Secondary battery, battery pack, and electronic device

Abstract

The utility model provides a secondary battery, a battery pack and an electronic device. The secondary battery comprises a shell, an electrode assembly, a current collecting component and a cover plate assembly, the shell comprises an end wall and a side wall; the electrode assembly is accommodated in the shell; the current collecting component and the tab are welded and connected to form a first welding mark; the cover plate assembly comprises a first cover plate and a second cover plate, the first cover plate covers the opening and is in welded connection with the side wall, the first cover plate comprises a first part and a second part, the second part is in welded connection with the current collecting component and forms a second welding mark, and the second welding mark extends from one side, facing the electrode assembly, of the current collecting component to the second part; the second cover plate is welded to the first cover plate and does not exceed the outer surface of the second part, the first part comprises a solid part and a hollow part, the projection of the hollow part on the current collecting component covers the welding mark, the solid part is used for supporting the inner periphery of the second part, and the second cover plate is welded to the first cover plate and seals the hollow part; the technical problem that the risk of burning a tab and a diaphragm exists when the current collecting component is welded to the outer side of the cover plate can be solved.

Description

Technical Field

[0001] This utility model relates to the field of battery technology, specifically to a secondary battery, battery pack, and electronic device. Background Technology

[0002] Large cylindrical batteries are increasingly favored by major automakers due to their advantages of high safety, long lifespan, excellent fast charging performance, good battery consistency, and low production cost.

[0003] Currently, the casing of large cylindrical batteries is generally charged, allowing the casing itself to be used as one of the positive and negative electrodes during battery assembly. One method of electrical connection between the electrode assembly and the casing involves first welding the electrode assembly to the current collector, then welding the cover plate to the current collector, and finally welding the cover plate to the casing, thus charging the casing. However, this process carries the risk of burning the electrode tabs and separator when welding the cover plate to the current collector. Utility Model Content

[0004] This invention provides a secondary battery, a battery pack, and an electronic device to improve the technical problem of the risk of burning the tabs and diaphragm when welding the current collector to the outside of the cover plate.

[0005] To achieve the above and other related objectives, this utility model provides a secondary battery, a battery pack, and an electronic device. The secondary battery includes: a housing, an electrode assembly, a current collector, and a cover assembly. The housing includes an end wall and a side wall surrounding the end wall, with an opening formed at one end of the side wall away from the end wall. The electrode assembly is housed within the housing and includes a tab facing the opening. The current collector is disposed at the end of the electrode assembly facing the opening, and is welded to the tab, forming a first weld mark. The cover assembly includes a first cover plate and a second cover plate. The first cover plate covers the opening and is welded to the side wall. The first cover plate includes a first portion and a second portion surrounding the first portion. The second portion is welded to the current collector and forms a second weld mark. The second weld mark extends from the side of the current collector facing the electrode assembly toward the second portion and does not exceed the outer surface of the second portion. The first portion includes a solid portion and a hollow portion. Along the height direction of the secondary battery, the projection of the hollow portion onto the current collector covers the first weld mark. The solid portion supports the inner periphery of the second portion. The second cover plate is welded to the first cover plate and seals the hollow portion.

[0006] In the above technical solution, the first cover plate includes a first part and a second part. The second part is welded to the current collector and forms a second weld mark. The second weld mark extends from the side of the current collector facing the electrode assembly to the second part. That is, the second weld mark is formed by welding from the side of the current collector facing the electrode assembly to the second part, replacing the process of welding from the outside of the cover plate to the current collector, reducing the risk of welding residual heat burning the tabs and separator. The first part includes a solid part and a hollow part. The current collector and the first cover plate can be welded together before the secondary battery is assembled, and then the current collector and the electrode assembly are welded through the hollow part. This arrangement reduces the number of assembly steps. Furthermore, the current collector and the first cover plate are welded before assembly. The laser irradiates from one side of the current collector, penetrating the relatively thin current collector and welding it to the first cover plate. The welding process window is large and the welding efficiency is high. At the same time, the second weld mark formed by this method is located on one side of the current collector and does not extend beyond the outer surface of the second part, which is beneficial for the rust prevention of the second weld mark and also makes the outer surface of the first cover plate smoother. This not only improves the aesthetics of the appearance but also improves the stability of the secondary battery when the first cover plate is placed downwards.

[0007] In addition, the solid part is used to support the inner periphery of the second part, which can improve the structural strength of the first cover plate, thereby reducing the welding deformation between the first cover plate and the side wall, improving the positioning accuracy of the first cover plate and the second cover plate, and thus reducing the welding difficulty between the second cover plate and the first cover plate.

[0008] In one example of the secondary battery of this utility model, the current collector has multiple sets of first solder marks. The multiple sets of first solder marks are evenly arranged circumferentially with the center of the current collector as the center. There is a non-welding area between every two adjacent sets of first solder marks. Along the height direction of the secondary battery, the projection of the solid part on the current collector falls into the non-welding area. The solid part is a rotationally symmetric structure with the center of the current collector as the center.

[0009] In the above technical solution, multiple sets of first weld marks are arranged circumferentially with the center of the current collector as the center, which is beneficial to improving welding quality and yield, reducing internal resistance and heat generation, and thus improving battery performance. The solid part is arranged in a central rotational symmetry, which can achieve the same shape and mass distribution, uniform stiffness distribution and uniform stress, so that the solid part has high stiffness and is conducive to improving the balance of the solid part, so as to better resist the thermal deformation that may be caused when the first cover plate is welded to the current collector and the shell, thereby improving the positioning accuracy of the first cover plate and the second cover plate, and reducing the welding difficulty between the second cover plate and the first cover plate.

[0010] In one example of the secondary battery of this utility model, the current collector is circular, and there are even numbers of first solder marks on the current collector. The solid part is a symmetrical structure with the diameter of the current collector as the axis of symmetry.

[0011] In the above technical solution, the solid part has a symmetrical structure with mirror symmetry. The structures on both sides of the axis of symmetry have the same shape and mass distribution. This symmetry makes the solid part balanced when subjected to force and can effectively resist the thermal deformation that may be caused when the first cover plate is welded to the current collection component and the shell. It further improves the positioning accuracy of the first cover plate and the second cover plate and reduces the welding difficulty between the second cover plate and the first cover plate.

[0012] In one example of the secondary battery of this utility model, the electrode assembly is a wound structure with a winding hole at the center. The solid part includes a stop portion, and the projection of the stop portion on the electrode assembly covers the winding hole along the height direction of the secondary battery.

[0013] In the above technical solution, since there is no binding force in the winding hole of the winding structure, under the action of radial outer clamping force, the winding hole of the winding structure will protrude to both sides in the axial direction. The setting of the stop part can limit the protrusion of the winding hole of the winding structure to both sides in the axial direction, so as to improve the overall performance of the electrode assembly.

[0014] In one example of the secondary battery of this utility model, a liquid injection hole is provided on the stop portion, and along the height direction of the secondary battery, the projection of the liquid injection hole on the electrode assembly at least partially coincides with the winding hole.

[0015] In the above technical solution, the stop portion is provided with the above-mentioned injection hole, which is beneficial to inject electrolyte into the winding hole, improve the efficiency of electrolyte injection and the wetting effect of electrolyte, and thus improve battery performance.

[0016] In one example of the secondary battery of this utility model, the inner periphery of the current collector connecting part is connected to a first recess that is recessed toward the electrode assembly. Both the hollow part and the solid part are provided in the first recess. Along the height direction of the secondary battery, the second cover plate is at least partially accommodated in the first recess.

[0017] In the above technical solution, the second cover plate is at least partially accommodated in the first recess along the height direction. On the one hand, this facilitates the rapid and accurate positioning of the second cover plate and the first cover plate during the assembly process. On the other hand, it reduces the welding difficulty between the first cover plate and the first recess.

[0018] In one example of the secondary battery of this utility model, the outer periphery of the first cover plate is provided with a second recess that is recessed toward the electrode assembly. The outer side of the second recess is surrounded by a limiting part. The limiting part extends radially outward toward the first cover plate and is fixedly connected to the end face of the opening. The side of the second cover plate away from the electrode assembly is lower than the side of the limiting part away from the electrode assembly.

[0019] In the above technical solution, the second recess has the effect of blocking the laser when welding the limiting part and the side wall of the shell. The setting of the side of the second cover plate away from the electrode assembly being lower than the side of the limiting part away from the electrode assembly can ensure that when the first cover plate is placed downwards, only the relatively flat limiting part surrounding the outermost ring contacts the external plane. On the one hand, the surrounding structure of the limiting part and the contact area per unit radial width are large. On the other hand, it avoids the contact between the second cover plate with possible solder marks on the surface and the external plane, which can improve the stability of the secondary battery when the first cover plate is placed downwards.

[0020] In one example of the secondary battery of this utility model, the thickness of the second cover plate is less than the thickness of the thinnest part of the first cover plate.

[0021] In the above technical solution, the second cover plate has high structural strength due to the solid part. Therefore, the thickness of the second cover plate can be designed to be thinner. While ensuring the overall strength of the cover plate assembly, the weight of the battery and the production cost can be reduced. At the same time, the thinner thickness of the second cover plate reduces the welding strength between the second cover plate and the first cover plate. Therefore, the second cover plate can be used as an explosion-proof valve to improve the safety performance of the secondary battery.

[0022] This utility model also provides a battery pack, which includes any of the above-mentioned secondary batteries.

[0023] This invention also provides an electronic device that includes the aforementioned battery pack.

[0024] This utility model relates to a secondary battery. The first cover plate includes a first part and a second part. The second part is welded to a current collector and has a second weld mark formed thereon. The second weld mark extends from the side of the current collector facing the electrode assembly toward the second part, but does not exceed the outer surface of the second part. The first part includes a solid portion and a hollow portion. The current collector and the first cover plate can be welded together before the secondary battery is assembled, and then the current collector and the electrode assembly are welded together through the hollow portion. This arrangement reduces assembly steps. Furthermore, welding the current collector and the first cover plate before assembly, with the second weld mark formed from the side of the current collector facing the electrode assembly toward the second part, replaces the step of welding the current collector from the outside of the cover plate, reducing the risk of welding heat burning the tabs and separator. The laser irradiates from one side of the current collector, penetrating the relatively thin current collector and welding it to the first cover plate. The welding process window is large and the welding efficiency is high. At the same time, the second weld mark formed by this method is located on one side of the current collector and does not extend beyond the outer surface of the second part. This is beneficial for the rust prevention of the second weld mark and also makes the outer surface of the first cover plate smoother. This not only improves the appearance but also enhances the stability of the secondary battery when the first cover plate is placed downwards.

[0025] In addition, the solid part is used to support the inner periphery of the second part, which can improve the structural strength of the first cover plate, thereby reducing the welding deformation between the first cover plate and the side wall, improving the positioning accuracy of the first cover plate and the second cover plate, and thus reducing the welding difficulty between the second cover plate and the first cover plate. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other embodiments can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the overall structure of a secondary battery according to an embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram of the electrode assembly of an embodiment of the secondary battery of this utility model;

[0029] Figure 3 This is a cross-sectional view of the electrode assembly of an embodiment of the secondary battery of this utility model;

[0030] Figure 4 for Figure 1 A magnified view of a section at point A in the middle;

[0031] Figure 5 This is an exploded view of the cover plate assembly of a secondary battery according to an embodiment of the present invention.

[0032] Figure 6 This is a top view of an embodiment of the secondary battery of this utility model without the second cover plate.

[0033] Figure 7 This is a top view of an embodiment of the secondary battery of this utility model without the second cover plate.

[0034] Figure 8 This is a schematic diagram of the overall structure of a secondary battery according to an embodiment of the present invention;

[0035] Figure 9 for Figure 8 A magnified view of a section at point B in the middle;

[0036] Figure 10 This is an exploded view of the cover plate assembly of a secondary battery according to an embodiment of the present invention.

[0037] Figure 11 This is a top view of an embodiment of the secondary battery of this utility model without the second and third cover plates.

[0038] Figure 12 This is a schematic diagram of the battery pack of this utility model in one embodiment;

[0039] Figure 13 This is a schematic diagram of the electronic device of the present invention in one embodiment.

[0040] Component designation explanation

[0041] 1. Electronic device; 10. Battery pack; 11. Working part; 101. Housing; 102. Housing cover; 100. Secondary battery; 110. Casing; 111. End wall; 112. Side wall; 113. Opening; 120. Electrode assembly; 121. First electrode; 1211. Negative current collector; 1212. First coated area; 1213. First uncoated area; 122. Separator; 123. Second electrode; 1231. Positive current collector; 1232. Second coated area; 1233. Second uncoated area; 124. First tab; 125. Second... 126. Electrode; 127. Winding structure; 130. Winding hole; 131. Current collector; 140. First weld mark; 141. Cover plate assembly; 141. First cover plate; 1411. First part; 14111. Solid part; 14112. Hollowed-out part; 14113. Stop part; 14114. Injection hole; 1412. Second part; 1413. Second weld mark; 1414. First recess; 1415. Second recess; 14151. Bottom surface; 1416. Limiting part; 142. Second cover plate; 143. Third cover plate; 150. Electrode post. Detailed Implementation

[0042] The following specific examples illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification. This utility model can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this utility model. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. It should also be understood that the terminology used in the embodiments of this utility model is for describing specific implementation schemes and not for limiting the scope of protection of this utility model. Test methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or according to the conditions recommended by the respective manufacturers.

[0043] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise specified in this invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention, as well as the prior art known to those skilled in the art and the description of this invention, may be implemented using any prior art methods, equipment, and materials similar to or equivalent to those in the embodiments of this invention.

[0044] It should be noted that the terms such as "upper", "lower", "left", "right", "middle" and "one" used in this specification are only for clarity of description and are not intended to limit the scope of implementation of this utility model. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered as within the scope of implementation of this utility model.

[0045] A secondary battery includes an electrode assembly, which is the component in a secondary battery where electrochemical reactions occur, and may contain one or more electrode assemblies.

[0046] The secondary battery also includes a casing, a cover plate, and a current collector. The casing includes an end wall and a side wall surrounding the end wall. One end of the side wall has an opening, through which the electrode assembly can be assembled into the casing. The casing itself is used as one of the positive and negative electrodes when the batteries are assembled. One way to electrically connect the electrode assembly inside the casing to the casing is as follows: first, the electrode assembly is welded to the current collector, then the cover plate is welded to the current collector, and finally the cover plate is welded to the casing, thus making the casing energized.

[0047] When welding the cover plate to the current collector, welding needs to be done from the outside of the cover plate. The inventors found that since the cover plate is usually thicker than the current collector, it requires high energy to penetrate the cover plate with a laser. The current collector is very thin and conducts heat quickly. The tabs and diaphragm located below the current collector are at risk of being burned by the residual heat of welding.

[0048] In view of this, the present invention provides a technical solution in which the current collector and the first cover plate can be welded together before the secondary battery is assembled, and then the current collector and the electrode assembly are welded through the hollow part on the first cover plate. This setting reduces the assembly steps, and the welding of the current collector and the first cover plate before assembly changes the process of welding the current collector to the outside of the cover plate, reducing the risk of welding residual heat burning the tabs and the separator.

[0049] Please see Figures 1 to 13 This utility model provides a secondary battery 100, a battery pack 10 and an electronic device 1. The secondary battery 100 includes: a housing 110, an electrode assembly 120, a current collector 130, a cover plate assembly 140 and a terminal post 150.

[0050] Please see Figure 1 and Figure 8 The housing 110 includes an end wall 111 and a side wall 112 surrounding the end wall 111. As long as a stable sealing and electrical connection can be formed, the connection between the end wall 111 and the side wall 112 can be achieved in various ways, such as integral stamping, integral casting, or separate welding. The circumference of the side wall 112 is not limited; it can be cylindrical or prismatic, or it can follow any other closed-loop contour that matches the end wall 111. In this embodiment, the outer edge of the end wall 111 is circular, and the side wall 112 is cylindrical, surrounding the outer edge of the end wall 111, with a circular opening 113 formed at the end of the side wall 112 facing away from the end wall 111. A receiving cavity is formed within the housing 110 formed by the end wall 111 and the side wall 112 to accommodate the electrode assembly 120, electrolyte, and other necessary battery components. Specifically, the diameter of the housing 110 can be determined according to the specific size of the electrode assembly 120, such as 18mm, 21mm, or 46mm. The shell 110 can be made of various materials, such as copper, iron, aluminum, steel, aluminum alloy, etc. In order to prevent the shell 110 from rusting during long-term use, a layer of anti-rust material such as metallic nickel can be plated on the surface of the shell 110.

[0051] Please see Figures 1 to 3 The electrode assembly 120 is housed within the casing 110 and is a component in the secondary battery 100 where electrochemical reactions occur. The casing 110 may contain one or more electrode assemblies 120. The electrode assembly 120 includes a first electrode 121, a second electrode 123, and a separator 122 stacked and wound to form a wound structure 126. The first electrode 121 and the second electrode 123 have opposite polarities. In some embodiments, the first electrode 121 is a positive electrode and the second electrode 123 is a negative electrode; in other embodiments, the first electrode 121 is a negative electrode and the second electrode 123 is a positive electrode.

[0052] Please see Figures 1 to 3 In this embodiment, the first electrode 121 is a negative electrode. The first electrode 121 includes a negative current collector 1211 and a negative active material. The negative active material is coated on the surface of the negative current collector 1211. The negative current collector 1211 includes a first coated area 1212 coated with active material and a first uncoated area 1213 uncoated with active material. The first uncoated area 1213 is located at the end of the first electrode 121. The first uncoated area 1213 extends out of the diaphragm 122 along the winding axis direction of the electrode assembly 120 and bends towards the winding axis to form a first tab 124. The first tab 124 is the corresponding negative tab.

[0053] Please see Figures 1 to 3The second electrode 123 is a positive electrode. Specifically, the second electrode 123 includes a positive current collector 1231 and a positive active material. The positive active material is coated on the surface of the positive current collector 1231. The positive current collector 1231 includes a second coated area 1232 coated with active material and a second uncoated area 1233 uncoated with active material. The second uncoated area 1233 is located at the end of the second electrode 123. The other end of the second uncoated area 1233 extends out of the diaphragm 122 along the winding axis of the electrode assembly 120 and is bent toward the winding axis to form a second tab 125. The second tab 125 is the corresponding positive tab.

[0054] Please see Figures 1 to 3 A separator 122 is disposed between the first electrode 121 and the second electrode 123 to isolate the positive electrode active material layer and the negative electrode active material layer. Taking a lithium-ion secondary battery 100 as an example, the positive electrode current collector 1231 can be made of aluminum, and the positive electrode active material layer includes positive electrode active material, which can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, etc. The negative electrode current collector 1211 can be made of copper, and the negative electrode active material layer includes negative electrode active material, which can be carbon or silicon, etc. The substrate material of the separator 122 can be polypropylene (PP) or polyethylene (PE), etc. To protect and insulate the electrode assembly 120, an insulating film can also be wrapped around the electrode assembly 120. The insulating film can be synthesized from PP, PE, polyethylene terephthalate (PET), polyvinyl chloride (PVC), or other polymer materials.

[0055] Please see Figure 1 and Figure 3 Furthermore, if the first tab 124 faces the end wall 111 or the opening 113, then the second tab 125 faces the other end of the housing 110. In this embodiment, the second tab 125 faces the end wall 111 and is electrically connected to the post 150, making the post 150 positively charged. The tab facing the opening 113 is the first tab 124, and the housing 110 is electrically connected to the first tab 124, thus becoming negatively charged. However, in another embodiment, the first tab 124 can be connected to the post 150, and the second tab 125 can be connected to the housing 110.

[0056] Please see Figure 1 and Figure 8The electrode post 150 is fixed to the end wall 111 and electrically connected to the electrode assembly 120. Specifically, the end wall 111 is provided with a hole for the electrode post 150, and the electrode post 150 is installed through the hole and insulated from the end wall 111. The end of the electrode post 150 facing the electrode assembly 120 passes through the end wall 111 and is directly electrically connected to the second electrode tab 125 or indirectly connected via a transfer connection. The structure of the electrode post 150 can be any suitable form that can pass through the end wall 111 and be electrically connected to the second electrode tab 125 of the electrode assembly 120. For example, the cross-section can be circular, square, prismatic, or an irregular contour that can achieve stable conductivity. The shape of the hole in the electrode post 150 corresponds to the shape of the electrode post 150. In this embodiment, the cross-section of the electrode post 150 is circular.

[0057] Please see Figure 1 and Figures 6 to 7 The electrode assembly 120 is electrically connected to the housing 110 via the current collector 130. The current collector 130 is also electrically connected to the electrode assembly 120. In a specific embodiment, the current collector 130 is welded to the first tab 124. The welding method can be ultrasonic welding, resistance welding, laser welding, etc., and is not limited thereto. In this embodiment, laser welding is used. The first tab 124 is the negative tab. Copper is the preferred material for the current collector 130. It should be noted that the shape of the current collector 130 can be any rotationally symmetrical shape, such as a circle, square, regular polygon, petal shape, or other shape with a center of symmetry that can coincide with the original shape after rotating around the center of symmetry by a certain angle. This is not limited thereto, as long as a stable and reliable electrical connection can be achieved. The center of the current collector 130 is its own center of symmetry. To improve the positioning, processing convenience, interchangeability, and uniformity of the current collector 130 during installation, the current collector 130 in this embodiment adopts a circular structure. After the current collector 130 is welded to the first electrode 124, a first weld mark 131 is formed on the current collector 130. The first weld mark 131 is formed through a heating and subsequent cooling process, and can characterize the welding path of the current collector 130 and the first electrode 124. The shape of the first weld mark 131 is not limited, and can be a straight line, a curve (wavy line, arc line, sine curve, etc.), a broken line, or other irregular shapes, such as... Figure 6 , Figure 7 and Figure 11 As shown, the number and position of the first solder mark 131 are not limited, as long as a stable electrical connection between the current collector 130 and the first electrode 124 can be achieved.

[0058] Please see Figures 4 to 5 and Figures 9 to 10The cover plate assembly 140 includes a first cover plate 141 and a second cover plate 142. The first cover plate 141 covers the opening 113, and 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 welded to the side wall 112 and seals the opening 113. The welding method between the outer edge of the first cover plate 141 and the side wall 112 can be a welding method that can achieve a seal at the welding position, such as welding with the welding head in a direction perpendicular to the side wall 112, and moving circumferentially relative to the secondary battery 100 to complete the welding during the welding process.

[0059] Specifically, please refer to Figures 4 to 7 and Figures 9 to 11 The first cover plate 141 includes a first portion 1411 and a second portion 1412 surrounding the first portion 1411. The second portion 1412 is welded to the current collector 130 and forms a second solder mark 1413. The second solder mark 1413 extends from the side of the current collector 130 facing the electrode assembly 120 toward the second portion 1412, but does not exceed the outer surface of the second portion 1412. That is, the second solder mark 1413 is formed by welding from the side of the current collector 130 facing the electrode assembly 120 toward the second portion 1412, replacing the process of welding from the outside of the cover plate assembly 140 to the current collector 130, reducing the risk of welding residual heat burning the first electrode tab 124 and the diaphragm 122. As long as a stable conductive connection between the second portion 1412 and the current collector 130 can be achieved, the welding position of the second portion 1412 and the current collector 130 and the shape of the second solder mark 1413 are not limited. The second part 1412 surrounds the periphery of the first cover plate 141. This arrangement helps to improve the current flow capacity between the current collector 130 and the first cover plate 141, thereby reducing the internal resistance of the battery. The shape of the second part 1412 is not limited. Preferably, the shape of the second part 1412 corresponds to the outer periphery of the first cover plate 141. For example, if the outer periphery of the first cover plate 141 is circular, the second part 1412 is an annulus; if the first cover plate 141 is square, the second part 1412 is square; if the outer periphery of the first cover plate 141 is polygonal, the second part 1412 is polygonal. In this embodiment, the outer periphery of the first cover plate 141 is circular, and the second part 1412 is an annulus.

[0060] The first part 1411 includes a solid part 14111 and a hollow part 14112. Along the height direction of the secondary battery 100, the projection of the hollow part 14112 on the current collector 130 covers the first solder mark 131. This can be understood as the hollow part being a through hole in the overall structure. The projection of the hollow part 14112 covering the first solder mark 131, i.e., the through hole covering the first solder mark 131, allows the current collector 130 to be welded to the first electrode tab 124 from within the hollow part 14112 of the first cover plate 141. The shape and number of through holes in the hollow part 14112 are not limited; for example, they can be circular, elliptical, fan-shaped, or other types with closed contours. For example, in one embodiment, such as... Figure 10 As shown, the hollow portion 14112 is shaped like a fan ring; in other embodiments, multiple hollow portions 14112 can be provided, and the design can be adapted according to the shape and number of the first solder mark 131, such as... Figure 5 As shown.

[0061] Please continue reading. Figure 5 and Figure 10 The solid part 14111 is used to support the inner periphery of the second part 1412. The solid part 14111 can improve the structural strength of the first cover plate 141, thereby reducing the welding deformation between the first cover plate 141 and the side wall 112, improving the positioning accuracy of the first cover plate 141 and the second cover plate 142, and thus reducing the welding difficulty between the second cover plate 142 and the first cover plate 141.

[0062] Please see Figures 4 to 7 In the above technical solution, the current collector 130 and the first cover plate 141 can be welded together before the secondary battery 100 is assembled. Then, the current collector 130 and the electrode assembly 120 are welded through the hollow part 14112 on the first cover plate 141. This arrangement reduces the assembly steps. The current collector 130 and the first cover plate 141 are welded together before assembly. The laser irradiates from one side of the current collector 130, penetrates the relatively thin current collector 130 and welds to the first cover plate 141. The welding process window is large and the welding efficiency is high. At the same time, the second weld mark 1413 formed by this method is located on one side of the current collector 130 and does not exceed the outer surface of the second part 1412. This is beneficial for the rust prevention of the second weld mark 1413 and also makes the outer surface of the first cover plate 141 smoother. This not only improves the appearance but also improves the stability of the secondary battery 100 when the first cover plate 141 side is placed downwards.

[0063] Please see Figures 4 to 7 and Figures 9 to 11The second cover plate 142 is welded to the first cover plate 141 and seals the perforated portion 14112. As long as the perforated portion 14112 can be effectively sealed, there are various ways for the second cover plate 142 to seal the perforated portion 14112. For example, the second cover plate 142 can be welded to the first cover plate 141 and seal the perforated portion 14112. The shape and number of the second cover plate 142 can correspond to the perforated portion 14112. In one embodiment, when the perforated portion 14112 is a fan-shaped ring, the second cover plate 142 can also be a fan-shaped ring, and the first weld mark 131 formed by the current collector 130 and the first electrode lug 124 is located in this fan-shaped ring, such as... Figure 10 and Figure 11 As shown; in other embodiments, when the cutout portion 14112 is multiple circles, the second cover plate 142 can be multiple circles; when the cutout portion 14112 is multiple squares, the second cover plate 142 is also multiple squares. The shape and number of the second cover plate 142 do not necessarily correspond to the shape and number of the cutout portion 14112. For example, when the cutout portion 14112 is multiple fan-shaped rings, the second cover plate 142 is a circle or square that can cover all the cutout portions 14112, such as... Figures 5 to 7 As shown. It should be noted that, Figure 6 , Figure 7 and Figure 11 The first solder mark 131 shown is only illustrative and is not intended to limit the shape of the first solder mark 131.

[0064] In one example of the secondary battery 100 of this utility model, the current collector 130 has multiple sets of first solder marks 131, for example, there can be 2 sets, 3 sets, 4 sets, 5 sets, 6 sets or more. For example, in one embodiment, please refer to... Figure 6 The first solder mark 131 has three sets, and the three sets of first solder marks 131 are evenly arranged circumferentially with the center of the current collector 130 as the center; in another embodiment, please refer to Figure 7There are four groups of first solder marks 131, which are evenly arranged circumferentially around the center of the current collector 130. This arrangement facilitates the uniform distribution of current through the first tab 124, reduces internal resistance and heat generation, thereby enhancing the performance of the secondary battery 100 and improving welding strength. There is a non-welding area between every two adjacent groups of first solder marks 131. Along the height direction of the secondary battery 100, the projection of the solid part 14111 on the current collector 130 falls within the non-welding area. It can be understood that the solid part 14111 is provided at all positions corresponding to the non-welding areas, or it can be provided only at positions corresponding to some of the non-welding areas, as long as it avoids the first solder marks 131 of the current collector 130 and the first tab 124. The solid part 14111 is connected to the inner side of the second part 1412 to provide better support for the second part 1412. For better support, the solid part 14111 is a rotationally symmetric structure centered on the center of the current collecting member 130. This allows for the same shape and mass distribution, uniform stiffness distribution, and uniform stress distribution. This results in the solid part 14111 having high stiffness and improving its balance. This helps to better resist thermal deformation that may occur when the first cover plate 141 is welded to the current collecting member 130 and the shell 110. It also further improves the positioning accuracy of the first cover plate 141 and the second cover plate 142, and reduces the welding difficulty between the second cover plate 142 and the first cover plate 141.

[0065] Please see Figure 5 and Figure 7 In one example of the secondary battery 100 of this utility model, the current collector 130 is circular, and the current collector 130 has an even number of first solder marks 131, such as 2, 4, 6, 8 or more. The solid part 14111 is an axisymmetric structure symmetrical about the diameter of the current collector 130. For example, in this embodiment, there are 4 sets of first solder marks 131, and the corresponding solid part 14111 is cross-shaped. The solid part 14111 has a symmetrical structure with mirror symmetry. The structures on both sides of the axis of symmetry have the same shape and mass distribution. This symmetry makes the solid part 14111 balanced under force and can effectively resist the thermal deformation that may be caused when the first cover plate 141 is welded to the current collector 130 and the shell 110. It further improves the positioning accuracy of the first cover plate 141 and the second cover plate 142, and reduces the welding difficulty between the second cover plate 142 and the first cover plate 141.

[0066] Please see Figure 2 , Figure 4 and Figure 9In one example of the secondary battery 100 of this utility model, the electrode assembly 120 is a wound structure 126. The center of the wound structure 126 has a wound hole 127. Since there is no binding force in the wound hole 127 of the wound structure 126, under the action of the radially outer pressing force, the wound hole 127 of the wound structure 126 will have the problem of extending to both sides in the axial direction. Therefore, the solid part 14111 includes a stop part 14113. Furthermore, along the height direction of the secondary battery 100, the projection of the stop part 14113 on the electrode assembly 120 covers the wound hole 127. This setting can limit the extension of the wound hole 127 of the wound structure 126 to both sides in the axial direction, so as to improve the overall performance of the electrode assembly 120.

[0067] Considering that the setting of the stop part 14113 will have a certain impact on the injection of electrolyte into the winding hole 127, in an example of the secondary battery 100 of this utility model, please refer to Figures 5 to 7 and Figures 10 to 11 The stop portion 14113 is provided with an injection hole 14114. The shape of the injection hole 14114 is not limited and can be circular, elliptical, or other shapes with a closed contour. Ideally, the projection of the injection hole 14114 onto the electrode assembly 120 should at least partially coincide with the winding hole 127 along the height direction of the secondary battery 100. In this embodiment, the injection hole 14114 is a circle concentric with the winding hole 127. This arrangement facilitates the injection of electrolyte into the winding hole 127, improving the efficiency of electrolyte injection and the wetting effect of the electrolyte, thereby improving battery performance. It should be noted that in some embodiments, the injection hole 14114 and the hollow portion 14112 are simultaneously sealed by a second cover plate 142, such as... Figure 5 As shown, in some other embodiments, such as Figure 10 As shown, when the hollow part 14112 is a fan-shaped ring, the second cover plate 142 is also a fan-shaped ring, which is only used to block the hollow part 14112. In this embodiment, a third cover plate 143 is also provided, which is used to separately block the injection hole 14114.

[0068] Please see Figures 4 to 5 and Figures 9 to 10In one example of the secondary battery 100 of this utility model, the inner periphery of the second part 1412 is connected to a first recess 1414 that is recessed toward the electrode assembly 120. Both the hollowed-out part 14112 and the solid part 14111 are disposed in the first recess 1414. The shape of the first recess 1414 can correspond to the second cover plate 142. For example, when the outer contour of the second cover plate 142 is circular, the outer contour projection of the first recess 1414 is also circular. Alternatively, the shape of the first recess 1414 may not correspond to the second cover plate 142. For example, when the outer contour of the second cover plate 142 is circular, the first recess 1414 has a square contour capable of accommodating the second cover plate 142. Along the height direction of the secondary battery 100, the second cover plate 142 is at least partially accommodated within the first recess 1414. This arrangement facilitates rapid and accurate positioning of the second cover plate 142 and the first cover plate 141 during assembly, and also reduces the welding difficulty between the first cover plate 141 and the first recess 1414. Preferably, the side of the second cover plate 142 facing away from the electrode assembly 120 is recessed into the first recess 1414 or flush with the outer surface of the first cover plate 141, so as to facilitate welding of the second cover plate 142 and the first recess 1414 and improve the welding quality.

[0069] Please see Figures 4 to 5 and Figures 9 to 10 In one example of the secondary battery 100 of this utility model, the outer periphery of the first cover plate 141 is provided with a second recess 1415 that is recessed toward the electrode assembly 120. The second recess 1415 has the effect of blocking the laser when welding the limiting part 1416 and the side wall 112 of the housing 110. The second recess 1415 includes a bottom surface 14151 facing the electrode assembly 120. The part where the current collector 130 is connected to the second part 1412 can be either the first recess 1414 or the second recess 1415, and there is no limitation on this. In this embodiment, the current collector 130 is welded and fixed to the bottom surface 14151. Since the bottom surface 14151 is close to the outer periphery of the first cover plate 141 and has a large area per unit width, this setting is beneficial to improving the current carrying capacity of the current collector 130.

[0070] Please see Figures 5 to 11Furthermore, a limiting portion 1416 surrounds the outer side of the second recess 1415. The limiting portion 1416 extends radially outward toward the first cover plate 141 and is fixedly connected to the end face of the opening 113. The side of the second cover plate 142 facing away from the electrode assembly 120 is lower than the side of the limiting portion 1416 facing away from the electrode assembly 120. This arrangement ensures that when the first cover plate 141 is placed downwards, only the relatively flat limiting portion 1416 surrounding the outermost ring contacts the external plane. On the one hand, the surrounding structure of the limiting portion 1416 and the contact area per unit radial width are large. On the other hand, it avoids contact between the second cover plate 142, whose surface may have solder marks, and the external plane, thereby improving the stability of the secondary battery 100 when the first cover plate 141 is placed downwards.

[0071] Please see Figure 5 The second cover plate 142 has high structural strength due to the solid part 14111. Therefore, the thickness of the second cover plate 142 can be designed to be thinner to meet the strength requirements of the cover plate assembly 140. In one example of the secondary battery 100 of this utility model, the thickness of the second cover plate 142 is less than the thickness of the thinnest part of the first cover plate 141. This technical solution can reduce the battery weight and production cost while ensuring the overall strength of the cover plate assembly 140. At the same time, the thinner thickness of the second cover plate 142 reduces the welding strength between the second cover plate 142 and the first cover plate 141. Therefore, the second cover plate 142 can be used as an explosion-proof valve to improve the safety performance of the secondary battery 100. Of course, pressure relief can also be achieved by setting grooves on the second cover plate 142 and the weld joint of the first cover plate 141 and the second cover plate 142, which are two weak points.

[0072] Please see Figure 12 This utility model also provides a battery pack 10, which includes the secondary battery 100 described above. In one embodiment of the battery pack 10, the battery pack 10 includes a housing 101, a cover 102, and multiple secondary batteries 100. The multiple secondary batteries 100 are placed in the housing 101 and are connected in series or parallel, or a combination of series and parallel connections. The cover 102 covers the housing 101 to protect the multiple secondary batteries 100. It should be noted that, in addition to the secondary battery 100 of this utility model, the battery pack 10 may also include a battery pack thermal management system, circuit board, etc. The battery pack 10 can be a battery module, a battery pack, an energy storage cabinet, etc.; these will not be described in detail here.

[0073] Please see Figure 13This utility model also provides an electronic device 1, which includes the aforementioned battery pack 10. A working part 11 is electrically connected to the battery pack 10 to obtain electrical power. As an example, the electronic device 1 is a vehicle, which can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, but are not limited thereto. The working part 11 is the vehicle body, and the battery pack 10 is located at the bottom of the vehicle body, providing electrical power for the vehicle's operation or the operation of its internal electrical components. However, in other embodiments, the electronic device 1 can also be a mobile phone, portable device, laptop computer, ship, spacecraft, electric toy, and power tool, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc.; the working part 11 can be a unit component capable of obtaining electrical power from the battery pack 10 and performing corresponding work, such as a fan blade rotation unit or a vacuum cleaner suction unit. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric boat toys, and electric airplane toys, etc.; power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. This application does not impose any special limitations on the aforementioned electronic device 1.

[0074] This utility model relates to a secondary battery. The first cover plate includes a first part and a second part. The second part is welded to a current collector and has a second weld mark formed thereon. The second weld mark extends from the side of the current collector facing the electrode assembly towards the second part. This means the second weld mark is formed by welding from the side of the current collector facing the electrode assembly towards the second part, replacing the welding process from the outside of the cover plate to the current collector, thus reducing the risk of welding heat burning the tabs and separator. Furthermore, the solid part supports the inner periphery of the second part, improving the structural strength of the first cover plate. This reduces the welding deformation between the first cover plate and the sidewall, improves the positioning accuracy of the first and second cover plates, and reduces the welding difficulty between the second and first cover plates. Therefore, this utility model effectively overcomes some practical problems in the prior art, thus having high utilization value and practical significance. The above embodiments are merely illustrative of the principles and effects of this utility model and are not intended to limit it. Any person skilled in the art can modify or change the above embodiments without departing from the spirit and scope of this utility model. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this utility model shall still be covered by the claims of this utility model.

Claims

1. A secondary battery, characterized in that, include: The housing includes an end wall and a side wall surrounding the end wall, wherein an opening is formed at one end of the side wall opposite to the end wall; An electrode assembly, housed within the housing, the electrode assembly including tabs facing the opening; A current collector is disposed at one end of the electrode assembly facing the opening. The current collector is welded to the tab and has a first solder mark. A cover plate assembly includes a first cover plate and a second cover plate. The first cover plate covers the opening and is welded to the sidewall. The first cover plate includes a first portion and a second portion surrounding the first portion. The second portion is welded to the current collector and has a second weld mark formed thereon. The second weld mark extends from the side of the current collector facing the electrode assembly toward the second portion and does not exceed the outer surface of the second portion. The first portion includes a solid portion and a hollow portion. Along the height direction of the secondary battery, the projection of the hollow portion on the current collector covers the first weld mark. The solid portion is used to support the inner periphery of the second portion. The second cover plate is welded to the first cover plate and seals the hollow portion.

2. The secondary battery according to claim 1, characterized in that, The current collector has multiple sets of the first solder marks, which are evenly arranged circumferentially with the center of the current collector as the center. There is a non-welding area between every two adjacent sets of first solder marks. Along the height direction of the secondary battery, the projection of the solid part on the current collector falls into the non-welding area. The solid part is a rotationally symmetric structure centered on the center of the current collector.

3. The secondary battery according to claim 2, characterized in that, The current collector is circular, and has an even number of the first solder marks on it. The solid part is a symmetrical structure with the diameter of the current collector as the axis of symmetry.

4. The secondary battery according to claim 1, characterized in that, The electrode assembly is a wound structure with a winding hole at its center. The solid part includes a stop portion, and along the height direction of the secondary battery, the projection of the stop portion on the electrode assembly covers the winding hole.

5. The secondary battery according to claim 4, characterized in that, The stop portion is provided with a liquid injection hole, and along the height direction of the secondary battery, the projection of the liquid injection hole onto the electrode assembly at least partially coincides with the winding hole.

6. The secondary battery according to claim 1, characterized in that, The inner periphery of the second part is connected to a first recess that is recessed toward the electrode assembly. Both the hollow part and the solid part are disposed in the first recess. Along the height direction of the secondary battery, the second cover plate is at least partially accommodated in the first recess.

7. The secondary battery according to claim 6, characterized in that, The outer periphery of the first cover plate is provided with a second recess that is recessed toward the electrode assembly. A limiting part surrounds the outer side of the second recess. The limiting part extends radially outward toward the first cover plate and is fixedly connected to the end face of the opening. Along the height direction of the secondary battery, the side of the second cover plate opposite to the electrode assembly is lower than the side of the limiting part opposite to the electrode assembly.

8. The secondary battery according to claim 1, characterized in that, The thickness of the second cover plate is less than the thickness of the thinnest part of the first cover plate.

9. A battery pack, characterized in that, The secondary battery includes any one of claims 1 to 8.

10. An electronic device, characterized in that, Includes the battery pack as described in claim 9.

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