Electrode sheet, battery cell, and electric device

Abstract

An electrode sheet, a battery cell, and an electric device. The electrode sheet comprises a current collector, a first transition layer, a second transition layer, two active material layers, a first conductive member, and a second conductive member. The current collector comprises a supporting layer, a first conductive layer, and a second conductive layer. The current collector further comprises a first section and a second section. The first transition layer is located in the first section. The second transition layer is located in the first section. One of the active material layers is arranged on the first transition layer, and the other of the active material layers is arranged on the second transition layer. The first conductive member is arranged on the first conductive layer. The second conductive member is arranged on the second conductive layer. The first conductive member and the second conductive member are welded and form a plurality of welding marks, and at least one welding mark is further connected to the current collector. The current collector further comprises a first part and a second part, the projection of an edge part of each active material layer adjacent to the welding marks and the projection of the first part overlap, and the second part is provided with welding marks. The tensile strength of the first part is smaller than that of the second part. The electrode sheet can improve the safety.

Description

Electrodes, battery cells and electrical equipment Technical Field

[0001] The present application relates to the field of energy storage technology, and in particular to a pole piece, a battery cell and an electrical device. Background Art

[0002] The existing composite current collector has a three-layer sandwich structure, with a central layer being a polymer layer and an outer layer being a metal layer. When the electrode piece made of the composite current collector is connected to the electrode terminal (such as the electrode tab), the composite current collector cannot be directly welded to the electrode terminal due to the polymer layer in the middle. It is necessary to weld an electrical connector between the metal layer and the electrode terminal to achieve electrical connection. When subjected to external force impact, the welding point of the electrical connector is prone to cracking to form peeling metal debris, which is easy to cause a short circuit and affect the safety of the electrode piece.

[0003] Summary of the Invention

[0004] In view of the above situation, it is necessary to provide a pole piece that can improve safety.

[0005] An embodiment of the present application provides a pole piece, which includes a current collector, a first transition layer, a second transition layer, two active material layers, a first conductive member, and a second conductive member. The current collector includes a support layer, and a first conductive layer and a second conductive layer arranged on both sides of the support layer in a first direction, where the first direction is the thickness direction of the current collector. The current collector also includes a first section and a second section arranged in sequence along a second direction, where the first direction is perpendicular to the second direction. The first transition layer is located in the first section and is arranged on the surface of the first conductive layer facing away from the support layer. The second transition layer is located in the first section and is arranged on the surface of the second conductive layer facing away from the support layer. One of the active material layers is arranged on the surface of the first transition layer facing away from the current collector, and the other active material layer is arranged on the surface of the second transition layer facing away from the current collector. The first conductive member is arranged on the surface of the first conductive layer facing away from the support layer, and one end of the first conductive member is located in the second section. When viewed along the first direction, the first conductive member is spaced apart from the first transition layer, and the other end of the first conductive member protrudes out of the current collector in the second direction. The second conductive member is disposed on a surface of the second conductive layer facing away from the support layer. One end of the second conductive member is located in the second section. When viewed in the first direction, the second conductive member is spaced apart from the second transition layer. The other end of the second conductive member protrudes out of the current collector in the second direction. The first and second conductive members are welded to form a plurality of weld marks arranged in the second direction, at least one of which is also connected to the current collector. The current collector further includes a first portion and a second portion. Along the first direction, the projection of an edge portion of the active material layer adjacent to the weld mark overlaps with the projection of the first portion, and the weld mark is disposed on the second portion. The tensile strength of the first portion is less than that of the second portion.

[0006] In the aforementioned pole piece, at least one weld mark is connected to the second portion of the current collector to enhance the tensile strength of the second portion. The tensile strength of the first portion is lower than that of the second portion, resulting in the second portion having greater tensile and bending resistance than the first portion. Even if the pole piece is damaged by an external impact and the first portion is damaged, the second portion can still maintain structural stability, reducing the risk of cracking of the weld mark, resulting in metal debris and causing a short circuit, thereby enhancing the safety of the pole piece.

[0007] In some embodiments of the present application, the tensile strength of the first portion is greater than 22 N / 15 mm to reduce the risk of the first portion being easily damaged by external forces due to low tensile strength. The tensile strength of the second portion is greater than 25 N / 15 mm to reduce the risk of the second portion being easily damaged by external forces due to low tensile strength.

[0008] In some embodiments of the present application, at least one of the weld marks is spaced apart from the current collector to improve the structural stability of the first conductive member and the second conductive member, and reduce the risk of the portion of the first conductive member or the second conductive member protruding out of the current collector being turned outward and causing a short circuit with other structural members.

[0009] In some embodiments of the present application, there are three weld marks, two of which are also connected to the current collector to increase the welding area between the weld mark and the current collector, thereby improving the stability of the connection between the weld mark and the current collector. The other weld mark is spaced apart from the current collector to improve the structural stability of the first and second conductive members and reduce the risk of the portion of the first or second conductive member protruding from the current collector being turned outward and causing a short circuit with other structural components.

[0010] In some embodiments of the present application, along the second direction, the spacing L1 between the first conductive member and the first transition layer satisfies the following conditions: 0.05 mm ≤ L1 ≤ 0.5 mm. This reduces the risk of the first conductive member and the first transition layer overlapping during processing, resulting in a short circuit between the first conductive member and other structural members in the first direction, and reduces the space occupied by the first conductive member in the second direction, which is beneficial for improving the energy density of the electrode. The spacing L2 between the second conductive member and the second transition layer satisfies the following conditions: 0.05 mm ≤ L2 ≤ 0.5 mm. This reduces the risk of the second conductive member and the second transition layer overlapping during processing, resulting in a short circuit between the second conductive member and other structural members in the first direction, and reduces the space occupied by the second conductive member in the second direction, which is beneficial for improving the energy density of the electrode.

[0011] In some embodiments of the present application, 0.2mm≤L1≤0.3mm is used to further reduce the risk of the first conductive member and the first transition layer overlapping during processing, resulting in a short circuit between the first conductive member and other structural members in the first direction, and to reduce the space occupied by the first conductive member in the second direction, which is beneficial to improving the energy density of the pole piece. 0.2mm≤L2≤0.3mm is used to further reduce the risk of the second conductive member and the second transition layer overlapping during processing, resulting in a short circuit between the second conductive member and other structural members in the first direction, and to reduce the space occupied by the second conductive member in the second direction, which is beneficial to improving the energy density of the pole piece.

[0012] In some embodiments of the present application, along the second direction, the spacing L3 between the first transition layer and the adjacent weld prints satisfies 0.05mm≤L3≤1mm; the spacing L4 between the second transition layer and the adjacent weld prints satisfies 0.05mm≤L4≤1mm, so as to reduce the risk of cold welding caused by the connection between the weld prints and the first transition layer and the second transition layer, and reduce the space occupied by the weld prints in the second direction, which is beneficial to improving the energy density of the electrode.

[0013] In some embodiments of the present application, 0.1mm≤L3≤0.2mm; 0.1mm≤L4≤0.2mm, so as to further reduce the risk of cold solder joints caused by the connection between the weld mark and the first transition layer and the second transition layer, and reduce the space occupied by the weld mark in the second direction, which is beneficial to improving the energy density of the electrode.

[0014] In some embodiments of the present application, when viewed along the first direction, the first transition layer includes two first outer edges that protrude from the corresponding active material layer on either side in the second direction, and the second transition layer includes two second outer edges that protrude from the corresponding active material layer on either side in the second direction. Along the second direction, the width of the first outer edges is 1 mm to 1.8 mm, while the width of the second outer edges is 1 mm to 1.8 mm. This minimizes space wastage caused by the portion of the first transition layer that protrudes beyond the corresponding active material layer while meeting manufacturing tolerance requirements.

[0015] In some embodiments of the present application, the width of the first outer edge portion is 1.6 mm to 1.8 mm; the width of the second outer edge portion is 1.6 mm ≤ L6 ≤ 1.8 mm, so as to further reduce the space waste caused by the portion of the first transition layer exceeding the corresponding active material layer while meeting the processing tolerance requirements.

[0016] In some embodiments of the present application, the width W1 of each weld mark along the second direction satisfies the following conditions: 1.5 mm ≤ W1 ≤ 4 mm, thereby improving connection strength, reducing the space occupied by the weld mark, and reducing the risk of interference with subsequent processes. The height H1 of each weld mark along the first direction satisfies the following conditions: 20 μm ≤ H1 ≤ 50 μm, thereby improving connection strength of the weld mark and reducing the risk of over-welding or cold solder joints.

[0017] In some embodiments of the present application, 1.6 mm ≤ W1 ≤ 2.2 mm to further improve connection strength, reduce the space occupied by the weld mark, and reduce the risk of interference with subsequent processes. 30 μm ≤ H1 ≤ 35 μm to further improve the connection strength of the weld mark and reduce the risk of over-welding or cold soldering.

[0018] In some embodiments of the present application, along the first direction, the thickness H2 of the current collector satisfies the following conditions: 4μm≤H2≤20μm, so as to meet the structural strength requirements of the current collector and reduce the space waste caused by the large space occupied by the current collector, which is beneficial to improving the energy density of the electrode. The thickness H3 of the first transition layer satisfies the following conditions: 0.5μm≤H3≤4μm, so as to improve the connection strength of the first transition layer and reduce the space waste caused by the first transition layer, which is beneficial to improving the energy density of the electrode. The thickness H4 of the second transition layer satisfies the following conditions: 0.5μm≤H4≤4μm, so as to improve the connection strength of the second transition layer and reduce the space waste caused by the second transition layer, which is beneficial to improving the energy density of the electrode.

[0019] In some embodiments of the present application, 6μm≤H2≤10μm is used to further meet the structural strength requirements of the current collector and reduce the space waste caused by the large space occupied by the current collector, which is beneficial to improving the energy density of the electrode. 1.5μm≤H3≤2.5μm is used to further improve the connection strength of the first transition layer and reduce the space waste caused by the first transition layer, which is beneficial to improving the energy density of the electrode. 1.5μm≤H4≤2.5μm is used to further improve the connection strength of the second transition layer and reduce the space waste caused by the first transition layer, which is beneficial to improving the energy density of the electrode.

[0020] In some embodiments of the present application, along the second direction, the width W2 of the second section satisfies 1mm≤W2≤5mm, so as to improve the connection strength between the second section and the first conductive member and the second conductive member, and reduce the space waste generated by the second section, which is conducive to improving the energy density of the pole piece.

[0021] In some embodiments of the present application, 1.5 mm ≤ W2 ≤ 2.2 mm, so as to further improve the connection strength between the second section and the first conductive member and the second conductive member, and reduce the space waste generated by the second section, which is beneficial to improving the energy density of the pole piece.

[0022] In some embodiments of the present application, the current collector further includes a third section. The third section is located along the second direction at an end of the first section away from the second section. The third section is used to connect to the electrode terminal. The width W3 of the third section satisfies 1 mm ≤ W3 ≤ 5 mm to improve the connection strength between the third section and the electrode terminal and reduce space waste in the third section, thereby facilitating increased energy density of the electrode sheet.

[0023] In some embodiments of the present application, the electrode sheet further includes two protective members, each located on either side of the current collector in the first direction. Two ends of one protective member are respectively bonded to the surface of the first conductive member facing away from the current collector and the surface of the corresponding edge of the active material layer facing away from the first transition layer. Two ends of the other protective member are respectively bonded to the surface of the second conductive member facing away from the current collector and the surface of the corresponding edge of the active material layer facing away from the second transition layer. The two protective members serve to improve the structural stability of the edge portion and to insulate the corresponding covered area from other structural members in the first direction, thereby reducing the risk of short circuits and improving the reliability of the electrode sheet.

[0024] In some embodiments of the present application, the first transition layer and the second transition layer respectively include inorganic materials, polymer materials and conductive particles, the inorganic materials include one or more of alumina, boehmite, silica, water-insoluble carbonates, and water-insoluble sulfates, the polymer materials include one or more of polyolefins, polyesters, and rubbers, and the conductive particles include one or more of conductive carbon and conductive carbon nanotubes.

[0025] An embodiment of the present application further provides a battery cell, which includes an electrode assembly, and the electrode assembly includes any one of the electrode sheets in the above embodiments.

[0026] An embodiment of the present application further provides an electrical device, comprising any one of the pole pieces in the above embodiments or any one of the battery cells in the above embodiments.

[0027] In the aforementioned pole piece, at least one weld mark is connected to the second portion of the current collector to enhance the tensile strength of the second portion. The tensile strength of the first portion is lower than that of the second portion, resulting in the second portion having greater tensile and bending resistance than the first portion. Even if the pole piece is damaged by an external impact and the first portion is damaged, the second portion can still maintain structural stability, reducing the risk of cracking of the weld mark, resulting in metal debris and causing a short circuit, thereby enhancing the safety of the pole piece. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG1 is a schematic plan view of a pole piece in one embodiment of the present application.

[0029] FIG2 is a cross-sectional view taken along the AA section line of FIG1 .

[0030] FIG3 is a plan view of a pole piece in another embodiment of the present application.

[0031] FIG4 is a cross-sectional view taken along the BB section line of FIG3 .

[0032] FIG5 is a schematic diagram of the structure of a battery cell in one embodiment of the present application.

[0033] FIG6 is a schematic structural diagram of an electrical device in an embodiment of the present application.

[0034] Description of main component symbols

[0035] Pole piece 100

[0036] Battery Cell 200

[0037] Electrical equipment 300

[0038] Current collector 10

[0039] First part 101

[0040] Second part 102

[0041] Support layer 11

[0042] First conductive layer 12

[0043] Second conductive layer 13

[0044] First section 10a

[0045] Second section 10b

[0046] The third section 10c

[0047] First transition layer 20

[0048] The first outer edge portion 21

[0049] Second transition layer 30

[0050] Second outer edge portion 31

[0051] Active material layer 40

[0052] Edge portion 40a

[0053] First conductive member 50

[0054] First gap 51

[0055] The second conductive member 60

[0056] Second gap 61

[0057] Protective member 70

[0058] Electrode assembly 201

[0059] First pole piece 100a

[0060] Second pole piece 100b

[0061] Diaphragm 80

[0062] Tab 202

[0063] Tab lead 203

[0064] First direction Z

[0065] Second direction X

[0066] The following specific implementation methods will further illustrate the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0067] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments.

[0068] It should be noted that when an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be a centrally located element. When an element is considered to be "set" on another element, it can be directly set on the other element or there may be a centrally located element. When a value is considered to be "equal" to another value, it means that the two values ​​are equal within a set deviation, and the set deviation range is within 5%. In other words, when at least one of the two values ​​fluctuates within the set deviation range, even if the values ​​are unequal, they are still judged to be approximately equal. When a value is considered to have a "1:1" ratio with another value, it means that the two values ​​are equal within a set deviation, and the set deviation range is within 5%. In other words, when at least one of the two values ​​fluctuates within the set deviation range, even if the values ​​are unequal, they are still judged to be equal in ratio.

[0069] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0070] It should be understood that, considering the factors of actual processing tolerance, the term "perpendicular" in the technical solution of this application is used to describe the ideal state between two components. In the actual production or use state, there may be a state that is approximately perpendicular between the two components. For example, in combination with the numerical description, perpendicularity can refer to the angle between two straight lines being between 90°±10°, perpendicularity can also refer to the dihedral angle between two planes being between 90°±10°, and perpendicularity can also refer to the angle between a straight line and a plane being between 90°±10°. The two components described as "perpendicular" may not be absolute straight lines or planes, but may be roughly straight lines or planes. From a macroscopic point of view, the components can be considered as "straight lines" or "planes" if the overall extension direction is a straight line or a plane.

[0071] An embodiment of the present application provides a pole piece, comprising a current collector, a first transition layer, a second transition layer, two active material layers, a first conductive member, and a second conductive member. The current collector comprises a support layer, and a first conductive layer and a second conductive layer disposed on either side of the support layer in a first direction, wherein the first direction is the thickness direction of the current collector. The current collector further comprises a first section and a second section disposed sequentially along a second direction, wherein the first direction is perpendicular to the second direction. The first transition layer is located in the first section and disposed on a surface of the first conductive layer facing away from the support layer. The second transition layer is located in the first section and disposed on a surface of the second conductive layer facing away from the support layer. One of the active material layers is disposed on a surface of the first transition layer facing away from the current collector, and the other active material layer is disposed on a surface of the second transition layer facing away from the current collector. The first conductive member is disposed on a surface of the first conductive layer facing away from the support layer, with one end of the first conductive member located in the second section. When viewed in the first direction, the first conductive member is spaced apart from the first transition layer, and the other end of the first conductive member protrudes out of the current collector in the second direction. A second conductive member is disposed on a surface of the second conductive layer facing away from the support layer. One end of the second conductive member is located in the second section. When viewed in the first direction, the second conductive member is spaced apart from the second transition layer. The other end of the second conductive member protrudes out of the current collector in the second direction. The first and second conductive members are welded to form a plurality of weld marks arranged in the second direction, at least one of which is also connected to the current collector. The current collector further includes a first portion and a second portion. Along the first direction, the projection of an edge portion of the active material layer adjacent to the weld mark overlaps with the projection of the first portion, and the weld mark is disposed on the second portion. The tensile strength of the first portion is less than that of the second portion.

[0072] In the aforementioned pole piece, at least one weld mark is connected to the second portion of the current collector to enhance the tensile strength of the second portion. The tensile strength of the first portion is lower than that of the second portion, resulting in the second portion having greater tensile and bending resistance than the first portion. Even if the pole piece is damaged by an external impact and the first portion is damaged, the second portion can still maintain structural stability, reducing the risk of cracking of the weld mark, resulting in metal debris and causing a short circuit, thereby enhancing the safety of the pole piece.

[0073] The embodiments of the present application are further described below with reference to the accompanying drawings.

[0074] Referring to Figures 1 and 2 , one embodiment of the present application provides an electrode sheet 100 . Electrode sheet 100 is used to form a battery cell for use in a secondary battery. A secondary battery is a battery that can be recharged after discharge to activate its active material for continued use. Electrode sheet 100 can optionally be a positive electrode sheet or a negative electrode sheet.

[0075] The pole piece 100 includes a current collector 10 , a first transition layer 20 , a second transition layer 30 , two active material layers 40 , a first conductive member 50 , a second conductive member 60 and two protective members 70 .

[0076] The current collector 10 is a composite current collector for collecting current. Specifically, the current collector 10 includes a support layer 11, and a first conductive layer 12 and a second conductive layer 13 disposed on both sides of the support layer 11 in a first direction Z. The first direction Z is the thickness direction of the current collector 10.

[0077] The support layer 11 is made of a polymer insulating material having high structural strength, low density and mass, and can reduce the thickness and weight of the current collector 10. Optionally, the polymer insulating material includes one or more of polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), polyimide (PI), polyetherketone (PEK), and polyphenylene sulfide (PPS).

[0078] First conductive layer 12 and second conductive layer 13 are made of a metal material. Compared to conventional metal current collectors, first conductive layer 12 and second conductive layer 13, disposed on both sides of support layer 11, are thinner. This helps reduce the generation of metal burrs when current collector 10 is mechanically damaged by external impact, thereby reducing the risk of short circuits. Optionally, the metal material includes one or more of aluminum, copper, nickel, silver, gold, and iron.

[0079] The current collector 10 further includes a first section 10a and a second section 10b sequentially arranged along a second direction Z. The first direction Z is perpendicular to the second direction X. Optionally, the second direction X is the width direction of the current collector 10. The first section 10a is used to connect the first transition layer 20 and the second transition layer 30, and the second section 10b is used to connect the first conductive member 50 and the second conductive member 60.

[0080] The first transition layer 20 is located in the first section 10a and is disposed on the surface of the first conductive layer 12 facing away from the support layer 11. The second transition layer 30 is also located in the first section 10a and is disposed on the surface of the second conductive layer 13 facing away from the support layer 11. The first transition layer 20 and the second transition layer 30 are respectively used to connect to the corresponding active material layer 40 to improve the connection strength between the active material layer 40 and the current collector 10. The first transition layer 20 and the second transition layer 30 also reduce the risk of sharp portions in the active material layer 40 puncturing the first conductive layer 12 or the second conductive layer 13.

[0081] The first transition layer 20 and the second transition layer 30 respectively include inorganic materials, polymer materials and conductive particles, the inorganic materials include one or more of aluminum oxide, boehmite, silicon dioxide, water-insoluble carbonates, and water-insoluble sulfates, the polymer materials include one or more of polyolefins, polyesters, and rubbers, and the conductive particles include one or more of conductive carbon and conductive carbon nanotubes.

[0082] One active material layer 40 is disposed on the surface of the first transition layer 20 facing away from the current collector 10, and the other active material layer 40 is disposed on the surface of the second transition layer 30 facing away from the current collector 10. The active material layers 40 are used to generate current, and the current generated by the active material layers 40 is collected on the current collector 10 through the corresponding first transition layer 20 and second transition layer 30.

[0083] In some embodiments, the active material layer 40 has a positive polarity and is coated on the surface of the first transition layer 20 facing away from the current collector 10 or the surface of the second transition layer 30 facing away from the current collector 10 by extrusion coating, transfer coating, spray coating, etc.

[0084] The coating weight of the active material layer 40 is 100 mg / 1540.25 mm 2 Up to 400mg / 1540.25mm 2 When the coating weight is too small (less than 100mg / 1540.25mm2), the energy density of the electrode 100 is likely to be too low; when the coating weight is too large (greater than 400mg / 1540.25mm2), it is likely to cause waste of ingredients. In severe cases, excessive capacity may occur, leading to dendrite precipitation, piercing the diaphragm and causing a short circuit, affecting the safety of the battery cell where the electrode 100 is located. By limiting the coating weight of the active material layer 40 to 100mg / 1540.25mm2 to 400mg / 1540.25mm2, the energy density of the electrode 100 can be increased, ingredient waste can be reduced, and the safety of the battery cell where the electrode 100 is located can be improved.

[0085] Optionally, the coating weight of the active material layer 40 can be any one of 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300, 310, 320, 330, 340, 350, 360, 370, 380, 390, 400, and the unit of the corresponding coating weight is mg / 1540.25mm2.

[0086] The first conductive member 50 is disposed on the surface of the first conductive layer 12 facing away from the support layer 11. One end of the first conductive member 50 is located in the second section 10b. When viewed along the first direction Z, the first conductive member 50 is spaced apart from the first transition layer 20, forming a first gap 51. This reduces the risk of overlap between the first conductive member 50 and the first transition layer 20, resulting in a short circuit between the first conductive member 50 and other structural components in the first direction Z. These other structural components may include, but are not limited to, adjacent pole pieces of different polarities. The other end of the first conductive member 50 protrudes beyond the current collector 10 in the second direction X to facilitate connection with the electrode terminal.

[0087] The second conductive member 60 is disposed on the surface of the second conductive layer 13 facing away from the support layer 11. One end of the second conductive member 60 is located in the second section 10b. When viewed along the first direction Z, the second conductive member 60 is spaced apart from the second transition layer 30, forming a second gap 61. This reduces the risk of overlap between the second conductive member 60 and the second transition layer 30, leading to a short circuit with other structural components in the first direction Z. These other structural components may include, but are not limited to, adjacent pole pieces of different polarities. The other end of the second conductive member 60 protrudes from the current collector 10 in the second direction X to facilitate connection with the electrode terminal.

[0088] Referring to Figures 1 and 2 , the first conductive member 50 and the second conductive member 60 are welded to form a plurality of weld marks 55 arranged along the second direction X. At least one weld mark 55 is connected to the current collector 10 to enhance the tensile strength of the corresponding portion of the current collector 10. Specifically, the first conductive member 50 and the second conductive member 60 are aluminum bars. The weld marks 55 connected to the current collector 10 are formed by roller welding the first conductive member 50, the second conductive member 60, and the current collector 10 positioned therebetween. The weld marks 55 penetrate the corresponding current collector 10 along the first direction Z to connect the first conductive member 50 and the second conductive member 60.

[0089] The current collector 10 also includes a first portion 101 and a second portion 102. The first portion 101 is located in the first section 10a, and the second portion 102 is located in the second section 10b. Along the first direction Z, the projection of the edge portion 40a of the active material layer 40 adjacent to the weld mark 55 overlaps with the projection of the first portion 101, and the second portion 102 is connected to the weld mark 55. The tensile strength of the first portion 101 is less than that of the second portion 102, so that the second portion 102 has better tensile and bending resistance than the first portion 101. If the pole piece 100 is damaged by an external impact and the first portion 101 is damaged, the second portion 102 can still maintain structural stability, reducing the risk of cracking of the weld mark 55 to form metal debris and cause a short circuit, thereby improving the safety of the pole piece 100.

[0090] Moreover, under the impact of external force, the first portion 101 is destroyed before the second portion 102 , which can also reduce the current collected by the current collector 10 , reduce the short circuit risk caused by large current when the weld mark 55 is destroyed, and further improve the safety of the electrode 100 .

[0091] It should be noted that the tensile strength of the first portion 101 and the second portion 102 was measured using the following tensile strength method. The pole piece 100 was cut into samples with a width of 15 mm, one of which included the first portion 101 and the other included the second portion 102. Each sample was stretched at a constant rate of 60 mm / min using a high-speed rail tensile testing machine, and the maximum tensile strength at the time of fracture of the first portion 101 and the maximum tensile strength at the time of fracture of the second portion 102 were recorded.

[0092] In the aforementioned pole piece 100, at least one weld mark 55 is connected to the second portion 102 of the current collector 10 to enhance the tensile strength of the second portion 102. The tensile strength of the first portion 101 is lower than that of the second portion 102, resulting in the second portion 102 having greater tensile and bending resistance than the first portion 101. If the pole piece 100 is subjected to an external impact that damages the first portion 101, the second portion 102 can still maintain structural stability, reducing the risk of cracking of the weld mark 55, forming metal debris and causing a short circuit, thereby enhancing the safety of the pole piece 100.

[0093] Referring to Figures 1 and 2 , in some embodiments, at least one weld mark 55 is spaced apart from the current collector 10 to improve the structural stability of the first conductive member 50 and the second conductive member 60 and reduce the risk of the portion of the first conductive member 50 or the second conductive member 60 protruding from the current collector 10 being turned outward and shorting with other structural components. Specifically, the weld mark 55 spaced apart from the current collector 10 is formed by roller welding the first conductive member 50 and the second conductive member 60.

[0094] In some embodiments, there are three weld marks 55, two of which are also connected to the current collector 10 to increase the welding area between the weld mark 55 and the current collector 10, thereby improving the stability of the connection between the weld mark 55 and the current collector 10. The other weld mark 55 is spaced apart from the current collector 10 to improve the structural stability of the first conductive member 50 and the second conductive member 60, and reduce the risk of the portion of the first conductive member 50 or the second conductive member 60 protruding from the current collector 10 being turned outward and causing a short circuit with other structural components.

[0095] Optionally, in other embodiments, the number of weld marks 55 can also be 2, 4, 5, 6, or any other natural number greater than 2.

[0096] In some embodiments, the tensile strength of the first portion 101 is greater than 22 N / 15 mm to reduce the risk of the first portion 101 being easily damaged by external forces due to a low tensile strength (less than 22 N / 15 mm). The tensile strength of the second portion 102 is greater than 25 N / 15 mm to reduce the risk of the second portion 102 being easily damaged by external forces due to a low tensile strength (less than 25 N / 15 mm).

[0097] Optionally, the tensile strength of the first portion 101 may be any one of 23 N / 15 mm, 24 N / 15 mm, 25 N / 15 mm, 26 N / 15 mm, 27 N / 15 mm, 28 N / 15 mm, 29 N / 15 mm, 30 N / 15 mm, or any other value greater than 22 N / 15 mm. Correspondingly, the tensile strength of the second portion 102 may be any one of 26 N / 15 mm, 27 N / 15 mm, 28 N / 15 mm, 29 N / 15 mm, 30 N / 15 mm, 31 N / 15 mm, 32 N / 15 mm, 33 N / 15 mm, 34 N / 15 mm, or any other value greater than 25 N / 15 mm.

[0098] It should be noted that the difference between the tensile strength of the second portion 102 and the tensile strength of the first portion 101 is at least 3N / 15mm. Optionally, the difference between the tensile strength of the second portion 102 and the first portion 101 is 3N / 15mm, 4N / 15mm, 5N / 15mm, 6N / 15mm, 7N / 15mm, or any other value greater than 3N / 15mm.

[0099] Please refer to Figures 1 and 2 together. In some embodiments, along the second direction X, the spacing L1 between the first conductive member 50 and the first transition layer 20 satisfies the following: 0.05mm≤L1≤0.5mm. When L1 is too small (less than 0.05mm), the first conductive member 50 and the first transition layer 20 may overlap during processing, resulting in a risk of the first conductive member 50 short-circuiting with other structural components in the first direction Z. When L1 is too large (greater than 0.5mm), the first conductive member 50 may occupy a large space in the second direction X, resulting in wasted space. By limiting the spacing to 0.05mm≤L1≤0.5mm, the risk of the first conductive member 50 short-circuiting with other structural components in the first direction Z due to overlap between the first conductive member 50 and the first transition layer 20 during processing is reduced, and the space occupied by the first conductive member 50 in the second direction X is reduced, which helps to improve the energy density of the pole piece 100.

[0100] Optionally, L1 may be 0.05 mm, 0.06 mm, 0.07 mm, 0.08 mm, 0.09 mm, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, and any other value within the range of 0.05 mm to 0.5 mm.

[0101] Furthermore, 0.2mm≤L1≤0.3mm can further reduce the risk of the first conductive member 50 and the first transition layer 20 overlapping during processing, resulting in a short circuit between the first conductive member 50 and other structural members in the first direction Z, and reduce the space occupied by the first conductive member 50 in the second direction X, which is beneficial to improving the energy density of the pole piece 100.

[0102] Please refer to Figures 1 and 2 together. In some embodiments, along the second direction X, the spacing L2 between the second conductive member 60 and the second transition layer 30 satisfies the following: 0.05mm≤L2≤0.5mm. When L2 is too small (less than 0.05mm), the second conductive member 60 and the second transition layer 30 may overlap during processing, resulting in a risk of the second conductive member 60 short-circuiting with other structural components in the first direction Z. When L2 is too large (greater than 0.5mm), the second conductive member 60 may occupy a large space in the second direction X, resulting in wasted space. By limiting the spacing to 0.05mm≤L2≤0.5mm, the risk of the second conductive member 60 short-circuiting with other structural components in the first direction Z due to overlap between the second conductive member 60 and the second transition layer 30 during processing is reduced, and the space occupied by the second conductive member 60 in the second direction X is reduced, which helps to improve the energy density of the pole piece 100.

[0103] Optionally, L2 may be 0.05 mm, 0.06 mm, 0.07 mm, 0.08 mm, 0.09 mm, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, and any other value within the range of 0.05 mm to 0.5 mm.

[0104] Furthermore, 0.2mm≤L2≤0.3mm can further reduce the risk of the second conductive member 60 and the second transition layer 30 overlapping during processing, resulting in a short circuit between the second conductive member 60 and other structural members in the first direction Z, and reduce the space occupied by the second conductive member 60 in the second direction X, which is beneficial to improving the energy density of the pole piece 100.

[0105] In some embodiments, L1=L2, and along the first direction Z, the projections of the first gap 51 and the second gap 61 coincide, so that the force positions between the first transition layer 20 and the first conductive member 50 and the force positions between the second transition layer 30 and the second conductive member 60 are roughly the same, which is beneficial to making the force on both sides of the current collector 10 uniform and improving the structural stability and reliability of the pole piece 100.

[0106] Referring to Figures 1 and 2 , in some embodiments, along the second direction X, the spacing L3 between the first transition layer 20 and adjacent weld marks 55 satisfies 0.05 mm ≤ L3 ≤ 1 mm; and the spacing L4 between the second transition layer 30 and adjacent weld marks 55 satisfies 0.05 mm ≤ L4 ≤ 1 mm. If the spacing between the first and second transition layers 20, 30 and the corresponding weld marks 55 is too small (less than 0.05 mm), the weld marks 55 may easily connect to the first and second transition layers 20, 30 during the formation process, resulting in the risk of a cold weld on the weld marks 55. If the spacing between the first and second transition layers 20, 30 and the corresponding weld marks 55 is too large (greater than 1 mm), the weld marks 55 may occupy a large space in the second direction X, resulting in wasted space. By limiting 0.05mm≤L3≤1mm and 0.05mm≤L4≤1mm, the risk of cold solder joints caused by the connection between the weld mark 55 and the first transition layer 20 and the second transition layer 30 is reduced, and the space occupied by the weld mark 55 in the second direction X is reduced, which is beneficial to improving the energy density of the electrode 100.

[0107] Optionally, L3 can be 0.05mm, 0.06mm, 0.07mm, 0.08mm, 0.09mm, 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, and any other value in the range of 0.05mm to 1mm; L4 can be 0.05mm, 0.06mm, 0.07mm, 0.08mm, 0.09mm, 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, and any other value in the range of 0.05mm to 1mm.

[0108] Furthermore, 0.1mm≤L3≤0.2mm; 0.1mm≤L4≤0.2mm, so as to further reduce the risk of cold soldering caused by the connection between the weld mark 55 and the first transition layer 20 and the second transition layer 30, and reduce the space occupied by the weld mark 55 in the second direction X, which is beneficial to improving the energy density of the electrode 100.

[0109] In some embodiments, L3=L4, so that the force position between the first transition layer 20 and the corresponding weld mark 55 and the force position between the second transition layer 30 and the corresponding weld mark 55 are roughly the same, which is beneficial to make the force on both sides of the current collector 10 uniform and improve the structural stability and reliability of the pole piece 100.

[0110] Referring to Figures 1 and 2 , in some embodiments, the width of the active material layer 40 on the first transition layer 20 along the second direction X is smaller than the width of the first transition layer 20. When viewed along the first direction Z, the first transition layer 20 includes two first outer edges 21 protruding from either side of the corresponding active material layer 40 in the second direction X. The width of the first outer edges 21 along the second direction X is 1 mm to 1.8 mm. If the width of the first outer edges 21 is too small (less than 1 mm), it is difficult to meet manufacturing tolerance requirements. If the width of the first outer edges 21 is too large (greater than 1.8 mm), the space occupied by the first outer edges 21 in the second direction X is large, resulting in wasted space. By limiting the width of the first outer edges 21 to 1 mm to 1.8 mm, the wasted space generated by the first outer edges 21 in the second direction X can be reduced while meeting manufacturing tolerance requirements.

[0111] Optionally, along the second direction X, the widths of the two first outer edge portions 21 are equal.

[0112] Optionally, the width of the first outer edge portion 21 may be 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, or any other value within the range of 1 mm to 1.8 mm.

[0113] Furthermore, the width of the first outer edge portion 21 is 1.6 mm to 1.8 mm, which further reduces the space waste generated by the first outer edge portion 21 in the second direction X while meeting the processing tolerance requirement.

[0114] Referring to Figures 1 and 2 , in some embodiments, the width of the active material layer 40 on the second transition layer 30 along the second direction X is smaller than the width of the second transition layer 30. When viewed along the first direction Z, the second transition layer 30 includes two second outer edges 31 protruding from either side of the corresponding active material layer 40 in the second direction X. The width of the second outer edges 31 along the second direction X is 1 mm to 1.8 mm. If the width of the second outer edges 31 is too small (less than 1 mm), it is difficult to meet manufacturing tolerance requirements. If the width of the second outer edges 31 is too large (greater than 1.8 mm), the space occupied by the second outer edges 31 in the second direction X is large, resulting in wasted space. By limiting the width of the second outer edges 31 to 1 mm to 1.8 mm, the wasted space generated by the second outer edges 31 in the second direction X can be reduced while meeting manufacturing tolerance requirements.

[0115] Optionally, along the second direction X, the widths of the two second outer edge portions 31 are equal.

[0116] Optionally, the width of the second outer edge portion 31 may be 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, or any other value within the range of 1 mm to 1.8 mm.

[0117] Furthermore, the width of the second outer edge portion 31 is 1.6 mm to 1.8 mm, which further reduces the space waste generated by the second outer edge portion 31 in the second direction X while meeting the processing tolerance requirement.

[0118] In some embodiments, the width of the first transition layer 20 and the width of the second transition layer 30 are equal along the second direction X. When viewed along the first direction Z, the projections of the first transition layer 20 and the second transition layer 30 are offset. The projection of the first transition layer 20 includes an offset region that does not overlap with the second transition layer 30. Correspondingly, the projection of the second transition layer 30 includes an offset region that does not overlap with the first transition layer 20. The two offset regions are spaced apart in the second direction X, and the widths of the two offset regions in the second direction X are equal and less than or equal to 2 mm. This facilitates defining the positional relationship between the active material layer 40, the first conductive member 50, and the second conductive member 60 during the production process by the first transition layer 20 and the second transition layer 30.

[0119] Optionally, the width of each misaligned area in the second direction X is 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2 mm, and any other value less than 2 mm.

[0120] It can be understood that the width of each dislocation region is 0, that is, along the first direction Z, the projection of the first transition layer 20 and the projection of the second transition layer 30 coincide with each other.

[0121] Referring to Figures 1 and 2 , in some embodiments, along the second direction X, the width W1 of each weld mark 55 satisfies the following conditions: 1.5 mm ≤ W1 ≤ 4 mm. A smaller width W1 (less than 1.5 mm) can lead to weaker connection strength. A larger width W1 (greater than 1.8 mm) can cause the weld mark 55 to occupy a larger space and interfere with the subsequent process of connecting the first conductive member 50 and the second conductive member 60 to the electrode terminals. By limiting the width W1 to 1.5 mm ≤ W1 ≤ 4 mm, the connection strength is improved, the space occupied by the weld mark 55 is reduced, and the risk of interference with subsequent processes is reduced.

[0122] Optionally, W1 can be 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm, 2mm, 2.1mm, 2.2mm, 2.3mm, 2.4mm, 2.5mm, 2.6mm, 2.7mm, 2.8mm, 2.9mm, 3mm, 3.1mm, 3.2mm, 3.3mm, 3.4mm, 3.5mm, 3.6mm, 3.7mm, 3.8mm, 3.9mm, 4mm, and any other value in the range of 1.5mm to 4mm.

[0123] Furthermore, 1.6 mm ≤ W1 ≤ 2.2 mm, so as to further improve the connection strength and reduce the space occupied by the weld mark 55, thereby reducing the risk of interference with subsequent processes.

[0124] Referring to Figures 1 and 2 , in some embodiments, along the first direction Z, the height H1 of each weld mark 55 satisfies the following conditions: 20 μm ≤ H1 ≤ 50 μm. When H1 is small (less than 20 μm), over-welding is more likely to occur during the welding process, causing the weld to break or fall off. When H1 is large (greater than 50 μm), cold solder joints are more likely to occur during the welding process, causing the weld to break or fall off. By limiting the range of 20 μm ≤ H1 ≤ 50 μm, the connection strength of the weld mark 55 is improved, reducing the risk of over-welding or cold solder joints.

[0125] Alternatively, H1 may be 20μm, 21μm, 22μm, 23μm, 24μm, 25μm, 26μm, 27μm, 28μm, 29μm, 30μm, 31μm, 32μm, 33μm, 34μm, 35μm, 36μm, 37μm, 38μm, 39μm, 40μm, 41μm, 42μm, 43μm, 44μm, 45μm, 46μm, 47μm, 48μm, 49μm, 50μm, and any other value in the range of 20μm to 50μm.

[0126] Furthermore, 30 μm≤H1≤35 μm, so as to further improve the connection strength of the weld mark 55 and reduce the risk of over-welding or cold welding.

[0127] Please refer to Figure 1 and Figure 2 together. In some embodiments, along the first direction Z, the thickness H2 of the current collector 10 satisfies: 4μm≤H2≤20μm, so as to meet the structural strength requirements of the current collector 10 and reduce the space waste caused by the large space occupied by the current collector 10, which is beneficial to improving the energy density of the electrode 100.

[0128] Alternatively, H2 may be 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, and any other value in the range of 4 μm to 20 μm.

[0129] Furthermore, 6 μm≤H2≤10 μm, so as to further meet the structural strength requirement of the current collector 10 and reduce the space waste caused by the large space occupied by the current collector 10 , which is beneficial to improving the energy density of the pole piece 100 .

[0130] Referring to Figures 1 and 2 , in some embodiments, along the first direction Z, the thickness H3 of the first transition layer 20 satisfies the following relationship: 0.5 μm ≤ H3 ≤ 4 μm. When H3 is too small (less than 0.5 μm), the connection strength of the first transition layer 20 is likely to be weak; when H3 is too large (greater than 4 μm), the first transition layer 20 occupies a large space, resulting in wasted space. By limiting the relationship to 0.5 μm ≤ H3 ≤ 4 μm, the connection strength of the first transition layer 20 is improved, and the wasted space generated by the first transition layer 20 is reduced, thereby increasing the energy density of the electrode 100.

[0131] Alternatively, H2 may be 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm, 3.5 μm, 3.6 μm, 3.7 μm, 3.8 μm, 3.9 μm, 4 μm, and any other value in the range of 0.5 μm to 4 μm.

[0132] Furthermore, 1.5 μm≤H3≤2.5 μm, so as to further improve the connection strength of the first transition layer 20 and reduce the space waste generated by the first transition layer 20, which is beneficial to improving the energy density of the pole piece 100.

[0133] Referring to Figures 1 and 2 , in some embodiments, along the first direction Z, the thickness H4 of the second transition layer 30 satisfies the following relationship: 0.5 μm ≤ H4 ≤ 4 μm. When H4 is too small (less than 0.5 μm), the connection strength of the second transition layer 30 is likely to be weak; when H4 is too large (greater than 4 μm), the second transition layer 30 occupies a large space, resulting in wasted space. By limiting the relationship to 0.5 μm ≤ H4 ≤ 4 μm, the connection strength of the second transition layer 30 is improved, and the wasted space generated by the second transition layer 30 is reduced, thereby increasing the energy density of the pole piece 100.

[0134] Alternatively, H2 may be 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm, 3.5 μm, 3.6 μm, 3.7 μm, 3.8 μm, 3.9 μm, 4 μm, and any other value in the range of 0.5 μm to 4 μm.

[0135] Furthermore, 1.5 μm≤H4≤2.5 μm, so as to further improve the connection strength of the second transition layer 30 and reduce the space waste generated by the second transition layer 30, which is beneficial to improving the energy density of the pole piece 100.

[0136] In some embodiments, H3 = H4, which is beneficial for making the forces on both sides of the current collector 10 uniform, thereby improving the structural stability and reliability of the pole piece 100 .

[0137] Referring to Figures 1 and 2 , in some embodiments, along the second direction X, the width W2 of the second segment 10b satisfies 1mm≤W2≤5mm. When W2 is too small (less than 1mm), the area where the second segment 10b connects to the first and second conductive members 50 and 60 is small, resulting in weak connection strength. When W2 is too large (greater than 5μm), the second segment 10b occupies a large space, resulting in wasted space. By limiting the range of 1mm≤W2≤5mm, the connection strength between the second segment 10b and the first and second conductive members 50 and 60 is improved, and the wasted space generated by the second segment 10b is reduced, which helps to increase the energy density of the pole piece 100.

[0138] Optionally, W2 may be 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, or any other value within the range of 1 mm to 5 mm.

[0139] Furthermore, 1.5 mm ≤ W2 ≤ 2.2 mm can further improve the connection strength between the second section 10 b and the first conductive member 50 and the second conductive member 60 , and reduce the space waste generated by the second section 10 b , which is beneficial to improving the energy density of the pole piece 100 .

[0140] Please refer to Figures 1 and 2 together. In some embodiments, the current collector 10 further includes a third section 10c. Along the second direction X, the third section 10c is located at the end of the first section 10a away from the second section 10b. The third section 10c is used to connect to the electrode terminal, and the width W3 of the third section satisfies 1mm≤W3≤5mm. When the width of the third section 10c is small (less than 1mm), it is easy to cause the area where the third section 10c is connected to the electrode terminal to be small, thereby resulting in weak connection strength; when the width of the third section 10c is large (greater than 5μm), it will cause the third section 10c to occupy a large space, resulting in space waste. By limiting 1mm≤W3≤5mm, the connection strength between the third section 10c and the electrode terminal is improved, and the space waste caused by the third section 10c is reduced, which is conducive to improving the energy density of the electrode sheet 100.

[0141] Referring to Figures 3 and 4 , in some embodiments, the electrode 100 further includes two protective members 70. The two protective members 70 are located on either side of the current collector 10 in the first direction Z. The protective members 70 comprise a polyolefin hot-melt adhesive and an inorganic salt pigment. The polyolefin hot-melt adhesive provides adhesion and insulation properties for the protective members 70, while the inorganic salt pigment imparts a color to distinguish the protective members 70 from other structural components. The two ends of one protective member 70 are respectively bonded to the surface of the first conductive member 50 facing away from the current collector 10 and the surface of the corresponding edge portion 40a of the active material layer 40 facing away from the first transition layer 20. The two ends of the other protective member 70 are respectively bonded to the surface of the second conductive member 60 facing away from the current collector 10 and the surface of the corresponding edge portion 40a of the active material layer 40 facing away from the second transition layer 30. The two protective members 70 enhance the structural stability of the edge portion 40a and insulate the corresponding covered area from other structural components in the first direction Z, reducing the risk of short circuits and improving the reliability of the electrode 100.

[0142] Please refer to FIG. 5 . An embodiment of the present application further provides a battery cell 200 , including an electrode assembly 201 . The electrode assembly 201 includes the electrode piece 100 in any of the above embodiments.

[0143] In some embodiments, the electrode assembly 201 includes a first electrode sheet 100a, a separator 80, and a second electrode sheet 100b stacked in sequence along a first direction Z. The first electrode sheet 100a has a positive polarity, and the second electrode sheet 100b has a negative polarity. At least one of the first electrode sheet 100a and the second electrode sheet 100b is an electrode sheet 100. When the first electrode sheet 100a is an electrode sheet 100, the corresponding active material layer 40 has a positive polarity. When the second electrode sheet 100b is an electrode sheet 100, the corresponding active material layer 40 has a negative polarity.

[0144] In some embodiments, the first electrode piece 100 a is the electrode piece 100 , and multiple first electrode pieces 100 a are spaced apart along a first direction Z. Projections of the second segments 10 b of the multiple first electrode pieces 100 a at least partially overlap along the first direction Z. The protective member 70 insulates the corresponding weld mark 55 from the adjacent second electrode piece 100 b, reducing the risk of internal short circuits in the battery cell 200 .

[0145] In some embodiments, the battery cell 200 further includes a plurality of tabs 202 and tab leads 203. One end of each tab 202 is connected to the first conductive member 50 and the second conductive member 60 of the first electrode sheet 100a, and the other end of each tab 202 extends outward. The outwardly extending ends of the plurality of tabs 202 are gathered and interconnected at one side of the electrode assembly 201 to connect to the tab leads 203. The tab leads 203 are used to connect to an external circuit.

[0146] In some embodiments, along the second direction X, the projection of the tab 202 is located within the projection range of the electrode assembly 201 , so as to improve the space utilization of the tab 202 on one side of the electrode assembly 201 , thereby improving the energy density of the battery cell 200 .

[0147] Optionally, the gathered parts of the plurality of tabs 202 are bent to facilitate connection with the tab leads 203 .

[0148] It is understood that in other embodiments, the electrode assembly 201 includes a first electrode sheet 100a, a separator 80, and a second electrode sheet 100b that are wound in sequence. The first electrode sheet 100a has a positive polarity, and the second electrode sheet 100b has a negative polarity. At least one of the first electrode sheet 100a and the second electrode sheet 100b is the electrode sheet 100.

[0149] Referring to FIG6 , one embodiment of the present application further provides an electric device 300, comprising the electrode 100 or the battery cell 200 of any of the above embodiments. The electric device 300 may be a vehicle, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy, or an electric tool.

[0150] In summary, in the aforementioned electrode sheet 100, battery cell 200, and electrical device 300, at least one weld mark 55 is connected to the second portion 102 of the current collector 10 to enhance the tensile strength of the second portion 102. The tensile strength of the first portion 101 is lower than that of the second portion 102, resulting in the second portion 102 having greater tensile and bending resistance than the first portion 101. Even if the electrode sheet 100 is damaged by an external impact, the second portion 102 can still maintain structural stability, reducing the risk of cracking of the weld mark 55, resulting in metal debris and causing a short circuit, thereby enhancing the safety of the electrode sheet 100.

[0151] In addition, those skilled in the art may also make other changes within the spirit of this application. Of course, these changes made according to the spirit of this application should be included in the scope disclosed in this application.

Claims

1. A pole piece, characterized in that: The pole piece comprises: A current collector, comprising a support layer, and a first conductive layer and a second conductive layer arranged on both sides of the support layer in a first direction, wherein the first direction is a thickness direction of the current collector, and the current collector further comprises a first section and a second section arranged in sequence along a second direction, wherein the first direction is perpendicular to the second direction; A first transition layer, located in the first section and disposed on a surface of the first conductive layer away from the support layer; A second transition layer, located in the first section and disposed on a surface of the second conductive layer away from the support layer; Two active material layers, one of which is disposed on the surface of the first transition layer away from the current collector, and the other of which is disposed on the surface of the second transition layer away from the current collector; a first conductive member, disposed on a surface of the first conductive layer away from the support layer, one end of the first conductive member being located in the second section, the first conductive member being spaced apart from the first transition layer when viewed along the first direction, and the other end of the first conductive member protruding out of the current collector in the second direction; a second conductive member, disposed on a surface of the second conductive layer away from the support layer, one end of the second conductive member being located in the second section, and the second conductive member being spaced apart from the second transition layer when viewed along the first direction, and the other end of the second conductive member protruding out of the current collector in the second direction; The first conductive member and the second conductive member are welded to form a plurality of weld marks arranged along the second direction, at least one of the weld marks is also connected to the current collector, the current collector further comprises a first portion and a second portion, along the first direction, a projection of an edge portion of the active material layer adjacent to the weld mark coincides with a projection of the first portion, the second portion is provided with the weld mark, and a tensile strength of the first portion is less than a tensile strength of the second portion.

2. The pole piece according to claim 1, characterized in that: The tensile strength of the first portion is greater than 22N / 15mm; the tensile strength of the second portion is greater than 25N / 15mm.

3. The pole piece according to claim 1, characterized in that: At least one of the weld marks is spaced apart from the current collector.

4. The pole piece according to claim 3, characterized in that: The number of the welding marks is three, two of which are also connected to the current collector, and the other welding mark is spaced apart from the current collector.

5. The pole piece according to claim 1, characterized in that: Along the second direction, a distance L1 between the first conductive member and the first transition layer satisfies: 0.05 mm≤L1≤0.5 mm; a distance L2 between the second conductive member and the second transition layer satisfies: 0.05 mm≤L2≤0.5 mm.

6. The pole piece according to claim 5, characterized in that: 0.2mm≤L1≤0.3mm; 0.2mm≤L2≤0.3mm.

7. The pole piece according to claim 1, characterized in that: Along the second direction, a distance L3 between the first transition layer and the adjacent weld marks satisfies 0.05 mm ≤ L3 ≤ 1 mm; a distance L4 between the second transition layer and the adjacent weld marks satisfies 0.05 mm ≤ L4 ≤ 1 mm.

8. The pole piece according to claim 7, characterized in that: 0.1mm≤L3≤0.2mm; 0.1mm≤L4 ≤0.2mm.

9. The pole piece according to claim 1, characterized in that: When viewed along the first direction, the first transition layer includes two first outer edges protruding from the corresponding two sides of the active material layer in the second direction, and the second transition layer includes two second outer edges protruding from the corresponding two sides of the active material layer in the second direction; Along the second direction, the width of the first outer edge portion is 1 mm to 1.8 mm; the width of the second outer edge portion is 1 mm to 1.8 mm.

10. The pole piece according to claim 9, characterized in that: The width of the first outer edge portion is 1.6 mm to 1.8 mm; the width of the second outer edge portion is 1.6 mm≤L6≤1.8 mm.

11. The pole piece according to claim 1, characterized in that: Along the second direction, the width W1 of each of the weld marks satisfies: 1.5 mm ≤ W1 ≤ 4 mm; along the first direction, the height H1 of each of the weld marks satisfies: 20 μm ≤ H1 ≤ 50 μm.

12. The pole piece according to claim 11, characterized in that: 1.6mm≤W1≤2.2mm; 30μm≤H1≤35μm.

13. The pole piece according to claim 1, characterized in that: Along the first direction, the thickness H2 of the current collector satisfies: 4 μm≤H2≤20 μm; the thickness H3 of the first transition layer satisfies: 0.5 μm≤H3≤4 μm; and the thickness H4 of the second transition layer satisfies: 0.5 μm≤H4≤4 μm.

14. The pole piece according to claim 13, characterized in that: 6μm≤H2≤10μm; 1.5μm≤H3≤2.5μm; 1.5μm≤H4≤2.5μm.

15. The pole piece according to claim 1, characterized in that: Along the second direction, a width W2 of the second section satisfies 1 mm ≤ W2 ≤ 5 mm.

16. The pole piece according to claim 15, characterized in that: 1.5mm≤W2≤2.2mm.

17. The pole piece according to claim 1, characterized in that: The current collector further includes a third section. Along the second direction, the third section is located at one end of the first section away from the second section. The third section is used to connect the electrode terminal. A width W3 of the third section satisfies 1mm≤W3≤5mm.

18. The pole piece according to claim 1, characterized in that: The pole piece also includes two protective members, which are respectively located on both sides of the current collector in the first direction, wherein two ends of one of the protective members are respectively bonded to the surface of the first conductive member facing away from the current collector and the surface of the corresponding edge of the active material layer facing away from the first transition layer, and two ends of the other protective member are respectively bonded to the surface of the second conductive member facing away from the current collector and the surface of the corresponding edge of the active material layer facing away from the second transition layer.

19. The pole piece according to claim 1, characterized in that: The first transition layer and the second transition layer respectively include inorganic materials, polymer materials and conductive particles, the inorganic materials include one or more of aluminum oxide, boehmite, silicon dioxide, water-insoluble carbonates, and water-insoluble sulfates, the polymer materials include one or more of polyolefins, polyesters, and rubbers, and the conductive particles include one or more of conductive carbon and conductive carbon nanotubes.

20. A battery cell, characterized in that: It comprises an electrode assembly, wherein the electrode assembly comprises a pole piece as claimed in any one of claims 1 to 19.

21. An electrical equipment, characterized in that: It comprises a pole piece as described in any one of claims 1 to 19 or a battery cell as described in claim 20.

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