Binder for secondary battery, separator, secondary battery, and power consumption device

Abstract

This application relates to the field of secondary battery technology, and particularly to binders for secondary batteries, separators, secondary batteries, and power consumption devices. The shape of the binder for secondary batteries includes an annular shape, and the binder contains an acrylic ester copolymer. The acrylic ester copolymer has good adhesiveness, and the contact part of the annular binder is the annular line of the annular binder, which has an adhesive site with a larger area compared to a spherical binder, and realizes good adhesive performance in the situation of reducing the usage amount of the annular binder.

Description

Cross - reference to related applications

[0001] This application claims the priority of the Chinese patent application with the application number 202310447240.5 filed on April 24, 2023, and all its contents are incorporated herein by reference.

Technical Field

[0002] This application relates to the field of secondary battery technology, and particularly to binders for secondary batteries, separators, secondary batteries, and power consumption devices.

Background Art

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

[0004] Currently, there is a problem of openings in battery cells, that is, gaps are easily formed between the polar sheet and the separator, thereby deteriorating the cycle characteristics of the battery.

Summary of the Invention

[0005] The main object of this application is to provide a binder for secondary batteries that improves the adhesion between the polar sheet and the separator and enhances the performance of the battery.

[0006] To achieve the above object, this application provides a binder for secondary batteries, the binder includes an acrylate copolymer, and the shape of the binder includes an annular shape.

[0007] The acrylate copolymer has good adhesion, and by using the acrylate copolymer, the adhesion between the separator and the polar sheet can be further improved.

[0008] The annular structure binder has a larger adhesion area. For example, when the annular structure binder contacts the polar sheet, the contact area is the annular line of the annular binder. In contrast, for the spherical binder, the contact area is a point contact. For annular structures and spherical binders of the same size, the adhesion performance of the annular structure binder is better. Moreover, the annular structure binder has a hollow through-hole. For annular structure binders and spherical binders of the same size, the mass of the annular structure binder is smaller. Therefore, good adhesion performance can be achieved while reducing the usage amount of the annular structure binder.

[0009] Optionally, the range value of the specific surface area of the binder is 0.4 m 2 / g to 1.2 m 2 / g, and preferably, the range value of the specific surface area of the binder is 0.6 m 2 / g to 0.9 m 2 / g.

[0010] The specific surface area refers to the total area of a material per unit mass. Based on the fact that the annular structure binder has a hollow through-hole, the specific surface area of the annular binder increases compared to the spherical structure binder of the same size. The range value of the specific surface area of the binder is 0.4 m 2 / g to 1.2 m 2 / g, and preferably, the range value of the specific surface area of the binder is 0.6 m 2 / g to 0.9 m 2 / g. This helps to improve the contact between the annular binder and the separator and the polar sheet, and improves the adhesion performance.

[0011] Optionally, the ratio of the surface area to the volume of the binder is 0.1×10 6 m -1 ~20×10 6 m -1 and preferably, the ratio of the surface area to the volume of the binder is 0.5×10 6 m -1 ~16×10 6 m -1 is.

[0012] The ratio of surface area to volume is the ratio of the total surface area of the material to the total volume of the material. Based on the fact that the annular structure binder has hollow through-holes, compared with a spherical structure binder of the same size, the ratio of the surface area to volume of the annular binder increases, and the ratio of the surface area to volume of the binder is 0.1×10 6 m -1 ~20×10 6 m -1 and preferably, the ratio of the surface area to volume of the binder is 0.5×10 6 m -1 ~16×10 6 m -1 This indicates that the annular binder has an increased surface area compared to the spherical binder, which helps to improve the contact between the annular binder and the separator and the polar sheet, and improves the adhesion performance.

[0013] Optionally, the range value of the bulk density of the binder is 0.3 g / cm 3 ~0.8 g / cm 3 and preferably, the range value of the bulk density of the binder is 0.4 g / cm 3 ~0.7 g / cm 3 is.

[0014] Bulk density is the mass per unit volume measured immediately after freely filling the powder into a container. Based on the fact that the annular structure binder has hollow through-holes, after filling the annular binder into the container, voids are formed in the through-holes of the annular binder. Compared with filling a spherical binder of the same size, the bulk density of the annular binder decreases, and the range value of the bulk density of the binder is 0.3 g / cm 3 ~0.8 g / cm 3 and preferably, the range value of the bulk density of the binder is 0.4 g / cm 3 ~0.7 g / cm 3 This indicates that even in the situation where the mass of the annular binder is reduced under certain conditions, the adhesion performance of the binder is improved.

[0015] Optionally, the shape of the binder includes an annular shape.

[0016] The annular shape is a shape that can be relatively easily realized based on experimental experience and the surface tension of the material.

[0017] Optionally, the range value of the volume-based particle size distribution Dv50 of the binder is 1 μm to 15 μm, and preferably, the range value of the volume-based particle size distribution Dv50 of the binder is 3 μm to 12 μm.

[0018] To improve the adhesion of the improved binder and improve the gap between the separator and the polar sheet, the range value of the volume-based particle size distribution Dv50 of the binder is 1 μm to 15 μm, and preferably, the range value of the volume-based particle size distribution Dv50 of the binder is 3 μm to 12 μm.

[0019] Optionally, the constituent monomer of the acrylic ester copolymer contains a first polymerization monomer, and the structure of the first polymerization monomer is [Chemical formula] including, where R1 contains a hydrogen atom or an alkyl group having 1 to 12 carbon atoms, and R2 contains an alkyl group having 1 to 12 carbon atoms.

[0020] The first polymerization monomer structure contains an ester group, which improves the compatibility between the acrylic ester copolymer and the electrolyte, enhances the ion conduction ability, improves the swelling resistance of the acrylic ester copolymer, and as a flexible monomer segment in the molecular segment, can adjust the glass transition temperature of the acrylic ester copolymer, which helps to improve the toughness during the coating of the binder and exert a good adhesion effect.

[0021] Optionally, the first polymerizable 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, 2-hydroxypropyl methacrylate.

[0022] Theoretically, the present application does not limit the type of the first polymerizable monomer, and the first polymerizable monomer satisfies the requirement of including the above structure, that is, the first polymerizable monomer includes the substances listed above and the substances not listed in the present application.

[0023] By using one or more of the above first polymerizable monomers, the glass transition temperature of the acrylate copolymer can be adjusted, and the swelling resistance of the acrylate copolymer can be improved.

[0024] Optionally, the constituent monomer of the acrylate copolymer includes a second polymerizable monomer, and the structure of the second polymerizable monomer is

Chemical formula

[0025] The structure of the second polymerizable monomer contains a carboxyl group, and the carboxyl group has the characteristic of strong polarity, which can improve the adhesiveness and flexibility of the binder. For example, the carboxyl group can form a binding force with the functional groups on the materials of the polar sheet and the separator, improving the adhesion effect.

[0026] Optionally, the second polymerizable monomer includes one or more of acrylic acid, methacrylic acid, crotonic acid, heptenoic acid.

[0027] Theoretically, the present application does not limit the type of the second polymerizable monomer, and the second polymerizable monomer satisfies the requirement of including the above structure, that is, the second polymerizable monomer includes the substances listed above and the substances not listed in the present application.

[0028] By using any one or more of the above second polymerizable monomers, the adhesion performance of the acrylate copolymer can be improved.

[0029] Optionally, the constituent monomer of the acrylate copolymer includes a third polymerizable monomer, and the structure of the third polymerizable monomer is

Chemical formula

[0030] The structure of the third polymerizable monomer contains an unsaturated cyano group, and the strongly polar cyano group helps to improve the ionic conductivity, and at the same time has the effects of swelling resistance and high adhesiveness.

[0031] Optionally, the third polymerizable monomer includes one or more of acrylonitrile and methacrylonitrile.

[0032] Theoretically, the present application does not limit the type of the third polymerizable monomer, and the third polymerizable monomer satisfies the requirement of including the above structure, that is, the third polymerizable monomer includes the substances listed above and the substances not listed in the present application.

[0033] By using any one or more of the above third polymerizable monomers, the ionic conductivity of the acrylate copolymer can be improved and the adhesiveness can be enhanced.

[0034] Optionally, the constituent monomer of the acrylate copolymer includes a fourth polymerizable monomer, and the structure of the fourth polymerizable monomer is

Chemical formula

[0035] The structure of the fourth polymerizable monomer contains an unsaturated amide group, and the amide group plays a role in improving the swelling property and enhancing the adhesion force.

[0036] Optionally, the fourth polymerizable monomer includes one or more of acrylamide, N-methylol acrylamide, and N-butoxymethyl acrylamide.

[0037] Theoretically, the present application does not limit the type of the fourth polymerizable monomer, and the fourth polymerizable monomer satisfies the requirement of including the above structure, that is, the fourth polymerizable monomer includes the substances listed above and the substances not listed in the present application.

[0038] By using one or more of the above fourth polymerizable monomers, the adhesiveness of the acrylate copolymer can be improved.

[0039] As can be understood, when at least two of the above four monomers are included, the adhesion effect is better. For example, the constituent monomers of the acrylate copolymer include at least the first polymerizable monomer and the second polymerizable monomer, or the constituent monomers of the acrylate copolymer include at least the first polymerizable monomer and the third polymerizable monomer, or the constituent monomers of the acrylate copolymer include at least the first polymerizable monomer and the fourth polymerizable monomer. When the constituent monomers of the acrylate copolymer include the above four monomers at the same time, the performance of the binder is better.

[0040] Optionally, the constituent monomers of the acrylic ester copolymer include a first polymerization monomer, a second polymerization monomer, a third polymerization monomer, and a fourth polymerization monomer, and the mass ratio of the first polymerization monomer, the second polymerization monomer, the third polymerization monomer, and the fourth polymerization monomer is 1:(0.01 - 0.8):(0.01 - 0.5):(0.01 - 0.3), and preferably, the mass ratio of the first polymerization monomer, the second polymerization monomer, the third polymerization monomer, and the fourth polymerization monomer is 1:(0.1 - 0.5):(0.15 - 0.45):(0.1 - 0.22).

[0041] When the constituent monomers of the acrylic ester copolymer simultaneously contain the above four monomers and the components of each monomer are within the above range, the comprehensive performance is better.

[0042] The present application further provides a separator including a base material and an adhesive layer provided on at least one side of the base material, and the adhesive layer contains the binder for secondary batteries.

[0043] Optionally, the range value of the surface density of the adhesive layer on the base material is 0.7 g / m 2 ~3 g / m 2 and preferably 0.8 g / m 2 ~2 g / m 2 is.

[0044] Based on the cyclic structure binder increasing the contact area between the binder and the polar sheet and the separator, that is, good adhesion performance can be achieved even in the situation where the usage amount of the cyclic structure binder is reduced. Therefore, the range value of the surface density of the adhesive layer on the base material is 0.7 g / m 2 ~3 g / m 2 and preferably, the range value of the surface density of the adhesive layer on the base material is 0.8 g / m 2 ~2 g / m 2 is.

[0045] The present application further provides a secondary battery including the separator.

[0046] The present application further provides a power consumption device including the secondary battery.

Brief Description of the Drawings

[0047] To more clearly explain the technical solutions in the embodiments of the present application or the prior art, the drawings necessary for the description of the embodiments or the prior art are briefly described below. The drawings shown below are only some embodiments of the present application. It is obvious that those skilled in the art can obtain other drawings based on the structures shown in these drawings without creative effort.

[0048]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Description of Reference Numerals

[0049] 1 Battery pack 2 Upper housing 3 Lower housing 4 Battery module 60 Annular wire 5 Secondary battery 51 Housing 52 Electrode Assembly 53 Top Cover Assembly 61 Through-Hole

[0050] The implementation examples will be further described with reference to the drawings by combining the realization of the object of the present application, the functional features and the advantages.

Embodiments for Carrying Out the Invention

[0051] With reference to the drawings in the embodiments of the present application below, the technical solutions in the embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the protection scope of the present application.

[0052] Hereinafter, embodiments of the binder of the present application, its manufacturing method, and a separator, an electrode assembly, a battery cell, a battery, and a power consumption device including the binder will be described in detail with reference to the drawings as appropriate. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters or overlapping descriptions of substantially the same structures may be omitted. This is to prevent the following description from becoming unnecessarily redundant and to facilitate the understanding of those skilled in the art. Also, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0053] The "range" disclosed in this application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting one lower limit and one upper limit, and the selected lower limit and upper limit define the boundaries of a specific range. A range defined in this way may or may not include the values at both ends, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are also understood to be contemplated. Also, if the minimum range values 1 and 2 are listed, and the maximum range values 3, 4, and 5 are listed, ranges of 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5 are all contemplated. In this application, unless otherwise stated, the numerical range "a - b" means an abbreviated representation of any combination of real numbers between a and b, and both a and b are real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" are all listed in this specification, and "0 - 5" is only an abbreviated representation of combinations of these numerical values. Also, when a parameter is expressed as an integer ≧ 2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0054] All embodiments and selectable embodiments of this application can be combined with each other to form new technical solutions unless otherwise specified.

[0055] All technical features and selectable technical features of this application can be combined with each other to form new technical solutions unless otherwise explained.

[0056] All steps of the present application can be carried out in order or randomly unless otherwise specified, and preferably in order. For example, when the method includes steps (a) and (b), it indicates that the method may include steps (a) and (b) carried out in order, or steps (b) and (a) carried out in order. For example, when it is said that the method may further include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0057] There is a problem with the opening in the battery cell, that is, a gap is easily formed between the polar sheet and the separator, thereby deteriorating the cycle characteristics of the battery.

[0058] For example, if the adhesion between the positive and negative electrode sheets and the separator is insufficient, problems such as cell opening always occur, and the requirements for the performance of the coated separator of the secondary battery cannot be met.

[0059] The cell is formed by adhering the positive and negative electrode sheets and the separator. The cell has a certain hardness, that is, the adhered positive and negative electrode sheets and the separator are bonded to each other and supported by each other, thus forming a structure with a certain thickness. The structure with a certain thickness has a certain hardness. However, during the charge and discharge process, the negative electrode expands. If the adhesion is weak, a gap is formed between the positive and negative electrode sheets and the separator, and the positive and negative electrode sheets and the separator cannot be bonded to each other and supported by each other, resulting in looseness in the cell and a decrease in hardness. At this time, the power characteristics of the cell deteriorate. For example, the rate characteristics deteriorate, and at the same time, the cycle characteristics deteriorate. For example, in an electric vehicle, when the battery cell loosens, the charging speed of the battery becomes slow, and at the same time, the cycle characteristics of the battery deteriorate, directly leading to a shortening of the battery life. In an electric vehicle, it is necessary to frequently replace the battery, increasing the cost for consumers in the electric vehicle.

[0060] Based on this, the present application provides a binder for a secondary battery. The binder contains an acrylic ester copolymer, and the shape of the binder includes an annular shape.

[0061] A binder is a material having adhesive performance and is used to adhere different substances.

[0062] An annular binder, in which a through-hole is formed in the structure of the binder. The through-hole is a hole that penetrates two opposing surfaces of the binder. As shown in FIGS. 1 and 2, it is an annular binder.

[0063] An annular line. As shown in FIG. 10, a through-hole 61 is formed in the structure of the annular binder, and an annular line 60 is formed around the through-hole 61. As can be understood, when the binder is disposed on the separator along the direction towards the through-hole 61 (that is, the opening of the through-hole 61 faces the separator), the periphery of the through-hole 61 contacts the separator, and the contact part is the annular line. Compared with the case where a spherical binder is provided on the separator, the spherical binder and the separator are in point contact, while the annular binder can contact the separator through the annular line, and the contact area increases.

[0064] Regarding the acrylic ester copolymer, the acrylic ester copolymer is a general term for polymers produced by copolymerizing an acrylic ester monomer and other comonomers.

[0065] The structure of the acrylic ester monomer has an acrylic ester group. For example, it is methyl acrylate, ethyl acrylate, n-butyl acrylate.

[0066] The acrylic ester copolymer has good adhesiveness. By using the acrylic ester copolymer, the adhesiveness between the separator and the polar sheet can be further improved.

[0067] The binder with an annular structure has a larger bonding area. For example, when the binder with an annular structure contacts the polar sheet, the contact part is the annular line of the annular binder. In contrast, for a spherical binder, the contact part is a point contact. Based on the fact that for an annular structure and a spherical binder of the same size, the annular structure has a larger contact area, the bonding performance of the binder with an annular structure is better. Moreover, the binder with an annular structure has a hollow through-hole. For an annular structure binder and a spherical binder of the same size, the mass of the annular structure binder is smaller. Therefore, good bonding performance can be realized while reducing the usage amount of the binder with an annular structure.

[0068] Applying the binder with an annular structure to the separator can increase the contact area between the binder and the polar sheet and the separator, reduce the usage amount of the binder, meet the requirements of the cold press adhesion force between the separator and the positive and negative electrode sheets during the cold press process, improve the hardness of the cell, and improve problems such as the opening of the cell and the softness of the cell. At the same time, applying this binder to the separator and applying it to a secondary battery can improve the cycle characteristics of the secondary battery with fixtures.

[0069] The cycle characteristics with a jig are the characteristics of the cycle functionality test of the cell. In the process of the test, a jig is given to the cell, and a certain force is applied to the jig to press the cell. When the cell is fully charged, it expands and is doubly pressed by the clamping force of the jig and the expansion force, and the cell may be deformed. This test is used to test the shape retention performance and pressure resistance performance of the cell. When using the binder of this solution, since the adhesion performance is good, the expansion of the cell is weakened, and the shape of the cell is well retained. The cell using the binder of this application maintains good performance under the test conditions with a jig, which indicates that the cell has excellent deformation retention performance obtained by using the binder of this solution. Even after the cell is assembled into the battery, the cell is not easily deformed, so the space for installing the cell in the battery can be saved, and thus the volume of the battery can be made smaller. If the cell is easily deformed, it will push out the structure near the cell. To improve this phenomenon, it is necessary to accommodate the deformed cell in a larger space, that is, it is necessary to ensure a space for accommodating the deformed part of the cell in the battery. Therefore, it occupies more space inside the battery.

[0070] At the same time, the high cycle characteristics with a jig of the cell also indicate that the cycle characteristics of the cell are excellent. For example, when the cell expands, the gap between the polar sheet and the separator becomes larger, and the path for lithium ions (taking a lithium-ion battery as an example, and of course it may also be other types of secondary batteries) to pass through the positive and negative electrodes becomes longer, and the cycle deteriorates.

[0071] The binder of this application can make the bonding between the separator and the polar sheet closer, improve the discharge capacity of the battery, reduce the internal resistance, reduce the polarization loss, extend the cycle life of the battery, and improve the utilization rate of the secondary battery.

[0072] In one embodiment, the range value of the specific surface area of the binder is 0.4m 2 / g to 1.2m 2 / g, and preferably, the range value of the binder specific surface area is 0.6m 2 / g to 0.9m 2is / g.

[0073] The specific surface area refers to the total area of a material per unit mass, and the unit is m 2 is / g.

[0074] Test of specific surface area: The BET specific surface area is measured by the BET method of N 2 adsorption.

[0075] Using the NOVA 2000 type specific surface area and pore size analyzer of Contact Chromatography Company in the United States, high-purity nitrogen gas with a purity of more than 99.999% is used as the adsorbent. Select a spherical sample tube with a diameter of 20 mm, weigh a binder sample of 1.4000 g ± 0.2000 g, cover it with a heating cover, evacuate it with a vacuum pump to 10 -2 Torr or more, slowly raise the temperature to a certain temperature after the pressure is stable, control the pretreatment time, cool for 30 min after the pretreatment is completed, and weigh the mass of the sample. Perform a full-process adsorption and desorption test on the pretreated sample to obtain the isothermal adsorption and desorption curve of the sample, process the data with the software attached to the instrument, and obtain the specific surface area parameters of the binder.

[0076] The specific surface area refers to the total area of a material per unit mass. Based on the fact that the binder with a cyclic structure has hollow through holes, compared with the binder with a spherical structure of the same size, the specific surface area of the cyclic binder increases, and the range value of the specific surface area of the binder is 0.4 m 2 / g ~ 1.2 m 2 / g, preferably, the range value of the specific surface area of the binder is 0.6 m 2 / g ~ 0.9 m 2 / g, which helps to improve the contact between the cyclic binder and the separator and the polar sheet, and improves the adhesion performance.

[0077] The above 0.4 m 2 / g ~ 1.2 m 2 / g, the value includes the minimum value and the maximum value of the range, and each value between this minimum value and the maximum value, and as specific examples, the end point values in the examples and 0.4 m 2 / g, 0.5 m 2 / g, 0.6 m 2 / g, 0.7 m 2 / g, 0.8 m 2 / g, 0.9 m 2 / g, 1.0 m 2 / g, 1.1 m 2 / g 1.2 m 2 / g etc., and including but not limited to the range values between any two of the above endpoint values.

[0078] The above 0.6 m 2 / g ~ 0.9 m 2 / g, the value includes the minimum value and the maximum value of the range, and each value between this minimum value and the maximum value. As a specific example, the endpoint values in the examples and 0.6 m 2 / g, 0.7 m 2 / g, 0.8 m 2 / g, 0.9 m 2 / g etc., and including but not limited to the range values between any two of the above endpoint values.

[0079] In one embodiment, the ratio of the surface area to the volume of the binder is 0.1×10 6 m -1 ~ 20×10 6 m -1 and preferably, the ratio of the surface area to the volume of the binder is 0.5×10 6 m -1 ~ 16×10 6 m -1 is.

[0080] The ratio of the surface area to the volume is the ratio of the total surface area of the material to the total volume of the material.

[0081] Regarding the test method of the ratio of the surface area to the volume, the surface area and the volume of a certain mass of the binder are measured respectively, and then the values of the surface area and the volume are divided to obtain the ratio of the surface area to the volume. It is defined to measure m1 grams of the binder, and the measurement method of the surface area can be obtained by using the above measurement method of the specific surface area. If the value of the above specific surface area is defined as am 2 / g, the surface area of m1 grams of the binder is (m1 * a), and the unit is m 2It is as follows. The volume of m1 grams of binder is measured using the drainage method. That is, take water with a volume of V1, put it into a container, and then put 1 gram of binder into the container to obtain a binder mixture. If the measured volume of the mixture is V2, the volume of m1 grams of binder is V2 - V1. The calculation formula for the ratio of surface area to volume is (m1 * a) / (V2 - V1), and the unit is m -1 It is as follows.

[0082] Based on the fact that the binder with an annular structure has a hollow through-hole, compared with a spherical binder with the same dimensions, the ratio of the surface area to the volume of the annular binder increases, and the ratio of the surface area to the volume of the binder is 0.1×10 6 m -1 ~20×10 6 m -1 It is as follows, and preferably, the ratio of the surface area to the volume of the binder is 0.5×10 6 m -1 ~16×10 6 m -1 It is as follows, which indicates that the surface area of the annular binder increases compared with the spherical binder, helps to improve the contact between the annular binder and the separator and the polar sheet, and improves the adhesion performance.

[0083] In the above 0.1×10 6 m -1 ~20×10 6 m -1 the value includes the minimum value and the maximum value of the range, and each value between this minimum value and the maximum value, and specific examples include the end point values in the examples and 0.1×10 6 m -1 、1×10 6 m -1 、2×10 6 m -1 、3×10 6 m -1 、4×10 6 m -1 、5×10 6 m -1 、6×10 6 m -1 、7×10 6 m -1 、8×10 6 m-1 、 9×10 6 m -1 、 10×10 6 m -1 、 11×10 6 m -1 、 12×10 6 m -1 、 13×10 6 m -1 、 14×10 6 m -1 、 15×10 6 m -1 、 16×10 6 m -1 、 17×10 6 m -1 、 18×10 6 m -1 、 19×10 6 m -1 、 20×10 6 m -1 etc., and including but not limited to the range values between any two of the above endpoint values.

[0084] In the above 0.5×10 6 m -1 ~ 16×10 6 m -1 In this case, the value includes the minimum value and the maximum value of the range, and each value between this minimum value and the maximum value. Specific examples include the endpoint values in the embodiments and 0.5×10 6 m -1 、 1×10 6 m -1 、 2×10 6 m -1 、 3×10 6 m -1 、 4×10 6 m -1 、 5×10 6 m -1 、 6×10 6 m -1 、 7×10 6 m -1 、 8×10 6 m -1 、 9×10 6 m -1 、 10×10 6 m -1 、 11×10 6 m -1 、 12×106 m -1 、 13×10 6 m -1 、 14×10 6 m -1 、 15×10 6 m -1 、 16×10 6 m -1 etc., and including, but not limited to, the range values between any two of the above endpoint values.

[0085] In one embodiment, the range value of the bulk density of the binder is 0.3 g / cm 3 ~0.8 g / cm 3 and preferably, the range value of the bulk density of the binder is 0.4 g / cm 3 ~0.7 g / cm 3 .

[0086] The bulk density is the mass per unit volume measured immediately after freely filling the powder into the container.

[0087] The specific test steps are as follows. Using the tap device method, place the sample in a 100 mL volumetric cylinder of the tap device, start the device, vibrate the volumetric cylinder with the vibration device of the tap device to tap the sample, and during the experiment, continuously add the sample until the sample volume no longer decreases. Finally, weigh the mass of the sample and divide the sample mass by the sample volume to obtain the bulk density.

[0088] Based on the fact that the binder with a ring structure has a hollow through-hole, after filling the container with the ring-shaped binder, voids are formed in the through-holes of the ring-shaped binder. Compared with filling a spherical binder of the same size, the bulk density of the ring-shaped binder decreases, and the range value of the bulk density of the binder is 0.3 g / cm 3 ~0.8 g / cm 3 and preferably, the range value of the bulk density of the binder is 0.4 g / cm 3 ~0.7 g / cm 3 and it shows that even in the situation where the mass of the ring-shaped binder is reduced under certain conditions, the adhesion performance of the binder is improved.

[0089] In the above 0.3 g / cm 3 ~0.8 g / cm 3 the value includes the minimum value and the maximum value of the range, and each value between this minimum value and the maximum value. As specific examples, the endpoint values in the examples and 0.3 g / cm 3 , 0.4 g / cm 3 , 0.5 g / cm 3 , 0.6 g / cm 3 , 0.7 g / cm 3 , 0.8 g / cm 3 etc., and includes, but is not limited to, the range values between any two of the above endpoint values.

[0090] In the above 0.4 g / cm 3 ~0.7 g / cm 3 the value includes the minimum value and the maximum value of the range, and each value between this minimum value and the maximum value. As specific examples, the endpoint values in the examples and 0.4 g / cm 3 , 0.5 g / cm 3 , 0.6 g / cm 3 , 0.7 g / cm 3 etc., and includes, but is not limited to, the range values between any two of the above endpoint values.

[0091] In one embodiment, the shape of the binder includes an annular shape.

[0092] The annular shape is a shape that can be relatively easily realized based on experimental experience and the surface tension of the material. The shape of the binder in the present application includes an annular shape. Furthermore, the annular shape in the present application may be a substantially annular shape. For example, as shown in FIG. 1, the structures of some binders are not a complete annular shape. For example, a certain part is crushed to form a substantially annular structure.

[0093] In one embodiment, the range value of the volume-based particle size distribution Dv50 of the binder is 1 μm to 15 μm, and preferably, the range value of the volume-based particle size distribution Dv50 of the binder is 3 μm to 12 μm.

[0094] For Dv50, in the sample particles, the particle size of 50% of the total volume of the particles is larger than this value, and the particle size of the other 50% of the total volume of the particles is smaller than this value. Dv50 represents the median particle size in the sample.

[0095] The volume-based particle size distribution Dv50 of the binder can be measured using methods known in the art. As an example, referring to GB / T 19077-2016, a characteristic evaluation test can be performed using a Malvern laser particle size analyzer, for example, measurement can be carried out using an apparatus such as Malvern's Mastersizer-3000.

[0096] To improve the adhesiveness of the binder and the gap between the separator and the polar sheet, the range value of the volume-based particle size distribution Dv50 of the binder is 1 μm to 15 μm, preferably, the range value of the volume-based particle size distribution Dv50 of the binder is 3 μm to 12 μm.

[0097] In the above 1 μm to 15 μm, the value includes the minimum value and the maximum value of the range, and each value between this minimum value and the maximum value. As specific examples, the endpoint values in the examples and 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, etc., and the range values between any two of the above endpoint values are included, but not limited thereto.

[0098] In the above 3 μm to 12 μm, the value includes the minimum value and the maximum value of the range, and each value between this minimum value and the maximum value. As specific examples, the endpoint 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 the range values between any two of the above endpoint values are included, but not limited thereto.

[0099] In one embodiment, the constituent monomer of the acrylate copolymer contains a first polymerization monomer, and the structure of the first polymerization monomer is

Chemical formula

[0100] The first polymerization monomer structure contains an ester group, which can improve the compatibility between the acrylate copolymer and the electrolyte, enhance the ion conduction ability, improve the swelling resistance of the acrylate copolymer, and, as a flexible monomer segment in the molecular segment, can adjust the glass transition temperature of the acrylate copolymer, improve the toughness during the coating of the binder, and help to exhibit a good adhesion effect.

[0101] In one embodiment, the first polymerization 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.

[0102] Theoretically, the present application does not limit the type of the first polymerization monomer, and the first polymerization monomer satisfies the requirement of including the above structure, that is, the first polymerization monomer includes the substances listed above and the substances not listed in the present application.

[0103] By using one or more of the above first polymerization monomers, the glass transition temperature of the acrylate copolymer can be adjusted, and the swelling resistance of the acrylate copolymer can be improved.

[0104] In one embodiment, the constituent monomer of the acrylate copolymer includes a second polymerization monomer, and the structure of the second polymerization monomer is

Chemical formula

[0105] The structure of the second polymerizable monomer contains a carboxyl group, and the carboxyl group has the characteristic of strong polarity, which can improve the adhesiveness and flexibility of the binder. For example, the carboxyl group can form a binding force with the functional groups on the materials of the polar sheet and the separator, improving the adhesion effect.

[0106] In one embodiment, the second polymerizable monomer includes one or more of acrylic acid, methacrylic acid, crotonic acid, and heptenoic acid.

[0107] Theoretically, the present application does not limit the type of the second polymerizable monomer, and the second polymerizable monomer satisfies the requirement of including the above structure, that is, the second polymerizable monomer includes the substances listed above and the substances not listed in the present application.

[0108] By using one or more of the above second polymerizable monomers, the adhesion performance of the acrylate copolymer can be improved.

[0109] In one embodiment, the constituent monomer of the acrylate copolymer includes a third polymerizable monomer, and the structure of the third polymerizable monomer is

Chemical formula

[0110] The structure of the third polymerizable monomer contains an unsaturated cyano group, and the strongly polar cyano group helps to improve the ionic conductivity and at the same time has the effects of swelling resistance and high adhesiveness.

[0111] In one embodiment, the third polymerizable monomer includes one or more of acrylonitrile and methacrylonitrile.

[0112] Theoretically, the present application does not limit the type of the fourth polymerizable monomer, and the fourth polymerizable monomer satisfies the requirement of including the above structure, that is, the fourth polymerizable monomer includes the substances listed above and the substances not listed in the present application.

[0113] By using any one or more of the above-mentioned third polymerizable monomers, the ionic conductivity of the acrylate copolymer can be improved and the adhesiveness can be enhanced.

[0114] In one embodiment, the constituent monomer of the acrylate copolymer includes a fourth polymerizable monomer, and the structure of the fourth polymerizable monomer is

Chemical formula

[0115] The structure of the fourth polymerizable monomer contains an unsaturated amide group, and the amide group plays a role in improving the swelling property and enhancing the adhesion.

[0116] In one embodiment, the fourth polymerizable monomer includes one or more of acrylamide, N-methylolacrylamide, and N-butoxymethylacrylamide.

[0117] Theoretically, the present application does not limit the type of the fourth polymerizable monomer, and the fourth polymerizable monomer satisfies the requirement of including the above structure, that is, the fourth polymerizable monomer includes the substances listed above and the substances not listed in the present application.

[0118] By using any one or more of the above-mentioned fourth polymerizable monomers, the adhesiveness of the acrylate copolymer can be improved.

[0119] As can be understood, when at least two of the above four monomers are included, the adhesion effect is even better. For example, the constituent monomers of the acrylate copolymer include at least the first polymerization monomer and the second polymerization monomer, or the constituent monomers of the acrylate copolymer include at least the first polymerization monomer and the third polymerization monomer, or the constituent monomers of the acrylate copolymer include at least the first polymerization monomer and the fourth polymerization monomer. When the constituent monomers of the acrylate copolymer simultaneously include the above four monomers, the performance of the binder is better.

[0120] In one embodiment, the constituent monomers of the acrylate copolymer include the first polymerization monomer, the second polymerization monomer, the third polymerization monomer and the fourth polymerization monomer, and the mass ratio of the first polymerization monomer, the second polymerization monomer, the third polymerization monomer and the fourth polymerization monomer is 1:(0.01~0.8):(0.01~0.5):(0.01~0.3), preferably, the mass ratio of the first polymerization monomer, the second polymerization monomer, the third polymerization monomer and the fourth polymerization monomer is 1:(0.1~0.5):(0.15~0.45):(0.1~0.22).

[0121] When the constituent monomers of the acrylate copolymer simultaneously include the above four monomers and the components of each monomer are within the above range, the comprehensive performance is better.

[0122] Regarding the measurement method of the mass ratio, in the production process of the acrylate copolymer, record the mass of each monomer for producing the acrylate copolymer input in the reaction process. Denote the mass of the first polymerization monomer as m1, the mass of the second polymerization monomer as m2, the mass of the third polymerization monomer as m3, and the mass of the fourth polymerization monomer as m4. The mass ratio of the four monomers is m1:m2:m3:m4.

[0123] In the case of the above 1:(0.01~0.8):(0.01~0.5):(0.01~0.3), the values include the minimum value and the maximum value of the range, and each value between this minimum value and the maximum value. Specific examples include the endpoint values in the examples and 1:0.01:0.01:0.01, 1:0.5:0.25:0.15, 1:0.8:0.5:0.3, etc., and the range values between any two of the above endpoint values, but are not limited thereto.

[0124] In the case of the above 1:(0.1~0.5):(0.15~0.45):(0.1~0.22), the values include the minimum value and the maximum value of the range, and each value between this minimum value and the maximum value. Specific examples include the endpoint values in the examples and 1:0.1:0.15:0.1, 1:0.3:0.3:0.15, 1:0.5:0.45:0.22, etc., and the range values between any two of the above endpoint values, but are not limited thereto.

[0125] In one embodiment, the present application further provides a method for manufacturing a binder, including the steps of manufacturing an acrylate copolymer emulsion and subjecting the acrylate copolymer emulsion to spray drying to obtain a binder having a cyclic structure.

[0126] In spray drying, due to mechanical action, the material to be dried (acrylate copolymer emulsion) is dispersed into very fine mist-like fine particles and brought into contact with hot air (which increases the evaporation area of moisture and accelerates the drying process) to instantaneously remove most of the moisture and dry the solid substances in the material into powder.

[0127] An acrylate copolymer emulsion is manufactured by emulsion polymerization, and spray drying is performed on the acrylate copolymer emulsion to obtain a cyclic binder. The mechanism is that due to the volatilization of moisture, the primary emulsion of the acrylate copolymer closely deposits to form a cyclic binder.

[0128] In one embodiment, the steps of manufacturing an acrylate copolymer emulsion include: putting water, an emulsifier, and constituent monomers of the acrylate copolymer into a container, stirring and emulsifying to obtain a preliminary emulsion of the monomers; adding the emulsifier and water to a reaction vessel, stirring and emulsifying, and adding the preliminary emulsion and an initiator solution under heating conditions, and performing a temperature-rising reaction to obtain an acrylate copolymer emulsion.

[0129] The preliminary emulsion is a solution obtained by preliminarily emulsifying the monomers. Emulsification is an action in which a liquid is uniformly dispersed in another liquid that does not dissolve in each other as very fine droplets. Water, the emulsifier, and the constituent monomers of the acrylate copolymer are mixed and stirred, and the constituent monomers of the acrylate copolymer are dispersed in water under the action of the emulsifier.

[0130] Regarding emulsion polymerization, emulsion polymerization is that the monomers are dispersed in water by an emulsifier and mechanical stirring to form an emulsion, and then an initiator is added to initiate the polymerization of the monomers.

[0131] Regarding the emulsifier, the emulsifier is a substance that converts oil and water that do not dissolve in each other into an emulsion that is difficult to separate. The emulsifier is generally a surfactant having both the properties of a hydrophilic polar group and a hydrophobic (lipophilic) non-polar group.

[0132] Regarding the initiator, the initiator is a substance that can initiate a polymerization reaction in the monomers. For example, a radical initiator refers to a compound that is easily decomposed by heat to form radicals (i.e., primary radicals), and can be used to initiate radical polymerization and copolymerization reactions of olefin-based and diene-based monomers.

[0133] In the steps of manufacturing an acrylate copolymer emulsion, first performing preliminary emulsification and then performing a polymerization reaction is used to mix the monomers more uniformly, and the obtained acrylate copolymer has more uniform particles and more stable performance. In the process of spray drying, it promotes the formation of a cyclic binder.

[0134] Vinylidene fluoride is widely used as the most common binder in separators. However, at present, the price of vinylidene fluoride fluctuates violently and the supply to the market is small. Coating the surface of the separator of a lithium battery with a vinylidene fluoride polymer can partially solve the problem of the high-temperature shrinkage of the separator. Cold pressing is performed on the wound cell. However, ordinary vinylidene fluoride is a homopolymer and has a crystallinity of about 50%, so the adhesive force with the positive and negative electrode sheets is insufficient, and the problem of cell opening always occurs, and the requirements for the coating performance of the separator in secondary batteries cannot be met.

[0135] That is, coating the surface of the separator of the battery with a vinylidene fluoride polymer can partially solve the problem of the high-temperature shrinkage of the separator. Cold pressing is performed on the wound cell. However, ordinary vinylidene fluoride is a homopolymer and has a crystallinity of about 50%, so the adhesive force with the positive and negative electrode sheets is insufficient, and the problem of cell opening always occurs. When an opening occurs in the cell, a gap is formed between the polar sheet and the separator, the structure of the whole cell becomes loose, the hardness of the cell decreases, and the cycle characteristics of the cell are affected.

[0136] Applying the binder with a cyclic structure of the present application to the separator and coating it on the separator can increase the contact area between the binder, the polar sheet, and the separator, reduce the usage amount, meet the requirements for the cold pressing adhesive force between the separator and the positive and negative electrode sheets during the cold pressing process, improve the hardness of the cell, and avoid problems such as cell opening and the cell being soft. At the same time, applying the binder to the separator and applying it to a secondary battery can improve the cycle characteristics of the secondary battery with fixtures.

[0137] In one embodiment, the present application further provides a separator including a substrate and an adhesive layer provided on at least one side of the substrate, the adhesive layer includes the binder for the secondary battery, or the adhesive layer includes a binder manufactured by the manufacturing method of the above-mentioned binder for the secondary battery.

[0138] The following layer is a structure composed of a binder coated on a separator.

[0139] Before applying the binder to the separator, first, the binder is dissolved in water to produce a binder paste, and the binder paste is applied to the separator and dried to obtain an adhesive layer.

[0140] As can be understood, when the binder is at room temperature (room temperature is about 23 ± 2 °C) after drying, there is no adhesive force when there is no pressure, that is, in the process of not applying pressure to the separator, the side of the adhesive layer away from the separator has no viscosity, satisfying the requirements of winding and unwinding the separator. When a certain pressure is applied, the binder shows pressure sensitivity and excellent adhesiveness, satisfying the requirements of the adhesive force between the separator and the positive and negative electrode polarity sheets. At the same time, the adhesiveness further forms an intermolecular force between the separator and the molecules on the polarity sheet, and the binder effectively adheres the separator and the polarity sheet.

[0141] Furthermore, after cold pressing, there is a situation where the hollow through-holes of the annular binder are not completely blocked, thereby forming voids. The voids promote the wetting of the electrolyte and improve the transmission of lithium ions (taking a lithium-ion battery as an example, but of course, it may also be other types of secondary batteries).

[0142] The binder powder material produced by the spray drying process realizes non-adhesiveness when there is no pressure at room temperature.

[0143] Pressure sensitivity means that after the binder is pressed, the binder deforms under the force and penetrates into the gap between the separator and the electrode sheet to achieve a mechanical interlocking effect and realize an adhesive effect.

[0144] In one embodiment, the range value of the surface density of the adhesive layer on the substrate is 0.7 g / m 2 ~3 g / m 2 and preferably 0.8 g / m 2 ~2 g / m2 It is as follows.

[0145] The areal density refers to the mass of the adhesive layer applied to one side of the separator.

[0146] The test method for the areal density is as follows. Take a separator of a certain area to obtain the separator area S, weigh the weight M1 of the separator with the binder added, weigh the mass M2 of the separator without the binder applied with the same area S, and the calculation formula for the areal density of the binder is (M1 - M2) / S.

[0147] Based on the fact that the cyclic structure binder increases the contact area between the binder and the polar sheet and the separator, that is, good adhesion performance can be realized even when the usage amount of the cyclic structure binder is reduced. Therefore, the range value of the areal density of the adhesive layer on the base material is 0.7 g / m 2 ~3 g / m 2 It is, and preferably, 0.8 g / m 2 ~2 g / m 2 It is as follows.

[0148] In the above 0.7 g / m 2 ~3 g / m 2 the value includes the minimum value and the maximum value of the range, and each value between this minimum value and the maximum value, and as specific examples, the endpoint values in the examples and 0.7 g / m 2 0.8 g / m 2 0.9 g / m 2 1 g / m 2 1.5 g / m 2 2 g / m 2 2.5 g / m 2 3 g / m 2 etc., and includes, but is not limited to, the range values between any two of the above endpoint values.

[0149] In the above 0.8 g / m 2 ~2 g / m 2 the value includes the minimum value and the maximum value of the range, and each value between this minimum value and the maximum value, and as specific examples, the endpoint values in the examples and 0.8 g / m 2 0.9 g / m 2 1 g / m2 , 1.2 g / m 2 , 1.5 g / m 2 , 1.7 g / m 2 , 1.9 g / m 2 , 2 g / m 2 etc., and including but not limited to the range values between any two of the above endpoint values.

[0150] Embodiments of the present application further provide a secondary battery including the separator.

[0151] The secondary battery includes forms such as a battery module, a battery cell, and a battery pack. When the secondary battery is a battery cell, the battery cell includes the above separator; when the secondary battery is a battery module, the battery module includes the above separator; when the secondary battery is a battery pack, the battery pack includes the above separator.

[0152] Embodiments of the present application further provide a power consumption device including the above battery cell or the above battery.

[0153] Also, the electrode assembly, battery cell, battery, and power consumption device of the present application will be described below with reference to the drawings as appropriate.

[0154] In one embodiment of the present application, an electrode assembly is provided.

[0155] Generally, the electrode assembly includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During the charge and discharge process of the battery, active ions reciprocate between the positive electrode sheet and the negative electrode sheet for insertion and desorption. The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is installed between the positive electrode sheet and the negative electrode sheet, mainly playing a role in preventing the short circuit between the positive and negative electrodes and at the same time allowing ions to pass through. The separator is the above improved separator of the present application.

[0156] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector.

[0157] As an example, the positive electrode current collector has two surfaces facing each other in its own thickness direction, and the positive electrode film layer is provided on one or both of the two opposing surfaces of the positive electrode current collector.

[0158] In some embodiments, a metal foil or a composite current collector can be used as the positive electrode current collector. As the metal foil, for example, an aluminum foil can be used. The composite current collector can include a polymer base material layer and a metal layer formed on at least one surface of the polymer base material layer. The composite current collector can be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymer material base (such as a base of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0159] In some embodiments, when the electrode assembly is a lithium-ion battery, a known positive electrode active material for a lithium-ion battery can be used as the positive electrode active material. As an example, the positive electrode active material may 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 the positive electrode active material of the battery may be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides are lithium cobalt oxide (e.g., LiCoO 2 ), lithium nickel oxide (e.g., LiNiO 2 ), lithium manganese oxide (e.g., LiMnO 2 , LiMn 2 O 4 ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 (abbreviation NCM 333)、LiNi 0.5 Co 0.2 Mn 0.3 O 2 (Abbreviation: NCM 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O 2 (Abbreviation: NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O 2 (Abbreviation: NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O 2 (Abbreviation: NCM 811 ))、Lithium nickel cobalt aluminum oxide (e.g., LiNi 0.85 Co 0.15 Al 0.05 O 2 ) and at least one of its modified compounds, etc. may be included, but not limited thereto. As the lithium-containing phosphate having an olivine structure, for example, lithium iron(II) phosphate (e.g., LiFePO 4 (Abbreviation: LFP)), a composite material of lithium iron(II) phosphate and carbon, lithium manganese phosphate (e.g., LiMnPO 4 ), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and at least one of a composite material of lithium manganese iron phosphate and carbon may be included, but not limited thereto.

[0160] In some embodiments, the positive electrode film layer can optionally further include a binder. As an example, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0161] In some embodiments, the positive electrode film layer can further selectively include a conductive agent. As an 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.

[0162] In some embodiments, the positive electrode sheet can be manufactured by the following method. Components for manufacturing the positive electrode sheet, such as a positive electrode active material, a conductive agent, a binder, and any other components, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode paste. The positive electrode paste is applied to a positive electrode current collector, and through steps such as drying and cold pressing, a positive electrode sheet can be obtained.

[0163] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material.

[0164] As an example, the negative electrode current collector has two surfaces facing each other in its own thickness direction, and the negative electrode film layer is provided on one or both of the two opposing surfaces of the negative electrode current collector.

[0165] In some embodiments, a metal foil or a composite current collector can be used as the negative electrode current collector. As the metal foil, for example, a copper foil can be used. The composite current collector can include a polymer base material layer and a metal layer formed on at least one surface of the polymer base material. The composite current collector can be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material base (such as a base of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0166] In some embodiments, known anode active materials for batteries can be used as the anode active material. As an example, the anode active material can include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like. The silicon-based material can include at least one of silicon alone, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy. The tin-based material can include at least one of tin alone, tin oxide, and tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as the anode active material of the battery may be used. These anode active materials may be used alone or in combination of two or more.

[0167] In some embodiments, the anode film layer can optionally further include a binder. The binder can include at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0168] In some embodiments, the anode film layer can optionally further include a conductive agent. 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.

[0169] In some embodiments, the anode film layer further optionally includes other auxiliaries such as a thickening agent (for example, sodium carboxymethyl cellulose (CMC-Na)).

[0170] In some embodiments, the negative electrode sheet can be manufactured in the following manner. Components for manufacturing the negative electrode sheet, such as a negative electrode active material, a conductive agent, a binder, and any other components, are dispersed in a solvent (e.g., deionized water) to form a negative electrode paste. The negative electrode paste is applied to a negative electrode current collector and, through steps such as drying and cold pressing, a negative electrode sheet can be obtained.

[0171] The electrolyte serves to conduct ions between the positive electrode sheet and the negative electrode sheet. The present application does not particularly limit the type of electrolyte, and it can be selected as needed.

[0172] In some embodiments, an electrolytic solution is used as the electrolyte. The electrolytic solution contains an electrolyte salt and a solvent.

[0173] In some embodiments, the electrolyte salt can include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium bis(oxalate) borate, lithium difluorooxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0174] In some embodiments, the solvent can include at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4 - butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0175] In some embodiments, the electrolytic solution further selectively contains additives. For example, the additives may include a negative electrode film-forming additive and a positive electrode film-forming additive, and further may include additives that can improve specific characteristics of the battery, such as additives that improve the overcharge characteristics of the battery, additives that improve the high-temperature or low-temperature characteristics of the battery, and the like.

[0176] In some embodiments, the electrode assembly further includes a separator. The present application does not particularly limit the type of the separator, and any known porous structure separator having good chemical stability and mechanical stability can be selected.

[0177] In some embodiments, the material of the separator can include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, and are not particularly limited.

[0178] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be manufactured into an electrode assembly through a winding process or a lamination process.

[0179] In some embodiments, the electrode assembly can include an exterior material. The exterior material is used to enclose the above electrode assembly and electrolyte.

[0180] In some embodiments, the exterior material of the electrode assembly may be a hard case such as a hard plastic case, an aluminum case, or a steel case. The exterior material of the electrode assembly may also be a soft pack such as a pouch-type soft pack. The material of the soft pack may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0181] The present application does not particularly limit the shape of the electrode assembly, which may be cylindrical, rectangular, or any other arbitrary shape. For example, FIG. 4 shows a secondary battery 5 having a rectangular structure as an example.

[0182] In some embodiments, referring to FIG. 5, the exterior material can include a housing 51 and a cover plate 53. The housing 51 includes a bottom plate and side plates connected to the bottom plate, and an accommodation cavity surrounded by the bottom plate and the side plates is formed. The housing 51 has an opening communicating with the accommodation cavity, and the cover plate 53 can cover the opening to seal the accommodation cavity. The positive electrode sheet, the negative electrode sheet, and the separator can form a secondary battery 52 through a winding process or a lamination process. The secondary battery 52 is encapsulated within the accommodation cavity. The electrolytic solution is impregnated within the secondary battery 52. The number of secondary batteries 52 included in the secondary battery 5 may be one or more, and those skilled in the art can select according to specific actual requirements.

[0183] In some embodiments, the electrode assembly can be assembled into a battery module, and the number of electrode assemblies included in the battery module may be one or more. The specific number can be selected by those skilled in the art according to the use and capacity of the battery module.

[0184] FIG. 6 shows a battery module 4 as an example. Referring to FIG. 6, in the battery module 4, a plurality of secondary batteries 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other arbitrary method. Further, the plurality of secondary batteries 5 can be fixed by fastening tools.

[0185] Optionally, the battery module 4 may further include an outer case having an accommodation space for accommodating a plurality of secondary batteries 5.

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

[0187] FIGS. 7 and 8 show a battery pack 1 as an example. Referring to FIGS. 7 and 8, the battery pack 1 can include a battery case and a plurality of battery modules 4 installed in the battery case. The battery case includes an upper housing 2 and a lower housing 3. The upper housing 2 can cover the lower housing 3 and form a sealed space for accommodating the battery module 4. The plurality of battery modules 4 can be arranged in the battery case in any manner.

[0188] In addition, the present application further provides a power consumption device including at least one of the electrode assembly, battery module, or battery pack according to the present application. The electrode assembly, battery module, or battery pack may be used as a power source of the power consumption device or as an energy storage element of the power consumption device. The power consumption device can include, but is not limited to, mobile devices (such as mobile phones, notebook computers, 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, satellites, energy storage systems, etc.

[0189] As the power consumption device, the electrode assembly, battery module, or battery pack can be selected according to its usage requirements.

[0190] FIG. 9 shows a power consumption device as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or the like. In order to meet the requirements of high output and high energy density of the electrode assembly of the power consumption device, a battery pack or a battery module can be used.

[0191] As another example, the device may be a mobile phone, a tablet computer, a notebook computer, etc. The device is generally required to be lightweight and thin, and an electrode assembly can be used as a power source.

[0192] Examples Hereinafter, examples of the present application will be described. The examples described below are exemplary and are merely for explaining the present application, and should not be construed as limiting the present application. When specific techniques or conditions are not shown in the examples, they are carried out according to the techniques or conditions described in the literature of this field or according to the product manual. When the manufacturer of the reagent or equipment used is not described, all are common commercially available products.

[0193] Example 1 Production of acrylic ester copolymer (1) Add 150 g of deionized water and 3.6 g of sodium dodecyl sulfate to a 500 ml three-necked flask, stir well for 15 min to emulsify, and add 76.34 g of ethyl acrylate as the first polymerization monomer, 0.76 g of acrylic acid as the second polymerization monomer, 15.27 g of acrylonitrile as the third polymerization monomer, and 7.63 g of N-methylolacrylamide as the fourth polymerization monomer in a mass ratio of 1:0.01:0.2:0.1. The total amount of monomers is 100 g. Stir well for 60 min to obtain a preliminary emulsion of the monomers, take it out and prepare for use.

[0194] (2) Add 100 ml of deionized water and 0.15 g of sodium dodecylbenzenesulfonate to a 500 ml four-necked flask equipped with a condenser tube, a stirring device, a peristaltic pump and a thermometer, heat to 75 °C, emulsify at a rotation speed of 2000 r / min for 15 min, and after sufficiently emulsifying the system, slowly drop the preliminary emulsion and the initiator solution (dissolve 0.2 g of potassium persulfate as the initiator in 30 g of deionized water to form a solution) prepared in the previous step. After the dropping is completed, raise the temperature to 90 °C and keep it warm for 1 h for the reaction, cool to below 40 °C, adjust the pH to neutral with ammonia water, then stop stirring, filter, and discharge to obtain a polymer emulsion.

[0195] The volume-based particle size distribution Dv50 of the acrylic ester copolymer is 0.1 μm ± 0.01 μm (the volume-based particle size distribution Dv50 of the acrylic ester copolymer in each example is 0.1 μm ± 0.01 μm).

[0196] Production of Binder The above-produced acrylic ester copolymer emulsion is spray-dried to obtain a binder having a cyclic structure. The parameters of the spray drying are an intake air temperature of 115°C, an exhaust air temperature of 65°C, and a wind pressure of 2200 Pa.

[0197] Examples 2 to 27 Based on Example 1, the types and mass ratios of the monomers to be introduced are changed, the monomer composition of the acrylic ester copolymer, the volume-based particle size distribution Dv50 of the binder, and the surface density of applying the binder to the substrate are adjusted to obtain Examples 2 to 27.

[0198] Comparative Example 1 A spherical binder is obtained by using an emulsion polymerization method.

[0199] (1) 150 g of deionized water and 3.6 g of sodium dodecyl sulfate are added to a 500 ml three-necked flask, and stirred thoroughly for 15 min to emulsify. At a mass ratio of 1:0.3:0.2:0.1, 76.34 g of ethyl acrylate as the first polymerization monomer, 22.9 g of acrylic acid as the second polymerization monomer, 15.27 g of acrylonitrile as the third polymerization monomer, and 7.63 g of N-methylolacrylamide as the fourth polymerization monomer are added. The total amount of the monomers is 100 g, and stirred thoroughly for 60 min to obtain a pre-emulsion of the monomers, which is taken out and prepared for use.

[0200] (2) Add 100 ml of deionized water and 0.15 g of sodium dodecylbenzenesulfonate to a 500 ml four-necked flask equipped with a condenser tube, a stirring device, a peristaltic pump and a thermometer, heat to 75 °C, emulsify at a rotation speed of 2000 r / min for 15 min. After the system is sufficiently emulsified, slowly drop the pre-emulsion and initiator solution prepared in the previous step (dissolve 0.2 g of potassium persulfate as the initiator in 30 g of deionized water to form a solution). After the dropping is completed, raise the temperature to 90 °C and keep it for 1 h for heat preservation reaction, cool to below 40 °C, adjust the pH to neutral with ammonia water, then stop stirring, filter and discharge to obtain the first polymer emulsion.

[0201] (3) Repeat step (1) to obtain the second part of the pre-emulsion. Add the second part of the pre-emulsion and the initiator solution (dissolve 0.2 g of potassium persulfate as the initiator in 30 g of deionized water to form a solution) to the first polymer emulsion obtained in step (2). After the dropping is completed, raise the temperature to 90 °C and keep it for 1 h for heat preservation reaction, cool to below 40 °C, adjust the pH to neutral with ammonia water, then stop stirring, filter and discharge to obtain the second polymer emulsion.

[0202] Manufacture of cells and manufacture of batteries (1) Manufacture of separator Use a commercially available PE porous film with a thickness of 7 μm and an average pore diameter of 80 nm (obtained from Zhuogao Electronic Technology Co., Ltd.) as the base material. Stir and mix the separator binder manufactured by the above method uniformly in deionized water to obtain a paste (solid content 20%). Apply the paste to both sides of the base material and dry to remove the solvent to obtain an adhesive layer. The surface density of the coating composition on the base material is 1.35 g / m 2 and obtain a separator.

[0203] (2) Manufacture of positive electrode sheet Manufacture a positive electrode paste by stirring polyvinylidene fluoride (PVDF), lithium iron phosphate (LFP), conductive agent carbon black and N-methylpyrrolidone (NMP) sufficiently at a mass ratio of 1.2:58.38:0.42:40 and mixing them uniformly. The positive electrode paste is 200 g / m2 At a loading amount of , it is uniformly coated on the aluminum foil of the positive electrode current collector, and then through drying, cold pressing, and cutting, a positive electrode sheet is obtained.

[0204] (3) Manufacture of negative electrode sheet Artificial graphite, acetylene black as a conductive agent, styrene-butadiene rubber (SBR) as a binder, and sodium carboxymethyl cellulose (CMC-Na) as a thickener are added to deionized water at a mass ratio of 96.2:1.0:1.6:1.2, and sufficiently stirred and uniformly mixed to manufacture a negative electrode paste (solid content 63%). The negative electrode paste is applied to the copper foil of the negative electrode current collector at a loading amount of 98 g / m 2 After that, through drying, cold pressing, and cutting, a negative electrode sheet is obtained.

[0205] (4) Manufacture of electrolyte At 25 °C, ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) are mixed at a volume ratio of 1:1:1 to obtain a mixed solvent. Next, LiPF 6 is dissolved in the above mixed solvent to obtain an electrolyte, and the concentration of LiPF 6 is 1 mol / L.

[0206] (5) Manufacture of secondary battery The above positive electrode sheet, separator, and negative electrode sheet are laminated and wound in sequence, and cold press molding is performed (during which the separator and the polar sheet are adhered), a cell is obtained, the cell is placed in an outer packaging material, the above manufactured electrolyte is added, and through processes such as encapsulation, standing, formation, and aging, a secondary battery is obtained.

[0207] Performance test (1) Test steps for cold press adhesion Stack the negative electrode sheet of the battery and the separator, place them in a hot press machine, set the parameters of the hot press machine to a temperature of 25°C, a pressure of 7t, and a time of 15s, and obtain a separator / negative electrode sheet sample adhered by applying pressure. Cut the separator / negative electrode sheet sample into rectangular strips of 150mm×20mm. Use double-sided tape to attach one side of the polar sheet of the above rectangular strip to a steel plate. At one end of the rectangular strip, separate the separator and the polar sheet by a length of 2 cm along the length direction to create a test sample.

[0208] Hold the steel plate horizontally and fix it with the lower clamp of a universal testing machine (manufactured by Xieqiang Instrument Manufacturing (Shanghai) Co., Ltd., model number CTM2100). Fix the peeled end of the above separator with the upper clamp of the universal testing machine and connect it to a tensile machine. Set the measurement conditions to a tensile speed of 20 mm / min and a horizontal tensile of 10 cm. After the tensile force is stable, record the value of the tensile force, and obtain the adhesion force between the separator and the polar sheet according to the ratio of the value of the tensile force to the sample width.

[0209] (2) Steps for measuring the cell hardness Place the cell on a table with both ends horizontal, fix the width of the central hollow part to 12 cm, place the cell naturally flat, measure the width by which the center position of the cell deviates from the horizontal reference line, and thereby evaluate the hardness of the cell. The greater the width by which the center position of the cell deviates from the horizontal reference line, the lower the hardness of the cell.

[0210] (3) Steps for the cycle characteristic test with fixtures Apply a force of 10,000 N from the outside to the cell using a jig, and perform a cycle test in this state. The test steps are as follows. At 25°C, charge the battery obtained in Example 1 at a constant current of 1 / 3C until it reaches 3.8V, and then charge it at a constant voltage of 3.8V until the current reaches 0.05C. Leave it for 5 minutes, and then discharge it at 1 / 3C until it reaches 2.0V. Take the obtained discharge capacity as the initial capacity C0, repeat the above steps for the same battery, and at the same time record the discharge capacity Cn of the battery after n cycles. The battery capacity retention rate Pn after each cycle is Pn = (Cn / C0) × 100%. The difference in cycle characteristics can be shown by the battery capacity retention rate at 500 cycles.

[0211]

Table 1

[0212]

Table 2

[0213]

Table 3

[0214] As can be seen from the above data, based on the fact that the binder with a cyclic structure increases the contact area between the binder and the separator and the polar sheet, good adhesion performance can be achieved even in the situation where the usage amount of the cyclic structure binder is reduced.

[0215] The above are only preferred embodiments of the present application, and do not limit the patent scope of the present application. Under the application concept of the present application, any equivalent structural transformation carried out using the content of the specification and drawings of the present application, or direct / indirect application to other related technical fields is included in the patent protection scope of the present application.

Claims

1. A binder for secondary batteries, which contains an acrylic ester copolymer and has a shape including a cyclic shape.

2. The range value of the specific surface area is 0.4 m ２ / g to 1.2 m ２ / g, and preferably, the range value of the specific surface area is 0.6 m ２ / g to 0.9 m ２ / g, the binder for secondary battery according to claim 1.

3. The ratio of the surface area to the volume is 0.1×10 ６ m －１ ~20×10 ６ m －１ and preferably, the ratio of the surface area to the volume is 0.5×10 ６ m －１ ~16×10 ６ m －１ The binder for a secondary battery according to claim 1 or 2.

4. The bulk density range value is 0.3 g / cm ３ to 0.8 g / cm ３ and preferably, the bulk density range value is 0.4 g / cm ３ to 0.7 g / cm ３ The binder for a secondary battery according to any one of claims 1 to 3.

5. The binder for secondary batteries according to any one of Claims 1 to 4, wherein the shape includes an annular shape.

6. The binder for secondary batteries according to any one of Claims 1 to 5, wherein the range value of the volume-based particle size distribution Dv50 is 1 μm to 15 μm, and preferably, the range value of the volume-based particle size distribution Dv50 is 3 μm to 12 μm.

7. The constituent monomer of the acrylic ester copolymer contains a first polymerization monomer, and the structure of the first polymerization monomer is 【Chemical Formula 9】 including, where R1 includes hydrogen or an alkyl group having 1 to 12 carbon atoms, and R2 includes an alkyl group having 1 to 12 carbon atoms. The binder for secondary batteries according to any one of Claims 1 to 6.

8. The first polymerization 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 secondary batteries according to Claim 7.

9. The constituent monomer of the acrylic ester copolymer contains a second polymerization monomer, and the structure of the second polymerization monomer is 【Chemical 10】 including, where R3 includes hydrogen or an alkyl group having 1 to 6 carbon atoms. The binder for secondary batteries according to any one of Claims 1 to 8.

10. The second polymerization monomer includes one or more of acrylic acid, methacrylic acid, crotonic acid, and heptenoic acid. The binder for secondary batteries according to Claim 9.

11. The constituent monomer of the acrylic ester copolymer contains a third polymerization monomer, and the structure of the third polymerization monomer is 【Chemical Formula 11】 including, where R4 includes a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. The binder for secondary batteries according to any one of Claims 1 to 10.

12. The binder for a secondary battery according to claim 11, wherein the third polymerizable monomer contains one or more of acrylonitrile and methacrylonitrile.

13. The constituent monomer of the acrylic ester copolymer contains a fourth polymerizable monomer, and the structure of the fourth polymerizable monomer is 【Chemical Formula 12】 including, where R5 includes a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R6 includes a hydrogen atom, a hydroxyl group-substituted alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. The binder for a secondary battery according to any one of claims 1 to 12.

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

15. The constituent monomer of the acrylic ester copolymer contains a first polymerizable monomer, a second polymerizable monomer, a third polymerizable monomer, and a fourth polymerizable monomer, and the mass ratio of the first polymerizable monomer, the second polymerizable monomer, the third polymerizable monomer, and the fourth polymerizable monomer is 1:(0.01 - 0.8):(0.01 - 0.5):(0.01 - 0.3), and preferably, the mass ratio of the first polymerizable monomer, the second polymerizable monomer, the third polymerizable monomer, and the fourth polymerizable monomer is 1:(0.1 - 0.5):(0.15 - 0.45):(0.1 - 0.22). The binder for a secondary battery according to any one of claims 1 to 14.

16. A separator including a base material and an adhesive layer provided on at least one side of the base material, wherein the adhesive layer contains the binder for a secondary battery according to any one of claims 1 to 15.

17. The range value of the surface density of the adhesive layer on the substrate is 0.7 g / m ２ to 3 g / m ２ and preferably, the range value of the surface density of the adhesive layer on the substrate is 0.8 g / m ２ to 2 g / m ２ The separator according to claim 16, wherein the separator is as described above.

18. A secondary battery including the separator according to claim 16 or 17.

19. A power consumption device including the secondary battery according to claim 18.

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