Method for preparing positive electrode slurry, positive electrode slurry, positive electrode sheet, secondary battery, and electric device

Abstract

The application provides a preparation method of a positive electrode slurry, the positive electrode slurry, a secondary battery and an electric device. The preparation method of the positive electrode slurry comprises first stirring, second stirring and third stirring. In the first stirring, a positive electrode active material is mixed and stirred with a binder to prepare a dry mixture. In the second stirring, a solvent is kneaded with the dry mixture to prepare a primary slurry. In the third stirring, a conductive agent and the solvent are mixed and stirred with the primary slurry to prepare a positive electrode slurry. The solvent used in the second stirring is the same as the solvent used in the third stirring, and the mass content of the solvent used in the second stirring is 10-15% based on the total mass of the positive electrode active material and the binder.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of secondary batteries, in particular to a preparation method of a positive electrode slurry, the positive electrode slurry, a positive electrode sheet, a secondary battery and an electric device. BACKGROUND

[0002] In recent years, with the application range of secondary batteries becoming more and more extensive, secondary batteries are widely used in energy storage power supply systems such as hydraulic, thermal, wind and solar power stations, and in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc.

[0003] The electrode slurry is the basis of the formed electrode and is the first process in the production of secondary batteries. The characteristics of the electrode slurry have a significant influence on the subsequent electrode production and battery performance. The positive electrode slurry is mainly a solid-liquid phase mixed system formed by the positive electrode active material, the conductive agent, the binder and the solvent. The system is in a metastable state, and the slurry preparation method, that is, the slurry mixing process, has a crucial influence on the dispersibility, uniformity and stability of the slurry. The slurry mixing process in the prior art is often a one-step method, in which the components in the positive electrode active slurry are directly mixed and stirred to obtain the slurry. The prepared slurry has a large delivery viscosity, and abnormal phenomena such as gelation and precipitation are likely to occur, which affects the subsequent coating, rolling process and the quality of the electrode sheet. SUMMARY

[0004] The present application is carried out in view of the above-mentioned problems, and aims to provide a preparation method of a secondary battery positive electrode slurry, which effectively reduces the delivery viscosity, the viscosity after standing for 24 hours and the difference in solid content between the upper and lower layers after standing for 24 hours of the slurry, improves the anti-settling property and anti-gel property of the slurry, widens the process window of the slurry coating, and improves the processing performance of the positive electrode slurry.

[0005] In order to achieve the above-mentioned purpose, the present application provides a preparation method of a positive electrode slurry, which comprises first stirring, second stirring and third stirring.

[0006] In the first stirring, the positive electrode active material is mixed and stirred with the binder to prepare a dry mixture;

[0007] In the second stirring, the solvent is kneaded with the dry mixture to prepare a primary slurry;

[0008] In the third stirring, the conductive agent and the solvent are mixed and stirred with the primary slurry to prepare the positive electrode slurry;

[0009] The solvent used in the second stirring is the same as the solvent used in the third stirring, and the mass content of the solvent used in the second stirring is 10% to 15% based on the total mass of the positive electrode active material and the binder.

[0010] Therefore, by the step-by-step slurry mixing and the matching of the stirring parameters, the slurry can have a low delivery viscosity, a low viscosity after 24 hours of static storage, a low difference in solid content between the upper and lower layers after 24 hours of static storage, improved anti-settling and anti-gelling properties, improved storage performance, and a widened process window for slurry coating.

[0011] In any embodiment, the mass content of the solvent used in the third stirring is 20% to 30% based on the total mass of the positive electrode active material and the binder.

[0012] Controlling the mass content of the solvent used in the third stirring within an appropriate range enables the slurry to have a low delivery viscosity, a low viscosity after 24 hours of static storage, excellent anti-settling and anti-gelling properties, and is beneficial to improving the coating performance, processing performance, and stability of the slurry.

[0013] In any embodiment, the revolution speed in the first stirring is 10 revolutions / minute to 20 revolutions / minute.

[0014] Controlling the revolution speed in the first stirring within an appropriate range enables the slurry to have a low delivery viscosity, a low viscosity after 24 hours of static storage, excellent anti-settling and anti-gelling properties, and is beneficial to improving the coating performance, processing performance, and stability of the slurry.

[0015] In any embodiment, the stirring time in the first stirring is 10 minutes to 15 minutes.

[0016] Controlling the stirring time in the first stirring within an appropriate range enables the slurry to have a low delivery viscosity, a low viscosity after 24 hours of static storage, excellent anti-settling and anti-gelling properties, and is beneficial to improving the coating performance, processing performance, and stability of the slurry.

[0017] In any embodiment, the revolution speed in the second stirring is 15 revolutions / minute to 25 revolutions / minute.

[0018] Controlling the revolution speed in the second stirring within an appropriate range enables the slurry to have a low delivery viscosity, a low viscosity after 24 hours of static storage, excellent anti-settling and anti-gelling properties, and is beneficial to improving the coating performance, processing performance, and stability of the slurry.

[0019] In any embodiment, the stirring time in the second stirring is 20 minutes to 30 minutes.

[0020] Controlling the stirring time in the second stirring within an appropriate range enables the slurry to have a low delivery viscosity, a low viscosity after 24 hours of static storage, excellent anti-settling and anti-gelling properties, and is beneficial to improving the coating performance, processing performance, and stability of the slurry.

[0021] In any embodiment, the revolution speed in the third stirring is 20-30 rpm.

[0022] The revolution speed in the third stirring is controlled in a proper range, so that the slurry has low delivery viscosity, low viscosity after 24 hours of static storage, excellent anti-settling property and anti-gelling property, which is beneficial to improve the coating performance, processing performance and stability of the slurry.

[0023] In any embodiment, the revolution speed in the third stirring is 20-30 rpm.

[0024] The revolution speed in the third stirring is controlled in a proper range, so that the slurry has low delivery viscosity, low viscosity after 24 hours of static storage, excellent anti-settling property and anti-gelling property, which is beneficial to improve the coating performance, processing performance and stability of the slurry.

[0025] In any embodiment, the revolution speed in the third stirring is 20-30 rpm.

[0026] The revolution speed in the third stirring is controlled in a proper range, so that the slurry has low delivery viscosity, low viscosity after 24 hours of static storage, excellent anti-settling property and anti-gelling property, which is beneficial to improve the coating performance, processing performance and stability of the slurry.

[0027] In any embodiment, the revolution speed in the third stirring is 20-30 rpm.

[0028] The slurry formed by the preparation method has proper viscosity and excellent processability, and the slurry can be directly used in the subsequent coating process, which can improve the production efficiency.

[0029] In any embodiment, the revolution speed in the third stirring is 20-30 rpm.

[0030] The slurry formed by the preparation method has excellent storage performance, which widens the process window of the slurry.

[0031] In any embodiment, the mass ratio of the total mass of the positive active material, the total mass of the binder and the mass of the conductive agent in the positive electrode slurry is (90-96):(2-6):(2-4).

[0032] The positive electrode slurry in the above range has good processability and excellent electrochemical performance of the formed positive electrode sheet.

[0033] The second aspect of the present application also provides a positive electrode slurry prepared by the method for preparing a positive electrode slurry of the first aspect.

[0034] The third aspect of the present application provides a positive electrode tab including a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, the positive electrode film layer being prepared from a positive electrode slurry prepared by the method for preparing a positive electrode slurry of the first aspect.

[0035] The fourth aspect of the present application provides a secondary battery including a separator, a negative electrode tab, and the positive electrode tab of the third aspect.

[0036] The fifth aspect of the present application provides an electric device characterized by including the secondary battery of the fourth aspect. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 is a schematic view of a secondary battery according to an embodiment of the present application;

[0038] Figure 2 is a schematic view of a battery module according to an embodiment of the present application; Figure 1 is an exploded view of the battery module according to an embodiment of the present application;

[0039] Figure 3 is a schematic view of a battery pack according to an embodiment of the present application;

[0040] Figure 4 is a schematic view of a battery pack according to an embodiment of the present application;

[0041] Figure 5 is an exploded view of the battery pack according to an embodiment of the present application; Figure 4

[0042] Figure 6 is a schematic view of an electric device using the secondary battery according to an embodiment of the present application as a power source.

[0043] REFERENCE NUMERALS

[0044] 1 battery pack; 2 upper case; 3 lower case; 4 battery module; 5 secondary battery; 51 case; 52 electrode assembly; 53 cover plate. DETAILED DESCRIPTION

[0045] ​Hereinafter, embodiments of the positive electrode active material and the method for manufacturing the same, the positive electrode sheet, the secondary battery, the battery module, the battery pack, and the electrical device of the present application will be specifically described with appropriate reference to the accompanying drawings. However, there will be cases where unnecessary detailed description is omitted. For example, there will be cases where detailed description of matters known well, repeated description of substantially identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0046] The ranges disclosed herein are defined by their lower and upper limits. Ranges can be inclusive or exclusive of their endpoints, and all ranges and sub-ranges are combinable. For example, if a range is listed as 60-120 and 80-110, it is understood that 60-110 and 80-120 are also expressly stated. Also, if a range is listed as 1-2 and 3-5, it is understood that 1-5, 1-3, 2-5, and 2-3 are also expressly stated. In the present application, unless otherwise indicated, a numerical range "a-b" is intended to indicate any and all sub-ranges of the same, including the end values and excluding the end values. For example, numerical ranges "0-5" is intended to indicate the full range of from "0 to 5," inclusive of "0" and "5," but not inclusive of any and all sub-ranges between (or within) the indicated range. Additionally, when a parameter is stated as being an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and the like.

[0047] All embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, unless otherwise specified.

[0048] All technical features and optional technical features of the present application can be combined with each other to form new technical solutions, unless otherwise specified.

[0049] If not otherwise specified, all steps of the present application can be carried out in sequence or randomly, preferably in sequence. For example, the method comprising steps (a) and (b) means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method further comprising step (c) means that step (c) can be added to the method in any sequence, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0050] If not otherwise specified, the terms "comprising" and "including" mentioned in the present application mean open-ended, and can also mean closed-ended. For example, the terms "comprising" and "including" can mean that other components not listed can also be included, or only the listed components can be included.

[0051] If not otherwise specified, in the present application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, either of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or A and B are both true (or exist).

[0052] The positive electrode slurry is mainly a solid-liquid phase mixed system formed by the positive electrode active material, the conductive agent, the binder and the solvent. In order to improve the uniformity of the distribution of different components in the system, the slurry is usually prepared by stirring, ball milling, ultrasonic and other processes. However, the slurry prepared by the slurry mixing process in the prior art is unstable, easy to settle and easy to gel, and is difficult to meet the production needs of the electrode sheet.

[0053] [Preparation method]

[0054] Based on this, the present application proposes a preparation method of a positive electrode slurry, comprising first stirring, second stirring and third stirring;

[0055] In the first stirring, the positive electrode active material is mixed and stirred with the binder to prepare a dry mixture;

[0056] In the second stirring, the solvent is kneaded with the dry mixture to prepare a primary slurry;

[0057] In the third stirring, the conductive agent, the solvent and the primary slurry are mixed and stirred to prepare the positive electrode slurry;

[0058] In the second stirring, the solvent used is the same as the solvent used in the third stirring, and the mass content of the solvent used in the second stirring is 10% to 15% based on the total mass of the positive electrode active material and the binder.

[0059] In some embodiments, the binder comprises polyvinylidene fluoride with a weight average molecular weight of 100,000-1,500,000.

[0060] In some embodiments, the positive active material comprises at least one of lithium iron phosphate and modified materials thereof, lithium cobaltate and modified materials thereof, lithium manganate and modified materials thereof, the modified materials being prepared by one or more of modification methods of doping, conductive carbon coating, conductive metal coating, and conductive polymer coating.

[0061] In some embodiments, the conductive agent can include at least one of superconducting carbon, carbon black, carbon nanotubes, graphene, and carbon nanofibers.

[0062] 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-methyl-2-pyrrolidone, N,N-dimethylpropionamide, N,N-diethylpropionamide, N,N-dipropylpropionamide, N,N-dibutylpropionamide, N,N-dimethyl ethyl propionamide, and 3-butoxy-N-methylpropionamide.

[0063] In this document, the term "kneading" refers to an operation of uniformly mixing a small amount of liquid in a solid powder to prepare a plastic material or a paste material.

[0064] In this document, the term "process window" refers to a process interval capable of ensuring product quality, including but not limited to a temperature interval, a pressure interval, a storage time length, etc. It can be understood that the wider the process window, the lower the requirement for process precision.

[0065] In the preparation method, the positive active material and the binder are first stirred to obtain a dry mixture, which is beneficial to uniformly dispersing and riveting the binder on the surface of the positive active material; then a small amount of solvent is added for second stirring, so that the positive active material and the binder simultaneously absorb the liquid, so that the slurry is in a state of moderate dryness and wetness, so as to facilitate the kneading process, so that the positive active material and the binder in the slurry do not agglomerate during kneading, and the dispersibility of the slurry is enhanced. At the same time, under the wetting action of the solvent, the chain segments of the binder are further stretched, and the binder is tightly wrapped on the surface of the positive active material; finally, the conductive agent and the solvent are added, so that the slurry changes from a kneaded state to a solution state, so that the various components are uniformly dispersed under the strong shearing action caused by stirring, and the dispersibility and stability of the slurry are improved. In addition, in the solution state, the chain segments of the binder can be fully stretched and tightly coated on the positive active material and the conductive agent, which plays a role in stabilizing and dispersing the materials in the slurry, and slows down the gelation of the slurry.

[0066] The mass content of the solvent used in the second stirring is 10% to 15% based on the total mass of the positive electrode active material and the binder. If the mass of the solvent added in the second stirring is too much or too little, the slurry cannot effectively reduce the delivery viscosity and the viscosity after 24 hours of standing, and cannot effectively improve the anti-settling property and the anti-gelling property of the slurry.

[0067] In summary, by means of the step-by-step slurry mixing and the matching of the stirring parameters, the delivery viscosity and the viscosity of the slurry after 24 hours of standing can be reduced, the difference in the solid content between the upper and lower layers of the slurry after 24 hours of standing can be reduced, the anti-settling property and the anti-gelling property of the slurry can be improved, the storage performance of the slurry can be improved, and the process window of the slurry coating can be widened.

[0068] In some embodiments, the mass content of the solvent used in the third stirring is 20% to 30% based on the total mass of the positive electrode active material and the binder.

[0069] In some embodiments, the mass content of the solvent used in the third stirring can be selected from any one of 20% to 25%, 20% to 30%, and 25% to 30% based on the total mass of the positive electrode active material and the binder.

[0070] Controlling the mass content of the solvent used in the third stirring within an appropriate range can reduce the delivery viscosity and the viscosity of the slurry after 24 hours of standing, improve the coatability and processability of the slurry, and improve the anti-settling property and the anti-gelling property of the slurry, improve the storage performance of the slurry, and widen the process window of the slurry coating. At the same time, controlling the mass content of the solvent used in the third stirring within an appropriate range can reduce the use of the solvent without significantly changing the delivery viscosity of the slurry, the viscosity of the slurry after 24 hours of standing, the difference in the solid content between the upper and lower layers of the slurry after 24 hours of standing, and the gelling phenomenon of the slurry, thereby reducing the cost and being able to balance the slurry mixing quality and the cost.

[0071] In some embodiments, the revolving speed in the first stirring is 10 revolutions per minute to 20 revolutions per minute.

[0072] In some embodiments, the revolving speed in the first stirring can be selected from any one of 10 revolutions per minute to 15 revolutions per minute, 10 revolutions per minute to 20 revolutions per minute, and 15 revolutions per minute to 20 revolutions per minute.

[0073] In this document, the term “rotational speed” refers to the speed at which the stirrer rotates around its own axis.

[0074] In this document, the term “revolving speed” refers to the speed at which the stirrer rotates around the kettle body loaded with the material.

[0075] The delivery viscosity refers to the viscosity of the positive electrode slurry immediately after the preparation is completed.

[0076] Controlling the revolution speed in the first stirring within a proper range is beneficial to further dispersion of the binder and the positive active material, beneficial to further riveting of the binder on the surface of the positive active material, improves the dispersion of the dry mixture, effectively reduces the delivery viscosity and the viscosity after 24 hours of the slurry, improves the coating and processing properties of the slurry, and improves the anti-settling and anti-gelling properties of the slurry, improves the storage property of the slurry, and widens the process window of the slurry coating. Controlling the revolution speed in the first stirring within a proper range can reduce the power of the stirrer, save energy, and balance the quality and cost of the slurry preparation without significantly changing the delivery viscosity of the slurry, the viscosity after 24 hours of the slurry, the difference of the solid content between the upper and lower layers of the slurry after 24 hours, and the gelling phenomenon of the slurry.

[0077] In some embodiments, the stirring time in the first stirring is 10-15 minutes.

[0078] Controlling the stirring time in the first stirring within a proper range is beneficial to further dispersion of the binder and the positive active material, beneficial to further riveting of the binder on the surface of the positive active material, improves the dispersion of the dry mixture, effectively reduces the delivery viscosity and the viscosity after 24 hours of the slurry, improves the coating and processing properties of the slurry, and improves the anti-settling and anti-gelling properties of the slurry, improves the storage property of the slurry, and widens the process window of the slurry coating. Controlling the stirring time in the first stirring within a proper range can reduce the working time of the slurry preparation, improve the working efficiency of the slurry preparation, and reduce the cost without significantly changing the delivery viscosity of the slurry, the viscosity after 24 hours of the slurry, the difference of the solid content between the upper and lower layers of the slurry after 24 hours, and the gelling phenomenon of the slurry.

[0079] In some embodiments, the revolution speed in the second stirring is 15-25 rpm. In some embodiments, the revolution speed in the second stirring can be selected from any one of 15-20 rpm, 15-25 rpm, and 20-25 rpm.

[0080] Controlling the revolution speed in the second stirring within a proper range is beneficial to improve the dispersion of the primary slurry, effectively reduces the delivery viscosity and the viscosity after 24 hours of the slurry, improves the coating and processing properties of the slurry, and improves the anti-settling and anti-gelling properties of the slurry, improves the storage property of the slurry, and widens the process window of the slurry coating. Controlling the revolution speed in the second stirring within a proper range can reduce the power of the stirrer, save energy, and balance the quality and cost of the slurry preparation without significantly changing the delivery viscosity of the slurry, the viscosity after 24 hours of the slurry, the difference of the solid content between the upper and lower layers of the slurry after 24 hours, and the gelling phenomenon of the slurry.

[0081] In some embodiments, the stirring time in the second stirring is 20-30 minutes. In some embodiments, the stirring time in the second stirring can be selected from any one of 20-25 minutes, 25-30 minutes, and 20-30 minutes.

[0082] Controlling the stirring time in the second stirring within a suitable range is conducive to improving the dispersibility of the primary slurry, effectively reducing the delivery viscosity and the viscosity after 24 hours of standing of the slurry, improving the coatability and processability of the slurry, and improving the anti-settling property and anti-gelling property of the slurry, improving the storage property of the slurry, and widening the process window of the slurry coating. Meanwhile, controlling the stirring time in the second stirring within a suitable range can reduce the working time for preparing the slurry, improve the working efficiency for preparing the slurry, and reduce the cost without significantly changing the delivery viscosity of the slurry, the viscosity after 24 hours of standing of the slurry, the difference in solid content between the upper and lower layers of the slurry after 24 hours of standing, and the gelling phenomenon of the slurry.

[0083] In some embodiments, the revolution speed in the third stirring is 20-30 revolutions per minute. In some embodiments, the revolution speed in the third stirring can be selected from any one of 20-25 revolutions per minute, 20-30 revolutions per minute, and 25-30 revolutions per minute.

[0084] Controlling the revolution speed in the third stirring within a suitable range is conducive to fully dispersing the conductive agent and the binder around the positive active material, effectively reducing the delivery viscosity and the viscosity after 24 hours of standing of the slurry, improving the coatability and processability of the slurry, and improving the anti-settling property and anti-gelling property of the slurry, improving the storage property of the slurry, and widening the process window of the slurry coating. Meanwhile, controlling the revolution speed in the third stirring within a suitable range can reduce the power of the stirrer, save energy, and balance the slurry mixing quality and cost without significantly changing the delivery viscosity of the slurry, the viscosity after 24 hours of standing of the slurry, the difference in solid content between the upper and lower layers of the slurry after 24 hours of standing, and the gelling phenomenon of the slurry.

[0085] In some embodiments, the revolution speed in the third stirring is 20-30 revolutions per minute. In some embodiments, the revolution speed in the third stirring can be selected from any one of 20-25 revolutions per minute, 20-30 revolutions per minute, and 25-30 revolutions per minute.

[0086] The self-rotation speed of the third stirring is controlled within a proper range, which is beneficial to the dispersion of the conductive agent and the binder around the positive active material, effectively reduces the delivery viscosity and the viscosity after 24 hours of the slurry, improves the coating property and the processability of the slurry, and improves the anti-settling property and the anti-gel property of the slurry, improves the storage property of the slurry, and widens the process window of the slurry coating. Meanwhile, the self-rotation speed of the third stirring is controlled within a proper range, without significantly changing the delivery viscosity of the slurry, the viscosity after 24 hours of the slurry, the difference of the solid content between the upper and lower layers of the slurry after 24 hours of the slurry, and the gel phenomenon of the slurry, the power of the stirrer can be reduced, the energy is saved, and the slurry mixing quality and the cost can be considered.

[0087] In some embodiments, the stirring time in the third stirring is 90 minutes to 110 minutes. In some embodiments, the stirring time in the third stirring is any one of 90 minutes to 100 minutes, 100 minutes to 110 minutes, and 100 minutes to 110 minutes.

[0088] The stirring time in the third stirring is controlled within a proper range, which is beneficial to the dispersion of the conductive agent and the binder around the positive active material, effectively reduces the delivery viscosity and the viscosity after 24 hours of the slurry, improves the coating property and the processability of the slurry, and improves the anti-settling property and the anti-gel property of the slurry, improves the storage property of the slurry, and widens the process window of the slurry coating. Meanwhile, the stirring time in the third stirring is controlled within a proper range, without significantly changing the delivery viscosity of the slurry, the viscosity after 24 hours of the slurry, the difference of the solid content between the upper and lower layers of the slurry after 24 hours of the slurry, and the gel phenomenon of the slurry, the working time of the slurry preparation can be reduced, the working efficiency of the slurry preparation is improved, and the cost is reduced.

[0089] In some embodiments, the solid content of the positive electrode slurry is 65% to 75%, and the delivery viscosity of the positive electrode slurry is 7500 mPa·s to 40000 mPa·s.

[0090] In some embodiments, the delivery viscosity of the cathode slurry can be selected from any one of 7500 mPa s to 10000 mPa s, 7500 mPa s to 15000 mPa s, 7500 mPa s to 20000 mPa s, 7500 mPa s to 25000 mPa s, 7500 mPa s to 30000 mPa s, 7500 mPa s to 35000 mPa s, 7500 mPa s to 40000 mPa s, 10000 mPa s to 15000 mPa s, 10000 mPa s to 20000 mPa s, 10000 mPa s to 25000 mPa s, 10000 mPa s to 30000 mPa s, 10000 mPa s to 35000 mPa s, 10000 mPa s to 40000 mPa s, 20000 mPa s to 25000 mPa s, 20000 mPa s to 30000 mPa s, 20000 mPa s to 35000 mPa s, 20000 mPa s to 40000 mPa s, 25000 mPa s to 30000 mPa s, 25000 mPa s to 35000 mPa s, 25000 mPa s to 40000 mPa s, 30000 mPa s to 35000 mPa s, 30000 mPa s to 40000 mPa s, 35000 mPa s to 40000 mPa s.

[0091] In some embodiments, the solid content of the cathode slurry is 65% to 75%, and the delivery viscosity of the cathode slurry is 7500 mPa s to 25000 mPa s.

[0092] In some embodiments, the delivery viscosity of the cathode slurry can be selected from any one of 7500 mPa s to 10000 mPa s, 7500 mPa s to 15000 mPa s, 7500 mPa s to 20000 mPa s, 7500 mPa s to 25000 mPa s, 10000 mPa s to 15000 mPa s, 10000 mPa s to 20000 mPa s, 10000 mPa s to 25000 mPa s, 20000 mPa s to 25000 mPa s.

[0093] The slurry formed by the preparation method of the present application has suitable viscosity and excellent processability, and the slurry can be directly used in subsequent coating process, thereby improving production efficiency.

[0094] In some embodiments, the solid content of the positive electrode slurry is 65-75%, and the viscosity of the positive electrode slurry is not more than any one of 49000 mPa·s, 45000 mPa·s, 40000 mPa·s, 35000 mPa·s, 30000 mPa·s, 25000 mPa·s, 20000 mPa·s, 15000 mPa·s, 10000 mPa·s after standing for 24 hours.

[0095] In some embodiments, the solid content of the positive electrode slurry is 65-75%, and the viscosity of the positive electrode slurry is not more than any one of 49000 mPa·s, 45000 mPa·s, 40000 mPa·s, 35000 mPa·s, 30000 mPa·s, 25000 mPa·s, 20000 mPa·s, 15000 mPa·s, 10000 mPa·s after standing for 24 hours.

[0096] In some embodiments, the solid content of the positive electrode slurry is 65-75%, and the viscosity of the positive electrode slurry is not more than 30000 mPa·s after standing for 24 hours.

[0097] In some embodiments, the solid content of the positive electrode slurry is 65-75%, and the viscosity of the positive electrode slurry is not more than any one of 30000 mPa·s, 25000 mPa·s, 20000 mPa·s, 15000 mPa·s, 10000 mPa·s after standing for 24 hours.

[0098] The slurry prepared by the preparation method of the present application has excellent storage performance, and widens the process window of the slurry.

[0099] In some embodiments, the mass ratio of the total mass of the positive electrode active material, the total mass of the binder, and the mass of the conductive agent in the positive electrode slurry is (90-96):(2-6):(2-4).

[0100] The positive electrode slurry within the above range has good processing performance, and also enables the positive electrode tab after forming to have excellent electrochemical performance.

[0101] In one embodiment of the present application, a positive electrode slurry is provided, which is prepared by the preparation method of the positive electrode slurry in any embodiment.

[0102] In some embodiments, a positive electrode tab is provided, which comprises a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, the positive electrode film layer being prepared from the positive electrode slurry prepared by the preparation method of the positive electrode slurry in any embodiment or being prepared from the positive electrode slurry in any embodiment.

[0103] In addition, the secondary battery, the battery module, the battery pack, and the power utilization device of the present application are described below with appropriate reference to the accompanying drawings.

[0104] In one embodiment of the present application, a secondary battery is provided, which comprises a separator, a negative electrode tab, and the positive electrode tab in any embodiment.

[0105] In some embodiments, the secondary battery is any one of a lithium ion battery, a sodium ion battery, a magnesium ion battery, and a potassium ion battery.

[0106] During the charging and discharging of the battery, active ions are inserted and extracted between the positive electrode sheet and the negative electrode sheet. The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is disposed between the positive electrode sheet and the negative electrode sheet, mainly to prevent short circuiting between the positive and negative electrodes, while allowing ions to pass through.

[0107] [Positive electrode sheet]

[0108] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, the positive electrode film layer being prepared from the slurry prepared by the preparation method of any embodiment of the present application.

[0109] As an example, the positive electrode current collector has two opposite surfaces in the thickness direction thereof, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0110] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, an aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0111] In some embodiments, the positive electrode active material can use a positive electrode active material for a battery known in the art. As an example, the positive electrode active material can include at least one of a lithium-containing phosphate of olivine structure, a lithium transition metal oxide, and a modified compound of each thereof. However, the present application is not limited to these materials, and other conventional materials that can be used as a positive electrode active material for a battery can also be used. These positive electrode active materials can be used alone only one or in combination of two or more. Among them, examples of the lithium transition metal oxide can include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (which can also be referred to as NCM333), LiNi 0.5Co 0.2 Mn 0.3 O2(also can be referred to as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2(also can be referred to as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2(also can be referred to as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2(also can be referred to as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and modified compounds thereof. Examples of the lithium-containing phosphate of olivine structure can include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4(also can be referred to as LFP)), a composite of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite of lithium manganese iron phosphate and carbon.

[0112] In some embodiments, the positive electrode film layer further optionally includes a binder. As an example, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0113] In some embodiments, the positive electrode film layer further optionally includes a conductive agent. As an example, the conductive agent can include at least one of super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0114] In some embodiments, the positive electrode tab can be prepared by coating the positive electrode slurry prepared by any of the above preparation methods on a positive electrode current collector, and after processes such as drying and cold pressing, a positive electrode tab can be obtained.

[0115] [Negative electrode tab]

[0116] The negative electrode tab includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer including a negative electrode active material.

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

[0118] In some embodiments, the negative current collector can employ a metal foil or a composite current collector. For example, as a metal foil, a copper foil can be employed. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer material base layer (e.g., a base layer of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0119] In some embodiments, the negative active material can employ a negative active material for a battery known in the art. As an example, the negative active material can include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, a silicon-based material, a tin-based material, and lithium titanate, etc. The silicon-based material can be selected from at least one of elemental silicon, a silicon oxide compound, a silicon-carbon composite, a silicon-nitrogen composite, and a silicon alloy. The tin-based material can be selected from at least one of elemental tin, a tin oxide compound, and a tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as a negative active material for a battery can also be used. These negative active materials can be used alone or in combination of two or more.

[0120] In some embodiments, the negative film layer can further optionally include 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).

[0121] In some embodiments, the negative film layer can further optionally include a conductive agent. The conductive agent can be selected from at least one of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0122] In some embodiments, the negative film layer can further optionally include other auxiliary agents, such as a thickening agent (e.g., sodium carboxymethyl cellulose (CMC-Na)) and the like.

[0123] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-described components for preparing the negative electrode sheet, such as the negative active material, the conductive agent, the binder, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry, coating the negative electrode slurry on a negative current collector, and drying, cold-pressing, etc.

[0124] [Electrolyte]

[0125] The electrolyte functions to conduct ions between the positive electrode sheet and the negative electrode sheet. The type of electrolyte is not particularly limited in the present application and can be selected as desired. For example, the electrolyte can be liquid, gel, or all-solid.

[0126] In some embodiments, the electrolyte employs an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0127] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluoro oxalato borate, lithium di-oxalato borate, lithium difluoro di-oxalato phosphate, and lithium tetrafluoro oxalato phosphate.

[0128] 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, cyclobutane sulfone, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0129] In some embodiments, the electrolyte solution can optionally further include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can further include an additive capable of improving certain properties of the battery, such as an additive for improving overcharge performance of the battery, an additive for improving high-temperature or low-temperature performance of the battery, etc.

[0130] [Separator]

[0131] In some embodiments, the secondary battery further includes a separator. The type of separator is not particularly limited in the present application and any known porous structure separator having good chemical stability and mechanical stability can be used.

[0132] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of the layers can be the same or different, and are not particularly limited.

[0133] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be used to make an electrode assembly through a winding process or a stacking process.

[0134] In some embodiments, the secondary battery can include an outer package. The outer package can be used to package the electrode assembly and the electrolyte described above.

[0135] In some embodiments, the outer package of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, or the like. The outer package of the secondary battery can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, and as plastic, polypropylene, polybutylene terephthalate, polybutylene succinate, or the like can be listed.

[0136] The shape of the secondary battery is not particularly limited in the present application, and it can be cylindrical, square, or any other shape. For example, Figure 1 is a square structure of a secondary battery 5 as an example.

[0137] In some embodiments, referring to Figure 2 , the outer package can include a shell 51 and a cover plate 53. The shell 51 can include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be provided on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet, and the separator can form an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is packaged in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, which can be selected by those skilled in the art according to specific actual needs.

[0138] In some embodiments, the secondary battery can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0139] Figure 3 is a battery module 4 as an example. Referring to Figure 3 , in the battery module 4, a plurality of secondary batteries 5 can be arranged in sequence along the length direction of the battery module 4. Of course, it can also be arranged in any other way. Further, the plurality of secondary batteries 5 can be fixed by fasteners.

[0140] Optionally, the battery module 4 can also include a housing having a receiving space, and the plurality of secondary batteries 5 are received in the receiving space.

[0141] In some embodiments, the above-mentioned battery module can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0142] Figure 4 and Figure 5 is a battery pack 1 as an example. Referring to Figure 4 and Figure 5In the battery pack 1, a battery case and a plurality of battery modules 4 disposed in the battery case can be included. The battery case includes an upper case 2 and a lower case 3, and the upper case 2 can be disposed on the lower case 3 to form an enclosed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery case in any manner.

[0143] In addition, the application also provides a power consuming device, which includes at least one of the secondary battery, the battery module, or the battery pack provided by the application. The secondary battery, the battery module, or the battery pack can be used as a power supply of the power consuming device, or can be used as an energy storage unit of the power consuming device. The power consuming device can include a mobile device (such as a mobile phone, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto.

[0144] As the power consuming device, the secondary battery, the battery module, or the battery pack can be selected according to the use requirement thereof.

[0145] Figure 6 The power consuming device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirement of the power consuming device for high power and high energy density of the secondary battery, the battery pack or the battery module can be used.

[0146] The power consuming device as another example can be a mobile phone, a tablet computer, a notebook computer, etc. The device usually requires thinning, and the secondary battery can be used as a power supply.

[0147] Example

[0148] Hereinafter, the embodiments of the application will be described. The embodiments described below are exemplary and are only used to explain the application, and cannot be understood as a limitation of the application. If the specific technology or condition is not indicated in the embodiments, the technology or condition described in the literature in the art or according to the product instruction is used. If the reagent or instrument is not indicated by the manufacturer, it is a conventional product that can be obtained by market purchase.

[0149] I. Preparation method

[0150] Example 1

[0151] 1) Preparation of positive electrode slurry

[0152] First stirring: 940 kg of positive electrode active material, 40 kg of polyvinylidene fluoride with a weight average molecular weight of 100,000 were added to a 1300 L double planetary stirrer for mixing to perform first stirring, the revolution speed of the first stirring was 15 revolutions per minute, the stirring time was 15 minutes, and dry mixture was obtained;

[0153] Second stirring: 127.4 kg of NMP (N-methyl pyrrolidone) solvent was added to the double planetary stirrer for mixing with the dry mixture to perform second stirring, wherein the mass of the NMP solvent added in the second stirring was 13% of the total mass of the positive electrode active material and the binder, the revolution speed was 20 revolutions per minute, and the stirring time was 25 minutes, and a primary slurry was obtained;

[0154] Third stirring: 20 kg of conductive carbon black and 245 kg of NMP solvent were mixed with the primary slurry to perform third stirring, wherein the mass of the NMP solvent added in the third stirring was 25% of the total mass of the positive electrode active material and the binder, the revolution speed was 25 revolutions per minute, the rotation speed was 1100 revolutions per minute, and the stirring time was 100 minutes, and a positive electrode slurry was obtained.

[0155] Examples 2-34

[0156] The preparation parameters of the positive electrode slurry were adjusted, and the specific parameters are shown in Table 1.

[0157] Comparative Examples 1-2

[0158] The preparation parameters of the positive electrode slurry were adjusted, and the specific parameters are shown in Table 1.

[0159] Comparative Example 3

[0160] 940 kg of positive electrode active material, 40 kg of polyvinylidene fluoride with a weight average molecular weight of 100,000 were added to a 1300 L double planetary stirrer for mixing to perform first stirring, the revolution speed of the first stirring was 15 revolutions per minute, the stirring time was 15 minutes, and dry mixture was obtained;

[0161] 372.4 kg of NMP (N-methyl pyrrolidone) solvent and 20 kg of conductive carbon black were added to the double planetary stirrer for mixing with the dry mixture to perform stirring, the revolution speed was 20 revolutions per minute, the stirring time was 125 minutes, and the rotation speed was 1100 revolutions per minute, and a positive electrode slurry was obtained.

[0162] The specific parameters are shown in Table 1.

[0163] II. Test Methods

[0164] 1. Test of the difference in solid content between the upper and lower layers of the slurry after 24 hours of standing

[0165] Take the aluminum foil in the moisture meter, weigh, record as M0, the model of the moisture meter is MOC-120H;

[0166] After the slurry is placed for 24 hours, take the upper slurry, a small amount of which is coated on the aluminum foil, the moisture meter is zeroed, and then put into the moisture meter for weighing, record as M1;

[0167] Close the device and start drying;

[0168] After the end, record the weighing data, record as M2, and calculate the solid content, the solid content is (M2-M0) / (M1-M0);

[0169] The solid content of the lower slurry is measured in the same way, and the difference between the solid content of the lower slurry and the solid content of the upper slurry is taken as the difference between the upper and lower solid contents after the slurry is placed for 24 hours

[0170] 2. Viscosity test of the shipped slurry

[0171] After the prepared positive electrode slurry is placed for 10 minutes, the viscosity value measured by the Dveslvtjo rotary viscosity tester (BROOKFIELD) is recorded as the shipped viscosity, wherein the test conditions are: 25℃, rotation speed 12rpm, when the slurry viscosity is not less than 2000mPa·s, 64 rotor is used, and when the slurry viscosity is less than 2000mPa·s, 62 rotor is used. Test in triplicate, and take the average value.

[0172] 3. Viscosity test after the slurry is placed for 24 hours

[0173] After the prepared positive electrode slurry is placed for 24 hours, the viscosity value measured by the Dveslvtjo rotary viscosity tester (BROOKFIELD) is recorded as the 24-hour viscosity, wherein the test conditions are: 25℃, rotation speed 12rpm, when the slurry viscosity is not less than 2000mPa·s, 64 rotor is used, and when the slurry viscosity is less than 2000mPa·s, 62 rotor is used. Test in triplicate, and take the average value.

[0174] 4. Gel state test after the slurry is placed for 24 hours

[0175] After the slurry is placed for 24 hours, the slurry in the beaker is picked up using a steel ruler, and whether the slurry is gel-free, slightly gelled, moderately gelled or severely gelled is determined according to the flow state of the slurry.

[0176] Gel-free state: the slurry flows continuously, and the slurry flows on the surface of the steel ruler without clumping;

[0177] Slightly gelled state: the slurry flows continuously, but the fluid is relatively fine, and the slurry is basically spread on the surface of the steel ruler with slight clumps;

[0178] State of moderate gel: slurry naturally drips, intermittent; discontinuous flow, slurry cannot be flat on the surface of the steel ruler, there are obvious block agglomeration;

[0179] State of severe gel: slurry cannot flow down, block into a lump or directly stay on the steel ruler and cannot flow down.

[0180] III. Analysis of test results of each embodiment and comparative example

[0181] The positive electrode slurry of each embodiment and comparative example was prepared according to the above method, and each parameter was measured, and the results are shown in Tables 1 and 2 below.

[0182] Table 1

[0183]

[0184]

[0185] Table 2

[0186]

[0187]

[0188] According to the results in Tables 1 and 2, the positive electrode slurries in Examples 1-34 are prepared by the slurry preparation method disclosed in the present application, including first stirring, second stirring and third stirring; in the first stirring, the positive electrode active material is mixed and stirred with the binder to prepare a dry mixture; in the second stirring, the solvent is kneaded with the dry mixture to prepare a primary slurry; in the third stirring, the conductive agent and the solvent are mixed and stirred with the primary slurry to prepare the positive electrode slurry; wherein the solvent used in the second stirring is the same as the solvent used in the third stirring, and the mass content of the solvent used in the second stirring is 10%-15% based on the total mass of the positive electrode active material and the binder.

[0189] As can be seen from the comparison of Examples 1-3 and Comparative Examples 1-2, controlling the mass content of the solvent used in the second stirring to be 10%-15% of the total mass of the positive electrode active material and the binder can reduce the delivery viscosity of the slurry and the viscosity of the slurry after standing for 24 hours, reduce the difference in solid content between the upper and lower layers of the slurry after standing for 24 hours, improve the anti-settling property and anti-gelling property of the slurry, improve the storage performance of the slurry, and broaden the process window of slurry coating.

[0190] From the comparison of Examples 1-3, 5-7, 9-10, 12-14, 16-18, 20-26, 28-30, 32-34 and Comparative Example 3, it can be seen that the preparation method of the present application can reduce the viscosity of the slurry after 24 hours of standing, reduce the difference in solid content between the upper and lower layers of the slurry after 24 hours of standing, slow down the gelation of the slurry, improve the anti-settling and anti-gel properties of the slurry, improve the storage performance of the slurry, and broaden the process window for coating the slurry.

[0191] From the comparison of Examples 1, 5-6 and Example 4, it can be seen that controlling the mass content of the solvent used in the third stirring to be 20%-30% of the total mass of the positive active material and the binder can reduce the delivery viscosity and the viscosity after 24 hours of standing of the slurry, improve the coatability and processability of the slurry, and can reduce the difference in solid content between the upper and lower layers of the slurry after 24 hours of standing, slow down the gelation of the slurry, improve the anti-settling and anti-gel properties of the slurry, improve the storage performance of the slurry, and broaden the process window for coating the slurry. From the comparison of Examples 1, 5-6 and Example 7, it can be seen that without significantly changing the delivery viscosity of the slurry, the viscosity of the slurry after 24 hours of standing, the difference in solid content between the upper and lower layers of the slurry after 24 hours of standing, and the gelation of the slurry, controlling the mass content of the solvent used in the third stirring to be 20%-30% of the total mass of the positive active material and the binder can reduce the use of solvent and reduce costs, and can balance the slurry quality and costs.

[0192] From the comparison of Examples 1, 12-13 and Example 11, it can be seen that controlling the revolution speed in the first stirring to be 10-20 rpm can reduce the delivery viscosity and the viscosity after 24 hours of standing of the slurry, improve the coatability and processability of the slurry, and can reduce the difference in solid content between the upper and lower layers of the slurry after 24 hours of standing, slow down the gelation of the slurry, improve the anti-settling and anti-gel properties of the slurry, and improve the stability and storage performance of the slurry. From the comparison of Examples 1, 12-13 and Example 14, it can be seen that without significantly changing the delivery viscosity of the slurry, the viscosity of the slurry after 24 hours of standing, the difference in solid content between the upper and lower layers of the slurry after 24 hours of standing, and the gelation of the slurry, controlling the revolution speed in the first stirring to be 10-20 rpm can reduce the power of the stirrer, save energy, and can balance the slurry quality and costs.

[0193] From the comparison of Example 1, 9 and Example 8, it can be seen that controlling the stirring time in the first stirring to be 10-15 minutes can reduce the delivery viscosity and the viscosity after 24 hours of the slurry, improve the coating property and processability of the slurry, and can reduce the difference of solid content between upper and lower layers of the slurry after 24 hours of standing, slow down the gel phenomenon of the slurry, improve the anti-settling property and anti-gel property of the slurry, and improve the stability and storage property of the slurry. From the comparison of Example 1, 9 and Example 10, it can be seen that without significantly changing the delivery viscosity of the slurry, the viscosity after 24 hours of standing of the slurry, the difference of solid content between upper and lower layers of the slurry after 24 hours of standing, and the gel phenomenon of the slurry, controlling the stirring time in the first stirring to be 10-15 minutes can reduce the working time of the slurry preparation, improve the working efficiency of the slurry preparation, and reduce the cost.

[0194] From the comparison of Example 1, 16-17 and Example 15, it can be seen that controlling the revolving speed in the second stirring to be 15-25 rpm can reduce the delivery viscosity and the viscosity after 24 hours of the slurry, improve the coating property and processability of the slurry, and can reduce the difference of solid content between upper and lower layers of the slurry after 24 hours of standing, slow down the gel phenomenon of the slurry, improve the anti-settling property and anti-gel property of the slurry, and improve the stability and storage property of the slurry. From the comparison of Example 1, 16-17 and Example 18, it can be seen that without significantly changing the delivery viscosity of the slurry, the viscosity after 24 hours of standing of the slurry, the difference of solid content between upper and lower layers of the slurry after 24 hours of standing, and the gel phenomenon of the slurry, controlling the revolving speed in the second stirring to be 15-25 rpm can reduce the power of the stirrer, save energy, and can balance the slurry quality and cost.

[0195] From the comparison of Example 1, 20-21 and Example 19, it can be seen that controlling the stirring time in the second stirring to be 20-30 minutes can reduce the delivery viscosity and the viscosity after 24 hours of the slurry, improve the coating property and processability of the slurry, and can reduce the difference of solid content between upper and lower layers of the slurry after 24 hours of standing, slow down the gel phenomenon of the slurry, improve the anti-settling property and anti-gel property of the slurry, and improve the stability and storage property of the slurry. From the comparison of Example 1, 20-21 and Example 22, it can be seen that without significantly changing the delivery viscosity of the slurry, the viscosity after 24 hours of standing of the slurry, the difference of solid content between upper and lower layers of the slurry after 24 hours of standing, and the gel phenomenon of the slurry, controlling the stirring time in the second stirring to be 20-30 minutes can reduce the working time of the slurry preparation, improve the working efficiency of the slurry preparation, and reduce the cost.

[0196] From the comparison of Example 1, 24-25 and Example 23, it can be seen that controlling the revolution speed in the third stirring to be 20-30 rpm can reduce the delivery viscosity and the viscosity after 24 hours of the slurry, improve the coating property and processability of the slurry, and can reduce the difference of solid content between the upper and lower layers of the slurry after 24 hours of standing, slow down the gel phenomenon of the slurry, improve the anti-settling property and anti-gel property of the slurry, and improve the stability and storage property of the slurry. From the comparison of Example 1, 24-25 and Example 26, it can be seen that controlling the revolution speed in the third stirring to be 20-30 rpm can reduce the power of the stirrer, save energy, and can balance the slurry quality and cost, without obviously changing the delivery viscosity, the viscosity after 24 hours of the slurry, the difference of solid content between the upper and lower layers of the slurry after 24 hours of standing, and the gel phenomenon of the slurry.

[0197] From the comparison of Example 1, 28-29 and Example 27, it can be seen that controlling the rotation speed in the third stirring to be 1000-1200 rpm can reduce the delivery viscosity and the viscosity after 24 hours of the slurry, improve the coating property and processability of the slurry, and can reduce the difference of solid content between the upper and lower layers of the slurry after 24 hours of standing, slow down the gel phenomenon of the slurry, improve the anti-settling property and anti-gel property of the slurry, and improve the stability and storage property of the slurry. From the comparison of Example 1, 28-29 and Example 30, it can be seen that controlling the rotation speed in the third stirring to be 1000-1200 rpm can reduce the power of the stirrer, save energy, and can balance the slurry quality and cost, without obviously changing the delivery viscosity, the viscosity after 24 hours of the slurry, the difference of solid content between the upper and lower layers of the slurry after 24 hours of standing, and the gel phenomenon of the slurry.

[0198] From the comparison of Example 1, 32-33 and Example 31, it can be seen that controlling the stirring time in the third stirring to be 90-110 minutes can reduce the delivery viscosity and the viscosity after 24 hours of the slurry, improve the coating property and processability of the slurry, and can reduce the difference of solid content between the upper and lower layers of the slurry after 24 hours of standing, slow down the gel phenomenon of the slurry, improve the anti-settling property and anti-gel property of the slurry, and improve the stability and storage property of the slurry. From the comparison of Example 1, 32-33 and Example 34, it can be seen that controlling the stirring time in the third stirring to be 90-110 minutes can reduce the working time of the slurry preparation, improve the working efficiency of the slurry preparation, and reduce the cost, without obviously changing the delivery viscosity, the viscosity after 24 hours of the slurry, the difference of solid content between the upper and lower layers of the slurry after 24 hours of standing, and the gel phenomenon of the slurry.

[0199] As can be seen from Examples 1 to 34, the delivery viscosity of the positive electrode slurry is 7500 mPa·s to 40000 mPa·s, the slurry has a suitable viscosity, which can improve the coating property and processability of the slurry, and meanwhile, the suitable slurry viscosity makes the slurry have good anti-settling property and anti-gelling property, thereby improving the stability and storability of the slurry.

[0200] It should be noted that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and embodiments having substantially the same configuration as the technical idea and exerting the same effects within the scope of the technical solution of the present application are all included in the technical scope of the present application. Furthermore, within the scope of the gist of the present application, various modifications that can be thought of by those skilled in the art, other modes constructed by combining part of the configuration elements of the embodiments are also included in the scope of the present application.

Claims

1. A method for preparing a positive electrode slurry, characterized by, The first stirring, the second stirring and the third stirring are included. In the first stirring, the positive active material is mixed with the binder to prepare a dry mixture; In the second stirring, the solvent is kneaded with the dry mixture to prepare a primary slurry; In the third stirring, the conductive agent and the solvent are mixed with the primary slurry to prepare a positive electrode slurry; The solvent used in the second stirring is the same as the solvent used in the third stirring, and the mass content of the solvent used in the second stirring is 10%-15% based on the total mass of the positive active material and the binder; The stirring time of the first stirring is 10-15 minutes, and the revolution speed is 10-20 revolutions per minute; The stirring time of the second stirring is 20-30 minutes, and the revolution speed is 15-25 revolutions per minute; The stirring time of the third stirring is 100-110 minutes, and the rotation speed is 1100-1200 revolutions per minute; and the mass content of the solvent used in the third stirring is 20%-30% based on the total mass of the positive active material and the binder.

2. The production method according to claim 1, characterized by, The third stirring satisfies the revolution speed of 20-30 revolutions per minute.

3. The production method according to claim 1 or 2, characterized by, In the positive electrode slurry, the mass ratio of the total mass of the positive active material, the total mass of the binder and the mass of the conductive agent is (90-96):(2-6):(2-4).

4. A positive electrode slurry, characterized by, The positive electrode slurry is prepared by the preparation method of the positive electrode slurry according to any one of claims 1-3.

5. The positive electrode slurry according to claim 4, characterized by, The solid content of the positive electrode slurry is 65%-75%, and the delivery viscosity of the positive electrode slurry is 7500-40000 mPa·s.

6. The positive electrode slurry according to claim 5, characterized by, The delivery viscosity of the positive electrode slurry is 7500-25000 mPa·s.

7. The positive electrode slurry according to claim 4, wherein The solid content of the positive electrode slurry is 65%-75%, and the viscosity of the positive electrode slurry after standing for 24 hours is not more than 49000 mPa·s.

8. The positive electrode slurry according to claim 7, characterized by, The viscosity of the positive electrode slurry after standing for 24 hours is not more than 30000 mPa·s.

9. A positive electrode sheet characterized by comprising: The positive electrode slurry is prepared by the preparation method of the positive electrode slurry according to any one of claims 1-3.

10. A secondary battery characterized by comprising: The secondary battery includes the separator film, the negative electrode tab and the positive electrode tab according to claim 9.

11. An electrical device, characterized by The secondary battery includes the secondary battery according to claim 10.

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