Adhesive manufacturing method

Abstract

The present application provides an adhesive, a manufacturing method, a secondary battery, a battery module, a battery pack, and a power consuming device. The adhesive includes a 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, JPEG2024526503000021.jpg43170 Here, n is selected from 0, 1, 2, or 3. The adhesive of the present application has strong adhesive strength, and the slurry containing it has a high solid content, and the cycle performance of the secondary battery is excellent.

Description

[Technical Field]

[0001] The present application relates to the field of lithium battery technology, and in particular to adhesives, manufacturing methods, secondary batteries, battery modules, battery packs, and power consumption devices. [Background technology]

[0002] In recent years, lithium-ion batteries have been widely applied in energy storage power systems such as hydroelectric power, thermal power, wind power and solar power plants, as well as in multiple fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. As the application of lithium-ion batteries becomes more widespread, 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, conventional adhesives are expensive and have poor adhesive properties, and there is an urgent need to develop polymers with excellent adhesive properties that can replace or partially replace conventional adhesives in order to reduce adhesive and battery costs and improve the electrical performance of batteries. Summary of the Invention

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

[0005] A first aspect of the present application provides an adhesive, the adhesive comprising 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 shown in formula I: JPEG0007724299000001.jpg44170 where n is selected from 0, 1, 2 or 3.

[0006] As a result, the present application uses a copolymer containing 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 as an adhesive, 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.

[0007] In an optional embodiment, the cyano group-containing monomer is selected from one or more of acrylonitrile, methacrylonitrile, halogenated acrylonitrile, and methoxyacrylonitrile.

[0008] In any embodiment, the mass content of the structural units derived from the monomer containing a cyano group is 80% to 95% 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.

[0009] In an optional embodiment, the ester group-containing monomer 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 fluorine-containing monomers, the cyano group-containing monomer and the ester group-containing monomer are inexpensive and can be mass-produced without policy restrictions, significantly reducing the cost of the adhesive.

[0010] In any embodiment, 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. Within this range, the copolymer C can further improve the adhesive performance of the adhesive and the cycling performance of the battery.

[0011] 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 C is 8:1 to 12:1, or 8:1 to 10:1. The monomer containing a cyano group can improve the mechanical strength and adhesive properties of copolymer B and further improve the cycle performance of the battery. The monomer containing a small amount of ester groups can improve the flexibility of copolymer B and prevent brittle fracture of the electrode plate. The ester groups provide a certain level of electrolyte absorption and retention ability, thereby alleviating the problem of poor ionic conductivity of fluorine-containing polymer A. Within this range, copolymer C can further improve the adhesive strength of the electrode plate and the cycle performance of the battery.

[0012] 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.

[0013] In any embodiment, 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 dispersibility of Copolymer B can be improved, and the produced slurry is less likely to produce precipitates, which is advantageous for increasing the solid content of the slurry and further increasing the electrode loading.

[0014] In any embodiment, the weight-average molecular weight of copolymer C is 400,000 to 700,000. By controlling the weight-average molecular weight of copolymer C, it is possible to achieve both the adhesive properties and processability of the adhesive. If the weight-average molecular weight of copolymer C is too low, the adhesive becomes extremely brittle, resulting in insufficient adhesive strength. If the weight-average molecular weight of copolymer C is too high, it is difficult for it to disperse the electrode active material. Furthermore, by rationally combining copolymers having different molecular weights, it is possible to improve the dispersibility of the electrode active material and further improve battery performance.

[0015] In some embodiments, the volume average particle diameter Dv50 of the copolymer C is 5 to 20 μm. If the volume average particle diameter Dv50 of the copolymer C is too large, it becomes difficult to dissolve, and the dispersion of the slurry becomes poor, causing the conductive agent or electrode active material and adhesive to aggregate, clogging the screen and affecting production. The aggregates are also washed away into the coating head, causing scratches by the coating particles and affecting coating quality. An appropriate volume average particle diameter Dv50 is advantageous for improving the dissolution rate of the copolymer C in the solvent and improving the processing efficiency of the electrode plate.

[0016] In any embodiment, the intrinsic viscosity of the copolymer C is 0.8 to 1.1 dL / g. By controlling the intrinsic viscosity of the copolymer C within an appropriate range, the copolymer C can have both excellent adhesive properties and processability. This avoids a viscosity that is too low to provide an effective adhesive effect, and also avoids a viscosity that is too high to make the slurry difficult to stir, manufacture, and apply.

[0017] A second 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, JPEG0007724299000002.jpg43170 where n is selected from 0, 1, 2 or 3; and polymerizing a monomer containing a cyano group, a monomer containing an ester group, and a monomer containing a group shown in Formula I under polymerizable conditions to produce a copolymer C.

[0018] The cost of the monomers produced by this method is low, and the reaction conditions are mild, which can reduce the cost of the adhesive.

[0019] In any embodiment, the mass ratio of the cyano group-containing monomer to the ester group-containing monomer is 8:1 to 12:1, or 8:1 to 10:1, and the mass content of the monomer containing the group shown in formula I is 0.1% to 2%, or 0.5% to 1.5%, based on the total mass of copolymer C.

[0020] In optional 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 the group shown in Formula I is selected from one or more of N-vinylpyrrolidone, N-propenylpyrrolidone.

[0021] 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, and the battery has improved cycle performance.

[0022] In any embodiment, the active cathode material is a lithium-containing transition metal oxide, optionally lithium iron phosphate, or doped modifications thereof, or at least one of conductive carbon-coated, conductive metal-coated, or conductive polymer-coated modifications thereof.

[0023] A fourth aspect of the present application provides a battery module including the secondary battery of the third aspect of the present application.

[0024] A fifth aspect of the present application provides a battery pack including the battery module of the fourth aspect of the present application.

[0025] A sixth aspect of the present application provides a power consumption 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.

[0026] The battery module of the fourth aspect and the battery pack of the fifth aspect of the present application include the secondary battery of the third aspect, and therefore have the same advantages as the secondary battery. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 is a diagram showing an adhesive performance test of the adhesives produced in Example 1 and Comparative Example 1. [Figure 2] 1 is a graph showing cycle test results of batteries manufactured in Example 1 and Comparative Example 1. [Figure 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 shown in FIG. 3 according to the embodiment of the present application. [Figure 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 shown in FIG. 6 according to the embodiment of the present application. [Figure 8] 1 is a schematic diagram of a power consumption device in which a secondary battery according to an embodiment of the present application is used as a power source; DETAILED DESCRIPTION OF THE INVENTION

[0028] Hereinafter, with reference to the accompanying drawings as appropriate, detailed descriptions will be given of embodiments specifically disclosing the adhesive, manufacturing method, electrode, battery, and power consumption device of the present application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and redundant descriptions of structures that are actually the same may be omitted. This is to avoid the following description becoming unnecessarily long and to facilitate understanding by those skilled in the art. Note that the drawings and the following description are provided to enable those skilled in the art to fully understand the present application, and are not intended to limit the subject matter described in the claims.

[0029] The "ranges" disclosed herein 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 single range. For example, if ranges of 60 to 120 and 80 to 110 are recited for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if minimum range values of 1 and 2 and maximum range values of 3, 4, and 5 are recited, the following ranges are also contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise specified, a numerical range "a to b" is a shorthand expression representing all combinations of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 and 5" are recited herein, and "0 to 5" is merely a shorthand notation 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.

[0030] Unless otherwise stated, all embodiments and optional embodiments of the present application may be combined with each other to form a new technical solution.

[0031] 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.

[0032] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, a description of a method including steps (a) and (b) means that the method may include sequential steps (a) and (b), or sequential steps (b) and (a). For example, a description of a method mentioned above that 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), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0033] Unless otherwise specified, the terms "comprise" and "comprises" used in this application may be open-ended or closed-ended. For example, the terms "comprise" and "comprises" may further include or include other components not listed, or may include or include only the listed components.

[0034] 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).

[0035] PVDF is a commonly used battery adhesive, but its low cost and poor adhesive strength cause the adhesive strength to weaken during battery cycling, further reducing the cycle performance of the battery. Based on the above technical problems, the present application has developed an adhesive that is low cost and provides excellent adhesion to the electrode plates, significantly improving the cycle performance of the battery.

[0036] [glue]

[0037] Based on this, 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.

[0038] 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 dispersing medium (e.g., water).

[0039] In some embodiments, the dispersion medium of the adhesive is an aqueous solvent, such as water.

[0040] 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.

[0041] In some embodiments, an adhesive is used to hold the electrode material and / or conductive agent in place and adhere them to the conductive metal member to form the electrode, hi some embodiments, the electrode does not include any conductive agent.

[0042] 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.

[0043] In some embodiments, the adhesive is used as a negative electrode adhesive to bond a negative electrode active material and / or a conductive agent to form a negative electrode.

[0044] As used herein, the term "polymer" includes, on the one hand, chemically uniform aggregates of macromolecules produced by polymerization reactions (copolymerization, homopolymerization), which differ in terms of their degree of polymerization, molar mass and chain length. On the other hand, the term also includes derivatives of such macromolecular aggregates formed by polymerization reactions, i.e. compounds or mixtures which can be obtained by reactions, for example addition or substitution, of functional groups in the macromolecules and which can be chemically uniform or chemically heterogeneous.

[0045] As used herein, the term "fluorine-containing polymer" refers to a polymer that contains elemental fluorine.

[0046] As used herein, the term "copolymer" refers to a polymer made by polymerizing two or more different types of monomers.

[0047] As used herein, the term "cyano" refers to a -CN group.

[0048] As used herein, the term "ester group" refers to a group of the general formula -COOR structural unit, where R is a C 1-5 Selected from alkyl groups, examples of ester groups include, but are not limited to, methyl, ethyl, propyl, butyl, amyl, isooctyl, and the like.

[0049] As used herein, the term "substituted" refers to substitution 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 alkoxy groups.

[0050] 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.

[0051] The structural units derived from monomers containing cyano groups effectively complex with the metal elements on the electrode active material as well as the metal on the current collector surface, ensuring strong adhesion between the electrode active material and the current collector. At the same time, the structural units derived from monomers containing ester groups improve the flexibility of the electrode plate, preventing brittle fractures. Furthermore, the cyano and ester groups on copolymer B and the fluorine elements in fluorine-containing polymer A create stronger adhesion between the electrode active material particles on the electrode plate through hydrogen bonding.

[0052] In the present application, a fluorine-containing polymer A and a copolymer B containing structural units derived from a monomer containing a cyano group and structural units derived from a monomer containing an ester group are jointly used as an adhesive, thereby significantly improving the adhesive performance of the adhesive between the electrode active material and the current collector, between the electrode active material and the conductive agent, and between the electrode active material and / or the conductive agent and the current collector, compared to using the fluorine-containing polymer A or the copolymer B alone as an adhesive, thereby significantly improving the cycle performance of the battery.

[0053] 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 x 10 5 ~7×10 5 , or 7 x 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 4×10 5 ~7×10 5 , or 4 x 10 5 ~6×10 5 , or 4 x 10 5 ~5×10 5 , or 5 x 10 5 ~7×10 5 , or 6 x 10 5 ~7×10 5 is selected from.

[0054] 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.

[0055] By controlling the weight-average molecular weight of the polymer, it is possible to achieve both adhesiveness and processability of the adhesive. If the weight-average molecular weight of the polymer is too low, it becomes extremely brittle, resulting in insufficient adhesive strength. If the weight-average molecular weight of the polymer is too high, it is difficult for it 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 battery performance.

[0056] 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 adhesive strength of the electrode plate and the cycle performance of the battery can be further improved.

[0057] In some embodiments, the fluorine-containing polymer A is selected from one or more of polyvinylidene fluoride and its copolymers with tetrafluoroethylene, hexafluoropropylene, trichloroethylene.

[0058] 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.

[0059] 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. The appropriate molecular weight ensures that the slurry containing the adhesive of the present application has excellent suspendability and dispersibility, preventing the adhesive from settling or flocculating, resulting in uneven dispersion in the slurry. The appropriate particle size effectively reduces the dissolution time of polyvinylidene fluoride, thereby reducing the time required to prepare the slurry. The appropriate crystallinity of polyvinylidene fluoride ensures good adhesion without causing brittleness in the electrode plate. The high melting point prevents polyvinylidene fluoride from dissolving and becoming inactive during coating and drying.

[0060] In some embodiments, the cyano group-containing monomer is selected from one or more of acrylonitrile, methacrylonitrile, halogenated acrylonitrile, and methoxyacrylonitrile.

[0061] In some embodiments, the ester group-containing monomer 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.

[0062] In some embodiments, the ester group-containing monomer is selected from isooctyl acrylate, which provides copolymer B with a lower glass transition temperature and better flexibility, which is advantageous for plate processing.

[0063] 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, thereby significantly reducing the cost of adhesives.

[0064] In some embodiments, the weight ratio of structural units derived from monomers containing a cyano group to structural units derived from monomers containing an ester group in copolymer B is 8:1 to 12:1. In some embodiments, the weight ratio of structural units derived from monomers containing a cyano group to structural units derived from monomers 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.

[0065] Monomers containing cyano groups can improve the mechanical strength and adhesive performance of copolymer B, further improving the cycle performance of the battery. Monomers containing a small amount of ester groups can improve the flexibility of copolymer B, preventing brittle fracture of the electrode plate. The ester groups also have a certain ability to absorb and retain electrolyte, which can alleviate the poor ionic conductivity of fluorine-containing polymer A and improve the ionic conductivity of the adhesive.

[0066] In some embodiments, copolymer B further comprises structural units derived from a monomer containing a group according to formula I: JPEG0007724299000003.jpg43170 where n is selected from 0, 1, 2 or 3.

[0067] When n is 0, the group shown in formula I is JPEG0007724299000004.jpg41170 and when n is 1, the group shown in formula I is JPEG0007724299000005.jpg39170 and when n is 2, the group shown in formula I is JPEG0007724299000006.jpg38170 and when n is 3, the group shown in formula I is JPEG0007724299000007.jpg37170 is.

[0068] The electronegativity of the oxygen atom in the group shown in formula I is greater than that of the nitrogen atom in the cyano group, and it is more likely to form hydrogen bonds with the electrode active material and conductive agent than the cyano group in copolymer B, and its bonding ability is stronger, which can significantly 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.

[0069] 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 are low cost, stable, and easy to process synthetically.

[0070] In some embodiments, the weight content of the structural units derived from the monomer containing the group of Formula I is 0.1% to 2%, based on the total weight of Copolymer B. In some embodiments, the weight 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 weight of Copolymer B. Inclusion of an appropriate amount of the group of Formula I in Copolymer B can improve the dispersibility of Copolymer B, reduce the formation of precipitates in the produced slurry, and advantageously increase the solids content of the slurry and further increase the electrode loading.

[0071] 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 shown in formula I: JPEG0007724299000008.jpg42170 where n is selected from 0, 1, 2 or 3.

[0072] When n is 0, the group shown in formula I is JPEG0007724299000009.jpg40170 and when n is 1, the group shown in formula I is JPEG0007724299000010.jpg39170 and when n is 2, the group shown in formula I is JPEG0007724299000011.jpg38170 and when n is 3, the group shown in formula I is JPEG0007724299000012.jpg37170 is.

[0073] 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.

[0074] Monomers containing cyano groups can effectively complex with metals on the current collector and electrode active material, ensuring strong adhesion between the electrode active material and the current collector.Monomers containing ester groups can improve the brittleness of the electrode plate and prevent brittle fracture of the electrode plate.

[0075] As a result, the present application uses a copolymer C, which includes 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 represented by formula I, as an adhesive, thereby reducing the cost of the adhesive and improving the adhesive performance of the adhesive and the cycle performance of the battery without reducing the solid content of the slurry.

[0076] In some embodiments, the cyano group-containing monomer is selected from one or more of acrylonitrile, methacrylonitrile, halogenated acrylonitrile, and methoxyacrylonitrile.

[0077] In some embodiments, the weight content of structural units derived from monomers containing a cyano group is 80% to 95% based on the total weight of copolymer C. In some embodiments, the weight content of 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 weight of copolymer C. Within this range, copolymer C can further improve the adhesive performance of the adhesive and the cycling performance of the battery.

[0078] In some embodiments, the ester group-containing monomer 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.

[0079] In some embodiments, the ester group-containing monomer is selected from isooctyl acrylate, which provides copolymer C with a lower glass transition temperature and better flexibility, which is advantageous for the processing and manufacturing of electrode plates.

[0080] 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, thereby significantly reducing the cost of adhesives.

[0081] In some embodiments, the mass content of structural units derived from monomers containing ester groups is 8% to 12%, based on the total mass of copolymer C. In some embodiments, the mass content of structural units derived from monomers containing ester groups is 8% to 11%, or 9% to 11%, based on the total mass of copolymer C. Within this range, copolymer C can further improve the adhesive performance of the adhesive and the cycling performance of the battery.

[0082] In some embodiments, the weight ratio of structural units derived from the monomer containing a cyano group to structural units derived from the monomer containing an ester group in copolymer C is 8:1 to 12:1. The monomer containing a cyano group can improve the mechanical strength and adhesive properties of copolymer C and further improve the cycle performance of the battery. The monomer containing a small amount of ester group can improve the flexibility of copolymer C and prevent brittle fracture of the electrode plate. The ester group provides a certain amount of electrolyte absorption and retention ability, thereby alleviating the problem of poor ionic conductivity of fluorine-containing polymer A. Within this range, copolymer C can further improve the adhesive strength of the electrode plate and the cycle performance of the battery.

[0083] 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.

[0084] 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 the copolymer C. When the copolymer C contains an appropriate amount of the group represented by Formula I, the dispersibility of the copolymer C can be improved, which is advantageous for allowing the produced slurry to contain a larger amount of the electrode active material and for increasing the solid content of the slurry.

[0085] 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 x 10 5 ~6×10 5 , or 4 x 10 5 ~5×10 5 , or 5 x 10 5 ~7×10 5 , or 6 x 10 5 ~7×10 5 is selected from.

[0086] By controlling the weight-average molecular weight of copolymer C, it is possible to achieve both adhesive strength and processability of the adhesive. If the weight-average molecular weight of copolymer C is too low, it becomes extremely brittle and the adhesive strength of the adhesive becomes insufficient. If the weight-average molecular weight of copolymer C is too high, it is difficult for it to disperse the electrode active material. Furthermore, by rationally combining copolymers with different molecular weights, it is possible to improve the dispersibility of the electrode active material and further improve battery performance.

[0087] In some embodiments, the volume average particle size Dv50 of copolymer C is 5 to 20 μm.

[0088] 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 particles with a larger particle size account for 50% and particles with a smaller particle size also account for 50%. Dv50 is also called the median size or median particle size.

[0089] If the average particle size Dv50 of copolymer C is too large, it will be difficult to dissolve, and the slurry will have poor dispersibility, causing the conductive agent or electrode active material and adhesive to aggregate, clogging the screen and affecting production. The aggregates will also be washed away by the coating head, causing scratches caused by the coating particles and affecting coating quality. An appropriate average particle size Dv50 is advantageous for improving the dissolution rate of copolymer C in the solvent and improving the processing efficiency of electrode plates.

[0090] In some embodiments, the intrinsic viscosity of copolymer C is 0.8 to 1.1 dl / g.

[0091] As used herein, 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 a polymer solution is close to zero. That is, it indicates 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.

[0092] In this application, the intrinsic viscosity was tested using the following method: First, a powder sample of copolymer C (ml) (0.15-0.17 g) was weighed and placed in a 100 mL Erlenmeyer flask. V1 (50-60 ml) of N,N-dimethylacetamide was added using a pipette. The flask was then sealed. The solution concentration was calculated as C0 = ml / V1. The Erlenmeyer flask was then placed in a constant-temperature water bath at 60°C for 2.5 hours. The dissolved sample solution was then filtered through a sand filter to prevent particulate impurities from clogging the Ubbelohde viscometer. Next, the filtered N,N-dimethylacetamide was aspirated into a disposable plastic straw to rinse the clean Ubbelohde viscometer. The viscometer was rinsed with solvent at least 4-5 times. 10 mL of N,N-dimethylacetamide was aspirated into the Ubbelohde viscometer using a pipette. The Ubbelohde viscometer was placed in a thermostatic water bath at 30.0°C ± 0.1°C and held there for 15-20 min. The efflux time (t0) was measured and recorded. Finally, the filtered colloid solution prepared in step 1 was aspirated into a disposable plastic straw. The plastic straw was rinsed with the colloid solution at least 4-5 times. 10 mL of the colloid solution was aspirated into the Ubbelohde viscometer using a pipette. The Ubbelohde viscometer was placed in a thermostatic water bath at 30.0°C ± 0.1°C and held there for 15-20 min. The efflux time (t1) was measured and recorded. The intrinsic viscosity (measured value) was (t1 / t0) / C0.

[0093] By controlling the intrinsic viscosity of copolymer C within an appropriate range, it is possible to achieve both excellent adhesive properties and processability of copolymer C. This avoids the inability to achieve effective adhesive effects due to a viscosity that is too low, and also avoids the difficulty of stirring, manufacturing, and applying the slurry due to a viscosity that is too high.

[0094] 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, JPEG0007724299000013.jpg43170 where n is selected from 0, 1, 2 or 3; and polymerizing a monomer containing a cyano group, a monomer containing an ester group, and a monomer containing a group shown in Formula I under polymerizable conditions to produce a copolymer C.

[0095] In some embodiments, copolymer C is obtained by copolymerizing an anionic emulsifier by conventional emulsion polymerization.

[0096] 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 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, after the first-stage reaction, adding to the system second amounts 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.

[0097] In some embodiments, the emulsifier is selected from one or more of alkali metal salts or alkyl acid salts of perfluorooctanoic acid. The alkali metal salts of perfluorooctanoic acid are selected from one or more of sodium perfluorooctanoate and potassium perfluorooctanoate. The alkyl acid salts are selected from one or more of alkyl sulfates and alkyl sulfonates.

[0098] 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 inorganic peroxide is selected from diisopropyl peroxydicarbonate.

[0099] In some embodiments, the reaction solvent is deionized water.

[0100] In some embodiments, the pH buffering agent is selected from one or more of aqueous ammonia, potassium carbonate, and potassium bicarbonate.

[0101] In some embodiments, the first portion of the cyano-containing monomer, ester-containing monomer, and organic monomer containing a group according to Formula I is 75-90% 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.

[0102] In some embodiments, the second portion of the cyano group-containing monomer, the ester group-containing monomer, and the hydroxyl monomer containing the group shown in 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.

[0103] In some embodiments, the weight ratio of the cyano group-containing monomer to the ester group-containing monomer is 8:1 to 12:1, and the weight content of the monomer containing the group shown in Formula I is 0.1% to 2%, based on the total weight of the copolymer C.

[0104] 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.

[0105] The cost of the monomers produced by this method is low, and the reaction conditions are mild, which can reduce the cost of the adhesive.

[0106] [Positive electrode]

[0107] 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, and the positive electrode film layer includes a positive electrode active material.

[0108] For example, the positive electrode current collector has two surfaces that face each other in the thickness direction thereof, and the positive electrode film layer is disposed on either one or both of the two facing surfaces of the positive electrode current collector.

[0109] In some embodiments, the positive electrode current collector may be a metal foil sheet or a composite current collector. For example, aluminum 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 base layer. The composite current collector may be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, or silver alloy) on a polymeric substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0110] 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 a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide, and a modified compound of each. However, the present application is not limited to these materials, and other conventional materials usable 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 lithium transition metal oxides include lithium cobalt oxide (e.g., LiCoO), lithium nickel oxide (e.g., LiNiO), lithium manganese oxide (e.g., LiMnO, LiMnO), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide (e.g., LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM 333 May be abbreviated as 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 O2) and modified compounds thereof, etc. 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.

[0111] 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.

[0112] In some embodiments, a positive electrode plate can be manufactured by the following method: The components for manufacturing a positive electrode plate, such as the positive electrode 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 electrode slurry, which is then applied to a positive electrode current collector, followed by drying, cold pressing, and other processes to obtain a positive electrode plate.

[0113] [Negative electrode]

[0114] 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.

[0115] For example, the negative electrode current collector has two surfaces that face each other in the thickness direction thereof, and the negative electrode film layer is disposed on either one or both of the two facing surfaces of the negative electrode current collector.

[0116] 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, or silver alloy) on a polymeric substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0117] In some embodiments, the negative electrode active material may be a battery negative electrode active material 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, a silicon-based material, a 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 usable as a battery negative electrode active material may also be used. These negative electrode active materials may be used alone or in combination.

[0118] 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).

[0119] In some embodiments, the negative electrode film 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.

[0120] In some embodiments, the negative electrode membrane layer optionally further comprises other auxiliary agents, such as a thickener (eg, sodium carboxymethylcellulose (CMC-Na)).

[0121] In some embodiments, the negative electrode plate can be manufactured by the following method: The components for manufacturing the negative electrode plate, such as the negative electrode active material, conductive agent, adhesive, and any other components, are dispersed in a solvent (e.g., deionized water) to form a negative electrode slurry, which is then applied to a negative electrode current collector, followed by drying, cold pressing, and other processes to obtain the negative electrode plate.

[0122] [Electrolyte]

[0123] The electrolyte serves to conduct ions between the positive and negative electrodes. 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.

[0124] In some embodiments, the electrolyte employs an electrolytic solution, the electrolytic solution including an electrolyte salt and a solvent.

[0125] 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.

[0126] 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.

[0127] 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 battery performance, such as an additive that improves the overcharge performance of the battery or an additive that improves the high-temperature or low-temperature performance of the battery.

[0128] [Separator]

[0129] In some embodiments, the secondary battery further includes a separator. The present application does not particularly limit the type of separator, and any separator with a well-known porous structure having good chemical stability and mechanical stability may be selected.

[0130] In some embodiments, the separator may be made of at least one material selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer thin film or a multi-layer composite thin film, without any particular limitation. When the separator is a multi-layer composite thin film, the materials of the layers may be the same or different, without any particular limitation.

[0131] [Secondary battery]

[0132] The present application provides a secondary battery, the secondary battery including an electrode assembly and an electrolyte, the electrode assembly including a positive electrode plate, a separator, and a negative electrode plate, the positive electrode plate including 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, and the secondary battery has better cycle performance.

[0133] In some embodiments, the positive electrode active material is a lithium-containing transition metal oxide, optionally lithium iron phosphate, or doped modifications thereof, or at least one of conductive carbon-coated, conductive metal-coated, or conductive polymer-coated modifications thereof.

[0134] 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.

[0135] In some embodiments, the positive and negative electrode plates and separator may be wound or stacked to form an electrode assembly.

[0136] A typical secondary battery includes a positive electrode plate, a negative electrode plate, an electrolyte, and a separator. During the charge and discharge process, active ions travel back and forth between the positive and negative electrodes, intercalating and deintercalating. The electrolyte serves to conduct ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes and allows ions to pass through.

[0137] In some embodiments, the secondary battery may include an outer casing, which may be used to package the electrode assembly and electrolyte.

[0138] In some embodiments, the secondary battery may be packaged in a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The secondary battery may also be packaged in a flexible packaging, such as a bag-type flexible packaging. The flexible packaging may be made of plastic, such as polypropylene, polybutylene terephthalate, or polybutylene succinate.

[0139] 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.

[0140] 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 side plates connected to the bottom plate, and the bottom plate and side plates surround and 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 and close the receiving cavity. The positive electrode plate, the negative electrode plate, and the separator can be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is packaged in the receiving cavity. An electrolyte permeates the electrode assembly 52. The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and can be selected by those skilled in the art according to actual specific needs.

[0141] In a fourth aspect of the present application, there is provided an electrode comprising an active electrode material and an adhesive composition or adhesive according to any embodiment, the active electrode material optionally being 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, a conductive metal-coated, or a conductive polymer-coated modification thereof.

[0142] This electrode has higher adhesion, which results in the battery having better cycling performance.

[0143] [Battery module]

[0144] 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 those skilled in the art based on the application and capacity of the battery module.

[0145] Fig. 5 shows an example of a battery module 4. Referring to Fig. 5, in the battery module 4, a plurality of secondary batteries 5 may be arranged in order along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the plurality of secondary batteries 5 may be fastened with fasteners.

[0146] Optionally, the battery module 4 may further include a housing having an accommodating space, and the plurality of secondary batteries 5 are accommodated in the accommodating space.

[0147] [Battery pack]

[0148] 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 those skilled in the art based on the application and capacity of the battery pack.

[0149] 6 and 7 show an example of a battery pack 1. Referring to FIGS. 6 and 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 can form a sealed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery case in any manner.

[0150] [Power consumption equipment]

[0151] A sixth aspect of the present application provides a power consumption device including the secondary battery according to any embodiment, the battery module according to any embodiment, or the battery pack according to any embodiment, wherein the power consumption device has a longer driving range.

[0152] 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.

[0153] The power consumption device may be a secondary battery, a battery module, or a battery pack, depending on the requirements of the use.

[0154] Figure 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. To meet the high power and high energy density requirements of the secondary battery of the power consumption device, a battery pack or a battery module can be adopted.

[0155] Other example devices may be mobile phones, tablet computers, laptop computers, etc. These devices are generally required to be lightweight and may employ secondary batteries as their power source.

[0156] Example

[0157] Examples of the present application are described below. The examples described below are illustrative and are used only to interpret the present application, and should not be understood as limiting the present application. 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. Reagents or equipment used without a specified manufacturer are all common products that can be purchased commercially.

[0158] Example 1

[0159] 1) Production of adhesives containing copolymer C The method for producing Polymer C is as follows: The polymerization vessel is a 10 L stainless steel autoclave, and the rotation speed is 100 r / min. First, the tightness of the polymerization system is checked, and then the autoclave is evacuated, filled with nitrogen, and then oxygen is discharged. 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. The mixture was evacuated to a polymerization pressure of 4.2MPa, heated to 55°C, and allowed to stand for 0.8 hours. After that, add 8g of ammonium persulfate. The mixture was heated to 75°C and stirred for 2-3 hours. Then, 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. The temperature was raised to 90°C and the reaction was continued for 4 hours. The polymerized product was obtained by flash evaporation, and the conductivity of the washing solution was increased to 1*10 after adding deionized water. -8 The copolymer was washed until the viscosity was less than 1000 s / cm and then vacuum dried to obtain N-vinylpyrrolidone-acrylonitrile-isooctyl acrylate copolymer. The copolymer obtained by this process had a weight average molecular weight of 700,000, a particle size Dv50 of 15 μm, and an intrinsic viscosity of 1.1 dL / g.

[0160] The adhesive was manufactured as follows: 4g of polyvinylidene fluoride (fluorine-containing polymer A) and 4g of N-vinylpyrrolidone-acrylonitrile-isooctyl acrylate copolymer were added to 250g of N-methylpyrrolidone solution, stirred at 500 r / min for 90 minutes using a stirrer / disperser, and then degassed for 30 minutes using an ultrasonic cleaner. The polyvinylidene fluoride used here was product 601A manufactured by Dongyangguang Co., Ltd., synthesized using the 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.

[0161] 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 15 minutes. The dry mixed product was added to the adhesive and stirred for 90 minutes at 1200 r / min using a stirrer disperser to produce a lithium battery positive electrode slurry.

[0162] The above slurry was knife-coated onto carbon-coated aluminum foil, baked at 110°C for 15 minutes, cold-pressed, and then cut into a 15 mm diameter disk. A button-type battery was then fabricated together with a metallic lithium plate, a separator, and an electrolyte.

[0163] 3) Separator A polypropylene membrane was used as the separator.

[0164] 4) Electrolyte production In an argon atmosphere glove box (H2O<0.1 ppm, O2<0.1 ppm), 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 a 1M LiPF6EC / EMC solution was placed to obtain an electrolyte.

[0165] 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; for specific parameters, see Table 1.

[0166] In Examples 2 to 7, the mass ratio of polyvinylidene fluoride to copolymer C was adjusted, and other parameters were the same as those in Example 1. See Table 1 for specific parameters.

[0167] 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. The specific parameters are shown in Table 1.

[0168] In Examples 12 and 13, the monomer polymerization ratio of acrylonitrile and isooctyl acrylate in N-vinylpyrrolidone-acrylonitrile-isooctyl acrylate copolymer was adjusted, and the weight ratio of polyvinylidene fluoride to N-vinylpyrrolidone-acrylonitrile-isooctyl acrylate copolymer was set to 2:1. Other parameters were the same as in Example 1. For specific parameters, see Table 1.

[0169] In Examples 14 and 15, the monomer polymerization ratio of acrylonitrile and isooctyl acrylate in N-vinylpyrrolidone-acrylonitrile-isooctyl acrylate copolymer was adjusted, and the weight ratio of polyvinylidene fluoride to N-vinylpyrrolidone-acrylonitrile-isooctyl acrylate copolymer was set to 3:1. Other parameters were the same as in Example 1. For specific parameters, see Table 1.

[0170] In Examples 16 and 17, the monomer polymerization ratio of acrylonitrile and isooctyl acrylate in N-vinylpyrrolidone-acrylonitrile-isooctyl acrylate copolymer was adjusted, and the weight ratio of polyvinylidene fluoride to N-vinylpyrrolidone-acrylonitrile-isooctyl acrylate copolymer was set to 4:1. Other parameters were the same as in Example 1. For specific parameters, see Table 1.

[0171] 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. The other parameters were the same as in Example 1. The specific parameters are shown in Table 1.

[0172] In Examples 21-22, in the copolymer preparation process, the temperature of the secondary replenishment solution was further increased to 90°C, and then the reaction time was adjusted from 4 hours to 3 hours and then 2.5 hours, and the molar ratio of acrylonitrile to isooctyl acrylate monomer in the N-vinylpyrrolidone-modified acrylonitrile-isooctyl acrylate copolymer was set to 10:1. The other parameters and steps were the same as those in Example 1, and the specific parameters are shown in Table 1.

[0173] In Example 23, N-allyl-2-pyrrolidone modified acrylonitrile-isooctyl acrylate copolymer is used, and other parameters are consistent with those in Example 1. The specific parameters are shown in Table 1.

[0174] In the process for preparing the copolymer in Example 24, N-vinylpyrrolidone was not added, and the molar ratio of acrylonitrile to isooctyl acrylate monomer in the acrylonitrile-isooctyl acrylate copolymer was set to 10:1, and other parameters were consistent with those in Example 1. The specific parameters are shown in Table 1.

[0175] In Example 25, the polyvinylidene fluoride used was the 401A product produced by Dongyangguang Co., Ltd., with a weight average molecular weight of 600,000. The other steps were the same as in Example 1, and the specific parameters were as shown in Table 1.

[0176] In Comparative Example 1, polyvinylidene fluoride was used alone as the adhesive; in Comparative Example 2, N-vinylpyrrolidone-modified acrylonitrile-isooctyl acrylate copolymer prepared in Example 9 was used alone as the adhesive; in Comparative Example 3, acrylonitrile-isooctyl acrylate copolymer prepared in Example 24 was used alone as the adhesive; the other steps were the same as in Example 1, and the specific parameters are shown in Table 1.

[0177] The relevant parameters of the adhesives of Examples 1 to 25 and Comparative Examples 1 to 3 are shown in Table 1 below.

[0178] Furthermore, performance tests were carried out on the electrode plates and batteries obtained in Examples 1 to 25 and Comparative Examples 1 to 3. The test methods are as follows, and Table 1 shows the test results.

[0179] 1. Testing the type of adhesive structural unit

[0180] 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 the sample test spectrum. The instrument model was Nicolet 5700 (Thermo Nicolet, USA). The standard linearity was better than 0.07%, and the resolution was 0.09 cm. -1 and the wavenumber range is 400 to 4000 cm -1 and sensitivity <9.65*10 -5 Abls. Used to detect molecular structure and chemical bonds.

[0181] 2. Molecular weight test

[0182] A Waters 2695 Isocratic HPLC gel chromatography system (differential refractive index detector 2141) was used. A 3.0% mass fraction polystyrene solution sample was used as the reference, and a matching chromatography column (oil-based: Styragel HT5 DMF 7.8*300mm + Styragel HT4) was selected. A 3.0% adhesive colloid solution was prepared using purified N-methylpyrrolidone (NMP) solvent. The prepared solution was allowed to stand for one day before use. During testing, tetrahydrofuran was first drawn into the syringe and flushed several times. 5 ml of the experimental solution was then drawn into the syringe, removing any air and allowing the needle to dry. Finally, the sample solution was slowly injected into the sample inlet. Data was acquired after the readings stabilized.

[0183] 3. Adhesion test (between the positive electrode plate active material layer and the positive electrode current collector)

[0184] Referring to the national standard GBT 2790-1995 "Test method for adhesive 180° peel strength", the adhesive strength test process for the examples and comparative examples of this application is as follows:

[0185] A 30mm wide x 100-160mm long sample was cut using a blade and attached to a steel plate with special double-sided tape (20mm wide x 90-150mm long). The electrode plate sample was attached to the double-sided tape with the test surface facing downwards and rolled three times in the same direction with a pressure roller.

[0186] 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.

[0187] The power supply for the Sanshisha tensile tester (sensitivity 1N) was turned on, the indicator light was turned on, the stopper was adjusted to the appropriate position, and the end of the steel sheet without the electrode plate attached was fixed with the lower jig. The paper wrapper was folded upward and fixed with the upper jig, and the position of the upper jig was adjusted using the "up" and "down" buttons on the manual controller attached to the tensile tester. The test was then performed and the numerical values were read. Comparative adhesive strength data for Example 1 and Comparative Example 1, shown in Figure 1, was obtained.

[0188] 4. Battery capacity retention rate test

[0189] Taking Example 1 as an example, the battery capacity retention test process is as follows: At 25°C, a battery corresponding to Example 1 was charged at a constant current of 1 / 3C to 3.65V, then charged at a constant voltage of 0.05C from 3.65V, left for 5 minutes, and then discharged at a constant voltage of 1 / 3C to 2.5V. The resulting capacity was designated as the initial capacity C0. The same battery was subjected to the above steps repeatedly, and the discharge capacity Cn of the battery after the nth cycle was recorded. The battery capacity retention rate after each cycle was calculated as Pn = Cn / C0 * 100%, where the values of 100 points P1, P2...P100 were taken as the ordinate and the corresponding cycle number as the abscissa, to obtain a graph of the battery capacity retention rate versus cycle number for Example 1 and Comparative Example 1, as shown in Figure 2.

[0190] 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 for 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 for Comparative Example 1 and other Examples is the same as above.

[0191] 5. Slurry solids content test

[0192] Solid content test method: Prepare a glass dish and record its weight (m1). Add a portion of the prepared cathode slurry to the glass dish and record its total weight (m2). Place the dish containing the cathode slurry in a dry box and heat it to 120°C for 1 hour. After drying, weigh the dish and record its weight (m3). The solid content is calculated as (m3 - m1) / (m2 - m1) * 100%. JPEG0007724299000014.jpg248166 JPEG0007724299000015.jpg224166 JPEG0007724299000016.jpg245166 JPEG0007724299000017.jpg255166

[0193] As shown in Figures 1 and 2, in Example 1, compared to Comparative Example 1, the adhesive performance of the adhesive on the electrode plate and the battery capacity retention rate were both improved because an acrylonitrile-isooctyl acrylate copolymer modified with a monomer having a pyrrolidone group was added.

[0194] As can be seen from the results in Table 1, Examples 1 to 25 all provide adhesive compositions containing polyvinylidene fluoride and an acrylonitrile-isooctyl acrylate copolymer containing structural units derived from acrylonitrile and structural units derived from isooctyl acrylate. Compared to Comparative Examples 1 to 3, all of them achieved better results, improving the adhesive performance of the adhesive on the electrode plate and the battery capacity retention rate.

[0195] 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, all of them achieved good results, improving the adhesive performance of the adhesive in the electrode plate and the battery capacity retention rate.

[0196] In Examples 1 to 25, the mass ratio of polyvinylidene fluoride to acrylonitrile-isooctyl acrylate copolymer in the adhesive composition was 1:4 to 4:1. Compared with Comparative Examples 1 to 3, all of these examples achieved good results, improving the adhesive performance of the adhesive on the electrode plate and the battery capacity retention rate.

[0197] 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 results, improving the adhesive performance of the adhesive in the electrode plate and the battery capacity retention rate. 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 of the adhesive in the electrode plate and the battery capacity retention rate were further improved.

[0198] 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 copolymer C modified with the monomer having a pyrrolidone group had stronger electrode plate adhesive strength and battery capacity retention rate than the unmodified version, and the solid content of the slurry was further improved.

[0199] In Examples 1 to 23 and 25, the mass content of the structural units derived from the monomer containing a pyrrolidone group was 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 on the electrode plate, the battery capacity retention rate, and the solids content of the slurry. In Examples 1 to 23 and 25, the mass content of the structural units derived from the monomer containing a pyrrolidone group was 0.5% to 1.5%, or 0.5% to 1.0%. Within this range, the solids content of the slurry was further improved.

[0200] 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 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 on the electrode plate, the battery capacity retention rate, and the solid content of the slurry.

[0201] 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 structural units 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 on the electrode plate, the battery capacity retention rate, and the solid content of the slurry.

[0202] A comparison between Comparative Example 2 and Comparative Example 3 shows that modifying the adhesive with a monomer having the group shown in Formula I can improve the solid content of the positive electrode slurry. A comparison between Example 9 and Example 24 shows that, under the same conditions, modifying the adhesive with a monomer having the group shown in Formula I can improve the solid content of the positive electrode slurry, significantly improving the adhesive strength between the corresponding current collector and negative electrode material layer and significantly improving the capacity retention rate of the battery.

[0203] It should be noted that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any embodiment that has substantially the same configuration as the technical idea and achieves similar functions and effects within the scope of the technical solution of the present application is considered to be within the technical scope of the present application. Furthermore, various modifications that a person skilled in the art may make to the embodiments without departing from the spirit of the present application, and other forms constructed by combining some of the components of the embodiments are also considered to be within the scope of the present application. [Explanation of symbols]

[0204] 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. A method for manufacturing an adhesive, comprising: providing a monomer containing a cyano group, a monomer containing an ester group, and a monomer containing a group according to formula I, where n is selected from 0, 1, 2 or 3; carrying out a first-stage reaction at a first polymerization temperature with a first amount of a cyano group-containing monomer, an ester group-containing monomer, and a monomer containing a group shown in Formula I under polymerizable conditions, and after the first-stage reaction, adding a second amount of a cyano group-containing monomer, an ester group-containing monomer, and a monomer containing a group shown in Formula I, and carrying out a second-stage reaction at a second polymerization temperature to produce a copolymer C; mixing the copolymer C with a fluorine-containing polymer; Including, the mass content of the structural units derived from the monomer containing the group represented by formula I in the copolymer C is 0.5 to 1.5% based on the total mass of the copolymer C; A method for producing an adhesive comprising the steps of:

2. 2. The method for producing an adhesive according to claim 1, wherein the mass ratio of the cyano group-containing monomer to the ester group-containing monomer is 8:1 to 12:1, or 8:1 to 10:

1.

3. the cyano group-containing monomer is selected from one or more of acrylonitrile, methacrylonitrile, halogenated acrylonitrile, methoxyacrylonitrile; and / or said monomers containing ester groups being 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 2. The method of claim 1, wherein the monomer containing the group shown in Formula I is selected from one or more of N-vinylpyrrolidone, N-propenylpyrrolidone.

4. 2. The method for producing an adhesive according to claim 1, wherein the cyano group-containing monomer is selected from one or more of acrylonitrile, methacrylonitrile, halogenated acrylonitrile, and methoxyacrylonitrile.

5. 2. The method for producing an adhesive according to claim 1, wherein the mass content of the structural units derived from the monomer containing a cyano group is 80% to 95% based on the total mass of the copolymer C.

6. 2. The method of claim 1, wherein the ester group-containing monomer 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 method for producing an adhesive according to claim 1, wherein 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.

8. 2. The method for producing an adhesive according to claim 1, wherein in the copolymer C, the mass 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 is 8:1 to 12:1, or 8:1 to 10:

1.

9. 2. The method of claim 1, wherein the monomer containing the group shown in formula I is selected from one or more of N-vinylpyrrolidone, N-allyl-2-pyrrolidone.

10. 2. The method for producing an adhesive according to claim 1, wherein the weight average molecular weight of the copolymer C is 400,000 to 700,000.

11. 2. The method for producing an adhesive according to claim 1, wherein the copolymer C has an average particle size Dv50 of 5 to 20 μm.

12. 2. The method for producing an adhesive according to claim 1, wherein the intrinsic viscosity of the copolymer C is 0.8 to 1.1 dl / g.

13. The method of claim 12, wherein the first stage reaction comprises adding 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; 10. The method of claim 1, further comprising adding a second amount of reaction solvent, a second amount of emulsifier, a second amount of pH buffer, and a second amount of initiator in the second stage reaction.

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