Binder for secondary battery and manufacturing method thereof, 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 technical field of secondary batteries, and more particularly to binders for secondary batteries and methods for producing the same, as well as separators, battery cells, batteries, and power consuming devices. [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 increasing attention.

[0004] Currently, battery cells have the 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. Summary of the Invention

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

[0006] To achieve the above object, the present application provides a binder for a secondary battery, the binder 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.

[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 pressure. The separator and polar sheet have voids in their structures. When pressure acts on the organic polymer, part of the organic polymer structure can penetrate into the voids in the separator and polar sheet, bonding the separator and binder together and providing a mechanical interlocking effect, thereby 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 rubbery state, while the structure containing the second glass transition temperature of the organic polymer is in a glassy state, resulting in the binder having the property of being both "soft and hard." After being applied to the separator, the binder is not viscous at a certain temperature and without pressure, meeting the requirements for winding and unwinding the separator. When a certain pressure is applied, the binder becomes pressure-sensitive, exhibiting excellent adhesion and meeting the requirements for adhesion between the separator and the positive and negative polarity sheets.

[0009] Therefore, when the binder of the present invention is used to apply a separator, the binder has no adhesive properties at a certain temperature, making it easy to wind and unwind the separator, but when the positive and negative electrode polar sheets are wound and subjected to a cold press process, the binder has excellent adhesive strength, tightly bonding the positive and negative electrode polar sheets and the separator to each other. Therefore, the binder of the present invention improves the cold press adhesive strength between the separator and the positive and negative electrode 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, and 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 remains in a rubbery state at a certain temperature, which helps the organic polymer to exert its adhesive properties during the cold pressing process, favors the adhesion between the separator and the polar sheet after cold pressing, and improves the performance of the battery.

[0012] Preferably, the second glass transition temperature ranges from 26°C to 100°C, and more preferably from 26°C to 90°C.

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

[0014] Preferably, the organic polymer includes an acrylic 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.

[0015] Acrylic acid ester copolymers have good adhesive properties, and the use of acrylic acid ester copolymers can further improve the adhesiveness 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 helps to adjust the glass transition temperature of the polymer within an appropriate range.

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

[0018] The acrylamide group serves to polymerize the monomer, which acts to control the molecular weight and at the same time has good adhesive properties.

[0019] The carbonyl group and 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 helps 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 1 μm to 5 μm, preferably 1 μm to 3 μm.

[0024] Theoretically, the volumetric particle size distribution Dv50 of the binder in this application can be less than 1 μm or greater than 15 μm. However, considering that the binder in this application is used in a separator, a volumetric particle size distribution Dv50 of the binder that is too large or too small is inappropriate. This prevents the binder from blocking the separator channels, reduces the problem of lithium ions (here, lithium ion secondary batteries are used as an example, but other types of secondary batteries can also be used) passing through the separator, and further alleviates the problem of the binder forming a thick coating on the separator, which affects the energy density of the battery that is subsequently manufactured. 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, reducing the problem of lithium ions (here, a lithium ion secondary battery is used as an example, but other types of secondary batteries may also be used) passing through the separator, and further, the problem of the binder forming a thick coating film when applied to the separator, which affects the energy density of the battery to be manufactured later, can be alleviated. 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 includes a first polymer and a second polymer, and the first polymer and the second polymer include an acrylic ester copolymer.

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

[0028] Acrylic acid ester copolymers have good adhesive properties, and the use of acrylic acid ester copolymers can further improve the adhesiveness between the separator and the polar sheet after cold pressing.

[0029] Preferably, the mass ratio of the first polymer to the second polymer is in the range of 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, it is possible to alleviate the problem of the binder being too soft and affecting cell performance, for example, by reducing the possibility of the binder being too soft clogging the pores of the separator, and also by reducing the problem of the binder being too hard and affecting adhesive properties. 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. Furthermore, as a flexible monomer segment in the molecular segment, it can adjust the glass transition temperature of the organic polymer, helping to adjust the glass transition temperature of the polymer within 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 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. The first polymer contains a second polymerizable monomer containing a carboxyl group, so that during the cold pressing process of pressing the separator and polar sheet together, the carboxyl group can form a bond with the functional groups on the polar sheet and separator materials, improving the adhesive effect.

[0037] Preferably, the second polymerized monomer comprises one or more of acrylic acid, methacrylic acid, crotonic acid, and 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 useful for the polymerization of the monomer, and the monomer functions to regulate 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-methylolacrylamide, and N-butoxymethylacrylamide.

[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 adhesiveness within a certain range of the molecular weight of the binder.

[0043] Preferably, the second polymer contains a fourth polymerizable monomer, and the fourth polymerizable monomer contains 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 useful for the polymerization of the monomer, improves 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 under 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 under heating to obtain a second polymer emulsion; a step of mixing the first polymer emulsion and the second polymer emulsion by stirring, and then spray-drying the mixture 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 the 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-described binder for a secondary battery or a binder produced by the above-described method for producing a binder for a secondary battery.

[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 explanation 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 any creative efforts.

[0056] [Figure 1] 1 is a scanning electron microscope image of a binder according to Example 1 of the present application. [Figure 2] 1 is a flowchart of a method for producing a binder according to an embodiment of the present application. [Figure 3] 1 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. [Figure 5]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 invention 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 housing 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 function of the present invention will be further explained in combination with the embodiments and with reference to the drawings. DETAILED DESCRIPTION OF THE INVENTION

[0059] The technical solutions in the embodiments of the present application will be described below clearly and completely with reference to the drawings in the embodiments of the present application, and it is obvious that 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 fall within the scope of protection of the present application.

[0060] Hereinafter, embodiments of the binder and its manufacturing method, as well as separators, electrode assemblies, battery cells, batteries, and power consuming devices containing the binder, according to the present application, will be described in detail with reference to the accompanying drawings as appropriate. However, unnecessary details may be omitted. For example, detailed descriptions of well-known matters and redundant descriptions of substantially identical structures may be omitted. This is to avoid unnecessary redundancy in the following description 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 terms of lower and upper limits. 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 be inclusive or exclusive of 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 to 120 and 80 to 110 are recited for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Also, if minimum range values ​​of 1 and 2 are recited and maximum range values ​​of 3, 4, and 5 are recited, then the ranges of 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5 are all contemplated. Unless otherwise specified, the numerical range "a to b" herein is a shorthand notation for any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 and 5" are recited herein, and "0 to 5" is merely a shorthand notation for combinations of these numbers. 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 alternative 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 order or randomly, and are preferably performed in order, unless otherwise specified. For example, when the method includes steps (a) and (b), this means that the method may include steps (a) and (b) performed in order, or may include steps (b) and (a) performed in order. For example, when the method may further include step (c), this means that step (c) may be added to the method in any order, such as 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" used herein refer to both open and closed forms 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 separators is polyvinylidene fluoride, but at present, the price of polyvinylidene fluoride fluctuates greatly and the market supply is limited, and at the same time, a hot pressing process is required to tightly bond the separator and polar sheet. As production speeds increase, the hot pressing process is gradually being replaced by a cold pressing process, and the cold pressing of battery polar sheets stabilizes the winding core, reduces the elasticity of the cell, and improves the pass rate of cell installation and the consistency of the thickness of the finished cell.

[0069] Insufficient adhesion between the positive and negative electrode sheets and the separator will result in cell opening and poor electrolyte penetration, making it impossible to meet the performance requirements for coated separators in secondary batteries. A tight bond between the separator and polar sheet can improve the battery's discharge capacity, reduce internal resistance, reduce polarization loss, extend the battery's cycle life, and improve the utilization rate of secondary batteries.

[0070] As is 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 sheets and the separator are bonded together and supported by each other, forming a structure with a certain thickness, and this structure with a certain thickness has a certain hardness. The negative electrode expands during charging and discharging. If the adhesive strength is weak, gaps will form between the positive and negative electrode sheets and the separator, and the positive and negative electrode sheets and the separator will not be bonded together and will not support each other, causing the cell to loosen and its hardness to decrease. This will result in a deterioration in the power performance of the cell, such as a decrease in rate characteristics and a decrease in cycle characteristics. For example, in an electric vehicle, loose battery cells will slow down the battery's charging speed and simultaneously deteriorate the battery's cycle characteristics, directly leading to a shortened battery life, requiring frequent battery replacement in the electric vehicle, and increasing the cost to electric vehicle consumers.

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

[0074] As can be understood, if 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 if 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 the binder is in a glassy state. The organic polymer structure containing the second glass transition temperature is hard and can serve as the skeletal structure of the binder powder material without imparting viscosity to the binder. The first glass transition temperature is lower than room temperature and the organic polymer structure containing the first glass transition temperature is in a rubbery state at room temperature and can have a certain "fluidity" after applying a certain pressure. The organic polymer structure containing the first glass transition temperature can fully penetrate into the voids of the positive and negative electrode sheets and the separator, increasing the mechanical interlocking effect and fully demonstrating its adhesive performance, further 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 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, part of the organic polymer structure can penetrate into the voids in the separator and polar sheet, bonding the separator and binder together and providing a mechanical interlocking effect, thereby realizing the adhesive function.

[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 rubbery state, while the structure containing the second glass transition temperature of the organic polymer is in a glassy state, resulting in the binder having the property of being both "soft and hard." After being applied to the separator, the binder is not viscous at a certain temperature and without pressure, meeting the requirements for winding and unwinding the separator. When a certain pressure is applied, the binder becomes pressure-sensitive, exhibiting excellent adhesion and meeting the requirements for adhesion between the separator and the positive and negative polarity sheets.

[0078] Therefore, when the binder of the present invention is used to coat a 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 electrode polar sheets are wound and subjected to a cold press process, the binder has excellent adhesive strength, tightly bonding the positive and negative electrode polar sheets and the separator to each other. Therefore, the binder of the present invention improves the cold press adhesive strength between the separator and the positive and negative electrode 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, but not limited to, −100° C., −90° C., −80° C., −70° C., −50° C., −30° C., −10° C., 10° C., 20° C., 24° C., 25° C., and ranges between any two of the above endpoints.

[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 ranges between any two of the above endpoints, without being specifically limited.

[0081] In one embodiment, the first glass transition temperature range 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 remains in a rubbery state at a certain temperature, which helps the organic polymer to exert its adhesive properties during the cold pressing process, favors the adhesion between the separator and the polar sheet after cold pressing, and improves 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 endpoint 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., as well as range values ​​between any two of the endpoint 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 endpoint 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., as well as range values ​​between any two of the endpoint values, but are not specifically limited.

[0085] In one embodiment, the second glass transition temperature range 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, which is in a glassy state at a certain temperature and serves to form a skeletal structure for the binder at a certain temperature, and the binder does not have viscosity, facilitating 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 endpoint 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 endpoint 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 endpoint 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 endpoint values, but are not specifically limited.

[0089] In one embodiment, 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.

[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, such as methyl acrylate, ethyl acrylate, or n-butyl acrylate.

[0093] Acrylic acid ester copolymers have good adhesive properties, and the use of acrylic acid ester copolymers can further improve the adhesiveness between the separator and the polar sheet after cold pressing.

[0094] The organic polymer structure is tested for ester, carboxyl, acrylamide, carbonyl, amide, and nitrile groups in accordance with the national standard GB / T 6040-2002, General Rules for Infrared Spectroscopy. The sample is pelletized using KBr transmission. A KBr background blank is subtracted from the sample's test spectrum (resolution: 4 cm). -1 , Wavenumber 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 helps to adjust the glass transition temperature of the polymer within an appropriate range.

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

[0097] The acrylamide group serves to polymerize the monomer, which acts to control the molecular weight and at the same time has good adhesive properties.

[0098] The carbonyl group and 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 helps 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 1 μm to 5 μm, preferably 1 μm to 3 μm.

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

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

[0105] Theoretically, the volumetric particle size distribution Dv50 of the binder in this application can be less than 1 μm or greater than 15 μm. However, considering that the binder in this application is used in a separator, a volumetric particle size distribution Dv50 of the binder that is too large or too small is inappropriate. This prevents the binder from blocking the separator channels, reduces the problem of lithium ions (here, lithium ion secondary batteries are used as an example, but other types of secondary batteries can also be used) passing through the separator, and further alleviates the problem of the binder forming a thick coating on the separator, which affects the energy density of the battery that is subsequently manufactured. 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, reducing the problem of lithium ions (here, a lithium ion secondary battery is used as an example, but other types of secondary batteries may also be used) passing through the separator, and further, the problem of the binder forming a thick coating film when applied to the separator, which affects the energy density of the battery to be manufactured later, can be alleviated. 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 this minimum and maximum value. Specific examples include, but are not limited to, the endpoint 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 endpoint 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, but are not limited to, the endpoint 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 endpoint values.

[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, but are not limited to, the endpoint values ​​in the examples and 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, etc., and range values ​​between any two of the endpoint values.

[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, but are not limited to, the endpoint 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 endpoint values.

[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, includes an organic polymer of the first polymer and the second polymer, the organic polymer including a first glass transition temperature and a second glass transition temperature.

[0113] Acrylic acid ester copolymers have good adhesive properties, and the use of acrylic acid ester copolymers can further improve the adhesiveness between the separator and the polar sheet after cold pressing.

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

[0115] The binder is a secondary particle formed by the aggregation of primary particles of the first polymer and primary particles of the second polymer, and both the primary particles of the first polymer and the primary particles of the second polymer have the 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 can be 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, it is possible to alleviate the problem of the binder being too soft and affecting cell performance, for example, by reducing the possibility of the binder being too soft clogging the pores of the separator, and also by reducing the problem of the binder being too hard and affecting adhesive properties. 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 value includes 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 endpoint 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 endpoint 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 this minimum and maximum value. Specific examples include, but are not limited to, the endpoint values ​​in the examples and range values ​​between any two of the endpoint values, such as 1:0.5, 1:1.5, 1:2, 1:2.5, 1:3, etc.

[0119] As can be seen from 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 serves as the skeleton within the binder. When the binder is not compressed, it has no adhesive properties. When compressed, the first polymer is deformed under the force and penetrates into the gaps between the separator and polar sheet, thereby achieving an 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. Furthermore, as a flexible monomer segment in the molecular segment, it can adjust the glass transition temperature of the organic polymer, helping to adjust the glass transition temperature of the polymer within 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 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 polymeric monomer, and the structure of the second polymeric 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. The first polymer contains a second polymerizable monomer containing a carboxyl group, so that during the cold pressing process of pressing the separator and polar sheet together, the carboxyl group can form a bond with the functional groups on the polar sheet and separator materials, improving the adhesive effect.

[0127] In one embodiment, the second polymerized 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 useful for the polymerization of the monomer, and the monomer functions to regulate 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-methylolacrylamide, and N-butoxymethylacrylamide.

[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 adhesiveness within a certain range of the molecular weight of the binder.

[0133] In one embodiment, the second polymer comprises a fourth polymeric monomer, and the structure of the fourth polymeric monomer is [ka] and R6 includes 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 useful for the polymerization of the monomer, improves 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] Conventional polyvinylidene fluoride binders require a hot pressing process to achieve better adhesion. As production speeds increase and capacity savings become more apparent, the hot pressing process is gradually being replaced by a cold pressing process. Cold pressing is performed after winding the cell, but typical polyvinylidene fluoride is a homopolymer with a crystallinity of approximately 50%, resulting in poor adhesion between the separator and the positive and negative electrode sheets. Conventional polyacrylic ester binders also lack the required adhesion under cold pressing, resulting in cell openings and cell softness. At the same time, their poor electrolyte penetration prevents them from meeting the performance requirements for coated separators in secondary batteries.

[0138] The acrylic ester copolymer prepared using the above monomers provides a binder with excellent adhesive properties. The binder includes a first polymer and a second polymer. The first polymer is prepared by emulsion polymerization of at least two of the first, second, and third polymer monomers. The first polymer exhibits superior performance when composed of the three monomers. The second polymer emulsion is prepared by emulsion polymerization of at least two of the first, third, and fourth polymer monomers. The second polymer exhibits superior performance when composed of the three monomers. The first and second polymers prepared using the above monomers have suitable glass transition temperatures. When applied to a separator, they not only satisfy the binder's non-adhesive properties at room temperature, but also meet the cold-press adhesive strength requirements between the separator and the positive and negative electrode sheets during the cold-press process, improving cell hardness and resolving issues such as cell opening and softness. At the same time, the binder can be applied to a separator and used in a secondary battery, thereby improving 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, i.e., 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] Regarding emulsifiers, they are substances that convert insoluble oil and water 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 initiators, initiators are substances that can initiate the polymerization reaction of monomers. For example, radical initiators refer to compounds that can easily decompose under heat to form radicals (i.e., primary radicals), and can be used to initiate the radical polymerization and copolymerization of olefin and diene monomers.

[0144] Water, an emulsifier, an initiator, and the constituent monomers of the polymer are mixed by stirring, and after the water and emulsifier are stirred and dispersed, an emulsion is formed. 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, resulting in an emulsion.

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

[0146] A binder composed of the first polymer and the second polymer is obtained by the spray drying process.

[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 mass ratio of the first polymer to 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 to 10), preferably 1:(0.5 to 3).

[0149] The present invention also provides a separator including the binder or a binder manufactured by the method for manufacturing a binder for a secondary battery. The binder uses 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 therefore further description thereof is omitted here.

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

[0151] The present invention also 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 therefore further description thereof is omitted here.

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

[0153] The embodiments of the present application further provide a battery including the above battery cell, which 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 therefore further 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 consumption device including the above battery cell or the above battery, which 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 therefore 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] Generally, an electrode assembly includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During the charge and discharge process of a battery, active ions are inserted and removed between the positive electrode sheet and the negative electrode sheet. 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 to prevent short-circuiting between the positive and negative electrodes while allowing ions to pass through. The separator is the improved separator described above.

[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 surfaces facing each other in the thickness direction thereof, and the positive electrode film layer is provided on one or both of the two facing 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, 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, or silver alloy) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0162] In some embodiments, when the electrode assembly is a lithium-ion battery, the positive electrode active material can be a known positive electrode active material for batteries. As an example, the positive electrode active material may include at least one of a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide, and a modified compound thereof. 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 also 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., LiCoO), lithium nickel oxide (e.g., LiNiO), lithium manganese oxide (e.g., LiMnO, LiMnO), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, and 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 modified compounds thereof, etc. The lithium-containing phosphate having an olivine structure may include, but is not limited to, for example, at least one of 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 may further include a binder, such as at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0164] In some embodiments, the positive electrode film layer may further include an optional conductive agent, such as 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, followed by steps such as drying and cold pressing, to obtain a positive electrode sheet.

[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 surfaces facing each other in the thickness direction thereof, and the negative electrode film layer is provided on one or both of the two facing 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, or silver alloy) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0169] In some embodiments, the negative electrode active material may be a known battery negative electrode active material. For example, the negative electrode active material may include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. 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 usable as negative electrode active materials in batteries may also be used. These negative electrode active materials may be used alone or in combination.

[0170] In some embodiments, the negative electrode film layer may further include a binder, which may 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 may further include an optional conductive agent, which may 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 thickener (eg, sodium carboxymethyl cellulose (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 it can be selected as needed.

[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 optionally further contains additives. For example, the additives may include a negative electrode film-forming additive, a positive electrode film-forming additive, and / or an additive capable of improving 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 separator, and any known porous separator having good chemical and mechanical stability can be selected.

[0180] In some embodiments, the separator may be made of at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may 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 the layers may be the same or different, and are 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 housing of the electrode assembly may be a hard case such as a hard plastic case, an aluminum case, or a steel case. The housing of the electrode assembly may be a soft pack such as a pouch-type soft pack. The soft pack may be made of plastic, such as polypropylene, polybutylene terephthalate, or 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, Figure 3 shows an example of a secondary battery 5 with a rectangular structure.

[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, forming a storage cavity surrounded by the bottom plate and the side plate. The housing 51 has an opening communicating with the storage cavity, and the cover plate 53 can cover the opening and seal the storage 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 stacking process. The electrode assembly 52 is sealed in the storage cavity. An electrolyte is impregnated in the electrode assembly 52. ​​The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and this can be selected by those skilled in the art according to specific actual requirements.

[0186] In some embodiments, the electrode assemblies 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 depending on 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 order along the length of the battery module 4. Of course, any other arrangement may be used. The plurality of secondary batteries 5 can also be fixed by fasteners.

[0188] Optionally, the battery module 4 may further include an outer case having an accommodating space for accommodating a plurality of secondary batteries 5.

[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 FIGS. 6 and 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 can be fitted 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 also 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 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 the requirements of its use.

[0193] 8 shows an example of a power consuming device, such as 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 electrode assembly of the power consuming device, a battery pack or a battery module can be used.

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

[0195] Example The following examples are provided for the present application. The examples described below are illustrative and are intended to illustrate the present application only and should not be construed as limiting the present application. If specific techniques or conditions are not specified 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 the manufacturer of the reagents or equipment used is not specified, they are all commercially available general products.

[0196] Preparation of the first polymer emulsion Manufacturing example A1 Based on a 90:5:5 weight ratio of the three monomers, the first polymerizable monomer (methyl acrylate), the second polymerizable monomer (acrylic acid), and the third polymerizable monomer (acrylamide) were weighed and mixed uniformly. In a 5000mL four-neck flask equipped with a mechanical stirrer, thermometer, and condenser, 1000g of the mixed monomers, 30g of sodium dodecyl sulfate emulsifier, 10g of ammonium persulfate initiator, and 1200g of deionized water were added and emulsified for 30 minutes with high-speed stirring. Under nitrogen gas protection, the mixture was heated to 75°C and reacted for 4 hours. After that, the mixture was cooled to below 40°C, the pH was adjusted to neutral, and the mixture was filtered and discharged. Polymer Emulsion A1 was obtained.

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

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

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

[0200] Example 1 Binder manufacturing Based on a weight ratio of the first polymer to the second polymer of 1:1, the first polymer emulsion A1 and the second polymer emulsion B2 were weighed and mixed uniformly by stirring. Then, the mixture was spray-dried to produce a separator binder. The spray-drying conditions were an intake air temperature of 110°C, an exhaust air 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 Examples 1 and 2 Based on Example 1, Comparative Examples 1 and 2 are obtained by adjusting the types of the first polymer emulsion and the second polymer emulsion.

[0203] Comparative Example 3 is based on Example 1, except that only the second polymer emulsion is weighed and subjected to a spray drying process under the same conditions to produce Comparative Example 3 of a separator binder.

[0204] Comparative Example 4 is based on Example 1, except that only the first polymer emulsion is weighed and subjected to a spray drying process under the same conditions to produce Comparative Example 4 of the separator binder.

[0205] Separator manufacturing A commercially available 7 μm thick PE microporous film (obtained from Zhuogao Electronics Technology Co., Ltd.) with an average pore size of 80 nm was used as the substrate. The separator binder prepared by the above method was uniformly mixed in deionized water by stirring to obtain a paste (solid content 20%). The paste was applied to both sides of the substrate and dried to remove the solvent, resulting in a coating density of 1.5 g / m2 on the substrate. 2 and obtain the separator.

[0206] Positive electrode sheet manufacturing A positive electrode paste was prepared by thoroughly stirring and homogeneously mixing polyvinylidene fluoride (PVDF), lithium iron phosphate (LFP), conductive carbon black, and N-methylpyrrolidone (NMP) in a mass ratio of 1.2:58.38:0.42:40. The positive electrode paste was prepared at a concentration of 200 g / m. 2 The coated aluminum foil is then dried, cold pressed, and cut to obtain a positive electrode sheet.

[0207] Manufacture of negative electrode sheets Artificial graphite, acetylene black as a conductive agent, styrene butadiene rubber (SBR) as a binder, and sodium carboxymethyl cellulose (CMC-Na) as a thickener were added to deionized water in a mass ratio of 96.2:1.0:1.6:1.2, and the mixture was thoroughly stirred to homogeneously mix, producing a negative electrode paste (solid content 63%). 2 After coating the copper foil of the negative electrode current collector with the amount of the support, 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) were mixed in a volume ratio of 1:1:1 to obtain a mixed solvent, and then LiPF6 was dissolved in the mixed solvent to obtain an electrolyte solution with a LiPF6 concentration of 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, the above-prepared electrolyte solution is added, and a secondary battery is obtained through processes such as sealing, leaving it to stand, chemical conversion, and aging.

[0210] Performance Test (1) Glass transition temperature test A sample weighing 6±0.05 mg was weighed and placed in an aluminum crucible. The crucible was flattened and then covered with a lid. Measurements were performed using a Netzsch DSC 3500 Sirius. The nitrogen atmosphere was maintained with a purge gas flow rate of 50 mL / min and a protective gas flow rate of 100 mL / min. The heating conditions were a heating rate of 10°C / min and a temperature range of -70 to 200°C.

[0211] (2) Particle size measurement Measurements were performed using a laser particle sizer (Malvern 3000, MasterSizer 3000), with a helium-neon red light source as the main light source. 1 g of the sample to be measured was placed in a clean small beaker, and 1 drop of surfactant and 20 ml of deionized water were added. The sample was then sonicated for 5 minutes at 53 kHz / 120 W to completely disperse the sample. The laser particle sizer was then started, and the optical path system was cleaned, after which the background was automatically measured. The sonicated solution to be measured was stirred to disperse it evenly, and if necessary, the solution was poured into the sample cell, and particle size measurement was initiated. The measurement results were then read from the instrument.

[0212] (3) Measurement step of cold press adhesion The battery's negative electrode sheet and separator were stacked and placed in a heat press. The heat press parameters were set to 25°C, 7T, and 15 seconds, and a bonded separator / positive electrode sheet sample was obtained. The separator / negative electrode sheet sample was then cut into a 150mm x 20mm rectangular strip. One side of the polar sheet of the rectangular strip was attached to a steel plate with double-sided tape, and the separator and polar sheet were separated at one end of the rectangular strip by a length of 2cm along the length to create a test sample.

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

[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 resulting battery was charged to 3.65V at a constant current of 1 / 3C, then further charged at a constant voltage of 3.65V until the current reached 0.05C. After 5 minutes, the battery was discharged at 1 / 3C until the voltage reached 2.5V. The resulting discharge capacity was designated as the initial capacity, C0. The above steps were repeated for the same battery, and the discharge capacity, Cn, of the battery after n cycles was recorded. The battery capacity retention rate after each cycle, Pn, was calculated as (Cn / C0) × 100%. The battery capacity retention rate after 500 cycles can indicate differences 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 using appropriate monomers, controlling the glass transition temperatures of the first polymer and the second polymer within an appropriate range, and then obtaining the binder through a spray drying process, the obtained binder has good adhesive properties within an appropriate range, and when applied to separators, it is advantageous to improve the performance of batteries.

[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. Any equivalent structural transformation made using the contents of the specification and drawings of the present application under the application concept of the present application, or any direct or 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 separator of a secondary battery, an organic polymer, the organic polymer having a first glass transition temperature and a second glass transition temperature, the first glass transition temperature being less than or equal to 25°C and the second glass transition temperature being greater than 25°C; A binder for a separator of a secondary battery, wherein the secondary particles of the binder have a volume-based particle size distribution Dv50 of 5 μm to 15 μm.

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

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

4. 3. The binder for a separator of a secondary battery according to claim 1, wherein the organic polymer contains an acrylic acid ester copolymer.

5. The binder for a separator of a secondary battery according to claim 1 or 2, wherein the shape includes a spherical shape.

6. 3. The binder for a separator of a secondary battery according to claim 1, wherein the secondary particles of the binder have a volume-based particle size distribution Dv50 of 5 μm to 10 μm and / or a number-based particle size distribution Dn10 of the secondary particles of the binder of 1 μm to 5 μm.

7. 3. The binder for a separator of a secondary battery according to claim 1, 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 copolymer.

8. 8. The binder for a separator of a secondary battery according to claim 7, wherein the mass ratio of the first polymer to the second polymer is in the range of 1:(0.1 to 10).

9. the first polymer and / or the second polymer contains a first polymerizable monomer, and the first polymerizable monomer contains a structure represented by formula (1), 【Chemistry 1】 8. The binder for a separator of 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 separator of 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 2】 8. The binder for a separator of a secondary battery according to claim 7, wherein in formula (2), R3 comprises a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms.

12. 12. The binder for a separator of 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), 【Transformation 3】 8. The binder for a separator of a secondary battery according to claim 7, wherein in formula (3), R4 contains a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R5 contains 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.

14. 14. The binder for a separator of 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 4】 8. The binder for a separator of a secondary battery according to claim 7, 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 separator of a secondary battery according to claim 15, wherein the fourth polymerizable monomer comprises one or more of acrylonitrile and methacrylonitrile.

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

18. A separator for a secondary battery comprising the binder for a separator according to claim 1 .

19. 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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