Core-shell structured polymer, conductive paste, secondary battery and power consumption device

Abstract

The present application provides a core-shell structured polymer (6), a conductive paste, a secondary battery (5), and a power consumption device. The core-shell structured polymer (6) comprises a core portion (61) and a shell portion (62) covering at least a part of the core portion (61), the core portion (61) comprising structural units derived from a monomer represented by formula I and structural units derived from a monomer represented by formula II, the shell portion (62) comprising structural units derived from a monomer represented by formula I and structural units derived from a monomer represented by formula III, and in formulas I, II, and III, R1, R2, and R3 are each independently hydrogen, fluorine, chlorine, or C substituted with fluorine. 1~3 alkyl groups, and R, R, R, R, R, R, and R are each independently selected from hydrogen, substituted or unsubstituted C 1~5 The alkyl group is selected from one or more of the following: JPEG2025535954000030.jpg33151

Description

[Technical Field]

[0001] The present application relates to the technical field of secondary batteries, and in particular to a core-shell structured polymer, a method for producing the same, a conductive paste, a method for producing the conductive paste, a secondary battery, a battery module, a battery pack, and a power consumption device. [Background technology]

[0002] In the manufacturing process of secondary batteries, conductive agents are generally added to improve the conductivity of the active material, thereby improving the overall performance of the battery. However, conventional conductive agents generally have a large specific surface area, and due to the action of van der Waals forces, they tend to aggregate easily, which affects their conductive effect and also tends to cause uneven distribution on the polar sheet, which affects the performance of the active material. Therefore, an urgent solution to this technical problem is needed. Summary of the Invention

[0003] The present application has been made in view of the above-mentioned problems, and an object of the present application is to provide a core-shell structured polymer that improves the dispersibility, processability, and storage stability of a conductive paste, thereby improving the performance of a battery, and a conductive paste containing the core-shell structured polymer.

[0004] According to a first aspect of the present application, there is provided a core-shell structured polymer, comprising a core portion and a shell portion covering at least a part of the core portion, wherein the core portion comprises a constitutional unit derived from a monomer represented by formula I and a constitutional unit derived from a monomer represented by formula II, and the shell portion comprises a constitutional unit derived from a monomer represented by formula I and a constitutional unit derived from a monomer represented by formula III, JPEG2025535954000002.jpg27157 where R1, R2, and R3 are each independently hydrogen, fluorine, chlorine, or fluorine-substituted C 1~3 alkyl groups, and R, R, R, R, R, R, and R are each independently selected from hydrogen, substituted or unsubstituted C 1~5 The alkyl group is selected from one or more of the following:

[0005] In any embodiment, R1 in formula I above is fluorine, and R2 and R3 are each independently selected from one or more of hydrogen, fluorine, chlorine, and trifluoromethyl.

[0006] The core-shell structured polymer provided by the present application can optimize the viscosity of the paste, which allows the paste to have excellent anti-settling properties, anti-gelling properties, and filterability, and can mitigate the settling and aggregation of the conductive agent without the need to add an additional dispersant, thereby improving the quality of the polar sheet and the performance of the battery.

[0007] In any embodiment, the mass content of the core portion is 70% to 90% and the mass content of the shell portion is 10% to 30% relative to the mass of the core-shell polymer.

[0008] When the mass content of the core part is controlled within an appropriate range, the core-shell structured polymer can further optimize the viscosity of the paste, thereby comprehensively improving the processability and application performance of the conductive paste.

[0009] In any embodiment, the molar content of the structural units derived from the monomer represented by formula I is 50% to 80% relative to the total number of moles of all structural units in the core-shell structure polymer.

[0010] When the molar content of the constitutional units derived from the monomer represented by Formula I is controlled within an appropriate range, the viscosity of the paste can be further optimized, and the processability and adhesiveness of the conductive paste can be comprehensively improved.

[0011] In any embodiment, the molar content of the structural units derived from the monomer represented by formula II is 10% to 20%, and the molar content of the structural units derived from the monomer represented by formula III is 10% to 30%, relative to the total number of moles of all structural units in the core-shell structure polymer.

[0012] When the molar contents of the constituent units derived from the monomer represented by formula II and the constituent units derived from the monomer represented by formula III are controlled within an appropriate range, the viscosity of the paste can be further optimized, and the processability and adhesiveness of the conductive paste can be comprehensively improved.

[0013] In any embodiment, the mass content of the structural units derived from the monomer represented by formula I in the core portion is 85% to 95% relative to the total mass of the structural units derived from the monomer represented by formula I in the core-shell structured polymer.

[0014] Since a large amount of fluorine-containing structural units is located in the core of the core-shell polymer, it helps to alleviate gelation of the paste and improve the storage stability of the conductive paste, thereby further reducing the production cost of the conductive paste and improving the production efficiency of the conductive paste.

[0015] In any embodiment, the weight average molecular weight of the core-shell polymer is 100,000 to 300,000.

[0016] When the weight average molecular weight of the core-shell structure polymer is controlled within an appropriate range, the adhesive strength of the polar sheet and the filterability of the paste can both be achieved, thereby improving the adhesiveness and processability of the polar sheet overall.

[0017] In any embodiment, the core-shell structured polymer has a Dv50 particle size of 100 nm to 8 μm. A core-shell structured polymer with an appropriate particle size improves the uniformity of the conductive paste and helps to produce polar sheets with uniform quality.

[0018] In any embodiment, the monomer shown in Formula I is selected from one or more of vinylidene fluoride, tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropylene.

[0019] In any embodiment, the monomer shown in Formula II is selected from one or more of acrylamide, methacrylamide, butenamide.

[0020] In any embodiment, the monomer shown in Formula III is selected from one or more of acrylonitrile, methacrylonitrile, 2-methyl-2-butenenitrile, 3-butenenitrile.

[0021] According to a second aspect of the present application, there is provided a method for producing a core-shell structured polymer, comprising the steps of:

[0022] a monomer represented by formula I and a monomer represented by formula II are polymerized under polymerizable conditions to prepare a core portion of the core-shell structured polymer, and a monomer represented by formula I and a monomer represented by formula III are polymerized to prepare a shell portion of the core-shell structured polymer, the shell portion covering at least a portion of the core portion; JPEG2025535954000003.jpg27157 where R1, R2, and R3 are each independently hydrogen, fluorine, chlorine, or fluorine-substituted C 1~3 alkyl groups, and R, R, R, R, R, R, and R are each independently selected from hydrogen, substituted or unsubstituted C 1~5 The alkyl group is selected from one or more of the following:

[0023] The core-shell polymer prepared by this method can reduce the viscosity of the paste and improve the filterability of the conductive paste, so that the paste will not gel even after standing for 60 days, improving the anti-gelling properties and storage stability of the conductive paste, significantly widening the process window of the conductive paste and improving the processability of the conductive paste, so that the conductive paste can meet the production requirements of conductive paste even without adding a dispersant, and further reducing the DC resistance of the battery.

[0024] In any embodiment, R1 in formula I above is fluorine, and R2 and R3 are each independently selected from one or more of hydrogen, fluorine, chlorine, and trifluoromethyl.

[0025] In any embodiment, the molar content of the monomer represented by formula I is 50% to 80% based on the total number of moles of the monomer represented by formula I, the monomer represented by formula II, and the monomer represented by formula III.

[0026] In any embodiment, the molar content of the monomer represented by formula II is 10% to 20% relative to the total number of moles of the monomer represented by formula I, the monomer represented by formula II, and the monomer represented by formula III.

[0027] In any embodiment, the molar content of the monomer represented by formula III is 10% to 30% relative to the total number of moles of the monomer represented by formula I, the monomer represented by formula II, and the monomer represented by formula III.

[0028] In an optional embodiment, the polymerization reaction comprises a first stage polymerization and a second stage polymerization;

[0029] First-stage polymerization: A first-stage polymerization is carried out by adding an initiator, a first emulsifier, at least one monomer represented by formula I, at least one monomer represented by formula II, and an aqueous medium to a reaction vessel, and in the first-stage polymerization, the monomer represented by formula I is continuously fed so as to maintain a constant reaction pressure.

[0030] Second-stage polymerization: After reacting for a certain time, an initiator, a second emulsifier, at least one monomer represented by formula III and an aqueous medium are added to the reaction vessel to carry out second-stage polymerization to obtain a core-shell structure polymer. During the second-stage polymerization, the monomer represented by formula I is continuously fed into the reaction vessel until all of the monomer represented by formula I is fed into the reaction vessel, and the reaction is stopped when the reaction pressure drops to 0-0.2 MPa.

[0031] The method provided herein first introduces a large amount of a monomer represented by Formula I and a monomer represented by Formula II to form a fluorine-containing core portion, which has high thermal stability. Then, small amounts of a monomer represented by Formula I and a monomer represented by Formula III are introduced to form a shell portion surrounding at least the core portion. A core-shell polymer is obtained by adding monomers with different hydrophilicities in separate steps in an emulsion system and polymerizing them. The core-shell polymer exists in the form of a core-shell structure in an aqueous medium. Compared with non-core-shell polymers prepared by simultaneously introducing all the monomers into a reaction vessel, the core-shell polymer has significantly improved stability and dispersibility, which contributes to improving the filterability and storage stability of the conductive paste. Furthermore, when the monomer represented by Formula III is introduced into a reaction vessel to perform the second-stage polymerization, the monomer represented by Formula I is continuously introduced into the reaction vessel to increase the compatibility between the core and shell portions of the core-shell polymer, thereby improving the stability of the core-shell polymer.

[0032] In either embodiment, the second stage polymerization comprises adding an initiator to a reaction vessel followed by adding a premix comprising a second emulsifier, at least one monomer according to Formula III, and an aqueous medium.

[0033] In any embodiment, the mass of the monomer represented by formula I introduced in the first-stage polymerization is 85% to 95% of the total mass of the monomer represented by formula I supplied in the polymerization reaction, and the mass of the monomer represented by formula I introduced in the second-stage polymerization is 5% to 15% of the total mass of the monomer represented by formula I supplied in the polymerization reaction.

[0034] Since a large amount of fluorine-containing structural units is located in the core of the core-shell polymer, it helps to alleviate gelation of the paste and improve the storage stability of the conductive paste, thereby further reducing the production cost of the conductive paste and improving the production efficiency of the conductive paste.

[0035] In any embodiment, the total mass percentage of the initiator added in the first stage polymerization and the second stage polymerization is 1% to 2% relative to the total mass of the monomer represented by Formula I, the monomer represented by Formula II, and the monomer represented by Formula III.

[0036] In any embodiment, the mass percentage of the first emulsifier is 0.1% to 0.5% relative to the total mass of the monomer represented by formula I, the monomer represented by formula II, and the monomer represented by formula III, and the mass percentage of the second emulsifier is 0.5% to 5% relative to the mass of the monomer represented by formula III.

[0037] In any embodiment, the mass percentage of the aqueous medium provided in the first-stage polymerization is 400% to 600% relative to the total mass of the monomer represented by Formula I, the monomer represented by Formula II, and the monomer represented by Formula III.

[0038] In any embodiment, the reaction pressure in the first stage polymerization is 6.0 MPa to 9.0 MPa, and the reaction temperature is 80°C to 100°C.

[0039] In any embodiment, the initial reaction pressure of the second stage polymerization is lower than the reaction pressure of the first stage polymerization, and the reaction temperature of the second stage polymerization is higher than the reaction temperature of the first stage polymerization.

[0040] In one embodiment, the first emulsifier is an alkali metal perfluorooctanoate and the second emulsifier is an ammonium polyoxyethylene-4-phenol ether sulfate.

[0041] In any embodiment, the initiator is one or two of N,N-dimethylbenzylamine, ammonium persulfate.

[0042] According to a third aspect of the present application, there is provided use of the core-shell structured polymer provided in the first aspect in a secondary battery.

[0043] According to a fourth aspect of the present application, there is provided an emulsion comprising an aqueous medium, an emulsifier, and the core-shell polymer according to the first aspect.

[0044] According to a fifth aspect of the present application, there is provided a conductive paste comprising a conductive agent, an aqueous medium, and the emulsion according to the fourth aspect.

[0045] Compared with the prior art, which directly adds a conductive agent during the production process of a negative electrode paste, the conductive paste provided by the present application can improve the dispersibility of the conductive agent in the negative electrode paste and improve the conductive effect of the conductive agent in the polar sheet, thereby effectively reducing the content of the conductive agent in the polar sheet and further increasing the amount of active material carried in the negative electrode sheet, thereby improving the output characteristics of the battery.

[0046] In any embodiment, the mass fraction of the conductive agent is 10.0% to 15.0% with respect to the total mass of the conductive paste.

[0047] When the mass fraction of the conductive agent is controlled within an appropriate range, the viscosity of the conductive paste can be optimized, and the processability and application performance of the paste can be comprehensively improved.

[0048] In any embodiment, the mass fraction of the core-shell structure polymer is 0.5% to 2.5% with respect to the total mass of the conductive paste.

[0049] When the mass fraction of the core-shell structured polymer relative to the total mass of the conductive paste is controlled within an appropriate range, the paste has an appropriate viscosity, which allows the polar sheet to have good adhesion, thereby comprehensively improving the processability and use performance of the paste.

[0050] In any one of the embodiments, the conductive paste has a solid content of 12% to 17%, and a viscosity of 500 mPa·s to 1500 mPa·s.

[0051] Conductive pastes with a solid content of 12% to 17% and a viscosity of 500 mPa·s to 1500 mPa·s can be directly mixed and stirred with active materials and binders to produce negative electrode paste, eliminating the need to add additional additives, which is advantageous for improving production efficiency and reducing production costs.

[0052] According to a sixth aspect of the present application, there is provided a negative electrode sheet including a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer including a negative electrode active material, a conductive agent, and a binder, and the conductive agent being a deposit of the conductive paste according to the fifth aspect.

[0053] Compared to negative electrode sheets manufactured by directly adding conductive agent powder in the prior art, the conductive agent in the negative electrode sheet disclosed in the present application is present in the negative electrode sheet in the form of a conductive paste deposit, which helps to further reduce the resistance of the battery.

[0054] In any embodiment, the adhesive strength per unit length between the negative electrode film layer and the negative electrode current collector is 12 N / m or more.

[0055] According to a seventh aspect of the present application, there is provided a secondary battery including a positive electrode sheet, a separator, an electrolyte, and the negative electrode sheet according to the sixth aspect of the present application, and 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.

[0056] According to an eighth aspect of the present invention, there is provided a battery module including the secondary battery according to the seventh aspect of the present invention.

[0057] According to a ninth aspect of the present application, there is provided a battery pack including the secondary battery according to the seventh aspect of the present application or the battery module according to the eighth aspect of the present application.

[0058] According to a tenth aspect of the present application, there is provided a power consumption device including at least one selected from the secondary battery according to the seventh aspect of the present application, the battery module according to the eighth aspect of the present application, and the battery pack according to the ninth aspect of the present application. [Brief explanation of the drawings]

[0059] [Figure 1] 1 is a structural schematic diagram of a core-shell structure polymer according to an embodiment of the present application. [Figure 2] 1 is a schematic diagram of a secondary battery according to an embodiment of the present application. [Figure 3] FIG. 3 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 2. [Figure 4] 1 is a schematic diagram of a battery module according to an embodiment of the present application; [Figure 5] 1 is a schematic diagram of a battery pack according to an embodiment of the present application; [Figure 6] FIG. 6 is an exploded view of the battery pack shown in FIG. 5 according to one embodiment of the present application. [Figure 7] 1 is a schematic diagram of a power consuming device that uses a secondary battery as a power source according to an embodiment of the present application; DETAILED DESCRIPTION OF THE INVENTION

[0060] Hereinafter, with appropriate reference to the drawings, embodiments specifically disclosing the adhesive, preparation method, electrode, battery, and power consumption device of the present application will be described in detail. However, unnecessary detailed description may be omitted. For example, detailed description of well-known matters and redundant description of actually identical structures may be omitted. This is to avoid the following description becoming unnecessarily long and to facilitate understanding by those skilled in the art. Note that the drawings and the following description are provided to enable those skilled in the art to fully understand the present application, and are not intended to limit the subject matter described in the claims.

[0061] The "ranges" disclosed in this application are defined in the form of lower and upper limits, and a given range is defined by selecting one lower limit and one upper limit, and the selected lower and upper limits define the boundaries of the particular range. Such defined ranges may be inclusive or exclusive of the end values, and are arbitrarily combinable; i.e., any lower limit can be combined with any upper limit to form a single range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if 1 and 2 are listed as minimum range values ​​and 3, 4, and 5 are listed as maximum range values, the ranges 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5 are all contemplated. In this application, unless otherwise specified, a numerical range "a to b" represents a shorthand notation for any combination of real numbers a to b, where a and b are both real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 and 5" are fully enumerated herein, and "0 to 5" is merely a shorthand notation for combinations of these numbers. Furthermore, expressing a parameter as an integer ≧2 is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0062] Unless otherwise stated, all embodiments and optional embodiments in the present application can be combined with each other to form a new technical solution.

[0063] Unless otherwise stated, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0064] Unless otherwise specified, all steps in this application may be performed in order or randomly, and are preferably performed in order. For example, when the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed in order, or steps (b) and (a) performed in order. For example, when the method mentioned above may further include step (c), it means that step (c) may be added to the method in any order, and for example, the method may include steps (a), (b), and (c), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0065] Unless otherwise specified, the terms "comprise" and "include" used in this application may be open-ended or closed-ended. For example, the terms "comprise" and "include" may indicate that other components not listed may be further included or included, or that only the listed components may be included or included.

[0066] Unless otherwise stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied by either A being true (or present) and B being false (or absent), or A being false (or absent) and B being true (or present), or both A and B being true (or present).

[0067] Conductive agents are commonly added during the manufacturing process of secondary batteries to improve electron transmission properties and thereby enhance overall battery performance. However, conventional conductive agents generally have a large specific surface area, which makes them prone to aggregation due to van der Waals forces, affecting their conductive properties and causing uneven distribution on the polar sheet, which in turn affects the performance of the active material. While adding a dispersant can improve the dispersion of the conductive agent, its incorporation into the paste is detrimental to the subsequent manufacture of the polar sheet and can lead to problems such as paste gelation, a narrower process window, and poor paste stability between batches. In response to these technical challenges, the present application develops a polymer that provides conductive paste with suitable viscosity and excellent filterability, anti-settling, and anti-gelling properties, thereby improving the production efficiency and quality of conductive paste.

[0068] [Core-shell structure polymer] Based on this, the present application provides a core-shell structured polymer, comprising a core portion and a shell portion covering at least a part of the core portion, wherein the core portion comprises a structural unit derived from a monomer represented by formula I and a structural unit derived from a monomer represented by formula II, and the shell portion comprises a structural unit derived from a monomer represented by formula I and a structural unit derived from a monomer represented by formula III, JPEG2025535954000004.jpg27157 where R1, R2, and R3 are each independently hydrogen, fluorine, chlorine, or fluorine-substituted C 1~3 alkyl groups, and R, R, R, R, R, R, and R are each independently selected from hydrogen, substituted or unsubstituted C 1~5 The alkyl group is selected from one or more of the following:

[0069] In this specification, the term "polymer" refers, on the one hand, to a collection of chemically uniform macromolecules produced via a polymerization reaction, but differing in the aspects of their degree of polymerization, molar mass and chain length, and, on the other hand, also to derivatives of such a collection of macromolecules formed by a polymerization reaction, i.e., products that can be obtained by reaction, for example addition or substitution, of functional groups in the macromolecules and that may be chemically uniform or chemically heterogeneous.

[0070] As used herein, "C 1~3 The term "alkyl group" refers to a straight or branched hydrocarbon chain radical composed solely of carbon and hydrogen, the radical being free of unsaturation, having from 1 to 3 carbon atoms, and attached to the rest of the molecule by a single bond.

[0071] As used herein, "C 1~5 The term "alkyl group" refers to the 1-3 This can be understood by reference to the definition of the term "alkyl group."

[0072] As used herein, the term "substituted" refers to at least one hydrogen atom of the compound or chemical moiety being replaced by another chemical moiety with a substituent, each of which is independently a hydroxyl group, a mercapto group, an amino group, a cyano group, a nitro group, an aldehyde group, a halogen atom, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, a C1-6 alkyl group, or a C1-6 alkoxy group.

[0073] In some embodiments, R1 in formula I is fluorine, and R2 and R3 are each independently selected from one or more of hydrogen, fluorine, chlorine, and trifluoromethyl.

[0074] As used herein, the term "trifluoromethyl" refers to the group -CF3.

[0075] In some embodiments, the monomer according to Formula I is selected from one or more of vinylidene fluoride, tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropylene.

[0076] In some embodiments, the monomer according to Formula II is selected from one or more of acrylamide, methacrylamide, butenamide.

[0077] In some embodiments, the monomer shown in Formula III is selected from one or more of acrylonitrile, methacrylonitrile, 2-methyl-2-butenenitrile, 3-butenenitrile.

[0078] 1 is a schematic diagram of the structure of a core-shell structured polymer in one embodiment of the present application. The core-shell structured polymer 6 comprises a core portion 61 and a shell portion 62, with the shell portion 62 covering the surface of the core portion 61. The core portion 61 comprises a structural unit derived from a monomer represented by formula I and a structural unit derived from a monomer represented by formula II, and the core portion 61 comprises a fluorine-containing structural unit, which can increase the thermal stability and adhesiveness of the structure. The shell portion comprises a structural unit derived from a monomer represented by formula I and a structural unit derived from a monomer represented by formula III, and the shell portion comprises a cyano group, which can improve the adhesiveness of the polymer.

[0079] Compared with conventional polyvinylidene fluoride, the core-shell structured polymer can reduce the contact area between the fluorine-containing structural unit and the solvent, thereby reducing the viscosity of the paste, stabilizing the paste, and alleviating the settling of the paste, thereby effectively improving the filterability of the paste.

[0080] The core-shell structured polymer provided by the present application can optimize the viscosity of the paste, which allows the paste to have excellent anti-settling properties, anti-gelling properties, and filterability, and can mitigate the settling and aggregation of the conductive agent without the need to add an additional dispersant, thereby improving the quality of the polar sheet and the performance of the battery.

[0081] In some embodiments, the mass content of the core portion relative to the mass of the core-shell structured polymer is 70% to 90%, and the mass content of the shell portion is 10% to 30%. In some embodiments, the mass content of the core portion relative to the mass of the core-shell structured polymer may be selected from any one of 70%, 75%, 80%, 85%, and 90%. In some embodiments, the mass content of the shell portion relative to the mass of the core-shell structured polymer may be selected from any one of 10%, 15%, 20%, 25%, and 30%.

[0082] When the mass content of the core part is controlled within an appropriate range, the core-shell structured polymer can further optimize the viscosity of the paste, avoiding problems such as poor application, drying efficiency, and adhesive strength due to a paste with too low viscosity, or difficulty in flow and application due to a paste with too high viscosity, thereby comprehensively improving the processability and application performance of the conductive paste.

[0083] In some embodiments, the molar content of the structural units derived from the monomer represented by Formula I relative to the total number of moles of all structural units in the core-shell structured polymer is 50% to 80%. In some embodiments, the molar content of the structural units derived from the monomer represented by Formula I relative to the total number of moles of all structural units in the core-shell structured polymer may be selected from any one of 50%, 60%, 70%, and 80%.

[0084] When the molar content of the constitutional units derived from the monomer represented by Formula I is controlled within an appropriate range, the viscosity of the paste can be further optimized, and the processability and adhesiveness of the conductive paste can be comprehensively improved.

[0085] In some embodiments, the molar content of the structural units derived from the monomer represented by Formula II is 10% to 20%, and the molar content of the structural units derived from the monomer represented by Formula III is 10% to 30%, relative to the total molar number of all structural units in the core-shell structured polymer. In some embodiments, the molar content of the structural units derived from the monomer represented by Formula II may be selected from any one of 10%, 15%, and 20%, relative to the total molar number of all structural units in the core-shell structured polymer. In some embodiments, the molar content of the structural units derived from the monomer represented by Formula III may be selected from any one of 10%, 20%, and 30%, relative to the total molar number of all structural units in the core-shell structured polymer.

[0086] When the molar contents of the constitutional units derived from the monomer represented by formula II and the constitutional units derived from the monomer represented by formula III are controlled within an appropriate range, the viscosity of the paste can be further optimized, and the processability and adhesion of the conductive paste can be comprehensively improved.

[0087] In some embodiments, the mass content of the structural units derived from the monomer represented by formula I in the core portion relative to the total mass of structural units derived from the monomer represented by formula I in the core-shell structured polymer is 85% to 95%. In some embodiments, the mass content of the structural units derived from the monomer represented by formula I in the core portion relative to the total mass of structural units derived from the monomer represented by formula I in the core-shell structured polymer may be selected from 85%, 90%, and 95%.

[0088] Since a large amount of fluorine-containing structural units is located in the core of the core-shell polymer, it helps to alleviate gelation of the paste and improve the storage stability of the conductive paste, thereby further reducing the production cost of the conductive paste and improving the production efficiency of the conductive paste.

[0089] In some embodiments, the weight-average molecular weight of the core-shell polymer is 100,000 to 300,000. In some embodiments, the weight-average molecular weight of the core-shell polymer may be selected from any one of 100,000, 200,000, and 300,000.

[0090] As used herein, the term "weight average molecular weight" refers to the sum of the products of the weight fractions of molecules of different molecular weights in a polymer and their corresponding molecular weights.

[0091] In this application, the weight-average molecular weight of a polymer can be measured using methods known in the art, for example, gel chromatography, such as a Waters 2695 Isocratic HPLC Gel Chromatograph (Differential Refractive Index Detector 2141). In some embodiments, the measurement method uses a 3.0% mass fraction polystyrene solution sample as a reference and selects a suitable chromatography column (oil-based: Styragel HT5 DMF 7.8 * 300 mm + Styragel HT4). A 3.0% core-shell structure polymer binder solution is prepared using purified N-methylpyrrolidone (NMP) solvent, and the prepared solution is allowed to stand for one day for later use. During measurement, tetrahydrofuran is first aspirated into a syringe and washed, and this process is repeated several times. Then, 5 ml of test solution is aspirated, the air is expelled from the syringe, and the needle tip is wiped dry. Finally, the sample solution is slowly injected into the injection port. After the display stabilizes, data is acquired and the weight-average molecular weight is read.

[0092] When the weight-average molecular weight of the core-shell structure polymer is controlled within an appropriate range, the core-shell structure polymer has good solubility in the paste and is less likely to aggregate with the conductive agent, thereby allowing the conductive agent to be uniformly dispersed in the paste. At the same time, the appropriate weight-average molecular weight helps the binder to form a three-dimensional mesh-like adhesive structure, which provides effective adhesion, thereby achieving both the adhesiveness of the polar sheet and the filterability of the paste, and comprehensively improving the adhesiveness and processability of the polar sheet.

[0093] In some embodiments, the Dv50 particle size of the core-shell structured polymer is 100 nm to 8 μm, In some embodiments, the Dv50 particle size of the core-shell structured polymer may be selected from any one of 100 nm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, and 8 μm.

[0094] In this specification, the term "Dv50 particle size" refers to the particle size corresponding to the point where the cumulative particle size distribution number of particles reaches 50% on a particle size distribution curve, and in its physical meaning, it means that 50% of particles have a particle size smaller (or larger) than that.

[0095] A core-shell structured polymer with an appropriate particle size improves the uniformity of the conductive paste and helps to produce polar sheets with uniform quality.

[0096] In one embodiment of the present application, there is provided a method for producing a core-shell structured polymer, comprising the steps of: Under polymerizable conditions, a monomer represented by formula I and a monomer represented by formula II are combined to form a core portion of the core-shell polymer, and a monomer represented by formula I and a monomer represented by formula III are combined to form a shell portion of the core-shell polymer, and the shell portion covers at least a portion of the core portion; JPEG2025535954000005.jpg27157 where R1, R2, and R3 are each independently hydrogen, fluorine, chlorine, or fluorine-substituted C 1~3 alkyl groups, and R, R, R, R, R, R, and R are each independently selected from hydrogen, substituted or unsubstituted C 1~5 The alkyl group is selected from one or more of the following:

[0097] As used herein, the term "polymerization conditions" includes conditions such as temperature, pressure, reactant concentrations, optional solvents / diluents, reactant mixing / addition parameters, and other conditions conducive to the reaction of one or more monomers in at least one polymerization reactor, selected by one skilled in the art.

[0098] The core-shell structured polymer prepared by this method can reduce the viscosity of the paste, improve the filterability of the paste, significantly widen the process window of the paste, and improve the processability of the paste, so that the paste can meet the production needs of aqueous conductive paste even without adding a dispersant, which is beneficial for optimizing the production process of aqueous conductive paste and improving its production efficiency.

[0099] In some embodiments, the molar content of the monomer represented by formula I is 50% to 80% relative to the total number of moles of the monomer represented by formula I, the monomer represented by formula II, and the monomer represented by formula III. In some embodiments, the molar content of the monomer represented by formula I may be selected from any one of 50%, 60%, 70%, and 80% relative to the total number of moles of the monomer represented by formula I, the monomer represented by formula II, and the monomer represented by formula III.

[0100] In some embodiments, the molar content of the monomer represented by formula II is 10% to 20% relative to the total number of moles of the monomer represented by formula I, the monomer represented by formula II, and the monomer represented by formula III. In some embodiments, the molar content of the monomer represented by formula II may be selected from any one of 10%, 15%, and 20% relative to the total number of moles of the monomer represented by formula I, the monomer represented by formula II, and the monomer represented by formula III.

[0101] In some embodiments, the molar content of the monomer represented by formula III relative to the total number of moles of the monomer represented by formula I, the monomer represented by formula II, and the monomer represented by formula III is 10% to 30%. In some embodiments, the molar content of the monomer represented by formula III relative to the total number of moles of the monomer represented by formula I, the monomer represented by formula II, and the monomer represented by formula III may be selected from any one of 10%, 20%, and 30%.

[0102] In some embodiments, the method comprises a first stage polymerization and a second stage polymerization; First-stage polymerization: A first-stage polymerization is carried out by adding an initiator, a first emulsifier, at least one monomer represented by formula I, at least one monomer represented by formula II, and an aqueous medium to a reaction vessel, and in the first-stage polymerization, the monomer represented by formula I is continuously fed so as to maintain a constant reaction pressure.

[0103] Second-stage polymerization: After reacting for a certain time, an initiator, a second emulsifier, at least one monomer represented by formula III and an aqueous medium are added to the reaction vessel to carry out a second-stage polymerization reaction to obtain a core-shell structure polymer. During the second-stage polymerization reaction, the monomer represented by formula I is continuously fed into the reaction vessel until all of the monomer represented by formula I is fed into the reaction vessel, and the reaction is stopped when the reaction pressure drops to 0-0.2 MPa.

[0104] As used herein, the term "continuously feed" refers to a slow, steady, gradual addition during the course of a polymerization.

[0105] The method provided by the present application first forms a fluorine-containing core by feeding a large amount of a monomer represented by formula I and a monomer represented by formula II, thereby providing the core with high thermal stability, and then introduces a small amount of a monomer represented by formula I and a monomer represented by formula III to form a shell surrounding at least the core. In an emulsion system, monomers with different hydrophilicities are added and polymerized in separate steps to obtain a core-shell structured polymer, which exists in the form of a core-shell structure in an aqueous medium. Compared with non-core-shell structured polymers produced by simultaneously introducing all the monomers into a reaction vessel, the core-shell structured polymer has significantly improved stability and dispersibility, which helps to improve the filterability and storage properties of the conductive paste.

[0106] In some embodiments, the mass of the monomer represented by formula I introduced in the first-stage polymerization is 85% to 95% of the total mass of the monomer represented by formula I supplied in the polymerization reaction, and the mass of the monomer represented by formula I introduced in the second-stage polymerization is 5% to 15% of the total mass of the monomer represented by formula I supplied in the polymerization reaction.

[0107] Since a large amount of fluorine-containing structural units is located in the core of the core-shell polymer, it helps to alleviate gelation of the paste and improve the storage stability of the conductive paste, thereby further reducing the production cost of the conductive paste and improving the production efficiency of the conductive paste.

[0108] In some embodiments, the second stage polymerization comprises adding an initiator to a reaction vessel followed by adding a premix comprising a second emulsifier, at least one monomer according to Formula II, a monomer according to Formula III, and an aqueous medium.

[0109] In some embodiments, the total mass percentage of the initiator added in the first stage polymerization and the second stage polymerization is 1% to 2% relative to the total mass of the monomer represented by Formula I, the monomer represented by Formula II, and the monomer represented by Formula III.

[0110] In some embodiments, the weight percent of the initiator provided in the first-stage polymerization is 0.05% to 1.5%, and the weight percent of the initiator provided in the second-stage polymerization is 0.005% to 0.5%, relative to the total weight of the monomer represented by Formula I, the monomer represented by Formula II, and the monomer represented by Formula III.

[0111] In some embodiments, the weight percentage of the first emulsifier is 0.1% to 0.5% relative to the total weight of the monomer represented by formula I, the monomer represented by formula II, and the monomer represented by formula III.

[0112] In some embodiments, the weight percentage of the second emulsifier relative to the weight of the monomer represented by Formula III is 0.5% to 5%.

[0113] In some embodiments, the mass percentage of the aqueous medium provided in the first-stage polymerization is 400% to 600%, and the mass percentage of the aqueous medium provided in the second-stage polymerization is 100% to 300%, based on the total mass of the monomer represented by Formula I, the monomer represented by Formula II, and the monomer represented by Formula III.

[0114] In some embodiments, the aqueous medium provided in the first-stage polymerization and the aqueous medium provided in the second-stage polymerization are deionized water having a conductivity of 2 μs / cm or less.

[0115] In some embodiments, the reaction pressure in the first stage polymerization is 6.0 MPa to 9.0 MPa, and the reaction temperature is 80°C to 100°C.

[0116] In some embodiments, the reaction pressure of the second polymerization is 4.0 MPa to 7.0 MPa, and the reaction temperature is 86°C to 95°C.

[0117] In some embodiments, the first initiator and the second initiator may be selected from one or two of N,N-dimethylbenzylamine, ammonium persulfate.

[0118] Both N,N-dimethylbenzylamine and ammonium persulfate can be effectively decomposed at temperatures above 60°C to generate radical ions or ion radicals, making them suitable as initiators for emulsion polymerization.

[0119] In some embodiments, the first emulsifier is an alkali metal salt of perfluorooctanoic acid, and sodium salt of perfluorooctanoic acid may be selected.

[0120] Alkali metal salts of perfluorooctanoic acid are often used as emulsifiers or dispersants in the polymerization reaction of fluorine-containing monomers.

[0121] In some embodiments, the second emulsifier is one or two of polyoxyethylene-4-phenol ether ammonium sulfate, nonylphenol polyoxyethylene ether ammonium sulfate.

[0122] Both polyoxyethylene-4-phenol ether ammonium sulfate and nonylphenol polyoxyethylene ether ammonium sulfate are anionic and nonionic emulsifiers, and have not only anionic but also nonionic properties. They can be used alone in emulsion polymerization and do not need to be used in combination with other emulsifiers.

[0123] In one embodiment of the present application, there is provided a use of the core-shell structured polymer of any of the embodiments in a secondary battery, and 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.

[0124] In some embodiments, the core-shell structured polymer is used as a binder in a secondary battery.

[0125] In some embodiments, the core-shell structured polymer is used as a binder for a conductive paste in a secondary battery.

[0126] [Conductive paste] One embodiment of the present application provides a conductive paste including a binder, a conductive agent, and an aqueous medium, wherein the binder includes the core-shell structured polymer described in any embodiment.

[0127] As used herein, the term "binder" refers to a chemical compound, polymer, or mixture that forms a colloidal solution or dispersion in a dispersing medium.

[0128] In some embodiments, the dispersion medium for the binder is an aqueous medium such as deionized water, i.e., the binder is dissolved in the aqueous medium.

[0129] The core-shell structured polymer has improved stability and dispersibility compared to non-core-shell structured polymers, which helps improve the filterability, dispersibility and storage properties of the conductive paste, thereby improving the performance of the battery.

[0130] In some embodiments, the core-shell structured polymer is added to the conductive paste in the form of an emulsion containing the core-shell structured polymer.

[0131] The core-shell structured polymer produced by the production method according to any of the above embodiments exists in the form of an emulsion, and can be directly added to a conductive paste for use, thereby reducing production costs and improving production efficiency.

[0132] In some embodiments, the mass fraction of the conductive agent is 10.0% to 15.0% with respect to the total mass of the conductive paste.

[0133] If the mass fraction of the conductive agent is less than 10.0% of the total mass of the conductive paste, the amount of remaining solvent is too small during the paste mixing process in the manufacturing process of the cell polar sheet, which is unfavorable for dissolving and dispersing the binder.If the mass fraction of the conductive agent is more than 15.0% of the total mass of the conductive paste, the viscosity of the conductive paste is high, the viscous rebound is large, and the fluidity is reduced, which is unfavorable for material addition in industrial production.

[0134] In some embodiments, the mass fraction of the core-shell polymer is 0.5% to 2.5% relative to the total mass of the conductive paste.

[0135] If the mass fraction of the core-shell polymer is less than 0.5% of the total mass of the conductive paste, the adhesiveness of the conductive paste will be reduced.If the mass fraction of the core-shell polymer is more than 2.5% of the total mass of the conductive paste, the viscosity of the conductive paste will be high, and the uniformity of the polar sheet will be reduced, which is unfavorable for reducing the battery resistance.

[0136] In some embodiments, when the solids content of the conductive paste is 12% to 17%, the viscosity of the conductive paste is 500 mPa·s to 1500 mPa·s. In some embodiments, the viscosity of the conductive paste is 600 mPa·s, 700 mPa·s, 800 mPa·s, 900 mPa·s, 1000 mPa·s, 1100 mPa·s, 1200 mPa·s, 1300 mPa·s, 1400 mPa·s, or 1500 mPa·s. A conductive paste with a solids content of 12% to 17% and a viscosity of 500 mPa·s to 1500 mPa·s provides an appropriate viscosity for conductive pastes made from core-shell polymers, eliminating the need for additional dispersants or thickeners to improve processability, and helping to improve production efficiency and optimize the production process.

[0137] In one embodiment of the present application, a secondary battery is provided, including a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte. In some embodiments, the secondary battery is at least one of a lithium ion battery, a sodium ion battery, a magnesium ion battery, and a potassium ion battery. During the charge and discharge process of the battery, active ions are inserted and removed between the positive electrode sheet and the negative electrode sheet. The electrolyte serves to conduct ions between the positive electrode sheet and the negative electrode sheet. The separator, located between the positive electrode sheet and the negative electrode sheet, primarily serves to prevent short-circuiting between the positive and negative electrodes while allowing ions to pass through.

[0138] [Positive electrode sheet] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector.

[0139] As an example, the positive electrode current collector has two surfaces facing each other in the thickness direction thereof, and the positive electrode film layer is provided on one or both of the two facing surfaces of the positive electrode current collector.

[0140] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. Examples of the metal foil include aluminum foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. The composite current collector may be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, or silver alloy) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0141] In some embodiments, the positive electrode active material may be a positive electrode active material for batteries known in the art. For example, the positive electrode active material may include at least one of a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide, and a modified compound thereof. However, the present application is not limited to these materials, and other conventional materials that can be used as a positive electrode active material for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Here, examples of lithium transition metal oxides include lithium cobalt oxide (e.g., LiCoO), lithium nickel oxide (e.g., LiNiO), lithium manganese oxide (e.g., LiMnO, LiMnO), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide (e.g., LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM 333 (may be abbreviated as "LiNi") 0.5 Co 0.2 Mn 0.3 O2(NCM 523 (may be abbreviated as "LiNi")0.5 Co 0.25 Mn 0.25 O2(NCM 211 (may be abbreviated as "LiNi") 0.6 Co 0.2 Mn 0.2 O2(NCM 622 (may be abbreviated as "LiNi") 0.8 Co 0.1 Mn 0.1 O2(NCM 811 ), lithium nickel cobalt aluminum oxide (e.g., LiNi 0.85 Co 0.15 Al 0.05 O2) and modified compounds thereof, etc. The lithium-containing phosphate having an olivine structure may include, but is not limited to, for example, at least one of lithium iron phosphate (e.g., LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (e.g., LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon.

[0142] In some embodiments, the positive electrode film layer may further include a binder, such as at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0143] In some embodiments, the positive electrode film layer may further include a conductive agent, for example, at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0144] In some embodiments, a positive electrode sheet can be manufactured by the following method: The components for manufacturing the positive electrode sheet, such as a positive electrode active material, a conductive agent, a binder, and any other components, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode paste. In any embodiment, the conductive paste is applied to the surface of a current collector and dried to form an aqueous conductive paste, i.e., an aqueous undercoated current collector. The positive electrode paste is then applied to the aqueous undercoated current collector, followed by processes such as drying and cold pressing to obtain a positive electrode sheet.

[0145] [Negative electrode sheet] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer including a negative electrode active material, a conductive agent, and a binder, and the conductive agent is a deposit of a conductive paste according to any one of the embodiments of the present application.

[0146] As an example, the negative electrode current collector has two surfaces facing each other in the thickness direction thereof, and the negative electrode film layer is provided on one or both of the two facing surfaces of the negative electrode current collector.

[0147] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. The metal foil may be, for example, a copper foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, or silver alloy) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0148] In some embodiments, the negative electrode active material may be a battery negative electrode active material known in the art. For example, the negative electrode active material may include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, a silicone-based material, a tin-based material, and lithium titanate. The silicone-based material may be selected from at least one of a silicone element, a silicone oxide, a silicone carbon composite, a silicone nitrogen composite, and a silicone alloy. The tin-based material may be selected from at least one of a tin element, a tin oxide, and a tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery negative electrode active material may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0149] In some embodiments, the negative electrode film layer optionally further comprises an adhesive, which may be selected from at least one of styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0150] In some embodiments, the negative electrode film layer further optionally includes a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0151] In some embodiments, the negative electrode film layer optionally further comprises other auxiliary agents, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0152] In some embodiments, the negative electrode sheet can be manufactured by the following method: Components for manufacturing the negative electrode sheet, such as the negative electrode active material, the conductive paste according to any embodiment of the present application, a binder, and any other components, are dispersed in a solvent (e.g., deionized water) to form a negative electrode paste, which is then applied to a negative electrode current collector, followed by steps such as drying and cold pressing, to obtain a negative electrode sheet.

[0153] [Electrolytes] The electrolyte serves to conduct ions between the positive electrode sheet and the negative electrode sheet. The present application does not specifically limit the type of electrolyte, and it can be selected according to needs. For example, the electrolyte may be liquid, gel, or all solid.

[0154] In some embodiments, the electrolyte is an electrolytic solution, which includes an electrolyte salt and a solvent.

[0155] In some embodiments, the electrolyte salt may be chosen 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.

[0156] In some embodiments, the solvent may be chosen 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.

[0157] In some embodiments, the electrolyte solution further optionally contains additives. For example, the additives may include a negative electrode film-forming additive, a positive electrode film-forming additive, and may further include additives that can improve some battery performance, such as an additive that improves the overcharge performance of the battery, or an additive that improves the high-temperature or low-temperature performance of the battery.

[0158] [Separator] In some embodiments, the secondary battery further includes a separator. The present application does not particularly limit the type of separator, and any known porous separator with good chemical stability and mechanical stability may be selected.

[0159] In some embodiments, the separator may be made of at least one material selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without any particular limitations. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without any particular limitations.

[0160] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be wound or stacked to form an electrode assembly.

[0161] In some embodiments, the secondary battery may include an exterior body, which may be used to package the electrode assembly and the electrolyte.

[0162] In some embodiments, the exterior of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The exterior of the secondary battery may be a pouch, such as a bag-shaped pouch. The pouch may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0163] The present application does not particularly limit the shape of the secondary battery, and it may be cylindrical, rectangular, or any other shape. For example, Fig. 2 shows a secondary battery 5 having a rectangular structure as an example.

[0164] In some embodiments, referring to FIG. 3 , the exterior material may include a housing 51 and a cover plate 53. The housing 51 may include a bottom plate and side plates connected to the bottom plate, forming a receiving cavity surrounded by the bottom plate and side plates. The case 51 has an opening communicating with the receiving cavity, and the cover plate 53 may cover the opening and seal the receiving cavity. The positive electrode sheet, the negative electrode sheet, and the separator may be wound or stacked to form an electrode assembly 52. ​​The electrode assembly 52 is packaged in the receiving cavity. An electrolyte is impregnated into 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 may select the number according to actual needs.

[0165] In some embodiments, the secondary batteries can be assembled into a battery module, and the number of secondary batteries included in the battery module can be one or more, and the specific number can be selected by those skilled in the art depending on the application and capacity of the battery module.

[0166] FIG. 4 shows an example of a battery module 4. Referring to FIG. 4, in the battery module 4, a plurality of secondary batteries 5 can be arranged in order along the length of the battery module 4. Of course, any other arrangement method may also be used. Furthermore, the plurality of secondary batteries 5 may be fixed by fasteners.

[0167] Optionally, the battery module 4 may further include a housing having an accommodating space, and the plurality of secondary batteries 5 are accommodated in this accommodating space.

[0168] In some embodiments, the battery modules can be further assembled into a battery pack, and the number of battery modules included in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0169] 5 and 6 show an example of a battery pack 1. Referring to FIGS. 5 and 6, the battery pack 1 may include a battery case and a plurality of battery modules 4 installed in the battery case. The battery case includes an upper housing 2 and a lower housing 3, and the upper housing 2 can be fitted over the lower housing 3 to form a sealed space for accommodating the plurality of battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0170] The present application also provides a power consuming device, the power consuming device including at least one of a secondary battery, a battery module, or a battery pack according to the present application. The secondary battery, the battery module, or the battery pack may be used as a power source for the power consuming device or as an energy storage unit for the power consuming device. The power consuming device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc.

[0171] The power consumption device can be selected from a secondary battery, a battery module, or a battery pack according to its usage requirements.

[0172] 7 shows an example of a power consuming device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the demand for high power output and high energy density of the secondary battery of this power consuming device, a battery pack or battery module can be used.

[0173] Other examples of the device may be a mobile phone, a tablet computer, a laptop computer, etc. These devices are generally required to be lightweight and can use a secondary battery as a power source.

[0174] Example The following describes examples of the present application. The examples described below are illustrative and are intended only to interpret the present application and should not be understood as limitations on the present application. If specific techniques or conditions are not specified in the examples, they will be carried out according to the techniques or conditions described in literature in the field or in accordance with the product specifications. If the manufacturer of the reagents or instruments used is not specified, they are all ordinary products that are commercially available.

[0175] 1. Preparation method Example 1 1) Preparation of core-shell structured polymers First-stage polymerization: 21 kg of deionized water, 17.45 g of sodium perfluorooctanoate, 84.77 g of N,N-dimethylbenzylamine, and 905 g of acrylamide monomer, of which the conductivity of deionized water is less than 2 μs / cm, are added to the reactor in sequence, and the reactor is closed.

[0176] The inside of the reactor is evacuated and filled with nitrogen gas, and this operation is repeated until the oxygen concentration inside the reactor is less than 100 ppm.

[0177] Vinylidene fluoride monomer is introduced into the reactor, and the reaction begins when the pressure inside the reactor reaches 8.0 MPa and the temperature inside the reactor rises to 85°C. During the reaction, vinylidene fluoride monomer is continuously introduced to maintain the reaction pressure inside the reactor constant.

[0178] Second-stage polymerization: 9 kg of deionized water (the conductivity of deionized water is 2 μs / cm or less), 10.14 g of polyoxyethylene-4-phenol ether sulfate ammonium salt, and 10.14 g of acrylonitrile monomer are added to a stirring tank and stirred uniformly to obtain a pre-mixed liquid.

[0179] When the total amount of vinylidene fluoride monomer introduced is 3877g, add 16.22g of 5% ammonium persulfate, adjust reaction pressure to 7.0MPa, raise temperature to 95℃, slowly add pre-mixture to reactor, add all pre-mixture in 1.0 hour, and at the same time slowly add remaining 204g of vinylidene fluoride monomer.

[0180] When the pressure inside the vessel drops to 0.2 MPa, the reaction is stopped.

[0181] The emulsion was cooled to room temperature and filtered to obtain an emulsion containing a core-shell structured polymer, the core of which was mainly composed of vinylidene fluoride and acrylamide, and the shell of which was composed of a small amount of vinylidene fluoride and acrylonitrile. The Dv50 particle size of the core-shell vinylidene fluoride-acrylamide-acrylonitrile copolymer was 260 nm.

[0182] 2) Manufacturing of conductive paste The solid content of the emulsion of vinylidene fluoride-acrylamide-acrylonitrile copolymer with a core-shell structure is adjusted to 40%.

[0183] Weigh out 16.4 kg of deionized water and 1 kg of the core-shell structured vinylidene fluoride-acrylamide-acrylonitrile copolymer emulsion and add them to a 35 L stirring tank. Stir at a stirring speed of 1000 rpm for 60 minutes to obtain a core-shell structured vinylidene fluoride-acrylamide-acrylonitrile copolymer pre-binder solution.

[0184] 2.6 kg of conductive carbon black powder was weighed and added to the stirring tank containing the pre-binder liquid, and stirred at a stirring speed of 1000 rpm for 60 minutes. The paste is filtered through a 300 mesh filter to obtain a conductive paste.

[0185] 3) Manufacturing of negative electrode sheets The active material, artificial graphite, the conductive paste, the binder, styrene butadiene rubber (SBR), and the thickener, sodium carboxymethyl cellulose (CMC), are mixed in deionized water to a weight ratio of 96.2:0.8:0.8:1.2, and the mixture is homogeneously mixed to produce the negative electrode paste. The negative electrode paste is then evenly applied to the negative electrode current collector copper foil in one or more batches, followed by drying, cold pressing, and cutting to obtain the negative electrode sheet.

[0186] 4) Manufacturing of positive electrode sheets Lithium nickel cobalt manganese (NCM) material, conductive carbon black, binder polyvinylidene fluoride, and N-methylpyrrolidone (NMP) are mixed uniformly in a weight ratio of 96.9:2.1:1:21 to obtain a positive electrode paste with a solid content of 73%. The positive electrode paste is then evenly applied to a positive electrode current collector aluminum foil, dried, cold pressed, and cut to obtain a positive electrode sheet.

[0187] 5) Separator A polypropylene film is used as the separator.

[0188] 6) Electrolyte production In a glove box under an argon atmosphere (H2O<0.1 ppm, O2<0.1 ppm), the organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed uniformly at a volume ratio of 3 / 7, and 12.5% ​​of the lithium salt LiPF6 was added and dissolved in the organic solvent, followed by stirring uniformly to obtain the electrolyte solution of Example 1.

[0189] 7) Battery manufacturing A positive electrode sheet, a separator, and a negative electrode sheet are stacked in this order, with a separator placed between the positive and negative electrode sheets to act as an insulator, and then wound to obtain a bare cell. A tab is welded to the bare cell, and the bare cell is placed in an aluminum case and baked at 80°C to remove water. An electrolyte is then injected and sealed to obtain an uncharged battery. The uncharged battery is then allowed to stand, hot and cold pressed, chemically formed, shaped, and capacity tested, etc., to obtain the lithium-ion battery product of Example 1.

[0190] Examples 2 to 5 The manufacturing method is essentially the same as that of Example 1, except that the molar contents of the core and shell parts and the blending ratios of each monomer in the synthesis of the core-shell structured polymer were adjusted, and the specific parameters are as shown in Tables 1 and 2.

[0191] Examples 6 to 9 The manufacturing method is essentially the same as that in Example 1, except that the mass of initiator and reaction temperature in the synthesis of the core-shell structure polymer are adjusted, so that the core-shell structure polymer has a different weight average molecular weight, and the specific parameters are as shown in Table 1 and Table 2.

[0192] Specifically, in the method for producing a core-shell polymer having a weight average molecular weight of 100,000 in Example 6, the amount of N,N-dimethylbenzylamine added was adjusted to 89.0 g.

[0193] In the method for producing a core-shell polymer having a weight average molecular weight of 300,000 in Example 7, the reaction temperature was adjusted to 80° C., and the amount of N,N-dimethylbenzylamine added was adjusted to 80.53 g.

[0194] In the method for producing a fluorine-containing polymer having a weight-average molecular weight of 50,000 in Example 8, the amount of N,N-dimethylbenzylamine added was adjusted to 93.25 g.

[0195] In the method for producing a fluorine-containing polymer having a weight-average molecular weight of 400,000 in Example 9, the reaction was adjusted to 80° C., and the amount of N,N-dimethylbenzylamine added was adjusted to 76.29 g.

[0196] Examples 10 to 12 The manufacturing method is essentially the same as that in Example 1, except that the type of comonomer used in the synthesis of the core-shell structure polymer is adjusted, and the specific parameters are as shown in Tables 1 and 2.

[0197] Examples 13 to 16 The manufacturing method is substantially the same as that of Example 1, except that the mass fraction of the core-shell structure polymer in the conductive paste is adjusted. The specific parameters are as shown in Tables 1 and 2.

[0198] Examples 17 to 20 The manufacturing method is substantially the same as that of Example 1, except that the mass fraction of the conductive agent in the conductive paste is adjusted. Specific parameters are as shown in Tables 1 and 2.

[0199] Comparative Example 1 The manufacturing method is substantially the same as that of Example 1, except that the core-shell structure polymer in the conductive paste is replaced with a vinylidene fluoride polymer.

[0200] Comparative Example 2 The manufacturing method is substantially the same as that of Example 1, except that the core-shell structure polymer in the conductive paste is replaced with a vinylidene fluoride-acrylamide polymer, and the manufacturing method is as follows.

[0201] Add 30kg of deionized water, 17.45g of perfluorooctanoic acid sodium salt, 84.77g of N,N-dimethylbenzylamine, 905g of acrylamide monomer, 10.14g of polyoxyethylene-4-phenol ether ammonium sulfate, and 1014g of acrylonitrile monomer into the reactor in order, where the conductivity of the deionized water is less than 2μs / cm, and then close the reactor.

[0202] The inside of the reactor is evacuated and filled with nitrogen gas, and this operation is repeated until the oxygen concentration inside the reactor is less than 100 ppm.

[0203] Vinylidene fluoride monomer is introduced into the reactor, and the reaction begins when the pressure inside the reactor reaches 8.0 MPa and the temperature inside the reactor rises to 85°C. During the reaction, vinylidene fluoride monomer is continuously introduced to maintain the reaction pressure inside the reactor constant.

[0204] After all 4081 g of vinylidene fluoride monomer has been introduced, the reaction is stopped when the pressure in the vessel drops to 0.2 MPa.

[0205] The mixture is cooled to room temperature and filtered to obtain a vinylidene fluoride-acrylamide copolymer.

[0206] Comparative Example 3 The manufacturing method is substantially the same as that of Example 1, except that the core-shell structure polymer in the conductive paste is replaced with a vinylidene fluoride-acrylonitrile polymer, and the manufacturing method is the same as that of Comparative Example 2.

[0207] Comparative Example 4 The manufacturing method is substantially the same as that of Example 1, except that the core-shell vinylidene fluoride-acrylamide-acrylonitrile copolymer emulsion is replaced with a vinylidene fluoride-acrylamide-acrylonitrile copolymer emulsion manufactured by a conventional method, and the synthesis method is as follows.

[0208] 30 kg of deionized water (the conductivity of deionized water is 2 μs / cm or less), 17.45 g of perfluorooctanoic acid sodium salt, 84.77 g of N,N-dimethylbenzylamine, 10.14 g of polyoxyethylene-4-phenol ether ammonium sulfate salt, 16.22 g of 5% ammonium persulfate solution, 1014 g of acrylonitrile, and 905 g of acrylamide are added to the reaction vessel in this order, and the reaction vessel is closed.

[0209] The inside of the reactor is evacuated and filled with nitrogen gas, and this operation is repeated until the oxygen concentration inside the reactor is less than 100 ppm.

[0210] Vinylidene fluoride monomer is introduced into the reaction vessel, and the reaction starts when the pressure inside the vessel reaches 8.0 MPa and the temperature inside the vessel rises to 85°C. During the reaction, vinylidene fluoride monomer is continuously introduced to keep the reaction pressure inside the vessel constant, and the total mass of vinylidene fluoride monomer introduced is 4.08 kg.

[0211] When the pressure inside the vessel drops to 0.2 MPa, the reaction is stopped and the unreacted vinylidene fluoride monomer is recovered.

[0212] The mixture is cooled to room temperature and filtered to obtain an emulsion containing vinylidene fluoride-acrylamide-acrylonitrile copolymer.

[0213] In Comparative Example 5, when preparing the negative electrode sheet, no conductive paste is added, but an equivalent mass of conductive carbon black is added.

[0214] In Comparative Example 6, a conductive paste was added when preparing a negative electrode sheet. The preparation method of the conductive paste was the same as that of Example 1, except that the core-shell vinylidene fluoride-acrylamide-acrylonitrile copolymer was replaced with the same mass of sodium carboxymethylcellulose (CMC).

[0215] II. Test Method 1. Characterization of core-shell structured polymers (1) Measurement of the weight-average molecular weight of core-shell structure polymers The emulsion containing the core-shell structured polymer is vacuum dried at 100° C. for 180 minutes to obtain a core-shell structured polymer powder.

[0216] A Waters 2695 Isocratic HPLC gel chromatograph (refractive index detector 2141) was used. A 3.0% mass fraction polystyrene solution sample was used as a reference and a suitable chromatography column (oil-based: Styragel HT5 DMF 7.8 x 300 mm + Styragel HT4) was selected. A 3.0% core-shell polymer solution was prepared using purified N-methylpyrrolidone (NMP) solvent, and the prepared solution was allowed to stand for one day for later use. For measurement, tetrahydrofuran was first aspirated into the syringe and washed, and this process was repeated several times. 5 ml of test solution was then aspirated, the air removed from the syringe, and the needle tip was wiped dry. Finally, the sample solution was slowly injected into the injection port. After the display stabilized, data was acquired and the weight-average molecular weight was read.

[0217] (2) Dv50 particle size test of core-shell structure polymer Using GB / T 19077-2016 particle size distribution laser diffraction method, weigh 0.1g-0.13g of core-shell polymer emulsion into a 50ml beaker, add 5g of deionized water, add a 2.5mm stir bar, and seal with plastic wrap. Place the sample in an ultrasonicator and sonicate for 5 minutes. Transfer to a magnetic stirrer and stir at 500 r / min for at least 20 minutes. Two samples from each batch of product are taken for testing. Measurements are performed using a laser particle size analyzer such as Malvern's Mastersizer 2000E laser particle size analyzer.

[0218] 2. Conductive paste characteristic test (1) Filterability test Take a 500 ml beaker and place it on the lower end of a 200 mesh filter holder, take 500 ml of conductive paste and put it into the filter to filter, and record the time when the volume of the paste in the beaker reaches 300 ml.

[0219] (2) The solid content of the conductive paste and the difference in the solid content between the upper and lower layers after leaving it for 24 hours Remove the copper foil and weigh it with a weight loss rate measuring instrument, set it as M0, and clear the display.

[0220] Take the conductive paste, apply a small amount to the copper foil, and then weigh it with a moisture meter to determine M1.

[0221] Close the device and begin drying.

[0222] After completion, the weighing data is recorded and designated as M2, and the solid content is calculated as (M2-M0) / (M1-M0).

[0223] Using the same method, measure the solid content of the upper and lower conductive paste layers after leaving them to stand for 24 hours, and subtract the solid content of the upper conductive paste layer from the solid content of the lower conductive paste layer to determine the difference in solid content between the upper and lower layers of the conductive paste after leaving them to stand for 24 hours.

[0224] (3) Gelling state test after leaving the conductive paste standing for 60 hours Pull up the paste in the beaker with a steel ruler and judge whether the paste has gelled or not based on the state of fluidity of the paste. If the paste has not gelled, mark it as "OK", and if the paste has gelled, mark it as "NG".

[0225] Gelling: The paste is lumpy or does not flow naturally and continuously.

[0226] Non-gelling: The paste flows naturally and continuously; it flows down the surface of a steel ruler and is free of lumps.

[0227] 3. Adhesion strength of polar sheet Referring to the GB-T2790-1995 national standard "Test Method for 180° Peel Strength of Adhesives," the adhesive strength testing process for the examples and comparative examples in this application was as follows: A blade was used to cut a sample 30 mm wide and 100-160 mm long, and a dedicated double-sided tape was attached to a steel plate. The tape was 20 mm wide and 90-150 mm long. The negative electrode film layer of the cut polar sheet sample was then attached to the double-sided tape, and rolled three times in the same direction with a 2 kg pressure roll. A paper tape the same width as the polar sheet and 250 mm long was attached to the polar sheet current collector and secured in place with masking tape. The Sansi tensile machine (1N sensitivity) was turned on, the lamp was lit, and the stopper block was adjusted to the appropriate position. The end of the steel plate not attached to the polar sheet was secured with the lower clamp. The paper tape was folded back and secured with the upper clamp, and the position of the upper clamp was adjusted using the "up" and "down" buttons on the manual controller attached to the tensile machine. The test is then performed and the readings are taken at a pulling speed of 50 mm / min. The force applied to the polar sheet when it is in equilibrium is divided by the tape width to characterize the adhesive strength between the negative electrode film layer and the current collector as the adhesive strength of the negative electrode sheet per unit length.

[0228] 4. Battery performance test (1) DC resistance of battery At 25°C, the secondary battery was charged to 4.2V at a constant current of 1 / 3C, then further charged at a constant voltage of 4.2V until the current reached 0.05C and allowed to stand for 5 minutes. It was then discharged at a 1 / 3C rate for 90 minutes, and the electrode assembly was adjusted to 50% SOC. After allowing to stand for 60 minutes, it was discharged at a 4C rate for 30 seconds, and the 50% SOC discharge DCR was determined based on the test data.

[0229] 3. Analysis of Test Results for Each Example and Comparative Example According to the above methods, the core-shell structured polymer, conductive paste, negative electrode sheet and secondary battery of each example and comparative example were manufactured, and the performance parameters were measured. The results are shown in Tables 1 and 2 below.

[0230] Table 1: Manufacturing parameters and test results for Examples and Comparative Examples TIFF2025535954000006.tif220153 TIFF2025535954000007.tif226153 TIFF2025535954000008.tif226153 TIFF2025535954000009.tif226153 TIFF2025535954000010.tif231153 TIFF2025535954000011.tif226153 TIFF2025535954000012.tif226153 TIFF2025535954000013.tif193153 TIFF2025535954000014.tif131153

[0231] Table 2: Manufacturing parameters and test results for Examples and Comparative Examples TIFF2025535954000015.tif199153 TIFF2025535954000016.tif216153 TIFF2025535954000017.tif216153 TIFF2025535954000018.tif216153 TIFF2025535954000019.tif216153 TIFF2025535954000020.tif211153 TIFF2025535954000021.tif227153 TIFF2025535954000022.tif216153 TIFF2025535954000023.tif216153 TIFF2025535954000024.tif216153 TIFF2025535954000025.tif205153 TIFF2025535954000026.tif179153 TIFF2025535954000027.tif168153

[0232] Examples 1 to 20 are all core-shell polymers disclosed herein, each comprising a core and a shell covering at least a portion of the core. The core comprises structural units derived from a fluorine-containing monomer (vinylidene fluoride or chlorotrifluoroethylene) and structural units derived from an unsaturated monomer containing an amide group (acrylamide or methacrylamide). The shell comprises structural units derived from the fluorine-containing monomer (vinylidene fluoride or chlorotrifluoroethylene) and structural units derived from an unsaturated monomer containing a cyano group (acrylonitrile or methacrylonitrile). As can be seen from a comparison of Examples 1 to 20 with Comparative Examples 1 to 4, the core-shell polymers disclosed herein can more effectively adjust the viscosity of conductive pastes than non-core-shell polymers produced by conventional manufacturing methods, thereby providing excellent anti-settling and filterability. The production of core-shell polymers significantly reduces gelation of conductive pastes, improving the shelf life of conductive pastes and reducing DC resistance of batteries. As can be seen from Examples 1 to 5, the mass content of the core portion is 70% to 90% and the mass content of the shell portion is 10% to 30% relative to the total mass of the core-shell structure polymer. The core-shell structure polymer can further optimize the viscosity of the paste and comprehensively improve the processability and adhesiveness of the conductive paste.

[0233] As can be seen from Examples 1 to 5, the molar content of the structural units derived from vinylidene fluoride is 50% to 80% of the total molar number of all structural units in the core-shell structure polymer. The core-shell structure polymer can further optimize the viscosity of the paste, thereby comprehensively improving the processability and adhesiveness of the conductive paste.

[0234] As can be seen from Examples 1 to 5, the molar content of the structural units derived from acrylamide is 10% to 20% of the total molar content of all structural units in the core-shell structure polymer. The core-shell structure polymer further optimizes the viscosity of the paste, thereby comprehensively improving the processability and adhesiveness of the conductive paste.

[0235] As can be seen from Examples 1 to 5, the molar content of the structural units derived from acrylonitrile is 10% to 30% of the total molar number of all structural units in the core-shell structure polymer. The core-shell structure polymer further optimizes the viscosity of the paste, comprehensively improving the processability and adhesiveness of the conductive paste. As can be seen from Examples 1 and 6 to 9, when the weight-average molecular weight of the core-shell structure polymer is 100,000 to 300,000, the core-shell structure polymer achieves both the adhesive strength of the polar sheet and the filterability of the paste, comprehensively improving the adhesiveness and processability of the polar sheet.

[0236] As can be seen from Examples 1 and 13 to 16, when the mass fraction of the core-shell structured polymer is 0.5% to 2.5% relative to the total mass of the conductive paste, the core-shell structured polymer can achieve both high adhesive strength for the polar sheet and low resistance for the battery, thereby comprehensively improving the adhesiveness and electrical and chemical properties of the battery.

[0237] As can be seen from Examples 1 and 17 to 20, when the mass fraction of the conductive agent is 10.0% to 15.0% relative to the total mass of the conductive paste, the core-shell structured polymer achieves both high adhesive strength of the polar sheet and low resistance of the battery, thereby comprehensively improving the adhesiveness and electrical and chemical properties of the battery.

[0238] As can be seen from a comparison between the Examples and Comparative Example 5, the aqueous conductive paste prepared using the core-shell structured polymer disclosed herein not only improves the adhesive strength of the polar sheet but also reduces the sheet resistance of the polar sheet compared to the case where conductive carbon black is directly added.

[0239] As can be seen from a comparison between the Examples and Comparative Example 6, the aqueous conductive paste prepared using the core-shell structured polymer disclosed herein not only effectively improves paste dispersibility, anti-settling properties, and anti-gelling properties compared to a conductive paste using a conventional CMC dispersant as a binder, but also effectively reduces the amount of conventional dispersant used in batteries, improving the adhesive strength of the polar sheet and further reducing battery resistance.

[0240] It should be noted that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any embodiment that has substantially the same configuration as the technical idea and achieves the same effects within the scope of the technical solution of the present application is included within the technical scope of the present application. It should be noted that various modifications that a person skilled in the art can make to the embodiments and other forms formed by combining some of the components of the embodiments are also included within the scope of the present application, as long as they do not deviate from the spirit of the present application. [Explanation of symbols]

[0241] 1 battery pack, 2 upper housing, 3 lower housing, 4 battery module, 5 secondary battery, 51 housing, 52 electrode assembly, 53 cover plate, 6 core-shell structured polymer, 61 core portion, 62 shell portion

Claims

1. A core-shell structured polymer comprising a core portion and a shell portion covering at least a part of the core portion, wherein the core portion comprises a structural unit derived from a monomer represented by formula I and a structural unit derived from a monomer represented by formula II, and the shell portion comprises a structural unit derived from a monomer represented by formula I and a structural unit derived from a monomer represented by formula III, Here, R 1 , R 2 , R 3 are each independently hydrogen, fluorine, chlorine, or C substituted with fluorine. 1~3 alkyl groups, R 4 , R 5 , R 6 , R 7 , R 8 , R 9 are each independently hydrogen, substituted or unsubstituted C 1~5 A core-shell structured polymer, characterized in that the alkyl group is selected from one or more of:

2. R in Formula I 1 is fluorine, and R 2 , R 3 2. The core-shell polymer according to claim 1, wherein each of the groups is independently selected from one or more of hydrogen, fluorine, chlorine, and trifluoromethyl.

3. 3. The core-shell structure polymer according to claim 1, wherein the mass content of the core portion is 70% to 90% and the mass content of the shell portion is 10% to 30% relative to the mass of the core-shell structure polymer.

4. The core-shell structure polymer according to any one of claims 1 to 3, wherein the molar content of the structural units derived from the monomer represented by formula I is 50% to 80% relative to the total number of moles of all structural units in the core-shell structure polymer.

5. The core-shell structure polymer according to any one of claims 1 to 4, wherein the molar content of the structural units derived from the monomer represented by formula II is 10% to 20%, and the molar content of the structural units derived from the monomer represented by formula III is 10% to 30%, relative to the total number of moles of all structural units in the core-shell structure polymer.

6. The core-shell structure polymer according to any one of claims 1 to 5, wherein the mass content of the structural units derived from the monomer represented by formula I in the core portion is 85% to 95% relative to the total mass of the structural units derived from the monomer represented by formula I in the core-shell structure polymer.

7. The core-shell structure polymer according to any one of claims 1 to 6, wherein the weight average molecular weight of the core-shell structure polymer is 100,000 to 300,000.

8. The core-shell structure polymer according to any one of claims 1 to 7, wherein the monomer represented by formula I is selected from one or more of vinylidene fluoride, tetrafluoroethylene, chlorotrifluoroethylene, and hexafluoropropylene.

9. The core-shell structure polymer according to any one of claims 1 to 8, wherein the monomer represented by formula II is selected from one or more of acrylamide, methacrylamide, and butenamide.

10. The core-shell structure polymer according to any one of claims 1 to 9, wherein the monomer represented by formula III is selected from one or more of acrylonitrile, methacrylonitrile, 2-methyl-2-butenenitrile, and 3-butenenitrile.

11. The core-shell structure polymer according to any one of claims 1 to 10, wherein the Dv50 particle size of the core-shell structure polymer is 100 nm to 8 µm.

12. A method for producing a core-shell structured polymer, comprising: a monomer represented by formula I and a monomer represented by formula II are polymerized under polymerizable conditions to prepare a core portion of the core-shell structured polymer, and a monomer represented by formula I and a monomer represented by formula III are polymerized to prepare a shell portion of the core-shell structured polymer, the shell portion covering at least a portion of the core portion; Here, R 1 , R 2 , R 3 are each independently hydrogen, fluorine, chlorine, or C substituted with fluorine. 1~3 alkyl groups, R 4 , R 5 , R 6 , R 7 , R 8 , R 9 are each independently hydrogen, substituted or unsubstituted C 1~5 1. A method for producing a core-shell structured polymer, comprising the step of selecting one or more of:

13. R in Formula I 1 is fluorine, and R 2 , R 3 and each independently selected from one or more of hydrogen, fluorine, chlorine, and trifluoromethyl.

14. The method for producing a core-shell polymer according to claim 12 or 13, wherein the molar content of the monomer represented by formula I is 50% to 80% based on the total number of moles of the monomer represented by formula I, the monomer represented by formula II, and the monomer represented by formula III.

15. The method for producing a core-shell polymer according to any one of claims 12 to 14, wherein the molar content of the monomer represented by formula II is 10% to 20% based on the total number of moles of the monomer represented by formula I, the monomer represented by formula II, and the monomer represented by formula III.

16. The method for producing a core-shell polymer according to any one of claims 12 to 15, wherein the molar content of the monomer represented by formula III is 10% to 30% based on the total number of moles of the monomer represented by formula I, the monomer represented by formula II, and the monomer represented by formula III.

17. The polymerization reaction is a first-stage polymerization in which an initiator, a first emulsifier, at least one monomer represented by formula I, at least one monomer represented by formula II, and an aqueous medium are added to a reaction vessel, and in the first-stage polymerization, the monomer represented by formula I is continuously fed so as to maintain a constant reaction pressure; and after reacting for a certain period of time, adding an initiator, a second emulsifier, at least one monomer represented by formula III, and an aqueous medium to the reaction vessel to carry out second-stage polymerization to obtain a core-shell polymer, in which the monomer represented by formula I is continuously fed into the reaction vessel during the second-stage polymerization until all of the monomer represented by formula I is fed into the reaction vessel, and the reaction is terminated when the reaction pressure drops to 0 to 0.2 MPa.

18. The second stage polymerization is 18. The method for producing a core-shell polymer according to claim 17, further comprising adding a premix containing a second emulsifier, at least one monomer represented by formula III, and an aqueous medium after adding the initiator to the reaction vessel.

19. The method for producing a core-shell polymer according to claim 17 or 18, wherein the mass of the monomer represented by formula I introduced in the first-stage polymerization is 85% to 95% of the total mass of the monomer represented by formula I supplied in the polymerization reaction, and the mass of the monomer represented by formula I introduced in the second-stage polymerization is 5% to 15% of the total mass of the monomer represented by formula I supplied in the polymerization reaction.

20. The method for producing a core-shell structured polymer according to any one of claims 17 to 19, characterized in that the total mass percentage of the initiators added in the first-stage polymerization and the second-stage polymerization is 1% to 2% relative to the total mass of the monomers represented by formula I, the monomers represented by formula II, and the monomers represented by formula III.

21. The method for producing a core-shell structured polymer according to any one of claims 17 to 20, characterized in that the mass percentage of the first emulsifier is 0.1% to 0.5% relative to the total mass of the monomer represented by formula I, the monomer represented by formula II, and the monomer represented by formula III, and the mass percentage of the second emulsifier is 0.5% to 5% relative to the mass of the monomer represented by formula III.

22. The method for producing a core-shell structured polymer according to any one of claims 17 to 21, characterized in that the mass percentage of the aqueous medium provided in the first stage polymerization is 400% to 600% relative to the total mass of the monomer represented by formula I, the monomer represented by formula II, and the monomer represented by formula III.

23. The method for producing a core-shell polymer according to any one of claims 17 to 22, wherein the reaction pressure of the first-stage polymerization is 6.0 MPa to 9.0 MPa and the reaction temperature is 80 ° C to 100 ° C.

24. The method for producing a core-shell polymer according to any one of claims 17 to 23, wherein the initiation reaction pressure of the second-stage polymerization is lower than the reaction pressure of the first-stage polymerization, and the reaction temperature of the second-stage polymerization is higher than the reaction temperature of the first-stage polymerization.

25. The method for producing a core-shell structure polymer according to any one of claims 17 to 24, characterized in that the first emulsifier is an alkali metal salt of perfluorooctanoic acid, and the second emulsifier is an ammonium salt of polyoxyethylene-4-phenol ether sulfate.

26. The method for producing a core-shell structured polymer according to any one of claims 17 to 25, wherein the initiator is one or two of N,N-dimethylbenzylamine and ammonium persulfate.

27. Use of the core-shell structured polymer according to any one of claims 1 to 11 in a secondary battery.

28. An emulsion comprising an aqueous medium, an emulsifier, and the core-shell structured polymer according to any one of claims 1 to 11.

29. A conductive paste comprising a conductive agent, an aqueous medium, and the core-shell structure polymer according to any one of claims 1 to 11 or the emulsion according to claim 28.

30. The conductive paste according to claim 29, wherein the mass fraction of the conductive agent is 10.0% to 15.0% with respect to the total mass of the conductive paste.

31. 31. The conductive paste according to claim 29 or 30, wherein the mass fraction of the core-shell structure polymer is 0.5% to 2.5% with respect to the total mass of the conductive paste.

32. The conductive paste according to any one of claims 29 to 31, characterized in that the solid content is 12% to 17% and the viscosity is 500 mPa·s to 1500 mPa·s.

33. A negative electrode sheet comprising: a negative electrode current collector; and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer comprising a negative electrode active material, a conductive agent, and a binder, the conductive agent being a deposit of the conductive paste according to any one of claims 29 to 32.

34. The negative electrode sheet according to claim 33, wherein the adhesive strength per unit length between the negative electrode film layer and the negative electrode current collector is 12 N / m or more.

35. A secondary battery comprising a positive electrode sheet, a separator, an electrolyte, and the negative electrode sheet according to claim 33 or 34.

36. 36. The secondary battery of claim 35, wherein the secondary battery comprises at least one of a lithium ion battery, a sodium ion battery, a magnesium ion battery, and a potassium ion battery.

37. A battery module comprising the secondary battery according to claim 35 or 36.

38. A battery pack comprising at least one of the secondary battery according to claim 35 or 36 and the battery module according to claim 37.

39. 39. A power consumption device comprising at least one selected from the group consisting of the secondary battery according to claim 35 or 36, the battery module according to claim 37, and the battery pack according to claim 38.

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