Secondary battery, battery pack, and electronic device

Abstract

To provide a secondary battery, a battery pack, and an electronic device which improve a technical problem that a welding failure between a current collecting member and a tab is likely to occur in a mechanical sealing process of a cylindrical battery.SOLUTION: The secondary battery includes a case including an annular side wall, an opening being formed at one end of the side wall, one end of the case close to the opening including a rolling groove recessed toward an interior of the case, an electrode assembly accommodated in the case and including a tab facing the opening, and a current collecting member including a current collector body and a case connecting portion connected to an outer peripheral edge of the current collector body. And a current collecting member, wherein the current collecting body is fixedly connected to the electrode tab, the housing connecting portion is bent toward the housing axis and is welded to a surface of the rolling groove facing the electrode assembly, an outer edge of the housing connecting portion facing the housing axis is provided with n first notches, and n ≥ 1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Mechanical sealing is the mainstream packaging method for conventional cylindrical batteries, and is widely used due to the advantages of mature processes and equipment and fast production cycle times. In conventional cylindrical batteries, a current collecting member is typically placed near the opening of the case, one end of the current collecting member is welded to the side wall of the case, and the other end is electrically connected to a tab on the electrode assembly, thereby achieving electrical connection between the case and the electrode assembly. Mechanical sealing is then performed. This involves rolling a recessed groove into the side wall of the case toward the inside of the case, and then crimping a cover plate using a stamping method. During this process, bending stress generated by the current collecting member can cause the current collecting member to warp internally, tearing the weld between the current collecting member and the tab, which can result in a loss of electrical connection in the electrode assembly. Summary of the Invention [Problem to be solved by the invention]

[0003] In view of the above-mentioned drawbacks of the prior art, the present invention provides a secondary battery, a battery pack, and an electronic device that solve the technical problem of poor welding between the current collecting member and the tab during the mechanical sealing process of a cylindrical battery. [Means for solving the problem]

[0004] In order to achieve the above and other related objects, the present invention provides a secondary battery, the secondary battery including: a case having an annular side wall, one end of the side wall having an opening formed therein, and one end of the case nearest the opening having a rolling groove recessed toward the inside of the case; an electrode assembly housed within the case and including a tab facing the opening; and a current collecting member including a current collector body and a case connecting portion connected to an outer peripheral edge of the current collector body, wherein the current collector body is fixedly connected to the tab and the case connecting portion is bent toward an axis of the case and welded to a surface of the rolling groove facing the electrode assembly, and n first notches are provided on the outer peripheral edge of the case connecting portion facing the axis of the case, where n≧1.

[0005] In the above technical solution, by providing a first notch on the outer peripheral edge of the case connection part, when the case connection part bends toward the axis of the case, the outer peripheral edge of the case connection part needs to be bent to a position with a smaller diameter. By providing the first notch, on the one hand, the area of ​​the outer peripheral edge of the case connection part is reduced and the generation of excess extrusion material is reduced, and on the other hand, the first notch can also accommodate the excess extrusion material. This solves the technical problem in the prior art that the outer peripheral edge of the case connection part cannot bend smoothly and there is a large stress transmission. This enables the case connection part to bend smoothly and improves the reliability of the connection between the case connection part and the case. At the same time, it reduces the bending stress of the case connection part and solves the problem of poor welding between the current collecting member and the tab due to the bending stress.

[0006] In one embodiment of the secondary battery of the present invention, the width of the root of the first notch is b, the width of the top of the first notch is a, and 0.1 mm≦b≦a≦2 mm.

[0007] In the above technical solution, by making the width of the top of the first notch greater than or equal to the width of the root of the first notch, the diameter of the case connection part is larger closer to the top, and there is more excess extruded material generated during bending. Therefore, by providing it in this way, the excess extruded material generated during bending of the case connection part can be better accommodated. By limiting the maximum value of the width of the first notch within 2 mm, while reducing the bending stress of the case connection part, the strength of the case connection part and the reliability of the connection with the case are made compatible.

[0008] In one embodiment of the secondary battery of the present invention, before the case connection part is bent, the distance from the outer peripheral edge of the case connection part to the side away from the electrode assembly of the current collector body is d, the depth of the first notch is c, and 0.5d ≤ c < d.

[0009] In the above technical solution, the case connection part forms an included angle of approximately 90° with the current collector body before bending, and the depth of the first notch is set to c < d, that is, the root of the first notch is made higher than the side away from the electrode assembly of the current collector body. In this way, the case connection part can have high strength and roundness while designing the first notch, which is advantageous for the reliability of welding with the case. It is limited that c ≥ 0.5d, that is, by making the depth of the first notch be more than half of the height of the case connection part, it is realized that the first notch has a space for accommodating sufficient extruded material.

[0010] In one embodiment of the secondary battery of the present invention, the current collector member includes a plurality of case connection parts, and the plurality of case connection parts are installed around the outer peripheral edge of the current collector body.

[0011] In the above technical solution, by arranging the plurality of case connection parts separately and annularly on the outer peripheral edge of the current collector body, on the one hand, it has high structural strength and a large contact area, has the effect of improving the heat dissipation performance and reducing the resistance, and at the same time has the effect of reducing the material use and reducing the stress concentration.

[0012] In one embodiment of the secondary battery of the present invention, the case connection portion is divided into n+1 connection segments along the circumferential direction of the case by first notches, and n+1 or more first weld marks are formed by welding on the case connection portion and the surface of the rolling groove facing the electrode assembly, with at least one first weld mark on each connection segment.

[0013] In the above technical solution, at least one first weld mark is formed at the part where each connection segment and the case are welded on each case connection part, i.e., each connection segment is welded to the case respectively, and is not welded at the first notch location. This arrangement achieves stable welding between the case connection part and the case, and at the same time does not affect the independent bending between each connection segment. Since each connection segment has little strength and is easily deformed, it is advantageous for absorbing bending stress that occurs when the case connection part is bent, and further improves the problem of poor welding between the current collecting member and the tab due to bending stress.

[0014] In one embodiment of the secondary battery of the present invention, the width of any point of the first notch is 0.2 mm or less, and at least one second weld mark is formed by welding between the case connection portion and the surface of the rolling groove facing the electrode assembly, and each second weld mark is continuous and spans all of the first notches.

[0015] In the above-mentioned technical solution, a single continuous second weld mark is formed by welding between the multiple connection segments on the case connection part and the case, and the continuous second weld mark is advantageous for improving welding efficiency. By limiting the width of any point of the first notch to 0.2 mm or less, the first notch is formed as a narrow gap, and even if the second weld mark is welded across the first notch, the first notch within this dimension range is easily filled with the molten material formed during welding, reducing the situation where the case is penetrated by welding at the first notch.

[0016] In one embodiment of the secondary battery of the present invention, the second weld mark has a penetration depth at the first notch position that is less than 0.7 times the thickness of the case.

[0017] In the above technical solution, the penetration depth of the second weld mark at the first notch is set to less than 0.7 times the case thickness, thereby reducing the risk of the case being penetrated by welding.

[0018] In one embodiment of the secondary battery of the present invention, the case connection portion includes a bent portion that connects to the current collector body, and a second notch is provided on each side of the bent portion along the circumferential direction of the case.

[0019] In the above technical solution, the provision of the second notch can reduce the width of the bent portion, further reducing the bending stress generated when the case connection portion is bent. At the same time, the strength of the bent portion is reduced, making it easier to deform, which is advantageous for absorbing bending stress, weakening the transmission of bending stress to the welded connection portion between the current collecting member and the tab, and further improving the problem of poor welding between the current collecting member and the tab due to bending stress.

[0020] In one embodiment of the secondary battery of the present invention, the case connection portion includes a bent portion that connects to the current collector body, and a weakened portion that extends along the circumferential direction of the case is provided on the bent portion.

[0021]

[0003] In the above technical solution, the provision of a weakened portion at the bending portion can reduce the stress generated when the case connection portion is bent. At the same time, because the strength of the weakened portion is low, the weakened portion at the bending portion will be the first to deform under stress, reducing the transmission of stress to the welded connection portion between the current collecting member and the tab, and further improving the problem of poor welding between the current collecting member and the tab due to bending stress. At the same time, the weakened portion can guide and position the bending portion, improving the accuracy of the bending position of the bent portion and contributing to the consistency of the assembly quality of secondary batteries. In addition, when welding the case connection portion and the case before machining the rolling groove, the weakened portion also functions as a reference line for the welding position, facilitating the positioning of the welding head during welding.

[0022] In one embodiment of the secondary battery of the present invention, when the total of the minimum current passing areas of all the weak parts is e and the total area of ​​the weld lines formed by welding the current collector body and the tab is s, e>s.

[0023] In the above technical solution, the minimum current passing area of ​​the weak parts is the point at which the cross-sectional area of ​​each weak part is smallest along the circumferential direction of the current collecting member, and the total area of ​​the weld line formed by welding the current collector body and the tab refers to the projected area of ​​the weld line itself in the axial direction of the electrode assembly. By setting the sum e of the minimum current passing areas of all weak parts to be greater than the total area s of the weld lines, it is possible to weaken the transmission of bending stress while not affecting the current conduction effect of the weak parts.

[0024] The present invention also provides a battery pack including any of the above secondary batteries.

[0025] The present invention also provides an electronic device including the above-described battery pack. [Effects of the Invention]

[0026] In the secondary battery of the present invention, by providing a first notch on the outer peripheral edge of the case connection portion, when the case connection portion is bent toward the axis of the case, the outer peripheral edge of the case connection portion must be bent to a position with a smaller diameter. By providing the first notch, on the one hand, the area at the outer peripheral edge of the case connection portion is reduced, reducing the generation of excess extrusion material, and on the other hand, the first notch can also accommodate the excess extrusion material. This solves the technical problem in the prior art that the outer peripheral edge of the case connection portion cannot be bent smoothly and there is a large stress transmission, realizes smooth bending of the case connection portion, improves the reliability of the connection between the case connection portion and the case, and at the same time weakens the bending stress of the case connection portion, solving the problem of poor welding between the current collecting member and the tab due to bending stress. [Brief explanation of the drawings]

[0027] In order to more clearly describe the embodiments of the present invention or the technical solutions in the prior art, the drawings necessary for use in the description of the embodiments or related art are briefly introduced below. Obviously, the drawings described below are only embodiments of the present application, and those skilled in the art can obtain other embodiments based on these drawings without expending creative efforts.

[0028] [Figure 1] 1 is an explanatory diagram of the overall structure of an embodiment of a secondary battery of the present invention; [Figure 2] 1 is a structural diagram of an electrode assembly of an embodiment of a secondary battery of the present invention; [Figure 3] 3 is a structural explanatory view of a current collecting member of an embodiment of a secondary battery of the present invention before being folded. FIG. [Figure 4] FIG. 4 is a front view of the current collecting member shown in FIG. [Figure 5] FIG. 4 is an explanatory view of the structure of the current collecting member shown in FIG. 3 after being bent. [Figure 6] 3 is a structural explanatory view of a current collecting member of an embodiment of a secondary battery of the present invention before being folded. FIG. [Figure 7] FIG. 7 is a front view of the current collecting member in FIG. 6. [Figure 8] FIG. 7 is an explanatory view of the structure of the current collecting member in FIG. 6 after being bent. [Figure 9] 3 is a structural explanatory view of a current collecting member of an embodiment of a secondary battery of the present invention before being folded. FIG. [Figure 10] FIG. 10 is a front view of the current collecting member in FIG. [Figure 11] 10 is an explanatory view of the structure of the current collecting member in FIG. 9 after being bent. FIG. [Figure 12] 3 is a structural explanatory view of a current collecting member of an embodiment of a secondary battery of the present invention before being folded. FIG. [Figure 13] FIG. 13 is a front view of the current collecting member in FIG. [Figure 14] 1 is an explanatory diagram of an embodiment of a battery pack of the present invention. [Figure 15] 1 is an explanatory diagram of an embodiment of an electronic device of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0029] The following describes the implementation of the present invention through certain specific embodiments, so that those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed herein. The present invention can be implemented or applied in other different specific embodiments, and the details of each item in this specification can be modified or changed in various ways based on different perspectives and applications without departing from the spirit of the present invention. Where not inconsistent, the following embodiments and features therein can be combined with each other. It should also be understood that the terms used in the embodiments of the present invention are intended to describe specific implementations 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 performed according to general conditions or conditions recommended by each manufacturer.

[0030] When a numerical range is indicated in this embodiment, it should be understood that any numerical value between the endpoints of each numerical range can be selected unless otherwise specified in the present invention. Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those skilled in the art understand in the existing technology and described in the present invention, and the present invention can be realized using any method, equipment, and material in the existing technology that is similar or equivalent to the method, equipment, and material described in the embodiments of the present invention.

[0031] Furthermore, terms such as "upper," "lower," "left," "right," "middle," and "one" cited in this specification are merely for the purpose of clarifying the description and do not limit the scope in which the present invention can be implemented. Changes or adjustments to their relative relationships are considered to be within the scope in which the present invention can be implemented, provided that there is no substantial change in the technical content.

[0032] A secondary battery includes an electrode assembly, which is the component that causes the electrochemical reaction in the secondary battery, and can include one or more electrode assemblies.

[0033] The secondary battery further includes a case, a cover plate, and electrode posts. The case includes end walls and side walls surrounding the end walls, one end of the side walls has an opening. The electrode assembly can be assembled into the case through the opening of the case. The cover plate is used to cover the opening of the case and achieve sealing. The electrode posts pass through the end walls and are electrically connected to the electrode assembly to conduct power generated by the electrode assembly.

[0034] The mainstream sealing method for conventional secondary batteries is mechanical sealing, which has the advantages of mature processes and equipment and fast production cycle times and is widely used. The current collecting member is simultaneously electrically connected to the electrode assembly and the case, thereby achieving an electrical connection between the electrode assembly and the case. Specifically, a circumferential rolling groove is first rolled into the side wall of the case, recessed toward the inside of the case, and the side of the rolling groove closest to the electrode assembly is pressed against the edge of the current collecting member, which can limit the axial displacement of the electrode assembly. A cover plate is installed on a step formed on the side of the rolling groove away from the electrode assembly, and a sealing member is installed between the cover plate and the case. The sealing member is then pressed against the cover plate at the edge of the opening using a hammering seal, forming a reliable connection and sealing the case.

[0035] There are various methods for connecting the current collecting member and the case. One commonly used method is to install a case connection part on the edge of the current collecting member, first weld the case connection part to the side wall of the case, and then roll a rolling groove on the side wall so that the case connection part is continuously bent toward the axis of the case. However, the inventor discovered that when the case connection part is bent toward the axis of the case, the outer edge of the case connection part needs to be bent to a position with a smaller diameter, which generates excess extrusion material that cannot be accommodated at the outer edge of the case connection part, and further transmits greater bending stress, causing the current collecting member to warp internally and tearing the welded point between the current collecting member and the tab, which creates a risk of the electrical connection of the electrode assembly failing.

[0036] In view of this, the present invention provides a technical solution in which a first notch is provided on the outer peripheral edge of the case connection portion, which on the one hand reduces the area at the outer peripheral edge of the case connection portion and reduces the generation of excess extrusion material, and on the other hand, the first notch can also accommodate the excess extrusion material, thereby improving the technical problem in the prior art that the outer peripheral edge of the case connection portion cannot bend smoothly, weakening the bending stress of the case connection portion and improving the problem of poor welding between the current collecting member and the tab due to the bending stress.

[0037] 1 to 15, the present invention provides a secondary battery 100, which includes a case 110, an electrode assembly 120, a pole 140, and a current collecting member 150.

[0038] 1 , case 110 includes end wall 111 and side wall 112 surrounding end wall 111. The connection between end wall 111 and side wall 112 can be realized in various ways, such as integral press molding, integral casting, or split welding, as long as a stable sealing and electrical connection can be formed. The shape of side wall 112 is not limited and can be cylindrical or prismatic, or can be any other closed loop shape compatible with end wall 111. In this embodiment, the outer edge of end wall 111 is circular, and side wall 112 cylindrically surrounds the outer edge of end wall 111, forming a circular opening 113 at one end of side wall 112 away from end wall 111. A chamber is formed within case 110, surrounded by end wall 111 and side wall 112, and used to accommodate electrode assembly 120, electrolyte, and other necessary battery components. Specifically, the diameter of the case 110 can be determined based on the specific dimensions of the electrode assembly 120, and may be 18 mm, 21 mm, 46 mm, etc. The case 110 may be made of various materials, such as copper, iron, aluminum, steel, aluminum alloy, etc. To prevent the case 110 from rusting during long-term use, the surface of the case 110 may be further plated with a layer of anti-rust material such as metallic nickel.

[0039] 1 and 2, an electrode assembly 120 is installed inside the case 110, and the electrode assembly 120 is a component where an electrochemical reaction occurs in the secondary battery 100. The case 110 may contain one or more electrode assemblies 120. The electrode assembly 120 includes an electrode sheet and a separator 122, which are wound together to form a wound structure. Specifically, in this embodiment, the electrode assembly 120 includes a positive electrode sheet 121, a separator 122, and a negative electrode sheet 123 wound around the axial direction of the case 110.

[0040] 1 and 2, the positive electrode sheet 121 includes a positive electrode current collector 1211 and a positive electrode active material layer coated on the positive electrode current collector 1211. A first coated region 1212 coated with the positive electrode active material layer and a first uncoated region 1213 not coated with the positive electrode active material layer are formed on the positive electrode current collector 1211. The first coated region 1212 and the first uncoated region 1213 are arranged along the axial direction of the case 110. The first uncoated region 1213 extends out of the separator 122 toward one end in the height direction of the secondary battery 100 and bends toward the axis of the case 110 to form a stacked positive electrode tab 125.

[0041] 1 and 2, the negative electrode sheet 123 includes a negative electrode current collector 1231 and a negative electrode active material layer coated on the negative electrode current collector 1231. A second coated region 1232 coated with the negative electrode active material layer and a second uncoated region 1233 not coated with the negative electrode active material layer are formed on the negative electrode current collector 1231. The second coated region 1232 and the second uncoated region 1233 are arranged along the axial direction of the case 110. The second uncoated region 1233 extends outside the separator 122 toward the other end of the height direction of the secondary battery 100 and bends toward the axis of the case 110 to form a stacked negative electrode tab 124.

[0042] 1 and 2, separator 122 is disposed between positive electrode sheet 121 and negative electrode sheet 123 to separate the positive electrode active material layer from the negative electrode active material layer. Taking a lithium-ion secondary battery as an example of secondary battery 100, the material of positive electrode current collector 1211 may be aluminum, the positive electrode active material layer includes a positive electrode active material, which may be lithium cobalt oxide, lithium iron phosphate, ternary lithium, lithium manganese oxide, or the like. The material of negative electrode current collector 1231 may be copper, and the negative electrode active material layer includes a negative electrode active material, which may be carbon, silicon, or the like. The substrate material of separator 122 may be polypropylene (PP), polyethylene (PE), or the like. To protect and insulate the battery cell, the outside of the battery cell can be coated with an insulating film, which can be made of PP, PE, polyethylene terephthalate (PET), polyvinyl chloride (PVC) or other high molecular weight polymer materials.

[0043] 1 and 2, when the positive electrode tab 125 in the present invention faces the end wall 111 or faces the opening 113, the negative electrode tab 124 faces the other end of the case 110, and in this embodiment, the positive electrode tab 125 faces the end wall 111 and is electrically connected to the electrode post 140, making the electrode post 140 positively charged, and the negative electrode tab 124 faces the opening 113 and is electrically connected to the case 110, making the negative electrode tab 124 negatively charged. However, in other embodiments, the negative electrode tab 124 may be connected to the electrode post 140, and the positive electrode tab 125 may be connected to the case 110.

[0044] 1 , the cover plate 130 is fitted to the opening 113 with a sealing fit. The outer edge of the cover plate 130 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 rolling groove 114 is formed by rolling a circumference of the side wall 112 of the case 110 in an area near the outer edge thereof. The rolling groove 114 is recessed toward the inside of the case 110. The rolling groove 114 includes a first side wall 1141 and a second side wall 1142. The first side wall 1141 is close to the electrode assembly 120 and can limit the axial displacement of the electrode assembly 120. The second side wall 1142 is annularly surrounding the case 110 on the side away from the rolling groove 114, forming an annular step. The cover plate 130 is placed on the step. A seal ring is installed between the cover plate 130 and the annular groove 1121. The edge of the opening 113 is sealed by a press-fitting method, with the cover plate 130 pressing the seal ring to form a reliable connection.

[0045] 1 and 2, the electrode post 140 is fixed to the end wall 111 and electrically connected to the electrode assembly 120. Specifically, an electrode post hole is provided in the end wall 111, and the electrode post 140 is attached by penetrating into the electrode post hole and is insulated from the end wall 111. One end of the electrode post 140 facing the electrode assembly 120 penetrates the end wall 111 and is electrically connected to the positive electrode tab 125 directly or by indirect contact. The structural form of the electrode post 140 can be any suitable form that can penetrate the end wall 111 and electrically connect to the positive electrode tab 125 of the electrode assembly 120. For example, the cross section can be circular, rectangular, prismatic, or a modified profile that can achieve stable conductivity. The shape of the electrode post hole and the shape of the electrode post 140 correspond to each other. In this embodiment, the cross section of the electrode post 140 is circular.

[0046] 1 , the current collecting member 150 is disposed between the electrode assembly 120 and the cover plate 130, and the case 110 and the electrode assembly 120 are electrically connected through the current collecting member 150. Specifically, the current collecting member 150 includes a current collecting body 151 and a case connecting part 152 connected to the outer periphery of the current collecting body 151. The case connecting part 152 may be an integral ring structure or one or more fan-shaped ring structures, as long as it satisfies the current conduction requirements and welding strength requirements between the current collecting member 150 and the case 110. Before rolling the rolling groove 114 into the case 110, the case connection portion 152 is first welded to the side wall 112 of the case 110. At the same time as rolling the rolling groove 114, the case connection portion 152 welded to the case 110 continues to bend toward the axis of the case 110, and finally forms a shape bent toward the axis of the case 110 and is welded to the surface of the rolling groove 114 facing the electrode assembly 120 (see Figures 1, 5, 8 and 11).

[0047] 3 , 5 , 6 , 8 , 9 , 11 , and 12 , the current collector body 151 is fixedly connected to the tab. The connection between the current collector body 151 and the tab can be achieved in various ways, such as by welding or by using a conductive adhesive, as long as it achieves electrical connection between the current collecting member 150 and the tab and satisfies current conduction requirements. In this embodiment, a welding connection is used. Furthermore, the portion where the current collector body 151 and the tab are welded is a tab connection portion 153, and the shape and position of the tab connection portion 153 are not limited. Preferably, in this embodiment, the current collector body 151 has four tab connection portions 153 welded to the tab, and the four tab connection portions 153 are evenly spaced around the circumferential direction of the current collector body 151. This arrangement improves the stability of the welding balance between the current collecting member 150 and the tab and provides a more uniform current conduction effect, thereby improving the stability of current conduction between the case 110 and the electrode assembly 120.

[0048] Referring to Figures 3 to 13, when case connection portion 152 bends toward the axis of case 110, the outer peripheral edge of case connection portion 152 bends to a position with a smaller diameter. This generates excess extrusion material that cannot be accommodated by the outer peripheral edge of case connection portion 152, resulting in even greater stress transmission. Furthermore, n first notches 1521 are provided on the outer peripheral edge of case connection portion 152 facing the axis of case 110, where n is greater than or equal to 1, and n can be set to any number depending on the dimensions and shape of case connection portion 152, for example, 1, 2, 3, 4, 5, 6 or more, and is not limited thereto. By providing the first notch 1521, on the one hand, the area at the outer edge of the case connection portion 152 is reduced, reducing the generation of excess extrusion material; on the other hand, the first notch 1521 can accommodate the excess extrusion material, thereby improving the technical problem in the prior art that the outer edge of the case connection portion 152 cannot bend smoothly and there is a large stress transmission, thereby realizing smooth bending of the case connection portion 152 and improving the reliability of the connection between the case connection portion 152 and the case 110, and at the same time weakening the bending stress of the case connection portion 152 and improving the problem of poor welding between the collecting member 150 and the tab due to bending stress.

[0049] The diameter of the case connection portion 152 closer to the top is larger, and therefore more excess extrusion material is generated when the case connection portion 152 is bent. Referring to FIGS. 3 to 13 , in one embodiment of the secondary battery 100 of the present invention, in order to better accommodate excess extrusion material generated when the case connection portion 152 is bent, the width of the base of the first notch 1521 is designated b and the width of the top of the first notch 1521 is designated a, preferably in the range of 0.1 mm≦b≦a≦2 mm. However, the dimensions a and b may be the same or a>b. For example, the values ​​of a and b may be 0.1 mm, 0.2 mm, 0.3 mm, 0.5 mm, 0.7 mm, 0.8 mm, 1 mm, 1.2 mm, 1.4 mm, 1.5 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2 mm, etc. By limiting the maximum width of the first notch 1521 to within 2 mm, the bending stress of the case connection portion 152 can be reduced while at the same time achieving both the strength of the case connection portion 152 and the reliability of the connection with the case 110.

[0050] Referring to FIGS. 3 to 13, in order to further reduce the bending stress of the case connection portion 152, in one embodiment of the secondary battery 100 of the present invention, before bending the case connection portion 152, the distance from the outer peripheral edge of the case connection portion 152 to the side away from the electrode assembly 120 of the current collector body 151 is d, and the depth of the first notch 1521 is c. Preferably, 0.5d ≤ c < d. For example, the value of c can be 0.5d, 0.6d, 0.7d, 0.8d, or 0.9d, etc. It should be noted that the case connection portion 152 forms an included angle of approximately 90° with the current collector body 151 before bending. The depth of the first notch 1521 is set to c < d, that is, the depth of the first notch 1521 is higher than the side away from the electrode assembly 120 of the current collector body 151. When the case connection portion 152 designs the first notch 1521, it can have higher strength and roundness at the same time, which is advantageous for the reliability of welding with the case 110. By limiting c ≥ 0.5d, that is, the depth of the first notch 1521 is more than half of the height of the case connection portion 152, it is realized that the first notch 1521 has a space for accommodating sufficient extruded material.

[0051] Referring to FIGS. 3 to 13, in order to reduce the bending stress of the case connection portion 152, in one embodiment of the secondary battery 100 of the present invention, the current collector member 150 includes a plurality of case connection portions 152, and the plurality of case connection portions 152 are installed around the outer peripheral edge of the current collector body 151. This installation has the effects of having higher structural strength and larger contact area on the one hand, improving the heat dissipation performance and reducing the resistance, and at the same time reducing the material usage and reducing the stress concentration. Further, in order to facilitate the positioning connection between the case connection portion 152 and the current collector member 150, in this embodiment, the plurality of case connection portions 152 have the same shape, and the plurality of case connection portions 152 are arranged along the circumferential direction of the current collector body 151. By installing in this way, a more uniform current conduction effect can be generated in the circumferential direction of the current collector member 150 and the side wall 112, thereby improving the stability of current conduction between the case 110 and the electrode assembly 120.

[0052] 3 to 13 , in one embodiment of the secondary battery 100 of the present invention, the case connection portion 152 is divided into n+1 connection segments by n first notches 1521 along the circumferential direction of the case 110, and n+1 or more first weld marks 1522 are welded to the surface of the case connection portion 152 and the rolling groove 114 facing the electrode assembly 120, where n can be any number depending on the size and shape of the case connection portion 152, and can be, for example, 1, 2, 3, 4, 5, 6, or more. This is not a limitation, and each connection segment has at least one first weld mark 1522. That is, each connection segment is welded to the case 110, but is not welded at the locations of the first notches 1521. This installation enables stable welding of the case connection portion 152 and the case 110, does not affect the independent bending between each connection segment, and is advantageous in absorbing the bending stress that occurs when the case connection portion 152 is bent, since each connection segment has little strength and is easily deformed, and further improves the problem of poor welding between the current collecting member 150 and the tab due to bending stress.

[0053] 12 and 13 , in order to improve welding efficiency, in one embodiment of the secondary battery 100 of the present invention, the width of any point of the first notch 1521 is 0.2 mm or less, and may be, for example, 0.1 mm, 0.12 mm, 0.15 mm, 0.16 mm, or 0.2 mm. At least one second weld mark 1523 is welded and formed on the surfaces of the case connection portion 152 and the rolling groove 114 facing the electrode assembly 120, and each second weld mark 1523 continuously straddles all of the first notches 1521. In other words, a single continuous second weld mark 1523 is formed by welding between the multiple connection segments on the case connection portion 152 and the case 110, and the continuous second weld mark 1523 is advantageous for improving welding efficiency. By limiting the width of any point of the first notch 1521 to 0.2 mm or less, the first notch 1521 is formed as a narrow gap, and even if the second weld mark 1523 is welded across the first notch 1521, the first notch 1521 within this dimension range is easily filled with the molten material formed during welding, reducing the situation in which the case 110 is penetrated by welding at the first notch 1521.

[0054] When welding at the position of first notch 1521 is considered, there is a risk of welding through case 110 due to the lack of shielding by case connection portion 152. In one embodiment of secondary battery 100 of the present invention, the penetration depth of second weld mark 1523 at the position of first notch 1521 is preferably less than 0.7 times the thickness of case 110. This arrangement can reduce the risk of welding through case 110.

[0055] 3 to 5, in one embodiment of the secondary battery 100 of the present invention, each case connection portion 152 is provided with one first notch 1521, and the first notch 1521 is V-shaped, with a width a of the top of the first notch 1521 being 1 mm, a width b of the base being 0.5 mm, and a depth c being 2.5 mm, and a distance d from the outer edge of the case connection portion 152 to the side of the current collector body 151 away from the electrode assembly 120 being 2.8 mm. The case connection portion 152 is divided into two connection ends by the one first notch 1521, and each connection segment and the case 110 are welded independently, forming two separate first weld marks 1522 on the case connection portion 152.

[0056] 6 to 8, in one embodiment of the secondary battery 100 of the present invention, two first notches 1521 are provided in each case connection portion 152. The first notches 1521 are V-shaped, with a width a of the top of the first notch 1521 being 0.4 mm, a width b of the base being 0.2 mm, and a depth c being 2.5 mm, and a distance d from the outer periphery of the case connection portion 152 to the side of the current collector body 151 away from the electrode assembly 120 being 3 mm. The case connection portion 152 is divided into three connection ends by the two first notches 1521, and each connection segment is welded to the case 110 independently, forming three separate first weld marks 1522 on the case connection portion 152.

[0057] 9 to 11, in one embodiment of the secondary battery 100 of the present invention, each case connection portion 152 is provided with three first notches 1521, and the first notches 1521 are V-shaped, with a width a of the top of the first notch 1521 being 1 mm, a width b of the base being 0.2 mm, and a depth c being 2 mm, and a distance d from the outer periphery of the case connection portion 152 to the side of the current collector body 151 away from the electrode assembly 120 being 3 mm. The case connection portion 152 is divided into four connection ends by the three first notches 1521, and each connection segment and the case 110 are welded independently, forming four separate first weld marks 1522 on the case connection portion 152.

[0058] 12 and 13, in one embodiment of the secondary battery 100 of the present invention, each case connection portion 152 is provided with three first notches 1521, each first notch 1521 is rectangular, the width a of the top of the first notch 1521 and the width b of the base of the first notch 1521 are the same and are both 0.1 mm, the depth c is 2 mm, and the distance d from the outer edge of the case connection portion 152 to the side of the current collector body 151 away from the electrode assembly 120 is 3 mm. The case connection portion 152 and the case 110 are continuously welded together, and a single second weld mark 1523 is formed on the case connection portion 152.

[0059] All four of the above embodiments address the technical issues of the prior art, where the outer edge of the case connection portion 152 cannot bend smoothly and there is a large amount of stress transmission, thereby enabling the case connection portion 152 to bend smoothly and improving the reliability of the connection between the case connection portion 152 and the case 110. At the same time, they reduce the bending stress of the case connection portion 152 and address the issue of poor welding between the current collecting member 150 and the tab due to the bending stress.

[0060] 3 to 13, in one embodiment of the secondary battery 100 of the present invention, the case connection portion 152 includes a bending portion 1524 that connects to the current collector body 151. Considering that deformation stress is likely to occur at the bending portion 1524 when the case connection portion 152 is bent, part of the deformation stress is transmitted to the tab connection portion 153, causing a certain degree of damage to the tab connection portion 153, and in serious cases, the welded portion between the current collecting member 150 and the tab may tear, posing a risk of poor electrical connection of the electrode assembly 120. Therefore, second notches 1525 are further provided on both sides of the bending portion 1524 along the circumferential direction of the case 110. By providing the second notch 1525, the width of the bending portion 1524 can be reduced, which reduces the bending stress generated when the case connection portion 152 is bent. At the same time, the strength of the bending portion 1524 is reduced, making it easier to deform, which is advantageous for absorbing the bending stress, weakening the transmission of the bending stress to the welded connection portion between the collecting member 150 and the tab, and improving the problem of poor welding between the collecting member 150 and the tab due to the bending stress.

[0061] 3, 6, 9, and 12, in one embodiment of the secondary battery 100 of the present invention, the case connection portion 152 includes a bent portion 1524 connected to the current collector body 151, and a weakened portion 1526 extending along the circumferential direction of the case 110 is provided on the bent portion 1524. The weakened portion 1526 may be provided at both ends or in the middle of the bent portion 1524, or may surround the entire circumferential direction of the bent portion 1524. The weakened portion 1526 may have a variety of forms, for example, one or a combination of crushing, notching, and cutting, as long as it can weaken the bending strength of the bent portion 1524 and facilitate bending and forming the bent portion 1524. In this embodiment, the weakened portion 1526 has a crushed structure extending along the entire circumferential direction of the bent portion 1524. The provision of the weakened portion 1526 on the bending portion 1524 reduces the stress that occurs when the case connection portion 152 is bent. At the same time, because the strength of the weakened portion 1526 is low, the weakened portion 1526 of the bending portion 1524 is the first to deform under stress, reducing the transmission of stress to the welded connection portion between the current collecting member 150 and the tab and improving the problem of poor welding between the current collecting member 150 and the tab due to bending stress. At the same time, the weakened portion 1526 can guide and position the bending of the bending portion 1524, improving the accuracy of the bending position of the bending portion 1524 and contributing to improving the consistency of the assembly quality of the secondary battery 100. In addition, when the case connection portion 152 and the case 110 are welded together before the processing of the rolling groove 114, the weakened portion 1526 also functions as a reference line for the welding position, facilitating the positioning of the welding head during welding.

[0062] In one embodiment of the secondary battery 100 of the present invention, the sum of the minimum current passing areas of all the weak portions 1526 is e, and the total area of ​​the weld lines formed by welding the current collector body 151 to the tabs is s, where e > s. It should be noted that the minimum current passing area of ​​the weak portions 1526 is the smallest point in the cross-sectional area of ​​each weak portion 1526 along the circumferential direction of the current collecting member 150, and the total area of ​​the weld lines refers to the projected area of ​​all the weld lines formed by welding the current collector body 151 to the tabs along the axial direction of the electrode assembly 120. By setting the sum of the minimum current passing areas of all the weak portions 1526, e, to be greater than the total weld line area s, it is possible to weaken bending stress transmission without affecting the current conducting effect of the weak portions 1526.

[0063] 14, the present invention further provides a battery pack 10, which includes any of the secondary batteries 100 described above. In one embodiment of the battery pack 10 of the present invention, the battery pack 10 includes a case 101, a case lid 102, and a plurality of secondary batteries 100, which are arranged in the case 101 and connected in series, parallel, or a combination of series and parallel, and the case lid 102 covers the case 101 to provide protection for the plurality of secondary batteries 100. It should be noted that the battery pack 10 may include not only the secondary battery 100 of the present invention but also other components such as a thermal management system and a circuit board for the battery pack 10, and the battery pack 10 may be a battery module, a battery pack, a storage cabinet, etc., which will not be described in detail here.

[0064] Referring to FIG. 15 , the present invention further provides an electronic device 1, which includes the above-mentioned battery pack 10. A working 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 fuel-powered vehicle, a gas-powered vehicle, or a new energy vehicle. The new energy vehicle may be, but is not limited to, a pure electric vehicle, a hybrid vehicle, or a step-up vehicle. The working unit 11 is a vehicle body, and the battery pack 10 is installed at the bottom of the body and provides power support for the vehicle's running or the operation of electrical components inside the vehicle. However, in some other embodiments, the electronic device 1 may also be a mobile phone, a portable device, a laptop, a boat, an aircraft, an electric toy, an electric tool, or the like. Aircraft include airplanes, rockets, space shuttles, and spacecraft. The working unit 11 may be a unit component that can obtain power from the battery pack 10 and perform a corresponding operation, such as a fan blade rotation unit or a vacuum cleaner dust collection unit. Electric toys include stationary and mobile electric toys, such as game consoles, electric car toys, electric boat toys, and electric airplane toys. The power tools include metal cutting power tools, grinding power tools, assembly power tools, and railroad power tools, such as electric drills, electric grinding machines, electric wrenches, electric screwdrivers, electric hammers, electric impact drills, concrete vibrators, and electric planes. The embodiments of the present invention do not impose any particular limitations on the above-mentioned electronic device 1.

[0065] The secondary battery of the present invention provides a first notch on the outer periphery of the case connection portion. This allows the outer periphery of the case connection portion to bend to a smaller diameter when bending toward the case axis. The provision of the first notch reduces the area of ​​the outer periphery of the case connection portion, reducing the generation of excess extrusion material. The first notch also accommodates the excess extrusion material, thereby resolving the technical problem of the prior art, in which the outer periphery of the case connection portion cannot be smoothly bent and large stress transmission occurs. This allows the case connection portion to bend smoothly, improving the connection reliability between the case connection portion and the case, and at the same time, reducing the bending stress of the case connection portion, thereby addressing the problem of poor welding between the current collecting member and the tab due to bending stress. Therefore, the present invention effectively overcomes some practical problems in the prior art and has great utility and significance. The above-described embodiments are illustrative of the principles and advantages of the present invention and are not intended to limit the present invention. Those skilled in the art may make modifications or variations to the above-described embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations that can be accomplished by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be included in the claims of the present invention. [Industrial Applicability]

[0066] The present invention relates to the field of battery technology, and more particularly to secondary batteries, battery packs, and electronic devices. [Explanation of symbols]

[0067] 1:Electronic equipment 10: Battery pack 11:Working section 101: Box body 102: Box lid 100: Secondary battery 110: Case 111: End wall 112: Side wall 113:Aperture 114: Rolling groove 1141: First side wall 1142: Second side wall 120: Electrode assembly 121: Positive electrode sheet 1211: Positive electrode current collector 1212: 1st application area 1213: 1st uncoated area 122: Separator 123: Negative electrode sheet 1231: Negative electrode current collector 1232:Second application area 1233: 2nd uncoated area 124: Negative electrode tab 125: Positive electrode tab 130: Cover plate 140: Polar pillar 150: Current collecting member 151: Current collector body 152: Case connection part 1521: First notch 1522: First welding mark 1523: Second welding mark 1524: Bend 1525: Second notch 1526: Weak part 153: Tab connection

Claims

1. a case including an annular side wall, an opening formed at one end of the side wall, and an end of the case close to the opening including a rolling groove recessed toward the inside of the case; an electrode assembly housed within the case and including a tab facing the opening; a current collecting member including a current collecting body and a case connecting portion connected to an outer peripheral edge of the current collecting body, wherein the current collecting body is fixedly connected to the tab, and the case connecting portion is bent toward an axis of the case and welded to a surface of the rolling groove facing the electrode assembly; Including, A secondary battery, characterized in that n first notches are provided on an outer peripheral edge of the case connection portion facing the axis of the case, where n≧1.

2. 2. The secondary battery according to claim 1, wherein the width of the root of the first notch is b, the width of the top of the first notch is a, and 0.1 mm≦b≦a≦2 mm.

3. 3. The secondary battery according to claim 2, wherein, before the case connection portion is bent, a distance from an outer peripheral edge of the case connection portion to a side of the current collector body away from the electrode assembly is d, a depth of the first notch is c, and 0.5d≦c<d.

4. The secondary battery according to claim 1 , wherein the current collecting member includes a plurality of the case connecting portions, and the plurality of case connecting portions are disposed around the outer periphery of the current collecting body.

5. 5. The secondary battery according to claim 4, wherein the case connection portion is divided into n+1 connection segments along the circumferential direction of the case by the first notches, n+1 or more first weld marks are formed by welding the case connection portion to the surface of the rolling groove facing the electrode assembly, and at least one first weld mark is provided on the connection segment of each stage.

6. 5. The secondary battery according to claim 4, wherein the width of any point of the first notch is 0.2 mm or less, at least one second weld mark is formed by welding the case connection portion and the surface of the rolling groove facing the electrode assembly, and each of the second weld marks is continuous and spans all of the first notches.

7. The secondary battery according to claim 6 , wherein the penetration depth of the second welding mark at the position of the first notch is less than 0.7 times the thickness of the case.

8. The secondary battery according to claim 4 , wherein the case connection portion includes a bent portion connected to the current collector body, and the bent portion has a second notch on each side along the circumferential direction of the case.

9. The secondary battery according to claim 4 , wherein the case connection portion includes a bent portion connected to the current collector body, and a weakened portion extending along the circumferential direction of the case is provided on the bent portion.

10. 10. The secondary battery according to claim 9, wherein the sum of the minimum current passing areas of all the fragile portions is e, the total area of ​​the weld line formed by welding the current collector body and the tab is s, and e>s.

11. A battery pack comprising the secondary battery according to any one of claims 1 to 10.

12. An electronic device comprising the battery pack of claim 11.

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