BAB type block copolymer, production method, positive electrode plate, secondary battery, battery module, battery pack, and power consumption device

Abstract

The present application provides a BAB-type block copolymer, a production method, a positive electrode plate, a secondary battery, a battery module, a battery pack, and an electric power consumption device. The BAB-type block copolymer includes a B-block and an A-block. The B-block contains a structural unit represented by Formula I, and the A-block contains one or more of a structural unit represented by Formula II and a structural unit represented by Formula III. Here, R 1 , R 2 , R 3 are each independently one or more selected from hydrogen, fluorine, and a C 1-3 alkyl group containing at least one fluorine atom, and R 4 , R 5 , R 6 are each independently selected from hydrogen and a substituted or unsubstituted C 1-5 alkyl group, and R 7 is selected from a carboxyl group, an ester group, a hydroxyl group, an amide group, a cyano group, and a substituted or unsubstituted aromatic group.

Description

Technical Field

[0001] The present application relates to the field of secondary battery technology, and particularly to a BAB type block copolymer, a manufacturing method, a positive electrode plate, a secondary battery, a battery module, a battery pack, and an electric power consumption device.

Background Art

[0002] In recent years, secondary batteries have been widely applied in many fields such as energy storage power systems such as hydraulic power, thermal power, wind power, and solar power plants, and electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. With the popularization of the application of secondary batteries, higher requirements are also demanded for their energy density, cycle performance, etc.

[0003] An adhesive is a commonly used material in secondary batteries and is widely applied in battery electrode plates, separators, packaging parts, etc. However, conventional adhesives have high production costs, insufficient production capacity, great harm to the environment, are prone to gel appearance during manufacturing, have poor slurry stability, high processing costs, and the electrode plates manufactured thereby have poor conductivity, high resistance, low yield rate, unstable battery performance, and it is difficult to meet the requirements of the market for battery cost and performance. Therefore, there is still room for improvement in conventional adhesives.

Summary of the Invention

[0004] The present application is made in view of the above problems, and aims to provide a BAB type block copolymer. By using the block copolymer as an adhesive, the adhesive force of the electrode plate can be effectively improved, the DC impedance growth rate and the metal deposition amount of the battery can be reduced, the electrode plate can have both low film resistance and excellent flexibility, and the battery can have both a high cycle capacity retention rate and a 45°C capacity retention rate.

[0005] A first aspect of the present application provides a BAB-type block copolymer, wherein the B-block contains a structural unit represented by Formula I, and the A-block contains one or more of a structural unit represented by Formula II and a structural unit represented by Formula III. JPEG2025516733000002.jpg60170Here, R 1 , R 2 , R 3 are each independently one or more selected from hydrogen, fluorine, and a C 1-3 alkyl group containing at least one fluorine atom, and R 4 , R 5 , R 6 are each independently selected from hydrogen and a substituted or unsubstituted C 1-5 alkyl group, and R 7 is selected from a carboxyl group, an ester group, a hydroxyl group, an amide group, a cyano group, and a substituted or unsubstituted aromatic group.

[0006] The adhesive produced from the BAB-type block copolymer can effectively reduce the orderly arrangement of the fluorine-containing block polymer because the non-fluorine block polymer is located in the middle of the fluorine-containing block polymer. At the same time, by introducing a functional group into the non-fluorine-containing polymer, the adhesion performance of the BAB-type block copolymer can be improved, and the advantages of the fluorine-containing adhesive and the non-fluorine adhesive can be fully exerted, and the complementary effect of the advantages can be realized. Compared with the conventional PVDF adhesive, the adhesive can effectively improve the adhesion force of the electrode plate, reduce the DC impedance growth rate and the metal deposition amount of the battery, and at the same time achieve both a low film resistance and excellent flexibility on the electrode plate, and ensure that the battery has both a high cycle capacity retention rate and a 45 °C capacity retention rate.

[0007] In any embodiment, the A-block contains a structural unit represented by Formula II in which R 7 is an amide group.

[0008] When the A-block is such that R 7Containing the structural unit shown in Formula II where R is an amide group is advantageous for improving the adhesion and flexibility of the electrode plate, reducing the membrane resistance of the electrode plate, and at the same time significantly reducing the elution of transition metals in the positive electrode.

[0009] In any embodiment, the A-block is R 7 containing the structural unit shown in Formula II where R is a cyano group and R 7 containing the structural unit shown in Formula II where R is an ester group.

[0010] When the A-block simultaneously contains the structural unit shown in Formula II where R 7 is a cyano group and the structural unit shown in Formula II where R 7 is an ester group, it is advantageous for improving the adhesion and flexibility of the electrode plate, reducing the membrane resistance of the electrode plate, reducing the DC impedance growth rate and metal deposition amount of the battery, and ensuring the coexistence of a high cycle capacity retention rate and a 45 °C capacity retention rate in the battery.

[0011] In any embodiment, the A-block is R 7 containing the structural unit shown in Formula II where R is a cyano group, R 7 containing the structural unit shown in Formula II where R is an ester group, and R 7 containing the structural unit shown in Formula II where R is a substituted or unsubstituted aromatic group.

[0012] According to the applicant's unexpected discovery, when the A-block simultaneously contains the structural unit shown in Formula II where R 7 is a cyano group, the structural unit shown in Formula II where R 7 is an ester group, and the structural unit shown in Formula II where R 7 is a substituted or unsubstituted aromatic group, it is advantageous for further improving the adhesion and flexibility of the electrode plate, and the cycle capacity retention rate and 45 °C capacity retention rate of the battery.

[0013] In any embodiment, the A-block is R 7 containing the structural unit shown in Formula II where R is a cyano group, R 7 containing the structural unit shown in Formula II where R is an amide group, and R7 contains the structural unit shown in Formula II where R is an ester group.

[0014] In the A-block, R 7 is a structural unit shown in Formula II where R is a cyano group, and R 7 is a structural unit shown in Formula II where R is an amide group, and R 7 is a structural unit shown in Formula II where R is an ester group, which can ensure both low membrane resistance, excellent adhesion and flexibility on the electrode plate, and at the same time can significantly reduce the metal deposition amount of the battery.

[0015] In any embodiment, the mass content of the A-block is 40% - 60% based on the total mass of all structural units in the block copolymer.

[0016] By controlling the mass content of the structural unit shown in Formula I in the BAB-type block copolymer within an appropriate range, the adhesive can effectively improve the adhesion and flexibility of the electrode plate, reduce the membrane resistance of the electrode plate, increase the cycle capacity retention rate and 45°C capacity retention rate of the battery, and reduce the DC impedance growth rate and metal deposition amount of the battery.

[0017] In any embodiment, the weight average molecular weight of the block copolymer is 400,000 - 2,000,000.

[0018] By controlling the weight average molecular weight of the block copolymer within an appropriate range, the adhesive can improve the adhesion of the electrode plate, reduce the DC impedance growth rate and metal deposition amount of the battery, and at the same time ensure both low membrane resistance and excellent flexibility on the electrode plate, and ensure both high cycle capacity retention rate and 45°C capacity retention rate for the battery.

[0019] In any embodiment, in the block copolymer, the weight average molecular weight of the A-block is 200,000 - 1,100,000.

[0020] By controlling the weight-average molecular weight of the A-block in the block copolymer within an appropriate range, the adhesive can improve the adhesion of the electrode plate, reduce the DC impedance growth rate and the metal deposition amount of the battery, and achieve both low film resistance and excellent flexibility in the electrode plate, and ensure both a high cycle capacity retention rate and a 45°C capacity retention rate in the battery.

[0021] In any embodiment, in the block copolymer, the weight-average molecular weight of each of the B-blocks is 100,000 to 500,000.

[0022] By controlling the weight-average molecular weight of each B-block in the block copolymer within an appropriate range, the adhesive can improve the adhesion of the electrode plate, reduce the DC impedance growth rate and the metal deposition amount of the battery, and achieve both low film resistance and excellent flexibility in the electrode plate, and ensure both a high cycle capacity retention rate and a 45°C capacity retention rate in the battery.

[0023] In any embodiment, the structural unit represented by the formula I is derived from the group consisting of vinylidene fluoride, tetrafluoroethylene, vinyl fluoride, hexafluoropropene, and combinations thereof.

[0024] In any embodiment, the structural unit represented by the formula II is derived from the group consisting of acrylonitrile, crotononitrile, styrene, vinyl alcohol, acrylamide, ethyl acrylate, ethyl methacrylate, butyl methacrylate, methacrylic acid, ethacrylic acid, methacrylamide, N-methacrylamide, N-methylmethacrylamide, N-isopropylacrylamide, N-isopropylmethacrylamide, N-t-butylacrylamide, N-t-butyl (meth)acrylamide, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N,N-diethylacrylamide, N,N-diethylmethacrylamide, acrylic acid, vinylbenzoic acid, acrylic acetate, acrylic esters, and combinations thereof.

[0025] The above raw materials are simple and easily available, and can significantly reduce the production cost compared with conventional adhesives.

[0026] The second aspect of the present application further provides a method for manufacturing a BAB-type block copolymer, the method comprising: polymerizing at least one monomer represented by formula V to produce a B-block, JPEG2025516733000003.jpg25170 Here, R′ 1 、R′ 2 、R′ 3 are each independently one or more selected from hydrogen, fluorine, and a C 1-3 alkyl group containing at least one fluorine atom, the step of producing a B-block; and polymerizing at least one monomer represented by formula VI to produce an A-block, or subjecting a monomer represented by formula VII to ring-opening polymerization to produce an A-block, JPEG2025516733000004.jpg39170 Here, R′ 4 、R′ 5 、R′ 6 are each independently selected from hydrogen, a substituted or unsubstituted C 1-5 alkyl group, and R′ 7 is one selected from a carboxyl group, an ester group, a hydroxyl group, an amide group, a cyano group, and a substituted or unsubstituted aromatic group, the step of producing an A-block; and a step of producing a BAB-type block copolymer by bonding the B-block and the A-block.

[0027] Compared with the conventional copolymerization method, the manufacturing method can maximize the weight-average molecular weights of the fluorine-containing block and the non-fluorine block, fully exert the respective advantages of the fluorine-containing adhesive and the non-fluorine adhesive, and realize the complementary effect of the advantages. The adhesive of the BAB-type triblock copolymer produced by this method can effectively improve the adhesive force of the electrode plate, reduce the DC impedance growth rate and the metal deposition amount of the battery, and at the same time achieve both low film resistance and excellent flexibility on the electrode plate, and ensure that the battery has both a high cycle capacity retention rate and a 45°C capacity retention rate.

[0028] In any embodiment, the manufacturing step of the B-block is reacting at least one monomer represented by formula V, a chain transfer agent, and a first initiator at a reaction temperature of 60-75°C by reversible addition-fragmentation chain transfer polymerization for 4-6 hours to obtain a B-block having an azide group or an alkynyl group at the end.

[0029] By adopting this manufacturing method, controllable polymerization can be realized, and the molecular weight distribution of the product is narrow.

[0030] In any embodiment, the manufacturing step of the A-block is reacting the monomer represented by formula VI and a second initiator at a reaction temperature of 80-95°C for 2.5-5 hours to obtain the A-block having alkynyl groups or azide groups at both ends.

[0031] By adopting this manufacturing method, the production of the A-block having azidation or terminal alkynylation at both ends is successful.

[0032] In any embodiment, the manufacturing step of the A-block is reacting the monomer represented by formula VII, an ionic initiator, and water at a reaction temperature of 60°C - 80°C for 6-8 hours to obtain a product having hydroxyl groups at both ends, It includes subjecting the hydroxyl groups of the product to a functionalization reaction to obtain the A-block having an alkynyl group or an azide group at both ends.

[0033] By adopting this production method, the production of the A-block having azidation or terminal alkynylation at both ends is successful.

[0034] In any embodiment, the production of the BAB-type block copolymer includes mixing the A-block having an azide group or an alkynyl group at both ends with the B-block having an alkynyl group or an azide group at the terminal, performing a click reaction to produce a BAB-type block copolymer, where the end groups of the A-block and the B-block are different.

[0035] The above production method has the advantages of high efficiency, stability, and high specificity, and improves the yield rate of the product.

[0036] In any embodiment, the chain transfer agent is a RAFT chain transfer agent containing a terminal alkynyl group or an azide group.

[0037] In any embodiment, the second initiator is a symmetric difunctional initiator.

[0038] In any embodiment, the first initiator is one or two selected from azobisisobutyronitrile and azobisisoheptonitrile.

[0039] The third aspect of this application provides the application of the BAB-type block copolymer in any embodiment in a secondary battery.

[0040] The fourth aspect of the present application provides a positive electrode plate, which 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 includes a positive electrode active material, a conductive agent, and an adhesive. The adhesive is a BAB-type block copolymer in any embodiment or a BAB-type block copolymer produced by the production method in any embodiment.

[0041] The positive electrode plate has low film resistance, excellent adhesion, and good flexibility. The battery has a low metal deposition amount, excellent cycle performance, and high-temperature storage performance.

[0042] In any embodiment, the adhesion per unit length between the positive electrode film layer and the positive electrode current collector is 11 N / m or more. There is high adhesion strength between the positive electrode film layer and the positive electrode current collector of the electrode plate. During use, the positive electrode film layer is not likely to fall off from the positive electrode current collector, which contributes to improving the cycle performance and safety of the battery.

[0043] In any embodiment, after the positive electrode plate undergoes more than 3 bending tests, a light transmission phenomenon occurs in the positive electrode plate. The fact that the electrode plate can undergo more than 3 bending tests indicates that the electrode plate has good flexibility, is not likely to collapse during production, and is not likely to have brittle fracture phenomena during use, which contributes to improving the yield rate of the battery and the safety performance of the battery.

[0044] In any embodiment, the film resistance of the positive electrode plate is 1.0 Ω or less. The fact that the electrode plate has low film resistance indicates that the dispersion of materials in the positive electrode film layer is uniform, and the fact that the positive electrode film layer has good electron transmission efficiency is advantageous for the performance of the battery.

[0045] The fifth aspect of the present application provides a secondary battery, which includes an electrode assembly and an electrolyte. The electrode assembly includes a separator, a negative electrode plate, and a positive electrode plate according to the fourth aspect of the present application.

[0046] The sixth aspect of the present application provides a battery module, which includes the secondary battery of the fifth aspect of the present application.

[0047] The seventh aspect of the present application provides a battery pack, which includes the battery module of the sixth aspect of the present application.

[0048] The eighth aspect of the present application provides a power consumption device, which includes at least one of the secondary battery of the fifth aspect of the present application, the battery module of the sixth aspect of the present application, or the battery pack of the seventh aspect of the present application.

Brief Description of the Drawings

[0049]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0050] Hereinafter, embodiments specifically disclosing the positive electrode active material of the present application, a method for manufacturing the same, a positive electrode plate, a secondary battery, a battery module, a battery pack, and an electric device will be described in detail with appropriate reference to the drawings. However, detailed descriptions that are not necessary may be omitted. For example, detailed descriptions of well-known matters and duplicate descriptions of actually identical structures may be omitted. This is to avoid the following description from becoming unnecessarily long and to enable those skilled in the art to easily understand. Note that the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and do not limit the theme described in the claims.

[0051] The "range" disclosed in the present application is limited in the form of a lower limit and an upper limit, and the given range is limited by selecting one lower limit and one upper limit. The selected lower limit and upper limit define the boundary of a specific range. The range thus limited may or may not include the end values, and any combination is possible, that is, any lower limit can be combined with any upper limit to form a range. For example, when ranges of 60 to 120 and 80 to 110 are listed for a specific parameter, ranges of 60 to 110 and 80 to 120 are also understood to be assumable. Note that if 1 and 2 are listed as the minimum range values and 3, 4, and 5 are listed as the maximum range values, all of the ranges of 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5 are assumable. In the present application, unless otherwise specified, the numerical range of "a to b" represents a shortened expression of any real number combination of a to b, where both a and b are real numbers. For example, the numerical range of "0 to 5" represents that all real numbers between "0 to 5" have already been listed in this specification, and "0 to 5" is only a shortened expression of the combination of these numerical values. Also, when a certain parameter is expressed as an integer ≧2, it corresponds to disclosing that this parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0052] Unless otherwise specified, all embodiments and alternative embodiments of this application can be combined with each other to form a new technical solution.

[0053] Unless otherwise specified, all technical features and alternative technical features of this application can be combined with each other to form a new technical solution.

[0054] Unless otherwise specified, all steps of this application may be performed in order or randomly, and preferably, they are performed in order. For example, the fact that the method includes steps (a) and (b) means that the method may include steps (a) and (b) performed in order, or steps (b) and (a) performed in order. For example, the fact that 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), or steps (a), (c), and (b), or steps (c), (a), and (b), etc.

[0055] Unless otherwise specified, the terms "comprising" and "including" mentioned in this application represent an open type and may also be a closed type. For example, the "comprising" and "including" may further comprise or include other components not listed, or may comprise or include only the listed components.

[0056] Unless otherwise specified, the term "or" in this application is inclusive. For example, the phrase "A or B" represents "A, B, or both A and B". More specifically, any of the conditions where A is true (or exists) and B is false (or does not exist), where A is false (or does not exist) but B is true (or exists), and where both A and B are true (or exist) satisfy "A or B".

[0057] In the prior art, polyvinylidene fluoride (PVDF) is always used as the electrode adhesive. However, there are many problems during the use of PVDF. For example, it is sensitive to the water content during production. During battery recycling, a large amount of HF is generated, polluting the environment, and it is restricted by environmental protection policies and cannot be recycled on a large scale. In the process of manufacturing the positive electrode slurry by mixing with a high-capacity positive electrode active material (for example, a high-nickel ternary material), the strong polar groups on PVDF activate the hydroxyl groups remaining on the positive electrode active material, and further cause a binding reaction with the metal elements (for example, nickel elements) in the positive electrode active material to form a chemical crosslink, ultimately causing slurry gelation, which affects the normal production of the slurry and subsequent electrode processing. In addition, PVDF is prone to crystallization, which is disadvantageous for the transmission of electrons in the electrode, further increasing the resistance of the electrode, deteriorating the electron transmission performance, and being disadvantageous for the performance of high-capacity positive electrode active materials.

[0058] [Adhesive] Based on this, the present application proposes a BAB-type block copolymer. The B-block contains a structural unit represented by Formula I, and the A-block contains one or more of the structural units represented by Formula II and the structural unit represented by Formula III. JPEG2025516733000005.jpg60170Here, R 1 , R 2 , R 3 are each independently one or more selected from hydrogen, fluorine, and a C 1-3 alkyl group containing at least one fluorine atom, and R 4 , R 5 , R 6 are each independently selected from hydrogen and a substituted or unsubstituted C 1-5 alkyl group, and R 7 is selected from a carboxyl group, an ester group, a hydroxyl group, an amide group, a cyano group, and a substituted or unsubstituted aromatic group.

[0059] In this specification, the term "block copolymer" is a special polymer produced by connecting two or more polymer segments with different properties. Block copolymers with specific structures exhibit different properties from simple linear polymers, many random copolymers, and even mixtures of homopolymers. Commonly, there are AB-type and BAB-type, where A and B are both long-chain segments, and there are also (AB)n-type multi-block copolymers, where the A and B segments are relatively short.

[0060] In this specification, the term "BAB-type block copolymer" is a triblock copolymer with an A-block in the middle and B-blocks on both sides. Here, the A-block and the B-block are polymer segments with a predetermined weight-average molecular weight formed by polymerizing different monomers respectively. In some embodiments, the B-block is a long sequence segment formed by the polymerization of fluorine-containing monomers, and the A-block is a long sequence segment formed by the polymerization of one or more fluorine-free monomers. The A-block and the B-block are bonded through covalent bonds in an orderly manner to form a BAB-type block copolymer. Taking the BAB-type block polymer produced in Example 1 as an example, here, the A-block poly(acrylonitrile-butyl methacrylate-styrene) is formed by polymerizing acrylonitrile monomer, butyl methacrylate monomer, and styrene monomer, and has a weight-average molecular weight of 480,000. The B-block is polyvinylidene fluoride, formed by polymerizing vinylidene fluoride monomer, and has a weight-average molecular weight of 400,000. The end groups on both sides of the B-block and the A-block are bonded to obtain a polyvinylidene fluoride-poly(acrylonitrile-butyl methacrylate-styrene)-polyvinylidene fluoride block copolymer (BAB-type block copolymer), and the weight-average molecular weight of the block copolymer is 1.2 million.

[0061] As used herein, the term "polymer" includes an aggregate of macromolecules that are chemically uniform but have different degrees of polymerization, mass contents, and chain lengths, and are produced by a polymerization reaction. Meanwhile, the term also includes derivatives of such macromolecular aggregates formed by a polymerization reaction, i.e., those obtained by reactions of functional groups in the above macromolecules, such as addition or substitution, and may be compounds that are chemically uniform or chemically non-uniform.

[0062] As used herein, the term "C" 1-3 "alkyl group" refers to a straight-chain or branched-chain hydrocarbon group composed only of carbon and hydrogen atoms, having no unsaturation in the group, having 1 to 3 carbon atoms, and being linked to other parts of the molecule through a single bond. C 1-3 Examples of C alkyl groups include, but are not limited to, methyl group, ethyl group, n-propyl group, 1-methylethyl group (isopropyl group).

[0063] As used herein, the term "C" 1-5 "alkyl group" refers to a straight-chain or branched-chain hydrocarbon group composed only of carbon and hydrogen atoms, having no unsaturation in the group, having 1 to 5 carbon atoms, and being linked to other parts of the molecule through a single bond. C 1-5 Examples of C alkyl groups include, but are not limited to, methyl group, ethyl group, n-propyl group, 1-methylethyl group (isopropyl group), n-butyl group, n-pentyl group.

[0064] As used herein, the term "carboxyl group" refers to the -COOH group.

[0065] As used herein, the term "ester group" refers to the -COOR 10 group, where R 10 is selected from substituted or unsubstituted C 1-5 alkyl groups.

[0066] As used herein, the term "hydroxyl group" refers to the -OH group.

[0067] In this specification, the term "amide group" refers to a -CO-NR 8 R 9 group, where R 8 and R 9 are each independently selected from substituted or unsubstituted C 1-5 alkyl groups.

[0068] In this specification, the term "cyano group" refers to a -CN group.

[0069] In this specification, the term "substituted" means that at least one hydrogen atom of the compound or chemical moiety is substituted by another chemical moiety, a substituent, where the substituents are each independently a hydroxy group, a mercapto group, an amino group, a cyano group, a nitro group, an aldehyde group, a halogen atom, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, a C 1-6 alkyl group, a C 1-6 alkoxy group.

[0070] In some embodiments, the BAB-type block copolymer is used as an electrode adhesive.

[0071] In this specification, the term "adhesive" refers to a chemical compound, polymer or mixture that forms a colloidal solution or colloidal dispersion in a dispersion medium.

[0072] In some embodiments, the dispersion medium of the adhesive is an aqueous solvent, such as water. That is, the adhesive is soluble in the aqueous solvent.

[0073] In some embodiments, the dispersion medium of the adhesive is an oily solvent, examples of which include, but are not limited to, dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, acetone, dimethyl carbonate, ethyl cellulose, polycarbonate. That is, the adhesive is soluble in the oily solvent.

[0074] In some embodiments, the adhesive is used to fix the electrode material and / or the conductive agent in place and adhere them to the conductive metal member to form an electrode.

[0075] In some embodiments, the adhesive is used as a positive electrode adhesive to adhere the positive electrode active material and / or the conductive agent to form an electrode.

[0076] In some embodiments, the adhesive is used as a negative electrode adhesive to adhere the negative electrode active material and / or the conductive agent to form an electrode.

[0077] The fluorine element contained in the B-block forms a hydrogen bond with the hydroxyl group and / or carboxyl group on the surface of the active material and the current collector surface, giving the electrode plate excellent adhesion. The amide group, carboxyl group, ester group, hydroxyl group or cyano group contained in the A-block can, on the one hand, form a hydrogen bond with the hydroxyl group on the surface of the positive electrode active material and the conductive agent particles to improve the adhesion of the electrode plate, and on the other hand, effectively bond with the transition metal in the positive electrode active material to suppress the elution of the transition metal during use and improve the cycle performance. At the same time, the insertion of the A-block between the B-blocks can reduce the orderly arrangement of the large area of the fluorine-containing segment, reduce the crystallinity, and enhance the flexibility. The adhesive produced from the BAB-type block copolymer can effectively reduce the orderly arrangement of the fluorine-containing block polymer because the non-fluorine-containing block polymer is located in the middle of the fluorine-containing block polymer. By introducing functional groups into the non-fluorine-containing polymer, the adhesion performance of the BAB-type block copolymer can be improved, and the advantages of the fluorine-containing adhesive and the non-fluorine adhesive can be fully exerted, and the complementary effect of the advantages can be realized. And the BAB-type block copolymer can effectively suppress the delamination phenomenon that occurs during the slurry production due to the interaction between the blocks compared with the simple blend of the fluorine-containing polymer and the non-fluorine polymer.

[0078] From the above, by using the BAB-type block copolymer as an adhesive, the adhesive strength of the electrode plate can be improved, the DC impedance growth rate of the battery and the elution amount of transition metals can be reduced, while achieving both low film resistance and excellent flexibility in the electrode plate, ensuring that the battery has a high cycle capacity retention rate and a 45°C capacity retention rate.

[0079] In this specification, the adhesive strength is mainly used to characterize the adhesive strength between the film layer produced from the positive electrode slurry and the current collector in the positive electrode plate, and it can be tested by any known method.

[0080] In this specification, the film resistance is mainly used to characterize the resistance of the positive electrode plate and can reflect the electronic conduction performance of the positive electrode plate, and it can be tested by any known method.

[0081] In this specification, the flexibility is mainly used to characterize the bending resistance ability of the positive electrode plate and can reflect the malleability of the positive electrode plate, and it can be tested by any known method.

[0082] In this specification, the DC impedance growth rate is mainly used to characterize the impedance performance of the battery and can reflect the increase rate of the impedance during the cycling of the battery, and it can be tested by any known method.

[0083] In this specification, the cycle performance is mainly used to characterize the cycle use performance of the battery and can reflect the cycle performance of the battery, and it can be tested by any known method.

[0084] In this specification, the high-temperature storage performance is mainly used to characterize the high-temperature use performance of the battery and can reflect the high-temperature stability of the battery, and it can be tested by any known method.

[0085] In some embodiments, the A-block is R 7contains a structural unit represented by Formula II in which R is an amide group. In some embodiments, R in Formula II 7 is as shown in Formula IV, JPEG2025516733000006.jpg27170where R 8 and R 9 are each independently selected from hydrogen, a substituted or unsubstituted C 1-5 alkyl group, The amide group contained in the A-block is likely to form a hydrogen bond with the hydroxyl groups of the positive electrode active material and the current collector, and can improve the adhesion of the electrode plate. In addition, the amide group contained in the A-block can improve the infiltration ability of the electrode plate in the electrolyte, contribute to the rapid formation of ion transmission channels on the electrode plate, reduce the membrane resistance of the electrode plate, and contribute to improving the cycle performance of the battery.

[0086] The fact that the A-block contains a structural unit represented by Formula II in which R 7 is an amide group is advantageous for improving the adhesion and flexibility of the electrode plate, reducing the membrane resistance of the electrode plate, and at the same time significantly reducing the elution of transition metals in the positive electrode.

[0087] In some embodiments, the A-block contains a structural unit represented by Formula II in which R 7 is a cyano group and a structural unit represented by Formula II in which R 7 is an ester group.

[0088] The A-block contains a cyano group which is a strong polar group and can form strong hydrogen bonds and dipole-dipole interactions with the hydroxyl groups on the surface of the positive electrode active material. That is, it can play a role in stabilizing and dispersing in the slurry, further improving the adhesion of the electrode plate, promoting the dispersion of the positive electrode active material, and contributing to reducing the film resistance of the electrode plate. And the cyano group, which is a strong polar group, can reinforce the stability of the molecular structure, improve the glass transition temperature of the block copolymer, improve the rigidity and thermal stability of the block copolymer, contribute to the improvement of the oxidation stability of the electrode plate, and can enhance the cycle and rate performance of the battery. In addition, due to the cyano group, the A-block has a certain coating property for the positive electrode active material. The cyano group in the A-block can complex with the transition metal ions on the surface of the positive electrode active material, prevent the elution of the transition metal ions, and further reduce the deposition of the transition metal ions on the surface of the negative electrode. The ester group contained in the A-block weakens the excessive dipole moment between the cyano groups, and reduces the brittleness problem of the electrode plate caused by the excessive interaction force between the heavy cyano groups of the A-block, which inhibits the free movement of the adhesive segments, and contributes to the improvement of the safety performance of the battery. Also, the ester group has good affinity with the electrolyte and contributes to strengthening the contact between the electrolyte and the positive electrode active material, thereby improving the ionic conductivity and reducing the film resistance of the electrode plate.

[0089] In the A-block, R 7 is a structural unit represented by Formula II where it is a cyano group, and R 7 is a structural unit represented by Formula II where it is an ester group are simultaneously contained, which is advantageous for improving the adhesion and flexibility of the electrode plate, reducing the film resistance of the electrode plate, reducing the DC impedance growth rate and the metal deposition amount of the battery, and ensuring the coexistence of a high cycle capacity retention rate and a 45 °C capacity retention rate in the battery.

[0090] In some embodiments, the A-block has R 7 is a structural unit represented by Formula II where it is a cyano group, and R 7 is a structural unit represented by Formula II where it is an ester group, and R 7It contains a structural unit represented by Formula II in which A-block is a substituted or unsubstituted aromatic group.

[0091] The aromatic group contained in the A-block contributes to the improvement of the mechanical strength of the electrode plate, thereby corresponding to the volume change of the positive electrode active material during charge and discharge, maintaining the structural integrity of the electrode during charge and discharge, and improving the cycle performance of the battery.

[0092] In the A-block, R 7 is a structural unit represented by Formula II in which it is a cyano group, and R 7 is a structural unit represented by Formula II in which it is an ester group, and R 7 is a structural unit represented by Formula II in which it is a substituted or unsubstituted aromatic group are simultaneously contained, which is also advantageous for further improving the adhesion and flexibility of the electrode plate.

[0093] In some embodiments, the A-block contains a structural unit represented by Formula II in which R 7 is a cyano group, a structural unit represented by Formula II in which R 7 is an amide group, and a structural unit represented by Formula II in which R 7 is an ester group.

[0094] In the A-block, R 7 is a structural unit represented by Formula II in which it is a cyano group, R 7 is a structural unit represented by Formula II in which it is an amide group, and R 7 is a structural unit represented by Formula II in which it is an ester group are simultaneously contained, which ensures the coexistence of low film resistance, excellent adhesion and flexibility in the electrode plate, and at the same time significantly reduces the metal deposition amount of the battery, and enables the battery to have a low DC impedance growth rate, a high cycle capacity retention rate and a 45 °C capacity retention rate.

[0095] In some embodiments, R 7 in Formula II is optionally one or more of a carboxyl group and a hydroxyl group.

[0096] In some embodiments, the structural unit represented by Formula II is derived from the group consisting of acrylonitrile, crotononitrile, styrene, vinyl alcohol, acrylamide, ethyl acrylate, ethyl methacrylate, butyl methacrylate, methacrylic acid, ethacrylic acid, methacrylamide, N-methacrylamide, N-methylmethacrylamide, N-isopropyl acrylamide, N-isopropyl methacrylamide, N-t-butyl acrylamide, N-t-butyl (meth)acrylamide, N,N-dimethyl acrylamide, N,N-dimethyl methacrylamide, N,N-diethyl acrylamide, N,N-diethyl methacrylamide, acrylic acid, vinyl benzoic acid, acrylic acetate ester, acrylic acid ester, and combinations thereof.

[0097] In some embodiments, the structural unit represented by Formula I is derived from the group consisting of vinylidene fluoride, tetrafluoroethylene, vinyl fluoride, hexafluoropropene, and combinations thereof.

[0098] In some embodiments, the BAB block copolymer is a poly(vinylidene fluoride)-poly(acrylonitrile-butyl methacrylate-styrene)-poly(vinylidene fluoride) block copolymer, a poly(vinylidene fluoride)-polyacrylamide-poly(vinylidene fluoride) block copolymer, a poly(vinylidene fluoride)-poly(acrylic acid-acrylamide-ethyl methacrylate)-poly(vinylidene fluoride) block copolymer, a poly(vinylidene fluoride)-poly(acrylonitrile-acrylamide-acrylic ester)-poly(vinylidene fluoride) block copolymer, a poly(vinylidene fluoride)-polystyrene-poly(vinylidene fluoride) block copolymer, a poly(vinylidene fluoride)-polyethylene oxide-poly(vinylidene fluoride) block copolymer, a poly(vinylidene fluoride)-polyvinyl alcohol-poly(vinylidene fluoride) block copolymer, a poly(vinylidene fluoride)-poly(acrylonitrile-acrylic acetate)-poly(vinylidene fluoride) block copolymer, a poly(vinyl fluoride)-poly(acrylonitrile-butyl methacrylate-styrene)-poly(vinyl fluoride) block copolymer, or a polytetrafluoroethylene-poly(acrylonitrile-butyl methacrylate-styrene)-polytetrafluoroethylene block copolymer.

[0099] In some embodiments, the mass content of the A-block is 40% to 60% based on the total mass of the block copolymer. In some embodiments, the mass content of the A-block is optionally 40%, 42%, 44%, 45%, 46%, 48%, 50%, 42%, 54%, 54%, 55%, 56%, 58%, or 60% based on the total mass of the block copolymer.

[0100] The BAB-type block copolymer with the mass content of the A-block within an appropriate range can improve the adhesion and flexibility of the electrode plate, reduce the membrane resistance of the electrode plate, increase the cycle capacity retention rate and the 45°C capacity retention rate of the battery, and reduce the DC impedance growth rate and the metal deposition amount of the battery.

[0101] In some embodiments, the weight average molecular weight of the block copolymer is from 400,000 to 2,000,000. In some embodiments, the weight average molecular weight of the block copolymer is optionally 400,000, 420,000, 450,000, 480,000, 500,000, 550,000, 600,000, 650,000, 700,000, 750,000, 800,000, 850,000, 900,000, 950,000, 1,000,000, 1,100,000, 1,200,000, 1,300,000, 1,400,000, 1,500,000, 1,600,000, 1,700,000, 1,800,000, 1,900,000, 2,000,000.

[0102] 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 the polymer and their corresponding molecular weights.

[0103] In this application, the test of the weight average molecular weight of the polymer can be carried out by methods known in the art. For example, gel chromatography is employed for the test, and for example, a Waters 2695 Isocratic HPLC type gel chromatograph (differential refractive index detector 2141) is adopted. A polystyrene solution sample with a mass fraction of 3.0% is used as a reference, and a corresponding column (oily: Styragel HT5DMF7.8×300mm + Styragel HT4) is selected. A 3.0% fluorine-containing polymer solution is prepared using a purified N-methylpyrrolidone (NMP) solvent, and the prepared solution is allowed to stand for one day for use. When testing, first, tetrahydrofuran is sucked into a syringe, washed, and repeated several times. Then, 5 ml of the experimental solution is sucked, the air in the syringe is discharged, and the needle tip is wiped clean. Finally, the sample solution is slowly injected into the sample inlet. Data is acquired after the indication number is stable, and the weight average molecular weight is read.

[0104] If the weight average molecular weight of the block copolymer is too large, it is difficult to dissolve the adhesive, it is easy to aggregate with the conductive agent, the internal resistance of the film increases, the viscosity of the slurry increases, the dispersibility of substances in the slurry decreases, and the flexibility of the electrode plate is affected. If the weight average molecular weight of the block copolymer is too small, it is difficult to form a three-dimensional network adhesive structure and cannot achieve an effective adhesive effect.

[0105] A BAB block copolymer having a weight-average molecular weight within an appropriate range can improve the adhesion of the electrode plate, reduce the DC impedance growth rate and the metal deposition amount of the battery, and at the same time achieve both a low film resistance and excellent flexibility in the electrode plate, and ensure that the battery has both a high cycle capacity retention rate and a 45°C capacity retention rate.

[0106] In some embodiments, the weight-average molecular weight of the A-block in the block copolymer is from 200,000 to 1,100,000. In some embodiments, the weight-average molecular weight of the A-block in the block copolymer is optionally 200,000, 250,000, 300,000, 350,000, 400,000, 450,000, 500,000, 550,000, 600,000, 650,000, 700,000, 750,000, 800,000, 850,000, 900,000, 950,000, 1,000,000, 1,050,000, 1,100,000.

[0107] If the weight-average molecular weight of the A-block in the block copolymer is too large, there are too many strong polar groups in the structural units of the monomers shown in Formula II or Formula III, which will affect the stability of the slurry. If the weight-average molecular weight of the A-block in the block copolymer is too small, the adhesion of the electrode plate will decrease.

[0108] A BAB block copolymer having a weight-average molecular weight of the A-block within an appropriate range can improve the adhesion of the electrode plate, reduce the DC impedance growth rate and the metal deposition amount of the battery, and at the same time achieve both a low film resistance and excellent flexibility in the electrode plate, and ensure that the battery has both a high cycle capacity retention rate and a 45°C capacity retention rate.

[0109] In some embodiments, the weight-average molecular weight of each B-block in the block copolymer is from 100,000 to 500,000. In some embodiments, the weight-average molecular weight of each B-block in the block copolymer is optionally 100,000, 120,000, 150,000, 170,000, 200,000, 220,000, 250,000, 280,000, 300,000, 320,000, 350,000, 370,000, 400,000, 430,000, 450,000, 470,000, 500,000.

[0110] A BAB block copolymer in which the weight average molecular weight of each B-block is within an appropriate range can improve the adhesion of the electrode plate, reduce the DC impedance growth rate and the metal deposition amount of the battery, achieve both low film resistance and excellent flexibility in the electrode plate, and ensure both a high cycle capacity retention rate and a 45°C capacity retention rate in the battery.

[0111] In one embodiment of the present application, a method for producing a BAB type block copolymer is provided, including the following steps: Production of B-block: Polymerize at least one monomer represented by Formula V to produce a B-block, JPEG2025516733000007.jpg25170 Here, R′ 1 、R′ 2 、R′ 3 are each independently one or more selected from hydrogen, fluorine, and a C 1-3 alkyl group containing at least one fluorine atom, Production of A-block: Polymerize at least one monomer represented by Formula VI to produce an A-block, or subject a monomer represented by Formula VII to ring-opening polymerization to produce an A-block, JPEG2025516733000008.jpg39170 Here, R′ 4 、R′ 5 、R′ 6 are each independently selected from hydrogen and a substituted or unsubstituted C 1-5 alkyl group, and R′ 7 is one selected from a carboxyl group, an ester group, a hydroxyl group, an amide group, a cyano group, and a substituted or unsubstituted aromatic group, Production of BAB type block copolymer: Combine the B-block and the A-block to produce a BAB type block copolymer.

[0112] The manufacturing method has inexpensive raw materials, can reduce costs and environmental pollution, and is beneficial to improving the yield of the adhesive. At the same time, the adhesive manufactured by this method can effectively improve the adhesion of the electrode plate, reduce the DC impedance growth rate and the metal deposition amount of the battery, and achieve both low film resistance and excellent flexibility on the electrode plate, and ensure that the battery has both a high cycle capacity retention rate and a 45°C capacity retention rate.

[0113] In some embodiments, the manufacturing step of the B-block is reacting at least one monomer shown in formula V, a chain transfer agent, and a first initiator by reversible addition-fragmentation chain transfer polymerization at a reaction temperature of 60-75°C for 4-6 hours to obtain a B-block having an azide group or an alkynyl group at the terminal.

[0114] In this specification, the term "azide group" refers to the -N 3 group.

[0115] In this specification, the term "alkynyl group" refers to the -C≡CH group.

[0116] In this specification, the term "reversible addition-fragmentation chain transfer polymerization" (RAFT polymerization) is a reversible deactivation radical polymerization, also called a "living" / controllable radical polymerization method. The main principle of RAFT polymerization is to add a RAFT reagent as a chain transfer reagent to radical polymerization to protect the easily terminated radicals in the form of chain transfer, convert most of the radicals in the polymerization reaction into dormant radical species, and have dormant segments and active segments coexist during the reaction, and continuously and rapidly switch with each other by a dynamic reversible reaction, so that only a small number of polymer chains exist in the form of active chains at any time, grow, and finally the growth probability of each polymer segment becomes approximately equal, and further exhibits the characteristics of living polymerization.

[0117] In some embodiments, a schematic diagram of the synthesis route of the B-block is as shown in the following figure, where the chain transfer agent is trithiocarbonate, Z' is an active group containing an alkynyl group or an azide group at the terminal, and R is an alkyl group. By the following reaction, a B-block having an alkynyl group or an azide group at the terminal was produced. JPEG2025516733000009.jpg32106

[0118] By adopting reversible addition-fragmentation chain transfer polymerization, controllable polymerization can be realized, and the molecular weight distribution of the product is narrow. And by the above reaction, the B-block has only an alkynyl group or an azide group at the terminal, and it is easy to orient and combine with the A-block in an efficient and mild manner to generate a BAB-type block copolymer.

[0119] In some embodiments, the manufacturing steps of the A-block are including polymerizing the monomer shown in Formula VI and the second initiator at a reaction temperature of 80 to 95 °C for 2.5 to 5 hours to obtain an A-block having an alkynyl group or an azide group at both ends.

[0120] In some embodiments, the synthesis route of the A-block is shown below. Under the action of the first initiator, the monomer shown in Formula I undergoes a polymerization reaction to generate an A-block. Since the terminal groups on both sides of the first initiator are alkyl groups substituted with halogen or trimethylsilylacetylene groups, the halogen or trimethylsilyl groups on both sides of the A-block are easily substituted to give an azide group or an alkynyl group at both ends of the A-block (in the figure, B 1 is an alkyl group substituted with halogen or a trimethylsilylacetylene group, and B 2 is an azide group or an alkynyl group). JPEG2025516733000010.jpg59157

[0121] By adopting an A-block with azidated or alkynylated ends on both sides produced by the manufacturing method, the A-block is linked to the B-block in an efficient and mild manner between the blocks, facilitating the generation of a BAB-type block copolymer.

[0122] In some embodiments, the manufacturing steps of the A-block are polymerizing the monomer shown in Formula VII, an ionic initiator, and water at a reaction temperature of 60 °C to 80 °C for 6 to 8 hours to obtain a product having hydroxyl groups at both ends, and subjecting the hydroxyl groups of the product to a functionalization reaction to obtain an A-block having alkynyl groups or azide groups at both ends.

[0123] In some embodiments, the synthesis route of the A-block is as follows: under the action of a first initiator, the monomer shown in Formula I undergoes a polymerization reaction to generate an A-block. Since the end groups on both sides of the first initiator are alkyl groups substituted with halogens or trimethylsilylacetylene groups, the halogens or trimethylsilyl groups on both sides of the A-block are easily substituted to give azide groups or alkynyl groups at both ends of the A-block (in the figure, B 1 is an alkyl group substituted with a halogen or a trimethylsilylacetylene group, and B 2 is an azide group or an alkynyl group). JPEG2025516733000011.jpg59159

[0124] By adopting an A-block with azidated or alkynylated ends on both sides produced by the manufacturing method, the A-block is linked to the B-block in an efficient and mild manner between the blocks, facilitating the generation of a BAB-type block copolymer.

[0125] In some embodiments, the production of the BAB-type block copolymer is Mixing an A-block having an azide group or an alkynyl group at both ends with a B-block having an alkynyl group or an azide group at the end, and performing a click reaction to produce a BAB-type block copolymer, where the end groups of the A-block and the B-block are different.

[0126] In this specification, the term "click reaction" refers to a reaction in which an alkynyl group undergoes a cycloaddition reaction with an azide group to connect the A-block and the B-block. In some embodiments, the click reaction is carried out at room temperature and normal pressure in the presence of a Cu(I) catalyst.

[0127] In some embodiments, the end group of the A-block is an azide group, and the end group of the B-block is an alkynyl group.

[0128] In some embodiments, the end group of the A-block is an alkynyl group, and the end group of the B-block is an azide group.

[0129] The above manufacturing method has the advantages of high yield, harmless by-products, simple and mild reaction conditions, and easy availability of reaction raw materials. It can achieve controllable polymerization of block polymers and is advantageous for improving the yield rate of products.

[0130] In some embodiments, the chain transfer agent is a RAFT chain transfer agent containing a terminal alkynyl group or an azide group. In some embodiments, the chain transfer agent is a trithiocarbonate containing a terminal alkynyl group or an azide group. In some embodiments, the structural formula of the chain transfer agent is selected from the following formulas: JPEG2025516733000012.jpg2888 JPEG2025516733000013.jpg2990 The RAFT chain transfer agent containing a terminal alkynyl group or an azide group provides a basis for the click reaction between the B-block and the A-block by introducing an alkynyl group or an azide group at the end of the B-block during the synthesis of the B-block, avoiding complex post-treatment steps and improving the reaction efficiency.

[0131] In some embodiments, the second initiator is a symmetric difunctional initiator. In some embodiments, the second initiator is 4-(chloromethyl) benzoyl peroxide. The symmetric difunctional initiator enables having the same active functional groups symmetrically on both sides of the A-block and contributes to the simultaneous realization of azidation or alkynylation of the end groups on both sides of the A-block.

[0132] In some embodiments, the first initiator is one or two selected from azobisisobutyronitrile and azobisisoheptonitrile. Azobisisobutyronitrile is a commonly used radical polymerization initiator, which easily decomposes to form radicals and easily causes radical polymerization.

[0133] In some embodiments, the BAB-type block copolymer may be used in a secondary battery. Optionally, the secondary battery includes at least one of a lithium-ion battery, a sodium-ion battery, a magnesium-ion battery, and a potassium-ion battery.

[0134] [Positive electrode plate] 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 includes a positive electrode active material, a conductive agent, and an adhesive. The adhesive is a BAB-type block copolymer in some embodiments or a BAB-type block copolymer manufactured by the manufacturing method in some embodiments.

[0135] The positive electrode plate has excellent flexibility and adhesion, and has a low film resistance.

[0136] In some embodiments, the adhesion per unit length between the positive electrode film layer and the positive electrode current collector is 11 N / m or more. In some embodiments, the adhesion per unit length between the positive electrode film layer and the positive electrode current collector is optionally 11 N / m, 11.5 N / m, 12 N / m, 12.5 N / m, 13 N / m, 13.5 N / m, 14 N / m, 14.5 N / m, 15 N / m, 15.5 N / m, 16 N / m, 16.5 N / m, 17 N / m, 17.5 N / m, 18 N / m, 18.5 N / m, 19 N / m, 19.5 N / m, 20 N / m.

[0137] The adhesion per unit length between the positive electrode film layer and the positive electrode current collector can be tested using any means known in the art. For example, refer to the national standard GB-T2790-1995 "Test Method for 180° Peel Strength of Adhesives" for testing. As an example, the positive electrode plate is cut into test samples with a size of 20 mm × 100 mm. In preparation for use, the electrode plate is adhered to one side of the positive electrode film layer with double-sided tape and rolled to consolidate, so that the double-sided tape and the electrode plate are completely adhered. The other side of the double-sided tape is attached to the surface of stainless steel. One end of the sample is bent in the reverse direction, and the bending angle is 180°. A high-strength iron tensile machine is used for testing. One end of the stainless steel is fixed to the fixture below the tensile machine, and the bent end of the sample is fixed to the fixture above. Adjust the angle of the sample to ensure that the upper and lower ends are in a vertical position. Then, at a speed of 50 mm / min, the sample is pulled until the positive electrode current collector is completely peeled off from the positive electrode film, and the displacement and acting force in this process are recorded. Divide the force when the force is balanced by the width of the electrode plate adhered to the double-sided tape (the width direction of the electrode plate is perpendicular to the peeling direction) to obtain the adhesion of the electrode plate per unit length. The width of the electrode plate in this test is 20 mm.

[0138] There is a high adhesion strength between the positive electrode film layer and the positive electrode current collector of the electrode plate. During use, the positive electrode film layer is less likely to fall off from the positive electrode current collector, contributing to improving the cycle performance and safety of the battery.

[0139] In some embodiments, after the positive electrode plate has undergone three or more folding tests, a light transmission phenomenon occurs in the positive electrode plate. In some embodiments, after the positive electrode plate has undergone 3.3, 3.5, 3.7 or four or more folding tests, a light transmission phenomenon occurs in the positive electrode plate.

[0140] The flexibility test of the positive electrode plate can be carried out by adopting a known method. For example, the positive electrode plate after cold pressing is cut into test samples with a size of 20×100 mm, folded in half in the positive direction, flattened with a 2 kg roll, unfolded, and it is inspected whether light transmission occurs in the gap towards the light. If no light transmission occurs, it is folded in half in the reverse direction, flattened with a 2 kg roll, and inspected again towards the light. Repeat in this way. When a light transmission phenomenon occurs in the gap, record the number of times of folding in half, repeat the test three times, take the average value, and use it as the reference data for the flexibility of the electrode plate.

[0141] The fact that the positive electrode plate can undergo three or more folding tests indicates that the electrode plate has good flexibility, is not prone to collapse during production, and is not prone to brittle fracture during use, contributing to improving the yield rate of the battery and the safety performance of the battery.

[0142] In some embodiments, the film resistance of the positive electrode plate is 1.0 Ω or less.

[0143] The film resistance refers to the resistance of the positive electrode film layer of the electrode plate and can be tested by using any means known in the art. For example, a resistance measuring instrument can be adopted for testing.

[0144] The film resistance can be tested by adopting a known method. For example, small discs with a diameter of 3 mm are cut at the left, middle and right of the electrode plate respectively. Turn on the indicator lamp of the Yuaneng Technology electrode plate resistance measuring instrument, place it at an appropriate position of the "probe" of the film resistance measuring instrument, click the "start" button, and read it after the indicated value stabilizes. Two positions are tested for each small disc, and finally the average value of six measurements is calculated as the film resistance of the electrode plate.

[0145] The fact that the electrode plate has a low membrane resistance indicates that the dispersion of the material in the positive electrode membrane layer is uniform, and the fact that the positive electrode membrane layer has good electron transmission efficiency is advantageous for the performance of the battery.

[0146] As an example, the positive electrode current collector has two opposing surfaces in its own thickness direction, and the positive electrode membrane layer is installed on one or both of the two opposing surfaces of the positive electrode current collector.

[0147] In some embodiments, the positive electrode current collector may employ a metal foil sheet or a composite current collector. For example, as the metal foil sheet, an aluminum foil may be employed. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material 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, and silver alloy, etc.) on a polymer material substrate (such as substrates like polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0148] In some embodiments, the positive electrode active material may employ a positive electrode active material for batteries well known in the art. As an example, the positive electrode active material may include at least one material among lithium-containing phosphates with an olivine structure, lithium metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as the positive electrode active material of the battery may also be used. These positive electrode active materials may be used alone, or two or more of them may be used in combination. Here, examples of lithium metal oxides are lithium cobalt oxide (e.g., LiCoO 2 )), lithium nickel oxide (e.g., LiNiO 2 ), lithium manganese oxide (e.g., LiMnO 2 , LiMn 2 O 4) Lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (for example, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 (NCM 333 which may be abbreviated), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM 523 which may be abbreviated), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (NCM 211 which may be abbreviated), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM 622 which may be abbreviated), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM 811 which may be abbreviated), lithium nickel cobalt aluminum oxide (for example, LiNi 0.85 Co 0.15 Al 0.05 O 2 ) and may include, but are not limited to, at least one of its modified compounds. Examples of olivine-structured lithium-containing phosphates are lithium iron phosphate (for example, LiFePO 4 (which may be abbreviated as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (for example, LiMnPO 4 ), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon, and may include, but are not limited to, at least one of them.

[0149] In some embodiments, the positive electrode film layer may further optionally contain a conductive agent. By way of example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0150] In some embodiments, the positive electrode plate may be manufactured in the following manner. The above components for manufacturing the positive electrode plate, such as the positive electrode active material, the conductive agent, the adhesive, and any other components, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry. The positive electrode slurry is coated on a positive electrode current collector, and through processes such as drying and cold pressing, a positive electrode plate is obtained.

[0151] [Negative electrode plate] 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, and the negative electrode film layer contains a negative electrode active material.

[0152] By way of example, the negative electrode current collector has two opposing surfaces in its own thickness direction, and the negative electrode film layer is disposed on either one or both of the two opposing surfaces of the negative electrode current collector.

[0153] In some embodiments, the negative electrode current collector may employ a metal foil sheet or a composite current collector. For example, as the metal foil sheet, a copper foil may be employed. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base. 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, etc.) on a polymer material base (such as a base of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0154] In some embodiments, the negative electrode active material may employ a negative electrode active material for batteries well known in the art. By way of example, the negative electrode active material may include at least one of materials such as artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may be selected from at least one of silicon alone, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy. The tin-based material may be selected from at least one of tin alone, tin oxide, and tin alloy. However, this application is not limited to these materials, and other conventional materials that can be used as the negative electrode active material of the battery may also be used. These negative electrode active materials may be used alone, or two or more of them may be used in combination.

[0155] In some embodiments, the negative electrode film layer may optionally further include an adhesive. The adhesive 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).

[0156] In some embodiments, the negative electrode film layer may optionally further include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0157] In some embodiments, the negative electrode film layer may optionally further include other auxiliaries, such as a thickening agent (e.g., sodium carboxymethyl cellulose (CMC-Na)) and the like.

[0158] In some embodiments, the negative electrode plate may be manufactured by the following method. The above components for manufacturing the negative electrode plate, such as the negative electrode active material, the conductive agent, the adhesive, and any other components, are dispersed in a solvent (for example, deionized water) to form a negative electrode slurry. The negative electrode slurry is coated on the negative electrode current collector, and through processes such as drying and cold pressing, a negative electrode plate is obtained.

[0159] [Electrolyte] The electrolyte functions to conduct ions between the positive electrode plate and the negative electrode plate. The present application does not specifically limit the type of the electrolyte, and it can be selected according to the demand. For example, the electrolyte may be liquid, gel-like, or all-solid.

[0160] In some embodiments, the electrolyte employs an electrolytic solution. The electrolytic solution contains an electrolyte salt and a solvent.

[0161] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, lithium difluorobis(oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate.

[0162] 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.

[0163] In some embodiments, the electrolyte further optionally contains an additive. For example, the additive may include a negative electrode film-forming additive and a positive electrode film-forming additive, and may further include additives that can improve some performances of the battery, such as additives that improve the overcharge performance of the battery, additives that improve the high-temperature or low-temperature performance of the battery, and the like.

[0164] [Separator] In some embodiments, the secondary battery further includes a separator. This application is not particularly limited to the type of separator, and any separator with a porous structure having good chemical stability and mechanical stability, which is well-known, may be selected.

[0165] In some embodiments, the material of the separator may be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer thin film or a multi-layer composite thin film, and there is no particular limitation. When the separator is a multi-layer composite thin film, the materials of each layer may be the same or different, and there is no particular limitation.

[0166] In some embodiments, the positive electrode plate, the negative electrode plate, and the separator may be used to manufacture an electrode assembly by a winding process or a lamination process.

[0167] In some embodiments, the secondary battery may include an outer package. This outer package may be used for packaging the above electrode assembly and electrolyte.

[0168] In some embodiments, the outer package of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The outer package of the secondary battery may be a pouch, such as a bag-shaped pouch. The material of the pouch may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0169] [Secondary battery] This application is not particularly limited with respect to the shape of the secondary battery, and it may be cylindrical, square, or any other arbitrary shape. For example, FIG. 2 shows a secondary battery 5 having a square structure as an example. The secondary battery may be a sodium ion battery, a magnesium ion battery, or a potassium ion battery.

[0170] In some embodiments, referring to FIG. 3, the exterior body may include a case 51 and a cover plate 53. Here, the case 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates surround to form an accommodation cavity. The housing 51 has an opening communicating with the accommodation cavity, and the cover plate 53 can close the accommodation cavity by covering the opening. The positive electrode plate, the negative electrode plate, and the separator can form an electrode assembly 52 by a winding process or a lamination process. The electrode assembly 52 is packaged in the accommodation cavity. The electrolyte infiltrates the electrode assembly 52. The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and those skilled in the art can select according to the actual specific requirements.

[0171] [Battery module] In some embodiments, the secondary battery may be assembled into a battery module, and the number of secondary batteries included in the battery module may be one or more. The specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0172] FIG. 4 shows a battery module 4 as an example. Referring to FIG. 4, 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 according to any other method. Further, the plurality of secondary batteries 5 may be fixed with a fastener.

[0173] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of secondary batteries 5 are accommodated in the accommodation space.

[0174] [Battery Pack] In some embodiments, the battery module may be further assembled into a battery pack. The number of battery modules included in the battery pack may be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery pack.

[0175] FIGS. 5 and 6 show a battery pack 1 as an example. Referring to FIGS. 5 and 6, the battery pack 1 may include a battery box and a plurality of battery modules 4 installed in the battery box. The battery box includes an upper housing 2 and a lower housing 3. The upper housing 2 is provided to cover the lower housing 3 and can form a sealed space for accommodating the battery module 4. The plurality of battery modules 4 may be arranged in the battery box according to any method.

[0176] [Power Consumption Device] In one embodiment of the present application, a power consumption device is provided, which includes at least one of the secondary battery, battery module, or battery pack of any embodiment.

[0177] The power consumption device includes at least one of the secondary battery, battery module, or battery pack according to the present application. The secondary battery, battery module, or battery pack may be used as a power source for the power consumption device or as an energy storage unit of the power consumption device. The power consumption device may include, but is not limited to, mobile devices (such as mobile phones, notebook computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), trains, ships, satellites, energy storage systems, etc.

[0178] As a power consumption device, a secondary battery, a battery module, or a battery pack can be selected according to the demand in use.

[0179] FIG. 7 shows a power consumption device as an example. The power consumption device is, for example, a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the demand for high power and high energy density of the secondary battery of the power consumption device, a battery pack or a battery module can be adopted.

[0180] Another example of the device may be a mobile phone, a tablet computer, a notebook computer, etc. The device is generally required to be lightweight, and a secondary battery can be adopted as a power source.

[0181] Examples Hereinafter, examples of the present application will be described. The examples described below are illustrative only and are merely for interpreting the present application, and should not be construed as a limitation to the present application. When specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature of the technical field or the product instruction manual are followed. For the reagents or instruments used, those not specified by the manufacturer are all common products that can be purchased commercially.

[0182] I. Manufacturing method Example 1 1) Manufacture of adhesive Manufacture of B-block: Using a RAFT chain transfer agent (CTA-alkyne) as a chain transfer agent, a polymerization reaction is carried out to produce an alkynyl group-terminated polyvinylidene fluoride. Here, the structural formula of the RAFT chain transfer agent is as shown below. JPEG2025516733000014.jpg2888

[0183] 4 g of vinylidene fluoride was weighed, 500 ml of tetrahydrofuran was taken and added to a four-necked flask. A large amount of nitrogen gas was introduced, the stirring speed was gradually increased to 1200 rpm, a RAFT chain transfer agent (CTA-alkyne) of 1% of the monomer mass and azobisisobutyronitrile of 0.1% of the monomer mass were added, and the temperature was raised to 75 °C. After reacting for 6 hours, the reaction was stopped by cooling in liquid nitrogen, and the solution was precipitated in a large amount of excess methanol. The polymer was collected by filtration and reprecipitated twice from chloroform using methanol. The obtained product was vacuum dried at room temperature overnight to remove all traces of residual solvent, and polyvinylidene fluoride having an alkynyl group at the end, that is, a B-block polymer was obtained.

[0184] The reaction process for producing the B-block polymer is as shown below. JPEG2025516733000015.jpg43160

[0185] Production of A-block: Using azide as an initiator, a polymerization reaction was carried out to produce azide-terminated poly(acrylonitrile-butyl methacrylate-styrene). 1% of the monomer mass of 4-(chloromethyl)benzoyl peroxide was dissolved in 300 ml of anhydrous acetonitrile, and the solution was introduced into a high-pressure reactor and purged with N 2 for 30 minutes. Then, at room temperature, acrylonitrile monomer, butyl methacrylate monomer and styrene monomer were weighed in a molar ratio of 8:1:1 and transferred to the reactor respectively. The temperature inside the reactor was raised to 90 °C, and the reaction mixture was stirred at a speed of 500 rpm for another 3 hours. The reactor was cooled to room temperature with water and depressurized to remove unreacted monomers. The solvent was removed under vacuum, and the obtained solid was washed several times with chloroform to remove initiator residues. Finally, the polymer was vacuum dried at 45 °C to obtain a white product. 3 mmol of chlorine-terminated poly(acrylonitrile-butyl methacrylate-styrene) and sodium azide (NaN 3) 60 mmol was dissolved in 600 ml of N,N-dimethylformamide (DMF) and stirred at 60 °C overnight. The polymer solution was concentrated and precipitated three times in a mixed solvent (with a volume ratio of methanol to water of 1:1). Then, the pale yellow product was vacuum dried at 45 °C to obtain poly(acrylonitrile-butyl methacrylate-styrene) containing azide groups at both ends, i.e., an A-block polymer.

[0186] Preparation of BAB type block copolymer: Poly(acrylonitrile-butyl methacrylate-styrene) having azide groups at both ends, polyvinylidene fluoride having an alkynyl group at the end, and cuprous bromide were added to a dried Schlenk tube in a molar ratio of 1:2.5:4. After degassing, 4 ml of anhydrous N,N-dimethylformamide (DMF) and 0.14 mmol of N,N,N’,N,’N’’-pentamethyldiethylenetriamine (PMDETA) were added. The reaction was carried out with stirring at 60 °C for 3 days and stopped by exposure to air. The reaction mixture was filtered through a neutral aluminum oxide column to remove the copper catalyst, the solution was concentrated under reduced pressure, precipitated in 20 times the excess of a mixed solvent (with a volume ratio of methanol to water of 1:1), filtered to recover the product, and vacuum dried to obtain a polyvinylidene fluoride-poly(acrylonitrile-butyl methacrylate-styrene)-polyvinylidene fluoride block copolymer with a weight average molecular weight of 1.2 million, which was used as a battery adhesive.

[0187] 2) Preparation of the positive electrode plate Lithium nickel cobalt manganese (NCM) material, conductive agent carbon black, the adhesive prepared in Example 1, and N-methylpyrrolidone (NMP) were stirred and uniformly mixed in a weight ratio of 96.9:2.1:1:21 to obtain a positive electrode slurry. The solid content of the slurry was 73%. Then, the positive electrode slurry was uniformly coated on a positive electrode current collector, and after drying, cold pressing, and slitting, a positive electrode plate was obtained.

[0188] 3) Preparation of the negative electrode plate Artificial graphite as the active material, carbon black as the conductive agent, styrene-butadiene rubber (SBR) as the adhesive, and sodium carboxymethyl cellulose (CMC-Na) as the thickener were dissolved in deionized water as the solvent at a weight ratio of 96.2:0.8:0.8:1.2 and uniformly mixed to produce a negative electrode slurry. The negative electrode slurry was uniformly coated on the copper foil of the negative electrode current collector one or several times, and then dried, cold pressed, and slit processed to obtain a negative electrode plate.

[0189] 4) Separator A polypropylene membrane was used as the separator.

[0190] 5) Preparation of electrolyte In a glove box under an argon gas atmosphere (H 2 O < 0.1 ppm, O 2 < 0.1 ppm), the organic solvents ethylene carbonate (EC) / ethyl methyl carbonate (EMC) were uniformly mixed at a volume ratio of 3 / 7, and 12.5% LiPF 6 lithium salt was added and dissolved in the organic solvent, and uniformly stirred to obtain the electrolyte of Example 1.

[0191] 6) Preparation of battery The positive electrode plate, the separator, and the negative electrode plate were laminated in sequence, and the separator was positioned between the positive and negative electrode plates to perform an isolation function, and then wound to obtain a bare cell. Tabs were welded to the bare cell, the bare cell was placed in an aluminum case, baked at 80 °C to remove moisture, immediately injected with the electrolyte and sealed to obtain a non-charged battery. For the non-charged battery, through processes such as standing, hot and cold pressing, formation, shaping, and capacity measurement in sequence, the finished lithium-ion battery of Example 1 was obtained.

[0192] Examples 2 to 5 The batteries of Examples 2 to 5 were similar to the battery manufacturing method of Example 1, but only the weight average molecular weight and its mass content of the A-block and B-block were adjusted respectively, and the weight average molecular weight of the polyvinylidene fluoride-poly(acrylonitrile-butyl methacrylate-styrene)-polyvinylidene fluoride block copolymer was maintained at 1.2 million. The specific parameters are as shown in Table 1.

[0193] Examples 6 to 9 The batteries of Examples 6 to 9 were similar to the battery manufacturing method of Example 1, but by adjusting the weight average molecular weight and its mass content of the A-block and B-block respectively, the weight average molecular weight of the polyvinylidene fluoride-poly(acrylonitrile-butyl methacrylate-styrene)-polyvinylidene fluoride block copolymer was adjusted. The specific parameters are as shown in Table 1.

[0194] Example 10 The battery of Example 10 was similar to the battery manufacturing method of Example 1, but the A-block was replaced with polyacrylamide having azide groups at both ends. The specific parameters are as shown in Table 1, and the manufacturing method is as follows.

[0195] 4-(Chloromethyl)benzoyl peroxide at 1% by mass of the monomer was dissolved in 300 ml of anhydrous acetonitrile, and the solution was introduced into a high-pressure reactor and purged with N 2 for 30 minutes. Then, at room temperature, a certain molar amount of acrylamide monomer was weighed and transferred to the reactor. The temperature inside the reactor was raised to 90 °C, and the reaction mixture was further stirred at a speed of 500 rpm for 3 hours. The reactor was cooled to room temperature with water and depressurized to remove unreacted monomers. The solvent was removed under vacuum, and the obtained solid was washed several times with chloroform to remove initiator residues. Finally, the polymer was dried under vacuum at 45 °C to obtain a white product. 3 mmol of chlorine-terminated polyacrylamide and sodium azide (NaN 3) 60 mmol was dissolved in 600 ml of N,N-dimethylformamide (DMF) and stirred at 60 °C overnight. The polymer solution was concentrated and precipitated three times in a mixed solvent (volume ratio of methanol to water is 1:1). Then, the pale yellow product was vacuum dried at 45 °C to obtain polyacrylamide with azide groups at both ends, that is, A-block polymer.

[0196] Example 11 The battery of Example 11 was similar to the battery manufacturing method of Example 1, but the A-block was replaced with poly(acrylic acid-acrylamide-ethyl methacrylate) having azide groups at both ends. The specific parameters are as shown in Table 1, and the manufacturing method is as follows.

[0197] 4-(Chloromethyl)benzoyl peroxide at 1% by mass of the monomer was dissolved in 300 ml of anhydrous acetonitrile, and the solution was introduced into a high-pressure reactor and purged with N 2 for 30 minutes. Then, at room temperature, acrylic acid monomer, acrylamide monomer, and ethyl methacrylate monomer were weighed in a molar ratio of 8:1:1 and transferred to the reactor respectively. The temperature inside the reactor was raised to 90 °C, and the reaction mixture was further stirred at a speed of 500 rpm for 3 hours. The reactor was cooled to room temperature with water and depressurized to remove unreacted monomers. The solvent was removed under vacuum, and the obtained solid was washed multiple times with chloroform to remove initiator residues. Finally, the polymer was vacuum dried at 45 °C to obtain a white product. 3 mmol of chlorine-terminated poly(acrylic acid-acrylamide-ethyl methacrylate) and sodium azide (NaN 3 ) 60 mmol was dissolved in 600 ml of N,N-dimethylformamide (DMF) and stirred at 60 °C overnight. The polymer solution was concentrated and precipitated three times in a mixed solvent (volume ratio of methanol to water is 1:1). Then, the pale yellow product was vacuum dried at 45 °C to obtain poly(acrylic acid-acrylamide-ethyl methacrylate) with azide groups at both ends, that is, A-block polymer.

[0198] Example 12 The battery of Example 12 is similar to the battery manufacturing method of Example 1, but the A-block is replaced with poly(acrylonitrile-acrylamide-acrylic acid ester) having azide groups at both ends. The specific parameters are as shown in Table 1, and the manufacturing method is as follows.

[0199] 4-(Chloromethyl)benzoyl peroxide at 1% of the monomer mass was dissolved in 300 ml of anhydrous acetonitrile, and the solution was introduced into a high-pressure reactor and purged with N 2 for 30 minutes. Then, at room temperature, acrylonitrile monomer, acrylamide monomer, and acrylic acid ester monomer were weighed in a molar ratio of 8:1:1 and transferred to the reactor respectively. The temperature inside the reactor was raised to 90 °C, and the reaction mixture was further stirred at a speed of 500 rpm for 3 hours. The reactor was cooled to room temperature with water and depressurized to remove unreacted monomers. The solvent was removed under vacuum, and the obtained solid was washed multiple times with chloroform to remove initiator residues. Finally, the polymer was dried under vacuum at 45 °C to obtain a white product. 3 mmol of chlorine-terminated poly(acrylonitrile-acrylamide-acrylic acid ester) and 60 mmol of sodium azide (NaN 3 ) were dissolved in 600 ml of N,N-dimethylformamide (DMF), and stirred at 60 °C overnight. The polymer solution was concentrated and precipitated 3 times in a mixed solvent (the volume ratio of methanol to water is 1:1). Then, a pale yellow product was dried under vacuum at 45 °C to obtain poly(acrylonitrile-acrylamide-acrylic acid ester) containing azide groups at both ends, that is, A-block polymer.

[0200] Example 13 The battery of Example 13 is similar to the battery manufacturing method of Example 1, but the A-block is replaced with polystyrene having azide groups at both ends. The specific parameters are as shown in Table 1, and the manufacturing method is as follows.

[0201] 4-(Chloromethyl)benzoyl peroxide at 1% of the monomer mass was dissolved in 300 ml of anhydrous acetonitrile, and the solution was introduced into a high-pressure reactor and purged with N2 It was purged for 30 minutes at [conditions not specified]. Then, at room temperature, a certain molar amount of styrene monomer was weighed and transferred to the reactor. The temperature inside the reactor was raised to 90 °C, and the reaction mixture was further stirred at a speed of 500 rpm for 3 hours. The reactor was cooled to room temperature with water, and the pressure was reduced to remove unreacted monomers. The solvent was removed under vacuum, and the resulting solid was washed multiple times with chloroform to remove initiator residues. Finally, the polymer was dried under vacuum at 45 °C to obtain a white product. 3 mmol of chlorine-terminated polystyrene and 60 mmol of sodium azide (NaN 3 ) were dissolved in 600 ml of N,N-dimethylformamide (DMF), and stirred at 60 °C overnight. The polymer solution was concentrated and precipitated three times in a mixed solvent (with a volume ratio of methanol to water of 1:1). Then, a pale yellow product was dried under vacuum at 45 °C to obtain polystyrene containing azide groups at both ends, that is, A-block polymer.

[0202] Example 14 The battery of Example 14 was similar to the battery manufacturing method of Example 1, but the A-block was replaced with polyethylene oxide having azide groups at both ends. The specific parameters are as shown in Table 1, and the manufacturing method is as follows.

[0203] Ethylene oxide monomer, water, and potassium hydroxide (KOH) were added to a high-pressure stirring kettle in a molar ratio of 1:0.1:0.02. After introducing a large amount of nitrogen gas to remove air, the pressure was increased to 0.3 MPa, the stirring speed was gradually increased to 1000 revolutions per minute, and the temperature was raised to 80 °C. After reacting for 6 hours, the pressure inside the kettle decreased. The pressure was briefly increased to remove excess monomers, and after purification, polyethylene oxide was obtained. 4-(Chloromethyl)benzoyl peroxide, which was 1% of the monomer mass, was dissolved in 300 ml of anhydrous acetonitrile, and the solution was introduced into a high-pressure reactor. Nitrogen gas (N 2) It was purged for 30 minutes. Then, the above polyethylene oxide was transferred to the reactor at room temperature. The temperature inside the reactor was raised to 90 °C, and the reaction mixture was further stirred at a speed of 500 rpm for 3 hours. The reactor was cooled with water to room temperature and depressurized to remove unreacted monomers. The solvent was removed under vacuum, and the obtained solid was washed several times with chloroform to remove initiator residues. Finally, the polymer was dried under vacuum at 45 °C to obtain a white product, 3 mmol of chlorine-terminated polyethylene oxide and sodium azide (NaN 3 ) 60 mmol were dissolved in 600 ml of N,N-dimethylformamide (DMF), and stirred at 60 °C overnight. The polymer solution was concentrated and precipitated three times in a mixed solvent (the volume ratio of methanol to water is 1:1). Then, the pale yellow product was dried under vacuum at 45 °C to obtain polyethylene oxide containing azide groups at both ends, that is, A-block polymer.

[0204] Example 15 The battery of Example 15 was similar to the battery manufacturing method of Example 1, but the A-block was replaced with polyvinyl alcohol. The specific parameters are as shown in Table 1, and the manufacturing method is as follows.

[0205] 4-(Chloromethyl)benzoyl peroxide at 1% of the monomer mass was dissolved in 300 ml of anhydrous acetonitrile, and the solution was introduced into a high-pressure reactor, N 2It was purged for 30 minutes. Then, at room temperature, a certain molar amount of vinyl acetate monomer was weighed and transferred to the reactor. The temperature inside the reactor was raised to 90 °C, and the reaction mixture was further stirred at a speed of 500 rpm for 3 hours. The reactor was cooled to room temperature with water, and the pressure was reduced to remove unreacted monomers. The solvent was removed under vacuum, and the obtained solid was washed several times with chloroform to remove initiator residues. Finally, the polymer was dried under vacuum at 45 °C to obtain a white product. Further, the chlorine-terminated polyvinyl acetate obtained by the above reaction was dissolved in a mixed solvent (the volume ratio of methanol to water is 79.5:0.5), where the mass fraction of polyvinyl acetate is 20%. At a temperature of 30 °C, a sodium hydroxide solution with a mass fraction of 1.5% was added, and alcoholysis was carried out for 2 hours. After thorough washing and filtration, chlorine-terminated polyvinyl alcohol was obtained. 3 mmol of chlorine-terminated polyvinyl alcohol and 60 mmol of sodium azide (NaN3) were dissolved in 600 ml of N,N-dimethylformamide (DMF), and stirred at 60 °C overnight. The polymer solution was concentrated and precipitated three times in a mixed solvent (the volume ratio of methanol to water is 1:1). Then, the pale yellow product was dried under vacuum at 45 °C to obtain polyvinyl alcohol containing azide groups at both ends, that is, A-block polymer.

[0206] Example 16 The battery of Example 16 is similar to the battery manufacturing method of Example 1, but the A-block is replaced with poly(acrylonitrile-acrylic acetate), and the specific parameters are as shown in Table 1. The manufacturing method is as follows.

[0207] 4-(Chloromethyl)benzoyl peroxide with a monomer mass of 1% was dissolved in 300 ml of anhydrous acetonitrile, and the solution was introduced into a high-pressure reactor, N 2It was purged for 30 minutes. Then, at room temperature, acrylonitrile monomer and acrylic acetate monomer were weighed in a molar ratio of 8:1 and transferred to the reactor respectively. The temperature inside the reactor was raised to 90 °C, and the reaction mixture was further stirred at a speed of 500 rpm for 3 hours. The reactor was cooled to room temperature with water and depressurized to remove unreacted monomers. The solvent was removed under vacuum, and the obtained solid was washed multiple times with chloroform to remove initiator residues. Finally, the polymer was dried in vacuo at 45 °C to obtain a white product. 3 mmol of chlorine-terminated poly(acrylonitrile-acrylic acetate) and sodium azide (NaN 3 ) 60 mmol were dissolved in 600 ml of N,N-dimethylformamide (DMF), stirred at 60 °C overnight. The polymer solution was concentrated and precipitated three times in a mixed solvent (the volume ratio of methanol to water is 1:1). Then, the pale yellow product was dried in vacuo at 45 °C to obtain poly(acrylonitrile-acrylic acetate) containing azide groups at both ends, that is, A-block polymer.

[0208] Example 17 The battery of Example 17 is similar to the battery manufacturing method of Example 1, but the B-block is replaced with a polyvinyl fluoride block. The specific parameters are as shown in Table 1, and the manufacturing method is as follows.

[0209] 4 g of vinyl fluoride was weighed, 500 ml of tetrahydrofuran was taken and added to a four-necked flask. A large amount of nitrogen gas was introduced, the stirring speed was gradually increased to 1200 rpm, a RAFT chain transfer agent (CTA-alkyne) of 1% of the monomer mass and azobisisobutyronitrile of 0.1% of the monomer mass were added, and the temperature was raised to 75 °C. After reacting for 6 hours, the reaction was stopped by cooling in liquid nitrogen, and the solution was precipitated in a large amount of excess methanol. The polymer was collected by filtration and precipitated twice again from chloroform using methanol. The obtained product was dried in vacuo at room temperature overnight to remove all trace amounts of residual solvent, and polyvinyl fluoride having an alkynyl group at the end, that is, B-block polymer, was obtained.

[0210] Example 18 The battery of Example 18 is similar to the battery manufacturing method of Example 1, but the B-block is replaced with a polytetrafluoroethylene block. The specific parameters are as shown in Table 1, and the manufacturing method is as follows.

[0211] Weigh 4 g of tetrafluoroethylene, take 500 ml of tetrahydrofuran, add it to a four-necked flask, introduce a large amount of nitrogen gas, gradually increase the stirring speed to 1200 rpm, add a RAFT chain transfer agent (CTA-alkyne) of 1% of the monomer mass and azobisisobutyronitrile of 0.1% of the monomer mass, and raise the temperature to 75 °C. After reacting for 6 hours, the reaction was stopped by cooling in liquid nitrogen, and the solution was precipitated in a large amount of excess methanol. The polymer was collected by filtration and reprecipitated twice from chloroform using methanol. The obtained product was vacuum dried at room temperature overnight to remove all trace amounts of residual solvent, and polytetrafluoroethylene having an alkynyl group at the end, that is, a B-block polymer, was obtained.

[0212] Comparative Example 1 The battery of Comparative Example 1 is similar to the battery manufacturing method of Example 1, but the adhesive is polyvinylidene fluoride, purchased from the Solvay Group, and the brand is 5130. The specific parameters are as shown in Table 1.

[0213] Comparative Example 2 The battery of Comparative Example 2 is similar to the battery manufacturing method of Comparative Example 1, but the adhesive is poly(acrylonitrile-butyl methacrylate-styrene), and the manufacturing method of poly(acrylonitrile-butyl methacrylate-styrene) is as follows.

[0214] Dissolve 4-(chloromethyl)benzoyl peroxide of 1% of the monomer mass in 300 ml of anhydrous acetonitrile, and introduce the solution into a high-pressure reactor, N 2It was purged for 30 minutes. Then, at room temperature, acrylonitrile monomer, butyl methacrylate monomer, and styrene monomer were weighed in a molar ratio of 8:1:1 and added to 300 ml of anhydrous acetonitrile, respectively. The temperature inside the reactor was raised to 55 °C, and the reaction mixture was further stirred at a speed of 500 rpm for 12 hours. The reactor was cooled to room temperature with water and depressurized to remove unreacted monomers. The solvent was removed under vacuum, and the obtained solid was washed multiple times with chloroform to remove initiator residues. Finally, the polymer was dried under vacuum at 45 °C to obtain a white product, namely poly(acrylonitrile-butyl methacrylate-styrene).

[0215] Comparative Example 3 The battery of Comparative Example 3 was similar to the battery manufacturing method of Comparative Example 1, but the adhesive was a blend of polyvinylidene fluoride and poly(acrylonitrile-butyl methacrylate-styrene). The specific parameters are as shown in Table 1, and the manufacturing method is as follows.

[0216] Blend: Poly(acrylonitrile-butyl methacrylate-styrene) in Comparative Example 2 and polyvinylidene fluoride in Comparative Example 1 were blended at a molar ratio of 6:4 to obtain an adhesive of a blend of polyvinylidene fluoride and polyvinyl alcohol.

[0217] Comparative Example 4 The battery of Comparative Example 4 was similar to the battery manufacturing method of Comparative Example 3, but the adhesive was a blend of polyvinylidene fluoride and polyacrylamide. The specific parameters are as shown in Table 1.

[0218] Comparative Example 5 The battery of Comparative Example 5 was similar to the battery manufacturing method of Comparative Example 3, but the adhesive was a blend of polyvinylidene fluoride and poly(acrylic acid-acrylamide-ethyl methacrylate). The specific parameters are as shown in Table 1.

[0219] Comparative Example 6 The battery of Comparative Example 6 was similar to the battery manufacturing method of Comparative Example 3, but the adhesive was a blend of polyvinylidene fluoride and polyvinyl alcohol, and the specific parameters are as shown in Table 1.

[0220] II. Performance Tests 1. Polymer Property Tests 1) Weight-Average Molecular Weight Test Method A Waters 2695 Isocratic Time HPLC type gel chromatograph (differential refractive index detector 2141) was adopted. A polystyrene solution sample with a mass fraction of 3.0% was used as a reference, and the corresponding column (oil-based: Styragel Time T5DMF7.8*300mm + Styragel Time T4) was selected. A 3.0% polymer gel solution was prepared with the purified N-methylpyrrolidone (NMP) solvent, and the prepared solution was left standing for one day for use. When testing, first, suck up tetrahydrofuran with a syringe, wash it, and repeat several times. Then, suck up 5 ml of the experimental solution, discharge the air in the syringe, wipe the needle tip clean, and finally, slowly inject the sample solution into the sample inlet. Data was acquired after the indication value became stable.

[0221] 2. Electrode Plate Performance Tests 1) Membrane Resistance Test Small discs with a diameter of 3 mm were cut from the left, middle, and right of the electrode plate respectively. Turn on the indicator lamp of the Yuaneng Technology electrode plate resistance measuring instrument, place it at the appropriate position of the "probe" of the membrane resistance measuring instrument, click the "start" button, and read the value after the indication value becomes stable. Two positions were tested for each small disc, and finally, the average value of six measurements was calculated as the membrane resistance of the electrode plate.

[0222] 2) Adhesion Test The positive electrode plate was cut into test samples with a size of 20 mm × 100 mm. In preparation for use, the electrode plate was adhered to one side of the positive electrode film layer with double-sided tape, and then rolled and compacted to ensure complete adhesion between the double-sided tape and the electrode plate. The other side of the double-sided tape was attached to the surface of the stainless steel. One end of the sample was bent in the reverse direction, and the bending angle was 180°. A high-strength iron tensile machine was used for the test. One end of the stainless steel was fixed to the fixture below the tensile machine, and the bent end of the sample was fixed to the fixture above. The angle of the sample was adjusted to ensure that the upper and lower ends were in a vertical position. Then, at a speed of 50 mm / min, the sample was pulled until the current collector was completely peeled off from the positive electrode film, and the displacement and acting force in this process were recorded. The force when the force was balanced was divided by the width of the electrode plate adhered to the double-sided tape (the width direction of the electrode plate is perpendicular to the peeling direction) to obtain the adhesion force of the electrode plate per unit length. The width of the electrode plate in this test was 20 mm.

[0223] 3) Flexibility test The positive electrode plate after cold pressing was cut into test samples with a size of 20 × 100 mm. After folding it in half in the positive direction, it was flattened with a 2 kg roll, and then unfolded to check whether light transmission occurred in the gap towards the light. If no light transmission occurred, it was folded in half in the reverse direction, flattened with a 2 kg roll, and inspected again towards the light. This was repeated. When a light transmission phenomenon occurred in the gap, the number of times of folding in half was recorded. The test was repeated 3 times, and the average value was taken as the reference data for the flexibility of the electrode plate.

[0224] 3. Battery performance test 1) DC impedance test of the battery The DC impedance test process of the battery is as follows. At 25°C, the battery is charged to 4.3V at a constant current of 1 / 3C, and then charged at a constant voltage of 4.3V until the current reaches 0.05C. After standing for 5 minutes, the voltage V1 is recorded. Then, it is discharged at 1 / 3C for 30 seconds, and the voltage V2 is recorded. The internal resistance DCR1 of the battery after the first cycle is obtained by (V2 - V1) / (1 / 3C). The above steps are repeated for the same battery, and the internal resistance DCRn (n = 1, 2, 3... 100) of the battery after the nth cycle is recorded. Taking the values of the 100 points of DCR1, DCR2, DCR3... DCR100 as the vertical coordinates and the corresponding cycle numbers as the horizontal coordinates, a curve diagram of the battery discharge DCR and the cycle number is obtained.

[0225] In this test process, the first cycle corresponds to n = 1, the second cycle corresponds to n = 2,..., and the 100th cycle corresponds to n = 100. The internal resistance increase ratio of the battery in Example 1 in Table 2 = (DCRn - DCR1) / DCR1 * 100%. The test processes of the comparative example and other examples are the same as above. The data in Table 2 are the data measured after 100 cycles under the above test conditions.

[0226] 2) Battery cycle capacity retention rate test The battery capacity retention rate test process is as follows. At 25°C, the manufactured battery is charged to 4.3V at a constant current of 1 / 3C, and then charged at a constant voltage of 4.3V until the current reaches 0.05C. After leaving it for 5 minutes, it is discharged to 2.8V at 1 / 3C, and the obtained capacity is taken as the initial capacity C0. While repeating the above steps for the same battery and recording the discharge capacity Cn of the battery after the nth cycle, the cycle-after battery capacity retention rate Pn = Cn / C0 × 100% after each cycle. Taking the values of 500 points, namely P1, P2... P500, as the vertical coordinates and the corresponding cycle numbers as the horizontal coordinates, a curve diagram of the battery capacity retention rate and the cycle number is obtained. In this test process, the first cycle corresponds to n = 1, the second cycle corresponds to n = 2,..., and the 500th cycle corresponds to n = 500. The battery capacity retention rate data corresponding to the examples or comparative examples in Table 2 are the data measured after 500 cycles under the above test conditions, that is, the value of P500. The test processes of the comparative examples and other examples are the same as above.

[0227] 3) Metal deposition amount test At room temperature, the manufactured lithium-ion battery is subjected to the first charge and discharge at a current of 0.5C (i.e., the current value that completely discharges the theoretical capacity within 2 hours). The charge is a constant current and constant voltage charge, the stop voltage is 4.2V, the cut-off current is 0.05C, the discharge stop voltage is 2.8V, and after leaving the battery for 24 hours, it is charged to 4.2V at a constant current and constant voltage of 0.5C, and then the fully charged battery is discharged at a current of 1C. The discharge stop voltage is 2.8V in all cases. The battery core is disassembled, the negative electrode plate is taken out, and the inductively coupled plasma (ICP) method is adopted to test the deposition amounts of metals Co and Mn.

[0228] 4) 45°C capacity retention rate test Charge to 4.2V at a constant current of 1C, and then charge at a constant voltage of 4.2V until the current reaches 0.05C. Leave it for 10 minutes, and then discharge to the cut-off voltage of 2.8V at a constant current of 1C, the capacity CAP before storage 1Record it, charge it at a constant current of 1C until cutoff at 4.2V, and further charge it at a constant voltage of 4.2V until the current reaches 0.05C. After leaving the lithium-ion battery in an oven at 45°C for 120 days, take it out and discharge it at a constant current of 1C until 2.8V. The capacity CAP after storage 2 Record it, and calculate the storage capacity retention rate of the lithium-ion secondary battery according to the following formula: Storage capacity retention rate of lithium-ion secondary battery (%) = CAP 2 / CAP 1 × 100%.

[0229] III. Analysis of test results of each example and comparative example Manufacture the batteries of each example and comparative example according to the above method, measure each performance parameter, and the results are as shown in Table 1 and Table 2 below.

[0230] Table 1 Manufacturing parameters and weight-average molecular weight test results of examples and comparative examples JPEG2025516733000016.jpg248154 JPEG2025516733000017.jpg144161

[0231] Table 2 Performance test results of examples and comparative examples JPEG2025516733000018.jpg251161 JPEG2025516733000019.jpg140160

[0232] As can be seen from the above results, the adhesives in Examples 1 to 18 are BAB type block copolymers, containing A-blocks and B-blocks. The B-block contains at least one structural unit derived from vinylidene fluoride, vinyl fluoride or tetrafluoroethylene, and the A-block contains at least one structural unit derived from acrylonitrile, butyl methacrylate, styrene, acrylamide, acrylic acid, ethyl methacrylate, acrylate, ethylene oxide, vinyl alcohol, or acrylic acetate. As can be seen from the comparison between Examples 1 to 18 and Comparative Example 1, compared with using a pure vinylidene fluoride polymer as an adhesive, poly(vinylidene fluoride-poly(acrylonitrile-butyl methacrylate-styrene)-vinylidene fluoride) block copolymer, poly(vinylidene fluoride-polyacrylamide-vinylidene fluoride) block copolymer, poly(vinylidene fluoride-poly(acrylic acid-acrylamide-ethyl methacrylate)-vinylidene fluoride) block copolymer, poly(vinylidene fluoride-poly(acrylonitrile-acrylamide-acrylate)-vinylidene fluoride) block copolymer, poly(vinylidene fluoride-polystyrene-vinylidene fluoride) block copolymer, poly(vinylidene fluoride-polyethylene oxide-vinylidene fluoride) block copolymer, poly(vinylidene fluoride-polyvinyl alcohol-vinylidene fluoride) block copolymer, poly(vinylidene fluoride-poly(acrylonitrile-acrylic acetate)-vinylidene fluoride) block copolymer, poly(vinyl fluoride-poly(acrylonitrile-butyl methacrylate-styrene)-vinyl fluoride) block copolymer, and poly(tetrafluoroethylene-poly(acrylonitrile-butyl methacrylate-styrene)-tetrafluoroethylene) BAB type block copolymer as adhesives can effectively improve the adhesion of the electrode plate, reduce the DC impedance growth rate and metal deposition amount of the battery, achieve both low film resistance and excellent flexibility on the electrode plate, and achieve both high cycle capacity retention rate and 45°C capacity retention rate in the battery.

[0233] The adhesives in Examples 1 to 18 are BAB-type block copolymers, which include A-blocks and B-blocks. The B-blocks contain fluorine-containing polymers, and the A-blocks contain non-fluorine-containing polymers. The adhesives in Comparative Examples 3 to 6 are blends of fluorine-containing polymers and non-fluorine-containing polymers. As can be seen from the comparison between Examples 1 to 18 and Comparative Examples 3 to 6, compared with using a blend of fluorine-containing polymer and non-fluorine-containing polymer as an adhesive, the above BAB-type block copolymer can effectively improve the adhesiveness and flexibility of the electrode plate, reduce the DC impedance growth rate and metal deposition amount of the battery, ensure a low film resistance of the electrode plate, and achieve both a high cycle capacity retention rate and a 45°C capacity retention rate of the battery.

[0234] The adhesives in Examples 10 to 12 are BAB-type block copolymers, which include A-blocks and B-blocks. The B-blocks contain structural units derived from vinylidene fluoride, and the A-blocks contain at least structural units derived from acrylamide. As can be seen from the comparison between Examples 10 to 12 and Comparative Example 1, compared with using a pure polyvinylidene fluoride polymer as an adhesive, the above BAB-type block copolymer can effectively improve the adhesive strength and flexibility of the electrode plate, reduce the film resistance of the electrode plate, increase the cycle capacity retention rate and 45°C capacity retention rate of the battery, and reduce the DC impedance growth rate and metal deposition amount of the battery.

[0235] In Examples 1 to 5, 12, and 16, the adhesive is a BAB-type block copolymer, which includes an A-block and a B-block. The B-block contains structural units derived from vinylidene fluoride, and the A-block contains at least structural units derived from acrylonitrile and structural units derived from butyl methacrylate, acrylic ester, or acryloacetic ester. As can be seen from the comparison between Examples 1 to 5, 12, 16 and Comparative Example 1, compared with using a pure polyvinylidene fluoride polymer as the adhesive, using the above BAB-type block copolymer as the adhesive can effectively improve the adhesion and flexibility of the electrode plate, reduce the membrane resistance of the electrode plate, reduce the DC impedance growth rate and metal deposition amount of the battery, and ensure that the battery has both a high cycle capacity retention rate and a 45°C capacity retention rate.

[0236] The adhesive of Example 4 is a BAB-type block copolymer, which includes an A-block and a B-block. The B-block contains structural units derived from vinylidene fluoride, and the A-block contains structural units derived from acrylonitrile, structural units derived from butyl methacrylate, and structural units derived from styrene. As can be seen from the comparison between Example 4 and Examples 10 to 16, using the polyvinylidene fluoride-poly(acrylonitrile-butyl methacrylate-styrene)-polyvinylidene fluoride BAB-type block copolymer as the adhesive can further significantly improve the adhesion and flexibility of the electrode plate, and can also further improve the cycle capacity retention rate and 45°C capacity retention rate of the battery.

[0237] The adhesive of Example 12 is a BAB-type block copolymer, which includes an A-block and a B-block. The B-block contains structural units derived from vinylidene fluoride, and the A-block includes structural units derived from acrylonitrile, structural units derived from acrylamide, and structural units derived from acrylic ester. As can be seen from the comparison between Example 12 and Examples 4, 10 to 11, 13 to 16, by using the poly(vinylidene fluoride)-poly(acrylonitrile-acrylamide-acrylic ester)-poly(vinylidene fluoride) block copolymer BAB-type block copolymer as the adhesive, the metal deposition amount of the battery can be significantly reduced.

[0238] As can be seen from the comparison between Examples 1 to 5 and Comparative Example 1, compared with using a pure poly(vinylidene fluoride) polymer as the adhesive, by using a BAB-type block copolymer with a mass content of the A-block of 40% to 60% as the adhesive, the adhesion and flexibility of the electrode plate can be improved, the membrane resistance of the electrode plate can be reduced, the cycle capacity retention rate of the battery can be increased, and the DC impedance growth rate and metal deposition amount of the battery can be reduced. As can be seen from the comparison between Examples 1 to 5 and Comparative Example 3, compared with using a blend of a fluorine-containing polymer and a non-fluorine-containing polymer as the adhesive, by using a BAB-type block copolymer with a mass content of the A-block of 40% to 60% as the adhesive, the adhesion and flexibility of the electrode plate can be improved, the DC impedance growth rate of the battery can be reduced, while ensuring a low membrane resistance for the electrode plate and a low metal deposition amount, a high cycle capacity retention rate, and a 45°C capacity retention rate for the battery.

[0239] As can be seen from the comparison between Examples 1, 6 to 9 and Comparative Example 1, by using a BAB-type block copolymer with a weight average molecular weight of 400,000 to 2,000,000 as an adhesive compared with the conventional PVDF adhesive, the adhesive strength of the electrode plate can be improved, the DC impedance growth rate of the battery can be reduced, while the electrode plate can have both a low film resistance and excellent flexibility, and the battery can have both a low metal deposition amount and a high cycle capacity retention rate. As can be seen from the comparison between Examples 1, 6 to 9 and Comparative Example 3, by using a BAB-type block copolymer with a weight average molecular weight of 400,000 to 2,000,000 as an adhesive compared with using a blend of a fluorine-containing polymer and a non-fluorine-containing polymer as an adhesive, the adhesive strength and flexibility of the electrode plate can be improved, the DC impedance growth rate of the battery can be reduced, while the electrode plate has a low film resistance, and the battery can have both a low metal deposition amount, a high cycle capacity retention rate and a 45°C capacity retention rate.

[0240] As can be seen from the comparison between Examples 1 to 5 and Comparative Example 1, by using a BAB-type block copolymer with a weight average molecular weight of 200,000 to 1,100,000 for the fluorine-containing block A-block and a weight average molecular weight of 100,000 to 500,000 for the B-block as an adhesive compared with using a pure polyvinylidene fluoride polymer as an adhesive, the adhesive strength and flexibility of the electrode plate can be improved, the film resistance of the electrode plate can be reduced, the cycle capacity retention rate and the 45°C capacity retention rate of the battery can be increased, and the DC impedance growth rate and the metal deposition amount of the battery can be reduced.

[0241] As can be seen from the comparison between Examples 1 to 5 and Comparative Example 3, by using a BAB-type block copolymer with a weight average molecular weight of 200,000 to 1,100,000 for the fluorine-containing block A-block and a weight average molecular weight of 100,000 to 500,000 for the B-block as an adhesive compared with using a blend of a fluorine-containing polymer and a non-fluorine-containing polymer as an adhesive, the adhesive strength and flexibility of the electrode plate can be improved, the DC impedance growth rate of the battery can be reduced, while the electrode plate can have a low film resistance, and the battery can have both a low metal deposition amount, a high cycle capacity retention rate and a 45°C capacity retention rate.

[0242] It should be noted that this application is not limited to the above embodiments. The above embodiments are illustrative, and embodiments that have substantially the same configuration as the technical idea within the scope of the technical solution of this application and exhibit the same effects are all included within the technical scope of this application. In addition, within the scope not departing from the spirit of this application, various modifications that can be conceived by those skilled in the art to the embodiments, and other forms constructed by combining some of the components in the embodiments are also included within the scope of this application.

Description of Reference Numerals

[0243] 1 Battery pack, 2 Upper housing, 3 Lower housing, 4 Battery module, 5 Secondary battery, 51 Case, 52 Electrode assembly, 53 Cover plate.

Claims

1. A BAB-type block copolymer, wherein the B-block contains a structural unit represented by Formula I, and the A-block contains one or more of a structural unit represented by Formula II and a structural unit represented by Formula III. Here, R 1 , R 2 , R 3 are each independently one or more selected from hydrogen, fluorine, and C 1-3 alkyl groups containing at least one fluorine atom, and R 4 , R 5 , R 6 are each independently selected from hydrogen and substituted or unsubstituted C 1-5 alkyl groups, and R 7 is selected from a carboxyl group, an ester group, a hydroxyl group, an amide group, a cyano group, and a substituted or unsubstituted aromatic group, and is characterized by a BAB-type block copolymer.

2. The A-block is R 7 The BAB type block copolymer according to claim 1, characterized in that it contains a structural unit represented by Formula II in which R is an amide group.

3. The A-block is R 7 is a structural unit represented by Formula II in which R is a cyano group, and R 7 is a structural unit represented by Formula II in which R is an ester group, The BAB type block copolymer according to claim 1, characterized by containing the same.

4. The A-block is R 7 is a structural unit represented by Formula II in which R is a cyano group, and R 7 is a structural unit represented by Formula II in which R is an ester group, and R 7 is a BAB-type block copolymer according to claim 1, characterized by containing a structural unit represented by Formula II in which R is a substituted or unsubstituted aromatic group.

5. The A-block is R 7 is a structural unit represented by Formula II in which R is a cyano group, and R 7 is a structural unit represented by Formula II in which R is an amide group, and R 7 is a structural unit represented by Formula II in which R is an ester group, and the BAB-type block copolymer according to claim 1, characterized in that it contains the same.

6. The BAB-type block copolymer according to claim 1, wherein the mass content of the A-block is 40% to 60% based on the total mass of the block copolymer.

7. The BAB-type block copolymer according to any one of claims 1 to 6, wherein the weight average molecular weight of the block copolymer is 400,000 to 2,000,000.

8. The BAB-type block copolymer according to any one of claims 1 to 6, wherein the weight average molecular weight of the A-block in the block copolymer is 200,000 to 1,100,000.

9. The BAB-type block copolymer according to any one of claims 1 to 6, wherein the weight average molecular weight of each B-block in the block copolymer is 100,000 to 500,000.

10. The BAB-type block copolymer according to any one of claims 1 to 6, wherein the structural unit represented by Formula I is derived from the group consisting of vinylidene fluoride, tetrafluoroethylene, vinyl fluoride, hexafluoropropene, and combinations thereof.

11. The BAB-type block copolymer according to claim 1, wherein the structural unit represented by Formula II is derived from the group consisting of acrylonitrile, crotononitrile, styrene, vinyl alcohol, acrylamide, ethyl acrylate, ethyl methacrylate, butyl methacrylate, methacrylic acid, ethacrylic acid, methacrylamide, N-methacrylamide, N-methylmethacrylamide, N-isopropylacrylamide, N-isopropylmethacrylamide, N-t-butylacrylamide, N-t-butyl (meth)acrylamide, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N,N-diethylacrylamide, N,N-diethylmethacrylamide, acrylic acid, vinyl benzoic acid, acrylic acetate ester, acrylic ester, and combinations thereof.

12. A method for producing a BAB-type block copolymer, Polymerize at least one monomer represented by formula V to produce a B-block, Here, R' 1 , R' 2 , R' 3 is each independently one or more selected from hydrogen, fluorine, and a C 1-3 alkyl group containing at least one fluorine atom, and a step for producing a B-block polymerize at least one monomer represented by formula VI to produce an A-block, or subject a monomer represented by formula VII to ring-opening polymerization to produce an A-block, Here, R' 4 , R' 5 , R' 6 are each independently selected from hydrogen, a substituted or unsubstituted C 1-5 alkyl group, and R' 7 is one selected from a carboxyl group, an ester group, a hydroxyl group, an amide group, a cyano group, a substituted or unsubstituted aromatic group, and the production step of the A-block and a step of producing a BAB-type block copolymer by bonding the B-block and the A-block, characterized in that it comprises a method for producing a BAB-type block copolymer.

13. The step of producing the B-block is reacting at least one monomer represented by formula V, a chain transfer agent, and a first initiator at a reaction temperature of 60 to 75 °C by reversible addition-fragmentation chain transfer polymerization for 4 to 6 hours to obtain a B-block having an azide group or an alkynyl group at the terminal, characterized in that the production method according to claim 12.

14. The step of producing the A-block is polymerizing at least one monomer represented by formula VI and a second initiator at a reaction temperature of 80 to 95 °C for 2.5 to 5 hours to obtain the A-block having an alkynyl group or an azide group at both terminals, characterized in that the production method according to claim 12 or 13.

15. The step of producing the A-block is reacting a monomer represented by formula VII, an ionic initiator, and water at a reaction temperature of 60 °C to 80 °C for 6 to 8 hours to obtain a product having hydroxyl groups at both terminals, and subjecting the hydroxyl groups of the product to a functionalization reaction to obtain the A-block having an alkynyl group or an azide group at both terminals, characterized in that the production method according to claim 12 or 13.

16. The production of the BAB-type block copolymer is mixing the A-block having an azide group or an alkynyl group at both terminals and the B-block having an alkynyl group or an azide group at the terminal, performing a click reaction, and producing a BAB-type block copolymer, wherein the terminal groups of the A-block and the B-block are different, characterized in that the production method according to any one of claims 12 to 15.

17. The chain transfer agent is a RAFT chain transfer agent containing a terminal alkynyl group or azide group, characterized in that the production method according to claim 12 or 13.

18. The second initiator is a symmetric difunctional initiator, characterized in that the production method according to claim 12 or 13.

19. The manufacturing method according to claim 12 or 13, wherein the first initiator is one or two selected from azobisisobutyronitrile and azobisisoheptanenitrile.

20. Application of the BAB type block copolymer according to any one of claims 1 to 11 in a secondary battery.

21. A positive electrode plate, comprising a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes a positive electrode active material, a conductive agent, and an adhesive, and the adhesive is a BAB type block copolymer according to any one of claims 1 to 11 or a BAB type block copolymer produced by the manufacturing method according to any one of claims 12 to 19. A positive electrode plate characterized by the above.

22. The positive electrode plate according to claim 21, wherein the adhesive force per unit length between the positive electrode film layer and the positive electrode current collector is 11 N / m or more.

23. The positive electrode plate according to claim 21, wherein after undergoing three or more bending tests, a light transmission phenomenon occurs in the positive electrode plate.

24. The positive electrode plate according to claim 21, wherein the film resistance of the positive electrode plate is 1.0 Ω or less.

25. A secondary battery, comprising an electrode assembly and an electrolytic solution, wherein the electrode assembly includes a separator, a negative electrode plate, and a positive electrode plate according to any one of claims 21 to 24. A secondary battery characterized by the above.

26. The secondary battery according to claim 25, wherein the secondary battery includes at least one of a lithium ion battery, a sodium ion battery, a magnesium ion battery, and a potassium ion battery.

27. A battery module, comprising the secondary battery according to claim 25 or 26. A battery module characterized by the above.

28. A battery pack, comprising the secondary battery according to claim 25 or 26 and the battery module according to claim 27. A battery pack characterized by the above.

29. A power consumption device, comprising at least one selected from the secondary battery according to claim 25 or 26, the battery module according to claim 27, or the battery pack according to claim 28. A power consumption device characterized by the above.

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