Separator, manufacturing method thereof, and related secondary battery, battery module, battery pack, and device

Abstract

A separator and its manufacturing method, and a secondary battery, battery module, and device including the separator. The separator includes a substrate (A) and a coating (B) provided on at least one surface of the substrate (A), the coating (B) including inorganic particles (B3) and organic particles, the organic particles including first organic particles (B1) and second organic particles (B2), the first organic particles (B1) and the second organic particles (B2) being embedded in the inorganic particles (B3), and the number of particles in the coating (B) is A, the second organic particles (B2) are primary particles, and the number of particles in the coating (B) is B, where A is the number of particles in the coating (B), B is the number of particles in the coating (B), and the separator satisfies 0.05≦A / B<1.

Description

[Technical field]

[0001] The present application belongs to the field of secondary battery technology, and specifically relates to a separator, a manufacturing method thereof, and related secondary batteries, battery modules, battery packs, and devices. [Background technology]

[0002] 2. Description of the Related Art Secondary batteries have outstanding characteristics such as light weight, no pollution, no memory effect, etc., and are therefore widely used in various consumer electronic products and electric vehicles.

[0003] With the development of the new energy industry, users are putting forward higher requirements for the use of secondary batteries. For example, the energy density design of secondary batteries is becoming higher and higher, but the improvement of the energy density of the battery tends to be unfavorable to the balance of kinetic performance, electrochemical performance or safety performance.

[0004] Therefore, how to make a battery have good multiplication performance, storage performance and safety performance at the same time is an important issue in the field of battery design. Summary of the Invention [Problem to be solved by the invention]

[0005] In view of the technical problems existing in the background art, a first aspect of the present application aims to provide a separator and to provide a secondary battery including the separator with good multiplication performance, storage performance and safety performance at the same time. [Means for solving the problem]

[0006] In order to achieve the above object, a separator according to a first aspect of the present application provides a separator including a substrate and a coating applied to at least one surface of the substrate. The coating includes inorganic particles and organic particles. The organic particles include first organic particles and second organic particles, and the first organic particles and the second organic particles are embedded in the inorganic particles and form protrusions on the surface of the coating. The first organic particles are secondary particles, and the number of the first organic particles in the coating is A, the second organic particles are primary particles, and the number of the second organic particles in the coating is B, whereby the separator satisfies 0.05≦A / B<1.

[0007] Compared with the prior art, the present application has at least the following beneficial effects:

[0008] The separator of the present application comprises inorganic particles and organic particles in the same coating, which greatly reduces the thickness of the separator, thereby improving the energy density of the battery, and the organic particles comprise first and second organic particles in a specific distribution state and quantity ratio range, which can effectively improve the adhesion between the separator and the electrode plate, and reduce the situation in which the separator forms wrinkles during the battery cycle process, thereby simultaneously achieving both safety performance and power consumption performance for the battery.

[0009] In any embodiment of the present application, the separator satisfies 0.2≦A / B≦0.6, and optionally 0.25≦A / B≦0.5. When A / B is within a certain range, the battery's multiplication performance, storage performance, and safety performance can be further improved.

[0010] In any embodiment of the present application, the number average particle diameter of the first organic particles is ≧8 μm. Optionally, the number average particle diameter of the first organic particles is 12 μm to 25 μm. When the number average particle diameter of the first organic particles is within a predetermined range, the multiplication performance of the battery can be further improved.

[0011] In any embodiment of the present application, the number average particle diameter of the second organic particles is ≧2 μm. Optionally, the number average particle diameter of the second organic particles is 3 μm to 7 μm. When the number average particle diameter of the second organic particles is within a predetermined range, the battery's magnification performance and safety performance can be further improved.

[0012] In any embodiment of the present application, the ratio of the number average particle diameter of the first organic particles to the number average particle diameter of the second organic particles is ≧2.0. Optionally, the ratio of the number average particle diameter of the first organic particles to the number average particle diameter of the second organic particles is 2.5 to 4.0. When the ratio of the number average particle diameter of the first organic particles to the number average particle diameter of the second organic particles is within a predetermined range, the battery's magnification performance and safety performance can be further improved.

[0013] In any embodiment of the present application, the weight percentage of the inorganic particles in the coating is ≦75%, and optionally, the weight percentage of the inorganic particles in the coating is 60%-75%.

[0014] In any embodiment of the present application, the mass percentage of the first organic particles in the coating is ≧12%, and optionally, the mass percentage of the first organic particles in the coating is 15%-25%.

[0015] In any embodiment of the present application, the weight percentage of the second organic particles in the coating is ≦10%, and optionally, the weight percentage of the second organic particles in the coating is 2% to 10%.

[0016] When the inorganic particles, the first organic particles, or the second organic particles are within the above-mentioned specified ranges, the three can exert a better synergistic effect, thereby further improving the cycle performance and energy density of the battery.

[0017] In any embodiment of the present application, the coating weight on one side of the separator per unit area is ≦3.0 g / m2 and optionally, the coating weight on one side of the separator per unit area is 1.5 g / m 2 ~3.0g / m 2 When the weight of the one-sided coating of the separator per unit area is within a certain range, the energy density of the battery can be further improved under the premise of ensuring the multiplication performance and safety performance of the battery.

[0018] In any embodiment of the present application, the first organic particles include one or more of a homopolymer or copolymer of a fluorine-containing alkyl group monomer unit, a homopolymer or copolymer of an alkylene group monomer unit, a homopolymer or copolymer of an unsaturated nitrile-based monomer unit, a homopolymer or copolymer of an alkylene oxide-based monomer unit, and a modified compound of each of the homopolymers or copolymers, In any embodiment of the present application, the first organic particles include one or more of polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polyethylene, polypropylene, polyacrylonitrile, polyethylene oxide, a copolymer of different fluorine-containing alkyl group monomer units, a copolymer of a fluorine-containing alkyl group monomer unit and an alkylene group monomer unit, a copolymer of a fluorine-containing alkyl group monomer unit and an acrylic acid monomer unit, a copolymer of a fluorine-containing alkyl group monomer unit and an acrylate monomer unit, and a modified compound of each of the above homopolymers or copolymers.

[0019] In any embodiment of the present application, the first organic particles include one or more of vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-trifluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene-acrylic acid copolymer, vinylidene fluoride-hexafluoropropylene-acrylate copolymer, and modified compounds of the copolymers.

[0020] In any embodiment of the present application, the second organic particles include one or more of a homopolymer or copolymer of an acrylate-based monomer unit, a homopolymer or copolymer of an acrylic acid-based monomer unit, a homopolymer or copolymer of a styrene-based monomer unit, a polyurethane-based compound, a rubber-based compound, and a modified compound of each of the homopolymers or copolymers described above.

[0021] In any embodiment of the present application, the second organic particles may include one or more of a copolymer of an acrylate-based monomer unit and a styrene-based monomer unit, a copolymer of an acrylic acid-based monomer unit and a styrene-based monomer unit, a copolymer of an acrylic acid-based monomer unit-acrylate-based monomer unit-styrene-based monomer unit, a copolymer of a styrene-based monomer unit and an unsaturated nitrile-based monomer unit, a copolymer of a styrene-based monomer unit-alkylene group monomer unit-unsaturated nitrile-based monomer unit, and a modifying compound of each of the copolymers.

[0022] In some embodiments, the second organic particles include one or more of butyl acrylate-styrene copolymer, butyl methacrylate-isooctyl methacrylate copolymer, isooctyl methacrylate-styrene copolymer, methacrylate-methacrylic acid-styrene copolymer, methyl acrylate-isooctyl methacrylate-styrene copolymer, butyl acrylate-isooctyl acrylate-styrene copolymer, butyl acrylate-isooctyl methacrylate-styrene copolymer, butyl methacrylate-isooctyl methacrylate-styrene copolymer, butyl methacrylate-isooctyl methacrylate-styrene copolymer, butyl methacrylate-isooctyl acrylate-styrene copolymer, butyl methacrylate-isooctyl acrylate-styrene copolymer, styrene-acrylonitrile copolymer, styrene-butadiene-acrylonitrile copolymer, methyl acrylate-styrene-acrylonitrile copolymer, isooctyl methacrylate-styrene-acrylonitrile copolymer, styrene-vinyl acetate copolymer, styrene-vinyl acetate-pyrrolidone copolymer, and modified compounds of the copolymers.

[0023] In any embodiment of the present application, the inorganic particles include one or more of boehmite (γ-AlOOH), alumina (Al2O3), barium sulfate (BaSO4), magnesium oxide (MgO), magnesium hydroxide (Mg(OH)2), silicon dioxide (SiO2), tin dioxide (SnO2), titanium oxide (TiO2), calcium oxide (CaO), zinc oxide (ZnO), zirconium dioxide (ZrO2), yttrium oxide (YO3), nickel oxide (NiO), cerium oxide (CeO2), zirconium titanate (SrTiO3), barium titanate (BaTiO3), and magnesium fluoride (MgF2).

[0024] In any embodiment of the present application, the separator has an air permeability of 100s / 100mL-300s / 100mL. Optionally, the separator has an air permeability of 150s / 100mL-250s / 100mL.

[0025] In any embodiment of the present application, the separator has a transverse tensile strength (MD) of 1500 kgf / cm 2 -3000kgf / cm 2 and optionally, the separator has a transverse tensile strength of 1800 kgf / cm 2 ~2500kgf / cm 2 It is.

[0026] In any embodiment of the present application, the separator has a longitudinal tensile strength (TD) of 1000 kgf / cm 2 ~2500kgf / cm 2 and optionally, the separator has a longitudinal tensile strength of 1400 kgf / cm 2 ~2000kgf / cm 2 It is.

[0027] In any embodiment of the present application, the separator has a transverse elongation at break of 50% to 200%, and optionally, the separator has a transverse elongation at break of 100% to 150%; In any embodiment of the present application, the separator has a longitudinal elongation at break of 50% to 200%, and optionally, the separator has a longitudinal elongation at break of 100% to 150%.

[0028] In any embodiment of the present application, the inorganic particles and the organic particles form non-uniform tunnel structures in the coating.

[0029] In any embodiment of the present application, if the distance between any two adjacent inorganic particles is L1 and the distance between any adjacent inorganic particle and organic particle is L2, then L1 <L2である。

[0030] The second aspect of the present application includes the steps of: (1) providing a substrate; (2) providing a coating slurry comprising component materials including inorganic particles, organic particles including first organic particles and second organic particles, and a solvent; and (3) applying the coating slurry described in step (2) to at least one side of the substrate described in step (1) to form a coating, and drying to obtain the separator, where the coating after drying comprises the inorganic particles, the first organic particles, and the second organic particles. The first organic particles and the second organic particles are embedded in the inorganic particles and form protrusions on the coating surface after drying. The first organic particles are secondary particles, and the number of the first organic particles in the coating after drying is A, and the second organic particles are primary particles, and the number of the second organic particles in the coating after drying is B, and the separator satisfies 0.05≦A / B<1.

[0031] In any embodiment of the present application, in step (2), the added mass of the first organic particles is 12% or more, and optionally 12% to 30%, of the sum of the dry weights of the component materials.

[0032] In any embodiment of the present application, in step (2), the added mass of the second organic particles is 10% or less, optionally 2% to 10%, of the sum of the dry weights of the component materials.

[0033] In any embodiment of the present application, in step (2), the solid content of the coating slurry is 28% to 45%, optionally 30% to 38%.

[0034] In any embodiment of the present application, in step (3), the coating utilizes a coater, the coater includes a gravure roll, and the ruling of the gravure roll is 100 LPI to 300 LPI, optionally 125 LPI to 190 LPI.

[0035] In any embodiment of the present application, in step (3), the speed of the coating is 30 m / min to 90 m / min, optionally 50 m / min to 70 m / min.

[0036] In any embodiment of the present application, in step (3), the linear velocity ratio of the coating is 0.8 to 2.5, optionally 0.8 to 1.5.

[0037] In any embodiment of the present application, in step (3), the drying temperature is 40°C to 70°C, optionally 50°C to 60°C.

[0038] In any embodiment of the present application, in step (3), the drying time is from 10 s to 120 s, optionally from 20 s to 80 s. A third aspect of the present application provides a secondary battery comprising a separator according to the first aspect of the present application or comprising a separator produced according to the method of the second aspect of the present application.

[0039] A fourth aspect of the present application provides a battery module including a secondary battery according to the third aspect of the present application.

[0040] A fifth aspect of the present application provides a battery pack including a battery module according to the fourth aspect of the present application.

[0041] A sixth aspect of the present application provides an apparatus including at least one of the secondary battery according to the third aspect of the present application, the battery module according to the fourth aspect of the present application, or the battery pack according to the fifth aspect of the present application.

[0042] The device herein includes at least one of the secondary batteries, battery modules, or battery packs provided herein, and thus has at least the same advantages as the secondary batteries.

[0043] In order to more clearly describe the technical solution of the present application, the drawings used in the present application are briefly described below. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can obtain other drawings based on the drawings without spending creative labor. [Brief description of the drawings]

[0044] [Figure 1] FIG. 2 is a structural schematic diagram of one embodiment of the separator of the present application. [Figure 2-1] 1 is a scanning electron microscope (SEM) photograph at 500x magnification of one embodiment of a separator of the present application. [Figure 2-2] 1 is a scanning electron microscope (SEM) photograph at 3000x magnification of one embodiment of a separator of the present application. [Diagram 3] 1 is a photograph of an ion-polished cross-section (CP) at 3000x magnification of one embodiment of a separator of the present application. [Figure 4-1] 1 is a schematic diagram showing the configuration of an embodiment of a separator according to the present application. [Figure 4-2] FIG. 2 is a schematic diagram showing a configuration of another embodiment of the separator of the present application. [Diagram 5] FIG. 1 is a schematic diagram illustrating an embodiment of a secondary battery. [Figure 6] FIG. 6 is an exploded view of FIG. 5. [Figure 7] FIG. 1 is a schematic diagram illustrating an embodiment of a battery module. [Figure 8] FIG. 1 is a schematic diagram illustrating one embodiment of a battery pack. [Figure 9]FIG. 9 is an exploded view of FIG. [Figure 10] FIG. 1 is a schematic diagram showing one embodiment of an apparatus that uses a secondary battery as a power source. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] The present application will now be further described with reference to specific embodiments, which will be understood to be merely illustrative of the present application and are not intended to limit the scope of the present application.

[0046] For simplicity, this specification specifically discloses only some numerical ranges. However, any lower limit can be combined with any upper limit to form an open range. Also, any lower limit can be combined with another lower limit to form an open range, and similarly any upper limit can be combined with another upper limit to form an open range. Also, each point or single numerical value disclosed individually can be combined with any other point or single numerical value, or with another lower limit or upper limit, as a lower limit or upper limit, to form an open range.

[0047] In the description of this specification, unless otherwise specified, "more than or equal to" and "less than or equal to" are inclusive of the number, and "multiple types" in "one type or multiple types" means two types or more than two types.

[0048] In the description of this specification, unless otherwise specified, the term "or" is inclusive. That is, the phrase [A or B] means "A, B, or both A and B." More specifically, any of the following conditions satisfy "A or B": A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), and A and B are both true (or exist).

[0049] Unless otherwise specified, the terms used herein have the meanings commonly understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of the parameters mentioned herein can be measured by various measurement methods commonly used in the art (e.g., the methods described in the examples of the present application).

[0050] secondary battery A secondary battery is a battery that can be continuously used by activating the active material through charging after discharging.

[0051] A secondary battery usually comprises a positive electrode plate, a negative electrode plate, a separator, and an electrolyte. During the charging and discharging process of the battery, active ions shuttle between the positive and negative electrodes, inserting and detaching. The separator is placed between the positive and negative electrodes to provide isolation. The electrolyte serves to conduct ions between the positive and negative electrodes.

[0052] [Separator] The present application provides a separator including a substrate and a coating disposed on at least one surface of the substrate. The coating includes inorganic particles and organic particles. The organic particles include first organic particles and second organic particles. The first organic particles and the second organic particles are embedded in the inorganic particles and form protrusions on the coating surface. The first organic particles are secondary particles, and the number of the first organic particles in the coating is A, the second organic particles are primary particles, and the number of the second organic particles in the coating is B, where the separator satisfies 0.05≦A / B<1.

[0053] The separator of the present application simultaneously contains inorganic particles, specific first organic particles and second organic particles in the same coating, which can further improve the battery's multiplication performance, high temperature storage performance and needle puncture safety performance under the premise of ensuring that the battery has high energy density.

[0054] The terms primary particle and secondary particle have the meanings well known in the art. A primary particle refers to a particle that is not in an aggregated state. A secondary particle refers to a particle in an aggregated state formed by two or more primary particles.

[0055] Without wishing to be bound by any theory, the inventors have found through many studies that the separator of the present application contains inorganic particles and organic particles in the same coating, and compared with a separator having two coatings, an inorganic particle layer and an organic particle layer, the thickness of the separator can be greatly reduced, thereby improving the energy density of the battery. At the same time, the organic particles include first organic particles and second organic particles, and the morphology and quantity of the first organic particles and the second organic particles are specially designed, the first organic particles are secondary particles, which contribute to the formation of a uniform coating interface, and can effectively improve the problem of tab misalignment during the battery manufacturing process, thereby improving the safety of the battery, and the second organic particles are primary particles, which are less likely to form a large gel film structure between the particles, thereby further improving the multiplication performance and safety performance of the battery. Meanwhile, the combination of the two can effectively improve the wettability and distribution uniformity of the electrolyte, and further improve the high-temperature storage performance of the battery. In particular, if a foreign object is pierced during use of the battery, the second organic particles can instantly wrap around the foreign object and the exposed copper foil or aluminum foil, forming a first polymer insulating layer, effectively reducing the probability of the positive and negative electrodes shorting out, and improving the safety performance of the battery; as the ambient temperature of the foreign object increases, the first organic particles form a more robust second polymer insulating layer around the first polymer insulating layer, thereby further improving the safety performance of the battery.

[0056] If A / B is too small (e.g., less than 0.05), the first organic particles are too few, or the second organic particles are too many. If the first organic particles are too few, when the battery is in a harsh operating environment, the separator is unlikely to form a strong second polymer insulating layer, thereby affecting the safety performance of the battery. If the second organic particles are too many, the adhesion between the separator and the electrode plate will be excessive, causing excessive consumption of the electrolyte, and reducing the wettability and uniformity of the electrolyte, which may affect the storage performance of the battery.

[0057] If A / B is too large (e.g., greater than 1), the first organic particles may be too many or the second organic particles may be too few. If the first organic particles are too many, the ion transport path may be too long, which may affect the battery's multiplication performance. If the second organic particles are too few, when the battery is in a harsh operating environment, the separator may find it difficult to instantaneously form the first polymer insulating layer, which may greatly increase the risk of battery short circuit and affect the safety performance of the battery.

[0058] As a result of intensive research, the inventors have found that the separator according to the present application satisfies the above design conditions, and furthermore, optionally, satisfies one or more of the following conditions, thereby further improving the performance of the secondary battery:

[0059] In some embodiments, the separator can satisfy 0.05≦A / B≦0.95, 0.1≦A / B<1, 0.15≦A / B<1, 0.15≦A / B≦0.8, 0.2≦A / B≦0.85, 0.2≦A / B≦0.6, 0.25≦A / B≦0.5, 0.3≦A / B≦0.75, 0.3≦A / B≦0.6, 0.3≦A / B≦0.5, 0.3≦A / B≦0.45. When A / B is within the predetermined range, the battery's multiplication performance, storage performance, and safety performance can be further improved.

[0060] As shown in FIG. 1, the separator includes a substrate (A) and a coating (B) containing first organic particles (B1), second organic particles (B2) and inorganic particles (B3), the first organic particles (B1) are secondary particles and the second organic particles (B2) are primary particles, the first organic particles and the second organic particles are both embedded in the inorganic particles (B3), and protrusions are formed on the surface of the coating (B).

[0061] In some embodiments, the number average particle diameter of the first organic particles is ≧8 μm. For example, the number average particle diameter of the first organic particles may be 10 μm to 20 μm, 10.5 μm to 18 μm, 12 μm to 25 μm, 12 μm to 18 μm, 13 μm to 20 μm, or 15 μm to 22 μm. When the number average particle diameter of the first organic particles is within a predetermined range, sufficient voids can be present between the organic particles, and sufficient ion transport paths can be formed even if the organic particles swell in the electrolyte, thereby further improving the battery magnification performance.

[0062] In some embodiments, the number average particle diameter of the second organic particles is ≧2 μm. For example, the number average particle diameter of the second organic particles may be 3 μm to 8 μm, 2.5 μm to 7 μm, 3 μm to 7 μm, 3 μm to 6 μm, or 3.5 μm to 6 μm. When the number average particle diameter of the second organic particles is within a predetermined range, the battery's magnification performance and safety performance can be further improved.

[0063] In some embodiments, the ratio of the number average particle diameter of the first organic particles to the number average particle diameter of the second organic particles is ≧2.0. For example, the ratio of the number average particle diameter of the first organic particles to the number average particle diameter of the second organic particles is 2.0 to 5.0, 2.0 to 4.5, 2.0 to 4.0, 2.5 to 4.0, or 3.0 to 4.0. When the ratio of the number average particle diameter of the first organic particles to the number average particle diameter of the second organic particles is within a predetermined range, the battery's magnification performance and safety performance can be further improved.

[0064] The number-average particle size of the organic particles means the arithmetic mean value of the particle size of the organic particles statistically calculated based on the number of organic particles in the separator coating. The particle size of the organic particles is the distance between the two most distant points on the organic particles.

[0065] In some embodiments, the first organic particles may include one or more of a homopolymer or copolymer of a fluorine-containing alkyl group monomer unit, a homopolymer or copolymer of an alkylene group monomer unit, a homopolymer or copolymer of an unsaturated nitrile-based monomer unit, a homopolymer or copolymer of an alkylene oxide-based monomer unit, and a modified compound of each of the homopolymers or copolymers.

[0066] In some embodiments, the fluorine-containing alkyl group monomer unit may be selected from one or more of difluoroethylene, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, and hexafluoropropylene.

[0067] In some embodiments, the alkylene group monomer units can be selected from one or more of ethylene, propylene, butadiene, isoprene.

[0068] In some embodiments, the unsaturated nitrile-based monomer units may be selected from one or more of acrylonitrile, methacrylonitrile.

[0069] In some embodiments, the alkylene oxide based monomer units can be selected from one or more of ethylene oxide, propylene oxide, and the like.

[0070] In some embodiments, the first organic particles can include one or more of polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polyethylene, polypropylene, polyacrylonitrile, polyethylene oxide, copolymers of different fluorine-containing alkyl group monomer units, copolymers of fluorine-containing alkyl group monomer units and alkylene group monomer units, copolymers of fluorine-containing alkyl group monomer units and acrylic acid-based monomer units, copolymers of fluorine-containing alkyl group monomer units and acrylate-based monomer units, and modified compounds of each of the homopolymers or copolymers.

[0071] In some embodiments, the first organic particles can include one or more of vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-trifluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene-acrylic acid copolymer, vinylidene fluoride-hexafluoropropylene-acrylate copolymer, and modified compounds of the copolymers.

[0072] In some embodiments, the second organic particles include one or more of a homopolymer or copolymer of an acrylate-based monomer unit, a homopolymer or copolymer of an acrylic acid-based monomer unit, a homopolymer or copolymer of a styrene-based monomer unit, a polyurethane-based compound, a rubber-based compound, and a modified compound of each of the homopolymers or copolymers.

[0073] In some embodiments, the second organic particles may include one or more of a copolymer of an acrylate-based monomer unit and a styrene-based monomer unit, a copolymer of an acrylic acid-based monomer unit and a styrene-based monomer unit, a copolymer of an acrylic acid-based monomer unit-acrylate-based monomer unit-styrene-based monomer unit, a copolymer of a styrene-based monomer unit and an unsaturated nitrile-based monomer unit, a copolymer of a styrene-based monomer unit-alkylene group monomer unit-unsaturated nitrile-based monomer unit, and a modified compound of each of the above materials.

[0074] In some embodiments, the acrylate monomer units can be selected from one or more of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, methyl methacrylate, butyl methacrylate, isooctyl methacrylate.

[0075] In some embodiments, the acrylic acid based monomer units can be selected from one or more of acrylic acid, methacrylic acid.

[0076] In some embodiments, the styrenic monomer units may be selected from one or more of styrene, methylstyrene.

[0077] In some embodiments, the unsaturated nitrile-based monomer units may be selected from one or more of acrylonitrile, methacrylonitrile.

[0078] In some embodiments, the second organic particles can include one or more of butyl acrylate-styrene copolymer, butyl methacrylate-isooctyl methacrylate copolymer, isooctyl methacrylate-styrene copolymer, methacrylate-methacrylic acid-styrene copolymer, methyl acrylate-isooctyl methacrylate-styrene copolymer, butyl acrylate-isooctyl acrylate-styrene copolymer, butyl acrylate-isooctyl methacrylate-styrene copolymer, butyl methacrylate-isooctyl methacrylate-styrene copolymer, butyl methacrylate-isooctyl methacrylate-styrene copolymer, butyl methacrylate-isooctyl acrylate-styrene copolymer, styrene-acrylonitrile copolymer, styrene-butadiene-acrylonitrile copolymer, methyl acrylate-styrene-acrylonitrile copolymer, isooctyl methacrylate-styrene-acrylonitrile copolymer, styrene-vinyl acetate copolymer, styrene-vinyl acetate-pyrrolidone copolymer, and modified compounds of each of the above materials.

[0079] The modified compound of each homopolymer or copolymer refers to a modified compound obtained by copolymerizing a monomer unit in each homopolymer or copolymer with a monomer unit containing a specific functional group. For example, a modified compound can be obtained by copolymerizing a fluorine-containing alkyl group monomer unit with a compound containing a carboxyl group-containing functional group.

[0080] In some embodiments, the number average molecular weight of the first organic particles is 300,000 to 800,000, for example, 400,000 to 650,000.

[0081] In some embodiments, the number average molecular weight of the second organic particles is from 10,000 to 100,000, for example, from 20,000 to 80,000.

[0082] In some embodiments, the inorganic particles can include one or more of boehmite (γ-AlOOH), alumina (Al2O3), barium sulfate (BaSO4), magnesium oxide (MgO), magnesium hydroxide (Mg(OH)2), silicon dioxide (SiO2), tin dioxide (SnO2), titanium oxide (TiO2), calcium oxide (CaO), zinc oxide (ZnO), zirconium dioxide (ZrO2), yttrium oxide (YO3), nickel oxide (NiO), cerium oxide (CeO2), zirconium titanate (SrTiO3), barium titanate (BaTiO3), and magnesium fluoride (MgF2).

[0083] In some embodiments, the inorganic particles have a volume average particle diameter Dv50≦2.5 μm, and for example, the inorganic particles may have a volume average particle diameter Dv50 of 0.5 μm to 2.5 μm, or 0.5 μm to 1 μm. When the volume average particle diameter of the inorganic particles is controlled within a predetermined range, it is possible to ensure that the volume energy density of the battery is improved under the premise of good cycle performance and safety performance of the battery.

[0084] In some embodiments, the mass ratio of the inorganic particles in the coating is ≦75% based on the total mass of the coating. For example, the mass ratio of the inorganic particles in the coating may be 60%-75%, 60%-70%, or 65%-75%. When the mass ratio of the inorganic particles is controlled within a certain range, it can ensure that the mass energy density of the battery is improved under the premise of having good safety performance.

[0085] In some embodiments, the mass ratio of the first organic particles in the coating is ≧12% based on the total mass of the coating. For example, the mass ratio of the first organic particles in the coating may be 12%-30%, 15%-30%, 15%-25%, or 15%-20%. By controlling the mass ratio of the first organic particles within a predetermined range, the above-mentioned A / B range of the present application can be more easily achieved, and at the same time, the appropriate mass ratio range can reduce the consumption of the separator to the electrolyte, thereby further improving the storage performance and safety performance of the battery.

[0086] In some embodiments, the mass ratio of the second organic particles in the coating is ≦10% based on the total mass of the coating, and may be, for example, 2% to 10%, 3% to 7%, or 3% to 5%. By controlling the mass ratio of the second organic particles within a predetermined range, the above-mentioned A / B range of the present application can be more easily achieved, and the separator can have an appropriate tunnel structure while ensuring adhesion, thereby further improving the battery's magnification performance and safety performance.

[0087] By selecting the appropriate contents of the inorganic particles, the first organic particles and the second organic particles, the three can be made to exhibit better synergy, and on the premise of ensuring the safety performance of the separator, it is possible to ensure that the separator has a more appropriate non-uniform tunnel structure and at the same time realizes a lightweight separator, thereby further improving the energy density of the battery.

[0088] In some embodiments, the coating weight per unit area of ​​the separator on one side is ≦3.0 g / m 2 For example, the coating weight on one side of the separator per unit area is 1.5 g / m 2 ~3.0g / m 2 , 1.5g / m 2 ~2.5g / m 2 , 1.8g / m 2 ~2.3g / m2 By controlling the coat weight per unit area on one side of the separator within a predetermined range, it is possible to achieve both battery magnification performance and safety performance on the premise of increasing the battery energy density.

[0089] In some embodiments, the coating may also include other organic compounds, such as polymers that improve heat resistance (simply referred to as "heat-resistant adhesives"), dispersants, wetting agents, other types of binders, etc. The above other organic compounds are all non-particulate substances in the coating. The present application does not particularly limit the types of the above other organic compounds, and any known material with good improving performance may be selected and used.

[0090] In the embodiment of the present application, the material of the substrate is not particularly limited, and any known substrate having good chemical stability and mechanical stability can be selected and used, such as one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The substrate may be a single layer film or a multi-layer composite film. When the substrate is a multi-layer composite film, the materials of each layer may be the same or different.

[0091] In some embodiments, the thickness of the substrate is ≦10 μm. For example, the thickness of the substrate may be 5 μm to 10 μm, 5 μm to 9 μm, or 7 μm to 9 μm. When the thickness of the substrate is controlled within a predetermined range, the energy density of the battery can be further improved under the premise of ensuring the magnification performance and safety performance of the battery.

[0092] In some embodiments, the separator may have an air permeability of 100s / 100mL-300s / 100mL. For example, the separator may have an air permeability of 150s / 100mL to 250s / 100mL, or 170s / 100mL-220s / 100mL.

[0093] In some embodiments, the separator has a longitudinal tensile strength (TD) of 1000 kgf / cm 2 ~2500kgf / cm 2 For example, the separator may have a longitudinal tensile strength of 1400 kgf / cm 2 ~2000kgf / cm 2 may be also possible.

[0094] In some embodiments, the separator may have a longitudinal elongation at break of 50% to 200%, for example, the separator may have a longitudinal elongation at break of 100% to 150%.

[0095] In some embodiments, the separator has a transverse tensile strength (MD) of 1500 kgf / cm 2 -3000kgf / cm 2 For example, the separator may have a lateral tensile strength of 1800 kgf / cm 2 ~2500kgf / cm 2 may be also possible.

[0096] In some embodiments, the separator may have a transverse elongation at break of 50% to 200%, for example, the separator may have a transverse elongation at break of 100% to 150%.

[0097] In some embodiments, the distance between any two adjacent inorganic particles is L1, and the distance between any adjacent inorganic particle and organic particle is L2. <L2である。

[0098] According to some embodiments, the ratio of the number of the first organic particles to the second organic particles can be tested using methods known in the art, for example, it can be measured using a scanning electron microscope. As an example, the method for testing the ratio of the number of the first organic particles to the second organic particles is to make a separator into a test sample of length x width = 50mm x 100mm, and test the organic particles in the coating using a scanning electron microscope (for example, ZEISS Sigma 300). It can be measured with reference to JY / T010-1996. Randomly select multiple (for example, 5) different areas in the test sample to perform a scanning test, and statistically measure the number of the first organic particles or the second organic particles in the test area at a certain magnification (for example, 500 times or 1000 times), and the average value of the number of the first organic particles in each test area is A, and the average value of the number of the second organic particles in each test area is B, and the value of A / B is calculated. To ensure the accuracy of the test results, multiple test samples (e.g., 10 samples) can be tested in duplicate, and the average calculated A / B value for each test sample can be taken as the final test result.

[0099] Figure 2-1 is a scanning electron microscope (SEM) photograph of a separator of an embodiment of the present application at a magnification of 500 times. In Figure 2-1, the quantity A in the coating of the first organic particles and the quantity B in the coating of the second organic particles can be statistically calculated by the above-mentioned method.

[0100] In some embodiments, the distance between any two adjacent inorganic particles is determined by arbitrarily taking two adjacent inorganic particles (if the inorganic particles have an irregular shape, a circumscribing process can be performed on the particles) from the coating in an SEM image of the separator, and measuring the center-to-center distance between the two inorganic particles as the distance between the two inorganic particles, which is designated as L1.

[0101] In some embodiments, the distance between any adjacent inorganic particles and organic particles is determined by arbitrarily taking one adjacent inorganic particle and one adjacent organic particle (if the inorganic particle or organic particle has an irregular shape, the particle can be subjected to circumscribing circle processing) from the coating in the SEM image of the separator, and measuring the center distance between the inorganic particle and the organic particle as the distance between the inorganic particle and the organic particle, which is designated as L2. The organic particle may be the first organic particle or the second organic particle.

[0102] The above-mentioned interval can be measured by a tool known in the art. For example, it can be measured by a scanning electron microscope. For example, the interval L2 between any adjacent inorganic particles and organic particles can be measured by the following method. The separator is prepared into a sample with a length x width of 50 mm x 100 mm, and the separator is measured using a scanning electron microscope (for example, ZEISS Sigma 300). The measurement can be performed with reference to JY / T010-1996. Randomly select an area from the sample, perform a scanning measurement, and obtain an SEM image of the separator at a certain magnification (for example, 3000 times), and in the SEM image, arbitrarily select one adjacent inorganic particle and one adjacent organic particle (if the inorganic particle or organic particle is an irregular body, the particle can be subjected to circumscribing process), and measure the distance between the center of the inorganic particle (or its circumscribing circle) and the center of the organic particle (or its circumscribing circle), which is the interval between adjacent inorganic particles and organic particles described in this application, and is L2. To ensure the accuracy of the measurement results, the above measurement is repeated for multiple sets of adjacent particles (eg, 10 sets) in the sample, and the average value of the measurement results for each set is taken as the final result.

[0103] Similarly, the distance L1 between any two adjacent inorganic particles can be measured by the above method.

[0104] Figure 2-2 is a scanning electron microscope (SEM) photograph at a magnification 3000 times that of the separator of the embodiment of the present application. As can be seen from Figure 2-2, the coating of the separator contains inorganic particles, first organic particles, and second organic particles. The first organic particles are secondary particles, the second organic particles are primary particles, and the first organic particles and the second organic particles are embedded in the inorganic particles to form protrusions on the coating surface. When measured by the method described above, L1 < L2 was obtained.

[0105] According to some embodiments, the shape of the organic particles (e.g., primary particle shape or secondary particle shape) can be measured using devices and methods known in the art. For example, a scanning electron microscope (e.g., ZEISS Sigma 300) can be used to conduct the test. As an example, it can be operated by the following steps. First, cut the separator into test samples of a certain size (e.g., 6 mm × 6 mm), sandwich the test sample with two conductive and thermally conductive sheets (e.g., copper foil), and adhere and fix the test sample and the sheet with an adhesive (e.g., double-sided adhesive). Press with a flat iron block of a certain mass (e.g., 400 g) for a certain time (e.g., 1 hour) to make the gap between the test sample and the copper foil as small as possible. Then, trim the edges with scissors and stick it to a sample stage with a conductive adhesive, and make the sample protrude slightly from the periphery of the sample stage. Next, fix the sample stage to a cycle holder, turn on the power of an argon ion cross-section polishing device (e.g., IB-19500CP), draw a vacuum (e.g., 10 Pa - 4 Pa), set the argon flow rate (e.g., 0.15 MPa), voltage (e.g., 8 KV), and polishing time (e.g., 2 hours), adjust the sample stage to the rocking mode and start polishing. After polishing, use a scanning electron microscope (e.g., ZEISS Sigma 300) to obtain an ion-polished cross-sectional shape (CP) image of the sample to be measured.

[0106] Figure 3 is an ion-polished cross-sectional (CP) photograph of a separator of an embodiment of the present application at 3000x magnification. As can be seen from Figure 3, the separator coating includes both first organic particles and second organic particles; the first organic particles are secondary particles composed of multiple primary particles and have irregular non-solid spherical cross-sections, and the non-agglomerated primary particles of the second organic particles have solid spherical cross-sections.

[0107] According to some embodiments, the particle size and number average particle size of organic particles can be measured by instruments and methods known in the art. For example, a scanning electron microscope (e.g. ZEISS Sigma 300) is used to obtain a scanning electron microscope (SEM) photograph of the separator with reference to JY / T010-1996. For example, it can be measured by the following method: A test sample with length x width = 50 mm x 100 mm is randomly taken on the separator, and multiple test areas (e.g. 5) are randomly taken in the test sample, and the particle size of each organic particle in each test area is read at a certain magnification (e.g. 500 times when the first organic particle is measured, and 1000 times when the second organic particle is measured) (i.e., the distance between the two most distant points on the organic particle is taken as the particle size of the organic particle), and the number and particle size values ​​of organic particles in each test area are statistically calculated, and the arithmetic average value of the particle size of the organic particles in each test area is taken, that is, the number average particle size of the organic particles in the test sample. To ensure accuracy of the test results, multiple test samples (eg, 10) may be repeated and the average value of each test sample may be taken as the final test result.

[0108] In some embodiments, the type of material of the organic particles can be measured using instruments and methods known in the art. For example, the type of material can be identified by measuring the infrared spectrum of the material and determining the characteristic peaks contained therein. Specifically, the organic particles can be subjected to infrared spectroscopy analysis using instruments and methods known in the art, for example, using an infrared spectrometer such as the IS10 Fourier transform infrared spectrometer from Nicolet, USA, according to GB / T6040-2002 General Rules for Infrared Spectroscopy Analysis Method.

[0109] According to some embodiments, the volume average particle size Dv50 of inorganic particles has a meaning known in the art and can be measured using an apparatus and method known in the art. For example, it can be measured using a laser particle size analyzer (e.g., Master Size 3000) with reference to GB / T 19077-2016 laser diffraction particle size distribution method.

[0110] In some embodiments, the separator's air permeability, transverse tensile strength (MD), longitudinal tensile strength (TD), transverse breaking elongation, and longitudinal breaking elongation all have meanings known in the art and can be measured by methods known in the art, for example, according to GB / T 36363-2018.

[0111] The present application further provides: (1) providing a substrate; Providing a coating slurry: (2) providing a coating slurry including a component material and a solvent, the component material including inorganic particles and organic particles including first organic particles; and (3) applying the coating slurry described in step (2) to at least one surface of the substrate described in step (1) to form a coating, and drying the coating to obtain the separator. Wherein, the dried coating comprises the inorganic particles, the first organic particles, and the second organic particles. The first organic particles and the second organic particles are embedded in the inorganic particles and form protrusions on the dried coating surface. The first organic particles are secondary particles, and the number of the first organic particles in the dried coating is A, the second organic particles are primary particles, and the number of the second organic particles in the dried coating is B, and the separator satisfies 0.05≦A / B<1.

[0112] As shown in FIG. 4-1, the separator includes a substrate (A) and a coating (B), and the coating (B) is provided on only one surface of the substrate (A).

[0113] As shown in FIG. 4-2, the separator includes a substrate (A) and a coating (B), and the coating (B) is provided on both sides of the substrate (A).

[0114] In the embodiment of the present application, the material of the substrate is not particularly limited, and any known substrate having good chemical stability and mechanical stability can be selected and used, such as one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The substrate may be a single layer film or a multi-layer composite film. When the substrate is a multi-layer composite film, the materials of each layer may be the same or different.

[0115] In some embodiments, in step (2), the solvent can be water, for example, deionized water.

[0116] In some embodiments, in step (2), the component material may include other organic compounds, such as polymers to improve heat resistance, dispersants, wetting agents, other types of binders, etc., all of which are non-particulate in the coating after drying.

[0117] In some embodiments, in step (2), the composition materials are added to a solvent and stirred uniformly to obtain a coating slurry.

[0118] In some embodiments, in step (2), the added mass of the first organic particles is 12% or more of the sum of the dry matter weights of the component materials, for example, 12% to 30%, 15% to 30%, 15% to 25%, 15% to 20%, or 16% to 22%.

[0119] In some embodiments, in step (2), the added mass of the second organic particles is 10% or less of the total dry weight of the component materials, for example, 2% to 10%, 3% to 7%, or 3% to 5%.

[0120] When the mass of the first organic particles or the second organic particles is within the above range, it contributes to controlling the ratio of the amount of the first organic particles and the second organic particles within a predetermined range. At the same time, the appropriate content of organic particles can reduce the static electricity generated between the separator and the battery winding tool (e.g., coil needle) or stacking tool during the battery manufacturing process, effectively reducing the probability of short-circuiting between the positive and negative electrodes, thereby improving the manufacturing yield rate of the battery.

[0121] If an ingredient is a solid, the dry weight of the ingredient is the mass of the ingredient added. If an ingredient is a suspension, emulsion or solution, the dry weight of the ingredient is the product of the mass of the ingredient added and the solid content of the ingredient. The sum of the dry weights of the ingredients is the sum of the dry weights of each ingredient.

[0122] In some embodiments, in step (2), the solid content of the coating slurry can be controlled to be 28%-45%, for example, 30%-38%. When the solid content of the coating slurry is in the above range, the occurrence probability of coating film surface problems and coating unevenness can be effectively reduced, and the cycle performance and safety performance of the battery can be further improved.

[0123] In some embodiments, in step (3), the coating is performed using a coater.

[0124] In the examples of the present application, the type of coater is not particularly limited, and any commercially available coater can be used.

[0125] In some embodiments, in step (3), the coating can be performed using a process such as transfer coating, rotary spray, or dip coating, for example, the coating can be performed using transfer coating.

[0126] In some embodiments, the coater includes a gravure roll, which is used to transfer the coating slurry to a substrate.

[0127] In some embodiments, the ruling of the gravure roll may be 100 LPI to 300 LPI, for example, 125 LPI to 190 LPI (LPI is lines per inch). When the ruling of the gravure roll is within the above range, the ratio of the number of the first organic particles to the number of the second organic particles can be controlled to be within a predetermined range, thereby further improving the cycleability and safety of the separator.

[0128] In some embodiments, in step (3), the coating speed can be controlled to 30 m / min to 90 m / min, for example, 50 m / min to 70 m / min. When the coating speed is within the above range, it contributes to controlling the ratio of the number of the first organic particles to the second organic particles within a predetermined range. It can also effectively reduce the coating film surface problem and reduce the probability of coating non-uniformity, thereby further improving the cycle performance and safety performance of the battery.

[0129] In some embodiments, in step (3), the linear velocity ratio of the coating may be controlled to be 0.8 to 2.5, for example, 0.8 to 1.5, or 1.0 to 1.5.

[0130] In some embodiments, in step (3), the drying temperature may be 40°C-70°C, for example 50°C-60°C.

[0131] In some embodiments, in step (3), the drying time may be from 10 s to 120 s, for example, from 20 s to 80 s, or from 20 s to 40 s.

[0132] By controlling each of the above process parameters within a predetermined range, the performance of the separator of the present application can be further improved. Those skilled in the art can selectively adjust and control one or more of the above process parameters according to the actual production situation.

[0133] In order to further improve the performance of the secondary battery, the inorganic particles and the organic particles can selectively further satisfy one or more of the above-mentioned parameter conditions, the description of which is omitted here.

[0134] The substrate, the first organic particles and the second organic particles are all commercially available.

[0135] The method for producing a separator according to the present invention produces a coating by a single application, greatly simplifying the production process flow of the separator; at the same time, the separator produced by the above method can be used in a battery to effectively improve the battery's multiplication performance, storage performance and safety performance.

[0136] [Positive plate] In the secondary battery, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer provided on the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material.

[0137] The positive electrode current collector may be a normal metal foil piece or a composite current collector (a composite current collector may be formed by providing a metal material on a polymer substrate). For example, the positive electrode current collector may be an aluminum foil.

[0138] The specific type of the positive electrode active material is not limited, and any active material that is applicable to the positive electrode of a secondary battery and known in the art may be used, and a person skilled in the art may select the active material according to actual requirements.

[0139] As an example, the positive electrode active material may include, but is not limited to, one or more of lithium transition metal oxides, lithium phosphates containing olivine type, and their respective modified compounds. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide, lithium nickel oxide, lithium manganate, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganate, lithium nickel cobalt manganate, lithium nickel cobalt aluminum oxide, and their respective modified compounds. Examples of lithium phosphates containing olivine type may include, but are not limited to, lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite material of lithium manganese iron phosphate and carbon, and their respective modified compounds. These materials are commercially available.

[0140] In some embodiments, the modified compound of each of the materials may be a doping modification and / or a surface coating modification of the material.

[0141] The positive electrode membrane layer generally optionally includes an adhesive, a conductive agent, and other optional auxiliary agents.

[0142] By way of example, the conductive agent may be one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, Super P (SP), graphene, and carbon nanofibers.

[0143] By way of example, the adhesive may be one or more of styrene butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB).

[0144] [Negative plate] In the secondary battery, the negative electrode plate includes a negative electrode current collector and a negative electrode film layer provided on the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material.

[0145] The negative electrode current collector may be a typical metal foil piece or a composite current collector (for example, a composite current collector may be formed by providing a metal material on a polymer substrate). For example, the negative electrode current collector may be an aluminum foil.

[0146] The specific type of the negative electrode active material is not limited, and active materials applicable to the negative electrode of a secondary battery and known in the art can be adopted, and those skilled in the art can select according to actual requirements. For example, the negative electrode active material can include, but is not limited to, one or more of artificial graphite, natural graphite, hard carbon, soft carbon, silicon-based material, and tin-based material. The silicon-based material can be selected from one or more of elemental silicon, silicon oxide (e.g., silicon monoxide), silicon carbon composite, silicon nitrogen composite, and silicon alloy. The tin-based material can be selected from one or more of elemental tin, tin oxide, and tin alloy. These materials are commercially available.

[0147] In some embodiments, to increase the energy density of the battery, the negative electrode active material can include a silicon-based material.

[0148] The negative electrode membrane layer generally optionally includes an adhesive, a conductive agent, and other optional auxiliary agents.

[0149] By way of example, the conductive agent may be one or more of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0150] By way of example, the adhesive may be one or more of styrene butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB).

[0151] By way of example, other optional auxiliary agents may be thickeners and dispersants (eg, sodium carboxymethylcellulose CMC-Na), PTC thermistor materials.

[0152] [Electrolyte] The secondary battery may include an electrolyte that serves to conduct ions between the positive electrode and the negative electrode. The electrolyte may include an electrolyte salt and a solvent.

[0153] By way of example, the electrolyte salt may be selected from one or more of LiPF6 (lithium hexafluorophosphate), LiBF4 (lithium tetrafluoroborate), LiClO4 (lithium perchlorate), LiAsF6 (lithium hexafluoroarsenate), LiFSI (lithium bis(fluorosulfonyl)imide), LiTFSI (lithium bis(trifluoromethanesulfonyl imide), LiTFS (lithium trifluoromethanesulfonate), LiDFOB (lithium difluoro(oxalato)borate), LiBOB (lithium bis(oxalato)borate), LiPO2F2 (lithium difluorophosphate), LiDFOP (lithium difluorobis(oxalato)phosphate), and LiTFOP (lithium tetrafluoro(oxalato)phosphate).

[0154] By way of example, the solvent may be one or more selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfone (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0155] In some embodiments, the electrolyte further includes an additive. For example, the additive may include an anode film-forming additive, a cathode film-forming additive, or an additive that can improve some performance of the battery, such as an additive that improves the overcharge performance of the battery, an additive that improves the high temperature performance of the battery, or an additive that improves the low temperature performance of the battery.

[0156] In some embodiments, the secondary battery may be a lithium ion secondary battery.

[0157] In the embodiment of the present application, the shape of the secondary battery is not particularly limited, and the secondary battery may be cylindrical, rectangular, or any other shape. Fig. 5 shows a secondary battery 5 having a rectangular structure as an example.

[0158] In some embodiments, the secondary battery can include an exterior packaging, which is used to package the positive and negative plates and the electrolyte.

[0159] 6, in some embodiments, the exterior can include a housing 51 and a cover plate 53. Here, the housing 51 can include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate form a surrounding storage chamber. The housing 51 has an opening communicating with the storage chamber, and the cover plate 53 can be placed over the opening to close the storage chamber.

[0160] The positive electrode plate, the negative electrode plate and the separator can be formed into an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is sealed in the housing. The electrolyte can be an electrolytic solution immersed in the electrode assembly 52. ​​The number of electrode units 52 included in the secondary battery 5 can be one or more and can be adjusted as needed.

[0161] In some embodiments, the exterior of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The exterior of the secondary battery may be a soft package, such as a bag-type soft package. The material of the soft pack may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0162] In some embodiments, the secondary batteries can be assembled into a battery module, and the number of secondary batteries included in the battery module can be multiple, and the specific number can be adjusted based on the application and capacity of the battery module.

[0163] Fig. 7 shows an example of a battery module 4. Referring to Fig. 7, in the battery module 4, the multiple secondary batteries 5 may be arranged in order along the vertical direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the multiple secondary batteries 5 may be fixed with a fastener.

[0164] In some embodiments, the battery module 4 may further include a housing having an accommodation space in which the multiple secondary batteries 5 are accommodated.

[0165] In some embodiments, the above battery modules can be further assembled into a battery pack, and the number of battery modules included in the battery pack can be adjusted based on the application and capacity of the battery pack.

[0166] 8 and 9 show an example of a battery pack 1. Referring to Fig. 8 and Fig. 9, the battery pack 1 may include a battery case and a plurality of battery modules 4 provided in the battery case. The battery case includes an upper case 2 and a lower case 3, and the upper case 2 is covered by the lower case 3 to form an enclosed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery case in any manner.

[0167] Device The present application further provides an apparatus comprising at least one of the secondary battery, battery module, or battery pack. The secondary battery, battery module, or battery pack may be used as a power source for the apparatus, or may be used as an energy storage means for the apparatus. The apparatus may be, but is not limited to, a mobile device (e.g., a mobile phone, a laptop, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), a train, a ship, a satellite, an energy storage system, etc.

[0168] The device can select a secondary battery, a battery module or a battery pack according to its usage requirements.

[0169] An example of an apparatus is shown in Figure 10. The apparatus may be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. The apparatus may use a battery pack or a battery module to meet the high power and high energy density requirements for the secondary battery.

[0170] Another example of the device may be a mobile phone, a tablet computer, or a notebook computer, which generally require light weight and may employ a secondary battery as a power source.

[0171] The beneficial effects of the present invention will be further illustrated below with reference to examples.

[0172] Working Example In order to make the technical problems, technical solutions and beneficial effects that the present application aims to solve more clear, the following will be described in more detail with reference to the embodiments and drawings. Obviously, the described embodiments are only some embodiments of the present application, but not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and in no way limits the present application and its application. Any other embodiments obtained based on the embodiments of the present application without the need for creative labor by those skilled in the art are within the scope of protection of the present application.

[0173] 1. Separator manufacturing Separator 1: (1) Provide a PE substrate, for example, the thickness of the substrate is 7 μm and the porosity is 40%; (2) A coating slurry is prepared by uniformly mixing inorganic particles of alumina (Al2O3), first organic particles of vinylidene fluoride-hexafluoropropene copolymer (number average molecular weight 550,000), second organic particles of butyl methacrylate-isooctyl acrylate-styrene copolymer (number average molecular weight 80,000), dispersant of sodium carboxymethylcellulose (CMC-Na), wetting agent of organosilicon modified polyether, and heat-resistant adhesive of acrylic acid-acrylonitrile copolymer in a dry weight ratio of 71:12:10:1.5:0.5:5 with an appropriate amount of solvent deionized water to obtain a coating slurry with a solid content of 38% by weight. Here, the volume average particle diameter Dv50 of the inorganic particles of alumina (Al2O3) is 1 μm, the first organic particles are secondary particles and have a number average particle diameter of 15.0 μm, and the second organic particles are primary particles and have a number average particle diameter of 4.8 μm. (3) The coating slurry prepared in step (2) is applied to two surfaces of the PE substrate by a coating machine, and the separator 1 is obtained through steps such as drying and striping. Here, the aforementioned coating blending process or coating process can be adjusted with assistance so that the number ratio A / B of the first organic particles to the second organic particles is 0.05. For example, the gravure roll line number of the coating machine is 125LPI, the coating speed is 50m / min, the coating linear speed ratio is 1.15, the drying temperature is 50℃, and the drying time is 25s. In the separator, the first organic particles and the second organic particles are both embedded in the inorganic particles, and protrusions are formed on the surface of the coating.

[0174] All materials used in the examples are commercially available. For example: The substrate can be purchased from Shanghai Enjie New Materials Co., Ltd.

[0175] The inorganic particles can be purchased from Issitong Materials Technology Co., Ltd.

[0176] The first organic particles can be purchased from Agoma (Changshu) Chemical Co., Ltd.

[0177] The second organic particles can be purchased from Sichuan Indile Technology Co., Ltd.

[0178] The heat-resistant adhesive can be purchased from Sichuan Indile Technology Co., Ltd.

[0179] The wetting agent can be purchased from Toshi Chemical Company.

[0180] The dispersant can be purchased from Changshu Weiyi Technology Co., Ltd.

[0181] The manufacturing method of the separator 2-40 is similar to that of the separator 1, but the differences are as follows: The number average particle size, mass ratio, and substance type of the first organic particles and the second organic particles are adjusted, and Table 1 is referred to for details.

[0182] Second, battery manufacturing Example 1 1. Manufacturing of positive electrode plates Positive electrode active material LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM523), carbon black (Super P) as a conductive agent, and polyvinylidene fluoride (PVDF) as an adhesive are mixed uniformly in a mass ratio of 96.2:2.7:1.1 with an appropriate amount of N-methylpyrrolidone (NMP) as a solvent to obtain a positive electrode slurry, which is then applied to an aluminum foil as a positive electrode current collector, and the positive electrode plate is obtained through heat drying, cold pressing, striping, and cutting processes. The positive electrode surface density is 0.207 mg / mm 2 and the compaction density is 3.5g / cm 3 It is.

[0183] 2. Manufacturing of negative electrode plates The negative electrode active material, artificial graphite, the conductive agent, carbon black (Super P), the adhesive, styrene butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC-Na), are mixed uniformly in a mass ratio of 96.4:0.7:1.8:1.1 with an appropriate amount of deionized water as a solvent to obtain a negative electrode slurry, which is then applied to copper foil as a negative electrode current collector, and the negative electrode plate is obtained through processes such as heating and drying, cold pressing, striping and cutting. The negative electrode surface density is 0.126 mg / mm2 and the compaction density is 1.7 g / cm 3 It is.

[0184] 3. Separator The separator used is the separator 1 manufactured as described above.

[0185] 4. Electrolyte production Ethylene carbonate (EC) and methyl ethyl carbonate (EMC) are mixed in a mass ratio of 30:70 to obtain an organic solvent, and thoroughly dried electrolyte salt LiPF6 is dissolved in the above mixed solvent to make the concentration of the electrolyte salt 1.0 mol / L. The mixture is mixed uniformly to obtain an electrolyte solution.

[0186] 5. Secondary battery manufacturing A positive electrode plate, a separator, and a negative electrode plate are stacked in this order, and a separator is interposed between the positive and negative electrodes to serve as an insulator. The electrode assembly is then wound up to obtain a battery. The electrode module is then placed in an outer casing. The electrolyte prepared above is injected into the secondary battery after drying, and the secondary battery is obtained through processes such as vacuum packaging, standing, chemical formation, and shaping.

[0187] The secondary batteries of Examples 2-36 and Comparative Examples 1-4 were produced by methods similar to that of the secondary battery of Example 1, but differed in that different separators were used; see Table 2 for details.

[0188] 3. Battery performance measurement 1.2C magnification performance test At 25°C, the secondary batteries of each Example and Comparative Example are charged at a constant current of 0.33C to 4.20V, then charged at a constant voltage until the current is 0.05C, left to stand for 5 minutes, and the charge capacity at that time is recorded and used as the initial charge capacity. After standing for 5 minutes, the secondary batteries are discharged at a constant current of 0.33C to 2.8V, and left to stand for 30 minutes. The secondary batteries are then charged at a constant current of 2C to 4.20V, then charged at a constant voltage until the current is 0.05C, left to stand for 5 minutes, and the charge capacity at that time is recorded. Battery capacity retention rate at 2C charging rate (%) = 2C charging capacity / 0.33C charging capacity x 100%

[0189] 2.60℃ high temperature storage performance test At 25°C, the secondary batteries manufactured in the examples and comparative examples are charged at 1C to a charge cut-off voltage of 4.2V, then charged at a constant voltage to a current of 0.05C, left to stand for 5 minutes, and discharged at a constant current of 0.33C to a discharge cut-off voltage of 2.8V to obtain the initial capacity of the battery. Then, the battery is charged at 1C to a charge cut-off voltage of 4.2V at 25°C, then charged at a constant voltage to a current of 0.05C, at which point the battery is in a fully charged state, and the fully charged battery is stored in a thermostatic box at 60°C. Every 7 days, the battery is taken out and discharged at 0.33C to a discharge cut-off voltage of 2.8V at 25°C, left to stand for 5 minutes, and then charged at 1C to a charge cut-off voltage of 4.2V, then charged at a constant voltage to a current of 0.05C, left to stand for 5 minutes, and discharged at a constant current of 0.33C, at which point the battery capacity is tested. Record the number of days of storage until the capacity is reduced to 80% of the initial capacity. (Note: After removing the battery and completing the capacity test, charge the battery at 1C up to the charge cut-off voltage of 4.2V, then charge it at a constant voltage up to 0.05C, store the battery in a fully charged state, and then store it in a 60℃ thermostatic box.)

[0190] 3.Pinprick test At 25°C, the secondary batteries manufactured in the examples and comparative examples (each example and comparative example includes multiple batteries) are charged at a constant current of 1C up to a charge cutoff voltage of 4.2V, then charged at a constant voltage up to a current of ≦0.05C and left to stand for 10 minutes. The surface of the battery is exposed and clamped with a clamp, and then pierced with a 1mm steel needle at a speed of 0.1mm / s until the battery goes into thermal runaway, and the piercing depth at that time is recorded as L0.

[0191] In addition, another battery is sampled and the above operation steps are repeated, except that the needle insertion depth is controlled to L0 to 0.1 mm and the battery is statically observed for 1 hour.

[0192] During the observation period, if the battery experiences thermal runaway, take a new battery and repeat the operation steps, with the difference that the needle penetration depth is controlled at L0-0.2mm.

[0193] In this way, the needle penetration depth at this time is recorded as L until the battery does not undergo thermal runaway during observation, and L is the needle penetration depth at which the battery can be used safely. [Table 1-1] [Table 1-2] [Table 1-3] [Table 2]

[0194] As is clear from Table 1, by setting the ratio of the number of the first organic particles and the second organic particles within the range of the present application, the fold performance, storage performance and safety performance of the battery can be significantly improved. In particular, by further optimizing the number average particle size, the ratio of the number average particle size, or the substance type of the first organic particles and the second organic particles, the fold performance, storage performance and safety performance of the battery can be further improved. In contrast, all of Comparative Examples 1-4 do not meet the requirements of the present application, so the battery cannot achieve good fold performance, storage performance and safety performance at the same time.

[0195] The present inventors have also conducted experiments using other amounts and materials of the inorganic particles, the first organic particles, and the second organic particles within the scope of the present application, other substrates, other coating process parameters, and other process conditions, and obtained the same effects of improving the battery's multiplication performance and safety performance as in Examples 1-36.

[0196] The above content is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto, and a person skilled in the art can easily think of various equivalent modifications and replacements within the technical scope disclosed in the present application, and all of these modifications and replacements belong to the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A separator, A substrate; a coating disposed on at least one surface of the substrate; the coating comprises inorganic particles and organic particles, the organic particles comprising first organic particles and second organic particles, the first organic particles and the second organic particles being embedded in the inorganic particles and forming protrusions on a surface of the coating; The first organic particles are secondary particles, and the number of the first organic particles in the coating is A, and the second organic particles are primary particles, and the number of the second organic particles in the coating is B, wherein the separator satisfies 0.05≦A / B<1.

2. The separator according to claim 1 , wherein the separator satisfies 0.2≦A / B≦0.

6.

3. 3. The separator according to claim 2, wherein 0.25≦A / B≦0.

5.

4. The separator according to claim 1 or 3, wherein the number average particle size of the first organic particles is 8 μm or more.

5. The separator according to claim 4, wherein the number average particle size of the first organic particles is 12 μm to 25 μm.

6. The separator according to any one of claims 1 to 5, wherein the number average particle size of the second organic particles is ≧2 μm.

7. The separator according to claim 6, wherein the number average particle size of the second organic particles is 3 μm to 7 μm.

8. 8. The separator according to claim 1, wherein a ratio of a number average particle size of the first organic particles to a number average particle size of the second organic particles is ≧2.

0.

9. 9. The separator according to claim 8, wherein a ratio of a number average particle size of the first organic particles to a number average particle size of the second organic particles is 2.5 to 4.

0.

10. The separator further comprises: (1) the mass fraction of the inorganic particles in the coating is ≦75%; (2) the mass percentage of the first organic particles in the coating is ≧12%; and (3) the mass ratio of the second organic particles in the coating is ≦10%; and (4) Coating weight per unit area of ​​separator on one side ≦3.0 g / m ２ The separator according to any one of claims 1 to 9, which satisfies one or more of the following conditions.

11. The separator further comprises: (1) the mass ratio of the inorganic particles in the coating is 60% to 75%; (2) the mass ratio of the first organic particles in the coating is 15% to 25%; and (3) the mass ratio of the second organic particles in the coating is 2% to 10%; and (4) Coating weight per unit area of ​​separator on one side: 1.5 g / m ２ ~3.0g / m ２ The separator according to claim 10 , which satisfies one or more of the following:

12. The separator according to any one of claims 1 to 11, wherein the first organic particles contain one or more of a homopolymer or copolymer of a fluorine-containing alkyl group monomer unit, a homopolymer or copolymer of an alkylene group monomer unit, a homopolymer or copolymer of an unsaturated nitrile-based monomer unit, a homopolymer or copolymer of an alkylene oxide-based monomer unit, and a modified compound of each of the homopolymers or copolymers.

13. 13. The separator according to claim 12, wherein the first organic particles contain one or more of polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polyethylene, polypropylene, polyacrylonitrile, polyethylene oxide, a copolymer of different fluorine-containing alkyl group monomer units, a copolymer of a fluorine-containing alkyl group monomer unit and an alkylene group monomer unit, a copolymer of a fluorine-containing alkyl group monomer unit and an acrylic acid-based monomer unit, a copolymer of a fluorine-containing alkyl group monomer unit and an acrylate-based monomer unit, and a modified compound of each of the homopolymers or copolymers.

14. The separator according to any one of claims 1 to 13, wherein the first organic particles include one or more of vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-trifluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene-acrylic acid copolymer, vinylidene fluoride-hexafluoropropylene-acrylate copolymer, and modified compounds of the copolymers.

15. The separator according to any one of claims 1 to 14, wherein the second organic particles contain one or more of a homopolymer or copolymer of an acrylate-based monomer unit, a homopolymer or copolymer of an acrylic acid-based monomer unit, a homopolymer or copolymer of a styrene-based monomer unit, a polyurethane-based compound, a rubber-based compound, and a modified compound of each of the homopolymers or copolymers.

16. 16. The separator according to claim 15, wherein the second organic particles include one or more of a copolymer of an acrylate-based monomer unit and a styrene-based monomer unit, a copolymer of an acrylic acid-based monomer unit and a styrene-based monomer unit, a copolymer of an acrylic acid-based monomer unit-acrylate-based monomer unit-styrene-based monomer unit, a copolymer of a styrene-based monomer unit and an unsaturated nitrile-based monomer unit, a copolymer of a styrene-based monomer unit-alkylene group monomer unit-unsaturated nitrile-based monomer unit, and a modified compound of each of the copolymers.

17. The separator according to any one of claims 1 to 16, wherein the second organic particles include one or more of a butyl acrylate-styrene copolymer, a butyl methacrylate-isooctyl methacrylate copolymer, an isooctyl methacrylate-styrene copolymer, a methacrylate-methacrylic acid-styrene copolymer, a methyl acrylate-isooctyl methacrylate-styrene copolymer, a butyl acrylate-isooctyl acrylate-styrene copolymer, a butyl acrylate-isooctyl methacrylate-styrene copolymer, a butyl methacrylate-isooctyl acrylate-styrene copolymer, a butyl methacrylate-isooctyl acrylate-styrene copolymer, a butyl methacrylate-isooctyl methacrylate-styrene copolymer, a styrene-acrylonitrile copolymer, a styrene-butadiene-acrylonitrile copolymer, a methyl acrylate-styrene-acrylonitrile copolymer, an isooctyl methacrylate-styrene-acrylonitrile copolymer, a styrene-vinyl acetate copolymer, a styrene-vinyl acetate-pyrrolidone copolymer, and a modified compound of the copolymer.

18. The inorganic particles include boehmite (γ-AlOOH), alumina (Al ２ O ３ ), barium sulfate (BaSO ４ ), magnesium oxide (MgO), magnesium hydroxide (Mg(OH) ２ ), silicon dioxide (SiO ２ ), tin dioxide (SnO ２ ), titanium oxide (TiO ２ ), calcium oxide (CaO), zinc oxide (ZnO), zirconium oxide (ZrO ２ ), yttrium oxide (Y ２ O ３ ), nickel oxide (NiO), cerium oxide (CeO ２ ), zirconium titanate (SrTiO ３ ), barium titanate (BaTiO ３ ), magnesium fluoride (MgF ２ The separator according to any one of claims 1 to 17, comprising one or more of the following:

19. The separator is (1) The separator has an air permeability of 100s / 100mL-300s / 100mL; (2) The separator has a transverse tensile strength (MD) of 1500 kgf / cm ２ ~3000kgf / cm ２ And, (3) The separator has a longitudinal tensile strength (TD) of 1000 kgf / cm ２ ~2500kgf / cm ２ And, (4) the separator has a transverse breaking elongation of 50% to 200%; (5) The separator according to any one of claims 1 to 18, which satisfies one or more of the following: (a) the longitudinal breaking elongation of the separator is 50% to 200%.

20. The separator is (1) The separator has an air permeability of 150 s / 100 mL to 250 s / 100 mL; (2) The separator has a lateral tensile strength of 1800 kgf / cm ２ ~2500kgf / cm ２ That is, (3) The separator has a longitudinal tensile strength of 1400 kgf / cm ２ ~2000kgf / cm ２ That is, (4) The separator has a transverse breaking elongation of 100% to 150%; (5) The separator according to claim 19, which satisfies one or more of the following: the longitudinal breaking elongation of the separator is 100% to 150%.

21. the inorganic particles and the organic particles form non-uniform tunnel structures in the coating; The separator according to any one of claims 1 to 20, wherein the non-uniform tunnel structure satisfies L1 < L2, the L1 being a distance between any two adjacent inorganic particles, and the L2 being a distance between any adjacent inorganic particle and organic particle.

22. A method for producing the separator according to any one of claims 1 to 21, (1) providing a substrate; (2) providing a coating slurry including component materials and a solvent, the component materials including inorganic particles and organic particles including first organic particles and second organic particles; and step (3) of applying the coating slurry described in step (2) to at least one side of the substrate described in step (1) to form a coating, and drying to obtain the separator. the dried coating comprises the inorganic particles, the first organic particles, and the second organic particles, the first organic particles and the second organic particles are embedded in the inorganic particles and form protrusions on a surface of the dried coating, the first organic particles are secondary particles, and the number of the first organic particles in the dried coating is A, the second organic particles are primary particles, and the number of the second organic particles in the dried coating is B, the separator satisfies 0.05≦A / B<1.

23. The method comprises: (1) In step (2), the added mass of the first organic particles is 12% or more of the total dry weight of the component materials; (2) In step (2), the added mass of the second organic particles is 10% or less of the total dry weight of the component materials; (3) In the step (2), the solid content of the coating slurry is 28% to 45% by weight; (4) In the step (3), the coating is performed using a coater including a gravure roll having a line count of 100 LPI to 300 LPI; (5) In the step (3), the coating speed is 30 m / min to 90 m / min; (6) In the step (3), the linear velocity ratio of the coating is 0.8 to 2.5; (7) In the step (3), the drying temperature is 40° C. to 70° C.; (8) In the step (3), the drying time is 10 s to 120 s.

23. The method of claim 22, wherein one or more of the following are satisfied:

24. The method comprises: (1) In step (2), the added mass of the first organic particles is 12% to 30% of the sum of the dry weights of the component materials; (2) In step (2), the added mass of the second organic particles is 2% to 10% of the sum of the dry weights of the component materials; (3) In step (2), the solid content of the coating slurry is 30% to 38%; (4) In step (3), the coating is performed using a coater, the coater is equipped with a gravure roll, and the ruling of the gravure roll is 125 LPI to 190 LPI; (5) In step (3), the coating speed is 50 m / min to 70 m / min; (6) In step (3), the linear velocity ratio of the coating is 0.8 to 1.5; (7) In step (3), the drying temperature is 50° C. to 60° C.; (8) The method according to claim 23, wherein in step (3), the drying time is 20 s to 80 s.

25. A secondary battery comprising the separator according to any one of claims 1 to 21.

26. A battery module comprising the secondary battery according to claim 25.

27. A battery pack comprising the battery module of claim 26.

28. An apparatus comprising at least one of the secondary battery according to claim 25, the battery module according to claim 26, or the battery pack according to claim 27.

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