Separator, manufacturing method thereof, and related secondary battery and power consumption device

Abstract

The present application provides a separator, a manufacturing method thereof, and a secondary battery and a power consumption device related thereto. The separator includes a porous substrate and a coating layer formed on at least one surface of the porous substrate, the coating layer including fibrous material, at least a portion of which is embedded in the pores of the porous substrate, and the depth H1 of the fibrous material embedded in the pores of the porous substrate along the thickness direction of the separator is 0.02 μm or more.

Description

[Technical Field]

[0001] The present application relates to a separator, a method for manufacturing the same, and related secondary batteries and power consuming devices. [Background technology]

[0002] In recent years, secondary batteries have been widely used in many fields, including energy storage power systems such as hydroelectric, thermal, wind, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. As secondary batteries become more widely used, their reliability, particularly their thermal stability, has received increasing attention. However, current methods for improving the thermal stability of secondary batteries often result in a poor balance between the energy density and service life of the secondary battery. Furthermore, a sustained increase in the temperature of a secondary battery can easily cause an internal short circuit, leading to thermal runaway and ultimately to safety hazards such as fire or explosion of the secondary battery. The above description is merely intended to provide background technical information related to the present application and does not necessarily constitute prior art. Summary of the Invention

[0003] The present application provides a separator that can reduce the degree of thermal runaway in a secondary battery, thereby preventing the occurrence of thermal runaway and effectively reducing safety hazards such as fire and explosion of the secondary battery, while simultaneously providing the secondary battery with high energy density, high thermal stability, long cycle life, and good dynamic performance, a manufacturing method thereof, and related secondary batteries and power consumption devices.

[0004] A first aspect of the present application provides a separator comprising a porous substrate and a coating layer provided on at least one surface of the porous substrate, wherein the coating layer contains fibrous material, at least some of the fibrous material is embedded in the pores of the porous substrate, and when the depth to which the fibrous material is embedded in the pores of the porous substrate along the thickness direction of the separator is H1, H1 is 0.02 μm or more.

[0005] By providing a coating layer containing fibrous material on the surface of the porous substrate of the separator and setting the depth at which the fibrous material is embedded in the pores of the porous substrate to 0.02 μm or more, the degree of thermal runaway of the secondary battery can be reduced, and ultimately the occurrence of thermal runaway of the secondary battery can be prevented. This can effectively reduce safety accidents such as fires and explosions of the secondary battery, and also enable the secondary battery to achieve both high energy density, high thermal stability, long cycle life, and good dynamic performance.

[0006] In any embodiment of the present application, H1 is 0.022 μm-0.150 μm, preferably 0.025 μm-0.100 μm, so that the molten porous substrate penetrates into the coating layer along the fibrous material due to the capillary effect, forming a membrane layer integrated with the separator, reducing the probability of the positive electrode and the negative electrode coming into direct contact with each other and causing an internal short circuit, reducing the degree of thermal runaway of the secondary battery, and ultimately preventing the occurrence of thermal runaway of the secondary battery, thereby effectively reducing safety hazards such as fire and explosion of the secondary battery, and further favoring the good cycle performance of the secondary battery.

[0007] In any embodiment of the present application, the thickness of the porous substrate is H2, expressed in μm, and H1 / H2 is 0.003 or more. Preferably, H1 / H2 is 0.004-0.025, more preferably 0.0045-0.020. By adjusting H1 / H2 within this range, the molten porous substrate penetrates the coating layer along the fibrous material due to the capillary effect, forming a membrane layer integrated with the separator. This reduces the probability of internal short circuit caused by direct contact between the positive and negative electrodes, reduces the degree of thermal runaway of the secondary battery, and ultimately prevents the occurrence of thermal runaway in the secondary battery, thereby effectively reducing safety hazards such as secondary battery fires and explosions. Furthermore, the separator has a high porosity and high ionic conductivity, which is advantageous for achieving both a long cycle life and good dynamic performance in the secondary battery.

[0008] In any embodiment of the present application, the thickness of the porous substrate is H2, which is 12 μm or less, preferably 3 μm-10 μm.

[0009] In any embodiment of the present application, the average length of the fibrous material, L, expressed in nm, is 0.03≦1000H1 / L≦0.5, preferably 0.05≦1000H1 / L≦0.35. Adjusting 1000H1 / L within this range reduces the probability of direct contact between the positive electrode and the negative electrode, causing an internal short circuit, and reduces the degree of thermal runaway in the secondary battery, thereby preventing thermal runaway and effectively reducing safety hazards such as fires and explosions in the secondary battery. This also has the advantage of providing a separator with high porosity and high ionic conductivity, which can provide the secondary battery with both a long cycle life and good dynamic performance.

[0010] In any embodiment of the present application, where V (unit: nm) is the average pore size of the porous substrate and D (unit: nm) is the average diameter of the fibrous material, V / D is 0.6≦V / D≦2.1, preferably 0.7≦V / D≦1.8, and more preferably 0.8≦V / D≦1.6. Adjusting V / D within the above range reduces the probability of direct contact between the positive electrode and the negative electrode, causing an internal short circuit, reduces the degree of thermal runaway in the secondary battery, and ultimately prevents thermal runaway in the secondary battery, thereby effectively reducing safety hazards such as fires and explosions in the secondary battery. Furthermore, excessive sacrifice of the porosity of the porous substrate can be avoided, allowing the separator to have high porosity and high ionic conductivity, and further achieving both long cycle life and good dynamic performance in the secondary battery.

[0011] In any embodiment of the present application, the average pore diameter of the porous substrate is V, expressed in nm, and is 20 nm≦V≦40 nm, preferably 25 nm≦V≦37 nm.

[0012] In any embodiment of the present application, the average pore size of the porous substrate is V (unit: nm), and the melting point of the porous substrate is T m(unit: °C), the average diameter of the fibrous material is D (unit: nm), and the average length of the fibrous material is L (unit: nm), then 0.03≦L / (D×T m )≦0.14, and preferably 0.04≦L / (D×T m )≦0.12, and more preferably 0.05≦L / (D×T m )≦0.10. L / (D×T m ) within the above range, the molten porous substrate enters the coating layer along the fibrous material due to the capillary effect, forming a membrane layer integrated with the separator, reducing the probability of an internal short circuit occurring due to direct contact between the positive electrode and the negative electrode, reducing the degree of thermal runaway of the secondary battery, and ultimately preventing the occurrence of thermal runaway of the secondary battery, thereby effectively reducing safety accidents such as fires and explosions of the secondary battery.

[0013] In any embodiment of the present application, the melting point of the porous substrate is T m Then, T m ≧120°C, preferably 120°C≦T m ≦180°C.

[0014] In any embodiment of the present application, the average diameter of the fibrous material is D, which is 15 nm or more, and preferably 20 nm to 35 nm. When the average diameter of the fibrous material is within the above range, the probability of an internal short circuit occurring due to direct contact between the positive electrode and the negative electrode is reduced, the degree of thermal runaway of the secondary battery is reduced, and the occurrence of thermal runaway of the secondary battery is prevented, thereby effectively reducing safety accidents such as fire and explosion of the secondary battery, and the ionic conductivity and voltage breakdown characteristics of the separator can be further improved, and the overlap between the fibrous material and the filler, etc., contributes to forming an integration effect, thereby further improving the heat resistance of the separator.

[0015] In any embodiment of the present application, the average length of the fibrous material is L, which is 100 nm to 600 nm, and preferably 200 nm to 500 nm. When the average length of the fibrous material is within the above range, the heat resistance and ionic conductivity of the separator can be further improved.

[0016] In any embodiment of the present application, the aspect ratio of the fibrous material is L / D, which is 3 to 40, and preferably 6 to 30. When the aspect ratio of the fibrous material is within the above range, the ionic conductivity of the separator and the impregnation and retention properties of the electrolyte can be further improved.

[0017] In any embodiment of the present application, the shape of the fibrous material includes at least one of rod-like, tubular, rod-like and fiber-like.

[0018] In any embodiment of the present application, the fibrous material comprises at least one of an organic material and an inorganic material.

[0019] In any embodiment of the present application, the organic material comprises at least one of nanocellulose, polytetrafluoroethylene nanofibers, and polyamide nanofibers, and preferably, the nanocellulose comprises at least one of cellulose nanofibers, cellulose nanowhiskers, and bacterial nanocellulose.

[0020] In any embodiment of the present application, the inorganic material comprises at least one of halloysite nanotubes, nanorod-shaped aluminum oxide, nanorod-shaped boehmite, nanorod-shaped silica, and glass fiber.

[0021] In any embodiment of the present application, the fibrous material comprises nanocellulose, and the nanocellulose comprises at least one of unmodified nanocellulose and modified nanocellulose.

[0022] In any embodiment of the present application, the modified nanocellulose contains a modifying group, which includes at least one of an amine group, a carboxyl group, an aldehyde group, a sulfonic acid group, a boric acid group, and a phosphate group, and preferably at least one of a sulfonic acid group, a boric acid group, and a phosphate group. When nanocellulose has the above-mentioned specific modifying group, it can effectively improve the heat resistance of the separator and the thermal stability of the secondary battery, and can also improve the adhesive strength between the coating layer and the porous substrate, which is also advantageous for forming an integrated effect by overlapping the nanocellulose and the filler.

[0023] In any embodiment of the present application, the modified nanocellulose contains hydroxyl groups and modifying groups, and the molar ratio of the modifying groups to the hydroxyl groups is 1:4-4:1, more preferably 2:3-7:3. When the molar ratio of the modifying groups to the hydroxyl groups is within the above range, the heat resistance, ionic conductivity, and electrolyte impregnation and retention properties of the separator can be further improved, and the thermal stability, cycle performance, and dynamic performance of the secondary battery can be improved.

[0024] In any embodiment of the present application, the fibrous material contains sulfonic acid groups, and the content of sulfur element in the fibrous material is 0.1 wt% or more, preferably 0.2 wt%-0.5 wt%, based on the total weight of the fibrous material.

[0025] In any embodiment of the present application, the coating layer includes a three-dimensional skeletal structure and a filler, the three-dimensional skeletal structure includes the fibrous material, and at least a portion of the filler is filled in the three-dimensional skeletal structure.

[0026] In any embodiment of the present application, the filler includes at least one of primary particles and secondary particles. The filler in the form of secondary particles can better overlap with the three-dimensional framework structure to form an integrated effect, thereby allowing the coating layer to have a more stable spatial network structure, further improving the heat resistance of the separator. The filler in the form of primary particles reduces the moisture content of the coating layer and improves the ionic conductivity of the coating layer, thereby contributing to improving the cycle performance of the secondary battery.

[0027] In any embodiment of the present application, when the average length of the fibrous material is L (unit: nm) and the volume distribution particle size Dv50 of the filler is A (unit: nm), L ≥ (A × √2) / 8. Adjusting L ≥ (A × √2) / 8 is advantageous in forming an integration effect due to the overlap between the fibrous material and the filler, thereby further improving the heat resistance, ionic conductivity, and electrolyte impregnation and retention properties of the separator, and improving the thermal stability, cycle performance, and kinetic performance of the secondary battery.

[0028] In any embodiment of the present application, when the volume distribution particle size Dv50 of the filler is A, it is 80 nm≦A≦220 nm, preferably 100 nm≦A≦200 nm.

[0029] In any embodiment of the present application, the content of the three-dimensional framework structure is 5 wt%-40 wt%, preferably 10 wt%-25 wt%, based on the total weight of the coating layer.

[0030] In any embodiment of the present application, the content of the filler is greater than 60 wt%, preferably 70 wt%-88 wt%, based on the total weight of the coating layer.

[0031] When the content of the three-dimensional skeletal structure is within the above range, the slurry of the coating layer can have an appropriate viscosity, which is advantageous for application, and is also advantageous for forming an integrated effect due to the overlap of the three-dimensional skeletal structure and the filler. As a result, the coating layer can have a more stable spatial network structure, which can further improve the heat resistance, ion conductivity, electrolyte impregnation and retention properties, and voltage breakdown capability of the separator.

[0032] In any embodiment of the present application, the coating layer further comprises a non-particulate binder. Preferably, the non-particulate binder comprises an aqueous binder. Preferably, the content of the non-particulate binder in the coating layer is 2 wt % or less based on the total weight of the coating layer.

[0033] In any embodiment of the present application, the thickness of the coating layer is 2 μm or less, preferably 0.5 μm-1.5 μm, which contributes to improving the energy density of the secondary battery.

[0034] In any embodiment of the present application, the separator further includes an adhesive layer, the adhesive layer being provided on at least a portion of the surface of the coating layer, and the adhesive layer including a particulate binder. Preferably, the particulate binder includes at least one of an acrylic acid ester-based monomer homopolymer or copolymer, an acrylic acid-based monomer homopolymer or copolymer, and a fluorine-containing olefin monomer homopolymer or copolymer. The adhesive layer not only prevents the coating layer from falling off and improves the reliability of the secondary battery, but also contributes to improving the cycle performance of the secondary battery by improving the interface between the separator and the electrode.

[0035] In any embodiment of the present application, the longitudinal heat shrinkage rate of the separator at 150°C for 1 hour is 4% or less, preferably 0.5%-3%.

[0036] In any embodiment of the present application, the separator has a transverse heat shrinkage of 4% or less at 150°C for 1 hour, preferably 0.5%-3%.

[0037] In any embodiment of the present application, the separator has a longitudinal tensile strength of 2200 kg / cm 2 or more, preferably 2500 kg / cm 2 -4500kg / cm 2 is.

[0038] In any embodiment of the present application, the separator has a transverse tensile strength of 2200 kg / cm 2 or more, preferably 2500 kg / cm 2 -4500kg / cm 2 is.

[0039] In any embodiment of the present application, the wetted length of the separator is 35mm or more, preferably 40mm-80mm.

[0040] In any embodiment of the present application, the wetting speed of the separator is 4 mm / s or more, preferably 4.5 mm / s-10 mm / s.

[0041] In any embodiment of the present application, the air permeability of the separator is 300s / 100mL or less, preferably 100s / 100mL-270s / 100mL.

[0042] A second aspect of the present application provides a method for producing the separator of the first aspect of the present application, the method comprising the steps of: providing a porous substrate; mixing fibrous material and a selectable filler in a solvent in a predetermined ratio to prepare a coating layer slurry; and applying the coating layer slurry to at least one surface of the porous substrate and drying to obtain a separator, wherein the separator comprises a porous substrate and a coating layer provided on at least one surface of the porous substrate, the coating layer comprising fibrous material, at least some of the fibrous material being embedded in the pores of the porous substrate, and where H1 is the depth to which the fibrous material is embedded in the pores of the porous substrate along the thickness direction of the separator, H1 is 0.02 μm or more.

[0043] In any embodiment of the present application, the dispersion linear velocity of the slurry of the coating layer is 8 m / s-22 m / s, preferably 12 m / s-18 m / s.

[0044] In any embodiment of the present application, the coating speed of the slurry of the coating layer is 30m / min-140m / min, preferably 90m / min-130m / min.

[0045] In any embodiment of the present application, the drying temperature of the coating layer slurry is 50°C-80°C, preferably 55°C-70°C.

[0046] In any embodiment of the present application, the total drying time of the coating layer slurry is 3s-11s, preferably 5s-10s.

[0047] In any embodiment of the present application, the drying is performed using a multi-stage oven, and preferably, the number of stages of the oven is 3-6.

[0048] In any embodiment of the present application, the drying is carried out using a multi-stage oven, and the temperature of the first stage oven is greater than 50°C, preferably greater than 55°C.

[0049] In any embodiment of the present application, the drying is performed using a multi-stage oven, and the drying time of the first stage oven is less than 4 seconds, preferably less than 3.5 seconds.

[0050] A third aspect of the present application provides a secondary battery including the separator according to the first aspect of the present application or a separator produced by the method according to the second aspect of the present application.

[0051] A fourth aspect of the present application provides a power consumption device including the secondary battery according to the third aspect of the present application.

[0052] The separator of the present application can reduce the degree of thermal runaway in secondary batteries, thereby preventing the occurrence of thermal runaway and effectively reducing safety hazards such as fires and explosions of secondary batteries, and can also enable secondary batteries to achieve high energy density, high thermal stability, long cycle life, and good dynamic performance. The power consumption device of the present application is equipped with the secondary battery of the present application, and therefore has at least the same advantages as the secondary battery. [Brief explanation of the drawings]

[0053] In order to more clearly explain the technical solutions of the embodiments of the present application, the drawings that need to be used in the embodiments of the present application are briefly described below. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can obtain other drawings based on the drawings without any creative efforts. The drawings are not necessarily drawn to scale.

[0054] [Figure 1] 1 is a schematic diagram of an embodiment of a secondary battery of the present application. [Figure 2] FIG. 2 is an exploded schematic view of the embodiment of the secondary battery of FIG. 1. [Figure 3] 1 is a schematic diagram of one embodiment of a battery module of the present application. [Figure 4] 1 is a schematic diagram of one embodiment of a battery pack of the present application. [Figure 5] 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 an embodiment of a power consuming device that includes a secondary battery of the present application as a power source. [Explanation of symbols]

[0055] 1 battery pack 2 Upper housing 3 Lower housing 4 Battery Module 5 Secondary battery 51 cases 52 Electrode Assembly 53 Cover plate DETAILED DESCRIPTION OF THE INVENTION

[0056] Hereinafter, with appropriate reference to the drawings, embodiments specifically disclosing the separator of the present application, its manufacturing method, and related secondary batteries and power consumption devices will be described in detail. However, unnecessary detailed description may be omitted. For example, detailed description of known matters or repeated description of substantially identical configurations 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 accompanying 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.

[0057] 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 that particular range. Such defined ranges may be inclusive or exclusive of the endpoints, and may be arbitrarily combined; i.e., any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are recited for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Furthermore, if minimum range values ​​of 1 and 2 and maximum range values ​​of 3, 4, and 5 are recited, then ranges of 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5 are all contemplated. Unless otherwise specified, the numerical range "ab" in this application is an abbreviation 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" indicates that all real numbers between "0-5" are listed herein, and "0-5" is an abbreviation for combinations of these numbers. Also, expressing a parameter as an integer greater than or equal to 2 (≧2) is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0058] Unless otherwise specified, all embodiments and optional embodiments of the present application may 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.

[0059] Unless otherwise specified, all technical features and optional technical features of the present application may 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.

[0060] Unless otherwise specified, all steps in this application may be performed in order or randomly, but are preferably performed in order. For example, when a method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed in order, or steps (b) and (a) performed in order. For example, when a method is described as further including step (c), it means that step (c) may be added to the method in any order. For example, 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.

[0061] Unless otherwise specified, the terms "comprise" and "include" used in this application mean open-ended and may also be closed-ended. For example, the terms "comprise" and "include" can mean "comprise" or "include" other components not listed, or "comprise" or "include" only the listed components.

[0062] 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, any of the following conditions are met for "A or B": A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), or both A and B are true (or exist).

[0063] Unless otherwise specified, in this application, terms such as "first," "second," etc. are used to distinguish between different objects and not to describe a particular order or hierarchical relationship.

[0064] Unless otherwise specified, terms used in this application have the known meanings commonly understood by those skilled in the art.

[0065] Unless otherwise specified, the numerical values ​​of each parameter mentioned in this application can be measured by various test methods commonly used in this field, for example, according to the test methods provided in the examples of this application. Unless otherwise specified, the test temperature for each parameter is 25°C.

[0066] Typically, a secondary battery includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separator. The separator is disposed between the positive electrode sheet and the negative electrode sheet and serves to prevent short circuits between the positive electrode and the negative electrode, while allowing active ions to pass freely through it to form a circuit.

[0067] Currently, separators used in commercial secondary batteries are generally polyolefin porous films, which have poor heat resistance. When exposed to heat, significant thermal contraction occurs, causing direct contact between the positive and negative electrodes inside the battery, leading to internal short circuits and potentially thermal runaway. In severe cases, this can lead to safety hazards such as fires and explosions in the secondary battery.

[0068] To address these issues, the current approach is to coat a heat-resistant inorganic ceramic layer on a polyolefin porous membrane, which increases the separator's mechanical strength, reduces its shrinkage when heated, and reduces the risk of short-circuiting between the positive and negative electrodes within the battery. However, the large particle size of commercially available inorganic ceramic particles increases the overall separator thickness, making it impossible to balance the energy density of the secondary battery, which is particularly detrimental to improving the driving range of power batteries. Furthermore, the effectiveness of commercially available inorganic ceramic particles in improving the separator's heat resistance is limited, and they are unable to prevent thermal runaway in secondary batteries.

[0069] Therefore, the separators of the prior art cannot prevent thermal runaway in secondary batteries, and it is difficult to achieve high energy density, high thermal stability, long cycle life, and good dynamic performance in secondary batteries.

[0070] In the course of their research, the inventors unexpectedly discovered that by providing a coating layer containing fibrous material on the surface of a separator porous substrate and setting the depth at which the fibrous material is embedded in the pores of the porous substrate to 0.02 μm or more, the degree of thermal runaway of the secondary battery can be reduced, and ultimately the occurrence of thermal runaway of the secondary battery can be prevented. This can effectively reduce safety accidents such as fires and explosions of the secondary battery, and also enable the secondary battery to achieve a combination of high energy density, high thermal stability, long cycle life, and good dynamic performance. Separator

[0071] A first aspect of an embodiment of the present application provides a separator, the separator including a porous substrate and a coating layer provided on at least one surface of the porous substrate, the coating layer including fibrous materials, at least some of the fibrous materials embedded in the pores of the porous substrate, and a depth H1 of the fibrous materials embedded in the pores of the porous substrate along the thickness direction of the separator, where H1 is 0.02 μm or more.

[0072] In the separator according to the embodiment of the present application, the fibrous material in the coating layer is embedded in the pores of the porous substrate to a depth of 0.02 μm or more, and when the internal temperature of the secondary battery reaches the melting point of the porous substrate, the molten porous substrate penetrates into the coating layer along the fibrous material due to the capillary effect, ultimately forming a membrane layer integrated with the separator. This membrane layer reduces the probability of internal short circuiting caused by direct contact between the positive and negative electrodes, reduces the degree of thermal runaway in the secondary battery, and ultimately prevents thermal runaway in the secondary battery, thereby effectively reducing safety hazards such as fires and explosions in the secondary battery.

[0073] The coating layer includes a fibrous material, which has the advantage of having a large specific surface area compared to inorganic ceramic particles, thereby enabling the coating layer to have high porosity and high ionic conductivity, and also to have high heat resistance even when the coating layer is thin, thereby enabling the secondary battery to have high energy density, high thermal stability, long cycle life, and good dynamic performance.

[0074] The term "fibrous material" refers to a material with an aspect ratio of 5 or greater. In some embodiments, the morphology of the fibrous material can include at least one of a rod, a tube (e.g., a hollow tube), a rod, and a fiber (e.g., a fiber thread).

[0075] In some embodiments, H1 may be 0.020-0.200 μm, 0.021-0.180 μm, 0.022-0.150 μm, 0.024-0.120 μm, 0.025-0.100 μm, 0.028-0.090 μm, or 0.035-0.085 μm. This allows the molten porous substrate to enter the coating layer along the fibrous material due to capillary effect, forming a membrane layer integrated with the separator, reducing the probability of internal short circuit caused by direct contact between the positive electrode and the negative electrode, reducing the degree of thermal runaway of the secondary battery, and ultimately preventing thermal runaway of the secondary battery, thereby effectively reducing safety hazards such as fire and explosion of the secondary battery, and also favoring good cycle performance of the secondary battery.

[0076] In some embodiments, H1 / H2 is 0.003 or greater, where H2 is the thickness of the porous substrate and is expressed in μm. Preferably, H1 / H2 is 0.003-0.035, 0.0035-0.032, 0.004-0.025, 0.0045-0.020, 0.0048-0.018, 0.005-0.016, or 0.0055-0.014.

[0077] By adjusting H1 / H2 within the above range, the molten porous substrate penetrates into the coating layer along the fibrous material due to the capillary effect, forming a membrane layer integrated with the separator, reducing the probability of direct contact between the positive and negative electrodes and causing an internal short circuit, reducing the degree of thermal runaway in the secondary battery, and ultimately preventing the occurrence of thermal runaway in the secondary battery, thereby effectively reducing safety hazards such as fire and explosion in the secondary battery. In addition, it is advantageous for the separator to have high porosity and high ionic conductivity, and further enables the secondary battery to achieve both a long cycle life and good dynamic performance.

[0078] In some embodiments, when the average length of the fibrous material is L in nm, the range is 0.03≦1000H1 / L≦0.5, preferably 0.05≦1000H1 / L≦0.35, 0.06≦1000H1 / L≦0.34, 0.08≦1000H1 / L≦0.35, 0.09≦1000H1 / L≦0.30, or 0.10≦1000H1 / L≦0.25.

[0079] By adjusting 1000H1 / L within the above range, some of the fibrous material is embedded in the pores of the porous substrate, and the other part is located in the coating layer, so that the molten porous substrate enters the coating layer along the fibrous material due to the capillary effect, forming a membrane layer integrated with the separator, reducing the probability of internal short circuit caused by direct contact between the positive electrode and the negative electrode, reducing the degree of thermal runaway of the secondary battery, and ultimately preventing the occurrence of thermal runaway of the secondary battery, thereby effectively reducing safety accidents such as fire and explosion of the secondary battery. In addition, it is advantageous for the separator to have high porosity and high ionic conductivity, and furthermore, it can achieve both long cycle life and good dynamic performance of the secondary battery.

[0080] The depth H1 of the fibrous material embedded in the pores of the porous substrate can be determined by ion-polished cross-sectional elemental analysis. During testing, the porous substrate is removed from the separator, a sample of the porous substrate (e.g., 6 cm x 6 cm) is cut, and the sample is overlapped with a copper piece and wrapped around 4-5 times. The sample is then polished using liquid nitrogen-frozen ion beams. The polished sample's interface is then sprayed with gold and placed in a dedicated scanning electron microscope fixture. The EDS mapping mode is selected, the output results are set to "line scan," and the scanning voltage is set to 5-10 KV. The depth H1 of the fibrous material embedded in the pores of the porous substrate CP is determined by the depth of the characteristic elements (e.g., S, P, B, etc.) that mark the fibrous material. For accuracy, the test results of multiple samples (e.g., 5-10 samples) can be averaged.

[0081] In some embodiments, when the average pore size of the porous substrate is V (unit: nm) and the average diameter of the fibrous material is D (unit: nm), 0.6≦V / D≦2.1, preferably 0.7≦V / D≦1.8, 0.8≦V / D≦1.6, 0.9≦V / D≦1.5, or 1.0≦V / D≦1.4.

[0082] By adjusting V / D within the above range, the fibrous material penetrates into the pores of the porous substrate, and after the porous substrate is melted by heat, the molten porous substrate enters the coating layer along the fibrous material due to the capillary effect, forming a membrane layer integrated with the separator. This reduces the probability of direct contact between the positive and negative electrodes and the occurrence of internal short circuits, reduces the degree of thermal runaway in the secondary battery, and ultimately prevents the occurrence of thermal runaway in the secondary battery, which is advantageous in effectively reducing safety accidents such as fires and explosions in the secondary battery, while avoiding excessive sacrifice of the porosity of the porous substrate, allowing the separator to have high porosity and high ionic conductivity, and further enabling the secondary battery to achieve both long cycle life and good dynamic performance.

[0083] In some embodiments, the melting point of the porous substrate is T m(unit: °C), the average diameter of the fibrous material is D (unit: nm), and the average length of the fibrous material is L (unit: nm), then 0.03≦L / (D×T m )≦0.14, and preferably 0.04≦L / (D×T m )≦0.12, 0.05≦L / (D×T m )≦0.10.

[0084] L / (D×T m ) within the above range, the molten porous substrate enters the coating layer along the fibrous material due to the capillary effect, forming a membrane layer integrated with the separator, reducing the probability of an internal short circuit occurring due to direct contact between the positive electrode and the negative electrode, reducing the degree of thermal runaway in the secondary battery, and ultimately preventing the occurrence of thermal runaway in the secondary battery, effectively reducing safety accidents such as fires and explosions in the secondary battery.

[0085] In some embodiments, the thickness of the porous substrate is designated H2, which may be 12 μm or less, and preferably 3 μm-10 μm.

[0086] In some embodiments, the melting point of the porous substrate is T m Then, T m ≧120°C, preferably 120°C≦T m ≦180℃, 132℃≦T m ≦175°C.

[0087] The melting point of the porous substrate has a meaning known in the art and can be measured by a method known in the art, for example, by differential scanning calorimetry, with reference to GB / T28724-2012.

[0088] In some embodiments, the average pore size of the porous substrate is V, which is 18 nm≦V≦45 nm, preferably 20 nm≦V≦40 nm, 25 nm≦V≦37 nm. This is advantageous for the fibrous material to be embedded in the pores of the porous substrate, and after the porous substrate is melted by heat, the molten porous substrate enters the coating layer along the fibrous material due to the capillary effect, forming a membrane layer integrated with the separator, reducing the probability of internal short circuit caused by direct contact between the positive electrode and the negative electrode, reducing the degree of thermal runaway of the secondary battery, and ultimately preventing the occurrence of thermal runaway of the secondary battery, thereby effectively reducing safety hazards such as fire and explosion of the secondary battery, while preventing the pores of the porous substrate from being blocked by the fibrous material, and further enabling the secondary battery to achieve both a long cycle life and good dynamic performance.

[0089] The average pore size of the porous substrate can be measured using a mercury porosimeter with reference to GB / T21650.1-2008.

[0090] In the embodiments of the present application, the material of the porous substrate is not particularly limited, and any substrate having known chemical and mechanical stability may be selected. For example, the porous substrate may include at least one of a porous polyolefin resin film (e.g., at least one of polyethylene, polypropylene, and polyvinylidene fluoride), a porous glass fiber, and a porous nonwoven fabric. The porous substrate may be a single-layer film or a multi-layer composite film. When the porous substrate is a multi-layer composite film, the materials of the layers may be the same or different.

[0091] In some embodiments, the coating layer may include a three-dimensional skeletal structure and a filler, the three-dimensional skeletal structure including the fibrous material, and at least a portion of the filler being filled in the three-dimensional skeletal structure. The term "three-dimensional skeletal structure" generally refers to a structure having a three-dimensional spatial shape and a certain amount of voids, and may be formed by overlapping fibrous materials with each other.

[0092] The filling of at least a portion of the filler into the three-dimensional skeletal structure contributes to the formation of a nesting effect between the filler and the three-dimensional skeletal structure, thereby improving the heat resistance of the separator, reducing the degree of shrinkage of the separator when exposed to heat, reducing the risk of short-circuiting between the positive and negative electrodes, providing high thermal stability for the secondary battery, maintaining high adhesive strength between the coating layer and the porous substrate, and reducing the probability of filler detachment during long-term charge and discharge of the secondary battery. At the same time, the filling of at least a portion of the filler into the three-dimensional skeletal structure further increases the contact points between the filler and the three-dimensional skeletal structure, thereby reducing the amount of binder used in the coating layer and effectively reducing the risk of binder blocking pores, thereby further improving the cycle performance and dynamic performance of the secondary battery.

[0093] In some embodiments, at least a portion of the filler may be filled into the three-dimensional skeletal structure, and another portion of the filler may be located on the surface of the three-dimensional skeletal structure and / or at the interface between the three-dimensional skeletal structure and the porous substrate. At the interface between the three-dimensional skeletal structure and the porous substrate, at least a portion of the filler may be embedded in the porous substrate. For example, during the winding process of the electrode assembly, at least a portion of the filler at the interface may be embedded in the matrix and / or pores of the porous substrate under the action of external pressure.

[0094] In some embodiments, the average diameter of the fibrous material is D, and D may be 15 nm or more, preferably 15 nm-42 nm, 15 nm-40 nm, 15 nm-38 nm, 15 nm-35 nm, 18 nm-40 nm, 18 nm-38 nm, 18 nm-35 nm, 20 nm-40 nm, 20 nm-38 nm, or 20 nm-35 nm. When the average diameter of the fibrous material is within the above range, the fibrous material is inserted into the pores of the porous substrate, and after the porous substrate is melted by heat, the melted porous substrate flows along the fibrous material into the coating layer due to the capillary effect, forming a membrane layer integrated with the separator, reducing the probability of internal short circuit caused by direct contact between the positive electrode and the negative electrode, reducing the degree of thermal runaway of the secondary battery, and ultimately preventing the occurrence of thermal runaway of the secondary battery, thereby effectively reducing safety accidents such as fire and explosion of the secondary battery. Furthermore, when the average diameter of the fibrous material is within the above range, the ionic conductivity and voltage breakdown characteristics of the separator are further improved, and the overlap between the fibrous material and the filler, etc. contributes to forming an integration effect, thereby further improving the heat resistance of the separator.

[0095] In some embodiments, the average length of the fibrous material is L, which may be 100 nm to 600 nm, preferably 200 nm to 500 nm. When the average length of the fibrous material is within this range, the heat resistance and ionic conductivity of the separator can be further improved. Furthermore, the following situations can be effectively avoided: if the average length of the fibrous material is too short, the overlap effect with the filler, etc. will be poor, resulting in poor heat resistance of the coating layer. Furthermore, during the drying process of the coating layer, the three-dimensional framework structure will be prone to collapse due to the lack of support from the filler, which will likely cause pore clogging problems, inhibit ion transport and moisture discharge, and potentially affect the thermal stability, cycle performance, and dynamic performance of the secondary battery. If the average length of the fibrous material is too long, the viscosity of the coating layer slurry will be high and the flow will be poor, which will affect the application of the coating layer slurry and further affect the quality of the coating layer, such as the heat resistance and ionic conductivity of the separator.

[0096] In some embodiments, the aspect ratio of the fibrous material, L / D, may be 3-40, preferably 4-38, 5-35, 5-32, or 6-30. When the aspect ratio of the fibrous material is within the above range, the ionic conductivity and the electrolyte impregnation and retention properties of the separator can be further improved. Furthermore, the following problems can be effectively avoided: If the aspect ratio of the fibrous material is too small, the overlap effect with the filler will be poor, resulting in poor heat resistance of the coating layer. Furthermore, during the drying process of the coating layer, the three-dimensional framework structure will be prone to collapse due to the lack of support from the filler, and pore clogging will be more likely to occur, hindering ion transport and moisture discharge, which may affect the thermal stability, cycle performance, and dynamic performance of the secondary battery. If the aspect ratio of the fibrous material is too large, the pores in the three-dimensional framework structure formed will be small, which may result in low ionic conductivity of the separator.

[0097] By adjusting the average diameter and / or average length of the nanocellulose, the depth to which the fibrous material is embedded in the pores of the porous substrate can be adjusted, and the included angle between the fibrous material and the thickness direction of the porous substrate can be adjusted within an appropriate range. For example, the included angle may be greater than or equal to 0° and less than 90°, preferably 30°-80°.

[0098] The average length and average diameter of the fibrous objects can be measured by the following method. A 3.6 mm × 3.6 mm sample is cut from any one area of ​​the separator, and the microtopography structure of the coating layer in the sample is measured using a scanning electron microscope (e.g., ZEISS Sigma 300) in high vacuum mode with an operating voltage of 3 kV and a magnification of 30,000 times to obtain an SEM image. Based on the obtained SEM image, multiple measurement areas (e.g., five or more) are selected and length statistics are performed, with each measurement area measuring 0.5 μm × 0.5 μm. The average value of the average lengths obtained in each measurement area is then used as the average length of the fibrous objects. Based on the obtained SEM image, multiple measurement areas (e.g., five or more) are selected and diameter statistics are performed using Nano Measurer particle size distribution statistical software, with each measurement area measuring 0.5 μm × 0.5 μm. The average value of the average diameters obtained in each measurement area is then used as the average diameter of the fibrous objects.

[0099] In some embodiments, the fibrous matter can include at least one of an organic material and an inorganic material.

[0100] Preferably, the organic material comprises at least one of nanocellulose, polytetrafluoroethylene nanofibers, and polyamide nanofibers.

[0101] Preferably, the inorganic material comprises at least one of halloysite nanotubes, alumina nanorods, boehmite nanorods, silica nanorods, and glass fibers.

[0102] In some embodiments, the fibrous material can comprise nanocellulose, preferably at least one of cellulose nanofibers (Cellulose nanofibrils, CNF, also known as nanofibril cellulose or microfibril cellulose), cellulose nanowhiskers (Cellulose nanocrystals, CNC, also known as cellulose nanocrystals or nanocrystalline cellulose), and bacterial nanocellulose (Bacterial nanocellulose, BNC, also known as bacterial cellulose or microbial cellulose).

[0103] Nanocellulose is a general term for cellulose in the nano-order (e.g., within 100 nm) in any dimension, possessing both the properties of cellulose and nanoparticles. Nanocellulose can be a polymeric nanomaterial extracted from natural sources such as wood or cotton by one or more methods, including chemical, physical, and biological methods. It offers advantages such as a wide range of sources, low cost, high biodegradability, high elastic modulus, and high specific surface area, making it an excellent alternative to traditional petroleum resources and effectively alleviating issues such as environmental pollution and the shortage of petroleum resources. Nanocellulose has excellent high-temperature resistance and small volume change after heating, thereby improving the heat resistance of separators. At the same time, its lower density compared to conventional inorganic ceramic particles reduces the weight of secondary batteries and improves their weight-to-weight energy density. Furthermore, the three-dimensional framework structure of nanocellulose may have tiny nanopores, which prevent current leakage, allowing separators to achieve both good electrolyte impregnation and retention properties and good voltage breakdown resistance.

[0104] In some embodiments, the nanocellulose comprises at least one of unmodified nanocellulose (also called hydroxy nanocellulose) and modified nanocellulose, preferably modified nanocellulose.

[0105] Modified nanocellulose refers to nanocellulose that includes modifying groups in addition to hydroxy groups. In some embodiments, the modified nanocellulose includes modifying groups, and the modifying groups may include at least one of an amine group, a carboxyl group, an aldehyde group, a sulfonic acid group, a boric acid group, and a phosphate group, or may include at least one of a sulfonic acid group, a boric acid group, and a phosphate group.

[0106] When nanocellulose has the above-mentioned specific modified groups, it can effectively improve the heat resistance of the separator, improving the thermal stability of the secondary battery, while also improving the adhesive strength between the coating layer and the porous substrate. When nanocellulose has the above-mentioned specific modified groups, it is also advantageous to form an integrated effect through overlapping between the nanocellulose and the filler, which results in a more stable spatial network structure for the coating layer, improving the separator's electrolyte impregnation and retention properties, and improving the separator's ionic conductivity and voltage breakdown characteristics. Furthermore, the presence of the modified groups also reduces the proportion of hydroxy groups, which can impart an appropriate viscosity to the coating layer slurry, making it easier to apply, further improving separator production efficiency and coating layer uniformity.

[0107] In some embodiments, the molar ratio of the modifying group to the hydroxy groups may be 1:4-4:1, preferably 2:3-7:3. When the molar ratio of the modifying group to the hydroxy groups is within this range, the heat resistance, ionic conductivity, and electrolyte impregnation and retention properties of the separator can be further improved, thereby improving the thermal stability, cycle performance, and dynamic performance of the secondary battery. Furthermore, the following situation can be effectively avoided: If the molar ratio of the modifying group to the hydroxy groups is too small, the further improvement effect of the modifying group on the heat resistance and ionic conductivity of the separator may be insignificant. If the molar ratio of the modifying group to the hydroxy groups is too large, the separator's electrolyte impregnation and retention properties may be poor, which may affect the cycle performance and reliability of the secondary battery, as well as the heat resistance of the separator, which may affect the improvement effect on the thermal stability of the secondary battery.

[0108] The type of modifying group in nanocellulose can be determined by infrared spectroscopy. For example, the type of modifying group can be determined by measuring the infrared spectrum of the material and determining the characteristic peaks contained therein. Specifically, infrared spectroscopy of the material can be performed using equipment and methods known in the art. For example, infrared spectroscopy can be performed using an infrared spectrometer (e.g., an IS10 Fourier transform infrared spectrometer manufactured by Nicolet, USA) in accordance with GB / T 6040-2019 General Rules for Infrared Spectroscopy.

[0109] In some embodiments, the fibrous material may contain sulfonic acid groups, and the content of sulfur element in the fibrous material is 0.1 wt% or more, preferably 0.2 wt%-0.5 wt%, based on the total weight of the fibrous material. Preferably, the fibrous material comprises nanocellulose.

[0110] The sulfur content of the fibrous material can be measured by drying the fibrous material, grinding it in a mortar (e.g., an agate mortar) for 30 minutes, and then measuring the sulfur content using an X-ray diffractometer (e.g., a Miniflex 600-C). During the measurement, a Cu target, a Ni filter, a tube voltage of 40 kV, and a tube current of 15 mA were used, and the angle was continuously scanned from 5° to 80°.

[0111] In some embodiments, when the average length of the fibrous material is L (unit: nm) and the volume distribution particle size Dv50 of the filler is A (unit: nm), L≧(A×√2) / 8.

[0112] Adjusting L≧(A×√2) / 8 is advantageous in forming an integrated effect due to the overlap between the fibrous material and the filler, and further improving the heat resistance, ionic conductivity, and electrolyte impregnation and retention properties of the separator, thereby improving the thermal stability, cycle performance, and dynamic performance of the secondary battery.

[0113] In some embodiments, when the volume distribution particle size Dv50 of the filler is A, it is 70 nm≦A≦250 nm, preferably 80 nm≦A≦220 nm, or 100 nm≦A≦200 nm.

[0114] The volume distribution particle size Dv50 of the filler has a meaning known in the art and can be measured using instruments and methods known in the art, for example, GB / T19077-2016, and can be tested using a laser particle size analyzer (e.g., Master Size 3000).

[0115] In some embodiments, the filler may include at least one of primary particles and secondary particles, and preferably includes secondary particles or a combination of primary and secondary particles. Fillers in the form of secondary particles can better overlap with the three-dimensional framework to form an integrated effect, thereby allowing the coating layer to have a more stable spatial network structure, further improving the heat resistance of the separator. Fillers in the form of primary particles can reduce the moisture content of the coating layer and improve the ionic conductivity of the coating layer, thereby contributing to improved cycle performance of the secondary battery.

[0116] In some embodiments, the filler may include a combination of primary particles and secondary particles, and the content of the filler in the form of primary particles is less than the content of the filler in the form of secondary particles, based on the total weight of the filler.

[0117] In some embodiments, the filler may include a combination of primary particles and secondary particles, and based on the total weight of the filler, the content of the filler in the form of primary particles may be 30 wt % or less.

[0118] In some embodiments, the filler may include at least one of inorganic particles and organic particles, preferably inorganic particles or a combination of inorganic and organic particles. Inorganic particles have high hardness, high thermal stability, and resistance to decomposition. Their surfaces typically contain hydroxyl groups, which facilitate the formation of a stable spatial network structure with fibrous materials (e.g., nanocellulose). Organic particles have excellent thermal stability and resistance to decomposition. When the internal temperature of a secondary battery reaches its melting point due to overcharging or overheating, the organic particles melt, acting as pore sealants and blocking agents, which is advantageous for improving the reliability of the secondary battery.

[0119] In some embodiments, the inorganic particles can include at least one 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 capable of electrochemical reactions.

[0120] Preferably, the inorganic particles having a dielectric constant of 5 or more are selected from the group consisting of 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 )O3-PbTiO3 (abbreviated as PMN-PT), and at least one of the modified inorganic particles. Preferably, the inorganic particles are modified by chemical and / or physical methods. The chemical modification methods include coupling agent modification (e.g., silane coupling agents, titanate coupling agents, etc.), surfactant modification, and polymer graft modification. The physical modification methods include mechanical force dispersion, ultrasonic dispersion, and high-energy treatment. The modification treatment can reduce the aggregation of the inorganic particles, thereby providing a more stable and uniform spatial network structure for the coating layer. Furthermore, modifying the inorganic particles by selecting a coupling agent, surfactant, or polymer with a specific functional group can improve the impregnation and retention properties of the coating layer and the adhesion of the coating layer to the porous substrate.

[0121] Preferably, the inorganic particles having ion conductivity but not storing ions are Li3PO4, lithium titanium phosphate Li x1 Ti y1 (PO4)3, lithium aluminum titanium 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 and 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 ion conductivity of the separator can be further improved.

[0122] Preferably, the electrochemically reactive inorganic particles may include at least one of lithium-containing transition metal oxides, lithium-containing phosphates, carbon-based materials, silicon-based materials, tin-based materials, and lithium titanium compounds.

[0123] In some embodiments, the organic particles include, but are not limited to, at least one of polystyrene particles, polyacrylic wax particles, polyethylene particles, polypropylene particles, cellulose, a cellulose modifier (e.g., carboxymethyl cellulose), melamine resin particles, phenolic resin particles, polyester particles (e.g., polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate), silicone resin particles, polyimide particles, polyamideimide particles, polyaramid particles, polyphenylene sulfide particles, polysulfone particles, polyethersulfone particles, polyetheretherketone particles, polyaryletherketone particles, and a copolymer of butyl acrylate and ethyl methacrylate (e.g., a crosslinked polymer of butyl acrylate and ethyl methacrylate).

[0124] In some embodiments, the filler may include inorganic particles in a secondary particle form, and the crystalline form of the inorganic particles in the secondary particle form may include at least one of a θ crystalline form, a γ crystalline form, and an η crystalline form. Preferably, the crystalline form of the inorganic particles in the secondary particle form may include at least one of a θ crystalline form and a γ crystalline form.

[0125] In some embodiments, the content of the inorganic particles in the form of secondary particles of the θ crystal form in the filler may be 50 wt% or more, preferably 55 wt%-84 wt%, based on the total weight of the inorganic particles in the form of secondary particles in the filler.

[0126] In some embodiments, the content of the inorganic particles in the form of secondary particles of the gamma crystal form in the filler may be 10 wt% or more, preferably 15 wt%-44 wt%, based on the total weight of the inorganic particles in the form of secondary particles in the filler.

[0127] In some embodiments, the content of the inorganic particles in the form of secondary particles of the η crystal form in the filler may be 5 wt % or less, preferably 2.5 wt % or less, and more preferably 1.5 wt % or less, based on the total weight of the inorganic particles in the form of secondary particles in the filler.

[0128] Inorganic particles with a θ crystal structure have a suitable specific surface area and hardness, and can therefore simultaneously improve the heat resistance and ionic conductivity of the separator, while inorganic particles with a γ crystal structure and an η crystal structure have the advantage of a large specific surface area.

[0129] Selection of a filler with a different crystal form contributes to improving at least one of the heat resistance, ionic conductivity, adhesive strength, and electrolyte impregnation and retention properties of the separator.

[0130] In some embodiments, the filler may comprise inorganic particles in secondary particle form, and the crystalline forms of the inorganic particles in secondary particle form may include θ crystalline form, γ crystalline form, and η crystalline form, and the content of the inorganic particles in secondary particle form of θ crystalline form in the filler may be 55 wt%-84 wt%, the content of the inorganic particles in secondary particle form of γ crystalline form may be 15 wt%-44 wt%, and the content of the inorganic particles in secondary particle form of η crystalline form may be 2.5 wt% or less, all based on the total weight of the inorganic particles in secondary particle form in the filler.

[0131] In some embodiments, inorganic particles in the form of secondary particles can be produced by a method in which a precursor solution of inorganic particles is oxidized by high-pressure sputtering, then heated at 600°C-1200°C (e.g., for 1 hour-3 hours) to form inorganic particles in the form of primary particles, and then dried and molded at 150°C-250°C (e.g., for 30 minutes-60 minutes) to obtain inorganic particles in the form of secondary particles (obtained by assembly of the primary particles).

[0132] In some embodiments, the filler may comprise inorganic particles in the form of primary particles, and the crystalline form of the inorganic particles in the form of primary particles may comprise at least one of an α-crystalline form and a γ-crystalline form, preferably an α-crystalline form. The α-crystalline form of the filler has advantages such as high hardness, good heat resistance, low dielectric constant, high safety, and high true density, which can further improve the heat resistance of the coating layer.

[0133] In some embodiments, the filler may comprise inorganic particles in the form of primary particles, and the crystalline form of the inorganic particles in the form of primary particles may comprise an α crystalline form, and the content of the α crystalline form is 70 wt% or more, preferably 75 wt%-100 wt%, 85 wt%-100 wt%, or 95 wt%-100 wt%, based on the total weight of the inorganic particles in the form of primary particles in the filler.

[0134] In the X-ray diffraction spectrum measured using an X-ray diffractometer, the θ-crystalline inorganic particles have diffraction peaks at 2θ of 36.68°±0.2° and 31.21°±0.2°. In the X-ray diffraction spectrum measured using an X-ray diffractometer, the γ-crystalline inorganic particles have diffraction peaks at 2θ of 66.95°±0.2° and 45.91°±0.2°. In the X-ray diffraction pattern measured using an X-ray diffractometer, the η-crystalline inorganic particles have diffraction peaks at 2θ of 31.89°±0.2° and 19.37°±0.2°. In the X-ray diffraction spectrum measured using an X-ray diffractometer, the α-crystalline inorganic particles have diffraction peaks at 2θ of 57.48°±0.2° and 43.34°±0.2°.

[0135] The X-ray diffraction spectrum of inorganic particles is obtained by drying the inorganic particles, grinding them in a mortar (e.g., an agate mortar) for 30 minutes, and then measuring them using an X-ray diffractometer (e.g., a Miniflex 600-C) to obtain an X-ray diffraction spectrum. During measurement, a Cu target, Ni filter, tube voltage of 40 kV, and tube current of 15 mA are used, and continuous scanning is possible in the range of 5°–80°.

[0136] In some embodiments, the content of the three-dimensional framework structure may be 5 wt%-40 wt%, preferably 8 wt%-30 wt%, 10 wt%-25 wt%, based on the total weight of the coating layer.

[0137] In some embodiments, the filler content may be greater than 60 wt%, preferably 65 wt%-90 wt%, 70 wt%-88 wt%, based on the total weight of the coating layer.

[0138] When the content of the three-dimensional skeletal structure is within the above range, the slurry of the coating layer can have an appropriate viscosity, which is advantageous for application, and is also advantageous for forming an integrated effect due to the overlap of the three-dimensional skeletal structure and the filler. This allows the coating layer to have a more stable spatial network structure, thereby further improving the heat resistance, ion conductivity, electrolyte impregnation and retention properties, and voltage breakdown capability of the separator.

[0139] In some embodiments, the coating layer may further include a non-particulate binder. In the present application, the type of non-particulate binder is not particularly limited, and any known material with good adhesive properties may be used. Preferably, the non-particulate binder may include an aqueous binder, which has the advantages of good thermodynamic stability and environmental friendliness, making it convenient for preparing and applying a coating layer slurry. For example, the aqueous binder may include at least one of an aqueous acrylic resin (e.g., a homopolymer of acrylic acid, methacrylic acid, or sodium acrylate monomer or a copolymer with other copolymerizable monomers), polyvinyl alcohol (PVA), isobutylene-maleic anhydride copolymer, and polyacrylamide.

[0140] In some embodiments, the content of the non-particulate binder in the coating layer may be 2 wt % or less based on the total weight of the coating layer, and the three-dimensional skeletal structure in the coating layer and the filler or the like can form a stable spatial network structure, thereby reducing the amount of binder used while maintaining high adhesion to the separator.

[0141] In some embodiments, the thickness of the coating layer may be 2 μm or less, preferably 0.5 μm-1.5 μm, which contributes to improving the energy density of the secondary battery. The thickness of the coating layer refers to the thickness of the coating layer located on one side of the porous substrate.

[0142] In some embodiments, the separator may further include an adhesive layer, the adhesive layer may be provided on at least a portion of the surface of the coating layer, and the adhesive layer may include a particulate binder. The adhesive layer not only prevents the coating layer from falling off and improves the reliability of the secondary battery, but also improves the interface between the separator and the electrodes, contributing to improving the cycle performance of the secondary battery.

[0143] Preferably, the particulate binder may contain at least one of an acrylic acid ester-based monomer homopolymer or copolymer, an acrylic acid-based monomer homopolymer or copolymer, and a fluorine-containing olefin monomer homopolymer or copolymer. The copolymerizable monomer includes at least one of an acrylic acid ester-based monomer, an acrylic acid-based monomer, an olefin monomer, a halogen-containing olefin monomer, a fluoroether-based monomer, and the like, but is not limited thereto.

[0144] Preferably, the particulate binder may comprise a vinylidene fluoride polymer, such as a homopolymer of vinylidene fluoride monomer (VDF) and / or a copolymer of vinylidene fluoride monomer and a copolymerizable monomer. The copolymerizable monomer may be at least one of an olefin monomer, a fluorine-containing olefin monomer, a chlorine-containing olefin monomer, an acrylic acid ester monomer, an acrylic monomer, and a fluoroether monomer. Preferably, the copolymerizable monomer may comprise at least one of trifluoroethylene (VF3), chlorotrifluoroethylene (CTFE), 1,2-difluoroethylene, tetrafluoroethylene (TFE), hexafluoropropylene (HFP), perfluoro(alkyl vinyl) ethers (e.g., perfluoro(methyl vinyl) ether PMVE, perfluoro(ethyl vinyl) ether PEVE, and perfluoro(propyl vinyl) ether PPVE), perfluoro(1,3-m-dioxole), and perfluoro(2,2-dimethyl-1,3-m-dioxole) (PDD).

[0145] In some embodiments, the separator may have a longitudinal heat shrinkage of 4% or less at 150° C. for 1 hour, preferably 0.5%-3%.

[0146] In some embodiments, the separator may have a transverse heat shrinkage of 4% or less at 150° C. for 1 hour, preferably 0.5%-3%.

[0147] The separator has a low thermal shrinkage rate in both the transverse and longitudinal directions at a high temperature of 150° C., thereby improving the reliability of the secondary battery.

[0148] In some embodiments, the separator has a longitudinal tensile strength of 2200 kg / cm 2 or more, preferably 2500 kg / cm 2 -4500kg / cm 2 is.

[0149] In some embodiments, the separator has a transverse tensile strength of 2200 kg / cm 2 or more, preferably 2500 kg / cm 2 -4500kg / cm 2 is.

[0150] Since the separator has high tensile strength in both the transverse and longitudinal directions, the probability of the separator being damaged when the secondary battery expands is low, and the reliability of the secondary battery can be improved.

[0151] In some embodiments, the separator has a wetted length of 35 mm or more, preferably 40 mm-80 mm.

[0152] In some embodiments, the separator wetting rate is 4 mm / s or greater, preferably 4.5 mm / s-10 mm / s.

[0153] When the separator has good electrolyte impregnation and retention properties, the ion conductivity of the separator and the capacity development properties of the secondary battery can be improved.

[0154] In some embodiments, the separator has an air permeability of 300 s / 100 mL or less, preferably 100 s / 100 mL to 270 s / 100 mL. The separator has good gas permeability, which can improve the ion conductivity and the capacity development characteristics of the secondary battery.

[0155] The heat shrinkage rate, tensile strength, and air permeability of the separator all have meanings known in the art and can be measured by methods known in the art, for example, by referring to GB / T36363-2018.

[0156] The separator wetting length and wetting rate are both known in the art and can be measured using methods known in the art. An exemplary measurement method involves cutting a separator into a 5 mm wide, 100 mm long sample, fixing both ends of the sample, and placing it horizontally. 0.5 mg of electrolyte is dropped onto the center of the sample. After a predetermined time (1 min in this application), the sample is photographed and the length of diffusion of the electrolyte is measured to obtain the separator wetting length and wetting rate. To ensure accuracy of the test results, multiple samples (e.g., 5-10 samples) are tested and averaged. The electrolyte is prepared by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a mass ratio of 30:50:20 to obtain an organic solvent. Thoroughly dried LiPF6 is dissolved in the organic solvent to prepare an electrolyte solution with a concentration of 1 mol / L.

[0157] The parameters of the coating layer of the separator (e.g., thickness, etc.) are all parameters of the coating layer on one side of the porous substrate. When coating layers are provided on both sides of the porous substrate, it is considered that the parameters of the coating layer on either side satisfy the present application and fall within the scope of protection of the present application. Manufacturing method

[0158] A second aspect of an embodiment of the present application provides a method for manufacturing the separator of the first aspect of an embodiment of the present application, the method comprising the steps of: providing a porous substrate; mixing fibrous material and an optional filler in a solvent in a predetermined ratio to prepare a coating layer slurry; and applying the coating layer slurry to at least one surface of the porous substrate and drying to obtain a separator, wherein the separator comprises a porous substrate and a coating layer provided on at least one surface of the porous substrate, the coating layer comprising fibrous material, at least a portion of which is embedded in the pores of the porous substrate.

[0159] In some embodiments, the linear dispersion velocity of the coating slurry can be 8 m / s-22 m / s, preferably 10 m / s-19 m / s, 12 m / s-18 m / s. By adjusting the linear dispersion velocity of the coating slurry, the depth to which the fibrous material is embedded in the pores of the porous substrate can be adjusted, and the included angle between the fibrous material and the thickness direction of the porous substrate can also be adjusted within a suitable range, for example, the included angle can be greater than or equal to 0° and less than 90°, preferably 30°-80°.

[0160] In some embodiments, the coating layer slurry application speed can be 30 m / min-140 m / min, preferably 90 m / min-130 m / min. By adjusting the coating layer slurry application speed, the depth to which the fibrous material is embedded in the pores of the porous substrate can be adjusted, and the included angle between the fibrous material and the thickness direction of the porous substrate can also be adjusted within a suitable range, for example, the included angle can be greater than or equal to 0° and less than 90°, preferably 30°-80°.

[0161] In some embodiments, the drying temperature of the coating layer slurry may be 50° C.-80° C., preferably 52° C.-75° C., 55° C.-70° C. By adjusting the drying temperature of the coating layer slurry, the depth to which the fibrous material is embedded in the pores of the porous substrate can be adjusted, and the included angle between the fibrous material and the thickness direction of the porous substrate can also be adjusted within a suitable range, for example, the included angle may be greater than or equal to 0° and less than 90°, preferably 30°-80°.

[0162] In some embodiments, the total drying time of the coating layer slurry can be 3 s-11 s, preferably 5 s-10 s. By adjusting the total drying time of the coating layer slurry, the depth to which the fibrous material is embedded in the pores of the porous substrate can be adjusted, and the included angle between the fibrous material and the thickness direction of the porous substrate can also be adjusted within a suitable range, for example, the included angle can be greater than or equal to 0° and less than 90°, preferably 30°-80°.

[0163] In some embodiments, the drying is performed using a multi-stage oven, and the number of stages of the oven is preferably 3 to 6, more preferably 4 to 5. By adjusting the number of stages of the oven, the depth to which the fibrous material is embedded in the pores of the porous substrate can be adjusted, and the included angle between the fibrous material and the thickness direction of the porous substrate can also be adjusted within an appropriate range, for example, the included angle can be greater than or equal to 0° and less than 90°, and is preferably 30° to 80°.

[0164] In some embodiments, the drying is performed using a multi-stage oven, and the temperature of the first stage oven can be greater than 50° C., preferably greater than 55° C. By adjusting the temperature of the first stage oven, the depth to which the fibrous material is embedded in the pores of the porous substrate can be adjusted, and the included angle between the fibrous material and the thickness direction of the porous substrate can also be adjusted within a suitable range, for example, the included angle can be greater than 0° and less than 90°, preferably 30°-80°.

[0165] In some embodiments, a multi-stage oven is used for drying, and the drying time of the first oven may be less than 4 seconds, preferably less than 3.5 seconds. By adjusting the drying time of the first oven, the depth to which the fibrous material is embedded in the pores of the porous substrate can be adjusted, and the included angle between the fibrous material and the thickness direction of the porous substrate can also be adjusted within a suitable range, for example, the included angle may be greater than or equal to 0° and less than 90°, preferably 30°-80°.

[0166] In some examples, the solvent used in preparing the coating layer slurry may be water, for example, deionized water.

[0167] In some embodiments, the coating layer slurry may further include other ingredients, such as dispersants, wetting agents, binders, surfactants, and the like.

[0168] In some embodiments, the fibrous material may comprise at least one of an organic material and an inorganic material. Preferably, the organic material may comprise at least one of nanocellulose, polytetrafluoroethylene nanofibers, and polyamide nanofibers. Preferably, the inorganic material may comprise at least one of halloysite nanotubes, alumina nanorods, boehmite nanorods, silica nanorods, and glass fibers.

[0169] In some embodiments, the fibrous material can include nanocellulose.

[0170] In some embodiments, nanocellulose can be obtained by providing a cellulose powder with a whiteness of ≥ 80%, mixing the resulting cellulose powder with a modifying solution to react, washing to remove impurities, adjusting the pH to neutral, grinding, and cutting to obtain nanocellulose.

[0171] Preferably, the cellulose powder having a whiteness of 80% or greater may be commercially available or may be obtained by employing a chemical method (e.g., acid decomposition, alkali treatment, Tempo catalytic oxidation), a biological method (e.g., enzyme treatment), a mechanical method (e.g., ultrafine grinding, ultrasonic crushing, high-pressure homogenization), etc. The fiber raw material for producing the cellulose powder having a whiteness of 80% or greater may include at least one of plant fibers such as cotton fiber (e.g., cotton fiber, kapok fiber), hemp fiber (e.g., sisal fiber, ramie fiber, jute fiber, flax fiber, hemp fiber, Manila fiber, etc.), palm fiber, wood fiber, bamboo fiber, and grass fiber.

[0172] In some embodiments, the cellulose powder having a whiteness of 80% or greater can also be produced by opening a fiber raw material, removing debris, and then cooking the raw material in an alkaline solution (for example, an aqueous NaOH solution, the concentration of which may be 4 wt%-20 wt%, preferably 5 wt%-15 wt%), followed by washing with water to remove impurities (for example, washing with water 3-6 times), bleaching (for example, with sodium hypochlorite and / or hydrogen peroxide), pickling to remove impurities, washing with water to remove impurities, removing water, and flash drying, thereby obtaining a cellulose powder.

[0173] In some embodiments, the denaturing solution can be an acid solution (e.g., aqueous sulfuric acid solution, aqueous boric acid solution, aqueous phosphoric acid solution, aqueous acetic acid solution) or an alkaline solution (e.g., organic solvent solution of urea). Preferably, the denaturing solution is an acid solution.

[0174] Preferably, the concentration of the acid solution may be 5 wt%-80 wt%. When a sulfuric acid aqueous solution is used as the modifying solution, a cellulose powder having sulfonic acid groups can be obtained by adjusting the concentration of the acid solution to 40 wt%-80 wt%. When a boric acid aqueous solution is used as the modifying solution, a cellulose powder having boric acid groups can be obtained by adjusting the concentration of the acid solution to 5 wt%-10 wt%. When a phosphoric acid aqueous solution is used as the modifying solution, a cellulose powder having phosphate groups can be obtained by adjusting the concentration of the acid solution to 45 wt%-75 wt%. When an acetic acid aqueous solution is used as the modifying solution, a cellulose powder having carboxylic acid groups can be obtained by adjusting the concentration of the acid solution to 40 wt%-80 wt%.

[0175] Preferably, the urea organic solvent solution is converted into a urea xylene solution, whereby a cellulose powder having an amine group can be obtained.

[0176] In some embodiments, the weight ratio of cellulose powder to modification solution may be 1:2.5-1:50, preferably 1:5-1:30.

[0177] When the modifying solution is a sulfuric acid aqueous solution, the mass ratio of the cellulose powder to the acid solution may be 1:5-1:30. When the modifying solution is a boric acid aqueous solution, the mass ratio of the cellulose powder to the acid solution may be 1:20-1:50. When the modifying solution is a phosphoric acid aqueous solution, the mass ratio of the cellulose powder to the acid solution may be 1:5-1:30. When the modifying solution is an acetic acid aqueous solution, the mass ratio of the cellulose powder to the acid solution may be 1:5-1:30. When the modifying solution is a urea organic solvent solution, the mass ratio of the cellulose powder to the urea organic solvent solution may be 1:4-1:40.

[0178] In some embodiments, when the modifying solution is an acid solution, the reaction can be carried out under conditions of 80°C or less, preferably under conditions of 30°C-60°C, and the reaction time between the cellulose powder and the modifying solution can be 0.5h-4h, preferably 1h-3h.

[0179] In some embodiments, when the modifying solution is an alkaline solution, the reaction may be carried out under conditions of 100°C-145°C, and the reaction time between the cellulose powder and the modifying solution may be 1 hour-5 hours.

[0180] In some embodiments, grinding may be performed using a grinder, and cutting may be performed using a high-pressure homogenizer. By adjusting the grinding parameters of the grinder (e.g., grinding frequency, grinding time, etc.) and the cutting parameters of the high-pressure homogenizer, nanocellulose having different average diameters and / or different average lengths can be obtained.

[0181] In some embodiments, a coating machine may be used to apply the slurry for the coating layer. In the present application, the model number of the coating machine is not particularly limited, and for example, a commercially available coating machine may be used. The coating machine may include a gravure roll for transferring the slurry to the porous substrate.

[0182] In some embodiments, the coating layer slurry may be applied by transfer coating, spin coating, dip coating, or the like.

[0183] In some embodiments, the manufacturing method may further include applying a slurry containing a particulate binder to at least a portion of the surface of the coating layer and drying the slurry to form an adhesive layer.

[0184] Parameters such as some raw materials used in the manufacturing method of the separator and their contents can be referenced in the separator according to the first aspect of the embodiment of the present application, but a description thereof will be omitted here.

[0185] Unless otherwise specified, each of the raw materials used in the method for producing the separator is commercially available. secondary battery

[0186] A third aspect of an embodiment of the present application provides a secondary battery.

[0187] 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. Typically, a secondary battery includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separator. The separator is disposed between the positive electrode sheet and the negative electrode sheet and serves to prevent short circuits between the positive electrode and the negative electrode while allowing active ions to pass through.

[0188] In the present application, the type of secondary battery is not particularly limited, and for example, the secondary battery may be a lithium ion battery, a sodium ion battery, a lithium metal battery, a sodium metal battery, etc., and in particular, the secondary battery may be a lithium ion battery.

[0189] A secondary battery according to a third embodiment of the present application includes a separator according to the first embodiment of the present application or a separator manufactured by the method according to the second embodiment of the present application, the separator being interposed between a positive electrode sheet and a negative electrode sheet. Preferably, at least the side of the separator closest to the negative electrode sheet has the coating layer according to the present application. This allows the secondary battery according to the examples of the present application to simultaneously achieve high energy density, high thermal stability, long cycle life, and good kinetic performance. [Positive electrode sheet]

[0190] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer including a positive electrode active material, the positive electrode current collector having two opposing surfaces in its thickness direction, and the positive electrode film layer being provided on one or both of the opposing surfaces of the positive electrode current collector.

[0191] 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 modified compounds thereof. Examples of lithium transition metal oxides 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 modified compounds thereof. Examples of lithium-containing phosphates include, but are not limited to, at least one of lithium iron phosphate, lithium iron phosphate and carbon composite, lithium manganese phosphate, lithium manganese phosphate and carbon composite, lithium manganese iron phosphate, lithium manganese iron phosphate and carbon composite, and modified compounds thereof.

[0192] In some embodiments, to further improve the energy density of the secondary battery, the positive electrode active material used in the lithium ion battery has the general formula Li aNi b Co c M d O e A f It may contain at least one of lithium transition metal oxides and their modified compounds that are as follows. 0.8 ≤ a ≤ 1.2, 0.5 ≤ b < 1, 0 < c < 1, 0 < d < 1, 1 ≤ e ≤ 2, 0 ≤ f ≤ 1, M is at least one selected from Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, and B, and A is at least one selected from N, F, S, and Cl.

[0193] For example, the cathode active material for a lithium-ion battery may contain at least one of 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 0.6 Co 0.2 Mn 0.2 O2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), LiNi 0.80 Co 0.15 Al 0.05 O2, LiFePO4, and LiMnPO4.

[0194] When the secondary battery is a sodium-ion battery, the cathode active material can contain at least one of sodium-containing transition metal oxides, polyanion materials (such as phosphates, fluorophosphates, pyrophosphates, sulfates, etc.), Prussian blue-based materials, but is not limited thereto.

[0195] For example, the cathode active material for a sodium-ion battery may contain at least one of NaFeO2, NaCoO2, NaCrO2, NaMnO2, NaNiO2, NaNi 1 / 2 Ti 1 / 2 O2, NaNi 1 / 2 Mn 1 / 2 O2, Na 2 / 3 Fe1 / 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 include at least one material of 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 + M' is a transition metal cation, preferably at least one of V, Ti, Mn, Fe, Co, Ni, Cu, and Zn; and Y is a halogen anion, preferably at least one of F, Cl, and Br.

[0196] The modified compounds of the above-mentioned positive electrode active materials are obtained by subjecting the positive electrode active material to doping modification and / or surface coating modification.

[0197] In some embodiments, the positive electrode film layer may further include a positive electrode conductive agent. In the present application, the type of the positive electrode conductive agent is not particularly limited, 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.

[0198] In some embodiments, the positive electrode film layer may preferably further include a positive electrode binder. In the present application, the type of the positive electrode binder is not particularly limited, and for example, the positive electrode binder 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 fluorine-containing acrylic ester resin.

[0199] 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 polymeric material base layer and a metal material layer formed on at least one surface of the polymeric material base layer. For example, the metal material may include at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. For example, the polymeric material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0200] The positive electrode film layer is typically formed by applying a positive electrode slurry to 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 binder, and any other components in a solvent and stirring the mixture uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP). [Negative electrode sheet]

[0201] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided 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 provided on one or both of the two facing surfaces of the negative electrode current collector.

[0202] 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, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may include at least one of silicon elemental, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material. The tin-based material may include at least one of tin elemental, tin oxide, and tin alloy material.

[0203] In some embodiments, the negative electrode film layer may further include a negative electrode conductive agent. In the present application, the type of the negative electrode conductive agent is not particularly limited, 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.

[0204] In some embodiments, the negative electrode film layer may preferably further include a negative electrode binder. In the present application, the type of the negative electrode binder is not particularly limited, and for example, the negative electrode binder may include at least one of styrene butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0205] In some embodiments, the negative electrode membrane layer may further preferably include other additives, such as thickeners, e.g., sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc.

[0206] 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 polymeric material base layer and a metal material layer formed on at least one surface of the polymeric material base layer. For example, the metal material may include at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. For example, the polymeric material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0207] The negative electrode film layer is typically formed by applying a negative electrode slurry to a negative electrode current collector, drying, and cold pressing. The negative electrode slurry is typically formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional auxiliary agents in a solvent and stirring the mixture uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0208] The negative electrode sheet does not exclude additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode sheet further includes a conductive undercoat layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode film layer and provided on the surface of the negative electrode current collector. In other embodiments, the negative electrode sheet described herein further includes a protective layer covering the surface of the negative electrode film layer. [Electrolyte]

[0209] During the charge and discharge process of the secondary battery, active ions are inserted and released back and forth between the positive electrode sheet and the negative electrode sheet, and the electrolyte serves to conduct the active ions between the positive electrode sheet and the negative electrode sheet. In this application, the type of electrolyte is not particularly limited and can be selected according to actual needs.

[0210] 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.

[0211] When the secondary battery is a lithium-ion battery, for example, the electrolyte salt may include at least one of lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium perchlorate (LiClO), lithium hexafluoroarsenate (LiAsF), lithium difluorosulfonylimide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium disoxalate borate (LiBOB), lithium difluorophosphate (LiPOF), lithium difluorodisoxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP), but is not limited thereto.

[0212] When the secondary battery is a sodium ion battery, for example, the electrolyte salt may include at least one of sodium hexafluorophosphate (NaPF), sodium tetrafluoroborate (NaBF), sodium perchlorate (NaClO), sodium hexafluoroarsenate (NaAsF), sodium difluorosulfonylimide (NaFSI), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), sodium trifluoromethanesulfonate (NaTFS), sodium difluorooxalyl borate (NaDFOB), sodium disoxalyl borate (NaBOB), sodium difluorophosphate (NaPOF), sodium difluorodisalyl phosphate (NaDFOP), and sodium tetrafluorooxalyl phosphate (NaTFOP), but is not limited thereto.

[0213] 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), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0214] In some embodiments, the electrolyte may preferably further include an additive. For example, the additive may include a negative electrode film-forming additive, a positive electrode film-forming additive, or an additive capable of improving certain performance of the battery, such as an additive that improves the overcharge performance of the battery, an additive that improves the high-temperature performance of the battery, or an additive that improves the low-temperature power performance of the battery.

[0215] In some embodiments, the positive electrode sheet, separator, and negative electrode sheet can be wound and / or stacked to form an electrode assembly.

[0216] In some embodiments, the secondary battery may include an outer casing, which is used to seal the electrode assembly and the electrolyte.

[0217] In some embodiments, the exterior of the secondary battery may be a hard case such as a hard plastic case, an aluminum case, or a steel case. The exterior of the secondary battery may be a soft pack, such as a soft pack bag. The material of the soft pack may be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0218] In the present application, the shape of the secondary battery is not particularly limited, and may be cylindrical, rectangular, or any other shape. Figure 1 shows a secondary battery 5 with a rectangular structure as an example.

[0219] In some embodiments, as shown in FIG. 2 , the exterior may include a case 51 and a cover plate 53. The case 51 includes a bottom plate and a side plate connected to the bottom plate, and the bottom plate and side plate together form a storage cavity. The case 51 has an opening communicating with the storage cavity, and the cover plate 53 covers the opening to close the storage cavity. The positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is packaged in the storage cavity. The electrode assembly 52 is impregnated with an electrolyte. The number of electrode assemblies 52 included in the secondary battery 5 may be one or more and can be adjusted as needed.

[0220] Methods for manufacturing secondary batteries are known. In some embodiments, a secondary battery can be formed by assembling a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte. For example, the positive electrode sheet, the separator, and the negative electrode sheet can be formed into an electrode assembly by a winding process or a lamination process, the electrode assembly can be placed in a housing, dried, and then an electrolyte can be injected. The secondary battery can be obtained by vacuum sealing, leaving it to stand, forming, shaping, and other steps.

[0221] In some embodiments of the present application, the secondary battery according to the present application may be assembled into a battery module, and the number of secondary batteries included in the battery module may be multiple, and the specific number may be adjusted according to the application and capacity of the battery module.

[0222] Fig. 3 is a schematic diagram of an example battery module 4. As shown in Fig. 3, in the battery module 4, the 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.

[0223] Preferably, the battery module 4 may further include a housing having an accommodating space for accommodating the plurality of secondary batteries 5.

[0224] In some embodiments, the battery modules may be assembled into a battery pack, and the number of battery modules included in the battery pack may be adjusted depending on the application and capacity of the battery pack.

[0225] 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 provided 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 to form an enclosed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner. power consumption equipment

[0226] A fourth aspect of an embodiment of the present application further provides a power consuming device including at least one of a secondary battery, a battery module, or a battery pack according to the embodiments 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 car, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.

[0227] A power consuming device can select a secondary battery, a battery module, or a battery pack according to its usage needs.

[0228] 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, which may employ a battery pack or battery module to meet the high power and high energy density requirements of the power consuming device.

[0229] Other examples of power consuming devices include mobile phones, tablet computers, laptop computers, etc. These power consuming devices are generally required to be thin and can use secondary batteries as their power source. Example

[0230] The following examples are provided to more specifically illustrate the disclosure of the present application, and are merely illustrative, since various modifications and variations within the scope of the disclosure of the present application will be apparent to those skilled in the art. Unless otherwise specified, all parts, percentages, and ratios described in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further treatment, and the equipment used in the examples is commercially available. Preparation of nanocellulose

[0231] The cotton linters were opened using a cotton opener to remove debris, and then digested in a 5 wt% NaOH aqueous solution at 150°C for 2 hours.Then, impurities were removed by washing with water (three times), bleached with sodium hypochlorite, impurities were removed by washing with dilute hydrochloric acid, impurities were removed by washing with water (one time), water was removed, and the cotton was dried with air flow, resulting in a cotton cellulose powder with a whiteness of ≥ 85%.

[0232] 1 kg of the obtained cotton cellulose powder was mixed with 30 kg of 60 wt% sulfuric acid aqueous solution and reacted at 55°C-60°C for 1.5 hours. After the reaction was completed, impurities were removed by washing with water (three times), filtered, acid was removed, and impurities were removed sequentially. The pH was adjusted to neutral with 10 wt% NaOH aqueous solution, and then polished with a polishing machine. The mixture was then cut into nanoscale pieces using a high-pressure homogenizer to obtain nanocellulose with sulfonic acid group-modified groups, and the molar ratio of sulfonic acid groups to surface hydroxyl groups was 5:3.

[0233] During the production process, nanocellulose with different average diameters and / or different average lengths can be obtained by adjusting the processing parameters of the grinder and the cutting parameters of the high-pressure homogenizer device.

[0234] The molar ratio of modifying groups to surface hydroxyl groups in nanocellulose can be measured using the phthalic anhydride method in GB / T12008.3-2009 to obtain the hydroxyl group values ​​(mg of potassium hydroxide equivalent to the hydroxyl group content per 1 g of sample) of the raw cellulose and nanocellulose, respectively, in units of mgKOH / g, which is then converted to mmol / g to obtain the hydroxyl group content. The modifying group content (i.e., the content of modified hydroxyl groups) is obtained by subtracting the hydroxyl group content of the nanocellulose from the hydroxyl group content of the raw cellulose, and the molar ratio of modifying groups to hydroxyl groups is then calculated. Example 1 Separator manufacturing

[0235] Thickness H2 is 6.5 μm, melting point T m A PE porous substrate having a melting point of 135.8°C and an average pore diameter V of 32 nm was provided.

[0236] Preparation of coating layer slurry: Secondary particles of aluminum oxide, nanocellulose shown in Table 1, and polyacrylic acid as a binder were uniformly mixed in a mass ratio of 75:23.5:1.5 in an appropriate amount of deionized water as a solvent to obtain a coating layer slurry.

[0237] Coating: The prepared coating layer slurry was applied to both sides of the PE porous substrate using a coater, and a separator was obtained through a drying and slitting step.

[0238] The linear dispersion velocity of the coating layer slurry, the application speed, and the setting parameters of the multi-stage oven are detailed in Table 1. Positive electrode sheet manufacturing

[0239] LiNi, the positive electrode active material 0.5 Co 0.2 Mn 0.3O2 (NCM523), carbon black (Super P) as a conductive agent, and polyvinylidene fluoride (PVDF) as a binder were uniformly mixed in a mass ratio of 96.2:2.7:1.1 with an appropriate amount of N-methylpyrrolidone (NMP) as a solvent to obtain a positive electrode slurry. The positive electrode slurry was then applied to aluminum foil as a positive electrode current collector, and a positive electrode sheet was obtained through processes such as drying, cold pressing, strip division, and cutting. Manufacture of negative electrode sheets

[0240] The negative electrode active material, artificial graphite, the conductive agent, carbon black (Super P), the binder, styrene butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC), were uniformly mixed in a mass ratio of 96.4:0.7:1.8:1.1 with an appropriate amount of deionized water as a solvent to obtain a negative electrode slurry. The negative electrode slurry was then applied to copper foil as a negative electrode current collector, followed by drying, cold pressing, stripe division, and cutting steps to obtain a negative electrode sheet. Electrolyte production

[0241] An electrolyte solution with a concentration of 1 mol / L was prepared by dissolving thoroughly dried LiPF6 in an organic solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a mass ratio of 30:70. Secondary battery manufacturing

[0242] The positive electrode sheet, separator, and negative electrode sheet are stacked in order and wound to obtain an electrode assembly. The electrode assembly is then placed in an outer aluminum plastic film. After drying, the electrolyte is injected, and the assembly goes through processes such as vacuum packaging, standing, chemical formation, and shaping to obtain a small soft-pack secondary battery with a capacity of 4240mAh. Examples 2-10 and Comparative Example 1

[0243] The secondary battery was manufactured in a manner similar to that of Example 1, except that the average length and / or average diameter of the nanocellulose used in the separator production was different, and the linear dispersion speed, coating speed, and / or setting parameters of the coating layer slurry were different. See Table 1 for specific parameters.

[0244] In Table 1, H1 is the depth to which the nanocellulose is embedded in the pores of the porous substrate, in μm, H2 is the thickness of the porous substrate, in Table 1, H2 is 6.5 μm, L is the average length of the nanocellulose, in nm, D is the average diameter of the nanocellulose, in nm, and V is the average pore size of the porous substrate, in Table 1, the average pore size V of the porous substrate corresponding to Examples 1-7 is 32 nm, and the average pore size V of the porous substrate corresponding to Examples 8-10 is 36 nm. These can be obtained based on the above test methods of the present application. Testing Department

[0245] (1) Separator heat shrinkage rate test Sample preparation: The separator prepared above was punched out into samples 50 mm wide and 100 mm long using a press, and five parallel samples were set and fixed on A4 paper. The A4 paper containing the samples was then set on cardboard with a thickness of 1 mm to 5 mm.

[0246] Sample test: Place an A4 sheet of paper on top of the cardboard in a ventilated oven, set the oven temperature to 150°C, and after the temperature reaches the set temperature and stabilizes for 30 minutes, start timing. After the set time (1 hour in this application) is reached, measure the length and width of the separator, and denote the values ​​as a and b respectively.

[0247] Calculation of heat shrinkage rate: Machine direction (MD) heat shrinkage rate = [(100-a) / 100] x 100%, the average value of five parallel samples is taken as the test result.

[0248] (2) Secondary battery heat box test At 25°C, the rechargeable batteries were charged at a constant current of 1C to 4.2V, then continued at a constant voltage until the current fell below 0.05C. After allowing to stand for 5 minutes, each rechargeable battery was measured using a jig in a DHG-9070A DHG series high-temperature oven. The temperature was increased from room temperature to 80°C ±2°C at a rate of 5°C / min and held for 30 minutes. The temperature was then increased at a rate of 5°C / min, with each 5°C interval maintained for 30 minutes. The surface temperature of the rechargeable battery was monitored during the heating process; the oven temperature at which the temperature began to rise rapidly was the battery's heat box expiration temperature. A higher heat box expiration temperature indicates better thermal stability. For accuracy, the average value of five parallel samples was used as the test result.

[0249] (3) Testing the cycle performance of secondary batteries At 25°C, the secondary battery was charged at a constant current of 1C to 4.2V, and then continued to be charged at a constant voltage until the current fell below 0.05C. At this point, the secondary battery was fully charged, and the charge capacity at this point, i.e., the first charge capacity, was recorded. After allowing the secondary battery to stand for 5 minutes, it was discharged at a constant current of 1C to 2.8V. This constitutes one cycle of charge / discharge, and the discharge capacity at this point, i.e., the first discharge capacity, was recorded. The secondary battery was subjected to a cycle charge / discharge test according to the above method, and the discharge capacity after one cycle was recorded. The capacity retention rate (%) of the secondary battery after 1000 cycles at 25°C = discharge capacity after 1000 cycles / first discharge capacity × 100%. For accuracy, the average value of five parallel samples was used as the test result.

[0250] As can be seen from Table 1, by providing a coating layer containing fibrous material on the surface of the porous substrate of the separator and setting the depth to which the fibrous material is embedded in the pores of the porous substrate to 0.02 μm or more, the heat box expiration temperature of the secondary battery is improved, the degree of thermal runaway of the secondary battery is reduced, and ultimately the occurrence of thermal runaway of the secondary battery is prevented, while also achieving a long cycle life for the secondary battery.

[0251] 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 configuration that is substantially identical to the technical idea and that provides similar effects within the technical scope 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 conceive of to the embodiments, and other forms constructed 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.

[0252] [Table 1]

Claims

1. A separator comprising a porous substrate and a coating layer provided on at least one surface of the porous substrate, The coating layer includes fibrous materials, and at least some of the fibrous materials are fitted into the pores of the porous substrate. The depth to which the fibrous materials are fitted into the pores of the porous substrate along the thickness direction of the separator is H １ Then, H １ is 0.02 μm or more.

2. H １ The separator according to claim 1, wherein the average particle size is 0.022µm to 0.150µm, preferably 0.025µm to 0.100µm.

3. The thickness of the porous substrate is H ２ If the unit is μm, H １ / H ２ is 0.003 or more, Preferably, H １ / H ２ is 0.004-0.025, more preferably 0.0045-0.020, Preferably, the thickness of the porous substrate is H ２ Then, H ２ The separator according to claim 1 or 2, wherein the thickness is 12 μm or less, more preferably 3 μm to 10 μm.

4. The average length of the fibrous material is L, expressed in nm, and 0.03≦1000H １ / L≦0.5, preferably 0.05≦1000H １ The separator according to any one of claims 1 to 3, wherein / L≦0.

35.

5. The average pore diameter of the porous substrate is V, expressed in nm; The average diameter of the fibrous material is D, expressed in nm, 0.6≦V / D≦2.1, Preferably, 0.7≦V / D≦1.8, more preferably 0.8≦V / D≦1.6; The separator according to any one of claims 1 to 4, wherein 20 nm≦V≦40 nm is preferred, and 25 nm≦V≦37 nm is more preferred.

6. The melting point of the porous substrate is T ｍ and the unit is °C. The average diameter of the fibrous material is D, expressed in nm; The average length of the fibrous material is L, expressed in nm. 0.03≦L / (D×T ｍ )≦0.14, Preferably, 0.04≦L / (D×T ｍ ) ≦ 0.12, more preferably 0.05 ≦ L / (D × T ｍ )≦0.10, Preferably, T ｍ ≧120°C, more preferably 120°C≦T ｍ 6. The separator of claim 1, wherein the temperature is ≦180° C.

7. The separator according to any one of claims 1 to 6, wherein the fibrous material satisfies at least one of the following conditions (1) to (4): (1) If the average diameter of the fibrous material is D, D is 15 nm or more, and preferably 20 nm to 35 nm. (2) The average length of the fibrous material is L, which is 100 nm to 600 nm, preferably 200 nm to 500 nm. (3) The aspect ratio of the fibrous material is L / D, which is 3-40, preferably 6-30. (4) The shape of the fibrous material includes at least one of rod-like, tubular, rod-like, and fibrous shapes.

8. the fibrous material contains at least one of an organic material and an inorganic material, Preferably, the organic material comprises at least one of nanocellulose, polytetrafluoroethylene nanofibers, and polyamide nanofibers; and preferably, the nanocellulose comprises at least one of cellulose nanofibers, cellulose nanowhiskers, and bacterial nanocellulose; The separator according to any one of claims 1 to 7, wherein the inorganic material preferably comprises at least one of halloysite nanotubes, alumina nanorods, boehmite nanorods, silica nanorods, and glass fibers.

9. The fibrous material comprises nanocellulose, and the nanocellulose comprises at least one of unmodified nanocellulose and modified nanocellulose; Preferably, the modified nanocellulose comprises a modifying group, the modifying group comprising at least one of an amine group, a carboxyl group, an aldehyde group, a sulfonic acid group, a boric acid group and a phosphate group, more preferably at least one of a sulfonic acid group, a boric acid group and a phosphate group, Preferably, the modified nanocellulose comprises hydroxy groups and modifying groups, and the molar ratio of the modifying groups to the hydroxy groups is 1:4-4:1, more preferably 2:3-7:

3. A separator according to any one of claims 1-8.

10. The separator according to any one of claims 1 to 9, wherein the fibrous material contains a sulfonic acid group, and the content of sulfur element in the fibrous material is 0.1 wt% or more, preferably 0.2 wt% to 0.5 wt%, based on the total weight of the fibrous material.

11. the coating layer includes a three-dimensional skeletal structure and a filler, the three-dimensional skeletal structure includes the fibrous material, and at least a portion of the filler is filled in the three-dimensional skeletal structure; The separator according to any one of claims 1 to 10, wherein the filler preferably includes at least one of primary particles and secondary particles.

12. The average length of the fibrous material is L, and the unit is nm. When the volume distribution particle diameter Dv50 of the filler is A and the unit is nm, L≧(A×√2) / 8, The separator according to claim 11, wherein 80 nm≦A≦220 nm is preferred, and 100 nm≦A≦200 nm is more preferred.

13. The content of the three-dimensional framework structure is 5 wt %-40 wt %, preferably 10 wt %-25 wt %, based on the total weight of the coating layer; and / or The separator according to claim 11 or 12, wherein the content of the filler is greater than 60 wt %, preferably 70 wt % to 88 wt %, based on the total weight of the coating layer.

14. the coating layer further comprises a non-particulate binder; Preferably, the non-particulate binder comprises an aqueous binder; The separator according to any one of claims 1 to 13, wherein the content of the non-particulate binder in the coating layer is preferably 2 wt% or less based on the total weight of the coating layer.

15. The separator according to any one of claims 1 to 14, wherein the coating layer has a thickness of 2 μm or less, preferably 0.5 μm to 1.5 μm.

16. the separator further includes an adhesive layer, the adhesive layer being provided on at least a portion of the surface of the coating layer, and the adhesive layer including a particulate binder; The separator according to any one of claims 1 to 15, wherein the particulate binder preferably comprises at least one of an acrylic acid ester-based monomer homopolymer or copolymer, an acrylic acid-based monomer homopolymer or copolymer, and a fluorine-containing olefin monomer homopolymer or copolymer.

17. The separator according to any one of claims 1 to 16, which satisfies at least one of the following conditions (1) to (7): (1) The separator has a longitudinal heat shrinkage rate of 4% or less at 150°C for 1 hour, and preferably 0.5% to 3%. (2) The separator has a transverse heat shrinkage of 4% or less at 150° C. for 1 hour, and preferably 0.5% to 3%. (3) The longitudinal tensile strength of the separator is 2200 kg / cm ２ or more, preferably 2500 kg / cm ２ -4500kg / cm ２ is. (4) The separator has a lateral tensile strength of 2200 kg / cm ２ or more, preferably 2500 kg / cm ２ -4500kg / cm ２ is. (5) The wet length of the separator is 35 mm or more, preferably 40 mm to 80 mm. (6) The wetting speed of the separator is 4 mm / s or more, preferably 4.5 mm / s to 10 mm / s. (7) The separator has an air permeability of 300 s / 100 mL or less, preferably 100 s / 100 mL to 270 s / 100 mL.

18. providing a porous substrate; mixing a fibrous material and an optional filler in a solvent in a predetermined ratio to prepare a coating layer slurry; applying the coating layer slurry to at least one surface of the porous substrate and drying to obtain a separator; The separator includes a porous substrate and a coating layer provided on at least one surface of the porous substrate, the coating layer including fibrous materials, at least some of the fibrous materials being fitted into the pores of the porous substrate, and the depth to which the fibrous materials are fitted into the pores of the porous substrate along the thickness direction of the separator is defined as H. １ Then, H １ The method for producing a separator according to any one of claims 1 to 17, wherein the average particle size is 0.02 µm or more.

19. The method according to claim 18, which satisfies at least one of the following conditions (1) to (7): (1) The linear dispersion velocity of the slurry for the coating layer is 8 m / s to 22 m / s, preferably 12 m / s to 18 m / s. (2) The coating speed of the slurry for the coating layer is 30 m / min to 140 m / min, preferably 90 m / min to 130 m / min. (3) The drying temperature of the coating layer slurry is 50°C to 80°C, preferably 55°C to 70°C. (4) The total drying time of the coating layer slurry is 3s-11s, preferably 5s-10s. (5) The drying is performed using a multi-stage oven, and preferably, the number of stages of the oven is 3-6. (6) The drying is carried out in a multi-stage oven, and the temperature of the first stage oven is higher than 50°C, preferably 55°C or higher. (7) The drying is performed in a multi-stage oven, and the drying time of the first stage oven is less than 4 seconds, preferably 3.5 seconds or less.

20. A secondary battery comprising the separator according to any one of claims 1 to 17 or the separator produced by the method according to any one of claims 18 to 19.

21. A power consuming device comprising the secondary battery of claim 20.

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