A pole piece assembly, a method of manufacturing a pole piece assembly, and an electrochemical device

Abstract

The embodiment of the present application relates to the technical field of energy storage, and discloses a pole piece assembly, a manufacturing method of the pole piece assembly and an electrochemical device, the pole piece assembly comprising a pole piece and a tab, the pole piece comprising an active material layer and a current collector, the current collector having oppositely arranged first and second surfaces, the current collector being provided with a through hole extending from the first surface to the second surface, and the active material layer being stacked on the current collector; the tab comprising a body and a riveting portion, the body being provided with a through hole, the riveting portion comprising a shaft portion and an end portion, one end of the shaft portion being connected to the edge of the through hole, the end portion being connected to the other end of the shaft portion, the body abutting against the first surface of the current collector, the shaft portion being arranged in the through hole, and the end portion abutting against the second surface of the current collector; along the direction in which the active material layer is stacked on the current collector, the area of the projection of the through hole on the first surface is A, and the following condition is satisfied: 1mm 2 ≤ A ≤ 3mm 2 . In the above manner, the embodiment of the present application can improve the stability of the connection between the pole piece and the tab.

Description

Technical Field

[0001] The present invention relates to the field of energy storage technology, and in particular to an electrode assembly, a method for manufacturing the electrode assembly, and an electrochemical device. Background Technology

[0002] In current electrochemical devices, the electrode and the tab are connected by welding. The electrode releases electrical energy to the outside world through the tab, or the external power source charges the electrochemical device through the tab.

[0003] During the implementation of this invention, the inventors discovered that connecting the tabs and the electrode sheets by welding can easily result in defects such as incomplete or false welding, which affects the charge and discharge performance of the electrochemical device. Summary of the Invention

[0004] The main technical problem solved by the embodiments of the present invention is to provide an electrode assembly, a method for manufacturing an electrode assembly, and an electrochemical device that can improve the stability of the connection between the electrode and the tab.

[0005] To solve the above-mentioned technical problems, one technical solution adopted in this embodiment of the invention is as follows: An electrode assembly is provided, including an electrode and a tab. The electrode includes an active material layer and a current collector. The current collector has a first surface and a second surface disposed opposite to each other. The current collector has a through hole extending from the first surface to the second surface. The active material layer is stacked on the current collector. The tab includes a body and a riveting portion. The body has a through hole. The riveting portion includes a shaft portion and an end portion. One end of the shaft portion is connected to the edge of the through hole, and the end portion is connected to the other end of the shaft portion. The body abuts against the first surface of the current collector, the shaft portion passes through the through hole, and the end portion abuts against the second surface of the current collector. Along the direction in which the active material layer is stacked on the current collector, the area of ​​the through hole projected onto the first surface is A, and satisfies: 1 mm. 2 ≤A≤3mm 2 .

[0006] In this embodiment, by having the body of the electrode tab abut against the first surface of the current collector, and the shaft connecting the body and the end respectively, with the shaft passing through the through hole of the current collector and the end abutting against the second surface of the current collector, the electrode tab and the current collector are riveted together. This eliminates the need for welding to fix the electrode tab to the current collector, improving the stability of the connection between the electrode and the electrode tab, thereby enhancing the charge-discharge performance of the electrochemical device. Furthermore, by having the area of ​​the through hole projected onto the first surface be A, and A satisfying A≥1mm... 2 It can improve the welding pull between the tab and the electrode, and improve the pass rate of the electrochemical device in the external short test. When A is too large, it will cause too much current collector to be removed, resulting in a lower current collector riveting pull.

[0007] In some embodiments, an active material layer is stacked on the first surface of the current collector, the active material layer is provided with a clearance opening, and along the direction in which the active material layer is stacked on the current collector, the projection of the through hole is located within the clearance opening, and a portion of the body is received within the clearance opening.

[0008] In this embodiment, by providing a clearance opening in the active material layer, a portion of the main body is housed within the clearance opening, which helps to reduce the thickness of the electrode assembly and improve the energy density of the electrochemical device.

[0009] In some embodiments, there are multiple through holes, multiple through holes and multiple riveting portions. Multiple through holes are spaced apart. The shaft portion of a riveting portion is connected to the edge of a through hole. The shaft portion of a riveting portion passes through a through hole. The ends of multiple riveting portions abut against the second surface of the current collector.

[0010] In this embodiment, by providing multiple riveting parts, the connection strength between the tab and the electrode sheet can be improved, reducing the risk of the tab detaching from the electrode sheet.

[0011] In some embodiments, along the direction in which the active material is stacked in the current collector, the area A of the projection of each through hole onto the first surface of the current collector satisfies: 1 mm 2 ≤A≤2mm 2 .

[0012] In this embodiment, the area A of the projection of each through hole onto the first surface of the current collector is made to satisfy: 1 ​​mm. 2 ≤A≤2mm 2 This can improve the pass rate of electrode assembly during the riveting process, increase the success rate of electrochemical devices in external short-circuit testing, and enhance the riveting pull force, thereby improving the riveting strength between the electrode and the tab.

[0013] In some embodiments, along the direction in which the active material is stacked in the current collector, the area of ​​the body projected onto the current collector is S, the total area of ​​the projection of the plurality of through holes onto the first surface of the current collector is B, and satisfies: 0.2*S≤B≤0.5*S.

[0014] In this embodiment, by ensuring that S and B satisfy 0.2*S≤B≤0.5*S, both the riveting pull force and the pass rate of the external short test can be improved, thereby increasing the riveting strength between the electrode and the tab and improving the safety of the electrochemical device.

[0015] In some embodiments, along the direction in which the active material is stacked in the current collector, the area S of the projection of the body onto the first surface of the current collector and the total area B of the projection of the plurality of through holes onto the first surface of the current collector satisfy: 0.2*S≤B≤0.3*S.

[0016] In this embodiment, by ensuring that S and B satisfy 0.2*S≤B≤0.3*S, the pass rate of the electrode assembly during the riveting process can be further improved while enhancing the riveting strength between the electrode and the tab and improving the safety of the electrochemical device.

[0017] In some embodiments, the current collector includes a first metal layer, a polymer layer, and a second metal layer. The polymer layer is located between the first metal layer and the second metal layer. The surface of the first metal layer facing away from the second metal layer constitutes the first surface of the current collector, and the surface of the second metal layer facing away from the first metal layer constitutes the second surface of the current collector. The through-hole penetrates the first metal layer, the polymer layer, and the second metal layer.

[0018] In some embodiments, the body and the riveting part are integrally formed.

[0019] In some embodiments, when viewed along the direction in which the active material layer and the current collector are stacked, the through hole is rounded square in shape. In this embodiment, by making the through hole square or rectangular, welding pull force, process yield rate, and external shortness test pass rate can be balanced, thereby improving the mechanical and electrical properties of the electrode assembly.

[0020] In some embodiments, when viewed along the direction in which the active material layer and the current collector are stacked, the shape of the end is square. In this embodiment, by making the end shape square, the pass rate of the external shortness test and the step optimization rate can be improved.

[0021] To solve the above-mentioned technical problems, another technical solution adopted in this embodiment of the invention is to provide an electrochemical device, including the above-mentioned electrode assembly.

[0022] To address the aforementioned technical problems, an embodiment of the present invention also employs a technical solution: providing a method for manufacturing an electrode assembly, the method comprising:

[0023] An electrode is provided, the electrode comprising an active material layer and a current collector, the active material layer being stacked on the current collector;

[0024] The current collector is punched to form through holes.

[0025] Place the tabs on the current collector and observe along the direction in which the tabs are placed on the current collector; the tabs cover the through hole.

[0026] Along the direction in which the tabs are stacked on the current collector, the portion of the tabs covering the through hole is impacted to bend the portion of the tabs covering the through hole towards the through hole to form a punched portion, wherein the punched portion penetrates the through hole and protrudes from the surface of the current collector away from the tabs;

[0027] The portion of the punched part that protrudes from the surface of the current collector away from the electrode ear is riveted so that the portion of the punched part that protrudes from the surface of the current collector away from the electrode ear forms an end portion. The portion of the punched part excluding the end portion is a shaft portion. The shaft portion and the end portion together constitute a riveted part.

[0028] In some embodiments, the step of riveting the portion of the punched part protruding from the surface of the current collector opposite to the electrode tab, so that the portion of the punched part protruding from the surface of the current collector opposite to the electrode tab forms an end portion, wherein the portion of the punched part excluding the end portion is a shaft portion, and the shaft portion and the end portion together constitute a riveted portion, further includes:

[0029] The portion of the punched part protruding from the surface of the current collector opposite to the electrode tab is riveted to form an end portion. The portion of the punched part excluding the end portion is a shaft portion, and the shaft portion and the end portion together constitute a riveting joint. The pressure applied to the electrode tab and current collector during riveting is a flattening pressure F, satisfying: 100MPa≤F≤400MPa. In this embodiment, by satisfying 100MPa≤F≤400MPa, the riveting tensile force, step yield rate, and external shortness test pass rate can be increased, giving the electrode sheet good mechanical and electrical properties.

[0030] The beneficial effects of this invention are as follows: Unlike existing technologies, in this invention, by having the body of the tab abut against the first surface of the current collector, with the shaft connecting the body and the end respectively, the shaft passing through a through hole in the current collector, and the end abutting against the second surface of the current collector, a riveting fixation between the tab and the current collector is achieved. This eliminates the need for welding to fix the tab to the current collector, improving the stability of the connection between the electrode and the tab, thereby enhancing the charge / discharge performance of the electrochemical device. Furthermore, by having the area of ​​the through hole projected onto the first surface be A, and A satisfying 1 mm², [the invention achieves a more stable connection]. 2 ≤A≤3mm 2 This can improve the welding pull between the tab and the electrode, and increase the pass rate of the electrochemical device in the external short test, while avoiding the current collector riveting pull being too low. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in specific embodiments of the present invention or the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0032] Figure 1 This is a schematic diagram of the electrochemical device provided in the embodiments of the present invention;

[0033] Figure 2 yes Figure 1 A schematic diagram after being cut along line AA;

[0034] Figure 3 yes Figure 1 Another schematic diagram after cutting along line AA;

[0035] Figure 4 yes Figure 1 Another schematic diagram after cutting along line AA;

[0036] Figure 5 This is a schematic diagram of the electrode assembly provided in an embodiment of the present invention;

[0037] Figure 6 yes Figure 5 A schematic diagram showing the result after cutting along line BB;

[0038] Figure 7 This is a flowchart of a method for manufacturing an electrode assembly provided in an embodiment of the present invention.

[0039] Attached icon number

[0040] 1000, Electrochemical device; 100, Battery cell; 2, First electrode; 3, Second electrode;

[0041] 4. Separator; 1. Electrode assembly; 11. Electrode; 111. Active material layer; 1111. Clearance opening; 112. Current collector; 1121. First surface; 1122. Second surface; 1123. Through hole; 1124. First metal layer; 1125. Polymer layer; 1126. Second metal layer; 12. Tab; 121. Body; 1211. Through hole; 122. Riveting part; 1221. Shaft part; 1222. End; 200. Packaging shell; Detailed Implementation

[0042] To facilitate understanding of the present invention, a more detailed description is provided below with reference to the accompanying drawings and specific embodiments. It should be noted that when an element is described as being "fixed to" another element, it can be directly on the other element, or one or more intermediate elements may exist between them. When an element is described as being "connected" to another element, it can be directly connected to the other element, or one or more intermediate elements may exist between them. The terms "upper," "lower," "inner," "outer," "vertical," "horizontal," etc., used in this specification indicate orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0043] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "and / or" as used in this specification includes any and all combinations of one or more of the associated listed items.

[0044] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0045] Please combine Figure 1-4 One embodiment of this application provides an electrochemical device 1000, which includes a packaging shell 200 and a battery cell 100. The battery cell 100 is disposed within the packaging shell 200, which protects the battery cell 100. The battery cell 100 includes a first electrode 2, a second electrode 3, and a separator, with the separator located between the first electrode 2 and the second electrode 3.

[0046] Understandably, the battery cell 100 can be either a wound structure or a laminated structure. When the battery cell 100 is a wound structure, such as... Figure 2 As shown, the first electrode 2, the second electrode 3, and the separator 4 are stacked and wound together. When the cell 100 adopts a stacked structure, as shown... Figure 3 or Figure 4 As shown, there are multiple first electrode 2, second electrode 3, and separator 4. These multiple first electrode 2, second electrode 3, and separator 4 are stacked along one direction, with separator 4 placed between adjacent first electrode 2 and second electrode 3. The thickness direction of the cell 100 can be the same as or different from the thickness direction of the electrochemical device 1000, such as... Figure 3As shown, the thickness direction of the battery cell 100 is the same as the thickness direction of the electrochemical device 1000, as... Figure 4 As shown, the thickness direction of the battery cell 100 is perpendicular to the thickness direction of the electrochemical device 1000.

[0047] To facilitate understanding of the structure of the first electrode 2 and / or the second electrode 3 of this application, please refer to... Figure 5 and Figure 6 In the following description, electrode assembly 1 will be used to refer to the first electrode 2 and / or the second electrode 3. Of course, the structure of electrode assembly 1 described below may be applicable only to the first electrode 2 or the second electrode 3, or it may be applicable to both, depending on the specific needs. The structure of electrode assembly 1 provided in the embodiments of this application will be described in detail below.

[0048] Please see Figure 5 and Figure 6 The electrode assembly 1 includes an electrode 11 and a tab 12. The electrode 11 includes an active material layer 111 and a current collector 112. The current collector 112 has a first surface 1121 and a second surface 1122 disposed opposite to each other. The current collector 112 is provided with a through hole 1123, which extends from the first surface 1121 to the second surface 1122. The active material layer 111 is stacked on the current collector 112. The tab 12 includes a body 121 and a riveting portion 122. The body 121 is provided with a through hole 1211. The riveting portion 122 includes a shaft portion 1221 and an end portion 1222. One end of the shaft portion 1221 is connected to the body 121, and the end portion 1222 is connected to the other end of the shaft portion 1221. The shaft portion 1221 is connected to the edge of the through hole 1211. The body 121 abuts against the first surface 1121 of the current collector 112, the shaft portion 1221 passes through the through hole 1123, and the end portion 1222 abuts against the second surface 1122 of the current collector 112, thereby achieving riveting fixation between the body 121 and the current collector 112. Along the direction in which the active material layer 111 is stacked on the current collector 112, the area of ​​the projection of the through hole 1211 onto the first surface 1121 is A, and satisfies: A ≥ 1 mm. 2 In this embodiment, by having the body 121 of the tab 12 abut against the first surface 1121 of the current collector 112, and the shaft portion 1221 connecting the body 121 and the end portion 1222 respectively, the shaft portion 1221 passing through the through hole 1123 of the current collector 112, and the end portion 1222 abutting against the second surface 1122 of the current collector 112, the tab 12 and the current collector 112 are riveted and fixed together, eliminating the need for welding to fix the tab 12 to the current collector 112. This improves the stability of the connection between the electrode 11 and the tab 12, thereby enhancing the charge and discharge performance of the electrochemical device 1000. Furthermore, by having the area of ​​the through hole 1211 projected onto the first surface 1121 be A, and A satisfying 1 mm... 2 ≤A≤3mm2 This can improve the welding pull force between the tab 12 and the electrode 11, and increase the pass rate of the electrochemical device 1000 in the external short test, thereby improving the safety performance of the electrochemical device 1000; in addition, by making A≥1mm 2 Furthermore, in the process of riveting the riveting part 122 to the collector 112, the step quality improvement rate can be increased, thereby improving product quality. The so-called "step quality improvement rate" refers to the percentage of successful riveting in the process of riveting the end 1222 of the riveting part 122 to the collector 112.

[0049] By making A≤3mm 2 This ensures that the amount of current collector removed from the electrode is not excessive, thus preventing the current collector riveting tension from being too low.

[0050] It is worth noting that the external short circuit test involves connecting a resistor of a certain resistance value between the two tabs 12 of a fully charged battery cell 100 or electrochemical device 1000, forcing the battery cell 100 to discharge with a large current. The test is then conducted by observing whether the battery cell 100 catches fire or fails. If it does not catch fire or fail, the external short circuit test is passed; otherwise, it fails. Furthermore, in this application, the riveting portion 122 is formed on a complete tab 12 by punching the tab 12 with a needle, thereby forming the aforementioned through hole 1211. A protrusion is formed at the edge of the through hole 1211. This protrusion, after a subsequent riveting process, forms the riveting portion 122, which includes a shaft portion 1221 and an end portion 1222. In other words, the area A of the projection of the through hole 1211 onto the first surface 1121 is the riveting area between the riveting portion 122 and the electrode 11. If the area A of the projection of the through hole 1211 onto the first surface 1121 is too small, the riveting area between the riveting part 122 and the electrode 11 will be too small. During external short-circuit testing, a large amount of heat will easily be generated at the riveting point, which may lead to a fire or explosion of the electrochemical device 1000. Therefore, in this application, the area A of the projection of the through hole 1211 onto the first surface 1121 is made to satisfy A≥1mm. 2 This can improve the pass rate of the electrochemical device 1000 in the external short test, thereby improving the safety performance of the electrochemical device 1000.

[0051] In some embodiments, please refer to Figure 6 Along the first direction X, at least a portion of the body 121 protrudes from the current collector 112. The first direction X is perpendicular to the direction in which the active material layer 111 is stacked on the current collector 112. The portion of the body 121 protruding from the current collector 112 is used to connect wires or other components to achieve electrical connection between the electrode assembly 1 and other devices.

[0052] In some embodiments, an active material layer 111 is stacked on the first surface 1121 of the current collector 112, and the active material layer 111 is provided with a clearance opening 1111 to expose at least a portion of the first surface 1121 of the current collector 112. Along the direction in which the active material layer 111 is stacked on the current collector 112, the projection of the through hole 1123 is located within the clearance opening 1111, and a portion of the body 121 is received within the clearance opening 1111 so that the body 121 abuts against the exposed portion of the first surface 1121, and another portion of the body 121 protrudes from the current collector 112 along a first direction X, with a gap between the boundary of the body 121 and the clearance opening 1111. In this embodiment, by providing a clearance opening 1111 in the active material layer 111, the body 121 can abut against the portion of the first surface 1121 exposed to the clearance opening 1111, and there is a gap between the boundary between the body 121 and the clearance opening 1111, thereby reducing the risk of the body 121 and the active material layer 111 overlapping, which is beneficial to reducing the thickness of the electrode assembly 1, and thus beneficial to improving the energy density of the electrochemical device 1000.

[0053] For ease of description, the "direction in which the active material layer 111 and the current collector 112 are stacked" will be referred to as the "second direction Y".

[0054] It is understood that the active material layer 111 can be stacked not only on the first surface 1121 of the current collector 112, but also on the second surface 1122 of the current collector 112, or the active material layer 111 can be stacked on both the first surface 1121 and the second surface 1122 of the current collector 112. Please refer to [link / reference]. Figure 6 When both the first surface 1121 and the second surface 1122 of the current collector 112 are stacked with active material layers 111, both the active material layer 111 stacked on the first surface 1121 and the active material layer 111 stacked on the second surface 1122 are provided with clearance openings 1111, and the projections of the two clearance openings 1111 overlap each other along the second direction Y. By providing clearance openings 1111 on both active material layers 111, the body 121 directly abuts against the first surface 1121, and the end 1222 of the riveting part 122 directly abuts against the second surface 1122, which helps to reduce the thickness of the electrode assembly 1.

[0055] In some embodiments, the current collector 112 is provided with a plurality of spaced through holes 1123, and the projections of the plurality of through holes 1123 along the second direction Y are all located within the clearance opening 1111. The tab 12 includes a plurality of riveting portions 122, and the body 121 is provided with a plurality of through holes 1211. The plurality of through holes 1211 are spaced apart, and one through hole 1211 corresponds to one through hole 1123. The shaft portion 1221 of one riveting portion 122 is connected to the edge of one through hole 1211, and the shaft portion 1221 of one riveting portion 122 passes through one through hole 1123. The ends 1222 of the plurality of riveting portions 122 all abut against the second surface 1122 of the current collector 112. In this embodiment, by providing multiple riveting portions 122, the shaft portion 1221 of one riveting portion 122 passes through a through hole 1123, and the ends 1222 of the multiple riveting portions 122 all abut against the second surface 1122 of the current collector 112, the riveting area between the tab 12 and the current collector 112 can be increased, thereby improving the connection strength between the tab 12 and the current collector 112.

[0056] In some embodiments, please refer to Figure 6 The current collector 112 includes a first metal layer 1124, a polymer layer 1125, and a second metal layer 1126. The polymer layer 1125 is located between the first metal layer 1124 and the second metal layer 1126. The surface of the first metal layer 1124 facing away from the second metal layer 1126 forms the first surface 1121 of the current collector 112, and the surface of the second metal layer 1126 facing away from the first metal layer 1124 forms the second surface 1122 of the current collector 112. The through hole 1123 penetrates the first metal layer 1124, the polymer layer 1125, and the second metal layer 1126. It is worth noting that, for the composite current collector, which employs a metal-polymer-metal three-layer sandwich structure, when welding the tab 12 to the composite current collector, only one of the first metal layer 1124 or the second metal layer 1126 can be welded to it. Compared to a regular current collector composed of a single metal layer, the composite current collector, due to its three-layer sandwich structure, results in a smaller thickness of the first metal layer 1124 or the second metal layer 1126, significantly increasing the risk of incomplete soldering, false soldering, or over-soldering when welding the tab. Therefore, in this application, when the current collector 112 includes a first metal layer 1124, a polymer layer 1125, and a second metal layer 1126 (i.e., the current collector is a composite current collector), fixing the tab 12 to the current collector 112 by riveting and simultaneously achieving electrical connection improves the charge-discharge performance of the electrochemical device and enhances the welding pull force between the current collector 112 and the tab 12.

[0057] In some embodiments, the body 121 and the riveting portion 122 are integrally formed. Compared to other forming methods, such as welding, by integrally forming the body 121 and the riveting portion 122, the connection strength between the body 121 and the riveting portion 122 can be improved, thereby improving the riveting strength between the tab 12 and the current collector 112 and reducing the risk of the tab 12 falling off the current collector 112.

[0058] In some embodiments, along the second direction Y, the area A of the projection of each through hole 1211 onto the first surface 1121 of the current collector 112 satisfies: 1 mm 2 ≤A≤2mm 2 In this embodiment, A is further made to satisfy 1mm. 2 ≤A≤2mm 2 At the same time, it can improve the pass rate of electrode assembly 1 in the riveting process and the success rate of electrochemical device 1000 in external short test, and improve the riveting pull force, thereby improving the riveting strength between electrode 11 and electrode tab 12.

[0059] In some embodiments, along the second direction Y, the projected area of ​​each through hole 1211 on the first surface 1121 of the current collector 112 is 1 mm. 2 ≤A≤1.5mm 2 In this embodiment, by making 1mm 2 ≤A≤1.5mm 2 This can further improve the pass rate of electrode assembly 1 during the riveting process.

[0060] In some embodiments, along the second direction Y, the area of ​​the projection of the body 121 onto the first surface 1121 of the current collector 112 is S, that is, the area of ​​the overlapping portion of the body 121 and the current collector 112 is S, and the total area of ​​the projection of the plurality of through holes 1211 onto the current collector 112 is B, and satisfies: 0.2*S≤B≤0.5*S. In this embodiment, by making 0.2*S≤B≤0.5*S, both the riveting pull force and the pass rate of the external short test can be improved, thereby improving the riveting strength between the electrode 11 and the tab 12 and improving the safety of the electrochemical device 1000.

[0061] In some embodiments, along the second direction Y, the area S of the projection of the body 121 onto the first surface 1121 of the current collector 112 and the total area B of the projection of the plurality of through holes 1211 onto the first surface 1121 of the current collector 112 satisfy: 0.2*S≤B≤0.3*S. In this embodiment, by making 0.2*S≤B≤0.3*S, the pass rate of the electrode assembly 1 during the riveting process can be further improved while enhancing the riveting strength between the electrode 11 and the tab 12 and improving the safety of the electrochemical device 1000.

[0062] In some embodiments, along the second direction Y, the area S of the projection of the body 121 onto the first surface 1121 of the current collector 112 and the total area B of the projection of the plurality of through holes 1211 onto the first surface 1121 of the current collector 112 satisfy: B = 0.2 * S. In this embodiment, by setting B = 0.2 * S, the efficiency of the process can be maximized while improving the riveting strength between the electrode 11 and the tab 12 and enhancing the safety of the electrochemical device 1000.

[0063] In some embodiments, when viewed along the second direction Y, the through hole 1211 is one or more of the following shapes: rounded square, circle, square and rectangle.

[0064] Furthermore, when viewed along the second direction Y, the through hole 1211 is a rounded square.

[0065] In some embodiments, when viewed along the second direction Y, the shape of the end portion 1222 of the riveting portion 122 is one or more of a square, a circle, and a rectangle.

[0066] Furthermore, when viewed along the second direction Y, the end portion 1222 of the riveting portion 122 is square in shape.

[0067] To help readers better understand the concept of this application, the following experiments are conducted to demonstrate its validity:

[0068] In this experiment, the size of the tab 12 used was 50mm*8mm*80μm. In the external short test, the test conditions were as follows: under constant temperature of 55℃, a resistor of a certain resistance value was connected between the positive and negative tabs 12 of the electrochemical device 1000, and a large current discharge was directly performed for one hour. The electrochemical device 1000 was observed to see if it caught fire, exploded, or failed. If it caught fire, exploded, or failed, the test failed. In this experiment, resistors with resistance values ​​of 80mohm and 60mohm were used for the test.

[0069] It is worth noting that in Tables 1 to 5, please refer to... Figure 6"A" represents the area of ​​the projection of a single through hole 1211 onto the first surface 1121 of the current collector 112 along the second direction Y, i.e., the riveting area between a single riveting portion 122 and the electrode 11. "Punching morphology" refers to the shape of the through hole 1211 as viewed along the second direction Y. "Riveting morphology" refers to the shape of the end portion 1222 of the riveting portion 122 as viewed along the second direction Y. "Ratio of B to S" refers to the ratio between the total area B of the projections of multiple through holes 1211 onto the first surface 1121 of the current collector 112 along the second direction Y and the area S of the projection of the body 121 onto the first surface 1121 of the current collector 112. "Flattening pressure F" refers to the pressure applied to the riveting portion 122 when pressing the end portion 1222 of the riveting portion 122 to abut against the second surface 1122 of the current collector 112. "Riveting pull force" refers to the pulling force required to pull the tab 12 along the first direction X to separate the tab 12 from the electrode 11. "Riveting resistance" refers to the resistance between the riveting part 122 and the current collector 112. "Step yield rate" refers to the percentage of successful riveting in the process of riveting the end 1222 of the riveting part 122 to the current collector 112.

[0070] Table 1:

[0071]

[0072] Please refer to Table 1, and in conjunction with Comparative Examples 1 and 2, and Examples 1-4, it can be seen that when A satisfies A≥1mm 2 At that time, the step quality rate was significantly improved, indicating that by making A ≥ 1mm 2 This can improve the pass rate of electrode assembly 1 during the riveting process, which is beneficial to improving product quality; in addition, it can also improve the pass rate of electrochemical device 1000 in the external short test using a 60 mohm resistor, thus improving the safety performance of electrochemical device 1000. When A > 3 mm², the riveting tension is too low; when A further meets 1 mm... 2 ≤A≤2mm 2 Furthermore, by improving the pass rate of electrode assembly 1 during the riveting process and increasing the success rate of electrochemical device 1000 in external short-circuit testing, the riveting pull force can be increased, thereby enhancing the riveting strength between electrode 11 and tab 12. When 1mm 2 ≤A≤1.5mm 2 This allows the process step quality rate to reach over 95%, ensuring that the pass rate of electrode assembly 1 during the riveting process is at a relatively high level.

[0073] Table 2:

[0074]

[0075]

[0076] Referring to Table 2 and examples 5-11, it can be seen that when the ratio of B to S is less than 0.2, the riveting tensile force is relatively small. When the ratio of B to S is greater than 0.5, the pass rate of the external shortness test under 60 mohm conditions decreases. Therefore, selecting B and S such that 0.2*S≤B≤0.5*S can balance improving both the riveting tensile force and the pass rate of the external shortness test. Referring to examples 5-11, it can be seen that when the ratio of B to S is greater than 0.3, the step-by-step yield rate decreases significantly. As a better embodiment, selecting B and S such that 0.2*S≤B≤0.3*S can further improve the step-by-step yield rate while increasing the riveting tensile force and improving the pass rate of the external shortness test. When the ratio of B to S is 0.2, the riveting tension reaches 25N / 15mm, and the process efficiency reaches 97%. In other words, as a better embodiment, choosing B and S to satisfy B = 0.2*S can maximize the process efficiency while increasing the riveting tension.

[0077] Table 3:

[0078]

[0079]

[0080] Referring to Table 3 and examples 12-15, it can be seen that when the punched hole shape is a rounded square, the riveting pull force is higher, and the process yield rate and the external shortness test pass rate are also higher. When the punched hole shape is circular, the process yield rate and the external shortness test pass rate are both lower. When the punched hole shape is square or rectangular, the process yield rate is lower. The principle is that when the punched hole shape is circular, compared with a square, rectangular, or rounded square, the shape of the riveted part is irregular, thus affecting the welding pull force, process yield rate, and external shortness test pass rate. Therefore, a square or rectangular punched hole shape is selected. Preferably, a rounded square punched hole shape is selected.

[0081] Table 4:

[0082]

[0083] Please refer to Table 4. In conjunction with Examples 16-18, it can be seen that when the riveting shape is square, the pass rate of the external short test and the step quality rate are both higher than those of circles and rectangles. The principle is that, compared with the riveting shape of circles or rectangles, the shape of square is more regular, and the step quality rate is higher when the riveting part is pressed. Therefore, as a preferred embodiment, the riveting shape is selected as square.

[0084] Table 5:

[0085]

[0086] Please refer to Table 5. The flattening pressure affects the riveting tensile force, the step-by-step yield rate, and the pass rate of the external shortness test. When the flattening pressure is too low, the end of the riveting part 122 cannot be pressed to the second surface 1122 of the current collector 112. When the flattening pressure is too high, the riveting part is easily damaged. As can be seen from Examples 19-23, when the flattening pressure reaches 500MPa, the decrease in riveting tensile force, step-by-step yield rate, and external shortness test pass rate increases, indicating that the riveting part has been damaged. Therefore, the flattening pressure should be selected as 100MPa≤F≤400MPa.

[0087] In this embodiment of the invention, by having the body 121 of the tab 12 abut against the first surface 1121 of the current collector 112, and the shaft portion 1221 connecting the body 121 and the end portion 1222 respectively, the shaft portion 1221 passing through the through hole 1123 of the current collector 112, and the end portion 1222 abutting against the second surface 1122 of the current collector 112, the tab 12 and the current collector 112 are riveted and fixed together, eliminating the need for welding to fix the tab 12 to the current collector 112. This improves the stability of the connection between the electrode 11 and the tab 12, thereby enhancing the charge and discharge performance of the electrochemical device 1000. Furthermore, by having the area of ​​the through hole 1211 projected onto the first surface 1121 be A, and A satisfies A≥0.5mm... 2 This can improve the welding pull between the tab 12 and the electrode 11, and improve the pass rate of the electrochemical device 1000 in the external short test, thereby improving the safety performance of the electrochemical device 1000.

[0088] This invention also provides a method for manufacturing the above-mentioned electrode assembly; please refer to [link to relevant documentation]. Figure 7 The method includes:

[0089] Step 01: Provide an electrode sheet, which includes an active material layer and a current collector, with the active material layer stacked on the current collector;

[0090] Step 02: Punch holes in the current collector to form through holes in the current collector;

[0091] Step 03: Place the tabs on the current collector and observe along the direction in which the tabs are placed on the current collector, with the tabs covering the through hole;

[0092] Step 04: Impact the portion of the electrode covering the through hole along the direction of the electrode tab stacked on the current collector, so that the portion of the electrode tab covering the through hole bends toward the through hole to form a punched part, wherein the punched part penetrates the through hole and protrudes from the surface of the current collector away from the electrode tab;

[0093] By impacting the portion of the electrode ear covering the through hole, the impact force required for impact can be reduced, and the punching part can be easily formed. The punching part can also pass through the through hole so that the punching part protrudes from the surface of the current collector away from the electrode ear.

[0094] Step 05: Rivet the part of the punched portion that protrudes from the surface of the current collector away from the electrode tab, so that the part of the punched portion that protrudes from the surface of the current collector away from the electrode tab forms an end portion. The part of the punched portion excluding the end portion is a shaft portion. The shaft portion and the end portion together constitute the riveting portion.

[0095] In this embodiment, by impacting the portion of the tab covering the through hole, a punched portion protruding from the surface of the current collector away from the tab is formed. Then, the portion of the punched portion protruding from the surface of the current collector away from the tab is riveted, so that the portion of the punched portion protruding from the surface of the current collector away from the tab forms an end. The end abuts against the surface of the current collector away from the tab, thereby achieving the riveting fixation between the tab and the electrode, thereby improving the connection strength between the tab and the electrode and reducing the risk of the tab detaching from the electrode.

[0096] In some embodiments, step 02: punching a hole in the current collector to form a through hole in the current collector, further includes:

[0097] Step 021: Punch holes at multiple locations on the current collector to form multiple through holes on the current collector, wherein the multiple through holes are spaced apart.

[0098] In this embodiment, by forming multiple through holes on the current collector, when the part of the electrode covering the through holes is impacted, multiple punched portions through the through holes can be formed, and multiple riveted portions riveted to the current collector can be formed, thereby further improving the connection strength between the electrode and the electrode sheet and further reducing the risk of the electrode detaching from the electrode sheet.

[0099] In some embodiments, in step 05: the portion of the punched part protruding from the surface of the current collector opposite to the electrode tab is riveted, so that the portion of the punched part protruding from the surface of the current collector opposite to the electrode tab forms an end portion, the portion of the punched part excluding the end portion is a shaft portion, and the shaft portion and the end portion together constitute a riveted part. Further including:

[0100] Step 051: Rivet the portion of the punched part that protrudes from the surface of the current collector away from the electrode ear, so that the portion of the punched part that protrudes from the surface of the current collector away from the electrode ear forms an end. The portion of the punched part excluding the end is a shaft portion. The shaft portion and the end portion together constitute a riveting part. The pressure applied to the electrode ear and the current collector during riveting is a flattening pressure F, which satisfies: 100MPa≤F≤400MPa.

[0101] In this embodiment, by satisfying 100MPa≤F≤400MPa, the riveting tensile force, the step yield rate, and the pass rate of the external short test can be increased, so that the electrode has good mechanical and electrical properties.

[0102] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. An electrode assembly, characterized in that, include: An electrode includes an active material layer and a current collector, the current collector having a first surface and a second surface disposed opposite to each other, the current collector being provided with a through hole extending from the first surface to the second surface, and the active material layer being stacked on the current collector; The electrode lug includes a body and a riveting part. The body is provided with a through hole. The riveting part includes a shaft and an end. One end of the shaft is connected to the edge of the through hole, and the end is connected to the other end of the shaft. The body abuts against the first surface of the current collector. The shaft passes through the through hole, and the end abuts against the second surface of the current collector. The number of the through holes, the through holes, and the riveting parts are all multiple. The multiple through holes are spaced apart. The shaft of one riveting part is connected to the edge of one through hole. The shaft of one riveting part passes through one through hole. The ends of the multiple riveting parts abut against the second surface of the current collector. Along the direction in which the active material is stacked on the current collector, the area of ​​the through hole projected onto the first surface is A, and satisfies: 1mm²≤A≤3mm²; Along the direction in which the active material is stacked on the current collector, the area of ​​the projection of the body onto the first surface of the current collector is S, and the total area of ​​the projection of the plurality of through holes onto the current collector is B, and satisfies: 0.2 S≤B≤0.5 S.

2. The electrode assembly according to claim 1, characterized in that, The active material is stacked on the first surface of the current collector, and the active material layer is provided with a clearance opening. Along the direction in which the active material layer is stacked in the current collector, the projection of the through hole is located within the clearance opening, and a portion of the body is received within the clearance opening.

3. The electrode assembly according to claim 1, characterized in that, Along the direction in which the active material is stacked on the current collector, the area A of the projection of each through hole onto the first surface of the current collector satisfies: 1mm²≤A≤2mm².

4. The electrode assembly according to claim 1, characterized in that, Along the direction in which the active material is stacked on the current collector, the area S of the projection of the body onto the first surface of the current collector and the total area B of the projection of the plurality of through holes onto the first surface of the current collector satisfy: 0.2 S≤B≤0.3 S.

5. The electrode assembly according to any one of claims 1-4, characterized in that, The current collector includes a first metal layer, a polymer layer, and a second metal layer. The polymer layer is located between the first metal layer and the second metal layer. The surface of the first metal layer facing away from the second metal layer constitutes the first surface of the current collector, and the surface of the second metal layer facing away from the first metal layer constitutes the second surface of the current collector. The through hole penetrates the first metal layer, the polymer layer, and the second metal layer.

6. The electrode assembly according to any one of claims 1-4, characterized in that, The main body and the riveting part are integrally formed.

7. The electrode assembly according to claim 1, characterized in that, When viewed along the direction in which the active material layer and the current collector are stacked, the shape of the through hole is a rounded square.

8. The electrode assembly according to claim 1, characterized in that, When viewed along the direction in which the active material layer and the current collector are stacked, the shape of the end is square.

9. An electrochemical device, characterized in that, Includes the electrode assembly described in any one of claims 1-8.

10. A method for manufacturing an electrode assembly as described in any one of claims 1-8, characterized in that, include: An electrode is provided, the electrode comprising an active material layer and a current collector, the active material layer being stacked on the current collector; The current collector is punched to form through holes in the current collector; The electrode tabs are stacked on the current collector, and when viewed along the direction in which the electrode tabs are stacked on the current collector, the electrode tabs cover the through hole; Along the direction in which the electrode tabs are stacked on the current collector, the portion of the electrode tabs covering the through hole is impacted to cause the portion of the electrode tabs covering the through hole to bend toward the through hole to form a punched portion, wherein the punched portion penetrates the through hole and protrudes from the surface of the current collector away from the electrode tabs; The portion of the punched part that protrudes from the surface of the current collector away from the electrode tab is riveted to form an end portion. The portion of the punched part excluding the end portion is a shaft portion, and the shaft portion and the end portion together constitute a riveted part.

11. The method according to claim 10, characterized in that, The step of riveting the portion of the punched part protruding from the surface of the current collector away from the electrode tab, so that the portion of the punched part protruding from the surface of the current collector away from the electrode tab forms an end portion, wherein the portion of the punched part excluding the end portion is a shaft portion, and the shaft portion and the end portion together constitute a riveted part, further includes: The portion of the punched part that protrudes from the surface of the current collector away from the electrode tab is riveted to form an end portion. The portion of the punched part excluding the end portion is a shaft portion. The shaft portion and the end portion together constitute a riveting portion. The pressure applied to the electrode tab and the current collector during riveting is a flattening pressure F, which satisfies the following condition: 100MPa≤F≤400MPa.

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