WO2024098419A1 - 正极浆料的制备方法、二次电池、电池包和用电装置 - Google Patents

正极浆料的制备方法、二次电池、电池包和用电装置 Download PDF

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Publication number
WO2024098419A1
WO2024098419A1 PCT/CN2022/131535 CN2022131535W WO2024098419A1 WO 2024098419 A1 WO2024098419 A1 WO 2024098419A1 CN 2022131535 W CN2022131535 W CN 2022131535W WO 2024098419 A1 WO2024098419 A1 WO 2024098419A1
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Prior art keywords
stirring
positive electrode
slurry
rpm
electrode slurry
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PCT/CN2022/131535
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English (en)
French (fr)
Inventor
邢祁
欧阳楚英
孙成栋
刘会会
段连威
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex Technology Co Ltd
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Priority to EP22964887.8A priority Critical patent/EP4593093A4/en
Priority to KR1020257013610A priority patent/KR20250078491A/ko
Priority to CN202280092936.4A priority patent/CN118786536A/zh
Priority to JP2025522837A priority patent/JP2025535420A/ja
Priority to PCT/CN2022/131535 priority patent/WO2024098419A1/zh
Publication of WO2024098419A1 publication Critical patent/WO2024098419A1/zh
Priority to US19/201,937 priority patent/US20250273685A1/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1397—Processes of manufacture of electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • H01M4/623—Binders being polymers fluorinated polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the technical field of secondary batteries, and in particular to a method for preparing a positive electrode slurry for a secondary battery, a secondary battery, a battery pack and an electrical device.
  • secondary batteries are widely used in energy storage power supply systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.
  • Electrode slurry is the basis for forming electrodes and is also the first step in the production of secondary batteries.
  • the characteristics of electrode slurry have a significant impact on subsequent electrode production and battery performance.
  • the positive electrode slurry is mainly a solid-liquid mixed system formed by positive electrode active materials, conductive agents, binders and solvents. This system is in a metastable state.
  • the slurry preparation process that is, the slurry preparation method, has a crucial influence on the dispersibility, uniformity, stability and other properties of the slurry.
  • the slurry preparation process in the prior art is often a one-step process, in which the components in the positive electrode active slurry are directly mixed and stirred.
  • the one-step preparation method cannot meet the manufacturing requirements of binders with different weight average molecular weights, and the slurry preparation process has poor versatility, which is not conducive to reducing manufacturing costs. Therefore, it is necessary to develop a new slurry preparation method that is suitable for binders with different weight average molecular weights.
  • the present application is made in view of the above-mentioned problems, and its purpose is to provide a method for preparing positive electrode slurry for secondary batteries to adapt to binders with different weight-average molecular weights, broaden the process window for coating the positive electrode slurry, and improve the processing performance of the positive electrode slurry.
  • the present application provides a method for preparing a positive electrode slurry, including first stirring, second stirring, third stirring and fourth stirring; in the first stirring, the positive electrode active material and the conductive agent are mixed and stirred to prepare a dry mixture; in the second stirring, the binder and the solvent are mixed and stirred to prepare a glue solution; in the third stirring, the dry mixture and the glue solution are mixed and stirred to prepare a primary slurry; in the fourth stirring, the binder, the solvent and the primary slurry are mixed and stirred to prepare a positive electrode slurry; the binder and the solvent used in the second stirring are respectively the same as the binder and the solvent used in the fourth stirring; based on the total mass of the binder used in the second stirring and the binder used in the fourth stirring, the mass ratio of the binder used in the second stirring is 50% to 70%, and the mass ratio of the binder used in the fourth stirring is 30% to 50%.
  • the preparation method of the positive electrode slurry disclosed in the present application is more widely applicable than the existing preparation method of the positive electrode slurry, and is suitable for slurries containing binders with different weight-average molecular weights.
  • the present application reduces the shipping viscosity of the positive electrode slurry and the viscosity after standing for 24 hours by step-by-step slurry mixing, alleviates the gelation phenomenon of the positive electrode slurry, and improves the applicability of the preparation method for binders with large molecular weight.
  • the preparation method has a wider universality, expands the process window for coating the positive electrode slurry, and improves the processing performance of the positive electrode slurry.
  • the binder comprises at least one polyvinylidene fluoride having a weight average molecular weight of 800,000 to 8,000,000.
  • the preparation method disclosed in the present application is universal for low molecular weight polyvinylidene fluoride binders and high molecular weight polyvinylidene fluoride binders, can effectively alleviate the gelation phenomenon of different slurries, help improve production efficiency, and broaden the coating window of the slurry.
  • the preparation method disclosed in the present application can be applied to binders with a weight average molecular weight of up to 8 million, so that the slurry containing the high weight average molecular weight binder still has low shipping viscosity and anti-gel properties, which can meet the use requirements of the new generation of binders.
  • the third stirring is performed firstly at a low speed and then at a high speed.
  • the dry mixture and the glue are first stirred at a low speed, so that the dry mixture is fully dispersed in the glue while avoiding excessive shearing of the dry mixture, thereby ensuring the integrity of the positive electrode active material and the conductive agent.
  • the glue is coated on the positive electrode active material and the conductive agent, which can avoid the subsequent high-speed stirring from destroying the structure and size of the positive electrode active material and the conductive agent.
  • High-speed stirring after low-speed stirring can reduce the viscosity of the slurry while ensuring the material performance.
  • the revolution speed of the low-speed stirring in the third stirring is 15 to 25 rpm, the rotation speed is 400 to 800 rpm, and the stirring time is 5 to 15 minutes.
  • the revolution speed, rotation speed and stirring time of the high-speed stirring in the third stirring are controlled within an appropriate range, so that the slurry has low shipping viscosity, low viscosity after standing for 24 hours and excellent anti-gelling property, which is beneficial to improving the coating performance, processing performance and stability of the slurry.
  • the revolution speed of the high-speed stirring in the third stirring is 20 to 30 rpm, the rotation speed is 1000 to 1300 rpm, and the stirring time is 50 to 80 minutes.
  • the revolution speed, rotation speed and stirring time of the high-speed stirring in the third stirring are controlled within an appropriate range, so that the slurry has low shipping viscosity, low viscosity after standing for 24 hours and excellent anti-gelling property, which is beneficial to improving the coating performance, processing performance and stability of the slurry.
  • the rotation speed of the first stirring is 0.
  • Controlling the rotation speed of the first stirring to 0 can minimize the shear force of the first stirring, fully reduce the possibility of excessive crushing of the positive electrode active material and the conductive agent, ensure that the positive electrode active material and the conductive agent have a certain particle size and specific surface area, help to improve the dispersion effect of the positive electrode active material and the conductive agent, reduce the viscosity of the slurry after standing for 24 hours, slow down the gelation phenomenon of the slurry, and improve the stability of the slurry.
  • the revolution speed of the first stirring is 20 rpm to 30 rpm.
  • the revolution speed of the first stirring is controlled within a suitable range so that the slurry has low shipping viscosity, low viscosity after standing for 24 hours and low anti-gelling property, which is beneficial to improving the coating performance, processing performance and stability of the slurry.
  • the stirring time of the first stirring is 5 minutes to 20 minutes.
  • the stirring time of the first stirring is controlled within a suitable range so that the slurry has low shipping viscosity, low viscosity after standing for 24 hours and low anti-gelling property, which is beneficial to improving the coating performance, processing performance and stability of the slurry.
  • the stirring time of the second stirring is 50 minutes to 80 minutes.
  • the stirring time of the second stirring is controlled within a suitable range so that the slurry has low shipping viscosity, low viscosity after standing for 24 hours and low gel resistance, which is beneficial to improving the coating performance, processing performance and stability of the slurry.
  • the revolution speed of the second stirring is 25 rpm to 40 rpm.
  • the revolution speed of the second stirring is controlled within a suitable range so that the slurry has a low shipping viscosity and a low viscosity after standing for 24 hours. This is also beneficial to slowing down the gel state of the slurry, improving the stability of the slurry, and widening the process window.
  • the rotation speed of the second stirring is 1000 rpm to 1300 rpm.
  • the rotation speed of the second stirring is controlled within a suitable range so that the slurry has low shipping viscosity, low viscosity after standing for 24 hours and low anti-gelling property, thereby improving the coating performance, processing performance and stability of the slurry.
  • the stirring time of the fourth stirring is 60 minutes to 90 minutes.
  • the stirring time of the fourth stirring is controlled within a suitable range so that the slurry has a low shipping viscosity and a low viscosity after standing for 24 hours. This is also beneficial for slowing down the gel state of the slurry, improving the stability of the slurry, and widening the process window.
  • the revolution speed of the fourth stirring is 25 rpm to 40 rpm.
  • the revolution speed of the fourth stirring is controlled within a suitable range so that the slurry has a low shipping viscosity and a low viscosity after standing for 24 hours. This is also beneficial to slowing down the gel state of the slurry, improving the stability of the slurry, and widening the process window.
  • the rotation speed of the fourth stirring is 1000 rpm to 1300 rpm.
  • the stirring time of the fourth stirring is controlled within a suitable range so that the slurry has a low shipping viscosity and a low viscosity after standing for 24 hours. This is also beneficial for slowing down the gel state of the slurry, improving the stability of the slurry, and widening the process window.
  • the solid content of the positive electrode slurry is 65% to 70%, and the viscosity of the positive electrode slurry is 6000 to 31000 mPa ⁇ s.
  • the slurry formed by the preparation method of the present application has a high solid content, suitable viscosity, and excellent processability.
  • the above slurry can be directly used in the subsequent coating process, which can improve production efficiency.
  • the mass percentage of the solvent used in the second stirring is 35% to 45%, and the mass percentage of the solvent used in the fourth stirring is 4% to 10%.
  • the ratio of the mass of the positive electrode active material, the total mass of the binder, and the mass of the conductive agent is (88-96):(2-4):(2-8).
  • the positive electrode slurry within the above range has good processing performance and also enables the formed positive electrode plate to have excellent electrochemical performance.
  • the positive electrode active material is at least one of lithium iron phosphate and its modified materials, lithium nickel cobalt manganese oxide and its modified materials, and the modified material is prepared by one or more modification methods of doping, conductive carbon coating, conductive metal coating, and conductive polymer coating.
  • the solvent is selected from one or more of N-methyl-2-pyrrolidone, N,N-dimethylpropionamide, N,N-diethylpropionamide, N,N-dipropylpropionamide, N,N-dibutylpropionamide, N,N-dimethylethylpropionamide and 3-butoxy-N-methylpropionamide.
  • the second aspect of the present application further provides a positive electrode slurry, which is prepared by the method for preparing the positive electrode slurry of the first aspect.
  • the solid content of the positive electrode slurry is 65% to 70%
  • the initial viscosity of the positive electrode slurry is 6000 to 31000 mPa ⁇ s
  • the viscosity of the positive electrode slurry does not exceed 49000 mPa ⁇ s.
  • the positive electrode slurry provided in the present application has a high solid content, suitable viscosity, and excellent processability, and the slurry also has excellent storage performance.
  • the third aspect of the present application also provides a secondary battery, comprising a positive electrode sheet, a separator, a negative electrode sheet and an electrolyte, wherein the positive electrode sheet is prepared by the positive electrode slurry prepared by the method for preparing the positive electrode slurry described in the first aspect or the positive electrode slurry described in the second aspect.
  • the positive electrode sheet has high quality and production efficiency.
  • the secondary battery is any one of a lithium ion battery, a sodium ion battery, a magnesium ion battery, and a potassium ion battery.
  • the fourth aspect of the present application further provides a battery module, comprising the secondary battery described in the third aspect of the present application.
  • a fifth aspect of the present application provides a battery pack, comprising the secondary battery described in the third aspect of the present application or the battery module described in the fourth aspect of the present application.
  • the sixth aspect of the present application provides an electrical device comprising at least one selected from the secondary battery of the third aspect of the present application, the battery module of the fourth aspect of the present application, or the battery pack of the fifth aspect of the present application.
  • FIG1 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG2 is an exploded view of the secondary battery according to one embodiment of the present application shown in FIG1 ;
  • FIG3 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG4 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG5 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG4 ;
  • FIG. 6 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.
  • “Scope” disclosed in the present application is defined in the form of lower limit and upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a particular range.
  • the scope defined in this way can include or exclude end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range.
  • the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected.
  • the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4 and 5 are listed, the following range can be fully expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5.
  • the numerical range "a-b” represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers.
  • the numerical range "0-5" represents that all real numbers between "0-5" have been fully listed herein, and "0-5" is just the abbreviation of these numerical combinations.
  • a parameter is expressed as an integer ⁇ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • the method may further include step (c), which means that step (c) may be added to the method in any order.
  • the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.
  • the “include” and “comprising” mentioned in this application represent open-ended or closed-ended expressions.
  • the “include” and “comprising” may represent that other components not listed may also be included or only the listed components may be included or only the listed components may be included.
  • the term "or” is inclusive.
  • the phrase “A or B” means “A, B, or both A and B”. More specifically, any 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 both A and B are true (or exist).
  • the positive electrode slurry is mainly a solid-liquid mixed system formed by positive electrode active materials, conductive agents, binders and solvents.
  • slurry is often mixed by stirring, ball milling, ultrasound and other processes.
  • the slurry mixing process in the prior art is usually only applicable to slurry systems with fixed components, and has poor versatility. After the physical properties of the components in the slurry change, the slurry mixing process often needs to be adjusted.
  • the slurry mixing process in the prior art cannot be applied to high molecular weight binders, nor can it be applied to binders with large weight average molecular weight dispersibility and poor batch stability.
  • the performance of slurries using different batches of binders prepared using the same slurry mixing process in the prior art is greatly different, and the slurry is prone to gel, which is difficult to meet the production requirements of pole pieces.
  • the present application proposes a method for preparing a positive electrode slurry, including first stirring, second stirring, third stirring and fourth stirring; in the first stirring, the positive electrode active material and the conductive agent are mixed and stirred to prepare a dry mixture; in the second stirring, the binder and the solvent are mixed and stirred to prepare a glue solution; in the third stirring, the dry mixture and the glue solution are mixed and stirred to prepare a primary slurry; in the fourth stirring, the binder, the solvent and the primary slurry are mixed and stirred to prepare a positive electrode slurry; the binder and the solvent used in the second stirring are respectively the same as the binder and the solvent used in the fourth stirring; based on the total mass of the binder used in the second stirring and the binder used in the fourth stirring, the mass ratio of the binder used in the second stirring is 50% to 70%, and the mass ratio of the binder used in the fourth stirring is 30% to 50%.
  • the positive electrode active material is a transition metal oxide containing lithium. In some embodiments, the positive electrode active material is at least one of lithium iron phosphate and its modified materials, lithium nickel cobalt manganese oxide and its modified materials, and the modified material is prepared by one or more modification methods selected from doping, conductive carbon coating, conductive metal coating, and conductive polymer coating.
  • the conductive agent may include at least one of superconducting carbon, carbon black, carbon nanotubes, graphene, and carbon nanofibers.
  • the solvent is an aqueous medium, such as deionized water.
  • 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-dimethylethylpropionamide and 3-butoxy-N-methylpropionamide.
  • the positive electrode active material and the conductive agent are first stirred to obtain a dry mixture, and the first stirring makes the two mechanically riveted to form a tight entanglement; then the binder and the solvent are mixed and stirred for the second time to prepare the glue solution, which can achieve effective dispersion of the binder in the solvent and avoid agglomeration and flocculation caused by direct mixing and stirring of the binder with other materials; then the dry mixture formed by the positive electrode active material and the conductive agent is mixed with the glue solution for the third stirring to prepare the primary slurry, and the third stirring can effectively disperse the positive electrode active material and the conductive agent in the glue solution, and the binder in the glue solution can improve the stability of the slurry through electrostatic action and steric hindrance, and reduce the agglomeration and sedimentation of the positive electrode active material and the conductive agent; finally, the binder and the solvent are mixed with the primary slurry for the fourth stirring to obtain the positive electrode slurry, and the binder added again
  • the mass ratio of the binder used in the second stirring is 50% to 70%, and the mass ratio of the binder used in the fourth stirring is 30% to 50%. If the mass of the binder added in the second stirring or the fourth stirring is too much or too little, it is impossible to effectively reduce the viscosity of the slurry after standing for 24 hours, and the purpose of slowing down the gelation of the slurry cannot be achieved.
  • the preparation method of the positive electrode slurry in the prior art has poor compatibility and cannot adapt to the difference in the weight average molecular weight of the binder in the slurry. Therefore, a very high precision requirement is put forward for the material.
  • the present application reduces the shipping viscosity and the viscosity of the positive electrode slurry after standing for 24 hours by step-by-step slurry mixing, alleviates the gelation phenomenon of the positive electrode slurry, and makes the slurry with a high weight average molecular weight binder still have a low shipping viscosity and viscosity and anti-coagulation after standing for 24 hours, thereby improving the universality of the preparation method.
  • the preparation method of the present application is not only applicable to binders with low weight average molecular weight, but also to binders with high weight average molecular weight, which can effectively alleviate the gelation phenomenon of different slurries, help to improve production efficiency, and broaden the process window of slurry coating.
  • process window refers to the process range that can ensure product quality, including but not limited to temperature range, pressure range, storage time length, etc. It can be understood that the wider the process window, the lower the requirement for process accuracy.
  • the binder comprises at least one polyvinylidene fluoride having a weight average molecular weight of 800,000 to 8,000,000.
  • the weight average molecular weight of the polyvinylidene fluoride can be any one of 800,000, 1,000,000, 1,500,000, 2,000,000, 2,500,000, 3,000,000, 3,500,000, 4,000,000, 4,500,000, 5,000,000, 5,500,000, 6,000,000, 6,500,000, 7,000,000, 7,500,000, and 8,000,000.
  • weight average molecular weight refers to the statistical average molecular weight of a polymer by mass, the molecular weight averaged over a unit weight.
  • the slurry mixing process in the prior art is difficult to apply to binders with high weight average molecular weight.
  • the positive electrode slurry with a high molecular weight binder prepared by the prior art tends to have a high shipping viscosity, which is difficult to meet the coating requirements and is prone to serious gelation.
  • the preparation method disclosed in the present application can be applied to binders with a weight average molecular weight of up to 8 million by adding the binder step by step and coordinating the stirring speed, so that the slurry still has a low shipping viscosity and viscosity after standing for 24 hours and good anti-gel properties, which can meet the use requirements of high molecular weight binders.
  • the third stirring is first performed at a low speed and then at a high speed. It is understood that the low speed and high speed stirring are relative. If the speed of the low speed stirring in the third stirring is v1 and the speed of the high speed stirring is v2, then v1 is lower than v2, and v1 and v2 represent the rotation speeds of the stirring.
  • the dry mixture and the glue liquid are first stirred at a low speed, so that the dry mixture is fully dispersed in the glue liquid while avoiding excessive shearing of the dry mixture, thereby ensuring the integrity of the positive electrode active material and the conductive agent structure.
  • the glue liquid is coated on the surface of the positive electrode active material and the conductive agent, which can avoid subsequent high-speed stirring causing excessive shearing of the positive electrode active material and the conductive agent.
  • High-speed stirring followed by low-speed stirring can reduce the viscosity of the slurry, thereby providing the possibility for the subsequent preparation of positive electrode slurry with low shipping viscosity.
  • the revolution speed of the low-speed stirring in the third stirring is 15 to 25 rpm, the rotation speed is 400 to 800 rpm, and the stirring time is 5 to 15 minutes.
  • rotational speed refers to the speed at which the agitator rotates about its own axis.
  • bital speed refers to the speed at which the agitator rotates around the vessel containing the material.
  • the revolution speed of the low-speed stirring in the third stirring may be any one of 15 rpm, 20 rpm, and 25 rpm.
  • the rotation speed of the low-speed stirring in the third stirring can be selected as any one of 400 rpm, 500 rpm, 600 rpm, 700 rpm, and 800 rpm.
  • the stirring time of the low-speed stirring in the third stirring may be any one of 5 minutes, 10 minutes, and 15 minutes.
  • the stirring device is a planetary mixer.
  • the working principle of the planetary mixer is that after the mixer is started, the planetary frame rotates, driving the stirring shaft in the box to rotate, and the stirring shaft rotates at high speed while revolving around the axis of the barrel, so that the material is subjected to strong shearing and kneading. It can be understood that the preparation method provided in this application is applicable to any type of planetary mixer.
  • the rotation speed of the low-speed stirring in the third stirring is too low or the rotation speed is too low or the stirring time is too short, the dry mixture formed by the conductive agent and the active material cannot be effectively dispersed in the glue solution, the viscosity of the slurry when shipped and the viscosity after standing for 24 hours are too large, the slurry is prone to gelling, and the stability of the slurry is poor; if the rotation speed of the low-speed stirring in the third stirring is too high or the rotation speed is too high or the stirring time is too long, it is impossible to further significantly improve the viscosity of the slurry when shipped, the viscosity of the slurry after standing for 24 hours, and the gelation phenomenon of the slurry, and it will lead to waste of energy and increase in preparation costs.
  • controlling the revolution speed, rotation speed and stirring time of the low-speed stirring in the third stirring within an appropriate range can make the slurry have low shipping viscosity, low viscosity after standing for 24 hours and excellent anti-gelling properties, which is beneficial to improving the coating performance, processing performance and stability of the slurry.
  • the revolution speed of the high-speed stirring in the third stirring is 20 rpm to 30 rpm, the rotation speed is 1000 rpm to 1300 rpm, and the stirring time is 50 minutes to 80 minutes.
  • the revolution speed of the high-speed stirring in the third stirring can be selected as any one of 20 rpm, 25 rpm, and 30 rpm.
  • the rotation speed of the high-speed stirring in the third stirring can be selected as any one of 1000 rpm, 1100 rpm, 1200 rpm, and 1300 rpm.
  • the stirring time of the high-speed stirring in the third stirring may be any one of 50 minutes, 60 minutes, 70 minutes, and 80 minutes.
  • the rotation speed of the high-speed stirring in the third stirring is too low or the rotation speed is too low or the stirring time is too short, the primary slurry cannot be strongly sheared, the slurry's shipping viscosity and the viscosity after standing for 24 hours are too large, the slurry is prone to gelling, and the slurry stability is poor; if the rotation speed of the high-speed stirring in the third stirring is too high or the rotation speed is too high or the stirring time is too long, it is impossible to further significantly improve the slurry's shipping viscosity, the slurry's viscosity after standing for 24 hours and the gelation phenomenon of the slurry, and it will lead to waste of energy and reduced production efficiency.
  • controlling the revolution speed, rotation speed and stirring time of the high-speed stirring in the third stirring within an appropriate range makes the slurry have low shipping viscosity, low viscosity after standing for 24 hours and excellent anti-gelling property, which is beneficial to improving the coating performance, processing performance and stability of the slurry.
  • the rotation speed of the first stirring is 0.
  • Controlling the rotation speed of the first stirring to 0 can minimize the shear force of the first stirring, fully reduce the possibility of excessive breakage of the active material and the conductive agent, ensure that the positive electrode active material and the conductive agent have a certain particle size and specific surface area, help to improve the dispersion effect of the positive electrode active material and the conductive agent, reduce the viscosity of the slurry after standing for 24 hours, slow down the gelation phenomenon of the slurry, and improve the stability of the slurry.
  • the revolution speed of the first stirring is 20 rpm to 30 rpm.
  • the revolution speed of the first stirring can be selected as any one of 20 rpm, 25 rpm, and 30 rpm.
  • the rotation speed of the first stirring is too low, the positive electrode active material and the conductive agent cannot be effectively mixed, the viscosity of the slurry as shipped and the viscosity after standing for 24 hours are too high, the slurry is prone to gelling, and the stability of the slurry is poor; if the rotation speed of the first stirring is too high, the viscosity of the slurry as shipped, the viscosity of the slurry after standing for 24 hours, and the gelation phenomenon of the slurry cannot be further significantly improved, but instead it leads to waste of energy and increase in production costs.
  • the revolution speed of the first stirring is controlled within a suitable range so that the slurry has low shipping viscosity, low viscosity after standing for 24 hours and low anti-gelling property, which is beneficial to improving the coating performance, processing performance and stability of the slurry.
  • the stirring time of the first stirring is 5 minutes to 20 minutes. In some embodiments, the stirring time of the first stirring can be any one of 5 minutes, 10 minutes, 15 minutes, and 20 minutes.
  • the stirring time of the first stirring is too short, the positive electrode active material and the conductive agent cannot be effectively mixed, the viscosity of the slurry as shipped and the viscosity after standing for 24 hours are too large, the slurry is prone to gelling, and the stability of the slurry is poor; if the stirring time of the first stirring is too long, it is impossible to further significantly improve the viscosity of the slurry as shipped, the viscosity of the slurry after standing for 24 hours, and the gelation phenomenon of the slurry, but instead lead to waste of energy and reduced production efficiency.
  • the stirring time of the first stirring is controlled within a suitable range so that the slurry has low shipping viscosity, low viscosity after standing for 24 hours and low anti-gelling property, which is beneficial to improving the coating performance, processing performance and stability of the slurry.
  • the stirring time of the second stirring is 50 minutes to 80 minutes. In some embodiments, the stirring time of the second stirring can be any one of 50 minutes, 60 minutes, 70 minutes, and 80 minutes.
  • the stirring time of the second stirring is too short, the binder and the solvent cannot be effectively mixed, the viscosity of the slurry when shipped and the viscosity after standing for 24 hours are too large, the slurry is prone to gel, and the stability of the slurry is poor; if the stirring time of the second stirring is too long, it is impossible to further significantly improve the viscosity of the slurry when shipped, the viscosity of the slurry after standing for 24 hours, and the gelation phenomenon of the slurry, but instead lead to waste of energy and reduced production efficiency.
  • the stirring time of the second stirring is controlled within a suitable range so that the slurry has low shipping viscosity, low viscosity after standing for 24 hours and low anti-gelling property, which is beneficial to improving the coating performance, processing performance and stability of the slurry.
  • the revolution speed of the second stirring is 25 rpm to 40 rpm. In some embodiments, the revolution speed of the second stirring can be any one of 25 rpm, 30 rpm, 35 rpm, and 40 rpm.
  • the revolution speed of the second stirring is controlled within a suitable range so that the slurry has a low shipping viscosity and a low viscosity after standing for 24 hours. This is also beneficial to slowing down the gel state of the slurry, improving the stability of the slurry, and widening the process window for slurry coating.
  • the second stirring rotation speed is 1000 rpm to 1300 rpm. In some embodiments, the second stirring rotation speed can be selected as any one of 1000 rpm, 1100 rpm, 1200 rpm, and 1300 rpm.
  • the rotation speed of the second stirring is too low, the binder and the solvent cannot be effectively mixed, the viscosity of the slurry when shipped and the viscosity after standing for 24 hours are too high, the slurry is prone to gelling, and the stability of the slurry is poor; if the rotation speed of the second stirring is too high, it is impossible to further significantly improve the viscosity of the slurry when shipped, the viscosity of the slurry after standing for 24 hours, and the gelation phenomenon of the slurry, but instead lead to waste of energy and increase in production costs.
  • the rotation speed of the second stirring is controlled within a suitable range so that the slurry has low shipping viscosity, low viscosity after standing for 24 hours and low anti-gelling property, which is beneficial to improving the coating performance, processing performance and stability of the slurry.
  • the stirring time of the fourth stirring is too short, the binder and the solvent cannot be effectively mixed with the primary slurry, the slurry's shipping viscosity and the viscosity after standing for 24 hours are too large, the slurry is prone to gelling, and the slurry's stability is poor; if the stirring time of the fourth stirring is too long, the positive electrode active material and the conductive agent are easily broken, and the slurry is prone to gelling.
  • the stirring time of the fourth stirring is controlled within a suitable range so that the slurry has a low shipping viscosity and a low viscosity after standing for 24 hours. This is also beneficial for slowing down the gel state of the slurry, improving the stability of the slurry, and widening the process window.
  • the revolution speed of the fourth stirring is 25 rpm to 40 rpm. In some embodiments, the revolution speed of the fourth stirring can be selected from any one of 25 rpm, 30 rpm, 35 rpm, and 40 rpm.
  • the rotation speed of the fourth stirring is too low, the binder and the solvent cannot be effectively mixed with the primary slurry, the slurry's shipping viscosity and the viscosity after standing for 24 hours are too high, the slurry is prone to gelling, and the slurry has poor stability; if the rotation speed of the fourth stirring is too high, the positive electrode active material and the conductive agent are easily broken, and the slurry is prone to gelling.
  • the revolution speed of the fourth stirring is controlled within a suitable range so that the slurry has a low shipping viscosity and a low viscosity after standing for 24 hours. This is also beneficial to slowing down the gel state of the slurry, improving the stability of the slurry, and widening the process window.
  • the fourth stirring rotation speed is 1000 rpm to 1300 rpm. In some embodiments, the fourth stirring rotation speed can be selected from any one of 1000 rpm, 1100 rpm, 1200 rpm, and 1300 rpm.
  • the rotation speed of the fourth stirring is too low, the binder and the solvent cannot be effectively mixed with the primary slurry, the slurry's shipping viscosity and the viscosity after standing for 24 hours are too large, the slurry is prone to gelling, and the slurry has poor stability; if the rotation speed of the fourth stirring is too high, the positive electrode active material and the conductive agent are easily broken, and the slurry is prone to gelling.
  • the stirring time of the fourth stirring is controlled within a suitable range so that the slurry has a low shipping viscosity and a low viscosity after standing for 24 hours. This is also beneficial for slowing down the gel state of the slurry, improving the stability of the slurry, and widening the process window.
  • the solid content of the positive electrode slurry is 65% to 70%, and the viscosity of the positive electrode slurry is 6000 to 31000 mPa ⁇ s.
  • the solid content and viscosity of the positive electrode slurry can be tested by any method known in the art.
  • the viscosity can be measured by a rotary viscometer, and the solid content can be tested by measuring the weight of the slurry before and after removing water.
  • the solid content of the positive electrode slurry may be any one of 65%, 66%, 67%, 68%, 69%, and 70%.
  • the viscosity of the positive electrode slurry may be 6000 mPa ⁇ s, 7000 mPa ⁇ s, 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, Any one of 17000mPa ⁇ s, 18000mPa ⁇ s, 19000mPa ⁇ s, 20000mPa ⁇ s, 21000mPa ⁇ s, 22000mPa ⁇ s, 23000mPa ⁇ s, 24000mPa ⁇ s, 25000mPa ⁇ s, 26000mPa ⁇ s, 27000mPa ⁇ s, 28000mPa ⁇ s, 29000mPa ⁇ s, 30000mPa ⁇ s, and 31000mPa ⁇ s.
  • the slurry formed by the preparation method of the present application has a high solid content, suitable viscosity, and excellent processability.
  • the slurry can be directly used in the subsequent coating process, which can improve production efficiency.
  • the mass percentage of the solvent used in the second stirring is 35% to 45%, and the mass percentage of the solvent used in the fourth stirring is 4% to 10%.
  • the ratio of the mass of the positive electrode active material, the total mass of the binder, and the mass of the conductive agent is (88-96): (2-4): (2-8).
  • the total mass of the binder refers to the mass of the binder used in the second stirring and the binder used in the fourth stirring.
  • the mass of the added binder, positive electrode active material and conductive agent can be determined by those skilled in the art according to the rated range of the stirring equipment.
  • the positive electrode slurry within the above range has good processing performance and also enables the formed positive electrode plate to have excellent electrochemical performance.
  • a positive electrode slurry wherein the solid content of the positive electrode slurry is 65% to 70%, the initial viscosity of the positive electrode slurry is 6000 to 31000 mPa ⁇ s, and after standing for 24 hours, the viscosity of the positive electrode slurry does not exceed 49000 mPa ⁇ s.
  • the initial viscosity refers to the shipping viscosity of the positive electrode slurry when it is just prepared.
  • the positive electrode slurry is prepared by the method for preparing the positive electrode slurry in any of the above embodiments.
  • the viscosity of the positive electrode slurry after standing for 24 hours does not exceed 48000 mPa ⁇ s, 45000 mPa ⁇ s, 41000 mPa ⁇ s, 35000 mPa ⁇ s, 31000 mPa ⁇ s or 26000 mPa ⁇ s.
  • the slurry formed by the preparation method of the present application has high solid content, suitable viscosity, and excellent processability, and the slurry also has excellent storage performance.
  • a secondary battery is provided.
  • a secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator.
  • the positive electrode sheet is prepared from a positive electrode slurry prepared by the preparation method in any embodiment.
  • the secondary battery is any one of a lithium ion battery, a sodium ion battery, a magnesium ion battery, and a potassium ion battery.
  • the electrolyte plays the role of conducting ions between the positive electrode and the negative electrode.
  • the separator is set between the positive electrode and the negative electrode, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, and the positive electrode film layer is prepared by the positive electrode slurry prepared by the preparation method of the positive electrode slurry in any embodiment of the present application or the positive electrode slurry in any embodiment.
  • the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • the metal foil aluminum foil may be used.
  • the composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • the composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive electrode active material may be a positive electrode active material for a battery known in the art.
  • the positive electrode active material may include at least one of the following materials: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds.
  • the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more.
  • lithium transition metal oxides may 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 LiNi1 / 3Co1 / 3Mn1 / 3O2 (also referred to as NCM333 ), LiNi0.5Co0.2Mn0.3O2 (also referred to as NCM523 ) , LiNi0.5Co0.25Mn0.25O2 (also referred to as NCM211 ) , LiNi0.6Co0.2Mn0.2O2 (also referred to as NCM622 ), LiNi0.8Co0.1Mn0.1O2 (also referred to as NCM811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05
  • lithium-containing phosphates with an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO 4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.
  • lithium iron phosphate such as LiFePO 4 (also referred to as LFP)
  • LiMnPO 4 lithium manganese phosphate
  • LiMnPO 4 lithium manganese phosphate
  • LiMnPO 4 lithium manganese phosphate and carbon
  • the positive electrode film layer may also optionally include a binder.
  • the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PTFE polytetrafluoroethylene
  • vinylidene fluoride-tetrafluoroethylene-propylene terpolymer vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer
  • the positive electrode film layer may further include a conductive agent, which may include, for example, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • a conductive agent which may include, for example, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and the solvent (such as N-methyl-2-pyrrolidone), are used to prepare the positive electrode slurry by the positive electrode slurry preparation method in any embodiment of the present application, the prepared positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.
  • the components for preparing the positive electrode sheet such as the positive electrode active material, the conductive agent, the binder and the solvent (such as N-methyl-2-pyrrolidone)
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • the metal foil copper foil may be used.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate.
  • the composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative electrode active material may adopt the negative electrode active material for the battery known in the art.
  • the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys.
  • the tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys.
  • the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.
  • the negative electrode film layer may further include a binder.
  • the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • a conductive agent which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).
  • a thickener eg, sodium carboxymethyl cellulose (CMC-Na)
  • the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.
  • a solvent such as deionized water
  • the electrolyte plays the role of conducting ions between the positive electrode and the negative electrode.
  • the present application has no specific restrictions on the type of electrolyte, which can be selected according to needs.
  • the electrolyte can be liquid, gel or all-solid.
  • the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.
  • the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.
  • the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • the electrolyte may further include additives, such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.
  • additives such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.
  • the secondary battery further includes a separator.
  • the present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.
  • the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation.
  • the materials of each layer can be the same or different, without particular limitation.
  • the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.
  • the secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the secondary battery may also be a soft package, such as a bag-type soft package.
  • the material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.
  • FIG1 is a secondary battery 5 of a square structure as an example.
  • the outer package may include a shell 51 and a cover plate 53.
  • the shell 51 may 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 connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity.
  • the positive electrode sheet, the negative electrode sheet and the isolation film can form an electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is encapsulated in the receiving cavity.
  • the electrolyte is infiltrated in the electrode assembly 52.
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.
  • secondary batteries may be assembled into a battery module.
  • the number of secondary batteries contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.
  • FIG3 is a battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of secondary batteries 5 may be fixed by fasteners.
  • the battery module 4 may further include a housing having a housing space, and the plurality of secondary batteries 5 are housed in the housing space.
  • the battery modules described above may also be assembled into a battery pack.
  • the battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.
  • FIG4 and FIG5 are battery packs 1 as an example.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be covered on the lower box body 3 to form a closed space for accommodating the battery modules 4.
  • the plurality of battery modules 4 can be arranged in the battery box in any manner.
  • the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application.
  • the secondary battery, battery module, or battery pack can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device.
  • the electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited to these.
  • a secondary battery, a battery module or a battery pack may be selected according to its usage requirements.
  • Fig. 6 is an example of an electric device.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.
  • a battery pack or a battery module may be used.
  • a device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be thin and light, and a secondary battery may be used as a power source.
  • Second stirring 17 kg of polyvinylidene fluoride binder with a weight average molecular weight of 1.8 million was mixed with 500 kg of N-methyl-2-pyrrolidone, with an orbital speed of 25 rpm and a rotational speed of 1200 rpm for 60 minutes to obtain a glue solution;
  • Third stirring add the dry blend to the glue solution and mix and stir at an orbital speed of 20 rpm and an autorotation speed of 600 rpm for 10 minutes, then at an orbital speed of 25 rpm and an autorotation speed of 1200 rpm for 70 minutes to obtain a primary slurry;
  • the preparation method is basically the same as that of Example 1, except that the mass ratio of the binder in the second stirring is adjusted. For specific parameters, see Table 1.
  • the preparation method is basically the same as that in Example 1, except that the weight average molecular weight of the polyvinylidene fluoride binder is adjusted. For specific parameters, see Table 1.
  • the preparation method is basically the same as that in Example 1, except that the stirring parameters are adjusted. For specific parameters, see Table 1.
  • the preparation method is basically the same as that of Comparative Example 1, except that the weight average molecular weight of the polyvinylidene fluoride binder is adjusted. For specific parameters, see Table 1.
  • the preparation method is basically the same as that of Comparative Example 6, except that the weight average molecular weight of the polyvinylidene fluoride binder is adjusted. For specific parameters, see Table 1.
  • the preparation method is basically the same as that of Example 1, except that the mass ratio of the binder in the second stirring is adjusted. For specific parameters, see Table 1.
  • the prepared positive electrode slurry was placed for 10 minutes before shipment.
  • the viscosity value first measured by Dveslvtjo rotary viscosity tester (BROOKFIELD) was recorded as the shipping viscosity, wherein the test conditions were: 25°C, 12 rpm, 64 rotor for measuring viscosity not less than 2000 mPa ⁇ s, and 62 rotor for measuring viscosity less than 2000 mPa ⁇ s. The measurement was performed three times in parallel and the average value was taken.
  • the slurry was retested for viscosity, and the viscosity value measured by Dveslvtjo rotary viscosity tester (BROOKFIELD) was recorded as the 24-hour viscosity, wherein the test conditions were: 25°C, rotation speed 12 rpm, 64 rotor for measuring viscosity not less than 200 mPa ⁇ s, and 62 rotor for measuring viscosity less than 2000 mPa ⁇ s. The measurements were repeated three times and the average value was taken.
  • Dveslvtjo rotary viscosity tester BROOKFIELD
  • a steel ruler was used to pick up the slurry in the beaker, and the gel state of the slurry was determined based on the flow state of the slurry.
  • the gel-free state means that the slurry flows naturally and continuously, and the slurry flows on the surface of the steel ruler without agglomeration.
  • the slight gel state is that the slurry flows naturally and continuously, but the fluid is thin, and the slurry is basically spread evenly on the surface of the steel ruler with slight small pieces;
  • the medium gel state is that the slurry drips naturally and intermittently; it does not flow continuously, the slurry cannot be spread evenly on the surface of the steel ruler, and there are obvious block agglomerations;
  • Severe gel state means that the slurry cannot flow down as a stream, falls off in lumps or remains directly on the steel ruler and cannot flow down.
  • the moisture analyzer is MOC-120H.
  • the positive electrode slurries of the embodiments and comparative examples were prepared according to the above method, and various parameters were measured. The results are shown in Table 1 below.
  • the positive electrode slurries in Examples 1 to 67 are all prepared by the slurry preparation method disclosed in the present application, and all include first stirring, second stirring, third stirring and fourth stirring; in the first stirring, the positive electrode active material and the conductive agent are mixed and stirred to prepare a dry mixture; in the second stirring, the binder and the solvent are mixed and stirred to prepare a glue solution; in the third stirring, the dry mixture and the glue solution are mixed and stirred to prepare a primary slurry; in the fourth stirring, the binder, the solvent and the primary slurry are mixed and stirred to prepare a positive electrode slurry; the binder and the solvent used in the second stirring are respectively the same as the binder and the solvent used in the fourth stirring; based on the total mass of the binder used in the second stirring and the binder used in the fourth stirring, the mass ratio of the binder used in the second stirring is 50% to 70%, and the mass ratio of the binder used in the fourth stirring is 30% to 50%.
  • the slurry preparation method disclosed in the present invention is universal and can be applied to slurries containing polyvinylidene fluoride binders with a weight average molecular weight of 200,000 to 8,000,000, and is universal for low molecular weight binders and high molecular weight binders.
  • the preparation process in the prior art cannot improve the gel state of the binder with a weight average molecular weight of 1.8 million.
  • the preparation method disclosed in the present application enables the slurry containing the binder with a weight average molecular weight of up to 8 million to still have low shipping viscosity and good anti-gel properties, which can meet the use requirements of the new generation of high molecular weight binders.
  • the weight average molecular weight of the polyvinylidene fluoride binder is controlled to be 800,000 to 8,000,000, without significantly changing the shipping viscosity of the slurry, the viscosity of the slurry after standing for 24 hours, and the gel phenomenon of the slurry, while also meeting the requirements of the electrode bonding performance.
  • Example 1 From the comparison between Example 1, Examples 11-12 and Example 10, it can be seen that controlling the stirring time of the low-speed stirring in the third stirring to be 5 minutes to 15 minutes can reduce the shipping viscosity of the slurry and the viscosity after standing for 24 hours, slow down the gelation of the slurry, and expand the process window of slurry coating. From the comparison between Example 1, Examples 11-12 and Example 13, it can be seen that controlling the stirring time of the low-speed stirring in the third stirring to be 5 minutes to 15 minutes can take into account both the quality and efficiency of the slurry, reduce the shipping viscosity, and slow down the gelation of the slurry.
  • Example 15-16 and Example 14 From the comparison between Example 1, Examples 15-16 and Example 14, it can be seen that controlling the revolution speed of the low-speed stirring in the third stirring to 15 rpm-25 rpm can reduce the shipping viscosity of the slurry and the viscosity after standing for 24 hours, slow down the gelation of the slurry, and expand the process window of slurry coating. From the comparison between Example 1, Examples 15-16 and Example 17, it can be seen that controlling the revolution speed of the low-speed stirring in the third stirring to 15 rpm-25 rpm can take into account both the quality and cost of the mixed slurry, reduce the shipping viscosity, and slow down the gelation of the slurry.
  • Example 1 From the comparison between Example 1, Examples 19 to 20 and Example 18, it can be seen that controlling the rotation speed of the low-speed stirring in the third stirring to 400 rpm to 800 rpm can reduce the shipping viscosity of the slurry and the viscosity after standing for 24 hours, slow down the gelation of the slurry, improve the storage performance of the slurry, and expand the process window of slurry coating. From the comparison between Example 1, Examples 19 to 20 and Example 21, it can be seen that controlling the rotation speed of the low-speed stirring in the third stirring to 400 rpm to 800 rpm can take into account both the quality and cost of the mixed slurry, reduce the shipping viscosity, and slow down the gelation of the slurry.
  • Example 1 From the comparison between Example 1, Examples 23 to 24 and Example 22, it can be seen that controlling the stirring time of the high-speed stirring in the third stirring to be 50 minutes to 80 minutes can reduce the shipping viscosity of the slurry and the viscosity after standing for 24 hours, slow down the gelation of the slurry, improve the storage performance of the slurry, and expand the process window of slurry coating. From the comparison between Example 1, Examples 23 to 24 and Example 25, it can be seen that controlling the stirring time of the high-speed stirring in the third stirring to be 50 minutes to 80 minutes can take into account the quality and efficiency of the slurry, reduce the shipping viscosity, and slow down the gelation of the slurry.
  • Example 1 From the comparison between Example 1, Examples 27 to 28 and Example 26, it can be seen that controlling the revolution speed of the high-speed stirring in the third stirring to 20 rpm to 30 rpm can reduce the shipping viscosity of the slurry and the viscosity after standing for 24 hours, slow down the gelation of the slurry, improve the storage performance of the slurry, and expand the process window of slurry coating. From the comparison between Example 1, Examples 15 to 16 and Example 17, it can be seen that controlling the revolution speed of the high-speed stirring in the third stirring to 15 rpm to 25 rpm can take into account the quality and cost of the slurry, reduce the shipping viscosity, and slow down the gelation of the slurry.
  • Example 1 From the comparison between Example 1, Examples 31 to 32 and Example 30, it can be seen that controlling the rotation speed of the high-speed stirring in the third stirring to 1000 rpm to 1300 rpm can reduce the shipping viscosity of the slurry and the viscosity after standing for 24 hours, slow down the gelation of the slurry, improve the storage performance of the slurry, and expand the process window of slurry coating. From the comparison between Example 1, Examples 31 to 32 and Example 33, it can be seen that controlling the rotation speed of the high-speed stirring in the third stirring to 1000 rpm to 1300 rpm can take into account the quality and cost of the slurry, reduce the shipping viscosity, and slow down the gelation of the slurry.
  • Example 1 From the comparison between Example 1 and Examples 34 to 35, it can be seen that controlling the rotation speed of the first stirring to 0 can reduce the viscosity of the slurry after standing for 24 hours, slow down the gelation of the slurry, improve the stability of the slurry, and widen the process window.
  • Example 1 From the comparison between Example 1, Examples 37-38 and Example 36, it can be seen that controlling the stirring time of the first stirring for 5 minutes to 20 minutes can reduce the shipping viscosity of the slurry and the viscosity after standing for 24 hours, slow down the gelation of the slurry, improve the stability of the slurry, and widen the process window. From the comparison between Example 1, Examples 37-38 and Example 39, it can be seen that controlling the stirring time of the first stirring for 5 minutes to 20 minutes can take into account the quality and efficiency of the slurry, reduce the shipping viscosity, and slow down the gelation of the slurry.
  • Example 1 From the comparison between Example 1, Examples 41-42 and Example 40, it can be seen that controlling the revolution speed of the first stirring to 20 rpm to 30 rpm can reduce the shipping viscosity of the slurry and the viscosity after standing for 24 hours, slow down the gelation of the slurry, improve the stability of the slurry, and widen the process window. From the comparison between Example 1, Examples 41-42 and Example 43, it can be seen that controlling the revolution speed of the first stirring to 20 rpm to 30 rpm can take into account the quality and cost of the slurry, reduce the shipping viscosity, and slow down the gelation of the slurry.
  • Example 1 From the comparison between Example 1, Examples 45-46 and Example 44, it can be seen that controlling the stirring time of the second stirring to 50 minutes to 80 minutes can reduce the shipping viscosity of the slurry and the viscosity after standing for 24 hours, slow down the gelation of the slurry, improve the stability of the slurry, and broaden the process window. From the comparison between Example 1, Examples 45-46 and Example 47, it can be seen that controlling the stirring time of the second stirring to 50 minutes to 80 minutes can take into account the quality and efficiency of the slurry, reduce the shipping viscosity, and slow down the gelation of the slurry.
  • Example 1 From the comparison between Example 1, Examples 49-50 and Example 48, it can be seen that controlling the revolution speed of the second stirring to 25 rpm to 40 rpm can reduce the viscosity of the slurry at delivery and the viscosity after standing for 24 hours, slow down the gelation of the slurry, improve the stability of the slurry, and widen the process window. From the comparison between Example 1, Examples 49-50 and Example 51, it can be seen that controlling the revolution speed of the second stirring to 25 rpm to 40 rpm can slow down the gelation of the slurry, improve the stability of the slurry, and widen the process window.
  • Example 1 From the comparison between Example 1, Examples 53-54 and Example 52, it can be seen that controlling the rotation speed of the second stirring to 1000 rpm to 1300 rpm can reduce the shipping viscosity of the slurry and the viscosity after standing for 24 hours, slow down the gelation of the slurry, improve the stability of the slurry, and widen the process window. From the comparison between Example 1, Examples 53-54 and Example 55, it can be seen that controlling the rotation speed of the second stirring to 1000 rpm to 1300 rpm can take into account the quality and cost of the slurry, reduce the shipping viscosity, and slow down the gelation of the slurry.
  • Example 1 From the comparison between Example 1, Examples 57-58 and Example 56, it can be seen that controlling the stirring time of the fourth stirring to 60 minutes to 90 minutes can reduce the shipping viscosity of the slurry and the viscosity after standing for 24 hours, slow down the gelation of the slurry, improve the stability of the slurry, and widen the process window. From the comparison between Example 1, Examples 57-58 and Example 59, it can be seen that controlling the stirring time of the fourth stirring to 60 minutes to 90 minutes can slow down the gelation of the slurry, improve the stability of the slurry, and widen the process window.
  • Example 1 From the comparison between Example 1, Examples 61-62 and Example 60, it can be seen that controlling the revolution speed of the fourth stirring to 25 rpm to 40 rpm can reduce the viscosity of the slurry at delivery and the viscosity after standing for 24 hours, slow down the gelation of the slurry, improve the stability of the slurry, and widen the process window. From the comparison between Example 1, Examples 61-62 and Example 63, it can be seen that controlling the revolution speed of the fourth stirring to 25 rpm to 40 rpm can slow down the gelation of the slurry, improve the stability of the slurry, and widen the process window.
  • Example 65-66 and Example 64 From the comparison between Example 1, Examples 65-66 and Example 64, it can be seen that controlling the rotation speed of the fourth stirring to 1000 rpm to 1300 rpm can reduce the viscosity of the slurry at the time of shipment and the viscosity after standing for 24 hours, slow down the gelation of the slurry, improve the stability of the slurry, and widen the process window. From the comparison between Example 1, Examples 65-66 and Example 67, it can be seen that controlling the rotation speed of the fourth stirring to 1000 rpm to 1300 rpm can slow down the gelation of the slurry, improve the stability of the slurry, and widen the process window.
  • the positive electrode slurry with a solid content of 65% to 70% disclosed in the present application has a viscosity of 6000 mPa ⁇ s to 31000 mPa ⁇ s, and the positive electrode slurry has good coating and processability.
  • the mass percentage of the solvent used in the second stirring is controlled to be 35% to 45%, and the mass percentage of the solvent used in the fourth stirring is controlled to be 4% to 10%.
  • the solid content of the positive electrode slurry disclosed in the present application is 65-70%
  • the initial viscosity of the positive electrode slurry is 6000-31000 mPa.s
  • the viscosity of the positive electrode slurry does not exceed 49000 mPa.s.

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Abstract

本申请提供了一种正极浆料的制备方法、二次电池、电池包和用电装置。该制备方法包括第一搅拌、第二搅拌、第三搅拌和第四搅拌；第一搅拌中，将正极活性材料与导电剂混合搅拌，制备干混料；第二搅拌中，将粘结剂与溶剂混合搅拌，制备胶液；第三搅拌中，将干混料与胶液混合搅拌，制备初级浆料；第四搅拌中，将粘结剂、溶剂与初级浆料混合搅拌，制备正极浆料；第二搅拌中使用的粘结剂和溶剂分别与第四搅拌中使用的粘结剂和溶剂相同；基于第二搅拌中使用的粘结剂和第四搅拌中使用的粘结剂的总质量计，第二搅拌中使用的粘结剂的质量比为50％～70％，第四搅拌中使用的粘结剂的质量比为30％～50％。

Description

正极浆料的制备方法、二次电池、电池包和用电装置 技术领域
本申请涉及二次电池技术领域，尤其涉及一种二次电池正极浆料的制备方法、二次电池、电池包和用电装置。
背景技术
近年来，随着二次电池的应用范围越来越广泛，二次电池广泛应用于水力、火力、风力和太阳能电站等储能电源系统，以及电动工具、电动自行车、电动摩托车、电动汽车、军事装备、航空航天等多个领域。
电极浆料是成型电极的基础，也是二次电池生产的第一道工序。电极浆料的特性对后续的电极生产、电池性能都有显著的影响。正极浆料主要是由正极活性材料、导电剂、粘结剂和溶剂形成的固-液相混合体系。该体系处于一种亚稳定状态，合浆工艺，也就是浆料的制备方法对浆料的分散性、均匀性、稳定性等性能有着至关重要的影响。现有技术中的合浆工艺常为一步法，将正极活性浆料中的各组分直接混合搅拌即得，然而一步法的制备方法无法满足不同重均分子量粘结剂的制造需求，合浆工艺通用性差，不利于制造成本的降低。因此，需要开发出一种新的浆料的制备方法，以适用于不同重均分子量的粘结剂。
发明内容
本申请是鉴于上述课题而进行的，其目的在于，提供一种二次电池正极浆料的制备方法，以适应不同重均分子量的粘结剂，拓宽正极浆料涂布的工艺窗口，提高正极浆料的加工性能。
为了达到上述目的，本申请提供了一种正极浆料的制备方法，包括第一搅拌、第二搅拌、第三搅拌和第四搅拌；第一搅拌中，将正极活性材料与导电剂混合搅拌，制备干混料；第二搅拌中，将粘结剂与 溶剂混合搅拌，制备胶液；第三搅拌中，将干混料与胶液混合搅拌，制备初级浆料；第四搅拌中，将粘结剂、溶剂与初级浆料混合搅拌，制备正极浆料；第二搅拌中使用的粘结剂和溶剂分别与第四搅拌中使用的粘结剂和溶剂相同；基于第二搅拌中使用的粘结剂和第四搅拌中使用的粘结剂的总质量计，第二搅拌中使用的粘结剂的质量比为50％～70％，第四搅拌中使用的粘结剂的质量比为30％～50％。
由此，本申请公开的正极浆料的制备方法相比于现有的正极浆料的制备方法更具有广泛的通用性，适用于包含不同重均分子量粘结剂的浆料，相比于现有的制备方法，本申请通过分步合浆，降低了正极浆料的出货粘度和静置24小时后的粘度，缓解了正极浆料的凝胶现象，提高了制备方法对于大分子量的粘结剂的适用性，制备方法具有更广泛的普适性，拓展了正极浆料涂布的工艺窗口，提高了正极浆料的加工性能。
在任意实施方式中，所述粘结剂包含至少一种重均分子量为80万～800万的聚偏氟乙烯。
本申请公开的制备方法对低分子量聚偏氟乙烯粘结剂和高分子量聚偏氟乙烯粘结剂具有普适性，能够有效缓解不同浆料的凝胶现象，有助于提高生产效率，拓宽浆料的涂覆窗口。本申请公开的制备方法能够适用于重均分子量高达800万的粘结剂，使得包含高重均分子量粘结剂的浆料依然具有低的出货粘度和抗凝胶性，能够满足新一代粘结剂的使用需求。
在任意实施方式中，所述第三搅拌中先进行低速搅拌，再进行高速搅拌。
第三搅拌中，先将干混料与胶液低速搅拌，使得干混料充分分散在胶液中的同时避免了干混料被过分剪切，保证了正极活性材料与导电剂的完整性，并且经过低速搅拌后胶液包覆于正极活性材料以及导电剂上，可以避免后续的高速搅拌破坏正极活性材料与导电剂的结构和尺寸；低速搅拌后再进行高速搅拌，可以在保证材料性能的基础上，降低浆料的粘度。
在任意实施方式中，第三搅拌中低速搅拌的公转速度为15转/分钟～25转/分钟，自转速度为400转/分钟～800转/分钟，搅拌时间为5分钟～15分钟。
控制第三搅拌中高速搅拌的公转速度、自转速度和搅拌时间在合适范围，使得浆料具有低的出货粘度、低的静置24小时后的粘度和优异的抗凝胶性，有利于提高浆料的涂布性能、加工性能和稳定性。
在任意实施方式中，第三搅拌中高速搅拌的公转速度为20转/分钟～30转/分钟，自转速度为1000转/分钟～1300转/分钟，搅拌时间为50分钟～80分钟。
控制第三搅拌中高速搅拌的公转速度、自转速度和搅拌时间在合适范围，使得浆料具有低的出货粘度、低的静置24小时后的粘度和优异的抗凝胶性，有利于提高浆料的涂布性能、加工性能和稳定性。
在任意实施方式中，第一搅拌的自转速度为0。
控制第一搅拌的自转速度为0，能够将第一搅拌的剪切力最小化，充分减少正极活性材料与导电剂被过分打碎的可能性，保证正极活性材料与导电剂具有一定的颗粒度和比表面积，有助于提高正极活性材料与导电剂的分散效果，降低浆料静置24小时后的粘度，减缓浆料的凝胶现象，提高浆料的稳定性。
在任意实施方式中，第一搅拌的公转速度为20转/分钟～30转/分钟。
控制第一搅拌的公转速度在合适范围内，使得浆料具有低的出货粘度、低的静置24小时后的粘度和抗凝胶性，有利于提高浆料的涂布性能、加工性能和稳定性。
在任意实施方式中，第一搅拌的搅拌时间为5分钟～20分钟。
控制第一搅拌的搅拌时间在合适的范围，使得浆料具有低的出货粘度、低的静置24小时后的粘度和抗凝胶性，有利于提高浆料的涂布性能、加工性能和稳定性。
在任意实施方式中，第二搅拌的搅拌时间为50分钟～80分钟。
控制第二搅拌的搅拌时间在合适的范围，使得浆料具有低的出货 粘度、低的静置24小时后的粘度和抗凝胶性，有利于提高浆料的涂布性能、加工性能和稳定性。
在任意实施方式中，第二搅拌的公转速度为25转/分钟～40转/分钟。
控制第二搅拌的公转速度在合适的范围，使得浆料具有低的出货粘度和低的静置24小时后的粘度，同时有利于减缓浆料的凝胶状态，提高浆料的稳定性，拓宽工艺窗口。
在任意实施方式中，第二搅拌的自转速度为1000转/分钟～1300转/分钟。
控制第二搅拌的自转速度在合适的范围，使得浆料具有低的出货粘度、低的静置24小时后的粘度和抗凝胶性，进而提高浆料的涂布性能、加工性能和稳定性。
在任意实施方式中，第四搅拌的搅拌时间为60分钟～90分钟。
控制第四搅拌的搅拌时间在合适的范围，使得浆料具有低的出货粘度和低的静置24小时后的粘度，同时有利于减缓浆料的凝胶状态，提高浆料的稳定性，拓宽工艺窗口。
在任意实施方式中，第四搅拌的公转速度为25转/分钟～40转/分钟。
控制第四搅拌的公转速度在合适的范围，使得浆料具有低的出货粘度和低的静置24小时后的粘度，同时有利于减缓浆料的凝胶状态，提高浆料的稳定性，拓宽工艺窗口。
在任意实施方式中，第四搅拌的自转速度为1000转/分钟～1300转/分钟。
控制第四搅拌的搅拌时间在合适的范围，使得浆料具有低的出货粘度和低的静置24小时后的粘度，同时有利于减缓浆料的凝胶状态，提高浆料的稳定性，拓宽工艺窗口。
在任意实施方式中，正极浆料的固含量为65％～70％，且所述正极浆料的粘度为6000～31000mPa·s。
本申请的制备方法成型的浆料固含量高，粘度适宜，具有优异的 加工性，上述浆料可以直接用于后续的涂布工艺，能够提高生产效率。
在任意实施方式中，基于所述正极活性材料、所述导电剂、所述第二搅拌中使用的粘结剂和所述第四搅拌中使用的粘结剂的总质量计，所述第二搅拌中使用的溶剂的质量百分数为35％～45％，所述第四搅拌中使用的溶剂的质量百分数为4％～10％。
在任意实施方式中，所述正极浆料中，所述正极活性材料的质量、所述粘结剂总质量、所述导电剂的质量的比值为(88～96)∶(2～4)∶(2～8)。
上述范围内的正极浆料既有良好的加工性能，又使得成型后的正极极片具有优异的电化学性能。
在任意实施方式中，正极活性材料为磷酸铁锂及其改性材料、锂镍钴锰氧化物及其改性材料中的至少一种，所述改性材料是通过掺杂、导电碳包覆、导电金属包覆、导电聚合物包覆中的一种或多种改性方式制备的。
在任意实施方式中，溶剂选自N-甲基-2-吡咯烷酮、N,N-二甲基丙酰胺、N,N-二乙基丙酰胺、N,N-二丙基丙酰胺、N,N-二丁基丙酰胺、N,N-二甲基乙基丙酰胺以及3-丁氧基-N-甲基丙酰胺中的一种或多种。
本申请的第二方面还提供一种正极浆料，所述正极浆料是通过第一方面的正极浆料的制备方法制备的。
在任意实施方式中，正极浆料的固含量为65％～70％，所述正极浆料的初始粘度为6000～31000mPa·s，且静置24小时后，所述正极浆料的粘度不超过49000mPa·s。
本申请提供的正极浆料固含量高，粘度适宜，具有优异的加工性，同时浆料具有优异的存储性能。
本申请的第三方面还提供一种二次电池，包括正极极片、隔离膜、负极极片以及电解液，所述正极极片由第一方面所述的正极浆料的制备方法制备的正极浆料或第二方面所述的正极浆料制备而得。该正极极片具有高的品质和生产效率。
在任意实施方式中，二次电池为锂离子电池、钠离子电池、镁离 子电池、钾离子电池中的任意一种。
本申请的第四方面还提供一种电池模块，包括本申请第三方面所述的二次电池。
本申请的第五方面提供一种电池包，包括本申请的第三方面所述的二次电池或本申请的第四方面的电池模块。
本申请的第六方面提供一种用电装置，包括选自本申请的第三方面的二次电池、本申请的第四方面的电池模块或本申请的第五方面的电池包中的至少一种。
附图说明
图1是本申请一实施方式的二次电池的示意图；
图2是图1所示的本申请一实施方式的二次电池的分解图；
图3是本申请一实施方式的电池模块的示意图；
图4是本申请一实施方式的电池包的示意图；
图5是图4所示的本申请一实施方式的电池包的分解图；
图6是本申请一实施方式的二次电池用作电源的用电装置的示意图。
附图标记说明：
1电池包；2上箱体；3下箱体；4电池模块；5二次电池；51壳体；52电极组件；53盖板。
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的正极活性材料及其制造方法、正极极片、二次电池、电池模块、电池包和电学装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了 特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
正极浆料主要是由正极活性材料、导电剂、粘结剂和溶剂形成的固-液相混合体系。为了提高体系中不同组分分布的均匀性，常通过搅拌、球磨、超声等工艺进行合浆。然而，现有技术中的合浆工艺通常只适用于固定组分的浆料体系，通用性差，浆料中各组分的物性发生变化后，合浆工艺往往需要调整。例如，现有技术中的合浆工艺不能适用于大分子量粘结剂，也无法适用于重均分子量分散性大、批次稳定性差的粘结剂。使用不同批次粘结剂的浆料采用相同的现有技术中的合浆工艺制备后性能差异性大，浆料容易出现凝胶，难以满足极片的生产需求。
[正极浆料的制备方法]
基于此，本申请提出了一种正极浆料的制备方法，包括第一搅拌、第二搅拌、第三搅拌和第四搅拌；第一搅拌中，将正极活性材料与导电剂混合搅拌，制备干混料；第二搅拌中，将粘结剂与溶剂混合搅拌，制备胶液；第三搅拌中，将干混料与胶液混合搅拌，制备初级浆料；第四搅拌中，将粘结剂、溶剂与初级浆料混合搅拌，制备正极浆料；第二搅拌中使用的粘结剂和溶剂分别与第四搅拌中使用的粘结剂和溶剂相同；基于第二搅拌中使用的粘结剂和第四搅拌中使用的粘结剂的总质量计，第二搅拌中使用的粘结剂的质量比为50％～70％，第四搅拌中使用的粘结剂的质量比为30％～50％。
在一些实施方式中，正极活性材料为含锂的过渡金属氧化物。在一些实施方式中，正极活性材料为磷酸铁锂及其改性材料、锂镍钴锰氧化物及其改性材料中的至少一种，所述改性材料是通过掺杂、导电碳包覆、导电金属包覆、导电聚合物包覆中的一种或多种改性方式制备的。
在一些实施方式中，导电剂可以包括超导碳、炭黑、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，溶剂为水性介质，如去离子水。
在一些实施方式中，溶剂为油性介质，选自N-甲基-2-吡咯烷酮、N,N-二甲基丙酰胺、N,N-二乙基丙酰胺、N,N-二丙基丙酰胺、N,N-二 丁基丙酰胺、N,N-二甲基乙基丙酰胺以及3-丁氧基-N-甲基丙酰胺中的一种或多种。
在该制备方法中，先将正极活性材料与导电剂进行第一搅拌得到干混料，第一搅拌使两者机械铆合，形成紧密缠结；然后将粘结剂与溶剂混合进行第二搅拌制备胶液，该步骤可以实现粘结剂在溶剂中的有效分散，避免粘结剂直接与其他材料混合搅拌导致的团聚和絮凝；然后将正极活性材料与导电剂形成的干混料与胶液混合进行第三搅拌制备初级浆料，第三搅拌可以有效地将正极活性材料和导电剂分散于胶液中，胶液中的粘结剂可以通过静电作用和空间位阻作用提高浆料的稳定性，减少正极活性材料和导电剂的团聚以及沉降；最后将粘结剂和溶剂与初级浆料混合进行第四搅拌，得到正极浆料，第四搅拌中通过再次加入的粘结剂包覆于正极活性材料以及导电剂上，对浆料中的物料起到维稳分散的作用，减缓浆料的凝胶，第四搅拌中通过再次加入的溶剂能够有效调节浆料的出货粘度，防止出货粘度过高，影响后续的涂布工作。
基于所述第二搅拌中使用的粘结剂和所述第四搅拌中使用的粘结剂的总质量计，所述第二搅拌中使用的粘结剂的质量比为50％～70％，所述第四搅拌中使用的粘结剂的质量比为30％～50％。若第二搅拌或第四搅拌中加入的粘结剂质量过多或过少，都无法有效降低浆料的出货粘度和静置24小时后的粘度，无法达到减缓浆料凝胶的目的。
现有技术中的正极浆料的制备方法兼容性差，无法适应浆料中粘结剂重均分子量的差异，因此，对于材料提出了很高的精度需求。本申请通过分步合浆，降低了正极浆料的出货粘度和静置24小时的粘度，缓解了正极浆料的凝胶现象，使得具有高重均分子量粘结剂的浆料依然具有低的出货粘度和静置24小时后的粘度和抗凝性，提高制备方法的普适性。本申请的制备方法不仅适用于低重均分子量的粘结剂，也能适用于高重均分子量的粘结剂，能够有效缓解不同浆料的凝胶现象，有助于提高生产效率、拓宽浆料涂覆的工艺窗口。
在本文中，术语“工艺窗口”指能够保证产品质量的工艺区间，包括但不限于温度区间、压力区间、存储时间长度等，可以理解的是工艺窗口越宽，对工艺精度的需求越低。
在一些实施方式中，所述粘结剂包含至少一种重均分子量为80万～800万的聚偏氟乙烯。在一些实施方式中，聚偏氟乙烯的重均分子量可选为80万、100万、150万、200万、250万、300万、350万、400万、450万、500万、550万、600万、650万、700万、750万、800万中的任意一种。
在本文中，术语“重均分子量”是指聚合物按质量的统计平均分子量，在单位重量上平均得到的分子量。
现有技术中的合浆工艺难以适用于高重均分子量的粘结剂。以现有技术制备出的具有高分子量粘结剂的正极浆料容易具有高的出货粘度，难以满足涂布需求，而且易于出现严重的凝胶现象。而本申请公开的制备方法通过分步加入粘结剂以及搅拌速度的相互配合能够适用于重均分子量高达800万的粘结剂，使得浆料依然具有低的出货粘度和静置24小时后的粘度以及良好的抗凝胶性，能够满足高分子量粘结剂的使用需求。
在一些实施方式中，所述第三搅拌中先进行低速搅拌，再进行高速搅拌。可以理解，低速搅拌和高速搅拌是相对而言的。若第三搅拌中低速搅拌的速度为v1，高速搅拌的速度为v2，则v1低于v2，v1和v2代表搅拌的自转速度。
第三搅拌中，先将干混料与胶液低速搅拌，使得干混料充分分散在胶液中的同时避免了干混料被过分剪切，保证了正极活性材料与导电剂结构的完整性，并且经过低速搅拌后胶液包覆在正极活性材料与导电剂表面，可以避免后续的高速搅拌对正极活性材料与导电剂进行过分剪切；低速搅拌后再进行高速搅拌，可以降低浆料的粘度，为后续制备低出货粘度的正极浆料提供了可能。
在一些实施方式中，第三搅拌中低速搅拌的公转速度为15转/分钟～25转/分钟，自转速度为400转/分钟～800转/分钟，搅拌时间为5 分钟～15分钟。
在本文中，术语“自转速度”是指搅拌器绕自身轴线转动的速度。
在本文中，术语“公转速度”是指搅拌器绕装载物料的釜体转动的速度。
在一些实施方式中，第三搅拌中低速搅拌的公转速度可选为15转/分钟、20转/分钟、25转/分钟中的任意一种。
在一些实施方式中，第三搅拌中低速搅拌的自转速度可选为400转/分钟、500转/分钟、600转/分钟、700转/分钟、800转/分钟中的任意一种。
在一些实施方式中，第三搅拌中低速搅拌的搅拌时间可选为5分钟、10分钟、15分钟中的任意一种。
在一些实施方式中，搅拌装置为行星搅拌机。行星搅拌机的工作原理是搅拌机启动后，行星架转动，带动箱内搅拌轴转动，在围绕料筒轴线公转的同时高速自转，从而物料受到强烈的剪切、捏合作用。可以理解，本申请提供的制备方法适用于任何类型的行星搅拌机。
若第三搅拌中低速搅拌的公转速度过小或自转速度过小或搅拌时间过短，导电剂与活性材料形成的干混料不能有效的分散于胶液中，浆料的出货粘度和静置24小时后的粘度过大，浆料容易出现凝胶，浆料的稳定性较差；若第三搅拌中低速搅拌的公转速度过大或自转速度过大或搅拌时间过长，无法进一步显著改善浆料的出货粘度、浆料静置24小时后的粘度、浆料的凝胶现象，且导致能源的浪费、制备成本的增加。
综上所述，控制第三搅拌中低速搅拌的公转速度、自转速度和搅拌时间在合适的范围，能够使得浆料具有低的出货粘度、低的静置24小时后的粘度和优异的抗凝胶性，有利于提高浆料的涂布性能、加工性能和稳定性。
在一些实施方式中，第三搅拌中高速搅拌的公转速度为20转/分钟～30转/分钟，自转速度为1000转/分钟～1300转/分钟，搅拌时间为50分钟～80分钟。
在一些实施方式中，第三搅拌中高速搅拌的公转速度可选为20转/分钟、25转/分钟、30转/分钟中的任意一种。
在一些实施方式中，第三搅拌中高速搅拌的自转速度可选为1000转/分钟、1100转/分钟、1200转/分钟、1300转/分钟中的任意一种。
在一些实施方式中，第三搅拌中高速搅拌的搅拌时间可选为50分钟、60分钟、70分钟、80分钟中的任意一种。
若第三搅拌中高速搅拌的公转速度过小或自转速度过小或搅拌时间过短，初级浆料不能被强力剪切，浆料的出货粘度和静置24小时后的粘度过大，浆料容易出现凝胶，浆料稳定性较差；若第三搅拌中高速搅拌的公转速度过大或自转速度过大或搅拌时间过长，无法进一步显著改善浆料的出货粘度、浆料静置24小时后的粘度和浆料的凝胶现象，且导致能源的浪费、生产效率的降低。
综上所述，控制第三搅拌中高速搅拌的公转速度、自转速度和搅拌时间在合适范围，使得浆料具有低的出货粘度、低的静置24小时后的粘度和优异的抗凝胶性，有利于提高浆料的涂布性能、加工性能和稳定性。
在一些实施方式中，第一搅拌的自转速度为0。
控制第一搅拌的自转速度为0，能够将第一搅拌的剪切力最小化，充分减少活性材料与导电剂被过分打碎的可能性，保证正极活性材料与导电剂具有一定的颗粒度和比表面积，有助于提高正极活性材料与导电剂的分散效果，降低浆料静置24小时后的粘度，减缓浆料的凝胶现象，提高浆料的稳定性。
在一些实施方式中，第一搅拌的公转速度为20转/分钟～30转/分钟。
在一些实施方式中，第一搅拌的公转速度可选为20转/分钟、25转/分钟、30转/分钟中的任意一种。
若第一搅拌的公转速度过小，正极活性材料和导电剂不能有效混合，浆料的出货粘度和静置24小时后的粘度过大，浆料容易出现凝胶，浆料的稳定性较差；若第一搅拌的公转速度过大，无法进一步显 著改善浆料的出货粘度、浆料静置24小时后的粘度、浆料的凝胶现象，反而导致能源的浪费、生产成本的提高。
控制第一搅拌的公转速度在合适范围内，使得浆料具有低的出货粘度、低的静置24小时后的粘度和抗凝胶性，有利于提高浆料的涂布性能、加工性能和稳定性。
在一些实施方式中，第一搅拌的搅拌时间为5分钟～20分钟。在一些实施方式中，第一搅拌的搅拌时间可选为5分钟、10分钟、15分钟、20分钟中任意一种。
若第一搅拌的搅拌时间过短，正极活性材料和导电剂不能有效混合，浆料的出货粘度和静置24小时后的粘度过大，浆料容易出现凝胶，浆料的稳定性较差；若第一搅拌的搅拌时间过大，无法进一步显著改善浆料的出货粘度、浆料静置24小时后的粘度、浆料的凝胶现象，反而导致能源的浪费、生产效率的降低。
控制第一搅拌的搅拌时间在合适的范围，使得浆料具有低的出货粘度、低的静置24小时后的粘度和抗凝胶性，有利于提高浆料的涂布性能、加工性能和稳定性。
在一些实施方式中，第二搅拌的搅拌时间为50分钟～80分钟。在一些实施方式中，第二搅拌的搅拌时间可选为50分钟、60分钟、70分钟、80分钟中的任意一种。
若第二搅拌的搅拌时间过短，粘结剂与溶剂不能有效混合，浆料的出货粘度和静置24小时后的粘度过大，浆料容易出现凝胶，浆料的稳定性较差；若第二搅拌的搅拌时间过长，无法进一步显著改善浆料的出货粘度、浆料静置24小时后的粘度、浆料的凝胶现象，反而导致能源的浪费、降低生产效率。
控制第二搅拌的搅拌时间在合适的范围，使得浆料具有低的出货粘度、低的静置24小时后的粘度和抗凝胶性，有利于提高浆料的涂布性能、加工性能和稳定性。
在一些实施方式中，第二搅拌的公转速度为25转/分钟～40转/分钟。在一些实施方式中，第二搅拌的公转速度可选为25转/分钟、30 转/分钟、35转/分钟、40转/分钟中的任意一种。
若第二搅拌的公转速度过小，粘结剂与溶剂不能有效混合，浆料的出货粘度和静置24小时后的粘度过大，浆料容易出现凝胶，浆料的稳定性较差；若第二搅拌的公转速度过大，浆料容易出现凝胶。
控制第二搅拌的公转速度在合适的范围，使得浆料具有低的出货粘度和低的静置24小时后的粘度，同时有利于减缓浆料的凝胶状态，提高浆料的稳定性，拓宽浆料涂覆的工艺窗口。
在一些实施方式中，第二搅拌的自转速度1000转/分钟～1300转/分钟，在一些实施方式中，第二搅拌的自转速度可选为1000转/分钟、1100转/分钟、1200转/分钟、1300转/分钟中的任意一种。
若第二搅拌的公转速度过小，粘结剂与溶剂不能有效混合，浆料的出货粘度和静置24小时后的粘度过大，浆料容易出现凝胶，浆料的稳定性较差；若第二搅拌的公转速度过大，无法进一步显著改善浆料的出货粘度、浆料静置24小时后的粘度、浆料的凝胶现象，反而导致能源的浪费、生产成本的提高。
控制第二搅拌的自转速度在合适的范围，使得浆料具有低的出货粘度、低的静置24小时后的粘度和抗凝胶性，有利于提高浆料的涂布性能、加工性能和稳定性。
在一些实施方式中，第四搅拌的搅拌时间为60分钟～90分钟。在些实施方式中，第四搅拌的搅拌时间可选为60分钟、70分钟、80分钟、90分钟中的任意一种。
若第四搅拌的搅拌时间过短，粘结剂与溶剂不能和初级浆料有效混合，浆料的出货粘度和静置24小时后的粘度过大，浆料容易出现凝胶，浆料的稳定性较差；若第四搅拌的搅拌时间过长，会导致正极活性材料和导电剂容易发生破碎，浆料容易出现凝胶。
控制第四搅拌的搅拌时间在合适的范围，使得浆料具有低的出货粘度和低的静置24小时后的粘度，同时有利于减缓浆料的凝胶状态，提高浆料的稳定性，拓宽工艺窗口。
在一些实施方式中，第四搅拌的公转速度为25转/分钟～40转/分 钟。在一些实施方式中，第四搅拌的公转速度可选为25转/分钟、30转/分钟、35转/分钟、40转/分钟中的任意一种。
若第四搅拌的公转速度过小，粘结剂与溶剂不能和初级浆料有效混合，浆料的出货粘度和静置24小时后的粘度过大，浆料容易出现凝胶，浆料的稳定性较差；若第四搅拌的公转速度过大，会导致正极活性材料和导电剂容易发生破碎，浆料容易出现凝胶。
控制第四搅拌的公转速度在合适的范围，使得浆料具有低的出货粘度和低的静置24小时后的粘度，同时有利于减缓浆料的凝胶状态，提高浆料的稳定性，拓宽工艺窗口。
在一些实施方式中，第四搅拌的自转速度为1000转/分钟～1300转/分钟。在一些实施方式中，第四搅拌的自转速度可选为1000转/分钟、1100转/分钟、1200转/分钟、1300转/分钟中的任意一种。
若第四搅拌的自转速度过小，粘结剂与溶剂不能和初级浆料有效混合，浆料的出货粘度和静置24小时后的粘度过大，浆料容易出现凝胶，浆料的稳定性较差；若第四搅拌的自转速度过大，会导致正极活性材料和导电剂容易发生破碎，浆料容易出现凝胶。
控制第四搅拌的搅拌时间在合适的范围，使得浆料具有低的出货粘度和低的静置24小时后的粘度，同时有利于减缓浆料的凝胶状态，提高浆料的稳定性，拓宽工艺窗口。
在一些实施方式中，正极浆料的固含量为65％～70％，且所述正极浆料的粘度为6000～31000mPa·s。
正极浆料的固含量和粘度均可以通过本领域已知的任意方法进行测试。如粘度可以采用旋转粘度剂测量，固含量可以通过测试浆料去除水分前后的重量进行测试。
在一些实施方式中，正极浆料的固含量可选为65％、66％、67％、68％、69％、70％中的任意一种。
在一些实施方式中，正极浆料的粘度可选为6000mPa·s、7000mPa·s、8000mPa·s、9000mPa·s、10000mPa·s、11000mPa·s、12000mPa·s、13000mPa·s、14000mPa·s、15000mPa·s、16000mPa·s、 17000mPa·s、18000mPa·s、19000mPa·s、20000mPa·s、21000mPa·s、22000mPa·s、23000mPa·s、24000mPa·s、25000mPa·s、26000mPa·s、27000mPa·s、28000mPa·s、29000mPa·s、30000mPa·s、31000mPa·s中的任意一种。
本申请的制备方法成型的浆料固含量高，粘度适宜，具有优异的加工性，上述浆料可以直接用于后续的涂布工艺，能够提高生产效率。
在一些实施方式中，基于所述正极活性材料、所述导电剂、所述第二搅拌中使用的粘结剂和所述第四搅拌中使用的粘结剂的总质量计，所述第二搅拌中使用的溶剂的质量百分数为35％～45％，所述第四搅拌中使用的溶剂的质量百分数为4％～10％。
在一些实施方式中，所述正极浆料中，所述正极活性材料的质量、所述粘结剂总质量、所述导电剂的质量的比值为(88～96)∶(2～4)∶(2～8)。
可以理解，粘结剂总质量是指所述第二搅拌中使用的粘结剂和所述第四搅拌中使用的粘结剂的质量和。加入的粘结剂、正极活性材料和导电剂的质量可以由本领域技术人员根据搅拌设备的额定范围确定。
上述范围内的正极浆料既有良好的加工性能，又使得成型后的正极极片具有优异的电化学性能。
[正极浆料]
本申请的一个实施方式中，提供一种正极浆料，正极浆料的固含量为65％～70％，所述正极浆料的初始粘度为6000～31000mPa·s，且静置24小时后，所述正极浆料的粘度不超过49000mPa·s。
初始粘度是指正极浆料刚配置完成时的出货粘度。
在一些实施方式中，所述正极浆料是由上述任意实施方式中的正极浆料的制备方法制备的。
在一些实施方式中，正极浆料在静置24小时后，粘度不超过48000mPa·s、45000mPa·s、41000mPa·s、35000mPa·s、31000mPa·s或26000mPa·s。
本申请的制备方法成型的浆料固含量高，粘度适宜，具有优异的加工性，同时浆料具有优异的存储性能。
另外，以下适当参照附图对本申请的二次电池、电池模块、电池包和用电装置进行说明。
本申请的一个实施方式中，提供一种二次电池。
通常情况下，二次电池包括正极极片、负极极片、电解质和隔离膜。正极极片由任意实施方式中的制备方法制备的正极浆料制备而得。
在一些实施方式中，二次电池为锂离子电池、钠离子电池、镁离子电池、钾离子电池中的任意一种。
在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之间起到传导离子的作用。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使离子通过。
[正极极片]
正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，正极膜层由本申请任意实施方式中的正极浆料的制备方法制备的正极浆料或任意实施方式中的正极浆料制备而得。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，所述正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，正极活性材料可采用本领域公知的用于电池 的正极活性材料。作为示例，正极活性材料可包括以下材料中的至少一种：橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。但本申请并不限定于这些材料，还可以使用其他可被用作电池正极活性材料的传统材料。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。其中，锂过渡金属氧化物的示例可包括但不限于锂钴氧化物(如LiCoO 2)、锂镍氧化物(如LiNiO 2)、锂锰氧化物(如LiMnO 2、LiMn 2O 4)、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物(如LiNi 1/3Co 1/3Mn 1/3O 2(也可以简称为NCM 333)、LiNi 0.5Co 0.2Mn 0.3O 2(也可以简称为NCM 523)、LiNi 0.5Co 0.25Mn 0.25O 2(也可以简称为NCM 211)、LiNi 0.6Co 0.2Mn 0.2O 2(也可以简称为NCM 622)、LiNi 0.8Co 0.1Mn 0.1O 2(也可以简称为NCM 811)、锂镍钴铝氧化物(如LiNi 0.85Co 0.15Al 0.05O 2)及其改性化合物等中的至少一种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂(如LiFePO 4(也可以简称为LFP))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO 4)、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料中的至少一种。
在一些实施方式中，正极膜层还可选地包括粘结剂。作为示例，所述粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。
在一些实施方式中，正极膜层还可选地包括导电剂。作为示例，所述导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极活性材料、导电剂、粘结剂和溶剂(例如N-甲基-2-吡咯烷酮)采用本申请任意实施方式中的正极浆料的制备方法进行正极浆料的制备，将制备的正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
[负极极片]
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，所述负极膜层包括负极活性材料。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面中的任意一者或两者上。
在一些实施方式中，所述负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，负极活性材料可采用本领域公知的用于电池的负极活性材料。作为示例，负极活性材料可包括以下材料中的至少一种：人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂等。所述硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的至少一种。所述锡基材料可选自单质锡、锡氧化合物以及锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性材料的传统材料。这些负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在一些实施方式中，负极膜层还可选地包括粘结剂。所述粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。
在一些实施方式中，负极膜层还可选地包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，负极膜层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可得到负极极片。
[电解质]
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的或全固态的。
在一些实施方式中，所述电解质采用电解液。所述电解液包括电解质盐和溶剂。
在一些实施方式中，电解质盐可选自六氟磷酸锂、四氟硼酸锂、高氯酸锂、六氟砷酸锂、双氟磺酰亚胺锂、双三氟甲磺酰亚胺锂、三氟甲磺酸锂、二氟磷酸锂、二氟草酸硼酸锂、二草酸硼酸锂、二氟二草酸磷酸锂及四氟草酸磷酸锂中的至少一种。
在一些实施方式中，溶剂可选自碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的至少一种。
在一些实施方式中，所述电解液还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
[隔离膜]
在一些实施方式中，二次电池中还包括隔离膜。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜， 也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施方式中，二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图1是作为一个示例的方形结构的二次电池5。
在一些实施方式中，参照图2，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔内。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或多个，本领域技术人员可根据具体实际需求进行选择。
在一些实施方式中，二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。
图3是作为一个示例的电池模块4。参照图3，在电池模块4中，多个二次电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个二次电池5容纳于该容纳空间。
在一些实施方式中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以为一个或多个，具体数量本领域技术人员可根据电池包的应用和容量进行选择。
图4和图5是作为一个示例的电池包1。参照图4和图5，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
另外，本申请还提供一种用电装置，所述用电装置包括本申请提供的二次电池、电池模块、或电池包中的至少一种。所述二次电池、电池模块、或电池包可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置可以包括移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等，但不限于此。
作为所述用电装置，可以根据其使用需求来选择二次电池、电池模块或电池包。
图6是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用二次电池作为电源。
实施例
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
一、制备方法
实施例1
1)正极浆料的制备
第一搅拌：将25kg导电炭黑与1200kg磷酸铁锂在双行星搅拌机中混合搅拌混合，搅拌时间为15分钟，公转速度为25转/分钟，自转速度为0，得到干混料；
第二搅拌：将17kg重均分子量为180万的聚偏氟乙烯粘结剂与500kg N-甲基-2-吡咯烷酮混合搅拌，公转速度25转/分钟，自转速1200转/分钟，搅拌时间60分钟，得到胶液；
第三搅拌：将干混料加入到胶液中混合搅拌，公转速度20转/分钟，自转速度600转/分钟，搅拌10分钟，再以公转速度25转/分钟，自转速度1200转/分钟，搅拌70分钟，得到初级浆料；
第四搅拌：将8kg重均分子量为180万的聚偏氟乙烯粘结剂、60kg N-甲基-2-吡咯烷酮和初级浆料混合搅拌，公转速度30转/分钟，自转速度1200转/分钟，搅拌70分钟，得到粘度为18000mPa·s、固含量为68％的正极浆料。
实施例2～3
制备方法与实施例1基本相同，区别在于调整了第二搅拌中粘结剂的质量比，具体参数参见表格1。
实施例4～9
制备方法与实施例1基本相同，区别在于调整了聚偏氟乙烯粘结剂的重均分子量，具体参数参见表格1。
实施例10～67
制备方法与实施例1基本相同，区别在于调整了搅拌参数，具体参数参见表1。
对比例1
1)将8kg导电炭黑与1200kg磷酸铁锂在双行星搅拌机中混合搅拌混合，搅拌时间为15分钟，公转速度为25转/分钟，自转速度为0，得到干混料；
2)将18kg重均分子量为180万的聚偏氟乙烯粘结剂与560kg N- 甲基-2-吡咯烷酮混合搅拌，公转速度25转/分钟，自转速1200转/分钟，搅拌时间60分钟，得到胶液；
3)将干混料加入胶液中，先进行低速搅拌，搅拌时间200分钟，公转速度25转/分钟，自转速度1200转/分钟；再进行高速搅拌，搅拌60分钟，公转速度为30转/分钟，自转速度为1300转/分钟，得到正极浆料。
对比例2～5
制备方法与对比例1基本相同，区别在于调整了聚偏氟乙烯粘结剂的重均分子量，具体参数参见表格1。
对比例6
1)将18kg重均分子量为180万的聚偏氟乙烯粘结剂与560kg N-甲基-2-吡咯烷酮混合搅拌，公转速度25转/分钟，自转速1200转/分钟，搅拌时间60分钟，得到胶液；
2)将1200kg磷酸铁锂加入到胶液混合搅拌，搅拌时间60分钟，公转速度为25转/分钟，自转速度为1200转/分钟，得到初级浆料；
3)将8kg导电炭黑加入到初级浆料混合搅拌，搅拌时间140分钟，公转速度为30转/分钟，自转速度为1200转/分钟，得到正极浆料。
对比例7～10
制备方法与对比例6基本相同，区别在于调整了聚偏氟乙烯粘结剂的重均分子量，具体参数参见表格1。
对比例11～12
制备方法与实施例1基本相同，区别在于调整了第二搅拌中粘结剂的质量比，具体参数参见表格1。
二、浆料性质测试
1、浆料出货粘度测试
将制得的正极浆料放置10分钟后出货，采用Dveslvtjo旋转粘度测试仪(BROOKFIELD)首次测得的粘度值记为出货粘度，其中，测试条件：25℃，转速12转/分钟，测定不低于2000mPa·s 粘度采用64转子，测定小于2000mPa·s粘度采用62转子。平行测定三次，取平均值。
2、浆料静置24小时之后的粘度变化测试
将静置24小时后的浆料重新进行粘度测试，采用Dveslvtjo旋转粘度测试仪(BROOKFIELD)测得的粘度值记为24小时粘度，其中，测试条件：25℃，转速12转/分钟，测定不低于200mPa·s粘度采用64转子，测定小于2000mPa·s粘度采用62转子。平行测定三次，取平均值。
3、浆料静置24小时之后的凝胶状态测试
在浆料静置24小时后，使用钢直尺挑起烧杯中的浆料，根据浆料流动状态判断浆料的凝胶状态。
无凝胶状态为浆料自然流动不断流，浆料在钢尺表面平流，无结块；
轻微凝胶状态为浆料自然流动不断流，但流体较细，浆料在钢尺表面基本平摊，有轻微小块；
中度凝胶状态为浆料自然滴落、时断时续；不连续成流，浆料在钢尺表面无法平摊，有明显块状团聚；
严重凝胶状态为浆料无法成流流下，结成块掉落或直接留在钢尺上无法流下。
4、浆料固含量测试
取小片铝箔于水分测定仪内称重，记为M0，清零，水分测定仪为MOC-120H；
取上层浆料，少量涂覆与极片上，然后放入水分测定仪内称重，记为M1；
合上设备，开始烘干；结束后，记录称重数据，记录为M2，并计算固含量，固含量为(M2-M0)/(M1-M0)。
三、各实施例、对比例测试结果分析
按照上述方法分别制备各实施例和对比例的正极浆料，并测量各项参数，结果见下表1。
表1实施例和对比例的制备参数和结果表
Figure PCTCN2022131535-appb-000001
Figure PCTCN2022131535-appb-000002
Figure PCTCN2022131535-appb-000003
Figure PCTCN2022131535-appb-000004
根据表1的结果可知，实施例1～67中的正极浆料，均是采用本申请公开的浆料制备方法制备的，均包括第一搅拌、第二搅拌、第三搅拌和第四搅拌；第一搅拌中，将正极活性材料与导电剂混合搅拌，制备干混料；第二搅拌中，将粘结剂与溶剂混合搅拌，制备胶液；第三搅拌中，将干混料与胶液混合搅拌，制备初级浆料；第四搅拌中，将粘结剂、溶剂与初级浆料混合搅拌，制备正极浆料；第二搅拌中使用的粘结剂和溶剂分别与第四搅拌中使用的粘结剂和溶剂相同；基于第二搅拌中使用的粘结剂和第四搅拌中使用的粘结剂的总质量计，第二搅拌中使用的粘结剂的质量比为50％～70％，第四搅拌中使用的粘结剂的质量比为30％～50％。
从实施例1～9与对比例1～10的对比可见，本公开的浆料制备方法具有通用性，能够适用于包含重均分子量在20万～800万的聚偏氟乙烯粘结剂的浆料，对于低分子量粘结剂和高分子量粘结剂具有普适性。
从对比例可见，现有技术中的制备工艺对于重均分子量为180万的粘结剂都始终无法改善其凝胶状态。而本申请公开的制备方法使得包含重均分子量高达800万粘结剂的浆料依然具有低的出货粘度和良好的抗凝胶性，能够满足新一代高分子量粘结剂的使用需求。
从实施例1～3与对比例11～12的对比可见，控制第一搅拌中加入的粘结剂的比例为粘结剂总质量的50％～70％，可以降低浆料的出货粘度，有效缓解浆料的凝胶，拓宽浆料涂覆的工艺窗口。
从实施例1、实施例5～9与实施例4的对比，控制聚偏氟乙烯粘结剂的重均分子量为80万～800万，在不明显改变浆料的出货粘度、浆料静置24小时后的粘度、浆料的凝胶现象的情况下，同时还能满足极片粘结性能的要求。
从实施例27～29与实施例26、实施例31～33与实施例30对比可见，第三搅拌中先进行低速搅拌，再进行高速搅拌，能够有效降低浆料的出货粘度和浆料静置24小时后的粘度，减缓浆料凝胶，改善浆料的涂布性和加工性。
从实施例1、实施例11～12与实施例10对比可见，控制第三搅拌中低速搅拌的搅拌时间为5分钟～15分钟，可以降低的浆料的出货粘度和静置24小时后的粘度，减缓浆料凝胶，扩展浆料涂覆的工艺窗口，从实施例1、实施例11～12与实施例13对比可见，控制第三搅拌中低速搅拌的搅拌时间为5分钟～15分钟，能够兼顾合浆质量和效率，降低出货粘度，减缓浆料凝胶。
从实施例1、实施例15～16与实施例14对比可见，控制第三搅拌中低速搅拌的公转速度为15转/分钟～25转/分钟，可以降低的浆料的出货粘度和静置24小时后的粘度，减缓浆料凝胶，扩展浆料涂覆的工艺窗口，从实施例1、实施例15～16与实施例17对比可见，控制第三搅拌中低速搅拌的公转速度为15转/分钟～25转/分钟，能够兼顾合浆质量和成本，降低出货粘度，减缓浆料凝胶。
从实施例1、实施例19～20与实施例18对比可见，控制第三搅拌中的低速搅拌的自转速度为400转/分钟～800转/分钟，可以降低的浆料的出货粘度和静置24小时后的粘度，减缓浆料凝胶，提高浆料的存储性能，扩展浆料涂覆的工艺窗口，从实施例1、实施例19～20与实施例21对比可见，控制第三搅拌低速搅拌的自转速度为400转/分钟～800转/分钟，能够兼顾合浆质量和成本，降低出货粘度，减缓浆料凝胶。
从实施例1、实施例23～24与实施例22对比可见，控制第三搅拌中高速搅拌的搅拌时间为50分钟～80分钟，可以降低的浆料的出货粘度和静置24小时后的粘度，减缓浆料凝胶，提高浆料的存储性能，扩展浆料涂覆的工艺窗口，从实施例1、实施例23～24与实施例25对比可见，控制第三搅拌中高速搅拌的搅拌时间为50分钟～80分钟，能够兼顾合浆质量和效率，降低出货粘度，减缓浆料凝胶。
从实施例1、实施例27～28与实施例26对比可见，控制第三搅拌中高速搅拌的公转速度为20转/分钟～30转/分钟，可以降低的浆料的出货粘度和静置24小时后的粘度，减缓浆料凝胶，提高浆料的存储性能，扩展浆料涂覆的工艺窗口，从实施例1、实施例15～16与实 施例17对比可见，控制第三搅拌中高速搅拌的公转速度为15转/分钟～25转/分钟，能够兼顾合浆质量和成本，降低出货粘度，减缓浆料凝胶。
从实施例1、实施例31～32与实施例30对比可见，控制第三搅拌中高速搅拌的自转速度为1000转/分钟～1300转/分钟，可以降低的浆料的出货粘度和静置24小时后的粘度，减缓浆料凝胶，提高浆料的存储性能，扩展浆料涂覆的工艺窗口，从实施例1、实施例31～32与实施例33对比可见，控制第三搅拌中高速搅拌的自转速度为1000转/分钟～1300转/分钟，能够兼顾合浆质量和成本，降低出货粘度，减缓浆料凝胶。
从实施例1与实施例34～35对比可见，控制第一搅拌的自转速度为0，可以降低浆料静置24小时后的粘度，减缓浆料的凝胶现象，提高浆料的稳定性，拓宽工艺窗口。
从实施例1、实施例37～38与实施例36对比可见，控制第一搅拌的搅拌时间5分钟～20分钟，可以降低的浆料的出货粘度和静置24小时后的粘度，减缓浆料的凝胶现象，提高浆料的稳定性，拓宽工艺窗口。从实施例1、实施例37～38与实施例39对比可见，控制第一搅拌的搅拌时间5分钟～20分钟，能够兼顾合浆质量和效率，降低出货粘度，减缓浆料凝胶。
从实施例1、实施例41～42与实施例40对比可见，控制第一搅拌的公转速度为20转/分钟～30转/分钟，可以降低的浆料的出货粘度和静置24小时后的粘度，减缓浆料的凝胶现象，提高浆料的稳定性，拓宽工艺窗口。从实施例1、实施例41～42与实施例43对比可见，控制第一搅拌的公转速度为20转/分钟～30转/分钟，能够兼顾合浆质量和成本，降低出货粘度，减缓浆料凝胶。
从实施例1、实施例45～46与实施例44对比可见，控制第二搅拌的搅拌时间50分钟～80分钟，可以降低的浆料的出货粘度和静置24小时后的粘度，减缓浆料的凝胶现象，提高浆料的稳定性，拓宽工艺窗口。从实施例1、实施例45～46与实施例47对比可见，控制第 二搅拌的搅拌时间50分钟～80分钟，能够兼顾合浆质量和效率，降低出货粘度，减缓浆料凝胶。
从实施例1、实施例49～50与实施例48对比可见，控制第二搅拌的公转速度为25转/分钟～40转/分钟，可以降低的浆料的出货粘度和静置24小时后的粘度，减缓浆料的凝胶现象，提高浆料的稳定性，拓宽工艺窗口。从实施例1、实施例49～50与实施例51对比可见，控制第二搅拌的公转速度为25转/分钟～40转/分钟，能够减缓浆料凝胶，提高浆料的稳定性，拓宽工艺窗口。
从实施例1、实施例53～54与实施例52对比可见，控制第二搅拌的自转速度为1000转/分钟～1300转/分钟，可以降低的浆料的出货粘度和静置24小时后的粘度，减缓浆料的凝胶现象，提高浆料的稳定性，拓宽工艺窗口。从实施例1、实施例53～54与实施例55对比可见，控制第二搅拌的自转速度为1000转/分钟～1300转/分钟，能够兼顾合浆质量和成本，降低出货粘度，减缓浆料凝胶。
从实施例1、实施例57～58与实施例56对比可见，控制第四搅拌的搅拌时间为60分钟～90分钟，可以降低的浆料的出货粘度和静置24小时后的粘度，减缓浆料的凝胶现象，提高浆料的稳定性，拓宽工艺窗口。从实施例1、实施例57～58与实施例59对比可见，控制第四搅拌的搅拌时间为60分钟～90分钟，能够减缓浆料凝胶，提高浆料的稳定性，拓宽工艺窗口。
从实施例1、实施例61～62与实施例60对比可见，控制第四搅拌的公转速度为25转/分钟～40转/分钟，可以降低的浆料的出货粘度和静置24小时后的粘度，减缓浆料的凝胶现象，提高浆料的稳定性，拓宽工艺窗口。从实施例1、实施例61～62与实施例63对比可见，控制第四搅拌的公转速度为25转/分钟～40转/分钟，能够减缓浆料凝胶，提高浆料的稳定性，拓宽工艺窗口。
从实施例1、实施例65～66与实施例64对比可见，控制第四搅拌的自转速度为1000转/分钟～1300转/分钟，可以降低的浆料的出货粘度和静置24小时后的粘度，减缓浆料的凝胶现象，提高浆料的稳 定性，拓宽工艺窗口。从实施例1、实施例65～66与实施例67对比可见，控制第四搅拌的自转速度为1000转/分钟～1300转/分钟，能够减缓浆料凝胶，提高浆料的稳定性，拓宽工艺窗口。
从实施例可见，本申请公开的固含量为65％～70％的正极浆料的粘度为6000mPa·s～31000mPa·s，该正极浆料具有良好的涂布性和加工性。
从实施例可见，基于正极活性材料、导电剂、第二搅拌中使用的粘结剂和第四搅拌中使用的粘结剂的总质量计，控制第二搅拌中使用的溶剂的质量百分数为35％～45％，第四搅拌中使用的溶剂的质量百分数为4％～10％。
从实施例可见，本申请公开的正极浆料的固含量为65～70％，正极浆料的初始粘度为6000～31000mPa.s，且静置24小时后，正极浆料的粘度不超过49000mPa·s。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (26)

  1. 一种正极浆料的制备方法，其特征在于，包括第一搅拌、第二搅拌、第三搅拌和第四搅拌；
    所述第一搅拌中，将正极活性材料与导电剂混合搅拌，制备干混料；
    所述第二搅拌中，将粘结剂与溶剂混合搅拌，制备胶液；
    所述第三搅拌中，将所述干混料与所述胶液混合搅拌，制备初级浆料；
    所述第四搅拌中，将粘结剂、溶剂与所述初级浆料混合搅拌，制备正极浆料；
    所述第二搅拌中使用的粘结剂和溶剂分别与所述第四搅拌中使用的粘结剂和溶剂相同；基于所述第二搅拌中使用的粘结剂和所述第四搅拌中使用的粘结剂的总质量计，所述第二搅拌中使用的粘结剂的质量比为50％～70％，所述第四搅拌中使用的粘结剂的质量比为30％～50％。
  2. 根据权利要求1所述的正极浆料的制备方法，其特征在于，所述粘结剂包含至少一种重均分子量为80万～800万的聚偏氟乙烯。
  3. 根据权利要求1或2所述的正极浆料的制备方法，其特征在于，所述第三搅拌中先进行低速搅拌，再进行高速搅拌。
  4. 根据权利要求3所述的正极浆料的制备方法，其特征在于，所述第三搅拌中低速搅拌的公转速度为15转/分钟～25转/分钟，自转速度为400转/分钟～800转/分钟，搅拌时间为5分钟～15分钟。
  5. 根据权利要求3或4所述的正极浆料的制备方法，其特征在于，所述第三搅拌中高速搅拌的公转速度为20转/分钟～30转/分钟，自转速度为1000转/分钟～1300转/分钟，搅拌时间为50分钟～80分钟。
  6. 根据权利要求1至5中任一项所述的正极浆料的制备方法，其特征在于，所述第一搅拌的自转速度为0。
  7. 根据权利要求1至6中任一项所述的正极浆料的制备方法，其特征在于，所述第一搅拌的公转速度为20转/分钟～30转/分钟。
  8. 根据权利要求1至7中任一项所述的正极浆料的制备方法，其特征在于，所述第一搅拌的搅拌时间为5分钟～20分钟。
  9. 根据权利要求1至8中任一项所述的正极浆料的制备方法，其特征在于，所述第二搅拌的搅拌时间为50分钟～80分钟。
  10. 根据权利要求1至9中任一项所述的正极浆料的制备方法，其特征在于，所述第二搅拌的公转速度为25转/分钟～40转/分钟。
  11. 根据权利要求1至10中任一项所述的正极浆料的制备方法，其特征在于，所述第二搅拌的自转速度1000转/分钟～1300转/分钟。
  12. 根据权利要求1至11中任一项所述的正极浆料的制备方法，其特征在于，所述第四搅拌的搅拌时间为60分钟～90分钟。
  13. 根据权利要求1至12中任一项所述的正极浆料的制备方法，其特征在于，所述第四搅拌的公转速度为25转/分钟～40转/分钟。
  14. 根据权利要求1至13中任一项所述的正极浆料的制备方法，其特征在于，所述第四搅拌的自转速度为1000转/分钟～1300转/分钟。
  15. 根据权利要求1至14中任一项所述的正极浆料的制备方法，其特征在于，所述正极浆料的固含量为65％～70％，且所述正极浆料的粘度为6000～31000mPa·s。
  16. 根据权利要求1至15中任一项所述的正极浆料的制备方法，其特征在于，基于所述正极活性材料、所述导电剂、所述第二搅拌中使用的粘结剂和所述第四搅拌中使用的粘结剂的总质量计，所述第二搅拌中使用的溶剂的质量百分数为35％～45％，所述第四搅拌中使用的溶剂的质量百分数为4％～10％。
  17. 根据权利要求1至16中任一项所述的正极浆料的制备方法，其特征在于，所述正极浆料中，所述正极活性材料的质量、所述粘结剂总质量、所述导电剂的质量的比值为(88～96)∶(2～4)∶(2～8)。
  18. 根据权利要求1至17中任一项所述的正极浆料的制备方法，其特征在于，所述正极活性材料为磷酸铁锂及其改性材料、锂镍钴锰氧化物及其改性材料中的至少一种，所述改性材料是通过掺杂、导电碳包覆、导电金属包覆、导电聚合物包覆中的一种或多种改性方式制备的。
  19. 根据权利要求1至18中任一项所述的正极浆料的制备方法，其特征在于，所述溶剂选自N-甲基-2-吡咯烷酮、N,N-二甲基丙酰胺、N,N-二乙基丙酰胺、N,N-二丙基丙酰胺、N,N-二丁基丙酰胺、N,N-二甲基乙基丙酰胺以及3-丁氧基-N-甲基丙酰胺中的一种或多种。
  20. 一种正极浆料，其特征在于，所述正极浆料是通过权利要求1至19中任一项所述的正极浆料的制备方法制备的。
  21. 根据权利要求20所述的正极浆料，所述正极浆料的固含量为65％～70％，所述正极浆料的初始粘度为6000～31000mPa·s，且静置24小时后，所述正极浆料的粘度不超过49000mPa·s。
  22. 一种二次电池，其特征在于，包括正极极片、隔离膜、负极极片以及电解液，所述正极极片由权利要求1至19中任一项所述的正极浆料的制备方法制备的正极浆料、权利要求20或21所述的正极浆料中的至少一种制备而得。
  23. 根据权利要求22所述的二次电池，其特征在于，所述二次电池为锂离子电池、钠离子电池、镁离子电池、钾离子电池中的任意一种。
  24. 一种电池模块，其特征在于，包括权利要求22或23所述的二次电池。
  25. 一种电池包，其特征在于，包括权利要求22或23所述的二次电池、权利要求24所述的电池模块中的至少一种。
  26. 一种用电装置，其特征在于，包括选自权利要求22或23所述的二次电池、权利要求24所述的电池模块或权利要求25所述的电池包中的至少一种。
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