WO2024065726A1 - 一种极片、电池单体、电池及用电装置 - Google Patents

一种极片、电池单体、电池及用电装置 Download PDF

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Publication number
WO2024065726A1
WO2024065726A1 PCT/CN2022/123380 CN2022123380W WO2024065726A1 WO 2024065726 A1 WO2024065726 A1 WO 2024065726A1 CN 2022123380 W CN2022123380 W CN 2022123380W WO 2024065726 A1 WO2024065726 A1 WO 2024065726A1
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Prior art keywords
active material
pole piece
battery
area
lithium
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Ceased
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PCT/CN2022/123380
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English (en)
French (fr)
Inventor
杜香龙
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex Technology Co Ltd
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Priority to PCT/CN2022/123380 priority Critical patent/WO2024065726A1/zh
Priority to CN202280092182.2A priority patent/CN118743043A/zh
Priority to EP22960344.4A priority patent/EP4550438A4/en
Publication of WO2024065726A1 publication Critical patent/WO2024065726A1/zh
Priority to US18/956,035 priority patent/US20250087676A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—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
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • 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
    • H01M2004/027—Negative electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of battery technology, and in particular to a pole piece, a battery cell, a battery and an electrical device.
  • the present application is made in view of the above-mentioned technical problems, and its purpose is to provide a pole piece, a battery cell, a battery and an electrical device, in which different active materials are arranged in the thinned area and the non-thinned area of the pole piece, respectively, which can effectively improve the problem of lithium deposition in the thinned area of the pole piece during the battery cycle, and improve the cycle performance and service life of the battery.
  • the present application provides a pole piece, comprising: a current collector, comprising a tab region, a thinned region and a non-thinned region, wherein the thinned region is located between the non-thinned region and the tab region; a film layer, arranged on the thinned region and the non-thinned region, the film layer comprising a first active material arranged on the thinned region and a second active material arranged on the non-thinned region, the thickness of the film layer in the thinned region is less than the thickness of the film layer in the non-thinned region, and the specific surface area of the first active material is greater than the specific surface area of the second active material.
  • the pole piece provided in the present application is provided with a first active material and a second active material in the thinned area and the non-thinned area, respectively, and the first active material has a larger specific surface area. Therefore, compared with the second active material, the pores in the first active material can absorb more electrolyte during the battery cycle, improve the ion dynamics of the thinned area, reduce the polarization of the thinned area, and effectively improve the battery polarization between the thinned areas of the positive and negative electrodes of the battery during the cycle, thereby solving the problem of easy lithium precipitation in the thinned area, helping to improve the battery cycle performance and extend the battery life.
  • first active material and the second active material may be the same type of active material or different types of active materials.
  • the D v 50 of the first active material is greater than the D v 50 of the second active material.
  • the first active material disposed in the thinned area has a larger particle size distribution, so that there are more gaps between the particles of the active material disposed in the thinned area. Compared with the non-thinned area, it can accommodate more electrolyte, which helps to improve the kinetics of the electrochemical reaction in the thinned area, thereby improving the cycle performance and service life of the battery.
  • the compaction density of the film layer in the thinned area is less than the compaction density of the film layer in the non-thinned area.
  • the compaction density of the film layer arranged in the thinning area is less than the compaction density of the film layer arranged in the non-thinning area, so that the structure of the film layer in the thinning area is looser than that in the non-thinning area, and can accommodate more electrolyte, thereby further improving the electrochemical reaction kinetics in the thinning area during the battery cycle, and further improving the cycle performance and service life of the battery.
  • the thickness of the film layer in the thinned area is 40 ⁇ m-300 ⁇ m.
  • the length of the thinned region in a first direction satisfies: 0 mm ⁇ w ⁇ 15 mm, and the first direction is the width direction of the pole piece.
  • the pole piece is a positive pole piece
  • the first active material is selected from at least one of nano lithium iron phosphate, nano lithium manganese phosphate, nano lithium iron manganese phosphate, nano lithium iron phosphate and carbon composite materials, nano lithium manganese phosphate and carbon composite materials, and nano lithium iron manganese phosphate and carbon composite materials
  • the second active material is selected from at least one of lithium iron phosphate, lithium manganese phosphate, lithium iron manganese phosphate, lithium iron phosphate and carbon composite materials, lithium manganese phosphate and carbon composite materials, and lithium iron manganese phosphate and carbon composite materials.
  • the carbon content of the first active material is greater than the carbon content of the second active material.
  • the carbon content of the first active material is greater than or equal to 1.5wt%, optionally 1.5wt%-2.7wt%, preferably 1.6wt%-2.2wt%, and further preferably 1.8wt%-2.0wt%; and/or the carbon content of the second active material is less than 1.5wt%.
  • the D v 50 of the first active material satisfies: D v 50 ⁇ 300 nm, preferably 100 nm ⁇ D v 50 ⁇ 200 nm, more preferably 100 nm ⁇ D v 50 ⁇ 150 nm; and/or the D v 50 of the second active material satisfies: D v 50 ⁇ 800 nm, preferably 800 nm ⁇ D v 50 ⁇ 1200 nm, more preferably 1000 nm ⁇ D v 50 ⁇ 1100 nm.
  • the specific surface area of the first active material satisfies: BET ⁇ 15 m 2 /g, optionally, 15 m 2 /g ⁇ BET ⁇ 20 m 2 /g, preferably, 18 m 2 /g ⁇ BET ⁇ 20 m 2 /g; and/or the specific surface area of the second active material satisfies: BET ⁇ 10 m 2 /g, optionally, 8 m 2 /g ⁇ BET ⁇ 10 m 2 /g.
  • the pole piece is a negative pole piece
  • the first active material is selected from at least one of natural graphite, hard carbon, nano silicon-based materials, nano tin-based materials, and nano lithium titanate
  • the second active material is selected from at least one of artificial graphite, soft carbon, silicon-based materials, tin-based materials, and lithium titanate.
  • the carbon content of the first active material is greater than or equal to 1.5wt%, optionally 1.5wt%-2.0wt%; and/or the carbon content of the second active material is greater than or equal to 0.9wt%, optionally 0.9wt%-1.3wt%.
  • the D v 50 of the first active material satisfies: 800 nm ⁇ D v 50 ⁇ 1400 nm; and/or the D v 50 of the second active material satisfies: 100 nm ⁇ D v 50 ⁇ 400 nm.
  • the specific surface area of the first active material satisfies: BET ⁇ 15 m 2 /g, optionally, 15 m 2 /g ⁇ BET ⁇ 20 m 2 /g; and/or the specific surface area of the second active material satisfies: BET ⁇ 7 m 2 /g, optionally, 7 m 2 /g ⁇ BET ⁇ 12 m 2 /g.
  • a battery cell comprising the pole piece in any embodiment of the first aspect.
  • a battery comprising the battery cell in the second aspect.
  • an electrical device comprising at least one of the battery cell in the second aspect or the battery in the third aspect, the battery cell and/or the battery being used to supply power to the electrical device.
  • FIG. 1 is a schematic structural diagram of a pole piece according to an embodiment of the present application.
  • FIG. 2 is a schematic top view of a pole piece according to an embodiment of the present application.
  • FIG. 3 is a schematic structural diagram of an electrode assembly according to an embodiment of the present application.
  • FIG. 4 is a graph showing the battery cycle performance of Example 1 of the present application.
  • FIG. 5 is a graph showing the battery cycle performance of Comparative Example 1 of the present application.
  • FIG6 is a diagram showing the DCR test results of Example 1 of the present application.
  • FIG. 7 is a graph showing the DCR test results of Comparative Example 1 of the present application.
  • range disclosed in the present application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range.
  • the range defined in this way can be inclusive or exclusive of end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60-120 and 80-110 is listed for a specific parameter, it is understood that the range of 60-110 and 80-120 is also expected.
  • the numerical range "a-b" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers.
  • the numerical range "0-5" represents that all real numbers between "0-5" have been fully listed herein, and "0-5" is just the abbreviation of these numerical combinations.
  • a parameter is expressed as an integer ⁇ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.
  • the “include” and “comprising” mentioned in this application represent open-ended or closed-ended expressions.
  • the “include” and “comprising” may represent that other components not listed may also be included or only the listed components may be included or only the listed components may be included.
  • the term "or” is inclusive.
  • the phrase “A or B” means “A, B, or both A and B”. More specifically, any of the following conditions satisfies the condition "A or B”: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).
  • a battery refers to a physical module that includes one or more battery cells to provide electrical energy.
  • the battery mentioned in this application may include a battery module or a battery pack.
  • a battery generally includes a box for encapsulating one or more battery cells, and the box can prevent liquid or other foreign matter from affecting the charging or discharging of the battery cells.
  • a battery usually includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator.
  • active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet.
  • the electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet.
  • the separator is set between the positive electrode sheet and the negative electrode sheet to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.
  • the battery may include a lithium-ion battery, a sodium-ion battery, a magnesium-ion battery, etc., which is not limited in the embodiments of the present application.
  • Lithium-ion batteries are a typical secondary battery. Because they rely on the chemical reaction of lithium ions as active ions to be deintercalated between the positive and negative electrodes for charging and discharging, lithium-ion batteries are also called rocking-chair batteries. During the charging process of lithium-ion batteries, lithium ions are removed from the positive electrode, moved to and embedded in the negative electrode; and during the discharging process, lithium ions are removed from the negative electrode, moved to and embedded in the positive electrode.
  • the positive electrode sheet, the negative electrode sheet and the separator are usually assembled into an electrode assembly, and then the electrode assembly is arranged in a shell containing the electrode assembly and the electrolyte to form a battery cell.
  • the electrode assembly can be a wound structure or a laminated structure.
  • the wound electrode assembly is prepared by winding a continuous long sheet of positive and negative electrodes separated by a separator.
  • the laminated electrode assembly is mainly prepared by stacking the positive and negative electrodes alternately in sequence, separated by a separator in a Z-shaped stack, so as to prepare a laminated electrode assembly.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer, the positive electrode film layer is coated on at least one surface of the positive electrode current collector, the current collector not coated with the positive electrode film layer protrudes from the current collector coated with the positive electrode film layer, and the current collector not coated with the positive electrode film layer serves as the positive electrode tab.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer, the negative electrode film layer is coated on at least one surface of the negative electrode current collector, the current collector not coated with the negative electrode film layer protrudes from the current collector coated with the negative electrode film layer, and the current collector not coated with the negative electrode film layer serves as the negative electrode tab.
  • the positive electrode film layer and the negative electrode film layer are usually thinned at the edge of the coating area close to the tab during the coating process, so that the thickness of the positive electrode film layer and the negative electrode film layer at the edge close to the tab is less than the thickness of the normal coating area.
  • lithium-ion batteries During the charge and discharge process of lithium-ion batteries, factors such as the change in the internal resistance of lithium-ion batteries, the balance between the speed of electrochemical reactions at the positive and negative electrodes and the speed of electron movement, and the diffusion rate of lithium ions involved in the electrochemical reaction will lead to the polarization of the battery, causing active ions (lithium ions) to precipitate from the surface of the negative electrode, i.e., lithium deposition.
  • the polarization of the battery and the occurrence of lithium deposition will greatly affect the cycle performance and service life of the battery, and may even cause safety problems in severe cases. Since the edges of the positive and negative electrode film layers are thinner after being thinned, the distance between the positive and negative electrode sheets at the edges is larger, and the battery polarization phenomenon at the edges is more prominent, making lithium deposition more likely to occur.
  • the embodiments of the present application provide a pole piece, a battery cell, a battery and an electric device, wherein the pole piece is provided with a first active material with a larger specific surface area in the thinned area, and a second active material with a smaller specific surface area in the non-thinned area.
  • the pole piece can accommodate more electrolyte in the thinned area, and during the battery cycle, the lithium deposition phenomenon in the thinned area of the pole piece can be effectively improved, thereby improving the cycle performance and service life of the battery.
  • lithium insertion and “embedding” processes described in this application refer to the process in which lithium ions are embedded in the positive electrode material and the negative electrode material due to electrochemical reactions
  • extraction, “delithium removal” and “extraction” processes described in this application refer to the process in which lithium ions are extracted from the positive electrode material and the negative electrode material due to electrochemical reactions.
  • Figure 1 is a schematic structural diagram of a pole piece according to an embodiment of the present application.
  • Figure 2 is a schematic top view of a pole piece according to an embodiment of the present application.
  • the pole piece 1 includes a current collector 2 and a film layer 3 .
  • the current collector 2 includes a tab region 21 , a thinned region 22 a and a non-thinned region 22 b , and the thinned region 22 a is located between the non-thinned region 22 b and the tab region 21 .
  • the membrane layer 3 is arranged on the thinning area 22a and the non-thinning area 22b, and the membrane layer 3 includes a first active material 31 and a second active material 32, wherein the thickness of the membrane layer 3 in the thinning area 22a is less than the thickness of the membrane layer 3 in the non-thinning area 22b, the first active material 31 is arranged on the thinning area 22a, and the second active material 32 is arranged on the non-thinning area 22b, and the specific surface area of the first active material 31 is greater than that of the second active material 32.
  • the film layer 3 is disposed on at least one surface of the current collector 2.
  • the pole piece 1 can be a positive pole piece or a negative pole piece.
  • the pole piece 1 can be used to form a wound electrode assembly or a stacked electrode assembly.
  • the first active material 31 is disposed on the thinned area 22a and the second active material 32 is disposed on the non-thinned area 22b, that is, the thickness of the first active material 31 on the thinned area 22a is less than the thickness of the second active material 32 on the non-thinned area 22b.
  • the pole ear region 21 is connected to one side of the thinned region 22a along the first direction x.
  • the pole piece 1 is wound along the second direction y to form a wound electrode assembly.
  • the first direction x is a direction perpendicular to the long side of the pole piece 1
  • the second direction y is a direction parallel to the long side of the pole piece 1.
  • the pole ear region 21 can be connected to one side of the thinned region 22a along the first direction x, or can be connected to one side of the thinned region 22a along the second direction y.
  • the pole pieces 1 are alternately stacked in sequence, and the separator is Z-wound in the middle to form a laminated electrode assembly.
  • the pole piece 1 of this embodiment by setting the first active material 31 on the thinned area 22a and setting the second active material 32 on the non-thinned area 22b, the pole piece can absorb and accommodate more electrolyte, especially liquid electrolyte, at the thinned area 22a. Therefore, during the cycle of the battery, the diffusion rate of lithium ions at the thinned area 22a can be effectively increased, and the lithium ion dynamics can be improved, thereby effectively improving the polarization phenomenon at the thinned area 22a, reducing the occurrence of lithium precipitation, and helping to improve the cycle performance and service life of the battery.
  • the first active material 31 and the second active material 32 can be the same type of active material. In other words, the first active material 31 and the second active material 32 can be the same type of active material but have different specific surface areas.
  • the first active material 31 is nano-lithium iron phosphate
  • the second active material 32 is lithium iron phosphate.
  • the first active material 31 and the second active material 32 can also be different types of active materials. In other words, the first active material 31 and the second active material 32 can be different types of active materials with different specific surface areas.
  • the first active material 31 is nano-lithium iron manganese phosphate
  • the second active material 32 is lithium iron phosphate.
  • the D v 50 of the first active material 31 is greater than the D v 50 of the second active material 32 .
  • D V 50 refers to the particle size corresponding to the particles with a cumulative volume particle size distribution percentage of 50% in the active material. It represents the average particle size of the active material. Materials with smaller particle sizes usually have larger specific surface areas. Therefore, a material with a larger D V 50 can be selected as the second active material 32, and an active material with a smaller D V 50 can be selected as the first active material 31, so that the specific surface area of the first active material 31 is larger than that of the second active material 32.
  • the specific surface area of the first active material 31 is greater than the specific surface area of the second active material 32.
  • the compaction density of the film layer 3 in the thinned region 22 a is less than the compaction density of the film layer 3 in the non-thinned region 22 b .
  • the active material is coated on the current collector, and after the active material is dried, the pole piece is cold pressed at a certain pressure.
  • the pressure of the cold pressing thinning area 22a and the non-thinning area 22b can be controlled to be different, so that the compaction density of the film layer 3 in the thinning area 22a is less than the compaction density of the film layer 3 in the non-thinning area 22b, thereby, the film layer 3 in the thinning area 22a can have a relatively loose structure.
  • the compaction density of the film layer 3 in the thinned area 22a is 1.9 g/cm 3 -2.3 g/cm 3 , preferably 2.0 g/cm 3 -2.2 g/cm 3 ; the compaction density of the film layer 3 in the non-thinned area is greater than 2.4 g/cm 3 .
  • the film layer 3 can have a relatively loose structure in the thinned area 22a, so that the first active material 31 arranged in the thinned area 22a can further accommodate more electrolyte during the cycle of the battery, thereby further improving the lithium deposition of the electrode 1 in the thinned area 22a, and improving the cycle performance and service life of the battery.
  • the thickness of the film layer 3 in the thinned region 22 a is 40 ⁇ m-300 ⁇ m.
  • the thickness of the film layer 3 in the thinning area 22a satisfies: 40 ⁇ m ⁇ d ⁇ 300 ⁇ m.
  • d can be 40 ⁇ m, 50 ⁇ m, 60 ⁇ m, 70 ⁇ m, 80 ⁇ m, 90 ⁇ m, 100 ⁇ m, 120 ⁇ m, 140 ⁇ m, 160 ⁇ m, 180 ⁇ m, 200 ⁇ m, 220 ⁇ m, 240 ⁇ m, 260 ⁇ m, 280 ⁇ m, 300 ⁇ m, or its value is within the range obtained by combining any two of the above values.
  • the thickness of the film layer 3 in the thinning area 22a can be a fixed value, or it can gradually decrease along the first direction x.
  • the thickness of the film layer 3 in the thinning area 22a described in the present application refers to the thickness of the film layer 3 at any position in the thinning area 22a.
  • the length of the thinned region 22a in the first direction x satisfies: 0mm ⁇ w ⁇ 15mm, and the first direction is the width direction of the pole piece.
  • the width w of the thinned area 22a satisfies 0mm ⁇ w ⁇ 15mm.
  • w can be 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, or its value is within the range obtained by combining any two of the above values.
  • the following is an introduction to specific embodiments of the electrode sheet 1 used as a positive electrode sheet or a negative electrode sheet in a battery.
  • 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 film layer includes a first active material 31 and a second active material 32. At this time, the first active material 31 and the second active material 32 are both positive electrode active materials.
  • the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • the metal foil aluminum foil may be used.
  • the composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • the composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the second active material 32 may be a positive electrode active material for a battery known in the art.
  • the second active material 32 may include at least one of the following materials: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds.
  • the present application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used.
  • These positive electrode active materials may be used alone or in combination of two or more.
  • lithium transition metal oxides may include, but are not limited to , lithium cobalt oxide (such as LiCoO2 ), lithium nickel oxide (such as LiNiO2 ), lithium manganese oxide (such as LiMnO2 , LiMn2O4 ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide , lithium nickel cobalt manganese oxide (such as LiNi1 / 3Co1 / 3Mn1 / 3O2 (also referred to as NCM333), LiNi0.5Co0.2Mn0.3O2 (also referred to as NCM523 ) , LiNi0.5Co0.25Mn0.25O2 (also referred to as NCM211 ), LiNi0.6Co0.2Mn0.2O2 (also referred to as NCM622 ), LiNi0.8Co0.1Mn0.1O2 (also referred to as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi0.85Co0.15Mn0 .
  • lithium-containing phosphates with an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO 4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.
  • lithium iron phosphate such as LiFePO 4 (also referred to as LFP)
  • LiMnPO 4 lithium manganese phosphate
  • LiMnPO 4 lithium manganese phosphate
  • LiMnPO 4 lithium manganese phosphate and carbon
  • the first active material 31 may also be a positive electrode active material for a battery known in the art, as long as the specific surface area of the first active material 31 used in the same pole piece 1 is greater than the specific surface area of the second active material 32.
  • the first active material 31 may include at least one of the following materials: nano-scale lithium-containing phosphates with an olivine structure, nano-scale lithium transition metal oxides, and their respective modified compounds.
  • nano-scale lithium transition metal oxides may include, but are not limited to, at least one of nano-lithium cobalt oxide, nano-lithium nickel oxide, nano-lithium manganese oxide, nano-lithium nickel cobalt oxide, nano-lithium manganese cobalt oxide, nano-lithium nickel manganese oxide, nano-lithium nickel cobalt manganese oxide, nano-lithium nickel cobalt aluminum oxide, and their modified compounds.
  • lithium-containing phosphates with a nano-olivine structure may include, but are not limited to, at least one of nano-lithium iron phosphate, a composite material of lithium iron phosphate and carbon, nano-lithium manganese phosphate, a composite material of nano-lithium manganese phosphate and carbon, nano-lithium iron manganese phosphate, and nano-lithium iron manganese phosphate and carbon composite materials.
  • These positive electrode active materials may be used alone or in combination of two or more.
  • D v 50 of the first active material 31 satisfies: D v 50 ⁇ 300 nm, preferably 100 nm ⁇ D v 50 ⁇ 200 nm, more preferably 100 nm ⁇ D v 50 ⁇ 150 nm.
  • the second active material 32 satisfies: D v 50 ⁇ 800 nm, preferably 800 nm ⁇ D v 50 ⁇ 1200 nm, more preferably 1000 nm ⁇ D v 50 ⁇ 1100 nm.
  • the D v 50 of the first active material 31 may be 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, 220 nm, 240 nm, 260 nm, 280 nm, 300 nm, or a value within the range obtained by combining any two of the above values.
  • the D v 50 of the second active material 32 may be 800 nm, 820 nm, 840 nm, 860 nm, 880 nm, 900 nm, 920 nm, 940 nm, 960 nm, 980 nm, 1000 nm, 1100 nm, 1200 nm, or a value within the range obtained by combining any two of the above values.
  • the specific surface area of the first active material 31 satisfies: BET ⁇ 15 m 2 /g, optionally, 15 m 2 /g ⁇ BET ⁇ 20 m 2 /g; preferably, 18 m 2 /g ⁇ BET ⁇ 20 m 2 /g.
  • the specific surface area of the second active material 32 satisfies: BET ⁇ 10 m 2 /g, optionally, 8 m 2 /g ⁇ BET ⁇ 10 m 2 /g.
  • the BET of the first active material 31 may be 15 m 2 /g, 16 m 2 /g, 17 m 2 /g, 18 m 2 /g, 19 m 2 /g, 20 m 2 /g, or a value within the range obtained by combining any two of the above values.
  • the BET of the second active material 32 may be 1 m 2 /g, 2 m 2 /g, 3 m 2 /g, 4 m 2 /g, 5 m 2 /g, 6 m 2 /g, 7 m 2 /g, 8 m 2 /g, 9 m 2 /g, 10 m 2 /g, or a value within the range obtained by combining any two of the above values.
  • the ability of the positive electrode film layer to absorb and accommodate electrolyte in the non-thinned area 22b and the thinned area 22a can be accurately controlled, thereby further improving the lithium ion dynamics in the thinned area 22a and improving the lithium plating problem of the battery.
  • the carbon content of the first active material 31 is greater than the carbon content of the second active material 32 .
  • the carbon content of the first active material 31 is 1.5%-2.7%, preferably 1.6%-2.2%, and more preferably 1.8%-2.0%. That is, the carbon content of the first active material 31 can be 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, or a value within the range obtained by combining any two of the above values.
  • the positive electrode film layer further includes a binder.
  • the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PTFE polytetrafluoroethylene
  • vinylidene fluoride-tetrafluoroethylene-propylene terpolymer vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer
  • the positive electrode film layer further includes 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 in the following manner: the components for preparing the positive electrode sheet are respectively formed into positive electrode slurries.
  • the first active material 31, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry 1.
  • the second active material 32, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry 2. Then the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, a positive electrode sheet can be obtained.
  • the negative electrode sheet generally includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector.
  • the negative electrode film layer includes a first active material 31 and a second active material 32.
  • the first active material 31 and the second active material 32 are both negative electrode active materials.
  • the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • a metal foil a copper foil may be used.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate.
  • the composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the second active material 32 may be a negative electrode active material for a battery known in the art.
  • the second active material 32 may include at least one of the following materials: artificial graphite, soft carbon, silicon-based materials, tin-based materials, lithium titanate, etc.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys.
  • the tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys.
  • the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.
  • the first active material 31 may also be a negative electrode material for a battery known in the art, as long as the specific surface area of the first active material 31 used on the same pole piece 1 is greater than the specific surface area of the second active material 32.
  • the first active material may include at least one of the following materials: natural graphite, hard carbon, nano-silicon-based materials, nano-tin-based materials, and nano-lithium titanate.
  • the nano-silicon-based material may be selected from at least one of nano-scale elemental silicon, nano-scale silicon oxide compounds, nano-scale silicon-carbon composites, nano-scale silicon-nitrogen composites, and nano-scale silicon alloys.
  • the nano-tin-based material may be selected from at least one of nano-scale elemental tin, nano-scale tin oxide compounds, and nano-scale tin alloys.
  • the specific surface area of the first active material 31 satisfies: BET ⁇ 15 m 2 /g, optionally, 15 m 2 /g ⁇ BET ⁇ 20 m 2 /g, preferably, the specific surface area of the second active material 31 is 16 m 2 /g; and/or, the specific surface area of the second active material 32 satisfies: BET ⁇ 7 m 2 /g, optionally, 7 m 2 /g ⁇ BET ⁇ 12 m 2 /g, preferably, the specific surface area of the second active material 32 is 8 m 2 /g.
  • Dv50 of the first active material 31 satisfies: 800nm ⁇ Dv50 ⁇ 1400nm , preferably, Dv50 of the first active material 31 is 1000nm; and/or Dv50 of the second active material 32 satisfies: 100nm ⁇ Dv50 ⁇ 400nm , preferably, Dv50 of the second active material 32 is 200nm.
  • the first active material 31 has a carbon content greater than or equal to 1.5wt%, optionally 1.5wt%-2.0wt%, preferably 2.0wt%; and/or the second active material 32 has a carbon content greater than or equal to 0.9wt%, optionally 0.9wt%-1.3wt%, preferably 1.2wt%.
  • the negative electrode film layer further includes 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 further includes a conductive agent, which can 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 can 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 further includes other additives, such as a thickener (such as sodium carboxymethyl cellulose (CMC-Na)) and the like.
  • a thickener such as sodium carboxymethyl cellulose (CMC-Na)
  • CMC-Na sodium carboxymethyl cellulose
  • the negative electrode sheet can be prepared in the following manner: the above components for preparing the negative electrode sheet are respectively formed into negative electrode slurries.
  • the first active material 31, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a negative electrode slurry 1.
  • the second active material 32, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a negative electrode slurry 2. Then 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.
  • the electrolyte plays the role of conducting ions between the positive electrode and the negative electrode.
  • the present application has no specific restrictions on the type of electrolyte, which can be selected according to needs.
  • the electrolyte can be liquid, gel or all-solid.
  • the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.
  • the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate and lithium tetrafluorooxalatophosphate.
  • the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • the electrolyte further includes additives, such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.
  • additives such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.
  • the secondary battery further includes a separator.
  • the present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.
  • the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation.
  • the materials of each layer can be the same or different, without particular limitation.
  • the positive electrode sheet, the negative electrode sheet and the separator can be made into an electrode assembly by a winding process or a lamination process.
  • the wound electrode assembly can be cylindrical, square or any other shape.
  • FIG3 is a schematic diagram of a cylindrical electrode assembly 3 as an example. As shown in FIG3, the tab area 21 of the positive electrode sheet forms the positive electrode tab 31 of the electrode assembly 3 after winding, the tab area 21 of the negative electrode sheet forms the negative electrode tab 32 of the electrode assembly 3 after winding, and the thinned area 22a and the non-thinned area 22b of the positive electrode sheet and the negative electrode sheet form the middle part 33 of the electrode assembly after winding.
  • An embodiment of the present application further provides a battery cell, which includes the pole piece in any embodiment of the present application.
  • the battery cell may include an outer packaging, which may 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, a steel shell, etc.
  • the outer packaging of the battery cell may also be a soft package, such as a bag-type soft package.
  • the material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.
  • the present application has no particular limitation on the shape of the battery cell, which may be cylindrical, square, or any other shape.
  • An embodiment of the present application also provides a battery, which includes at least one battery cell in an embodiment of the present application.
  • multiple battery cells are first integrated into a battery module, and then the battery module is installed in a battery box to form a battery pack.
  • multiple battery cells can also be directly installed in a box to form a battery pack, eliminating the intermediate state of the battery module, thereby reducing the quality of the battery pack and increasing the energy density of the battery.
  • the second production and processing technology can also be called a cell to pack packaging technology, and the battery pack is referred to as a battery in this application.
  • multiple battery cells may be directly integrated into a battery module, and the battery module may be directly used to power an electrical device.
  • the battery module is also referred to as a battery in this application.
  • the present application also provides an electric device, which includes at least one of the battery cells or batteries in any embodiment of the present application.
  • the battery cells and batteries can be used as the power source of the electric device, and can also be used as the energy storage unit of the electric device.
  • the electric device may include vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys and electric tools, etc.
  • the vehicle may be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc.
  • the spacecraft includes an airplane, a rocket, a space shuttle and a spacecraft, etc.
  • the electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys and electric airplane toys, etc.
  • the electric tools include metal cutting electric tools, grinding electric tools, assembly electric tools and railway electric tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators and electric planers, etc., but the present application is not limited thereto.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.
  • a battery module or a battery can be used as a power source.
  • a device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be thin and light, and a battery cell may be used as a power source.
  • Nano lithium iron phosphate was used as the first active material 31, and the conductive agent acetylene black and the binder polyvinylidene fluoride (PVDF) were dissolved in the solvent N-methylpyrrolidone (NMP) at a mass ratio of 97:0.8:2.2, and the positive electrode slurry 1 was obtained after being fully stirred and mixed.
  • Lithium iron phosphate was used as the second active material 32, and the conductive agent acetylene black and the binder polyvinylidene fluoride (PVDF) were dissolved in the solvent N-methylpyrrolidone (NMP) at a mass ratio of 97:0.8:2.2, and the positive electrode slurry 2 was obtained after being fully stirred and mixed.
  • the positive electrode slurry 1 was evenly coated on the thinned area 22a of the positive electrode current collector aluminum foil, and the positive electrode slurry 2 was evenly coated on the non-thinned area 22b of the positive electrode current collector aluminum foil, and then dried, cold pressed, and cut to obtain the positive electrode sheet.
  • the BET of lithium iron phosphate in the positive electrode sheet is 8 m 2 /g
  • the BET of nano lithium iron phosphate is 16 m 2 /g
  • the length w of the thinned region 22 a in the first direction is 10 mm.
  • the positive electrode sheet, the separator, and the negative electrode sheet are stacked in order, so that the separator is located between the positive electrode sheet and the negative electrode sheet and can separate the positive electrode sheet from the negative electrode sheet; then the stacked components are wound to obtain an electrode assembly; the electrode assembly is set in a shell, and after drying, a LiPF6 electrolyte with a mass fraction of 11% is injected; after processes such as formation and standing, a battery cell is obtained.
  • Example 2 Compared with the battery cell of Example 1, Example 2 only changes the BET and D V 50 of the nano-lithium iron phosphate, wherein the BET of the nano-lithium iron phosphate in Example 2 is 18 m 2 /g and its D V 50 is 600 nm. Specific parameters are shown in Table 1.
  • Example 5 uses a composite material of nano lithium iron phosphate and carbon as the first active material 31 and a composite material of lithium iron phosphate and carbon as the second active material 32, wherein the carbon content of the first active material is 1.18% and the carbon content of the second active material is 2.01%.
  • Example 6 Compared with the battery cell of Example 5, Example 6 only changes the carbon content of the composite material of nano-lithium iron phosphate and carbon. The specific parameters are shown in Table 1.
  • Na 0.85 Ni 0.25 Mn 0.75 O 2 with a BET of 1.15 m 2 /g was used as the first active material 31, and was dissolved in a solvent N-methylpyrrolidone (NMP) with a mass ratio of 90:5:5 with a conductive agent acetylene black and a binder polyvinylidene fluoride (PVDF), and was fully stirred and mixed to obtain a positive electrode slurry 1.
  • NMP N-methylpyrrolidone
  • PVDF polyvinylidene fluoride
  • Na 0.85 Ni 0.25 Mn 0.75 O 2 with a BET of 0.8 m 2 /g was used as the second active material 32, and was dissolved in a solvent N-methylpyrrolidone (NMP) with a mass ratio of 90:5:5 with a conductive agent acetylene black and a binder polyvinylidene fluoride (PVDF), and was fully stirred and mixed to obtain a positive electrode slurry 2. Then, the positive electrode slurry 1 is evenly coated on the thinned area 22a of the positive electrode current collector aluminum foil, and the positive electrode slurry 2 is evenly coated on the non-thinned area 22b of the positive electrode current collector aluminum foil, and then dried, cold pressed, and cut to obtain the positive electrode sheet.
  • NMP N-methylpyrrolidone
  • PVDF binder polyvinylidene fluoride
  • the negative electrode active material hard carbon, the conductive agent acetylene black, the binder styrene butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC) are dissolved in the solvent deionized water according to the mass ratio of 90:4:4:2, and mixed evenly to obtain the negative electrode slurry.
  • the negative electrode slurry is evenly coated on the thinned area 22a and the non-thinned area 22b of the negative electrode current collector copper foil once or multiple times, and then dried, cold pressed, and cut to obtain the negative electrode sheet.
  • the BET of hard carbon is 4.5m2 /g.
  • the battery cell of Example 7 is prepared by the same method as that of Example 1, except that a NaPF 6 electrolyte with a mass fraction of 11% is used, which will not be described in detail here.
  • Lithium iron phosphate, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) are dissolved in a solvent N-methylpyrrolidone (NMP) at a mass ratio of 97:0.8:2.2, and the mixture is stirred and mixed to obtain a positive electrode slurry.
  • NMP N-methylpyrrolidone
  • the positive electrode slurry is then evenly coated on the thinned area 22a and the non-thinned area 22b of the positive electrode current collector aluminum foil, and then dried, cold pressed, and cut to obtain a positive electrode sheet.
  • the BET of lithium iron phosphate in the positive electrode sheet is 8m2 /g.
  • Natural graphite as the first active material 31 conductive agent acetylene black, binder styrene butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are dissolved in solvent deionized water at a mass ratio of 96.5:0.7:1.8:1, and mixed evenly to obtain negative electrode slurry 1.
  • Artificial graphite as the second active material 32, conductive agent acetylene black, binder styrene butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are dissolved in solvent deionized water at a mass ratio of 96.5:0.7:1.8:1, and mixed evenly to obtain negative electrode slurry 2.
  • negative electrode slurry 1 is evenly coated on the thinned area 22a of the negative electrode current collector copper foil, and negative electrode slurry 2 is evenly coated on the non-thinned area 22b of the negative electrode current collector copper foil, and then dried, cold pressed, and cut to obtain a negative electrode sheet.
  • the BET of artificial graphite in the negative electrode sheet is 3m2 /g, and the BET of natural graphite is 4m2 /g.
  • the length w of the thinned region 22 a in the first direction is 10 mm.
  • the battery cell of Example 8 is prepared by the same method as that of Example 1, which will not be described again.
  • Lithium iron phosphate, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) are dissolved in a solvent N-methylpyrrolidone (NMP) at a mass ratio of 97:0.8:2.2, and the positive electrode slurry is obtained after being fully stirred and mixed.
  • NMP N-methylpyrrolidone
  • the positive electrode slurry is then evenly coated on the thinned area 22a and the thinned area 22b of the positive electrode current collector aluminum foil, and then dried, cold pressed, and cut to obtain the positive electrode sheet.
  • Comparative Example 1 adopts the same preparation method as Example 1, which will not be repeated here.
  • the positive electrode active material Na 0.85 Ni 0.25 Mn 0.75 O 2 , the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) were dissolved in a solvent N-methylpyrrolidone (NMP) at a mass ratio of 90:5:5, and the positive electrode slurry was obtained after being fully stirred and mixed. Subsequently, the negative positive electrode slurry was evenly coated on the thinned area 22a and the thinned area 22b of the positive electrode current collector aluminum foil, and then dried, cold pressed, and cut to obtain the positive electrode sheet.
  • NMP N-methylpyrrolidone
  • the negative electrode active material hard carbon, the conductive agent acetylene black, the binder styrene butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC) are dissolved in the solvent deionized water according to a mass ratio of 90:4:4:2, and mixed evenly to obtain the negative electrode slurry. Subsequently, the negative electrode slurry is evenly coated on the thinned area 22a and the thinned area 22b of the negative electrode current collector copper foil, and then dried, cold pressed, and cut to obtain the negative electrode sheet.
  • Comparative Example 2 and Example 7 use the same method and steps to prepare the battery monomer, which will not be repeated here.
  • active material 1 refers to the first active material 31
  • BET-1 refers to the specific surface area of the first active material 31
  • active material 2 refers to the second active material 32
  • BET-2 refers to the specific surface area of the second active material 32
  • Dv50-1 refers to the particle size distribution of the first active material 31
  • Dv50-2 refers to the particle size distribution of the second active material 32
  • C-1 refers to the carbon content of the first active material
  • C-2 refers to the carbon content of the second active material 32
  • w refers to the length of the thinning region 22a in the first direction.
  • Example 1-6, Example 8 and Comparative Example 1 it can be seen from Examples 1-6, Example 8 and Comparative Example 1 that, whether nano lithium iron phosphate is arranged in the positive electrode thinning area of the battery, or natural graphite is arranged in the negative electrode thinning area of the battery, by arranging an active material with a larger specific surface area in the thinning area than in the non-thinning area, the cycle performance and service life of the lithium ion battery can be effectively improved. It can be seen from Example 7 and Comparative Example 2 that the arrangement of an active material with a relatively large specific surface area in the thinning area can also improve the cycle performance and cycle life of the sodium ion battery.
  • test method refers to the standard GB/T19587-2004 "Determination of specific surface area of solid substances by gas adsorption BET method".
  • the secondary batteries prepared in each embodiment and comparative example are charged at a constant current of 1C rate to a charging cut-off voltage of 3.65V, then charged at a constant voltage to a current ⁇ 0.05C, left to stand for 5 minutes, and then discharged at a constant current of 1C rate to a discharge cut-off voltage of 2.5V, left to stand for 5 minutes, which is a charge and discharge cycle.
  • the battery is subjected to a cyclic charge and discharge test until the battery capacity decays to 80%. The number of cycles at this time is the cycle life of the battery.
  • Table 2 the battery cycle performance test results of Example 1 and Comparative Example 1 are shown in Figures 4 and 5, respectively.
  • the DCR test results of comparative example 1 and embodiment 1 are shown in Figures 6 and 7, respectively.
  • the DCR of embodiment 1 is reduced by 6.87 milliohms at -25°C; the DCR is reduced by 3.46 milliohms at -10°C, and the DCR is reduced by 1.42 milliohms at 25°C, the internal resistance is significantly reduced, and the dynamics is significantly improved.

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Abstract

本申请提供了一种极片、电池单体、电池及用电装置，该极片包括：集流体，包括极耳区域、削薄区域和非削薄区域，削薄区域位于非削薄区域与极耳区域之间；膜层，设置于削薄区域和非削薄区域上，膜层包括设置于削薄区域上的第一活性材料和设置于非削薄区域上的第二活性材料，削薄区域的膜层的厚度小于非削薄区域的膜层的厚度，第一活性材料的比表面积大于第二活性材料的比表面积。析锂现象在该极片的削薄区域能够得到明显改善，帮助减少极片在电池循环过程中的极化，提高电池的循环性能和使用寿命。

Description

一种极片、电池单体、电池及用电装置 技术领域
本申请涉及电池技术领域，特别是涉及一种极片、电池单体、电池及用电装置。
背景技术
近年来，二次电池由于其较高的能量密度以及可循环性能，被广泛应用于储能系统、电动工具、电动自行车、电动汽车、军事装备、航空航天等众多领域。随着二次电池取得的快速发展以及广泛应用，对其循环性能、使用寿命等性能也提出了更高的要求。
因此，如何提高电池的循环性能和使用寿命是一项亟待解决的技术问题。
发明内容
本申请是鉴于上述技术问题而进行的，其目的在于，提供一种极片、电池单体、电池及用电装置，该极片在削薄区域与非削薄区域分别设置了不同的活性材料，能够有效改善极片削薄区域在电池循环过程中容易析锂的问题，提高电池的循环性能以及使用寿命。
第一方面，本申请提供一种极片，所述极片包括：集流体，包括极耳区域、削薄区域和非削薄区域，所述削薄区域位于所述非削薄区域与所述极耳区域之间；膜层，设置于所述削薄区域和所述非削薄区域上，所述膜层包括设置于所述削薄区域上的第一活性材料和设置于所述非削薄区域上的第二活性材料，所述削薄区域的所述膜层的厚度小于所述非削薄区域的所述膜层的厚度，所述第一活性材料的比表面积大于所述第二活性材料的比表面积。
本申请提供的极片在削薄区域和非削薄区域分别设置了第一活性材料和第二活性材料，第一活性材料具有更大的比表面积。因此，与第二活性材料相比，第一活性材料中的孔隙在电池的循环过程中能够吸附更多的电解液，提高削薄区域的离子动力学，降低削薄区域的极化作用，有效改善循环过程中电池正负极的削薄区域之间的电 池极化，从而解决了削薄区域容易析锂的问题，帮助提高了电池的循环性能并延长了电池的使用寿命。
应理解，第一活性材料和第二活性材料可以是相同种类的活性材料，也可以是不同种类的活性材料。
在一些实施例中，所述第一活性材料的D v50大于所述第二活性材料的D v50。
本申请的实施例中，设置于削薄区域的第一活性材料具有更大的粒径分布，使得设置于削薄区域的活性材料的颗粒之间具有更多的空隙，与非削薄区域相比，能够容纳更多的电解液，有助于提高削薄区域电化学反应的动力学，从而提高电池的循环性能和使用寿命。
在一些实施例中，所述膜层在所述削薄区域的压实密度小于所述膜层在所述非削薄区域的压实密度。
本申请的实施例中，设置于削薄区域的膜层的压实密度小于设置于非削薄区域的膜层的压实密度，使得削薄区域膜层的结构较非削薄区域更加松散，能够容纳更多的电解液从而进一步提高削薄区域在电池循环过程中的电化学反应动力学，进一步提高电池的循环性能和使用寿命。
在一些实施例中，所述膜层在所述削薄区域的厚度为40μm-300μm。
在一些实施例中，所述削薄区域在第一方向上的长度满足：0mm＜w≤15mm，所述第一方向为所述极片的宽度方向。
在一些实施例中，所述极片为正极极片，所述第一活性材选自纳米磷酸铁锂、纳米磷酸锰锂、纳米磷酸铁锰锂、纳米磷酸铁锂与碳的复合材料、纳米磷酸锰锂与碳的复合材料、纳米磷酸铁锰锂与碳的复合材料中的至少一种；和/或，所述第二活性材料选自磷酸铁锂、磷酸锰锂、磷酸铁锰锂、磷酸铁锂与碳的复合材料、磷酸锰锂与碳的复合材料、磷酸锰铁锂与碳的复合材料中的至少一种。
在一些实施例中，所述第一活性材料的含碳量大于所述第二活性材料的含碳量。
在一些实施例中，所述第一活性材料的含碳量大于或等于1.5wt％，可选地为1.5wt％-2.7wt％，优选为1.6wt％-2.2wt％，进一步优选为1.8wt％-2.0wt％；和/或，所述第二活性材料的含碳量小于1.5wt％。
在一些实施例中，所述第一活性材料的D v50满足：D v50≤300nm，优选地，100nm≤D v50≤200nm，进一步优选地，100nm≤D v50≤150nm；和/或，所述第二活 性材料的D v50满足：D v50≥800nm，优选地，800nm≤D v50≤1200nm，进一步优选地，1000nm≤D v50≤1100nm。
在一些实施例中，所述第一活性材料的比表面积满足：BET≥15m 2/g，可选地，15m 2/g≤BET≤20m 2/g，优选地，18m 2/g≤BET≤20m 2/g；和/或，所述第二活性材料的比表面积满足：BET＜10m 2/g，可选地，8m 2/g≤BET≤10m 2/g。
在一些实施例中，所述极片为负极极片，所述第一活性材料选自天然石墨、硬碳、纳米硅基材料、纳米锡基材料、纳米钛酸锂中的至少一种；和/或，所述第二活性材料选自人造石墨、软碳、硅基材料、锡基材料、钛酸锂中的至少一种。
在一些实施例中，所述第一活性材料的含碳量为大于或等于1.5wt％，可选地为1.5wt％-2.0wt％；和/或，所述第二活性材料的含碳量大于或等于0.9wt％，可选地为0.9wt％-1.3wt％。
在一些实施例中，所述第一活性材料的D v50满足：800nm≤D v50≤1400nm；和/或，所述第二活性材料的D v50满足：100nm≤D v50≤400nm。
在一些实施例中，所述第一活性材料的比表面积满足：BET≥15m 2/g，可选地，15m 2/g≤BET≤20m 2/g；和/或，所述第二活性材料的比表面积满足：BET≥7m 2/g，可选地，7m 2/g≤BET≤12m 2/g。
第二方面，提供一种电池单体，所述电池单体包括第一方面任一实施例中的极片。
第三方面，提供一种电池，所述电池包括第二方面中的电池单体。
第四方面，提供一种用电装置，所述用电装置包括第二方面中的电池单体或第三方面中的电池中的至少一种，所述电池单体和/或所述电池用于为所述用电装置供电。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将对本申请实施例中所需要使用的附图作简单地介绍，显而易见地，下面所描述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，还可以根据附图获得其他的附图。在附图中，附图并未按照实际的比例绘制。
图1是本申请实施例一种极片的示意性结构图。
图2是本申请实施例一种极片的示意性俯视图。
图3是本申请实施例一种电极组件的示意性结构图。
图4是本申请实施例1的电池循环性能图。
图5是本申请对比例1的电池循环性能图。
图6是本申请实施例1的DCR测试结果图。
图7是本申请对比例1的DCR测试结果图。
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的负极集流体、含有其的二次电池、电池模块以及电学装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
在本申请的描述中，需要说明的是，除非另有说明，“多个”的含义是两个以上；术语“上”、“下”、“左”、“右”、“内”、“外”等指示的方位或位置关系仅是为了便于描述本申请和简化描述，而不是指示或暗示所指的装置或元件必须具有特定的方位、以特定的方位构造和操作，因此不能理解为对本申请的限制。此外，术语“第一”、“第二”、“第三”等仅用于描述目的，而不能理解为指示或暗示相对重要性。“垂直”并不是严格意 义上的垂直，而是在误差允许范围之内。“平行”并不是严格意义上的平行，而是在误差允许范围之内。
下述描述中出现的方位词均为图中示出的方向，并不是对本申请的具体结构进行限定。在本申请的描述中，还需要说明的是，除非另有明确的规定和限定，术语“安装”、“相连”、“连接”应做广义理解，例如，可以是固定连接，也可以是可拆卸连接，或一体地连接；可以是直接相连，也可以通过中间媒介间接相连。对于本领域的普通技术人员而言，可视具体情况理解上述术语在本申请中的具体含义。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
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。
本申请中，电池是指包括一个或多个电池单体以提供电能的物理模块。例如，本申请中所提到的电池可以包括电池模块或电池包等。电池一般包括用于封装一个或多个电池单体的箱体，箱体可以避免液体或其他异物影响电池单体的充电或放电。
电池通常包括正极极片、负极极片、电解质和隔离件。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之间起到传导离子的作用。隔离件设置于正极极片和负极极片之间以防止正负极短路，同时可以使离子通过。
可选地，电池可以包括锂离子电池、钠离子电池、镁离子电池等，本申请实施例对此不做限定。
本申请以锂离子电池为示例，锂离子电池是一种典型的二次电池，由于其依靠锂离子作为活性离子在正负极之间脱嵌的化学反应进行充放电，锂离子电池又被称为 摇椅式电池。锂离子电池的充电过程中，锂离子从正极脱出，移动并嵌入到负极；而放电过程中，锂离子从负极脱出，移动并嵌入正极。
在电池的加工过程中，通常将正极极片、负极极片和隔离件组成电极组件，再将电极组件设置于容纳电极组件和电解质的壳体中以组成电池单体。电极组件可以是卷绕式结构，也可以是叠片式结构。
卷绕式电极组件是把连续的长片型正极极片和负极极片中间用隔膜隔开，然后通过卷绕的方式制备成具有卷绕式电极组件。叠片式电极组件主要是将正极极片和负极极片依次交替叠放，中间由隔膜呈Z字叠绕隔开，从而制备成具有叠片式电极组件。
正极极片包括正极集流体和正极膜层，正极膜层涂覆于正极集流体的至少一个表面，未涂覆正极膜层的集流体凸出于已涂覆正极膜层的集流体，未涂覆正极膜层的集流体作为正极极耳。负极极片包括负极集流体和负极膜层，负极膜层涂覆于负极集流体的至少一个表面，未涂覆负极膜层的集流体凸出于已涂覆负极膜层的集流体，未涂覆负极膜层的集流体作为负极极耳。考虑到极片在后续加工过程中需要被卷绕或叠片，为了保持极耳的完整性，避免极耳的机械性损坏，正极膜层和负极膜层在涂布的过程中通常会在涂布区域靠近极耳一侧的边缘被削薄，使得正极膜层和负极膜层在靠近极耳的边缘处的厚度小于正常涂布区域的厚度。
在锂离子电池的充放电过程中，锂离子电池的内阻变化、正负极电化学反应的速度与电子运动速度之间的平衡以及参与电化学反应的锂离子的扩散速度等因素都将导致电池的极化，使得活性离子(锂离子)从负极极片表面析出，即发生析锂。电池的极化和析锂现象的出现将极大地影响电池的循环性能以及使用寿命，严重时还可能引发电池出现安全问题。而由于正极膜层和负极膜层的边缘在被削薄后厚度较小，使得正极极片与负极极片在边缘的间距较大，边缘处的电池极化现象更为凸出，更加容易发生析锂。
有鉴于此，本申请实施例提供了一种极片、电池单体、电池及用电装置，其中，该极片在削薄区域设置有比表面积较大的第一活性材料，在非削薄区域设置有比表面积较小的第二活性材料。由此，该极片在削薄区域能够容纳更多的电解质，在电池的循环过程中，能够有效改善极片的削薄区域的析锂现象，从而提高电池的循环性能和使用寿命。
应理解，本申请所述“嵌锂”、“嵌入”过程指锂离子由于电化学反应在正极材 料和负极材料中嵌入的过程，本申请所述“脱出”、“脱锂”、“脱嵌”过程指锂离子由于电化学反应在正极材料和负极材料中脱出的过程。
首先，本申请提供一种极片。图1为本申请实施例一种极片的示意性结构图。图2为本申请实施例一种极片的示意性俯视图。
如图1和图2所示，极片1包括集流体2和膜层3。其中，集流体2包括极耳区域21、削薄区域22a和非削薄区域22b，削薄区域22a位于非削薄区域22b与极耳区域21之间。
膜层3设置于削薄区域22a和非削薄区域22b上，膜层3包括第一活性材料31和第二活性材料32，其中，削薄区域22a的膜层3的厚度小于非削薄区域22b的膜层3的厚度，削薄区域22a上设置有第一活性材料31，非削薄区域22b上设置有第二活性材料32，第一活性材料31的比表面积大于第二活性材料32。
具体地，膜层3设置于集流体2的至少一个表面上。极片1可以是正极极片，也可以是负极极片。极片1可以用于组成卷绕式电极组件，也可以用于组成叠片式电极组件。削薄区域22a上设置有第一活性材料31而非削薄区域22b上设置有第二活性材料32，也就是说，削薄区域22a上的第一活性材料31的厚度小于非削薄区域22b上第二活性材料32的厚度。
在卷绕式电极组件中，极耳区域21沿第一方向x与削薄区域22a的一侧连接，在后续的组装过程中，极片1沿第二方向y卷绕形成卷绕式电极组件。第一方向x为垂直于极片1的长边的方向，第二方向y为平行于极片1的长边的方向。在叠片式电极组件中，极耳区域21可以沿第一方向x与削薄区域22a的一侧连接，也可以沿第二方向y与削薄区域22a的一侧连接，在后续的组装过程中，极片1依次交替叠放，中间由隔膜Z字叠绕以形成叠片式电极组件。
本实施例的极片1中，通过在削薄区域22a上设置第一活性材料31，在非削薄区域22b上设置第二活性材料32，使得极片在削薄区域22a处能够吸收、容纳更多的电解质，尤其是液态电解质。由此，在电池的循环过程中，能够有效提高削薄区域22a处锂离子的扩散速度，提高锂离子动力学，从而有效改善削薄区域22a处的极化现象，减少析锂的发生，帮助提高了电池的循环性能和使用寿命。
应理解，第一活性材料31与第二活性材料32可以是相同种类的活性材料。换言之，第一活性材料31与第二活性材料32可以是同种类的活性材料只是拥有不同的 比表面积。例如，第一活性材料31为纳米磷酸铁锂，第二活性材料32为磷酸铁锂。第一活性材料31与第二活性材料32也可以是不同种类的活性材料。换言之，第一活性材料31与第二活性材料32可以是不同种类且拥有不同比表面积的活性材料。例如，第一活性材料31为纳米磷酸铁锰锂，第二活性材料32为磷酸铁锂。
在一个实施例中，第一活性材料31的D v50大于第二活性材料32的D v50。
具体来说，D V50指的是活性材料中累计体积粒度分布百分数达到50％的粒子所对应的粒径。代表了活性材料的平均粒径。粒径更小的材料通常拥有更大的比表面积，因此，可以选择D V50较大的材料作为第二活性材料32，选择D V50较小的活性材料作为第一活性材料31，使得第一活性材料31的比表面积大于第二活性材料32。
本实施例中，通过控制第一活性材料31的平均粒径小于第二活性材料32的平均粒径，使得第一活性材料31的比表面积大于第二活性材料32的比表面积的同时，第一活性材料31的颗粒之间还具有更多的空隙，能够进一步容纳更多的电解液，帮助进一步改善电池循环过程中削薄区域22a极化导致的析锂问题，从而进一步提高电池的循环性能和使用寿命。
在一个实施例中，膜层3在削薄区域22a的压实密度小于膜层3在非削薄区域22b的压实密度。
具体来说，在制备极片1的过程中，在集流体上涂布上活性材料、待活性材料干燥后，会按照一定的压力对极片进行冷压。此时可以控制冷压削薄区域22a和非削薄区域22b的压力不同，使得膜层3在削薄区域22a的压实密度小于膜层3在非削薄区域22b的压实密度，由此，膜层3在削薄区域22a能够具有相对松散的结构。
在一个更为具体的实施例中，膜层3在削薄区域22a的压实密度为1.9g/cm 3-2.3g/cm 3，优选为2.0g/cm 3-2.2g/cm 3；膜层3在非削薄区域的压实密度大于2.4g/cm 3。
本实施例中，通过控制膜层3在削薄区域22a具有更小的压实密度，能够使膜层3在削薄区域22a具有相对松散的结构，使得设置于削薄区域22a的第一活性材料31在电池的循环过程中能够进一步容纳更多的电解液，从而进一步改善极片1在削薄区域22a的析锂情况，提高电池的循环性能和使用寿命。
在一个实施例中，膜层3在削薄区域22a的厚度为40μm-300μm。
具体来说，参见图1，膜层3在削薄区域22a的厚度满足：40μm≤d≤300μm。d可以是40μm、50μm、60μm、70μm、80μm、90μm、100μm、120μm、140μm、 160μm、180μm、200μm、220μm、240μm、260μm、280μm、300μm，或者其数值在上述任意两个数值组合所获得的范围之内。膜层3在削薄区域22a的厚度可以是固定的值，也可以沿第一方向x逐渐减小，本申请所述的膜层3在削薄区域22a的厚度指膜层3在削薄区域22a中任一位置处膜层3的厚度。
在一个实施例中，削薄区域22a在第一方向x上的长度满足：0mm＜w≤15mm，所述第一方向为所述极片的宽度方向。
具体来说，参见图2，削薄区域22a的宽度w满足0mm＜w≤15mm。w可以是0.1mm、0.2mm、0.3mm、0.4mm、0.5mm、0.6mm、0.7mm、0.8mm、0.9mm、1mm、2mm、3mm、4mm、5mm、6mm、7mm、8mm、9mm、10mm、11mm、12mm、13mm、14mm、15mm，或者其数值在上述任意两个数值组合所获得的范围之内。
下面对极片1在电池中作为正极极片、负极极片的具体实施例进行介绍。
[正极极片]
正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，正极膜层包括第一活性材料31和第二活性材料32，此时的第一活性材料31和第二活性材料32均为正极活性材料。
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。
可选地，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。
可选地，第二活性材料32可采用本领域公知的用于电池的正极活性材料。作为示例，第二活性材料32可包括以下材料中的至少一种：橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。但本申请并不限定于这些材料，还可以使用其他可被用作电池正极活性材料的传统材料。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。其中，锂过渡金属氧化物的示例可包括但不限于锂钴氧化物(如LiCoO 2)、锂镍氧化物(如LiNiO 2)、锂锰氧化物(如LiMnO 2、 LiMn 2O 4)、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物(如LiNi 1/3Co 1/3Mn 1/3O 2(也可以简称为NCM333)、LiNi 0.5Co 0.2Mn 0.3O 2(也可以简称为NCM523)、LiNi 0.5Co 0.25Mn 0.25O 2(也可以简称为NCM211)、LiNi 0.6Co 0.2Mn 0.2O 2(也可以简称为NCM622)、LiNi 0.8Co 0.1Mn 0.1O 2(也可以简称为NCM811)、锂镍钴铝氧化物(如LiNi 0.85Co 0.15Al 0.05O 2)及其改性化合物等中的至少一种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂(如LiFePO 4(也可以简称为LFP))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO 4)、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料中的至少一种。
可选地，第一活性材料31也可以采用本领域公知的用于电池的正极活性材料，只要使用在同一极片1中的第一活性材料31的比表面积大于第二活性材料32的比表面积即可。作为示例，第一活性材料31可以包括以下材料中的至少一种：橄榄石结构的纳米级含锂磷酸盐、纳米级锂过渡金属氧化物及其各自的改性化合物。其中，纳米级锂过渡金属氧化物的示例可包括但不限于纳米锂钴氧化物、纳米锂镍氧化物、纳米锂锰氧化物、纳米锂镍钴氧化物、纳米锂锰钴氧化物、纳米锂镍锰氧化物、纳米锂镍钴锰氧化物、纳米锂镍钴铝氧化物及其改性化合物等中的至少一种。纳米级橄榄石结构的含锂磷酸盐的示例可包括但不限于纳米磷酸铁锂、磷酸铁锂与碳的复合材料、纳米磷酸锰锂、纳米磷酸锰锂与碳的复合材料、纳米磷酸锰铁锂、纳米磷酸锰铁锂与碳的复合材料中的至少一种。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在一个实施例中，第一活性材料31的D v50满足：D v50≤300nm；优选地，100nm≤D v50≤200nm；进一步优选地，100nm≤D v50≤150nm。第二活性材料32的满足：D v50≥800nm，优选地，800nm≤D v50≤1200nm，进一步优选地，1000nm≤D v50≤1100nm。
具体来说，第一活性材料31的D v50可以是10nm、20nm、30nm、40nm、50nm、60nm、70nm、80nm、90nm、100nm、110nm、120nm、130nm、140nm、150nm、160nm、170nm、180nm、190nm、200nm、220nm、240nm、260nm、280nm、300nm，或者其数值在上述任意两个数值组合所获得的范围之内。第二活性材料32的D v50可以是800nm、820nm、840nm、860nm、880nm、900nm、920nm、940nm、960nm、980nm、1000nm、1100nm、1200nm，或者其数值在上述任意两个数 值组合所获得的范围之内。
在一个实施例中，第一活性材料31的比表面积满足：BET≥15m 2/g，可选地，15m 2/g≤BET≤20m 2/g；优选地，18m 2/g≤BET≤20m 2/g。第二活性材料32的比表面积满足：BET≤10m 2/g，可选地，8m 2/g≤BET≤10m 2/g。
具体来说，第一活性材料31的BET可以是15m 2/g、16m 2/g、17m 2/g、18m 2/g、19m 2/g、20m 2/g，或者其数值在上述任意两个数值组合所获得的范围之内。第二活性材料32的BET可以是1m 2/g、2m 2/g、3m 2/g、4m 2/g、5m 2/g、6m 2/g、7m 2/g、8m 2/g、9m 2/g、10m 2/g，或者其数值在上述任意两个数值组合所获得的范围之内。
本申请的实施例中，通过选择比表面积、平均粒径在一定范围内的活性材料分别作为第一正极活性材料、第二正极活性材料，能够准确控制正极膜层在非削薄区域22b和削薄区域22a吸收、容纳电解质的能力，进一步提高削薄区域22a的锂离子动力学并改善电池的析锂问题。
在一个实施例中，在正极活性材料含碳的情况下，第一活性材料31的含碳量大于第二活性材料32的含碳量。
在一个具体的示例中，第一活性材料31的含碳量为1.5％-2.7％，优选为1.6％-2.2％，进一步优选为1.8％-2.0％。即第一活性材料31的含碳量可以是1.5％、1.6％、1.7％、1.8％、1.9％、2.0％、2.1％、2.2％，或者其数值在上述任意两个数值组合所获得的范围之内。
可选地，正极膜层还包括粘结剂。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。
可选地，正极膜层还包括导电剂。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分别形成正极浆料。例如将第一活性材料31、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1。又例如，将第二活性材料32、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2。然后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]
负极极片通常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，负极膜层包括第一活性材料31和第二活性材料32，此时第一活性材料31和第二活性材料32均为负极活性材料。
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的其中任意一者或两者上。
可选地，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。
可选地，第二活性材料32可采用本领域公知的用于电池的负极活性材料。作为示例，第二活性材料32可包括以下材料中的至少一种：人造石墨、软碳、硅基材料、锡基材料和钛酸锂等。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。
可选地，第一活性材料31也可以采用本领域公知的用于电池的负极材料，只要用于同一极片1上的第一活性材料31的比表面积大于第二活性材料32的比表面积即可。作为示例，第一活性材料可以包括以下材料中的至少一种：天然石墨、硬碳、纳米硅基材料、纳米锡基材料和纳米钛酸锂等。纳米硅基材料可选自纳米级单质硅、纳米级硅氧化合物、纳米级硅碳复合物、纳米级硅氮复合物以及纳米级硅合金中的至少一种。纳米锡基材料可选自纳米级单质锡、纳米级锡氧化合物以及纳米级锡合金中的至少一种。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。
可选地，第一活性材料31的比表面积满足：BET≥15m 2/g，可选地，15m 2/g≤BET≤20m 2/g，优选地，第二活性材料31的比表面积为16m 2/g；和/或，第二活性材料32的比表面积满足：BET≥7m 2/g，可选地，7m 2/g≤BET≤12m 2/g，优选地，第二 活性材料32的比表面积为8m 2/g。
可选地，第一活性材料31的Dv50满足：800nm≤D v50≤1400nm，优选地，第一活性材料31的D v50为1000nm；很/或第二活性材料32的Dv50满足：100nm≤D v50≤400nm，优选地，第二活性材料32的D v50为200nm。
可选地，在负极活性材料含碳的情况下，第一活性材料31得到含碳量大于或等于1.5wt％，可选地为1.5wt％-2.0wt％，优选为2.0wt％；和/或，第二活性材料32的含碳量大于或等于0.9wt％，可选地为0.9wt％-1.3wt％，优选为1.2wt％。
可选地，负极膜层还包括粘结剂。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。
可选地，在一个实施例中，负极膜层还包括导电剂。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。
可选地，负极膜层还包括其他助剂，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分别形成负极浆料。例如将第一活性材料31、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，形成负极浆料1。再例如将第二活性材料32、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，形成负极浆料2。然后将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可得到负极极片。
[电解质]
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的或全固态的。
可选地，电解质采用电解液。电解液包括电解质盐和溶剂。
可选地，电解质盐可选自六氟磷酸锂、四氟硼酸锂、高氯酸锂、六氟砷酸锂、双氟磺酰亚胺锂、双三氟甲磺酰亚胺锂、三氟甲磺酸锂、二氟磷酸锂、二氟草酸硼酸锂、二草酸硼酸锂、二氟二草酸磷酸锂及四氟草酸磷酸锂中的至少一种。
可选地，溶剂可选自碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸二乙酯、碳 酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的至少一种。
可选地，电解液还包括添加剂。例如添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
[隔离膜]
在一些实施方式中，二次电池中还包括隔离膜。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
可选地，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
可选地，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。卷绕式电极组件可以是圆柱形、方形或其他任意的形状。例如，图3是作为一个示例的圆柱形的电极组件3的示意图。如图3所示，正极极片的极耳区域21经过卷绕后形成了电极组件3的正极极耳31，负极极片的极耳区域21经过卷绕后形成了电极组件3的负极极耳32，正极极片和负极极片的削薄区域22a和非削薄区域22b经过卷绕后形成了电极组件的中间部分33。
本申请实施例还提供一种电池单体，该电池单体包括本申请任一实施例中的极片。
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。
本申请实施例还提供一种电池，该电池包括至少一个本申请实施例中的电池单 体。
在一些实施方式中，首先将多个电池单体(cell)先整合为电池模组(module)，然后将电池模组安装于电池的箱体中，形成电池包(pack)。在另一些生产加工技术中，也可直接将多个电池单体安装设置于箱体中形成电池包，去除了电池模组这个中间状态，从而可降低电池包的质量并提高电池的能量密度。第二种生产加工技术也可以称之为电池单体至电池包(cell to pack)的封装技术，该电池包在本申请中简称为电池。
在另一些实施方式中，也可以将多个电池单体直接整合成电池模组，直接使用电池模组为用电装置供电，该电池模组在本申请中也简称为电池。
另外，本申请还提供一种用电装置，该用电装置包括本申请任一实施例中电池单体或电池中的至少一种。电池单体、电池可以用作该用电装置的电源，也可以用作用电装置的能量存储单元。用电装置可以包括车辆、手机、便携式设备、笔记本电脑、轮船、航天器、电动玩具和电动工具等等。车辆可以是燃油汽车、燃气汽车或新能源汽车，新能源汽车可以是纯电动汽车、混合动力汽车或增程式汽车等；航天器包括飞机、火箭、航天飞机和宇宙飞船等等；电动玩具包括固定式或移动式的电动玩具，例如，游戏机、电动汽车玩具、电动轮船玩具和电动飞机玩具等等；电动工具包括金属切削电动工具、研磨电动工具、装配电动工具和铁道用电动工具，例如，电钻、电动砂轮机、电动扳手、电动螺丝刀、电锤、冲击电钻、混凝土振动器和电刨等，但本申请不限于此。
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的高功率和高能量密度的需求，可以采用电池模块或电池作为电源。
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。
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
实施例1
(1)正极极片的制备
将纳米磷酸铁锂作为第一活性材料31，与导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按质量比97:0.8:2.2溶解于溶剂N-甲基吡咯烷酮(NMP)中，充分搅拌混合均匀后得到正极浆料1。将磷酸铁锂作为第二活性材料32，与导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按质量比97:0.8:2.2溶解于溶剂N-甲基吡咯烷酮(NMP)中，充分搅拌混合均匀后得到正极浆料2。随后将正极浆料1均匀涂覆于正极集流体铝箔的削薄区域22a上，将正极浆料2均匀涂覆于正极集流体铝箔的非削薄区域22b上，再经过烘干、冷压、分切得到正极极片。其中正极极片中磷酸铁锂的BET为8m 2/g，纳米磷酸铁锂的BET为16m 2/g，削薄区域22a在第一方向上的长度w＝10mm。
(2)负极极片的制备
将人造石墨、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC)按照质量比96.5:0.7:1.8:1溶解于溶剂去离子水中，混合均匀后得到负极浆料。随后将负极浆料均匀涂覆于负极集流体铜箔的削薄区域22a和非削薄区域22b上，再经过烘干、冷压、分切得到负极极片。其中负极极片中人造石墨的BET为2.0m 2/g。
(3)电池单体的组装
将正极极片、隔离膜、负极极片按顺序叠放，使得隔离膜处于正极极片和负极极片之间并能够隔离正极极片与负极极片；然后将上述叠放好的部件卷绕得到电极组件；将电极组件设置于壳体中，干燥后注入质量分数为11％的LiPF 6电解液；经过化成、静置等工艺后得到电池单体。
实施例2-3
与实施例1的电池单体相比，实施例2仅改变了纳米磷酸铁锂的BET、D V50，其中实施例2中纳米磷酸铁锂的BET为18m 2/g，其D V50为600nm。具体的参数详见表1。
实施例4
与实施例1的电池单体相比，实施例3仅改变了削薄区域22a在第一方向上的长度w，w＝15mm，具体的参数详见表1。
实施例5
与实施例1的电池单体相比，实施例5使用纳米磷酸铁锂和碳的复合材料作为第一活性材料31，使用磷酸铁锂和碳的复合材料作为第二活性材料32，其中，第一活 性材料的含碳量为1.18％，第二活性材料的含碳量为2.01％。
实施例6
与实施例5的电池单体相比，实施例6仅改变了纳米磷酸铁锂和碳的复合材料的含碳量，具体的参数详见表1。
实施例7
(1)正极极片的制备
将BET为1.15m 2/g的Na 0.85Ni 0.25Mn 0.75O 2作为第一活性材料31，与导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按质量比90:5:5溶解于溶剂N-甲基吡咯烷酮(NMP)中，充分搅拌混合均匀后得到正极浆料1。将BET为0.8m 2/g的Na 0.85Ni 0.25Mn 0.75O 2作为第二活性材料32，与导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按质量比90:5:5溶解于溶剂N-甲基吡咯烷酮(NMP)中，充分搅拌混合均匀后得到正极浆料2。随后将正极浆料1均匀涂覆于正极集流体铝箔的削薄区域22a上，将正极浆料2均匀涂覆于正极集流体铝箔的非削薄区域22b上，再经过烘干、冷压、分切得到正极极片。
(2)负极极片的制备
将负极活性材料硬碳、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC)按照质量比90:4:4:2溶解于溶剂去离子水中，混合均匀后得到负极浆料。将负极浆料一次或多次均匀涂覆在负极集流体铜箔的削薄区域22a和非削薄区域22b上，再经过烘干、冷压、分切得到负极极片。硬碳的BET为4.5m 2/g。
(3)电池单体的制备
实施例7的电池单体采用与实施例1相同的制备方法，区别仅在于使用质量分数为11％的NaPF 6电解液，在此不再赘述。
实施例8
(1)正极极片的制备
将磷酸铁锂、导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按质量比97:0.8:2.2溶解于溶剂N-甲基吡咯烷酮(NMP)中，充分搅拌混合均匀后得到正极浆料。随后将正极浆料均匀涂覆于正极集流体铝箔的削薄区域22a和非削薄区域22b上，再经过烘干、冷压、分切得到正极极片。其中正极极片中磷酸铁锂的BET为8m 2/g。
(2)负极极片的制备
将天然石墨作为第一活性材料31、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC)按照质量比96.5:0.7:1.8:1溶解于溶剂去离子水中，混合均匀后得到负极浆料1。将人造石墨作为第二活性材料32、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC)按照质量比96.5:0.7:1.8:1溶解于溶剂去离子水中，混合均匀后得到负极浆料2。随后将负极浆料1均匀涂覆于负极集流体铜箔的削薄区域22a，将负极浆料2均匀涂覆于负极集流体铜箔的非削薄区域22b，再经过烘干、冷压、分切得到负极极片。其中负极极片中人造石墨的BET为3m 2/g，天然石墨的BET为4m 2/g。削薄区域22a在第一方向上的长度w＝10mm。
(3)电池单体的组装
实施例8的电池单体采用与实施例1相同的制备方法，在此不再赘述。
对比例1
(1)正极极片的制备
将磷酸铁锂、导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按质量比97:0.8:2.2溶解于溶剂N-甲基吡咯烷酮(NMP)中，充分搅拌混合均匀后得到正极浆料。随后将正极浆料均匀涂覆于正极集流体铝箔的削薄区域22a和削薄区域22b上，再经过烘干、冷压、分切得到正极极片。
(2)负极极片的制备
将人造石墨、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC)按照质量比96.5:0.7:1.8:1溶解于溶剂去离子水中，混合均匀后得到负极浆料。随后将负极浆料均匀涂覆于负极集流体铜箔的削薄区域22a和削薄区域22b上，再经过烘干、冷压、分切得到负极极片。
(3)电池单体的制备
对比例1采用与实施例1相同的制备方法，在此不再赘述。
对比例2
(1)正极极片的制备
将正极活性材料Na 0.85Ni 0.25Mn 0.75O 2、导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按质量比90:5:5溶解于溶剂N-甲基吡咯烷酮(NMP)中，充分搅拌混合均匀后得到正极浆料。随后将负正极浆料均匀涂覆于正极集流体铝箔的削薄区域22a和削薄区域22b上，再经过烘干、冷压、分切得到正极极片。
(2)负极极片的制备
将负极活性材料硬碳、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC)按照质量比90:4:4:2溶解于溶剂去离子水中，混合均匀后得到负极浆料。随后将负极浆料均匀涂覆于负极集流体铜箔的削薄区域22a和削薄区域22b上，再经过烘干、冷压、分切得到负极极片。
(3)电池单体的制备
对比例2与实施例7采用相同的方法和步骤制备电池单体，在此不再赘述。
不同实施例的产品参数详见表1。
表1：对比例及不同实施例的产品参数
Figure PCTCN2022123380-appb-000001
Figure PCTCN2022123380-appb-000002
表1中，活性材料1指的是第一活性材料31，BET-1指的是第一活性材料31的比表面积；活性材料2指的是第二活性材料32，BET-2指的是第二活性材料32的比表面积；Dv50-1指的是第一活性材料31的粒径分布，Dv50-2指的是第二活性材料32的粒径分布；C-1指的是第一活性材料31的含碳量，C-2指的是第二活性材料32的含碳量，w指的是削薄区域22a在第一方向上的长度。
上述实施例1-5以及对比例1的电池性能测试结果详见表2。
表2：对比例及不同实施例循环寿命测试结果
Figure PCTCN2022123380-appb-000003
由实施例1-6、实施例8和对比例1可以看出，不论是在电池的正极削薄区设置纳米磷酸铁锂，或是在电池的负极削薄区设置天然石墨，通过在削薄区设置比表面 积大于非削薄区的活性材料，能够有效提高锂离子电池的循环性能和使用寿命。通过实施例7和对比例2可以看出，该在削薄区设置比表面积相对较大的活性材料同样能够提高钠离子电池的循环性能和循环寿命。
接下来，对上述电池的参数测试过程进行简单介绍。
1.BET测试
测试方法参考标准GB/T19587-2004《气体吸附BET法测定固态物质比表面积》。
取待测样品8-15g装到样品管中，记录待测样品的初始质量。将称重的待测样品装入设备NOVA2000e中。然后开始脱气，并将待测样品加热至200℃后，保持2h。之后记录脱气后待测样品的质量。然后将脱气后的待测样品重新装入设备中，倒入液氮进行BET测试。设定氮气压力0.08MPa-0.12MPa，加热温度为40℃-350℃。测试结束后，从测试结果中读取比表面积。
2.电池性能测试
25℃下，将各实施例和对比例制备得到的二次电池以1C倍率恒流充电至充电截止电压3.65V，之后恒压充电至电流≤0.05C，静置5min，再以1C倍率恒流放电至放电截止电压2.5V，静置5min，此为一个充放电循环。按照此方法对电池进行循环充放电测试，直至电池容量衰减至80％。此时的循环圈数即为电池的循环寿命。测试结果如表2所示。其中，实施例1和对比例1的电池循环性能测试结果分别如图4和图5所示。由图4和图5可以看出，实施例1的容量降低速度明显小于对比例1，将根据曲线的趋势(如图中箭头所示)，对比例1的循环寿命将明显长于对比例1的循环寿命。
3.DCR测试
取电池，进行充放电测试。先将电池在25℃条件下进行满充，满充后搁置30min。搁置后以1C放电倍率放电30min，调节至50％SOC，搁置10min。调节温箱温度为-20℃-10℃，搁置120min，测得放电初始电压。然后以3C放电速率放电10s，并记录放电过程中的最低电压，然后搁置10min，用3C放电初始电压与3C放电过程中最低电压差值除以电流值(放电倍率为3C，电流为78A)即得DCR。
其中，对比例1和实施例1的DCR测试结果分别如图6和图7所示。由图6和图7可知：实施例1与对比例1相比在-25℃条件下，DCR降低了6.87毫欧；在-10℃条件下，DCR降低了3.46毫欧，25℃DCR降低了1.42毫欧，内阻明显降低，动力学 明显提升。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (17)

  1. 一种极片，其中，所述极片包括：
    集流体，包括极耳区域、削薄区域和非削薄区域，所述削薄区域位于所述非削薄区域与所述极耳区域之间；
    膜层，设置于所述削薄区域和所述非削薄区域上，所述膜层包括设置于所述削薄区域上的第一活性材料和设置于所述非削薄区域上的第二活性材料，所述削薄区域的所述膜层的厚度小于所述非削薄区域的所述膜层的厚度，所述第一活性材料的比表面积大于所述第二活性材料的比表面积。
  2. 根据权利要求1所述的极片，其中，所述第一活性材料的D v50大于所述第二活性材料的D v50。
  3. 根据权利要求1或2所述的极片，其中，所述膜层在所述削薄区域的压实密度小于所述膜层在所述非削薄区域的压实密度。
  4. 根据权利要求1-3中任一项所述的极片，其中，所述膜层在所述削薄区域的厚度为40μm-300μm。
  5. 根据权利要求1-4中任一项所述的极片，其中，所述削薄区域在第一方向上的长度满足：0mm＜w≤15mm，所述第一方向为所述极片的宽度方向。
  6. 根据权利要求1-5中任一项所述的极片，其中，所述极片为正极极片，所述第一活性材选自纳米磷酸铁锂、纳米磷酸锰锂、纳米磷酸铁锰锂、纳米磷酸铁锂与碳的复合材料、纳米磷酸锰锂与碳的复合材料、纳米磷酸铁锰锂与碳的复合材料中的至少一种；和/或，
    所述第二活性材料选自磷酸铁锂、磷酸锰锂、磷酸铁锰锂、磷酸铁锂与碳的复合材料、磷酸锰锂与碳的复合材料、磷酸锰铁锂与碳的复合材料中的至少一种。
  7. 根据权利要求1-6中任一项所述的极片，其中，所述第一活性材料的含碳量大于所述第二活性材料的含碳量。
  8. 根据权利要求7所述的极片，其中，所述第一活性材料的含碳量大于或等于1.5wt％，可选地为1.5wt％-2.7wt％，优选为1.6wt％-2.2wt％，进一步优选为1.8wt％-2.0wt％；和/或，
    所述第二活性材料的含碳量小于1.5wt％。
  9. 根据权利要求1-8中任一项所述的极片，其中，所述第一活性材料的D v50满足：D v50≤300nm，优选地，100nm≤D v50≤200nm，进一步优选地，100nm≤D v50≤150nm；和/或，
    所述第二活性材料的D v50满足：D v50≥800nm，优选地，800nm≤D v50≤1200nm，进一步优选地，1000nm≤D v50≤1100nm。
  10. 根据权利要求1-9中任一项所述的极片，其中，所述第一活性材料的比表面积满足：BET≥15m 2/g，可选地，15m 2/g≤BET≤20m 2/g，优选地，18m 2/g≤BET≤20m 2/g；和/或，
    所述第二活性材料的比表面积满足：BET≤10m 2/g，可选地，8m 2/g≤BET≤10m 2/g。
  11. 根据权利要求1-5中任一项所述的极片，其中，所述极片为负极极片，所述第一活性材料选自天然石墨、硬碳、纳米硅基材料、纳米锡基材料、纳米钛酸锂中的至少一种；和/或，
    所述第二活性材料选自人造石墨、软碳、硅基材料、锡基材料、钛酸锂中的至少一种。
  12. 根据权利要求11所述的极片，其中，所述第一活性材料的含碳量大于或等于1.5wt％，可选地为1.5wt％-2.0wt％；和/或，
    所述第二活性材料的含碳量大于或等于0.9wt％，可选地为0.9wt％-1.3wt％。
  13. 根据权利要求1-12中任一项所述的极片，其中，所述第一活性材料的D v50满足：800nm≤D v50≤1400nm；和/或，
    所述第二活性材料的D v50满足：100nm≤D v50≤400nm。
  14. 根据权利要求1-13中任一项所述的极片，其中，所述第一活性材料的比表面积满足：BET≥15m 2/g，可选地，15m 2/g≤BET≤20m 2/g；和/或，
    所述第二活性材料的比表面积满足：BET≥7m 2/g，可选地，7m 2/g≤BET≤12m 2/g。
  15. 一种电池单体，其中，所述电池单体包括如权利要求1-14中任一项所述的极片。
  16. 一种电池，其中，所述电池包括至少一个如权利要求15所述的电池单体。
  17. 一种用电装置，其中，所述用电装置包括如权利要求15所述的电池单体或如权利要求16所述的电池中的至少一种，所述电池单体和/或所述电池用于为所述用电装置供电。
PCT/CN2022/123380 2022-09-30 2022-09-30 一种极片、电池单体、电池及用电装置 Ceased WO2024065726A1 (zh)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2017059297A (ja) * 2015-09-14 2017-03-23 日立マクセル株式会社 非水二次電池
CN109980177A (zh) * 2019-03-29 2019-07-05 宁德新能源科技有限公司 电极极片和包含所述电极极片的电化学装置
CN111816838A (zh) * 2020-07-22 2020-10-23 珠海冠宇电池股份有限公司 锂离子电池正极片及其制备方法以及锂离子电池
CN114665064A (zh) * 2022-05-26 2022-06-24 宁德新能源科技有限公司 电化学装置

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP7408297B2 (ja) * 2019-05-29 2024-01-05 株式会社Ａｅｓｃジャパン リチウムイオン二次電池素子、リチウムイオン二次電池およびリチウムイオン二次電池素子を製造する方法
CN112420984A (zh) * 2020-11-26 2021-02-26 珠海冠宇电池股份有限公司 一种负极片和锂离子电池
CN114551980B (zh) * 2022-02-28 2024-08-20 宁德新能源科技有限公司 电化学装置和电子装置

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2017059297A (ja) * 2015-09-14 2017-03-23 日立マクセル株式会社 非水二次電池
CN109980177A (zh) * 2019-03-29 2019-07-05 宁德新能源科技有限公司 电极极片和包含所述电极极片的电化学装置
CN111816838A (zh) * 2020-07-22 2020-10-23 珠海冠宇电池股份有限公司 锂离子电池正极片及其制备方法以及锂离子电池
CN114665064A (zh) * 2022-05-26 2022-06-24 宁德新能源科技有限公司 电化学装置

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of EP4550438A4 *

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