Separators, secondary batteries and power consumption devices

Abstract

The present application provides a separator, a secondary battery, and a power consumption device, the separator comprising a first base film, a second base film, and an adhesive layer, the adhesive layer being disposed between the first base film and the second base film, the bending resistance of the separator in the transverse direction being denoted as T0, the bending resistance of the separator in the longitudinal direction being denoted as M0, T0 being 1.0-8.0 mN×cm, and M0 being 1.2-7.0 mN×cm.

Description

[Technical Field]

[0001] The present application relates to a separator, a secondary battery and a power consuming device. [Background technology]

[0002] In recent years, secondary batteries have been widely used in energy storage power systems such as hydroelectric, thermal, wind and solar power plants, as well as in multiple fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. With the application and widespread use of secondary batteries, the requirements for their reliability are becoming increasingly stringent. Summary of the Invention

[0003] The present application provides a separator, a secondary battery, and a power consumption device that can improve the production yield of secondary batteries and further improve the reliability of secondary batteries.

[0004] A first aspect of the present application provides a separator, comprising a first base film, a second base film, and an adhesive layer, wherein the adhesive layer is disposed between the first base film and the second base film, and wherein the bending resistance of the separator in the horizontal direction is denoted as T0 and the bending resistance of the separator in the vertical direction is denoted as M0, where T0 is 1.0-8.0 mN×cm and M0 is 1.2-7.0 mN×cm.

[0005] The separator includes a first base film, a second base film, and an adhesive layer located between the first base film and the second base film. The separator has a transverse bending resistance T0 of 1.0 mN×cm to 8.0 mN×cm and a longitudinal bending resistance M0 of 1.2 mN×cm to 7.0 mN×cm. This reduces the likelihood of abnormalities such as curling, rounding, wrinkles, and creases occurring during the separator production, processing, slitting, and secondary battery manufacturing processes, and maintains the regular shape of the separator, thereby improving the production yield of secondary batteries. It also allows for more accurate control of the separator size, reducing the likelihood of localized shorting of the separator after processing. This reduces the likelihood of short-circuiting between the positive and negative electrodes, reducing the likelihood of safety hazards such as fires and explosions in secondary batteries, and improving the reliability of secondary batteries. Furthermore, the separator can have good heat resistance and high mechanical strength, and when used in a secondary battery, dendrites growing on the negative electrode side are less likely to break through the separator. At the same time, the separator has a relatively small thermal shrinkage rate, which improves the reliability of the secondary battery. Therefore, the separator according to the embodiments of the present application can improve the production yield of secondary batteries and further improve the reliability of secondary batteries.

[0006] In any embodiment of the present application, the separator has a bending resistance T0 in the transverse direction of 1.7-5.0 mN×cm, and optionally 1.9-4.7 mN×cm.

[0007] In any embodiment of the present application, the bending resistance M0 of the separator in the machine direction is 1.2-4.0 mN×cm, and optionally 1.5-3.3 mN×cm.

[0008] This further improves the heat resistance of the separator, improves the reliability of the secondary battery, and also improves the production yield of the secondary battery.

[0009] In any embodiment of the present application, T0 / M0 is 1.0-2.5, and optionally 1.2-2.0, which can further improve the heat resistance of the separator, improve the reliability of the secondary battery, and further improve the production yield of the secondary battery.

[0010] In any embodiment of the present application, the bending resistance of the first base film in the transverse direction is designated as T1, and T1 is 0.25-4.5 mN×cm, and optionally 0.9-3.0 mN×cm.

[0011] In any embodiment of the present application, the bending resistance of the first base film in the machine direction is designated as M1, and M1 is 0.15-4.0 mN×cm, and optionally 0.6-3.0 mN×cm.

[0012] In any embodiment of the present application, T1 / M1 is 1.0-3.0, and optionally 1.2-2.0.

[0013] By adjusting the bending resistance T1 in the transverse direction, the bending resistance M1 in the longitudinal direction, and the ratio T1 / M1 of the two of the first base film within the above ranges, the heat resistance of the separator can be further improved, the reliability of the secondary battery can be improved, and the production yield of the secondary battery can be further improved.

[0014] In any embodiment of the present application, the bending resistance of the second base film in the cross direction is designated as T2, and T2 is 0.3-5.0 mN×cm, and optionally 0.8-3.5 mN×cm.

[0015] In any embodiment of the present application, the bending resistance of the second base film in the machine direction is denoted as M2, and M2 is 0.2-4.5 mN×cm, and optionally 0.5-3.0 mN×cm.

[0016] In any embodiment of the present application, T2 / M2 is 1.0-3.5, and optionally 1.1-1.9.

[0017] By adjusting the transverse bending resistance T2, the longitudinal bending resistance M2, and the ratio T2 / M2 of the two of the second base film within the above ranges, the heat resistance of the separator can be further improved, the reliability of the secondary battery can be improved, and the production yield of the secondary battery can be further improved.

[0018] In any embodiment of the present application, the first base film has an average filament diameter of 80-300 nm, optionally 100-280 nm.

[0019] In any embodiment of the present application, the average filament diameter of the second base film is 100-300 nm, optionally 120-280 nm.

[0020] By adjusting the average filament diameter of the first base film and / or the average filament diameter of the second base film within the above range, the bending resistance of the first base film, the second base film, and the separator can be adjusted, and the separator can also be provided with good heat resistance and high ionic conductivity, thereby not only improving the reliability of the secondary battery but also further improving the electrochemical performance of the secondary battery.

[0021] In any embodiment of the present application, the ratio of the crystallinity of the second base film to the crystallinity of the first base film is greater than 1, optionally 1.03-1.5, and further optionally 1.05-1.25.

[0022] The first base film of the separator faces the negative electrode, and the second base film faces the positive electrode. By adjusting the ratio of the crystallinity of the second base film to the crystallinity of the first base film to be greater than 1, the bending resistance of the first base film, the second base film, and the separator can be adjusted, which is also advantageous for producing a wound electrode assembly.

[0023] In any embodiment of the present application, the crystallinity of the first base film is 33%-70%, and optionally 35%-45%.

[0024] In any embodiment of the present application, the crystallinity of the second base film is 35%-80%, and optionally 40%-55%.

[0025] By adjusting the crystallinity of the first base film and / or the crystallinity of the second base film within the above range, the bending resistance of the first base film, the second base film and the separator can be adjusted, and the separator can be given good mechanical strength and elasticity, which is not only advantageous for improving the high temperature resistance and reliability of the secondary battery, but also advantageous for the production of wound electrode assemblies.

[0026] In any embodiment of the present application, the ratio of the thickness of the second base film to the thickness of the first base film is greater than 1, optionally 1.02-5.0, and further optionally 1.2-2.5.

[0027] The first base film of the separator faces the negative electrode, and the second base film faces the positive electrode. By adjusting the ratio of the thickness of the second base film to the thickness of the first base film to be greater than 1, the bending resistance of the first base film, the second base film, and the separator can be adjusted. In addition, if the thickness of the first base film is relatively small and the stretching ratio during production is generally relatively large, the degree of orientation of the first base film is relatively high and the physical strength (e.g., puncture strength) is relatively high. Furthermore, if it faces the negative electrode, dendrite growth can be better alleviated and the reliability of the secondary battery can be improved.

[0028] In any embodiment of the present application, the thickness of the first base film is 12 μm or less, and optionally 2.5-5 μm.

[0029] In any embodiment of the present application, the thickness of the second base film is 14 μm or less, and optionally 3-6 μm.

[0030] By adjusting the thickness of the first base film and / or the second base film within the above range, the bending resistance of the first base film, the second base film, and the separator can be adjusted, which is also advantageous for the secondary battery to have a high energy density.

[0031] In any embodiment of the present application, the ratio of the melting point of the first base film to the melting point of the second base film is less than 1, optionally 0.2-0.95, and further optionally 0.35-0.90.

[0032] The first base film of the separator faces the negative electrode, and the second base film faces the positive electrode. By adjusting the ratio of the melting point of the first base film to the melting point of the second base film to be less than 1, the bending resistance of the first base film, the second base film, and the separator can be adjusted. Furthermore, since the melting point of the first base film is relatively low and its physical strength (e.g., puncture strength) is relatively high, when it faces the negative electrode, it can better mitigate dendrite growth and improve the reliability of the secondary battery.

[0033] In any embodiment of the present application, the melting point of the first base film is 110°C or higher, optionally 120°C-165°C.

[0034] In any embodiment of the present application, the melting point of the second base film is 150°C or higher, optionally 165°C-330°C.

[0035] By adjusting the melting point of the first base film and / or the melting point of the second base film within the above range, the bending resistance of the first base film, the second base film, and the separator can be adjusted, and the separator can be given good pore-closing properties, which is advantageous for improving the reliability of the secondary battery.

[0036] In any embodiment of the present application, the ratio of the porosity of the second base film to the porosity of the first base film is greater than 1, optionally 1.01-2.8, and further optionally 1.1-2.0.

[0037] The first base film of the separator faces the negative electrode, and the second base film faces the positive electrode. By adjusting the ratio of the porosity of the second base film to the porosity of the first base film so that it is greater than 1, the bending resistance of the first base film, the second base film, and the separator can be adjusted. In addition, the first base film, which has a relatively small porosity, faces the negative electrode, which can better mitigate dendrite growth and improve the reliability of the secondary battery.

[0038] In any embodiment of the present application, the porosity of the first base film is 28%-70%, optionally 30%-50%.

[0039] In any embodiment of the present application, the porosity of the second base film is 30%-80%, optionally 35%-60%.

[0040] By adjusting the porosity of the first base film and / or the porosity of the second base film within the above range, the bending resistance of the first base film, the second base film, and the separator can be adjusted, and the separator can be given good ionic conductivity, which further contributes to improving the cycle performance, dynamic performance, etc. of the secondary battery.

[0041] In any embodiment of the present application, the porosity of the separator is 27%-65%, optionally 33%-55%.

[0042] In any embodiment of the present application, the ratio of the average pore size of the second base film to the average pore size of the first base film is greater than 1, optionally 1.05-2.5, and further optionally 1.1-2.

[0043] The first base film of the separator faces the negative electrode, and the second base film faces the positive electrode. By adjusting the ratio of the average pore size of the second base film to the average pore size of the first base film so that it is greater than 1, the bending resistance of the first base film, the second base film, and the separator can be adjusted. In addition, the first base film with a relatively small average pore size faces the negative electrode, which can better mitigate dendrite growth and further more uniformize the ion flow from the positive electrode, thereby reducing problems such as rapid dendrite growth and excessively sharp dendrite morphology caused by excessively high ion concentration at local locations on the negative electrode, and also contributing to improving the cycle performance and dynamic performance of the secondary battery.

[0044] In any embodiment of the present application, the first base film has an average pore size of 48-1800 nm, optionally 50-300 nm.

[0045] In any embodiment of the present application, the average pore size of the second base film is 50-2000 nm, optionally 100-400 nm.

[0046] By adjusting the average pore size of the first base film and / or the average pore size of the second base film within the above range, the bending resistance of the first base film, the second base film, and the separator can be adjusted, and the first base film and the second base film can be made to better exert the effect of mitigating dendrite growth, improving the reliability of the secondary battery, and also imparting good ionic conductivity to the separator, thereby further contributing to improvements in the cycle performance, dynamic performance, etc. of the secondary battery.

[0047] In any embodiment of the present application, the ratio of the air permeability of the first base film to the air permeability of the second base film is greater than 1, optionally 1.05-3.0, and further optionally 1.08-2.0.

[0048] The first base film of the separator faces the negative electrode, and the second base film faces the positive electrode. By adjusting the ratio of the air permeability of the first base film to the air permeability of the second base film to be greater than 1, the bending resistance of the first base film, the second base film, and the separator can be adjusted. In addition, the first base film, which has a relatively high air permeability, faces the negative electrode, which can better mitigate dendrite growth and improve the reliability of the secondary battery.

[0049] In any embodiment of the present application, the air permeability of the first base film is 300s / 100cc or less, optionally 120-260s / 100cc.

[0050] In any embodiment of the present application, the air permeability of the second base film is 250s / 100cc or less, optionally 110-220s / 100cc.

[0051] By adjusting the air permeability of the first base film and / or the air permeability of the second base film within the above range, the bending resistance of the first base film, the second base film, and the separator can be adjusted, and the separator can also be given good ionic conductivity, which also contributes to improving the cycle performance, dynamic performance, etc. of the secondary battery.

[0052] In any embodiment of the present application, the first base film and the second base film each independently comprise one or more of polyolefins and derivatives thereof, halogenated polyolefins and derivatives thereof, polyethers and derivatives thereof, polyetheretherketones and derivatives thereof, polyesters and derivatives thereof, polyimides and derivatives thereof, and polyvinyl alcohols and derivatives thereof.

[0053] In any embodiment of the present application, the halogenated polyolefin and its derivatives include one or more of polytetrafluoroethylene and its derivatives, polyvinyl fluoride and its derivatives, and polyvinylidene fluoride and its derivatives.

[0054] In any embodiment of the present application, the polyester and its derivatives include one or more of polyethylene terephthalate and its derivatives, polybutylene terephthalate and its derivatives.

[0055] In any embodiment of the present application, the adhesive layer includes an adhesive that ensures adhesive strength and uniformity between the first base film and the second base film, and also imparts good heat resistance to the separator, thereby contributing to improved reliability of the secondary battery.

[0056] In any embodiment of the present application, the adhesive layer includes an adhesive and a filler. The filler can further improve the heat resistance and physical properties (e.g., puncture strength) of the separator, thereby contributing to improved reliability of the secondary battery. In addition, by interposing the filler between the first base film and the second base film, problems such as powder shedding can be reduced.

[0057] In any embodiment of the present application, the adhesive comprises one or more of polyacrylate, polyacrylic acid, polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride-trichloroethylene copolymer, polyvinylpyrrolidone, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyethylene oxide, polyarylate, carboxymethyl cellulose, hydroxypropyl cellulose, regenerated cellulose, cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate, polyacrylonitrile, polyvinyl alcohol, polyethylene, polypropylene, starch, and cyanoethyl amylopectin.

[0058] In any embodiment of the present application, the filler includes at least one of inorganic particles, organic particles, and an organic-metallic framework material. Optionally, the inorganic particles include one or more of inorganic particles having a dielectric constant of 5 or greater, inorganic particles having ionic conductivity but not storing ions, and inorganic particles capable of generating an electrochemical reaction. Optionally, the organic particles include one or more of polycarbonate, polythiophene, polypyridine, polystyrene, polyacrylic wax, polyethylene, polypropylene, cellulose, cellulose modifier, melamine resin, phenolic resin, polyester, silicone resin, polyimide, polyamideimide, polyaramid, polyphenylene sulfide, polysulfone, polyethersulfone, polyetheretherketone, polyaryletherketone, and a copolymer of butyl acrylate and ethyl methacrylate. Optionally, the organic-metallic framework material includes one or more of a nitrogen-containing heterocyclic ligand-based framework, an organic carboxylic acid-based framework, and a nitrogen-containing oxygen gas mixture-based framework.

[0059] In any embodiment of the present application, the thickness of the adhesive layer is 0.3 μm or more, and optionally 0.5-4 μm, and when the thickness of the adhesive layer is within the above range, the separator can have an appropriate thickness, and the separator can have good heat resistance and physical strength, thereby improving the reliability of the secondary battery.

[0060] In any embodiment of the present application, the areal density of the adhesive layer is 1.0-6.0 g / m 2 and selectively 1.2-5.0 g / m 2 is.

[0061] In any embodiment of the present application, the adhesive strength between the adhesive layer and the first base film is 3 N / m or more, optionally 4-15 N / m.

[0062] In any embodiment of the present application, the adhesive strength between the adhesive layer and the second base film is 3 N / m or more, optionally 4-15 N / m.

[0063] In any embodiment of the present application, the content of the adhesive is 10% or more, optionally 10%-30%, based on the total weight of the adhesive layer.

[0064] In any embodiment of the present application, the content of the filler is 90% or less, optionally 60%-80%, based on the total weight of the adhesive layer.

[0065] In any embodiment of the present application, the volume distribution particle size Dv50 of the filler is less than 1.5 μm, and optionally 0.1-1.4 μm.

[0066] In any embodiment of the present application, the separator has a transverse tensile strength of 700 kg / cm 2 or more, and optionally 1000 kg / cm 2 That's all.

[0067] In any embodiment of the present application, the separator has a longitudinal tensile strength of 1000 kg / cm 2 or more, and selectively 1200 kg / cm 2 That's all.

[0068] In any embodiment of the present application, the separator has a transverse heat shrinkage of 5% or less, and optionally 2% or less, at 250° C. for 1 hour.

[0069] In any embodiment of the present application, the separator has a longitudinal heat shrinkage rate of 5% or less, optionally 2% or less, at 250°C for 1 hour.

[0070] A second aspect of the present application provides a secondary battery including the separator of the first aspect of the present application.

[0071] In any embodiment of the present application, the secondary battery includes a positive electrode plate and a negative electrode plate, the separator is disposed between the positive electrode plate and the negative electrode plate, and a first base film of the separator faces the negative electrode plate, and a second base film of the separator faces the positive electrode plate.

[0072] A third aspect of the present application provides a power consuming device including the secondary battery of the second aspect of the present application.

[0073] The power consuming device of the present application includes a secondary battery according to the present application, and therefore has at least the same advantages as said secondary battery. [Brief explanation of the drawings]

[0074] In order to more clearly explain the technical solutions of the embodiments of the present application, the following briefly introduces the drawings that need to be used in the embodiments of the present application. It is obvious that 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 any creative efforts. [Figure 1] 1 is a schematic diagram of one embodiment of a secondary battery according to the present application. [Figure 2] 1 is an exploded schematic view of an embodiment of a secondary battery according to the present application. [Figure 3] 1 is a schematic diagram of one embodiment of a battery module according to the present application. [Figure 4] 1 is a schematic diagram of one embodiment of a battery pack according to the present application. [Figure 5] FIG. 5 is an exploded schematic view of the embodiment of the battery pack shown in FIG. 4. [Figure 6] 1 is a schematic diagram of one embodiment including a secondary battery-powered power consuming device according to the present application. DETAILED DESCRIPTION OF THE INVENTION

[0075] Hereinafter, with appropriate reference to the drawings, embodiments specifically disclosing the separator, secondary battery, and power consumption device of the present application will be described in detail. However, unnecessary detailed description may be omitted. For example, detailed description of well-known matters or repeated description of structures that are actually the same may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. Note that the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0076] The "ranges" disclosed in this application are defined in the form of lower and upper limits. A given range is defined by selecting one lower limit and one upper limit, and the selected lower and upper limits define the boundaries of the particular range. Such defined ranges may be inclusive or exclusive, and may be arbitrarily combined; i.e., any lower limit may be combined with any upper limit to form a single range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Furthermore, if 1 and 2 are listed as minimum range values ​​and 3, 4, and 5 are listed as maximum range values, the following ranges are also contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. Unless otherwise specified, the numerical range "ab" in this application is a shorthand notation for any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" represents a list of all real numbers between "0-5" already listed in this specification, and "0-5" is merely a shorthand representation of combinations of these numbers. Also, expressing a parameter as an integer ≧2 is equivalent to disclosing that this parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0077] Unless otherwise stated, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure content of the present application.

[0078] Unless otherwise stated, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure content of the present application.

[0079] Unless otherwise specified, all steps in this application may be performed in order or randomly, preferably in order. For example, a description of a method including steps (a) and (b) means that the method may include steps (a) and (b) performed in order, or steps (b) and (a) performed in order. For example, a description of a method that may further include step (c) means that step (c) may be added to the method in any order, e.g., the method may include steps (a), (b), and (c), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0080] Unless otherwise specified, the terms "comprise" and "comprises" used in this application may be open ended or closed ended. For example, the terms "comprise" and "comprises" may indicate that other components not listed may be further included or included, or that only the listed components may be included or included.

[0081] Unless otherwise stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, "A or B" is satisfied when A is true (or exists) and B is false (or does not exist), when A is false (or does not exist) but B is true (or exists), or when both A and B are true (or exist).

[0082] Unless otherwise stated, in this application, the terms "first," "second," etc. are not intended to describe a particular order or hierarchy, but rather to distinguish between different objects.

[0083] In this application, the terms "plurality," "various," and the like refer to two or more.

[0084] Unless otherwise specified, terms used in this application have the known meanings commonly understood by those skilled in the art.

[0085] Unless otherwise specified, the numerical values ​​of each parameter mentioned in this application can be measured using various test methods commonly used in the art, for example, according to the test methods given in the examples of this application. Unless otherwise specified, the test temperature for each parameter is 25°C.

[0086] Unless otherwise specified, all ratio parameters in this application are compared when the units are the same. For example, if the thickness of A and B is 1.2:1, then the thickness units of A and B are the same.

[0087] Generally, a secondary battery includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode plate, a negative electrode plate, and a separator. The separator is installed between the positive electrode plate and the negative electrode plate and mainly serves to prevent short circuits between the positive electrode and the negative electrode.

[0088] The separator according to the embodiment of the present application comprises a first base film, a second base film, and an adhesive layer, and the adhesive layer is disposed between the first base film and the second base film. The bending resistance of the separator in the transverse (TD) direction is denoted as TO, and the bending resistance of the separator in the longitudinal (MD) direction is denoted as MO, where TO is 1.0-8.0 mN×cm and MO is 1.2-7.0 mN×cm.

[0089] For example, the bending resistance T0 in the transverse (TD) direction of the separator may be 1.0 mN×cm, 1.5 mN×cm, 1.7 mN×cm, 2.0 mN×cm, 2.3 mN×cm, 2.5 mN×cm, 2.8 mN×cm, 3.1 mN×cm, 3.4 mN×cm, 3.7 mN×cm, 4.0 mN×cm, 4.2 mN×cm, 4.5 mN×cm, 4.7 mN×cm, 4.9 mN×cm, 5.0 mN×cm, 5.2 mN×cm, 5.5 mN×cm, 5.8 mN×cm, 6.0 mN×cm, 6.2 mN×cm, 6.5 mN×cm, 6.8 mN×cm, 7.0 mN×cm, 7.5 mN×cm, 8.0 mN×cm, or a range consisting of any two of the above numerical values.

[0090] The bending resistance M0 of the separator in the machine direction (MD) may be 1.2 mN×cm, 1.5 mN×cm, 1.8 mN×cm, 1.9 mN×cm, 2.0 mN×cm, 2.2 mN×cm, 2.5 mN×cm, 2.7 mN×cm, 3.0 mN×cm, 3.3 mN×cm, 3.5 mN×cm, 3.8 mN×cm, 4.0 mN×cm, 4.2 mN×cm, 4.5 mN×cm, 4.8 mN×cm, 5.0 mN×cm, 5.2 mN×cm, 5.5 mN×cm, 5.8 mN×cm, 6.0 mN×cm, 6.2 mN×cm, 6.5 mN×cm, 6.8 mN×cm, 7.0 mN×cm, or a range consisting of any two of the above numerical values.

[0091] Currently, the separators used in commercial secondary batteries are generally made of polyolefins, such as porous polyethylene membranes or porous polypropylene membranes. However, these separators have relatively low heat resistance and undergo significant thermal contraction when heated, which can lead to direct contact between the positive and negative electrodes of the battery, potentially causing internal short circuits and increasing safety risks for the secondary battery. To address these issues, a commonly used approach is to coat the surface of a polyolefin separator with a heat-resistant inorganic ceramic layer. However, the inorganic ceramic layer's effectiveness in improving the overall heat resistance of the separator is limited, and the inorganic ceramic layer's poor adhesion can easily lead to problems such as powder shedding.

[0092] Furthermore, polyethylene porous membranes, polypropylene porous membranes, and the like are prone to abnormal phenomena such as curling, rounding, wrinkles, and creases during production, processing, slitting, and other processes, and are also prone to causing the finished separator to be locally too short in size. When used in secondary batteries, this can easily lead to short-circuiting between the positive and negative electrodes, affecting the reliability of the secondary batteries.

[0093] Without wishing to be bound by any theory, the inventors have discovered through extensive research that the separator comprises a first base film, a second base film, and an adhesive layer located between the first base film and the second base film, and the separator has a transverse (TD) direction bending resistance T0 of 1.0 mN×cm to 8.0 mN×cm and a longitudinal (MD) direction bending resistance M0 of 1.2 mN×cm to 7.0 mN×cm, which can reduce the probability of abnormal problems such as curling, rounding, wrinkles, and creases occurring during the separator production, processing, slitting, and secondary battery manufacturing processes, and can maintain the regularity of the separator shape, thereby improving the production yield of secondary batteries. In addition, the size of the separator can be more accurately controlled, which can reduce the probability of the separator being locally too short after processing, thereby reducing the probability of short-circuiting between the positive and negative electrodes and reducing the probability of safety accidents such as fires and explosions occurring in secondary batteries, and improving the reliability of secondary batteries.

[0094] The bending resistance T0 of the separator in the transverse (TD) direction is between 1.0 mN×cm and 8.0 mN×cm, and the bending resistance M0 of the separator in the longitudinal (MD) direction is between 1.2 mN×cm and 7.0 mN×cm. Furthermore, the separator can have good heat resistance and high mechanical strength. When used in a secondary battery, dendrites grown on the negative electrode side are less likely to break through the separator. At the same time, the separator has a relatively small thermal shrinkage rate, thereby improving the reliability of the secondary battery.

[0095] Therefore, the separator according to the embodiment of the present application can improve the production yield of secondary batteries and further improve the reliability of secondary batteries.

[0096] In research, the inventors have found that if the bending resistance T0 of the separator in the transverse (TD) direction is less than 1.0 mN×cm and / or the bending resistance M0 of the separator in the longitudinal (MD) direction is less than 1.2 mN×cm, abnormal phenomena such as curling, rounding, wrinkles, and creases are likely to occur during the processes of separator production and processing, slitting, and secondary battery production, resulting in a low production yield of secondary batteries. At the same time, the heat resistance of the produced separator is poor, and further, the phenomenon of localized sizes being too short is likely to occur, resulting in a relatively high probability of short-circuiting between the positive and negative electrodes, which will affect the reliability of secondary batteries.

[0097] If the separator's transverse (TD) bending resistance (T0) is greater than 8.0 mN×cm and / or its longitudinal (MD) bending resistance (M0) is greater than 7.0 mN×cm, the separator's bending resistance is too high, resulting in reduced flexibility and difficulty in folding and compressing, which in turn reduces the production yield of secondary batteries. Furthermore, during the winding and compression processes, the first base film and / or second base film are prone to deformed or separate from the adhesive layer, thereby increasing safety risks. Furthermore, if the separator's bending resistance is too high, its thickness generally increases, which increases the degree to which the separator filaments thermally shrink when heated. Ultimately, this increases the separator's thermal shrinkage rate, which increases the likelihood of short-circuiting between the positive and negative electrodes and reduces the reliability of secondary batteries.

[0098] Optionally, in some embodiments, the separator has a transverse (TD) bending resistance, T0, of 1.5-7.0 mN×cm, 1.7-7.0 mN×cm, 1.9-7.0 mN×cm, 2.0-7.0 mN×cm, 1.5-6.0 mN×cm, 1.7-6.0 mN×cm, 1.9-6.0 mN×cm, 2.0-6.0 mN×cm, 1.5-5.0 mN×cm m, 1.7-5.0mN×cm, 1.9-5.0mN×cm, 2.0-5.0mN×cm, 1.5-4.7mN×cm, 1.7-4.7mN×cm, 1.9-4.7mN×cm, 2.0-4.7mN×cm, 1.5-4.5mN×cm, 1.7-4.5mN×cm, 1.9-4.5mN×cm, 2.0-4.5mN×cm.

[0099] Optionally, in some embodiments, the bending resistance M0 of the separator in the machine direction (MD) is 1.2-6.0 mN×cm, 1.5-6.0 mN×cm, 1.6-6.0 mN×cm, 1.7-6.0 mN×cm, 1.8-6.0 mN×cm, 1.9-6.0 mN×cm, 1.2-5.0 mN×cm, 1.5-5.0 mN×cm, 1.6-5.0 mN×cm, 1.7-5.0 mN×cm, 1.8-5.0 mN×cm, 1.9-5.0 mN×cm, 1.2-4.0 mN×cm, 1.5-4.0 mN×cm m, 1.6-4.0mN×cm, 1.7-4.0mN×cm, 1.8-4.0mN×cm, 1.9-4.0mN×cm, 1.2-3.5mN×cm, 1.5-3.5mN×cm, 1.6-3.5mN×cm, 1.7-3.5mN×cm, 1.8-3.5mN×cm, 1.9-3.5mN×cm, 1.2-3.3mN×cm, 1.5-3.3mN×cm, 1.6-3.3mN×cm, 1.7-3.3mN×cm, 1.8-3.3mN×cm, 1.9-3.3mN×cm.

[0100] This further improves the heat resistance of the separator, improves the reliability of the secondary battery, and also improves the production yield of the secondary battery.

[0101] In some embodiments, the ratio T / M of the separator's bending resistance in the transverse (TD) direction T to the separator's bending resistance in the machine (MD) direction M may be 1.0-2.5, and optionally 1.1-2.0, 1.15-2.0, 1.2-2.0, 1.25-2.0, 1.1-1.8, 1.15-1.8, 1.2-1.8, 1.25-1.8, 1.1-1.75, 1.15-1.75, 1.2-1.75, 1.25-1.75, 1.1-1.7, 1.15-1.7, 1.2-1.7, or 1.25-1.7. This can further improve the heat resistance of the separator, thereby improving the reliability of secondary batteries and further increasing the production yield of secondary batteries.

[0102] In some embodiments, the bending resistance of the first base film in the transverse (TD) direction is designated as T1, and T1 may be 0.25-4.5 mN×cm, such as 0.25 mN×cm, 0.5 mN×cm, 0.8 mN×cm, 0.9 mN×cm, 1.0 mN×cm, 1.2 mN×cm, 1.5 mN×cm, 1.7 mN×cm, 2.0 mN×cm, 2.2 mN×cm, 2.5 mN×cm, 3.0 mN×cm, 3.5 mN×cm, 4.0 mN×cm, 4.5 mN×cm, or a range consisting of any two of the foregoing values. Optionally, in some embodiments, the bending resistance T1 in the transverse (TD) direction of the first base film may be 0.5-4 mN×cm, 0.5-3.5 mN×cm, 0.5-3.0 mN×cm, 0.5-2.5 mN×cm, 0.5-2.0 mN×cm, 0.8-4 mN×cm, 0.8-3.5 mN×cm, 0.8-3.0 mN×cm, 0.8-2.5 mN×cm, 0.8-2.0 mN×cm, 0.9-4 mN×cm, 0.9-3.5 mN×cm, 0.9-3.0 mN×cm, 0.9-2.5 mN×cm, or 0.9-2.0 mN×cm.

[0103] In some embodiments, the bending resistance of the first base film in the machine direction (MD) is designated as M1, and M1 may be 0.15-4.0 mN×cm, such as 0.15 mN×cm, 0.3 mN×cm, 0.5 mN×cm, 0.6 mN×cm, 0.75 mN×cm, 0.9 mN×cm, 1.0 mN×cm, 1.1 mN×cm, 1.3 mN×cm, 1.5 mN×cm, 1.8 mN×cm, 2.0 mN×cm, 2.5 mN×cm, 3.0 mN×cm, 3.5 mN×cm, 4.0 mN×cm, or a range consisting of any two of the above values. Optionally, in some embodiments, the bending resistance M1 in the machine direction (MD) of the first base film may be 0.5-3.5 mN×cm, 0.5-3.0 mN×cm, 0.5-2.5 mN×cm, 0.5-2.0 mN×cm, 0.5-1.8 mN×cm, 0.6-3.5 mN×cm, 0.6-3.0 mN×cm, 0.6-2.5 mN×cm, 0.6-2.0 mN×cm, 0.6-1.8 mN×cm, 0.75-3.5 mN×cm, 0.75-3.0 mN×cm, 0.75-2.5 mN×cm, 0.75-2.0 mN×cm, or 0.75-1.8 mN×cm.

[0104] In some embodiments, the ratio T1 / M1 of the bending resistance T1 in the transverse (TD) direction to the bending resistance M1 in the machine (MD) direction of the first base film may be 1.0-3.0, and optionally 1.1-2.0, 1.15-2.0, 1.2-2.0, 1.25-2.0, 1.1-1.8, 1.15-1.8, 1.2-1.8, 1.25-1.8, 1.1-1.75, 1.15-1.75, 1.2-1.75, 1.25-1.75, 1.1-1.7, 1.15-1.7, 1.2-1.7, or 1.25-1.7.

[0105] By adjusting the bending resistance T1 in the transverse (TD) direction, the bending resistance M1 in the longitudinal (MD) direction, and the ratio T1 / M1 of the two of the first base film within the above ranges, the heat resistance of the separator can be further improved, the reliability of the secondary battery can be improved, and the production yield of the secondary battery can be further improved.

[0106] In some embodiments, the bending resistance of the second base film in the transverse (TD) direction is designated T2, and T2 may be 0.3-5.0 mN×cm, such as 0.3 mN×cm, 0.5 mN×cm, 0.8 mN×cm, 0.9 mN×cm, 1.1 mN×cm, 1.3 mN×cm, 1.5 mN×cm, 1.8 mN×cm, 2.0 mN×cm, 2.3 mN×cm, 2.5 mN×cm, 2.8 mN×cm, 3.0 mN×cm, 3.5 mN×cm, 4.0 mN×cm, 4.5 mN×cm, 5.0 mN×cm, or a range consisting of any two of the foregoing values. Optionally, in some embodiments, the bending resistance T2 of the second base film in the transverse (TD) direction may be 0.5-4 mN×cm, 0.5-3.5 mN×cm, 0.5-3.0 mN×cm, 0.5-2.5 mN×cm, 0.8-4 mN×cm, 0.8-3.5 mN×cm, 0.8-3.0 mN×cm, 0.8-2.5 mN×cm, 0.9-4 mN×cm, 0.9-3.5 mN×cm, 0.9-3.0 mN×cm, or 0.9-2.5 mN×cm.

[0107] In some embodiments, the bending resistance of the second base film in the machine direction (MD) is referred to as M2, and M2 may be 0.2-4.5 mN×cm, such as 0.2 mN×cm, 0.3 mN×cm, 0.5 mN×cm, 0.6 mN×cm, 0.8 mN×cm, 0.9 mN×cm, 1.0 mN×cm, 1.1 mN×cm, 1.2 mN×cm, 1.5 mN×cm, 1.7 mN×cm, 2.1 mN×cm, 2.5 mN×cm, 3.0 mN×cm, 3.5 mN×cm, 4.0 mN×cm, 4.5 mN×cm, or a range consisting of any two of the foregoing values. Optionally, in some embodiments, the bending resistance M2 of the second base film in the machine direction (MD) may be 0.5-4.0 mN×cm, 0.5-3.5 mN×cm, 0.5-3.0 mN×cm, 0.5-2.5 mN×cm, 0.5-2.1 mN×cm, 0.6-4.0 mN×cm, 0.6-3.5 mN×cm, 0.6-3.0 mN×cm, 0.6-2.5 mN×cm, 0.6-2.1 mN×cm, 0.8-4.0 mN×cm, 0.8-3.5 mN×cm, 0.8-3.0 mN×cm, 0.8-2.5 mN×cm, or 0.8-2.1 mN×cm.

[0108] In some embodiments, the ratio of the bending resistance in the transverse (TD) direction to the bending resistance in the machine (MD) direction, T2 / M2, of the second base film is 1.0-3.5, optionally 1.1-2.5, 1.15-2.5, 1.2-2.5, 1.22-2.5, 1.1-2.2, 1.15-2.2, 1.2-2.2, 1.22-2.2, 1.1-1.9, 1.15-1.9, 1.2-1.9, 1.22-1.9, 1.1-1.7, 1.15-1.7, 1.2-1.7, or 1.22-1.7.

[0109] By adjusting the bending resistance T2 in the transverse (TD) direction, the bending resistance M2 in the longitudinal (MD) direction, and the ratio T2 / M2 of the two of the second base film within the above ranges, the heat resistance of the separator can be further improved, the reliability of the secondary battery can be improved, and the production yield of the secondary battery can be further improved.

[0110] The bending resistance in the transverse (TD) direction and machine direction (MD) direction of the separator, first base film, and second base film, respectively, has a meaning known in the art and can be measured using known instruments and methods. For example, referring to GB / T 18318-2009 and ZB WO 4003-87, the test can be performed using the inclined plane method. A fully automatic bending resistance tester (e.g., a Dreck DRK309 automatic textile bending resistance tester) can be used as the test equipment. During testing, multiple samples (e.g., 12 samples) can be punched out of the separator using a press. The sample size can be 25 mm x 250 mm, with the long sides of half the samples parallel to the transverse (TD) direction of the separator and the long sides of the other half parallel to the machine direction (MD) of the separator. The angle of the inclined plane can be 41.5°, and the sample propulsion speed can be 4 mm / s.

[0111] The bending resistance of the separator in the transverse (TD) direction can be obtained by adjusting one or more of the parameters such as the bending resistance of the first base film in the transverse (TD) direction, the bending resistance of the second base film in the transverse (TD) direction, and the composition and thickness of the adhesive layer.

[0112] The bending resistance in the machine direction (MD) of the separator can be obtained by adjusting one or more of the parameters such as the bending resistance in the machine direction (MD) of the first base film, the bending resistance in the machine direction (MD) of the second base film, and the composition and thickness of the adhesive layer.

[0113] The bending resistance in the transverse (TD) direction and the longitudinal (MD) direction of the first base film can be obtained by adjusting the parameters of the first base film (e.g., one or more of the composition, degree of orientation, average filament diameter, crystallinity, average pore size, thickness, melting point, porosity, air permeability, density, etc.) and / or the manufacturing process parameters of the first base film (e.g., one or more of the stretching parameters, heat setting parameters, etc.).

[0114] The bending resistance in the transverse (TD) direction and the longitudinal (MD) direction of the second base film can be obtained by adjusting the parameters of the second base film (e.g., one or more of the composition, degree of orientation, average filament diameter, crystallinity, average pore size, thickness, melting point, porosity, air permeability, density, etc.) and / or the manufacturing process parameters of the second base film (e.g., one or more of the stretching parameters, heat setting parameters, etc.).

[0115] In some embodiments, the first base film may have an average filament diameter of 80-300 nm, such as 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 160 nm, 180 nm, 200 nm, 220 nm, 240 nm, 260 nm, 280 nm, 300 nm, or a range consisting of any two of the foregoing values. Optionally, in some embodiments, the first base film may have an average filament diameter of 80-280 nm, 100-280 nm, 110-280 nm, 130-280 nm, 80-260 nm, 100-260 nm, 110-260 nm, 130-260 nm, 80-240 nm, 100-240 nm, 110-240 nm, or 130-240 nm.

[0116] In some embodiments, the average filament diameter of the second base film can be 100-300 nm, such as 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 180 nm, 200 nm, 220 nm, 240 nm, 260 nm, 280 nm, 300 nm, or a range consisting of any two of the foregoing values. Optionally, in some embodiments, the average filament diameter of the second base film can be 120-280 nm, 140-280 nm, 100-260 nm, 120-260 nm, 140-260 nm, 100-240 nm, 120-240 nm, or 140-240 nm.

[0117] By adjusting the average filament diameter of the first base film and / or the average filament diameter of the second base film within the above range, the bending resistance of the first base film, the second base film, and the separator can be adjusted, and the separator can be provided with good heat resistance and high ionic conductivity, thereby not only improving the reliability of the secondary battery but also improving the electrochemical performance of the secondary battery, such as cycle performance and kinetic performance.

[0118] The average filament diameter of a base film (e.g., a first base film, a second base film) has a meaning known in the art and can be measured using known instruments and methods. For example, a scanning electron microscope (e.g., a ZEISS Sigma 300) is used to obtain a scanning electron microscope (SEM) photograph of the base film in accordance with JY / T010-1996. Specifically, a test sample of length x width = 5 mm x 5 mm is randomly selected from the base film, and multiple test areas (e.g., 5) are randomly selected from the test sample and clearly observed at a certain magnification (e.g., 10K times), and multiple positions (e.g., at least 30 positions) are selected on a scale to measure the average of the multiple filament diameters, which is the average filament diameter of the base film.

[0119] In some embodiments, the ratio of the crystallinity of the second base film to the crystallinity of the first base film can be greater than 1, such as 1.03, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, or a range consisting of any two of the foregoing values. Optionally, in some embodiments, the ratio of the crystallinity of the second base film to the crystallinity of the first base film can be 1.03-1.5, 1.05-1.5, 1.1-1.5, 1.15-1.5, 1.03-1.4, 1.05-1.4, 1.1-1.4, 1.15-1.4, 1.03-1.3, 1.05-1.3, 1.1-1.3, 1.15-1.3, 1.03-1.25, 1.05-1.25, 1.1-1.25, or 1.15-1.25.

[0120] The first base film of the separator faces the negative electrode, and the second base film faces the positive electrode. By adjusting the ratio of the crystallinity of the second base film to the crystallinity of the first base film to be greater than 1, the bending resistance of the first base film, the second base film, and the separator can be adjusted, which is also advantageous for producing a wound electrode assembly.

[0121] In some embodiments, the crystallinity of the first base film may be 33%-70%, 35%-65%, 35%-60%, 35%-55%, 35%-50%, 35%-45%.

[0122] In some embodiments, the crystallinity of the second base film may be 35%-80%, optionally 35%-75%, 35%-65%, 35%-55%, 35%-50%, 40%-75%, 40%-65%, 40%-55%.

[0123] By adjusting the crystallinity of the first base film and / or the crystallinity of the second base film within the above range, the bending resistance of the first base film, the second base film and the separator can be adjusted, and the separator can be given good mechanical strength and elasticity, which is not only advantageous for improving the high temperature resistance and reliability of the secondary battery, but also advantageous for the production of wound electrode assemblies.

[0124] The crystallinity of the first base film and the second base film has a meaning known in the art and can be measured using known instruments and methods. For example, it can be measured using differential scanning calorimetry. For details, see GB / T 19466.3-2004. For example, it can be measured as follows: a 4-6 mg sample is placed in the sample chamber of a differential scanning calorimeter, and the temperature is increased from 25°C to 350°C at a heating rate of 10°C / min. The melting endothermic curve of the sample is obtained, and the peak area of ​​the curve and the reference value for a 100% crystalline sample are calculated to obtain the crystallinity of the sample.

[0125] In some embodiments, the ratio of the thickness of the second base film to the thickness of the first base film can be greater than 1, such as 1.01, 1.02, 1.05, 1.1, 1.2, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, or a range consisting of any two of the foregoing values. Alternatively, in some embodiments, the ratio of the thickness of the second base film to the thickness of the first base film can be 1.02-5.0, 1.02-4.0, 1.02-3.0, 1.02-2.5, 1.02-2.0, 1.1-5.0, 1.1-4.0, 1.1-3.0, 1.1-2.5, 1.1-2.0, 1.2-5.0, 1.2-4.0, 1.2-3.0, or 1.2-2.5.

[0126] The first base film of the separator faces the negative electrode, and the second base film faces the positive electrode. By adjusting the ratio of the thickness of the second base film to the thickness of the first base film to be greater than 1, the bending resistance of the first base film, the second base film, and the separator can be adjusted. In addition, if the thickness of the first base film is relatively small and the stretching ratio during production is generally relatively large, the degree of orientation of the first base film is relatively high and the physical strength (e.g., puncture strength) is relatively high. Furthermore, if it faces the negative electrode, dendrite growth can be better alleviated and the reliability of the secondary battery can be improved.

[0127] In some embodiments, the thickness of the first base film can be 12 μm or less, such as 1.5 μm, 2 μm, 2.5 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, or a range consisting of any two of the foregoing values. Alternatively, in some embodiments, the thickness of the first base film can be 1.8-12 μm, 1.8-10 μm, 1.8-8 μm, 1.8-7 μm, 1.8-6 μm, 1.8-5 μm, 2-10 μm, 2-8 μm, 2-7 μm, 2-6 μm, 2-5 μm, 2.5-10 μm, 2.5-8 μm, 2.5-7 μm, 2.5-6 μm, or 2.5-5 μm.

[0128] In some embodiments, the thickness of the second base film can be 14 μm or less, 2 μm, 2.5 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, or a range consisting of any two of the foregoing values. Alternatively, in some embodiments, the thickness of the second base film can be 2-14 μm, 2-12 μm, 2-10 μm, 2-8 μm, 2-7 μm, 2-6 μm, 3-14 μm, 3-12 μm, 3-10 μm, 3-8 μm, 3-7 μm, or 3-6 μm.

[0129] By adjusting the thickness of the first base film and / or the second base film within the above range, the bending resistance of the first base film, the second base film, and the separator can be adjusted, which is also advantageous for the secondary battery to have a high energy density.

[0130] The thickness of the first base film and the second base film has a meaning known in the art and can be measured using known instruments and methods. For example, six sets of parallel samples are taken, and the thickness of each set of samples is measured at different positions using a multimeter thickness meter, and each set of samples is measured at at least 20 positions, and the average thickness of the six sets of samples is taken as the thickness of the sample.

[0131] In some embodiments, the ratio of the melting point of the first base film to the melting point of the second base film may be less than 1, such as 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.82, 0.85, 0.9, 0.92, 0.95, or a range consisting of any two of the foregoing values. Optionally, in some embodiments, the ratio of the melting point of the first base film to the melting point of the second base film can be 0.2-0.95, 0.25-0.95, 0.3-0.95, 0.35-0.95, 0.4-0.95, 0.2-0.92, 0.25-0.92, 0.3-0.92, 0.35-0.92, 0.4-0.92, 0.2-0.90, 0.25-0.90, 0.3-0.90, 0.35-0.90, 0.4-0.90, 0.2-0.85, 0.25-0.85, 0.3-0.85, 0.35-0.85, or 0.4-0.85.

[0132] The first base film of the separator faces the negative electrode, and the second base film faces the positive electrode. By adjusting the ratio of the melting point of the first base film to the melting point of the second base film to be less than 1, the bending resistance of the first base film, the second base film, and the separator can be adjusted. Furthermore, since the melting point of the first base film is relatively low and its physical strength (e.g., puncture strength) is relatively high, when it faces the negative electrode, it can better mitigate dendrite growth and improve the reliability of the secondary battery.

[0133] In some embodiments, the melting point of the first base film may be 110°C or greater, such as 110°C, 115°C, 120°C, 130°C, 135°C, 140°C, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, 180°C, or a range consisting of any two of the foregoing values. Optionally, in some embodiments, the melting point of the first base film may be 120°C-180°C, 120°C-170°C, 120°C-165°C, 120°C-160°C, 120°C-155°C, 120°C-150°C, 125°C-180°C, 125°C-170°C, 125°C-165°C, 125°C-160°C, 125°C-155°C, 125°C-150°C, 135°C-180°C, 135°C-170°C, 135°C-165°C, 135°C-160°C, 135°C-155°C, or 135°C-150°C.

[0134] In some embodiments, the melting point of the second base film may be 150° C. or higher, such as 150° C., 160° C., 165° C., 170° C., 180° C., 190° C., 200° C., 220° C., 240° C., 260° C., 280° C., 300° C., 320° C., 330° C., 350° C., or a range consisting of any two of the foregoing values. Optionally, in some embodiments, the melting point of the second base film may be 165° C.-330° C., 165° C.-320° C., 165° C.-300° C., 165° C.-280° C., 170° C.-330° C., 170° C.-320° C., 170° C.-300° C., 170° C.-280° C., 180° C.-330° C., 180° C.-320° C., 180° C.-300° C., or 180° C.-280° C.

[0135] By adjusting the melting point of the first base film and / or the melting point of the second base film within the above range, the bending resistance of the first base film, the second base film, and the separator can be adjusted, and the separator can be given good pore-closing properties, which is advantageous for improving the reliability of the secondary battery.

[0136] The melting points of the first and second base films have meanings known in the art and can be measured using known instruments and methods. For example, they can be measured using differential scanning calorimetry. For details, see GB / T 19466.3-2004. For example, they can be measured as follows: a 4-6 mg sample is placed in the sample chamber of a differential scanning calorimeter, and the temperature is increased from 25°C to 400°C at a heating rate of 10°C / min. A melting endothermic curve of the sample is obtained, and the temperature corresponding to the peak of the curve is the melting point of the sample.

[0137] In some embodiments, the ratio of the average pore size of the second base film to the average pore size of the first base film can be greater than 1, such as 1.05, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.8, 2.0, 2.2, 2.5, 2.8, or a range consisting of any two of the foregoing values. Alternatively, in some embodiments, the ratio of the average pore size of the second base film to the average pore size of the first base film can be 1.05-2.5, 1.05-2.2, 1.05-2, 1.05-1.8, 1.05-1.5, 1.1-2.5, 1.1-2.2, 1.1-2, 1.1-1.8, 1.1-1.5, 1.2-2.5, 1.2-2.2, 1.2-2, or 1.2-1.8.

[0138] The first base film of the separator faces the negative electrode, and the second base film faces the positive electrode. By adjusting the ratio of the average pore size of the second base film to the average pore size of the first base film so that it is greater than 1, the bending resistance of the first base film, the second base film, and the separator can be adjusted. In addition, the first base film with a relatively small average pore size faces the negative electrode, which can better mitigate dendrite growth and further more uniformize the ion flow from the positive electrode, thereby reducing problems such as rapid dendrite growth and excessively sharp dendrite morphology caused by excessively high ion concentration at local locations on the negative electrode, and also contributing to improving the cycle performance and dynamic performance of the secondary battery.

[0139] In some embodiments, the average pore size of the first base film can be 48-1800 nm, such as 48 nm, 55 nm, 60 nm, 80 nm, 90 nm, 100 nm, 150 nm, 180 nm, 200 nm, 220 nm, 250 nm, 300 nm, 350 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, 1200 nm, 1400 nm, 1600 nm, 1800 nm, or a range consisting of any two of the foregoing values. Optionally, in some embodiments, the average pore size of the first base film can be 50-1400 nm, 60-1400 nm, 70-1400 nm, 80-1400 nm, 50-1000 nm, 60-1000 nm, 70-1000 nm, 80-1000 nm, 50-600 nm, 60-600 nm, 70-600 nm, 80-600 nm, 50-300 nm, 60-300 nm, 70-300 nm, 80-300 nm, 50-200 nm, 60-200 nm, 70-200 nm, or 80-200 nm.

[0140] In some embodiments, the average pore size of the second base film can be 50-2000 nm, such as 50 nm, 60 nm, 80 nm, 90 nm, 100 nm, 150 nm, 180 nm, 200 nm, 220 nm, 250 nm, 300 nm, 350 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, 1200 nm, 1400 nm, 1600 nm, 1800 nm, 2000 nm, or a range consisting of any two of the foregoing values. Optionally, in some embodiments, the average pore size of the second base film may be 60-1600 nm, 80-1600 nm, 100-1600 nm, 120-1600 nm, 60-1200 nm, 80-1200 nm, 100-1200 nm, 120-1200 nm, 60-800 nm, 80-800 nm, 100-800 nm, 120-800 nm, 60-400 nm, 80-400 nm, 100-400 nm, 120-400 nm, 60-300 nm, 80-300 nm, 100-300 nm, or 120-300 nm.

[0141] By adjusting the average pore size of the first base film and / or the average pore size of the second base film within the above range, the bending resistance of the first base film, the second base film, and the separator can be adjusted, and the first base film and the second base film can be made to better exert the effect of mitigating dendrite growth, improving the reliability of the secondary battery, and also imparting good ionic conductivity to the separator, thereby further contributing to improvements in the cycle performance, dynamic performance, etc. of the secondary battery.

[0142] The average pore size of the first base film and the second base film has a meaning known in the art and can be measured using known instruments and methods, for example, by testing using a mercury porosimeter in accordance with GB / T 21650.1-2008.

[0143] In some embodiments, the ratio of the porosity of the second base film to the porosity of the first base film may be greater than 1, such as 1.01, 1.05, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, or a range consisting of any two of the foregoing values. Optionally, in some embodiments, the ratio of the porosity of the second base film to the porosity of the first base film may be 1.01-2.8, 1.05-2.8, 1.1-2.8, 1.2-2.8, 1.3-2.8, 1.01-2.4, 1.05-2.4, 1.1-2.4, 1.2-2.4, 1.3-2.4, 1.01-2.0, 1.05-2.0, 1.1-2.0, 1.2-2.0, or 1.3-2.0.

[0144] The first base film of the separator faces the negative electrode, and the second base film faces the positive electrode. By adjusting the ratio of the porosity of the second base film to the porosity of the first base film so that it is greater than 1, the bending resistance of the first base film, the second base film, and the separator can be adjusted. In addition, the first base film, which has a relatively small porosity, faces the negative electrode, which can better mitigate dendrite growth and improve the reliability of the secondary battery.

[0145] In some embodiments, the porosity of the first base film is 28%-70%, such as 28%, 30%, 32%, 35%, 38%, 40%, 42%, 45%, 48%, 50%, 52%, 55%, 58%, 60%, 65%, 70%, or a range consisting of any two of the foregoing values. Optionally, in some embodiments, the porosity of the first base film may be 30%-70%, 30%-60%, 30%-55%, 30%-52%, 30%-50%, 32%-70%, 32%-60%, 32%-55%, 32%-52%, or 32%-50%.

[0146] In some embodiments, the porosity of the second base film can be 30%-80%, such as 30%, 33%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, or a range consisting of any two of the foregoing values. Optionally, in some embodiments, the porosity of the second base film can be 33%-80%, 33%-75%, 33%-70%, 33%-65%, 33%-60%, 33%-55%, 35%-80%, 35%-75%, 35%-70%, 35%-65%, 35%-60%, or 35%-55%.

[0147] By adjusting the porosity of the first base film and / or the porosity of the second base film within the above range, the bending resistance of the first base film, the second base film, and the separator can be adjusted, and the separator can be given good ionic conductivity, which further contributes to improving the cycle performance, dynamic performance, etc. of the secondary battery.

[0148] In some embodiments, the porosity of the separator may be 27%-65%, and optionally 33%-55%.

[0149] The porosity of the separator, the first base film, and the second base film has a meaning known in the art and can be measured using known instruments and methods, for example, by testing using a mercury porosimeter in accordance with GB / T 21650.1-2008.

[0150] In some embodiments, the ratio of the air permeability of the first base film to the air permeability of the second base film may be greater than 1, such as 1.05, 1.08, 1.1, 1.15, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.2, 2.4, 2.6, 2.8, 3.0, or a range consisting of any two of the foregoing values. Optionally, in some embodiments, the ratio of the air permeability of the first base film to the air permeability of the second base film may be 1.05-3.0, 1.05-2.6, 1.05-2.4, 1.05-2.2, 1.05-2.0, 1.08-3.0, 1.08-2.6, 1.08-2.4, 1.08-2.2, 1.08-2.0, 1.1-3.0, 1.1-2.6, 1.1-2.4, 1.1-2.2, 1.1-2.0, 1.2-3.0, 1.2-2.6, 1.2-2.4, 1.2-2.2, or 1.2-2.0.

[0151] The first base film of the separator faces the negative electrode, and the second base film faces the positive electrode. By adjusting the ratio of the air permeability of the first base film to the air permeability of the second base film to be greater than 1, the bending resistance of the first base film, the second base film, and the separator can be adjusted. In addition, the first base film, which has a relatively high air permeability, faces the negative electrode, which can better mitigate dendrite growth and improve the reliability of the secondary battery.

[0152] In some embodiments, the air permeability of the first base film may be 300 s / 100 cc or less, such as 110 s / 100 cc, 120 s / 100 cc, 140 s / 100 cc, 160 s / 100 cc, 180 s / 100 cc, 200 s / 100 cc, 220 s / 100 cc, 240 s / 100 cc, 260 s / 100 cc, 280 s / 100 cc, 300 s / 100 cc, or a range consisting of any two of the foregoing values. Optionally, in some embodiments, the air permeability of the first base film may be 110-300s / 100cc, 110-280s / 100cc, 110-260s / 100cc, 110-240s / 100cc, 120-300s / 100cc, 120-280s / 100cc, 120-260s / 100cc, or 120-240s / 100cc.

[0153] In some embodiments, the air permeability of the second base film may be 250 s / 100 cc or less, such as 100 s / 100 cc, 110 s / 100 cc, 120 s / 100 cc, 140 s / 100 cc, 160 s / 100 cc, 180 s / 100 cc, 200 s / 100 cc, 220 s / 100 cc, 230 s / 100 cc, 250 s / 100 cc, or a range consisting of any two of the foregoing values. Optionally, in some embodiments, the air permeability of the second base film may be 100-250s / 100cc, 100-230s / 100cc, 100-220s / 100cc, 100-200s / 100cc, 110-230s / 100cc, 110-220s / 100cc, or 110-200s / 100cc.

[0154] By adjusting the air permeability of the first base film and / or the air permeability of the second base film within the above range, the bending resistance of the first base film, the second base film, and the separator can be adjusted, and the separator can also be given good ionic conductivity, which also contributes to improving the cycle performance, dynamic performance, etc. of the secondary battery.

[0155] The air permeability of the separator, the first base film, and the second base film has a meaning known in the art and can be measured using known instruments and methods. For example, they may be tested in accordance with GB / T 36363-2018. The test gas may be 100 cc of air.

[0156] The term "air permeability" refers to the test result of the air permeability of the base film, and the higher the air permeability of the base film, the worse the air permeability.

[0157] In some embodiments, the first base film and the second base film may each independently comprise one or more of polyolefins and their derivatives, halogenated polyolefins and their derivatives, polyethers and their derivatives, polyetheretherketones and their derivatives, polyesters and their derivatives, polyimides (PIs) and their derivatives, and polyvinyl alcohols and their derivatives.

[0158] Alternatively, the polyolefin and its derivatives may include one or more of polyethylene (PE) and its derivatives, and polypropylene (PP) and its derivatives.

[0159] Optionally, the halogenated polyolefin and its derivatives may include one or more of polytetrafluoroethylene (PTFE) and its derivatives, polyvinyl fluoride and its derivatives, and polyvinylidene fluoride and its derivatives.

[0160] Alternatively, the polyester and its derivatives may include one or more of polyethylene terephthalate (PET) and its derivatives, polybutylene terephthalate (PBT) and its derivatives.

[0161] A derivative generally refers to a product derived from a polymer by replacing a hydrogen atom or atomic group with another atom or atomic group.

[0162] In some embodiments, the adhesive layer includes an adhesive that ensures adhesive strength and uniformity between the first base film and the second base film, and also provides the separator with good heat resistance, thereby contributing to improved reliability of the secondary battery.

[0163] In some examples, the adhesive may include one or more of polyacrylate, polyacrylic acid, polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride-trichloroethylene copolymer, polyvinylpyrrolidone, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyethylene oxide, polyarylate, carboxymethyl cellulose, hydroxypropyl cellulose, regenerated cellulose, cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate, polyacrylonitrile, polyvinyl alcohol, polyethylene, polypropylene, starch, and cyanoethyl amylopectin.

[0164] In some embodiments, the adhesive layer may include an adhesive and a filler. The filler can further improve the heat resistance and physical properties (e.g., puncture strength) of the separator, thereby contributing to improved reliability of the secondary battery. In addition, by interposing the filler between the first base film and the second base film, problems such as powder shedding can be reduced.

[0165] By way of example, in some embodiments, the filler may include at least one of inorganic particles, organic particles, and organic-metallic framework materials.

[0166] Optionally, the inorganic particles may include one or more of inorganic particles having a dielectric constant of 5 or greater, inorganic particles that are ionically conductive but do not store ions, and inorganic particles that are capable of generating an electrochemical reaction.

[0167] Alternatively, the inorganic particles having a dielectric constant of 5 or more may be boehmite, aluminum oxide, zinc oxide, silicon oxide, titanium oxide, zirconium oxide, barium oxide, calcium oxide, magnesium oxide, nickel oxide, tin oxide, cerium oxide, yttrium oxide, hafnium oxide, aluminum hydroxide, magnesium hydroxide, silicon carbide, boron carbide, aluminum nitride, silicon nitride, boron nitride, magnesium fluoride, calcium fluoride, barium fluoride, barium sulfate, magnesium aluminum silicate, magnesium lithium silicate, magnesium sodium silicate, bentonite, hectorite, zirconium titanate, barium titanate, Pb(Zr,Ti)O3 (abbreviated as PZT), Pb 1-m La m Zr 1-n Ti n O3 (abbreviated as PLZT, 0 <m<1、0<n<1)、Pb(Mg3Nb 2 / 3 The adhesive includes at least one of )O3-PbTiO3 (abbreviated as PMN-PT) and modified inorganic particles. Optionally, the inorganic particles may be modified chemically and / or physically. The chemical modification may include coupling agent modification (e.g., using a silane coupling agent, a titanate coupling agent, etc.), surfactant modification, polymer graft modification, etc. The physical modification may include mechanical dispersion, ultrasonic dispersion, high-energy treatment, etc. The modification treatment can reduce the aggregation of the inorganic particles, thereby resulting in a more stable and uniform structure of the adhesive layer. Furthermore, by selecting a coupling agent, surfactant, or polymer with a specific functional group to modify the inorganic particles, the adhesive layer's wetting and retention properties with respect to the electrolyte can be improved, contributing to improved adhesion of the adhesive layer to the first and second base films.

[0168] Optionally, the inorganic particles that are ionically conductive but do not store ions include Li3PO4, lithium titanium phosphate, Li x1 Ti y1 (PO4)3, Lithium titanium aluminum phosphate Li x2 Al y2 Ti z1(PO4)3, (LiAlTiP) x3 O y3 type glass, lithium lanthanum titanate Li x4 La y4 TiO3, lithium germanium thiophosphate Li x5 Ge y5 P z2 S w , lithium nitride Li x6 N y6 , SiS2 type glass Li x7 Si y7 S z3 and P2S5 type glass Li x8 P y8 S z4 may include at least one of them, where 0 < x1 < 2, 0 < y1 < 3, 0 < x2 < 2, 0 < y2 < 1, 0 < z1 < 3, 0 < x3 < 4, 0 < y3 < 13, 0 < x4 < 2, 0 < y4 < 3, 0 < x5 < 4, 0 < y5 < 1, 0 < z2 < 1, 0 < w < 5, 0 < x6 < 4, 0 < y6 < 2, 0 < x7 < 3, 0 < y7 < 2, 0 < z3 < 4, 0 < x8 < 3, 0 < y8 < 3, 0 < z4 < 7. Thereby, the ionic conductivity of the separator can be further improved.

[0169] Optionally, the inorganic particles capable of electrochemical reaction may include at least one of lithium-containing transition metal oxides, lithium-containing phosphates, carbon-based materials, silicone-based materials, tin-based materials, and lithium titanium compounds.

[0170] Optionally, the organic particles may comprise one or more of polycarbonate, polythiophene, polypyridine, polystyrene, polyacrylic wax, polyethylene, polypropylene, cellulose, cellulose modifiers (e.g., carboxymethyl cellulose), melamine resin, phenolic resin, polyester (e.g., polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate), silicone resin, polyimide, polyamideimide, polyaramid, polyphenylene sulfide, polysulfone, polyethersulfone, polyetheretherketone, polyaryletherketone, copolymer of butyl acrylate and ethyl methacrylate (crosslinked polymer of butyl acrylate and ethyl methacrylate).

[0171] Optionally, the organic-metal framework material may include one or more of a nitrogen-containing heterocyclic ligand-based structure, an organic carboxylic acid-based ligand-based structure, and a nitrogen-containing oxygen gas mixture-based ligand-based structure.

[0172] In some embodiments, the adhesive content may be 10% or more, and optionally 10%-30%, based on the total weight of the adhesive layer.

[0173] In some embodiments, the filler content may be up to 90% based on the total weight of the adhesive layer, optionally 40%-90%, 60%-80%.

[0174] In some embodiments, the adhesive layer may further include a dispersant, such as carboxymethyl cellulose, which can adjust the viscosity of the adhesive layer slurry and improve the quality and uniformity of the adhesive layer.

[0175] In some embodiments, the dispersant content may be 25% or less, and optionally 20% or less, based on the total weight of the adhesive layer.

[0176] In some embodiments, the thickness of the adhesive layer may be 0.3 μm or more, and optionally 0.5-4 μm. When the thickness of the adhesive layer is within this range, the separator can have an appropriate thickness, and the separator can have good heat resistance and physical strength, thereby improving the reliability of the secondary battery.

[0177] The test method for the thickness of the adhesive layer can be referred to the test method for the thickness of the first base film and the second base film.

[0178] In some embodiments, the areal density of the adhesive layer is 1.0-6.0 g / m 2 and optionally 1.2-5.0 g / m 2 is.

[0179] In some embodiments, the adhesive strength between the adhesive layer and the first base film may be 3 N / m or more, optionally 4-15 N / m.

[0180] In some embodiments, the adhesive strength between the adhesive layer and the second base film may be 3 N / m or more, optionally 4-15 N / m.

[0181] This makes it possible to prevent separation of the adhesive layer from the first base film and the second base film, thereby contributing to improved reliability of the secondary battery.

[0182] In some embodiments, the volume distribution particle size Dv50 of the filler may be less than or equal to 1.5 μm, optionally 0.1-1.4 μm, 0.15-1.0 μm, 0.2-0.8 nm, or 0.3-0.7 nm.

[0183] In some embodiments, the separator has a transverse (TD) tensile strength of 700 kg / cm 2 or more, and optionally 1000 kg / cm 2 That's all.

[0184] In some embodiments, the separator has a machine direction (MD) tensile strength of 1000 kg / cm 2 or more, and optionally 1200 kg / cm 2 That's all.

[0185] In some embodiments, the separator may have a transverse (TD) direction heat shrinkage of 5% or less, and optionally 2% or less, at 250° C. for 1 hour.

[0186] In some embodiments, the separator may have a machine-direction (MD) heat shrinkage of 5% or less, and optionally 2% or less, at 250° C. for 1 hour.

[0187] When at least one of the transverse tensile strength, longitudinal tensile strength, transverse thermal shrinkage rate, and longitudinal thermal shrinkage rate of the separator satisfies a given range, the separator can have good heat resistance and physical strength, thereby contributing to improving the reliability of the secondary battery.

[0188] The transverse tensile strength, longitudinal tensile strength, transverse heat shrinkage rate, and longitudinal heat shrinkage rate of the separator all have meanings known in the art and can be measured using known instruments and methods, for example, they can be tested in accordance with GB / T 36363-2018.

[0189] [Manufacturing method] The embodiments of the present application further provide methods of manufacturing separators according to the embodiments of the present application.

[0190] The method includes the steps of providing a first base film and a second base film, providing an adhesive layer slurry containing an adhesive, applying the adhesive layer slurry to the first base film and / or the second base film, and combining the first base film and the second base film to obtain a separator.

[0191] The first and second base films are combined using an adhesive layer slurry, which simplifies the process and improves the heat resistance and physical strength of the separator, thereby contributing to improved reliability of secondary batteries. The first and second base films are combined using an adhesive layer slurry, which also avoids process defects that occur during the process of directly hot-pressing the first and second base films together. In the process of directly hot-pressing the first and second base films together, the applied force is generally in the MPa range. If the applied temperature is too high, the porosity of the separator will decrease and its breathability will be poor. If the applied temperature is too low, the adhesion between the first and second base films will be weak. Therefore, it is necessary to select an appropriate hot-pressing temperature, which will require more stringent direct hot-pressing conditions.

[0192] In some embodiments, the adhesive layer slurry may further include a filler. Optionally, the filler may include at least one of inorganic particles, organic particles, and an organic-metallic framework material.

[0193] In some embodiments, the solids content of the adhesive layer slurry may be 35%-50%.

[0194] In some embodiments, the viscosity of the adhesive layer slurry may be 250-380 mpa.s.

[0195] In some embodiments, the application speed of the adhesive layer slurry may be greater than 50 m / min.

[0196] In some embodiments, the method of providing the first base film or the second base film may include commercial purchase.

[0197] In some examples, a method of providing a first base film may include providing a feedstock for forming the first base film, and melt-extruding, stretching, and heat-setting the feedstock to obtain the first base film.

[0198] In some embodiments, in the step of providing a first base film, the machine direction (MD) stretching ratio may be 8-12 times.

[0199] In some embodiments, in the step of providing a first base film, the transverse (TD) direction stretching ratio may be 2-6 times.

[0200] In some embodiments, in the step of providing a first base film, the heat setting temperature may be 100°C-160°C.

[0201] In some embodiments, in the step of providing a first base film, the heat setting time may be 20-60 seconds.

[0202] The bending resistance of the first base film can be adjusted by adjusting the manufacturing parameters of the first base film, such as the stretching parameters and heat setting parameters.

[0203] In some examples, a method for providing a second base film may include providing a feedstock for forming the second base film, and melt-extruding, stretching, and heat-setting the feedstock to obtain the second base film.

[0204] In some embodiments, in the step of providing a second base film, the machine direction (MD) stretching ratio may be 5-15 times.

[0205] In some embodiments, the step of providing the second base film may or may not involve stretching in the transverse (TD) direction. If stretching in the transverse (TD) direction is performed, the stretching ratio may be 1.5 to 6 times.

[0206] In some embodiments, in the step of providing a second base film, the heat setting temperature may be 80°C-130°C.

[0207] In some embodiments, in the step of providing a second base film, the heat setting time may be 30-60 seconds.

[0208] The bending resistance of the second base film can be adjusted by adjusting the production parameters of the second base film, such as the stretching parameters and heat setting parameters.

[0209] In some embodiments, the adhesive layer slurry may be applied by transfer coating, spin spray coating, dip coating, or the like, but the embodiments of the present application are not limited thereto.

[0210] Unless otherwise specified, each of the raw materials used in the method for producing the separator (for example, the first base film, the second base film, the adhesive, the filler, etc.) is commercially available.

[0211] secondary battery An embodiment of the present application further provides a secondary battery.

[0212] A secondary battery, also known as a rechargeable battery or storage battery, is a battery that can be continuously used by activating the active material through charging after discharging. Generally, a secondary battery includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode plate, a negative electrode plate, and a separator. The separator is disposed between the positive electrode plate and the negative electrode plate and mainly serves to prevent short circuits between the positive electrode and the negative electrode and allows active ions to pass through.

[0213] The present application does not particularly limit the type of secondary battery, and for example, the secondary battery may be a lithium ion battery, a sodium ion battery, a lithium metal battery, a sodium metal battery, a lithium air battery, a sodium air battery, a lithium sulfur battery, a sodium sulfur battery, or the like, and in particular, the secondary battery may be a lithium ion battery or a sodium ion battery.

[0214] A secondary battery according to an embodiment of the present application includes the separator of the present application or a separator manufactured by the method of the present application, and the separator can improve the production yield of secondary batteries and further improve the reliability of secondary batteries.

[0215] In some embodiments, the secondary battery includes a positive electrode plate and a negative electrode plate, a separator disposed between the positive electrode plate and the negative electrode plate, and a first base film of the separator facing (i.e., adjacent to) the negative electrode plate and a second base film of the separator facing (i.e., adjacent to) the positive electrode plate.

[0216] [Positive electrode plate] The composition and structure of the positive electrode plate can be selected depending on the type of secondary battery, and the examples of the present application do not limit this.

[0217] In some embodiments, the positive electrode plate may include a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector and including a positive electrode active material. For example, the positive electrode current collector has two surfaces facing each other in the thickness direction of the positive electrode current collector, and the positive electrode film layer is disposed on one or both of the two facing surfaces of the positive electrode current collector.

[0218] The type of positive electrode active material can be selected depending on the type of secondary battery, and the examples of the present application are not limited thereto.

[0219] For example, when the secondary battery is a lithium-ion battery, the positive electrode active material may include, but is not limited to, at least one of lithium transition metal oxides, lithium-containing phosphates, and their respective modified compounds. Examples of lithium transition metal oxides may include, but are not limited to, at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds. Examples of lithium-containing phosphates may include, but are not limited to, at least one of 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.

[0220] In some embodiments, in order to further improve the energy density of the secondary battery, the positive electrode active material used in the lithium-ion battery may include at least one of lithium transition metal oxides and their modified compounds having the general formula Li a Ni b Co c M d O e A f where 0.8 ≤ a ≤ 1.2, 0.5 ≤ b < 1, 0 < c < 1, 0 < d < 1, 1 ≤ e ≤ 2, 0 ≤ f ≤ 1, M includes at least one of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, and B, and A includes at least one of N, F, S, and Cl.

[0221] As an example, the positive electrode active material used in the lithium-ion battery is LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM523), LiNi 0.6Co 0.2 Mn 0.2 O2(NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.85 Co 0.15 Al 0.05 It may contain at least one of O2, LiFePO4, and LiMnPO4.

[0222] For example, when the secondary battery is a sodium ion battery, the positive electrode active material may include at least one of a sodium-containing transition metal oxide, a polyanion material (e.g., phosphate, fluorophosphate, pyrophosphate, sulfate, etc.), and a Prussian blue-based material, but is not limited thereto.

[0223] For example, the positive electrode active materials used in sodium ion batteries are NaFeO2, NaCoO2, NaCrO2, NaMnO2, NaNiO2, NaNi 1 / 2 Ti 1 / 2 O2, NaNi 1 / 2 Mn 1 / 2 O2, Na 2 / 3 Fe 1 / 3 Mn 2 / 3 O2, NaNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, NaFePO4, NaMnPO4, NaCoPO4, Prussian blue-based materials, general formula X p M' q (PO4) r O x Y 3-x The compound may comprise at least one of the materials represented by the general formula X p M' q (PO4) r O x Y 3-x In, 0 <p≦4、0<q≦2、1≦r≦3、0≦x≦2であり、Xは、H + , Li + , Na + , K. + and NH4 +wherein M' comprises a transition metal cation and optionally comprises at least one of V, Ti, Mn, Fe, Co, Ni, Cu, and Zn; and Y comprises a halogen anion and optionally comprises at least one of F, Cl, and Br.

[0224] The modifying compounds for the positive electrode active material are used to modify the positive electrode active material by doping and / or surface coating.

[0225] In some embodiments, the positive electrode film layer may further include a positive electrode conductive agent. The present application does not particularly limit the type of the positive electrode conductive agent, and examples of the positive electrode conductive agent include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0226] In some embodiments, the positive electrode membrane layer may further include a positive electrode adhesive. The present application is not particularly limited to the type of the positive electrode adhesive, and the positive electrode adhesive may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0227] In some embodiments, the positive electrode current collector may be a metal foil sheet or a composite current collector. An example of the metal foil sheet is aluminum foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. For example, the metal layer may include at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. For example, the polymer base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0228] The positive electrode film layer is typically obtained by coating a positive electrode slurry on a positive electrode current collector, drying, and cold pressing. The positive electrode slurry is typically formed by dispersing a positive electrode active material, an optional conductive agent, an optional adhesive, and any other optional components in a solvent and stirring the resulting mixture uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP).

[0229] [Negative electrode plate] The composition and structure of the negative electrode plate can be selected depending on the type of secondary battery, and the examples of the present application do not limit this.

[0230] In some embodiments, the negative electrode plate may include a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and including a negative electrode active material. For example, the negative electrode current collector has two surfaces facing each other in the thickness direction of the negative electrode current collector, and the negative electrode film layer is disposed on one or both of the two facing surfaces of the negative electrode current collector.

[0231] The negative electrode active material may be any negative electrode active material for secondary batteries known in the art. For example, the negative electrode active material may include, but is not limited to, at least one of natural graphite, artificial graphite, soft carbon, hard carbon, a silicone-based material, a tin-based material, and lithium titanate. The silicone-based material may include at least one of a silicone element, a silicone oxide, a silicone carbon composite, a silicone nitrogen composite, and a silicone alloy material. The tin-based material may include at least one of a tin element, a tin oxide, and a tin alloy material.

[0232] In some embodiments, the negative electrode film layer may further include a negative electrode conductive agent. The present application does not particularly limit the type of the negative electrode conductive agent, and the negative electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0233] In some embodiments, the negative electrode film layer may further optionally include a negative electrode adhesive. The present application is not particularly limited to the type of negative electrode adhesive, and the negative electrode adhesive may include, for example, at least one of styrene butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-soluble acrylic acid-based resin (e.g., polyacrylic acid (PAA), polymethacrylic acid (PMAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0234] In some embodiments, the negative electrode membrane layer may further optionally include other additives, such as thickeners, e.g., sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc.

[0235] In some embodiments, the negative electrode current collector may be a metal foil sheet or a composite current collector. An example of the metal foil sheet is copper foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. For example, the metal layer may include at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. For example, the polymer base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0236] The negative electrode film layer is typically obtained by coating a negative electrode slurry on a negative electrode current collector, drying, and cold pressing. The negative electrode slurry is typically formed by dispersing a negative electrode active material, an optional conductive agent, an optional adhesive, and other optional auxiliary agents in a solvent and stirring the resulting mixture uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0237] The negative electrode plate does not exclude additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode plate further includes a conductive undercoating (e.g., composed of a conductive agent and an adhesive) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In some embodiments, the negative electrode plate of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0238] [Electrolyte] During the charge and discharge process of the secondary battery, active ions are absorbed and released by moving back and forth between the positive and negative electrodes, and the electrolyte serves to conduct the active ions between the positive and negative electrodes. The present application does not particularly limit the type of electrolyte, and it can be selected according to actual needs.

[0239] The electrolyte solution includes an electrolyte salt and a solvent, and the types of the electrolyte salt and the solvent are not specifically limited and can be selected according to actual needs.

[0240] For example, when the secondary battery is a lithium-ion battery, the electrolyte salt may include at least one of lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium perchlorate (LiClO), lithium hexafluoroarsenate (LiAsF), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluorophosphate (LiPOF), lithium difluorobis(oxalato)phosphate (LiDFOP), and lithium tetrafluoro(oxalato)phosphate (LiTFOP), by way of example.

[0241] For example, when the secondary battery is a sodium-ion battery, the electrolyte salt may include at least one of sodium hexafluorophosphate (NaPF), sodium tetrafluoroborate (NaBF), sodium perchlorate (NaClO), sodium hexafluoroarsenate (NaAsF), sodium bisfluorosulfonylimide (NaFSI), sodium bistrifluoromethanesulfonylimide (NaTFSI), sodium trifluoromethanesulfonate (NaTFS), sodium difluoro(oxalato)borate (NaDFOB), sodium bis(oxalato)borate (NaBOB), sodium difluorophosphate (NaPOF), sodium difluorobis(oxalato)phosphate (NaDFOP), and sodium tetrafluoro(oxalato)phosphate (NaTFOP), by way of example.

[0242] By way of example, the solvent may include, but is not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl 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), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE).

[0243] In some embodiments, the electrolyte solution may further optionally contain additives. For example, the additives may include a negative electrode film-forming additive, a positive electrode film-forming additive, and may further include additives that can improve some battery performance, 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 power performance of the battery.

[0244] In some embodiments, the positive electrode plate, separator, and negative electrode plate may be fabricated into an electrode assembly by a winding process and / or a stacking process.

[0245] In some embodiments, the secondary battery may include an exterior body, which may be used to package the electrode assembly and the electrolyte.

[0246] In some embodiments, the exterior of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The exterior of the secondary battery may be a pouch, such as a bag-shaped pouch. The material of the pouch may be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0247] The present application does not particularly limit the shape of the secondary battery, and the secondary battery may be cylindrical, rectangular, or any other shape. Figure 1 shows an example of a secondary battery 5 having a rectangular structure.

[0248] In some embodiments, as shown in FIG. 2 , the exterior body may include a case 51 and a cover plate 53. The case 51 may include a bottom plate and side plates connected to the bottom plate, which together form a surrounding accommodating cavity. The case 51 has an opening communicating with the accommodating cavity, and the cover plate 53 is used to cover the opening and seal the accommodating cavity. The positive electrode plate, the negative electrode plate, and the separator may be formed into an electrode assembly 52 through a winding process and / or a stacking process. The electrode assembly 52 is packaged in the accommodating cavity. An electrolyte is impregnated into the electrode assembly 52. ​​The number of electrode assemblies 52 included in the secondary battery 5 may be one or more and can be adjusted as needed.

[0249] Methods for manufacturing secondary batteries are well known. In some embodiments, a secondary battery can be formed by assembling a positive electrode plate, a separator, a negative electrode plate, and an electrolyte. For example, the positive electrode plate, the separator, and the negative electrode plate can be formed into an electrode assembly through a winding process and / or a stacking process. The electrode assembly can be placed in an outer casing, dried, and then injected with an electrolyte. The secondary battery can be obtained through processes such as vacuum packaging, standing, chemical formation, and shaping.

[0250] In some embodiments, the secondary battery according to the present application 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 according to the application and capacity of the battery module.

[0251] Fig. 3 is a schematic diagram of an example battery module 4. As shown in Fig. 3, in the battery module 4, a plurality of secondary batteries 5 may be arranged in order along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the plurality of secondary batteries 5 may be fixed by fasteners.

[0252] Optionally, the battery module 4 may further include a housing having an accommodating space, and the plurality of secondary batteries 5 are accommodated in this accommodating space.

[0253] In some embodiments, the battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0254] 4 and 5 are schematic diagrams of an example battery pack 1. As shown in FIGS. 4 and 5, the battery pack 1 may include a battery box and a plurality of battery modules 4 installed in the battery box. The battery box includes an upper housing 2 and a lower housing 3, and the upper housing 2 covers the lower housing 3 and is used to form a sealed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0255] power consumption equipment An embodiment of the present application further provides a power consuming device, the power consuming device including at least one of a secondary battery, a battery module, or a battery pack according to the embodiment of the present application. The secondary battery, the battery module, or the battery pack may be used as a power source for the power consuming device or as an energy storage unit for the power consuming device. The power consuming device 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.), an electric train, a ship, a satellite, an energy storage system, etc.

[0256] The power consumption device may select a secondary battery, a battery module, or a battery pack depending on its usage needs.

[0257] 6 is a schematic diagram of an example power consuming device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, that may employ a battery pack or battery module to meet the high power and high energy density demands of the power consuming device.

[0258] Other examples of power consuming devices include mobile phones, tablet computers, notebook computers, etc. These power consuming devices generally require a thin design and can employ secondary batteries as their power source.

[0259] Example The following examples will more specifically describe the contents disclosed in this application, and these examples are for illustrative purposes only, as various modifications and variations within the scope of the contents disclosed in this application will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages and ratios reported in the following examples are by weight, and all reagents used in the examples can be obtained commercially or synthesized according to conventional methods and can be used directly without further treatment, and all instruments used in the examples can be obtained commercially.

[0260] The secondary batteries of Examples 1-12 and Comparative Examples 1-3 were all manufactured according to the following method.

[0261] Separator manufacturing A first base film is provided, and a second base film is provided. The parameters of the first base film and the second base film are shown in Table 1.

[0262] Preparation of adhesive layer slurry: Boehmite, polyacrylate, and carboxymethyl cellulose were uniformly mixed in a mass ratio of 4:1:1 with an appropriate amount of deionized water as a solvent to prepare an adhesive layer slurry.

[0263] The adhesive layer slurry was applied to a first base film using an applicator, and another unwinding roll was a second base film, which was then bonded to the adhesive layer slurry surface of the first base film.The oven temperature was controlled to 40°C, the film was dried for 5 seconds, and the film was pressed at a pressure of 10 N to obtain a separator.

[0264] Positive electrode plate manufacturing LiNi, the positive electrode active material 0.8 Co 0.1 Mn 0.1O2 (NCM811), carbon black (Super P) as a conductive agent, and polyvinylidene fluoride (PVDF) as an adhesive were uniformly mixed in an appropriate amount of solvent N-methylpyrrolidone (NMP) in a mass ratio of 96.2:2.7:1.1 to obtain a positive electrode slurry. The positive electrode slurry was then applied to a positive electrode current collector aluminum foil, and after processes such as drying, cold pressing, slitting, and cutting, a positive electrode plate was obtained.

[0265] Negative electrode plate manufacturing The negative electrode active material, artificial graphite, the conductive agent, carbon black (Super P), the adhesive, styrene butadiene rubber (SBR) and carboxymethyl cellulose sodium (CMC-Na), were uniformly mixed in a mass ratio of 96.4:0.7:1.8:1.1 in an appropriate amount of deionized water solvent to obtain a negative electrode slurry. The negative electrode slurry was then applied to a negative electrode current collector copper foil, and the mixture was dried, cold pressed, slit, and cut to obtain a negative electrode plate.

[0266] Electrolyte production Ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) were mixed in a mass ratio of 30:30:40 to obtain an organic solvent, and thoroughly dried LiPF6 was dissolved in the organic solvent to prepare an electrolyte solution with a concentration of 1 mol / L.

[0267] Secondary battery manufacturing A positive electrode plate, a separator, and a negative electrode plate were stacked in this order and wound to obtain an electrode assembly. The electrode assembly was then placed in an outer casing, dried, and then an electrolyte was added. After undergoing processes such as vacuum packaging, standing, chemical conversion, and shaping, a secondary battery was obtained.

[0268] In the above examples and comparative examples, the bending resistance of the separator, first base film, and second base film in the transverse (TD) and longitudinal (MD) directions can be tested using the inclined plane method in accordance with GB / T 18318-2009 and ZB WO 4003-87. A fully automatic bending resistance tester (e.g., a Dreck DRK309 automatic textile bending resistance tester) can be used as the testing equipment. During testing, multiple samples (e.g., 12 samples) can be punched out of the separator using a press. The sample size can be 25 mm × 250 mm, with the long sides of half the samples parallel to the transverse (TD) direction of the separator and the long sides of the other half parallel to the longitudinal (MD) direction of the separator. The angle of the inclined plane can be 41.5°, and the sample propulsion speed can be 4 mm / s.

[0269] In Table 1, the bending resistance of the separator in the transverse (TD) direction is denoted as T0, the bending resistance of the separator in the longitudinal (MD) direction is denoted as M0, the bending resistance of the first base film in the transverse (TD) direction is denoted as T1, the bending resistance of the first base film in the longitudinal (MD) direction is denoted as M1, the bending resistance of the second base film in the transverse (TD) direction is denoted as T2, and the bending resistance of the second base film in the longitudinal (MD) direction is denoted as M2.

[0270] Testing section (1) Separator heat shrinkage test Sample preparation: The separator prepared above was punched into samples with a width of 50 mm and a length of 100 mm using a press, and five parallel samples were taken and placed on a glass plate to fix them.

[0271] Sample test: Set the temperature of the blast oven to 250°C, and after the temperature reaches the set temperature and stabilizes for 60 minutes, place the glass plate in the blast oven and time it for 1 hour. After that, measure the width of the separator and mark the value as a.

[0272] Calculation of heat shrinkage: transverse (TD) direction heat shrinkage = [(50-a) / 50] x 100%, the average value of five parallel samples was taken as the test result.

[0273] (2) Needle stick test for secondary batteries At 25°C, the secondary battery was charged at a constant current of 1C to 4.2V, then continued to be charged at a constant voltage until the current reached ≤0.05C and allowed to rest for 5 minutes, at which point the secondary battery was in a 100% SOC state. A pin puncture test was performed using a 1mm diameter high-temperature resistant steel needle (with a 30° cone angle at the tip). The needle puncture speed was 0.01mm / s, and the test was stopped when the puncture depth reached 3mm. The test was held for 60 minutes, and the secondary battery was observed for failure. The criterion for failure of the secondary battery was a voltage drop to 0V. Ten secondary batteries were tested, and the number of secondary batteries that passed the pin puncture test was counted.

[0274] The more secondary batteries that pass the needle stick test, the more reliable the secondary batteries are.

[0275] (3) Secondary battery production yield test The secondary battery is placed in the test position of the hot press machine, and the pressure is set to 5 MPa, the temperature to 95°C, and the hot press time to 5 seconds. The display on the machine is observed, and if the machine displays OK, it is judged as passed; if any other display is abnormal, it is judged as abnormal. 100 secondary batteries are taken for testing, and the pass rate of the hot press test is taken as the production yield of secondary batteries.

[0276] As can be seen from the test results in Table 1, the separator includes a first base film, a second base film, and an adhesive layer located between the first base film and the second base film, and the bending resistance T0 of the separator in the transverse (TD) direction is between 1.0 mN×cm and 8.0 mN×cm, and the bending resistance M0 of the separator in the longitudinal (MD) direction is between 1.2 mN×cm and 7.0 mN×cm, which can reduce the thermal shrinkage rate of the separator, improve the pass rate of the pin puncture test of secondary batteries, improve the reliability of secondary batteries, and further improve the production yield of secondary batteries.

[0277] It should be noted that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any embodiment that has substantially the same configuration as the technical idea and achieves the same effects within the scope of the technical solution of the present application is included within the technical scope of the present application. In addition, various modifications that a person skilled in the art can make to the embodiments and other methods configured by combining some of the components of the embodiments are also included within the scope of the present application, as long as they do not deviate from the spirit of the present application.

[0278] [Table 1] JPEG2025540767000003.jpg245170 [Explanation of symbols]

[0279] 1: battery pack, 2: upper housing, 3: lower housing, 4: battery module, 5: secondary battery, 51: case, 52: electrode assembly, 53: cover plate.

Claims

1. A separator, a first base film; a second base film, and an adhesive layer disposed between the first base film and the second base film; The bending resistance in the lateral direction of the separator is T ０ The bending resistance of the separator in the longitudinal direction is expressed as M ０ and T ０ is 1.0-8.0 mN×cm, and M ０ is 1.2-7.0 mN×cm, separator.

2. The bending resistance T of the separator in the lateral direction ０ is 1.7-5.0 mN×cm, optionally 1.9-4.7 mN×cm, and / or The bending resistance M of the separator in the longitudinal direction ０ 2. The separator of claim 1, wherein the tensile strength is 1.2-4.0 mN×cm, and optionally 1.5-3.3 mN×cm.

3. T ０ / M ０ The separator of claim 1 or 2, wherein is 1.0-2.5, and optionally 1.2-2.

0.

4. The bending resistance in the transverse direction of the first base film is T １ and T １ is 0.25-4.5 mN×cm, optionally 0.9-3.0 mN×cm, and / or The bending resistance in the machine direction of the first base film is M １ and M １ is 0.15-4.0 mN×cm, optionally 0.6-3.0 mN×cm, and / or The bending resistance in the transverse direction of the second base film is T ２ and T ２ is 0.3-5.0 mN×cm, optionally 0.8-3.5 mN×cm, and / or The bending resistance in the machine direction of the second base film is M ２ and M ２ The separator of any one of claims 1 to 3, wherein the elongation strength is 0.2-4.5 mN x cm, and optionally 0.5-3.0 mN x cm.

5. T １ / M １ is 1.0-3.0, optionally 1.2-2.0, and / or T ２ / M ２ The separator of claim 4, wherein is 1.0-3.5, and optionally 1.1-1.

9.

6. the average filament diameter of the first base film is 80-300 nm, optionally 100-280 nm; and / or The separator of any one of claims 1 to 5, wherein the average filament diameter of the second base film is 100-300 nm, optionally 120-280 nm.

7. the ratio of the crystallinity of the second base film to the crystallinity of the first base film is greater than 1, preferably 1.03-1.5, more preferably 1.05-1.25; and / or The crystallinity of the first base film is 33%-70%, optionally 35%-45%, and / or The separator according to any one of claims 1 to 6, wherein the crystallinity of the second base film is 35%-80%, and optionally 40%-55%.

8. the ratio of the thickness of the second base film to the thickness of the first base film is greater than 1, preferably 1.02-5.0, more preferably 1.2-2.5; and / or the thickness of the first base film is less than or equal to 12 μm, optionally between 2.5 and 5 μm; and / or The separator according to any one of claims 1 to 7, wherein the thickness of the second base film is 14 µm or less, and optionally 3-6 µm.

9. the ratio of the melting point of the first base film to the melting point of the second base film is less than 1, preferably 0.2-0.95, more preferably 0.35-0.90; and / or The melting point of the first base film is 110°C or higher, optionally 120°C-165°C; and / or The separator according to any one of claims 1 to 8, wherein the melting point of the second base film is 150°C or higher, and optionally 165°C to 330°C.

10. the ratio of the porosity of the second base film to the porosity of the first base film is greater than 1, preferably 1.01-2.8, more preferably 1.1-2.0; and / or The porosity of the first base film is 28%-70%, optionally 30%-50%, and / or the porosity of the second base film is 30%-80%, optionally 35%-60%; and / or The separator according to any one of claims 1 to 9, wherein the porosity of the separator is 27%-65%, optionally 33%-55%.

11. the ratio of the average pore size of the second base film to the average pore size of the first base film is greater than 1, preferably 1.05-2.5, more preferably 1.1-2; and / or the first base film has an average pore size of 48-1800 nm, optionally 50-300 nm; and / or The separator according to any one of claims 1 to 10, wherein the average pore size of the second base film is 50-2000 nm, optionally 100-400 nm.

12. the ratio of the air permeability of the first base film to the air permeability of the second base film is greater than 1, preferably 1.05-3.0, more preferably 1.08-2.0; and / or The air permeability of the first base film is 300 s / 100 cc or less, optionally 120-260 s / 100 cc; and / or The separator according to any one of claims 1 to 11, wherein the air permeability of the second base film is 250s / 100cc or less, and optionally 110-220s / 100cc.

13. the first base film and the second base film each independently comprise one or more of polyolefins and derivatives thereof, halogenated polyolefins and derivatives thereof, polyethers and derivatives thereof, polyetheretherketones and derivatives thereof, polyesters and derivatives thereof, polyimides and derivatives thereof, and polyvinyl alcohols and derivatives thereof; Optionally, the halogenated polyolefin and its derivatives include one or more of polytetrafluoroethylene and its derivatives, polyvinyl fluoride and its derivatives, and polyvinylidene fluoride and its derivatives; Optionally, the polyester and its derivatives include one or more of polyethylene terephthalate and its derivatives, and polybutylene terephthalate and its derivatives.

14. the adhesive layer comprises an adhesive; Optionally, the adhesive layer comprises an adhesive and a filler; Optionally, the adhesive comprises one or more of polyacrylate, polyacrylic acid, polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride-trichloroethylene copolymer, polyvinylpyrrolidone, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyethylene oxide, polyarylate, carboxymethyl cellulose, hydroxypropyl cellulose, regenerated cellulose, cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate, polyacrylonitrile, polyvinyl alcohol, polyethylene, polypropylene, starch, cyanoethyl amylopectin; Optionally, the filler comprises at least one of inorganic particles, organic particles, and organic-metallic framework materials; Optionally, the inorganic particles include one or more of inorganic particles having a dielectric constant of 5 or more, inorganic particles having ionic conductivity but not storing ions, and inorganic particles capable of generating an electrochemical reaction; Optionally, the organic particles comprise one or more of polycarbonate, polythiophene, polypyridine, polystyrene, polyacrylic wax, polyethylene, polypropylene, cellulose, cellulose modifier, melamine resin, phenolic resin, polyester, silicone resin, polyimide, polyamideimide, polyaramid, polyphenylene sulfide, polysulfone, polyethersulfone, polyetheretherketone, polyaryletherketone, copolymer of butyl acrylate and ethyl methacrylate; Optionally, the organic-metal framework material comprises one or more of a nitrogen-containing heterocyclic ligand structure, an organic carboxylic acid ligand structure, and a nitrogen-containing oxygen gas mixture ligand structure.

15. the thickness of the adhesive layer is 0.3 μm or more, optionally 0.5-4 μm; and / or The surface density of the adhesive layer is 1.0-6.0 g / m ２ and optionally 1.2-5.0 g / m ２ and / or The adhesive strength between the adhesive layer and the first base film is 3 N / m or more, optionally 4-15 N / m; and / or The separator according to any one of claims 1 to 14, wherein the adhesive strength between the adhesive layer and the second base film is 3 N / m or more, and optionally 4-15 N / m.

16. The content of the adhesive is 10% or more, optionally 10%-30% based on the total weight of the adhesive layer; and / or The content of the filler is 90% or less, optionally 60%-80% based on the total weight of the adhesive layer; and / or The separator according to claim 14 or 15, wherein the volume distribution particle size Dv50 of the filler is 1.5 μm or less, and optionally 0.1-1.4 μm.

17. The separator satisfies the following conditions (1) to (4): (1) The separator has a lateral tensile strength of 700 kg / cm ２ or more, and optionally 1000 kg / cm ２ That is all, and (2) The longitudinal tensile strength of the separator is 1000 kg / cm ２ or more, and optionally 1200 kg / cm ２ That is all, and (3) The separator has a transverse heat shrinkage rate of 5% or less, optionally 2% or less, at 250°C for 1 hour; (4) The separator according to any one of claims 1 to 16, wherein the separator has a longitudinal heat shrinkage rate of 5% or less at 250°C for 1 hour, and optionally 2% or less.

18. A secondary battery comprising the separator according to any one of claims 1 to 17.

19. 19. The secondary battery of claim 18, wherein the secondary battery includes a positive electrode plate and a negative electrode plate, the separator is disposed between the positive electrode plate and the negative electrode plate, and a first base film of the separator faces the negative electrode plate and a second base film of the separator faces the positive electrode plate.

20. A power consuming device comprising the secondary battery according to claim 18 or 19.

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