Isolating membrane and preparation method thereof, secondary battery and electric device

Abstract

Provided are an isolating membrane and a preparation method thereof, a secondary battery (5) and an electric device, the isolating membrane comprising a base material and a coating layer provided on at least one side of the base material, the coating layer comprising first particles and second particles, the first particles being organic particles, the second particles having a porous structure, the isolating membrane having the characteristics of good heat resistance and ion transport characteristics, and the thermal safety performance and the cycle performance of the battery using the isolating membrane can be improved.

Description

Separator and preparation method thereof, secondary battery and electric device Technical Field

[0001] The present application belongs to the field of battery technology, and specifically relates to an isolation membrane and a preparation method thereof, a secondary battery and an electrical device. Background Art

[0002] In recent years, with the development of battery technology, it has the characteristics of high energy density, good cycle performance and safety performance, and is therefore widely used in power tools such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, electric planers, and electric vehicles such as electric motorcycles, electric cars, electric vans, light commercial vehicles, electric trucks, electric buses, electric leisure boats, electric commercial short-distance and deep-sea ships, and electric manned aircraft.

[0003] With the promotion and application of batteries in many fields, the requirements for their thermal safety and cycle performance have also increased. However, in related technologies, the thermal safety performance of batteries decreases during temperature increase, and their cycle performance also decreases. Therefore, there is an urgent need to improve the thermal safety and cycle performance of batteries.

[0004] Summary of the Invention

[0005] The purpose of the present application is to provide an isolation membrane and a preparation method thereof, a secondary battery and an electrical device. The isolation membrane has good heat resistance and ion transport properties, thereby improving the thermal safety and cycle performance of the battery using the isolation membrane.

[0006] In a first aspect, the present application provides an isolation membrane comprising a substrate and a coating, wherein the coating is disposed on at least one side of the substrate, wherein the coating comprises first particles and second particles, the first particles are organic particles, and the second particles have a pore structure.

[0007] In the separator provided in this application, the first particles in the coating are organic particles. Since organic particles have good heat resistance, and when the separator shrinks due to heat, the first particles, the second particles, and / or the first and second particles in the coating may abut against each other as the substrate shrinks, thereby providing a force to the substrate in the opposite direction of contraction, reducing the degree of contraction of the separator and thereby reducing the risk of short circuits between the positive and negative electrodes in the battery, thereby improving the thermal safety performance of the battery. In addition, the second particles with a porous structure can store electrolyte, improve the liquid absorption rate and liquid retention rate of the separator, and their pore size can serve as an ion channel to transmit ions, thereby enabling the battery to have good heat resistance while also taking into account good cycle performance.

[0008] In any embodiment of the present application, the average pore diameter of the second particles is 0.1 nm-10 nm, and optionally 0.4 nm-5 nm.

[0009] In any embodiment of the present application, the porosity of the second particles is 10%-60%, and optionally 30%-50%.

[0010] In any embodiment of the present application, the average particle size of the second particles is less than or equal to 2 μm, and can be selected from 0.1 μm to 1 μm. The average particle size of the second particles within the above-mentioned suitable range not only facilitates electrolyte wetting of the separator to improve battery cycle performance, but also facilitates bonding between the particles. This, when the separator is heated, quickly provides a force in the opposite direction of the heat applied to the separator, thereby reducing the degree of shrinkage of the separator when heated and improving the thermal safety of the battery.

[0011] In any embodiment of the present application, the specific surface area of ​​the second particles is greater than or equal to 100 m 2 / g, optional 500m 2 / g-2000m 2 The specific surface area of ​​the second particles is set within the above-mentioned suitable range, which can increase the contact area between the second particles and the electrolyte, thereby helping to improve the electrolyte's wetting effect on the separator and the electrolyte retention effect.

[0012] In any embodiment of the present application, based on the weight of the coating, the ratio of the weight proportion A of the first particles to the weight proportion B of the second particles satisfies: 1

[0013] In any embodiment of the present application, based on the weight of the coating layer, a ratio of a weight proportion A of the first particles to a weight proportion B of the second particles satisfies: 5≤A / B≤15.

[0014] In any embodiment of the present application, the weight proportion B of the second particles in the coating is less than or equal to 20%, and can be optionally 0.1%-15%.

[0015] In any embodiment of the present application, the second particles include one or more of inorganic particles and metal-organic framework materials;

[0016] In any embodiment of the present application, the inorganic particles include one or more of titanium oxide, zirconium oxide, barium oxide, magnesium oxide, barium sulfate, magnesium aluminum silicate, zirconium titanate, and barium titanate.

[0017] In any embodiment of the present application, the metal-organic framework material includes one or more of IRMOFs, ZIFs, MILs, PCNs, CPLs, and UiOs.

[0018] ​In any embodiment of the present application, the second particles have a through-pore structure.

[0019] In any embodiment of the present application, the first particles include one or more of silicone particles, melamine formaldehyde resin particles, phenolic resin particles, polyester particles, polyimide particles, polyamideimide particles, polyaramid particles, polyphenylene sulfide particles, polysulfone particles, polyethersulfone particles, polyetheretherketone particles and polyaryletherketone particles; optionally, the first particles include silicone particles.

[0020] In any embodiment of the present application, the first particles include silicone particles, and the silicone particles include a first polymer, and the first polymer includes a first structural unit, a second structural unit, and a third structural unit;

[0021] The first structural unit has a structure as shown in formula (I):

[0022]

[0023] In formula (I), R1 includes a hydrogen atom, or one or more substituted or unsubstituted C1-C5 alkyl groups; alternatively, R1 includes a hydrogen atom, or one or more substituted or unsubstituted C1-C3 alkyl groups;

[0024] R2 includes one or more of a substituted or unsubstituted C1-C20 alkyl group, a substituted or unsubstituted C3-C20 cycloalkyl group, or a substituted or unsubstituted C1-C20 hydroxyalkyl group; alternatively, R2 includes one or more of a C1-C12 alkyl group, a C3-C12 cycloalkyl group, or a C1-C12 hydroxyalkyl group;

[0025] The second structural unit is shown in formula (II):

[0026]

[0027] In formula (II), R3 includes one or more of a hydrogen atom, or a substituted or unsubstituted C1-C5 alkyl group; alternatively, R3 includes one or more of a hydrogen atom, or a substituted or unsubstituted C1-C3 alkyl group;

[0028] The third structural unit is shown in formula (III):

[0029]

[0030] In formula (III), R4 to R 11 Each independently comprises a substituted or unsubstituted C1-C10 alkyl group, or one or more structural units as shown in formula (III-1), wherein R4 to R 11At least one of them is a structural unit represented by formula (III-1).

[0031]

[0032]

[0033] In formula (III-1), R 12 includes a hydrogen atom, or one or more of substituted or unsubstituted C1-C5 alkyl groups; optionally, R 12 includes a hydrogen atom, or one or more of substituted or unsubstituted C1-C3 alkyl groups;

[0034] R 13 includes substituted or unsubstituted C1-C10 alkyl groups; optionally, R 13 includes substituted or unsubstituted C3-C10 alkyl groups.

[0035] In any embodiment of the present application, 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%, 70 ≤ a ≤ 90; optionally, 75 ≤ a ≤ 85; and / or, 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%, 0 < b ≤ 16; optionally, 5 ≤ b ≤ 15; and / or

[0036] 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%, 2 ≤ c ≤ 15; optionally, 5 ≤ c ≤ 10.

[0037] In any embodiment of the present application, 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 silicone particles satisfy one or more of the conditions (1) to (3):

[0038] (1) 4 ≤ a / b ≤ 15;

[0039] (2) 5 ≤ a / c ≤ 14;

[0040] (3) a:b:c is (13-16):(1-3):(3-4).

[0041] In any embodiment of the present application, the first particles include silicone particles, and the silicone particles include a second polymer, and the second polymer includes a structural unit represented by formula (a):

[0042]

[0043] In formula (a), R 14 and R 15 Each independently comprises one or more of substituted or unsubstituted C1-C10 alkyl, hydroxyl or amino; optionally, R 14 and R 15 Each independently includes one or more of a substituted or unsubstituted C1-C6 alkyl group, a hydroxyl group or an amino group.

[0044] In any embodiment of the present application, the number average molecular weight of the organosilicon particles is 35,000-70,000, and can be optionally 40,000-55,000.

[0045] In any embodiment of the present application, based on the mass of the organosilicon particles, the moisture content of the organosilicon particles is less than or equal to 2500 μg / g, and can be optionally 700 μg / g-2000 μg / g.

[0046] In any embodiment of the present application, the average particle size of the organosilicon particles is less than or equal to 3 μm.

[0047] In any embodiment of the present application, the average particle size of the organosilicon particles is 0.01 μm-2 μm.

[0048] In any embodiment of the present application, the specific surface area of ​​the organosilicon particles is less than or equal to 12.0 m 2 / g; 5.0m is optional 2 / g-10.0m 2 / g.

[0049] In any embodiment of the present application, the thickness of the substrate is less than or equal to 16 μm, and can be optionally 3 μm-12 μm.

[0050] In any embodiment of the present application, the porosity of the substrate is greater than or equal to 25%, and can be optionally 30%-45%.

[0051] In any embodiment of the present application, the longitudinal heat shrinkage rate of the separator at 150° C. for 1 hour is less than or equal to 2%.

[0052] In any embodiment of the present application, the transverse thermal shrinkage of the separator at 150° C. for 1 hour is less than or equal to 2%.

[0053] In any embodiment of the present application, the air permeability of the isolation membrane is less than or equal to 230s / 100cc, and can be optionally 160s / 100cc-200s / 100cc.

[0054] In any embodiment of the present application, the longitudinal tensile strength of the separator is greater than or equal to 2700 kg / cm 2 , optional 3000kg / cm2 -4500kg / cm 2 .

[0055] In any embodiment of the present application, the transverse tensile strength of the separator is greater than or equal to 2000 kg / cm 2 , optional 2500kg / cm 2 -4500kg / cm 2 .

[0056] In any embodiment of the present application, the ion conductivity of the separator is 0.8 S / m-1.5 S / m.

[0057] A second aspect of the present application provides a method for preparing the isolation film of the first aspect of the present application, comprising the following steps:

[0058] providing a substrate;

[0059] Mixing organic particles as first particles and second particles having a porous structure in a solvent to prepare a coating slurry;

[0060] The coating slurry is applied on at least one side of the substrate to form a slurry film layer, and the slurry film layer is dried to form a coating layer, so as to obtain an isolation film.

[0061] A third aspect of the present application provides a battery, comprising the isolation membrane of the first aspect of the present application or the isolation membrane obtained by the preparation method of the second aspect of the present application.

[0062] A fourth aspect of the present application provides an electrical device comprising the secondary battery of the third aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] In order to more clearly illustrate the technical solutions of the embodiments of this application, the following briefly introduces the drawings required for use in the embodiments of this application. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without inventive effort.

[0064] FIG1 is a schematic diagram of an embodiment of a secondary battery of the present application.

[0065] FIG. 2 is an exploded schematic diagram of an embodiment of the secondary battery of FIG. 1 .

[0066] FIG3 is a schematic diagram of an embodiment of a battery module of the present application.

[0067] FIG4 is a schematic diagram of an embodiment of a battery pack of the present application.

[0068] FIG. 5 is an exploded schematic diagram of the embodiment of the battery pack shown in FIG. 4 .

[0069] FIG6 is a schematic diagram of an embodiment of an electric device including the secondary battery of the present application as a power source.

[0070] In the accompanying drawings, the drawings are not necessarily drawn to scale.

[0071] The following are the descriptions of the reference numerals:

[0072] 1-battery pack, 2-upper box, 3-lower box, 4-battery module, 5-secondary battery, 51-housing, 52-electrode assembly, 53-cover. DETAILED DESCRIPTION

[0073] Below, the embodiments of the separator and its preparation method, secondary battery, and electrical device of the present application are described in detail with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially the same structures may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, 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.

[0074] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is merely an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0075] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0076] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of this application.

[0077] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0078] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0079] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0080] In this application, the terms "first", "second", etc. are used for descriptive purposes only and should not be understood as indicating or implying relative importance.

[0081] In this application, the terms "plurality" and "multiple" refer to two or more.

[0082] Unless otherwise specified, the terms used in this application have the common meanings that are commonly understood by those skilled in the art.

[0083] Unless otherwise stated, the numerical values ​​of the parameters mentioned in this application can be measured using various test methods commonly used in the art, for example, they can be measured according to the test methods given in the embodiments of this application.

[0084] Typically, a battery includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separator. The separator is arranged between the positive electrode sheet and the negative electrode sheet. Its main function is to prevent the positive and negative electrodes from short-circuiting, while allowing active ions to pass freely to form a loop.

[0085] With the promotion and application of batteries in many fields, the requirements for their thermal safety and cycle performance have also increased. The separator is one of the most important components for improving the thermal safety and cycle performance of batteries. The separators currently used in commercial batteries are usually polyolefin membranes. The melting point of polyolefin membranes is between 130°C and 160°C. When heated, they will experience a significant thermal shrinkage effect. This will not only reduce their wetting effect on the electrolyte, but also reduce the area for active materials to pass through, thereby causing active materials to accumulate on the surface of the separator, thereby reducing the battery's cycle performance. Dendrites may even form on the surface of the separator, puncturing the separator, causing direct contact between the positive and negative electrodes inside the battery, resulting in an internal short circuit, thereby increasing the safety risk of the battery.

[0086] In view of this, the present application provides an isolation membrane and a preparation method thereof, a secondary battery and an electrical device. The isolation membrane has the characteristics of excellent heat resistance and ion transport properties, thereby improving the thermal safety performance and cycle performance of the battery using the isolation membrane.

[0087] Isolation film

[0088] A first aspect of an embodiment of the present application provides an isolation membrane, comprising a substrate and a coating, wherein the coating is disposed on at least one side of the substrate, wherein the coating comprises first particles and second particles, the first particles are organic particles, and the second particles have a porous structure.

[0089] In the separator provided in this application, the first particles in the coating are organic particles. Because organic particles have good heat resistance, and when the separator shrinks due to heat, the first particles, the second particles, and / or the first and second particles in the coating may abut against each other as the substrate shrinks, thereby providing a force to the substrate in the opposite direction of the shrinkage, reducing the degree of shrinkage of the separator, thereby reducing the risk of short circuits between the positive and negative electrodes in the battery, and improving the thermal safety performance of the battery. At the same time, the inventors found that if only organic particles are used in the coating, if the particles are not packed tightly together, the separator will shrink severely. If the particles are packed tightly together, the heat resistance can be improved, but the coating will have low porosity and fewer ion channels, which is not conducive to improving the cycle performance of the battery. After extensive research, the inventors found that when the coating contains both the first and second particles, the above problems can be effectively solved. The inventors speculate that the second particles with a porous structure can store electrolyte, improve the liquid absorption rate and liquid holdup of the separator, and their pore size can act as ion channels to transmit ions, so that the battery can have good heat resistance and good cycle performance.

[0090] In some embodiments of the present application, the average pore size of the second particles is 0.1 nm to 10 nm, and optionally 0.4 nm to 5 nm. The average pore size of the second particles within the above range can help improve the electrolyte's wetting and retention of the coating, thereby improving the battery's cyclability.

[0091] For example, the average pore size of the second particles can be, but is not limited to, 0.4 nm, 0.42 nm, 0.44 nm, 0.46 nm, 0.48 nm, 0.50 nm, 0.52 nm, 0.54 nm, 0.56 nm, 0.58 nm, 0.60 nm, 0.62 nm, 0.64 nm, 0.66 nm, 0.68 nm, 0.70 nm, 0.72 nm, 0.74 nm, 0.76 nm, 0.78 nm, 0.80 nm, 0.8 2nm, 0.84nm, 0.86nm, 0.88nm, 0.90nm, 0.92nm, 0.94nm, 0.96nm, 0.98nm, 1.0nm, 1.5nm, 2.0nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm or a range consisting of any two of the above values. Optionally, the average pore size of the second particles can be 0.4nm-10nm, 0.42nm-9nm, 0.50nm-8nm, 0.60nm-7nm, or 1nm-6nm.

[0092] The average pore size is well known in the art and can be measured using instruments and methods known in the art. For example, it can be calculated using the BET (Brunauer Emmett Teller) method according to GB / T 21650.2-2008, and can be measured using a Micromeritics Tri-Star 3020 surface area pore size analyzer.

[0093] In some embodiments of the present application, the porosity of the second particles is 10%-60%, and optionally 30%-50%. The porosity of the second particles within the above range not only improves the electrolyte's wetting and retention of the coating, thereby facilitating ion transport and thus improving the battery's cyclability, but also provides the second particles with greater mechanical strength, thereby enabling...

[0094] The porosity of a material is well known in the art and refers to the ratio of the intragranular pore volume to the total particle volume. It can be measured using instruments and methods known in the art. For example, reference can be made to the national standard GB / T 24586-2009, Determination of Apparent Density, True Density, and Porosity of Iron Ore, and porosity can be determined using the AccuPyc II 1340 fully automatic true density tester from Micromeritics, USA. Porosity = (V1-V2) / V1*100%, where V1 refers to the apparent volume of the material and V2 refers to the true volume of the material. V1 can be measured using mercury intrusion porosimetry, while V2 can be measured using nitrogen gas adsorption.

[0095] In some examples, the porosity of the second particles may be, but is not limited to, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60% or a range consisting of any two of the above values. Optionally, the porosity of the second particles may be 10%-50%, 16%-40%, 20%-36%, or 24%-32%.

[0096] In some embodiments of the present application, the average particle size of the second particles is less than or equal to 2 μm. The average particle size of the second particles within the above-mentioned suitable range not only facilitates electrolyte wetting of the separator to improve battery cycle performance, but also facilitates bonding between the particles. This, when the separator is heated, rapidly provides a force in the opposite direction of the heat applied to the separator, thereby reducing shrinkage of the separator when heated and improving the thermal safety of the battery.

[0097] In this application, the term "average particle size" has a well-known meaning in the art and can be measured using instruments and methods known in the art. For example, a scanning electron microscope, a transmission electron microscope, or a particle size distribution instrument can be used to measure the material or separator to obtain an image. A plurality (e.g., more than 100) test particles (e.g., the first particles or the second particles) can be randomly selected from the image, and the average value of the shortest diagonal length of the particles can be calculated as the average particle size.

[0098] In other embodiments of the present application, the average particle size of the second particles may be 0.1 μm-1 μm.

[0099] In some examples, the average particle size of the second particles may be, but is not limited to, 0.01 μm, 0.02 μm, 0.03 μm, 0.04 μm, 0.05 μm, 0.06 μm, 0.07 μm, 0.08 μm, 0.09 μm, 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm, 0.45 μm, 0.5 μm, 0.55 μm, 0.6 μm, 0.65 μm, 0.7 μm, 0.75μm, 0.80μm, 0.85μm, 0.9μm, 0.95μm, 1.0μm, 1.05μm, 1.1μm, 1.15μm, 1.2μm , 1.25μm, 1.3μm, 1.35μm, 1.4μm, 1.45μm, 1.5μm, 1.55μm, 1.60μm, 1.65μm, 1.7μm , 1.75μm, 1.8μm, 1.85μm, 1.9μm, 1.95μm, 2.0μm or a range consisting of any two of the above values. Optionally, the average particle size of the second particles can be 0.01μm-1.8μm, 0.06μm-1.6μm, 0.1μm-1.2μm, 0.2μm-1μm, or 0.4μm-0.8μm.

[0100] In some embodiments of the present application, the specific surface area of ​​the second particles is greater than or equal to 100 m 2 / g, optional 500m 2 / g-2000m 2 The specific surface area of ​​the second particles is set within the above-mentioned suitable range, which can increase the contact area between the second particles and the electrolyte, thereby helping to improve the electrolyte's wetting effect on the separator and the electrolyte retention effect.

[0101] In this application, the specific surface area of ​​particles is well known in the art and can be measured using instruments and methods known in the art. For example, the specific surface area analysis method based on nitrogen adsorption can be used in accordance with GB / T 19587-2017 and calculated using the BET (Brunauer-Emmett-Teller) method. Alternatively, the specific surface area analysis based on nitrogen adsorption can be performed using a Micromeritics Tri-Star 3020 specific surface area pore size analyzer.

[0102] In some examples, the specific surface area of ​​the second particles may be, but is not limited to, 100 m 2 / g, 150m 2 / g, 200m 2 / g, 250m 2 / g、300m 2 / g、350m 2 / g, 400m2 / g, 450m 2 / g、500m 2 / g、550m 2 / g、600m 2 / g、650m 2 / g、700m 2 / g、750m 2 / g、800m 2 / g、850m 2 / g、900m 2 / g、950m 2 / g、1000m 2 / g、1050m 2 / g、1100m 2 / g、1150m 2 / g、1200m 2 / g、1250m 2 / g、1300m 2 / g、1350m 2 / g、1400m 2 / g、1450m 2 / g、1500m 2 / g、1550m 2 / g、1600m 2 / g、1650m 2 / g、1700m 2 / g、1750m 2 / g、1800m 2 / g、1850m 2 / g、1900m 2 / g、1950m 2 / g、2000m 2 / g or a range consisting of any two of the above values, optionally, 100m 2 / g-1900m 2 / g,200m 2 / g-1600m 2 / g,600m 2 / g-1000m 2 / g, or 700m 2 / g-900m 2 / g.

[0103] In an embodiment of the present application, the weight proportion of the first particles and the weight proportion of the second particles in the coating satisfy a suitable relationship, which not only helps to reduce the shrinkage of the isolation membrane to improve the thermal safety performance of the battery, but also enables the first particles to be better overlapped together, while allowing the second particles to be dispersed between adjacent first particles, so that more gaps are formed between the particles, thereby further improving the wetting effect of the electrolyte to improve the cycle performance of the battery.

[0104] In some embodiments of the present application, based on the weight of the coating, the ratio of the weight proportion A of the first particles to the weight proportion B of the second particles satisfies: 1

[0105] In some examples, the ratio of the weight proportion A of the first particles to the weight proportion B of the second particles can be 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5, 20 or a range consisting of any two of the above values, optionally, 1-19, 5-25, 8-20 or 10-18.

[0106] In some embodiments of the present application, the weight proportion B of the second particles in the coating is less than or equal to 20%, and can be optionally 0.1%-15%.

[0107] Furthermore, in some embodiments of the present application, the coating may include, in addition to the first particles and the second particles, additives such as adhesives, dispersants, and wetting agents.

[0108] In some embodiments of the present application, the second particles include one or more of inorganic particles and metal-organic framework materials. Porous inorganic particles and metal-organic framework materials (e.g., MOF materials), when used in conjunction with the first particles, can enhance the electrolyte wetting and retention properties of the separator.

[0109] Alternatively, the inorganic particles having a porous structure may include one or more of titanium oxide, zirconium oxide, barium oxide, magnesium oxide, barium sulfate, magnesium aluminum silicate, zirconium titanate, and barium titanate.

[0110] ​Metal-Organic Frameworks (MOFs) generally refer to a class of materials consisting of metal ions and organic ligands.

[0111] Optionally, the metal-organic framework material may include one or more of IRMOFs (Isoreticular Metal-Organic Frameworks), ZIFs (Zeolitic Imidazolate Frameworks), MILs (Metaria lsofistitute Lavoisier Frameworks), PCNs (Porous Coordination Networks), CPLs (Coordination Pillared-Layers), and UiOs (University of Oslos).

[0112] Optionally, the IRMOFs include one or more of IRMOF-1, IRMOF-3, IRMOF-4, IRMOF-8, IRMOF-9, IRMOF-10, IRMOF-11, IRMOF-12, IRMOF-13, IRMOF-14, IRMOF-16, IRMOF-18, IRMOF-61, and IRMOF-62.

[0113] Alternatively, ZIFs include ZIF-1, ZIF-2, ZIF-4, ZIF-5, ZIF-7, ZIF-8, nZIF-8, ZIF-9, ZIF-10, ZIF-11, ZIF-12, ZIF-14, ZIF-20, ZIF-23, ZIF-60, ZIF-61, ZIF-62, ZIF-64, One or more of ZIF-65, ZIF-67, ZIF-68, ZIF-69, ZIF-70, ZIF-71, ZIF-72, ZIF-73, ZIF-74, ZIF-75, ZIF-76, ZIF-77, ZIF-78, ZIF-95, ZIF-100, ZIF-268, ZIF-224.

[0114] Optionally, the MILs include one or more of MIL-53Cr, MIL-100Cr, MIL-101Cr, MIL-100Fe, MIL-177-LT, MIL-177-HT, MIL-45Co, MIL-45Fe, MIL-53AI, MIL-53Sc, MIL-88Sc, MIL-8, MIL-9, MIL-47, MIL-51, MIL-59, MIL-69, MIL-88, MIL-91, MIL-96, MIL-101, MIL-103, MIL-102, MIL-110, and MIL-125.

[0115] Optionally, the PCNs include one or more of PCN-800, PCN-777, PCN-700, PCN-426, and PCN-333.

[0116] Optionally, the CPLs include one or more of CPL-1, CPL-2, CPL-4, CPL-5, CPL-6, and Al-CPL.

[0117] Optionally, UiOs includes one or more of UiO-66(Ce), UiO-66(Zr), UiO-66(Hf), UiO-66(Th), UiO-66(Ti), Im-UiO-66, UiO-67, UiO-68, UiO-15, UiO-7, UiO-15, UiO-21, UiO-22, UiO-28, UiO-26, UiO-27, DBP-UiO, and UiO-66-COOH.

[0118] In some embodiments of the present application, the second particles have a through-hole structure, which can shorten the ion transmission path and store more electrolyte, thereby helping to improve the cycle performance of the secondary battery.

[0119] As described above, the first particles in the coating have good heat resistance, which can make the isolation membrane have good heat resistance to reduce its shrinkage. Therefore, suitable organic particles can further improve the heat resistance of the isolation membrane, thereby making the battery have better thermal safety performance.

[0120] In some embodiments of the present application, the first particles include one or more of silicone particles, melamine formaldehyde resin particles, phenolic resin particles, polyester particles, polyimide particles, polyamideimide particles, polyaramid particles, polyphenylene sulfide particles, polypropylene particles, polysulfone particles, polyethersulfone particles, polyetheretherketone particles and polyaryletherketone particles.

[0121] Optionally, the first particles include organosilicon particles, which refer to organosilicon particles whose main chain is a silicon-oxygen-silicon bond (-Si-O-Si-). Since the silicon-oxygen-silicon bond is an inorganic bond, the bond energy is large, which can give the organosilicon very high heat resistance and chemical stability. For example, the organosilicon can be used for a long time below 200°C. The side chain of the organosilicon may not be grafted with other groups, or it may be grafted with organic groups. When grafted with organic groups, it can give the organosilicon good dispersibility, etc., which can improve the coating performance of the organosilicon coating and the affinity with the substrate. The organosilicon particles are dispersed in the coating so that the isolation membrane has good heat resistance, thereby improving the thermal safety performance of the secondary battery. In addition, a structure with gaps can be formed between the organosilicon particles, which can enhance the wetting and retention properties of the isolation membrane for the electrolyte, thereby promoting the transmission of active ions in the isolation membrane, so that the isolation membrane can improve the cycle performance of the secondary battery when applied to the secondary battery.

[0122] In some embodiments of the present application, the first particles include organosilicon particles, and the organosilicon particles include a first polymer, and the first polymer includes a first structural unit, a second structural unit, and a third structural unit.

[0123] The first structural unit has a structure as shown in formula (I):

[0124]

[0125] In formula (I), R1 includes a hydrogen atom, or one or more substituted or unsubstituted C1-C5 alkyl groups; alternatively, R1 includes a hydrogen atom, or one or more substituted or unsubstituted C1-C3 alkyl groups;

[0126] R2 includes one or more of a substituted or unsubstituted C1-C20 alkyl group, a substituted or unsubstituted C3-C20 cycloalkyl group, or a substituted or unsubstituted C1-C20 hydroxyalkyl group; alternatively, R2 includes one or more of a C1-C12 alkyl group, a C3-C12 cycloalkyl group, or a C1-C12 hydroxyalkyl group;

[0127] The second structural unit is shown in formula (II):

[0128]

[0129] In formula (II), R3 includes one or more of a hydrogen atom, or a substituted or unsubstituted C1-C5 alkyl group; alternatively, R3 includes one or more of a hydrogen atom, or a substituted or unsubstituted C1-C3 alkyl group;

[0130] The third structural unit is shown in formula (III):

[0131]

[0132] In formula (III), R4 to R 11 Each independently comprises a substituted or unsubstituted C1-C10 alkyl group, or one or more structural units as shown in formula (III-1), and R4 to R 11 At least one of them is a structural unit represented by formula (III-1),

[0133]

[0134] In formula (III-1), R 12 Including one or more of a hydrogen atom, or a substituted or unsubstituted C1-C5 alkyl group; Optionally, R 12 Including one or more of hydrogen atoms, or substituted or unsubstituted C1-C3 alkyl groups; R 13 Including substituted or unsubstituted C1-C10 alkyl; optionally, R 13 This includes substituted or unsubstituted C3-C10 alkyl groups.

[0135] The first structural unit can adjust the glass transition temperature of the polymer, improve the toughness and peel strength of the first polymer, and help to exert a good bonding effect. The second structural unit can produce excellent anti-swelling properties, that is, when the first polymer is applied to the isolation membrane, the first polymer is in contact with the electrolyte, and the first polymer is not easy to swell, and it has good anti-swelling properties. The polysilsesquioxane in the third structural unit can be considered as a material containing an organic-inorganic hybrid core-shell structure, whose internal inorganic framework serves as the core, that is, a skeleton structure composed of Si-O-Si or Si-O bonds; its outer shell is composed of organic substituents (C1-C5 alkyl), the organic substituents are wrapped around the skeleton structure, and the organic substituents are connected to the Si element of the skeleton structure. The core structure of polysilsesquioxane can give the polymer advantages in heat resistance and mechanical properties. Its poor shrinkage can ensure the thermal stability of the first polymer during the long-term cycle charge and discharge of the battery, effectively isolate the positive and negative electrodes, and thus ensure the thermal safety performance of the battery; and because polysilsesquioxane has a small particle size and a large specific surface area, it is similar to most polymer chain segments in physical scale, which makes the atoms on the surface of polysilsesquioxane have high reactivity. The polymer modified with polysilsesquioxane has good heat resistance, flame retardancy and antioxidant properties.

[0136] Furthermore, the various structural units in the first polymer can act synergistically. Specifically, the first structural unit and the third structural unit can act synergistically to improve the adhesive properties and heat resistance of the first polymer; and the first structural unit and the second structural unit can act synergistically to improve the first polymer's anti-swelling properties.

[0137] In some embodiments of the present application, 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 70 ≤ a ≤ 90. When the molar content of the first structural unit is within the above range, the flexibility of the first polymer can be improved, thereby further enhancing the adhesiveness of the first polymer; when the first polymer is applied to the separator, the binding force between the first polymer and the substrate of the separator can be increased. Optionally, 75 ≤ a ≤ 85. Exemplarily, the molar content of the first structural unit can be 70%, 75%, 80%, 85%, 90% or a range composed of any two of the above values.

[0138] In some embodiments of the present application, 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 ≤ 16. When the molar content of the second structural unit is within the above range, the anti-swelling property of the first polymer can be significantly improved. Optionally, 5 ≤ b ≤ 15. Exemplarily, the molar content of the second structural unit can be 5%, 8%, 10%, 12%, 15% or a range composed of any two of the above values.

[0139] In some embodiments of the present application, 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 2 ≤ 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 ensured, and its proportion is relatively small, which is beneficial to increasing the proportions of the first structural unit and the second structural unit, and improving the overall adhesiveness and thermal stability of the first polymer. Optionally, 5 ≤ c ≤ 10. Exemplarily, the molar content of the third structural unit can be 5%, 8%, 10%, 12%, 15% or a range composed of any two of the above values.

[0140] In the present application, the first structural unit in the first polymer endows the first polymer with good adhesiveness; however, when the first polymer is applied to the separator, it will inevitably come into contact with the electrolyte, and the swelling effect of the electrolyte will reduce the adhesiveness of the first polymer to a certain extent; the cyano group contained in the second structural unit in the first polymer can play a synergistic role with the first structural unit to jointly improve the anti-swelling property and adhesiveness of the first polymer; especially when the present application further satisfies 4 ≤ a / b ≤ 15, the first structural unit and the second structural unit can play a more sufficient synergistic role to improve the adhesiveness and anti-swelling property of the first polymer. Exemplarily, a / b can be 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or a range composed of any two of the above values.

[0141] Furthermore, the third structural unit in the first polymer, comprising an inorganic polysilsesquioxane structure, can synergize with the first structural unit to improve the overall heat resistance and adhesion properties of the first polymer. In particular, when the ratio 5 ≤ a / c ≤ 14 is satisfied, the first structural unit and the third structural unit can further enhance the synergistic effect, improving the adhesion and heat resistance of the first polymer. For example, a / c can be 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or a range consisting of any two of these values.

[0142] In some embodiments of the present application, the degree of polymerization a of the first structural unit, the degree of polymerization b of the second structural unit, and the degree of polymerization c of the third structural unit satisfy the following ratio: a:b:c = (13-16): (1-3): (3-4). When the degrees of polymerization of the first structural unit, the second structural unit, and the third structural unit satisfy the above ratio, the three structural units in the organosilicon particles can synergize with each other while leveraging their respective performance advantages to jointly improve the adhesion, anti-swelling, and heat resistance of the polymer.

[0143] The first structural unit includes a variety of chemical structures, and the specific chemical structure of the first structural unit is described below.

[0144] In some embodiments of the present application, R1 is selected from a hydrogen atom and / or a methyl group.

[0145] In some embodiments of the present application, R2 includes one or more of methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, n-octyl, isooctyl, 2-ethylhexyl, dodecyl or isobornyl.

[0146] Illustratively, the first structural unit includes one or more of the structures represented by formula (I-1) to formula (I-8):

[0147]

[0148] The second structural unit includes a variety of chemical structures, and the specific chemical structure of the second structural unit is described below.

[0149] In some embodiments of the present application, R3 is selected from a hydrogen atom or a methyl group.

[0150] Illustratively, the second structural unit includes one or more of the structures represented by formula (II-1) to the structures represented by formula (II-4):

[0151]

[0152]

[0153] The third structural unit includes a variety of chemical structures, and the specific chemical structure of the third structural unit is described below.

[0154] In some embodiments of the present application, R4 to R 11 Each independently selected from the structural unit shown in formula (III-1); optionally, R 12 including one or more of a hydrogen atom, a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, a sec-butyl group, a tert-butyl group or a n-pentyl group; and / or R 13 The alkyl radicals include one or more of n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, n-octyl, isooctyl and 2-ethylhexyl.

[0155] In some embodiments, R4 to R 11 One of them is selected from the structural unit shown in formula (III-1); optionally, R 12 including one or more of a hydrogen atom, a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, a sec-butyl group, a tert-butyl group or a n-pentyl group; and / or R 13 The alkyl radicals include one or more of n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, n-octyl, isooctyl and 2-ethylhexyl.

[0156] In the present application, the group types in the first polymer can be measured using infrared spectroscopy. For example, the infrared spectrum of the material can be tested to determine the characteristic peaks contained therein, thereby determining the type of the modified group. Specifically, the material can be subjected to infrared spectroscopy analysis using instruments and methods well known in the art, for example, using an infrared spectrometer (such as the IS10 Fourier transform infrared spectrometer of Nicolet, USA), and tested according to GB / T 6040-2019 General Rules for Infrared Spectroscopy Analysis Methods.

[0157] In some embodiments of the present application, the first polymer has an infrared spectrum at 1750 cm -1 to 1735cm -1 , which indicates the presence of ester groups.

[0158] In some embodiments of the present application, the first polymer has a wavelength of 2260 cm in the infrared spectrum. -1 to 2220cm -1 , which indicates the presence of a cyano group.

[0159] In some embodiments of the present application, the first polymer has an infrared spectrum of 1100 nm. -1 to 1120cm -1 The characteristic peaks of silsesquioxane are shown in FIG1 , which indicates the presence of the Si-O-Si skeleton of silsesquioxane.

[0160] In some embodiments of the present application, the first polymer can be prepared by the following method, which includes:

[0161] Step S100, providing a first monomer, a second monomer and a third monomer;

[0162] In step S200 , a first monomer, a second monomer, and a third monomer are mixed and polymerized under the action of an initiator to generate a first polymer.

[0163] In the present application, the first monomer, the second monomer and the third monomer are mixed and copolymerized, and the formed first polymer is a copolymer of the three monomers.

[0164] The first monomer has a structure represented by formula (IV),

[0165]

[0166] In formula (IV), R1 includes a hydrogen atom, or a substituted or unsubstituted C1-C5 alkyl group; alternatively, R1 is selected from one or more of a hydrogen atom, or a substituted or unsubstituted C1-C3 alkyl group;

[0167] R2 includes substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted C3-C20 cycloalkyl, substituted or unsubstituted C1-C20 hydroxyalkyl; alternatively, R2 is selected from one or more of C1-C12 alkyl, C3-C12 cycloalkyl, and C1-C12 hydroxyalkyl.

[0168] The first monomer is an acrylic acid ester compound, and when it is polymerized, the carbon-carbon double bond opens to form a first structural unit.

[0169] Illustratively, the first monomer includes 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.

[0170] The second monomer has a structure represented by formula (V),

[0171]

[0172] In formula (V), R3 includes a hydrogen atom, or one or more substituted or unsubstituted C1-C5 alkyl groups; alternatively, R3 includes a hydrogen atom, or one or more substituted or unsubstituted C1-C3 alkyl groups.

[0173] The second monomer is an acrylonitrile compound, and when it is polymerized, the carbon-carbon double bond opens to form a second structural unit.

[0174] Illustratively, the second monomer includes acrylonitrile and / or methacrylonitrile.

[0175] The third monomer has a structure shown in formula (VI),

[0176]

[0177] In formula (VI), R 30 to R 37 It includes one or more independently selected from substituted or unsubstituted C1-C10 alkyl groups, or structural units as shown in formula (VI-1), wherein R 30 to R 37 At least one of them is a structural unit represented by formula (VI-1),

[0178]

[0179]

[0180] In formula (VI-1), R 12 Including one or more of a hydrogen atom, or a substituted or unsubstituted C1-C5 alkyl group; Optionally, R 12 including one or more of a hydrogen atom, or a substituted or unsubstituted C1-C3 alkyl group;

[0181] R 13 Including substituted or unsubstituted C1-C10 alkyl; optionally, R 13 This includes substituted or unsubstituted C3-C10 alkyl groups.

[0182] Illustratively, the third monomer includes one or more of methacryloxypropyl cage polysilsesquioxane, methacryloxypropyl heptaisobutyl polysilsesquioxane, methacryloxypropyl heptaoctyl polysilsesquioxane, acryloxypropyl cage polysilsesquioxane, acryloxypropyl heptaisobutyl polysilsesquioxane, and methacryloxypropyl heptaoctyl polysilsesquioxane.

[0183] In some embodiments of the present application, step S200 specifically includes:

[0184] Step S210, adding a first monomer, a second monomer, and a third monomer into a solvent and an emulsifier and mixing them to form a mixed system;

[0185] In step S220 , an initiator is added to the mixed system, and a polymerization reaction occurs under the action of the initiator to generate a first polymer.

[0186] The present invention can copolymerize multiple monomers via emulsion polymerization, which is a simpler polymerization method. Of course, the present invention can also employ other polymerization methods, such as solution polymerization and suspension polymerization. The process parameters used in the polymerization process can be selected from those commonly used in the art and will not be detailed here.

[0187] In some embodiments of the present application, the emulsifier includes one or more of sodium lauryl sulfate, sodium dodecylbenzene sulfonate, alkyl diphenyl oxide disulfonate, and ethoxylated alkylphenol ammonium sulfate.

[0188] In some embodiments of the present application, the ratio of the mass percentage of the emulsifier to the mass percentage 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 the emulsifier used is 0.1% to 5% of the mass of the three monomers. When the mass percentage of the emulsifier is within the above range, the first monomer, the second monomer, and the third monomer can be emulsified and dispersed in the solvent to form a relatively uniform system.

[0189] In some embodiments of the present application, the initiator includes potassium persulfate and / or ammonium persulfate.

[0190] In some embodiments of the present application, the ratio of the mass percentage of the initiator to the mass percentage of the second monomer, the third monomer, and the third monomer, based on the total mass of the mixed system, is 0.15% to 1%. That is, the amount of the initiator used is 0.1% to 5% of the mass of the three monomers. When the mass percentage of the initiator is within this range, sufficient polymerization can be ensured.

[0191] In some embodiments of the present application, the solvent may include water such as deionized water.

[0192] As a specific embodiment, the method includes:

[0193] Preparation of prepolymer: deionized water, emulsifier, first polymerizable monomer, second polymerizable monomer and third polymerizable monomer are mixed and stirred uniformly to obtain a prepolymer;

[0194] Preparation of the first polymer: Add an emulsifier and deionized water to a container, stir and emulsify for 30 to 60 minutes to obtain a uniform and stable emulsion; then slowly dropwise add the prepolymer prepared in the previous step and the initiator solution (the initiator potassium persulfate and / or ammonium persulfate is dissolved in deionized water to form a solution), after the dropwise addition is completed, heat to 90° C. to 110° C. and keep warm for 0.5 hours, cool to 40° C., adjust the pH to 7 to 8 with ammonia water, filter, discharge, and dry to obtain a polymer.

[0195] In other embodiments of the present application, the first particles include organosilicon particles, the organosilicon particles include a second polymer, and the second polymer includes a structural unit represented by formula (a):

[0196]

[0197] In formula (a), R 14 and R 15 Includes one or more independently selected from substituted or unsubstituted C1-C10 alkyl, hydroxyl or amino. 14 and R 15 Each includes one or more independently selected from substituted or unsubstituted C1-C6 alkyl, hydroxyl or amino groups.

[0198] In some embodiments of the present application, the second polymer includes one or more of polymethylsiloxane, polydimethylsiloxane, polydiethylsiloxane, polymethylhydroxysiloxane, and polymethylaminosiloxane.

[0199] Illustratively, the organosilicon particles include at least one of the structures represented by formula (a-1) to the structures represented by formula (a-5):

[0200]

[0201] The first polymer and the second polymer in this application are only used to distinguish the types of materials and have no limiting effect on the order and quantity.

[0202] In some embodiments of the present application, the number average molecular weight of the organosilicon particles is 35,000-70,000, optionally 40,000-50,000. For example, the number average molecular weight of the polymer can be 35,000, 40,000, 45,000, 50,000, 55,000, 60,000, 65,000, 70,000, or a range consisting of any two of the above values. When the number average molecular weight of the organosilicon particles is within the above range, they have a relatively high viscosity, which is beneficial for improving the adhesion between the separator and the positive and negative electrode sheets when the organosilicon particles are applied to the separator. When the number average molecular weight of the organosilicon particles is within the above range, it is beneficial to form organosilicon particles with a smaller particle size. When applied to the separator, it can achieve a thin coating of the separator coating, reduce the overall thickness of the separator, and thus facilitate the improvement of the energy density of the battery. In addition, the particle size of the organosilicon particles formed by the polymer is not too small, which can reduce the risk of the organosilicon particles clogging the substrate in the separator and improve the overall air permeability and other properties of the separator.

[0203] In the present application, the number average molecular weight of the first polymer can be measured by gel permeation chromatography (GPC). Specifically, the measurement is performed using a GPC1515 instrument from Waters, USA. The sample is dissolved in tetrahydrofuran for more than 12 hours at a concentration of 4 mg / ml. The sample is filtered and prepared. The test temperature is 25°C and the test flow rate is 1 ml / min.

[0204] The inventors have found through research that during the long-term charge and discharge process of the battery, the moisture in the isolation membrane will gradually be released and enter the electrolyte, and the electrolyte is highly sensitive to moisture and easily produces hydrofluoric acid HF when it comes into contact with water, thereby increasing the acidity of the electrolyte, causing corrosion of active materials and current collectors, etc., and may cause the dissolution of transition metal ions in the active materials, thereby affecting the electrochemical performance of the battery. Therefore, the present application regulates the moisture content of the silicone particles to be less than or equal to 2500μg / g, and can be optionally 700μg / g-2500μg / g, based on the mass of the silicone particles. When the moisture content of the silicone particles is within the above range, the moisture content contained therein is relatively small, which can reduce the risk of side reactions in the electrolyte during the long-term charge and discharge cycle of the battery, thereby improving the electrochemical performance of the battery. Illustratively, the moisture content of the organosilicon particles may be 700 μg / g, 800 μg / g, 1000 μg / g, 1200 μg / g, 1500 μg / g, 1800 μg / g, 2000 μg / g, 2500 μg / g, or a range consisting of any two of the foregoing values.

[0205] In the present application, the moisture content of the organosilicon particles can be measured by a moisture meter, the testing method can adopt the Karl Fischer moisture determination method, and the testing instrument can adopt the Swiss Metrohm 831 Karl Fischer moisture meter.

[0206] In some embodiments of the present application, the average particle size of the organosilicon particles is less than or equal to 3 μm, and can be selected from 0.01 μm to 2 μm. When the coating has an appropriate thickness, an average particle size of the organosilicon particles within this range allows for better overlap between the particles. Consequently, when the separator is heated, the compression between the particles effectively reduces shrinkage of the separator, further improving the thermal safety of the battery.

[0207] In some examples, the average particle size of the silicone particles can be, but is not limited to, 0.01 μm, 0.02 μm, 0.03 μm, 0.04 μm, 0.05 μm, 0.06 μm, 0.07 μm, 0.08 μm, 0.09 μm, 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm, 0.45 μm, 0.5 μm, 0.55 μm, 0.6 μm, 0.65 μm, 0.7 μm, 0.75 μm, 0.80 μm, 0.85 μm, 0.9 μm, 0.95 μm, 1.0 μm, 1.05 μm, 1.1 μm, 1.15 μm, 1.2 μm, or 1.25 μm. , 1.3μm, 1.35μm, 1.4μm, 1.45μm, 1.5μm, 1.55μm, 1.60μm, 1.65μm, 1.7μm, 1.75μm, 1.8μm, 1.85μm, 1.9μm, 1.95μm, 2.0μm, 2.05μm, 2.1μm, 2.15μm, 2.2μm, 2.25μm, 2.3μm, 2.35μm, 2.4μm, 2.45μm, 2.5μm, 2.55μm, 2.6μm, 2.65μm, 2.7μm, 2.75μm, 2.8μm, 2.85μm, 2.9μm, 2.95μm, 3.0μm or a range consisting of any two of the above values. For example, the average particle size of the silicone particles may be 0.01 μm to 2 μm, 0.05 μm to 1.8 μm, 0.1 μm to 1.5 μm, or 0.3 μm to 1.2 μm.

[0208] In some embodiments of the present application, the specific surface area of ​​the organosilicon particles is less than or equal to 12.0 m 2 / g; optionally, 5.0m 2 / g-10.0m 2When the specific surface area of ​​the organosilicon particles is within the above range, not only can the contact area with the electrolyte be increased, thereby improving the electrolyte's wetting effect on the separator and the electrolyte's retention effect in the separator, but it can also facilitate good overlap between the particles, making it easier to form a pore structure between the organosilicon particles, which is beneficial to the migration of active ions.

[0209] In some embodiments of the present application, the substrate has a thickness of 16 μm or less. Optionally, the substrate has a thickness of 3 μm to 12 μm. The coating of the present application can improve the thermal safety and cycling performance of the separator, thereby enabling the use of a thinner substrate, thereby further increasing the energy density of the battery.

[0210] In some embodiments of the present application, the substrate has a porous structure, and the porosity of the substrate is greater than or equal to 25%. Optionally, the porosity of the substrate is 30%-45%. When the porosity of the porous substrate is within the above-mentioned suitable range, it is beneficial to further improve the ion transport properties of the separator and thus improve the cycle performance of the battery.

[0211] The present application does not particularly limit the material of the substrate. Any known substrate with good chemical and mechanical stability can be selected. For example, the substrate can include at least one of a porous polyolefin-based resin film (e.g., at least one of polyethylene, polypropylene, and polyvinylidene fluoride), a porous glass fiber, and a porous non-woven fabric. The porous substrate can be a single-layer film or a multi-layer composite film. When the porous substrate is a multi-layer composite film, the materials of each layer can be the same or different.

[0212] In some embodiments of the present application, the longitudinal thermal shrinkage of the isolation film at 150° C. for 1 hour is less than or equal to 2%.

[0213] In some embodiments of the present application, the transverse thermal shrinkage of the isolation film at 150° C. for 1 hour is less than or equal to 2%.

[0214] In the above embodiments, the separator of the present application has low thermal shrinkage in both the transverse and longitudinal directions, thereby further improving the thermal safety performance of the battery.

[0215] In some embodiments of the present application, the separator has an air permeability of less than or equal to 230 s / 100 cc. Alternatively, the separator has an air permeability of 160 s / 100 cc to 200 s / 100 cc. The separator of the present application has good air permeability, thereby improving ion transport properties, reducing battery resistance, and thereby enhancing battery cycle performance.

[0216] In some embodiments of the present application, the longitudinal tensile strength of the separator is greater than or equal to 2700 kg / cm 2 , optional 3000kg / cm2 -4500kg / cm 2 .

[0217] In some embodiments of the present application, the transverse tensile strength of the separator is greater than or equal to 2000 kg / cm 2 , optional 2500kg / cm 2 -4500kg / cm 2 .

[0218] In some embodiments of the present application, the wetted length of the separator is greater than or equal to 65 mm, and can be 70 mm to 100 mm. The separator of the present application has good electrolyte wetting properties, thereby improving ion transport properties and battery capacity.

[0219] In this application, the wetting length of the isolation membrane has a meaning well known in the art and can be measured using methods known in the art. An exemplary test method is as follows: cut the isolation membrane into samples with a width of 5 mm and a length of 100 mm, fix the two ends of the sample and place it horizontally; take 0.5 mg of electrolyte and drop it in the center of the sample. After reaching the specified time (1 min in this application), take a picture and measure the length of the electrolyte diffusion to obtain the wetting length of the isolation membrane. In order to ensure the accuracy of the test results, multiple (for example, 5 to 10) samples can be taken for testing, and the test results are obtained by calculating the average value. The electrolyte can be prepared as follows: ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed in a mass ratio of 30:50:20 to obtain an organic solvent, and fully dried LiPF6 is dissolved in the above organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0220] In the above embodiments, the separator of the present application has high tensile strength in both the transverse and longitudinal directions. Therefore, when the battery expands, the separator is less likely to be damaged, thereby further improving the safety performance of the battery.

[0221] In this application, the thermal shrinkage, tensile strength, and air permeability of the separator have meanings commonly known in the art and can be measured using methods known in the art. For example, they can all be tested in accordance with standard GB / T 36363-2018.

[0222] In some embodiments of the present application, the ion conductivity of the separator is 0.8 S / m-1.5 S / m. The ion conductivity of the separator is within the above range, which can help improve the cycle performance of the battery.

[0223] The ionic conductivity of the isolation membrane can be obtained through AC impedance spectroscopy experiments. Specifically, the isolation membrane is cut into discs of a certain area, dried, and placed between two stainless steel electrodes. After absorbing a sufficient amount of electrolyte, it is sealed to form a button battery and an AC impedance spectroscopy experiment is performed. The intersection of the linear part and the real axis in the obtained AC impedance spectrum is the bulk resistance of the electrolyte. From this, the ionic conductivity of the isolation membrane can be calculated according to the formula σ=(L / A)×R. L represents the thickness of the isolation membrane (cm), and A represents the contact area between the stainless steel electrode and the isolation membrane (cm 2 ), R represents the bulk resistance of the electrolyte (mS).

[0224] The electrolyte used can be prepared as follows: ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed in a mass ratio of 30:50:20 to obtain an organic solvent, and fully dried LiPF6 is dissolved in the above organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0225] It should be noted that the coating parameters of the above-mentioned isolation membrane are all coating parameters of a single side of the substrate.

[0226] When the coating is provided on both sides of the substrate, the coating parameters on either side satisfy the present application and are considered to fall within the protection scope of the present application.

[0227] Isolation film preparation method

[0228] The second aspect of the present application provides a method for preparing an isolation membrane as the first aspect of the present application, comprising the following steps: S1, providing a substrate; S2, mixing organic particles as first particles and second particles having a porous structure in a solvent to prepare a coating slurry; S3, applying the coating slurry to at least one side of the substrate to form a slurry film layer, and drying the slurry film layer to form a coating to obtain an isolation membrane.

[0229] In some embodiments of the present application, in S2, the solvent may be water, such as deionized water. The binder may be an aqueous solution binder, which has the advantages of good thermodynamic stability and environmental protection, thereby facilitating the preparation and application of the coating slurry. As an example, the aqueous solution binder may include at least one of an aqueous solution acrylic resin (e.g., acrylic acid, methacrylic acid, sodium acrylate monomer homopolymer or a copolymer with other comonomers), polyvinyl alcohol (PVA), isobutylene-maleic anhydride copolymer, and polyacrylamide. In addition, the coating slurry may further include other components, for example, a dispersant, a wetting agent, etc.

[0230] In some embodiments of the present application, in S3, coating is performed using a coating machine. The present application does not particularly limit the model of the coating machine, for example, a commercially available coating machine can be used. Optionally, the coating machine includes a gravure roller, which is used to transfer the coating slurry to the substrate. Optionally, the line count of the gravure roller is 180LPI-250LPI, and more preferably 190LPI-140LPI. In addition, the coating method can be transfer coating, spin spray coating, dip coating, etc.

[0231] By controlling the above process parameters within the given ranges, the performance of the isolation membrane of the present application can be further improved. Those skilled in the art can selectively adjust one or more of the above process parameters according to actual production conditions.

[0232] The method for preparing the isolation membrane of the present application obtains the coating layer through one-time coating, which greatly simplifies the production process of the isolation membrane.

[0233] The parameters of some raw materials and their contents used in the preparation method of the isolation membrane of the present application can be referred to the isolation membrane of the first embodiment of the present application, and will not be repeated here. Unless otherwise specified, the raw materials used in the preparation method of the isolation membrane of the present application can be obtained commercially.

[0234] secondary batteries

[0235] A third aspect of the present application provides a secondary battery. A secondary battery, also known as a rechargeable battery or storage battery, refers to a battery that can be recharged after discharge to activate its active materials for continued use. Typically, a secondary battery includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separator. The separator is disposed between the positive electrode sheet and the negative electrode sheet, primarily preventing a short circuit between the positive and negative electrodes while allowing active ions to pass through.

[0236] The present application has no particular limitation on the type of secondary battery. For example, the secondary battery may be a lithium-ion battery, a sodium-ion battery, etc. In particular, the secondary battery may be a lithium-ion secondary battery.

[0237] The secondary battery of the present application includes the separator of the first aspect of the present application or the separator obtained by the preparation method of the second aspect of the present application, the separator being interposed between the positive electrode sheet and the negative electrode sheet. Optionally, at least the side of the separator proximal to the negative electrode sheet is coated with the coating of the present application. As a result, the secondary battery of the present application exhibits excellent thermal safety and cycling performance.

[0238] [Positive electrode]

[0239] In some embodiments of the present application, a positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector and comprising a positive electrode active material. For example, the positive electrode current collector has two opposing sides in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposing surfaces of the positive electrode current collector.

[0240] When the secondary battery of the present application is a lithium-ion secondary 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 respective modified compounds. Examples of lithium transition metal oxides may include, but are not limited to, at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds. Examples of lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, a composite material of lithium iron manganese phosphate and carbon, and their respective modified compounds.

[0241] In some embodiments of the present application, in order to further improve the energy density of the secondary battery, the positive electrode active material for the lithium ion secondary battery may include a general formula of Li a Ni b Co c M d O e A f At least one of lithium transition metal oxides and modified compounds thereof. 0.8≤a≤1.2, 0.5≤b<1, 0<c<1, 0<d<1, 1≤e≤2, 0≤f≤1, M is selected from at least one of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and A is selected from at least one of N, F, S and Cl.

[0242] As an example, the positive electrode active material for lithium ion secondary batteries may include 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 0.15Al 0.05 At least one of O2, LiFePO4, and LiMnPO4.

[0243] When the secondary battery of the present application is a sodium ion secondary battery, the positive electrode active material may include but is not limited to at least one of sodium-containing transition metal oxides, polyanion materials (such as phosphates, fluorophosphates, pyrophosphates, sulfates, etc.), and Prussian blue materials.

[0244] As an example, the positive active material for a sodium ion secondary battery may include 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 materials, general formula X p M' q (PO4) r O x Y 3-x At least one of the materials. p M' q (PO4) r O x Y 3-x , 0<p≤4, 0<q≤2, 1≤r≤3, 0≤x≤2, X is selected from H + 、Li + 、Na + , K + and NH4 + At least one of , 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.

[0245] In the present application, the modified compounds of the above-mentioned positive electrode active materials may be the ones subjected to doping modification and / or surface coating modification on the positive electrode active materials.

[0246] In some embodiments of the present application, the positive electrode film layer may further optionally include a positive electrode conductive agent. The present application does not particularly limit the type of the positive electrode conductive agent. By way of example, the positive 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 of the present application, the mass percentage of the positive electrode conductive agent is ≤ 6 wt % based on the total weight of the positive electrode film layer.

[0247] In some embodiments of the present application, the positive electrode film layer may further optionally include a positive electrode binder. The present application has no particular restrictions on the type of positive electrode binder. As an example, the positive electrode binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and at least one of fluorine-containing acrylic resins. In some embodiments of the present application, based on the total weight of the positive electrode film layer, the mass percentage of the positive electrode binder is ≤5wt%.

[0248] In some embodiments of the present application, the positive electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, aluminum foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one side of the polymer material base layer. As an example, the metal material may include at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0249] The positive electrode film is typically formed by coating a positive electrode slurry onto a positive electrode current collector, drying it, and cold pressing it. The positive electrode slurry is typically formed by dispersing the positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring them uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP).

[0250] [Negative electrode]

[0251] In some embodiments of the present application, a negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector and comprising a negative electrode active material. For example, the negative electrode current collector has two opposing sides in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposing surfaces of the negative electrode current collector.

[0252] The negative electrode active material may be any negative electrode active material known in the art for use in secondary batteries. For example, the negative electrode active material may include, but is not limited to, at least one of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. Silicon-based materials may include at least one of elemental silicon, silicon oxide, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include at least one of elemental tin, tin oxide, and tin alloys.

[0253] In some embodiments of the present application, the negative electrode film layer may further optionally include a negative electrode conductive agent. The present application does not particularly limit the type of negative electrode conductive agent. By way of 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 of the present application, the mass percentage of the negative electrode conductive agent is ≤7 wt % based on the total weight of the negative electrode film layer.

[0254] In some embodiments of the present application, the negative electrode film layer may further optionally include a negative electrode binder. The present application does not particularly limit the type of negative electrode binder. As an example, the negative electrode binder may include at least one of styrene-butadiene rubber (SBR), a water-soluble unsaturated resin SR-1B, a water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). In some embodiments of the present application, the mass percentage of the negative electrode binder is ≤6 wt% based on the total weight of the negative electrode film layer.

[0255] In some embodiments of the present application, the negative electrode film layer may optionally include other additives. For example, the other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc. In some embodiments of the present application, the mass percentage of the other additives is ≤ 3 wt % based on the total weight of the negative electrode film layer.

[0256] In some embodiments of the present application, the negative electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, copper foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one side of the polymer material base layer. As an example, the metal material may include at least one of copper, a copper alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, and a silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0257] The negative electrode film layer is typically formed by coating the negative electrode slurry onto the negative electrode current collector, drying it, and cold pressing it. The negative electrode slurry is typically formed by dispersing the negative electrode active material, an optional conductive agent, an optional binder, and other optional additives in a solvent and stirring them uniformly. The solvent can be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0258] The negative electrode sheet does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode sheet of the present application further includes a conductive primer layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In other embodiments, the negative electrode sheet of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0259] [Electrolyte]

[0260] During the charge and discharge process of a secondary battery, active ions are embedded and released back and forth between the positive and negative electrodes, and the electrolyte conducts the active ions between the positive and negative electrodes. This application does not specifically limit the type of electrolyte, and the electrolyte can be selected according to actual needs.

[0261] The electrolyte solution includes an electrolyte salt and a solvent. The types of the electrolyte salt and the solvent are not particularly limited and can be selected according to actual needs.

[0262] When the secondary battery of the present application is a lithium ion secondary battery, as an example, the electrolyte salt may include but is not limited to at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobisoxalatophosphate (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

[0263] When the secondary battery of the present application is a sodium ion secondary battery, as an example, the electrolyte salt may include but is not limited to sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), sodium perchlorate (NaClO4), sodium hexafluoroarsenate (NaAsF6), sodium bis(fluorosulfonyl)imide (NaFSI), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), sodium trifluoromethanesulfonate (NaTFS), sodium difluorooxalatoborate (NaDFOB), sodium dioxalatoborate (NaBOB), sodium difluorophosphate (NaPO2F2), sodium difluorodioxalatophosphate (NaDFOP) and sodium tetrafluorooxalatophosphate (NaTFOP). At least one of the group.

[0264] As an 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).

[0265] In some embodiments of the present application, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, or additives capable of improving certain properties of the secondary battery, such as additives that improve the overcharge performance of the secondary battery, additives that improve the high-temperature performance of the secondary battery, and additives that improve the low-temperature power performance of the secondary battery.

[0266] In some embodiments of the present application, the positive electrode sheet, the separator, and the negative electrode sheet may be formed into an electrode assembly through a winding process and / or a lamination process.

[0267] In some embodiments of the present application, the secondary battery may further include an outer package that can be used to encapsulate the electrode assembly and the electrolyte.

[0268] In some embodiments of the present application, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery can also be a soft package, such as a bag-type soft package. The material of the soft package can be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0269] The present application has no particular limitation on the shape of the secondary battery, which can be cylindrical, square, or any other shape. FIG1 shows a secondary battery 5 with a square structure as an example.

[0270] In some embodiments of the present application, as shown in FIG2 , the outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 is used to cover the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 52 through a winding process and / or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, which can be adjusted according to demand.

[0271] The preparation method of the secondary battery of the present application is well known. In some embodiments of the present application, a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte can be assembled to form a secondary battery. As an example, the positive electrode sheet, the separator, and the negative electrode sheet can be formed into an electrode assembly through a winding process and / or a lamination process. The electrode assembly is placed in an outer packaging, dried, and then injected with an electrolyte. The secondary battery is obtained through vacuum packaging, static standing, formation, and shaping processes.

[0272] In some embodiments of the present application, the secondary batteries according to the present application can be assembled into a battery module. The battery module can contain multiple secondary batteries, and the specific number can be adjusted according to the application and capacity of the battery module.

[0273] Figure 3 is a schematic diagram of an example battery module. As shown in Figure 3 , within a battery module 4, multiple secondary batteries 5 may be arranged sequentially along the length of the battery module 4. Of course, any other arrangement is also possible. Furthermore, the multiple secondary batteries 5 may be secured using fasteners.

[0274] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of secondary batteries 5 are received in the receiving space.

[0275] In some embodiments of the present application, the above-mentioned battery modules may also be assembled into a battery pack, and the number of battery modules contained in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0276] Figures 4 and 5 are schematic diagrams of an exemplary battery pack 1. As shown in Figures 4 and 5, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 covers the lower case 3 and forms an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0277] Electrical devices

[0278] In a fourth aspect, the present application provides an electrical device, which includes at least one of the secondary battery, battery module, or secondary battery pack of the third aspect of the present application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device can be, but is not limited to, a mobile device (such as a mobile phone, a laptop computer, etc.), an electric vehicle (such as 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.

[0279] The electrical device can select a secondary battery, a battery module or a battery pack according to its usage requirements.

[0280] Figure 6 is a schematic diagram of an exemplary electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of this device, a battery pack or battery module may be used.

[0281] As another example, the electric device may be a mobile phone, a tablet computer, a laptop computer, etc. Such an electric device is usually required to be lightweight and thin, and may use a secondary battery as a power source.

[0282] The following embodiments describe the present disclosure in more detail, and these embodiments are intended to be illustrative only, as various modifications and variations within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are by mass, and all reagents used in the embodiments are commercially available or synthesized according to conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0283] Example 1-1

[0284] Preparation of silicone particles

[0285] Preparation of prepolymer: 1500 g of deionized water and 7.5 g of sodium lauryl sulfate were added to a 5L three-necked flask, stirred and emulsified at a speed of 1800 r / min for 40 min to obtain a uniform and stable emulsion, and then 688.72 g of methyl acrylate, 26.53 g of acrylonitrile and 995.25 g of methacryloyloxypropyl cage polysilsesquioxane (the molar content ratio of methyl acrylate, acrylonitrile and methacryloyloxypropyl cage polysilsesquioxane is 16:1:3) were added in sequence, and stirring was continued at a speed of 1800 r / min for 40 min to obtain a uniform prepolymer.

[0286] Polymer preparation: In a dry three-necked flask, add 4.5g of sodium lauryl sulfate and 1500g of deionized water, and emulsify with high-speed stirring for 40 minutes to obtain a uniform and stable emulsion; then, use a peristaltic pump to slowly dropwise add the prepolymer prepared in the previous step and the initiator solution (4.5g of potassium persulfate is dissolved in 45g of deionized water to form a solution). After the addition is complete, raise the temperature to 90°C and keep the temperature to react for 1 hour. Cool to 40°C, adjust the pH to 7-8 with ammonia water, filter, discharge, and dry to obtain silicone particles with a number average molecular weight of 52763, which are recorded as F1.

[0287] The average particle size of the organosilicon particles F1 is 0.8 μm, the moisture content is 800 μg / g, and the specific surface area is 8 g / m 2 .

[0288] Preparation of isolation membrane

[0289] Provide PE substrate: thickness 6.0μm, porosity 35%.

[0290] Preparation of coating slurry: The organosilicon particles F1 and ZIF-8 particles prepared above were mixed in water in a proportion (weight ratio of 5:1) to prepare a coating slurry, wherein the average pore size of the ZIF-8 particles was 1 nm and the porosity was 30%.

[0291] Coating: The prepared coating slurry is coated on both sides of the PE substrate using a coating machine, and the isolation film is obtained through drying and slitting processes.

[0292] Preparation of positive electrode

[0293] The active material LiNi 0.8 Mn 0.1 Co 0.1 O2 (NCM811), conductive agent acetylene black, and binder polyvinylidene fluoride are mixed uniformly in an appropriate amount of solvent N-methylpyrrolidone (NMP) in a weight ratio of 94:3:3 to obtain a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector aluminum foil, and the positive electrode sheet is obtained through processes such as drying, cold pressing, slitting, and cutting.

[0294] Preparation of negative electrode sheet

[0295] The negative electrode active material artificial graphite, the conductive agent carbon black (Super P), the binder styrene-butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC) are mixed evenly in an appropriate amount of solvent deionized water at a mass ratio of 95:2:2:1 to obtain a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector copper foil, and the negative electrode sheet is obtained through the processes of drying, cold pressing, slitting and cutting.

[0296] Preparation of electrolyte

[0297] Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a mass ratio of 30:70 to obtain an organic solvent, and fully dried LiPF6 was dissolved in the organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0298] Preparation of secondary batteries

[0299] The positive electrode sheet, separator, and negative electrode sheet are stacked and wound in sequence to obtain an electrode assembly; the electrode assembly is placed in an outer package, dried, and then injected with electrolyte. After vacuum packaging, standing, formation, shaping and other processes, a secondary battery is obtained.

[0300] Examples 1-2 to 1-11

[0301] The preparation was carried out using a method similar to that of Example 1-1, except that the relevant parameters of the coating of the isolation membrane were as shown in Table 1.

[0302] Comparative Example 1-1

[0303] The method is similar to that of Example 1-1, except that the coating-related parameters of the isolation film are outside the protection range of right 1, that is, the first particles are silicone particles F1, and the second particles are non-porous alumina. The specific parameters are detailed in Table 1.

[0304] Examples 2-1 to 2-4

[0305] The preparation method is similar to that of Example 1-1, except that the contents of the first particles and the second particles contained in the coating layer of the isolation film are changed. The specific parameters are shown in Table 2.

[0306] Comparative Example 2-1

[0307] The preparation method is similar to that of Example 2-1, except that the contents of the first particles and the second particles contained in the coating layer of the isolation film are changed. The specific parameters are shown in Table 2.

[0308] Test section

[0309] (1) Thermal shrinkage test of isolation film

[0310] The thermal shrinkage of the release film can be tested according to the standard GB / T 36363-2018. The specific test is as follows: Sample Preparation: Punch the release film prepared above into samples with a width of 50 mm and a length of 100 mm along the TD and MD directions using a punch press. Place five parallel samples on A4 paper. The A4 paper with the samples is then placed on corrugated paper with a thickness of 1 mm to 5 mm.

[0311] 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 the A4 paper placed on the corrugated paper into the blast oven, start timing, and after the set time (1 hour in this application) is reached, measure the length and width of the isolation film, and mark the values ​​as a and b respectively.

[0312] Calculation of thermal shrinkage: longitudinal (MD) thermal shrinkage = [(100-a) / 100] × 100%, transverse (TD) thermal shrinkage = [(50-b) / 50] × 100%, and the average value of 5 parallel samples is taken as the test result.

[0313] (2) Ion conductivity test of isolation membrane

[0314] The ionic conductivity of the isolation membrane can be obtained through AC impedance spectroscopy experiments. Specifically, the isolation membrane is cut into discs of a certain area, dried, and placed between two stainless steel electrodes. After absorbing a sufficient amount of electrolyte, it is sealed to form a button battery and an AC impedance spectroscopy experiment is performed. The intersection of the linear part and the real axis in the obtained AC impedance spectrum is the bulk resistance of the electrolyte. From this, the ionic conductivity of the isolation membrane can be calculated according to the formula σ=(L / A)×R. L represents the thickness of the isolation membrane (cm), and A represents the contact area between the stainless steel electrode and the isolation membrane (cm 2 ), R represents the bulk resistance of the electrolyte (mS).

[0315] The electrolyte used can be prepared as follows: ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed in a mass ratio of 30:50:20 to obtain an organic solvent, and fully dried LiPF6 is dissolved in the above organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0316] (3) Battery capacity retention test

[0317] At 25°C, charge the battery to 4.3V at a constant current of 1 / 3C, then charge it to a current of 0.05C at a constant voltage of 4.3V, let it sit for 5 minutes, and then discharge it to 2.8V at a constant current of 1 / 3C. The resulting capacity is recorded as the initial capacity C0. Repeat the above steps and record the discharge capacity C0 of the battery after the 1000th cycle. 1000 , then the battery capacity retention rate P after 1000 cycles 1000 =C 1000 / C0*100%.

[0318] Table 1 lists the test results of the coatings in Examples 1-1 to 1-5 and Comparative Example 1-1 under different parameters.

[0319] Table 1

[0320]

[0321] As shown in Table 1, in the separator provided in this application, the first particles in the coating are organic particles. Since organic particles have good heat resistance, and when the separator shrinks due to heat, the first particles, the second particles, and / or the first and second particles in the coating may abut against each other as the substrate shrinks, thereby providing a force to the substrate in the opposite direction of contraction, reducing the degree of contraction of the separator and thereby reducing the risk of short circuits between the positive and negative electrodes in the battery, thereby improving the thermal safety performance of the battery. In addition, the second particles with a porous structure can store electrolyte, improve the liquid absorption rate and liquid retention rate of the separator, and their pore size can serve as an ion channel to transmit ions, thereby enabling the battery to have good heat resistance while also taking into account good cycle performance.

[0322] Table 1 lists the test results of Examples 1-1, 2-1 to 2-4 and Comparative Example 2-1 when the coating contains different weights of organosilicon particles F1 and ZIF-8.

[0323] Table 2

[0324]

[0325] As can be seen from Table 2, the weight of the organic particles in the coating is larger than that of the second particles, which not only helps to reduce the shrinkage of the separator to improve the thermal safety performance of the battery, but also enables the organic particles to be better overlapped together, forming more ion transmission channels between the particles, thereby improving the ion conductivity of the separator, thereby improving the cycle performance of the battery.

[0326] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and within the scope of the technical solution of the present application, embodiments having substantially the same structure as the technical idea and exerting the same effects are all included in the technical scope of the present application. In addition, within the scope of the subject matter of the present application, various modifications that can be conceived by those skilled in the art to the embodiments, and other methods constructed by combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A separator comprising: substrate, and The coating is disposed on at least one side of the substrate, and the coating comprises first particles and second particles, wherein the first particles are organic particles, and the second particles have a pore structure.

2. The isolation film according to claim 1, wherein The average pore diameter of the second particles is 0.1 nm-10 nm, and can be optionally 0.4 nm-5 nm.

3. The separator according to claim 1 or 2, wherein: The porosity of the second particles is 10%-60%, and optionally 30%-50%.

4. The isolation film according to any one of claims 1 to 3, wherein The average particle size of the second particles is less than or equal to 2 μm, and can be optionally 0.1 μm-1 μm.

5. The isolation film according to any one of claims 1 to 4, wherein The specific surface area of ​​the second particles is greater than or equal to 100 m 2 / g; 500m can be selected 2 / g-2000m 2 / g.

6. The isolation film according to any one of claims 1 to 5, wherein: Based on the weight of the coating, a ratio of a weight proportion A of the first particles to a weight proportion B of the second particles satisfies:

1. a weight proportion B of the second particles in the coating is less than or equal to 20%; 7. The isolation film according to any one of claims 1 to 6, wherein: The optional range is 0.1%-15%. The second particles include one or more of inorganic particles and metal-organic framework materials; 8. The isolation film according to any one of claims 1 to 7, wherein: Optionally, the inorganic particles include one or more of titanium oxide, zirconium oxide, barium oxide, magnesium oxide, barium sulfate, magnesium aluminum silicate, zirconium titanate, and barium titanate; Optionally, the metal-organic framework material includes one or more of IRMOFs, ZIFs, MILs, PCNs, CPLs, and UiOs. The second particles have a through-pore structure.

9. The isolation film according to any one of claims 1 to 8, wherein The first particles include one or more of silicone particles, melamine formaldehyde resin particles, phenolic resin particles, polyester particles, polyimide particles, polyamideimide particles, polyaramid particles, polyphenylene sulfide particles, polysulfone particles, polyethersulfone particles, polyetheretherketone particles and polyaryletherketone particles; optionally, the first particles include silicone particles.

10. The isolation film according to any one of claims 1 to 9, wherein The first particles include organosilicon particles, and the organosilicon particles include a first polymer, and the first polymer includes a first structural unit, a second structural unit, and a third structural unit; 11. The isolation film according to any one of claims 1 to 10, wherein: The first structural unit has a structure as shown in formula (I): In formula (I), R1 includes a hydrogen atom, or one or more substituted or unsubstituted C1-C5 alkyl groups; alternatively, R1 includes a hydrogen atom, or one or more substituted or unsubstituted C1-C3 alkyl groups; R2 includes one or more of a substituted or unsubstituted C1-C20 alkyl group, a substituted or unsubstituted C3-C20 cycloalkyl group, or a substituted or unsubstituted C1-C20 hydroxyalkyl group; alternatively, R2 includes one or more of a C1-C12 alkyl group, a C3-C12 cycloalkyl group, or a C1-C12 hydroxyalkyl group; The second structural unit is shown in formula (II): In formula (II), R3 includes one or more of a hydrogen atom, or a substituted or unsubstituted C1-C5 alkyl group; alternatively, R3 includes one or more of a hydrogen atom, or a substituted or unsubstituted C1-C3 alkyl group; The third structural unit is shown in formula (III): 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 recorded as a%, 70≤a≤90; optionally, 75≤a≤85; and / or In formula (III), R4 to R 11 Each independently comprises a substituted or unsubstituted C1-C10 alkyl group, or one or more structural units as shown in formula (III-1), wherein R4 to R 11 At least one of them is a structural unit represented by formula (III-1), In formula (III-1), R 12 Including one or more of a hydrogen atom, or a substituted or unsubstituted C1-C5 alkyl group; Optionally, R 12 including one or more of a hydrogen atom, or a substituted or unsubstituted C1-C3 alkyl group; R 13 Including substituted or unsubstituted C1-C10 alkyl; optionally, R 13 This includes substituted or unsubstituted C3-C10 alkyl groups.

12. The isolation film according to claim 11, wherein ​ 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%, where 0 < b ≤ 16; optionally, 5 ≤ b ≤ 15; and / or 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%, where 2 ≤ c ≤ 15; optionally, 5 ≤ c ≤ 10.

13. The isolation film according to claim 11 or 12, wherein: 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 silicone particles satisfy one or more of the conditions (1) to (3): (1) 4 ≤ a / b ≤ 15; (2) 5 ≤ a / c ≤ 14; (3) a:b:c is (13 - 16):(1 - 3):(3 - 4).

14. The isolation film according to any one of claims 1 to 13, wherein: The first particles include silicone particles, and the silicone particles include a second polymer, and the second polymer includes a structural unit represented by formula (a): In formula (a), R 14 and R 15 Each independently comprises one or more of substituted or unsubstituted C1-C10 alkyl, hydroxyl or amino; optionally, R 14 and R 15 Each independently comprises one or more of a substituted or unsubstituted C1-C6 alkyl group, a hydroxyl group or an amino group; Optionally, the second polymer includes one or more of polymethylsiloxane, polydimethylsiloxane, poly(diethylsiloxane), polymethylhydroxysiloxane, and polymethylaminosiloxane.

15. The isolation film according to any one of claims 10 to 14, wherein: The number average molecular weight of the silicone particles is 35,000 - 70,000, and optionally 40,000 - 55,000.

16. The isolation film according to any one of claims 10 to 15, wherein: Based on the mass of the silicone particles, the moisture content of the silicone particles is less than or equal to 2500 μg / g; Optionally, it is 700 μg / g - 2000 μg / g.

17. The isolation film according to any one of claims 10 to 16, wherein: The average particle size of the silicone particles is less than or equal to 3 μm; optionally, it is 0.01 μm - 2 μm.

18. The isolation film according to any one of claims 10 to 17, wherein: The specific surface area of ​​the organic silicon particles is less than or equal to 12.0 m 2 / g; 5.0m is optional 2 / g-10.0m 2 / g.

19. The isolation film according to any one of claims 1 to 18, wherein: The thickness of the substrate is less than or equal to 16 μm; optionally, it is 3 μm - 12 μm.

20. The isolation film according to any one of claims 1 to 19, wherein The porosity of the substrate is greater than or equal to 25%; optionally, it is 30% - 45%.

21. The isolation film according to any one of claims 1 to 20, wherein: The separator film satisfies at least one of the following characteristics: (1) The longitudinal thermal shrinkage rate of the separator film at 150 °C for 1 h is less than or equal to 2%; (2) The transverse thermal shrinkage rate of the separator film at 150 °C for 1 h is less than or equal to 2%; (3) The air permeability of the separator film is less than or equal to 230 s / 100 cc; optionally, it is 160 s / 100 cc - 200 s / 100 cc; (4) The longitudinal tensile strength of the separator is greater than or equal to 2700 kg / cm 2 ; Optional 3000kg / cm 2 -4500kg / cm 2 ; (5) The transverse tensile strength of the separator is greater than or equal to 2000 kg / cm 2 ; Optional 2500kg / cm 2 -4500kg / cm 2 ; (6) The wetting length of the separator film is greater than or equal to 65 mm; optionally, it is 70 mm - 100 mm; (7) The ionic conductivity of the separator film is 0.8 S / m - 1.5 S / m.

22. A method for preparing a separator film according to any one of claims 1 - 21, comprising: Providing a substrate; Mixing organic particles as the first particles and second particles having a pore structure in a solvent to prepare a coating slurry; Coating the coating slurry on at least one side of the substrate to form a slurry film layer, and drying the slurry film layer to form a coating to obtain a separator film.

23. A secondary battery, comprising the separator film according to any one of claims 1 - 21 or the separator film obtained by the preparation method according to claim 22.

24. An electric device comprising the secondary battery according to claim 23.

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