WO2024087200A1 - 集流体、极片及其制备方法、电极组件及二次电池 - Google Patents

集流体、极片及其制备方法、电极组件及二次电池 Download PDF

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Publication number
WO2024087200A1
WO2024087200A1 PCT/CN2022/128367 CN2022128367W WO2024087200A1 WO 2024087200 A1 WO2024087200 A1 WO 2024087200A1 CN 2022128367 W CN2022128367 W CN 2022128367W WO 2024087200 A1 WO2024087200 A1 WO 2024087200A1
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WIPO (PCT)
Prior art keywords
current collector
area
corner
perforations
electrode sheet
Prior art date
Application number
PCT/CN2022/128367
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English (en)
French (fr)
Inventor
刘智
史东洋
吕瑞景
邓亚茜
王羽臻
金海族
李白清
Original Assignee
宁德时代新能源科技股份有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
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 PCT/CN2022/128367 priority Critical patent/WO2024087200A1/zh
Priority to EP22937658.7A priority patent/EP4391120A1/en
Priority to US18/418,371 priority patent/US20240162450A1/en
Publication of WO2024087200A1 publication Critical patent/WO2024087200A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/70—Carriers or collectors characterised by shape or form
    • H01M4/76—Containers for holding the active material, e.g. tubes, capsules
    • 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
    • H01M10/058—Construction or manufacture
    • H01M10/0587—Construction or manufacture of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/88—Processes of manufacture
    • H01M4/8878—Treatment steps after deposition of the catalytic active composition or after shaping of the electrode being free-standing body
    • H01M4/8896—Pressing, rolling, calendering

Definitions

  • the present application relates to the field of battery technology, and in particular to a current collector, a pole piece and a preparation method thereof, an electrode assembly and a secondary battery.
  • the electrode assembly is a component in a secondary battery where electrochemical reactions occur. It is mainly formed by winding or stacking a positive electrode sheet and a negative electrode sheet, and a separator is usually provided between the negative electrode sheet and the positive electrode sheet. When winding, the electrode assembly can form a straight portion and two bent portions on both sides of the straight portion.
  • the negative electrode sheets and the positive electrode sheets are stacked alternately.
  • the present application provides a current collector for winding in a first direction, the current collector comprising: a current collector body having a plurality of corner regions spaced apart along the first direction, the corner regions being used to be opposite to the bending portions of the electrode assembly; wherein at least one corner region has a perforation extending through it along the thickness direction of the current collector.
  • the above-mentioned current collector is provided with a perforation penetrating the current collector body in at least one corner area, so that the electrode assembly formed by winding the pole piece with the current collector will have a perforation feature inside at least one pole piece in the bend.
  • the lithium ions on the convex side and the concave side of the pole piece will be interconnected through the perforation, ensuring that the lithium insertion concentration on both sides of the pole piece is balanced, reducing the risk of lithium plating between the negative pole piece and the positive pole piece in the bend, which is conducive to improving the service life of the secondary battery.
  • in the corner area with perforations there are multiple perforations, and all the perforations are spaced apart in the corner area. In this way, multiple perforations are spaced apart in the corner area, which is beneficial to speed up the passing rate of lithium ion concentration on both sides of the pole piece and promote the dynamic balance of lithium ion concentration on both sides of the pole piece.
  • the perforations are arranged in rows in the second direction, and the sum of the opening areas of any row of perforations is recorded as S0.
  • the sum of the opening areas of each row S0 is smaller as it is closer to any end of the corner area along the second direction, and the first direction is perpendicular to the second direction. In this way, it is helpful to reduce the number of openings near one end of the corner area, avoid stress concentration caused by too many openings, and effectively avoid the risk of fracture of the pole piece during the cold pressing process.
  • the number of openings in each row of perforations gradually decreases from the middle of the corner region to any end of the corner region along the second direction. In this design, the number of openings is reduced closer to one end of the corner region, ensuring the structural strength of the edge of the current collector body and avoiding fracture during the cold pressing process.
  • the current collector body has a coating area for coating the active material layer, the coating area extends along the first direction and passes through each corner area in sequence, the perforations in the corner area are all located in the coating area in the second direction, and the first direction is perpendicular to the second direction.
  • the opening position of the perforations is limited to the coating area, so that lithium ions can flow effectively on both sides of the pole piece; at the same time, it is also avoided that the perforations are opened in the pole ear part, which will cause its structural strength to be weakened.
  • At least one stress zone is provided in the coating area, the stress zone extends along an edge of the coating area in the second direction, and the perforations in the corner area are all located in the area of the coating area excluding the stress zone in the second direction. In this way, a stress zone is left near an edge of the coating area without perforations, thereby ensuring the mechanical strength of at least one side of the current collector, avoiding breakage or tearing problems during processing, and improving production efficiency.
  • the width of each stress zone in the second direction is recorded as D, where D ⁇ 3 mm.
  • the minimum threshold of the width of the stress zone is reasonably limited so that there is a section of the area at an edge of the coating zone along the second direction without openings, thereby ensuring the mechanical strength of at least one side of the current collector.
  • two stress regions are provided in the coating region along the second direction, and the two stress regions are respectively adjacent to two opposite edges of the coating region along the second direction. In this way, stress regions are left near two opposite edges of the coating region without perforations, thereby ensuring the mechanical strength of both sides of the current collector, avoiding breakage or tearing during processing, and improving production efficiency.
  • the current collector body also has a blank area, which is located on at least one side of the coating area along the second direction. In this way, a blank area is reserved on at least one side of the current collector body to make the tab part required for the electrode assembly, which is conducive to improving the manufacturing efficiency.
  • the sum of the opening areas of all perforations is recorded as S1
  • the area of the corner area on the current collector is recorded as S2, wherein 0.1% ⁇ S1/S2 ⁇ 50%.
  • the first n corner regions are all provided with perforations, where n ⁇ 6. In this way, by making holes in the first n corner regions, the positions where lithium deposition problems are prone to occur in the electrode assembly can be improved in a targeted manner, and the hole making operation can be reduced while ensuring that the lithium deposition problem is reduced, thereby improving the mechanical strength of the current collector.
  • the present application provides a pole piece, comprising: a current collector as described in any of the above items; and an active material layer disposed on at least one surface of the current collector body.
  • the present application provides a method for preparing a pole piece, which is used to prepare the above pole piece, comprising the following steps: providing a current collecting body; drilling holes in the corner area of the current collecting body to form a current collector; coating an active material layer on the surface of the current collector; and rolling the coated current collector.
  • the step of rolling the coated current collector includes: pressing the tension roller surface of the pressure roller and the extension roller surfaces on both sides of the tension roller surface respectively on the active material layer and the blank areas on both sides of the active material layer on the current collector, and controlling the extension roller surface to leave a gap between the side facing the tension roller surface and the area where the perforation is located.
  • a gap is controlled between one side of the extension roller surface and the area where the perforation is located to avoid stress concentration caused by the perforation opening position being close to the extension roller surface, thereby avoiding the electrode sheet from being easily broken during rolling.
  • the present application provides an electrode assembly, which is constructed as a winding structure, including a positive electrode sheet, a negative electrode sheet and a separator separated from the positive electrode sheet and the negative electrode sheet, and the winding structure includes a bending portion; wherein the positive electrode sheet and/or the negative electrode sheet are the above electrode sheets, and the position of the bending portion is opposite to the corner area after winding.
  • the present application provides a secondary battery comprising the above electrode assembly.
  • FIG1 is a schematic diagram of an exploded structure of a secondary battery provided in some embodiments of the present application.
  • FIG2 is a schematic diagram of the structure of an electrode assembly provided in some embodiments of the present application.
  • FIG3 is a schematic diagram of a current collector structure provided in some embodiments of the present application.
  • FIG4 is a schematic diagram of a first process of a method for preparing a pole piece provided in some embodiments of the present application.
  • FIG5 is a second schematic flow diagram of a method for preparing a pole piece provided in some embodiments of the present application.
  • FIG. 6 is a schematic diagram of the pressure roller structure provided in some embodiments of the present application.
  • 100 secondary battery; 10, electrode assembly; 20, end cap; 30, electrode terminal; 40, shell; 1, pole piece; 1a, current collector; 11, current collector body; 12, perforation; 13, corner area; 14, coating area; 15, stress area; 16, blank area; 17, opening area; 18, straight area; 2, positive pole piece; 3, negative pole piece; 4, diaphragm; 5, straight portion; 6, bending portion; 200, pressure roller; 210, extension roller surface; 220, tension roller surface; X, first direction; Y, second direction.
  • the term "and/or" is only a description of the association relationship of associated objects, indicating that three relationships may exist.
  • a and/or B can represent: A exists alone, A and B exist at the same time, and B exists alone.
  • the character "/" in this article generally indicates that the associated objects before and after are in an "or" relationship.
  • multiple refers to more than two (including two).
  • multiple groups refers to more than two groups (including two groups), and “multiple pieces” refers to more than two pieces (including two pieces).
  • Power batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, but also widely used in electric vehicles such as electric bicycles, electric motorcycles, electric cars, as well as military equipment and aerospace and other fields. With the continuous expansion of the application field of power batteries, the market demand is also constantly expanding.
  • the electrode assembly when configured as a winding structure, it includes a straight portion and a bending portion provided on both sides of the straight portion.
  • the bending portion there are alternating layers of positive and negative electrode sheets with different curvature radii, and both the positive and negative electrode sheets will form concave and convex surfaces when bent.
  • the concave side and convex side correspond to the inner and outer layers of the positive electrode sheets, that is, the concave side of the negative electrode sheet is opposite to the convex side of the inner positive electrode sheet, and its convex side is opposite to the concave side of the outer positive electrode sheet.
  • the active material capacity of the concave surface of the negative electrode sheet will be larger than the active material capacity of the convex surface of the positive electrode sheet, and the corresponding NP values of the two are larger than 1, which can also be simply understood as the concentration of lithium insertion vacancies is larger than the concentration of lithium insertion ions, and there are surplus lithium insertion vacancies.
  • the active material capacity of the concave surface of the negative electrode sheet will be smaller than the active material capacity of the convex surface of the positive electrode sheet, and the corresponding NP values of the two are smaller than 1, which can also be simply understood as the concentration of lithium insertion vacancies cannot meet the insertion of lithium insertion ions, and the risk of lithium precipitation is prone to occur during charging.
  • the applicant has designed a current collector after in-depth research, in which a perforation is provided through the current collector along the thickness direction in at least one corner area so that the lithium ions on both sides of the current collector can flow to each other.
  • the above-mentioned current collector is provided with a through hole penetrating the current collector body in at least one corner area.
  • a pole piece prepared using the current collector such as a positive pole piece or a negative pole piece, will allow lithium ions on both sides of the pole piece to pass through the through hole, thereby ensuring that the lithium ion concentration on both sides of the pole piece reaches a balance, for example: the side with a high lithium ion concentration flows into the side with a low lithium ion concentration through the through hole, etc.
  • the electrode assembly After the electrode sheet prepared by the current collector is wound to form an electrode assembly, the electrode assembly will have a perforation feature inside at least one layer of the electrode sheet in the bend. At this time, during the cyclic charging process, the lithium ions on the convex side and the concave side of the electrode sheet will communicate with each other through the perforations to ensure that the lithium insertion concentration on both sides of the electrode sheet is balanced.
  • the lithium ions on the convex side of the negative electrode sheet flow through the perforations to the lithium ions on the concave side of the negative electrode sheet, so that the lithium insertion concentration on the convex side is reduced, ensuring that the local NP is greater than or equal to 1, reducing the risk of lithium deposition between the negative electrode sheet and the positive electrode sheet in the bend, and improving the service life of the secondary battery.
  • the secondary battery disclosed in the embodiment of the present application can be used in, but not limited to, electrical devices such as vehicles, ships, or aircraft.
  • a power supply system having the secondary battery disclosed in the present application and the like can be used to form the electrical device.
  • the multiple secondary batteries can be connected in series, in parallel, or in a mixed connection.
  • a mixed connection means that the multiple secondary batteries are both connected in series and in parallel.
  • Multiple secondary batteries can be directly connected in series, in parallel, or in a mixed connection, and then the whole formed by the multiple secondary batteries is accommodated in a box; of course, the battery can also be a battery module formed by connecting multiple secondary batteries in series, in parallel, or in a mixed connection, and then the multiple battery modules are connected in series, in parallel, or in a mixed connection to form a whole, and accommodated in a box.
  • the battery can also include other structures.
  • the battery can also include a confluence component for realizing electrical connection between multiple secondary batteries.
  • the secondary battery can be cylindrical, flat, rectangular, or in other shapes.
  • FIG. 1 is a schematic diagram of the exploded structure of a secondary battery 100 provided in some embodiments of the present application.
  • the secondary battery 100 refers to the smallest unit of a battery.
  • the secondary battery 100 includes an end cap 20, a housing 40, an electrode assembly 10, and other functional components.
  • the end cap 20 refers to a component that covers the opening of the shell 40 to isolate the internal environment of the secondary battery 100 from the external environment.
  • the shape of the end cap 20 can be adapted to the shape of the shell 40 to match the shell 40.
  • the end cap 20 can be made of a material with a certain hardness and strength (such as aluminum alloy), so that the end cap 20 is not easily deformed when squeezed and collided, so that the secondary battery 100 can have a higher structural strength and the safety performance can also be improved.
  • Functional components such as electrode terminals 30 can be provided on the end cap 20. The electrode terminal 30 can be used to electrically connect to the electrode assembly 10 for outputting or inputting electrical energy of the secondary battery 100.
  • the end cap 20 can also be provided with a pressure relief mechanism for releasing the internal pressure when the internal pressure or temperature of the secondary battery 100 reaches a threshold.
  • the material of the end cap 20 can also be a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiment of the present application does not impose any special restrictions on this.
  • an insulating member may be provided inside the end cap 20, and the insulating member may be used to isolate the electrical connection components in the housing 40 from the end cap 20 to reduce the risk of short circuit.
  • the insulating member may be plastic, rubber, or the like.
  • the shell 40 is a component used to cooperate with the end cap 20 to form the internal environment of the secondary battery 100, wherein the formed internal environment can be used to accommodate the electrode assembly 10, the electrolyte and other components.
  • the shell 40 and the end cap 20 can be independent components, and an opening can be set on the shell 40, and the internal environment of the secondary battery 100 is formed by covering the opening with the end cap 20 at the opening.
  • the end cap 20 and the shell 40 can also be integrated.
  • the end cap 20 and the shell 40 can form a common connection surface before other components enter the shell, and when the interior of the shell 40 needs to be encapsulated, the end cap 20 covers the shell 40.
  • the shell 40 can be of various shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, a hexagonal prism, etc. Specifically, the shape of the shell 40 can be determined according to the specific shape and size of the electrode assembly 10.
  • the material of the shell 40 can be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiment of the present application does not impose any special restrictions on this.
  • the electrode assembly 10 is a component in the secondary battery 100 where an electrochemical reaction occurs.
  • One or more electrode assemblies 10 may be included in the housing 40.
  • the electrode assembly 10 is mainly formed by winding or stacking a positive electrode sheet 2 and a negative electrode sheet 3, and a separator 4 is usually provided between the positive electrode sheet 2 and the negative electrode sheet 3.
  • the parts of the positive electrode sheet 2 and the negative electrode sheet 3 with active materials constitute the main body of the electrode assembly 10, and the parts of the positive electrode sheet 2 and the negative electrode sheet 3 without active materials each constitute a tab.
  • the positive tab and the negative tab may be located at one end of the main body or at both ends of the main body respectively.
  • the positive active material and the negative active material react with the electrolyte, and the tabs are connected to the electrode terminals 30 to form a current loop.
  • the present application provides a current collector 1a for winding in a first direction X.
  • the current collector 1a includes: a current collector body 11.
  • the current collector body 11 has a plurality of corner areas 13 spaced apart along the first direction X.
  • the corner area 13 is used to be opposite to the bent portion 6 of the electrode assembly 10.
  • a through hole 12 is provided in at least one corner area 13 along the thickness direction of the current collector 1a.
  • the current collector body 11 refers to the core structure of the main components of the current collector 1a. Of course, it can also be understood as the components on the current collector 1a except for features such as perforations 12.
  • the current collector body 11 can not only carry active substances, but also collect and output the current generated by the electrode active substances.
  • the material of the current collector body 11 can be selected differently according to the polarity of the electrode sheet 1.
  • the material of the current collector body 11 can be but not limited to metal materials such as aluminum and nickel, and can also be composite materials such as conductive resins, titanium-nickel shape memory alloys, and carbon-coated aluminum foil.
  • the material of the current collector body 11 can be but not limited to metal materials such as copper, and of course it can also be composite materials such as conductive resins and titanium-nickel shape memory alloys.
  • the corner area 13 refers to the curvature formed on several sections of the current collector body 11 when the current collector body 11 is wound along the first direction X during the preparation of the electrode assembly 10, and the area corresponding to the curvature in the current collector body 11 is the corner area 13.
  • the electrode assembly 10 formed by winding will form a bending portion 6, and the bending portion 6 includes a plurality of stacked current collector bodies 11 with corner areas 13, that is, the corner area 13 is used to correspond to the bending portion 6 of the electrode assembly 10, which can be understood as: the corner area 13 after winding is at the same position as or overlaps with the bending portion 6 of the electrode assembly 10.
  • corner regions 13 are arranged at intervals along the first direction X on the current collecting body 11, and a straight region 18 is left between two adjacent corner regions 13, which is opposite to the straight portion 5 of the electrode assembly 10.
  • the two adjacent corner regions 13 are respectively located on different bending portions 6 of the electrode assembly 10.
  • the two bending portions 6 of the electrode assembly 10 can be defined as the left bending portion 6 and the right bending portion 6, respectively.
  • the first corner region 13 is wound on the left bending portion 6, and the second corner region 13 is wound on the right bending portion 6; then, the third corner region 13 is wound on the left bending portion 6, and the fourth corner region 13 is wound on the right bending portion 6, and so on.
  • the remaining corner regions 13 are respectively wound on different bending portions 6.
  • corner regions 13 on the current collecting body 11 only some of the corner regions 13 may be provided with the through holes 12 , or all of the corner regions 13 may be provided with the through holes 12 .
  • the perforations 12 in the corner area 13 need to be arranged through the thickness direction of the current collector 1a to ensure that the formed electrode 1 has a channel for lithium ions to pass through.
  • the number and shape of the perforations 12 can be designed in various ways, for example: the number of perforations 12 in the corner area 13 can be one or more, etc.; the shape of the perforations 12 in the corner area 13 can be regular shapes such as but not limited to circular, triangular, square, pentagonal, elliptical, etc.; of course, it can also be designed into irregular shapes, etc.
  • a through hole 12 penetrating the current collector body 11 is provided in at least one corner area 13, so that the electrode assembly 10 formed by winding the pole piece 1 having the current collector 1a will have a through hole 12 feature inside at least one layer of the pole piece 1 in the bend portion 6.
  • the lithium ions on the convex side and the concave side of the pole piece 1 will be interconnected through the through hole 12, ensuring that the lithium insertion concentration on both sides of the pole piece 1 is balanced, reducing the risk of lithium plating between the negative pole piece 3 and the positive pole piece 2 in the bend portion 6, and is conducive to improving the service life of the secondary battery 100.
  • a corner area 13 having a through hole 12 there are a plurality of through holes 12 , and all the through holes 12 are distributed at intervals in the corner area 13 .
  • the plurality of perforations 12 are distributed at intervals, and there are various ways of distributing the intervals, for example, the plurality of perforations 12 in the corner area 13 can be arranged in a matrix, in concentric rings, etc., or in an irregular dense arrangement, etc.
  • the plurality of through holes 12 are arranged at intervals in the corner area 13 , which is beneficial to accelerating the passing rate of the lithium ion concentration on both sides of the pole piece 1 and promoting the dynamic balance of the lithium ion concentration on both sides of the pole piece 1 .
  • the perforations 12 are arranged in rows and spaced apart in the second direction Y.
  • the sum of the opening areas of any row of the perforations 12 is recorded as S0.
  • the sum of the opening areas of each row S0 is smaller as it is closer to any end of the corner area 13 along the second direction Y.
  • the first direction X is perpendicular to the second direction Y.
  • the perforations 12 are arranged in rows and spaced apart in the corner area 13, which should be understood as a plurality of perforations 12 being arranged in rows linearly and spaced apart along the first direction X, and each row being spaced apart along the second direction Y. In the same row, the opening areas of each perforation 12 may be consistent or inconsistent.
  • the size of the sum of the opening areas S0 is related to the number of perforations 12 in each row and the opening area of a single perforation 12.
  • the opening area of a single perforation 12 between rows can be consistent or inconsistent; at the same time, the number of perforations 12 between rows can be consistent or inconsistent, but it should be noted that these two parameters cannot be consistent at the same time.
  • the closer to any end of the corner region 13 along the second direction Y means that in the second direction Y, the closer to one end of the corner region 13, the smaller the sum of the opening areas of the perforations 12 is.
  • the perforations 12 in the corner region 13 are designed to be small at both ends and large in the middle.
  • the sum of the opening areas S0 of each row of perforations 12 gradually decreases from the middle of the corner region 13 to any end of the corner region 13 along the second direction Y.
  • the first direction X can be the length direction of the current collecting body 11
  • the second direction Y can be the width direction of the current collecting body 11.
  • Such a design is conducive to reducing the number of openings near one end of the corner area 13, avoiding stress concentration caused by too many openings, and thus effectively avoiding the risk of fracture of the pole piece 1 during the cold pressing process.
  • the number of openings of each row of perforations 12 gradually decreases from the middle of the corner area 13 to either end of the corner area 13 along the second direction Y.
  • the number of perforations 12 at one end of the corner area 13 along the second direction Y can be designed to be zero, that is, no holes are opened at one end of the corner area 13.
  • a non-perforated area 17 is left between the perforation 12 closest to one end of the corner area 13 and one end of the corner area 13.
  • the opening areas of the individual perforations 12 between the rows may be consistent or inconsistent.
  • the opening areas of the individual perforations 12 between the rows are inconsistent, it is necessary to ensure that the sum S0 of the opening areas of the rows is designed to be smaller as it is closer to the corner area 13.
  • the middle of the corner area 13 should be understood as: the corner area 13 is in the middle position in the second direction Y, and can also be understood as the middle position of the current collecting body 11 along its own width direction.
  • the current collector body 11 has a coating area 14 for coating the active material layer.
  • the coating area 14 extends along the first direction X and passes through each corner area 13 in sequence.
  • the through holes 12 in the corner area 13 are all located in the coating area 14 in the second direction Y.
  • the first direction X is perpendicular to the second direction Y.
  • the coating area 14 refers to the area on the current collector body 11 where the active material can be coated.
  • the distribution of the coating area 14 on the current collector body 11 may have overlapping parts with each corner area 13, or may directly cover each corner area 13.
  • the processing of the tab part can be performed by cutting the current collector 1a in the previous process to obtain a strip tab; or, welding a strip tab on the current collector 1a, etc.
  • the perforations 12 in the corner area 13 are all located in the coating area 14 in the second direction Y, which should be understood as follows: the perforations 12 in the corner area 13 will not extend beyond the edge of the coating area 14 in the second direction Y. It should be noted that if the holes are opened beyond the coating area 14, it means that there are also perforations 12 in the partial area not coated with the active material layer, and this partial area is usually used as the pole ear part in the electrode assembly 10. Therefore, opening holes in this partial area not only fails to achieve effective lithium ion circulation, but also weakens the structural strength of the pole ear part.
  • the opening position of the through hole 12 is limited to the coating area 14, so that lithium ions can flow effectively on both sides of the electrode sheet 1; at the same time, it is also avoided that the through hole 12 is opened in the electrode ear part, which will cause its structural strength to be weakened.
  • At least one stress zone 15 is provided in the coating area 14, and the stress zone 15 extends along an edge of the coating area 14 in the second direction Y.
  • the perforations 12 in the corner area 13 are all located in the area of the coating area 14 excluding the stress zone 15 in the second direction Y.
  • the perforations 12 in the corner area 13 are all located in the area of the coating area 14 excluding the stress area 15, that is, in the second direction Y, there is an unperforated area 17 between the perforations 12 and an edge of the coating area 14. Since there is stress concentration at the edge of the coating area 14 during the roller cold pressing of the pole piece 1, if a hole is opened near an edge of the coating area 14, a weak point will be formed, resulting in the breakage of the current collector 1a or the pole piece 1, thereby causing the pole piece 1 to be scrapped, reducing production efficiency and increasing costs. For this reason, the opening area 17 on the current collector 1a avoids the stress area 15, which can ensure the mechanical strength of at least one side of the current collector 1a, avoid breakage or tearing problems during processing, and improve production efficiency.
  • the opening area 17 may be understood as an area enclosed by all the through holes 12 in the corner area 13 .
  • a stress area 15 is left near an edge of the coating area 14 without a perforation 12, thereby ensuring the mechanical strength of at least one side of the current collector 1a, avoiding breakage or tearing during processing, and improving production efficiency.
  • each stress region 15 in the second direction Y is denoted as D, where D ⁇ 3 mm.
  • the width D of the stress region 15 may be greater than 3 mm.
  • the specific value of the width D of the stress region 15 may also be determined according to the overall width of the current collector 1 a.
  • the minimum threshold of the width of the stress region 15 is reasonably limited so that a region at an edge of the coating region 14 along the second direction Y has no openings, thereby ensuring the mechanical strength of at least one side of the current collector 1 a .
  • two stress regions 15 are spaced apart in the coating region 14 along the second direction Y.
  • the two stress regions 15 are adjacent to two opposite edges of the coating region 14 along the second direction Y, respectively.
  • Stress areas 15 are left near the two opposite edges of the coating area 14 without perforations 12, so as to ensure the mechanical strength of both sides of the current collector 1a, avoid breakage or tearing during processing, and improve production efficiency.
  • the current collecting body 11 further has a blank area 16.
  • the blank area 16 is located on at least one side of the coating area 14 along the second direction Y.
  • the blank area 16 refers to the area of the current collector body 11 other than the coating area 14, that is, the area not coated with the active material layer and not opened. This part can be used as the pole ear part in the production of the electrode assembly 10, for example: the blank area 16 is wound to form a full pole ear structure.
  • the two blank areas 16 are located on opposite sides of the coating area 14 along the second direction Y.
  • the position of the perforation 12 in the same corner area 13 constitutes an opening area 17, and there is a stress area 15 between the opening area 17 and the blank area 16.
  • the width of the opening area 17 along the second direction Y is recorded as C
  • the width of the coating area 14 is recorded as B
  • the width of the blank area 16 is recorded as A
  • the width of the current collecting body 11 is recorded as L.
  • the width of the opening area 17 can be reversed in the subsequent confirmation of ownership by the following method, such as: taking the perforations 12 on the outermost sides of the corner area 13 in the second direction Y, and using lines parallel to the first direction X to make tangents to the two perforations 12 respectively, and obtaining the maximum distance between the two tangents can be used as the width C of the opening area 17.
  • a blank area 16 is reserved on at least one side of the current collecting body 11 to facilitate manufacturing of the tab portion required for the electrode assembly 10 , which is beneficial to improving manufacturing efficiency.
  • the sum of the opening areas of all perforations 12 is recorded as S1
  • the area of the corner region 13 on the current collecting body 11 is recorded as S2 , wherein 0.1% ⁇ S1/S2 ⁇ 50%.
  • the corner region 13 having the through hole 12 should be understood as one of the corner regions 13 having the through hole 12 , rather than all the corner regions 13 having the through hole 12 .
  • S1/S2 can take a value between 0.1% and 50%, for example, S1/S2 can be but not limited to 0.1% and 50%. It should be noted that the ratio of S1/S2 should not be too large. If the ratio of the two is greater than 50%, it is easy to weaken the structural strength of the corner area 13, resulting in the risk of belt breakage during the cold pressing process.
  • the first n corner regions 13 are all provided with through holes 12 , wherein n ⁇ 6.
  • the starting end of the winding of the current collector body 11 refers to: when the current collector body 11 is wound along the first direction X, the end that starts to be wound first is the starting end.
  • the first n corner regions 13 refer to the first to nth corner regions 13 counted from the starting end of the current collecting body 11.
  • n is a positive integer, for example, it can be 1, 2, 3, 4, 5, 6.
  • Drilling holes in the first n corner regions 13 can improve the locations of the electrode assembly 10 that are prone to lithium deposition problems in a targeted manner. While ensuring that the lithium deposition problem is reduced, the number of hole drilling operations can be reduced and the mechanical strength of the current collector 1a can be improved.
  • the present application provides a pole piece 1.
  • the pole piece 1 comprises: an active material layer and a current collector 1a as in any of the above schemes.
  • the active material layer is disposed on at least one surface of a current collector body 11.
  • the active material layer refers to the active material coated on the current collector 1a, and its material can be selected according to the polarity of the electrode 1.
  • the material of the active material layer can be but not limited to lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium iron phosphate, ternary materials, etc.
  • the material of the active material layer can be but not limited to graphite, silicon oxide, etc.
  • the active material layer can be coated only on one side of the current collector 1a, or it can be coated on both opposite sides of the current collector 1a at the same time.
  • the above-mentioned pole piece 1 adopts the above-mentioned current collector 1a.
  • the lithium ions on the convex side and the concave side of the pole piece 1 will communicate with each other through the perforations 12, ensuring that the lithium insertion concentration on both sides of the pole piece 1 is balanced, reducing the risk of lithium plating between the negative pole piece 3 and the positive pole piece 2 in the bending portion 6, which is beneficial to improving the service life of the secondary battery 100.
  • the present application provides a method for preparing a pole piece 1, which is used to prepare the pole piece 1, and includes the following steps:
  • the current collector body 11 in step S100 refers to a current collector 1a without holes, such as aluminum foil, copper foil, etc.
  • step S200 there are many ways to open a hole in the corner area 13 , such as laser opening, mechanical cutting and drilling, etc.
  • coating is a process of uniformly coating the suspension slurry containing positive and negative electrode active materials on the aluminum foil or copper foil sheet using relevant equipment, and then drying to form a film.
  • the specific coating process at least includes shear coating, wetting and leveling, drying and other processes. The specific operations of these processes are not described here, and can be directly referred to the existing literature.
  • step S300 rolling is usually arranged after the coating and drying process. It is a process in which the coated powder electrode material on the positive and negative metal current collectors 1a is compacted by a roller press, which is used for the rearrangement and densification of the powder.
  • a through hole 12 is opened on the current collecting body 11, so that the lithium ions on both sides of the electrode 1 can flow to each other through the through hole 12.
  • the lithium ions on the convex side and the concave side of the electrode 1 can communicate with each other through the through hole 12, ensuring that the lithium insertion concentration on both sides of the electrode 1 is balanced, reducing the risk of lithium plating between the negative electrode 3 and the positive electrode 2 in the bending portion 6, which is beneficial to improving the service life of the secondary battery 100.
  • the step of rolling the coated current collector 1a comprises:
  • the pressure roller 200 refers to a component that is pressed on the coated current collector 1a to compact the active material.
  • the surface of the pressure roller 200 has a tension roller surface 220 and an extension roller surface 210 located on both sides of the tension roller surface 220.
  • the extension roller surface 210 is pressed on the blank area 16 of the current collector 1a, and the tension roller surface 220 is pressed on the active material layer of the current collector 1a.
  • the extension roller surface 210 and the tension roller surface 220 are both circumferentially extended on the pressure roller 200, and the diameter of the extension roller surface 210 is larger than the diameter of the tension roller surface 220.
  • the present application provides an electrode assembly 10, which is constructed as a winding structure.
  • the electrode assembly 10 includes a positive electrode sheet 2, a negative electrode sheet 3, and a separator 4 arranged between the positive electrode sheet 2 and the negative electrode sheet 3, and the winding structure includes a bending portion 6.
  • the positive electrode sheet 2 and/or the negative electrode sheet 3 is the above electrode sheet 1, and the position of the bending portion 6 is opposite to the corner area 13 after winding.
  • the present application provides a secondary battery 100 including the above electrode assembly 10 .
  • the present application provides a current collector 1a. According to the winding size of the electrode assembly 10, the position of the corner area 13 on the current collector 1a is determined, and then the perforations 12 are punched in the corner area 13.
  • the shape and arrangement of the perforations 12 are not limited.
  • the ratio of the opening area of all perforations 12 to the area of the corner area 13 is 0.1 to 50%.
  • the width of the area where the perforations 12 are located along the second direction Y is limited to the coating area 14, and the sum of the opening areas of each row gradually decreases from the middle to both sides. Outside the edge of the coating area 14 is a blank area 16, and the blank area 16 (the area without active material coating) is not punched.
  • the positive electrode active material ternary material nickel cobalt manganese (NCM811), the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) are mixed evenly in a mass ratio of 97:2:1 and added into the solvent NMP to prepare a positive electrode slurry; the positive electrode slurry is evenly coated on an aluminum foil, dried at 85°C and then cold pressed, and then die-cut and slit to prepare a lithium-ion battery positive electrode sheet 2.
  • the coating weight of the active material of the positive electrode sheet 2 is 17.6 mg/cm 2 , and the thickness of the current collector 1 a of the positive electrode sheet 2 is 13 ⁇ m.
  • the negative electrode active material graphite, the conductive agent acetylene black, the thickener sodium carboxymethyl cellulose (CMC), and the binder styrene butadiene rubber (SBR) are added to the solvent water in a mass ratio of 96:2:1:1, mixed evenly and made into a negative electrode slurry; the negative electrode slurry is evenly coated on the copper foil, dried at 85°C and then cold pressed to make a negative electrode sheet 3.
  • the coating weight of the negative electrode sheet 3 is 10 mg/cm 2 , the thickness of the current collector 1a of the negative electrode sheet 3 is 8 ⁇ m, the width of the current collector 1a is 170 mm, and the width of the active material coating area 14 of the negative electrode sheet 3 is 100 mm.
  • no perforation 12 is formed in the corner area 13 of the current collector 1a of the negative electrode sheet 3 .
  • a polyethylene microporous film is used as a porous isolation membrane substrate, and inorganic alumina powder, polyvinylpyrrolidone and acetone solvent are evenly mixed in a weight ratio of 3:1.5:5.5 to form a slurry, which is then coated on one side of the substrate and dried to obtain an isolation membrane.
  • Lithium hexafluorophosphate is dissolved in a mixed solvent of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate (the volume ratio of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate is 1:2:1) to obtain a lithium ion battery electrolyte.
  • the positive electrode sheet 2, the negative electrode sheet 3 and the isolation film are wound to obtain a bare cell, and then a lithium-ion battery is obtained through packaging, liquid injection, formation, exhaust and other processes.
  • the designed charging N/P of the battery is 1.03, and the designed capacity of the cell is 160Ah.
  • the secondary battery 100 prepared in the above comparative example and embodiment was used to record the fracture frequency during the cold pressing process. At the same time, after the secondary battery 100 was manufactured, it was charged to 4.25V at a constant current and constant voltage of 0.5C and then the battery cell was disassembled to observe whether lithium was deposited at the bending portion 6 of the electrode assembly 10.
  • the specific results can be referred to Table 1.
  • Example 1 and Example 2 are the same as the width of the active material coating area 14, the mechanical strength of the electrode 1 will be weakened, causing the electrode 1 to be easily broken during the cold pressing process.
  • Example 2 By comparing Example 2, Example 3 and Example 4 with Comparative Example 2, it can be seen that if the width of the opening area 17 is smaller than the width of the active material coating area 14, a stress area 15 without an opening is left between the edge of the opening area 17 and the coating area 14, which can effectively reduce the number of times the electrode 1 breaks.

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Abstract

本申请涉及一种集流体、极片及其制备方法、电极组件及二次电池，在至少一个拐角区内设置贯穿集流本体的穿孔，这样具有该集流体的极片卷绕形成的电极组件，会在弯折部中至少一层的极片内部具有穿孔特征。此时，在循环充电过程中，该极片的凸面侧和凹面侧的锂离子会通过穿孔实现互通，保证极片两侧的嵌锂浓度达到平衡，降低弯折部中负极片与正极片之间出现析锂风险，有利于提升二次电池的使用寿命。

Description

集流体、极片及其制备方法、电极组件及二次电池 技术领域
本申请涉及电池技术领域，特别是涉及集流体、极片及其制备方法、电极组件及二次电池。
背景技术
电极组件是二次电池中发生电化学反应的部件，其主要由正极片和负极片卷绕或层叠放置形成，且通常在负极片与正极片之间设有隔膜。卷绕时，电极组件可形成平直部及位于平直部两侧的两个弯折部。
在弯折区内，负极片与正极片依次交替堆叠设置。然而受限于电极组件的结构设计缺陷，导致循环充放时，很容易在负极片与正极片之间出现析锂风险，严重影响二次电池的使用寿命。
发明内容
基于此，有必要提供一种集流体、极片及其制备方法、电极组件及二次电池，降低析锂风险，提升二次电池的使用寿命。
第一方面，本申请提供了一种集流体，用于在第一方向上进行卷绕，集流体包括：集流本体，沿第一方向间隔具有若干拐角区，拐角区用于与电极组件的弯折部相对；其中，至少一个拐角区内沿集流体的厚度方向贯穿设有穿孔。
上述的集流体，在至少一个拐角区内设置贯穿集流本体的穿孔，这样具有该集流体的极片卷绕形成的电极组件，会在弯折部中至少一层的极片内部具有穿孔特征。此时，在循环充电过程中，该极片的凸面侧和凹面侧的锂离子会 通过穿孔实现互通，保证极片两侧的嵌锂浓度达到平衡，降低弯折部中负极片与正极片之间出现析锂风险，有利于提升二次电池的使用寿命。
在一些实施例中，在具有穿孔的拐角区内，穿孔为多个，且全部穿孔在拐角区内间隔分布。如此，在拐角区内间隔开设多个穿孔，有利于加快极片两侧锂离子浓度的通过速率，促进极片两侧锂离子浓度实现动态平衡。
在一些实施例中，在具有穿孔的拐角区内，穿孔在第二方向上成排间隔分布，任一排穿孔的开孔面积之和记为S0，各排的开孔面积之和S0越靠近拐角区沿第二方向上的任一端越小，第一方向与第二方向垂直。如此，有利于减少接近拐角区一端处的开孔，避免因开孔过多而导致应力集中，从而有效避免冷压过程中极片发生断裂的风险。
在一些实施例中，在具有穿孔的拐角区内，各排穿孔的开孔数量自拐角区的中部至拐角区沿第二方向上的任一端逐渐减小。如此设计，减少越接近拐角区一端处的开孔数量，保证集流本体边缘上的结构强度，避免冷压过程易发生断裂。
在一些实施例中，集流本体上具有供活性物质层涂布的涂覆区，涂覆区沿第一方向延伸并依次经过各拐角区，拐角区内的穿孔在第二方向上均位于涂覆区内，第一方向与第二方向垂直。如此，将穿孔的开设位置局限在涂覆区内，实现锂离子在极片两侧有效流通；同时也避免将穿孔开在极耳部分而导致其结构强度减弱。
在一些实施例中，涂覆区内设有至少一应力区，应力区沿涂覆区在第二方向上的一边缘延伸，拐角区内的穿孔在第二方向上均位于涂覆区除去应力区的区域中。如此，在靠近涂覆区一边缘留有应力区不设置穿孔，保证集流体至少一侧的机械强度，避免加工过程中出现断裂或撕裂问题，提高生产效率。
在一些实施例中，各应力区在第二方向上的宽度记为D，其中，D≥3mm。如此，合理限制应力区的宽度的最小阈值，使得距离涂覆区沿第二方向的一边缘处具有一段区域不开孔，确保集流体至少一侧的机械强度。
在一些实施例中，涂覆区内沿第二方向间隔设有两个应力区，两个应力区分别对应邻接于涂覆区沿第二方向上的相对两边缘。如此，在靠近涂覆区相对两边缘处留有应力区不设置穿孔，保证集流体两侧的机械强度，避免加工过程中出现断裂或撕裂问题，提高生产效率。
在一些实施例中，集流本体上还具有空白区，空白区位于涂覆区沿第二方向上的至少一侧。如此，在集流本体的至少一侧预留空白区，以便制作电极组件所需的极耳部分，有利于提升制作效率。
在一些实施例中，在具有穿孔的拐角区内，全部穿孔的开孔面积之和记为S1，拐角区在集流本体上的面积记为S2，其中，0.1％≤S1/S2≤50％。如此，合理控制S1/S2的比值范围值，既能保证锂离子在极片的两侧流通顺畅，又能保证集流本体具有一定结构强度，避免发生断带的风险。
在一些实施例中，自集流本体卷绕的起始端开始，前n个拐角区内均设有穿孔，其中，n≤6。如此，在前n个拐角区内进行开孔，能有针对性改善电极组件易出现析锂问题的位置，在保证析锂问题降低的前提下，减少开孔操作，提升集流体的机械强度。
第二方面，本申请提供了一种极片，包括：如以上任一项的集流体；活性物质层，设于集流本体的至少一表面。
第三方面，本申请提供了一种极片的制备方法，用于制备以上的极片，包括如下步骤：提供集流本体；在集流本体上的拐角区中开穿孔，以形成集流体；在集流体的表面上涂布活性物质层；对涂布后的集流体进行辊压。
在一些实施例中，对涂布后的集流体进行辊压的步骤，包括：将压力辊的张力辊面和位于张力辊面两侧的延展辊面分别对应压在活性物质层、以及集流体上位于活性物质层两侧的空白区上，并控制延展辊面朝向张力辊面的一侧与穿孔所在区域之间留有间距。如此，在冷压活性物质时，控制延展辊面的一侧与穿孔所在区域之间留有间距，避免穿孔开设位置紧靠延展辊面处而导致应力集中，从而避免极片在辊压时易出现断带。
第四方面，本申请提供了一种电极组件，被构造为卷绕结构，包括正极片、负极片及隔设于正极片与负极片之间的隔膜，且卷绕结构包括弯折部；其中，正极片和/或负极片为以上的极片，弯折部所在位置与卷绕后的拐角区相对。
第五方面，本申请提供了一种二次电池，包括以上的电极组件。
上述说明仅是本申请技术方案的概述，为了能够更清楚了解本申请的技术手段，而可依照说明书的内容予以实施，并且为了让本申请的上述和其它目的、特征和优点能够更明显易懂，以下特举本申请的具体实施方式。
附图说明
通过阅读对下文优选实施方式的详细描述，各种其他的优点和益处对于本领域普通技术人员将变得清楚明了。附图仅用于示出优选实施方式的目的，而并不认为是对本申请的限制。而且在全部附图中，用相同的附图标号表示相同的部件。在附图中：
图1为本申请一些实施例提供的二次电池的分解结构示意图；
图2为本申请一些实施例提供的电极组件结构示意图；
图3为本申请一些实施例提供的集流体结构示意图；
图4为本申请一些实施例提供的极片的制备方法的流程示意图一；
图5为本申请一些实施例提供的极片的制备方法的流程示意图二；
图6为本申请一些实施例提供的压力辊结构示意图。
100、二次电池；10、电极组件；20、端盖；30、电极端子；40、壳体；1、极片；1a、集流体；11、集流本体；12、穿孔；13、拐角区；14、涂覆区；15、应力区；16、空白区；17、开孔区域；18、平直区；2、正极片；3、负极片；4、隔膜；5、平直部；6、弯折部；200、压力辊；210、延展辊面；220、张力辊面；X、第一方向；Y、第二方向。
具体实施方式
下面将结合附图对本申请技术方案的实施例进行详细的描述。以下实施例仅用于更加清楚地说明本申请的技术方案，因此只作为示例，而不能以此来限制本申请的保护范围。
除非另有定义，本文所使用的所有的技术和科学术语与属于本申请的技术领域的技术人员通常理解的含义相同；本文中所使用的术语只是为了描述具体的实施例的目的，不是旨在于限制本申请；本申请的说明书和权利要求书及上述附图说明中的术语“包括”和“具有”以及它们的任何变形，意图在于覆盖不排他的包含。
在本申请实施例的描述中，技术术语“第一”“第二”等仅用于区别不同对象，而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特征的数量、特定顺序或主次关系。在本申请实施例的描述中，“多个”的含义是两个以上，除非另有明确具体的限定。
在本文中提及“实施例”意味着，结合实施例描述的特定特征、结构或特性可以包含在本申请的至少一个实施例中。在说明书中的各个位置出现该短语并 不一定均是指相同的实施例，也不是与其它实施例互斥的独立的或备选的实施例。本领域技术人员显式地和隐式地理解的是，本文所描述的实施例可以与其它实施例相结合。
在本申请实施例的描述中，术语“和/或”仅仅是一种描述关联对象的关联关系，表示可以存在三种关系，例如A和/或B，可以表示：单独存在A，同时存在A和B，单独存在B这三种情况。另外，本文中字符“/”，一般表示前后关联对象是一种“或”的关系。
在本申请实施例的描述中，术语“多个”指的是两个以上(包括两个)，同理，“多组”指的是两组以上(包括两组)，“多片”指的是两片以上(包括两片)。
在本申请实施例的描述中，技术术语“中心”“纵向”“横向”“长度”“宽度”“厚度”“上”“下”“前”“后”“左”“右”“竖直”“水平”“顶”“底”“内”“外”“顺时针”“逆时针”“轴向”“径向”“周向”等指示的方位或位置关系为基于附图所示的方位或位置关系，仅是为了便于描述本申请实施例和简化描述，而不是指示或暗示所指的装置或元件必须具有特定的方位、以特定的方位构造和操作，因此不能理解为对本申请实施例的限制。
在本申请实施例的描述中，除非另有明确的规定和限定，技术术语“安装”“相连”“连接”“固定”等术语应做广义理解，例如，可以是固定连接，也可以是可拆卸连接，或成一体；也可以是机械连接，也可以是电连接；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或两个元件的相互作用关系。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实施例中的具体含义。
目前，从市场形势的发展来看，动力电池的应用越加广泛。动力电池不仅被应用于水力、火力、风力和太阳能电站等储能电源系统，而且还被广泛应 用于电动自行车、电动摩托车、电动汽车等电动交通工具，以及军事装备和航空航天等多个领域。随着动力电池应用领域的不断扩大，其市场的需求量也在不断地扩增。
本申请人注意到，当电极组件被构造成卷绕结构时，其包括平直部及设于平直部两侧的弯折部。在弯折部中，有交替多层不同曲率半径的正极片和负极片，且正极片和负极片在弯折时均会形成凹面和凸面。以其中一层负极片为例，(当然，也可以其中一层正极片为例进行说明)，其凹面侧和凸面侧分别对应与内外两层正极片对应，即该负极片的凹面侧与内层正极片的凸面相对，其凸面侧与外层正极片凹面相对。
由于负极片的凹面的曲率半径大于内层正极片的凸面的曲率半径，因此，负极片的凹面的活性物质容量会大于正极片的凸面的活性物质容量，两者对应的NP值大于1，即也可简单理解为嵌锂空位浓度大于嵌锂离子浓度，嵌锂空位有剩余。相反，由于负极片的凹面的曲率半径小于外层正极片的凸面的曲率半径，因此，负极片的凹面的活性物质容量会小于正极片的凸面的活性物质容量，两者对应的NP值小于1，即也可简单理解为嵌锂空位浓度无法满足嵌锂离子嵌入，在充电时易出现析锂风险。
基于此，为了解决电极组件的弯折部处正极片与负极片之间易出现析锂而影响二次电池的使用寿命的问题，本申请人经过深入研究，设计了一种集流体，在至少一个拐角区内沿集流体的厚度方向贯穿设有穿孔，以便集流体两侧的锂离子能够相互流通。
上述的集流体，在至少一个拐角区内设置贯穿集流本体的穿孔，如此，利用该集流体制备的极片，如制备成正极片或负极片，会允许极片两侧的锂离子通过穿孔，保证极片两侧的锂离子浓度达到平衡，比如：锂离子浓度高的一 侧通过穿孔流入至锂离子浓度低的一侧等。
采用该集流体制备的极片卷绕形成电极组件后，该电极组件会在弯折部中至少一层的极片内部具有穿孔特征。此时，在循环充电过程中，该极片的凸面侧和凹面侧的锂离子会通过穿孔实现互通，保证极片两侧的嵌锂浓度达到平衡，例如：负极片凸面侧的锂离子通过穿孔流通至负极片凹面侧的锂离子，使得凸面侧的嵌锂浓度降低，保证局部NP大于或等于1，降低弯折部中负极片与正极片之间出现析锂风险，提升二次电池的使用寿命。
本申请实施例公开的二次电池可以但不限用于车辆、船舶或飞行器等用电装置中。可以使用具备本申请公开的二次电池等组成该用电装置的电源系统。
在电池系统中，二次电池可以是多个，多个二次电池之间可串联或并联或混联，混联是指多个二次电池中既有串联又有并联。多个二次电池之间可直接串联或并联或混联在一起，再将多个二次电池构成的整体容纳于箱体内；当然，电池也可以是多个二次电池先串联或并联或混联组成电池模块形式，多个电池模块再串联或并联或混联形成一个整体，并容纳于箱体内。电池还可以包括其他结构，例如，该电池还可以包括汇流部件，用于实现多个二次电池之间的电连接。其中，二次电池可呈圆柱体、扁平体、长方体或其它形状等。
请参照图1，图1为本申请一些实施例提供的二次电池100的分解结构示意图。二次电池100是指组成电池的最小单元。如图1，二次电池100包括有端盖20、壳体40、电极组件10以及其他的功能性部件。
端盖20是指盖合于壳体40的开口处以将二次电池100的内部环境隔绝于外部环境的部件。不限地，端盖20的形状可以与壳体40的形状相适应以配合壳体40。可选地，端盖20可以由具有一定硬度和强度的材质(如铝合金)制成，这样，端盖20在受挤压碰撞时就不易发生形变，使二次电池100能够具备 更高的结构强度，安全性能也可以有所提高。端盖20上可以设置有如电极端子30等的功能性部件。电极端子30可以用于与电极组件10电连接，以用于输出或输入二次电池100的电能。在一些实施例中，端盖20上还可以设置有用于在二次电池100的内部压力或温度达到阈值时泄放内部压力的泄压机构。端盖20的材质也可以是多种的，比如，铜、铁、铝、不锈钢、铝合金、塑胶等，本申请实施例对此不作特殊限制。在一些实施例中，在端盖20的内侧还可以设置有绝缘件，绝缘件可以用于隔离壳体40内的电连接部件与端盖20，以降低短路的风险。示例性的，绝缘件可以是塑料、橡胶等。
壳体40是用于配合端盖20以形成二次电池100的内部环境的组件，其中，形成的内部环境可以用于容纳电极组件10、电解液以及其他部件。壳体40和端盖20可以是独立的部件，可以于壳体40上设置开口，通过在开口处使端盖20盖合开口以形成二次电池100的内部环境。不限地，也可以使端盖20和壳体40一体化，具体地，端盖20和壳体40可以在其他部件入壳前先形成一个共同的连接面，当需要封装壳体40的内部时，再使端盖20盖合壳体40。壳体40可以是多种形状和多种尺寸的，例如长方体形、圆柱体形、六棱柱形等。具体地，壳体40的形状可以根据电极组件10的具体形状和尺寸大小来确定。壳体40的材质可以是多种，比如，铜、铁、铝、不锈钢、铝合金、塑胶等，本申请实施例对此不作特殊限制。
请参照图2，电极组件10是二次电池100中发生电化学反应的部件。壳体40内可以包含一个或更多个电极组件10。电极组件10主要由正极片2和负极片3卷绕或层叠放置形成，并且通常在正极片2与负极片3之间设有隔膜4。正极片2和负极片3具有活性物质的部分构成电极组件10的主体部，正极片2和负极片3不具有活性物质的部分各自构成极耳。正极极耳和负极极耳可以共 同位于主体部的一端或是分别位于主体部的两端。在电池的充放电过程中，正极活性物质和负极活性物质与电解液发生反应，极耳连接电极端子30以形成电流回路。
根据本申请的一些实施例，请参照图2与图3，本申请提供了一种集流体1a，用于在第一方向X上进行卷绕。集流体1a包括：集流本体11。集流本体11沿第一方向X间隔具有若干拐角区13。拐角区13用于与电极组件10的弯折部6相对。其中，至少一个拐角区13内沿集流体1a的厚度方向贯穿设有穿孔12。
集流本体11是指集流体1a上主要组成的核心结构，当然，也可理解为集流体1a上除穿孔12等特征外的部件。集流本体11不仅能承载活性物质，而且还能将电极活性物质产生的电流汇集并输出。集流本体11的材料可根据极片1的极性不同有不同的选择，比如：在正极片2中，集流本体11的材料可为但不限于铝、镍等金属材料，也可为导电树脂、钛镍形状记忆合金、覆碳铝箔等复合材料。在正极片2中，集流本体11的材料可为但不限于铜等金属材料，当然也可为导电树脂、钛镍形状记忆合金等复合材料。
拐角区13是指在制备电极组件10中，集流本体11沿第一方向X进行卷绕时会在若干部分段上形成弯曲状，该弯曲状在集流本体11所对应的区域为拐角区13。同时，请参照图2，卷绕形成的电极组件10会形成弯折部6，该弯折部6包括层叠的多个拐角区13的集流本体11，即拐角区13用于与电极组件10的弯折部6相对可理解为：卷绕后的拐角区13与电极组件10的弯折部6所在位置相同或重叠。
若干拐角区13在集流本体11沿第一方向X间隔排布，相邻两个拐角区13之间留有平直区18，与电极组件10的平直部5相对。同时，相邻两个拐角 区13在卷绕后，则分别位于电极组件10的不同弯折部6上，为便于理解，可将电极组件10的两个弯折部6分别定义为左弯折部6和右弯折部6，在卷绕时，第一个拐角区13绕在左弯折部6上，第二个拐角区13绕在右弯折部6上；接着，第三个拐角区13绕在左弯折部6上，第四个拐角区13又绕在右弯折部6上等，按如此逻辑，其余拐角区13分别对应绕在不同的弯折部6上。
集流本体11上所有的拐角区13中，可仅有部分拐角区13设置穿孔12，也可全部拐角区13均设置穿孔12等。
穿孔12在拐角区13内需沿集流体1a的厚度方向贯穿设置，保证形成的极片1内部具有可供锂离子通过的通道。穿孔12的数量和形状均有多种设计，比如：穿孔12在拐角区13内的数量可为一个或者多个等；穿孔12在拐角区13内的形状可为但不限于圆形、三角形、方形、五边形、椭圆形等规则形状；当然，也可设计成非规则的形状等。
在至少一个拐角区13内设置贯穿集流本体11的穿孔12，这样具有该集流体1a的极片1卷绕形成的电极组件10，会在弯折部6中至少一层的极片1内部具有穿孔12特征。此时，在循环充电过程中，该极片1的凸面侧和凹面侧的锂离子会通过穿孔12实现互通，保证极片1两侧的嵌锂浓度达到平衡，降低弯折部6中负极片3与正极片2之间出现析锂风险，有利于提升二次电池100的使用寿命。
根据本申请的一些实施例，请参照图3，在具有穿孔12的拐角区13内，穿孔12为多个，且全部穿孔12在拐角区13内间隔分布。
在同一拐角区13内，多个穿孔12为间隔分布，其间隔分布方式有多种，比如：多个穿孔12在拐角区13内可呈矩阵排列、同心圆环排布等；也可呈无规则的密排方式等。
在拐角区13内间隔开设多个穿孔12，有利于加快极片1两侧锂离子浓度的通过速率，促进极片1两侧锂离子浓度实现动态平衡。
根据本申请的一些实施例，请参照图3，在具有穿孔12的拐角区13内，穿孔12在第二方向Y上成排间隔分布，任一排穿孔12的开孔面积之和记为S0，各排的开孔面积之和S0越靠近拐角区13沿第二方向Y上的任一端越小，第一方向X与第二方向Y垂直。
穿孔12在拐角区13内成排间隔分布应理解为若干穿孔12沿第一方向X线性间隔排列成排，各排之间沿第二方向Y间隔分布。在同一排中，各个穿孔12的开孔面积可保持一致，也可不一致等。
开孔面积之和S0的大小分别各排中穿孔12的数量和单个穿孔12的开孔面积有关。在各排之间的单个穿孔12的开孔面积可保持一致，也可不一致；同时，各排之间的穿孔12的数量也可保持一致，也可不一致，但需注意这两个参数不能同时保持一致。
越靠近拐角区13沿第二方向Y上的任一端是指在第二方向Y上，越接近拐角区13的一端的穿孔12开孔面积之和越小，如此设计，拐角区13内的穿孔12呈两端小，中间大设计。在一些实施例中，各排穿孔12的开孔面积之和S0自拐角区13的中部至拐角区13沿第二方向Y上的任一端逐渐减小。同时，第一方向X可为集流本体11的长度方向，第二方向Y可为集流本体11的宽度方向。
如此设计，有利于减少接近拐角区13一端处的开孔，避免因开孔过多而导致应力集中，从而有效避免冷压过程中极片1发生断裂的风险。
根据本申请的一些实施例，请参照图3，在具有穿孔12的拐角区13内，各排穿孔12的开孔数量自拐角区13的中部至拐角区13沿第二方向Y上的任一 端逐渐减小。
在开孔过程中，可将拐角区13沿第二方向Y上的一端处的穿孔12数量设计为零，即不在拐角区13的一端处开孔，此时最接近拐角区13一端的穿孔12与拐角区13的一端之间留有不开孔区域17。
各排之间的单个穿孔12的开孔面积可保持一致，也可不一致等。当各排之间的单个穿孔12的开孔面积不一致时，需保证各排的开孔面积之和S0越靠近拐角区13一端越小设计。
拐角区13的中部应理解为：拐角区13在第二方向Y上处于中间的位置，也可理解为集流本体11沿自身宽度方向的中间位置。
如此设计，减少越接近拐角区13一端处的开孔数量，保证集流本体11边缘上的结构强度，避免冷压过程易发生断裂。
根据本申请的一些实施例，请参照图3，集流本体11上具有供活性物质层涂布的涂覆区14。涂覆区14沿第一方向X延伸并依次经过各拐角区13，拐角区13内的穿孔12在第二方向Y上均位于涂覆区14内，第一方向X与第二方向Y垂直。
涂覆区14是指集流本体11上可涂布活性物质的区域。涂覆区14在集流本体11的分布可与各个拐角区13之间具有重叠部分，也可直接覆盖各个拐角区13。当涂覆区14覆盖各个拐角区13时，这说明涂覆区14沿第二方向Y上的宽度与集流本体11的宽度一致，即集流本体11整个表面均涂布有活性物质，此时，极耳部分的加工，可在前期工序对集流体1a进行切割，以获取条状极耳；或者，在集流体1a上焊接条状极耳等。
拐角区13内的穿孔12在第二方向Y上均位于涂覆区14内应理解为：拐角区13内的穿孔12在第二方向Y上，不会超出涂覆区14的边缘外。需要说明 的是，若超出涂覆区14外开孔，则说明未涂布活性物质层的部分区域内也具有穿孔12，而这部分区域在电极组件10中通常被作为极耳部分，因此，在该部分区域开孔，不仅无法实现锂离子有效流通，而且还减弱极耳部分的结构强度。
将穿孔12的开设位置局限在涂覆区14内，实现锂离子在极片1两侧有效流通；同时也避免将穿孔12开在极耳部分而导致其结构强度减弱。
根据本申请的一些实施例，请参照图3，涂覆区14内设有至少一应力区15，应力区15沿涂覆区14在第二方向Y上的一边缘延伸，拐角区13内的穿孔12在第二方向Y上均位于涂覆区14除去应力区15的区域中。
拐角区13内的穿孔12均位于涂覆区14除去应力区15的区域中，即在第二方向Y上，穿孔12与涂覆区14的一边缘之间具有未开孔区域17。由于在极片1过辊冷压中，涂覆区14的边缘处存在应力集中，若在靠近涂覆区14一边缘处开孔，会形成薄弱点，导致集流体1a或极片1断裂，从而导致极片1报废，降低了生产效率，提高了成本。为此，集流体1a上的开孔区域17避开应力区15，可以保证集流体1a至少一侧的机械强度，避免加工过程中出现断裂或撕裂问题，提高生产效率。
其中，开孔区域17可理解为在拐角区13内，所有穿孔12所围合形成的区域。
在靠近涂覆区14一边缘留有应力区15不设置穿孔12，保证集流体1a至少一侧的机械强度，避免加工过程中出现断裂或撕裂问题，提高生产效率。
根据本申请的一些实施例，请参照图3，各应力区15在第二方向Y上的宽度记为D，其中，D≥3mm。
应力区15的宽度D可取大于3mm的一值。当然，应力区15的宽度D的具体值也可根据集流体1a的整体宽度而定。
合理限制应力区15的宽度的最小阈值，使得距离涂覆区14沿第二方向Y的一边缘处具有一段区域不开孔，确保集流体1a至少一侧的机械强度。
根据本申请的一些实施例，请参照图3，涂覆区14内沿第二方向Y间隔设有两个应力区15，两个应力区15分别对应邻接于涂覆区14沿第二方向Y上的相对两边缘。
在第二方向Y上，涂覆区14内间隔具有两个应力区15，此时拐角区13内的穿孔12所在位置应为两个应力区15之间。
在靠近涂覆区14相对两边缘处留有应力区15不设置穿孔12，保证集流体1a两侧的机械强度，避免加工过程中出现断裂或撕裂问题，提高生产效率。
根据本申请的一些实施例，集流本体11上还具有空白区16。空白区16位于涂覆区14沿第二方向Y上的至少一侧。
空白区16是指集流本体11除涂覆区14以外的区域，即不涂覆活性物质层，也不开孔的区域，该部分在电极组件10的制作中，可作为极耳部分，比如：空白区16卷绕形成全极耳结构等。
空白区16可为一个，也可为两个。当空白区16为两个时，两个空白区16分别位于涂覆区14沿第二方向Y上的相对两侧。在一些实施例中，在同一拐角区13内的穿孔12所在位置构成开孔区域17，开孔区域17与空白区16之间具有应力区15。为便于理解各自区域之间的宽度关系，将开孔区域17沿第二方向Y上的宽度记为C，涂覆区14的宽度记为B，空白区16的宽度记为A，集流本体11的宽度记为L。此时，开孔区域17的宽度满足的条件为：C≤B＝L-n×A，其中，n可为0、1或2。需要说明的是，开孔区域17的宽度在后期确权中，可采用如下方法进行反向，如：取拐角区13内位于第二方向Y上最外两侧的穿孔12，以平行第一方向X的线分别作两个穿孔12的切线，获取两个切线 之间最大间距可作为开孔区域17的宽度C。
在集流本体11的至少一侧预留空白区16，以便制作电极组件10所需的极耳部分，有利于提升制作效率。
根据本申请的一些实施例，在具有穿孔12的拐角区13内，全部穿孔12的开孔面积之和记为S1，拐角区13在集流本体11上的面积记为S2，其中，0.1％≤S1/S2≤50％。
在具有穿孔12的拐角区13应理解为具有穿孔12的其中一个拐角区13，而非指所有具有穿孔12的拐角区13。
S1/S2可在0.1％～50％中取一值，比如：S1/S2可为但不仅限于0.1％和50％等。需要说明的是，S1/S2的比值不宜过大，若两者比值大于50％，容易导致拐角区13处的结构强度变弱，从而导致冷压过程中，容易出现断带的风险。
合理控制S1/S2的比值范围值，既能保证锂离子在极片1的两侧流通顺畅，又能保证集流本体11具有一定结构强度，避免发生断带的风险。
根据本申请的一些实施例，自集流本体11卷绕的起始端开始，前n个拐角区13内均设有穿孔12，其中，n≤6。
集流本体11卷绕的起始端是指：集流本体11沿第一方向X卷绕时，最先开始卷绕的一端为起始端。
前n个拐角区13是指从集流本体11的起始端开始数，第一个至第n个的拐角区13为前n个拐角区13。其中，n正整数，如，其可为1、2、3、4、5、6。
经过申请人深入研究，二次电池100在循环充放电时，最易出现析锂问题的地方主要集中在电极组件10的最内圈至第三圈处，即对应集流本体11上前6个拐角区13。为此，本申请在前n个拐角区13内进行开孔，以有效解决电 极组件10析锂问题。
在前n个拐角区13内进行开孔，能有针对性改善电极组件10易出现析锂问题的位置，在保证析锂问题降低的前提下，减少开孔操作，提升集流体1a的机械强度。
根据本申请的一些实施例，本申请提供了一种极片1。极片1包括：活性物质层和如以上任一方案中的集流体1a。活性物质层设于集流本体11的至少一表面。
活性物质层是指涂覆在集流体1a上的活性物质，其材料可根据极片1的极性进行选择。比如：在正极片2中，活性物质层的材料可为但不限于钴酸锂、锰酸锂、镍酸锂、磷酸铁锂、三元材料等。在负极片3中，活性物质层的材料可为但不限于石墨、硅氧化物等。活性物质层可仅涂布在集流体1a的一侧面上，也可同时涂布在集流体1a的相对两侧面上。
上述极片1，采用以上的集流体1a，在循环充电过程中，该极片1的凸面侧和凹面侧的锂离子会通过穿孔12实现互通，保证极片1两侧的嵌锂浓度达到平衡，降低弯折部6中负极片3与正极片2之间出现析锂风险，有利于提升二次电池100的使用寿命。
根据本申请的一些实施例，请参照图3与图4，本申请提供了一种极片1的制备方法，用于制备以上的极片1，包括如下步骤：
S100、提供集流本体11；
S200、在集流本体11上的拐角区13中开穿孔12，以形成集流体1a；
S300、在集流体1a的表面上涂布活性物质层；
S400、对涂布后的集流体1a进行辊压。
步骤S100中的集流本体11是指未打孔的集流体1a，比如：铝箔、铜箔 等。
步骤S200中，在拐角区13内开孔方式有多种，比如：可为激光开孔、机械切割打孔等。
步骤S300中，涂布是利用相关设备将含有正负极活性物质的悬浮液浆料均匀涂布在铝箔或铜箔片幅上，然后干燥成膜的过程。具体涂布过程至少包括剪切涂布、润湿和流平、干燥等工序。而这些工序的具体操作在此不作赘述，可直接参考现有文献。
步骤S300中，辊压通常安排在涂布干燥工序之后，是正负极金属集流体1a上的涂布粉体电极材料经过辊压机压实的过程，用于粉体的重排和致密化的过程。
上述极片1的制备方法，在集流本体11上开穿孔12，使得极片1两侧的锂离子可通过穿孔12相互流通，这样在循环充电过程中，该极片1的凸面侧和凹面侧的锂离子会通过穿孔12实现互通，保证极片1两侧的嵌锂浓度达到平衡，降低弯折部6中负极片3与正极片2之间出现析锂风险，有利于提升二次电池100的使用寿命。
根据本申请的一些实施例，请参照图5与图6，S400、对涂布后的集流体1a进行辊压的步骤，包括：
S410、将压力辊200的张力辊面220和位于张力辊面220两侧的延展辊面210分别对应压在活性物质层、以及集流体1a上位于活性物质层两侧的空白区16上，并控制延展辊面210朝向张力辊面220的一侧与穿孔12所在区域之间留有间距。
请参照图6，压力辊200是指压在涂布后的集流体1a上，以压实活性物质的部件。压力辊200的表面具有张力辊面220和位于张力辊面220两侧的延 展辊面210。延展辊面210压在集流体1a的空白区16上，张力辊面220压在集流体1a的活性物质层上。同时，延展辊面210和张力辊面220均周向延伸设于压力辊200上，且延展辊面210的直径大于张力辊面220的直径。
在冷压活性物质时，控制延展辊面210的一侧与穿孔12所在区域之间留有间距，避免穿孔12开设位置紧靠延展辊面210处而导致应力集中，从而避免极片1在辊压时易出现断带。
根据本申请的一些实施例，请参照图2，本申请提供了一种电极组件10，被构造为卷绕结构。电极组件10包括正极片2、负极片3及隔设于正极片2与负极片3之间的隔膜4，且卷绕结构包括弯折部6。其中，正极片2和/或负极片3为以上的极片1，弯折部6所在位置与卷绕后的拐角区13相对。
根据本申请的一些实施例，请参照图1，本申请提供了一种二次电池100，包括以上的电极组件10。
根据本申请的一些实施例，请参照图1至图6，本申请提供了一种集流体1a。根据电极组件10的卷绕尺寸，确认出集流体1a上拐角区13所在位置，然后在拐角区13打穿孔12，穿孔12的形状和排列方式不限。全部穿孔12的开孔面积与拐角区13的面积的比值为0.1～50％。穿孔12所在区域沿第二方向Y上的宽度限定在涂覆区14内，且各排的开孔面积之和从中间向两边逐渐减小。涂覆区14的边缘外为空白区16，而空白区16(未涂布活性材料区域)不打孔。
为了使本申请的目的、技术方案及优点更加简洁明了，本申请用以下具体实施例进行说明，但本申请绝非仅限于这些实施例。以下所描述的实施例仅为本申请较好的实施例，可用于描述本申请，不能理解为对本申请的范围的限制。应当指出的是，凡在本申请的精神和原则之内所做的任何修改、等同替换和改进等，均应包含在本申请的保护范围之内。
为了更好地说明本申请，下面结合实施例对本申请内容作进一步说明。以下为具体实施例。
对比例1
正极片2：
将正极活性物质三元材料镍钴锰(NCM811)、导电剂乙炔黑、粘结剂聚偏氟乙烯(PVDF)按质量比97：2：1混合均匀并加入到溶剂NMP中，制成正极浆料；将正极浆料均匀涂布在铝箔上，在85℃下烘干后冷压，再进行模切、分条，制成锂离子电池正极片2。
其中，正极片2的活性物质的涂布重量为17.6毫克每平方厘米(mg/cm 2)，正极片2的集流体1a厚度为13微米(μm)。
负极片3：
将负极活性物质石墨、导电剂乙炔黑、增稠剂羟甲基纤维素钠(CMC)、粘结剂丁苯橡胶(SBR)按质量比96：2：1：1加入溶剂水中混合均匀并制成负极浆料；将负极浆料均匀涂布在铜箔上，在85℃下烘干后进行冷压，制成负极片3。
其中，负极片3的涂布重量为10mg/cm 2，负极片3的集流体1a厚度8μm，集流体1a的宽度为170毫米(mm)，负极片3活性物质涂覆区14的宽度为100mm。另外，负极片3的集流体1a的拐角区13内不开穿孔12。
隔膜4：
采用聚乙烯微孔薄膜作为多孔隔离膜基材，将无机三氧化铝粉末、聚乙烯呲咯烷酮、丙酮溶剂按重量比3：1.5：5.5混合均匀制成浆料并涂布于基材的一面并烘干，得到隔离膜。
电解液：
将六氟磷酸锂溶解于碳酸乙烯酯、碳酸二甲酯和碳酸甲乙酯的混合溶剂 中(碳酸乙烯酯、碳酸二甲酯、碳酸甲乙酯的体积比为1：2：1)，得到锂离子电池电解液。
二次电池100的制备：
将上述正极片2、负极片3以及隔离膜进行卷绕，得到裸电芯，之后经过封装、注液、化成、排气等工序，制得锂离子电池，该电池的设计充电N/P＝1.03，电芯设计容量为160Ah。
对比例2
与对比例1基本相同，区别仅在于：在负极片3集流体1a的前6个拐角区13开孔，且开孔面积与拐角区13所在面积之比为10％，开孔区域17的宽度为120mm。
实施例1
与对比例1基本相同，区别仅在于：在负极片3集流体1a的前6个拐角区13开孔，且开孔面积与拐角区13所在面积之比为1％，开孔区域17的宽度为100mm。
实施例2
与对比例1基本相同，区别仅在于：在负极片3集流体1a的前6个拐角区13开孔，且开孔面积与拐角区13所在面积之比为10％，开孔区域17的宽度为100mm。
实施例3
与对比例1基本相同，区别仅在于：在负极片3集流体1a的前6个拐角区13开孔，且开孔面积与拐角区13所在面积之比为10％，开孔区域17的宽度为80mm。
实施例4
与对比例1基本相同，区别仅在于：在负极片3集流体1a的前6个拐角区13开孔，且开孔面积与拐角区13所在面积之比为20％，开孔区域17的宽度为60mm。
采用以上对比例和实施例中制备的二次电池100，记录在冷压过程中的断裂频次。同时，二次电池100制作完成后以0.5C恒流恒压充电到4.25V以后拆解电芯，观察电极组件10弯折部6处是否析锂，具体结果可参考表1。
表1
Figure PCTCN2022128367-appb-000001
从表1中可知，实施例2至实施例4，分别与对比例1比较可得出，在集流体1a的拐角区13内打穿孔12，能够有效降低弯折部6处析锂问题。
同时，实施例1和实施例2分别与对比例1比较可知，若开孔区域17宽度均和活性物质涂覆区14的宽度相同时，会减弱极片1的机械强度，导致极片1冷压过程中容易发生断裂。
实施例2、实施例3和实施例4分别与对比例2比较可知，若开孔区域17宽度小于活性物质涂覆区14的宽度时，开孔区域17与涂覆区14的边缘之间留有不开孔的应力区15，能有效减少极片1断裂的次数。
最后应说明的是：以上各实施例仅用以说明本申请的技术方案，而非对其限制；尽管参照前述各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 者对其中部分或者全部技术特征进行等同替换；而这些修改或者替换，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范围，其均应涵盖在本申请的权利要求和说明书的范围当中。尤其是，只要不存在结构冲突，各个实施例中所提到的各项技术特征均可以任意方式组合起来。本申请并不局限于文中公开的特定实施例，而是包括落入权利要求的范围内的所有技术方案。

Claims (16)

  1. 一种集流体(1a)，用于在第一方向(X)上进行卷绕，所述集流体(1a)包括：
    集流本体(11)，沿所述第一方向(X)间隔具有若干拐角区(13)，所述拐角区(13)用于与电极组件(10)的弯折部(6)相对；
    其中，至少一个所述拐角区(13)内沿所述集流体(1a)的厚度方向贯穿设有穿孔(12)。
  2. 根据权利要求1所述的集流体(1a)，其中，在具有所述穿孔(12)的拐角区(13)内，所述穿孔(12)为多个，且全部所述穿孔(12)在所述拐角区(13)内间隔分布。
  3. 根据权利要求2所述的集流体(1a)，其中，在具有所述穿孔(12)的拐角区(13)内，所述穿孔(12)在第二方向(Y)上成排间隔分布，任一排所述穿孔(12)的开孔面积之和记为S0，各排的开孔面积之和S0越靠近所述拐角区(13)沿所述第二方向(Y)上的任一端越小，所述第一方向(X)与所述第二方向(Y)垂直。
  4. 根据权利要求3所述的集流体(1a)，其中，在具有所述穿孔(12)的拐角区(13)内，各排所述穿孔(12)的开孔数量自所述拐角区(13)的中部至所述拐角区(13)沿所述第二方向(Y)上的任一端逐渐减小。
  5. 根据权利要求2所述的集流体(1a)，其中，所述集流本体(11)上具有供活性物质层涂布的涂覆区(14)，所述涂覆区(14)沿所述第一方向(X)延伸并依次经过各所述拐角区(13)，所述拐角区(13)内的穿孔(12)在第二方向(Y)上均位于所述涂覆区(14)内，所述第一方向(X)与所述第二方向(Y)垂直。
  6. 根据权利要求5所述的集流体(1a)，其中，所述涂覆区(14)内设有至少一应力区(15)，所述应力区(15)沿所述涂覆区(14)在所述第二方向(Y)上的一边缘延伸，所述拐角区(13)内的穿孔(12)在所述第二方向(Y)上均位于所述涂覆区(14)除去所述应力区(15)的区域中。
  7. 根据权利要求6所述的集流体(1a)，其中，各所述应力区(15)在所述第二方向(Y)上的宽度记为D，其中，D≥3mm。
  8. 根据权利要求6所述的集流体(1a)，其中，所述涂覆区(14)内沿所述第二方向(Y)间隔设有两个所述应力区(15)，两个所述应力区(15)分别对应邻接于所述涂覆区(14)沿所述第二方向(Y)上的相对两边缘。
  9. 根据权利要求5-8任一项所述的集流体(1a)，其中，所述集流本体(11)上还具有空白区(16)，所述空白区(16)位于所述涂覆区(14)沿所述第二方向(Y)上的至少一侧。
  10. 根据权利要求1-9任一项所述的集流体(1a)，其中，在具有所述穿孔(12)的拐角区(13)内，全部所述穿孔(12)的开孔面积之和记为S1，所述拐角区(13)在所述集流本体(11)上的面积记为S2，其中，0.1％≤S1/S2≤50％。
  11. 根据权利要求1-10任一项所述的集流体(1a)，其中，自所述集流本体(11)卷绕的起始端开始，前n个所述拐角区(13)内均设有所述穿孔(12)，其中，n≤6。
  12. 一种极片(1)，包括：
    如权利要求1-11任一项所述的集流体(1a)；
    活性物质层，设于所述集流本体(11)的至少一表面。
  13. 一种极片的制备方法，用于制备权利要求12所述的极片(1)，包括如下步骤：
    提供集流本体(11)；
    在所述集流本体(11)上的拐角区(13)中开穿孔(12)，以形成集流体(1a)；
    在所述集流体(1a)的表面上涂布活性物质层；
    对涂布后的所述集流体(1a)进行辊压。
  14. 根据权利要求13所述的极片的制备方法，其中，对涂布后的所述集流 体(1a)进行辊压的步骤，包括：
    将压力辊(200)的张力辊面(220)和位于所述张力辊面(220)两侧的延展辊面(210)分别对应压在所述活性物质层、以及所述集流体(1a)上位于所述活性物质层两侧的空白区(16)上，并控制所述延展辊面(210)朝向所述张力辊面(220)的一侧与所述穿孔(12)所在区域之间留有间距。
  15. 一种电极组件(10)，被构造为卷绕结构，包括正极片(2)、负极片(3)及隔设于所述正极片(2)与所述负极片(3)之间的隔膜(4)，且所述卷绕结构包括弯折部(6)；
    其中，所述正极片(2)和/或负极片(3)为权利要求12所述的极片(1)，所述弯折部(6)所在位置与卷绕后的所述拐角区(13)相对。
  16. 一种二次电池(100)，包括权利要求15所述的电极组件(10)。
PCT/CN2022/128367 2022-10-28 2022-10-28 集流体、极片及其制备方法、电极组件及二次电池 WO2024087200A1 (zh)

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CN103022408A (zh) * 2011-09-27 2013-04-03 三菱自动车工业株式会社 二次电池
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