) Due to the presence of the pad film, the equipment needs to additionally add a pad film unwinder, a winder and a control system, resulting in high equipment costs; (2) The presence of the pad film makes the preparation process complicated, and it is extremely difficult to control the consistency of the coating thickness on both sides of the separator (the middle layer is the substrate), and the coating thickness deviation on both sides of the substrate can reach 80 microns.

[0004] Therefore, in this field, it is desirable to develop a separator with a simple preparation method and a small thickness deviation between the coatings on both sides of the separator. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a separator and a preparation method and application thereof.

[0006] To achieve the purpose of this invention, the present invention adopts the following technical solutions:

[0007] In the first aspect, the present invention provides a preparation method of a separator, and the preparation method includes the following steps:

[0008] S1: Double-sidedly coat a substrate to obtain a first film material;

[0009] S2: Subject the first film material to phase inversion to obtain the separator;

[0010] Among them, the double-sided coating is carried out by two slit dies arranged oppositely. When the substrate is double-sidedly coated by the double slit dies, the distances between the substrate and the two slit dies are the same;

[0011] Denote the die lip opening of the slit die as S, the thickness of the substrate as T, and the sum of the distances from the two slit dies to the substrate as D. S, T and D satisfy the following relationship: 3S ≤ D - T ≤ 55S. For example, D - T is equal to 3S, 5S, 8S, 10S, 13S, 15S, 18S, 20S, 23S, 25S, 28S, 30S, 33S, 35S, 38S, 40S, 43S, 45S, 48S, 50S, 53S, 55S, etc.

[0012] By using the method for preparing the separator provided by the present invention, there is no need to additionally use a unwinder, a rewinder and a control system for the cushion film, reducing the equipment cost; the present invention uses a double slit die to coat face to face, and by defining the relationship among the die lip opening of the slit die, the thickness of the substrate, and the sum of the distances from the two slit dies to the substrate, the consistency of the thickness on both sides of the separator is ensured, so that the thickness deviation of the coatings on both sides of the prepared separator is small.

[0013] Preferably, 3S ≤ D - T ≤ 25S, for example, D - T is equal to 3S, 5S, 8S, 10S, 12S, 14S, 16S, 18S, 20S, 22S, 24S, 25S, etc. More preferably, 3S ≤ D - T ≤ 10S, for example, D - T is equal to 3S, 4S, 5S, 6S, 7S, 8S, 9S, 10S, etc. When 3S ≤ D - T ≤ 10S, the coating effect is better, without phenomena such as missed coating, uneven coating, and sagging, and the thickness deviation of the coatings on both sides can be controlled within ±20 μm.

[0014] Preferably, the thickness T of the substrate is 100 - 300 μm, for example, 100 μm, 120 μm, 140 μm, 160 μm, 180 μm, 200 μm, 220 μm, 240 μm, 260 μm, 280 μm, 300 μm, etc.

[0015] It should be noted that the present invention does not specifically limit the material of the substrate. For example, it can be polyphenylene sulfide (PPS), polypropylene (PP), polyethylene terephthalate (PET), etc.

[0016] Preferably, the die lip opening of the slit die S is 100 - 400 μm, for example, 100 μm, 120 μm, 140 μm, 160 μm, 180 μm, 200 μm, 220 μm, 240 μm, 260 μm, 280 μm, 300 μm, 320 μm, 340 μm, 360 μm, 380 μm, 400 μm, etc., and preferably 250 - 350 μm.

[0017] Preferably, the viscosity of the slurry used for double-sided coating is 5000-30000 cps, such as 5000 cps, 6000 cps, 7000 cps, 8000 cps, 9000 cps, 10000 cps, 11000 cps, 12000 cps, 13000 cps, 14000 cps, 15000 cps, 16000 cps, 17000 cps, 18000 cps, 19000 cps, 20000 cps, 21000 cps, 22000 cps, 23000 cps, 24000 cps, 25000 cps, 26000 cps, 27000 cps, 28000 cps, 29000 cps, 30000 cps, etc., preferably 7000-10000 cps. If the viscosity of the slurry is too small and the fluidity is too good, the slurry will easily drip from the substrate and cannot adhere; if the viscosity of the slurry is too large and the fluidity is too poor, it will not be able to be extruded from the slit die head.

[0018] It should be noted that the present invention does not specifically limit the specific composition of the slurry, and it can be the slurry used for the partition members commonly used in the prior art.

[0019] Preferably, in the preparation method, S2 further includes:

[0020] S201: Perform double-sided gas-phase separation on the first film material;

[0021] And / or,

[0022] S202: Perform double-sided liquid-phase separation on the first film material.

[0023] As a preferred technical solution of the present invention, the preparation method provided by the present invention includes a double-sided gas-phase separation process section, which can improve the bubble point of the partition member; the preparation method provided by the present invention includes a double-sided liquid-phase separation process section. Because the coatings on both sides of the substrate are in full contact with the mixed liquid in the non-solvent tank at the same time, effective functional skin layers are respectively formed. In terms of the core performance of the product, it is equivalent to the effect of using two products of the pad film method stacked together.

[0024] Preferably, the temperature of the double-sided gas-phase separation in S201 is 50-150 °C, such as 50 °C, 60 °C, 70 °C, 80 °C, 90 °C, 100 °C, 110 °C, 120 °C, 130 °C, 140 °C, 150 °C, etc., preferably 80-120 °C. Limiting the temperature inside the circulating oven within the range of 50-150 °C is beneficial to more uniform pore formation and thickness control on both sides of the coating.

[0025] Preferably, S201 uses a circulating oven for double-sided gas-phase separation.

[0026] Preferably, the wind speed inside the circulating oven is 3 - 12 m / s, such as 3 m / s, 4 m / s, 5 m / s, 6 m / s, 7 m / s, 8 m / s, 9 m / s, 10 m / s, 11 m / s, 12 m / s, etc., and preferably 7 - 10 m / s. Limiting the wind speed inside the circulating oven within the range of 3 - 12 m / s is beneficial to preventing jitter and damage to the coating caused by the wind force, and at the same time can perform pre-drying treatment on the coating.

[0027] Preferably, the concentration of the solvent gas in the circulating air inside the circulating oven is ≤ 40% relative to the saturation value at the same temperature, such as 40%, 35%, 30%, 25%, 20%, 15%, 10%, 5%, etc., and preferably ≤ 30%. The solvent gas may include, for example, N-methylpyrrolidone (NMP).

[0028] Preferably, the time required for the same position on the first membrane material to pass through the circulating oven is 0.5 - 10 min, such as 0.5 min, 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, etc.

[0029] Preferably, S202 uses a non-solvent tank for double-sided liquid phase separation. The non-solvent tank is provided with a non-solvent, and the mass concentration of the organic solvent in the non-solvent is controlled at ≤ 40%, such as 40%, 35%, 30%, 25%, 20%, 15%, 10%, 5%, etc., and preferably 20% - 30%. Limiting the concentration of the organic solvent within the range of ≤ 40% can make the pore formation of the separator more uniform.

[0030] Preferably, the organic solvent includes N-methylpyrrolidone.

[0031] Preferably, the liquid temperature in the non-solvent tank is 5 - 30 °C, such as 5 °C, 10 °C, 15 °C, 20 °C, 25 °C, 30 °C, etc., and preferably 15 - 25 °C. Limiting the liquid temperature in the non-solvent tank within the range of 5 - 30 °C can make the separator have good consistency. Considering economy, 15 - 25 °C is preferred.

[0032] Preferably, the time required for the same position on the first membrane material to pass through the non-solvent tank is 2 - 20 min, such as 2 min, 5 min, 8 min, 10 min, 12 min, 14 min, 16 min, 18 min, 20 min, etc.

[0033] In a second aspect, the present invention provides a separator, which includes a substrate and coatings coated on both sides of the substrate, and the separator is prepared by using the preparation method described in the first aspect.

[0034] Preferably, the thickness deviation of the coatings on both sides of the separator is ≤ 20 μm, such as 20 μm, 19 μm, 18 μm, 17 μm, 16 μm, 15 μm, 14 μm, 13 μm, 12 μm, 11 μm, 10 μm, 9 μm, 8 μm, 7 μm, 6 μm, 5 μm, 4 μm, 3 μm, 2 μm, 1 μm, etc.

[0035] Preferably, the average pore size of the separator is 50 - 500 nm, such as 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, etc.

[0036] Preferably, the film-forming thickness of the separator is 500 ± 50 μm, such as 450 μm, 460 μm, 470 μm, 480 μm, 490 μm, 500 μm, 510 μm, 520 μm, 530 μm, 540 μm, 550 μm, etc.

[0037] Preferably, the bubble point of the separator is 4 - 20 bar, such as 4 bar, 6 bar, 8 bar, 10 bar, 12 bar, 14 bar, 16 bar, 18 bar, 20 bar, etc.

[0038] Preferably, the surface resistance of the separator is 0.1 - 2 Ω·cm 2 , such as 0.1 Ω·cm 2 , 0.2 Ω·cm 2 , 0.3 Ω·cm 2 , 0.4 Ω·cm 2 , 0.5 Ω·cm 2 , 0.6 Ω·cm 2 , 0.7 Ω·cm 2 , 0.8 Ω·cm 2 , 0.9 Ω·cm 2 , 1 Ω·cm 2 , 1.1 Ω·cm 2 , 1.2 Ω·cm 2 , 1.3 Ω·cm 2 , 1.4 Ω·cm 2 , 1.5 Ω·cm 2 , 1.6 Ω·cm 2 , 1.7 Ω·cm 2 , 1.8 Ω·cm 2 , 1.9 Ω·cm 2 , 2 Ω·cm 2 , etc., preferably 0.1 - 0.2 Ω·cm 2 .

[0039] Preferably, the curl of the separator is ≤ 15 mm, such as 15 mm, 14 mm, 13 mm, 12 mm, 11 mm, 10 mm, 8 mm, 6 mm, 5 mm, 3 mm, 1 mm, etc.

[0040] Preferably, the number of bubbles per 100 square centimeters of the separator is ≤ 8, such as 8, 7, 6, 5, 4, 3, 2, 1, 0, etc.

[0041] In a third aspect, the present invention provides an electrolytic cell comprising a separator prepared by the preparation method described in the first aspect or a separator described in the second aspect.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] By using the preparation method of the separator provided by the present invention, there is no need to additionally use a unwind machine, a rewind machine and a control system for the cushion film, reducing the equipment cost; the present invention uses a double slit die to coat face to face, and by defining the relationship among the die lip opening of the slit die, the thickness of the substrate, and the sum of the distances from the two slit dies to the substrate, the consistency of the thickness on both sides of the separator is ensured, so that the thickness deviation of the coatings on both sides of the prepared separator is small. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 Schematic diagram of the positional relationship between the slit die and the substrate in the preparation method provided for Example 1;

[0045] Wherein, S: die lip opening of the slit die, T: thickness of the substrate, D: sum of the distances from the two slit dies to the substrate, 1 / 2: slit die. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0046] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0047] Example 1

[0048] In this example, a preparation method of a separator is provided, and the preparation method includes the following steps:

[0049] S1: Double-sidedly coat the substrate to obtain a first film material;

[0050] S2: Pass the first film material through a circulating oven, complete double-sided gas-phase separation in the circulating oven, and then pass the first film material through a non-solvent tank for double-sided liquid-phase separation to obtain the separator;

[0051] Among them, the double-sided coating is carried out by two slit dies arranged oppositely. When the substrate is double-sided coated by the double slit die, the distances between the substrate and the two slit dies are the same;

[0052] Denote the die lip opening of the slit die as S, the thickness of the substrate as T, and the sum of the distances from the two slit dies to the substrate as D. S, T, and D satisfy the following relationship: 3S ≤ D - T ≤ 10S. Specifically, S is 170 μm, T is 268 μm, and D is 1016 μm.

[0053] Among them, the material of the substrate is polyphenylene sulfide PPS; the slurry composition is as follows: a mixed solution of polysulfone PSU, ZrO 2 , and NMP with a mass ratio of 2:3:5. The viscosity of the slurry is 10000 cps; the temperature inside the circulating oven is 75 °C, the wind speed is 8 m / s, and the concentration of the solvent gas (NMP) in the circulating air is 25% relative to the saturation value at the same temperature; the time required for the same position on the first film to pass through the circulating oven is 5 min; the non-solvent tank contains water, and during the production of the separator, the mass concentration of NMP in the water is controlled to be less than 5%; the liquid temperature in the non-solvent tank is 20 °C; the time required for the same position on the first film to pass through the non-solvent tank is 2 min.

[0054] In the preparation method provided in this embodiment, the schematic diagram of the positional relationship between the slit die and the substrate is as Figure 1 shown.

[0055] Example 2

[0056] In this embodiment, a method for preparing a separator is provided. The preparation method includes the following steps:

[0057] S1: Double-sided coat the substrate to obtain a first film;

[0058] S2: Pass the first film through a circulating oven to complete double-sided gas-phase separation inside the circulating oven, and then pass the first film through a non-solvent tank for double-sided liquid-phase separation to obtain the separator;

[0059] Among them, the double-sided coating is carried out by two slit dies arranged oppositely. When the substrate is double-sided coated by the double slit die, the distances between the substrate and the two slit dies are the same;

[0060] Denote the die lip opening of the slit die as S, the thickness of the substrate as T, and the sum of the distances from the two slit dies to the substrate as D. S, T, and D satisfy the following relationship: 3S ≤ D - T ≤ 25S. Specifically, S is 170 μm, T is 268 μm, and D is 2200 μm.

[0061] Among them, the substrate is made of PPS; the slurry composition is as follows: a mixture of PSU, ZrO, and NMP with a mass ratio of 2:3:5, and the viscosity of the slurry is 10,000 cps; 2 The concentration of the solvent gas (NMP) in the circulating air is 25% relative to the saturation value at the same temperature; the time required for the same position on the first film to pass through the circulating oven is 5 minutes; the non-solvent tank contains a mixture of water and NMP, where the mass concentration of NMP is 5%; the liquid temperature in the non-solvent tank is 20°C; the time required for the same position on the first film to pass through the non-solvent tank is 2 minutes.

[0062] Example 3

[0063] In this example, a method for preparing a separator is provided, and the preparation method includes the following steps:

[0064] S1: Double-sidedly coat the substrate to obtain a first film;

[0065] S2: Pass the first film through a circulating oven to complete double-sided gas-phase separation in the circulating oven, and then pass the first film through a non-solvent tank for double-sided liquid-phase separation to obtain the separator;

[0066] Among them, the double-sided coating is carried out by two slit dies arranged oppositely. When the substrate is double-sidedly coated by the double slit die, the distance between the substrate and the two slit dies is the same;

[0067] Denote the die lip opening of the slit die as S, the thickness of the substrate as T, and the sum of the distances from the two slit dies to the substrate as D. S, T, and D satisfy the following relationship: 3S ≤ D - T ≤ 55S. Specifically, S is 170 μm, T is 268 μm, and D is 6000 μm.

[0068] Among them, the substrate is made of PPS; the slurry composition is as follows: a mixture of PSU, ZrO, and NMP with a mass ratio of 2:3:5, and the viscosity of the slurry is 10,000 cps; 2 The concentration of the solvent gas (NMP) in the circulating air is 25% relative to the saturation value at the same temperature; the time required for the same position on the first film to pass through the circulating oven is 5 minutes; the non-solvent tank contains a mixture of water and NMP, where the mass concentration of NMP is 5%; the liquid temperature in the non-solvent tank is 20°C; the time required for the same position on the first film to pass through the non-solvent tank is 2 minutes.

[0069] Example 4

[0070] This embodiment is different from Embodiment 1 only in that S is 120 μm, T is 268 μm, and D is 748 μm.

[0071] Embodiment 5

[0072] This embodiment is different from Embodiment 1 only in that S is 60 μm, T is 160 μm, and D is 400 μm.

[0073] Embodiment 6

[0074] This embodiment is different from Embodiment 1 only in that the temperature inside the circulating oven is 150 °C.

[0075] Embodiment 7

[0076] This embodiment is different from Embodiment 1 only in that the temperature inside the circulating oven is 45 °C.

[0077] Embodiment 8

[0078] This embodiment is different from Embodiment 1 only in that the concentration of the solvent gas (NMP) in the circulating air is 45% relative to the saturation value at the same temperature.

[0079] Embodiment 9

[0080] This embodiment is different from Embodiment 1 only in that the mass concentration of NMP in the non-solvent tank is 45%.

[0081] Embodiment 10

[0082] This embodiment is different from Embodiment 1 only in that the liquid temperature in the non-solvent tank is 3 °C.

[0083] Embodiment 11

[0084] This embodiment is different from Embodiment 1 only in that the time required for the same position on the first film material to pass through the circulating oven is 12 min.

[0085] Embodiment 12

[0086] This embodiment is different from Embodiment 1 only in that the time required for the same position on the first film material to pass through the non-solvent tank is 1.5 min.

[0087] Embodiment 13

[0088] This embodiment is different from Embodiment 1 only in that the substrate material is changed to PET and the temperature inside the circulating oven is 155 °C.

[0089] Comparative Example 1

[0090] The only difference between this comparative example and Example 1 is that S is 170 μm, T is 268 μm, and D is 608 μm.

[0091] Comparative Example 2

[0092] The only difference between this comparative example and Example 1 is that S is 170 μm, T is 268 μm, and D is 10468 μm.

[0093] Comparative Example 3

[0094] The only difference between this comparative example and Example 1 is that the gas-phase separation process section is not included in the preparation method, which is specifically as follows:

[0095] S1: Double-sidedly coat the substrate to obtain the first film material;

[0096] S2: Pass the first film material through a non-solvent tank for double-sided liquid-phase separation to obtain the separator;

[0097] Among them, the double-sided coating is carried out through two slit dies arranged oppositely. When the substrate is double-sidedly coated through the double slit dies, the distances between the substrate and the two slit dies are the same;

[0098] The substrate material, slurry formula, and specific process parameters involved are all the same as those in Example 1.

[0099] Perform performance tests on the separators provided in the examples and comparative examples. The test methods are as follows:

[0100] (1) Thickness deviation of the two-side coatings: Use a Gemini 360 instrument to take an SEM image of the product cross-section, and measure the thickness dimensions of the coatings on both sides of the substrate according to the captured results;

[0101] (2) Average pore size: Use an instrument CFP-1500-AE to measure the pore size and pore size distribution of the product, and obtain the average pore size of the product;

[0102] (3) Bubble point: Refer to GB / T 32361-2015, and use an instrument CFP-1500-AE to measure the bubble point pressure of the product;

[0103] (4) Surface resistance: Refer to SJ / T 10171-2016, use a Chenhua 604E instrument, use 30% potassium hydroxide solution as the electrolyte, and perform the test at room temperature;

[0104] (5) Curling degree: Measure using an IG-028 sensor. The measurement method is to unroll the product film by more than 1 m, ensure that both ends of the detection section are horizontal, and the middle section bends naturally, and place the sensor at the middle section to measure the value;

[0105] (6) Number of appearance defects: Use a CCD online scanning detection system to scan and count the number of product bubbles per 100 square centimeters.

[0106] The performance test results are shown in Table 1.

[0107] Table 1

[0108]

[0109] As can be seen from Table 1, the thickness deviation of the coatings on both sides of the separator provided in the embodiments of the present invention is small (can be controlled within ±20 μm), and the separator has a high bubble point (3.4 - 9.2 bar), a low surface resistance, a small degree of curl, and a small number of appearance defects (≤7).

[0110] Compared with Example 1, the thickness deviation of the coatings on both sides of the separator provided in Comparative Example 1 becomes larger; the thickness of the coatings on both sides of the separator provided in Comparative Example 2 becomes significantly larger, the bubble point decreases, the degree of curl becomes significantly larger, and the number of appearance defects increases significantly; the bubble point of the separator provided in Comparative Example 3 decreases.

[0111] The applicant declares that the present invention uses the above embodiments to illustrate the separator of the present invention, its preparation method and application, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent substitution of the raw materials selected for the present invention, the addition of auxiliary components, and the selection of specific methods, etc., all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for preparing a separator, characterized in that: The preparation method comprises the following steps: S1: coating the substrate on both sides to obtain a first film material; S2: performing double-sided gas phase separation on the first membrane material, and then performing double-sided liquid phase separation on the first membrane material using a non-solvent tank to obtain the separator; Wherein, the double-sided coating is performed by two slot dies arranged opposite to each other, and when the substrate is double-sided coated by the double slot dies, the distance between the substrate and the two slot dies is the same; The non-solvent tank contains a mixture of water and an organic solvent, and the mass concentration of the organic solvent is controlled to be ≤40%, and the organic solvent includes N-methylpyrrolidone; The lip opening of the slit die is recorded as S, the thickness of the substrate is recorded as T, and the sum of the distances from the two slit dies to the substrate is recorded as D. S, T and D satisfy the following relationship: 3S≤DT≤55S; The lip opening S of the slit die is 100-400 μm; The thickness T of the substrate is 100-300 μm.

2. The preparation method according to claim 1, characterized in that: 3S≤DT≤25S.

3. The preparation method according to claim 2, characterized in that: 3S≤DT≤10S.

4. The preparation method according to claim 1, characterized in that: The lip opening S of the slit die is 250-350 μm.

5. The preparation method according to claim 1, characterized in that: The viscosity of the slurry used for the double-sided coating is 5000-30000 cps.

6. The preparation method according to claim 5, characterized in that: The viscosity of the slurry used for the double-sided coating is 7000-10000 cps.

7. The preparation method according to claim 1, characterized in that: The temperature of the double-sided gas phase separation is 50-150°C.

8. The preparation method according to claim 7, characterized in that: The temperature of the double-sided gas phase separation is 80-120°C.

9. The preparation method according to claim 1, characterized in that: A circulating oven was used for double-sided gas phase separation.

10. The preparation method according to claim 9, characterized in that: The wind speed inside the circulation oven is 3-12 m / s.

11. The preparation method according to claim 10, characterized in that: The wind speed inside the circulation oven is 7-10 m / s.

12. The preparation method according to claim 9, characterized in that: The concentration of the solvent gas in the circulating air inside the circulating oven is ≤40% relative to the saturation value at the same temperature.

13. The preparation method according to claim 12, characterized in that: The concentration of the solvent gas in the circulating air inside the circulating oven is ≤30% relative to the saturation value at the same temperature.

14. The preparation method according to claim 9, characterized in that: The time required for the same position on the first film material to pass through the circulation oven is 0.5 to 10 min.

15. The preparation method according to claim 1, characterized in that: The mass concentration of the organic solvent is controlled at 20% to 30%.

16. The preparation method according to claim 1, characterized in that: The liquid temperature in the non-solvent tank is 5-30°C.

17. The preparation method according to claim 16, characterized in that: The liquid temperature in the non-solvent tank is 15-25°C.

18. The preparation method according to claim 1, characterized in that: The time required for the same position on the first membrane to pass through the non-solvent tank is 2 to 20 minutes.

19. A separator, comprising a substrate and a coating applied on both sides of the substrate, characterized in that: The separator is prepared by the preparation method according to any one of claims 1 to 18.

20. The separator according to claim 19, characterized in that The thickness deviation of the coatings on both sides of the separator is ≤20 μm.

21. The separator according to claim 19, characterized in that The average pore size of the separator is 50-500 nm.

22. The separator according to claim 19, characterized in that The separator has a film thickness of 500±50 μm.

23. The separator according to claim 19, characterized in that The bubble point of the separator is 4-20 bar.

24. The separator according to claim 19, characterized in that The surface resistance of the separator is 0.1~2 Ω·cm².

25. The separator according to claim 24, characterized in that The surface resistance of the separator is 0.1-0.2 Ω·cm².

26. The separator according to claim 19, characterized in that The curling degree of the separator is ≤15 mm.

27. The separator according to claim 19, characterized in that The number of bubbles per 100 square centimeters of the separator is ≤8.

28. An electrolytic cell, characterized in that: It includes a separator made by the preparation method as claimed in claim 1 or a separator as claimed in claim 19.

Images