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

TECHNICAL FIELD

[0001] The present application relates to the technical field of secondary batteries, in particular to a current collector, a preparation method thereof, an electrode pole piece, a secondary battery and an electric device. BACKGROUND

[0002] As one of the basic components of a secondary battery, the current collector has an important influence on the performance of the battery. With the continuous deepening of the research on secondary batteries, high-strength current collectors have emerged as the times require. The improvement of the strength of the current collector can make the current collector maintain a more stable structure during the processing of the battery, but the traditional high-strength current collector has a large polarization degree, which further restricts the further improvement of the performance of the battery. SUMMARY

[0003] The present application provides a current collector, comprising 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.

[0004] In the above-mentioned current collector, by designing the structure of the high-strength current collector, the thickness of the first region is greater than the thickness of the second region, which can correspondingly reduce the internal resistance of the first region, improve the current-carrying capacity of the first region, reduce the polarization degree of the high-strength current collector, and thus the performance of the battery can be improved.

[0005] In some embodiments, the thickness T1 of the first region and the thickness T2 of the second region satisfy: a≤T2 / T1≤0.99, wherein a is the ratio of the width of the first region to the width of the second region.

[0006] In some embodiments, the thickness T1 of the first region and the thickness T2 of the second region satisfy: 0.67≤T2 / T1≤0.9.

[0007] In some embodiments, the elongation rate p1 of the first region and the elongation rate p2 of the second region satisfy: b≤p1 / p2≤10, wherein b is the ratio of the thickness of the first region to the thickness of the second region.

[0008] In some embodiments, the thickness of the second region is 3-20 μm.

[0009] In some embodiments, the thickness of the second region is 4-10 μm.

[0010] In some embodiments, the thickness of the first region is 3-30 μm.

[0011] In some embodiments, the thickness of the first region is 4.5-17 μm.

[0012] In some embodiments, the material of the current collector comprises at least one of nickel, iron and stainless steel.

[0013] In some embodiments, the stainless steel comprises a nickel-iron alloy.

[0014] In some embodiments, the mass ratio of nickel to iron in the nickel-iron alloy is (2-3):(2-3).

[0015] In some embodiments, the current collector further comprises a transition zone, two ends of the transition zone being connected with the first region and the second region respectively.

[0016] In some embodiments, the length of the transition zone in the direction from the first region to the second region is 2mm-10mm.

[0017] In some embodiments, the thickness of the transition zone gradually decreases in the direction from the first region to the second region.

[0018] In some embodiments, the maximum thickness of the transition zone is equal to the thickness of one end of the first region close to the transition zone, and the minimum thickness of the transition zone is equal to the thickness of one end of the second region close to the transition zone.

[0019] The present application also provides a method for preparing a current collector, comprising the following steps:

[0020] selecting a material of the current collector, the tensile strength of the material of the current collector being not less than 500MPa;

[0021] configuring the material of the current collector into an electroplating solution, forming a first region and a second region on a predetermined position of an electroplating support by electroplating through the electroplating solution, 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;

[0022] separating the product formed by electroplating from the electroplating support.

[0023] In some embodiments, when the thickness of the first region is controlled to be greater than the thickness of the second region, the thickness of the first region and the second region is adjusted by adjusting the current density of electroplating.

[0024] The present application also provides an electrode tab, comprising the above-mentioned current collector, and an active film layer, the active film layer being arranged on at least one surface of the second region.

[0025] In some embodiments, the active film layer extends to part of the surface of the first region.

[0026] In some embodiments, 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.

[0027] In some embodiments, 0.5mm≤L1-L2≤15mm.

[0028] In some embodiments, the current collector further comprises a transition region, two ends of the transition region being connected with 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

[0029] In some embodiments, in the direction from the first region to the second region, the length of the transition region is 2mm-10mm.

[0030] In some embodiments, in the direction from the first region to the second region, the thickness of the transition region gradually decreases.

[0031] In some embodiments, the maximum thickness of the transition region is equal to the thickness of one end of the first region close to the transition region, and the minimum thickness of the transition region is equal to the thickness of one end of the second region close to the transition region.

[0032] The application also provides a secondary battery, the positive electrode tab and / or the negative electrode tab of which is selected from the above electrode tabs.

[0033] In some embodiments, the active film layer of the negative electrode tab comprises at least one of graphite, soft carbon, hard carbon, silicon-based material, tin-based material and lithium titanate.

[0034] In some embodiments, the active film layer of the negative electrode tab comprises graphite and silicon-based material, and the mass ratio of graphite and silicon-based material is (3-5):1, optionally.

[0035] In some embodiments, the active film layer of the positive electrode tab comprises 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.

[0036] The application also provides an electric device comprising the above secondary battery. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 is a schematic diagram of a secondary battery according to an embodiment of the application.

[0038] Figure 2 isFigure 1 exploded view of a secondary battery according to an embodiment of the present application.

[0039] Figure 3 is a schematic view of an electric device using a secondary battery according to an embodiment of the present application as a power source.

[0040] Figure 4 is a schematic view of an electrode sheet before slitting in the thickness direction according to an embodiment of the present application.

[0041] Figure 5 is a schematic view of an electrode sheet before slitting according to another embodiment of the present application. Figure 4 is a plan view of a current collector of an electrode sheet before slitting.

[0042] Figure 6 is a schematic view of a plating roller for processing a current collector according to an embodiment of the present application.

[0043] Figure 7 is a schematic view of a plating roller for processing a current collector according to another embodiment of the present application.

[0044] Explanation of Reference Numerals:

[0045] 5, secondary battery; 51, case; 52, electrode assembly; 53, top cap assembly; 6, electrode sheet; 7, current collector; 71, first region; 72, second region; 73, transition region; 8, active film layer; 9, plating roller; 91, rotation axis; 92, edge plating region; 93, middle plating region; 94, transition region. DETAILED DESCRIPTION

[0046] Hereinafter, embodiments of a battery assembly, a battery cell, a secondary battery, and an electric device according to the present application are specifically disclosed with appropriate reference to the accompanying drawings. However, there will be cases where unnecessary detailed description is omitted. For example, there will be cases where detailed description of matters that are well known, repeated description of substantially identical structures are omitted. This is to avoid the following description becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided so that those skilled in the art can fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0047] 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.

[0048] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0049] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0050] 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.

[0051] 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.

[0052] If not specifically stated, the term "or" in the present application is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following satisfy the condition "A or B": A is true or present, and B is false or not present; A is false or not present, and B is true or present; or both A and B are true, or both A and B are present.

[0053] If not specifically stated, the term "positive tab" and "positive electrode tab" have the same meaning and can be used interchangeably in the present application. The term "negative tab" and "negative electrode tab" have the same meaning and can be used interchangeably in the present application. The term "separator" and "separating membrane" have the same meaning and can be used interchangeably in the present application.

[0054] 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 tensile strength of the whole current collector is not less than 500 MPa.

[0055] In a secondary battery, a high-strength current collector with a tensile strength ≥ 500 MPa can maintain a more stable structure during the processing of the battery. However, the traditional high-strength current collector has the problem of a large degree of polarization. The application of the traditional high-strength current collector to the battery may restrict the further improvement of the performance of the battery. In the current collector of the present embodiment, by designing the structure of the high-strength current collector, the thickness of the first region is greater than the thickness of the second region, which can correspondingly reduce the internal resistance of the first region, improve the current-carrying capacity of the first region, reduce the polarization degree of the high-strength current collector, and thus can improve the performance of the battery.

[0056] Further, in the preparation process of the battery, the first region can be used to lead out the current, and the first region usually needs to be welded. In the current collector of the present embodiment, the thickness of the first region is large, which can improve the welding performance of the first region and reduce the risk of welding cracks in the first region.

[0057] Further, in the current collector of the present embodiment, the thickness of the first region is large, which can reduce the risk of belt breakage during cold pressing, and thus can improve the production yield of the battery.

[0058] In some embodiments, the tensile strength of the whole of the current collector is ≥ 500 MPa, or the tensile strength of the whole of the current collector is ≥ 600 MPa, or the tensile strength of the whole of the current collector is ≥ 700 MPa, or the tensile strength of the whole of the current collector is ≥ 800 MPa, or the tensile strength of the whole of the current collector is ≥ 900 MPa, or the tensile strength of the whole of the current collector is ≥ 1000 MPa, or the tensile strength of the whole of the current collector is ≥ 1100 MPa, or the tensile strength of the whole of the current collector is ≥ 1200 MPa. Alternatively, the tensile strength of the whole of the current collector is 500-1200 MPa.

[0059] It can be understood that in the present application, the tensile strength can be tested as follows: a current collector sample with a length of 100 mm and a width of 15 mm is cut, with a precision of 0.05 mm, and clamped on the upper and lower clamps of a tensile testing machine, with a distance of 50 mm between the upper and lower clamps. The clamps are started and kept at 5 mm / min for stable loading, and the maximum load at which the sample is sheared and broken is recorded.

[0060] It can be understood that in the present application, the second region can be used for coating an active film layer, and in the preparation of an electrode tab, the active film layer is coated on at least one surface of the second region of the current collector. The first region is used for conducting current, and the first region is not coated with an active film layer, or a part of the first region is coated with an active film layer. The first region can be used as a tab, or an external tab can be welded.

[0061] It can also be understood that the first region and the second region are in contact, which can be direct contact between the first region and the second region, or contact between the first region and the second region through an intermediate region. For example, when the first region and the second region are in contact through an intermediate region, the first region and the second region can be in contact through a transition zone located between the first region and the second region.

[0062] Please refer to Figure 4 and Figure 5 , in which the thickness, length and width are shown. In Figure 4 and Figure 5 , the Z direction represents the thickness direction, X represents the length direction, and Y represents the width direction. Specifically, the thickness direction of the current collector is the Z direction. The direction of 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.

[0063] It can be understood that the schematic diagrams of the electrode tab and the current collector before slitting are shown in Figure 4 and Figure 5 . In the actual processing process, the Figure 4 and Figure 5The structure shown in FIG. 1 is slit along the center line in the length direction as a slitting position to obtain two slit electrode tabs and a current collector. In the present application, the length in the length direction refers to the length of the corresponding region of the electrode tab and the current collector after slitting.

[0064] In some embodiments, 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 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, etc. Figure 5 In some embodiments, the ratio of the width of the first region 71 to the width of the second region 72 is a. Optionally, 0.1 ≤ a ≤ 0.9, and 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 shown in FIG. 1. Figure 4 In some embodiments, the width W1 of the first region 71 and the width W2 of the second region 72 are as shown in FIG. 1. Figure 5 In some embodiments, the width W1 of the first region 71 and the width W2 of the second region 72 are as shown in FIG. 1.

[0065] It can be understood that for the current collector of the stacked battery, the width of the first region and the width of the second region respectively represent the width of the first region and the width of the second region of a single current collector. For the current collector of the 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, and the width of the second region represents the width of the entire second region of the current collector.

[0066] 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.

[0067] 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, 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. Further optionally, the thickness of the second region is 4 μm to 10 μm.

[0068] 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. Further optionally, the thickness of the first region is 4.5 μm to 17 μm.

[0069] In some embodiments, the first region has an elongation rate p1 and the second region has an elongation rate p2, and p1 / p2 satisfies: b≤p1 / p2≤10, where b is the ratio of the thickness of the first region to the thickness of the second region. A suitable p1 / p2 can reduce the risk of fish tail and cracking of the first region during cold pressing and welding, further improve the stability of the current collector structure, and thus improve the performance of the battery. When p1 / p2 is too small, the improvement effect is not obvious. When p1 / p2 is too large, the strength of the current collector may be low, and the risk of deformation of the first region increases.

[0070] In some embodiments, the material of the current collector includes at least one of nickel, iron, and stainless steel. At this time, the current collector can have a relatively high 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). Still further optionally, the mass ratio of nickel to iron in the nickel-iron alloy is 1:1, 2:3, 3:2, etc. Yet further optionally, the material of the first region and the material of the second region are the same.

[0071] Referring to Figure 4 and Figure 5 In some embodiments, the current collector 7 further includes a transition region 73, and the two ends of the transition region 73 are connected with the first region 71 and the second region 73, respectively. By providing the transition region, a relatively stable transition between the first region and the second region with different thicknesses can be achieved, and the stability of the current collector structure during processing can be improved.

[0072] In some embodiments, in the direction from the first region to the second region, the length of the transition region is 2-10 mm. Optionally, the length of the transition region is 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, etc.

[0073] In some embodiments, in the direction from the first region to the second region, the thickness of the transition region gradually decreases. In the direction from the first region to the second region, the thickness of the transition region gradually decreases, which can make the transition between the first region and the second region smoother. Optionally, the maximum thickness of the transition region is equal to the thickness of the end of the first region close to the transition region, and the minimum thickness of the transition region is equal to the thickness of the end of the second region close to the transition region.

[0074] Optionally, the second region is a second region with uniform thickness, i.e., the thickness of the second region is equal everywhere. Further optionally, the first region is a first region with uniform thickness, i.e., the thickness of the first region is equal everywhere.

[0075] Another embodiment of the present application provides an electrode tab, which includes the above-mentioned current collector 7 and an active film layer 8, and the active film layer 8 is arranged on at least one surface of the second region 72.

[0076] In some embodiments, the active film layer extends to part of the surface of the first region (not shown in the figure). At this time, the active film layer has a certain tension on the first region, which can effectively reduce the risk of collapse of the first region. Specifically, when coating the active film layer, the active slurry is coated on the second region, and the active slurry is coated on part of the surface of the first region. At this time, during the cold pressing process, the active slurry will form a certain tension on the first region, which can reduce the risk of collapse of the first region during subsequent processes such as cold pressing, and is beneficial to maintaining the stability of the current collector structure.

[0077] Optionally, 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, when the transition region is not provided, the first region and the second region are directly in contact, and at this time, L1-L2 can be represented as the length of the surface of the first region to which the active film layer extends. Optionally, L1-L2≥1mm. Further optionally, L1-L2≥1.2mm. Still further optionally, L1-L2≥1.5mm. Yet further optionally, L1-L2≥2mm. It can be understood that the active film layer extends to part of the surface of the first region, and L1-L2 is less than the length of the first region. Still further optionally, 0.5mm≤L1-L2≤15mm.

[0078] Referring to Figure 4 and Figure 5 In some embodiments, the current collector of the electrode tab further comprises a transition region, two ends of the transition region are connected with 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

[0079] Referring again to Figure 5 , the length L1 of the active film layer, the length L2 of the second region and the length L3 of the transition region are respectively exemplified in Figure 5 .

[0080] Optionally, in the direction from the first region to the second region, the length of the transition region is 2mm-10mm. Optionally, in the direction from the first region to the second region, the thickness of the transition region gradually decreases. Further optionally, the maximum thickness of the transition region is equal to the thickness of the end of the first region close to the transition region, and the minimum thickness of the transition region is equal to the thickness of the end of the second region close to the transition region.

[0081] The application also has an embodiment to provide a secondary battery, the positive electrode tab and / or the negative electrode tab of which is selected from the above electrode tab.

[0082] In some embodiments, the active film layer of the negative electrode tab includes at least one of graphite, soft carbon, hard carbon, silicon-based material, tin-based material, and lithium titanate. Optionally, the active film layer of the negative electrode tab includes graphite and silicon-based material. Further optionally, the active film layer of the negative electrode tab includes graphite and silicon-based material, wherein the mass ratio of graphite and silicon-based material is (3-5): 1. Still further optionally, the active film layer of the negative electrode tab includes graphite and silicon-based material, wherein the mass ratio of graphite and silicon-based material is 3:1, 3.5:1, 4:1, 4.5:1, 5:1, etc. When the current collector in the present application is matched with the silicon-based negative electrode active material, the expansion problem of the silicon-based material in the cold pressing process can be effectively improved, which is conducive to maintaining the stable structure of the negative electrode tab.

[0083] In some embodiments, the active film layer of the positive electrode tab 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 ternary material matched with the silicon-based material can better exert the energy density of the material, further improving the performance of the battery.

[0084] The present application also provides a preparation method of a current collector. The preparation method of the current collector includes the following steps: selecting a material of the current collector, the tensile strength of the material of the current collector is not less than 500 MPa; configuring the material of the current collector into an electroplating solution, and forming a second area for coating an active film layer and a first area for conducting current on a predetermined position of an electroplating carrier by electroplating through the electroplating solution, wherein the first area and the second area are controlled to be in contact, and the thickness of the first area is controlled to be greater than the thickness of the second area; and separating the product formed by electroplating from the electroplating carrier.

[0085] In some embodiments, when the thickness of the first area is controlled to be greater than the thickness of the second area, the thicknesses of the first area and the second area are adjusted by adjusting the current density of electroplating.

[0086] In one embodiment, the electroplating carrier is an electroplating roller. Optionally, the electroplating roller is as shown in Figure 6 The electroplating roller 9 includes a rotating shaft 91, a middle plating area 93 and an edge plating area 92 located at the outer edge of the rotating shaft 91. The edge plating area 92 is located at both ends of the middle plating area 93. In the electroplating process, the rotating shaft 91 rotates, and the edge plating area 92 and the middle plating area 93 are used for electroplating the first area and the second area, respectively.

[0087] Further, please refer to Figure 7 A transition area 94 is further provided between the edge plating area 92 and the middle plating area 93. At this time, in the electroplating process, the rotating shaft 91 rotates, and the edge plating area 92, the middle plating area 93, and the middle plating area 94 are used for electroplating the first area, the second area, and the transition area, respectively.

[0088] Optionally, the diameter of the edge plating area is slightly smaller than the diameter of the middle plating area. The material of the edge plating area has a higher electrical conductivity than the material of the middle plating area, for example, the material of the edge plating area is a copper-titanium alloy and the material of the middle plating area is titanium. Further optionally, an insulating ring can be arranged on the electroplating roller. Still further optionally, the edge plating area, the middle plating area and the transition area are supplied with different power sources, so that the thicknesses of the first area, the second area and the transition area of the current collector can be controlled respectively by controlling the current density.

[0089] The application also provides a battery module. The battery module comprises the secondary battery.

[0090] The application also provides a battery pack. The battery pack comprises the secondary battery or the battery module.

[0091] The application also provides a power utilization device. The power utilization device comprises at least one of the secondary battery, the battery module and the battery pack.

[0092] The secondary battery will be described below with reference to the relevant drawings.

[0093] Generally, the secondary battery comprises a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. During the charging and discharging of the battery, active ions are inserted into and extracted from the positive electrode sheet and the negative electrode sheet. The electrolyte conducts ions between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet and mainly prevents the short circuit of the positive electrode and the negative electrode while allowing ions to pass through.

[0094] [Positive electrode sheet]

[0095] The positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector.

[0096] For example, the positive electrode current collector has two opposite surfaces in the thickness direction thereof, and the positive electrode film layer is arranged on any one or both of the two opposite surfaces of the positive electrode current collector. Optionally, the positive electrode current collector is the current collector described above.

[0097] 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).

[0098] 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 the lithium-containing phosphate of olivine structure can include, but are not limited to, at least one of lithium iron phosphate, a composite of lithium iron phosphate and carbon, lithium manganese phosphate, a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite of lithium manganese iron phosphate and carbon. Optionally, the lithium iron phosphate includes LiFeP04(LFP). The lithium manganese phosphate includes LiMnP04.

[0099] In some embodiments, when the secondary battery is a sodium ion battery, the positive active material can employ a positive active material for a sodium ion battery known in the art. As an example, the positive active material can be used alone only one or in combination of two or more. Among them, the positive active material can be selected from sodium iron complex oxide, sodium cobalt complex oxide, sodium chromium complex oxide, sodium manganese complex oxide, sodium nickel complex oxide, sodium nickel titanium complex oxide, sodium nickel manganese complex oxide, sodium iron manganese complex oxide, sodium nickel cobalt manganese complex oxide, sodium iron phosphate compound, sodium manganese phosphate compound, sodium cobalt phosphate compound, Prussian blue-based material, polyanion material, etc., but the present application is not limited to these materials, and other conventionally known materials that can be used as a positive active material for a sodium ion battery can also be used. Optionally, the sodium iron complex oxide includes NaFe02. The sodium cobalt complex oxide includes NaCo02. The sodium chromium complex oxide includes NaCr02. The sodium manganese complex oxide includes NaMn02. The sodium nickel complex oxide includes NaNi02. The sodium nickel titanium complex oxide includes NaNiTi02. The sodium nickel manganese complex oxide includes NaNiMn02. The sodium iron manganese complex oxide includes NaFeMn02. The sodium nickel cobalt manganese complex oxide includes NaNiCoMn02. The sodium iron phosphate compound includes NaFeP04. The sodium manganese phosphate compound includes NaMnP04. The sodium cobalt phosphate compound includes NaCoP04. The polyanion material includes at least one of phosphate, fluorophosphate, pyrophosphate, and sulfate. 1 / 2 Ti 1 / 2 O2. The sodium nickel manganese complex oxide includes NaNi 1 / 2 Mn 1 / 2 O2. The sodium iron manganese complex oxide includes Na 2 / 3 Fe 1 / 3 Mn 2 / 3 O2. The sodium nickel cobalt manganese complex oxide includes NaNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2. The sodium iron phosphate compound includes NaFeP04. The sodium manganese phosphate compound includes NaMnP04. The sodium cobalt phosphate compound includes NaCoP04. The polyanion material includes at least one of phosphate, fluorophosphate, pyrophosphate, and sulfate.

[0100] In some embodiments, the positive electrode film layer can further optionally include a binder. As an example, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0101] In some embodiments, the positive electrode film layer can also optionally include a conductive agent. As an example, the conductive agent can include at least one of super-P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0102] In some embodiments, the positive electrode tab can be prepared by dispersing the above-mentioned components for preparing the positive electrode tab, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry on a positive electrode current collector; and drying, cold-pressing, or the like, to obtain the positive electrode tab. Optionally, the solvent includes N-methylpyrrolidone.

[0103] [Positive electrode tab]

[0104] The negative electrode tab includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer including a negative electrode active material.

[0105] As an example, the negative electrode current collector has two surfaces opposite in the thickness direction thereof, and the negative electrode film layer is disposed on either one or both of the two opposite surfaces of the negative electrode current collector. Optionally, the negative electrode current collector is the above-mentioned current collector.

[0106] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. As a metal foil, for example, a copper foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material on a polymer material base layer. Optionally, the metal material includes at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. The polymer material includes at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0107] In some embodiments, the negative electrode active material can be a negative electrode active material known in the art for use in a battery. As an example, the negative electrode active material can include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, and lithium titanate, etc. The silicon-based material can be selected from at least one of elemental silicon, silicon oxide compound, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy. The tin-based material can be selected from at least one of elemental tin, tin oxide compound, and tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as a negative electrode active material for a battery can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0108] In some embodiments, the negative film layer further optionally comprises a binder. The binder can 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), polyethylenimine (PEI), polyimide (PI), and t-butyl acrylate triethoxy vinyl silane (TBATEVS).

[0109] In some embodiments, the negative film layer further optionally comprises a conductive agent. The conductive agent can be selected from at least one of super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0110] In some embodiments, the negative film layer further optionally comprises other auxiliary agents, such as a thickening agent. Optionally, the thickening agent comprises sodium carboxymethyl cellulose (CMC-Na).

[0111] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as the negative active material, the conductive agent, the binder, and any other components, in a solvent to form a negative electrode slurry; coating the negative electrode slurry on a negative current collector, and after processes such as drying, cold pressing, etc., the negative electrode sheet can be obtained. Optionally, the solvent comprises deionized water.

[0112] [Electrolyte]

[0113] The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. The type of electrolyte is not specifically limited in the present application and can be selected as needed.

[0114] In some embodiments, the electrolyte comprises an electrolyte salt and a solvent.

[0115] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorobisoxalate borate, lithium bisoxalate borate, lithium difluorobisoxalate phosphate, and lithium tetrafluorobisoxalate phosphate.

[0116] In some embodiments, the solvent can 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, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclobutane sulfone, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0117] In some embodiments, the electrolyte solution can further optionally include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can further include an additive capable of improving certain performance of the battery, such as an additive capable of improving overcharge performance of the battery, an additive capable of improving high-temperature or low-temperature performance of the battery, and the like.

[0118] [Separator]

[0119] In some embodiments, a separator is further included in the secondary battery. The type of the separator is not particularly limited in the present application, and any known porous structure separator having good chemical stability and mechanical stability can be used.

[0120] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of the respective layers can be the same or different, and are not particularly limited.

[0121] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a stacking process.

[0122] In some embodiments, the secondary battery can include an outer package. The outer package can be used to package the electrode assembly and the electrolyte solution described above.

[0123] In some embodiments, the outer package of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, and the like. The outer package of the secondary battery can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, and as the plastic, polypropylene, polybutylene terephthalate, polybutylene succinate, and the like can be listed.

[0124] The shape of the secondary battery is not particularly limited in the present application, and can be cylindrical, square, or any other shape. For example, Figure 1 is a square structure secondary battery 5 as an example.

[0125] In some embodiments, with reference to Figure 2 , the outer package can include a shell 51 and a cover plate 53. The shell 51 can include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be provided on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is packaged in the receiving cavity. The electrolyte solution is impregnated in the electrode assembly 52. The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and a person skilled in the art can select according to the specific actual needs.

[0126] In some embodiments, the secondary battery can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0127] The application also provides a power consuming device comprising the secondary battery provided by the application. The secondary battery can be used as a power source of the power consuming device, or can be used as an energy storage unit of the power consuming device. The power consuming device can include a mobile device, an electric vehicle, an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto. For example, the mobile device includes a mobile phone, a notebook computer, etc. The electric vehicle includes a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.

[0128] As the power consuming device, the secondary battery can be selected according to the use requirement thereof.

[0129] Figure 3 The power consuming device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. as an example.

[0130] The device as another example can be a mobile phone, a tablet computer, a notebook computer, etc. The device usually requires thinning, and the secondary battery can be used as a power source.

[0131] Embodiments

[0132] Hereinafter, the embodiments of the application are described. The embodiments described below are exemplary and are only used to explain the application, and cannot be understood as a limitation of the application. If the specific technology or condition is not indicated in the embodiments, the technology or condition described in the literature in the art or according to the product instruction is used. If the reagent or instrument is not indicated by the manufacturer, it is a conventional product that can be obtained by market purchase.

[0133] Embodiment 1

[0134] In this embodiment, the material of the current collector is nickel-iron alloy, the first region and the second region are in direct contact, and the materials of the first region and the second region 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 between the first region and the second region, the ratio a of the width W1 of the first region to the width W2 of the second region = W1 / W2 = 0.2. The elongation rate p1 of the first region and the elongation rate p2 of the second region satisfy p1 / p2 = 2.1.

[0135] Embodiment 2

[0136] The structure of the current collector in this embodiment is shown in Figure 5 The transition zone is arranged between the first region and the second region. The material of the current collector is 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 a of the width W1 of the first region to the width W2 of the second region is a = W1 / W2 = 0.18. The elongation rate p1 of the first region and the elongation rate p2 of the second region satisfy p1 / p2 = 2.1.

[0137] Examples 3-17

[0138] Compared with Example 2, Examples 3-17 differ in 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 zone, and the specific differences are shown in Table 1.

[0139] Comparative Example 1

[0140] The current collector in this comparative example is a copper foil with a thickness of 6 μm.

[0141] Comparative Example 2

[0142] The current collector in this comparative example 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.

[0143] Comparative Example 3

[0144] Compared with Example 2, the difference between this comparative example and Example 2 is that the thickness of the first region is less than the thickness of the second region, and the specific differences are shown in Table 1. In the direction from the first region to the second region, the thickness of the transition zone gradually increases, realizing the connection between the first region and the second region.

[0145] Preparation of the battery

[0146] (1) Preparation of the negative electrode tab

[0147] The negative electrode active material, the CMC thickener, the SP conductive agent and the SBR binder are mixed uniformly in a mass ratio of 96.2:1.1:0.7:2, and then deionized water is added as a solvent. The system is stirred to be uniform under the action of a vacuum stirrer, and a negative electrode active slurry is obtained. The negative electrode active slurry is directly coated on the current collector of the examples and comparative examples, and a negative electrode tab is obtained by cold pressing. The negative electrode active material is a mixture of graphite and SiOx silicon-based material, and the mass ratio of graphite to silicon-based material is 4:1. 0 < x < 2.

[0148] (2) Preparation of the positive electrode tab

[0149] The positive electrode active material lithium iron phosphate, SP conductive agent, and PVDF binder were mixed uniformly in a mass ratio of 96.8:1:2.2, and then NMP was added as a solvent. The system was stirred under the action of a vacuum stirrer until it became uniform, to obtain a positive electrode active slurry. The positive electrode active slurry was directly coated on a 13 μm Al foil, and cold-pressed to obtain a positive electrode tab.

[0150] (3) Preparation of the electrolyte

[0151] The electrolyte solvent was EC:DMC=3:7, and the lithium salt was LiPF6, with a concentration of 1M.

[0152] (4) The positive electrode tab, the separator, and the negative electrode tab were stacked in order, with the separator in the middle of the positive and negative electrodes to play a separating role, and were wound to obtain a bare battery cell. The bare battery cell was placed in an outer package, electrolyte was injected, and the package was sealed to obtain a battery. The separator was a polyethylene separator.

[0153] Test example

[0154] (1) DCR was tested according to the conventional HPPC process, 3 cl of 0.33C rate charging and discharging was performed at an ambient temperature of 25°C, the 3 cl capacity was taken as the standard capacity CO, 4C0 discharging was performed for 30 s after charging to 50% SOC, the process data was recorded, the voltage difference between the 1 s voltage and the initial voltage was taken, DCR=1 s voltage difference / current. Unit: mΩ. The results are shown in Table 1.

[0155] (2) Capacity was tested at an ambient temperature of 25°C, 3 cl of 0.33C rate charging and discharging was performed, and the 3 cl capacity was taken. Unit: Ah. The results are shown in Table 1.

[0156] (3) The belt breaking frequency was tested during cold pressing production, the compaction density was 1.6 g / cm 3 , 100 m of the number of belt breaks was recorded, and the cold pressing speed was 20 m / min. Unit: times / 100 m. The results are shown in Table 1.

[0157] (4) The first area bruise frequency was the number of first area bruises during the die cutting / winding process of 100 m of the electrode tab. Unit: pieces / 100 m. The results are shown in Table 1.

[0158] (5) The welding abnormality frequency was the number of virtual welds or weld cracks during welding, totaling 50 ea. Unit: times / 50 ea. The results are shown in Table 1.

[0159] (6) The full-charging ductility test method is as follows: after winding, the wound body is disassembled, and three lines are drawn on the upper, middle and lower parts of the anode large surface at intervals of 100 mm, and a total of nine lines are drawn on the three large surfaces, the width value w1 of each interval is recorded, then the pole piece is wound again, assembled into a battery, and after the battery is fully charged at room temperature, the battery is disassembled, and the line width w2 is measured again, the ductility = (w2-w1) / w1*100%, and the average of the nine lines is taken. The results are shown in Table 1.

[0160] (7) The 100cls capacity retention rate is the ratio of the capacity after 100cls to the initial capacity under the condition of 0.5C / 0.5C charging and discharging at room temperature. The results are shown in Table 1.

[0161] Table 1

[0162]

[0163]

[0164] In Table 1, in the current collector material column, nickel: iron indicates that the material of the current collector is a nickel-iron alloy, and indicates the mass ratio of nickel and iron in the nickel-iron alloy. a indicates the width ratio of the first region and the second region.

[0165] As can be seen from Table 1, when the current collector uses a high-strength material, the thickness of the first region being greater than the thickness of the second region is beneficial to reduce the frequency of broken strips, the frequency of collisions and the frequency of welding abnormalities in the processing process, and also improves the cycle performance of the battery.

[0166] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and embodiments having the same technical idea and playing the same role and effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, within the scope of the main idea of the present application, various modifications that can be thought of by those skilled in the art, and other ways constructed by combining part of the components in the embodiments are also included in the scope of the present application.

Claims

1. A current collector characterized by comprising: The current collector comprises 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, the tensile strength of the whole current collector satisfies not less than 500 MPa; the thickness T1 of the first region and the thickness T2 of the second region satisfy: a≤T2 / T1≤0.99, wherein a is the ratio of the width of the first region to the width of the second region.

2. The current collector of claim 1, wherein The thickness T1 of the first region and the thickness T2 of the second region satisfy: 0.67≤T2 / T1≤0.

9.

3. The current collector of claim 1, wherein The elongation rate ρ1 of the first region and the elongation rate ρ2 of the second region satisfy: b≤ρ1 / ρ2≤10, wherein b is the ratio of the thickness of the first region to the thickness of the second region.

4. The current collector of claim 1, wherein The thickness of the second region is 3 μm~20 μm.

5. The current collector of claim 4, wherein The thickness of the second region is 4 μm~10 μm.

6. The current collector of claim 4, wherein The thickness of the first region is 3 μm~30 μm.

7. The current collector of claim 4, wherein The thickness of the first region is 4.5 μm~17 μm.

8. The current collector of claim 1, wherein The material of the current collector comprises at least one of nickel, iron and stainless steel.

9. The current collector of claim 8, wherein The stainless steel comprises a nickel-iron alloy.

10. The current collector of claim 9, wherein The mass ratio of nickel to iron in the nickel-iron alloy is (2~3):(2~3).

11. The current collector of any one of claims 1-10, wherein, Further comprising a transition region, two ends of the transition region are connected with the first region and the second region respectively.

12. The current collector of claim 11, wherein The transition region satisfies at least one of the following characteristics (1)~(2): (1) In the direction from the first region to the second region, the length of the transition region is 2 mm~10 mm; (2) In the direction from the first region to the second region, the thickness of the transition region gradually decreases.

13. The current collector of claim 12, wherein The maximum thickness of the transition region is equal to the thickness of one end of the first region close to the transition region, and the minimum thickness of the transition region is equal to the thickness of one end of the second region close to the transition region.

14. A method of making a current collector, characterized by, The method comprises the following steps: Selecting a material of a current collector, the tensile strength of the material of the current collector satisfies not less than 500 MPa; Configuring the material of the current collector into an electroplating solution, forming a first region and a second region on a predetermined position of an electroplating support by electroplating through the electroplating solution, 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; Separating the product formed by electroplating from the electroplating support.

15. The preparation method according to claim 14, characterized in that, When the thickness of the first region is controlled to be greater than the thickness of the second region, the thickness of the first region and the second region is adjusted by adjusting the current density of electroplating.

16. An electrode, characterized by The method comprises the current collector of any one of claims 1~13, and an active film layer, the active film layer is arranged on at least one surface of the second region.

17. The electrode patch of claim 16, wherein, The active film layer extends to part of the surface of the first region.

18. The electrode patch of claim 17, wherein, 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≥0.5 mm.

19. The electrode patch of claim 18, wherein, 0.5 mm≤L1-L2≤15 mm.

20. The electrode panel of any one of claims 16-19, wherein, The current collector further comprises a transition region, two ends of the transition region being connected with the first region and the second region respectively; in a direction from the first region to the second region, a length L1 of the active film layer, a length L2 of the second region, and a length L3 of the transition region satisfy: 0 < L1-L2-L3≤1mm.

21. The electrode patch of claim 20, wherein, The transition region satisfies at least one of the following characteristics (1) and (2): (1) in the direction from the first region to the second region, the length of the transition region is 2mm-10mm; (2) in the direction from the first region to the second region, the thickness of the transition region gradually decreases.

22. The electrode patch of claim 21, wherein, The maximum thickness of the transition region is equal to the thickness of one end of the first region close to the transition region, and the minimum thickness of the transition region is equal to the thickness of one end of the second region close to the transition region.

23. A secondary battery characterized by comprising: The positive electrode tab and / or the negative electrode tab is selected from the electrode tab of any one of claims 16-22.

24. The secondary battery according to claim 23, characterized by The active film layer of the negative electrode tab comprises at least one of graphite, soft carbon, hard carbon, silicon-based material, tin-based material, and lithium titanate.

25. The secondary battery according to claim 24, characterized by The active film layer of the negative electrode tab comprises graphite and silicon-based material.

26. The secondary battery according to claim 25, characterized by The mass ratio of graphite and silicon-based material is (3-5):

1.

27. The secondary battery according to any one of claims 23 to 26, characterized by The active film layer of the positive electrode tab comprises 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.

28. An electrical device, comprising: The secondary battery comprising any one of claims 23-27.

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