WO2022257717A1 - 一种正极片及电池 - Google Patents

一种正极片及电池 Download PDF

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Publication number
WO2022257717A1
WO2022257717A1 PCT/CN2022/093612 CN2022093612W WO2022257717A1 WO 2022257717 A1 WO2022257717 A1 WO 2022257717A1 CN 2022093612 W CN2022093612 W CN 2022093612W WO 2022257717 A1 WO2022257717 A1 WO 2022257717A1
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active material
material layer
positive electrode
electrode sheet
lithium
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PCT/CN2022/093612
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English (en)
French (fr)
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陈博
彭冲
韦世超
李俊义
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珠海冠宇电池股份有限公司
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Publication of WO2022257717A1 publication Critical patent/WO2022257717A1/zh
Priority to US18/498,826 priority Critical patent/US20240072254A1/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
    • H01M4/131—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
    • 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
    • H01M4/62—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
    • H01M2004/021—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 application belongs to the technical field of lithium ion batteries, and in particular relates to a positive electrode sheet and a battery.
  • lithium-ion battery technology With the continuous development of lithium-ion battery technology, the utilization rate of lithium-ion batteries in people's daily life is getting higher and higher.
  • the wide application of lithium-ion batteries makes the requirements for the energy density of lithium-ion batteries themselves higher and higher. Therefore, It is necessary to increase the gram capacity of the positive electrode active material in the lithium ion battery to increase the energy density of the lithium ion battery.
  • increasing the gram capacity of the positive active material in the lithium-ion battery will increase the delithiation of lithium cobaltate in the positive plate, resulting in a decrease in the structural stability of lithium cobaltate, which in turn will lead to poor high-temperature cycling of the lithium-ion battery.
  • the embodiment of the present application provides a positive electrode sheet and a battery to solve the problem that the structural stability of the existing lithium cobaltate is reduced, which further leads to the deterioration of the high-temperature cycle of the lithium-ion battery.
  • an embodiment of the present application provides a positive electrode sheet, including: a current collector, the current collector includes a first side and a second side oppositely arranged, and the first side and the second side are An active material layer is provided on at least one side, and the active material layer includes a first active material layer and a second active material layer;
  • the aluminum element content of the lithium cobalt oxide particles in the first active material layer is 5600 to 7200 ppm, and the aluminum element content of the lithium cobalt oxide particles in the second active material layer is 6000 to 6000 ppm. 8300ppm;
  • the aluminum element content of the lithium cobaltate particles in the first active material layer is 4700 to 6300ppm, and the aluminum element content of the lithium cobaltate particles in the second active material layer is 6000 to 7600ppm;
  • the number of broken lithium cobalt oxide particles in the bottom active material layer is the first number
  • the number of broken lithium cobalt oxide particles in the top active material layer is the second number
  • the first number is less than or equal to the second number. quantity.
  • the ratio of the thickness of the first active material layer to the thickness of the positive electrode sheet is 5 : 95 ⁇ 95:5.
  • the ratio of the first quantity to the second quantity is 80%-100%.
  • the areal density of the first active material layer is a first areal density
  • the areal density of the second active material layer is a second areal density
  • the first areal density is less than or equal to the second areal density. density, or the first areal density is greater than or equal to the second areal density.
  • the thickness of the positive electrode sheet is 60 to 130 ⁇ m.
  • the tap density of the active material layer is 2.0 g/cm 3 -3.5 g/cm 3 .
  • the lithium cobaltate particles in the first active material layer meet at least one of the following conditions:
  • the D10 of the lithium cobaltate particles is 2 ⁇ m to 4 ⁇ m;
  • the median diameter D50 of the lithium cobaltate particles is 10 ⁇ m to 15 ⁇ m;
  • the D90 of the lithium cobaltate particles is 20 ⁇ m to 35 ⁇ m.
  • the lithium cobaltate particles in the second active material layer meet at least one of the following conditions:
  • the D10 of the lithium cobaltate particles is 3 ⁇ m to 5 ⁇ m;
  • the median diameter D50 of the lithium cobaltate particles is 15 ⁇ m to 30 ⁇ m;
  • the D90 of the lithium cobaltate particles is 30 ⁇ m to 45 ⁇ m.
  • the doping element of the active material layer includes at least one of aluminum, magnesium and titanium.
  • the embodiment of the present application further provides a battery, which is characterized in that it includes the positive electrode sheet as described in the first aspect.
  • the aluminum element content of the lithium cobalt oxide particles in the first active material layer is 5600 to 7200 ppm, and the cobalt oxide particles in the second active material layer
  • the aluminum element content of the lithium cobaltate particles is 6000 to 8300ppm; when the thickness of the positive electrode sheet is greater than 110 microns, the aluminum element content of the lithium cobaltate particles of the first active material layer is 4700 to 6300ppm, and the cobalt oxide particles of the second active material layer
  • the aluminum element content of lithium oxide particles is 6000 to 7600ppm; after 300 cycles, the number of broken lithium cobalt oxide particles in the bottom active material layer is the first, and the broken number of lithium cobalt oxide particles in the top active material layer is the second Quantity, the first quantity is less than or equal to the second quantity.
  • the aluminum element content of the lithium cobalt oxide particles of the first active material layer and the aluminum element content of the lithium cobalt oxide particles of the second active material layer according to the different thicknesses of the pole pieces, it is possible to make the lithium cobalt oxide in the active material layer
  • the stability of the particles increases layer by layer from the bottom layer to the surface layer, which can also improve the high-temperature stability of the positive electrode sheet, and at the same time help to improve the cycle performance of the battery.
  • FIG. 1 is a schematic structural view of a positive electrode sheet provided in an embodiment of the present application
  • Fig. 2 is an EDS line scan image of a lithium cobaltate provided in the embodiment of the present application.
  • Fig. 3 is the lithium-ion cutting SEM picture of the positive electrode sheet after 300 cycles of the battery of the comparative example of the present application;
  • Fig. 4 is a lithium-ion cut SEM picture of the positive electrode sheet after 300 cycles of the battery of the embodiment of the present application.
  • a positive electrode sheet including:
  • a current collector 101 includes a first side and a second side opposite to each other, at least one of the first side and the second side is provided with an active material layer, and the active material layer including a first active material layer 102 and a second active material layer 103;
  • the aluminum element content of the lithium cobalt oxide particles in the first active material layer 102 is 5600 to 7200 ppm, and the aluminum element content of the lithium cobalt oxide particles in the second active material layer 103 is 6000 to 8300ppm;
  • the aluminum element content of the lithium cobalt oxide particles in the first active material layer 102 is 4700 to 6300 ppm, and the aluminum element content of the lithium cobalt oxide particles in the second active material layer 103 is 6000 to 6000 ppm. 7600ppm;
  • the number of broken lithium cobalt oxide particles in the bottom active material layer is the first number
  • the number of broken lithium cobalt oxide particles in the top active material layer is the second number
  • the first number is less than or equal to the second number. quantity.
  • the current collector 101 is a positive current collector 101, so that two active material layers are arranged on the first side of the current collector 101, which are the first active material layer 102 close to the current collector 101 and the first active material layer 102 disposed on the first active material layer.
  • the second active material layer 103 on the material layer 102 is described in detail as an example, which is only used as an example and not limited here.
  • the material formulation of the positive electrode sheet can include a main material, a conductive agent and a binder, wherein the main material can be lithium cobaltate, lithium iron phosphate, lithium manganate or ternary materials.
  • the main material can be lithium cobaltate, lithium iron phosphate, lithium manganate or ternary materials.
  • the blending of one or more materials, the conductive agent can be carbon black, carbon nanotubes, graphene and other conductive materials, the conductive agent can be one of them, or it can be a combination of multiple conductive agents; it needs to be pointed out
  • the main material includes at least lithium cobalt oxide.
  • the binder can be polyvinylidene fluoride (PVDF) or polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polyethylene oxide (PEO), etc., or it can be SBR or polyacrylate One or more of materials such as classes.
  • PVDF polyvinylidene fluoride
  • PMMA polymethyl methacrylate
  • PAN polyacrylonitrile
  • PEO polyethylene oxide
  • SBR polyacrylate
  • One or more of materials such as classes.
  • the content range of each component in the formula is as follows: the main material is 92 to 98%, the conductive agent is 0.5 to 4%, and the binder is 0.5 to 4%.
  • the type of auxiliary material in the material formula of the positive electrode sheet The content is the same as the material formula of the existing positive electrode sheet, the difference lies in the difference of the main material lithium cobalt oxide, that is, the content of aluminum (Al) in the lithium cobalt oxide particles and the particle size of the lithium cobalt oxide particles are different.
  • two active material layers are provided on the first side of the current collector 101.
  • the active material layer on the side close to the current collector 101 is coated with a relatively low content of aluminum element.
  • the active material layer on the side away from the current collector 101 that is, the side close to the diaphragm 104 is coated with a relatively large amount of aluminum.
  • this embodiment establishes the relationship between the thickness of the pole piece, the distribution of lithium cobaltate with different aluminum content structures, and the cycle performance of the full battery; that is, according to the thickness of the pole piece, the lithium cobaltate with the appropriate aluminum content is selected , and change the distribution in the thickness direction of the positive electrode sheet, so that the Al content in the thickness direction of the electrode sheet generally shows a distribution trend that the Al content in the bottom layer is less than that in the surface layer, and the Al content in the surface layer is more.
  • the advantages of lithium cobalt oxide in terms of gram capacity and cycle performance achieve both energy density and long cycle life.
  • a coating layer 105 can be provided in each active material layer, and in some feasible implementation manners, the color of Al can be judged by the color of the surface coating layer 105. For example, the darker the color, the thicker the cladding layer 105 is, and the larger the Al content is, which is only an example and not limited.
  • the above-mentioned positive electrode sheet by selecting different kinds of lithium cobalt oxide particles according to the thickness of the electrode sheet, the image of the lithium cobalt oxide particles during linear scanning is shown in Figure 2, wherein the aluminum element of each lithium cobalt oxide particle The contents are different, and after 300 cycles are set, the number of broken lithium cobalt oxide particles in the bottom active material layer is the first number, and the number of broken lithium cobalt oxide particles in the top active material layer is the second number, and the first number Less than or equal to the second number; the stability of the lithium cobaltate particles in the N-layer active material layer can be improved layer by layer from the bottom layer to the surface layer, and the high-temperature stability of the positive electrode sheet can also be improved, and it is also beneficial to improve the cycle performance of the battery.
  • the ratio of the first quantity to the second quantity is 80%-100%.
  • the bottom layer is close to 50% of the thickness of the current collector 101, and the top layer is far away from the 50% thickness of the current collector 101. It should be noted that, in some feasible, when there are only two active material layers, the bottom layer may be the first active material layer 102, and the top layer may be the second active material layer 103. When the active material layer includes multiple layers, the 50 near the current collector 101 % thickness is the bottom layer, and the 50% thickness away from the current collector 101 is the top layer.
  • both the first active material layer 102 and the second active material layer 103 can include multiple layers, and the first active material layer Layer 102 may include bottom and top active material layers, and second active material layer 103 may also include bottom and top active material layers; as shown in FIG. 4 , it can effectively improve the degree of fragmentation of lithium cobaltate during cycling.
  • the lower part in the figure is the top layer, and the upper part is the bottom layer.
  • the current collector 101 shall prevail.
  • the bottom layer is close to 50% of the thickness of the current collector 101. 50% of the thickness is the top layer.
  • a part of a particle is located at the bottom layer and the other part is located at the top layer, which layer the particle is located in has more area, and the layer with more area is regarded as the particle of the layer.
  • the area shown by the square dotted line box is 50x 50 ( ⁇ m) unit area area, 50 ⁇ m is the thickness of the active layer on one side of the pole piece, when the thickness of the active layer is not 50 ⁇ m, the value is taken according to the thickness of the active layer; it should be noted that the particles It is difficult to observe the particle size below 10 ⁇ m. When the particle size is 10-20 ⁇ m, the observation result can indicate the degree of particle breakage.
  • the lithium cobaltate particles on the surface of the positive side are broken to some extent, and the bottom layer is broken.
  • the degree of broken lithium cobalt oxide particles is very slight.
  • the number of broken particles in the particle size range of 10-20 ⁇ m is 4, the number of broken particles in the top 50% area is 3, and the number of broken particles in the bottom 50% area is 1; in Figure 3, almost all the particles with a particle size in the range of 10-20 ⁇ m have broken marks, wherein the broken marks indicate that cracks with a length greater than 10% of the particle size appear in the particles.
  • the particle size here is an equivalent particle size (an irregular shape is calculated as a circle with equal area).
  • the content of the aluminum element in the first active material layer 102 and the second active material layer 103 can be reflected by the content of the aluminum element in the lithium cobaltate particles in the active material layer.
  • the content of four kinds of lithium cobaltate Al elements can be set to be M1 lithium cobaltate particles (the first lithium cobaltate particles) Al content in the range of 6100 to 6700ppm (that is, 6400 ⁇ 300ppm); M2 lithium cobaltate particles (second lithium cobaltate particles) Al content ranges from 7200 to 7800ppm (i.e.
  • N1 lithium cobaltate particles (third lithium cobaltate particles) Al content range is 5200 to 5800ppm (ie 5500 ⁇ 300ppm); the Al content range of the M2 lithium cobaltate particle (the fourth lithium cobaltate particle) is 6500 to 7100ppm (ie 6800 ⁇ 300ppm). This is just an example, not a limitation.
  • the ratio of the thickness of the first active material layer 102 to the thickness of the positive electrode sheet is 5:95 ⁇ 95:5.
  • the areal density of the first active material layer 102 is a first areal density
  • the areal density of the second active material layer 103 is a second areal density
  • the first areal density is less than or equal to the first areal density.
  • dihedral density alternatively, the first areal density is greater than or equal to the second areal density.
  • the positive electrode sheet has a thickness of 60 to 130 ⁇ m.
  • the elements in the active material layer further include one or more of magnesium, manganese, titanium, zirconium, and yttrium-zirconium.
  • the Al content shows different distribution trends at different positions (thickness direction) of the same pole piece.
  • the thickness of the positive electrode sheet is 100 ⁇ m
  • the slurries of M1 lithium cobaltate and M2 lithium cobaltate are prepared respectively, and the M1 lithium cobaltate is coated on the end close to the current collector 101, and the M2 lithium cobaltate is coated on the M1 cobaltate above the lithium oxide, that is, near the end of the diaphragm 104.
  • the distribution of Al content showed a trend of less bottom layer and more surface layer; when the thickness of the positive electrode sheet was 120 ⁇ m, the slurry of N1 lithium cobaltate and N2 lithium cobaltate were prepared respectively, and N1 lithium cobaltate was coated on Near the end of the current collector 101 , the N2 lithium cobaltate is coated on the N1 lithium cobaltate, that is, near the end of the diaphragm 104 .
  • the distribution of Al content presents a trend of less bottom layer and more surface layer.
  • the distribution range of the Al content can be controlled by the coating dosage of different active layers.
  • Slurries with different formulations can be coated on the current collector 101 at the same time during coating, or can be coated layer by layer. After the coating is completed, other processes do not change, and soft-packed polymer lithium-ion batteries are made according to the normal processes of rolling, winding, packaging, liquid injection, chemical formation, and sorting.
  • the tap density of the active material layer is 2.0 g/cm 3 -3.5 g/cm 3 . If the tap density is within this range, the conductivity of the positive electrode can be ensured, and the energy density per unit volume of the positive electrode can be increased.
  • the particle size of the lithium cobaltate particles in the active material layer increases layer by layer from the bottom layer close to the current collector 101 to the top layer far away from the current collector 101 . Since the lithium cobalt oxide particles with a smaller particle size are more active, the smaller the particle size of the lithium cobalt oxide particles located at the bottom layer of the positive electrode sheet, the easier it is to escape from the bottom layer, so that the bottom layer and surface layer of the positive electrode sheet The delithiation amount is more balanced, the uneven distribution of the delithiation amount between the surface layer and the bottom layer of the positive electrode sheet is improved, and the high-temperature cycle performance of the battery is further improved.
  • the lithium cobaltate particles in the first active material layer 102 satisfy at least one of the following conditions:
  • the D10 of the lithium cobaltate particles is 2 ⁇ m to 4 ⁇ m;
  • the median diameter D50 of the lithium cobaltate particles is 10 ⁇ m to 15 ⁇ m;
  • the D90 of the lithium cobaltate particles is 20 ⁇ m to 35 ⁇ m.
  • the lithium cobaltate particles in the second active material layer 103 satisfy at least one of the following conditions:
  • the D10 of the lithium cobaltate particles is 3 ⁇ m to 5 ⁇ m;
  • the median diameter D50 of the lithium cobaltate particles is 15 ⁇ m to 30 ⁇ m;
  • the D90 of the lithium cobaltate particles is 30 ⁇ m to 45 ⁇ m.
  • the embodiment of the present application also provides a battery, the battery includes the positive electrode sheet provided in the embodiment of the present application. It should be noted that the battery includes all the technical features of the positive electrode sheet provided by the embodiment of the present application, and can realize all the technical effects of the positive electrode sheet provided by the embodiment of the present application. To avoid repetition, details are not repeated here.
  • the surface density of the negative electrode is the sum of the density of each layer in the double layer.
  • the agent and the conductive agent are not limited to those described in the examples.
  • M1 and M2 lithium cobaltate were blended according to 5:5 and used as the main material of the positive electrode to prepare a slurry of the above positive electrode 97.5% formula, with a solid content of 65% to 85% and a viscosity of 2000 to 7000mPa.
  • s according to the normal coating method, use the extrusion coating machine to coat the slurry on the 9 ⁇ m aluminum foil, and complete the coating and rolling process.
  • the thickness of the positive electrode sheet is 100 ⁇ m after rolling; the negative electrode sheet can be prepared according to the mass production process. .
  • the positive and negative electrode sheets are prepared, they are wound with a ceramic and glue-coated separator with a total thickness of 9 ⁇ m, and then the cell production is completed according to the mass production process.
  • N1 and N2 lithium cobaltate were blended according to 5:5 and used as the main material of the positive electrode to prepare a slurry of the above positive electrode 97.5% formula, with a solid content of 65% to 85% and a viscosity of 2000 to 7000mPa.
  • s according to the normal coating method, use the extrusion coating machine to coat the slurry on the 9 ⁇ m aluminum foil, and complete the coating and rolling process.
  • the thickness of the positive electrode sheet is 100 ⁇ m after rolling; the negative electrode sheet can be prepared according to the mass production process.
  • the positive and negative electrode sheets are prepared, they are wound with a ceramic and glue-coated separator with a total thickness of 9 ⁇ m, and then the cell production is completed according to the mass production process.
  • M1 and M2 lithium cobaltate were blended according to 5:5 and used as the main material of the positive electrode to prepare a slurry of the above positive electrode 97.5% formula, with a solid content of 65% to 85% and a viscosity of 2000 to 7000mPa.
  • s according to the normal coating method, use the extrusion coating machine to coat the slurry on the 9 ⁇ m aluminum foil, and complete the coating and rolling process.
  • the thickness of the positive electrode sheet is 120 ⁇ m after rolling; the negative electrode sheet can be prepared according to the mass production process. .
  • the positive and negative electrode sheets are prepared, they are wound with a ceramic and glue-coated separator with a total thickness of 9 ⁇ m, and then the cell production is completed according to the mass production process.
  • N1 and N2 lithium cobaltate were blended according to 5:5 and used as the main material of the positive electrode to prepare a slurry of the above positive electrode 97.5% formula, with a solid content of 65% to 85% and a viscosity of 2000 to 7000mPa.
  • s according to the normal coating method, use the extrusion coating machine to coat the slurry on the 9 ⁇ m aluminum foil, and complete the coating and rolling process.
  • the thickness of the positive electrode sheet is 120 ⁇ m after rolling; the negative electrode sheet can be prepared according to the mass production process. .
  • the positive and negative electrode sheets are prepared, they are wound with a ceramic and glue-coated separator with a total thickness of 9 ⁇ m, and then the cell production is completed according to the mass production process.
  • M1 slurry M1 lithium cobaltate is used as the main material, and M1 slurry is prepared according to 97.5% formula
  • M2 slurry M2 lithium cobaltate is used as the main material, according to 97.5%
  • the formula is prepared as M2 slurry; use a double-layer coater to coat two layers at the same time, coat M1 slurry near the aluminum foil area, and coat M2 slurry near the diaphragm area.
  • ):m(M2) 5:5 to complete the coating, and the rolling thickness is 100 ⁇ m; the negative electrode sheet can be prepared according to the mass production process.
  • the positive and negative electrode sheets are prepared, they are wound with a ceramic and glue-coated separator with a total thickness of 9 ⁇ m, and then the cell production is completed according to the mass production process.
  • N1 slurry use N1 lithium cobaltate as the main material, and prepare N1 slurry according to the 97.5% formula
  • N2 slurry use N2 lithium cobaltate as the main material, according to 97.5%
  • the formula is prepared as N2 slurry; use a double-layer coater to coat two layers at the same time, apply N1 slurry near the aluminum foil area, and apply N2 slurry near the diaphragm area.
  • m(N2) 5:5 to complete the coating, and the rolling thickness is 100 ⁇ m; the negative electrode sheet can be prepared according to the mass production process.
  • the positive and negative electrode sheets are prepared, they are wound with a ceramic and glue-coated separator with a total thickness of 9 ⁇ m, and then the cell production is completed according to the mass production process.
  • M1 slurry M1 lithium cobaltate is used as the main material, and M1 slurry is prepared according to 97.5% formula
  • M2 slurry M2 lithium cobaltate is used as the main material, according to 97.5%
  • the formula is prepared as M2 slurry; use a double-layer coater to coat two layers at the same time, coat M1 slurry near the aluminum foil area, and coat M2 slurry near the diaphragm area.
  • ):m(M2) 5:5 to complete the coating, and the rolling thickness is 120 ⁇ m; the negative electrode sheet can be prepared according to the mass production process.
  • the positive and negative electrode sheets are prepared, they are wound with a ceramic and glue-coated separator with a total thickness of 9 ⁇ m, and then the cell production is completed according to the mass production process.
  • N1 slurry use N1 lithium cobaltate as the main material, and prepare N1 slurry according to the 97.5% formula
  • N2 slurry use N2 lithium cobaltate as the main material, according to 97.5%
  • the formula is prepared as N2 slurry; use a double-layer coater to coat two layers at the same time, apply N1 slurry near the aluminum foil area, and apply N2 slurry near the diaphragm area.
  • m(N2) 5:5 to complete the coating, and the rolling thickness is 120 ⁇ m; the negative electrode sheet can be prepared according to the mass production process.
  • the positive and negative electrode sheets are prepared, they are wound with a ceramic and glue-coated separator with a total thickness of 9 ⁇ m, and then the cell production is completed according to the mass production process.
  • Example 2 when the thickness of the pole piece is 100 ⁇ m, the aluminum content of the surface layer In the following range, energy density and cycle performance can be guaranteed at the optimal level, that is, 6000ppm ⁇ Al content in the surface active material layer ⁇ 6800ppm; in Example 3, when the thickness of the pole piece is 120 ⁇ m, the surface aluminum content is in the following range When , the energy density and cycle performance can be guaranteed at the optimal level, that is, 6800ppm ⁇ Al content in the surface active material layer ⁇ 7500ppm.
  • Example 2 and Example 3 The energy density and gram capacity in Example 2 and Example 3 are higher, and the gram capacity retention rate at 25°C cycle and 45°C cycle is higher. It can be seen that by setting the content of the aluminum element of lithium cobaltate particles in the N-layer active material layer from the bottom layer close to the current collector to the surface layer away from the current collector, the cobalt acid in the i-th active material layer is set.
  • the number of broken lithium particles is less than the number of broken steps of lithium cobalt oxide particles in the i+1th active material layer, so that the stability of lithium cobalt oxide particles in the N-layer active material layer is promoted layer by layer from the bottom layer to the surface layer, and also It can improve the high-temperature stability of the positive electrode sheet, and is also beneficial to improve the cycle performance of the battery.

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Abstract

本申请提供一种正极片及电池，涉及锂离子电池技术领域。正极片包括：集流体，集流体包括相背设置的第一侧面和第二侧面，第一侧面和第二侧面中的至少一个侧面上设置有活性材料层，活性材料层包括第一活性材料层和第二活性材料层；在正极片的厚度小于或等于110微米的情况下，第一活性材料层的钴酸锂颗粒的铝元素含量为5600至7200ppm，第二活性材料层的钴酸锂颗粒的铝元素含量为6000至8300ppm；在正极片的厚度大于110微米的情况下，第一活性材料层的钴酸锂颗粒的铝元素含量为4700至6300ppm，第二活性材料层的钴酸锂颗粒的铝元素含量为6000至7600ppm。可以解决现有的钴酸锂的结构稳定性降低，进而导致锂离子电池高温循环变差的问题。

Description

一种正极片及电池
本申请要求于2021年06月11日提交中国专利局、申请号为202110652687.7、申请名称为“一种正极片及电池”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
本申请属于锂离子电池技术领域，具体涉及一种正极片及电池。
背景技术
随着锂离子电池技术的不断发展，锂离子电池在人们日常生活中的使用率越来越高，锂离子电池的广泛应用使得对锂离子电池本身的能量密度的要求越来越高，因此，需要提高锂离子电池中正极活性物质的克容量以提高锂离子电池的能量密度。但是，提高锂离子电池中正极活性物质的克容量，会使得正极片中的钴酸锂脱锂量的增加，导致钴酸锂的结构稳定性降低，进而导致锂离子电池高温循环变差。
申请内容
本申请实施例提供一种正极片及电池，以解决现有的钴酸锂的结构稳定性降低，进而导致锂离子电池高温循环变差的问题。
第一方面，本申请实施例提供了一种正极片，包括：集流体，所述集流体包括相背设置的第一侧面和第二侧面，所述第一侧面和所述第二侧面中的至少一个侧面上设置有活性材料层，所述活性材料层包括第一活性材料层和第二活性材料层；
在正极片的厚度小于或等于110微米的情况下，第一活性材料层的钴酸锂颗粒的铝元素含量为5600至7200ppm，第二活性材料层的钴酸锂颗粒的铝元素含量为6000至8300ppm；
在正极片的厚度大于110微米的情况下，第一活性材料层的钴酸锂颗粒的铝元素含量为4700至6300ppm，第二活性材料层的钴酸锂颗粒的铝元素含 量为6000至7600ppm；
循环300次后，底层活性材料层的钴酸锂颗粒的破碎个数为第一数量，顶层活性材料层的钴酸锂颗粒的破碎数量为第二数量，所述第一数量小于或等于第二数量。
可选地，所述第一活性材料层的厚度占正极片的厚度的比例为5 ∶95～95∶5。
可选地，所述第一数量与所述第二数量之比为80％-100％。
可选地，所述第一活性材料层的面密度为第一面密度，所述第二活性材料层的面密度为第二面密度，所述第一面密度小于或者等于所述第二面密度，或者，所述第一面密度大于或者等于所述第二面密度。
可选地，正极片的厚度为60至130μm。
可选地，所述活性材料层的振实密度为2.0g/cm 3～3.5g/cm 3。
可选地，所述第一活性材料层中钴酸锂颗粒满足以下至少一项条件：
所述钴酸锂颗粒的D10为2μm至4μm；
所述钴酸锂颗粒的中位径D50为10μm至15μm；
所述钴酸锂颗粒的D90为20μm至35μm。
可选地，所述第二活性材料层中钴酸锂颗粒满足以下至少一项条件：
所述钴酸锂颗粒的D10为3μm至5μm；
所述钴酸锂颗粒的中位径D50为15μm至30μm；
所述钴酸锂颗粒的D90为30μm至45μm。
可选地，所述活性材料层的掺杂元素包括铝、镁和钛中的至少一种。
第二方面，本申请实施例还提供了一种电池，其特征在于，包括如第一方面所述的正极片。
本申请实施例提供的技术方案中，在正极片的厚度小于或等于110微米的情况下，第一活性材料层的钴酸锂颗粒的铝元素含量为5600至7200ppm，第二活性材料层的钴酸锂颗粒的铝元素含量为6000至8300ppm；在正极片的厚度大于110微米的情况下，第一活性材料层的钴酸锂颗粒的铝元素含量为4700至6300ppm，第二活性材料层的钴酸锂颗粒的铝元素含量为6000至7600ppm；循环300次后，底层活性材料层的钴酸锂颗粒的破碎个数为第一数量，顶层活性材料层的钴酸锂颗粒的破碎数量为第二数量，第一数量小于或 等于第二数量。这样，通过根据极片的不同厚度，设置第一活性材料层的钴酸锂颗粒的铝元素含量和第二活性材料层的钴酸锂颗粒的铝元素含量，可以使得活性材料层中钴酸锂颗粒的稳定性由底层向表层逐层提升，还可以提升正极片的高温稳定性，同时还有利于提升电池的循环性能。
附图说明
为了更清楚地说明本申请实施例或相关技术中的技术方案，下面对本申请实施例或相关技术描述中所需要使用的附图作简单地介绍。显而易见地，下面描述中的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其它的附图。
图1是本申请实施例提供的一种正极片的结构示意图；
图2是本申请实施例提供的一种钴酸锂的EDS线扫描图像。
图3是本申请对比例的电池循环300次后，正极片的锂离子切割SEM图片；
图4是本申请实施例的电池循环300次后，正极片的锂离子切割SEM图片。
附图标记：
101、集流体；102、第一活性材料层；103、第二活性材料层；104、隔膜；105、包覆层。
具体实施方式
下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其它实施例，都属于本申请保护的范围。
请参照图1，本申请实施例提供了一种正极片，包括：
集流体101，所述集流体101包括相背设置的第一侧面和第二侧面，所述第一侧面和所述第二侧面中的至少一个侧面上设置有活性材料层，所述活性材料层包括第一活性材料层102和第二活性材料层103；
在正极片的厚度小于或等于110微米的情况下，第一活性材料层102的钴酸锂颗粒的铝元素含量为5600至7200ppm，第二活性材料层103的钴酸锂颗粒的铝元素含量为6000至8300ppm；
在正极片的厚度大于110微米的情况下，第一活性材料层102的钴酸锂颗粒的铝元素含量为4700至6300ppm，第二活性材料层103的钴酸锂颗粒的铝元素含量为6000至7600ppm；
循环300次后，底层活性材料层的钴酸锂颗粒的破碎个数为第一数量，顶层活性材料层的钴酸锂颗粒的破碎数量为第二数量，所述第一数量小于或等于第二数量。
在该实施方式中，集流体101为正极集流体101，以在集流体101的第一侧面设置2层活性材料层，分别为靠近集流体101的第一活性材料层102和设于第一活性材料层102上的第二活性材料层103为例进行详细说明，此处，仅作示例，不做限定。
需要说明的是，在实际应用中，正极片的材料配方可以包括主材、导电剂和粘结剂，其中，主材可以是钴酸锂、磷酸铁锂、锰酸锂或者三元材料中的一种或多种材料的掺混，导电剂可以是炭黑、碳纳米管、石墨烯等导电材料，导电剂可以是其中的一种，也可以是其中的多种导电剂复配；需要指出的是，在该实施方式中，主材至少包括钴酸锂。粘结剂可以是聚偏氟乙烯(PVDF)或功能类似的聚甲基丙烯酸甲酯(PMMA)、聚丙烯腈(PAN)、聚氧化乙烯(PEO)等，也可以是SBR类或聚丙烯酸酯类等材料中的一种或多种。配方中各组分的含量范围如下：主材为92至98％，导电剂为0.5至4％，粘结剂为0.5至4％，本实施方式中，正极片的材料配方中的辅材种类与含量与现有的正极片的材料配方相同，区别在于主材钴酸锂的不同，即钴酸锂颗粒中铝(Al)含量和钴酸锂颗粒的粒径大小不同。
在该实施方式中，在集流体101的第一侧面设置2层活性材料层，在设置该2层活性材料层时，在靠近集流体101的一侧的活性材料层涂覆铝元素的含量较小，在远离集流体101的一侧，也即靠近隔膜104的一侧的活性材料层涂覆铝元素的含量较大。具体地，本实施方式建立了极片厚度、不同铝元素含量结构钴酸锂的分布以及全电池循环性能三者之间的关系；即按照极片的厚度，选取合适铝元素含量的钴酸锂，并改变在正极片厚度方向上的分 布，总体上使得极片厚度方向的Al含量呈现底层A1含量少表层Al含量多的分布趋势，此种极片结构可根据特定的极片厚度，充分发挥钴酸锂在克容量和循环性能的优势，达到能量密度和长循环寿命兼顾的目的。
需要说明的是，在一个可行的实施方式中，可以在每一层活性材料层中设置一层包覆层105，在一些可行的实施方式中，可以通过表面包覆层105的颜色判断Al的含量，例如，颜色越深，说明包覆层105厚度越厚，说明Al的含量越大，此处仅做示例，不做限定。
上述的正极片，通过根据极片的厚度不同，选择不同种的钴酸锂颗粒，钴酸锂颗粒在线性扫描时的图像如图2所示，其中，每一种钴酸锂颗粒的铝元素含量不同，并设置循环300次后，底层活性材料层的钴酸锂颗粒的破碎个数为第一数量，顶层活性材料层的钴酸锂颗粒的破碎数量为第二数量，所述第一数量小于或等于第二数量；可以使得N层活性材料层中钴酸锂颗粒的稳定性由底层向表层逐层提升，还可以提升正极片的高温稳定性，同时还有利于提升电池的循环性能。
可选地，第一数量与所述第二数量之比为80％-100％。
具体而言，如附图3所示，对比例所述的常规电池在300次(cycles，cls)循环后，对极片在电子显微镜放大700倍的情况下进行观测，正极侧钴酸锂颗粒从顶层到底层都出现破碎情况，顶层的破碎程度比底层更为严重，会导致高温循环恶化严重；针对这种状况，本申请采用在正极片厚度方向上从底层到表层涂覆不同Al含量的钴酸锂，图3中横向的虚线是极片厚度的中线，靠近集流体101的50％厚度的是底层，远离集流体101的50％厚度的是顶层，需要说明的是，在一些可行的实施方式中，当只有两层活性材料层的时候，底层可以是第一活性材料层102，顶层可以是第二活性材料层103，当活性材料层包括多层的时候，靠近集流体101的50％厚度的是底层，远离集流体101的50％厚度的是顶层，换言之，在该实施方式中，第一活性材料层102和第二活性材料层103都可以包括多层，且第一活性材料层102可能包括底层和顶层的活性材料层，第二活性材料层103也可能包括底层和顶层的活性材料层；如图4所示，可以有效改善循环过程中钴酸锂的破碎程度。图3和图4中，需要说明的是，图中的下部分为顶层，上部分为底层，实际以集流体101为准，靠近集流体101的50％厚度的是底层，远离集流体101的50％厚度的 是顶层，需要说明的是，若某个颗粒的其中一部分位于底层，另一部分位于顶层，则该颗粒位于哪一层的面积更多，将该面积更多的层视为该颗粒的所在层。方形的虚线框所示的区域即为50x 50(μm)单位面积区域，50μm是极片单面活性层厚度，当活性层厚度不是50μm时，按照活性层厚度取值；需要说明的是，颗粒粒径在10μm以下不易观测，当颗粒在10～20μm时，观测结果可以表示颗粒破碎程度，图4中，实施例中电池拆解后，正极侧表层钴酸锂颗粒有一些程度的破碎，底层钴酸锂颗粒破碎程度非常轻微，例如，颗粒粒径在10～20μm范围内的颗粒破碎个数为4，其中顶层50％区域的颗粒破碎个数为3，底层50％区域的颗粒破碎个数为1；图3中，颗粒粒径在10～20μm范围内的颗粒几乎全部出现破碎痕迹，其中，破碎痕迹指示颗粒中出现长度大于颗粒粒径10％的裂纹。此处的粒径是等效粒径(不规则形状按照面积相等的圆形来计算)。
需要说明的是，第一活性材料层102和第二活性材料层103的铝元素的含量可以通过该层活性材料层中的钴酸锂颗粒中的铝元素的含量体现。可选地，在一个可行的实施方式中，可以设置四种钴酸锂Al元素的含量可以是M1钴酸锂颗粒(第一钴酸锂颗粒)Al的含量范围为6100至6700ppm(即6400±300ppm)；M2钴酸锂颗粒(第二钴酸锂颗粒)Al的含量范围为7200至7800ppm(即7500±300ppm)；N1钴酸锂颗粒(第三钴酸锂颗粒)Al的含量范围为5200至5800ppm(即5500±300ppm)；M2钴酸锂颗粒(第四钴酸锂颗粒)Al的含量范围为6500至7100ppm(即6800±300ppm)。此处仅作示例，不做限定。
可选地，第一活性材料层102的厚度占正极片的厚度的比例为5∶95～95∶5。可选地，所述第一活性材料层102的面密度为第一面密度，所述第二活性材料层103的面密度为第二面密度，所述第一面密度小于或者等于所述第二面密度，或者，所述第一面密度大于或者等于所述第二面密度。
在该实施方式中，正极片的厚度为60至130μm。
可选地，所述活性材料层中的元素还包括镁锰元素、钛元素、锆元素、和钇锆元素中的一种或者多种。
例如，以双层涂布为例，可以根据极片的厚度，使得在同一个极片的不同位置(厚度方向)，Al含量呈现不同的分布趋势。具体来说，当正极片厚度为100μm时，分别制备M1钴酸锂和M2钴酸锂的浆料，将M1钴酸锂涂布 在靠近集流体101端，M2钴酸锂涂布在M1钴酸锂上面，即靠近隔膜104端。正极片厚度方向上，Al含量的分布呈现底层少、表层多的趋势；当正极片厚度为120μm时，分别制备N1钴酸锂和N2钴酸锂的浆料，将N1钴酸锂涂布在靠近集流体101端，N2钴酸锂涂布在N1钴酸锂上面，即靠近隔膜104端。正极片厚度方向上，Al含量的分布呈现底层少、表层多的趋势。
在一些可行的实施方式中，在极片的不同区域(厚度方向)，Al含量大小的分布范围，可以通过不同活性层的涂布用量来控制。比如涂布时，控制M1钴酸锂与M2钴酸锂的面密度比例为m(A)∶m(B)＝3∶7，即当极片的厚度为100μm(辊压后厚度)时，可保证底层活性物质占30％的厚度，表层活性物质占70％的厚度；控制M1钴酸锂与M2钴酸锂的面密度比例为m(A)∶m(B)＝5∶5时，即可保证底层活性物质占50％的厚度，表层活性物质占50％的厚度；如此，调整M1钴酸锂与M2钴酸锂的涂布面密度比例即可控制极片厚度方向上Al含量的分布。
值得强调的是，不同钴酸锂浆料，如M1和M2钴酸锂需同时配料，并尽量维持待涂布的浆料具有相近的固含和黏度，两种浆料的固含和黏度必须在可正常涂布的工艺范围内，一般正极固含量的范围为60％～80％，黏度范围为2000～7000，同时为避免浆料沉降影响最终的电池性能，需保证在出料后的24h内完成涂布；双层或多层涂布时按正常涂布标准管控，保证增重、厚度和外观无异常即可。
在本可选的实施方式中，为了使极片底部颗粒破碎程度小于顶部颗粒破碎程度，还可以通过控制底层和表层颗粒大小的分布，增加稀土元素修饰等。此处仅做示例，不做限定。
对于不同配方的浆料，在涂布时，可以同时涂布在集流体101上，也可以一层一层的涂布。涂布完成后，其他工序不发生变化，按正常的辊压、卷绕、封装、注液、化成、分选等工序制成软包聚合物锂离子电池。
可选地，所述活性材料层的振实密度为2.0g/cm 3～3.5g/cm 3。振实密度在此范围内，可以保证正极导电性，提升正极单位体积能量密度。
本实施方式中，所述活性材料层中钴酸锂颗粒的颗粒粒径由靠近集流体101的底层向远离集流体101的顶层逐层增大。由于颗粒粒径越小的钴酸锂颗粒越活跃，因此位于所述正极片底层的钴酸锂颗粒的颗粒粒径越小，则越容 易从底层脱出，以使得所述正极片的底层和表层的脱锂量更加均衡，改善所述正极片表层与底层脱锂量分布不均，进一步提升电池高温循环性能。
在一实现方式中，所述第一活性材料层102中钴酸锂颗粒满足以下至少一项条件：
所述钴酸锂颗粒的D10为2μm至4μm；
所述钴酸锂颗粒的中位径D50为10μm至15μm；
所述钴酸锂颗粒的D90为20μm至35μm。
在又一实现方式中，所述第二活性材料层103中钴酸锂颗粒满足以下至少一项条件：
所述钴酸锂颗粒的D10为3μm至5μm；
所述钴酸锂颗粒的中位径D50为15μm至30μm；
所述钴酸锂颗粒的D90为30μm至45μm。
本申请实施例还提供了一种电池，所述电池包括本申请实施例提供的正极片。需要说明的是，所述电池包括本申请实施例提供的正极片的全部技术特征，且可实现本申请实施例提供的正极片的全部技术效果，为避免重复，在此不再赘述。
下面介绍采用本申请实施方式制作的锂离子电池的实施例和几个不同对比例的实验说明：
需要说明的是，在采用本申请实施方式制作锂离子电池时，在双层涂布技术中，负极片面密度为双层中每层面密度的总和，正、负极涂布完成后，再按照工艺设计厚度进行辊压，以确定正负极压实密度符合工艺要求，之后进行制片(焊接极耳)和卷绕(正极+隔膜+负极)，搭配本申请所述隔膜；然后进行封装、注液和化成，再进行二封，最后进行分选后完成软包聚合物锂离子电池的制作，再报检测试。本申请实施例中正极配方为：钴酸锂∶粘接剂(PVDF)∶导电剂(炭黑)＝97.5％∶1.5％∶1％(质量比)；正极配方中所选主材、粘接剂和导电剂不局限于实施例中所述种类。
上述步骤为本申请实施方式制作锂离子电池的工艺步骤，对于具体参数取值，将在下面的实施例中具体介绍。
对比例1
(1)将M1和M2钴酸锂等按照5∶5掺混后作为正极主材，制备成上述正极 97.5％配方的成浆料，固含量为65％～85％，粘度为2000～7000mPa.s，按照正常涂布方式用挤压式涂布机将浆料涂布在9μm铝箔上，完成涂布和辊压工序，正极片辊压后厚度为100μm；负极片按照量产工艺制备即可。
(2)正负极片制备完成后，搭配总厚度为9μm的陶瓷和胶涂覆隔膜进行卷绕，再按照量产工艺完成电芯制作。
对比例2
(1)将N1和N2钴酸锂等按照5∶5掺混后作为正极主材，制备成上述正极97.5％配方的成浆料，固含量为65％～85％，粘度为2000～7000mPa.s，按照正常涂布方式用挤压式涂布机将浆料涂布在9μm铝箔上，完成涂布和辊压工序，正极片辊压后厚度为100μm；负极片按照量产工艺制备即可
(2)正负极片制备完成后，搭配总厚度为9μm的陶瓷和胶涂覆隔膜进行卷绕，再按照量产工艺完成电芯制作。
对比例3
(1)将M1和M2钴酸锂等按照5∶5掺混后作为正极主材，制备成上述正极97.5％配方的成浆料，固含量为65％～85％，粘度为2000～7000mPa.s，按照正常涂布方式用挤压式涂布机将浆料涂布在9μm铝箔上，完成涂布和辊压工序，正极片辊压后厚度为120μm；负极片按照量产工艺制备即可。
(2)正负极片制备完成后，搭配总厚度为9μm的陶瓷和胶涂覆隔膜进行卷绕，再按照量产工艺完成电芯制作。
对比例4
(1)将N1和N2钴酸锂等按照5∶5掺混后作为正极主材，制备成上述正极97.5％配方的成浆料，固含量为65％～85％，粘度为2000～7000mPa.s，按照正常涂布方式用挤压式涂布机将浆料涂布在9μm铝箔上，完成涂布和辊压工序，正极片辊压后厚度为120μm；负极片按照量产工艺制备即可。
(2)正负极片制备完成后，搭配总厚度为9μm的陶瓷和胶涂覆隔膜进行卷绕，再按照量产工艺完成电芯制作。
实施例1
(1)同时制备两种正极浆料：M1浆料：以M1钴酸锂为主材，按照97.5％配方制备成M1浆料；M2浆料：以M2钴酸锂为主材，按照97.5％配方制备成M2浆料；采用双层涂布机两层同时涂布，靠近铝箔区域涂布M1浆料，靠 近隔膜区域涂布M2浆料，按照两种浆料面密度的比为m(M1)∶m(M2)＝5∶5完成涂布，辊压厚度为100μm；负极片按照量产工艺制备即可。
(2)正负极片制备完成后，搭配总厚度为9μm的陶瓷和胶涂覆隔膜进行卷绕，再按照量产工艺完成电芯制作。
实施例2
(1)同时制备两种正极浆料：N1浆料：以N1钴酸锂为主材，按照97.5％配方制备成N1浆料；N2浆料：以N2钴酸锂为主材，按照97.5％配方制备成N2浆料；采用双层涂布机两层同时涂布，靠近铝箔区域涂布N1浆料，靠近隔膜区域涂布N2浆料，按照两种浆料面密度的比为m(N1)∶m(N2)＝5∶5完成涂布，辊压厚度为100μm；负极片按照量产工艺制备即可。
(2)正负极片制备完成后，搭配总厚度为9μm的陶瓷和胶涂覆隔膜进行卷绕，再按照量产工艺完成电芯制作。
实施例3
(1)同时制备两种正极浆料：M1浆料：以M1钴酸锂为主材，按照97.5％配方制备成M1浆料；M2浆料：以M2钴酸锂为主材，按照97.5％配方制备成M2浆料；采用双层涂布机两层同时涂布，靠近铝箔区域涂布M1浆料，靠近隔膜区域涂布M2浆料，按照两种浆料面密度的比为m(M1)∶m(M2)＝5∶5完成涂布，辊压厚度为120μm；负极片按照量产工艺制备即可。
(2)正负极片制备完成后，搭配总厚度为9μm的陶瓷和胶涂覆隔膜进行卷绕，再按照量产工艺完成电芯制作。
实施例4
(1)同时制备两种正极浆料：N1浆料：以N1钴酸锂为主材，按照97.5％配方制备成N1浆料；N2浆料：以N2钴酸锂为主材，按照97.5％配方制备成N2浆料；采用双层涂布机两层同时涂布，靠近铝箔区域涂布N1浆料，靠近隔膜区域涂布N2浆料，按照两种浆料面密度的比为m(N1)∶m(N2)＝5∶5完成涂布，辊压厚度为120μm；负极片按照量产工艺制备即可。
(2)正负极片制备完成后，搭配总厚度为9μm的陶瓷和胶涂覆隔膜进行卷绕，再按照量产工艺完成电芯制作。
在该实验中，采用上述各对比例和实施例得到的性能如下表1所示。
表1实验性能表
Figure PCTCN2022093612-appb-000001
通过上述表1可知，在该实验中，采用本申请实施方式的实施例2和3体现出了最优的性能，具体表现在，实施例2中，当极片厚度为100μm时，表层铝含量在如下范围时，可以保证能量密度和循环性能在最优的水平，即6000ppm≤表层活性材料层中Al含量≤6800ppm；实施例3中，当极片厚度为120μm时，表层铝含量在如下范围时，可以保证能量密度和循环性能在最优的水平，即6800ppm≤表层活性材料层中Al含量≤7500ppm。
实施例2和实施例3中的能量密度和克容量较高，且，在25℃循环和45℃循环下的克容量保持率都较高。可见，通过设置N层活性材料层中钴酸锂颗粒的铝元素的含量由靠近所述集流体的底层向远离所述集流体的表层逐层增大，设置第i层活性材料层的钴酸锂颗粒的破碎个数小于第i+1层活性材料层的钴酸锂颗粒的破碎程个数，可以得N层活性材料层中钴酸锂颗粒的稳定性由底层向表层逐层提升，还可以提升正极片的高温稳定性，同时还有利于提升电池的循环性能。
本说明书中的各个实施例均采用相关的方式描述，各个实施例之间相同相似的部分互相参见即可，每个实施例重点说明的都是与其它实施例的不同之处。以上仅为本申请的较佳实施例而已，并非用于限定本申请的保护范围。 凡在本申请的精神和原则之内所作的任何修改、等同替换、改进等，均包含在本申请的保护范围内。

Claims (10)

  1. 一种正极片，其中，包括：集流体，所述集流体包括相背设置的第一侧面和第二侧面，所述第一侧面和所述第二侧面中的至少一个侧面上设置有活性材料层，所述活性材料层包括第一活性材料层和第二活性材料层；
    在正极片的厚度小于或等于110微米的情况下，第一活性材料层的钴酸锂颗粒的铝元素含量为5600至7200ppm，第二活性材料层的钴酸锂颗粒的铝元素含量为6000至8300ppm；
    在正极片的厚度大于110微米的情况下，第一活性材料层的钴酸锂颗粒的铝元素含量为4700至6300ppm，第二活性材料层的钴酸锂颗粒的铝元素含量为6000至7600ppm；
    循环300次后，底层活性材料层的钴酸锂颗粒的破碎个数为第一数量，顶层活性材料层的钴酸锂颗粒的破碎数量为第二数量，所述第一数量小于或等于第二数量。
  2. 根据权利要求1所述的正极片，其中，所述第一活性材料层的厚度占正极片的厚度的比例为5∶95～95∶5。
  3. 根据权利要求1或2所述的正极片，其中，所述第一数量与所述第二数量之比为80％-100％。
  4. 根据权利要求1-3任一项所述的正极片，其中，所述第一活性材料层的面密度为第一面密度，所述第二活性材料层的面密度为第二面密度，所述第一面密度小于或者等于所述第二面密度，或者，所述第一面密度大于或者等于所述第二面密度。
  5. 根据权利要求1-4任一项所述的正极片，其中，正极片的厚度为60至130μm。
  6. 根据权利要求1-5任一项所述的正极片，其中，所述活性材料层的振实密度为2.0g/cm 3～3.5g/cm 3。
  7. 根据权利要求1-6任一项所述的正极片，其中，所述第一活性材料层中钴酸锂颗粒满足以下至少一项条件：
    所述钴酸锂颗粒的D10为2μm至4μm；
    所述钴酸锂颗粒的中位径D50为10μm至15μm；
    所述钴酸锂颗粒的D90为20μm至35μm。
  8. 根据权利要求1-7任一项所述的正极片，其中，所述第二活性材料层中钴酸锂颗粒满足以下至少一项条件：
    所述钴酸锂颗粒的D10为3μm至5μm；
    所述钴酸锂颗粒的中位径D50为15μm至30μm；
    所述钴酸锂颗粒的D90为30μm至45μm。
  9. 根据权利要求1-8任一项所述的正极片，其中，所述活性材料层的掺杂元素包括铝、镁和钛中的至少一种。
  10. 一种电池，其中，包括如权利要求1至9中任一项所述的正极片。
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