Secondary battery, battery pack, and electronic device
By setting a weak point at the bending section of the current collector, the problem of welding failure during mechanical sealing is solved, the welding strength and conductivity of the battery are improved, and the reliability of the product is enhanced.
Patent Information
- Application Number
- CN202423015604.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-06
- Publication Date
- 2025-12-05
- Estimated Expiration
- 2034-12-06
AI Technical Summary
In the mechanical sealing process of existing cylindrical batteries, the welding between the current collector and the casing is prone to failure, resulting in a decrease in product yield.
A first weak point is set at the bend of the current collector to reduce the risk of welding failure by reducing the stress at the bend and to reduce the risk of the current collector being pressed into the electrode assembly during the sealing process.
This improved the welding strength and conductivity of the current collector, reduced the risk of breakage at the bend, and increased product yield.
Smart Images
Figure CN223638456U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to battery technology field, concretely relates to a secondary battery, battery pack and electronic device. BACKGROUND
[0002] Mechanical sealing is the mainstream packaging mode of the existing cylindrical battery, which is widely used because of its mature process and equipment and fast production rhythm. The existing cylindrical battery usually sets a current collecting member near the opening of the shell, so that one end of the current collecting member is welded to the side wall of the shell, and the other end is electrically connected with the tab of the electrode assembly, thereby realizing the electrical connection between the shell and the electrode assembly, and then mechanical sealing is carried out.
[0003] The mechanical sealing includes rolling a groove recessed towards the inside of the shell on the side wall of the shell, and then the cover plate is pressed tightly by the bump sealing method. During the rolling process, the current collecting member will be bent due to the deformation of the groove. Because of the bending stress, the welding between the current collecting member and the shell is prone to failure. SUMMARY
[0004] The utility model provides a kind of secondary battery, battery pack and electronic device to improve the technical problem that current collecting member and shell are prone to welding failure during the mechanical sealing process of secondary battery.
[0005] To achieve the above object and other related purposes, the utility model provides a kind of secondary battery, battery pack and electronic device, the secondary battery includes electrode assembly, shell and current collecting member;The shell contains electrode assembly, one end of the shell includes opening, the side of the shell near the opening includes the groove recessed towards the inside of the shell, and the groove limits the movement of electrode assembly to the opening direction;Current collecting member is at least partially arranged between the groove and electrode assembly, and the current collecting member includes current collecting body and connecting sheet connected to the peripheral edge of current collecting body, and the current collecting body is connected with electrode assembly, and the connecting sheet is bent towards the center of current collecting body, and the connecting sheet is welded with the surface of the groove facing electrode assembly, and is formed with first welding mark;Connecting sheet includes bending portion between first welding mark and current collecting body, and the part near first welding mark of bending portion is provided with first weak portion for reducing the stress transmission to first welding mark when bending portion is bent.
[0006] In the above technical solution, the first weak portion is arranged on the bending portion, which can reduce the stress when the bending portion is bent, make the bending portion itself more easily bent, not easy to break, and also can reduce the stress transmission to the first welding mark when the bending portion is bent, thereby reducing the risk of breaking of the current collecting member at the first welding mark. Further, it can also reduce the risk of the edge of the current collecting member being pressed into the electrode assembly during the bump sealing process, thereby improving the product yield.
[0007] In the secondary battery example of the utility model, the first weak part extends to the current collecting body away from the first welding mark.
[0008] In the above technical solution, the first weak part extends to the current collecting body, so that the bending stress at the junction of the first weak part and the current collecting body is weakened, which is beneficial to the bending of the connecting piece. At the same time, the junction of the first weak part and the current collecting body will deform first during the bending process to reduce the transmission of stress to the welding connection part of the current collecting member and the tab, thereby improving the problem of welding failure between the current collecting member and the tab caused by bending stress. In addition, the setting of a≤b means that the first weak part can be distributed on the bending part or partially set on the bending part. This setting can reduce the stress when the bending part is bent, make the bending part itself more easily bent and not easily broken, and thus reduce the risk of the edge of the current collecting member being pressed into the electrode assembly during the sealing process.
[0009] In the secondary battery example of the utility model, the thickness of the first weak part is c, and the thickness of the current collecting body is d, wherein c
[0010] In the above technical solution, the thickness of the first weak part is thinner than the thickness of the current collecting body, and the effect of reducing the bending stress of the first weak part is achieved by reducing the thickness. This structure has low processing cost and obvious effect of reducing bending stress.
[0011] In the secondary battery example of the utility model, 0.05mm≤c≤0.15mm.
[0012] In the above technical solution, the thickness c of the first weak part is ≤0.15mm, which can achieve the effect of reducing the bending stress of the first weak part and facilitate the bending of the first weak part. The thickness c of the first weak part is ≥0.05mm, which provides the first weak part with sufficient mechanical strength and facilitates the conduction of current, ensuring the conductivity of the current collecting member.
[0013] In the secondary battery example of the utility model, along the extension direction of the first weak part, the length of the first weak part is a, and 1.5mm≤a≤3mm.
[0014] In the above technical solution, along the extension direction of the first weak part, the length a of the first weak part is ≥1.5mm, which can make the first weak part have a larger length and achieve the effect of further reducing the bending stress of the bending part. The bending part can be bent to a greater extent, which further reduces the tension on the first welding mark when the bending part is bent, thereby reducing the risk of the current collecting member breaking at the first welding mark. The limitation of a≤3mm can achieve the effect of the connecting piece being easy to bend and not easy to break, and also having high strength.
[0015] In the secondary battery example of the utility model, along the extension direction of the first weak part, the length of the bending part is b, the thickness of the connecting sheet at the first welding mark is f, wherein a < b and c < f.
[0016] In the above technical solution, a < b means that the first weak part is arranged in part of the bending part, which can reduce the stress when the bending part is bent, make the bending part itself more easily bent, not easily broken, and further reduce the risk of the edge of the current collecting member being pressed into the electrode assembly during the sealing process. c < f means that the thickness of the connecting sheet at the first welding mark is greater than the thickness of the first weak part, so as to form a thicker molten pool at the first welding mark, so that the connecting sheet and the side wall have higher welding strength.
[0017] In the secondary battery example of the utility model, the thickness of the connecting sheet as a whole is c.
[0018] In the above technical solution, the thickness of the connecting sheet as a whole is c, which means that the connecting sheet has a thickness thinner than the current collecting body, which can further reduce the bending stress of the bending part, and the bending part can be bent to a greater extent and is not easily broken. The connecting sheet is simple to process, the effect of reducing the bending stress is obvious, and even if the bending part is broken, the bending stress of the bending part itself is reduced, which makes it easier to bend during the sealing process, thereby reducing the risk of inserting the electrode assembly and causing damage to the electrode assembly.
[0019] In the secondary battery example of the utility model, the bending part is bent to form a first corner with an overall circular arc transition.
[0020] In the above technical solution, the bending part has a lower bending stress and can be bent to an overall circular arc transition shape to the greatest extent. The bending stress of the bending part of this shape is more balanced, and the internal stress is reduced, so the tension on the first welding mark is reduced when bending, thereby reducing the risk of the current collecting member breaking at the first welding mark. In addition, the bent bending part has a small thickness in the height direction of the secondary battery, which can reduce the risk of the current collecting member being pressed into the electrode assembly during sealing, thereby improving the conductivity and safety performance of the secondary battery.
[0021] In the secondary battery example of the utility model, the first weak part has a plurality of first weak parts arranged in the direction from the first welding mark to the current collecting body.
[0022] In the above technical solution, the first weak part can be intermittent, which can make the connecting sheet have the effects of easy bending and not easy breaking, and also have high strength.
[0023] In the secondary battery example of the utility model, the second weak part is arranged between the current collecting body and the bending part, the second weak part is arranged at the part of the bending part far from the first welding mark, and the second weak part is used for reducing the stress transmission to the current collecting body when the bending part is bent.
[0024] In the above technical solution, when the bending part is bent, deformation occurs at the first weak part and the second weak part first, the deformation of the first weak part can reduce the transmission of stress to the first welding mark, thereby improving the problem that the first welding mark is easily broken, and the deformation of the second weak part can reduce the transmission of stress to the current collecting member and the welding connection part between the tab, thereby improving the problem of welding failure between the current collecting member and the tab caused by the bending stress.
[0025] In the secondary battery example of the utility model, the current collecting body includes a plurality of folding parts, the folding parts are configured to start folding from the middle of the current collecting body in the direction away from the electrode assembly when the internal pressure of the secondary battery exceeds a threshold value, a second corner is formed at the second weak part, a third corner is formed at the first weak part, and the distance from the second corner to the inner wall of the shell is less than the distance from the third corner to the inner wall of the shell along the radial direction of the shell.
[0026] In the above technical solution, when the bending part is bent, deformation occurs at the first weak part and the second weak part first, so a third corner is formed at the first weak part, and a second corner is formed at the second weak part, the part between the bending part, the current collecting body and the free end of the connecting sheet to the first welding mark forms a triangular structure, the triangular structure has higher stability; in addition, when the secondary battery is pressure released, the folding part starts to fold from the middle of the current collecting body in the direction away from the electrode assembly, since the distance from the second corner to the inner wall of the shell is less than the distance from the third corner to the inner wall of the shell, the bending part and the current collecting body form an acute angle structure, the second corner of the structure can provide a fulcrum for the folded current collecting member, so that the folding part can be folded by a larger amplitude to obtain a larger pressure release area and improve the safety performance of the secondary battery.
[0027] In the secondary battery example of the utility model, the folding part and the electrode assembly are welded to form a second welding mark, and each folding part is at least partially collinear with the connecting sheet along the radial direction of the shell.
[0028] In the above technical solution, the arrangement that each folding part is at least partially collinear with the connecting sheet can realize that the second corner is also at least partially collinear with the folding part, further improve the supporting effect of the second corner on the folding part when the secondary battery is pressure released, so that the folding part can be folded by a larger amplitude to obtain a larger pressure release area and further improve the safety performance of the secondary battery.
[0029] In the secondary battery example of the utility model, the distance from the end of the first weak part close to the first welding mark to the first welding mark is e, wherein e≥0.2mm.
[0030] In the technical scheme, the first weak part and the first welding mark have a safety distance of greater than or equal to 0.2 mm, so that the strength of the first weak part can be prevented from being reduced due to welding heat.
[0031] In the secondary battery example, the second weak part includes one or more combinations of thinning, notching and hollowing.
[0032] In the technical scheme, the one or more combinations of thinning, notching and hollowing can reduce the strength of the second weak part by reducing the cross-sectional area of the second weak part.
[0033] In the secondary battery example, the first weak part includes one or more combinations of thinning, notching and hollowing.
[0034] In the technical scheme, the one or more combinations of thinning, notching and hollowing can reduce the strength of the first weak part by reducing the cross-sectional area of the first weak part.
[0035] In the secondary battery example, along the radial direction of the shell, the distance from the first welding mark close to the center of the current collector body to the free end of the connecting piece is g, and the unfolded size of the connecting piece is h, wherein g≤h / 3.
[0036] In the technical scheme, by limiting the relative size between the distance A and the size B, the distance between the first welding mark and the free end of the connecting piece is limited to g≤h / 3, so that the bending moment generated by the rolling groove force on the first welding mark is small during the rolling groove process, the probability of breaking of the connecting piece at the first welding mark position is reduced, and the probability of the edge of the current collecting member being pressed into the electrode assembly is reduced, thereby improving the product yield. At the same time, the bending moment generated by the rolling groove force on the first welding mark is small, and the deformation stress transmitted from the first welding mark position to the periphery of the current collector body during the rolling groove process is also reduced, thereby reducing the downward pressure generated by the periphery of the current collector body on the electrode assembly, and further reducing the probability of the edge of the current collecting member being pressed into the electrode assembly.
[0037] In the secondary battery example, 0.2mm≤g≤1mm.
[0038] In the technical scheme, 0.2mm≤g≤1mm is limited, which can meet the welding position requirements between most current collecting members and side walls, and can further reduce the probability of breaking of the connecting piece at the first welding mark position during the rolling groove process.
[0039] In the secondary battery example of the utility model, along the radial direction of the secondary battery, the distance from the point on the rolling groove closest to the axis of the shell to the outer circumferential surface of the shell is i, and the distance from the first welding mark to the outer circumferential surface of the shell is j, wherein j <= 0.5i.
[0040] In the above technical solution, j <= 0.5i is limited, which can reduce the pulling force on the first welding mark when the side of the rolling groove close to the axis of the shell is stretched and deformed during the rolling process, and further improve the problem that the connecting piece is easily pulled off at the first welding mark.
[0041] The utility model also provides a battery pack, the battery pack includes the secondary battery of any one of the above.
[0042] The utility model also provides an electronic device, the electronic device includes the battery pack.
[0043] The secondary battery of the utility model is provided with a first weak part on the bending part, which can reduce the stress when the bending part is bent, make the bending part itself more easily bent, not easy to break, in addition, the stress when the bending part is bent can be further transmitted to the first welding mark, and the risk of breaking of the current collecting member at the first welding mark is reduced. Further, the risk of the edge of the current collecting member being pressed into the electrode assembly during the sealing process is also reduced, thereby improving the product yield. BRIEF DESCRIPTION OF DRAWINGS
[0044] In order to more clearly illustrate the technical solutions in the embodiments of the utility model or the prior art, the drawings needed in the embodiment or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the utility model, and those skilled in the art can also obtain other embodiments according to these drawings without creating any creative labor.
[0045] Figure 1 It is a structural schematic view of an embodiment of the secondary battery of the utility model;
[0046] Figure 2 It is a structural schematic view of the electrode assembly in an embodiment of the secondary battery of the utility model;
[0047] Figure 3 It is a local enlarged view of the connecting part between the connecting piece and the shell in an embodiment of the secondary battery of the utility model;
[0048] Figure 4 It is Figure 1 a local enlarged view of C in the above figure;
[0049] Figure 5 It is Figure 4 a local enlarged view of D in the above figure;
[0050] Figure 6Structure diagram of a secondary battery embodiment of the utility model;
[0051] Figure 7 Partial enlarged view of the connecting piece and the shell connecting part in a secondary battery embodiment of the utility model;
[0052] Figure 8 For Figure 6 Partial enlarged view of E in the middle;
[0053] Figure 9 For Figure 8 Partial enlarged view of F in the middle;
[0054] Figure 10 Structure diagram of a secondary battery embodiment of the utility model;
[0055] Figure 11 Partial enlarged view of the connecting piece and the shell connecting part in a secondary battery embodiment of the utility model;
[0056] Figure 12 For Figure 10 Partial enlarged view of A in the middle;
[0057] Figure 13 For Figure 12 Partial enlarged view of B in the middle;
[0058] Figure 14 Partial enlarged view of the connecting piece and the shell connecting part in a secondary battery embodiment of the utility model;
[0059] Figure 15 Structure diagram of a current collecting member in a secondary battery embodiment of the utility model;
[0060] Figure 16 Structure diagram of a current collecting member in a secondary battery embodiment of the utility model;
[0061] Figure 17 Plan view of a current collecting member and an electrode assembly in a secondary battery embodiment of the utility model;
[0062] Figure 18 Schematic diagram of a battery pack embodiment of the utility model;
[0063] Figure 19 Schematic diagram of an electronic device embodiment of the utility model.
[0064] Element number explanation
[0065] 1. Electronic device; 10. Battery pack; 11. Working part; 101. Box body; 102. Box cover; 100. Secondary battery; 110. Housing; 111. End wall; 112. Side wall; 113. Opening; 114. Roll groove; 120. Electrode assembly; 121. First tab; 1211. Negative current collector; 1212. First coating area; 1213. First uncoated area; 122. Separator; 123. Second tab; 1231. Positive current collector; 1232. Second coating area; 1233. Second uncoated area; 124. First tab; 125. Second tab; 130. Current collecting member; 131. Current collecting body; 1311. Turnover part; 132. Connecting piece; 1322. Bending part; 1323. First weak part; 1324. First corner; 1325. First welding mark; 1326. Second welding mark; 1327. Second corner; 1328. Third corner; 1329. Second weak part; 140. Cover plate; 150. Pole. DETAILED DESCRIPTION
[0066] The above and other advantages and effects of the present application will become readily apparent to those of ordinary skill in the art from the following description in which preferred embodiments of the present application are set forth in sufficient detail. The present application can also be applied or embodied in various ways without departing from the spirit thereof, and the various details of the specification can be modified in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that the following embodiments and features in the embodiments can be combined with each other in the case of no conflict. It should also be understood that the terms used in the embodiments of the present application are intended to describe specific embodiments and are not intended to limit the scope of protection of the present application. The test methods in the following embodiments are not specified, and are generally performed under conventional conditions or under conditions recommended by the manufacturers.
[0067] When the embodiments give numerical ranges, it should be understood that, unless otherwise specified by the present application, each numerical range has two endpoints and any number between the two endpoints can be selected. Unless otherwise defined, all technical and scientific terms used in the present application are used by those skilled in the art in the present technical field and in the description of the present application, and any method, device and material of the prior art similar or equivalent to the method, device and material in the embodiments of the present application can be used to implement the present application.
[0068] It should be understood that the terms such as "upper", "lower", "left", "right", "middle" and "one" used in the specification are only for the convenience of clear description, and are not intended to limit the scope of the present application, and the change or adjustment of the relative relationship without substantial change of the technical content is also regarded as the scope of the present application.
[0069] The secondary battery includes an electrode assembly, which is a component in which electrochemical reactions occur in the secondary battery, and can include one or more electrode assemblies.
[0070] The secondary battery further includes a case, a cover plate, and a pole, the case including an end wall and a side wall surrounding the end wall, one end of the side wall having an opening, the electrode assembly being assembled into the case via the opening of the case, the cover plate being used to cover the opening of the case to achieve sealing, and the pole being electrically connected to the electrode assembly through the end wall to guide the electrical energy generated by the electrode assembly out.
[0071] The mainstream packaging method of the existing secondary battery is mechanical sealing, which has the advantages of mature process and equipment and fast production rhythm, and is widely used. The current collecting member is electrically connected to the electrode assembly and the case at the same time to achieve the electrical connection between the electrode assembly and the case. Specifically, a rolling groove recessed toward the inside of the case is rolled on the side wall of the case, the edge of the current collecting member is pressed against the side of the rolling groove close to the electrode assembly, the rolling groove can limit the axial displacement of the electrode assembly, the cover plate is installed on the step formed on the side of the rolling groove away from the electrode assembly, a sealing member is arranged between the cover plate and the case, and the cover plate is pressed against the sealing member in a potted manner at the edge of the opening to form a reliable connection and achieve the sealing of the case.
[0072] There are various connection methods of the current collecting member and the case, and a commonly used method is as follows: a connecting piece is arranged at the edge of the current collecting member, the connecting piece is first welded and fixed to the side wall of the case, and then the rolling groove is rolled on the side wall to make the connecting piece continue to bend toward the axis of the case. However, the inventor finds that the connecting piece has a large pulling force at the welding position of the connecting piece and the side wall during the bending process, which causes the risk of breakage of the connecting piece at the above-mentioned welding position. During the subsequent potted process, the edge of the broken current collecting member is close to the vertical state, and the current collecting member may be inserted into the electrode assembly after being pressed, thereby causing damage to the electrode assembly and reducing the product yield.
[0073] In view of this, the utility model provides a technical scheme, a first weak part is arranged on the bending part, which can reduce the stress during the bending of the bending part, make the bending part itself more easily bent, not easy to break, further, can further reduce the risk of the edge of the current collecting member being pressed into the electrode assembly during the potted process, and thereby improve the product yield.
[0074] Please refer to Figures 1 to 19 The utility model provides a kind of secondary battery 100, which includes a case 110, an electrode assembly 120, a current collecting member 130, a cover plate 140 and a pole 150.
[0075] Please refer to Figure 1The shell 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 in various ways, such as one-piece stamping, one-piece casting or separate welding, as long as a stable sealing and electrical connection relationship can be formed. The surrounding of the side wall 112 is not limited, and can be cylindrical or prismatic, or any other closed-loop profile that can be matched with the end wall 111. In the embodiment, the outer edge of the end wall 111 is circular, and the side wall 112 is cylindrical and surrounds the outer edge of the end wall 111. A circular opening 113 is formed at the end of the side wall 112 away from the end wall 111. The shell 110 formed by the end wall 111 and the side wall 112 has a receiving cavity for accommodating the electrode assembly 120, electrolyte and other necessary components of the battery. Specifically, the diameter of the shell 110 can be determined according to the specific size of the electrode assembly 120, such as 18 mm, 21 mm, 46 mm, etc. The shell 110 can be made of various materials, such as copper, iron, aluminum, steel, aluminum alloy, etc. In order to prevent rusting of the shell 110 during long-term use, a layer of anti-rust material such as metal nickel can be plated on the surface of the shell 110.
[0076] Referring to Figures 1 to 2 The electrode assembly 120 is accommodated in the shell 110, and the electrode assembly 120 is a component for electrochemical reaction in the secondary battery 100. One or more electrode assemblies 120 can be contained in the shell 110. The electrode assembly 120 includes a first electrode tab 121, a second electrode tab 123 and a separator 122 stacked and wound to form a wound structure. The first electrode tab 121 and the second electrode tab 123 have opposite polarities. In some embodiments, the first electrode tab 121 is a positive electrode tab, and the second electrode tab 123 is a negative electrode tab. In other embodiments, the first electrode tab 121 is a negative electrode tab, and the second electrode tab 123 is a positive electrode tab.
[0077] Referring to Figures 1 to 2 In the embodiment, the first electrode tab 121 is a negative electrode tab, and the first electrode tab 121 includes a negative electrode current collector 1211 and a negative electrode active material coated on the surface of the negative electrode current collector 1211. The negative electrode current collector 1211 includes a first coated area 1212 coated with the active material and a first uncoated area 1213 not coated with the active material. The first uncoated area 1213 is located at the end of the first electrode tab 121, and the first uncoated area 1213 extends beyond the separator 122 along the winding axis direction of the electrode assembly 120 and bends towards the winding axis to form a first tab 124. The first tab 124 is a corresponding negative electrode tab.
[0078] Referring to Figures 1 to 2The second tab 123 is a positive electrode tab. Specifically, the second tab 123 includes a positive electrode current collector 1231 and a positive electrode active material coated on a surface of the positive electrode current collector 1231. The positive electrode current collector 1231 includes a second coated area 1232 coated with the positive electrode active material and a second uncoated area 1233 uncoated with the positive electrode active material. The second uncoated area 1233 is located at an end of the second tab 123, extends out of the separator 122 along the winding axis direction of the electrode assembly 120, and is bent towards the winding axis to form a second tab 125. The second tab 125 is a corresponding positive electrode tab.
[0079] Referring to Figures 1 to 2 The separator 122 is arranged between the first tab 121 and the second tab 123 to separate the positive electrode active material layer and the negative electrode active material layer. For example, in the lithium ion secondary battery 100, the material of the positive electrode current collector 1231 can be aluminum, the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material can be lithium cobaltate, lithium iron phosphate, ternary lithium, or lithium manganate. The material of the negative electrode current collector 1211 can be copper, the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material can be carbon or silicon. The base material of the separator 122 can be polypropylene (PP) or polyethylene (PE). To protect and insulate the electrode assembly 120, an insulating film can be wrapped outside the electrode assembly 120. The insulating film can be made of PP, PE, polyethylene terephthalate (PET), polyvinyl chloride (PVC), or other high polymer materials.
[0080] Referring to Figure 1 and Figure 2 Further, the first tab 124 faces the end wall 111 or the opening 113, and 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 150 to make the pole 150 positively charged. The first tab 124 faces the opening 113, and the housing 110 is electrically connected to the first tab 124 to make the housing 110 negatively charged. However, in another embodiment, the first tab 124 can be connected to the pole 150, and the second tab 125 can be connected to the housing 110.
[0081] Referring to Figure 1The pole 150 is fixed to the end wall 111 and electrically connected with the electrode assembly 120. Specifically, the end wall 111 is provided with a pole 150 hole, the pole 150 is installed through the pole 150 hole, and the pole 150 is insulated from the end wall 111. The end of the pole 150 towards the electrode assembly 120 is directly or indirectly electrically connected with the second pole lug 125 through the end wall 111. The pole 150 can be in any suitable form that can be electrically connected with the second pole lug 125 of the electrode assembly 120 through the end wall 111, such as a circular, square, prism or special-shaped profile that can achieve stable conduction. The pole 150 hole corresponds to the shape of the pole 150. In the embodiment, the cross section of the pole 150 is circular.
[0082] Referring to Figure 1 and Figure 5 , the cover plate 140 is sealingly installed in the opening 113. The outer edge of the cover plate 140 corresponds to the shape of the opening 113 and is connected with the side wall 112 to seal the opening 113. In a specific embodiment, a groove 114 is rolled on the side wall 112 of the shell 110 near the outer end, which is recessed towards the inside of the shell 110. The groove 114 can limit the movement of the electrode assembly 120 towards the opening 113. An annular step is formed around the shell 110 on the side of the groove 114 away from the electrode assembly 120, and the cover plate 140 is placed on the step. A sealing ring is provided between the cover plate 140 and the shell 110. The edge of the opening 113 is potted to press the sealing ring tightly and form a reliable connection.
[0083] Referring to Figure 1 , Figure 4 , Figure 5 and Figure 17 , the current collecting member 130 is at least partially provided between the groove 114 and the electrode assembly 120. The electrode assembly 120 is electrically connected with the shell 110 through the current collecting member 130. It should be noted that the current collecting member 130 can be in any rotationally symmetric shape, such as a circle, a square, a regular polygon, a petal shape or other shapes with a center of symmetry and a shape that can coincide with the original shape after rotating a certain angle around the center of symmetry. The center of the current collecting member 130 is the center of symmetry of the current collecting member 130.
[0084] Specifically, referring to Figure 4The current collecting member 130 includes a current collecting body 131 and a connecting sheet 132 connected to the outer periphery of the current collecting body 131, and the current collecting body 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. In this embodiment, laser welding is used, the first tab 124 is a negative tab, and the material of the current collecting member 130 is preferably copper metal. It should be noted that the current collecting body 131 is the part of the current collecting member 130 that is attached to the first tab 124 and can be used for welding the current collecting member 130 to the first tab 124. In order to improve the positioning, processing convenience, interchangeability and uniformity of the current collecting member 130 during installation, the current collecting body 131 in this embodiment adopts a circular structure.
[0085] Please refer to Figures 3 to 5 and Figure 17 The connecting sheet 132 can be a whole annular structure or one or more sector annular structures, as long as it meets the flow guiding requirements and welding strength requirements between the connecting sheet 132 and the shell 110. The connecting sheet 132 in this embodiment is a four-sector annular structure evenly connected to the outer periphery of the current collecting body 131. Before the shell 110 is rolled in the rolling groove 114, the connecting sheet 132 is first welded to the side wall 112 of the shell 110 and forms a first welding mark 1325. At the same time of rolling in the rolling groove 114, the connecting sheet 132 welded to the shell 110 continues to bend towards the center of the current collecting body 131, and finally forms a structure that bends towards the axis of the shell 110 and is welded to the surface of the rolling groove 114 facing the electrode assembly 120.
[0086] Considering that the connecting sheet 132 will have a large pulling force at the first welding mark 1325 during the bending process, which may cause the connecting sheet 132 to break at the above-mentioned first welding mark 1325. In the subsequent potting process, the current collecting member 130 is subjected to downward pressure, and the edge of the broken current collecting member 130 approaches a vertical state, which may be inserted into the electrode assembly 120 after being pressed. In an example of the secondary battery 100 of the present application, please refer to Figure 5 , Figure 9 and Figure 13The connecting piece 132 comprises a bending portion 1322 between the first welding mark 1325 and the current collecting body 131, and a first weak portion 1323 is arranged on a portion of the bending portion 1322 close to the first welding mark 1325, so as to reduce the stress of the bending portion 1322 when the bending portion 1322 is bent. The shape and size of the first weak portion 1323 are not limited, for example, the first weak portion 1323 can be a combination of one or more of thinning, notching and hollowing and all forms capable of reducing the stress of the bending portion 1322 when the bending portion 1322 is bent. The above forms can all 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. The first weak portion 1323 arranged on the bending portion 1322 can reduce the stress of the bending portion 1322 when the bending portion 1322 is bent, so that the bending portion 1322 itself is more likely to bend and is not easy to break, and in addition, the stress of the bending portion 1322 when the bending portion 1322 is bent can be reduced to the first welding mark 1325, thereby reducing the risk of the current collecting member 130 breaking at the first welding mark 1325. Further, the risk of the edge of the current collecting member 130 being pressed into the electrode assembly 120 during the sealing process can be reduced, thereby improving the product yield.
[0087] In an example of the secondary battery 100, the first weak portion 1323 extends to the current collecting body 131 away from the first welding mark 1325, and the form of the first weak portion 1323 is various, in an embodiment, the first weak portion 1323 is thinning, please refer to Figure 3 and Figure 7 ; in another embodiment, the first weak portion 1323 is a hollow structure, please refer to Figure 15 , it can be understood that the shape of the hollow structure is not limited to the circular hole of Figure 15 , but can also be an oval, a rhombus or any other shape capable of reducing the stress of the bending portion 1322 when the bending portion 1322 is bent; in some other embodiments, the first weak portion 1323 can also be notching or a combination structure of the above various forms. The first weak portion 1323 can be continuous, as shown in Figure 3 and Figure 7 ; or can be intermittent, as shown in Figure 14 and Figure 15 . It should be noted that the shapes of the starting end and the terminal end of the first weak portion 1323 are not limited, and can be rounded or right-angled. In order to reduce the stress concentration problem caused by the sudden change of the cross-sectional area, preferably, rounded corners are arranged at the starting end and the terminal end of the first weak portion 1323, as shown in Figure 7 , Figure 11 and Figure 14As shown. In the technical solution, the bending stress at the junction of the first weak part 1323 and the current collecting body 131 is weakened, which is beneficial to the bending of the connecting piece 132; at the same time, the junction of the first weak part 1323 and the current collecting body 131 will deform first in the bending process, so as to reduce the transmission of stress to the welding connection part between the current collecting member 130 and the tab, and further improve the problem of welding failure between the current collecting member 130 and the tab caused by the bending stress.
[0088] Please refer to Figure 3 and Figure 7 In an example of the secondary battery 100 of the utility model, the thickness of the first weak part 1323 is c, the thickness of the current collecting body 131 is d, and c < d. That is, the thickness of the first weak part 1323 is thinner than the thickness of the current collecting body 131. The technical solution realizes the effect of reducing the bending stress of the first weak part 1323 by adopting the way of thinning the thickness. It should be noted that the way of thinning the thickness includes thinning or removing materials, and the like, which are not limited. In the embodiment, the way of thinning is adopted, and the processing cost of the structure is low, and the effect of reducing the bending stress is obvious.
[0089] Please refer to Figure 3 and Figure 7 In an example of the secondary battery 100 of the utility model, 0.05mm ≤ c ≤ 0.15mm. Limiting the thickness c of the first weak part 1323 to be ≤ 0.15mm can realize the effect of reducing the bending stress of the first weak part 1323, which is beneficial to the bending of the first weak part 1323. The limitation that the thickness c of the first weak part 1323 is ≥ 0.05mm can make the first weak part 1323 have sufficient mechanical strength, and at the same time, it is beneficial to the conduction of current, and ensure the conductivity of the current collecting member 130.
[0090] Please refer to Figure 3 and Figure 7 In an example of the secondary battery 100 of the utility model, along the extension direction of the first weak part 1323, the length of the first weak part 1323 is a, and 1.5mm ≤ a ≤ 3mm. It should be noted that the above extension direction refers to the direction of the bending part 1322 from the first welding mark 1325 to the bending of the current collecting body 131. Limiting the length a of the first weak part 1323 to be ≥ 1.5mm can make the first weak part 1323 have a larger length, realize the effect of further reducing the bending stress of the bending part 1322, and the bending part 1322 can be bent to a greater extent, so that the tension on the first welding mark 1325 is further reduced when the bending part 1322 is bent, and the risk of fracture of the current collecting member 130 at the first welding mark 1325 is further reduced. The limitation that a ≤ 3mm can realize that the connecting piece 132 has the effects of easy bending and not easy to break, and also has high strength.
[0091] Please refer to Figure 6 andFigure 9 In the secondary battery 100 example of the utility model, along the extension direction of the first weak part 1323, the length of the bending part 1322 is b, the thickness of the connecting sheet 132 at the first welding mark 1325 is f, wherein a < b and c < f. a < b means that the partial area of the bending part 1322 is provided with the first weak part 1323. The first weak part 1323 can reduce the stress when the bending part 1322 is bent, make the bending part 1322 itself more easily bent, not easy to break, and further reduce the risk of the edge of the current collecting member 130 being pressed into the electrode assembly 120 during the potted process. Further, c < f means that the thickness of the connecting sheet 132 at the first welding mark 1325 is greater than the thickness of the first weak part 1323, which can form a thicker molten pool at the first welding mark 1325, so that the connecting sheet 132 has higher welding strength with the side wall 112, and the fracture probability of the connecting sheet 132 can be reduced. It should be noted that the thickness of the connecting sheet 132 between the free end of the connecting sheet 132 and the first welding mark 1325 can be equal or not equal, which is not limited, and in the embodiment, please refer to the figure, the thickness of the connecting sheet 132 from the free end to the first welding mark 1325 is f, the equal thickness processing technology is simpler, the welding process window between the connecting sheet 132 and the rolling groove 114 is large, and the welding strength is improved.
[0092] Further, in the secondary battery 100 example of the utility model, 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 is a whole circular arc transition, as shown in Figure 8 and Figure 9 The bending part 1322 can be bent to form a first corner 1324 that is a whole circular arc transition to the greatest extent due to the lower bending stress, and it should be noted that the first corner 1324 is not limited to the angle, as long as the bent part is smooth transition, it can be considered as the form covered by the technical solution. The bending stress of the bending part 1322 in various places is more balanced, the internal stress is reduced, so the tension at the first welding mark 1325 is reduced when bending, and further the risk of the current collecting member 130 breaking at the first welding mark 1325 is reduced. In addition, the bending part 1322 after bending has a smaller thickness in the height direction of the secondary battery 100, which can reduce the risk of the current collecting member 130 being pressed into the electrode assembly 120 during the potted process, and further improve the conductivity and safety performance of the secondary battery 100.
[0093] Please refer to Figure 1 and Figures 3 to 5In the secondary battery 100 example of the utility model, the thickness of the whole connecting piece 132 is c, the whole bending part 1322 is equivalent to the first weak part 1323, and because c < d, the thickness of the whole connecting piece 132 is reduced relative to the thickness of the current collecting body 131, the effect of further reducing the bending stress of the bending part 1322 is realized, the bending part 1322 can be bent to a greater extent and is not easy to break; and the connecting piece 132 is simple in processing technology and obvious in the effect of reducing bending stress; in addition, even if the bending part 1322 breaks, because the bending stress of the bending part 1322 is reduced, the bending part 1322 is more easily bent during the potting process, and the risk of damaging the electrode assembly 120 caused by the insertion of the electrode assembly 120 is still reduced.
[0094] Further, referring to Figure 4 and Figure 5 , based on the structure of the bending part 1322 in the above-mentioned embodiment, the bending part 1322 is bent to form a first corner 1324 that is a whole circular arc transition. The bending part 1322 can be bent to form a first corner 1324 that is a whole circular arc transition to the greatest extent due to the low bending stress, and it should be noted that the first corner 1324 is not limited to an angle, as long as the bent part is smooth transition, it can be considered as the form covered by the technical solution. The bending stress of the bending part 1322 in this shape is relatively balanced, and the internal stress is reduced, so the tension at the first welding mark 1325 is reduced when bending, and the risk of breaking of the current collecting member 130 at the first welding mark 1325 is further reduced. In addition, the bending part 1322 after bending has a small thickness in the height direction of the secondary battery 100, which can reduce the risk of the current collecting member 130 being pressed into the electrode assembly 120 during potting, and further improve the conductivity and safety performance of the secondary battery 100.
[0095] In the secondary battery 100 example of the utility model, the first weak part 1323 has a plurality of first weak parts 1323 arranged in the direction from the first welding mark 1325 to the current collecting body 131. That is, the plurality of first weak parts 1323 are discontinuously arranged, for example, in an embodiment, as shown in Figure 14 , the first weak part 1323 includes four thinning areas arranged at intervals; in another embodiment, as shown in Figure 15 , the first weak part 1323 includes four hollow areas arranged at intervals. The discontinuous arrangement of the plurality of first weak parts 1323 can make the connecting piece 132 have the effects of easy bending and not easy to break, and also have high strength.
[0096] Referring to Figures 10 to 13In the secondary battery 100 example of the utility model, the current collecting body 131 and the bending part 1322 are provided with the second weak part 1329, the second weak part 1329 is arranged at the part of the bending part 1322 far away from the first welding mark 1325. The second weak part 1329 is used to reduce the stress transmission to the current collecting body 131 when the bending part 1322 bends. The form of the second weak part 1329 includes one or more combinations of thinning, notch and hollowing, but is not limited to this, the above forms can all realize the effect of reducing the strength of the second weak part 1329 by the way of reducing the sectional area of the second weak part 1329. For example, in an embodiment, the second weak part 1329 is a thinning structure, as shown in Figure 11 ; in another embodiment, the second weak part 1329 is a hollow structure, as shown in Figure 16 .
[0097] Preferably, the bending strength of the part between the first weak part 1323 and the second weak part 1329 of the bending part 1322 is higher than the bending strength of the first weak part 1323 and the second weak part 1329. When the bending part 1322 bends, the first weak part 1323 and the second weak part 1329 will first deform at two positions, the deformation of the first weak part 1323 can reduce the stress transmission to the first welding mark 1325, thereby improving the problem that the first welding mark 1325 is easy to be pulled off, the deformation of the second weak part 1329 can reduce the stress transmission to the welding connection part between the current collecting member 130 and the first tab 124, thereby improving the problem of welding failure between the current collecting member 130 and the first tab 124 caused by the bending stress. In addition, the bending strength of the part between the first weak part 1323 and the second weak part 1329 of the bending part 1322 is high, which is conducive to improving the structural strength of the bending part 1322, and at the same time, when pressure relief occurs, it can support the torn current collecting member 130, and facilitate the folding to form a larger pressure relief area.
[0098] Based on the structure form of the first weak part 1323 in the above embodiment, in the secondary battery 100 example of the utility model, please refer to Figure 12 , Figure 13 and Figure 17The current collecting body 131 includes a plurality of folding portions 1311 configured to fold away from the electrode assembly 120 from the middle of the current collecting body 131 when the internal pressure of the secondary battery 100 exceeds the threshold value, and the plurality of folding portions 1311 can be an integrated structure connected in the circumferential direction or can be independent structures separated from each other, and no limitation is made thereto as long as the folding can be achieved to achieve pressure relief when the internal pressure of the secondary battery 100 exceeds the threshold value. Further, a second corner 1327 is formed at the second weak portion 1329, and a third corner 1328 is formed at the first weak portion 1323, and after the current collecting member 130 is bent due to the deformation of the rolling groove, the bent portion 1322, the current collecting body 131, and the portion between the free end of the connecting piece 132 and the first welding mark 1325 form a triangular structure, and the triangular structure has higher stability; in addition, when the secondary battery 100 is relieved, the folding portion 1311 will fold away from the electrode assembly 120 from the middle of the current collecting body 131. Further, the distance from the second corner 1327 to the inner wall of the shell 110 is less than the distance from the third corner 1328 to the inner wall of the shell 110, and the bent portion 1322 and the current collecting body 131 form an acute angle structure, and the second corner 1327 of the structure can provide a fulcrum for the folded folding portion 1311, so that the folding portion 1311 can be folded to a greater extent to obtain a larger pressure relief area and improve the safety performance of the secondary battery 100.
[0099] Please refer to Figure 17 In an example of the secondary battery 100 of the utility model, the folding portion 1311 and the electrode assembly 120 are welded to form a second welding mark 1326, specifically, the folding portion 1311 and the first tab 124 are welded and connected, and the shape and position of the second welding mark 1326 are not limited, for example, it can be a straight line, a curve (a wavy line, a circular arc line, a sinusoidal curve, etc.), a broken line or other irregular shapes, as long as it can realize stable current transmission between the electrode assembly 120 and the current collecting member 130, in the embodiment, the current collecting body 131 includes four folding portions 1311 distributed along the circumference of the current collecting body 131, and there are also four groups of second welding marks 1326 on the four folding portions 1311, that is, the four folding portions 1311 are respectively welded to form the first tab 124, specifically, each group of second welding marks 1326 includes three wavy-shaped welding marks, which can make the welding balance between the current collecting member 130 and the first tab 124 more stable and have a more uniform current guiding effect, thereby improving the stability of current guiding between the shell 110 and the electrode assembly 120.
[0100] Considering that when the internal pressure of the battery exceeds the threshold value, pressure relief will occur at one end where the cover plate 140 is located, and the part where the folding portion 1311 and the first tab 124 are welded and connected will limit the folding of the current collecting member 130, affecting the effect of pressure relief, in the embodiment, please refer to Figure 17, along the radial direction of the shell 110, each of the folded portions 1311 is at least partially collinear with the connecting piece 132. This arrangement can achieve that the second corner 1327 is also at least partially collinear with the folded portion 1311, and can further improve the supporting effect of the second corner 1327 on the folded portion 1311 when the secondary battery 100 is pressure released. In addition, since the bending portion 1322 is located between the first weak portion 1323 and the second weak portion 1329, the bending strength of the bending portion 1322 is high, which is beneficial to the folding of the folded portion 1311 to a greater extent, so as to obtain a larger pressure release area and improve the safety performance of the secondary battery 100.
[0101] Please refer to Figure 7 、 Figure 11 and Figure 14 , in an example of the secondary battery 100 of the utility model, the distance from the first weak portion 1323 to the first welding mark 1325 is e, wherein e≥0.2mm. This arrangement can make the first weak portion 1323 and the first welding mark 1325 have a safety distance of greater than or equal to 0.2mm, which can prevent the strength of the first weak portion 1323 from being reduced due to the influence of welding heat.
[0102] In an example of the secondary battery 100 of the utility model, the second weak portion 1329 includes one or more combinations of thinning, notching and hollowing. For example, in an embodiment, the second weak portion 1329 is thinned, please refer to Figure 11 ; in another embodiment, the second weak portion 1329 is a hollow structure, please refer to Figure 16 . One or more combinations of thinning, notching and hollowing can achieve the effect of reducing the strength of the first weak portion 1323 by reducing the cross-sectional area of the second weak portion 1329.
[0103] In an example of the secondary battery 100 of the utility model, the first weak portion 1323 includes one or more combinations of thinning, notching and hollowing. For example, in an embodiment, the second weak portion 1329 is thinned, please refer to Figure 3 and Figure 7 ; in another embodiment, the second weak portion 1329 is a hollow structure, please refer to Figure 15 . One or more combinations of thinning, notching and hollowing 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.
[0104] Please refer to Figure 3 and Figure 5In the secondary battery 100 example of the utility model, along the radial of the current collecting body 131, the distance from the first welding mark 1325 near the center of the current collecting body 131 to the free end of the connecting piece 132 is g, and the unfolding size of the connecting piece 132 is h, wherein g≤h / 3. By limiting the relative size between distance A and size B, the distance between the first welding mark 1325 and the free end of the connecting piece 132 is limited in the range of g≤h / 3, which can ensure that the bending moment generated by the rolling groove force on the first welding mark 1325 is small during the rolling groove process, reduce the probability of the connecting piece 132 being broken at the position of the first welding mark 1325, so that the probability of the edge of the current collecting member 130 being pressed into the electrode assembly 120 can be reduced, and the product yield can be improved. At the same time, the bending moment generated by the rolling groove force on the first welding mark 1325 is small, and then the deformation stress transmitted from the position of the first welding mark 1325 to the circumference of the current collecting body 131 during the rolling groove process is also reduced, so that the downward pressure generated by the circumference of the current collecting body 131 on the electrode assembly 120 can be reduced, and the probability of the edge of the current collecting member 130 being pressed into the electrode assembly 120 can be further reduced.
[0105] Please refer to Figure 5 In the secondary battery 100 example of the utility model, further, the range of the distance g from the first welding mark 1325 near the center of the current collecting body 131 to the free end of the connecting piece 132 is 0.2mm≤g≤1mm. The welding position requirement between most of the current collecting member 130 and the side wall 112 can be met, and at the same time, the probability of the connecting piece 132 being broken at the position of the first welding mark 1325 during the rolling groove process can be further reduced.
[0106] Please refer to Figure 5 In the secondary battery 100 example of the utility model, along the radial of the secondary battery 100, the distance from the point on the rolling groove 114 closest to the axis of the shell 110 to the outer circumferential surface of the shell 110 is i, the distance from the first welding mark 1325 to the outer circumferential surface of the shell 110 is j, and j≤0.5i is limited. The limitation can reduce the pulling force on the first welding mark 1325 when the side of the rolling groove 114 near the axis of the shell 110 is stretched and deformed during the rolling groove process, and further improve the problem that the connecting piece 132 is easily pulled off at the first welding mark 1325.
[0107] Please refer to Figure 18The utility model also provides a kind of battery pack 10, battery pack 10 includes the secondary battery 100 of any one of above, in the embodiment of the utility model battery pack 10, battery pack 10 includes box 101, box cover 102 and multiple secondary batteries 100, multiple secondary batteries 100 are placed in box 101, and are connected in series or parallel with each other, or series and parallel hybrid, box cover 102 is capped on box 101, to protect multiple secondary batteries 100.It needs to be explained, battery pack 10 except the secondary battery 100 of the utility model can also include battery pack 10 thermal management system, circuit board etc., battery pack 10 can be battery module or battery pack, energy storage electric cabinet etc.;Here is not expanded to explain one by one.
[0108] Please refer to Figure 19 The utility model also provides a kind of electronic device 1, electronic device 1 includes the battery pack 10 of above. Working part 11 is electrically connected with battery pack 10, to obtain electric energy support.As an example, electronic device 1 is vehicle, and vehicle can be fuel automobile, gas automobile or new energy automobile, and new energy automobile can be pure electric vehicle, hybrid vehicle or range extended vehicle etc., but not limited. Working part 11 is vehicle body, and battery pack 10 is arranged at the bottom of vehicle body, and provides electric energy support for the running of vehicle or the operation of electrical element in vehicle. However in some other embodiments, electronic device 1 can also be mobile phone, portable device, notebook computer, ship, spacecraft, electric toy and electric tool etc. Spacecraft includes airplane, rocket, space shuttle and spaceship etc.;Working part 11 can be the unit component that can obtain the electric energy of battery pack 10 and make corresponding work, for example, fan blade rotating unit, dust collection working unit of dust collector etc. Electric toy includes fixed or mobile electric toy, for example, game machine, electric car toy, electric ship toy and electric plane toy etc. Electric tool includes metal cutting electric tool, grinding electric tool, assembly electric tool and railway electric tool, for example, electric drill, electric grinder, electric wrench, electric screwdriver, electric hammer, impact drill, concrete vibrator and electric planer etc. The embodiment of the application does not specially limit above-mentioned electronic device 1.
[0109] The secondary battery is provided with a first weak part on the bending part, stress during bending of the bending part can be reduced, the bending part itself is easier to bend, and is not easy to break. In addition, the transmission of stress during bending of the bending part to the first welding mark can be reduced, and the risk of breaking of the current collecting member at the first welding mark is reduced. Further, the risk of the edge of the current collecting member being pressed into the electrode assembly during the sealing process is reduced, and the product yield is improved. Therefore, the utility model effectively overcomes some practical problems in the prior art, thereby having high utilization value and use significance. The above embodiments only exemplarily illustrate the principle and effect of the utility model, and are not used to limit the utility model. Any person skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the utility model. Therefore, all equivalent modifications or changes completed by those skilled in the art under the spirit and technical concept disclosed by the utility model should be covered by the claims of the utility model.
Claims
1. A secondary battery characterized by comprising: The application relates to a secondary battery, comprising: an electrode assembly; a shell accommodating the electrode assembly, one end of the shell comprising an opening, one side of the shell close to the opening comprising a groove recessed towards the inside of the shell, the groove limiting the movement of the electrode assembly towards the opening; a current collecting member at least partially arranged between the groove and the electrode assembly, the current collecting member comprising a current collecting body and a connecting sheet connected to the peripheral edge of the current collecting body, the current collecting body being connected to the electrode assembly, the connecting sheet being bent towards the center of the current collecting body, the connecting sheet being welded to the surface of the groove facing the electrode assembly and being formed with a first welding mark; wherein the connecting sheet comprises a bending part between the first welding mark and the current collecting body, the part of the bending part close to the first welding mark being provided with a first weak part for reducing the stress transmitted to the first welding mark when the bending part is bent.
2. The secondary battery according to claim 1, characterized by The part of the first weak part away from the first welding mark extends to the current collecting body.
3. The secondary battery according to claim 2, characterized by The thickness of the first weak part is c and the thickness of the current collecting body is d, wherein c < d.
4. The secondary battery according to claim 3, characterized by 0.05 mm < c < 0.15 mm.
5. The secondary battery according to claim 4, characterized by The length of the first weak part along the extension direction of the first weak part is a, and 1.5 mm < a < 3 mm.
6. The secondary battery according to claim 5, characterized by The length of the bending part along the extension direction of the first weak part is b, and the thickness of the connecting sheet at the first welding mark is f, wherein a < b and c < f.
7. The secondary battery according to claim 4, characterized by The thickness of the connecting sheet as a whole is c.
8. The secondary battery according to any one of claims 6 or 7, characterized by, The bending part is bent to form a first corner with a whole circular arc transition.
9. The secondary battery according to claim 1, characterized by The first weak part has a plurality of first weak parts arranged from the first welding mark to the current collecting body.
10. The secondary battery according to claim 1, characterized by A second weak part is arranged between the current collecting body and the bending part, the second weak part being arranged at the part of the bending part away from the first welding mark, and the second weak part being used for reducing the stress transmitted to the current collecting body when the bending part is bent.
11. The secondary battery according to claim 10, characterized by The current collecting body comprises a plurality of folding parts configured to be folded away from the electrode assembly from the middle part of the current collecting body when the internal pressure of the secondary battery exceeds a threshold value, a second corner is formed at the second weak part, a third corner is formed at the first weak part, and along the radial direction of the shell, the distance from the second corner to the inner wall of the shell is less than the distance from the third corner to the inner wall of the shell.
12. The secondary battery according to claim 11, characterized by The folding part is welded to the electrode assembly to form a second welding mark, and along the radial direction of the shell, each folding part is at least partially collinear with the connecting sheet.
13. The secondary battery according to any one of claims 6 or 10, characterized by, The distance from one end of the first weak part close to the first welding mark to the first welding mark is e, wherein e >= 0.2 mm.
14. The secondary battery according to any one of claims 10 to 12, characterized by The second weak part comprises one or more combinations of thinning, notching and hollowing.
15. The secondary battery according to any one of claims 1 to 7, characterized by The first weak part comprises one or more combinations of thinning, notching and hollowing.
16. The secondary battery according to claim 1, characterized by Along the radial direction of the shell, the distance from one side of the first welding mark close to the center of the current collecting body to the free end of the connecting sheet is g, and the unfolded size of the connecting sheet is h, wherein g <= h / 3.
17. The secondary battery according to claim 16, characterized by 0.2 mm < g < 1 mm.
18. The secondary battery according to claim 16, characterized by A distance from a point on the roll groove closest to an axis of the case to an outer circumferential surface of the case is i, and a distance from the first weld mark to the outer circumferential surface of the case is j, in a radial direction of the secondary battery, where j≤0.5i.
19. A battery pack, characterized by A secondary battery including any one of claims 1 to 18.
20. An electronic device, comprising: A battery pack including claim 19.