Binder for secondary battery and its manufacturing method, separator, battery cell, battery and power consumption device

Abstract

The present application relates to the technical field of secondary batteries, in particular to a binder for secondary batteries and a manufacturing method thereof, and a separator, battery cell, battery, and power consumption device including the binder. The binder for secondary batteries includes an organic polymer, the organic polymer includes a first glass transition temperature and a second glass transition temperature, the first glass transition temperature being below 25°C, and the second glass transition temperature being higher than 25°C. When applied to a separator, the binder is not viscous at room temperature, and the separator can be easily wound and unwound. When the positive and negative polarity sheets are wound and subjected to a cold pressing process, the binder has excellent adhesive strength, and the positive and negative polarity sheets and the separator are closely attached to each other. Thus, the binder of the present application improves the cold pressing adhesive strength between the separator and the positive and negative polarity sheets, thereby improving the hardness of the cell and the cycle characteristics of the secondary battery.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to a Chinese patent application with application number 202310369599.5, filed on April 7, 2023, the entire contents of which are incorporated herein by reference. [Technical field]

[0002] The present application relates to the field of secondary battery technology, and in particular to a binder for secondary batteries and a manufacturing method thereof, as well as a separator, a battery cell, a battery, and a power consuming device. [Background technology]

[0003] With the rapid growth of portable electronic devices, electric vehicles, etc., the demand for power batteries is also increasing, and the electrical and chemical properties of batteries are attracting more and more attention.

[0004] Currently, there exists a problem in battery cells that the opening is large, that is, gaps are easily formed between the polar sheet and the separator, which deteriorates the cycle characteristics of the battery. Summary of the Invention

[0005] The main objective of the present application is to provide a binder that improves the adhesive strength between the separator and the polar sheet and improves the cycling characteristics of the battery.

[0006] In order to achieve the above object, the present application provides a binder for a secondary battery, the binder comprising an organic polymer, the organic polymer comprising a first glass transition temperature and a second glass transition temperature, the first glass transition temperature being 25°C or less and the second glass transition temperature being higher than 25°C.

[0007] At a certain temperature, the organic polymer has a soft structure at its first glass transition temperature, and can be deformed when subjected to a compressive force. The separator and polar sheet have voids in their structures. When a compressive force is applied to the organic polymer, a part of the organic polymer structure can penetrate into the voids in the separator and polar sheet, bonding the separator and binder together, achieving a mechanical interlocking effect and realizing the adhesive function.

[0008] There is a clear difference between the first and second glass transition temperatures of the organic polymer, and when cold pressed at a certain temperature, the structure containing the first glass transition temperature of the organic polymer is in a rubber state, and the structure containing the second glass transition temperature of the organic polymer is in a glass state, so the binder has the property of being both "soft and hard". After it is applied on the separator, when there is no pressure at a certain temperature, the binder has no viscosity, which meets the requirements for winding and unwinding the separator, and when a certain pressure is applied, the binder exhibits pressure sensitivity and shows excellent adhesion, which meets the requirements for the adhesive force between the separator and the positive and negative polarity sheets.

[0009] Therefore, when the binder of the present application is used to apply the separator, the binder has no adhesiveness at a certain temperature, making it easy to wind and unwind the separator, but when the positive and negative polar sheets are wound and subjected to a cold press process, the binder has excellent adhesive strength to tightly bond the positive and negative polar sheets and the separator to each other. Therefore, the binder of the present application improves the cold press adhesive strength between the separator and the positive and negative polar sheets, thereby improving the hardness of the cell and the cycle characteristics of the secondary battery.

[0010] Preferably, the range of the first glass transition temperature is from -80°C to 25°C, more preferably from -60°C to 25°C.

[0011] Within the above range, the organic polymer contains a structure with a first glass transition temperature and is in a rubbery state at a certain temperature, which helps to exert its adhesiveness during the cold pressing process, and is favorable for the adhesion between the separator and the polar sheet after cold pressing, thereby improving the performance of the battery.

[0012] Preferably, the second glass transition temperature is in the range of 26°C to 100°C, more preferably 26°C to 90°C.

[0013] Within the above range, the organic polymer contains a structure with a second glass transition temperature, and is in a glassy state at a certain temperature, which serves to form a skeletal structure of the binder at a certain temperature, and the binder does not have viscosity, which facilitates the operation of the winding and unwinding steps of the separator at a certain temperature.

[0014] Preferably, the organic polymer comprises an acrylic ester copolymer, and / or the organic polymer comprises at least one of an ester group, a carboxyl group, an acrylamide group, a carbonyl group, an amide group, and a nitrile group.

[0015] Acrylic acid ester copolymers have good adhesion, and can be used to further improve the adhesion between the separator and the polar sheet after cold pressing.

[0016] The ester group can improve the swelling resistance of the polymer, and as a flexible monomer segment in the molecular segment, can adjust the glass transition temperature of the organic polymer, which is helpful in adjusting the glass transition temperature of the polymer in an appropriate range.

[0017] The carboxyl group can form a bond with the functional groups on the material of the polar sheet and the separator, improving the adhesive effect.

[0018] The acrylamide group aids in the polymerization of the monomer, which acts to control the molecular weight while at the same time having good adhesive properties.

[0019] The carbonyl group and the amide group are useful for improving the viscosity of the binder.

[0020] The nitrile groups help to improve ionic conductivity and improve adhesion.

[0021] Preferably, the shape of the binder comprises a sphere.

[0022] The spherical shape is advantageous for uniform dispersion during the paste stirring process and aids in uniform application.

[0023] Preferably, the binder has a volume-based particle size distribution Dv50 of 1 μm to 15 μm, preferably 5 μm to 10 μm, and / or a number-based particle size distribution Dn10 of the binder of 1 μm to 5 μm, preferably 1 μm to 3 μm.

[0024] Theoretically, the volumetric particle size distribution Dv50 of the binder in the present application may be less than 1 μm or more than 15 μm, but considering that the binder in the present application is used in a separator, the volumetric particle size distribution Dv50 of the binder is not appropriate if it is too large or too small, thereby improving the binder's blocking of the separator channel, reducing the problem of lithium ions (here, lithium ion secondary batteries are taken as an example, but other types of secondary batteries may also be used) passing through the separator, and further improving the problem that the binder is applied to the separator to form a thick coating film, which affects the energy density of the battery to be manufactured later. Therefore, the volumetric particle size distribution Dv50 of the binder is 1 μm to 15 μm, preferably 5 μm to 10 μm.

[0025] By having the number-based particle size distribution Dn10 of the binder within the above range, the binder is prevented from blocking the channels of the separator, the problem of lithium ions (here, a lithium ion secondary battery is taken as an example, but other types of secondary batteries may be used) passing through the separator is reduced, and further, the problem of the binder forming a thick coating film when applied to the separator and affecting the energy density of the battery to be manufactured later can be improved. Therefore, the number-based particle size distribution Dn10 of the binder is 1 μm to 5 μm, and preferably 1 μm to 3 μm.

[0026] Preferably, the organic polymer comprises a first polymer and a second polymer, and the first polymer and the second polymer comprise an acrylic ester copolymer.

[0027] The organic polymer includes a first polymer and a second polymer, and as will be understood, the organic polymer includes the first polymer and the second polymer, the organic polymer includes a first glass transition temperature and a second glass transition temperature.

[0028] Acrylic acid ester copolymers have good adhesion, and can be used to further improve the adhesion between the separator and the polar sheet after cold pressing.

[0029] Preferably, the range value of the mass ratio of the first polymer to the second polymer is 1:(0.1 to 10), and more preferably, 1:(0.5 to 3).

[0030] By setting the mass ratio of the first polymer to the second polymer within the above range, the problem of the binder being too soft and affecting the performance of the cell can be improved, for example, the possibility of the binder being too soft blocking the pores of the separator and the problem of the binder being too hard affecting the adhesive effect are improved. Therefore, the range value of the mass ratio of the first polymer to the second polymer is 1: (0.1 to 10), preferably 1: (0.5 to 3).

[0031] Preferably, the first polymer and / or the second polymer includes a first polymerizable monomer, and the first polymerizable monomer includes a structure represented by (Formula 1), [ka] In formula (1), R1 includes a hydrogen atom or an alkyl group having 1 to 12 carbon atoms, and R2 includes an alkyl group having 1 to 12 carbon atoms.

[0032] The first polymerizable monomer contains an unsaturated ester group, which is advantageous for the polymerization of the monomer, and can simultaneously improve the swelling resistance of the polymer. As a flexible monomer segment in the molecular segment, it can adjust the glass transition temperature of the organic polymer, which is helpful in adjusting the glass transition temperature of the polymer in an appropriate range.

[0033] Preferably, the first polymerized monomer comprises one or more of methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, n-propyl acrylate, cyclohexyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate.

[0034] By using any one or more of the first polymerizable monomers described above, the glass transition temperature of the polymer can be adjusted, and the swelling resistance of the polymer can be improved.

[0035] Preferably, the first polymer contains a second polymerizable monomer, and the second polymerizable monomer contains a structure represented by formula (2): [ka] In formula (2), R3 includes a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms.

[0036] The second polymerizable monomer contains an unsaturated carboxyl group, which is useful for the polymerization of the monomer. Since the first polymer contains the second polymerizable monomer containing a carboxyl group, during the process of pressing the separator and the polar sheet using a cold pressing process, the carboxyl group can form a bond with the functional groups on the materials of the polar sheet and the separator, thereby improving the adhesive effect.

[0037] Preferably, the second polymerizable monomer comprises one or more of acrylic acid, methacrylic acid, crotonic acid, heptenoic acid.

[0038] By using one or more of the second polymerizable monomers described above, the adhesive properties of the first polymer can be adjusted.

[0039] Preferably, the first polymer and / or the second polymer comprises a third polymerizable monomer, The third polymerizable monomer comprises a structure represented by formula (3), [ka] In formula (3), R4 includes a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R5 includes a hydrogen atom, a hydroxyl-substituted alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.

[0040] The structure of the third polymerizable monomer contains an unsaturated amide group, which is conducive to the polymerization of the monomer, and the monomer plays the role of regulating the molecular weight, and at the same time has good adhesive properties.

[0041] Preferably, the third polymerized monomer comprises one or more of acrylamide, N-methylol acrylamide, and N-butoxymethyl acrylamide.

[0042] The use of one or more of the above third polymerizable monomers can play a role in adjusting the molecular weight, and is used to adjust the molecular weight of the polymer, which helps to improve the adhesion within a certain range of the molecular weight of the binder.

[0043] Preferably, the second polymer comprises a fourth polymerizable monomer, and the fourth polymerizable monomer comprises a structure represented by formula (4), [ka] In formula (4), R6 contains a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

[0044] The structure of the fourth polymerizable monomer contains an unsaturated cyano group, which is conducive to the polymerization of the monomer, conducive to improving ionic conductivity, and improves adhesion.

[0045] Preferably, the fourth polymerized monomer comprises one or more of acrylonitrile, methacrylonitrile.

[0046] By using one or more of the fourth polymerizable monomers, the ionic conductivity of the binder can be improved.

[0047] The present application further provides: A step of mixing water, an emulsifier, an initiator, and constituent monomers of a first polymer by stirring and reacting them by heating to obtain a first polymer emulsion; a step of mixing water, an emulsifier, an initiator, and constituent monomers of a second polymer by stirring and reacting them by heating to obtain a second polymer emulsion; and mixing the first polymer emulsion and the second polymer emulsion by stirring, followed by spray drying to obtain a binder.

[0048] In the present invention, the first polymer emulsion and the second polymer emulsion are obtained by emulsion polymerization, and the binder is obtained by spray drying.

[0049] Preferably, the step of mixing the first polymer emulsion and the second polymer emulsion by stirring and spray drying to obtain a binder comprises: The first polymer emulsion and the second polymer emulsion are mixed by stirring to obtain a mixed emulsion, and the range value of the mass ratio of the first polymer to the second polymer in the mixed emulsion is 1:(0.1 to 10), preferably 1:(0.5 to 3).

[0050] In order to obtain a binder having an appropriate blending value of the second polymer and the second polymer in the binder and to obtain a binder with appropriate performance, when the first polymer emulsion and the second polymer emulsion are mixed by stirring to obtain a mixed emulsion, the range value of the mass ratio of the first polymer to the second polymer in the mixed emulsion is 1:(0.1 to 10), and preferably 1:(0.5 to 3).

[0051] An embodiment of the present application provides a separator including the above-mentioned secondary battery binder or a binder produced by the above-mentioned method for producing a secondary battery binder.

[0052] An embodiment of the present application provides a battery cell including the separator described above.

[0053] An embodiment of the present application provides a battery including the battery cell described above.

[0054] An embodiment of the present application provides a power consuming device including the above battery cell or the above battery. [Brief description of the drawings]

[0055] In order to more clearly describe the embodiments of the present application or the technical solutions in the prior art, the drawings necessary for describing the embodiments or the prior art are briefly described below. The drawings shown below are only some embodiments of the present application, and it is obvious that a person skilled in the art can obtain other drawings based on the structures shown in these drawings without creative efforts.

[0056] [Figure 1] 1 is a scanning electron microscope image of a binder according to Example 1 of the present application. [Diagram 2] 1 is a flowchart of a method for producing a binder according to an embodiment of the present application. [Diagram 3] FIG. 2 is a schematic diagram of an electrode assembly according to an embodiment of the present application. [Figure 4] FIG. 4 is an exploded view of the electrode assembly shown in FIG. 3 according to the embodiment of the present application. [Diagram 5]FIG. 1 is a schematic diagram of a battery module according to an embodiment of the present application. [Figure 6] 1 is a schematic diagram of a battery pack according to an embodiment of the present application. [Figure 7] FIG. 7 is an exploded view of the battery pack according to the embodiment of the present application shown in FIG. [Figure 8] 1 is a schematic diagram of a power consuming device according to an embodiment of the present application; [Explanation of symbols]

[0057] 1 Battery pack 2 Upper case 3 Lower case 4 Battery Module 5 Secondary battery 51 Housing 52 Electrode Assembly 53 Top cover assembly

[0058] The realization of the object, features and advantages of the present invention will be further described in conjunction with the embodiments and with reference to the drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0059] The technical solutions in the embodiments of the present application are described below clearly and completely with reference to the drawings in the embodiments of the present application, and obviously, the described embodiments are only some of the embodiments of the present application, not all of the embodiments, and all other embodiments obtained by those skilled in the art based on the embodiments of the present application without any creative efforts are all within the scope of protection of the present application.

[0060] Hereinafter, the binder and its manufacturing method, as well as the separator, electrode assembly, battery cell, battery, and power consuming device containing the binder according to the present application will be described in detail with reference to the drawings as appropriate. However, unnecessary detailed description may be omitted. For example, detailed description of well-known matters and redundant description of substantially identical structures may be omitted. This is to prevent the following description from becoming unnecessarily redundant and to facilitate understanding by those skilled in the art. Furthermore, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application, and are not intended to limit the subject matter described in the claims.

[0061] The "ranges" disclosed herein are defined in the form of lower and upper limits, and a given range is defined by selecting one lower limit and one upper limit, and the selected lower and upper limits define the boundaries of the particular range. Ranges defined in this manner may or may not include the endpoints and may be arbitrarily combined, i.e., any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are recited for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Also, if minimum range values ​​1 and 2 are recited, and maximum range values ​​3, 4, and 5 are recited, the ranges 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5 are all contemplated. In this application, unless otherwise stated, the numerical range "a-b" means a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are recited herein, and "0-5" is merely a shorthand for combinations of these numerical values. Furthermore, expressing a parameter as an integer ≧2 is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0062] All embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, unless otherwise specified.

[0063] All technical features and optional technical features in the present application can be combined with each other to form new technical solutions, unless otherwise stated.

[0064] All steps in this application can be performed in sequence or randomly, and are preferably performed in sequence, unless otherwise stated. For example, when the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed in sequence, or may include steps (b) and (a) performed in sequence. For example, when the method may further include step (c), it means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0065] The terms "comprise" and "comprises" referred to in this application refer to both open and closed formats unless otherwise specified. For example, the terms "comprise" and "comprises" can indicate that other elements not listed may also be included or may include, or that only the listed elements may be included or may include.

[0066] 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).

[0067] The battery cell has a problem of large openings, that is, gaps are easily formed between the polar sheets and the separator, which deteriorates the cycle characteristics of the battery.

[0068] The binder commonly used for the binder on the separator is polyvinylidene fluoride, but at present, the price of polyvinylidene fluoride fluctuates greatly, the supply to the market is small, and at the same time, the hot pressing process is required to tightly bond the separator and the polar sheet. As the production speed improves, the hot pressing process is gradually replaced by the cold pressing process, and the cold pressing of the battery polar sheet can standardize the winding core, reduce the elasticity of the cell, and improve the pass rate of the cell installation and the consistency of the thickness of the finished cell.

[0069] When the adhesive strength between the positive electrode sheet, the negative electrode sheet and the separator is insufficient, problems such as cell opening will occur, and at the same time, the electrolyte infiltration will be poor, and the secondary battery coating separator performance requirements cannot be met. If the separator and polar sheet are tightly bonded, the discharge capacity of the battery can be improved, the internal resistance can be reduced, the polarization loss can be reduced, the cycle life of the battery can be extended, and the utilization rate of the secondary battery can be improved.

[0070] As can be understood, a cell is formed by bonding a positive electrode sheet, a negative electrode sheet and a separator. The cell has a certain hardness, that is, the bonded positive and negative electrode polarity sheets and the separator are bonded together and supported by each other to form a structure with a certain thickness, and the structure with a certain thickness has a certain hardness. The negative electrode expands during charging and discharging, and if the adhesive strength is weak, a gap will be formed between the positive and negative electrode polarity sheets and the separator, and the positive and negative electrode polarity sheets and the separator cannot be bonded together and cannot support each other, causing the cell to loosen and the hardness to decrease. At this time, the power performance of the cell will deteriorate, for example, the rate characteristic will deteriorate, and at the same time, the cycle characteristic will also deteriorate. For example, in an electric vehicle, when a battery cell loosens, the charging speed of the battery will slow down, and at the same time, the cycle characteristic of the battery will deteriorate, which will directly lead to a shortened battery life, and the electric vehicle will need to replace the battery frequently, which will increase the consumer cost of the electric vehicle.

[0071] Based on this, the present application provides a binder for a secondary battery, the binder comprising an organic polymer, the organic polymer comprising a first glass transition temperature and a second glass transition temperature, the first glass transition temperature being 25°C or less, and the second glass transition temperature being higher than 25°C.

[0072] A binder is a material that has adhesive properties and is used to bond different substances together.

[0073] Glass transition temperature is the temperature at which high polymers transition from a highly elastic state to a glassy state, and refers to the temperature at which amorphous polymers (including the non-crystalline part in crystalline polymers) transition from a glassy state to a highly elastic state or from the latter to the former, and is the lowest temperature at which the polymer segments of amorphous polymers can move freely, and is usually represented by Tg. Above the glass transition temperature, high polymers show elasticity, and below the glass transition temperature, high polymers show brittleness, and glass transition temperature can be measured by the method commonly used in this field, for example, can be tested by differential scanning calorimetry with reference to GB / T19466.2.

[0074] As can be understood, when the first glass transition temperature is 25° C., the structure containing the organic polymer with the first glass transition temperature is in a rubbery state at a constant temperature, and when the second glass transition temperature is higher than 25° C., the structure containing the organic polymer with the second glass transition temperature is in a glassy state at a constant temperature.

[0075] For example, if the first glass transition temperature is lower than room temperature and the second glass transition temperature is higher than room temperature, when no pressure is applied to the binder at room temperature, the second glass transition temperature is higher than room temperature and belongs to a glass state, and the structure of the organic polymer containing the second glass transition temperature is hard and can be used as the skeleton structure of the binder powder material and does not give the binder viscosity. At room temperature, the first glass transition temperature is lower than room temperature and belongs to a rubber state, and can have a certain "fluidity" after applying a certain pressure, and the structure of the organic polymer containing the first glass transition temperature can be fully infiltrated into the voids of the positive and negative polar sheets and the separator, increasing the mechanical interlocking effect and fully exerting its adhesive performance, which is further helpful in improving the dynamic properties of the battery.

[0076] As can be seen, at a certain temperature, the organic polymer has a soft structure at its first glass transition temperature, and can be deformed with the application of pressure. The separator and polar sheet have voids in their structures. As the pressure acts on the organic polymer, a part of the organic polymer structure can penetrate into the voids in the separator and polar sheet, bonding the separator and binder together, achieving a mechanical interlocking effect and realizing the function of adhesion.

[0077] There is a clear difference between the first and second glass transition temperatures of the organic polymer, and when cold pressed at a certain temperature, the structure containing the first glass transition temperature of the organic polymer is in a rubber state, and the structure containing the second glass transition temperature of the organic polymer is in a glass state, so the binder has the property of being both "soft and hard". After it is applied on the separator, when there is no pressure at a certain temperature, the binder has no viscosity, which meets the requirements for winding and unwinding the separator, and when a certain pressure is applied, the binder exhibits pressure sensitivity and shows excellent adhesion, which meets the requirements for the adhesive force between the separator and the positive and negative polarity sheets.

[0078] Therefore, when the binder of the present application is used to coat the separator, the binder has no viscosity at a certain temperature, making it easy to wind and unwind the separator, and when the positive and negative polar sheets are wound and subjected to a cold press process, the binder has excellent adhesive strength to tightly bond the positive and negative polar sheets and the separator to each other. Therefore, the binder of the present application improves the cold press adhesive strength between the separator and the positive and negative polar sheets, thereby improving the hardness of the cell and the cycle characteristics of the secondary battery.

[0079] As will be appreciated, the first glass transition temperature can be any value, such as -100°C, -90°C, -80°C, -70°C, -50°C, -30°C, -10°C, 10°C, 20°C, 24°C, 25°C, and a range value between any two of the above endpoint values, without being specifically limited.

[0080] As will be appreciated, the second glass transition temperature can be any value, such as 26° C., 30° C., 50° C., 80° C., 100° C., 200° C., and range values ​​between any two of the above endpoints, without being specifically limited.

[0081] In one embodiment, the first glass transition temperature range value is -80°C to 25°C, preferably -60°C to 25°C.

[0082] Within the above range, the organic polymer contains a structure with a first glass transition temperature and is in a rubbery state at a certain temperature, which helps to exert its adhesiveness during the cold pressing process, and is favorable for the adhesion between the separator and the polar sheet after cold pressing, thereby improving the performance of the battery.

[0083] In the above range of -80°C to 25°C, the values ​​include the minimum and maximum values ​​of the range, and each value between the minimum and maximum values. Specific examples include the end values ​​in the examples and -80°C, -70°C, -60°C, -50°C, -40°C, -30°C, -20°C, -10°C, 0°C, 10°C, 20°C, 25°C, etc., and range values ​​between any two of the above end values, but are not specifically limited.

[0084] In the above range of -60°C to 25°C, the values ​​include the minimum and maximum values ​​of the range, and each value between the minimum and maximum values. Specific examples include the end values ​​in the examples and -60°C, -50°C, -40°C, -30°C, -20°C, -10°C, 0°C, 10°C, 20°C, 25°C, etc., and range values ​​between any two of the above end values, but are not specifically limited.

[0085] In one embodiment, the second glass transition temperature range value is 26°C to 100°C, preferably 26°C to 90°C.

[0086] Within the above range, the organic polymer contains a structure with a second glass transition temperature, and is in a glassy state at a certain temperature, which serves to form a skeletal structure of the binder at a certain temperature, and the binder does not have viscosity, which facilitates the operation of the winding and unwinding steps of the separator at a certain temperature.

[0087] In the above range of 26°C to 100°C, the values ​​include the minimum and maximum values ​​of the range, and each value between the minimum and maximum values. Specific examples include the end values ​​in the examples and 26°C, 28°C, 30°C, 50°C, 80°C, 90°C, 100°C, etc., and range values ​​between any two of the above end values, but are not specifically limited.

[0088] In the above range of 26°C to 90°C, the values ​​include the minimum and maximum values ​​of the range, and each value between the minimum and maximum values. Specific examples include the end values ​​in the examples and 26°C, 28°C, 30°C, 50°C, 80°C, 90°C, etc., and range values ​​between any two of the above end values, but are not specifically limited.

[0089] In one embodiment, the organic polymer comprises an acrylate-based copolymer and / or the organic polymer comprises at least one of an ester group, a carboxyl group, an acrylamide group, a carbonyl group, an amide group, and a nitrile group.

[0090] Copolymers are formed by the polymerization reaction of two or more monomers, called copolymerization, to form polymers containing two or more monomer units, and are also called copolymers and interpolymers.

[0091] Regarding the acrylic acid ester copolymer, the acrylic acid ester copolymer is a general term for polymers produced by copolymerizing an acrylic acid ester monomer with another comonomer.

[0092] The structure of the acrylic monomer has an acrylate ester group, for example, methyl acrylate, ethyl acrylate, or n-butyl acrylate.

[0093] Acrylic acid ester copolymers have good adhesion, and can be used to further improve the adhesion between the separator and the polar sheet after cold pressing.

[0094] The test for ester, carboxyl, acrylamide, carbonyl, amide and nitrile groups in the organic polymer structure is based on the national standard GB / T 6040-2002 general rules for infrared spectroscopy analysis. The tablet transmission method is used, the sample is made into a KBr tablet, the KBr background blank is subtracted by the transmission method, and the test spectrum of the sample (resolution: 4 cm -1 , Wave number range: 400cm -1 ~4000cm -1 ) is obtained.

[0095] The ester group can improve the swelling resistance of the polymer, and as a flexible monomer segment in the molecular segment, can adjust the glass transition temperature of the organic polymer, which is helpful in adjusting the glass transition temperature of the polymer in an appropriate range.

[0096] The carboxyl group can form a bond with the functional groups on the material of the polar sheet and the separator, improving the adhesive effect.

[0097] The acrylamide group aids in the polymerization of the monomer, which acts to control the molecular weight while at the same time having good adhesive properties.

[0098] The carbonyl group and the amide group are useful for improving the viscosity of the binder.

[0099] The nitrile groups help to improve ionic conductivity and improve adhesion.

[0100] In one embodiment, the shape of the binder comprises a sphere.

[0101] The spherical shape is advantageous for uniform dispersion during the paste stirring process and aids in uniform application.

[0102] In one embodiment, the binder has a volume-based particle size distribution Dv50 of 1 μm to 15 μm, preferably 5 μm to 10 μm, and / or a number-based particle size distribution Dn10 of the binder of 1 μm to 5 μm, preferably 1 μm to 3 μm.

[0103] Regarding Dv50, in the sample particles, 50% of the particles in the total volume have a particle size larger than this value, and the other 50% of the particles in the total volume have a particle size smaller than this value, and Dv50 represents the particle size value in the sample.

[0104] For Dn10, the particle size of 10% of the total volume of the sample particles is smaller than this value. The volumetric particle size distribution Dv50 and the number-based particle size distribution Dn10 of the binder can be measured using methods known in the art. For example, see GB / T 19077-2016, and the characterization test can be performed using a Malvern laser granulometer, such as a Malvern Mastersizer-3000.

[0105] Theoretically, the volumetric particle size distribution Dv50 of the binder in the present application may be less than 1 μm or more than 15 μm, but considering that the binder in the present application is used in a separator, the volumetric particle size distribution Dv50 of the binder is not appropriate if it is too large or too small, thereby improving the binder's blocking of the separator channel, reducing the problem of lithium ions (here, lithium ion secondary batteries are taken as an example, but other types of secondary batteries may also be used) passing through the separator, and further improving the problem that the binder is applied to the separator to form a thick coating film, which affects the energy density of the battery to be manufactured later. Therefore, the volumetric particle size distribution Dv50 of the binder is 1 μm to 15 μm, preferably 5 μm to 10 μm.

[0106] By having the number-based particle size distribution Dn10 of the binder within the above range, the binder is prevented from blocking the channels of the separator, the problem of lithium ions (here, a lithium ion secondary battery is taken as an example, but other types of secondary batteries may be used) passing through the separator is reduced, and further, the problem of the binder forming a thick coating film when applied to the separator and affecting the energy density of the battery to be manufactured later can be improved. Therefore, the number-based particle size distribution Dn10 of the binder is 1 μm to 5 μm, and preferably 1 μm to 3 μm.

[0107] In the above range of 1 μm to 15 μm, the values ​​include the minimum and maximum values ​​of the range, and each value between the minimum and maximum values. Specific examples include, but are not limited to, the end values ​​in the examples and 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, etc., and range values ​​between any two of the above end values.

[0108] In the above range of 5 μm to 10 μm, the values ​​include the minimum and maximum values ​​of the range, and each value between the minimum and maximum values. Specific examples include the end values ​​in the examples and 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, etc., and range values ​​between any two of the above end values, but are not limited thereto.

[0109] In the above range of 1 μm to 5 μm, the values ​​include the minimum and maximum values ​​of the range, and each value between the minimum and maximum values. Specific examples include the end values ​​in the examples and 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, etc., and range values ​​between any two of the above end values, but are not limited thereto.

[0110] In the above range of 1 μm to 3 μm, the values ​​include the minimum and maximum values ​​of the range, and each value between the minimum and maximum values. Specific examples include the end values ​​in the examples and 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, etc., and range values ​​between any two of the above end values, but are not limited thereto.

[0111] In one embodiment, the organic polymer comprises a first polymer and a second polymer, and the first polymer and the second polymer comprise an acrylate-based copolymer.

[0112] The organic polymer includes a first polymer and a second polymer, and as will be understood, the organic polymer includes the first polymer and the second polymer, the organic polymer includes a first glass transition temperature and a second glass transition temperature.

[0113] Acrylic acid ester copolymers have good adhesion, and can be used to further improve the adhesion between the separator and the polar sheet after cold pressing.

[0114] In one embodiment, the range value of the mass ratio of the first polymer to the second polymer is 1:(0.1-10), preferably 1:(0.5-3).

[0115] The binder is a secondary particle formed by agglomeration of primary particles of a first polymer and primary particles of a second polymer, and both the primary particles of the first polymer and the primary particles of the second polymer have an opportunity to be exposed on the surface of the secondary particles. By adjusting the mass ratio of the first polymer to the second polymer, the opportunity for the first polymer to be exposed on the surface of the secondary particles can be adjusted, and this is used to adjust the adhesiveness of the binder.

[0116] By setting the mass ratio of the first polymer to the second polymer within the above range, the problem of the binder being too soft and affecting the performance of the cell can be improved, for example, the possibility of the binder being too soft blocking the pores of the separator and the problem of the binder being too hard affecting the adhesive effect are improved. Therefore, the range value of the mass ratio of the first polymer to the second polymer is 1: (0.1 to 10), preferably 1: (0.5 to 3).

[0117] In the above 1: (0.1 to 10), the values ​​include the minimum and maximum values ​​of the range, and each value between the minimum and maximum values. Specific examples include, but are not limited to, the end values ​​in the examples and 1:0.1, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, etc., and range values ​​between any two of the above end values.

[0118] In the above 1:(0.5 to 3), the values ​​include the minimum and maximum values ​​of the range, and each value between the minimum and maximum values. Specific examples include, but are not limited to, the end values ​​in the examples and 1:0.5, 1:1.5, 1:2, 1:2.5, 1:3, etc., and range values ​​between any two of the above end values.

[0119] As can be understood, as shown in FIG. 1, the binder particles are secondary particles formed by the aggregation of primary particles of the first polymer and primary particles of the second polymer, and therefore the second polymer becomes the skeleton therein. When the binder is not pressed, the binder has no adhesiveness. When pressed, the first polymer is subjected to force and deforms, penetrating into the gaps between the separator and the polar sheet, thereby realizing the adhesive effect.

[0120] As can be seen, the primary particle size of the polymer latex of the first polymer and the second polymer is about 100 nm to 150 nm, and after the two latexes are mixed and spray-dried, the particles are 1 μm to 15 μm, and the primary particles of the two polymers are mixed together and together form secondary particle spheres after spray-drying.

[0121] In one embodiment, the first polymer and / or the second polymer comprises a first polymeric monomer, the first polymer and / or the second polymer comprises a first polymeric monomer; The structure of the first polymerized monomer is [ka] wherein R1 includes a hydrogen atom or an alkyl group having 1 to 12 carbon atoms, and R2 includes an alkyl group having 1 to 12 carbon atoms.

[0122] The first polymerizable monomer contains an unsaturated ester group, which is advantageous for the polymerization of the monomer, and can simultaneously improve the swelling resistance of the polymer. As a flexible monomer segment in the molecular segment, it can adjust the glass transition temperature of the organic polymer, which is helpful in adjusting the glass transition temperature of the polymer in an appropriate range.

[0123] In one embodiment, the first polymerized monomer comprises one or more of methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, n-propyl acrylate, cyclohexyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate.

[0124] By using any one or more of the first polymerizable monomers described above, the glass transition temperature of the polymer can be adjusted, and the swelling resistance of the polymer can be improved.

[0125] In one embodiment, the first polymer comprises a second polymerizable monomer, and the structure of the second polymerizable monomer is [ka] R3 includes a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms.

[0126] The second polymerizable monomer contains an unsaturated carboxyl group, which is useful for the polymerization of the monomer. Since the first polymer contains the second polymerizable monomer containing a carboxyl group, during the process of pressing the separator and the polar sheet using a cold pressing process, the carboxyl group can form a bond with the functional groups on the materials of the polar sheet and the separator, thereby improving the adhesive effect.

[0127] In one embodiment, the second polymerizable monomer comprises one or more of acrylic acid, methacrylic acid, crotonic acid, and heptenoic acid.

[0128] By using one or more of the second polymerizable monomers described above, the adhesive properties of the first polymer can be adjusted.

[0129] In one embodiment, the first polymer and / or the second polymer comprises a third polymeric monomer, and the structure of the third polymeric monomer is [ka] wherein R4 comprises a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R5 comprises a hydrogen atom, a hydroxyl-substituted alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.

[0130] The structure of the third polymerizable monomer contains an unsaturated amide group, which is conducive to the polymerization of the monomer, and the monomer plays the role of regulating the molecular weight, and at the same time has good adhesive properties.

[0131] In one embodiment, the third polymerized monomer comprises one or more of acrylamide, N-methylol acrylamide, and N-butoxymethyl acrylamide.

[0132] The use of one or more of the above third polymerizable monomers can play a role in adjusting the molecular weight, and is used to adjust the molecular weight of the polymer, which helps to improve the adhesion within a certain range of the molecular weight of the binder.

[0133] In one embodiment, the second polymer comprises a fourth polymerizable monomer, and the structure of the fourth polymerizable monomer is [ka] and R6 comprises a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

[0134] The structure of the fourth polymerizable monomer contains an unsaturated cyano group, which is conducive to the polymerization of the monomer, conducive to improving ionic conductivity, and improves adhesion.

[0135] In one embodiment, the fourth polymerized monomer comprises one or more of acrylonitrile, methacrylonitrile.

[0136] By using one or more of the fourth polymerizable monomers, the ionic conductivity of the binder can be improved.

[0137] Ordinary polyvinylidene fluoride binders need to be subjected to the hot pressing process to better exert their adhesive effect. With the increase in production speed and the saving of production capacity, the hot pressing process is gradually being replaced by the cold pressing process. Cold pressing is performed after winding the cell, but ordinary polyvinylidene fluoride is a homopolymer with a crystallinity of about 50%, which leads to insufficient adhesive strength between the separator and the positive and negative polarity sheets. Conventional polyacrylic ester binders also do not meet the adhesive strength requirements under cold pressing, and problems such as cell opening and soft cell always occur. At the same time, the infiltration of the electrolyte is poor, and the requirements for the performance of the coated separator of the secondary battery cannot be met.

[0138] The binder has good adhesion by using the above monomers to prepare the acrylic ester copolymer. As can be understood, the binder includes a first polymer and a second polymer. The first polymer is prepared by emulsion-polymerizing at least two of the first polymer monomer, the second polymer monomer, and the third polymer monomer, and as can be understood, the performance of the first polymer is better when it is composed of the above three monomers. The second polymer emulsion is prepared by emulsion-polymerizing at least two of the first polymer monomer, the third polymer monomer, and the fourth polymer monomer, and as can be understood, the performance of the second polymer is better when it is composed of the above three monomers. The first polymer and the second polymer prepared using the above monomers have appropriate glass transition temperatures, and when applied to a separator, they can not only meet the requirement of the binder's non-adhesiveness at room temperature, but also meet the requirement of the cold press adhesive force between the separator and the positive and negative polarity sheets during the cold press process, and improve the hardness of the cell, improving problems such as cell opening and soft cell. At the same time, the binder can be applied to a separator and used in a secondary battery to improve the cycle characteristics of the secondary battery.

[0139] The present application further provides a method for producing a binder for a secondary battery, including the steps of: stirring and mixing water, an emulsifier, an initiator, and constituent monomers of a first polymer, and heating and reacting them to obtain a first polymer emulsion; stirring and mixing water, an emulsifier, an initiator, and constituent monomers of a second polymer, and heating and reacting them to obtain a second polymer emulsion; and stirring and mixing the first polymer emulsion and the second polymer emulsion, and spray drying them to obtain a binder.

[0140] In the present invention, a first polymer emulsion and a second polymer emulsion are obtained by emulsion polymerization, and a binder is obtained by spray drying, that is, the organic polymer includes a first polymer and a second polymer.

[0141] Regarding emulsion polymerization, emulsion polymerization is a method in which a monomer is dispersed in water with an emulsifier and mechanical stirring to form an emulsion, and then an initiator is added to start the polymerization of the monomer.

[0142] About emulsifiers: Emulsifiers are substances that convert oil and water, which are not soluble in each other, into emulsions that are difficult to separate. Emulsifiers are generally surfactants that combine the properties of both hydrophilic polar groups and hydrophobic (lipophilic) non-polar groups.

[0143] Regarding the initiator, the initiator is a substance that can initiate the polymerization reaction of monomers. For example, a radical initiator refers to a compound that can be easily decomposed by heat to form a radical (i.e., a primary radical), and can be used to initiate the radical polymerization and copolymerization reaction of olefin and diene monomers.

[0144] Water, an emulsifier, an initiator, and the constituent monomers of the polymer are mixed by stirring, and the water and the emulsifier are dispersed by stirring to form an emulsion; that is, the emulsifier forms micelles in the aqueous phase, and the monomers are solubilized in most of the micelles. Under heating conditions, the initiator causes the monomers to polymerize inside the micelles, thereby obtaining an emulsion.

[0145] Spray drying is a process in which the material to be dried (a mixture of the first and second polymer emulsions) is dispersed by mechanical action into very fine mist-like particles, which are then contacted with hot air (which increases the surface area for water evaporation and accelerates the drying process) to instantly remove most of the water and dry the solid substances in the material into a powder.

[0146] The spray drying process yields a binder comprised of the first polymer and the second polymer.

[0147] In one embodiment, the step of stirring and mixing the first polymer emulsion and the second polymer emulsion and spray drying to obtain a binder includes: stirring and mixing the first polymer emulsion and the second polymer emulsion to obtain a mixed emulsion, in which the range value of the mass ratio of the first polymer to the mass ratio of the second polymer in the mixed emulsion is 1:(0.1-10), preferably 1:(0.5-3).

[0148] In order to obtain a binder having an appropriate blending value of the second polymer and the second polymer in the binder and to obtain a binder with appropriate performance, when the first polymer emulsion and the second polymer emulsion are mixed by stirring to obtain a mixed emulsion, the range value of the mass ratio of the first polymer to the second polymer in the mixed emulsion is 1:(0.1-10), preferably 1:(0.5-3).

[0149] The present invention further provides a separator comprising the binder or the binder produced by the method for producing a binder for a secondary battery, the binder using all the technical solutions of the above embodiments, and therefore has at least all the beneficial effects of the technical solutions of the above embodiments, and the description thereof is omitted here.

[0150] The separator is coated with the above binder, which can improve the adhesive performance between the polar sheet and the binder, and improve the traditional problem that the cells open in the process of preliminary cold pressing.

[0151] The present invention further provides a battery cell including the separator described above. The separator uses all the technical solutions of all the above embodiments, and therefore has at least all the beneficial effects of the technical solutions of the above embodiments, and the description thereof is omitted here.

[0152] By applying the above separator to a battery cell, the jig-loaded cycle characteristics of the battery cell can be improved.

[0153] The embodiments of the present application further provide a battery including the above-mentioned battery cell, which uses all the technical solutions of all the above-mentioned embodiments, and thus has at least all the beneficial effects of the technical solutions of the above-mentioned embodiments, and the description thereof is omitted here.

[0154] The battery pack includes a battery module and a battery pack.

[0155] The embodiments of the present application further provide a power consuming device including the above battery cell or the above battery, the battery cell or the battery uses all the technical solutions of all the embodiments, and therefore has at least all the beneficial effects of the technical solutions of the embodiments, and the description here is omitted.

[0156] The electrode assembly, battery cell, battery, and power consuming device of the present application will be described below with reference to the drawings as appropriate.

[0157] In one embodiment of the present application, an electrode assembly is provided.

[0158] In general, the electrode assembly includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During the charging and discharging process of the battery, active ions shuttle between the positive electrode sheet and the negative electrode sheet to be inserted and removed. The electrolyte serves to conduct ions between the positive electrode sheet and the negative electrode sheet. The separator is disposed between the positive electrode sheet and the negative electrode sheet, and serves mainly to prevent short circuit between the positive and negative electrodes, while allowing ions to pass through. The separator is the improved separator of the present application.

[0159] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector.

[0160] As an example, the positive electrode current collector has two opposing surfaces in the thickness direction of itself, and the positive electrode film layer is provided on either one or both of the two opposing surfaces of the positive electrode current collector.

[0161] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. The metal foil can be, for example, an aluminum foil. The composite current collector can include a polymer substrate layer and a metal layer formed on at least one surface of the polymer substrate layer. The composite current collector can be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0162] In some embodiments, when the electrode assembly is a lithium ion battery, the positive electrode active material may be a known positive electrode active material for batteries. As an example, the positive electrode active material may include at least one of lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include lithium cobalt oxide (e.g., LiCoO2), lithium nickel oxide (e.g., LiNiO2), lithium manganese oxide (e.g., LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., LiNi 1 / 3 Co 1 / 3 Mn 1 / 3O2 (abbreviated as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (abbreviated as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (abbreviated as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (abbreviated as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (abbreviated as NCM 811 )), lithium nickel cobalt aluminum oxide (e.g. LiNi 0.85 Co 0.15 Al 0.05 O2) and its modified compounds, etc., but are not limited thereto. The lithium-containing phosphate having an olivine structure may include, but is not limited to, at least one of, for example, lithium iron phosphate (e.g., LiFePO4 (abbreviated as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (e.g., LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon.

[0163] In some embodiments, the positive electrode film layer can further include a binder. For example, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0164] In some embodiments, the positive electrode film layer can optionally further include a conductive agent, for example, the conductive agent can include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0165] In some embodiments, the positive electrode sheet can be manufactured by the following method: Components for manufacturing the positive electrode sheet, such as a positive electrode active material, a conductive agent, a binder, and any other components, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode paste, which is then applied to a positive electrode current collector, and the positive electrode sheet can be obtained through steps such as drying and cold pressing.

[0166] The negative electrode sheet includes a negative electrode active material and includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector.

[0167] As an example, the negative electrode current collector has two opposing surfaces in the thickness direction of the negative electrode current collector, and the negative electrode film layer is provided on either one or both of the two opposing surfaces of the negative electrode current collector.

[0168] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. The metal foil can be, for example, a copper foil. The composite current collector can include a polymer substrate layer and a metal layer formed on at least one surface of the polymer substrate. The composite current collector can be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0169] In some embodiments, the negative electrode active material may be a known negative electrode active material for batteries. As an example, the negative electrode active material may include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, lithium titanate, and the like. The silicon-based material may include at least one of silicon elemental, silicon oxide, silicon carbon composite, silicon nitrogen composite, and silicon alloy. The tin-based material may include at least one of tin elemental, tin oxide, and tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as a negative electrode active material for a battery may be used. These negative electrode active materials may be used alone or in combination of two or more types.

[0170] In some embodiments, the negative electrode film layer can optionally further include a binder, which can include at least one of styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0171] In some embodiments, the negative electrode film layer can further include an optional conductive agent, which can include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0172] In some embodiments, the negative electrode film layer optionally further comprises other auxiliary agents, such as a thickening agent (eg, sodium carboxymethylcellulose (CMC-Na)).

[0173] In some embodiments, the negative electrode sheet can be manufactured in the following manner: Components for manufacturing the negative electrode sheet, such as a negative electrode active material, a conductive agent, a binder, and any other components, are dispersed in a solvent (e.g., deionized water) to form a negative electrode paste, which is then applied to a negative electrode current collector, and the negative electrode sheet can be obtained through steps such as drying and cold pressing.

[0174] The electrolyte serves to conduct ions between the positive electrode sheet and the negative electrode sheet. The present application does not particularly limit the type of electrolyte, and the electrolyte may be selected as necessary.

[0175] In some embodiments, the electrolyte uses an electrolyte solution, which includes an electrolyte salt and a solvent.

[0176] In some embodiments, the electrolyte salt can include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonylimide, lithium bistrifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium bisoxalate borate, lithium difluorooxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0177] In some embodiments, the solvent can include at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0178] In some embodiments, the electrolyte solution further includes optional additives. For example, the additives may include a negative electrode film-forming additive, a positive electrode film-forming additive, and may further include additives that can improve specific battery characteristics, such as an additive that improves the overcharge characteristics of the battery, or an additive that improves the high-temperature or low-temperature characteristics of the battery.

[0179] In some embodiments, the electrode assembly further includes a separator. The present application does not particularly limit the type of the separator, and any known porous structure separator having good chemical stability and mechanical stability can be selected.

[0180] In some embodiments, the material of the separator can include at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, and is not particularly limited.

[0181] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be fabricated into an electrode assembly via a winding or lamination process.

[0182] In some embodiments, the electrode assembly can include a sheath, which is used to encapsulate the electrode assembly and electrolyte.

[0183] In some embodiments, the exterior material of the electrode assembly may be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The exterior material of the electrode assembly may be a soft pack, such as a pouch-type soft pack, etc. The material of the soft pack may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0184] The present application does not particularly limit the shape of the electrode assembly, and it may be cylindrical, rectangular, or any other shape. For example, FIG. 3 shows a secondary battery 5 having a rectangular structure as an example.

[0185] In some embodiments, referring to FIG. 4, the exterior material may include a housing 51 and a cover plate 53. The housing 51 includes a bottom plate and a side plate connected to the bottom plate, and a receiving cavity surrounded by the bottom plate and the side plate is formed. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can cover the opening to seal the receiving cavity. The electrode assembly 52 may be formed from a positive electrode sheet, a negative electrode sheet and a separator through a winding process or a lamination process. The electrode assembly 52 is sealed in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. ​​The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and can be selected by those skilled in the art according to specific practical requirements.

[0186] In some embodiments, the electrode assembly can be assembled into a battery module, and the number of electrode assemblies included in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0187] Fig. 5 shows an example of a battery module 4. Referring to Fig. 5, in the battery module 4, a plurality of secondary batteries 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they may be arranged in any other manner. The plurality of secondary batteries 5 can be fixed by fasteners.

[0188] Optionally, the battery module 4 may further include an outer case having an accommodation space in which a plurality of secondary batteries 5 are accommodated.

[0189] 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 one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0190] 6 and 7 show an example of a battery pack 1. Referring to Fig. 6 and Fig. 7, 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 may be placed over the lower housing 3 to form 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.

[0191] The present application further provides a power consuming device including at least one of the electrode assembly, battery module, or battery pack according to the present application. The electrode assembly, battery module, or battery pack may be used as a power source for the power consuming device, or may be used as an energy storage element for the power consuming device. The power consuming device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), trains, ships, satellites, energy storage systems, etc.

[0192] As the power consuming device, an electrode assembly, a battery module or a battery pack can be selected according to its usage requirements.

[0193] 8 is an example of a power consuming device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. A battery pack or a battery module can be used to meet the requirements of high power and high energy density of the electrode assembly of the power consuming device.

[0194] Another example of the device may be a mobile phone, a tablet computer, a laptop, etc. Such devices are generally required to be lightweight and thin, and may use an electrode assembly as a power source.

[0195] Working Example The following is a description of the examples of the present application. The examples described below are illustrative and are only intended to explain the present application, and should not be understood as limiting the present application. If no specific techniques or conditions are shown in the examples, they are carried out according to the techniques or conditions described in the literature in this field, or according to the product instructions. If no manufacturer is listed for the reagents or equipment used, they are all commercially available general products.

[0196] Preparation of the first polymer emulsion Manufacturing example A1 Based on the mass ratio of the three monomers of 90:5:5, the first polymerized monomer, methyl acrylate, the second polymerized monomer, acrylic acid, and the third polymerized monomer, acrylamide, are weighed and mixed uniformly. 1000g of mixed monomers, 30g of sodium dodecyl sulfate emulsifier, 10g of ammonium persulfate initiator, and 1200g of deionized water are added to a 5000mL four-neck flask equipped with a mechanical stirrer, a thermometer, and a condenser, and emulsified for 30min by high-speed stirring. Under nitrogen gas protection, the temperature is raised to 75℃ and reacted for 4h, then cooled to below 40℃, the pH is adjusted to neutral, and the mixture is filtered and discharged. The first polymer emulsion A1 is obtained.

[0197] Regarding Production Examples A2 to A14, in Production Examples A2 to A14, first polymer emulsions A2 to A14 are obtained by adjusting the types and mass ratios of monomers based on Production Example A1.

[0198] Preparation of the Second Polymer Emulsion Manufacturing example B1 Based on the mass ratio of the three monomers of 80:10:10, the first polymerized monomer methyl acrylate, the second polymerized monomer acrylamide, and the third polymerized monomer acrylonitrile are weighed and mixed uniformly. 200g of mixed monomers, 6g of sodium dodecyl sulfate emulsifier, 2g of ammonium persulfate initiator, and 300g of deionized water are added to a 1000mL four-neck flask equipped with a mechanical stirrer, a thermometer, and a condenser, and emulsified for 30min with high speed stirring. Under nitrogen gas protection, the temperature is raised to 75℃ and reacted for 4h, then cooled to below 40℃, the pH is adjusted to neutral, and the mixture is filtered and discharged. The second polymer emulsion B1 is obtained.

[0199] Regarding Production Examples B2 to B14, in Production Examples B2 to B14, second polymer emulsions B2 to B14 are obtained by adjusting the types and mass ratios of monomers based on Production Example B1.

[0200] Example 1 Binder manufacturing Based on the weight ratio of the first polymer to the second polymer of 1:1, the first polymer emulsion A1 and the second polymer emulsion B2 are weighed and stirred to be uniformly mixed, and then the separator binder is produced through a spray drying process, and the conditions of the spray drying process are an intake temperature of 110°C, an exhaust temperature of 50°C, and an air pressure of 0.5 kPa.

[0201] Examples 2 to 23 are obtained based on Example 1 by adjusting the types of the first polymer emulsion and the second polymer emulsion, as well as the mass ratio and Dv50.

[0202] Comparative Example 1 and Comparative Example 2 Based on Example 1, the types of the first polymer emulsion and the second polymer emulsion are adjusted to obtain Comparative Example 1 and Comparative Example 2.

[0203] In Comparative Example 3, based on Example 1, only the second polymer emulsion was weighed, and the binder for separator, Comparative Example 3, was produced through a spray drying process under the same conditions.

[0204] In Comparative Example 4, based on Example 1, only the first polymer emulsion was weighed, and the binder for separator, Comparative Example 4, was produced through a spray drying process under the same conditions.

[0205] Separator manufacturing A commercially available PE microporous film with a thickness of 7 μm and an average pore size of 80 nm (obtained from Zhuogao Electronics Technology Co., Ltd.) is used as the substrate. The separator binder prepared by the above method is uniformly stirred and mixed in deionized water to obtain a paste (solid content 20%). The paste is applied to both sides of the substrate and dried to remove the solvent, and the coating density of the coating composition on the substrate is 1.5 g / m 2 and a separator is obtained.

[0206] Manufacture of positive electrode sheets A positive electrode paste is produced by thoroughly stirring and homogeneously mixing polyvinylidene fluoride (PVDF), lithium iron phosphate (LFP), carbon black as a conductive agent, and N-methylpyrrolidone (NMP) in a mass ratio of 1.2:58.38:0.42:40. The positive electrode paste is 200 g / m 2 The aluminum foil positive electrode current collector is uniformly coated with the carrier in an amount of 0.1g / g, and then dried, cold pressed, and cut to obtain a positive electrode sheet.

[0207] Manufacture of negative electrode sheets The artificial graphite, the conductive agent acetylene black, the binder styrene butadiene rubber (SBR), and the thickener sodium carboxymethylcellulose (CMC-Na) are added to deionized water in a mass ratio of 96.2:1.0:1.6:1.2, and thoroughly stirred to mix uniformly to produce a negative electrode paste (solid content 63%). 2 After coating the copper foil of the negative electrode current collector with the carrier in an amount of 1000g, the negative electrode sheet is obtained by drying, cold pressing, and cutting.

[0208] Electrolyte production At 25°C, ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain a mixed solvent, and then LiPF6 is dissolved in the above mixed solvent to obtain an electrolyte solution, in which the concentration of LiPF6 is 1 mol / L.

[0209] Secondary battery manufacturing The positive electrode sheet, separator, and negative electrode sheet are laminated and wound in this order, and cold press molding is performed (during which the separator and polar sheet are bonded together) to obtain a cell. The cell is then placed in an exterior material, and the above-prepared electrolyte is added. A secondary battery is obtained through processes such as sealing, leaving it to stand, chemical conversion, and aging.

[0210] Performance Testing (1) Glass transition temperature test A sample of 6±0.05mg was weighed and placed in an Al crucible, flattened, and covered with a lid. The sample was measured using a Netzsch DSC 3500 Sirius. The nitrogen gas atmosphere was used, with a purge gas rate of 50mL / min and a protective gas rate of 100mL / min. The heating conditions were a heating rate of 10℃ / min and a temperature range of -70 to 200℃.

[0211] (2) Particle size measurement Measurements were performed using a laser particle sizer (Malvern 3000, MasterSizer3000), with a helium-neon red light source used as the main light source. Place 1 g of the sample to be measured in a clean small beaker, add 1 drop of surfactant and 20 ml of deionized water, and ultrasonicate at 53 KHz / 120 W for 5 min to completely disperse the sample. Start the laser particle sizer, clean the optical path system, and then automatically measure the background. Stir the ultrasonically treated solution to be measured, disperse it evenly, and if necessary, put it into the sample cell to start measuring the particle size. Read the measurement results from the device.

[0212] (3) Measurement step of cold press adhesion The battery negative electrode sheet and separator are stacked and placed in a heat press, and the parameters of the heat press are set to 25°C temperature, 7t pressure, and 15s time. Pressurize to obtain a bonded separator / positive electrode sheet sample, and cut the separator / negative electrode sheet sample into a 150mm x 20mm rectangular strip. One side of the polar sheet of the rectangular strip is attached to a steel plate with double-sided tape, and at one end of the rectangular strip, the separator and polar sheet are separated by a length of 2cm along the length to create a test sample.

[0213] The steel plate is held horizontally and fixed with the lower clamp of a universal testing machine (Xieqiang Instrument Manufacturing (Shanghai) Co., Ltd., model CTM2100), and the peeled end of the separator is fixed with the upper clamp of the universal testing machine and connected to a tensile machine. The measurement conditions are set to a tensile speed of 20 mm / min and a horizontal tensile of 10 cm. After the tensile force is stabilized, the tensile force value is recorded, and the adhesive strength between the separator and the polar sheet is obtained by the ratio of the tensile force value to the sample width.

[0214] (4) Cell hardness measurement step The cell is placed on a table with both ends horizontal, the width of the hollow part in the center is fixed at 12 cm, the cell is laid naturally flat, and the width by which the center position of the cell deviates from the horizontal reference line is measured to evaluate the hardness of the cell. The greater the width by which the center position of the cell deviates from the horizontal reference line, the lower the hardness of the cell.

[0215] (5) Measurement of battery cycle characteristics At 25°C, the manufactured battery is charged to 3.65V at a constant current of 1 / 3C, further charged at a constant voltage of 3.65V until the current becomes 0.05C, left for 5 minutes, and further discharged to 2.5V at 1 / 3C, the obtained discharge capacity is the initial capacity C0, and the above steps are repeated for the same battery, and at the same time, the discharge capacity Cn of the battery after n cycles is recorded, and the battery capacity retention rate after each cycle is Pn = (Cn / C0) x 100%. The battery capacity retention rate after 500 cycles can show the difference in cycle characteristics.

[0216] [Table 1]

[0217] [Table 2]

[0218] [Table 3]

[0219] [Table 4]

[0220] By preparing the first polymer and the second polymer with suitable monomers, controlling the glass transition temperatures of the first polymer and the second polymer within a suitable range, and obtaining the binder through a spray drying process, the obtained binder has good adhesive performance within a suitable range, and can be applied to the separator to improve the performance of the battery.

[0221] The above is merely a preferred embodiment of the present application, and does not limit the scope of the patent of the present application. Under the application concept of the present application, any equivalent structural transformation made by utilizing the contents of the specification and drawings of the present application, or any direct / indirect application to other related technical fields, is included in the scope of protection of the patent of the present application.

Claims

1. A binder for a secondary battery comprising an organic polymer, the organic polymer having a first glass transition temperature and a second glass transition temperature, the first glass transition temperature being 25°C or less and the second glass transition temperature being higher than 25°C.

2. 2. The binder for secondary batteries according to claim 1, wherein the range of the first glass transition temperature is from -80°C to 25°C, preferably from -60°C to 25°C.

3. 3. The binder for secondary batteries according to claim 1, wherein the range of the second glass transition temperature is 26°C to 100°C, preferably 26°C to 90°C.

4. The binder for a secondary battery according to any one of claims 1 to 3, wherein the organic polymer includes an acrylic acid ester copolymer, and / or the organic polymer includes at least one of an ester group, a carboxyl group, an acrylamide group, a carbonyl group, an amide group, and a nitrile group.

5. The binder for secondary batteries according to any one of claims 1 to 4, wherein the shape includes a spherical shape.

6. The binder for secondary batteries according to any one of claims 1 to 5, wherein the volume-based particle size distribution Dv50 is 1 µm to 15 µm, preferably 5 µm to 10 µm, and / or the number-based particle size distribution Dn10 is 1 µm to 5 µm, preferably 1 µm to 3 µm.

7. The binder for a secondary battery according to any one of claims 1 to 6, wherein the organic polymer includes a first polymer and a second polymer, and the first polymer and the second polymer include an acrylic acid ester-based copolymer.

8. The binder for secondary batteries according to claim 7, wherein the range value of the mass ratio of the first polymer to the second polymer is 1:(0.1 to 10), preferably 1:(0.5 to 3).

9. The first polymer and / or the second polymer includes a first polymerizable monomer, and the first polymerizable monomer includes a structure represented by formula (1), 【Chemistry 9】 9. The binder for a secondary battery according to claim 7, wherein in formula (1), R1 contains a hydrogen atom or an alkyl group having 1 to 12 carbon atoms, and R2 contains an alkyl group having 1 to 12 carbon atoms.

10. 10. The binder for a secondary battery according to claim 9, wherein the first polymerizable monomer comprises one or more of methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, n-propyl acrylate, cyclohexyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate.

11. The first polymer includes a second polymerizable monomer, and the second polymerizable monomer includes a structure represented by formula (2), 【Chemistry 10】 The binder for a secondary battery according to any one of claims 7 to 10, wherein in formula (2), R3 contains a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms.

12. 12. The binder for a secondary battery according to claim 11, wherein the second polymerizable monomer comprises one or more of acrylic acid, methacrylic acid, crotonic acid, and heptenoic acid.

13. The first polymer and / or the second polymer includes a third polymerizable monomer, and the third polymerizable monomer includes a structure represented by formula (3), 【Chemistry 11】 In formula (3), R4 includes a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R5 includes a hydrogen atom, a hydroxyl group-substituted alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. The binder for a secondary battery according to any one of claims 7 to 12.

14. 14. The binder for a secondary battery according to claim 13, wherein the third polymerizable monomer comprises one or more of acrylamide, N-methylolacrylamide, and N-butoxymethylacrylamide.

15. The second polymer includes a fourth polymerizable monomer, and the fourth polymerizable monomer includes a structure represented by formula (4), 【Chemistry 12】 The binder for a secondary battery according to any one of claims 7 to 14, wherein in formula (4), R6 contains a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

16. 16. The binder for a secondary battery according to claim 15, wherein the fourth polymerized monomer comprises one or more of acrylonitrile, methacrylonitrile.

17. A method for producing the binder for a secondary battery according to any one of claims 1 to 16, a step of mixing water, an emulsifier, an initiator, and constituent monomers of a first polymer by stirring and reacting them by heating to obtain a first polymer emulsion; a step of mixing water, an emulsifier, an initiator, and constituent monomers of the second polymer by stirring and reacting them by heating to obtain a second polymer emulsion; a step of mixing the first polymer emulsion and the second polymer emulsion by stirring, and spray-drying the mixture to obtain a binder.

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

19. 20. A battery cell comprising the separator of claim 18.

20. A battery comprising the battery cell of claim 19.

21. 21. A power consuming device comprising a battery cell according to claim 19 or a battery according to claim 20.

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