WO2023060517A1 - 一种极片、电极组件、电池单体、电池以及用电设备 - Google Patents

一种极片、电极组件、电池单体、电池以及用电设备 Download PDF

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WO2023060517A1
WO2023060517A1 PCT/CN2021/123916 CN2021123916W WO2023060517A1 WO 2023060517 A1 WO2023060517 A1 WO 2023060517A1 CN 2021123916 W CN2021123916 W CN 2021123916W WO 2023060517 A1 WO2023060517 A1 WO 2023060517A1
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Prior art keywords
active material
pole piece
material layer
material region
width direction
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PCT/CN2021/123916
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English (en)
French (fr)
Inventor
车欢
陈威
李世松
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宁德时代新能源科技股份有限公司
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Priority to PCT/CN2021/123916 priority Critical patent/WO2023060517A1/zh
Priority to CN202180093108.8A priority patent/CN116868402A/zh
Priority to EP21929449.3A priority patent/EP4195347A1/en
Priority to US17/939,961 priority patent/US20230123434A1/en
Publication of WO2023060517A1 publication Critical patent/WO2023060517A1/zh

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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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/043—Processes of manufacture in general involving compressing or compaction
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—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
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—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
    • H01M4/364—Composites as mixtures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • 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, in particular, to a pole piece, an electrode assembly, a battery cell, a battery and an electrical device.
  • Batteries are widely used in electrical equipment, such as mobile phones, laptop computers, battery cars, electric cars, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes and electric tools, etc.
  • Insufficient wetting efficiency of the pole piece in the width direction (that is, the electrode assembly in the height direction) is a common phenomenon, which will lead to the loss of production capacity of the electrode assembly during the manufacturing process, and also cause the electrolyte supply in the middle of the electrode assembly during the cycle. Insufficient problems affect the cycle life of the electrode assembly.
  • Embodiments of the present application provide a pole piece, an electrode assembly, a battery cell, a battery, and an electrical device, which can effectively improve the wetting efficiency of the pole piece in the width direction.
  • the present application provides a pole piece including a current collector; and an active material layer located on at least one side surface of the current collector, the active material layer having a first active material area and a second active material area;
  • the cross-sectional area of the second active material region is S 2
  • the cross-sectional area of the active material layer is S, and S 2 ⁇ S
  • the surface of the current collector where the active material layer is located is the preset Assuming a surface, the preset section is parallel to the preset surface and passes through the second active material zone;
  • the porosity of the first active material zone is P 1
  • the porosity of the second active material zone is P 2 , P 1 ⁇ P 2 ;
  • the pore diameters of the first active material region and the second active material region are both ⁇ 1 ⁇ m.
  • the porosity of the second active material region is greater than that of the first active material region, and the wetting efficiency of the active material layer can be improved by configuring the second active material region with relatively large porosity.
  • the second active material region is configured to be locally distributed in the transverse section, that is, in the extreme In the width direction of the sheet, there are regions with relatively large porosity and regions with relatively small porosity, so the wetting efficiency of the pole sheet in the width direction can be effectively improved.
  • the difference between P 2 and P 1 is 3%-20%, optionally 7%-15%, and further optionally 10%-15%.
  • the second active material region and the first active material region have an appropriate porosity difference, which effectively improves the infiltration efficiency and at the same time reduces the energy density loss of the pole piece as much as possible.
  • P1 is 15% to 35%, optionally 15% to 25%, further optionally 20% to 25%; and/or, P2 is 20% to 50%, which can be Optionally, it is 20%-40%, further optionally, it is 25%-40%.
  • the second active material region and the first active material region select a specific porosity to ensure the infiltration efficiency and at the same time control the pole piece to have an appropriate energy density.
  • the compacted density of the first active material region is C 1
  • the compacted density of the second active material region is C 2
  • any of the following conditions (a) to (c) are satisfied:
  • the active material in the first active material area and the second active material area is lithium iron phosphate, and the ratio of C1 to C2 is 1.02-1.7; optionally, C1 is 2.3g /cm 3 to 2.7g/cm 3 , C 2 is 1.6g/cm 3 to 2.2g/cm 3 ;
  • the active materials in the first active material area and the second active material area are both ternary
  • the ratio of C 1 to C 2 is 1.02 to 1.5; optionally, C 1 is 3.1g/cm 3 to 3.7g/cm 3 , and C 2 is 2.5g/cm 3 to 3g/cm 3 ;
  • the active materials in the first active material zone and the second active material zone are both graphite, and the ratio of C 1 to
  • the specific compaction density corresponding to different active materials is selected respectively to ensure that the second active material area and the first active material area have appropriate porosity and porosity difference, effectively improve the infiltration efficiency, and control the pole piece have a suitable energy density.
  • At least one of the following conditions (d) to (e) is satisfied: (d) S ⁇ 2.5% ⁇ S 2 ⁇ S ⁇ 30%; (e) the thickness of the active material layer is h, The thickness of the second active material region is h 2 , h ⁇ 30% ⁇ h 2 ⁇ h ⁇ 100%.
  • the second active material region satisfies a specific area ratio and/or thickness ratio, so that the second active material region has a suitable distribution ratio, ensures the infiltration efficiency, and controls the pole piece to have a suitable energy density .
  • the size of the active material layer is M, which satisfies the following condition (f): (f) in the width direction of the pole piece, the second The minimum distance between the active material region and the center of the active material layer is d 1 , where d 1 ⁇ M ⁇ 35%.
  • the minimum distance between the second active material region and the center of the active material layer is less than or equal to a certain standard, so that the second active material region has a suitable distribution position and effectively improves the wetting efficiency.
  • the size of the active material layer is M, which satisfies the following condition (g): (g) in the width direction of the pole piece, the second The minimum distance between the active material region and the edge of the active material layer is d 2 , where d 2 ⁇ M ⁇ 20%.
  • the minimum distance between the second active material region and the edge of the active material layer is less than or equal to a certain standard, so that the second active material region has a suitable distribution position and effectively improves the wetting efficiency.
  • the size of the active material layer is M; there are multiple second active material regions, and there are multiple second active material regions along the pole piece.
  • the length direction of the sheet is distributed at intervals; at least one of the following conditions (h) to (i) is satisfied: (h) in the width direction of the pole piece, the center of the second active material region and the active material layer The minimum distance is d 1 , d 1 ⁇ M ⁇ 10%; (i) in the width direction of the pole piece, the distance between the two ends of each second active material region is d 3 , d 3 ⁇ M ⁇ 30%.
  • the minimum distance between the second active material region and the center of the active material layer is controlled to be less than or equal to a specific standard, and/or the distance between the two ends of the second active material region is controlled to be greater than or equal to a specific standard. Standard, so that the plurality of second active material regions distributed at intervals along the length direction of the pole piece have a suitable distribution position, effectively improving the wetting efficiency.
  • the size of the active material layer is M; there are multiple second active material regions, and there are multiple second active material regions along the pole piece.
  • the sheets are distributed at intervals in the width direction; in the width direction of the pole sheet, the distance between two adjacent second active material regions is d 4 , where d 4 ⁇ M ⁇ 20%.
  • the distance between two adjacent second active material regions is controlled to be less than or equal to a certain standard, so that the plurality of second active material regions distributed along the width direction of the pole piece have Appropriate distribution position can effectively improve the infiltration efficiency.
  • the thickness of the active material layer is h
  • the thickness of the second active material region is h 2 , h ⁇ 30% ⁇ h 2 ⁇ h ⁇ 60%
  • the second active material region to The distance from the surface of the active material layer is d 5
  • the distance from the active material layer to the preset surface is d 6
  • d 5 ⁇ d 6 the second active material region occupies a partial area of the active material layer in the thickness direction, effectively improving the wetting efficiency and controlling the pole piece to have a suitable energy density.
  • controlling the arrangement of the second active material region closer to the surface of the active material layer can better play the role of the second active material in improving the wetting efficiency.
  • the present application provides an electrode assembly, including a positive pole piece, a separator, and a negative pole piece, at least one of the positive pole piece and the negative pole piece is the pole piece in the above embodiment.
  • the electrode assembly has a winding structure, the width direction of the pole piece is the same as the axial direction of the electrode assembly, and the length direction of the pole piece is the same as the winding direction of the electrode assembly;
  • the diameter of the electrode assembly is d, and in the winding direction of the electrode assembly, at least a part of the second active material region is located in each area with an arc length of ⁇ d/4.
  • at least a part of the second active material region exists in each region with an arc length of ⁇ d/4, so that the distribution pitch of the second active material region in the winding direction of the electrode assembly is less than or equal to a specific standard, Ensure better wetting effect of the electrode assembly.
  • the present application provides a battery cell, including a casing and the electrode assembly in the above embodiment; the electrode assembly is accommodated in the casing.
  • the present application provides a battery, including a box body and the battery cells in the above embodiments; the battery cells are accommodated in the box body.
  • the present application provides an electric device, including the battery in the above embodiment.
  • Fig. 1 is a schematic structural diagram of a vehicle provided by some embodiments of the present application.
  • Figure 2 is an exploded view of a battery provided in some embodiments of the present application.
  • Fig. 3 is the explosion of the battery cell shown in Fig. 2;
  • Fig. 4 is a schematic structural view of an electrode assembly partially deployed along the winding direction provided by some embodiments of the present application;
  • Fig. 5 is a schematic diagram of the first structure of the pole piece in the longitudinal section provided by some embodiments of the present application.
  • Fig. 6 is a schematic diagram of the first structure of the pole piece in the transverse section provided by some embodiments of the present application.
  • Fig. 7 is a second structural schematic diagram of a pole piece provided in some embodiments of the present application in a transverse section;
  • Fig. 8 is a schematic diagram of the third structure of the pole piece in the transverse section provided by some embodiments of the present application.
  • Fig. 9 is a schematic diagram of the fourth structure of the pole piece in the transverse section provided by some embodiments of the present application.
  • Fig. 10 is a schematic diagram of the fifth structure of the pole piece in the transverse section provided by some embodiments of the present application.
  • Fig. 11 is a schematic diagram of the second structure of the pole piece in the longitudinal section provided by some embodiments of the present application.
  • Fig. 12 is a schematic diagram of the third structure of the pole piece in the longitudinal section provided by some embodiments of the present application.
  • Fig. 13 is a schematic diagram of the fourth structure of the pole piece in the longitudinal section provided by some embodiments of the present application.
  • Fig. 14 is the electrode assembly comprising the pole piece shown in Fig. 6;
  • Fig. 15 is the electrode assembly comprising the pole piece shown in Fig. 8;
  • Fig. 16 is the electrode assembly comprising the pole piece shown in Fig. 9;
  • FIG. 17 is an electrode assembly including the pole piece shown in FIG. 10 .
  • Box body 10 first part 11, second part 12, accommodation space 13;
  • a battery cell 20 a casing 21, an electrode assembly 22, an electrode terminal 23, and a pressure relief structure 24;
  • Housing 211 cover body 212, sealed space 213, positive pole piece 221, negative pole piece 222, separator 223;
  • Winding direction A axial direction B, width direction C, length direction D.
  • the battery cells may include lithium-ion secondary batteries, lithium-ion primary batteries, lithium-sulfur batteries, sodium-lithium-ion batteries, sodium-ion batteries, or magnesium-ion batteries, which are not limited in the embodiments of the present application.
  • the battery cell can be in the form of a cylinder, a flat body, a cuboid or other shapes, which is not limited in this embodiment of the present application.
  • Battery cells are generally divided into three types according to packaging methods: cylindrical battery cells, square battery cells and pouch battery cells, which are not limited in this embodiment of the present application.
  • the battery cell includes an electrode assembly and an electrolyte, and the electrode assembly is composed of a positive electrode sheet, a negative electrode sheet, and a separator.
  • a battery cell works primarily by moving metal ions between the positive and negative plates.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer, the positive electrode active material layer is coated on the surface of the positive electrode current collector, and the positive electrode current collector that is not coated with the positive electrode active material layer protrudes from the positive electrode collector that has been coated with the positive electrode active material layer , the positive electrode current collector not coated with the positive electrode active material layer is used as the positive electrode tab.
  • the material of the positive electrode current collector can be aluminum, and the positive electrode active material can be lithium cobaltate, lithium iron phosphate, ternary lithium or lithium manganate.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer is coated on the surface of the negative electrode current collector, and the negative electrode current collector that is not coated with the negative electrode active material layer protrudes from the negative electrode collector that has been coated with the negative electrode active material layer , the negative electrode current collector not coated with the negative electrode active material layer is used as the negative electrode tab.
  • the material of the negative electrode current collector may be copper, and the negative electrode active material may be carbon or silicon.
  • the number of positive pole tabs is multiple and stacked together, and the number of negative pole tabs is multiple and stacked together.
  • the material of the isolation film may be PP (polypropylene, polypropylene) or PE (polyethylene, polyethylene).
  • the electrode assembly may be a wound structure or a laminated structure, which is not limited in the embodiment of the present application.
  • a battery refers to a single physical module that includes one or more battery cells to provide higher voltage and capacity.
  • the battery mentioned in this application may include a battery module or a battery pack, and the like.
  • Batteries generally include a case for enclosing one or more battery cells. The box can prevent liquid or other foreign objects from affecting the charging or discharging of the battery cells.
  • the porosity of the active material layer of the electrode used decreases after rolling, resulting in poor ion conduction and a decrease in wettability, making it difficult for the electrolyte in the battery cell to flow from the pole piece in the width direction.
  • the two ends on the top reach the middle area of the pole piece in the width direction, which leads to insufficient wetting efficiency of the pole piece in the width direction (in the battery, that is, the electrode assembly in the height direction).
  • the inventors have noticed that the above-mentioned problems can be improved by not coating the active material in the middle of the width direction of the surface of the current collector and making holes.
  • the capacity of the area not coated with the active material is greatly lost, resulting in a significant drop in the energy density of the pole piece; the strength of the area not coated with the active material is greatly reduced, which destroys the stress structure of the pole piece and the electrode assembly, making the electrode assembly
  • the overall structure is prone to torsion, and may even be twisted to puncture the isolation membrane; drilling holes in areas not coated with active materials will increase the complexity of the process, and there is a risk of current collector fracture.
  • the inventors also found that the surface of the current collector is coated with a complete active material layer, and the porosity of the active material layer is locally increased in the transverse section through the local pore regulation strategy, that is, in the width direction of the pole piece. , having both a region with a relatively large porosity and a region with a relatively small porosity, so that the wetting efficiency of the pole piece in the width direction can be effectively improved. Moreover, the above local pore regulation strategy can effectively overcome or improve the problems caused by not coating active materials and punching holes.
  • the embodiment of the present application provides a technical solution, in which a first active material region and a second active material region are provided in the active material layer, and the second active material region is controlled to have a larger porosity than the first active material region, And the second active material area is configured to be locally distributed in the transverse section.
  • the above technical solution can reduce the loss of capacity, thereby reducing the decline of energy density; the integrity of the active material layer is preserved, and the stress structure of the pole piece and the electrode assembly is not damaged; the manufacturing process is simple without increasing the cost of the pole piece , to avoid the breakage of the current collector caused by punching and ensure safety, and it has good adaptability to electrode assemblies of various structures; it effectively improves the wetting efficiency of the pole piece in the width direction, can increase the production capacity of the electrode assembly, and can Improve the problem of insufficient electrolyte supply in the middle of the electrode assembly during the cycle, thereby improving the cycle life of the electrode assembly.
  • electric equipment can be in various forms, for example, mobile phones, portable devices, notebook computers, battery cars, electric vehicles, ships, spacecraft, electric toys and electric tools, etc.
  • spacecraft include airplanes, rockets, Space shuttles and spaceships, etc.
  • Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric boat toys and electric airplane toys, etc.
  • Electric tools include metal cutting electric tools, grinding electric tools , Assembling electric tools and electric tools for railways, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators and electric planers.
  • FIG. 1 is a schematic structural diagram of a vehicle 1000 provided by some embodiments of the present application.
  • a battery 100 is disposed inside the vehicle 1000 .
  • the battery 100 can be used for power supply of the vehicle 1000 , for example, the battery 100 can be used as an operating power source of the vehicle 1000 .
  • the vehicle 1000 may further include a controller 200 and a motor 300 , the controller 200 is used to control the battery 100 to supply power to the motor 300 , for example, for starting, navigating and running the vehicle 1000 .
  • the battery 100 can not only be used as an operating power source for the vehicle 1000 , but can also be used as a driving power source for the vehicle 1000 to provide driving power for the vehicle 1000 instead of or partially replacing fuel oil or natural gas.
  • FIG. 2 is an exploded view of a battery 100 provided by some embodiments of the present application.
  • the battery 100 may include a box body 10 and a battery cell 20 , and the battery cell 20 is accommodated in the box body 10 .
  • the box body 10 is used to accommodate the battery cells 20, and the box body 10 may have various structures.
  • the box body 10 may include a first part 11 and a second part 12, the first part 11 and the second part 12 cover each other, the first part 11 and the second part 12 jointly define a The accommodation space 13.
  • the second part 12 can be a hollow structure with an open end, the first part 11 is a plate-like structure, and the first part 11 covers the opening side of the second part 12 to form a box body 10 with an accommodation space 13; the first part 11 and The second part 12 can also be a hollow structure with one side open, and the open side of the first part 11 covers the open side of the second part 12 to form the box body 10 with the receiving space 13 .
  • the first part 11 and the second part 12 can be in various shapes, such as cylinder, cuboid and so on.
  • a sealing member (not shown in the figure), such as a sealant, a sealing ring, etc., may also be provided between the first part 11 and the second part 12 .
  • the battery 100 there may be one or a plurality of battery cells 20 . If there are multiple battery cells 20 , the multiple battery cells 20 may be connected in series, in parallel or in parallel. The mixed connection means that the multiple battery cells 20 are both in series and in parallel.
  • the battery cell 20 may be in the form of a cylinder, a cuboid or other shapes. In FIG. 2 , for example, the battery cell 20 is in the shape of a cylinder.
  • the plurality of battery cells 20 can be directly connected in series, in parallel or mixed together, and then the whole composed of the plurality of battery cells 20 is housed in the case 10 . It is also possible that a plurality of battery cells 20 are connected in series or in parallel or in series to form a battery module, and then the battery modules are connected in series or in parallel or in series to form a whole and accommodated in the case 10 .
  • a plurality of battery cells 20 can be electrically connected through a confluence component (not shown in the figure), so as to realize parallel connection, series connection or mixed connection of the plurality of battery cells 20 .
  • FIG. 3 is an exploded view of the battery cell 20 shown in FIG. 2 .
  • the battery cell 20 may include a case 21 and an electrode assembly 22 accommodated in the case 21 .
  • housing 21 may also be used to contain electrolyte, such as electrolytic solution.
  • the shell 21 can be in various structural forms.
  • the housing 21 may include a housing 211 and a cover 212, the housing 211 is a hollow structure with one side open, the cover 212 covers the opening of the housing 211 and forms a sealed connection, so as to form a The sealed space 213 accommodates the electrode assembly 22 and the electrolyte.
  • the electrode assembly 22 can be put into the casing 211 first, and electrolyte is filled into the casing 211 , and then the cover 212 is closed on the opening of the casing 211 .
  • the housing 211 can be in various shapes, such as a cylinder, a cuboid, and the like.
  • the shape of the casing 211 may be determined according to the specific shape of the electrode assembly 22 .
  • the cover body 212 can also be of various structures, for example, the cover body 212 is a plate-shaped structure, a hollow structure with one end open, and the like. Exemplarily, in FIG.
  • the casing 211 is a cylindrical structure
  • the cover 212 is a plate-shaped structure
  • the electrode assembly 22 is a cylindrical structure
  • the electrode assembly 22 is accommodated in the casing 211
  • the cover 212 is covered on the casing.
  • the battery cell 20 may further include an electrode terminal 23 installed on the cover 212 .
  • the electrode terminal 23 is electrically connected with the electrode assembly 22 to output the electric energy generated by the battery cell 20 .
  • the electrode terminal 23 and the electrode assembly 22 can be electrically connected through an adapter sheet (not shown).
  • the battery cell 20 may further include a pressure relief structure 24 for releasing the pressure inside the battery cell 20 when the internal pressure or temperature of the battery cell 20 reaches a predetermined value.
  • the pressure relief structure 24 may be a component such as an explosion-proof valve, a burst disk, an air valve, a pressure relief valve, or a safety valve.
  • the electrode assembly 22 with a winding structure is taken as an example for description.
  • the electrode assembly 22 includes a positive pole piece 221 , a separator 223 and a negative pole piece 222 .
  • the positive electrode sheet 221 , the separator 223 and the negative electrode sheet 222 are sequentially stacked in the thickness direction of the separator 223 and wound along the winding direction A to form a winding structure.
  • the winding direction A is the direction in which the positive pole piece 221 , the separator 223 and the negative pole piece 222 are wound along the circumferential direction from the inside to the outside, which is the direction A in FIG. 4 .
  • the height direction of the electrode assembly 22 is the axial direction B of the winding structure, which is the B direction in FIG. 4 .
  • the winding structure can be in the form of a cylinder or a flat body. Exemplarily, as shown in FIG. 4 , the winding structure is a cylinder.
  • the pole piece may refer to the positive pole piece 221 or the negative pole piece 222 .
  • the pole piece includes a current collector 2211 and an active material layer 2212 , and the active material layer 2212 is located on at least one side surface of the current collector 2211 .
  • the active material layer 2212 has a first active material region 2212a and a second active material region 2212b; in the preset cross section 2212c, the cross-sectional area of the second active material region 2212b is S2 , and the cross-sectional area of the active material layer 2212 is S, S 2 ⁇ S; the surface where the active material layer 2212 in the current collector 2211 is located is the predetermined surface 2211a, the predetermined cross section 2212c is parallel to the predetermined surface 2211a, and passes through the second active material region 2212b; the porosity of the first active material region 2212a is P 1 , the porosity of the second active material region 2212b is P 2 , P 1 ⁇ P 2 ; the pore diameters of the first active material region 2212a and the second active material region
  • the area of the current collector 2211 not provided with the active material layer 2212 is the tab area, and the current collector 2211 in the tab area is the tab structure 2213 .
  • an insulating coating 2214 is optionally provided, and the insulating coating 2214 is located at the edge of the side of the active material layer 2212 close to the tab region.
  • the pore diameters of the pores of the first active material region 2212a and the second active material region 2212b are both ⁇ 1 ⁇ m, and the pore diameters of the pores of the first active material region 2212a and the second active material region 2212b are, for example, 0.05 ⁇ m to 1 ⁇ m.
  • the pore size of the pore structure formed by pressing the active material is matched, so that the first active material region 2212a and the second active material region 2212b can be formed by rolling.
  • the first active material region 2212a and the second active material region 2212b have a structure formed by rolling.
  • transverse section refers to the section parallel to the predetermined surface 2211a; the longitudinal section refers to the section perpendicular to the predetermined surface 2211a.
  • the C direction is the width direction C of the pole piece, which is consistent with the axial direction B of the winding structure in the electrode assembly 22 .
  • the D direction is the length direction D of the pole piece, which is consistent with the arc length direction of the winding structure in the electrode assembly 22 .
  • the embodiment of the present application is not limited to the number of the second active material region 2212b, which may be one or a plurality of spaced distributions.
  • the embodiment of the present application is not limited to the shape of the second active material region 2212b in the transverse cross-section, which may be a strip-shaped area, a square area, a circular area or other regular-shaped areas, and may also be an irregular-shaped area.
  • the second active material region 2212b is taken as an elongated region as an example, and the extending direction of the elongated region is not limited.
  • the length extension direction of the second active material region 2212b is inclined relative to the edge of the pole piece, and the length extension direction of the second active material region 2212b is between the width direction C of the pole piece and the length of the pole piece Between direction D.
  • the two ends of the second active material region 2212b are close to the edge of the active material layer 2212; in Fig. 7, in the width direction C of the pole piece, the two ends of the second active material region 2212b One end is close to the edge of the active material layer 2212 , and the other end of the second active material region 2212 b is close to the middle of the active material layer 2212 .
  • the length extension direction of the second active material region 2212 b is the length direction D of the pole piece.
  • the length extending direction of the second active material region 2212b is the width direction C of the pole piece.
  • the two ends of the second active material region 2212b are close to the edge of the active material layer 2212; in Fig. 10, in the width direction C of the pole piece, the two ends of the second active material region 2212b One end is close to the edge of the active material layer 2212 , and the other end of the second active material region 2212 b is close to the middle of the active material layer 2212 .
  • An active material layer 2212 can be respectively provided on both sides of the current collector 2211 in the thickness direction, as shown in FIG. 5; One of the surfaces in the direction is provided with an active material layer 2212 .
  • the present application is not limited to the distribution of the second active material region 2212b in the longitudinal section, and the thickness of the second active material region 2212b may be equal to the thickness of the active material layer 2212, as shown in FIG. 5 .
  • the thickness of the second active material region 2212b may also be smaller than the thickness of the active material layer 2212, as shown in FIGS. 11 to 13 .
  • the second active material region 2212b when the thickness of the second active material region 2212b is smaller than the thickness of the active material layer 2212, in the longitudinal section, the second active material region 2212b may be located on the surface of the active material layer 2212, as shown in FIG. 11; the second active material region 2212b may be located at the bottom of the active material layer 2212, as shown in FIG. 12 ; the second active material region 2212b may be located in the middle of the active material layer 2212, as shown in FIG. 13 .
  • the electrolyte infiltrates from both ends of the pole piece to the middle in the width direction C of the pole piece. Therefore, during the wetting process, usually the middle region of the pole piece in the width direction C is difficult to be wetted by the electrolyte, resulting in insufficient wetting efficiency of the pole piece in the width direction C.
  • the porosity of the second active material region 2212b is greater than the porosity of the first active material region 2212a, the porosity of the first active material region 2212a can be configured according to known porosity requirements, and then the porosity of the second active material region 2212b can be configured according to Porosities greater than known require configuration.
  • the wetting efficiency of the active material layer 2212 can be improved by configuring the second active material region 2212b with a relatively large porosity.
  • the second active material region 2212b is configured to be locally distributed in the transverse cross section, also That is to say, in the width direction C of the pole piece, there are both areas with relatively large porosity and areas with relatively small porosity, so the wetting efficiency of the pole piece in the width direction C can be effectively improved.
  • the difference between P 2 and P 1 is 3%-20%, optionally 7%-15%, and further optionally 10%-15%.
  • the difference between P2 and P1 is, for example but not limited to, one of 3%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, and 20%. Any one value or a range between any two values.
  • the difference between P 2 and P 1 is related to the increase in wetting efficiency and the loss of energy density of the pole piece. If the difference between P 2 and P 1 is small, the infiltration efficiency cannot be effectively improved; if the difference between P 2 and P 1 is large, the energy density loss of the pole piece will be large.
  • the second active material region 2212b and the first active material region 2212a have an appropriate porosity difference, which effectively improves the infiltration efficiency and at the same time reduces the energy density loss of the pole piece as much as possible.
  • P 1 is 15% to 35%, optionally 15% to 25%, further optionally 20% to 25%; and/or, P 2 is 20% %-50%, optionally 20%-40%, further optionally 25%-40%.
  • P1 is, for example but not limited to, any one of 15%, 20%, 21%, 22%, 23%, 24%, 25%, 30% and 35% or a range between any two values .
  • P2 is for example but not limited to 20%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 40% and 50% Any value in % or the range between any two values.
  • the values of P 1 and P 2 are related to the wetting efficiency and the energy density of the pole piece. If the values of P 1 and P 2 are small, the infiltration efficiency is low and the energy density is high; if the values of P 1 and P 2 are large, the infiltration efficiency is high and the energy density is low.
  • a specific porosity is selected for the second active material region 2212b and the first active material region 2212a to ensure the infiltration efficiency and at the same time control the pole piece to have an appropriate energy density.
  • the compacted density of the first active material region 2212a is C 1
  • the compacted density of the second active material region 2212b is C 2
  • the materials of the second active material region 2212b and the first active material region 2212a may be the same or different.
  • the manufacturing process is simple.
  • the ratio of C1 and C2 is, for example but not limited to, any one of 1.02, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6 and 1.7 or a range between any two values .
  • C 1 is, for example but not limited to, any one of 2.3g/cm 3 , 2.4g/cm 3 , 2.5g/cm 3 , 2.6g/cm 3 and 2.7g/cm 3 or between any two values range.
  • C 2 is, for example but not limited to, 1.6g/cm 3 , 1.7g/cm 3 , 1.8g/cm 3 , 1.9g/cm 3 , 2.0g/cm 3 , 2.1g/ cm 3 , 2.2g/cm 3 Any value in or the range between any two values.
  • the ratio of C 1 to C 2 is, for example but not limited to, any one of 1.02, 1.1, 1.2, 1.3, 1.4 and 1.5 or a range between any two values.
  • C 1 is, for example but not limited to, 3.1 g/cm 3 , 3.2 g/cm 3 , 3.3 g/cm 3 , 3.4 g/cm 3 , 3.5 g/cm 3 , 3.6 g/cm 3 and 3.7 g/cm 3 Any value in or the range between any two values.
  • C 2 is, for example but not limited to, any one of 2.5g/cm 3 , 2.6g/cm 3 , 2.7g/cm 3 , 2.8g/cm 3 , 2.9g/cm 3 and 3.0g/cm 3 or A range between any two values.
  • the ratio of C1 to C2 is, for example but not limited to, any one of 1.1, 1.2, 1.3, 1.4, 1.5, 1.6 and 1.7 or a range between any two values.
  • C 1 is, for example but not limited to, any one of 1.3g/cm 3 , 1.4g/cm 3 , 1.5g/cm 3 , 1.6g/cm 3 , 1.7g/cm 3 and 1.8g/cm 3 or A range between any two values.
  • C 2 is, for example but not limited to, any one of 1.1g/cm 3 , 1.2g/cm 3 , 1.3g/cm 3 , 1.4g/cm 3 and 1.5g/cm 3 or between any two values range.
  • Compacted density is related to porosity.
  • the compacted density and porosity satisfy different specific relationships.
  • the corresponding specific compaction density is selected for different active materials to ensure that the second active material area 2212b and the first active material area 2212a have appropriate porosity and porosity difference, effectively improve the infiltration efficiency, and control the pole piece to have a suitable Energy Density.
  • At least one of the following conditions (d) to (e) is satisfied: (d) S ⁇ 2.5% ⁇ S 2 ⁇ S ⁇ 30%; (e) active material layer 2212 The thickness of the second active material region 2212b is h 2 , h ⁇ 30% ⁇ h 2 ⁇ h ⁇ 100%.
  • the values of S2 are, for example but not limited to, S ⁇ 2.5%, S ⁇ 5%, S ⁇ 10%, S ⁇ 15%, S ⁇ 20%, S ⁇ 25% and S ⁇ Any value within 30% or a range between any two values.
  • the value of h2 is, for example but not limited to, h ⁇ 30%, h ⁇ 40%, h ⁇ 50%, h ⁇ 60%, h ⁇ 70%, h ⁇ 80%, h ⁇ Any one of 90% and h ⁇ 100% or the range between any two values.
  • S 2 represents the distribution range of the second active material region 2212b in the transverse section. If S 2 is small, it will affect the infiltration efficiency; if S 2 is large, it will affect the energy density.
  • h 2 represents the distribution range of the second active material region 2212b in the longitudinal section, and if h 2 is small, the infiltration efficiency will be affected.
  • the second active material region 2212b satisfies a specific area ratio and/or thickness ratio, so that the second active material region 2212b has an appropriate distribution ratio, ensures the infiltration efficiency, and controls the pole piece to have an appropriate energy density.
  • the size of the active material layer 2212 is M, which satisfies the following condition (f): (f) in the width direction C of the pole piece, the The minimum distance between the second active material region 2212b and the center of the active material layer 2212 is d 1 , where d 1 ⁇ M ⁇ 35%.
  • d 1 ⁇ M ⁇ 35% which means that in the width direction C, at least a part of the second active material region 2212b is located in the middle part of the active material layer 2212 within the specific width region.
  • the minimum distance between the second active material region 2212b and the center of the active material layer 2212 is less than or equal to a certain standard, so that the second active material region 2212b has a suitable distribution position and effectively improves the wetting efficiency.
  • the size of the active material layer 2212 is M, which satisfies the following condition (g): (g) in the width direction C of the pole piece, the second The minimum distance between the active material region 2212b and the edge of the active material layer 2212 is d 2 , where d 2 ⁇ M ⁇ 20%.
  • d 2 ⁇ M ⁇ 20% means that in the width direction C, at least a part of the second active material region 2212b is located within the region of the specific width at the edge of the active material layer 2212 .
  • d 2 0, it means that the second active material region 2212b reaches the edge of the active material layer 2212 in the width direction C.
  • the minimum distance between the second active material region 2212b and the edge of the active material layer 2212 is less than or equal to a certain standard, so that the second active material region 2212b has a suitable distribution position and effectively improves the wetting efficiency.
  • the size of the active material layer 2212 is M; there are multiple second active material regions 2212b, and the multiple second active material regions 2212b are along The longitudinal direction D of the sheet is distributed at intervals; at least one of the following conditions (h) to (i) is satisfied: (h) in the width direction C of the pole sheet, the minimum distance between the second active material region 2212b and the center of the active material layer 2212 The distance is d 1 , d 1 ⁇ M ⁇ 10%; (i) in the width direction C of the pole piece, the distance between the two ends of each second active material region 2212b is d 3 , d 3 ⁇ M ⁇ 30%.
  • each second active material region 2212b can be arranged obliquely, as shown in FIG. 6 and FIG. 7 .
  • Each second active material region 2212b may also extend along the width direction C of the pole piece, as shown in FIG. 9 and FIG. 10 .
  • d 1 ⁇ M ⁇ 10% which means that in the width direction C, at least a part of the second active material region 2212b is located in the middle part of the active material layer 2212 within the specified width.
  • d 3 ⁇ M ⁇ 30% means that in the width direction C, the second active material region 2212b at least satisfies the specific distribution range.
  • the minimum distance between the second active material region 2212b and the center of the active material layer 2212 is controlled to be less than or equal to a specific standard, and/or, the distance between the two ends of the second active material region 2212b is controlled to be greater than or equal to a specific standard , so that the plurality of second active material regions 2212b distributed at intervals along the length direction D of the pole piece have proper distribution positions, effectively improving the wetting efficiency.
  • the size of the active material layer 2212 is M; there are multiple second active material regions 2212b, and the multiple second active material regions 2212b are along
  • the width direction C of the sheet is distributed at intervals; in the width direction C of the pole sheet, the distance between two adjacent second active material regions 2212b is d 4 , and d 4 ⁇ M ⁇ 20%.
  • each second active material region 2212b can be arranged obliquely, as shown in FIG. 6 and FIG. 7 .
  • Each second active material region 2212b can also extend along the length direction D of the pole piece, as shown in FIG. 8 .
  • the distance between two adjacent second active material regions 2212b is controlled to be less than or equal to a certain standard, so that the plurality of second active material regions 2212b distributed at intervals along the width direction C of the pole piece have a suitable The distribution position can effectively improve the infiltration efficiency.
  • the thickness of the active material layer 2212 is h
  • the thickness of the second active material region 2212b is h 2 , h ⁇ 30% ⁇ h 2 ⁇ h ⁇ 60%
  • the second active material The distance from the region 2212b to the surface of the active material layer 2212 is d 5
  • the distance from the active material layer 2212 to the preset surface 2211a is d 6 , d 5 ⁇ d 6 .
  • d 5 0.
  • d 5 ⁇ d 6 means that in the longitudinal section, the second active material region 2212 b is arranged closer to the surface of the active material layer 2212 .
  • d 5 0 means that in the longitudinal section, the second active material region 2212 b is located on the surface of the active material layer 2212 , as shown in FIG. 11 .
  • the second active material region 2212b occupies a local area of the active material layer 2212 in the thickness direction, effectively improving the wetting efficiency and controlling the pole piece to have an appropriate energy density. At the same time, controlling the arrangement of the second active material region 2212b closer to the surface of the active material layer 2212 can better play the role of the second active material in improving the wetting efficiency.
  • the present application also provides an electrode assembly 22, including a positive pole piece 221, a separator 223 and a negative pole piece 222, and the positive pole piece 221 and the negative pole piece At least one of 222 is the pole piece of any of the above schemes.
  • FIG. 14 is an electrode assembly 22 comprising the pole piece shown in FIG. 6;
  • FIG. 15 is an electrode assembly 22 comprising the pole piece shown in FIG. 8;
  • FIG. 16 is an electrode assembly 22 comprising the pole piece shown in FIG. 9;
  • FIG. 17 is an electrode assembly 22 including the pole piece shown in FIG. 10 .
  • the positive pole piece 221 Since the compaction density of the positive pole piece 221 is generally large, the porosity of the positive pole piece 221 is usually small, so the positive pole piece 221 usually has a phenomenon of insufficient infiltration efficiency, especially if the active material is small particles of lithium iron phosphate.
  • Positive pole piece 221 Based on this, in the electrode assembly 22, its exemplary positive pole piece 221 is a pole piece of any of the above schemes, the negative pole piece 222 can be a pole piece of any of the above schemes, and the negative pole piece 222 can also be an active material layer 2212 Structure with consistent overall porosity.
  • the electrode assembly 22 is a winding structure
  • the width direction C of the pole piece is the same as the axial direction B of the electrode assembly 22
  • the length direction D of the pole piece is the same as the winding direction of the electrode assembly 22.
  • A is the same;
  • the diameter of the electrode assembly 22 is d, and in the winding direction A of the electrode assembly 22 , there is at least a part of the second active material region 2212b in each area with an arc length of ⁇ d/4.
  • Each region with an arc length of ⁇ D/4 has at least a part of the second active material region 2212b, so that the distribution pitch of the second active material region 2212b in the winding direction A of the electrode assembly 22 is less than or equal to a specific standard, ensuring that the electrode assembly 22 Better infiltration effect.
  • the present application also provides a battery cell, including a casing and an electrode assembly 22 according to any of the above schemes; the electrode assembly 22 is accommodated in the casing.
  • the present application also provides a battery, including a box body and a battery cell according to any of the above schemes; the battery cell is accommodated in the box body.
  • the present application also provides an electric device, including the battery of any one of the above schemes.
  • the entire coating is the active material layer 2212
  • the coating in the area coated with less slurry is the second active material area 2212 b
  • the remaining area is the first active material area 2212 a.
  • the slurry with less weight can be coated in some areas by arranging a convex structure on the coating back roller, or arranging a slurry blocking structure on the gasket.
  • the fourth preparation method of the pole piece of any of the above schemes which is used, for example, to prepare the active material layer 2212 with h 2 ⁇ h ⁇ 100%, includes: adopting a multi-layer coating method to form the second active material region 2212b In the coating layer, different slurries are used in different areas, so that some areas are coated with less weight slurries. After the multi-layer coating is completed, the entire slurry coating is cold-pressed into a structure with a consistent thickness. The entire coating is the active material layer 2212 , the coating in the area coated with less slurry is the second active material area 2212 b , and the remaining area is the first active material area 2212 a.
  • Positive electrode sheet preparation mix the active material, conductive agent (super P carbon black), polyvinylidene fluoride (PVDF), and N-methylpyrrolidone (NMP) according to the mass ratio of 92:3:5:100, at 800r/ A slurry was obtained after stirring at min speed for 12 h. The slurry is coated on the aluminum foil by extrusion coating, and a convex structure (used to form the second active material area) is arranged in the middle of the back roller used for coating, and the positive electrode sheet is obtained after baking, rolling and slitting.
  • the active material is lithium iron phosphate.
  • Negative electrode sheet preparation Active material, conductive agent (super P carbon black), sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), and deionized water are mixed according to the quality of 90:2.5:2.5:5:100 Proportional mixing, stirring at 800r/min for 12 hours to prepare a slurry, coating the slurry on a copper foil by extrusion coating, baking, rolling, and cutting to obtain negative electrode sheets.
  • Electrolyte preparation In an argon atmosphere glove box with a water content ⁇ 10ppm, mix ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) with a mass ratio of 25:20:55 Uniform mixing is performed to obtain a mixed solvent; then fully dried lithium hexafluorophosphate (LiPF 6 ) is dissolved in the above mixed solvent, and after uniform stirring, an electrolyte solution is obtained. Among them, the concentration of lithium hexafluorophosphate (LiPF 6 ) is 1.2 mol/L.
  • Assembly Assemble the above-mentioned positive electrode sheet, separator, and negative electrode sheet in sequence, and then wind them into a cylindrical winding structure along the winding direction. After adding the above-mentioned electrolyte, let it rest for infiltration, and seal to obtain a battery cell.
  • the isolation film adopts polyethylene film.
  • Table 1 shows the parameter conditions of the battery cells of each embodiment and comparative example.
  • the position of the second active material region refers to the position of the second active material region in the thickness direction of the active material layer in the longitudinal section.
  • Embodiment 1 to Embodiment 6 the structure of the positive pole piece in the transverse section is shown in FIG. 8 .
  • Embodiment 7 to Embodiment 12 the structure of the positive pole piece in the transverse section is shown in FIG. 9 .
  • d2 on both sides is 50mm, and d3 is 300mm; in the length direction of the pole piece, the size of each second active material area is 10mm, and the distance between the centers of two adjacent second active material areas is 40mm; S 2 is S ⁇ 18.75%.
  • the battery monomer is activated, and the capacity test is carried out according to 1C charge and discharge, and then the cycle test is carried out according to the 1C charge and discharge process.
  • the capacity loss rate of the battery cells of each embodiment is calculated; the cycle life data is represented by the cycle capacity retention rate of 300 cycles.
  • the positive electrode sheet is configured such that the porosity of the second active material region is greater than the porosity of the first active material region.
  • the positive pole piece is configured such that the porosity of the second active material region is equal to the porosity of the first active material region.
  • Examples 1 to 12 show: the cell capacity loss rate is small; the cycle capacity retention rate is high, so that the cycle life is improved; the soaking time is significantly reduced, indicating that the soaking efficiency is improved. It shows that the setting of the second active material region with relatively large porosity can effectively improve the infiltration efficiency and cycle life, and has little effect on the battery capacity.
  • the difference between P2 and P1 in embodiment 2 is in the scope of 10% ⁇ 15%
  • the difference between P2 and P1 in embodiment 1 and embodiment 3 is not in 10 % ⁇ 15% range.
  • the difference between P2 and P1 in embodiment 7, embodiment 9 and embodiment 12 is in the scope of 10% ⁇ 15%
  • P2 The difference with P1 is not in the range of 10% to 15%.
  • Example 2 has a higher cycle capacity retention rate. Compared with Example 2 and Example 3, the cycle capacity retention rate of Example 2 is higher, and the soaking time is shorter. Compared with Example 8, Example 7, Example 9 and Example 12 all show that the cycle capacity retention rate is higher and the soaking time is shorter. It shows that when the difference between P 2 and P 1 is in the range of 10% to 15%, the second active material region can better improve the wetting efficiency and improve the cycle life.
  • the second active material area is located on the surface of the active material layer in Example 2, and the second active material area is located at the bottom of the active material layer in Example 5.
  • the second active material region in embodiment 9 is distributed on the entire thickness direction of the active material layer, the second active material region in embodiment 10 is located on the surface of the active material layer, and the second active material region in embodiment 11 The region is located at the bottom of the active material layer.
  • Example 9 the cycle capacity retention rate of Example 2 is higher, and the soaking time is shorter. It shows that setting the second active material region close to the surface of the active material layer can better improve the wetting efficiency and improve the cycle life.
  • the soaking time gradually increases, illustrating that: the second active material zone is distributed in the entire thickness direction of the active material layer to have better infiltration efficiency; the second active material zone is distributed in the active material layer. For a local area in the thickness direction of the active material layer, disposing the second active material region close to the surface of the active material layer can better improve the wetting efficiency and improve the cycle life.

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Abstract

本申请实施例提供了一种极片、电极组件、电池单体、电池以及用电设备，属于电池技术领域。其中，极片包括集流体；以及活性物质层，位于所述集流体的至少一侧表面，所述活性物质层具有第一活性物质区和第二活性物质区；在预设截面中，所述第二活性物质区的截面积为S2，所述活性物质层的截面积为S，S2＜S；所述集流体中所述活性物质层所在表面为预设表面，所述预设截面平行于所述预设表面，且经过所述第二活性物质区；所述第一活性物质区的孔隙率为P1，所述第二活性物质区的孔隙率为P2，P1＜P2；所述第一活性物质区和所述第二活性物质区的孔的孔径均≤1μm。这种结构的极片，能够有效改善极片在宽度方向上的浸润效率。

Description

一种极片、电极组件、电池单体、电池以及用电设备 技术领域
本申请涉及电池技术领域，具体而言，涉及一种极片、电极组件、电池单体、电池以及用电设备。
背景技术
电池广泛用于用电设备，例如手机、笔记本电脑、电瓶车、电动汽车、电动飞机、电动轮船、电动玩具汽车、电动玩具轮船、电动玩具飞机和电动工具等等。
极片在宽度方向上(即电极组件在高度方向上)浸润效率不足是一种常见的现象，会导致电极组件在制造过程中的产能损失，还导致电极组件在循环过程中存在中部电解液供应不足的问题而影响电极组件循环寿命。
发明内容
本申请实施例提供一种极片、电极组件、电池单体、电池以及用电设备，能够有效改善极片在宽度方向上的浸润效率。
第一方面，本申请提供了一种极片包括集流体；以及活性物质层，位于所述集流体的至少一侧表面，所述活性物质层具有第一活性物质区和第二活性物质区；在预设截面中，所述第二活性物质区的截面积为S 2，所述活性物质层的截面积为S，S 2＜S；所述集流体中所述活性物质层所在表面为预设表面，所述预设截面平行于所述预设表面，且经过所述第二活性物质区；所述第一活性物质区的孔隙率为P 1，所述第二活性物质区的孔隙率为P 2，P 1＜P 2；所述第一活性物质区和所述第二活性物质区的孔的孔径均≤1μm。
本申请实施例的技术方案中，第二活性物质区的孔隙率大于第一活性物质区的孔隙率，通过配置孔隙率相对较大的第二活性物质区，能够提高活性物质层的浸润效率。在平行于预设表面的预设截面中，由于第二活性物质区的截面积小于活性物质层的截面积，即将第二活性物质区配置为在横向截面内局部分布，也就是说，在极片的宽度方向上，兼具孔隙率相对较大的区域和孔隙率相对较小的区域，因此能够有效改善极片在宽度方向上的浸润效率。
在一些实施例中，P 2和P 1的差值为3％～20％，可选地为7％～15％，进一步可选地为10％～15％。上述实施例中，第二活性物质区和第一活性物质区有合适的孔隙率差值，有效提高浸润效率的同时，尽可能减少极片能量密度损失的量。
在一些实施例中，P 1为15％～35％，可选地为15％～25％，进一步可选地为20％～25％；和/或，P 2为20％～50％，可选地为20％～40％，进一步可选地为25％～40％。上述实施例中，第二活性物质区和第一活性物质区选择特定的孔隙率，保证浸润效率的同时，控制极片具有合适的能量密度。
在一些实施例中，所述第一活性物质区的压实密度为C 1，所述第二活性物质区的压实密度为C 2，且满足如下条件(a)～(c)中的任意一个：(a)所述第一活性物质区和所述第二活性物质区的活性物质均为磷酸铁锂，C 1和C 2的比值为1.02～1.7；可选的，C 1为2.3g/cm 3～2.7g/cm 3，C 2为1.6g/cm 3～2.2g/cm 3；(b)所述第一活性物质区和所述第二活性物质区的活性物质均为三元正极材料，C 1和C 2的比值为1.02～1.5；可选的，C 1为3.1g/cm 3～3.7g/cm 3，C 2为2.5g/cm 3～3g/cm 3；(c)所述第一活性物质区和所述第二活性物质区的活性物质均为石墨，C 1和C 2的比值为1.1～1.7；可选的，C 1为1.3g/cm 3～1.8g/cm 3，C 2为1.1g/cm 3～1.5g/cm 3。上述实施例中，不同活性物质分别选择对应的特定压实密度，保证第二活性物质区和第一活性物质区具有合适的孔隙率及孔隙率差值，有效提高浸润效率的同时，控制极片具有合适的能量密度。
在一些实施例中，满足如下条件(d)～(e)中的至少一个：(d)S×2.5％≤S 2≤S×30％；(e)所述活性物质层的厚度为h，所述第二活性物质区的厚度为h 2，h×30％≤h 2≤h×100％。上述实 施例中，第二活性物质区满足特定的面积占比和/或厚度占比，使得第二活性物质区具有合适的分布占比，保证浸润效率的同时，控制极片具有合适的能量密度。
在一些实施例中，在所述极片的宽度方向上，所述活性物质层的尺寸为M，满足如下条件(f)：(f)在所述极片的宽度方向上，所述第二活性物质区与所述活性物质层的中心的最小距离为d 1，d 1≤M×35％。上述实施例中，在极片的宽度方向上，第二活性物质区与活性物质层的中心的最小距离小于等于特定标准，使得第二活性物质区具有合适的分布位置，有效提高浸润效率。
在一些实施例中，在所述极片的宽度方向上，所述活性物质层的尺寸为M，满足如下条件(g)：(g)在所述极片的宽度方向上，所述第二活性物质区的与所述活性物质层的边缘的最小距离为d 2，d 2≤M×20％。上述实施例中，在极片的宽度方向上，第二活性物质区与活性物质层的边缘的最小距离小于等于特定标准，使得第二活性物质区具有合适的分布位置，有效提高浸润效率。
在一些实施例中，在所述极片的宽度方向上，所述活性物质层的尺寸为M；所述第二活性物质区有多个，多个所述第二活性物质区沿所述极片的长度方向间隔分布；满足如下条件(h)～(i)中的至少一个：(h)在所述极片的宽度方向上，所述第二活性物质区与所述活性物质层的中心的最小距离为d 1，d 1≤M×10％；(i)在所述极片的宽度方向上，每个所述第二活性物质区的两端的距离为d 3，d 3≥M×30％。上述实施例中，在极片的宽度方向上，控制第二活性物质区与活性物质层的中心的最小距离小于等于特定标准，和/或，控制第二活性物质区的两端距离大于等于特定标准，使得沿极片的长度方向间隔分布的多个第二活性物质区具有合适的分布位置，有效提高浸润效率。
在一些实施例中，在所述极片的宽度方向上，所述活性物质层的尺寸为M；所述第二活性物质区有多个，多个所述第二活性物质区沿所述极片的宽度方向间隔分布；在所述极片的宽度方向上，相邻两个所述第二活性物质区之间的间距为d 4，d 4≤M×20％。上述实施例中，在极片的宽度方向上，控制相邻两个第二活性物质区之间的距离小于等于特定标准，使得沿极片的宽度方向间隔分布的多个第二活性物质区具有合适的分布位置，有效提高浸润效率。
在一些实施例中，所述活性物质层的厚度为h，所述第二活性物质区的厚度为h 2，h×30％≤h 2≤h×60％，所述第二活性物质区到所述活性物质层的表面的距离为d 5，所述活性物质层到所述预设表面的距离为d 6，d 5＜d 6。上述实施例中，在厚度方向上第二活性物质区占活性物质层的局部区域，有效提高浸润效率的同时，控制极片具有合适的能量密度。同时，控制第二活性物质区更接近活性物质层的表面设置，能够更好地发挥第二活性物质改善浸润效率的作用。
第二方面，本申请提供了一种电极组件，包括正极极片、隔离膜和负极极片，所述正极极片和所述负极极片中的至少一者为上述实施例中的极片。
在一些实施例中，所述电极组件为卷绕结构，所述极片的宽度方向与所述电极组件的轴向相同，所述极片的长度方向与所述电极组件的卷绕方向相同；所述电极组件的直径为d，在所述电极组件的卷绕方向上，每个弧长为πd/4的区域内均具有所述第二活性物质区的至少一部分。上述实施例中，每个弧长为πd/4的区域内均具有所述第二活性物质区的至少一部分，使得在电极组件卷绕方向上第二活性物质区的分布间距小于等于特定标准，保证电极组件较好的浸润效果。
第三方面，本申请提供了一种电池单体，包括外壳以及上述实施例中的电极组件；所述电极组件容纳于所述外壳内。
第四方面，本申请提供了一种电池，包括箱体以及上述实施例中的电池单体；所述电池单体容纳于所述箱体内。
第五方面，本申请提供了一种用电设备，包括如上述实施例中的电池。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将对实施例中所需要使用的附图作简单地介绍，应当理解，以下附图仅示出了本申请的某些实施例，因此不应被看作是对范围的限定，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他相关的附图。
图1为本申请一些实施例提供的车辆的结构示意图；
图2为本申请一些实施例提供的电池的爆炸图；
图3为图2所示的电池单体的爆炸；
图4为本申请一些实施例提供的电极组件沿卷绕方向局部展开的结构示意图；
图5为本申请一些实施例提供的极片在纵向截面中的第一种结构示意图；
图6为本申请一些实施例提供的极片在横向截面中的第一种结构示意图；
图7为本申请一些实施例提供的极片在横向截面中的第二种结构示意图；
图8为本申请一些实施例提供的极片在横向截面中的第三种结构示意图；
图9为本申请一些实施例提供的极片在横向截面中的第四种结构示意图；
图10为本申请一些实施例提供的极片在横向截面中的第五种结构示意图；
图11为本申请一些实施例提供的极片在纵向截面中的第二种结构示意图；
图12为本申请一些实施例提供的极片在纵向截面中的第三种结构示意图；
图13为本申请一些实施例提供的极片在纵向截面中的第四种结构示意图；
图14为包含图6所示的极片的电极组件；
图15为包含图8所示的极片的电极组件；
图16为包含图9所示的极片的电极组件；
图17为包含图10所示的极片的电极组件。
具体实施方式中的附图标号如下：
车辆1000；
电池100，控制器200，马达300；
箱体10，第一部分11，第二部分12，容纳空间13；
电池单体20，外壳21，电极组件22，电极端子23，泄压结构24；
壳体211，盖体212，密封空间213，正极极片221，负极极片222，隔离膜223；
集流体2211，活性物质层2212；极耳结构2213，绝缘涂层2214；
预设表面2211a，第一活性物质区2212a，第二活性物质区2212b，预设截面2212c；
卷绕方向A，轴向B，宽度方向C，长度方向D。
具体实施方式
下面将结合附图对本申请技术方案的实施例进行详细的描述。以下实施例仅用于更加清楚地说明本申请的技术方案，因此只作为示例，而不能以此来限制本申请的保护范围。
除非另有定义，本文所使用的所有的技术和科学术语与属于本申请的技术领域的技术人员通常理解的含义相同；本文中所使用的术语只是为了描述具体的实施例的目的，不是旨在于限制本申请；本申请的说明书和权利要求书及上述附图说明中的术语“包括”和“具有”以及它们的任何变形，意图在于覆盖不排他的包含。
在本申请实施例的描述中，技术术语“第一”、“第二”等仅用于区别不同对象，而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特征的数量、特定顺序或主次关系。
在本申请实施例的描述中，“多个”的含义是两个以上，除非另有明确具体的限定。
在本申请实施例的描述中，术语“和/或”仅仅是一种描述关联对象的关联关系，表示可以存在三种关系，例如A和/或B，可以表示：单独存在A，同时存在A和B，单独存在B这三种情况。另外，本文中字符“/”，一般表示前后关联对象是一种“或”的关系。
在本文中提及“实施例”意味着，结合实施例描述的特定特征、结构或特性可以包含在本申请的至少一个实施例中。在说明书中的各个位置出现该短语并不一定均是指相同的实施例，也不是与其它实施例互斥的独立的或备选的实施例。本领域技术人员显式地和隐式地理解的是，本文所描述的实施例可以与其它实施例相结合。
在本申请的实施例中，相同的附图标记表示相同的部件，并且为了简洁，在不同实施例中，省略对相同部件的详细说明。应理解，附图示出的本申请实施例中的各种部件的厚度、长宽等尺寸，以及集成装置的整体厚度、长宽等尺寸仅为示例性说明，而不应对本申请构成任何限定。
本申请中，电池单体可以包括锂离子二次电池、锂离子一次电池、锂硫电池、钠锂离子电池、钠离子电池或镁离子电池等，本申请实施例对此并不限定。电池单体可呈圆柱体、扁平体、长方体或其它形状等，本申请实施例对此也不限定。电池单体一般按封装的方式分成三种：柱形电池单体、方形电池单体和软包电池单体，本申请实施例对此也不限定。
电池单体包括电极组件和电解液，电极组件由正极片、负极片和隔离膜组成。电池单体主要依靠金属离子在正极片和负极片之间移动来工作。正极片包括正极集流体和正极活性物质层，正极活性物质层涂覆于正极集流体的表面，未涂敷正极活性物质层的正极集流体凸出于已涂覆正极活性物质层的正极集流体，未涂敷正极活性物质层的正极集流体作为正极极耳。以锂离子电池为例，正极集流体的材料可以为铝，正极活性物质可以为钴酸锂、磷酸铁锂、三元锂或锰酸锂等。负极片包括负极集流体和负极活性物质层，负极活性物质层涂覆于负极集流体的表面，未涂敷负极活性物质层的负极集流体凸出于已涂覆负极活性物质层的负极集流体，未涂敷负极活性物质层的负极集流体作为负极极耳。负极集流体的材料可以为铜，负极活性物质可以为碳或硅等。为了保证通过大电流而不发生熔断，正极极耳的数量为多个且层叠在一起，负极极耳的数量为多个且层叠在一起。隔离膜的材质可以为PP(polypropylene，聚丙烯)或PE(polyethylene，聚乙烯)等。此外，电极组件可以是卷绕式结构，也可以是叠片式结构，本申请实施例并不限于此。
本申请中，电池是指包括一个或多个电池单体以提供更高的电压和容量的单一的物理模块。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。
发明人发现，近年来，随着电子产品和电动汽车的快速发展，对电池单体大电流充放电的要求也越来越高。电池单体的电极组件中，所使用的电极在经过辊压后活性物质层孔隙率降低，导致离子传导变差的同时浸润性能降低，使得电池单体中的电解液难以从极片在宽度方向上的两端到达极片在宽度方向上的中间区域，进而导致极片在宽度方向上(在电池中，即电极组件在高度方向上)的浸润效率不足。
发明人注意到，通过在集流体表面的宽度方向中部不涂覆活性材料并进行打孔，能够改善上述问题。但是，不涂覆活性材料的区域的容量大量损失，造成极片能量密度大幅度下降；不涂覆活性材料的区域的强度大幅降低，破坏了极片和电极组件的受力结构，使得电极组件受力时容易出现结构整体扭转的情况，甚至可能扭断而刺穿隔离膜；不涂覆活性材料的区域进行打孔还会增加工艺复杂性，且有集流体断裂风险。
发明人还研究发现，在集流体的表面涂覆完整的活性物质层，通过局部孔隙调控策略，在横向截面内局部增大活性物质层的孔隙率，也就是说，在极片的宽度方向上，兼具孔隙率相对较大的区域和孔隙率相对较小的区域，因此能够有效改善极片在宽度方向上的浸润效率。而且，上述的局部孔隙调控策略，能够有效克服或改善不涂覆活性材料和打孔所造成的问题。
鉴于此，本申请实施例提供一种技术方案，在活性物质层设置第一活性物质区和第二活性物质区，调控第二活性物质区相对于第一活性物质区具有较大的空隙率，并将第二活性物质区配置为在横向截面内局部分布。上述技术方案，能够减少容量的损失，从而减小能量密度的下降幅度；保留了活性物质层的完整性，不破坏极片和电极组件的受力结构；制造工艺简单而不会增加极片成 本，避免打孔导致集流体断裂而保证了安全性，且与各类结构的电极组件的适配性好；有效改善了极片在宽度方向上的浸润效率，能够提高电极组件的产能，且能改善电极组件在循环过程中存在的中部电解液供应不足的问题，从而能改善电极组件的循环寿命。
本申请实施例描述的技术方案适用于电极组件、使用电极组件的电池单体、使用电池单体的电池以及使用电池的用电设备。
本申请中，用电设备可以为多种形式，例如，手机、便携式设备、笔记本电脑、电瓶车、电动汽车、轮船、航天器、电动玩具和电动工具等等，例如，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。
以下实施例为了方便说明，以用电设备为车辆为例进行说明。
请参照图1，图1为本申请一些实施例提供的车辆1000的结构示意图，车辆1000的内部设置有电池100，电池100可以设置在车辆1000的底部或头部或尾部。电池100可以用于车辆1000的供电，例如，电池100可以作为车辆1000的操作电源。
车辆1000还可以包括控制器200和马达300，控制器200用来控制电池100为马达300供电，例如，用于车辆1000的启动、导航和行驶时的工作用电需求。
在本申请一些实施例中，电池100不仅仅可以作为车辆1000的操作电源，还可以作为车辆1000的驱动电源，代替或部分地代替燃油或天然气为车辆1000提供驱动动力。
请参照图2，图2为本申请一些实施例提供的电池100的爆炸图，电池100可以包括箱体10和电池单体20，电池单体20容纳于箱体10内。
箱体10用于容纳电池单体20，箱体10可以是多种结构。在一些实施例中，箱体10可以包括第一部分11和第二部分12，第一部分11与第二部分12相互盖合，第一部分11和第二部分12共同限定出用于容纳电池单体20的容纳空间13。第二部分12可以是为一端开口的空心结构，第一部分11为板状结构，第一部分11盖合于第二部分12的开口侧，以形成具有容纳空间13的箱体10；第一部分11和第二部分12也可以是均为一侧开口的空心结构，第一部分11的开口侧盖合于第二部分12的开口侧，以形成具有容纳空间13的箱体10。当然，第一部分11和第二部分12可以是多种形状，比如，圆柱体、长方体等。
为提高第一部分11与第二部分12连接后的密封性，第一部分11与第二部分12之间也可以设置密封件(图未示出)，比如，密封胶、密封圈等。
在电池100中，电池单体20可以是一个，也可以是多个。若电池单体20为多个，多个电池单体20之间可串联或并联或混联，混联是指多个电池单体20中既有串联又有并联。电池单体20可以呈圆柱体、长方体或其他形状等。在图2中，示例性的，电池单体20呈圆柱体。
多个电池单体20之间可直接串联或并联或混联在一起，再将多个电池单体20构成的整体容纳于箱体10内。也可以是多个电池单体20先串联或并联或混联组成电池模块，多个电池模块再串联或并联或混联形成一个整体，并容纳于箱体10。
多个电池单体20之间可通过汇流部件(图未示出)实现电连接，以实现多个电池单体20的并联或串联或混联。
请参照图3，图3为图2所示的电池单体20的爆炸图。电池单体20可以包括外壳21和电极组件22，电极组件22容纳于外壳21内。
在一些实施例中，外壳21还可用于容纳电解质，例如电解液。外壳21可以是多种结构形式。
在一些实施例中，外壳21可以包括壳体211和盖体212，壳体211为一侧开口的空心结 构，盖体212盖合于壳体211的开口处并形成密封连接，以形成用于容纳电极组件22和电解质的密封空间213。
在组装电池单体20时，可先将电极组件22放入壳体211内，并向壳体211内填充电解质，再将盖体212盖合于壳体211的开口。
壳体211可以是多种形状，比如，圆柱体、长方体等。壳体211的形状可根据电极组件22的具体形状来确定。比如，若电极组件22为圆柱体结构，则可选用为圆柱体壳体；若电极组件22为长方体结构，则可选用长方体壳体。当然，盖体212也可以是多种结构，比如，盖体212为板状结构、一端开口的空心结构等。示例性的，在图3中，壳体211为圆柱体结构，盖体212为板状结构，电极组件22为圆柱体结构，电极组件22容纳于壳体211内，盖体212盖合于壳体211顶部的开口处。
在一些实施例中，电池单体20还可以包括电极端子23，电极端子23安装于盖体212上。电极端子23与电极组件22电连接，以输出电池单体20所产生的电能。示例性的，电极端子23与电极组件22可通过转接片(图未示出)实现电连接。
在一些实施例中，电池单体20还可以包括泄压结构24，泄压结构24用于在电池单体20的内部压力或温度达到预定值时泄放电池单体20内部的压力。
示例性的，泄压结构24可以是诸如防爆阀、防爆片、气阀、泄压阀或安全阀等部件。
接下来结合附图对电极组件22的具体结构进行详细阐述。为了方便说明，以卷绕结构的电极组件22为例进行说明。
请参阅图4，电极组件22包括正极极片221、隔离膜223和负极极片222。正极极片221、隔离膜223和负极极片222在隔离膜223的厚度方向上依次层叠设置，并沿卷绕方向A卷绕形成卷绕结构。
其中，卷绕方向A即为正极极片221、隔离膜223和负极极片222从内向外沿周向卷绕的方向，为如图4中的A方向。电极组件22的高度方向即为卷绕结构的轴向B，为如图4中的B方向。
卷绕结构可以呈圆柱体，也可以呈扁平体。示例性的，如图4所示，卷绕结构呈圆柱体。
为了方便说明，接下来将极片的结构进行说明，极片可以是指正极极片221，也可以是指负极极片222。
请参阅图5和图6，极片包括集流体2211以及活性物质层2212，活性物质层2212位于集流体2211的至少一侧表面。活性物质层2212具有第一活性物质区2212a和第二活性物质区2212b；在预设截面2212c中，第二活性物质区2212b的截面积为S 2，活性物质层2212的截面积为S，S 2＜S；集流体2211中活性物质层2212所在表面为预设表面2211a，预设截面2212c平行于预设表面2211a，且经过第二活性物质区2212b；第一活性物质区2212a的孔隙率为P 1，第二活性物质区2212b的孔隙率为P 2，P 1＜P 2；第一活性物质区2212a和第二活性物质区2212b的孔的孔径均≤1μm。
集流体2211未设置有活性物质层2212的区域为极耳区域，极耳区域的集流体2211为极耳结构2213。在预设表面2211a中，可选地设置有绝缘涂层2214，该绝缘涂层2214位于活性物质层2212靠近极耳区域所在的一侧的边缘。
第一活性物质区2212a和第二活性物质区2212b的孔的孔径均≤1μm，第一活性物质区2212a和第二活性物质区2212b的孔的孔径例如均在0.05μm～1μm，该孔径与辊压活性物质形成的孔结构的孔径匹配，使得第一活性物质区2212a和第二活性物质区2212b可以通过辊压形成。在本申请的实施例中，第一活性物质区2212a和第二活性物质区2212b具有通过辊压形成的结构。
图中，横向截面是指平行于预设表面2211a的截面；纵向截面是指垂直于预设表面2211a的截面。
如图中所示，C方向为极片的宽度方向C，其在电极组件22中与卷绕结构的轴向B一致。D方向为极片的长度方向D，其在电极组件22中与卷绕结构的弧长方向一致。
本申请实施例对第二活性物质区2212b的数量不限，其可以是一个，也可以是间隔分布的多个。
本申请实施例对第二活性物质区2212b在横向截面中的形状不限，其可以是长条形区域、方形区域、圆形区域或者其他规则形状区域，还可以是不规则形状区域。
图6至图10中以第二活性物质区2212b为长条形区域作为示例，该长条形区域的长度延伸方向不限。
如图6和图7所示，第二活性物质区2212b的长度延伸方向相对于极片边缘倾斜设置，第二活性物质区2212b的长度延伸方向介于极片的宽度方向C和极片的长度方向D之间。图6中，在极片的宽度方向C上，第二活性物质区2212b的两端靠近活性物质层2212的边缘；图7中，在极片的宽度方向C上，第二活性物质区2212b的一端靠近活性物质层2212的边缘，第二活性物质区2212b的另一端靠近活性物质层2212的中部。
如图8所示，第二活性物质区2212b的长度延伸方向为极片的长度方向D。
如图9和图10所示，第二活性物质区2212b的长度延伸方向为极片的宽度方向C。图9中，在极片的宽度方向C上，第二活性物质区2212b的两端靠近活性物质层2212的边缘；图10中，在极片的宽度方向C上，第二活性物质区2212b的一端靠近活性物质层2212的边缘，第二活性物质区2212b的另一端靠近活性物质层2212的中部。
本申请对活性物质层2212在纵向截面中的分布情况不限，可以在集流体2211厚度方向上的两侧表面分别设置一个活性物质层2212，如图5所示；也可以在集流体2211厚度方向上的其中一个表面设一个活性物质层2212。
本申请对第二活性物质区2212b在纵向截面中的分布情况不限，第二活性物质区2212b的厚度可以等于活性物质层2212的厚度，如图5所示。第二活性物质区2212b的厚度也可以小于活性物质层2212的厚度，如图11至图13所示。
其中，第二活性物质区2212b的厚度小于活性物质层2212的厚度时，在纵向截面中，第二活性物质区2212b可以位于活性物质层2212的表面，如图11所示；第二活性物质区2212b可以位于活性物质层2212的底部，如图12所示；第二活性物质区2212b可以位于活性物质层2212的中部，如图13所示。
在电池单体中，电极组件22浸润电解液时，在极片的宽度方向C上，电解液从极片的两端往中部浸润。因此，在浸润过程中，通常是极片在宽度方向C上的中部区域难以被电解液浸润，从而导致极片在宽度方向C上的浸润效率不足。
第二活性物质区2212b的孔隙率大于第一活性物质区2212a的孔隙率，第一活性物质区2212a的孔隙率可以按照公知的孔隙率要求进行配置，然后第二活性物质区2212b的孔隙率按照大于公知的孔隙率要求进行配置。
通过配置孔隙率相对较大的第二活性物质区2212b，能够提高活性物质层2212的浸润效率。在平行于预设表面2211a的预设截面2212c中，由于第二活性物质区2212b的截面积小于活性物质层2212的截面积，即将第二活性物质区2212b配置为在横向截面内局部分布，也就是说，在极片的宽度方向C上，兼具孔隙率相对较大的区域和孔隙率相对较小的区域，，因此能够有效改善极片在宽度方向C上的浸润效率。
根据本申请的一些实施例，可选地，P 2和P 1的差值为3％～20％，可选地为7％～15％，进一步可选地为10％～15％。
作为示例，P 2和P 1的差值例如但不限于为3％、7％、8％、9％、10％、11％、12％、13％、14％、15％和20％中的任意一个值或者任意两个值之间的范围。
P 2和P 1的差值同浸润效率提高和极片能量密度损失相关。若P 2和P 1的差值较小，则不能有效地提高浸润效率；若P 2和P 1的差值较大，则会使得极片能量密度损失较大。
第二活性物质区2212b和第一活性物质区2212a有合适的孔隙率差值，有效提高浸润效率的同时，尽可能减少极片能量密度损失的量。
根据本申请的一些实施例，可选地，P 1为15％～35％，可选地为15％～25％，进一步可选地为20％～25％；和/或，P 2为20％～50％，可选地为20％～40％，进一步可选地为25％～40％。
作为示例，P 1例如但不限于为15％、20％、21％、22％、23％、24％、25％、30％和35％中的任意一个值或者任意两个值之间的范围。P 2例如但不限于为20％、25％、26％、27％、28％、29％、30％、31％、32％、33％、34％、35％、36％、40％和50％中的任意一个值或者任意两个值之间的范围。
P 1和P 2的值同浸润效率和极片能量密度相关。若P 1和P 2的值较小，则浸润效率低且能量密度高；若P 1和P 2的值较大，则浸润效率高且能量密度低。
第二活性物质区2212b和第一活性物质区2212a选择特定的孔隙率，保证浸润效率的同时，控制极片具有合适的能量密度。
根据本申请的一些实施例，可选地，第一活性物质区2212a的压实密度为C 1，第二活性物质区2212b的压实密度为C 2，且满足如下条件(a)～(c)中的任意一个：(a)第一活性物质区2212a和第二活性物质区2212b的活性物质均为磷酸铁锂，C 1和C 2的比值为1.02～1.7；可选的，C 1为2.3g/cm 3～2.7g/cm 3，C 2为1.6g/cm 3～2.2g/cm 3；(b)第一活性物质区2212a和第二活性物质区2212b的活性物质均为三元正极材料，C 1和C 2的比值为1.02～1.5；可选的，C 1为3.1g/cm 3～3.7g/cm 3，C 2为2.5g/cm 3～3g/cm 3；(c)第一活性物质区2212a和第二活性物质区2212b的活性物质均为石墨，C 1和C 2的比值为1.1～1.7；可选的，C 1为1.3g/cm 3～1.8g/cm 3，C 2为1.1g/cm 3～1.5g/cm 3。
本申请实施例中，第二活性物质区2212b和第一活性物质区2212a材质可以相同，也可以不同。第二活性物质区2212b和第一活性物质区2212a材质相同时，制造工艺简单。
作为示例，对于(a)条件，C 1和C 2的比值例如但不限于为1.02、1.1、1.2、1.3、1.4、1.5、1.6和1.7中的任意一个值或者任意两个值之间的范围。
C 1的值例如但不限于为2.3g/cm 3、2.4g/cm 3、2.5g/cm 3、2.6g/cm 3和2.7g/cm 3中的任意一个值或者任意两个值之间的范围。
C 2的值例如但不限于为1.6g/cm 3、1.7g/cm 3、1.8g/cm 3、1.9g/cm 3、2.0g/cm 3、2.1g/cm 3、2.2g/cm 3中的任意一个值或者任意两个值之间的范围。
作为示例，对于(b)条件，C 1和C 2的比值例如但不限于为1.02、1.1、1.2、1.3、1.4和1.5中的任意一个值或者任意两个值之间的范围。
C 1的值例如但不限于为3.1g/cm 3、3.2g/cm 3、3.3g/cm 3、3.4g/cm 3、3.5g/cm 3、3.6g/cm 3和3.7g/cm 3中的任意一个值或者任意两个值之间的范围。
C 2的值例如但不限于为2.5g/cm 3、2.6g/cm 3、2.7g/cm 3、2.8g/cm 3、2.9g/cm 3和3.0g/cm 3中的任意一个值或者任意两个值之间的范围。
作为示例，对于(b)条件，C 1和C 2的比值例如但不限于为1.1、1.2、1.3、1.4、1.5、1.6和1.7中的任意一个值或者任意两个值之间的范围。
C 1的值例如但不限于为1.3g/cm 3、1.4g/cm 3、1.5g/cm 3、1.6g/cm 3、1.7g/cm 3和1.8g/cm 3中的任意一个值或者任意两个值之间的范围。
C 2的值例如但不限于为1.1g/cm 3、1.2g/cm 3、1.3g/cm 3、1.4g/cm 3和1.5g/cm 3中的任意一个值或者任意两个值之间的范围。
压实密度与孔隙率相关。对于不同活性物质种类的活性物质层2212，压实密度与孔隙率 满足不同的特定关系。
不同活性物质分别选择对应的特定压实密度，保证第二活性物质区2212b和第一活性物质区2212a具有合适的孔隙率及孔隙率差值，有效提高浸润效率的同时，控制极片具有合适的能量密度。
根据本申请的一些实施例，可选地，满足如下条件(d)～(e)中的至少一个：(d)S×2.5％≤S 2≤S×30％；(e)活性物质层2212的厚度为h，第二活性物质区2212b的厚度为h 2，h×30％≤h 2≤h×100％。
作为示例，对于(d)条件，S 2的值例如但不限于为S×2.5％、S×5％、S×10％、S×15％、S×20％、S×25％和S×30％中的任意一个值或者任意两个值之间的范围。
作为示例，对于(e)条件，h 2的值例如但不限于为h×30％、h×40％、h×50％、h×60％、h×70％、h×80％、h×90％和h×100％中的任意一个值或者任意两个值之间的范围。
S 2代表第二活性物质区2212b在横向截面的分布范围，若S 2较小，则影响浸润效率；若S 2较大，则影响能量密度。h 2代表第二活性物质区2212b在纵向截面的分布范围，若h 2较小，则影响浸润效率。
第二活性物质区2212b满足特定的面积占比和/或厚度占比，使得第二活性物质区2212b具有合适的分布占比，保证浸润效率的同时，控制极片具有合适的能量密度。
根据本申请的一些实施例，可选地，在极片的宽度方向C上，活性物质层2212的尺寸为M，满足如下条件(f)：(f)在极片的宽度方向C上，第二活性物质区2212b与活性物质层2212的中心的最小距离为d 1，d 1≤M×35％。
d 1≤M×35％，代表在宽度方向C上，第二活性物质区2212b的至少一部分位于活性物质层2212中部该特定宽度的区域内。当d 1＝0，则代表在宽度方向C上第二活性物质区2212b会达到或经过活性物质层2212的中心。
在极片的宽度方向C上，第二活性物质区2212b与活性物质层2212的中心的最小距离小于等于特定标准，使得第二活性物质区2212b具有合适的分布位置，有效提高浸润效率。
根据本申请的一些实施例，可选地，极片的宽度方向C上，活性物质层2212的尺寸为M，满足如下条件(g)：(g)在极片的宽度方向C上，第二活性物质区2212b的与活性物质层2212的边缘的最小距离为d 2，d 2≤M×20％。
d 2≤M×20％，代表在宽度方向C上，第二活性物质区2212b的至少一部分位于活性物质层2212边缘该特定宽度的区域内。当d 2＝0，则代表在宽度方向C上第二活性物质区2212b会达到活性物质层2212边缘。
在极片的宽度方向C上，第二活性物质区2212b与活性物质层2212的边缘的最小距离小于等于特定标准，使得第二活性物质区2212b具有合适的分布位置，有效提高浸润效率。
根据本申请的一些实施例，可选地，在极片的宽度方向C上，活性物质层2212的尺寸为M；第二活性物质区2212b有多个，多个第二活性物质区2212b沿极片的长度方向D间隔分布；满足如下条件(h)～(i)中的至少一个：(h)在极片的宽度方向C上，第二活性物质区2212b与活性物质层2212的中心的最小距离为d 1，d 1≤M×10％；(i)在极片的宽度方向C上，每个第二活性物质区2212b的两端的距离为d 3，d 3≥M×30％。
其中，每个第二活性物质区2212b可以第二活性物质区2212b倾斜设置，如图6和图7。每个第二活性物质区2212b也可以沿极片的宽度方向C延伸，如图9和图10。
d 1≤M×10％，代表在宽度方向C上，第二活性物质区2212b的至少一部分位于活性物质层2212中部该特定宽度的区域内。d 3≥M×30％，代表在宽度方向C上，第二活性物质区2212b至少满足该特定的分布范围。
在极片的宽度方向C上，控制第二活性物质区2212b与活性物质层2212的中心的最小距 离小于等于特定标准，和/或，控制第二活性物质区2212b的两端距离大于等于特定标准，使得沿极片的长度方向D间隔分布的多个第二活性物质区2212b具有合适的分布位置，有效提高浸润效率。
根据本申请的一些实施例，可选地，在极片的宽度方向C上，活性物质层2212的尺寸为M；第二活性物质区2212b有多个，多个第二活性物质区2212b沿极片的宽度方向C间隔分布；在极片的宽度方向C上，相邻两个第二活性物质区2212b之间的间距为d 4，d 4≤M×20％。
其中，每个第二活性物质区2212b可以第二活性物质区2212b倾斜设置，如图6和图7。每个第二活性物质区2212b也可以沿极片的长度方向D延伸，如图8。
在极片的宽度方向C上，控制相邻两个第二活性物质区2212b之间的距离小于等于特定标准，使得沿极片的宽度方向C间隔分布的多个第二活性物质区2212b具有合适的分布位置，有效提高浸润效率。
根据本申请的一些实施例，可选地，活性物质层2212的厚度为h，第二活性物质区2212b的厚度为h 2，h×30％≤h 2≤h×60％，第二活性物质区2212b到活性物质层2212的表面的距离为d 5，活性物质层2212到预设表面2211a的距离为d 6，d 5＜d 6。
作为示例，d 5＝0。
其中，d 5＜d 6代表在纵向截面中，第二活性物质区2212b更靠近活性物质层2212的表面设置。d 5＝0则代表在纵向截面中，第二活性物质区2212b位于活性物质层2212的表面，如图11所示。
在厚度方向上第二活性物质区2212b占活性物质层2212的局部区域，有效提高浸润效率的同时，控制极片具有合适的能量密度。同时，控制第二活性物质区2212b更接近活性物质层2212的表面设置，能够更好地发挥第二活性物质改善浸润效率的作用。
根据本申请的一些实施例，请进一步参阅图14至17，本申请还提供了一种电极组件22，包括正极极片221、隔离膜223和负极极片222，正极极片221和负极极片222中的至少一者为以上任一方案的极片。
其中，图14为包含图6所示的极片的电极组件22；图15为包含图8所示的极片的电极组件22；图16为包含图9所示的极片的电极组件22；图17为包含图10所示的极片的电极组件22。
由于正极极片221的压实密度通常较大，导致正极极片221的孔隙率通常较小，因此正极极片221通常存在浸润效率不足的现象，特别是活性材料为小颗粒的磷酸铁锂的正极极片221。基于此，在电极组件22中，其示例性的正极极片221为以上任一方案的极片，负极极片222可以为以上任一方案的极片，负极极片222也可以为活性物质层2212整体孔隙率一致的结构。
根据本申请的一些实施例，可选地，电极组件22为卷绕结构，极片的宽度方向C与电极组件22的轴向B相同，极片的长度方向D与电极组件22的卷绕方向A相同；电极组件22的直径为d，在电极组件22的卷绕方向A上，每个弧长为πd/4的区域内均具有第二活性物质区2212b的至少一部分。
每个弧长为πD/4的区域内均具有第二活性物质区2212b的至少一部分，使得在电极组件22卷绕方向A上第二活性物质区2212b的分布间距小于等于特定标准，保证电极组件22较好的浸润效果。
根据本申请的一些实施例，本申请还提供了一种电池单体，包括外壳以及以上任一方案的电极组件22；电极组件22容纳于外壳内。
根据本申请的一些实施例，本申请还提供了一种电池，包括箱体以及以上任一方案的电池单体；电池单体容纳于箱体内。
根据本申请的一些实施例，本申请还提供了一种用电设备，包括以上任一方案的电池。
下面对本申请实施例的极片的制备方法进行示例性地说明。
以上任一方案的极片的第一种制备方法，其例如用于制备h 2＝h×100％的活性物质层2212，包括：在浆料涂布阶段，在部分区域涂布重量较少的浆料，然后将整个浆料涂层冷压成厚度一致的结构。整个涂层为活性物质层2212，涂布较少浆料的区域的涂层为第二活性物质区2212b，剩余区域为第一活性物质区2212a。
其中，可以通过在涂布背辊上设置凸起结构，或者在垫片上设置浆料阻拦结构，实现在部分区域涂布重量较少的浆料。
以上任一方案的极片的第二种制备方法，其例如用于制备h 2＝h×100％的活性物质层2212，包括：在浆料涂布阶段完成后，通过激光等手段对部分区域的涂层减薄，然后将整个浆料涂层冷压成厚度一致的结构。整个涂层为活性物质层2212，激光减薄区域的涂层为第二活性物质区2212b，剩余区域为第一活性物质区2212a。
以上任一方案的极片的第三种制备方法，其例如用于制备h 2＝h×100％的活性物质层2212，包括：在浆料涂布阶段完成后，采用刻蚀了局部区域的初轧轧辊，然后再采用平整的轧辊轧制，将整个浆料涂层冷压成厚度一致的结构。整个涂层为活性物质层2212，初轧轧辊刻蚀区域对应的涂层为第二活性物质区2212b，剩余区域为第一活性物质区2212a。
以上任一方案的极片的第四种制备方法，其例如用于制备h 2＜h×100％的活性物质层2212，包括：采用多层涂布方式，在需要形成第二活性物质区2212b的涂布层中，不同区域使用不同的浆料，使得部分区域涂布重量较少的浆料。多层涂布完成后，将整个浆料涂层冷压成厚度一致的结构。整个涂层为活性物质层2212，涂布较少浆料的区域的涂层为第二活性物质区2212b，剩余区域为第一活性物质区2212a。
下面列举了一些具体实施例以更好地对本申请进行说明。
正极极片制备：将活性材料、导电剂(super P碳黑)、聚偏氟乙烯(PVDF)、N-甲基吡咯烷酮(NMP)按照92:3:5:100的质量比例混合，以800r/min速度搅拌12h后制得浆料。采用挤压涂布将浆料涂覆在铝箔上，涂布所用背辊中间设置凸起结构(用于形成第二活性物质区)，经烘烤，辊压、分切后得到正极极片。其中，活性材料为磷酸铁锂。
负极极片制备：将活性材料、导电剂(super P碳黑)、羧甲基纤维素钠(CMC)、丁苯橡胶(SBR)、去离子水按照90:2.5:2.5:5:100的质量比例混合，以800r/min速度搅拌12h后制得浆料，采用挤压涂布将浆料涂覆在铜箔上，经烘烤，辊压、分切后得到负极极片。
电解液制备：在含水量<10ppm的氩气气氛手套箱中，将质量比为25:20:55的碳酸亚乙酯(EC)、碳酸二甲酯(DMC)、碳酸甲乙酯(EMC)进行均匀混合，得到混合溶剂；再将充分干燥的六氟磷酸锂(LiPF 6)溶解于上述混合溶剂中，搅拌均匀后，获得电解液。其中，六氟磷酸锂(LiPF 6)的浓度为1.2mol/L。
装配：将上述正极极片、隔离膜、负极极片按顺序进行组装然后沿卷绕方向卷绕成圆柱状的卷绕结构，加入上述电解液后进行搁置浸润，封口，得到电池单体。
其中，隔离膜采用聚乙烯膜。
各实施例和对比例的电池单体的参数条件如表1所示。
Figure PCTCN2021123916-appb-000001
其中，第二活性物质区位置，是指在纵向截面中第二活性物质区在活性物质层的厚度方向上的位置。
在实施例1至实施例6中，正极极片在横向截面中的结构如图8所示。其中，第二活性物质区为6个，沿极片的宽度方向均匀分布；两侧的d 2均为50mm，d 3为20mm，d 4为36mm，S 2为S×30％。
在实施例7至实施例12中，正极极片在横向截面中的结构如图9所示。其中，两侧的d 2均为50mm，d 3为300mm；在极片的长度方向上，每个第二活性物质区的尺寸为10mm，相邻两个第二活性物质区的中心的距离为40mm；S 2为S×18.75％。
对搁置浸润的时间进行记录。
按照0.1C充电对电池单体进行化成激活，并按1C充放电进行容量测试，然后按照1C充放电流程进行循环测试，循环按电池单体100％电量进行充放，得到循环寿命数据。
其中，以对比例作为参比，计算各实施例的电池单体的容量损失率；以循环300圈的循环容量保持率表示循环寿命数据。
各实施例和对比例的电池单体的性能数据如表2所示。
表2
Figure PCTCN2021123916-appb-000002
根据表1和表2可知：
实施例1至实施例12中，正极极片配置为第二活性物质区域的孔隙率大于第一活性物质区域的孔隙率。对比例中，正极极片配置为第二活性物质区域的孔隙率等于第一活性物质区域的孔隙率。
实施例1至实施例12分别与对比例相比，均表现出：电芯容量损失率较小；循环容量保持率高，使得循环寿命得到改善；浸润时间明显减少，说明浸润效率提高。说明孔隙率相对较大的第二活性物质区的设置能够有效提高浸润效率并提高循环寿命，且对电芯容量影响较小。
实施例1至实施例3中，实施例2中P 2和P 1的差值在10％～15％的范围内，实施例1和实施例3的中P 2和P 1的差值不在10％～15％的范围内。实施例7至实施例9以及实施例12中，实施 例7、实施例9以及实施例12中P 2和P 1的差值在10％～15％的范围内，实施例8的中P 2和P 1的差值不在10％～15％的范围内。
实施例2和实施例1相比，实施例2的循环容量保持率更高。实施例2和实施例3相比，实施例2的循环容量保持率更高，且浸润时间更短。与实施例8相比，实施例7、实施例9以及实施例12均表现出：循环容量保持率更高，且浸润时间更短。说明P 2和P 1的差值在10％～15％的范围内时，第二活性物质区域能够较好地提高浸润效率并提高循环寿命。
在实施例2和实施例5中，实施例2中第二活性物质区位于活性物质层表面，实施例5中第二活性物质区位于活性物质层底部。实施例9至实施例11中，实施例9中第二活性物质区在活性物质层整个厚度方向上分布，实施例10第二活性物质区位于活性物质层表面，实施例11中第二活性物质区位于活性物质层底部。
和实施例5相比，实施例2的循环容量保持率更高，且浸润时间更短。说明将第二活性物质区域靠近活性物质层表面设置，能够更好地提高浸润效率并提高循环寿命。在实施例9至实施例11中，浸润时间逐渐增加，说明：将第二活性物质区在活性物质层整个厚度方向上分布有较好的浸润效率；第二活性物质区在活性物质层分布在活性物质层厚度方向上的局部时，将第二活性物质区域靠近活性物质层表面设置，能够更好地提高浸润效率并提高循环寿命。

Claims (15)

  1. 一种极片，包括集流体；以及活性物质层，位于所述集流体的至少一侧表面，其中，
    所述活性物质层具有第一活性物质区和第二活性物质区；在预设截面中，所述第二活性物质区的截面积为S 2，所述活性物质层的截面积为S，S 2＜S；所述集流体中所述活性物质层所在表面为预设表面，所述预设截面平行于所述预设表面，且经过所述第二活性物质区；
    所述第一活性物质区的孔隙率为P 1，所述第二活性物质区的孔隙率为P 2，P 1＜P 2；
    所述第一活性物质区和所述第二活性物质区的孔的孔径均≤1μm。
  2. 根据权利要求1所述的极片，其中，P 2和P 1的差值为3％～20％，可选地为7％～15％，进一步可选地为10％～15％。
  3. 根据权利要求1或2所述的极片，其中，
    P 1为15％～35％，可选地为15％～25％，进一步可选地为20％～25％；和/或，P 2为20％～50％，可选地为20％～40％，进一步可选地为25％～40％。
  4. 根据权利要求1～3中任一项所述的极片，其中，所述第一活性物质区的压实密度为C 1，所述第二活性物质区的压实密度为C 2，且满足如下条件(a)～(c)中的任意一个：
    (a)所述第一活性物质区和所述第二活性物质区的活性物质均为磷酸铁锂，C 1和C 2的比值为1.02～1.7；
    可选的，C 1为2.3g/cm 3～2.7g/cm 3，C 2为1.6g/cm 3～2.2g/cm 3；
    (b)所述第一活性物质区和所述第二活性物质区的活性物质均为三元正极材料，C 1和C 2的比值为1.02～1.5；
    可选的，C 1为3.1g/cm 3～3.7g/cm 3，C 2为2.5g/cm 3～3g/cm 3；
    (c)所述第一活性物质区和所述第二活性物质区的活性物质均为石墨，C 1和C 2的比值为1.1～1.7；
    可选的，C 1为1.3g/cm 3～1.8g/cm 3，C 2为1.1g/cm 3～1.5g/cm 3。
  5. 根据权利要求1～4中任一项所述的极片，其中，满足如下条件(d)～(e)中的至少一个：
    (d)S×2.5％≤S 2≤S×30％；
    (e)所述活性物质层的厚度为h，所述第二活性物质区的厚度为h 2，h×30％≤h 2≤h×100％。
  6. 根据权利要求1～5中任一项所述的极片，其中，在所述极片的宽度方向上，所述活性物质层的尺寸为M，满足如下条件(f)：
    (f)在所述极片的宽度方向上，所述第二活性物质区与所述活性物质层的中心的最小距离为d 1，d 1≤M×35％。
  7. 根据权利要求1～6中任一项所述的极片，其中，在所述极片的宽度方向上，所述活性物质层的尺寸为M，满足如下条件(g)：
    (g)在所述极片的宽度方向上，所述第二活性物质区的与所述活性物质层的边缘的最小距离为d 2，d 2≤M×20％。
  8. 根据权利要求1～7中任一项所述的极片，其中，在所述极片的宽度方向上，所述活性物质层的尺寸为M；所述第二活性物质区有多个，多个所述第二活性物质区沿所述极片的长度方向间隔分布；满足如下条件(h)～(i)中的至少一个：
    (h)在所述极片的宽度方向上，所述第二活性物质区与所述活性物质层的中心的最小距离为d 1，d 1≤M×10％；
    (i)在所述极片的宽度方向上，每个所述第二活性物质区的两端的距离为d 3，d 3≥M×30％。
  9. 根据权利要求1～8中任一项所述的极片，其中，在所述极片的宽度方向上，所述活性物质层的尺寸为M；所述第二活性物质区有多个，多个所述第二活性物质区沿所述极片的宽度方向间隔分布；
    在所述极片的宽度方向上，相邻两个所述第二活性物质区之间的间距为d 4，d 4≤M×20％。
  10. 根据权利要求1～9中任一项所述的极片，其中，所述活性物质层的厚度为h，所述第二活性物质区的厚度为h 2，h×30％≤h 2≤h×60％，所述第二活性物质区到所述活性物质层的表面的距离为d 5，所述活性物质层到所述预设表面的距离为d 6，d 5＜d 6。
  11. 一种电极组件，包括正极极片、隔离膜和负极极片，其中，所述正极极片和所述负极极片中的至少一者为如权利要求1～10中任一项所述的极片。
  12. 根据权利要求11所述的电极组件，其中，所述电极组件为卷绕结构，所述极片的宽度方向与所述电极组件的轴向相同，所述极片的长度方向与所述电极组件的卷绕方向相同；
    所述电极组件的直径为d，在所述电极组件的卷绕方向上，每个弧长为πd/4的区域内均具有所述第二活性物质区的至少一部分。
  13. 一种电池单体，其中，包括外壳以及如权利要求11或12所述的电极组件；
    所述电极组件容纳于所述外壳内。
  14. 一种电池，其中，包括箱体以及如权利要求13所述的电池单体；
    所述电池单体容纳于所述箱体内。
  15. 一种用电设备，其中，包括如权利要求14所述的电池。
PCT/CN2021/123916 2021-10-14 2021-10-14 一种极片、电极组件、电池单体、电池以及用电设备 WO2023060517A1 (zh)

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