Polymer, conductive slurry, positive electrode plate, secondary battery and power consumption device

Abstract

This application relates to a polymer, a conductive slurry, a positive electrode plate, a secondary battery, and a power consumption device. The polymer includes a structural unit represented by formula (1) and a structural unit represented by formula (2), where R1, R2, and R3 are each independently selected from a hydrogen atom, a halogen atom, or a substituted or unsubstituted C1-C10 alkyl group. The polymers in the examples of this application have good dispersibility and can be used as dispersants when used in secondary batteries, especially when used to prepare conductive slurries. This makes the particles in the slurry less likely to agglomerate, ensuring uniform dispersion and ensuring the electrochemical performance of the secondary battery. JPEG2025534770000016.jpg69160

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims priority to Chinese Patent Application No. 202211266304.3, entitled "Polymer, Conductive Slurry, Positive Electrode Plate, Secondary Battery and Power Consumption Device," proposed on October 17, 2022, the entire contents of which are incorporated herein by reference.

[0002] The present application relates to the field of battery production technology, and in particular to polymers, conductive slurries, positive electrode plates, secondary batteries, and power consuming devices. [Background technology]

[0003] Due to their characteristics such as high capacity and long life, secondary batteries are widely used in electronic devices such as mobile phones, laptops, battery-powered vehicles, electric cars, electric airplanes, electric steamships, electric toy cars, electric toy steamships, electric toy airplanes, and power tools.

[0004] As the range of battery applications continues to expand, the performance requirements for secondary batteries are also becoming more stringent. To improve the performance of secondary batteries, the electrode plates in the secondary batteries are typically optimized and improved. However, the performance of the membrane layers in current electrode plates is not uniform, and when used in secondary batteries, the electrochemical performance of the secondary batteries is relatively poor. Summary of the Invention

[0005] The present application has been made in view of the above-mentioned problems, and its object is to provide a polymer, a conductive slurry, a positive electrode plate, a secondary battery, and a power consuming device.

[0006] A first aspect of the present application provides a polymer, the polymer comprising a structural unit represented by formula (1) and a structural unit represented by formula (2), JPEG2025534770000002.jpg60164In formula (2), R1, R2 and R3 are each independently selected from a hydrogen atom, a halogen atom or a substituted or unsubstituted C1-C10 alkyl group, and optionally R1, R2 and R3 are each independently selected from a hydrogen atom, a halogen atom or a substituted or unsubstituted C1-C5 alkyl group.

[0007] The polymers in the examples of the present application have good dispersibility while still maintaining a certain degree of adhesiveness. When the polymers are used in secondary batteries, especially when used in the production of conductive slurries, they can be used as dispersants and auxiliary materials for adhesives, reducing the amount of adhesive with relatively high adhesive performance used. This makes it difficult for particles in the slurry to agglomerate, allowing for uniform dispersion, and improves the adhesive strength between particles and between particles and current collectors, ensuring the structural stability of the electrode plate and thereby ensuring the electrochemical performance of the secondary battery.

[0008] In some embodiments, the structural unit shown in formula (2) is selected from the group consisting of formulas (2-1) to (2-10): It contains one or more of the structural units shown in JPEG2025534770000003.jpg201170.

[0009] In some embodiments, the weight average molecular weight of the polymer is 1.5×10 5 Da ~ 2.0 × 10 5 It's Da.

[0010] In some embodiments, the number of structural units represented by formula (1) is n, and 100≦n≦150, and / or the number of structural units represented by formula (2) is m, and 100≦m≦150. When the weight-average molecular weight of the polymer is within the above range, the solubility of the polymer is ensured to be constant, thereby ensuring the viscosity of the polymer, and the viscosity rebound is small, allowing for relatively good adhesion to active materials, etc.

[0011] In some embodiments, the polymer satisfies at least one of conditions (1) to (3): (1) the viscosity of the polymer is C mPa*s and 500≦C≦3000; (2) the glass transition temperature of the polymer is Tg °C and 150≦Tg≦180; and (3) the crystallinity of the polymer as measured by a differential scanning calorimeter (DSC) is 40% to 50%.

[0012] Therefore, when the viscosity of the polymer of the present application is within the above range, the viscosity is moderate, and when the polymer is used in a secondary battery, the active material particles are uniformly dispersed, and aggregation between the particles is less likely to occur, resulting in more uniform electrode plate performance and favorable electrochemical performance of the secondary battery. When the glass transition temperature of the polymer is within the above range, the toughness of the electrode plate can be improved, the mechanical properties of the electrode plate can be reinforced, and the viscosity of the polymer can be moderate. When the crystallinity of the polymer is within the above range, it has little effect on the flow-through of molecules in the electrolyte, ensuring the charge and discharge performance of the secondary battery.

[0013] In some embodiments, the polymer is particulate, and the volume average particle size of the polymer is Dv50 μm, where 1≦Dv50≦5. When the volume average particle size of the polymer is in the above range, it dissolves to some extent in the slurry system and can act as an adhesive and dispersant.

[0014] A second aspect of the present application further provides a method of making a polymer, the method comprising the steps of providing a first monomer and a second monomer comprising a structural unit shown in formula (2); and polymerizing the first monomer and the second monomer in the presence of a radical initiator to form a polymer, wherein the first monomer comprises vinylidene fluoride and the structural unit shown in formula (2) is: JPEG2025534770000004.jpg42154In formula (2), R1, R2 and R3 are each independently selected from a hydrogen atom, a halogen atom or a substituted or unsubstituted C1-C10 alkyl group, and optionally R1, R2 and R3 are each independently selected from a hydrogen atom, a halogen atom or a substituted or unsubstituted C1-C5 alkyl group.

[0015] In some embodiments, polymerizing the first monomer and the second monomer in the presence of a radical initiator to form a polymer includes homopolymerizing the first monomer in the presence of a radical initiator to form a first block polymer; copolymerizing the first monomer, the second monomer, and the first block polymer in the presence of a radical initiator to form a second block polymer; and copolymerizing the first monomer and the second block polymer in the presence of a radical initiator to form the polymer.

[0016] In some embodiments, the ratio of the percentage molar content of the second monomer to the percentage molar content of the first monomer, based on the total molar amount of the first monomer and the second monomer, is A, and 0.10≦A≦0.30.

[0017] A third aspect of the present application further provides a method of producing a conductive slurry, the method comprising the steps of adding a polymer to a solvent and mixing them as a pre-formulated adhesive liquid, and dispersing a conductive agent in the pre-formulated adhesive liquid to form a conductive slurry, wherein the polymer comprises a polymer according to any one of the embodiments of the first aspect of the present application or a polymer obtainable by a method according to any one of the embodiments of the second aspect of the present application.

[0018] In some embodiments, the weight content of the polymer is p% based on the total weight of the conductive slurry, and the weight content of the conductive agent is q% based on the total weight of the conductive slurry, where 2≦q / p≦20, and further optionally 3≦q / p≦15.

[0019] A fourth aspect of the present application further provides a conductive slurry, the conductive slurry comprising a conductive agent and a polymer, the polymer comprising a polymer according to any one of the embodiments of the first aspect of the present application and a polymer obtainable by a method according to any one of the embodiments of the second aspect of the present application.

[0020] In some embodiments, the weight content of the polymer is p% based on the total weight of the conductive slurry, and the weight content of the conductive agent is q% based on the total weight of the conductive slurry, where 2≦q / p≦20, and further optionally 3≦q / p≦15.

[0021] A fifth aspect of the present application further provides a method for manufacturing a positive electrode plate, the method including the steps of providing a positive electrode current collector; adding a positive electrode active material, a polymer, a conductive agent, and an adhesive to a solvent and mixing them to form a positive electrode slurry; coating the positive electrode slurry on the positive electrode current collector; and curing the positive electrode slurry to form a positive electrode plate, wherein the polymer includes a polymer according to any one of the embodiments of the first aspect of the present application or a polymer obtained by the method according to any one of the embodiments of the second aspect of the present application.

[0022] In some embodiments, adding the positive electrode active material, polymer, conductive agent, and adhesive to a solvent and mixing them to form a positive electrode slurry includes adding the polymer to a solvent and mixing them to form a pre-formulated adhesive solution; dispersing the conductive agent in the pre-formulated adhesive solution to form a conductive slurry; and mixing the conductive slurry with the active material to form a positive electrode slurry.

[0023] In some embodiments, the weight content of the polymer is p% based on the total weight of the conductive slurry, and the weight content of the conductive agent is q% based on the total weight of the conductive slurry, where 2≦q / p≦20, and further optionally 3≦q / p≦15.

[0024] A sixth aspect of the present application further provides a positive electrode plate, the positive electrode plate being obtained by a method according to any one of the embodiments of the fifth aspect of the present application.

[0025] A seventh aspect of the present application further provides a secondary battery, the secondary battery including the positive electrode plate according to any one of the embodiments of the sixth aspect of the present application.

[0026] An eighth aspect of the present application further provides a power consuming device, the power consuming device including the secondary battery according to the seventh aspect of the present application. [Brief explanation of the drawings]

[0027] In order to more clearly explain the technical solutions of the embodiments of the present application, the following briefly introduces the drawings that need to be used in the embodiments of the present application, it is obvious that the drawings described below are only some embodiments of the present application, and those skilled in the art can obtain other drawings based on the drawings without making any creative efforts, and the drawings are not necessarily drawn to scale. [Figure 1] 1 is a schematic diagram of an embodiment of a secondary battery of the present application. [Figure 2] FIG. 2 is an exploded schematic view of the embodiment of the secondary battery of FIG. 1. [Figure 3] 1 is a schematic diagram of one embodiment of a battery module of the present application. [Figure 4] 1 is a schematic diagram of one embodiment of a battery pack of the present application. [Figure 5] FIG. 5 is an exploded schematic view of the embodiment of the battery pack shown in FIG. 4. [Figure 6] 1 is a schematic diagram of an embodiment of a power consuming device in which a secondary battery of the present application is used as a power source; DETAILED DESCRIPTION OF THE INVENTION

[0028] In order to make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the following will clearly describe the technical solutions in the embodiments of the present application in conjunction with the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only some of the embodiments of the present application, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present application without any creative efforts fall within the scope of protection of the present application.

[0029] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by those skilled in the art of this application, and the terms used in the specification of this application are only for describing specific embodiments and are not intended to limit this application, and the terms "comprises," "has," and any variations thereof in the specification and claims of this application and the above drawings are intended to cover a non-exclusive "comprise." The terms "first," "second," etc. in the specification and claims of this application or the above drawings are not intended to describe a specific order or a hierarchical relationship, but are intended to distinguish different objects.

[0030] An "embodiment" referred to in this application means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearances of this phrase in various places in the specification do not necessarily all refer to the same embodiment, nor are they mutually exclusive, separate, or alternative embodiments of other embodiments.

[0031] In the description of this application, it should be explained that unless otherwise clearly defined or limited, the terms "attached," "connected," "joined," and "attached" should be understood in a broad sense, and may refer to, for example, a fixed connection, a detachable connection, or an integral connection, a direct connection, an indirect connection via an intermediate medium, or internal communication between two elements. Those skilled in the art can understand the specific meanings of the above terms in this application according to specific circumstances.

[0032] The term "and / or" in this application merely describes the relationship between related objects and indicates that three relationships may exist, for example, A and / or B may represent three cases: A alone, a combination of A and B, and B alone. Also, the character " / " in this application generally indicates that the related objects before and after are in an "or" relationship.

[0033] In the embodiments of the present application, the same reference numerals represent the same elements, and for the sake of brevity, detailed descriptions of the same elements will be omitted in different embodiments. It should be understood that the thickness, length, width, and other dimensions of various elements in the embodiments of the present application shown in the drawings, and the overall thickness, length, width, and other dimensions of the integrated device, are illustrative examples and should not be construed as any limitation on the present application.

[0034] The term "plurality" as used herein refers to two or more (including two).

[0035] An electrode plate typically includes a current collector and a membrane layer disposed on the current collector. To adhere the active material to the current collector and ensure adhesion between the active material particles and between the active material and the current collector, an adhesive is typically used to ensure adhesion and advantageously form an interfacial film on the membrane layer. The adhesive is typically a polymer, typically polyvinyl alcohol (PVA), polytetrafluoroethylene (PTFE), or polyvinylidene fluoride (PVDF). Due to its excellent chemical, physical, and thermal processing properties, polyvinylidene fluoride (PVDF) has been extensively and in-depth studied.

[0036] According to the inventors' findings, when PVDF is used as an adhesive in a secondary battery, if the amount of PVDF is too high, it may cause aggregation between the active material particles, resulting in uneven distribution of the active material particles and an increase in the internal resistance of the secondary battery. Therefore, it is generally necessary to additionally add N-methylpyrrolidone (NMP) as a dispersant and use the two in combination. If the amount of PVDF is too low, the film formation effect will be relatively poor and the film layer may be easily detached from the current collector during the charge and discharge process.

[0037] Therefore, the inventors have improved the performance of PVDF itself by modifying the composition structure of PVDF, so that the improved PVDF has good dispersibility and can maintain a certain degree of adhesiveness. The technical solution of this application will now be described in detail.

[0038] polymer In a first aspect, the present application proposes a polymer.

[0039] The polymer comprises a structural unit shown in formula (1): JPEG2025534770000005.jpg31148The polymer further comprises a structural unit shown in formula (2). JPEG2025534770000006.jpg47148

[0040] The structural unit shown in formula (1) is derived from vinylidene fluoride (VDF), which is the main monomer of synthetic polymers. The carbon chain of the polymer portion formed by VDF is zigzag-shaped, and after the hydrogen atoms are replaced with fluorine atoms with relatively large electronegative properties, the fluorine atoms repel each other, preventing the fluorine atoms from being on the same plane. Instead, the fluorine atoms are distributed helically along the carbon chain. As a result, the carbon chain is surrounded by a series of stable fluorine atoms, forming a spatial barrier that makes it difficult for other atoms or groups to enter the structure and destroy the carbon chain. This results in extremely high chemical and thermal stability. The polarizability of the carbon-fluorine bond in the polymer is relatively low, the molecular structure is dense, and the polymer has relatively good hydrophobicity and lipophilicity. The polymer also exhibits high insulating properties.

[0041] The structural unit shown in formula (2) contains a carboxyl graft group. The carboxyl group can reinforce the cohesive force of the polymer. Furthermore, since the carboxyl group is a polar group, the introduction of the polar group into the side chain of the polymer can improve the dispersibility of the polymer. When this polymer is used in a secondary battery, the polymer can easily infiltrate the surface of particles such as conductive agents, thereby improving the wetting speed.

[0042] The structural unit shown in formula (1) exhibits lipophilicity, and the structural unit shown in formula (2) exhibits hydrophilicity. By using a combination of the structural unit shown in formula (1) and the structural unit shown in formula (2), the polymer can be made to have both lipophilicity and hydrophilicity, and particles such as conductive agents can be uniformly dispersed in the system, thereby exhibiting good dispersion performance.

[0043] By using a combination of the structural unit shown in formula (1) and the structural unit shown in formula (2), the polymer that is formed can have an appropriate degree of crystallinity, thereby improving the cohesive strength of the polymer itself and ensuring that the polymer still has a certain degree of adhesiveness. However, the adhesive strength is relatively poor, and by using it in combination with other adhesives, the adhesive performance to conductive agents, etc. can be supplemented and improved.

[0044] As a result, the polymers in the examples of the present application have good dispersibility while still maintaining a certain degree of adhesiveness. When the polymers are used in secondary batteries, especially when used in the production of conductive slurries, they can be used as dispersants and auxiliary materials for adhesives, reducing the amount of adhesive with relatively high adhesive performance used. The particles in the slurry are less likely to agglomerate and can be dispersed uniformly, improving the adhesive strength between particles and between particles and current collectors, and ensuring the structural stability of the electrode plate, thereby ensuring the electrochemical performance of the secondary battery.

[0045] In some embodiments, in formula (2), R1 is selected from a hydrogen atom, a halogen atom, or a substituted or unsubstituted C1-C10 alkyl group, and R2 and R3 are each independently selected from a hydrogen atom, a halogen atom, or a substituted or unsubstituted C1-C10 alkyl group. When substituted, the substituent may optionally be a halogen atom or other atom such as a sulfur atom.

[0046] The halogen atom may be a fluorine atom, a chlorine atom, a bromine atom, or the like.

[0047] The alkyl group may be a straight-chain or linear alkyl group. For example, the alkyl group may be a C1-C10 alkyl group, a C1-C8 alkyl group, a C1-C5 alkyl group, a C2-C8 alkyl group, or a C2-C6 alkyl group. Specifically, the alkyl group may include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a cyclobutyl group, a pentyl group, an isopentyl group, a neopentyl group, a tert-pentyl group, a cyclopentyl group, a hexyl group, a cyclohexyl group, a heptyl group, a cycloheptyl group, an octyl group, a cyclooctyl group, a nonyl group, and a decyl group. The alkyl group may also be optionally substituted, and the substituent may be a halogen atom or another atom such as a sulfur atom.

[0048] When the structural unit shown in formula (2) constitutes a part of a polymer, the structural units shown in formula (2) may be directly connected to each other, or the structural units shown in formula (2) may be alternately bonded to the structural units shown in formula (1). For example, a C atom bonded to R1 in formula (2) may be bonded to -CH2 in formula (1), and a C atom bonded to R2 in formula (2) may be bonded to -CF2 in formula (1).

[0049] Because the number of carbon atoms in R1, R2 and R3 is relatively small, the side chain structure of the structural unit of formula (2) is not too long, and three-dimensional cross-linking polymerization is unlikely to occur during the polymerization process. The polymerization method is mainly embodied as linear polymerization, that is, when the structural unit of formula (2) is polymerized, the side chain has little interference with the polymerization process, thereby ensuring the normal progress of polymerization. The molecular chain structure of the formed polymer is relatively symmetrical, making the polymer more likely to crystallize, thereby further improving the adhesiveness of the polymer. In addition, as the number of carbon atoms in the side chain structure increases, its hydrophobicity tends to be enhanced. The relatively short side chain can ensure the hydrophilicity of the entire structural unit of formula (2).

[0050] Optionally, R1, R2 and R3 are each independently selected from a hydrogen atom, a halogen atom or a substituted or unsubstituted C1-C5 alkyl group.

[0051] Alternatively, the structural unit shown in formula (2) may be any of the structural units shown in formula (2-1) to formula (2-10): It contains one or more of the structural units shown in JPEG2025534770000007.jpg195170.

[0052] The structural unit shown in formula (2) of the above structure, when introduced into a polymer, can reinforce the cohesive force of the polymer and ensure that its adhesive performance is improved, while also introducing hydrophilic properties and improving the dispersibility of the polymer.

[0053] In some embodiments, the weight average molecular weight of the polymer is 1.5×10 5 Da ~ 2.0 × 10 5It's Da.

[0054] When the weight-average molecular weight of the polymer is within the above range, the solubility of the polymer can be ensured to be constant, the viscosity of the polymer can be ensured, and the viscosity rebound is small, so that the active material can be adhered relatively well. For example, the weight-average molecular weight of the polymer is 1.5×10 5 Da, 1.6 × 10 5 Da, 1.7 × 10 5 Da, 1.8 × 10 5 Da, 1.9 × 10 5 Da or 2.0 × 10 5 Da, or a range consisting of any two of the above values.

[0055] In some embodiments, the number of structural units shown in formula (1), n, is 100≦n≦150, and optionally 100≦n≦133. Illustratively, n can be 100, 110, 120, 125, 130, 133, 138, 140, 145, 150, or a range consisting of any two of the foregoing values.

[0056] When the structural units shown in formula (1) constitute the molecular chain of a polymer, the symmetry of the molecular chain is relatively high, and the crystallinity of the polymer is relatively good, which mainly contributes to the adhesive performance of the polymer. Therefore, when the number n of the structural units shown in formula (1) is within the above range, the viscosity of the polymer can be ensured appropriately, and aggregation of active materials, conductive agents, etc. is less likely to occur.

[0057] In some embodiments, the number of structural units shown in formula (2) is m, and 100≦m≦150, optionally 100≦m≦133. Illustratively, m can be 100, 110, 120, 125, 130, 133, 138, 140, 145, 150, or a range consisting of any two of the foregoing values.

[0058] When the structural unit shown in formula (2) constitutes the molecular chain of a polymer, it is possible to improve the dispersibility of the polymer by introducing a functional group such as a carboxyl group into the side chain of the polymer to improve the hydrophilicity of the polymer, and also to improve the cohesive force of the polymer and the adhesive performance of the polymer by introducing a carboxyl group. Therefore, when the number m of the structural units shown in formula (2) is within the above range, it is possible to ensure an appropriate viscosity of the polymer and to provide the polymer with a certain degree of dispersibility.

[0059] In some embodiments, the viscosity of the polymer is C mPa*s, where 500≦C≦3000.

[0060] When the viscosity of the polymer is within the above range, the viscosity is appropriate, and when the polymer is used in a secondary battery, the active material particles are uniformly dispersed and aggregation between the particles is unlikely to occur, which is advantageous for making the performance of the electrode plate more uniform and fully demonstrating the electrochemical performance of the secondary battery. For example, the viscosity of the polymer may be 500 mPa*s, 600 mPa*s, 700 mPa*s, 800 mPa*s, 900 mPa*s, 1000 mPa*s, 1200 mPa*s, 1500 mPa*s, 1800 mPa*s, 1900 mPa*s, 2000 mPa*s, 2500 mPa*s, or a range consisting of any two of the above values.

[0061] In some embodiments, the polymer has a glass transition temperature, Tg °C, where 150 < Tg < 180.

[0062] When the glass transition temperature of the polymer is in the above range, the toughness of the electrode plate can be improved, the mechanical properties of the electrode plate can be reinforced, and the viscosity of the polymer can be moderate. For example, the glass transition temperature of the polymer may be 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, 180°C, or a range consisting of any two of the above values.

[0063] In some embodiments, the polymer has a crystallinity of 40% to 50% by differential scanning calorimetry (DSC) testing.

[0064] When the crystallinity of the polymer is within the above range, it has little effect on the flow-through of molecules in the electrolyte, and can ensure the charge / discharge performance of the secondary battery. For example, the crystallinity of the polymer may be 40%, 42%, 45%, 48%, 49%, 50%, or a range consisting of any two of the above values.

[0065] In some embodiments, the polymer is particulate and the polymer has a volume average particle size Dv50 μm, where 1≦Dv50≦5.

[0066] When the volume average particle diameter of the polymer is within the above range, it dissolves to some extent in the slurry system and can function as an adhesive and dispersant. For example, the volume average particle diameter Dv50 μm of the polymer may be 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, or 5 μm, or a range consisting of any two of the above values.

[0067] In this application, the volume average particle size Dv50 of a material has the meaning known in the art, which means the particle size corresponding to when the cumulative volume distribution percentage of the material reaches 50%, and can be tested using equipment and methods known in the art, for example, GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method, which can be easily tested using a laser particle size analyzer, such as the Mastersizer 2000E laser particle size analyzer from Malvern Instruments Ltd., UK.

[0068] In this application, the specific surface area of ​​a material has the meaning known in the art and can be tested using instruments and methods known in the art. For example, the specific surface area can be tested using the nitrogen adsorption specific surface area analysis test method in accordance with GB / T 19587-2017 and calculated using the Brunauer Emmett Teller (BET) method. The nitrogen adsorption specific surface area analysis test can be performed using a Tri-Star 3020 specific surface area hole diameter analyzer manufactured by Micromeritics, Inc., USA.

[0069] Method for producing a polymer In a second aspect, the present application proposes a method for producing a polymer, said method being obtainable by producing a polymer according to any one embodiment of the first aspect of the present application.

[0070] The method comprises: Step S100 of providing a first monomer and a second monomer comprising a structural unit shown in formula (2); and a step S200 of polymerizing the first monomer and the second monomer in the presence of a radical initiator to form a polymer; wherein the first monomer contains vinylidene fluoride, and the structural unit shown in formula (2) is as follows: JPEG2025534770000008.jpg46158In equation (2), R1 is selected from a hydrogen atom, a halogen atom, or a substituted or unsubstituted C1-C10 alkyl group; R2 and R3 are each independently selected from a hydrogen atom, a halogen atom, or a substituted or unsubstituted C1-C10 alkyl group. Optionally, R1, R2, and R3 are each independently selected from a hydrogen atom, a halogen atom, or a substituted or unsubstituted C1-C5 alkyl group.

[0071] A polymer is formed by copolymerizing a first monomer and a second monomer, and the order of adding the first monomer and the second monomer may be adjusted according to production needs, for example, a part of the first monomer may be added first, the first monomer may be homopolymerized, and then the second monomer and the first monomer may be added, and the first monomer and the second monomer may be copolymerized, etc. Alternatively, the first monomer may be added first, the first monomer may be copolymerized, the second monomer may be added, and the second monomer may be copolymerized, and then the block polymer obtained after copolymerizing the first monomer and the block polymer obtained after copolymerizing the second monomer may be polymerized.

[0072] Regardless of the polymerization method, the polymer formed has a -CH2-CF2- main chain, which can be supplemented by the structural unit shown in formula (2), and a carboxyl group can be introduced into the side chain of the polymer to improve the adhesion and dispersibility of the polymer. The polymerization method of this application is relatively simple, and the formed polymer has good dispersibility while still maintaining a certain degree of adhesion.

[0073] The polymer can be polymerized by suspension polymerization or emulsion polymerization. The amount of dispersant adsorbed by the polymer formed by suspension polymerization is small and easy to remove, the purity of the product is relatively high, and the post-treatment process is relatively simple. The polymerization rate of emulsion polymerization is fast, the molecular weight of the product is relatively high, and the polymerization can be performed at a relatively high temperature.

[0074] Suspension polymerization can be carried out as follows: add a certain amount of deionized water and dispersant into the reactor, seal the reactor, evacuate, replace oxygen gas with inert gas, such as nitrogen gas, and then evacuate again and fill with nitrogen gas, so that the pressure in the reactor is slightly higher than atmospheric pressure, and is adjusted to the oxygen gas content in the reactor.Stir the system in the reactor, increase the temperature to about 50 ℃, and increase the pressure to about 3.5 MPa.Add some monomer and initiator, etc., to start polymerization.Continue to add monomer and initiator, etc. during polymerization, maintain the temperature and pressure in the reactor until all monomer addition is completed, and reduce the pressure to about 2.8 MPa, stop stirring, and terminate the reaction.

[0075] Emulsion polymerization can be carried out in the following manner: the reactor is evacuated, and oxygen gas is replaced with an inert gas, such as nitrogen gas, to achieve the oxygen gas content in the reactor as a standard; deionized water, emulsifier, initiator, etc. are introduced into the reactor, a small amount of monomer is added, the reactor is heated to the reaction temperature, and as the reaction proceeds, monomer is continuously added, and the pressure in the reactor is maintained until the reaction is completed; during the reaction, the polymer undergoes processes such as coagulation, washing, and drying to obtain the final polymer product.

[0076] In some embodiments, step S200 includes:

[0077] Step S210, the first monomer is homopolymerized in the presence of a radical initiator to form a first block polymer.

[0078] By homopolymerizing the first monomer in advance to form the first block polymer, it is possible to ensure that the molecular chain of the polymer is a linear main chain, thereby ensuring a certain degree of regularity of the polymer, which is advantageous for enhancing the crystallization ability of the polymer.

[0079] Step S220: copolymerizing the first monomer, the second monomer and the first block polymer in the presence of a radical initiator to form a second block polymer.

[0080] A second monomer is introduced, and the first and second monomers continue to polymerize based on the first block polymer, introducing a carboxyl group into the side chain of the polymer, thereby improving the adhesion and dispersibility of the polymer.

[0081] Step S230, copolymerizing the first monomer and the second block polymer in the presence of a radical initiator to form the polymer.

[0082] Based on the second block polymer, the polymerization of the first monomer continues, ensuring that the entire polymer is a linear molecular chain.

[0083] In some embodiments, the ratio of the percentage molar content of the second monomer to the percentage molar content of the first monomer, based on the total molar amount of the first monomer and the second monomer, is A, and 0.10≦A≦0.30.

[0084] The total molar amount of the first monomer and the second monomer is the sum of the molar amount of the first monomer and the molar amount of the second monomer introduced throughout the entire reaction process. The molar content percentage of the first monomer is the percentage of the molar amount of the first monomer to the total molar amount. The molar content percentage of the second monomer is the percentage of the molar amount of the second monomer to the total molar amount. Exemplarily, the ratio A of the molar content percentage of the second monomer to the molar content percentage of the first monomer may be 0.10, 0.15, 0.20, 0.25, 0.30, or a range consisting of any two of the above values.

[0085] When the ratio A of the molar content percentage of the second monomer to the molar content percentage of the first monomer is within the above range, the adhesiveness of the polymer can be ensured, and the dispersibility of the polymer can also be ensured.

[0086] In some embodiments, emulsifiers and solvents may be added to facilitate emulsion polymerization.

[0087] The emulsifier includes an alkali metal salt of perfluorooctanoic acid.

[0088] Method for producing conductive slurry In a third aspect, the present application proposes a method for producing a conductive slurry.

[0089] The inventors discovered that conductive agents, such as conductive carbon black, are an important component in the battery production process, and their dispersibility in the slurry significantly affects the resistance of the electrode plate and the performance of the secondary battery. Conductive carbon black has a particle size on the order of microns, a large specific surface area, and a tendency to agglomerate. Conventional methods involve directly mixing dry conductive carbon black powder with the cathode active material and then adding it to a solvent. This makes it difficult to achieve uniform dispersion through mechanical stirring, requiring prolonged stirring and slurry formation, which not only impacts production efficiency but also its conductivity. Related technologies also pre-preparing conductive carbon black into a conductive slurry requires the addition of other additives, such as dispersants and surfactants. However, the different additives in different systems can easily lead to incompatibility issues with the slurry system during the synthesis slurry production process for secondary batteries. Furthermore, the PVDF adhesive used in battery production has a molecular weight of 500,000 to 1.2 million, resulting in a high adhesive viscosity, making it difficult to uniformly disperse the conductive carbon black and resulting in high electrode plate resistance. Even if the stirring time is extended to achieve uniform dispersion, the dispersed carbon black particles will aggregate after the slurry is allowed to stand, and the viscosity of the slurry will increase, causing gelation, which will affect its production and use.

[0090] In response to the above problem, the inventor has proposed a method for producing a conductive slurry, the method comprising: adding a polymer to a solvent and mixing it as a pre-formed adhesive solution; and dispersing a conductive agent in the pre-formulated adhesive liquid to form a conductive slurry; wherein said polymer comprises a polymer according to any one of the embodiments of the first aspect of the present application or a polymer obtainable by the method according to any one of the embodiments of the second aspect of the present application.

[0091] Specifically, a polymer powder may be added to a solvent and mixed to form a pre-prepared adhesive solution, and a conductive agent, such as conductive carbon black, may be dispersed in the pre-prepared adhesive solution to form a conductive slurry. The conductive agent in the resulting conductive slurry is more uniformly dispersed, eliminating the occurrence of phenomena such as excessive aggregation due to the relatively small particle size of the conductive agent. This results in a more uniform distribution of the conductive agent, which can reduce the resistance of the positive electrode membrane layer to a certain extent and improve the electrochemical performance of the secondary battery. In this application, the solvent in the pre-prepared adhesive solution can be selected from solvents commonly used in positive electrode slurries, such as N-methylpyrrolidone (NMP).

[0092] Furthermore, the mass content of the polymer is defined as p %, based on the total mass of the conductive slurry, and 0.5≦p≦2.5.

[0093] When the polymer mass content is within the above range, uniform dispersion of the conductive agent in the polymer can be ensured, and the conductive slurry has a certain viscosity, for example greater than 40 mPa*s, which makes the conductive slurry relatively stable, less likely to cause sedimentation of the conductive agent, and the conductive slurry has a moderate viscosity, which rarely causes problems such as gelation due to viscosity rebound, which is advantageous for long-term storage of the conductive slurry. For example, the polymer mass content may be 0.5%, 1%, 1.5%, 2%, or 2.5%, or a range consisting of any two of the above values.

[0094] Furthermore, the mass content of the conductive agent is defined as q% based on the total mass of the conductive slurry, and is 7.5≦q≦15.5.

[0095] When the mass content of the conductive agent is within the above range, the solvent content can be ensured, which is advantageous for dissolving and dispersing the polymer, and the dosage of the conductive agent is appropriate, resulting in relatively good overall fluidity of the conductive slurry, which is advantageous for addition in industrial production. For example, the mass content of the conductive agent may be 7.5%, 8%, 8.5%, 9%, 9.5%, 10.5%, 11.0%, 12.0%, 13.0%, 13.5%, 14.0%, 15.0%, 15.5%, or a range consisting of any two of the above values.

[0096] Furthermore, 2≦q / p≦20. Optionally, 3≦q / p≦15. Illustratively, q / p may be 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 16, 18, 19, 20, or a range consisting of any two of the above values. When q / p is within the above range, the dispersion performance of the conductive agent by the dispersant polymer is better, the dispersion of the conductive agent is uniform, and the performance of the formed conductive slurry is stable. When used in a positive electrode plate, this is advantageous for reducing the diaphragm resistance of the positive electrode plate.

[0097] Conductive Slurry In a fourth aspect, the present application proposes a conductive slurry.

[0098] The conductive slurry comprises a conductive agent and a polymer, and the polymer comprises a polymer according to any one of the embodiments of the first aspect of the present application or a polymer obtained by the method according to any one of the embodiments of the second aspect of the present application.

[0099] The conductive slurry may be obtained by the method according to any one of the embodiments of the third aspect of the present application.

[0100] The conductive slurry of the present application has relatively good dispersibility, is not prone to aggregation and sedimentation, and can ensure uniform and stable performance during long-term storage.

[0101] Optionally, the mass content of the polymer is p% based on the total mass of the conductive slurry, and the mass content of the conductive agent is q% based on the total mass of the conductive slurry, and 2≦q / p≦20, and further optionally 3≦q / p≦15.

[0102] positive electrode plate In a fifth aspect, the present application proposes a positive electrode plate.

[0103] In some embodiments, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector. For example, the positive electrode current collector has two opposing surfaces in its thickness direction, and the positive electrode film layer is disposed on one or both of the two opposing surfaces of the positive electrode current collector. The positive electrode film layer includes a polymer according to any one of the embodiments of the first aspect of the present application or a polymer obtained by manufacturing according to any one of the embodiments of the second aspect of the present application. The polymer has good dispersibility and certain adhesive properties, so it may be used as a dispersant and adhesive auxiliary in the positive electrode film layer. The positive electrode film layer does not require the addition of other dispersants, which reduces the risk of damage to the positive electrode active material caused by other dispersants and ensures the structural stability of the positive electrode film layer.

[0104] The positive electrode film layer includes a positive electrode active material, which may be any positive electrode active material for secondary batteries known in the art. For example, the positive electrode active material may include at least one of layered positive electrode active materials (e.g., ternary, lithium / sodium nickelate, lithium / sodium cobaltate, lithium / sodium manganate, lithium / sodium-rich layered materials, and rock salt layered materials), olivine-type phosphate active materials, and spinel-structured positive electrode active materials (e.g., spinel lithium manganate, spinel lithium nickel manganate, lithium-rich spinel lithium manganate, and lithium nickel manganate).

[0105] For example, the general formula of the layered positive electrode active material is Li x A y Ni a Cob Mn c M (1-a-b-c) Y z where 0≦x≦2.1, 0≦y≦2.1, and 0.9≦x+y≦2.1, 0≦a≦1, 0≦b≦1, 0≦c≦1, and 0.1≦a+b+c≦1, and 1.8≦z≦3.5; A is selected from one or more of Na, K, and Mg; M is selected from one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; and Y is selected from one or more of O and F. Optionally, y=0. Specifically, the layered structure positive electrode active material is lithium cobalt oxide (LCO), lithium nickel oxide (LNO), lithium manganese oxide (LMO), LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM333), LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811) and LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM523) may be included.

[0106] For example, the general formula of the olivine-type phosphate active material is Li x A y Me a M b P 1-c X c Y zwherein 0≦x≦1.3, 0≦y≦1.3 and 0.9≦x+y≦1.3, 0.9≦a≦1.5, 0≦b≦0.5 and 0.9≦a+b≦1.5, 0≦c≦0.5, 3≦z≦5; A is selected from one or more of Na, K, and Mg; Me is selected from one or more of Mn, Fe, Co, and Ni; M is selected from one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X is selected from one or more of S, Si, Cl, B, C, and N; and Y is selected from one or more of O and F. Specifically, the olivine-type phosphate active material includes one or more of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4.

[0107] For example, the general formula of the positive electrode active material having a spinel structure is Li x A y Mn a M 2-a Y z where 0≦x≦2, 0≦y≦1, and 0.9≦x+y≦2, 0.5≦a≦2, 3≦z≦5, A is selected from one or more of Na, K, and Mg, M is selected from one or more of Ni, Co, B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce, and Y is selected from one or more of O and F. Specifically, the positive electrode active material having a spinel structure is LiMn2O4, LiNi 0.5 Mn 1.5 O4, LiCr 0.3 Mn 1.7 O4, Li 1.1 Al 0.1 Mn 1.9 O4, Li2Mn2O4 and Li 1.5 Mn2O4.

[0108] In some embodiments, the positive electrode current collector may be a metal foil sheet or a composite current collector. Examples of the metal foil sheet include aluminum foil or aluminum alloy 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. For example, the metal layer may include one or more combinations selected from aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. The polymer base layer may include one or more combinations selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0109] In some embodiments, the positive electrode film layer further optionally includes a positive electrode conductive agent. The present application is not particularly limited to the type of the positive electrode conductive agent, and examples of the positive electrode conductive agent include one or more combinations selected from superconducting carbon, conductive carbon black, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage content of the positive electrode conductive agent is 5% or less, based on the total mass of the positive electrode film layer.

[0110] In some embodiments, the positive electrode membrane layer optionally further includes a positive electrode adhesive. The present application is not particularly limited to the type of positive electrode adhesive. For example, the positive electrode adhesive may include one or more combinations selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin. In some embodiments, the mass percentage content of the positive electrode adhesive is 5% or less, and optionally, the mass percentage content of the positive electrode adhesive is 1.0% to 2.5%, based on the total mass of the positive electrode membrane layer. In the present application, the molecular weight of the positive electrode adhesive is 500,000 to 2,000,000. For example, the molecular weight of polyvinylidene fluoride (PVDF) used in the positive electrode adhesive is 500,000 to 2,000,000. The polymer in the embodiment described in the first aspect of the present application can be used as an auxiliary agent for the positive electrode adhesive, which can improve the adhesive performance of the positive electrode membrane layer and reduce the risk of aggregation of the positive electrode active material.

[0111] The positive electrode film layer is generally obtained by coating a positive electrode slurry on a positive electrode current collector, drying, and cold pressing. The positive electrode slurry is generally formed by dispersing a positive electrode active material, an optional conductive agent, an optional adhesive, and any other optional components in a solvent and stirring the mixture uniformly.

[0112] In some embodiments, the positive electrode plate is manufactured by the following steps: providing a positive electrode current collector, mixing a positive electrode active material, a polymer, a conductive agent, and an adhesive in a solvent to form a positive electrode active slurry, coating the positive electrode active slurry onto the positive electrode current collector, and curing to form a positive electrode plate. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP).

[0113] In some embodiments, the conductive agent may be prepared in advance as a conductive slurry, and the conductive slurry and the positive electrode active material may be mixed to form a positive electrode slurry. The conductive slurry may be a conductive slurry prepared by the method according to any one of the third and fourth aspects of the present application. Alternatively, the conductive slurry may be prepared directly by using the polymer according to any one of the first and second aspects of the present application or the polymer prepared by the method according to any one of the second and third aspects of the present application.

[0114] Specifically, a polymer powder may be added to a solvent and mixed to form a pre-prepared adhesive solution, and a conductive agent, such as conductive carbon black, may be dispersed in the pre-prepared adhesive solution to form a conductive slurry. A positive electrode active material, a positive electrode adhesive, etc. may then be dispersed in the conductive slurry to form a positive electrode slurry. The conductive agent in the conductive slurry thus prepared is more uniformly dispersed, and phenomena such as excessive aggregation due to the relatively small particle size of the conductive agent do not occur. This results in a more uniform distribution of the conductive agent, which can reduce the resistance of the positive electrode film layer to a certain extent and improve the electrochemical performance of the secondary battery. In this application, the solvent in the pre-prepared adhesive solution can be selected from solvents commonly used in positive electrode slurries, such as N-methylpyrrolidone (NMP).

[0115] secondary battery In a sixth aspect, the present application proposes a secondary battery.

[0116] The secondary battery includes a positive electrode plate, a negative electrode plate, and a separator, and the separator is disposed between the positive electrode plate and the negative electrode plate to separate the positive electrode plate and the negative electrode plate.

[0117] In some embodiments, the positive electrode plate may employ the positive electrode plate according to any one of the embodiments of the fifth aspect of the present application, so as to reduce the resistance of the plate and improve the cycle performance and charge / discharge performance of the secondary battery.

[0118] Negative electrode plate The negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer including a negative electrode active material. The negative electrode film layer includes a polymer according to any one of the embodiments of the first aspect of the present application or a polymer obtained by manufacturing the polymer according to any one of the embodiments of the second aspect of the present application. The polymer has good dispersibility and certain adhesive properties, and can therefore be used as a dispersant and adhesive auxiliary in the negative electrode film layer. No other dispersant may be added to the negative electrode film layer, reducing the risk of other dispersants damaging the negative electrode active material and ensuring the structural stability of the negative electrode film layer.

[0119] For example, the negative electrode current collector has two surfaces that face each other in the thickness direction thereof, and the negative electrode film layer is disposed on either one or both of the two facing surfaces of the negative electrode current collector.

[0120] In some embodiments, the negative electrode current collector may be a metal foil sheet or a composite current collector. For example, a copper foil may be used as the metal foil sheet. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base. The composite current collector may be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, or silver alloy) on a polymer base (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0121] In some embodiments, the negative electrode active material may be any 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 usable as battery negative electrode active materials may also be used. These negative electrode active materials may be used alone or in combination.

[0122] 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, conductive carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0123] In some embodiments, the negative electrode membrane layer optionally further comprises other additives, such as a thickener (eg, sodium carboxymethylcellulose (CMC-Na)).

[0124] In some embodiments, the negative electrode membrane layer optionally further includes a negative electrode adhesive. The negative electrode adhesive may be selected from at least one of styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS). In some embodiments, based on the total mass of the negative electrode membrane layer, the mass percentage content of the negative electrode adhesive is 5% or less, and optionally the mass percentage content of the negative electrode adhesive is 1.5% to 3%. In the present application, the molecular weight of the negative electrode adhesive is 500,000 to 2,000,000. For example, the molecular weight of the styrene-butadiene rubber (SBR) used in the negative electrode adhesive is 500,000 to 2,000,000. The polymer in the embodiment described in the first aspect of the present application may be used as an auxiliary agent for the styrene-butadiene rubber adhesive, which can improve the adhesive particle size of the negative electrode membrane layer and reduce the risk of aggregation of the styrene-butadiene rubber active material.

[0125] In some embodiments, a negative electrode plate can be manufactured in the following manner: Components for manufacturing the negative electrode plate, such as a negative electrode active material, an optional conductive agent, an optional adhesive, and any other components, are dispersed in a solvent (e.g., deionized water) to form a negative electrode slurry, which is then coated onto a negative electrode current collector, and the negative electrode plate is obtained after processes such as drying and cold pressing.

[0126] [Electrolyte] The secondary battery further includes an electrolyte, which functions to conduct ions between the positive electrode plate and the negative electrode plate. 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.

[0127] In some embodiments, the electrolyte is an electrolytic solution, which includes an electrolyte salt and a solvent.

[0128] By way of example, the lithium salt may include one or more combinations selected from lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium perchlorate (LiClO), lithium hexafluoroarsenate (LiAsF), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluorophosphate (LiPOF), lithium difluorobis(oxalato)phosphate (LiDFOP), and lithium tetrafluoro(oxalato)phosphate (LiTFOP).

[0129] By way of example, the organic solvent may comprise one or more combinations selected from ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE).

[0130] In some embodiments, the electrolyte solution may further optionally contain additives, such as an additive for forming a negative electrode film or a positive electrode film, and may further include additives that can improve some battery performance, such as an additive for improving the overcharge performance of the battery or an additive for improving the high-temperature or low-temperature performance of the battery.

[0131] [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.

[0132] In some embodiments, the separator may be made of one or more materials 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. When the separator is a multi-layer composite film, the materials of each layer may be the same or different.

[0133] In some embodiments, the positive electrode plate, separator, and negative electrode plate can be fabricated into an electrode assembly by a winding process or a stacking process.

[0134] The present application does not particularly limit the shape of the secondary battery, which may be cylindrical, rectangular, or any other shape. Figure 1 shows a secondary battery 5 with a rectangular structure as an example.

[0135] In some embodiments, as shown in FIGS. 1 and 2 , the exterior body may include a case 51 and a cover plate 53. Here, the case 51 may include a bottom plate and a side plate connected to the bottom plate, which together form a surrounding accommodating cavity. The case 51 has an opening communicating with the accommodating cavity, and the cover plate 53 is used to cover the opening to seal the accommodating cavity. The positive electrode plate, the negative electrode plate, and the separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is packaged in the accommodating 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 can be adjusted as needed.

[0136] The manufacturing method of the secondary battery of the present application is well known. In some embodiments, a secondary battery may be formed by assembling a positive electrode plate, a separator, a negative electrode plate, and an electrolyte. For example, the positive electrode plate, the separator, and the negative electrode plate may be wound or stacked to form an electrode assembly, the electrode assembly may be placed in an outer package, dried, and then the electrolyte may be injected. The secondary battery may then be obtained by vacuum packaging, standing, forming, shaping, or other processes.

[0137] In some embodiments of the present application, the secondary battery according to the present application may be assembled into a battery module, and the number of secondary batteries included in the battery module may be multiple, and the specific number may be adjusted according to the application and capacity of the battery module.

[0138] Fig. 3 is a schematic diagram of an example battery module 4. As shown in Fig. 3, in the battery module 4, the plurality of secondary batteries 5 may be arranged in order along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the plurality of secondary batteries 5 may be fixed by fasteners.

[0139] 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.

[0140] In some embodiments, the battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0141] 4 and 5 are schematic diagrams of an example battery pack 1. As shown in FIGS. 4 and 5, the battery pack 1 may include a battery box and a plurality of battery modules 4 installed in the battery box. The battery box includes an upper housing 2 and a lower housing 3, and the upper housing 2 covers the lower housing 3 and is used to form a sealed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0142] power consumption equipment In a seventh aspect, the present application provides a power consuming device, the power consuming device including at least one of the secondary battery, battery module, and battery pack of the present application. The secondary battery, battery module, and 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 be, but is not limited to, a mobile device (e.g., a mobile phone, a laptop, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, an energy storage system, etc.

[0143] The power consumption device can select a secondary battery, a battery module, or a battery pack according to its usage needs.

[0144] 6 is a schematic diagram of an example power consuming device 6, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. A battery pack 1 or battery module may be employed to meet the high power and high energy density demands of the power consuming device.

[0145] Other examples of power consuming devices may be mobile phones, tablet computers, laptop computers, etc. These power consuming devices are generally required to be thin and may employ secondary batteries as their power source.

[0146] Example The following describes examples of the present application. The examples described below are illustrative and are intended to interpret the present application, but should not be understood as limitations on the present application. If no specific techniques or conditions are described in the examples, they are carried out according to the techniques, conditions, or product specifications described in documents within the field. If no manufacturer is listed for the reagents or equipment used, they are all ordinary products that are commercially available.

[0147] Example 1 Manufacture of dispersant polyvinylidene fluoride Example 1-1 Step S1: 30 kg of deionized water (conductivity of 2 μs / cm or less), 15 g of 100% emulsifier perfluorooctanoic acid alkali metal salt, and 36 g of initiator (5% potassium persulfate solution) accounting for 40% of the total amount are added in order into a 50 L reactor, and the reactor is closed. Step S2: Vacuum the reactor and fill it with nitrogen gas. Repeat this process until the oxygen gas concentration in the reactor is less than 100 ppm. Step S3: Inject vinylidene fluoride monomer into the reactor until the pressure inside the reactor reaches 7.0 MPa; Step S4: The temperature in the reactor is raised to 80°C to start the reaction, and during the reaction, vinylidene fluoride monomer is continuously injected to maintain the reaction pressure in the reactor constant; Step S5: When the amount of vinylidene fluoride monomer added reaches 50% of the total amount, i.e., 2.4 kg, add 36 g of initiator (5% potassium persulfate solution), which accounts for 40% of the total amount; maintain the reaction pressure at 7.0 MPa; and inject a mixed gas of vinylidene fluoride monomer and a second monomer into the reactor (vinylidene fluoride monomer and the second monomer, methacrylic acid monomer, are added simultaneously in a mass ratio of 1:1); Step S6: Add 1.2 kg of the second monomer until the amount of vinylidene fluoride added reaches 80% of the total amount, i.e., 3.6 kg. Add 18 g of initiator, which is the remaining 20%, and maintain the reaction pressure at 7.0 MPa. Inject 1.2 kg of the remaining 20% ​​vinylidene fluoride monomer into the reactor; Step S7: When the reaction is completed, the pressure in the reactor reaches 2.0 MPa, and the unreacted vinylidene fluoride monomer is recovered. Step S8, the reaction product was flocculated, washed, separated, dried and pulverized to obtain polymer PVDF.

[0148] Examples 1-2 and 1-3 In Examples 1-2 and 1-3, the dispersant PVDF was prepared according to a method similar to that of Example 1-1, except that the molar ratio of the second monomer was adjusted in Examples 1-2 and 1-3.

[0149] Examples 1-4 and 1-5 Examples 1-4 and 1-5 were prepared using a similar method to Example 1-1 to prepare a PVDF dispersant. The difference between Examples 1-4 and 1-5 and Example 1-1 was that at least one of the reaction temperature in step S4 and the reaction pressure in step S3 was adjusted.

[0150] Examples 1-6 In Example 1-6, the dispersant PVDF was prepared according to a method similar to that of Example 1-1, except that the type of the second monomer in Example 1-6 was adjusted.

[0151] Examples 1-7 to 1-9 Examples 1-7 to 1-9 were prepared using a similar method to Example 1-1 to prepare PVDF dispersions. The difference from Example 1-1 is that Examples 1-7 to 1-9 adjusted the amount of initiator and the reaction rate to adjust the particle size of the polymer. For example, compared with Example 1-1, the amount of initiator in Example 1-7 was increased by 10%, the amount of initiator in Example 1-8 was increased by 5%, and the amount of initiator in Example 1-9 was increased by 2%.

[0152] The parameters of Examples 1-1 to 1-9 are as shown in Table 1.

[0153] [Table 1]

[0154] Example 2 Example 2-1 1. Manufacturing of positive electrode plates 1.1 Aluminum foil with a thickness of 12 μm was used as the positive electrode current collector.

[0155] 1.2 Preparation of conductive slurry 16,000 g of N-methylpyrrolidone, the solvent, was added to the stirring tank. 300 g of the dispersant PVDF prepared in Example 1-1 was added to the solvent NMP in a stirring tank, and the mixture was stirred at room temperature at a rotation speed of 1000 rpm for 60 minutes to obtain a pre-prepared adhesive liquid. 1600 g of conductive carbon black powder was added to the pre-prepared adhesive liquid, and the mixture was stirred at a rotation speed of 800 rpm for 60 minutes. Cooling water circulation in the stirring tank was started, and after stirring was completed, a conductive slurry was obtained.

[0156] 1.3 Preparation of cathode slurry Cathode active material (LiNi 0.6 Co 0.2 Mn 0.2 O2), polyvinylidene fluoride was added to the conductive slurry and thoroughly stirred to form a uniform positive electrode slurry. The solids content of the positive electrode slurry was 73%. The positive electrode slurry was uniformly coated on the surface of a positive electrode current collector aluminum foil, dried, and cold-pressed to obtain a positive electrode plate. The molecular weight of the polytetrafluoroethylene (PTFE) was 800,000. The mass ratio of the positive electrode active material, conductive carbon black powder, polyvinylidene fluoride, and NMP was 96.9:2.1:1:21.

[0157] 2. Manufacturing of negative electrode plates A copper foil with a thickness of 8 μm was used as the negative electrode current collector.

[0158] The negative electrode active material, graphite, the adhesive, styrene butadiene rubber (SBR), the thickener, sodium carboxymethyl cellulose (CMC-Na), and the conductive agent, carbon black (Super P), were mixed in a weight ratio of 96.2:1.8:1.2:0.8 with an appropriate amount of deionized water as a solvent and stirred thoroughly to form a uniform negative electrode slurry. The negative electrode slurry was then uniformly coated on the surface of the negative electrode current collector copper foil, dried, and cold-pressed to obtain a negative electrode plate.

[0159] 3. Separator A porous polyethylene (PE) membrane was used as the separator.

[0160] 4. Electrolyte production In an environment with a water content of less than 10 ppm, non-aqueous organic solvents ethylene carbonate (EC) and diethyl carbonate were mixed in a volume ratio of 1:1 to obtain an electrolyte solvent, and then lithium salt and the resulting solvent were mixed to prepare an electrolyte solution with a lithium salt concentration of 1 mol / L.

[0161] 5. Secondary battery manufacturing The positive electrode plate, separator, and negative electrode plate were stacked in this order, with a separator positioned between the positive electrode plate and the negative electrode plate to provide isolation, and then wound to obtain an electrode assembly. The electrode assembly was placed in an outer case, dried, and then an electrolyte was injected. After vacuum packaging, standing, chemical formation, shaping, and other processes, a lithium ion battery was obtained.

[0162] Examples 2-2 to 2-9 In Examples 2-2 to 2-9, secondary batteries were manufactured according to a method similar to that of Example 2-1, but the difference from Example 2-1 is that the type of dispersant PVDF used in Examples 2-2 to 2-9 was adjusted, and the dispersant PVDF manufactured in Examples 1-2 to 1-9 was used, respectively.

[0163] Examples 2-10 to 2-13 In Examples 2-10 to 2-13, secondary batteries were manufactured according to a method similar to that of Example 2-1, except that the amount of dispersant PVDF was adjusted in Examples 2-10 to 2-13.

[0164] Comparative Example In the comparative example, a secondary battery was manufactured according to a method similar to that of Example 2-1. The difference from Example 2-1 is that the manufacturing method of the positive electrode slurry in the comparative example was adjusted, specifically as follows: 0.6 Co 0.2 Mn 0.2O2), conductive carbon black powder, polyvinylidene fluoride, and NMP were thoroughly mixed in a mass ratio of 96.9:2.1:1:21 and stirred to form a uniform positive electrode slurry. The positive electrode slurry was uniformly coated on the surface of a positive electrode current collector aluminum foil, dried, and cold-pressed to obtain a positive electrode plate.

[0165] The parameters of Examples 2-1 to 2-13 and the comparative example are as shown in Table 2.

[0166] Testing section 1. Polymer performance testing 1. Polymer weight average molecular weight test A Waters 2695 Isocratic HPLC gel chromatograph (differential refractive index detector 2141) was used. A 3.0% mass fraction polystyrene solution sample was used as a reference, and a matching chromatography column (oil-based: Styragel HT5 DMF 7.8 x 300 mm + Styragel HT4) was selected. A 3.0% polymer solution was prepared in purified N-methylpyrrolidone (NMP) solvent, and the prepared solution was allowed to stand for one day as a backup. During testing, the syringe was first sucked up and rinsed with tetrahydrofuran, and this was repeated several times. Then, 5 ml of the experimental solution was sucked up, the air in the syringe was removed, and the needle tip was dried. Finally, the sample solution was slowly injected into the sample inlet. After the display stabilized, data was acquired and the weight-average molecular weight was read.

[0167] 2. Conductive slurry viscosity test The viscosity of the conductive slurry was measured using a rotational viscometer. An appropriate rotor was selected, the viscometer rotor was fixed, and the conductive slurry was placed under the rotor so that the rotor's graduations were just submerged. The instrument model was Shanghai Fanrui NDJ-5S, rotors were set to 63# (2000-10000 mPa.s), 64# (10000-50000 mPa.s), rotation speed was 12 rpm, test temperature was 25°C, and the test time was 5 minutes. The data was read once the display stabilized.

[0168] 3. Conductive slurry filtration performance test A 500 ml beaker was placed on the bottom of a 200 mesh filter holder, and 500 ml of conductive slurry was taken and put into the filter to filter. The time when the volume of the slurry in the beaker reached 300 ml was recorded, and this time was used to judge the filtration performance of the slurry. A filtration time of less than 120 seconds indicated that the filtration performance of the slurry was OK, and if the slurry could not pass through the filter, it indicated that the filtration performance of the slurry was poor and was judged as "NG".

[0169] 4. The difference in solid content between the upper and lower layers after leaving the conductive slurry standing for 24 hours A small piece of the electrode plate was taken and weighed in the moisture meter, designated as M0, and cleared. A small amount of the upper layer conductive slurry was taken and coated on an electrode plate, and then placed in the moisture meter and weighed, designated as M1. The device was closed and drying began. After completion, the weighing data was recorded and recorded as M2. The solid content was calculated, which was (M2-M0) / (M1-M0). The solid content of the lower layer conductive slurry was measured in the same way, and the solid content of the upper layer conductive slurry was subtracted from the solid content of the lower layer conductive slurry to determine the difference in solid content between the upper and lower layers after the conductive slurry was left to stand for 24 hours.

[0170] Secondary battery performance testing 5. Adhesion strength of the positive electrode plate Referring to the GB-T2790-1995 national standard, "Testing Method for 180° Peel Strength of Adhesives," the adhesive strength testing process for the examples and comparative examples was as follows: A 30mm wide, 100-160mm long sample was cut with a blade and attached to a steel plate with special double-sided tape, measuring 20mm wide and 90-150mm long. The insulating coating side of the cut electrode plate sample was then attached to the double-sided tape, and rolled three times in the same direction with a 2kg press roller. A paper tape measuring the same width as the electrode plate and 250mm long was fixed onto the current collector and secured with adhesive. The Sanshisha tensioning machine (1N sensitivity) was turned on, and the indicator light came on. The stopper was adjusted to the appropriate position, and the end of the steel plate not attached to the electrode plate was secured with the lower fixture. The paper tape was folded upward and secured with the upper fixture, and the position of the upper fixture was adjusted using the "up" and "down" buttons on the tensioning machine's manual controller. The test was then performed and the numerical value was read. The pulling speed was 50 mm / min. The force when the electrode plate forces were balanced was divided by the tape width to obtain the adhesive strength of the positive electrode film layer per unit length, which characterized the adhesive strength between the positive electrode film layer and the current collector.

[0171] 6. Diaphragm resistance of the positive electrode plate After drying, cut the positive electrode plate into small 3mm diameter discs at the left, center, and right positions. Turn on the Yuan Neng Technology electrode resistance meter, place it on the electrode resistance meter's "probe" in the appropriate position, click the "Start" button, and read once the display stabilizes. Test each small disc in two positions, and finally calculate the average of the six measurements to determine the film resistance of this electrode plate.

[0172] 7. DC impedance DCR (Ω) of secondary battery The DC impedance test process for the secondary battery was as follows: at 25°C, a battery corresponding to Example 1 was charged to 4.3V at a constant current of 1 / 3*C, and then further charged at a constant voltage of 4.3V until the current reached 0.05C. After leaving the battery for 5 minutes, the voltage V1 was recorded. The battery was then discharged at 1 / 3C for 30 seconds, and the voltage V2 was recorded. The internal resistance DCR of the secondary battery was calculated as 3*(V2-V1) / C.

[0173] Test results The effect of the present invention in improving the performance of secondary batteries is shown in Table 2.

[0174] [Table 2] JPEG2025534770000011.jpg252145JPEG2025534770000012.jpg25293

[0175] As can be seen from Table 2, the comparative example directly mixed conductive carbon black powder and a positive electrode active material to form a positive electrode slurry, resulting in a relatively high risk of conductive carbon black agglomeration, relatively high plate resistance, and relatively poor power characteristics. In contrast, Examples 2-1 to 2-9 of the present application prepared conductive carbon black powder as a conductive slurry in advance, and used a polymer as a dispersant to effectively and uniformly disperse the conductive carbon black powder. This resulted in relatively good dispersion performance of the conductive slurry, less sedimentation, and relatively uniform performance. Mixing the conductive slurry and a positive electrode active material to form a positive electrode slurry improved the resistance and power characteristics of the positive electrode plate. Furthermore, the polymer's consistent viscosity helped improve the adhesion within the positive electrode plate. Furthermore, the storage performance of the examples was relatively stable, with little gel sedimentation occurring after 24 hours of standing and no gel sedimentation occurring even after 60 days (60D) of storage.

[0176] In Examples 2-10 to 2-13, by adjusting the dosage of the dispersant polymer, the degree of dispersion in the conductive agent could be adjusted, reducing the resistance of the electrode plate, and the controlled viscosity could be adjusted to a certain extent to adjust the adhesive strength within the electrode plate.

[0177] Although the present application has been described with reference to preferred embodiments, various modifications may be made thereto without departing from the scope of the present application, and equivalents may be substituted for the components therein. In particular, the respective technical features mentioned in the respective embodiments may be combined in any manner unless there is a structural conflict. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims. [Explanation of symbols]

[0178] The symbols are explained as follows: 1, battery pack, 2, upper housing, 3, lower housing, 4, battery module, 5. Secondary battery, 51. Case, 52. Electrode assembly, 53, cover plate, 6, power consumption equipment.

Claims

1. A polymer comprising a structural unit represented by formula (1) and a structural unit represented by formula (2), In formula (2), R １ , R ２ and R ３ are each independently selected from a hydrogen atom, a halogen atom, or a substituted or unsubstituted C1-C10 alkyl group.

2. R １ , R ２ and R ３ are each independently selected from a hydrogen atom, a halogen atom, or a substituted or unsubstituted C1-C5 alkyl group.

3. The structural unit shown in the formula (2) is represented by formulas (2-1) to (2-10):

3. The polymer of claim 1, comprising one or more of the structural units shown in

4. The polymer satisfies conditions (I) to (III): (I) The weight average molecular weight of the polymer is 1.5 × 10 ５ Da ~ 2.0 x 10 ５ Being Da, and (II) the number of structural units represented by the formula (1) is n, and 100≦n≦150; (III) The polymer according to any one of claims 1 to 3, wherein the number of structural units represented by the formula (2) is m, and 100≦m≦150 is satisfied.

5. The polymer satisfies conditions (1) to (3): (1) the viscosity of the polymer is C mPa*s, and 500≦C≦3000; (2) the polymer has a glass transition temperature Tg °C, and 150≦Tg≦180; (3) The polymer according to any one of claims 1 to 4, wherein the polymer has a crystallinity of 40% to 50% as determined by a differential scanning calorimeter (DSC) test.

6. The polymer according to any one of claims 1 to 5, wherein the polymer is in a particulate form and has a volume average particle size Dv50 µm, where 1 ≤ Dv50 ≤ 5.

7. 1. A method for producing a polymer, comprising: Providing a first monomer and a second monomer comprising a structural unit shown in formula (2); polymerizing the first monomer and the second monomer in the presence of a radical initiator to form a polymer, wherein: the first monomer comprises vinylidene fluoride; The structural unit represented by the formula (2) is as follows: In formula (2), R １ , R ２ and R ３ are each independently selected from a hydrogen atom, a halogen atom, or a substituted or unsubstituted C1-C10 alkyl group.

8. The step of polymerizing the first monomer and the second monomer in the presence of a radical initiator to form a polymer comprises: homopolymerizing the first monomer in the presence of a radical initiator to form a first block polymer; copolymerizing the first monomer, the second monomer, and the first block polymer in the presence of a radical initiator to form a second block polymer; and copolymerizing the first monomer and the second block polymer in the presence of a radical initiator to form the polymer.

9. 9. The method according to claim 7 or 8, wherein the ratio of the percentage of the molar content of the second monomer to the percentage of the molar content of the first monomer, based on the total molar amount of the first monomer and the second monomer, is A, and 0.10≦A≦0.

30.

10. 1. A method for producing a conductive slurry, comprising: adding a polymer to a solvent and mixing it as a pre-formed adhesive solution; and dispersing a conductive agent in the pre-formulated adhesive liquid to form a conductive slurry; 10. A method according to claim 1, wherein the polymer comprises a polymer according to any one of claims 1 to 6 or a polymer obtainable by a method according to any one of claims 7 to 9.

11. The mass content of the polymer is p% based on the total mass of the conductive slurry, The mass content of the conductive agent is q% based on the total mass of the conductive slurry, 11. The method of claim 10, wherein 2≦q / p≦20.

12. 12. The method of claim 11, wherein 3≦q / p≦15.

13. 10. A conductive slurry comprising a conductive agent and a polymer, wherein the polymer comprises the polymer of any one of claims 1 to 6 or the polymer obtainable by the method of any one of claims 7 to 9.

14. The mass content of the polymer is p% based on the total mass of the conductive slurry, The mass content of the conductive agent is q% based on the total mass of the conductive slurry, 14. The conductive slurry of claim 13, wherein 2≦q / p≦20.

15. 15. The conductive slurry of claim 14, wherein 3≦q / p≦15.

16. A method for manufacturing a positive electrode plate, comprising: providing a positive electrode current collector; adding a positive electrode active material, a polymer, a conductive agent, and an adhesive to a solvent and mixing them to form a positive electrode slurry; coating the positive electrode slurry on the positive electrode current collector; and curing the positive electrode slurry to form a positive electrode plate, wherein the polymer comprises the polymer described in any one of claims 1 to 6 or the polymer obtained by the method described in any one of claims 7 to 9.

17. The step of adding the positive electrode active material, the polymer, the conductive agent, and the adhesive to a solvent and mixing them to form a positive electrode slurry includes: adding the polymer to a solvent and mixing it as a pre-formulated adhesive solution; dispersing the conductive agent in the pre-prepared adhesive liquid to form a conductive slurry; 17. The method of claim 16, comprising combining the conductive slurry and the active cathode material as a cathode slurry.

18. A positive electrode plate produced by the method according to claim 16 or 17.

19. A secondary battery comprising the positive electrode plate according to claim 18.

20. 20. A power consuming device comprising the secondary battery of claim 19.

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