Binders, separators, secondary batteries, and power consumption devices for secondary batteries

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 of related applications

[0001] This application claims priority to the Chinese patent application filed on April 24, 2023, application number 202310447240.5, all of which are incorporated herein by reference. [Technical Field]

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

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

[0004] Currently, battery cells have an opening problem, specifically, a gap easily forms between the polarity sheet and the separator, which degrades the battery's cycle characteristics. [Overview of the Initiative]

[0005] The main objective of this invention is to provide a binder for secondary batteries that improves the adhesion between the polar sheet and the separator, thereby improving the performance of the battery.

[0006] To achieve the above objective, this application provides a binder for secondary batteries, wherein the binder comprises an acrylic acid ester copolymer, and the shape of the binder includes an annular shape.

[0007] Acrylic acid ester copolymers have good adhesive properties, and by using acrylic acid ester copolymers, the adhesion between the separator and the polar sheet can be further improved.

[0008] The annular structure binder has a larger bonding 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 an annular structure and a spherical binder of the same size, the bonding performance of the annular structure binder is better. Moreover, the annular structure binder 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 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, compared with a binder having a spherical structure of the same size, the specific surface area of the annular binder increases. 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 bonding 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 to the total volume of a material. Because an annular binder has hollow through holes, the ratio of surface area to volume of an annular binder is increased compared to a spherical binder of the same dimensions, and the ratio of surface area to volume of the binder is 0.1 × 10⁻⁶. 6 m -1 ~20×10 6 m -1 Preferably, the ratio of the surface area to the volume of the binder is 0.5 × 10⁻⁶. 6 m -1 ~16×10 6 m -1 This indicates that annular binders have a larger surface area compared to spherical binders, which helps improve contact between the annular binder and the separator and polar sheet, thereby improving adhesive performance.

[0013] Selectively, the bulk density range of the binder is 0.3 g / cm³. 3 ~0.8g / cm 3 Preferably, the bulk density range of the binder is 0.4 g / cm³. 3 ~0.7g / cm 3 That is the case.

[0014] Bulk density is the mass per unit volume measured immediately after filling a container with powder. Because annular binders have hollow through-holes, after filling a container with them, voids are formed in the through-holes of the annular binder. Compared to filling with spherical binders of the same dimensions, the bulk density of annular binders decreases, and the range of bulk density for binders is 0.3 g / cm³. 3 ~0.8g / cm 3 Preferably, the bulk density of the binder is in the range of 0.4 g / cm³. 3 ~0.7g / cm 3 This indicates that, under certain conditions, the adhesive performance of the binder is improved even when the mass of the annular binder is reduced.

[0015] Selectively, the shape of the binder includes annular shapes.

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

[0017] Selectively, 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 reduce 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 3 μm to 12 μm.

[0019] Selectively, the constituent monomers of the acrylic acid ester copolymer include a first polymer monomer, and the structure of the first polymer monomer is [ka] This includes, 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 ester groups, improving the compatibility between the acrylic ester copolymer and the electrolyte, enhancing ionic conductivity, improving the swelling resistance of the acrylic ester copolymer, and acting as a flexible monomer segment in the molecular segment, it can adjust the glass transition temperature of the acrylic ester copolymer, improving the toughness of the binder during coating and contributing to good adhesion.

[0021] Selectively, the first polymer monomer comprises one or more of methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, n-propyl acrylate, cyclohexyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate.

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

[0023] By using one or more of the above-mentioned primary polymerization monomers, the glass transition temperature of the acrylic ester copolymer can be adjusted, thereby improving the swelling resistance of the acrylic ester copolymer.

[0024] Selectively, the constituent monomers of the acrylic acid ester copolymer include a second polymer monomer, and the structure of the second polymer monomer is [ka] This includes, where R3 contains hydrogen or an alkyl group having 1 to 6 carbon atoms.

[0025] The structure of the second polymerization monomer contains carboxyl groups, which are characterized by their strong polarity. This can improve the adhesion and flexibility of the binder. For example, the carboxyl groups can form bonding forces with functional groups on the polar sheet and separator material, thereby improving the adhesive effect.

[0026] Selectively, the second polymerized monomer comprises one or more of acrylic acid, methacrylic acid, crotonic acid, and heptenoic acid.

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

[0028] By using one or more of the above-mentioned secondary polymerization monomers, the adhesive performance of the acrylic acid ester copolymer can be improved.

[0029] Selectively, the constituent monomers of the acrylic acid ester copolymer include a third polymer monomer, and the structure of the third polymer monomer is [ka] This includes, where R4 contains a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

[0030] The structure of the third polymerization monomer contains unsaturated cyano groups. These highly polar cyano groups help improve ionic conductivity and simultaneously provide swelling resistance and high adhesion.

[0031] Selectively, the third polymerized monomer comprises one or more of acrylonitrile and methacrylonitrile.

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

[0033] By using one or more of the above-mentioned third polymerization monomers, the ionic conductivity of the acrylic acid ester copolymer can be improved, thereby enhancing its adhesive properties.

[0034] Selectively, the constituent monomers of the acrylic acid ester copolymer include a fourth polymer monomer, and the structure of the fourth polymer monomer is [ka] This includes, where R5 contains a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R6 contains a hydrogen atom, a hydroxyl-substituted alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.

[0035] The structure of the fourth polymerization monomer contains an unsaturated amide group, which improves swelling and enhances adhesion.

[0036] Selectively, the fourth polymerized monomer comprises one or more of acrylamide, N-methylolacrylamide, and N-butoxymethylacrylamide.

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

[0038] The adhesion of the acrylic acid ester copolymer can be improved by using one or more of the above-mentioned fourth polymerization monomers.

[0039] As can be understood, the adhesive effect is even better when at least two of the above four monomers are included. For example, the constituent monomers of the acrylic ester copolymer include at least the first polymer monomer and the second polymer monomer, or the constituent monomers of the acrylic ester copolymer include at least the first polymer monomer and the third polymer monomer, or the constituent monomers of the acrylic ester copolymer include at least the first polymer monomer and the fourth polymer monomer. The binder performance is better when the constituent monomers of the acrylic ester copolymer include all four monomers simultaneously.

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

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

[0042] The present invention further provides a separator comprising a substrate and an adhesive layer provided on at least one side of the substrate, wherein the adhesive layer comprises the binder for the secondary battery.

[0043] Selectively, the range value of the surface density of the adhesive layer on the substrate is 0.7 g / m². 2 ~3g / m 2 The concentration is preferably 0.8 g / m². 2 ~2g / m 2 That is the case.

[0044] Based on the fact that the annular structure binder increases the contact area between the binder and the polar sheet and separator, that is, good adhesive performance can be achieved even when the amount of annular structure binder used is reduced. For this reason, the range value of the surface density of the adhesive layer on the substrate is 0.7 g / m². 2 ~3g / m 2 Preferably, the surface density range value of the adhesive layer on the substrate is 0.8 g / m². 2 ~2g / m 2 That is the case.

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

[0046] The present invention further provides a power consumption device including the aforementioned secondary battery. [Brief explanation of the drawing]

[0047] To more clearly explain the embodiments of the present application or the technical solutions in the prior art, the drawings necessary for describing the embodiments or the prior art are briefly described below. The drawings shown below represent only a few embodiments of the present application, and it will be obvious to those skilled in the art that other drawings can be obtained based on the structures shown in these drawings without requiring any creative effort.

[0048] [Figure 1] This is a scanning electron microscope image of the binder according to Example 1 of the present application. [Figure 2] This is a scanning electron microscope image of the binder according to Example 1 of the present application. [Figure 3] This is a flowchart of the method for manufacturing the binder according to the embodiment of the present application. [Figure 4] This is a schematic diagram of a secondary battery according to an embodiment of the present invention. [Figure 5] Figure 4 is an exploded view of a secondary battery according to an embodiment of the present invention. [Figure 6] This is a schematic diagram of a battery module according to an embodiment of the present invention. [Figure 7] This is a schematic diagram of a battery pack according to an embodiment of the present invention. [Figure 8] Figure 7 is an exploded view of a battery pack according to an embodiment of the present invention. [Figure 9] This is a schematic diagram of a power consumption device that uses a secondary battery as a power source according to an embodiment of the present invention. [Figure 10] This is a schematic diagram of the binder according to Embodiment 1 of the present application. [Explanation of Symbols]

[0049] 1 Battery pack 2 Upper cabinet 3 Lower cabinet 4 Battery Modules 60 Loop Line 5 Secondary battery 51 Housing 52 Electrode Assembly 53 Top cover assembly 61 Through hole

[0050] The realization of the objectives of this application, the features of its functions, and its advantages will be further explained by combining examples and referring to the drawings. [Modes for carrying out the invention]

[0051] The technical solutions in the embodiments of this application will be described below clearly and completely with reference to the drawings of the embodiments, and it should be noted that the embodiments described are only a selection of embodiments of this application, not all embodiments. All other embodiments obtained by a person skilled in the art based on the embodiments of this application without requiring any creative effort are all within the scope of protection of this application.

[0052] The binder of this application and its manufacturing method, as well as embodiments of separators, electrode assemblies, battery cells, batteries, and power consumption devices containing the binder, will be described in detail below with reference to the drawings as appropriate. However, unnecessary details may be omitted. For example, detailed explanations of well-known matters or redundant explanations of substantially identical structures may be omitted. This is to avoid unnecessarily verbose explanations and to facilitate understanding by those skilled in the art. Furthermore, the drawings and the following explanation are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter described in the claims.

[0053] The “range” disclosed herein is defined in the form of a lower and upper limit, and a given range is defined by selecting one lower limit and one upper limit, the selected lower and upper limits defining the boundaries of a particular range. Ranges defined in this manner may or may not include the values ​​at both ends and can be combined in any way, that is, any lower limit can be combined with any upper limit to form a range. For example, if the ranges 60-120 and 80-110 are listed for a particular parameter, it is understood that the ranges 60-110 and 80-120 are also expected. Similarly, if the minimum range values ​​1 and 2 are listed, and the maximum range values ​​3, 4 and 5 are listed, the ranges 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5 are all intended. In this application, unless otherwise specified, the numerical range “a-b” means an abbreviated expression for any combination of real numbers between a and b, where both a and b are real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" are listed in this specification, and "0 to 5" is merely an abbreviated expression for combinations of these numbers. Also, when a parameter is described as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

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

[0055] All of the technical features and selectable technical features of this application can be combined to form new technical solutions, unless otherwise specified.

[0056] All steps of this application may be performed sequentially or randomly unless otherwise specified, preferably in order. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, if 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] Battery cells have an opening problem; specifically, gaps tend to form between the polarity sheet and the separator, which degrades the battery's cycle characteristics.

[0058] For example, if the adhesive strength between the positive and negative electrode sheets and the separator is insufficient, problems such as cell openings will always occur, making it impossible to meet the performance requirements for the coated separator of a secondary battery.

[0059] A cell is formed by bonding positive and negative electrode sheets to a separator. The cell has a certain hardness; that is, the bonded positive and negative electrode sheets and separator are adhered to and supported by each other, forming a structure with a certain thickness. A structure with a certain thickness has a certain hardness. However, expansion occurs in the negative electrode during the charging and discharging process, and if the adhesive force is weak, a gap is formed between the positive and negative electrode sheets and the separator. The positive and negative electrode sheets and the separator are not adhered to and cannot support each other, causing the cell to loosen and its hardness to decrease. At this time, the power characteristics of the cell deteriorate, for example, the rate characteristics deteriorate, and simultaneously, the cycle characteristics deteriorate. For example, in an electric vehicle, if the battery cell loosens, the battery charging speed slows down, and at the same time, the battery's cycle characteristics deteriorate, directly leading to a shortened battery life. This necessitates frequent battery replacement in electric vehicles, increasing consumer costs for electric vehicles.

[0060] Based on this, the present application provides a binder for secondary batteries, the binder comprising an acrylic acid ester copolymer, and the shape of the binder including an annular shape.

[0061] A binder is a material that possesses adhesive properties and is used to bond different materials together.

[0062] This is an annular binder, in which through-holes are formed in the structure of the binder, and the through-holes are holes that penetrate two opposing surfaces of the binder, and as shown in Figures 1 and 2, it is an annular binder.

[0063] The annular binder has an annular line, and as shown in Figure 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 placed on the separator in the direction toward the through hole 61 (i.e., the opening of the through hole 61 faces the separator), the area around the through hole 61 is in contact with the separator, and the contact area is the annular line. Compared to a spherical binder being placed on a separator, the spherical binder and the separator are in point contact, whereas the annular binder can contact the separator via the annular line, increasing the contact area.

[0064] Regarding acrylic acid ester copolymers, they are a general term for polymers produced by copolymerizing acrylic acid ester monomers with other copolymers.

[0065] The structure of acrylic acid ester monomers has an acrylic acid ester group, and examples include methyl acrylate, ethyl acrylate, and n-butyl acrylate.

[0066] Acrylic acid ester copolymers have good adhesive properties, and by using acrylic acid ester copolymers, the adhesion between the separator and the polar sheet can be further improved.

[0067] Annular binders have a larger bonding area. For example, when an annular binder and a polar sheet come into contact, the contact area is the annular edge of the annular binder, whereas with a spherical binder, the contact area is a point contact. Based on the fact that an annular binder has a larger contact area than a spherical binder of the same dimensions, the bonding performance of annular binders is superior. Furthermore, annular binders have hollow through holes, and for annular binders and spherical binders of the same dimensions, the mass of the annular binder is smaller. Therefore, good bonding performance can be achieved in situations where the amount of annular binder used is reduced.

[0068] By applying an annular binder to the separator, the contact area between the binder, polarity sheet, and separator can be increased, reducing the amount of binder used. This also allows the cold-press adhesion requirements between the separator and the positive and negative electrode sheets during the cold-press process to be met, improving cell hardness and mitigating problems such as cell opening and cell softness. Simultaneously, applying this binder to the separator and applying it to a secondary battery can improve the jig-assisted cycle characteristics of the secondary battery.

[0069] The jig-assisted cycle characteristics test is a characteristic of the cell's cycle functionality test. During the test, a jig is attached to the cell, and a constant force is applied to the jig to press the cell. When the cell is fully charged, it expands and is double-pressed by the clamping force of the jig and the force of expansion, which may cause the cell to deform. This test is used to test the cell's shape retention performance and pressure resistance performance. When using the binder of this solution, the adhesion performance is good, so the cell expansion is reduced and the cell shape is well maintained. Cells using this binder maintain good performance under the jig-assisted test conditions, which indicates that the deformation retention performance of cells obtained using the binder of this solution is excellent. Even after the cells are assembled into a battery, they are less likely to deform, so the space required to install the cells in the battery can be saved, and thus the volume of the battery can be made smaller. If a cell is easily deformed, it will push out the surrounding structure. To mitigate this phenomenon, it is necessary to house the deformed cell in a larger space. In other words, space must be secured within the battery to accommodate the deformed portion of the cell, which occupies more space inside the battery.

[0070] At the same time, high cyclic characteristics of a cell with a fixture also indicate excellent cyclic characteristics of the cell. For example, when a cell expands, the gap between the polarity sheet and the separator increases, lengthening the path for lithium ions (using lithium-ion batteries as an example, but of course this could also apply to other types of secondary batteries) through the positive and negative electrodes, thus degrading the cycle performance.

[0071] The binder of this invention can make the bonding between the separator and the polarity sheet tighter, improving the discharge capacity of the battery, reducing internal resistance, reducing polarization loss, extending the battery cycle life, and improving the utilization rate of the secondary battery.

[0072] In one embodiment, the specific surface area range of the binder is 0.4 m². 2 / g~1.2m 2 The specific surface area of ​​the binder is preferably 0.6 m² / g. 2 / g~0.9m 2It is / g.

[0073] Specific surface area refers to the total surface area of ​​a unit mass of material, and its unit is m². 2 It is / g.

[0074] Specific surface area test: BET specific surface area is measured using the BET method for N2 adsorption.

[0075] Using a NOVA 2000 specific surface area and pore size analyzer from Cantachrome, Inc. of the United States, high-purity nitrogen gas with a purity of 99.999% or higher is used as the adsorbent. A spherical sample tube with a diameter of 20 mm is selected, 1.4000 g ± 0.2000 g of binder sample is weighed, a heating bag is placed over it, and a vacuum pump is used to evaporate it for 10 minutes. -2 The sample is vacuumed to a level above Thor, and after the pressure stabilizes, it is slowly heated to a constant temperature, controlling the pretreatment time. After pretreatment is complete, it is cooled for 30 minutes, and the mass of the sample is weighed. Adsorption and desorption tests are performed on the pretreated sample for the entire process, and the isothermal adsorption and desorption curve of the sample is obtained. The data is processed using the software attached to the instrument to obtain the specific surface area parameter of the binder.

[0076] Specific surface area refers to the total surface area of ​​a unit mass of material. Based on the fact that annular binders have hollow through-holes, the specific surface area of ​​annular binders is increased compared to spherical binders of the same dimensions, and the specific surface area of ​​binders is in the range of 0.4 m². 2 / g~1.2m 2 The specific surface area of ​​the binder is preferably 0.6 m² / g, and preferably within a range of 0.6 m². 2 / g~0.9m 2 The ratio is / g, which helps improve contact between the annular binder and separator, and the polar sheet, thereby improving adhesive performance.

[0077] The above 0.4m 2 / g~1.2m 2 In / g, the value includes the minimum and maximum values ​​of the range, and the values ​​between the minimum and maximum values, as well as specific examples such as the endpoint values ​​in the example and 0.4m 2 / g, 0.5m 2 / g, 0.6m2 / g, 0.7m 2 / g, 0.8m 2 / g, 0.9m 2 / g, 1.0m 2 / g, 1, 1m 2 / g1.2m 2 This includes, but is not limited to, values ​​such as / g, and range values ​​between any two endpoint values ​​mentioned above.

[0078] The above 0.6m 2 / g~0.9m 2 In / g, the value includes the minimum and maximum values ​​of the range, and the values ​​between these minimum and maximum values, as well as specific examples such as the endpoint values ​​in the example and 0.6m 2 / g, 0.7m 2 / g, 0.8m 2 / g, 0.9m 2 This includes, but is not limited to, values ​​such as / g, and range values ​​between any two endpoint values ​​mentioned above.

[0079] In one embodiment, the ratio of the surface area to the volume of the binder is 0.1 × 10⁻⁶. 6 m -1 ~20×10 6 m -1 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 That is the case.

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

[0081] Regarding the test method for the ratio of surface area to volume, the surface area and volume of a certain mass of binder are measured, respectively, and then the ratio of surface area to volume is obtained by dividing the values ​​of surface area by volume. If we define that m1 gram of binder is to be measured, the surface area can be obtained using the above-mentioned method for measuring specific surface area, and the value of the specific surface area is given by am 2 If defined as / g, the surface area of ​​m1 grams of 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, water with a volume of V1 is taken and placed in a container. Then, 1 gram of binder is added to 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. 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. 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. This indicates that the surface area of the annular binder increases compared with 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.

[0083] In the above 0.1×10​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​-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 This includes, but is not limited to, the range values ​​between any two of the above endpoint values.

[0084] The above 0.5 × 10 6 m -1 ~16×10 6 m -1 In this case, the value includes the minimum and maximum values ​​of the range, and the values ​​between the minimum and maximum values, and as a specific example, the endpoint value in the example and 0.5 × 10 6 m -1 , 1 x 10 6 m -1 , 2×10 6 m -1 , 3 x 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 This includes, but is not limited to, the range values ​​between any two of the above endpoint values.

[0085] In one example, the range value for the bulk density of the binder is 0.3 g / cm³. 3 ~0.8g / cm 3 Preferably, the bulk density of the binder is in the range of 0.4 g / cm³. 3 ~0.7g / cm 3 That is the case.

[0086] Bulk density is the mass per unit volume measured immediately after filling a container with powder.

[0087] The specific test steps are as follows: Using the tapping instrument method, the sample is placed in a 100 mL graduated cylinder of the tapping instrument, the instrument is started, and the graduated cylinder is vibrated with the vibrator of the tapping instrument to tap the sample. Throughout the experiment, the sample is continuously added until the sample volume no longer decreases, and finally the mass of the sample is weighed and the bulk density is obtained by dividing the sample mass by the sample volume.

[0088] Because annular binders have hollow through-holes, after filling a container with annular binders, voids are formed in the through-holes of the annular binders. Compared to filling with spherical binders of the same dimensions, the bulk density of annular binders is reduced, with a range of 0.3 g / cm³. 3 ~0.8g / cm 3 Preferably, the bulk density of the binder is in the range of 0.4 g / cm³. 3 ~0.7g / cm 3 This indicates that, under certain conditions, the adhesive performance of the binder is improved even when the mass of the annular binder is reduced.

[0089] Above 0.3g / cm 3 ~0.8g / cm 3 In this context, the values ​​include the minimum and maximum values ​​within the range, as well as the values ​​between these minimum and maximum values. Specific examples include the endpoint values ​​in the examples and 0.3 g / cm³. 3 , 0.4 g / cm³ 3 , 0.5 g / cm 3 , 0.6 g / cm³ 3 , 0.7 g / cm³ 3 0.8 g / cm³ 3 This includes, but is not limited to, the range values ​​between any two of the above endpoint values.

[0090] The above 0.4 g / cm³ 3 ~0.7g / cm 3 In this context, the values ​​include the minimum and maximum values ​​within the range, as well as the values ​​between these minimum and maximum values. Specific examples include the endpoint values ​​in the examples and 0.4 g / cm³. 3 , 0.5 g / cm 3 , 0.6 g / cm³ 3 , 0.7 g / cm³ 3 This 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] Annular shapes are relatively easily achievable based on experimental experience and the surface tension of the material, and the binder shapes in this application include annular shapes. Furthermore, the annular shapes in this application may be approximately annular, for example, as shown in Figure 1, the structures of some binders are not perfectly annular, but rather, for example, some parts are compressed to form an approximately 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] Regarding Dv50, in a sample of particles, 50% of the particles by total volume have a particle size greater than this value, while the remaining 50% of the particles by total volume have a particle size less 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 this art. For example, characterization tests can be performed using a Malvern laser particle size analyzer, as described in GB / T 19077-2016, such as the Malvern Mastersizer-3000.

[0096] To improve the adhesion of the binder and reduce 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 3 μm to 12 μm.

[0097] In the range of 1 μm to 15 μm mentioned above, the values ​​include the minimum and maximum values ​​within that range, as well as the values ​​between the minimum and maximum values. Specific examples include, but are not limited to, the endpoint values ​​in the examples and the range values ​​between any two endpoint values, such as 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.

[0098] In the range of 3 μm to 12 μm mentioned above, the values ​​include the minimum and maximum values ​​within that range, as well as the values ​​between the minimum and maximum values. Specific examples include, but are not limited to, the endpoint values ​​in the examples and the range values ​​between any two endpoint values, such as 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, etc.

[0099] In one embodiment, the constituent monomers of the acrylic acid ester copolymer include a first polymer monomer, and the structure of the first polymer monomer is [ka] This includes, where R1 contains hydrogen or an alkyl group having 1 to 12 carbon atoms, and R2 contains an alkyl group having 1 to 12 carbon atoms.

[0100] The first polymerization monomer structure contains ester groups, improving the compatibility between the acrylic ester copolymer and the electrolyte, enhancing ionic conductivity, improving the swelling resistance of the acrylic ester copolymer, and acting as a flexible monomer segment in the molecular segment, it can adjust the glass transition temperature of the acrylic ester copolymer, improving the toughness of the binder during coating and contributing to good adhesion.

[0101] In one example, the first polymer monomer contains one or more of the following: 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, this application does not limit the type of first polymer monomer, and satisfies the requirement that the first polymer monomer includes the above structure, that is, the first polymer monomer includes the substances listed above and substances not listed in this application.

[0103] By using one or more of the above-mentioned primary polymerization monomers, the glass transition temperature of the acrylic ester copolymer can be adjusted, thereby improving the swelling resistance of the acrylic ester copolymer.

[0104] In one example, the constituent monomers of the acrylic acid ester copolymer include a second polymer monomer, and the structure of the second polymer monomer is [ka] This includes, where R3 contains hydrogen or an alkyl group having 1 to 6 carbon atoms.

[0105] The structure of the second polymerization monomer contains carboxyl groups, which are characterized by their strong polarity. This can improve the adhesion and flexibility of the binder. For example, the carboxyl groups can form bonding forces with functional groups on the polar sheet and separator material, thereby improving the adhesive effect.

[0106] In one example, the second polymer monomer contains one or more of acrylic acid, methacrylic acid, crotonic acid, and heptenoic acid.

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

[0108] By using one or more of the above-mentioned secondary polymerization monomers, the adhesive performance of the acrylic acid ester copolymer can be improved.

[0109] In one example, the constituent monomers of the acrylic acid ester copolymer include a third polymer monomer, and the structure of the third polymer monomer is [ka] This includes, where R4 contains hydrogen or an alkyl group having 1 to 6 carbon atoms.

[0110] The structure of the third polymerization monomer contains unsaturated cyano groups. These highly polar cyano groups help improve ionic conductivity and simultaneously provide swelling resistance and high adhesion.

[0111] In one example, the third polymerization monomer comprises one or more of acrylonitrile and methacrylonitrile.

[0112] Theoretically, this application does not limit the type of third polymerization monomer, and satisfies the requirement that the third polymerization monomer includes the above structure, that is, the third polymerization monomer includes the substances listed above and substances not listed in this application.

[0113] By using one or more of the above-mentioned third polymerization monomers, the ionic conductivity of the acrylic acid ester copolymer can be improved, thereby enhancing its adhesive properties.

[0114] In one example, the constituent monomers of the acrylic acid ester copolymer include a fourth polymer monomer, and the structure of the fourth polymer monomer is [ka] This includes, where R5 contains hydrogen or an alkyl group having 1 to 6 carbon atoms, and R6 contains a hydrogen atom, a hydroxyl-substituted alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.

[0115] The structure of the fourth polymerization monomer contains an unsaturated amide group, which improves swelling and enhances adhesion.

[0116] In one example, the fourth polymerized monomer comprises one or more of acrylamide, N-methylolacrylamide, and N-butoxymethylacrylamide.

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

[0118] The adhesion of the acrylic acid ester copolymer can be improved by using one or more of the above-mentioned fourth polymerization monomers.

[0119] As can be understood, the adhesive effect is even better when at least two of the above four monomers are included. For example, the constituent monomers of the acrylic ester copolymer include at least the first polymer monomer and the second polymer monomer, or the constituent monomers of the acrylic ester copolymer include at least the first polymer monomer and the third polymer monomer, or the constituent monomers of the acrylic ester copolymer include at least the first polymer monomer and the fourth polymer monomer. The binder performance is better when the constituent monomers of the acrylic ester copolymer include all four monomers simultaneously.

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

[0121] When the constituent monomers of an acrylic acid ester copolymer simultaneously contain the above four monomers, and the components of each monomer fall within the above range, the overall performance is better.

[0122] Regarding the method for measuring the mass ratio, in the manufacturing process of acrylic acid ester copolymers, the mass of each monomer introduced into the reaction process to produce the acrylic acid ester copolymer is recorded. The mass of the first polymerization monomer is denoted 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 above 1:(0.01~0.8):(0.01~0.5):(0.01~0.3), the values ​​include the minimum and maximum values ​​within the range, and each value between the minimum and maximum values. 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., as well as the range values ​​between any two of the above endpoint values, but are not limited to these.

[0124] In the above 1:(0.1~0.5):(0.15~0.45):(0.1~0.22), the values ​​include the minimum and maximum values ​​within the range, and each value between the minimum and maximum values. 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., as well as the range values ​​between any two of the above endpoint values, but are not limited to these.

[0125] In one embodiment, the present invention further provides a method for producing a binder, comprising the steps of producing an acrylic acid ester copolymer emulsion and spray-drying the acrylic acid ester copolymer emulsion to obtain a binder with a cyclic structure.

[0126] Spray drying uses mechanical action to disperse the material to be dried (acrylic ester copolymer emulsion) into very fine mist particles, and then brings them into contact with hot air (which increases the surface area for water evaporation and accelerates the drying process) to instantly remove most of the water, drying the solid substances in the material and turning them into powder.

[0127] An acrylic ester copolymer emulsion is produced by emulsion polymerization, and a cyclic binder is obtained by spray drying the acrylic ester copolymer emulsion. The mechanism is that, due to the evaporation of water, the primary emulsion of the acrylic ester copolymer deposits tightly, forming a cyclic binder.

[0128] In one embodiment, the step of producing an acrylic acid ester copolymer emulsion includes the steps of: placing water, an emulsifier, and constituent monomers of the acrylic acid ester copolymer in a container, stirring to emulsify, and obtaining a preliminary emulsion of monomers; and adding an emulsifier and water to a reaction vessel, stirring to emulsify, adding the preliminary emulsion and initiator solution under heating conditions, and carrying out a heating reaction to obtain an acrylic acid ester copolymer emulsion.

[0129] A pre-emulsified solution is a solution obtained by pre-emulsifying monomers. Emulsification is the process by which a liquid is uniformly dispersed in another liquid as very small droplets that do not mix with each other. This is done by mixing water, an emulsifier, and the constituent monomers of an acrylic ester copolymer and stirring, thereby dispersing the constituent monomers of the acrylic ester copolymer in water under the action of the emulsifier.

[0130] Emulsion polymerization is a process in which 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 emulsifiers, they are substances that convert oil and water, which do not mix with each other, into an emulsion that is difficult to separate into layers. Emulsifiers are generally surfactants that possess the properties of both hydrophilic polar groups and hydrophobic (lipophilic) nonpolar groups.

[0132] Regarding initiators, they are substances that can initiate polymerization reactions in monomers. For example, radical initiators refer to compounds that readily decompose upon heat to form radicals (i.e., primary radicals), and can be used to initiate radical polymerization and copolymerization reactions of olefin and diene monomers.

[0133] In the step of producing an acrylic ester copolymer emulsion, the monomers are further homogenized by first pre-emulsifying and then polymerizing, resulting in an acrylic ester copolymer with more uniform particle size and more stable performance. The spray-drying process promotes the formation of a cyclic binder.

[0134] Polyvinylidene fluoride is widely used as the most common binder in separators, but currently, its price fluctuates significantly and its market supply is limited. Applying polyvinylidene fluoride polymer to the surface of lithium battery separators can partially solve the problem of high-temperature shrinkage of the separator. Cold pressing is performed on the wound cells, but ordinary polyvinylidene fluoride is a homopolymer with a crystallinity of about 50%, resulting in insufficient adhesion to the positive and negative electrode sheets, which always causes problems with cell openings and fails to meet the requirements for separator coating performance in secondary batteries.

[0135] Specifically, applying polyvinylidene fluoride polymer to the surface of the battery separator can partially solve the problem of high-temperature shrinkage of the separator. Cold pressing is performed on the wound cells, but ordinary polyvinylidene fluoride is a homopolymer with a crystallinity of about 50%, resulting in insufficient adhesion to the positive and negative electrode sheets, and the problem of cell openings always occurs. When openings occur in the cell, a gap is formed between the polarity sheet and the separator, the overall structure of the cell loosens, the hardness of the cell decreases, and the cycle characteristics of the cell are affected.

[0136] By applying the annular binder structure of this invention to a separator and coating it with the binder, the contact area between the binder, polarity sheet, and separator can be increased, reducing the amount used, meeting the requirements for cold-press adhesion between the separator and positive and negative electrode sheets during the cold-press process, improving cell hardness, and avoiding problems such as cell opening and cell softness. At the same time, by coating the binder with the separator and applying it to a secondary battery, the jig-assisted cycle characteristics of the secondary battery can be improved.

[0137] In one embodiment, the present invention further provides a separator comprising a substrate and an adhesive layer provided on at least one side of the substrate, wherein the adhesive layer comprises the binder for secondary batteries, or the adhesive layer comprises a binder manufactured by the method for manufacturing the binder for secondary batteries described above.

[0138] The adhesive layer is a structure composed of a binder applied to a separator.

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

[0140] As can be understood, after drying, the binder has no adhesive force at room temperature (room temperature is approximately 23±2℃) 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 is non-viscous, satisfying the requirements for winding and unwinding the separator. When a certain pressure is applied, the binder becomes pressure-sensitive, exhibiting excellent adhesion and satisfying the requirements for adhesion between the separator and the positive and negative polarity sheets. At the same time, the adhesion further forms intermolecular forces between the molecules on the separator and the polarity sheets, thereby effectively bonding the separator and the polarity sheets with the binder.

[0141] Furthermore, after cold pressing, the hollow through-holes in the annular binder are not completely sealed, creating voids. These voids promote wetting of the electrolyte, improving the transmission of lithium ions (although lithium-ion batteries are used as an example, other types of secondary batteries can certainly be used).

[0142] The binder powder material, manufactured using a spray-drying process, achieves non-adhesion at room temperature and without pressure.

[0143] Pressure sensitivity refers to the process where, after the binder is pressed, it deforms under pressure, penetrates the gaps between the separator and electrode sheets, and creates a mechanical interlocking effect, thereby achieving 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 / m². 2 ~3g / m 2 The concentration is preferably 0.8 g / m². 2 ~2g / m2 That is the case.

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

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

[0147] Based on the fact that the annular structure binder increases the contact area between the binder and the polar sheet and separator, that is, good adhesive performance can be achieved even when the amount of annular structure binder used is reduced. For this reason, the range value of the surface density of the adhesive layer on the substrate is 0.7 g / m². 2 ~3g / m 2 Preferably, 0.8 g / m 2 ~2g / m 2 That is the case.

[0148] The above 0.7g / m 2 ~3g / m 2 In this context, the values ​​include the minimum and maximum values ​​within the range, as well as the values ​​between these minimum and maximum values. Specific examples include the endpoint values ​​in the examples and 0.7 g / m². 2 , 0.8g / m 2 , 0.9g / m 2 , 1g / m 2 1.5g / m 2 , 2g / m 2 2.5g / m 2 , 3g / m 2 This includes, but is not limited to, the range values ​​between any two of the above endpoint values.

[0149] The above 0.8g / m 2 ~2g / m 2 In this context, the values ​​include the minimum and maximum values ​​within the range, as well as the values ​​between these minimum and maximum values. Specific examples include the endpoint values ​​in the examples and 0.8 g / m². 2 , 0.9g / m 2 , 1g / m2 1.2g / m 2 1.5g / m 2 1.7g / m 2 1.9g / m 2 , 2g / m 2 This includes, but is not limited to, the range values ​​between any two of the above endpoint values.

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

[0151] A secondary battery includes forms such as a battery module, battery cells, and battery pack. If the secondary battery is a battery cell, the battery cell includes the separator; if the secondary battery is a battery module, the battery module includes the separator; and if the secondary battery is a battery pack, the battery pack includes the separator.

[0152] The embodiments of the present application further provide a power consumption device including the above-mentioned battery cell or the above-mentioned battery.

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

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

[0155] Generally, an electrode assembly includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During the charging and discharging process of the battery, active ions reciprocate between the positive and negative electrode sheets for insertion and removal. The electrolyte plays a role in conducting ions between the positive and negative electrode sheets. The separator is placed between the positive and negative electrode sheets and primarily serves to prevent short circuits between the positive and negative electrodes while simultaneously allowing ions to pass through. The separator is the improved separator described in this 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] For example, the positive electrode current collector has two opposing surfaces 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, the positive electrode current collector can be a metal foil or a composite current collector. As the metal foil, for example, aluminum foil can be used. The composite current collector may include a polymer substrate layer and a metal layer formed on at least one surface of the polymer substrate layer. The composite current collector can be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymer material substrate (for example, a substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0159] In some embodiments, when the electrode assembly is a lithium-ion battery, known positive electrode active materials for lithium-ion batteries can be used. For example, the positive electrode active material may include at least one of olivine-structured lithium-containing phosphates, lithium transition metal oxides, and modified compounds thereof. However, the present application is not limited to these materials, and other conventional materials usable as positive electrode active materials for batteries may be used. These positive electrode active materials may be used individually or in combination of two or more. Examples of lithium transition metal oxides include lithium cobalt oxide (e.g., LiCoO2), lithium nickel oxide (e.g., LiNiO2), lithium manganese oxide (e.g., LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide (e.g., LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (abbreviated as NCM) 333 ), LiLi 0.5 Co 0.2 Mn 0.3 O2 (abbreviated as NCM) 523), LiLi 0.5 Co 0.25 Mn 0.25 O2 (abbreviated as NCM) 211 ), LiLi 0.6 Co 0.2 Mn 0.2 O2 (abbreviated as NCM) 622 ), LiLi 0.8 Co 0.1 Mn 0.1 O2 (abbreviated as NCM) 811 )), Lithium nickel cobalt aluminum oxide (e.g., LiNi 0.85 Co 0.15 Al 0.05 The olivine structure lithium-containing phosphate may include, but is not limited to, at least one of O2 and its modified compounds. For example, the olivine structure lithium-containing phosphate may include, but is not limited to, at least one of lithium ferric phosphate (e.g., LiFePO4 (abbreviated as LFP)), a composite material of lithium ferric phosphate and carbon, lithium manganese phosphate (e.g., LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0160] In some embodiments, the positive electrode film layer may selectively further contain a binder. As an example, the binder may 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 resins.

[0161] In some embodiments, the positive electrode film layer may further selectively contain a conductive agent. As an example, the conductive agent may 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, a 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 the positive electrode sheet can be obtained through steps such as drying and cold pressing.

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

[0164] For example, the negative electrode current collector has two opposing surfaces 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, the negative electrode current collector can be a metal foil or a composite current collector. For example, copper foil can be used as the metal foil. The composite current collector may include a polymer substrate layer and a metal layer formed on at least one surface of the polymer substrate. The composite current collector can be formed by forming a metal material (such as copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys) on a polymer material substrate (for example, a substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0166] In some embodiments, the negative electrode active material can be any known negative electrode active material for batteries. For example, the negative electrode active material may include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy. The tin-based material may include at least one of elemental tin, tin oxide, and tin alloy. However, this application is not limited to these materials, and other conventional materials usable as negative electrode active materials for batteries may be used. These negative electrode active materials may be used individually or in combination of two or more types.

[0167] In some embodiments, the negative electrode film layer may selectively further contain a binder. The binder 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).

[0168] In some embodiments, the negative electrode film layer may further selectively contain a conductive agent. The conductive agent may 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 negative electrode film layer further comprises other additives, such as a selective thickener (e.g., sodium carboxymethylcellulose (CMC-Na)).

[0170] In some embodiments, a 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 then applied to a negative electrode current collector, and the negative electrode sheet can be obtained through steps such as drying and cold pressing.

[0171] The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. This invention does not particularly limit the type of electrolyte, and it can be selected as needed.

[0172] In some embodiments, an electrolyte solution is used. The electrolyte solution comprises an electrolyte salt and a solvent.

[0173] In some embodiments, the electrolyte salt may include at least one of lithium hexafluoride phosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoride arsenate, lithium bisfluorosulfonylimide, lithium bistrifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium bisoxalate borate, lithium difluorooxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0174] In some embodiments, the solvent may 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 electrolyte selectively further comprises additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and further additives that can improve specific characteristics of the battery, such as additives that improve the overcharge characteristics of the battery, or additives that improve the high-temperature or low-temperature characteristics of the battery.

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

[0177] In some embodiments, the material of the separator may include at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film, and is not particularly limited. If the separator is a multilayer 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, negative electrode sheet, and separator can be manufactured into an electrode assembly via a winding process or a lamination process.

[0179] In some embodiments, the electrode assembly may include an outer covering. This outer covering is used to enclose the electrode assembly and the electrolyte.

[0180] In some embodiments, the outer packaging of the electrode assembly may be a hard case such as a rigid plastic case, an aluminum case, or a steel case. The outer packaging 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 plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0181] This application does not particularly limit the shape of the electrode assembly, and it may be cylindrical, rectangular, or any other shape. For example, Figure 4 shows a rectangular secondary battery 5 as an example.

[0182] In some embodiments, referring to Figure 5, the exterior material may include a housing 51 and a cover plate 53. The housing 51 includes a bottom plate and side plates connected to the bottom plate, forming a housing cavity enclosed by the bottom plate and side plates. The housing 51 has an opening that communicates with the housing cavity, and the cover plate 53 can cover the opening and seal the housing cavity. The positive electrode sheet, negative electrode sheet and separator are formed through a winding process or a lamination process. Electrode assembly 52 It is possible to form this. Electrode assembly 52 It is sealed inside the containment cavity. The electrolyte is Electrode assembly 52 It is impregnated inside. It is included in secondary battery 5. Electrode assembly 52 The number of these may be one or more, and a person skilled in the art can select them according to the specific practical requirements.

[0183] In some embodiments, electrode assemblies 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 of which can be selected by those skilled in the art depending on the application and capacity of the battery module.

[0184] Figure 6 shows an example of a battery module 4. Referring to Figure 6, in the battery module 4, multiple secondary batteries 5 can be installed in sequence along the length of the battery module 4. Of course, they can be arranged in any other way. Furthermore, these multiple secondary batteries 5 can be fixed in place by fasteners.

[0185] Selectively, the battery module 4 may further comprise an outer case having a housing space for accommodating multiple 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 and 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, or a plug-in hybrid electric vehicle, etc. 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] The device as another example 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 illustrative only and are merely for explaining the present application, and should not be construed as limiting the present application. When specific technologies or conditions are not indicated in the examples, they are implemented according to the technologies or conditions described in the literature of this field or according to the product manuals. When the manufacturer of the reagents or equipment used is not described, they are all common commercially available products.

[0193] Example 1 Production of acrylate copolymer (1) Add 150 g of deionized water and 3.6 g of sodium dodecyl sulfate to a 500 ml three-neck 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 at 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 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-neck 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 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 warm for 1 h for 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] Binder manufacturing The acrylic ester copolymer emulsion produced above is spray-dried to obtain a cyclic binder. The spray-drying parameters are an intake air temperature of 115°C, an exhaust air temperature of 65°C, and an air pressure of 2200 Pa.

[0197] Examples 2 to 27 Based on Example 1, the type and mass ratio of monomers to be added were changed, and the monomer composition of the acrylic ester copolymer, the volume-based particle size distribution Dv50 of the binder, and the surface density of the binder applied to the substrate were adjusted to obtain Examples 2 to 27.

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

[0199] (1) Add 150 g of deionized water and 3.6 g of sodium dodecyl sulfate to each of the 500 ml three-necked flasks, and stir thoroughly for 15 mins to emulsify. Add 76.34 g of ethyl acrylate (first polymerization monomer), 22.9 g of acrylic acid (second polymerization monomer), 15.27 g of acrylonitrile (third polymerization monomer), and 7.63 g of N-methylolacrylamide (quaternary polymerization monomer) in a mass ratio of 1:0.3:0.2:0.1, so that the total amount of monomers is 100 g. Stir thoroughly for 60 mins to obtain a preliminary emulsion of monomers, which is then removed 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, stirrer, peristaltic pump and thermometer, heat to 75 °C, and emulsify at a rotation speed of 2000 r / min for 15 min until the system is thoroughly emulsified. Then, slowly add the pre-emulsified solution and initiator solution (formed by dissolving 0.2 g of potassium persulfate, the initiator, in 30 g of deionized water) prepared in the previous step dropwise. After the dropwise addition is complete, raise the temperature to 90 °C and allow the reaction to be maintained for 1 hour. Cool to below 40 °C, adjust the pH to neutral with ammonia water, then stop stirring, filter, and drain to obtain the first polymer emulsion.

[0201] (3) Repeat step (1) to obtain the second part of the preliminary emulsifier. Add the second part of the preliminary emulsifier and the initiator solution (form a solution by dissolving 0.2 g of potassium persulfate, the initiator, in 30 g of deionized water) to the first polymer emulsion obtained in step (2). After the dropwise addition is complete, raise the temperature to 90°C and allow the reaction to proceed for 1 hour. Cool to below 40°C, adjust the pH to neutral using ammonia water, then stop stirring, filter, and drain to obtain the second polymer emulsion.

[0202] Cell manufacturing and battery manufacturing (1) Manufacturing of separators A commercially available PE porous film with a thickness of 7 μm and an average pore size of 80 nm (obtained from Zhuoga Electronics Technology Co., Ltd.) is used as the substrate. The separator binder produced by the above method is uniformly stirred and mixed in deionized water to obtain a paste (solid content 20%). The paste is applied to both sides of the substrate, dried to remove the solvent, and an adhesive layer is obtained, with a surface density of 1.35 g / m² of the coating composition on the substrate. 2 And thus, a separator is obtained.

[0203] (2) Manufacturing of positive electrode sheets A positive electrode paste is manufactured by thoroughly stirring and uniformly mixing polyvinylidene fluoride (PVDF), lithium iron phosphate (LFP), the conductive agents carbon black and N-methylpyrrolidone (NMP) in a mass ratio of 1.2:58.38:0.42:40. The positive electrode paste is then applied in a quantity of 200 g / m².2 After uniformly coating the aluminum foil of the positive electrode current collector with the appropriate amount of material, the positive electrode sheet is obtained by drying, cold pressing, and cutting.

[0204] (3) Manufacturing of negative electrode sheets A negative electrode paste is manufactured by adding artificial graphite, the conductive agent acetylene black, the binder styrene-butadiene rubber (SBR), and the thickener sodium carboxymethylcellulose (CMC-Na) to deionized water in a mass ratio of 96.2:1.0:1.6:1.2, and stirring thoroughly to mix uniformly (solid content 63%). The negative electrode paste is then applied at a rate of 98 g / m². 2 After applying the specified amount to the copper foil of the negative electrode current collector, the negative electrode sheet is obtained by drying, cold pressing, and cutting.

[0205] (4) Manufacturing of electrolyte At 25°C, ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain a mixed solvent. Then, LiPF6 is dissolved in the above mixed solvent to obtain an electrolyte solution with a LiPF6 concentration of 1 mol / L.

[0206] (5) Manufacturing of secondary batteries The positive electrode sheet, separator, and negative electrode sheet are laminated and wound in sequence, and then cold-press molded (during which the separator and polarity sheet are bonded) to obtain a cell. The cell is then placed in an outer casing, the manufactured electrolyte is added, and a secondary battery is obtained through processes such as sealing, standing, chemical conversion, and aging.

[0207] Performance testing (1) Test step for cold press adhesion strength Overlap 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 7 t, and a time of 15 s, and obtain a separator / negative electrode sheet sample adhered by applying pressure. Cut the separator / negative electrode sheet sample into a rectangular strip with a size of 150 mm × 20 mm. 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 along the length direction with a length of 2 cm 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 peeling 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 distance of 10 cm. After the tensile force stabilizes, record the value of the tensile force, and obtain the adhesion force between the separator and the polar sheet based on 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 flat naturally, 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 larger the width by which the center position of the cell deviates from the horizontal reference line, the lower the hardness of the cell indicates.

[0210] (3) Steps for the cycle characteristic test with fixtures An external force of 10,000 N is applied to the cell using a jig, and a cycle test is performed in this state. The test steps are as follows: At 25°C, the battery obtained in Example 1 is charged to 3.8V with a constant current of 1 / 3C, then charged further with a constant voltage of 3.8V until the current becomes 0.05C, left for 5 minutes, and then discharged at 1 / 3C until it becomes 2.0V. The obtained discharge capacity is taken as the initial capacity C0, and the above steps are repeated for the same battery, while simultaneously recording the discharge capacity Cn of the battery after n cycles. The battery capacity retention rate after each cycle Pn = (Cn / C0) × 100%. The battery capacity retention rate after 500 cycles can be used to show the differences in cycle characteristics.

[0211] [Table 1]

[0212] [Table 2]

[0213] [Table 3]

[0214] As can be seen from the data above, the annular binder structure increases the contact area between the binder, separator, and polar sheet, and therefore good adhesive performance can be achieved even when the amount of annular binder used is reduced.

[0215] The foregoing are merely preferred embodiments of the present application and do not limit the scope of the patent. Any equivalent structural transformations or direct / indirect applications to other related technical fields, performed using the contents of the specification and drawings of the present application under the concept of the present application, are all included within the scope of the patent protection of the present application.

Claims

1. A binder for secondary batteries containing an acrylic acid ester copolymer, with particles having a cyclic shape, and a volume-based particle size distribution Dv50 in the range of 3 μm to 12 μm.

2. The specific surface area range is 0.4 m². ２ / g to 1.2m ２ A binder for secondary batteries according to claim 1, wherein the amount is / g.

3. The ratio of surface area to volume is 0.1 × 10⁻⁶ ６ I understand －１ ~20 x 10 ６ I understand －１ The binder for secondary batteries according to claim 1.

4. The range value for bulk density is 0.3 g / cm³. ３ ~0.8 g / cm ３ The binder for secondary batteries according to claim 1.

5. The binder for secondary batteries according to claim 1, wherein the particle shape includes annular shapes.

6. The binder for secondary batteries according to Claim 1, wherein the constituent monomer of the acrylic acid ester copolymer comprises a first polymer monomer, and the first polymer monomer comprises one or more of methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, n-propyl acrylate, cyclohexyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate.

7. The binder for secondary batteries according to claim 1, wherein the constituent monomer of the acrylic acid ester copolymer comprises a second polymer monomer, and the second polymer monomer comprises one or more of acrylic acid, methacrylic acid, crotonic acid, and heptenoic acid.

8. The constituent monomers of the acrylic acid ester copolymer include a third polymer monomer, and the structure of the third polymer monomer is, 【Chemistry 1】 The binder for secondary batteries according to claim 1, wherein R4 comprises a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

9. The binder for secondary batteries according to claim 8, wherein the third polymerized monomer comprises one or more of acrylonitrile and methacrylonitrile.

10. The constituent monomers of the acrylic acid ester copolymer include a fourth polymer monomer, and the structure of the fourth polymer monomer is, 【Chemistry 2】 A binder for secondary batteries according to claim 1, wherein R5 comprises a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R6 comprises a hydrogen atom, a hydroxyl-substituted alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.

11. The binder for secondary batteries according to claim 10, wherein the fourth polymerized monomer comprises one or more of acrylamide, N-methylolacrylamide, and N-butoxymethylacrylamide.

12. The binder for secondary batteries according to claim 1, wherein the constituent monomers of the acrylic acid ester copolymer include a first polymer monomer, a second polymer monomer, a third polymer monomer, and a fourth polymer monomer, and the mass ratio of the first polymer monomer, the second polymer monomer, the third polymer monomer, and the fourth polymer monomer is 1:(0.01 to 0.8):(0.01 to 0.5):(0.01 to 0.3).

13. A separator comprising a base material and an adhesive layer provided on at least one side of the base material, wherein the adhesive layer comprises the binder for secondary batteries described in claim 1.

14. The range value of the areal density of the adhesive layer on the base material is 0.7 g / m ２ to 3 g / m ２ The separator according to claim 13, wherein the separator is as described above.

15. A secondary battery comprising the separator described in claim 13.

16. A power consumption device including a secondary battery as described in claim 15.

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