Secondary battery and electronic device

Abstract

A secondary battery and an electronic device. The secondary battery comprises a metal housing, a wound electrode assembly, a first tab, and a first layer. The housing comprises a first wall and a first conductive member provided on the first wall. The first tab comprises a first extension segment, a second extension segment, and a third extension segment. The first extension segment comprises a first end connected to a first electrode sheet. The first extension segment extends from the first end toward a first side in a thickness direction of the electrode assembly and is inclined relative to the thickness direction. The second extension segment comprises a second end connected to the first extension segment. Viewed in a third direction, the second extension segment extends from the second end toward the first side and is inclined relative to the thickness direction. The third extension segment is electrically connected to the first conductive member and comprises a third end connected to the second extension segment. The distance between the third end and the first wall is greater than the distance between the second end and the first wall. The first layer is disposed on a surface of the second extension segment facing the electrode assembly and extends to the first extension segment and the third extension segment. Reliability and service life can be improved.

Description

Secondary batteries and electronic devices Technical Field

[0001] This application relates to the field of energy storage technology, and more particularly to a secondary battery and an electronic device having the secondary battery. Background Technology

[0002] With the increasing popularity of consumer electronics products such as laptops, mobile phones, handheld game consoles, tablets, power banks, and drones, people are becoming more and more demanding in their requirements for rechargeable batteries.

[0003] A secondary battery typically consists of a metal casing, an electrode assembly located within the metal casing, and tabs electrically connecting the electrode assembly to the metal casing. However, during safety tests such as drop tests and roll tests, the tabs are prone to breakage, and the connection points between the tabs and the electrode assembly or metal casing may be subjected to significant impacts, causing the tabs to detach from the electrode assembly or metal casing, thereby reducing the reliability and lifespan of the secondary battery. Summary of the Invention

[0004] In view of the above shortcomings, it is necessary to provide a secondary battery that can improve reliability and service life.

[0005] In addition, it is necessary to provide an electronic device having the aforementioned secondary battery.

[0006] This application provides a secondary battery, including a casing, an electrode assembly, and a first tab. The casing is made of metal and includes a first wall and a first conductive element disposed on the first wall. The electrode assembly and the first tab are disposed within the casing. The electrode assembly has a wound structure and includes a first electrode plate. The thickness direction of the electrode assembly is a first direction, which has a first side and a second side opposite to the first side. The direction from the electrode assembly to the first wall is a second direction, which is perpendicular to the first direction. The first tab includes a first extension, a second extension, and a third extension connected in sequence. The first extension includes a first end connected to the first electrode plate. Viewed along a third direction perpendicular to the first and second directions, the first extension extends from the first end toward the first side and away from the electrode assembly, and the first extension is inclined relative to the first direction. The second extension includes a second end connected to the first extension. Viewed along a third direction, the second extension extends from the second end toward the first side and toward the electrode assembly, and the second extension is inclined relative to the first direction. The third extension includes a third end connected to the second extension. In the second direction, the distance between the second end and the first wall is L2, and the distance between the third end and the first wall is L3, where L3 is greater than L2. The third extension is electrically connected to the first conductive element. The secondary battery also includes a first layer containing an insulating material. The second extension includes a first surface facing the electrode assembly and a second surface facing away from the first surface. The first layer is disposed on the first surface and extends to the first and third extensions.

[0007] In this application, the first extension segment and the second extension segment extend in opposite directions in the second direction. Therefore, the first tab can have a large degree of bending. When the secondary battery undergoes safety tests such as drop tests and roll tests, causing the electrode assembly to shift within the casing and pull on the first tab, the first tab itself can provide a large buffer space to disperse mechanical stress. This reduces the risk of the first tab breaking due to the electrode assembly pulling on it, and also reduces the risk of the first tab detaching from the electrode assembly and the first conductive element, leading to a decrease in the secondary battery's output voltage or even the inability to continue charging and discharging. This improves the reliability and lifespan of the secondary battery. Simultaneously, the large degree of bending of the first tab not only increases its surface area, thereby reducing internal resistance to meet the demands of high-current charging, but also makes the current distribution on the first tab more dispersed and uniform during charging. This further disperses heat at the first tab during high-current charging, reducing the risk of localized overheating and further improving the reliability and lifespan of the secondary battery. Furthermore, the first layer works synergistically with the bent first tab to not only protect it and further reduce the risk of breakage, thus maintaining the stability of the electrical connection between the first tab, the electrode assembly, and the first conductive element, but also to insulate it from heat from the electrode assembly, further reducing the risk of localized overheating of the first tab. The first layer also electrically isolates the first tab from the second electrode of different polarity, reducing the risk of short circuits when the first tab contacts the second electrode, and simultaneously reducing corrosion of the first tab in the electrolyte. Therefore, the synergistic effect between the first layer and the first tab further improves the reliability and lifespan of the secondary battery.

[0008] In some possible implementations, the secondary battery further includes a second layer comprising an insulating material. The second layer is disposed on the second surface and extends to the first and third extensions, and the first and second layers are integrally formed. Therefore, the first tab is protected to further reduce the risk of breakage, thereby maintaining the stability of the electrical connection between the first tab and the electrode assembly and the first conductive element. The integral formation of the first and second layers also further reduces the corrosion of the first tab in the electrolyte.

[0009] In some possible implementations, viewed along a third direction, the third extension includes a first segment and a second segment connected together. The first segment extends from a third end toward a first side and is inclined relative to the first direction. Viewed along a third direction, the second segment includes a connecting end connecting to the first segment. The second segment extends from the connecting end toward a second side and is electrically connected to a first conductive element. Therefore, it facilitates electrical connection between the first conductive element and the third extension, and allows the first electrode tab as a whole to have a greater degree of bending.

[0010] In some possible implementations, in the second direction, the distance between the connecting end and the first wall is L0, where L0 is less than L2. This facilitates electrical connection between the first conductive element and the third extension and improves the connection strength between them.

[0011] In some possible implementations, 0.2mm ≤ L0 ≤ 0.5mm, and 0.5mm ≤ L2 ≤ 0.8mm. This facilitates electrical connection between the first conductive element and the third extension segment and improves the connection strength between them.

[0012] In some possible implementations, viewed along the second direction, at least a portion of the first conductive element is disposed between the second and third ends in the first direction. This facilitates the formation of a first tab with a greater degree of curvature, and also facilitates electrical connection between the first conductive element and the third extension, thereby improving the connection strength between them.

[0013] In some possible implementations, viewed along the second direction, at least a portion of the second segment is located between the second and third ends in the first direction. This facilitates the formation of a first tab with a greater degree of curvature, and also facilitates electrical connection between the first conductive element and the third extension, thereby increasing the connection strength between them.

[0014] In some possible implementations, 1 / 2 ≤ L2 / L3. By limiting the lower limit of the ratio of L2 to L3, the risk of excessive bending of the first electrode tab can be reduced, thereby reducing the risk of material fatigue and fracture caused by increased local stress in the first electrode tab itself, reducing the risk of local overheating of the first electrode tab due to increased internal thermal stress, and reducing the risk of the first electrode tab easily detaching from the first conductive component.

[0015] In some possible implementations, 0.5mm≤L2≤0.8mm and 0.9mm≤L3≤1.5mm. Therefore, the risk of excessive bending of the first electrode tab can be reduced, thereby reducing the risk of material fatigue and fracture caused by increased local stress in the first electrode tab itself, reducing the risk of local overheating caused by increased internal thermal stress in the first electrode tab, and reducing the risk of the first electrode tab easily detaching from the first conductive component.

[0016] In some possible implementations, the secondary battery further includes a first adhesive element that bonds the surface of the first layer away from the first tab. A first extension includes a welding area, through which the first extension is welded to the first electrode. Viewed along a first direction, the first adhesive element covers the welding area. Therefore, the first adhesive element can enhance the protective effect of the first layer on the first tab, further reducing the risk of breakage. The first adhesive element can also cover welding burrs in the welding area, reducing the risk of such burrs piercing the separator and causing a short circuit between the first and second electrodes.

[0017] In some possible implementations, the secondary battery further includes a first structural member comprising an insulating material. The first structural member is located on the side of the second extension facing away from the electrode assembly. Viewed along a second direction, the first structural member covers the second end. The first structural member reduces the risk of a short circuit between the second end and the first wall, and also provides some cushioning for the electrode assembly.

[0018] In some possible implementations, viewed along a third direction, the first extension has a first curved region, and the third extension has a second curved region. The curvature of the first curved region is smaller than that of the second curved region. Because the curvature of the first curved region is smaller, it is more conducive to forming a first tab with a greater degree of curvature, while reducing the risk of a short circuit between the second extension and the second electrode. Because the curvature of the second curved region is larger, it facilitates electrical connection between the first conductive element and the third extension and improves the connection strength between them.

[0019] In some possible implementations, the first extension connects to the outermost first electrode plate. This facilitates further increasing the bending degree of the first electrode tab.

[0020] In some possible implementations, the width of the first tab in the third direction is W1, and the width of the first layer in the third direction is W, where 2mm ≤ W1 ≤ 6mm, and W1 < W ≤ 1.5W1. This allows the first layer to fully cover the surface of the first tab, thereby working in conjunction with the first tab to improve the reliability and lifespan of the secondary battery. Furthermore, it reduces the risk of the first layer being too wide, which could negatively impact heat dissipation and increase costs.

[0021] In some possible implementations, the thickness of the first layer is T, where 100μm ≤ T ≤ 200μm. This allows the first layer to fully cover the surface of the first tab, thereby working in conjunction with the first tab to improve the reliability and lifespan of the secondary battery. Furthermore, it reduces the risk of impaired heat dissipation and increased costs due to an excessively thick first layer.

[0022] In some possible implementations, the insulating material of the first layer is selected from at least one of polypropylene, polyethylene, polyethylene terephthalate, polyethylene naphthalate, polypropylene modified material, or polyethylene modified material, so that the first layer can be well attached to the surface of the first tab.

[0023] In some possible implementations, the housing further includes a second conductive element disposed on the first wall. The electrode assembly further includes a second electrode plate. The secondary battery further includes a second tab, which includes a fourth extension, a fifth extension, and a sixth extension connected in sequence. The fourth extension includes a fourth end connected to the second electrode plate. Viewed along a third direction, the fourth extension extends from the fourth end toward the first side and away from the electrode assembly, and the fourth extension is inclined relative to the first direction. The fifth extension includes a fifth end connected to the fourth extension. Viewed along a third direction, the fifth extension extends from the fifth end toward the first side and toward the electrode assembly, and the fifth extension is inclined relative to the first direction. The sixth extension includes a sixth end connected to the fifth extension. In a second direction, the distance between the fifth end and the first wall is L5, and the distance between the sixth end and the first wall is L6, where L6 is greater than L5, and the sixth extension is electrically connected to the second conductive element. The secondary battery further includes a third layer comprising an insulating material. The fifth extension includes a third surface facing the electrode assembly and a fourth surface away from the third surface, and the third layer is disposed on the third surface and extends to the fourth and sixth extensions.

[0024] In this application, the second tab can have a significant degree of bending. When the secondary battery undergoes safety tests such as drop tests and rollover tests, causing the electrode assembly to shift within the casing and pull on the second tab, this reduces the risk of the second tab breaking due to the electrode assembly pulling on it. It also reduces the risk of the second tab detaching from the electrode assembly and the second conductive element, leading to a decrease in the secondary battery's output voltage or even the inability to continue charging and discharging, thus improving the reliability and lifespan of the secondary battery. Simultaneously, the significant bending of the second tab not only increases its surface area, thereby reducing internal resistance, but also allows for a more dispersed and uniform distribution of current during charging, reducing the risk of localized overheating and further improving the reliability and lifespan of the secondary battery. Furthermore, the third layer can work synergistically with the bent second tab, not only protecting it to further reduce the risk of breakage and maintaining the stability of the electrical connection between the second tab and the electrode assembly and the second conductive element, but also isolating it from heat from the electrode assembly, further reducing the risk of localized overheating. The third layer also reduces the risk of short circuits when the second tab contacts the first electrode and reduces corrosion of the second tab in the electrolyte. Therefore, the synergistic effect between the third layer and the second tab can further improve the reliability and service life of the secondary battery.

[0025] In some possible implementations, the housing also includes a second wall. In a second direction, the second wall is closer to the electrode assembly than the first wall. Therefore, there is space between the first wall and the electrode assembly to accommodate a portion of the first conductive element, a portion of the second conductive element, the first tab, and the second tab. Simultaneously, by reducing the space between the second wall and the electrode assembly, the energy density of the secondary battery is increased.

[0026] A second aspect of this application provides an electronic device including a battery compartment. The electronic device also includes a secondary battery as described above, housed within the battery compartment. The electronic device is powered by the aforementioned secondary battery, and the electronic device exhibits improved reliability and lifespan. Attached Figure Description

[0027] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0028] Figure 1 is a schematic diagram of the structure of a secondary battery provided in one embodiment of this application.

[0029] Figure 2 is a cross-sectional view of the secondary battery shown in Figure 1 along section line II-II.

[0030] Figure 3 is a magnified view of the secondary battery shown in Figure 2 at point A.

[0031] Figure 4 is a top view of the secondary battery shown in Figure 1 after the first wall of the casing has been removed.

[0032] Figure 5 is a cross-sectional view of the secondary battery shown in Figure 1 along the cutting line VV.

[0033] Figure 6 is a magnified view of the secondary battery shown in Figure 5 at point B.

[0034] Figure 7 is a schematic diagram of the structure of an electronic device provided in one embodiment of this application.

[0035] Key Component Symbols Explanation: Electronic Device 1; Housing 10; First Wall 11; Second Wall 12; Side Wall 13; First Conductive Component 14; Second Conductive Component 15; Electrode Assembly 20; First Electrode 21; Second Electrode 22; Separator 23; First Tab 30; First Extension 31; Second Extension 32; First Surface 32A; Second Surface 32B; Third Extension 33; Second Tab 40; Fourth Extension 41; Fifth Extension 42; Third Surface 42A; Fourth Surface 42B; Sixth Extension 43; First Layer 50; Second Layer 51; First Adhesive Component 60; Second Adhesive Component 61; First Structural Component 70; Third Layer 80; Secondary Battery 100; Battery Compartment 101; First Opening 111; Second Opening 112; First Region 201; Second Region 202; First Current Collector 210; First Active Material Layer 211; Second Current Collector 220; Second Active Material Layer 221; First End 310; First Bending Region 311; First Straight Region 312; Welding Area 313; Second End 320; Third End 330; Second Bending Region 331 Second straight area 332 First segment 333 Second segment334 Fourth end 410 Fifth end 420 Sixth end 430 Connecting end 3340 First direction X Second direction Y Third direction Z First side X1 Second side X2 Winding center axis O Winding center surface P Distance L0, L1, L2, L3, L4, L5, L6 Width W1, W Thickness T

[0036] The following detailed description, in conjunction with the accompanying drawings, will further illustrate this application. Detailed Implementation

[0037] The technical solutions in the embodiments of this application are described clearly and in detail below. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the specification of this application is for the purpose of describing particular embodiments only and is not intended to limit this application.

[0038] The embodiments of this application will be described in detail below. However, this application may be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. Rather, these exemplary embodiments are provided to provide a thorough and detailed understanding of this application to those skilled in the art.

[0039] Additionally, for brevity and clarity, the dimensions or thicknesses of various components and layers may be enlarged in the accompanying drawings. Throughout the text, the same numerical values ​​refer to the same elements. As used herein, the terms "and / or" and "and / or" include any and all combinations of one or more of the associated enumerated items. Furthermore, it should be understood that when element A is referred to as "connecting" element B, element A may be directly connected to element B, or there may be an intermediate element C and element A and element B may be indirectly connected to each other.

[0040] Furthermore, when describing the implementation of this application, the word "may" refers to "one or more implementations of this application".

[0041] The technical terms used herein are for the purpose of describing particular embodiments and are not intended to limit this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. It should be further understood that the term "comprising," as used in this specification, means the presence of the described features, values, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, values, steps, operations, elements, components, and / or combinations thereof.

[0042] Spatial terms, such as "above," may be used herein for convenience in describing the relationship between one element or feature and another element (or feature) or feature (or feature) illustrated in the figures. It should be understood that, in addition to the directions depicted in the figures, spatial terms are intended to include different orientations of the device or apparatus during use or operation. For example, if the device in the figure is flipped, an element described as "above" or "on" other elements or features would be oriented "below" or "under" other elements or features. Therefore, the exemplary term "above" can include both above and below orientations. It should be understood that although the terms first, second, third, etc., may be used herein to describe various elements, components, regions, layers, and / or portions, these elements, components, regions, layers, and / or portions should not be limited by these terms. These terms are used to distinguish one element, component, region, layer, or portion from another element, component, region, layer, or portion. Therefore, a first element, component, region, layer, or portion discussed below may be referred to as a second element, component, region, layer, or portion without departing from the teachings of the exemplary embodiments.

[0043] In this application, the design relationships of greater than, less than, or not equal to parameter values ​​need to exclude reasonable errors of the measuring equipment.

[0044] Referring to Figures 1 and 2, one embodiment of this application provides a secondary battery 100, including a housing 10, an electrode assembly 20, an electrolyte (not shown), a first tab 30, and a second tab 40. The housing 10 is made of metal. The housing 10 includes a first wall 11, a second wall 12, a side wall 13, a first conductive element 14, and a second conductive element 15. The first wall 11 and the second wall 12 are disposed opposite to each other, and the side wall 13 is connected to the first wall 11 and the second wall 12 respectively. The first conductive element 14 and the second conductive element 15 are respectively disposed on the first wall 11 and electrically isolated from the first wall 11. The surface of the first wall 11 is substantially parallel to the surface of the second wall 12, and the surface of the side wall 13 is substantially perpendicular to the surface of the first wall 11. The first wall 11, the second wall 12, and the side wall 13 enclose a receiving space, within which the electrode assembly 20, the electrolyte, the first tab 30, and the second tab 40 are all received. In some embodiments, the secondary battery 100 is a prismatic battery. The casing 10 can be made entirely of steel. For example, the steel casing 10 may include the elements Fe and C, and may also include one or more of the elements Ni, Co, Al, Mn, Cr, Cu, Mg, Mo, S, Si, Ti, V, Pb, Sb, N, and P. As shown in Figure 1, the first wall 11 has a first opening 111 and a second opening 112 that are spaced apart. The first conductive element 14 can be installed in the first opening 111 by means of bonding or riveting, and the second conductive element 15 can be installed in the second opening 112 by means of bonding or riveting. The first conductive element 14 and the second conductive element 15 can specifically be electrodes. In some embodiments, the secondary battery 100 can also be a cylindrical battery, in which case the second conductive element 15 can be omitted.

[0045] The electrode assembly 20 has a wound structure, including a first electrode 21, a second electrode 22, and a separator 23 disposed between the first electrode 21 and the second electrode 22. The first electrode 21, the separator 23, and the second electrode 22 are sequentially stacked and wound to form the electrode assembly 20. The separator 23 is used to prevent the first electrode 21 and the second electrode 22 from directly contacting each other, thereby reducing the risk of short circuit between the first electrode 21 and the second electrode 22. There is one first tab 30, which is electrically connected to the first electrode 21 and the first conductive element 14. There is one second tab 40, which is electrically connected to the second electrode 22 and the second conductive element 15. Therefore, the first conductive element 14 and the second conductive element 15 can have opposite polarities, so that the secondary battery 100 can supply power to external components (not shown). For example, when the first electrode 21 is the positive electrode and the second electrode 22 is the negative electrode, the first conductive element 14 is positive and the second conductive element 15 is negative. In other embodiments, when the second conductive element 15 is omitted, the second tab 40 can also be electrically connected to the second electrode 22 and the second wall 12, in which case the entire housing 10 is negatively polarized. In some embodiments, in the second direction Y, the second wall 12 is closer to the electrode assembly 20 than the first wall 11. The first tab 30 and the second tab 40 are both disposed between the first wall 11 and the electrode assembly 20. Therefore, there is space between the first wall 11 and the electrode assembly 20 to accommodate part of the first conductive element 14, part of the second conductive element 15, the first tab 30, and the second tab 40, while reducing the space between the second wall 12 and the electrode assembly 20 increases the energy density of the secondary battery 200.

[0046] A three-dimensional coordinate system is established based on three mutually perpendicular directions: a first direction X, a second direction Y, and a third direction Z. In this application, the first direction X is the thickness direction of the electrode assembly 20, and the first direction X has a first side X1 and a second side X2 opposite to the first side X1. The second direction Y is the direction from the electrode assembly 20 to the first wall 11, and in some embodiments, it is also the direction of the winding center axis O of the electrode assembly 20. The third direction Z is the direction from the first conductive element 14 to the second conductive element 15.

[0047] As shown in Figure 2, the first electrode 21 includes a first current collector 210 and a first active material layer 211 stacked together, and a first tab 30 is electrically connected to the first current collector 210. In some embodiments, the first tab 30 can be connected to the first current collector 210 by welding, thereby improving the connection strength between the first tab 30 and the first current collector 210. The first electrode 21 can be a positive electrode or a negative electrode. Correspondingly, the first current collector 210 can be a positive current collector or a negative current collector, and the first active material layer 211 can be a positive active material layer or a negative active material layer. The second electrode 22 includes a second current collector 220 and a second active material layer 221 stacked together, and a second tab 40 is electrically connected to the second current collector 220. In some embodiments, the second tab 40 can be connected to the second current collector 220 by welding, thereby improving the connection strength between the second tab 40 and the second current collector 220. The second electrode 22 can be a negative electrode or a positive electrode. Correspondingly, the second current collector 220 can be a negative current collector or a positive current collector, and the second active material layer 221 can be a negative active material layer or a positive active material layer. In some embodiments, the first electrode 21 is a positive electrode, and the second electrode 22 is a negative electrode.

[0048] Please refer to Figure 3. The first electrode tab 30 is bent. The first electrode tab 30 includes a first extension 31, a second extension 32, and a third extension 33 connected in sequence. The first extension 31 is connected to the first electrode 21 and includes a first end 310 connected to the first electrode 21. When the first extension 31 is connected to the first electrode 21 by welding, the projection of the first end 310 in the first direction X is located within the projection of the first electrode 21 in the first direction X. Viewed along the third direction Z, the first extension 31 extends from the first end 310 toward the first side X1 and away from the electrode assembly 20, and the first extension 31 is inclined relative to the first direction X. The second extension 32 includes a second end 320 connected to the first extension 31. In the second direction Y, the distance L2 between the second end 320 and the first wall 11 is less than the distance L1 between the first end 310 and the first wall 11. Viewed along the third direction Z, the second extension 32 extends from the second end 320 toward the first side X1 and toward the electrode assembly 20, and the second extension 32 is inclined relative to the first direction X. The third extension 33 includes a third end 330 connecting the second extension 32. In the second direction Y, the distance L3 between the third end 330 and the first wall 11 is greater than the distance L2 between the second end 320 and the first wall 11. The third extension 33 is electrically connected to the first conductive element 14. In some embodiments, the third extension 33 can be connected to the first conductive element 14 by welding. As shown in FIG4, in some embodiments, a plane passing through the winding center axis O and perpendicular to the first direction X is defined as the winding center plane P, which is a virtual plane that passes through the entire electrode assembly 20 along the second direction Y. Viewed along the third direction Z, the electrode assembly 20 includes a first region 201 and a second region 202 located on both sides of the winding center plane P. The direction from the second region 202 to the first region 201 is defined as the first side X1, and the direction from the first region 201 to the second region 202 is defined as the second side X2. A first extension 31 connects to the first electrode 21 located in the second region 202. It is understood that the winding center plane P is only used to divide the structure of the electrode assembly 20 located on both sides of this virtual plane, which does not mean that the electrode assemblies 20 located on both sides of the winding center plane P must be strictly symmetrical with respect to the winding center plane P.

[0049] In this application, the measurement steps for L1, L2, and L3 can be as follows: (1) Using X-rays to perform two-dimensional projection and scanning tests on the secondary battery 100 along the third direction Z, the instrument can be an instrument or device known to those skilled in the art (e.g., GE Phoenix vtomex S device), thereby obtaining a CT image; (2) Marking the first end 310, the second end 320, and the third end 330 on the CT image; (3) Measuring the distance L1 between the first end 310 and the first wall 11, the distance L2 between the second end 320 and the first wall 11, and the distance L3 between the third end 330 and the first wall 11 from the image. It can be understood that on the CT image obtained along the third direction Z, the second end 320 is the first point with a slope of zero relative to the first direction X from the first extension segment 31 to the second extension segment 32, and the second end 320 can be regarded as the boundary position between the first extension segment 31 and the second extension segment 32. The third end 330 is the next point from the second extension segment 32 to the third extension segment 33 with a slope of zero relative to the first direction X, except for the second end 320. The third end 330 can be regarded as the dividing position between the second extension segment 32 and the third extension segment 33.

[0050] As shown in Figure 3, in some embodiments, viewed along the third direction Z, the first extension segment 31 has a first curved region 311, which can connect to the second end 320, but the first curved region 311 can be separated from the electrode assembly 20 in the second direction Y. For example, the first extension segment 31 may also have a first straight region 312 connected to the first curved region 311. The first straight region 312 can extend from the first end 310 to connect with the first curved region 311, and the first extension segment 31 is connected to the first electrode 21 through the first straight region 312, thereby improving the connection strength between the first tab 30 and the first electrode 21. The third extension segment 33 has a second curved region 331, which can extend from the third end 330, but the second curved region 331 can be separated from the first conductive element 14 in the first direction X. For example, the second extension 32 may also have a second straight region 332 connected to the second curved region 331, and the third extension 33 is connected to the first conductive element 14 through the second straight region 332, thereby improving the connection strength between the first tab 30 and the first conductive element 14. The second extension 32 can be a straight section or a curved section.

[0051] The secondary battery 100 also includes a first layer 50 comprising an insulating material. The second extension 32 includes a first surface 32A facing the electrode assembly 20 and a second surface 32B facing away from the first surface 32A. The first layer 50 is disposed on the first surface 32A and extends to the first extension 31 and the third extension 33. In some embodiments, the first layer 50 covers the entire first surface 32A of the second extension 32. The first layer 50 also extends to the first extension 31 to at least cover a first curved region 311 of the first extension 31, and the first layer 50 also extends to the third extension 33 to at least cover a second curved region 331 of the third extension 33. In some embodiments, the insulating material of the first layer 50 is selected from at least one of polypropylene, polyethylene, polyethylene terephthalate, polyethylene naphthalate, a polypropylene-modified material, or a polyethylene-modified material, such that the first layer 50 can be well attached to the surface of the first tab 30.

[0052] In this application, since the second extension segment 32 extends from the second end 320 toward the first side X1, and the distance L3 between the third end 330 and the first wall 11 is greater than the distance L2 between the second end 320 and the first wall 11, the extension directions of the first extension segment 31 and the second extension segment 32 in the second direction Y are opposite. Therefore, the first tab 30 can have a large degree of bending. When the secondary battery 100 undergoes safety tests such as drop tests and roll tests, causing the electrode assembly 20 to move within the casing 10 and pull the first tab 30, the first tab 30 itself can provide a large buffer space to disperse mechanical stress. This reduces the risk of the first tab 30 breaking due to the electrode assembly 20 pulling the first tab 30, and also reduces the risk of the first tab 30 detaching from the electrode assembly 20 and the first conductive element 14, resulting in a decrease in the output voltage of the secondary battery 100 or even the inability to continue charging and discharging. This improves the reliability and service life of the secondary battery 100. Meanwhile, the greater curvature of the first tab 30 not only helps to increase the surface area of ​​the first tab 30 and thus reduce the internal resistance to meet the needs of high-current charging, but also makes the current distribution on the first tab 30 more dispersed and uniform during charging. This makes the heat at the first tab 30 more dispersed during high-current charging, reduces the risk of local overheating of the first tab 30, and further improves the reliability and service life of the secondary battery 100.

[0053] Furthermore, since the first layer 50 is disposed on the first surface 32A and extends to the first extension section 31 and the third extension section 33, the first layer 50 can work synergistically with the bent first tab 30. This not only protects the first tab 30 to further reduce the risk of breakage and maintain the stability of the electrical connection between the first tab 30 and the electrode assembly 20 and the first conductive element 14, but also insulates against heat from the electrode assembly 20, further reducing the risk of localized overheating of the first tab 30. The first layer 50 can also electrically isolate the first tab 30 from the second electrode 22 of different polarity, reducing the risk of short circuits when the first tab 30 contacts the second electrode 22, and simultaneously reducing the corrosion of the first tab 30 in the electrolyte. Therefore, the synergistic effect between the first layer 50 and the first tab 30 can further improve the reliability and service life of the secondary battery 100.

[0054] In some embodiments, the secondary battery 100 further includes a second layer 51 comprising an insulating material. The second layer 51 is disposed on the second surface 32B and extends to the first extension 31 and the third extension 33. In some embodiments, the second layer 51 covers the entire second surface 32B of the second extension 32. The second layer 51 also extends to the first extension 31 to at least cover the first curved region 311 of the first extension 31, and the second layer 51 also extends to the third extension 33 to at least cover the second curved region 331 of the third extension 33. The first layer 50 and the second layer 51 are integrally disposed, for example, the first layer 50 and the second layer 51 are integrally connected to the side of the first electrode 30 to enclose the first electrode 30 therein, thereby further protecting the first electrode 30 to further reduce the risk of breakage, and thus maintaining the stability of the electrical connection between the first electrode 30 and the electrode assembly 20 and the first conductive element 14. Moreover, the integral disposal of the first layer 50 and the second layer 51 can also further reduce the corrosion of the first electrode 30 in the electrolyte. In some embodiments, the insulating material of the second layer 51 is selected from at least one of polypropylene, polyethylene, polyethylene terephthalate, polyethylene naphthalate, modified polypropylene material, or modified polyethylene material, and the insulating material of the first layer 50 is the same as the insulating material of the second layer 51.

[0055] Referring to Figure 4, in some embodiments, the width of the first tab 30 in the third direction Z is W1, and the width of the first layer 50 in the third direction Z is W, where 2mm ≤ W1 ≤ 6mm, and W1 < W ≤ 1.5W1. This allows the first layer 50 to fully cover the surface of the first tab 30, thereby working in conjunction with the first tab 30 to improve the reliability and lifespan of the secondary battery 100. Furthermore, it also reduces the risk of the first layer 50 being too wide, affecting heat dissipation and increasing costs. The width of the second layer 51 can be approximately the same as the width of the first layer 50.

[0056] As shown in Figure 3, in some embodiments, the thickness of the first layer 50 is T, where 100μm ≤ T ≤ 200μm. This allows the first layer 50 to fully cover the surface of the first tab 30, thereby working in conjunction with the first tab 30 to improve the reliability and lifespan of the secondary battery 100. Furthermore, it reduces the risk of excessive heat dissipation and increased costs associated with an overly thick first layer 50. The thickness of the second layer 51 can be approximately the same as that of the first layer 50.

[0057] In some embodiments, the first electrode 21 is wound to form a multi-layer structure, and the first extension 31 can connect to the outermost first electrode 21. Therefore, this facilitates further improvement in the bending degree of the first tab 30. The separator 23 can be the outermost layer of the entire electrode assembly 20. The separator 23 forms a protective layer, preventing short circuits caused by wear on the electrode inside this portion of the separator 23, thereby increasing the electrode assembly 20's resistance to mechanical shock. In other embodiments, the outermost layer of the electrode assembly 20 can also be either the first electrode 21 or the second electrode 22.

[0058] In some embodiments, in the second direction Y, the distance L2 between the second end 320 and the first wall 11 and the distance L3 between the third end 330 and the first wall 11 also satisfy: 1 / 2 ≤ L2 / L3. By limiting the lower limit of the ratio of L2 to L3, the risk of excessive bending of the first electrode tab 30 can be reduced. When the bending of the first electrode tab 30 is excessive, the local stress of the first electrode tab 30 itself increases, which can easily lead to material fatigue and fracture. The internal thermal stress of the first electrode tab 30 also increases, which can easily lead to local overheating of the first electrode tab 30. Secondly, the first electrode tab 30 occupies a large space at the head of the electrode assembly 20, reducing the energy density, and the risk of short circuit between the first electrode tab 30 and the second electrode plate 22 increases. Thirdly, the first electrode tab 30 is prone to detaching from the first conductive element 14. In some embodiments, 1.8mm ≤ L1 ≤ 2.5mm, 0.5mm ≤ L2 ≤ 0.8mm, and 0.9mm ≤ L3 ≤ 1.5mm.

[0059] In some embodiments, the curvature of the first bending region 311 is smaller than that of the second bending region 331. That is, the degree of curvature of the first bending region 311 is greater than that of the second bending region 331. Because the curvature of the first bending region 311 is smaller, it is more conducive to forming a first electrode tab 30 with a larger degree of curvature, while reducing the risk of a short circuit between the second extension segment 32 and the second electrode plate 22. Because the curvature of the second bending region 331 is larger, it facilitates the electrical connection between the first conductive element 14 and the third extension segment 33 and improves the connection strength between them. In this application, the curvature can be measured by calculating the ratio of the arc length to the radius corresponding to the first bending region 311 or the second bending region 331 on the CT image.

[0060] In some embodiments, viewed along a third direction Z, the third extension 33 includes a first segment 333 and a second segment 334 connected together. The first segment 333 extends from a third end 330 toward a first side X1, and is inclined relative to the first direction X. Viewed along a third direction Z, the second segment 334 includes a connecting end 3340 connecting to the first segment 333, and extends from the connecting end 3340 toward a second side X2. A portion of the second curved region 331 is located in the first segment 333, and another portion is located in the second segment 334. A second straight region 332 is located in the second segment 334. The second segment 334 is electrically connected to the first conductive element 14; for example, the second segment 334 can be electrically connected to the first conductive element 14 through the second straight region 332. By providing the third extension 33 including the first segment 333 and the second segment 334, it is convenient for the first conductive element 14 to be electrically connected to the third extension 33, and the first electrode 30 as a whole can have a greater degree of curvature. At this point, when viewed along the third direction Z, the first electrode 30 is roughly set in an "S" shaped bend.

[0061] In some embodiments, in the second direction Y, the distance L0 between the connecting end 3340 and the first wall 11 is less than the distance L2 between the second end 320 and the first wall 11. Therefore, it facilitates the electrical connection between the first conductive element 14 and the third extension 33 and improves the connection strength between them. In some embodiments, 0.2mm ≤ L0 ≤ 0.5mm, 0.5mm ≤ L2 ≤ 0.8mm. In this application, the measurement of L0 can be performed by obtaining a CT image of the secondary battery 100 using the same method, marking the connecting end 3340 on the CT image, and then measuring the distance L0 between the connecting end 3340 and the first wall 11 from the image. It can be understood that on the CT image, the slope direction of any point on the first segment 333 is opposite to the slope direction of any point on the second segment 334, thus the position of the connecting end 3340 (which can be considered as the boundary between the first segment 333 and the second segment 334) can be determined.

[0062] In some embodiments, when viewed from the second direction Y, at least a portion of the first conductive element 14 is disposed between the second end 320 and the third end 330 in the first direction X. This facilitates the formation of an "S"-shaped bent first tab 30, and also facilitates electrical connection between the first conductive element 14 and the third extension 33, thereby improving the connection strength between them.

[0063] In some embodiments, when viewed from the second direction Y, at least a portion of the second segment 334 is disposed between the second end 320 and the third end 330 in the first direction X. More specifically, in some embodiments, a second straight region 332 of the second segment 334 is disposed between the second end 320 and the third end 330 in the first direction X. This also facilitates the formation of the first tab 30 with an "S"-shaped bend, and also facilitates the electrical connection between the first conductive element 14 and the third extension 33 and improves the connection strength between them.

[0064] In some embodiments, the secondary battery 100 may further include a first adhesive 60, which bonds the surface of the first layer 50 away from the first tab 30. A first extension 31 includes a welding region 313, through which the first extension 31 is welded to the first electrode 21. The welding region 313 may be located between a first straight region 312 of the first extension 31 and a first current collector 210. Viewed from the first direction X, the first adhesive 60 covers the welding region 313. Therefore, the first adhesive 60 can enhance the protective effect of the first layer 50 on the first tab 30, further reducing the risk of breakage. The first adhesive 60 can also reduce the risk of the first layer 50 detaching from the first tab 30. The first adhesive 60 can also cover welding burrs in the welding region 313, reducing the risk of these burrs piercing the separator 23 and causing a short circuit between the first electrode 21 and the second electrode 22. The secondary battery 100 may further include a second adhesive member 61, which bonds the second layer 51 to the surface facing away from the first tab 30. Viewed from the first direction X, the second adhesive member 61 covers the welding area 313. Therefore, the second adhesive member 61 can enhance the protective effect of the second layer 51 on the first tab 30, further reducing the risk of breakage. The second adhesive member 61 can also reduce the risk of the second layer 51 detaching from the first tab 30. The second adhesive member 61 can also cover welding burrs in the welding area 313, reducing the risk of such burrs piercing the housing 10 and causing damage or leakage to the housing 10. The first adhesive member 60 and the second adhesive member 61 may be insulating tape.

[0065] The secondary battery 100 may further include a first structural member 70, which comprises an insulating material. The first structural member 70 is located on the side of the second extension 32 facing away from the electrode assembly 20. Viewed from the second direction Y, the first structural member 70 covers the second end 320, which is relatively close to the first wall 11. When the second tab 40 is electrically connected to the second electrode 22 and the second wall 12, making the entire housing 10 negatively polarized, the second structural member can reduce the risk of a short circuit between the second end 320 and the first wall 11. Moreover, during safety tests such as drop tests and roll tests, the first structural member 70 can provide a certain buffering effect on the electrode assembly 20. The first structural member 70 may be a plate-shaped element, and the insulating material of the first structural member 70 may be selected from at least one of polypropylene, polyethylene terephthalate, polystyrene, polyimide, nylon, or Teflon.

[0066] As shown in Figures 5 and 6, in some embodiments, the second electrode tab 40 is also bent. The second electrode tab 40 includes a fourth extension 41, a fifth extension 42, and a sixth extension 43 connected in sequence. The fourth extension 41 includes a fourth end 410 connected to the second electrode 22. When the fourth extension 41 is connected to the second electrode 22 by welding, when viewed along the first direction X, the projection of the fourth end 410 in the first direction X is located within the projection of the second electrode 22 in the first direction X. When viewed along the third direction Z, the fourth extension 41 extends from the fourth end 410 toward the first side X1 and away from the electrode assembly 20, and the fourth extension 41 is inclined relative to the first direction X. The fifth extension 42 includes a fifth end 420 connected to the fourth extension 41. In the second direction Y, the distance L5 between the fifth end 420 and the first wall 11 is less than the distance L4 between the fourth end 410 and the first wall 11. Viewed along the third direction Z, the fifth extension 42 extends from the fifth end 420 toward the first side X1 and toward the electrode assembly 20, and the fifth extension 42 is inclined relative to the first direction X. The sixth extension 43 includes a sixth end 430 connecting to the fifth extension 42. In the second direction Y, the distance L6 between the sixth end 430 and the first wall 11 is greater than the distance L5 between the fifth end 420 and the first wall 11, and the sixth extension 43 is electrically connected to the second conductive element 15. In some embodiments, the sixth extension 43 can be connected to the second conductive element 15 by welding.

[0067] The secondary battery 100 also includes a third layer 80, which comprises an insulating material. The fifth extension 42 includes a third surface 42A facing the electrode assembly 20 and a fourth surface 42B facing away from the third surface 42A. The third layer 80 is disposed on the third surface 42A and extends to the fourth extension 41 and the sixth extension 43. In some embodiments, the insulating material of the third layer 80 is selected from at least one of polypropylene, polyethylene, polyethylene terephthalate, polyethylene naphthalate, modified polypropylene, or modified polyethylene, such that the third layer 80 can be well attached to the surface of the second tab 40.

[0068] In this application, the second tab 40 can have a large degree of bending. When the secondary battery 100 undergoes safety tests such as drop tests and rollover tests, causing the electrode assembly 20 to move within the casing 10 and pull on the second tab 40, this reduces the risk of the second tab 40 breaking due to the electrode assembly 20 pulling on the second tab 40. It also reduces the risk of the second tab 40 detaching from the electrode assembly 20 and the second conductive element 15, resulting in a decrease in the output voltage of the secondary battery 100 or even the inability to continue charging and discharging, thereby improving the reliability and service life of the secondary battery 100. At the same time, the large degree of bending of the second tab 40 not only helps to increase the surface area of ​​the second tab 40 and thus reduce the internal resistance, but also makes the current distribution on the second tab 40 more dispersed and uniform during charging, reducing the risk of local overheating of the second tab 40, further improving the reliability and service life of the secondary battery 100.

[0069] Furthermore, since the third layer 80 is disposed on the third surface 42A and extends to the fourth extension 41 and the sixth extension 43, the third layer 80 can work synergistically with the bent second tab 40. This not only protects the second tab 40 to further reduce the risk of breakage and maintain the stability of the electrical connection between the second tab 40 and the electrode assembly 20 and the second conductive element 15, but also insulates against heat from the electrode assembly 20, further reducing the risk of localized overheating of the second tab 40. The third layer 80 can also reduce the risk of short circuits when the second tab 40 contacts the first electrode 21, and simultaneously reduce the corrosion of the second tab 40 in the electrolyte. Therefore, the synergistic effect between the third layer 80 and the second tab 40 can further improve the reliability and service life of the secondary battery 100.

[0070] In some embodiments, viewed along a third direction Z, the sixth extension 43 has a structure similar to the third extension 33, such that the second tab 40 is generally bent in an "S" shape. The secondary battery 100 may also include a fourth layer 81, which contains an insulating material. The fourth layer 81 is disposed on the fourth surface 42B and extends to the first extension 31 and the third extension 33. The third layer 80 is integrally disposed with the fourth layer 81 to enclose the second tab 40 therein.

[0071] The secondary battery 100 of this application can be a lithium secondary battery, including lithium metal secondary batteries, lithium-ion secondary batteries, lithium polymer secondary batteries and lithium-ion polymer secondary batteries.

[0072] Referring to Figure 7, one embodiment of this application also provides an electronic device 1, including a battery compartment 101 and a secondary battery 100 disposed within the battery compartment 101. The electronic device 1 is powered by the aforementioned secondary battery 100, and the electronic device 1 has improved reliability and lifespan. In one embodiment, the electronic device 1 of this application may be, but is not limited to, a laptop computer, a pen input computer, a mobile computer, an e-book player, a portable telephone, a portable fax machine, a portable copier, a portable printer, a stereo headset, a video recorder, an LCD TV, a portable cleaner, a portable CD player, a mini CD-ROM, a transceiver, an electronic notebook, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, a car, a motorcycle, an electric bicycle, a bicycle, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, household large-capacity batteries, and lithium-ion capacitors, etc.

[0073] The present application will be described in detail below through specific embodiments and comparative examples. Specifically, a lithium-ion secondary battery, a first electrode as a positive electrode, and a second electrode as a negative electrode are used as examples to illustrate the present application, along with specific preparation processes and testing methods. Those skilled in the art should understand that the preparation methods described in this application are merely examples, and any other suitable preparation methods are within the scope of this application.

[0074] Examples 1-5

[0075] Preparation of the first electrode: Lithium cobalt oxide (LiCoO2), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 96.5:1.5:2. N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 75 wt%, and the mixture was stirred evenly. Foaming adhesive was pre-applied to a portion of the aluminum foil (8 μm thick) as the positive electrode current collector. The slurry was then uniformly coated onto one surface of the aluminum foil. Heating was performed to remove the foaming adhesive, exposing a portion of the aluminum foil surface. The foil was then dried at 90°C. The coating process was repeated on the other surface of the aluminum foil to obtain a double-coated positive electrode. The initial positive electrode was cold-pressed to obtain a single layer of positive active material with a coating thickness of 77 μm. This layer was then cut to obtain the final positive electrode. Finally, a first tab, made of aluminum, was welded onto the exposed aluminum foil.

[0076] Preparation of the second electrode: Artificial graphite (anode active material), silicon carbide, conductive carbon black (Super P), polyacrylic acid binder (PAA), and lithium difluorophosphate (LDPF) were mixed in a weight ratio of 69:5:6:19:1. Deionized water was added as a solvent to prepare a slurry with a weight percentage of 55 wt%, and the mixture was stirred evenly. Foaming adhesive was pre-applied to a portion of the copper foil (anode current collector) with a thickness of 5 μm. The slurry was then uniformly coated onto one surface of the copper foil. Heating was performed to remove the foaming adhesive, exposing the copper foil surface. The foil was then dried at 90°C. The coating process was repeated on the other surface of the copper foil to obtain a double-coated negative electrode. The initial negative electrode was then rolled to obtain a 70 μm thick layer of negative active material. Finally, a second tab, made of copper, was welded onto the exposed copper foil.

[0077] Preparation of electrolyte: In a dry argon atmosphere, the organic solvents ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were first mixed in a mass ratio of EC:EMC:DEC = 30:50:20. Then, lithium salt lithium hexafluorophosphate (LiPF6) was added to the organic solvent to dissolve and mix evenly to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.

[0078] Preparation of the isolation membrane: A polyethylene (PE) membrane with a thickness of 9 μm was selected.

[0079] Fabrication of the secondary battery: The first electrode, separator, and second electrode are sequentially stacked and wound to obtain an electrode assembly. This assembly is then placed inside a stainless steel casing. The first extension of the first tab is connected to the outermost first electrode. As shown in Figures 2 and 3, a first layer of polypropylene (PP) is applied to the surface of the first tab. The first tab is bent into an "S" shape and then welded to the first conductive element. The structural and positional relationship between the first tab and the first layer is not detailed here. The second tab is bent and welded to the second conductive element. Finally, electrolyte is injected and the battery is encapsulated to obtain the secondary battery. The distances L0, L1, L2, and L3 are measured using CT images and recorded in Table 1.

[0080] Example 6

[0081] The difference from Example 1 is that a second layer made of polypropylene (PP) is provided on the surface of the first electrode tab away from the first layer, and the first layer and the second layer are integrally formed.

[0082] Comparative Examples 1-2

[0083] The difference from Example 1 lies in the relationship between L2 and L3.

[0084] Comparative Example 3

[0085] The difference from Embodiment 1 is that the first electrode tab only includes two connected segments. The first segment of the first electrode tab is connected to the first electrode plate (the extension direction is the same as in Embodiment 1), and the second segment of the first electrode tab is bent relative to the first segment and then directly welded to the first conductive element.

[0086] Comparative Example 4

[0087] The difference from Example 1 is that the first layer is omitted.

[0088] Then, drop tests and temperature rise tests were conducted on the secondary batteries of each embodiment and comparative example. Ten secondary batteries from each embodiment and comparative example were tested, and the corresponding test results are recorded in Table 1.

[0089] The drop test steps are as follows: 1) Under an environment of 25±5℃, charge the secondary battery to 100% SOC; 2) Place the secondary battery in the clamping chamber and use an automatic drop device to drop the bottom, side, and top surfaces of the secondary battery sequentially from a position of 1.8m onto the steel plate, for a total of 6 rounds, or 18 drops; 3) After the drop test is completed, disassemble the secondary battery and observe whether the first tab is broken and whether the first tab has detached from the electrode assembly or the first conductive component. If the first tab is not broken and has not detached from the electrode assembly and the first conductive component, the secondary battery passes the drop test.

[0090] The temperature rise test steps are as follows: 1) Under an ambient temperature of 25±5℃, charge the secondary battery at a constant current of 2.0C to 4.25V, and then at a constant voltage of 1.5C; 2) Let it stand for 5 minutes; 3) Charge it at a constant current of 1.5C to 4.38V, and then at a constant voltage of 1.0C; 4) Let it stand for 5 minutes; 5) Charge it at a constant current of 1.0C to 4.43V, and then at a constant voltage of 0.05C; 6) Let it stand for 5 minutes; 7) Discharge it at a constant current of 0.2C to 3.0V. Before charging, use a multi-channel temperature measuring instrument to measure the temperature near the first tab as t1. After charging, disassemble the secondary battery and use a multi-channel temperature measuring instrument to measure the temperature near the first tab as t2. The temperature rise Δt = t2 - t1. If the temperature rise Δt is less than 30℃, the secondary battery is considered to have passed the temperature rise test. The test results are recorded in Table 1.

[0091] Table 1

[0092] In Table 1, the drop test pass rate is n / 10, indicating that out of the 10 tested secondary batteries, n batteries passed the test. The meanings of other percentage values ​​are deduced similarly.

[0093] As can be seen from the data in Table 1, compared with Comparative Examples 1-4, in Example 1, the first tab is bent into an "S" shape and combined with the setting of the first layer, so that the risk of breakage of the first tab of the secondary battery in Example 1 after the drop test is reduced, and the risk of the first tab detaching from the electrode assembly and the first conductive member is also reduced. Moreover, the risk of local overheating of the secondary battery in Example 1 during high-current charging is reduced. Therefore, the passing rates of the drop test and the temperature rise test of Example 1 are relatively high.

[0094] Compared with Example 3, Examples 1-2 satisfy 1 / 2≤L2 / L3. Therefore, the risk of excessive bending of the first tab can be reduced. Combined with the setting of the first layer, the passing rates of the drop test and the temperature rise test of Examples 1-2 are relatively high.

[0095] Compared with Examples 4-5, Example 1 satisfies L0<L2, which is convenient for the first conductive member to be electrically connected to the third extension section of the first tab and improves the connection strength therebetween. Therefore, the passing rate of the drop test of Example 1 is relatively high.

[0096] Compared with Example 1, a second layer is further provided in Example 6. Therefore, the passing rate of the drop test of Example 6 is further improved.

[0097] The above-disclosed content is only the preferred embodiment of the present application. Of course, the present application cannot be limited thereby. Therefore, equivalent changes made according to the present application still fall within the scope covered by the present application.

Claims

1. A secondary battery, comprising a casing, an electrode assembly, and a first electrode tab, wherein the casing is made of metal, the casing includes a first wall and a first conductive element disposed on the first wall, and the electrode assembly and the first electrode tab are disposed within the casing, wherein... The electrode assembly is a wound structure and includes a first electrode sheet. The thickness direction of the electrode assembly is a first direction, which has a first side and a second side opposite to the first side. The direction from the electrode assembly to the first wall is a second direction, which is perpendicular to the first direction. The first electrode tab includes a first extension segment, a second extension segment, and a third extension segment connected in sequence. The first extension segment includes a first end connected to the first electrode plate. When viewed along a third direction perpendicular to the first direction and the second direction, the first extension segment extends from the first end toward the first side and away from the electrode assembly, and the first extension segment is inclined relative to the first direction. The second extension segment includes a second end connected to the first extension segment. When viewed along the third direction, the second extension segment extends from the second end toward the first side and toward the electrode assembly, and the second extension segment is inclined relative to the first direction. The third extension segment includes a third end connected to the second extension segment. In the second direction, the distance between the second end and the first wall is L2, and the distance between the third end and the first wall is L3, where L3 is greater than L2. The third extension segment is electrically connected to the first conductive element. The secondary battery further includes a first layer comprising an insulating material, and a second extension comprising a first surface facing the electrode assembly and a second surface facing away from the first surface, the first layer being disposed on the first surface and extending to the first extension and the third extension.

2. The secondary battery as described in claim 1, wherein, The secondary battery also includes: The second layer comprises an insulating material, is disposed on the second surface and extends to the first extension and the third extension, and the first layer and the second layer are integrally disposed.

3. The secondary battery as described in claim 1 or 2, wherein, Viewed along the third direction, the third extension segment includes a first segment and a second segment connected together. The first segment extends from the third end toward the first side and is inclined relative to the first direction. Viewed along the third direction, the second segment includes a connecting end connected to the first segment. The second segment extends from the connecting end toward the second side and is electrically connected to the first conductive element.

4. The secondary battery as described in claim 3, wherein, In the second direction, the distance between the connecting end and the first wall is L0, where L0 is less than L2.

5. The secondary battery as described in claim 3 or 4, wherein, Viewed along the second direction, at least a portion of the first conductive element is disposed between the second end and the third end in the first direction.

6. The secondary battery as described in any one of claims 3 to 5, wherein, Viewed along the second direction, at least a portion of the second segment is located between the second end and the third end in the first direction.

7. The secondary battery according to any one of claims 1 to 6, wherein, 1 / 2 ≤ L2 / L3.

8. The secondary battery according to any one of claims 1 to 7, wherein, The secondary battery satisfies at least one of the following conditions: (1)0.5mm≤L2≤0.8mm, 0.9mm≤L3≤1.5mm; (2) In the second direction, the distance between the connecting end and the first wall is L0, 0.2mm≤L0≤0.5mm, 0.5mm≤L2≤0.8mm.

9. The secondary battery according to any one of claims 1 to 8, wherein, The secondary battery also includes: A first adhesive is bonded to the surface of the first layer opposite to the first tab. The first extension includes a welding area, and the first extension is welded to the first electrode through the welding area. When viewed along the first direction, the first adhesive covers the welding area.

10. The secondary battery according to any one of claims 1 to 9, wherein, The secondary battery also includes: A first structural member, comprising an insulating material, is disposed on the side of the second extension away from the electrode assembly, and when viewed along the second direction, the first structural member covers the second end.

11. The secondary battery according to any one of claims 1 to 10, wherein, Viewed along the third direction, the first extension has a first curved region, and the third extension has a second curved region, wherein the curvature of the first curved region is smaller than that of the second curved region.

12. The secondary battery according to any one of claims 1 to 11, wherein, The first extension is connected to the outermost first electrode.

13. The secondary battery according to any one of claims 1 to 12, wherein, The width of the first tab in the third direction is W1, and the width of the first layer in the third direction is W, where 2mm≤W1≤6mm and W1<W≤1.5W1.

14. The secondary battery according to any one of claims 1 to 13, wherein, The thickness of the first layer is T, where 100μm≤T≤200μm.

15. The secondary battery according to any one of claims 1 to 14, wherein, The insulating material of the first layer is selected from at least one of polypropylene, polyethylene, polyethylene terephthalate, polyethylene naphthalate, modified polypropylene material, or modified polyethylene material.

16. The secondary battery according to any one of claims 1 to 15, wherein, The housing also includes a second conductive element disposed on the first wall; The electrode assembly further includes a second electrode plate, and the secondary battery further includes a second tab. The second tab includes a fourth extension section, a fifth extension section, and a sixth extension section connected in sequence. The fourth extension section includes a fourth end connected to the second electrode plate. Viewed along the third direction, the fourth extension section extends from the fourth end and away from the electrode assembly toward the first side, and the fourth extension section is inclined relative to the first direction. The fifth extension section includes a fifth end connected to the fourth extension section. Viewed along the third direction, the fifth extension section extends from the fifth end toward the first side and toward the electrode assembly, and the fifth extension section is inclined relative to the first direction. The sixth extension section includes a sixth end connected to the fifth extension section. In the second direction, the distance between the fifth end and the first wall is L5, and the distance between the sixth end and the first wall is L6, where L6 is greater than L5. The sixth extension section is electrically connected to the second conductive element. The secondary battery further includes a third layer comprising an insulating material, and the fifth extension includes a third surface facing the electrode assembly and a fourth surface facing away from the third surface, the third layer being disposed on the third surface and extending to the fourth extension and the sixth extension.

17. The secondary battery according to any one of claims 1 to 16, wherein, The housing also includes a second wall, which is closer to the electrode assembly than the first wall in the second direction.

18. An electronic device comprising a battery compartment, wherein, The electronic device further includes a secondary battery as claimed in any one of claims 1 to 17, the secondary battery being housed in the battery compartment.

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