A coated separator, its preparation method and use

Abstract

The application provides a coated diaphragm and a preparation method and application thereof, the coated diaphragm comprising a substrate and a coating layer coated on at least one side of the substrate, and the preparation raw material of the coating layer comprises an emulsion type adhesive, a solvent type adhesive and inorganic particles; the average particle size of the emulsion type adhesive is denoted as A, the average particle size of the inorganic particles is denoted as B, the average pore size of the substrate is denoted as C, and the D10 particle size of the inorganic particles is denoted as D, and A, B, C and D satisfy the following relationship: C:A:B=(0.4-0.8):1:(2-9); A+D>=3.5C. In the application, the addition of the emulsion type adhesive in the preparation raw material of the coating layer can improve the water resistance of the coated diaphragm, and by controlling the ratio of the emulsion type adhesive particle size, the inorganic particle size and the substrate pore size within a specific range, the diaphragm has good air permeability.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of diaphragm, and relates to a coated diaphragm and a preparation method and application thereof. BACKGROUND

[0002] In the structure of a lithium ion battery, a diaphragm is one of the key inner components. The performance of the diaphragm determines the interface structure, internal resistance, etc. of the battery, and directly affects the capacity, cycle, safety performance and other characteristics of the battery. A diaphragm with excellent performance plays an important role in improving the overall performance of the battery. The main function of the diaphragm is to separate the positive and negative electrodes of the battery to prevent short circuiting caused by contact between the two electrodes, and the diaphragm also has the function of allowing electrolyte ions to pass through.

[0003] At present, an inorganic coating layer is often coated on the surface of a base film to improve the heat resistance of the diaphragm. However, the inorganic coating layer causes the overall air permeability of the diaphragm to decrease. In order to improve the adhesion of the coated diaphragm to the electrode, a polymer coating layer is often coated on the surface of the coated diaphragm. In the process of coating the polymer coating layer, the coating layer needs to be solidified by water bath. The inorganic coating layer has poor water resistance, and the inorganic coating layer dissolves or falls off in the water bath, which causes the overall heat resistance of the diaphragm to decrease.

[0004] Therefore, it is desirable in the art to develop a coated diaphragm with good water resistance and air permeability. SUMMARY

[0005] In view of the deficiencies of the prior art, the purpose of the present application is to provide a coated diaphragm and a preparation method and application thereof. The diaphragm with the existing high-heat-resistant formula will weaken its heat resistance when it comes into contact with water. The performance of the diaphragm will decay (the coating layer dissolves and falls off) in the water bath after the secondary water-based coating or oil-based coating on the surface of the diaphragm, which causes the 150℃ heat shrinkage rate of the diaphragm to be greater than 5%. In the present application, the emulsion type adhesive and the solvent type adhesive are compounded in the process of preparing the slurry, and the ratio of the particle size of the emulsion type adhesive, the particle size of the inorganic particles and the pore size of the base material is controlled within a specific range, so that the diaphragm has good air permeability. In addition, the water resistance of the inorganic coating layer is improved, which improves the heat resistance of the diaphragm to a certain extent. As a further preferred solution, a crosslinking agent is added to the coating system, and a coating layer with better water resistance and heat resistance can be formed on the surface of the diaphragm after low-temperature baking, which can effectively improve the above problems. In addition, the breaking temperature of the diaphragm after crosslinking can also be improved, which greatly improves the safety performance of the battery.

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

[0007] In a first aspect, the present application provides a coated diaphragm, which comprises a base material and a coating layer coated on at least one side (for example, one side or both sides) of the base material. The preparation raw materials of the coating layer include an emulsion type adhesive, a solvent type adhesive and inorganic particles.

[0008] The average particle size of the emulsion adhesive is denoted as A, the average particle size of the inorganic particles is denoted as B, the average pore size of the substrate is denoted as C, and the D10 particle size of the inorganic particles is denoted as D. A, B, C, and D satisfy the following relationship: C:A:B=(0.4-0.8):1:(2-9); A+D≥3.5C. Here, 0.4-0.8 can be, for example, any value among 0.4, 0.5, 0.6, 0.7, 0.8, etc., or a range between any two values; 2-9 can be, for example, any value among 2, 3, 4, 5, 6, 7, 8, 9, etc., or a range between any two values; and A+D can be, for example, any ratio among 3.5C, 4C, 4.5C, 5C, 5.5C, 6C, 6.5C, 7C, 7.5C, 8C, etc., or a range between any two ratios.

[0009] In the present invention, the addition of an emulsion adhesive to the raw materials for preparing the coating can improve the water resistance of the coated membrane. By controlling the ratio of the emulsion adhesive particle size, the inorganic particle particle size, and the substrate pore size within a specific range, the membrane has better air permeability.

[0010] If the average particle size of the emulsion adhesive is too large, the coating will not be dense enough (i.e., the coating cannot cover the entire surface of the substrate), resulting in reduced heat resistance. At the same time, if the average particle size of the emulsion adhesive is too large, its own stability will deteriorate, the viscosity will increase, and the construction performance will deteriorate. If the average particle size of the emulsion adhesive is too small, it will easily penetrate into the pores of the substrate, causing the pores of the substrate to be blocked, affecting the air permeability of the diaphragm, and also affecting the bonding of inorganic particles (the glue involved in bonding the inorganic particles penetrates into the pores).

[0011] Preferably, 3.5C≤A+D≤6C. By controlling A+D to be greater than or equal to 3.5C, inorganic particles and emulsion adhesives are less likely to fall into the pores of the substrate. By controlling A+D to be less than or equal to 6C, the coating thickness can be controlled to meet the requirement that the single-sided coating thickness is less than or equal to 1.2μm, achieving lightweight and thin coating.

[0012] Preferably, the emulsion adhesive includes any one or a combination of at least two of polyacrylate, polystyrene-acrylate, polymethyl methacrylate, polybutyl methacrylate, polyethyl acrylate, polyvinyl acetate or ethylene-vinyl acetate.

[0013] Preferably, the molecular structure of the solvent-based adhesive contains carboxyl groups and / or amide groups.

[0014] Preferably, the solvent-based adhesive comprises polyacrylic acid and / or polyacrylamide.

[0015] Preferably, the average particle size (D50) of the inorganic particles is 0.1-1.0 μm, for example, any value among 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, etc., or a range value between any two values.

[0016] It is understood that the particle size D10 and D50 of the inorganic particles described in the present invention can be measured by using an OMEC LS609 laser particle size analyzer to detect the inorganic particle powder, selecting the refractive index of the corresponding material, obtaining the cumulative particle size distribution of the inorganic particle powder, and recording the particle size of 10% cumulatively from the particle side as D10, and the particle size of 50% cumulatively as D50. The particle size test of the emulsion adhesive can be performed by using an OMEC TOPSIZER laser particle size analyzer to detect the emulsion, selecting the refractive index of the corresponding material, obtaining the cumulative particle size distribution of the emulsion, and recording the particle size of 50% cumulatively from the particle side as the average particle size of the emulsion adhesive. Of course, other instruments and equipment can also be used for testing, and the present invention is not limited to this.

[0017] Preferably, the inorganic particles include any one of aluminum oxide, boehmite, barium titanate, silicon dioxide, magnesium oxide, titanium dioxide, and double metal hydroxide, or a combination of at least two thereof.

[0018] Preferably, the double metal hydroxide includes any one of magnesium aluminum double metal hydroxide, lithium aluminum double metal hydroxide (LiAlLDH), zinc aluminum double metal hydroxide, nickel aluminum double metal hydroxide, or a combination of at least two thereof.

[0019] Preferably, the inorganic particles are porous inorganic particles, such as LiAlLDH. Porous inorganic particles can further improve the air permeability and wettability of the coated separator.

[0020] Preferably, the raw materials for preparing the coating further include a cross-linking agent.

[0021] As a preferred technical solution of the present invention, a cross-linking agent is added to the raw materials for preparing the coating, and the solvent-based adhesive and the cross-linking agent can undergo a cross-linking reaction under the conventional baking conditions of the coated membrane (i.e., the baking temperature of 60-80°C mentioned later) (the emulsion-type adhesive does not participate in the cross-linking reaction) to form a cross-linked network structure. The formed organic cross-linked skeleton can improve the heat resistance of the coated membrane. The cross-linked coated membrane will not have obvious powdering after passing through the water bath stage of the oil coating process, and the thermal shrinkage of the coating at 150°C is ≤5%. At the same time, the membrane rupture temperature of the cross-linked coated membrane is also improved to a certain extent, which greatly improves the safety performance of the battery.

[0022] That is, the addition of the cross-linking agent can further improve the water resistance and heat resistance of the coated separator, and the above effects can be achieved with a smaller coating amount.

[0023] Preferably, the crosslinking agent comprises a carboxyl crosslinking agent.

[0024] Preferably, the crosslinking agent has a functionality of 2-4, such as 2, 2.2, 2.4, 2.6, 2.8, 3, 3.2, 3.4, 3.6, 3.8, 4, etc. Crosslinking of the body structure occurs when the crosslinking agent has a functionality of 2 or more. The higher the functionality or the more crosslinking agent is added, the higher the crosslinking degree will be. A crosslinking agent with a functionality greater than 4 will not significantly improve the crosslinking degree due to steric hindrance, and will not significantly improve the performance of the separator product. In addition, due to the high functionality and high activity of the crosslinking agent, premature crosslinking may occur, making it more difficult for the molecular chain to spread on the surface of the inorganic particles, resulting in a decrease in adhesion. In addition, due to the curling of the molecular chain and the reaction of the carboxyl group, the solubility of the crosslinking agent in water decreases, and the viscosity of the slurry decreases, resulting in an increase in production cost and difficulty.

[0025] Preferably, the crosslinking agent comprises any one or a combination of at least two of a blocked isocyanate crosslinking agent, a carbodiimide crosslinking agent, an aziridine crosslinking agent, or an epoxy silane crosslinking agent. It can be understood that the carbodiimide, aziridine, and epoxy silane here refer to polymers containing corresponding functional groups that can be used as crosslinking agents.

[0026] Preferably, the crosslinking agent comprises an aziridine-modified isocyanate.

[0027] Preferably, the preparation raw material of the coating further comprises any one or a combination of at least two of water, a dispersing agent, and a surfactant.

[0028] Preferably, the water comprises pure water.

[0029] Preferably, the dispersing agent comprises any one or a combination of at least two of ammonium polyacrylate, sodium tripolyphosphate, sodium hexametaphosphate, and sodium pyrophosphate.

[0030] Preferably, the surfactant comprises any one or a combination of at least two of a polyether silane copolymer, a polyether-modified polysiloxane, an alkylphenol polyoxyethylene ether, a fatty alcohol polyoxyethylene ether, a fatty acid polyoxyethylene ether, a fatty amine polyoxyethylene ether, or a fluorinated alkyl ethoxyl alcohol ether.

[0031] Preferably, the preparation raw material of the coating comprises the following components in terms of weight fraction:

[0032]

[0033] Preferably, the amount of water in the preparation of the coating layer can be any one of 60 parts, 62 parts, 64 parts, 66 parts, 68 parts, 70 parts, 72 parts, 74 parts, 76 parts, 78 parts, 80 parts, 82 parts, 84 parts, 85 parts, or a range between any two of the values.

[0034] Preferably, the amount of inorganic particles in the preparation of the coating layer can be any one of 20 parts, 22 parts, 24 parts, 26 parts, 28 parts, 30 parts, 32 parts, 34 parts, 36 parts, 38 parts, 40 parts, or a range between any two of the values.

[0035] Preferably, the amount of dispersant in the preparation of the coating layer can be any one of 0.8 parts, 0.9 parts, 1 part, 1.1 parts, 1.2 parts, or a range between any two of the values.

[0036] Preferably, the amount of emulsion adhesive in the preparation of the coating layer can be any one of 0.1 parts, 0.3 parts, 0.5 parts, 0.8 parts, 1 part, 1.2 parts, 1.4 parts, 1.6 parts, 1.8 parts, 2 parts, 2.2 parts, 2.4 parts, 2.6 parts, 2.8 parts, 3 parts, or a range between any two of the values.

[0037] Preferably, the amount of solvent adhesive in the preparation of the coating layer can be any one of 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1 part, 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts, 1.5 parts, or a range between any two of the values.

[0038] Preferably, the amount of cross-linking agent in the preparation of the coating layer can be any one of 0.01 parts, 0.02 parts, 0.03 parts, 0.04 parts, 0.05 parts, 0.06 parts, 0.07 parts, 0.08 parts, 0.09 parts, 0.1 parts, 0.11 parts, 0.12 parts, 0.13 parts, 0.14 parts, 0.15 parts, 0.16 parts, 0.17 parts, 0.18 parts, 0.19 parts, 0.2 parts, or a range between any two of the values.

[0039] Preferably, the amount of surfactant in the preparation of the coating layer can be any one of 0.05 parts, 0.06 parts, 0.07 parts, 0.08 parts, 0.09 parts, 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1 part, or a range between any two of the values.

[0040] Preferably, the mass ratio of the emulsion adhesive to the solvent adhesive is 3:(0.5-3), and 0.5-3 can be, for example, any value among 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.2, 1.4, 1.6, 1.8, 2, 2.2, 2.4, 2.6, 2.8, 3, etc., or a range value between any two values.

[0041] Preferably, the mass ratio of the solvent-based adhesive to the cross-linking agent is 100:(3-12), where 3-12 can be, for example, any value among 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc., or a range between any two values.

[0042] Preferably, the total coating amount of the coating is 2.4-3.2 g / m 2 , for example 2.4g / m 2 , 2.5g / m 2 , 2.6g / m 2 , 2.7g / m 2 , 2.8g / m 2 , 2.9g / m 2 , 3g / m 2 , 3.1g / m 2 3.2g / m 2 Any value or a range between any two values.

[0043] Preferably, the single-sided thickness of the coating is 0.5-4 μm, for example, any value among 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm, 3 μm, 3.2 μm, 3.4 μm, 3.6 μm, 3.8 μm, 4 μm, etc., or a range value between any two values.

[0044] Preferably, the substrate may be, for example, a PP base film, a PE base film, a PP / PE / PP composite base film, or the like.

[0045] In a second aspect, the present invention provides a method for preparing the coated diaphragm according to the first aspect, the preparation method comprising the following steps:

[0046] (1) mixing the raw materials for preparing the coating to obtain a slurry;

[0047] (2) The slurry is coated on one side or both sides of the base film and baked to obtain the coated separator.

[0048] Preferably, step (1) specifically includes the following steps:

[0049] Mix water and a dispersant, then add inorganic particles and disperse them, then add an emulsion adhesive, a solvent adhesive, a crosslinking agent, and a surfactant and disperse them evenly to obtain a slurry;

[0050] Preferably, the step of adding inorganic particles and dispersing the particles further includes a sand grinding step;

[0051] Preferably, the flow rate of the sand mill is 800-1200 L / h, for example, any value among 800 L / h, 850 L / h, 900 L / h, 950 L / h, 1000 L / h, 1050 L / h, 1100 L / h, 1150 L / h, 1200 L / h, etc., or a range value between any two values, and the speed of the sand mill is 700-800 rpm, for example, any value among 700 rpm, 720 rpm, 740 rpm, 760 rpm, 780 rpm, 800 rpm, etc., or a range value between any two values.

[0052] Preferably, the emulsion adhesive, solvent adhesive, crosslinking agent and surfactant are added in sequence, and the next raw material is added after they are evenly dispersed (for example, the emulsion adhesive is added, and the solvent adhesive is added after it is evenly dispersed).

[0053] Preferably, the coating method in step (2) includes coating using a micro-concave roller.

[0054] Preferably, the baking temperature is 60-80°C, for example, any value among 60°C, 62°C, 64°C, 66°C, 68°C, 70°C, 72°C, 74°C, 76°C, 78°C, 80°C, etc., or a range between any two values.

[0055] Preferably, the baking time is 10-30s, for example, any value among 10s, 12s, 14s, 16s, 18s, 20s, 22s, 24s, 26s, 28s, 30s, etc., or a range value between any two values.

[0056] In a third aspect, the present invention provides a use of the coated separator as described in the first aspect in a battery.

[0057] Compared with the prior art, the present invention has at least the following beneficial effects:

[0058] In the present invention, the addition of an emulsion adhesive to the raw materials for preparing the coating can improve the water resistance of the coated membrane. By controlling the ratio of the emulsion adhesive particle size, the inorganic particle particle size, and the substrate pore size within a specific range, the membrane has better air permeability. DETAILED DESCRIPTION

[0059] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0060] Example 1

[0061] In this embodiment, a coated diaphragm is provided. The coated diaphragm includes a substrate and a coating applied on both sides of the substrate. The raw materials for preparing the coating include the following components in parts by weight:

[0062]

[0063]

[0064] The specific selection and parameters of each raw material are shown in Table 1.

[0065] The preparation method comprises the following steps:

[0066] (1) mixing the raw materials for preparing the coating according to the formula to obtain a slurry;

[0067] (2) The slurry was coated on both sides of the base film using a micro-concave roller and baked at 70° C. for 20 seconds to obtain the coated diaphragm.

[0068] Example 2-12

[0069] In Examples 2-12, a coated diaphragm is provided respectively. The substrate material and parameters of the coated diaphragm, the specific selection of raw materials for preparing the coating, parameters and dosage (number of dosages), preparation method and other parameters are shown in Tables 1 and 2. For the contents not shown in Tables 1 and 2, they are the same as in Example 1.

[0070] Comparative Examples 1-4

[0071] In Comparative Examples 1-4, a coated diaphragm is provided respectively. The substrate material and parameters of the coated diaphragm, the specific selection, parameters and dosage (number of dosages) of the raw materials for preparing the coating, the preparation method and other parameters are shown in Table 3. For the contents not shown in Table 3, they are the same as those in Example 1.

[0072] Table 1

[0073]

[0074]

[0075] Table 2

[0076]

[0077]

[0078] Table 3

[0079]

[0080]

[0081] The performance test of the coated diaphragms provided in the examples and comparative examples was carried out as follows:

[0082] (1) Shrinkage at 150°C: Cut the coated diaphragms provided in the Examples and Comparative Examples into samples of 160 mm x 130 mm, draw lines of 100 mm x 100 mm on the cut samples, place 11 A4 papers on the top and bottom of the samples, and place them in a 150°C oven. Test at 150°C for 30 min.

[0083] (2) Water resistance: Take an A4-sized test film and weigh it as X. Soak it in 500 mL of pure water for 10 min. Take out the coating and dry it. Weigh it as X1. The coating loss per unit area is G (g / m 2 ) is recorded as G = (X-X1) / 0.06237;

[0084] (3) Air permeability increment: The time required for 100 mL of air to pass through the base film and the coated membrane provided by the present invention was tested using an Asahi EG01-55-1MR thin film permeability meter. The difference between the time required for air to pass through the coated membrane and the time required for air to pass through the base film was the air permeability increment.

[0085] The performance test results are shown in Table 4.

[0086] Table 4

[0087]

[0088] It can be seen from Table 4 that the coated diaphragm provided by the embodiment of the present invention has better water resistance and heat resistance (150°C shrinkage rate, TD: 1%-4.8%, MD: 0.9%-4.7%) than the comparative example when the coating thickness is small (the coating layer is thin), and has better air permeability (air permeability increment: 8.7-39s / 100mL).

[0089] Compared with Example 1, the heat resistance of the coated membrane provided by Comparative Example 1 deteriorates; the air permeability of the coated membrane provided by Comparative Example 3 deteriorates; the heat resistance of the coated membrane provided by Comparative Example 4 deteriorates significantly; compared with Example 3, the air permeability and water resistance of the coated membrane provided by Comparative Example 2 deteriorate significantly.

[0090] The applicant declares that the present invention uses the above-mentioned embodiments to illustrate the coated diaphragm, its preparation method, and its application. However, the present invention is not limited to the above-mentioned embodiments, which does not mean that the present invention must rely on the above-mentioned embodiments in order to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent replacements for various raw materials in the product of the present invention, addition of auxiliary ingredients, and selection of specific methods, etc., are all within the scope of protection and disclosure of the present invention.

Claims

1. A coated diaphragm, characterized in that: The coated diaphragm comprises a substrate and a coating applied on at least one side of the substrate. The raw materials for preparing the coating include an emulsion adhesive, a solvent adhesive, inorganic particles and a cross-linking agent. The total coating amount of the coating is 2.4-3.2 g / m 2 ; The average particle size of the emulsion adhesive is denoted as A, the average particle size of the inorganic particles is denoted as B, the average pore size of the substrate is denoted as C, and the D10 particle size of the inorganic particles is denoted as D. A, B, C, and D satisfy the following relationship: C:A:B=(0.4-0.8):1:(2-9); 3.5C≤A+D≤6C; The molecular structure of the solvent-based adhesive contains carboxyl groups and / or amide groups; The average particle size of the inorganic particles is 0.1-1.0 μm.

2. The coated diaphragm according to claim 1, characterized in that The emulsion adhesive includes any one or a combination of at least two of polyacrylate, polystyrene-acrylate, polymethyl methacrylate, polybutyl methacrylate, polyethyl acrylate, polyvinyl acetate or ethylene-vinyl acetate.

3. The coated diaphragm according to claim 1, characterized in that The solvent-based adhesive includes polyacrylic acid and / or polyacrylamide.

4. The coated diaphragm according to claim 1, characterized in that The inorganic particles include any one of aluminum oxide, boehmite, barium titanate, silicon dioxide, magnesium oxide, titanium dioxide, and double metal hydroxide, or a combination of at least two thereof.

5. The coated diaphragm according to claim 4, characterized in that The double metal hydroxide includes any one of magnesium aluminum double metal hydroxide, lithium aluminum double metal hydroxide, zinc aluminum double metal hydroxide, and nickel aluminum double metal hydroxide, or a combination of at least two thereof.

6. The coated diaphragm according to claim 1, characterized in that The inorganic particles are porous inorganic particles.

7. The coated diaphragm according to claim 1, characterized in that The cross-linking agent includes a carboxyl cross-linking agent.

8. The coated diaphragm according to claim 1, characterized in that The functionality of the crosslinking agent is 2-4.

9. The coated diaphragm according to claim 1, characterized in that The crosslinking agent includes any one of a blocked isocyanate crosslinking agent, a carboimide crosslinking agent, an aziridine crosslinking agent or an epoxysilane crosslinking agent, or a combination of at least two of them.

10. The coated diaphragm according to claim 9, characterized in that The cross-linking agent includes aziridine-modified isocyanate.

11. The coated diaphragm according to claim 1, characterized in that The raw materials for preparing the coating further include any one of water, a dispersant, and a surfactant, or a combination of at least two of them.

12. The coated diaphragm according to claim 11, characterized in that The water includes pure water.

13. The coated membrane according to claim 11, wherein The dispersant includes any one of ammonium polyacrylate, sodium tripolyphosphate, sodium hexametaphosphate, and sodium pyrophosphate, or a combination of at least two of them.

14. The coated diaphragm according to claim 11, characterized in that The surfactant includes any one or a combination of at least two of polyether silane copolymer, polyether modified polysiloxane, alkylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, fatty acid polyoxyethylene ether, fatty amine polyoxyethylene ether or fluoroalkyl ethoxy alcohol ether.

15. The coated membrane according to claim 1, wherein The raw materials for preparing the coating include the following components in parts by weight:

16. The coated membrane according to claim 1, wherein The mass ratio of the emulsion adhesive to the solvent adhesive is 3:(0.5-3).

17. The coated membrane according to claim 1, wherein The mass ratio of the solvent-based adhesive to the cross-linking agent is 100:(3-12).

18. The coated membrane according to claim 1, wherein The single-side thickness of the coating is 0.5-4 μm.

19. A method for preparing a coated diaphragm according to any one of claims 1 to 18, characterized in that: The preparation method comprises the following steps: (1) mixing the raw materials for preparing the coating to obtain a slurry; (2) The slurry is coated on one side or both sides of the base film and baked to obtain the coated separator.

20. The preparation method according to claim 19, characterized in that The coating method in step (2) includes coating with a micro-concave roller.

21. The preparation method according to claim 19, characterized in that The baking temperature is 60-80°C.

22. The preparation method according to claim 19, characterized in that The baking time is 10-30s.

23. Use of the coated separator according to any one of claims 1 to 18 in a battery.

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