Separator, battery cell, battery and power consuming device

Abstract

The present application provides a separator, a battery cell 5, a battery, and a power consumption device 6, the separator comprising a liquid-retaining polymer, the separator satisfying the formula (m2-M) / (m1-M)≧25%, where M is the mass of the separator without absorbing electrolyte, in g; m1 is the mass of the separator weighed under ambient pressure after being wetted with electrolyte for 2 hours, in g; and m2 is the mass of the separator weighed under a pressure of 10,000 N at ambient pressure after being wetted with electrolyte for 2 hours, in g.

Description

[Technical Field]

[0001] This application relates to the field of battery technology, and more particularly to separators, battery cells, batteries, and power consuming devices. [Background technology]

[0002] Due to their characteristics such as large capacity and long life, battery cells are widely used in electronic devices such as mobile phones, laptops, battery cars, electric vehicles, electric aircraft, electric ships, electric toy cars, electric toy ships, electric toy aircraft, and power tools.

[0003] As the range of battery applications continues to expand, the requirements for battery cell performance are also gradually becoming more stringent. However, the cycle characteristics of current battery cells are poor, and further improvement is required. Summary of the Invention

[0004] The embodiments of the present application have been made in view of the above-mentioned problems, and have an object to provide a separator, a battery cell, a battery, and a power consuming device.

[0005] According to a first aspect of an embodiment of the present application, there is provided a separator comprising a liquid-retaining polymer,

[0006] The separator is

number

[0007] M represents the mass of the separator without absorbing the electrolyte, and is expressed in g.

[0008] m1 represents the mass of the separator weighed under ambient pressure after being wetted with the electrolyte for 2 hours, and is expressed in g;

[0009] m2 represents the mass of the separator weighed under a pressure of 10,000 N at ambient pressure after the separator has been wetted with the electrolyte for 2 hours, and the unit is g.

[0010] The separator of the embodiment of the present application contains a liquid-retaining polymer. Because the separator contains a liquid-retaining polymer, the separator has a high liquid-retaining capacity, and the electrolyte is less likely to be pushed out during the cycle charge / discharge process of the battery cell. This reduces the liquid shortage situation during the cycle charge / discharge process, reduces battery polarization, and improves the cycle characteristics of the battery cell.

[0011] In some embodiments, the separator comprises:

number

[0012] Therefore, when the separator of the present embodiment satisfies the above conditions, the electrolyte retention capacity can be further improved, the electrolyte shortage situation during the cycle charge / discharge process can be further reduced, the polarization of the battery can be reduced, and the cycle characteristics of the battery cell can be improved.

[0013] In some embodiments, the separator comprises:

number

[0014] Therefore, when the separator of the embodiment of the present application satisfies the above conditions, the liquid absorption capacity can be further improved, the liquid shortage situation during the cycle charge / discharge process can be further reduced, the polarization of the battery can be reduced, and the cycle characteristics of the battery cell can be improved.

[0015] In some embodiments, the separator comprises:

number

[0016] Thus, when the separator of the embodiment of the present application satisfies the above conditions, it can have good liquid retention ability even under pressurized conditions, further reduce the situation of liquid shortage in the cycle charge and discharge process, reduce the polarization of the battery, and improve the cycle characteristics of the battery cell.

[0017] In some embodiments, the liquid retention polymer includes a fluoropolymer.

[0018] Optionally, the crystallinity of the fluoropolymer measured by differential scanning calorimetry is Xc1, where 0 < Xc1 ≤ 30%, and the melting temperature of the fluoropolymer is T m1 in °C, where 0 < T m1 ≤ 140.

[0019] In some embodiments, the glass transition temperature of the fluoropolymer is T g1 in °C, where -150 ≤ T g1 ≤ 60.

[0020] In some embodiments, the fluoropolymer includes at least one of the structural units represented by formula (AI) to formula (AIII).

Chemical formula

[0021] In formula (AI) and formula (AII), R 11 , R 12 , R 13 and R 14 each independently include a hydrogen atom, a fluorine atom, a bromine atom, a substituted or unsubstituted C1-C3 alkyl group or a substituted or unsubstituted C1-C3 alkoxy group, and at least one of R 11 , R 12 , R 13 and R 14 includes a fluorine atom.

Chemical formula

[0022] In formula (AIII),

[0023] R 15 represents a single bond, a substituted or unsubstituted C1-C3 alkyl group, p is selected from positive integers of 1 to 3, and n is selected from positive integers of 1000 to 30000.

[0024] In some embodiments, the liquid-retaining polymer further includes an ether-based polymer, the ether-based polymer is manufactured into a sheet-like structure, and the sheet-like structure is subjected to a dynamic frequency sweep test at (T m2 +20)°C to obtain a storage modulus G'-loss modulus G" curve, and the slope of the storage modulus G'-loss modulus G" curve is K1, where 1 < K1 < ∞, T m2 teeth which represents the melting temperature of the ether-based polymer, The unit is °C, Optionally, 1 < K1 ≤ 100, and more optionally, 1 < K1 ≤ 10.

[0025] In some embodiments, the liquid-retaining polymer includes an ether-based polymer.

[0026] Optionally, the ether-based polymer includes a structural unit represented by formula (BI) and / or a structural unit represented by formula (BII),

Chemical formula

[0027] In formula (BI), R 21 and R 22 each independently include a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group, or a substituted or unsubstituted C1-C3 alkoxy group, and R 23 includes a substituted or unsubstituted C1-C5 alkylene group,

Chemical formula

[0029] In some embodiments, the liquid retention polymer includes an ester-based polymer.

[0030] Optionally, the ester-based polymer is manufactured into a sheet-like structure, and a dynamic frequency sweep test is performed on the sheet-like structure at (T m3 +20)°C to obtain a storage modulus G’ - loss modulus G” curve, and the slope of the storage modulus G’ - loss modulus G” curve is K2, where 1 < K2 < ∞, T m3 teeth which represents the melting temperature of the ester-based polymer, The unit is °C, Optionally, 1 < K2 ≤ 100, and further optionally, 1 < K2 ≤ 10.

[0031] In some embodiments, the ester-based polymer includes a structural unit represented by formula (CI) and / or a structural unit represented by formula (CII),

Chemical formula

[0032] In formula (CI), R 31 , R 32 and R 33 each independently includes a hydrogen atom or a substituted or unsubstituted C1-C8 alkyl group, and R 34 includes a substituted or unsubstituted C1-C8 alkyl group or a substituted or unsubstituted C1-C8 hydroxyalkyl group,

Chemical formula

[0033] In formula (CII), R 35 contains a substituted or unsubstituted C2-C6 methylene group, and optionally, R 35 each independently contains a substituted or unsubstituted C2-C4 methylene group.

[0034] In some embodiments, the liquid-retaining polymer includes an aldehyde-ketone polymer.

[0035] Optionally, the aldehyde-ketone polymer is manufactured into a sheet-like structure, and the sheet-like structure is subjected to a dynamic frequency sweep test at (T m4 +20)°C to obtain a storage modulus G'-loss modulus G'' curve, and the slope of the storage modulus G'-loss modulus G'' curve is K3, where 0.8 ≤ K3 < ∞, T m4 teeth which represents the melting temperature of the aldehyde-ketone polymer, The unit is °C, Optionally, 0.8 < K3 ≤ 100, and further optionally, 0.8 < K3 ≤ 10.

[0036] In some embodiments, the aldehyde-ketone polymer includes a structural unit represented by formula (DI) and / or a structural unit represented by formula (DII),

Chemical formula

[0037] In formula (DI), R 41 is a single bond, contains a substituted or unsubstituted C1-C6 methylene group, and R 42 is a hydrogen atom, contains a substituted or unsubstituted C1-C6 alkyl group, ?

Chemical formula

[0038] In formula (DII), R 43 ~R 46 It should be noted that there may be some inaccuracies in the translation of chemical-related content as the original text seems to have some incomplete or unclear chemical formula notations. It is recommended to double-check with the original chemical knowledge and context for the most accurate understanding.each independently comprises a hydrogen atom, a hydroxyl group, a substituted or unsubstituted C1-C3 alkyl group, a substituted or unsubstituted C1-C3 hydroxyalkyl group, or a substituted or unsubstituted C1-C3 alkoxy group, and r and s are each independently selected from integers of 0 to 5, and at least one of r and s is selected from a positive integer.

[0039] In some embodiments, the molecular weight of the liquid-retaining polymer is 1.2×10 5 g / mol to 1.0 × 10 6 g / mol. When the molecular weight of the polymer is in the above range, polymer can have excellent liquid retention capacity, which is advantageous for improving the liquid retention capacity of the separator.

[0040] In some embodiments, the Separator The method includes a substrate, and the polymer layer is disposed on at least one surface of the substrate.

[0041] In some embodiments, the separator comprises a porous substrate, and the liquid-retaining polymer is distributed within the voids of the porous substrate.

[0042] In some embodiments, the separator includes a porous substrate and a polymer layer disposed on at least one surface of the porous substrate, the polymer layer including the liquid-retaining polymer.

[0043] In some embodiments, the coating weight of the liquid-retaining polymer is 0.5 mg / 1540.25 mm 2 From 5mg / 1540.25mm 2 When the coating basis weight is within the above range, the liquid retention capacity of the separator can be further improved.

[0044] According to a second aspect, the present application provides a battery cell including a separator according to any embodiment of the first aspect of the present application.

[0045] According to a third aspect, the present application provides a battery comprising a battery cell according to any embodiment of the second aspect of the present application.

[0046] According to a fourth aspect, the present application provides a power consuming device comprising a battery according to any embodiment of the third aspect of the present application. [Brief explanation of the drawings]

[0047] In order to more clearly describe the technical solutions in the embodiments of the present application, the following briefly describes the drawings required for the embodiments of the present application. It should be understood that the drawings shown below are only some embodiments of the present application, and those skilled in the art can further obtain other drawings based on the drawings without any creative efforts.

[0048] [Figure 1] 1 is a schematic diagram of one embodiment of a battery cell of the present application.

[0049] [Figure 2] 2 is an exploded schematic view of the battery cell shown in FIG. 1 according to an embodiment.

[0050] [Figure 3] 1 is a schematic diagram of a battery module according to an embodiment of the present application;

[0051] [Figure 4] 1 is a schematic diagram of an embodiment of a battery pack of the present application.

[0052] [Figure 5] 5 is an exploded schematic view of the battery pack shown in FIG. 4 according to the embodiment.

[0053] [Figure 6] 1 is a schematic diagram of one embodiment of a power consuming device that includes a battery cell of the present application as a power source.

[0054] The drawings are not drawn to scale.

[0055] [Explanation of symbols]

[0056] 1 battery pack, 2 upper housing, 3 lower housing, 4 battery module,

[0057] 5 battery cell, 51 housing, 52 electrode assembly,

[0058] 53 cover plate,

[0059] 6 Power consumption equipment. DETAILED DESCRIPTION OF THE INVENTION

[0060] Hereinafter, embodiments specifically disclosing the separator, battery cell, battery, and power consumption device of the present application will be described in detail. However, unnecessary details may be omitted. For example, detailed descriptions of well-known matters and redundant descriptions of structures that are actually the same may be omitted. This is to avoid the following description becoming unnecessarily long and to facilitate understanding by those skilled in the art. Note that the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0061] The "ranges" disclosed herein are defined in the form of lower and upper limits, and a given range is defined by selecting one lower limit and one upper limit, with the selected lower and upper limits defining the boundaries of the particular range. Such defined ranges may be inclusive or exclusive of their endpoints, and are arbitrarily combinable; i.e., any lower limit can be combined with any upper limit to form a single range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if 1 and 2 are listed as minimum range values ​​and 3, 4, and 5 are listed as maximum range values, the ranges 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5 are all contemplated. In this application, unless otherwise specified, a numerical range "a to b" is a shorthand representation of any combination of real numbers a to b, where a and b are both real numbers. For example, the numerical range "0-5" represents a list of all real numbers between "0-5" in this specification, and "0-5" is merely a shorthand representation of combinations of these numbers. Also, expressing a parameter as an integer ≧2 is equivalent to disclosing that this parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0062] Unless otherwise stated, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution. Unless otherwise stated, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0063] All steps in this application can be performed sequentially or randomly, and are preferably performed sequentially, unless otherwise specified. For example, if a method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, if it is said that the method may further include step (c), it means that step (c) may be added to the method in any order, e.g., the method may include steps (a), (b), and (c), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0064] The terms "comprise" and "comprises" referred to herein refer to both open and closed forms unless otherwise specified. For example, "comprise" and "comprises" can indicate that other elements not listed may also be included or may be included, or that only the listed elements may be included or included.

[0065] In this application, unless otherwise stated, the term "or" is 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 by either A being true (or present) and B being false (or absent), or A being false (or absent) and B being true (or present), or both A and B being true (or present).

[0066] As used herein, the terms "plurality" and "plurality" mean two or more.

[0067] The term "alkyl group" encompasses straight-chain and branched alkyl groups. For example, the alkyl group may be a C1-C5 alkyl group, a C1-C4 alkyl group, a C1-C3 alkyl group, or a C1-C2 alkyl group. In some embodiments, the alkyl group includes methyl, ethyl, propyl, isopropyl, butyl, isobutyl, and the like. The alkyl group may also be optionally substituted. When substituted, the substituent may include a fluorine atom.

[0068] The term "alkoxy group" refers to a group in which an alkyl group and an oxygen atom are joined by a single bond. For example, the alkoxy group may be a C1-C5 alkoxy group, a C1-C3 alkoxy group, or a C1-C2 alkoxy group. In some embodiments, the alkoxy group may include methoxy, ethoxy, and propoxy. Additionally, the alkoxy group may be optionally substituted.

[0069] The term "halogen atom" refers to fluorine atom, chlorine atom, bromine atom, and the like.

[0070] The term "hydrogen" refers to 1H (protium, H), 2H (deuterium, D), or 3H (tritium, T). In each embodiment, "hydrogen" may be 1H (protium, H).

[0071] A battery cell includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte. The separator is located between the positive electrode sheet and the negative electrode sheet to separate them. During the charge-discharge cycle of the battery cell, the electrode assembly undergoes volume expansion. The expansion force is particularly large in the later stages of the battery cell cycle, which extrudes the electrolyte, increasing the risk of liquid shortage and the appearance of bridges on the polar sheets, which increases the risk of metal dendrite precipitation, deteriorating the cycle characteristics of the battery cell and potentially shortening the cycle life of the battery cell.

[0072] In view of the above problems, an embodiment of the present application provides a separator, which includes a liquid-retaining polymer and has a high liquid-retaining capacity, which makes it difficult for the electrolyte to be extruded during the cycle charge / discharge process of the battery cell, thereby reducing the liquid shortage situation during the cycle charge / discharge process, reducing battery polarization, and improving the cycle characteristics of the battery cell.

[0073] Separator

[0074] According to a first aspect, an embodiment of the present application provides a separator, the separator comprising a liquid-retaining polymer, the liquid-retaining polymer comprising at least one of:

number

[0075] M is the above Mass of separator that does not absorb electrolyte The unit is g,

[0076] m1 represents the mass of the separator weighed under ambient pressure after being wetted with the electrolyte for 2 hours, and is expressed in g;

[0077] m2 indicates the mass, in g, of the separator weighed after being wetted with the electrolyte for 2 hours and then subjected to an acting force of 10,000 N at ambient pressure.

[0078] When calculating the above formulas specifically, only the specific values ​​are substituted, and the units of each parameter are not substituted.

[0079]

number

[0080] The separator of the embodiment of the present application contains a liquid-retaining polymer. Because the separator contains a liquid-retaining polymer, the separator has a high liquid-retaining capacity, and the electrolyte is less likely to be pushed out during the cycle charge / discharge process of the battery cell. This reduces the liquid shortage situation during the cycle charge / discharge process, reduces the risk of metal dendrites precipitating within the battery cell, and improves the cycle characteristics of the battery cell.

[0081] The separator may be made of a substrate and a liquid-retaining polymer, etc. Alternatively, the separator may be derived from a battery cell. The battery cell is disassembled, and the separator soaked in the electrolyte in the battery cell is removed. The separator is washed with deionized water and then vacuum-dried at 80°C for 12 hours to obtain the separator, which is then used for testing the separator for mass measurement, liquid absorption rate, porosity, etc.

[0082] M indicates the mass of the separator without absorbing the electrolyte, and can also be understood as the mass of the separator itself. 2 The sheet is cut into a circular shape and its mass is weighed on an electronic balance.

[0083] m1 indicates the mass of the separator weighed under ambient pressure after it has been wetted with the electrolyte for 2 hours. Specifically, the mass of 10 separators weighed at 1540.25 mm 2 The circular sheet is then cut into a circular sheet, and after wetting the circular sheet in the electrolyte for 2 hours, the circular sheet is taken out and suspended under atmospheric pressure for 2 minutes, and its mass is then weighed.

[0084] m2 indicates the mass of the separator weighed after applying a force of 10,000 N at ambient pressure after the separator has been wetted with the electrolyte for 2 hours. Specifically, the mass of 10 separators weighed is 1540.25 mm 2 The circular sheets are cut into circular sheets, and the circular sheets are soaked in the electrolyte for 2 hours. Then, the circular sheets are taken out and stacked one after another. After applying a force of 10,000 N at ambient pressure, the mass of the separator is weighed.

[0085] In this application, measurements are performed using a standard electrolyte as a test sample. For the specific composition of the electrolyte, please refer to the composition of the electrolyte in the examples. For example, the electrolyte contains ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 1:1:1, and further contains lithium hexafluorophosphate (LiPF6) with a molar concentration of 1 mol / L.

[0086] Selectively,

number

[0087] When the separator satisfies the above conditions, the separator has high liquid absorption and retention capabilities, which can reduce the liquid shortage situation during cyclic charging and discharging, reduce battery polarization, and improve the cycle characteristics of the battery cell.

[0088] For example,

number

[0089] 25.1%, 25.5%, 26%, 26.5%, 27%, 27.5%, 28%, 28.5%, 29%, 29.5%, 30%, 30.5%, 31%, 31.5%, 32%, 32.5%, 33%, 33.5%, 34%, 34.5%, 36%, 36.5%, 37%, 37.5%, 38%, 39%, 40 %, 41%, 42%, 45%, 46%, 48%, 50%, 52%, 55%, 60%, 62%, 65%, 68%, 70%, 72%, 75%, 78%, 80%, 82%, 85%, 88%, 90%, 92%, 95%, 96%, 97%, 98%, 99%, or a range consisting of any two of the above values.

[0090] In some embodiments, the separator comprises:

number

[0091] m1-M indicates the ratio of the amount of liquid absorbed by the separator to the mass of the separator itself, and can characterize the separator's liquid absorption capacity, i.e., the amount of electrolyte absorbed, and can relatively improve its liquid retention capacity.

[0092]

number

[0093] If the separator satisfies the above conditions, the separator has good liquid absorption ability, which is advantageous for improving the absorption rate of the electrolyte, thereby further improving the cycle characteristics of the battery cell.

[0094] For example,

number

[0095] 88%, 90%, 92%, 95%, 96%, 97%, 98%, 99%, 100%, 105%, 110%, 120%, 130%, 140%, 150%, 160%, 170%, 180%, 190%, 200%, 210%, 220%, 230%, 240%, 250%, 260%, 270%, 280%, 290%, 300%, or a range consisting of any two of the above values.

[0096] In some embodiments, the separator comprises:

number

[0097] (m-M) / M indicates the ratio of the amount of liquid retained in the separator after it is subjected to an external force to the mass of the separator itself, which can characterize the liquid retention capacity of the separator after it is pressurized.

[0098]

number

[0099] When the separator satisfies the above conditions, the separator has good liquid retention capacity, and the electrolyte adsorbed by the separator is less likely to be pushed out, thereby increasing the migration rate of active ions and further improving the cycle characteristics of the battery cell.

[0100] For example,

number

[0101] 22.5%, 25.1%, 25.5%, 26%, 26.5%, 27%, 27.5%, 28%, 28.5%, 29%, 29.5%, 30%, 30.5%, 31%, 31.5%, 32%, 32.5%, 33%, 33.5%, 34%, 34.5%, 36%, 36.5%, 37%, 37.5%, 38%, 39%, 40%, 41%, 42%, 45%, 46%, 48%, 50%, 52%, 55%, 60%, 62%, 65%, 68%, 70% %, 72%, 75%, 78%, 80%, 82%, 85%, 88%, 90%, 92%, 95%, 96%, 97%, 98%, 99%, 100%, 105%, 110%, 120%, 130%, 140%, 150%, 160%, 170%, 180%, 190%, 200%, 210%, 220%, 230%, 240%, 250%, 260%, 270%, 280%, 290%, 300%, or a range consisting of any two of the above numbers.

[0102] The liquid-retaining polymer may be selected from at least one of a fluoropolymer, an ether-based polymer, an ester-based polymer, and an aldehyde ketone polymer.

[0103] In some embodiments, the liquid-retaining polymer comprises a fluoropolymer, and the fluoropolymer has a crystallinity measured by differential scanning calorimetry of X C1and 0 <X C1 ≦30%, and the melting temperature of the fluoropolymer is T m1 The unit is °C, and 0 <T m1 ≦140.

[0104] Crystallization refers to the process by which atoms, ions, or molecules in a material are arranged in a certain spatial order to form an order. The structure of a polymer in a crystal is determined by both intramolecular and intermolecular forces, and intermolecular forces affect the packing density between molecular chains. Crystallinity X C1 is used to characterize the degree of crystallization in a material and can be measured using differential scanning calorimetry (DSC). Specifically, the measurement steps are as follows: Take a 0.5g-0.8g sample, place it in a crucible, and heat and cool the sample under a nitrogen atmosphere at a heating rate of 10°C / min to measure the intrinsic T of the material. g1 Starting at a temperature 20°C lower than the material's inherent T m1 The temperature is raised to the cutoff temperature of the process, which is 20°C higher than the actual glass transition temperature T of the material based on the heat absorption / dissipation peak value or transition point of the material in the process. g1 and melting temperature T m1 etc. will be determined.

[0105] As a result, fluoropolymers have a relatively low crystallinity and melting temperature, which means that the molecular chains tend to be sparsely aligned, the inter-chain forces are small, adjacent molecular chains open more easily, and segmental movement is achieved through intermolecular internal rotation, forming a relatively flexible molecular chain structure. Furthermore, the fluoropolymer and the electrolyte in the battery cell can form a gel-like substance, improving the cycle characteristics of the battery cell.

[0106] For example, the crystallinity X of the fluoropolymer measured by differential scanning calorimetry C1 may be 5%, 10%, 15%, 20%, 25%, 30%, or a range consisting of any two of the above values.

[0107] Illustratively, the melting temperature of the fluoropolymer may be 10°C, 20°C, 50°C, 70°C, 90°C, 100°C, 120°C, 140°C, or a range consisting of any two of the foregoing values.

[0108] In some embodiments, the glass transition temperature of the fluoropolymer is T g1 The unit is °C, and -150≦T g1 ≦60.

[0109] The glass transition temperature (GTC) is the temperature at which a polymer segment transitions from frozen to mobile. The GTC has a certain effect on the flexibility of the polymer molecular chain. The lower the GTC, the better the flexibility of the polymer molecular chain at room temperature. The higher the GTC, the worse the flexibility of the molecular chain at room temperature. The GTC can be measured using differential scanning calorimetry (DSC). When the GTC of a polymer is relatively low, the flexibility of the molecular chain segments is good, and adjacent molecular chains open more easily. For example, the GTC of a fluoropolymer may be -150°C, -120°C, -100°C, -80°C, -60°C, -30°C, 0°C, 30°C, 60°C, or a range consisting of any two of the above values.

[0110] In some embodiments, the fluoropolymer comprises a structural unit shown in formula (AI): [ka]

[0111] In formula (AI), R 11 , R 12 , R 13 and R 14 each independently comprises a hydrogen atom, a fluorine atom, a bromine atom, a substituted or unsubstituted C1-C3 alkyl group, or a substituted or unsubstituted C1-C3 alkoxy group, and R 11 , R 12 , R 13 and R 14 At least one of them contains a fluorine atom.

[0112] In some embodiments, the fluoropolymer comprises structural units shown in formula (AII): [ka]

[0113] formula In (AII), R 11 , R 12 , R 13 and R 14 each independently comprises a hydrogen atom, a fluorine atom, a bromine atom, a substituted or unsubstituted C1-C3 alkyl group, or a substituted or unsubstituted C1-C3 alkoxy group, and R 11 , R 12 , R 13 and R 14 At least one of them contains a fluorine atom.

[0114] In some embodiments, the fluoropolymer has the formula (AII I ) containing the structural unit shown in [ka]

[0115] In formula (AIII), R 15 includes a single bond, a substituted or unsubstituted C1-C3 alkyl group.

[0116] The above polymers are merely examples of structural groups in the main molecular chain, and in the embodiments of the present application, the polymer may be obtained by copolymerizing the above structural groups with other types of structural groups (for example, structural units such as olefin-based structural units, ester-based monomers, nitrile-based monomers, and amide-based monomers).

[0117] When the above groups are substituted, the substituents may include one or more of a nitrile group (-CN), a nitro group, a sulfonic acid group, a sulfonyl group, an amide group, a carboxyl group, an ester group, and a halogen atom (e.g., a chlorine atom, a fluorine atom, a bromine atom). The above substituents are pressure-resistant substituents, which are further advantageous in stabilizing the structure of the polymer.

[0118] In some embodiments, p is selected from a positive integer of 1-3.

[0119] In some embodiments, the degree of polymerization n of the fluoropolymer is selected from positive integers of 1,000 to 30,000.

[0120] In some embodiments, R 11 , R 12 , R 13 and R 14 each independently comprise a hydrogen atom, a fluorine atom, a bromine atom, a substituted or unsubstituted C1-C2 alkyl group, or a substituted or unsubstituted C1-C2 alkoxy group, and optionally R 11 , R 12 , R 13 and R 14 each independently includes a hydrogen atom, a fluorine atom, a chlorine atom, a methyl group, a fluoromethyl group, a methoxy group, or a perfluoromethoxy group.

[0121] In some embodiments, the fluoropolymer comprises at least one of structural units shown in formula (AI-1) to structural units shown in formula (AI-11): [ka]

[0122] In some embodiments, the fluoropolymer comprises at least one of the structural units shown in formula (AII-1) to (AII-5): [ka]

[0123] In some embodiments, the fluoropolymer comprises at least one of the structural units shown in formula (AIII-1) to the structural unit shown in formula (AIII-3): [ka]

[0124] Exemplarily, the fluoropolymer includes one or more of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), perfluoroethylenepropene copolymer (FEP), perfluoroalkoxyalkane (PFA), perfluoropolyether (PFPE), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyvinylidene fluoride-trifluoroethylene copolymer (PVDF-TrFE), and perfluoro(1-butenyl vinyl ether) polymer (abbreviated as CYTOP).

[0125] Optionally, the fluoropolymer comprises one or more of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), perfluoroethylene propene copolymer (FEP), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyvinylidene fluoride-trifluoroethylene copolymer (PVDF-TrFE).

[0126] The fluoropolymer may be derived from one or more of the following monomers: fluorocyclohexane, fluoroethylene, 1,2-difluoroethylene, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene, 3,3,3-trifluoropropylene, trifluoropropylene, tetrafluoropropylene, and pentafluoropropylene. Alternatively, the fluoropolymer may be derived from at least two of the following monomers: fluorocyclohexane, fluoroethylene, 1,2-difluoroethylene, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene, 3,3,3-trifluoropropylene, trifluoropropylene, tetrafluoropropylene, and pentafluoropropylene.

[0127] The monomers used in the above fluoropolymers are all short-chain monomers, which are advantageous for polymerizing to form a linear structure or a short-chain branched structure. This structural type has a low degree of entanglement, which is advantageous for improving the flexibility of the molecular chains, and the molecular chains can be sufficiently spread in the electrolyte, which is advantageous for the polymer and the electrolyte to form a three-dimensional gel-like substance, which is helpful for further improving the liquid absorption rate.

[0128] In some embodiments, the degree of polymerization n of the fluoropolymer is selected from positive integers of 5,000 to 20,000.

[0129] In some embodiments, the molecular weight of the fluoropolymer is 1.2×10 5 g / mol to 1.5 × 10 6 g / mol, and selectively 1.2 × 10 5 g / mol to 1.0 × 10 6 g / mol. When the molecular weight of the polymer is in the above range, polymer can have excellent liquid retention capacity, which is advantageous for improving the liquid retention capacity of the separator.

[0130] Illustratively, the molecular weight of the polymer is 1.2×10 5 g / mol, 2 × 10 5 g / mol, 5 × 10 5 g / mol, 8 × 10 5 g / mol, 1×10 6 g / mol, 1.5 × 10 6 It may be g / mol or a range consisting of any two of the above values.

[0131] [Ether polymer]

[0132] In some embodiments, the liquid-retaining polymer comprises an ether-based polymer, and the ether-based polymer is formed into a sheet-like structure, and the sheet-like structure is (T m2 A dynamic frequency sweep test was performed at +20°C to obtain the elastic modulus G'-loss elastic modulus G" curve, and the slope of the elastic modulus G'-loss elastic modulus G" curve was K1, and 1 <K1<∞であり、 T m2 teeth The melting temperature of the ether polymer is The unit is °C. .

[0133] Specifically, the process for producing the sheet-like structure is as follows: The ether-based polymer is vacuum-dried at 80°C for 12 hours. After drying, the ether-based polymer is hot-pressed into thin pieces using a vulcanization press. The hot-press temperature is (T m2 +20℃) and roll thickness is 1-2 mm The rolling time is 2 minutes and the pressure is 8 MPa. After rolling for 2 minutes, the sample is removed and cold-pressed in another vulcanizing press of the same type at a pressure of 10 MPa. A circular mold with a diameter of 25 mm is used to obtain a fixed-size circular polymer sheet (sheet-like structure). For example, the sheet-like structure may be a circular sheet with a thickness of 1 to 2 mm and a diameter of 25 mm. Standard samples may be prepared according to the requirements of the testing equipment.

[0134] According to the conclusions of conventional linear viscoelasticity, for polymers, especially linear polymers, the storage modulus G’ - loss modulus G” in the terminal region of the G’-G” curve (the range of the interval towards the maximum value of the angular velocity) conforms to frequency dependence, and the longest chains of the polymer contribute to the viscoelastic behavior.

[0135] The specific steps of the dynamic frequency sweep test are as follows. A dynamic frequency sweep test is performed using a TA-AR2000EX rotational rheometer (TA instruments, USA). The diameter of the parallel plates is 25 mm and the thickness is 0.9 mm. To ensure the test in the linear viscoelastic region, the strain during the dynamic frequency sweep test is 2%, the test temperature is T m2 +20 °C, and the frequency sweep range of the test is 500 rad / s ≤ ω 2 ≤ 0.05 rad / s, so as to easily obtain data in the lowest possible frequency region.

[0136] The dynamic frequency sweep test can characterize the degree of entanglement of molecular chains in the solid phase melting (melt state). Compared with the linear structure or short-chain branched structure, the long-chain branched structure, network structure, and low cross-linking structure have a greater degree of entanglement, show behavior deviating from the linear end, and the ether-based polymer shows solid-phase behavior. When the ether-based polymer of the embodiment of the present application satisfies the above range, the entanglement state of the molecular chains can be further reduced, which is beneficial for solvent molecules in the electrolyte to diffuse between the molecular chains, and moreover, the ether-based polymer still maintains a certain molecular chain entanglement state and can form an electrolyte and a gel-like substance, improving the cycle characteristics and storage performance of the battery cell.

[0137] In some embodiments, 1 < K1 ≤ 100, and optionally, 1 < K1 ≤ 10. Exemplarily, K1 may be 1.01, 1.1, 2, 5, 10, 15, 20, 30, 50, 100, 200, 500, 1000, 5000, 10000, or a range consisting of any two of the above numerical values.

[0138] In some embodiments, the glass transition temperature of the ether-based polymer is T g2The unit is °C, and -100≦T g2 ≦50, and optionally, −80≦T g2 ≦30. For example, the glass transition temperature of the ether-based polymer may be −100° C., −80° C., −60° C., −30° C., 0° C., 30° C., 50° C., or a range consisting of any two of the above values.

[0139] In some embodiments, the ether-based polymer comprises a structural unit shown in formula (BI): [ka]

[0140] In formula (BI), R 21 and R 22 each independently comprises a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group, or a substituted or unsubstituted C1-C3 alkoxy group; R 23 includes substituted or unsubstituted C1-C5 methylene groups.

[0141] In some embodiments, R 21 and R 22 each independently comprises a hydrogen atom or a substituted or unsubstituted C1-C2 alkyl group.

[0142] In some embodiments, R 23 includes a single bond, a substituted or unsubstituted C1-C4 methylene group.

[0143] Exemplarily, the ether-based polymer includes at least one of the structural units represented by formula (BI-1) to the structural unit represented by formula (BI-8), [ka]

[0144] In some embodiments, the ether-based polymer comprises a structural unit according to formula (BII): [ka]

[0145] In formula (BII), R 24 ~R 27 each independently comprises a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group, a substituted or unsubstituted C1-C3 alkoxy group, or an ether group, and R 24 ~R 27 At least one of the groups contains a substituted or unsubstituted C1-C3 alkoxy or ether group.

[0146] In some embodiments, R 24 ~R 27 each independently comprises a hydrogen atom, a substituted or unsubstituted C1-C2 alkyl group, a substituted or unsubstituted C1-C2 alkoxy group, or an ether group, and R 24 ~R 27 At least one of the groups contains a substituted or unsubstituted C1-C2 alkoxy or ether group.

[0147] In some embodiments, the ether-based polymer comprises at least one of structural units represented by formula (BII-1) to structural units represented by formula (BII-7): [ka]

[0148] The monomers used in the above-mentioned ether polymers are multi-membered rings, for example, six-membered rings or less, or short-chain monomers, which are advantageous for forming a high content of -O- structure upon polymerization. This structural type is advantageous for reducing the degree of entanglement and improving the flexibility of the molecular chains, allowing the molecular chains to spread sufficiently in the electrolyte and easily form a gel material with the electrolyte, thereby improving the cycle characteristics and storage performance of the battery cell.

[0149] The above polymers are merely examples of structural groups in the main molecular chain, and in the embodiments of the present application, the polymer may be obtained by copolymerizing the above structural groups with other types of structural groups (for example, structural units such as olefin-based structural units, ester-based monomers, nitrile-based monomers, and amide-based monomers).

[0150] When the above groups are substituted, the substituents may include one or more of a nitrile group (-CN), a nitro group, a sulfonic acid group, a sulfonyl group, an amide group, a carboxyl group, an ester group, and a halogen atom (e.g., a chlorine atom, a fluorine atom, a bromine atom). The above substituents are pressure-resistant substituents, which are further advantageous in stabilizing the structure of the polymer.

[0151] In some embodiments, the degree of polymerization n of the ether-based polymer is selected from positive integers of 1,500 to 25,000.

[0152] Optionally, the degree of polymerization n of the ether-based polymer is selected from a positive integer of 3,000 to 18,000.

[0153] In some embodiments, the molecular weight of the polymer is 1.2×10 5 g / mol to 1.0 × 10 6 g / mol.

[0154] Illustratively, the molecular weight of the polymer is 1.2×10 5 g / mol, 2 × 10 5 g / mol, 5 × 10 5 g / mol, 8 × 10 5 g / mol, 1×10 6 It may be g / mol or a range consisting of any two of the above values.

[0155] [Ester polymer]

[0156] In some embodiments, the liquid-retaining polymer comprises an ester-based polymer, and the ester-based polymer is formed into a sheet-like structure, and the sheet-like structure is (T m3A dynamic frequency sweep test is performed at +20)°C to obtain a storage modulus G’ - loss modulus G” curve, and the slope of the storage modulus G’ - loss modulus G” curve is K2, where 1 < K2 < ∞, T m3 teeth indicating the melting temperature of the ester polymer The unit is °C. .

[0157] When the ester polymer of the embodiment of the present application satisfies the above range, the entanglement state of the molecular chains can be further reduced, which is advantageous for the diffusion of solvent molecules in the electrolyte between the molecular chains, and the ester polymer still retains a certain entanglement state of the molecular chains and can form an electrolyte and a gel substance, improving the liquid absorption rate, thereby improving the cycle characteristics and storage performance of the battery cell.

[0158] In some embodiments, 1 < K2 ≤ 100, and optionally, 1 < K2 ≤ 10.

[0159] Exemplarily, K2 may be 1.01, 1.1, 1.2, 1.5, 2, 5, 10, 15, 20, 30, 50, 100, 200, 500, 1000, 5000, 10000, or a range consisting of any two of the above numerical values.

[0160] In some embodiments, the glass transition temperature of the ester polymer is T g3 in °C, and -100 ≤ T g3 ≤ 50, and optionally, -80 ≤ T g3 ≤ 30. <0​​​​​​​​​​​​

[0163] In formula (CI), R 31 , R 32 and R 33 each independently comprises a hydrogen atom or a substituted or unsubstituted C1-C8 alkyl group; R 34 comprises a substituted or unsubstituted C1-C8 alkyl group or a substituted or unsubstituted C1-C8 hydroxyalkyl group, optionally R 34 includes a substituted or unsubstituted C1-C6 alkyl group, or a substituted or unsubstituted C1-C6 hydroxyalkyl group.

[0164] Selectively, R 31 includes a hydrogen atom or a substituted or unsubstituted methyl group.

[0165] Selectively, R 32 and R 33 each independently contains a hydrogen atom.

[0166] Selectively, R 34 includes a substituted or unsubstituted C1-C4 alkyl group, or a substituted or unsubstituted C1-C4 hydroxyalkyl group.

[0167] Exemplarily, the ester-based polymer includes at least one of the structural units represented by formula (CI-1) to formula (CI-15): [ka] TIFF2026502891000111.tif65170

[0168] In some embodiments, the ester-based polymer comprises a structural unit shown in formula (CII): [ka]

[0169] In formula (CII), R35 includes substituted or unsubstituted C2-C6 methylene groups.

[0170] Selectively, R 35 each independently comprises a substituted or unsubstituted C2-C4 methylene group.

[0171] Exemplarily, the ester-based polymer includes at least one of the structural units represented by formula (CII-1) to formula (CII-5), [ka]

[0172] The degree of entanglement of the molecular chains of the ester polymer is small, which is advantageous in improving the flexibility of the molecular chains, and the molecular chains spread sufficiently in the electrolyte solution, easily forming a gel substance with the electrolyte solution.

[0173] The above polymers are merely examples of structural groups in the main molecular chain, and in the embodiments of the present application, the polymer may be obtained by copolymerizing the above structural groups with other types of structural groups (for example, structural units such as olefin-based structural units, ester-based monomers, nitrile-based monomers, and amide-based monomers).

[0174] When the above groups are substituted, the substituents may include one or more of a nitrile group (-CN), a nitro group, a sulfonic acid group, a sulfonyl group, an amide group, a carboxyl group, an ester group, and a halogen atom (e.g., a chlorine atom, a fluorine atom, a bromine atom). The above substituents are pressure-resistant substituents, which are further advantageous in stabilizing the structure of the polymer.

[0175] In some embodiments, the degree of polymerization n of the ester-based polymer is selected from any positive integer from 800 to 20,000.

[0176] Optionally, the degree of polymerization n of the ester-based polymer is selected from positive integers of 1,000 to 15,000.

[0177] In some embodiments, the molecular weight of the ester-based polymer is 1.2×10 5 g / mol to 1.0 × 10 6 g / mol.

[0178] For example, the molecular weight of the ester polymer is 1.2×10 5 g / mol, 2 × 10 5 g / mol, 5 × 10 5 g / mol, 8 × 10 5 g / mol, 1×10 6 g / mol, 1.5 × 10 6 It may be g / mol or a range consisting of any two of the above values.

[0179] [Aldehyde-ketone polymers]

[0180] In some embodiments, the liquid-retaining polymer comprises an aldehyde ketone polymer, and the aldehyde ketone polymer is fabricated into a sheet-like structure, and the sheet-like structure is (T m4 A dynamic frequency sweep test was performed at +20°C to obtain the elastic modulus G'-loss elastic modulus G" curve, and the slope of the elastic modulus G'-loss elastic modulus G" curve was K3, 0.8 <K3<∞であり、 T m4 teeth The melting temperature of the aldehyde ketone polymer is The unit is °C. .

[0181] In some embodiments, 0.8≦K3≦100, and optionally, 0.8≦K3≦10.

[0182] Illustratively, K3 may be 0.8, 0.9, 1, 2, 5, 10, 15, 20, 30, 50, 100, 200, 500, 1000, 5000, 10000, or a range consisting of any two of the above values.

[0183] In some embodiments, the glass transition temperature of the aldehyde ketone polymer is T g4 The unit is °C, and -100≦T g4≦50, and optionally, −80≦T g4 ≦30.

[0184] For example, the glass transition temperature of the aldehyde ketone polymer may be −100° C., −90° C., −80° C., −60° C., −30° C., 0° C., 30° C., 50° C., or a range consisting of any two of the foregoing values.

[0185] In some embodiments, the aldehyde ketone polymer comprises a structural unit shown in formula (DI): [ka]

[0186] In formula (DI), R 41 contains a single bond, a substituted or unsubstituted C1-C6 methylene group, and R 42 contains a hydrogen atom, a substituted or unsubstituted C1-C6 alkyl group,

[0187] Selectively, R 41 includes a single bond, a substituted or unsubstituted C1-C2 methylene group,

[0188] Selectively, R 42 includes a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group.

[0189] In the present embodiment, a single bond means that the group is absent and the atoms on both sides of the group are connected by a single bond, e.g., R 41 is a single bond, R 41 This means that the carbon atoms on both sides of the bond are bonded in the form of a single bond.

[0190] Exemplarily, the aldehyde ketone polymer includes at least one of the structural units represented by formula (DI-1) to formula (DI-6): [ka]

[0191] Illustratively, the aldehyde ketone polymer comprises a structural unit shown in formula (DII): [ka]

[0192] In formula (DII), R 43 ~R 46 each independently comprises a hydrogen atom, a hydroxyl group, a substituted or unsubstituted C1-C3 alkyl group, a substituted or unsubstituted C1-C3 hydroxyalkyl group, or a substituted or unsubstituted C1-C3 alkoxy group; r and s are each independently selected from integers of 0 to 5, and at least one of r and s is selected from a positive integer; and optionally, R 43 ~R 46 each independently comprises a hydrogen atom, a hydroxyl group, a substituted or unsubstituted C1-C3 alkyl group, a substituted or unsubstituted C1-C2 hydroxyalkyl group, or a substituted or unsubstituted C1-C2 alkoxy group.

[0193] In some embodiments, the aldehyde ketone polymer comprises at least one of structural units shown in formula (DII-1) to structural units shown in formula (DII-4): [ka]

[0194] The degree of entanglement of the molecular chains of the aldehyde ketone polymer is small, which is advantageous for improving the flexibility of the molecular chains, and the molecular chains are advantageous for sufficiently spreading in the electrolyte solution and forming a gel-like substance with the electrolyte solution.

[0195] The above polymers are merely examples of structural groups in the main molecular chain, and in the embodiments of the present application, the polymer may be obtained by copolymerizing the above structural groups with other types of structural groups (for example, structural units such as olefin-based structural units, ester-based monomers, nitrile-based monomers, and amide-based monomers).

[0196] When the above groups are substituted, the substituents may include one or more of a nitrile group (-CN), a nitro group, a sulfonic acid group, a sulfonyl group, an amide group, a carboxyl group, an ester group, and a halogen atom (e.g., a chlorine atom, a fluorine atom, a bromine atom). The above substituents are pressure-resistant substituents, which are further advantageous in stabilizing the structure of the polymer.

[0197] In some embodiments, the degree of polymerization, n, of the aldehyde ketone polymer is selected from positive integers of 500 to 15,000.

[0198] Optionally, the degree of polymerization n of the aldehyde ketone polymer is selected from a positive integer of 500 to 10,000.

[0199] In some embodiments, the aldehyde ketone polymer has a molecular weight of 1.2×10 5 g / mol to 1.0 × 10 6 g / mol.

[0200] Illustratively, the molecular weight of the aldehyde ketone polymer is 1.2×10 5 g / mol, 2 × 10 5 g / mol, 5 × 10 5 g / mol, 8 × 10 5 g / mol, 1×10 6 g / mol, 1.0 × 10 6 It may be g / mol or a range consisting of any two of the above values.

[0201] The relevant parameters of the polymers of the present embodiments can be measured using the following methods.

[0202] The polymer groups of the present embodiments can be detected using infrared spectroscopy (IR), specifically, the liquid-holding polymers were measured using a Thermo Nicolet Nexus 670 Attenuated Total Reflectance Fourier Transform Infrared Spectrometer (FTIR-ATR), mark Measurements were performed in accordance with GB / T6040-2002, with the test range as follows: ATR 600-4000 cm -1, Reproducibility: ±2cm -1 , resolution: 4cm -1 Superior penetration depth of 0.2~0.6μm.

[0203] The structure of the polymer of the present embodiment can be detected using nuclear magnetic resonance (NMR), specifically, 1H NMR and 13C NMR were performed on a Varian Mercury Plus-400 nuclear magnetic resonance instrument, the test temperature was 20°C, TMS was used as the internal standard, CDCl3 was used as the solvent, and the proton resonance frequency was 400 MHz.

[0204] The polymer monomer type of the polymer in the embodiment of this application (especially applicable to monomers with a small proportion in the polymer) is measured by a combined decomposition-gas chromatography-mass spectrometry, and the specific measurement steps are as follows: 0.5 mg of sample is accurately weighed and placed in a sample cup, which is then attached to a sample rod and placed in a decomposition device attached near the GC (gas chromatography) sample inlet. After the temperature of the decomposition device reaches the set temperature, the sample injection button is pressed, and the sample cup quickly falls into the core of the decomposition furnace by free fall. In an inert gas N2 atmosphere, the volatile components instantly vaporize and enter the gas chromatography column with the carrier gas for separation. Finally, the sample is detected via a flame ionization detector (FID) or mass spectrometer (MS) to obtain a gas chromatogram or total ion chromatogram.

[0205] The molecular weight of the polymer in the embodiments of the present application has a meaning known in the art and can be measured using devices and methods known in the art, such as gel permeation chromatography (GPC). The specific test steps are as follows: Take an appropriate amount of sample to be measured (the sample concentration should be 8%-12% opaque), add 20 ml of deionized water, and simultaneously ultrasonicate for 5 minutes (53 KHz / 120 W) to ensure complete dispersion of the sample. Then, measure the sample according to GB / T19077-2016 / ISO 13320:2009 standard.

[0206] Alternatively, the SEC-SAMLL data is measured using a multi-angle light scattering detector (MALLS), specifically, a GPC system using a Dawn Heleos II multi-angle light scattering instrument, an Optilab T-rEX refractive index (RI) detector, and a Visco Star II viscometer (Wyatt Technology Corporation, USA). Measurements are performed at 30°C with tetrahydrofuran as the flow phase at a flow rate of 1.0 ml / min, and the molecular weight parameters are obtained by processing the SEC-SAMLL data using the commercially available software ASTRA6.

[0207] In some embodiments, a liquid-retaining polymer is added to a first solvent at 70°C to form a polymer system, the polymer system is allowed to stand at 70°C for 8 hours, and then allowed to stand at 25°C for ≥ 24 hours. After the polymer system is filtered through a 200 mesh filter, a first substance remains, the mass of the liquid-retaining polymer is q in g, the mass of the first substance is m in g, and the liquid-retaining polymer and the first substance satisfy 5 ≤ m / q ≤ 1000.

[0208] The liquid-retaining polymer has excellent liquid absorption and retention properties, and is advantageous in improving the liquid absorption and retention capabilities of the separator.

[0209] In some embodiments, 10≦m / q≦1000, and more optionally, 10≦m / q≦50. Illustratively, m / q can be 5, 10, 20, 25, 28, 30, 32, 35, 40, 50, 80, 100, 200, 500, 1000, or a range consisting of any two of the foregoing values.

[0210] The polymer system is left to stand at 70°C for 8 hours and then at 25°C for at least 24 hours. After undergoing this two-step standing treatment, the polymer system is partially transformed into a gel-state substance through swelling and adsorption. When the polymer system comes into contact with the electrolyte, the polymer molecular chains are fully opened, allowing the electrolyte to diffuse between the molecular chains. The swelling of the polymer molecular chains and adsorption of the electrolyte are beneficial to improving the liquid absorption and retention capabilities of the separator, further improving the cycle performance of the battery cell.

[0211] Illustratively, the ratio of the mass content of the liquid-retaining polymer to the mass content of the first solvent, relative to the mass of the polymer system, ranges from 1:100 to 1:10, for example 3:50.

[0212] For example, the first solvent and the electrolyte solvent may be the same or similar, and the first solvent may include at least one of a carbonate-based solvent and an ether-based solvent, for example, a carbonate-based solvent may include a cyclic carbonate solvent and / or a linear carbonate solvent.

[0213] Taking cyclic carbonate solvents as an example, the cyclic carbonate solvents include one or more of ethylene carbonate (EC), vinylene carbonate (VC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), vinylethylene carbonate (VEC), and dioctyl carbonate (CC).

[0214] Taking linear carbonate solvents as an example, linear carbonate solvents include dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), diphenyl carbonate (DPC), methyl allyl carbonate (MAC) and polycarbonate ( PC )

[0215] Taking the ether-based solvent as an example, the ether-based solvent includes one or more of tetrahydrofuran (THF), 2-methyltetrahydrofuran (2me-thf), 1,3-dioxolane (DOL), dimethoxymethane (DMM), 1,2-dimethoxyethane (DME), and diethylene glycol dimethyl ether (DG).

[0216] Alternatively, the first solvent may simultaneously contain a lithium salt and an electrolyte additive, such as lithium hexafluorophosphate, vinylene carbonate (VC), fluoroethylene carbonate (FEC), and the like.

[0217] In this application, m / q is also referred to as the sedimentation value and characterizes the rate at which a liquid-holding polymer and solvent is converted into a gel-state material.

[0218] The first substance mainly comprises a gel-state substance formed by a liquid-retaining polymer and a first solvent, and in the gel-state substance, the molecular structure of the polymer does not fundamentally change.

[0219] In some embodiments, the first substance is dried at 80°C for 12 hours, the first solvent in the first substance is removed, and the main component of the first substance after drying is the liquid-retaining polymer described above, as detected by infrared spectroscopy (IR) or nuclear magnetic resonance (NMR).

[0220] In the present embodiment, the liquid-retaining polymer molecular chains are expanded by increasing the temperature within the safe operating temperature range of the battery cell, promoting mutual attraction and physical bonding between the polymer molecular chains and the electrolyte. At room temperature, the liquid-retaining polymer molecular chain segments become less active, adhere to the separator, and trap the electrolyte in the spatial environment where the liquid-retaining polymer is located, forming a gel or gel-like state, which increases the transport rate of active ions, such as lithium ions, and improves cycle performance.

[0221] In some embodiments, the separator includes a porous substrate, and the liquid-retaining polymer is distributed within the pores of the porous substrate. The porous substrate is primarily made of a polymer, and the polymer has a network structure, and the liquid-retaining polymer can be dispersed within the network structure, i.e., the liquid-retaining polymer is dispersed throughout the porous substrate.

[0222] In another embodiment, the separator includes a porous substrate and a polymer layer provided on at least one surface of the porous substrate, the polymer layer including a liquid-retaining polymer. The phrase "the polymer layer is provided on at least one surface of the porous substrate" means that the polymer layer may be provided on one surface of the porous substrate or on two surfaces of the porous substrate. The liquid-retaining polymer may be dispersed in a solvent to form a polymer mixture, which is then applied to the porous substrate via a coating process such as spray coating or gravure coating.

[0223] The present embodiment does not particularly limit the material of the porous substrate, and any known porous substrate having good chemical and mechanical stability can be selected. For example, the porous substrate may include at least one of a polyolefin resin film (e.g., at least one of polyethylene, polypropylene, and polyvinylidene fluoride), a porous glass fiber, and a porous nonwoven fabric. The porous substrate may be a single-layer film or a multi-layer composite film. When the porous substrate is a multi-layer composite film, the materials of each layer may be the same or different.

[0224] In some embodiments, the porosity of the porous substrate is 25% or more, preferably 25% to 50%. When the porosity of the porous substrate is in the above range, the porosity of the porous substrate is improved, which is favorable for the migration of active ions, and the relatively small porosity can further improve the mechanical properties of the porous substrate, and the polymer layer can provide good support.

[0225] In some embodiments, the thickness of the porous substrate may be 16 μm or less, and optionally 5 μm to 12 μm. Illustratively, the thickness of the porous substrate may be 1 μm, 2 μm, 3 μm, 5 μm, 10 μm, 12 μm, 15 μm, 16 μm, or a range consisting of any two of the foregoing values.

[0226] Optionally, the polymer layer contains heat-resistant particles. The heat-resistant particles and the liquid-retaining polymer work together to further improve the heat resistance and ion transport performance of the entire separator. The liquid-retaining polymer and the heat-resistant particles can be dispersed in a solvent to form a polymer mixture, which can be applied to the porous substrate via a coating process such as spray coating or gravure coating.

[0227] In some embodiments, the ratio of the mass percent content of the liquid-retaining polymer to the mass percent content of the heat-resistant particles relative to the total mass of the polymer layer is (0.2 to 5.0): 1, and optionally (0.5 to 2.0): 1. When the contents of the heat-resistant particles and the liquid-retaining polymer are within the above ranges, the heat resistance and ion transport performance of the entire separator can be further improved. For example, the ratio of the mass percent content of the liquid-retaining polymer to the mass percent content of the heat-resistant particles may be 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.8:1, 1.0:1, 1.2:1, 1.5:1, 1.8:1, 2.0:1, 2.5:1, 2.8:1, 3.0:1, 3.2:1, 3.5:1, 3.8:1, 4.0:1, 4.2:1, 4.5:1, 4.8:1, 5.0:1, or a range consisting of any two of the above values.

[0228] In some embodiments, the thickness of the polymer layer may be 0.5 μm to 3.0 μm, and optionally 1.0 μm to 2.0 μm. When the thickness of the polymer layer is within this range, the heat resistance and ion transport performance of the entire separator can be further improved. For example, the thickness of the polymer layer may be 0.5 μm, 0.8 μm, 1.0 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2.0 μm, 2.3 μm, 2.5 μm, 2.8 μm, 3.0 μm, or a range consisting of any two of the above values.

[0229] Optionally, the separator may further include a heat-resistant coating layer, the heat-resistant coating layer being located on at least one surface of the porous substrate, and the polymer layer being located on the opposite side of the heat-resistant coating layer from the porous substrate.

[0230] The heat-resistant coating layer may contain heat-resistant particles. In some embodiments, the heat-resistant particles include at least one of inorganic particles and organic particles. By adding heat-resistant particles, the heat-resistant performance of the separator can be improved.

[0231] In some embodiments, the mass percentage content of the inorganic particles in the heat-resistant coating layer ≦ 30. Exemplarily, the mass percentage content of the inorganic particles in the heat-resistant coating layer is 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30% or a range consisting of any two of the above numerical values.

[0232] The inorganic particles include at least one of inorganic particles with a dielectric constant of 5 or more, inorganic particles having the ability to transport active ions, and inorganic particles capable of generating electrochemical oxidation and reduction.

[0233] In some embodiments, the inorganic particles with a dielectric constant of 5 or higher are boehmite (γ-AlOOH), aluminum oxide (Al2O3), barium sulfate (BaSO4), magnesium oxide (MgO), magnesium hydroxide (Mg(OH)2), silicon oxide SiO x (0 < x ≦ 2), tin dioxide (SnO2), titanium oxide (TiO2), calcium oxide (CaO), zinc oxide (ZnO), zirconium oxide (ZrO2), yttrium oxide (Y2O3), nickel oxide (NiO), hafnium oxide (HfO2), cerium oxide (CeO2), zirconium titanate (ZrTiO3), barium titanate (BaTiO3), magnesium titanate (MgF2), Pb(Zr,Ti)O3 (abbreviation PZT), Pb 1-m La m Zr 1-n Ti <​​​​​​In some embodiments, the inorganic particles having the ability to transport active ions may include at least one of lithium phosphate (Li3PO4), lithium titanium phosphate (Li x Ti y (PO4)3, 0 < x < 2, 0 < y < 3), lithium aluminum titanium phosphate (Li x Al y Ti z (PO4)3, 0 < x < 2, 0 < y < 1, 0 < z < 3), (LiAlTiP) x O y -based glass (0 < x < 4, 0 < y < 13), lithium lanthanum titanate (Li x La y TiO3, 0 < x < 2, 0 < y < 3), lithium germanium thiophosphate (Li x Ge y P z S w , 0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), lithium nitride (Li x N y , 0 < x < 4, 0 < y < 2), SiS2-based glass (Li x Si y S z , 0 < x < 3, 0 < y < 2, 0 < z < 4) and P2S5-based glass (Li x P y S z , 0 < x < 3, 0 < y < 3, 0 < z < 7).

[0235] In some embodiments, the inorganic particles capable of generating electrochemical oxidation and reduction may include at least one of lithium-containing transition metal oxides, olivine-structured lithium-containing phosphates, carbon-based materials, silicon-based materials, tin-based materials, and lithium titanium compounds.

[0236] In some embodiments, the heat-resistant coating layer may further include other organic particles, for example, the organic particles may include at least one of polystyrene, polyethylene, polyimide, melamine resin, phenolic resin, polypropylene, polyester (e.g., polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate), polyphenylene sulfide, polyaramid, polyamideimide, polyimide, copolymer of butyl acrylate and ethyl methacrylate, and mixtures thereof.

[0237] In some embodiments, the heat-resistant coating layer may further include a binder. For example, the binder may include at least one of a water-soluble acrylic resin (e.g., a homopolymer of acrylic acid, methacrylic acid, or sodium acrylate monomer or a copolymer with other comonomers), polyvinyl alcohol (PVA), an isobutylene-maleic anhydride copolymer, and a polyacrylamide.

[0238] In some embodiments, the thickness of the heat-resistant coating layer is ≦4 μm, which is advantageous for improving the energy density of the battery cell. In the embodiments of the present application, the thickness of the heat-resistant coating layer refers to the thickness of the heat-resistant coating layer located on one side of the substrate. For example, the thickness of the heat-resistant coating layer may be 0.1 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, or a range consisting of any two of the above values.

[0239] In some embodiments, the coating weight of the liquid-retaining polymer is 0.5 mg / 1540.25 mm 2 From 5mg / 1540.25mm 2 is.

[0240] When the coating basis weight is within the above range, the liquid retention capacity of the separator can be further improved.

[0241] Optionally, the coating weight of the polymer layer is 0.5 mg / 1540.25 mm2 From 3.5mg / 1540.25mm 2 may be.

[0242] Exemplarily, the coating weight of the polymer layer is 0.5 mg / 1540.25 mm 2 , 0.6mg / 1540.25mm 2 , 0.8mg / 1540.25mm 2 , 1.0mg / 1540.25mm 2 , 1.2mg / 1540.25mm 2 , 1.5mg / 1540.25mm 2 , 1.8mg / 1540.25mm 2 , 2.0mg / 1540.25mm 2 , 2.5mg / 1540.25mm 2 , 3mg / 1540.25mm 2 , 3.5mg / 1540.25mm 2 , 4mg / 1540.25mm 2 , 4.5mg / 1540.25mm 2 , 5mg / 1540.25mm 2 Alternatively, it may be a range consisting of any two of the above values.

[0243] In the embodiment of the present application, the coating weight refers to the coating weight of the liquid-retaining polymer on one side of the separator, and can be measured using an apparatus and method known in the art. For example, when the same master roll substrate and separator are coated on a 1540.25 mm 2 The weight of each of the 10 small circular separator sheets is measured, and the basis weight of the highly liquid absorbent polymer applied to the separator can be calculated.

[0244] Battery cell

[0245] According to a second aspect, an embodiment of the present application provides a battery cell including an electrode assembly and an electrolyte, the electrode assembly including a positive electrode sheet, a negative electrode sheet, and a separator, the separator being disposed between the positive electrode sheet and the negative electrode sheet, and the separator including any of the separators according to the first aspect of the present application.

[0246] [Positive electrode sheet]

[0247] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector.

[0248] As an example, the positive electrode current collector has two surfaces that face each other in the thickness direction of the positive electrode current collector, and the positive electrode active material layer is provided on either one or both of the two facing surfaces of the positive electrode current collector.

[0249] The positive electrode active material layer includes a positive electrode active material, and the positive electrode active material may be any positive electrode active material for battery cells known in the art. For example, the positive electrode active material may include at least one of a lithium-containing phosphate compound, a lithium-containing transition metal oxide, a sodium-containing phosphate compound, and a sodium-containing transition metal oxide material.

[0250] For example, the general formula of an olivine-type phosphate active material (lithium-containing phosphate compound) is Li x A y Me a M b P 1-c X c Y z where 0≦x≦1.3, 0≦y≦1.3, and 0.9≦x+y≦1.3. 0.9≦a≦1.5, 0≦b≦0.5, and 0.9≦a+b≦1.5. 0≦c≦0.5, 3≦z≦5. A includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of S, Si, Cl, B, C, and N; and Y includes one or more of O and F. Specifically, the olivine-type phosphate active material includes one or more of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4.

[0251] Exemplary examples include lithium transition metal oxides (layered materials such as ternary, lithium / sodium nickelate, lithium / sodium cobaltate, lithium / sodium manganate, lithium-rich layered, and rock salt phase layered materials). The general formula for layered cathode active materials is Li x A y Ni a Co b Mn c M (1-a-b-c) Y z where 0≦x≦2.1, 0≦y≦2.1, and 0.9≦x+y≦2.1. 0≦a≦1, 0≦b≦1, 0≦c≦1, and 0.1≦a+b+c≦1, and 1.8≦z≦3.5. A includes one or more of Na, K, and Mg; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; and Y includes one or more of O and F. Optionally, y=0. Specifically, the layered structure positive electrode active material is lithium cobalt oxide (LCO), lithium nickel oxide (LNO), lithium manganese oxide (LMO), 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 One or more of O2 (NCM811) and NCA may be included.

[0252] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. The metal foil may be, for example, an aluminum foil or an aluminum alloy foil. The composite current collector may include a polymer substrate layer and a metal material layer formed on at least one surface of the polymer substrate layer. For example, the metal material may include one or more combinations selected from aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. The polymer substrate layer may include one or more combinations selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0253] In some embodiments, the positive electrode active material layer may optionally further include a positive electrode conductive agent. The present embodiment does not particularly limit the type of positive electrode conductive agent. For example, the positive electrode conductive agent may include one or more combinations selected from superconducting carbon, conductive carbon black, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage of the positive electrode conductive agent is 5% or less with respect to the total mass of the positive electrode active material layer.

[0254] In some embodiments, the positive electrode active material layer may optionally further include a positive electrode binder. The present embodiment does not particularly limit the type of positive electrode binder. For example, the positive electrode binder may include one or more combinations selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene ternary copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene ternary copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylic resin. In some embodiments, the weight percentage of the positive electrode binder is 5% or less, based on the total weight of the positive electrode active material layer. The positive electrode binder has a higher crystallinity than the fluoropolymer of the present embodiment. The positive electrode binder has a higher melting temperature than the fluoropolymer of the present embodiment.

[0255] The positive electrode active material layer is typically formed by applying a positive electrode paste to a positive electrode current collector, drying it, and cold pressing it. The positive electrode paste is typically formed by dispersing the positive electrode active material, optionally a conductive agent, optionally a binder, and any other components in a solvent and stirring the mixture uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP). The production of the positive electrode sheet is not limited to the above method, and the production methods described above may also be used.

[0256] [Negative electrode sheet]

[0257] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector and including a negative electrode active material.

[0258] For example, the negative electrode current collector has two surfaces that face each other in the thickness direction thereof, and the negative electrode active material layer is provided on one or both of the two facing surfaces of the negative electrode current collector.

[0259] The negative electrode active material can be any negative electrode active material for battery cells known in the art. Examples of the negative electrode active material include, but are not limited to, at least one of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material can include at least one of silicon elemental, silicon oxide, silicon carbon composite, silicon nitrogen composite, and silicon alloy material. The tin-based material can include at least one of tin elemental, tin oxide, and tin alloy material.

[0260] In some embodiments, the negative electrode active material layer may further include a negative electrode conductive agent. The present embodiment does not particularly limit the type of the negative electrode conductive agent. For example, the negative electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage of the negative electrode conductive agent relative to the total mass of the negative electrode active material layer is ≦5%.

[0261] In some embodiments, the negative electrode active material layer may optionally further include a negative electrode binder. The present embodiment does not particularly limit the type of the negative electrode binder. For example, the negative electrode binder may include at least one of styrene butadiene rubber (SBR), water-soluble unsaturated resin (SR-1B), water-based acrylic resin (e.g., polyacrylic acid (PAA), polymethacrylic acid (PMAA), sodium polyacrylate (PAAS)), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). In some embodiments, the weight percent of the negative electrode binder is ≦5% relative to the total weight of the negative electrode active material layer.

[0262] In some embodiments, the negative electrode active material layer may optionally further include other additives. For example, the other additives may include a thickener, such as sodium carboxymethyl cellulose (CMC), a PTC thermistor material, etc. In some embodiments, the weight percentage of the other additives relative to the total weight of the negative electrode active material layer is ≦2%.

[0263] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, the metal foil may be copper foil. The composite current collector may include a polymer substrate layer and a metal material layer formed on at least one surface of the polymer substrate layer. For example, the metal material may include at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. For example, the polymer substrate layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0264] The negative electrode active material layer is typically formed by applying a negative electrode paste to a negative electrode current collector, drying, and cold pressing. The negative electrode paste is typically formed by dispersing the negative electrode active material, optionally a conductive agent, optionally a binder, and other optional additives in a solvent and stirring the mixture uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water. The manufacturing method of the negative electrode sheet is not limited to the above method, and the manufacturing method described above may also be used.

[0265] The negative electrode sheet does not exclude additional functional layers other than the negative electrode active material layer. For example, in some embodiments, the negative electrode sheet described herein 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 active material layer and provided on the surface of the negative electrode current collector. In some other embodiments, the negative electrode sheet described herein further includes a protective layer covering the surface of the negative electrode active material layer.

[0266] [Electrolytes]

[0267] During the charge and discharge process of the battery cell, active ions are inserted and removed between the positive electrode sheet and the negative electrode sheet, and the electrolyte serves to conduct the active ions between the positive electrode sheet and the negative electrode sheet. The present application does not particularly limit the type of electrolyte, and it can be selected according to actual needs.

[0268] The electrolyte solution includes an electrolyte salt and a solvent, and the types of the electrolyte salt and the solvent are not specifically limited and can be selected according to actual needs.

[0269] When the battery cell of the present application is a lithium-ion battery, for example, the electrolyte salt may include at least one of lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium perchlorate (LiClO), lithium hexafluoroarsenate (LiAsF), lithium bisfluorosulfonylimide (LiFSI), lithium bistrifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium bisoxalatoborate (LiBOB), lithium difluorophosphate (LiPOF), lithium difluorobisoxalatophosphate (LiDFOP), and lithium tetrafluorooxalatophosphate (LiTFOP), but is not limited thereto.

[0270] When the battery cell of the present application is a sodium-ion battery, for example, the electrolyte salt may include at least one of sodium hexafluorophosphate (NaPF), sodium tetrafluoroborate (NaBF), sodium perchlorate (NaClO), sodium hexafluoroarsenate (NaAsF), sodium bisfluorosulfonylimide (NaFSI), sodium bistrifluoromethanesulfonylimide (NaTFSI), sodium trifluoromethanesulfonate (NaTFS), sodium difluorooxalatoborate (NaDFOB), sodium bisoxalatoborate (NaBOB), sodium difluorophosphate (NaPOF), sodium difluorobisoxalatophosphate (NaDFOP), and sodium tetrafluorooxalatophosphate (NaTFOP), but is not limited thereto.

[0271] Examples of the solvent include 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), methylsulfonylmethane (MSM), ethyl methanesulfonate (EMS), diethylsulfone (ESE), tetrahydrofuran THF, 2-methyltetrahydrofuran 2me-thf, 1,3-dioxolane DOL, dimethoxymethane DMM, 1,2-dimethoxyethane DME, and diethylene glycol dimethyl ether DG.

[0272] In some embodiments, the electrolyte solution optionally further contains additives. For example, the additives may include a negative electrode film-forming additive, a positive electrode film-forming additive, and additives that can improve specific battery performance, such as an additive that improves the overcharge characteristics of the battery, an additive that improves the high-temperature characteristics of the battery, or an additive that improves the low-temperature power output characteristics of the battery.

[0273] In some embodiments, an electrode assembly can be manufactured from the positive electrode sheet, the separator, and the negative electrode sheet through a winding process and / or a stacking process.

[0274] In some embodiments, the battery cell may include a housing material that is used to encapsulate the electrode assembly and the electrolyte.

[0275] In some embodiments, the battery cell exterior may be a hard case such as a hard plastic case, an aluminum case, or a steel case. The battery cell exterior may be a soft pack such as a pouch-type soft pack. The soft pack may be made of plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0276] In some embodiments, the positive electrode sheet, separator, and negative electrode sheet can be fabricated into an electrode assembly via a winding or lamination process.

[0277] The present application does not particularly limit the shape of the battery cell, and it may be cylindrical, rectangular, or any other shape. Figure 1 shows a battery cell 5 with a rectangular structure as an example.

[0278] In some embodiments, as shown in FIGS. 1 and 2 , the exterior material may include a housing 51 and a cover plate 53. The housing 51 may include a bottom plate and side plates connected to the bottom plate, forming a storage cavity surrounded by the bottom plate and side plates. The housing 51 has an opening communicating with the storage cavity, and the cover plate 53 is used to cover the opening and seal the storage cavity. The positive electrode sheet, the negative electrode sheet, and the separator may form an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is sealed in the storage cavity. An electrolyte is impregnated in the electrode assembly 52. ​​The number of electrode assemblies 52 included in the battery cell 5 may be one or more and can be adjusted as needed.

[0279] The manufacturing method of the battery cell of the present application is well known. In some embodiments, a battery cell can be formed by assembling a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte. For example, an electrode assembly can be formed from the positive electrode sheet, the separator, and the negative electrode sheet through a winding process or a stacking process. The electrode assembly can then be placed in a housing, dried, and then injected with an electrolyte. The battery cell can then be obtained through processes such as vacuum sealing, standing, chemical conversion, and shaping.

[0280] In some embodiments of the present application, the battery cells of the present application can be assembled into a battery module, and the battery module may include multiple battery cells, the specific number of which can be adjusted according to the application and capacity of the battery module.

[0281] FIG. 3 is a schematic diagram of an example battery module 4. As shown in FIG. 3, in the battery module 4, a plurality of battery cells 5 can be arranged in sequence along the length of the battery module 4. Of course, any other arrangement may also be used. The plurality of battery cells 5 can also be fastened together using fasteners.

[0282] Optionally, the battery module 4 may further include an outer case having an accommodating space for accommodating the plurality of battery cells 5.

[0283] In some embodiments, the battery modules can be further assembled into a battery pack, and the number of battery modules included in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0284] The battery module 4 and the battery pack can both be specific examples of the battery in the embodiments of the present application.

[0285] 4 and 5 are schematic diagrams of an example battery pack 1. As shown in FIGS. 4 and 5, the battery pack 1 may include a battery case and a plurality of battery modules 4 installed in the battery case. The battery case includes an upper housing 2 and a lower housing 3, and the upper housing 2 is used to cover the lower housing 3 and forms a sealed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery case in any manner.

[0286] power consumption equipment

[0287] According to a third aspect, the present application provides a power consuming device including at least one of a battery cell, a battery module, and a battery pack according to the present application. The battery cell, the battery module, and the battery pack may be used as a power source for the power consuming device or as an energy storage element for the power consuming device. The power consuming device may be, but is not limited to, a mobile device (e.g., a mobile phone, a laptop, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), a train, a ship, a satellite, an energy storage system, etc.

[0288] A power consuming device can be configured as a battery cell, a battery module, or a battery pack depending on its usage conditions. FIG. 6 is a schematic diagram of an example power consuming device. The power consuming device 6 may be 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 the power consuming device, a battery pack 1 or a battery module may be used. Another example power consuming device may be a mobile phone, a tablet computer, a laptop computer, etc. The power consuming device is generally required to be lightweight and thin, and can use a battery cell as a power source.

[0289] Example

[0290] Examples of the present application are described below. The examples described below are illustrative and are intended only to explain the present application and should not be understood as limitations on the present application. If specific techniques or conditions are not specified in the examples, they will be carried out according to techniques or conditions described in literature in the field or according to product specifications. If the manufacturer of the reagents or equipment used is not specified, they are all commercially available general products.

[0291] Example 1: Manufacture of a lithium-ion battery

[0292] (1) Manufacturing of positive electrode sheet:

[0293] The positive electrode current collector is an aluminum foil with a thickness of 12 μm.

[0294] Positive electrode active material LiNi 0.6 Co 0.2 Mn 0.2The positive electrode paste is prepared by thoroughly mixing O2 (NCM622), conductive carbon black, and polyvinylidene fluoride (PVDF) binder in an appropriate amount of N-methylpyrrolidone (NMP). The mass ratio of NCM622, conductive carbon black, and PVDF in the positive electrode paste is 97.5:1.4:1.1. The positive electrode paste is applied to an aluminum foil current collector, vacuum dried at 100°C, cold pressed, trimmed, cut, and slit, and then vacuum dried at 85°C for 4 hours to produce a positive electrode sheet.

[0295] (2) Manufacturing of negative electrode sheet:

[0296] A copper foil with a thickness of 8 μm is used as the negative electrode current collector.

[0297] The negative electrode paste is prepared by uniformly mixing the negative electrode active material (artificial graphite), conductive agent (carbon black), binder (styrene butadiene rubber (SBR)), and thickener (sodium carboxymethyl cellulose (CMC)) in a weight ratio of 97.4:2:0.5:0.1, followed by the addition of deionized water. The negative electrode paste is applied to a copper foil current collector and dried at 85°C. After that, the copper foil is cold pressed, trimmed, cut, and slit, and then dried under vacuum at 120°C for 12 hours to produce a negative electrode sheet.

[0298] (3) Electrolyte production:

[0299] In an environment with a water content of less than 10 ppm, the nonaqueous organic solvents ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate are mixed in a volume ratio of 1:1:1 to obtain an electrolyte solvent, which is then mixed with lithium salt LiPF6 to prepare an electrolyte with a lithium salt concentration of 1 mol / L.

[0300] (4) Separator manufacturing

[0301] The base material is a 7 μm polyethylene film (PE).

[0302] The liquid-retaining polymer was dispersed in a solvent, dimethyl carbonate (DMC), to form a mixture, which was then spray-coated onto two surfaces of a polyethylene film to form a polymer layer. Water was used as the spray solvent, and the mass content of the mixture was 1%.

[0303] (5) Lithium-ion battery manufacturing:

[0304] The positive electrode sheet, separator, and negative electrode sheet are stacked in this order (the separator serves to separate the positive and negative electrode sheets), and then wound to obtain an electrode assembly. The electrode assembly is placed in a housing, dried, and then an electrolyte is injected. After vacuum sealing, standing, chemical formation, shaping, and other processes, a lithium-ion battery is obtained.

[0305] Comparative Example 1

[0306] A lithium ion battery was produced in the same manner as in Example 1, except that the separator in Comparative Example 1 was a polyethylene film (PE) of 7 μm.

[0307] Comparative Example 2

[0308] A lithium ion battery was produced in the same manner as in Example 1, except that the material of the liquid-retaining polymer of the separator in Comparative Example 2 was changed from that in Example 1.

[0309] Examples 1-2 to 1-6

[0310] Lithium ion batteries were produced in the same manner as in Example 1, except that the coating weight of the liquid-retaining polymer in the polymer layer of the separator in Examples 1-2 to 1-6 was adjusted.

[0311] Examples 2-1 to 2-3

[0312] Lithium ion batteries were produced in the same manner as in Example 1, except that the type of liquid-retaining polymer in the polymer layer of the separator in Examples 2-1 to 2-3 was adjusted.

[0313] Example 3-1

[0314] The lithium ion battery was manufactured in the same manner as in Example 1. The difference between Example 3-1 and Example 1 is that the installation position of the polymer layer in the separator was adjusted. Specifically, the separator manufacturing steps included the following:

[0315] A 7 μm polyethylene film (PE) is used as the separator substrate.

[0316] Silicon oxide particles and aqueous polyacrylic acid as a binder are mixed uniformly in a mass ratio of 20:80 in an appropriate amount of deionized water as a solvent to obtain a coating paste.

[0317] The prepared coating paste is applied to two surfaces of the PE substrate using a coating device to form a heat-resistant coating layer.

[0318] The liquid-retaining polymer and the binder are dispersed in a solvent, dimethyl carbonate (DMC), to form a mixture system, which is then spray-coated on the surface of the heat-resistant coating layer to form a polymer layer, thereby obtaining a separator.

[0319] Examples 3-2 to 3-5

[0320] A lithium ion battery was manufactured in the same manner as in Example 1. The difference from Example 1 is that 3 Examples 3-5 to 4-2 describe the manufacturing method of the separator. Specifically, the manufacturing steps of the separator include:

[0321] A 7 μm polyethylene film (PE) is used as the separator substrate.

[0322] The liquid-retaining polymer, silicon oxide particles, and aqueous polyacrylic acid as a binder are mixed uniformly in a mass ratio of 80:20 in an appropriate amount of deionized water as a solvent to obtain a coating paste.

[0323] The prepared coating paste is applied to two surfaces of the PE substrate using a coating device to form a heat-resistant coating layer.

[0324] The liquid-retaining polymer and the binder are dispersed in a solvent, dimethyl carbonate (DMC), to form a mixture system, which is then spray-coated on the surface of the heat-resistant coating layer to form a polymer layer, thereby obtaining a separator.

[0325] In Example 3-2, the mass ratio of the liquid-retaining polymer to the silicon oxide particles is 1.5:1.

[0326] In Example 3-3, the mass ratio of the liquid-retaining polymer to the silicon oxide particles is 0.5:1.

[0327] In Example 3-4, the mass ratio of the liquid-retaining polymer to the silicon oxide particles is 2:1.

[0328] In Examples 3-5, the mass ratio of the liquid-retaining polymer to the silicon oxide particles is 0.2:1.

[0329] The data for the examples and comparative examples are shown in Table 1.

[0330] Exam section

[0331] 1. High-rate cycling characteristics of lithium-ion batteries

[0332] A lithium-ion battery is charged at 25°C with a constant current of 4 C to 4.25 V, then charged at a constant voltage of 4.25 V to a current of 0.05 C, and then discharged at a constant current of 1 C to 2.8 V. This constitutes one charge-discharge cycle. The initial discharge capacity is taken as 100%, and the number of battery cycles is calculated under the condition that the battery capacity decays by 80%.

[0333] 2. Separator parameter testing

[0334] The mass M of the separator is tested as follows: 2 Ten separators of this type are obtained and weighed on an electronic balance, and the weight of the separator at this time is defined as M.

[0335] The test for m1 is as follows: The cut area is 1540.25 mm 2 Ten separators are placed in 10 mL of an electrolyte containing 1 M LiPF6, EC, EMC and DMC in a volume ratio of 1:1:1 for 2 hours, then removed and suspended for 2 minutes, and weighed on an electronic balance to obtain m1.

[0336] The liquid retention rate is calculated as (m1-M) / M x 100%.

[0337] The m2 test is as follows: Place the separator immersed in the electrolyte in a pressure device, apply a pressure of 10,000 N, hold the pressure for 5 minutes, remove it and weigh it on an electronic balance, and the result is m2.

[0338] The liquid retention rate after pressure application is calculated as (m2-M) / M x 100%.

[0339] The liquid retention capacity is

number

[0340] Test results

[0341] The test results are shown in Tables 1 and 2.

[0342] [Table 1-1] [Table 1-2]

[0343] In Table 1, 80% VDF means that the mole percent content of vinylidene fluoride (VDF) is 80% relative to the total molar amount of vinylidene fluoride (VDF), hexafluoropropylene (HFP), and tetrafluoroethylene (TFE).

[0344] [Table 2]

[0345] Compared with Comparative Example 1, in the Example of the present application, the polymer of the embodiment of the present application was added to the separator, and the cycle characteristics of the lithium ion battery were improved.

[0346] In Comparative Example 2, a polymer is added to the separator, but the polymer has low liquid retention and absorption capabilities, and the cycle characteristics of the lithium ion battery cannot be effectively improved.

[0347] Compared to Comparative Example 1, the examples of the present application have a polymer layer on the surface of the separator, and the introduction of the polymer can improve the liquid absorption rate and liquid retention capacity of the separator, further improving the cycle characteristics of the battery cell.

[0348] Although the present application has been described with reference to preferred embodiments, various modifications may be made and equivalents may be substituted for the components thereof without departing from the scope of the present application. In particular, as long as there is no structural contradiction, the technical features recited in each embodiment may be combined in any manner. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A separator comprising a liquid-retaining polymer, the separator comprising: [Equation 1] Fulfilling M represents the mass of the separator without absorbing the electrolyte, and is expressed in g. m １ indicates the mass of the separator weighed under ambient pressure after being wetted with the electrolyte for 2 hours, in g; m ２ indicates the mass of the separator weighed under a pressure of 10,000 N at ambient pressure after the separator has been wetted with the electrolyte for 2 hours, and the unit is g.

2. The separator is [Equation 2] The separator according to claim 1 , wherein

3. The separator is [Equation 3] The separator according to claim 1 or 2, which satisfies the following:

4. The separator is [Equation 4] The separator according to any one of claims 1 to 3, which satisfies the following:

5. the liquid-retaining polymer comprises a fluoropolymer; Alternatively, the crystallinity of the fluoropolymer as measured by differential scanning calorimetry is Xc １ and 0<Xc １ ≦30%; The melting temperature of the fluoropolymer is T ｍ１ and the unit is ° C., and 0<T ｍ１ ≦140, More preferably, the glass transition temperature of the fluoropolymer is T ｇ１ The unit is °C, and −150≦T ｇ１ ≦60, More preferably, the fluoropolymer comprises at least one of the structural units shown in formula (AI) to the structural unit shown in formula (AIII): 【Chemistry 1】 In formula (AI) and formula (AII), R １１ , R １２ , R １３ and R １４ each independently comprises a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, a substituted or unsubstituted C1-C3 alkyl group, or a substituted or unsubstituted C1-C3 alkoxy group, and R １１ , R １２ , R １３ and R １４ at least one of which contains a fluorine atom; 【Chemistry 2】 In formula (AIII), R １５ comprises a single bond or a substituted or unsubstituted C1-C3 alkyl group, p is selected from positive integers of 1 to 3, and n is selected from positive integers of 1,000 to 30,000.

6. the liquid-retaining polymer comprises an ether-based polymer, Optionally, the ether-based polymer is formed into a sheet-like structure, and the sheet-like structure is (T ｍ２ A dynamic frequency sweep test was performed at 20°C to obtain a modulus of elasticity G'-loss modulus of elasticity G" curve, and the slope of the modulus of elasticity G'-loss modulus of elasticity G" curve was K １ and 1<K １ <∞, and T ｍ２ ° C. represents the melting temperature of the ether-based polymer, Further optionally, the ether-based polymer comprises at least one of a structural unit represented by formula (BI) and a structural unit represented by formula (BII), 【Transformation 3】 In formula (BI), R ２１ and R ２２ each independently comprises a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group, or a substituted or unsubstituted C1-C3 alkoxy group; R ２３ comprises a substituted or unsubstituted C1-C5 alkylene group; 【Chemistry 4】 In formula (BII), R ２４ ~R ２７ each independently comprises a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group, a substituted or unsubstituted C1-C3 alkoxy group, or an ether group, and R ２４ ~R ２７ The battery cell according to any one of claims 1 to 5, wherein at least one of comprises a substituted or unsubstituted C1-C3 alkoxy group or ether group.

7. the liquid-retaining polymer includes the ester-based polymer, Optionally, the ester-based polymer is formed into a sheet-like structure, and the sheet-like structure is (T ｍ３ A dynamic frequency sweep test was performed at 20°C to obtain a modulus of elasticity G'-loss modulus of elasticity G" curve, and the slope of the modulus of elasticity G'-loss modulus of elasticity G" curve was K ２ and 1<K ２ <∞, and T ｍ３ °C represents the melting temperature of the ester polymer, and optionally 1 < K ２ ≦100, and further optionally, 1<K ２ ≦10, Further optionally, the ester-based polymer comprises at least one of a structural unit represented by formula (CI) and a structural unit represented by formula (CII): 【Transformation 5】 In formula (CI), R ３１ , R ３２ and R ３３ each independently comprises a hydrogen atom or a substituted or unsubstituted C1-C8 alkyl group; R ３４ comprises a substituted or unsubstituted C1-C8 alkyl group or a substituted or unsubstituted C1-C8 hydroxyalkyl group; 【Transformation 6】 In formula (CII), R ３５ comprises a substituted or unsubstituted C2-C6 methylene group, and optionally R ３５ each independently comprises a substituted or unsubstituted C2-C4 methylene group.

8. the liquid-retaining polymer comprises an aldehyde ketone polymer; Optionally, the aldehyde ketone polymer is formed into a sheet-like structure, and the sheet-like structure is (T ｍ４ A dynamic frequency sweep test was performed at 20°C to obtain a modulus of elasticity G'-loss modulus of elasticity G" curve, and the slope of the modulus of elasticity G'-loss modulus of elasticity G" curve was K ３ and 0.8≦K ３ <∞, and T ｍ４ °C denotes the melting temperature of the aldehyde ketone polymer, optionally 0.8 < K ３ ≦100, and more optionally, 0.8<K ３ ≦10, Further optionally, the aldehyde ketone polymer comprises at least one of a structural unit shown in formula (DI) and a structural unit shown in formula (DII): 【Transformation 7】 In formula (DI), R ４１ contains a single bond, a substituted or unsubstituted C1-C6 methylene group, and R ４２ contains a hydrogen atom, a substituted or unsubstituted C1-C6 alkyl group, 【Transformation 8】 In formula (DII), R ４３ ~R ４６ each independently comprise a hydrogen atom, a hydroxyl group, a substituted or unsubstituted C1-C3 alkyl group, a substituted or unsubstituted C1-C3 hydroxyalkyl group, or a substituted or unsubstituted C1-C3 alkoxy group; r and s are each independently selected from integers of 0 to 5, and at least one of r and s is selected from a positive integer.

9. The separator according to any one of claims 1 to 8, wherein the separator includes a porous substrate, and the liquid-retaining polymer is distributed within pores of the porous substrate.

10. The separator according to any one of claims 1 to 9, wherein the separator comprises a porous substrate and a polymer layer provided on at least one surface of the porous substrate, the polymer layer comprising the liquid-retaining polymer.

11. The coating weight of the liquid-retaining polymer was 0.5 mg / 1540.25 mm ２ From 5 mg / 1540.25 mm ２ The separator according to any one of claims 1 to 10,

12. A battery cell comprising the separator according to any one of claims 1 to 11.

13. A battery comprising the battery cell of claim 12.

14. 14. A power consuming device comprising the battery of claim 13.

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