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

Abstract

The present application provides a separator, a method for manufacturing the same, and a secondary battery and a power consumption device related thereto. The separator includes a base material and a coating provided on at least one surface of the base material, the coating contains silicone particles, and the volume distribution particle size Dv90 of the silicone particles satisfies 0 < Dv90 ≤ 3.0 μm. The present application is advantageous in obtaining a separator with a relatively thin thickness by adopting silicone particles with the above particle size, and since the coating has good heat resistance performance and stability, the separator can effectively isolate the positive electrode and the negative electrode of the secondary battery, thereby improving the safety performance of the secondary battery.

Description

Technical Field

[0001] This application relates to the field of batteries, specifically to separators, their manufacturing methods, and related secondary batteries and power-consuming devices.

Background Art

[0002] Secondary batteries have characteristics such as high capacity and long lifespan, and thus are widely applied to electronic devices such as mobile phones, notebook computers, battery vehicles, electric vehicles, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, and electric tools.

[0003] As the application range of batteries becomes increasingly wide, the requirements for the performance of secondary batteries, especially the safety performance of secondary batteries, are also becoming increasingly strict. How to further improve the safety performance during the use process of batteries remains one of the issues that those skilled in the art need to continuously break through.

Summary of the Invention

[0004] This application is made in view of the above problems, and its purpose is to provide a separator, its manufacturing method, and related secondary batteries and power-consuming devices.

[0005] The first aspect of this application provides a separator, which includes a base material and a coating provided on at least one surface of the base material. The coating contains silicone particles, and the volume distribution particle size Dv90 of the silicone particles satisfies 0 < Dv90 ≤ 3.0 μm.

[0006] In some embodiments, 0.1 μm ≤ Dv90 ≤ 2.0 μm.

[0007] Therefore, in this application, when setting 0 < Dv90 ≤ 3.0 μm, especially when setting 0.1 μm ≤ Dv90 ≤ 2.0 μm, the particle size of the silicone particles is less than the thickness of the coating, which is advantageous for forming a coating with a relatively thin thickness. Thereby, a separator with a relatively thin overall thickness can be obtained, and since the coating has good heat resistance performance and stability, the separator can effectively isolate the positive electrode and the negative electrode of the secondary battery, thereby improving the safety performance of the secondary battery.

[0008] In some embodiments, the particle size distribution of the silicone particles satisfies (Dv90 - Dv10) / Dv50 ≤ 2.0, and optionally, 0.1 ≤ (Dv90 - Dv10) / Dv50 ≤ 1.0.

[0009] Therefore, when the particle size distribution of the silicone particles in this application satisfies the above range, since the particle size distribution of the silicone particles is more uniform, it is advantageous for the silicone particles to be uniformly dispersed in the coating to form a coating with a more uniform thickness.

[0010] In some embodiments, the volume distribution particle size Dv50 of the silicone particles satisfies 0.01 μm ≤ Dv50 ≤ 2 μm.

[0011] Thereby, this application is set so that the volume distribution particle size Dv50 of the silicone particles satisfies 0.01 μm ≤ Dv50 ≤ 2 μm, and the coating of the separator can be applied to a relatively small thickness. At the same time, due to the size of the above particle size, a tight contact is formed between the silicone particles in the coating. When the separator receives heat, the silicone particles quickly contact and press against each other to receive force, reducing the risk of the substrate being subjected to tensile force and shrinking, thereby ensuring that the separator effectively isolates the positive electrode and the negative electrode and improving the safety performance of the secondary battery.

[0012] In some embodiments, the specific surface area SSA of the silicone particles is 2.0 cm 2 / g to 50 cm 2 / g, and optionally 8.5 cm2 / g~20.5cm 2 / g.

[0013] Therefore, when the specific surface area SSA of the silicone particles is within the above range, the specific surface area SSA of the silicone particles is relatively large, which is advantageous for good contact between the particles and makes it easier to form a void structure between the silicone particles, which is advantageous for the movement of active ions.

[0014] In some embodiments, the silicone particles include primary particles, which have a relatively small particle size, which is advantageous for uniform dispersion of the silicone particles when applied to a coating, resulting in more uniform performance of the resulting film layer.

[0015] In some embodiments, the shape of the silicone particles includes at least one of spherical, near-spherical, cubic, rhomboidal, fibrous, tubular, rod-like, and sheet-like shapes. The silicone particles may be randomly arranged, which is advantageous for better contact between particles and for increasing the number of contact points between particles, thereby improving the shrinkage resistance of the entire coating and making the separator structure more stable.

[0016] In some embodiments, the silicone particles comprise a first polymer, the first polymer comprising first structural units, second structural units, and third structural units, the first structural units comprising structural units shown in Formula (I): [ka] In formula (I), R1 comprises one or more of a hydrogen atom, a substituted or unsubstituted C1-C5 alkyl group, optionally R1 comprises one or more of a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group, R2 comprises one or more of a substituted or unsubstituted C1-C20 alkyl group, a substituted or unsubstituted C3-C20 cycloalkyl group, a substituted or unsubstituted C1-C20 hydroxyalkyl group, optionally R2 comprises one or more of a C1-C12 alkyl group, a C3-C12 cycloalkyl group, a C1-C12 hydroxyalkyl group; The second structural unit comprises a structural unit represented by formula (II): [ka] In formula (II), R3 comprises one or more of a hydrogen atom, a substituted or unsubstituted C1-C5 alkyl group, optionally R3 comprises one or more of a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group; The third structural unit includes a structural unit represented by formula (III): [ka] In formula (III), R4 to R 11 each independently comprises a substituted or unsubstituted C1-C10 alkyl group, one or more structural units represented by formula (III-1), and R4 to R 11 At least one of the structural units is represented by formula (III-1), [ka] In formula (III-1), R 12 contains one or more of a hydrogen atom, a substituted or unsubstituted C1-C5 alkyl group, and optionally R 12 contains one or more of a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group, and R 13 comprises a substituted or unsubstituted C1-C10 alkyl group, optionally R 13 includes substituted or unsubstituted C3-C10 alkyl groups.

[0017] In some embodiments, the silicone particles contain a second polymer, and the second polymer contains a structural unit represented by formula (a),

Chemical formula

[0018] Thereby, when the silicone particles contain the polymer of the above structural unit, the heat resistance performance and stability of the entire separator can be further improved.

[0019] In some examples, based on the total molar amount of the first structural unit, the second structural unit and the third structural unit, the molar content of the first structural unit is denoted as A%, and 75 ≦ A < 100, and optionally, 75 ≦ A ≦ 80.

[0020] In some examples, based on the total molar amount of the first structural unit, the second structural unit and the third structural unit, the molar content of the second structural unit is denoted as B%, and 0 < B ≦ 15, and optionally, 5 ≦ B ≦ 15.

[0021] In some examples, based on the total molar amount of the first structural unit, the second structural unit and the third structural unit, the molar content of the third structural unit is denoted as C%, and 0 < C ≦ 15, and optionally, 5 ≦ C ≦ 15.

[0022] In some embodiments, based on the total molar amount of the first structural unit, the second structural unit, and the third structural unit, the molar content of the first structural unit is denoted as A%, the molar content of the second structural unit is denoted as B%, and the molar content of the third structural unit is denoted as C%. The first polymer satisfies one or more of the conditions (1) to (3): (1) the condition that 5 ≤ A / B ≤ 15; (2) the condition that 5 ≤ A / C ≤ 15; and (3) the condition that A:B:C is (12 to 15):(1 to 3):(1 to 3).

[0023] In some embodiments, the number average molecular weight of the silicone particles is from 22,000 to 79,000, and optionally from 24,000 to 48,000. When the number average molecular weight of the silicone particles is within the above range, it has a relatively high viscosity, and when the silicone particles are applied to the separator, it is advantageous for improving the adhesion force between the separator and the positive and negative electrode plates.

[0024] In some embodiments, based on the mass of the silicone particles, the moisture content of the silicone particles is 3500 μg / g or less, and optionally from 500 μg / g to 3000 μg / g. When the moisture content of the silicone particles is within the above range, the moisture content contained therein is relatively low, reducing the risk of side reactions of the electrolyte during the long-term charge-discharge cycle of the secondary battery, thereby improving the electrochemical performance of the secondary battery.

[0025] In some embodiments, based on the mass of the coating, the mass percentage content of the silicone particles is m1%, where 50 ≤ m1 < 100, and optionally 80 ≤ m1 ≤ 95, thereby ensuring the heat resistance performance and stability of the coating.

[0026] In some embodiments, the coating further includes inorganic particles, and optionally, the mass percentage content of the inorganic particles in the coating is m2%, where 0 < m2 ≤ 30. By adding inorganic particles, the heat resistance performance of the coating can be further improved.

[0027] In some embodiments, the separator further satisfies at least one of conditions (a) to (c): (a) the porosity of the substrate is 25% or more, and optionally 28% to 41%, (b) the thickness of the substrate is 16 μm or less, and optionally 3 μm to 12 μm, and (c) the thickness of the coating is 0.1 μm to 4 μm, and optionally 0.5 μm to 3 μm. When the separator satisfies the above conditions, the heat resistance performance and lightweight and thin design of the separator can be further improved.

[0028] In some embodiments, the separator satisfies any one of conditions (I) to (VII): (I) the separator has a longitudinal heat shrinkage rate η≦3.0% at 150° C. for 1 hour; (II) the separator has a transverse heat shrinkage rate η≦2.0% at 150° C. for 1 hour; and (III) the separator has a longitudinal tensile strength R m1 ≧2700kgf / cm 2 and selectively 2700 kgf / cm 2 ≦R m1 ≦4500kgf / cm 2 (IV) the separator has a transverse tensile strength R m2 ≧2000kgf / cm 2 and selectively 2500 kgf / cm 2 ≦R m2 ≦4500kgf / cm 2 (V) the wetting length of the separator is L≧30 mm, optionally 30 mm≦L≦60 mm; (VI) the wetting speed of the separator is u≧2 mm / s, optionally 2 mm / s≦u≦4 mm / s; and (VII) the air permeability of the separator is MAP≦300 s / 100 mL, optionally 130 s / 100 mL≦MAP≦250 s / 100 mL.

[0029] The second aspect of the present application provides a method for manufacturing a separator for manufacturing a separator of any one of the embodiments of the first aspect of the present application. The method includes, in S1, providing a base material; in S2, mixing silicone particles into a solvent to prepare a coating slurry; and in S3, applying the coating slurry to at least one surface of the base material, forming a coating and drying it to obtain a separator. Here, the volume distribution particle size Dv90 of the silicone particles satisfies 0 < Dv90 ≤ 3.0 μm, and optionally satisfies 0.1 μm ≤ Dv90 ≤ 2.0 μm.

[0030] In some embodiments, based on the mass of the coating, the mass percentage content of the silicone particles is 50% or more, optionally 80% - 95%, and / or the solid content of the coating slurry is 10% to 40%, optionally 20% to 30%.

[0031] The third aspect of the present application provides a secondary battery, which includes a separator described in any one of the embodiments of the first aspect of the present application or a separator manufactured based on the manufacturing method described in any one of the embodiments of the second aspect of the present application.

[0032] The fourth aspect of the present application provides a power consumption device, which includes a secondary battery according to the third aspect of the present application.

Brief Description of Drawings

[0033] To more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings that need to be used in the embodiments of the present application. It is self-evident that the drawings in the following description are only some embodiments of the present application. On the premise that no creative effort is required from those skilled in the art, other drawings can also be obtained based on these drawings. [Figure 1] It is a schematic diagram of an embodiment of the secondary battery of the present application. [Figure 2] It is an exploded schematic diagram of the embodiment of the secondary battery in 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] FIG. 5 is an exploded schematic view of the embodiment of the battery pack shown in FIG. 4. [Figure 6] 1 is a schematic diagram of one embodiment of the present application including a secondary battery-powered power consuming device. The drawings are not necessarily drawn to scale. DETAILED DESCRIPTION OF THE INVENTION

[0034] Hereinafter, embodiments specifically disclosing the separator, its manufacturing method, and related secondary batteries and power consumption devices of the present application will be described in detail. However, unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of structures that are actually the same may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. Note that the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0035] The "ranges" disclosed in this application are defined in the form of lower and upper limits, and a given range is defined by selecting one lower limit and one upper limit, with the selected lower and upper limits defining the boundaries of the particular range. Such defined ranges may be inclusive or exclusive, and any combination is possible; i.e., any lower limit may be combined with any upper limit to form a single range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also possible. Furthermore, if 1 and 2 are listed as minimum range values and 3, 4, and 5 are listed as maximum range values, the ranges 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5 are all possible. In this application, unless otherwise specified, the numerical range "ab" represents a shorthand notation for any combination of real numbers a to b, where a and b are both real numbers. For example, the numerical range "0-5" represents a list of all real numbers between "0-5" already listed in this specification, and "0-5" is merely a shorthand representation of combinations of these numbers. Also, expressing a parameter as an integer ≧2 is equivalent to disclosing that this parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0036] Unless otherwise stated, all embodiments and optional embodiments of this application can be combined with each other to form new technical solutions. Unless otherwise stated, all technical features and optional technical features of this application can be combined with each other to form new technical solutions.

[0037] Unless otherwise stated, all steps in this application may be performed in sequence or randomly, preferably in sequence. For example, a method including steps (a) and (b) means that the method may include steps (a) and (b) performed in sequence, or may include steps (b) and (a) performed in sequence. For example, a method that may further include step (c) means that step (c) may be added to the method in any order, e.g., the method may include steps (a), (b), and (c), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0038] Unless otherwise specified, the terms "comprise" and "comprises" referred to in this application may be open ended or closed ended. For example, "comprise" and "comprises" may indicate that other unlisted components may be further included or included, or that only the listed components may be included or included.

[0039] Unless otherwise stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, "A or B" is satisfied when A is true (or exists) and B is false (or does not exist), when A is false (or does not exist) but B is true (or exists), or when both A and B are true (or exist).

[0040] In this application, the terms "first," "second," etc. are used for descriptive purposes only and should not be understood to denote or imply relative importance.

[0041] As used in this application, the terms "plurality" and "various" mean two or more.

[0042] Unless otherwise specified, terms used in this application have the known meanings commonly understood by those skilled in the art.

[0043] Unless otherwise specified, the numerical values of each parameter mentioned in this application can be measured using various test methods commonly used in the art, for example, according to the test methods given in the examples of this application.

[0044] The term "alkyl group" encompasses straight-chain and branched-chain alkyl groups. For example, the alkyl group can be a C1-C50 alkyl group, a C1-C40 alkyl group, a C1-C30 alkyl group, a C1-C20 alkyl group, a C1-C12 alkyl group, a C1-C10 alkyl group, a C1-C6 alkyl group, or a C1-C4 alkyl group. In some embodiments, the alkyl group includes a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, or the like. Additionally, the alkyl group can be optionally substituted.

[0045] When the above groups are substituted, the substituents may be halogen atoms or heteroatoms. Optionally, the heteroatoms may include nitrogen atoms, and the substituents may be nitrogen atoms or halogen atoms.

[0046] The term "halogen atom" refers to fluorine atom, chlorine atom, bromine atom, and the like.

[0047] The term "heteroatom" refers to nitrogen, sulfur, phosphorus, and the like atoms.

[0048] The term "hydrogen" refers to 1H (protium, H), 2H (deuterium, D), or 3H (tritium, T). In some embodiments, "hydrogen" may be 1H (protium, H).

[0049] At various places in this specification, substituents of compounds are disclosed in groups or in ranges, and such descriptions are expressly intended to include each individual subcombination of the members of those groups and ranges. For example, the term "C1-C8 alkyl group" is expressly intended to disclose C1, C2, C3, C4, C5, C6, C7, C8, C1-C8, C1-C7, C1-C6, C1-C5, C1-C4, C1-C3, C1-C2, C2-C8, C2-C7, C2-C6, C2-C5, C2-C4, C2-C3, C3-C8, C3-C7, C3-C6, C3-C5, C3-C4, C4-C8, C4-C7, C4-C6, C4-C5, C5-C8, C5-C7, C5-C6, C6-C8, C6-C7 and C7-C8 alkyl groups individually.

[0050] As another example, a range of integers from 5 to 40 is expressly contemplated to individually disclose 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, and 40; a range of integers from 1 to 20 is expressly contemplated to individually disclose 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20, so that other groups or ranges can be clearly contemplated.

[0051] Generally, a secondary battery includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode plate, a negative electrode plate, and a separator. The separator is installed between the positive electrode plate and the negative electrode plate and serves mainly to prevent short-circuiting between the positive electrode plate and the negative electrode plate, while allowing active ions to pass freely through the separator to complete a circuit.

[0052] With the increasing application and popularity of secondary batteries, people's demands for the energy density of secondary batteries are increasing. Thinning the separator is an effective means of improving the energy density of secondary batteries.

[0053] When designing the separator to be thinner, the separator is generally a polyolefin porous membrane, such as a polyethylene porous membrane, a polypropylene porous membrane, or a three-layer composite membrane of polypropylene / polyethylene / polypropylene. After the separator is thinned, its heat resistance deteriorates, and a significant heat shrinkage effect occurs when heated, causing the positive electrode plate and the negative electrode plate inside the battery to come into direct contact and cause an internal short circuit, further increasing the safety risk of the secondary battery. Moreover, when the separator is thinned, its mechanical performance is relatively poor, it is easy to deform, and it further affects the safety performance of the secondary battery.

[0054] In view of this, the inventor provides a separator including a substrate and a coating, and by further adjusting the volume distribution particle size Dv90 of the coating, the thickness of the coating can be made smaller, which is beneficial to the design of the overall thinning of the separator. Next, the technical solution of this application will be described in detail.

[0055] Separator According to a first aspect, the present application provides a separator.

[0056] The separator includes a substrate and a coating provided on at least one surface of the substrate. The coating contains silicone particles, and the volume distribution particle size Dv90 of the silicone particles satisfies 0 < Dv90 ≤ 3 μm, optionally 0.1 μm ≤ Dv90 ≤ 2 μm.

[0057] The coating applied to the substrate contains silicone particles. Silicone refers to an organosiloxane whose main chain has a silicon bond (-Si-O-Si-). Because the silicon bond is an inorganic bond, it has a relatively large bond energy, which gives the silicone high heat resistance and chemical stability. For example, silicone can be used for long periods at temperatures below 200°C. The silicone side chains can be ungrafted or grafted with organic groups. Grafting organic groups can impart good dispersibility to the silicone, improving the application performance of the silicone coating and its affinity with the substrate. The dispersion of silicone particles in the coating imparts good heat resistance to the coating and forms a structure with voids between the silicone particles, which increases the ion conduction paths in the separator, promoting the transport of active ions and simultaneously improving the separator's electrolyte penetration and retention properties. When the separator is used in a secondary battery, it can improve the secondary battery's long cycle life and good rate performance.

[0058] When the inventor designs the separator to be thinner, the base material is used as the main body support structure of the separator, which needs to meet certain mechanical properties. Since there is a certain positive correlation between mechanical properties and thickness, it is necessary to ensure the thickness of the base material. Therefore, it is found that the thickness of the base material cannot be infinitely reduced. The coating, as a functional layer structure on the base material, can be thinned, but the particle size of the silicone particles in the coating limits the thickness of the coating. In particular, the volume distribution particle size Dv90 of the silicone particles affects the minimum value of the coating thickness. The larger the volume distribution particle size Dv90, the thicker the corresponding coating thickness, which is disadvantageous for the thinning treatment of the entire separator. The smaller the volume distribution particle size Dv90, the more advantageous it is to form a relatively thin coating when forming the coating, which is advantageous for the thinning treatment of the entire separator. In this application, it is set to 0 < Dv90 ≤ 3.0 μm. The particle size of the silicone particles is less than or equal to the thickness of the coating, which is advantageous for forming a relatively thin coating, so that a separator with a relatively thin overall thickness can be obtained. And because the coating has good heat resistance and stability, the separator can effectively isolate the positive and negative electrodes of the secondary battery, thereby improving the safety performance of the secondary battery. Optionally, 0.1 μm ≤ Dv90 ≤ 2.0 μm. Exemplarily, the volume distribution particle size Dv90 of the silicone particles may be in the range of 0.05, 0.1, 0.2, 0.5, 0.8, 1.0, 2.0, 2.2, 2.5, 2.8, 3.0 or any range composed of two of the above numerical values.

[0059] In some embodiments, the particle size distribution of the silicone particles satisfies (Dv90 - Dv10) / Dv50 ≤ 2.0.

[0060] When the particle size distribution of the silicone particles satisfies the above range, the silicone particles have a more uniform particle size distribution, which is advantageous for the silicone particles to be more uniformly dispersed in the coating and form a coating with a more uniform thickness. Furthermore, when the coating slurry is applied to the substrate surface, the risk of the silicone particles falling into the voids of the substrate can be reduced, thereby ensuring the air permeability of the substrate. Furthermore, since the silicone particles are mainly distributed in the coating, the heat resistance performance of the entire coating can be ensured. Alternatively, 0.1≦(Dv90−Dv10) / Dv50≦1.0 can be used. For example, (Dv90−Dv10) / Dv50 can be 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.5, 0.6, 0.8, 0.9, 1.0, 1.2, 1.5, 1.8, 2.0, or a range consisting of any two of the above values.

[0061] In some embodiments, the volume distribution particle size Dv50 of the silicone particles satisfies 0.01 μm≦Dv50≦2 μm.

[0062] If the volume distribution particle size Dv50 of the silicone particles is too small, the particle size of the silicone particles will be relatively small, and when the coating slurry is applied to the surface of the substrate, the silicone particles will tend to accumulate in the voids of the substrate as the slurry flattens out, reducing the air permeability of the entire separator and its ionic conductivity. This will result in a relatively poor ion conduction function of the separator during the charge and discharge processes of the secondary battery, and will further degrade the dynamic performance of the secondary battery.

[0063] If the volume distribution particle size Dv50 of the silicone particles is too large, three to five layers will accumulate between the silicone particles, which is likely to cause the coating to be too thick and increase the overall thickness of the separator. In addition, if the silicone particles are too large, it will be difficult to form effective contact between the silicone particles when the paint is applied. Due to the relatively large gaps between the particles, when the separator is heated, the silicone particles will tend to gradually come into contact with the substrate as it shrinks, reducing the heat resistance of the separator. In addition, the shrinkage of the separator will likely reduce the isolation effect between the positive and negative electrodes, making it more likely that a short circuit will occur between the positive and negative electrodes.

[0064] Therefore, the present application specifies that the volume distribution particle size Dv50 of the silicone particles satisfies the range of 0.01 μm≦Dv50≦2 μm, allowing the separator coating to be applied to a relatively thin thickness. At the same time, this particle size allows the silicone particles in the coating to form a tight contact with each other. When the separator is heated, the silicone particles quickly come into contact and press together, applying a tensile force to the substrate and reducing the risk of the substrate shrinking. This ensures that the separator effectively isolates the positive and negative electrodes and improves the safety performance of the secondary battery. For example, the volume distribution particle size Dv50 of the silicone particles may be 0.01 μm, 0.05 μm, 0.08 μm, 0.1 μm, 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2 μm, or a range consisting of any two of the above values.

[0065] In some embodiments, the volume distribution particle size Dv10 of the silicone particles satisfies 0.01 μm≦Dv10≦2.80 μm.

[0066] When the volume distribution particle size Dv10 of the silicone particles satisfies the above range, the particle size distribution of the silicone particles is relatively concentrated, which is advantageous for the uniformity of the coating thickness. For example, the volume distribution particle size Dv10 of the silicone particles may be 0.01 μm, 0.02 μm, 0.05 μm, 0.08 μm, 0.10 μm, 0.15 μm, 0.20 μm, 0.50 μm, 0.80 μm, 1.00 μm, 1.20 μm, 1.50 μm, 1.80 μm, 2.00 μm, 2.20 μm, 2.50 μm, 2.80 μm, or a range consisting of any two of the above values.

[0067] In the present application, the volume distribution particle size Dv90 of a material has the meaning known in the art, which means the particle size corresponding to when the cumulative volume distribution percentage of the material reaches 90%, and can be measured using instruments and methods known in the art, for example, GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method, and can be measured using a laser particle size analyzer (e.g., Master Size 3000).

[0068] In the present application, the volume distribution particle size Dv50 of a material has the meaning known in the art, which means the particle size corresponding to when the cumulative volume distribution percentage of the material reaches 50%, and can be measured using instruments and methods known in the art, for example, referring to GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method, and can be measured using a laser particle size analyzer (e.g., Master Size 3000).

[0069] In the present application, the volume distribution particle size Dv10 of a material has the meaning known in the art, which means the particle size corresponding to when the cumulative volume distribution percentage of the material reaches 10%, and can be measured using instruments and methods known in the art, for example, GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method, and can be measured using a laser particle size analyzer (e.g., Master Size 3000).

[0070] In some embodiments, the specific surface area SSA of the silicone particles is 2.0 cm 2 / g~50cm 2 / g, and selectively 8.5 cm 2 / g~20.5m 2 / g.

[0071] When the specific surface area SSA of the silicone particles is within the above range, the specific surface area SSA of the silicone particles is relatively large, which is advantageous for good contact between the particles and allows a void structure to be more easily formed between the silicone particles, which is advantageous for the movement of active ions. For example, the specific surface area SSA of the silicone particles is 2.0 cm 2 / g, 5.0cm 2 / g, 8.0cm 2 / g, 8.5cm 2 / g, 10.0cm 2 / g, 15.0cm 2 / g, 20.0 cm 2 / g, 20.5cm 2 / g, 25.0 cm 2 / g, 30.0 cm 2 / g, 35.0 cm 2 / g, 40.0 cm 2 / g, 42.0 cm 2 / g, 45.0 cm 2 / g, 48.0cm 2 / g, 50.0 cm 2 / g or a range consisting of any two of the above values.

[0072] The specific surface area SSA of silicone particles can be tested by methods known in the art.For example, it can be tested by nitrogen gas adsorption specific surface area analysis test method with reference to GB / T 19587-2017, and calculated by Brunauer Emmett Teller (BET) method, where nitrogen gas adsorption specific surface area analysis test can be carried out by Micromeritics Tri-Star 3020 type specific surface area pore size analyzer, USA.

[0073] Through further research, the inventors discovered that the morphology of the silicone particles has a certain effect on the coating, and that when the morphology of the silicone particles satisfies the following conditions, the heat resistance, stability, etc. of the separator can be further improved.

[0074] In some embodiments, the morphology of the silicone particles includes at least one of spherical, near-spherical, cubic, rhomboidal, fibrous, tubular, rod-like, and sheet-like.

[0075] When the silicone particles are spherical and / or near-spherical, they ensure good contact between the particles, improving the heat resistance and stability of the coating. The presence of voids between the particles is beneficial for establishing a stable spatial network structure, thereby improving the ion transport properties and external pressure resistance of the separator. Furthermore, the relatively large voids between the spherical and / or near-spherical particles mitigate the impact of the coating on the air permeability of the substrate, further improving the overall air permeability and ionic conductivity of the separator and improving the dynamic performance of the secondary battery. Furthermore, the relatively large void ratio between the spherical and / or near-spherical particles is beneficial for improving the separator's electrolyte wettability and electrolyte retention, further improving the dynamic performance of the secondary battery. Furthermore, the relatively large void ratio contributes to weight reduction, improving the energy density per unit weight of the secondary battery. It also reduces the amount of silicone particles used in the coating, thereby reducing the cost of the secondary battery.

[0076] When the silicone particles are cubic, rhomboidal, fibrous, tubular, rod-like, or sheet-like, the silicone particles may be arranged irregularly, which is advantageous for better contact between the particles and for increasing the contact points between the particles, thereby improving the shrinkage resistance of the entire coating, and making the structure of the entire separator more stable.

[0077] In particular, when the silicone particles contain two or more types of morphology, the contact between the particles becomes tighter, which can further improve the shrinkage resistance of the entire coating and make the structure of the entire separator more stable.

[0078] Illustratively, the silicone particles include spheres, cubes, etc. Alternatively, the silicone particles include cubes, rhombuses, etc.

[0079] In some embodiments, the silicone particles include primary particles, which have a relatively small particle size, which is advantageous for uniform dispersion of the silicone particles when applied to a coating, resulting in more uniform performance of the resulting film layer.

[0080] In this application, the morphology of silicone particles can be observed by a scanning electron microscope (SEM), for example, a JSM-5610LV scanning electron microscope manufactured by FEI Corporation, USA, is used to observe the morphology of the sample after vacuum gold spraying.

[0081] Silicone is a type of polymer, and when the polymer satisfies at least one of the following conditions, the heat resistance performance and stability of the entire separator can be further improved.

[0082] In some embodiments, the silicone particles comprise a first polymer, the first polymer comprising a first structural unit, a second structural unit, and a third structural unit.

[0083] The first structural unit comprises a structural unit represented by formula (I): [ka] In formula (I), R1 comprises one or more of a hydrogen atom, a substituted or unsubstituted C1-C5 alkyl group, optionally R1 comprises one or more of a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group, R2 comprises one or more of a substituted or unsubstituted C1-C20 alkyl group, a substituted or unsubstituted C3-C20 cycloalkyl group, a substituted or unsubstituted C1-C20 hydroxyalkyl group, optionally R2 comprises one or more of a C1-C12 alkyl group, a C3-C12 cycloalkyl group, a C1-C12 hydroxyalkyl group, The second structural unit comprises a structural unit represented by formula (II): [ka] In formula (II), R3 comprises one or more of a hydrogen atom, a substituted or unsubstituted C1-C5 alkyl group, and optionally R3 comprises one or more of a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group.

[0084] The third structural unit comprises a structural unit represented by formula (III): [ka] In formula (III), R4 to R 11 each independently comprises a substituted or unsubstituted C1-C10 alkyl group, one or more structural units represented by formula (III-1), and R4 to R 11 At least one of the above contains a structural unit represented by formula (III-1): [ka] In formula (III-1), R 12 contains one or more of a hydrogen atom, a substituted or unsubstituted C1-C5 alkyl group, and optionally R 12 contains one or more of a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group, and R 13 comprises a substituted or unsubstituted C1-C10 alkyl group, optionally R 13 includes substituted or unsubstituted C3-C10 alkyl groups.

[0085] The first structural unit can be formed by the opening of a carbon-carbon double bond of an acrylate-based monomer during the polymerization process, and the flexible monomer chain segment in the molecular chain segment can adjust the glass transition temperature of the first polymer and improve the toughness and peel strength of the first polymer, thereby contributing to good adhesion, improving the adhesive strength with the substrate, and reducing the risk of the coating peeling off from the substrate. The second structural unit can be formed by the opening of a carbon-carbon double bond of an acrylonitrile-based monomer during the polymerization process, and the second structural unit can produce excellent swelling resistance and high adhesion, and contribute to improving the ionic conductivity of the secondary battery.

[0086] The third structural unit is formed by polysilsesquioxane containing a substituted or unsubstituted acryloyloxyalkyl group by opening the carbon-carbon double bond of the substituted or unsubstituted acryloyloxy group during the polymerization process, and polysilsesquioxane may be considered as a material having an organic-inorganic hybrid core-shell structure, with the inner inorganic framework as the core, i.e., the framework structure composed of Si-O-Si or Si-O bonds, and the housing composed of organic substituents (C1-C5 alkyl groups), the organic substituents being wrapped around the outside of the framework structure and connected to the Si element of the framework structure. The core structure of polysilsesquioxane can endow the polymer with advantages in terms of heat resistance and mechanical performance, and its relatively low shrinkage can ensure the stability of the polymer during the long-term cycle charge-discharge process of the secondary battery, effectively isolating the positive and negative electrodes, and thereby ensuring the safety performance of the secondary battery. Furthermore, because polysilsesquioxane has a small particle size and a large specific surface area, it is similar to many polymer segments on a physical scale, so the atoms on the polysilsesquioxane surface have relatively high reactivity, and polymers modified with polysilsesquioxane have relatively high properties such as heat resistance, flame retardancy, and oxidation resistance.

[0087] The above analysis was carried out based on each structural unit, but the synergistic effect between each structural unit cannot be ignored. Specifically, the first structural unit, the second structural unit, and the third structural unit can exert a synergistic effect, improving the adhesion performance and heat resistance performance of the first polymer in the silicone particles, so that when the coating is lightly and thinly applied, the heat resistance effect of the coating can still be guaranteed.

[0088] In some embodiments, based on the total molar amount of the first structural unit, the second structural unit, and the third structural unit, the molar content of the first structural unit is denoted as A%, and 75 ≦ A < 100. When the molar content of the first structural unit is within the above range, the occupancy rate in the first polymer is relatively large, the flexibility of the first polymer can be improved, thereby significantly improving the adhesion of the first polymer. When the first polymer is applied to the separator, the bonding force between the silicone particles and the substrate of the separator can be improved. Optionally, 75 ≦ A ≦ 80. Exemplarily, the molar content of the first structural unit may be 75%, 78%, 80%, 85%, or a range consisting of any two of the above numerical values.

[0089] In some embodiments, based on the total molar amount of the first structural unit, the second structural unit, and the third structural unit, the molar content of the second structural unit is denoted as B%, and 0 < B ≦ 15. When the molar content of the second structural unit is within the above range, the stability of the first polymer can be significantly improved. Optionally, 5 ≦ B ≦ 15. Exemplarily, the molar content of the second structural unit may be 2%, 5%, 8%, 10%, 12%, 15%, or a range consisting of any two of the above numerical values.

[0090] In some embodiments, based on the total molar amount of the first structural unit, the second structural unit, and the third structural unit, the molar content of the third structural unit is denoted as C%, and 0 < C ≤ 15. When the molar content of the third structural unit is within the above range, the heat resistance of the first polymer can be guaranteed, and its occupancy is relatively small, which is beneficial to improving the occupancy of the first structural unit and the second structural unit and enhancing the performance such as adhesiveness and stability of the entire first polymer. Optionally, 5 ≤ C ≤ 20. Exemplarily, the molar content of the third structural unit may be 2%, 5%, 8%, 10%, 12%, 15%, or a range consisting of any two of the above numerical values.

[0091] The first polymer further includes a second structural unit, and the second structural unit exhibits a synergistic effect with the first structural unit and can jointly improve the swelling resistance and adhesive performance of the first polymer. Particularly when the present application further satisfies 5 ≤ A / B ≤ 15, a more sufficient synergistic effect can be exerted between the first structural unit and the second structural unit, and the adhesiveness and stability of the first polymer can be improved. Exemplarily, A / B may be 5, 8, 10, 12, 15, or a range consisting of any two of the above numerical values.

[0092] The first polymer further includes a third structural unit, and the inorganic structure of polysilsesquioxane in the third structural unit synergistically acts with the first structural unit and can improve the heat resistance performance and adhesive performance of the entire first polymer. Particularly when the present application further satisfies 5 ≤ A / C ≤ 15, a more sufficient synergistic effect can be exerted between the first structural unit and the third structural unit, and the adhesive performance and heat resistance performance of the first polymer can be improved. Exemplarily, A / C may be 5, 8, 10, 12, 15, or a range consisting of any two of the above numerical values.

[0093] In some embodiments, A:B:C is (12 to 15):(1 to 3):(1 to 3). When the molar contents of the first structural unit, the second structural unit, and the third structural unit satisfy the above ratio, the three types of structural units in the first polymer can cooperate with each other to jointly improve the adhesiveness, stability, swelling resistance, and thermal stability of the first polymer.

[0094] The first structural unit includes a plurality of chemical structures, and specific chemical structures of the first structural unit will be described below.

[0095] In some embodiments, R1 comprises a hydrogen atom or a methyl group.

[0096] In some embodiments, R2 comprises a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an n-octyl group, an isooctyl group, a 2-ethylhexyl group, a dodecyl group, or an isobornyl group.

[0097] Exemplarily, the first structural unit includes one or more of the structures shown in formula (I-1) to formula (I-8), [ka] The second structural unit includes a plurality of chemical structures, and specific chemical structures of the second structural unit will be described below.

[0098] In some embodiments, R3 comprises a hydrogen atom or a methyl group.

[0099] Exemplarily, the second structural unit includes one or more of the structures shown in formula (II-1) to formula (II-4), [ka]

[0100] The third structural unit includes a plurality of chemical structures, and specific chemical structures of the third structural unit will be described below.

[0101] In some embodiments, R4 to R 11 each independently contains a structural unit represented by formula (III-1), i.e., R4 to R 11 Each of these contains the structural unit shown in formula (III-1), but R4 to R 11may be the same or different. 12 contains a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group or an n-pentyl group, and / or R 13 includes an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an n-octyl group, an isooctyl group, or a 2-ethylhexyl group.

[0102] In some embodiments, R4 to R 11 One of the groups includes a structural unit shown in formula (III-1), i.e., R4 to R 11 Only one of R contains the structural unit shown in formula (III-1). 12 contains a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group or an n-pentyl group, and / or R 13 includes an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an n-octyl group, an isooctyl group, or a 2-ethylhexyl group.

[0103] In the present application, the type of group in the polymer can be measured by infrared spectroscopy. For example, the type of modifying group can be determined by examining the infrared spectrum of the material and determining the characteristic peaks contained therein. Specifically, infrared spectroscopy analysis of the material can be performed using an instrument and method known in the art, for example, an infrared spectrometer (e.g., an IS10 Fourier transform infrared spectrometer manufactured by Nicolet, USA) in accordance with GB / T 6040-2019 General Methods for Infrared Spectroscopy Analysis.

[0104] In some embodiments, the infrared spectrum of the first polymer shows a peak at 1750 cm indicating the presence of an ester group. -1 From 1735cm -1 It has a characteristic peak.

[0105] In some embodiments, the infrared spectrum of the first polymer shows a peak at 2260 cm indicating the presence of cyano groups. -1 From 2220cm -1 It has a characteristic peak.

[0106] In some embodiments, the infrared spectrum of the first polymer exhibits a peak at 1100 cm indicating the presence of a silsesquioxane Si—O—Si framework. -1 From 1120cm -1 It has a characteristic peak.

[0107] In some embodiments, the first polymer may be prepared by a process comprising: Step S100 of providing a first monomer, a second monomer, and a third monomer; and step S200 of mixing the first monomer, the second monomer, and the third monomer, and causing a polymerization reaction under the action of an initiator to produce a first polymer.

[0108] In the present application, a first monomer, a second monomer and a third monomer are mixed and then copolymerized, and the formed first polymer is a copolymer of the three types of monomers.

[0109] The first monomer comprises a structural unit shown in formula (IV): [ka] In formula (IV), R1 comprises one or more of a hydrogen atom, a substituted or unsubstituted C1-C5 alkyl group, optionally R1 comprises one or more of a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group, R2 comprises one or more of a substituted or unsubstituted C1-C20 alkyl group, a substituted or unsubstituted C3-C20 cycloalkyl group, a substituted or unsubstituted C1-C20 hydroxyalkyl group, optionally R2 comprises one or more of a C1-C12 alkyl group, a C3-C12 cycloalkyl group, a C1-C12 hydroxyalkyl group, The first monomer is an acrylate compound, which when polymerized opens a carbon-carbon double bond to form a first structural unit.

[0110] Illustratively, the first monomer comprises one or more of methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, n-pentyl acrylate, n-octyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, lauryl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate.

[0111] The second monomer comprises a structural unit shown in formula (V): [ka] In formula (V), R3 comprises one or more of a hydrogen atom, a substituted or unsubstituted C1-C5 alkyl group, and optionally R3 comprises one or more of a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group.

[0112] The second monomer is an acrylonitrile-based compound, and when it undergoes polymerization, the carbon-carbon double bond opens to form a second structural unit.

[0113] Illustratively, the second monomer includes acrylonitrile and / or methacrylonitrile.

[0114] The third monomer comprises a structural unit shown in formula (VI): [ka] In formula (VI), R30 From R 37 each independently comprises a substituted or unsubstituted C1-C10 alkyl group or one or more structural units represented by formula (VI-1), and R 30 From R 37 At least one of the above contains a structural unit represented by formula (VI-1): [ka] In formula (VI-1), R 12 contains one or more of a hydrogen atom or a substituted or unsubstituted C1-C5 alkyl group, and optionally R 12 contains one or more of a hydrogen atom or a substituted or unsubstituted C1-C3 alkyl group, R 13 comprises a substituted or unsubstituted C1-C10 alkyl group, optionally R 13 includes substituted or unsubstituted C3-C10 alkyl groups.

[0115] Illustratively, the third monomer includes one or more of methacryloyloxypropyl cage-type polysilsesquioxane, methacryloyloxypropylheptaisobutylpolysilsesquioxane, acryloyloxypropylheptaisobutylpolysilsesquioxane, and methacryloyloxypropylheptaoctylpolysilsesquioxane.

[0116] In some embodiments, step S200 specifically Step S210: adding a first monomer, a second monomer, and a third monomer to a solvent and an emulsifier and mixing them to form a mixed system; and step S220 of adding an initiator to the mixed system and causing a polymerization reaction by the action of the initiator to produce a first polymer.

[0117] In the present application, the copolymerization of multiple monomers can be carried out by emulsion polymerization, which is a more convenient polymerization method. Of course, other polymerization methods can also be used in the present application, such as solution polymerization, suspension polymerization, etc., and the process parameters used in the polymerization process can be selected from those commonly used in the art, and will not be further described here.

[0118] In some examples, the emulsifier comprises one or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, alkyl diphenyloxide disulfonate, ethoxylated alkyl phenol ammonium sulfate.

[0119] In some embodiments, the ratio of the mass percentage content of the emulsifier to the mass percentage content of the first monomer, the second monomer, and the third monomer, based on the total mass of the mixed system, is 0.1% to 5%, i.e., the amount of emulsifier used is 0.1% to 5% of the total mass of the three monomers. When the mass percentage content of the emulsifier is in the above range, the first monomer, the second monomer, and the third monomer may be emulsified and dispersed in a solvent to form a relatively homogeneous system.

[0120] In some embodiments, the initiator comprises potassium persulfate and / or ammonium persulfate.

[0121] In some embodiments, the ratio of the mass percentage content of the initiator to the mass percentage content of the second monomer, the second monomer, and the third monomer, based on the total mass of the mixed system, is 0.15% to 1%, that is, the amount of initiator used is 0.1% to 5% of the total mass of the three monomers.When the mass percentage content of the initiator is in the above range, sufficient polymerization can be ensured.

[0122] In some examples, the solvent may include water, for example, deionized water.

[0123] As a specific example, the method includes:

[0124] Preparation of prepolymer: deionized water, emulsifier, first polymerizable monomer, second polymerizable monomer and third polymerizable monomer are mixed and stirred uniformly to obtain prepolymer; Preparation of first polymer: Add emulsifier and deionized water to a vessel and emulsify for 30 to 60 minutes under stirring to obtain a uniform and stable emulsion. Then, slowly add the prepolymer and initiator solution (the initiator potassium persulfate and / or ammonium persulfate is dissolved in deionized water to form a solution) prepared in the previous step. After the addition is complete, the temperature is raised to 90-110°C and kept at that temperature for 0.5 hours to react. Then, the mixture is cooled to 40°C, and the pH is adjusted to 7-8 with aqueous ammonia. The mixture is then filtered, discharged, and dried to obtain the first polymer.

[0125] In some embodiments, the silicone particles further comprise a second polymer, the second polymer comprising structural units shown in formula (a): [ka] In formula (a), R 14 and R 15 each independently comprises one or more of a substituted or unsubstituted C1-C10 alkyl group, hydroxy, or amino group. 14 and R 15 each independently contain one or more of a substituted or unsubstituted C1-C6 alkyl group, hydroxy, or amino group.

[0126] Exemplarily, the second polymer includes one or more of the structures shown in formula (a-1) to formula (a-5): [ka]

[0127] Illustratively, the second polymer includes one or more of polymethylsiloxane, polydimethylsiloxane, polydiethylsiloxane, polymethylhydroxysiloxane, polymethylaminosiloxane.

[0128] In this application, the terms "first polymer" and "second polymer" are used only to distinguish between types of materials, and have no limiting effect on the order or quantity.

[0129] In some embodiments, the number average molecular weight of the silicone particles is 22,000 to 79,000, and optionally 24,000 to 48,000. Illustratively, the number average molecular weight of the polymer may be 22,000, 23,000, 24,000, 25,000, 30,000, 35,000, 40,000, 45,000, 46,000, 47,000, 48,000, or a range consisting of any two of the foregoing values. When the number average molecular weight of the silicone particles is in the above range, it has a relatively high viscosity, which is advantageous for improving the adhesive strength between the separator and positive and negative electrode plates when the silicone particles are applied to the separator. When the number average molecular weight of the silicone particles is within the above range, it is advantageous to form silicone particles with a relatively small particle size. When applied to a separator, a light and thin coating can be applied to the separator, reducing the overall thickness of the separator and thereby helping to improve the energy density of the secondary battery. In addition, the particle size of the silicone particles formed by the polymer is not too small, which reduces the risk of the silicone particles blocking the substrate in the separator and improves the performance of the separator, such as its overall air permeability.

[0130] In this application, the number average molecular weight of the polymer can be measured by gel permeation chromatography (GPC). Specifically, it is measured using a GPC1515 instrument manufactured by Waters, USA. The sample is dissolved in tetrahydrofuran, the dissolution time is 12 hours or more, the sample concentration is 4 mg / ml, and the sample is filtered to prepare the sample. The measurement temperature is 25°C, and the measurement flow rate is 1 ml / min.

[0131] The inventors further researched and found that during the long-term charge-discharge cycle of a secondary battery, moisture in the separator is gradually released into the electrolyte, which is highly sensitive to moisture and is prone to producing hydrofluoric acid (HF) upon contact with water, thereby increasing the acidity of the electrolyte, causing corrosion of the active material and current collector, and potentially causing the leaching of transition metal ions in the active material, thereby affecting the electrochemical performance of the secondary battery. Therefore, the present application adjusts the moisture content of the silicone particles to 3500 μg / g or less, optionally between 500 μg / g and 3000 μg / g, calculated based on the mass of the silicone particles. When the moisture content of the silicone particles is within the above range, the moisture content is relatively low, reducing the risk of side reactions in the electrolyte during the long-term charge-discharge cycle of the secondary battery, thereby improving the electrochemical performance of the secondary battery. For example, the moisture content of the silicone particles may be 300 μg / g, 500 μg / g, 800 μg / g, 1000 μg / g, 1200 μg / g, 1500 μg / g, 1800 μg / g, 2000 μg / g, 2500 μg / g, 2800 μg / g, 3000 μg / g, 3500 μg / g, or a range consisting of any two of the above values.

[0132] The moisture content of the silicone particles can be measured using a moisture meter. The test method may use the Karl Fischer moisture measurement method, and the test instrument may be a Karl Fischer moisture meter model 831 manufactured by Metrohm AG, Switzerland.

[0133] In some embodiments, the mass percentage content of the silicone particles is m1%, and is 50≦m1<100, and optionally 80≦m1≦95, thereby ensuring the heat resistance and stability of the coating. For example, the mass percentage content of the silicone particles may be 50%, 60%, 70%, 80%, 85%, 90%, 95%, 97%, or a range consisting of any two of the above values.

[0134] In some embodiments, the coating may further include inorganic particles. By adding inorganic particles, the heat resistance performance of the coating can be further improved.

[0135] In some embodiments, the mass percentage content of the inorganic particles in the coating is m2%, where 0 < m2 ≦ 30. Exemplarily, the mass percentage content of the inorganic particles in the coating may be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30% or a range consisting of any two of the above numerical values.

[0136] The inorganic particles may include at least one of inorganic particles having a dielectric constant of 5 or more, inorganic particles having the ability to transport active ions, and inorganic particles in which electrochemical oxidation and reduction can occur.

[0137] In some embodiments, the inorganic particles having a dielectric constant of 5 or more are boehmite (γ-AlOOH), aluminum oxide (Al2O3), barium sulfate (BaSO4), magnesium oxide (MgO), magnesium hydroxide (Mg(OH)2), silicon oxide SiO x (0 < x ≦ 2), tin dioxide (SnO2), titanium oxide (TiO2), calcium oxide (CaO), zinc oxide (ZnO), zirconium oxide (ZrO2), yttrium oxide (Y2O3), nickel oxide (NiO), hafnium dioxide (HfO2), cerium oxide (CeO2), zirconium titanate (ZrTiO3), barium titanate (BaTiO3), and magnesium fluoride (MgF2), 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) and Pb(Mg3Nb 2 / 3 )O3-PbTiO3 (abbreviated as PMN-PT) may include at least one of them.

[0138] In some embodiments, the inorganic particles having the ability to transport active ions are lithium phosphate (Li3PO4), lithium titanium phosphate (Li x Ti y (PO4)3, 0 < x < 2, 0 < y < 3), lithium aluminum titanium phosphate (Li x Al y Ti z (PO4)3, 0 < x < 2, 0 < y < 1, 0 < z < 3), (LiAlTiP) x O y -based glass (0 < x < 4, 0 < y < 13), lithium lanthanum titanate (Li x La y TiO3, 0 < x < 2, 0 < y < 3), lithium germanium thiophosphate (Li x Ge y P z S w , 0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), lithium nitride (Li x N y , 0 < x < 4, 0 < y < 2), SiS2-based glass (Li x Si y S z , 0 < x < 3, 0 < y < 2, 0 < z < 4) and P2S5-based glass (Li x P y S z , 0 < x < 3, 0 < y < 3, 0 < z < 7), at least one of which.

[0139] In some embodiments, the inorganic particles capable of undergoing electrochemical oxidation and reduction include at least one of lithium-containing transition metal oxides, olivine-structured lithium-containing phosphates, carbon-based materials, silicone-based materials, tin-based materials, and lithium titanium compounds.

[0140] In some embodiments, the coating may further include other organic particles, for example, the organic particles may include at least one of polystyrene, polyethylene, polyimide, melamine resin, phenolic resin, polypropylene, polyester (e.g., polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate), polyphenylene sulfide, polyaramid, polyamideimide, copolymers of butyl acrylate and ethyl methacrylate, and mixtures thereof.

[0141] In some embodiments, the coating may further include an adhesive, for example, the adhesive may include at least one of a water-soluble 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.

[0142] In some embodiments, the coating thickness may be 0.1 μm to 4 μm, and optionally 0.5 μm to 3 μm, thereby contributing to improving the energy density of the secondary battery. In this application, the coating thickness refers to the thickness of the coating located on one side of the substrate. For example, the coating thickness may be 0.1 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, or a range consisting of any two of the above values.

[0143] In some embodiments, the thickness of the substrate may be 16 μm or less, and optionally 3 μm to 12 μm. The coating of the present application can significantly improve the heat resistance of the separator, allowing for the selection of thinner substrates, thereby contributing to improving the energy density of secondary batteries. For example, the thickness of the substrate may be 1 μm, 2 μm, 3 μm, 5 μm, 10 μm, 12 μm, 15 μm, 16 μm, or a range consisting of any two of the above values.

[0144] In some embodiments, the porosity of the substrate is 25% or more, preferably 28% to 41%. When the porosity of the substrate is in this range, the air permeability of the substrate can be ensured to be favorable for the migration of active ions, and the relatively small porosity can further ensure the mechanical performance of the substrate and provide good support for the coating.

[0145] The present application does not particularly limit the material of the substrate, and any known substrate having good chemical and mechanical stability can be selected. For example, the 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 substrate may be a single-layer film or a multi-layer composite film. When the substrate is a multi-layer composite film, the materials of each layer may be the same or different.

[0146] In some embodiments, the separator further includes an adhesive layer disposed on at least a portion of the surface of the coating, the adhesive layer including an adhesive. The adhesive layer not only prevents the coating from falling off, improves adhesion between the coating and the substrate, and improves the safety performance of the secondary battery, but also improves the interface between the separator and the electrodes, thereby improving the cycle performance of the secondary battery.

[0147] Optionally, the adhesive includes at least one of an acrylate-based monomer homopolymer or copolymer, an acrylic-based monomer homopolymer or copolymer, and a fluorine-containing olefin monomer homopolymer or copolymer, and the copolymerizable monomer includes at least one of an acrylate-based monomer, an acrylic-based monomer, an olefin monomer, a halogen-containing olefin monomer, a fluoroether-based monomer, etc., but is not limited thereto.

[0148] Optionally, the adhesive includes a vinylidene fluoride polymer, such as a homopolymer of vinylidene fluoride monomer (VDF) and / or a copolymer of a copolymerizable monomer with vinylidene fluoride monomer. The copolymerizable monomer may be at least one of an olefin monomer, a fluorine-containing olefin monomer, a chlorine-containing olefin monomer, an acrylate-based monomer, an acrylic-based monomer, and a fluoroether-based monomer. Optionally, the copolymerizable monomer may include at least one of trifluoroethylene (VF3), chlorotrifluoroethylene (CTFE), 1,2-difluoroethylene, tetrafluoroethylene (TFE), hexafluoropropylene (HFP), perfluoro(alkyl vinyl) ether (e.g., perfluoro(methyl vinyl) ether PMVE, perfluoro(ethyl vinyl) ether PEVE, perfluoro(propyl vinyl) ether PPVE), perfluoro(1,3-dioxole), and perfluoro(2,2-dimethyl-1,3-dioxole) (PDD).

[0149] In some embodiments, the separator has a longitudinal heat shrinkage rate η1≦3.0% at 150° C. for 1 hour.

[0150] In some embodiments, the separator has a transverse heat shrinkage η2≦2.0% at 150° C. for 1 hour.

[0151] The separator of the present application has low thermal shrinkage in both the transverse and longitudinal directions at a high temperature of 150°C, thereby improving the safety performance of the secondary battery.

[0152] In some embodiments, the separator has a longitudinal tensile strength of R m1 ≧2700kgf / cm 2 and selectively 2700 kgf / cm 2 ≦R m1 ≦4500kgf / cm 2 is.

[0153] In some embodiments, the separator has a transverse tensile strength of R m2≧2000kgf / cm 2 and selectively 2500 kgf / cm 2 ≦R m2 ≦4500kgf / cm 2 is.

[0154] The separator of the present application has high tensile strength in both the horizontal and vertical directions, so that the probability of the separator being damaged when the secondary battery expands is relatively low, thereby improving the safety performance of the secondary battery.

[0155] In some embodiments, the wetted length of the separator is L≧30 mm, optionally 30 mm≦L≦60 mm.

[0156] In some embodiments, the wetting rate of the separator is u≧2 mm / s, optionally 2 mm / s≦u≦4 mm / s.

[0157] The separator of the present application has good electrolyte infiltration and retention properties, and therefore can improve the ionic conductivity of the separator and the secondary battery capacity development properties.

[0158] In some embodiments, the separator has an air permeability of MAP≦300 s / 100 mL, and optionally 130 s / 100 mL≦MAP≦250 s / 100 mL. The separator of the present application has good air permeability, which can improve ionic conductivity and secondary battery capacity performance.

[0159] In this application, the heat shrinkage rate, tensile strength, and air permeability of the separator all have meanings known in the art and can be measured using methods known in the art, for example, they may be tested in accordance with standard GB / T 36363-2018.

[0160] In this application, both the wetting length and wetting speed of the separator have meanings known in the art and can be measured using methods known in this field. Exemplary test methods are as follows: Cut the separator into samples with a width of 5 mm and a length of 100 mm, horizontally arrange them after fixing both ends of the samples, take 0.5 mg of electrolyte and drop it onto the center of the sample. After reaching a predetermined time (1 min in this application), take a photo and measure the diffusion length of the electrolyte, thereby obtaining the wetting length and wetting speed of the separator. To ensure the accuracy of the test results, multiple (for example, 5 to 10) samples can be used for the test, and the test results can be obtained by calculating the average value. The electrolyte can be 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, dissolving sufficiently dried LiPF6 in the above organic solvent, and preparing an electrolyte with a concentration of 1 mol / L.

[0161] It should be noted that the coating parameters (such as thickness, etc.) of the above separator are the coating parameters on one side of the substrate. When the coating is installed on both sides of the substrate, if the coating parameters on either side meet the requirements of this application, it is considered to fall within the protection scope of this application.

[0162] Manufacturing method According to a second aspect, this application provides a method for manufacturing a separator, and the method can be used for manufacturing the separator described in any one of the embodiments of the first aspect of this application.

[0163] The method includes, in S1, a step of providing a substrate; in S2, a step of mixing silicone particles into a solvent to prepare a coating slurry; and in S3, a step of coating the coating slurry on at least one surface of the substrate, forming a coating and drying it to obtain a separator, where the volume distribution particle size Dv90 of the silicone particles satisfies 0 < Dv90 ≤ 3.0 μm.

[0164] In some embodiments, 0.1 μm≦Dv90≦2.0 μm.

[0165] In some embodiments, in S2, the solvent may be water, for example, deionized water.

[0166] In some embodiments, in S2, the coating slurry may further include other ingredients, such as dispersants, wetting agents, adhesives, and the like.

[0167] In some embodiments, in S2, based on the weight of the coating, the weight percentage of the silicone particles is ≧50%, optionally 80% to 95%. When the weight percentage of the silicone particles is in the above range, the heat resistance and stability of the coating can be significantly improved.

[0168] In some embodiments, the solids content of the coating slurry is between 10% and 40%, and optionally between 20% and 30%.

[0169] In some embodiments, in S3, the coating is performed using a coater. The present application does not particularly limit the model number of the coater, and for example, a commercially available coater may be used. The coater includes an intaglio roller, and the intaglio roller is used to transfer the slurry onto the substrate.

[0170] In some embodiments, in S3, the coating method may be transfer coating, spin spray coating, dip coating, or the like.

[0171] In some embodiments, the method further includes a step of applying a second coating, S4, of applying a slurry containing an adhesive to at least a portion of the surface of the coating and drying to form an adhesive layer.

[0172] The separator manufacturing method of the present application produces and obtains a coating in a single application, greatly simplifying the separator manufacturing process flow.

[0173] Parameters such as some raw materials used in the manufacturing method of the separator of the present application and their contents can be referred to the separator of the first aspect of the embodiment of the present application, and will not be further described here.

[0174] Unless otherwise specified, each of the raw materials used in the manufacturing method of the separator of the present application is commercially available.

[0175] secondary battery According to a third aspect, the present application further provides a secondary battery.

[0176] A secondary battery, also known as a rechargeable battery or storage battery, is a battery that can be continuously used by activating the active material through charging after discharging. Generally, a secondary battery includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode plate, a negative electrode plate, and a separator. The separator is disposed between the positive electrode plate and the negative electrode plate and mainly serves to prevent short circuits between the positive electrode and the negative electrode and allows active ions to pass through.

[0177] The present application is not particularly limited to the type of secondary battery, and for example, the secondary battery may be a lithium ion battery, a sodium ion battery, etc., and in particular may be a lithium ion secondary battery.

[0178] The secondary battery described herein includes a separator according to the first aspect of the present application or a separator manufactured by the method according to the second aspect of the present application, the separator being interposed between the positive electrode plate and the negative electrode plate. Optionally, the separator may have the coating according to the present application on at least one side thereof closer to the negative electrode plate. Furthermore, the separator may have the coating according to the present application on one side thereof closer to the positive electrode plate, and the separator may also have the coating according to the present application on one side thereof closer to the negative electrode plate. This allows the secondary battery according to the present application to improve its own energy density and safety performance.

[0179] [Positive electrode plate] In some embodiments, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector and containing a positive electrode active material. For example, the positive electrode current collector has two opposing surfaces in its thickness direction, and the positive electrode film layer is disposed on either one or both of the two opposing surfaces of the positive electrode current collector.

[0180] When the secondary battery of the present application is a lithium-ion battery, the positive electrode active material may include, but is not limited to, at least one of a lithium-containing transition metal oxide, a lithium-containing phosphate, and their modified compounds. Examples of the lithium-containing transition metal oxide may include, but are not limited to, at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds. Examples of the lithium-containing phosphate may include, but are not limited to, at least one of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite material of lithium manganese iron phosphate and carbon, and their modified compounds.

[0181] In some embodiments, in order to further improve the energy density of the secondary battery, the positive electrode active material used in the lithium-ion battery may include at least one of a lithium transition metal oxide represented by the general formula Li a Ni b Co c M d O e A f and its modified compounds. Here, 0.8 ≦ a ≦ 1.2, 0.5 ≦ b < 1, 0 < c < 1, 0 < d < 1, 1 ≦ e ≦ 2, 0 ≦ f ≦ 1, M includes at least one of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, and B, and A includes at least one of N, F, S, and Cl.

[0182] For example, the positive electrode active materials used in lithium ion batteries are 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 0.85 Co 0.15 Al 0.05 It may contain at least one of O2, LiFePO4, and LiMnPO4.

[0183] When the secondary battery of the present application is a sodium ion battery, the positive electrode active material may include at least one of a sodium-containing transition metal oxide, a polyanion material (e.g., phosphate, fluorophosphate, pyrophosphate, sulfate, etc.), and a Prussian blue-based material, but is not limited thereto.

[0184] For example, the positive electrode active materials used in sodium ion batteries are NaFeO2, NaCoO2, NaCrO2, NaMnO2, NaNiO2, NaNi 1 / 2 Ti 1 / 2 O2, NaNi 1 / 2 Mn 1 / 2 O2, Na 2 / 3 Fe 1 / 3 Mn 2 / 3 O2, NaNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, NaFePO4, NaMnPO4, NaCoPO4, Prussian blue-based materials, general formula X p M' q (PO4) r O x Y 3-x The compound may comprise at least one of the materials represented by the general formula X p M'q (PO4) r O x Y 3-x In, 0 <p≦4、0<q≦2、1≦r≦3、0≦x≦2であり、Xは、H + , Li + , Na + , K. + and NH 4+ wherein M' is a transition metal cation, optionally at least one of V, Ti, Mn, Fe, Co, Ni, Cu, and Zn; and Y is a halogen anion, optionally at least one of F, Cl, and Br.

[0185] In the present application, the modifying compound for each of the positive electrode active materials is a compound that modifies the positive electrode active material by doping and / or surface coating.

[0186] In some embodiments, the positive electrode film layer further optionally includes a positive electrode conductive agent. The present application does not particularly limit the type of the positive electrode conductive agent, and the positive electrode conductive agent may include, for example, at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage content of the positive electrode conductive agent is ≦5% based on the total mass of the positive electrode film layer.

[0187] In some embodiments, the positive electrode film layer optionally further includes a positive electrode adhesive. The present application does not particularly limit the type of the positive electrode adhesive. For example, the positive electrode adhesive may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin. In some embodiments, the mass percentage content of the positive electrode adhesive is ≦5% based on the total mass of the positive electrode film layer.

[0188] In some embodiments, the positive electrode current collector may be a metal foil sheet or a composite current collector. An example of a metal foil sheet is aluminum foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. For example, the metal layer may include at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. For example, the polymer base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0189] The positive electrode film layer is typically obtained by coating a positive electrode slurry on a positive electrode current collector, drying, and cold pressing. The positive electrode slurry is typically formed by dispersing a positive electrode active material, an optional conductive agent, an optional adhesive, and any other optional components in a solvent and stirring the resulting mixture uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP).

[0190] [Negative electrode plate] In some embodiments, the negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and including a negative electrode active material. For example, the negative electrode current collector has two surfaces facing each other in a thickness direction thereof, and the negative electrode film layer is disposed on one or both of the two facing surfaces of the negative electrode current collector.

[0191] The negative electrode active material may be any negative electrode active material for secondary batteries known in the art. For example, the negative electrode active material may include, but is not limited to, at least one of natural graphite, artificial graphite, soft carbon, hard carbon, a silicone-based material, a tin-based material, and lithium titanate. The silicone-based material may include at least one of a silicone element, a silicone oxide, a silicone carbon composite, a silicone nitrogen composite, and a silicone alloy material. The tin-based material may include at least one of a tin element, a tin oxide, and a tin alloy material.

[0192] In some embodiments, the negative electrode film layer optionally further includes a negative electrode conductive agent. The present application does not particularly limit the type of the negative electrode conductive agent, and for example, 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. In some embodiments, the mass percentage content of the negative electrode conductive agent is ≦5% based on the total mass of the negative electrode film layer.

[0193] In some embodiments, the negative electrode film layer optionally further includes a negative electrode adhesive. The present application does not particularly limit the type of the negative electrode adhesive. For example, the negative electrode adhesive may include at least one of styrene butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-soluble acrylic acid-based resin (e.g., polyacrylic acid (PAA), polymethacrylic acid (PMAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). In some embodiments, the mass percentage content of the negative electrode adhesive is ≦5% based on the total mass of the negative electrode film layer.

[0194] In some embodiments, the negative electrode membrane layer further optionally contains other additives. For example, the other additives may include a thickener, such as sodium carboxymethylcellulose (CMC), a PTC thermistor material, etc. In some embodiments, the mass percentage content of the other additives is ≦2%, based on the total mass of the negative electrode membrane layer.

[0195] In some embodiments, the negative electrode current collector may be a metal foil sheet or a composite current collector. An example of a metal foil sheet is copper foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. For example, the metal layer may include at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. For example, the polymer base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0196] The negative electrode film layer is typically obtained by coating a negative electrode slurry on a negative electrode current collector, drying, and cold pressing. The negative electrode slurry is typically formed by dispersing a negative electrode active material, an optional conductive agent, an optional adhesive, and other optional auxiliary agents in a solvent and stirring the resulting mixture uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0197] The negative electrode plate does not exclude additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode plate described herein further includes a conductive undercoating (e.g., composed of a conductive agent and an adhesive) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In other embodiments, the negative electrode plate described herein further includes a protective layer covering the surface of the negative electrode film layer.

[0198] [Electrolyte] During the charge and discharge process of the secondary battery, active ions are absorbed and released by moving back and forth between the positive and negative electrodes, and the electrolyte serves to conduct the active ions between the positive and negative electrodes. The present application does not particularly limit the type of electrolyte, and it can be selected according to actual needs.

[0199] 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 may be selected according to actual needs.

[0200] When the secondary battery of the present application 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 bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluorophosphate (LiPOF), lithium difluorobis(oxalato)phosphate (LiDFOP), and lithium tetrafluoro(oxalato)phosphate (LiTFOP).

[0201] When the secondary battery of the present application 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 bisfluorosulfonylimide (NaFSI), sodium bistrifluoromethanesulfonylimide (NaTFSI), sodium trifluoromethanesulfonate (NaTFS), sodium difluoro(oxalato)borate (NaDFOB), sodium bis(oxalato)borate (NaBOB), sodium difluorophosphate (NaPOF), sodium difluorobis(oxalato)phosphate (NaDFOP), and sodium tetrafluoro(oxalato)phosphate (NaTFOP).

[0202] By way of example, the solvent may include, but is not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE).

[0203] In some embodiments, the electrolyte solution optionally further contains additives. For example, the additives may include a negative electrode film-forming additive, a positive electrode film-forming additive, and / or an additive that can improve some battery performance, such as an additive that improves the overcharge performance of the battery, an additive that improves the high-temperature performance of the battery, or an additive that improves the low-temperature power performance of the battery.

[0204] In some embodiments, the positive electrode plate, the separator, and the negative electrode plate may be fabricated into an electrode assembly by a winding process and / or a stacking process.

[0205] In some embodiments, the secondary battery may include an exterior body, which may be used to package the electrode assembly and the electrolyte solution.

[0206] In some embodiments, the exterior of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The exterior of the secondary battery may be a pouch, such as a bag-shaped pouch. The material of the pouch may be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0207] The present application does not particularly limit the shape of the secondary battery, and the secondary battery may be cylindrical, rectangular, or any other shape. Figure 1 shows an example of a secondary battery 5 having a rectangular structure.

[0208] In some embodiments, as shown in FIG. 2 , the exterior body may include a case 51 and a cover plate 53. The case 51 may include a bottom plate and side plates connected to the bottom plate, which together form a surrounding accommodating cavity. The case 51 has an opening communicating with the accommodating cavity, and the cover plate 53 is used to cover the opening and seal the accommodating cavity. The positive electrode plate, the negative electrode plate, and the separator may be formed into an electrode assembly 52 through a winding process and / or a stacking process. The electrode assembly 52 is packaged in the accommodating cavity. An electrolyte is impregnated into the electrode assembly 52. The number of electrode assemblies 52 included in the secondary battery 5 may be one or more and can be adjusted as needed.

[0209] The method for manufacturing the secondary battery of the present application is well known. In some embodiments, a secondary battery can be formed by assembling a positive electrode plate, a separator, a negative electrode plate, and an electrolyte. For example, the positive electrode plate, the separator, and the negative electrode plate can be formed into an electrode assembly through a winding process and / or a stacking process. The electrode assembly can be placed in an outer casing, dried, and then injected with an electrolyte. The secondary battery can be obtained through processes such as vacuum packaging, standing, chemical formation, and shaping.

[0210] In some embodiments of the present application, the secondary battery according to the present application can be assembled into a battery module, and the number of secondary batteries included in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0211] Fig. 3 is a schematic diagram of an example battery module 4. As shown in Fig. 3, in the battery module 4, a plurality of secondary batteries 5 may be arranged in order along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the plurality of secondary batteries 5 may be fixed by fasteners.

[0212] Optionally, the battery module 4 may further include a housing having an accommodating space, and the plurality of secondary batteries 5 are accommodated in this accommodating space.

[0213] In some embodiments, the battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0214] 4 and 5 are schematic diagrams of an example battery pack 1. As shown in FIGS. 4 and 5, the battery pack 1 may include a battery box and a plurality of battery modules 4 installed in the battery box. The battery box includes an upper housing 2 and a lower housing 3, and the upper housing 2 covers the lower housing 3 and is used to form a sealed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0215] power consumption equipment A fourth aspect of the present application provides a power consuming device, the power consuming device including at least one of the secondary battery, battery module, or battery pack of the present application. The secondary battery, battery module, or battery pack may be used as a power source for the power consuming device or as an energy storage unit for the power consuming device. The power consuming device may be, but is not limited to, a mobile device (e.g., a mobile phone, a laptop, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, an energy storage system, etc.

[0216] The power consumption device may select a secondary battery, a battery module, or a battery pack according to its usage needs.

[0217] 6 is a schematic diagram of an example power consuming device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, that may employ a battery pack or battery module to meet the high power and high energy density demands of the power consuming device.

[0218] Other examples of power consuming devices include mobile phones, tablet computers, notebook computers, etc. These power consuming devices generally require a thin design and can employ secondary batteries as their power source.

[0219] Example The following examples will more specifically describe the contents disclosed in this application, and these examples are for illustrative purposes only, as various modifications and variations within the scope of the contents disclosed in this application will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages and ratios reported in the following examples are by weight, and all reagents used in the examples can be obtained commercially or synthesized according to conventional methods and can be used directly without further treatment, and all instruments used in the examples can be obtained commercially.

[0220] Silicone particle production Example A Prepolymer production A 5-L three-neck flask was charged with 1400 g of deionized water and 7 g of sodium dodecyl sulfate, and emulsified by stirring at a rotation speed of 1500 r / min for 30 minutes to obtain a uniform and stable emulsion. Next, n-butyl acrylate, acrylonitrile, and methacryloyloxypropyl cage-type polysilsesquioxane (the molar content ratio of n-butyl acrylate, acrylonitrile, and methacryloyloxypropyl cage-type polysilsesquioxane was 15:3:2) were added in that order, and stirring was continued at a rotation speed of 1500 r / min for 30 minutes to obtain a uniform prepolymer.

[0221] Silicone particle production 3g of emulsifier and 1000g of deionized water were added to a dry three-neck flask and emulsified under high-speed stirring for 30 minutes to obtain a uniform and stable emulsion. Next, using a peristaltic pump, the prepolymer and initiator solution prepared in the previous step (3g of initiator, potassium persulfate, dissolved in 30g of deionized water to form a solution) were slowly added dropwise. After the addition was complete, the temperature was raised to 90°C and kept at that temperature for 0.5 hours to react. The mixture was then cooled to 40°C, and the pH was adjusted to 7-8 with aqueous ammonia. The mixture was then filtered, discharged, and dried to produce silicone particles.

[0222] Example 1 Separator manufacturing The PE substrate was provided with a thickness of 7 μm, a porosity of 40%, an ionic conductivity of 1.20 mS / cm, and an average particle size of 0.3 μm.

[0223] Preparation of coating slurry: The silicone particles produced in Example A, aqueous adhesive polyacrylic acid and additives were uniformly mixed in a mass ratio of 92:7:1 with an appropriate amount of deionized water as a solvent to obtain a coating slurry.

[0224] Coating: The prepared coating slurry was applied to two surfaces of the PE substrate using a coating machine, and then dried and slit to obtain a separator. The surface density of the coating on one side of the PE substrate was 0.9 g / m. 2 and the thickness was 0.45 μm.

[0225] Positive electrode plate manufacturing A 12 μm thick aluminum foil was used as the positive electrode current collector.

[0226] Positive electrode active material LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM333), conductive carbon black (Super P), and adhesive polyvinylidene fluoride (PVDF) were mixed uniformly in a mass ratio of 96.2:2.7:1.1 in an appropriate amount of solvent N-methylpyrrolidone (NMP) to obtain a positive electrode slurry. The positive electrode slurry was then applied to a positive electrode current collector aluminum foil, followed by drying, cold pressing, slitting, cutting, and other processes to obtain a positive electrode plate. The areal density of the positive electrode plate was 0.207 mg / mm 2 and the compaction density is 3.5 g / cm 3 is.

[0227] Negative electrode plate manufacturing A copper foil with a thickness of 8 μm was used as the negative electrode current collector.

[0228] The negative electrode active material, natural graphite, conductive agent Super P, thickener CMC, and adhesive styrene-butadiene rubber (SBR) were uniformly mixed in deionized water to prepare a negative electrode slurry. The solids content of the negative electrode slurry was 30 wt%, and the mass ratio of graphite, Super P, CMC, and adhesive styrene-butadiene rubber (SBR) in the solids was 80:15:3:2. The negative electrode slurry was applied to a copper foil current collector and dried at 85°C. After cold pressing, trimming, cutting, and slitting, the resulting material was dried in a vacuum at 120°C for 12 hours to produce a negative electrode plate.

[0229] Electrolyte production In an environment with a water content of less than 10 ppm, the non-aqueous organic solvents ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1 to obtain an electrolyte solvent, which was then mixed with a lithium salt and the resulting solvent was mixed to prepare an electrolyte with a lithium salt concentration of 1 mol / L.

[0230] Secondary battery manufacturing A positive electrode plate, a separator, and a negative electrode plate were stacked in this order and wound to obtain an electrode assembly. The electrode assembly was then placed in an outer casing, dried, and then an electrolyte was added. After undergoing processes such as vacuum packaging, standing, chemical conversion, and shaping, a secondary battery was obtained.

[0231] Comparative Example 1, Examples 2 to 12 The secondary battery was manufactured in a similar manner to that of Example 1, except that the manufacturing parameters of the separator were different. The specific parameter details are as shown in Table 1.

[0232] The test results are shown in Table 1.

[0233] Testing part 1. Separator heat shrinkage rate test Sample preparation: The separator prepared above is punched out into samples 50 mm wide and 100 mm long in the TD and MD directions using a press. Five parallel samples are placed on an A4 sheet of paper, and the A4 sheet of paper containing the samples is then placed on a piece of cardboard 1 mm to 5 mm thick.

[0234] Sample test: Set the temperature of the blast oven to 150°C. After the temperature reaches the set temperature and stabilizes for 30 minutes, place an A4 size sheet of paper on a piece of cardboard into the blast oven and start timing. After the set time (1 hour in this application) is reached, measure the length and width of the separator and mark the values as a and b respectively.

[0235] Calculation of heat shrinkage rate: Machine direction (MD) heat shrinkage rate = [(100-a) / 100] x 100%, Transverse direction (TD) heat shrinkage rate = [(50-b) / 50] x 100%, the average value of five parallel samples is taken as the test result.

[0236] 2. Hot box test of secondary batteries At 25°C, the secondary batteries were charged at a constant current of 1C to 4.2V, and then continued to be charged at a constant voltage until the current reached ≤0.05C. After 5 minutes of rest, each secondary battery was then tested in a DHG-9070ADHG series high-temperature oven with a jig attached. The temperature was increased from room temperature to 80°C + / -2°C at a rate of 5°C / min and maintained at that temperature for 30 minutes. The temperature was then increased at a rate of 5°C / min, with each 5°C increase being maintained for 30 minutes until the secondary battery expired. The temperature change on the surface of the secondary battery was monitored during the heating process; the oven temperature at which the temperature began to rise rapidly was the hot box expiration temperature of the secondary battery. A higher hot box expiration temperature indicates better thermal safety performance of the secondary battery.

[0237] [Table 1]

[0238] As can be seen from Table 1, the Dv90 of the silicone particles in Comparative Example 1 is 3.50 μm. The separator using silicone particles with this particle size has a higher thermal shrinkage rate and lower stability in the long-term cycle of the lithium-ion battery. The Dv90 of the silicone particles is closely related to the minimum coating thickness in the separator. The maximum thickness is generally smaller than Dv90; otherwise, the coating is likely to leak. When the coating thickness is constant, the smaller the Dv90, the more layers of coating-deposited particles there are, and the better the heat resistance.

[0239] In Examples 1 to 12, by adjusting the Dv90 of the silicone particles to satisfy 0 < Dv90 ≤ 3.0 μm, especially when 0.1 μm ≤ Dv90 ≤ 2.0 μm is satisfied, it is possible to reduce the thermal shrinkage rate of the separator and improve the mechanical properties of the separator when providing a relatively thin coating on the separator. Moreover, the separator has better air permeability, which is advantageous for the movement of active ions. Further, by adjusting (Dv90 - Dv10) / Dv50, the mechanical properties and air permeability of the separator can be further improved. Also, as the coating thickness increases, the deposited silicone particles increase, and the heat resistance of the separator improves, but the air permeability may decrease to some extent.

[0240] Although this application has been described with reference to the preferred embodiments, various improvements can be made to it without departing from the scope of this application, and the members thereof can be replaced with equivalents. In particular, as long as there is no structural conflict, each technical feature mentioned in each embodiment can be combined in any manner. This application is not limited to the specific embodiments disclosed in the specification, but includes all technical solutions within the scope of the claims.

Description of Reference Numerals

[0241] 1: Battery pack, 2: Upper housing, 3: Lower housing, 4: Battery module, 5: Secondary battery, 51: Case, 52: Electrode assembly, 53: Cover plate, 6: Power consumption device.

Claims

1. A separator comprising: a substrate; and a coating provided on at least one surface of the substrate; the coating contains silicone particles; and the silicone particles have a volume distribution particle size Dv90 that satisfies 0<Dv90≦3.0 μm.

2. 2. The separator according to claim 1, wherein 0.1 μm≦Dv90≦2.0 μm.

3. 3. The separator according to claim 1, wherein the particle size distribution of the silicone particles satisfies (Dv90-Dv10) / Dv50≦2.0, and optionally 0.1≦(Dv90-Dv10) / Dv50≦1.

0.

4. The separator according to claim 1 , wherein the volume distribution particle size Dv50 of the silicone particles satisfies 0.01 μm≦Dv50≦2 μm.

5. The separator satisfies conditions (1) to (3), (1) The specific surface area (SSA) of the silicone particles is 2.0 cm ２ / g ~ 50cm ２ / g, and optionally 8.5 cm ２ / g ~ 20.5 cm ２ / g, and (2) the silicone particles include primary particles; (3) The separator according to any one of claims 1 to 4, wherein the shape of the silicone particles satisfies at least one of the following conditions: spherical, near-spherical, cubic, rhombic, fibrous, tubular, rod-like, and sheet-like.

6. the silicone particles comprise a first polymer; The first polymer comprises a first structural unit, a second structural unit, and a third structural unit, and the first structural unit comprises a structural unit shown in formula (I): 【Chemical 1】 In formula (I), R １ contains one or more of a hydrogen atom, a substituted or unsubstituted C1-C5 alkyl group, and optionally R １ contains one or more of a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group, R ２ comprises one or more of a substituted or unsubstituted C1-C20 alkyl group, a substituted or unsubstituted C3-C20 cycloalkyl group, a substituted or unsubstituted C1-C20 hydroxyalkyl group, and optionally R ２ comprises one or more of a C1-C12 alkyl group, a C3-C12 cycloalkyl group, a C1-C12 hydroxyalkyl group; The second structural unit comprises a structural unit represented by formula (II): 【Chemistry 2】 In formula (II), R ３ contains one or more of a hydrogen atom, a substituted or unsubstituted C1-C5 alkyl group, and optionally R ３ contains one or more of a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group, The third structural unit includes a structural unit represented by formula (III): 【Chemistry 3】 In formula (III), R ４ From R １１ each independently comprises one or more of a substituted or unsubstituted C1-C10 alkyl group, a structural unit represented by formula (III-1), and R ４ From R １１ At least one of the above contains a structural unit represented by formula (III-1): 【Chemistry 4】 In formula (III-1), R １２ contains one or more of a hydrogen atom, a substituted or unsubstituted C1-C5 alkyl group, and optionally R １２ contains one or more of a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group, R １３ comprises a substituted or unsubstituted C1-C10 alkyl group, optionally R １３ The separator according to any one of claims 1 to 5, wherein comprises a substituted or unsubstituted C3-C10 alkyl group.

7. the molar content of the first structural unit is expressed as A% based on the total molar amount of the first structural unit, the second structural unit and the third structural unit, and is 75≦A<100, and optionally 75≦A≦80; and / or the molar content of the second structural unit is designated as B% based on the total molar amount of the first structural unit, the second structural unit and the third structural unit, where 0<B≦15, optionally 5≦B≦15; and / or The polymer according to claim 6, wherein the molar content of the third structural unit is expressed as C% based on the total molar amount of the first structural unit, the second structural unit, and the third structural unit, and 0<C≦15, optionally 5≦C≦15.

8. Based on the total molar amount of the first structural unit, the second structural unit, and the third structural unit, the molar content of the first structural unit is represented as A%, the molar content of the second structural unit is represented as B%, and the molar content of the third structural unit is represented as C%, and the first polymer satisfies conditions (1) to (3). (1) the condition that 5≦A / B≦15; (2) the condition that 5≦A / C≦15; (3) A:B:C is (12 to 15):(1 to 3):(1 to 3). The polymer according to claim 6 or 7, which satisfies one or more of the following conditions.

9. The silicone particles include a second polymer, the second polymer including a structural unit shown in formula (a): 【Chemistry 5】 In formula (a), R １４ and R １５ each independently comprise one or more of a substituted or unsubstituted C1-C10 alkyl group, hydroxy or amino group, and optionally R １４ and R １５ each independently comprises one or more of a substituted or unsubstituted C1-C6 alkyl group, hydroxy, or amino group; 9. The separator of claim 1, wherein the second polymer optionally comprises one or more of polymethylsiloxane, polydimethylsiloxane, polydiethylsiloxane, polymethylhydroxysiloxane, and polymethylaminosiloxane.

10. The separator according to any one of claims 1 to 9, wherein the number average molecular weight of the silicone particles is 22,000 to 79,000, and optionally 24,000 to 48,000.

11. 11. The separator according to claim 1, wherein the moisture content of the silicone particles is 3500 μg / g or less, and optionally 500 μg / g to 3000 μg / g, based on the mass of the silicone particles.

12. Based on the weight of the coating, the mass percentage content of the silicone particles is m １ %, and 50≦m １ <100, and optionally 80≦m １ 12. The separator of claim 1, wherein the tensile strength is ≦95.

13. The coating further comprises inorganic particles, and optionally the mass percentage content of the inorganic particles in the coating is m ２ %, and 0<m ２ 13. The separator of claim 1, wherein the R s is ≦30.

14. The separator satisfies conditions (a) to (c), (a) the porosity of the substrate is 25% or more, and optionally 28% to 41%; (b) the thickness of the substrate is 16 μm or less, and optionally 3 μm to 12 μm; 14. The separator of claim 1, further satisfying at least one of the following conditions: (c) the thickness of the coating is 0.1 μm to 4 μm, and optionally 0.5 μm to 3 μm.

15. The separator satisfies the conditions (I) to (VII): (I) The separator has a longitudinal heat shrinkage rate of η at 150°C for 1 hour. １ ≦3.0%; (II) The separator has a transverse heat shrinkage rate of η at 150°C for 1 hour. ２ ≦2.0%; (III) The longitudinal tensile strength of the separator is R ｍ１ ≧2700kgf / cm ２ and optionally 2700 kgf / cm ２ ≦R ｍ１ ≦4500kgf / cm ２ and (IV) The lateral tensile strength of the separator is R ｍ２ ≧2000kgf / cm ２ and optionally 2500 kgf / cm ２ ≦R ｍ２ ≦4500kgf / cm ２ and (V) the wet length of the separator is L≧30 mm, and optionally 30 mm≦L≦60 mm; (VI) the wetting speed of the separator is u≧2 mm / s, optionally 2 mm / s≦u≦4 mm / s; (VII) The separator according to any one of claims 1 to 14, wherein the separator has an air permeability that satisfies at least one of the following conditions: MAP≦300 s / 100 mL, and optionally, 130 s / 100 mL≦MAP≦250 s / 100 mL.

16. A method for manufacturing a separator, comprising: In S1, providing a substrate; In S2, silicone particles are mixed into a solvent to prepare a coating slurry; In S3, the coating slurry is applied to at least one surface of the substrate to form a coating, and the coating is dried to obtain a separator; wherein the volume distribution particle size Dv90 of the silicone particles satisfies 0<Dv90≦3.0 μm.

17. the mass percentage content of the silicone particles is 50% or more, optionally 80% to 95%, based on the mass of the coating; and / or The manufacturing method according to claim 16, wherein the solid content of the coating slurry is 10% to 40%, and optionally 20% to 30%.

18. A secondary battery comprising the separator according to any one of claims 1 to 15 or a separator produced by the manufacturing method according to claim 16 or 17.

19. 20. A power consuming device comprising the secondary battery of claim 18.

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