Method for manufacturing positive electrode paste, positive electrode sheet, secondary battery, battery module, battery pack, and power consumption device

Abstract

The present application provides a method for manufacturing a positive electrode paste, a positive electrode sheet, a secondary battery, a battery module, a battery pack, and an electric power consuming device. The manufacturing method includes a first stirring, a second stirring, a third stirring, and a fourth stirring. In the first stirring, a positive electrode active material, a conductive agent, and a first binder are mixed and stirred to produce a dry mixture. In the second stirring, a second binder and a solvent are mixed and stirred to produce an adhesive. In the third stirring, the dry mixture and the adhesive are mixed and stirred to produce a primary paste. In the fourth stirring, a solvent and the primary paste are mixed and stirred to produce a positive electrode paste. The weight average molecular weight of the polymer in the second binder is smaller than the weight average molecular weight of any polymer in the first binder.

Description

[Technical Field]

[0001] The present invention relates to the technical field of secondary batteries, and more particularly to a method for manufacturing positive electrode paste, a positive electrode sheet, a secondary battery, a battery module, a battery pack, and a power consumption device. [Background technology]

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

[0003] Electrode paste is the foundation for forming electrodes and is the first process in secondary battery manufacturing. The properties of the electrode paste significantly affect the subsequent electrode manufacturing and battery performance. The positive electrode paste is a solid-liquid phase mixture system mainly formed by positive electrode active material, conductive agent, binder, and solvent. This system is in a metastable state, and the paste mixing process, i.e., the paste manufacturing method, has a significant impact on the paste's properties such as dispersibility, uniformity, and stability. Conventional paste mixing processes are generally one-step methods, where each component of the positive electrode active material paste is directly mixed and stirred. However, the resulting paste has high viscosity upon shipment, is prone to abnormal phenomena such as gelation and precipitation, and affects the quality of subsequent coating and rolling processes and polar sheet quality. [Overview of the Initiative]

[0004] This invention was made in view of the above-mentioned problems, and its purpose is to provide a method for manufacturing a positive electrode paste for secondary batteries that reduces the viscosity of the positive electrode paste at the time of shipment, widens the process window for coating the positive electrode paste, and improves the processability of the positive electrode paste.

[0005] According to a first aspect of the present application, a method for producing a positive electrode paste is provided, comprising a first stirring, a second stirring, a third stirring, and a fourth stirring.

[0006] In the first stirring, the positive electrode active material, conductive agent, and first binder are mixed and stirred to produce a dry mixture.

[0007] In the second stirring step, the second binder and the solvent are mixed and stirred to produce the adhesive.

[0008] In the third stirring step, the dry mixture and the adhesive are mixed and stirred to produce a primary paste.

[0009] In the fourth stirring step, the solvent and the primary paste are mixed and stirred to produce the positive electrode paste.

[0010] The weight-average molecular weight of the polymer in the second binder is smaller than the weight-average molecular weight of any polymer in the first binder.

[0011] This invention reduces the viscosity of the cathode paste at the time of shipment and improves the processability of the cathode paste by using a stepwise combination of a low molecular weight second binder and a relatively high molecular weight first binder. Furthermore, this method has broad applicability and can be applied to the production of pastes containing a new generation of high molecular weight polymer binders.

[0012] The cathode paste produced by the manufacturing method disclosed herein can effectively exhibit the properties of polyvinylidene fluoride binders of different molecular weights, and due to the interaction of long-chain and short-chain segments and steric hindrance, it has appropriate viscosity and excellent processability.

[0013] In any embodiment, the second binder is polyvinylidene fluoride having a weight-average molecular weight of 4 million or less.

[0014] By controlling the second binder to polyvinylidene fluoride with a weight-average molecular weight of 4000000 or less, the viscosity of the positive electrode paste at the time of shipment and the viscosity after standing for 24 hours can be effectively reduced, the gelation of the positive electrode paste can be alleviated, the filtration performance of the positive electrode paste can be improved, and the adhesion of the positive electrode sheet can be improved.

[0015] In any embodiment, the second binder is polyvinylidene fluoride with a weight-average molecular weight of 2000000 or less.

[0016] By making the second binder polyvinylidene fluoride with a weight-average molecular weight of 2000000 or less, the viscosity of the positive electrode paste at the time of shipment and the viscosity after standing for 24 hours can be significantly reduced, the gelation of the positive electrode paste can be alleviated to a considerable extent, the filtration performance of the positive electrode paste can be improved, and the adhesion of the positive electrode sheet can be improved.

[0017] In any embodiment, the second binder is polyvinylidene fluoride with a weight-average molecular weight of 1500000 or less.

[0018] By making the second binder polyvinylidene fluoride with a weight-average molecular weight of 1500000 or less, it is advantageous for further reducing the viscosity of the positive electrode paste at the time of shipment and the viscosity after standing for 24 hours, significantly alleviating the gelation of the positive electrode paste, and improving the filtration performance of the positive electrode paste.

[0019] In any embodiment, the first binder includes polyvinylidene fluoride with one or more weight-average molecular weights, and the first binder includes polyvinylidene fluoride with a weight-average molecular weight of 2000000 or more.

[0020] In any embodiment, the first binder includes polyvinylidene fluoride with a weight-average molecular weight of 4000000 or more.

[0021] The manufacturing method disclosed in the present application has versatility with respect to a low weight-average molecular weight polyvinylidene fluoride binder and a high weight-average molecular weight polyvinylidene fluoride binder, enabling the positive electrode paste containing a binder with a weight-average molecular weight of up to 8 million to still have an appropriate viscosity, and the polar sheet manufactured from the positive electrode paste to have excellent adhesiveness, thus meeting the usage requirements of the new generation of binders.

[0022] In any embodiment, with respect to the total mass of the first binder and the second binder, the mass content of the second binder is 30% to 50%.

[0023] When controlling the mass content of the second binder to be 30% to 50% with respect to the total mass of the first binder and the second binder, it is possible not only to effectively reduce the viscosity of the positive electrode paste at the time of shipment and after standing for 24 hours, relieve the gelation of the positive electrode paste, improve the filtration performance of the positive electrode paste, and enhance the adhesiveness of the positive electrode sheet, but also to be advantageous for reducing the manufacturing cost.

[0024] In any embodiment, the revolution speed of the first stirring is 10 rpm to 20 rpm.

[0025] By controlling the revolution speed of the first stirring to be 10 rpm to 20 rpm, it is possible not only to effectively reduce the viscosity of the positive electrode paste at the time of shipment and after standing for 24 hours, improve the filtration performance of the positive electrode paste, and enhance the adhesiveness of the positive electrode sheet, but also to be advantageous for reducing the manufacturing cost.

[0026] In any embodiment, the stirring time of the first stirring is 10 minutes to 25 minutes.

[0027] By controlling the stirring time of the first stirring to be 10 minutes to 25 minutes, it is possible not only to effectively reduce the viscosity of the positive electrode paste at the time of shipment and after standing for 24 hours, relieve the gelation of the positive electrode paste, improve the filtration performance of the positive electrode paste, and enhance the adhesiveness of the positive electrode sheet, but also to be advantageous for improving the manufacturing efficiency and reducing the manufacturing cost.

[0028] In any embodiment, the orbital speed of the second stirring is 20 rpm to 30 rpm.

[0029] By controlling the orbital speed of the second stirring mechanism to 20 rpm to 30 rpm, the viscosity of the cathode paste at the time of shipment and after 24 hours of standing can be effectively reduced, gelling of the cathode paste can be mitigated, the filtration performance of the cathode paste can be improved, and the adhesion of the cathode sheet can be enhanced. This is also advantageous in reducing manufacturing costs.

[0030] In any embodiment, the rotation speed of the second stirring device is 1000 rpm to 1400 rpm.

[0031] By controlling the rotation speed of the second stirring device to 1000 rpm to 1400 rpm, the viscosity of the cathode paste at the time of shipment and after standing for 24 hours can be effectively reduced, gelling of the cathode paste can be mitigated, the filtration performance of the cathode paste can be improved, and the adhesion of the cathode sheet can be enhanced. This is also advantageous in reducing manufacturing costs.

[0032] In any embodiment, the stirring time for the second stirring is 60 to 90 minutes.

[0033] By controlling the stirring time of the second stirring to 60 to 90 minutes, the viscosity of the cathode paste at the time of shipment and after standing for 24 hours can be effectively reduced, gelling of the cathode paste can be mitigated, the filtration performance of the cathode paste can be improved, and the adhesion of the cathode sheet can be enhanced. Furthermore, this is advantageous in terms of improving manufacturing efficiency and reducing manufacturing costs.

[0034] In any embodiment, the stirring time for the third stirring is 60 to 90 minutes, the orbital speed is 20 to 30 rpm, and the rotational speed is 500 to 800 rpm.

[0035] In the third stirring, the dry mixture produced in the first stirring is added to the adhesive produced in the second stirring and stirred slowly, thereby reducing the risk of aggregation and gelation of the high molecular weight polymer in the first binder and improving the uniformity of the mixing between the materials.

[0036] In any embodiment, the orbital speed of the fourth stirring device is 20 rpm to 30 rpm, the rotational speed is 1000 rpm to 1400 rpm, and the stirring time is 90 minutes to 120 minutes.

[0037] In the fourth stirring stage, rapid stirring at a high stirring rotation speed ensures sufficient mixing and dispersion of the materials, thereby allowing the paste to meet the processability and electrical properties requirements of lithium-ion batteries.

[0038] In any embodiment, the solid content of the positive electrode paste is 63% to 73%, and the initial viscosity of the positive electrode paste is 8000 mPa·s to 35000 mPa·s.

[0039] The paste formed by the manufacturing method of this invention has a high solid content, appropriate viscosity, and excellent processability. This paste can be used directly in subsequent coating processes, thereby improving manufacturing efficiency.

[0040] In any embodiment, 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% of the total mass of the conductive agent, the positive electrode active material, the first binder, and the second binder, while the mass content of the solvent used in the fourth stirring is 5% to 10%.

[0041] In any embodiment, in the positive electrode paste, the mass ratio of the positive electrode active material to the total mass of the first binder and the second binder and the conductive agent is (82-95):(3-10):(2-8).

[0042] The positive electrode paste within the above range not only exhibits good processability, but also results in superior electrical and chemical properties for the resulting positive electrode sheet after molding.

[0043] In any embodiment, the positive electrode active material is one or more of lithium iron phosphate, lithium cobalt oxide, and lithium manganese oxide.

[0044] In any embodiment, the conductive agent is one or more of conductive carbon black, graphite, and carbon nanotubes.

[0045] According to a second aspect of the present application, a positive electrode paste manufactured by the method for manufacturing a positive electrode paste of the first aspect is further provided.

[0046] In any embodiment, the viscosity of the positive electrode paste is 8000 mPa·s to 35000 mPa·s, and the viscosity of the positive electrode paste after standing for 24 hours does not exceed 48000 mPa·s.

[0047] The positive electrode paste provided in this application has appropriate viscosity, excellent stability, and good processability.

[0048] A third aspect of the present application provides a positive electrode sheet comprising a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, wherein the positive electrode film layer is manufactured from a positive electrode paste manufactured by the manufacturing method according to the first aspect. The positive electrode sheet has excellent uniformity and adhesive strength.

[0049] In any embodiment, the adhesive strength per unit length between the positive electrode film layer and the positive electrode current collector is greater than 20 N / m. The positive electrode sheet has high adhesive strength between the positive electrode film layer and the positive electrode current collector, which is advantageous in improving the battery's cycle characteristics and safety, as the positive electrode film layer does not easily peel off from the positive electrode current collector during use.

[0050] A fourth aspect of the present application further provides a secondary battery comprising a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte, wherein the positive electrode sheet is manufactured from a positive electrode paste manufactured by the manufacturing method according to the first aspect or from a positive electrode paste according to the second aspect.

[0051] In any embodiment, the secondary battery is one of a lithium-ion battery, a sodium-ion battery, a magnesium-ion battery, or a potassium-ion battery.

[0052] According to the fifth aspect of the present application, a battery module including a secondary battery according to the fourth aspect of the present application is further provided.

[0053] According to the sixth aspect of this application, a battery pack is provided that includes a secondary battery according to the fourth aspect of this application or a battery module according to the fifth aspect of this application.

[0054] According to the seventh aspect of this application, a power consumption device is provided that includes at least one selected from a secondary battery according to the fourth aspect of this application, a battery module according to the fifth aspect of this application, or a battery pack according to the sixth aspect of this application. [Brief explanation of the drawing]

[0055] [Figure 1] This is a schematic diagram of a secondary battery according to one embodiment of the present invention. [Figure 2] Figure 1 is an exploded view of a secondary battery according to one embodiment of the present invention. [Figure 3] This is a schematic diagram of a battery module according to one embodiment of the present invention. [Figure 4] This is a schematic diagram of a battery pack according to one embodiment of the present invention. [Figure 5] Figure 4 is an exploded view of a battery pack according to one embodiment of the present invention. [Figure 6] This is a schematic diagram of a power consumption device that uses a secondary battery as a power source according to one embodiment of the present invention. [Modes for carrying out the invention]

[0056] The following describes in detail embodiments specifically disclosing the binder, manufacturing method, electrodes, battery, and power consumption device of the present application, with reference to the drawings as appropriate. However, unnecessary details may be omitted. For example, detailed explanations of well-known matters or redundant explanations of substantially identical structures may be omitted. This is to avoid unnecessarily verbose explanations and to facilitate understanding by those skilled in the art. Furthermore, the drawings and the following explanation are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0057] The “range” disclosed herein is defined in the form of a lower and upper limit, and a given range is defined by selecting one lower limit and one upper limit, the selected lower and upper limits defining the boundaries of a particular range. Ranges defined in this manner may or may not include the values ​​at both ends and can be combined in any way, 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 are also expected. Similarly, if the minimum range values ​​1 and 2 are listed, and the maximum range values ​​3, 4 and 5 are listed, the ranges 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5 are all intended. In this application, unless otherwise specified, the numerical range “a-b” means an abbreviated expression for any combination of real numbers between a and b, where both a and b are real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" are listed in this specification, and "0 to 5" is merely an abbreviated expression for combinations of these numbers. Also, when a parameter is described as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0058] All embodiments and optional embodiments of this application can be combined to form new technical solutions unless otherwise specified.

[0059] All of the technical features and selectable technical features of this application can be combined to form new technical solutions, unless otherwise specified.

[0060] All steps of this application may be performed sequentially or randomly unless otherwise specified, preferably in order. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, if the method may further include step (c), it means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b), and (c), or steps (a), (c), and (b), or steps (c), (a), and (b), etc.

[0061] As used herein, “includes” and “inclusive” refer to both open and closed forms unless otherwise specified. For example, “includes” and “inclusive” may include or include other components not listed, or may include or include only the listed components.

[0062] In this application, unless otherwise specified, the term “or” is inclusive. For example, the phrase “A or B” means “A, B, or both A and B.” More specifically, the condition “A or B” is satisfied by either A being true (or existing) and B being false (or not existing), A being false (or not existing) and B being true (or existing), or both A and B being true (or existing).

[0063] A positive electrode paste is a solid-liquid phase mixture system mainly composed of a positive electrode active material, a conductive agent, a binder, and a solvent. To improve the uniformity of the distribution of different components in the system, paste mixing is generally performed by processes such as stirring, ball milling, and ultrasonic mixing. However, conventional paste mixing processes are generally only applicable to paste systems with fixed components, lacking versatility, and often require adjustment when the physical properties of each component in the paste change. For example, conventional paste mixing processes cannot be applied to high molecular weight binders, but as a result of extensive research, the applicant has found that high molecular weight binders can effectively reduce the amount of binder used in polar sheets and improve the load-bearing capacity of the polar sheet. However, pastes containing high molecular weight binders have high viscosity at the time of shipment and are prone to gelation, making it difficult to meet the manufacturing requirements of polar sheets.

[0064] [Positive electrode paste] Based on this, the present invention provides a method for producing a positive electrode paste comprising a first stirring, a second stirring, a third stirring, and a fourth stirring, wherein in the first stirring, a positive electrode active material, a conductive agent, and a first binder are mixed and stirred to produce a dry mixture; in the second stirring, the second binder and a solvent are mixed and stirred to produce an adhesive; in the third stirring, the dry mixture and the adhesive are mixed and stirred to produce a primary paste; and in the fourth stirring, the solvent and the primary paste are mixed and stirred to produce a positive electrode paste, wherein the weight-average molecular weight of the polymer in the second binder is smaller than the weight-average molecular weight of any polymer in the first binder.

[0065] In some embodiments, the positive electrode active material is one or more of lithium iron phosphate, lithium cobalt oxide, and lithium manganese oxide.

[0066] In some embodiments, the conductive agent comprises one or more of conductive carbon black, graphite, and carbon nanotubes.

[0067] In some embodiments, the solvent is an aqueous medium such as deionized water. In some embodiments, the solvent is an oily medium selected from one or more of N-methylpyrrolidone, N,N-dimethylpropionamide, N,N-diethylpropionamide, N,N-dipropylpropionamide, N,N-dibutylpropionamide, N,N-dimethylethylpropionamide, and 3-butoxy-N-methylpropionamide.

[0068] In this manufacturing method, first, a positive electrode active material, a conductive agent, and a first binder with a relatively high molecular weight are stirred to obtain a dry mixture. The first stirring mechanically binds the three components together, forming a tight entanglement. Next, a second binder and a solvent are mixed and stirred to produce an adhesive. The weight-average molecular weight of the polymer in the second binder is smaller than the weight-average molecular weight of any polymer in the binder, and the adhesive has relatively low viscosity, which is advantageous for subsequently dispersing a dry mixture containing a polymer with a high molecular weight into the adhesive. Furthermore, the dry mixture produced by the first stirring and the adhesive are mixed and stirred a third time to produce a primary paste. The third stirring effectively disperses the positive electrode active material and conductive agent into the adhesive. The binder in the adhesive improves the stability of the paste through electrostatic and steric hindrance effects, reducing aggregation and sedimentation of the positive electrode active material and conductive agent. Finally, the solvent and primary paste are mixed and a fourth stirring is performed to obtain the positive electrode paste. In the fourth stirring, the added solvent can be used to effectively adjust the viscosity of the paste at the time of shipment, preventing the viscosity from being too high at the time of shipment from affecting subsequent coating work.

[0069] This invention reduces the viscosity of the cathode paste at the time of shipment and improves the processability of the cathode paste by stepwise mixing a low molecular weight second binder with a relatively high molecular weight first binder. Furthermore, this method has broad applicability and can be applied to the production of pastes containing a new generation of high molecular weight polymer binders.

[0070] In any embodiment, the second binder is polyvinylidene fluoride with a weight-average molecular weight of 4 million or less.

[0071] By controlling the second binder to polyvinylidene fluoride with a weight-average molecular weight of 4 million or less, the viscosity of the cathode paste at the time of shipment and after standing for 24 hours can be effectively reduced, gelation of the cathode paste can be mitigated, the filtration performance of the cathode paste can be improved, and the adhesion of the cathode sheet can be enhanced.

[0072] In some embodiments, the weight-average molecular weight of polyvinylidene fluoride in the second binder may be selected from any one of the following: 100,000, 200,000, 300,000, 400,000, 500,000, 600,000, 700,000, 800,000, 900,000, 1,000,000, 1,100,000, 1,200,000, 1,300,000, 1,400,000, 1,500,000, 1,600,000, 1,700,000, 1,800,000, 1,900,000, 2,000,000, 2,500,000, 3,000,000, 3,500,000, and 4,000,000.

[0073] In this specification, the term "weight-average molecular weight" refers to the statistical average molecular weight of the polymer averaged by its mass per unit weight. In this application, the weight-average molecular weight of a polymer can be measured using methods known in the art, for example, by using gel chromatography such as a Waters 2695 Isocratic HPLC gel chromatograph (differential refractive index detector 2141). A suitable chromatography column (oil-based: Styragel HT5DMF 7.8 × 300 mm + Styragel HT4) is selected using a 3.0% polystyrene solution sample as a reference. A 3.0% polymer solution is prepared using purified N-methylpyrrolidone (NMP) solvent, and the prepared solution is allowed to stand for one day for later use. At the time of measurement, tetrahydrofuran is first drawn into the syringe, washed, and this is repeated several times. Next, 5 ml of the test solution is drawn into the syringe, the air is removed from the syringe, and the needle tip is wiped dry. Finally, the sample solution is slowly injected into the inlet. After the display stabilizes, the data is acquired and the weight-average molecular weight is read.

[0074] In any embodiment, the second binder is polyvinylidene fluoride with a weight-average molecular weight of 2 million or less.

[0075] By controlling the second binder to polyvinylidene fluoride with a weight-average molecular weight of 2 million or less, the viscosity of the cathode paste at the time of shipment and after standing for 24 hours can be further reduced, significantly mitigating the gelation of the cathode paste and improving its filtration performance.

[0076] In any embodiment, the second binder is polyvinylidene fluoride with a weight-average molecular weight of 1.5 million or less.

[0077] By controlling the second binder to polyvinylidene fluoride with a weight-average molecular weight of 1.5 million or less, the viscosity of the cathode paste at the time of shipment and after standing for 24 hours can be further reduced, significantly mitigating the gelation of the cathode paste and improving its filtration performance.

[0078] In any embodiment, the first binder comprises one or more polyvinylidene fluorides having a weight-average molecular weight, and the first binder comprises polyvinylidene fluorides having a weight-average molecular weight of 2 million or more. In some embodiments, the first binder comprises one polyvinylidene fluoride having a weight-average molecular weight, and the weight-average molecular weight of that polyvinylidene is 2 million or more. In some embodiments, the first binder comprises two or more polyvinylidene fluorides having different weight-average molecular weights, and the weight-average molecular weight of at least one of the polyvinylidene fluorides is 2 million or more. In some embodiments, the first binder comprises polyvinylidene fluorides having a weight-average molecular weight of 4 million or more.

[0079] The weight-average molecular weight of polyvinylidene fluoride with a weight-average molecular weight of 2 million or more may be selected from one or more of the following: 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, 8 million, 8.5 million, and 9 million.

[0080] Conventional methods for manufacturing cathode pastes have low compatibility and cannot meet the manufacturing requirements for binders with different molecular weights, nor can they produce high-quality paste mixtures of new-generation high-molecular-weight polymer binders. The manufacturing method disclosed herein is versatile and suitable for binders with different weight-average molecular weights, and in particular can meet the manufacturing requirements for new-generation high-molecular-weight polymer binders. It effectively reduces the viscosity of cathode paste at the time of shipment and after 24 hours of standing, and helps to improve the coating and processability of cathode paste.

[0081] In some embodiments, the mass content of the second binder is 30% to 50% of the total mass of the first and second binders. In some embodiments, the mass content of the second binder may be selected from any one of 30%, 32%, 34%, 35%, 36%, 38%, 40%, 42%, 44%, 45%, 46%, 48%, or 50%.

[0082] By controlling the mass content of the second binder to 30% to 50% of the total mass of the first and second binders, the high adhesive performance of the high molecular weight polymer in the first binder can be fully utilized, improving the adhesion of the positive electrode sheet and ensuring the processability of the positive electrode paste. In particular, it is guaranteed that the viscosity at the time of shipment and the viscosity after 24 hours of standing are low, and that it has excellent gelation prevention properties and filterability.

[0083] In some embodiments, the rotational speed of the first stirring is 0. In some embodiments, the orbital speed of the first stirring is 10 rpm to 20 rpm. In some embodiments, the orbital speed of the first stirring may be selected from any one of 10 rpm, 11 rpm, 12 rpm, 13 rpm, 14 rpm, 15 rpm, 16 rpm, 17 rpm, 18 rpm, 19 rpm, and 20 rpm.

[0084] In this specification, the term "rotational speed" refers to the speed at which an agitator rotates around its own axis.

[0085] In this specification, the term "orbital velocity" refers to the speed at which the agitator rotates around the tank containing the material.

[0086] In some embodiments, the agitator is a planetary mixer. The operating principle of a planetary mixer is that when the mixer is started, the planetary carrier rotates, driving the agitator shaft inside the box to rotate, which rotates at high speed while revolving around the barrel axis, thereby subjecting the material to a strong shearing and kneading action. The manufacturing method provided in this application is suitable for all types of planetary mixers.

[0087] By controlling the rotation speed of the first agitator to 0, damage to the material during the drying and mixing process can be reduced. By controlling the orbital speed of the first agitator to 10 rpm to 20 rpm, the viscosity of the cathode paste at the time of shipment and after 24 hours of standing can be effectively reduced, improving the filtration performance of the cathode paste and enhancing the adhesion of the cathode sheet, as well as contributing to a reduction in manufacturing costs.

[0088] In some embodiments, the stirring time for the first stirring is 10 to 25 minutes. In some embodiments, the stirring time for the first stirring can be selected from any one of 10 minutes, 12 minutes, 14 minutes, 15 minutes, 16 minutes, 18 minutes, 20 minutes, 22 minutes, 24 minutes, or 25 minutes.

[0089] By controlling the stirring time of the first stirring to 10 to 25 minutes, the viscosity of the cathode paste at the time of shipment and after standing for 24 hours can be effectively reduced, gelling of the cathode paste can be mitigated, the filtration performance of the cathode paste can be improved, and the adhesion of the cathode sheet can be enhanced. This is also advantageous in terms of improving manufacturing efficiency and reducing manufacturing costs.

[0090] In some embodiments, the orbital speed of the second stirring is 20 rpm to 30 rpm. In some embodiments, the orbital speed of the second stirring may be selected from any one of 20 rpm, 21 rpm, 22 rpm, 23 rpm, 24 rpm, 25 rpm, 26 rpm, 27 rpm, 28 rpm, 29 rpm, and 30 rpm.

[0091] By controlling the orbital speed of the second stirring to 20 rpm to 30 rpm, the viscosity of the cathode paste at the time of shipment and after 24 hours of standing can be effectively reduced, gelling of the cathode paste can be mitigated, the filtration performance of the cathode paste can be improved, and the adhesion of the cathode sheet can be enhanced. This is also advantageous in reducing manufacturing costs.

[0092] In some embodiments, the rotation speed of the second stirring is 1000 rpm to 1400 rpm. In some embodiments, the rotation speed of the second stirring may be selected from any one of 1000 rpm, 1050 rpm, 1100 rpm, 1150 rpm, 1200 rpm, 1250 rpm, 1300 rpm, 1350 rpm, or 1400 rpm.

[0093] By controlling the rotation speed of the second stirring to 1000 rpm to 1400 rpm, the viscosity of the cathode paste at the time of shipment and after standing for 24 hours can be effectively reduced, gelling of the cathode paste can be mitigated, the filtration performance of the cathode paste can be improved, and the adhesion of the cathode sheet can be enhanced. This is also advantageous in reducing manufacturing costs.

[0094] In some embodiments, the stirring time for the second stirring is 60 to 90 minutes. In some embodiments, the stirring time for the second stirring may be selected from any one of 60 minutes, 62 minutes, 65 minutes, 68 minutes, 70 minutes, 73 minutes, 75 minutes, 77 minutes, 80 minutes, 85 minutes, or 90 minutes.

[0095] By controlling the stirring time of the second stirring to 60 to 90 minutes, the viscosity of the cathode paste at the time of shipment and after standing for 24 hours can be effectively reduced, gelling of the cathode paste can be mitigated, the filtration performance of the cathode paste can be improved, and the adhesion of the cathode sheet can be enhanced. This is also advantageous in terms of improving manufacturing efficiency and reducing manufacturing costs.

[0096] In some embodiments, the stirring time for the third stirring is 60 to 90 minutes, the orbital speed is 20 to 30 rpm, and the rotational speed is 500 to 800 rpm.

[0097] In some embodiments, the stirring time for the third stirring may be selected from 60 minutes, 70 minutes, 80 minutes, or 90 minutes. In some embodiments, the orbital speed may be selected from 20 rpm, 25 rpm, or 30 rpm. In some embodiments, the rotational speed may be selected from 500 rpm, 550 rpm, 600 rpm, 650 rpm, 700 rpm, 750 rpm, or 800 rpm.

[0098] In the third stirring stage, the dry mixture produced in the first stirring stage is added to the adhesive produced in the second stirring stage and stirred slowly. This reduces the risk of high molecular weight polymers in the first binder agglomerating and gelling, and improves the uniformity of the mixing between the materials.

[0099] In some embodiments, the orbital speed of the fourth stirring is 20 rpm to 30 rpm, the rotational speed is 1000 rpm to 1400 rpm, and the stirring time is 90 minutes to 120 minutes.

[0100] In some embodiments, the orbital speed of the fourth stirring may be selected from 20 rpm, 25 rpm, or 30 rpm. In some embodiments, the rotational speed may be selected from 1000 rpm, 1100 rpm, 1200 rpm, 1300 rpm, or 1400 rpm. In some embodiments, the stirring time may be selected from 90 minutes, 100 minutes, 110 minutes, or 120 minutes.

[0101] In some embodiments, the fourth stirring stage involves rapid stirring at a high stirring rotation speed to achieve sufficient mixing and dispersion of the materials, thereby ensuring that the paste meets the processability and electrical properties requirements of lithium-ion batteries.

[0102] In any embodiment, the solid content of the positive electrode paste is 63% to 73%, and the initial viscosity of the positive electrode paste is 8000 mPa·s to 35000 mPa·s.

[0103] In some embodiments, the solid content of the positive electrode paste is 63% to 73%, and the initial viscosity of the positive electrode paste is 8000 mPa·s to 35000 mPa·s. In some embodiments, the initial viscosity of the positive electrode paste is 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, and 22000 mPa·s. You may choose any one of the following: .s, 23000mPa.s, 24000mPa.s, 25000mPa.s, 26000mPa.s, 27000mPa.s, 28000mPa.s, 29000mPa.s, 30000mPa.s, 30500mPa.s, 31000mPa.s, 32000mPa.s, 33000mPa.s, 34000mPa.s, or 35000mPa·s.

[0104] The initial viscosity of the positive electrode paste refers to the viscosity of the positive electrode paste at the time of shipment. The viscosity at the time the manufacturing of the positive electrode paste is completed and shipped is recorded as the initial viscosity of the positive electrode paste.

[0105] In this application, the viscosity of the positive electrode paste can be measured using methods known in the art, for example, by measuring the viscosity of the paste using a rotational viscometer. Select an appropriate rotor, fix the viscometer rotor, and place the paste below the viscometer rotor so that it is just submerged up to the scale line of the rotor. Instrument model number: Shanghai Fangrui NDJ-5S, Rotor: 63# (2000-10000 mPa.s), 64# (10000-50000 mPa.s), Rotation speed: 12 rpm, Test temperature: 25°C, Test time: 5 minutes, and read the data after the display has stabilized.

[0106] The initial viscosity of the cathode paste with a solid content of 63% to 73% is 8000 mPa·s to 35000 mPa·s, and this cathode paste has good coating and processability, broadening the process window for coating.

[0107] In some embodiments, 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% of the total mass of the conductive agent, positive electrode active material, first binder, and second binder, while the mass content of the solvent used in the fourth stirring is 5% to 10%.

[0108] 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, the first binder, and the second binder, and the mass content of the solvent used in the fourth stirring may be selected from 5%, 6%, 7%, 8%, 9%, or 10%.

[0109] In some embodiments, the mass ratio of the positive electrode active material to the total mass of the first and second binders and the conductive agent in the positive electrode paste is (82-95):(3-10):(2-8). In some embodiments, the mass ratio of the positive electrode active material to the total mass of the first and second binders and the conductive agent in the positive electrode paste may be selected from any one of the following: 95:3:2, 94:4:2, 93:5:2, 92:5:3, 91:6:3, 90:8:2, 90:5:5, 90:7:2, 88:8:4, 88:5:7, and 82:10:8.

[0110] The positive electrode paste within the above range not only exhibits good processability, but also results in superior electrical and chemical properties for the resulting positive electrode sheet after molding.

[0111] In some embodiments, the positive electrode active material is one or more of lithium iron phosphate, lithium cobalt oxide, and lithium manganese oxide.

[0112] Using the above-mentioned positive electrode active material increases the energy density of the battery, which is advantageous in improving the battery's cycle characteristics.

[0113] In some embodiments, the conductive agent is one or more of conductive carbon black, graphite, and carbon nanotubes.

[0114] The above conductive agent is advantageous for improving the conductivity of batteries.

[0115] This application provides a positive electrode paste manufactured by a manufacturing method in any embodiment of this application.

[0116] In some embodiments, the solid content of the positive electrode paste is 63% to 73%, the initial viscosity of the positive electrode paste is 8000 mPa·s to 35000 mPa·s, and after standing for 24 hours, the viscosity of the positive electrode paste does not exceed 48000 mPa·s. In some embodiments, the initial viscosity of the positive electrode paste is 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, 22000 mPa·s. You may choose any one of the following: .s, 23000mPa.s, 24000mPa.s, 25000mPa.s, 26000mPa.s, 27000mPa.s, 28000mPa.s, 29000mPa.s, 30000mPa.s, 30500mPa.s, 31000mPa.s, 32000mPa.s, 33000mPa.s, 34000mPa.s, or 35000mPa·s. In some embodiments, after standing for 24 hours, the viscosity of the positive electrode paste is 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, 22000 mPa.s, 23000 mPa.s, and 24000 mPa.s. , or any one of the following values ​​may be selected: 25,000 mPa.s, 26,000 mPa.s, 27,000 mPa.s, 28,000 mPa.s, 29,000 mPa.s, 30,000 mPa.s, 30,500 mPa.s, 31,000 mPa.s, 32,000 mPa.s, 33,000 mPa.s, 34,000 mPa.s, 36,000 mPa.s, 38,000 mPa.s, 40,000 mPa.s, 42,000 mPa.s, 44,000 mPa.s, or 48,000 mPa.s.

[0117] The positive electrode paste has appropriate viscosity, excellent stability, and good processability.

[0118] [Positive electrode sheet] The present invention provides a positive electrode sheet comprising a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, wherein the positive electrode film layer is manufactured by a manufacturing method in any embodiment of the present application. For example, the positive electrode current collector has two opposing surfaces in its thickness direction, and the positive electrode film layer is provided on one or both of the two opposing surfaces of the positive electrode current collector.

[0119] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. As the metal foil, for example, aluminum foil can be used. The composite current collector may include a polymer substrate layer and a metal layer formed on at least one surface of the polymer substrate layer. The composite current collector can 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 (for example, a substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0120] In some embodiments, the positive electrode active material can be any positive electrode active material for batteries known in the art. For example, the positive electrode active material may include at least one of olivine-structured lithium-containing phosphates, lithium transition metal oxides, and modified compounds thereof. However, the present application is not limited to these materials, and other conventional materials usable as positive electrode active materials for batteries may be used. These positive electrode active materials may be used individually or in combination of two or more. Examples of lithium transition metal oxides include lithium cobalt oxide (LiCoO2, etc.), lithium nickel oxide (LiNiO2, etc.), lithium manganese oxide (LiMnO2, LiMn2O4, etc.), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM333 (also called), LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM 523 also called) LiNi 0.5 Co 0.25 Mn 0.25 O2 (NCM 211 also called), LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM 622 also called), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM 811 also called), lithium nickel cobalt aluminum oxide (LiNi 0.85 Co 0.15 Al 0.05 O2, etc.) and at least one of its modified compounds may be included, but is not limited thereto. As the olivine-structured lithium-containing phosphate, for example, lithium iron phosphate (e.g., LiFePO4 (also called LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and at least one of a composite material of lithium manganese iron phosphate and carbon may be included, but is not limited thereto.

[0121] In some embodiments, the adhesion per unit length between the positive electrode film layer and the positive electrode current collector is greater than 20 N / m. In some embodiments, the adhesion per unit length between the positive electrode film layer and the positive electrode current collector is selectively 20 N / m to 30 N / m. In some embodiments, the adhesion per unit length between the positive electrode film layer and the positive electrode current collector may be selected from any one of 20 N / m, 20.5 N / m, 21 N / m, 21.5 N / m, 22 N / m, 22.5 N / m, 23 N / m, 23.5 N / m, 24 N / m, 24.5 N / m, 25 N / m, 27 N / m, 30 N / m.

[0122] In this specification, adhesive strength is primarily used to characterize the adhesive strength between the film layer manufactured from the positive electrode paste in the positive electrode sheet and the current collector, and can be measured by any known method. As an example, the adhesive strength per unit length between the positive electrode film layer and the positive electrode current collector can be measured using a method known in the art, for example, referring to the national standard GB-T2790-1995 "Test Method for 180° Peel Strength of Adhesives," and the adhesive strength test process for the examples and comparative examples of this application is as follows: A sample with a width of 30 mm and a length of 100-160 mm is cut with a blade, and special double-sided tape is attached to a steel plate, resulting in a sample with a width of 20 mm and a length of 90-150 mm. After attaching the coated surface of the polar sheet sample cut earlier to the double-sided tape, it is rolled three times in the same direction with a 2 kg pressure roller. Paper tape with the same width as the polar sheet and a length of 250 mm is fixed to the polar sheet current collector and secured with masking tape. Turn on the power to the Sanshisha tensile device (sensitivity set to 1N), illuminate the indicator light, adjust the stopper to the appropriate position, and secure the end of the steel plate that does not have the polarity sheet attached with the lower clamp. Fold the paper tape upwards and secure it with the upper clamp, and adjust the position of the upper clamp using the "up" and "down" buttons on the manual controller attached to the tensile device. Then, perform the test and read the values, with the tensile speed being 50 mm / min. Divide the force acting on the polarity sheet when the force is balanced by the width of the tape to obtain the adhesive strength of the polarity sheet per unit length, and characterize the adhesive strength between the positive electrode film layer and the current collector.

[0123] [Negative electrode sheet] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer containing a negative electrode active material, which is installed on at least one surface of the negative electrode current collector.

[0124] For example, the negative electrode current collector has two opposing surfaces in its own thickness direction, and the negative electrode film layer is provided on one or both of the two opposing surfaces of the negative electrode current collector.

[0125] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. For example, copper foil can be used as the metal foil. The composite current collector may include a polymer substrate layer and a metal layer formed on at least one surface of the polymer substrate. The composite current collector can 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)).

[0126] In some embodiments, the negative electrode active material can be any known negative electrode active material for batteries. For example, the negative electrode active material may include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. Silicon-based materials can be selected from at least one of elemental silicon, silicon oxide, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials can be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials usable as negative electrode active materials for batteries may be used. These negative electrode active materials may be used individually or in combination of two or more types.

[0127] In some embodiments, the negative electrode film layer may selectively further contain a binder. The binder can 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).

[0128] In some embodiments, the negative electrode film layer may further selectively contain a conductive agent. The conductive agent can be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0129] In some embodiments, the negative electrode film layer further comprises other additives, such as a selective thickener (e.g., sodium carboxymethylcellulose (CMC-Na)).

[0130] In some embodiments, a negative electrode sheet can be manufactured by the following method: Components for manufacturing the negative electrode sheet, such as a negative electrode active material, a conductive agent, a binder, and any other components, are dispersed in a solvent (e.g., deionized water) to form a negative electrode paste, the negative electrode paste is coated onto a negative electrode current collector, and the negative electrode sheet can be obtained through steps such as drying and cold pressing.

[0131] [Electrolytes] The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. This application does not particularly limit the type of electrolyte, and it can be selected as needed. For example, the electrolyte may be a liquid, a gel, or a solid.

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

[0133] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluoride phosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoride arsenate, lithium bisfluorosulfonylimide, lithium bistrifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium bisoxalate borate, lithium difluorooxalate phosphate, and lithium tetrafluorooxalate phosphate.

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

[0135] In some embodiments, the electrolyte selectively further comprises additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and further additives that can improve specific characteristics of the battery, such as additives that improve the overcharge characteristics of the battery, or additives that improve the high-temperature or low-temperature characteristics of the battery.

[0136] [Separator] In some embodiments, the secondary battery further includes a separator. The present application does not particularly limit the type of separator, and any known porous structure separator having good chemical and mechanical stability can be selected.

[0137] In some embodiments, the material of the separator can 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. If the separator is a multilayer composite film, the materials of each layer may be the same or different, and are not particularly limited.

[0138] In some embodiments, the positive electrode sheet, negative electrode sheet, and separator can be manufactured into an electrode assembly via a winding process or a lamination process.

[0139] In some embodiments, the secondary battery may include an outer casing. This casing is used to enclose the electrode assembly and electrolyte.

[0140] In some embodiments, the casing material of the secondary battery may be a hard case such as a rigid plastic case, an aluminum case, or a steel case. The casing material of the secondary battery may also be a soft pack such as a pouch-type soft pack. The material of the soft pack may be plastic, and examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0141] This invention does not particularly limit the shape of the secondary battery, and it may be cylindrical, prismatic, or any other shape. For example, Figure 1 shows a prismatic secondary battery 5 as an example.

[0142] In some embodiments, referring to Figure 2, the exterior material may include a housing 51 and a cover plate 53. The housing 51 may include a bottom plate and side plates connected to the bottom plate, forming a housing cavity enclosed by the bottom plate and side plates. The housing 51 has an opening that communicates with the housing cavity, and the cover plate 53 can be placed over the opening to seal the housing cavity. The positive electrode sheet, negative electrode sheet, and separator can be formed into an electrode assembly 52 via a winding or laminating process. The electrode assembly 52 is sealed 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 select according to specific practical requirements.

[0143] In some embodiments, the secondary batteries can be assembled into a battery module, and the number of secondary batteries included in the battery module may be one or more, the specific number of which can be selected by those skilled in the art depending on the application and capacity of the battery module.

[0144] Figure 3 shows an example of a battery module 4. Referring to Figure 3, in the battery module 4, multiple secondary batteries 5 can be installed in sequence along the length of the battery module 4. Of course, they can be arranged in any other way. Furthermore, these multiple secondary batteries 5 can be fixed in place with fasteners.

[0145] Selectively, the battery module 4 may further comprise an outer case having a housing space for accommodating multiple secondary batteries 5.

[0146] In some embodiments, the battery modules can be further assembled into a battery pack, and the number of battery modules in the battery pack may be one or more, the specific number of which can be selected by those skilled in the art depending on the application and capacity of the battery pack.

[0147] 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 case and a plurality of battery modules 4 installed inside the battery case. The battery case includes an upper housing 2 and a lower housing 3, the upper housing 2 can be placed over the lower housing 3 and form a sealed space for housing the battery modules 4. The plurality of battery modules 4 can be arranged inside the battery case in any way.

[0148] Furthermore, the present application provides a power consumption device comprising at least one of a secondary battery, battery module, or battery pack relating to the present application. The secondary battery, battery module, or battery pack may be used as a power source for the power consumption device, or as an energy storage element 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.), trains, ships and satellites, energy storage systems, etc.

[0149] As a power consumption device, a secondary battery, battery module, or battery pack can be selected according to the usage requirements.

[0150] 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, etc. To meet the high power output and high energy density requirements for the secondary battery of this power consumption device, a battery pack or battery module can be used.

[0151] Other examples of such devices may include mobile phones, tablet computers, and laptop computers. These devices are generally required to be lightweight and thin, and can use rechargeable batteries as a power source.

[0152] Examples The following describes examples of the present application. The examples described below are illustrative and are for illustrative purposes only, and should not be understood as limiting the present application. If specific techniques or conditions are not shown in the examples, they should be carried out in accordance with the techniques or conditions described in the literature in the art, or in accordance with the product instructions. If the manufacturer of the reagents or equipment used is not specified, they are all commercially available common products.

[0153] 1. Manufacturing method Example 1 1) Manufacturing of positive electrode paste Weighing of raw materials: The raw materials are weighed according to the mixing ratio of the positive electrode paste, so that the mass ratio of positive electrode active material:first binder:second binder:conductive agent is 95:1.5:1.5:2. The mass of the positive electrode active material is 1200 kg, the positive electrode active material is lithium iron phosphate, the first binder is polyvinylidene fluoride with a weight-average molecular weight of 2 million, the second binder is polyvinylidene fluoride with a weight-average molecular weight of 1 million, and the conductive agent is conductive carbon black.

[0154] First stirring: Lithium iron phosphate, conductive carbon black, and the first binder are mixed and stirred thoroughly at an orbital speed of 15 rpm, a rotational speed of 0, and a stirring time of 15 minutes to obtain a dry mixture.

[0155] Second stirring: The second binder and N-methylpyrrolidone (NMP) solvent are mixed and stirred thoroughly. The mass of NMP solvent added in the second stirring is 35% of the total mass of the positive electrode active material, the first binder, the second binder, and the conductive agent. The rotational speed is 25 rpm, the rotational speed is 1200 rpm, and the stirring time is 60 minutes to obtain the adhesive.

[0156] Third stirring: Add the above dry mixture to the above adhesive and stir thoroughly at an orbital speed of 25 rpm, a rotational speed of 600 rpm, and a stirring time of 60 minutes to obtain a primary paste.

[0157] Fourth stirring: NMP solvent is added to the primary paste. The mass of NMP solvent added in the fourth stirring is 10% of the total mass of the positive electrode active material, the first binder, the second binder, and the conductive agent. The rotational speed is 25 rpm, the rotational speed is 1200 rpm, and the stirring time is 110 minutes. A positive electrode paste with a solid content of 68% ± 5% is obtained.

[0158] 2) Manufacturing of polarity sheets The positive electrode paste produced in Example 1 is uniformly coated onto the aluminum foil of the positive electrode current collector, and then dried, cold-pressed, and cut to obtain a positive electrode sheet.

[0159] Examples 2-3 The manufacturing method is basically the same as in Example 1, the only difference being that the first binder in the first stirring was adjusted to polyvinylidene fluoride with a weight-average molecular weight of 4 million and polyvinylidene fluoride with a weight-average molecular weight of 8 million, respectively. The specific parameters are shown in Table 1.

[0160] Examples 4-8 The manufacturing method is basically the same as in Example 3, the only difference being that the second binder in the second stirring was adjusted to polyvinylidene fluoride with a weight-average molecular weight of 4 million, polyvinylidene fluoride with a weight-average molecular weight of 3 million, polyvinylidene fluoride with a weight-average molecular weight of 2 million, polyvinylidene fluoride with a weight-average molecular weight of 1.5 million, and polyvinylidene fluoride with a weight-average molecular weight of 500,000, respectively. The specific parameters are shown in Table 1.

[0161] Examples 9-12 The manufacturing method is basically the same as in Example 3, the only difference being the adjustment of the mass ratio between the first binder and the second binder. The specific parameters are shown in Table 1.

[0162] Examples 13-16 The manufacturing method is basically the same as in Example 1, the difference being that the first binder was prepared as a composition. Taking Example 13 as an example, the first binder is a composition of polyvinylidene fluoride with a weight-average molecular weight of 2 million and polyvinylidene fluoride with a weight-average molecular weight of 4 million. In the first binder, the polyvinylidene fluoride with a weight-average molecular weight of 2 million accounts for 30% of the total binder amount, and the polyvinylidene fluoride with a weight-average molecular weight of 4 million accounts for 40% of the total binder amount. In the second binder, the polyvinylidene fluoride with a weight-average molecular weight of 1 million accounts for 30% of the total binder amount. Specific parameters in other examples are shown in Table 1.

[0163] Examples 17-44 The manufacturing method is basically the same as in Example 3, the only difference being that the stirring parameters for the first and second stirring were adjusted, and the specific parameters are shown in Table 1.

[0164] Comparative Example 1 Weighing of raw materials: The raw materials are weighed according to the mixing ratio of the positive electrode paste, so that the mass ratio of positive electrode active material:binder:conductive agent is 95:3:2. The mass of the positive electrode active material is 1200 kg, the positive electrode active material is lithium iron phosphate, the binder is polyvinylidene fluoride with a weight-average molecular weight of 2 million, and the conductive agent is conductive carbon black.

[0165] First stirring: Lithium iron phosphate and conductive carbon black are mixed and stirred thoroughly at an orbital speed of 15 rpm, a rotational speed of 0, and a stirring time of 15 minutes to obtain a dry mixture.

[0166] Second stirring: The second binder and NMP solvent are mixed and stirred thoroughly. The mass of the solvent added is 35% of the total mass of the positive electrode active material, binder, and conductive agent. The orbital speed is 25 rpm, the rotational speed is 1200 rpm, and the stirring time is 60 minutes to obtain the adhesive.

[0167] Third stirring: The dry mixture produced in the first stirring is added to the adhesive produced in the second stirring and stirred thoroughly at an orbital speed of 25 rpm, a rotational speed of 600 rpm, and a stirring time of 60 minutes to obtain the primary paste.

[0168] Fourth stirring: NMP solvent is added to the primary paste. The mass of the solvent added is 10% of the total mass of the positive electrode active material, binder, and conductive agent. The orbital speed is 25 rpm, the rotational speed is 1200 rpm, and the stirring time is 110 minutes. A positive electrode paste with a solid content of 68% ± 5% is obtained.

[0169] Comparative Examples 2-8 This is basically the same as Comparative Example 1, the only difference being the adjustment of the weight-average molecular weight of the binder. The specific parameters are shown in Table 1.

[0170] 2. Test Method 1. Weight average molecular weight A Waters 2695 isocratic HPLC gel chromatograph (differential refractive index detector 2141) was used. A suitable chromatography column (oil-based: Styragel HT5DMF 7.8 × 300 mm + Styragel HT4) was selected using a 3.0% polystyrene solution sample as a reference. A 3.0% polymer solution was prepared using purified N-methylpyrrolidone (NMP) solvent, and the prepared solution was allowed to stand for one day for later use. Before measurement, tetrahydrofuran was first drawn into the syringe, washed, and this was repeated several times. Next, 5 ml of the test solution was drawn, air was removed from the syringe, and the needle tip was wiped dry. Finally, the sample solution was slowly injected into the inlet. After the display stabilized, data was acquired and the weight-average molecular weight was read.

[0171] 2. Paste viscosity test The viscosity of the paste is measured using a rotational viscometer. Select an appropriate rotor, fix the viscometer rotor in place, and place the paste under the viscometer rotor so that it is just submerged up to the rotor's scale line. Equipment model number: Shanghai Fangrui NDJ-5S, Rotor: 63# (2000-10000 mPa.s), 64# (10000-50000 mPa.s), Rotation speed: 12 rpm, Test temperature: 25°C, Test time: 5 minutes, and read the data after the display has stabilized.

[0172] 3. Viscosity test after the paste has been left to stand for 24 hours. After standing for 24 hours, the viscosity of the paste is measured again using a rotational viscometer. Select an appropriate rotor, fix the viscometer rotor in place, and place the paste below the viscometer rotor so that it is just submerged up to the scale line on the rotor. Instrument model number: Shanghai Fangrui NDJ-5S, Rotor: 63# (2000-10000 mPa.s), 64# (10000-50000 mPa.s), Rotation speed: 12 rpm, Test temperature: 25°C, Test time: 5 minutes, and read the data after the display has stabilized.

[0173] 4. Gelation state test after the paste has been left to stand for 24 hours. After letting the paste stand for 24 hours, the paste in the beaker is lifted out with a steel ruler, and the gelation state is determined from the fluidity of the paste.

[0174] A non-gelled state is characterized by the paste flowing naturally and continuously, advection across the surface of the steel scale, and the absence of aggregation.

[0175] The slight gelling state means the paste flows naturally and continuously, but the fluid is thin, and the paste spreads basically flat on the surface of the steel scale, although there are slight lumps.

[0176] A moderate gelling state is characterized by the paste dripping spontaneously, with occasional interruptions, discontinuous flow, and the paste not spreading evenly across the steel scale surface, but rather exhibiting obvious clumping.

[0177] A severe gelling condition is when the paste cannot flow down but falls in clumps or remains on the steel scale without flowing away.

[0178] 5. Filtration performance test Take a 500ml beaker, place it on the bottom of a 200-mesh filter holder, take 500ml of conductive paste, filter it, and record the time it takes for the volume of paste in the beaker to reach 300ml.

[0179] 6. Adhesion strength test of polar sheets Referring to the national standard GB-T2790-1995 "Method for Testing 180° Peel Strength of Adhesives," the adhesive strength test process for the examples and comparative examples of this application is as follows: A sample with a width of 30 mm and a length of 100-160 mm is cut with a blade, and special double-sided tape is attached to the steel plate, resulting in a sample with a width of 20 mm and a length of 90-150 mm. After attaching the coated surface of the polar sheet sample cut earlier to the double-sided tape, it is rolled three times in the same direction with a 2 kg pressure roller. A paper tape with the same width as the polar sheet and a length of 250 mm is fixed to the polar sheet current collector and secured with masking tape. The power of the Sanshi tensile device is turned on (sensitivity is 1N), the indicator light is turned on, the stopper is adjusted to the appropriate position, and the end of the steel plate that does not have the polar sheet attached is fixed with the lower clamp. The paper tape is folded up and fixed with the upper clamp, and the position of the upper clamp is adjusted using the "up" and "down" buttons on the manual controller attached to the tensile device. Next, a test was conducted and the values ​​were read, with a tensile speed of 50 mm / min. The force acting on the polar sheet when the force is balanced was divided by the width of the tape to obtain the adhesive strength of the polar sheet per unit length, and the adhesive strength between the positive electrode film layer and the current collector was characterized.

[0180] 3. Analysis of the test results of each example and comparative example. The results of manufacturing each example and comparative example according to the above method, and measuring each performance parameter, are shown in Tables 1 and 2 below.

[0181] Table 1 Manufacturing parameters of examples and comparative examples TIFF0007880993000001.tif241164 TIFF0007880993000002.tif199164 TIFF0007880993000003.tif199164 TIFF0007880993000004.tif199164 TIFF0007880993000005.tif199164 TIFF0007880993000006.tif177164

[0182] Table 2 Performance parameter test results for examples and comparative examples TIFF0007880993000007.tif234155 TIFF0007880993000008.tif78155

[0183] As can be seen from the above results, the positive electrode pastes in Examples 1 to 44 were all manufactured using the paste manufacturing method disclosed in this application, and each method included a first stirring, a second stirring, a third stirring, and a fourth stirring. In the first stirring, lithium iron phosphate (positive electrode active material), conductive carbon black (conductive agent), and polyvinylidene fluoride (first binder) were mixed and stirred to produce a dry mixture. In the second stirring, polyvinylidene fluoride (second binder) and NMP solvent were mixed and stirred to produce an adhesive. In the third stirring, the dry mixture and adhesive were mixed and stirred to produce a primary paste. In the fourth stirring, the NMP solvent and primary paste were mixed and stirred to produce a positive electrode paste. The weight-average molecular weight of polyvinylidene fluoride in the second binder was smaller than the weight-average molecular weight of any polyvinylidene fluoride in the first binder. As can be seen from the comparison between Examples 1-44 and Comparative Examples 1-8, the method for producing a cathode paste according to the present invention can effectively reduce the viscosity of the cathode paste and improve the processability of the paste. This method is not only suitable for polymers in the prior art, but is particularly suitable for high molecular weight polymers and has broad applicability.

[0184] As can be seen from the comparison between Examples 3-8 and Comparative Example 6, by controlling the second binder to polyvinylidene fluoride with a weight-average molecular weight of 4 million or less, the viscosity of the cathode paste at the time of shipment and after standing for 24 hours can be effectively reduced, gelling of the cathode paste is mitigated, the filtration performance of the cathode paste is improved, and the adhesion of the cathode sheet is enhanced. As can be seen from the comparison between Examples 3, 6-8 and Example 6, by controlling the second binder to polyvinylidene fluoride with a weight-average molecular weight of 2 million or less, the viscosity of the cathode paste at the time of shipment and after standing for 24 hours can be further reduced, gelling of the cathode paste is mitigated to a considerable extent, and the filtration performance of the cathode paste is improved. As can be seen from the comparison between Examples 3, 7-8 and Example 6, by controlling the second binder to polyvinylidene fluoride with a weight-average molecular weight of 1.5 million or less, the viscosity of the cathode paste at the time of shipment and after standing for 24 hours can be further reduced, significantly mitigating the gelation of the cathode paste and improving the filtration performance of the cathode paste.

[0185] As can be seen from the comparison between Examples 1-16 and Comparative Examples 1-8, the manufacturing method is suitable for polyvinylidene fluoride containing one or more weight-average molecular weights in the first binder, and is particularly applicable to the first binder containing polyvinylidene fluoride having a weight-average molecular weight of 2 million or more.

[0186] As can be seen from the comparison between Examples 3, 10-11 and Examples 9 and 12, by controlling the mass content of the second binder to 30%-50% of the total mass of the first and second binders, the effect of the high adhesion performance of the high molecular weight polymer in the first binder can be fully utilized, improving the adhesion of the positive electrode sheet and ensuring the processability of the positive electrode paste. In particular, it is guaranteed that the viscosity at the time of shipment and the viscosity after standing for 24 hours are low, and that it has excellent gelation prevention properties and filterability.

[0187] As can be seen from the comparison between Examples 3, 18-19 and Example 17, by controlling the orbital speed of the first stirring to 10 rpm to 20 rpm, the viscosity of the cathode paste at the time of shipment and the viscosity after standing for 24 hours can be effectively reduced, improving the filtration performance of the cathode paste and enhancing the adhesion of the cathode sheet. Furthermore, as can be seen from the comparison between Examples 3, 18-19 and Example 20, by controlling the orbital speed of the first stirring to 10 rpm to 20 rpm, manufacturing costs can be reduced while ensuring the adhesion and filtration performance of the cathode paste and the adhesion of the cathode sheet.

[0188] As can be seen from the comparison between Examples 3, 22-23 and Example 21, by controlling the stirring time of the first stirring to 10-25 minutes, the viscosity of the cathode paste at the time of shipment and the viscosity after standing for 24 hours can be effectively reduced, gelation of the cathode paste can be mitigated, the filtration performance of the cathode paste can be improved, and the adhesion of the cathode sheet can be improved. Furthermore, as can be seen from the comparison between Examples 3, 22-23 and Example 24, by controlling the stirring time of the first stirring to 10-25 minutes, while ensuring the adhesion and filtration performance of the cathode paste and the adhesion of the cathode sheet, manufacturing efficiency can be improved and manufacturing costs can be reduced.

[0189] As can be seen from the comparison between Examples 3, 26-27 and Example 25, by controlling the orbital speed of the second stirring to 20 rpm to 30 rpm, the viscosity of the cathode paste at the time of shipment and the viscosity after standing for 24 hours can be effectively reduced, gelation of the cathode paste can be mitigated, the filtration performance of the cathode paste can be improved, and the adhesion of the cathode sheet can be improved. Furthermore, as can be seen from the comparison between Examples 3, 26-27 and Example 28, by controlling the orbital speed of the second stirring to 20 rpm to 30 rpm, manufacturing costs can be reduced while ensuring the adhesion and filtration performance of the cathode paste and the adhesion of the cathode sheet.

[0190] As can be seen from the comparison between Examples 3, 30-31 and Example 29, by controlling the rotation speed of the second stirring to 1000 rpm to 1400 rpm, the viscosity of the cathode paste at the time of shipment and the viscosity after standing for 24 hours can be effectively reduced, gelling of the cathode paste can be mitigated, the filtration performance of the cathode paste can be improved, and the adhesion of the cathode sheet can be enhanced. As can be seen from the comparison between Examples 3, 30-31 and Example 32, by controlling the rotation speed of the second stirring to 1000 rpm to 1400 rpm, while guaranteeing the adhesion and filtration performance of the cathode paste and the adhesion of the cathode sheet, the cathode paste can be softened and manufacturing costs can be reduced.

[0191] As can be seen from the comparison between Examples 3, 34-35 and Example 33, by controlling the stirring time of the second stirring to 60-90 minutes, the viscosity of the cathode paste at the time of shipment and the viscosity after standing for 24 hours can be effectively reduced, gelation of the cathode paste can be mitigated, the filtration performance of the cathode paste can be improved, and the adhesion of the cathode sheet can be enhanced. Furthermore, as can be seen from the comparison between Examples 3, 34-35 and Example 36, by controlling the stirring time of the second stirring to 60-90 minutes, manufacturing efficiency can be improved and manufacturing costs can be reduced while ensuring the adhesion and filtration performance of the cathode paste and the adhesion of the cathode sheet.

[0192] As can be seen from the comparison between Examples 3, 38-39 and Example 37, by controlling the rotation speed of the third stirrer to 500 rpm to 800 rpm, the viscosity of the cathode paste at the time of shipment and after standing for 24 hours can be effectively reduced, gelling of the cathode paste can be mitigated, the filtration performance of the cathode paste can be improved, and the adhesion of the cathode sheet can be enhanced. Furthermore, as can be seen from the comparison between Examples 3, 38-39 and Example 40, by controlling the rotation speed of the third stirrer to 500 rpm to 800 rpm, costs can be reduced while ensuring the adhesion and filtration performance of the cathode paste and the adhesion of the cathode sheet.

[0193] As can be seen from the comparison between Examples 3, 42-43 and Example 41, by controlling the rotation speed of the fourth stirrer to 1000 rpm to 1400 rpm, the viscosity of the cathode paste at the time of shipment and after standing for 24 hours can be effectively reduced, gelation of the cathode paste can be mitigated, the filtration performance of the cathode paste can be improved, and the adhesion of the cathode sheet can be enhanced. Furthermore, as can be seen from the comparison between Examples 3, 42-43 and Example 44, by controlling the rotation speed of the fourth stirrer to 1000 rpm to 1400 rpm, manufacturing costs can be reduced while ensuring the adhesion and filtration performance of the cathode paste and the adhesion of the cathode sheet.

[0194] As can be seen from the examples, the positive electrode paste disclosed herein has a solid content of 63% to 73%, and a viscosity of 8000 mPa·s to 35000 mPa·s, and the positive electrode paste has good coating properties and processability.

[0195] Furthermore, this application is not limited to the embodiments described above. The embodiments described above are merely illustrative, and any embodiment that has a substantially identical configuration to the technical idea and exhibits similar effects, within the scope of the technical solutions of this application, is included in the technical scope of this application. In addition, any modifications to the embodiments that can be conceived by a person skilled in the art, or other forms constructed by combining some of the components of the embodiments, are also included in the scope of this application, as long as they do not depart from the spirit of this application. Preferred embodiments of the present invention are as follows: [1] Including the first stirring, second stirring, third stirring and fourth stirring, In the first stirring, the positive electrode active material, conductive agent, and first binder are mixed and stirred to produce a dry mixture. In the second stirring step, the second binder and the solvent are mixed and stirred to produce the adhesive. In the third stirring, the dry mixture and the adhesive are mixed and stirred to produce a primary paste. In the fourth stirring step, the solvent and the primary paste are mixed and stirred to produce a positive electrode paste. A method for producing a cathode paste, characterized in that the weight-average molecular weight of the polymer in the second binder is smaller than the weight-average molecular weight of any polymer in the first binder. [2] The manufacturing method according to [1], characterized in that the second binder is polyvinylidene fluoride having a weight-average molecular weight of 4 million or less. [3] The manufacturing method according to [1] or [2], characterized in that the second binder is polyvinylidene fluoride having a weight-average molecular weight of 2 million or less. [4] The manufacturing method according to any one of [1] to [3], characterized in that the first binder contains one or more polyvinylidene fluorides having a weight-average molecular weight, and the first binder contains polyvinylidene fluorides having a weight-average molecular weight of 2 million or more. [5] The manufacturing method according to any one of [1] to [4] above, characterized in that the first binder contains polyvinylidene fluoride having a weight-average molecular weight of 4 million or more. [6] The manufacturing method according to any one of the above [1] to [5], characterized in that the mass content of the second binder is 30% to 50% of the total mass of the first binder and the second binder. [7] The manufacturing method according to any one of the above items [1] to [6], characterized in that the first stirring has a rotational speed of 0 and an orbital speed of 10 rpm to 20 rpm. [8] The manufacturing method according to any one of the above [1] to [7], characterized in that the stirring time in the first stirring is 10 to 25 minutes. [9] The manufacturing method according to any one of the above items [1] to [8], characterized in that the orbital speed of the second stirring is 20 rpm to 30 rpm.

[10] The manufacturing method according to any one of the above items [1] to [9], characterized in that the rotation speed of the second stirring is 1000 rpm to 1400 rpm.

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

[10] , characterized in that the stirring time in the second stirring is 60 to 90 minutes.

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

[11] , characterized in that the third stirring is performed for a stirring time of 60 to 90 minutes, with an orbital speed of 20 rpm to 30 rpm and a rotational speed of 500 rpm to 800 rpm.

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

[12] , characterized in that the orbital speed of the fourth stirring is 20 rpm to 30 rpm, the rotational speed is 1000 rpm to 1400 rpm, and the stirring time is 90 minutes to 120 minutes.

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

[13] , characterized in that the solid content of the positive electrode paste is 63% to 73%, and the initial viscosity of the positive electrode paste is 8000 mPa·s to 35000 mPa·s.

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

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

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

[15] , characterized in that, in the positive electrode paste, the mass ratio of the positive electrode active material to the total mass of the first binder and the second binder and the conductive agent is (82-95):(3-10):(2-8).

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

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

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

[17] , wherein the conductive agent is one or more of conductive carbon black, graphite, and carbon nanotubes.

[19] A positive electrode paste characterized by being manufactured by the manufacturing method described in any one of the above items [1] to

[18] .

[20] The positive electrode paste according to

[19] , characterized in that the solid content is 63% to 73%, the initial viscosity is 8000 mPa·s to 35000 mPa·s, and the viscosity does not exceed 48000 mPa·s after standing for 24 hours.

[21] A positive electrode sheet comprising a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, wherein the positive electrode film layer is manufactured from a positive electrode paste manufactured by the manufacturing method described in any one of the above items [1] to

[18] .

[22] The positive electrode sheet according to

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

[23] A secondary battery comprising a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte, wherein the positive electrode sheet is manufactured from a positive electrode paste produced by the manufacturing method described in any one of the above items [1] to

[18] or from a positive electrode paste described in any one of the above items

[19] to

[20] .

[24] The secondary battery described in

[23] , characterized in that it is a lithium-ion battery, a sodium-ion battery, a magnesium-ion battery, or a potassium-ion battery.

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

[23] or

[24] above.

[26] A battery pack characterized by including the secondary battery described in

[23] or

[24] above or the battery module described in

[25] above.

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

[23] or

[24] , the battery module described in

[25] , and the battery pack described in

[26] . [Explanation of Symbols]

[0196] 1 Battery pack 2 Upper cabinet 3 Lower cabinet 4 Battery Modules 5 Secondary battery 51 Housing 52 Electrode Assembly 53 Cover Plate

Claims

1. This includes a first stirring, a second stirring, a third stirring, and a fourth stirring, In the first stirring, the positive electrode active material, conductive agent, and first binder are mixed and stirred to produce a dry mixture. In the second stirring step, the second binder and the solvent are mixed and stirred to produce the adhesive. In the third stirring step, the dry mixture and the adhesive are mixed and stirred to produce a primary paste. In the fourth stirring step, the solvent and the primary paste are mixed and stirred to produce a positive electrode paste. A method for producing a cathode paste, characterized in that the weight-average molecular weight of the polymer in the second binder is smaller than the weight-average molecular weight of any polymer in the first binder.

2. The manufacturing method according to claim 1, characterized in that the second binder is polyvinylidene fluoride having a weight-average molecular weight of 4 million or less.

3. The manufacturing method according to claim 1, characterized in that the second binder is polyvinylidene fluoride having a weight-average molecular weight of 2 million or less.

4. The manufacturing method according to claim 1, characterized in that the first binder contains one or more polyvinylidene fluorides having a weight-average molecular weight, and the first binder contains polyvinylidene fluorides having a weight-average molecular weight of 2 million or more.

5. The manufacturing method according to claim 1, characterized in that the first binder contains polyvinylidene fluoride having a weight-average molecular weight of 4 million or more.

6. The manufacturing method according to claim 1, characterized in that the mass content of the second binder is 30% to 50% of the total mass of the first binder and the second binder.

7. The manufacturing method according to claim 1, characterized in that the first stirring has a rotational speed of 0 and an orbital speed of 10 rpm to 20 rpm.

8. The manufacturing method according to claim 1, characterized in that the stirring time in the first stirring is 10 to 25 minutes.

9. The manufacturing method according to claim 1, characterized in that the orbital speed of the second stirring is 20 rpm to 30 rpm.

10. The manufacturing method according to claim 1, characterized in that the rotation speed of the second stirring is 1000 rpm to 1400 rpm.

11. The manufacturing method according to claim 1, characterized in that the stirring time in the second stirring is 60 to 90 minutes.

12. The manufacturing method according to claim 1, characterized in that the third stirring is performed for a stirring time of 60 to 90 minutes, with an orbital speed of 20 rpm to 30 rpm and a rotational speed of 500 rpm to 800 rpm.

13. The manufacturing method according to claim 1, characterized in that the orbital speed of the fourth stirring is 20 rpm to 30 rpm, the rotational speed is 1000 rpm to 1400 rpm, and the stirring time is 90 minutes to 120 minutes.

14. The manufacturing method according to claim 1, characterized in that the solid content of the positive electrode paste is 63% to 73%, and the initial viscosity of the positive electrode paste is 8,000 mPa·s to 35,000 mPa·s.

15. The manufacturing 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, the mass content of the solvent used in the second stirring is 35% to 40% of the total mass of the conductive agent, the positive electrode active material, the first binder and the second binder, and the mass content of the solvent used in the fourth stirring is 5% to 10%.

16. The manufacturing method according to claim 1, characterized in that, in the positive electrode paste, the mass ratio of the mass of the positive electrode active material, the total mass of the first binder and the second binder, and the conductive agent is (82-95):(3-10):(2-8).

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

18. The manufacturing method according to claim 1, wherein the conductive agent is one or more of conductive carbon black, graphite, and carbon nanotubes.

19. The manufacturing method according to Claim 1, characterized in that the solid content of the positive electrode paste is 63% to 73%, the initial viscosity of the positive electrode paste is 8,000 mPa·s to 35,000 mPa·s, and after standing for 24 hours, the viscosity of the positive electrode paste does not exceed 48,000 mPa·s.

20. A method for manufacturing a positive electrode sheet, comprising a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, wherein the positive electrode film layer is manufactured from a positive electrode paste manufactured by the manufacturing method described in any one of claims 1 to 19.

21. The manufacturing method according to claim 20, characterized in that the adhesive force per unit length between the positive electrode film layer and the positive electrode current collector is greater than 20 N / m.

22. A method for manufacturing a secondary battery comprising a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte, wherein the positive electrode sheet is manufactured from a positive electrode paste manufactured by the manufacturing method described in any one of claims 1 to 19.

23. The manufacturing method according to claim 22, characterized in that the secondary battery is a lithium-ion battery, a sodium-ion battery, a magnesium-ion battery, or a potassium-ion battery.

24. A method for manufacturing a battery module including a secondary battery, characterized in that the secondary battery is manufactured by the manufacturing method described in Claim 22.

25. A method for manufacturing a battery pack including a secondary battery, characterized in that the secondary battery is manufactured by the manufacturing method described in Claim 22.

26. A method for manufacturing a power consumption device including a secondary battery, characterized in that the secondary battery is manufactured by the manufacturing method described in Claim 22.

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