Secondary battery, battery pack, and electronic device

Abstract

To provide a secondary battery, a battery pack, and an electronic apparatus with which it is possible to mitigate poor connections by being pushed out in an encapsulation process.SOLUTION: The secondary battery pack includes a case, a terminal, an electrode assembly, a first current collector, and a cover assembly. The case includes an end wall and a side wall surrounding the end wall. An opening is formed at an edge of the side wall. The terminal penetrates the end wall and is insulated from the end wall. The electrode assembly is accommodated in the case, and includes a first tab and a second tab electrically connected to the terminal. The first current collector is located at edge of the electrode assembly facing the opening and is connected to the first tab by welding. The cover assembly includes a first lid plate and a second lid plate. The first lid plate covers the opening, is connected to the side wall and the first current collector by welding, and includes an open hole. The second lid plate is welded to the first lid plate and seals the open hole.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to battery technology, and more particularly to a secondary battery, a battery pack, and an electronic device. [Background technology]

[0002] Today, large cylindrical batteries are preferred by many automobile manufacturers due to their high safety, long service life, excellent fast charging performance, excellent battery consistency, and low production costs.

[0003] Currently, in large cylindrical batteries, the case itself is charged, so that when assembling the battery, the case itself is generally used as the positive or negative electrode. Regarding the electrical connection between the electrode assembly in the case and the case, the electrode assembly is connected to a first current collector on the case opening side, and the first current collector is welded to the side wall of the case, so that the case is charged. In the subsequent battery sealing process, a relatively large pushing force is applied to the side wall of the case, so there is a risk of poor connection between the first current collector and the case. Therefore, there is a demand for a secondary battery, a battery pack, and an electronic device that solve the above problems. Summary of the Invention [Problem to be solved by the invention]

[0004] In view of the above-mentioned shortcomings of the conventional technology, the present invention aims to provide a secondary battery, a battery pack, and an electronic device that can reduce poor connection caused by the first current collector being pushed out during the sealing process when the first current collector is welded to the side wall of the case. [Means for solving the problem]

[0005] In order to achieve the above and other related objects, one aspect of the present invention provides a secondary battery. The secondary battery pack includes a case, a terminal, an electrode assembly, a first current collector, and a cover assembly. The case includes an end wall and a side wall surrounding the end wall. An opening is formed at an end of the side wall remote from the end wall. A terminal penetrates the end wall and is insulated from the end wall. The electrode assembly is housed within the case and includes a first tab facing the opening and a second tab facing the end wall. The second tab is electrically connected to the terminal. The first current collector is disposed at an end of the electrode assembly facing the opening. The first current collector is connected to the first tab by welding. The cover assembly includes a first cover plate and a second cover plate. The first cover plate covers the opening and is connected to the side wall by welding. The first cover plate is connected to the first current collector by welding. The first cover plate includes a through hole. The second cover plate is welded to the first cover plate to seal the through hole.

[0006] In one embodiment of the secondary battery according to the present invention, the first current collector includes a cover plate weld and a tab weld, the cover plate weld being connected to the first cover plate by welding and the tab weld being connected to the first tab by welding.

[0007] In one embodiment of the secondary battery according to the present invention, along the height direction of the secondary battery, the projection of the through hole on the first current collector covers the tab weld.

[0008] In one embodiment of the secondary battery according to the present invention, the cover plate weld is disposed between the first cover plate and the electrode assembly, and one side of the cover plate weld away from the electrode assembly is connected to the first cover plate by welding.

[0009] In one embodiment of the secondary battery according to the present invention, the surface of the cover plate welded portion on one side away from the first cover plate includes an inner weld mark.

[0010] In one embodiment of the secondary battery according to the present invention, the surface of the cover plate welded portion on one side away from the first cover plate does not include a weld mark.

[0011] In one embodiment of a secondary battery according to the present invention, a surface of the first cover plate away from the cover plate weld includes an outer weld mark, and along the height direction of the secondary battery, the projected area of ​​the inner weld mark is larger than the projected area of ​​the outer weld mark.

[0012] In one embodiment of the secondary battery according to the present invention, the cover plate weld is welded to the edge of the through hole, and the tab weld is recessed toward the electrode assembly side from the cover plate weld and connected to the first tab by welding.

[0013] In one embodiment of the secondary battery according to the present invention, the case is cylindrical, the first cover plate is annular, and the through hole is disposed coaxially with the first cover plate.

[0014] In one embodiment of the secondary battery according to the present invention, the side wall has an outer diameter D, the tab welds are distributed within an annular region centered on the end face center of the electrode assembly, the inner diameter of the annular region is 0.25D or more, and the outer diameter of the annular region is 0.87D or less.

[0015] In one embodiment of the secondary battery according to the present invention, the inner circular diameter of the annular region is 12 mm or more, and the outer circular diameter of the annular region is 40 mm or less.

[0016] In one embodiment of the secondary battery according to the present invention, the through hole has a diameter of 0.43D or more and 0.96D or less.

[0017] In one embodiment of the secondary battery according to the present invention, the inner edge of the first cover plate includes a recess, the through-hole is disposed in the recess, and the second cover plate is at least partially received in the recess.

[0018] In one embodiment of the secondary battery according to the present invention, the bottom of the recess includes a platform region, the platform region is disposed around the through hole, and the second cover plate is attached to one side of the platform region away from the electrode assembly and connected to the platform region by welding.

[0019] In one embodiment of the secondary battery according to the present invention, the width of the platform region along the radial direction is from 0.2 mm to 5 mm.

[0020] In one embodiment of the secondary battery according to the present invention, the width of the platform region along the radial direction is from 0.5 mm to 3 mm.

[0021] In one embodiment of the secondary battery according to the present invention, the guide structure is disposed on the second cover plate and / or the recess.

[0022] In one embodiment of the secondary battery according to the present invention, the guide structure includes one or more combinations of rounded corners, chamfers, or beveled surfaces.

[0023] In one embodiment of the secondary battery according to the present invention, the guide structure includes a first annular inclined surface that surrounds the through hole and decreases from one side away from the electrode assembly to one side of the first cover plate, and the inclination angle of the first annular inclined surface is 95° to 160°.

[0024] In one embodiment of the secondary battery according to the present invention, the explosion-proof structure is disposed on the second cover plate.

[0025] In one embodiment of the secondary battery according to the present invention, the explosion-proof structure includes a notch disposed in the second cover plate, with an opening of the notch being proximate to the electrode assembly.

[0026] In one embodiment of the secondary battery according to the present invention, the explosion-proof structure includes a second weld mark between the first cover plate and the second cover plate.

[0027] In one embodiment of the secondary battery according to the present invention, the first cover plate includes a protrusion that fits into the opening, the protrusion protrudes toward the electrode assembly side and is arranged around the through hole, the outer edge of the protrusion fits into the side wall, and the protrusion is configured to block the laser when the first cover plate and the opening are welded together.

[0028] In one embodiment of the secondary battery according to the present invention, the height of the protrusion is 0.1 mm to 5 mm along the height direction of the secondary battery, and the width of the protrusion in the radial direction is 1 mm to 10 mm.

[0029] In one embodiment of the secondary battery according to the present invention, the height of the protrusion is 0.5 mm to 2.5 mm.

[0030] In one embodiment of the secondary battery according to the present invention, the first cover plate further includes a position restricting portion disposed around the protrusion, and the end face of the side wall abuts against the position restricting portion.

[0031] In one embodiment of the secondary battery according to the present invention, the first weld mark is disposed around the opening between the first cover plate and the opening, and the first weld mark is located on the contact surface between the position restriction portion and the side wall.

[0032] In one embodiment of the secondary battery according to the present invention, the cover plate weld is connected to one side of the protrusion facing the electrode assembly by welding.

[0033] In one embodiment of the secondary battery according to the present invention, the case is cylindrical, the electrode assembly includes a central through hole, and the side of the convex portion facing the electrode assembly is an annular surface, which is arranged coaxially with the case.

[0034] In one embodiment of the secondary battery according to the present invention, an opening is disposed in the center of the first current collector, and a projection of the central through hole of the first current collector along the height direction of the secondary battery at least partially overlaps with the opening.

[0035] In one embodiment of the secondary battery according to the present invention, a recess corresponding to the protrusion is formed on a surface of the first cover plate on one side remote from the electrode assembly, and the depth of the recess is 0.1 mm to 5 mm.

[0036] In one embodiment of the secondary battery according to the present invention, the distance from the end face on which the first tab is located to the outer surface of the cover plate is 0.6 mm to 4 mm.

[0037] In one embodiment of the secondary battery according to the present invention, the secondary battery further includes a solution injection hole and a blocking plate, where the solution injection hole is disposed on the terminal and the blocking plate is welded to the terminal to seal the solution injection hole.

[0038] The present invention further provides a battery pack including any of the secondary batteries described above.

[0039] The present invention further provides an electronic device including the above battery pack. Effect of the Invention

[0040] In the secondary battery according to the present invention, the outer edge of the first cover plate is connected to the side wall by welding to seal the opening, and the first current collector is connected to the first cover plate by welding. In the case where the first current collector and the side wall of the case are not connected and the first current collector is welded to the side wall of the case, poor connection caused by being pushed out during the sealing process inside the case can be reduced. At the same time, in the present invention, the secondary battery can be hermetically sealed without performing roll groove processing or pier seal processing on the case. Therefore, the process is simplified, the assembly efficiency is improved, and the height of the roll groove can be saved. Therefore, the space utilization of the secondary battery is facilitated.

[0041] In the present invention, the first current collector and the first cover plate may be integrated by welding before assembling the secondary battery. Then, the first current collector and the electrode assembly are welded through the through hole of the first cover plate. Therefore, the assembly man-hours are reduced. Furthermore, the first current collector and the first cover plate are welded before assembly. The laser is irradiated from one side of the first current collector and can reach the first cover plate through the relatively thin first current collector. The welding process window is large and the welding efficiency is high. [Brief description of the drawings]

[0042] [Figure 1] 1 is a schematic diagram showing an overall configuration of an embodiment of a secondary battery of the present invention. [Diagram 2] FIG. 2 is a partially enlarged view showing region I in FIG. [Diagram 3] FIG. 3 is a partially enlarged view showing region II in FIG. [Figure 4] FIG. 4 is a partially enlarged view showing region III in FIG. [Diagram 5] FIG. 2 is a cross-sectional view showing an embodiment of a secondary battery of the present invention after a first cover plate and a first current collector are welded together. [Figure 6] FIG. 2 is a three-dimensional view showing an embodiment of a secondary battery according to the present invention after a first cover plate and a first current collector are welded together. [Figure 7] FIG. 2 is an exploded view of a secondary battery according to one embodiment of the present invention before a first cover plate and a first current collector are welded together. [Figure 8] 4 is a three-dimensional view showing the first cover plate in the embodiment of the secondary battery of the present invention, viewed from another angle. FIG. [Figure 9] FIG. 4 is a schematic diagram showing a connection between a first cover plate and a first current collector in another embodiment of the secondary battery of the present invention. [Figure 10] FIG. 11 is a schematic diagram showing a connection between a first cover plate and a first current collector in still another embodiment of the secondary battery of the present invention. [Figure 11] 3 is a partially enlarged view of region II in FIG. 2 in another embodiment of the present invention. [Figure 12] 4 is a schematic three-dimensional view showing the state after the second cover plate has been removed from the opening side of the case of the secondary battery of the present invention. FIG. [Figure 13] 1 is a schematic diagram showing a structure in which a solution injection hole is arranged on an end wall side of a case in one embodiment of a secondary battery of the present invention. [Figure 14] 1 is a schematic diagram illustrating an electronic device according to an embodiment of the present invention. [Figure 15] 1 is a schematic diagram showing a battery pack in one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0043] The implementation of the present invention will be described below through a specific embodiment. Those skilled in the art can easily understand other advantages and effects of the present invention from the disclosure of this specification. The present invention can also be implemented or applied through other different detailed embodiments. Various details of this specification can be modified or changed in various ways based on various viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features of each embodiment may be combined unless inconsistent. It should also be understood that the terms used in the embodiments of the present invention are used to describe specific embodiments, but should not be interpreted as limiting the scope of the present invention. In the following embodiments, the test methods that do not specify specific conditions generally follow conventional conditions or conditions recommended by each manufacturer.

[0044] In one embodiment, when a numerical range is set, it should be understood that the two end points of each numerical range and any value between the two end points can be selected unless otherwise specified in the present invention. Unless otherwise defined, all technical and scientific terms used in the present invention are consistent with the understanding of the prior art by those skilled in the art and the description of the present invention. The present invention can also be implemented using any method, device, and material of the prior art that is similar or equivalent to the method, device, and material described in the embodiments of the present invention.

[0045] In addition, terms such as "upper", "lower", "left", "right", "middle", and "one side" used in the specification are intended to facilitate explanation and do not limit the scope of the present invention. As long as there is no substantial change in the technical content, any change or adjustment of the relative relationship is also considered to be included in the scope of the present invention.

[0046] 1 to 15, the present invention provides a secondary battery 100, a battery pack 10 including the secondary battery 100, and an electronic device 1. In the secondary battery 100, the first current collector 143 and the side wall 112 of the case 110 are not connected, and when the first current collector 143 is welded to the side wall 112 of the case 110, it is possible to reduce connection defects caused by being pushed out during a sealing process inside the case.

[0047] Referring to FIG. 1, a secondary battery 100 according to the present invention includes a case 110 , a terminal 120 , an electrode assembly 130 , a first current collector 143 , and a cover plate assembly 140 .

[0048] Referring to FIG. 1, the case 110 includes an end wall 111 and a side wall 112 surrounding the end wall 111. The connection between the end wall 111 and the side wall 112 can be realized by various methods such as integral press molding, integral forging, and split welding, as long as a stable sealing and electrical connection relationship can be formed. The surrounding manner of the side wall 112 is not particularly limited. The side wall 112 can be surrounded to form a cylindrical shape or any closed annular contour that fits the end wall 111. In this embodiment, the outer edge of the end wall 111 is circular, and the side wall 112 forms a cylindrical shape surrounding the outer edge of the end wall 111. Furthermore, a circular opening 113 is formed at the end of the side wall 112 away from the end wall 111. The case 110 defined by the end wall 111 and the side wall 112 has a storage chamber formed therein. The storage chamber is configured to store the electrode assembly 130, an electrolyte (not shown), and other components required for the battery. Specifically, the diameter of the case 110 may be determined according to the specific size of the electrode assembly 130, and may be, for example, 18 mm, 21 mm, 46 mm, etc. The case 110 may be made of various materials, such as copper, iron, aluminum, steel, aluminum alloy, etc. To prevent the case 110 from rusting due to long-term use, the surface of the case 110 may be coated with a layer of an anti-rust material, such as metallic nickel.

[0049] Referring to FIG. 1, the electrode assembly 130 is a component housed in the case 110 and in which an electrochemical reaction occurs in the secondary battery 100. One or more electrode assemblies 130 may be disposed in the case 110. The electrode assembly 130 is mainly formed by rolling or laminating a positive electrode piece and a negative electrode piece. In addition, a separator is generally provided between the positive electrode piece and the negative electrode piece. The positive electrode piece includes a positive electrode current collector and a positive electrode active material. The positive electrode active material is applied to the surface of the positive electrode current collector. The positive electrode current collector includes a coated area where the active material is applied and a non-coated area where the active material is not applied. The positive electrode tab of the electrode assembly is formed by rolling the non-coated area. The negative electrode piece includes a negative electrode current collector and a negative electrode active material. The negative electrode active material is applied to the surface of the negative electrode current collector. The negative electrode current collector includes a coated area where the active material is applied and a non-coated area where the active material is not applied. The negative electrode tab of the electrode assembly is formed by rolling the uncoated area. For example, in a lithium-ion secondary battery, the material of the positive electrode collector may be aluminum, the positive electrode active material layer includes a positive electrode active material, which may be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganate, etc. The material of the negative electrode collector may be copper, the negative electrode active material layer includes a negative electrode active material, which may be carbon, silicon, etc. The material of the separator may be polypropylene (PP), polyethylene (PE), etc. To protect and insulate the cell, the outside of the cell may be covered with an insulating film. The insulating film may be obtained by compounding PP, PE, PET, PVC, or other polymer materials. The electrode assembly 130 of the present invention includes a first tab 132 facing the opening 113 and a second tab 131 facing the end wall 111. The second tab 131 may be a positive electrode tab or a negative electrode tab. The first tab 132 and the second tab 131 have opposite electrical properties. In this embodiment, the second tab 131 is a positive tab, and the terminal 120 is electrically connected to the second tab 131 and is positively charged. The first tab 132 is a negative tab, and the case 110 is electrically connected to the first tab 132 on one side of the opening 113 opposite the end wall 111 and is negatively charged.However, in other embodiments, the second tab 131 may be a negative tab and the first tab 132 may be a positive tab. The second tab 131 is electrically connected to the terminal 120 via the second current collector 134. A first current collector 143 is disposed at the end of the electrode assembly 130 facing the opening 113 and is connected to the first tab 132 by welding.

[0050] Referring to FIG. 1 , the terminal 120 penetrates the end wall 111 and is insulated from the end wall 111. The structural form of the terminal 120 can be any suitable form that can penetrate the end wall 111 and electrically connect to the second tab 131 of the electrode assembly 130. For example, the cross section may be circular, rectangular, prismatic, or have an irregular contour that can stably conduct power. The end of the terminal 120 facing the electrode assembly 130 penetrates the end wall 111 and is directly or indirectly electrically connected to the second tab 131. In this embodiment, the terminal 120 transitions through the second current collector 134 to be electrically connected to the second tab 131. The end of the terminal 120 facing the opening 113 is connected to the second current collector 134 by welding. One side of the second current collector 134 remote from the terminal 120 is connected to the second tab 131 by welding. The end of the terminal 120 away from the electrode assembly 130 is exposed to the outside of the case 110 and forms a corresponding electrode. The electrical properties of the terminal 120 may be positive or negative. For example, in one embodiment, the second tab 131 is a negative electrode tab, so that the terminal 120 becomes a negative electrode, and the case 110 forms a corresponding positive electrode. In this embodiment, the second tab 131 is a positive electrode tab, so that the terminal 120 becomes a positive electrode, and the case forms a corresponding negative electrode. A terminal mounting hole is arranged in the end wall 111. The terminal 120 is attached by penetrating the terminal mounting hole in a sealed and insulated state. This structure of the case 110 improves the attachment efficiency and improves the ease of assembly and sealing, compared to the case 110 having openings 113 formed at both ends. The terminal 120 is made of a conductive metal material. The material of the terminal 120 is, for example, aluminum (Al). Since the material of the terminal 120 is aluminum, riveting is easy. In this embodiment, the material of the terminal is aluminum, and the terminal is a positive electrode. The material of the case is low carbon steel corresponding to the terminal, and forms a negative electrode corresponding thereto. The terminal 120 is electrically insulated from the case 110. Various methods can be adopted to electrically insulate the terminal 120 and the end wall 111 of the case 110 from each other. For example, insulation can be achieved by disposing an insulating washer between the terminal 120 and the end wall 111. Alternatively, insulation can be achieved by forming an insulating coating layer on a part of the terminal 120.Alternatively, some of these measures may be combined.

[0051] 1 and 2, in the present invention, the materials of the first current collector 143 and the second current collector 134 are selected according to the electrode polarity of the tab to which the first current collector 143 and the second current collector 134 are connected. For example, when the second current collector 134 is connected to the positive electrode tab, aluminum metal can be selected as the second current collector 134. In this case, unlike the second current collector 134, the first current collector 143 is connected to the negative electrode tab, and copper metal can be selected as the material of the first current collector 143. When the second current collector 134 is connected to the negative electrode tab, copper metal can be selected as the second current collector 134. In this case, unlike the second current collector 134, the first current collector 143 is connected to the positive electrode tab, and aluminum metal can be selected as the first current collector 143. The shapes and structures of the second current collector 134 and the first current collector 143 are not particularly limited and can be appropriately selected to achieve stable and reliable electrical connection.

[0052] 1, 2, and 3, the cover plate assembly 140 seals and blocks the opening 113. The cover plate assembly 140 includes a first cover plate 141 and a second cover plate 142. The shape of the outer edge of the first cover plate 141 corresponds to the shape of the opening 113. The outer edge of the first cover plate 141 is connected to the side wall 112 by welding to seal the opening 113. The outer edge of the first cover plate 141 and the side wall 112 may be welded to seal the welding position. For example, a welding head may perform welding in a direction perpendicular to the side wall 112 (i.e., the X direction in FIG. 3) and move in a circumferential direction relative to the secondary battery 110 during the welding process to form a ring-shaped first weld mark 144 on the side wall 112. Alternatively, as shown in FIG. 11, the welding head may perform welding along the height direction of the secondary battery 100 (i.e., the direction from the opening 113 toward the end wall 111) and rotate along the circumferential direction of the first cover plate 141 relative to the secondary battery 100 during the welding process, forming a closed annular first weld mark 144 at a position where the outer edge of the first cover plate 141 and the end face of the side wall 112 come into contact with each other. Note that the shape of the first weld mark 144 in FIG. 3 and the shape of the first weld mark 144 in FIG. 11 are both examples and should not be construed as limiting the shape of the first weld mark 144. The first cover plate 141 includes a through hole 1411. The shape of the through hole 1411 is not particularly limited, and may be, for example, a circle or an ellipse having a closed contour. The through hole 1411 penetrates the first cover plate 141 along the thickness direction of the first cover plate 141. The first cover plate 141 and the first current collector 143 are connected by welding. As long as a stable conductive connection between the first cover plate 141 and the first current collector 143 can be realized, the position where the first cover plate 141 and the first current collector 143 are welded and the shape of the weld mark are not particularly limited. The second cover plate 142 is fixed to the first cover plate 141 and seals and covers the through hole 1411. As a method for the second cover plate 142 to seal and cover the through hole 1411, various methods can be adopted as long as the through hole 1411 can be effectively sealed and blocked. For example, the second cover plate 142 may be welded to the first cover plate 141 to seal and block the through hole 1411. The shape of the second cover plate 142 may correspond to the through hole 1411.For example, when the through hole 1411 is circular, the second cover plate 142 may be circular, and when the through hole 1411 is square, the second cover plate 142 may be square. The shape of the second cover plate 142 does not have to correspond to the shape of the through hole 1411. For example, when the through hole 1411 is circular, the second cover plate 142 may be square so long as it can cover the through hole 1411, and when the through hole 1411 is square, the second cover plate 142 may be circular so as to cover the through hole 1411. When the second cover plate 142 is provided with a solution injection hole or an explosion-proof structure, both the solution injection hole and the explosion-proof structure need to be disposed within the projection range of the through hole 1411 in the height direction of the secondary battery 100.

[0053] In the secondary battery 100 according to the present invention, there is no need to connect the first current collector 143 and the side wall 112 of the case 110, and when the first current collector 143 is welded to the side wall 112 of the case 110, the poor connection caused by extrusion in the sealing process of the prior art can be reduced. Furthermore, according to the secondary battery 100 of the present invention, the secondary battery 100 can be hermetically sealed without performing roll groove processing or pierce seal processing. Therefore, the process is simplified, the assembly efficiency is improved, and the height of the roll groove can be saved. Therefore, in terms of height, the space utilization of the secondary battery 100 is facilitated.

[0054] In the secondary battery 100 according to the present invention, after the electrode assembly 130 is installed in the case 110, the assembly process on the opening 113 side includes the following:

[0055] S1: The first current collecting plate 143 and the first cover plate 141 are previously welded together to be integrated.

[0056] S2: The opening 113 is sealed and covered with the first cover plate 141, and the first cover plate 141 is connected to the side wall 112 by welding.

[0057] S3: The first current collector 143 and the first tab 132 are connected by welding through the through hole 1411 of the first cover plate 141.

[0058] S4: The second cover plate 142 is welded to the first cover plate 141, and the through hole 1411 is sealed.

[0059] According to this assembly process, the first current collector 143 and the first cover plate 141 can be integrated by welding before assembling the secondary battery. Next, the first current collector 143 is welded to the first tab 132 of the electrode assembly 130 through the through hole of the first cover plate 141. As a result, the assembly process after the electrode assembly 130 is installed in the case 110 is reduced. Furthermore, by welding the first current collector 143 and the first cover plate 141 before assembling them, the laser can be irradiated from one side of the first current collector 143 and reach the first cover plate through the relatively thin first current collector 143. This provides a larger welding process window and improves welding efficiency.

[0060] 1 and 3, in one embodiment of the secondary battery 100 according to the present invention, the first current collector 143 includes a cover plate weld 1432 and a tab weld 1431. The shape of the cover plate weld 1432, the shape of the tab weld 1431, and the relative positions of the cover plate weld 1432 and the tab weld 1431 are not particularly limited. In this embodiment, the projection of the cover plate weld 1432 is annular along the height direction of the secondary battery 100, and the projection of the tab weld 1431 is distributed inside the projection of the cover plate weld 1432. The cover plate weld 1432 is connected to the first cover plate 141 by welding, and the tab weld 1431 is connected to the first tab 132 by welding.

[0061] In this embodiment, the secondary battery 100 is a cylindrical secondary battery 100. The side wall 112 of the case 110 is formed in a cylindrical shape. Along the height direction of the secondary battery 100 (i.e., the axial direction of the cylinder), the projection of the through hole 1411 on the first current collector 143 covers the tab weld 1431. With this arrangement, after the welding of the first cover plate 141 and the side wall 112 is completed, one side of the tab weld 1431 away from the electrode assembly 130 is exposed in the through hole 1411, and the tab weld 1431 and the side wall 112 can be welded to each other through the through hole 1411 from the outside of the first cover plate 141. At the same time, when this arrangement is adopted, the projection of the through hole 1411 covers the tab weld 1431. Therefore, the size of the through hole 1411 is increased. As a result, the electrolyte can be simultaneously injected into the case 110 through the through hole 1411. The solution injection efficiency can be improved, and there is no need to provide a separate solution injection hole.

[0062] 2 and 3, the relative positions of the cover plate weld 1432, the electrode assembly 130, and the first cover plate 141 in the height direction of the secondary battery 100 according to the present invention may have a number of arrangements. In one embodiment of the secondary battery 100 according to the present invention, the cover plate weld 1432 is disposed between the first cover plate 141 and the electrode assembly 130 along the height direction of the secondary battery 100, and one side of the cover plate weld 1432 away from the electrode assembly 130 is connected to the first cover plate 141 by welding. In this way, when the first cover plate 141 and the second current collector 134 are integrated in advance (i.e., the first current collector plate 143 and the first cover plate 141 are integrated in advance by welding before assembling the secondary battery), the cover plate weld 1432 and the first cover plate 141 may be welded from the electrode assembly 130 side. Because the wall thickness of the second current collector 134 is thinner than the wall thickness of the first cover plate 141, the welding process window can be increased.

[0063] In one embodiment of the secondary battery 100 according to the present invention, the surface of one side of the cover plate weld 1432 away from the first cover plate 141 includes an inner weld mark 1471. The inner weld mark 1471 is formed by welding from the cover plate weld 1432 side toward the first cover plate 141 side. In one embodiment of the secondary battery according to the present invention, the energy employed during welding is appropriate, so that the molten pool does not penetrate the first cover plate 141 from the cover plate weld 1432 side toward the first cover plate 141 side during welding. Therefore, the surface of one side of the first cover plate 141 away from the cover plate weld 1432 does not have a weld mark. However, considering the narrower process window in the conventional welding technology, in another embodiment, the surface of one side of the cover plate weld 1432 away from the first cover plate 141 includes an inner weld mark 1471. The surface of the first cover plate 141 away from the cover plate weld 1432 includes an outer weld mark 1472. Since welding is performed from the cover plate welded portion 1432 side toward the first cover plate 141 side along the height direction of the secondary battery, the projected area of ​​the inner weld mark 1471 is larger than the projected area of ​​the outer weld mark 1472 .

[0064] The type of weld mark is not particularly limited. In one embodiment, the inner weld mark 1471 includes a plurality of separate weld marks in annular shapes distributed at intervals along the edge of the cover plate welded portion 1432. In another embodiment, the inner weld mark 1472 includes linear weld marks. The linear weld marks are distributed continuously or intermittently along the edge of the first cover plate 141.

[0065] 9 and 10, in one embodiment of the secondary battery 100 according to the present invention, the cover plate weld 1432 is welded to an end of the through hole 1411, for example, an end on one side facing the electrode assembly 130 or an end on one side away from the electrode assembly 130. The tab weld 1431 is recessed toward the electrode assembly 130 from the cover plate weld 1432 and abuts against the first tab 132, and is connected and fixed by welding. By adopting such an arrangement, the size of the first current collector 143 can be reduced, and the weight of the battery can be reduced. At the same time, a smooth communication relationship between each layer of the electrode assembly 130 is maintained, facilitating injection of an electrolyte and ventilation between each layer.

[0066] 2 and 6, in one embodiment of the secondary battery 100 according to the present invention, the case 110 is cylindrical, the first cover plate 141 is annular, the first current collector plate 143 is annular, an opening 1433 is formed inside the annular shape, the through hole 1411 is arranged coaxially with the first cover plate 141, the first current collector 143 is also arranged coaxially with the through hole 1411, the surface of the first current collector 143 exposed in the through hole 1411 is an annular flat area arranged around the opening 1433, and the tab welds 1431 are distributed within the annular flat area. Since the first cover plate 141 is annular, when the first cover plate 141 is welded to the case 110, thermal deformation of the edge of the through hole 1411 can be more uniform. Furthermore, since the tab welds 1431 are distributed in an annular planar area arranged coaxially with the through hole 1411, positioning during welding can be performed more smoothly compared to a structure in which holes, protrusions, grooves, etc. are provided in the area where the tab welds 1431 are located.

[0067] 2 and 12, in one embodiment of the present invention, the outer diameter of the side wall is D, the tab welds 1431 are distributed in an annular region 1434 centered on the center of the end face of the electrode assembly 130, and the inner circle diameter D1 of the annular region 1434 is 0.25D or more, and the outer circle diameter D2 of the annular region 1434 is 0.87D or less. Considering the specifications of conventional secondary batteries, the inner circle diameter D1 of the annular region 1434 may be 12mm or more, and the outer circle diameter D2 of the annular region 1434 may be 40mm or less. In this way, before the second cover plate 142 is installed, the first current collector plate 143 and the first tab 132 can be welded through the through hole 1411. When the first current collector 143 and the first tab 132 are welded in this way, a weld line such as the third weld line 149 in FIG. 12 is formed on the surface of the first current collector 143 in the through hole 1411. The third weld line 149 is merely for the purpose of diagrammatically illustrating the weld line between the first current collector 143 and the first tab 131, and does not limit the shape of the weld line. Other types of weld lines may be selected as necessary, and will not be listed here one by one. Considering the specifications of conventional cylindrical secondary batteries, the tab welds 1431 may be distributed within an annular region having a diameter of 12 mm to 40 mm, and the annular region 1434 is disposed coaxially with the through hole 1411. In the annular region 1434, the tab of the electrode assembly 130 is relatively thick and uniform, so that stable welding between the tab welds 1431 and the first tab 132 is possible, and the thermal effect on the electrode assembly 130 due to welding heat is reduced.

[0068] In one embodiment of the secondary battery 100 according to the present invention, the diameter of the through hole 1411 may be 0.43D or more and 0.96D or less, taking into consideration the distribution of the tabs in the electrode assembly 130. Within this range, most of the tab welded portion 1431 can be covered, the diameter of the through hole 1411 can be increased, and injection of the electrolyte can be facilitated.

[0069] 3 and 5, in one embodiment of the secondary battery 100 according to the present invention, the inner edge of the first cover plate 141 includes a recess 1414. The shape of the recess 1414 may correspond to the shape of the second cover plate 142. For example, if the outer shape of the second cover plate 142 is circular, the projection of the outer shape of the recess 1414 is also circular. Also, the shape of the recess 1414 may not correspond to the second cover plate 142. For example, if the outer shape of the second cover plate 142 is circular, the outer shape of the recess 1414 is square and can accommodate the second cover plate 142. The depth of the recess 1414 is such that the second cover plate 142 is at least partially accommodated in the height direction. The through hole 1411 is disposed in the recess 1414. The second cover plate 142 is at least partially accommodated in the recess 1414 in the height direction. The surface of the second cover plate 142 on one side away from the electrode assembly 130 is recessed into a recess 1414 or is flush with the outer surface of the first cover plate 141 to prevent an increase in the overall height of the secondary battery.

[0070] 1, 3 and 5, in one embodiment of the secondary battery 100 according to the present invention, the bottom of the recess 1414 includes a platform region 1416. The platform region 1416 is integrally connected to the sidewall of the recess 1414. The platform region 1416 is disposed around the through hole 1411. The second cover plate 142 is disposed on one side of the platform region 1416 away from the electrode assembly 130 and is sealingly connected to the platform region 1416 of the recess 1414 by welding. It should be noted that the second cover plate 142 may be sealed to the sidewall of the recess 1414 and the platform region 1416 by welding. In one embodiment of the secondary battery 100 according to the present invention, the width L of the platform region 1416 along the radial direction of the secondary battery 100 is 0.2 mm to 5 mm. Due to such a width range, the second cover plate 142 and the platform region 1416 can have a relatively stable fitting relationship. In one embodiment of the secondary battery 100 according to the present invention, the width L of the platform region along the radial direction may be 0.5 mm to 3 mm. Within this range, a fitting relationship can be obtained and the weight is relatively light.

[0071] 3, 4 and 11, in one embodiment of the secondary battery 100 according to the present invention, the guide structure 145 is disposed on the second cover plate 142 and / or the recess 1414. The guide structure 145 may be disposed only on the second cover plate 142 or the recess 1414, or may be disposed on both the second cover plate 142 and the recess 1414. The guide structure 145 includes one or more combinations of a rounded corner, a chamfer, or an inclined surface. In this embodiment, the guide structure 145 includes a first annular inclined surface 1415. The first annular inclined surface 1415 is a part of a conical surface. The first annular inclined surface 1415 surrounds the through hole 1411 and decreases from one side of the first cover plate 141 away from the electrode assembly 130 toward the electrode assembly 130. The inclination angle α of the first annular inclined surface 1415 is 95°-160° to ensure quick fitting and welding between the second cover plate 142 and the platform region 1416 of the recess 1414. In this embodiment, the guide structure 145 further includes a second annular inclined surface 1423 disposed on the side wall of the second cover plate 142. The second annular inclined surface 1423 is a part of a cone surface. The second annular inclined surface 1423 surrounds the outer edge of the second cover plate 142 and decreases from one side of the first cover plate 141 away from the electrode assembly 130 toward the electrode assembly 130 side. The first annular inclined surface 1415 and the second annular inclined surface 1423 are arranged coaxially, and a gap 146 is formed between the first annular inclined surface 1415 and the second annular inclined surface 1423. The cylindrical section 1422 is disposed on one side of the second cover plate 142 that is remote from the electrode assembly 130. The cylindrical section 1422 is connected to one side of the second annular inclined surface 1423 that is remote from the electrode assembly 130. With this arrangement, when the second cover plate 142 and the first cover plate 141 are welded together, the end of the second cover plate 142 on the gap 146 is easily melted quickly, and the molten metal material can flow into the gap 146 quickly. Therefore, the second weld mark 148 between the second cover plate 142 and the first cover plate 141 exhibits higher strength and sealing performance. Note that the position of the second weld mark 148 is shown in FIG. 11, but the shape of the second weld mark 148 in the drawing is an example and should not be interpreted as limiting the shape of the weld mark.Other shapes of weld marks may be selected as necessary, and will not be listed here one by one.

[0072] 1 and 2, in one embodiment of the secondary battery 100 according to the present invention, the explosion-proof structure 1421 is disposed on the second cover plate 142. The explosion-proof structure 1421 is configured to be at least partially released when the air pressure in the case 110 reaches a predetermined level, thereby releasing the pressure in the case 110. The type of the explosion-proof structure 1421 is not particularly limited. For example, the explosion-proof structure 1421 may be an explosion-proof valve assembly disposed on the second cover plate 142. In one embodiment of the secondary battery 100 according to the present invention, the explosion-proof structure 1421 includes a notch disposed on the second cover plate 142, and the notch has an annular structure. Note that the annular structure is not particularly limited to the notch being a circular annular structure or an elliptical annular structure. In the present invention, as long as the start point and the end point of the notch are connected, it is recognized as an annular structure. Of course, in other embodiments, as long as the explosion-proof structure can be released when the pressure is greater than a set threshold value, the start point and the end point of the notch may not be connected. For example, the notch may have a non-annular profile, such as a C-shape or a cross-shape. With such an arrangement, the notch corresponds to an explosion-proof valve piece, and the position where the notch is arranged is a region of low strength in the second cover plate 142. When the air pressure inside the case 110 exceeds a threshold (the strength at the position of the notch can be calculated so that at least a part is released when a certain threshold is exceeded), the air pressure inside the case 110 is discharged from the rupture portion to prevent the secondary battery from exploding in the case and causing module-level thermal runaway. Considering that the notch may damage the nickel coating layer on the surface of the second cover plate 142, and the damage may make the position of the notch prone to rust, the opening of the notch may be provided on one side of the second cover plate facing the electrode assembly 130. In this way, the notch is located in the sealed space inside the case 110, so that the contact between the notch and the air is reduced, the degree of rusting of the notch is reduced, and the service life of the notch can be improved.

[0073] Although the provision of the notch in the second cover plate 142 provides an explosion-proof effect, in another embodiment of the secondary battery 100 of the present invention shown in FIG. 11, no notch is provided in the plate body of the second cover plate 142. As shown in FIG. 11, the explosion-proof structure 1421 is the second weld mark 148 between the first cover plate 141 and the second cover plate 142. When the air pressure in the case 110 exceeds the strength of the second weld mark 148 between the first cover plate 141 and the second cover plate 142, the second weld mark 148 between the first cover plate 141 and the second cover plate 142 is broken, and the pressure is released. In this way, the explosion-proof effect is also achieved. Of course, two weak positions, namely the notch and the second weld mark 148, may be provided to provide a double guarantee that the explosion-proof assembly will release pressure.

[0074] 2 and 3, in one embodiment of the secondary battery 100 according to the present invention, the first cover plate 141 includes a protrusion 1412 that fits into the opening 113. The protrusion 1412 protrudes toward the electrode assembly 130. The outer edge of the protrusion 1412 fits into the side wall 112. The protrusion 1412 is configured to guide the assembly of the first cover plate 141 and the opening 113 and the fitting of the side wall 112 of the case 110 and the first cover plate 141, thereby allowing the first cover plate 141 and the opening 113 to be quickly positioned in the circumferential direction, facilitating welding efficiency and radial positional accuracy. The protrusion 1412 may be integrally and continuously arranged around the through hole 1411. Alternatively, a plurality of independent protrusions 1412 may be arranged around the through hole 1411. In one embodiment, the protrusion 1412 may be continuously disposed around the through hole 1411, and may be configured to block a laser when the first cover plate 141 and the opening 113 are welded together. The connection between the protrusion 1412 and the first cover plate 141 is not particularly limited. The connection may be formed by integral press molding. Alternatively, the protrusion 1412 may be obtained by removing material from the first cover plate 141 by machining. In one embodiment of the secondary battery 100 according to the present invention, the protrusion 1412 is obtained by press processing, and the height H1 of the protrusion 1412 is 0.1 mm to 5 mm along the height direction of the secondary battery 100, and the radial width M of the protrusion 1412 is 1 mm to 10 mm. The height H1 of the protrusion 1412 may be 0.5 mm to 2.5 mm. When the height H1 is within this range, a stable fitting relationship can be obtained and the weight can be reduced. A recess 1418 corresponding to the protrusion 1412 is formed on the surface of the first cover plate 141 on one side away from the electrode assembly 130. The depth H2 of the recess 1418 is 0.1 mm to 5 mm.

[0075] 2 and 3, in one embodiment of the secondary battery 100 according to the present invention, the first cover plate 141 further includes a position restricting portion 1413 arranged around the protruding portion 1412. The end face of the opening 113 abuts against the position restricting portion 1413. The first weld mark 144 between the first cover plate 141 and the opening 113 is arranged around the opening 113 and is located on a surface where the position restricting portion 1413 and the end face are in contact with each other. By providing the position restricting portion 1413, it is possible to position the first cover plate 141 and the case 110 in the axial direction, and the airtightness of the first weld mark 144 between the first cover plate 141 and the side wall 112 of the case 110 can be improved.

[0076] 1 and 5 to 8, in one embodiment of the secondary battery 100 according to the present invention, the case 110 is cylindrical, and an annular surface 1417 is disposed on one side of the protrusion 1412 facing the electrode assembly 130, and the annular surface 1417 is disposed coaxially with the first cover plate 141 and the case 110, and the cover plate welded portion 1432 is connected to one side of the annular surface facing the electrode assembly 130 by welding, and the electrode assembly 130 includes a central through-hole 133, and the opening 1433 is disposed in the center of the first current collector 143, and the projection of the central through-hole 133 on the first current collector 143 at least partially overlaps with the opening 1433 along the height direction of the secondary battery 100. With this arrangement, the chambers at both ends of the electrode assembly 130 can smoothly communicate with each other through the central through-hole 133.

[0077] 3, in one embodiment of the secondary battery 100 according to the present invention, the distance H3 from the end face where the first tab 132 is located to the outer surface of the cover plate is 0.6 mm to 4 mm. Therefore, according to the configuration of the present invention, it is possible to realize good space utilization along the height direction of the secondary battery 100. As a result, it is possible to improve the energy density of the secondary battery 100.

[0078] According to the secondary battery of the present invention, the electrolyte can be injected into the secondary battery 100 through the through hole 1411. However, a solution injection hole 121 for injecting the electrolyte may be further provided. The secondary battery 100 of the present invention may further include the solution injection hole 121 and a blocking plate 122 for sealing and blocking the solution injection hole 121. The solution injection hole 122 may be disposed in the end wall 111 of the case 110 or in the terminal 120. For example, referring to FIG. 13, in one embodiment of the present invention, the solution injection hole 121 is disposed in the terminal 120, and the blocking plate 122 is welded to the terminal 120 after the electrolyte is injected to block the solution injection hole 121. Compared to the case where the solution is injected through the through hole 1411, when the solution injection hole 121 is disposed in the terminal 120, the solution can be injected after the second cover plate 142 is welded to the first cover plate 141. Therefore, after the solution is injected through the through hole 1411, the welded trace between the second cover plate 142 and the first cover plate 141 becomes long, and the problem that the electrolyte may be decomposed due to the influence of welding heat can be solved. Furthermore, when sealing the solution injection hole 121 of the terminal 120, the welding position is away from the electrode assembly 130, so that the influence of heat is small. In one embodiment of the present invention, the terminal 120 is positively charged and functions as the positive terminal of the secondary battery 100, and the entire case 110 is negatively charged and functions as the negative terminal of the secondary battery 100. In another embodiment, the terminal 120 may be negatively charged and functions as the negative terminal of the secondary battery 100, and the entire case 110 may be positively charged and functions as the positive terminal of the secondary battery 100.

[0079] The present invention further provides a battery pack 10. The battery pack 10 includes any of the embodiments of the secondary battery 100. Referring to FIG. 15, in one embodiment of the battery pack 10 according to the present invention, the battery pack 10 includes a housing body 101, a housing cover 102, and a plurality of secondary batteries 100. The secondary batteries 100 are disposed in the housing body 101. The secondary batteries 100 are connected to each other in series or parallel, or in a mixed series and parallel configuration. The housing cover 102 seals and covers the housing body 101 to protect the secondary batteries 100. In addition to the secondary battery 100 according to the present invention, the battery pack 10 may further include a battery pack thermal management system, a circuit board, and the like. Details regarding this will not be described further below.

[0080] Referring to FIG. 14, the present invention further provides an electronic device 1. The electronic device 1 includes an operating unit 11 and a battery pack 10. The operating unit 11 is electrically connected to the battery pack 10 to receive power. As an example, in this embodiment, the electronic device 1 is a vehicle. The vehicle may be a fuel vehicle, a gasoline vehicle, or a new energy vehicle. The new energy vehicle may be a pure electric vehicle, a hybrid vehicle, or a vehicle with extended range. However, the present invention is not limited thereto. The operating unit 11 is a vehicle body. The battery pack 10 is disposed at the bottom of the vehicle body and supplies power to drive the vehicle and operate the on-board electrical components. However, in other embodiments, the electronic device may be a mobile phone, a portable device, a notebook computer, a ship, an aircraft, an electric toy, an electric tool, etc. The aircraft may include an airplane, a rocket, a space shuttle, a spacecraft, etc. The operating unit may be a unit component that receives power from the battery pack and performs a corresponding operation, such as a blade rotating part of a fan or a vacuum operating part of a vacuum cleaner. The electric toys may include static or mobile electric toys such as game machines, electric car toys, electric boat toys, electric plane toys, etc. The power tools may include metal cutting power tools, grinding power tools, assembly power tools, and railroad power tools, such as power drills, power grinders, power wrenches, power drivers, power hammers, impact drills, concrete vibrators, and planers. The embodiments of the present invention are not intended to impose any particular limitations on the electric devices. [Industrial Applicability]

[0081] In the secondary battery 100 according to the present invention, the outer edge of the first cover plate 141 is connected to the side wall 112 by welding, and the opening 113 is sealed. The first current collector plate 143 is connected to the first cover plate 141 by welding. The first cover plate 141 includes a through hole 1411. The second cover plate 142 is fixed to the first cover plate 141, and seals and covers the through hole 1411. The secondary battery 100 can be hermetically sealed without performing roll groove processing or pierce seal processing on the case 110. Therefore, the process is simplified, the assembly efficiency is improved, and the height of the roll groove can be saved. Therefore, the space utilization of the secondary battery 100 is facilitated. Furthermore, in the secondary battery 100 according to the present invention, the electrical connection between the first current collector 143 and the case 110 may be further realized through a conductive connection between the first current collector 143 and the first cover plate 141. Therefore, such a structure allows the first cover plate 141 and the first current collector 143 to be attached to the outside of the case 110 in advance as one body, and the number of assembly steps is reduced. At the same time, damage to the electrode assembly 130 when welding the electrode assembly 130 between the first current collector 143 and the first cover plate 141 is also reduced. Furthermore, in the secondary battery 100 according to the present invention, the influence of the roll groove on the first current collector 143 and the difficulty of welding the case 110 are avoided, and the first cover plate 141 has a greater degree of freedom in structure and thickness relative to the first current collector 143. Compared with the case 110 and the first current collector 143 being welded, welding the case 110 and the first cover plate 141 increases the welding process window, reduces welding leakage and welding penetration in the process of welding the first current collector 143 and the case 110, and also reduces the intrusion of foreign matter into the case 110. Therefore, the present invention effectively addresses some practical problems in the prior art, and creates great value and utility in terms of practical application. The above-described embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the scope of the present invention. Anyone familiar with this technology can modify or change the above-described embodiments without departing from the spirit and scope of the present invention.Therefore, all equivalent modifications or changes made by a person having ordinary skill in the art without departing from the spirit and technical ideas disclosed in the present invention shall likewise be included within the scope of the claims of the present invention. [Explanation of symbols]

[0082] 1: Electronic equipment 10: Battery Pack 11: Operating section 101: Housing body 102: Housing cover 100: Secondary battery 110: Case 111: End wall 112: Side wall 113: Opening 120: Terminal 121: Solution injection hole 122: Barrier 130: Electrode assembly 131: Second Tab 132: First tab 133: Center through hole 134: Second current collector 140: Cover plate assembly 141: First cover plate 1411: Through hole 1412: Convex 1413: Position regulation part 1414: Recess 1415: First annular ramp 1416: Platform area 1417: Annular surface 1418: Recess 142: Lid plate 1421: Explosion-proof structure 1422: Cylindrical section 1423: Second annular ramp 143: First current collector 1431: Tab Weld 1432: Cover plate weld 1433: Opening 1434: Annular region 144: First Weld Scar 145: Guide structure 146: Gap 1471: Inner weld mark 1472: External weld marks 148: Second Weld Scar 149: The third weld mark

Claims

1. A case including an end wall and a side wall surrounding the end wall, the case having an opening formed at an end of the side wall remote from the end wall; a terminal extending through the end wall and insulated from the end wall; an electrode assembly housed within the case, the electrode assembly including a first tab facing the opening and a second tab facing the end wall, the second tab being electrically connected to the terminal; a first current collector disposed at an end of the electrode assembly facing the opening, the first current collector being connected to the first tab by welding; a cover assembly including a first cover plate and a second cover plate, the first cover plate covering the opening and connected to the side wall by welding, the first cover plate connected to the first current collector by welding, the first cover plate including a through hole, and the second cover plate welded to the first cover plate to seal the through hole; A secondary battery comprising:

2. 2. The secondary battery of claim 1, wherein the first current collector includes a cover plate weld and a tab weld, the cover plate weld being connected to the first cover plate by welding, and the tab weld being connected to the first tab by welding.

3. The secondary battery according to claim 2 , wherein a projection of the through hole on the first current collector covers the tab weld along a height direction of the secondary battery.

4. 4. The secondary battery of claim 3, wherein the cover plate weld is disposed between the first cover plate and the electrode assembly, and one side of the cover plate weld away from the electrode assembly is connected to the first cover plate by welding.

5. 4. The secondary battery according to claim 3, wherein the cover plate weld is welded to an end of the through hole, and the tab weld is recessed toward the electrode assembly side from the cover plate weld and is connected to a first tab by the welding.

6. The secondary battery according to claim 3 , wherein the case is cylindrical, the first cover plate is annular, and the through hole is disposed coaxially with the first cover plate.

7. 4. The secondary battery of claim 3, wherein the sidewall has an outer diameter D, the tab welds are distributed within an annular region centered on the end face center of the electrode assembly, the inner diameter of the annular region is 0.25D or more, and the outer diameter of the annular region is 0.87D or less.

8. The secondary battery according to claim 7 , wherein the through hole has a diameter of 0.43D or more and 0.96D or less.

9. The secondary battery according to claim 1 , wherein an inner edge of the first cover plate includes a recess, the through hole is disposed in the recess, and the second cover plate is at least partially housed in the recess.

10. 10. The secondary battery of claim 9, wherein a bottom of the recess includes a platform area, the platform area is disposed around the through hole, and the second cover plate is attached to one side of the platform area away from the electrode assembly and connected to the platform area by welding.

11. 2. The secondary battery of claim 1, wherein an explosion-proof structure is disposed on the second cover plate, the explosion-proof structure including a notch disposed on the second cover plate, the opening of the notch being near the electrode assembly.

12. The secondary battery according to claim 1 , wherein an explosion-proof structure is disposed on the second cover plate, and the explosion-proof structure includes a second weld mark between the first cover plate and the second cover plate.

13. The secondary battery according to claim 3 , further comprising a solution injection hole and a blocking plate, the solution injection hole being disposed on the terminal, and the blocking plate being welded to the terminal to seal the solution injection hole.

14. A battery pack comprising the secondary battery according to any one of claims 1 to 13.

15. An electronic device comprising the battery pack according to claim 14.

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