Adhesive composition, secondary battery, battery module, battery pack, and power consuming device

Abstract

The present application provides an adhesive composition, an electrode, a battery, and a power consuming device. The adhesive composition includes a fluorine-containing polymer A and a copolymer B, and the copolymer B includes a structural unit derived from a monomer containing a cyano group and a structural unit derived from a monomer containing an ester group. The adhesive of the present application has a strong adhesive force, and a secondary battery containing the adhesive has excellent cycle performance.

Description

[Technical field]

[0001] The present application relates to the field of lithium battery technology, and in particular to an adhesive composition, a secondary battery, a battery module, a battery pack and a power consuming device. [Background technology]

[0002] In recent years, lithium-ion batteries have been widely used in energy storage power systems such as hydroelectric, thermal, wind and solar power stations, as well as in multiple fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. With the widespread use of lithium-ion batteries, higher requirements are being placed on their performance and cost.

[0003] Adhesives are commonly used materials in lithium-ion batteries, and are in high demand for battery plates, separators, packaging, etc. However, traditional adhesives have high costs and poor adhesion, which increases the cost of batteries and reduces the cycle performance of batteries. Therefore, traditional adhesives still need to be improved. Summary of the Invention

[0004] The present application has been made in view of the above problems, and an object of the application is to provide an adhesive composition that can reduce the cost of adhesives and has excellent adhesive performance.

[0005] A first aspect of the present application provides an adhesive composition, which comprises a fluorine-containing polymer A and a copolymer B, wherein the copolymer B comprises structural units derived from a monomer containing a cyano group and structural units derived from a monomer containing an ester group.

[0006] As a result, the present application provides an adhesive having both a fluorine-containing polymer A and a copolymer B containing a structural unit derived from a monomer containing a cyano group and a structural unit derived from a monomer containing an ester group, thereby making it possible to further improve the adhesive performance of the adhesive and the cycle performance of the battery compared to using only the fluorine-containing polymer A or copolymer B as the adhesive.

[0007] In any embodiment, the weight average molecular weight of the fluorine-containing polymer A is 600,000 to 900,000, and the weight average molecular weight of the copolymer B is 400,000 to 700,000. By controlling the weight average molecular weight of the polymer, it is possible to achieve both the adhesiveness and processability of the adhesive. If the weight average molecular weight of the polymer is too low, the adhesive is very brittle and the adhesive strength is insufficient. If the weight average molecular weight of the polymer is too high, it is difficult to disperse the electrode active material. And by rationally combining polymers having different molecular weights, it is possible to improve the dispersibility of the electrode active material and further improve the battery performance.

[0008] In any embodiment, the mass ratio of the fluorine-containing polymer A to the copolymer B is 1:4 to 4:1. By rationally combining the fluorine-containing polymer A and the copolymer B within a certain mass range, the adhesive performance of the adhesive and the cycle performance of the battery can be further improved.

[0009] In an optional embodiment, the fluorine-containing polymer A is selected from one or more of polyvinylidene fluoride and its copolymers with tetrafluoroethylene, hexafluoropropylene, trichloroethylene.

[0010] In an optional embodiment, the cyano group-containing monomer is selected from one or more of acrylonitrile, methacrylonitrile, halogenated acrylonitrile, and methoxyacrylonitrile.

[0011] In any embodiment, the monomer containing an ester group is selected from one or more of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, isoamyl acrylate, isooctyl acrylate, methyl methacrylate, ethyl methacrylate, hydroxyethyl acrylate, and hydroxypropyl acrylate. Compared with the fluorine-containing monomer, the above-mentioned monomer containing a cyano group and monomer containing an ester group are low in cost, and can be mass-produced without policy restrictions, which can greatly reduce the cost of the adhesive.

[0012] In any embodiment, the mass ratio of the structural unit derived from the monomer containing a cyano group to the structural unit derived from the monomer containing an ester group in the copolymer B is 8:1 to 12:1. The monomer containing a cyano group can improve the mechanical strength and adhesive performance of the copolymer B, and can further improve the cycle performance of the battery, the monomer containing a small amount of ester group can improve the flexibility of the copolymer B and prevent the brittle fracture of the electrode plate, and the ester group has a certain electrolyte absorption and retention ability, and can improve the problem of poor ionic conductivity of the fluorine-containing polymer A.

[0013] In an optional embodiment, copolymer B further comprises structural units derived from a monomer containing a group according to formula I, JPEG0007676568000001.jpg44170 Here, n is selected from 0, 1, 2 or 3.

[0014] The electronegativity of the oxygen element in the group shown in formula I is greater than that of the nitrogen element in the cyano group, and it is easier to form hydrogen bonds with the electrode active material and the conductive agent than the cyano group in copolymer B, and has a stronger bonding ability, which can greatly improve the dispersibility of the slurry, make the solid material in the slurry less likely to precipitate, and increase the solid content of the slurry. At the same time, the addition of the group shown in formula I can further improve the adhesive strength of the battery plate and the cycle durability of the battery.

[0015] In an optional embodiment, the monomer containing the group shown in formula I is selected from one or more of N-vinylpyrrolidone, N-allyl-2-pyrrolidone, which have low cost, good stability and easy synthesis processing.

[0016] In any embodiment, the mass content of the structural unit derived from the monomer containing the group shown in formula I is 0.1% to 2% based on the total mass of copolymer B. When copolymer B contains an appropriate amount of the group shown in formula I, the dispersibility of copolymer B can be improved, and the produced slurry is less likely to produce precipitates, which is advantageous for improving the solid content of the slurry and further improving the electrode loading.

[0017] A third aspect of the present application provides a secondary battery, the secondary battery comprising an electrode assembly and an electrolyte, the electrode assembly comprising a positive electrode plate, a separator, and a negative electrode plate, the positive electrode plate comprising a positive electrode active material and the adhesive of the first or second aspect of the present application, the battery having better cycle performance.

[0018] In any embodiment, the positive electrode active material is a lithium-containing transition metal oxide, optionally lithium iron phosphate, or a doped modification thereof, or at least one of a conductive carbon-coated, conductive metal-coated, or conductive polymer-coated modification thereof.

[0019] A fourth aspect of the present application provides a battery module including the secondary battery of the third aspect of the present application.

[0020] A fifth aspect of the present application provides a battery pack including the battery module of the fourth aspect of the present application.

[0021] A sixth aspect of the present application provides a power consuming device including at least one of the secondary battery of the third aspect of the present application, the battery module of the fourth aspect of the present application, and the battery pack of the fifth aspect of the present application.

[0022] The battery module of the fourth embodiment and the battery pack of the fifth embodiment of the present application include the secondary battery of the third embodiment, and therefore have the same advantages as the secondary battery. [Brief description of the drawings]

[0023] [Figure 1] FIG. 2 is a diagram showing an adhesive performance test of the adhesives prepared in Example 1 and Comparative Example 1. [Diagram 2] 1 is a cycle test graph of the batteries manufactured in Example 1 and Comparative Example 1. [Diagram 3] 1 is a schematic diagram of a secondary battery according to an embodiment of the present application; [Figure 4] FIG. 4 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 3. [Diagram 5] 1 is a schematic diagram of a battery module according to an embodiment of the present application; [Figure 6] 1 is a schematic diagram of a battery pack according to an embodiment of the present application; [Figure 7] FIG. 7 is an exploded view of the battery pack according to the embodiment of the present application shown in FIG. 6. [Figure 8] 1 is a schematic diagram of a power consuming device in which a secondary battery according to an embodiment of the present application is used as a power source; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, with reference to the accompanying drawings as appropriate, an embodiment specifically disclosing the adhesive, manufacturing method, electrode, battery, and power consumption device of the present application will be described in detail. However, unnecessary detailed description may be omitted. For example, detailed description of well-known matters and duplicated description of structures that are actually the same may be omitted. This is to avoid the following description becoming unnecessarily long and to allow those skilled in the art to easily understand. Note that the drawings and the following description are provided to allow those skilled in the art to fully understand the present application, and are not intended to limit the subject matter described in the claims.

[0025] The "ranges" disclosed in this application are defined in the form of lower and upper limits, and a given range is defined by selecting one lower limit and one upper limit that define the boundaries of the particular range. Such defined ranges may or may not include the end values, and may be arbitrarily combined, i.e., any lower limit and any upper limit may be combined to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. It is noted that if minimum range values ​​1 and 2 and maximum range values ​​3, 4 and 5 are listed, the following ranges 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" is a shorthand expression representing all real number combinations between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are recited herein, with "0-5" merely being a shorthand for combinations of these numbers. Also, when a parameter is described as an integer ≧2, this is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0026] Unless otherwise stated, all the embodiments and optional embodiments in the present application may be combined with each other to form a new technical solution.

[0027] Unless otherwise stated, all technical features and optional technical features in the present application may be combined with each other to form a new technical solution.

[0028] Unless otherwise stated, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b) means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method mentioned above may further include step (c) means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), may include steps (a), (c) and (b), may include steps (c), (a) and (b), etc.

[0029] Unless otherwise specified, the terms "comprise" and "comprises" referred to in this application may be open ended or closed ended. For example, the terms "comprise" and "comprises" may further include or include other ingredients not listed, or may include or include only the listed ingredients.

[0030] Unless otherwise stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any one of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), or both A and B are true (or exist).

[0031] PVDF is a commonly used battery adhesive, but its cost is low, its adhesive strength is poor, and its adhesive strength weakens during battery cycling, which leads to further deterioration of the battery cycle performance. Based on the above technical problems, the present application has developed an adhesive that has low cost and excellent adhesive strength to the electrode plate, and significantly improves the battery cycle performance.

[0032] [glue]

[0033] On this basis, the present application provides an adhesive composition, which comprises a fluorine-containing polymer A and a copolymer B, wherein the copolymer B comprises structural units derived from a monomer containing a cyano group and structural units derived from a monomer containing an ester group.

[0034] As used herein, the term "adhesive composition" refers to a mixture of chemical compounds or polymers that form a colloidal solution or dispersion in a dispersion medium (eg, water).

[0035] In some embodiments, the dispersion medium of the adhesive is an aqueous solvent, such as water.

[0036] In some embodiments, the dispersion medium of the adhesive is an oil-based solvent, examples of which include, but are not limited to, dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, acetone, dimethyl carbonate, ethyl cellulose, and polycarbonate.

[0037] In some embodiments, an adhesive is used to hold the electrode materials and / or conductive agents in place and adhere them to the conductive metal members to form the electrodes, hi some embodiments, the electrodes do not include any conductive agents.

[0038] In some embodiments, the adhesive is used as a positive electrode adhesive to adhere a positive electrode active material and / or a conductive agent to form a positive electrode.

[0039] In some embodiments, the adhesive is used as a negative electrode adhesive to adhere a negative electrode active material and / or a conductive agent to form a negative electrode.

[0040] In this specification, the term "polymer" includes, on the one hand, an assembly of large molecules produced by polymerization reactions (copolymerization, homopolymerization), which are chemically uniform but differ in terms of their degree of polymerization, molar mass and chain length. On the other hand, the term also includes derivatives of such large molecular assemblies formed by polymerization reactions, i.e. compounds or mixtures which are obtainable by reactions, for example addition or substitution, of functional groups in said macromolecules and which may be chemically uniform or chemically heterogeneous.

[0041] As used herein, the term "fluorine-containing polymer" refers to a polymer that contains elemental fluorine.

[0042] As used herein, the term "copolymer" refers to a polymer made by polymerizing two or more different types of monomers.

[0043] As used herein, the term "cyano" refers to a -CN group.

[0044] As used herein, the term "ester group" refers to a group having the general formula -COOR9 structural unit, where R9 is a C 1-5 Examples of ester groups are selected from alkyl groups, including, but not limited to, methyl, ethyl, propyl, butyl, amyl, isooctyl, and the like.

[0045] As used herein, the term "substituted" refers to being substituted with a substituent, each of which is independently a hydroxyl group, a mercapto group, an amino group, a cyano group, a nitro group, an aldehyde group, a halogen atom, a C 1-6 Alkyl group, C 1-6 The alkoxy group is selected from the group consisting of aryl, ... and aryl groups.

[0046] In some embodiments, copolymer B is selected from one or more of acrylonitrile-methyl acrylate copolymer, acrylonitrile-2-methyl methacrylate copolymer, acrylonitrile-2-ethyl methacrylate copolymer, acrylonitrile-ethyl acrylate copolymer, acrylonitrile-butyl acrylate copolymer, acrylonitrile-isooctyl acrylate copolymer, acrylonitrile-butyl acrylate-hydroxyethyl acrylate copolymer, acrylonitrile-butyl acrylate-ethyl acrylate copolymer, acrylonitrile-isoamyl acrylate-hydroxypropyl acrylate copolymer, acrylonitrile-butyl acrylate-isooctyl acrylate-methyl methacrylate copolymer, acrylonitrile-butyl acrylate-isooctyl acrylate-ethyl methacrylate copolymer. In some embodiments, copolymer B is acrylonitrile-isooctyl acrylate copolymer.

[0047] The structural unit derived from the monomer containing a cyano group can effectively complex with the metal on the surface of the collector as well as with the metal element on the electrode active material, ensuring strong adhesion between the electrode active material and the collector. At the same time, the structural unit derived from the monomer containing an ester group can improve the flexibility of the electrode plate and prevent brittle breakage of the electrode plate. In addition, the cyano group, ester group on the copolymer B and the fluorine element in the fluorine-containing polymer A can generate stronger adhesion between the electrode active material particles on the electrode plate through hydrogen bonding.

[0048] In the present application, a fluorine-containing polymer A and a copolymer B containing a structural unit derived from a monomer containing a cyano group and a structural unit derived from a monomer containing an ester group are jointly used as an adhesive, thereby significantly improving the adhesive performance between an electrode active material and a current collector, between an electrode active material and a conductive agent, and between an electrode active material and / or a conductive agent and a current collector, and significantly improving the cycle performance of a battery, compared to using the fluorine-containing polymer A or the copolymer B alone as an adhesive.

[0049] In some embodiments, the weight average molecular weight of the fluorine-containing polymer A is 6×10 5 ~9×10 5 and the weight average molecular weight of copolymer B is 4×10 5 ~7×10 5 In some embodiments, the weight average molecular weight of the fluorine-containing polymer A is 6×10 5 ~8×10 5 , or 6 × 10 5 ~7×10 5 , or 7 × 10 5 ~9×10 5 , or 8 x 10 5 ~9×10 5 In some embodiments, the weight average molecular weight of copolymer B is selected from the group consisting of 4×10 5 ~7×10 5 , or 4 × 10 5 ~6×10 5 , or 4 × 10 5 ~5×10 5 , or 5 × 10 5 ~7×10 5 , or 6 × 10 5 ~7×10 5 is selected from.

[0050] As used herein, the term "weight average molecular weight" refers to the sum of the products of the weight fractions of molecules of different molecular weights in a polymer and the corresponding molecular weights.

[0051] By controlling the weight-average molecular weight of the polymer, it is possible to achieve both the adhesiveness and processability of the adhesive. If the weight-average molecular weight of the polymer is too low, the adhesive will be extremely brittle and the adhesive strength will be insufficient. If the weight-average molecular weight of the polymer is too high, it will be difficult to disperse the electrode active material. By rationally combining polymers with different molecular weights, it is possible to improve the dispersibility of the electrode active material and further improve the battery performance.

[0052] In some embodiments, the mass ratio of the fluorine-containing polymer A to the copolymer B is 1:4 to 4:1. In some embodiments, the mass ratio of the fluorine-containing polymer A to the copolymer B is 1:4 to 3:1, or 1:4 to 2:1, or 1:4 to 1:1, or 1:2 to 1:4, or 1:2 to 4:1, or 1:1 to 4:1, or 2:1 to 4:1, or 3:1 to 4:1. By rationally combining the fluorine-containing polymer A and the copolymer B within a certain mass range, the adhesion of the electrode plate and the cycle performance of the battery can be further improved.

[0053] In some embodiments, the fluorine-containing polymer A is selected from one or more of polyvinylidene fluoride and its copolymers with tetrafluoroethylene, hexafluoropropylene, trichloroethylene.

[0054] In some embodiments, the fluorine-containing polymer A is polyvinylidene fluoride, which is synthesized by an emulsion method, and the particle volume average particle size Dv50 is 5-10 μm, the crystallinity is 35-40%, and the melting point is 160-170° C.

[0055] Compared with PVDF synthesized by the suspension method, polyvinylidene fluoride synthesized by the emulsion method has a larger synthesis capacity per run and is less expensive. With a suitable molecular weight, the slurry containing the adhesive of the present application has excellent suspending and dispersing properties, and prevents the adhesive from being unevenly dispersed in the slurry due to settling or agglomeration. With a suitable particle size, the dissolution time of polyvinylidene fluoride can be effectively reduced, thereby reducing the time required for producing the slurry. With a suitable crystallinity of polyvinylidene fluoride, good adhesion can be guaranteed and the brittleness of the plate will not be caused. With a high melting point, polyvinylidene fluoride will not be dissolved and deactivated during application and drying.

[0056] In some embodiments, the cyano group-containing monomer is selected from one or more of acrylonitrile, methacrylonitrile, halogenated acrylonitrile, and methoxyacrylonitrile.

[0057] In some embodiments, the monomer containing an ester group is selected from one or more of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, isoamyl acrylate, isooctyl acrylate, methyl methacrylate, ethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate.

[0058] In some embodiments, the monomer containing an ester group is selected from isooctyl acrylate, which provides copolymer B with a lower glass transition temperature and better flexibility, which is advantageous for plate processing.

[0059] Compared with fluorine-containing monomers, the above-mentioned cyano group-containing monomers and ester group-containing monomers are inexpensive and can be mass-produced without policy restrictions, which can significantly reduce the cost of the adhesive.

[0060] In some embodiments, the weight ratio of the structural units derived from the monomer containing a cyano group to the structural units derived from the monomer containing an ester group in copolymer B is 8:1 to 12:1. In some embodiments, the weight ratio of the structural units derived from the monomer containing a cyano group to the structural units derived from the monomer containing an ester group in copolymer B is 8:1 to 11:1, or 8:1 to 10:1, or 8:1 to 9:1, or 9:1 to 12:1, or 10:1 to 12:1, or 11:1 to 12:1.

[0061] The monomer containing a cyano group can improve the mechanical strength and adhesive performance of copolymer B, and further improve the cycle performance of the battery. The monomer containing a small amount of ester group can improve the flexibility of copolymer B and prevent brittle fracture of the electrode plate. At the same time, the ester group has a certain electrolyte absorption and retention ability, which can improve the problem of poor ionic conductivity of fluorine-containing polymer A and improve the ionic conductivity ability of the adhesive.

[0062] In some embodiments, copolymer B further comprises structural units derived from a monomer containing a group according to formula I: JPEG0007676568000002.jpg44170 Here, n is selected from 0, 1, 2 or 3.

[0063] When n is 0, the group shown in formula I is JPEG0007676568000003.jpg40170 and when n is 1, the group shown in formula I is JPEG0007676568000004.jpg41170 and when n is 2, the group shown in formula I is JPEG0007676568000005.jpg38170 and when n is 3, the group shown in formula I is JPEG0007676568000006.jpg37170 It is.

[0064] The electronegativity of the oxygen element in the group shown in formula I is greater than that of the nitrogen element in the cyano group, and it is easier to form hydrogen bonds with the electrode active material and the conductive agent than the cyano group in copolymer B, and has a stronger bonding ability, which can greatly improve the dispersibility of the slurry and increase the solid content of the slurry. At the same time, the addition of the group shown in formula I can further improve the adhesive strength of the adhesive and the cycle performance of the battery.

[0065] In some embodiments, the monomer containing the group shown in Formula I is selected from one or more of N-vinylpyrrolidone, N-allyl-2-pyrrolidone, which have low cost, good stability, and easy synthesis processing.

[0066] In some embodiments, the mass content of the structural units derived from the monomer containing the group of formula I is 0.1% to 2%, based on the total mass of copolymer B. In some embodiments, the mass content of the structural units derived from the monomer containing the group of formula I is 0.5% to 2%, or 0.5% to 1.5%, based on the total mass of copolymer B. When copolymer B contains an appropriate amount of the group of formula I, the dispersibility of copolymer B can be improved, and the produced slurry is less likely to produce precipitates, which is advantageous for improving the solid content of the slurry and further improving the electrode loading.

[0067] A second aspect of the present application provides an adhesive, which comprises a copolymer C comprising structural units derived from a monomer containing a cyano group, structural units derived from a monomer containing an ester group, and structural units derived from a monomer containing a group as shown in formula I, JPEG0007676568000007.jpg42170 Here, n is selected from 0, 1, 2 or 3.

[0068] When n is 0, the group shown in formula I is JPEG0007676568000008.jpg41170 and when n is 1, the group shown in formula I is JPEG0007676568000009.jpg41170 and when n is 2, the group shown in formula I is JPEG0007676568000010.jpg39170 and when n is 3, the group shown in formula I is JPEG0007676568000011.jpg37170 It is.

[0069] The electronegativity of the oxygen element in the group shown in formula I is greater than that of the nitrogen element in the cyano group, and compared with the cyano group in the copolymer, it is more likely to form hydrogen bonds with the electrode active material and the conductive agent, and has stronger bonding ability, which can greatly improve the dispersibility of the slurry and increase the solid content of the slurry.

[0070] The monomer containing a cyano group can effectively complex with the metal on the current collector and the electrode active material, ensuring strong adhesion between the electrode active material and the current collector. The monomer containing an ester group can improve the brittleness of the electrode plate and avoid brittle fracture of the electrode plate.

[0071] As a result, the present application provides an adhesive comprising copolymer C including a structural unit derived from a monomer containing a cyano group, a structural unit derived from a monomer containing an ester group, and a structural unit derived from a monomer containing a group shown in formula I, thereby reducing the cost of the adhesive without reducing the solid content of the slurry, and improving the adhesive performance of the adhesive and the cycle performance of the battery.

[0072] In some embodiments, the cyano group-containing monomer is selected from one or more of acrylonitrile, methacrylonitrile, halogenated acrylonitrile, and methoxyacrylonitrile.

[0073] In some embodiments, the mass content of the structural units derived from monomers containing a cyano group is 80% to 95% based on the total mass of the copolymer C. In some embodiments, the mass content of the structural units derived from monomers containing a cyano group is 81% to 95%, or 82% to 95%, or 83% to 95%, or 84% to 95%, or 85% to 95%, or 86% to 95%, or 87% to 95%, or 88% to 95%, or 88% to 94%, or 88% to 93%, or 88% to 92%, or 88% to 91%, based on the total mass of the copolymer C. Within this range, the copolymer C can further improve the adhesive performance of the adhesive and the cycle performance of the battery.

[0074] In some embodiments, the monomer containing an ester group is selected from one or more of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, isoamyl acrylate, isooctyl acrylate, methyl methacrylate, ethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate.

[0075] In some embodiments, the monomer containing an ester group is selected from isooctyl acrylate, which provides copolymer C with a lower glass transition temperature and better flexibility, which is advantageous for plate processing.

[0076] Compared with fluorine-containing monomers, the above-mentioned cyano group-containing monomers and ester group-containing monomers are inexpensive and can be mass-produced without policy restrictions, which can significantly reduce the cost of the adhesive.

[0077] In some embodiments, the mass content of the structural units derived from the monomer containing an ester group is 8% to 12%, based on the total mass of the copolymer C. In some embodiments, the mass content of the structural units derived from the monomer containing an ester group is 8% to 11%, or 9% to 11%, based on the total mass of the copolymer C. Within this range, the copolymer C can further improve the adhesive performance of the adhesive and the cycling performance of the battery.

[0078] In some embodiments, the mass ratio of the structural unit derived from the monomer containing a cyano group to the structural unit derived from the monomer containing an ester group in the copolymer C is 8:1 to 12:1. The monomer containing a cyano group can improve the mechanical strength and adhesive performance of the copolymer B, and can further improve the cycle performance of the battery. The monomer containing a small amount of ester group can improve the flexibility of the copolymer B and prevent the brittle fracture of the electrode plate, and the ester group has a certain electrolyte absorption and retention ability, and can improve the problem of poor ionic conductivity of the fluorine-containing polymer A. Within this range, the copolymer C can further improve the adhesive strength of the electrode plate and the cycle performance of the battery.

[0079] In some embodiments, the monomer containing a group according to formula I is selected from one or more of N-vinylpyrrolidone, N-allyl-2-pyrrolidone.

[0080] In some embodiments, the mass content of the structural units derived from the monomer containing the group represented by formula I is 0.1% to 2%, or 0.5 to 1.5%, based on the total mass of copolymer C. When copolymer B contains an appropriate amount of the group represented by formula I, the dispersing performance of copolymer B can be improved, which is advantageous for allowing the produced slurry to contain more electrode active material and for improving the solid content of the slurry.

[0081] In some embodiments, the weight average molecular weight of copolymer C is 4×10 5 ~7×10 5In some embodiments, the weight average molecular weight of copolymer C is 4×10 5 ~7×10 5 , or 4 × 10 5 ~6×10 5 , or 4 × 10 5 ~5×10 5 , or 5 × 10 5 ~7×10 5 , or 6 × 10 5 ~7×10 5 is selected from.

[0082] By controlling the weight-average molecular weight of copolymer C, it is possible to achieve both the adhesiveness and processability of the adhesive. If the weight-average molecular weight of copolymer C is too low, the adhesive will be extremely brittle and the adhesive strength will be insufficient. If the weight-average molecular weight of copolymer C is too high, it will not be able to disperse the electrode active material. By rationally combining copolymers with different molecular weights, it is possible to improve the dispersibility of the electrode active material and further improve the battery performance.

[0083] In some embodiments, the copolymer C has a volume average particle size Dv50 of 5 to 20 μm.

[0084] As used herein, the term "Dv50" refers to the particle size corresponding to the cumulative particle size distribution percentage of particles reaching 50%. Its physical meaning is that 50% of particles have a larger particle size and 50% of particles have a smaller particle size, and Dv50 is also called the median size or median particle size.

[0085] If the average particle size Dv50 of the copolymer C is too large, it is difficult to dissolve, and the poor dispersibility of the slurry causes the conductive agent or electrode active material and the adhesive to aggregate, clogging the screen and affecting production, and the aggregates are washed away by the coating head, causing scratches by the coating particles and affecting the coating quality. An appropriate average particle size Dv50 is favorable for improving the dissolution rate of the copolymer C in the solvent and improving the processing efficiency of the electrode plate.

[0086] In some embodiments, the intrinsic viscosity of copolymer C is between 0.8 and 1.1 dl / g.

[0087] In this specification, the term "intrinsic viscosity" refers to the most commonly used expression of polymer solution viscosity. It is defined as the reduced viscosity when the concentration of the polymer solution is close to zero. That is, it is a viscosity that shows the contribution of a single molecule to the solution viscosity, reflects the properties of the polymer, and its value does not change with concentration. The intrinsic viscosity of the present invention refers to the intrinsic viscosity measured in N,N-dimethylacetamide at 30°C.

[0088] In this application, the intrinsic viscosity was tested by the following method: First, copolymer C finished powder sample m1 (0.15-0.17g) was weighed and placed in a 100mL Erlenmeyer flask, and V1 (50-60ml) of N,N-dimethylacetamide was added using a pipette, the Erlenmeyer flask was sealed, and the solution concentration C0=m1 / V1 was calculated, and the Erlenmeyer flask was placed in a constant temperature water bath at 60°C for 2.5h to dissolve. The sample solution after dissolution was filtered through a sand core filter to prevent particle impurities from clogging the Ubbelohde type viscosity gauge. Next, the filtered N,N-dimethylacetamide was aspirated with a disposable plastic straw to rinse the clean Ubbelohde viscometer, rinsed with solvent at least 4-5 times, 10 mL of N,N-dimethylacetamide was aspirated with a pipette and injected into the Ubbelohde viscometer, the Ubbelohde viscometer was placed in a thermostatic water bath at 30.0 °C ± 0.1 °C, and the outflow time was measured and recorded t0 after 15-20 min. Finally, the filtered colloidal solution prepared in step 1 was aspirated with a disposable plastic straw, the plastic straw was rinsed with the colloidal solution at least 4-5 times, 10 mL of the colloidal solution was aspirated with a pipette and injected into the Ubbelohde viscometer, the Ubbelohde viscometer was placed in a thermostatic water bath at 30.0 °C ± 0.1 °C, and the outflow time was measured and recorded t1 after 15-20 min. The measured intrinsic viscosity was (t1 / t0) / C0.

[0089] By controlling the intrinsic viscosity of copolymer C within an appropriate range, it is possible to achieve both excellent adhesive performance and processability of copolymer C. It is possible to avoid a situation in which the viscosity is too low to achieve an effective adhesive effect, and to avoid a situation in which the viscosity is too high to make it difficult to stir, manufacture, and apply the slurry.

[0090] A third aspect of the present application provides a method for producing an adhesive, the method comprising: Providing a monomer containing a cyano group, a monomer containing an ester group, and a monomer containing a group according to formula I, JPEG0007676568000012.jpg44170 where n is selected from 0, 1, 2 or 3; and polymerizing, under polymerizable conditions, a monomer containing a cyano group, a monomer containing an ester group, and a monomer containing a group shown in formula I to produce a copolymer C.

[0091] In some embodiments, the copolymer C is obtained by copolymerizing an anionic emulsifier by conventional emulsion polymerization.

[0092] In some embodiments, polymerizing the cyano group-containing monomer, the ester group-containing monomer, and the monomer containing the group shown in Formula I under polymerizable conditions to produce the copolymer C includes conducting a first stage reaction under polymerization pressure with first amounts of the cyano group-containing monomer, the ester group-containing monomer, and the monomer containing the group shown in Formula I, a first amount of a reaction solvent, a first amount of an emulsifier, a first amount of a pH buffer, and a first amount of an initiator at a first polymerization temperature, and adding to the system after the first stage reaction a second amount of the cyano group-containing monomer, the ester group-containing monomer, and the monomer containing the group shown in Formula I, a second amount of a reaction solvent, a second amount of an emulsifier, a second amount of a pH buffer, and a second amount of an initiator, and conducting a second stage reaction at a second polymerization temperature.

[0093] In some embodiments, the emulsifier is selected from one or more of an alkali metal salt or an alkyl acid salt of perfluorooctanoic acid. The alkali metal salt of perfluorooctanoic acid is selected from one or more of sodium perfluorooctanoate and potassium perfluorooctanoate. The alkyl acid salt is selected from one or more of an alkyl sulfate and an alkyl sulfonate.

[0094] In some embodiments, the initiator is selected from a peroxide, the peroxide is selected from one or more of a persulfate-based inorganic peroxide, a peroxide carbonate-based inorganic peroxide is selected from one or more of ammonium persulfate, potassium persulfate, and the peroxide carbonate-based is selected from diisopropyl peroxydicarbonate.

[0095] In some embodiments, the reaction solvent is deionized water.

[0096] In some embodiments, the pH buffering agent is selected from one or more of aqueous ammonia, potassium carbonate, and potassium bicarbonate.

[0097] In some embodiments, the first portion of the cyano-containing monomer, ester-containing monomer, and monomer containing a group according to formula I is 75-90% of the amount of each monomer, the first portion of the reaction solvent is 70-80% of the total amount of monomers added in the first stage reaction, the first portion of the emulsifier is 0.2-0.3% of the total amount of monomers added in the first stage reaction, the first portion of the pH buffer is 0.05-0.2% of the total amount of monomers added in the first stage reaction, and the first portion of the initiator is 0.15-1% of the total amount of monomers added in the first stage reaction. The first polymerization temperature is 70-80°C, and the reaction time of the first stage reaction is 2-3 hours.

[0098] In some embodiments, the second portion of the cyano-containing monomer, the ester-containing monomer, and the monomer containing a group according to Formula I is 10-25% of each monomer, the second portion of the reaction solvent is 20-30% of the total amount of monomers added in the second stage reaction, the second portion of the emulsifier is 0.05-0.1% of the total amount of monomers added in the second stage reaction, the second portion of the initiator is 0.05-0.3% of the total amount of monomers added in the second stage reaction, the second polymerization temperature is 85-90°C, and the reaction time of the second stage reaction is 3-4 hours.

[0099] In some embodiments, the weight ratio of the monomer containing a cyano group to the monomer containing an ester group is from 8:1 to 12:1, and the weight content of the monomer containing the group shown in formula I is from 0.1% to 2%, based on the total weight of the copolymer C.

[0100] In some embodiments, the monomer containing a cyano group is selected from one or more of acrylonitrile, methacrylonitrile, halogenated acrylonitrile, methoxyacrylonitrile, and / or the monomer containing an ester group is selected from one or more of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, isoamyl acrylate, isooctyl acrylate, methyl methacrylate, ethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, and / or the monomer containing a group shown in formula I is selected from one or more of N-vinylpyrrolidone, N-propenylpyrrolidone.

[0101] The monomers produced by this method are low cost and the reaction conditions are mild, which can reduce the cost of the adhesive.

[0102] [Positive plate]

[0103] The positive electrode plate includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, the positive electrode film layer including a positive electrode active material.

[0104] For example, the positive electrode current collector has two opposing surfaces in the thickness direction of the positive electrode current collector, and the positive electrode film layer is disposed on either or both of the two opposing surfaces of the positive electrode current collector.

[0105] In some embodiments, the positive electrode current collector may be a metal foil sheet or a composite current collector. For example, an aluminum foil may be used as the metal foil. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base layer. The composite current collector may be formed by forming a metal material (such as aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys) on a polymeric material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0106] In some embodiments, the positive electrode active material may be a positive electrode active material for batteries well known in the art. For example, the positive electrode active material may include at least one of lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Here, examples of the lithium transition metal oxide 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, lithium nickel cobalt manganese oxide (e.g., LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM 333 LiNi 0.5 Co 0.2 Mn 0.3O2(NCM 523 (may be abbreviated as LiNi 0.5 Co 0.25 Mn 0.25 O2(NCM 211 (may be abbreviated as LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM 622 (may be abbreviated as LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM 811 Lithium nickel cobalt aluminum oxide (e.g., LiNi 0.85 Co 0.15 Al 0.05 Examples of the lithium-containing phosphate having an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (e.g., LiFePO4 (which may be abbreviated as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (e.g., LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon.

[0107] In some embodiments, the cathode membrane layer optionally further comprises a conductive agent, which may include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0108] In some embodiments, the positive plate can be manufactured by the following method: The components for manufacturing the positive plate, such as the positive active material, the conductive agent, the adhesive of the present application, and any other components, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive slurry, and the positive slurry is applied to a positive current collector, followed by drying, cold pressing, and other processes to obtain a positive plate.

[0109] [Negative plate]

[0110] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer including a negative electrode active material.

[0111] For example, the negative electrode current collector has two opposing surfaces in the thickness direction of the negative electrode current collector, and the negative electrode film layer is disposed on either one or both of the two opposing surfaces of the negative electrode current collector.

[0112] In some embodiments, the negative electrode current collector may be a metal foil sheet or a composite current collector. For example, a copper foil may be used as the metal foil. The composite current collector may include a polymeric base layer and a metal layer formed on at least one surface of the polymeric substrate. The composite current collector may be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymeric substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0113] In some embodiments, the negative electrode active material may be a negative electrode active material for batteries well known in the art. For example, the negative electrode active material may include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, and lithium titanate. The silicon-based material may be selected from at least one of silicon elemental, silicon oxide, silicon carbon composite, silicon nitrogen composite, and silicon alloy. The tin-based material may be selected from at least one of tin elemental, tin oxide, and tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as a negative electrode active material for batteries may be used. These negative electrode active materials may be used alone or in combination of two or more.

[0114] In some embodiments, the negative electrode membrane layer optionally further comprises another adhesive, which may be selected from 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).

[0115] In some embodiments, the negative electrode membrane layer optionally further comprises a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0116] In some embodiments, the negative electrode membrane layer optionally further comprises other auxiliary agents, such as a thickening agent (eg, sodium carboxymethylcellulose (CMC-Na)).

[0117] In some embodiments, the negative plate can be manufactured by the following method: The components for manufacturing the negative plate, such as the negative active material, conductive agent, adhesive, and any other components, are dispersed in a solvent (e.g., deionized water) to form a negative slurry, which is then applied to a negative current collector, and the negative plate is obtained through processes such as drying and cold pressing.

[0118] [Electrolyte]

[0119] The electrolyte serves to conduct ions between the positive and negative plates. The present application does not specifically limit the type of electrolyte, and it can be selected according to needs. For example, the electrolyte may be liquid, gel, or all solid.

[0120] In some embodiments, the electrolyte employs an electrolytic solution, the electrolytic solution including an electrolyte salt and a solvent.

[0121] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonimide, lithium bistrifluoromethanesulfonimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, lithium difluorobis(oxalato)borate, and lithium tetrafluoro(oxalato)phosphate.

[0122] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, ethyl methyl sulfone, and diethyl sulfone.

[0123] In some embodiments, the electrolyte solution optionally further includes additives. For example, the additives may include an anode film-forming additive and a cathode film-forming additive, and may further include additives that can improve some performance of the battery, such as an additive that improves the overcharge performance of the battery, an additive that improves the high temperature or low temperature performance of the battery, etc.

[0124] [Separator]

[0125] In some embodiments, the secondary battery further includes a separator. The present application is not particularly limited to the type of separator, and any well-known separator with a porous structure having good chemical stability and mechanical stability may be selected.

[0126] In some embodiments, the separator may be made of at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layered thin film or a multi-layered composite thin film, without any particular limitation. When the separator is a multi-layered composite thin film, the materials of the layers may be the same or different, without any particular limitation.

[0127] [Secondary battery]

[0128] The present application provides a secondary battery, the secondary battery comprising an electrode assembly and an electrolyte, the electrode assembly comprising a positive electrode plate, a separator, and a negative electrode plate, the positive electrode plate comprising a positive electrode active material and the adhesive of any embodiment of the present application or the adhesive manufactured by the manufacturing method of any embodiment of the present application, the secondary battery having better cycle performance.

[0129] In some embodiments, the positive electrode active material is a lithium-containing transition metal oxide, optionally lithium iron phosphate, or a doped modification thereof, or at least one of a conductive carbon-coated, conductive metal-coated, or conductive polymer-coated modification thereof.

[0130] In some embodiments, the lithium-containing transition metal oxide is optionally at least one of lithium cobalt oxide, lithium nickel manganese cobalt oxide, lithium nickel manganese aluminate, lithium iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium iron silicate, lithium vanadium silicate, lithium cobalt silicate, lithium manganese silicate, lithium manganese spinel oxide, lithium nickel manganese spinel oxide, lithium titanate, or doped modifications thereof, or conductive carbon-coated, conductive metal-coated, or conductive polymer-coated modifications thereof.

[0131] In some embodiments, the positive and negative plates and the separator may be fabricated into an electrode assembly by a winding or lamination process.

[0132] Typically, a secondary battery includes a positive electrode plate, a negative electrode plate, an electrolyte, and a separator. During the charge and discharge process of the battery, active ions shuttle between the positive electrode plate and the negative electrode plate to perform intercalation and deintercalation. The electrolyte serves to conduct ions between the positive electrode plate and the negative electrode plate. The separator is installed between the positive electrode plate and the negative electrode plate, and serves mainly to prevent short circuits between the positive and negative electrodes, while allowing ions to pass through.

[0133] In some embodiments, the secondary battery may include an exterior case that may be used to package the electrode assembly and electrolyte.

[0134] In some embodiments, the exterior of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The exterior of the secondary battery may be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0135] In the present application, there is no particular limitation on the shape of the secondary battery, which may be cylindrical, rectangular or any other shape. For example, FIG. 3 shows a secondary battery 5 having a rectangular structure as an example.

[0136] In some embodiments, referring to FIG. 4, the exterior may include a housing 51 and a cover plate 53. Here, the housing 51 may include a bottom plate and a side plate connected on the bottom plate, and the bottom plate and the side plate surround the housing 51 to form a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be provided to cover the opening to close the receiving cavity. The positive electrode plate, the negative electrode plate and the separator can form an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is packaged in the receiving cavity. An electrolyte is permeated into the electrode assembly 52. ​​The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and may be selected by those skilled in the art according to actual specific needs.

[0137] A fourth aspect of the present application provides an electrode comprising an active electrode material and an adhesive composition or adhesive according to any of the embodiments, the active electrode material being optionally a positive electrode active material, the positive electrode active material being a lithium-containing transition metal oxide. In some embodiments, the lithium-containing transition metal oxide is optionally at least one of lithium cobalt oxide, lithium nickel manganese cobalt oxide, lithium nickel manganese aluminate, lithium iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium iron silicate, lithium vanadium silicate, lithium cobalt silicate, lithium manganese silicate, lithium manganese spinel oxide, lithium nickel manganese spinel oxide, lithium titanate, or doped modifications thereof, or conductive carbon-coated, conductive metal-coated, or conductive polymer-coated modifications thereof. In some embodiments, the lithium-containing transition metal oxide is optionally lithium iron phosphate, or a doped modification thereof, or at least one of a conductive carbon-coated, conductive metal-coated, or conductive polymer-coated modification thereof.

[0138] This electrode has higher adhesion and therefore the battery has better cycling performance.

[0139] [Battery module]

[0140] In some embodiments, the secondary batteries may be assembled into a battery module, and the number of secondary batteries included in the battery module may be one or more, with the specific number being selectable by one skilled in the art based on the application and capacity of the battery module.

[0141] Fig. 5 shows an example of a battery module 4. Referring to Fig. 5, in the battery module 4, the secondary batteries 5 may be arranged in sequence along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the secondary batteries 5 may be fixed by fasteners.

[0142] Optionally, the battery module 4 may further include a housing having an accommodating space, and the multiple secondary batteries 5 are accommodated in the accommodating space.

[0143] [Battery pack]

[0144] In some embodiments, the battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack may be one or more, and the specific number may be selected by one skilled in the art based on the application and capacity of the battery pack.

[0145] 6 and 7 show an example of a battery pack 1. Referring to Fig. 6 and Fig. 7, the battery pack 1 may include a battery case and a plurality of battery modules 4 installed in the battery case. The battery case includes an upper case 2 and a lower case 3, and the upper case 2 is provided to cover the lower case 3 and may form a sealed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery case according to any manner.

[0146] [Power consumption equipment]

[0147] A sixth aspect of the present application provides a power consuming device including the secondary battery according to any embodiment, the battery module according to any embodiment, or the battery pack according to any embodiment, the power consuming device having a longer driving range.

[0148] The secondary battery, battery module, or battery pack may be used as a power source for the power consuming device, or as an energy storage unit for the power consuming device, which may include, but is not limited to, mobile equipment (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0149] The power consuming device may be a secondary battery, a battery module, or a battery pack, depending on the needs of the usage.

[0150] 8 shows an example of a power consumption device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. A battery pack or a battery module can be adopted to meet the high power and high energy density requirements of the secondary battery of the power consumption device.

[0151] Another example of the device may be a mobile phone, a tablet computer, a notebook computer, etc. Such devices are generally required to be lightweight and may employ a secondary battery as a power source.

[0152] Working Example The following describes the examples of the present application. The examples described below are illustrative and are used only to interpret the present application, and should not be understood as limiting the present application. In the examples, specific techniques or conditions are not specified, but are carried out according to the techniques or conditions described in the technical literature or product instructions. For reagents or equipment used, those without the manufacturer are all common products that can be purchased commercially.

[0153] Example 1

[0154] 1) Manufacturing of adhesives containing copolymer C The preparation method of polymer C is as follows: The polymerization vessel is a 10L stainless steel autoclave, the rotation speed is 100 r / min, the sealing property of the polymerization system is checked first, the autoclave is evacuated, filled with nitrogen, and oxygen is discharged, and this process is repeated three times. Add 2000g of deionized water, 1.6g of ammonia water, and 3.2g of sodium alkyl sulfate, then add 1408g of acrylonitrile monomer, 176g of isooctyl acrylate monomer, and 16g of N-vinylpyrrolidone monomer, and evacuate to a polymerization pressure of 4.2Mpa, heat to 55°C, and leave for 0.8h, then add 8g of ammonium persulfate, heat to 75°C, and carry out polymerization reaction for 2~3h while stirring. Add 352g of acrylonitrile monomer, 44g of isooctyl acrylate monomer, 4g of N-vinylpyrrolidone monomer, 400g of deionized water, 1.6g of sodium alkyl sulfate, and 0.8g of ammonium persulfate to the polymerization kettle, and raise the temperature to 90°C and keep the reaction for 4h. Obtain the polymerized product by flash evaporation, and use deionized water to make the conductivity of the washing liquid 1*10 -8 After washing until the viscosity was less than s / cm and vacuum drying, N-vinylpyrrolidone-acrylonitrile-isooctyl acrylate copolymer was obtained. The copolymer obtained by the production has a weight average molecular weight of 700,000, a particle size Dv50 of 15 μm, and an intrinsic viscosity of 1.1 dl / g.

[0155] The adhesive is manufactured as follows. 4g of polyvinylidene fluoride (fluorine-containing polymer A) and 4g of N-vinylpyrrolidone-acrylonitrile-isooctyl acrylate copolymer are taken, and added to 250g of N-methylpyrrolidone solution, stirred for 90 minutes at a rotation speed of 500r / min by a stirring disperser, and after stirring, degassed for 30 minutes by an ultrasonic cleaner. Here, polyvinylidene fluoride is a 601A product produced by Dongyang Guang Co., Ltd., synthesized by emulsion method, with a weight average molecular weight of 900,000, a particle size Dv50 of 20μm, a crystallinity of 40%, and a melting point of 170°C.

[0156] 2) Button battery manufacturing 398g of lithium iron phosphate and 2.8g of conductive carbon black were added to an agate mortar and dry mixed for 15min. The dry mixed product was added to the adhesive and stirred for 90min at 1200r / min by a stirring disperser to produce a lithium battery positive electrode slurry.

[0157] The above slurry was knife-coated onto carbon-coated aluminum foil, baked at 110°C for 15 min, cold-pressed, and then cut into a disk with a diameter of 15 mm. A button-type battery was then fabricated together with a metallic lithium plate, a separator, and an electrolyte.

[0158] 3) Separator A polypropylene membrane served as the separator.

[0159] 4) Electrolyte production In a glove box with an argon atmosphere (H2O<0.1ppm, O2<0.1ppm), the organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed uniformly in a volume ratio of 3 / 7, LiPF6 lithium salt was dissolved in the organic solvent, stirred uniformly, and 1M LiPF6EC / EMC solution was placed to obtain an electrolyte.

[0160] The manufacturing methods of the batteries of Examples 2 to 25 and the button battery of Comparative Example 1 are similar to those of the button battery of Example 1, but the raw materials and compounding ratios for producing copolymer C or the compounding ratios of each component in the adhesive are adjusted, and specific parameters are shown in Table 1.

[0161] In Examples 2 to 7, the mass ratio of polyvinylidene fluoride and copolymer C was adjusted, and other parameters were the same as those in Example 1. See Table 1 for specific parameters.

[0162] In Examples 8 to 11, the monomer polymerization ratio of acrylonitrile and isooctyl acrylate in N-vinylpyrrolidone-acrylonitrile-isooctyl acrylate copolymer was adjusted, and other parameters were the same as those in Example 1. See Table 1 for specific parameters.

[0163] In Examples 12 to 13, the monomer polymerization ratio of acrylonitrile and isooctyl acrylate in N-vinylpyrrolidone-acrylonitrile-isooctyl acrylate copolymer is adjusted, and the weight ratio of polyvinylidene fluoride to N-vinylpyrrolidone-acrylonitrile-isooctyl acrylate copolymer is set to 2:1, and other parameters are consistent with Example 1. For specific parameters, see Table 1.

[0164] In Examples 14 to 15, the monomer polymerization ratio of acrylonitrile and isooctyl acrylate in N-vinylpyrrolidone-acrylonitrile-isooctyl acrylate copolymer is adjusted, and the weight ratio of polyvinylidene fluoride to N-vinylpyrrolidone-acrylonitrile-isooctyl acrylate copolymer is set to 3:1, and other parameters are consistent with Example 1. For specific parameters, see Table 1.

[0165] In Examples 16 to 17, the monomer polymerization ratio of acrylonitrile and isooctyl acrylate in N-vinylpyrrolidone-acrylonitrile-isooctyl acrylate copolymer is adjusted, and the weight ratio of polyvinylidene fluoride to N-vinylpyrrolidone-acrylonitrile-isooctyl acrylate copolymer is set to 4:1, and other parameters are consistent with Example 1. For specific parameters, see Table 1.

[0166] In Examples 18 to 20, the mass of N-vinylpyrrolidone added to polymer B was adjusted, and the molar ratio of acrylonitrile to isooctyl acrylate monomer in N-vinylpyrrolidone-acrylonitrile-isooctyl acrylate copolymer was set to 10:1, and other parameters were consistent with Example 1. The specific parameters are shown in Table 1.

[0167] In Examples 21-22, in the copolymer preparation process, the secondary replenishment temperature is further increased to 90°C, and then the reaction time is adjusted from 4h to 3h and 2.5h in sequence, and the molar ratio of acrylonitrile and isooctyl acrylate monomer in N-vinylpyrrolidone modified acrylonitrile-isooctyl acrylate copolymer is set to 10:1, and other parameters and steps are consistent with Example 1, and specific parameters are referred to Table 1.

[0168] In Example 23, N-allyl-2-pyrrolidone modified acrylonitrile-isooctyl acrylate copolymer is adopted, and other parameters are consistent with those in Example 1, and the specific parameters are referred to in Table 1.

[0169] In the process of preparing the copolymer in Example 24, N-vinylpyrrolidone is not added, and the molar ratio of acrylonitrile and isooctyl acrylate monomer in acrylonitrile-isooctyl acrylate copolymer is set to 10:1, and other parameters are consistent with Example 1, and the specific parameters are referred to Table 1.

[0170] In Example 25, the 401A product produced by Dongyangguang Co., Ltd. is used as polyvinylidene fluoride, and its weight average molecular weight is 600,000. The other steps are the same as those in Example 1. The specific parameters are shown in Table 1.

[0171] In Comparative Example 1, polyvinylidene fluoride is used alone as the adhesive, in Comparative Example 2, N-vinylpyrrolidone modified acrylonitrile-isooctyl acrylate copolymer prepared in Example 9 is used alone as the adhesive, in Comparative Example 3, acrylonitrile-isooctyl acrylate copolymer prepared in Example 24 is used alone as the adhesive, and other steps are the same as in Example 1, and the specific parameters are shown in Table 1.

[0172] The relevant parameters of the adhesives of Examples 1 to 25 and Comparative Examples 1 to 3 are as shown in Table 1 below.

[0173] In addition, performance tests were carried out on the electrodes and batteries obtained in the above Examples 1 to 25 and Comparative Examples 1 to 3. The test methods are as follows, and Table 1 shows the test results.

[0174] 1. Testing the type of adhesive structural unit

[0175] In the tablet press transmission method, the sample was pressed into a KBr tablet, and the KBr background blank was removed by the transmission method to obtain a sample test spectrum. The model number of the instrument was Nicolet 5700 (Thermo Nicolet, USA), and the standard linearity was better than 0.07%, and the resolution was 0.09 cm. -1 and the wavenumber range is 400-4000 cm -1 and sensitivity < 9.65*10 -5 Abls. Used to detect molecular structure and chemical bonds.

[0176] 2. Molecular weight test

[0177] A Waters 2695 Isocratic HPLC type gel chromatography (differential refractive index detector 2141) was adopted. A polystyrene solution sample with a mass fraction of 3.0% was used as the reference, and a matching chromatography column (oil-based: Styragel HT5 DMF7.8*300mm+Styragel HT4) was selected. A 3.0% adhesive colloid solution was placed using purified N-methylpyrrolidone (NMP) solvent, and the placed solution was left to stand for one day and prepared for use. During the test, first, tetrahydrofuran was sucked into the syringe, flushed, and repeated several times. Then, 5 ml of the experimental solution was sucked, the air in the syringe was removed, and the needle tip was dried. Finally, the sample solution was gradually injected into the sample injection port. Data was acquired after the indicated values ​​were stabilized.

[0178] 3. Adhesion test (between the positive electrode plate active material layer and the positive electrode current collector)

[0179] According to the national standard GBT 2790-1995 "Test method for 180° peel strength of adhesive", the adhesive strength test process of the examples and comparative examples of this application is as follows:

[0180] A sample with a width of 30 mm and a length of 100 to 160 mm was cut using a blade, and a special double-sided tape was attached to a steel plate, the tape being 20 mm wide and 90 to 150 mm long. The electrode plate sample cut out earlier was attached to the double-sided tape, the test surface was turned downward, and the plate was rolled three times in the same direction with a pressure roller.

[0181] A paper strip with a width equal to that of the electrode plate and a length 80 to 200 mm longer than the length of the sample was inserted under the electrode plate and fixed with corrugated tape.

[0182] The power supply (sensitivity is 1N) of the Sanshisha tension machine was turned on, the indicator light was turned on, the stopper was adjusted to an appropriate position, and the end of the steel sheet to which the pole plate was not attached was fixed with the lower jig. The paper strip was folded up and fixed with the upper jig, and the position of the upper jig was adjusted with the "up" and "down" buttons on the manual controller attached to the tension machine. Then, a test was performed and the numerical value was read. The adhesive strength comparison data of Example 1 and Comparative Example 1 shown in FIG. 1 was obtained.

[0183] 4. Battery capacity retention rate test

[0184] Taking Example 1 as an example, the battery capacity retention test process is as follows: At 25°C, the battery corresponding to Example 1 is charged at a constant current of 1 / 3C to 3.65V, then charged at a constant voltage of 0.05C at 3.65V, left for 5 minutes, and discharged at 1 / 3C to 2.5V, and the obtained capacity is recorded as the initial capacity C0. When the above steps are repeated for the same battery, and the discharge capacity Cn of the battery after the nth cycle is recorded, the battery capacity retention rate after each cycle is Pn=Cn / C0*100%, and the values ​​of 100 points P1, P2...P100 are taken as the ordinate, and the corresponding cycle number is taken as the abscissa, and the graph of the battery capacity retention rate vs. cycle number of Example 1 and Comparative Example 1 shown in Figure 2 is obtained.

[0185] In this test process, the first cycle corresponds to n=1, the second cycle corresponds to n=2, ... the 100th cycle corresponds to n=100. The battery capacity retention rate data corresponding to Example 1 in Table 1 is the data measured after 500 cycles under the above test conditions, i.e., the P500 value. The test process of Comparative Example 1 and other Examples is the same as above.

[0186] 5. Slurry solids content test Solid content test method: Prepare a glass dish and record its weight m1. Put a part of the prepared positive electrode slurry into the glass dish and record its total weight m2. Put the dish containing the positive electrode slurry into a dry box and heat it at 120°C for 1h. Weigh the dish after drying and record its weight m3. Solid content = (m3-m1) / (m2-m1)*100%.

[0187] JPEG0007676568000013.jpg214170 JPEG0007676568000014.jpg188170 JPEG0007676568000015.jpg210170 JPEG0007676568000016.jpg210170

[0188] As shown in Figures 1 and 2, in Example 1, since an acrylonitrile-isooctyl acrylate copolymer modified with a monomer having a pyrrolidone group was added, both the adhesive performance of the adhesive and the battery capacity retention rate were improved compared to Comparative Example 1.

[0189] As can be seen from the results in Table 1, Examples 1 to 25 all provide adhesive compositions, which include polyvinylidene fluoride and an acrylonitrile-isooctyl acrylate copolymer containing structural units derived from acrylonitrile and structural units derived from isooctyl acrylate. Compared with Comparative Examples 1 to 3, all of them have achieved good effects, improving the adhesive performance and battery capacity retention rate of the adhesive.

[0190] The weight average molecular weight of the polyvinylidene fluoride in Examples 1 to 25 is 600,000 to 900,000, and the weight average molecular weight of the acrylonitrile-isooctyl acrylate copolymer is 400,000 to 700,000. Compared with Comparative Examples 1 to 3, they all achieved good effects, improving the adhesive performance of the adhesive and the battery capacity retention rate.

[0191] In Examples 1 to 25, the mass ratio of polyvinylidene fluoride to acrylonitrile-isooctyl acrylate copolymer in the adhesive composition is 1:4 to 4:1. Compared with Comparative Examples 1 to 3, all of them have good effects, improving the adhesive performance and battery capacity retention rate of the adhesive.

[0192] In Examples 1 to 25, the mass ratio of the structural units derived from acrylonitrile to the structural units derived from isooctyl acrylate in the acrylonitrile-isooctyl acrylate copolymer was 8:1 to 12:1, all of which achieved good effects, improving the adhesive performance and battery capacity retention rate of the adhesive. When the mass ratio of the structural units derived from acrylonitrile to the structural units derived from isooctyl acrylate in the acrylonitrile-isooctyl acrylate copolymer was 8:1 to 10:1, the adhesive performance and battery capacity retention rate of the adhesive were further improved.

[0193] The acrylonitrile-isooctyl acrylate copolymers in Examples 1 to 23 and 25 were modified with a monomer having a pyrrolidone group, so that the copolymers contained structural units derived from the monomer having a pyrrolidone group. The acrylonitrile-isooctyl acrylate copolymers modified with the monomer having a pyrrolidone group had stronger adhesive performance and battery capacity retention rate than those before modification, and the solid content of the slurry was further improved.

[0194] In Examples 1 to 23 and 25, the mass content of the structural unit derived from the monomer containing a pyrrolidone group is 0.1% to 2% based on the total mass of the acrylonitrile-isooctyl acrylate copolymer. Within this range, the copolymer improved the adhesive performance of the adhesive, the battery capacity retention rate, and the solid content of the slurry. In Examples 1 to 23 and 25, the mass content of the structural unit derived from the monomer containing a pyrrolidone group is 0.5% to 1.5%, or 0.5% to 1.0%. Within this range, the solid content of the slurry was further improved.

[0195] The acrylonitrile-isooctyl acrylate copolymers in Examples 1 to 23 and 25 were modified with a monomer having a pyrrolidone group, and the mass content of the structural units derived from acrylonitrile was 80% to 95% based on the total mass of the copolymer. Within this range, the copolymer improved the adhesive performance of the adhesive, the battery capacity retention rate, and the solid content of the slurry.

[0196] The acrylonitrile-isooctyl acrylate copolymers in Examples 1 to 23 and 25 were modified with a monomer having a pyrrolidone group, and the mass content of the structural unit derived from isooctyl acrylate was 8% to 12% based on the total mass of the copolymer. Within this range, the copolymer improved the adhesive performance of the adhesive, the battery capacity retention rate, and the solid content of the slurry.

[0197] As can be seen from the comparison between Comparative Example 2 and Comparative Example 3, the solid content of the positive electrode slurry can be improved by modifying the adhesive with a monomer having a group shown in Formula I. As can be seen from the comparison between Example 9 and Example 24, when other conditions are the same, the solid content of the positive electrode slurry can be improved by modifying the adhesive with a monomer having a group shown in Formula I, and the adhesive strength between the corresponding current collector and the negative electrode material layer is significantly improved, and the capacity retention rate of the battery is significantly improved.

[0198] It should be noted that the present application is not limited to the above embodiment. The above embodiment is merely an example, and any embodiment having substantially the same configuration as the technical idea and having similar actions and effects within the scope of the technical proposal of the present application is included in the technical scope of the present application. In addition, various modifications that a person skilled in the art can conceive of to the embodiment are implemented within the scope of the gist of the present application, and other forms constructed by combining some of the components in the embodiment are also included in the scope of the present application. [Explanation of symbols]

[0199] 1 battery pack, 2 upper case, 3 lower case, 4 battery module, 5 secondary battery, 51 housing, 52 electrode assembly, 53 top cover assembly.

Claims

1. An adhesive composition comprising a fluorine-containing polymer A and a copolymer B, the copolymer B comprising a structural unit derived from a monomer containing a cyano group and a structural unit derived from a monomer containing an ester group, The copolymer B further comprises structural units derived from a monomer containing a group as shown in formula I, where n is selected from 0, 1, 2 or 3; The adhesive composition, wherein the mass content of the structural unit derived from the monomer containing the group represented by formula I is 0.1% to 1.5% based on the total mass of the copolymer B.

2. 2. The adhesive composition according to claim 1, wherein the weight average molecular weight of the fluorine-containing polymer A is 600,000 to 900,000, and the weight average molecular weight of the copolymer B is 400,000 to 700,000.

3. 2. The adhesive composition according to claim 1, wherein a mass ratio of the fluorine-containing polymer A to the copolymer B is 1:4 to 4:

1.

4. 2. The adhesive composition according to claim 1, wherein the fluorine-containing polymer A is selected from one or more of polyvinylidene fluoride and its copolymers with tetrafluoroethylene, hexafluoropropylene, and trichloroethylene.

5. 2. The adhesive composition of claim 1, wherein the cyano group-containing monomer is selected from one or more of acrylonitrile, methacrylonitrile, halogenated acrylonitrile, and methoxyacrylonitrile.

6. 2. The adhesive composition of claim 1, wherein the monomer containing an ester group is selected from one or more of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, isoamyl acrylate, isooctyl acrylate, methyl methacrylate, ethyl methacrylate, hydroxyethyl acrylate, and hydroxypropyl acrylate.

7. 2. The adhesive composition according to claim 1, wherein in the copolymer B, a mass ratio of the structural units derived from a monomer containing a cyano group to the structural units derived from a monomer containing an ester group is 8:1 to 12:1, or 8:1 to 10:

1.

8. 2. The adhesive composition of claim 1, wherein the monomer containing a group according to formula I is selected from one or more of N-vinylpyrrolidone, N-allyl-2-pyrrolidone.

9. The adhesive composition according to claim 1, characterized in that the mass content of the structural units derived from the monomer containing the group shown in formula I is 0.5% to 1.0% based on the total mass of the copolymer B.

10. 10. A secondary battery comprising: an electrode assembly and an electrolyte; the electrode assembly comprising a positive electrode plate, a separator, and a negative electrode plate; the positive electrode plate comprising a positive electrode active material and the adhesive composition according to claim 1.

11. 11. The secondary battery according to claim 10, wherein the positive electrode active material is a lithium-containing transition metal oxide, and optionally at least one of lithium iron phosphate, or a doped modification thereof, or a conductive carbon-coated modification thereof, a conductive metal-coated modification thereof, or a conductive polymer-coated modification thereof.

12. A battery module comprising the secondary battery according to claim 10.

13. A battery pack comprising the battery module according to claim 12.

14. A power consuming device comprising the secondary battery according to claim 10.

15. A power consuming device comprising the battery module of claim 12.

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