Binder for secondary battery and manufacturing method thereof, separator, battery unit, battery and electric 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, as well as a separator, a battery unit, a battery, and an electric device containing the binder. The binder for secondary batteries includes a first polymer containing an acrylic acid ester copolymer and a second polymer containing a water-soluble polymer. When applying the binder to a separator, the binder is uniformly stirred in water, applied to the separator and dried, and an adhesive layer is formed on the separator, including a side facing the separator and a side facing away from the separator, and the adhesive layer adheres to the separator and the side facing away from the separator is not adhesive, thus making it easy to wind and unwind the separator. When the separator is wound with the positive electrode pieces and the negative electrode pieces and then subjected to a cold rolling process, the binder has excellent adhesive strength, which makes the positive electrode pieces and the negative electrode pieces closely bonded to the separator, thereby improving the hardness of the battery cell and the cycling performance of the secondary battery.

Description

[Technical Field]

[0001] The present application relates to the technical field of secondary batteries, and in particular to a binder for secondary batteries and a method for producing the same, as well as a separator, a battery unit, a battery, and an electric device. [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims priority to a Chinese patent application bearing application number 202310402475.2, filed on April 14, 2023, the entire contents of which are incorporated herein by reference. [Background technology]

[0002] With the rapid growth of portable electronic devices and electric vehicles, the demand for power batteries is also increasing, and the electrochemical performance of batteries is also attracting more and more attention.

[0003] Currently, there is a problem with large openings in battery cells, i.e., gaps are easily formed between the pole pieces and the separator, which reduces the cycling performance of the battery. Summary of the Invention

[0004] The main object of the present application is to provide a binder for secondary batteries that improves the adhesive strength between the separator and the pole pieces and improves the cycling performance of the battery.

[0005] To achieve the above object, the present application provides a binder for a secondary battery, which comprises a first polymer including an acrylic acid ester copolymer and a second polymer including a water-soluble polymer.

[0006] The acrylic ester copolymer has a relatively high adhesiveness, and the use of the acrylic ester copolymer results in a higher adhesiveness between the separator and the pole pieces after cold rolling.

[0007] Water-soluble polymers are soluble in water and are not viscous in their dry state.

[0008] The binder comprises a first polymer including an acrylic ester copolymer and a second polymer including a water-soluble polymer. When the binder is applied to the separator, the water-soluble polymer acts as a support to support the first polymer, linking the first polymer to the water-soluble polymer and adhering the first polymer to the separator. Specifically, in the process of applying the binder to the separator, the binder is mixed with water to form a slurry, and the slurry is then applied to the separator. The water-soluble polymer has adhesive properties after contact with water, allowing the water-soluble polymer to adhere to the separator, and the water-soluble polymer can adhere the first polymer (including the acrylic ester copolymer) to the separator. Part of the acrylic ester copolymer and / or the water-soluble polymer in the binder penetrates into the gaps in the separator and achieves adhesion to the separator. After the slurry dries, the water evaporates, causing the water-soluble polymer molecules to become entangled with each other, resulting in intermolecular interactions, thereby forming a network structure and allowing the first polymer (acrylic acid ester copolymer) to adhere to the separator. The water-soluble polymer (including the acrylic ester copolymer) serves as a support and connection for the first polymer particles, adhering them to the separator; the slurry layer becomes an adhesive layer after drying, and the adhesive layer has a side facing the separator and a side facing away from the separator. During the process of applying the slurry, the water-soluble polymer adheres to the separator, or part of the acrylic ester copolymer and / or water-soluble polymer in the binder penetrates into the gaps in the separator, thereby achieving adhesion to the separator, and the adhesive layer adheres to the separator; and since the acrylic ester copolymer and the water-soluble polymer are not viscous after drying, the side of the adhesive layer facing away from the separator is not viscous, which makes it easy to wind and unwind the separator.

[0009] When the positive and negative electrode pieces are wound and then subjected to a cold-rolling process, the binder has excellent adhesive strength, allowing the positive and negative electrode pieces to be tightly bonded to the separator. Specifically, after cold-rolling, the adhesive strength is mainly provided by the mechanical interlocking effect caused by the acrylic ester copolymer and water-soluble polymer in the binder penetrating into the gaps between the electrode pieces, and by the intermolecular interaction of the acrylic ester copolymer. Therefore, the binder of the present application improves the adhesive strength between the separator and the positive and negative electrode pieces during cold-rolling, reducing problems such as opening of battery cells and soft battery cells, thereby improving the hardness of the battery cell. At the same time, applying the binder to the separator in a secondary battery can improve the dynamic performance of the secondary battery, reduce electrochemical impedance, and improve the rechargeability and cycling performance of the secondary battery.

[0010] Optionally, the mass ratio of the first polymer to the second polymer is 1:(0.1 to 10), preferably 1:(0.2 to 5).

[0011] By setting the mass ratio of the first polymer to the second polymer within the above range, the adhesive layer forms a continuous network structure, which helps adhere the first polymer to the separator and improve the adhesiveness of the adhesive layer at room temperature.

[0012] In other words, in the process of changing from a smaller amount to a larger amount of the second polymer, the adhesive strength of the adhesive layer tends to increase and then decrease, and by controlling the mass of the first polymer and the second polymer within the above range, the adhesive strength of the binder applied to the separator is effectively improved.

[0013] Optionally, the second polymer comprises one or more of polyacrylamide, polyacrylic acid, polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, polymaleic anhydride.

[0014] The second polymer contains the water-soluble polymer, which contains both hydrophilic and hydrophobic groups, and therefore has a certain surface activity, reducing the surface tension of water to a certain extent and enhancing the solubility and dispersibility of the binder in the aqueous phase. When used to prepare a slurry for coating the separator, the water-soluble polymer controls the viscosity and rheological properties of the slurry, improving the dispersion and suspension of the binder. The second polymer also has chemically reactive functionality (e.g., carboxyl groups, hydroxyl groups, etc., that react with other groups). The polar groups in the water-soluble polymer structure can form hydrogen bonds between the first polymer and the separator and the pole pieces, improving the adhesion between the separator and the pole pieces.

[0015] Optionally, the binder has a volume particle size distribution Dv50 of 1 μm to 15 μm, preferably 3 μm to 12 μm.

[0016] Theoretically, the volume average particle diameter Dv50 of the binder in this application can be less than 1 μm or more than 15 μm. However, considering the application of the binder in this application to separators, setting the volume average particle diameter Dv50 of the binder in the above range alleviates the problem of the binder blocking the pores of the separator and reducing the permeability of lithium ions (for lithium ion batteries, for example, but of course other types of secondary batteries can also be used) through the separator, and the problem of the binder forming a thick coating layer when applied to the separator, which affects the energy density of the subsequently manufactured battery. Therefore, the volume particle diameter distribution Dv50 of the binder is 1 μm to 15 μm, preferably 3 μm to 12 μm.

[0017] As can be seen from FIG. 1, the binder particles are secondary particles comprising primary particles of a first polymer and primary particles of a second polymer. Thus, the second polymer acts as a backbone within the binder slurry. When the binder slurry is applied to the separator, the second polymer supports and connects the first polymer, adhering the first polymer to the separator. After the slurry dries to form an adhesive layer, the adhesive layer can adhere to the separator, but the side of the adhesive layer away from the separator has no adhesive strength, making it easy to wind and unwind the separator. When the separator is wound with the positive and negative electrode pieces and then subjected to a cold rolling process, the first and second polymers are deformed by force after being extruded and penetrate into the gaps between the separator and the electrode pieces, thereby achieving an adhesive effect.

[0018] Optionally, the shape of the binder comprises a sphere.

[0019] The spherical shape helps in uniform distribution and coating during the process of stirring the slurry.

[0020] Optionally, the first polymer comprises an acrylate ester monomer, and the structure of the acrylate ester monomer is: JPEG0007814419000001.jpg3454, wherein R1 is a hydrogen atom or an alkyl group containing 1 to 12 carbon atoms, and R2 is an alkyl group containing 1 to 12 carbon atoms.

[0021] The acrylic acid ester monomer contains an unsaturated ester group which can enhance the anti-swelling ability of the polymer, adjust the glass transition temperature of the polymer as a flexible monomer segment among the molecular segments, improve the flexibility of the binder during use, and help to exert good adhesive properties.

[0022] Optionally, the acrylic acid ester monomer includes 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.

[0023] By using one or more of the above acrylic acid ester monomers, the glass transition temperature of the polymer can be adjusted and the anti-swelling ability of the polymer can be improved.

[0024] Optionally, the first polymer comprises an acrylonitrile-based monomer, and the structure of the acrylonitrile-based monomer is: JPEG0007814419000002.jpg3233, where R3 is a hydrogen atom or an alkyl group containing 1 to 6 carbon atoms.

[0025] The presence of an unsaturated cyano group in the structure of the acrylonitrile monomer helps to increase ionic conductivity and improve adhesion.

[0026] Optionally, the acrylonitrile-based monomer includes one or more of acrylonitrile and methacrylonitrile.

[0027] By using one or more of the above acrylonitrile-based monomers, the ionic conductivity of the binder can be increased.

[0028] Optionally, the first polymer comprises an acrylamide-based monomer, and the structure of the acrylamide-based monomer is JPEG0007814419000003.jpg3543, wherein R4 is a hydrogen atom or an alkyl group containing 1 to 6 carbon atoms, and R5 is a hydrogen atom, an alkyl group containing 1 to 6 carbon atoms substituted with a hydroxy group, or an alkoxy group of 1 to 6 carbon atoms.

[0029] The third unit contains an unsaturated amide group which provides cross-linking and at the same time has relatively high tack.

[0030] Optionally, the acrylamide-based monomer comprises one or more of acrylamide, N-methylolacrylamide, and N-butoxymethacrylamide.

[0031] The use of one or more of the above acrylamide monomers can adjust the molecular weight of the polymer, thereby controlling the molecular weight of the binder within a certain range, which helps to improve adhesion.

[0032] As can be understood, the constituent monomers of the first polymer can include, but are not limited to, one, two, or three of the above three types of monomers.

[0033] Optionally, the first polymer contains an acrylic acid ester-based monomer, an acrylonitrile-based monomer, and an acrylamide-based monomer, and the mass ratio of the acrylic acid ester-based monomer, the acrylonitrile-based monomer, and the acrylamide-based monomer is in the range of 100:(1-80):(1-20), preferably 100:(20-60):(5-15).

[0034] In order to improve the overall performance of the first polymer, the first polymer contains an acrylic acid ester monomer, an acrylonitrile monomer, and an acrylamide monomer, and when the mass ratio of the acrylic acid ester monomer, the acrylonitrile monomer, and the acrylamide monomer is in the range of 100:(1-80):(1-20), preferably 100:(20-60):(5-15), excellent adhesive effect is achieved.

[0035] The present application further provides a method for producing a binder for a secondary battery, the method including: co-mixing water, an emulsifier, an initiator, and constituent monomers of a first polymer, stirring the mixture, and heating to cause a reaction, thereby obtaining a first polymer emulsion; and mixing the first polymer emulsion and the second polymer, stirring the mixture, and spray-drying the mixture to obtain a binder.

[0036] The present application obtains a first polymer emulsion by emulsion polymerization and obtains a binder by spray drying.

[0037] The binder particles are secondary particles comprising primary particles of a first polymer and primary particles of a second polymer, in which the second polymer acts as a backbone to support the first polymer. When the binder is made into a slurry and applied to a separator, the second polymer adheres the first polymer to the separator. After the slurry on the separator is dried, the second polymer forms a network structure, providing support and connection for the first polymer while adhering the first polymer particles to the separator.

[0038] 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.

[0039] An embodiment of the present application provides a battery unit including the separator described above.

[0040] An embodiment of the present application provides a battery including the above-described battery unit.

[0041] An embodiment of the present application provides the above battery alone or an electric device including the above battery. [Brief explanation of the drawings]

[0042] In order to more clearly describe the technical solutions in the embodiments of the present application or the prior art, the following will briefly describe the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can also obtain other drawings based on the structures shown in these drawings without any creative efforts. [Figure 1] 1 is a scanning electron microscope image of a binder provided by Example 1 of the present application. [Figure 2] FIG. 2 is a partially enlarged schematic view of the binder in Example 1 of FIG. [Figure 3] FIG. 1 is a structural diagram of a separator provided by an embodiment of the present application. [Figure 4] 1 is a flowchart of a method for manufacturing a binder for a secondary battery provided by an embodiment of the present application. [Figure 5] 1 is a schematic diagram of an electrode assembly provided by an embodiment of the present application. [Figure 6] FIG. 6 is an exploded view of an electrode assembly provided in accordance with an embodiment of the present application shown in FIG. 5. [Figure 7] 1 is a schematic diagram of a battery module provided by an embodiment of the present application. [Figure 8] 1 is a schematic diagram of a battery pack provided by an embodiment of the present application. [Figure 9] FIG. 9 is an exploded view of a battery pack provided by an embodiment of the present application shown in FIG. 8. [Figure 10] 1 is a schematic diagram of an electrical device provided by an embodiment of the present application.

[0043] Drawing symbol explanation: JPEG0007814419000004.jpg56133 The realization of the object, functional features and advantages of the present application will be further explained in conjunction with the embodiments and with reference to the drawings. DETAILED DESCRIPTION OF THE INVENTION

[0044] The following clearly and completely describes the technical solutions of the embodiments of the present application in accordance with the drawings of the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all of the embodiments. Based on the embodiments of the present application, those skilled in the art can obtain all other embodiments without any creative effort, and all of them fall within the scope of protection of the present application.

[0045] Hereinafter, with appropriate reference to the drawings, embodiments specifically disclosing the binder and its manufacturing method, as well as separators, electrode assemblies, individual batteries, batteries, and electric devices each including the binder, will be described in detail. However, unnecessary detailed description may be omitted. For example, detailed description of well-known matters and repeated description of substantially the same structure may be omitted. This is intended 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 scope of the claims.

[0046] The "ranges" disclosed herein are defined by lower and upper limits, and a given range is defined by selecting lower and upper limits that define the boundaries of that particular range. Ranges defined in this manner may or may not include the endpoint values ​​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. Furthermore, if minimum range values ​​1 and 2 are recited and maximum range values ​​3, 4, and 5 are recited, all of the following ranges are contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. Unless otherwise specified, the numerical range "a to b" herein represents a shorthand notation for any combination of real numbers between a and b, where both a and b are real numbers. For example, the numerical range "0 to 5" indicates that all real numbers between "0 and 5" are listed herein, and "0 to 5" is merely shorthand for combinations of these values. Furthermore, when describing a parameter as an integer of 2 or greater, this is equivalent to disclosing that the parameter is an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0047] Unless otherwise stated, all embodiments and alternative embodiments in the present application can be combined with each other to form new technical solutions.

[0048] Unless otherwise stated, all technical features and optional technical features in the present application can be combined with each other to form new technical solutions.

[0049] Unless otherwise specified, all steps in the present application can be performed sequentially or randomly, and are preferably performed sequentially. For example, when the method includes steps (a) and (b), it means that the method can include steps (a) and (b) performed sequentially, or can include steps (b) and (a) performed sequentially. For example, when the method mentioned above can further include step (c), it means that step (c) can be added to the method in any order, for example, the method can include steps (a), (b), and (c), or can include steps (a), (c), and (b), or can include steps (c), (a), and (b), etc.

[0050] Unless otherwise specified, the terms "comprise" and "include" used in this application can mean either open or closed. For example, the terms "comprise" and "include" can indicate that the composition may further comprise or include other components not listed, or may only comprise or include the listed components.

[0051] Unless otherwise stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following conditions satisfy the condition "A or B": A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), or both A and B are true (or exist).

[0052] The problem is that the battery cell has a large opening, i.e., gaps are easily formed between the pole pieces and the separator, which reduces the cycling performance of the battery.

[0053] The binder commonly used for separators is polyvinylidene fluoride, but at present, the price of polyvinylidene fluoride is rising and the market supply is tight. At the same time, a hot rolling process is required to tightly adhere the separator to the pole pieces. However, as production speeds increase, the hot rolling process is gradually being replaced by a cold rolling process. The cold rolling of battery pole pieces is intended to fix the winding core, reduce the elasticity of the battery cell, improve the pass rate of core assembly, and ensure the consistency of the thickness of the battery cell products.

[0054] When the adhesion between the positive and negative electrode pieces and the separator is insufficient, problems such as opening of the battery cell frequently occur, and the electrolyte infiltration is low, which makes it impossible to meet the coating performance requirements for the separator of the secondary battery. By closely adhering the separator to the electrode pieces, the discharge capacity of the battery can be improved, the internal resistance can be reduced, the polarization loss can be lowered, the cycle life of the battery can be extended, and the utilization rate of the secondary battery can be improved.

[0055] As can be understood, a battery cell is formed by adhering positive and negative electrode pieces and a separator. The battery cell has a certain hardness, i.e., the adhered positive and negative electrode pieces and the separator are stuck together and supported to form a structure with a certain thickness. A structure with a certain thickness also has a certain hardness. The negative electrode swells during the charge and discharge process. If the adhesion is weak, gaps are likely to form between the positive and negative electrode pieces and the separator, making it difficult for the positive and negative electrode pieces and the separator to stick together and support each other. This can lead to loosening of the battery cell and a decrease in hardness, which can reduce the dynamic performance of the battery cell, such as reduced power rating and cycling performance. For example, in electric vehicles, loosening of the battery cell can slow down the battery's charging speed and reduce its cycling performance, directly shortening the battery life and requiring frequent battery replacement, thereby increasing the cost to electric vehicle consumers.

[0056] Based on this, the present application provides a binder for a secondary battery, which comprises a first polymer including an acrylic acid ester copolymer and a second polymer including a water-soluble polymer.

[0057] Binder refers to a material with adhesive properties, which is used to adhere different substances together.

[0058] The acrylic acid ester copolymer is a general term for polymers produced by copolymerization of an acrylic acid ester monomer and another copolymerizable monomer.

[0059] The structure of the acrylate monomer has an acrylate group such as methyl acrylate, ethyl acrylate, or n-butyl acrylate.

[0060] The acrylic ester copolymer has a relatively high adhesiveness, and the use of the acrylic ester copolymer results in a higher adhesiveness between the separator and the pole pieces after cold rolling.

[0061] Water-soluble polymers are hydrophilic polymeric materials that can dissolve or swell in water to form a solution or dispersion, but that are not viscous in the dry state.

[0062] The binder comprises a first polymer including an acrylic ester copolymer and a second polymer including a water-soluble polymer. When the binder is applied to the separator, the water-soluble polymer acts as a support to support the first polymer, linking the first polymer to the water-soluble polymer and adhering the first polymer to the separator. Specifically, in the process of applying the binder to the separator, the binder is mixed with water to form a slurry, and the slurry is then applied to the separator. The water-soluble polymer has adhesive properties after contact with water, allowing the water-soluble polymer to adhere to the separator, and the water-soluble polymer can adhere the first polymer (including the acrylic ester copolymer) to the separator. Part of the acrylic ester copolymer and / or the water-soluble polymer in the binder penetrates into the gaps in the separator and achieves adhesion to the separator. After the slurry dries, the water evaporates, causing the water-soluble polymer molecules to become entangled with each other, resulting in intermolecular interactions, thereby forming a network structure and allowing the first polymer (acrylic acid ester copolymer) to adhere to the separator. The water-soluble polymer (including the acrylic ester copolymer) serves as a support and connection for the first polymer particles, adhering them to the separator; the slurry layer becomes an adhesive layer after drying, and the adhesive layer has a side facing the separator and a side facing away from the separator. During the process of applying the slurry, the water-soluble polymer adheres to the separator, or part of the acrylic ester copolymer and / or water-soluble polymer in the binder penetrates into the gaps in the separator, thereby achieving adhesion to the separator, and the adhesive layer adheres to the separator; and since the acrylic ester copolymer and the water-soluble polymer are not viscous after drying, the side of the adhesive layer facing away from the separator is not viscous, which makes it easy to wind and unwind the separator.

[0063] When the positive and negative electrode pieces are wound and then subjected to a cold-rolling process, the binder has excellent adhesive strength, allowing the positive and negative electrode pieces to be tightly bonded to the separator. Specifically, after cold-rolling, the adhesive strength is mainly provided by the mechanical interlocking effect caused by the acrylic ester copolymer and water-soluble polymer in the binder penetrating into the gaps between the electrode pieces, and by the intermolecular interaction of the acrylic ester copolymer. Therefore, the binder of the present application improves the adhesive strength between the separator and the positive and negative electrode pieces during cold-rolling, reducing problems such as opening of battery cells and soft battery cells, thereby improving the hardness of the battery cell. At the same time, applying the binder to the separator in a secondary battery can improve the dynamic performance of the secondary battery, reduce electrochemical impedance, and improve the rechargeability and cycling performance of the secondary battery.

[0064] That is, the water-soluble polymer becomes adhesive after dissolving in water, and when the slurry is applied to the separator, the water-soluble polymer can adhere to the separator. A portion of the acrylic ester copolymer and / or water-soluble polymer in the binder penetrates into the gaps in the separator, allowing the acrylic ester copolymer and water-soluble polymer in the binder to adhere to the separator. That is, as shown in FIG. 3, the side 21 of the adhesive layer 20 facing the separator adheres to the separator 10.

[0065] After drying, the side 23 of the adhesive layer 20 away from the separator is not sticky, which makes it easier to roll up the separator. During the process of placing the pole pieces on the surface of the adhesive layer and cold rolling, some of the acrylic ester copolymer and / or water-soluble polymer in the binder further penetrates into the gap between the separator and the pole pieces, forming intermolecular forces between the molecules on the separator and the pole pieces, and the binder effectively adheres the separator and the pole pieces together.

[0066] In one embodiment, the mass ratio of the first polymer to the second polymer is 1:(0.1-10), preferably 1:(0.2-5).

[0067] The binder is defined as comprising a first polymer and a second polymer, with the mass of the first polymer being M1, the mass of the second polymer being M2, and the mass ratio of the first polymer to the second polymer being M1:M2.

[0068] The mass ratio test method is as follows: in the binder manufacturing process, the mass M1 of the first polymer and the mass M2 of the second polymer added are recorded, and the mass ratio of the first polymer to the second polymer is M1:M2.

[0069] By setting the mass ratio of the first polymer to the second polymer within the above range, the adhesive layer forms a continuous network structure, which helps adhere the first polymer to the separator and improves the decrease in adhesiveness of the adhesive layer at room temperature.

[0070] In other words, in the process of changing from a smaller amount to a larger amount of the second polymer, the adhesive strength of the adhesive layer tends to increase and then decrease, and by controlling the mass of the first polymer and the second polymer within the above range, the adhesive strength of the binder applied to the separator is effectively improved.

[0071] In the above 1: (0.1 to 10), the value includes the minimum and maximum values ​​of the range, as well as each value between the minimum and maximum values. Specific examples include, but are not limited to, the point 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 point values.

[0072] In the above 1: (0.2 to 5), the value includes the minimum and maximum values ​​of the range, as well as each value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the examples, 1:0.2, 1:1, 1:2, 1:3, 1:4, 1:5, etc., and range values ​​between any two of the above point values.

[0073] In one embodiment, the second polymer comprises one or more of polyacrylamide, polyacrylic acid, polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, polymaleic anhydride, polyethyleneimine.

[0074] The second polymer contains the water-soluble polymer, which contains both hydrophilic and hydrophobic groups, and therefore has a certain surface activity, reducing the surface tension of water to a certain extent and enhancing the solubility and dispersibility of the binder in the aqueous phase. When used in a separator slurry, the water-soluble polymer controls the viscosity and rheological properties of the slurry, improving the dispersion and suspension of the binder. The second polymer also has chemically reactive functionality (e.g., carboxyl groups, hydroxyl groups, etc., that react with other groups). The polar groups in the water-soluble polymer structure can form hydrogen bonds between the first polymer and the separator and the pole pieces, improving the adhesion between the separator and the pole pieces.

[0075] In one embodiment, the volume particle size distribution Dv50 of the binder is 1 μm to 15 μm, preferably 3 μm to 12 μm.

[0076] Regarding Dv50, the particle diameter of the sample particles that occupy 50% of the total volume is larger than this value, and the particle diameter of the other particles that occupy 50% of the total volume is smaller than this value. Dv50 can represent the median diameter of the sample.

[0077] The volume average particle size Dv50 of the binder can be tested using methods known in the art. For example, see GB / T 19077-2016, and characterization tests can be performed using a Malvern laser particle size analyzer. For example, testing can be performed using an instrument such as Malvern's Mastersizer-3000.

[0078] Theoretically, the volume average particle diameter Dv50 of the binder in this application can be less than 1 μm or more than 15 μm. However, considering the application of the binder in this application to separators, setting the volume average particle diameter Dv50 of the binder in the above range alleviates the problem of the binder blocking the pores of the separator and reducing the permeability of lithium ions (lithium ion batteries are used as an example, but other types of secondary batteries can also be used). It also alleviates the problem of the binder forming a thick coating layer on the separator, which affects the energy density of the subsequently manufactured battery. Therefore, the volume particle diameter distribution Dv50 of the binder is 1 μm to 15 μm, preferably 3 μm to 12 μm.

[0079] In the above range of 1 μm to 15 μm, the values ​​include the minimum and maximum values ​​of the range, as well as each value between the minimum and maximum values. Specific examples include, but are not limited to, the point 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 point values.

[0080] In the above range of 3 μm to 12 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 point values ​​in the examples and 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, etc., and range values ​​between any two of the above point values.

[0081] As can be seen from Figures 1 and 2, the binder particles are secondary particles comprising primary particles of a first polymer and primary particles of a second polymer. Thus, the second polymer acts as a backbone within the binder slurry. When the binder slurry is applied to a separator, the second polymer acts to support and connect the first polymer, adhering the first polymer to the separator. After the slurry dries to form an adhesive layer, the adhesive layer can adhere to the separator, but the side of the adhesive layer away from the separator has no adhesive strength, making it easy to wind and unwind the separator. When the separator is wound with the positive and negative electrode pieces and then subjected to a cold rolling process, the first and second polymers are deformed by force after being extruded and penetrate into the gaps between the separator and the electrode pieces, thereby achieving an adhesive effect.

[0082] In one embodiment, the shape of the binder comprises a sphere.

[0083] Theoretically, the shape of the binder in the present application is not limited, and may be, for example, spherical, rod-like, etc., and is preferably spherical, since a spherical shape is useful for uniformly dispersing and applying the binder in the process of stirring the slurry.

[0084] In one embodiment, the first polymer comprises an acrylate ester monomer, and the structure of the acrylate ester monomer is: JPEG0007814419000005.jpg3450, wherein R1 is a hydrogen atom or an alkyl group containing 1 to 12 carbon atoms, and R2 is an alkyl group containing 1 to 12 carbon atoms.

[0085] The acrylic acid ester monomer contains an unsaturated ester group, which can increase the anti-swelling ability of the polymer, adjust the glass transition temperature of the polymer as a flexible monomer segment among the molecular segments, improve the flexibility of the binder during use, and help to exert good adhesive properties.

[0086] In one embodiment, the acrylate 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.

[0087] Theoretically, the present application does not limit the type of acrylic ester-based monomer as long as the acrylic ester-based monomer contains the above structure; that is, the acrylic ester-based monomer includes the substances listed above and substances not listed in the present application.

[0088] By using one or more of the above acrylic acid ester monomers, the glass transition temperature of the polymer can be adjusted and the anti-swelling ability of the polymer can be improved.

[0089] In one embodiment, the first polymer comprises an acrylonitrile-based monomer, and the structure of the acrylonitrile-based monomer is: JPEG0007814419000006.jpg2737, where R3 is a hydrogen atom or an alkyl group containing 1 to 6 carbon atoms.

[0090] The presence of an unsaturated cyano group in the structure of the acrylonitrile monomer helps to increase ionic conductivity and improve adhesion.

[0091] In one embodiment, the acrylonitrile-based monomer includes one or more of acrylonitrile, methacrylonitrile.

[0092] Theoretically, the present application does not limit the type of acrylonitrile-based monomer as long as the acrylonitrile-based monomer contains the above structure, i.e., the acrylonitrile-based monomer includes the substances listed above and substances not listed in the present application.

[0093] By using one or more of the above acrylonitrile-based monomers, the ionic conductivity of the binder can be increased.

[0094] In one embodiment, the first polymer comprises an acrylamide-based monomer, and the structure of the acrylamide-based monomer is: JPEG0007814419000007.jpg3746, wherein R4 is a hydrogen atom or an alkyl group containing 1 to 6 carbon atoms, and R5 is a hydrogen atom, an alkyl group containing 1 to 6 carbon atoms substituted with a hydroxy group, or an alkoxy group of 1 to 6 carbon atoms.

[0095] The third unit contains an unsaturated amide group which provides cross-linking and at the same time has relatively high tack.

[0096] In one embodiment, the acrylamide-based monomers include one or more of acrylamide, N-methylolacrylamide, and N-butoxymethacrylamide.

[0097] Theoretically, the present application does not limit the type of acrylamide-based monomer as long as the acrylamide-based monomer contains the above structure; that is, acrylamide-based monomers include the substances listed above and substances not listed in the present application.

[0098] The use of one or more of the above acrylamide monomers can adjust the molecular weight of the polymer, thereby controlling the molecular weight of the binder within a certain range, which helps to improve adhesion.

[0099] As can be understood, the constituent monomers of the first polymer can include, but are not limited to, one, two, or three of the above three types of monomers. As can be understood, when the first polymer is produced using three types of monomers simultaneously, the adhesion of the first polymer is better.

[0100] Commonly used polyvinylidene fluoride binders require a hot rolling process to achieve better adhesion. As production speeds improve and energy savings become more common, the hot rolling process is gradually being replaced by a cold rolling process. Battery cells are wound and then cold rolled. Conventional polyvinylidene fluoride is a homopolymer with a crystallinity of around 50%, resulting in insufficient adhesion between the separator and the positive and negative electrode pieces. Conventional polyacrylate binders do not meet the adhesive strength requirements during cold rolling, resulting in frequent problems such as openings and soft battery cells. Furthermore, their poor electrolyte infiltration makes them unable to meet the coating performance requirements for secondary battery separators.

[0101] The binder contains an acrylic ester copolymer prepared using the above-mentioned monomers and a water-soluble polymer, which gives the binder relatively high adhesion.

[0102] In one embodiment, the first polymer includes an acrylic acid ester monomer, an acrylonitrile monomer, and an acrylamide monomer, and the mass ratio of the acrylic acid ester monomer, the acrylonitrile monomer, and the acrylamide monomer is 100:(1-80):(1-20), preferably 100:(20-60):(5-15).

[0103] In order to improve the overall performance of the first polymer, the first polymer contains an acrylic acid ester monomer, an acrylonitrile monomer, and an acrylamide monomer, and when the mass ratio of the acrylic acid ester monomer, the acrylonitrile monomer, and the acrylamide monomer is in the range of 100:(1-80):(1-20), preferably 100:(20-60):(5-15), excellent adhesive effect is achieved.

[0104] In the above 100:(1-80):(1-20), the values ​​include the minimum and maximum values ​​of the range, as well as each value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the examples and 100:1:1, 100:10:1, 100:30:1, 100:50:1, 100:80:1, 100:10:5, 100:10:10, 100:10:20, 100:30:10, 100:30:20, 100:50:20, 100:80:20, etc., and range values ​​between any two of the above point values.

[0105] In the above 100:(20-60):(5-15), the values ​​include the minimum and maximum values ​​of the range, as well as each value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the examples, and range values ​​between any two of the above point values, such as 100:20:5, 100:30:10, 100:60:15, etc.

[0106] The present application further provides a method for producing a binder for a secondary battery, the method comprising: mixing water, an emulsifier, an initiator, and constituent monomers of a first polymer together, stirring the mixture, and heating the mixture to react with each other to obtain a first polymer emulsion;

[0107] mixing and stirring the first polymer emulsion with the second polymer, and spray drying to obtain the binder.

[0108] The present application obtains a first polymer emulsion by emulsion polymerization and obtains a binder by spray drying.

[0109] Regarding emulsion polymerization, emulsion polymerization is a method in which a monomer is dispersed in water with an emulsifier by mechanical agitation to form an emulsion, and an initiator is added to start the polymerization of the monomer.

[0110] Regarding emulsifiers, they are substances that can convert incompatible oil and water into an emulsion that is difficult to separate. Emulsifiers are usually surfactants that have both hydrophilic polar groups and hydrophobic (lipophilic) non-polar groups.

[0111] Regarding initiators, initiators are substances that can initiate the polymerization reaction of monomers. For example, free radical initiators refer to compounds that readily decompose into free radicals (i.e., primary free radicals) under heat and can be used to initiate the free radical polymerization and copolymerization of olefin and diene monomers.

[0112] Water, emulsifier, initiator, and polymer constituent monomers are mixed and stirred, 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 starts polymerization of the monomers inside the micelles, resulting in an emulsion.

[0113] With regard to spray drying, the material requiring drying (a mixture of a first polymer emulsion and a second polymer) is dispersed through mechanical action into very fine, mist-like particles (increasing the surface area for water evaporation and accelerating the drying process) and then contacted with hot air, which instantly removes most of the water and dries the solids in the material into a powder.

[0114] A binder comprising the first polymer and the second polymer is obtained by a spray drying process.

[0115] The present invention also provides a separator including the above-described secondary battery binder or a binder manufactured by the above-described method for manufacturing a secondary battery binder. Since all the technical solutions of all the above-described embodiments are used in the binder, the separator has at least all the beneficial effects provided by the technical solutions of the above-described embodiments, and detailed descriptions thereof will be omitted here.

[0116] The binder applied to the separator can improve the adhesive performance between the pole pieces and the binder, and improve the opening problem in the conventional pre-cold rolling process of the battery cell.

[0117] The present invention also provides a battery unit including the separator described above. Since all the technical solutions of all the above embodiments are used in the separator, the separator has at least all the beneficial effects provided by the technical solutions of the above embodiments, and detailed descriptions thereof are omitted here.

[0118] By applying the separator to a single battery, the large jig circulation performance of the single battery can be improved.

[0119] The present invention also provides a battery including the above-mentioned battery unit, which uses all the technical solutions of all the above-mentioned embodiments, and thus has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, and detailed descriptions thereof are omitted here.

[0120] The battery includes a battery module and a battery pack.

[0121] The embodiments of the present application further provide the above-mentioned battery unit or an electric device including the above-mentioned battery, which uses all the technical solutions of all the above-mentioned embodiments, and thus has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, and detailed descriptions thereof are omitted here.

[0122] The electrode assembly, the battery unit, the battery, and the electric device of the present application will be described below with appropriate reference to the drawings.

[0123] In one embodiment of the present application, an electrode assembly is provided.

[0124] Generally, an electrode assembly includes a positive electrode piece, a negative electrode piece, an electrolyte, and a separator. During the charge / discharge process of a battery, active ions are inserted and extracted back and forth between the positive electrode piece and the negative electrode piece. The electrolyte functions to conduct ions between the positive electrode piece and the negative electrode piece. The separator, located between the positive electrode piece and the negative electrode piece, primarily functions to prevent short-circuiting between the positive electrode and the negative electrode piece while allowing ions to pass through. The separator is the improved separator described in this application.

[0125] The positive electrode piece includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.

[0126] For example, the positive electrode current collector has two surfaces that face each other in the thickness direction of the positive electrode current collector, and the positive electrode film layer is disposed on either one or both of the two facing surfaces of the positive electrode current collector.

[0127] In some embodiments, the positive electrode current collector may be a metal foil piece or a composite current collector. For example, aluminum foil may be used as the metal foil piece. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base layer. The composite current collector may be formed by forming a metal material (such as aluminum, an aluminum alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, or a silver alloy) on a polymeric material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0128] In some embodiments, when the electrode assembly is a lithium-ion battery, the positive electrode active material can be a positive electrode active material known in the art and used for lithium-ion batteries. For example, the positive electrode active material can include at least one of a lithium-containing phosphate having 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 the positive electrode active material of a battery can also be used. These positive electrode active materials can 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 (LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM 333 (also abbreviated as LiNi) 0.5 Co 0.2 Mn 0.3 O2(NCM 523 (also abbreviated as LiNi) 0.5 Co 0.25 Mn 0.25 O2(NCM 211 (also abbreviated as LiNi) 0.6 Co 0.2 Mn 0.2 O2(NCM 622 (also abbreviated as LiNi) 0.8 Co 0.1 Mn 0.1 O2(NCM 811 Lithium nickel cobalt aluminum oxide (LiNi 0.85 Co 0.15 Al 0.05Examples of the lithium-containing phosphate having an olivine structure include, but are not limited to, at least one of lithium iron phosphate (LiFePO4 (also abbreviated as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (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.

[0129] In some embodiments, the positive electrode membrane layer optionally further comprises a binder, for example, at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0130] In some embodiments, the positive electrode film layer optionally further includes a conductive agent, for example, superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0131] In some embodiments, the positive electrode pieces can be manufactured by the following method: The above-mentioned components for manufacturing the positive electrode pieces, such as the positive electrode active material, the conductive agent, the binder, and any other components, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry, which is then applied to a positive electrode current collector, and the positive electrode pieces can be obtained after processes such as drying and cold rolling.

[0132] The negative electrode piece includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer including a negative electrode active material.

[0133] For example, the negative electrode current collector has two surfaces that face each other in the thickness direction of the negative electrode current collector, and the negative electrode film layer is disposed on either one or both of the two facing surfaces of the negative electrode current collector.

[0134] In some embodiments, the negative electrode current collector may be a metal foil strip or a composite current collector. For example, the metal foil strip may be a copper foil. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material substrate. The composite current collector may be formed by forming a metal material (such as copper, a copper alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, or a silver alloy) on a polymeric material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0135] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art and used in batteries. 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, and lithium titanate. Silicon-based materials may include at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include at least one of elemental tin, tin oxide compounds, and tin alloys. 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.

[0136] In some embodiments, the negative electrode membrane layer optionally further comprises 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).

[0137] In some embodiments, the negative electrode film layer optionally further comprises a 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.

[0138] In some embodiments, the negative electrode membrane layer optionally further comprises other auxiliary agents, such as a thickener (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0139] In some embodiments, the negative electrode pieces can be manufactured by the following method: The components for manufacturing the negative electrode pieces, such as the negative electrode active material, conductive agent, binder, and any other components, are dispersed in a solvent (e.g., deionized water) to form a negative electrode slurry, which is then applied to a negative electrode current collector, and the negative electrode pieces can be obtained after processes such as drying and cold rolling.

[0140] The electrolyte serves to conduct ions between the positive and negative electrode pieces. The present application is not specifically limited to the type of electrolyte, and it can be selected as needed.

[0141] In some embodiments, the electrolyte uses an electrolyte solution, which includes an electrolyte salt and a solvent.

[0142] 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 dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0143] In some embodiments, the solvent can include at least one of ethylene carbonate, propylene carbonate, ethyl methyl 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.

[0144] In some embodiments, the electrolyte solution may optionally further contain additives. For example, the additives may include a negative electrode film-forming additive, a positive electrode film-forming additive, or an additive that can improve specific battery performance, such as an additive that improves the overcharge performance of the battery or an additive that improves the high-temperature or low-temperature performance of the battery.

[0145] In some embodiments, the electrode assembly further includes a separator. The present application is not particularly limited to the type of separator, and any known porous separator having good chemical and mechanical stability can be selected.

[0146] 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 thin film or a multi-layer composite thin film, and is not particularly limited. When the separator is a multi-layer composite thin film, the materials of the layers may be the same or different, and is not particularly limited.

[0147] In some embodiments, the positive pole pieces, negative pole pieces, and separators can be fabricated into an electrode assembly by a winding or lamination process.

[0148] In some embodiments, the electrode assembly can include an outer package that can be used to package the electrode assembly and electrolyte.

[0149] In some embodiments, the outer packaging of the electrode assembly may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the electrode assembly may be a soft bag, such as a soft bag. The soft bag may be made of plastic. Examples of plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0150] The present application is not particularly limited to the shape of the electrode assembly, and it may be cylindrical, rectangular, or any other shape. For example, Figure 5 shows an example of a secondary battery 5 with a rectangular structure.

[0151] In some embodiments, referring to FIG. 6 , the outer package may include a case 51 and a cover plate 53. Here, the case 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and side plates surround and form a storage chamber. The case 51 has an opening communicating with the storage chamber, and the cover plate 53 may cover the opening to close the storage chamber. The positive electrode piece, the negative electrode piece, and the separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is packaged in the storage chamber. An electrolyte is impregnated into the electrode assembly 52. ​​The secondary battery 5 may include one or more electrode assemblies 52, and this can be selected by those skilled in the art according to specific practical needs.

[0152] In some embodiments, the electrode assemblies can be assembled into a battery module. The number of electrode assemblies included in the battery module can be one or more, and those skilled in the art can select the specific number according to the application and capacity of the battery module.

[0153] FIG. 7 shows an example of a battery module 4. Referring to FIG. 7, in the battery module 4, the secondary batteries 5 may be arranged in order along the length of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the secondary batteries 5 may be fixed by a fastening member.

[0154] Optionally, the battery module 4 may further include an outer shell having an accommodating space in which a plurality of secondary batteries 5 are accommodated.

[0155] In some embodiments, the battery modules can be assembled into a battery pack. The battery pack can include one or more battery modules, and those skilled in the art can select the specific number according to the application and capacity of the battery pack.

[0156] 8 and 9 show an example battery pack 1. Referring to FIGS. 8 and 9, the battery pack 1 may include a battery box and a plurality of battery modules 4 installed in the battery box. The battery box includes an upper box 2 and a lower box 3, and the upper box 2 is installed to cover the lower box 3, forming an enclosed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0157] The present application also provides an electric device including at least one of the electrode assembly, battery module, or battery pack provided herein. The electrode assembly, battery module, or battery pack can be used as a power source for the electric device or as an energy storage unit for the electric device. The electric device can include, but is not limited to, mobile devices (such as mobile phones and laptops), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, and electric trucks), trains, ships, satellites, energy storage systems, and the like.

[0158] As an electrical device, an electrode assembly, a battery module or a battery pack can be selected according to the usage needs.

[0159] 10 is an example of an electric device. The electric device may be a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements for the electrode assembly of the electric device, a battery pack or a battery module can be used.

[0160] Another example device may be a mobile phone, tablet, laptop, etc. Such devices typically require light weight and may use an electrode assembly as a power source. Example

[0161] Examples of the present application are described below. The examples described below are illustrative and are used only to interpret the present application, and should not be understood as limiting the present application. If specific techniques or conditions are not specified in the examples, they will be carried out in accordance with the techniques or conditions described in the literature in the field or in accordance with the product specifications. If the manufacturer of the reagents or equipment used is not specified, they are all ordinary products that are commercially available. Preparation of the first polymer emulsion Manufacturing Example 1

[0162] The acrylic ester monomer methyl acrylate, the acrylonitrile monomer acrylonitrile, and the acrylamide monomer acrylamide were weighed out and mixed uniformly in a 100:1:10 weight ratio. A 1000 mL four-neck flask equipped with a mechanical stirrer, thermometer, and condenser was charged with 200 g of the mixed monomers, 5 g of emulsifier (sodium lauryl sulfate), 1.8 g of initiator (ammonium persulfate), and 260 g of deionized water, and emulsified with high-speed stirring for 30 minutes. Under nitrogen gas protection, the mixture was heated to 75°C and reacted for 4 hours. The temperature was then lowered to below 40°C, the pH was adjusted to neutral with aqueous ammonia, and the mixture was filtered to obtain Preparation Example 1, a first polymer emulsion. Manufacturing Examples 2 to 12

[0163] Based on Production Example 1, the types and mass ratios of the monomers were adjusted to obtain Production Examples 2 to 12. Example 1 Binder manufacturing

[0164] The first and second polymers were weighed and added in a 1:1 weight ratio, and deionized water was added to adjust the solid content of the system to 20%. After stirring to achieve uniform mixing, the separator binder was prepared by a spray-drying process under the conditions of an inlet air temperature of 110°C and an outlet air temperature of 50°C. Examples 2 to 24

[0165] Based on Example 1, the types and weight ratios of the first polymer and the second polymer were adjusted to obtain Examples 2 to 24. Comparative Example 1

[0166] A binder was prepared based on Example 1 using only the second polymer. Comparative Example 2

[0167] A binder was prepared based on Example 7 using only the first polymer. Battery cell and battery manufacturing Separator manufacturing

[0168] A commercially available PE microporous membrane (manufactured by Zhuoga Electronics Technology Co., Ltd.) with a thickness of 7 μm and an average pore size of 80 nm was used as the substrate. The separator binder prepared above was stirred into deionized water to uniformly mix, yielding a slurry (solid content 20%). The slurry was sprayed onto two surfaces of the substrate and dried to remove the solvent, resulting in a coating density of 1.5 g / m2 of the coating composition on the substrate. 2 A separator was obtained in this way. Positive electrode piece manufacturing

[0169] Polyvinylidene fluoride (PVDF), lithium iron phosphate (LFP), carbon black (a conductive agent), and N-methylpyrrolidone (NMP) were thoroughly mixed in a mass ratio of 1.2:58.38:0.42:40 and then stirred thoroughly to form a positive electrode slurry. The positive electrode slurry was prepared at a concentration of 200 g / m 2 The coating was uniformly applied to an aluminum foil positive electrode current collector in a loading amount of 1000 ppm, and then dried, cold rolled, and divided to obtain positive electrode pieces. Negative electrode piece manufacturing

[0170] 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 after thorough stirring to mix uniformly, anode slurry (solid content 63%) was prepared. The anode slurry was prepared at 98 g / m 2The coating was applied to a copper foil negative electrode current collector in a loading amount of 1000 ppm, and then dried, cold rolled, and divided to obtain negative electrode pieces. Electrolyte production

[0171] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed at 25°C 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. Secondary battery manufacturing

[0172] The positive electrode pieces, separator, and negative electrode pieces are stacked in this order, wound up, and cold-rolled to form a battery cell (during this process, the separator adheres to the electrode pieces). The battery cell is then placed in an outer package, and the above-prepared electrolyte is added. After going through processes such as packaging, standing, chemical synthesis, and aging, a secondary battery is obtained. Performance Test Cold Rolled Adhesion Test:

[0173] The battery's negative electrode and separator were stacked and placed in a hot press. The hot press parameters were set to 25°C, 7 T, and 30 s, and pressure was applied to produce a bonded separator / positive electrode sample. The separator / electrode sample was cut into a 150 mm x 20 mm rectangular spline. One side of the splined electrode was attached to a steel plate with double-sided tape, and the separator and electrode were separated by 2 cm along the length at one end of the rectangular spline to produce a test sample.

[0174] The steel plate was held horizontally and fixed with the lower clamp of a universal testing machine (Xieqiang Instrument Manufacturing (Shanghai) Co., Ltd., model number CTM2100). The peeled end of the separator was fixed with the upper clamp of the universal testing machine, and a tensile testing machine was connected. The test conditions were set to a tensile speed of 20 mm / min and a horizontal tensile distance of 10 cm. After the tensile force stabilized, the tensile force value was recorded, and the adhesive strength between the separator and the pole piece was obtained from the ratio of the tensile force value to the sample width. EIS data (electrochemical impedance spectrum):

[0175] Using Shanghai Chenhua's CHI660D electrochemical workstation, a sinusoidal voltage signal of frequency W1 and small amplitude was applied to the battery system, and the system generated a sinusoidal current response of frequency W2. The change in the ratio between the excitation voltage and the response current is the impedance spectrum of the electrochemical system. In the AC impedance test, the test frequency range was 10mHz to 100kHz, and the amplitude was 5mV. Through the test, information such as the real and imaginary parts of the impedance at various frequencies could be obtained. Lithium-ion battery multiplication performance:

[0176] Using a Wuhan King Nuo Electronics CT-2001 A LAND battery testing system, the test environment was a room temperature of 25°C, a voltage range of 2.5 to 3.65 V, and constant current charge-discharge cycles of 0.2C, 0.5C, 1C, 2C, 5C, and 0.2C were performed on test batteries assembled with the electrode materials. The specific cycles were 0.2C (5 cycles, the fifth capacity is designated C1), followed by 0.5C (5 cycles), 1C (5 cycles), 2C (5 cycles), 5C (5 cycles), and 0.2C (5 cycles, the fifth capacity is designated C2). That is, the battery capacity after the first 5 constant current charge-discharge cycles at 0.2C is designated C1, and the battery capacity after the second 5 constant current charge-discharge cycles at 0.2C is designated C2. The cycle performance was expressed as P = (C2 / C1) × 100%.

[0177] [Table 1]

[0178] [Table 2]

[0179] [Table 3]

[0180] By preparing a first polymer using appropriate monomers, controlling the mass ratio of the first polymer to the second polymer within an appropriate range, and then obtaining a binder through a spray drying process, the obtained binder has relatively high adhesion within an appropriate range, and when applied to a separator, it helps improve battery performance.

[0181] The above is merely a preferred embodiment of the present application, and does not limit the scope of the patent of the present application. Equivalent structural modifications made based on the application idea of ​​the present application and the contents of the specification and drawings of the present application, or direct / indirect applications to other related technical fields, are all included in the scope of protection of the patent of the present application.

Claims

1. A binder for a separator of a secondary battery, a first polymer including an acrylic acid ester copolymer and a second polymer including a water-soluble polymer; the binder particles are secondary particles including primary particles of a first polymer and primary particles of a second polymer, The volume particle size distribution Dv50 of the binder particles is 3 μm to 15 μm. Binder for secondary battery separators.

2. the mass ratio of the first polymer to the second polymer is 1:(0.1 to 10); The binder for a separator of a secondary battery according to claim 1 .

3. the second polymer comprises one or more of polyacrylamide, polyacrylic acid, polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, polymaleic anhydride, and polyethyleneimine; The binder for a separator of a secondary battery according to claim 1 or 2.

4. The volume particle size distribution Dv50 of the binder particles is 3 μm to 12 μm; The binder for a separator of a secondary battery according to claim 1 or 2.

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

6. The first polymer contains an acrylate ester-based monomer, and the structure of the acrylate ester-based monomer is Including, wherein R1 is a hydrogen atom or an alkyl group containing 1 to 12 carbon atoms, and R2 is an alkyl group containing 1 to 12 carbon atoms; The binder for a separator of a secondary battery according to claim 1 or 2.

7. The acrylic acid ester monomer includes 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. The binder for a separator of a secondary battery according to claim 6 .

8. The first polymer contains an acrylonitrile-based monomer, and the structure of the acrylonitrile-based monomer is Including, wherein R3 is a hydrogen atom or an alkyl group containing 1 to 6 carbon atoms; The binder for a separator of a secondary battery according to claim 1 or 2.

9. The acrylonitrile-based monomer includes one or more of acrylonitrile and methacrylonitrile. The binder for a separator of a secondary battery according to claim 8 .

10. The first polymer contains an acrylamide-based monomer, and the structure of the acrylamide-based monomer is Including, wherein R4 is a hydrogen atom or an alkyl group containing 1 to 6 carbon atoms, and R5 is a hydrogen atom, an alkyl group containing 1 to 6 carbon atoms substituted with a hydroxy group, or an alkoxy group of 1 to 6 carbon atoms. The binder for a separator of a secondary battery according to claim 1 or 2.

11. The acrylamide-based monomer includes one or more of acrylamide, N-methylolacrylamide, and N-butoxymethacrylamide. The binder for a separator of a secondary battery according to claim 10.

12. the first polymer includes an acrylic acid ester-based monomer, an acrylonitrile-based monomer, and an acrylamide-based monomer, and the mass ratio of the acrylic acid ester-based monomer, the acrylonitrile-based monomer, and the acrylamide-based monomer is in the range of 100:(1 to 80):(1 to 20); The binder for a separator of a secondary battery according to claim 1 or 2.

13. A method for producing the binder for a separator of a secondary battery according to claim 1, co-mixing, stirring, and heating water, an emulsifier, an initiator, and constituent monomers of a first polymer to react them to obtain a first polymer emulsion; and mixing and stirring the first polymer emulsion and the second polymer, and spray drying to obtain a binder. method.

14. A secondary battery separator comprising the binder according to claim 1. Separator.

15. Comprising the separator of claim 14 . Battery alone.

16. The battery unit according to claim 15, battery.

17. The battery according to claim 15 or the battery according to claim 16, Electrical equipment.

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