WO2022165690A1 - 电极组件及其制造方法和制造系统、电池单体以及电池 - Google Patents

电极组件及其制造方法和制造系统、电池单体以及电池 Download PDF

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Publication number
WO2022165690A1
WO2022165690A1 PCT/CN2021/075166 CN2021075166W WO2022165690A1 WO 2022165690 A1 WO2022165690 A1 WO 2022165690A1 CN 2021075166 W CN2021075166 W CN 2021075166W WO 2022165690 A1 WO2022165690 A1 WO 2022165690A1
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WIPO (PCT)
Prior art keywords
active material
unit area
per unit
pole piece
bending
Prior art date
Application number
PCT/CN2021/075166
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English (en)
French (fr)
Inventor
黄思应
刘金龙
王耀辉
邹启凡
毛恒山
林亮标
林银祥
Original Assignee
宁德时代新能源科技股份有限公司
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Application filed by 宁德时代新能源科技股份有限公司 filed Critical 宁德时代新能源科技股份有限公司
Priority to EP21904630.7A priority Critical patent/EP4068452A4/en
Priority to PCT/CN2021/075166 priority patent/WO2022165690A1/zh
Priority to CN202180006321.0A priority patent/CN115210925A/zh
Priority to US17/843,370 priority patent/US20220320596A1/en
Publication of WO2022165690A1 publication Critical patent/WO2022165690A1/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
    • 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
    • H01M10/058—Construction or manufacture
    • H01M10/0587—Construction or manufacture of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators
    • 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
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/50—Current conducting connections for cells or batteries
    • H01M50/531—Electrode connections inside a battery casing
    • H01M50/538—Connection of several leads or tabs of wound or folded electrode stacks
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/50—Current conducting connections for cells or batteries
    • H01M50/543—Terminals
    • H01M50/552—Terminals characterised by their shape
    • H01M50/553—Terminals adapted for prismatic, pouch or rectangular cells
    • H01M50/557—Plate-shaped terminals
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present application relates to the field of battery technology, and more particularly, to an electrode assembly, a manufacturing method and a manufacturing system thereof, a battery cell, and a battery.
  • lithium-ion batteries are generally used in vehicles.
  • As a rechargeable battery lithium-ion batteries have the advantages of small size, high energy density, high power density, many cycles of use and long storage time.
  • a rechargeable battery generally includes a casing and an electrode assembly.
  • the casing is used to accommodate the electrode assembly and electrolyte.
  • the electrode assembly generally includes a positive electrode and a negative electrode, and metal ions (such as lithium ions) are used in the positive electrode and the negative electrode. move between the sheets to generate electricity.
  • the present application provides an electrode assembly, a manufacturing method and a manufacturing system thereof, a battery cell, a battery and an electrical device, so as to improve the problem of unreasonable arrangement of active materials in the electrode sheet.
  • an embodiment of the present application provides an electrode assembly, which includes a negative electrode piece and a positive electrode piece, the negative electrode piece and the positive electrode piece are wound along a winding direction to form a winding structure, and the winding structure includes a bending Area.
  • Both the negative pole piece and the positive pole piece include a plurality of bending parts located in the bending region.
  • At least one innermost bent portion in the negative pole piece is a first bent portion, and the active material capacity per unit area outside the first bent portion is greater than the active material capacity per unit area inside the first bent portion; and/ Or, at least one innermost bent portion of the positive electrode sheet is the second bent portion, and the active material capacity per unit area outside the second bent portion is greater than the active material capacity per unit area inside the second bent portion.
  • the active material capacity per unit area on the outside of the first bent portion of the negative pole piece is greater than the active material capacity per unit area on the inside of the first bent portion.
  • the arrangement of the active material in at least part of the region of the negative electrode pole piece (the region where the first bent portion is located) is more reasonable.
  • the capacity of active material per unit area outside the second bent portion of the positive electrode sheet is greater than the capacity of active material per unit area inside the second bent portion, and it is not easy to cause insufficient active material on the outside of the second bent portion, while the inner side of the second bent portion is less likely to occur.
  • the arrangement of the active material in at least part of the region of the positive electrode sheet (the region where the second bending portion is located) is more reasonable.
  • the arrangement of the active material in at least a part of the region of the pole piece is more reasonable and has better economical efficiency.
  • At least one innermost folded portion in the negative pole piece is a first folded portion
  • at least one innermost folded portion in the positive pole piece is a second folded portion
  • the first folded portion is A second bent portion adjacent to the first bent portion is arranged on the outer side of the portion.
  • the active material capacity per unit area outside the first bending portion is greater than the first bending portion.
  • the active material capacity per unit area inside the second bending part is larger than the active material capacity per unit area inside the second bending part, which can increase the CB value of the outer part of the first bending part, Thereby reducing the occurrence of lithium precipitation.
  • At least one innermost bent portion of the negative pole piece is the first bent portion.
  • the bending portion adjacent to the first bending portion is the third bending portion.
  • the active material capacity per unit area of the outer side of the third bent portion is equal to the active material capacity per unit area of the inner side of the third bent portion.
  • the bending part adjacent to the first bending part in the positive electrode piece is the third bending part, and the active material capacity per unit area outside the first bending part is greater than the unit area inside the first bending part.
  • the active material capacity per unit area outside the third bending portion may be equal to the active material capacity per unit area inside the third bending portion, which can simplify the manufacturing process of the positive electrode sheet.
  • At least one innermost bent portion of the positive electrode sheet is the second bent portion.
  • the bending part adjacent to the second bending part is the fourth bending part.
  • the active material capacity per unit area of the outer side of the fourth bent portion is equal to the active material capacity per unit area of the inner side of the fourth bent portion.
  • the active material capacity per unit area outside the second bent portion may be greater than the active material capacity per unit area inside the second bent portion
  • the active material capacity per unit area outside the fourth bent portion may be equal to the inside of the fourth bent portion The active material capacity per unit area to simplify the manufacturing process of the negative pole piece.
  • the first bent portion includes a first current collecting portion, a first active material portion, and a second active material portion.
  • the first current collecting part has a first inner surface and a first outer surface arranged opposite to each other in its thickness direction, the first active material part is provided on the first outer surface, and the second active material part is provided on the first inner surface.
  • the thickness of the first active material portion is greater than the thickness of the second active material portion.
  • the thickness of the first active material portion is greater than the thickness of the second active material portion, so that the active material capacity per unit area of the first active material portion is greater than the active material capacity per unit area of the second active material portion, thereby realizing the first active material portion.
  • the capacity per unit area of the active material outside the bent portion is larger than the capacity per unit area of the active material inside the first bent portion.
  • the first bent portion further includes a first conductive portion, the first conductive portion is connected between the second active material portion and the first inner surface, and the thickness of the first active material portion is greater than or equal to the second active material portion The total thickness of the substance portion and the first conductive portion.
  • the thickness of the first active material portion is greater than or equal to the total thickness of the second active material portion and the first conductive portion, In order to realize that the thickness of the first active material portion is greater than the thickness of the second active material portion.
  • the gram capacity of active material in the first active material portion is greater than the gram capacity of active material in the second active material portion.
  • the gram capacity of the active material in the first active material portion is greater than the gram capacity of the active material in the second active material portion, so that the active material capacity per unit area of the first active material portion is greater than that of the second active material portion.
  • the capacity of the active material per unit area, so that the capacity of the active material per unit area outside the first bending portion is greater than the capacity per unit area of the active material inside the first bending portion.
  • the weight ratio of the active material in the first active material part to the first active material part is greater than the weight ratio of the active material in the second active material part to the second active material part, so as to realize the first bending
  • the capacity per unit area of the active material outside the portion is larger than the capacity per unit area of the active material inside the first bent portion.
  • the first bending portion further includes a first conductive portion, the first conductive portion is connected between the first active material portion and the first outer surface, and the first conductive portion contains an active material.
  • the thickness of the second active material portion is greater than or equal to the total thickness of the first active material portion and the first conductive portion.
  • the gram capacity of the active material in the first active material part is smaller than the gram capacity of the active material in the first conductive part, so that the active material capacity per unit area outside the first bending part is greater than the active material per unit area inside the first bending part or, the weight ratio of the active material in the first active material part to the first active material part is smaller than the weight ratio of the active material in the first conductive part to the first conductive part, so as to realize the outer side of the first bending part.
  • the capacity of the active material per unit area is larger than the capacity of the active material per unit area inside the first bent portion.
  • the second bent portion includes a second current collecting portion, a third active material portion, and a fourth active material portion.
  • the second current collecting portion has a second inner surface and a second outer surface oppositely arranged in the thickness direction thereof, the third active material portion is provided on the second outer surface, and the fourth active material portion is provided on the second inner surface.
  • the thickness of the third active material portion is greater than the thickness of the fourth active material portion.
  • the thickness of the third active material portion is greater than the thickness of the fourth active material portion, so that the capacity of the active material per unit area of the third active material portion is greater than the capacity of the active material per unit area of the fourth active material portion, thereby achieving The capacity per unit area of the active material outside the second bent portion is larger than the capacity per unit area of the active material inside the second bent portion.
  • the second bent portion further includes a second conductive portion, the second conductive portion is connected between the fourth active material portion and the second inner surface, and the thickness of the third active material portion is greater than or equal to the thickness of the fourth active material portion and the second conductive portion the total thickness of the part.
  • the gram capacity of the active material in the third active material portion is greater than the gram capacity of the active material in the fourth active material portion, so that the active material capacity per unit area of the third active material portion is greater than that of the fourth active material
  • the active material capacity per unit area of the second bending part is larger than the active material capacity per unit area of the inner side of the second bending part.
  • the weight ratio of the active material in the third active material part to the third active material part is greater than the weight ratio of the active material in the fourth active material part to the fourth active material part, so that the third active material
  • the active material capacity per unit area of the fourth active material portion is greater than that of the fourth active material portion, so that the active material capacity per unit area outside the second bending portion is greater than the active material capacity per unit area inside the second bending portion.
  • the negative electrode sheet includes a negative electrode current collector, a first negative electrode active material layer and a second negative electrode active material layer, the first negative electrode active material layer is located outside the negative electrode current collector, and the second negative electrode active material layer is located on the negative electrode collector inside of the fluid.
  • the first negative electrode active material layer includes a first portion and a second portion disposed along the winding direction, the first portion extending from the starting end of the first negative electrode active material layer along the winding direction, and the second portion being arranged continuously with the first portion along the winding direction , and the thickness of the first part is greater than the thickness of the second part, and the thickness of the second part is equal to the thickness of the second negative electrode active material layer.
  • the first active material part is a part of the first part located in the first bending part.
  • the first portion is wound at least one turn along the winding direction, so that at least one innermost bent portion of the negative pole piece can be the first bent portion.
  • the positive electrode sheet includes a positive electrode current collector, a first positive electrode active material layer and a second positive electrode active material layer, the first positive electrode active material layer is located outside the positive electrode current collector, and the second positive electrode active material layer is located on the positive electrode collector inside of the fluid.
  • the second positive electrode active material layer includes a third portion and a fourth portion arranged along the winding direction, the third portion extending from the starting end of the second positive electrode active material layer along the winding direction, and the fourth portion and the third portion along the winding direction
  • the parts are arranged continuously, and the thickness of the third part is smaller than the thickness of the fourth part, and the thickness of the fourth part is equal to the thickness of the first positive electrode active material layer.
  • the fourth active material portion is a portion of the third portion located in the second bent portion.
  • the third portion is wound at least one turn along the winding direction, so that at least one innermost bent portion of the positive pole piece can be the second bent portion.
  • the plurality of bent portions in the negative pole piece sequentially arranged from the innermost to the outside are the first bent portions.
  • the bending part located outside the plurality of first bending parts is the fourth bending part, and the active material capacity per unit area outside the fourth bending part is equal to the activity per unit area inside the fourth bending part material capacity.
  • the fourth bent portion does not need to increase the capacity of the active material per unit area on the outside, so that the amount of active material can be saved.
  • the plurality of bent portions in the positive electrode piece that are sequentially arranged from the innermost to the outside are the second bent portions.
  • the bent portion located outside the plurality of second bent portions is the third bent portion, and the active material capacity per unit area outside the third bent portion is equal to the activity per unit area of the inner side of the third bent portion. material capacity.
  • the third bent portion does not need to reduce the capacity of the active material per unit area inside, so that the capacity of the electrode assembly can be guaranteed.
  • an embodiment of the present application provides a battery cell, which includes a casing and the electrode assembly provided by any embodiment of the above-mentioned first aspect.
  • the electrode assembly is accommodated in the housing.
  • an embodiment of the present application provides a battery, which includes a case and the battery cell provided by any embodiment of the second aspect.
  • the battery cells are accommodated in the case.
  • an embodiment of the present application provides an electrical device, which includes the battery provided by any embodiment of the third aspect, and the battery is used to provide electrical energy.
  • an embodiment of the present application provides a method for manufacturing an electrode assembly, which includes: providing a positive pole piece; providing a negative pole piece; winding the negative pole piece and the positive pole piece along a winding direction to form a winding structure .
  • the winding structure includes a bending area
  • both the negative pole piece and the positive pole piece include a plurality of bending parts located in the bending area.
  • At least one innermost bent portion in the negative pole piece is a first bent portion, and the active material capacity per unit area outside the first bent portion is greater than the active material capacity per unit area inside the first bent portion; and/or, At least one innermost bent portion in the positive electrode sheet is a second bent portion, and the active material capacity per unit area outside the second bent portion is greater than the active material capacity per unit area inside the second bent portion.
  • the step of providing a negative electrode sheet includes: providing a negative electrode current collector; coating a first negative electrode active material layer on one surface of the negative electrode current collector; coating a second negative electrode active material layer on the other surface of the negative electrode current collector material layer.
  • the first negative electrode active material layer is located on the outer side of the negative electrode current collector, and the second negative electrode active material layer is located on the inner side of the negative electrode current collector;
  • the first negative electrode active material layer includes the first part and The second part, the first part extends from the starting end of the first negative electrode active material layer in the winding direction, the second part is arranged continuously with the first part in the winding direction, and the thickness of the first part is greater than that of the second part, the second part is is equal to the thickness of the second negative electrode active material layer. At least a portion of the first portion is located at the first bent portion.
  • the step of coating a first negative electrode active material layer on one surface of the negative electrode current collector includes: coating a negative electrode active slurry on one surface of the negative electrode current collector to form a first active coating; A part of the surface of the active coating layer facing away from the negative electrode current collector is coated with negative electrode active slurry to form a second active coating layer; the first active coating layer and the second active coating layer are cured to form a first negative electrode active material layer.
  • the part of the first active coating that is coated with the second active coating and the second active coating form the first part after curing; the part of the first active coating that is not coated with the second active coating is cured after curing form the second part.
  • the step of providing a positive electrode sheet includes: providing a positive electrode current collector; coating a first positive electrode active material layer on one surface of the positive electrode current collector; coating a second positive electrode active material layer on the other surface of the positive electrode current collector material layer.
  • the first positive electrode active material layer is located on the outer side of the positive electrode current collector, and the second positive electrode active material layer is located on the inner side of the positive electrode current collector;
  • the second positive electrode active material layer includes a third part arranged along the winding direction and a fourth part, the third part extends from the starting end of the second positive electrode active material layer in the winding direction, the fourth part is arranged continuously with the third part in the winding direction, and the thickness of the third part is smaller than that of the fourth part , the thickness of the fourth part is equal to the thickness of the first positive electrode active material layer.
  • At least part of the third portion is located at the second bent portion.
  • the step of coating the second positive electrode active material layer on the other surface of the positive electrode current collector includes: coating the positive electrode active slurry on the other surface of the positive electrode current collector to form a third active coating layer; A portion of the surface of the third active coating layer facing away from the positive electrode current collector is coated with positive electrode active slurry to form a fourth active coating layer; the third active coating layer and the fourth active coating layer are cured to form a second positive electrode active material layer.
  • the portion of the third active coating that is not coated with the fourth active coating forms a third portion after curing, and the portion of the third active coating that is coated with the fourth active coating and the fourth active coating are cured after curing. Then form the fourth part.
  • an embodiment of the present application provides a manufacturing system for an electrode assembly, which includes: a first providing device for providing a positive pole piece; a second providing device for providing a negative pole piece; and an assembling device for providing a negative pole piece
  • the pole piece and the positive pole piece are wound along the winding direction and form a winding structure.
  • the winding structure includes a bending area
  • both the negative pole piece and the positive pole piece include a plurality of bending parts located in the bending area.
  • At least one innermost bent portion in the negative pole piece is a first bent portion, and the active material capacity per unit area outside the first bent portion is greater than the active material capacity per unit area inside the first bent portion; and/or, At least one innermost bent portion in the positive electrode sheet is a second bent portion, and the active material capacity per unit area outside the second bent portion is greater than the active material capacity per unit area inside the second bent portion.
  • FIG. 1 is a schematic structural diagram of a vehicle provided by some embodiments of the present application.
  • FIG. 2 is an exploded schematic diagram of a battery provided by some embodiments of the present application.
  • FIG. 3 is a schematic structural diagram of the battery module shown in FIG. 2;
  • FIG. 4 is an exploded schematic diagram of the battery cell shown in FIG. 3;
  • FIG. 5 is a schematic structural diagram of an electrode assembly provided by some embodiments of the present application.
  • FIG. 6 is an enlarged schematic view of the electrode assembly shown in FIG. 5 at block D;
  • FIG. 7 is a schematic structural diagram of electrode assemblies provided by further embodiments of the present application.
  • FIG. 8 is a schematic structural diagram of electrode assemblies provided by other embodiments of the present application.
  • FIG. 9 is a partial enlarged schematic view of the bending region of the electrode assembly shown in FIG. 8;
  • FIG. 10 is a partial schematic diagram of the negative pole piece shown in FIG. 8 in an unfolded state
  • FIG. 11 is an enlarged schematic view of the electrode assembly shown in FIG. 8 at block E;
  • FIG. 12 is a partial enlarged view of a portion of the electrode assembly located in the bending region provided by some embodiments of the present application;
  • FIG. 13 is a partial enlarged view of a portion of the electrode assembly located in the bending region provided by other embodiments of the present application;
  • FIG. 14 is a partial enlarged view of a portion of the electrode assembly located in the bending region according to further embodiments of the present application.
  • FIG. 15 is a schematic structural diagram of electrode assemblies provided by further embodiments of the present application.
  • FIG. 16 is a partially enlarged schematic view of the bending region of the electrode assembly shown in FIG. 15;
  • FIG. 17 is a partial schematic view of the positive pole piece shown in FIG. 15 in an unfolded state
  • FIG. 18 is an enlarged schematic view of the electrode assembly shown in FIG. 15 at block F;
  • FIG. 19 is a partial enlarged view of a portion of the electrode assembly located in the bending region according to further embodiments of the present application.
  • FIG. 20 is a partial enlarged view of a portion of the electrode assembly located in the bending region provided by other embodiments of the present application;
  • FIG. 21 is a partial enlarged view of a portion of the electrode assembly located in the bending region according to further embodiments of the present application.
  • 22 is a flowchart of a method for manufacturing an electrode assembly provided by some embodiments of the present application.
  • FIG. 23 is a schematic diagram of the negative pole piece provided in some embodiments of the present application during the forming process
  • 24 is another schematic diagram of the negative electrode pole piece provided by some embodiments of the present application during the forming process
  • FIG. 25 is a schematic diagram of the positive pole piece provided in some embodiments of the present application during the forming process
  • FIG. 26 is another schematic diagram of the positive pole piece provided by some embodiments of the application during the forming process.
  • FIG. 27 is a schematic block diagram of a manufacturing system of an electrode assembly provided by some embodiments of the present application.
  • the terms “installed”, “connected”, “connected” and “attached” should be understood in a broad sense, for example, it may be a fixed connection, It can also be a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be internal communication between two components.
  • installed should be understood in a broad sense, for example, it may be a fixed connection, It can also be a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be internal communication between two components.
  • plural refers to two or more (including two).
  • the battery cells may include lithium-ion secondary battery cells, lithium-ion primary battery cells, lithium-sulfur battery cells, sodium-lithium-ion battery cells, sodium-ion battery cells, or magnesium-ion battery cells, etc., This embodiment of the present application does not limit this.
  • the battery cell may be in the form of a cylinder, a flat body, a rectangular parallelepiped, or other shapes, which are not limited in the embodiments of the present application.
  • the battery cells are generally divided into three types according to the packaging method: cylindrical battery cells, square battery cells, and soft-pack battery cells, which are not limited in the embodiments of the present application.
  • the battery mentioned in the embodiments of the present application refers to a single physical module including one or more battery cells to provide higher voltage and capacity.
  • the batteries mentioned in this application may include battery modules or battery packs, and the like.
  • Batteries typically include a case for enclosing one or more battery cells. The box can prevent liquids or other foreign objects from affecting the charging or discharging of the battery cells.
  • the battery cell includes an electrode assembly and an electrolyte, and the electrode assembly is composed of a positive pole piece, a negative pole piece and a separator.
  • the battery cell mainly relies on the movement of metal ions between the positive pole piece and the negative pole piece to work.
  • 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 without the positive electrode active material layer protrudes from the positive electrode collector coated with the positive electrode active material layer.
  • the fluid, the positive electrode current collector without the positive electrode active material layer was 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 cobalt oxide, lithium iron phosphate, ternary lithium or lithium manganate, etc.
  • the negative electrode pole piece 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 without the negative electrode active material layer is protruded from the negative electrode collector that has been coated with the negative electrode active material layer. Fluid, the negative electrode current collector without the negative electrode active material layer is used as the negative electrode tab.
  • the material of the negative electrode current collector can be copper, and the negative electrode active material can be carbon or silicon.
  • the number of positive tabs is multiple and stacked together, and the number of negative tabs is multiple and stacked together.
  • the material of the isolation film may be PP (polypropylene, polypropylene) or PE (polyethylene, polyethylene) or the like.
  • the electrode assembly may be a wound structure or a laminated structure, and the embodiment of the present application is not limited thereto.
  • the thickness of the inner active material layer of the negative pole piece in the electrode assembly is equal to the thickness of the outer active material layer of the negative pole piece, and the active material of the inner active material layer of the negative pole piece and the outer active material layer is the same;
  • the thickness of the inner active material layer of the sheet is equal to that of the outer active material layer of the positive electrode sheet, and the active material of the inner active material layer of the positive electrode sheet is the same as the active material of the outer active material layer.
  • the radius of the inner active material layer of the negative pole piece is larger than the radius of the outer active material layer of the positive pole piece located inside the negative pole piece, while the radius of the outer active material layer of the negative pole piece will be smaller than The radius of the inner active material layer of the positive pole piece on the outside of the negative pole piece, so that the inner active material of the bending part of the negative pole piece in the bending area is excessive, and the outer active material is insufficient.
  • the outer active material of the bent portion of the positive pole piece is insufficient and the inner active material is excessive; in particular, the closer to the center of the winding, the more serious this situation is.
  • the electrode assembly of this structure has unreasonable arrangement of the active material in the pole piece, and is less economical.
  • both the negative pole piece and the positive pole piece include a plurality of bending parts located in the bending area, and at least one innermost bending part in the negative pole piece is the first bending part Bending part, the active material capacity per unit area outside the first bending part is greater than the active material capacity per unit area inside the first bending part; and/or, at least one innermost bending part in the positive electrode piece is the second bending part.
  • the capacity per unit area of the active material outside the second folded portion is greater than the capacity of the active material per unit area on the inner side of the second folded portion.
  • Electrical equipment can be vehicles, mobile phones, portable devices, notebook computers, ships, spacecraft, electric toys and power tools, and so on.
  • Vehicles can be fuel vehicles, gas vehicles or new energy vehicles, and new energy vehicles can be pure electric vehicles, hybrid vehicles or extended-range vehicles, etc.
  • spacecraft include airplanes, rockets, space shuttles, spacecraft, etc.
  • electric toys include fixed Electric toys that are portable or mobile, such as game consoles, electric car toys, electric ship toys and electric airplane toys, etc.
  • electric tools include metal cutting power tools, grinding power tools, assembling power tools and railway power tools, such as, Electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, electric impact drills, concrete vibrators and electric planers, etc.
  • the embodiments of the present application do not impose special restrictions on the above-mentioned electrical equipment.
  • the electric device is a vehicle as an example for description.
  • FIG. 1 is a schematic structural diagram of a vehicle 1 according to some embodiments of the present application.
  • a battery 2 is disposed inside the vehicle 1 , and the battery 2 can be disposed at the bottom, head or tail of the vehicle 1 .
  • the battery 2 can be used for power supply of the vehicle 1 , for example, the battery 2 can be used as an operating power source of the vehicle 1 .
  • the vehicle 1 may also include a controller 3 and a motor 4, and the controller 3 is used to control the battery 2 to supply power to the motor 4, for example, for starting, navigating, and driving the vehicle 1 for work power requirements.
  • the battery 2 can not only be used as the operating power source of the vehicle 1 , but can also be used as the driving power source of the vehicle 1 to provide driving power for the vehicle 1 instead of or partially instead of fuel or natural gas.
  • FIG. 2 is an exploded schematic diagram of a battery 2 provided by some embodiments of the present application.
  • the battery 2 includes a case 5 and battery cells (not shown in FIG. 2 ), and the battery cells are accommodated in the case 5 .
  • the box body 5 is used for accommodating the battery cells, and the box body 5 can have various structures.
  • the box body 5 may include a first box body part 51 and a second box body part 52, the first box body part 51 and the second box body part 52 are covered with each other, and the first box body part 51 and the second box body part 52 cover each other.
  • the two box parts 52 together define an accommodating space 53 for accommodating battery cells.
  • the second box portion 52 may be a hollow structure with one end open, the first box portion 51 is a plate-like structure, and the first box portion 51 is covered with the opening side of the second box portion 52 to form an accommodating space 53
  • the first box part 51 and the second box part 52 can also be hollow structures with one side open, and the opening side of the first box part 51 is covered with the opening side of the second box part 52 , so as to form the box body 5 with the accommodating space 53 .
  • the first case portion 51 and the second case portion 52 may have various shapes, such as a cylinder, a rectangular parallelepiped, and the like.
  • a sealing member such as a sealant, a sealing ring, etc., may also be provided between the first case part 51 and the second case part 52 .
  • the first case portion 51 may also be referred to as an upper case cover, and the second case portion 52 may also be referred to as a lower case body.
  • the battery 2 there may be one battery cell or a plurality of battery cells. If there are multiple battery cells, the multiple battery cells can be connected in series or in parallel or in a mixed connection.
  • a mixed connection means that there are both series and parallel connections in the multiple battery cells. Multiple battery cells can be directly connected in series or in parallel or mixed together, and then the whole composed of multiple battery cells can be accommodated in the box 5; of course, multiple battery cells can also be connected in series or in parallel or
  • the battery modules 6 are formed in a mixed connection, and a plurality of battery modules 6 are connected in series or in parallel or in a mixed connection to form a whole, and are accommodated in the box 5 .
  • FIG. 3 is a schematic structural diagram of the battery module 6 shown in FIG. 2 .
  • a plurality of battery modules 6 are connected in series or in parallel or mixed to form a whole, and are accommodated in the box.
  • the plurality of battery cells 7 in the battery module 6 can be electrically connected through a bus component, so as to realize parallel connection, series connection or mixed connection of the plurality of battery cells 7 in the battery module 6 .
  • FIG. 4 is an exploded schematic diagram of the battery cell 7 shown in FIG. 3 .
  • the battery cell 7 provided in the embodiment of the present application includes an electrode assembly 10 and a casing 20 , and the electrode assembly 10 is accommodated in the casing 20 .
  • the housing 20 may also be used to contain an electrolyte, such as an electrolyte.
  • the housing 20 can be in a variety of configurations.
  • the housing 20 may include a housing 21 and an end cover 22, the housing 21 is a hollow structure with an opening on one side, and the end cover 22 covers the opening of the housing 21 and forms a sealing connection to form a A sealed space for accommodating the electrode assembly 10 and the electrolyte.
  • the electrode assembly 10 When assembling the battery cell 7 , the electrode assembly 10 can be put into the casing 21 first, and then the end cap 22 is closed on the opening of the casing 21 , and then the electrode material is injected into the casing through the electrolyte injection port on the end cap 22 . inside body 21.
  • the housing 21 can be in various shapes, such as a cylinder, a rectangular parallelepiped, and the like.
  • the shape of the housing 21 may be determined according to the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 has a cylindrical structure, a cylindrical casing can be selected; if the electrode assembly 10 has a cuboid structure, a cuboid casing can be selected.
  • the end cap 22 can also have various structures, for example, the end cap 22 is a plate-like structure, a hollow structure with one end open, and the like. Exemplarily, in FIG. 4 , the casing 21 is a rectangular parallelepiped structure, the end cover 22 is a plate-like structure, and the end cover 22 covers the opening at the top of the casing 21 .
  • the battery cell 7 may further include a positive electrode terminal 30 , a negative electrode terminal 40 and a pressure relief mechanism 50 , and the positive electrode terminal 30 , the negative electrode terminal 40 and the pressure relief mechanism 50 are all mounted on the end cap 22 . Both the positive electrode terminal 30 and the negative electrode terminal 40 are used for electrical connection with the electrode assembly 10 to output electric energy generated by the electrode assembly 10 .
  • the pressure relief mechanism 50 is used to release the pressure inside the battery cell 7 when the internal pressure or temperature of the battery cell 7 reaches a predetermined value.
  • the pressure relief mechanism 50 is located between the positive electrode terminal 30 and the negative electrode terminal 40, and the pressure relief mechanism 50 may be a component such as an explosion-proof valve, a rupture disk, a gas valve, a pressure relief valve or a safety valve.
  • the housing 20 may also have other structures.
  • the housing 20 includes a housing 21 and two end caps 22 .
  • the housing 21 is a hollow structure with openings on opposite sides, and one end cap 22 corresponds to a cap. It is closed at an opening of the case 21 and forms a sealed connection to form a sealed space for accommodating the electrode assembly 10 and the electrolyte.
  • the positive electrode terminal 30 and the negative electrode terminal 40 can be installed on the same end cover 22, or can be installed on different end covers 22; it can be that a pressure relief mechanism 50 is installed on one end cover 22, The pressure relief mechanism 50 may also be installed on both end caps 22 .
  • the number of electrode assemblies 10 accommodated in the casing 20 may be one or a plurality of them. Exemplarily, in FIG. 4 , there are two electrode assemblies 10 .
  • FIG. 5 is a schematic structural diagram of an electrode assembly 10 provided by some embodiments of the present application.
  • the electrode assembly 10 of the embodiment of the present application includes a negative electrode piece 11 and a positive electrode piece 12, the negative electrode piece 11 and the positive electrode piece 12 are wound along the winding direction A to form a winding structure, and the winding structure includes a bending area B, Both the negative pole piece 11 and the positive pole piece 12 include a plurality of bending portions 14 located in the bending region B. As shown in FIG.
  • At least one innermost bent portion 14 in the negative pole piece 11 is a first bent portion, and the active material capacity per unit area outside the first bent portion is greater than the active material capacity per unit area inside the first bent portion; And/or, at least one innermost bent portion 14 in the positive electrode sheet 12 is a second bent portion, and the active material capacity per unit area outside the second bent portion is greater than the active material per unit area inside the second bent portion. capacity.
  • the active material capacity per unit area outside the first bent portion of the negative electrode sheet 11 is greater than the active material capacity per unit area inside the first bent portion, the active material inside the first bent portion is less likely to be excessive, and the first bent portion is less likely to have excess active material capacity per unit area. If the active material on the outside of the portion is insufficient, the arrangement of the active material in at least a part of the region of the negative pole piece 11 (the region where the first bending portion is located) is more reasonable.
  • the capacity of active material per unit area outside the second bent portion of the positive electrode sheet 12 is greater than the capacity of active material per unit area inside the second bent portion, it is unlikely that the active material on the outside of the second bent portion is insufficient, and the second bent portion In the case of excess active material inside the positive electrode plate 12, the active material arrangement in at least part of the region of the positive electrode sheet 12 (the region where the second bending portion is located) is more reasonable. In the electrode assembly 10 with this structure, the arrangement of the active material in at least part of the region of the pole piece is more reasonable and has better economy.
  • the capacity of the active material per unit area inside the first bending part meets the design requirements, that is, the capacity per unit area of the active material inside the first bending part reaches the first preset value, so that the active material inside the first bending part is not easy to Lithium precipitation occurs, because the capacity of active material per unit area outside the first bending portion is greater than the capacity of active material per unit area inside the first bending portion, relative to the first preset value, it is equivalent to increasing the outside of the first bending portion.
  • the active material capacity per unit area can increase the CB value of the outer active material of the first bending part, so that the lithium deposition phenomenon is less likely to occur in the outer active material of the first bending part.
  • the capacity of the active material per unit area outside the second bending portion meets the design requirements, that is, the capacity of the active material per unit area outside the second bending portion reaches the second preset value, so that the negative electrode pole piece 11 is located in the second bending portion.
  • the inner active material of the outer bending portion 14 is not prone to lithium precipitation, because the unit active material capacity outside the second bending portion is greater than the unit area active material capacity inside the second bending portion, relative to the second preset value, equivalent.
  • the active material outside the bending portion 14 where the negative pole piece 11 is located inside the second bending portion is also less prone to lithium deposition.
  • the CB (Cell Balance) value is the ratio of the capacity of the negative electrode active material per unit area to the capacity of the positive electrode active material per unit area.
  • the CB (Cell Balance) value of the outer active material of the bent portion 14 of the negative electrode sheet 11 Q1/Q2, wherein the active material per unit area of the active material of the outer active material of one bent portion 14 in the negative electrode sheet 11 The capacity is Q1, and the active material capacity per unit area of the active material inside the bent portion 14 located outside the one bent portion 14 and adjacent to the one bent portion 14 of the positive electrode sheet 12 is Q2.
  • the inventor also found that when the positive pole piece 12 and the negative pole piece 11 are wound, the positive pole piece 12 and the negative pole piece 11 are bent in the bending area B, so the respective active materials may fall off, which is called Powder phenomenon.
  • the innermost bent portion 14 in the negative electrode sheet 11 and the innermost bent portion 14 in the positive electrode sheet 12 have the largest bending degree and are more likely to cause the active material to fall off. Due to the shedding of the active material, especially the shedding of the active material on the negative pole piece 11, the lithium insertion site of the active material of the negative pole piece 11 may be less than the lithium ion that can be provided by the active material of the adjacent positive pole piece 12. Therefore, the lithium-ion battery is prone to lithium precipitation when it is charged.
  • the capacity of active material per unit area outside the first bent portion is greater than the capacity of active material per unit area inside the first bent portion, it is equivalent to increasing the capacity of active material per unit area outside the first bent portion, That is, the CB value of the active material outside the first bending part is increased, so that even if the active material outside the first bending part falls off during the bending process, the active material outside the first bending part can satisfy the CB value. value requirements, thereby reducing the risk of lithium precipitation.
  • the capacity per unit area of active material outside the second folded portion is greater than the capacity per unit area of the active material inside the second folded portion, it is equivalent to reducing the capacity of active material per unit area inside the second folded portion, even if the negative electrode sheet 11.
  • the outer active material of the bending part 14 located on the inner side of the second bending part falls off, which can also reduce the risk of lithium precipitation of the active material on the outer side of the bending part 14 of the negative pole piece 11 located at the inner side of the second bending part. .
  • the winding direction A refers to the direction in which the positive pole piece 12 and the negative pole piece 11 are wound circumferentially from the inside to the outside. In FIG. 5, the winding direction A is the clockwise direction.
  • the electrode assembly 10 may further include a separator 13 for isolating the positive electrode 12 and the negative electrode 11 to reduce the risk of short circuit between the positive electrode 12 and the negative electrode 11 .
  • the isolation film 13 has a large number of through-holes, which can ensure the free passage of electrolyte ions and have good permeability to lithium ions. Therefore, the isolation film 13 basically cannot block the passage of lithium ions.
  • the material of the isolation film 13 may be PP (polypropylene, polypropylene) or PE (polyethylene, polyethylene) or the like.
  • the winding structure further includes a straight area C, the straight area C is connected to the bending area B, and the opposite ends of the straight area C may be provided with the bending area B.
  • the flat region C is the region where the winding structure has a flat structure, and the portion of the positive pole piece 12 in the flat region C and the portion of the negative pole piece 11 in the flat region C are arranged substantially flat.
  • the bending area B is the area where the winding structure has a bending structure, the part of the positive pole piece 12 located in the bending area B (the bending part 14 ) and the part of the negative pole piece 11 located in the bending area B (the bending part 14 ) ) are flexurally distributed.
  • the bent portion 14 of the positive pole piece 12 and the bent portion 14 of the negative pole piece 11 are both arc-shaped.
  • first bending portion is arranged in the bending area B
  • first bending portion it may be that only one bending area B is arranged with the first bending portion, or both bending areas B may be arranged.
  • a first bending part is arranged; in the case where a second bending part is arranged in the bending area B, only one bending area B is arranged with the second bending part, or two bending areas B are arranged A second bending portion is arranged inside.
  • the plurality of bending parts 14 in the positive electrode pole piece 12 and the plurality of bending parts 14 in the negative electrode pole piece 11 are alternately arranged, that is, when bending In area B, one bent portion 14 of the negative pole piece 11 , one bent portion 14 of the positive pole piece 12 , one bent portion 14 of the negative pole piece 11 . . . are arranged in order.
  • the innermost bent portion 14 of the positive pole piece 12 is located outside the innermost bent portion 14 of the negative pole piece 11 .
  • FIG. 6 is an enlarged schematic view of the electrode assembly 10 shown in FIG. 5 at block D.
  • the negative electrode sheet 11 includes a negative electrode current collector 111 and is disposed in the thickness direction of the negative electrode current collector 111
  • the negative electrode active material layers on both sides of the negative electrode current collector 111 and the negative electrode active material layers on both sides in the thickness direction of the negative electrode current collector 111 are respectively referred to as the first negative electrode active material layer 112 and the second negative electrode active material layer 113 .
  • the first negative electrode active material layer 112 is located outside the negative electrode current collector 111
  • the second negative electrode active material layer 113 is located inside the negative electrode current collector 111 .
  • the first negative electrode active material layer 112 is coated on the outer surface of the negative electrode current collector 111
  • the second negative electrode active material layer 113 is coated on the inner surface of the negative electrode current collector 111 .
  • the positive electrode sheet 12 includes a positive electrode current collector 121 and a positive electrode active material layer disposed on both sides of the positive electrode current collector 121 in the thickness direction, and the positive electrode active material layers on both sides in the thickness direction of the positive electrode current collector 121 are respectively referred to as the first positive electrode.
  • the active material layer 122 and the second positive electrode active material layer 123 are respectively referred to as the first positive electrode.
  • the active material layer 122 and the second positive electrode active material layer 123 In the wound structure, the first positive electrode active material layer 122 is located outside the positive electrode current collector 121 , and the second positive electrode active material layer 123 is located inside the positive electrode current collector 121 .
  • the first positive electrode active material layer 122 is coated on the outer surface of the positive electrode current collector 121 , and the second positive electrode active material layer 123 is coated on the inner surface of the positive electrode current collector 121 .
  • the negative electrode current collector 111 may have a part that is not coated with the negative electrode active material layer, which is the negative electrode tab (not shown in the figure); the positive electrode current collector 121 may have a part that is not coated with the positive electrode active material layer, and this part is Positive tab (not shown).
  • the positive tab is used for electrical connection with the positive electrode terminal 30 (see FIG. 4 ), and the negative tab is used for electrical connection with the negative electrode terminal 40 (see FIG. 4 ).
  • FIG. 7 is a schematic structural diagram of an electrode assembly provided by further embodiments of the present application.
  • the electrode assembly 10 may be a cylinder as a whole.
  • one circle of the positive pole piece 11 is a bending portion 14 ;
  • one circle of the negative pole piece 12 is one bending portion 14 .
  • FIG. 8 is a schematic structural diagram of an electrode assembly 10 provided by other embodiments of the present application;
  • FIG. 9 is a partially enlarged schematic diagram of the bending area B of the electrode assembly 10 shown in FIG. 8 ;
  • FIG. 10 is a negative electrode piece shown in FIG. 8 .
  • 11 is a partial schematic view in the unfolded state;
  • FIG. 11 is an enlarged schematic view of the electrode assembly 10 shown in FIG. 8 at block E.
  • At least one innermost bent portion 14 in the negative electrode pole piece 11 is the first bent portion 141 , and the active material per unit area outside the first bent portion 141 The capacity is larger than the capacity of the active material per unit area inside the first bent portion 141 .
  • the bent portion 14 adjacent to the first bent portion 141 in the positive electrode piece 12 is the third bent portion 143 , and the active material capacity per unit area outside the third bent portion 143 is equal to the inner side of the third bent portion 143 The active material capacity per unit area.
  • the active material capacity per unit area outside the first bending portion 141 is greater than the active material capacity per unit area inside the first bending portion 141
  • the active material capacity per unit area outside the third bending portion 143 may be equal to the third bending portion 143 .
  • the capacity per unit area of the active material inside the folded portion 143 is to simplify the manufacturing process of the positive electrode sheet 12 .
  • the first bending portion 141 includes a first current collecting portion 1411 , a first active material portion 1412 and a second active material portion 1413 .
  • the first active material part 1412 and the second active material part 1413 are respectively located on both sides of the first current collecting part 1411 .
  • the first current collecting part 1411 has a first inner surface 1411a and a first outer surface 1411b oppositely arranged in the thickness direction thereof, the first active material part 1412 is provided on the first outer surface 1411b, and the second active material The portion 1413 is provided on the first inner surface 1411a.
  • the third bent portion 143 includes a third current collecting portion 1431 , a fifth active material portion 1432 and a sixth active material portion 1433 .
  • the third current collecting portion 1431 has a third inner surface 1431a and a third outer surface 1431b arranged opposite to each other in the thickness direction thereof, the fifth active material portion 1432 is provided on the third outer surface 1431b, and the sixth active material portion 1433 is provided on the third outer surface 1431b.
  • the first current collecting portion 1411 is a part of the negative electrode current collector 111 (see FIG. 6 ) located at the first bending portion 141
  • the first active material portion 1412 is the first negative electrode active material layer 112 (see FIG. 6 )
  • the second active material portion 1413 is a portion of the second negative electrode active material layer 113 (see FIG. 6 ) located in the first bent portion 141
  • the third current collecting portion 1431 is a part of the positive electrode current collector 121 (see FIG. 6 ) located at the third bent portion 143
  • the fifth active material portion 1432 is a portion of the first positive electrode active material layer 122 (see FIG. 6 ) located at the third bending portion 143
  • a part of the bent portion 143 and the sixth active material portion 1433 is a part of the second positive active material layer 123 (see FIG. 6 ) located in the third bent portion 143 .
  • the active material capacity per unit area outside the first bent portion 141 is larger than the active material capacity per unit area inside the first bent portion 141 , that is, the activity per unit area of the first active material portion 1412 (outer portion of the first bent portion 141 ).
  • the material capacity is larger than the active material capacity per unit area of the second active material portion 1413 (the inner portion of the first bent portion 141 ).
  • the active material capacity per unit area outside the first bent portion 141 is the ratio of the active material capacity of the first active material portion 1412 to the area of the first outer surface 1411b, and the active material capacity per unit area inside the first bent portion 141 is the is the ratio of the active material capacity of the second active material portion 1413 to the area of the first inner surface 1411a.
  • the active material capacity per unit area outside the third bent portion 143 is equal to the active material capacity per unit area inside the third bent portion 143 , that is, the activity per unit area of the fifth active material portion 1432 (outer portion of the third bent portion 143 ).
  • the material capacity is equal to the active material capacity per unit area of the sixth active material portion 1433 (the inner portion of the third bent portion 143 ).
  • the active material capacity per unit area outside the third bending portion 143 is the ratio of the active material capacity of the fifth active material portion 1432 to the area of the third outer surface 1431b, and the active material capacity per unit area inside the third bending portion 143, That is, the ratio of the active material capacity of the sixth active material portion 1433 to the third inner surface 1431a.
  • all the bent portions 14 may be the first bent portions 141, or some of the bent portions 14 may be the first bent portions 141. If all the bent portions 14 in the negative electrode sheet 11 are the first bent portions 141 , the active material capacity per unit area outside all the bent portions 14 in the negative electrode sheet 11 is larger than the active material capacity per unit area inside. If only part of the bent portion 14 of the negative electrode sheet 11 is the first bent portion 141, the bent portion 14 of the negative electrode sheet 11 other than the first bent portion 141 can be used as the outer active material capacity per unit area equal to the inner one. The structure of the active material capacity per unit area. In the positive pole piece 12 , all the bent portions 14 may be the third bent portions 143 , or only some of the bent portions 14 may be the third bent portions 143 .
  • all the bent portions 14 in the positive electrode sheet 12 are the third bent portions 143 to simplify the manufacturing process of the positive electrode sheet 12 .
  • some bent portions 14 near the outer side of the negative pole piece 11 may adopt a structure in which the capacity of the active material per unit area on the outer side is equal to the capacity per unit area of the active material on the inner side.
  • At least the innermost one bending portion 14 in the negative pole piece 11 is the first bending portion 141
  • at least one outermost bending portion 14 in the negative pole piece 11 is the fourth bending portion 144
  • the active material capacity per unit area of the outer side of the fourth bending portion 144 is equal to the active material capacity per unit area of the inner side of the fourth bending portion 144
  • the active material capacity per unit area of the inner side of the fourth bending portion 144 is equal to the active material capacity per unit area of the inner side of the first bending portion 141 .
  • the fourth bent portion 144 includes a fourth current collecting portion 1441 , a seventh active material portion 1442 and an eighth active material portion 1443 .
  • the fourth current collecting portion 1441 has a fourth inner surface 1441a and a fourth outer surface 1441b arranged opposite to each other in the thickness direction thereof, the seventh active material portion 1442 is provided on the fourth outer surface 1441b, and the eighth active material portion 1443 is provided on the fourth outer surface 1441b.
  • Four inner surfaces 1441a It can be understood that the fourth current collecting part 1441 is the part of the negative electrode current collector 111 (see FIG. 6 ) located at the fourth bending part 144 , and the seventh active material part 1442 is the first negative electrode active material layer 112 (see FIG. 6 )
  • the eighth active material portion 1443 is the portion of the second negative electrode active material layer 113 (see FIG. 6 ) located at the fourth bent portion 144 .
  • the active material capacity per unit area outside the fourth bent portion 144 is equal to the active material capacity per unit area inside the fourth bent portion 144 , that is, the activity per unit area of the seventh active material portion 1442 (outer portion of the fourth bent portion 144 ).
  • the material capacity is equal to the active material capacity per unit area of the eighth active material portion 1443 (the inner portion of the fourth bent portion 144 ).
  • the active material capacity per unit area outside the fourth bending portion 144 is the ratio of the active material capacity of the seventh active material portion 1442 to the area of the fourth outer surface 1441b, and the active material capacity per unit area inside the fourth bending portion 144, That is, the ratio of the active material capacity of the eighth active material portion 1443 to the area of the fourth inner surface 1441a.
  • the plurality of bent portions 14 in the negative pole piece 11 arranged in sequence from the innermost to the outside are the first bent portions 141 .
  • the bent portion 14 located outside the plurality of first bent portions 141 is the fourth bent portion 144 .
  • the number of the bent parts 14 in the negative pole piece 11 is equal to the sum of the number of the first bent parts 141 and the number of the fourth bent parts 144 .
  • the number of the first bending parts 141 is two.
  • the fourth bent portion 144 does not need to increase the capacity of the active material per unit area on the outside, so that the amount of active material can be saved.
  • the active material capacity per unit area outside the first bending portion 141 may be greater than the active material capacity per unit area inside the first bending portion 141 in various ways.
  • the thickness of the first active material portion 1412 is greater than the thickness of the second active material portion 1413 , so that the active material capacity per unit area outside the first bending portion 141 is greater than the unit area inside the first bending portion 141 Active substance capacity.
  • the first active material portion 1412 is the same as the second active material portion 1413 except for the thickness; for example, the active material of the first active material portion 1412 and the active material of the second active material portion 1413
  • the weight ratio of the active material of the active material part 1412 to the first active material part 1412 is larger than the weight ratio of the active material of the second active material part 1413 to the second active material part 1413 .
  • the thickness of the first active material portion 1412 is greater than the thickness of the second active material portion 1413, so that the unit area of the first active material portion 1412 can be activated
  • the material capacity is larger than the active material capacity per unit area of the second active material portion 1413 , so that the active material capacity per unit area outside the first bending portion 141 is greater than the active material capacity per unit area inside the first bending portion 141 .
  • Both the active material of the first active material portion 1412 and the active material of the second active material portion 1413 may be a compound of graphite or silicon, or the like.
  • the second active material portion 1413 and the first active material portion 1412 are formed by curing an active slurry having the same composition.
  • the thickness of the first active material portion 1412 is greater than that of the second active material portion 1413 by 0.5%-20%.
  • the thickness of the first active material portion 1412 is greater than that of the second active material portion 1413 by 1.5%-12%.
  • the first anode active material layer 112 includes a first portion 1121 and a second portion 1122 disposed along the winding direction A, and the first portion 1121 is along the winding direction A from the starting end 112a of the first anode active material layer 112 Extending, the second portion 1122 is continuously arranged with the first portion 1121 along the winding direction A, and the thickness of the first portion 1121 is greater than that of the second portion 1122 .
  • the starting end 112 a of the first negative electrode active material layer 112 is the inner end along the winding direction A of the first negative electrode active material layer 112 .
  • the thickness of the second portion 1122 is equal to the thickness of the second anode active material layer 113 .
  • the first active material portion 1412 is a portion of the first portion 1121 located at the first bent portion 141
  • the seventh active material portion 1442 is a portion of the second portion 1122 located at the fourth bent portion 144 .
  • the active material capacity per unit area outside the first bent portion 141 can be greater than the unit area inside the first bent portion 141
  • the active material capacity and the active material capacity per unit area outside the fourth bent portion 144 are equal to the active material capacity per unit area inside the fourth bent portion 144 .
  • the first portion 1121 is wound along the winding direction A at least one turn. That is, the first negative electrode active material layer 112 is wound in multiple turns along the winding direction A, and at least the first turn of the first negative electrode active material layer 112 is the first portion 1121 .
  • the starting point of the first circle is the starting end 112a of the first negative electrode active material layer 112, the end point of the first circle is located outside the starting end 112a of the first negative electrode active material layer 112, and the starting point and ending point of the first circle are at the first circle.
  • the anode active material layer 112 is flush in the thickness direction.
  • the first portion 1121 is wound along the winding direction A at least once, so that at least one innermost bent portion 14 in the negative electrode pole piece 11 can be the first bent portion 141 .
  • the first portion 1121 is wound in the winding direction A twice.
  • FIG. 12 is a partial enlarged view of a portion of the electrode assembly located in the bending region B according to some embodiments of the present application.
  • the first bending portion 141 further includes a first conductive portion 1414 , the first conductive portion 1414 is connected between the second active material portion 1413 and the first inner surface 1411 a , the first active material portion 1411 a
  • the thickness of the material portion 1412 is greater than or equal to the total thickness of the second active material portion 1413 and the first conductive portion 1414 .
  • the thickness of the first active material portion 1412 is greater than or equal to the thickness of the second active material portion 1413 and the first conductive portion 1411.
  • the total thickness of the portion 1414 is adjusted so that the thickness of the first active material portion 1412 is greater than the thickness of the second active material portion 1413 .
  • the thickness of the first active material portion 1412 may be greater than or equal to The thickness of the second active material portion 1413 .
  • the first conductive part 1414 can be a pure conductive coating, for example, the first conductive part 1414 is a pure conductive coating composed of an adhesive and a conductive agent; the first conductive part 1414 can also be an active coating containing lithium ions layer, for example, the first conductive part 1414 is an active coating containing lithium ions composed of a lithium-rich material, a binder and a conductive agent; the first conductive part 1414 can also be an inactive coating containing lithium ions, for example, The first conductive portion 1414 is a lithium ion-containing inactive coating composed of a binder, a conductive agent and lithium powder coated with lithium carbonate.
  • the active material capacity per unit area outside the first bending portion 141 may be greater than the active material capacity per unit area inside the first bending portion 141 by other means.
  • FIG. 13 is a partial enlarged view of a portion of the electrode assembly located in the bending region B according to other embodiments of the present application.
  • the gram capacity of the active material in the first active material portion 1412 is greater than the gram capacity of the active material in the second active material portion 1413, so that the active material capacity per unit area of the first active material portion 1412 is greater than that of the second active material portion 1413.
  • the active material capacity per unit area of the second active material portion 1413 is realized so that the active material capacity per unit area outside the first bending portion 141 is greater than the active material capacity per unit area inside the first bending portion 141 .
  • the first active material portion 1412 and the second active material portion 1413 are the same except for the gram capacity; for example, the thickness of the first active material portion 1412 and the thickness of the second active material portion 1413
  • the weight ratio of the active material of the material part 1412 to the first active material part 1412 is equal to the weight ratio of the active material of the second active material part 1413 to the second active material part 1413 .
  • the gram capacity refers to the ratio of the capacitance released by the active material to the mass of the active material.
  • the active material of the first active material part 1412 is different from the active material of the second active material part 1413 , for example, the active material of the first active material part 1412 is a silicon compound, and the active material of the second active material part 1413 The material is graphite.
  • the gram capacity of the active material in the first active material part 1412 is 0.5%-20% larger than the gram capacity of the active material in the second active material part 1413 .
  • the gram capacity of the active material in the first active material portion 1412 is 1.5%-12% greater than the gram capacity of the active material in the second active material portion 1413 .
  • the weight ratio of the active material in the first active material part 1412 to the first active material part 1412 is greater than the weight ratio of the active material in the second active material part 1413 to the second active material part 1413 , so that It is realized that the capacity of active material per unit area outside the first bending portion 141 is larger than the capacity per unit area of the active material inside the first bending portion 141 .
  • Both the first active material part 1412 and the second active material part 1413 include active materials, adhesives and conductive agents. By increasing the weight ratio of the active materials in the first active material The capacity of active material per unit area is larger than the capacity of active material per unit area inside the first bent portion 141 .
  • the thickness of the first active material part 1412 and the thickness of the second active material part 1413 are the same, the active material of the first active material part 1412 and the active material of the second active material part 1413 are the same, the first active material
  • the weight ratio of the active material in the part 1412 to the first active material part 1412 is greater than the weight ratio of the active material in the second active material part 1413 to the second active material part 1413 .
  • FIG. 14 is a partial enlarged view of a portion of the electrode assembly 10 located in the bending region B according to further embodiments of the present application.
  • the first bending portion 141 further includes a first conductive portion 1414 , the first conductive portion 1414 is connected between the first active material portion 1412 and the first outer surface 1411b, and the first conductive portion 1414 contains an active material.
  • the first conductive part 1414 is an active coating layer containing lithium ions, for example, the first conductive part 1414 is an active coating layer containing lithium ions composed of a lithium-rich material, a binder and a conductive agent.
  • the thickness of the second active material portion 1413 is greater than or equal to the total thickness of the first active material portion 1412 and the first conductive portion 1414 .
  • the first active material portion 1412 and the second active material portion 1413 are the same except for thickness; for example, the active material of the first active material portion 1412 and the active material of the second active material portion 1413
  • the weight ratio of the active material of the active material part 1412 to the first active material part 1412 is equal to the weight ratio of the active material of the second active material part 1413 to the second active material part 1413 .
  • the second active material portion 1413 and the first active material portion 1412 are formed by curing an active slurry having the same composition.
  • the gram capacity of the active material in the first active material portion 1412 is smaller than the gram capacity of the active material in the first conductive portion 1414; by adding an active material with a larger gram capacity in the first conductive portion 1414, The active material capacity per unit area outside the first bending portion 141 is increased, so that the active material capacity per unit area outside the first bending portion 141 is greater than the active material capacity per unit area inside the first bending portion 141 .
  • the weight ratio of the active material of the first conductive portion 1414 to the first conductive portion 1414 is equal to the weight ratio of the active material of the first active material portion 1412 to the first active material portion 1412 .
  • the weight ratio of the active material in the first active material part 1412 to the first active material part 1412 is smaller than the weight ratio of the active material in the first conductive part 1414 to the first conductive part 1414, so as to realize the first
  • the capacity per unit area of the active material outside the first bent portion 141 is greater than the capacity per unit area of the active material inside the first bent portion 141 .
  • the active material in the first active material portion 1412 is the same as the active material in the first conductive portion 1414 .
  • the active material capacity per unit area outside the third bending portion 143 may be equal to the active material capacity per unit area inside the third bending portion 143 in various ways.
  • the active material of the fifth active material portion 1432 in the third bending portion 143 is the same as the active material of the sixth active material portion 1433
  • the thickness of the fifth active material portion 1432 is equal to the thickness of the sixth active material portion 1433 .
  • the capacity per unit area of the active material outside the fourth bending portion 144 can be equal to the capacity per unit area of the active material inside the fourth bending portion 144 in various ways.
  • the active material of the seventh active material portion 1442 in the fourth bending portion 144 is the same as the active material of the eighth active material portion 1443 , and the thickness of the seventh active material portion 1442 is equal to the thickness of the eighth active material portion 1443 .
  • FIG. 15 is a schematic structural diagram of an electrode assembly 10 provided by further embodiments of the present application
  • FIG. 16 is a partial enlarged schematic diagram of the bending area B of the electrode assembly 10 shown in FIG. 15
  • FIG. 17 is a positive electrode piece shown in FIG. 15
  • 12 is a partial schematic view in the unfolded state
  • FIG. 18 is an enlarged schematic view at block F of the electrode assembly 10 shown in FIG. 15 .
  • At least one innermost bent portion 14 of the positive electrode sheet 12 is the second bent portion 142 , and the active material capacity per unit area outside the second bent portion 142 It is larger than the capacity of the active material per unit area inside the second bent portion 142 .
  • the bending part 14 adjacent to the second bending part 142 in the negative pole piece 11 is the fourth bending part 144 , and the active material capacity per unit area outside the fourth bending part 144 is equal to the inner side of the fourth bending part 144 The active material capacity per unit area.
  • the active material capacity per unit area outside the second bending portion 142 is greater than the active material capacity per unit area inside the second bending portion 142
  • the active material capacity per unit area outside the fourth bending portion 144 may be equal to the fourth bending portion 144 .
  • the capacity of the active material per unit area inside the folded portion 144 is to simplify the manufacturing process of the negative pole piece 11 .
  • the second bending portion 142 includes a second current collecting portion 1421 , a third active material portion 1422 and a fourth active material portion 1423 .
  • the third active material part 1422 and the fourth active material part 1423 are respectively provided on both sides of the second current collecting part 1421 .
  • the second current collecting portion 1421 has a second inner surface 1421a and a second outer surface 1421b arranged opposite to each other in the thickness direction thereof, the third active material portion 1422 is provided on the second outer surface 1421b, and the fourth active material portion 1423 is provided on the second inner surface 1421a.
  • the second current collecting portion 1421 is a part of the positive electrode current collector 121 (see FIG. 6 ) located at the second bending portion 142
  • the third active material portion 1422 is the first positive electrode active material layer 122 (see FIG. 6 )
  • the fourth active material portion 1423 is a portion of the second positive active material layer 123 (see FIG. 6 ) located in the second bent portion 142 .
  • the active material capacity per unit area outside the second bent portion 142 is larger than the active material capacity per unit area inside the second bent portion 142 , that is, the activity per unit area of the third active material portion 1422 (outer portion of the second bent portion 142 ).
  • the material capacity is larger than the active material capacity per unit area of the fourth active material portion 1423 (the inner portion of the second bent portion 142 ).
  • the active material capacity per unit area outside the second bent portion 142 is the ratio of the active material capacity of the third active material portion 1422 to the area of the second outer surface 1421b, and the active material capacity per unit area inside the third bent portion 143 is the is the ratio of the active material capacity of the fourth active material portion 1423 to the area of the second inner surface 1421a.
  • all the bent portions 14 may be the second bent portions 142 , or some of the bent portions 14 may be the second bent portions 142 . If all the bent portions 14 in the positive electrode sheet 12 are the second bent portions 142 , the active material capacity per unit area on the outside of all the bent portions 14 in the positive electrode sheet 12 is larger than the active material capacity per unit area on the inside. If only part of the bent portion 14 of the positive electrode sheet 12 is the second bent portion 142, the bent portion 14 of the positive electrode sheet 12 other than the second bent portion 142 can be used as the active material capacity per unit area on the outside equal to the inside. The structure of the active material capacity per unit area. In the negative pole piece 11 , all the bent portions 14 may be the fourth bent portions 144 , or only a part of the bent portions 14 may be the fourth bent portions 144 .
  • all the bent portions 14 in the negative electrode pole piece 11 are the fourth bent portion 144 to simplify the manufacturing process of the negative electrode pole piece 11 .
  • some bent portions 14 of the positive electrode sheet 12 near the outer side may adopt a structure in which the capacity per unit area of the active material on the outer side is equal to the capacity per unit area of the active material on the inner side.
  • At least the innermost one bending portion 14 in the positive pole piece 12 is the second bending portion 142
  • at least one outermost bending portion 14 in the positive pole piece 12 is the third bending portion 143
  • the active material capacity per unit area of the outer side of the third bending portion 143 is equal to the active material capacity per unit area of the inner side of the third bending portion 143
  • the active material capacity per unit area of the outer side of the third bending portion 143 is equal to the active material capacity per unit area of the outer side of the second bending portion 142 .
  • the plurality of bent portions 14 in the positive pole piece 12 arranged in sequence from the innermost to the outside are the second bent portions 142 .
  • the bent portion 14 of the positive pole piece 12 located outside the plurality of second bent portions 142 is the third bent portion 143 .
  • the number of the bent parts 14 in the positive pole piece 12 is equal to the sum of the number of the second bent parts 142 and the number of the third bent parts 143 .
  • the number of the second bending portions 142 is two.
  • the third bent portion 143 does not need to reduce the capacity of the active material per unit area inside, so that the capacity of the electrode assembly 10 can be ensured.
  • the active material capacity per unit area outside the second bending portion 142 may be larger than the active material capacity per unit area inside the second bending portion 142 in various ways.
  • the thickness of the third active material portion 1422 is greater than the thickness of the fourth active material portion 1423 , so that the active material capacity per unit area outside the second bending portion 142 is greater than the unit area inside the second bending portion 142 Active substance capacity.
  • the third active material portion 1422 and the fourth active material portion 1423 are the same except for the thickness; for example, the active material of the third active material portion 1422 in the second bent portion 142 is the same as the fourth active material portion
  • the active material of 1423 is the same, and the weight ratio of the active material of the third active material part 1422 to the third active material part 1422 is equal to the weight ratio of the active material of the fourth active material part 1423 to the fourth active material part 1423 .
  • the thickness of the third active material portion 1422 is greater than the thickness of the fourth active material portion 1423, so that the unit area of the third active material portion 1422 can be activated
  • the material capacity is larger than the active material capacity per unit area of the fourth active material portion 1423 , so that the active material capacity per unit area outside the second bending portion 142 is greater than the active material capacity per unit area inside the second bending portion 142 .
  • Both the active material of the third active material part 1422 and the active material of the fourth active material part 1423 may be lithium iron phosphate, lithium manganate, ternary lithium, lithium cobaltate, or the like.
  • the third active material portion 1422 and the fourth active material portion 1423 are formed by curing an active slurry having the same composition.
  • the thickness of the third active material portion 1422 is greater than that of the fourth active material portion 1423 by 0.5%-20%.
  • the thickness of the third active material portion 1422 is greater than that of the fourth active material portion 1423 by 1.5%-12%.
  • the second positive active material layer 123 includes a third portion 1231 and a fourth portion 1232 arranged along the winding direction A, and the third portion 1231 is wound from the starting end 123 a of the second positive active material layer 123 along the winding direction A. Extending in the direction A, the fourth portion 1232 is continuously arranged with the third portion 1231 along the winding direction A, and the thickness of the third portion 1231 is smaller than that of the fourth portion 1232 .
  • the starting end 123a of the second positive electrode active material layer 123 is the inner end of the second positive electrode active material layer 123 along the winding direction A.
  • the thickness of the fourth portion 1232 is equal to the thickness of the first cathode active material layer 122 .
  • the fourth active material portion 1423 is a portion of the third portion 1231 located at the second bent portion 142
  • the sixth active material portion 1433 is a portion of the fourth portion 1232 located at the third bent portion 143 .
  • the third portion 1231 is wound along the winding direction A at least one turn. That is, the second positive electrode active material layer 123 is wound in a plurality of turns along the winding direction A, and at least the first turn of the second positive electrode active material layer 123 is the third portion 1231 .
  • the starting point of the first circle is the start end 123a of the second positive electrode active material layer 123
  • the end point of the first circle is located outside the start end 123a of the second positive electrode active material layer 123
  • the start point and end point of the first circle are in the second circle.
  • the positive electrode active material layer 123 is flush in the thickness direction.
  • the third portion 1231 is wound along the winding direction A at least once, so that at least one innermost bent portion 14 in the positive electrode pole piece 12 can be the second bent portion 142 .
  • the third portion 1231 is wound along the winding direction A twice.
  • FIG. 19 is a partial enlarged view of a portion of the electrode assembly located in the bending region B according to further embodiments of the present application.
  • the second bending portion 142 further includes a second conductive portion 1424 .
  • the second conductive portion 1424 is connected between the fourth active material portion 1423 and the second inner surface 1421 a , and the thickness of the third active material portion 1422 is greater than or equal to the total thickness of the fourth active material portion 1423 and the second conductive portion 1424 .
  • the thickness of the third active material portion 1422 is greater than or equal to the thickness of the fourth active material portion 1423 and the second conductive portion 1421.
  • the total thickness of the portion 1424 is adjusted so that the thickness of the third active material portion 1422 is greater than the thickness of the fourth active material portion 1423 .
  • the thickness of the third active material portion 1422 is only necessary to make the thickness of the third active material portion 1422 greater than or equal to the total thickness of the fourth active material portion 1423 and the second conductive portion 1424, so that the thickness of the third active material portion 1422 can be greater than or equal to The thickness of the fourth active material portion 1423 .
  • the second conductive part 1424 can be a pure conductive coating, for example, the second conductive part 1424 is a pure conductive coating composed of an adhesive and a conductive agent; the second conductive part 1424 can also be an active coating containing lithium ions layer, for example, the second conductive part 1424 is an active coating containing lithium ions composed of a lithium-rich material, a binder and a conductive agent; the second conductive part 1424 can also be an inactive coating containing lithium ions, for example, The second conductive portion 1424 is a lithium ion-containing inactive coating composed of a binder, a conductive agent, and lithium powder coated with lithium carbonate.
  • the fourth active material portion 1423 may also be connected between the second conductive portion 1424 and the second inner surface 1421a.
  • FIG. 20 is a partial enlarged view of a portion of the electrode assembly located in the bending region B according to other embodiments of the present application.
  • the gram capacity of the active material in the third active material portion 1422 is greater than the gram capacity of the active material in the fourth active material portion 1423, so that the active material capacity per unit area of the fourth active material portion 1423 is smaller than that of the fourth active material portion 1423.
  • the active material capacity per unit area of the three active material portions 1422 is realized, so that the active material capacity per unit area outside the second bending portion 142 is greater than the active material capacity per unit area inside the second bending portion 142 .
  • the third active material portion 1422 and the fourth active material portion 1423 are the same except for the gram capacity; for example, the thickness of the third active material portion 1422 is equal to the thickness of the fourth active material portion 1423, The weight ratio of the active material of the material portion 1422 to the third active material portion 1422 is equal to the weight ratio of the active material of the fourth active material portion 1423 to the fourth active material portion 1423 .
  • the active material of the third active material part 1422 may be different from the active material of the fourth active material part 1423.
  • the active material of the third active material part 1422 is ternary lithium
  • the active material in the part 1423 is lithium iron phosphate.
  • the gram capacity of the active material in the third active material part 1422 is 0.5%-20% greater than the gram capacity of the active material in the fourth active material part 1423 .
  • the gram capacity of the active material in the third active material portion 1422 is 1.5%-12% greater than the gram capacity of the active material in the fourth active material portion 1423 .
  • the weight ratio of the active material in the third active material part 1422 to the third active material part 1422 is greater than the weight ratio of the active material in the fourth active material part 1423 to the fourth active material part 1423 , so that It is achieved that the active material capacity per unit area outside the second bending portion 142 is greater than the active material capacity per unit area inside the second bending portion 142 .
  • Both the third active material portion 1422 and the fourth active material portion 1423 include active materials, adhesives and conductive agents. By reducing the weight ratio of the active materials in the fourth active material portion 1423, the outer side of the second bending portion 142 can be realized. The capacity of active material per unit area is greater than the capacity of active material per unit area inside the second bent portion 142 .
  • the thickness of the third active material portion 1422 is the same as that of the fourth active material portion 1423
  • the active material in the third active material portion 1422 is the same as the active material in the fourth active material portion 1423
  • the third active material portion 1422 has the same thickness as the fourth active material portion 1423 .
  • the weight ratio of the active material in the active material part 1422 to the third active material part 1422 is greater than the weight ratio of the active material in the fourth active material part 1423 to the fourth active material part 1423 .
  • FIG. 21 is a partial enlarged view of a portion of the electrode assembly located in the bending region B according to still other embodiments of the present application, and at least one innermost bending portion of the negative pole piece 11 14 is the first bending portion 141, the active material capacity per unit area outside the first bending portion 141 is greater than the active material capacity per unit area inside the first bending portion 141; at least one of the innermost one of the positive pole pieces 12 is bent
  • the portion 14 is the second bent portion 142 , and the active material capacity per unit area outside the second bent portion 142 is larger than the active material capacity per unit area inside the second bent portion 142 .
  • the thickness of the first active material part 1412 of the first bending part 141 can be made larger than the thickness of the second active material part 1413 , or by making the first active material part of the first bending part 141 thicker
  • the gram capacity of the active material of the portion 1412 is greater than the gram capacity of the active material of the second active material portion 1413 , or in other ways, so that the active material capacity per unit area outside the first bent portion 141 is greater than the inside of the first bent portion 141 The active material capacity per unit area.
  • the thickness of the fourth active material portion 1423 can be made smaller than the thickness of the third active material portion 1422 of the second bent portion 142, or by making the gram capacity of the active material of the fourth active material portion 1423 smaller than the second active material portion 1423.
  • the gram capacity of the active material of the third active material portion 1422 of the bent portion 142 or other methods, make the active material capacity per unit area outside the second bent portion 142 greater than the activity per unit area inside the second bent portion 142 material capacity.
  • the thickness of the first active material portion 1412 of the first bending portion 141 is greater than the thickness of the second active material portion 1413
  • the thickness of the third active material portion 1422 of the second bending portion 142 is greater than that of the second active material portion 1413 .
  • the thickness of the fourth active material portion 1423 is the same as the active material of the second active material portion 1413
  • the active material of the first active material portion 1412 is the same as the active material of the first active material portion 1412
  • the weight ratio of is equal to the weight ratio of the active material of the second active material part 1413 to the weight ratio of the second active material part 1413 .
  • the active material of the third active material portion 1422 of the second bending portion 142 is the same as the active material of the fourth active material portion 1423
  • the active material of the third active material portion 1422 is the same as the active material of the third active material portion 1422
  • the weight ratio of is equal to the weight ratio of the active material of the fourth active material part 1423 to the fourth active material part 1423 .
  • a second bending part 142 adjacent to the first bending part 141 is arranged on the outer side of the first bending part 141 .
  • the active material capacity per unit area outside the first bending portion 141 is greater than that of the first bending portion
  • the capacity of active material per unit area inside 141 and the capacity of active material per unit area outside the second bending part 142 are larger than the capacity per unit area of active material inside the second bending part 142, which can increase the capacity of the outer part of the first bending part 141. CB value, thereby reducing the occurrence of lithium precipitation.
  • all the bent portions 14 may be the first bent portions 141 , or some of the bent portions 14 may be the first bent portions 141 .
  • all the bent portions 14 may be the second bent portions 142 , or some of the bent portions 14 may be the second bent portions 142 .
  • a portion of the bent portion 14 in the negative pole piece 11 is a first bent portion 141
  • a portion of the bent portion 14 in the positive electrode piece 12 is a second bent portion 142 .
  • the plurality of bending parts 14 in the negative pole piece 11 arranged in order from the innermost to the outside are the first bending parts 141
  • the bending parts 14 in the negative pole piece 11 located outside the plurality of first bending parts 141 are the first bending parts 141 .
  • the portion 14 is the fourth bent portion 144 .
  • the plurality of bent portions 14 in the positive electrode piece 12 arranged in sequence from the innermost to the outside are the second bent portions 142 , and the bent portions 14 located outside the plurality of second bent portions 142 in the positive electrode piece 12 are The third bent portion 143 .
  • the innermost bent portion 14 of the positive electrode pole piece 12 is located outside the innermost bent portion 14 of the negative electrode pole piece 11 , and the first bent portion 141 and the second bent portion 142 are both two indivual.
  • test steps for active material capacity per unit area and CB value are as follows:
  • Step 1) Average discharge capacity test of the single-sided active material layer of the positive electrode. Take the positive electrode pieces of the above-mentioned embodiments, and use a punching die to obtain a small round piece containing a positive electrode single-sided active material layer. Using lithium metal sheet as the counter electrode, Celgard film as the separator, EC+DMC+DEC dissolved with LiPF6 (1mol/L) (ethylene carbonate, dimethyl carbonate, diethyl carbonate with a volume ratio of 1:1:1) The solution of ester) was the electrolyte, and 6 identical CR2430 button cells were assembled in an argon-protected glove box.
  • LiPF6 1mol/L
  • the positive electrode active material is lithium iron phosphate (LFP)
  • the upper limit cut-off voltage x 1 V 3.75V
  • the lower limit cut-off voltage y 1 V 2V
  • the positive electrode active material is lithium nickel cobalt manganese oxide (NCM)
  • the upper limit cut-off voltage x 1 V 4.25V
  • the lower limit cut-off voltage y 1 V 2.8V.
  • Step 2) Average charge capacity test of the single-sided active material layer of the negative electrode. Take the negative pole pieces of each of the above embodiments, and use a punching die to obtain a small round piece with the same area as the positive small round piece in the above step 1) and including a negative electrode single film layer. Using lithium metal sheet as the counter electrode, Celgard film as the separator, EC+DMC+DEC dissolved with LiPF6 (1mol/L) (ethylene carbonate, dimethyl carbonate, diethyl carbonate with a volume ratio of 1:1:1) The solution of ester) was the electrolyte, and six CR2430 button cells were assembled in an argon-protected glove box.
  • the average value of the charging capacity of the 6 button batteries is the average charging capacity of the negative electrode single film layer.
  • the negative electrode active material is graphite
  • the upper limit cut-off voltage x 2 V 2V
  • the lower limit cut-off voltage y 2 V 5mV.
  • the negative electrode active material is silicon
  • the upper limit cut-off voltage x 2 V 2V
  • the lower limit cut-off voltage y 2 V 5mV.
  • FIG. 22 is a flowchart of a method for manufacturing an electrode assembly provided by some embodiments of the present application
  • FIG. 23 is a schematic diagram of a negative electrode pole piece provided by some embodiments of the present application during the forming process
  • FIG. 24 is a schematic diagram of some embodiments of the present application.
  • Another schematic diagram of the negative pole piece during the forming process
  • FIG. 25 is a schematic diagram of the positive pole piece provided by some embodiments of the application during the forming process
  • FIG. 26 is the positive pole piece provided by some embodiments of the application during the forming process.
  • the manufacturing method of the electrode assembly includes:
  • the winding structure includes a bending area
  • both the negative pole piece and the positive pole piece include a plurality of bending parts located in the bending area.
  • At least one innermost bent portion in the negative pole piece is a first bent portion, and the active material capacity per unit area outside the first bent portion is greater than the active material capacity per unit area inside the first bent portion; and/or, At least one innermost bent portion in the positive electrode sheet is a second bent portion, and the active material capacity per unit area outside the second bent portion is greater than the active material capacity per unit area inside the second bent portion.
  • a separator for separating the positive pole piece and the negative pole piece is also provided, and the first pole piece, the separator and the second pole piece are wound along the winding direction to form a winding structure.
  • step S200 includes:
  • S220 Referring to FIG. 23, coating a first negative electrode active material layer 112 on one surface of the negative electrode current collector 111;
  • the first negative electrode active material layer 112 is located on the outside of the negative electrode current collector 111, and the second negative electrode active material layer 113 is located on the inner side of the negative electrode current collector 111;
  • a provided first portion 1121 and second portion 1122, the first portion 1121 extends from the starting end of the first negative electrode active material layer 112 along the winding direction A, the second portion 1122 is arranged continuously with the first portion 1121 along the winding direction A, and
  • the thickness of the first portion 1121 is greater than that of the second portion 1122 , and the thickness of the second portion 1122 is equal to the thickness of the second negative electrode active material layer 113 ; at least part of the first portion 1121 is located at the first bending portion.
  • step S220 includes:
  • the part of the first active coating 112b coated with the second active coating 112c and the second active coating 112c form the first part 1121 after curing; the first active coating 112b is not coated with the second active coating
  • the portion of 112c forms a second portion 1122 after curing.
  • the negative electrode current collector 111 passes through the negative electrode coating device during the tape running process, and the negative electrode coating device includes a first coating head 81 and a second coating head 82 .
  • the first coating head 81 continuously coats one surface of the anode current collector 111 to form the first active coating layer 112b.
  • the negative electrode current collector 111 coated with the first active coating 112b passes through the second coating head 82, by controlling the opening and closing time of the second coating head 82, the first active coating 112b is away from the negative electrode current collector 111 by controlling the opening and closing time of the second coating head 82.
  • a set area of the surface of the 112c forms the second active coating 112c.
  • step S100 includes:
  • the second positive electrode active material layer 123 is coated on the other surface of the positive electrode current collector 121 .
  • the first positive electrode active material layer 122 is located on the outside of the positive electrode current collector 121, and the second positive electrode active material layer 123 is located on the inner side of the positive electrode current collector 121;
  • the third portion 1231 and the fourth portion 1232 provided by A, the third portion 1231 extends from the starting end of the second positive electrode active material layer 123 along the winding direction A, and the fourth portion 1232 is continuous with the third portion 1231 along the winding direction A
  • the thickness of the third part 1231 is smaller than that of the fourth part 1232 , and the thickness of the fourth part 1232 is equal to the thickness of the first positive electrode active material layer 122 ;
  • step S130 includes:
  • the part of the third active coating 123b that is not coated with the fourth active coating 123c forms a third part 1231 after curing, and the part of the third active coating 123b coated with the fourth active coating 123c and the fourth The reactive coating 123c forms a fourth portion 1232 after curing.
  • the positive electrode current collector 121 passes through the positive electrode coating device during the tape running process, and the positive electrode coating device includes a third coating head 83 and a fourth coating head 84 .
  • the third coating head 83 continuously coats the other surface of the positive electrode current collector 121 to form the third active coating layer 123b.
  • the positive electrode current collector 121 coated with the third active coating 123b passes through the fourth coating head 84, by controlling the opening and closing time of the fourth coating head 84, the third active coating 123b is away from the positive electrode current collector 121 by controlling the opening and closing time of the fourth coating head 84.
  • a set area of the surface of the 123C forms the fourth active coating 123c. This double-layer coating method is easy to control and helps to simplify the coating process.
  • step S100 and step S200 may be performed in no particular order, and may be performed simultaneously; step S230 may be performed first, and then step S220 may be performed; step S130 may be performed first, and then step S120 may be performed.
  • FIG. 27 is a schematic block diagram of a manufacturing system of an electrode assembly provided by some embodiments of the present application.
  • the manufacturing system of the electrode assembly includes: a first providing device 91 for providing a positive electrode plate; a second providing device 92 , used to provide a negative pole piece; and an assembly device 93, the negative pole piece and the positive pole piece are wound along the winding direction and form a winding structure.
  • the winding structure includes a bending area
  • both the negative pole piece and the positive pole piece include a plurality of bending parts located in the bending area.
  • At least one innermost bent portion in the negative pole piece is a first bent portion, and the active material capacity per unit area outside the first bent portion is greater than the active material capacity per unit area inside the first bent portion; and/or, At least one innermost bent portion in the positive electrode sheet is a second bent portion, and the active material capacity per unit area outside the second bent portion is greater than the active material capacity per unit area inside the second bent portion.
  • the manufacturing system further includes a third providing means (not shown) for providing a separator for isolating the positive pole piece and the negative pole piece.
  • the assembling device 93 is used for winding the first pole piece, the isolation film and the second pole piece along the winding direction to form a winding structure.

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Abstract

本申请实施例提供一种电极组件及其制造方法和制造系统、电池单体以及电池。电极组件，其包括负极极片和正极极片，负极极片和正极极片沿卷绕方向卷绕并形成卷绕结构，卷绕结构包括弯折区。负极极片和正极极片均包括位于弯折区的多个弯折部。其中，负极极片中的至少最内侧的一个弯折部为第一弯折部，第一弯折部外侧的单位面积活性物质容量大于第一弯折部内侧的单位面积活性物质容量；和/或，正极极片中的至少最内侧的一个弯折部为第二弯折部，第二弯折部外侧的单位面积活性物质容量大于第二弯折部内侧的单位面积活性物质容量。这种结构的电极组件中极片的至少部分区域的活性物质布置更为合理，具有更好的经济性。

Description

电极组件及其制造方法和制造系统、电池单体以及电池 技术领域
本申请涉及电池技术领域，并且更具体地，涉及一种电极组件及其制造方法和制造系统、电池单体以及电池。
背景技术
目前，车辆使用较多的电池一般是锂离子电池，锂离子电池作为一种可再充电电池，具有体积小、能量密度高、功率密度高、循环使用次数多和存储时间长等优点。
可再充电电池一般包括壳体和电极组件，壳体用于容纳电极组件和电解液，电极组件一般包括正极极片和负极极片，通过金属离子(如锂离子)在正极极片和负极极片之间移动来产生电能。
对于一般的电极组件而言，极片中的活性物质布置不合理，经济性较差。
发明内容
本申请提供了一种电极组件及其制造方法和制造系统、电池单体、电池以及用电设备，以改善极片中的活性物质布置不合理的问题。
第一方面，本申请实施例提供了一种电极组件，其包括负极极片和正极极片，负极极片和正极极片沿卷绕方向卷绕并形成卷绕结构，卷绕结构包括弯折区。负极极片和正极极片均包括位于弯折区的多个弯折部。其中，负极极片中的至少最内侧的一个弯折部为第一弯折部，第一弯折部外侧的单位面积活性物质容量大于第一弯折部内侧的单位面积活性物质容量；和/或，正极极片中的至少最内侧的一个弯折部为第二弯折部，第二弯折部外侧的单位面积活性物质容量大于第二弯折部内侧的单位面积活性物质容量。
上述方案中，负极极片的第一弯折部外侧的单位面积活性物质容量大于第一弯折部内侧的单位面积活性物质容量，不易出现第一弯折部的内侧活性物质过剩，而第一弯折部的外侧活性物质不足的情况，使得负极极片至少部分区域(第一弯折部所在的区域)的活性物质布置更为合理。正极极片的第二弯折部外侧的单位活性物质容量大于第二弯折部内侧的单位面积活性物质容量，不易出现第二弯折部的外侧活性物质不足，而第二弯折部的内侧活性物质过剩的情况，使得正极极片至少部分区域(第二弯折部所在的区域)的活性物质布置更为合理。这种结构的电极组件中极片的至少部分区域的活性物质布置更为合理，具有更好的经济性。
在一些实施例中，负极极片中的至少最内侧的一个弯折部为第一弯折部，正极 极片中的至少最内侧的一个弯折部为第二弯折部，第一弯折部的外侧布置有与第一弯折部相邻的第二弯折部。
上述方案中，在第一弯折部内侧单位面积活性物质容量和第二弯折部外侧单位面积活性物质容量满足设计要求时，第一弯折部外侧的单位面积活性物质容量大于第一弯折部内侧的单位面积活性物质容量，第二弯折部外侧的单位面积活性物质容量大于第二弯折部内侧的单位面积活性物质容量，可增大第一弯折部的外侧部分的CB值，从而降低析锂现象的发生。
在一些实施例中，负极极片中的至少最内侧的一个弯折部为第一弯折部。正极极片中与第一弯折部相邻的弯折部为第三弯折部。第三弯折部的外侧的单位面积活性物质容量等于第三弯折部的内侧的单位面积活性物质容量。
上述方案中，正极极片中与第一弯折部相邻的弯折部为第三弯折部，在第一弯折部外侧的单位面积活性物质容量大于第一弯折部内侧的单位面积活性物质容量的情况下，第三弯折部外侧的单位面积活性物质容量可以等于第三弯折部内侧的单位面积活性物质容量，可简化正极极片的制造工艺。
在一些实施例中，正极极片中的至少最内侧的一个弯折部为第二弯折部。负极极片中与第二弯折部相邻的弯折部为第四弯折部。第四弯折部的外侧的单位面积活性物质容量等于第四弯折部的内侧的单位面积活性物质容量。
在第二弯折部外侧的单位面积活性物质容量大于第二弯折部内侧的单位面积活性物质容量的情况下，第四弯折部外侧的单位面积活性物质容量可以等于第四弯折部内侧的单位面积活性物质容量，以简化负极极片的制造工艺。
在一些实施例中，第一弯折部包括第一集流部、第一活性物质部和第二活性物质部。第一集流部在其厚度方向上具有相对布置的第一内表面和第一外表面，第一活性物质部设于第一外表面，第二活性物质部设于第一内表面。
在一些实施例中，第一活性物质部的厚度大于第二活性物质部的厚度。
上述方案中，第一活性物质部的厚度大于第二活性物质部的厚度，可使得第一活性物质部的单位面积活性物质容量大于第二活性物质部的单位面积活性物质容量，从而实现第一弯折部外侧的单位面积活性物质容量大于第一弯折部内侧的单位面积活性物质容量。
在一些实施例中，第一弯折部还包括第一导电部，第一导电部连接于第二活性物质部与第一内表面之间，第一活性物质部的厚度大于或等于第二活性物质部与第一导电部的总厚度。
上述方案中，通过在第二活性物质部与第一集流部之间设置第一导电部，使得第一活性物质部的厚度大于或等于第二活性物质部与第一导电部的总厚度，以实现第一活性物质部的厚度大于第二活性物质部的厚度。
在一些实施例中，第一活性物质部中的活性材料的克容量大于第二活性物质部中的活性材料的克容量。
上述方案中，第一活性物质部中的活性材料的克容量大于第二活性物质部中的活性材料的克容量，可使得第一活性物质部的单位面积活性物质容量大于第二活性物 质部的单位面积活性物质容量，从而实现第一弯折部外侧的单位面积活性物质容量大于第一弯折部内侧的单位面积活性物质容量。
在一些实施例中，第一活性物质部中的活性材料与第一活性物质部的重量比大于第二活性物质部中的活性材料与第二活性物质部的重量比，从而实现第一弯折部外侧的单位面积活性物质容量大于第一弯折部内侧的单位面积活性物质容量。
在一些实施例中，第一弯折部还包括第一导电部，第一导电部连接于第一活性物质部与第一外表面之间，且第一导电部中包含有活性材料。第二活性物质部的厚度大于或等于第一活性物质部与第一导电部的总厚度。第一活性物质部中的活性材料的克容量小于第一导电部中的活性材料的克容量，从而实现第一弯折部外侧的单位面积活性物质容量大于第一弯折部内侧的单位面积活性物质容量；或者，第一活性物质部中的活性材料与第一活性物质部的重量比小于第一导电部中的活性材料与第一导电部的重量比，从而实现第一弯折部外侧的单位面积活性物质容量大于第一弯折部内侧的单位面积活性物质容量。
在一些实施例中，第二弯折部包括第二集流部、第三活性物质部和第四活性物质部。第二集流部在其厚度方向上具有相对布置的第二内表面和第二外表面，第三活性物质部设于第二外表面，第四活性物质部设于第二内表面。
在一些实施例中，第三活性物质部的厚度大于第四活性物质部的厚度。
上述方案中，第三活性物质部的厚度大于所述第四活性物质部的厚度，可使得第三活性物质部的单位面积活性物质容量大于第四活性物质部的单位面积活性物质容量，从而实现第二弯折部外侧的单位面积活性物质容量大于第二弯折部内侧的单位面积活性物质容量。
第二弯折部还包括第二导电部，第二导电部连接于第四活性物质部与第二内表面之间，第三活性物质部的厚度大于或等于第四活性物质部与第二导电部的总厚度。通过在第四活性物质部与第二集流部之间设置第二导电部，使得第三活性物质部的厚度大于或等于第四活性物质部与第二导电部的总厚度，以实现第三活性物质部的厚度大于第四活性物质部的厚度。
在一些实施例中，第三活性物质部中的活性材料的克容量大于第四活性物质部中的活性材料的克容量，可使得第三活性物质部的单位面积活性物质容量大于第四活性物质部的单位面积活性物质容量，从而实现第二弯折部外侧的单位面积活性物质容量大于第二弯折部内侧的单位面积活性物质容量。
在一些实施例中，第三活性物质部中的活性材料与第三活性物质部的重量比大于第四活性物质部中的活性材料与第四活性物质部的重量比，可使得第三活性物质部的单位面积活性物质容量大于第四活性物质部的单位面积活性物质容量，从而实现第二弯折部外侧的单位面积活性物质容量大于第二弯折部内侧的单位面积活性物质容量。
在一些实施例中，负极极片包括负极集流体、第一负极活性物质层和第二负极活性物质层，第一负极活性物质层位于负极集流体的外侧，第二负极活性物质层位于负极集流体的内侧。第一负极活性物质层包括沿卷绕方向设置的第一部分和第二部分，第一部分从第一负极活性物质层的起始端沿卷绕方向延伸，第二部分沿卷绕方向与第 一部分连续布置，且第一部分的厚度大于第二部分的厚度，第二部分的厚度等于第二负极活性物质层的厚度。
上述方案中，第一活性物质部为第一部分的位于第一弯折部的一部分。通过将第一负极活性物质层设置为具有不同厚度的第一部分和第二部分，可以实现第一弯折部外侧的单位面积活性物质容量大于第一弯折部内侧的单位面积活性物质容量。
在一些实施例中，第一部分沿卷绕方向至少卷绕一圈，这样能使负极极片中的至少最内侧的一个弯折部为第一弯折部。
在一些实施例中，正极极片包括正极集流体、第一正极活性物质层和第二正极活性物质层，第一正极活性物质层位于正极集流体的外侧，第二正极活性物质层位于正极集流体的内侧。第二正极活性物质层包括沿卷绕方向设置的第三部分和第四部分，第三部分从第二正极活性物质层的起始端沿卷绕方向延伸，第四部分沿卷绕方向与第三部分连续布置，且第三部分的厚度小于第四部分的厚度，第四部分的厚度等于第一正极活性物质层的厚度。
上述方案中，第四活性物质部为第三部分的位于第二弯折部的一部分。通过将第二正极活性物质层设置为具有不同厚度的第三部分和第四部分，可以实现第二弯折部外侧的单位面积活性物质容量大于第二弯折部内侧的单位面积活性物质容量。
在一些实施例中，第三部分沿卷绕方向至少卷绕一圈，这样能使正极极片中的至少最内侧的一个弯折部为第二弯折部。
在一些实施例中，负极极片中的从最内侧向外依次设置的多个弯折部为第一弯折部。负极极片中的位于多个第一弯折部外侧的弯折部为第四弯折部，第四弯折部的外侧的单位面积活性物质容量等于第四弯折部的内侧的单位面积活性物质容量。第四弯折部无需增大外侧的单位面积活性物质容量，从而可以节约活性材料的用量。
在一些实施例中，正极极片中的从最内侧向外依次设置的多个弯折部为第二弯折部。正极极片中的位于多个第二弯折部外侧的弯折部为第三弯折部，第三弯折部的外侧的单位面积活性物质容量等于第三弯折部的内侧的单位面积活性物质容量。第三弯折部无需减小内侧的单位面积活性物质容量，这样可以保证电极组件的容量。
第二方面，本申请实施例提供了一种电池单体，其包括外壳和上述第一方面任一实施例提供的电极组件。电极组件容纳于外壳内。
第三方面，本申请实施例提供了一种电池，其包括箱体和上述第二方面任一实施例提供的电池单体。电池单体容纳于箱体内。
第四方面，本申请实施例提供了一种用电设备，其包括上述第三方面任一实施例提供的电池，电池用于提供电能。
第五方面，本申请实施例提供了一种电极组件的制造方法，其包括：提供正极极片；提供负极极片；将负极极片和正极极片沿卷绕方向卷绕并形成卷绕结构。其中，卷绕结构包括弯折区，负极极片和正极极片均包括位于弯折区的多个弯折部。负极极片中的至少最内侧的一个弯折部为第一弯折部，第一弯折部外侧的单位面积活性物质容量大于第一弯折部内侧的单位面积活性物质容量；和/或，正极极片中的至少最内侧的一个弯折部为第二弯折部，第二弯折部外侧的单位面积活性物质容量大于第二弯折 部内侧的单位面积活性物质容量。
在一些实施例中，提供负极极片的步骤包括：提供负极集流体；在负极集流体的一个表面上涂覆第一负极活性物质层；在负极集流体的另一个表面涂覆第二负极活性物质层。其中，在卷绕结构中，第一负极活性物质层位于负极集流体的外侧，第二负极活性物质层位于负极集流体的内侧；第一负极活性物质层包括沿卷绕方向设置的第一部分和第二部分，第一部分从第一负极活性物质层的起始端沿卷绕方向延伸，第二部分沿卷绕方向与第一部分连续布置，且第一部分的厚度大于第二部分的厚度，第二部分的厚度等于第二负极活性物质层的厚度。第一部分的至少部分位于第一弯折部。
在一些实施例中，在负极集流体的一个表面上涂覆第一负极活性物质层的步骤包括：在负极集流体的一个表面上涂覆负极活性浆料以形成第一活性涂层；在第一活性涂层的背离负极集流体的表面的一部分区域涂覆负极活性浆料以形成第二活性涂层；第一活性涂层和第二活性涂层固化后形成第一负极活性物质层。其中，第一活性涂层的涂覆有第二活性涂层的部分和第二活性涂层在固化后形成第一部分；第一活性涂层的未涂覆第二活性涂层的部分在固化后形成第二部分。
在一些实施例中，提供正极极片的步骤包括：提供正极集流体；在正极集流体的一个表面上涂覆第一正极活性物质层；在正极集流体的另一个表面涂覆第二正极活性物质层。其中，在卷绕结构中，第一正极活性物质层位于正极集流体的外侧，第二正极活性物质层位于正极集流体的内侧；第二正极活性物质层包括沿卷绕方向设置的第三部分和第四部分，第三部分从第二正极活性物质层的起始端沿卷绕方向延伸，第四部分沿卷绕方向与第三部分连续布置，且第三部分的厚度小于第四部分的厚度，第四部分的厚度等于第一正极活性物质层的厚度。第三部分的至少部分位于第二弯折部。
在一些实施例中，在正极集流体的另一个表面涂覆第二正极活性物质层的步骤包括：在正极集流体的另一个表面上涂覆正极活性浆料以形成第三活性涂层；在第三活性涂层的背离正极集流体的表面的一部分区域涂覆正极活性浆料以形成第四活性涂层；第三活性涂层和第四活性涂层固化后形成第二正极活性物质层。其中，第三活性涂层的未涂覆第四活性涂层的部分在固化后形成第三部分，第三活性涂层的涂覆有第四活性涂层的部分和第四活性涂层在固化后形成第四部分。
第六方面，本申请实施例提供了一种电极组件的制造系统，其包括：第一提供装置，用于提供正极极片；第二提供装置，用于提供负极极片；以及组装装置，负极极片和正极极片沿卷绕方向卷绕并形成卷绕结构。其中，卷绕结构包括弯折区，负极极片和正极极片均包括位于弯折区的多个弯折部。负极极片中的至少最内侧的一个弯折部为第一弯折部，第一弯折部外侧的单位面积活性物质容量大于第一弯折部内侧的单位面积活性物质容量；和/或，正极极片中的至少最内侧的一个弯折部为第二弯折部，第二弯折部外侧的单位面积活性物质容量大于第二弯折部内侧的单位面积活性物质容量。
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。
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示意图；
图3为图2所示的电池模块的结构示意图；
图4为图3所示的电池单体的爆炸示意图；
图5为本申请一些实施例提供的电极组件的结构示意图；
图6为图5所示的电极组件在方框D处的放大示意图；
图7为本申请又一些实施例提供的电极组件的结构示意图；
图8为本申请另一些实施例提供的电极组件的结构示意图；
图9为图8所示的电极组件的弯折区的局部放大示意图；
图10为图8所示的负极极片在展开状态下的局部示意图；
图11为图8所示的电极组件在方框E处的放大示意图；
图12为本申请一些实施例提供的电极组件位于弯折区的部分的局部放大图；
图13为本申请另一些实施例提供的电极组件位于弯折区的部分的局部放大图；
图14为本申请又一些实施例提供的电极组件位于弯折区的部分的局部放大图；
图15为本申请又一些实施例提供的电极组件的结构示意图；
图16为图15所示的电极组件的弯折区的局部放大示意图；
图17为图15所示的正极极片在展开状态下的局部示意图；
图18为图15所示的电极组件在方框F处的放大示意图；
图19为本申请再一些实施例提供的电极组件位于弯折区的部分的局部放大图；
图20为本申请另一些实施例提供的电极组件位于弯折区的部分的局部放大图；
图21为本申请又一些实施例提供的电极组件位于弯折区的部分的局部放大图；
图22为本申请一些实施例提供的电极组件的制造方法的流程图；
图23为本申请一些实施例提供的负极极片在成型过程中的一示意图；
图24为本申请一些实施例提供的负极极片在成型过程中的另一示意图；
图25为本申请一些实施例提供的正极极片在成型过程中的一示意图；
图26为本申请一些实施例提供的正极极片在成型过程中的另一示意图；
图27为本申请一些实施例提供的电极组件的制造系统的示意性框图。
在附图中，附图并未按照实际的比例绘制。
具体实施方式
为使本申请实施例的目的、技术方案和优点更加清楚，下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚地描述，显然，所描述的实施例是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通 技术人员在没有作出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
除非另有定义，本申请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；本申请中在申请的说明书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。本申请的说明书和权利要求书或上述附图中的术语“第一”、“第二”等是用于区别不同对象，而不是用于描述特定顺序或主次关系。
在本申请中提及“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。
在本申请的描述中，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”、“附接”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，可以是两个元件内部的连通。对于本领域的普通技术人员而言，可以根据具体情况理解上述术语在本申请中的具体含义。
本申请中术语“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，本申请中字符“/”，一般表示前后关联对象是一种“或”的关系。
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。
本申请中出现的“多个”指的是两个以上(包括两个)。
本申请中，电池单体可以包括锂离子二次电池单体、锂离子一次电池单体、锂硫电池单体、钠锂离子电池单体、钠离子电池单体或镁离子电池单体等，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。
本申请的实施例所提到的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。
电池单体包括电极组件和电解液，电极组件由正极极片、负极极片和隔离膜组成。电池单体主要依靠金属离子在正极极片和负极极片之间移动来工作。正极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。
对于一般的电极组件而言，极片中的活性物质层布置不合理，经济性较差。
发明人发现，电极组件中的负极极片的内侧活性物质层厚度与负极极片的外侧活性物质层厚度等厚，负极极片的内侧活性物质层与外侧活性物质层的活性材料相同；正极极片的内侧活性物质层厚度与正极极片的外侧活性物质层等厚，正极极片的内侧活性物质层的活性材料相同与外侧活性物质层的活性材料相同。在电极组件的弯折区内，负极极片的内侧活性物质层的半径大于位于负极极片内侧的正极极片的外侧活性物质层的半径，而负极极片的外侧活性物质层的半径会小于负极极片的外侧的正极极片的内侧活性物质层的半径，这样就会出现负极极片在弯折区内的弯折部的内侧活性物质过剩，外侧活性物质不足的情况，同样，也可能会出现正极极片在弯折区内的弯折部的外侧活性物质不足，而内侧活性物质过剩的情况；特别地，越靠近卷绕的中心，这种情况越严重。这种结构的电极组件，极片中的活性物质布置不合理，经济性较差。
鉴于此，本申请实施例提供一种技术方案，负极极片和正极极片均包括位于弯折区的多个弯折部，负极极片中的至少最内侧的一个弯折部为第一弯折部，第一弯折部外侧的单位面积活性物质容量大于第一弯折部内侧的单位面积活性物质容量；和/或，正极极片中的至少最内侧的一个弯折部为第二弯折部，第二弯折部外侧的单位面积活性物质容量大于第二弯折部内侧的单位面积活性物质容量。这种结构使得极片在弯折区的至少部分区域的活性物质布置更为合理，具有更好的经济性。
本申请实施例描述的技术方案适用于电池以及使用电池的用电设备。
用电设备可以是车辆、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等。本申请实施例对上述用电设备不做特殊限制。
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1的结构示意图，车辆1的内部设置有电池2，电池2可以设置在车辆1的底部或头部或尾部。电池2可以用于车辆1的供电，例如，电池2可以作为车辆1的操作电源。
车辆1还可以包括控制器3和马达4，控制器3用来控制电池2为马达4供电，例如，用于车辆1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2不仅仅可以作为车辆1的操作电源，还可以作为车辆1的驱动电源，代替或部分地代替燃油或天然气为车辆1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2的爆炸示意图，电池2包括箱体5和电池单体(图2未示出)，电池单体容纳于箱体5内。
箱体5用于容纳电池单体，箱体5可以是多种结构。在一些实施例中，箱体5可以包括第一箱体部51和第二箱体部52，第一箱体部51与第二箱体部52相互盖合，第一箱体部51和第二箱体部52共同限定出用于容纳电池单体的容纳空间53。第二箱体部52可以是一端开口的空心结构，第一箱体部51为板状结构，第一箱体部51盖合于第二箱体部52的开口侧，以形成具有容纳空间53的箱体5；第一箱体部51和第二箱体部52也均可以是一侧开口的空心结构，第一箱体部51的开口侧盖合于第二箱体部52的开口侧，以形成具有容纳空间53的箱体5。当然，第一箱体部51和第二箱体部52可以是多种形状，比如，圆柱体、长方体等。
为提高第一箱体部51与第二箱体部52连接后的密封性，第一箱体部51与第二箱体部52之间也可以设置密封件，比如，密封胶、密封圈等。
假设第一箱体部51盖合于第二箱体部52的顶部，第一箱体部51亦可称之为上箱盖，第二箱体部52亦可称之为下箱体。
在电池2中，电池单体可以是一个，也可以是多个。若电池单体为多个，多个电池单体之间可串联或并联或混联，混联是指多个电池单体中既有串联又有并联。多个电池单体之间可直接串联或并联或混联在一起，再将多个电池单体构成的整体容纳于箱体5内；当然，也可以是多个电池单体先串联或并联或混联组成电池模块6，多个电池模块6再串联或并联或混联形成一个整体，并容纳于箱体5内。
在一些实施例中，请参照图3，图3为图2所示的电池模块6的结构示意图。电池单体为多个，多个电池单体先串联或并联或混联组成电池模块6。多个电池模块6再串联或并联或混联形成一个整体，并容纳于箱体内。
电池模块6中的多个电池单体7之间可通过汇流部件实现电连接，以实现电池模块6中的多个电池单体7的并联或串联或混联。
请参照图4，图4为图3所示的电池单体7的爆炸示意图。本申请实施例提供的电池单体7包括电极组件10和外壳20，电极组件10容纳于外壳20内。
在一些实施例中，外壳20还可用于容纳电解质，例如电解液。外壳20可以是多种结构形式。
在一些实施例中，外壳20可以包括壳体21和端盖22，壳体21为一侧开口的空心结构，端盖22盖合于壳体21的开口处并形成密封连接，以形成用于容纳电极组件10和电解质的密封空间。
在组装电池单体7时，可先将电极组件10放入壳体21内，再将端盖22盖合于壳体21的开口，然后经由端盖22上的电解质注入口将电极质注入壳体21内。
壳体21可以是多种形状，比如，圆柱体、长方体等。壳体21的形状可根据电 极组件10的具体形状来确定。比如，若电极组件10为圆柱体结构，则可选用为圆柱体壳体；若电极组件10为长方体结构，则可选用长方体壳体。当然，端盖22也可以是多种结构，比如，端盖22为板状结构、一端开口的空心结构等。示例性的，在图4中，壳体21为长方体结构，端盖22为板状结构，端盖22盖合于壳体21顶部的开口处。
在一些实施例中，电池单体7还可以包括正极电极端子30、负极电极端子40和泄压机构50，正极电极端子30、负极电极端子40和泄压机构50均安装于端盖22上。正极电极端子30和负极电极端子40均用于与电极组件10电连接，以输出电极组件10所产生的电能。泄压机构50用于在电池单体7的内部压力或温度达到预定值时泄放电池单体7内部的压力。
示例性的，泄压机构50位于正极电极端子30和负极电极端子40之间，泄压机构50可以是诸如防爆阀、防爆片、气阀、泄压阀或安全阀等部件。
当然，在一些实施例中，外壳20也可以是其他结构，比如，外壳20包括壳体21和两个端盖22，壳体21为相对的两侧开口的空心结构，一个端盖22对应盖合于壳体21的一个开口处并形成密封连接，以形成用于容纳电极组件10和电解质的密封空间。在这种结构中，正极电极端子30和负极电极端子40可安装在同一个端盖22上，也可以安装在不同的端盖22上；可以是一个端盖22上安装有泄压机构50，也可以是两个端盖22上均安装有泄压机构50。
需要说明的是，在电池单体7中，容纳于外壳20内的电极组件10可以是一个，也可以是多个。示例性的，在图4中，电极组件10为两个。
接下来结合附图对电极组件10的具体结构进行详细阐述。
请参照图5，图5为本申请一些实施例提供的电极组件10的结构示意图。本申请实施例的电极组件10包括负极极片11和正极极片12，负极极片11和正极极片12沿卷绕方向A卷绕并形成卷绕结构，卷绕结构包括弯折区B，负极极片11和正极极片12均包括位于弯折区B的多个弯折部14。
其中，负极极片11中的至少最内侧的一个弯折部14为第一弯折部，第一弯折部外侧的单位面积活性物质容量大于第一弯折部内侧的单位面积活性物质容量；和/或，正极极片12中的至少最内侧的一个弯折部14为第二弯折部，第二弯折部外侧的单位面积活性物质容量大于第二弯折部内侧的单位面积活性物质容量。
若负极极片11的第一弯折部外侧的单位面积活性物质容量大于第一弯折部内侧的单位面积活性物质容量，不易出现第一弯折部的内侧活性物质过剩，而第一弯折部的外侧活性物质不足的情况，使得负极极片11至少部分区域(第一弯折部所在的区域)的活性物质布置更为合理。若正极极片12的第二弯折部外侧的单位活性物质容量大于第二弯折部内侧的单位面积活性物质容量，不易出现第二弯折部的外侧活性物质不足，而第二弯折部的内侧活性物质过剩的情况，使得正极极片12至少部分区域(第二弯折部所在的区域)的活性物质布置更为合理。这种结构的电极组件10中极片的至少部分区域的活性物质布置更为合理，具有更好的经济性。
此外，在第一弯折部内侧的单位面积活性物质容量满足设计要求时，即第一弯折部内侧单位面积活性物质容量达到第一预设值，使得第一弯折部的内侧活性物质不 易出现析锂，由于第一弯折部外侧的单位面积活性物质容量大于第一弯折部内侧的单位面积活性物质容量，相对于第一预设值，相当于增大了第一弯折部外侧的单位面积活性物质容量，可增大第一弯折部的外侧活性物质的CB值，从而使得第一弯折部的外侧活性物质不易出现析锂现象。同样，在第二弯折部外侧单位面积活性物质容量满足设计要求时，即第二弯折部外侧单位面积活性物质容量达到第二预设值，使得负极极片11位于第二弯折部的外侧的弯折部14的内侧活性物质不易出现析锂，由于第二弯折部外侧的单位活性物质容量大于第二弯折部内侧的单位面积活性物质容量，相对于第二预设值，相当于减小了第二弯折部内侧的单位面积活性物质容量，使得负极极片11位于第二弯折部的内侧的弯折部14的外侧活性物质也不易出现析锂现象。
其中，CB(Cell Balance)值为单位面积的负极活性物质容量与单位面积的正极活性物质容量的比值。例如，负极极片11的弯折部14的外侧活性物质的CB(Cell Balance)值＝Q1/Q2，其中，负极极片11中的一个弯折部14的外侧活性物质的单位面积的活性物质容量为Q1，正极极片12中位于该一个弯折部14的外侧且与该一个弯折部14相邻的弯折部14的内侧活性物质的单位面积的活性物质容量为Q2。
发明人还发现，在卷绕正极极片12和负极极片11时，正极极片12和负极极片11在弯折区B进行折弯，所以可能会导致各自的活性物质脱落，称之为掉粉现象。尤其是负极极片11中最内侧的一个弯折部14和正极极片12中最内侧的一个弯折部14，其弯折程度最大，更容易导致活性物质脱落。由于活性物质的脱落，尤其是负极极片11上活性物质的脱落，可能导致该负极极片11的活性物质的嵌锂位少于其相邻的正极极片12的活性物质能够提供的锂离子数量，因此，锂离子电池在充电时，容易发生析锂现象。
在本申请中，由于第一弯折部外侧的单位面积活性物质容量大于第一弯折部内侧的单位面积活性物质容量，相当于增大了第一弯折部外侧的单位面积活性物质容量，即增大了第一弯折部外侧的活性物质的CB值，这样，即使第一弯折部外侧的活性物质在弯折过程中脱落，也能满足第一弯折部外侧的活性物质对CB值的要求，进而降低析锂的风险。同样，由于第二弯折部外侧的单位活性物质容量大于第二弯折部内侧的单位面积活性物质容量，相当于减小了第二弯折部内侧的单位面积活性物质容量，即使负极极片11位于第二弯折部的内侧的弯折部14的外侧活性物质出现脱落情况，也能降低负极极片11位于第二弯折部的内侧的弯折部14的外侧活性物质的析锂风险。
在本申请实施例中，卷绕方向A即为正极极片12和负极极片11从内向外周向卷绕的方向。在图5中，卷绕方向A为顺时针方向。
在一些实施例中，电极组件10还可以包括隔离膜13，隔离膜13用于将正极极片12和负极极片11隔离，以降低正极极片12与负极极片11之间出现短路的风险。隔离膜13具有大量贯通的微孔，能够保证电解质离子自由通过，对锂离子有很好的透过性，所以，隔离膜13基本上不能阻挡锂离子通过。
隔离膜13的材质可以为PP(polypropylene，聚丙烯)或PE(polyethylene，聚乙烯)等。
在一些实施例中，卷绕结构还包括平直区C，平直区C与弯折区B相连，可以 是平直区C相对的两端均设有弯折区B。平直区C即为卷绕结构具有平直结构的区域，正极极片12位于平直区C内的部分和负极极片11位于平直区C内的部分均基本平直布置。弯折区B即为卷绕结构具有弯折结构的区域，正极极片12位于弯折区B的部分(弯折部14)和负极极片11位于弯折区B的部分(弯折部14)均弯折分布。示例性的，正极极片12的弯折部14和负极极片11的弯折部14均为圆弧形。
需要说明的是，在弯折区B内布置有第一弯折部的情况下，可以是只有一个弯折区B内布置有第一弯折部，也可以是两个弯折区B内均布置有第一弯折部；在弯折区B内布置有第二弯折部的情况下，可以是只有一个弯折区B布置有第二弯折部，也可以是两个弯折区B内均布置有第二弯折部。
示例性的，如图5所示，在弯折区B中，正极极片12中的多个弯折部14与负极极片11中的多个弯折部14交错排布，即在弯折区B中，以负极极片11的一个弯折部14、正极极片12的一个弯折部14、负极极片11的一个弯折部14……的顺序依次排布。在一些实施例中，正极极片12的最内侧的一个弯折部14位于负极极片11的最内侧的一个弯折部14的外侧。
在一些实施例中，请参照图6，图6为图5所示的电极组件10在方框D处的放大示意图，负极极片11包括负极集流体111和设置于负极集流体111厚度方向上的两侧的负极活性物质层，负极集流体111厚度方向上的两侧的负极活性物质层分别称之为第一负极活性物质层112和第二负极活性物质层113。在卷绕结构中，第一负极活性物质层112位于负极集流体111的外侧，第二负极活性物质层113位于负极集流体111的内侧。在一些示例中，第一负极活性物质层112涂覆于负极集流体111的外表面，第二负极活性物质层113涂覆于负极集流体111的内表面。
正极极片12包括正极集流体121和设置于正极集流体121厚度方向上的两侧的正极活性物质层，正极集流体121厚度方向上的两侧的正极活性物质层分别称之为第一正极活性物质层122和第二正极活性物质层123。在卷绕结构中，第一正极活性物质层122位于正极集流体121的外侧，第二正极活性物质层123位于正极集流体121的内侧。在一些示例中，第一正极活性物质层122涂覆于正极集流体121的外表面，第二正极活性物质层123涂覆于正极集流体121的内表面。
其中，负极集流体111可以具有未涂覆负极活性物质层的部分，该部分为负极极耳(图未示出)；正极集流体121可以具有未涂覆正极活性物质层的部分，该部分为正极极耳(图未示出)。正极极耳用于与正极电极端子30(参见图4)电连接，负极极耳用于与负极电极端子40(参见图4)电连接。
在其他实施例中，请参照图7，图7为本申请又一些实施例提供的电极组件的结构示意图，卷绕结构中可以只有弯折区B，而没有平直区C，这种结构的电极组件10整体可以为圆柱体。在正极极片11中，正极极片11的一圈极片即为一个弯折部14；在负极极片12中，负极极片12的一圈极片即为一个弯折部14。
图8为本申请另一些实施例提供的电极组件10的结构示意图；图9为图8所示的电极组件10的弯折区B的局部放大示意图；图10为图8所示的负极极片11在展开状态下的局部示意图；图11为图8所示的电极组件10在方框E处的放大示意图。
在一些实施例中，如图8至图11所示，负极极片11中的至少最内侧的一个弯折部14为第一弯折部141，第一弯折部141外侧的单位面积活性物质容量大于第一弯折部141内侧的单位面积活性物质容量。正极极片12中与第一弯折部141相邻的弯折部14为第三弯折部143，第三弯折部143的外侧的单位面积活性物质容量等于第三弯折部143的内侧的单位面积活性物质容量。
在第一弯折部141外侧的单位面积活性物质容量大于第一弯折部141内侧的单位面积活性物质容量的情况下，第三弯折部143外侧的单位面积活性物质容量可以等于第三弯折部143内侧的单位面积活性物质容量，以简化正极极片12的制造工艺。
其中，第一弯折部141包括第一集流部1411、第一活性物质部1412和第二活性物质部1413。第一活性物质部1412和第二活性物质部1413分别位于第一集流部1411的两侧。在一些示例中，第一集流部1411在其厚度方向上具有相对布置的第一内表面1411a和第一外表面1411b，第一活性物质部1412设于第一外表面1411b，第二活性物质部1413设于第一内表面1411a。第三弯折部143包括第三集流部1431、第五活性物质部1432和第六活性物质部1433。第三集流部1431在其厚度方向上具有相对布置的第三内表面1431a和第三外表面1431b，第五活性物质部1432设于第三外表面1431b，第六活性物质部1433设于第三内表面1431a。
可理解的，第一集流部1411为负极集流体111(参见图6)的位于第一弯折部141的一部分，第一活性物质部1412为第一负极活性物质层112(参见图6)的位于第一弯折部141的一部分，第二活性物质部1413为第二负极活性物质层113(参见图6)的位于第一弯折部141的一部分。第三集流部1431为正极集流体121(参见图6)的位于第三弯折部143的一部分，第五活性物质部1432为第一正极活性物质层122(参见图6)的位于第三弯折部143的一部分，第六活性物质部1433为第二正极活性物质层123(参见图6)的位于第三弯折部143的一部分。
第一弯折部141外侧的单位面积活性物质容量大于第一弯折部141内侧的单位面积活性物质容量，即第一活性物质部1412(第一弯折部141的外侧部分)的单位面积活性物质容量大于第二活性物质部1413(第一弯折部141的内侧部分)的单位面积活性物质容量。第一弯折部141外侧的单位面积活性物质容量即为第一活性物质部1412的活性物质容量与第一外表面1411b的面积的比值，第一弯折部141内侧的单位面积活性物质容量即为第二活性物质部1413的活性物质容量与第一内表面1411a的面积的比值。
第三弯折部143外侧的单位面积活性物质容量等于第三弯折部143内侧的单位面积活性物质容量，即第五活性物质部1432(第三弯折部143的外侧部分)的单位面积活性物质容量等于第六活性物质部1433(第三弯折部143的内侧部分)的单位面积活性物质容量。第三弯折部143外侧的单位面积活性物质容量即为第五活性物质部1432的活性物质容量与第三外表面1431b的面积的比值，第三弯折部143内侧的单位面积活性物质容量，即为第六活性物质部1433的活性物质容量与第三内表面1431a的比值。
在负极极片11中，可以是全部弯折部14为第一弯折部141，也可以是部分弯 折部14为第一弯折部141。若负极极片11中的全部弯折部14为第一弯折部141，负极极片11中的全部弯折部14外侧的单位面活性物质容量大于内侧的单位面积活性物质容量。若负极极片11只有部分弯折部14为第一弯折部141，负极极片11中除了第一弯折部141以外的弯折部14均可以采用外侧的单位面积活性物质容量等于内侧的单位面积活性物质容量的结构。在正极极片12中，可以是全部弯折部14为第三弯折部143，也可以是只有部分弯折部14为第三弯折部143。
在一些实施例中，正极极片12中的全部弯折部14均为第三弯折部143，以简化正极极片12的制造工艺。
在负极极片11的多个弯折部14中，在从内到外的方向上，多个弯折部14的半径逐渐增大，其在折弯过程中掉粉的情况越轻微。因此，负极极片11的靠近外侧的一些弯折部14可以采用外侧的单位面积活性物质容量等于内侧的单位面积活性物质容量的结构。在一些实施例中，负极极片11中的至少最内侧的一个弯折部14为第一弯折部141，负极极片11中的至少最外侧的一个弯折部14为第四弯折部144，第四弯折部144的外侧的单位面积活性物质容量等于第四弯折部144的内侧的单位面积活性物质容量。在一些实施例中，第四弯折部144的内侧的单位面积活性物质容量等于第一弯折部141的内侧的单位面积活性物质容量。
第四弯折部144包括第四集流部1441、第七活性物质部1442和第八活性物质部1443。第四集流部1441在其厚度方向上具有相对布置的第四内表面1441a和第四外表面1441b，第七活性物质部1442设于第四外表面1441b，第八活性物质部1443设于第四内表面1441a。可以理解地，第四集流部1441为负极集流体111(参见图6)的位于第四弯折部144的部分，第七活性物质部1442为第一负极活性物质层112(参见图6)的位于第四弯折部144的部分，第八活性物质部1443为第二负极活性物质层113(参见图6)的位于第四弯折部144的部分。
第四弯折部144外侧的单位面积活性物质容量等于第四弯折部144内侧的单位面积活性物质容量，即第七活性物质部1442(第四弯折部144的外侧部分)的单位面积活性物质容量等于第八活性物质部1443(第四弯折部144的内侧部分)的单位面积活性物质容量。第四弯折部144外侧的单位面积活性物质容量即为第七活性物质部1442的活性物质容量与第四外表面1441b的面积的比值，第四弯折部144内侧的单位面积活性物质容量，即为第八活性物质部1443的活性物质容量与第四内表面1441a的面积的比值。
在一些实施例中，负极极片11中的从最内侧向外依次设置的多个弯折部14为第一弯折部141。负极极片11中的位于多个第一弯折部141外侧的弯折部14为第四弯折部144。负极极片11中的弯折部14的数量等于第一弯折部141的数量和第四弯折部144的数量之和。在一些示例中，在各弯折区B内，第一弯折部141的数量为两个。第四弯折部144无需增大外侧的单位面积活性物质容量，从而可以节约活性材料的用量。
在本申请实施例中，可通过多种方式来实现第一弯折部141外侧的单位面积活性物质容量大于第一弯折部141内侧的单位面积活性物质容量。
在一些实施例中，第一活性物质部1412的厚度大于第二活性物质部1413的厚 度，以使第一弯折部141外侧的单位面积活性物质容量大于第一弯折部141内侧的单位面积活性物质容量。在一些实施例中，除厚度外，第一活性物质部1412与第二活性物质部1413相同；例如，第一活性物质部1412的活性材料和第二活性物质部1413的活性材料相同，第一活性物质部1412的活性材料与第一活性物质部1412的重量比大于第二活性物质部1413的活性材料与第二活性物质部1413的重量比。
在其它参数(例如活性材料种类、活性材料重量比等)相同的情况下，第一活性物质部1412的厚度大于第二活性物质部1413的厚度，可使得第一活性物质部1412的单位面积活性物质容量大于第二活性物质部1413的单位面积活性物质容量，从而实现第一弯折部141外侧的单位面积活性物质容量大于第一弯折部141内侧的单位面积活性物质容量。
第一活性物质部1412的活性材料和第二活性物质部1413的活性材料均可以是石墨或硅的化合物等。第二活性物质部1413和第一活性物质部1412由成分相同的活性浆料固化而成。
可选地，第一活性物质部1412的厚度比第二活性物质部1413的厚度大0.5％-20％。
示例性的，第一活性物质部1412的厚度比第二活性物质部1413的厚度大1.5％-12％。
在一些实施例中，第一负极活性物质层112包括沿卷绕方向A设置的第一部分1121和第二部分1122，第一部分1121从第一负极活性物质层112的起始端112a沿卷绕方向A延伸，第二部分1122沿卷绕方向A与第一部分1121连续布置，且第一部分1121的厚度大于第二部分1122的厚度。第一负极活性物质层112的起始端112a即为第一负极活性物质层112沿卷绕方向A的内端。在一些示例中，第二部分1122的厚度等于第二负极活性物质层113的厚度。
在一些实施例中，第一活性物质部1412为第一部分1121的位于第一弯折部141的一部分，第七活性物质部1442为第二部分1122的位于第四弯折部144的一部分。通过将第一负极活性物质层112设置为具有不同厚度的第一部分1121和第二部分1122，可以实现第一弯折部141外侧的单位面积活性物质容量大于第一弯折部141内侧的单位面积活性物质容量、第四弯折部144外侧的单位面积活性物质容量等于第四弯折部144内侧的单位面积活性物质容量。
在一些实施例中，第一部分1121沿卷绕方向A至少卷绕一圈。也就是说，第一负极活性物质层112沿卷绕方向A卷绕为多圈，第一负极活性物质层112的至少第一圈为第一部分1121。第一圈的起点即为第一负极活性物质层112的起始端112a，第一圈的终点位于第一负极活性物质层112的起始端112a的外侧，且第一圈的起点和终点在第一负极活性物质层112的厚度方向上齐平。在本申请实施例中，第一部分1121沿卷绕方向A至少卷绕一圈，这样能使负极极片11中的至少最内侧的一个弯折部14为第一弯折部141。可选地，第一部分1121沿卷绕方向A卷绕两圈。
图12为本申请一些实施例提供的电极组件位于弯折区B的部分的局部放大图。在一些实施例中，请参照图12，第一弯折部141还包括第一导电部1414，第一导电部 1414连接于第二活性物质部1413与第一内表面1411a之间，第一活性物质部1412的厚度大于或等于第二活性物质部1413与第一导电部1414的总厚度。也就是说，通过在第二活性物质部1413与第一集流部1411之间设置第一导电部1414，使得第一活性物质部1412的厚度大于或等于第二活性物质部1413与第一导电部1414的总厚度，以实现第一活性物质部1412的厚度大于第二活性物质部1413的厚度。
在生产负极极片11时，只需使第一活性物质部1412的厚度大于或等于第二活性物质部1413与第一导电部1414的总厚度，则可实现第一活性物质部1412的厚度大于第二活性物质部1413的厚度。
其中，第一导电部1414可以是纯导电涂层，比如，第一导电部1414为由粘接剂和导电剂组成的纯导电涂层；第一导电部1414也可以是含有锂离子的活性涂层，比如，第一导电部1414为由富锂材料、粘接剂和导电剂组成的含有锂离子的活性涂层；第一导电部1414也可以是含锂离子的非活性涂层，比如，第一导电部1414为由粘接剂、导电剂和被碳酸锂包覆的锂粉组成的含锂离子的非活性涂层。
在一些实施例中，也可通过其他方式来实现第一弯折部141外侧的单位面积活性物质容量大于第一弯折部141内侧的单位面积活性物质容量。请参照图13，图13为本申请另一些实施例提供的电极组件位于弯折区B的部分的局部放大图。
在一些实施例中，第一活性物质部1412中的活性材料的克容量大于第二活性物质部1413中的活性材料的克容量，可使得第一活性物质部1412的单位面积活性物质容量大于第二活性物质部1413的单位面积活性物质容量，从而实现第一弯折部141外侧的单位面积活性物质容量大于第一弯折部141内侧的单位面积活性物质容量。在一些实施例中，除克容量外，第一活性物质部1412和第二活性物质部1413相同；例如，第一活性物质部1412的厚度和第二活性物质部1413的厚度相同，第一活性物质部1412的活性材料与第一活性物质部1412的重量比等于第二活性物质部1413的活性材料与第二活性物质部1413的重量比。
克容量是指活性材料所释放出的电容量与活性材料的质量之比。
本实施例中，第一活性物质部1412的活性材料与第二活性物质部1413的活性材料不同，比如，第一活性物质部1412的活性材料为硅的化合物，第二活性物质部1413的活性材料为石墨。
可选地，第一活性物质部1412中的活性材料的克容量比第二活性物质部1413中的活性材料的克容量大0.5％-20％。
示例性的，第一活性物质部1412中的活性材料的克容量比第二活性物质部1413中的活性材料的克容量大1.5％-12％。
在另一些实施例中，第一活性物质部1412中的活性材料与第一活性物质部1412的重量比大于第二活性物质部1413中的活性材料与第二活性物质部1413的重量比，从而实现第一弯折部141外侧的单位面积活性物质容量大于第一弯折部141内侧的单位面积活性物质容量。第一活性物质部1412和第二活性物质部1413均包括活性材料、粘接剂和导电剂，通过增加第一活性物质部1412中活性材料的重量比，可以实现第一弯折部141外侧的单位面积活性物质容量大于第一弯折部141内侧的单位面积活性 物质容量。
在一些实施例中，第一活性物质部1412的厚度和第二活性物质部1413的厚度相同，第一活性物质部1412的活性材料和第二活性物质部1413的活性材料相同，第一活性物质部1412中的活性材料与第一活性物质部1412的重量比大于第二活性物质部1413中的活性材料与第二活性物质部1413的重量比。
在一些实施例中，请参照图14，图14为本申请又一些实施例提供的电极组件10位于弯折区B的部分的局部放大图，第一弯折部141还包括第一导电部1414，第一导电部1414连接于第一活性物质部1412与第一外表面1411b之间，且第一导电部1414中包含有活性材料。第一导电部1414是含有锂离子的活性涂层，比如，第一导电部1414为由富锂材料、粘接剂和导电剂组成的含有锂离子的活性涂层。
第二活性物质部1413的厚度大于或等于第一活性物质部1412与第一导电部1414的总厚度。
在一些实施例中，除厚度外，第一活性物质部1412和第二活性物质部1413相同；例如，第一活性物质部1412的活性材料和第二活性物质部1413的活性材料相同，第一活性物质部1412的活性材料与第一活性物质部1412的重量比等于第二活性物质部1413的活性材料与第二活性物质部1413的重量比。第二活性物质部1413和第一活性物质部1412由成分相同的活性浆料固化而成。
在一些实施例中，第一活性物质部1412中的活性材料的克容量小于第一导电部1414中的活性材料的克容量；通过在第一导电部1414中添加克容量较大的活性材料，增大第一弯折部141外侧的单位面积活性物质容量，从而实现第一弯折部141外侧的单位面积活性物质容量大于第一弯折部141内侧的单位面积活性物质容量。
在一些实施例中，第一导电部1414的活性材料与第一导电部1414的重量比等于第一活性物质部1412的活性材料与第一活性物质部1412的重量比。
在另一些实施例中，第一活性物质部1412中的活性材料与第一活性物质部1412的重量比小于第一导电部1414中的活性材料与第一导电部1414的重量比，从而实现第一弯折部141外侧的单位面积活性物质容量大于第一弯折部141内侧的单位面积活性物质容量。在一些实施例中，第一活性物质部1412中的活性材料与第一导电部1414中的活性材料相同。
需要说明的是，在本申请实施例中，也可通过多种方式来实现第三弯折部143外侧的单位面积活性物质容量等于第三弯折部143内侧的单位面积活性物质容量。比如，第三弯折部143中的第五活性物质部1432的活性材料与第六活性物质部1433的活性材料相同，第五活性物质部1432的厚度等于第六活性物质部1433的厚度。也可通过多种方式来实现第四弯折部144外侧的单位面积活性物质容量等于第四弯折部144内侧的单位面积活性物质容量。比如，第四弯折部144中的第七活性物质部1442的活性材料与第八活性物质部1443的活性材料相同，第七活性物质部1442的厚度等于第八活性物质部1443的厚度。
图15为本申请又一些实施例提供的电极组件10的结构示意图；图16为图15所示的电极组件10的弯折区B的局部放大示意图；图17为图15所示的正极极片12在 展开状态下的局部示意图；图18为图15所示的电极组件10在方框F处的放大示意图。
在一些实施例中，请参照图15至图18，正极极片12中的至少最内侧的一个弯折部14为第二弯折部142，第二弯折部142外侧的单位面积活性物质容量大于第二弯折部142内侧的单位面积活性物质容量。负极极片11中与第二弯折部142相邻的弯折部14为第四弯折部144，第四弯折部144的外侧的单位面积活性物质容量等于第四弯折部144的内侧的单位面积活性物质容量。
在第二弯折部142外侧的单位面积活性物质容量大于第二弯折部142内侧的单位面积活性物质容量的情况下，第四弯折部144外侧的单位面积活性物质容量可以等于第四弯折部144内侧的单位面积活性物质容量，以简化负极极片11的制造工艺。
其中，第二弯折部142包括第二集流部1421、第三活性物质部1422和第四活性物质部1423。第三活性物质部1422和第四活性物质部1423分别设置于第二集流部1421的两侧。具体地，第二集流部1421在其厚度方向上具有相对布置的第二内表面1421a和第二外表面1421b，第三活性物质部1422设于第二外表面1421b，第四活性物质部1423设于第二内表面1421a。
可理解的，第二集流部1421为正极集流体121(参见图6)的位于第二弯折部142的一部分，第三活性物质部1422为第一正极活性物质层122(参见图6)的位于第二弯折部142的一部分，第四活性物质部1423为第二正极活性物质层123(参见图6)的位于第二弯折部142的一部分。
第二弯折部142外侧的单位面积活性物质容量大于第二弯折部142内侧的单位面积活性物质容量，即第三活性物质部1422(第二弯折部142的外侧部分)的单位面积活性物质容量大于第四活性物质部1423(第二弯折部142的内侧部分)的单位面积活性物质容量。第二弯折部142外侧的单位面积活性物质容量即为第三活性物质部1422的活性物质容量与第二外表面1421b的面积的比值，第三弯折部143内侧的单位面积活性物质容量即为第四活性物质部1423的活性物质容量与第二内表面1421a的面积的比值。
在正极极片12中，可以是全部弯折部14为第二弯折部142，也可以是部分弯折部14为第二弯折部142。若正极极片12中的全部弯折部14为第二弯折部142，正极极片12中的全部弯折部14外侧的单位面积活性物质容量大于内侧的单位面积活性物质容量。若正极极片12只有部分弯折部14为第二弯折部142，正极极片12中除了第二弯折部142以外的弯折部14均可以采用外侧的单位面积活性物质容量等于内侧的单位面积活性物质容量的结构。在负极极片11中，可以是全部弯折部14为第四弯折部144，也可以是只有部分弯折部14为第四弯折部144。
在一些实施例中，负极极片11中的全部弯折部14均为第四弯折部144，以简化负极极片11的制造工艺。
在负极极片11的多个弯折部14中，在从内到外的方向上，多个弯折部14的半径逐渐增大，其在折弯过程中掉粉的情况越轻微。因此，正极极片12的靠近外侧的一些弯折部14可以采用外侧的单位面积活性物质容量等于内侧的单位面积活性物质容量的结构。
在一些实施例中，正极极片12中的至少最内侧的一个弯折部14为第二弯折部142，正极极片12中的至少最外侧的一个弯折部14为第三弯折部143，第三弯折部143的外侧的单位面积活性物质容量等于第三弯折部143的内侧的单位面积活性物质容量。在一些实施例中，第三弯折部143的外侧的单位面积活性物质容量等于第二弯折部142的外侧的单位面积活性物质容量。
在一些实施例中，正极极片12中的从最内侧向外依次设置的多个弯折部14为第二弯折部142。正极极片12中的位于多个第二弯折部142外侧的弯折部14为第三弯折部143。正极极片12中的弯折部14的数量等于第二弯折部142的数量和第三弯折部143的数量之和。在一些示例中，在各弯折区B内，第二弯折部142的数量为两个。第三弯折部143无需减小内侧的单位面积活性物质容量，从而可以保证电极组件10的容量。
在本申请实施例中，可通过多种方式来实现第二弯折部142外侧的单位面积活性物质容量大于第二弯折部142内侧的单位面积活性物质容量。
在一些实施例中，第三活性物质部1422的厚度大于第四活性物质部1423的厚度，以使第二弯折部142外侧的单位面积活性物质容量大于第二弯折部142内侧的单位面积活性物质容量。在一些实施例中，除厚度外，第三活性物质部1422和第四活性物质部1423相同；例如，第二弯折部142中的第三活性物质部1422的活性材料与第四活性物质部1423的活性材料相同，第三活性物质部1422的活性材料与第三活性物质部1422的重量比等于第四活性物质部1423的活性材料与第四活性物质部1423的重量比。
在其它参数(例如活性材料种类、活性材料重量比等)相同的情况下，第三活性物质部1422的厚度大于第四活性物质部1423的厚度，可使得第三活性物质部1422的单位面积活性物质容量大于第四活性物质部1423的单位面积活性物质容量，从而实现第二弯折部142外侧的单位面积活性物质容量大于第二弯折部142内侧的单位面积活性物质容量。
第三活性物质部1422的活性材料和第四活性物质部1423的活性材料均可以是磷酸铁锂、锰酸锂、三元锂、钴酸锂等。第三活性物质部1422和第四活性物质部1423由成分相同的活性浆料固化而成。
可选地，第三活性物质部1422的厚度比第四活性物质部1423的厚度大0.5％-20％。
示例性的，第三活性物质部1422的厚度比第四活性物质部1423的厚度大1.5％-12％。
在一些实施例中，第二正极活性物质层123包括沿卷绕方向A设置的第三部分1231和第四部分1232，第三部分1231从第二正极活性物质层123的起始端123a沿卷绕方向A延伸，第四部分1232沿卷绕方向A与第三部分1231连续布置，且第三部分1231的厚度小于第四部分1232的厚度。第二正极活性物质层123的起始端123a即为第二正极活性物质层123沿卷绕方向A的内端。在一些示例中，第四部分1232的厚度等于第一正极活性物质层122的厚度。
在一些示例中，第四活性物质部1423为第三部分1231的位于第二弯折部142 的一部分，第六活性物质部1433为第四部分1232的位于第三弯折部143的一部分。通过将第二正极活性物质层123设置为具有不同厚度的第三部分1231和第四部分1232，可以实现第二弯折部142外侧的单位面积活性物质容量大于第二弯折部142内侧的单位面积活性物质容量、第三弯折部143外侧的单位面积活性物质容量等于第三弯折部143内侧的单位面积活性物质容量。
在一些实施例中，第三部分1231沿卷绕方向A至少卷绕一圈。也就是说，第二正极活性物质层123沿卷绕方向A卷绕为多圈，第二正极活性物质层123的至少第一圈为第三部分1231。第一圈的起点即为第二正极活性物质层123的起始端123a，第一圈的终点位于第二正极活性物质层123的起始端123a的外侧，且第一圈的起点和终点在第二正极活性物质层123的厚度方向上齐平。在本申请实施例中，第三部分1231沿卷绕方向A至少卷绕一圈，这样能使正极极片12中的至少最内侧的一个弯折部14为第二弯折部142。可选地，第三部分1231沿卷绕方向A卷绕两圈。
在一些实施例中，请参照图19，图19为本申请再一些实施例提供的电极组件位于弯折区B的部分的局部放大图，第二弯折部142还包括第二导电部1424，第二导电部1424连接于第四活性物质部1423与第二内表面1421a之间，第三活性物质部1422的厚度大于或等于第四活性物质部1423与第二导电部1424的总厚度。也就是说，通过在第四活性物质部1423与第二集流部1421之间设置第二导电部1424，使得第三活性物质部1422的厚度大于或等于第四活性物质部1423与第二导电部1424的总厚度，以实现第三活性物质部1422的厚度大于第四活性物质部1423的厚度。
在生产正极极片12时，只需使第三活性物质部1422的厚度大于或等于第四活性物质部1423与第二导电部1424的总厚度，则可实现第三活性物质部1422的厚度大于第四活性物质部1423的厚度。
其中，第二导电部1424可以是纯导电涂层，比如，第二导电部1424为由粘接剂和导电剂组成的纯导电涂层；第二导电部1424也可以是含有锂离子的活性涂层，比如，第二导电部1424为由富锂材料、粘接剂和导电剂组成的含有锂离子的活性涂层；第二导电部1424也可以是含锂离子的非活性涂层，比如，第二导电部1424为由粘接剂、导电剂和被碳酸锂包覆的锂粉组成的含锂离子的非活性涂层。
需要说明的是，在其它实施例中，也可以是第四活性物质部1423连接于第二导电部1424和第二内表面1421a之间。
在一些实施例中，请参照图20，图20为本申请另一些实施例提供的电极组件位于弯折区B的部分的局部放大图。
在一些实施例中，第三活性物质部1422中的活性材料的克容量大于第四活性物质部1423中的活性材料的克容量，可使得第四活性物质部1423的单位面积活性物质容量小于第三活性物质部1422的单位面积活性物质容量，从而实现第二弯折部142外侧的单位面积活性物质容量大于第二弯折部142内侧的单位面积活性物质容量。在一些实施例中，除克容量外，第三活性物质部1422和第四活性物质部1423相同；例如，第三活性物质部1422的厚度与第四活性物质部1423的厚度相等，第三活性物质部1422的活性材料与第三活性物质部1422的重量比等于第四活性物质部1423的活性材料与第 四活性物质部1423的重量比。
本实施例中，可以是第三活性物质部1422的活性材料与第四活性物质部1423的活性材料不同，比如，第三活性物质部1422中的活性物质材质为三元锂，第四活性物质部1423中的活性物质材质为磷酸铁锂。
可选地，第三活性物质部1422中的活性材料的克容量比第四活性物质部1423中的活性材料的克容量大0.5％-20％。
示例性的，第三活性物质部1422中的活性材料的克容量比第四活性物质部1423中的活性材料的克容量大1.5％-12％。
在另一些实施例中，第三活性物质部1422中的活性材料与第三活性物质部1422的重量比大于第四活性物质部1423中的活性材料与第四活性物质部1423的重量比，从而实现第二弯折部142外侧的单位面积活性物质容量大于第二弯折部142内侧的单位面积活性物质容量。第三活性物质部1422和第四活性物质部1423均包括活性材料、粘接剂和导电剂，通过减小第四活性物质部1423中活性材料的重量比，可以实现第二弯折部142外侧的单位面积活性物质容量大于第二弯折部142内侧的单位面积活性物质容量。
在一些实施例中，第三活性物质部1422的厚度与第四活性物质部1423的厚度相同，第三活性物质部1422中的活性材料与第四活性物质部1423中的活性材料相同，第三活性物质部1422中的活性材料与第三活性物质部1422的重量比大于第四活性物质部1423中的活性材料与第四活性物质部1423的重量比。
在一些实施例中，请参照图21，图21为本申请又一些实施例提供的电极组件位于弯折区B的部分的局部放大图，负极极片11中的至少最内侧的一个弯折部14为第一弯折部141，第一弯折部141外侧的单位面积活性物质容量大于第一弯折部141内侧的单位面积活性物质容量；正极极片12中的至少最内侧的一个弯折部14为第二弯折部142，第二弯折部142外侧的单位面积活性物质容量大于第二弯折部142内侧的单位面积活性物质容量。
在本实施例中，可以通过使第一弯折部141的第一活性物质部1412的厚度大于第二活性物质部1413的厚度的方式，或通过使第一弯折部141的第一活性物质部1412的活性材料的克容量大于第二活性物质部1413的活性材料的克容量的方式，或者其它方式，使得第一弯折部141外侧的单位面积活性物质容量大于第一弯折部141内侧的单位面积活性物质容量。同样，可以通过使第四活性物质部1423的厚度的厚度小于第二弯折部142的第三活性物质部1422的方式，或通过使第四活性物质部1423的活性材料的克容量小于第二弯折部142的第三活性物质部1422的活性材料的克容量的方式，或者其它方式，使得第二弯折部142外侧的单位面积活性物质容量大于第二弯折部142内侧的单位面积活性物质容量。
示例性的，在图21中，第一弯折部141的第一活性物质部1412的厚度大于第二活性物质部1413的厚度，第二弯折部142的第三活性物质部1422的厚度大于第四活性物质部1423的厚度。在一些实施例中，第一弯折部141的第一活性物质部1412的活性材料与第二活性物质部1413的活性材料相同，第一活性物质部1412的活性材料与第 一活性物质部1412的重量比等于第二活性物质部1413的活性材料与第二活性物质部1413的重量比。在一些实施例中，第二弯折部142的第三活性物质部1422的活性材料与第四活性物质部1423的活性材料相同，第三活性物质部1422的活性材料与第三活性物质部1422的重量比等于第四活性物质部1423的活性材料与第四活性物质部1423的重量比。
在一些实施例中，第一弯折部141的外侧布置有与第一弯折部141相邻的第二弯折部142。
在第一弯折部141内侧单位面积活性物质容量和第二弯折部142外侧单位面积活性物质容量满足设计要求时，第一弯折部141外侧的单位面积活性物质容量大于第一弯折部141内侧的单位面积活性物质容量，第二弯折部142外侧的单位面积活性物质容量大于第二弯折部142内侧的单位面积活性物质容量，可增大第一弯折部141的外侧部分的CB值，从而降低析锂现象的发生。
在本实施例中，在负极极片11中，可以是全部弯折部14为第一弯折部141，也可以是部分弯折部14为第一弯折部141。在正极极片12中，可以是全部弯折部14为第二弯折部142，也可以是部分弯折部14为第二弯折部142。
在一些实施例中，负极极片11中的部分弯折部14为第一弯折部141，正极极片12中的部分弯折部14为第二弯折部142。具体地，负极极片11中的从最内侧向外依次设置的多个弯折部14为第一弯折部141，负极极片11中的位于多个第一弯折部141外侧的弯折部14为第四弯折部144。正极极片12中的从最内侧向外依次设置的多个弯折部14为第二弯折部142，正极极片12中的位于多个第二弯折部142外侧的弯折部14为第三弯折部143。在一些实施例中，正极极片12中最内侧的弯折部14位于负极极片11中最内侧的弯折部14的外侧，第一弯折部141和第二弯折部142均为两个。
其中，关于单位面积活性物质容量和CB值测试步骤如下：
步骤1)：正极单面活性物质层的平均放电容量测试。取上述各实施例的正极极片，利用冲片模具获得含正极单面活性物质层的小圆片。以金属锂片为对电极，Celgard膜为隔离膜，溶解有LiPF6(1mol/L)的EC+DMC+DEC(体积比为1:1:1的碳酸乙烯酯、碳酸二甲酯、碳酸二乙酯)的溶液为电解液，在氩气保护的手套箱中组装6个相同的CR2430型扣式电池。①电池组装完后静置12h，②在0.1C的充电电流下进行恒流充电，直到电压到达上限截止电压x 1V，然后保持电压x 1V进行恒压充电，直到电流为50uA，③静置5min，④最后在0.1C的放电电流下进行恒流放电，直到电压到达下限截止电压y 1V，⑤静置5min,重复2-5步骤，记录第2次循环的放电容量。6个扣式电池放电容量的平均值即为正极单面活性物质层的平均放电容量。例如，当正极活性材料为磷酸铁锂(LFP)时，上限截止电压x 1V＝3.75V，下限截止电压y 1V＝2V。当正极活性材料为锂镍钴锰氧化物(NCM)时，上限截止电压x 1V＝4.25V，下限截止电压y 1V＝2.8V。
步骤2)：负极单面活性物质层的平均充电容量测试。取上述各实施例的负极极片，利用冲片模具获得与上述步骤1)中正极小圆片面积相同且包含负极单面膜层的小圆片。以金属锂片为对电极，Celgard膜为隔离膜，溶解有LiPF6(1mol/L)的EC+DMC+DEC(体积比为1:1:1的碳酸乙烯酯、碳酸二甲酯、碳酸二乙酯)的溶液为电解 液，在氩气保护的手套箱中组装6个CR2430型扣式电池。①电池组装完后静置12h，②在0.05C的放电电流下进行恒流放电，直到电压到达下限截止电压y 2mV，③然后再用50uA的放电电流进行恒流放电，直到电压达到下限截止电压y 2mV，④静置5min，⑤接着用10uA的放电电流进行恒流放电，直到达到下限截止电压y 2mV，⑥静置5分钟，⑦最后在0.1C的充电电流下进行恒流充电，直到最终电压达到上限截至电压x 2V，⑧静置5分钟，重复2-8步骤，记录第2次循环的充电容量。6个扣式电池充电容量的平均值即为负极单面膜层的平均充电容量。例如，当负极活性材料为石墨时，上限截止电压x 2V＝2V，下限截止电压y 2V＝5mV。当负极极活性材料为硅时，上限截止电压x 2V＝2V，下限截止电压y 2V＝5mV。
步骤3)：根据CB值＝上述负极单面活性物质层的平均充电容量(mAh)/上述正极单面活性物质层的平均放电容量(mAh)，计算得出CB值。
图22为本申请一些实施例提供的电极组件的制造方法的流程图；图23为本申请一些实施例提供的负极极片在成型过程中的一示意图；图24为本申请一些实施例提供的负极极片在成型过程中的另一示意图；图25为本申请一些实施例提供的正极极片在成型过程中的一示意图；图26为本申请一些实施例提供的正极极片在成型过程中的另一示意图。
参照图22，电极组件的制造方法包括：
S100：提供正极极片；
S200：提供负极极片；
S300：将负极极片和正极极片沿卷绕方向卷绕并形成卷绕结构。
其中，卷绕结构包括弯折区，负极极片和正极极片均包括位于弯折区的多个弯折部。负极极片中的至少最内侧的一个弯折部为第一弯折部，第一弯折部外侧的单位面积活性物质容量大于第一弯折部内侧的单位面积活性物质容量；和/或，正极极片中的至少最内侧的一个弯折部为第二弯折部，第二弯折部外侧的单位面积活性物质容量大于第二弯折部内侧的单位面积活性物质容量。
在一些实施例中，还提供用于将正极极片和负极极片隔离的隔离膜，将第一极片、隔离膜和第二极片沿卷绕方向卷绕并形成卷绕结构。
在一些实施例中，步骤S200包括：
S210：提供负极集流体111；
S220：参照图23，在负极集流体111的一个表面上涂覆第一负极活性物质层112；
S230：参照图24，在负极集流体111的另一个表面涂覆第二负极活性物质层113。
其中，在卷绕结构中，第一负极活性物质层112位于负极集流体111的外侧，第二负极活性物质层113位于负极集流体111的内侧；第一负极活性物质层112包括沿卷绕方向A设置的第一部分1121和第二部分1122，第一部分1121从第一负极活性物质层112的起始端沿卷绕方向A延伸，第二部分1122沿卷绕方向A与第一部分1121连续布置，且第一部分1121的厚度大于第二部分1122的厚度，第二部分1122的厚度等 于第二负极活性物质层113的厚度；第一部分1121的至少部分位于第一弯折部。
参照图23，步骤S220包括：
S221：在负极集流体111的一个表面上涂覆负极活性浆料以形成第一活性涂层112b；
S222：在第一活性涂层112b的背离负极集流体111的表面的一部分区域涂覆负极活性浆料以形成第二活性涂层112c；
S223：第一活性涂层112b和第二活性涂层112c固化后形成第一负极活性物质层112。
其中，第一活性涂层112b的涂覆有第二活性涂层112c的部分和第二活性涂层112c在固化后形成第一部分1121；第一活性涂层112b的未涂覆第二活性涂层112c的部分在固化后形成第二部分1122。
负极集流体111在走带过程中穿过负极涂布设备，负极涂布设备包括第一涂布头81和第二涂布头82。负极集流体111经过第一涂布头81时，第一涂布头81在负极集流体111的一个表面上连续涂布以形成第一活性涂层112b。涂覆有第一活性涂层112b的负极集流体111经过第二涂布头82时，可以通过控制第二涂布头82的启闭时间，在第一活性涂层112b的背离负极集流体111的表面的设定区域形成第二活性涂层112c。这种双层涂布的方式便于控制，有助于简化涂布工艺。
在一些实施例中，步骤S100包括：
S110：提供正极集流体121；
S120：参照图25，在正极集流体121的一个表面上涂覆第一正极活性物质层122；
S130：参照图26，在正极集流体121的另一个表面涂覆第二正极活性物质层123。
其中，在卷绕结构中，第一正极活性物质层122位于正极集流体121的外侧，第二正极活性物质层123位于正极集流体121的内侧；第二正极活性物质层123包括沿卷绕方向A设置的第三部分1231和第四部分1232，第三部分1231从第二正极活性物质层123的起始端沿卷绕方向A延伸，第四部分1232沿卷绕方向A与第三部分1231连续布置，且第三部分1231的厚度小于第四部分1232的厚度，第四部分1232的厚度等于第一正极活性物质层122的厚度；第三部分1231的至少部分位于第二弯折部142。
在一些实施例中，参照图26，步骤S130包括：
S131：在正极集流体121的另一个表面上涂覆正极活性浆料以形成第三活性涂层123b；
S132：在第三活性涂层123b的背离正极集流体121的表面的一部分区域涂覆正极活性浆料以形成第四活性涂层123c；
S133：第三活性涂层123b和第四活性涂层123c固化后形成第二正极活性物质层123。
其中，第三活性涂层123b的未涂覆第四活性涂层123c的部分在固化后形成第三部分1231，第三活性涂层123b的涂覆有第四活性涂层123c的部分和第四活性涂层 123c在固化后形成第四部分1232。
正极集流体121在走带过程中穿过正极涂布设备，正极涂布设备包括第三涂布头83和第四涂布头84。正极集流体121经过第三涂布头83时，第三涂布头83在正极集流体121的另一个表面上连续涂布以形成第三活性涂层123b。涂覆有第三活性涂层123b的正极集流体121经过第四涂布头84时，可以通过控制第四涂布头84的启闭时间，在第三活性涂层123b的背离正极集流体121的表面的设定区域形成第四活性涂层123c。这种双层涂布的方式便于控制，有助于简化涂布工艺。
需要说明的是，通过上述电极组件的制造方法制造出的电极组件的相关结构，可参见上述各实施例提供的电极组件。
在基于上述的电极组件的制造方法组装电极组件时，不必按照上述步骤依次进行，也就是说，可以按照实施例中提及的顺序执行步骤，也可以不同于实施例中提及的顺序执行步骤，或者若干步骤同时执行。例如，步骤S100和步骤S200的执行不分先后，也可以同时进行；可以先执行步骤S230，再执行步骤S220；可以先执行步骤S130，再执行步骤S120。
请参照图27，图27为本申请一些实施例提供的电极组件的制造系统的示意性框图，电极组件的制造系统包括：第一提供装置91，用于提供正极极片；第二提供装置92，用于提供负极极片；以及组装装置93，负极极片和正极极片沿卷绕方向卷绕并形成卷绕结构。
其中，卷绕结构包括弯折区，负极极片和正极极片均包括位于弯折区的多个弯折部。负极极片中的至少最内侧的一个弯折部为第一弯折部，第一弯折部外侧的单位面积活性物质容量大于第一弯折部内侧的单位面积活性物质容量；和/或，正极极片中的至少最内侧的一个弯折部为第二弯折部，第二弯折部外侧的单位面积活性物质容量大于第二弯折部内侧的单位面积活性物质容量。
在一些实施例中，制造系统还包括第三提供装置(未示出)，第三提供装置用于提供将正极极片和负极极片隔离的隔离膜。组装装置93用于将第一极片、隔离膜和第二极片沿卷绕方向卷绕并形成卷绕结构。
通过上述制造系统制造出的电极组件的相关结构，可参见上述各实施例提供的电极组件。
需要说明的是，在不冲突的情况下，本申请中的实施例及实施例中的特征可以相互组合。
最后应说明的是：以上实施例仅用以说明本申请的技术方案，而非对其限制；尽管参照前述实施例对本申请进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分技术特征进行等同替换，但这些修改或者替换，并不使相应技术方案的本质脱离本申请各实施例技术方案的精神和范围。

Claims (30)

  1. 一种电极组件，其特征在于，包括负极极片和正极极片，所述负极极片和所述正极极片沿卷绕方向卷绕并形成卷绕结构，所述卷绕结构包括弯折区；
    所述负极极片和所述正极极片均包括位于所述弯折区的多个弯折部；
    其中，所述负极极片中的至少最内侧的一个弯折部为第一弯折部，所述第一弯折部外侧的单位面积活性物质容量大于所述第一弯折部内侧的单位面积活性物质容量；和/或，所述正极极片中的至少最内侧的一个弯折部为第二弯折部，所述第二弯折部外侧的单位面积活性物质容量大于所述第二弯折部内侧的单位面积活性物质容量。
  2. 根据权利要求1所述的电极组件，其特征在于，所述负极极片中的至少最内侧的一个弯折部为所述第一弯折部，所述正极极片中的至少最内侧的一个弯折部为所述第二弯折部，所述第一弯折部的外侧布置有与所述第一弯折部相邻的所述第二弯折部。
  3. 根据权利要求1所述的电极组件，其特征在于，所述负极极片中的至少最内侧的一个弯折部为所述第一弯折部；
    所述正极极片中与所述第一弯折部相邻的弯折部为第三弯折部；
    所述第三弯折部的外侧的单位面积活性物质容量等于所述第三弯折部的内侧的单位面积活性物质容量。
  4. 根据权利要求1所述的电极组件，其特征在于，所述正极极片中的至少最内侧的一个弯折部为所述第二弯折部；
    所述负极极片中与所述第二弯折部相邻的弯折部为第四弯折部；
    所述第四弯折部的外侧的单位面积活性物质容量等于所述第四弯折部的内侧的单位面积活性物质容量。
  5. 根据权利要求1-3任一项所述的电极组件，其特征在于，所述第一弯折部包括第一集流部、第一活性物质部和第二活性物质部；
    所述第一集流部在其厚度方向上具有相对布置的第一内表面和第一外表面，所述第一活性物质部设于所述第一外表面，所述第二活性物质部设于所述第一内表面。
  6. 根据权利要求5所述的电极组件，其特征在于，所述第一活性物质部的厚度大于所述第二活性物质部的厚度。
  7. 根据权利要求6所述的电极组件，其特征在于，所述第一弯折部还包括第一导电部，所述第一导电部连接于所述第二活性物质部与所述第一内表面之间，所述第一活性物质部的厚度大于或等于所述第二活性物质部与所述第一导电部的总厚度。
  8. 根据权利要求5所述的电极组件，其特征在于，所述第一活性物质部中的活性材料的克容量大于所述第二活性物质部中的活性材料的克容量。
  9. 根据权利要求5所述的电极组件，其特征在于，所述第一活性物质部中的活性材料与所述第一活性物质部的重量比大于所述第二活性物质部中的活性材料与所述第二活性物质部的重量比。
  10. 根据权利要求5所述的电极组件，其特征在于，所述第一弯折部还包括第一导电部，所述第一导电部连接于所述第一活性物质部与所述第一外表面之间，且所述第 一导电部中包含有活性材料；
    所述第二活性物质部的厚度大于或等于所述第一活性物质部与所述第一导电部的总厚度；
    所述第一活性物质部中的活性材料的克容量小于所述第一导电部中的活性材料的克容量；或者，所述第一活性物质部中的活性材料与所述第一活性物质部的重量比小于所述第一导电部中的活性材料与所述第一导电部的重量比。
  11. 根据权利要求1、2或4所述的电极组件，其特征在于，所述第二弯折部包括第二集流部、第三活性物质部和第四活性物质部；
    所述第二集流部在其厚度方向上具有相对布置的第二内表面和第二外表面，所述第三活性物质部设于所述第二外表面，所述第四活性物质部设于所述第二内表面。
  12. 根据权利要求11所述的电极组件，其特征在于，
    所述第三活性物质部的厚度大于所述第四活性物质部的厚度。
  13. 根据权利要求12所述的电极组件，其特征在于，所述第二弯折部还包括第二导电部，所述第二导电部连接于所述第四活性物质部与所述第二内表面之间，所述第三活性物质部的厚度大于或等于所述第四活性物质部与所述第二导电部的总厚度。
  14. 根据权利要求11所述的电极组件，其特征在于，
    所述第三活性物质部中的活性材料的克容量大于所述第四活性物质部中的活性材料的克容量。
  15. 根据权利要求11所述的电极组件，其特征在于，
    所述第三活性物质部中的活性材料与所述第三活性物质部的重量比大于所述第四活性物质部中的活性材料与所述第四活性物质部的重量比。
  16. 根据权利要求1-15任一项所述的电极组件，其特征在于，所述负极极片包括负极集流体、第一负极活性物质层和第二负极活性物质层，所述第一负极活性物质层位于所述负极集流体的外侧，所述第二负极活性物质层位于所述负极集流体的内侧；
    所述第一负极活性物质层包括沿所述卷绕方向设置的第一部分和第二部分，所述第一部分从所述第一负极活性物质层的起始端沿所述卷绕方向延伸，所述第二部分沿所述卷绕方向与所述第一部分连续布置，且所述第一部分的厚度大于所述第二部分的厚度，所述第二部分的厚度等于所述第二负极活性物质层的厚度。
  17. 根据权利要求16所述的电极组件，其特征在于，所述第一部分沿所述卷绕方向至少卷绕一圈。
  18. 根据权利要求1-17任一项所述的电极组件，其特征在于，所述正极极片包括正极集流体、第一正极活性物质层和第二正极活性物质层，所述第一正极活性物质层位于所述正极集流体的外侧，所述第二正极活性物质层位于所述正极集流体的内侧；
    所述第二正极活性物质层包括沿所述卷绕方向设置的第三部分和第四部分，所述第三部分从所述第二正极活性物质层的起始端沿所述卷绕方向延伸，所述第四部分沿所述卷绕方向与所述第三部分连续布置，且所述第三部分的厚度小于所述第四部分的厚度，所述第四部分的厚度等于所述第一正极活性物质层的厚度。
  19. 根据权利要求18所述的电极组件，其特征在于，所述第三部分沿所述卷绕方向 至少卷绕一圈。
  20. 根据权利要求1-19任一项所述的电极组件，其特征在于，
    所述负极极片中的从最内侧向外依次设置的多个弯折部为所述第一弯折部；
    所述负极极片中的位于多个所述第一弯折部外侧的弯折部为第四弯折部，所述第四弯折部的外侧的单位面积活性物质容量等于所述第四弯折部的内侧的单位面积活性物质容量。
  21. 根据权利要求1-20任一项所述的电极组件，其特征在于，
    所述正极极片中的从最内侧向外依次设置的多个弯折部为所述第二弯折部；
    所述正极极片中的位于多个所述第二弯折部外侧的弯折部为第三弯折部，所述第三弯折部的外侧的单位面积活性物质容量等于所述第三弯折部的内侧的单位面积活性物质容量。
  22. 一种电池单体，其特征在于，包括外壳和根据权利要求1-21任一项所述的电极组件；
    所述电极组件容纳于所述外壳内。
  23. 一种电池，其特征在于，包括箱体和根据权利要求22所述的电池单体；
    所述电池单体容纳于所述箱体内。
  24. 一种用电设备，其特征在于，包括权利要求23所述的电池，所述电池用于提供电能。
  25. 一种电极组件的制造方法，其特征在于，包括：
    提供正极极片；
    提供负极极片；
    将所述负极极片和所述正极极片沿卷绕方向卷绕并形成卷绕结构；
    其中，所述卷绕结构包括弯折区，所述负极极片和所述正极极片均包括位于所述弯折区的多个弯折部；
    所述负极极片中的至少最内侧的一个弯折部为第一弯折部，所述第一弯折部外侧的单位面积活性物质容量大于所述第一弯折部内侧的单位面积活性物质容量；和/或，所述正极极片中的至少最内侧的一个弯折部为第二弯折部，所述第二弯折部外侧的单位面积活性物质容量大于所述第二弯折部内侧的单位面积活性物质容量。
  26. 根据权利要求25所述的制造方法，其特征在于，所述提供负极极片的步骤包括：提供负极集流体；在所述负极集流体的一个表面上涂覆第一负极活性物质层；在所述负极集流体的另一个表面涂覆第二负极活性物质层；
    其中，在所述卷绕结构中，所述第一负极活性物质层位于所述负极集流体的外侧，所述第二负极活性物质层位于所述负极集流体的内侧；所述第一负极活性物质层包括沿所述卷绕方向设置的第一部分和第二部分，所述第一部分从所述第一负极活性物质层的起始端沿所述卷绕方向延伸，所述第二部分沿所述卷绕方向与所述第一部分连续布置，且所述第一部分的厚度大于所述第二部分的厚度，所述第二部分的厚度等于所述第二负极活性物质层的厚度；所述第一部分的至少部分位于所述第一弯折部。
  27. 根据权利要求26所述的制造方法，其特征在于，所述在所述负极集流体的一个 表面上涂覆第一负极活性物质层的步骤包括：在所述负极集流体的一个表面上涂覆负极活性浆料以形成第一活性涂层；在所述第一活性涂层的背离所述负极集流体的表面的一部分区域涂覆所述负极活性浆料以形成第二活性涂层，所述第一活性涂层和所述第二活性涂层固化后形成所述第一负极活性物质层；
    其中，所述第一活性涂层的涂覆有所述第二活性涂层的部分和所述第二活性涂层在固化后形成所述第一部分，所述第一活性涂层的未涂覆所述第二活性涂层的部分在固化后形成所述第二部分。
  28. 根据权利要求25-27任一项所述的制造方法，其特征在于，所述提供正极极片的步骤包括：提供正极集流体；在所述正极集流体的一个表面上涂覆第一正极活性物质层；在所述正极集流体的另一个表面涂覆第二正极活性物质层；
    其中，在所述卷绕结构中，所述第一正极活性物质层位于所述正极集流体的外侧，所述第二正极活性物质层位于所述正极集流体的内侧；所述第二正极活性物质层包括沿所述卷绕方向设置的第三部分和第四部分，所述第三部分从所述第二正极活性物质层的起始端沿所述卷绕方向延伸，所述第四部分沿所述卷绕方向与所述第三部分连续布置，且所述第三部分的厚度小于所述第四部分的厚度，所述第四部分的厚度等于所述第一正极活性物质层的厚度；所述第三部分的至少部分位于所述第二弯折部。
  29. 根据权利要求28所述的制造方法，其特征在于，
    所述在所述正极集流体的另一个表面涂覆第二正极活性物质层的步骤包括：在所述正极集流体的另一个表面上涂覆正极活性浆料以形成第三活性涂层；在所述第三活性涂层的背离所述正极集流体的表面的一部分区域涂覆所述正极活性浆料以形成第四活性涂层；所述第三活性涂层和所述第四活性涂层固化后形成所述第二正极活性物质层；
    其中，所述第三活性涂层的未涂覆所述第四活性涂层的部分在固化后形成所述第三部分，所述第三活性涂层的涂覆有所述第四活性涂层的部分和所述第四活性涂层在固化后形成所述第四部分。
  30. 一种电极组件的制造系统，其特征在于，包括：
    第一提供装置，用于提供正极极片；
    第二提供装置，用于提供负极极片；以及
    组装装置，所述负极极片和所述正极极片沿卷绕方向卷绕并形成卷绕结构；
    其中，所述卷绕结构包括弯折区，所述负极极片和所述正极极片均包括位于所述弯折区的多个弯折部；
    所述负极极片中的至少最内侧的一个弯折部为第一弯折部，所述第一弯折部外侧的单位面积活性物质容量大于所述第一弯折部内侧的单位面积活性物质容量；和/或，所述正极极片中的至少最内侧的一个弯折部为第二弯折部，所述第二弯折部外侧的单位面积活性物质容量大于所述第二弯折部内侧的单位面积活性物质容量。
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