WO2022127761A1 - 一种正极片及包括该正极片的锂离子电池 - Google Patents

一种正极片及包括该正极片的锂离子电池 Download PDF

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Publication number
WO2022127761A1
WO2022127761A1 PCT/CN2021/137729 CN2021137729W WO2022127761A1 WO 2022127761 A1 WO2022127761 A1 WO 2022127761A1 CN 2021137729 W CN2021137729 W CN 2021137729W WO 2022127761 A1 WO2022127761 A1 WO 2022127761A1
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Prior art keywords
positive electrode
coating
current collector
lithium
electrode current
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PCT/CN2021/137729
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English (en)
French (fr)
Inventor
张健
彭冲
李俊义
徐延铭
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珠海冠宇电池股份有限公司
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Priority claimed from CN202011469382.4A external-priority patent/CN112599722A/zh
Priority claimed from CN202011469365.0A external-priority patent/CN112599721A/zh
Priority claimed from CN202011468013.3A external-priority patent/CN112582581A/zh
Application filed by 珠海冠宇电池股份有限公司 filed Critical 珠海冠宇电池股份有限公司
Priority to EP21905690.0A priority Critical patent/EP4160719A1/en
Publication of WO2022127761A1 publication Critical patent/WO2022127761A1/zh
Priority to US18/168,704 priority patent/US20230207820A1/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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • 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
    • 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • 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
    • 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
    • H01M4/366—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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being 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
    • H01M4/621—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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/30—Batteries in portable systems, e.g. mobile phone, laptop
    • 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
    • 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 invention belongs to the technical field of lithium ion batteries, and in particular relates to a positive electrode sheet and a lithium ion battery including the positive electrode sheet.
  • Lithium-ion batteries are widely used in smart phones, notebook computers, Bluetooth, wearable devices and other fields due to their high platform voltage, high energy density, no memory effect, and long life.
  • the lithium-ion battery suffers mechanical damage (acupuncture, heavy object impact, etc.)
  • an internal short circuit will occur, and the lithium-ion battery with an internal short circuit will release a lot of heat in a very short period of time, resulting in the battery Fire failure, has a great safety hazard.
  • the invention provides a positive electrode sheet and a lithium ion battery including the positive electrode sheet.
  • the use of the positive electrode sheet can solve the problems of fire failure of the lithium ion battery under the condition of mechanical abuse, and improve the safety performance of the lithium ion battery.
  • the cycle performance of the lithium ion battery is not affected, which is comparable to the cycle performance of the existing lithium ion battery, that is, the safety performance of the lithium ion battery is significantly improved on the premise of maintaining the cycle performance of the lithium ion battery.
  • a positive electrode sheet the positive electrode sheet comprises a positive electrode current collector and a positive electrode coating
  • the positive electrode coating comprises a first coating layer and a second coating layer
  • the first coating layer is coated on the surface of the positive electrode current collector
  • the The second coating layer is coated on the surface of the first coating layer
  • the first coating layer includes an inorganic filler, a first conductive agent and a first binder
  • the second coating layer includes a positive electrode active material, a second conductive agent and a second binder
  • the content of the first binder in the first coating is greater than the content of the second binder in the second coating
  • the positive electrode sheet satisfies at least one of the following conditions (1) to (7):
  • the bonding force between the first coating and the positive electrode current collector is greater than 30N/m;
  • the maximum thickness of the positive electrode coating remaining on the positive electrode current collector is greater than or equal to 2 ⁇ m;
  • the thickness of the positive electrode coating remaining on the positive electrode current collector accounts for more than 5% of the thickness of the positive electrode coating on the positive electrode current collector before peeling;
  • the total mass of the positive electrode coating remaining on the positive electrode current collector accounts for more than 10% of the total mass of the positive electrode coating on the positive electrode current collector before peeling;
  • the total area of the positive electrode coating remaining on the positive electrode current collector accounts for more than 70% of the total area of the positive electrode coating before peeling.
  • the bonding force between the first coating and the positive electrode current collector is greater than the bonding force between the first coating and the second coating, and/or, when the first coating
  • the bonding force between the layer and the positive electrode current collector is greater than the bonding force between the positive electrode active material particles of the second coating layer
  • the positive electrode current collector can be protected in the event of mechanical abuse (such as needle punching, heavy object impact).
  • the surface of the fluid is well protected by the first coating and is not easy to be exposed, so that the contact probability between the positive electrode current collector and the negative electrode sheet is reduced, thereby reducing the short circuit probability between the positive electrode current collector and the negative electrode sheet, and improving the safety of the battery.
  • the bonding force between the first coating and the positive electrode current collector is greater than 30 N/m, it can be realized that the surface of the positive electrode current collector is covered by the first coating in the case of mechanical abuse (such as needle punching, heavy object impact).
  • the layer is well protected and is not easy to be exposed, so that the contact probability between the positive electrode current collector and the negative electrode sheet is reduced, thereby reducing the short circuit probability between the positive electrode current collector and the negative electrode sheet, and improving the safety of the battery.
  • the positive electrode coating of the positive electrode sheet is peeled off (the test process is described below), when the thickness of the positive electrode coating remaining on the positive electrode current collector accounts for more than 5% of the thickness of the positive electrode coating on the positive electrode current collector before peeling, it can be achieved.
  • mechanical abuse such as acupuncture, heavy object impact
  • the surface of the positive electrode current collector is well protected by the first coating and is not easily exposed, which reduces the contact probability between the positive electrode current collector and the negative electrode sheet, thereby reducing the positive electrode current collector-
  • the short-circuit probability of the negative electrode sheet improves the safety of the battery.
  • the use of the positive electrode sheet can further reduce the probability of contact between the positive electrode current collector and the negative electrode sheet in the case of mechanical abuse (such as acupuncture, heavy object impact), thereby reducing the short circuit probability of the positive electrode current collector and the negative electrode sheet, and improving the battery. security.
  • the use of the positive electrode sheet can further reduce the probability of contact between the positive electrode current collector and the negative electrode sheet in the case of mechanical abuse (such as acupuncture, heavy object impact), thereby reducing the short circuit probability of the positive electrode current collector and the negative electrode sheet, and improving the battery. security.
  • the present invention also provides a lithium ion battery, the lithium ion battery includes the above-mentioned positive electrode sheet.
  • the present invention provides a positive electrode sheet and a lithium ion battery including the positive electrode sheet, wherein the positive electrode sheet satisfies at least one of the following conditions (1) to (7): (1) the first coating and the positive electrode The bonding force between the current collectors is greater than 30N/m; (2) the bonding force between the first coating and the positive electrode current collector is greater than the bonding force between the first coating and the second coating (3) the cohesive force between the described first coating and the positive electrode current collector is greater than the cohesive force between the positive active material particles of the second coating; (4) the positive electrode coating of the described positive electrode sheet is peeled off Then, the maximum thickness of the positive electrode coating remaining on the positive electrode current collector is greater than or equal to 2 ⁇ m; (5) after the positive electrode coating of the positive electrode sheet is peeled off, the thickness of the positive electrode coating remaining on the positive electrode current collector accounts for the thickness of the positive electrode current collector before peeling off.
  • the total mass of the positive electrode coating remaining on the positive electrode current collector accounts for the total mass of the positive electrode coating on the positive electrode current collector before peeling off.
  • the total area of the positive electrode coating remaining on the positive electrode current collector accounts for more than 70% of the total area of the positive electrode coating before peeling.
  • Fig. 1 The surface state of the pole piece after the peel test in Example 1.
  • Fig. 2 Residual SEM on the surface of the pole piece after peeling test in Example 1.
  • Fig. 3 Residual EDS on the surface of the pole piece after peeling test in Example 1.
  • Fig. 5 The surface state of the pole piece after the peel test in Example 2.
  • Fig. 7 Residual EDS on the surface of the pole piece after peeling test in Example 2.
  • Figure 9 Comparative Example 1 The surface state of the pole piece after the peel test.
  • the present invention provides a positive electrode sheet
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode coating
  • the positive electrode coating includes a first coating layer and a second coating layer
  • the first coating layer coats On the surface of the positive electrode current collector, the second coating layer is coated on the surface of the first coating layer
  • the first coating layer includes an inorganic filler, a first conductive agent and a first binder
  • the second coating layer includes a positive electrode active material, a second conductive agent and a second binder
  • the content of the first binder in the first coating is greater than the content of the second binder in the second coating
  • the positive electrode current collector and the A part of the first binder is bonded, and a part of the positive active material is bonded with another part of the first binder;
  • the positive electrode sheet satisfies at least one of the following conditions (1) to (7):
  • the bonding force between the first coating and the positive electrode current collector is greater than 30 N/m;
  • the maximum thickness of the positive electrode coating remaining on the positive electrode current collector is greater than or equal to 2 ⁇ m;
  • the thickness of the positive electrode coating remaining on the positive electrode current collector accounts for more than 5% of the thickness of the positive electrode coating on the positive electrode current collector before peeling;
  • the total mass of the positive electrode coating remaining on the positive electrode current collector accounts for more than 10% of the total mass of the positive electrode coating on the positive electrode current collector before peeling;
  • the total area of the positive electrode coating remaining on the positive electrode current collector accounts for more than 70% of the total area of the positive electrode coating before peeling off.
  • the positive electrode sheet satisfies (1) that the adhesive force between the first coating layer and the positive electrode current collector is greater than 30 N/m.
  • the positive electrode sheet satisfies (2) the bonding force between the first coating and the positive electrode current collector is greater than the bonding force between the first coating and the second coating; and/or , (3) the bonding force between the first coating and the positive electrode current collector is greater than the bonding force between the positive electrode active material particles of the second coating; and (4) the positive electrode coating of the positive electrode sheet carries out After peeling off, the maximum thickness of the cathode coating remaining on the cathode current collector is greater than or equal to 2 ⁇ m.
  • the positive electrode sheet satisfies (2) the bonding force between the first coating and the positive electrode current collector is greater than the bonding force between the first coating and the second coating; and/or , (3) the bonding force between the first coating and the positive electrode current collector is greater than the bonding force between the positive electrode active material particles of the second coating; and (5) the positive electrode coating of the positive electrode sheet is carried out After stripping, the thickness of the cathode coating remaining on the cathode current collector accounts for more than 5% of the thickness of the cathode coating on the cathode current collector before stripping.
  • the positive electrode sheet satisfies (2) the bonding force between the first coating and the positive electrode current collector is greater than the bonding force between the first coating and the second coating; and/or , (3) the bonding force between the first coating and the positive electrode current collector is greater than the bonding force between the positive active material particles of the second coating; and (6) the positive electrode coating of the positive electrode sheet performs After stripping, the total mass of the cathode coating remaining on the cathode current collector accounts for more than 10% of the total mass of the cathode coating on the cathode current collector before stripping.
  • the positive electrode sheet satisfies (2) the bonding force between the first coating and the positive electrode current collector is greater than the bonding force between the first coating and the second coating; and/or , (3) the bonding force between the first coating and the positive electrode current collector is greater than the bonding force between the positive active material particles of the second coating; and (7) the positive electrode coating of the positive electrode sheet performs After stripping, the total area of the cathode coating remaining on the cathode current collector accounts for more than 70% of the total area of the cathode coating before stripping.
  • the maximum thickness of the cathode coating remaining on the cathode current collector is greater than or equal to the thickness of the first coating. At this time, it can be shown that the first coating in some areas is hardly peeled off, the bonding performance is high, and the safety performance of the pole piece is good.
  • the maximum thickness of the remaining positive electrode coating refers to the maximum thickness of the positive electrode coating remaining on the surface of the positive electrode current collector.
  • the total mass of the residual positive electrode coating refers to the sum of the mass of the positive electrode coating remaining on the surface of the positive electrode current collector
  • the total mass of the positive electrode coating on the positive electrode current collector before peeling refers to the total mass of the positive electrode coating before peeling off The sum of the mass of the cathode coating on the surface of the cathode current collector.
  • the total area of the residual positive electrode coating refers to the sum of the areas of the positive electrode coating remaining on the surface of the positive electrode current collector, and the total area of the positive electrode coating on the positive electrode current collector before peeling refers to the total area of the positive electrode coating before peeling off.
  • the thickness of the residual positive electrode coating refers to the thickness of the positive electrode coating remaining on the surface of the positive electrode current collector
  • the thickness of the positive electrode coating on the positive electrode current collector before peeling refers to the surface of the positive electrode current collector before peeling off thickness of the cathode coating
  • the binding force between the positive electrode active material particles of the second coating layer refers to the binding force between the positive electrode active material particles forming the second coating layer.
  • the bonding force between the first coating and the positive electrode current collector is greater than 30 N/m.
  • the bonding force between the first coating and the positive electrode current collector is greater than or equal to 35 N/m and less than or equal to 300 N/m; preferably, the bonding force between the first coating and the positive electrode current collector The force is greater than or equal to 35N/m and less than or equal to 200N/m.
  • the adhesion between the first coating and the positive electrode current collector is 35N/m, 40N/m, 45N/m, 50N/m, 55N/m, 60N/m, 65N/m, 70N /m, 75N/m, 80N/m, 85N/m, 90N/m, 100N/m, 110N/m, 120N/m, 130N/m, 140N/m, 150N/m, 160N/m, 170N/m , 180N/m, 190N/m or 200N/m.
  • the adhesive force is measured after the lithium ion battery is completely discharged and the positive electrode sheet is left for 2 hours.
  • the lithium-ion battery is fully discharged (discharged from 0.5C to 3.0V), dissected, the positive electrode sheet is taken out, and the positive electrode sheet is placed in an environment with a temperature of 25 ⁇ 3°C and a dew point ⁇ -30°C for 2 hours, and then the Cut the positive electrode piece into small pieces with a length of 240mm and a width of 30mm.
  • Use NITTO No.5000NS tape to cut the tape into small pieces of tape with a length of 200mm and a width of 24mm, and stick one side of the small piece of tape to a steel plate (260mm*50mm).
  • only the second coating layer on the surface of the positive electrode current collector, and/or part of the particles of the first coating layer can be peeled off from the surface of the positive electrode current collector after the peeling test.
  • the inorganic filler is lithium iron phosphate
  • the positive electrode active material is lithium cobalt oxide
  • the EDS on the surface of the positive electrode coating remaining on the positive electrode current collector is in the EDS. Co and O elements were detected. This result at least indicates that the adhesion between the first coating and the positive current collector is greater than the adhesion between the first coating and the second coating, and/or, the first coating
  • the binding force with the positive electrode current collector is greater than the binding force between the positive electrode active material particles of the second coating layer.
  • the thickness of the positive electrode coating remaining on the positive electrode current collector accounts for more than 10%, or more than 20%, or 30% of the thickness of the positive electrode coating on the positive electrode current collector before peeling off. % or more, or 40% or more, or 50% or more, or 60% or more.
  • the total mass of the positive electrode coating remaining on the positive electrode current collector accounts for more than 20%, or more than 30% of the total mass of the positive electrode coating on the positive electrode current collector before peeling, Or more than 40%, or more than 50%, or more than 60%, or more than 70%, or more than 80%, or more than 90%.
  • the total area of the positive electrode coating remaining on the positive electrode current collector accounts for more than 80%, or more than 90% of the total area of the positive electrode coating on the positive electrode current collector before peeling.
  • the median particle size D 50 of the inorganic filler is smaller than the median particle size D 50 of the positive electrode active material.
  • the median particle size D 50 of the inorganic filler is smaller than the median particle size D 50 of the positive electrode active material, and the positive electrode active material in the second coating layer will be embedded in the first coating layer (specifically Refer to the SEM image shown in FIG. 10), so that a part of the first binder in the first coating is in contact with the positive electrode current collector, and another part of the first binder is in contact with the positive electrode active material, that is, the positive electrode current collector is formed A structure in which a part of the first binder is bonded, and a part of the positive electrode active material is bonded with another part of the first binder.
  • the median particle size D50 of the inorganic filler is 0.05-8 ⁇ m.
  • the use of small particle size inorganic fillers can make the first coating thinner and denser.
  • the median particle diameter D50 of the positive electrode active material is 10-20 ⁇ m. Selection of this particle size range can provide a higher compaction density, increasing capacity density.
  • the first conductive agent and the second conductive agent forming the first coating layer and the second coating layer and their contents are the same or different, and the first binder and the second binder and their contents are the same or different.
  • the mass percentage content of each component in the first coating layer is: 40-93 wt % of inorganic filler, 2-15 wt % of first conductive agent, and 5-58 wt % of first binder.
  • the mass percentage content of each component in the first coating layer is: 60-91 wt % of inorganic filler, 3-10 wt % of first conductive agent, and 8-30 wt % of first binder.
  • first binder When the first binder is within this range, it can have a good bonding effect with the positive electrode current collector. If the content of the first binder is too high, the energy density will be reduced, and the performance of the cell will be deteriorated. Selecting this range, combined with an inorganic filler with a median particle size D 50 of 0.05-8 ⁇ m, can form a strong and dense primer.
  • the mass percentage content of the inorganic filler in each component in the first coating layer is 40wt%, 45wt%, 48wt%, 50wt%, 55wt%, 58wt%, 60wt%, 62wt%, 65wt%, 68wt%, 70wt%, 72wt%, 75wt%, 78wt%, 80wt%, 82wt%, 85wt%, 88wt%, 90wt%, 92wt%, 93wt%;
  • the mass percentage content of the first conductive agent in each component in the first coating is 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt% %, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%;
  • the mass percentage content of the first binder in each component in the first coating is 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 18wt%, 20wt%, 22wt%, 25wt%, 28wt%, 30wt%, 33wt%, 35wt%, 38wt%, 40wt%, 45wt%, 48wt%, 50wt%, 55wt% , 58wt%.
  • the mass percentage content of each component in the second coating layer is: 93-99 wt % of the positive active material, 0.5-5 wt % of the second conductive agent, 0.5-2 wt % of the second binder . Selecting the second binder in this content range provides better bonding effect while maintaining a higher energy density.
  • the mass percentage content of each component in the second coating layer is: 95-98 wt % of the positive active material, 1-3 wt % of the second conductive agent, and 1-2 wt % of the second binder.
  • the mass percentage content of the positive active material in each component in the second coating layer is 93wt%, 94wt%, 95wt%, 96wt%, 97wt%, 98wt%, 99wt%;
  • the mass percentage content of the second conductive agent in each component in the second coating is 0.5wt%, 1wt%, 1.5wt%, 1.8wt%, 2wt%, 2.2wt%, 2.5wt% , 2.8wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%;
  • the mass percentage content of the second binder in each component in the second coating is 0.5wt%, 0.8wt%, 1wt%, 1.2wt%, 1.5wt%, 1.8wt%, 2wt% %.
  • the first conductive agent and the second conductive agent are the same or different, and are independently selected from at least one of conductive carbon black, carbon nanotubes, and graphene.
  • the first binder and the second binder are the same or different, and are independently selected from at least one of polyvinylidene fluoride and modified polyvinylidene fluoride.
  • polyvinylidene fluoride and the modified polyvinylidene fluoride are both commercially available products.
  • the crystallinity of the first binder is less than 40%, because a low crystallinity is beneficial to have a better bonding effect.
  • the crystallinity of the second binder is less than 40%, because a low crystallinity is beneficial to have a better bonding effect.
  • the modified polyvinylidene fluoride is acrylate-modified polyvinylidene fluoride.
  • the acrylate group contains a carboxyl group, which can form a chemical bond with the positive electrode current collector (such as aluminum foil) to achieve a strong bond with the positive electrode current collector.
  • the molecular weight of the polyvinylidene fluoride or modified polyvinylidene fluoride is 1 million to 1.5 million, for example, 1.1 million and 1.3 million. Selecting a binder with a larger molecular weight can enhance the bonding performance, while reducing the content of the binder and enhancing its energy density.
  • the inorganic filler is selected from lithium-containing transition metal oxides, specifically selected from lithium cobalt oxide (LCO), nickel-cobalt-manganese ternary material (NCM), nickel-cobalt-aluminum ternary material (NCA), nickel-cobalt-manganese ternary material
  • LCO lithium cobalt oxide
  • NCM nickel-cobalt-manganese ternary material
  • NCA nickel-cobalt-aluminum ternary material
  • nickel-cobalt-manganese ternary material nickel-cobalt-manganese ternary material
  • aluminum quaternary material NCMA
  • lithium iron phosphate LFP
  • LMP lithium manganese phosphate
  • LVP lithium vanadium phosphate
  • LMO lithium manganate
  • lithium-rich manganese base lithium-containing transition metal oxides
  • the inorganic filler is selected from ceramic materials, specifically selected from one or more of alumina, boehmite, magnesium oxide, and magnesium hydroxide;
  • the inorganic filler is selected from a mixture of at least one of lithium-containing transition metal oxides and at least one of ceramic materials.
  • the inorganic filler plays the role of skeleton support.
  • the positive active material is selected from lithium cobalt oxide (LCO), nickel-cobalt-manganese ternary material (NCM), nickel-cobalt-aluminum ternary material (NCA), nickel-cobalt-manganese-aluminum quaternary material (NCMA), phosphoric acid
  • LCO lithium cobalt oxide
  • NCM nickel-cobalt-manganese ternary material
  • NCA nickel-cobalt-aluminum ternary material
  • NCMA nickel-cobalt-manganese-aluminum quaternary material
  • phosphoric acid One or more of lithium iron (LFP), lithium manganese phosphate (LMP), lithium vanadium phosphate (LVP), and lithium manganate (LMO).
  • the positive electrode current collector is selected from aluminum foil.
  • the thickness of the positive electrode current collector is 8-15 ⁇ m.
  • the thickness of the first coating layer is 2-10 ⁇ m, such as 2 ⁇ m, 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, 6 ⁇ m, 8 ⁇ m, 10 ⁇ m;
  • the thickness of the second coating layer (rolling thickness) post thickness) is 30-80 ⁇ m, such as 30 ⁇ m, 35 ⁇ m, 40 ⁇ m, 45 ⁇ m, 50 ⁇ m, 55 ⁇ m, 60 ⁇ m, 65 ⁇ m, 70 ⁇ m, 75 ⁇ m or 80 ⁇ m.
  • the present invention also provides a method for preparing the above-mentioned positive electrode sheet, the method comprising the following steps:
  • the coating is double-layer coating, gravure coating, extrusion coating, and transfer coating.
  • step 2) specifically includes the following steps:
  • the present invention also provides a lithium ion battery, the lithium ion battery includes the above-mentioned positive electrode sheet.
  • the lithium ion battery further includes a negative electrode sheet.
  • the negative electrode sheet includes a negative electrode active material selected from one or more of artificial graphite, natural graphite, mesocarbon microspheres, lithium titanate, silicon carbon negative electrode, and silicon oxygen negative electrode .
  • the present invention also provides a method for preparing the above-mentioned lithium ion battery, the method comprising the following steps:
  • the lithium ion battery is prepared by subjecting the positive electrode sheet and the negative electrode sheet to the processes of rolling, slitting, filming, winding (or lamination), packaging, liquid injection, chemical formation, volume separation, and OCV.
  • the modified PVDF used in the following examples is acrylate-modified PVDF, commercially available under the trade name Solef 5130.
  • the acrylate-modified PVDF has a molecular weight of 1.1 million and a crystallinity of 30-32%.
  • the PVDF1 used in the following examples can be purchased commercially, and is a polyvinylidene fluoride with the brand name HSV-900 produced by Arkema Company.
  • the molecular weight of the PVDF1 is 1 million, and the crystallinity is 25%.
  • the PVDF2 used in the following examples can be purchased commercially, and is purchased from the polyvinylidene fluoride with the grade of 2536 produced by Sinochem Lantian Group Co., Ltd.
  • the molecular weight of the PVDF2 is 1.3 million, and the crystallinity is 43.5%.
  • test method for the adhesion test used in the following examples is as follows:
  • a hand-held roller (diameter 95mm, width 45mm, weight 2kg) to roll back and forth 3 times, and bond the positive electrode piece and the tape piece on the At the same time, then use the tensile machine (the tensile machine model Dongguan Kejian KJ-1065 series) to test (180 degree peeling), the test equipment automatically records the tensile force value that changes with the peeling displacement, and draws a curve of the tensile force value changing with the peeling displacement.
  • the coordinate is the peeling displacement
  • the ordinate is the tensile force value
  • the tensile force value when the curve is flat and the peeling displacement is greater than 5mm is the adhesive force.
  • test method that the total mass of the positive electrode coating remaining on the positive electrode current collector used in the following examples accounts for the total mass of the positive electrode coating on the positive electrode current collector before stripping is:
  • the mass of the stripped substance can be obtained by subtracting the mass of the positive electrode sheet before and after stripping.
  • the test method that the thickness of the positive electrode coating remaining on the positive electrode current collector used in the following examples accounts for the thickness of the positive electrode coating on the positive electrode current collector before stripping is:
  • test method of the safety test used in the following examples is as follows:
  • the first step prepare the first coating slurry, mix 40wt% lithium iron phosphate (LFP), 45wt% modified PVDF, 15wt% carbon black, add NMP, and prepare a slurry by stirring.
  • LFP lithium iron phosphate
  • NMP add NMP
  • the second step prepare the second coating slurry, mix 97wt% lithium cobalt oxide, 1wt% conductive carbon black, 0.8wt% carbon nanotube, 1.2wt% PVDF1, add NMP, and prepare a slurry by stirring.
  • the third step preparing negative electrode slurry, mixing 96wt% artificial graphite, 1wt% conductive carbon black, 1.5wt% SBR and 1.5wt% CMC, adding deionized water, and stirring to prepare a slurry.
  • the fourth step preparation of the positive electrode plate, using the extrusion coating process to coat the first coating slurry of step 1 on the surface of the positive electrode current collector to form a first coating with a thickness of 5 ⁇ m, and apply the second coating of step 2 to the surface of the current collector.
  • the slurry was coated on the surface of the first coating layer to form a second coating layer with a thickness of 40 ⁇ m to obtain a positive electrode sheet.
  • the fifth step preparation of the negative pole piece, the negative pole piece is obtained by coating the negative pole slurry of step 3 on the negative pole current collector.
  • the sixth step the positive and negative pole pieces are rolled, cut, filmed, rolled (or laminated), packaged, injected, chemically formed, divided into volumes, OCV and other processes to prepare lithium ion batteries.
  • the prepared lithium ion battery was tested for adhesion.
  • the surface state of the pole piece after peeling test is shown in Figure 1, Figure 2 and Figure 3. Only part of the particles of the second coating were peeled off from the positive electrode piece, and the peeled Only the lithium cobalt oxide particles of the second coating can be detected on the surface of the pole piece (Co, O elements are detected in the EDS), and the lithium iron phosphate particles of the first coating are not detected (the P element is not detected by the EDS), and the average bonding
  • the force was 62.65N/m, indicating that the first coating of the positive electrode sheet was not peeled off from the positive electrode current collector at this time, indicating that the bonding force between the first coating and the positive electrode current collector was >62.65 N/m.
  • the bonding force between the first coating and the positive electrode current collector is greater than the bonding force between the first coating and the second coating, and the quality of the residual coating on the peeled surface of the positive electrode sheet is divided by the single-sided coating on the positive electrode sheet.
  • the total mass is 96%.
  • the cross-sectional SEM of the positive electrode sheet is shown in Figure 4.
  • the total thickness of the first coating and the second coating is 45 ⁇ m, and the total thickness of the remaining first coating and the second coating after peeling is between 23 ⁇ m and 45 ⁇ m.
  • the thickness of the residual coating on the peeled surface of the positive electrode sheet divided by the thickness of the single-sided coating of the positive electrode sheet is 51% (calculated based on the minimum thickness of the coating).
  • Figure 10 is the SEM of the front pole piece before the peeling test in Example 1. It can be seen from Figure 10 that the large-sized particles (positive electrode active material) of the top layer (the second coating layer) will be embedded in the bottom layer (the second coating layer) due to the rolling pressure.
  • One coating so that part of the first binder in the bottom layer (first coating) will be in contact with the positive electrode current collector, and part of the first binder will be in contact with the large particle size particles (positive electrode active material) in the top layer.
  • a structure is formed in which the positive electrode current collector is bonded with a part of the first binder, and a part of the positive electrode active material is bonded with another part of the first binder.
  • the first step preparing the first coating slurry, mixing 93wt% LFP, 5wt% modified PVDF, 2wt% carbon black, adding NMP, and stirring to prepare a slurry.
  • the second to sixth steps are the same as those in Embodiment 1.
  • the prepared lithium-ion battery was tested for adhesion.
  • the surface state of the pole piece after the peel test is shown in Figure 5, Figure 6 and Figure 7.
  • Part of the coating particles were peeled off from the positive electrode piece, and the surface of the peeled pole piece was peeled off.
  • Co, O, and P elements were detected, indicating that the bonding force between the first coating and the current collector was greater than the bonding force between the coating particles, and the average bonding force was 45.78 N/m.
  • the first coating of the positive electrode sheet was It is not peeled off from the current collector, indicating that the adhesive force between the first coating and the current collector is >45.78 N/m.
  • the bonding force between the first coating and the positive electrode current collector is greater than the bonding force between the first coating and the second coating, and the quality of the residual coating on the peeled surface of the positive electrode sheet is divided by the single-sided coating on the positive electrode sheet.
  • the total mass is 45%.
  • the cross-sectional SEM of the positive electrode sheet is shown in Figure 8, the total thickness of the first coating and the second coating is 45 ⁇ m, and the total thickness of the remaining first coating and the second coating after peeling is 14 ⁇ m ⁇ 17.8 ⁇ m In between, the thickness of the residual coating on the peeled surface of the positive electrode sheet divided by the thickness of the single-sided coating of the positive electrode sheet is 31% (calculated based on the minimum thickness of the coating).
  • the prepared lithium-ion battery of Comparative Example 1 was tested for adhesion. After the peeling test, the surface state of the pole piece was shown in Figure 9. Both the first coating and the second coating were peeled off from the positive electrode current collector. The adhesion between the first coating and the current collector is smaller than the adhesion between the coating particles, and the average adhesion is 8.13N/m, indicating that the average adhesion between the first coating and the current collector is 8.13N/m .
  • the thickness of the positive electrode coating remaining on the positive electrode current collector accounts for the thickness of the positive electrode coating on the positive electrode current collector before peeling off.
  • the use of the positive electrode sheet can solve the problems such as fire failure of the lithium ion battery under the condition of mechanical abuse, improve the safety performance of the lithium ion battery, and at the same time, the cycle performance of the lithium ion battery is not affected, and The cycle performance of the existing lithium ion battery is comparable, that is, the safety performance of the lithium ion battery is significantly improved on the premise of maintaining the cycle performance of the lithium ion battery.

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Abstract

本发明提供了一种正极片及包括该正极片的锂离子电池，所述正极片包括正极集流体和正极涂层，所述正极涂层包括第一涂层和第二涂层，所述第一涂层涂覆在正极集流体表面，所述第二涂层涂覆在第一涂层表面；所述锂离子电池具有好的安全性能，在发生机械滥用(针刺、重物冲击)时，电池起火失效的概率大大降低。

Description

一种正极片及包括该正极片的锂离子电池
本申请要求于2020年12月14日提交中国专利局、申请号为202011469382.4，申请名称为“一种正极片及包括该正极片的锂离子电池”的中国专利申请的优先权，以及要求于2020年12月14日提交中国专利局、申请号为202011469365.0，申请名称为“一种正极片及包括该正极片的锂离子电池”的中国专利申请的优先权，以及要求于2020年12月14日提交中国专利局、申请号为202011468013.3，发明名称为“一种正极片及包括该正极片的锂离子电池”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本发明属于锂离子电池技术领域，具体涉及一种正极片及包括该正极片的锂离子电池。
背景技术
锂离子电池因具有平台电压高、能量密度大、无记忆效应、寿命长等优点广泛应用于智能手机、笔记本电脑、蓝牙、穿戴设备等领域。然而在一些极端情况下，如锂离子电池遭受机械破坏(针刺、重物冲击等)时会发生内短路，发生内短路的锂离子电池在很短的时间内会放出大量的热，导致电池起火失效，具有很大的安全隐患。
研究发现，锂离子电池在发生内短路时，会有多种短路模式，其中正极集流体箔与负极片短路是最危险的模式。
发明内容
本发明提供一种正极片及包括该正极片的锂离子电池，所述正极片的使用可以解决锂离子电池在机械滥用的情况下起火失效等问题，提升锂离子电池的安全性能，同时所述锂离子电池的循环性能不受影响，与现有的锂离子电池的循环性能效果相当，即在保持锂离子电池的循环性能的前提下显著提升其安全性能。
本发明是通过如下技术方案实现的：
一种正极片，所述正极片包括正极集流体和正极涂层，所述正极涂层包括第一涂层和第二涂层，所述第一涂层涂覆在正极集流体表面，所述第二涂层涂覆在第一涂层表面；所述第一涂层包括无机填料、第一导电剂和第一粘结剂，所述第二涂层包括正极活性物质、第二导电剂和第二粘结剂；所述第一涂层中第一粘结剂的含量大于所述第二涂层中第二粘结剂的含量；所述正极集流体与一部分所述第一粘结剂粘结，一部分所述正极活性物质与另一部分所述第一粘结剂粘结；
所述正极片满足如下(1)～(7)所列条件中的至少一个：
(1)所述第一涂层与正极集流体之间的粘结力大于30N/m；
(2)所述第一涂层和正极集流体之间的粘结力大于所述第一涂层和第二涂层之间的粘结力；
(3)所述第一涂层和正极集流体之间的粘结力大于第二涂层的正极活性物质颗粒之间的粘结力；
(4)所述正极片的正极涂层进行剥离后，正极集流体上残留的正极涂层的最大厚度大于等于2μm；
(5)所述正极片的正极涂层进行剥离后，正极集流体上残留的正极涂层厚度占剥离前正极集流体上的正极涂层厚度的5％以上；
(6)所述正极片的正极涂层进行剥离后，正极集流体上残留的正极涂层总质量占剥离前正极集流体上的正极涂层总质量的10％以上；
(7)所述正极片的正极涂层进行剥离后，正极集流体上残留的正极涂 层总面积占剥离前正极涂层总面积的70％以上。
研究发现，当所述第一涂层和正极集流体之间的粘结力大于所述第一涂层和第二涂层之间的粘结力时，和/或，当所述第一涂层和正极集流体之间的粘结力大于第二涂层的正极活性物质颗粒之间的粘结力时，可以实现在发生机械滥用(如针刺、重物冲击)的情况下，正极集流体表面被第一涂层很好保护，不易裸露，使得正极集流体与负极片接触几率降低，从而降低正极集流体-负极片的短路几率，提高电池的安全性。
当所述第一涂层与正极集流体之间的粘结力大于30N/m时，可以实现在发生机械滥用(如针刺、重物冲击)的情况下，正极集流体表面被第一涂层很好保护，不易裸露，使得正极集流体与负极片接触几率降低，从而降低正极集流体-负极片的短路几率，提高电池的安全性。
当所述正极片的正极涂层进行剥离(测试过程如下所述)后，正极集流体上残留的正极涂层厚度占剥离前正极集流体上的正极涂层厚度的5％以上时，可以实现在发生机械滥用(如针刺、重物冲击)的情况下，正极集流体表面被第一涂层很好保护，不易裸露，使得正极集流体与负极片接触几率降低，从而降低正极集流体-负极片的短路几率，提高电池的安全性。
当所述正极片的正极涂层进行剥离(测试过程如下所述)后，正极集流体上残留的正极涂层总质量占剥离前正极集流体上的正极涂层总质量的10％以上时，所述正极片的使用可以进一步实现在发生机械滥用(如针刺、重物冲击)的情况下，正极集流体与负极片接触几率降低，从而降低正极集流体-负极片的短路几率，提高电池的安全性。
当所述正极片的正极涂层进行剥离(测试过程如下所述)后，正极集流体上残留的正极涂层总面积占剥离前正极集流体上的正极涂层总面积的70％以上时，所述正极片的使用可以进一步实现在发生机械滥用(如针刺、重物冲击)的情况下，正极集流体与负极片接触几率降低，从而降低正极集流体-负极片的短路几率，提高电池的安全性。
本发明还提供一种锂离子电池，所述锂离子电池包括上述的正极片。
本发明的有益效果：
本发明提供了一种正极片及包括该正极片的锂离子电池，所述正极片满足如下(1)～(7)所列条件中的至少一个：(1)所述第一涂层与正极集流体之间的粘结力大于30N/m；(2)所述第一涂层和正极集流体之间的粘结力大于所述第一涂层和第二涂层之间的粘结力；(3)所述第一涂层和正极集流体之间的粘结力大于第二涂层的正极活性物质颗粒之间的粘结力；(4)所述正极片的正极涂层进行剥离后，正极集流体上残留的正极涂层的最大厚度大于等于2μm；(5)所述正极片的正极涂层进行剥离后，正极集流体上残留的正极涂层厚度占剥离前正极集流体上的正极涂层厚度的5％以上；(6)所述正极片的正极涂层进行剥离后，正极集流体上残留的正极涂层总质量占剥离前正极集流体上的正极涂层总质量的10％以上；(7)所述正极片的正极涂层进行剥离后，正极集流体上残留的正极涂层总面积占剥离前正极涂层总面积的70％以上。包括所述正极片的锂离子电池具有好的安全性能，在发生机械滥用(针刺、重物冲击)时，电池起火失效的概率大大降低。
附图说明
图1实施例1剥离测试后极片表面状态。
图2实施例1剥离测试后极片表面残留SEM。
图3实施例1剥离测试后极片表面残留EDS。
图4实施例1剥离测试后极片截面SEM。
图5实施例2剥离测试后极片表面状态。
图6实施例2剥离测试后极片表面残留SEM。
图7实施例2剥离测试后极片表面残留EDS。
图8实施例2剥离测试后极片截面SEM。
图9对比例1剥离测试后极片表面状态。
图10实施例1剥离测试前极片的SEM。
具体实施方式
如上所述，本发明提供了一种正极片，所述正极片包括正极集流体和正极涂层，所述正极涂层包括第一涂层和第二涂层，所述第一涂层涂覆在正极集流体表面，所述第二涂层涂覆在第一涂层表面；所述第一涂层包括无机填料、第一导电剂和第一粘结剂，所述第二涂层包括正极活性物质、第二导电剂和第二粘结剂；所述第一涂层中第一粘结剂的含量大于所述第二涂层中第二粘结剂的含量；所述正极集流体与一部分所述第一粘结剂粘结，一部分所述正极活性物质与另一部分所述第一粘结剂粘结；
所述正极片满足如下(1)～(7)所列条件中的至少一个：
(1)所述第一涂层与正极集流体之间的粘结力大于30N/m；
(2)所述第一涂层和正极集流体之间的粘结力大于所述第一涂层和第二涂层之间的粘结力；
(3)所述第一涂层和正极集流体之间的粘结力大于第二涂层的正极活性物质颗粒之间的粘结力；
(4)所述正极片的正极涂层进行剥离后，正极集流体上残留的正极涂层的最大厚度大于等于2μm；
(5)所述正极片的正极涂层进行剥离后，正极集流体上残留的正极涂层厚度占剥离前正极集流体上的正极涂层厚度的5％以上；
(6)所述正极片的正极涂层进行剥离后，正极集流体上残留的正极涂层总质量占剥离前正极集流体上的正极涂层总质量的10％以上；
(7)所述正极片的正极涂层进行剥离后，正极集流体上残留的正极涂层总面积占剥离前正极涂层总面积的70％以上。
示例性地，所述正极片满足(1)所述第一涂层与正极集流体之间的粘 结力大于30N/m。
示例性地，所述正极片满足(2)所述第一涂层和正极集流体之间的粘结力大于所述第一涂层和第二涂层之间的粘结力；和/或，(3)所述第一涂层和正极集流体之间的粘结力大于第二涂层的正极活性物质颗粒之间的粘结力；以及(4)所述正极片的正极涂层进行剥离后，正极集流体上残留的正极涂层的最大厚度大于等于2μm。
示例性地，所述正极片满足(2)所述第一涂层和正极集流体之间的粘结力大于所述第一涂层和第二涂层之间的粘结力；和/或，(3)所述第一涂层和正极集流体之间的粘结力大于第二涂层的正极活性物质颗粒之间的粘结力；以及(5)所述正极片的正极涂层进行剥离后，正极集流体上残留的正极涂层厚度占剥离前正极集流体上的正极涂层厚度的5％以上。
示例性地，所述正极片满足(2)所述第一涂层和正极集流体之间的粘结力大于所述第一涂层和第二涂层之间的粘结力；和/或，(3)所述第一涂层和正极集流体之间的粘结力大于第二涂层的正极活性物质颗粒之间的粘结力；以及(6)所述正极片的正极涂层进行剥离后，正极集流体上残留的正极涂层总质量占剥离前正极集流体上的正极涂层总质量的10％以上。
示例性地，所述正极片满足(2)所述第一涂层和正极集流体之间的粘结力大于所述第一涂层和第二涂层之间的粘结力；和/或，(3)所述第一涂层和正极集流体之间的粘结力大于第二涂层的正极活性物质颗粒之间的粘结力；以及(7)所述正极片的正极涂层进行剥离后，正极集流体上残留的正极涂层总面积占剥离前正极涂层总面积的70％以上。
根据本发明，正极集流体上残留的正极涂层的最大厚度大于等于第一涂层的厚度。此时可以说明部分区域的第一涂层几乎未被剥离，粘结性能高，极片的安全性能好。
本发明中，所述的残留的正极涂层的最大厚度是指残留在正极集流体表面的正极涂层的最大厚度。
本发明中，所述的残留的正极涂层总质量是指残留在正极集流体表面的正极涂层的质量之和，所述的剥离前正极集流体上的正极涂层总质量是指剥离前正极集流体表面的正极涂层的质量之和。
本发明中，所述的残留的正极涂层总面积是指残留在正极集流体表面的正极涂层的面积之和，所述的剥离前正极集流体上的正极涂层总面积是指剥离前正极集流体表面的正极涂层的面积之和。
本发明中，所述的残留的正极涂层厚度是指残留在正极集流体表面的正极涂层的厚度，所述的剥离前正极集流体上的正极涂层厚度是指剥离前正极集流体表面的正极涂层的厚度。
本发明中，所述第二涂层的正极活性物质颗粒之间的粘结力是指形成第二涂层的正极活性物质颗粒之间的粘结力。
根据本发明，所述第一涂层与正极集流体之间的粘结力大于30N/m。
根据本发明，所述第一涂层与正极集流体之间的粘结力大于等于35N/m且小于等于300N/m；优选地，所述第一涂层与正极集流体之间的粘结力大于等于35N/m且小于等于200N/m。
示例性地，所述第一涂层与正极集流体之间的粘结力为35N/m、40N/m、45N/m、50N/m、55N/m、60N/m、65N/m、70N/m、75N/m、80N/m、85N/m、90N/m、100N/m、110N/m、120N/m、130N/m、140N/m、150N/m、160N/m、170N/m、180N/m、190N/m或200N/m。
本发明中，所述的粘结力是将锂离子电池放电完全后取正极片静置2h后测量得到的。示例性地，将锂离子电池放电完全(0.5C放电至3.0V)后解剖，取出正极片，将正极片放置在温度25±3℃，露点<-30℃的环境中静置2h，然后将正极片裁切成长度240mm、宽度30mm的正极片小片，使用NITTO No.5000NS胶带，将胶带按照长度200mm、宽度24mm的规格裁切成胶带小片，将胶带小片的一面粘在钢板(260mm*50mm)上，将正极片小片粘在胶带小片的另一面上，保证正极片小片完全覆盖住胶带小片，使 用手持滚筒(直径95mm，宽度45mm，重量2kg)往复滚动3次，将正极片小片与胶带小片粘接在一起，然后使用拉力机(拉力机型号东莞科建KJ-1065系列)测试(180度剥离)，测试设备自动记录随着剥离位移变化的拉力值，作出拉力值随剥离位移变化的曲线，横坐标为剥离位移，纵坐标为拉力值，取曲线走平且剥离位移大于5mm时的拉力值即为粘结力。
根据本发明，经剥离测试后仅能将正极集流体表面的第二涂层，和/或，第一涂层的部分颗粒从正极集流体表面上剥离下来。
示例性地，经剥离测试后的极片表面仅第二涂层部分颗粒从正极片上剥离下来，被剥离的极片表面仅可以检测到第二涂层的正极活性物质颗粒，未检测到第一涂层的颗粒；或者，
经剥离测试后的极片表面涂层部分颗粒从正极片上剥离下来，被剥离的极片表面可以检测到第一涂层的无机填料颗粒和第二涂层的正极活性物质颗粒，但是未漏出正极集流体。
还具体地，当所述无机填料为磷酸铁锂，所述正极活性物质为钴酸锂时，所述正极片的正极涂层进行剥离后，正极集流体上残留的正极涂层表面的EDS中检测出Co、O元素。这一结果至少表示所述第一涂层和正极集流体之间的粘结力大于所述第一涂层和第二涂层之间的粘结力，和/或，所述第一涂层和正极集流体之间的粘结力大于第二涂层的正极活性物质颗粒之间的粘结力。
根据本发明，所述正极片的正极涂层进行剥离后，正极集流体上残留的正极涂层厚度占剥离前正极集流体上的正极涂层厚度的10％以上，或者20％以上，或者30％以上，或者40％以上，或者50％以上，或者60％以上。
根据本发明，所述正极片的正极涂层进行剥离后，正极集流体上残留的正极涂层总质量占剥离前正极集流体上的正极涂层总质量的20％以上，或者30％以上，或者40％以上，或者50％以上，或者60％以上，或者70％以上，或者80％以上，或者90％以上。
根据本发明，所述正极片的正极涂层进行剥离后，正极集流体上残留的正极涂层总面积占剥离前正极集流体上的正极涂层总面积的80％以上，或者90％以上。
根据本发明，所述无机填料的中值粒径D 50小于所述正极活性物质的中值粒径D 50。
本发明中，所述无机填料的中值粒径D 50小于所述正极活性物质的中值粒径D 50，所述的第二涂层中的正极活性物质会嵌入第一涂层中(具体可以参见图10所示的SEM图)，使得第一涂层中的一部分第一粘结剂和正极集流体接触，另一部分第一粘结剂和正极活性物质接触，即形成所述正极集流体与一部分所述第一粘结剂粘结，一部分所述正极活性物质与另一部分所述第一粘结剂粘结的结构。
根据本发明，所述无机填料的中值粒径D 50为0.05-8μm。小粒径的无机填料的使用可以使第一涂层较薄且更致密。
根据本发明，所述正极活性物质的中值粒径D 50为10-20μm。此粒径范围的选择可以提供一个较高的压实密度，提升能力密度。
根据本发明，形成第一涂层和第二涂层的第一导电剂和第二导电剂及其含量相同或不同、第一粘结剂和第二粘结剂及其含量相同或不同。
根据本发明，所述第一涂层中各组分的质量百分含量为：40-93wt％的无机填料、2-15wt％的第一导电剂、5-58wt％的第一粘结剂。
优选地，所述第一涂层中各组分的质量百分含量为：60-91wt％的无机填料、3-10wt％的第一导电剂、8-30wt％的第一粘结剂。第一粘结剂在此范围内时可以和正极集流体有较好的粘结效果，第一粘结剂的含量过高会降低能量密度，会恶化电芯性能，第一粘结剂的含量选择此范围，与中值粒径D 50为0.05-8μm的无机填料结合，能形成粘结强且致密的底涂层。
示例性地，所述无机填料占第一涂层中各组分的质量百分含量为40wt％、45wt％、48wt％、50wt％、55wt％、58wt％、60wt％、62wt％、 65wt％、68wt％、70wt％、72wt％、75wt％、78wt％、80wt％、82wt％、85wt％、88wt％、90wt％、92wt％、93wt％；
示例性地，所述第一导电剂占第一涂层中各组分的质量百分含量为2wt％、3wt％、4wt％、5wt％、6wt％、7wt％、8wt％、9wt％、10wt％、11wt％、12wt％、13wt％、14wt％、15wt％；
示例性地，所述第一粘结剂占第一涂层中各组分的质量百分含量为5wt％、6wt％、7wt％、8wt％、9wt％、10wt％、11wt％、12wt％、13wt％、14wt％、15wt％、18wt％、20wt％、22wt％、25wt％、28wt％、30wt％、33wt％、35wt％、38wt％、40wt％、45wt％、48wt％、50wt％、55wt％、58wt％。
根据本发明，所述第二涂层中各组分的质量百分含量为：93-99wt％的正极活性物质、0.5-5wt％的第二导电剂、0.5-2wt％的第二粘结剂。选择此含量范围的第二粘结剂，提供较好的粘结效果，同时保持较高的能量密度。
优选地，所述第二涂层中各组分的质量百分含量为：95-98wt％的正极活性物质、1-3wt％的第二导电剂、1-2wt％的第二粘结剂。
示例性地，所述正极活性物质占第二涂层中各组分的质量百分含量为93wt％、94wt％、95wt％、96wt％、97wt％、98wt％、99wt％；
示例性地，所述第二导电剂占第二涂层中各组分的质量百分含量为0.5wt％、1wt％、1.5wt％、1.8wt％、2wt％、2.2wt％、2.5wt％、2.8wt％、3wt％、3.5wt％、4wt％、4.5wt％、5wt％；
示例性地，所述第二粘结剂占第二涂层中各组分的质量百分含量为0.5wt％、0.8wt％、1wt％、1.2wt％、1.5wt％、1.8wt％、2wt％。
根据本发明，所述第一导电剂和第二导电剂相同或不同，彼此独立地选自导电炭黑、碳纳米管、石墨烯中的至少一种。
根据本发明，所述第一粘结剂和第二粘结剂相同或不同，彼此独立地选自聚偏氟乙烯、改性聚偏氟乙烯中的至少一种。
其中，所述聚偏氟乙烯和改性聚偏氟乙烯均为市售的产品。
根据本发明，所述第一粘结剂的结晶度<40％，这是因为低的结晶度有利于具有较好的粘接效果。
根据本发明，所述第二粘结剂的结晶度<40％，这是因为低的结晶度有利于具有较好的粘接效果。
根据本发明，所述改性聚偏氟乙烯为丙烯酸酯改性聚偏氟乙烯。丙烯酸酯基团中含有羧基，其能和正极集流体(如铝箔)形成化学键，实现和正极集流体形成强力结合。
根据本发明，所述聚偏氟乙烯或改性聚偏氟乙烯的分子量为100-150万，例如为110万、130万。选择较大分子量的粘结剂，能够增强粘结性能，同时降低粘结剂的含量，增强其能量密度。
根据本发明，所述无机填料选自含锂过渡金属氧化物，具体选自钴酸锂(LCO)、镍钴锰三元材料(NCM)、镍钴铝三元材料(NCA)、镍钴锰铝四元材料(NCMA)、磷酸铁锂(LFP)、磷酸锰锂(LMP)、磷酸钒锂(LVP)、锰酸锂(LMO)、富锂锰基中的一种或多种；
或，所述无机填料选自陶瓷材料，具体选自氧化铝、勃姆石、氧化镁、氢氧化镁中一种或多种；
或，所述无机填料选自含锂过渡金属氧化物中的至少一种和陶瓷材料中的至少一种的混合物。
本发明中，所述无机填料起骨架支撑的作用。
根据本发明，所述正极活性物质选自钴酸锂(LCO)、镍钴锰三元材料(NCM)、镍钴铝三元材料(NCA)、镍钴锰铝四元材料(NCMA)、磷酸铁锂(LFP)、磷酸锰锂(LMP)、磷酸钒锂(LVP)、锰酸锂(LMO)中的一种或多种。
根据本发明，所述正极集流体选自铝箔。
根据本发明，所述正极集流体的厚度为8-15μm。
根据本发明，所述第一涂层的厚度(辊压后的厚度)为2-10μm，如2μm、 3μm、4μm、5μm、6μm、8μm、10μm；所述第二涂层的厚度(辊压后的厚度)为30-80μm，如30μm、35μm、40μm、45μm、50μm、55μm、60μm、65μm、70μm、75μm或80μm。
本发明还提供上述正极片的制备方法，所述方法包括如下步骤：
1)分别配制形成第一涂层的浆料和形成第二涂层的浆料；
2)将形成第一涂层的浆料和形成第二涂层的浆料涂布在正极集流体的两侧表面，制备得到所述正极片。
根据本发明，步骤2)中，所述涂布为双层涂布、凹版涂布、挤压涂布、转移涂布。
示例性地，步骤2)具体包括如下步骤：
将形成第一涂层的浆料涂覆在正极集流体表面形成第一涂层，将形成第二涂层的浆料涂覆在第一涂层表面形成第二涂层，得到正极片。
本发明还提供一种锂离子电池，所述锂离子电池包括上述的正极片。
根据本发明，所述锂离子电池还包括负极片。
根据本发明，所述负极片包括负极活性物质，所述负极活性物质选自人造石墨、天然石墨、中间相碳微球、钛酸锂、硅碳负极、硅氧负极中的一种或多种。
本发明还提供上述锂离子电池的制备方法，所述方法包括如下步骤：
a)制备正极片和负极片；
b)将正极片和负极片进辊压、分切、制片、卷绕(或叠片)、封装、注液、化成、分容、OCV等工序制备得到锂离子电池。
下文将结合具体实施例对本发明做更进一步的详细说明。应当理解，下列实施例仅为示例性地说明和解释本发明，而不应被解释为对本发明保护范围的限制。凡基于本发明上述内容所实现的技术均涵盖在本发明旨在保护的范围内。
下述实施例中所使用的实验方法如无特殊说明，均为常规方法；下述实施例中所用的试剂、材料等，如无特殊说明，均可从商业途径得到。
下述实施例中所使用的改性PVDF是丙烯酸酯改性的PVDF，商业购买获得，牌号为Solef 5130。所述丙烯酸酯改性的PVDF的分子量为110万，结晶度为30-32％。
下述实施例中所使用的PVDF1可以商业购买获得，购买自Arkema公司生产的牌号为HSV-900的聚偏氟乙烯。所述PVDF1的分子量为100万，结晶度为25％。
下述实施例中所使用的PVDF2可以商业购买获得，购买自中化蓝天集团有限公司生产的牌号为2536的聚偏氟乙烯。所述PVDF2的分子量为130万，结晶度为43.5％。
在本发明的描述中，需要说明的是，术语“第一”、“第二”等仅用于描述目的，而并非指示或暗示相对重要性。
下述实施例中所使用的粘结力测试的测试方法如下：
将锂离子电池放电完全(0.5C放电至3.0V)后解剖，取出正极片，将正极片放置在温度25±3℃，露点<-30℃的环境中静置2h，然后将正极片裁切成长度240mm、宽度30mm的正极片小片，使用NITTO No.5000NS胶带，将胶带按照长度200mm、宽度24mm的规格裁切成胶带小片，将胶带小片的一面粘在钢板(260mm*50mm)上，将正极片小片粘在胶带小片的另一面上，保证正极片小片完全覆盖住胶带小片，使用手持滚筒(直径95mm，宽度45mm，重量2kg)往复滚动3次，将正极片小片与胶带小片粘接在一起，然后使用拉力机(拉力机型号东莞科建KJ-1065系列)测试(180度剥离)，测试设备自动记录随着剥离位移变化的拉力值，作出拉力值随剥离位移变化的曲线，横坐标为剥离位移，纵坐标为拉力值，取曲线走平且剥离位移大于5mm时的拉力值即为粘结力。
下述实施例中所使用的正极集流体上残留的正极涂层总质量占剥离前 正极集流体上的正极涂层总质量的测试方法为：
称量剥离前的正极片的质量，减去正极集流体的质量(可以通过厚度计算)，除以2即得到单面涂层的质量。被剥离的物质的质量可以通过测量剥离前后正极片的质量相减得到。
下述实施例中所使用的正极集流体上残留的正极涂层厚度占剥离前正极集流体上的正极涂层厚度的测试方法为：
测量剥离前的正极片的总厚度，减去正极集流体的厚度，除以2即得到单面涂层的厚度D 0。测量被剥离面的正极涂层的厚度，减去正极集流体的厚度，除以2即得到残留的正极涂层的厚度D 1，二者的比值即为正极集流体上残留的正极涂层厚度占剥离前正极集流体上的正极涂层厚度。
下述实施例中所使用的安全性测试的测试方法如下：
(1)针刺测试：
取电池充满电，使用3mm钢针，以130mm/s速度垂直电池平面刺破电池中心。
(2)重物冲击测试：
取电池充满电，将电芯放置于一平面，将一个直径15.8±0.2mm的钢柱置于电芯中心，钢柱的纵轴平行于平面，让质量为9.1±0.1kg的重物从610±25mm的高度自由落到电池中心上方的钢柱上。
实施例1
第一步：制备第一涂层浆料，将40wt％磷酸铁锂(LFP)、45wt％改性PVDF、15wt％炭黑混合，加入NMP，经过搅拌配制成浆料。
第二步：制备第二涂层浆料，将97wt％钴酸锂、1wt％导电炭黑、0.8wt％碳纳米管、1.2wt％PVDF1混合，加入NMP，经过搅拌配制成浆料。
第三步：制备负极浆料，将96wt％人造石墨、1wt％导电炭黑、1.5wt％SBR和1.5wt％CMC混合，加入去离子水，经搅拌制备成浆料。
第四步：正极极片制备，使用挤压涂布工艺将步骤一的第一涂层浆料 涂覆在正极集流体表面形成厚度为5μm的第一涂层，将步骤二的第二涂层浆料涂覆在第一涂层表面形成厚度为40μm的第二涂层，得到正极极片。
第五步：负极极片制备，将步骤三的负极浆料涂覆在负极集流体上得到负极极片。
第六步：正负极极片进辊压、分切、制片、卷绕(或叠片)、封装、注液、化成、分容、OCV等工序制备得到锂离子电池。
对制备得到的锂离子电池进行粘结力测试，经剥离测试后的极片表面状态如图1、图2和图3所示，仅第二涂层部分颗粒从正极片上剥离下来，被剥离的极片表面仅可以检测到第二涂层的钴酸锂颗粒(EDS中检测出Co、O元素)，未检测到第一涂层的磷酸铁锂颗粒(EDS未检测P元素)，平均粘结力为62.65N/m，说明此时正极片的第一涂层未与正极集流体剥离，说明第一涂层与正极集流体之间的粘结力>62.65N/m。还能说明第一涂层与正极集流体的粘结力大于第一涂层和第二涂层之间的粘结力，正极片上被剥离面残留涂层的质量除以正极片单面涂层总质量为96％。
同时，正极片的截面SEM如图4所示，第一涂层和第二涂层的总厚度为45μm，被剥离后剩余的第一涂层和第二涂层的总厚度在23μm～45μm之间，正极片上被剥离面残留涂层的厚度除以正极片单面涂层厚度为51％(以涂层最低厚度计算)。
此外，图10为实施例1剥离测试前极片的SEM，从图10中可以看出，顶层(第二涂层)的大粒径的颗粒(正极活性物质)由于辊压会嵌入底层(第一涂层)中，使得底层(第一涂层)中的部分第一粘结剂会和正极集流体接触，部分第一粘结剂会和顶层的大粒径的颗粒(正极活性物质)接触，即形成所述正极集流体与一部分所述第一粘结剂粘结，一部分所述正极活性物质与另一部分所述第一粘结剂粘结的结构。
实施例2
第一步：制备第一涂层浆料，将93wt％LFP、5wt％改性PVDF、2wt％ 炭黑混合，加入NMP，经过搅拌配制成浆料。
第二步～第六步同实施例1。
对制备得到的锂离子电池进行粘结力测试，经剥离测试后的极片表面状态如图5、图6和图7所示，涂层部分颗粒从正极片上剥离下来，被剥离的极片表面检测出Co、O、P元素，说明第一涂层与集流体的粘结力大于涂层颗粒间的粘结力，平均粘结力为45.78N/m，此时正极片的第一涂层未与集流体剥离，说明第一涂层与集流体之间的粘结力>45.78N/m。还能说明第一涂层与正极集流体的粘结力大于第一涂层和第二涂层之间的粘结力，正极片上被剥离面残留涂层的质量除以正极片单面涂层总质量为45％。
同时，正极片的截面SEM如图8所示，第一涂层和第二涂层的总厚度为45μm，被剥离后剩余的第一涂层和第二涂层的总厚度在14μm～17.8μm之间，正极片上被剥离面残留涂层的厚度除以正极片单面涂层厚度为31％(以涂层最低厚度计算)。
实施例3-10
其他步骤同实施例1，区别仅在于第一步中各物料选择和含量不同，具体如表1所示。
对比例1-2
其他步骤同实施例1，区别仅在于第一步中各物料选择和含量不同，具体如表1所示。
对制备得到的对比例1的锂离子电池进行粘结力测试，经剥离测试后，极片表面状态如图9，第一涂层和第二涂层都从正极集流体上剥离下来，说明第一涂层与集流体的粘结力小于涂层颗粒间的粘结力，平均粘结力为8.13N/m，说明第一涂层与集流体之间的平均粘结力为8.13N/m。
表1.各实施例和对比例的极片粘结力大小及安全测试结果
Figure PCTCN2021137729-appb-000001
Figure PCTCN2021137729-appb-000002
从上述实施例和对比例可以看出，当所述第一涂层与正极集流体之间的粘结力大于30N/m时，和/或，当所述第一涂层和正极集流体之间的粘结力大于所述第一涂层和第二涂层之间的粘结力时，和/或，当所述第一涂层和正极集流体之间的粘结力大于第二涂层的正极活性物质颗粒之间的粘结力时，和/或，当所述正极片的正极涂层进行剥离后，正极集流体上残留的正极涂层总质量占剥离前正极集流体上的正极涂层总质量的10％以上时， 和/或，当所述正极片的正极涂层进行剥离后，正极集流体上残留的正极涂层厚度占剥离前正极集流体上的正极涂层厚度的5％以上时，所述正极片的使用可以解决锂离子电池在机械滥用的情况下起火失效等问题，提升锂离子电池的安全性能，同时所述锂离子电池的循环性能不受影响，与现有的锂离子电池的循环性能效果相当，即在保持锂离子电池的循环性能的前提下显著提升其安全性能。
以上，对本发明的实施方式进行了说明。但是，本发明不限定于上述实施方式。凡在本发明的精神和原则之内，所做的任何修改、等同替换、改进等，均应包含在本发明的保护范围之内。

Claims (10)

  1. 一种正极片，其特征在于，所述正极片包括正极集流体和正极涂层，所述正极涂层包括第一涂层和第二涂层，所述第一涂层涂覆在正极集流体表面，所述第二涂层涂覆在第一涂层表面；所述第一涂层包括无机填料、第一导电剂和第一粘结剂，所述第二涂层包括正极活性物质、第二导电剂和第二粘结剂；所述第一涂层中第一粘结剂的含量大于所述第二涂层中第二粘结剂的含量；所述正极集流体与一部分所述第一粘结剂粘结，一部分所述正极活性物质与另一部分所述第一粘结剂粘结；
    其中，所述正极片满足如下(1)～(7)所列条件中的至少一个：
    (1)所述第一涂层与正极集流体之间的粘结力大于30N/m；
    (2)所述第一涂层和正极集流体之间的粘结力大于所述第一涂层和第二涂层之间的粘结力；
    (3)所述第一涂层和正极集流体之间的粘结力大于第二涂层的正极活性物质颗粒之间的粘结力；
    (4)所述正极片的正极涂层进行剥离后，正极集流体上残留的正极涂层的最大厚度大于等于2μm；
    (5)所述正极片的正极涂层进行剥离后，正极集流体上残留的正极涂层厚度占剥离前正极集流体上的正极涂层厚度的5％以上；
    (6)所述正极片的正极涂层进行剥离后，正极集流体上残留的正极涂层总质量占剥离前正极集流体上的正极涂层总质量的10％以上；
    (7)所述正极片的正极涂层进行剥离后，正极集流体上残留的正极涂层总面积占剥离前正极涂层总面积的70％以上。
  2. 根据权利要求1所述的正极片，其特征在于，所述第一涂层与正极集流体之间的粘结力大于等于35N/m且小于等于300N/m。
  3. 根据权利要求1或2所述的正极片，其特征在于，所述无机填料的中值粒径D 50小于所述正极活性物质的中值粒径D 50；和/或，
    所述无机填料的中值粒径D 50为0.05-8μm；和/或，所述正极活性物质的中值粒径D 50为10-20μm。
  4. 根据权利要求1所述的正极片，其特征在于，所述第一涂层中各组分的质量百分含量为：40-93wt％的无机填料、2-15wt％的第一导电剂、5-58wt％的第一粘结剂。
  5. 根据权利要求1-所述的正极片，其特征在于，所述第二涂层中各组分的质量百分含量为：93-99wt％的正极活性物质、0.5-5wt％的第二导电剂、0.5-2wt％的第二粘结剂。
  6. 根据权利要求1所述的正极片，其特征在于，所述第一粘结剂和第二粘结剂相同或不同，彼此独立地选自聚偏氟乙烯、改性聚偏氟乙烯中的至少一种；和/或，
    所述第一粘结剂的结晶度<40％；和/或，
    所述改性聚偏氟乙烯为丙烯酸酯改性聚偏氟乙烯；和/或，
    所述聚偏氟乙烯或改性聚偏氟乙烯的分子量为100-150万。
  7. 根据权利要求1所述的正极片，其特征在于，所述无机填料选自含锂过渡金属氧化物，具体选自钴酸锂(LCO)、镍钴锰三元材料(NCM)、镍钴铝三元材料(NCA)、镍钴锰铝四元材料(NCMA)、磷酸铁锂(LFP)、磷酸锰锂(LMP)、磷酸钒锂(LVP)、锰酸锂(LMO)、富锂锰基中的一种或多种；或，
    所述无机填料选自陶瓷材料，具体选自氧化铝、勃姆石、氧化镁、氢氧化镁中一种或多种；或，
    所述无机填料选自含锂过渡金属氧化物中的至少一种和陶瓷材料中的至少一种的混合物；和/或，
    所述正极活性物质选自钴酸锂(LCO)、镍钴锰三元材料(NCM)、镍钴铝三元材料(NCA)、镍钴锰铝四元材料(NCMA)、磷酸铁锂(LFP)、磷酸锰锂(LMP)、磷酸钒锂(LVP)、锰酸锂(LMO)中的一种或多种。
  8. 根据权利要求7所述的正极片，其特征在于，所述无机填料为磷酸铁锂， 所述正极活性物质为钴酸锂，所述正极片的正极涂层进行剥离后，正极集流体上残留的正极涂层表面的EDS中检测出Co、O元素。
  9. 根据权利要求1所述的正极片，其特征在于，所述第一涂层的厚度为2-10μm；所述第二涂层的厚度为30-80μm。
  10. 一种锂离子电池，其特征在于，所述锂离子电池包括权利要求1-9任一项所述的正极片。
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CN115133035A (zh) * 2022-08-30 2022-09-30 宁德时代新能源科技股份有限公司 正极浆料及其制备方法、二次电池、电池模块、电池包和用电装置
CN115133035B (zh) * 2022-08-30 2023-03-10 宁德时代新能源科技股份有限公司 正极浆料及其制备方法、二次电池、电池模块、电池包和用电装置

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