Pole piece assembly, method for manufacturing pole piece assembly and electrochemical device

Abstract

The embodiment of the invention relates to the technical field of energy storage, and discloses a pole piece assembly, a method for manufacturing the pole piece assembly and an electrochemical device.The pole piece assembly comprises a pole piece and a pole lug, the pole piece comprises an active material layer and a current collector, the current collector is provided with a first surface and a second surface which are oppositely arranged, and the current collector is provided with a through hole; the through holes extend from the first surface to the second surface, and the active material layer is stacked on the current collector; the tab comprises a body and a riveting part, the body is provided with a through hole, the riveting part comprises a shaft part and an end part, one end of the shaft part is connected to the edge of the through hole, the end part is connected to the other end of the shaft part, the body abuts against the first surface of the current collector, the shaft part penetrates through the through hole, and the end part abuts against the second surface of the current collector; along the direction of stacking the active material layer on the current collector, the projection area of the through holes on the first surface is A, and A is greater than or equal to 1 mm < 2 > and less than or equal to 3 mm < 2 >. According to the embodiment of the invention, the stability of connection between the pole piece and the tab can be improved.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of energy storage technology, and in particular to a pole piece assembly, a method for manufacturing a pole piece assembly, and an electrochemical device. Background Art

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

[0003] During the implementation of the embodiments of the present invention, the inventors found that the use of welding to connect the pole ear and the pole piece is prone to defects such as cold welding and 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 a pole piece assembly, a method for manufacturing a pole piece assembly and an electrochemical device, which can improve the stability of the connection between the pole piece and the pole ear.

[0005] In order to solve the above technical problems, a technical solution adopted in an embodiment of the present invention is: to provide a pole piece assembly, including a pole piece and a pole ear, the pole piece includes an active material layer and a current collector, the current collector has a first surface and a second surface arranged oppositely, the current collector is provided with a through hole, the through hole extends from the first surface to the second surface, and the active material layer is stacked on the current collector; the pole ear includes a body and a riveted portion, the body is provided with a through hole, the riveted 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 the first surface of the current collector, the shaft portion is penetrated through the through hole, and the end portion abuts 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 on the first surface is A, and satisfies: 1mm 2 ≤A≤3mm 2 .

[0006] In this embodiment, the body of the pole tab is abutted against the first surface of the current collector, the shaft portion is respectively connected to the body and the end portion, the shaft portion is inserted into the through hole of the current collector, and the end portion is abutted against the second surface of the current collector, thereby realizing the riveting fixation between the pole tab and the current collector, and there is no need to fix the pole tab to the current collector by welding, which is conducive to improving the stability of the connection between the pole piece and the pole tab, and thus improving the charge and discharge performance of the electrochemical device. In addition, by making the area of ​​the through hole projected on the first surface A, and A satisfies A≥1mm 2 , which can increase the welding tension between the pole ear and the pole piece, and improve the pass rate of the electrochemical device in the external short test. When A is too large, it will cause too much removal of the current collector, resulting in a lower riveting tension of the current collector.

[0007] In some embodiments, the active material layer is stacked on the first surface of the current collector, and the active material layer is provided with an avoidance opening. 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 avoidance opening, and part of the body is accommodated in the avoidance opening.

[0008] In this embodiment, by providing a relief opening in the active material layer, part of the body is accommodated in the relief opening, which is beneficial to reducing the thickness of the electrode assembly and improving the energy density of the electrochemical device.

[0009] In some embodiments, the number of through holes, through holes and riveted parts is multiple, the multiple through holes are arranged at intervals, the shaft of a riveted part is connected to the edge of a through hole, the shaft of a riveted part is passed through a through hole, and the ends of the multiple riveted parts are all in contact with the second surface of the collector.

[0010] In this embodiment, by providing a plurality of riveted portions, the connection strength between the pole tab and the pole piece can be improved, and the risk of the pole tab being separated from the pole piece can be reduced.

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

[0012] In this embodiment, the projection area A of each through hole on the first surface of the current collector satisfies: 1 mm 2 ≤A≤2mm 2 It can improve the riveting tension and the riveting strength between the pole piece and the pole ear on the basis of improving the qualified rate of the pole piece assembly in the riveting process and improving the success rate of the electrochemical device in the external short test.

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

[0014] In this embodiment, by making S and B satisfy 0.2*S≤B≤0.5*S, it is possible to improve both the riveting tension and the passing rate of the external short test, thereby improving the riveting strength between the pole piece and the pole ear and improving the safety of the electrochemical device.

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

[0016] In this embodiment, by making S and B satisfy 0.2*S≤B≤0.3*S, the pass rate of the pole piece assembly during the riveting process can be further improved while improving the riveting strength between the pole piece and the pole lug and 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, the surface of the second metal layer facing away from the first metal layer constitutes the second surface of the current collector, and the through hole penetrates the first metal layer, the polymer layer and the second metal layer.

[0018] In some embodiments, the body and the rivet portion are integrally formed.

[0019] In some embodiments, the through hole is in a rounded square shape when viewed along the direction in which the active material layer and the current collector overlap. In this embodiment, by making the through hole in a square or rectangular shape, the welding tension, process step excellence rate, and external short test pass rate can be taken into account, thereby improving the mechanical and electrical properties of the pole piece assembly.

[0020] In some embodiments, when viewed along the direction in which the active material layer and the current collector overlap, the shape of the end portion is a square. In this embodiment, by making the shape of the end portion a square, the passing rate of the external short test and the process step excellence rate can be improved.

[0021] In order to solve the above technical problem, a technical solution also adopted in an embodiment of the present invention is: to provide an electrochemical device, including the above-mentioned pole piece assembly.

[0022] In order to solve the above technical problems, a technical solution also adopted in an embodiment of the present invention is: providing a method for manufacturing a pole piece assembly, the method comprising:

[0023] Providing a pole piece, the pole piece comprising an active material layer and a current collector, wherein the active material layer is stacked on the current collector;

[0024] Punching the current collector to form a through hole on the current collector;

[0025] The tab is stacked on the current collector, and when viewed along the direction in which the tab is stacked on the current collector, the tab covers the through hole;

[0026] Impacting the portion of the electrode tab covering the through hole along the direction in which the electrode tab is stacked on the current collector, so that the portion of the electrode tab covering the through hole is bent toward the through hole to form a punching portion, wherein the punching portion penetrates the through hole and protrudes from the surface of the current collector away from the electrode tab;

[0027] The portion of the punched portion protruding from the surface of the current collector away from the pole ear is riveted to form an end portion, and the portion of the punched portion excluding the end portion is the shaft portion, and the shaft portion and the end portion together constitute the riveted portion.

[0028] In some embodiments, the step of press-riveting the portion of the punched portion protruding from the surface of the current collector away from the tab so that the portion of the punched portion protruding from the surface of the current collector away from the tab forms an end portion, the portion of the punched portion except the end portion is a shaft portion, and the shaft portion and the end portion together constitute a riveted portion, further comprises:

[0029] The portion of the punched portion protruding from the surface of the current collector away from the pole ear is riveted, so that the portion of the punched portion protruding from the surface of the current collector away from the pole ear forms an end portion, the portion of the punched portion except the end portion is an axis portion, and the axis portion and the end portion together constitute a riveted portion, wherein the pressure applied to the pole ear and the current collector during riveting is a flattening pressure F, and satisfies: 100MPa≤F≤400MPa. In this embodiment, by satisfying 100MPa≤F≤400MPa, the riveting tension, process step excellence rate, and external short test pass rate can be increased, so that the pole piece has good mechanical and electrical properties.

[0030] The beneficial effect of the embodiment of the present invention is that, different from the prior art, in the embodiment of the present invention, by making the body of the pole ear abut against the first surface of the current collector, the shaft portion connects the body and the end portion respectively, the shaft portion is inserted into the through hole of the current collector, and the end portion abuts against the second surface of the current collector, thereby realizing the riveting fixation between the pole ear and the current collector, and there is no need to fix the pole ear to the current collector by welding, which is beneficial to improving the stability of the connection between the pole piece and the pole ear, and thus improving the charge and discharge performance of the electrochemical device. In addition, by making the area of ​​the through hole projected on the first surface A, and A satisfies 1mm 2 ≤A≤3mm 2 , which can increase the welding tension between the pole ear and the pole piece, and improve the pass rate of the electrochemical device in the external short test, while avoiding the current collector riveting tension being too low. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the specific embodiments or the prior art description. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, each element or part is not necessarily drawn according to the actual scale.

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

[0033] Figure 2 yes Figure 1 Schematic diagram after cutting along line AA;

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

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

[0036] Figure 5 is a schematic structural diagram of a pole piece assembly provided in an embodiment of the present invention;

[0037] Figure 6 yes Figure 5 Schematic diagram after cutting along line BB;

[0038] Figure 7 It is a flow chart of a method for manufacturing a pole piece assembly provided in an embodiment of the present invention.

[0039] Reference Numbers

[0040] 1000, electrochemical device; 100, battery cell; 2, first pole piece; 3, second pole piece;

[0041] 4. Isolation film; 1. Pole piece assembly; 11. Pole piece; 111. Active material layer; 1111. Avoidance; 112. Current collector; 1121. First surface; 1122. Second surface; 1123. Through hole; 1124. First metal layer; 1125. Polymer layer; 1126. Second metal layer; 12. Pole ear; 121. Body; 1211. Through hole; 122. Riveted part; 1221. Shaft; 1222. End; 200. Packaging shell; DETAILED DESCRIPTION

[0042] In order to facilitate the understanding of the present invention, the present invention is described in more detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that when an element is described as "fixed to" another element, it can be directly on another element or there can be one or more centered elements therebetween. When an element is described as "connected" to another element, it can be directly connected to another element or there can be one or more centered elements therebetween. The orientation or positional relationship indicated by the terms "upper", "lower", "inner", "outer", "vertical", "horizontal", etc. used in this specification is based on the orientation or positional relationship shown in the accompanying drawings, only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0043] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used in this specification includes any and all combinations of one or more of the related listed items.

[0044] In addition, the technical features involved in 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 The electrochemical device 1000 provided in one embodiment of the present application includes a packaging shell 200 and a battery cell 100. The battery cell 100 is disposed in the packaging shell 200. The packaging shell 200 is used to protect the battery cell 100. The battery cell 100 includes a first pole piece 2, a second pole piece 3 and a diaphragm. The diaphragm is located between the first pole piece 2 and the second pole piece 3.

[0046] It is understandable that the battery cell 100 may adopt a winding structure or a laminated structure. Figure 2 As shown, the first pole piece 2, the second pole piece 3 and the isolation film 4 are stacked and wound. When the battery cell 100 adopts a stacked structure, as shown in FIG. Figure 3 or Figure 4 As shown, there are multiple first pole pieces 2, second pole pieces 3 and isolation films 4, and multiple first pole pieces 2, second pole pieces 3 and isolation films 4 are stacked along a direction, and isolation films 4 are arranged between adjacent first pole pieces 2 and second pole pieces 3. The thickness direction of the battery cell 100 can be the same as or different from the thickness direction of the electrochemical device 1000. Figure 3As shown, the thickness direction of the battery cell 100 is the same as the thickness direction of the electrochemical device 1000. Figure 4 As shown, the thickness direction of the battery cell 100 is perpendicular to the thickness direction of the electrochemical device 1000 .

[0047] In order to facilitate understanding of the structure of the first pole piece 2 and / or the second pole piece 3 of the present application, please refer to Figure 5 and Figure 6 , the pole piece assembly 1 is used to refer to the first pole piece 2 and / or the second pole piece 3 for unified description. Of course, the structure of the pole piece assembly 1 described below may be applicable only to the first pole piece 2 or the second pole piece 3, or to both, and is specifically configured as required. The structure of the pole piece assembly 1 provided in the embodiment of the present application is described in detail below.

[0048] See also Figure 5 and Figure 6 The pole piece assembly 1 includes a pole piece 11 and a pole ear 12. The pole piece 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 that are arranged opposite to each other. The current collector 112 is provided with a through hole 1123. The through hole 1123 extends from the first surface 1121 to the second surface 1122. The active material layer 111 is superimposed on the current collector 112. The pole ear 12 includes a body 121 and a riveted portion 122. The body 121 is provided with a through hole 1211. The riveted 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, wherein the shaft portion 1221 is connected to the edge of the through hole 1211. The body 121 is in contact with the first surface 1121 of the current collector 112, the shaft 1221 passes through the through hole 1123, and the end 1222 is in contact with 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 superimposed on the current collector 112, the area of ​​the projection of the through hole 1211 on the first surface 1121 is A, and satisfies: A ≥ 1 mm 2 In this embodiment, the main body 121 of the pole tab 12 is abutted against the first surface 1121 of the current collector 112, the shaft 1221 connects the main body 121 and the end 1222 respectively, the shaft 1221 is passed through the through hole 1123 of the current collector 112, and the end 1222 is abutted against the second surface 1122 of the current collector 112, thereby achieving riveting fixation between the pole tab 12 and the current collector 112, and there is no need to fix the pole tab 12 to the current collector 112 by welding, which is beneficial to improving the stability of the connection between the pole piece 11 and the pole tab 12, and further improving the charge and discharge performance of the electrochemical device 1000. In addition, by making the area of ​​the through hole 1211 projected on the first surface 1121 be A, and A satisfies 1mm 2 ≤A≤3mm2 , the welding tension between the pole ear 12 and the pole piece 11 can be increased, and the passing rate of the electrochemical device 1000 in the external short test can be increased, thereby improving the safety performance of the electrochemical device 1000; in addition, by making A ≥ 1 mm 2 In the process of riveting the riveted portion 122 to the current collector 112, the process step optimization rate can be improved, thereby improving product quality. The so-called "process step optimization rate" refers to the ratio of successful riveting in the process of riveting the end portion 1222 of the riveted portion 122 to the current collector 112.

[0049] By making A≤3mm 2 , so that the part of the pole piece current collector removed will not be too much, avoiding the current collector riveting tension being too low.

[0050] It is worth noting that the external short test is to add a resistor of a certain resistance between the two pole ears 12 of the fully charged battery cell 100 or the electrochemical device 1000 and then electrically connect them, so that the battery cell 100 is forced to discharge with a large current, and observe whether the battery cell 100 catches fire and fails. If there is no fire or failure, it means that the external short test has passed, otherwise, the external short test has failed. In addition, in the present application, the rivet portion 122 is formed on a complete pole ear 12 by punching the pole ear 12 with a needle, so as to form the above-mentioned through hole 1211 on the pole ear 12, and form a protrusion at the edge of the through hole 1211, and the protrusion is subjected to a subsequent riveting process to form the above-mentioned riveted portion 122 including the shaft portion 1221 and the end portion 1222. That is to say, the area A of the projection of the through hole 1211 on the first surface 1121 is the riveting area between the rivet portion 122 and the pole piece 11. If the area A projected on the first surface 1121 by the through hole 1211 is too small, the riveting area between the riveted portion 122 and the pole piece 11 is too small. When the external short test is performed, a large amount of heat is easily generated at the riveting site, which may easily cause the electrochemical device 1000 to catch fire and explode. Therefore, in the present application, the area A projected on the first surface 1121 by the through hole 1211 satisfies A≥1mm. 2 , thereby improving the passing 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, see Figure 6 Along the first direction X, at least part 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 part of the body 121 protruding from the current collector 112 is used to connect wires or other components to achieve electrical connection between the pole piece assembly 1 and other devices.

[0052] In some embodiments, the active material layer 111 is superimposed on the first surface 1121 of the current collector 112, and the active material layer 111 is provided with a avoidance opening 1111 to expose at least part of the first surface 1121 of the current collector 112. Along the direction in which the active material layer 111 is superimposed on the current collector 112, the projection of the through hole 1123 is located in the avoidance opening 1111, and a portion of the body 121 is received in the avoidance 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 the first direction X, and there is a gap between the boundary of the body 121 and the avoidance opening 1111. In this embodiment, a clearance opening 1111 is provided in the active material layer 111 so that the main body 121 can abut against the portion of the first surface 1121 exposed to the clearance opening 1111, and a gap is provided between the boundary of the main body 121 and the clearance opening 1111, thereby reducing the risk of overlapping of the main body 121 and the active material layer 111, which is beneficial to reducing the thickness of the pole piece assembly 1, and further beneficial to improving the energy density of the electrochemical device 1000.

[0053] For the convenience of description, the “direction in which the active material layer 111 and the current collector 112 overlap” is collectively referred to as the “second direction Y” hereinafter.

[0054] It is understood that the active material layer 111 may be stacked on the first surface 1121 of the current collector 112 or on the second surface 1122 of the current collector 112, or the active material layer 111 may be stacked on both the first surface 1121 and the second surface 1122 of the current collector 112. Figure 6 When the first surface 1121 and the second surface 1122 of the current collector 112 are both stacked with an active material layer 111, the active material layer 111 stacked on the first surface 1121 and the active material layer 111 stacked on the second surface 1122 are both provided with avoidance openings 1111, and the projections of the two avoidance openings 1111 overlap each other along the second direction Y. By providing avoidance openings 1111 on both active material layers 111, the body 121 directly abuts the first surface 1121, and the end 1222 of the rivet 122 directly abuts the second surface 1122, which is conducive to reducing the thickness of the pole piece assembly 1.

[0055] In some embodiments, the current collector 112 is provided with a plurality of through holes 1123 distributed at intervals, and along the second direction Y, the projections of the plurality of through holes 1123 are all located within the avoidance opening 1111. The tab 12 includes a plurality of riveted portions 122, and the body 121 is provided with a plurality of through holes 1211, and the plurality of through holes 1211 are arranged at intervals, and one through hole 1211 corresponds to one through hole 1123, and the shaft portion 1221 of one riveted portion 122 is connected to the edge of one through hole 1211, and the shaft portion 1221 of one riveted portion 122 passes through one through hole 1123, and the ends 1222 of the plurality of riveted portions 122 are all in contact with the second surface 1122 of the current collector 112. In this embodiment, by providing a plurality of riveted portions 122, the shaft portion 1221 of a riveted portion 122 passes through a through hole 1123, and the end portions 1222 of the plurality of riveted portions 122 are all in contact with the second surface 1122 of the current collector 112, thereby increasing the riveting area between the pole tab 12 and the current collector 112 and improving the connection strength between the pole tab 12 and the current collector 112.

[0056] In some embodiments, see 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 constitutes a first surface 1121 of the current collector 112. The surface of the second metal layer 1126 facing away from the first metal layer 1124 constitutes a 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, it adopts a metal-polymer-metal three-layer sandwich structure. When the pole ear 12 is welded and fixed to the composite current collector by welding, the pole ear 12 can only be welded to one of the first metal layer 1124 or the second metal layer 1126. Compared with the ordinary current collector composed of a single metal layer, the composite current collector adopts a three-layer sandwich structure, resulting in a smaller thickness of the first metal layer 1124 or the second metal layer 1126, so that when welding the pole ear, the risk of false welding, false welding or over-welding is greatly increased. Therefore, for the present application, when the current collector 112 includes a first metal layer 1124, a polymer layer 1125 and a second metal layer 1126 (that is, the current collector is a composite current collector), the pole ear 12 is fixed to the current collector 112 by riveting, and electrical connection is achieved at the same time, which improves the charge and discharge performance of the electrochemical device. The effect of improving the welding tension between the current collector 112 and the pole ear 12 is also better.

[0057] In some embodiments, the body 121 and the rivet 122 are integrally formed. Compared with other forming methods, such as welding forming, by integrally forming the body 121 and the rivet 122, the connection strength between the body 121 and the rivet 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 from the current collector 112.

[0058] In some embodiments, along the second direction Y, the projection area A of each through hole 1211 on the first surface 1121 of the current collector 112 satisfies: 1 mm 2 ≤A≤2mm 2 In this embodiment, by making A further satisfy 1mm 2 ≤A≤2mm 2 In this way, the riveting tension can be increased, thereby improving the riveting strength between the pole piece 11 and the pole ear 12 on the basis of improving the qualified rate of the pole piece assembly 1 in the riveting process and improving the success rate of the electrochemical device 1000 in the external short test.

[0059] In some embodiments, along the second direction Y, the projection 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 , which can further improve the pass rate of the pole piece assembly 1 during the riveting process.

[0060] In some embodiments, along the second direction Y, the area of ​​the projection of the body 121 on 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 on the current collector 112 is B, and the following conditions are satisfied: 0.2*S≤B≤0.5*S. In this embodiment, by making 0.2*S≤B≤0.5*S, it is possible to improve both the riveting tension and the passing rate of the external short test, thereby improving the riveting strength between the pole piece 11 and the pole 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 on the first surface 1121 of the current collector 112 and the total area B of the projection of the plurality of through holes 1211 on 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 qualified rate of the pole piece assembly 1 in the riveting process can be further improved while improving the riveting strength between the pole piece 11 and the pole lug 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 on the first surface 1121 of the current collector 112 and the total area B of the projection of the plurality of through holes 1211 on the first surface 1121 of the current collector 112 satisfy: B=0.2*S. In this embodiment, by setting B=0.2*S, the process step optimization rate can be improved as much as possible while improving the riveting strength between the pole piece 11 and the pole tab 12 and the safety of the electrochemical device 1000.

[0063] In some embodiments, when viewed along the second direction Y, the through hole 1211 has a shape of one or more of a rounded square, a circle, a square, and a rectangle.

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

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

[0066] Further, when viewed along the second direction Y, the shape of the end portion 1222 of the rivet portion 122 is a square.

[0067] In order to make the readers better understand the concept of this application, the following experiments are carried out to prove that:

[0068] In this experiment, the size of the pole ear 12 used is 50mm*8mm*80μm. In the external short test, the test condition is to connect a resistor of a certain resistance between the positive and negative pole ears 12 of the electrochemical device 1000 at a constant temperature of 55℃, and directly discharge with a large current for one hour to observe whether the electrochemical device 1000 catches fire, explodes or fails. If fire, explosion or failure occurs, the test fails. In this experiment, resistors with resistances of 80mohm and 60mohm were used for testing respectively.

[0069] It is worth noting that in Tables 1 to 5, please combine Figure 6"A" represents the projected area of ​​a single through hole 1211 on the first surface 1121 of the current collector 112 along the second direction Y, that is, the riveting area between a single rivet 122 and the pole piece 11. "Punching morphology" refers to the shape of the through hole 1211 observed along the second direction Y. "Riveting morphology" refers to the shape of the end 1222 of the rivet 122 observed along the second direction Y. "The ratio of B to S" refers to the ratio between the total area B of the projections of multiple through holes 1211 on 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 on the first surface 1121 of the current collector 112. "Flattening pressure F" refers to the pressure applied to the rivet 122 when the end 1222 of the rivet 122 is pressed so that the end 1222 abuts against the second surface 1122 of the current collector 112. “Riveting tension” refers to the tension required to pull the tab 12 along the first direction X to separate the tab 12 from the pole piece 11. “Riveting resistance” refers to the resistance between the riveted portion 122 and the current collector 112. “Processing step efficiency” refers to the ratio of successful riveting in the process of riveting the end 1222 of the riveted portion 122 to the current collector 112.

[0070] Table 1:

[0071]

[0072] Please refer to Table 1, combined with Comparative Example 1, Comparative Example 2, and Examples 1-4, it can be seen that when A satisfies A≥1mm 2 When A ≥ 1 mm, the process step rate is significantly improved, indicating that by making A ≥ 1 mm 2 , which can improve the pass rate of the electrode assembly 1 during the riveting process, which is beneficial to improving product quality; in addition, it can also improve the pass rate of the electrochemical device 1000 in the external short test using a 60mohm resistor, thereby improving the safety performance of the electrochemical device 1000. When A>3mm 2 When A further meets 1mm, the riveting tension is too low. 2 ≤A≤2mm 2 When 1mm is used, the riveting tension can be increased on the basis of improving the qualified rate of the pole piece assembly 1 in the riveting process and the success rate of the electrochemical device 1000 in the external short test, thereby improving the riveting strength between the pole piece 11 and the pole ear 12. 2 ≤A≤1.5mm 2 When the process is performed, the process step optimization rate can reach more than 95%, so that the qualified rate of the pole piece assembly 1 in the riveting process is at a relatively good level.

[0073] Table 2:

[0074]

[0075]

[0076] Please refer to Table 2. In combination with Examples 5-11, it can be seen that when the ratio between B and S is less than 0.2, the riveting tension is small. When the ratio between B and S is greater than 0.5, the pass rate of the external short test under 60mohm conditions decreases. Therefore, selecting B and S to meet 0.2*S≤B≤0.5*S can take into account both improving the riveting tension and improving the pass rate of the external short test. In combination with Examples 5-11, it can be seen that when the ratio between B and S is greater than 0.3, the process step optimization rate decreases significantly. As a more optimal embodiment, selecting B and S to meet 0.2*S≤B≤0.3*S can further improve the process step optimization rate while improving the riveting tension and improving the pass rate of the external short test. When the ratio of B to S is 0.2, the riveting tension reaches 25N / 15mm, and at the same time, the process step optimization rate reaches 97%. That is to say, as a more optimal embodiment, selecting B and S to satisfy B=0.2*S can improve the process step optimization rate as much as possible while improving the riveting tension.

[0077] Table 3:

[0078]

[0079]

[0080] Please refer to Table 3. In combination with Examples 12-15, it can be seen that when the punching morphology is a rounded square, the riveting tension is higher, the process step rate and the external short test pass rate are higher, when the punching morphology is a circle, the process step rate and the external short test pass rate are lower, and when the punching morphology is a square or a rectangle, the process step rate is lower. The principle is that when the punching morphology is a circle, compared with a square or a rectangle or a rounded square, the shape of the riveted part formed is irregular, thereby affecting the welding tension, the process step rate and the external short test pass rate. Therefore, the punching morphology is selected to be a square or a rectangle. Preferably, the punching morphology is selected to be a rounded square.

[0081] Table 4:

[0082]

[0083] Please refer to Table 4. In combination with Examples 16-18, it can be seen that when the riveted morphology is a square, the pass rate of the external short test and the process step excellence rate are higher than those of a circle or a rectangle. The principle is that compared with the riveted morphology being a circle or a rectangle, the square morphology is more regular, and when the riveted part is press-riveted, the process step excellence rate is higher. Therefore, as a preferred embodiment, the riveted morphology is selected to be a square.

[0084] Table 5:

[0085]

[0086] Please refer to Table 5. The flattening pressure has an impact on the riveting tension, the process step rate and the external short test pass rate. When the flattening pressure is too small, the end of the riveted part 122 cannot be pressed to the second surface 1122 of the current collector 112. When the flattening pressure is too large, the riveted part is easily crushed. In combination with Examples 19-23, it can be seen that when the flattening pressure reaches 500MPa, the decrease in the riveting tension, the process step rate and the external short test pass rate increases, indicating that the riveted part has been crushed. Therefore, the flattening pressure is selected to be 100MPa≤F≤400MPa.

[0087] In the embodiment of the present invention, the body 121 of the pole tab 12 is abutted against the first surface 1121 of the current collector 112, the shaft 1221 is respectively connected to the body 121 and the end 1222, the shaft 1221 is penetrated through the through hole 1123 of the current collector 112, and the end 1222 is abutted against the second surface 1122 of the current collector 112, thereby realizing the riveting fixation between the pole tab 12 and the current collector 112, and there is no need to fix the pole tab 12 to the current collector 112 by welding, which is conducive to improving the stability of the connection between the pole piece 11 and the pole tab 12, and thus improving the charge and discharge performance of the electrochemical device 1000. In addition, by making the area of ​​the through hole 1211 projected on the first surface 1121 be A, and A satisfies A≥0.5mm 2 , the welding tension between the pole ear 12 and the pole piece 11 can be increased, and the passing rate of the electrochemical device 1000 in the external short test can be increased, thereby improving the safety performance of the electrochemical device 1000.

[0088] The present invention also provides a method for manufacturing the above-mentioned pole piece assembly, please refer to Figure 7 , the method comprising:

[0089] Step 01: Providing a pole piece, the pole piece includes an active material layer and a current collector, and the active material layer is stacked on the current collector;

[0090] Step 02: Punching the current collector to form a through hole on the current collector;

[0091] Step 03: stack the tab on the current collector, and observe along the direction in which the tab is stacked on the current collector, the tab covers the through hole;

[0092] Step 04: impacting the portion of the electrode tab covering the through hole along the direction in which the electrode tab is superimposed on the current collector, so that the portion of the electrode tab covering the through hole is bent toward the through hole to form a punching portion, wherein the punching portion penetrates the through hole and protrudes from the surface of the current collector away from the electrode tab;

[0093] Among them, by impacting the portion of the pole ear covering the through hole, the impact force required for the impact can be reduced, and the punching portion can be easily formed and penetrated through the through hole so that the punching portion protrudes from the surface of the current collector away from the pole ear.

[0094] Step 05: The portion of the punched portion protruding from the surface of the current collector away from the pole ear is riveted to form an end portion, and the portion of the punched portion excluding the end portion is the shaft portion, and the shaft portion and the end portion together constitute the riveted portion.

[0095] In this embodiment, the portion of the pole ear covering the through hole is impacted to form a punched portion protruding from the surface of the current collector away from the pole ear, and then the portion of the punched portion protruding from the surface of the current collector away from the pole ear is riveted, so that the portion of the punched portion protruding from the surface of the current collector away from the pole ear forms an end, and the end abuts the surface of the current collector away from the pole ear, thereby achieving riveting fixation between the pole ear and the pole piece, thereby improving the connection strength between the pole ear and the pole piece and reducing the risk of the pole ear detaching from the pole piece.

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

[0097] Step 021: Punching multiple positions of the current collector to form a plurality of through holes on the current collector, wherein the plurality of through holes are distributed at intervals.

[0098] In this embodiment, by forming a plurality of through holes on the current collector, when the portion of the pole ear covering the through holes is impacted, a plurality of punched portions penetrating the through holes can be formed, and a plurality of riveted portions riveted to the current collector can be formed, thereby further improving the connection strength between the pole ear and the pole piece and further reducing the risk of the pole ear detaching from the pole piece.

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

[0100] Step 051: The portion of the punched portion protruding from the surface of the current collector away from the pole ear is riveted to form an end portion, and the portion of the punched portion excluding the end portion is the shaft portion, and the shaft portion and the end portion together constitute a riveted portion, wherein the pressure applied to the pole ear and the current collector during riveting is the flattening pressure F, and satisfies: 100MPa≤F≤400MPa.

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

[0102] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A pole piece assembly, It is characterized in that include: A pole piece, comprising an active material layer and a current collector, wherein the current collector has a first surface and a second surface arranged opposite to each other, the current collector is provided with a through hole, the through hole extends from the first surface to the second surface, and the active material layer is stacked on the current collector; The tab comprises a body and a riveted portion, wherein the body is provided with a through hole, the riveted portion comprises 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 is passed 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 projected area of ​​the through hole on the first surface is A, and satisfies: 1mm 2 ≤A≤3mm 2 .

2. The pole piece assembly according to claim 1, It is characterized in that The active material layer is stacked on the first surface of the current collector, and the active material layer is provided with an escape opening. Along the direction in which the active material layer is stacked on the current collector, the projection of the through hole is located in the escape opening, and part of the body is accommodated in the escape opening.

3. The pole piece assembly according to claim 2, It is characterized in that The number of the through holes, the penetration holes and the riveted parts are all multiple, the multiple through holes are arranged at intervals, the shaft of a riveted part is connected to the edge of a penetration hole, the shaft of a riveted part is passed through a through hole, and the ends of the multiple riveted parts are all in contact with the second surface of the collector.

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

5. The pole piece assembly according to claim 3, It is characterized in that Along the direction in which the active material layer is stacked on the current collector, the projected area of ​​the body on the first surface of the current collector is S, the total projected area of ​​the plurality of through holes on the current collector is B, and the following conditions are satisfied: 0.2*S≤B≤0.5*S.

6. The pole piece assembly according to claim 5, It is characterized in that Along the direction in which the active material layer is stacked on the current collector, an area S of the projection of the body on the first surface of the current collector and a total area B of the projections of the plurality of through holes on the first surface of the current collector satisfy: 0.2*S≤B≤0.3*S.

7. The pole piece assembly according to any one of claims 1 to 6, It is 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, the surface of the second metal layer facing away from the first metal layer constitutes the second surface of the current collector, and the through hole penetrates the first metal layer, the polymer layer and the second metal layer.

8. The pole piece assembly according to any one of claims 1 to 6, It is characterized in that The main body and the riveting portion are integrally formed.

9. The pole piece assembly according to claim 1, It is characterized in that When viewed along the direction in which the active material layer and the current collector overlap, the through hole has a rounded square shape.

10. The pole piece assembly according to claim 1, It is characterized in that When viewed along the direction in which the active material layer and the current collector overlap, the shape of the end portion is a square.

11. An electrochemical device, It is characterized in that Comprising the pole piece assembly described in any one of claims 1-10.

12. A method for manufacturing a pole piece assembly as claimed in any one of claims 1 to 10, It is characterized in that include: Providing a pole piece, the pole piece comprising an active material layer and a current collector, the active material layer being stacked on the current collector; Punching the current collector to form through holes on the current collector; The tab is stacked on the current collector, and when viewed from the direction in which the tab is stacked on the current collector, the tab covers the through hole; Impacting the portion of the electrode tab covering the through hole along the direction in which the electrode tab is superimposed on the current collector, so that the portion of the electrode tab covering the through hole is bent toward the through hole to form a punching portion, wherein the punching portion penetrates the through hole and protrudes from the surface of the current collector away from the electrode tab; The portion of the punched portion protruding from the surface of the current collector away from the pole lug is riveted to form an end portion, and the portion of the punched portion excluding the end portion is an axis portion, and the axis portion and the end portion together constitute a riveted portion.

13. The method according to claim 12, It is characterized in that The step of press-riveting the portion of the punched portion protruding from the surface of the current collector away from the pole lug so that the portion of the punched portion protruding from the surface of the current collector away from the pole lug forms an end portion, the portion of the punched portion excluding the end portion is a shaft portion, and the shaft portion and the end portion together constitute a riveted portion, further comprises: The portion of the punched portion protruding from the surface of the current collector away from the pole ear is riveted to form an end portion, and the portion of the punched portion except the end portion is an axis portion, and the axis portion and the end portion together constitute a riveted portion, wherein the pressure applied to the pole ear and the current collector during riveting is a flattening pressure F, and satisfies: 100MPa≤F≤400MPa.

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