Method for preparing positive electrode slurry, positive electrode plate, secondary battery, and power consumption device

Abstract

The present application provides a method for preparing a positive electrode slurry, a positive electrode plate, a secondary battery, and a power consumption device. The method for preparing a positive electrode slurry includes a first stirring, a second stirring, a third stirring, and a fourth stirring, and during the first stirring, a positive electrode active material and an adhesive are mixed and stirred to prepare a dry mixture, during the second stirring, an adhesive and a solvent are mixed and stirred to prepare an adhesive liquid, during the third stirring, the dry mixture and the adhesive liquid are mixed and stirred to prepare a primary slurry, and during the fourth stirring, a positive electrode active material, a conductive agent, a solvent, and the primary slurry are mixed and stirred to prepare a positive electrode slurry, and the adhesive used in the first stirring is the same as the adhesive used in the second stirring.

Description

[Technical Field]

[0001] This application relates to the technical field of secondary batteries, and more particularly to a method for preparing a positive electrode slurry, a positive electrode plate, a secondary battery, and a power consumption device. [Background technology]

[0002] In recent years, as the range of applications for secondary batteries has expanded, they are widely used in energy storage and power systems such as hydroelectric, thermal, wind, and solar power plants, as well as in many fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace.

[0003] Electrode slurry is the foundation for forming electrodes and the first step in secondary battery production. The properties of the electrode slurry significantly affect subsequent electrode production and battery performance. The positive electrode slurry is a solid-liquid phase mixture mainly consisting of positive electrode active material, conductive agent, adhesive, and solvent. Conventional slurry preparation methods are often one-step methods, where each component in the positive electrode slurry is directly mixed and stirred. However, one-step preparation methods cannot meet the demand for preparing adhesives with different mass-average molecular weights, resulting in poor versatility of the mixing process and disadvantages in reducing preparation costs. Therefore, it is necessary to develop new slurry preparation methods that can be applied to adhesives with different mass-average molecular weights. [Overview of the Initiative]

[0004] This application has been made in view of the above-mentioned problems, and its purpose is to provide a method for preparing a positive electrode slurry for application to adhesives with different mass-average molecular weights.

[0005] According to a first aspect of this application, a method for preparing a positive electrode slurry is provided, which includes a first stirring, a second stirring, a third stirring, and a fourth stirring. During the first stirring, the positive electrode active material and the adhesive are mixed and stirred to prepare a dry mixture. During the second stirring, the adhesive and solvent are mixed and stirred to prepare the adhesive solution. During the third stirring, the dry mixture and the adhesive liquid are mixed and stirred to prepare a primary slurry. During the fourth stirring, the positive electrode active material, the conductive agent, the solvent, and the primary slurry are mixed and stirred to prepare the positive electrode slurry. The adhesive used in the first stirring and the adhesive used in the second stirring are the same.

[0006] The cathode slurry preparation method disclosed in this application has broader versatility than conventional cathode slurry preparation methods and is applicable to slurries containing adhesives with different mass-average molecular weights. Compared to conventional preparation methods, this application allows for uniform coating of the cathode active material with the adhesive by adding and mixing the adhesive multiple times, effectively dispersing the adhesive in the slurry and avoiding severe adhesion of the adhesive. This improves the applicability of the preparation method to adhesives with high molecular weights, enhances the versatility of the slurry preparation method, and reduces preparation costs.

[0007] In any embodiment, the adhesive comprises at least one polyvinylidene fluoride having a mass-average molecular weight of 1 million to 8 million.

[0008] The preparation method disclosed in this application is versatile for both low molecular weight and high molecular weight polyvinylidene fluoride adhesives, broadens the slurry application window, and ensures that the slurry still has an appropriate viscosity for slurries containing adhesives with a mass-average molecular weight of up to 8 million, while also ensuring that the electrode plates have excellent adhesive performance and meeting the demand for next-generation adhesives.

[0009] In any embodiment, the adhesive comprises at least two polyvinylidene fluorides having a difference in mass-average molecular weight of 7 million or less.

[0010] The positive electrode slurry prepared by the preparation method disclosed in this application can effectively exhibit the properties of polyvinylidene fluoride adhesives of different molecular weights, and through the interbonding and steric hindrance between large and small segments, the slurry has an appropriate viscosity, and the electrode plates have relatively high adhesive strength, shear strength, and cohesive strength.

[0011] In any embodiment, the mass content of the adhesive used for the first stirring is 30% to 50% of the total mass of the adhesive used for the first stirring and the adhesive used for the second stirring, and the mass content of the adhesive used for the second stirring is 50% to 70%.

[0012] By controlling the mass content of the adhesive used in the first stirring to 30% to 50% and the mass content of the adhesive used in the second stirring to 50% to 70% of the total mass of the adhesives used in the first stirring and the adhesive used in the second stirring, it is possible to ensure that the viscosity of the slurry is within an appropriate range, and also to ensure that the electrode plates have high adhesive strength, shear strength, and cohesive force, thereby broadening the electrode plate manufacturing process window and improving the adhesive performance of the electrode plates.

[0013] In any embodiment, the orbital speed of the first stirring is 10 revolutions / min to 20 revolutions / min.

[0014] By controlling the orbital speed of the first stirring to 10 revolutions / min to 20 revolutions / min, it is possible to ensure that the viscosity of the slurry is within an appropriate range, and also to ensure that the electrode plates have high adhesive strength, shear strength, and cohesive force, thereby broadening the electrode plate manufacturing process window and improving the adhesive performance of the electrode plates.

[0015] In any of the embodiments, the rotation speed of the first stirring is 0.

[0016] By controlling the rotation speed of the first stirring to 0, the shear force of the first stirring is reduced, the possibility that the positive electrode active material and the adhesive are excessively pulverized is reduced, it is ensured that the positive electrode active material and the adhesive have a certain particle size and specific surface area, the dispersion effect of the positive electrode active material and the adhesive is improved, the viscosity of the slurry is reduced, and it contributes to improving the adhesive force, shear strength and cohesion of the electrode plate.

[0017] In any embodiment, the stirring time of the first stirring is 10 minutes to 20 minutes.

[0018] By controlling the stirring time of the first stirring to 10 minutes to 20 minutes, it can be ensured that the viscosity of the slurry is within an appropriate range, and it can also be ensured that the electrode plate has high adhesive force, shear strength and cohesion, expanding the electrode plate manufacturing process window and improving the adhesion performance of the electrode plate.

[0019] In any embodiment, the revolution speed of the second stirring is 20 revolutions per minute to 30 revolutions per minute.

[0020] By controlling the revolution speed of the second stirring to 20 revolutions per minute to 30 revolutions per minute, it can be ensured that the viscosity of the slurry is within an appropriate range, and it can also be ensured that the electrode plate has high adhesive force, shear strength and cohesion, expanding the electrode plate manufacturing process window and improving the adhesion performance of the electrode plate.

[0021] In any embodiment, the rotation speed of the second stirring is 1100 revolutions per minute to 1300 revolutions per minute.

[0022] By controlling the rotation speed of the second stirring to 1100 revolutions per minute to 1300 revolutions per minute, it can be ensured that the viscosity of the slurry is within an appropriate range, and it can also be ensured that the electrode plate has high adhesive force, shear strength and cohesion. At the same time, it is possible to avoid the situation where the rotation speed of the second stirring is too high, which causes the load of the device to be too large and affects the service life of the device, and it can also reduce the cost loss.

[0023] In any of the embodiments, the stirring time for the second stirring is 60 to 80 minutes.

[0024] By controlling the stirring time of the second stirring to 60 to 80 minutes, it is possible to ensure that the viscosity of the slurry is within an appropriate range, and that the electrode plates have high adhesive strength, shear strength, and cohesive force. Furthermore, it is possible to avoid the situation where the stirring time of the second stirring is too long, which leads to a reduction in production efficiency, and thus save production costs.

[0025] In any of the embodiments, the orbital speed of the third stirring is 20 revolutions / min to 30 revolutions / min.

[0026] By controlling the orbital speed of the third stirring mechanism to 20 revolutions / min to 30 revolutions / min, it is possible to ensure that the viscosity of the slurry is within an appropriate range, and that the electrode plates have high adhesive strength, shear strength, and cohesive force. Furthermore, it is possible to avoid excessive load on the equipment due to an excessively high orbital speed of the third stirring mechanism, which would affect the service life of the equipment and thus reduce cost losses.

[0027] In any of the embodiments, the rotation speed of the third stirring is 500 revolutions / min to 800 revolutions / min.

[0028] By controlling the rotation speed of the third stirring mechanism to 500 rpm to 800 rpm, it is possible to ensure that the viscosity of the slurry is within an appropriate range, and that the electrode plates have high adhesive strength, shear strength, and cohesive force. Furthermore, it is possible to avoid excessive load on the equipment due to an excessively high rotation speed of the third stirring mechanism, which would affect the service life of the equipment, thereby reducing cost losses.

[0029] In any of the embodiments, the stirring time for the third stirring is 40 to 60 minutes.

[0030] By controlling the stirring time of the third stirring to 40 to 60 minutes, it is possible to ensure that the viscosity of the slurry is within an appropriate range, and that the electrode plates have high adhesive strength, shear strength, and cohesive force. Furthermore, it is possible to avoid the situation where the stirring time of the third stirring is too long, which leads to a reduction in production efficiency, and thus save production costs.

[0031] In any embodiment, the orbital speed of the fourth stirring is 20 revolutions / min to 30 revolutions / min.

[0032] By controlling the orbital speed of the fourth stirring mechanism to 20 to 30 revolutions per minute, it is possible to ensure that the viscosity of the slurry is within an appropriate range, and that the electrode plates have high adhesive strength, shear strength, and cohesive force. Furthermore, it is possible to avoid excessive load on the equipment due to an excessively high orbital speed of the fourth stirring mechanism, which would affect the service life of the equipment and thus reduce cost losses.

[0033] In any embodiment, the rotation speed of the fourth stirring is 1100 revolutions / min to 1400 revolutions / min.

[0034] By controlling the rotation speed of the fourth stirring mechanism to 1100 rpm to 1400 rpm, it is possible to ensure that the viscosity of the slurry is within an appropriate range, and that the electrode plates have high adhesive strength, shear strength, and cohesive force. Furthermore, it is possible to avoid excessive load on the equipment due to an excessively high rotation speed of the fourth stirring mechanism, which would affect the service life of the equipment, thereby reducing cost losses.

[0035] In any of the embodiments, the stirring time for the fourth stirring is 100 to 120 minutes.

[0036] By controlling the stirring time of the fourth stirring to 100 to 120 minutes, it is possible to ensure that the viscosity of the slurry is within an appropriate range, and that the electrode plates have high adhesive strength, shear strength, and cohesive force. Furthermore, it is possible to avoid the situation where the stirring time of the fourth stirring is too long, which leads to a reduction in production efficiency, and thus save production costs.

[0037] In any of the embodiments, when the solid content of the positive electrode slurry is 68%, the viscosity of the positive electrode slurry is 8000 mPa·s to 41000 mPa·s.

[0038] A cathode slurry with a solid content of 68% has a viscosity of 8000 mPa·s to 41000 mPa·s. This cathode slurry has good applicability and processability, broadening the process window for slurry application.

[0039] In any embodiment, the positive electrode active material used for the first stirring and the positive electrode active material used for the fourth stirring are the same, and the mass content of the positive electrode active material used for the first stirring is 50% to 70% of the total mass of the positive electrode active materials used for the first stirring and the positive electrode active material used for the fourth stirring is 30% to 50%.

[0040] By controlling the mass content of the positive electrode active material used in the first stirring to 50% to 70% and the mass content of the positive electrode active material used in the fourth stirring to 30% to 50% of the total mass of the positive electrode active material used in the first stirring and the positive electrode active material used in the fourth stirring, the viscosity of the slurry can be reduced, the adhesion, shear strength, and cohesive force of the electrode plates can be improved, the process window for slurry coating can be broadened, and the performance of the electrode plates can be improved.

[0041] In any embodiment, the solvent used for the second stirring and the solvent used for the fourth stirring are the same, and the mass content of the solvent used for the second stirring is 35% to 40% and the mass content of the solvent used for the fourth stirring is 5% to 10% relative to the total mass of the conductive agent, the positive electrode active material used for the first stirring, the positive electrode active material used for the fourth stirring, the adhesive used for the first stirring, and the adhesive used for the second stirring.

[0042] In any embodiment, the mass ratio of the total mass of the positive electrode active material, the total mass of the adhesive, and the conductive agent in the positive electrode slurry is (86-98):(1-8):(1-6). A positive electrode slurry within this range has good processing performance and provides the molded positive electrode plate with excellent adhesive and electrochemical properties.

[0043] In any embodiment, the positive electrode active material is one or more of lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, and lithium nickel cobalt manganese oxide. The positive electrode active material provides the battery with a high energy density and is advantageous for improving the battery's cycle performance.

[0044] In any embodiment, the conductive agent is one or more of conductive carbon black, graphite, and carbon nanotubes. The conductive agent is advantageous for improving the conductivity of the battery.

[0045] According to a second aspect of this application, a positive electrode plate is provided, which comprises a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, wherein the positive electrode film layer is manufactured from a positive electrode slurry prepared by the preparation method described in the first aspect of this application.

[0046] In any of the embodiments, the adhesive force per unit length between the positive electrode film layer and the positive electrode current collector is 20 N / m to 30 N / m.

[0047] In any of the embodiments, the shear strength of the positive electrode film layer is 0.64 mPa to 0.91 mPa.

[0048] In any of the embodiments, the cohesive force of the positive electrode film layer is 70 N / m to 90 N / m.

[0049] A third aspect of this application provides a secondary battery comprising an electrode assembly and an electrolyte, wherein the electrode assembly comprises a separator, a negative electrode plate, and a positive electrode plate as described in the second aspect of this application.

[0050] In any embodiment, the secondary battery is one of a lithium-ion battery, a sodium-ion battery, a magnesium-ion battery, and a potassium-ion battery.

[0051] According to a fourth aspect of this application, a battery module including a secondary battery according to a third aspect of this application is provided.

[0052] According to the fifth aspect of this application, a battery pack is provided that includes a secondary battery according to the third aspect of this application or a battery module according to the fourth aspect of this application.

[0053] According to a sixth aspect of this application, a power consumption device is provided which includes at least one selected from a secondary battery according to a third aspect of this application, a battery module according to a fourth aspect of this application, or a battery pack according to a fifth aspect of this application. [Brief explanation of the drawing]

[0054] [Figure 1] This is a schematic diagram of a secondary battery according to one embodiment of the present application. [Figure 2] Figure 1 is an exploded view of a secondary battery according to one embodiment of this application. [Figure 3] This is a schematic diagram of a battery module according to one embodiment of the present application. [Figure 4] This is a schematic diagram of a battery pack according to one embodiment of the present application. [Figure 5] Figure 4 is an exploded view of a battery pack according to one embodiment of this application. [Figure 6]This is a schematic diagram of a power consumption device using a secondary battery as a power source according to one embodiment of the present application. [Modes for carrying out the invention]

[0055] The following describes in detail embodiments of the adhesive, preparation method, electrode, battery, and power consumption device of this application, with appropriate reference to the drawings. However, unnecessary details may be omitted. For example, detailed explanations of well-known matters and redundant explanations of structures that are actually the same may be omitted. This is to avoid making the following explanation unnecessarily long and to make it easily understandable to those skilled in the art. The drawings and the following explanation are provided to enable those skilled in the art to fully understand this application and are not intended to limit the topics described in the claims.

[0056] The “range” disclosed in this application is limited in the form of a lower limit and an upper limit, and a given range is limited by selecting one lower limit and one upper limit, which define the boundary of a particular range. The range thus limited may or may not include the endpoints, and any combination is possible, that is, any lower limit can be combined with any upper limit to form a range. For example, if the ranges 60-120 and 80-110 are listed for a particular parameter, it is understood that the ranges 60-110 and 80-120 can also be assumed. Furthermore, if 1 and 2 are listed as the minimum range values ​​and 3, 4, and 5 are listed as the maximum range values, then the ranges 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5 can all be assumed. In this application, unless otherwise specified, the numerical range “a-b” represents an abbreviated expression for any combination of real numbers a-b, where a and b are both real numbers. For example, the numerical range "0 to 5" indicates that all real numbers between "0 to 5" have already been listed in this specification, and "0 to 5" is simply a shortened expression for combinations of these numbers. Also, when a parameter is described as an integer ≥ 2, it is equivalent to disclosing that this 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 embodiments and optional embodiments of this application can be combined to form new technical inventions.

[0058] Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical concepts.

[0059] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, the fact that the method includes steps (a) and (b) means that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, the fact that the method referred to above may further include step (c) means that step (c) may be added to the method in any order, for example the method may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), and so on.

[0060] Unless otherwise specified, the terms “includes” and “inclusive” as used in this application may be open-ended or closed-ended. For example, “includes” and “inclusive” may further include or include other components not listed, or may include or include only the components listed.

[0061] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the conditions A is true (or exists) and B is false (or does not exist), the condition A is false (or does not exist) but B is true (or exists), and the condition both A and B are true (or exist) all satisfy "A or B."

[0062] A positive electrode slurry is a solid-liquid phase mixture system mainly consisting of positive electrode active material, conductive agent, adhesive, and solvent. Conventional slurry preparation methods are only applicable to slurries containing low molecular weight adhesives and cannot meet the demand for next-generation high molecular weight adhesives. The applicant's research has shown that high molecular weight adhesives help to increase the load of active material in the electrode plate, which is advantageous for improving the energy density and capacity of the battery. However, conventional slurry preparation methods, when forming slurries containing high molecular weight adhesives, result in a rapid increase in slurry viscosity, making application difficult and reducing electrode plate performance.

[0063] [Method for preparing positive electrode slurry] Based on this, this application proposes a method for preparing a positive electrode slurry, which includes a first stirring, a second stirring, a third stirring, and a fourth stirring, wherein during the first stirring, the positive electrode active material and the adhesive are mixed and stirred to prepare a dry mixture; during the second stirring, the adhesive and the solvent are mixed and stirred to prepare an adhesive solution; during the third stirring, the dry mixture and the adhesive solution are mixed and stirred to prepare a primary slurry; and during the fourth stirring, the positive electrode active material, the conductive agent, the solvent, and the primary slurry are mixed and stirred to prepare a positive electrode slurry, wherein the adhesive used in the first stirring and the adhesive used in the second stirring are the same.

[0064] In this preparation method, first, a first stirring is performed on the positive electrode active material and a portion of the adhesive to obtain a dry mixture. The first stirring mechanically crimps both together, forming a tight entanglement. Next, the remaining adhesive and a portion of the solvent are mixed and a second stirring is performed to obtain an adhesive solution. The second stirring contributes to the uniform dispersion of the adhesive in the solvent. Then, a third stirring is performed on the dry mixture prepared in the first stirring and the adhesive solution prepared in the second stirring to obtain a primary slurry. The third stirring contributes to the uniform dispersion of the positive electrode active material in the primary slurry system, and the positive electrode active material is uniformly coated with the adhesive and can entangle with it. Finally, a fourth stirring is performed on the remaining positive electrode active material, conductive agent, solvent, and primary slurry to obtain a positive electrode slurry. The fourth stirring thoroughly mixes the conductive agent and the positive electrode active material, uniformly disperses the positive electrode active material and conductive agent in the slurry, and contributes to uniformly coating the surfaces of the positive electrode active material and conductive agent with the adhesive.

[0065] This application describes a method for uniformly coating the positive electrode active material and conductive agent with an adhesive by dispersion and mixing, effectively dispersing the adhesive and positive electrode active material in the slurry while avoiding severe aggregation of the adhesive. This improves the applicability of the preparation method to adhesives with high molecular weight, enhances the versatility of the slurry preparation method, and reduces preparation costs.

[0066] In some embodiments, the adhesive comprises at least one polyvinylidene fluoride having a mass-average molecular weight of 1 million to 8 million. In some embodiments, the mass-average molecular weight of the polyvinylidene fluoride is selectively one of 1 million, 1.5 million, 2 million, 2.5 million, 3 million, 3.5 million, 4 million, 4.5 million, 5 million, 5.5 million, 6 million, 6.5 million, 7 million, 7.5 million, or 8 million.

[0067] In this specification, the term "mass-average molecular weight" refers to the average molecular weight of a polymer statistically determined based on its mass, and is the molecular weight obtained by averaging it per unit mass.

[0068] In this application, the mass-average molecular weight of the polymer can be tested using methods known in the art, such as gel chromatography, for example, a Waters 2695 Isocratic HPLC gel chromatograph (differential refractive detector 2141). A 3.0% polystyrene solution sample is used as a reference, and a matching chromatography column (oil-based: Styragel HT5DMF 7.8 × 300 mm + Styragel HT4) is selected. A 3.0% adhesive solution is prepared using purified N-methylpyrrolidone (NMP) solvent, and the prepared solution is allowed to stand for 1 day. Before testing, tetrahydrofuran is first drawn into the syringe, washed, and repeated several times. Then 5 ml of the test solution is drawn, the air is removed from the syringe, and the needle tip is wiped dry. Finally, the sample solution is slowly injected into the inlet. When the displayed number stops changing, the data is acquired, and the mass-average molecular weight is read.

[0069] The preparation method disclosed in this application allows a slurry containing polyvinylidene fluoride adhesive with a mass-average molecular weight of 8 million to still have appropriate viscosity, and its electrode adhesive strength, shear strength, and cohesive force all meet the product requirements, thus meeting the demand for next-generation high-molecular-weight adhesives.

[0070] In some embodiments, the adhesive comprises at least two polyvinylidene fluorides having a weight-average molecular weight difference of 7 million or less. In some embodiments, the weight-average molecular weight difference of the two or more polyvinylidene fluorides is selectively one of 100,000, 500,000, 1,000,000, 1,000,000, 2,000,000, 3,000,000, 4,000,000, 5,000,000, 6,000,000, and 7,000,000.

[0071] The positive electrode slurry prepared by the preparation method disclosed in this application can effectively exhibit the properties of polyvinylidene fluoride adhesives of different molecular weights, and due to the interbonding and steric hindrance between large and small segments, the slurry has an appropriate viscosity, and the positive electrode plate produced from this slurry has high adhesive strength, shear strength, and cohesive strength.

[0072] In this specification, adhesive strength is used primarily to characterize the adhesive strength between the film layer produced by the positive electrode slurry on the positive electrode plate and the current collector, and can be tested by any known method.

[0073] In this specification, shear strength is used primarily to characterize the shear resistance strength of the film layer produced in the positive electrode slurry on the positive electrode plate, and can be tested by any known method.

[0074] In this specification, cohesive force is primarily used to characterize the adhesive force within the film layer produced by the positive electrode slurry on the positive electrode plate, and can indicate the adhesive strength between the positive electrode active material and the adhesive, and can be tested by any known method.

[0075] In some embodiments, the mass content of the adhesive used in the first stirring is 30% to 50% of the total mass of the adhesives used in the first stirring and the adhesives used in the second stirring, and the mass content of the adhesive used in the second stirring is 50% to 70%.

[0076] In some embodiments, the mass content of the adhesive used in the first stirring may be selected from 30%, 35%, 40%, 45%, or 50% of the total mass of the adhesives used in the first stirring and the adhesives used in the second stirring, and the mass content of the adhesive used in the second stirring may be selected from 50%, 55%, 60%, 65%, or 70%.

[0077] If the mass content of the adhesive used in the first stirring is too low, or the mass content of the adhesive used in the second stirring is too high, and the mass of adhesive coating the positive electrode active material surface during the first stirring is too low, and the viscosity of the adhesive solution prepared during the second stirring is too high, effective coating of the adhesive on the positive electrode active material surface cannot be achieved. As a result, the positive electrode active material cannot be effectively dispersed in the adhesive solution, the viscosity of the slurry becomes too high, making it difficult for the adhesive to disperse in the positive electrode active material and exhibit adhesive performance, and the adhesive strength, shear strength, and cohesive force of the electrode plate are all reduced.

[0078] If the mass content of the adhesive used in the first stirring is too high, or the mass content of the adhesive used in the second stirring is too low, and the mass of adhesive coating the positive electrode active material surface during the first stirring is too high, it can easily lead to entanglement between the adhesives. This is detrimental to mechanical crimping through mutual bonding between the positive electrode active material and the adhesive surface, and prevents improvements in the adhesive strength, shear strength, and cohesive force of the electrode plate.

[0079] By controlling the mass content of the adhesive used in the first stirring to 30% to 50% and the mass content of the adhesive used in the second stirring to 50% to 70% of the total mass of the adhesives used in the first and second stirrings, it is possible to ensure that the viscosity of the slurry is within an appropriate range, and also to ensure that the electrode plates have high adhesive strength, shear strength, and cohesive force, thereby broadening the electrode plate manufacturing process window and improving the adhesive performance of the electrode plates.

[0080] In this specification, the term "process window" refers to the process period in which product quality can be ensured, and includes, but is not limited to, temperature periods, pressure periods, and storage time lengths. To make it clear, the wider the process window, the lower the demand for process precision.

[0081] In some embodiments, the orbital speed of the first stirring is 10 revolutions / min to 20 revolutions / min. In some embodiments, the orbital speed of the first stirring is selectively one of 10 revolutions / min, 12 revolutions / min, 15 revolutions / min, 18 revolutions / min, or 20 revolutions / min.

[0082] In some embodiments, the stirring time for the first stirring is 10 to 20 minutes. In some embodiments, the stirring time for the first stirring is selectively one of 10 minutes, 12 minutes, 15 minutes, 18 minutes, or 20 minutes.

[0083] In this specification, the term "orbital velocity" refers to the speed at which the agitator rotates around the kettle containing the material.

[0084] In some embodiments, the agitator is a planetary mixer. The operating principle of a planetary mixer is that, after the mixer is started, the planetary carrier rotates, causing the agitation shaft in the box to rotate rapidly while simultaneously revolving around the axis of the material cylinder, thereby subjecting the material to strong shearing and kneading action. As can be understood, the preparation method according to this application is applicable to any type of planetary mixer.

[0085] If the orbital speed of the first stirring is too low or the stirring time is too short, the positive electrode active material and adhesive cannot be effectively mixed, the viscosity of the slurry is too high, and the adhesive performance of the electrode plates is poor. On the other hand, if the orbital speed of the first stirring is too high or the stirring time is too long, the positive electrode active material and adhesive are easily crushed, the adhesive performance of the adhesive is reduced, and the adhesive strength, shear strength, and cohesive force of the electrode plates are reduced.

[0086] In summary, by controlling the orbital speed of the first stirring to 10 to 20 revolutions per minute or the stirring time of the first stirring to 10 to 20 minutes, it is possible to ensure that the viscosity of the slurry is within an appropriate range, and also to ensure that the electrode plates have high adhesive strength, shear strength, and cohesive force, thereby broadening the electrode plate manufacturing process window and improving the adhesive performance of the electrode plates.

[0087] In some embodiments, the rotational speed of the first stirring is 0.

[0088] In this specification, the term "rotational speed" means the speed at which the agitator rotates around its own axis.

[0089] By controlling the rotation speed of the first stirring to zero, the shear force of the first stirring is reduced, the possibility of excessive pulverization of the positive electrode active material and adhesive is reduced, ensuring that the positive electrode active material and adhesive have a certain particle size and specific surface area, improving the dispersion effect of the positive electrode active material and adhesive, reducing the viscosity of the slurry, and contributing to improving the adhesive strength, shear strength, and cohesive force of the positive electrode plate produced from this slurry.

[0090] In some practical embodiments, the orbital speed of the second stirring is 20 revolutions / min to 30 revolutions / min. In some embodiments, the orbital speed of the second stirring is selectively one of 10 revolutions / min, 15 revolutions / min, 20 revolutions / min, 25 revolutions / min, or 30 revolutions / min.

[0091] If the orbital speed of the second stirring is too low, the adhesive cannot be effectively dispersed in the solvent, the viscosity of the slurry becomes too high, the adhesive performance of the positive electrode plates is poor, and the product cannot meet demand. On the other hand, if the orbital speed of the second stirring is too high, the adhesive is at risk of being crushed, leading to a reduction in molecular chains and a decrease in adhesive performance.

[0092] By controlling the orbital speed of the second stirring to 20 to 30 revolutions per minute, it is possible to ensure that the viscosity of the slurry is within an appropriate range, and also to ensure that the electrode plates have high adhesive strength, shear strength, and cohesive force, thereby broadening the electrode plate manufacturing process window and improving the adhesive performance of the electrode plates.

[0093] In some embodiments, the rotation speed of the second stirring is 1100 rpm to 1300 rpm. In some embodiments, the rotation speed of the second stirring is selectively one of 1100 rpm, 1150 rpm, 1200 rpm, 1250 rpm, or 1300 rpm.

[0094] If the rotation speed of the second stirring is too low, the adhesive cannot be effectively dispersed in the solvent, the viscosity of the slurry will be too high, the adhesive performance of the positive electrode plates will be poor, and the product will not meet demand. On the other hand, if the rotation speed of the second stirring is too high, the viscosity of the slurry and the adhesive strength, shear strength, and cohesive force of the electrode plates will not be significantly improved. In such cases, an excessively fast rotation speed will increase the load on the equipment, affect the lifespan of the equipment, and increase production costs.

[0095] By controlling the rotation speed of the second stirring mechanism to 1100 rpm to 1300 rpm, it is possible to ensure that the viscosity of the slurry is within an appropriate range, and that the electrode plates have high adhesive strength, shear strength, and cohesive force. Furthermore, it is possible to avoid excessive load on the equipment due to an excessively high rotation speed of the second stirring mechanism, which would affect the service life of the equipment, thereby reducing cost losses.

[0096] In some embodiments, the stirring time for the second stirring is 60 to 80 minutes. In some embodiments, the stirring time for the second stirring is selectively one of 60 minutes, 65 minutes, 70 minutes, 75 minutes, or 80 minutes.

[0097] If the stirring time in the second stirring stage is too short, the adhesive cannot be effectively dispersed in the solvent, the slurry viscosity will be too high, the adhesive performance of the positive electrode plates will be poor, and the product will not meet demand. On the other hand, if the stirring time in the second stirring stage is too long, the slurry viscosity, and the adhesive strength, shear strength, and cohesive force of the electrode plates will not be significantly improved, and the excessively long stirring time will actually lead to energy waste and reduce production efficiency.

[0098] By controlling the stirring time of the second stirring to 60 to 80 minutes, it is possible to ensure that the viscosity of the slurry is within an appropriate range, and that the electrode plates have high adhesive strength, shear strength, and cohesive force. This also avoids the problem of excessively long stirring times in the second stirring stage, which can lead to reduced production efficiency and thus save production costs.

[0099] In some embodiments, the orbital speed of the third stirring is 20 revolutions / min to 30 revolutions / min. In some embodiments, the orbital speed of the third stirring is selectively one of 20 revolutions / min, 22 revolutions / min, 25 revolutions / min, 28 revolutions / min, or 30 revolutions / min.

[0100] If the rotational speed of the third stirring is too low, the dry mixture and adhesive liquid cannot be mixed uniformly, meaning that the positive electrode active material and adhesive cannot be effectively dispersed in the solvent, the viscosity of the slurry will be too high, the adhesive performance of the positive electrode plates will be poor, and the product will not meet demand. On the other hand, if the rotational speed of the third stirring is too high, the viscosity of the slurry and the adhesive strength, shear strength, and cohesive force of the electrode plates cannot be clearly improved, and the rotational speed that is too high will actually increase the load on the equipment, affect the lifespan of the equipment, and increase production costs.

[0101] By controlling the orbital speed of the third stirring element to 20 to 30 revolutions per minute, it is possible to ensure that the viscosity of the slurry is within an appropriate range, and that the electrode plates have high adhesive strength, shear strength, and cohesive force. Furthermore, it is possible to avoid excessive load on the equipment due to an excessively high orbital speed of the third stirring element, which would affect the service life of the equipment, thereby reducing cost losses.

[0102] In some embodiments, the rotation speed of the third stirrer is 500 rpm to 800 rpm. In some embodiments, the rotation speed of the third stirrer is selectively one of 500 rpm, 600 rpm, 700 rpm, 750 rpm, or 800 rpm.

[0103] If the rotation speed of the third stirring is too low, the dry mixture and adhesive liquid cannot be mixed uniformly, meaning that the positive electrode active material and adhesive cannot be effectively dispersed in the solvent, the viscosity of the slurry will be too high, the adhesive performance of the positive electrode plates will be poor, and the product will not meet demand. On the other hand, if the rotation speed of the third stirring is too high, the viscosity of the slurry and the adhesive strength, shear strength, and cohesive force of the electrode plates cannot be clearly improved. In such cases, an excessively high rotation speed will actually increase the load on the equipment, affect the lifespan of the equipment, and increase production costs.

[0104] By controlling the rotation speed of the third stirrer to 500 rpm to 800 rpm, it is possible to ensure that the viscosity of the slurry is within an appropriate range, and that the electrode plates have high adhesive strength, shear strength, and cohesive force. Furthermore, it is possible to avoid excessive load on the equipment due to an excessively high rotation speed of the third stirrer, which would affect the service life of the equipment and reduce cost losses.

[0105] In some embodiments, the stirring time for the third stirring is 40 to 60 minutes. In some embodiments, the stirring time for the third stirring is selectively one of 40 minutes, 45 minutes, 50 minutes, 55 minutes, or 60 minutes.

[0106] If the stirring time in the third stirring stage is too short, the dry mixture and adhesive liquid cannot be mixed uniformly, meaning that the positive electrode active material and adhesive cannot be effectively dispersed in the solvent. As a result, the viscosity of the slurry becomes too high, the adhesive performance of the positive electrode plates is poor, and the product cannot meet demand. On the other hand, if the stirring time in the third stirring stage is too long, and the viscosity of the slurry, as well as the adhesive strength, shear strength, and cohesive force of the electrode plates, cannot be significantly improved, then the excessively long stirring time will actually lead to energy waste and reduce production efficiency.

[0107] By controlling the stirring time of the third stirring to 40 to 60 minutes, it is possible to ensure that the viscosity of the slurry is within an appropriate range, and that the electrode plates have high adhesive strength, shear strength, and cohesive force. Furthermore, it is possible to avoid the reduction in production efficiency that can result from excessively long stirring times in the third stirring, thereby saving production costs.

[0108] In some embodiments, the orbital speed of the fourth stirring is 20 revolutions / min to 30 revolutions / min. In some embodiments, the orbital speed of the fourth stirring is selectively one of 20 revolutions / min, 23 revolutions / min, 25 revolutions / min, 27 revolutions / min, or 30 revolutions / min.

[0109] If the rotational speed of the fourth stirring is too low, the positive electrode active material, adhesive, and conductive agent cannot be effectively dispersed in the solvent, resulting in excessive slurry viscosity, poor adhesion of the positive electrode plates, and inability to meet product demand. On the other hand, if the rotational speed of the fourth stirring is too high, and the viscosity of the slurry, as well as the adhesion, shear strength, and cohesive force of the electrode plates, cannot be significantly improved, then an excessively fast rotational speed will actually increase the load on the equipment, affect its lifespan, and increase production costs.

[0110] By controlling the orbital speed of the fourth stirrer to 20 to 30 revolutions per minute, it is possible to ensure that the viscosity of the slurry is within an appropriate range, and that the electrode plates have high adhesive strength, shear strength, and cohesive force. Furthermore, it is possible to avoid excessive load on the equipment due to an excessively high orbital speed of the fourth stirrer, which would affect the service life of the equipment and reduce cost losses.

[0111] In some embodiments, the rotation speed of the fourth stirrer is 1100 rpm to 1400 rpm. In some embodiments, the rotation speed of the fourth stirrer is selectively one of 1100 rpm, 1150 rpm, 1200 rpm, 1250 rpm, 1300 rpm, or 1400 rpm.

[0112] If the rotation speed of the fourth stirring is too low, the positive electrode active material, adhesive, and conductive agent cannot be effectively dispersed in the solvent, the slurry viscosity will be too high, the adhesion performance of the positive electrode plates will be poor, and the product will not meet demand. On the other hand, if the rotation speed of the fourth stirring is too high, the slurry viscosity, and the adhesion, shear strength, and cohesive force of the electrode plates will not be significantly improved. In such cases, an excessively fast rotation speed will actually increase the load on the equipment, affect the lifespan of the equipment, and increase production costs.

[0113] By controlling the rotation speed of the fourth stirrer to 1100 rpm to 1400 rpm, it is possible to ensure that the viscosity of the slurry is within an appropriate range, and that the electrode plates have high adhesive strength, shear strength, and cohesive force. Furthermore, it is possible to avoid excessive load on the equipment due to an excessively high rotation speed of the fourth stirrer, which would affect the service life of the equipment and reduce cost losses.

[0114] In some embodiments, the stirring time for the fourth stirring is 100 to 120 minutes. In some embodiments, the stirring time for the fourth stirring is one of 100 minutes, 105 minutes, 110 minutes, 115 minutes, or 120 minutes.

[0115] If the stirring time in the fourth stirring stage is too short, the positive electrode active material, adhesive, and conductive agent cannot be effectively dispersed in the solvent, resulting in excessive slurry viscosity, poor adhesion of the positive electrode plates, and inability to meet product demand. On the other hand, if the stirring time in the fourth stirring stage is too long, and the viscosity of the slurry, as well as the adhesion, shear strength, and cohesive force of the electrode plates, cannot be significantly improved, then excessively long stirring times will actually lead to energy waste and reduce production efficiency.

[0116] By controlling the stirring time of the fourth stirring stage to 100 to 120 minutes, it is possible to ensure that the viscosity of the slurry is within an appropriate range, and that the electrode plates have high adhesive strength, shear strength, and cohesive force. Furthermore, it is possible to avoid the situation where the stirring time of the fourth stirring stage is too long, which leads to a reduction in production efficiency, and thus save on production costs.

[0117] In some embodiments, when the solid content of the positive electrode slurry is 68%, the viscosity of the positive electrode slurry is 8000 mPa·s to 41000 mPa·s. In some embodiments, the viscosity of the positive electrode slurry is selectively 8000 mPa·s, 9000 mPa·s, 10000 mPa·s, 11000 mPa·s, 12000 mPa·s, 13000 mPa·s, 14000 mPa·s, 15000 mPa·s, 16000 mPa·s, 17000 mPa·s, 18000 mPa·s, 19000 mPa·s, 20000 mPa·s. It is one of the following: mPa·s, 22000mPa·s, 24000mPa·s, 25000mPa·s, 26000mPa·s, 28000mPa·s, 30000mPa·s, 32000mPa·s, 34000mPa·s, 35000mPa·s, 36000mPa·s, 38000mPa·s, 40000mPa·s, or 41000mPa·s.

[0118] In this application, the viscosity of the positive electrode slurry can be tested by methods known in the art, such as a rotating viscometer. For example, a suitable rotor is selected, the viscometer rotor is fixed, and the positive electrode slurry is placed under the viscometer rotor so that the slurry just reaches the scale line of the rotor. The instrument model number is Shanghai Fangrui NDJ-5S, rotor number 63 is used to measure the viscosity of slurries between 2000 and 10000 mPa·s, and rotor number 64 is used to measure the viscosity of slurries between 10000 and 50000 mPa·s. The rotation speed is 12 revolutions / minute, the test temperature is 25°C, and the test time is 5 minutes. The data is read when the displayed number stops changing.

[0119] The viscosity of the positive electrode slurry with a solid content of 68% is 8000 mPa·s to 41000 mPa·s. This positive electrode slurry has good coating and processability, broadening the coating process window.

[0120] In some embodiments, the positive electrode active material used for the first stirring and the positive electrode active material used for the fourth stirring are the same, and the mass content of the positive electrode active material used for the first stirring is 50% to 70% of the total mass of the positive electrode active materials used for the first stirring and the positive electrode active material used for the fourth stirring is 30% to 50%.

[0121] In some embodiments, the mass content of the positive electrode active material used in the first stirring may be selected from 50%, 53%, 55%, 58%, 60%, 62%, 67%, or 70% of the total mass of the positive electrode active material used in the first stirring and the positive electrode active material used in the fourth stirring, and the mass content of the positive electrode active material used in the fourth stirring may be selected from 30%, 33%, 38%, 40%, 42%, 45%, 47%, or 50%.

[0122] If the mass content of the positive electrode active material used in the first stirring is too small, i.e., if the mass content of the positive electrode active material used in the fourth stirring is too large, it is disadvantageous to control the dispersion of the positive electrode active material in the slurry during the fourth stirring, resulting in a slurry viscosity that is too high and poor adhesion performance of the positive electrode plates. If the mass content of the positive electrode active material used in the first stirring is too large, i.e., if the mass content of the positive electrode active material used in the fourth stirring is too small, it is disadvantageous to control the mechanical crimping between the positive electrode active material and the adhesive during the first stirring, resulting in poor dispersibility of the dry mixture prepared in the first stirring into the subsequent slurry, a slurry viscosity that is too high and poor adhesion performance of the positive electrode plates.

[0123] By controlling the mass content of the positive electrode active material used in the first stirring to 50% to 70% of the total mass of the positive electrode active material used in the first stirring and the positive electrode active material used in the fourth stirring to 30% to 50%, the viscosity of the slurry can be reduced, the adhesion, shear strength, and cohesive force of the electrode plates can be improved, the process window for slurry coating can be widened, and the performance of the electrode plates can be improved.

[0124] In some embodiments, the solvent used for the second stirring and the solvent used for the fourth stirring are the same, and the mass content of the solvent used for the second stirring is 35% to 40% of the total mass of the conductive agent, the positive electrode active material used for the first stirring, the positive electrode active material used for the fourth stirring, the adhesive used for the first stirring, and the adhesive used for the second stirring, while the mass content of the solvent used for the fourth stirring is 5% to 10%.

[0125] In some embodiments, the mass content of the solvent used in the second stirring may be selected from 35%, 36%, 37%, 38%, 39%, or 40% relative to the total mass of the conductive agent, the positive electrode active material used in the first stirring, the positive electrode active material used in the fourth stirring, the adhesive used in the first stirring, and the adhesive used in the second stirring, and the mass content of the solvent used in the fourth stirring may be selected from 5%, 6%, 7%, 8%, 9%, or 10%.

[0126] In some embodiments, the mass ratio of the total mass of the positive electrode active material, the total mass of the adhesive, and the conductive agent in the positive electrode slurry is (86-98):(1-8):(1-6). In some embodiments, the mass ratio of the total mass of the positive electrode active material, the total mass of the adhesive, and the conductive agent is selectively one of 96:2:2, 96:3:1, 97:1:2, or 98:1:1.

[0127] The positive electrode slurry within the above range has good processing performance and provides excellent electrochemical properties to the positive electrode plate after molding.

[0128] In some embodiments, the positive electrode active material is one or more of lithium iron phosphate, lithium cobaltate, lithium manganate, and lithium nickel cobalt manganese oxide.

[0129] The above-mentioned positive electrode active material provides the battery with a high energy density, which is advantageous for improving the battery's cycle performance.

[0130] In some embodiments, the conductive agent is one or more of conductive carbon black, graphite, and carbon nanotubes.

[0131] The above conductive agent is advantageous for improving the conductivity of the electrode plate.

[0132] [Positive electrode plate] This application provides a positive electrode plate comprising a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, the positive electrode film layer being manufactured from a positive electrode slurry prepared by a preparation method according to any embodiment of this application.

[0133] For example, a positive electrode current collector has two surfaces that are opposite to each other in the thickness direction of itself, and the positive electrode film layer is installed on one or both of the two opposite surfaces of the positive electrode current collector.

[0134] In some embodiments, the positive electrode current collector may use a metal foil sheet or a composite current collector. For example, aluminum foil may be used as the metal foil sheet. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymer material substrate (such as substrates of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0135] In some embodiments, the positive electrode active material may use a positive electrode active material for a battery known in the art. As an example, the positive electrode active material may include at least one of lithium-containing phosphates having 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 battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Here, examples of lithium transition metal oxides are lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (which may be abbreviated as NCM 333 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (which may be abbreviated as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (which may be abbreviated as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2O2(NCM 622 (It may also be abbreviated as LiNi) 0.8 Co 0.1 Mn 0.1 O2(NCM 811 (May be abbreviated as LiNi) Lithium nickel cobalt aluminum oxide (e.g., LiNi 0.85 Co 0.15 Al 0.05 The olivine structure lithium-containing phosphate may include, but is not limited to, at least one of O2 and its modified compounds. Examples of lithium-containing phosphates with an olivine structure may include, but is not limited to, at least one of lithium iron phosphate (e.g., LiFePO4 (which may be abbreviated as LFP)), composite materials of lithium iron phosphate and carbon, lithium manganese phosphate (e.g., LiMnPO4), composite materials of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and composite materials of lithium iron manganese phosphate and carbon.

[0136] In some embodiments, the adhesive force per unit length between the positive electrode film layer and the positive electrode current collector is 20 N / m to 30 N / m. In some embodiments, the adhesive force per unit length between the positive electrode film layer and the positive electrode current collector is selectively one of 20 N / m, 21 N / m, 22 N / m, 23 N / m, 24 N / m, 25 N / m, 26 N / m, 26.5 N / m, 27 N / m, 27.5 N / m, 28 N / m, 29 N / m, and 30 N / m.

[0137] In this application, the adhesive strength per unit length between the positive electrode film layer and the positive electrode current collector can be tested by methods known in the art, for example, referring to the "180° Peel Strength Test Method for Adhesives" in Chinese Standard GB-T2790-1995, a sample with a width of 30 mm and a length of 100 to 160 mm is cut with a blade, and a special double-sided tape with a width of 20 mm and a length of 90 to 150 mm is attached to the steel plate. The positive electrode film layer surface of the previously cut electrode plate sample is attached to the double-sided tape, and then rolled three times in the same direction with a 2 kg rolling roller. Paper tape with a width equal to the electrode plate and a length of 250 mm is fixed to the electrode plate current collector, and then secured with crepe tape. The power to the Sansi tensile machine (sensitivity of 1 N) is turned on, the lamp lights up, the stopper block is adjusted to the appropriate position, and the end of the steel plate that does not have the electrode plate attached is fixed with a lower jig. The paper tape is folded upwards and secured with an upper jig. The position of the upper jig is adjusted using the "up" and "down" buttons on a manual controller with a tensioner. Then the test is performed and the values ​​are read, with a tensioning speed of 50 mm / min. The adhesive strength between the positive electrode film layer and the current collector is characterized by the adhesive strength of the electrode per unit length, which is calculated by dividing the force at which the forces on the electrode plates are balanced by the width of the tape.

[0138] In some embodiments, the shear strength of the positive electrode film layer is 0.64 mPa to 0.91 mPa. In some embodiments, the shear strength of the positive electrode film layer is selectively one of 0.64 mPa, 0.68 mPa, 0.72 mPa, 0.74 mPa, 0.78 mPa, 0.80 mPa, 0.81 mPa, 0.83 mPa, 0.86 mPa, 0.88 mPa, 0.90 mPa, or 0.91 mPa.

[0139] In this application, the shear strength of the positive electrode film layer can be tested by a method known in the art, for example, by a tensile machine, by cutting a piece of double-sided tape about 60 mm long, attaching the double-sided tape along the longitudinal direction of the electrode plate, cutting the electrode plate along the edge of the double-sided tape with a blade, selecting a steel plate with a flat appearance, polishing the surface of the steel plate with sandpaper, wiping the surface of the steel plate with alcohol on a cotton gauze, drying, attaching double-sided tape to the steel plate, ensuring that the distance between the bottom edge of the tape and the bottom edge of the steel plate is >1 cm, and placing the steel plate in an oven at 60-80°C. After letting it stand for 5 minutes, remove the steel plate, lightly scrape off the top layer of release paper from the tape with a blade, attach the previously cut electrode plate to the double-sided tape on the steel plate so that the test surface faces downwards, roll it back and forth three times with a 2kg rolling roller, turn on the power to the Sanshi tensile machine, turn on the lamp until it lights up, adjust the stopper block to the appropriate position, fix the end of the steel plate that does not have the electrode plate attached with the lower jig, fix the end of the electrode plate that does not have the steel plate attached with the upper jig, and then perform the test and read the values, which indicate a tensile speed of 10 mm / min.

[0140] In some embodiments, the cohesive force of the positive electrode film layer is 70 N / m to 90 N / m. In some embodiments, the cohesive force of the positive electrode film layer is selectively one of 72 N / m, 74 N / m, 76 N / m, 78 N / m, 80 N / m, 82 N / m, 84 N / m, 86 N / m, 88 N / m, or 90 N / m.

[0141] In this application, the cohesive force of the positive electrode film layer can be tested by methods known in the art, such as a tensile machine, by cutting an electrode plate sample with a width of 30 mm and a length of 90 to 150 mm with a blade, cutting a special double-sided tape with a width of 20 mm and a length of 90 to 150 mm, attaching the cut special double-sided tape to a steel plate, attaching the cut electrode plate sample to the cut double-sided tape with the test surface facing upwards, and applying a low-viscosity glycerin with a width of 20 mm and a length 80 to 200 mm greater than the length of the sample. The green tape is adhered flat to the test surface, rolled three times in the same direction with a rolling roller, the power to the Sanshi tensile machine is turned on, the lamp lights up, the stopper block is adjusted to the appropriate position, the end of the steel plate without the electrode plate attached is secured with the lower jig, the green tape with the hard paper attached is folded upwards and secured with the upper jig, the position of the upper jig is adjusted using the "up" and "down" buttons on the manual controller attached to the tensile machine, and the test is performed and the values ​​are read, with the tensile speed being 10 mm / min.

[0142] In some embodiments, a positive electrode plate can be manufactured in the following manner. A positive electrode slurry is prepared using the positive electrode slurry preparation method in any embodiment of this application, using the above-mentioned components for manufacturing a positive electrode plate, such as a positive electrode active material, a conductive agent, an adhesive, and a solvent (e.g., N-methylpyrrolidone). The prepared positive electrode slurry is applied to a positive electrode current collector, and after processes such as drying and cold pressing, a positive electrode plate is obtained.

[0143] [Negative electrode plate] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer placed on at least one surface of the negative electrode current collector, the negative electrode film layer containing a negative electrode active material.

[0144] For example, a negative electrode current collector has two surfaces that are opposite to each other in the thickness direction of itself, and the negative electrode film layer is placed on one or both of the two opposite surfaces of the negative electrode current collector.

[0145] In some embodiments, the negative electrode current collector may be a metal foil sheet or a composite current collector. For example, copper foil may be used as the metal foil sheet. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (such as copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys) on a polymer material substrate (for example, a substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0146] In some embodiments, the negative electrode active material may be a negative electrode active material for batteries known in the art. For example, the negative electrode active material may include at least one material from among artificial graphite, natural graphite, soft carbon, hard carbon, silicone-based materials, tin-based materials, and lithium titanate. The silicone-based material may be selected from at least one of elemental silicone, silicone oxide, silicone-carbon composite, silicone-nitrogen composite, and silicone alloy. The tin-based material may be selected from at least one of elemental tin, tin oxide, and tin alloy. However, this application is not limited to these materials, and other conventional materials that can be used as battery negative electrode active materials may be used. These negative electrode active materials may be used individually or in combination of two or more.

[0147] In some embodiments, the negative electrode film layer further selectively includes an adhesive. The adhesive may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0148] In some embodiments, the negative electrode film layer further selectively includes 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.

[0149] In some embodiments, the negative electrode film layer further selectively includes other auxiliary agents, such as thickeners (e.g., sodium carboxymethylcellulose (CMC-Na)).

[0150] In some embodiments, the negative electrode plate can be manufactured by the following method. Components for manufacturing the negative electrode plate, such as a negative electrode active material, a conductive agent, an adhesive, and any other component, are dispersed in a solvent (e.g., deionized water) to form a negative electrode slurry. The negative electrode slurry is then applied onto a negative electrode current collector, and after processes such as drying and cold pressing, the negative electrode plate is obtained.

[0151] [Electrolytes] The electrolyte plays a role in conducting ions between the positive and negative electrodes. This application does not specifically limit the type of electrolyte, which can be selected according to the requirements. For example, the electrolyte may be a liquid, a gel, or an all-solid.

[0152] In some embodiments, an electrolyte solution is used as the electrolyte. The electrolyte solution comprises an electrolyte salt and a solvent.

[0153] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, lithium difluorobis(oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate.

[0154] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, ethyl methyl sulfone, and diethyl sulfone.

[0155] In some embodiments, the electrolyte further selectively includes additives. For example, the additives may include negative electrode film forming additives, positive electrode film forming additives, and may also include additives that can improve some of the battery's performance characteristics, such as additives that improve the battery's overcharge performance, or additives that improve the battery's high-temperature or low-temperature performance.

[0156] [Separator] In some embodiments, the secondary battery further includes a separator. This application is not particularly limited to the type of separator, and any known porous separator having good chemical and mechanical stability may be selected.

[0157] In some embodiments, the material of the separator may be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film, and is not particularly limited. When the separator is a multilayer composite film, the materials of each layer may be the same or different, and is not particularly limited.

[0158] In some embodiments, the positive electrode plate, negative electrode plate, and separator can be manufactured as an electrode assembly by a winding process or a lamination process.

[0159] In some embodiments, the secondary battery may include an outer casing. This casing may be used to package the electrode assembly and electrolyte.

[0160] In some embodiments, the casing of the secondary battery may be a rigid case, such as a rigid plastic case, an aluminum case, or a steel case. The casing of the secondary battery may also be a pouch, such as a bag-shaped pouch. The material of the pouch may be plastic, and examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0161] This application does not particularly limit the shape of the secondary battery, which may be cylindrical, rectangular, or any other shape. For example, Figure 1 shows a rectangular secondary battery 5 as an example.

[0162] In some embodiments, referring to Figure 2, the casing may include a case 51 and a cover plate 53. Here, the case 51 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates enclosing and forming a housing cavity. The case 51 has an opening that communicates with the housing cavity, and the cover plate 53 can cover the opening and seal the housing cavity. The positive electrode plate, negative electrode plate and separator can form an electrode assembly 52 by a winding process or a lamination process. The electrode assembly 52 is packaged within the housing cavity. The electrolyte is impregnated into the electrode assembly 52. ​​The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and those skilled in the art can specifically select them according to actual needs.

[0163] In some embodiments, the secondary batteries may be assembled into a battery module, and the number of secondary batteries included in the battery module may be one or more, and the specific number can be selected by those skilled in the art depending on the application and capacity of the battery module.

[0164] Figure 3 shows an example of a battery module 4. Referring to Figure 3, in the battery module 4, multiple secondary batteries 5 may be installed in a sequential arrangement along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, these multiple secondary batteries 5 may be fixed in place with fasteners.

[0165] Selectively, the battery module 4 may further include a housing having a housing space, in which a plurality of secondary batteries 5 are housed.

[0166] In some embodiments, the battery modules may be further assembled into a battery pack, the number of battery modules included in the battery pack may be one or more, and the specific number can be selected by those skilled in the art depending on the application and capacity of the battery pack.

[0167] Figures 4 and 5 show an example of a battery pack 1. Referring to Figures 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, the upper housing 2 being covered by the lower housing 3 and forming a sealed space for housing the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0168] The present application further provides a power consumption device comprising at least one of a secondary battery, battery module, or battery pack as described herein. The secondary battery, battery module, or battery pack may be used as a power source for the power consumption device or as an energy storage unit for the power consumption device. The power consumption 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.

[0169] The aforementioned power consumption device can be selected from a secondary battery, battery module, or battery pack depending on the usage demand.

[0170] Figure 6 shows an example of a power consumption device. This power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the demand for high output and high energy density of the secondary battery in this power consumption device, a battery pack or battery module can be used.

[0171] Other examples of such devices may include mobile phones, tablet computers, and laptop computers. These devices generally require to be lightweight and can use rechargeable batteries as a power source.

[0172] Examples The following describes embodiments of this application. The embodiments described below are illustrative and are for interpretive purposes only and should not be considered limitations thereto. Where no specific technical or condition is specified in the embodiments, the techniques or conditions described in the literature in the art or in accordance with product specifications shall apply. Unless the manufacturer is specified for the reagents and equipment used, they are all common commercially available products.

[0173] 1. Preparation method Example 1 Preparation of positive electrode slurry Weighing of raw materials: 1200 kg of lithium iron phosphate (positive electrode active material), 25 kg of polyvinylidene fluoride (adhesive), and 25 kg of conductive carbon black (conductive agent) were weighed. Here, the mass-average molecular weight of polyvinylidene fluoride is 1.8 million. First stirring: 720 kg of lithium iron phosphate and 10 kg of polyvinylidene fluoride are mixed in a double planetary mixer, and the first stirring is performed for 15 minutes at an orbital speed of 15 revolutions / min and a rotational speed of 0 to obtain a dry mixture. Second stirring: 15 kg of polyvinylidene fluoride and 437.5 kg of N-methylpyrrolidone (NMP) solvent were mixed in a double planetary mixer, and a second stirring was performed for 70 minutes at an orbital speed of 25 revolutions / min and a rotational speed of 1200 revolutions / min to obtain the adhesive solution. Third stirring: The dry mixture prepared in the first stirring is added to the adhesive liquid prepared in the second stirring, and the third stirring is performed for 50 minutes at an orbital speed of 25 revolutions / min and a rotational speed of 600 revolutions / min to obtain a primary slurry. Fourth stirring: 480 kg of lithium iron phosphate, 25 kg of conductive carbon black, and 125 kg of N-methylpyrrolidone (NMP) solvent were added to the primary slurry prepared in the third stirring, and the fourth stirring was performed for 110 minutes at an orbital speed of 25 revolutions / min and a rotational speed of 1300 revolutions / min, to obtain a cathode slurry with a solid content of 68%.

[0174] Examples 2-7 Aside from adjusting the mass-average molecular weight of the polyvinylidene fluoride adhesive, this is essentially the same as Example 1. For specific parameters, please refer to Table 1.

[0175] Examples 8-10 Aside from adding various adhesives with different mass-average molecular weights, the process is basically the same as in Example 1. For specific parameters, please refer to Table 1. In Example 8, the mass ratio of polyvinylidene fluoride with a mass-average molecular weight of 1 million to polyvinylidene fluoride with a mass-average molecular weight of 8 million was 1:1. In Example 9, the mass ratio of polyvinylidene fluoride with a mass-average molecular weight of 1 million, polyvinylidene fluoride with a mass-average molecular weight of 4 million, and polyvinylidene fluoride with a mass-average molecular weight of 8 million was 1:1:1. In Example 10, the mass ratio of polyvinylidene fluoride with a mass-average molecular weight of 1.8 million to polyvinylidene fluoride with a mass-average molecular weight of 6 million was 1:1.

[0176] Examples 11-14 Aside from adjusting the mass content of the polyvinylidene fluoride adhesive during the first stirring, the procedure is basically the same as in Example 2. For specific parameters, please refer to Table 1.

[0177] Examples 15-60 Aside from adjusting the stirring parameters, the procedure is basically the same as in Example 2. For specific parameters, please refer to Table 1.

[0178] Examples 61-64 Aside from adjusting the mass content of lithium iron phosphate during the first stirring, the procedure is basically the same as in Example 2. For specific parameters, please refer to Table 1.

[0179] Comparative Example 1 Weighing of raw materials: 1200 kg of lithium iron phosphate (positive electrode active material), 25 kg of polyvinylidene fluoride (adhesive), and 25 kg of conductive carbon black (conductive agent) were weighed. Here, the mass-average molecular weight of polyvinylidene fluoride is 1.8 million. First stirring: 1200 kg of lithium iron phosphate and 25 kg of conductive carbon black are mixed and thoroughly stirred for 15 minutes at an orbital speed of 15 revolutions / min and a rotational speed of 0 to obtain a dry mixture. Second stirring: 25 kg of polyvinylidene fluoride is added to 437.5 kg of NMP solvent, and the mixture is thoroughly stirred for 70 minutes at an orbital speed of 25 revolutions / min and a rotational speed of 1200 revolutions / min to obtain the adhesive solution. Third stirring: The dry mixture is added to the adhesive liquid and stirred thoroughly for 50 minutes at an orbital speed of 25 revolutions / min and a rotational speed of 600 revolutions / min to obtain a primary slurry. Fourth stirring: 125 kg of NMP solvent was added to the primary slurry and stirred for 110 minutes at an orbital speed of 25 revolutions / min and a rotational speed of 1300 revolutions / min to obtain a cathode slurry with a solid content of 68%.

[0180] Comparative Examples 2-5 Aside from the mass-average molecular weights of polyvinylidene fluoride being 2 million, 3 million, 4 million, and 8 million respectively, the parameters are basically the same as in Comparative Example 1. Please refer to Table 1 for specific parameters.

[0181] 2. Test Method 1. Viscosity test of positive electrode slurry The viscosity of the primer slurry was measured using a rotating viscometer. An appropriate rotor was selected, the viscometer rotor was fixed in place, and the primer slurry was placed under the viscometer rotor so that the slurry just dipped up to the rotor's scale line. The instrument model number was Shanghai Fangrui NDJ-5S. Rotor number 63 was used to measure the viscosity of slurries between 2000 and 10000 mPa·s, and rotor number 64 was used to measure the viscosity of slurries between 10000 and 50000 mPa·s. The rotation speed was 12 revolutions / minute, the test temperature was 25°C, and the test time was 5 minutes. The data was read when the displayed number stopped changing.

[0182] 2. Adhesion strength test of the electrode plates Referring to the "180° Peel Strength Test Method for Adhesives" of Chinese Standard GB-T2790-1995, the adhesive strength test process for the examples and comparative examples of this application was as follows: A sample with a width of 30 mm and a length of 100-160 mm was cut with a blade, and a special double-sided tape with a width of 20 mm and a length of 90-150 mm was attached to the steel plate. The positive electrode film layer surface of the electrode plate sample that had been cut earlier was attached to the double-sided tape, and then rolled three times in the same direction with a 2 kg rolling roller. A paper tape with a width equal to the electrode plate and a length of 250 mm was fixed to the electrode plate current collector and secured with crepe tape. The power to the Sansi tensile machine (sensitivity of 1 N) was turned on, the lamp lit up, the stopper block was adjusted to the appropriate position, and the end of the steel plate that did not have the electrode plate attached was fixed with a lower jig. The paper tape was folded upwards and secured with an upper jig. The position of the upper jig was adjusted using the "up" and "down" buttons on a manual controller with a tensioner. A test was then conducted, and the values ​​were read. The tensioning speed was 50 mm / min. The adhesive strength between the positive electrode film layer and the current collector was characterized by dividing the force at which the electrode forces balance by the width of the tape as the adhesive force of the electrode per unit length.

[0183] 3. Shear strength test of electrode plates A piece of double-sided tape approximately 60 mm long was cut and attached along the longitudinal direction of the electrode plate. The electrode plate was then cut along the edge of the double-sided tape with a blade. A steel plate with a flat surface was selected, the surface of the steel plate was polished with sandpaper, the surface of the steel plate was wiped with alcohol on a cotton gauze, and allowed to dry. Double-sided tape was then attached to the steel plate, with the distance between the bottom edge of the tape and the bottom edge of the steel plate being >1 cm. The steel plate was placed in an oven at 60-80°C for 5 minutes, the steel plate was removed, the top layer of release paper on the tape was lightly scraped off with a blade, and the previously cut electrode plate was attached to the double-sided tape on the steel plate so that the test surface was facing downwards. The steel plate was rolled back and forth three times with a 2 kg rolling roller, the power to the Sanshi tensile machine was turned on, the lamp lit up, the stopper block was adjusted to the appropriate position, the end of the steel plate not to which the electrode plate was attached was fixed with a lower jig, the end of the electrode plate not to which the steel plate was attached was clamped with an upper jig, and the test was performed and the values ​​were read. The tensile speed was 10 mm / min.

[0184] 4. Cohesive force test of electrode plates A 30mm wide, 90-150mm long electrode plate sample was cut with a blade, a 20mm wide, 90-150mm long special double-sided tape was cut, the cut special double-sided tape was attached to the steel plate, the cut electrode plate sample was attached to the cut double-sided tape with the test surface facing upwards, a 20mm wide, 80-200mm longer low-viscosity green tape was flatly adhered to the test surface, it was rolled three times in the same direction with a rolling roller, the power to the Sanshi tensile machine was turned on, the lamp lit up, the stopper block was adjusted to the appropriate position, the end of the steel plate without the electrode plate attached was fixed with the lower jig, the green tape with the hard paper attached was folded upwards and fixed with the upper jig, the position of the upper jig was adjusted using the "up" and "down" buttons on the manual controller with the tensile machine, and the test was performed and the values ​​were read, and the tensile speed was 10mm / min.

[0185] III. Analysis of Test Results for Each Example and Comparative Example According to the method described above, positive electrode slurries for each example and comparative example were prepared, and each parameter was measured. The results are shown in Table 1 below.

[0186] Table 1 Preparation parameters and test results of the examples and comparative examples TIFF0007852084000001.tif206166 TIFF0007852084000002.tif239166 TIFF0007852084000003.tif239166 TIFF0007852084000004.tif178166

[0187] As can be seen from the results in Table 1, the positive electrode slurries in Examples 1 to 64 were all prepared by the slurry preparation method disclosed in this application, which includes a first, second, third, and fourth stirring. During the first stirring, lithium iron phosphate positive electrode active material and polyvinylidene fluoride adhesive were mixed and stirred to prepare a dry mixture. During the second stirring, polyvinylidene fluoride and N-methylpyrrolidone (NMP) solvent were mixed and stirred to prepare an adhesive solution. During the third stirring, the dry mixture prepared in the first stirring and the adhesive solution prepared in the second stirring were mixed and stirred to prepare a primary slurry. During the fourth stirring, lithium iron phosphate, conductive carbon black as a conductive agent, NMP solvent, and the primary slurry prepared in the third stirring were mixed and stirred to prepare the positive electrode slurry.

[0188] As can be seen from the comparison between Examples 1-10 and Comparative Examples 1-4, the preparation method disclosed in this application has broad versatility and can be applied to slurries of one or more polyvinylidene fluoride adhesives with a mass-average molecular weight of 1 million to 8 million. This preparation method is versatile for both low and high mass-average molecular weight polyvinylidene fluoride adhesives and contributes to reducing preparation costs and improving production efficiency.

[0189] As can be seen from Comparative Examples 3 to 5, the preparation process in the prior art makes it difficult to reduce the viscosity of the slurry when using a polyvinylidene fluoride adhesive with a mass-average molecular weight of 3 million, making it impossible to apply the slurry. With the preparation method of this application, a slurry containing a polyvinylidene fluoride adhesive with a mass-average molecular weight of 8 million still has an appropriate viscosity, and the adhesive strength, shear strength, and cohesive force of the electrode plate all meet product requirements, thus meeting the demand for next-generation high-molecular-weight adhesives.

[0190] As can be seen from Examples 8-10, when the slurry synthesized by this preparation method contains an adhesive with a weight-average molecular weight difference of 7 million or less, the slurry can still maintain low viscosity, and the electrode plates can maintain high adhesive strength, shear strength, and cohesive force.

[0191] As can be seen from the comparison between Examples 8-10 and Examples 5-6, when the slurry synthesized by this preparation method contains adhesives with a difference in mass-average molecular weight of 7 million or less, the slurry containing adhesives with different mass-average molecular weights can have its viscosity further reduced and its adhesive strength, shear strength, or cohesive strength further improved compared to a slurry containing only an adhesive with a single mass-average molecular weight.

[0192] As can be seen from Examples 2 and 11-14, by controlling the ratio of polyvinylidene fluoride adhesive added during the first stirring to 30%-50% of the total mass of polyvinylidene fluoride adhesive, this preparation method ensures that the slurry has an appropriate viscosity, improves the adhesive strength, shear strength and cohesive force of the electrode plates, broadens the electrode plate manufacturing process window, and improves the adhesive performance of the electrode plates.

[0193] As can be seen from Examples 2 and 15-18, by controlling the orbital speed of the first stirring to 10 revolutions / min to 20 revolutions / min, it is possible to ensure that the viscosity of the slurry is within an appropriate range, and also to ensure that the electrode plates have high adhesive strength, shear strength, and cohesive force, thereby broadening the electrode plate manufacturing process window and improving the adhesive performance of the electrode plates.

[0194] As can be seen from Examples 2 and 19-22, by controlling the stirring time of the first stirring to 10-20 minutes, it is possible to ensure that the viscosity of the slurry is within an appropriate range, and also to ensure that the electrode plates have high adhesive strength, shear strength, and cohesive force, thereby broadening the electrode plate manufacturing process window and improving the adhesive performance of the electrode plates.

[0195] As can be seen from Examples 2 and 23-26, by controlling the orbital speed of the second stirring to 20 revolutions / min to 30 revolutions / min, it is possible to ensure that the viscosity of the slurry is within an appropriate range, and also to ensure that the electrode plates have high adhesive strength, shear strength, and cohesive force, thereby broadening the electrode plate manufacturing process window and improving the adhesive performance of the electrode plates.

[0196] As can be seen from Examples 2 and 27-30, by controlling the rotation speed of the second stirring to 1100 rpm to 1300 rpm, it is possible to ensure that the viscosity of the slurry is within an appropriate range, and that the electrode plates have high adhesive strength, shear strength, and cohesive force. Furthermore, it is possible to avoid excessive load on the equipment due to an excessively high rotation speed of the second stirring, which would affect the service life of the equipment, and thus reduce cost losses.

[0197] As can be seen from Examples 2 and 31-34, by controlling the stirring time of the second stirring to 60-80 minutes, it is possible to ensure that the viscosity of the slurry is within an appropriate range, and that the electrode plates have high adhesive strength, shear strength, and cohesive force. Furthermore, it is possible to avoid the reduction in production efficiency that can result from excessively long stirring times in the second stirring, thereby saving production costs.

[0198] As can be seen from Examples 2 and 35-38, by controlling the orbital speed of the third stirrer to 20 revolutions / min to 30 revolutions / min, it is possible to ensure that the viscosity of the slurry is within an appropriate range, and that the electrode plates have high adhesive strength, shear strength, and cohesive force. Furthermore, it is possible to avoid excessive load on the equipment due to an excessively high orbital speed of the third stirrer, which would affect the service life of the equipment, and thus reduce cost losses.

[0199] As can be seen from Examples 2 and 39-43, by controlling the rotation speed of the third stirrer to 500 rpm to 800 rpm, it is possible to ensure that the viscosity of the slurry is within an appropriate range, and that the electrode plates have high adhesive strength, shear strength, and cohesive force. Furthermore, it is possible to avoid excessive load on the equipment due to an excessively high rotation speed of the third stirrer, which would affect the service life of the equipment, and thus reduce cost losses.

[0200] As can be seen from Examples 2 and 44-47, by controlling the stirring time of the third stirring to 40-60 minutes, it is possible to ensure that the viscosity of the slurry is within an appropriate range, and that the electrode plates have high adhesive strength, shear strength, and cohesive force. Furthermore, it is possible to avoid the reduction in production efficiency that can result from excessively long stirring times in the third stirring, thereby saving production costs.

[0201] As can be seen from Examples 2 and 48-51, by controlling the orbital speed of the fourth stirrer to 20 revolutions / min to 30 revolutions / min, it is possible to ensure that the viscosity of the slurry is within an appropriate range, and that the electrode plates have high adhesive strength, shear strength, and cohesive force. Furthermore, it is possible to avoid excessive load on the equipment due to an excessively high orbital speed of the fourth stirrer, which would affect the service life of the equipment, and thus reduce cost losses.

[0202] As can be seen from Examples 2 and 52-56, by controlling the rotation speed of the fourth stirrer to 1100 rpm to 1400 rpm, it is possible to ensure that the viscosity of the slurry is within an appropriate range, and that the electrode plates have high adhesive strength, shear strength, and cohesive force. Furthermore, it is possible to avoid excessive load on the equipment due to an excessively high rotation speed of the fourth stirrer, which would affect the service life of the equipment, and thus reduce cost losses.

[0203] As can be seen from Examples 2 and 57-60, by controlling the stirring time of the fourth stirring to 100-120 minutes, it is possible to ensure that the viscosity of the slurry is within an appropriate range, and that the electrode plates have high adhesive strength, shear strength, and cohesive force. Furthermore, it is possible to avoid the reduction in production efficiency that can occur due to excessively long stirring times in the fourth stirring, thereby saving production costs.

[0204] As can be seen from the examples, the positive electrode slurry disclosed in this application, having a solid content of 68%, has a viscosity of 8000 mPa·s to 41000 mPa·s, and this positive electrode slurry has good coating and processability.

[0205] As can be seen from Examples 2 and 61-64, by controlling the mass content of lithium iron phosphate used in the first stirring to 50%-70%, the viscosity of the slurry can be reduced, the adhesive strength, shear strength and cohesive force of the electrode plates can be improved, the process window for slurry coating can be broadened, and the performance of the electrode plates can be improved.

[0206] It should be noted that this application is not limited to the embodiments described above. The embodiments described above are merely examples, and any embodiment that has substantially the same configuration as the technical idea and produces the same effects within the scope of the technical proposal of this application is included within the scope of the technical proposal. Furthermore, other forms that are constructed by adding various modifications to the embodiments that a person skilled in the art could conceive of, and by combining some of the components of the embodiments, are also included within the scope of this application, without departing from the spirit of this application. Preferred embodiments of the present invention are as follows: [1] A method for preparing a positive electrode slurry, comprising first stirring, second stirring, third stirring and fourth stirring, During the first stirring, the positive electrode active material and the adhesive are mixed and stirred to prepare a dry mixture. During the second stirring, the adhesive and solvent are mixed and stirred to prepare the adhesive solution. During the third stirring, the dry mixture and the adhesive liquid are mixed and stirred to prepare a primary slurry. During the fourth stirring, the positive electrode active material, the conductive agent, the solvent, and the primary slurry are mixed and stirred to prepare the positive electrode slurry. A method for preparing a positive electrode slurry, characterized in that the adhesive used for the first stirring and the adhesive used for the second stirring are the same. [2] The preparation method according to [1], characterized in that the adhesive contains at least one polyvinylidene fluoride having a mass-average molecular weight of 1 million to 8 million. [3] The preparation method according to [1] or [2], characterized in that the adhesive contains at least two polyvinylidene fluorides having a difference in mass-average molecular weight of 7 million or less. [4] The preparation method according to any one of the above items [1] to [3], characterized in that, with respect to the total mass of the adhesive used in the first stirring and the adhesive used in the second stirring, the mass content of the adhesive used in the first stirring is 30% to 50%, and the mass content of the adhesive used in the second stirring is 50% to 70%. [5] The preparation method according to any one of the above items [1] to [4], characterized in that the orbital speed of the first stirring is 10 revolutions / min to 20 revolutions / min. [6] The preparation method according to any one of the above items [1] to [5], characterized in that the rotation speed of the first stirring is 0. [7] The preparation method according to any one of the above items [1] to [6], characterized in that the stirring time for the first stirring is 10 to 20 minutes. [8] The preparation method according to any one of the above items [1] to [7], characterized in that the orbital speed of the second stirring is 20 revolutions / min to 30 revolutions / min. [9] The preparation method according to any one of the above items [1] to [8], characterized in that the rotation speed of the second stirring is 1100 revolutions / min to 1300 revolutions / min.

[10] The preparation method according to any one of the above items [1] to [9], characterized in that the stirring time for the second stirring is 60 to 80 minutes.

[11] The preparation method according to any one of the above items [1] to

[10] , characterized in that the orbital speed of the third stirring is 20 revolutions / min to 30 revolutions / min.

[12] The preparation method according to any one of the above items [1] to

[11] , characterized in that the rotation speed of the third stirring is 500 revolutions per minute to 800 revolutions per minute.

[13] The preparation method according to any one of the above items [1] to

[12] , characterized in that the stirring time for the third stirring is 40 minutes to 60 minutes.

[14] The preparation method according to any one of the above items [1] to

[13] , characterized in that the orbital speed of the fourth stirring is 20 revolutions / min to 30 revolutions / min.

[15] The preparation method according to any one of the above items [1] to

[14] , characterized in that the rotation speed of the fourth stirring is 1100 revolutions / min to 1400 revolutions / min.

[16] The preparation method according to any one of the above items [1] to

[15] , characterized in that the stirring time for the fourth stirring is 100 minutes to 120 minutes.

[17] The preparation method according to any one of the above items [1] to

[16] , characterized in that when the solid content of the positive electrode slurry is 68%, the viscosity of the positive electrode slurry is 8000 mPa·s to 41000 mPa·s.

[18] The preparation method according to any one of the above [1] to

[17] , characterized in that the positive electrode active material used for the first stirring and the positive electrode active material used for the fourth stirring are the same, and the mass content of the positive electrode active material used for the first stirring is 50% to 70% of the total mass of the positive electrode active material used for the first stirring and the positive electrode active material used for the fourth stirring, and the mass content of the positive electrode active material used for the fourth stirring is 30% to 50%.

[19] The preparation method according to any one of the above [1] to

[18] , characterized in that the solvent used for the second stirring and the solvent used for the fourth stirring are the same, and the mass content of the solvent used for the second stirring is 35% to 40% and the mass content of the solvent used for the fourth stirring is 5% to 10% with respect to the total mass of the conductive agent, the positive electrode active material used for the first stirring, the positive electrode active material used for the fourth stirring, the adhesive used for the first stirring, and the adhesive used for the second stirring.

[20] The preparation method according to any one of the above [1] to

[19] , characterized in that the mass ratio of the total mass of the positive electrode active material, the total mass of the adhesive, and the conductive agent in the positive electrode slurry is (86-98):(1-8):(1-6).

[21] The preparation method according to any one of the above [1] to

[20] , characterized in that the positive electrode active material is one or more of lithium iron phosphate, lithium cobaltate, lithium manganate, and lithium nickel cobalt manganese oxide.

[22] The preparation method according to any one of the above items [1] to

[21] , characterized in that the conductive agent is one or more of conductive carbon black, graphite, and carbon nanotubes.

[23] A positive electrode plate comprising a positive electrode current collector and a positive electrode film layer installed on at least one surface of the positive electrode current collector, wherein the positive electrode film layer is manufactured from a positive electrode slurry prepared by the preparation method described in any one of [1] to

[22] above.

[24] The positive electrode plate according to

[23] , characterized in that the adhesive force per unit length between the positive electrode film layer and the positive electrode current collector is 20 N / m to 30 N / m.

[25] The positive electrode plate according to

[23] or

[24] , characterized in that the shear strength of the positive electrode film layer is 0.64 mPa to 0.91 mPa.

[26] The positive electrode plate according to any one of the above items

[23] to

[25] , characterized in that the cohesive force of the positive electrode film layer is 70 N / m to 90 N / m.

[27] A secondary battery comprising an electrode assembly and an electrolyte, wherein the electrode assembly comprises a separator, a negative electrode plate, and a positive electrode plate as described in any one of

[23] to

[26] .

[28] The secondary battery according to

[27] , characterized in that the secondary battery is one of a lithium-ion battery, a sodium-ion battery, a magnesium-ion battery, and a potassium-ion battery.

[29] A battery module characterized by including the secondary battery described in

[27] or

[28] above.

[30] A battery pack comprising at least one of the secondary battery described in

[27] or

[28] and the battery module described in

[29] .

[31] A power consumption device characterized by comprising at least one selected from the secondary battery described in

[27] or

[28] , the battery module described in

[29] , and the battery pack described in

[30] . [Explanation of symbols]

[0207] 1. Battery pack, 2. Upper casing, 3. Lower casing, 4. Battery module, 5. Rechargeable battery, 5. Case, 5. Electrode assembly, 5. Cover plate.

Claims

1. A method for preparing a positive electrode slurry, comprising a first stirring, a second stirring, a third stirring, and a fourth stirring, During the first stirring, the positive electrode active material and the adhesive are mixed and stirred to prepare a dry mixture. During the second stirring, the adhesive and solvent are mixed and stirred to prepare the adhesive solution. During the third stirring, the dry mixture and the adhesive liquid are mixed and stirred to prepare a primary slurry. During the fourth stirring, the positive electrode active material, the conductive agent, the solvent, and the primary slurry are mixed and stirred to prepare the positive electrode slurry. A method for preparing a positive electrode slurry, characterized in that the adhesive used for the first stirring and the adhesive used for the second stirring are the same.

2. The preparation method according to claim 1, characterized in that the adhesive contains at least one polyvinylidene fluoride having a mass-average molecular weight of 1 million to 8 million.

3. The preparation method according to claim 1, characterized in that the adhesive contains at least two polyvinylidene fluorides having a difference in mass-average molecular weight of 7 million or less.

4. The preparation method according to claim 1, characterized in that, with respect to the total mass of the adhesive used in the first stirring and the adhesive used in the second stirring, the mass content of the adhesive used in the first stirring is 30% to 50%, and the mass content of the adhesive used in the second stirring is 50% to 70%.

5. The preparation method according to claim 1, characterized in that the orbital speed of the first stirring is 10 revolutions / min to 20 revolutions / min.

6. The preparation method according to claim 1, characterized in that the rotation speed of the first stirring is 0.

7. The preparation method according to claim 1, characterized in that the stirring time for the first stirring is 10 to 20 minutes.

8. The preparation method according to claim 1, characterized in that the orbital speed of the second stirring is 20 revolutions / min to 30 revolutions / min.

9. The preparation method according to claim 1, characterized in that the rotation speed of the second stirring is 1100 revolutions / min to 1300 revolutions / min.

10. The preparation method according to claim 1, characterized in that the stirring time for the second stirring is 60 to 80 minutes.

11. The preparation method according to claim 1, characterized in that the orbital speed of the third stirring is 20 revolutions / min to 30 revolutions / min.

12. The preparation method according to claim 1, characterized in that the rotation speed of the third stirring is 500 revolutions per minute to 800 revolutions per minute.

13. The preparation method according to claim 1, characterized in that the stirring time for the third stirring is 40 to 60 minutes.

14. The preparation method according to claim 1, characterized in that the orbital speed of the fourth stirring is 20 revolutions / min to 30 revolutions / min.

15. The preparation method according to claim 1, characterized in that the rotation speed of the fourth stirring is 1100 revolutions / min to 1400 revolutions / min.

16. The preparation method according to claim 1, characterized in that the stirring time for the fourth stirring is 100 to 120 minutes.

17. The preparation method according to claim 1, characterized in that when the solid content of the positive electrode slurry is 68%, the viscosity of the positive electrode slurry is 8,000 mPa·s to 41,000 mPa·s.

18. The preparation method according to claim 1, characterized in that the positive electrode active material used in the first stirring and the positive electrode active material used in the fourth stirring are the same, and the mass content of the positive electrode active material used in the first stirring is 50% to 70% of the total mass of the positive electrode active material used in the first stirring and the positive electrode active material used in the fourth stirring, and the mass content of the positive electrode active material used in the fourth stirring is 30% to 50%.

19. The preparation method according to claim 1, characterized in that the solvent used in the second stirring and the solvent used in the fourth stirring are the same, and the mass content of the solvent used in the second stirring is 35% to 40% and the mass content of the solvent used in the fourth stirring is 5% to 10% with respect to the total mass of the conductive agent, the positive electrode active material used in the first stirring, the positive electrode active material used in the fourth stirring, the adhesive used in the first stirring, and the adhesive used in the second stirring.

20. The preparation method according to claim 1, characterized in that the mass ratio of the total mass of the positive electrode active material, the total mass of the adhesive, and the conductive agent in the positive electrode slurry is (86-98):(1-8):(1-6).

21. The preparation method according to claim 1, characterized in that the positive electrode active material is one or more of lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, and lithium nickel cobalt manganese oxide.

22. The preparation method according to claim 1, characterized in that the conductive agent is one or more of conductive carbon black, graphite, and carbon nanotubes.

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