WO2025161663A1 - 电极极片及其制备方法、电池和用电装置 - Google Patents

电极极片及其制备方法、电池和用电装置

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Publication number
WO2025161663A1
WO2025161663A1 PCT/CN2024/136194 CN2024136194W WO2025161663A1 WO 2025161663 A1 WO2025161663 A1 WO 2025161663A1 CN 2024136194 W CN2024136194 W CN 2024136194W WO 2025161663 A1 WO2025161663 A1 WO 2025161663A1
Authority
WO
WIPO (PCT)
Prior art keywords
coating
sub
current collector
slurry
battery
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/CN2024/136194
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English (en)
French (fr)
Inventor
杨周飞
裴振兴
李晓伟
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Contemporary Amperex Technology Co Ltd
Original Assignee
Contemporary Amperex Technology Co Ltd
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Filing date
Publication date
Application filed by Contemporary Amperex Technology Co Ltd filed Critical Contemporary Amperex Technology Co Ltd
Publication of WO2025161663A1 publication Critical patent/WO2025161663A1/zh
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • 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
    • 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
    • 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
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • 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
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • 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
    • H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1397—Processes of manufacture of electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or 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
    • 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

Definitions

  • the present application relates to the field of battery technology, and in particular to an electrode plate and a preparation method thereof, a battery and an electrical device.
  • Secondary batteries have been widely used in various consumer electronic products and electric vehicles due to their advantages such as high energy density, high output voltage, good safety, no pollution and no memory effect.
  • the main purpose of this application is to provide an electrode plate to improve the performance of the battery.
  • the present application proposes an electrode plate, which includes a current collector and a coating provided on at least one side of the current collector, the coating being provided with a pore, the bottom of the pore of the pore being located in the coating, and the pore passing through the surface of the coating.
  • the power density of a battery cell is primarily affected by liquid-phase concentration polarization. During the discharge process, this influence generates a large overpotential, leading to insufficient power density.
  • pores are incorporated into the coating. The pores, with their bottoms located within the coating, penetrate the surface of the coating, creating liquid-phase diffusion channels and forming liquid-phase pathways. This shortens the distance for ion diffusion, thereby reducing ion concentration polarization and contributing to improved battery cell power performance.
  • the bottom of the pores is located within the coating.
  • the bottom of the pores is located within the coating, indicating that the current collector is covered by the coating, preventing the current collector from being directly exposed to the electrolyte, reducing the erosion of the electrolyte on the current collector, and at the same time allowing the coating to cover the surface of the current collector, increasing the contact area between the active material and the current collector, improving the electron transmission efficiency, and the volume energy density of the battery.
  • the aperture of the pore is in an expanding shape that gradually expands toward the coating surface.
  • the flared shape refers to the gradual increase in pore diameter from the bottom of the pore to the opening on the coating surface, forming a trumpet-like shape. This shape results in smaller pores as the coating approaches the current collector, providing the coating with a certain degree of mechanical strength and maintaining its original shape during the subsequent electrode cold pressing process. Furthermore, the pores opening at their largest on the coating surface facilitate rapid diffusion of electrolyte into the pores, improving the efficiency of liquid-phase mass transfer.
  • the maximum pore size d1 of the pores on the surface of the coating satisfies 5 ⁇ m to 300 ⁇ m.
  • the channels in this application can be regular or irregular in shape.
  • the bottom of the channel or the shape of the channel on the coating surface can be circular, elliptical, or other irregular shapes.
  • the maximum pore size at the bottom of the channel and the maximum pore size of the channel on the coating surface are used to describe it.
  • the maximum pore diameter d2 at the bottom of the pore is smaller than the maximum pore diameter d1 of the pore on the coating surface, so that the pore diameter is expanded gradually toward the coating surface.
  • test steps for the maximum pore diameter d1 of the pores on the coating surface are as follows: take a picture of the electrode through the CCD of an optical microscope, identify the area of the pores, and then use the area to calculate the equivalent radius.
  • the maximum pore size d1 of the pores on the coating surface falls within the above range, which can increase the liquid phase diffusion rate and further reduce ion concentration polarization. It is understandable that pore sizes smaller than 5 ⁇ m result in poor diffusion rate, while pore sizes greater than 500 ⁇ m result in a significant loss in volumetric energy density.
  • the surface area of the coating is defined as A, and the opening area of the pores on the surface of the coating is defined as a, and the following condition is satisfied: 1% ⁇ a/A ⁇ 100% ⁇ 10%.
  • the porosity in the coating is within a certain range and can provide abundant liquid phase pathways.
  • the surface area of the coating is defined as A, and the opening area of the pores on the coating surface is defined as a, which satisfies the above relationship. This helps to obtain more liquid phase diffusion channels, form liquid phase pathways, shorten the distance of ion diffusion, and thus weaken the concentration polarization behavior of the ions, which helps to improve the power performance of the battery cell.
  • the coating includes at least two sub-coating layers, the at least two sub-coating layers include a first sub-coating layer and a second sub-coating layer, the first sub-coating layer is disposed on the current collector, and the second sub-coating layer is disposed on a side of the first sub-coating layer away from the current collector;
  • the pores are located in the second sub-coating layer and penetrate the surface of the second sub-coating layer.
  • the coating of the present application includes at least two sub-coatings, and the at least two sub-coatings include a first sub-coating and a second sub-coating.
  • the first sub-coating is arranged on the current collector, and the second sub-coating is arranged on the side of the first sub-coating away from the current collector, so that the surface of the second sub-coating is exposed to the electrolyte, and the pores are located in the second sub-coating and penetrate the surface of the second sub-coating.
  • the pores are only in the second sub-coating, so that the first sub-coating completely covers the current collector, avoiding direct exposure of the current collector to the electrolyte, reducing the erosion of the electrolyte on the current collector, and at the same time, the first sub-coating covers the surface of the current collector, thereby increasing the contact area between the active material and the current collector, improving the electron transmission efficiency, and the volume energy density of the battery.
  • the thickness D1 of the first sub-coating layer is less than or equal to the thickness D2 of the second sub-coating layer.
  • D1 and D2 satisfy 3 ⁇ D2/D1 ⁇ 10;
  • D1 satisfies 30 ⁇ m ⁇ D1 ⁇ 150 ⁇ m;
  • D2 satisfies 570 ⁇ m ⁇ D2 ⁇ 450 ⁇ m.
  • the thickness D1 of the first sub-coating is less than or equal to the thickness D2 of the second sub-coating, and the pores are located in the second sub-coating
  • D1 is less than or equal to D2
  • the pores have a certain depth in the coating, shortening the distance for ion diffusion, thereby weakening the ion concentration polarization behavior, and helping to improve the power performance of the battery cell.
  • D1>D2 the pore depth is insufficient and the pore creation effect is poor.
  • the primary particle size Dv50 of the active material in the first sub-coating layer and the second sub-coating layer is 100 nm to 1000 nm.
  • the active material in the coating layer includes lithium iron phosphate.
  • the solid phase expansion inside the particles can be improved.
  • the power capacity of the electrode can be further improved.
  • a primer layer is provided between the current collector and the coating layer.
  • a primer layer is provided between the current collector and the coating.
  • the active material in the coating includes but is not limited to lithium iron phosphate. It is understood that when the active material includes lithium iron phosphate, the battery performance effect is relatively good.
  • the present application also provides a method for preparing an electrode plate, comprising the following steps:
  • the coating slurry comprises a first sub-coating slurry and a second sub-coating slurry
  • a second sub-coating slurry is coated on the side of the first sub-coating away from the current collector, so that the second sub-coating slurry covers the first sub-coating, and pores are formed in situ in the second sub-coating, and then dried to obtain an electrode plate.
  • the second sub-coating slurry and the surface of the first coating are similar to the principle of dewdrops forming on the surface of a lotus leaf, forming a surface tension difference, forming channels in situ in the second sub-coating, and drying to obtain electrode plates.
  • the electrode plate preparation method proposed in this application is achieved by applying a first sub-coating slurry to the current collector and, after drying, applying a second sub-coating slurry.
  • a surface tension difference is created between the second sub-coating slurry and the first coating surface, similar to the formation of dewdrops on a lotus leaf.
  • this preparation method facilitates the preservation of the electrode pore structure. Furthermore, the pores are generated in situ during the slurry coating process, resulting in relatively good structural consistency. This has no impact on the efficiency of the electrode production process, does not require additional production equipment, and does not affect the production cycle of the battery cell.
  • the preparation method of this application is simple and easy to operate, suitable for large-scale production, and has the advantages of good consistency, low cost, and high production speed.
  • the preparation method of the present application has a trumpet-shaped channel, the structure of the coating has good mechanical strength, and the structure of the coating and the channel will not be damaged during the cold pressing process.
  • laser pore forming requires cutting off the coating material, which wastes material, generates metal debris, ablates active materials, and increases costs.
  • pore formation is achieved through the consumption of the pore-forming agent, and the pore-forming agent is difficult to completely remove in the subsequent electrode drying process, requiring the addition of new materials.
  • the pore-forming agent as a consumable, does not contribute to the improvement of battery performance, and adds new steps, which increases labor intensity and production cycle.
  • the preparation method of the present application does not require the use of related consumables.
  • the viscosity P of the second sub-coating slurry ranges from 1000 mPa ⁇ s to 8000 mPa ⁇ s.
  • the viscosity of the slurry is required to be flexibly adjusted, so as to ultimately achieve a wetting state between the slurry and the electrode surface.
  • the contact angle of the second sub-coating slurry on the surface of the first sub-coating is in the range of 15° to 60°.
  • the contact angle is a quantitative measure of surface wettability and is represented by the angle between the liquid interface and the solid surface.
  • the test steps for the contact angle of the second sub-coating slurry on the surface of the first sub-coating are to drop a drop of slurry used for the second sub-coating on the surface of the electrode, capture the image of the two when they are in contact through a high-speed CCD, draw the tangent line extending from the contact point of the slurry and the electrode to the surface of the slurry, and calculate the angle between the common tangent line and the horizontal plane, which is the contact angle.
  • the present application further provides a battery, comprising the electrode plate as described above;
  • the battery includes an electrode plate obtained by the electrode plate preparation method as described above.
  • the present application also provides an electrical device, which includes the battery as described above.
  • the electrode plate in this application includes a current collector and a coating disposed on at least one side of the current collector.
  • the coating is provided with pores, the bottom of the pores of the pores being located within the coating and the pores penetrating the surface of the coating.
  • the pores are provided in the coating, are located within the coating, and penetrate the surface of the coating, thereby forming liquid-phase diffusion channels and liquid-phase pathways, shortening the distance for ion diffusion, thereby reducing ion concentration polarization behavior, and contributing to improved power performance of the battery cell.
  • FIG1 is a schematic structural diagram of an electrode plate according to an embodiment of the present application.
  • FIG2 is a schematic diagram of the cross-sectional structure of an electrode plate according to an embodiment of the present application.
  • FIG3 is a schematic cross-sectional view of an electrode sheet according to another embodiment of the present application.
  • FIG4 is a schematic flow chart of a method for preparing an electrode sheet according to an embodiment of the present application.
  • FIG5 is a schematic diagram of a battery cell according to an embodiment of the present application.
  • FIG6 is an exploded view of the battery cell according to one embodiment of the present application shown in FIG5 ;
  • FIG7 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG8 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG9 is an exploded view of the battery pack according to one embodiment of the present application shown in FIG8 ;
  • FIG. 10 is a schematic diagram of an electrical device using a battery cell as a power source according to an embodiment of the present application.
  • range disclosed in the application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range.
  • the scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination.
  • any lower limit can form a range with any upper limit combination.
  • the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected.
  • the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5.
  • the numerical range " a-b " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers.
  • a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations.
  • a parameter is expressed as an integer ⁇ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.
  • the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.
  • Secondary batteries have been widely used in various consumer electronic products and electric vehicles due to their advantages such as high energy density, high output voltage, good safety, no pollution and no memory effect.
  • the power density of a battery cell is primarily affected by liquid phase concentration polarization.
  • the porous electrode concentration polarization generates a large overpotential, resulting in insufficient power density.
  • This application proposes an electrode plate comprising a current collector and a coating disposed on at least one side of the current collector.
  • the coating is provided with pores, the bottom of which is located within the coating, and the pores extend through the surface of the coating.
  • the electrode plates include positive and negative plates.
  • the positive plates include a current collector and a cathode material disposed on the current collector.
  • the negative plates include a current collector and an anode material disposed on the current collector.
  • the electrode plate of the present application can be a positive electrode plate or a negative electrode plate.
  • a current collector is a structure or component that collects current. For example, in lithium-ion batteries, this primarily refers to metal foil, such as copper or aluminum foil.
  • the current collector serves as a substrate for the positive or negative active material, collecting the current generated by the active material and delivering a high current output.
  • aluminum foil is used as the positive current collector, while copper foil is used for the negative current collector.
  • the coating refers to a layered structure disposed on the current collector, and the coating includes active substances.
  • the pores as shown in FIG2 , have an open pore structure with a certain depth.
  • the electrode plate 100 shown in Figures 1 to 3 is provided with a channel 30 in the coating 20, and the bottom 31 of the channel 30 is located in the coating 20.
  • the channel 30 penetrates the surface of the coating 20 to obtain a liquid phase diffusion channel, forming a liquid phase passage, shortening the diffusion distance of the ions, and thereby weakening the concentration polarization behavior of the ions, which helps to improve the power performance of the battery cell.
  • the bottom 31 of the pore 30 is located in the coating 20, indicating that the bottom 31 of the pore does not contact the current collector 10.
  • the current collector 10 is covered by the coating 20, which prevents the current collector 10 from being directly exposed to the electrolyte, reduces the corrosion of the electrolyte on the current collector, and at the same time allows the coating to cover the surface of the current collector, thereby increasing the contact area between the active material and the current collector, improving the electron transmission efficiency, and the volume energy density of the battery.
  • the aperture of the pores is in an expanding shape that gradually expands toward the coating surface.
  • the flared shape refers to the gradual increase in pore size from the bottom of the pore to the opening on the coating surface, forming a trumpet-like shape.
  • This shape results in smaller pores as the coating approaches the current collector, providing the coating with a certain degree of mechanical strength and maintaining its original shape during the subsequent electrode cold pressing process.
  • the pores opening at their largest on the coating surface facilitate rapid diffusion of electrolyte into the pores, improving the efficiency of liquid-phase mass transfer.
  • the maximum pore size d2 of the bottom of the pore channel is smaller than the maximum pore size d1 of the pore channel on the coating surface; the maximum pore size d1 of the pore channel on the coating surface satisfies 5 ⁇ m to 300 ⁇ m.
  • the channels in this application can be regular or irregular in shape.
  • the bottom of the channel or the shape of the channel on the coating surface can be circular, elliptical, or other irregular shapes.
  • the maximum pore size at the bottom of the channel and the maximum pore size of the channel on the coating surface are used to describe it.
  • the maximum pore diameter d2 at the bottom of the pore is smaller than the maximum pore diameter d1 of the pore on the surface of the coating, so that the pore diameter is expanded gradually toward the surface of the coating.
  • the maximum pore diameter d1 of the pores on the coating surface satisfies the above range, which can increase the liquid phase diffusion rate and further weaken the ion concentration polarization.
  • test steps for the maximum pore diameter d1 of the pores on the coating surface are as follows: take a picture of the electrode through the CCD of an optical microscope, identify the area of the pores, and then use the area to calculate the equivalent radius.
  • the values include the minimum and maximum values of the range, as well as every value between such minimum and maximum values.
  • Specific examples include but are not limited to the point values in the embodiments and 50 ⁇ m, 60 ⁇ m, 80 ⁇ m, 100 ⁇ m, 120 ⁇ m, 150 ⁇ m, 160 ⁇ m, 180 ⁇ m, 200 ⁇ m, 300 ⁇ m, 500 ⁇ m, etc., as well as the range values between any two of the above-mentioned point values.
  • the surface area of the coating is defined as A, and the opening area of the pores on the coating surface is defined as a, and the following condition is satisfied: 1% ⁇ a/A ⁇ 100% ⁇ 10%.
  • the porosity in the coating is within a certain range, which can not only provide abundant liquid phase pathways, but also ensure that the electrode has a certain mechanical strength.
  • the surface area of the coating is defined as A, and the opening area of the pores on the coating surface is a, then the above relationship is satisfied. In this way, it is helpful to obtain more liquid phase diffusion channels, form liquid phase pathways, shorten the distance of ion diffusion, and then weaken the concentration polarization behavior of the ions, which is helpful to improve the power performance of the battery cell.
  • the values include the minimum and maximum values of the range, and every value between the minimum and maximum values. Specific examples include but are not limited to the point values in the embodiments and 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc., as well as the range values between any two of the above point values.
  • the coating includes at least two sub-coatings, the at least two sub-coatings include a first sub-coating and a second sub-coating, the first sub-coating is arranged on the current collector, and the second sub-coating is arranged on the side of the first sub-coating away from the current collector; the channel is located in the second sub-coating and runs through the surface of the second sub-coating.
  • the coating of the present application includes at least two layers of sub-coatings, and the at least two layers of sub-coatings include a first sub-coating 21 and a second sub-coating 22.
  • the first sub-coating 21 is arranged on the current collector 10
  • the second sub-coating 22 is arranged on the side of the first sub-coating 21 away from the current collector 10, so that the surface of the second sub-coating 22 is exposed to the electrolyte, and the channel 30 is located in the second sub-coating 22 and passes through the surface of the second sub-coating 22.
  • the channel 30 is only in the second sub-coating 22, so that the first sub-coating 21 completely covers the current collector 10, avoiding direct exposure of the current collector 10 to the electrolyte, reducing the erosion of the electrolyte on the current collector, and at the same time, the first sub-coating covers the surface of the current collector, thereby increasing the contact area between the active material and the current collector, improving the electron transmission efficiency, and the volume energy density of the battery.
  • a third sub-coating layer 23 may be further disposed between the current collector 10 and the first sub-coating layer 21 .
  • the thickness D1 of the first sub-coating layer is less than or equal to the thickness D2 of the second sub-coating layer.
  • D1 and D2 satisfy 3 ⁇ D2/D1 ⁇ 10.
  • D1 satisfies 30 ⁇ m ⁇ D1 ⁇ 150 ⁇ m; in one embodiment, D2 satisfies 570 ⁇ m ⁇ D2 ⁇ 450 ⁇ m.
  • the thickness D1 of the first sub-coating is less than or equal to the thickness D2 of the second sub-coating, and the pores are located in the second sub-coating. In this way, the pores have a certain depth in the coating, shortening the distance of ion diffusion, thereby weakening the concentration polarization behavior of the ions, and helping to improve the power performance of the battery cell.
  • the thickness D1 of the first sub-coating layer and the thickness D2 of the second sub-coating layer satisfy the above ranges, which can also reduce the cost of producing the electrode.
  • the values include the minimum and maximum values of the range, and every value between the minimum and maximum values. Specific examples include but are not limited to the point values in the embodiment and 3, 4, 5, 6, 7, 8, 9, 10, etc., as well as the range values between any two of the above point values.
  • the primary particle size Dv50 of the active material in the first sub-coating layer and the second sub-coating layer is 100 nm to 1000 nm; and the active material comprises lithium iron phosphate.
  • the solid phase diffusion behavior can be improved by using active materials with smaller particle size in the coating, thereby further improving the power capacity of the pole piece.
  • Dv50 is the particle size at which the cumulative particle size distribution of a sample reaches 50%. Its physical meaning is that 50% of the particles are larger than this value, and 50% of the particles are smaller than this value. Dv50 is also called the median diameter or median particle size. Dv50 is often used to indicate the average particle size of a powder.
  • the volume average particle size Dv50 of the active material can be measured using methods known in the art. For example, a scanning electron microscope can be used for characterization testing.
  • the values include the minimum and maximum values of the range, as well as every value between such minimum and maximum values. Specific examples include but are not limited to the point values in the embodiments and 100nm, 120nm, 140nm, 160nm, 180nm, 200nm, 500nm, 800nm, 1000nm, etc., as well as the range values between any two of the above-mentioned point values.
  • the slurry of the first sub-coating is first applied to the current collector, and then the slurry of the second sub-coating is applied after drying, the formation of the pores is achieved after the second sub-coating slurry is applied to the surface of the first sub-coating.
  • the second sub-coating slurry forms tension with the surface of the first layer of slurry, and the pore structure is spontaneously formed in situ in the form of dewdrops on a lotus leaf.
  • the viscosity range of the second sub-coating slurry is controlled in the range of 1000mPa ⁇ s-8000mPa ⁇ s.
  • the viscosity of the second sub-coating slurry meets the above range, which helps to achieve wetting with the surface of the first sub-coating, thereby spontaneously forming pores.
  • a primer layer is provided between the current collector and the coating layer.
  • a primer layer is provided between the current collector and the coating.
  • the active material in the coating layer includes but is not limited to at least one of lithium iron phosphate, lithium nickel cobalt manganese oxide, and lithium cobalt oxide.
  • the present application also provides a method for preparing an electrode plate, comprising the following steps: preparing a coating slurry, the coating slurry including a first sub-coating slurry and a second sub-coating slurry; coating the first sub-coating slurry on at least one side of a current collector, drying, and forming a first sub-coating on the current collector; coating the second sub-coating slurry on the side of the first sub-coating facing away from the current collector, so that the second sub-coating slurry covers the first sub-coating, and forming channels in situ in the second sub-coating, and drying to obtain an electrode plate.
  • this is achieved by applying a first sub-coating slurry to the current collector and then applying a second sub-coating slurry after drying.
  • the surface tension difference between the second sub-coating slurry and the first coating is similar to the principle of dewdrops forming on the surface of a lotus leaf, forming a trumpet-shaped channel in situ.
  • This trumpet-shaped channel has a mechanical geometric structure with a large pore size on the coating surface and a small pore size at the bottom of the channel, which gives the coating a certain mechanical strength and can maintain its original shape during the subsequent electrode cold pressing process.
  • this preparation method facilitates the preservation of the electrode pore structure. Furthermore, the pores are generated in situ during the slurry coating process, resulting in relatively good structural consistency. This has no impact on the efficiency of the electrode production process, does not require additional production equipment, and does not affect the production cycle of the battery cell.
  • the preparation method of this application is simple and easy to operate, suitable for large-scale production, and has the advantages of good consistency, low cost, and high production speed.
  • the preparation method of the present application has a trumpet-shaped pore, the coating structure has good mechanical strength, and the coating and pore structure will not be damaged during the cold pressing process.
  • laser pore forming requires cutting off the coating material, which wastes material and increases cost.
  • pore formation is achieved through the consumption of pore-forming agents, which requires the addition of new materials.
  • the pore-forming agent as a consumable, does not help improve battery performance, and adds new steps, which increases labor intensity and production cycle.
  • the preparation method of the present application does not require the use of related consumables.
  • the viscosity P of the second sub-coating slurry is 1000 mPa ⁇ s to 8000 mPa ⁇ s.
  • the viscosity of the slurry is required to be flexibly adjusted, so as to ultimately achieve a wetting state between the slurry and the electrode surface.
  • the values include the minimum and maximum values of the range, as well as every value between such minimum and maximum values. Specific examples include but are not limited to the point values in the embodiments and 1000mPa ⁇ s, 2000mPa ⁇ s, 3000mPa ⁇ s, 4000mPa ⁇ s, 4500mPa ⁇ s, 5000mPa ⁇ s, 5500mPa ⁇ s, 6000mPa ⁇ s, 7000mPa ⁇ s, 8000mPa ⁇ s, etc., as well as the range values between any two of the above-mentioned point values.
  • the contact angle of the second sub-coating slurry on the surface of the first sub-coating is in a range of 15° to 60°.
  • the contact angle is a quantitative measure of surface wettability and is represented by the angle between the liquid interface and the solid surface.
  • the values include the minimum and maximum values of the range, as well as every value between the minimum and maximum values. Specific examples include but are not limited to the point values in the embodiments and 15°, 20°, 30°, 40°, 50°, 60°, etc., as well as the range values between any two of the above-mentioned point values.
  • the present application further provides a battery, which includes the electrode plate as described above; or, the battery includes the electrode plate obtained by the preparation method of the electrode plate as described above.
  • the battery structure can be one of a winding structure, a laminated structure, and a soft pack structure.
  • the gap between the pole pieces is relatively small, and the injection efficiency is low.
  • the pores help to provide space for the rapid passage and infiltration of the electrolyte, thereby improving the injection efficiency.
  • the electrolyte climbs to the top of the battery cell, due to the effect of gravity, the electrolyte is difficult to climb to the top of the battery cell.
  • the setting of the pores in the coating can reserve space for storing the electrolyte, thereby alleviating the problem of insufficient electrolyte infiltration at the top of the battery cell and the occurrence of lithium precipitation.
  • the present application also provides an electrical device, which includes the battery as described above.
  • a secondary battery is provided.
  • a secondary battery typically includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator.
  • active ions are embedded in and released from the positive and negative electrodes.
  • the electrolyte conducts ions between the positive and negative electrodes.
  • the separator is located between the positive and negative electrodes, primarily preventing a short circuit between the positive and negative electrodes while allowing ions to pass through.
  • the separator is the separator described above in this application.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector.
  • the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • aluminum foil may be used as the metal foil.
  • the composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • the composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the battery's charge and discharge processes involve the intercalation and deintercalation of lithium, leading to different molar Li contents at different discharge states.
  • the molar Li contents listed in this application for cathode materials refer to the initial state of the material, i.e., the state before addition of the materials. When the cathode material is used in a battery system, the molar Li content will change after charge and discharge cycles.
  • the molar content of O is only a theoretical value. Lattice oxygen release will cause the molar content of oxygen to change, and the actual molar content of O will fluctuate.
  • the positive electrode film layer may further optionally include a binder.
  • the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • the positive electrode film layer may further include a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.
  • a solvent such as N-methylpyrrolidone
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • copper foil may be used as the metal foil.
  • the composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base material.
  • the composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative electrode active material may be a negative electrode active material for a battery that is well known in the art.
  • the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, etc.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys.
  • the tin-based material may be selected from at least one of elemental tin, tin oxides, and tin alloys.
  • the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.
  • the negative electrode film layer may further include a binder.
  • the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).
  • the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • a conductive agent which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).
  • a thickener eg, sodium carboxymethyl cellulose (CMC-Na)
  • the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.
  • a solvent such as deionized water
  • the electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. This application has no specific restrictions on the type of electrolyte, and it can be selected according to needs.
  • the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.
  • the electrolyte may optionally include additives.
  • the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.
  • the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.
  • the battery cell may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.
  • the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell.
  • the outer packaging of the battery cell may be a soft shell, such as a pouch-type soft shell.
  • the soft shell may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.
  • FIG5 shows a battery cell 5 with a square structure as an example.
  • the outer packaging may include an outer shell 51 and a cover plate 53.
  • the outer shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity.
  • the outer shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity.
  • the positive electrode sheet, the negative electrode sheet and the diaphragm can be formed into an electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is encapsulated in the receiving cavity.
  • the electrolyte is infiltrated in the electrode assembly 52.
  • the number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.
  • a battery cell pool may be assembled into a battery module.
  • the number of battery cells contained in the battery module may be one or more. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.
  • FIG7 shows an example battery module 4.
  • multiple battery cells 5 may be arranged sequentially along the length of the battery module 4. Of course, they may also be arranged in any other manner. Furthermore, the multiple battery cells 5 may be secured together using fasteners.
  • the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.
  • the battery modules described above may also be assembled into a battery pack.
  • the battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box.
  • the battery box comprises an upper case 2 and a lower case 3.
  • the upper case 2 can be positioned over the lower case 3 to form an enclosed space for accommodating the battery modules 4.
  • the multiple battery modules 4 can be arranged in any manner within the battery box.
  • the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application.
  • the secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device.
  • the electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.
  • a battery cell, battery module or battery pack can be selected according to its usage requirements.
  • FIG 10 shows an example of an electric device.
  • This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • a battery pack or battery module can be used.
  • Another example device may be a mobile phone, a tablet computer, a notebook computer, etc.
  • Such a device is usually required to be lightweight and thin, and may use a battery cell as a power source.
  • Acetylene black, CMC, PAA, and calcium hydroxide were stirred and evenly mixed in a percentage ratio of 80%, 5%, 5%, and 5% to obtain a primer slurry; the slurry was then evenly coated on a 15 ⁇ m aluminum foil current collector by extrusion spraying, and then dried to obtain a primer substrate coated with a primer layer.
  • Lithium iron phosphate (Dv50) 300nm, acetylene black, and PVDF were mixed in proportions of 96%, 2%, and 2%, respectively, using NMP as the solvent with a solid content of 55% to obtain a first sub-coating slurry.
  • Lithium iron phosphate (Dv50) 300nm, acetylene black, and PVDF were mixed in proportions of 96%, 2%, and 2%, respectively, using NMP as the solvent with a solid content of 35% to obtain a second sub-coating slurry with a viscosity of 5000mPa ⁇ s.
  • the first sub-coating slurry was first applied to the primer substrate using an extrusion coating machine.
  • the second sub-coating slurry was then applied to the surface of the first sub-coating.
  • the total coating weight was controlled to be 400mg/ 1540.25mm2 , and the coating weight ratio of the second sub-coating layer to the lower layer of the first sub-coating layer was 15%:85%.
  • the positive electrode sheet was then dried, cold pressed, and slit.
  • Polypropylene film is used as the isolation film.
  • the positive electrode, negative electrode, electrolyte, and separator were assembled into a square wound battery for testing. Specifically, the positive electrode sheet, separator, and negative electrode sheet prepared in the above steps were stacked in order, with the separator positioned between the positive and negative electrode sheets to separate the positive and negative electrodes. The cells were wound to form a bare battery cell, the tabs welded, and the bare cell placed in an outer package. The prepared electrolyte was injected into the dried cell, which was then packaged, allowed to stand, and slowly formed. The cell was then shaped to produce a lithium-ion battery.
  • the thickness ratio of the first sub-coating layer to the second sub-coating layer is adjusted.
  • Example 1 Based on Example 1, the primary particle size Dv50 of the active material was adjusted.
  • Example 1 Based on Example 1, the preparation method of the positive electrode sheet was adjusted. Lithium iron phosphate with a Dv50 of 300 nm, acetylene black, and PVDF were uniformly mixed in a ratio of 96%, 2%, and 2%, respectively, with NMP as the solvent and a solid content of 55% to obtain a first sub-coating slurry. The slurry was applied to the primer substrate using an extrusion coater, with a total coating weight of 400 mg/1540.25 mm 2 . The positive electrode sheet was then dried, cold pressed, and slit.
  • Lithium iron phosphate with a Dv50 of 300 nm, acetylene black, and PVDF were uniformly mixed in a ratio of 96%, 2%, and 2%, respectively, with NMP as the solvent and a solid content of 55% to obtain a first sub-coating slurry.
  • the slurry was applied to the primer substrate using an extrusion coater, with a total coating weight of 400
  • ⁇ is the tortuosity
  • ⁇ is the porosity
  • l is the electrode thickness
  • S is the electrode area
  • kint is the lithium ion conductivity of the electrolyte
  • Rion is the lithium ion impedance.
  • Rh 3 ⁇ (Rh - Rl), where Rh is the high-frequency intercept of the impedance spectrum and Rl is the low-frequency intercept.
  • pore ratio calculation Calculation of the ratio of the open area of the pores on the coating surface to the total area of the coating surface: Flatten the cold-pressed positive electrode and place it under a CCD microscope. Count the diameter and number of pores within a 1mm x 1mm range. Assuming the average pore diameter is R and the total number is N, the pore ratio is N* ⁇ * R2 / 1mm2 *100%.
  • Room-Temperature Rate Retention At 25°C, charge the assembled battery at 1/3C to 3.8V lithium iron phosphate, let it rest for 30 minutes, and then discharge it at 1/3C to 2.0V lithium iron phosphate. Record the discharge capacity at this point as C0. Then, discharge it at 3C to 2.0V lithium iron phosphate. Record the discharge capacity at this point as C1. C1/C0 is the rate retention rate.
  • Room temperature DCR At 25°C, charge the assembled battery at 1/3C to 3.8V lithium iron phosphate, let it sit for 30 minutes, then discharge it at 1/3C to 0.5C0 capacity (50% SOC), let it sit for 30 minutes, record the voltage at this time as V0, then discharge it continuously at a 2C discharge rate for 60 seconds, record the voltage at 60 seconds as V10 and V60.
  • 60sDCR (V0-V60)/(2*C0).
  • the positive electrode sheet of the present application is adopted, and by providing channels in the second sub-coating, the rate performance and 60sDCR performance of the battery in the examples are improved.
  • the channels are provided in the coating, the channels are located within the coating, and penetrate the surface of the coating, thereby obtaining liquid phase diffusion channels, forming liquid phase pathways, shortening the distance of ion diffusion, and thereby weakening the concentration polarization behavior of the ions, which helps to improve the power performance of the battery cell.

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Abstract

涉及一种电极极片及其制备方法、电池和用电装置。所述电极极片包括集流体和设于集流体至少一侧的涂层，涂层设有孔道，孔道位于涂层内，并贯穿涂层的表面。在涂层中设有孔道，孔道的孔底部位于涂层内，孔道贯穿涂层的表面，得到液相扩散通道，形成液相通路，缩短离子扩散的距离，进而减弱离子的浓差极化行为，有助于电芯功率性能的改善。

Description

电极极片及其制备方法、电池和用电装置
相关申请
本申请要求于2024年2月2日申请的、申请号为202410155108.1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
本申请涉及电池技术领域，特别涉及一种电极极片及其制备方法、电池和用电装置。
背景技术
二次电池主因其具有能量密度大，输出电压高，安全性好，以及无污染、无记忆效应等优点，已被广泛应用于各类消费类电子产品和电动车辆中。
随着新能源汽车渗透率不断攀升，混动、增程式汽车逐渐走入市场，对电池的功率性能提出了更高的要求。
发明内容
本申请的主要目的是提供一种电极极片，旨在改善电池的性能。
为实现上述目的，本申请提出的一种电极极片，所述电极极片包括集流体和设于所述集流体至少一侧的涂层，所述涂层设有孔道，所述孔道的孔底部位于所述涂层内，所述孔道贯穿所述涂层的表面。
电芯的功率密度主要受液相浓差极化的影响，电芯放电过程由于电极浓差极化的影响，产生较大的过电位，导致电芯功率密度不足。为了改善电池的性能，在涂层中设有孔道，孔道的孔底部位于涂层内，孔道贯穿涂层的表面，得到液相扩散通道，形成液相通路，缩短离子扩散的距离，进而减弱离子的浓差极化行为，有助于电芯功率性能的改善。
并且，孔道的孔底部位于涂层内。
孔道的孔底部位于涂层内，表明集流体被涂层所覆盖，避免集流体直接暴露在电解液中，降低电解液对集流体的侵蚀，同时使涂层覆盖在集流体表面，提高活性材料与集流体的接触面积，提高电子的传输效率，以及电池的体积能量密度。
可选地，所述孔道的口径呈向所述涂层表面逐渐扩大的扩口状。
扩口状是指孔道沿孔道底部到孔道在涂层表面的开口方向，孔径是逐渐变大的，形成类似于喇叭状的形状，该形状使得涂层越靠近集流体侧，其涂层中的孔越小，使涂层具备一定的机械强度，在后续极片冷压过程中可以保持原有形状。另外，孔道在涂层表面开口最大，也有利于电解液快速扩散至孔道内，提高液相传质的效率。
可选地，所述孔道在所述涂层表面的最大孔径d1满足5μm至300μm，
可以理解的是，本申请中的孔道可以是规则或者不规则的形状，例如，孔道的孔底部或者孔道在涂层表面的孔形状可以是圆形、椭圆形，或其他不规则的形状，为了方便描述孔道孔径的大小，以孔道的孔底部最大孔径和孔道在涂层表面的最大孔径来描述。
孔道的孔底部的最大孔径d2小于孔道在涂层表面的最大孔径d1，如此，使得孔道的口径呈向涂层表面逐渐扩大的扩口状。
孔道在涂层表面的最大孔径d1的测试步骤：通过光学显微镜CCD对极片进行拍照，之后识别出来孔的面积，然后用面积计算等效半径。
孔道在涂层表面的最大孔径d1满足上述范围，能提高液相扩散速率，进一步减弱离子浓差极化。可以理解的是，孔径小于5μm扩散速率不佳，孔径大于500μm，体积能量密度损失较大。
可选地，定义所述涂层的表面面积为A，所述孔道在所述涂层表面的开孔面积为a，则满足：1％≤a/A×100％≤10％。
可以理解的是，在涂层中的造孔率在一定范围，可以提供丰富的液相通路，本申请中，定义涂层的表面面积为A，孔道在涂层表面的开孔面积为a，则满足上述关系，如此，有助于得到较多的液相扩散通道，形成液相通路，缩短离子扩散的距离，进而减弱离子的浓差极化行为，有助于电芯功率性能的改善。
可选地，所述涂层包括至少两层子涂层，所述至少两层子涂层包括第一子涂层和第二子涂层，所述第一子涂层设于所述集流体，所述第二子涂层设于所述第一子涂层背离所述集流体的一侧；
所述孔道位于所述第二子涂层，并贯穿所述第二子涂层的表面。
本申请的涂层包括至少两层子涂层，至少两层子涂层包括第一子涂层和第二子涂层，第一子涂层设于集流体，第二子涂层设于第一子涂层背离所述集流体的一侧，以使第二子涂层的表面暴露于电解液中，且孔道位于第二子涂层，并贯穿第二子涂层的表面，如此，使得孔道仅在第二子涂层中，使得第一子涂层完全覆盖集流体，避免集流体直接暴露在电解液中，降低电解液对集流体的侵蚀，同时使第一子涂层覆盖在集流体表面，提高活性材料与集流体的接触面积，提高电子的传输效率，以及电池的体积能量密度。
可选地，所述第一子涂层的厚度D1小于等于所述第二子涂层的厚度D2。
可选地，所述D1和所述D2满足3<D2/D1<10；
和/或，所述D1满足30μm<D1<150μm；
和/或，所述D2满足570μm<D2<450μm。
可以理解的是，第一子涂层的厚度D1小于等于第二子涂层的厚度D2，且孔道位于第二子涂层，当D1小于等于D2的情况下，使得孔道在涂层中具有一定的深度，缩短离子扩散的距离，进而减弱离子的浓差极化行为，有助于电芯功率性能的改善。还可以理解的是，当D1>D2的时候，孔的深度不够，造孔效果不佳。
可选地，所述第一子涂层和所述第二子涂层中活性材料的一次粒度Dv50为100nm至1000nm。
可选地，所述涂层中活性材料包括磷酸铁锂。
通过第一子涂层、第二子涂层中包括颗粒粒度较小的活性材料，可以改善颗粒内部的固相扩展，结合极片造孔的液相浓差改善效果，进一步提高极片功率能力。
可以理解的是，当液相浓差极化被改善后，反应的瓶颈由浓差极化转变为活性颗粒内部的固相扩散极化。小颗粒的活性材料的比表面积大，反应位点多，粒径小扩散距离短，因此搭配造孔的效果，可以进一步提高极片的功率能力。
可选地，所述集流体与所述涂层之间设有底涂层。
为了提高涂层与集流体之间的粘结性，在集流体与涂层之间设有底涂层。
涂层中的活性材料包括但不限于磷酸铁锂。可以理解的是，活性材料包括磷酸铁锂，电池性能效果比较好。
可选地，本申请还提供一种电极极片的制备方法，包括以下步骤：
准备涂层的浆料，所述涂层的浆料包括第一子涂层浆料和第二子涂层浆料；
在集流体的至少一侧涂覆所述第一子涂层浆料，烘干，在所述集流体上形成第一子涂层；
在所述第一子涂层背离所述集流体的一侧涂覆第二子涂层浆料，使所述第二子涂层浆料覆盖所述第一子涂层，并在所述第二子涂层中原位形成孔道，烘干得到电极极片。
可以理解的是，第二子涂层浆料与第一涂层表面类似荷叶表面形成露珠的原理，形成表面张力差，原位在第二子涂层中形成孔道，烘干得到电极极片。
本申请所提出的电极极片的制备方法，是通过在集流体涂敷第一子涂层浆料，干燥后涂敷第二子涂层浆料来实现的。使得第二子涂层浆料中的活性物质涂敷在第一子涂层上时，第二子涂层浆料与第一涂层表面类似荷叶表面形成露珠的原理，形成表面张力差，原位形成喇叭状孔道，该喇叭状孔道具有在涂层表面孔径大，在孔道底部孔径小的机械几何结构，使得涂层具备一定的机械强度，在后续极片冷压过程中可以保持原有形状。
因此该制备方法有利于极片孔道结构的保持。同时该孔道在浆料涂敷过程中原位生成，具有较为良好的结构一致性，对极片制作过程效率无任何影响，不需要添加生产设备，不影响电芯的生产节拍。本申请的制备方法简单易操作，适用大规模生产，一致性好，成本低，生产速度快等优点。
本申请的制备方法，相比其他采用激光成孔的制备方法，本申请的孔道呈喇叭状，涂层的结构具有较好的机械强度，冷压过程中不会破坏涂层、孔道的结构，另外，激光成孔需要将涂层材料切掉，浪费材料，产生金属碎屑，烧蚀活性材料，增加成本；相比其他采用致孔剂的材料，通过致孔剂的消耗来实现造孔，造孔剂难以在后续极片干燥工序完全去除，需要增加新的材料，且该致孔剂作为耗材，无助于电池性能的提升，以及增加新的步骤，增加了劳动强度以及生产周期，采用本申请的制备方法，无需相关耗材的使用。
可选地，所述第二子涂层浆料的粘度P范围为1000mPa·s至8000mPa·s。
为了实现类似荷叶表面露珠的表面张力造孔方式，在第一子涂层表面涂布第二子涂层浆料过程中，要求浆料的粘度可以灵活调变，最终实现浆料与极片表面处于润湿的状态。
可选地，所述第二子涂层浆料在所述第一子涂层表面的接触角范围值为15°至60°。
接触角是表面润湿性的定量量度，由液体界面与固体表面的夹角表示。
第二子涂层浆料在第一子涂层表面的接触角的测试步骤为将第二子涂层所用的一滴浆料滴在极片表面，通过高速CCD抓拍二者接触时的图像，绘制浆料与极片接触点延伸至浆料表面的切线，计算公切线与水平面的夹角即为接触角。
可以理解的是，接触角满足上述范围，可以实现类似荷叶造孔的原理，在极片表面原位形成孔道。
可选地，本申请还提供一种电池，所述电池包括如所述的电极极片；
或者，所述电池包括如所述的电极极片的制备方法得到的电极极片。
可选地，本申请还提供一种用电装置，所述用电装置包括如所述的电池。
本申请中的电极极片包括集流体和设于集流体至少一侧的涂层，涂层设有孔道，孔道的孔底部位于涂层内，孔道贯穿涂层的表面。在涂层中设有孔道，孔道位于涂层内，并贯穿涂层的表面，得到液相扩散通道，形成液相通路，缩短离子扩散的距离，进而减弱离子的浓差极化行为，有助于电芯功率性能的改善。
附图说明
为了更清楚地说明本申请实施例或现有技术中的技术方案，下面将对实施例或现有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示出的结构获得其他的附图。
图1为本申请一实施方式的电极极片的结构示意图；
图2为本申请一实施方式的电极极片的剖面结构示意图；
图3为本申请另一实施方式的电极极片的剖面结构示意图；
图4为本申请一实施方式的电极极片的制备方法流程示意图；
图5是本申请一实施方式的电池单体的示意图；
图6是图5所示的本申请一实施方式的电池单体的分解图；
图7是本申请一实施方式的电池模块的示意图；
图8是本申请一实施方式的电池包的示意图；
图9是图8所示的本申请一实施方式的电池包的分解图；
图10是本申请一实施方式的电池单体用作电源的用电装置的示意图。
附图标号说明：
本申请目的的实现、功能特点及优点将结合实施例，参照附图做进一步说明。
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的一部分实施例，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作出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
以下，适当地参照附图详细说明具体公开了本申请的电极极片及其制备方法、电池和用电装置。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
二次电池主因其具有能量密度大，输出电压高，安全性好，以及无污染、无记忆效应等优点，已被广泛应用于各类消费类电子产品和电动车辆中。
随着新能源汽车渗透率不断攀升，混动、增程式汽车逐渐走入市场，对电池的功率性能提出了更高的要求。
电芯的功率密度主要受液相浓差极化的影响，电芯放电过程由于多孔电极浓差极化的影响，产生较大的过电位，导致电芯功率密度不足。本申请提出一种电极极片，电极极片包括集流体和设于集流体至少一侧的涂层，涂层设有孔道，孔道的孔底部位于涂层内，孔道贯穿涂层的表面。
电极极片包括正极极片和负极极片，正极极片包括集流体及设置在集流体上的阴极材料。负极极片包括集流体及设置在集流体上的阳极材料。
可以理解的是，本申请的电极极片可以是正极极片也可以是负极极片。
集流体，是指汇集电流的结构或零件，例如，在锂离子电池上主要指的是金属箔，如铜箔、铝箔。集流体作为基材用于附着正极或负极活性物质，起到将活性材料产生的电流汇集，对外进行大电流输出的作用。一般铝箔作为正极集流体，铜箔作为负极集流体。
涂层，是指设置在集流体上的层状结构，涂层中包括活性物质。
孔道，如图2所示，具有一定深度的开口状孔隙结构。
为了改善电池的性能，如图1至图3所示的电极极片100，在涂层20中设有孔道30，孔道30的孔底部31位于涂层20内，孔道30贯穿涂层20的表面，得到液相扩散通道，形成液相通路，缩短离子扩散的距离，进而减弱离子的浓差极化行为，有助于电芯功率性能的改善。
如图3所示，孔道30的孔底部31位于涂层20内，说明孔道底部31并未接触集流体10，集流体10被涂层20所覆盖，避免集流体10直接暴露在电解液中，降低电解液对集流体的侵蚀，同时使涂层覆盖在集流体表面，提高活性材料与集流体的接触面积，提高电子的传输效率，以及电池的体积能量密度。
在一实施例中，孔道的口径呈向涂层表面逐渐扩大的扩口状。
如图3所示，扩口状是指孔道沿孔道底部到孔道在涂层表面的开口方向，孔径是逐渐变大的，形成类似于喇叭状的形状，该形状使得涂层越靠近集流体侧，其涂层中的孔越小，使涂层具备一定的机械强度，在后续极片冷压过程中可以保持原有形状。另外，孔道在涂层表面开口最大，也有利于电解液快速扩散至孔道内，提高液相传质的效率。
在一实施例中，孔道的孔底部的最大孔径d2小于孔道在涂层表面的最大孔径d1；孔道在涂层表面的最大孔径d1满足5μm至300μm。
可以理解的是，本申请中的孔道可以是规则或者不规则的形状，例如，孔道的孔底部或者孔道在涂层表面的孔形状可以是圆形、椭圆形，或其他不规则的形状，为了方便描述孔道孔径的大小，以孔道的孔底部最大孔径和孔道在涂层表面的最大孔径来描述。
孔道的孔底部的最大孔径d2小于孔道在涂层表面的最大孔径d1，如此，使得孔道的口径呈向涂层的表面逐渐扩大的扩口状。
孔道在涂层表面的最大孔径d1满足上述范围，能提高液相扩散速率，进一步减弱离子浓差极化。
孔道在涂层表面的最大孔径d1的测试步骤：通过光学显微镜CCD对极片进行拍照，之后识别出来孔的面积，然后用面积计算等效半径。
上述5μm至300μm中，取值包括该范围的最小值及最大值，以及这种最小值与最大值之间的每一个值，具体示例包括但不限于实施例中的点值以及50μm、60μm、80μm、100μm、120μm、150μm、160μm、180μm、200μm、300μm、500μm等，以及上述任意两个点值之间的范围值。
在一实施例中，定义涂层的表面面积为A，孔道在涂层表面的开孔面积为a，则满足：1％≤a/A×100％≤10％。
可以理解的是，在涂层中的造孔率在一定范围，不仅可以提供丰富的液相通路，还能保证极片具有一定的机械强度，本申请中，定义涂层的表面面积为A，孔道在涂层表面的开孔面积为a，则满足上述关系，如此，有助于得到较多的液相扩散通道，形成液相通路，缩短离子扩散的距离，进而减弱离子的浓差极化行为，有助于电芯功率性能的改善。
上述1％≤a/A×100％≤10％中，取值包括该范围的最小值及最大值，以及这种最小值与最大值之间的每一个值，具体示例包括但不限于实施例中的点值以及1％、2％、3％、4％、5％、6％、7％、8％、9％、10％等，以及上述任意两个点值之间的范围值。
在一实施例中，涂层包括至少两层子涂层，至少两层子涂层包括第一子涂层和第二子涂层，第一子涂层设于集流体，第二子涂层设于第一子涂层背离集流体的一侧；孔道位于第二子涂层，并贯穿第二子涂层的表面。
如图2和图3所示，本申请的涂层包括至少两层子涂层，至少两层子涂层包括第一子涂层21和第二子涂层22，第一子涂层21设于集流体10，第二子涂层22设于第一子涂层21背离集流体10的一侧，以使第二子涂层22的表面暴露于电解液中，且孔道30位于第二子涂层22，并贯穿第二子涂层22的表面，如此，使得孔道30仅在第二子涂层22中，使得第一子涂层21完全覆盖集流体10，避免集流体10直接暴露在电解液中，降低电解液对集流体的侵蚀，同时使第一子涂层覆盖在集流体表面，提高活性材料与集流体的接触面积，提高电子的传输效率，以及电池的体积能量密度。
如图3所示，还可以在集流体10与第一子涂层21之间设置第三子涂层23。
在一实施例中，第一子涂层的厚度D1小于等于第二子涂层的厚度D2；在一实施例中，D1和D2满足3<D2/D1<10。
进一步地，在一实施例中，D1满足30μm<D1<150μm；在一实施例中，D2满足570μm<D2<450μm。
第一子涂层的厚度D1小于等于第二子涂层的厚度D2，且孔道位于第二子涂层，如此，使得孔道在涂层中具有一定的深度，缩短离子扩散的距离，进而减弱离子的浓差极化行为，有助于电芯功率性能的改善。
第一子涂层的厚度D1和第二子涂层的厚度D2满足上述范围，还可以降低极片制作的成本。
上述3<D2/D1<10中，取值包括该范围的最小值及最大值，以及这种最小值与最大值之间的每一个值，具体示例包括但不限于实施例中的点值以及3、4、5、6、7、8、9、10等，以及上述任意两个点值之间的范围值。
在一实施例中，第一子涂层和第二子涂层中活性材料的一次粒度Dv50为100nm至1000nm；活性材料包括磷酸铁锂。
在极片局部喇叭状液相传输通道的基础上，通过在涂层中采用颗粒粒度较小的活性材料可以改善固相扩散行为，进一步提高极片功率能力。
可以理解的是，小颗粒的活性材料的比表面积大，反应位点多，靠近集流体的活性材料反应位点多，且产生的电流也能更快的通过集流体收集，提高极片的功率能力。
Dv50，一个样品的累计粒度分布百分数达到50％时所对应的粒径。它的物理意义是粒径大于它的颗粒占50％，小于它的颗粒也占50％，Dv50也叫中位径或中值粒径。Dv50常用来表示粉体的平均粒径。
活性材料的体积平均粒径Dv50可以采用本领域公知的方法进行测试。作为示例的，可以采用扫描电镜进行表征测试。
上述100nm至1000nm中，取值包括该范围的最小值及最大值，以及这种最小值与最大值之间的每一个值，具体示例包括但不限于实施例中的点值以及100nm、120nm、140nm、160nm、180nm、200nm、500nm、800nm、1000nm等，以及上述任意两个点值之间的范围值。
考虑到在制备电极极片的过程中，利用的是先涂敷第一子涂层的浆料至集流体，干燥后涂敷第二子涂层的浆料实现的，孔道的形成是在第一子涂层表面涂覆第二子涂层浆料后，第二子涂层浆料与第一层浆料表面形成张力，以类似荷叶上露珠的形式原位自发形成孔道结构。为了实现张力驱动的自发造孔行为，第二子涂层浆料粘度范围被控制在1000mPa·s-8000mPa·s的范围。第二子涂层的浆料粘度满足上述范围，有助于实现与第一子涂层表面的润湿，从而自发造孔。
在一实施例中，集流体与涂层间设有底涂层。
为了提高涂层与集流体之间的粘结性，在集流体与涂层之间设有底涂层。
涂层中的活性材料包括但不限于磷酸铁锂、镍钴锰酸锂、钴酸锂中的至少一种。
在一实施例中，本申请还提供一种电极极片的制备方法，包括以下步骤：准备涂层的浆料，涂层的浆料包括第一子涂层浆料和第二子涂层浆料；在集流体的至少一侧涂覆第一子涂层浆料，烘干，在集流体上形成第一子涂层；在第一子涂层背离集流体的一侧涂覆第二子涂层浆料，使第二子涂层浆料覆盖第一子涂层，并在第二子涂层中原位形成孔道，烘干得到电极极片。
如图4所示，是通过在集流体涂敷第一子涂层浆料，干燥后涂敷第二子涂层浆料来实现的。使得第二子涂层浆料中的活性物质涂敷在第一子涂层上时，第二子涂层浆料与第一涂层表面类似荷叶表面形成露珠的原理，形成表面张力差，原位形成喇叭状孔道，该喇叭状孔道具有在涂层表面孔径大，在孔道底部孔径小的机械几何结构，使得涂层具备一定的机械强度，在后续极片冷压过程中可以保持原有形状。
因此该制备方法有利于极片孔道结构的保持。同时该孔道在浆料涂敷过程中原位生成，具有较为良好的结构一致性，对极片制作过程效率无任何影响，不需要添加生产设备，不影响电芯的生产节拍。本申请的制备方法简单易操作，适用大规模生产，一致性好，成本低，生产速度快等优点。
本申请的制备方法，相比其他采用激光成孔的制备方法，本申请的孔道呈喇叭状，涂层的结构具有较好的机械强度，冷压过程中不会破坏涂层、孔道的结构，另外，激光成孔需要将涂层材料切掉，浪费材料，增加成本；相比其他采用致孔剂的材料，通过致孔剂的消耗来实现造孔，需要增加新的材料，且该致孔剂作为耗材，无助于电池性能的提升，以及增加新的步骤，增加了劳动强度以及生产周期，采用本申请的制备方法，无需相关耗材的使用。
在一实施例中，第二子涂层浆料的粘度P为1000mPa·s至8000mPa·s。
为了实现类似荷叶表面露珠的表面张力造孔方式，在第一子涂层表面涂布第二子涂层浆料过程中，要求浆料的粘度可以灵活调变，最终实现浆料与极片表面处于润湿的状态。
上述1000mPa·s至8000mPa·s中，取值包括该范围的最小值及最大值，以及这种最小值与最大值之间的每一个值，具体示例包括但不限于实施例中的点值以及1000mPa·s、2000mPa·s、3000mPa·s、4000mPa·s、4500mPa·s、5000mPa·s、5500mPa·s、6000mPa·s、7000mPa·s、8000mPa·s等，以及上述任意两个点值之间的范围值。
在一实施例中，第二子涂层浆料在第一子涂层表面的接触角范围值15°至60°。
接触角是表面润湿性的定量量度，由液体界面与固体表面的夹角表示。
可以理解的是，接触角满足上述范围，可以实现类似荷叶造孔的原理，在极片表面原位形成孔道。
上述15°至60°中，取值包括该范围的最小值及最大值，以及这种最小值与最大值之间的每一个值，具体示例包括但不限于实施例中的点值以及15°、20°、30°、40°、50°、60°等，以及上述任意两个点值之间的范围值。
在一实施例中，本申请还提供一种电池，电池包括如上述的电极极片；或者，电池包括如上述的电极极片的制备方法得到的电极极片。
可以理解的是，电池结构可以是卷绕结构、叠片结构、软包结构中的其中一种。特别是，对于圆柱电池，考虑到圆柱电池卷绕的比较紧，极片间的间隙比较小，注液效率较低，采用本申请的极片，孔道有助于提供空间供电解液的快速通过和浸润，提高注液效率。另外，考虑到电解液爬升至电芯的顶部过程中，因重力的作用，电解液难以爬升至电芯顶部，如此，会存在电芯顶部出现电解液浸润不足的现象，由此会引发在电芯顶部析锂的问题(以锂离子电池为例)，采用本申请的极片，涂层中孔道的设置，可以预留空间存储电解液，减轻电解液在电芯顶部浸润不足而出现析锂的问题。
本申请还提供一种用电装置，用电装置包括如上述的电池。
另外，以下适当参照附图对本申请的电池(二次电池、电池模块、电池包)和用电装置进行说明。
本申请的一个实施方式中，提供一种二次电池。
通常情况下，二次电池包括正极极片、负极极片、电解质和隔膜。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之间起到传导离子的作用。隔膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使离子通过。隔膜为本申请上述提高的隔膜。
正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极膜层。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
电池在充放电过程中会伴随Li的脱嵌及消耗，电池在放电到不同状态时Li的摩尔含量不同。本申请中关于正极材料的列举中，Li的摩尔含量为材料初始状态，即投料前状态，正极材料应用于电池体系中，经过充放电循环，Li的摩尔含量会发生变化。
本申请中关于正极材料的列举中，O的摩尔含量仅为理论状态值，晶格释氧会导致氧的摩尔含量发生变化，实际O的摩尔含量会出现浮动。
在一些实施方式中，正极膜层还可选地包括粘结剂。作为示例，粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。
在一些实施方式中，正极膜层还可选地包括导电剂。作为示例，导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，负极膜层包括负极活性材料。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面中的任意一者或两者上。
在一些实施方式中，负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，负极活性材料可采用本领域公知的用于电池的负极活性材料。作为示例，负极活性材料可包括以下材料中的至少一种：人造石墨、天然石墨、软炭、硬炭、硅基材料等。硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的至少一种。锡基材料可选自单质锡、锡氧化合物以及锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性材料的传统材料。这些负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在一些实施方式中，负极膜层还可选地包括粘结剂。粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。
在一些实施方式中，负极膜层还可选地包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，负极膜层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可得到负极极片。
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有具体的限制，可根据需求进行选择。
在一些实施方式中，电解质采用电解液。电解液包括电解质盐和溶剂。
在一些实施方式中，电解液还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
在一些实施方式中，正极极片、负极极片和隔膜可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施方式中，电池单体可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，电池单体的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。电池单体的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
本申请对电池单体的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图5是作为一个示例的方形结构的电池单体5。
在一些实施方式中，参照图6，外包装可包括外壳51和盖板53。其中，外壳51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。外壳51具有与容纳腔连通的开口，盖板53能够盖设于开口，以封闭容纳腔。正极极片、负极极片和隔膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于容纳腔内。电解液浸润于电极组件52中。电池单体5所含电极组件52的数量可以为一个或多个，本领域技术人员可根据具体实际需求进行选择。
在一些实施方式中，电池单体池可以组装成电池模块，电池模块所含电池单体的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。
图7是作为一个示例的电池模块4。参照图7，在电池模块4中，多个电池单体5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个电池单体5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个电池单体5容纳于该容纳空间。
在一些实施方式中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以为一个或多个，具体数量本领域技术人员可根据电池包的应用和容量进行选择。
图8和图9是作为一个示例的电池包1。参照图8和图9，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
另外，本申请还提供一种用电装置，用电装置包括本申请提供的二次电池、电池模块、或电池包中的至少一种。二次电池、电池模块、或电池包可以用作用电装置的电源，也可以用作用电装置的能量存储单元。用电装置可以包括移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等，但不限于此。
作为用电装置，可以根据其使用需求来选择电池单体、电池模块或电池包。
图10是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对电池单体的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用电池单体作为电源。
实施例
实施例1
底涂的制备
将乙炔黑、CMC、PAA、氢氧化钙以百分含量80％、5％、5％、5％比例搅拌混合均匀，得到底涂浆料；之后将浆料通过挤压喷涂的方式均匀涂覆于15μm铝箔集流体上，之后经过烘干得到涂敷有底涂层的底涂基材。
正极极片的制备
将Dv50＝300nm的磷酸铁锂、乙炔黑、PVDF分别以百分含量96％、2％、2％比例搅拌混合均匀，以NMP为溶剂，固含量为55％，得到第一子涂层浆料；将Dv50＝300nm的磷酸铁锂、乙炔黑、PVDF以百分含量96％、2％、2％比例搅拌混合均匀，以NMP为溶剂，固含量为35％，得到第二子涂层浆料，粘度为5000mPa·s；先通过挤压涂布机器将第一子涂层浆料涂布在底涂基材上，干燥后将上述第二子涂层浆料涂覆于第一子涂层表面，控制总涂布重量为400mg/1540.25mm2，第二子涂层与第一子涂层下层涂布重量比例为15％：85％。之后经过烘干、冷压、分切，得到正极极片。
负极极片的制备
将人造石墨、乙炔黑、CMC、SBR以百分含量95.5％、1.0％、1.5％、2.0％比例搅拌混合均匀，得到负极浆料；之后将浆料通过双层挤压涂布头，以挤压喷涂的方式均匀涂覆于6μm铜箔集流体上，之后经过烘干、冷压、分切，得到负极极片。
电解液的制备
在氩气气氛手套箱中(H2O<0.1ppm，O2<0.1ppm)，将有机溶剂碳酸乙烯酯(EC)/碳酸甲乙酯(EMC)按照体积比3/7混合均匀，加入12.5％ LiPF6锂盐溶解于有机溶剂中，搅拌均匀，得到实施例1的电解液。
隔离膜
以聚丙烯膜作为隔离膜。
电池组装
将上述正极、负极、电解液、隔离膜组装成为方形卷绕电池进行测试。具体地，将上述步骤制得的正极极片、隔膜、负极极片按顺序层叠，使隔膜处于正负极片中间起到隔离正负极的作用，卷绕得到裸电芯，焊接极耳，将裸电芯置于外包装中。将上述制备的电解液注入到干燥后的电芯中，经封装、静置后，缓慢化成，然后经整形，制备得到锂离子电池。
实施例2和实施例3
在实施例1的基础上，调节第二子涂层浆料的粘度。
实施例4和实施例5
在实施例1的基础上，调节第一子涂层和第二子涂层的厚度比值。
实施例6和实施例7
在实施例1的基础上，调节活性材料的一次粒度Dv50。
对比例1
在实施例1的基础上，调节正极极片的制备方法，将Dv50＝300nm的磷酸铁锂、乙炔黑、PVDF分别以百分含量96％、2％、2％比例搅拌混合均匀，以NMP为溶剂，固含量为55％，得到第一子涂层浆料；将浆料以挤压涂布机涂覆于底涂基材上，控制总涂布重量为400mg/1540.25mm2，之后经过烘干、冷压、分切，得到正极极片。
相关参数测试
曲折度计算：将材料组装成对称电池，每个电池添加60uL 50mM四丁基高氯酸铵+EC/DMC(EC:DMC＝1:1，锂离子电导率为1.7mS/cm)，在200kHz to 50mHz频率范围内测试电化学阻抗谱图。利用τ/ε＝Rion×S×kint/l可以计算出曲折度。其中，τ为曲折度，ε为孔隙率，l为极片厚度，S为极片面积，kint为电解液的锂离子电导率，Rion为锂离子阻抗。Rion＝3×(Rh－Rl)，Rh为阻抗谱图高频的截距，Rl为低频截距。
孔道平均直径计算：将冷压后正极极片展平，放置在CCD显微镜下。使用CCD软件识别孔的实际面积S，利用R＝(S/π)0.5计算平均直径R。
孔道在涂层表面的开孔面积占涂层表面的面积的占比计算(造孔率计算)：将冷压后正极极片展平，放置在CCD显微镜下。以1mm×1mm范围为统计区间，对孔道直径和数量进行统计，设孔道平均直径为R，总数量为N，则造孔率为N*π*R2/1mm2*100％。
粘度的测试步骤：
采用旋转式粘度计，将样品注入500ML烧杯内，插入转子，启动仪器，调节合适的旋转速率，从显示屏中读出当前测试浆料的粘度。
电化学性能测试：
常温倍率保持率：在25℃下，将组装好的电池以1/3C充电至3.8V磷酸铁锂，搁置30min，再以1/3C放电至2.0V磷酸铁锂记录此时放电容量为C0。之后，以3C放电至2.0V磷酸铁锂记录此时放电容量为C1。C1/C0即为倍率保持率。
常温DCR：在25℃下，将组装好的电池以1/3C充电至3.8V磷酸铁锂，搁置30min，再以1/3C放电至0.5C0容量(50％SOC)，搁置30min，记录此时电压为V0，之后以2C放电倍率连续放电60s，记录60s时电压为V10,V60。以如下公式计算10s，60sDCR：
60sDCR＝(V0-V60)/(2*C0)。
表1实验数据列表
表2实施例及对比例测试结果
由上表可以看出，比较实施例与对比例，实施例中，采用本申请的正极极片，通过在第二子涂层设置孔道，实施例中电池的倍率性能和60sDCR性能得到改善。说明在涂层中设有孔道，孔道位于涂层内，并贯穿涂层的表面，得到液相扩散通道，形成液相通路，缩短离子扩散的距离，进而减弱离子的浓差极化行为，有助于电芯功率性能的改善。
上仅为本申请的优选实施例，并非因此限制本申请的专利范围，凡是在本申请的申请构思下，利用本申请说明书及附图内容所作的等效结构变换，或直接/间接运用在其他相关的技术领域均包括在本申请的专利保护范围内。

Claims (14)

  1. 一种电极极片，其中，所述电极极片(100)包括集流体(10)和设于所述集流体(10)至少一侧的涂层(20)，所述涂层(20)设有孔道(30)，所述孔道(30)的孔底部(31)位于所述涂层(20)内，所述孔道(30)贯穿所述涂层(20)的表面。
  2. 如权利要求1所述的电极极片，其中，所述孔道(30)的口径呈向所述涂层(20)表面逐渐扩大的扩口状。
  3. 如权利要求1或2所述的电极极片，其中，所述孔道(30)在所述涂层表面的最大孔径d1满足5μm至300μm。
  4. 如权利要求1至3中任一项所述的电极极片，其中，定义所述涂层(20)的表面面积为A，所述孔道(30)在所述涂层表面的开孔面积为a，则满足：1％≤a/A×100％≤10％。
  5. 如权利要求1至4中任一项所述的电极极片，其中，所述涂层(20)包括至少两层子涂层，所述至少两层子涂层包括第一子涂层(21)和第二子涂层(22)，所述第一子涂层(21)设于所述集流体(10)，所述第二子涂层(22)设于所述第一子涂层(21)背离所述集流体(10)的一侧；
    所述孔道(30)位于所述第二子涂层(22)，并贯穿所述第二子涂层(22)的表面。
  6. 如权利要求5所述的电极极片，其中，所述第一子涂层(21)的厚度D1小于等于所述第二子涂层(22)的厚度D2。
  7. 如权利要求6所述的电极极片，其中，所述D1和所述D2满足3<D2/D1<10；
    和/或，所述D1满足30μm<D1<150μm；
    和/或，所述D2满足570μm<D2<450μm。
  8. 如权利要求5至7中任一项所述的电极极片，其中，所述第一子涂层(21)和所述第二子涂层(22)中活性材料的一次粒度Dv50范围为100nm至1000nm。
  9. 如权利要求1至8中任一项所述的电极极片，其中，所述集流体(10)与所述涂层(20)之间设有底涂层；
    和/或，所述涂层(20)中活性材料包括磷酸铁锂。
  10. 一种如权利要求1至9中任一项所述的电极极片的制备方法，其中，包括以下步骤：
    准备涂层的浆料，所述涂层的浆料包括第一子涂层浆料和第二子涂层浆料；
    在集流体的至少一侧涂覆所述第一子涂层浆料，烘干，在所述集流体上形成第一子涂层；
    在所述第一子涂层背离所述集流体的一侧涂覆第二子涂层浆料，使所述第二子涂层浆料覆盖所述第一子涂层，并在所述第二子涂层中原位形成孔道，烘干得到电极极片。
  11. 如权利要求10所述的电极极片的制备方法，其中，所述第二子涂层浆料的粘度P范围为1000mPa·s至8000mPa·s。
  12. 如权利要求10或11所述的电极极片的制备方法，其中，所述第二子涂层浆料在所述第一子涂层表面的接触角范围值为15°至60°。
  13. 一种电池，其中，所述电池包括如权利要求1至9中任一项所述的电极极片；
    或者，所述电池包括如权利要求10至12中任一项所述的电极极片的制备方法得到的电极极片。
  14. 一种用电装置，其中，所述用电装置包括如权利要求13所述的电池。
PCT/CN2024/136194 2024-02-02 2024-12-02 电极极片及其制备方法、电池和用电装置 Pending WO2025161663A1 (zh)

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WO2022253174A1 (zh) * 2021-06-01 2022-12-08 比亚迪股份有限公司 集流体及制备的方法、负极和电化学储能装置
CN218975472U (zh) * 2022-12-27 2023-05-05 比亚迪股份有限公司 一种电极极片、二次电池及用电设备
CN219180540U (zh) * 2022-12-27 2023-06-13 比亚迪股份有限公司 电极极片、二次电池及用电设备
CN116759531A (zh) * 2023-01-09 2023-09-15 宁德时代新能源科技股份有限公司 负极极片、电池单体、电池和用电装置

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CN218975472U (zh) * 2022-12-27 2023-05-05 比亚迪股份有限公司 一种电极极片、二次电池及用电设备
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