Secondary battery, electrical device and manufacturing method for secondary battery

Abstract

Disclosed in the present application are a secondary battery, an electrical device and a manufacturing method for the secondary battery. The secondary battery comprises an electrode assembly, a first tab bundle and a first adapter tab. The first tab bundle comprises a plurality of first tabs, each of the first tabs is electrically connected to the electrode assembly. The first tab bundle comprises a first portion, a bent portion and a second portion which are successively connected, the first portion being connected to the electrode assembly, and the bent portion connecting the first portion and the second portion. The first adapter tab comprises a first connection portion and a second connection portion; the first connection portion comprises a first surface and a second surface, the first surface facing the electrode assembly, and the first surface being connected to the second portion; the second connection portion is connected to the first connection portion, and the second connection portion and the second surface are located on the same side of the first connection portion. In the secondary battery, the first adapter tab can be as close to the bent portion of the first tab bundle as possible in the thickness direction of the electrode assembly, which is beneficial to reducing the space occupied by the first tab bundle and the first adapter tab in the thickness direction of the electrode assembly.

Description

Secondary batteries, electrical equipment, and methods for preparing secondary batteries Technical Field

[0001] This application relates to the field of energy storage technology, and in particular to a secondary battery, an electrical device, and a method for preparing the secondary battery. Background Technology

[0002] Currently, multi-tab secondary batteries typically bundle multiple tabs together along the thickness direction of the secondary battery to form a tab bundle. Then, an adapter tab is connected to the tab bundle, and the tab bundle and the adapter tab are bent so that a part of the adapter tab extends out of the casing approximately perpendicular to the thickness direction of the secondary battery. In this state, the adapter tab is roughly L-shaped. Summary of the Invention

[0003] The inventors of this application discovered that when the aforementioned secondary battery is dropped, the electrode assembly moves relative to the casing. During this movement, the electrode assembly repeatedly pulls on the adapter tab, causing the adapter tab to be repeatedly bent, which makes it prone to breakage.

[0004] In view of the above situation, it is necessary to provide a secondary battery that can help reduce the possibility of breakage of the adapter tab of the secondary battery.

[0005] A first aspect of this application provides a secondary battery, which includes an electrode assembly, a first tab bundle, and a first adapter tab. The first tab bundle includes a plurality of first tabs, each electrically connected to the electrode assembly; the plurality of first tabs are stacked to form the first tab bundle. The first tab bundle is U-shaped and includes a first portion, a bent portion, and a second portion connected in sequence. The first portion is connected to the electrode assembly, and the bent portion connects the first portion and the second portion. The first adapter tab includes a first connecting portion and a second connecting portion. The first connecting portion includes a first surface and a second surface disposed opposite to each other along its thickness direction. The first surface faces the electrode assembly and is connected to the second portion. The second connecting portion is connected to the first connecting portion, and the second connecting portion and the second surface are located on the same side of the first connecting portion. Along the extending direction of the first connecting portion, the first connecting portion has a first end portion and a second end portion disposed opposite to each other, and the second connecting portion is located between the first end portion and the second end portion. The length of the first connecting portion is L, the distance from the second connecting portion to the first end portion is L1, the distance from the second connecting portion to the second end portion is L2, L1 ≥ 0.2L, and L2 ≥ 0.2L.

[0006] In this secondary battery, there is a distance between the second connecting portion and both the first and second ends of the first connecting portion. When the secondary battery is dropped, the electrode assembly moves relative to the casing, causing the first adapter tab to bend repeatedly. The distance between the two ends of the second connecting portion and the first connecting portion helps to reduce the bending amplitude of the first adapter tab, thereby reducing the possibility of breakage. Setting L1≥0.2L and L2≥0.2L ensures an appropriate distance between the two ends of the second connecting portion and the first connecting portion, further reducing the bending amplitude of the first adapter tab and thus the possibility of breakage.

[0007] In one or more embodiments of this application, L1 ≥ 0.4L and L2 ≥ 0.4L. This helps to further reduce the distance between the centerline of the second connecting portion and the first connecting portion, further reduce the bending amplitude of the first adapter tab, and thus further reduce the possibility of the first adapter tab breaking.

[0008] In one or more embodiments of this application, the first portion contacts the second portion. This helps to reduce the space occupied by the first electrode bundle on the head of the secondary battery, thereby reducing the volume of the secondary battery and increasing its energy density.

[0009] In one or more embodiments of this application, the first connecting portion and the second connecting portion are integrally formed. This simplifies the structure of the first and second connecting portions and facilitates manufacturing.

[0010] In one or more embodiments of this application, the first adapter tab includes a first connector and a second connector. The first connector includes a third portion and a fourth portion. The third portion is connected to the end of the fourth portion, and the third portion and the fourth portion are arranged at an angle. The third portion is connected to the second connector, and the third portion and the second connector extend in opposite directions. The third portion and the second connector together form a first connecting portion, and the fourth portion forms the second connecting portion.

[0011] In one or more embodiments of this application, the first adapter tab includes a first connector and a second connector. The first connector includes a third portion and a fourth portion, with the third portion connected to the end of the fourth portion and the third portion and the fourth portion arranged at an angle. The second connector includes a fifth portion and a sixth portion, with the fifth portion connected to the end of the sixth portion and the fifth portion and the sixth portion arranged at an angle. The fourth portion connects to the fifth portion, and the third portion and the sixth portion extend in opposite directions, with the fourth portion and the fifth portion located on the same side of the third portion and the sixth portion. The third portion and the sixth portion together form a first connecting portion, and the fourth portion and the fifth portion together form a second connecting portion.

[0012] In one or more embodiments of this application, the length of the welded portion between the fourth and fifth portions along the extending direction of the fourth portion is at least 1 mm. This is beneficial for improving the connection stability between the fourth and fifth portions.

[0013] In one or more embodiments of this application, the first connecting portion is welded to the second portion to form a first solder mark. Along the length of the second portion, the width of the first solder mark is W, where 0.8mm ≤ W ≤ 1.2mm. Setting W ≥ 0.8mm prevents the width of the first solder mark from being too small, which is beneficial for improving the stability of the welding between the first connecting portion and the second portion. Setting W ≤ 1.2mm prevents the width of the solder mark between the first connecting portion and the second portion from being too large, which is beneficial for reducing the size of the first electrode bundle in the thickness direction of the electrode assembly. Furthermore, the unwelded portion of the second portion is not too small, which is beneficial for dispersing stress and reducing the possibility of breakage of the first electrode bundle.

[0014] In one or more embodiments of this application, the first connecting portion has a first region and a second region. Along the extending direction of the first connecting portion, the first region and the second region are located on opposite sides of the second connecting portion. The second region is closer to the bending portion than the first region. The first region is welded to the second portion to form a first weld mark, while the second region is not connected to the second portion. In this way, mutual movement can occur between the first adapter tab and the first tab bundle, thereby facilitating stress release and reducing the possibility of damage to the connection structure of the first adapter tab and the first tab bundle.

[0015] In one or more embodiments of this application, the first connecting portion has a first region and a second region. Along the extending direction of the first connecting portion, the first region and the second region are located on opposite sides of the second connecting portion. The second region is closer to the bending portion than the first region. The first region is welded to the second portion to form a first weld mark, while the second region is not connected to the second portion. In this way, the first connecting portion can move relative to the second portion, which helps to release stress and reduces the possibility of breakage of the first electrode bundle and the first adapter electrode.

[0016] In one or more embodiments of this application, the distance from the first solder mark to the first end along the extending direction of the first connecting portion is L3, and the length of the first connecting portion is L, where L3 ≥ 0.2L. Thus, an appropriate distance exists between the first solder mark and the bent portion of the first electrode bundle, allowing the first electrode bundle and the first adapter to release some stress through opening and closing deformation, thereby helping to reduce the possibility of breakage of the first electrode bundle and the first adapter electrode.

[0017] In one or more embodiments of this application, the shell is a flexible packaging bag.

[0018] In one or more embodiments of this application, the first connection portion is welded to the second portion, forming a first solder mark. The secondary battery also includes a first adhesive member that covers the first solder mark and is bonded to the surface of the second portion facing the first portion. This helps to reduce the possibility of burrs formed during the welding process puncturing the separator and causing a short circuit.

[0019] In one or more embodiments of this application, the first tab bundle is located on one side of the electrode assembly along a first direction, which is perpendicular to the thickness direction of the electrode assembly. Along the first direction, the projections of the first tab bundle and the first adapter tab are located within the projection range of the electrode assembly. This helps to reduce the impact of the first tab bundle and the first adapter tab on the thickness of the secondary battery.

[0020] A second aspect of the embodiments of this application provides an electrical device that includes a secondary battery as described in any of the foregoing embodiments.

[0021] A third party to an embodiment of this application provides a method for preparing a secondary battery, the method comprising the following steps:

[0022] Take an electrode assembly, which is connected to a first electrode ear bundle;

[0023] Take a first adapter tab and connect the first connecting part and the second part; the first connecting part has a first region and a second region. Along the extending direction of the first connecting part, the first region and the second region are located on opposite sides of the second connecting part. The second region is closer to the bend than the first region. At least one of the first region and the second region is connected to the second part.

[0024] In one or more embodiments of this application, the method for manufacturing the secondary battery includes the following steps: cutting a first region and a second portion, thereby shortening the length of the second portion and the first connecting portion along the extending direction of the first connecting portion. Cutting the first region and the second portion helps to reduce the space occupied by the first electrode bundle and the first connecting portion, thereby increasing the energy density of the secondary battery.

[0025] In one or more embodiments of this application, the method for preparing the secondary battery includes the following steps:

[0026] The first adapter tab includes a first extension, a second extension, and a connecting portion. The first extension is integrally connected to the connecting portion, and the second extension is integrally connected to the connecting portion. The first extension and the second extension are separated so that the first extension and the second extension extend in opposite directions. The first extension and the second extension form the first connecting portion, and the connecting portion forms the second connecting portion. Attached Figure Description

[0027] Figure 1 is a schematic diagram of the overall structure of the secondary battery in one embodiment of this application.

[0028] Figure 2 is a schematic diagram of the cross-sectional structure of II-II in Figure 1.

[0029] Figure 3 is an enlarged view of point A in Figure 2.

[0030] Figure 4 is a cross-sectional structural diagram of a secondary battery in one embodiment of this application.

[0031] Figure 5 is a cross-sectional structural diagram of a secondary battery in one embodiment of this application.

[0032] Figure 6 is a cross-sectional structural diagram of a secondary battery in one embodiment of this application.

[0033] Figure 7 is a cross-sectional structural diagram of a secondary battery in one embodiment of this application.

[0034] Figure 8 is an enlarged view of point B in Figure 7.

[0035] Figure 9 is a schematic diagram of the cross-sectional structure at point III-III in Figure 1.

[0036] Figure 10 is a schematic diagram of the structure of the first adapter tab in one embodiment of this application.

[0037] Figure 11 is a schematic diagram of the structure of an electrical device in one embodiment of this application.

[0038] Key Component Symbols: Secondary Battery 100; Casing 10; Electrode Assembly 20; Positive Electrode 21; Positive Current Collector 211; Positive Active Material Layer 212; Negative Electrode 22; Negative Current Collector 221; Negative Active Material Layer 222; Separator 23; First Tab Bundle 30; First Tab 31; Third End 311; First Part 32; Bending Part 33; First Reference Point 33a; Second Part 34; First Solder Mark 34a; First Adapter Tab 40; First Connecting Part 41; First Surface 41a; Second Surface 41b; First End 411; Second End 412; First Region 413; Second Region414 Second connecting part; 42 First connecting member; 43 Third part; 431 Fourth part; 432 Second connecting member; 44 Fifth part; 441 Sixth part; 442 First extension; 401 Second extension; 402 Joint; 403 First adhesive member; 50 Second electrode bundle; 60 Second electrode; 61 Second adapter electrode; 70 Electrical equipment; 1000 First direction X

[0039] The following detailed description, in conjunction with the accompanying drawings, will further illustrate this application. Detailed Implementation

[0040] The technical solutions of the embodiments of this application will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0041] It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or may also have a component that is centrally located. When a component is considered to be "set" on another component, it can be directly set on the other component or may also have a component that is centrally located.

[0042] 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 herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0043] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0044] In the description of the embodiments of this application, the term "perpendicular" is used to describe the ideal state between two components. In actual production or use, two components may exist in a state that is approximately perpendicular. The two components described as "perpendicular" may not be absolutely straight lines or planes, but may be approximately straight lines or planes. From a macroscopic perspective, if the overall extension direction is a straight line or plane, the component can be considered as a "straight line" or "plane".

[0045] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. Where there is no conflict, the various embodiments in this application can be combined with each other.

[0046] It should be noted that the thickness, length, width, and other dimensions of various components in the embodiments of this application shown in the accompanying drawings, as well as the overall thickness, length, width, and other dimensions of the integrated device, are merely illustrative examples and should not constitute any limitation on this application.

[0047] Embodiments of this application provide a secondary battery, which includes an electrode assembly, a first tab bundle, and a first adapter tab. The first tab bundle includes a plurality of first tabs, each electrically connected to the electrode assembly; the plurality of first tabs are stacked to form the first tab bundle. The first tab bundle is U-shaped and includes a first portion, a bent portion, and a second portion connected in sequence. The first portion is connected to the electrode assembly, and the bent portion connects the first portion and the second portion. The first adapter tab includes a first connecting portion and a second connecting portion. The first connecting portion includes a first surface and a second surface disposed opposite to each other along its thickness direction. The first surface faces the electrode assembly and is connected to the second portion. The second connecting portion is connected to the first connecting portion, and the second connecting portion and the second surface are located on the same side of the first connecting portion. Along the extending direction of the first connecting portion, the first connecting portion has a first end and a second end disposed opposite to each other, and the second connecting portion is located between the first end and the second end.

[0048] In this secondary battery, there is a distance between the second connection part and the first end and the second end of the first connection part. When the secondary battery is dropped, the electrode assembly moves relative to the shell, causing the first adapter tab to bend repeatedly. The distance between the two ends of the second connection part and the first connection part helps to reduce the bending amplitude of the first adapter tab, thereby reducing the possibility of the first adapter tab breaking.

[0049] The embodiments of this application will be further described below with reference to the accompanying drawings.

[0050] As shown in Figures 1 and 2, an embodiment of this application provides a secondary battery 100, including a housing 10, an electrode assembly 20, a first electrode bundle 30, a second electrode bundle 60, a first adapter electrode 40, and a second adapter electrode 70. The electrode assembly 20, the first electrode bundle 30, and the second electrode bundle 60 are housed within the housing 10. Both the first electrode bundle 30 and the second electrode bundle 60 are connected to the electrode assembly 20. The first adapter electrode 40 is connected to the first electrode bundle 30, and the second adapter electrode 70 is connected to the second electrode bundle 60. A portion of the first adapter electrode 40 and a portion of the second adapter electrode 70 extend out of the housing 10.

[0051] In some embodiments, the housing 10 is a flexible packaging bag, such as an aluminum-plastic film.

[0052] In some embodiments, the housing 10 is made of a rigid material, such as steel.

[0053] In some embodiments, as shown in FIG2, the electrode assembly 20 includes a positive electrode 21, a negative electrode 22, and a separator 23.

[0054] In some embodiments, the positive electrode 21, the separator 23, and the negative electrode 22 are stacked and then wound to form a wound structure.

[0055] In some embodiments, a plurality of positive electrode plates 21, a plurality of separators 23 and a plurality of negative electrode plates 22 are alternately stacked to form a stacked structure.

[0056] In some embodiments, as shown in FIG2, the positive electrode 21 includes a positive current collector 211 and a positive active material layer 212, wherein the positive active material layer 212 is disposed on one or both sides of the positive current collector 211 along its thickness direction.

[0057] In some embodiments, as shown in FIG2, the negative electrode sheet 22 includes a negative electrode current collector 221 and a negative electrode active material layer 222, wherein the negative electrode active material layer 222 is disposed on one or both sides of the negative electrode current collector 221 along its thickness direction.

[0058] In some embodiments, both the positive current collector 211 and the negative current collector 221 are metal layers. As an example, the positive current collector 211 may be a metal layer comprising at least one of aluminum, nickel, tantalum, and titanium, such as aluminum foil. The negative current collector 221 may be a metal layer comprising at least one of copper, nickel, tantalum, and titanium, such as copper foil.

[0059] In some embodiments, the positive electrode active material layer 212 includes a positive electrode active material, which includes at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium manganese iron phosphate, or lithium manganese oxide.

[0060] In some embodiments, the negative electrode active material layer 222 includes a negative electrode active material, which includes at least one of graphite, hard carbon, soft carbon, silicon, silicon-oxygen materials, and silicon-carbon materials.

[0061] In some embodiments, the separator 23 is an insulating film material such as a polyethylene film, a polypropylene film, a polyester film, or a polyimide film.

[0062] In some embodiments, the electrolyte comprises an electrolyte salt. The electrolyte salt comprises at least one of an organic lithium salt or an inorganic lithium salt.

[0063] In some embodiments, the electrolyte salt includes, but is not limited to, at least one of lithium hexafluorophosphate (LiPF6), lithium bis(fluoromethanesulfonyl)imide LiN(CF3SO2)2 (LiTFSI), lithium bis(fluorosulfonyl)imide Li(N(SO2F)2) (LiFSI), lithium hexafluorocesium oxide (LiCsF6), lithium perchlorate (LiClO4), or lithium trifluoromethanesulfonate (LiCF3SO3).

[0064] In some embodiments, the first electrode bundle 30 is welded to the first adapter electrode 40.

[0065] In some embodiments, the first electrode bundle 30 and the first adapter electrode 40 are bonded together with conductive adhesive.

[0066] In some embodiments, as shown in FIG2, the first tab bundle 30 includes a plurality of first tabs 31, each of which is electrically connected to the electrode assembly 20. Specifically, the first tabs 31 are electrically connected to one of the positive electrode plate 21 and the negative electrode plate 22. The plurality of first tabs 31 are stacked to form the first tab bundle 30. The first tab bundle 30 is U-shaped and includes a first portion 32, a bent portion 33, and a second portion 34 connected in sequence. The first portion 32 is connected to the electrode assembly 20, and the bent portion 33 is connected to the first portion 32 and the second portion 34. Bending the first tab bundle 30 into a U-shape helps to reduce the space occupied by the first tab bundle 30 in the head space of the secondary battery 100 and improves the energy density.

[0067] In some embodiments, as shown in FIG2, the first adapter tab 40 includes a first connecting portion 41 and a second connecting portion 42. The first connecting portion 41 includes a first surface 41a and a second surface 41b disposed opposite to each other along its thickness direction. The first surface 41a faces the electrode assembly 20 and is connected to the second portion 34. The second connecting portion 42 is connected to the first connecting portion 41, and the second connecting portion 42 and the second surface 41b are located on the same side of the first connecting portion 41. Along the extending direction of the first connecting portion 41, the first connecting portion 41 has a first end portion 411 and a second end portion 412 disposed opposite to each other, and the second connecting portion 42 is located between the first end portion 411 and the second end portion 412.

[0068] In this secondary battery 100, there is a distance between the second connecting part 42 and the first end 411 and the second end 412 of the first connecting part 41. When the secondary battery 100 is dropped, the electrode assembly 20 moves relative to the housing 10, causing the first adapter tab 40 to bend repeatedly. The distance between the two ends of the second connecting part 42 and the first connecting part 41 helps to reduce the bending amplitude of the first adapter tab 40, thereby reducing the possibility of the first adapter tab 40 breaking.

[0069] In some embodiments, as shown in FIG3, the length of the first connecting portion 41 is L, the distance from the second connecting portion 42 to the first end 411 is L1, and the distance from the second connecting portion 42 to the second end 412 is L2, where L1 ≥ 0.2L and L2 ≥ 0.2L. Setting L1 ≥ 0.2L and L2 ≥ 0.2L ensures that there is an appropriate distance between both ends of the second connecting portion 42 and the first connecting portion 41, which helps to reduce the bending amplitude of the first adapter tab 40, thereby reducing the possibility of the first adapter tab 40 breaking.

[0070] In some embodiments, L1 ≥ 0.4L and L2 ≥ 0.4L. This helps to further reduce the distance between the center lines of the second connecting portion 42 and the first connecting portion 41, further reducing the bending amplitude of the first adapter tab 40, thereby further reducing the possibility of the first adapter tab 40 breaking.

[0071] In some embodiments, the first portion 32 contacts the second portion 34. This helps to reduce the space occupied by the first electrode bundle 30 on the head of the secondary battery 100, thereby reducing the volume of the secondary battery 100 and increasing its energy density.

[0072] In some embodiments, as shown in FIG3, the first tab 31 includes a third end 311 located in the second portion 34. Along the extending direction of the second portion 34, the distance between the third ends 311 of any two first tabs 31 is D1, where 0 ≤ D1 ≤ 1 mm. Along the extending direction of the second portion 34, the distance between the third end 311 of any first tab 31 and the second end 412 is D2, where 0 ≤ D2 ≤ 1 mm. Setting D1 ≤ 1 mm prevents the distance between the third ends 311 of adjacent first tabs 31 from being too large. Setting D2 ≤ 1 mm also prevents the distance between the third end 311 of the first tab 31 and the first connecting portion 41 from being too large. This improves the flatness of the ends of the first tabs 31 and the first connecting portion 41, thereby reducing the dimensions of the first tab bundle 30 and the first connecting portion 41 in the thickness direction of the electrode assembly 20. In the embodiments of this application, after connecting the second part 34 with the first connecting part 41, the first region 413 and the second part 34 can be cut so that the distance between the third ends 311 of any two first tabs 31 and the distance between the third end 311 of any one first tab 31 and the second end 412 can satisfy the aforementioned value range requirements.

[0073] In some embodiments, as shown in Figures 2 and 4, the first connecting portion 41 and the second connecting portion 42 are integral structures. For example, Figure 2 shows the first adapter tab 40 manufactured by an integral molding process, and Figure 4 shows the state of the first adapter tab 40 shown in Figure 10 after bending in the product. Thus, the structure of the first connecting portion 41 and the second connecting portion 42 is simple and easy to manufacture.

[0074] In some embodiments, as shown in FIG5, the first adapter tab 40 includes a first connector 43 and a second connector 44. The first connector 43 includes a third portion 431 and a fourth portion 432. The third portion 431 is connected to the end of the fourth portion 432, and the third portion 431 and the fourth portion 432 are arranged at an angle. The third portion 431 is connected to the second connector 44, and the third portion 431 and the second connector 44 extend in opposite directions. The third portion 431 and the second connector 44 together form a first connecting portion 41, and the fourth portion 432 forms a second connecting portion 42.

[0075] In some embodiments, as shown in FIG6, the first adapter tab 40 includes a first connector 43 and a second connector 44. The first connector 43 includes a third portion 431 and a fourth portion 432, with the third portion 431 connected to the end of the fourth portion 432 at an angle. The second connector 44 includes a fifth portion 441 and a sixth portion 442, with the fifth portion 441 connected to the end of the sixth portion 442 at an angle. The fourth portion 432 connects to the fifth portion 441, and the third portion 431 and the sixth portion 442 extend in opposite directions, with the fourth portion 432 and the fifth portion 441 located on the same side of the third portion 431 and the sixth portion 442. The third portion 431 and the sixth portion 442 together form a first connecting portion 41, and the fourth portion 432 and the fifth portion 441 together form a second connecting portion 42.

[0076] In some embodiments, the length of the welded portion between the fourth portion 432 and the fifth portion 441 along the extending direction of the fourth portion 432 is at least 1 mm. This is beneficial for improving the connection stability between the fourth portion 432 and the fifth portion 441.

[0077] In some embodiments, as shown in Figures 2 and 3, the first connecting portion 41 is welded to the second portion 34 to form a first weld mark 34a. The width of the first weld mark 34a along the length of the second portion 34 is W, where 0.8 mm ≤ W ≤ 1.2 mm. Setting W ≥ 0.8 mm prevents the width of the first weld mark 34a from being too small, which is beneficial for improving the stability of the welding between the first connecting portion 41 and the second portion 34. Setting W ≤ 1.2 mm prevents the width of the weld mark between the first connecting portion 41 and the second portion 34 from being too large, which is beneficial for reducing the size of the first electrode bundle 30 in the thickness direction of the electrode assembly 20. Furthermore, the unwelded portion of the second portion 34 is not too small, which is beneficial for dispersing stress and reducing the possibility of breakage of the first electrode bundle 30. Here, a weld mark refers to the area containing multiple weld points formed during the welding process. The width of the first weld mark 34a along the length of the second portion 34 refers to the distance between the two furthest weld points in the first weld mark 34a along the length of the second portion 34.

[0078] In some embodiments, as shown in FIG6, the first connecting portion 41 has a first region 413 and a second region 414. Along the extending direction of the first connecting portion 41, the first region 413 and the second region 414 are located on opposite sides of the second connecting portion 42. The second region 414 is closer to the bending portion 33 than the first region 413. The first region 414 is welded to the second portion 34 to form a first weld mark 34a, while the second region 414 is not connected to the second portion 34. In this way, the first connecting portion 41 can move relative to the second portion 34, which helps to release stress and reduces the possibility of breakage of the first electrode bundle 30 and the first adapter electrode 40.

[0079] In some embodiments, as shown in Figures 7 and 8, the distance from the first solder mark 34a to the first end 411 along the extending direction of the first connecting portion 41 is L3, and the length of the first connecting portion 41 is L, where L3 ≥ 0.2L. Thus, an appropriate distance exists between the first solder mark 34a and the bent portion 33 of the first electrode bundle 30, allowing the first electrode bundle 30 and the first adapter 40 to release some stress through opening and closing deformation, thereby reducing the possibility of breakage of the first electrode bundle 30 and the first adapter electrode 40.

[0080] In some embodiments, as shown in Figures 2 and 3, the first connecting portion 41 is welded to the second portion 34 to form a first solder mark 34a. The secondary battery 100 also includes a first adhesive 50, which covers the first solder mark 34a and is bonded to the surface of the second portion 34 facing the first portion 32. This helps to reduce the possibility of burrs formed during the welding process puncturing the separator 23 and causing a short circuit.

[0081] In some embodiments, as shown in FIG2, the first tab bundle 30 is located on one side of the electrode assembly 20 along a first direction X, the first direction X being perpendicular to the thickness direction of the electrode assembly 20. Along the first direction X, the projections of the first tab bundle 30 and the first adapter tab 40 are located within the projection range of the electrode assembly 20. This helps to reduce the impact of the first tab bundle 30 and the first adapter tab 40 on the thickness of the secondary battery 100.

[0082] In some embodiments, as shown in FIG9, the secondary battery 100 further includes a second electrode bundle 60 and a second adapter electrode 70. The second electrode bundle 60 includes a plurality of second electrodes 61, which are stacked to form the second electrode bundle 60. The second electrode bundle 60 is connected to the electrode assembly 20. Specifically, the first electrode bundle 30 and the second electrode bundle 60 are respectively connected to one of the positive electrode plate 21 and the negative electrode plate 22, and the second adapter electrode 70 is connected to the second electrode bundle 60.

[0083] In some embodiments, the connection structure of the second electrode bundle 60 and the second adapter electrode 70 can refer to the connection structure of the first electrode bundle 30 and the first electrode 31, which will not be described again here.

[0084] As shown in FIG11, an embodiment of this application also provides an electrical device 1000, which includes a secondary battery 100 as described in any of the foregoing embodiments.

[0085] In some embodiments, the electrical device 1000 includes, but is not limited to, mobile phones, laptops, power tools, and electric toys.

[0086] Embodiments of this application also provide a method for preparing a secondary battery 100, the method comprising the following steps:

[0087] Take an electrode assembly 20, which is connected to a first electrode ear bundle 30;

[0088] Take a first adapter tab 40 and connect the first connecting part 41 and the second part 34; the first connecting part 41 has a first region 413 and a second region 414. Along the extending direction of the first connecting part 41, the first region 413 and the second region 414 are located on opposite sides of the second connecting part 42. The second region 414 is closer to the bend 33 than the first region 413. At least one of the first region 413 and the second region 414 is connected to the second part 34.

[0089] In some embodiments, the method for preparing the secondary battery 100 includes the following steps:

[0090] Cutting the first region 413 and the second part 34 shortens the length of the second part 34 and the first connecting part 41 along the extending direction of the first connecting part 41. Cutting the first region 413 and the second part 34 helps to reduce the space occupied by the first electrode bundle 30 and the first connecting part 41, and improves the energy density of the secondary battery 100.

[0091] In some embodiments, as shown in Figures 2 and 10, the method for preparing the secondary battery 100 includes the following steps:

[0092] The first adapter tab 40 includes a first extension 401, a second extension 402, and a connecting portion 403. The first extension 401 is integrally connected to the connecting portion 403, and the second extension 402 is integrally connected to the connecting portion 403. The first extension 401 and the second extension 403 are separated so that the first extension 401 and the second extension 402 extend in opposite directions. The first extension 401 and the second extension 402 form a first connecting portion 41, and the connecting portion 403 forms a second connecting portion 42.

[0093] To verify the effectiveness of the embodiments of this application, the inventors conducted the following experiments, which included 17 experimental groups, including 2 comparative examples and 15 specific examples. Each experimental group included 20 secondary batteries 100. In the experiments, the positive electrode bundle was used as the first electrode bundle 30, and the negative electrode bundle was used as the second electrode bundle 60.

[0094] The preparation process of the secondary battery 100 in Example 1 includes the following steps:

[0095] (1) Preparation of positive electrode 21: Lithium cobalt oxide (LiCoO2), conductive carbon black (Super P), CNTs (carbon nanotubes), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 97.5:0.5:0.5:1.5, and N-methylpyrrolidone (NMP) was added as a solvent to prepare a positive electrode active material with a solid content of 75 wt%, and stirred evenly for later use. A 10 μm thick aluminum foil was used as the positive electrode current collector 211. The above active material was uniformly coated on one side of the positive electrode current collector 211 using a slot coater, and then dried at 90°C to obtain a positive electrode 21 with a single-sided coating of positive electrode active material. At this time, the thickness of the positive electrode active material layer 212 was 50 μm. Then, the above coating steps were repeated on the other side of the positive electrode current collector to obtain a positive electrode 21 with positive electrode active material layers 212 coated on both sides. The coated positive electrode sheet 21 is then cold-pressed, resulting in a positive electrode active material layer 212 thickness of 35 μm. The area of ​​the positive electrode current collector 211 not covered by the positive electrode active material layer 212 is the positive electrode empty foil area, which is then die-cut to obtain multiple positive electrode tabs.

[0096] (2) Preparation of negative electrode 22: Artificial graphite, conductive carbon black (Super P), styrene-butadiene rubber (SBR), and CMC (sodium carboxymethyl cellulose) were mixed in a weight ratio of 97:0.5:1.3:1.2. Deionized water was added as a solvent to prepare a negative electrode active material with a weight percentage of 50 wt%, and the mixture was stirred evenly for later use. A copper foil with a thickness of 10 μm was used as the negative electrode current collector 221. The above negative electrode active material was uniformly coated onto one side of the negative electrode current collector 221 using a slot coater, and then dried at 110°C to obtain a negative electrode 22 with a single-sided coating of the negative electrode active material layer 222. At this time, the thickness of the negative electrode active material layer 222 was 55 μm. The above steps were then repeated on the other side of the negative electrode current collector 221 to obtain a negative electrode 22 with a double-sided coating of the negative electrode active material layer 222. The coated negative electrode 22 was then cold-pressed, and the thickness of the cold-pressed negative electrode active material layer 222 was 45 μm. The area of ​​the negative electrode current collector 221 that is not covered by the negative electrode active material layer is the negative electrode empty foil area. Die cutting the negative electrode empty foil area yields multiple negative electrode tabs.

[0097] (3) Preparation of electrolyte: In a dry argon atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are first mixed in a mass ratio of EC:EMC:DEC = 30:50:20 to form a basic organic solvent. Then, lithium salt lithium hexafluorophosphate (LiPF6) is added to the basic organic solvent to dissolve and mix evenly to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.

[0098] (4) Preparation of the isolation membrane: A 7μm thick porous polyethylene polymer film was used as the isolation membrane.

[0099] (5) Electrode assembly fabrication: The positive electrode sheet, separator, and negative electrode sheet are stacked and wound together. Multiple positive electrode tabs are gathered along the thickness direction of the electrode assembly to form a positive electrode tab bundle, and the negative electrode tabs are gathered along the thickness direction of the electrode assembly to form a negative electrode tab bundle. The positive electrode tab bundle is bent to form a U-shaped structure in which the first part, the bent part, and the second part are connected in sequence, and the first adapter tab is welded to the positive electrode tab bundle; the negative electrode tab bundle is bent to form a U-shaped structure, and the second adapter tab is welded to the negative electrode tab bundle.

[0100] (6) Assembly of the secondary battery: Place the dented aluminum-plastic film in the assembly fixture with the dented surface facing upwards, place the electrode assembly 20 in the dent, and apply external force to press it firmly. Then, cover the electrode assembly 20 with another dented aluminum-plastic film with the dented surface facing downwards, and heat-seal the three edges of the two aluminum-plastic films by hot pressing. The unsealed edge is the side of the first and second adapter tabs that protrude from the housing 10. After that, electrolyte is injected through the unsealed edge, and after vacuum sealing, standing, hot pressing formation, shaping and other processes, the secondary battery 100 is obtained.

[0101] The preparation process of the secondary battery 100 in Comparative Examples 1, 2, and Examples 2 to 15 is basically the same as that in Example 1. The difference lies in that some parameters of the secondary battery 100 in Comparative Examples 1, 2, and Examples 2 to 10 are different from those of the secondary battery 100 in Example 1. The specific differences are recorded in Table 1. It should be noted that in all experimental groups, the length L of the first connecting part 41 is 4 mm.

[0102] After the secondary batteries 100 in Comparative Examples 1, 2 and Examples 1 to 15 were prepared, drop tests were conducted on the secondary batteries 100 in Comparative Examples 1, 2 and Examples 1 to 15, and then tensile tests were conducted on the secondary batteries 100 in Examples 4 and 8 to 10.

[0103] The drop test process is as follows:

[0104] Fix the secondary battery to the drop test fixture with double-sided tape. Number the six sides of the fixture as 1, 2, 3, 4, 5, and 6 in sequence, and number the four corners of the fixture as C1, C2, C3, and C4 in sequence.

[0105] At 25℃, place the fixture on a test platform 1.5m high, drop the secondary batteries in the order of numbers 1-6, and then drop the lithium-ion secondary batteries in the order of numbers C1-C4. Repeat this cycle 6 times to complete the drop test. Let it stand for 1 hour.

[0106] Disassemble the lithium-ion secondary battery and observe whether the first adapter tab 40 and the second adapter tab 70 are broken. If neither is broken, it is considered to have passed the drop test. Count the number of secondary batteries 100 that passed the drop test in each experimental group and calculate the pass rate Q of the drop test. Q = number of secondary batteries 100 that passed the drop test in the group / total number of secondary batteries 100 in the group.

[0107] The tensile test process is as follows:

[0108] Disassemble the secondary battery 100, and remove the positive electrode bundle and the first adapter tab connected to it as a sample. Wipe the electrolyte off the surface with lint-free paper. Along the length of the sample, fix the side of the positive electrode bundle without the first adapter tab to a steel plate. Fix the steel plate to the corresponding position on the high-speed rail tensile testing machine, pull up one end of the first adapter tab on the other side of the sample, and clamp it in the clamp. The angle between the pulled-up first adapter tab and the steel plate is 180°. Pull the sample at a speed of 5±0.2 mm / s. The average tensile force in the stable region is recorded as the peel strength between the positive electrode bundle and the first adapter tab, expressed in N / mm. The stable region refers to the area where the tensile force does not change significantly over time when plotted as a line graph of the tensile force of the clamp pulling the first adapter tab. Calculate the average peel strength F for each experimental group and record the results in Table 1.

[0109] After the experiment, the results were recorded in Table 1.

[0110] Table 1 Note: In Table 1, " / " indicates that the data is not available.

[0111] As shown in Table 1, the secondary batteries 100 in Examples 1 to 15 satisfy L1 ≥ 0.2L and L2 ≥ 0.2L. Compared with Comparative Examples 1 and 2, the secondary batteries 100 in Examples 1 to 10 have a higher pass rate in drop tests. It is evident that when the secondary battery 100 is dropped, the electrode assembly 20 moves relative to the housing 10, causing the first adapter tab 40 to bend repeatedly. The appropriate distance between the two ends of the second connecting part 42 and the first connecting part 41 helps to reduce the bending amplitude of the first adapter tab 40, thereby reducing the possibility of breakage.

[0112] In Examples 3 to 5, the secondary battery 100 satisfies L1≥0.4L and L2≥0.4L. Compared with Examples 1, 2, 6, and 7, the secondary battery 100 in Examples 3 to 5 has a higher pass rate in drop tests. It is evident that setting L1≥0.4L and L2≥0.4L helps to further reduce the distance between the centerline of the second connecting part 42 and the first connecting part 41, further reducing the bending amplitude of the first adapter tab 40, thereby further reducing the possibility of the first adapter tab 40 breaking.

[0113] In Examples 4, 9, and 10, the secondary battery 100 satisfies W ≥ 0.8 mm. Compared to Example 8, the secondary battery 100 in Examples 4, 9, and 10 exhibits greater average peel strength. It is evident that setting W ≥ 0.8 mm prevents the width of the first solder mark 34a from becoming too small, which is beneficial for improving the stability of the welding between the first connecting portion 41 and the second portion 34. Furthermore, setting W ≤ 1.2 mm ensures that while maintaining the peel strength of the first connecting portion 41 and the second portion 34, the width of the first solder mark 34a is not excessively large. This helps reduce the size of the first electrode bundle 30 in the thickness direction of the electrode assembly 20, and also prevents the unwelded portion of the second portion 34 from becoming too small, which helps to disperse stress and reduce the possibility of breakage of the first electrode bundle 30.

[0114] In Examples 4 and 11 to 14, the secondary battery 100 satisfies L3 ≥ 0.2L. Compared to Example 15, the secondary battery 100 has a higher pass rate in the drop test. It is evident that setting L3 ≥ 0.2L ensures an appropriate distance between the first welding mark 34a and the bent portion 33 of the first electrode bundle 30. This allows the first electrode bundle 30 and the first adapter 40 to release some stress through opening and closing deformation, thereby reducing the possibility of breakage of the first electrode bundle 30 and the first adapter electrode 40.

[0115] Those skilled in the art should recognize that the above embodiments are only used to illustrate this application and are not intended to limit this application. Any appropriate changes and variations made to the above embodiments within the essential spirit and scope of this application fall within the scope of this application.

Claims

1. A secondary battery, characterized in that, include: Electrode assembly; The first electrode bundle includes a plurality of first electrodes, all of which are electrically connected to the electrode assembly; The plurality of first electrode tabs are stacked to form the first electrode tab bundle; the first electrode tab bundle includes a first part, a bent part and a second part connected in sequence, the first part is connected to the electrode assembly, and the bent part is connected to the first part and the second part; and The first adapter tab includes a first connecting portion and a second connecting portion. The first connecting portion includes a first surface and a second surface disposed opposite to each other along its thickness direction. The first surface faces the electrode assembly. The first surface is connected to the second portion. The second connecting portion is connected to the first connecting portion, and the second connecting portion and the second surface are located on the same side of the first connecting portion. Along the extending direction of the first connecting portion, the first connecting portion has a first end and a second end disposed opposite to each other, and the second connecting portion is located between the first end and the second end; The length of the first connecting part is L, the distance from the second connecting part to the first end is L1, the distance from the second connecting part to the second end is L2, L1≥0.2L, and L2≥0.2L.

2. The secondary battery as described in claim 1, characterized in that, L1≥0.4L, and L2≥0.4L.

3. The secondary battery as described in claim 1, characterized in that, The first part contacts the second part.

4. The secondary battery as described in claim 1, characterized in that, The first connecting part and the second connecting part are an integral structure.

5. The secondary battery as described in claim 1, characterized in that, The first adapter tab includes a first connector and a second connector. The first connector includes a third part and a fourth part. The third part is connected to the end of the fourth part, and the third part and the fourth part are arranged at an angle. The third part connects to the second connector, and the third part and the second connector extend in opposite directions; the third part and the second connector together form the first connecting portion, and the fourth part forms the second connecting portion.

6. The secondary battery as described in claim 1, characterized in that, The first adapter tab includes a first connector and a second connector. The first connector includes a third part and a fourth part. The third part is connected to the end of the fourth part, and the third part and the fourth part are arranged at an angle. The second connector includes a fifth part and a sixth part, wherein the fifth part is connected to the end of the sixth part, and the fifth part and the sixth part are arranged at an angle; The fourth part connects to the fifth part, the third part and the sixth part extend in opposite directions, and the fourth part and the fifth part are located on the same side of the third part and the sixth part; the third part and the sixth part together form the first connecting part, and the fourth part and the fifth part together form the second connecting part.

7. The secondary battery as described in claim 6, characterized in that, Along the extending direction of the fourth part, the length of the welded portion of the fourth part and the fifth part is at least 1 mm.

8. The secondary battery as described in any one of claims 1-7, characterized in that, The first connecting part is welded to the second part to form a first solder mark. Along the length direction of the second part, the width of the first solder mark is W, 0.8mm≤W≤1.2mm.

9. The secondary battery as described in claim 8, characterized in that, The first connecting portion has a first region and a second region. Along the extending direction of the first connecting portion, the first region and the second region are located on opposite sides of the second connecting portion. The second region is closer to the bending portion than the first region. The first region is welded to the second portion to form the first weld mark. The second region is not connected to the second portion.

10. The secondary battery as described in claim 8, characterized in that, Along the extending direction of the first connecting portion, the distance from the first solder mark to the first end is L3, and the length of the first connecting portion is L, where L3 ≥ 0.2L.

11. The secondary battery according to any one of claims 1-10, characterized in that, The shell is a flexible packaging bag.

12. The secondary battery as described in any one of claims 1-11, characterized in that, The first connecting portion is welded to the second portion, forming a first solder mark; The secondary battery further includes a first adhesive component that covers the first solder mark and is bonded to the surface of the second portion facing the first portion.

13. The secondary battery as described in any one of claims 1-12, characterized in that, The first electrode bundle is U-shaped and is located on one side of the electrode assembly along a first direction, which is perpendicular to the thickness direction of the electrode assembly. Along the first direction, the projections of the first tab bundle and the first adapter tab are located within the projection range of the electrode assembly.

14. An electrical appliance, characterized in that, Includes the secondary battery as described in any one of claims 1 to 13.

15. A method for preparing a secondary battery, used to manufacture the secondary battery as described in claim 1, characterized in that, Includes the following steps: Take one of the electrode assemblies, the electrode assembly being connected to the first electrode ear bundle; Take one of the first adapter tabs and connect the first connecting portion to the second portion; the first connecting portion has a first region and a second region, and along the extending direction of the first connecting portion, the first region and the second region are located on opposite sides of the second connecting portion, the second region is closer to the bend than the first region, and at least one of the first region and the second region is connected to the second portion.

16. The method for preparing a secondary battery as described in claim 15, characterized in that, Includes the following steps: The first region and the second portion are cut so that the length of the second portion and the first connecting portion along the extending direction of the first connecting portion is shortened.

17. The method for preparing a secondary battery as described in claim 15, characterized in that, Includes the following steps: The first adapter tab includes a first extension, a second extension, and a connecting portion. The first extension is integrally connected to the connecting portion, and the second extension is integrally connected to the connecting portion. Separate the first extension and the second extension, so that the first extension and the second extension extend in opposite directions, the first extension and the second extension form the first connecting portion, and the connecting portion forms the second connecting portion.

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