Method for preparing positive electrode sheet, positive electrode sheet, battery cell, battery, and electric device

Abstract

Embodiments of the present application provide a preparation method of a positive electrode tab, a positive electrode tab, a battery monomer, a battery and an electric device. The preparation method of the positive electrode tab comprises: preparing a positive electrode slurry, wherein the positive electrode slurry comprises a polyurethane prepolymer; coating the positive electrode slurry on at least one side of a positive electrode current collector; and drying the positive electrode slurry coated on at least one side of the positive electrode current collector to obtain the positive electrode tab. The technical solution provided by the present application can improve the performance of the battery.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a method for preparing a positive electrode, a positive electrode, a battery cell, a battery, and an electrical device. Background Technology

[0002] In recent years, lithium-ion batteries have been used in a wide range of applications, including energy storage systems in hydropower, thermal power, wind power and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric cars, military equipment, aerospace and many other fields.

[0003] As a component of a battery, the performance of the positive electrode is crucial to the battery's overall performance. Therefore, how to provide a positive electrode that improves battery performance is a pressing technical problem that needs to be solved. Summary of the Invention

[0004] This application is made in view of the above-mentioned technical problems, and its purpose is to provide a method for preparing a positive electrode sheet, thereby preparing a positive electrode sheet with good performance and improving the performance of the battery containing the positive electrode sheet.

[0005] To achieve the above objectives, embodiments of this application provide a method for preparing a positive electrode sheet, a positive electrode sheet, a battery cell, a battery, and an electrical device.

[0006] In a first aspect, a method for preparing a positive electrode sheet is provided, comprising: preparing a positive electrode slurry, wherein the positive electrode slurry comprises a polyurethane prepolymer; coating the positive electrode slurry onto at least one side of a positive electrode current collector; and drying the positive electrode slurry coated onto at least one side of the positive electrode current collector to obtain the positive electrode sheet.

[0007] In the method for preparing the positive electrode sheet provided in this application embodiment, the positive electrode slurry includes a polyurethane prepolymer. After coating the positive electrode slurry onto at least one side of the positive electrode current collector, the positive electrode slurry coated onto at least one side of the positive electrode current collector is dried. During the drying process, the polyurethane prepolymer in the positive electrode slurry undergoes cross-linking and curing to form a high-molecular-weight polyurethane cross-linked material. The polyurethane cross-linked material has a cross-linked network structure and long molecular chains, exhibiting good bonding strength and toughness compared to general crystalline binder materials, thereby improving the toughness of the positive electrode sheet and obtaining a positive electrode sheet with good performance. Simultaneously, polyurethane helps to increase the transport rate of active metal ions (e.g., lithium ions), thereby improving the internal resistance of the battery and enhancing its cycle performance. In the technical solution provided in this application embodiment, the uncross-linked polyurethane prepolymer has a lower viscosity. Adding it to the positive electrode slurry can increase the solid content of the polyurethane binder in the positive electrode slurry, and the positive electrode slurry is easily dispersed during coating, improving the processing efficiency of the positive electrode sheet. During the drying process of the positive electrode slurry coated on at least one side of the positive electrode current collector, the polyurethane prepolymer undergoes cross-linking and curing to form a high molecular weight cross-linked material with good bonding strength and toughness, which can improve the performance of the positive electrode sheet and thus enhance the performance of the battery.

[0008] In one possible implementation, the drying temperature of the positive electrode slurry ranges from 60°C to 150°C, and optionally, the drying temperature ranges from 80°C to 140°C.

[0009] Setting the drying temperature of the positive electrode slurry within the above range is beneficial to the cross-linking and curing of the polyurethane prepolymer and the drying of the slurry, which is conducive to the preparation of a positive electrode sheet with good performance.

[0010] In one possible implementation, the preparation of the positive electrode slurry includes: preparing a binder precursor solution, adding a positive electrode active material, a conductive agent, a dispersant, and a crosslinking agent to the binder precursor solution, mixing, and obtaining the positive electrode slurry.

[0011] Conductive agents act as collectors of microcurrents between active materials, reducing electrode contact resistance and accelerating electron mobility. They also effectively increase the migration rate of metal ions within the electrode material, thereby improving charge / discharge efficiency. Dispersants facilitate uniform dispersion of solids in the positive electrode slurry within the solvent. Crosslinking agents catalyze the crosslinking and curing of the polyurethane prepolymer. Including these substances in the positive electrode slurry is beneficial for preparing high-performance positive electrode sheets.

[0012] In one possible implementation, the conductive agent includes at least one of conductive carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0013] Due to the unique composition of carbon structure, carbon-based conductive agents possess excellent electrical conductivity. For example, conductive carbon black has advantages such as low resistance and high conductivity, small particle size, large and rough specific surface area, high structure, and clean surface (few compounds); Ketjen black has a unique branched morphology, resulting in high conductivity; carbon atoms in carbon nanotubes adopt a spline structure. 2 Due to their hybrid nature, carbon nanotubes possess high modulus and high strength, as well as good flexibility, stretchability, and electrical conductivity. Conductive carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers can be used as conductive agents to improve the conductivity of batteries.

[0014] In one possible implementation, the dispersant comprises polyvinylpyrrolidone.

[0015] Polyvinylpyrrolidone has good stability and has advantages such as colloidal protection, film-forming properties, adhesiveness, hygroscopicity, solubilization or coagulation in reaction systems.

[0016] In one possible implementation, the crosslinking agent includes at least one of sucrose, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, diethyltoluenediamine, dimethylthiotoluenediamine, three-armed polycaprolactone, and four-armed polycaprolactone.

[0017] In one possible implementation, the preparation of the binder precursor solution includes: preparing the polyurethane prepolymer; dispersing the polyurethane prepolymer in an N-methylpyrrolidone solvent to obtain the binder precursor solution.

[0018] In one possible implementation, the preparation of the polyurethane prepolymer includes: drying a polyether polyol and / or a polyester polyol; mixing the dried polyether polyol and / or the polyester polyol with an isocyanate and a catalyst to carry out a prepolymerization reaction; after the prepolymerization reaction is completed, adding a blocking agent to the reaction product to obtain the polyurethane prepolymer.

[0019] A blocking agent is added to the reaction product of the prepolymerization reaction. The blocking agent can cause the isocyanate active groups to lose their activity at a lower temperature. When the coated electrode is baked at high temperature in an oven, the blocking agent loses its effect, and the isocyanate is exposed.

[0020] In one possible implementation, the drying temperature of the polyether polyol and / or the polyester polyol is in the range of 90°C to 95°C, and the drying time is in the range of 2 to 3 hours.

[0021] Setting the drying temperature and drying time within the above range is beneficial for polyether polyols and / or polyester polyols to reach a suitable state for polymerization, and is also beneficial for prepolymerization with isocyanates.

[0022] In one possible implementation, the isocyanate includes a diisocyanate, which includes at least one of aromatic diisocyanate and aliphatic diisocyanate.

[0023] In one possible implementation, the isocyanate comprises at least one of isotoluene-2,3-diisocyanate, toluene-2,4-diisocyanate, toluene-2,5-diisocyanate, toluene-2,6-diisocyanate, toluene-3,4-diisocyanate, toluene-3,5-diisocyanate, 1,5-naphthalene diisocyanate, terephthalene diisocyanate, isophthalene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, L-lysine ethyl ester diisocyanate, hydrogenated toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, and hydrogenated diphenylmethane diisocyanate.

[0024] In one possible implementation, the molar ratio R of isocyanate to hydroxyl groups in the polyurethane prepolymer ranges from 1.1 to 2.0, and optionally, the value of R ranges from 1.2 to 1.8.

[0025] Setting the molar ratio of isocyanate to hydroxyl groups in the polyurethane prepolymer within the above range is beneficial to the subsequent crosslinking and curing reaction of the polyurethane prepolymer.

[0026] In one possible implementation, the polyether polyol includes at least one of polyethylene glycol, polypropylene glycol, polyethylene oxide glycol, polytetrahydrofuran ether glycol, and polyethylene glycol-propylene glycol copolymer.

[0027] In one possible implementation, the polyester polyol includes at least one of polycaprolactone, polycarbonate diol, polylactic acid diol, and polyglycolic acid-lactide copolymer.

[0028] In one possible implementation, the catalyst includes at least one of organotin catalysts, organobismuth catalysts, and tertiary amine catalysts.

[0029] In one possible implementation, the catalyst comprises at least one of dibutyltin dilaurate, stannous octoate, N-ethylmorpholine, N-methylmorpholine, and triethylamine.

[0030] The above substances can effectively catalyze the prepolymerization reaction of polyether polyols and / or polyester polyols with isocyanates.

[0031] In one possible implementation, the blocking agent comprises at least one of trichloroethanol, trifluoroethanol, dodecyl mercaptan, triphenyl mercaptan, hexamethylene mercaptan, N,N-butanediol acetamide, ethylene glycol monohexyl ether, N,N-diol amide, phenol, pyridine, methyl ethyl ketone oxime, caprolactam, and ethyl acetoacetate.

[0032] In one possible implementation, the mass percentage of the catalyst in the prepolymerization reaction feedstock is in the range of 0.001% to 1.0%, based on the total mass of the prepolymerization reaction feedstock.

[0033] Controlling the catalyst within the above range is beneficial for catalyzing the prepolymerization reaction of polyether polyols and / or polyester polyols with isocyanates.

[0034] In a second aspect, a positive electrode sheet is provided, prepared by a method according to the first aspect and any possible implementation thereof.

[0035] In one possible implementation, the positive electrode sheet includes a positive active material layer, and based on the total mass of the positive active material layer, the mass percentage of the binder in the positive active material layer ranges from 0.3% to 4.2%.

[0036] Setting the mass percentage of the binder in the positive electrode active material layer within the above range is beneficial to improving the performance of the positive electrode sheet.

[0037] Thirdly, a battery cell is provided, including the positive electrode sheet described in the second aspect.

[0038] Fourthly, a battery is provided, comprising the battery cell described in the third aspect.

[0039] Fifthly, an electrical device is provided, comprising the battery described in the fourth aspect.

[0040] This application provides a method for preparing a positive electrode sheet. The positive electrode slurry includes a polyurethane prepolymer. After coating the positive electrode slurry onto at least one side of a positive electrode current collector, the positive electrode slurry coated onto at least one side of the current collector is dried. During the drying process, the polyurethane prepolymer in the positive electrode slurry undergoes cross-linking and curing to form a high-molecular-weight polyurethane cross-linked material. This cross-linked polyurethane material has a cross-linked network structure and a long molecular chain structure, exhibiting good bonding strength and toughness compared to general crystalline binder materials. This improves the toughness of the positive electrode sheet, resulting in a positive electrode sheet with good performance. Simultaneously, polyurethane helps to increase the transport rate of active metal ions (e.g., lithium ions), thereby improving the internal resistance of the battery and enhancing its cycle performance. In the technical solution provided by this application, the uncross-linked polyurethane prepolymer has a lower viscosity. Adding it to the positive electrode slurry can increase the solid content of the polyurethane binder in the positive electrode slurry, and the positive electrode slurry is easily dispersed during coating, improving the processing efficiency of the positive electrode sheet. During the drying process of the positive electrode slurry coated on at least one side of the positive electrode current collector, the polyurethane prepolymer undergoes cross-linking and curing to form a high molecular weight cross-linked material with good bonding strength and toughness, which can improve the performance of the positive electrode sheet and thus enhance the performance of the battery. Attached Figure Description

[0041] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0042] Figure 1 This is a schematic diagram of a method for preparing a positive electrode sheet according to an embodiment of this application;

[0043] Figure 2 This is a schematic diagram of the positive electrode sheet according to an embodiment of this application;

[0044] Figure 3 This is a schematic diagram of the positive electrode sheet according to an embodiment of this application;

[0045] Figure 4 This is a schematic diagram of a method for preparing a positive electrode sheet according to an embodiment of this application;

[0046] Figure 5 This is a schematic diagram of a method for preparing a positive electrode sheet according to an embodiment of this application;

[0047] Figure 6 This is a schematic diagram of a method for preparing a positive electrode sheet according to an embodiment of this application;

[0048] Figure 7This is a schematic diagram of a battery cell disclosed in an embodiment of this application;

[0049] Figure 8 This is an exploded structural diagram of a battery cell disclosed in an embodiment of this application;

[0050] Figure 9 This is an exploded structural diagram of a battery disclosed in an embodiment of this application;

[0051] Figure 10 This is a schematic diagram of an electrical device disclosed in an embodiment of this application;

[0052] The accompanying drawings are not drawn to scale. Detailed Implementation

[0053] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.

[0054] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the electrode plates, battery cells, batteries, and power-consuming devices of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0055] In the description of this application, it should be noted that, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," etc., indicating orientation or positional relationships are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0056] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0057] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0058] Unless otherwise specified, the terms "comprising" and "including" as used in this application are open-ended. For example, "comprising" and "including" may mean including or containing other components not listed.

[0059] Unless otherwise specified, the term "and / or" is inclusive in this application. For example, the phrase "A and / or B" means "A, B, or both A and B". More specifically, the condition "A and / or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0060] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0061] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0062] Secondary batteries are widely used in mobile phones, electric vehicles, and energy storage stations due to their high energy density, high voltage, and long lifespan. As a component of the battery, the performance of the positive electrode is crucial to the overall battery performance.

[0063] Binders are a crucial factor affecting the performance of positive electrode sheets. During the preparation of positive electrode sheets, binders are typically added to the positive electrode slurry to adhere the positive electrode active material and conductive agent to the positive electrode current collector, maintaining the structural stability of the positive electrode sheet. Polyurethane binders are widely used due to their good adhesion, storage stability, and numerous active metal ion channels. However, the large molecular weight of cross-linked and cured polyurethane binders significantly increases the viscosity of the positive electrode slurry, reducing the uniformity of solid dispersion. This makes it difficult to coat the positive electrode slurry evenly onto the positive electrode current collector, increasing production difficulty and reducing efficiency. Furthermore, to ensure the usability of the positive electrode slurry, the molecular weight of the polyurethane binder must be controlled to prevent excessively high molecular weights, which significantly reduces its adhesive properties and is detrimental to the preparation of high-performance positive electrode sheets.

[0064] In view of this, this application provides a method for preparing a positive electrode sheet. The positive electrode slurry includes a polyurethane prepolymer. After coating the positive electrode slurry onto at least one side of a positive electrode current collector, the positive electrode slurry coated onto at least one side of the current collector is dried. During the drying process, the polyurethane prepolymer in the positive electrode slurry undergoes cross-linking and curing to form a high-molecular-weight polyurethane cross-linked material. This cross-linked polyurethane material has a cross-linked network structure and a long molecular chain structure, exhibiting good bonding strength and toughness compared to general crystalline binder materials. This improves the toughness of the positive electrode sheet, resulting in a positive electrode sheet with good performance. Simultaneously, polyurethane helps to increase the transport rate of active metal ions (e.g., lithium ions), thereby improving the internal resistance of the battery and enhancing its cycle performance. In the technical solution provided by this application, the uncross-linked polyurethane prepolymer has a lower viscosity. Adding it to the positive electrode slurry can increase the solid content of the polyurethane binder in the positive electrode slurry, and the positive electrode slurry is easily dispersed during coating, improving the processing efficiency of the positive electrode sheet. During the drying process of the positive electrode slurry coated on at least one side of the positive electrode current collector, the polyurethane prepolymer undergoes cross-linking and curing to form a high molecular weight cross-linked material with good bonding strength and toughness, which can improve the performance of the positive electrode sheet and thus enhance the performance of the battery.

[0065] The following describes several embodiments of this application in detail.

[0066] [Preparation method of positive electrode sheet]

[0067] Figure 1 This is a schematic diagram illustrating a method for preparing a positive electrode sheet according to an embodiment of this application. Figure 1 As shown, the preparation method includes the following steps.

[0068] Step 101: Prepare the positive electrode slurry.

[0069] The positive electrode slurry includes polyurethane prepolymer.

[0070] Step 102: Coat the positive electrode slurry onto at least one side of the positive electrode current collector.

[0071] Step 103: Dry the positive electrode slurry coated on at least one side of the positive electrode current collector to obtain the positive electrode sheet.

[0072] The method for preparing the positive electrode sheet provided in this application embodiment includes a positive electrode slurry containing a polyurethane prepolymer. After coating the positive electrode slurry onto at least one side of a positive electrode current collector, the slurry coated onto at least one side of the current collector is dried. During the drying process, the polyurethane prepolymer in the positive electrode slurry undergoes cross-linking and curing to form a high-molecular-weight polyurethane cross-linked material. This cross-linked polyurethane material has a cross-linked network structure and long molecular chain structure, exhibiting good bonding strength and toughness compared to general crystalline binder materials. This improves the toughness of the positive electrode sheet, resulting in a positive electrode sheet with excellent performance. Simultaneously, polyurethane helps to increase the transport rate of active metal ions (e.g., lithium ions), thereby improving the internal resistance of the battery and enhancing its cycle performance. In the technical solution provided in this application embodiment, the uncross-linked polyurethane prepolymer has a lower viscosity. Adding it to the positive electrode slurry can increase the solid content of the polyurethane binder in the positive electrode slurry, and the positive electrode slurry is easily dispersed during coating, improving the processing efficiency of the positive electrode sheet. During the drying process of the positive electrode slurry coated on at least one side of the positive electrode current collector, the polyurethane prepolymer undergoes cross-linking and curing to form a high molecular weight cross-linked material with good bonding strength and toughness, which can improve the performance of the positive electrode sheet and thus enhance the performance of the battery.

[0073] Figure 2 This is a schematic diagram of the positive electrode sheet according to an embodiment of this application. Figure 2 As shown, the positive electrode 2 includes a positive current collector 21 and a positive electrode material layer 22. The positive electrode material layer 22 is formed by coating the positive electrode slurry onto the positive current collector 21 and then drying it. The positive electrode material layer 22 extends along the thickness direction of the positive electrode 2 (e.g., along the thickness direction of the positive electrode 2). Figure 2 In the z-direction), the positive electrode current collector 21 and the positive electrode material layer 22 are arranged sequentially.

[0074] The positive current collector 21 has two surfaces arranged along its thickness direction. Optionally, as... Figure 1As shown, both surfaces of the positive current collector 21 are provided with a positive electrode material layer 22.

[0075] Figure 3 This is a schematic diagram of the positive electrode sheet according to one embodiment of this application. In some other embodiments, such as... Figure 3 As shown, one of the two surfaces of the positive electrode current collector 21 that are opposite each other along the thickness direction is provided with a positive electrode material layer 22.

[0076] Optionally, in some embodiments, the drying temperature of the positive electrode slurry ranges from 60°C to 150°C, and optionally, the drying temperature ranges from 80°C to 140°C.

[0077] Specifically, the drying temperature of the positive electrode slurry can be 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, or any value between any two of the above.

[0078] Setting the drying temperature of the positive electrode slurry within the above range is beneficial to the cross-linking and curing of the polyurethane prepolymer and the drying of the slurry, which is conducive to the preparation of a positive electrode sheet with good performance.

[0079] Optionally, in some embodiments, the preparation of the positive electrode slurry includes: preparing a binder precursor solution, adding a positive electrode active material, a conductive agent, a dispersant, and a crosslinking agent to the binder precursor solution, mixing, and obtaining the positive electrode slurry. (Reference) Figure 4 , Figure 4 This is a schematic diagram of a method for preparing a positive electrode sheet according to an embodiment of this application. Figure 4 Steps 403-404 are similar to steps 102-103 in the previous embodiments, and can be referred to the previous embodiments. For the sake of brevity, they will not be repeated here.

[0080] Step 401: Prepare the binder precursor solution.

[0081] Step 402: Add positive electrode active material, conductive agent, dispersant and crosslinking agent to binder precursor solution, mix and prepare positive electrode slurry.

[0082] Conductive agents act as collectors of microcurrents between active materials, reducing electrode contact resistance and accelerating electron mobility. They also effectively increase the migration rate of metal ions within the electrode material, thereby improving charge / discharge efficiency. Dispersants facilitate uniform dispersion of solids in the positive electrode slurry within the solvent. Crosslinking agents catalyze the crosslinking and curing of the polyurethane prepolymer. Including these substances in the positive electrode slurry is beneficial for preparing high-performance positive electrode sheets.

[0083] Optionally, in some embodiments, the conductive agent includes at least one of conductive carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0084] Due to the unique composition of carbon structure, carbon-based conductive agents possess excellent electrical conductivity. For example, conductive carbon black has advantages such as low resistance and high conductivity, small particle size, large and rough specific surface area, high structure, and clean surface (few compounds); Ketjen black has a unique branched morphology, resulting in high conductivity; carbon atoms in carbon nanotubes adopt a spline structure. 2 Due to their hybrid nature, carbon nanotubes possess high modulus and high strength, as well as good flexibility, stretchability, and electrical conductivity. Conductive carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers can be used as conductive agents to improve the conductivity of batteries.

[0085] Optionally, in some embodiments, the dispersant includes polyvinylpyrrolidone.

[0086] Polyvinylpyrrolidone has good stability and has advantages such as colloidal protection, film-forming properties, adhesiveness, hygroscopicity, solubilization or coagulation in reaction systems.

[0087] Optionally, in some embodiments, the crosslinking agent includes at least one selected from sucrose, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, diethyltoluenediamine, dimethylthiotoluenediamine, three-armed polycaprolactone, and four-armed polycaprolactone.

[0088] Optionally, in some embodiments, preparing the adhesive precursor solution includes: preparing a polyurethane prepolymer; dispersing the polyurethane prepolymer in an N-methylpyrrolidone solvent to obtain the adhesive precursor solution. (Reference) Figure 5 , Figure 5 This is a schematic diagram of a method for preparing a positive electrode sheet according to an embodiment of this application. Figure 5 Steps 503-505 are similar to steps 402-404 in the previous embodiments, and can be referred to the previous embodiments. For the sake of brevity, they will not be repeated here.

[0089] Step 501: Prepare polyurethane prepolymer.

[0090] Step 502: Disperse the polyurethane prepolymer in N-methylpyrrolidone solvent to obtain an adhesive precursor solution.

[0091] Optionally, in some embodiments, the polyurethane prepolymer comprises: dried polyether polyol, and / or polyester polyol; mixing the dried polyether polyol, and / or polyester polyol, with isocyanate and catalyst to perform a prepolymerization reaction; after the prepolymerization reaction is completed, adding a blocking agent to the reaction product to obtain the polyurethane prepolymer. Reference Figure 6 , Figure 6 This is a schematic diagram of a method for preparing a positive electrode sheet according to an embodiment of this application. Figure 6 Steps 604-607 are similar to steps 502-505 in the previous embodiments, and can be referred to the previous embodiments. For the sake of brevity, they will not be repeated here.

[0092] Step 601: Dry the polyether polyol and / or the polyester polyol.

[0093] Step 602: The dried polyether polyol and / or polyester polyol are mixed with isocyanate and catalyst to carry out a prepolymerization reaction.

[0094] Step 603: Add a blocking agent to the reaction product of the prepolymerization reaction to obtain a polyurethane prepolymer.

[0095] A blocking agent is added to the reaction product of the prepolymerization reaction. The blocking agent can cause the isocyanate active groups to lose their activity at a lower temperature. When the coated electrode is baked at high temperature in an oven, the blocking agent loses its effect, and the isocyanate is exposed.

[0096] Optionally, in some embodiments, the drying temperature of the polyether polyol and / or polyester polyol ranges from 90°C to 95°C, and the drying time ranges from 2 to 3 hours.

[0097] Specifically, the drying temperature of polyether polyols and / or polyester polyols can be 90°C, 91°C, 92°C, 93°C, 94°C, 95°C, or any two of the above values; the drying time can be 2 hours, 2.5 hours, 3 hours, or any two of the above values.

[0098] Setting the drying temperature and drying time within the above range is beneficial for polyether polyols and / or polyester polyols to reach a suitable state for polymerization, and is also beneficial for prepolymerization with isocyanates.

[0099] Optionally, in some embodiments, the isocyanate includes diisocyanate, and optionally, the diisocyanate includes at least one of aromatic diisocyanate and aliphatic diisocyanate.

[0100] Specifically, the isocyanate may include at least one of isotoluene-2,3-diisocyanate, toluene-2,4-diisocyanate, toluene-2,5-diisocyanate, toluene-2,6-diisocyanate, toluene-3,4-diisocyanate, toluene-3,5-diisocyanate, 1,5-naphthalene diisocyanate, terephthalene diisocyanate, isophthalene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, L-lysine ethyl ester diisocyanate, hydrogenated toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, and hydrogenated diphenylmethane diisocyanate.

[0101] Optionally, in some embodiments, the polyether polyol includes at least one of polyethylene glycol, polypropylene glycol, polyethylene oxide glycol, polytetrahydrofuran ether glycol, and polyethylene glycol-propylene glycol copolymer.

[0102] Optionally, in some embodiments, the polyester polyol includes at least one of polycaprolactone, polycarbonate diol, polylactic acid diol, and polyglycolic acid-lactide copolymer.

[0103] Optionally, in some embodiments, the molar ratio R of isocyanate to hydroxyl groups in the polyurethane prepolymer ranges from 1.1 to 2.0, and optionally, the value of R ranges from 1.2 to 1.8.

[0104] Specifically, the molar ratio R of isocyanate to hydroxyl groups in the polyurethane prepolymer can be 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, or any value between any two of the above.

[0105] Setting the molar ratio of isocyanate to hydroxyl groups in the polyurethane prepolymer within the above range is beneficial to the subsequent crosslinking and curing reaction of the polyurethane prepolymer.

[0106] Optionally, in some embodiments, the catalyst includes at least one of organotin catalysts, organobismuth catalysts, and tertiary amine catalysts.

[0107] Specifically, the catalyst may include at least one of dibutyltin dilaurate, stannous octoate, N-ethylmorpholine, N-methylmorpholine, and triethylamine.

[0108] The above substances can effectively catalyze the prepolymerization reaction of polyether polyols and / or polyester polyols with isocyanates.

[0109] Optionally, in some embodiments, the blocking agent includes at least one of trichloroethanol, trifluoroethanol, dodecyl mercaptan, triphenyl mercaptan, hexamethylene mercaptan, N,N-butanediol acetamide, ethylene glycol monohexyl ether, N,N-diol amide, phenol, pyridine, methyl ethyl ketone oxime, caprolactam, and ethyl acetoacetate.

[0110] Optionally, in some embodiments, the mass percentage of the catalyst in the prepolymerization reaction feedstock is in the range of 0.001% to 1.0%, based on the total mass of the prepolymerization reaction feedstock.

[0111] Specifically, the mass percentage of the catalyst in the prepolymerization reaction feedstock can be 0.001%, 0.01%, 0.05%, 0.1%, 0.5%, 1.0%, or any value between any two of the above.

[0112] [Positive electrode plate]

[0113] This application provides a positive electrode sheet prepared according to the above preparation method, with reference to... Figure 2-3 The positive electrode 2 includes a positive current collector 21 and a positive electrode material layer 22.

[0114] The positive electrode material layer 22 includes a binder, and the mass percentage of the binder in the positive electrode material layer 22, based on the total mass of the positive electrode material layer 22, ranges from 0.3% to 4.2%.

[0115] Specifically, the mass percentage of the binder in the positive electrode material layer 22 can be 0.3%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.2%, or any value between any two of the above.

[0116] In some embodiments, the adhesive includes a polyurethane adhesive, which has excellent shear strength and impact resistance, as well as excellent flexibility.

[0117] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0118] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate 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 (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0119] In some embodiments, the positive electrode material layer includes a positive electrode active material, which may be a positive electrode active material known in the art for lithium-ion batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for lithium-ion batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3Co 1 / 3 Mn 1 / 3 O2 (also known as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0120] In some embodiments, the adhesive may also include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene-propylene terpolymer, ethylene-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0121] [Negative electrode plate]

[0122] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0123] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0124] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate 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 (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0125] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0126] In some embodiments, the negative electrode film layer may optionally include a binder. The binder 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).

[0127] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0128] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0129] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0130] [Electrolytes]

[0131] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0132] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0133] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0134] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl 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, methyl ethyl sulfone, and diethyl sulfone.

[0135] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0136] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0137] In some embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0138] In some embodiments, the outer packaging of the battery cell can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the battery cell can also be a flexible package, such as a pouch. The material of the flexible package can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0139] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 7 The example shown is a square-structured battery cell 70.

[0140] In some implementations, refer to Figure 8 The outer packaging may include a housing 71 and a cover 73. The housing 71 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 71 has an opening communicating with the receiving cavity, and the cover 73 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator can be formed into an electrode assembly 72 by a winding process or a stacking process. The electrode assembly 72 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 72. The number of electrode assemblies 72 contained in the battery cell 70 can be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0141] In some embodiments, battery 80 may include a plurality of battery cells 70. For example, such as Figure 9 The diagram shown is a structural schematic of a battery 80 according to an embodiment of this application. The battery 80 may include multiple battery cells 70. The battery 80 may also include a housing 81, which has a hollow interior, and the multiple battery cells 70 are housed within the housing 81. For example, the multiple battery cells 70 may be connected in parallel, series, or a combination thereof and then placed inside the housing 81.

[0142] Optionally, the battery 80 may also include other structures, which will not be described in detail here. For example, the battery 80 may also include a busbar component for realizing the electrical connection between multiple battery cells 70, such as parallel, series, or mixed connection. Specifically, the busbar component realizes the electrical connection between battery cells 70 by connecting the electrode terminals of the battery cells 70. Further, the busbar component can be fixed to the electrode terminals of the battery cells 70 by welding. The electrical energy of the multiple battery cells 70 can be further led out through the housing 81 via a conductive mechanism. Optionally, the conductive mechanism may also be part of the busbar component.

[0143] The number of battery cells 70 can be set to any value depending on different power requirements. Multiple battery cells 70 can be connected in series, parallel, or a combination thereof to achieve a larger capacity or power. Since each battery 80 may contain a large number of battery cells 70, for ease of installation, the battery cells 70 can be grouped, with each group of battery cells 70 forming a battery module. The number of battery cells 70 included in a battery module is unlimited and can be set according to requirements. A battery can include multiple battery modules, which can be connected in series, parallel, or a combination thereof.

[0144] In addition, this application also provides an electrical device, which includes at least one of the battery cell, battery module, or battery provided in this application. The battery cell, battery module, or battery can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical 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 and satellites, energy storage systems, etc.

[0145] As for this electrical device, battery cells, battery modules, or batteries can be selected according to its usage requirements.

[0146] Figure 10 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of individual battery cells, batteries or battery modules can be used.

[0147] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0148] [Example]

[0149] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0150] 1. Preparation of positive electrode sheet

[0151] Positive electrode plate 1:

[0152] 100,000 kg of polyethylene glycol (PEG, molecular weight 1000) was added to a reactor and dried at 95°C for 3 hours. Then, 18,500 kg of hexamethylene diisocyanate and 2.405 g of triethylamine catalyst were added to the reactor and reacted at 75°C. During the reaction, the content of isocyanate groups (-NCO) was monitored until the -NCO content reached the theoretical value. Then, 1.742 kg of methyl ethyl ketone oxime, a blocking agent, was added to the reactor to continue the reaction. After the reaction was completed, a polyurethane prepolymer was obtained.

[0153] 97.300 kg of lithium iron phosphate (LiFePO4) positive electrode active material, 1.000 kg of polyurethane prepolymer, and 1.400 kg of acetylene black conductive agent were stirred in a planetary mixer at a revolution speed of 25 r / min for 20 min. 53.850 kg of N-methylpyrrolidone (NMP) solution was added to the mixer, and the mixture was stirred at a revolution speed of 25 r / min and a rotation speed of 900 r / min for 50 min. 300.000 g of polyvinylpyrrolidone (PVP) dispersant and 0.487 kg of triethylenetetramine crosslinking agent were added to the mixer, and the mixture was stirred at a revolution speed of 25 r / min and a rotation speed of 1400 r / min for 50 min to obtain the positive electrode slurry.

[0154] The positive electrode slurry prepared above was coated onto carbon-coated aluminum foil and baked at 110°C for 15 minutes to obtain positive electrode sheet 1.

[0155] The isocyanate group (-NCO) content mentioned above can be detected according to the method for detecting isocyanate group content provided in the national standard GB / T 12009.4. The theoretical value of -NCO content is a theoretical value obtained by calculation based on the ratio of reactants in the polyurethane prepolymerization reaction in the examples.

[0156] Positive electrode 2: The preparation of positive electrode 2 is similar to that of positive electrode 1. The difference is that in the preparation of positive electrode 2, the amount of hexamethylene diisocyanate added is 20.177 kg, the amount of triethylamine catalyst added is 2.473 g, the amount of methyl ethyl ketone oxime blocking agent added is 3.485 kg, and the amount of triethylenetetramine crosslinking agent added is 0.975 kg, thus obtaining positive electrode 2.

[0157] Positive electrode 3: The preparation of positive electrode 3 is similar to that of positive electrode 1. The difference is that in the preparation of positive electrode 3, the amount of hexamethylene diisocyanate added is 21.858 kg, the amount of triethylamine catalyst added is 2.542 g, the amount of methyl ethyl ketone oxime added is 5.227 kg, and the amount of triethylenetetramine crosslinking agent added is 1.462 kg, thus obtaining positive electrode 3.

[0158] Positive electrode 4: The preparation of positive electrode 4 is similar to that of positive electrode 1. The difference is that in the preparation of positive electrode 4, the amount of hexamethylene diisocyanate added is 23.540 kg, the amount of triethylamine catalyst added is 2.610 g, the amount of methyl ethyl ketone oxime added is 6.970 kg, and the amount of triethylenetetramine crosslinking agent added is 1.950 kg, thus obtaining positive electrode 4.

[0159] Positive electrode 5: The preparation of positive electrode 5 is similar to that of positive electrode 1. The difference is that in the preparation of positive electrode 5, the amount of hexamethylene diisocyanate added is 25.221 kg, the amount of triethylamine catalyst added is 2.679 g, the amount of methyl ethyl ketone oxime added is 8.712 kg, and the amount of triethylenetetramine crosslinking agent added is 2.437 kg, thus obtaining positive electrode 5.

[0160] Positive electrode 6: The preparation of positive electrode 6 is similar to that of positive electrode 1. The difference is that in the preparation of positive electrode 6, the amount of hexamethylene diisocyanate added is 26.902 kg, the amount of triethylamine catalyst added is 2.747 g, the amount of methyl ethyl ketone oxime blocking agent added is 10.454 kg, and the amount of triethylenetetramine crosslinking agent added is 2.925 kg, thus obtaining positive electrode 6.

[0161] Positive electrode 7: The preparation of positive electrode 7 is similar to that of positive electrode 1. The difference is that in the preparation of positive electrode 7, the amount of hexamethylene diisocyanate added is 28.584 kg, the amount of triethylamine catalyst added is 2.816 g, the amount of methyl ethyl ketone oxime added is 12.197 kg, and the amount of triethylenetetramine crosslinking agent added is 3.412 kg, thus obtaining positive electrode 7.

[0162] Positive electrode 8: The preparation of positive electrode 8 is similar to that of positive electrode 1. The difference is that in the preparation of positive electrode 8, the amount of hexamethylene diisocyanate added is 30.265 kg, the amount of triethylamine catalyst added is 2.884 g, the amount of methyl ethyl ketone oxime added is 13.939 kg, and the amount of triethylenetetramine crosslinking agent added is 3.899 kg, thus obtaining positive electrode 8.

[0163] Positive electrode 9: The preparation of positive electrode 9 is similar to that of positive electrode 1. The difference is that in the preparation of positive electrode 9, the amount of hexamethylene diisocyanate added is 33.638 kg, the amount of triethylamine catalyst added is 3.021 g, the amount of methyl ethyl ketone oxime blocking agent added is 17.424 kg, and the amount of triethylenetetramine crosslinking agent added is 4.874 kg, thus obtaining positive electrode 9.

[0164] Positive electrode 10: The preparation of positive electrode 10 is similar to that of positive electrode 1. The difference is that in the preparation of positive electrode 10, 60.000 kg of PEG is added, 40.000 kg of polybutanediol (PTMG, molecular weight 1000) is added as a reaction raw material for polyurethane prepolymer, 25.221 kg of hexamethylene diisocyanate is added, 2.679 g of triethylamine catalyst is added, 8.712 kg of methyl ethyl ketone oxime blocking agent is added, and 2.437 kg of triethylenetetramine crosslinking agent is added to obtain positive electrode 10.

[0165] Positive electrode 11: The preparation of positive electrode 11 is similar to that of positive electrode 1. The difference is that in the preparation of positive electrode 11, 60.000 kg of PEG is added, 40.000 kg of polycaprolactone (PCL, molecular weight 1000) is added as a reaction raw material for polyurethane prepolymer, 25.221 kg of hexamethylene diisocyanate is added, 2.679 g of triethylamine catalyst is added, 8.712 kg of methyl ethyl ketone oxime blocking agent is added, and 2.437 kg of triethylenetetramine crosslinking agent is added to obtain positive electrode 11.

[0166] Positive electrode 12: The preparation of positive electrode 12 is similar to that of positive electrode 1. The difference is that in the preparation of positive electrode 12, the amount of PEG added is 60.000 kg, and 40.000 kg of polycarbonate diol (PCDL, molecular weight 1000) is added as a reaction raw material for polyurethane prepolymer. The amount of hexamethylene diisocyanate added is 25.221 kg, the amount of triethylamine catalyst added is 2.679 g, the amount of methyl ethyl ketone oxime added as blocking agent is 8.712 kg, and the amount of triethylenetetramine crosslinking agent added is 2.437 kg, thus obtaining positive electrode 12.

[0167] Positive electrode 13: The preparation of positive electrode 13 is similar to that of positive electrode 1. The difference is that in the preparation of positive electrode 13, 60.000 kg of PEG is added, 40.000 kg of polypropylene glycol (PPG, molecular weight 1000) is added as a reaction raw material for polyurethane prepolymer, 25.221 kg of hexamethylene diisocyanate is added, 2.679 g of triethylamine catalyst is added, 8.712 kg of methyl ethyl ketone oxime blocking agent is added, and 2.437 kg of triethylenetetramine crosslinking agent is added to obtain positive electrode 13.

[0168] Positive electrode 14: The preparation of positive electrode 14 is similar to that of positive electrode 1. The difference is that in the preparation of positive electrode 14, 60.000 kg of PEG is added, 40.000 kg of polydimethylsiloxane (PDMS, molecular weight 1000) is added as a reaction raw material for polyurethane prepolymer, 25.221 kg of hexamethylene diisocyanate is added, 2.679 g of triethylamine catalyst is added, 8.712 kg of methyl ethyl ketone oxime blocking agent is added, and 2.437 kg of triethylenetetramine crosslinking agent is added to obtain positive electrode 14.

[0169] Positive electrode 15: The preparation of positive electrode 15 is similar to that of positive electrode 1. The difference is that in the preparation of positive electrode 15, 60.000 kg of PEG is added, and 40.000 kg of polylactic acid-glycolic acid copolymer (PLGA, molecular weight 1000) is added as a reaction raw material for polyurethane prepolymer. The amount of hexamethylene diisocyanate added is 25.221 kg, the amount of triethylamine catalyst added is 2.679 g, the amount of methyl ethyl ketone oxime blocking agent added is 8.712 kg, and the amount of triethylenetetramine crosslinking agent added is 2.437 kg, thus obtaining positive electrode 15.

[0170] Positive electrode 16: 100.000 kg of polyethylene glycol (PEG, molecular weight 1000) was added to a reactor and dried at 95°C for 3 h. Then, 25.221 kg of hexamethylene diisocyanate, 2.679 g of triethylamine catalyst, and 0.487 kg of triethylenetetramine crosslinking agent were added to the reactor and reacted at 115°C to obtain polyurethane adhesive.

[0171] 97.300 kg of positive electrode active material LiFePO4, 1.000 kg of polyurethane binder, and 1.400 kg of conductive agent acetylene black were stirred in a planetary mixer at a revolution speed of 25 r / min for 20 min. 53.850 kg of NMP solution was added to the mixer, and the mixture was stirred at a revolution speed of 25 r / min and a rotation speed of 900 r / min for 50 min. 300.000 g of dispersant PVP was added to the mixer, and the mixture was stirred at a revolution speed of 25 r / min and a rotation speed of 1400 r / min for 50 min to obtain the positive electrode slurry.

[0172] The positive electrode slurry prepared above was coated onto carbon-coated aluminum foil and baked at 110°C for 15 minutes to obtain the positive electrode sheet 16.

[0173] Positive electrode 17: 3.97 kg of positive electrode active material LiFePO4, 16.4 g of binder polyvinylidene fluoride, and 57.4 g of conductive agent acetylene black were placed in a planetary mixer and stirred for 20 min at a revolution speed of 25 r / min. Then, 2.4 kg of NMP solution was added to the mixer, and the mixture was stirred for 50 min at a revolution speed of 25 r / min and a rotation speed of 900 r / min. Finally, 12.3 g of dispersant PVP was added to the mixer, and the mixture was stirred for 50 min at a revolution speed of 25 r / min and a rotation speed of 1400 r / min to obtain the positive electrode slurry.

[0174] The positive electrode slurry prepared above was coated onto carbon-coated aluminum foil and baked at 110°C for 15 minutes to obtain positive electrode sheet 17.

[0175] The positive electrode sheet prepared according to the method provided in the embodiments of this application is obtained by scraping the dried positive electrode slurry from the positive electrode current collector and dissolving it with NMP solution. The polyurethane in the solution is non-resolvable due to its large molecular weight and remains solid in the solvent.

[0176] 2. Preparation of battery cells

[0177] [Example 1]

[0178] (1) Positive electrode plate

[0179] The positive electrode sheet is the positive electrode sheet 1 prepared as described above.

[0180] (2) Preparation of negative electrode sheet

[0181] Artificial graphite, conductive carbon black, styrene-butadiene rubber (SBR), and CMC are dissolved in deionized water at a weight ratio of 95.5:1.2:1.3:1.5 and mixed evenly to prepare a negative electrode slurry. The negative electrode slurry is then evenly coated onto a negative electrode current collector, dried, and a negative electrode film is obtained. The film is then cold-pressed and slit to obtain a negative electrode sheet.

[0182] (3) Preparation of electrolyte

[0183] In an argon-atmospheric glove box with a water content of <10 ppm, thoroughly dried lithium salt (LiPF6) was dissolved in a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 20:20:60. Then, vinylene carbonate (VC) was added as an additive, and the mixture was thoroughly mixed to obtain the electrolyte. The concentration of lithium salt was 1 mol / L.

[0184] (4) Preparation of the separating membrane

[0185] Conventional polypropylene film is used as the separator.

[0186] (5) Assembly of lithium-ion batteries

[0187] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The electrode assembly is then wound to obtain an electrode assembly. The electrode assembly is placed in a battery casing, dried, and then injected with electrolyte. After formation and settling processes, a lithium-ion battery 1 is obtained, which is Example 1.

[0188] [Examples 2-15, Comparative Examples 1-2]

[0189] The lithium-ion batteries of Examples 2-15 and Comparative Examples 1-2 are prepared in a similar manner to the lithium-ion battery of Example 1, except that different positive electrode plates are used (positive electrode plate 1-15 is used in Examples 1-15, and positive electrode plate 16-17 is used in Comparative Examples 1-2), as detailed in Table 1.

[0190] 3. Performance testing of the positive electrode sheet

[0191] (1) Adhesion test of binder in positive electrode sheet

[0192] Referring to the national standard "Test Method for 180° Peel Strength of Adhesives", a positive electrode sheet with a width of 30mm and a length of 100-160mm is cut with a blade. Special double-sided adhesive tape with a width of 20mm and a length of 90-150mm is applied to a steel plate. The cut positive electrode sheet is then attached to the double-sided adhesive tape, with the test side facing down, and then rolled three times in the same direction using a pressure roller.

[0193] Insert a paper strip with the same width as the positive electrode and a length 80-200mm longer than the positive electrode into the bottom of the positive electrode and fix it with crease glue.

[0194] Turn on the power of the Sansi tensile testing machine (sensitivity 1N). The indicator light will illuminate. Adjust the limit block to the appropriate position. Secure the end of the steel plate without the positive electrode attached using the lower clamp. Fold the paper tape upwards and secure it using the upper clamp. Use the "up" and "down" buttons on the manual controller provided with the tensile testing machine to adjust the position of the upper clamp. Then perform the test and read the values.

[0195] (2) Film resistance test of positive electrode

[0196] The prepared positive electrode sheet was tested using a four-probe resistance meter. Three parallel samples were tested for each sample, and the average value was taken.

[0197] 4. Battery performance test

[0198] (1) Initial DC Resistance (DCR) Test

[0199] At room temperature, the batteries of each embodiment and comparative example were charged at a constant current of 0.5C to 3.65V, and then charged at a constant voltage to a current of 0.05C. The batteries were then discharged at a constant current of 0.5C for 60 minutes to adjust the batteries to 50% SOC, and the voltage of the batteries at this time was recorded as U1. The batteries were then discharged at a constant current of 4C for 30 seconds, and the voltage at the end of the discharge was recorded as U2 using a 0.1-second sampling time. The initial DCR of the battery was represented by the discharge DCR at 50% SOC, and the initial DCR of the battery was calculated as (U1-U2) / 4C.

[0200] (2) Battery capacity retention test

[0201] At 25℃, a lithium-ion battery is charged at a constant current of 1 / 3C to 3.65V, then charged at a constant voltage of 3.65V to a current of 0.05C. After resting for 5 minutes, it is discharged at 1 / 3C to 2.5V. The resulting capacity is recorded as the initial capacity C0. The above steps are repeated, and the discharge capacity Cn of the battery after the nth cycle is recorded. The battery capacity retention rate (%) after n cycles is calculated as (Cn / C0) × 100%.

[0202] For example, the capacity retention rate (%) of a lithium-ion battery after 500 cycles at 25°C = (discharge capacity of the 500th cycle / discharge capacity of the first cycle) × 100%.

[0203] Please refer to Table 1 for the product parameters of different embodiments and comparative examples, as well as the test results of the performance tests of the positive electrode sheets 1-17 prepared according to the above method. The R value of the polyurethane prepolymer in Table 1 refers to the molar ratio R of isocyanate to hydroxyl groups in the polyurethane prepolymer. Please refer to Table 2 for the battery performance tests of comparative examples 1-2 and examples 1-15 prepared according to the above method.

[0204] Table 1: Product parameters and performance test results of positive electrode sheets 1-17 in the examples and comparative examples

[0205]

[0206] Table 2: Performance test results of Examples 1-15 and Comparative Examples 1-2

[0207]

[0208] A comparison of the results from Comparative Examples 1-2 and Examples 1-15 shows that, in the preparation of the positive electrode sheet, the inclusion of polyurethane prepolymer in the positive electrode slurry results in a positive electrode sheet with better adhesion and lower film resistance. Consequently, the lithium-ion battery exhibits a lower DCR and better capacity retention.

[0209] A comparison of the results from Examples 1-9 shows that controlling the ratio of PEG and hexamethylene diisocyanate, the reactants in the prepolymerization reaction of the polyurethane prepolymer, thereby controlling the molar ratio R of isocyanate to hydroxyl groups in the polyurethane prepolymer, and setting R within a suitable range, results in better performance of the positive electrode and the lithium-ion battery. In this application, under constant conditions, controlling the molar ratio R of isocyanate to hydroxyl groups in the polyurethane prepolymer within the range of 1.2 to 1.8 results in better adhesion of the positive electrode and lower film resistance; correspondingly, the lithium-ion battery has a lower DCR and better capacity retention.

[0210] Although this application has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this application. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for preparing a positive electrode sheet, comprising: A positive electrode slurry is prepared, wherein the positive electrode slurry comprises a polyurethane prepolymer; The positive electrode slurry is coated on at least one side of the positive electrode current collector; The positive electrode slurry coated on at least one side of the positive electrode current collector is dried to obtain the positive electrode sheet; The preparation of the polyurethane prepolymer includes: Dry polyether polyols and / or polyester polyols; The dried polyether polyol and / or polyester polyol are mixed with isocyanate and catalyst to carry out a prepolymerization reaction; After the prepolymerization reaction is completed, a blocking agent is added to the reaction product to obtain the polyurethane prepolymer. The blocking agent includes at least one of methyl ethyl ketone oxime and ethyl acetoacetate; The drying temperature of the positive electrode slurry ranges from 60℃ to 150℃.

2. The preparation method according to claim 1, characterized in that, The preparation of the positive electrode slurry includes: Preparation of binder precursor solution; The positive electrode active material, conductive agent, dispersant and crosslinking agent are added to the binder precursor solution and mixed to obtain the positive electrode slurry.

3. The preparation method according to claim 2, characterized in that, The conductive agent includes at least one of conductive carbon, acetylene black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

4. The preparation method according to claim 2, characterized in that, The dispersant includes polyvinylpyrrolidone.

5. The preparation method according to claim 2, characterized in that, The crosslinking agent includes at least one of sucrose, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, diethyltoluenediamine, dimethylthiotoluenediamine, three-armed polycaprolactone, and four-armed polycaprolactone.

6. The preparation method according to claim 2, characterized in that, The preparation of the binder precursor solution includes: Prepare the polyurethane prepolymer; The polyurethane prepolymer was dispersed in an N-methylpyrrolidone solvent to prepare the binder precursor solution.

7. The preparation method according to claim 1, characterized in that, The drying temperature of the polyether polyol and / or the polyester polyol ranges from 90°C to 95°C, and the drying time ranges from 2 to 3 hours.

8. The preparation method according to any one of claims 1 to 7, characterized in that, The isocyanate includes diisocyanate.

9. The preparation method according to claim 8, characterized in that, The diisocyanate includes at least one of aromatic diisocyanate and aliphatic diisocyanate.

10. The preparation method according to any one of claims 1 to 7, characterized in that, The isocyanate includes at least one of toluene-2,3-diisocyanate, toluene-2,4-diisocyanate, toluene-2,5-diisocyanate, toluene-2,6-diisocyanate, toluene-3,4-diisocyanate, toluene-3,5-diisocyanate, 1,5-naphthalene diisocyanate, terephthalene diisocyanate, isophthalene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, L-lysine ethyl ester diisocyanate, hydrogenated toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, and hydrogenated diphenylmethane diisocyanate.

11. The preparation method according to any one of claims 1 to 7, characterized in that, The molar ratio R of isocyanate to hydroxyl groups in the polyurethane prepolymer ranges from 1.1 to 2.

0.

12. The preparation method according to claim 11, characterized in that, The value of R ranges from 1.2 to 1.

8.

13. The preparation method according to any one of claims 1 to 7, characterized in that, The polyether polyol includes at least one of polyethylene glycol, polypropylene glycol, polyethylene oxide glycol, polytetrahydrofuran ether glycol, and polyethylene glycol-propylene glycol copolymer.

14. The preparation method according to any one of claims 1 to 7, characterized in that, The polyester polyol includes at least one of polycaprolactone, polycarbonate diol, polylactic acid diol, and polyglycolic acid-lactide copolymer.

15. The preparation method according to any one of claims 1 to 7, characterized in that, The catalyst includes at least one of organotin catalysts, organobismuth catalysts, and tertiary amine catalysts.

16. The preparation method according to any one of claims 1 to 7, characterized in that, The catalyst includes at least one of dibutyltin dilaurate, stannous octoate, N-ethylmorpholine, N-methylmorpholine, and triethylamine.

17. The preparation method according to any one of claims 1 to 7, characterized in that, Based on the total mass of the reaction raw materials for the prepolymerization reaction, the mass percentage of the catalyst in the reaction raw materials for the prepolymerization reaction ranges from 0.001% to 1.0%.

18. A positive electrode sheet prepared by any one of claims 1 to 17.

19. The positive electrode sheet according to claim 18, characterized in that, The positive electrode sheet includes a positive electrode material layer. Based on the total mass of the positive electrode material layer, the mass percentage of the binder in the positive electrode material layer ranges from 0.3% to 4.2%.

20. A battery cell comprising a positive electrode sheet according to claim 18 or 19.

21. A battery comprising a battery cell according to claim 20.

22. An electrical device comprising the battery according to claim 21.

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