WO2022222092A1 - 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
WO2022222092A1
WO2022222092A1 PCT/CN2021/088914 CN2021088914W WO2022222092A1 WO 2022222092 A1 WO2022222092 A1 WO 2022222092A1 CN 2021088914 W CN2021088914 W CN 2021088914W WO 2022222092 A1 WO2022222092 A1 WO 2022222092A1
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WIPO (PCT)
Prior art keywords
active material
straight
pole piece
bent portion
per unit
Prior art date
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PCT/CN2021/088914
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English (en)
French (fr)
Inventor
郑义
康海杨
许虎
孙成栋
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 EP21923592.6A priority Critical patent/EP4102591A4/en
Priority to CN202180007207.XA priority patent/CN115516691A/zh
Priority to PCT/CN2021/088914 priority patent/WO2022222092A1/zh
Priority to US17/875,163 priority patent/US20220367921A1/en
Publication of WO2022222092A1 publication Critical patent/WO2022222092A1/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
    • H01M10/058—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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/04—Construction or manufacture in general
    • H01M10/0404—Machines for assembling batteries
    • H01M10/0409—Machines for assembling batteries for cells with wound electrodes
    • 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
    • H01M10/04—Construction or manufacture in general
    • H01M10/0431—Cells with wound or folded electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/10—Primary casings; Jackets or wrappings
    • H01M50/102—Primary casings; Jackets or wrappings characterised by their shape or physical structure
    • 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
    • H01M50/10—Primary casings; Jackets or wrappings
    • H01M50/102—Primary casings; Jackets or wrappings characterised by their shape or physical structure
    • H01M50/103—Primary casings; Jackets or wrappings characterised by their shape or physical structure prismatic or rectangular
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • 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.
  • a rechargeable battery cell which can be called a secondary battery cell, refers to a battery cell that can activate active materials by charging and continue to be used after the battery cell is discharged.
  • Rechargeable battery cells are widely used in electronic devices, such as cell phones, laptop computers, battery cars, electric vehicles, electric planes, electric ships, electric toy cars, electric toy ships, electric toy planes, and electric tools, among others.
  • 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, including 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. and a straight area connected to the bend area.
  • Both the negative pole piece and the positive pole piece include a plurality of bent portions located in the bending region and a plurality of straight portions located in the straight region.
  • At least one bent portion in the positive pole piece is a first bent portion
  • at least one straight portion in the positive pole piece is a first straight portion connected to the first bent portion, and the inner side of the first bent portion
  • the active material capacity per unit area is less than the active material capacity per unit area inside the first straight portion
  • at least one bent portion in the negative pole piece is the second bent portion
  • at least one straight portion in the negative pole piece is The portion is a second straight portion connected to 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 outside the second straight portion.
  • the capacity of active material per unit area inside the first bent portion is smaller than the capacity of active material per unit area inside the first straight portion, it is unlikely that there is too much active material inside the first bent portion.
  • the active material arrangement of the tablet is more reasonable and the risk of lithium precipitation is reduced. If the active material capacity per unit area outside the second bent portion is greater than the active material capacity per unit area outside the second straight portion, it is less likely that the active material outside the second bent portion is insufficient, and the risk of lithium precipitation is reduced.
  • the arrangement of the active material of the electrode assembly in the electrode assembly with this structure is more reasonable, has better economy, and reduces the risk of lithium precipitation.
  • At least one bent portion in the positive electrode sheet is a first bent portion
  • at least one bent portion in the negative electrode sheet is a second bent portion
  • an outer side of the second bent portion is arranged with a The second bent portion is adjacent to the first bent portion
  • the active material capacity per unit area inside the first straight portion and the active material capacity per unit area outside the second straight portion meet the design requirements, the active material capacity per unit area inside the first bent portion is smaller than the first.
  • the active material capacity per unit area inside the straight portion and the active material capacity per unit area outside the second bent portion is greater than the active material capacity per unit area outside the second straight portion, so that the active material outside the second bent portion can be increased. CB value, thereby reducing the occurrence of lithium precipitation.
  • At least one bent portion in the positive electrode sheet is a first bent portion.
  • the bent portion adjacent to the first bent portion in the negative electrode piece is a third bent portion, and at least one straight portion in the negative electrode piece is a third straight portion connected to the third bent portion.
  • the active material capacity per unit area outside the third bent portion is equal to the active material capacity per unit area outside the third straight portion. In this way, the manufacturing process of the negative pole piece can be simplified.
  • At least one bent portion in the negative pole piece is the second bent portion.
  • the bent portion adjacent to the second bent portion in the positive electrode piece is a fourth bent portion, and at least one straight portion in the positive electrode piece is a fourth straight portion connected to the fourth bent portion.
  • the active material capacity per unit area inside the fourth bent portion is equal to the active material capacity per unit area inside the fourth straight portion. In this way, the manufacturing process of the positive electrode sheet can be simplified.
  • the first bent portion includes a first current collecting portion, a first inner active material portion disposed inside the first current collecting portion, and connected between the first current collecting portion and the first inner active material portion of the first conductive part.
  • the capacity of the active material per unit area inside the first bending portion is reduced by arranging the first conductive portion.
  • the first straight portion includes a second current collecting portion and a second inner active material portion disposed inside the second current collecting portion.
  • the thickness of the second inner active material portion is greater than that of the first inner active material portion, so that the active material capacity per unit area inside the first bent portion is smaller than the active material capacity per unit area inside the first straight portion.
  • the first straight portion further includes a third inner active material portion and a second conductive portion, the third inner active material portion is disposed inside the second current collecting portion, and the second conductive portion is connected to the second current collecting portion between the flow portion and the third inner active material portion.
  • the second conductive portion is connected between the first conductive portion and the second inner active material portion, and the third inner active material portion is connected between the first inner active material portion and the second inner active material portion.
  • the first conductive portion includes an active material therein.
  • the gram capacity of the active material in the first conductive portion is smaller than the gram capacity of the active material in the first inner active material portion.
  • the capacity of the active material per unit area inside the first bending part is reduced, so that the capacity per unit area of the active material inside the first bending part is smaller than that of the first bending part.
  • the active material capacity per unit area inside the flat portion is reduced, so that the capacity per unit area of the active material inside the first bending part is smaller than that of the first bending part.
  • the weight ratio of the active material in the first conductive part to the first conductive part is smaller than the weight ratio of the active material in the first inner active material part to the first inner active material part, so as to reduce the first bending
  • the active material capacity per unit area inside the folded portion can be achieved, so that the active material capacity per unit area inside the first bent portion is smaller than the active material capacity per unit area inside the first straight portion.
  • the second bent portion includes a third current collecting portion and a first outer active material portion disposed outside the third current collecting portion, and the second straight portion includes a fourth current collecting portion and a first outer active material portion disposed outside the third current collecting portion.
  • the second outer active material part outside the current collecting part.
  • the thickness of the first outer active material portion is greater than the thickness of the second outer active material portion, so that the active material capacity per unit area outside the second bent portion is greater than the active material per unit area outside the second straight portion capacity.
  • the gram capacity of active material in the first outer active material portion is greater than the gram capacity of active material in the second outer active material portion.
  • the weight ratio of the active material in the first outer active material part to the first outer active material part is greater than the weight ratio of the active material in the second outer active material part to the second outer active material part, which can
  • the active material capacity per unit area of the first outer active material portion is larger than the active material capacity per unit area of the second outer active material portion, so that the active material capacity per unit area outside the second bent portion is greater than the unit area outside the second straight portion Area active material capacity.
  • the second bending portion includes a third conductive portion, the third conductive portion is connected between the third current collecting portion and the first outer active material portion, and the third conductive portion contains an active material.
  • the gram capacity of the active material in the third conductive portion is greater than the gram capacity of the active material in the first outer active material portion; or, the weight ratio of the active material in the third conductive portion to the third conductive portion is greater than that of the first outer active material The weight ratio of the active material in the part to the first outer active material part.
  • the capacity of the active material per unit area outside the second bending portion is increased by arranging the third conductive portion.
  • the second straight portion further includes a third outer active material portion and a fourth conductive portion, the third outer active material portion is disposed outside the fourth current collecting portion, and the fourth conductive portion is connected to the fourth current collecting portion between the flow portion and the third externally active material portion.
  • the fourth conductive part is connected between the third conductive part and the second external active material part, and the third external active material part is connected between the first external active material part and the second external active material part.
  • At least one innermost bent portion of the positive electrode plate is the first bent portion. Since the capacity of active material per unit area inside the first bent portion is smaller than the capacity of active material per unit area inside the first straight portion, it is equivalent to reducing the capacity of active material per unit area inside the first bent portion.
  • the outer active material of the bent portion located inside the first bent portion may fall off, which can also reduce the risk of lithium deposition in the bent portion of the negative electrode sheet located inside the first bent portion.
  • At least one innermost bent portion of the negative pole piece is the second bent portion. Since the capacity of the active material per unit area outside the second bent portion is greater than the capacity of the active material per unit area outside the second straight portion, it is equivalent to increasing the capacity of the active material per unit area outside the second bent portion, that is, increasing the capacity of the active material per unit area outside the second bent portion.
  • the CB value of the active material outside the second bending portion so that even if the active material outside the second bending portion falls off during the bending process, it can meet the requirements of the CB value for the active material outside the second bending portion, and then Reduce the risk of lithium precipitation.
  • an embodiment of the present application provides a battery cell, which includes a casing and the electrode assembly according to any embodiment of the first aspect, and the electrode assembly is accommodated in the casing.
  • an embodiment of the present application provides a battery, including a case body and a battery cell according to any embodiment of the second aspect, wherein the battery cell is accommodated in the case body.
  • an embodiment of the present application provides an electrical device, including the battery according to 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, including: providing a negative pole piece; providing a positive pole piece; winding the negative pole piece and the positive pole piece along a winding direction to form a winding structure.
  • the coiled structure includes a bent region and a straight region connected to the bent region.
  • Both the negative pole piece and the positive pole piece include a plurality of bent portions located in the bending region and a plurality of straight portions located in the straight region.
  • At least one bent portion in the positive pole piece is a first bent portion, at least one straight portion in the positive pole piece is a first straight portion connected to the first bent portion, and the unit inside the first bent portion
  • the area active material capacity is less than the unit area active material capacity inside the first straight portion; and/or, at least one bent portion in the negative pole piece is the second bent portion, and at least one straight portion in the negative pole piece is
  • the second straight portion connected to the second bent portion has a larger active material capacity per unit area outside the second bent portion than the outside of the second straight portion.
  • an embodiment of the present application provides a manufacturing system for an electrode assembly, including: a first providing device for providing a negative pole piece; a second providing device for providing a positive pole piece; an assembling device for assembling the negative pole piece
  • the sheet and the positive electrode sheet are wound along the winding direction and form a wound structure.
  • the coiled structure includes a bent region and a straight region connected to the bent region.
  • Both the negative pole piece and the positive pole piece include a plurality of bent portions located in the bending region and a plurality of straight portions located in the straight region.
  • At least one bent part in the positive pole piece is a first bent part, and at least one straight part in the positive pole piece is a first straight part connected to the first bent part, and the unit inside the first bent part
  • the area active material capacity is less than the unit area active material capacity inside the first straight portion; and/or, at least one bent portion in the negative pole piece is the second bent portion, and at least one straight portion in the negative pole piece is The second straight portion connected to the second bent portion has a larger active material capacity per unit area outside the second bent portion than the outside of the second straight 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 a battery module provided by some embodiments of the present application.
  • 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 partial cross-sectional view of an electrode assembly provided by some embodiments of the present application.
  • FIG. 8 is a partial cross-sectional schematic diagram of an electrode assembly provided by other embodiments of the present application.
  • FIG. 9 is a partial cross-sectional schematic diagram of an electrode assembly provided by further embodiments of the present application.
  • FIG. 10 is a schematic partial cross-sectional view of an electrode assembly provided by further embodiments of the present application.
  • FIG. 11 is a partial cross-sectional schematic diagram of an electrode assembly provided by other embodiments of the present application.
  • FIG. 12 is a partial cross-sectional schematic diagram of an electrode assembly provided by further embodiments of the present application.
  • FIG. 13 is a partial cross-sectional schematic diagram of an electrode assembly provided by further embodiments of the present application.
  • FIG. 14 is a partial cross-sectional schematic diagram of an electrode assembly provided by other embodiments of the present application.
  • 15 is a schematic flowchart of a method for manufacturing an electrode assembly provided by some embodiments of the present application.
  • FIG. 16 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
  • the positive electrode active material layer includes a positive electrode active material
  • 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, the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material can be carbon or silicon or the like.
  • 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 separator can be PP (polypropylene, polypropylene) or PE (polyethylene, polyethylene), and 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 electrode assembly of the wound structure includes a straight region and a bent region.
  • the inventor found that the thickness of the inner active material layer of the positive pole piece located in the flat region is equal to the thickness of the inner active material layer of the positive pole piece located in the bending region, and the inner active material layer of the positive pole piece located in the flat region is the same as the positive electrode.
  • the inner active material layer of the pole piece located in the bending area adopts the same material; the thickness of the outer active material layer of the negative pole piece located in the flat area is equal to the thickness of the outer active material layer of the negative pole piece located in the bending area, and the negative pole piece is located in the bending area.
  • the same material is used for the outer active material layer of the sheet located in the flat region and the outer active material layer of the negative electrode plate located in the bent region.
  • the radius of the inner active material layer of the positive pole piece is larger than the radius of the outer active material layer of the negative pole piece located inside the positive pole piece, that is to say, the radius of the outer active material layer of the negative pole piece is smaller than the radius of the outer active material layer of the negative pole piece
  • the inner active material layer of the positive pole piece outside the pole piece.
  • the inner active material layer of the positive electrode piece and the outer active material layer of the negative electrode piece are arranged correspondingly.
  • the inner active material layer of the positive pole piece located in the flat area meets the requirements, the inner active material layer of the positive pole piece located in the bending area is too much, which makes the negative pole piece located on the inner side of the positive pole piece prone to precipitation. lithium.
  • the outer active material layer of the negative pole piece located in the bent region is likely to be insufficient and lead to lithium deposition. Therefore, in the electrode assembly of this structure, the arrangement of the active material in the pole piece is unreasonable, the economy is poor, and it is easy to cause the risk of lithium precipitation.
  • the electrode assembly includes a negative pole piece and a positive pole piece.
  • the negative pole piece and the positive pole piece are wound along the winding direction to form a winding structure, and the winding structure includes a bending area and a straight area connected to the bending area.
  • Both the negative pole piece and the positive pole piece include a plurality of bent portions located in the bending region and a plurality of straight portions located in the straight region.
  • At least one bent part in the positive pole piece is a first bent part, and at least one straight part in the positive pole piece is a first straight part connected to the first bent part, and the unit inside the first bent part
  • the area active material capacity is less than the unit area active material capacity inside the first straight portion; and/or, at least one bent portion in the negative pole piece is the second bent portion, and at least one straight portion in the negative pole piece is
  • the second straight portion connected to the second bent portion has a larger active material capacity per unit area outside the second bent portion than the outside of the second straight portion.
  • Electrical devices 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 device.
  • the electric device is a vehicle as an example for description.
  • FIG. 1 is a schematic structural diagram of a vehicle according to some embodiments of the present application.
  • the interior of the vehicle 1 is provided with a battery 2 , and the battery 2 may be provided 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 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 box body portion 51 and the second box body 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 a battery module provided by some embodiments of the present application. As shown in FIG. 3 , in some embodiments, there are multiple battery cells 7 , and the multiple battery cells 7 are first connected in series or in parallel or mixed to form a battery module 6 . 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 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 housing 21 can be in various shapes, such as a cylinder, a rectangular parallelepiped, and the like.
  • the shape of the case 21 may be determined according to the specific shape of the electrode assembly 10 .
  • the end cap 22 may 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.
  • the casing 21 is a rectangular parallelepiped structure
  • the end cover 22 is a plate-like structure
  • the end cover 22 is covered with 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 for releasing 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 be of 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 The cover 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 provided by some embodiments of the present application.
  • the electrode assembly 10 of the embodiment of the present application includes a positive electrode piece 11 and a negative electrode piece 12 , and the negative electrode piece 12 and the positive electrode piece 11 are wound along the winding direction A to form a winding structure. It includes a bending area B and a straight area C connected to the bending area B. Both the negative pole piece 12 and the positive pole piece 11 include a plurality of bent parts 14 located in the bending region B and a plurality of straight parts 15 located in the straight region C.
  • At least one bent portion 14 in the positive pole piece 11 is a first bent portion, and at least one straight portion 15 in the positive pole piece 11 is a first straight portion connected to the first bent portion.
  • the active material capacity per unit area on the inner side of the first straight portion is less than the active material capacity per unit area on the inner side of the first straight portion;
  • the at least one straight portion 15 is a second straight portion connected to 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 outside the second straight portion.
  • the active material capacity per unit area inside the first bent portion is smaller than the active material capacity per unit area inside the first straight portion, it is less likely that the active material inside the first bent portion is too much, which will make the active material of the positive electrode sheet 11 less active.
  • the material arrangement is more reasonable and the risk of lithium precipitation is reduced.
  • the active material capacity per unit area outside the second bent portion is greater than the active material capacity per unit area outside the second straight portion, it is less likely that the active material outside the second bent portion is insufficient, and the risk of lithium precipitation is reduced.
  • the electrode assembly 10 with this structure has a more reasonable arrangement of the active material of the electrode pieces, has better economy, and reduces the risk of lithium precipitation.
  • the capacity of the active material per unit area inside the first straight portion meets the design requirements, that is, the capacity of the active material per unit area inside the first straight portion reaches the first preset value, so that the negative pole piece 12 is located inside the first straight portion
  • the active material on the outer side of the straight portion 15 is not prone to lithium deposition; since the capacity of the active material per unit area inside the first bent portion is smaller than the capacity of the active material per unit area inside the first straight portion, relative to the first preset value, it is equivalent to In order to reduce the capacity of the active material per unit area inside the first bent portion, the bent portion 14 of the negative electrode sheet 12 located inside the first bent portion is less prone to lithium precipitation.
  • the capacity of the active material per unit area outside the second straight portion meets the design requirements, that is, the capacity of the active material per unit area outside the second straight portion reaches the second preset value, so that the active material outside the second straight portion is active
  • the material is not prone to lithium precipitation; since the capacity of the active material per unit area outside the second bent portion is greater than the capacity of the active material per unit area outside the second straight portion, compared with the second preset value, it is equivalent to increasing the second bending portion.
  • the capacity per unit area of the active material on the outside of the part can increase the CB value of the active material on the outside of the second bending part, so that the lithium deposition phenomenon is less likely to occur in the active material on the outside of the second bending part.
  • 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 active material on the outer side of the bent portion 14 of the negative electrode sheet 12 Q1/Q2, where the active material per unit area of the active material on the outer side of one bent portion 14 in the negative electrode sheet 12 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 in the positive electrode sheet 11 is Q2.
  • the CB (Cell Balance) value of the active material on the outer side of the flat portion 15 of the negative pole piece 12 Q3/Q4, wherein the active material capacity per unit area of the active material on the outer side of one flat portion 15 in the negative pole piece 12 is Q3, the active material capacity per unit area of the active material in the inner side of the straight portion 15 located outside the one straight portion 15 and adjacent to the one straight portion 15 in the positive electrode sheet 11 is Q4.
  • the inventors also found that when the positive electrode and the negative electrode are wound, the positive electrode and the negative electrode are bent in the bending area, which may cause their respective active materials to fall off, which is called the phenomenon of powder falling.
  • the innermost bent portion of the negative electrode and the innermost bent portion of the positive electrode have the largest bending degree, which is 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, the lithium insertion site of the active material of the negative pole piece may be less than the number of lithium ions that the active material of the adjacent positive pole piece can provide. Therefore, Lithium-ion cells are prone to precipitation during charging.
  • At least one innermost bent portion 14 of the positive electrode sheet 11 is the first bent portion. Since the active material capacity per unit area inside the first bent portion is smaller than the active material capacity per unit area inside the first straight portion, it is equivalent to reducing the active material capacity per unit area inside the first bent portion, even if the negative electrode sheet 12 If the active material on the outside of the bent portion 14 located inside the first bent portion falls off, the risk of lithium precipitation in the bent portion 14 of the negative electrode sheet 12 located inside the first bent portion can also be reduced.
  • At least one innermost bent portion 14 of the negative pole piece 12 is the second bent portion. Since the capacity of the active material per unit area outside the second bent portion is greater than the capacity of the active material per unit area outside the second straight portion, it is equivalent to increasing the capacity of the active material per unit area outside the second bent portion, that is, increasing the capacity of the active material per unit area outside the second bent portion.
  • the CB value of the active material outside the second bending portion so that even if the active material outside the second bending portion falls off during the bending process, it can meet the requirements of the CB value for the active material outside the second bending portion, and then Reduce the risk of lithium precipitation.
  • the winding direction A refers to the direction in which the positive pole piece 11 and the negative pole piece 12 are wound circumferentially from the inside to the outside.
  • the winding direction A is the clockwise direction.
  • the electrode assembly 10 may further include a separator 13 for isolating the positive electrode 11 and the negative electrode 12 to reduce the risk of short circuit between the positive electrode 11 and the negative electrode 12 .
  • 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 straight area C is the area where the winding structure has a straight structure, and the straight portion 15 of the positive pole piece 11 and the straight portion 15 of the negative pole piece 12 are arranged substantially straight.
  • the bending area B is the area where the winding structure has a bending structure, the part of the positive pole piece 11 located in the bending area B (the bending part 14 ) and the part of the negative pole piece 12 located in the bending area B (the bending part 14 ) ) are flexurally distributed.
  • the bent portion 14 of the positive pole piece 11 and the bent portion 14 of the negative pole piece 12 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. Exemplarily, as shown in FIG.
  • the plurality of bending parts 14 in the positive electrode pole piece 11 and the plurality of bending parts 14 in the negative electrode pole piece 12 are alternately arranged, that is, when bending In area B, one bent portion 14 of the negative pole piece 12 , one bent portion 14 of the positive pole piece 11 , one bent portion 14 of the negative pole piece 12 . . . are arranged in order.
  • the innermost bent portion 14 of the positive pole piece 11 is located outside the innermost bent portion 14 of the negative pole piece 12 .
  • FIG. 6 is an enlarged schematic view of the electrode assembly shown in FIG. 5 at block D.
  • FIG. 6 is an enlarged schematic view of the electrode assembly shown in FIG. 5 at block D.
  • the negative electrode sheet 12 includes a negative electrode current collector 121 and negative electrode active material layers disposed on both sides of the negative electrode current collector 121 in the thickness direction, and the negative electrode current collector 121 on both sides in the thickness direction
  • the negative electrode active material layers are referred to as the inner negative electrode active material layer 123 and the outer negative electrode active material layer 122, respectively.
  • the inner negative electrode active material layer 123 is coated on the inner surface of the negative electrode current collector 121
  • the outer negative electrode active material layer 122 is coated on the outer surface of the negative electrode current collector 121 .
  • the positive electrode sheet 11 includes a positive electrode current collector 111 and positive electrode active material layers disposed on both sides of the positive electrode current collector 111 in the thickness direction, and the positive electrode active material layers on both sides in the thickness direction of the positive electrode current collector 111 are respectively referred to as inner positive electrode active material layers.
  • the material layer 113 and the outer positive electrode active material layer 112 are respectively referred to as inner positive electrode active material layers.
  • the inner positive electrode active material layer 113 is coated on the inner surface of the positive electrode current collector 111
  • the outer positive electrode active material layer 112 is coated on the outer surface of the positive electrode current collector 111 .
  • the negative electrode current collector 121 may have a portion 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 111 may have a portion that is not coated with the positive electrode active material layer, and this portion is Positive tab (not shown).
  • the positive electrode tab is used for electrical connection with the positive electrode terminal, and the negative electrode tab is used for electrical connection with the negative electrode terminal.
  • FIG. 7 is a partial cross-sectional schematic diagram of an electrode assembly provided by some embodiments of the present application.
  • At least one bent portion of the positive electrode sheet 11 is a first bent portion 141 , and at least one straight portion of the positive electrode sheet 11 is connected to the first bent portion In the first straight portion 151 of the 141 , the active material capacity per unit area inside the first bent portion 141 is smaller than the active material capacity per unit area inside the first straight portion 151 .
  • both ends of the first bent portion 141 along the winding direction are respectively connected to the two first straight portions 151 .
  • the bent portion adjacent to the first bent portion 141 in the negative pole piece 12 is the third bent portion 143 , and at least one straight portion in the negative pole piece 12 is the third flat portion connected to the third bent portion 143 .
  • Straight portion 153 is the third bent portion 143 .
  • the active material capacity per unit area outside the third bent portion 143 is equal to the active material capacity per unit area outside the third straight portion 153 .
  • both ends of the third bent portion 143 along the winding direction are respectively connected to the two third straight portions 153 .
  • both sides of the first bending portion 141 are arranged with the bending portion of the negative electrode pole piece 12 adjacent to it, at least located inside the first bending portion 141 and are opposite to the first bending portion 141 .
  • the bent portion of the adjacent negative pole piece 12 is the third bent portion 143 .
  • the bent portions of the negative pole piece 12 located on both sides of the first bent portion 141 and adjacent to the first bent portion 141 are all third bent portions 143 .
  • the active material capacity per unit area outside the third bent portion 143 may be equal to the third flat portion 151 .
  • the capacity per unit area of the active material outside the straight portion 153 is to simplify the manufacturing process of the negative pole piece 12 .
  • the first bending portion 141 includes a first current collecting portion 1411 and a first inner active material portion 1412 disposed inside the first current collecting portion 1411 . Understandably, the first current collector 1411 is a part of the positive electrode current collector located at the first bent part 141 , and the first inner active material part 1412 is a part of the inner positive active material layer located at the first bent part 141 .
  • the first bending portion 141 further includes a first conductive portion 1413 connected between the first current collecting portion 1411 and the first inner active material portion 1412 .
  • the first conductive portion 1413 is coated on the inner surface of the first current collecting portion 1411
  • the first inner active material portion 1412 is coated on the surface of the first conductive portion 1413 away from the first current collecting portion 1411 .
  • the capacity of the active material per unit area inside the first bending portion 141 is reduced by arranging the first conductive portion 1413 .
  • the first straight portion 151 includes a second current collecting portion 1511 and a second inner active material portion 1512 disposed inside the second current collecting portion 1511 .
  • the second current collector 1511 is a part of the positive electrode current collector located in the first straight part 151
  • the second inner active material part 1512 is a part of the inner positive active material layer located in the first straight part 151 .
  • the second inner active material part 1512 is coated on the inner surface of the second current collecting part 1511 .
  • the active material capacity per unit area inside the first bent portion 141 is smaller than the active material capacity per unit area inside the first straight portion 151 .
  • the active material capacity per unit area inside the first bent portion 141 is: the ratio of the active material capacity of the first coating portion located inside the first current collecting portion 1411 to the area of the first coating portion, wherein the first coating The part includes the first inner active material part 1412 and the first conductive part 1413, and the area of the first coating part is equal to the area of the area of the inner surface of the first current collecting part 1411 where the first coating part is coated.
  • the active material capacity per unit area inside the first straight portion 151 is: the ratio of the active material capacity of the second coating portion located inside the second current collecting portion 1511 to the area of the second coating portion, wherein the second coating The part includes the second inner active material part 1512, and the area of the second coating part is equal to the area of the area of the inner surface of the second current collecting part 1511 where the second coating part is coated.
  • the third bent portion 143 includes a fifth current collecting portion 1431 and a fourth outer active material portion 1432 disposed outside the fifth current collecting portion 1431 .
  • the fifth current collecting part 1431 is a part of the negative electrode current collector located at the third bending part 143
  • the fourth outer active material part 1432 is a part of the outer negative electrode active material layer located at the third bending part 143 .
  • the fourth outer active material part 1432 is coated on the outer surface of the fifth current collecting part 1431 .
  • the third straight portion 153 includes a sixth current collecting portion 1531 and a fifth outer active material portion 1532 disposed outside the sixth current collecting portion 1531 .
  • the sixth current collecting part 1531 is a part of the negative electrode current collector located in the third straight part 153
  • the fifth outer active material part 1532 is a part of the outer negative electrode active material layer located in the third straight part 153 .
  • the fifth outer active material part 1532 is coated on the outer surface of the sixth current collecting part 1531 .
  • the active material capacity per unit area outside the third bent portion 143 is equal to the active material capacity per unit area outside the third straight portion 153 , that is, the active material capacity per unit area of the fourth outer active material portion 1432 is equal to the fifth outer active material portion 1532
  • the active material capacity per unit area outside the third bent portion 143 is the ratio of the active material capacity of the fourth external active material portion 1432 to the area of the fourth external active material portion 1432 , wherein the area of the fourth external active material portion 1432 It is equal to the area of the area of the outer surface of the fifth current collecting portion 1431 coated with the fourth outer active material portion 1432 .
  • the active material capacity per unit area outside the third straight portion 153 is the ratio of the active material capacity of the fifth outer active material portion 1532 to the area of the fifth outer active material portion 1532 , wherein the area of the fifth outer active material portion 1532 It is equal to the area of the area of the outer surface of the sixth current collecting part 1531 coated with the fifth outer active material part 1532 .
  • all the bent portions may be the first bent portions 141 , or some of the bent portions may be the first bent portions 141 .
  • all the bent portions may be the third bent portions 143 , or only part of the bent portions may be the third bent portions 143 .
  • all the bent portions in the negative electrode pole piece 12 are the third bent portions 143 , so as to simplify the manufacturing process of the negative electrode pole piece 12 .
  • the active material capacity per unit area inside the first bent portion 141 may be smaller than the active material capacity per unit area inside the first straight portion 151 in various ways.
  • the thickness of the second inner active material portion 1512 is greater than the thickness of the first inner active material portion 1412 , so that the active material capacity per unit area inside the first bent portion 141 is smaller than that inside the first straight portion 151 Active material capacity per unit area.
  • other parameters of the first inner active material portion 1412 are substantially the same as the second inner active material portion 1512 except for the thickness.
  • the active material of the first inner active material part 1412 is the same as the active material of the second inner active material part 1512, and the weight ratio of the active material of the first inner active material part 1412 to the first inner active material part 1412 is equal to the weight ratio of the second inner active material part 1412. The weight ratio of the active material of the active material portion 1512 to the second inner active material portion 1512 .
  • the thickness of the second inner active material portion 1512 is greater than the thickness of the first inner active material portion 1412, so that the thickness of the second inner active material portion 1512 can be reduced.
  • the active material capacity per unit area is larger than that of the first inner active material portion 1412 , so that the active material capacity per unit area inside the first bent portion 141 is smaller than that inside the first straight portion 151 .
  • Both the active material of the first inner active material part 1412 and the active material of the second inner active material part 1512 may be lithium iron phosphate, lithium manganate, ternary lithium, lithium cobaltate, or the like.
  • the first inner active material portion 1412 and the second inner active material portion 1512 are formed by curing an active slurry with the same composition.
  • the thickness of the second inner active material portion 1512 is greater than that of the first inner active material portion 1412 by 0.5%-20%.
  • the thickness of the second inner active material portion 1512 is greater than or equal to the total thickness of the first inner active material portion 1412 and the first conductive portion 1413 .
  • the thickness of the second inner active material part 1512 is equal to the total thickness of the first inner active material part 1412 and the first conductive part 1413 .
  • the first internal active material portion may also be connected between the first conductive portion and the first current collecting portion.
  • the first conductive part 1413 can be a pure conductive coating, for example, the first conductive part 1413 is a pure conductive coating composed of an adhesive and a conductive agent; the first conductive part 1413 can also be a lithium-containing coating
  • the active coating of ions for example, the first conductive part 1413 is an active coating containing lithium ions composed of a lithium-rich material, a binder and a conductive agent; the first conductive part 1413 can also be an inactive coating containing lithium ions.
  • the layer, for example, the first conductive portion 1413 is a lithium ion-containing inactive coating composed of a binder, a conductive agent, and lithium powder coated with lithium carbonate.
  • the first conductive portion 1413 includes an active material therein.
  • the gram capacity of the active material in the first conductive portion 1413 is smaller than the gram capacity of the active material in the first inner active material portion 1412 ; in the present application, by adding an active material with a smaller gram capacity in the first conductive portion 1413 , the first conductive portion 1413 is reduced.
  • the capacity per unit area of the active material inside the first bent portion 141 is smaller than that inside the first straight portion 151 .
  • the weight ratio of the active material in the first conductive part 1413 to the first conductive part 1413 is equal to the weight ratio of the active material in the first inner active material part 1412 to the first inner active material part 1412 .
  • the gram capacity refers to the ratio of the capacitance released by the active material to the mass of the active material.
  • the first conductive portion 1413 contains an active material.
  • the weight ratio of the active material in the first conductive portion 1413 to the first conductive portion 1413 is smaller than the weight ratio of the active material in the first inner active material portion 1412 to the first inner active material portion 1412, so as to reduce the first bending portion
  • the active material capacity per unit area inside the first bent portion 141 is smaller than the active material capacity per unit area inside the first straight portion 151 .
  • the gram capacity of the active material in the first conductive portion 1413 is equal to the gram capacity of the active material in the first inner active material portion 1412 .
  • the active material capacity per unit area outside the third bent portion 143 can be equal to the active material capacity per unit area outside the third straight portion 153 in various ways.
  • the active material of the fourth outer active material portion 1432 of the third bent portion 143 is the same as the active material of the fifth outer active material portion 1532 of the third straight portion 153, and the thickness of the fourth outer active material portion 1432 is equal to the thickness of the fourth outer active material portion 1432. The thickness of the outer active material portion 1532.
  • FIG. 8 is a partial cross-sectional schematic diagram of electrode assemblies provided by other embodiments of the present application.
  • the first straight portion 151 further includes a third inner active material portion 1513 and a second conductive portion 1514 , and the third inner active material portion 1513 is disposed inside the second current collecting portion 1511 , the second conductive part 1514 is connected between the second current collecting part 1511 and the third inner active material part 1513 .
  • the second conductive part 1514 is connected between the first conductive part 1413 and the second internal active material part 1512 , and the third internal active material part 1513 is connected between the first internal active material part 1412 and the second internal active material part 1512 .
  • the active material capacity per unit area inside the first straight portion 151 is: the ratio of the active material capacity of the second coating portion located inside the second current collecting portion 1511 to the area of the second coating portion, wherein the second coating The part includes a second inner active material part 1512, a third inner active material part 1513 and a second conductive part 1514, and the area of the second coating part is equal to that of the inner surface of the second current collecting part 1511 coated with the second coating part area of the area.
  • the thickness of the first conductive portion 1413 is equal to the thickness of the second conductive portion 1514 .
  • the material of the first conductive portion 1413 and the material of the second conductive portion 1514 are the same, for example, the first conductive portion 1413 and the second conductive portion 1514 are formed by curing the same conductive paste.
  • the conductive paste in the coating process of the positive electrode sheet 11, the conductive paste can be coated on the first current collecting part 1411 and the second current collecting part 1511 at the same time, and there is no need to strictly limit the conductive paste to the first current collecting part 1411 and the second current collecting part 1511.
  • a current collecting part 1411 reduces the precision requirement of the coating process.
  • the thickness of the first inner active material portion 1412 is equal to the thickness of the third inner active material portion 1513 .
  • the first inner active material part 1412 , the second inner active material part 1512 and the third inner active material part 1513 are made of the same material, for example, the three are made of the same active paste cured.
  • FIG. 9 is a partial cross-sectional schematic diagram provided by further embodiments of the present application.
  • At least one bent portion of the negative electrode piece 12 is the second bent portion 142 , and at least one straight portion of the negative electrode piece 12 is connected to the second bent portion In the second straight portion 152 of the 142 , the active material capacity per unit area outside the second bent portion 142 is larger than the active material capacity per unit area outside the second straight portion 152 .
  • both ends of the second bent portion 142 along the winding direction are respectively connected to the two second straight portions 152 .
  • the bent portion adjacent to the second bent portion 142 in the positive pole piece 11 is the fourth bent portion 144 , and at least one straight portion in the positive pole piece 11 is the fourth flat portion connected to the fourth bent portion 144 .
  • Straight portion 154 The capacity per unit area of the active material inside the fourth bent portion 144 is equal to the capacity per unit area of the active material inside the fourth straight portion 154 .
  • both ends of the fourth bent portion 144 along the winding direction are respectively connected to the two fourth straight portions 154 .
  • both sides of the second bending portion 142 are arranged with the bending portion of the positive electrode piece 11 adjacent thereto, at least located outside the second bending portion 142 and opposite to the second bending portion 142 .
  • the bent portion of the adjacent positive pole piece 11 is the fourth bent portion 144 .
  • the bending parts of the positive pole piece 11 located on both sides of the second bending part 142 and adjacent to the second bending part 142 are all fourth bending parts 144 .
  • the active material capacity per unit area inside the fourth bent portion 144 may be equal to the fourth flat portion 152 .
  • the capacity per unit area of the active material inside the straight portion 154 is to simplify the manufacturing process of the positive electrode sheet 11 .
  • the second bent portion 142 includes a third current collecting portion 1421 and a first outer active material portion 1422 disposed outside the third current collecting portion 1421 .
  • the third current collecting part 1421 is a part of the negative electrode current collector located at the third bending part 143
  • the first outer active material part 1422 is a part of the outer negative electrode active material layer located at the third bending part 143 .
  • the first outer active material part 1422 is coated on the outer surface of the third current collecting part 1421 .
  • the second straight portion 152 includes a fourth current collecting portion 1521 and a second outer active material portion 1522 disposed outside the fourth current collecting portion 1521 .
  • the fourth current collecting part 1521 is a part of the negative electrode current collector located in the second straight part 152
  • the second outer active material part 1522 is a part of the outer negative electrode active material layer located in the second straight part 152 .
  • the second outer active material part 1522 is coated on the outer surface of the fourth current collecting part 1521 .
  • the active material capacity per unit area outside the second bent portion 142 is larger than the active material capacity per unit area outside the second straight portion 152 .
  • the active material capacity per unit area outside the second bent portion 142 is: the ratio of the active material capacity of the third coating portion outside the third current collecting portion 1421 to the area of the third coating portion, wherein the third coating The part includes the first outer active material part 1422 , and the area of the third coating part is equal to the area of the area of the outer surface of the third current collecting part 1421 where the third coating part is coated.
  • the active material capacity per unit area outside the second straight portion 152 is: the ratio of the active material capacity of the fourth coating portion outside the fourth current collecting portion 1521 to the area of the fourth coating portion, wherein the fourth coating The part includes the second outer active material part 1522, and the area of the fourth coating part is equal to the area of the area of the outer surface of the fourth current collecting part 1521 where the fourth coating part is coated.
  • the fourth bent portion 144 includes a seventh current collecting portion 1441 and a fourth inner active material portion 1442 disposed inside the seventh current collecting portion 1441 .
  • the seventh current collector 1441 is a part of the positive electrode current collector located at the fourth bent part 144
  • the fourth inner active material part 1442 is a part of the inner positive active material layer located at the fourth bent part 144 .
  • the fourth inner active material part 1442 is coated on the inner surface of the seventh current collecting part 1441 .
  • the fourth straight portion 154 includes an eighth current collecting portion 1541 and a fifth inner active material portion 1542 disposed inside the eighth current collecting portion 1541 .
  • the eighth current collecting portion 1541 is a portion of the positive electrode current collector 111 located in the fourth straight portion 154
  • the fifth inner active material portion 1542 is a portion of the inner positive active material layer 113 located in the fourth straight portion 154 .
  • the fifth inner active material part 1542 is coated on the inner surface of the eighth current collecting part 1541 .
  • the active material capacity per unit area inside the fourth bent portion 144 is equal to the active material capacity per unit area inside the fourth straight portion 154 , that is, the active material capacity per unit area of the fourth inner active material portion 1442 is equal to the fifth inner active material portion 1542 The active material capacity per unit area.
  • the active material capacity per unit area inside the fourth bent portion 144 is: the ratio of the active material capacity of the fourth inner active material portion 1442 to the area of the fourth inner active material portion 1442 , wherein the area of the fourth inner active material portion 1442 It is equal to the area of the inner surface of the seventh current collecting portion 1441 coated with the fourth inner active material portion 1442 .
  • the active material capacity per unit area inside the fourth straight portion 154 is: the ratio of the active material capacity of the fifth inner active material portion 1542 to the area of the fifth inner active material portion 1542 , wherein the area of the fifth inner active material portion 1542 It is equal to the area of the inner surface of the eighth current collecting portion 1541 coated with the fifth inner active material portion 1542 .
  • all the bent portions may be the second bent portions 142 , or some of the bent portions may be the second bent portions 142 .
  • all the bent portions may be the fourth bent portions 144 , or only part of the bent portions may be the fourth bent portions 144 .
  • all the bent portions in the positive electrode sheet 11 are the fourth bent portions 144 to simplify the manufacturing process of the positive electrode sheet 11 .
  • the active material capacity per unit area outside the second bent portion 142 may be greater than the active material capacity per unit area outside the second straight portion 152 in various ways.
  • the gram capacity of the active material in the first outer active material portion 1422 is greater than the gram capacity of the active material in the second outer active material portion 1522, so that the active material capacity per unit area of the first outer active material portion 1422 can be made larger than the second outer active material portion 1422.
  • the active material capacity per unit area of the material portion 1522 is realized so that the active material capacity per unit area outside the second bent portion 142 is greater than the active material capacity per unit area outside the second straight portion 152 .
  • other parameters of the first outer active material portion 1422 are the same as the second outer active material portion 1522 except for the gram capacity; for example, the thickness of the first outer active material portion 1422 is equal to the thickness of the second outer active material portion 1522 thickness, the weight ratio of the active material of the first outer active material part 1422 to the first outer active material part 1422 is equal to the weight ratio of the active material of the second outer active material part 1522 to the second outer active material part 1522 .
  • the active material of the first external active material part 1422 is different from the active material of the second external active material part 1522, for example, the active material of the first external active material part 1422 is a silicon compound, and the second external active material The active material of portion 1522 is graphite.
  • the weight ratio of the active material in the first outer active material part 1422 to the first outer active material part 1422 is greater than the weight ratio of the active material in the second outer active material part 1522 to the second outer active material part 1522 Therefore, the capacity of the active material per unit area outside the second bent portion 142 is greater than the capacity per unit area of the active material outside the second straight portion 152 .
  • the first outer active material portion 1422 and the second outer active material portion 1522 both include active materials, adhesives and conductive agents. By increasing the weight ratio of the active materials in the first outer active material portion 1422, the second bending portion 142 is realized.
  • the active material capacity per unit area on the outside is larger than the active material capacity per unit area on the outside of the second straight portion 152 .
  • the thickness of the first outer active material portion 1422 and the thickness of the second outer active material portion 1522 are the same, and the active material in the first outer active material portion 1422 and the active material in the second outer active material portion 1522 Likewise, the weight ratio of the active material in the first outer active material part 1422 to the first outer active material part 1422 is greater than the weight ratio of the active material in the second outer active material part 1522 to the second outer active material part 1522 .
  • FIG. 10 is a partial cross-sectional schematic diagram of an electrode assembly provided by further embodiments of the present application.
  • the thickness of the first outer active material portion 1422 is greater than the thickness of the second outer active material portion 1522 , so that the active material capacity per unit area outside the second bending portion 142 is greater than that of the second outer active material portion 142 The active material capacity per unit area outside the straight portion 152 .
  • first outer active material portion 1422 other parameters of the first outer active material portion 1422 are the same as the second outer active material portion 1522 except for the thickness; for example, the active material of the first outer active material portion 1422 and the second outer active material portion 1522
  • the active material in the first outer active material part 1422 is equal to the weight ratio of the active material in the second outer active material part 1522 to the second outer active material part 1522 .
  • Both the active material of the first external active material part 1422 and the active material of the second external active material part 1522 may be a compound of graphite or silicon, or the like.
  • the first outer active material part 1422 and the second outer active material part 1522 are formed by curing an active slurry with the same composition.
  • the thickness of the first outer active material part 1422 is larger than that of the second outer active material part 1522 by 0.5%-20%.
  • FIG. 11 is a schematic partial cross-sectional view of an electrode assembly provided by other embodiments of the present application.
  • the second bending portion 142 includes a third conductive portion 1423 , and the third conductive portion 1423 is connected between the third current collecting portion 1421 and the first external active material portion 1422 .
  • the third conductive portion 1423 contains an active material.
  • the third conductive part 1423 is coated on the outer surface of the third current collecting part 1421
  • the first outer active material part 1422 is coated on the surface of the third conductive part 1423 that is away from the third current collecting part 1421 .
  • the capacity of the active material per unit area outside the second bending portion 142 is increased by arranging the third conductive portion 1423 .
  • the active material capacity per unit area outside the second bent portion 142 is: the ratio of the active material capacity of the third coating portion outside the third current collecting portion 1421 to the area of the third coating portion, wherein the third coating The part includes the first outer active material part 1422 and the third conductive part 1423, and the area of the third coating part is equal to the area of the area of the outer surface of the third current collecting part 1421 where the third coating part is coated.
  • the thickness of the second outer active material portion 1522 is greater than the thickness of the first outer active material portion 1422 . Except for the thickness, other parameters of the first outer active material part 1422 are substantially the same as those of the second outer active material part 1522 . For example, the active material of the first external active material part 1422 is the same as the active material of the second external active material part 1522 .
  • the thickness of the second outer active material portion 1522 is greater than or equal to the total thickness of the first outer active material portion 1422 and the third conductive portion 1423 .
  • the thickness of the second outer active material part 1522 is equal to the total thickness of the first outer active material part 1422 and the third conductive part 1423 .
  • the first external active material portion 1422 may also be connected between the third conductive portion 1423 and the third current collecting portion 1421 .
  • the gram capacity of the active material in the third conductive part 1423 is greater than the gram capacity of the active material in the first outer active material part 1422 ; the present application adds a larger gram capacity in the third conductive part 1423
  • the active material increases the active material capacity per unit area outside the second bent portion 142 , so that the active material capacity per unit area outside the second bent portion 142 is greater than the active material capacity per unit area outside the second straight portion 152 .
  • the weight ratio of the active material in the third conductive part 1423 to the third conductive part 1423 is equal to the weight ratio of the active material in the first outer active material part 1422 to the first outer active material part 1422 .
  • the weight ratio of the active material in the third conductive portion 1423 to the third conductive portion 1423 is greater than the weight ratio of the active material in the first outer active material portion 1422 to the first outer active material portion 1422, so as to The active material capacity per unit area outside the second bent portion 142 is increased, so that the active material capacity per unit area outside the second bent portion 142 is greater than the active material capacity per unit area outside the second straight portion 152 .
  • the gram capacity of the active material in the third conductive part 1423 is equal to the gram capacity of the active material in the first outer active material part 1422 .
  • the active material capacity per unit area inside the fourth bent portion 144 can be equal to the active material capacity per unit area inside the fourth straight portion 154 in various ways.
  • the active material of the fourth inner active material portion 1442 of the fourth bent portion 144 is the same as the active material of the fifth inner active material portion 1542 of the fourth straight portion 154, and the thickness of the fourth inner active material portion 1442 is equal to the thickness of the fourth inner active material portion 1442. The thickness of the inner active material portion 1542.
  • FIG. 12 is a partial cross-sectional schematic diagram of an electrode assembly provided by further embodiments of the present application.
  • the second straight portion 152 further includes a third outer active material portion 1523 and a fourth conductive portion 1524 , the third outer active material portion 1523 is disposed outside the fourth current collecting portion 1521 , and the fourth conductive portion 1524 is connected between the fourth current collecting part 1521 and the third external active material part 1523 .
  • the fourth conductive part 1524 is connected between the third conductive part 1423 and the second external active material part 1522 , and the third external active material part 1523 is connected between the first external active material part 1422 and the second external active material part 1522 .
  • the active material capacity per unit area outside the second straight portion 152 is: the ratio of the active material capacity of the fourth coating portion outside the fourth current collecting portion 1521 to the area of the fourth coating portion, wherein the fourth coating The part includes the second outer active material part 1522, the third outer active material part 1523 and the fourth conductive part 1524, and the area of the fourth coating part is equal to that of the outer surface of the fourth current collecting part 1521 coated with the fourth coating part area of the area.
  • the thickness of the third conductive portion 1423 is equal to the thickness of the fourth conductive portion 1524 .
  • the material of the third conductive portion 1423 and the material of the fourth conductive portion 1524 are the same, for example, the third conductive portion 1423 and the fourth conductive portion 1524 are formed by curing the same conductive paste.
  • the conductive paste in the coating process of the negative pole piece 12, the conductive paste can be coated on the third current collecting part 1421 and the fourth current collecting part 1521 at the same time, and there is no need to strictly limit the conductive paste to the third current collecting part 1421 and the fourth current collecting part 1521 The three current collecting parts 1421 reduce the precision requirements of the coating process.
  • the thickness of the first outer active material portion 1422 is equal to the thickness of the third outer active material portion 1523 .
  • the first outer active material part 1422 , the second outer active material part 1522 and the third outer active material part 1523 are made of the same material, for example, the three are cured from the same active paste.
  • FIG. 13 is a partial cross-sectional schematic diagram of an electrode assembly provided by further embodiments of the present application.
  • At least one bent portion of the positive electrode sheet 11 is a first bent portion 141 , and at least one straight portion of the positive electrode sheet 11 is connected to the first bent portion In the first straight portion 151 of 141, the active material capacity per unit area inside the first bent portion 141 is smaller than the active material capacity per unit area inside the first straight portion 151; at least one bent portion in the negative pole piece 12 is the first The two bent portions 142, at least one straight portion of the negative pole piece 12 is the second straight portion 152 connected to the second bent portion 142, and the capacity of the active material per unit area outside the second bent portion 142 is greater than that of the second bent portion 142.
  • the active material capacity per unit area outside the straight portion 152 is a first bent portion 141 , and at least one straight portion of the positive electrode sheet 11 is connected to the first bent portion In the first straight portion 151 of 141, the active material capacity per unit area inside the first bent portion 141 is smaller than the active material capacity per unit area inside the first straight portion 151; at least one bent portion in the
  • the active material capacity per unit area inside the first bending portion 141 can be made smaller than the unit area inside the first straight portion 151 by adding the first conductive portion 1413 to the first bending portion 141 , etc. Active substance capacity.
  • the thickness of the first outer active material part 1422 can be made larger than that of the second outer active material part 1522 , or by making the gram capacity of the active material of the first outer active material part 1422 larger than that of the second outer active material part 1522
  • the gram capacity of the active material is increased, or by adding a third conductive portion 1423 to the second bent portion 142, or other methods, so that the active material capacity per unit area outside the second bent portion 142 is greater than that of the second straight portion
  • the active material capacity per unit area outside the portion 152 is increased, or by adding a third conductive portion 1423 to the second bent portion 142, or other methods, so that the active material capacity per unit area outside the second bent portion 142 is greater than that of the second straight portion
  • the first bent portion 141 includes a first conductive portion 1413 connected between the first current collecting portion 1411 and the first inner active material portion 1412
  • the second bent portion 142 includes a first conductive portion 1413 connected between the first current collecting portion 1411 and the first inner active material portion 1412
  • the third conductive part 1423 between the third current collecting part 1421 and the first outer active material part 1422 .
  • a first bending part 141 adjacent to the second bending part 142 is arranged on the outer side of the second bending part 142 .
  • the active material capacity per unit area inside the first straight portion 151 and the active material capacity per unit area outside the second straight portion 152 meet the design requirements, the active material capacity per unit area inside the first bending portion 141 is smaller than the first flat portion 141 .
  • the active material capacity per unit area inside the straight portion 151 and the active material capacity per unit area outside the second bent portion 142 are greater than the active material capacity per unit area outside the second straight portion 152, so that the capacity of the second bent portion 142 can be increased.
  • the CB value of the outer active material can reduce the occurrence of lithium deposition.
  • FIG. 14 is a partial cross-sectional schematic diagram of electrode assemblies provided by other embodiments of the present application.
  • At least one bent portion in the positive electrode sheet 11 is a first bent portion 141
  • at least one straight portion in the positive electrode sheet 11 is a first straight portion connected to the first bent portion 141
  • the active material capacity per unit area inside the first bent part 141 is smaller than the active material capacity per unit area inside the first straight part 151
  • the active material capacity per unit area outside the first bent part 141 is smaller than the first straight part The active material capacity per unit area outside 151.
  • the first bending portion 141 includes a sixth outer active material portion 1414 and a fifth conductive portion 1415 , the sixth outer active material portion 1414 is located outside the first current collecting portion 1411 , and the fifth conductive portion 1415 is connected between the first current collecting part 1411 and the sixth outer active material part 1414 .
  • the capacity of the active material per unit area outside the first bending portion 141 is reduced.
  • At least one bent portion of the negative pole piece 12 is the second bent portion 142
  • at least one straight portion of the negative pole piece 12 is a second straight portion connected to the second bent portion 142 .
  • part 152 the active material capacity per unit area on the outside of the second bent part 142 is greater than the active material capacity per unit area on the outside of the second straight part 152
  • the active material capacity per unit area on the inside of the second bent part 142 is greater than the second straight part Active material capacity per unit area inside 152.
  • the second bending portion 142 includes a sixth inner active material portion 1424 and a sixth conductive portion 1425, the sixth inner active material portion 1424 is located inside the third current collecting portion 1421, and the sixth conductive portion 1425 is connected between the third current collecting part 1421 and the sixth inner active material part 1424 .
  • the capacity of the active material per unit area inside the second bending portion 142 is increased by arranging the sixth conductive portion 1425 .
  • test steps for the capacity of active material 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 examples, and use a punching die to obtain a small round piece containing a positive electrode single-sided active material layer.
  • the lithium metal sheet is used as the counter electrode
  • the Celgard film is used as the separator
  • the EC+DMC+DEC of LiPF6 (1mol/L) is dissolved (ethylene carbonate, dimethyl carbonate, and 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.
  • 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.
  • the lithium metal sheet is used as the counter electrode
  • the Celgard film is used as the separator
  • the EC+DMC+DEC of LiPF6 (1mol/L) is dissolved (ethylene carbonate, dimethyl carbonate, and 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. 15 is a schematic flowchart of a method for manufacturing an electrode assembly provided by some embodiments of the present application.
  • the manufacturing method of the electrode assembly includes:
  • the coiled structure includes a bent region and a straight region connected to the bent region.
  • Both the negative pole piece and the positive pole piece include a plurality of bent portions located in the bending region and a plurality of straight portions located in the straight region.
  • At least one bent part in the positive pole piece is a first bent part, and at least one straight part in the positive pole piece is a first straight part connected to the first bent part, and the unit inside the first bent part
  • the area active material capacity is less than the unit area active material capacity inside the first straight portion; and/or, at least one bent portion in the negative pole piece is the second bent portion, and at least one straight portion in the negative pole piece is The second straight portion connected to the second bent portion has a larger active material capacity per unit area outside the second bent portion than the outside of the second straight portion.
  • the manufacturing method of the present application further includes: providing a separator for isolating the positive electrode piece and the negative electrode piece, and winding the first pole piece, the separator film and the second pole piece along the winding direction and Form a coiled structure.
  • step S100 and step S200 is not sequential, and may be executed simultaneously.
  • FIG. 16 is a schematic block diagram of a manufacturing system of an electrode assembly provided by some embodiments of the present application.
  • the manufacturing system 9 of the electrode assembly includes: a first providing device 91 for providing negative pole pieces; a second providing device 92 for providing positive pole pieces; and an assembling device 93 for providing The negative pole piece and the positive pole piece are wound along the winding direction and form a winding structure.
  • the coiled structure includes a bent region and a straight region connected to the bent region.
  • Both the negative pole piece and the positive pole piece include a plurality of bent portions located in the bending region and a plurality of straight portions located in the straight region.
  • At least one bent part in the positive pole piece is a first bent part, and at least one straight part in the positive pole piece is a first straight part connected to the first bent part, and the unit inside the first bent part
  • the area active material capacity is less than the unit area active material capacity inside the first straight portion; and/or, at least one bent portion in the negative pole piece is the second bent portion, and at least one straight portion in the negative pole piece is The second straight portion connected to the second bent portion has a larger active material capacity per unit area outside the second bent portion than the outside of the second straight 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 assembly device 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。电极组件包括负极极片和正极极片，负极极片和正极极片卷绕并形成卷绕结构，卷绕结构包括弯折区和平直区。负极极片和正极极片均包括位于弯折区的多个弯折部和位于平直区的多个平直部。正极极片中的至少一个弯折部为第一弯折部，正极极片中的至少一个平直部为连接于第一弯折部的第一平直部，第一弯折部内侧的单位面积活性物质容量小于第一平直部内侧的单位面积活性物质容量；和/或，负极极片中的至少一个弯折部为第二弯折部，负极极片中的至少一个平直部为连接于第二弯折部的第二平直部，第二弯折部外侧的单位面积活性物质容量大于第二平直部外侧的单位面积活性物质容量。

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
可再充电电池单体，可以称为二次电池单体，是指在电池单体放电后可通过充电的方式使活性物质激活而继续使用的电池单体。可再充电电池单体广泛用于电子设备，例如手机、笔记本电脑、电瓶车、电动汽车、电动飞机、电动轮船、电动玩具汽车、电动玩具轮船、电动玩具飞机和电动工具等等。
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、电池以及用电装置，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，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和连接于弯折区的平直区。负极极片和正极极片均包括位于弯折区的多个弯折部和位于平直区的多个平直部。其中，正极极片中的至少一个弯折部为第一弯折部，正极极片中的至少一个平直部为连接于第一弯折部的第一平直部，第一弯折部内侧的单位面积活性物质容量小于第一平直部内侧的单位面积活性物质容量；和/或，负极极片中的至少一个弯折部为第二弯折部，负极极片中的至少一个平直部为连接于第二弯折部的第二平直部，第二弯折部外侧的单位面积活性物质容量大于第二平直部外侧的单位面积活性物质容量。
上述方案中，若第一弯折部内侧的单位面积活性物质容量小于第一平直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多的情况，使得正极极片的活性物质布置更为合理，并降低析锂风险。若第二弯折部外侧的单位面积活性物质容量大于第二平直部外侧的单位面积活性物质容量，那么不易出现第二弯折部的外侧活性物质不足的情况，并降低析锂风险。这种结构的电极组件中极片的活性物质布置更为合理，具有更好的经济性，降低析锂的风险。
在一些实施例中，正极极片中的至少一个弯折部为第一弯折部，负极极片中的至少一个弯折部为第二弯折部，第二弯折部的外侧布置有与第二弯折部相邻的第一弯 折部。
上述方案中，在第一平直部内侧的单位面积活性物质容量和第二平直部外侧的单位面积活性物质容量满足设计要求时，第一弯折部内侧的单位面积活性物质容量小于第一平直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平直部外侧的单位面积活性物质容量，这样可以增大第二弯折部的外侧活性物质的CB值，从而减少析锂现象的发生。
在一些实施例中，正极极片中的至少一个弯折部为第一弯折部。负极极片中与第一弯折部相邻的弯折部为第三弯折部，负极极片中的至少一个平直部为连接于第三弯折部的第三平直部。第三弯折部外侧的单位面积活性物质容量等于第三平直部外侧的单位面积活性物质容量。这样可以简化负极极片的制造工艺。
在一些实施例中，负极极片中的至少一个弯折部为第二弯折部。正极极片中与第二弯折部相邻的弯折部为第四弯折部，正极极片中的至少一个平直部为连接于第四弯折部的第四平直部。第四弯折部内侧的单位面积活性物质容量等于第四平直部内侧的单位面积活性物质容量。这样可以简化正极极片的制造工艺。
在一些实施例中，第一弯折部包括第一集流部、设置于第一集流部内侧的第一内活性物质部以及连接于第一集流部和第一内活性物质部之间的第一导电部。本申请实施例通过设置第一导电部来减小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，第一平直部包括第二集流部和设置于第二集流部内侧的第二内活性物质部。第二内活性物质部的厚度大于第一内活性物质部的厚度，以使第一弯折部内侧的单位面积活性物质容量小于第一平直部内侧的单位面积活性物质容量。
在一些实施例中，第一平直部还包括第三内活性物质部和第二导电部，第三内活性物质部设置于第二集流部的内侧，第二导电部连接于第二集流部和第三内活性物质部之间。第二导电部连接于第一导电部和第二内活性物质部之间，第三内活性物质部连接于第一内活性物质部和第二内活性物质部之间。
在一些实施例中，第一导电部中包含有活性材料。第一导电部中的活性材料的克容量小于第一内活性物质部中的活性材料的克容量。本申请通过在第一导电部中添加克容量较小的活性材料，减小第一弯折部内侧的单位面积活性物质容量，从而实现第一弯折部内侧的单位面积活性物质容量小于第一平直部内侧的单位面积活性物质容量。
在一些实施例中，第一导电部中的活性材料与第一导电部的重量比小于第一内活性物质部中的活性材料与第一内活性物质部的重量比，以减小第一弯折部内侧的单位面积活性物质容量，从而实现第一弯折部内侧的单位面积活性物质容量小于第一平直部内侧的单位面积活性物质容量。
在一些实施例中，第二弯折部包括第三集流部和设置于第三集流部外侧的第一外活性物质部，第二平直部包括第四集流部和设置于第四集流部外侧的第二外活性物质部。
在一些实施例中，第一外活性物质部的厚度大于第二外活性物质部的厚度，以使第二弯折部外侧的单位面积活性物质容量大于第二平直部外侧的单位面积活性物质 容量。
在一些实施例中，第一外活性物质部中的活性材料的克容量大于第二外活性物质部中的活性材料的克容量。
在一些实施例中，第一外活性物质部中的活性材料与第一外活性物质部的重量比大于第二外活性物质部中的活性材料与第二外活性物质部的重量比，这样可以使第一外活性物质部的单位面积活性物质容量大于第二外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平直部外侧的单位面积活性物质容量。
在一些实施例中，第二弯折部包括第三导电部，第三导电部连接于第三集流部和第一外活性物质部之间，且第三导电部中含有活性材料。第三导电部中的活性材料的克容量大于第一外活性物质部中的活性材料的克容量；或者，第三导电部中的活性材料与第三导电部的重量比大于第一外活性物质部中的活性材料与第一外活性物质部的重量比。本申请实施例通过设置第三导电部来增大第二弯折部外侧的单位面积活性物质容量。
在一些实施例中，第二平直部还包括第三外活性物质部和第四导电部，第三外活性物质部设置于第四集流部的外侧，第四导电部连接于第四集流部和第三外活性物质部之间。第四导电部连接于第三导电部和第二外活性物质部之间，第三外活性物质部连接于第一外活性物质部和第二外活性物质部之间。
在一些实施例中，正极极片中至少最内侧的一个弯折部为第一弯折部。由于第一弯折部内侧的单位面积活性物质容量小于第一平直部内侧的单位面积活性物质容量，相当于减小了第一弯折部内侧的单位面积活性物质容量，即使负极极片的位于第一弯折部内侧的弯折部的外侧活性物质出现脱落情况，也能够降低负极极片的位于第一弯折部内侧的弯折部的析锂风险。
在一些实施例中，负极极片中至少最内侧的一个弯折部为第二弯折部。由于第二弯折部外侧的单位面积活性物质容量大于第二平直部外侧的单位面积活性物质容量，相当于增大了第二弯折部外侧的单位面积活性物质容量，即增大了第二弯折部外侧的活性物质的CB值，这样，即使第二弯折部外侧的活性物质在弯折过程中脱落，也能满足第二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。
第二方面，本申请实施例提供了一种电池单体，其包括外壳和第一方面任一实施例的电极组件，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，包括箱体和第二方面任一实施例的电池单体，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装置，包括第三方面任一实施例的电池，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，包括：提供负极极片；提供正极极片；将负极极片和正极极片沿卷绕方向卷绕并形成卷绕结构。卷绕结构包括弯折区和连接于弯折区的平直区。负极极片和正极极片均包括位于弯折区的多个弯折部和位于平直区的多个平直部。正极极片中的至少一个弯折部为第一弯折部， 正极极片中的至少一个平直部为连接于第一弯折部的第一平直部，第一弯折部内侧的单位面积活性物质容量小于第一平直部内侧的单位面积活性物质容量；和/或，负极极片中的至少一个弯折部为第二弯折部，负极极片中的至少一个平直部为连接于第二弯折部的第二平直部，第二弯折部外侧的单位面积活性物质容量大于第二平直部外侧的单位面积活性物质容量。
第六方面，本申请实施例提供了一种电极组件的制造系统，包括：第一提供装置，用于提供负极极片；第二提供装置，用于提供正极极片；组装装置，将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和连接于弯折区的平直区。负极极片和正极极片均包括位于弯折区的多个弯折部和位于平直区的多个平直部。正极极片中的至少一个弯折部为第一弯折部，正极极片中的至少一个平直部为连接于第一弯折部的第一平直部，第一弯折部内侧的单位面积活性物质容量小于第一平直部内侧的单位面积活性物质容量；和/或，负极极片中的至少一个弯折部为第二弯折部，负极极片中的至少一个平直部为连接于第二弯折部的第二平直部，第二弯折部外侧的单位面积活性物质容量大于第二平直部外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为本申请一些实施例提供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为本申请一些实施例提供的电极组件的局部剖视示意图；
图8为本申请另一些实施例提供的电极组件的局部剖视示意图；
图9为本申请又一些实施例提供的电极组件的局部剖视示意图；
图10为本申请再一些实施例提供的电极组件的局部剖视示意图；
图11为本申请另一些实施例提供的电极组件的局部剖视示意图；
图12为本申请又一些实施例提供的电极组件的局部剖视示意图；
图13为本申请再一些实施例提供的电极组件的局部剖视示意图；
图14为本申请另一些实施例提供的电极组件的局部剖视示意图；
图15为本申请一些实施例提供的电极组件的制造方法的流程示意图；
图16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，正极活性物质层包括正极活性物质，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，负极活性物质层包括负极活性物质，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，极片中的活性物质布置不合理，经济性较差。
卷绕结构的电极组件包括平直区和弯折区。发明人发现，正极极片的位于平直区的内侧活性物质层厚度等于正极极片的位于弯折区的内侧活性物质层厚度，且正极极片的位于平直区的内侧活性物质层与正极极片的位于弯折区的内侧活性物质层采用相同的材料；负极极片的位于平直区的外侧活性物质层厚度等于负极极片的位于弯折区的外侧活性物质层厚度，且负极极片的位于平直区的外侧活性物质层与负极极片的位于弯折区的外侧活性物质层采用相同的材料。
在弯折区，正极极片的内侧活性物质层的半径大于位于正极极片内侧的负极极片的外侧活性物质层的半径，也就是说，负极极片的外侧活性物质层的半径小于位于负极极片外侧的正极极片的内侧活性物质层。在平直区，正极极片的内侧活性物质层与负极极片的外侧活性物质层对应设置。
当正极极片的位于平直区的内侧活性物质层的容量设计满足要求时，正极极片的位于弯折区的内侧活性物质层过多，使得位于正极极片内侧的负极极片容易出现析锂。当负极极片的位于平直区的外侧活性物质层的容量设计满足要求时，负极极片的位于弯折区的外侧活性物质层容易出现不足的情况并导致析锂。因此，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，容易引发析锂的风险。
有鉴于此，本申请实施例提供了一种技术方案。在该技术方案中，电极组件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和连接于弯折区的平直区。负极极片和正极极片均包括位于弯折区的多个弯折部和位于平直区的多个平直部。正极极片中的至少一个弯折部为第一弯折部，正极极片中的至少一个平直部为连接于第一弯折部的第一平直部，第一弯折部内侧的单位面积活性物质容量小于第一平直部内侧的单位面积活性物质容量；和/或，负极极片中的至少一个弯折部为第二弯折部，负极极片中的至少一个平直部为连接于第二弯折部的第二平直部，第二弯折部外侧的单位面积活性物质容量大于第二平直部外侧的 单位面积活性物质容量。这种结构使得极片的活性物质布置更为合理，具有更好的经济性，并降低析锂风险。
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装置
用电装置可以是车辆、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装置不做特殊限制。
以下实施例为了方便说明，以用电装置为车辆为例进行说明。
图1为本申请一些实施例提供的车辆的结构示意图。如图1所示，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。
图2为本申请一些实施例提供的电池的爆炸示意图。如图2所示，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。
图3为本申请一些实施例提供的电池模块的结构示意图。如图3所示，在一些实施例中，电池单体7为多个，多个电池单体7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。
图4为图3所示的电池单体的爆炸示意图。如图4所示，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。
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，在另一些实施例中，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。
图5为本申请一些实施例提供的电极组件的结构示意图。
如图5所示，本申请实施例的电极组件10包括正极极片11和负极极片12，负极极片12和正极极片11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和连接于弯折区B的平直区C。负极极片12和正极极片11均包括位于弯折区B的多个弯折部14和位于平直区C的多个平直部15。
正极极片11中的至少一个弯折部14为第一弯折部，正极极片11中的至少一个平直部15为连接于第一弯折部的第一平直部，第一弯折部内侧的单位面积活性物质容量小于第一平直部内侧的单位面积活性物质容量；和/或，负极极片12中的至少一个弯折部14为第二弯折部，负极极片12中的至少一个平直部15为连接于第二弯折部的第二平直部，第二弯折部外侧的单位面积活性物质容量大于第二平直部外侧的单位面积活性物质容量。
若第一弯折部内侧的单位面积活性物质容量小于第一平直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多的情况，使得正极极片11的活性物质布置更为合理，并降低析锂风险。若第二弯折部外侧的单位面积活性物质容量大于第二平直部外侧的单位面积活性物质容量，那么不易出现第二弯折部的外侧活性物质不足的情况，并降低析锂风险。这种结构的电极组件10中极片的活性物质布置更为合理，具有更好的经济性，降低析锂的风险。
在第一平直部内侧的单位面积活性物质容量满足设计要求时，即第一平直部内侧单位面积活性物质容量达到第一预设值，使得负极极片12的位于第一平直部内侧的平直部15的外侧活性物质不易出现析锂；由于第一弯折部内侧的单位面积活性物质容量小于第一平直部内侧的单位面积活性物质容量，相对于第一预设值，相当于减小了第一弯折部内侧的单位面积活性物质容量，使得负极极片12的位于第一弯折部内侧的弯折部14不易出现析锂现象。
同样地，若第二平直部外侧的单位面积活性物质容量满足设计要求时，即第二平直部外侧的单位面积活性物质容量达到第二预设值，使得第二平直部的外侧活性物质不易出现析锂；由于第二弯折部外侧的单位面积活性物质容量大于第二平直部外侧的单位面积活性物质容量，相对于第二预设值，相当于增大了第二弯折部外侧的单位面积活性物质容量，可增大第二弯折部的外侧活性物质的CB值，使得第二弯折部的外侧活性物质不易出现析锂现象。
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12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12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11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。负极极片12的平直部15的外侧活性物质的CB(Cell Balance)值＝Q3/Q4，其中，负极极片12中的一个平直部15的外侧活性物质的单位面积的活性物质容量为Q3，正极极片11中位于该一个平直部15的外侧且与该一个平直部15相邻的平直部15的内侧活性物质的单位面积的活性物质容量为Q4。
发明人还发现，在卷绕正极极片和负极极片时，正极极片和负极极片在弯折区进行折弯，所以可能会导致各自的活性物质脱落，称之为掉粉现象。尤其是负极极片中最内侧的一个弯折部和正极极片中最内侧的一个弯折部，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，尤其是负极极片上活性物质的脱落，可能导致该负极极片的活性物质的嵌锂位少于其相邻的正极极片的活性物质能够提供的锂 离子数量，因此，锂离子电池单体在充电时，容易发生析锂现象。
在一些实施例中，正极极片11中至少最内侧的一个弯折部14为第一弯折部。由于第一弯折部内侧的单位面积活性物质容量小于第一平直部内侧的单位面积活性物质容量，相当于减小了第一弯折部内侧的单位面积活性物质容量，即使负极极片12的位于第一弯折部内侧的弯折部14的外侧活性物质出现脱落情况，也能够降低负极极片12的位于第一弯折部内侧的弯折部14的析锂风险。
在一些实施例中，负极极片12中至少最内侧的一个弯折部14为第二弯折部。由于第二弯折部外侧的单位面积活性物质容量大于第二平直部外侧的单位面积活性物质容量，相当于增大了第二弯折部外侧的单位面积活性物质容量，即增大了第二弯折部外侧的活性物质的CB值，这样，即使第二弯折部外侧的活性物质在弯折过程中脱落，也能满足第二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。
在本申请实施例中，卷绕方向A即为正极极片11和负极极片12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11和负极极片12隔离，以降低正极极片11与负极极片12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，弯折区B为两个且分别设置于平直区C的两端。平直区C即为卷绕结构具有平直结构的区域，正极极片11的平直部15和负极极片12的平直部15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11位于弯折区B的部分(弯折部14)和负极极片12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11的弯折部14和负极极片12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11中的多个弯折部14与负极极片12中的多个弯折部14交错排布，即在弯折区B中，以负极极片12的一个弯折部14、正极极片11的一个弯折部14、负极极片12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11的最内侧的一个弯折部14位于负极极片12的最内侧的一个弯折部14的外侧。
图6为图5所示的电极组件在方框D处的放大示意图。
如图6所示，在一些实施例中，负极极片12包括负极集流体121和设置于负极集流体121厚度方向上的两侧的负极活性物质层，负极集流体121厚度方向上的两侧的负极活性物质层分别称之为内侧负极活性物质层123和外侧负极活性物质层122。在一些示例中，内侧负极活性物质层123涂覆于负极集流体121的内表面，外侧负极活性物质层122涂覆于负极集流体121的外表面。
正极极片11包括正极集流体111和设置于正极集流体111厚度方向上的两侧的正极活性物质层，正极集流体111厚度方向上的两侧的正极活性物质层分别称之为内侧正极活性物质层113和外侧正极活性物质层112。在一些示例中，内侧正极活性物质层113涂覆于正极集流体111的内表面，外侧正极活性物质层112涂覆于正极集流体111的外表面。
其中，负极集流体121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111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电连接，负极极耳用于与负极电极端子电连接。
图7为本申请一些实施例提供的电极组件的局部剖视示意图。
如图7所示，在一些实施例中，正极极片11中的至少一个弯折部为第一弯折部141，正极极片11中的至少一个平直部为连接于第一弯折部141的第一平直部151，第一弯折部141内侧的单位面积活性物质容量小于第一平直部151内侧的单位面积活性物质容量。示例性地，第一弯折部141沿卷绕方向的两端分别连接于两个第一平直部151。
负极极片12中与第一弯折部141相邻的弯折部为第三弯折部143，负极极片12中的至少一个平直部为连接于第三弯折部143的第三平直部153。第三弯折部143外侧的单位面积活性物质容量等于第三平直部153外侧的单位面积活性物质容量。示例性地，第三弯折部143沿卷绕方向的两端分别连接于两个第三平直部153。
在一些实施例中，第一弯折部141的两侧均布置有与其相邻的负极极片12的弯折部，至少位于第一弯折部141的内侧且与第一弯折部141相邻的负极极片12的弯折部为第三弯折部143。可选地，位于第一弯折部141的两侧且与第一弯折部141相邻的负极极片12的弯折部均为第三弯折部143。
在第一弯折部141内侧的单位面积活性物质容量小于第一平直部151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平直部153外侧的单位面积活性物质容量，以简化负极极片12的制造工艺。
第一弯折部141包括第一集流部1411和设置于第一集流部1411内侧的第一内活性物质部1412。可理解地，第一集流部1411为正极集流体的位于第一弯折部141的一部分，第一内活性物质部1412为内侧正极活性物质层的位于第一弯折部141的一部分。
在一些实施例中，第一弯折部141还包括连接于第一集流部1411和第一内活性物质部1412之间的第一导电部1413。示例性地，第一导电部1413涂覆于第一集流部1411的内表面，第一内活性物质部1412涂覆于第一导电部1413的背离第一集流部1411的表面。本申请实施例通过设置第一导电部1413来减小第一弯折部141内侧的单位面积活性物质容量。
第一平直部151包括第二集流部1511和设置于第二集流部1511内侧的第二内活性物质部1512。可理解地，第二集流部1511为正极集流体的位于第一平直部151的一部分，第二内活性物质部1512为内侧正极活性物质层的位于第一平直部151的一部分。示例性地，第二内活性物质部1512涂覆于第二集流部1511的内表面。
第一弯折部141内侧的单位面积活性物质容量小于第一平直部151内侧的单位面积活性物质容量。第一弯折部141内侧的单位面积活性物质容量为：位于第一集流部1411内侧的第一涂覆部分的活性物质容量与第一涂覆部分的面积的比值，其中，第一涂覆部分包括第一内活性物质部1412和第一导电部1413，第一涂覆部分的面积等于第一集流部1411的内表面的涂覆有第一涂覆部分的区域的面积。第一平直部151内侧的单位面积活性物质容量为：位于第二集流部1511内侧的第二涂覆部分的活性物质容量与第二涂覆部分的面积的比值，其中，第二涂覆部分包括第二内活性物质部1512，第二涂覆部分的面积等于第二集流部1511的内表面的涂覆有第二涂覆部分的区域的面积。
第三弯折部143包括第五集流部1431和设置于第五集流部1431外侧的第四外活性物质部1432。可理解地，第五集流部1431为负极集流体的位于第三弯折部143的一部分，第四外活性物质部1432为外侧负极活性物质层的位于第三弯折部143的一部分。示例性地，第四外活性物质部1432涂覆于第五集流部1431的外表面。
第三平直部153包括第六集流部1531和设置于第六集流部1531外侧的第五外活性物质部1532。可理解地，第六集流部1531为负极集流体的位于第三平直部153的一部分，第五外活性物质部1532为外侧负极活性物质层的位于第三平直部153的一部分。示例性地，第五外活性物质部1532涂覆于第六集流部1531的外表面。
第三弯折部143外侧的单位面积活性物质容量等于第三平直部153外侧的单位面积活性物质容量，即第四外活性物质部1432的单位面积活性物质容量等于第五外活性物质部1532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为：第四外活性物质部1432的活性物质容量与第四外活性物质部1432的面积的比值，其中，第四外活性物质部1432的面积等于第五集流部1431的外表面的涂覆有第四外活性物质部1432的区域的面积。第三平直部153外侧的单位面积活性物质容量为：第五外活性物质部1532的活性物质容量与第五外活性物质部1532的面积的比值，其中，第五外活性物质部1532的面积等于第六集流部1531的外表面的涂覆有第五外活性物质部1532的区域的面积。
在正极极片11中，可以是全部弯折部为第一弯折部141，也可以是部分弯折部为第一弯折部141。在负极极片12中，可以全部弯折部为第三弯折部143，也可以是只有部分弯折部为第三弯折部143。
在一些实施例中，负极极片12中的全部弯折部均为第三弯折部143，以简化负极极片12的制造工艺。
在本申请实施例中，可通过多种方式来实现第一弯折部141内侧的单位面积活性物质容量小于第一平直部151内侧的单位面积活性物质容量。
在一些实施例中，第二内活性物质部1512的厚度大于第一内活性物质部1412的厚度，以使第一弯折部141内侧的单位面积活性物质容量小于第一平直部151内侧的单位面积活性物质容量。
在一些实施例中，除厚度外，第一内活性物质部1412的其它参数和第二内活性物质部1512基本相同。例如，第一内活性物质部1412的活性材料与第二内活性物质 部1512的活性材料相同，第一内活性物质部1412的活性材料与第一内活性物质部1412的重量比等于第二内活性物质部1512的活性材料与第二内活性物质部1512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，第二内活性物质部1512的厚度大于第一内活性物质部1412的厚度，可使得第二内活性物质部1512的单位面积活性物质容量大于第一内活性物质部1412的单位面积活性物质容量，从而实现第一弯折部141内侧的单位面积活性物质容量小于第一平直部151内侧的单位面积活性物质容量。
第一内活性物质部1412的活性材料和第二内活性物质部1512的活性材料均可以是磷酸铁锂、锰酸锂、三元锂、钴酸锂等。第一内活性物质部1412和第二内活性物质部1512由成分相同的活性浆料固化而成。
可选地，第二内活性物质部1512的厚度比第一内活性物质部1412的厚度大0.5％-20％。
在一些实施例中，第二内活性物质部1512的厚度大于或等于第一内活性物质部1412和第一导电部1413的总厚度。可选地，第二内活性物质部1512的厚度等于第一内活性物质部1412和第一导电部1413的总厚度。
需要说明的是，在其它实施例中，也可以是第一内活性物质部连接于第一导电部和第一集流部之间。
在一些实施例中，第一导电部1413可以是纯导电涂层，比如，第一导电部1413为由粘接剂和导电剂组成的纯导电涂层；第一导电部1413也可以是含有锂离子的活性涂层，比如，第一导电部1413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1413也可以是含锂离子的非活性涂层，比如，第一导电部1413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，第一导电部1413中包含有活性材料。第一导电部1413中的活性材料的克容量小于第一内活性物质部1412中的活性材料的克容量；本申请通过在第一导电部1413中添加克容量较小的活性材料，减小第一弯折部141内侧的单位面积活性物质容量，从而实现第一弯折部141内侧的单位面积活性物质容量小于第一平直部151内侧的单位面积活性物质容量。示例性地，第一导电部1413中的活性材料与第一导电部1413的重量比等于第一内活性物质部1412中的活性材料与第一内活性物质部1412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。
在另一些实施例中，第一导电部1413中包含有活性材料。第一导电部1413中的活性材料与第一导电部1413的重量比小于第一内活性物质部1412中的活性材料与第一内活性物质部1412的重量比，以减小第一弯折部141内侧的单位面积活性物质容量，从而实现第一弯折部141内侧的单位面积活性物质容量小于第一平直部151内侧的单位面积活性物质容量。示例性地，第一导电部1413中的活性材料的克容量等于第一内活性物质部1412中的活性材料的克容量。
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平直部153外侧的单位面积活性物质容量。比 如，第三弯折部143的第四外活性物质部1432的活性材料与第三平直部153的第五外活性物质部1532的活性材料相同，第四外活性物质部1432的厚度等于第五外活性物质部1532的厚度。
图8为本申请另一些实施例提供的电极组件的局部剖视示意图。
如图8所示，在一些实施例，第一平直部151还包括第三内活性物质部1513和第二导电部1514，第三内活性物质部1513设置于第二集流部1511的内侧，第二导电部1514连接于第二集流部1511和第三内活性物质部1513之间。第二导电部1514连接于第一导电部1413和第二内活性物质部1512之间，第三内活性物质部1513连接于第一内活性物质部1412和第二内活性物质部1512之间。
第一平直部151内侧的单位面积活性物质容量为：位于第二集流部1511内侧的第二涂覆部分的活性物质容量与第二涂覆部分的面积的比值，其中，第二涂覆部分包括第二内活性物质部1512、第三内活性物质部1513和第二导电部1514，第二涂覆部分的面积等于第二集流部1511的内表面的涂覆有第二涂覆部分的区域的面积。
在一些实施例中，第一导电部1413的厚度等于第二导电部1514的厚度。第一导电部1413的材料和第二导电部1514的材料相同，例如第一导电部1413和第二导电部1514由相同的导电浆料固化而成。在本申请实施例中，在正极极片11的涂布工艺中，导电浆料可以同时涂布在第一集流部1411和第二集流部1511，无需将导电浆料严格地限制在第一集流部1411，降低对涂布工艺的精度要求。
在一些实施例中，第一内活性物质部1412的厚度等于第三内活性物质部1513的厚度。
在一些实施例中，第一内活性物质部1412、第二内活性物质部1512以及第三内活性物质部1513由相同的材料制成，例如，三者由相同的活性浆料固化而成。
图9为本申请又一些实施例提供的的局部剖视示意图。
如图9所示，在一些实施例中，负极极片12中的至少一个弯折部为第二弯折部142，负极极片12中的至少一个平直部为连接于第二弯折部142的第二平直部152，第二弯折部142外侧的单位面积活性物质容量大于第二平直部152外侧的单位面积活性物质容量。示例性地，第二弯折部142沿卷绕方向的两端分别连接于两个第二平直部152。
正极极片11中与第二弯折部142相邻的弯折部为第四弯折部144，正极极片11中的至少一个平直部为连接于第四弯折部144的第四平直部154。第四弯折部144内侧的单位面积活性物质容量等于第四平直部154内侧的单位面积活性物质容量。示例性地，第四弯折部144沿卷绕方向的两端分别连接于两个第四平直部154。
在一些实施例中，第二弯折部142的两侧均布置有与其相邻的正极极片11的弯折部，至少位于第二弯折部142的外侧且与第二弯折部142相邻的正极极片11的弯折部为第四弯折部144。可选地，位于第二弯折部142的两侧且与第二弯折部142相邻的正极极片11的弯折部均为第四弯折部144。
在第二弯折部142外侧的单位面积活性物质容量大于第二平直部152外侧的单位面积活性物质容量的情况下，第四弯折部144内侧的单位面积活性物质容量可以等于第四平直部154内侧的单位面积活性物质容量，以简化正极极片11的制造工艺。
第二弯折部142包括第三集流部1421和设置于第三集流部1421外侧的第一外活性物质部1422。可理解地，第三集流部1421为负极集流体的位于第三弯折部143的一部分，第一外活性物质部1422为外侧负极活性物质层的位于第三弯折部143的一部分。示例性地，第一外活性物质部1422涂覆于第三集流部1421的外表面。
第二平直部152包括第四集流部1521和设置于第四集流部1521外侧的第二外活性物质部1522。可理解地，第四集流部1521为负极集流体的位于第二平直部152的一部分，第二外活性物质部1522为外侧负极活性物质层的位于第二平直部152的一部分。示例性地，第二外活性物质部1522涂覆于第四集流部1521的外表面。
第二弯折部142外侧的单位面积活性物质容量大于第二平直部152外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为：位于第三集流部1421外侧的第三涂覆部分的活性物质容量与第三涂覆部分的面积的比值，其中，第三涂覆部分包括第一外活性物质部1422，第三涂覆部分的面积等于第三集流部1421的外表面的涂覆有第三涂覆部分的区域的面积。第二平直部152外侧的单位面积活性物质容量为：位于第四集流部1521外侧的第四涂覆部分的活性物质容量与第四涂覆部分的面积的比值，其中，第四涂覆部分包括第二外活性物质部1522，第四涂覆部分的面积等于第四集流部1521的外表面的涂覆有第四涂覆部分的区域的面积。
第四弯折部144包括第七集流部1441和设置于第七集流部1441内侧的第四内活性物质部1442。可理解地，第七集流部1441为正极集流体的位于第四弯折部144的一部分，第四内活性物质部1442为内侧正极活性物质层的位于第四弯折部144的一部分。示例性地，第四内活性物质部1442涂覆于第七集流部1441的内表面。
第四平直部154包括第八集流部1541和设置于第八集流部1541内侧的第五内活性物质部1542。可理解地，第八集流部1541为正极集流体111的位于第四平直部154的一部分，第五内活性物质部1542为内侧正极活性物质层113的位于第四平直部154的一部分。示例性地，第五内活性物质部1542涂覆于第八集流部1541的内表面。
第四弯折部144内侧的单位面积活性物质容量等于第四平直部154内侧的单位面积活性物质容量，即第四内活性物质部1442的单位面积活性物质容量等于第五内活性物质部1542的单位面积活性物质容量。第四弯折部144内侧的单位面积活性物质容量为：第四内活性物质部1442的活性物质容量与第四内活性物质部1442的面积的比值，其中，第四内活性物质部1442的面积等于第七集流部1441的内表面的涂覆有第四内活性物质部1442的区域的面积。第四平直部154内侧的单位面积活性物质容量为：第五内活性物质部1542的活性物质容量与第五内活性物质部1542的面积的比值，其中，第五内活性物质部1542的面积等于第八集流部1541的内表面的涂覆有第五内活性物质部1542的区域的面积。
在负极极片12中，可以是全部弯折部为第二弯折部142，也可以是部分弯折部为第二弯折部142。在正极极片11中，可以全部弯折部为第四弯折部144，也可以是只有部分弯折部为第四弯折部144。
在一些实施例中，正极极片11中的全部弯折部均为第四弯折部144，以简化正极极片11的制造工艺。
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平直部152外侧的单位面积活性物质容量。
第一外活性物质部1422中的活性材料的克容量大于第二外活性物质部1522中的活性材料的克容量，可以使第一外活性物质部1422的单位面积活性物质容量大于第二外活性物质部1522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平直部152外侧的单位面积活性物质容量。在一些实施例中，除克容量外，第一外活性物质部1422的其它参数和第二外活性物质部1522相同；例如，第一外活性物质部1422的厚度等于第二外活性物质部1522的厚度，第一外活性物质部1422的活性材料与第一外活性物质部1422的重量比等于第二外活性物质部1522的活性材料与第二外活性物质部1522的重量比。
本实施例中，第一外活性物质部1422的活性材料不同于第二外活性物质部1522的活性材料，例如，第一外活性物质部1422的活性材料为硅的化合物，第二外活性物质部1522的活性材料为石墨。
在另一些实施例中，第一外活性物质部1422中的活性材料与第一外活性物质部1422的重量比大于第二外活性物质部1522中的活性材料与第二外活性物质部1522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平直部152外侧的单位面积活性物质容量。第一外活性物质部1422和第二外活性物质部1522均包括活性材料、粘接剂和导电剂，通过增加第一外活性物质部1422中活性材料的重量比，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平直部152外侧的单位面积活性物质容量。
在一些实施例中，第一外活性物质部1422的厚度与第二外活性物质部1522的厚度相同，第一外活性物质部1422中的活性材料与第二外活性物质部1522中的活性材料相同，第一外活性物质部1422中的活性材料与第一外活性物质部1422的重量比大于第二外活性物质部1522中的活性材料与第二外活性物质部1522的重量比。
图10为本申请再一些实施例提供的电极组件的局部剖视示意图。
如图10所示，在一些实施例中，第一外活性物质部1422的厚度大于第二外活性物质部1522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平直部152外侧的单位面积活性物质容量。
在一些实施例中，除厚度外，第一外活性物质部1422的其它参数与第二外活性物质部1522相同；例如，第一外活性物质部1422的活性材料与第二外活性物质部1522的活性材料相同，第一外活性物质部1422中的活性材料与第一外活性物质部1422的重量比等于第二外活性物质部1522中的活性材料与第二外活性物质部1522的重量比。
第一外活性物质部1422的活性材料与第二外活性物质部1522的活性材料均可以是石墨或硅的化合物等。示例性地，第一外活性物质部1422和第二外活性物质部1522由成分相同的活性浆料固化而成。
可选地，第一外活性物质部1422的厚度比第二外活性物质部1522的厚度大0.5％-20％。
图11为本申请另一些实施例提供的电极组件的局部剖视示意图。
如图11所示，第二弯折部142包括第三导电部1423，第三导电部1423连接于第三集流部1421和第一外活性物质部1422之间。第三导电部1423中含有活性材料。示例性地，第三导电部1423涂覆于第三集流部1421的外表面，第一外活性物质部1422涂覆于第三导电部1423的背离第三集流部1421的表面。本申请实施例通过设置第三导电部1423来增大第二弯折部142外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为：位于第三集流部1421外侧的第三涂覆部分的活性物质容量与第三涂覆部分的面积的比值，其中，第三涂覆部分包括第一外活性物质部1422和第三导电部1423，第三涂覆部分的面积等于第三集流部1421的外表面的涂覆有第三涂覆部分的区域的面积。
在一些实施例中，第二外活性物质部1522的厚度大于第一外活性物质部1422的厚度。除厚度外，第一外活性物质部1422的其它参数和第二外活性物质部1522基本相同。例如，第一外活性物质部1422的活性材料与第二外活性物质部1522的活性材料相同。
在一些实施例中，第二外活性物质部1522的厚度大于或等于第一外活性物质部1422和第三导电部1423的总厚度。可选地，第二外活性物质部1522的厚度等于第一外活性物质部1422和第三导电部1423的总厚度。
需要说明的是，在其它实施例中，也可以是第一外活性物质部1422连接于第三导电部1423和第三集流部1421之间。
在一些实施例中，第三导电部1423中的活性材料的克容量大于第一外活性物质部1422中的活性材料的克容量；本申请通过在第三导电部1423中添加克容量较大的活性材料，增大第二弯折部142外侧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平直部152外侧的单位面积活性物质容量。示例性地，第三导电部1423中的活性材料与第三导电部1423的重量比等于第一外活性物质部1422中的活性材料与第一外活性物质部1422的重量比。
在另一些实施例中，第三导电部1423中的活性材料与第三导电部1423的重量比大于第一外活性物质部1422中的活性材料与第一外活性物质部1422的重量比，以增大第二弯折部142外侧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平直部152外侧的单位面积活性物质容量。示例性地，第三导电部1423中的活性材料的克容量等于第一外活性物质部1422中的活性材料的克容量。
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四弯折部144内侧的单位面积活性物质容量等于第四平直部154内侧的单位面积活性物质容量。比如，第四弯折部144的第四内活性物质部1442的活性材料与第四平直部154的第五内活性物质部1542的活性材料相同，第四内活性物质部1442的厚度等于第五内活性物质部1542的厚度。
图12为本申请又一些实施例提供的电极组件的局部剖视示意图。
如图12所示，第二平直部152还包括第三外活性物质部1523和第四导电部 1524，第三外活性物质部1523设置于第四集流部1521的外侧，第四导电部1524连接于第四集流部1521和第三外活性物质部1523之间。第四导电部1524连接于第三导电部1423和第二外活性物质部1522之间，第三外活性物质部1523连接于第一外活性物质部1422和第二外活性物质部1522之间。
第二平直部152外侧的单位面积活性物质容量为：位于第四集流部1521外侧的第四涂覆部分的活性物质容量与第四涂覆部分的面积的比值，其中，第四涂覆部分包括第二外活性物质部1522、第三外活性物质部1523和第四导电部1524，第四涂覆部分的面积等于第四集流部1521的外表面的涂覆有第四涂覆部分的区域的面积。
在一些实施例中，第三导电部1423的厚度等于第四导电部1524的厚度。第三导电部1423的材料和第四导电部1524的材料相同，例如第三导电部1423和第四导电部1524由相同的导电浆料固化而成。在本申请实施例中，在负极极片12的涂布工艺中，导电浆料可以同时涂布在第三集流部1421和第四集流部1521，无需将导电浆料严格地限制在第三集流部1421，降低对涂布工艺的精度要求。
在一些实施例中，第一外活性物质部1422的厚度等于第三外活性物质部1523的厚度。
在一些实施例中，第一外活性物质部1422、第二外活性物质部1522以及第三外活性物质部1523由相同的材料制成，例如，三者由相同的活性浆料固化而成。
图13为本申请再一些实施例提供的电极组件的局部剖视示意图。
如图13所示，在一些实施例中，正极极片11中的至少一个弯折部为第一弯折部141，正极极片11中的至少一个平直部为连接于第一弯折部141的第一平直部151，第一弯折部141内侧的单位面积活性物质容量小于第一平直部151内侧的单位面积活性物质容量；负极极片12中的至少一个弯折部为第二弯折部142，负极极片12中的至少一个平直部为连接于第二弯折部142的第二平直部152，第二弯折部142外侧的单位面积活性物质容量大于第二平直部152外侧的单位面积活性物质容量。
在本申请实施例中，可以通过在第一弯折部141添加第一导电部1413等方式，使得第一弯折部141内侧的单位面积活性物质容量小于第一平直部151内侧的单位面积活性物质容量。同样地，可以通过使第一外活性物质部1422的厚度大于第二外活性物质部1522的方式，或通过使第一外活性物质部1422的活性材料的克容量大于第二外活性物质部1522的活性材料的克容量的方式，或通过在第二弯折部142添加第三导电部1423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平直部152外侧的单位面积活性物质容量。
示例性地，在图13中，第一弯折部141包括连接于第一集流部1411和第一内活性物质部1412之间的第一导电部1413，第二弯折部142包括连接于第三集流部1421和第一外活性物质部1422之间的第三导电部1423。
在一些实施例中，第二弯折部142的外侧布置有与第二弯折部142相邻的第一弯折部141。
在第一平直部151内侧的单位面积活性物质容量和第二平直部152外侧的单位面积活性物质容量满足设计要求时，第一弯折部141内侧的单位面积活性物质容量小 于第一平直部151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平直部152外侧的单位面积活性物质容量，这样可以增大第二弯折部142的外侧活性物质的CB值，从而减少析锂现象的发生。
图14为本申请另一些实施例提供的电极组件的局部剖视示意图。
在一些实施例中，正极极片11中的至少一个弯折部为第一弯折部141，正极极片11中的至少一个平直部为连接于第一弯折部141的第一平直部151，第一弯折部141内侧的单位面积活性物质容量小于第一平直部151内侧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小于第一平直部151外侧的单位面积活性物质容量。
在一些实施例中，第一弯折部141包括第六外活性物质部1414和第五导电部1415，第六外活性物质部1414位于第一集流部1411的外侧，第五导电部1415连接于第一集流部1411和第六外活性物质部1414之间。本申请实施例通过设置第五导电部1415，减小第一弯折部141外侧的单位面积活性物质容量。
在一些实施例中，负极极片12中的至少一个弯折部为第二弯折部142，负极极片12中的至少一个平直部为连接于第二弯折部142的第二平直部152，第二弯折部142外侧的单位面积活性物质容量大于第二平直部152外侧的单位面积活性物质容量，第二弯折部142内侧的单位面积活性物质容量大于第二平直部152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142包括第六内活性物质部1424和第六导电部1425，第六内活性物质部1424位于第三集流部1421的内侧，第六导电部1425连接于第三集流部1421和第六内活性物质部1424之间。本申请实施例通过设置第六导电部1425，增大第二弯折部142内侧的单位面积活性物质容量。
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15为本申请一些实施例提供的电极组件的制造方法的流程示意图。
如图15所示，电极组件的制造方法包括：
S100、提供负极极片；
S200、提供正极极片；
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。
卷绕结构包括弯折区和连接于弯折区的平直区。负极极片和正极极片均包括位于弯折区的多个弯折部和位于平直区的多个平直部。
正极极片中的至少一个弯折部为第一弯折部，正极极片中的至少一个平直部为连接于第一弯折部的第一平直部，第一弯折部内侧的单位面积活性物质容量小于第一平直部内侧的单位面积活性物质容量；和/或，负极极片中的至少一个弯折部为第二弯折部，负极极片中的至少一个平直部为连接于第二弯折部的第二平直部，第二弯折部外侧的单位面积活性物质容量大于第二平直部外侧的单位面积活性物质容量。
在一些实施例中，本申请的制造方法还包括：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。
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。
图16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。
如图16所示，本申请实施例的电极组件的制造系统9包括：第一提供装置91，用于提供负极极片；第二提供装置92，用于提供正极极片；组装装置93，将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和连接于弯折区的平直区。负极极片和正极极片均包括位于弯折区的多个弯折部和位于平直区的多个平直部。
正极极片中的至少一个弯折部为第一弯折部，正极极片中的至少一个平直部为 连接于第一弯折部的第一平直部，第一弯折部内侧的单位面积活性物质容量小于第一平直部内侧的单位面积活性物质容量；和/或，负极极片中的至少一个弯折部为第二弯折部，负极极片中的至少一个平直部为连接于第二弯折部的第二平直部，第二弯折部外侧的单位面积活性物质容量大于第二平直部外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。
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 (20)

  1. 一种电极组件，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和连接于所述弯折区的平直区；
    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和位于所述平直区的多个平直部；
    其中，
    所述正极极片中的至少一个弯折部为第一弯折部，所述正极极片中的至少一个平直部为连接于所述第一弯折部的第一平直部，所述第一弯折部内侧的单位面积活性物质容量小于所述第一平直部内侧的单位面积活性物质容量；和/或，所述负极极片中的至少一个弯折部为第二弯折部，所述负极极片中的至少一个平直部为连接于所述第二弯折部的第二平直部，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平直部外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，其中，所述正极极片中的至少一个弯折部为所述第一弯折部，所述负极极片中的至少一个弯折部为所述第二弯折部，所述第二弯折部的外侧布置有与所述第二弯折部相邻的所述第一弯折部。
  3. 根据权利要求1所述的电极组件，其中，所述正极极片中的至少一个弯折部为所述第一弯折部；
    所述负极极片中与所述第一弯折部相邻的弯折部为第三弯折部，所述负极极片中的至少一个平直部为连接于所述第三弯折部的第三平直部；
    所述第三弯折部外侧的单位面积活性物质容量等于所述第三平直部外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，其中，所述负极极片中的至少一个弯折部为所述第二弯折部；
    所述正极极片中与所述第二弯折部相邻的弯折部为第四弯折部，所述正极极片中的至少一个平直部为连接于所述第四弯折部的第四平直部；
    所述第四弯折部内侧的单位面积活性物质容量等于所述第四平直部内侧的单位面积活性物质容量。
  5. 根据权利要求1-3中任一项所述的电极组件，其中，所述第一弯折部包括第一集流部、设置于所述第一集流部内侧的第一内活性物质部以及连接于所述第一集流部和所述第一内活性物质部之间的第一导电部。
  6. 根据权利要求5所述的电极组件，其中，所述第一平直部包括第二集流部和设置于所述第二集流部内侧的第二内活性物质部；
    所述第二内活性物质部的厚度大于所述第一内活性物质部的厚度。
  7. 根据权利要求6所述的电极组件，其中，所述第一平直部还包括第三内活性物质部和第二导电部，所述第三内活性物质部设置于所述第二集流部的内侧，所述第二导电部连接于所述第二集流部和所述第三内活性物质部之间；
    所述第二导电部连接于所述第一导电部和所述第二内活性物质部之间，所述第三 内活性物质部连接于所述第一内活性物质部和所述第二内活性物质部之间。
  8. 根据权利要求5-7中任一项所述的电极组件，其中，所述第一导电部中包含有活性材料；
    所述第一导电部中的活性材料的克容量小于所述第一内活性物质部中的活性材料的克容量；或者，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小于所述第一内活性物质部中的活性材料与所述第一内活性物质部的重量比。
  9. 根据权利要求1、2或4所述的电极组件，其中，所述第二弯折部包括第三集流部和设置于所述第三集流部外侧的第一外活性物质部，所述第二平直部包括第四集流部和设置于所述第四集流部外侧的第二外活性物质部。
  10. 根据权利要求9所述的电极组件，其中，所述第一外活性物质部的厚度大于所述第二外活性物质部的厚度。
  11. 根据权利要求9所述的电极组件，其中，
    第一外活性物质部中的活性材料的克容量大于所述第二外活性物质部中的活性材料的克容量；或者
    第一外活性物质部中的活性材料与所述第一外活性物质部的重量比大于所述第二外活性物质部中的活性材料与所述第二外活性物质部的重量比。
  12. 根据权利要求9所述的电极组件，其中，所述第二弯折部包括第三导电部，所述第三导电部连接于所述第三集流部和所述第一外活性物质部之间，且所述第三导电部中含有活性材料；
    所述第三导电部中的活性材料的克容量大于所述第一外活性物质部中的活性材料的克容量；或者，所述第三导电部中的活性材料与所述第三导电部的重量比大于所述第一外活性物质部中的活性材料与所述第一外活性物质部的重量比。
  13. 根据权利要求12所述的电极组件，其中，所述第二平直部还包括第三外活性物质部和第四导电部，所述第三外活性物质部设置于所述第四集流部的外侧，所述第四导电部连接于所述第四集流部和所述第三外活性物质部之间；
    所述第四导电部连接于所述第三导电部和所述第二外活性物质部之间，所述第三外活性物质部连接于所述第一外活性物质部和所述第二外活性物质部之间。
  14. 根据权利要求1-13中任一项所述的电极组件，其中，所述正极极片中至少最内侧的一个弯折部为所述第一弯折部。
  15. 根据权利要求1-14中任一项所述的电极组件，其中，所述负极极片中至少最内侧的一个弯折部为所述第二弯折部。
  16. 一种电池单体，包括外壳和根据权利要求1-15任一项所述的电极组件，所述电极组件容纳于所述外壳内。
  17. 一种电池，包括箱体和根据权利要求16所述的电池单体，所述电池单体容纳于所述箱体内。
  18. 一种用电装置，包括权利要求17所述的电池，所述电池用于提供电能。
  19. 一种电极组件的制造方法，包括：
    提供负极极片；
    提供正极极片；
    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和连接于所述弯折区的平直区；
    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和位于所述平直区的多个平直部；
    所述正极极片中的至少一个弯折部为第一弯折部，所述正极极片中的至少一个平直部为连接于所述第一弯折部的第一平直部，所述第一弯折部内侧的单位面积活性物质容量小于所述第一平直部内侧的单位面积活性物质容量；和/或，所述负极极片中的至少一个弯折部为第二弯折部，所述负极极片中的至少一个平直部为连接于所述第二弯折部的第二平直部，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平直部外侧的单位面积活性物质容量。
  20. 一种电极组件的制造系统，包括：
    第一提供装置，用于提供负极极片；
    第二提供装置，用于提供正极极片；
    组装装置，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和连接于所述弯折区的平直区；
    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和位于所述平直区的多个平直部；
    所述正极极片中的至少一个弯折部为第一弯折部，所述正极极片中的至少一个平直部为连接于所述第一弯折部的第一平直部，所述第一弯折部内侧的单位面积活性物质容量小于所述第一平直部内侧的单位面积活性物质容量；和/或，所述负极极片中的至少一个弯折部为第二弯折部，所述负极极片中的至少一个平直部为连接于所述第二弯折部的第二平直部，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平直部外侧的单位面积活性物质容量。
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