Secondary batteries, battery packs, and electronic devices

Abstract

The present invention provides a battery pack and an electronic device, and improves the technical problem of welding failure between the current collector and the housing being prone to occurring during the mechanical sealing process of secondary batteries. [Solution] The housing houses the electrode assembly, one end of the housing includes an opening, and the side of the housing closer to the opening includes a roll groove recessed toward the interior of the housing, the roll groove restricting the movement of the electrode assembly toward the opening. A current collector is positioned at least partially between the roll groove and the electrode assembly, the current collector includes a current collector and a connecting piece connected to the outer periphery of the current collector, the current collector connects to the electrode assembly, the connecting piece is bent toward the center of the current collector and the connecting piece is welded to the surface of the roll groove facing the electrode assembly, forming a first weld. The connecting piece includes a bent portion located between the first weld and the current collector, and a first weakened portion is provided in the portion of the bent portion closer to the first weld to reduce the transmission of stress to the first weld when bending the bent portion.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and more specifically, to secondary batteries, battery packs, and electronic devices.

Background Art

[0002] Mechanical sealing is the mainstream packaging method for existing cylindrical batteries. It has the advantages of mature processes and equipment, and fast production tact, so it is widely applied. In existing cylindrical batteries, usually, a current collector member is installed at a position close to the opening of the housing, one end of the current collector member is welded and connected to the side wall of the housing, and the other end is electrically connected to the tab of the electrode assembly, thereby realizing the electrical connection between the housing and the electrode assembly, and then mechanical sealing is performed.

[0003] Mechanical sealing includes roll-rolling a roll groove recessed toward the inside of the housing on the side wall of the housing, and further adhering a cover plate by a pierce seal method. In the process of the roll groove, the current collector member is bent as the roll groove is deformed, and due to the existence of bending stress, it is easy to cause welding failure between the current collector member and the housing.

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present invention provides a secondary battery, a battery pack, and an electronic device, and improves the technical problem that welding failure between the current collector member and the housing is likely to occur during the mechanical sealing process of the secondary battery.

Means for Solving the Problems

[0005] To achieve the above-mentioned objectives and other related objectives, the present invention provides a secondary battery, a battery pack and an electronic device, the secondary battery comprising an electrode assembly, a housing and a current collector. The housing houses the electrode assembly, and one end of the housing includes an opening, and the side of the housing near the opening includes a roll groove recessed toward the interior of the housing, the roll groove restricting the movement of the electrode assembly toward the opening. The current collector is positioned at least partially between the roll groove and the electrode assembly, and the current collector includes a current collector and a connecting piece connected to the outer periphery of the current collector, the current collector connecting to the electrode assembly, the connecting piece being bent toward the center of the current collector, and the connecting piece being welded to the surface of the roll groove facing the electrode assembly, forming a first weld. The connecting piece includes a bent portion located between the first weld and the current collector, and a first weakened portion is provided in the portion of the bent portion near the first weld to reduce the transmission of stress to the first weld when bending the bent portion.

[0006] In the above technical solution, by installing a first weak point on the bent portion, the stress when bending the portion can be reduced, making it easier to bend the portion itself and less prone to fracture. Furthermore, the transmission of stress to the first weld when bending the portion can be reduced, thereby reducing the risk of fracture at the first weld of the current collector member. In addition, the risk of the edge of the current collector member being pushed into the electrode assembly during the pier sealing process can be reduced, thereby improving product yield.

[0007] In one embodiment of the secondary battery of the present invention, the portion of the first weak point that is away from the first weld mark extends to the current collector.

[0008] In the above technical solution, the extension of the first weak point to the current collector weakens the bending stress at the boundary between the first weak point and the current collector, which is advantageous for bending the connecting piece. At the same time, the boundary between the first weak point and the current collector undergoes deformation first during the bending process, reducing the transmission of stress to the welded connection between the current collector and the tab, thereby improving the problem of weld failure between the current collector and the tab due to bending stress. Furthermore, setting a≦b means either evenly distributing the first weak point over the bend or partially distributing the first weak point. This arrangement reduces the stress when bending the bend, making the bend itself easier to induce and less prone to fracture, and consequently reducing the risk of the edge of the current collector being pushed into the electrode assembly during the pier-sealing process.

[0009] In one embodiment of the secondary battery of the present invention, the thickness of the first vulnerable portion is c, and the thickness of the current collector is d, and of these, c <dである。

[0010] In the above technical solution, the thickness of the first weak point is thinner than the thickness of the current collector. By adopting a method to reduce the thickness, the bending stress of the first weak point is reduced, the processing cost of the structure is low, and the bending stress reduction effect is clear.

[0011] In one embodiment of the secondary battery of the present invention, 0.05 mm ≤ c ≤ 0.15 mm.

[0012] In the above technical solution, a thickness c ≤ 0.15 mm of the first weak point can reduce the bending stress of the first weak point and is advantageous for bending the first weak point, while a thickness c ≥ 0.05 mm of the first weak point provides sufficient mechanical strength to the first weak point and is advantageous for current conduction, thus guaranteeing the conductive performance of the current collector.

[0013] In one embodiment of the secondary battery of the present invention, the length of the first weak portion is a along the extending direction of the first weak portion, and 1.5 mm ≤ a ≤ 3 mm.

[0014] In the above technical solution, along the extending direction of the first weak part, the length a of the first weak part satisfies a ≧ 1.5 mm, which enables the first weak part to have a greater length, realizes the effect of further reducing the bending stress of the bending part, allows the bending part to bend to a greater extent, further reduces the tensile force on the site of the first welding mark when bending the bending part, and thus reduces the risk that the current collecting member breaks at the site of the first welding mark. The limitation of a ≦ 3 mm has the effect that the connecting piece is easy to bend and difficult to break, and can achieve higher strength.

[0015] In an embodiment of the secondary battery of the present invention, along the extending direction of the first weak part, let the length of the bending part be b and the thickness of the connecting piece at the site of the first welding mark be f, among which, a < b and c < f.

[0016] In the above technical solution, a < b means that the first weak part is installed in a partial area of the bending part. This installation can reduce the stress when bending the bending part, easily generate bending on the bending part itself, make it difficult to break, and thus reduce the risk that the edge of the current collecting member is pushed into the electrode assembly during the pierce sealing process. c < f means that the thickness of the connecting piece at the site of the first welding mark is greater than the thickness of the first weak part, realizes forming a thicker molten pool at the site of the first welding mark, and the connecting piece and the side wall have higher welding strength.

[0017] In an embodiment of the secondary battery of the present invention, the overall thickness of the connecting piece is c.

[0018] In the above technical solution, the limitation that the overall thickness of the connecting piece is c means that the connecting piece has a thickness thinner than that of the current collector, realizes the effect of further reducing the bending stress of the bending part, allows the bending part to bend to a greater extent and is difficult to break. And this installed connecting piece has a simple processing process and an obvious bending stress reduction effect. Also, even if the bending part breaks, due to the reduction of the bending stress of the bending part itself, it is easier to bend during the pierce sealing process, and thus reduces the risk that the electrode assembly is inserted into it and damages the electrode assembly.

[0019] In one embodiment of the secondary battery of the present invention, the bent portion bends to form a first corner in which the entire structure exhibits an arc transition.

[0020] In the above technical solution, the bent portion has a relatively low bending stress, allowing it to be bent to its maximum extent to form an overall arc-transition shape. The bending stress at each part of the bent portion of this shape is relatively balanced, reducing internal stress. This reduces the tensile force on the first welded area during bending, thereby reducing the risk of the current collector breaking at the first welded area. Furthermore, the bent portion after bending has a relatively small thickness in the height direction of the secondary battery, reducing the risk of the current collector being pressed into the electrode assembly during peer sealing, thereby improving the conductivity and safety performance of the secondary battery.

[0021] In one embodiment of the secondary battery of the present invention, there are multiple first weak points, and the multiple first weak points are arranged along the direction from the first weld mark toward the current collector.

[0022] In the above technical solution, the first vulnerable section can be intermittent, and this arrangement provides the effect of making the connecting piece easy to bend and difficult to break, while also providing relatively high strength.

[0023] In one embodiment of the secondary battery of the present invention, a second weak point is provided between the current collector and the bent portion, the second weak point is provided in a portion of the bent portion away from the first weld mark, and the second weak point is used to reduce the transmission of stress to the current collector when bending the bent portion.

[0024] In the above technical solution, when the bent portion is folded, deformation occurs first at two locations: a first weak point and a second weak point. The deformation of the first weak point reduces the transmission of stress to the first weld joint, thereby improving the problem of the first weld joint being prone to tensile fracture. The deformation of the second weak point reduces the transmission of stress to the welded connection between the current collector and the tab, thereby improving the problem of weld failure between the current collector and the tab due to bending stress.

[0025] In an embodiment of the secondary battery of the present invention, the current collector includes a plurality of folded portions, and the folded portions are arranged so that when the internal pressure of the secondary battery exceeds a threshold value, they can be folded away from the electrode assembly from the central portion of the current collector, a second corner is formed at the site of the second weak portion, and a third corner is formed at the site of the first weak portion.

[0026] In the above technical solution, when the bending portion is bent, deformation occurs first at two positions of the first weak portion and the second weak portion. Therefore, a third corner is formed at the site of the first weak portion, and a second corner is formed at the site of the second weak portion. A portion between the bending portion, the current collector, and the free end of the connection piece to the first weld mark forms a structure similar to a triangle, and the triangular structure has higher stability. Further, when the pressure of the secondary battery is released, the folded portion folds away from the central portion of the current collector in a direction away from the electrode assembly, and the second corner can provide a fulcrum for the current collector member to fold, so that the folded portion can fold more significantly, obtaining a larger pressure release area and improving the safety performance of the secondary battery.

[0027] In an embodiment of the secondary battery of the present invention, the folded portion and the electrode assembly are welded to form a second weld mark, and along the radial direction of the housing, each folded portion and the connection piece are at least partially collinear.

[0028] In the above technical solution, by arranging each folded portion and the connection piece to be at least partially collinear, it can be realized that the second corner and the folded portion are also at least partially collinear. When the pressure of the secondary battery is released, the supporting effect of the second corner on the folded portion is further improved, enabling the folded portion to fold more significantly, obtaining a larger pressure release area, and further improving the safety performance of the secondary battery.

[0029] In an embodiment of the secondary battery of the present invention, the distance from the end of the first weak portion close to the first weld mark to the first weld mark is set as e, where e ≥ 0.2 mm.

[0030] In the above technical solution, this installation allows for a safety distance of 0.2 mm or more between the first weak point and the first weld mark, preventing a decrease in the strength of the first weak point due to the effects of welding heat.

[0031] In one embodiment of the secondary battery of the present invention, the second vulnerable portion includes one or a combination of one or more of the following: thinness, incision, and watermark.

[0032] In the above technical solutions, one or more combinations of thin walls, incisions, and perforations all enable the reduction of the strength of the second weak point by reducing the cross-sectional area of ​​the second weak point.

[0033] In one embodiment of the secondary battery of the present invention, the first vulnerable portion includes one or a combination of one or more of the following: thinness, incision, and watermark.

[0034] In the above technical solutions, one or more combinations of thin walls, incisions, and perforations all enable the reduction of the strength of the first weak point by reducing the cross-sectional area of ​​the first weak point.

[0035] In one embodiment of the secondary battery of the present invention, the distance from the side of the first weld mark closest to the center of the current collector to the free end of the connecting piece along the radial direction of the housing is g, and the unfolded dimension of the connecting piece is h, where g ≤ h / 3.

[0036] In the above technical solution, by limiting the relative size between distance g and dimension h along the radial direction of the housing, the distance between the first weld mark and the free end of the connecting piece is limited to g ≤ h / 3. This reduces the bending moment generated by the rolling force in the groove against the first weld mark during the process in the roll groove, thereby reducing the probability that the connecting piece will break at the location of the first weld mark. This reduces the probability that the edge of the current collector will be pressed into the electrode assembly, thereby improving product yield. At the same time, the bending moment generated by the rolling force in the groove against the first weld mark is small, and the deformation stress transmitted from the location of the first weld mark to the periphery of the current collector during the process in the roll groove is also reduced accordingly. This reduces the downward pressure generated by the periphery of the current collector against the electrode assembly, further reducing the probability that the edge of the current collector will be pressed into the electrode assembly.

[0037] In one embodiment of the secondary battery of the present invention, 0.2 mm ≤ g ≤ 1 mm.

[0038] In the above technical solution, by limiting the range to 0.2 mm ≤ g ≤ 1 mm, the welding position requirements between most current collectors and side walls can be met, and at the same time, the probability of the connecting piece breaking at the position of the first weld mark during the process in the roll groove can be further reduced.

[0039] In one embodiment of the secondary battery of the present invention, i is the distance from the point on the roll groove closest to the axis of the housing along the radial direction of the secondary battery to the outer surface of the housing, and j is the distance from the first weld mark to the outer surface of the housing, where j ≤ 0.5i.

[0040] In the above technical solution, by limiting j ≤ 0.5i, the tensile force at the first weld mark when the side of the roll groove housing closer to the axis undergoes tensile deformation during the process in the roll groove can be reduced, further improving the problem of the connecting piece being easily torn off at the first weld mark.

[0041] The present invention also provides a battery pack comprising a secondary battery as described in any one of the above.

[0042] The present invention also provides an electronic device, which includes the battery pack described above. [Effects of the Invention]

[0043] The secondary battery of the present invention reduces the stress when bending the bent portion by placing a first weak point on the bent portion, making it easier to bend the bent portion itself and less prone to fracture. Furthermore, it reduces the transmission of stress to the first weld mark when bending the bent portion, thereby reducing the risk of the current collector member fracturing at the first weld mark. In addition, it reduces the risk of the edge of the current collector member being pushed into the electrode assembly during the pier sealing process, thereby improving product yield.

[0044] To more clearly illustrate the embodiments of the present invention or the prior art, the accompanying drawings that may be used in the description of the embodiments or prior art are briefly introduced below. It is clear that the accompanying drawings in the following description represent only a few embodiments of the present invention, and those skilled in the art can obtain other embodiments based on these accompanying drawings without any creative effort. [Brief explanation of the drawing]

[0045] [Figure 1] This is a schematic diagram of the structure of one embodiment of the secondary battery of the present invention. [Figure 2] This is a schematic diagram of the structure of an electrode assembly in one embodiment of the secondary battery of the present invention. [Figure 3] This is a close-up view of the connection portion between the connecting piece and the housing in one embodiment of the secondary battery of the present invention. [Figure 4] This is a close-up view of section C in Figure 1. [Figure 5] This is a close-up view of section D in Figure 4. [Figure 6] This is a schematic diagram of the structure of one embodiment of the secondary battery of the present invention. [Figure 7] This is a close-up view of the connection portion between the connecting piece and the housing in one embodiment of the secondary battery of the present invention. [Figure 8]This is a close-up view of section E in Figure 6. [Figure 9] This is a close-up view of section F in Figure 8. [Figure 10] This is a schematic diagram of the structure of one embodiment of the secondary battery of the present invention. [Figure 11] This is a close-up view of the connection portion between the connecting piece and the housing in one embodiment of the secondary battery of the present invention. [Figure 12] This is a close-up view of section A in Figure 10. [Figure 13] This is a close-up view of section B in Figure 12. [Figure 14] This is a close-up view of the connection portion between the connecting piece and the housing in one embodiment of the secondary battery of the present invention. [Figure 15] This is a schematic diagram of the structure of a current collector in one embodiment of the secondary battery of the present invention. [Figure 16] This is a schematic diagram of the structure of a current collector in one embodiment of the secondary battery of the present invention. [Figure 17] This is a top view of the current collector and electrode assembly in one embodiment of the secondary battery of the present invention. [Figure 18] This is a schematic diagram of one embodiment of the battery pack of the present invention. [Figure 19] This is a schematic diagram of one embodiment of the electronic device of the present invention. [Modes for carrying out the invention]

[0046] The embodiments of the present invention will be described below through specific examples, and those skilled in the art will readily understand other advantages and effects of the present invention from what is disclosed herein. The present invention can be implemented or applied in yet another different specific embodiment, and the details of each item herein can be modified or changed in various ways based on different perspectives and applications without departing from the spirit of the invention. It should be noted that, where not inconsistent, the following embodiments and features can be combined with each other. It should also be understood that the terms used in the embodiments of the present invention are for describing specific specific embodiments and are not intended to limit the scope of protection of the present invention. In the following embodiments, test methods for which specific conditions are not specified are usually carried out according to standard conditions or according to conditions recommended by each manufacturer.

[0047] Where numerical ranges are indicated in these embodiments, it should be understood that, unless otherwise stated in the Invention, any numerical values ​​can be selected at both endpoints of each numerical range and between those endpoints. Unless otherwise defined, all technical and scientific terms used in this Invention, along with the understanding of the existing art by those skilled in the art and the description of this Invention, allow the Invention to be realized using any existing methods, equipment and materials that are similar or equivalent to the methods, equipment and materials in the embodiments of this Invention.

[0048] Furthermore, terms such as "up," "down," "left," "right," "middle," and "one" used herein are merely for the purpose of clarifying the description and are not used to limit the scope within which the present invention can be implemented. Any changes or adjustments to their relative relationships are considered to fall within the scope within which the present invention can be implemented, provided that there is no substantial change in the technical content.

[0049] A secondary battery includes an electrode assembly, which is a component in the secondary battery where electrochemical reactions occur, and may include one or more electrode assemblies.

[0050] The secondary battery further includes a housing, a cover plate, and an electrode column. The housing includes end walls and side walls surrounding the end walls, one end of which has an opening. The electrode assembly can be assembled inside the housing through the opening. The cover plate is used to cover the opening of the housing and achieve sealing. The electrode column penetrates the end walls and is electrically connected to the electrode assembly, deriving the power generated by the electrode assembly.

[0051] The mainstream packaging method for existing secondary batteries is mechanical sealing. Mechanical sealing has the advantages of mature processes and equipment, and fast production cycles, and is widely applied. The current collector is electrically connected to the electrode assembly and housing simultaneously, achieving electrical connection between the electrode assembly and the housing. Specifically, a roll groove is first rolled around the side wall of the housing, recessed toward the inside of the housing. The side of the roll groove closest to the electrode assembly is in close contact with the edge of the current collector, and this roll groove can limit the axial displacement of the electrode assembly. The cover plate is placed on a step formed on the side of the roll groove away from the electrode assembly, a sealing member is installed between the cover plate and the housing, and a pier seal method is adopted at the edge of the opening so that the cover plate is in close contact with the sealing member, forming a reliable connection and achieving housing sealing.

[0052] There are various methods for connecting current collectors to housings. One commonly used method involves placing a connecting piece on the edge of the current collector, first welding the connecting piece to the side wall of the housing, then rolling a groove onto the side wall to continuously bend the connecting piece toward the axis of the housing. However, the inventor discovered that during the bending process, the connecting piece exerts a relatively large tensile force on the welded area between the connecting piece and the side wall, creating a risk of the connecting piece fracturing at the aforementioned welded area. In the subsequent pier-sealing process, the current collector is subjected to downward pressure, and the edge of the fractured current collector is nearly vertical. After being subjected to pressure, it may be inserted into the electrode assembly, leading to damage to the electrode assembly and reducing product yield.

[0053] In view of this, the present invention provides a technical solution that allows for the placement of a first weak point on the bent portion, thereby reducing the stress when bending the bent portion, making it easier to induce bending in the bent portion itself and making it less prone to fracture, further reducing the risk of the edge of the current collector member being pushed into the electrode assembly during the pier sealing process, and further improving product yield.

[0054] Referring to Figures 1 to 19, the present invention provides a secondary battery 100, which includes a housing 110, an electrode assembly 120, a current collector 130, a cover plate 140, and an electrode column 150.

[0055] Referring to Figure 1, the housing 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 achieved through various methods, as long as a stable sealing and electrical connection relationship can be formed, for example, by integral press molding, integral casting, or partial welding. The enclosure method of the side wall 112 is not limited and can be cylindrical or prismatic, or it can be enclosed along any other arbitrary closed ring contour that can be arranged in conjunction with the end wall 111. In this embodiment, the outer edge of the end wall 111 is circular, and the side wall 112 cylindrically encloses the outer edge of the end wall 111, forming a circular opening 113 at one end of the side wall 112 away from the end wall 111. A housing chamber is formed inside the housing 110 enclosed by the end wall 111 and the side wall 112, and is used to house the electrode assembly 120, electrolyte, and other components necessary for the battery. Specifically, the diameter of the housing 110 can be determined based on the specific dimensions of the electrode assembly 120, for example, 18 mm, 21 mm, 46 mm, etc. The housing 110 can be made of various materials, such as copper, iron, aluminum, steel, aluminum alloy, etc., and to prevent the housing 110 from rusting during long-term use, a layer of rust-preventive material, such as metallic nickel, can be plated onto the surface of the housing 110.

[0056] Referring to Figures 1 and 2, the electrode assembly 120 is housed within the housing 110 and is a component in the secondary battery 100 where an electrochemical reaction occurs. The housing 110 can contain one or more electrode assemblies 120. The electrode assembly 120 includes a wound structure formed by stacking and winding a first electrode sheet 121, a second electrode sheet 123, and a separator 122, with the polarities of the first electrode sheet 121 and the second electrode sheet 123 being opposite. In some embodiments, the first electrode sheet 121 is the positive electrode sheet and the second electrode sheet 123 is the negative electrode sheet, while in other embodiments, the first electrode sheet 121 is the negative electrode sheet and the second electrode sheet 123 is the positive electrode sheet.

[0057] Referring to Figures 1 and 2, in this embodiment, the first electrode sheet 121 is a negative electrode sheet and includes a negative electrode current collector 1211 and a negative electrode active material, the negative electrode active material being applied to the surface of the negative electrode current collector 1211. The negative electrode current collector 1211 includes a first coated region 1212 to which the active material is applied and a first uncoated region 1213 to which the active material is not applied, the first uncoated region 1213 being located at the end of the first electrode sheet 121 and the first uncoated region 1213 being a first tab 124 formed by extending from the separator 122 along the winding axis of the electrode assembly 120 and bending toward the winding axis, the first tab 124 being the corresponding negative electrode tab.

[0058] Referring to Figures 1 and 2, the second electrode sheet 123 is a positive electrode sheet, specifically comprising a positive electrode current collector 1231 and a positive electrode active material, the positive electrode active material being coated on the surface of the positive electrode current collector 1231. The positive electrode current collector 1231 comprises a second coated region 1232 to which the active material is coated and a second uncoated region 1233 to which the active material is not coated, the second uncoated region 1233 located at the end of the second electrode sheet 123, and the second uncoated region 1233 is a second tab 125 formed by extending from the separator 122 along the other end of the electrode assembly 120 in the winding axis direction and bending toward the winding axis, the second tab 125 being the corresponding positive electrode tab.

[0059] Referring to Figures 1 and 2, the separator 122 is placed between the first electrode sheet 121 and the second electrode sheet 123, separating the positive electrode active material layer from the negative electrode active material layer. Taking lithium-ion secondary battery 100 as an example, the material of the positive electrode current collector 1231 can be aluminum, and the positive electrode active material layer contains a positive electrode active material, which can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, etc. The material of the negative electrode current collector 1211 can be copper, and the negative electrode active material layer contains a 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 provide protection and insulation to the electrode assembly 120, an insulating film may be coated on the outside of the electrode assembly 120. The insulating film can be synthesized from PP, PE, polyethylene terephthalate (PET), polyvinyl chloride (PVC), or other polymer materials.

[0060] Referring to Figures 1 and 2, if the first tab 124 faces the end wall 111 or the opening 113, 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 pole column 150, making the pole column 150 positively charged, while the first tab 124 faces the opening 113, making the housing 110 and the first tab 124 electrically connected, thereby becoming negatively charged. However, in other embodiments, the first tab 124 can be connected to the pole column 150, and the second tab 125 can be connected to the housing 110.

[0061] Referring to Figure 1, the electrode column 150 is fixed to the end wall 111 and electrically connected to the electrode assembly 120. Specifically, the electrode column 150 holes are provided in the end wall 111, and the electrode column 150 is installed through the electrode column 150 holes and insulated from the end wall 111. One end of the electrode column 150 facing the electrode assembly 120 is electrically connected either directly to the second tab 125 by passing through the end wall 111 or by indirect transfer contact. The structural form of the electrode column 150 can be any suitable form that allows it to pass through the end wall 111 and be electrically connected to the second tab 125 of the electrode assembly 120, for example the cross-section can be circular, square, prismatic, or an irregularly shaped contour that can achieve stable conductivity, and the shape of the electrode column 150 holes and the electrode column 150 correspond to each other. In this embodiment, the cross-section of the electrode column 150 is circular.

[0062] Referring to Figures 1 and 5, the cover plate 140 is sealed and installed over the opening 113. The outer edge shape of the cover plate 140 corresponds to the shape of the opening 113 and connects with the side wall 112 to seal the opening 113. In a specific embodiment, a circumferential roll groove 114 is rolled and recessed toward the interior of the housing 110 in a region near the outer end of the side wall 112 of the housing 110. The roll groove 114 can restrict the movement of the electrode assembly 120 toward the opening 113. The side of the roll groove 114 away from the electrode assembly 120 surrounds the housing 110 and forms an annular step. The cover plate 140 is placed on this step, a seal ring is installed between the cover plate 140 and the housing 110, and the edge of the opening 113 employs a pier seal method to tightly seal the cover plate 140 with the seal ring, forming a reliable connection.

[0063] Referring to Figures 1, 4, 5, and 17, the current collector 130 is positioned at least partially between the roll groove 114 and the electrode assembly 120, and the electrode assembly 120 is electrically connected to the housing 110 through the current collector 130. It should be noted that the shape of the current collector 130 can be any rotationally symmetric shape, such as a circle, square, regular polygon, petal shape, or other shape having a center of symmetry that, after rotating by a certain angle around the center of symmetry, overlaps with the original shape, and is not limited thereto, as long as it can realize a stable and reliable electrical connection relationship, and the center of the current collector 130 is its own center of symmetry.

[0064] Specifically, referring to Figure 4, the current collector 130 includes a current collector 131 and a connecting piece 132 connected to the outer edge of the current collector 131. The current collector 131 is welded to the first tab 124 of the electrode assembly 120. 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 electrode tab, and it is preferable to select copper metal as the material for the current collector 130. To explain, the current collector 131 is the part to which the current collector 130 and the first tab 124 are bonded, and can be used for welding the current collector 130 and the first tab 124. In order to improve positioning, ease of processing, interchangeability, and uniformity during the installation process of the current collector 130, the current collector 131 in this embodiment adopts a circular structure.

[0065] Referring to Figures 3 to 5 and Figure 17, the connecting piece 132 can be an overall annular structure or one or more fan-ring structures, as long as the flow guidance requirements and weld strength requirements between the connecting piece 132 and the housing 110 are met. In this embodiment, the connecting piece 132 consists of four fan-ring structures evenly connected to the outer periphery of the current collector 131. Before the housing 110 rolls the roll groove 114, the connecting piece 132 is first welded to the side wall 112 of the housing 110, forming a first weld mark 1325. As the roll groove 114 is rolled, the connecting piece 132, welded to the housing 110, continues to bend toward the center of the current collector 131, eventually forming a shape that bends toward the axis of the housing 110, and is welded to the surface of the roll groove 114 facing the electrode assembly 120.

[0066] Considering that the connecting piece 132 applies a relatively large tensile force to the area of ​​the first weld 1325 during the bending process, there is a risk that the connecting piece 132 may break at the area of ​​the first weld 1325. In the subsequent pier-sealing process, the current collector 130 will be subjected to downward pressure, and the edge of the current collector 130 after breakage will approach a vertical position and may be inserted into the electrode assembly 120 after being subjected to pressure. In one embodiment of the secondary battery 100 of the present invention, referring to Figures 5, 9, and 13, the connecting piece 132 includes a bent portion 1322 located between a first weld mark 1325 and a current collector 131. A first weak portion 1323 is provided in the portion of the bent portion 1322 closest to the first weld mark 1325 to reduce the stress when bending the bent portion 1322. The shape and dimensions of the first weak portion 1323 are not limited and can be any form that can reduce the stress when bending the bent portion 1322, such as thin wall, notch, and perforation, or any combination thereof. All of the above forms can achieve the effect of reducing the strength of the first weak portion 1323 by reducing the cross-sectional area of ​​the first weak portion 1323. By installing the first weak point 1323 in the bent portion 1322, the stress when bending the bent portion 1322 can be reduced, making the bent portion 1322 itself easier to bend and less prone to fracture. Furthermore, the transmission of stress to the first weld mark 1325 when bending the bent portion 1322 can be reduced, thereby reducing the risk of the current collector member 130 fracturing at the first weld mark 1325. In addition, the risk of the edge of the current collector member 130 being pushed into the electrode assembly 120 during the pier sealing process can be reduced, thereby improving the product yield.

[0067] In an embodiment of the secondary battery 100 of the present invention, the portion of the first weak part 1323 away from the first weld mark 1325 extends to the current collector 131. There are various forms of the first weak part 1323. In one embodiment, the first weak part 1323 is thin. Referring to FIGS. 3 and 7, in another embodiment, the first weak part 1323 has a watermark structure. Referring to FIG. 15, it can be understood that the shape of the watermark structure is not limited to the circular hole in FIG. 15 and can be an ellipse, a rhombus or any other shape that can reduce the stress when bending the bending part 1322. In some other embodiments, the first weak part 1323 can also be a notch or a combined structure of various forms as above. As shown in FIGS. 3 and 7, the first weak part 1323 can be continuous. Also, as shown in FIGS. 14 and 15, it can be intermittent. It should be noted that the shapes of the starting point and the ending point of the first weak part 1323 are not limited and can be rounded corners or right angles. Preferably, as shown in FIGS. 7, 11 and 14, rounded corners are provided at the starting point and the ending point of the first weak part 1323 to reduce the stress concentration problem caused by the sudden change of the cross-sectional area. In the technical solution, the bending stress at the boundary between the first weak part 1323 and the current collector 131 is weakened, which is beneficial to the bending of the connection piece 132. At the same time, the boundary between the first weak part 1323 and the current collector 131 first generates deformation during the bending process, reducing the transmission of stress to the current collecting member 130 and the welding connection part of the pole tab, and thus improving the problem of welding failure between the current collecting member 130 and the pole tab caused by bending stress.

[0068] Referring to FIGS. 3 and 7, in an embodiment of the secondary battery 100 of the present invention, the thickness of the first weak part 1323 is c, the thickness of the current collector 131 is d, and c < d. That is, the thickness of the first weak part 1323 is thinner than that of the current collector 131. The technical solution adopts a method of making the thickness thinner to achieve the effect of reducing the bending stress of the first weak part 1323. It should be noted that the method of making the thickness thinner includes thinning or material removal, etc., and is not limited thereto. In this embodiment, it is obtained by adopting the method of thinning. The processing cost of this structure is low, and the effect of reducing bending stress is obvious.

[0069] Referring to Figures 3 and 7, in one embodiment of the secondary battery 100 of the present invention, 0.05 mm ≤ c ≤ 0.15 mm. By limiting the thickness c of the first weak point 1323 to ≤ 0.15 mm, the effect of reducing the bending stress of the first weak point 1323 can be achieved, which is advantageous for bending the first weak point 1323. By limiting the thickness c of the first weak point 1323 to ≥ 0.05 mm, the first weak point 1323 has sufficient mechanical strength, which is advantageous for current conduction, and at the same time, guarantees the conductive performance of the current collector 130.

[0070] Referring to Figures 3 and 7, in one embodiment of the secondary battery 100 of the present invention, the length of the first weak point 1323 along the extending direction of the first weak point 1323 is a, where 1.5 mm ≤ a ≤ 3 mm. To explain, the above extending direction refers to the direction in which the bent portion 1322 bends from the first weld mark 1325 toward the current collector 131. By limiting the length of the first weak point 1323 to a ≥ 1.5 mm, the first weak point 1323 can have a larger length, which further reduces the bending stress of the bent portion 1322, allows the bent portion 1322 to be bent to a greater extent, further reduces the tensile force on the area of ​​the first weld mark 1325 when bending the bent portion 1322, and further reduces the risk of the current collector member 130 breaking at the area of ​​the first weld mark 1325. The limitation a ≤ 3 mm makes the connecting piece 132 easy to bend and difficult to break, and also allows it to have higher strength.

[0071] Referring to FIGS. 6 and 9, in an embodiment of the secondary battery 100 of the present invention, along the extending direction of the first weak portion 1323, the length of the bending portion 1322 is b, and the thickness at the position of the first welding mark 1325 of the connection piece 132 is f, where a < b and c < f. a < b means that the first weak portion 1323 is installed in a partial region of the bending portion 1322. The first weak portion 1323 can reduce the stress when bending the bending portion 1322, more easily generate bending by the bending portion 1322 itself, make it less likely to break, and further reduce the risk that the edge of the current collecting member 130 is pushed into the electrode assembly 120 during the pierce seal process. Furthermore, c < f means that the thickness at the position of the first welding mark 1325 of the connection piece 132 is greater than the thickness of the first weak portion 1323. By this installation, it is possible to form a thicker molten pool at the position of the first welding mark 1325, the connection piece 132 and the side wall 112 have a higher welding strength, and the breaking probability of the connection piece 132 can be reduced. It should be noted that the thickness of the connection piece 132 between the free end of the connection piece 132 and the first welding mark 1325 may or may not be equal, and this is not limited. In this embodiment, referring to the figure, the thickness of the portion between the free end and the first welding mark 1325 on the connection piece 132 is uniformly f. The process of equal thickness is simpler, the process window of the welding between the connection piece 132 and the roll groove 114 is larger, and it is advantageous for improving the welding strength.

[0072] Furthermore, in one embodiment of the secondary battery 100 of the present invention, as shown in FIGS. 8 and 9, based on the form of the above-mentioned first weak part 1323, the bending part 1322 is bent to form a first corner 1324 that presents an overall arc transition. Since the bending part 1322 has a lower bending stress, it can be bent to the maximum extent to form the first corner 1324 that presents an overall arc transition. It should be noted that the first corner 1324 is not limited by an angle, and as long as the bent part presents a smooth transition, it can be recognized as a form included in the present technical solution. At each location of the bending part 1322 with such a shape, the bending stresses are more balanced, reducing the internal stress. Therefore, when bending, the tensile force on the part of the first weld mark 1325 is reduced, and further the risk that the current collector member 130 breaks at the location of the first weld mark 1325 is reduced. Also, the bent bending part 1322 has a relatively small thickness in the height direction of the secondary battery 100, which can reduce the risk that the current collector member 130 is pushed into the electrode assembly 120 during the pierce seal, and further improve the conductive performance and safety performance of the secondary battery 100.

[0073] Referring to FIGS. 1, 3 to 5, in one embodiment of the secondary battery 100 of the present invention, the overall thickness of the connection piece 132 is c. That is, the entire bending part 1322 is equivalent to the first weak part 1323, and since c < d, it means that the overall thickness of the connection piece 132 is entirely thinner than the thickness of the current collector 131, achieving the effect of further reducing the bending stress of the bending part 1322, enabling the bending part 1322 to be bent to a greater extent and being difficult to break. And the installed connection piece 132 has a simple processing technique, and the effect of reducing the bending stress is obvious. Also, even if the bending part 1322 breaks, due to the reduction of the bending stress of the bending part 1322 itself, it can be bent more easily during the pierce seal process, still reducing the risk that its interior is inserted into the electrode assembly 120 and causing damage to the electrode assembly 120.

[0074] Furthermore, referring to Figures 4 and 5, based on the structural form of the bent portion 1322 in the above embodiment, the bent portion 1322 is bent to form a first corner 1324 in which the entire structure exhibits an arc transition. Since the bent portion 1322 has a relatively low bending stress, it can be bent to the maximum extent to form a first corner 1324 in which the entire structure exhibits an arc transition. It should be noted that the angle of the first corner 1324 is not limited, and as long as the bent portion exhibits a smooth transition, any form can be considered to be included in this technical solution. The bending stress at each part of the bent portion 1322 in this shape is relatively balanced, reducing internal stress, which reduces the tensile force on the first weld mark 1325 when bending, and further reduces the risk of the current collector member 130 breaking at the first weld mark 1325. Furthermore, the bent portion 1322 after bending has a relatively small thickness in the height direction of the secondary battery 100, which reduces the risk of the current collector 130 being pressed into the electrode assembly 120 during peer sealing, and further improves the conductivity and safety performance of the secondary battery 100.

[0075] In one embodiment of the secondary battery 100 of the present invention, there are multiple first weak points 1323, and the multiple first weak points 1323 are arranged along the direction from the first weld mark 1325 toward the current collector 131. That is, the multiple first weak points 1323 are arranged intermittently, for example, in one embodiment, as shown in Figure 14, the first weak points 1323 include four thinned regions arranged at intervals. In another embodiment, as shown in Figure 15, the first weak points 1323 include four perforated regions arranged at intervals. By setting the multiple first weak points 1323 in an intermittent arrangement, the connecting piece 132 has the effect of being easy to bend and difficult to break, and can also have relatively high strength.

[0076] Referring to Figures 10 to 13, in one embodiment of the secondary battery 100 of the present invention, a second weak point 1329 is installed between the current collector 131 and the bent portion 1322, and the second weak point 1329 is installed in a portion of the bent portion 1322 away from the first weld mark 1325. The second weak point 1329 is used to reduce the transmission of stress to the current collector 131 when the bent portion 1322 is bent. The form of the second weak point 1329 includes, but is not limited to, one or a combination of thin-walled, engraved, and perforated structures, and any of the above forms can achieve the effect of reducing the strength of the second weak point 1329 by reducing the cross-sectional area of ​​the second weak point 1329. For example, in one embodiment, as shown in Figure 11, the second weak point 1329 is a thin-walled structure. In another embodiment, as shown in Figure 16, the second weak point 1329 is a perforated structure.

[0077] Preferably, the bending strength of the portion of the bent section 1322 between the first weak point 1323 and the second weak point 1329 is higher than the bending strength of the first weak point 1323 and the second weak point 1329. When the bent section 1322 is bent, deformation occurs first at two locations, the first weak point 1323 and the second weak point 1329. The deformation of the first weak point 1323 can reduce the transmission of stress toward the first weld joint 1325, further improving the problem of tearing at the first weld joint 1325. The deformation of the second weak point 1329 can reduce the transmission of stress toward the welded connection between the current collector 130 and the first tab 124, further improving the problem of weld failure between the current collector 130 and the first tab 124 caused by bending stress. Furthermore, the high bending strength of the portion between the first weak point 1323 and the second weak point 1329 of the bent portion 1322 is advantageous for improving the structural strength of the bent portion 1322, and at the same time, it can provide support to the ruptured current collector member 130 when pressure release occurs, and is convenient for folding back to form a relatively large pressure release region.

[0078] Based on the structural form of the first vulnerable portion 1323 in the above embodiment, in one embodiment of the secondary battery 100 of the present invention, referring to Figures 12, 13 and 17, the current collector 131 includes a plurality of folded portions 1311, and the folded portions 1311 are configured to fold back from the central part of the current collector 131 toward the electrode assembly 120 when the internal pressure of the secondary battery 100 exceeds a threshold, and the plurality of folded portions 1311 may be an integrated structure connected along the circumferential direction, or they may be independent structures separated from each other, and are not limited thereto, as long as the folding can be realized and pressure release can be achieved when the internal pressure of the secondary battery 100 exceeds a threshold. Furthermore, a second corner 1327 is formed in the second weak point 1329, and a third corner 1328 is formed in the first weak point 1323. After the current collector 130 is bent due to the deformation of the roll groove, the bent portion 1322, the current collector 131, and the portion between the free end of the connecting piece 132 and the first weld mark 1325 form a triangular-like structure, and the structural stability of the triangular shape is higher. In addition, when the secondary battery 100 releases pressure, the folded portion 1311 folds back from the center of the current collector 131 away from the electrode assembly 120, and the second corner 1327 can provide a fulcrum to the folded portion 1311, so that the folded portion 1311 can fold back more significantly, obtaining a larger pressure release area and improving the safety performance of the secondary battery 100.

[0079] Referring to Figure 17, in one embodiment of the secondary battery 100 of the present invention, the folded portion 1311 and the electrode assembly 120 are welded to form a second weld mark 1326. Specifically, the folded portion 1311 and the first tab 124 are welded together. The shape and position of the second weld mark 1326 are not limited and may be, for example, a straight line, a curve (wavy line, arc line, sine curve, etc.), a broken line, or other irregular shape, as long as stable current transmission can be achieved between the electrode assembly 120 and the current collector 130. In this embodiment, the current collector 131 includes four folded portions 1311 evenly arranged along the circumferential direction of the current collector 131, and there are also four sets of second weld marks 1326, each located on one of the four folded portions 1311, that is, each of the four folded portions 1311 is welded to the first tab 124. Specifically, the second weld marks 1326 of each set include three wavy weld marks, and this arrangement improves the weld balance stability between the current collector 130 and the first tab 124 and provides a more uniform flow guidance effect, thereby improving the flow guidance stability between the housing 110 and the electrode assembly 120.

[0080] Considering that pressure release occurs at one end where the cover plate 140 is located when the internal pressure of the battery exceeds a threshold, the area where the folded portion 1311 and the first tab 124 are welded together restricts the folding of the current collector member 130 and affects the effect of pressure release. In this embodiment, referring to Figure 17, along the radial direction of the housing 110, each folded portion 1311 and the connecting piece 132 are at least partially on the same line. This arrangement makes it possible to ensure that the second corner 1327 and the folded portion 1311 are also at least partially on the same line, further improving the support effect of the second corner 1327 on the folded portion 1311 when pressure is released from the secondary battery 100. Furthermore, the bending strength is high because the bent portion 1322 is located between the first weak portion 1323 and the second weak portion 1329, which is advantageous for a greater folding of the folded portion 1311, resulting in a larger pressure release area and improving the safety performance of the secondary battery 100.

[0081] Referring to Figures 7, 11, and 14, in one embodiment of the secondary battery 100 of the present invention, the distance from one end of the first weak point 1323 closest to the first weld mark 1325 to the first weld mark 1325 is denoted as e, where e ≥ 0.2 mm. This installation ensures that the first weak point 1323 and the first weld mark 1325 have a safe distance of 0.2 mm or more, preventing a decrease in the strength of the first weak point 1323 due to the effects of welding heat.

[0082] In one embodiment of the secondary battery 100 of the present invention, the second weak point 1329 includes one or more combinations of thinness, indentation, and perforation. For example, in one embodiment, referring to Figure 11, the second weak point 1329 is thin. In another embodiment, referring to Figure 16, the second weak point 1329 has a perforated structure. Any combination of one or more of thinness, indentation, and perforation can reduce the strength of the first weak point 1323 by reducing the cross-sectional area of ​​the second weak point 1329.

[0083] In one embodiment of the secondary battery 100 of the present invention, the first weak point 1323 includes one or more combinations of thinness, indentation, and perforation. For example, in one embodiment, referring to Figures 3 and 7, the first weak point 1323 is thin. In another embodiment, referring to Figure 15, the first weak point 1323 has a perforated structure. Any combination of one or more of thinness, indentation, and perforation can reduce the strength of the first weak point 1323 by reducing the cross-sectional area of ​​the first weak point 1323.

[0084] Referring to Figures 3 and 5, in one embodiment of the secondary battery 100 of the present invention, the distance from the side of the first weld mark 1325 closer to the center of the current collector 131 to the free end of the connecting piece 132 along the radial direction of the current collector 131 is g, and the unfolded dimension of the connecting piece 132 is h, where g ≤ h / 3. By limiting the relative size between distance g and dimension h, the distance between the first weld mark 1325 and the free end of the connecting piece 132 is limited to the range g ≤ h / 3, thereby reducing the bending moment generated by the rolling force in the groove on the first weld mark 1325 during the process in the roll groove, and reducing the probability that the connecting piece 132 will break at the location of the first weld mark 1325. This reduces the probability that the edge of the current collector member 130 will be pressed into the electrode assembly 120, thereby improving the product yield. At the same time, the rolling force in the groove reduces the bending moment generated relative to the first weld mark 1325, and the deformation stress transmitted from the position of the first weld mark 1325 to the periphery of the current collector 131 during the process in the roll groove is also reduced accordingly. This reduces the downward pressure generated by the periphery of the current collector 131 relative to the electrode assembly 120, further reducing the probability that the edge of the current collector 130 is pressed into the electrode assembly 120.

[0085] Referring to Figure 5, in one embodiment of the secondary battery 100 of the present invention, the range of distance g from the side of the first weld mark 1325 closer to the center of the current collector 131 to the free end of the connecting piece 132 is further limited to 0.2 mm ≤ g ≤ 1 mm. This satisfies the welding position requirements for most current collector members 130 and side walls 112, and at the same time further reduces the probability that the connecting piece 132 will break at the position of the first weld mark 1325 during the process in the roll groove.

[0086] Referring to Figure 5, in one embodiment of the secondary battery 100 of the present invention, the distance from the point on the roll groove 114 closest to the axis of the housing 110 to the outer surface of the housing 110 along the radial direction of the secondary battery 100 is defined as i, and the distance from the first weld mark 1325 to the outer surface of the housing 110 is defined as j, with j ≤ 0.5i. This limitation reduces the tensile force on the area of ​​the first weld mark 1325 when the side of the roll groove 114 closer to the axis of the housing 110 undergoes tensile deformation during the process in the roll groove, and further improves the problem of the connecting piece 132 being easily torn off at the area of ​​the first weld mark 1325.

[0087] Referring to Figure 18, the present invention further provides a battery pack 10 which includes a secondary battery 100 according to any one of the above, and in one embodiment of the battery pack 10 of the present invention, the battery pack 10 includes a casing 101, a casing cover 102 and a plurality of secondary batteries 100, the plurality of secondary batteries 100 arranged in the casing 101 and connected to each other in series, parallel, or a mixture of series and parallel, and the casing cover 102 seals the casing 101 and provides protection for the plurality of secondary batteries 100. It should be noted that the battery pack 10 may include parts other than the secondary battery 100 of the present invention such as a battery pack 10 thermal management system and a circuit board, and the battery pack 10 may be a battery module, a battery bag, a power storage cabinet, etc., and these will not be explained in detail here.

[0088] Referring to Figure 19, the present invention further provides an electronic device 1, which includes the battery pack 10 described above. A work unit 11 is electrically connected to the battery pack 10 to obtain power support. In one embodiment, the electronic device 1 is a vehicle, which may be a gasoline car, a gas car, or a new energy car, and the new energy car may be, but is not limited to, a battery electric car, a hybrid car, or a range extender car. The work unit 11 is the vehicle body, and the battery pack 10 is installed at the bottom of the vehicle body to provide power support for the vehicle's movement or the operation of in-vehicle electrical components. However, in several other embodiments, the electronic device 1 may further be a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy, and a power tool, etc. Spacecraft include airplanes, rockets, spacecraft, and spaceships. The work unit 11 may also be a unit component that receives power from the battery pack 10 and performs a corresponding task, such as a fan blade rotation unit or a vacuum cleaner suction work unit. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric boat toys, and electric airplane toys. Power tools include metal cutting power tools, polishing 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. The embodiments of the present invention do not impose any special limitations on the electronic device 1 described above.

[0089] The secondary battery of the present invention, by providing a first weak point at the bent portion, can reduce the stress when the bent portion is bent, making the bent portion itself easier to bend and less prone to fracture, and further reducing the transmission of stress to the first weld when the bent portion is bent, thereby reducing the risk of the current collector member fracturing at the first weld point. Furthermore, it can reduce the risk of the edge of the current collector member being pushed into the electrode assembly during the pier sealing process, thereby improving product yield. Therefore, the present invention effectively overcomes some practical problems in the existing art and has very high utility and significance. The above embodiments are illustrative in illustrating the principle and effects of the present invention and do not limit the present invention. Anyone familiar with this art can modify or change the above embodiments without violating the spirit and scope of the present invention. Accordingly, all equivalent modifications or changes completed by those skilled in the art without departing from the spirit and technical idea disclosed herein should still be included within the scope of protection of the present invention. [Industrial applicability]

[0090] The secondary battery, battery pack, and electronic device of the present invention can be applied in the field of battery technology. [Explanation of symbols]

[0091] 1:Electronic equipment 10: Battery pack 11: Work Unit 101: Box body 102: Box cover 100: Secondary battery 110: Cabinet 111: End wall 112: Side wall 113:Aperture 114: Roll groove 120: Electrode Assembly 121: First pole sheet 1211: Negative electrode current collector 1212: First coating area 1213: First uncoated area 122: Separator 123: Second pole sheet 1231: Positive electrode current collector 1232: Second coating area 1233: Second uncoated area 124: Tab 1 125: Tab 2 130: Current collector 131: Current collector 1311: Folded section 132: Connecting piece 1322: Bending section 1323: First Vulnerable Part 1324: First corner 1325: First weld mark 1326: Second weld mark 1327: Second corner 1328: Third Corner 1329: Second Vulnerable Area 140: Cover board 150: Polar column

Claims

1. Electrode assembly and A housing for the electrode assembly, wherein one end of the housing includes an opening, the side of the housing closer to the opening includes a roll groove recessed toward the interior of the housing, and the roll groove restricts the movement of the electrode assembly in the direction of the opening. At least a portion of the current collector member is installed between the roll groove and the electrode assembly, the current collector member includes a current collector and a connecting piece connected to the outer periphery of the current collector, the current collector is connected to the electrode assembly, the connecting piece is bent toward the center of the current collector, and the connecting piece is welded to the surface of the roll groove facing the electrode assembly, forming a first weld mark. The connecting piece includes a bent portion located between the first weld and the current collector, and a first weakened portion is provided in the portion of the bent portion closest to the first weld to reduce the transmission of stress to the first weld when bending the bent portion. A secondary battery characterized by the following features.

2. The secondary battery according to claim 1, wherein the portion of the first weak point that is away from the first weld mark extends to the current collector.

3. The secondary battery according to claim 2, wherein the thickness of the first vulnerable portion is c, the thickness of the current collector is d, and c < d.

4. The secondary battery according to claim 3, wherein 0.05 mm ≤ c ≤ 0.15 mm.

5. The secondary battery according to claim 4, wherein the length of the first weak portion is a along the extending direction of the first weak portion, and 1.5 mm ≤ a ≤ 3 mm.

6. The secondary battery according to claim 5, wherein, along the extending direction of the first weak portion, the length of the bent portion is b, and the thickness of the connecting piece at the first weld mark is f, and a < b and c < f.

7. The secondary battery according to claim 4, wherein the overall thickness of the connecting piece is c.

8. The secondary battery according to claim 6, wherein the bent portion bends to form a first corner in which the entire structure exhibits an arc transition.

9. The secondary battery according to claim 1, wherein there are multiple first weak points, and the multiple first weak points are arranged along the direction from the first weld mark toward the current collector.

10. The secondary battery according to claim 1, wherein a second weak point is provided between the current collector and the bent portion, the second weak point is provided in a portion of the bent portion away from the first weld mark, and the second weak point is used to reduce the transmission of stress to the current collector when bending the bent portion.

11. The current collector includes a plurality of folded portions, the folded portions are arranged so that when the internal pressure of the secondary battery exceeds a threshold, the current collector can be folded back in a direction away from the electrode assembly from the central portion, a second corner is formed at the portion of the second weak portion, a third corner is formed at the portion of the first weak portion, and the distance from the second corner to the inner wall of the housing is smaller than the distance from the third corner to the inner wall of the housing along the radial direction of the housing.

12. The secondary battery according to claim 11, wherein the folded portion and the electrode assembly are welded to form a second weld mark, and each of the folded portions and the connecting piece are at least partially on the same line along the radial direction of the housing.

13. The secondary battery according to claim 6, wherein the distance from one end of the first weak portion near the first weld mark to the first weld mark is e, and e ≥ 0.2 mm.

14. The secondary battery according to claim 10, wherein the second vulnerable portion includes one or a combination of one or more of the following: thinness, incision, and watermark.

15. The secondary battery according to claim 1, wherein the first vulnerable portion includes one or a combination of one or more of the following: thinness, incision, and watermark.

16. The secondary battery according to claim 1, wherein g is the distance from the side of the first weld mark closest to the center of the current collector to the free end of the connecting piece along the radial direction of the housing, and h is the unfolded dimension of the connecting piece, where g ≤ h / 3.

17. The secondary battery according to claim 16, wherein 0.2 mm ≤ g ≤ 1 mm.

18. The secondary battery according to claim 16, wherein i is the distance from the point on the roll groove closest to the axis of the housing along the radial direction of the secondary battery to the outer surface of the housing, and j is the distance from the first weld mark to the outer surface of the housing, and j ≤ 0.5i.

19. A battery pack characterized by including a secondary battery according to any one of claims 1 to 18.

20. An electronic device characterized by including the battery pack described in claim 19.

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