Current collector, method of manufacturing, electrode sheet, secondary battery, and electric device

Abstract

The application provides a current collector, a preparation method thereof, an electrode sheet, a secondary battery and an electric device. In the current collector, the thickness of the first region is greater than the thickness of the second region by designing the structure of the high-strength current collector, the internal resistance of the first region can be reduced accordingly, the current conduction capacity of the first region can be improved, the polarization degree of the high-strength current collector can be reduced, and thus the performance of the battery can be improved.

Description

[0001] Related applications

[0002] This application is a divisional application of the Chinese patent application filed by the applicant on March 2, 2023, with application number 202310192932X, entitled "Current collector and preparation method, electrode sheet, secondary battery and power supply device". Technical Field

[0003] This application relates to the field of secondary battery technology, and in particular to a current collector and its preparation method, electrode sheets, secondary batteries, and electrical devices. Background Technology

[0004] As a fundamental component of rechargeable batteries, the current collector has a significant impact on battery performance. With the continuous advancement of rechargeable battery research, high-strength current collectors have emerged. Increasing the current collector's strength allows for a more stable structure during battery manufacturing; however, traditional high-strength current collectors exhibit significant polarization, thus limiting further improvements in battery performance. Summary of the Invention

[0005] This application provides a current collector, including a first region and a second region, which are in contact with each other. The thickness of the first region is greater than the thickness of the second region, and the overall tensile strength of the current collector is not less than 500 MPa.

[0006] In the aforementioned current collector, by designing the structure of the high-strength current collector so that the thickness of the first region is greater than that of the second region, the internal resistance of the first region can be reduced accordingly, the conductivity of the first region can be improved, the polarization of the high-strength current collector can be reduced, and thus the performance of the battery can be improved.

[0007] In some implementations, the thickness T1 of the first region and the thickness T2 of the second region satisfy: a≤T2 / T1≤0.99, where a is the ratio of the width of the first region to the width of the second region.

[0008] In some implementations, the thickness T1 of the first region and the thickness T2 of the second region satisfy: 0.67≤T2 / T1≤0.9.

[0009] In some implementations, the elongation ρ1 of the first region and the elongation ρ2 of the second region satisfy: b ≤ ρ1 / ρ2 ≤ 10, where b is the ratio of the thickness of the first region to the thickness of the second region.

[0010] In some embodiments, the thickness of the second region is 3 μm to 20 μm.

[0011] In some embodiments, the thickness of the second region is 4 μm to 10 μm.

[0012] In some embodiments, the thickness of the first region is 3 μm to 30 μm.

[0013] In some embodiments, the thickness of the first region is 4.5 μm to 17 μm.

[0014] In some embodiments, the material of the current collector includes at least one of nickel, iron, and stainless steel.

[0015] In some embodiments, the stainless steel comprises a nickel-iron alloy.

[0016] In some embodiments, the mass ratio of nickel to iron in the nickel-iron alloy is (2~3):(2~3).

[0017] In some embodiments, the current collector further includes a transition region, the two ends of which are connected to the first region and the second region, respectively.

[0018] In some embodiments, the length of the transition zone is 2 mm to 10 mm in the direction from the first region to the second region.

[0019] In some implementations, the thickness of the transition region gradually decreases along the direction from the first region to the second region.

[0020] In some embodiments, the maximum thickness of the transition region is equal to the thickness of the first region at the end closest to the transition region, and the minimum thickness of the transition region is equal to the thickness of the second region at the end closest to the transition region.

[0021] This application also provides a method for preparing a current collector, comprising the following steps:

[0022] The material of the current collector shall have a tensile strength of not less than 500 MPa.

[0023] The material of the current collector is configured as an electroplating solution, and a first region and a second region are formed on the electroplating carrier by electroplating through the electroplating solution at a preset position. The first region and the second region are controlled to be in contact, and the thickness of the first region is controlled to be greater than the thickness of the second region.

[0024] Separate the electroplated product from the electroplating carrier.

[0025] In some embodiments, when the thickness of the first region is greater than the thickness of the second region, the thicknesses of the first region and the second region are adjusted by adjusting the current density of the electroplating.

[0026] This application also provides an electrode sheet, including the above-mentioned current collector and an active film layer, wherein the active film layer is disposed on at least one surface of the second region.

[0027] In some embodiments, the active film layer extends to a portion of the surface of the first region.

[0028] In some embodiments, the length L1 of the active film layer and the length L2 of the second region in the direction from the first region to the second region satisfy: L1-L2≥0.5mm.

[0029] In some implementations, 0.5mm ≤ L1 - L2 ≤ 15mm.

[0030] In some embodiments, the current collector further includes a transition region, the two ends of which are connected to the first region and the second region, respectively; in the direction from the first region to the second region, the length L1 of the active film layer, the length L2 of the second region, and the length L3 of the transition region satisfy: 0 < L1 - L2 - L3 ≤ 1 mm.

[0031] In some embodiments, the length of the transition zone is 2 mm to 10 mm in the direction from the first region to the second region.

[0032] In some implementations, the thickness of the transition region gradually decreases along the direction from the first region to the second region.

[0033] In some embodiments, the maximum thickness of the transition region is equal to the thickness of the first region at the end closest to the transition region, and the minimum thickness of the transition region is equal to the thickness of the second region at the end closest to the transition region.

[0034] This application also provides a secondary battery, wherein the positive electrode and / or negative electrode are selected from the above-mentioned electrode plates.

[0035] In some embodiments, the active film layer of the negative electrode sheet includes at least one of graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate.

[0036] In some embodiments, the active film layer of the negative electrode sheet comprises graphite and silicon-based materials, optionally with a mass ratio of graphite to silicon-based materials of (3~5):1.

[0037] In some embodiments, the active film layer of the positive electrode includes at least one of lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

[0038] This application also provides an electrical device, including the aforementioned secondary battery. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0040] Figure 2 yes Figure 1 An exploded view of a secondary battery according to one embodiment of this application is shown.

[0041] Figure 3 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0042] Figure 4 This is a schematic diagram of the electrode sheet in the thickness direction before slitting in one embodiment of this application.

[0043] Figure 5 for Figure 4 A top view of the current collector of the corresponding electrode sheet before it was cut.

[0044] Figure 6 This is a schematic diagram of an electroplating roller for processing current collectors according to one embodiment of this application.

[0045] Figure 7 This is a schematic diagram of an electroplating roller for processing current collectors according to another embodiment of this application.

[0046] Explanation of reference numerals in the attached figures:

[0047] 5. Secondary battery; 51. Housing; 52. Electrode assembly; 53. Top cover assembly; 6. Electrode plate; 7. Current collector; 71. First region; 72. Second region; 73. Transition region; 8. Active film layer; 9. Electroplating roller; 91. Rotating shaft; 92. Edge plating area; 93. Middle plating area; 94. Transition region. Detailed Implementation

[0048] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the battery assembly, battery cell, secondary battery, and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0049] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0050] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0051] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0052] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0053] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0054] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true or exists, and B is false or does not exist; A is false or does not exist, and B is true or exists; or both A and B are true, or both A and B exist.

[0055] Unless otherwise specified, in this application, the terms "positive electrode sheet" and "positive electrode plate" have the same meaning and can be used interchangeably. The terms "negative electrode sheet" and "negative electrode plate" have the same meaning and can be used interchangeably. The terms "diaphragm" and "separating membrane" have the same meaning and can be used interchangeably.

[0056] One embodiment of this application provides a current collector, including a first region and a second region, the first region and the second region being in contact, the thickness of the first region being greater than the thickness of the second region, and the overall tensile strength of the current collector being not less than 500 MPa.

[0057] In secondary batteries, high-strength current collectors with a tensile strength ≥500MPa can maintain a more stable structure during battery manufacturing. However, traditional high-strength current collectors suffer from significant polarization, which may limit further improvements in battery performance. In the current collector of this embodiment, by designing the structure of the high-strength current collector such that the thickness of the first region is greater than that of the second region, the internal resistance of the first region can be reduced, the conductivity of the first region can be increased, and the polarization of the high-strength current collector can be reduced, thereby improving battery performance.

[0058] Furthermore, during the battery manufacturing process, the first region can be used to conduct current. Typically, the first region needs to be welded. In the current collector of this embodiment, the thickness of the first region is relatively large, which can improve the welding performance of the first region and reduce the risk of weld cracking in the first region.

[0059] Furthermore, in this embodiment, the thickness of the first region in the current collector is relatively large, which can reduce the risk of strip breakage during the cold pressing process and thus improve the production yield of the battery.

[0060] In some embodiments, the overall tensile strength of the current collector is ≥500 MPa, or ≥600 MPa, or ≥700 MPa, or ≥800 MPa, or ≥900 MPa, or ≥1000 MPa, or ≥1100 MPa, or ≥1200 MPa. Optionally, the overall tensile strength of the current collector is 500 MPa to 1200 MPa.

[0061] It is understood that, in this application, tensile strength can be tested as follows: cut a current collector sample with a length of 100 mm and a width of 15 mm with an accuracy of 0.05 mm, clamp it on the upper and lower clamps of a tensile testing machine with a clamping distance of 50 mm, start the clamps and maintain a loading speed of 5 mm / min, and record the maximum load that causes shear failure of the sample.

[0062] It is understood that in this application, the second region can be used to coat an active film layer. During the fabrication of the electrode sheet, an active film layer is coated on at least one surface of the second region of the current collector. The first region is used to conduct current; the first region may not be coated with an active film layer, or a portion of the first region may be coated with an active film layer. The first region can be used as a tab, or an external tab can be soldered onto it.

[0063] It is also understandable that the first and second regions come into contact either directly or through an intermediate region. For example, when the first and second regions come into contact through an intermediate region, they can also come into contact through a transition zone located between them.

[0064] Please see Figure 4 and Figure 5 The thickness, length, and width are shown. Figure 4 and Figure 5 In this diagram, the Z-direction represents the thickness direction, the X-direction represents the length direction, and the Y-direction represents the width direction. Specifically, the thickness direction of the current collector is the Z-direction. The direction from the first region to the second region is the length direction, i.e., the X-direction. The direction perpendicular to the length direction is the width direction, i.e., the Y-direction.

[0065] Understandably, in Figure 4 and Figure 5 The diagram shows the electrode plates and current collector before slitting. In actual processing, the electrode plates and current collector can be... Figure 4 and Figure 5The structure shown is cut along the centerline in the length direction to obtain two cut electrode plates and a current collector. In this application, the length in the length direction represents the length of the corresponding region in the cut electrode plate and the current collector.

[0066] In some implementations, the thickness T1 of the first region and the thickness T2 of the second region satisfy: a ≤ T2 / T1 ≤ 0.99, where a is the ratio of the width of the first region to the width of the second region. As an example, a is... Figure 5 The ratio of the width of the first region 71 to the width of the second region 72. Optionally, 0.1 ≤ a ≤ 0.9, and optionally, a is 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, etc. As an example, the thickness T1 of the first region 71 and the thickness T2 of the second region 72 are as follows: Figure 4 As shown in the figure. For example, the width W1 of the first region 71 and the width W2 of the second region 72 are as follows... Figure 5 As shown in the image.

[0067] It is understandable that, for the current collector of a stacked battery, the width of the first region and the width of the second region represent the width of the first region and the width of the second region of a single current collector, respectively. For the current collector of a wound battery, there are multiple first regions, and the width of the first region represents the sum of the widths of the multiple first regions, while the width of the second region represents the width of the entire second region of the current collector.

[0068] Optionally, the thickness T1 of the first region and the thickness T2 of the second region satisfy: 0.67 ≤ T2 / T1 ≤ 0.9. Further optionally, T2 / T1 is 0.7, 0.75, 0.8, 0.85, 0.9, etc.

[0069] In some embodiments, the thickness of the second region is 3 μm to 20 μm. Optionally, the thickness of the second region is 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, etc. More preferably, the thickness of the second region is 4 μm to 10 μm.

[0070] In some embodiments, the thickness of the first region is 3 μm to 30 μm. Optionally, the thickness of the first region is 3 μm, 3.3 μm, 4 μm, 4.5 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 16 μm, 17 μm, 18 μm, 20 μm, 22 μm, 25 μm, 28 μm, 30 μm, etc. More optionally, the thickness of the first region is 4.5 μm to 17 μm.

[0071] In some implementations, the elongation ρ1 of the first region and the elongation ρ2 of the second region satisfy: b ≤ ρ1 / ρ2 ≤ 10, where b is the ratio of the thickness of the first region to the thickness of the second region. A suitable ρ1 / ρ2 can reduce the risk of fishtail marks and cracking in the first region during cold pressing and welding, further improving the stability of the current collector structure and thus enhancing battery performance. When ρ1 / ρ2 is too small, the improvement effect is not significant. When ρ1 / ρ2 is too large, it may lead to a decrease in the strength of the current collector, increasing the risk of deformation in the first region.

[0072] In some embodiments, the current collector material includes at least one of nickel, iron, and stainless steel. This allows the current collector to have higher tensile strength. Optionally, the stainless steel includes a nickel-iron alloy. Further optionally, the mass ratio of nickel to iron in the nickel-iron alloy is (2~3):(2~3). Even further optionally, the mass ratio of nickel to iron in the nickel-iron alloy is 1:1, 2:3, 3:2, etc. Still further optionally, the material of the first region and the material of the second region are the same.

[0073] Please see Figure 4 and Figure 5 In some embodiments, the current collector 7 further includes a transition zone 73, the two ends of which are connected to the first region 71 and the second region 73, respectively. By setting the transition zone, a more stable transition can be achieved between the first region and the second region, which have different thicknesses, thereby improving the stability of the current collector structure during processing.

[0074] In some embodiments, the length of the transition zone along the direction from the first region to the second region is 2mm to 10mm. Optionally, the length of the transition zone is 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, etc.

[0075] In some embodiments, the thickness of the transition region gradually decreases along the direction from the first region to the second region. This gradual decrease in thickness along the direction from the first region to the second region allows for a smoother transition between the first and second regions. Optionally, the maximum thickness of the transition region is equal to the thickness of the first region near the end of the transition region, and the minimum thickness of the transition region is equal to the thickness of the second region near the end of the transition region.

[0076] Optionally, the second region is a region of uniform thickness. That is, the thickness is equal at all points in the second region. More optionally, the first region is a region of uniform thickness, that is, the thickness is equal at all points in the first region.

[0077] Another embodiment of this application provides an electrode sheet including the above-mentioned current collector 7 and an active film layer 8, wherein the active film layer 8 is disposed on at least one surface of the second region 72.

[0078] In some embodiments, the active film layer extends to a portion of the surface of the first region (not shown in the figure). In this case, the active film layer exerts a certain tensile force on the first region, effectively reducing the risk of collapse in the first region. Specifically, when coating the active film layer, the active slurry is applied to a portion of the surface of the first region while applying it to the second region. During cold pressing, the active slurry exerts a certain tensile force on the first region, thus reducing the risk of collapse in the first region during subsequent conveying processes such as cold pressing, and helping to maintain the stability of the current collector structure.

[0079] Optionally, along the direction from the first region to the second region, the length L1 of the active film layer and the length L2 of the second region satisfy: L1-L2≥0.5mm. Optionally, without a transition zone, the first region and the second region are in direct contact, and L1-L2 can be expressed as the length of the active film layer extending to the surface of the first region. Optionally, L1-L2≥1mm. Further optional, L1-L2≥1.2mm. Still further optional, L1-L2≥1.5mm. Yet still optional, L1-L2≥2mm. It can be understood that for the portion of the active film layer extending to the surface of the first region, L1-L2<the length of the first region. Even more optional, 0.5mm≤L1-L2≤15mm.

[0080] Please see Figure 4 and Figure 5 In some embodiments, the current collector of the electrode sheet further includes a transition region, the two ends of which are connected to the first region and the second region, respectively; in the direction from the first region to the second region, the length L1 of the active film layer, the length L2 of the second region, and the length L3 of the transition region satisfy: 0 < L1 - L2 - L3 ≤ 1 mm. Optionally, L1 - L2 - L3 ≤ 0.5 mm.

[0081] Please refer to it again. Figure 5 The lengths of the active film layer (L1), the second region (L2), and the transition region (L3) are respectively located at... Figure 5 An example was provided in the text.

[0082] Optionally, the length of the transition zone is 2mm to 10mm along the direction from the first region to the second region. Optionally, the thickness of the transition zone gradually decreases along the direction from the first region to the second region. Further optionally, the maximum thickness of the transition zone is equal to the thickness of the first region near the end of the transition zone, and the minimum thickness of the transition zone is equal to the thickness of the second region near the end of the transition zone.

[0083] Another embodiment of this application provides a secondary battery in which the positive electrode and / or negative electrode are selected from the above-mentioned electrode plates.

[0084] In some embodiments, the active film layer of the negative electrode includes at least one of graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. Optionally, the active film layer of the negative electrode includes graphite and silicon-based materials. Further optionally, the active film layer of the negative electrode includes graphite and silicon-based materials, wherein the mass ratio of graphite to silicon-based materials is (3~5):1. Still further optionally, the active film layer of the negative electrode includes graphite and silicon-based materials, wherein the mass ratio of graphite to silicon-based materials is 3:1, 3.5:1, 4:1, 4.5:1, 5:1, etc. When the current collector of this application is used in conjunction with the silicon-based negative electrode active material, the expansion problem of silicon-based materials during cold pressing can be effectively improved, which is beneficial to maintaining a stable structure of the negative electrode.

[0085] In some embodiments, the active film layer of the positive electrode includes at least one of lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide. The combination of ternary materials and silicon-based materials can better utilize the energy density of the materials, further improving battery performance.

[0086] Another embodiment of this application provides a method for preparing a current collector. The method includes the following steps: selecting a material for the current collector, wherein the tensile strength of the material is not less than 500 MPa; preparing the material for the current collector into an electroplating solution; and forming a second region for coating an active film layer and a first region for conducting current at predetermined positions on an electroplating carrier using electroplating, wherein the first region and the second region are controlled to be in contact, and the thickness of the first region is controlled to be greater than the thickness of the second region; and separating the electroplated product from the electroplating carrier.

[0087] In some implementations, when the thickness of the first region is greater than the thickness of the second region, the thickness of the first region and the second region are adjusted by adjusting the current density of the electroplating.

[0088] In one embodiment, the electroplating support is an electroplating roller. Optionally, the electroplating roller is as follows: Figure 6 As shown. The electroplating roller 9 includes a rotating shaft 91, an intermediate plating area 93 and an edge plating area 92 located on the outer edge of the rotating shaft 91. The edge plating area 92 is located at both ends of the intermediate plating area 93. During the electroplating process, the rotating shaft 91 rotates, and the first and second areas are electroplated using the edge plating area 92 and the intermediate plating area 93, respectively.

[0089] Further, please refer to Figure 7 A transition zone 94 is provided between the edge plating zone 92 and the intermediate plating zone 93. At this time, during the electroplating process, the rotating shaft 91 rotates, and the first region, the second region, and the transition zone are electroplated using the edge plating zone 92, the intermediate plating zone 93, and the intermediate plating zone 94, respectively.

[0090] Optionally, the diameter of the edge plating area is slightly smaller than the diameter of the middle plating area. The electrical conductivity of the material in the edge plating area is higher than that in the middle plating area; for example, the material in the edge plating area is a copper-titanium alloy, and the material in the middle plating area is titanium. Further optionally, an insulating ring can be provided on the electroplating roller. Still further optionally, the edge plating area, the middle plating area, and the transition area use different power supplies, thereby controlling the thickness of the first region, the second region, and the transition area of ​​the current collector by controlling the current density.

[0091] This application also provides a battery module. The battery module includes the aforementioned secondary battery.

[0092] This application also provides a battery pack. The battery pack includes the aforementioned secondary battery or the aforementioned battery module.

[0093] This application also provides an electrical device. The electrical device includes at least one of the above-mentioned secondary battery, the above-mentioned battery module, and the above-mentioned battery pack.

[0094] The secondary battery will be explained below with reference to the relevant accompanying drawings.

[0095] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0096] [Positive electrode plate]

[0097] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector.

[0098] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector. Optionally, the positive current collector is the aforementioned current collector.

[0099] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material on the polymer substrate. Optionally, the metal material may include, but is not limited to, one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Optionally, the polymer substrate may include, but is not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0100] In some embodiments, when the secondary battery is a lithium-ion battery, the positive electrode active material may be a positive electrode active material known in the art for lithium-ion batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds. Optionally, lithium cobalt oxide includes LiCoO2. Lithium nickel oxide includes LiNiO2. Lithium manganese oxide includes at least one of LiMnO2 and LiMn2O4. Lithium nickel cobalt manganese oxide includes LiNi... 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM) 622 ) and LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM) 811 At least one of the following. Lithium nickel cobalt aluminum oxides include LiNi 0.85 Co 0.15 Al0.05 O2. Examples of lithium phosphates with an olivine structure may include, but are not limited to, at least one of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites. Optionally, lithium iron phosphate includes LiFePO4 (LFP). Lithium manganese phosphate includes LiMnPO4.

[0101] In some embodiments, when the secondary battery is a sodium-ion battery, the positive electrode active material can be any positive electrode active material known in the art for sodium-ion batteries. As an example, the positive electrode active material can be a single material or a combination of two or more. The positive electrode active material can be selected from sodium-iron composite oxides, sodium-cobalt composite oxides, sodium-chromium composite oxides, sodium-manganese composite oxides, sodium-nickel composite oxides, sodium-nickel-titanium composite oxides, sodium-nickel-manganese composite oxides, sodium-iron-manganese composite oxides, sodium-nickel-cobalt-manganese composite oxides, sodium-iron phosphate compounds, sodium-manganese phosphate compounds, sodium-cobalt phosphate compounds, Prussian blue-based materials, polyanionic materials, etc., but this application is not limited to these materials. Other conventionally known materials that can be used as positive electrode active materials for sodium-ion batteries can also be used. Optionally, the sodium-iron composite oxide includes NaFeO2. The sodium-cobalt composite oxide includes NaCoO2. The sodium-chromium composite oxide includes NaCrO2. The sodium-manganese composite oxide includes NaMnO2. The sodium-nickel composite oxide includes NaNiO2. The sodium-nickel-titanium composite oxide includes NaNi 1 / 2 Ti 1 / 2 O2. Sodium-nickel-manganese composite oxides include NaNi 1 / 2 Mn 1 / 2 O2. Sodium-iron-manganese composite oxides include Na 2 / 3 Fe 1 / 3 Mn 2 / 3 O2. Sodium-nickel-cobalt-manganese composite oxides include NaNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2. Sodium iron phosphate compounds include NaFePO4. Sodium manganese phosphate compounds include NaMnPO4. Sodium cobalt phosphate compounds include NaCoPO4. Polyanionic materials include at least one of phosphates, fluorophosphates, pyrophosphates, and sulfates.

[0102] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0103] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0104] In some embodiments, the positive electrode sheet can be prepared by dispersing the components used to prepare the positive electrode sheet, such as the positive electrode active material, conductive agent, binder, and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry onto a positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing, and other processes. Optionally, the solvent includes N-methylpyrrolidone.

[0105] [Negative electrode plate]

[0106] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0107] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector. Optionally, the negative electrode current collector is the current collector described above.

[0108] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material on the polymer material substrate. Optionally, the metal material includes at least one of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The polymer material includes at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0109] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0110] In some embodiments, the negative electrode film layer may optionally include an adhesive. The adhesive may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), carboxymethyl chitosan (CMCS), polyamide-imide (PAI), polyethyleneimine (PEI), polyimide (PI), and tert-butyl polyacrylate-triethoxyvinylsilane (TBATEVS).

[0111] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0112] In some embodiments, the negative electrode film layer may optionally include other additives, such as thickeners. Optionally, the thickener includes sodium carboxymethyl cellulose (CMC-Na).

[0113] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder, and any other components, in a solvent to form a negative electrode slurry; coating the negative electrode slurry onto a negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing, and other processes. Optionally, the solvent includes deionized water.

[0114] Electrolyte

[0115] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements.

[0116] In some embodiments, the electrolyte comprises an electrolyte salt and a solvent.

[0117] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0118] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0119] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0120] [Isolation membrane]

[0121] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0122] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0123] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0124] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0125] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0126] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 This is an example of a square-structured secondary battery 5.

[0127] In some implementations, refer to Figure 2 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 52 using a winding or stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0128] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0129] This application also provides an electrical device, which includes the secondary battery provided in this application. The secondary battery can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc. For example, mobile devices include mobile phones, laptops, etc. Electric vehicles include pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.

[0130] As the electrical device, a secondary battery can be selected according to its usage requirements.

[0131] Figure 3 This is an example of an electrical device. The electrical device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.

[0132] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0133] Example

[0134] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0135] Example 1

[0136] In this embodiment, the current collector is made of nickel-iron alloy. The first and second regions are in direct contact, and the materials of the first and second regions are the same. The mass ratio of nickel to iron in the nickel-iron alloy is 1:1. The thickness T1 of the first region is 7.5 μm, and the thickness T2 of the second region is 6 μm. T1 / T2 = 1.25. At the contact point between the first and second regions, the ratio of the width W1 of the first region to the width W2 of the second region is a = W1 / W2 = 0.2. The elongation ρ1 of the first region and the elongation ρ2 of the second region satisfy ρ1 / ρ2 = 2.1.

[0137] Example 2

[0138] The structure of the current collector in this embodiment is as follows: Figure 5 As shown, a transition zone is provided between the first and second regions. The current collector is made of nickel-iron alloy, and the materials of the first region, the second region, and the transition zone are the same. The length L3 of the transition zone is 5 mm. The mass ratio of nickel to iron in the nickel-iron alloy is 1:1. The thickness T1 of the first region is 7.5 μm, and the thickness T2 of the second region is 6 μm. T1 / T2 = 1.25. The ratio of the width W1 of the first region to the width W2 of the second region is a = W1 / W2 = 0.18. The elongation ρ1 of the first region and the elongation ρ2 of the second region satisfy ρ1 / ρ2 = 2.1.

[0139] Examples 3 to 17

[0140] Compared with Example 2, Examples 3 to 17 differ in that the material of the current collector and / or the thickness of the first region and / or the thickness of the second region and / or the length L3 of the transition region are different, as shown in Table 1.

[0141] Comparative Example 1

[0142] In this comparative example, the current collector is a copper foil with a thickness of 6 μm.

[0143] Comparative Example 2

[0144] In this comparative example, the current collector is a nickel-iron alloy with a thickness of 6 μm. The mass ratio of nickel to iron in the nickel-iron alloy is 1:1.

[0145] Comparative Example 3

[0146] Compared to Example 2, the difference in this comparative example is that the thickness of the first region is less than the thickness of the second region, as shown in Table 1. Along the direction from the first region to the second region, the thickness of the transition region gradually increases, achieving a connection between the first and second regions.

[0147] Battery manufacturing

[0148] (1) Preparation of negative electrode sheet

[0149] The negative electrode active material, CMC thickener, SP conductive agent, and SBR binder were mixed uniformly at a mass ratio of 96.2:1.1:0.7:2. Deionized water was then added as a solvent, and the mixture was stirred under vacuum until homogeneous, yielding the negative electrode active slurry. This slurry was directly coated onto the current collectors of the examples and comparative examples, and then cold-pressed to obtain the negative electrode sheet. The negative electrode active material was a mixture of graphite and SiOx silicon-based material, with a mass ratio of graphite to silicon-based material of 4:1. Where 0 < x < 2.

[0150] (2) Preparation of positive electrode sheet

[0151] Lithium iron phosphate (LiFePO4), SP conductive agent, and PVDF binder were mixed uniformly at a mass ratio of 96.8:1:2.2. NMP was then added as a solvent, and the mixture was stirred under vacuum until homogeneous, yielding the positive electrode active slurry. This slurry was then directly coated onto a 13 μm Al foil and cold-pressed to obtain the positive electrode sheet.

[0152] (3) Preparation of electrolyte

[0153] The electrolyte solvent is EC:DMC=3:7, the lithium salt is LiPF6, and the concentration is 1M.

[0154] (4) Stack the positive electrode, separator, and negative electrode in sequence, with the separator positioned between the positive and negative electrodes to provide isolation, and then wind them to obtain a bare cell. Place the bare cell in an outer packaging, inject electrolyte, and seal it to obtain a battery. The separator is a polyethylene separator.

[0155] Test case

[0156] (1) The DCR was performed according to the conventional HPPC process, maintaining an ambient temperature of 25℃. It was charged and discharged at a rate of 0.33C for 3cls, and the capacity of the 3rd cl was taken as the standard capacity C0. After charging to 50% SOC, it was discharged at 4C0 for 30s. The process data was recorded, and the difference between the voltage at 1s of discharge and the initial voltage was taken. DCR = 1s voltage difference / current. Unit: mΩ. The results are shown in Table 1.

[0157] (2) The capacity was determined by maintaining an ambient temperature of 25°C and charging / discharging at a rate of 0.33C for 3cls, and the capacity of the 3rd cl was recorded. The unit is Ah. The results are shown in Table 1.

[0158] (3) The breakage frequency was due to cold pressing production, and the compaction density was 1.6 g / cm³. 3 The number of belt breaks was recorded every 100m, with a cold pressing speed of 20m / min. The unit is times / 100m. The results are shown in Table 1.

[0159] (4) The frequency of impact damage in the first region is the number of impact damages in the first region during the die-cutting / winding process of producing 100m electrode sheets. The unit is units / 100m. The results are shown in Table 1.

[0160] (5) The frequency of welding abnormalities is the number of times a weld is not welded or cracked during welding, totaling 50ea. The unit is times / 50ea. The results are shown in Table 1.

[0161] (6) The full charge elongation test method is as follows: After winding, the winding body is unwound, and three lines (top, middle, and bottom) are drawn at 100mm intervals on the anode surface, for a total of nine lines on the three surfaces. The width value w1 of each interval is recorded. Then, the electrode sheet is rewound, assembled into a cell, and the cell is fully charged at room temperature and then disassembled. The width w2 of the drawn lines is measured again. The elongation rate is calculated as (w2-w1) / w1*100%, and the average value of the nine lines is taken. The results are shown in Table 1.

[0162] (7) The 100cls capacity retention rate is the ratio of the capacity to the initial capacity after 100cls of charge-discharge at 0.5C / 0.5C at room temperature. The results are shown in Table 1.

[0163] Table 1

[0164] The thickness of the first region is T1 (μm). The thickness of the second region is T2 (μm). T1 / T2 a ρ1 / ρ2 Transition zone length L3 (mm) Current collector materials Overall tensile strength of the current collector (MPa) DCR capacity Frequency of band break Frequency of collisions in Zone 1 Frequency of welding abnormalities Full charge extension rate (%) 100cls retention rate (%) Example 1 7.5 6 1.25 0.2 2.1 0 Nickel: Iron = 1:1 759 312.5 1.91 1 2 1 0.40 84.40 Example 2 7.5 6 1.25 0.18 2.1 5 Nickel: Iron = 1:1 759 298.3 1.91 0 0 1 0.40 84.50 Example 3 9 6 1.5 0.18 3.5 5 Nickel: Iron = 1:1 759 287.7 1.92 0 0 0 0.40 85.10 Example 4 6 4 1.5 0.18 2.7 5 Nickel: Iron = 1:1 759 340.2 1.87 1 4 2 0.52 83.20 Example 5 15 10 1.5 0.18 3.8 5 Nickel: Iron = 1:1 759 274.6 1.94 0 0 0 0.35 86.70 Example 6 30 20 1.5 0.18 4.2 5 Nickel: Iron = 1:1 759 265.6 1.94 0 1 2 0.33 87.00 Example 7 37.5 25 1.5 0.18 4.2 5 Nickel: Iron = 1:1 759 260.1 1.94 0 3 4 0.27 86.90 Example 8 10.5 6 1.75 0.18 5 5 Nickel: Iron = 1:1 759 279.1 1.94 0 3 0 0.41 85.10 Example 9 12 6 2 0.18 6.4 5 Nickel: Iron = 1:1 759 278.9 1.94 0 12 0 0.41 84.90 Example 10 9 6 1.5 0.18 3.7 5 Nickel: Iron = 2:3 824 296.8 1.91 0 0 3 0.39 84.50 Example 11 9 6 1.5 0.18 3.2 5 Nickel: Iron = 3:2 628 276.8 1.93 0 0 0 0.45 84.20 Example 12 9 6 1.5 0.18 4.3 5 nickel 419 270.5 1.94 0 0 0 0.82 83.30 Example 13 9 6 1.5 0.18 1.8 5 iron 906 340.2 1.88 0 0 11 0.21 Inner short Example 14 9 6 1.5 0.18 3.5 2 Nickel: Iron = 1:1 759 289.1 1.92 0 1 0 0.40 84.80 Example 15 9 6 1.5 0.15 3.5 10 Nickel: Iron = 1:1 759 285.5 1.93 0 0 0 0.40 85.20 Example 16 9 6 1.5 0.2 3.5 1 Nickel: Iron = 1:1 759 301.6 1.91 1 2 0 0.40 84.60 Example 17 9 6 1.5 0.14 3.5 12 Nickel: Iron = 1:1 759 296.7 1.92 0 0 0 0.40 85.00 Comparative Example 1 6 6 1 0.2 1 0 copper 298 265.8 1.94 2 2 0 1.20 81.90 Comparative Example 2 6 6 1 0.2 1 0 Nickel: Iron = 1:1 759 336.6 1.91 1 0 5 0.50 83.70 Comparative Example 3 6 8 0.75 0.18 0.7 5 Nickel: Iron = 1:1 759 311.2 1.94 2 0 0 0.30 84.20

[0165] In Table 1, under the "Current Collector Material" column, "Nickel:Iron" indicates that the current collector material is a nickel-iron alloy, and also indicates the mass ratio of nickel to iron in the nickel-iron alloy. 'a' represents the width ratio of the first region to the second region.

[0166] As can be seen from Table 1, when the current collector is made of high-strength material, the thickness of the first region is greater than that of the second region, which helps to reduce the frequency of strip breakage, impact damage and welding abnormalities during processing, and can also improve the cycle performance of the battery.

[0167] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A current collector, characterized in that, It includes a first region and a second region, the first region and the second region are in contact, the thickness of the first region is greater than the thickness of the second region, and the overall tensile strength of the current collector is not less than 500 MPa.

2. The current collector according to claim 1, characterized in that, The second region is used to coat the active film layer; the first region is not coated with the active film layer, or a portion of the first region is coated with the active film layer.

3. The current collector according to any one of claims 1 to 2, characterized in that, The thickness T1 of the first region and the thickness T2 of the second region satisfy: a≤T2 / T1≤0.99, where a is the ratio of the width of the first region to the width of the second region; Optionally, 0.1 ≤ a ≤ 0.9; Optionally, the thickness T1 of the first region and the thickness T2 of the second region satisfy: 0.67≤T2 / T1≤0.

9.

4. The current collector according to any one of claims 1 to 3, characterized in that, The elongation ρ1 of the first region and the elongation ρ2 of the second region satisfy: b≤ρ1 / ρ2≤10, where b is the ratio of the thickness of the first region to the thickness of the second region.

5. The current collector according to any one of claims 1 to 4, characterized in that, The thickness of the second region is 3μm~20μm; Optionally, the thickness of the second region is 4μm to 10μm.

6. The current collector according to claim 5, characterized in that, The thickness of the first region is 3μm~30μm; Optionally, the thickness of the first region is 4.5 μm to 17 μm.

7. The current collector according to any one of claims 1 to 6, characterized in that, The material of the current collector includes at least one of nickel, iron, and stainless steel; Optionally, the stainless steel comprises a nickel-iron alloy, and more preferably, the mass ratio of nickel to iron in the nickel-iron alloy is (2~3):(2~3).

8. The current collector according to any one of claims 1 to 7, characterized in that, It also includes a transition region, the two ends of which are connected to the first region and the second region, respectively.

9. The current collector according to claim 8, characterized in that, The transition region satisfies at least one of the following characteristics (1) to (2): (1) The length of the transition zone is 2 mm to 10 mm in the direction from the first region to the second region; (2) The thickness of the transition zone gradually decreases along the direction from the first region to the second region. Optionally, the maximum thickness of the transition zone is equal to the thickness of the first region near the end of the transition zone, and the minimum thickness of the transition zone is equal to the thickness of the second region near the end of the transition zone.

10. An electrode sheet, characterized in that, The current collector includes any one of claims 1 to 9, and an active film layer, wherein the active film layer is disposed on at least one surface of the second region.

11. The electrode sheet according to claim 10, characterized in that, The active film extends to a portion of the surface of the first region.

12. The electrode sheet according to claim 11, characterized in that, In the direction from the first region to the second region, the length L1 of the active film layer and the length L2 of the second region satisfy: L1-L2≥0.5mm; Optionally, 0.5mm ≤ L1 - L2 ≤ 15mm.

13. The electrode sheet according to any one of claims 19 to 12, characterized in that, The current collector further includes a transition region, the two ends of which are connected to the first region and the second region, respectively; in the direction from the first region to the second region, the length L1 of the active film layer, the length L2 of the second region, and the length L3 of the transition region satisfy: 0 < L1 - L2 - L3 ≤ 1 mm.

14. The electrode sheet according to claim 13, characterized in that, The transition region satisfies at least one of the following characteristics (1) to (2): (1) The length of the transition zone is 2 mm to 10 mm in the direction from the first region to the second region; (2) The thickness of the transition zone gradually decreases along the direction from the first region to the second region. Optionally, the maximum thickness of the transition zone is equal to the thickness of the first region near the end of the transition zone, and the minimum thickness of the transition zone is equal to the thickness of the second region near the end of the transition zone.

15. A secondary battery, characterized in that, Its positive electrode and / or negative electrode are selected from the electrode plates of any one of claims 10 to 14.

16. The secondary battery according to claim 15, characterized in that, The active film layer of the negative electrode sheet includes at least one of graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. Optionally, the active film layer of the negative electrode sheet includes graphite and silicon-based materials, and optionally, the mass ratio of graphite to silicon-based materials is (3~5):

1.

17. The secondary battery according to any one of claims 15-16, characterized in that, The active film layer of the positive electrode includes at least one of lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

18. An electrical appliance, characterized in that, The secondary battery includes any one of claims 15 to 17.

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