Secondary battery, electric device, and method for manufacturing electrode sheet

Abstract

The application discloses a secondary battery, an electric device and a manufacturing method of an electrode sheet. The secondary battery comprises a first electrode sheet, the first electrode sheet comprises a first current collector, a first active material layer, a second active material layer and a first tab, the first current collector comprises a first main body part and a first connecting part, the first active material layer is arranged on a first surface of the first main body part, and the second active material layer is arranged on a second surface of the first main body part. The first active material layer is provided with a first groove, the first connecting part is connected with the first main body part, and at least part of the first connecting part is located in the first groove. The first tab comprises a first part, the first part is welded with the first connecting part, a projection of the first part along a first direction is located in the first groove, and part of the first tab extends out of the first groove along a second direction; the second direction is perpendicular to the first direction. In the secondary battery, the first tab is connected with the first main body part through the first connecting part, and does not need to be directly welded to the first surface, so that the energy density of the secondary battery is improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of energy storage, and particularly relates to a secondary battery, a power consumption device, and a manufacturing method of an electrode sheet. BACKGROUND

[0002] For the existing secondary battery, the structure of welding the tab in the middle of the electrode sheet (MMT) is a common structure for connecting the current collector and the tab. When welding the current collector and the tab, if the ultrasonic welding method is used, the active material layer on both sides of the current collector along the thickness direction needs to be slotted in order to facilitate the cooperation of the welding head and the welding seat of the ultrasonic welding machine. This slotting method has a large capacity loss for the electrode sheet. If the laser welding method is used, the active material layer on only one surface of the current collector along the thickness direction can be slotted. However, the active material layer on the opposite side of the slot is easy to lose capacity under the influence of the high temperature generated during laser welding. Therefore, compared with ultrasonic welding, although laser welding only needs to slot the active material layer on one side of the current collector, the capacity of the secondary battery is not obviously improved. On this basis, for the secondary battery with multiple tabs connected on the same electrode sheet, the adverse effects of ultrasonic welding and laser welding on the capacity of the secondary battery will be further amplified. SUMMARY

[0003] In view of the above situation, it is necessary to provide a secondary battery, a power consumption device, and a manufacturing method of an electrode sheet to improve the capacity of the secondary battery.

[0004] A first aspect of an embodiment of the present application provides a secondary battery, comprising a first electrode sheet, a second electrode sheet, and a separator, the first electrode sheet, the separator, and the second electrode sheet are stacked along a first direction, the first direction being the thickness direction of the first electrode sheet. The first electrode sheet comprises a first current collector, a first active material layer, a second active material layer, and a first tab, the first current collector comprises a first main body part and a first connecting part, the first main body part comprises a first surface and a second surface oppositely arranged along the first direction, the first active material layer is arranged on the first surface, and the second active material layer is arranged on the second surface. The first active material layer is provided with a first slot, at least part of the projection of the first slot in the first direction is located within the projection area of the second active material layer, the first slot penetrates the first active material layer along the first direction, and part of the surface of the first surface is exposed in the first slot. The first connecting part connects the first main body part, and at least part of the first connecting part is located in the first slot. The first tab comprises a first part, the first part is welded to the first connecting part, the projection of the first part in the first direction is located in the first slot, part of the first tab extends out of the first slot along a second direction, and the second direction is perpendicular to the first direction; the thickness of the first connecting part in the first direction is less than the thickness of the first tab in the first direction.

[0005] In the secondary battery, the first tab is connected to the first body portion through the first connecting portion, and the first tab does not need to be directly welded to the surface of the portion of the first face exposed in the first groove, thereby facilitating reduction of the degree to which the portion of the second active material layer corresponding to the first groove in the first direction is affected by heat generated in the process of welding the first tab to the first current collector, so as to keep the capacity of the portion as much as possible and improve the energy density of the secondary battery. Moreover, at least part of the first connecting portion and part of the first tab are accommodated in the first groove, which facilitates reduction of the occupation of the first connecting portion and the first tab to the internal space of the shell of the secondary battery, thereby facilitating improvement of the energy density of the secondary battery.

[0006] In an optional embodiment of the present application, the first connecting portion includes a first end portion and a second end portion, the first end portion is integrally connected to the first body portion, the second end portion is located in the first groove, and the second end portion is stacked with the first body portion in the first direction; and the first portion is welded to the second end portion. The first connecting portion and the first body portion are in an integrated structure, which facilitates improvement of the stability of the connection between the first connecting portion and the first body portion, and the first connecting portion and the first body portion do not need to be welded, thereby further reducing the influence of the welding energy on the second active material layer.

[0007] In an optional embodiment of the present application, the length of the first groove in the second direction is L1, the length of the first connecting portion in the second direction is L in the flattened state of the first connecting portion, L1>L, and 0.1mm≤L1-L≤3mm. L1-L≤3mm is set to facilitate reduction of the difficulty in connecting the first connecting portion and the first tab and improvement of the production efficiency by preventing the length of the first connecting portion from being too short. 0.1mm≤L1-L is set to facilitate reduction of the thickness of the first connecting portion stacked in the first direction when the first connecting portion is accommodated in the first groove, thereby facilitating improvement of the energy density of the secondary battery by preventing the length of the first connecting portion from being too long.

[0008] In an optional embodiment of the present application, the width of the first groove in the third direction is W1, the width of the first connecting portion in the third direction is W, 0.1mm≤W1-W≤3mm, and the first direction, the second direction and the third direction are perpendicular to each other. W1-W≤3mm is set to facilitate reduction of the difficulty in welding the first connecting portion and the first tab by preventing the width of the first connecting portion from being too small. 0.1mm≤W1-W is set to facilitate reduction of the possibility that the edge of the first connecting portion in the third direction is too close to the edge of the first groove in the third direction, thereby facilitating reduction of the possibility that the first active material layer is extruded or rubbed by the first connecting portion to cause the active material of the first active material layer to fall off. i

[0009] ​In an optional embodiment of the present application, the first connecting part comprises a first end part, an intermediate part and a second end part, the second end part, the first end part and the first main part are sequentially stacked along the first direction, the first end part and the second end part extend along the second direction, the intermediate part connects the first end part and the second end part, the first end part is welded to the part surface of the first face exposed to the first groove, and the first part is welded to the second end part; the thickness of the first end part along the first direction is less than the thickness of the first tab along the first direction. The thickness of the first end part along the first direction is less than the thickness of the first tab along the first direction, and in the process of welding the first end part to the first face, compared with directly welding the first tab to the first face, the energy required for melting the first end part is less, in other words, the heat generated in the process of welding the first end part to the first face is less, which is beneficial to maintaining the capacity of the part of the second active material layer corresponding to the first groove along the first direction, thereby being beneficial to improving the energy density of the secondary battery.

[0010] In an optional embodiment of the present application, the thickness of the first end part along the first direction is T, 4 μ m≤T≤30 μ m. T≥4 is set μ m, the thickness of the first connecting part is not too small, which is beneficial to improving the structural strength of the first connecting part; T≤30 is set μ m, the thickness of the first connecting part is not too large, which is beneficial to reducing the energy required for welding the first connecting part and the first current collector, so as to maintain the capacity of the part of the second active material layer corresponding to the first groove along the first direction as much as possible.

[0011] In an optional embodiment of the present application, the first connecting part comprises a first end part, an intermediate part and a second end part, the second end part, the first end part and the first main part are sequentially stacked along the first direction, the first end part and the second end part extend along the second direction, the intermediate part connects the first end part and the second end part, the first end part is welded to the part surface of the first face exposed to the first groove, and the first part is welded to the second end part. The first end part is bonded to the first face, without welding, which is beneficial to further reducing the influence of the energy of welding on the second active material layer.

[0012] In an optional embodiment of the present application, the first slot has a length L1 along the second direction, and the first connecting portion has a length L along the second direction in the flattened state of the first connecting portion, L>L1, and 0.1mm≤L1-L / 2≤3mm. The setting of L1-L / 2≤3mm is to prevent the length of the first connecting portion from being too short, which is conducive to reducing the difficulty of connecting the first connecting portion and the first tab and improving the production efficiency. The setting of 0.1mm≤L1-L / 2 is to prevent the length of the first connecting portion from being too long, which is conducive to taking into account the thickness of the first connecting portion stacked along the first direction and the removal amount of the first active material layer for forming the first slot, thereby being conducive to improving the energy density of the secondary battery.

[0013] In an optional embodiment of the present application, the first slot has a width W1 along the third direction, and the first connecting portion has a width W along the third direction, 0.1mm≤W1-W≤3mm, and the first direction, the second direction and the third direction are perpendicular to each other. The setting of W1-W≤3mm is to prevent the width of the first connecting portion from being too small, which is conducive to reducing the difficulty of welding the first connecting portion and the first tab. The setting of 0.1mm≤W1-W is to prevent the edge of the first connecting portion along the third direction from being too close to the edge of the first slot along the third direction, which is conducive to reducing the possibility of the active material of the first active material layer falling off due to the extrusion or friction of the first connecting portion on the first active material layer.

[0014] In an optional embodiment of the present application, the secondary battery further comprises a first adhesive, and the first adhesive adheres the second end portion and the first end portion. In this way, it is conducive to reducing the possibility of tab shaking during use of the secondary battery.

[0015] In an optional embodiment of the present application, the secondary battery further comprises a first adhesive, and a part of the second end portion exceeds the first end portion along the second direction, and the first adhesive adheres the part of the second end portion exceeding the first end portion and the first current collector. In this way, it is conducive to reducing the possibility of tab shaking during use of the secondary battery.

[0016] In an optional embodiment of the present application, the second end portion is welded to the first end portion. In this way, it is conducive to reducing the possibility of tab shaking during use of the secondary battery.

[0017] In an optional embodiment of the present application, the first portion protrudes beyond the first slot in the first direction. The second tab includes a second current collector and a third active material layer connected to each other, and the third active material layer is arranged on a side of the second current collector facing the first tab in the first direction. The second tab includes a second adhesive member adhering to the third active material layer, and a projection of the second adhesive member in the first direction overlaps a projection of the first portion in the first direction. The second adhesive member adhering to the third active material layer can further reduce the possibility of the burr of the first portion piercing the separator and causing internal short circuit of the secondary battery.

[0018] In an optional embodiment of the present application, the first slot has a first opening facing the first direction, and the secondary battery includes a second adhesive member adhering to the first active material layer and covering the first portion and the first opening. The second adhesive member covering the first portion can reduce the possibility of the burr of the first portion piercing the separator and causing internal short circuit of the secondary battery.

[0019] In an optional embodiment of the present application, the second tab includes a second current collector and a third active material layer connected to each other, and the third active material layer is arranged on a side of the second current collector facing the first tab in the first direction. The secondary battery includes a third adhesive member adhering to the third active material layer, and a projection of the third adhesive member in the first direction overlaps a projection of the first portion in the first direction. The third adhesive member adhering to the third active material layer can further reduce the possibility of the burr of the first portion piercing the separator and causing internal short circuit of the secondary battery.

[0020] In an optional embodiment of the present application, the first tab is a positive tab, the second tab is a negative tab, a width of the first main portion in the second direction is less than a width of the second tab in the second direction, and an edge of the second tab in the second direction and on the same side as the first tab protrudes beyond the first tab. The first tab includes a second portion, the first portion and the second portion are arranged in sequence in the second direction, a projection of the second portion in the first direction overlaps a partial projection of the second tab in the first direction, and the secondary battery further includes a fourth adhesive member adhering to and covering a surface of the second portion facing the second tab.

[0021] A second aspect of the embodiments of the present application provides a power consumption device including the secondary battery according to any one of the preceding embodiments.

[0022] A third aspect of the embodiments of the present application provides a manufacturing method of a tab, including the following steps:

[0023] A first current collector is provided, and the first current collector includes a first surface, the first surface being a surface of the first current collector in a first direction, and the first direction being a thickness direction of the first current collector;

[0024] coating an active material on a part of the first surface to form a first active material layer, and a part of the first surface not coated with the first active material layer forms an empty foil area;

[0025] opening a first groove in the first active material layer, the first groove extending through the first active material layer along the first direction so that a part of the first surface is exposed to the first groove;

[0026] cutting the empty foil area to form a first connecting part;

[0027] welding the first tab and the first connecting part, the welding position of the first tab and the first connecting part being located outside the first groove;

[0028] bending the first connecting part so that a part of the first connecting part and a part of the first tab are accommodated in the first groove.

[0029] A fourth aspect of an embodiment of the present application provides a method for manufacturing a tab, comprising the following steps:

[0030] providing a first current collector, the first current collector comprising a first surface, the first surface being a surface of the first current collector along a first direction, the first direction being a thickness direction of the first current collector, and coating an active material on at least a part of the first surface to form a first active material layer;

[0031] opening a first groove in the first active material layer, the first groove extending through the first active material layer along the first direction so that a part of the first surface is exposed to the first groove;

[0032] taking a long strip-shaped metal foil as a first connecting part, and welding the first tab and the first connecting part;

[0033] welding the first connecting part and the surface of the first surface exposed to the first groove;

[0034] bending the first connecting part so that a part of the first tab is accommodated in the first groove. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is a schematic diagram of the overall structure of a secondary battery in an embodiment of the present application.

[0036] Figure 2 is a schematic diagram of the overall structure of a secondary battery in an embodiment of the present application. Figure 1 is a schematic diagram of the cross-sectional structure at II-II in

[0037] Figure 3 is a schematic diagram of the structure of a first tab in a flattened state in an embodiment of the present application.

[0038] Figure 4 is a schematic diagram of the cross-sectional structure at IV-IV in Figure 3

[0039] Figure 5 ​This is a cross-sectional structural diagram of the first electrode in one embodiment of this application.

[0040] Figure 6 yes Figure 2 Enlarged view of point A in the middle.

[0041] Figure 7 yes Figure 1 A schematic diagram of the cross-sectional structure at point VII-VII.

[0042] Figure 8 This is a schematic diagram of the structure of the first electrode and the fourth adhesive member in one embodiment of this application.

[0043] Figure 9 yes Figure 2 Enlarged view of point B in the middle.

[0044] Figure 10 This is a schematic diagram of the structure of the second electrode in one embodiment of this application.

[0045] Figure 11 yes Figure 10 Cross-sectional view at point XI-XI.

[0046] Figure 12 This is a schematic diagram of the structure of an electrical device in one embodiment of this application.

[0047] Figure 13 This is a schematic diagram of the structure of the first electrode in a preparation state in one embodiment of this application.

[0048] Figure 14 This is a schematic diagram of the structure of the first electrode in a preparation state in one embodiment of this application.

[0049] Figure 15 This is a schematic diagram of the structure of the first electrode in a preparation state in one embodiment of this application.

[0050] Explanation of main component symbols

[0051] 1000 rechargeable batteries

[0052] Electrode assembly 100

[0053] First Polaroid 10

[0054] First current collector 11

[0055] First Main Body Section 111

[0056] First 1111

[0057] First edge 1111a

[0058] Second edge 1111b

[0059] second surface 1112

[0060] third edge 1112a

[0061] fourth edge 1112b

[0062] first connecting portion 112

[0063] first end portion 1121

[0064] second end portion 1122

[0065] middle portion 1123

[0066] first active material layer 12

[0067] first groove 121

[0068] first opening 1211

[0069] second active material layer 13

[0070] second tab 20

[0071] second current collector 21

[0072] second main body portion 211

[0073] third surface 2111

[0074] fourth surface 2112

[0075] second connecting portion 212

[0076] third active material layer 22

[0077] second groove 221

[0078] third groove 222

[0079] fourth active material layer 23

[0080] separation film 30

[0081] first tab 40

[0082] first portion 41

[0083] second portion 42

[0084] second adhesive member 50

[0085] third adhesive member 60

[0086] fourth adhesive member 70

[0087] second tab 80

[0088] Third portion 81

[0089] Housing 200

[0090] Electric device 10000

[0091] First direction X

[0092] Second direction Y

[0093] Third direction Z

[0094] The following detailed description will further describe the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0095] 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 some of the embodiments of the present application, not all the embodiments.

[0096] 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 can exist simultaneously with a middle element. When an element is considered to be "provided" on another element, it can be directly provided on the other element or can exist simultaneously with a middle element.

[0097] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the specification of the present application is only for the purpose of describing specific embodiments and is not intended to limit the present application.

[0098] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly specified.

[0099] In the description of the embodiments of the present application, the term "vertical" is used to describe the ideal state between two components. In the actual production or use state, there can be an approximate vertical state between the two components. The two components described as "vertical" can not be an absolute straight line, plane, but can be approximately straight or planar, and the overall extension direction is a straight line or plane from a macroscopic point of view. The components can be considered as "straight line" or "plane".

[0100] Reference to“an embodiment” herein means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase“in an embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of one another. Various features that are described in the specification can be combined in any combination.

[0101] An embodiment of the application provides a secondary battery, comprising a first electrode sheet, a second electrode sheet and a separator, the first electrode sheet, the separator and the second electrode sheet are stacked along a first direction, the first direction being a thickness direction of the first electrode sheet. The first electrode sheet comprises a first current collector, a first active material layer, a second active material layer and a first tab, the first current collector comprises a first main body and a first connecting part, the first main body comprises a first surface and a second surface, the first surface and the second surface are oppositely arranged along the first direction, the first active material layer is arranged on the first surface, and the second active material layer is arranged on the second surface. The first active material layer is provided with a first groove, at least part of a projection of the first groove is located within a projection area of the second active material layer along the first direction, the first groove penetrates the first active material layer along the first direction, and part of the surface of the first surface is exposed in the first groove. The first connecting part is connected to the first main body, and at least part of the first connecting part is located in the first groove. The first tab comprises a first part, the first part is welded to the first connecting part, a projection of the first part along the first direction is located in the first groove, and part of the first tab extends out of the first groove along a second direction; the second direction is perpendicular to the first direction.

[0102] In the secondary battery, the first tab is connected to the first main body through the first connecting part, and the first tab does not need to be directly welded to the part of the surface of the first surface exposed in the first groove, thereby facilitating to reduce the degree of influence of the part of the second active material layer corresponding to the first groove along the first direction by heat generated in the process of welding the first tab to the first current collector, so as to keep the capacity of the part as much as possible and improve the energy density of the secondary battery. Moreover, at least part of the first connecting part and part of the first tab are accommodated in the first groove, thereby facilitating to reduce the occupation of the first connecting part and the first tab to the internal space of the shell of the secondary battery, so as to facilitate to improve the energy density of the secondary battery.

[0103] The embodiments of the application are further described below with reference to the drawings.

[0104] As shown in Figure 1 and Figure 2 An embodiment of the application provides a secondary battery 1000, comprising an electrode assembly 100 and a shell 200, the electrode assembly 100 is accommodated in the shell 200.

[0105] In some embodiments, the electrode assembly 100 includes a first tab 10, a second tab 20, and a separator 30, the first tab 10, the separator 30, and the second tab 20 are stacked along a first direction X, the first direction X being a thickness direction of the first tab 10.

[0106] In some embodiments, as shown in FIG. 1A, the first tab 10, the separator 30, and the second tab 20 are stacked along the first direction X and then wound to form a wound structure. Figure 2

[0107] In some embodiments, as shown in FIG. 1B, a plurality of the first tabs 10, a plurality of the separators 30, and a plurality of the second tabs 20 are stacked to form a laminated structure, and for any adjacent positive tab and negative tab, a separator 30 is arranged therebetween.

[0108] In some embodiments, as shown in FIG. 1C, the first tab 10 includes a first current collector 11, a first active material layer 12, a second active material layer 13, and a first tab 40, the first active material layer 12, the first current collector 11, and the second active material layer 13 are sequentially stacked along a first direction μ, and the first tab 40 is connected to the first current collector 11. The first direction X is a thickness direction of the first tab 10. Figure 2

[0109] In some embodiments, as shown in FIG. 1D, the second tab 20 includes a second current collector 21, a third active material layer 22, a fourth active material layer 23, and a second tab 80, the third active material layer 22, the second current collector 21, and the fourth active material layer 23 are sequentially stacked along the first direction X, and the second tab 80 is connected to the second current collector 21. Figure 2

[0110] In some embodiments, one of the first tab 10 and the second tab 20 is a positive tab, and the other is a negative tab. When the first tab 10 is a positive tab, the first current collector 11 is a positive current collector, the first active material layer 12 and the second active material layer 13 are positive active material layers, the first tab 40 is a positive tab, the second current collector 21 is a negative current collector, the third active material layer 22 and the fourth active material layer 23 are negative active material layers, and the second tab 80 is a negative tab. When the first tab 10 is a negative tab, the first current collector 11 is a negative current collector, the first active material layer 12 and the second active material layer 13 are negative active material layers, the first tab 40 is a negative tab, the second current collector 21 is a positive current collector, the third active material layer 22 and the fourth active material layer 23 are positive active material layers, and the second tab 80 is a positive tab.

[0111] In some embodiments, the positive current collector is a metal layer. As an exemplary example, the positive current collector can be a metal layer including at least one of aluminum, nickel, tantalum, titanium, such as an aluminum foil. ​​​

[0112] In some embodiments, the positive electrode active material layer includes a positive electrode active material, the positive electrode active material including at least one of lithium cobaltate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium iron phosphate, lithium manganese iron phosphate, or lithium manganate.

[0113] In some embodiments, the negative electrode tab includes a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer being provided to at least one side of the negative electrode current collector in a thickness direction thereof.

[0114] In some embodiments, the negative electrode current collector is a metal layer. As an illustrative example, the negative electrode current collector can be a metal layer including at least one of copper, nickel, tantalum, titanium, for example, a copper foil.

[0115] In some embodiments, at least one of the positive electrode current collector and the negative electrode current collector is a composite current collector.

[0116] In some embodiments, the negative electrode active material layer includes a negative electrode active material, the negative electrode active material including at least one of graphite, hard carbon, soft carbon, silicon, silicon-oxygen material, silicon-carbon material.

[0117] In some embodiments, the separator film 30 is an insulating film material such as a polyethylene film, a polypropylene film, a polyester film, or a polyimide film.

[0118] In some embodiments, the secondary battery 1000 further includes an electrolyte (not shown), the electrolyte being housed in the case.

[0119] In some embodiments, the electrolyte includes an electrolyte salt. The electrolyte salt includes at least one of an organic lithium salt or an inorganic lithium salt.

[0120] In some embodiments, the electrolyte salt includes, but is not limited to, at least one of lithium hexafluorophosphate (LiPF6), lithium bis-trifluoromethanesulfonimide LiN(CF3SO2)2 (LiTFSI), lithium bis(fluorosulfonyl)imide Li(N(SO2F)2) (LiFSI), lithium hexafluorocerate (LiCsF6), lithium perchlorate (LiClO4), or lithium trifluoromethanesulfonate (LiCF3SO3).

[0121] In some embodiments, as shown in FIG. 1, the first current collector 11 includes a first body portion 111 and a first connecting portion 112, the first body portion 111 including a first face 1111 and a second face 1112, the first face 1111 and the second face 1112 being oppositely disposed along a first direction X, the first active material layer 12 being provided to the first face 1111, and the second active material layer 13 being provided to the second face 1112. The first body portion 111 is connected to the first connecting portion 112, and the first tab 40 is welded to the first connecting portion 112. Figure 3 Figure 4 As shown in FIG. 1, the first current collector 11 includes a first body portion 111 and a first connecting portion 112, the first body portion 111 including a first face 1111 and a second face 1112, the first face 1111 and the second face 1112 being oppositely disposed along a first direction X, the first active material layer 12 being provided to the first face 1111, and the second active material layer 13 being provided to the second face 1112. The first body portion 111 is connected to the first connecting portion 112, and the first tab 40 is welded to the first connecting portion 112.

[0122] ​In some embodiments, such as Figure 3 and Figure 4 As shown, the first active material layer 12 has a first groove 121 along the first direction X, and at least a portion of the projection of the first groove 121 is located within the projection area of ​​the second active material layer 13. The first groove 121 penetrates the first active material layer 12 along the first direction X, and a portion of the surface of the first surface 1111 is exposed within the first groove 121. A first connecting portion 112 connects to the first main body portion 111, and at least a portion of the first connecting portion 112 is located within the first groove 121. The first electrode tab 40 includes a first portion 41, the first portion 41 is welded to the first connecting portion 112, and the projection of the first portion 41 along the first direction X is located within the first groove 121. A portion of the first electrode tab 40 extends out of the first groove 121 along the second direction Y. The thickness of the first connecting portion 112 along the first direction X is less than the thickness of the first electrode tab 40 along the first direction X. The second direction Y is perpendicular to the first direction X. The thickness of the first connecting portion 112 refers to the thickness of the first connecting portion 112 in its flattened state.

[0123] In this embodiment, the first tab 40 is connected to the first main body 111 via the first connecting portion 112. The first tab 40 does not need to be directly welded to the exposed surface of the first 1111 within the first groove 121. This helps to reduce the impact of heat generated during the welding process of the second active material layer 13 corresponding to the first groove 121 along the first direction X during the connection of the first tab 40 and the first current collector 11, thus preserving the capacity of that portion as much as possible and improving the energy density of the secondary battery 1000. Furthermore, at least a portion of the first connecting portion 112 and a portion of the first tab 40 are housed within the first groove 121, which helps to reduce the space occupied by the first connecting portion 112 and the first tab 40 within the internal space of the secondary battery 1000, thereby improving the energy density of the secondary battery 1000.

[0124] In some embodiments, the first groove 121 is formed by laser removal of a portion of the first active material layer 12.

[0125] In some embodiments, before the active material of the first active material layer 12 is coated, a portion of the surface of the first side 1111 is covered with adhesive tape. After the active material is coated and dried, the adhesive tape, along with the active material covering the surface of the adhesive tape, falls off, thereby forming the first groove 121.

[0126] In some embodiments, such as Figure 4As shown, the first connecting portion 112 includes a first end portion 1121 and a second end portion 1122, the first end portion 1121 is integrally connected with the first body portion 111, and the second end portion 1122 is located in the first groove 121 and is stacked with the first body portion 111 along the first direction X, and the first portion 41 is welded to the second end portion 1122. The first connecting portion 112 and the first body portion 111 are in an integrated structure, which is conducive to improving the stability of the connection between the first connecting portion 112 and the first body portion 111, and the first connecting portion 112 and the first body portion 111 do not need to be welded, which further reduces the influence of welding energy on the second active material layer 13.

[0127] The state in which the second end portion 1122 is stacked with the first body portion 111 is formed after the first connecting portion 112 is bent, and the extension direction of the first connecting portion 112 corresponds to the length direction of the first connecting portion 112 in the flattened state.

[0128] In order to improve the energy density of the secondary battery 1000, it is generally necessary to accommodate the first connecting portion 112 in the first groove 121 as much as possible to reduce the possibility of the first connecting portion 112 being stacked along the end surface of the electrode assembly 100 in the second direction Y. On this basis, if the energy density of the secondary battery 1000 is to be further improved, it is necessary to reduce the area of the projection of the first groove 121 along the first direction X, that is, to reduce the mass of the removed first active material layer 12. At this time, when the first connecting portion 112 is accommodated into the first groove 121, the thickness of the first connecting portion 112 stacked along the first direction X may increase, affecting the further improvement of the energy density of the secondary battery 1000. If the area of the projection of the first groove 121 along the first direction X is increased to reduce the thickness of the first connecting portion 112 stacked along the first direction X, the mass of the first active material layer 12 to be removed increases, also affecting the further improvement of the energy density of the secondary battery 1000.

[0129] Figure 13 The structure of the first tab 10 in a preparation state in an embodiment of the present application is shown, Figure 13 In the first end portion 1121 of the first connecting portion 112 is integrally connected with the first current collector 11, and part of the first tab 40 has not been folded into the first groove 121, and the first connecting portion 112 is in a flattened state.

[0130] In some embodiments, as Figure 13As shown, the first slot 121 has a length L1 along the second direction, and the first connecting portion 112 has a length L along the second direction in the flattened state of the first connecting portion 112, L1>L, and 0.1 mm≤L1-L≤3 mm. The setting of L1-L≤3 mm prevents the length of the first connecting portion from being too short, which is conducive to reducing the difficulty of connecting the first connecting portion and the first tab and improving the production efficiency. The setting of 0.1 mm≤L1-L prevents the length of the first connecting portion from being too long, which is conducive to reducing the thickness of the first connecting portion stacked along the first direction when the first connecting portion is accommodated in the first slot, thereby being conducive to improving the energy density of the secondary battery.

[0131] In some embodiments, as shown in FIG. 1, the first connecting portion 112 includes a first end portion 1121, an intermediate portion 1123, and a second end portion 1122, which are sequentially stacked along the first direction X, and the first end portion 1121 and the second end portion 1122 extend along the second direction Y, and the intermediate portion 1123 connects the first end portion 1121 and the second end portion 1122. Figure 5

[0132] In some embodiments, the first end portion 1121 is welded to a part of the surface of the first face 1111 exposed to the first slot 121, and the first portion 41 is welded to the second end portion 1122. The thickness of the first end portion 1121 along the first direction X is less than the thickness of the first tab 40 along the first direction X. Since the thickness of the first end portion 1121 along the first direction X is less than the thickness of the first tab 40 along the first direction X, less energy is required to melt the first end portion 1121 during welding of the first end portion 1121 and the first face 1111, in other words, less heat is generated during welding of the first end portion 1121 and the first face 1111, which is conducive to maintaining the capacity of the part of the second active material layer 13 corresponding to the first slot 121 along the first direction X, thereby being conducive to improving the energy density of the secondary battery 1000.

[0133] In some embodiments, as shown in FIG. 1, the first end portion 1121 and the second end portion 1122 are stacked in a state formed by bending the first connecting portion 112, and the extension direction of the first connecting portion 112 corresponds to the length direction of the first connecting portion 112 in the flattened state.

[0134] In some embodiments, as shown in FIG. 1, the first connecting portion 112 includes a first end portion 1121, an intermediate portion 1123, and a second end portion 1122, which are sequentially stacked along the first direction X, and the first end portion 1121 and the second end portion 1122 extend along the second direction Y, and the intermediate portion 1123 connects the first end portion 1121 and the second end portion 1122. Figure 4 Figure 5 ​​As shown, the thickness of the first end portion 1121 along the first direction X is T, and 4 pm≤T≤30 pm. T is set to be≥4 pm, so that the thickness of the first end portion 1121 is not too small, which is conducive to improving the structural strength of the first end portion 1121. T is set to be≤30 pm, so that the thickness of the first end portion 1121 is not too large, which is conducive to reducing the energy required for welding the first end portion 1121 and the first current collector 11, so as to maintain the capacity of the part of the second active material layer 13 corresponding to the first groove 121 along the first direction X as much as possible.

[0135] In the embodiments of the present application, the thickness of the first end portion 1121 can be measured by using a micrometer.

[0136] In some embodiments, the first end portion 1121 is bonded to the part of the surface of the first 1111 exposed to the first groove 121, and the first portion 41 is welded to the second end portion 1122. The first end portion 1121 is bonded to the first surface 1111, and does not need to be welded, which is conducive to further reducing the influence of the welding energy on the second active material layer 13.

[0137] Figure 14 Fig. 1 shows a structural schematic diagram of the first tab 10 in a preparation state in an embodiment of the present application, Figure 14 In the embodiment, the first end portion 1121 of the first connecting portion 112 is welded to the first current collector 11, and part of the first lug 40 has not been folded into the first groove 121, and the first connecting portion 112 is in a flat state.

[0138] In some embodiments, as shown in Fig. 1, Figure 14 As shown, 0.1 mm≤L1-L / 2≤3 mm. L1-L / 2 is set to be≤3 mm, so that the length of the first connecting portion 112 is not too short, which is conducive to reducing the difficulty of connecting the first connecting portion 112 and the first lug 40 and improving the production efficiency. L1-L / 2 is set to be≥0.1 mm, so that the length of the first connecting portion 112 is not too long, which is conducive to taking into account the thickness of the first connecting portion 112 stacked along the first direction X and the removal amount of the first active material layer 12 for forming the first groove 121 when the first connecting portion 112 is accommodated into the first groove 121, thereby being conducive to improving the energy density of the secondary battery 1000.

[0139] In some embodiments, as shown in Fig. 1, Figure 13 and Figure 14As shown, the first slot 121 has a width W1 along the third direction Z, and the first connecting portion 112 has a width W along the third direction Z, 0.1mm≤W1-W≤3mm; the first direction X, the second direction Y and the third direction Z are perpendicular to each other. By setting W1-W≤3mm, the width of the first connecting portion 112 is not too small, which is conducive to reducing the difficulty of welding the first connecting portion 112 and the first tab 40; by setting 0.1mm≤W1-W, the edge of the first connecting portion 112 along the third direction Z is not too close to the edge of the first slot 121 along the third direction Z, which is conducive to reducing the possibility of the active material of the first active material layer 12 falling off due to the extrusion or friction of the first active material layer 12 by the first connecting portion 112; and it is also conducive to reducing the possibility of the first connecting portion 112 and the first active material layer 12 being stacked when the first connecting portion 112 is folded during the production of the secondary battery 1000, so as to reduce the influence of the thickness of the first connecting portion on the thickness of the secondary battery.

[0140] In the embodiments of this application, the length L of the first connecting portion 112, the width W of the first connecting portion 112, the length L1 of the first slot 121 and the width W1 of the first slot 121 can all be measured by using a micrometer.

[0141] In some embodiments, as an exemplary example, the first connecting portion 112 is one of aluminum, nickel and copper, or the first connecting portion 112 is one of an aluminum alloy, a nickel alloy or a copper alloy.

[0142] In some embodiments, as shown, Figure 3 As shown, the first 1111 includes a first edge 1111a and a second edge 1111b oppositely arranged along the second direction Y, and the first active material layer 12 extends to the first edge 1111a and the second edge 1111b along the first direction X; the second surface 1112 includes a third edge 1112a and a fourth edge 1112b oppositely arranged along the second direction Y, and the second active material layer 13 extends to the third edge 1112a and the fourth edge 1112b along the second direction Y. In this way, it is conducive to fully utilizing the width of the first main body portion 111 of the first current collector 11 along the second direction Y, thereby facilitating increasing the coating area of the first active material layer 12 and the second active material layer 13, and improving the energy density of the secondary battery 1000.

[0143] In some embodiments, the secondary battery 1000 further includes a first adhesive (not shown in the figure), which bonds the second end portion 1122 and the first end portion 1121. In this way, it is conducive to reducing the possibility of tab shaking during use of the secondary battery 1000.

[0144] In some embodiments, the secondary battery 1000 further comprises a first adhesive (not shown in the figure), a portion of the second end portion 1122 is beyond the first end portion 1121 in the second direction Y, and the first adhesive adheres the portion of the second end portion 1122 beyond the first end portion 1121 and the first current collector. In this way, it is beneficial to reduce the possibility of the tab shaking during use of the secondary battery 1000.

[0145] In some embodiments, the first adhesive is conductive glue or epoxy resin glue.

[0146] In some embodiments, the conductive glue comprises a glue layer matrix and a conductive body, and the conductive body is dispersed in the glue layer matrix.

[0147] In some embodiments, the glue layer matrix comprises at least one of silicone rubber, polyurethane rubber, neoprene rubber, hot melt glue, tackifying resin.

[0148] In some embodiments, the conductive body comprises at least one of gold, silver, copper, aluminum, nickel, graphite.

[0149] In some embodiments, the first adhesive is adhesive tape.

[0150] In some embodiments, the second end portion 1122 is welded to the first end portion 1121. In this way, it is beneficial to reduce the possibility of the tab shaking during use of the secondary battery 1000.

[0151] In some embodiments, the first portion 41 is beyond the first slot 121 in the first direction X. The third active material layer 22 is arranged on a side of the second current collector 21 facing the first electrode tab 10 in the first direction X, and the third active material layer 22 is provided with a second slot 221, and a projection of the second slot 221 in the first direction X covers a projection of the first portion 41 in the first direction X. In this way, the portion of the first tab 40 beyond the first slot 121 in the first direction X can be at least partially accommodated in the second slot 221, which is beneficial to reduce the thickness of the secondary battery 1000 in the first direction X and improve the energy density of the secondary battery 1000.

[0152] In some embodiments, as shown in Figure 6 the first slot 121 has a first opening 1211 facing the first direction μ, and the secondary battery 1000 comprises a second adhesive 50, the second adhesive 50 is adhered to the first active material layer 12 and covers the first portion 41 and the first opening 1211. The second adhesive 50 covers the first portion 41, which is beneficial to reduce the possibility of the burr of the first portion 41 piercing the separator 30 and causing internal short circuit of the secondary battery 1000.

[0153] In some embodiments, as shown in Figure 6As shown, the third active material layer 22 is arranged on the side of the second current collector 21 facing the first tab 10 along the first direction μ. The secondary battery 1000 includes a third adhesive 60 bonding the third active material layer 22, and a projection of the third adhesive 60 along the first direction μ overlaps a projection of the first portion 41 along the first direction X. The third adhesive 60 is additionally arranged on the basis of the second adhesive 50, which is advantageous for further reducing the possibility of the burr of the first portion 41 penetrating the separator 30 and causing internal short circuit of the secondary battery 1000.

[0154] In some embodiments, the first tab 10 is a negative tab, the second tab 20 is a positive tab, and along the first direction X, the projection of the third adhesive 60 covers the projection of the second adhesive 50. In this way, it is advantageous to increase the CB (Cell Balance, ratio of unit area negative electrode capacity to unit area positive electrode capacity) of the positive and negative tabs, and to reduce the possibility of lithium precipitation phenomenon of the electrode assembly 100 during the cycle process.

[0155] In some embodiments, as shown in Figure 6 the first tab 10 is a positive tab, the second tab 20 is a negative tab, and along the first direction X, the projection of the second adhesive 50 covers the projection of the third adhesive 60. In this way, it is advantageous to increase the CB of the positive and negative tabs, and to reduce the possibility of lithium precipitation phenomenon of the electrode assembly 100 during the cycle process.

[0156] In some embodiments, as shown in Figure 7 and Figure 8 the first tab 10 is a positive tab, the second tab 20 is a negative tab, and the width of the first main body 111 along the second direction Y is less than the width of the second tab 20 along the second direction Y, and the edge of the second tab 20 along the second direction Y and on the same side as the first tab 40 exceeds the first tab 10. The first tab 40 includes a second portion 42, the first portion 41 and the second portion 42 are arranged in sequence along the second direction Y, and the projection of the second portion 42 along the first direction X coincides with the partial projection of the second tab 20 along the first direction c. The secondary battery 1000 further includes a fourth adhesive 70 bonding and covering the surface of the second portion 42 facing the second tab 20. In this way, it is advantageous to reduce the possibility of the burr of the second portion 42 penetrating the separator 30 and causing internal short circuit of the secondary battery 1000.

[0157] In some embodiments, at least one of the second adhesive 50, the third adhesive 60 and the fourth adhesive 70 is a gummed paper.

[0158] In some embodiments, the gummed paper includes a base material layer and a glue layer.

[0159] In some embodiments, the substrate layer can be selected from one of polyethylene terephthalate, co-extruded polypropylene, oriented polystyrene, thermoplastic polyurethane, polylactic acid, polyolefin, polyimide.

[0160] In some embodiments, the adhesive layer is made of one or a combination of several of natural rubber, styrene-butadiene rubber, isoprene rubber, styrene-polybutadiene-styrene block copolymer, hydrogenated styrene-polybutadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, hydrogenated styrene-polyisoprene-styrene block copolymer, polyisobutylene, amorphous alpha olefin copolymer, petroleum resin, terpene resin, rosin resin.

[0161] In some embodiments, as shown in FIG. 1, the second current collector 21 includes a second body portion 211 and a second connecting portion 212, the second body portion 211 includes a third face 2111 and a fourth face 2112, the third face 2111 and the fourth face 2112 are oppositely arranged along the first direction X, the third active material layer 22 is arranged on the third face 2111, and the fourth active material layer 23 is arranged on the fourth face 2112. The second body portion 211 is connected to the second connecting portion 212, and the second tab 80 is welded to the second connecting portion 212. Figure 9 to Figure 11 In some embodiments, as shown in FIG. 1, the fourth active material layer 23 is provided with a third groove 222, and at least part of the projection of the third groove 222 is located within the projection area of the third active material layer 22 along the first direction X. The third groove 222 penetrates the fourth active material layer 23 along the first direction X, and part of the surface of the fourth face 2112 is exposed in the third groove 222. The second connecting portion 212 is connected to the second body portion 212, and at least part of the second connecting portion 212 is located within the third groove 222; the second tab 80 includes a third portion 81, the third portion 81 is welded to the second connecting portion 212, the projection of the third portion 81 along the first direction X is located within the third groove 222, and part of the second tab 80 extends out of the third groove 222 along the second direction Y. The second tab 80 is connected to the second body portion 211 through the second connecting portion 212, and the second tab 80 does not need to be directly welded to the part of the surface of the fourth face 2112 exposed in the third groove 222. In the process of connecting the second tab 80 to the second current collector 21, the part of the third active material layer 22 corresponding to the third groove 222 along the first direction X is not affected by the heat generated by the welding process of the second tab 80, so that the capacity can be maintained, and the energy density of the secondary battery 1000 can be improved. Moreover, at least part of the second connecting portion 212 and part of the second tab 80 are accommodated in the third groove 222, which is conducive to reducing the occupation of the second connecting portion 212 and the second tab 80 to the internal space of the shell of the secondary battery 1000, thereby facilitating the improvement of the energy density of the secondary battery 1000.

[0162] Figure 9 to Figure 11 In some embodiments, as shown in FIG. 1, the fourth active material layer 23 is provided with a third groove 222, and at least part of the projection of the third groove 222 is located within the projection area of the third active material layer 22 along the first direction X. The third groove 222 penetrates the fourth active material layer 23 along the first direction X, and part of the surface of the fourth face 2112 is exposed in the third groove 222. The second connecting portion 212 is connected to the second body portion 212, and at least part of the second connecting portion 212 is located within the third groove 222; the second tab 80 includes a third portion 81, the third portion 81 is welded to the second connecting portion 212, the projection of the third portion 81 along the first direction X is located within the third groove 222, and part of the second tab 80 extends out of the third groove 222 along the second direction Y. The second tab 80 is connected to the second body portion 211 through the second connecting portion 212, and the second tab 80 does not need to be directly welded to the part of the surface of the fourth face 2112 exposed in the third groove 222. In the process of connecting the second tab 80 to the second current collector 21, the part of the third active material layer 22 corresponding to the third groove 222 along the first direction X is not affected by the heat generated by the welding process of the second tab 80, so that the capacity can be maintained, and the energy density of the secondary battery 1000 can be improved. Moreover, at least part of the second connecting portion 212 and part of the second tab 80 are accommodated in the third groove 222, which is conducive to reducing the occupation of the second connecting portion 212 and the second tab 80 to the internal space of the shell of the secondary battery 1000, thereby facilitating the improvement of the energy density of the secondary battery 1000. ​

[0163] As Figure 12 shown, embodiments of the present application also provide a power-using device 10000, which includes the secondary battery 1000 involved in any of the foregoing embodiments.

[0164] Embodiments of the present application provide a method for manufacturing a pole piece, which includes the following steps:

[0165] A first current collector 11 is provided, which includes a first surface 1111, which is a surface of the first current collector 11 along a first direction X, which is the thickness direction of the first current collector 11;

[0166] An active material is coated on part of the first surface 1111 to form a first active material layer 12, and the part without the first active material layer 12 forms an empty foil area;

[0167] A first slot 121 is opened in the first active material layer 12, which penetrates the first active material layer 12 along the first direction X, so that part of the first surface 1111 is exposed to the first slot 121;

[0168] The empty foil area is cut to form a first connecting part 112;

[0169] The first connecting part 112 and the first tab 40 are welded, and the welding position of the first connecting part 112 and the first tab 40 is located outside the first slot 121;

[0170] The first connecting part 112 is bent so that part of the first connecting part 112 and part of the first tab 40 are accommodated in the first slot 121.

[0171] Embodiments of the present application provide another method for manufacturing a pole piece, which includes the following steps:

[0172] A first current collector 11 is provided, which includes a first surface 1111, which is a surface of the first current collector 11 along a first direction μ, which is the thickness direction of the first current collector 11, and an active material is coated on at least part of the first surface 1111 to form a first active material layer 12;

[0173] A first slot 121 is opened in the first active material layer 12, which penetrates the first active material layer 12 along the first direction μ, so that part of the first surface 1111 is exposed to the first slot 121;

[0174] A long strip-shaped metal foil is taken as the first connecting part 112, and the first tab 40 and the first connecting part 112 are welded;

[0175] welding the first connecting portion 112 to the first 1111 surface exposed to the first groove 121;

[0176] bending the first connecting portion 112 such that the partial first tab 40 is accommodated in the first groove 121.

[0177] It should be noted that in the foregoing steps, the step of welding the first tab 40 to the first connecting portion 112 and the step of welding the first connecting portion 112 to the first current collector 11 are not strictly time-limited, i.e., the first tab 40 can be welded to the first connecting portion 112 first, then the first connecting portion 112 is welded to the first current collector 11, or the first connecting portion 112 is welded to the first current collector 11 first, then the first tab 40 is welded to the first connecting portion 112.

[0178] In some embodiments, as shown in FIG. 6, when welding the first tab 40 to the first connecting portion 112, the first tab 40 is welded to the surface of the first connecting portion 112 on the same side as the second surface 1112 in the first direction X, and the end of the first tab 40 not welded to the first connecting portion 112 is directed toward the middle of the first current collector 11 in the second direction Y, and then the first connecting portion 112 is bent (indicated by the curved arrow in FIG. 6) such that the first tab 40 and the first 1111 are on the same side of the first current collector 11. Figure 13 to Figure 15 Figure 15

[0179] Those skilled in the art should recognize that the above embodiments are only used to illustrate the present application, and are not used as a limitation to the present application, and as long as the above embodiments are within the spirit and scope of the present application, any suitable changes and variations made to the above embodiments are within the scope of the present application.​​

Claims

1. A secondary battery comprising a first electrode sheet, a second electrode sheet, and a separator, the first electrode sheet, the separator, and the second electrode sheet being stacked in a first direction, the first direction being a thickness direction of the first electrode sheet, characterized in that, the first electrode sheet comprises a first current collector, a first active material layer, a second active material layer, and a first tab, the first current collector comprises a first main body portion and a first connecting portion, the first main body portion comprises a first face and a second face that are oppositely disposed in the first direction, the first active material layer is provided on the first face, and the second active material layer is provided on the second face; the first active material layer is provided with a first groove, a projection of the first groove is at least partially located within a projection area of the second active material layer in the first direction, the first groove penetrates the first active material layer in the first direction, and a part of the surface of the first face is exposed in the first groove; the first connecting portion connects the first main body portion, and at least a part of the first connecting portion is located in the first groove; the first tab comprises a first portion, the first portion is welded to the first connecting portion, a projection of the first portion in the first direction is located in the first groove, and a part of the first tab extends out of the first groove in a second direction, the second direction being perpendicular to the first direction; a thickness of the first connecting portion in the first direction is smaller than a thickness of the first tab in the first direction.

2. The secondary battery according to claim 1, wherein the first connecting portion comprises a first end portion and a second end portion, the first end portion is integrally connected to the first main body portion, the second end portion is located in the first groove, and the second end portion and the first main body portion are stacked in the first direction; and the first portion is welded to the second end portion.

3. The secondary battery according to claim 2, wherein the first connecting portion satisfies at least one of the following conditions a and b: a.a length of the first groove in the second direction is L1, a length of the first connecting portion in the second direction is L in a flattened state of the first connecting portion, L1 > L, and 0.1 mm ≤ L1 - L ≤ 3 mm; b.a width of the first groove in a third direction is W1, a width of the first connecting portion in the third direction is W, 0.1 mm ≤ W1 - W ≤ 3 mm, and the first direction, the second direction, and the third direction are perpendicular to each other.

4. The secondary battery according to claim 1, wherein the first connecting portion comprises a first end portion, an intermediate portion, and a second end portion, the second end portion, the first end portion, and the first main body portion are sequentially stacked in the first direction, the first end portion and the second end portion extend in the second direction, the intermediate portion connects the first end portion and the second end portion, the first end portion is welded to a part of the surface of the first face exposed in the first groove, and the first portion is welded to the second end portion; a thickness of the first end portion in the first direction is smaller than a thickness of the first tab in the first direction.

5. The secondary battery according to claim 4, wherein a thickness of the first end portion in the first direction is T, and 4 μm ≤ T ≤ 30 μm.

6. The secondary battery according to claim 1, wherein The first connecting portion includes a first end portion, an intermediate portion, and a second end portion, the second end portion, the first end portion, and the first body portion are sequentially stacked along the first direction, the first end portion and the second end portion extend along the second direction, the intermediate portion connects the first end portion and the second end portion, the first end portion is bonded to the surface of the first face exposed to the first groove, and the first portion is welded to the second end portion.

7. The secondary battery according to claim 4 or 6, wherein The first connecting portion satisfies at least one of the following conditions c and d: c. The length of the first groove along the second direction is L1, the length of the first connecting portion along the second direction is L in a flattened state of the first connecting portion, L>L1, and 0.1mm≤L1-L / 2≤3mm; d. The width of the first groove along the third direction is W1, the width of the first connecting portion along the third direction is W, 0.1mm≤W1-W≤3mm, and the first direction, the second direction, and the third direction are perpendicular to each other.

8. The secondary battery according to claim 2 or 4 or 6, wherein The secondary battery satisfies at least one of the following conditions e, f, and g: e. The secondary battery further includes a first bonding member that bonds the second end portion and the first end portion; f. The secondary battery further includes a first bonding member, a portion of the second end portion protrudes beyond the first end portion along the second direction, and the first bonding member bonds the portion of the second end portion that protrudes beyond the first end portion and the first current collector; g. The second end portion is welded to the first end portion.

9. The secondary battery according to claim 1, wherein The first portion protrudes beyond the first groove along the first direction; The second tab includes a second current collector and a third active material layer connected to each other, the third active material layer is provided on a side of the second current collector facing the first tab along the first direction, and the third active material layer is provided with a second groove, a projection of the second groove along the first direction covers a projection of the first portion along the first direction.

10. The secondary battery according to claim 1, wherein The first groove has a first opening facing the first direction, and the secondary battery further includes a second bonding member bonded to the first active material layer and covering the first portion and the first opening.

11. The secondary battery according to claim 10, wherein The second tab includes a second current collector and a third active material layer connected to each other, the third active material layer is provided on a side of the second current collector facing the first tab along the first direction; The secondary battery includes a third bonding member that bonds the third active material layer, and a projection of the third bonding member along the first direction overlaps a projection of the first portion along the first direction.

12. The secondary battery according to claim 1, wherein The first tab is a positive tab, the second tab is a negative tab, the width of the first body portion along the second direction is smaller than the width of the second tab along the second direction, and an edge of the second tab along the second direction and on the same side as the first tab protrudes beyond the first tab; The first tab includes a second portion, the first portion and the second portion are sequentially arranged along the second direction, and a projection of the second portion along the first direction coincides with a partial projection of the second tab along the first direction; The secondary battery further includes a fourth adhesive member that adheres and covers a surface of the second portion facing the second tab.

13. An electrical device, characterized by A secondary battery including any one of claims 1-12.

14. A method of manufacturing a pole piece, characterized by, The method includes the steps of: providing a first current collector including a first face, the first face being a surface of the first current collector along a first direction, the first direction being a thickness direction of the first current collector; coating an active material on a portion of the first face to form a first active material layer, a portion of the first face not coated with the first active material layer forming an empty foil region; opening a first slot in the first active material layer, the first slot extending through the first active material layer along the first direction such that a portion of the first face is exposed in the first slot; cutting the empty foil region to form a first connecting portion; welding a first tab to the first connecting portion, the welding position of the first tab and the first connecting portion being outside the first slot; bending the first connecting portion such that a portion of the first connecting portion and a portion of the first tab are accommodated in the first slot.

15. A method of manufacturing an electrode sheet, characterized by, The method includes the steps of: providing a first current collector including a first face, the first face being a surface of the first current collector along a first direction, the first direction being a thickness direction of the first current collector, and coating an active material on at least a portion of the first face to form a first active material layer; opening a first slot in the first active material layer, the first slot extending through the first active material layer along the first direction such that a portion of the first face is exposed in the first slot; providing a first connecting portion in the form of a long strip-shaped metal foil, and welding a first tab to the first connecting portion; welding the first connecting portion to the surface of the first face exposed in the first slot; bending the first connecting portion such that a portion of the first tab is accommodated in the first slot.

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