Battery cells, batteries and power consuming devices

Abstract

The present application provides a battery cell, a battery, and a power consumption device, the battery cell including an electrode assembly, the electrode assembly including an electrode sheet and a separator. The electrode sheet includes a current collector and a film layer disposed on at least one surface of the current collector, the film layer containing an active material and a liquid-absorbing polymer. The electrode sheet satisfies v / λ≧1.2, where v represents the liquid absorption rate of the film layer in mg / s, and λ represents the porosity of the film layer. The separator includes a liquid-retaining polymer, and the separator satisfies (m2-M) / (m1-M)≧25%, where M represents the mass of the separator without absorbing electrolyte in g, m1 represents the mass of the separator weighed under ambient pressure after 2 hours of immersion in electrolyte, also in g, and m2 represents the mass of the separator weighed under a pressure of 10,000 N at ambient pressure after 2 hours of immersion in electrolyte, also in g.

Description

[Technical Field]

[0001] This application relates to the field of batteries, and more particularly to 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 battery cell, a battery, and a power consuming device.

[0005] According to a first aspect of the present application, there is provided a battery cell including an electrode assembly, the electrode assembly including an electrode sheet and a separator, the electrode sheet including a current collector and a film layer provided on at least one surface of the current collector, the film layer containing an active material and a liquid-absorbing polymer, the electrode sheet satisfying v / λ≧1.2, where v represents a liquid absorption rate of the film layer, expressed in mg / s, and λ represents a porosity of the film layer, the separator including a liquid-retaining polymer, and the separator is

number

[0006] The electrode sheets of the battery cell of this embodiment are provided with a liquid-absorbing polymer, which helps the electrode sheets absorb the electrolyte, allowing the electrolyte to wet the electrode sheets more evenly and thoroughly, improving the stability of the battery cell during cycling.The separator of the battery cell is provided with a liquid-retaining polymer, which has a high liquid-retaining capacity and makes it difficult for the electrolyte to be extruded during charging and discharging cycles of the battery cell, reducing liquid shortage situations during charging and discharging cycles, lowering battery polarization, and improving the cycle characteristics of the battery cell.

[0007] In some embodiments, the active material comprises a positive electrode active material, and the electrode sheet satisfies 1.2≦v / λ≦4.50. When the electrode sheet satisfies this range, its liquid absorption rate is fast, which can improve the rate of electrolyte absorption and thereby improve the cycle characteristics of the battery cell.

[0008] In some embodiments, the active material comprises a negative electrode active material, and the electrode sheet satisfies 3≦v / λ<50.00. When the electrode sheet satisfies this range, its liquid absorption rate is fast, which can improve the rate of electrolyte absorption and thereby improve the cycle characteristics of the battery cell.

[0009] In some embodiments, the separator comprises:

number

[0010] 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 charge / discharge cycle process can be further reduced, the polarization of the battery can be reduced, and the cycle characteristics of the battery cell can be improved.

[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 charge / discharge cycle 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 present embodiment satisfies the above conditions, the electrolyte retention capacity can be further improved, the electrolyte shortage situation during the charge / discharge cycle 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 further comprises a liquid-absorbing polymer, and optionally, when the mass per unit volume of the liquid-absorbing polymer located in the electrode sheet is A1 and the mass per unit volume of the liquid-absorbing polymer located in the separator is A2, 1.0≦A1 / A2≦1.6, and optionally 1.2≦A1 / A2≦1.5.

[0016] In some embodiments, the electrode sheet further comprises a liquid-retaining polymer, and optionally, when the mass per unit volume of the liquid-retaining polymer located in the electrode sheet is B1 and the mass per unit volume of the liquid-retaining polymer located in the separator is B2, 0.4≦B1 / B2≦0.9, and optionally 0.5≦B1 / B2≦0.8.

[0017] In some embodiments, when the mass per unit volume of the liquid-absorbing polymer located in the electrode sheet is C1 and the mass per unit volume of the liquid-retaining polymer located in the separator is C2, 0.1≦C1 / C2≦5.

[0018] In some embodiments, the liquid-retaining polymer comprises an ether-based polymer.

[0019] Optionally, the ether-based polymer comprises a structural unit represented by formula (BI) and / or a structural unit represented by formula (BII).

Chemical formula

[0020] , 24 , , 24 , , , , 27 , 27 , ,

[0021] , and R 22 each independently comprise a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group or a substituted or unsubstituted C1-C3 alkoxy group, and R 23 comprises a substituted or unsubstituted C1-C5 alkylene group.

Chemical formula

[0020] In some embodiments, the liquid-retaining polymer comprises an ester-based polymer.

[0021] Optionally, the ester-based polymer is made into a sheet-like structure, and the sheet-like structure is subjected to a dynamic frequency sweep test 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 < ∞, and T m3 °C represents the melting temperature of the ester-based polymer. Optionally, 1 < K2 ≤ 100, and further optionally, 1 < K2 ≤ 10.

[0022] In some embodiments, the ester polymer includes a structural unit represented by formula (CI) and / or a structural unit represented by formula (CII), [Chemical formula] In formula (CI), R 31 , R 32 and R 33 each independently include 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] In formula (CII), R 35 includes a substituted or unsubstituted C2-C6 methylene group, and optionally, R 35 each independently includes a substituted or unsubstituted C2-C4 methylene group.

[0023] In some embodiments, the liquid retention polymer includes a fluoropolymer.

[0024] 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 , with the unit in °C, and 0 < T m1 ≤ 140.

[0025] In some embodiments, the glass transition temperature of the fluoropolymer is T g1 , with the unit in °C, and -150 ≤ T g1 ≤ 60.

[0026] In some embodiments, the fluoropolymer includes at least one of the structural units represented by formula (AI) to formula (AIII). [Chemical formula] In Formula (AI) and Formula (AII), R 11 , R 12 , R 13 and R 14 each independently contains 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,

Chemical Formula

[0027] In some embodiments, the liquid holding polymer further contains an ether-based polymer, the ether-based polymer is made 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, the slope of the storage modulus G’ - loss modulus G” curve is K1, 1 < K1 < ∞, T m2 °C represents the melting temperature of the ether-based polymer, optionally, 1 < K1 ≤ 100, and further optionally, 1 < K1 ≤ 10.

[0028] In some embodiments, the liquid holding polymer contains an aldehyde ketone polymer.

[0029] Optionally, the aldehyde ketone polymer is made 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, the slope of the storage modulus G’ - loss modulus G” curve is K3, 0.8 ≤ K3 < ∞, T m4°C represents the melting temperature of the aldehyde ketone polymer, and selectively, 0.8 < K3 ≤ 100, and further selectively, 0.8 < K3 ≤ 10.

[0030] 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] In formula (DI), R 41 represents a single bond, a substituted or unsubstituted C1-C6 methylene group, and R 42 represents a hydrogen atom, a substituted or unsubstituted C1-C6 alkyl group, [Chemical formula] In formula (DII), R 43 ~R 46 each independently represents 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 between 0 and 5, and at least one of r and s is selected from positive integers.

[0031] [[ID=3×]]In some embodiments, the isolation body includes a substrate, and the polymer layer is provided on at least one surface of the substrate.

[0032] In some embodiments, the separator includes a porous substrate, and the liquid retention polymer is distributed within the voids of the porous substrate.

[0033] In some embodiments, the separator includes a porous substrate and a polymer layer provided on at least one surface of the porous substrate, and the polymer layer includes the liquid retention polymer.

[0034] It should be noted that in the original text, there is an error in the line number of item . It should be instead of [[ID=×]]. This translation is based on the corrected content. If there are other specific requirements or corrections, please let me know.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.

[0035] According to a second aspect, the present application provides a battery including a battery cell according to any embodiment of the first aspect of the present application.

[0036] According to a third aspect, the present application provides a power consuming device comprising a battery according to any embodiment of the second aspect of the present application. [Brief explanation of the drawings]

[0037] 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.

[0038] [Figure 1] 1 is a schematic diagram of one embodiment of a battery cell of the present application. [Figure 2] 2 is an exploded schematic view of the battery cell shown in FIG. 1 according to an embodiment. [Figure 3] 1 is a schematic diagram of a battery module according to an embodiment of the present application; [Figure 4] 1 is a schematic diagram of an embodiment of a battery pack of the present application. [Figure 5] 5 is an exploded schematic view of the battery pack shown in FIG. 4 according to the embodiment. [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.

[0039] The drawings are not drawn to scale. [Explanation of symbols]

[0040] 1 battery pack, 2 upper housing, 3 lower housing, 4 battery module, 5 battery cell, 51 housing, 52 electrode assembly, 53 cover plate, 6 Power consumption equipment. DETAILED DESCRIPTION OF THE INVENTION

[0041] Hereinafter, detailed descriptions will be given of embodiments specifically disclosing the battery cell, battery, and power consumption device of the present application. However, unnecessary detailed descriptions 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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).

[0047] As used herein, the terms "plurality" and "plurality" mean two or more.

[0048] 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.

[0049] 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.

[0050] The term "halogen atom" refers to fluorine atom, chlorine atom, bromine atom, and the like.

[0051] The term "hydrogen" refers to 1H (protium, H), 2H (deuterium, D), or 3H (tritium, T). In each embodiment, "hydrogen" may be 1H (protium, H).

[0052] 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, causing the electrolyte to be pushed out and making it difficult for the battery cell to absorb the electrolyte. This increases the risk of electrolyte shortage and the appearance of bridges in the electrode sheets, which can deteriorate the cycle characteristics of the battery cell and shorten the cycle life of the battery cell.

[0053] In view of the above, an embodiment of the present application provides a battery cell, in which an electrode sheet of the battery cell is provided with a liquid-absorbing polymer, which helps the electrode sheet absorb the electrolyte, allowing the electrolyte to wet the electrode sheet more uniformly and thoroughly, thereby improving the stability of the battery cell during cycling. The separator of the battery cell is provided with a liquid-retaining polymer, which has a high liquid-retaining ability and is less likely to extrude the electrolyte during charging and discharging cycles of the battery cell, thereby reducing liquid shortage during charging and discharging cycles, lowering battery polarization, and improving the cycle characteristics of the battery cell.

[0054] Battery cell According to a first aspect, an embodiment of the present application provides a battery cell including an electrode assembly, the electrode assembly including an electrode sheet and a separator; the electrode sheet includes a current collector and a film layer provided on at least one surface of the current collector, the film layer containing an active material and a liquid-absorbing polymer, the electrode sheet satisfying v / λ≧1.20; v represents the liquid absorption rate of the film layer, expressed in mg / s; λ represents the porosity of the film layer, The separator includes a liquid-retaining polymer, and the separator comprises:

number

[0055] When calculating the above formulas specifically, only the specific values ​​are substituted, and the units of each parameter are not substituted.

[0056] In the battery cell of the present embodiment, the electrode sheets are provided with a liquid-absorbing polymer, which helps the electrode sheets absorb the electrolyte, allowing the electrolyte to wet the electrode sheets more evenly and thoroughly, improving the stability of the battery cell during cycling.The separator of the battery cell is provided with a liquid-retaining polymer, which has a high liquid-retaining ability and makes it difficult for the electrolyte to be extruded during the charge-discharge cycle of the battery cell, reducing the liquid shortage situation during the charge-discharge cycle, lowering battery polarization, and improving the cycle characteristics of the battery cell.

[0057] In this application, the method for measuring the liquid absorption rate of a polar sheet includes the following steps.

[0058] A capillary tube is used to absorb a predetermined amount of electrolyte.

[0059] The capillary tube is brought into contact with the electrode sheet, and the electrode sheet to be measured absorbs the electrolyte in the capillary tube due to capillary action.

[0060] After a predetermined time t has elapsed, the liquid level h of the absorbed electrolyte in the capillary is recorded, and the amount of absorbed electrolyte is calculated based on the liquid level h, diameter d, and density ρ of the electrolyte in the capillary. The liquid absorption rate v of the electrode sheet is quantitatively calculated based on the ratio of the absorbed amount to the predetermined time t.

[0061] Illustratively, the value of d is 0.2 to 1, for example, the value is 0.2, and the value of h is 3 to 5, for example, the value is 3.

[0062] The capillary has a capillary channel, which allows the capillary to directly absorb the electrolyte by capillary action, providing liquid absorption without the need for an external driving unit. This allows for more accurate control of the amount of electrolyte absorbed when absorbing the electrolyte by capillary action. On the other hand, the electrode sheet itself absorbs the electrolyte by capillary action. When the capillary comes into contact with the polar sheet to be measured, the electrode sheet draws out the electrolyte from inside the capillary. When the contact is removed, the electrolyte inside the capillary no longer flows out. This allows the amount of electrolyte absorbed in the capillary to accurately reflect the absorption of a corresponding volume of electrolyte by the electrode sheet, further improving the accuracy of the measurement results and enabling quantitative calculation of the absorption rate of the electrode sheet.

[0063] In the present application, measurements were carried out using standard electrolyte solutions as test samples, and the specific formulation of the electrolyte solution can be referred to in the examples.

[0064] The liquid-absorbing polymer of the present invention is introduced into the film layer manufacturing process, which can form uniform high wet points in the film layer, improve the liquid absorption rate of the entire film layer, and improve the cycle performance of the battery cell.

[0065] In an embodiment of the present application, the porosity of the film layer in the electrode sheet is the ratio of the pore volume in the film layer to the volume of the entire film layer, and can be measured using an apparatus and method known in the art, for example, with reference to GB / T 21650.2-2008 "Determination of Pore Size Distribution and Porosity of Solid Materials by Mercury Intrusion and Gas Adsorption Methods, Part 2: Analysis of Mesopores and Macropores by Gas Adsorption Methods" and ASTM D2873-941 "Standard Test Method for Interior Porosity of Poly(Vinyl Choride) (PVC) Resins by Mercury Intrusion Porosimetry."

[0066] Alternatively, the porosity of the film layer is calculated using the formula (1-P1 / P2), P1 represents the actual compressed density of the film layer, expressed in g / cm 3 The actual compressed density P1 refers to the ratio of the mass and thickness of the active material layer per unit area in the electrode sheet. The actual compressed density is determined by the force applied by the roller after applying the electrode sheet, and is expressed in g / cm. 3 The specific test steps are as follows: take an electrode sheet with a certain area S, weigh the mass M of its active material layer, and measure the thickness D of the film layer; the actual compressed density = M / (S × D).

[0067] P2 represents the true compressed density of the active material, expressed in g / cm 3 The true compressed density P2 refers to the density of the active material itself in the active material layer.

[0068] If the active material is a negative electrode active material, for example, graphite, the density of graphite is 2.25 g / cm 3 and the true compressed density of the active material is 2.25 g / cm 3 is.

[0069] When the active material is a positive electrode active material, the true packed density is specifically the mass per unit of the "actual volume (excluding open pores, closed pores, and interparticle voids) of a solid material in a compacted state," and is measured to obtain the true volume V, and then the true packed density is calculated based on P=m / V. The measurement can be performed in accordance with GB / T24586-2009, and the measurement steps are specifically as follows:

[0070] 1) Pretreatment: Place a clean, dry sample cup on the balance, reset it, add the powder sample to the sample cup so that it occupies approximately 1 / 2 of the volume of the sample cup, and record the sample mass.

[0071] 2) The sample cup containing the sample is placed in the true density measuring device, the measuring system is sealed, helium gas is introduced according to the process, the pressure of the gas in the sample chamber and the expansion chamber is measured, and then the true volume is calculated according to Bohr's law (PV=nRT), thereby calculating the true compressed density.

[0072] 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 such as mass measurement, liquid absorption rate, and porosity.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077]

number

[0078] The separator of the present embodiment includes a liquid-retaining polymer, and the separator has a high liquid-retaining capacity, which makes it difficult for the electrolyte to be extruded during the charge-discharge cycle of the battery cell, thereby reducing the liquid shortage situation during the charge-discharge cycle, reducing battery polarization, and improving the cycle characteristics of the battery cell.

[0079] Selectively,

number

[0080] If the separator satisfies the above conditions, the separator will have a high electrolyte retention capacity, which will reduce the occurrence of electrolyte shortage during charge-discharge cycles, reduce battery polarization, and improve the cycle characteristics of the battery cell.

[0081] For example,

number

[0082] 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.

[0083] In some embodiments, the separator comprises:

number

[0084] 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 liquid absorption capacity of the separator, i.e., the amount of electrolyte absorbed by the separator, and can relatively improve its liquid retention capacity.

[0085]

number

[0086] 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.

[0087] For example,

number

[0088] 80%, 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 values.

[0089] In some embodiments, the separator comprises:

number

[0090] (m2-M) / M indicates the ratio of the amount of liquid retained in the separator after the separator is subjected to an external action to the mass of the separator itself, which can characterize the liquid retention capacity of the separator.

[0091]

number

[0092] When the separator satisfies the above conditions, the separator has good liquid retention capacity even when the separator is under pressure, and the electrolyte adsorbed by the separator is not easily pushed out, thereby increasing the migration rate of active ions and further improving the cycle characteristics of the battery cell.

[0093] For example,

number

[0094] 20.0%, 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.

[0095] In some embodiments, the separator further comprises a liquid-absorbing polymer. The introduction of the liquid-absorbing polymer can improve the liquid absorption capacity of the separator, thereby increasing the rate at which the separator absorbs the electrolyte.

[0096] In some embodiments, the battery cell has a temperature of 0≦y / V 総孔 Meets ≦15% y represents the volume of free electrolyte in the battery cell, expressed in mL; V 総孔 indicates the void volume of the electrode assembly, in mL.

[0097] When calculating a formula, only the numerical value is substituted, not the unit.

[0098] When the battery cell satisfies the above conditions, the content of free electrolyte in the battery cell is extremely small, and even the battery cell contains substantially no free electrolyte, thereby significantly improving the usage reliability and cycle characteristics of the battery cell.

[0099] For example, y / V 総孔 y / V may be 0%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or a range consisting of any two of the above values. 総孔 If 0, it indicates that the amount of free electrolyte is 0 mL, i.e., there is substantially no free electrolyte in the battery cell.

[0100] The electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separator, and the void volume of the electrode assembly is the sum of the void volume of the positive electrode sheet, the void volume of the negative electrode sheet, and the void volume of the separator. In the embodiments of the present application, the void volume has a meaning known in the art and can be measured using an apparatus and method known in the art, for example, by a gas displacement method. The void volume is vm, where v represents the apparent volume (i.e., the total volume), and m represents the actual volume.

[0101] In some embodiments, the battery cell further satisfies 0≦y / Ah≦15%; y represents the volume of free electrolyte in the battery cell, expressed in mL; Ah indicates the nominal capacity of the battery cell, and is expressed in Ah units.

[0102] When calculating a formula, only the numerical values ​​are substituted into the formula, not the units.

[0103] The volume y (mL) of free electrolyte can be measured using the following method: a new battery cell is fully discharged to 0% SOC, a hole with a diameter of 5 to 8 mm is drilled at a local position on the battery cell, the battery cell is placed above a container with the hole facing downward and directly above the container, and the free electrolyte inside the battery cell drips into the container below. The battery cell is left in this state for 3 to 5 hours until all the free electrolyte inside drips into the container, and the volume of the electrolyte inside the container is then measured to obtain y. In this embodiment, the new battery cell may be a battery cell that has just been shipped (and has not been used for any charge-discharge cycles since formation), or a battery cell that has been installed in a power-consuming device and has been used for fewer than 10 cycles.

[0104] When the battery cell satisfies the above conditions, the content of free electrolyte in the battery cell is extremely small, and even the battery cell contains substantially no free electrolyte, thereby significantly improving the usage reliability and cycle characteristics of the battery cell.

[0105] For example, y / Ah may be 0%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or a range consisting of any two of the above values. y / Ah of 0 indicates that the amount of free electrolyte is 0, i.e., there is substantially no free electrolyte in the battery cell.

[0106] In some embodiments, after the battery cell is subjected to a linear sweep vibration test, the battery cell is charged to 100% SOC, a hole is drilled in the battery cell, and the hole is placed at the lowest vertical position. The volume of electrolyte flowing out of the battery cell is recorded as M1, where 0 mL≦M1≦0.5 mL, and optionally, M1 is 0 mL; where: The vibration direction of the linear sweep vibration test is a simple vertical harmonic motion, The vibration frequency of the linear sweep vibration test is 10 Hz to 55 Hz, The maximum acceleration of the linear sweep vibration test is 30 m / s 2 and The number of sweep cycles in the linear sweep vibration test is 10; The vibration time for the linear sweep vibration test is 3 hours.

[0107] In the related art, during use, a battery cell may experience vibrations or other phenomena due to the action of external forces. The electrolyte located in the electrode assembly may detach from the electrode assembly under the action of vibration, forming free electrolyte. The free electrolyte in the battery cell may leak, causing corrosion of the battery cell and posing risks such as battery cell failure. In embodiments of the present application, the battery cell is subjected to a static and vibration treatment to effectively collect and discharge the liquid electrolyte inside the battery cell, thereby more accurately determining whether liquid electrolyte is present between the battery cell housing and the electrode assembly and determining the free electrolyte content. When the battery cell of the present application satisfies the above conditions, the free electrolyte content within the battery cell is extremely low, or even substantially free of free electrolyte, thereby significantly improving the usage reliability and cycle characteristics of the battery cell.

[0108] Illustratively, M1 may be 0 mL, 0.05 mL, 0.1 mL, 0.15 mL, 0.2 mL, 0.25 mL, 0.3 mL, 0.35 mL, 0.4 mL, 0.45 mL, 0.5 mL, or a range consisting of any two of the above values. If M1 is 0 mL, it indicates that the amount of free electrolyte is 0, that is, the battery cell has substantially no free electrolyte inside after the linear sweep vibration test.

[0109] In some embodiments, after the vibration test, the battery cell is disassembled, the electrode assembly is removed, and a pressing test is performed. The volume of the electrolyte flowing out of the electrode assembly is recorded as M2 (the pressing device is empty, and a weighing balance and an electrolyte collecting container are installed at the bottom). The volume of the electrolyte flowing out of the electrode assembly is 0 mL≦M2≦0.5 mL, and optionally, M2 is 0 mL. where: The pressing direction of the pressing test is perpendicular to the thickness direction of the electrode assembly 52, The pressure level in the compression test is 0.35 MPa.

[0110] In the related art, a battery cell may be subjected to external pressure during use, and the electrolyte located in the electrode assembly may detach from the electrode assembly under pressure, forming free electrolyte. The free electrolyte in the battery cell may leak, causing corrosion of the battery cell and posing risks such as battery cell failure. In embodiments of the present application, a pressure test is performed on the battery cell to effectively force the liquid electrolyte inside the battery cell to flow out, thereby more accurately determining whether liquid electrolyte exists between the battery cell housing and the electrode assembly and determining the free electrolyte content. If the battery cell of the present application satisfies the above conditions, the free electrolyte content in the battery cell is extremely low, or even substantially free of free electrolyte, after pressing, thereby significantly improving the usage reliability and cycle characteristics of the battery cell.

[0111] For example, M2 may be 0 mL, 0.05 mL, 0.1 mL, 0.15 mL, 0.2 mL, 0.25 mL, 0.3 mL, 0.35 mL, 0.4 mL, 0.45 mL, 0.5 mL, or a range consisting of any two of the above values. If M2 is 0 mL, it indicates that the amount of free electrolyte is 0, that is, the battery cell has substantially no free electrolyte inside after the compression test.

[0112] In some embodiments, a voltage of 200V is applied to the battery cell to form a circuit, the duration is 4 hours, and the absolute value of the temperature change of the battery cell is ≦4° C.

[0113] For example, if a 200V current circuit is formed by connecting the negative terminal of a battery cell to the inside of the outer case, the temperature fluctuation range of the battery cell will be 4°C or less within 4 hours, and there will be no malfunctions such as fire or explosion. In particular, when the free electrolyte y=0, the temperature fluctuation range is small, greatly improving the reliability of the battery cell.

[0114] In some embodiments, when the mass per unit volume of the liquid-absorbent polymer located in the electrode sheet is A1 and the mass per unit volume of the liquid-absorbent polymer located in the separator is A2, 1.0≦A1 / A2≦1.6, and optionally 1.2≦A1 / A2≦1.5.

[0115] When a battery cell satisfies the above conditions, the electrode sheet has good liquid absorption performance and the separator has good liquid retention performance. Through the combined action of these two, the electrolyte is less likely to be extruded from the electrode assembly during the charge / discharge cycle of the battery cell, and good wetting effect can be achieved on the electrode sheet, improving the cycle characteristics of the battery cell.

[0116] For example, A1 / A2 may be 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, or a range consisting of any two of the above values.

[0117] In some embodiments, the electrode sheet further comprises a liquid-retaining polymer, which can improve the liquid-retaining ability of the electrode sheet and improve the wetting ability of the electrolyte to the electrode sheet.

[0118] In some embodiments, when the mass per unit volume of the liquid-retaining polymer located in the electrode sheet is B1 and the mass per unit volume of the liquid-retaining polymer located in the separator is B2, 0.4≦B1 / B2≦0.9, and optionally 0.5≦B1 / B2≦0.8.

[0119] When a battery cell satisfies the above conditions, the electrode sheet has good liquid absorption performance and the separator has good liquid retention performance. Through the combined action of these two, the electrolyte is less likely to be extruded from the electrode assembly during the charge / discharge cycle of the battery cell, and good wetting effect can be achieved on the electrode sheet, improving the cycle characteristics of the battery cell.

[0120] For example, B1 / B2 may be 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or a range consisting of any two of the above values.

[0121] In some embodiments, the fluid-absorbing polymer comprises at least one of an ether-based polymer and an ester-based polymer.

[0122] [Ether polymer] In some embodiments, the liquid-absorbing polymer comprises an ether-based polymer, and the ether-based polymer is fabricated 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 ° C. indicates the melting temperature of the ether polymer.

[0123] 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 The temperature is set at +20°C, the rolling thickness is 1 to 2 min, the rolling time is 2 min, and the pressure is 8 MPa. After rolling for 2 min, the sample is removed and cold-pressed in another vulcanizing press of the same type, with the cold-press pressure being 10 MPa. A circular mold with a diameter of 25 mm can be 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, and standard samples may be prepared according to the requirements of the testing equipment.

[0124] According to the conventional conclusion of linear viscoelasticity, for polymers, especially linear polymers, the elastic modulus G'-loss modulus G" curve conforms to the frequency dependence in the terminal region (the range toward the maximum angular velocity) of the elastic modulus G'-loss modulus G" curve, and the longest chain of the polymer contributes to the viscoelastic behavior.

[0125] The specific steps of the dynamic frequency sweep test are as follows: The dynamic frequency sweep test was performed using a TA-AR2000EX rotational rheometer (TA Instruments, USA), with a parallel plate diameter of 25 mm and a thickness of 0.9 mm. To ensure the test was performed in the linear viscoelastic region, the strain during the dynamic frequency sweep test was 2% and the test temperature was T m2 +20℃, and the test frequency sweep range is 500rad / s≦w 2 ≦0.05 rad / s, which makes it easier to obtain data in the lowest possible frequency range.

[0126] 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 and show behavior deviating from the linear end, while 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 advantageous for the diffusion of solvent molecules in the electrolyte between the molecular chains. Moreover, the ether-based polymer still maintains a certain molecular chain entanglement state and can form an electrolyte and a gel substance, improving the cycle characteristics and storage performance of the battery cell.

[0127] 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.

[0128] In some embodiments, the glass transition temperature of the ether-based polymer is T g2 where the unit is °C, and -100 ≤ T g2 ≤ 50, and optionally, -80 ≤ T g2 ≤ 30. Exemplarily, 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 numerical values.

[0129] In some embodiments, the ether-based polymer contains a structural unit represented by formula (BI),

Chemical formula

[0130] In some embodiments, R 21 and R 22 each independently comprises a hydrogen atom or a substituted or unsubstituted C1-C2 alkyl group.

[0131] In some embodiments, R 23 includes a single bond, a substituted or unsubstituted C1-C4 methylene group.

[0132] 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]

[0133] In some embodiments, the ether-based polymer comprises a structural unit according to formula (BII): [ka] 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.

[0134] 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.

[0135] 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]

[0136] 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.

[0137] 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).

[0138] 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. The above substituents are pressure-resistant and are further advantageous in stabilizing the polymer structure. The halogen atoms may include fluorine atoms, chlorine atoms, bromine atoms, etc.

[0139] In some embodiments, the degree of polymerization n of the ether-based polymer is selected from positive integers of 1,500 to 25,000.

[0140] Optionally, the degree of polymerization n of the ether-based polymer is selected from a positive integer of 3,000 to 18,000.

[0141] In some embodiments, the molecular weight of the polymer is 1.2×10 5from g / mol to 1.0×10 6 g / mol.

[0142] Exemplarily, the molecular weight of the polymer may be 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 or a range consisting of any two of the above numerical values.

[0143] [Ester-based polymer] In some embodiments, the liquid absorption polymer includes an ester-based polymer, the ester-based polymer is made into a sheet-like structure, and the sheet-like structure is subjected to a dynamic frequency sweep test at (T m3 +20)°C to obtain a storage modulus G’ - loss modulus G” curve. The slope of the storage modulus G’ - loss modulus G” curve is K2, and 1 < K2 < ∞, where T m3 °C represents the melting temperature of the ester-based polymer.

[0144] When the ester-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 advantageous for the solvent molecules in the electrolyte to diffuse between the molecular chains. Moreover, the ester-based polymer still maintains a certain molecular chain entanglement state and can form an electrolyte and a gel-like substance, improving the liquid absorption rate, thereby improving the cycle characteristics and storage performance of the battery cell.

[0145] In some embodiments, 1 < K2 ≤ 100, and optionally, 1 < K2 ≤ 10.

[0146] 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.

[0147] In some embodiments, the glass transition temperature of the ester-based polymer is T g3 The unit is °C, and -100≦T g3 ≦50, and optionally, −80≦T g3 ≦30.

[0148] For example, the glass transition temperature of the ester-based 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 above values.

[0149] In some embodiments, the ester-based polymer comprises a structural unit shown in formula (CI): [ka] 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.

[0150] Selectively, R 31 includes a hydrogen atom or a substituted or unsubstituted methyl group.

[0151] Selectively, R 32 and R 33 each independently contains a hydrogen atom.

[0152] Selectively, R 34 includes a substituted or unsubstituted C1-C4 alkyl group, or a substituted or unsubstituted C1-C4 hydroxyalkyl group.

[0153] Exemplarily, the ester-based polymer includes at least one of the structural units represented by formula (CI-1) to formula (CI-15): [ka] [ka]

[0154] In some embodiments, the ester-based polymer comprises a structural unit shown in formula (CII): [ka] In formula (CII), R 35 includes substituted or unsubstituted C2-C6 methylene groups.

[0155] Selectively, R 35 independently comprises a substituted or unsubstituted C2-C4 methylene group.

[0156] Exemplarily, the ester-based polymer includes at least one of the structural units represented by formula (CII-1) to formula (CII-5), [ka]

[0157] 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.

[0158] 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).

[0159] 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, and a bromine atom). The above substituents are pressure-resistant substituents, which are further advantageous in stabilizing the structure of the polymer. The above substituents are pressure-resistant substituents, which are further advantageous in stabilizing the structure of the polymer.

[0160] In some embodiments, the degree of polymerization n of the ester-based polymer is selected from any positive integer from 800 to 20,000.

[0161] Optionally, the degree of polymerization n of the ester-based polymer is selected from positive integers of 1,000 to 15,000.

[0162] 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.

[0163] 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.

[0164] In some embodiments, the liquid-retaining polymer comprises at least one of a fluoropolymer and an aldehyde ketone polymer.

[0165] In some embodiments, the liquid-retaining polymer comprises a fluoropolymer, and the fluoropolymer has a crystallinity measured by differential scanning calorimetry of X C1 and 0 <X C1 ≦30%, and the melting temperature of the fluoropolymer is T m1The unit is °C, and 0 <T m1 ≦140.

[0166] 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.

[0167] 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.

[0168] 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.

[0169] 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.

[0170] In some embodiments, the glass transition temperature of the fluoropolymer is T g1 The unit is °C, and -150≦T g1 ≦60.

[0171] 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.

[0172] In some embodiments, the fluoropolymer comprises structural units shown in formula (AI): [ka] 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.

[0173] In some embodiments, the fluoropolymer comprises structural units shown in formula (AII): [ka] 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 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.

[0174] In some embodiments, the fluoropolymer comprises structural units shown in formula (AII): [ka] In formula (AIII), R 15 includes a single bond, a substituted or unsubstituted C1-C3 alkyl group.

[0175] 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. The above substituents are pressure-resistant substituents, which are further advantageous in stabilizing the polymer structure. The halogen atoms may include fluorine atoms, chlorine atoms, bromine atoms, etc. Optionally, the halogen atoms include fluorine atoms.

[0176] In the embodiment of the present application, the polymer may further be one obtained by copolymerizing the above structural group with a small amount of other types of structural group (for example, structural units such as olefin-based structural units, ester-based monomers, nitrile-based monomers, and amide-based monomers).

[0177] In some embodiments, p is selected from a positive integer of 1-3.

[0178] In some embodiments, the degree of polymerization n of the fluoropolymer is selected from positive integers of 1,000 to 30,000.

[0179] 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.

[0180] 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]

[0181] In some embodiments, the fluoropolymer comprises at least one of the structural units shown in formula (AII-1) to (AII-5): [ka]

[0182] 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]

[0183] 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).

[0184] 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).

[0185] 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.

[0186] 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.

[0187] In some embodiments, the degree of polymerization n of the fluoropolymer is selected from positive integers of 5,000 to 20,000.

[0188] 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 When the molecular weight of the polymer is in the above range, the polymer can have excellent liquid-retaining ability, which is advantageous for improving the liquid-retaining ability of the separator.

[0189] 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.

[0190] [Aldehyde-ketone polymers] 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°C indicates the melting temperature of the aldehyde ketone polymer.

[0191] In some embodiments, 0.8≦K3≦100, and optionally, 0.8≦K3≦10.

[0192] 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.

[0193] 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.

[0194] 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.

[0195] In some embodiments, the aldehyde ketone polymer comprises a structural unit shown in formula (DI): [ka] 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, Selectively, R 41 includes a single bond, a substituted or unsubstituted C1-C2 methylene group, Selectively, R 42 includes a hydrogen atom, a substituted or unsubstituted C1-C3 alkyl group.

[0196] 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., R41 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.

[0197] Exemplarily, the aldehyde ketone polymer includes at least one of the structural units represented by formula (DI-1) to formula (DI-6), [ka]

[0198] Illustratively, the aldehyde ketone polymer comprises a structural unit shown in formula (DII): [ka] 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.

[0199] 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]

[0200] 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.

[0201] 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 further be one obtained by copolymerizing the above structural groups with other types of structural groups (e.g., olefin-based structural units, enol-based structural units, acrylonitrile-based structural units, etc.).

[0202] When the above groups are substituted, the substituents may include one or more of a nitrile group (-CN), a nitro group, a sulfonyl group, a carboxyl group, an ester group, a chlorine atom, a fluorine atom, and a bromine atom. The above substituents are pressure-resistant substituents, which are further advantageous in stabilizing the structure of the polymer.

[0203] In some embodiments, the degree of polymerization, n, of the aldehyde ketone polymer is selected from positive integers of 500 to 15,000.

[0204] Optionally, the degree of polymerization n of the aldehyde ketone polymer is selected from a positive integer of 500 to 10,000.

[0205] 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.

[0206] 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.

[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 retention capacity 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 the 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 capacity, further improving the cycle performance of the battery cell.

[0211] Illustratively, the ratio of the mass content of the liquid-absorbing 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, the linear carbonate solvents include one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), diphenyl carbonate (DPC), methyl allyl carbonate (MAC), and polycarbonate (VA).

[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-absorbing polymer and solvent is transformed 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-absorbing polymer described above, as determined by infrared spectroscopy (IR) or nuclear magnetic resonance (NMR) testing.

[0220] In the present embodiment, the liquid-absorbing 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-absorbing polymer molecular chain segments become less active, adhere to the separator, and trap the electrolyte in the spatial environment where the liquid-absorbing polymer is located, forming a gel or gel-like state, which can improve the transport rate of active ions, such as lithium ions, and improve cycle performance.

[0221] The relevant parameters of the polymers of the present embodiments can be measured using the following methods.

[0222] The polymer groups of the present embodiment can be detected using infrared spectroscopy (IR). Specifically, the liquid-holding polymer was measured using a Thermo Nicolet Nexus 670 attenuated total reflectance Fourier transform infrared spectrometer (FTIR-ATR) in accordance with standard 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.

[0223] 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.

[0224] 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 combination of decomposition, gas chromatography, and mass spectrometry. 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 installed 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 are instantly vaporized and separated by the carrier gas into the gas chromatography column, and finally detected via a flame ionization detector (FID) or mass spectrometer (MS) to obtain a gas chromatogram or total ion chromatogram.

[0225] 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.

[0226] 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.

[0227] In some embodiments, the separator comprises a porous substrate, and the liquid-retaining polymer is distributed within the voids of the porous substrate.

[0228] 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.

[0229] 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.

[0230] 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.

[0231] 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.

[0232] 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.

[0233] 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.

[0234] 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.

[0235] 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.

[0236] The heat-resistant coating layer may include heat-resistant particles. In some embodiments, the heat-resistant particles include at least one of inorganic particles and organic particles. Adding the heat-resistant particles can improve the heat resistance performance of the separator.

[0237] In some embodiments, the mass percent content of the inorganic particles in the heat-resistant coating layer is ≦30. Illustratively, the mass percent 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 foregoing values.

[0238] The inorganic particles include at least one of inorganic particles having a dielectric constant of 5 or greater, inorganic particles having the ability to transport active ions, and inorganic particles capable of generating electrochemical oxidation and reduction.

[0239] In some embodiments, the inorganic particles having a dielectric constant of 5 or higher include boehmite (γ-AlOOH), aluminum oxide (AlO), barium sulfate (BaSO), magnesium oxide (MgO), magnesium hydroxide (Mg(OH), silicon oxide (SiO), x(0 < x ≤ 2), tin dioxide (SnO2), titanium dioxide (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 fluoride (MgF2), Pb(Zr,Ti)O3 (abbreviated as PZT), Pb 1-m La m Zr 1-n Ti n O3 (abbreviated as PLZT, 0 < m < 1, 0 < n < 1) and Pb(Mg3Nb 2 / 3 )O3 - PbTiO3 (abbreviated as PMN - PT) may contain at least one of them.

[0240] In some embodiments, the inorganic particles having the ability to transport active ions are lithium phosphate (Li3PO4), lithium titanium phosphate (Li x Ti y (PO4)3, 0 < x < 2, 0 < y < 3), lithium aluminum titanium phosphate (Li x Al y Ti z (PO4)3, 0 < x < 2, 0 < y < 1, 0 < z < 3), (LiAlTiP) x O y - based glass (0 < x < 4, 0 < y < 13), lithium lanthanum titanate (Li x La y TiO3, 0 < x < 2, 0 < y < 3), lithium germanium thiophosphate (Li x Ge y P z S w , 0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), lithium nitride (Li x N y , 0 < x < 4, 0 < y < 2), SiS2 - based glass (Li x Si y S z , 0 < x < 3, 0 < y < 2, 0 < z < 4) and P2S5 - based glass (Li x P y S zIt may also include at least one of (0 < x < 3, 0 < y < 3, 0 < z < 7).

[0241] 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.

[0242] 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, phenol resin, polypropylene, polyester (such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate), polyphenylene sulfide, polyaramide, polyamideimide, polyimide, copolymers of butyl acrylate and ethyl methacrylate, and mixtures thereof.

[0243] In some embodiments, the heat-resistant coating layer can further include a binder. As an example, the binder may include at least one of aqueous acrylic resins (such as homopolymers of acrylic acid, methacrylic acid, sodium acrylate monomers or copolymers with other comonomers), polyvinyl alcohol (PVA), isobutylene-maleic anhydride copolymers, and polyacrylamide.

[0244] In some embodiments, the thickness of the heat-resistant coating layer ≤ 4 μm. This 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. Exemplarily, 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 numerical values.

[0245] 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.

[0246] When the coating basis weight is within the above range, the liquid retention capacity of the separator can be further improved.

[0247] Optionally, the coating weight of the polymer layer is 0.5 mg / 1540.25 mm 2 From 3.5mg / 1540.25mm 2 may be.

[0248] 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.

[0249] 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 2The 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.

[0250] [Positive electrode sheet] The battery cell includes a positive electrode sheet, which includes a positive electrode current collector and a positive electrode film layer disposed on the positive electrode current collector.

[0251] In some embodiments, the positive electrode film layer comprises a positive electrode active material and a fluid-absorbing polymer.

[0252] For example, the positive electrode film layer includes a polymer layer containing a liquid-absorbing polymer and a positive electrode active material layer containing positive electrode active material particles, the positive electrode active material layer is disposed on at least one surface of the positive electrode current collector, and the polymer layer is disposed on the surface of the positive electrode active material layer opposite to the positive electrode current collector.

[0253] As another example, the positive electrode active material particles are plural, and there is a gap between two adjacent positive electrode active material particles, and the liquid-absorbing polymer is distributed in the gap.

[0254] In some embodiments, the positive electrode film layer may further include a liquid-retaining polymer.

[0255] 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.

[0256] In some embodiments, 1.20≦v / λ≦4.50. Illustratively, v / λ may be 1.20, 1.40, 1.80, 2.00, 2.50, 3.00, 3.50, 3.60, 3.80, 3.90, 4.0, 4.2, 4.5, or a range consisting of any two of the foregoing values.

[0257] In some embodiments, the mass percent content of the liquid-absorbing polymer is 0.1% to 1.5% relative to the mass of the positive electrode active material layer.

[0258] When the mass percent content of the liquid-absorbing polymer is within the above range, the liquid absorption capacity of the positive electrode active material layer can be significantly improved. For example, the mass percent content of the liquid-absorbing polymer may be 0.1%, 0.2%, 0.5%, 0.8%, 1.0%, 1.2%, 1.5%, or a range consisting of any two of the above values.

[0259] 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.

[0260] 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.

[0261] 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 may be lithium cobalt oxide (LCO), lithium nickel oxide (LNO), lithium manganese oxide (LMO), or 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.

[0262] 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).

[0263] 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.

[0264] 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.

[0265] 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 a positive electrode active material, a liquid-absorbing polymer, an optional conductive agent, an optional binder, and any other components in a solvent and stirring the mixture uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP). The production of the positive electrode sheet is not limited to the above method, and the production methods described above may also be used.

[0266] [Negative electrode sheet] The battery cell includes a negative electrode sheet.

[0267] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector. For example, the negative electrode current collector has two opposing surfaces in its thickness direction, and the negative electrode film layer is provided on one or both of the opposing surfaces of the negative electrode current collector.

[0268] In some embodiments, the negative electrode film layer comprises a negative electrode active material and a liquid-absorbing polymer.

[0269] For example, the negative electrode film layer includes a polymer layer containing a liquid-absorbing polymer and a negative electrode active material layer containing negative electrode active material particles, the negative electrode active material layer is disposed on at least one surface of the negative electrode current collector, and the polymer layer is disposed on the surface of the negative electrode active material layer opposite to the negative electrode current collector.

[0270] As another example, the negative electrode active material particles are plural, and there is a gap between two adjacent negative electrode active material particles, and the liquid-absorbing polymer is distributed in the gap.

[0271] In some embodiments, the negative electrode film layer may further include a liquid-retaining polymer.

[0272] In some embodiments, 3.00≦v / λ<50.00. Illustratively, v / λ may be 3.00, 3.20, 3.40, 3.50, 4.00, 4.50, 5.00, 5.50, 6.00, 6.50, 7.00, 8.00, 9.00, 9.50, 10.00, 10.50, 11.00, 12.00, 13.00, 14.00, 15.00, 20.00, 25.00, 28.00, 30.00, 35.00, 40.00, 45.00, 50.00, or a range consisting of any two of the foregoing values.

[0273] In some embodiments, the mass percent content of the liquid-absorbent polymer is 0.2% to 5.0% relative to the mass of the negative electrode active material layer. When the mass percent content of the liquid-absorbent polymer is in this range, the liquid absorption capacity of the negative electrode active material layer can be significantly improved. For example, the mass percent content B% of the liquid-absorbent polymer may be 0.2%, 0.5%, 0.8%, 1.0%, 1.2%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, or a range consisting of any two of the above values.

[0274] 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.

[0275] 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%.

[0276] 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-soluble 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.

[0277] 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%.

[0278] 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).

[0279] The negative electrode active material layer is typically formed by applying a negative electrode paste to a negative electrode current collector, drying it, and cold-pressing it. The negative electrode paste is typically formed by dispersing a negative electrode active material, a liquid-absorbing polymer, an optional conductive agent, an optional binder, and other optional auxiliary agents in a solvent and stirring the mixture uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water. The production of the negative electrode sheet is not limited to the above method, and the production methods described above may also be used.

[0280] 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.

[0281] [Electrolyte] 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.

[0282] 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.

[0283] 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.

[0284] 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.

[0285] By way of example, the solvent may be 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), propionate (P ... The additives may include, but are not limited to, at least one of 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).

[0286] 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.

[0287] 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 lamination process.

[0288] In some embodiments, the battery cell may include a housing material that is used to encapsulate the electrode assembly and the electrolyte.

[0289] 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).

[0290] In some embodiments, the positive electrode sheet, separator, and negative electrode sheet can be fabricated into an electrode assembly via a winding or laminating process.

[0291] 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.

[0292] 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 lamination 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.

[0293] 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 lamination 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.

[0294] 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.

[0295] 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.

[0296] Optionally, the battery module 4 may further include an outer case having an accommodating space for accommodating the plurality of battery cells 5.

[0297] 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.

[0298] The battery module 4 and the battery pack can both be specific examples of the battery in the embodiments of the present application.

[0299] 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.

[0300] power consumption equipment 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. In some embodiments, the battery cell includes a fill hole for injecting electrolyte, and when the battery cell is applied to the power consuming device, the fill hole is located at the bottom along the vertical direction of the battery cell. Because the amount of free electrolyte in the battery cell is very small, or even absent, providing the fill hole at the bottom along the vertical direction of the battery cell can also improve the reliability of the battery cell and the power consuming device.

[0301] 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.

[0302] Example 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.

[0303] Example 1: Manufacture of a lithium-ion battery (1) Manufacturing of positive electrode sheet: An aluminum foil with a thickness of 12 μm is used as the positive electrode current collector.

[0304] Liquid absorption polymer, positive electrode active material LiNi 0.6 Co 0.2 Mn 0.2 The positive electrode paste is prepared by thoroughly mixing O2 (NCM622), the conductive agent carbon black, and the binder polyvinylidene fluoride (PVDF) in an appropriate amount of N-methylpyrrolidone (NMP). The mass ratio of the liquid-absorbing polymer, NCM622, conductive carbon black, and PVDF in the positive electrode paste is 0:97.5:1.4:1.1. The positive electrode paste is applied to an aluminum foil current collector, dried in a vacuum at 100°C, cold-pressed, trimmed, cut, and slit, and then dried in a vacuum at 85°C for 4 hours to produce a positive electrode sheet.

[0305] (2) Manufacturing of negative electrode sheet: A copper foil with a thickness of 8 μm is used as the negative electrode current collector.

[0306] The liquid-absorbing polymer, artificial graphite (negative active material), carbon black (conductive agent), styrene butadiene rubber (SBR) binder, and sodium carboxymethyl cellulose (CMC) thickener are mixed uniformly in a weight ratio of 1.5:95.9:2:0.5:0.1, and then deionized water is added to prepare the negative electrode paste. The negative electrode paste is applied to a copper foil current collector and dried at 85°C. After that, the negative electrode is cold-pressed, trimmed, cut, and slit, and then dried at 120°C under vacuum for 12 hours to produce a negative electrode sheet.

[0307] (3) Electrolyte production: 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.

[0308] (4) Separator manufacturing The base material is a 7 μm polyethylene film (PE).

[0309] 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%.

[0310] (5) Lithium-ion battery manufacturing: 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.

[0311] Comparative Example 1 A lithium ion battery was produced in the same manner as in Example 1, except that the positive electrode sheet, negative electrode sheet, and separator of Comparative Example 1 were all different from those of Example 1. The separator of Comparative Example 1 was a 7 μm polyethylene film (PE).

[0312] The positive electrode sheet was produced as follows.

[0313] An aluminum foil with a thickness of 12 μm is used as the positive electrode current collector.

[0314] Positive electrode active material LiNi 0.6 Co0.2 Mn 0.2 The 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.

[0315] Negative electrode sheet manufacturing: A copper foil with a thickness of 8 μm is used as the negative electrode current collector.

[0316] 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.

[0317] Comparative Example 2 A lithium ion battery was manufactured in the same manner as in Example 1, except that in Comparative Example 2, the material of the liquid-retaining polymer in the separator was changed, and the material of the liquid-absorbing polymer in the positive electrode sheet and negative electrode sheet was changed.

[0318] Examples 1-2 to 1-10 Lithium ion batteries were produced in the same manner as in Example 1, except that the contents of the liquid-absorbing polymer in the positive electrode sheet and negative electrode sheet were adjusted in Examples 1-2 to 1-10.

[0319] Examples 2-1 to 2-6 Lithium ion batteries were produced in the same manner as in Example 1, but differed from Example 1 in that at least one of the liquid-retaining polymer and the liquid-absorbing polymer was changed in Examples 2-1 to 2-6.

[0320] Examples 3-1 to 3-5 Lithium ion batteries were produced in the same manner as in Example 1, except that in Examples 3-1 to 3-5, the coating basis weight of the liquid-retaining polymer in the separator was adjusted.

[0321] Example 4-1 The lithium ion battery was manufactured in the same manner as in Example 1. The difference from Example 1 is that Example 4-1 adjusts the installation position of the polymer layer in the separator. Specifically, the separator manufacturing steps include the following:

[0322] A 7 μm polyethylene film (PE) is used as the separator substrate.

[0323] 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.

[0324] The prepared coating paste is applied to two surfaces of the PE substrate using a coating device to form a heat-resistant coating layer.

[0325] 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.

[0326] Example 4-2 The lithium ion battery was manufactured in the same manner as in Example 1. The difference from Example 1 is that Example 4-2 adjusted the manufacturing method of the separator. Specifically, the manufacturing steps of the separator include:

[0327] A 7 μm polyethylene film (PE) is used as the separator substrate.

[0328] The liquid-retaining polymer, silicon oxide particles, and aqueous polyacrylic acid binder were mixed uniformly in a mass ratio of 80:20 in an appropriate amount of deionized water to obtain a coating paste. The mass ratio of the liquid-retaining polymer to the silicon oxide particles was 1.5:1.

[0329] The prepared coating paste is applied to two surfaces of the PE substrate using a coating device to form a heat-resistant coating layer.

[0330] 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.

[0331] The data for the examples and comparative examples are shown in Table 1.

[0332] Exam section 1. Wetting performance of polar sheets and separators in lithium-ion batteries After hot pressing at 80°C, the negative electrode sheet + separator structure was taken. The structure was 2.0 cm wide and 10 cm high. The structure was placed vertically in the electrolyte, with the polar sheet at a height of 1 mm in the electrolyte. The rise in the electrolyte height was recorded after 2 minutes, and the rise in the liquid height / time was recorded to characterize the liquid absorption speed of the entire negative electrode sheet + separator structure.

[0333] After hot pressing at 80°C, the positive electrode sheet + separator structure was taken. The structure was 2.0 cm wide and 10 cm high. The structure was placed vertically in the electrolyte, with the polar sheet at a height of 1 mm in the electrolyte. The rise in the electrolyte height was recorded after 2 minutes, and the rise in the liquid height / time was recorded to characterize the liquid absorption speed of the entire positive electrode sheet + separator structure.

[0334] 2. Cycle characteristics of lithium-ion batteries under 5C conditions Charge a lithium-ion battery at 25°C at a rate of 5C and discharge at a rate of 1C. The initial discharge capacity is taken as 100%, and the capacity retention rate after 200 battery cycles is calculated. Capacity retention rate after 200 battery cycles (%) = discharge capacity at 200 / initial discharge capacity x 100%.

[0335] Test results The test results are shown in Tables 1 and 2.

[0336] [Table 1A] [Table 1B]

[0337] In Table 1, 60% methyl methacrylate means that the mole percent content of methyl methacrylate is 60% based on the total molar amount of methyl methacrylate, butyl acrylate, and acrylonitrile.

[0338] In Table 1, the liquid retention capacity

number

[0339] The liquid retention rate (before pressure application) is (m1-M) / M x 100%.

[0340] The liquid retention rate (after pressure application) is (m2-M) / M x 100%.

[0341] [Table 2]

[0342] In Table 2, 75% VDF means that the mole percent content of vinylidene fluoride (VDF) is 75% relative to the total molar amount of vinylidene fluoride (VDF), hexafluoropropylene (HFP), and ethylene.

[0343] [Table 3]

[0344] In Table 3, the porosity of the positive electrode film layer in the positive electrode sheet of each of the Examples and Comparative Examples is 30.1%, and the porosity of the negative electrode film layer in the negative electrode sheet is 44.2%.

[0345] In Table 3, the ratio of the mass per unit volume of the liquid-absorbing polymer in the polar sheet to the mass per unit volume of the liquid-retaining polymer in the separator refers to the ratio of the sum of the monomer volume masses of the liquid-absorbing polymer in the positive electrode sheet and the negative electrode sheet to the mass per unit volume of the liquid-retaining polymer in the separator.

[0346] In Comparative Example 1, the liquid-retaining polymer of the present invention was not added to the separator, and the liquid-absorbing polymer was not added to the polar sheet, resulting in poor cycle characteristics of the battery cell.

[0347] In Comparative Example 2, a polymer is added to the separator and polar sheet, but the polymer has low liquid retention and absorption capabilities, and the cycle characteristics of the lithium ion battery cannot be effectively improved.

[0348] Compared to Comparative Example 1, the polar sheets of the present example are provided with a liquid-absorbing polymer, which helps the electrode sheets absorb the electrolyte, allowing the electrolyte to wet the electrode sheets more evenly and thoroughly, improving the stability of the battery cell during cycling.The separator of the battery cell is provided with a liquid-retaining polymer, which has a high liquid-retaining ability and makes it less likely for the electrolyte to be extruded during the charge-discharge cycle of the battery cell.This reduces the liquid shortage during the charge-discharge cycle, lowers battery polarization, and improves the cycle characteristics of the battery cell.

[0349] 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 battery cell including an electrode assembly, the electrode assembly includes an electrode sheet and a separator; the electrode sheet includes a current collector and a film layer provided on at least one surface of the current collector, the film layer containing an active material and a liquid-absorbing polymer, the electrode sheet satisfies v / λ≧1.2, v represents a liquid absorption rate of the film layer, and is expressed in mg / s; λ represents the porosity of the film layer, The separator includes a liquid-retaining polymer, and the separator comprises: [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 battery cell 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 active material includes a positive electrode active material, The battery cell according to claim 1 , wherein the electrode sheet satisfies 1.2≦v / λ≦4.

50.

3. the active material includes a negative electrode active material, The battery cell according to claim 1 or 2, wherein the electrode sheet satisfies 3≦v / λ<50.

00.

4. The separator is [Equation 2] The battery cell according to any one of claims 1 to 3, which satisfies the above.

5. The separator is [Equation 3] The battery cell according to any one of claims 1 to 4, which satisfies the above.

6. The separator is [Equation 4] The battery cell according to any one of claims 1 to 5, which satisfies the above.

7. the separator further comprises a liquid-absorbing polymer; Selectively, A1 is the mass per unit volume of the liquid-absorbent polymer located in the electrode sheet, When the mass per unit volume of the liquid-absorbing polymer located in the separator is A2, The battery cell according to any one of claims 1 to 6, wherein 1.0≦A1 / A2≦1.6, and optionally 1.2≦A1 / A2≦1.

5.

8. the electrode sheet further comprises a liquid-retaining polymer; Selectively, The mass per unit volume of the liquid-retaining polymer located in the electrode sheet is defined as B1, When the mass per unit volume of the liquid-retaining polymer located in the separator is B2, The battery cell according to any one of claims 1 to 7, wherein 0.4≦B1 / B2≦0.9, and optionally 0.5≦B1 / B2≦0.

8.

9. The mass per unit volume of the liquid-absorbing polymer located in the electrode sheet is C1, and the mass per unit volume of the liquid-retaining polymer located in the separator is C2. The battery cell according to any one of claims 1 to 8, wherein 0.1 ≦ C1 / C2 ≦ 5.

10. the liquid-absorbing polymer includes at least one of an ether-based polymer and an ester-based polymer; Optionally, the liquid-absorbing polymer is fabricated into a sheet-like structure, and the sheet-like structure is (T ｍ１ 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 ｍ１ °C denotes the melting temperature of said liquid-absorbing polymer, optionally 1 < K １ ≦100, and further optionally, 1<K １ 10. The battery cell according to claim 1, wherein the resistance of the battery cell is ≦10.

11. The ether-based polymer comprises at least one of a structural unit represented by formula (BI) and a structural unit represented by formula (BII), 【Chemistry 1】 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 2】 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 11. The battery cell of claim 10, wherein at least one of comprises a substituted or unsubstituted C1-C3 alkoxy or ether group.

12. 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 3】 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; 【Chemistry 4】 In formula (CII), R ３５ comprises a substituted or unsubstituted C2-C6 methylene group, and optionally R ３５ The battery cell of claim 10 or 11, wherein each independently comprises a substituted or unsubstituted C2-C4 methylene group.

13. the liquid-retaining polymer comprises at least one of a fluoropolymer and an aldehyde ketone polymer; Alternatively, the crystallinity of the fluoropolymer as measured by differential scanning calorimetry is Xc ２ and 0<Xc ２ ≦30%, and the melting temperature of the fluoropolymer is T ｍ２ and the unit is ° C., and 0<T ｍ２ ≦140, Optionally, the aldehyde ketone 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 ３ and 0.8≦K ３ <∞, and T ｍ３ °C denotes the melting temperature of the aldehyde ketone polymer, optionally 0.8 < K ３ ≦100, and more optionally, 0.8<K ３ 13. The battery cell according to claim 1, wherein the resistance is ≦10.

14. The crystallinity of the fluoropolymer 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): 【Transformation 5】 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; 【Transformation 6】 In formula (AIII), R １５ comprises 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 1,000 to 30,000.

15. The aldehyde ketone polymer comprises at least one of a structural unit represented by formula (DI) and a structural unit represented by formula (DII), 【Transformation 7】 In formula (DI), R ４１ includes 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.

16. The battery cell according to any one of claims 1 to 15, wherein the separator includes a porous substrate, and the liquid-retaining polymer is distributed within pores of the porous substrate.

17. The battery cell according to any one of claims 1 to 16, wherein the separator includes a porous substrate and a polymer layer provided on at least one surface of the porous substrate, and the polymer layer includes the liquid-retaining polymer.

18. The coating weight of the liquid-retaining polymer was 0.5 mg / 1540.25 mm ２ From 5 mg / 1540.25 mm ２ The battery cell according to any one of claims 1 to 17,

19. A battery cell comprising the battery cell according to any one of claims 1 to 18.

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

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