Binder for secondary battery and its manufacturing method, 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 manufacturing method thereof, 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 having 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, electric vehicles, etc., 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 that the battery cell has a large opening, i.e., a gap is easily generated between the pole piece and the separator, which reduces the cycling performance of the battery. Summary of the Invention

[0004] The main objective of the present application is to provide a binder for secondary batteries, which improves the adhesion between the separator and the pole pieces and thereby improves the cycling performance of the battery.

[0005] In order to achieve the above object, the present application provides a binder for a secondary battery, comprising 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 adhesion, and the use of the acrylic ester copolymer results in higher adhesion 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 containing an acrylic acid ester copolymer and a second polymer containing a water-soluble polymer, and when the binder is applied to the separator, the water-soluble polymer supports the first polymer as a support, connects the first polymer to the water-soluble polymer, and adheres 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 then the slurry is applied to the separator, the water-soluble polymer has adhesion after contacting with water, and the water-soluble polymer can adhere to the separator, and the water-soluble polymer can adhere the first polymer (containing the acrylic acid ester copolymer) to the separator, and a part of the acrylic acid ester copolymer and / or the water-soluble polymer in the binder can penetrate into the gaps of the separator and realize adhesion with the separator, and after the slurry is dried, the water evaporates, and the water-soluble polymer molecules are entangled with each other, and interactions occur between the molecules, thereby forming a network structure, and the first polymer (acrylic acid The water-soluble polymer in the binder plays a supporting and connecting role for the acrylic ester-based copolymer (including the acrylic ester-based copolymer), and adheres the first polymer particles to the separator; the slurry layer becomes an adhesive layer after drying, and the adhesive layer has a side toward the separator and a side away from the separator; during the process of applying the slurry, the water-soluble polymer adheres to the separator, or a part of the acrylic ester-based copolymer and / or the water-soluble polymer in the binder penetrates into the gaps of the separator to achieve adhesion with the separator, so that the adhesive layer adheres to the separator; and since the acrylic ester-based copolymer and the water-soluble polymer have no viscosity after drying, the adhesive layer has no viscosity on the side away from the separator, thus facilitating winding and unwinding of the separator.

[0009] When the cold rolling process is performed after winding the positive and negative pole pieces, the binder has excellent adhesion, and the positive and negative pole pieces are closely attached to the separator. Specifically, after cold rolling, the adhesion is mainly provided by the mechanical interlocking action caused by the acrylic acid ester copolymer and the water-soluble polymer in the binder penetrating into the gaps between the pole pieces, and by the intermolecular action of the acrylic acid ester copolymer. Therefore, the binder of the present application improves the adhesion of the separator to the positive and negative pole pieces during cold rolling, and reduces problems such as opening of the battery cell and soft battery cell, thereby improving the hardness of the battery cell. At the same time, the application of the binder to the separator in the secondary battery can improve the dynamic performance of the secondary battery, reduce the electrochemical impedance, and improve the magnification performance and cycling performance of the secondary battery.

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

[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 improves the adhesion 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 above-mentioned water-soluble polymer containing hydrophilic groups and a certain amount of hydrophobic groups, so it has a certain surface activity, can reduce the surface tension of water to a certain extent, and can increase the solubility and dispersibility of the binder in the aqueous phase; that is, when it is made into a slurry for coating the separator, the water-soluble polymer is used to control the viscosity and rheological properties of the slurry, and can make the dispersion and suspension of the binder better. And the second polymer also has a chemical reaction function (such as a carboxyl group, a hydroxyl group, etc. that reacts with other groups), and the polar group in the water-soluble polymer structure can form hydrogen bonds between the first polymer and the separator and the pole pieces, and can improve 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 the present application may be less than 1 μm or more than 15 μm, but considering the application of the binder in the present application to the separator, the volume average particle diameter Dv50 of the binder is set to the above range to improve the problem that the binder blocks the pores of the separator and reduces the permeability of the separator to lithium ions (for example, lithium ion batteries, and of course other types of secondary batteries may also be used), and to improve the problem that the binder is applied to the separator to form a thick coating layer, which affects the energy density of the battery subsequently manufactured. 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, as shown in FIG. 1, the binder particles are secondary particles including primary particles of a first polymer and primary particles of a second polymer, in this way, the second polymer serves as a skeleton therein, when the binder slurry is applied to the separator, the second polymer plays the role of supporting and connecting the first polymer, and causes the first polymer to adhere to the separator, and 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 force, making it easier 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 under the force after being extruded, and can penetrate into the gaps between the separator and the electrode pieces to achieve 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 monomer, and the structure of the acrylate monomer is JPEG2025515526000002.jpg3454, where 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 a good adhesive effect.

[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 any 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 enhanced.

[0024] Optionally, the first polymer comprises an acrylonitrile-based monomer, and the structure of the acrylonitrile-based monomer is JPEG2025515526000003.jpg3233, where R3 is a hydrogen atom or an alkyl group containing 1 to 6 carbon atoms.

[0025] The inclusion 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, 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 JPEG2025515526000004.jpg3543, wherein R4 is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R5 is a hydrogen atom, an alkyl group having 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 adhesion.

[0030] Optionally, the acrylamide-based monomers include 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, and can adjust the molecular weight of the binder within a certain range, which helps 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] Alternatively, 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 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 includes 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), the adhesive effect is excellent.

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

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

[0037] The binder particles are secondary particles comprising primary particles of a first polymer and primary particles of a second polymer, in this way the second polymer serves 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 secondary battery binder or a binder produced by the above-described method for producing a secondary battery binder.

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

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

[0041] An embodiment of the present application provides an electric device including the above-mentioned battery alone or the above-mentioned battery. [Brief description 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 briefly describes 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 creative efforts. [Figure 1] 1 is a scanning electron microscope image of a binder provided by Example 1 of the present application. [Diagram 2] FIG. 2 is a partially enlarged schematic view of the binder in Example 1 of FIG. [Diagram 3] FIG. 2 is a structural diagram of a separator provided according to an embodiment of the present application. [Figure 4] 1 is a flowchart of a method for producing a binder for a secondary battery provided by an embodiment of the present application. [Diagram 5] FIG. 2 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 the embodiment of the present application shown in FIG. 5. [Figure 7] FIG. 2 is a schematic diagram of a battery module provided by an embodiment of the present application. [Figure 8] FIG. 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 the embodiment of the present application shown in FIG. 8. [Figure 10] 1 is a schematic diagram of an electrical device provided in accordance with an embodiment of the present application.

[0043] Explanation of drawing symbols: JPEG2025515526000005.jpg56133 The realization of the object, functional features and advantages of the present application will be further described in conjunction with the embodiments and with reference to the drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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, and not all of the embodiments. Based on the embodiments in the present application, those skilled in the art can easily obtain all other embodiments without any creative effort, and all of them belong to 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 a separator, an electrode assembly, a single battery, a battery, and an electric device containing 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. The purpose is to avoid unnecessary redundancy in the following description and to make it easy to understand for those skilled in the art. In addition, the drawings and the following description are provided to allow those skilled in the art to fully understand the present application, and are not intended to limit the subject matter described in the claims.

[0046] The "ranges" disclosed herein are defined in the form of lower and upper limits, with a given range being defined by selecting lower and upper limits that define the boundaries of the 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 60-120 and 80-110 are recited for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Also, if minimum range values ​​1 and 2 are recited, and maximum range values ​​3, 4, and 5 are recited, all of the following ranges are contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "a-b" represents a shorthand representation of any combination of real numbers between a and b, where both a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" are recited herein, and "0-5" is merely shorthand for combinations of these values. Additionally, 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 the embodiments and optional embodiments in the present application can be combined with each other to form a new technical solution.

[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 stated, all steps in the present application can be performed sequentially or randomly, and preferably sequentially. For example, the method includes steps (a) and (b), which means that the method can include steps (a) and (b) performed sequentially, and can also include steps (b) and (a) performed sequentially. For example, the method mentioned above can further include step (c), which means that step (c) can be added to the method in any order, for example, the method can include steps (a), (b) and (c), can include steps (a), (c) and (b), can include steps (c), (a) and (b), etc.

[0050] Unless otherwise stated, the terms "comprise" and "include" referred to in this application can mean open-ended or closed-ended. For example, the terms "comprise" and "include" can indicate that the composition may further comprise or include other components not listed, or that the composition 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" as follows: 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] There is a problem 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 commonly used binder on the separator is polyvinylidene fluoride, but at present the price of polyvinylidene fluoride is rising, and the market supply is tight, and at the same time, the hot rolling process is required to make the separator adhere closely to the pole piece. However, with the improvement of production speed, the hot rolling process is gradually replaced by the cold rolling process, and the cold rolling of the battery pole piece is to fix the winding core, reduce the elasticity of the battery cell, improve the pass rate of the core assembly and ensure the consistency of the thickness of the battery cell product.

[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 at the same time, the infiltration of the electrolyte is low, and the coating performance requirements for the separator of the secondary battery cannot be met. By closely attaching 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 reduced, 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 adhesion of a positive electrode piece, a negative electrode piece and a separator, and the battery cell has a certain hardness, that is, the adhered positive electrode piece, negative electrode piece and separator are stuck together and supported by each other to form a structure with a certain thickness, and the structure with a certain thickness has a certain hardness, and the negative electrode swells during the charging and discharging process, and if the adhesion is weak, gaps are likely to occur between the positive electrode piece, the negative electrode piece and the separator, and the positive electrode piece, the negative electrode piece and the separator are difficult to stick together and support each other, which leads to the loosening and hardness reduction of the battery cell, and in this case, the dynamic performance of the battery cell is reduced, for example, the multiplication performance is reduced and the cycling performance is reduced. For example, in an electric vehicle, the loosening of the battery cell slows down the charging speed of the battery and at the same time reduces the cycling performance of the battery, which directly leads to a shortened battery life, and the electric vehicle needs to replace the battery frequently, which increases the cost of the electric vehicle consumer.

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

[0057] A binder refers to a material that has adhesive properties and is used to adhere different substances together.

[0058] The acrylic acid ester copolymer is a general term for polymers produced by a copolymerization reaction 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 adhesion, and the use of the acrylic ester copolymer results in higher adhesion 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 containing an acrylic acid ester copolymer and a second polymer containing a water-soluble polymer, and when the binder is applied to the separator, the water-soluble polymer supports the first polymer as a support, connects the first polymer to the water-soluble polymer, and adheres 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 then the slurry is applied to the separator, the water-soluble polymer has adhesion after contacting with water, and the water-soluble polymer can adhere to the separator, and the water-soluble polymer can adhere the first polymer (containing the acrylic acid ester copolymer) to the separator, and a part of the acrylic acid ester copolymer and / or the water-soluble polymer in the binder can penetrate into the gaps of the separator and realize adhesion with the separator, and after the slurry is dried, the water evaporates, and the water-soluble polymer molecules are entangled with each other, and interactions occur between the molecules, thereby forming a network structure, and the first polymer (acrylic acid The water-soluble polymer in the binder plays a supporting and connecting role for the acrylic ester-based copolymer (including the acrylic ester-based copolymer), and adheres the first polymer particles to the separator; the slurry layer becomes an adhesive layer after drying, and the adhesive layer has a side toward the separator and a side away from the separator; during the process of applying the slurry, the water-soluble polymer adheres to the separator, or a part of the acrylic ester-based copolymer and / or the water-soluble polymer in the binder penetrates into the gaps of the separator to achieve adhesion with the separator, so that the adhesive layer adheres to the separator; and since the acrylic ester-based copolymer and the water-soluble polymer have no viscosity after drying, the adhesive layer has no viscosity on the side away from the separator, thus facilitating winding and unwinding of the separator.

[0063] When the cold rolling process is performed after winding the positive and negative pole pieces, the binder has excellent adhesion, and the positive and negative pole pieces are closely attached to the separator. Specifically, after cold rolling, the adhesion is mainly provided by the mechanical interlocking action caused by the acrylic acid ester copolymer and the water-soluble polymer in the binder penetrating into the gaps between the pole pieces, and by the intermolecular action of the acrylic acid ester copolymer. Therefore, the binder of the present application improves the adhesion of the separator to the positive and negative pole pieces during cold rolling, and reduces problems such as opening of the battery cell and soft battery cell, thereby improving the hardness of the battery cell. At the same time, the application of the binder to the separator in the secondary battery can improve the dynamic performance of the secondary battery, reduce the electrochemical impedance, and improve the magnification performance and cycling performance of the secondary battery.

[0064] That is, the water-soluble polymer has adhesive properties after being dissolved in water, and when the slurry is applied to a 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, side 21 of adhesive layer 20 facing the separator adheres to separator 10.

[0065] After drying, the side 23 of the adhesive layer 20 away from the separator is not sticky, in which case the separator can be easily rolled up. In the process of placing the pole pieces on the surface of the adhesive layer and cold rolling, some of the acrylic ester copolymers and / or water-soluble polymers in the binder further penetrate into the gaps between the separator and the pole pieces, forming intermolecular forces between the separator and the molecules on the pole pieces, and the binder effectively adheres the separator and the pole pieces to each other.

[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, 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 test method for the mass ratio 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 adheres the first polymer to the separator and helps improve 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 masses 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, and 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, and each value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the examples and 1:0.2, 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 above-mentioned water-soluble polymer containing hydrophilic groups and a certain amount of hydrophobic groups, so it has a certain surface activity, can reduce the surface tension of water to a certain extent, and can increase the solubility and dispersibility of the binder in the aqueous phase; that is, when it is made into a slurry for use in the separator, the water-soluble polymer is used to control the viscosity and rheological properties of the slurry, and can improve the dispersion and suspension of the binder. And the second polymer also has a chemical reaction function (such as a carboxyl group, a hydroxyl group, etc. that reacts with other groups), and the polar group in the water-soluble polymer structure can form hydrogen bonds between the first polymer and the separator and the pole pieces, and can improve the adhesion between the separator and the pole pieces.

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

[0076] Regarding Dv50, the particle size of the sample particles that occupies 50% of the total volume is larger than this value, and the particle size 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 testing can be performed using a Malvern laser particle size analyzer, for example, a Malvern Mastersizer-3000.

[0078] Theoretically, the volume average particle diameter Dv50 of the binder in the present application may be less than 1 μm or more than 15 μm, but considering the application of the binder in the present application to the separator, the volume average particle diameter Dv50 of the binder is set to the above range to improve the problem that the binder blocks the pores of the separator and reduces the permeability of the separator to lithium ions (for example, lithium ion batteries, and of course other types of secondary batteries may also be used), and to improve the problem that the binder is applied to the separator to form a thick coating layer, which affects the energy density of the battery subsequently manufactured. 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 1 μm to 15 μm, 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 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 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 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, as shown in Figures 1 and 2, the binder particles are secondary particles including primary particles of a first polymer and primary particles of a second polymer, in this way, the second polymer serves as a skeleton therein, when the binder slurry is applied to the separator, the second polymer plays the role of supporting and connecting the first polymer, and causes the first polymer to adhere to the separator, and 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 force, making it easier 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 under force after being extruded, and can penetrate into the gaps between the separator and the electrode pieces to achieve 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 preferably includes a spherical shape, considering that the spherical shape is useful for uniform dispersion and uniform application in the process of stirring the slurry.

[0084] In one embodiment, the first polymer comprises an acrylate monomer, and the structure of the acrylate monomer is: JPEG2025515526000006.jpg3450, where 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 a good adhesive effect.

[0086] In one embodiment, the acrylate monomers include 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 monomer as long as the acrylic ester monomer contains the above structure, i.e., the acrylic ester monomer includes the substances listed above and substances not listed in the present application.

[0088] By using any 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 enhanced.

[0089] In one embodiment, the first polymer comprises an acrylonitrile-based monomer, and the structure of the acrylonitrile-based monomer is JPEG2025515526000007.jpg2737, where R3 is a hydrogen atom or an alkyl group containing 1 to 6 carbon atoms.

[0090] The inclusion 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, that is, 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, the structure of the acrylamide-based monomer being: JPEG2025515526000008.jpg3746, wherein R4 is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R5 is a hydrogen atom, an alkyl group having 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 adhesion.

[0096] In one embodiment, the acrylamide-based monomers include one or more of acrylamide, N-methylol acrylamide, 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, i.e., the acrylamide-based monomer includes 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, and can adjust the molecular weight of the binder within a certain range, which helps 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] The commonly used polyvinylidene fluoride binder needs a hot rolling process to better exert its adhesive effect. As the production speed improves and energy is saved, the hot rolling process is gradually replaced by the cold rolling process. The battery cell is wound and then cold rolled. The traditional polyvinylidene fluoride is a homopolymer with a crystallinity of about 50%, so the adhesive strength between the separator and the positive and negative electrode pieces is insufficient. The traditional polyacrylic ester binder does not meet the adhesive strength requirements during cold rolling, so problems such as opening of the battery cell and soft battery cell frequently occur. At the same time, the electrolyte has low infiltration ability and cannot meet the requirements for coating performance on the separator of the secondary battery.

[0101] The binder comprises an acrylic ester-based copolymer prepared using the above monomers and a water-soluble polymer, which gives the binder a 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 in the range of 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), the adhesive effect is excellent.

[0104] In the above 100: (1-80): (1-20), 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 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, and each value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the examples and 100:20:5, 100:30:10, 100:60:15, etc., and range values ​​between any two of the above point values.

[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 a monomer constituting 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 the method of emulsion polymerization, and obtains a binder by the method of spray drying.

[0109] Regarding emulsion polymerization, emulsion polymerization is when monomers are dispersed in water with an emulsifier through mechanical agitation to form an emulsion, and then an initiator is added to start the polymerization of the monomers.

[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 start the polymerization reaction of monomers. For example, free radical initiators refer to compounds that are easily decomposed into free radicals (i.e., primary free radicals) when exposed to heat, and can be used to start the free radical polymerization and copolymerization reactions of olefin and diene monomers.

[0112] Water, an emulsifier, an initiator, and the monomers constituting the polymer are mixed together and stirred. After the water and the 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 the condition of heating, the initiator starts the polymerization of the monomers inside the micelles, thereby obtaining 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 by mechanical action into very fine mist-like particles (increasing the surface area for the water to evaporate, accelerating the drying process) and then contacted with hot air, which instantly removes most of the water and dries the solid substances in the material into powder.

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

[0115] The embodiments of the present application further provide a separator comprising the above-mentioned secondary battery binder or a binder manufactured by the above-mentioned method for manufacturing a secondary battery binder. Since all the technical solutions of all the above-mentioned embodiments are used in the binder, the binder has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, and detailed descriptions are omitted here.

[0116] The binder is applied to the separator to improve the adhesion 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 embodiment further 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 are omitted here.

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

[0119] The embodiments of the present application further provide a battery including the above-mentioned battery unit, in which all the technical solutions of all the above-mentioned embodiments are used, and therefore the battery unit has at least all the beneficial effects provided 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 an electric device including the above-mentioned battery alone or the above-mentioned battery, in which all the technical solutions of all the above-mentioned embodiments are used, and therefore the battery alone or the electric device has at least all the beneficial effects provided by the technical solutions of the above-mentioned embodiments, and detailed description thereof is 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, the electrode assembly includes a positive electrode piece, a negative electrode piece, an electrolyte, and a separator. During the charging and discharging process of the battery, active ions are inserted and extracted back and forth between the positive electrode piece and the negative electrode piece. The electrolyte serves to conduct ions between the positive electrode piece and the negative electrode piece. The separator is disposed between the positive electrode piece and the negative electrode piece, and serves mainly to prevent short circuit between the positive electrode and the negative electrode, while allowing ions to pass through. The separator is the improved separator described in this application.

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

[0126] For example, the positive electrode current collector has two opposing surfaces 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 opposing surfaces of the positive electrode current collector.

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

[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 used for lithium ion batteries known in the art. For example, the positive electrode active material can include at least one of lithium-containing phosphates having an olivine structure, lithium transition metal oxides, and modified compounds 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 can also be used. These positive electrode active materials can be used alone or in combination of two or more. Here, examples of lithium transition metal oxides include lithium cobalt oxide (LiCoO 2 etc.), lithium nickel oxide (LiNiO 2 etc.), lithium manganese oxide (LiMnO 2 , LiMn 2 O 4 etc.), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 (NCM 333 (also abbreviated as LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM 523 (also abbreviated as LiNi 0.5 Co 0.25 Mn 0.25 O 2 (NCM 211 (also abbreviated as LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM 622 (also abbreviated as LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM 811 Lithium nickel cobalt aluminum oxide (LiNi 0.85 Co 0.15 Al 0.05 O 2Examples of lithium-containing phosphates having an olivine structure include, but are not limited to, lithium iron phosphate (LiFePO 4 (also abbreviated as LFP), lithium iron phosphate and carbon composites, lithium manganese phosphate (LiMnPO 4 etc.), a composite of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite of lithium iron manganese phosphate and carbon, but are not limited to these.

[0129] In some embodiments, the positive electrode membrane layer optionally further comprises a binder. For example, the binder can comprise 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 membrane layer optionally further comprises a conductive agent. For example, the conductive agent can include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[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, and the positive electrode slurry is applied to a positive electrode current collector, and after processes such as drying and cold rolling, the positive electrode pieces can be obtained.

[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 opposing surfaces 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 opposing surfaces of the negative electrode current collector.

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

[0135] In some embodiments, the negative electrode active material can be a negative electrode active material used in batteries known in the art. For example, the negative electrode active material can include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material can include at least one of elemental silicon, silicon oxide compounds, silicon carbon composites, silicon nitrogen composites, and silicon alloys. The tin-based material can 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 that can be used as negative electrode active materials in batteries can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[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 membrane 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 thickening agent (eg, sodium carboxymethylcellulose (CMC-Na)).

[0139] In some embodiments, the negative electrode pieces can be manufactured by the following method: The above-mentioned components for manufacturing the negative electrode pieces, such as the negative electrode active material, the conductive agent, the binder, and any other components, are dispersed in a solvent (e.g., deionized water) to form a negative electrode slurry, and the negative electrode slurry is 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, which 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 may further include optional additives. For example, the additives may include anode film-forming additives, cathode film-forming additives, or additives that can improve specific performance of the battery, such as additives that improve the overcharge performance of the battery, or additives that improve 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 structure separator having good chemical stability and mechanical stability can be selected.

[0146] In some embodiments, the material of the separator can include at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layered thin film or a multi-layered composite thin film, and is not particularly limited. When the separator is a multi-layered composite thin film, the materials of each layer can 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 the electrolyte.

[0149] In some embodiments, the outer package of the electrode assembly may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the electrode assembly may be a soft bag, such as a bag-shaped soft bag. The material of the soft bag may be plastic. Examples of plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

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

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

[0152] In some embodiments, the electrode assembly 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 is an example of a battery module 4. Referring to Fig. 7, in the battery module 4, the multiple secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the multiple secondary batteries 5 can 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 Fig. 8 and Fig. 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 may include an upper box 2 and a lower box 3, and the upper box 2 may be installed to cover the lower box 3, forming a closed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box according to any manner.

[0157] The present application also provides an electric device comprising at least one of the electrode assembly, battery module, or battery pack provided by the present application. The electrode assembly, battery module, or battery pack can be used as a power source for the electric device, and can also be used 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, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), trains, ships, and satellites, energy storage systems, etc.

[0158] As an electrical device, an electrode assembly, a battery module or a battery pack can be selected according to its 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 can use the electrode assembly as a power source. Working Example

[0161] The following examples of the present application are described. 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 no specific techniques or conditions are specified in the examples, they will be carried out according to the techniques or conditions described in the literature in the field or according to the product specifications. If no manufacturer is specified, the reagents or equipment used are all ordinary products available on the market. Preparation of the First Polymer Emulsion Manufacturing Example 1

[0162] According to the mass ratio of the three monomers of 100:1:10, the acrylic acid ester monomer methyl acrylate, the acrylonitrile monomer acrylonitrile, and the acrylamide monomer acrylamide were weighed out and mixed uniformly. 200g of mixed monomers, 5g of emulsifier of sodium lauryl sulfate, 1.8g of initiator of ammonium persulfate, and 260g of deionized water were added to a 1000mL four-neck flask equipped with a mechanical stirrer, a thermometer, and a cooler, and emulsified by high-speed stirring for 30min. Under the protection of nitrogen gas, the temperature was raised to 75°C and reacted for 4h, then the temperature was lowered to below 40°C, the pH was adjusted to neutral with ammonia water, and filtered to obtain Preparation Example 1, which is a first polymer emulsion. Manufacturing Example 2 to Manufacturing Example 12

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

[0164] The first polymer and the second polymer were weighed and added according to the weight percentage of 1:1, deionized water was added to adjust the solid content of the system to 20%, and after stirring to mix uniformly, the separator binder was produced by the spray drying process. The conditions of the spray drying process were: inlet temperature 110°C, exhaust temperature 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 according to Example 7 using only the first polymer. Battery cell and battery manufacturing Separator manufacturing

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

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

[0170] Artificial graphite, acetylene black as a conductive agent, styrene-butadiene rubber (SBR) as a binder, and sodium carboxymethylcellulose (CMC-Na) as a thickener were added to deionized water in a mass ratio of 96.2:1.0:1.6:1.2, thoroughly stirred to mix uniformly, and then 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 g, 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 in a volume ratio of 1:1:1 at 25°C to obtain a mixed solvent, which was then cooled to 100°C. 6 was dissolved in the above mixed solvent, and LiPF 6 An electrolyte solution with a concentration of 1 mol / L was obtained. Secondary battery manufacturing

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

[0173] The battery negative pole piece and separator were stacked on top of each other and placed on a hot press. The hot press parameters were set to a temperature of 25°C, a pressure of 7t, and a time of 30s, and pressure was applied to produce an adhered separator / positive pole piece sample. The separator / pole piece sample was cut into a rectangular spline of 150mm x 20mm. One side of the spline pole piece was attached to a steel plate with double-sided tape, and the separator and pole piece were separated by 2cm 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), and 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 of 10 cm. After the tensile force stabilized, the tensile force value was recorded, and the adhesive force 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 spectroscopy):

[0175] Using Shanghai Chenhua's CHI660D electrochemical workstation, a sinusoidal voltage signal with frequency W1 and small amplitude is applied to the battery system, and the system generates a sinusoidal current response with 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 is 10mHz~100kHz, and the amplitude is 5mV. Through the test, information such as the real part and imaginary part of the impedance at various frequencies can be obtained. Lithium-ion battery multiplier performance:

[0176] Using Wuhan Jinnuo Electronics' CT-2001 A LAND battery test system, the test battery assembled with the electrode material manufactured at room temperature of 25°C, voltage range of 2.5 to 3.65V, and the charge / discharge cycle was performed 5 times at constant current at 0.2C, 0.5C, 1C, 2C, 5C, and 0.2C. The specific flow was 0.2C (5 cycles, the capacity at the 5th cycle is written as C1), then 0.5C (5 cycles), 1C (5 cycles), 2C (5 cycles), 5C (5 cycles), and 0.2C (5 cycles, the capacity at the 5th cycle is written as C2). That is, the battery capacity after the first 5 cycles of charge / discharge at 0.2C is written as C1, and the battery capacity after the second 5 cycles of charge / discharge at 0.2C is written as C2, and the charge / discharge cycle performance was expressed as P=(C2 / C1)×100%.

[0177] [Table 1]

[0178] [Table 2]

[0179] [Table 3]

[0180] By preparing a first polymer from an appropriate monomer, controlling the mass ratio of the first polymer to the second polymer within an appropriate range, and 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 is helpful in improving 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 concept of the present application and the contents of the specification and drawings of the present application, or direct / indirect applications in other related technical fields are all within the scope of protection of the patent of the present application.

Claims

1. A first polymer including an acrylic acid ester copolymer and a second polymer including a water-soluble polymer. Binder for secondary batteries.

2. The mass ratio of the first polymer to the second polymer is 1:(0.1 to 10), preferably 1:(0.2 to 5); The binder for 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, polyethyleneimine; The binder for a secondary battery according to claim 1 or 2.

4. The volume particle size distribution Dv50 of the binder is 1 μm to 15 μm, preferably 3 μm to 12 μm; The binder for a secondary battery according to any one of claims 1 to 3.

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

6. The first polymer includes an acrylate ester monomer, and the structure of the acrylate ester 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 secondary battery according to any one of claims 1 to 5.

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 secondary battery according to claim 6 .

8. The first polymer includes an acrylonitrile-based monomer, and the structure of the acrylonitrile-based monomer is Including, where R3 is a hydrogen atom or an alkyl group containing 1 to 6 carbon atoms; The binder for a secondary battery according to any one of claims 1 to 7.

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

10. The first polymer includes an acrylamide-based monomer, and the structure of the acrylamide-based monomer is Including, wherein R4 is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R5 is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms substituted with a hydroxyl group, or an alkoxy group having 1 to 6 carbon atoms. The binder for a secondary battery according to any one of claims 1 to 9.

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

12. 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 in the range of 100:(1-80):(1-20), preferably 100:(20-60):(5-15); The binder for a secondary battery according to any one of claims 1 to 11.

13. A method for producing the binder for a secondary battery according to any one of claims 1 to 12, mixing water, an emulsifier, an initiator, and constituent monomers of a first polymer together, stirring, and heating 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. The binder for secondary batteries according to any one of claims 1 to 12 or the binder produced by the method for producing a binder for secondary batteries according to claim 13, Separator.

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

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

17. A battery comprising the battery according to claim 15 or the battery according to claim 16. Electrical equipment.

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