Secondary battery, battery pack, and electronic device

Abstract

The utility model provides a secondary battery, a battery pack and an electronic device. The secondary battery includes a case, an electrode assembly, and a collector plate. And the first extension part of the current collecting plate extends outwards from the outer edge of the main body part along the radial direction of the main body part to be in contact with the outer ring tab. One end of the second extension part is connected to the main body part between two adjacent first extension parts, and the other end is conductively connected with the rolling groove. An outer edge surface is formed on the outer edge of the second extension part along the circumferential direction, an outer edge surface projection is formed on a plane which is orthographically projected on the outer ring tab along the height direction of the electrode assembly and is vertical to the height direction, and the outer edge surface projection is at least partially overlapped with each outer ring tab between two adjacent first extension parts. The problem that in the process that the electrode assembly is put into the shell, the outer ring tab is possibly turned over outwards to the outside of the electrode assembly due to stress in the process step, so that the diameter of the electrode assembly is increased, and the shell entering is poor can be solved.

Description

TECHNICAL FIELD

[0001] The utility model relates to a battery field, concretely relates to a secondary battery, battery pack and electronic device. BACKGROUND

[0002] In recent years, with the rapid development of electric vehicles, consumer electronics, new energy storage systems, for electric vehicles, battery technology is an important factor for its development.

[0003] In the development of battery technology, how to improve the assembly efficiency of the battery is a technical problem that needs to be solved in the battery technology. UTILITY MODEL CONTENTS

[0004] The utility model aims at providing a secondary battery, can solve the problem that the outer ring tab may be folded outward due to stress in the process of putting the electrode assembly into the shell.

[0005] The utility model discloses a secondary battery, including: shell, electrode assembly and current collector disc. The shell includes the lateral wall of cylinder, and one end of the lateral wall includes the opening, and the lateral wall forms the rolling groove recessed to the inside of the shell at the position close to the opening. The electrode assembly is contained in the shell, and the rolling groove limits the movement of the electrode assembly in the shell along the height direction of the secondary battery. The one end of the electrode assembly along the height direction close to the rolling groove has the tab, and the tab bending to the center hole of the electrode assembly and closest to the outer edge of the electrode assembly is constituted as the outer ring tab of the electrode assembly. The current collector disc includes the main part, a plurality of first extension and a plurality of second extension, and the main part is arranged between the rolling groove and the electrode assembly, and one side surface of the main part is in conductive connection with the tab. The first extension is in the same plane with the main part, and the first extension extends to the contact with the outer ring tab from the outer edge of the main part along the radial direction of the main part. The one end of the second extension is connected to the main part between the adjacent two first extensions, and the other end is in conductive connection with the rolling groove. The outer edge of the second extension forms the outer edge surface along the circumferential direction, and the outer edge surface is projected on the plane perpendicular to the height direction where the outer ring tab is located along the height direction of the electrode assembly and forms the outer edge surface projection, and the outer edge surface projection at least partially overlaps with every outer ring tab between the adjacent two first extensions.

[0006] In the secondary battery of the optional technical scheme of the utility model, the second extension includes the rolling groove fixed part and the bridging part, the two ends of the bridging part are connected with the outer edge of the main part and the rolling groove fixed part respectively, the rolling groove fixed part is welded and fixed with the side of the rolling groove away from the electrode assembly, the bridging part is bent in the mode of having the stress deformation towards the rolling groove, or the tab is the cut-over tab.

[0007] In the secondary battery of the optional technical scheme of the utility model, stress deformation is elastic deformation, when the fixing of the second extension part and the rolling groove is released, the end of the bridging part close to the rolling groove elastically restores in the form of deformation away from the electrode assembly.

[0008] In the secondary battery of the optional technical scheme of the utility model, the second extension part and the rolling groove are conductively connected in the form of welding, and each rolling groove fixing part is welded and fixed with the rolling groove by using multiple mutually spaced welding marks.

[0009] In the secondary battery of the optional technical scheme of the utility model, the welding mark is a straight welding mark extending in the circumferential direction.

[0010] In the secondary battery of the optional technical scheme of the utility model, the length L of each welding mark satisfies: 2mm≤L≤(W-(n+1)) / n mm, wherein W is the maximum circumferential length of each rolling groove fixing part, and n is the number of welding marks on each rolling groove fixing part.

[0011] In the secondary battery of the optional technical scheme of the utility model, the current collecting disc has four first extension parts uniformly distributed in the circumferential direction and four second extension parts uniformly distributed in the circumferential direction, the first extension parts and the second extension parts are sequentially and spaced apart, and each first extension part and each second extension part are provided with a reserved gap at the outer peripheral edge of the main body part.

[0012] In the secondary battery of the optional technical scheme of the utility model, a cover plate is further included, and the cover plate is used for sealing the opening of the shell. The other end of the side wall includes an end wall, the end wall is provided with a mounting hole, and the mounting hole is used for mounting the pole. An insulating piece is further arranged between the pole and the end wall, and the insulating piece is used for electrically insulating the end wall and the pole. The diameter d of the cylindrical battery and the depth D of the rolling groove satisfy the following relationship: 12≤d / D≤23. Preferably, the depth D of the rolling groove satisfies: D≤4mm.

[0013] The second aspect of the utility model provides a battery pack comprising the secondary battery provided by the first aspect of the utility model.

[0014] The third aspect of the utility model provides an electronic device comprising the battery pack provided by the second aspect of the utility model. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 A structure schematic view of the electrode assembly in the embodiment is shown;

[0016] Figure 2 A structure schematic view of the negative electrode tab in the embodiment is shown;

[0017] Figure 3 A three-dimensional schematic view of the first current collecting disc in the embodiment is shown;

[0018] Figure 4 A top view of the first current collecting plate in the embodiment is shown;

[0019] Figure 5 A projection of the first current collecting plate along the Z direction on the plane of the outer ring tab after the first current collecting plate is welded with the negative tab in the embodiment is shown;

[0020] Figure 6 A schematic view of the state of the electrode assembly with the first current collecting plate welded into the case in the embodiment is shown;

[0021] Figure 7 A schematic view of the state of the welding connection process between the first current collecting plate and the case in the embodiment is shown;

[0022] Figure 8 A schematic view of the cooperation between the press fitting tool and the rolling groove fixing part in the embodiment is shown;

[0023] Figure 9 A schematic view of the structure of the secondary battery in the embodiment is shown;

[0024] Figure 10 A partial enlarged view of Figure 9 ;

[0025] Figure 11 A top view of the secondary battery after the cover plate is removed in the embodiment is shown

[0026] Figure 12 A partial enlarged view of Figure 11 ;

[0027] Figure 13 A schematic view of the battery pack in the embodiment is shown;

[0028] Figure 14 A schematic view of the electronic device in the embodiment is shown;

[0029] Figure 15 A partial structure schematic view of the secondary battery in the embodiment is shown.

[0030] Reference signs:

[0031] Secondary battery 100, housing 1, side wall 10, groove 101, first wall 1011, second wall 1012, opening 12, end wall 13, electrode assembly 2, negative tab 20, outer ring tab 201, center hole 21, first current collector 3, main body 30, first extension 31, second extension 32, groove fixing part 321, bridge part 322, first current collector projection 903, first extension projection 9031, outer edge surface projection 9032, gap 33, welding mark 4, cover plate 5, second current collector 6, pole 7, pressing tool 8, first pressing part 81, second pressing part 82, third pressing part 83, hob 500, working part 600, battery pack 700, box 710, box cover 720, electronic device 800, explosion-proof valve 400. DETAILED DESCRIPTION

[0032] It should be noted that the following will be described in an exemplary manner according to the structure features and advantages of the secondary battery of the present application, but it should be understood that all the descriptions are given only for example, and therefore should not be understood as forming any limitation on the present application.

[0033] In addition, for any single technical feature described or implied in the embodiments mentioned herein, or any single technical feature shown or implied in the drawings, the present application still allows any combination or deletion between these technical features (or their equivalents) to continue without any technical obstacles, thereby obtaining more other embodiments of the present application which can not be directly mentioned herein.

[0034] SUMMARY

[0035] The electrode assembly of the prior art secondary battery is formed by winding the positive electrode sheet, the separator and the negative electrode sheet. At the end of the electrode assembly, the tab is provided and is shaped parallel to the end face of the electrode assembly by bending or the like, and then is welded to the main body of the current collector. After the welding is completed, the electrode assembly and the current collector are loaded into the housing, and the extension of the current collector is welded to the inner periphery of the housing.

[0036] However, in the process of loading the electrode assembly into the housing, the tab of the outer ring may be folded outward due to stress in the process steps, resulting in an increase in the diameter of the electrode assembly, affecting the assembly precision. In addition, the welding operation of the extension of the current collector to the inner periphery of the housing is difficult, and poor welding may easily occur, thereby affecting the overall performance and reliability of the battery.

[0037] Referring to the drawings generally, according to the exemplary embodiments, an electrode assembly 2, a first current collector 3 connected with a negative tab 20 of the electrode assembly 2, a case 1 accommodating the electrode assembly 2 and electrically connected with the first current collector 3, and a secondary battery 100 having the above-mentioned components are shown. By improving the design of the first current collector 3 and the combined structure of the first current collector 3 and the case 1, the secondary battery 100 has advantages such as easy assembly, enhanced stability of the connection structure, etc.

[0038] <electrode assembly 2>

[0039] Figure 1 A structure diagram of the electrode assembly 2 in the present embodiment is shown. The electrode assembly 2 is formed by winding a positive sheet, a separator and a negative sheet. The positive sheet includes a positive current collector and a positive active material layer. The positive current collector includes a coated region and a non-coated region. The positive active material layer is coated on the coated region of the positive current collector, and the non-coated region of the positive current collector forms a positive tab. The negative sheet includes a negative current collector and a negative active material layer. The negative current collector includes a coated region and a non-coated region. The negative active material layer is coated on the coated region of the negative current collector, and the non-coated region of the negative current collector forms a negative tab 20.

[0040] As a specific example, the material of the positive current collector can be aluminum, the positive active material layer includes a positive active material, and the positive active material can be lithium cobaltate, lithium iron phosphate, ternary lithium or lithium manganate, etc. The material of the negative current collector can be copper, the negative active material layer includes a negative active material, and the negative active material can be carbon or silicon, etc. The material of the separator can be PP (polypropylene), PE (polyethylene), etc. In order to protect and insulate the electrode assembly 2, an insulating film can also be coated on the outside of the electrode assembly 2, and the insulating film can be synthesized by PP, PE, PET, PVC or other high polymer materials.

[0041] Continuing to refer to Figure 1 , the plurality of negative tabs 20 are shown in a state of being bent and stacked. In order to form the negative tab 20 as shown in Figure 1 , a plurality of ways can be used. For example, one of the specific implementation ways is to cut and stack the non-coated region of the negative current collector, divide it into a plurality of tabs, and then perform a flattening process from the height direction of the electrode assembly, so that the negative tab 20 is parallel to the end surface of the electrode assembly 2, thereby facilitating welding with the first current collector 3 to be introduced later. Although Figure 1 does not show the state of the positive tab, it can be understood that the positive tab can have a similar state to the negative tab 20, which will not be described here.

[0042] Among the multiple negative electrode tabs 20, the negative electrode tab 20 that bends towards the central hole 21 of the electrode assembly 2 and is closest to the outer edge of the electrode assembly 2 constitutes the outer ring tab 201 of the electrode assembly 2. It should be noted that the outer ring tab 201 refers to the outermost bent negative electrode tab 20, and not necessarily the outermost negative electrode tab 20. This is because, in some embodiments, such as... Figure 2 As shown (direction A is the direction away from the central hole 21), the outermost negative electrode tab 20 is not bent, and this negative electrode tab 20 is not the outer ring tab 201 described in this article.

[0043] <Episode 1, Streaming Disk 3>

[0044] Figure 3 A three-dimensional schematic diagram of the first collector disk 3 in this embodiment is shown. Figure 4 A top view of the first collector plate 3 in this embodiment is shown. Although Figure 4 The first collector disk 3 in the middle is not displayed. Figure 3 The opening shown is acceptable, but it is understandable. Figure 4 The first collector plate 3 in the figure can actually have similar openings, but they are not shown in this figure.

[0045] like Figure 3 As shown, the first current collector 3 includes a main body 30, multiple first extensions 31, and multiple second extensions 32. The main body 30 is annular, and the four first extensions 31 are located on the same plane as the main body 30. The first extensions 31 extend radially outward from the outer edge of the main body 30, forming a petal-like shape. Here, "the first extensions 31 and the main body 30 are on the same plane" means that both the first extensions 31 and the main body 30 are mainly electrically connected to the negative electrode tab 20 of the electrode assembly 2, and since the negative electrode tab 20 is basically located on the same plane, the first extensions 31 and the main body 30 are also basically on the same plane. It should be noted that "same plane" here includes the same plane or approximately the same plane, because after the secondary battery undergoes formation and charging / discharging, the first extensions 31 and the main body 30 may undergo some deformation, but at this time they are still close to the same plane or approximately the same plane. The second extensions 32 include a groove fixing part 321 and a bridging part 322. One end of the groove fixing part 321 is connected to the main body part 30 between two adjacent first extensions 31, and the other end is connected to the groove fixing part 321. The groove fixing part 321 is used for conductive connection with the groove 101 of the housing 1, which will be described in detail later. However, it should be noted here that since the plane where the groove 101 of the housing 1 is located is offset from the plane where the negative electrode tab 20 is located in the height direction of the electrode assembly 2, i.e., the Z direction, therefore, as Figure 3 As shown, the groove fixing part 321 is offset from the main body part 30 and the first extension part 31 in the Z direction, and the bridging part 322 has a height in the Z direction.

[0046] As Figure 4 shown, the outer edges of the plurality of first extensions 31 and the plurality of second extensions 32 substantially achieve a circumferential coverage of 360°. The advantages brought by this arrangement will be elaborated in the following.

[0047] It can be understood that the shape of the main body 30, the number and shape of the first extensions 31, and the number and shape of the second extensions 32 shown in the illustrated embodiment are only an example and do not constitute a limitation on the present application. In other embodiments, the number of the first extensions 31 and the second extensions 32 can be 3 or 6.

[0048] <Assembly process>

[0049] The process of connecting the first current collector 3 with the electrode assembly 2 and the case 1 respectively will be introduced in the following.

[0050] First, the first current collector 3 is connected to the negative tab 20 by welding, so that the main body 30 and the first extensions 31 of the first current collector 3 are connected with the negative tab 20 and the first extensions 31 are ensured to be in contact with the outer ring tab 201. Then, the electrode assembly 2 with the first current collector 3 welded is put into the case 1, i.e. the in-casing step is performed.

[0051] Figure 5 A projection diagram of the first current collector 3 along the Z direction in the plane where the outer ring tab 201 is located is shown after the first current collector 3 is welded with the negative tab 20 in the present embodiment.

[0052] As Figure 5 shown, the gray part is the first current collector projection 903. Since the first extensions 31 are parallel to the plane where the negative tab 20 is located and the first extensions 31 are connected with the negative tab 20, the first extension projection 9031 and the first extensions 31 are substantially completely overlapped in shape.

[0053] Referring to Figure 5 , the first extension projection 9031 is in contact with the outer ring tab 201, and the main body 30 of the first current collector 3 is in contact with the negative tab 20. Figure 5The left first extension projection 9031 overlaps at least part of the outer ring tabs 201a, 201b, 201c, 201d, 201e, and the right first extension projection 9031 overlaps at least part of the outer ring tabs 201j, 201k, 201m, 201n. Each of the outer ring tabs 201f, 201g, 201h, 201i between the two first extension projections 9031 (i.e. corresponding to the two first extensions 31 corresponding to the two first extension projections 9031) at least partially overlaps the outer edge surface projection 9032 of the second extension 32.

[0054] The left first extension projection 9031 overlapping at least part of the outer ring tabs 201a, 201b, 201c, 201d, 201e means that the first extension 31 corresponding to the first extension projection 9031 contacts the outer ring tabs 201a, 201b, 201c, 201d, 201e, thereby preventing the outer ring tabs 201a, 201b, 201c, 201d, 201e from being affected by the process steps (e.g. air flow, etc.) and turned outward during the process of entering the shell. Similarly, the right first extension projection 9031 overlapping at least part of the outer ring tabs 201j, 201k, 201m, 201n means that the first extension 31 corresponding to the first extension projection 9031 contacts the outer ring tabs 201j, 201k, 201m, 201n, thereby preventing the outer ring tabs 201j, 201k, 201m, 201n from being turned outward. The outer edge surface projection 9032 of the second extension 32 between the two first extension projections 9031 at least partially overlaps each of the outer ring tabs 201f, 201g, 201h, 201i, meaning that the outer edge surface of the second extension 32 corresponding to the outer edge surface projection 9032 can block the outer ring tabs 201f, 201g, 201h, 201i from being turned outward during the process of entering the shell, thereby avoiding affecting the diameter of the electrode assembly 2.

[0055] Figure 6 A schematic view of the electrode assembly 2 with the first current collector 3 welded therein being placed into the shell 1 is shown in the embodiment. As shown, the free end of the bridging portion 322 (i.e. the end away from the main body portion 30) is raised upward in the Z direction, thereby avoiding the hob 500 used to process the rolling groove 101, so as to avoid interference with the first current collector 3 during the process of processing the rolling groove 101. Figure 6

[0056] Figure 7 ​This diagram illustrates the welding process between the first collector plate 3 and the housing 1 in this embodiment. (Reference) Figure 7 After the electrode assembly 2 with the first collector plate 3 welded to it is placed into the housing 1, a groove 101 recessed into the housing 1 can be formed on the side wall 10 of the housing 1 near the opening 12 using a tool such as a hobbing cutter 500. The groove 101 has a first wall 1011 and a second wall 1012 spaced apart in the Z direction. The second wall 1012 restricts the movement of the electrode assembly 2 in the Z direction within the housing 1. The free end of the bridging portion 322 is connected to the groove fixing portion 321. For the purpose of avoiding the hobbing cutter 500 as described above, the groove fixing portion 321 is tilted upwards without the action of external force, thus creating a certain distance between it and the first wall 1011. To weld the groove fixing portion 321 to the first wall 1011, a press-fitting fixture 8 can be used. The press-fitting fixture 8 applies external force to the second extension 32, causing the bridging portion 322 to bend and the groove fixing portion 321 to fit against the first wall 1011.

[0057] Figure 8 This diagram illustrates the engagement of the press-fitting fixture 8 with the groove fixing part 321 in this embodiment. (See reference) Figure 8 The press-fitting fixture 8 includes a first presser 81, a second presser 82, and a third presser 83. The first presser 81 and the second presser 82 press against the two ends of the grooving fixing part 321, respectively, and the third presser 83 presses against the middle position of the grooving fixing part 321. With the first presser 81, the second presser 82, and the third presser 83 respectively pressing against the two ends and the middle position of the grooving fixing part 321, welding is performed between the first presser 81 and the third presser 83, and between the second presser 82 and the third presser 83, to form two short straight weld marks 4.

[0058] According to the above welding method, by using a press-fitting fixture 8 with a third presser 83, a pressure point is added in the middle of the groove fixing part 321, forming two short straight weld marks 4, replacing the welding method in the prior art that forms a long arc weld mark. In this way, since the welding adopts the form of short straight weld marks 4, there is no need to rotate the electrode assembly 2 during the welding process, thereby reducing the welding difficulty and improving the welding stability. At the same time, this method can effectively avoid the problem of poor contact caused by a potential explosion point in the middle of the weld mark when forming a long arc weld mark in the prior art.

[0059] Then, the opening 12 of the housing 1 can be sealed using the cover plate 5, and the following can be obtained: Figure 9 The secondary battery 100 is shown.

[0060] Although in the above, the conductive connection mode of the first current collecting plate 3 and the negative tab 20 and the rolling groove 101 is introduced by taking welding as an example, the utility model is not limited to this. As long as the conductive connection of the first current collecting plate 3 and the negative tab 20 and the rolling groove 101 can be realized, the specific conductive connection mode is not particularly limited. It can be understood that the assembly process introduced in the above is only one preferred embodiment, and does not constitute a limitation on the utility model.

[0061] <Secondary battery 100>

[0062] Figure 9 The structure schematic diagram of the secondary battery 100 in the embodiment is shown. Figure 9 As shown, the secondary battery 100, as a specific example, is a cylindrical battery. The secondary battery 100 comprises a shell 1, an electrode assembly 2, a pole 7, a cover plate 5, a first current collecting plate 3 and a second current collecting plate 6. The shell 1 comprises a cylindrical side wall 10 and an end wall 13 at one end of the side wall 10. The electrode assembly 2 is accommodated in the inside of the shell 1. The pole 7 passes through the mounting hole of the end wall 13 and is insulated from the end wall 13 by an insulating piece. The cover plate 5 covers and seals the opening 12 at the end of the side wall 10 away from the end wall 13. The side wall 10 is formed with a rolling groove 101 recessed to the inside of the shell 1 at the position close to the opening 12. The first current collecting plate 3 is connected with the negative end of the electrode assembly 2 and the shell 1 (the rolling groove 101) respectively, and the second current collecting plate 6 is connected with the positive end of the electrode assembly 2 and the pole 7 respectively.

[0063] Among them, the specific size of the shell 1 can be determined according to the specific size of the electrode assembly 2, for example, the diameter is 46mm, the height is 80mm, 95mm, 120mm, etc. The material of the shell 1 can be various, such as copper, iron, aluminum, steel, aluminum alloy, etc. In order to prevent the shell 1 from rusting after long-term use, a layer of anti-rust material such as metal nickel can also be plated on the surface of the shell 1.

[0064] Figure 10 For Figure 9 The partial enlarged view of the shell 1 is shown. Figure 11 The top view schematic diagram of the secondary battery 100 after removing the cover plate 5 in the embodiment is shown.

[0065] Referring to Figure 10 , the main body part 30 of the first current collecting plate 3 is located between the rolling groove 101 and the electrode assembly 2 in the Z direction, and the side surface of the main body part 30 facing the electrode assembly 2 is in conductive connection with the negative tab 20 (not shown in the figure) of the negative electrode of the electrode assembly 2. Figure 9

[0066] Referring to Figure 10 and Figure 15 ​, the cylindrical battery 100. For the cylindrical battery 100, the electrode assembly 2 is put into the case 1 from the negative electrode side and is sealed at the negative electrode side. The cylindrical battery 100 is provided with a burst valve 400 at the negative electrode side, and pressure is released at the negative electrode. Therefore, the assembly process of putting the electrode assembly 2 into the case 1 to the sealing, the assembly quality and the structure can affect the pressure release effect of the cylindrical battery 100. The main functions of the burst valve include pressure release, explosion prevention, battery structure protection and safety protection. When the internal pressure of the lithium battery abnormally rises, the burst valve will automatically open to release the accumulated gas inside, thereby reducing the pressure and preventing the battery from breaking or exploding.

[0067] Reference Figure 10 and Figure 11 , the first extension part 31 of the first current collecting disc 3 is located in the same plane as the main body part 30, and the first extension part 31 extends outward along the radial direction of the main body part 30 from the outer edge of the main body part 30. One end of the second extension part 32 is connected to the main body part 30 between the two adjacent first extension parts 31, and the other end is in conductive connection with the first wall 1011 of the rolling groove 101. The rolling groove depth D of the rolling groove 101 satisfies: D≤4mm. The depth D of the rolling groove 101 refers to the depth of the rolling groove 101 recessed with respect to the side wall 10 of the case 1, specifically the depth in the radial direction of the case 1 as shown in Figure 10 .

[0068] Although in the illustrated embodiment, the cross section of the rolling groove 101 is in the shape of a U letter, and the second extension part 32 is fixed on the first wall 1011 of the rolling groove 101, the present application is not limited thereto. As long as it is a structure formed by recessing the side wall 10 towards the inside of the case 1, it is within the technical scope of the rolling groove 101 described in the present application. The second extension part 32 can be fixed on the rolling groove 101 at any position suitable for conductive connection, without particular limitation. The depth D of the rolling groove 101 is generally small, for example, less than or equal to 4mm, but in other embodiments, the depth D can also be greater than 4mm.

[0069] Figure 11 A top view schematic diagram of the secondary battery 100 after removing the cover plate 5 in the present embodiment is shown, at this time the first current collecting disc 3 is in conductive connection with the negative electrode tab 20 and the rolling groove 101. Figure 5 A projection schematic diagram of the first current collecting disc 3 along the Z direction in the plane of the outer ring tab 201 when the first current collecting disc 3 is in conductive connection with the negative electrode tab 20 and has not yet been in conductive connection with the rolling groove 101 in the present embodiment is shown. Although the position of the second extension part 32 will change a little before and after being in conductive connection with the rolling groove 101, this change is slight. Therefore, the projection of the first current collecting disc 3 along the Z direction in the plane of the outer ring tab 201 in the secondary battery 100 after leaving the factory can be understood with reference to Figure 5 .

[0070] ReferenceFigure 11 and Figure 5 The first extension 31 extends radially outward from the outer edge of the main body 30 to contact the outer- ring tab 201. The outer edge of the second extension 32 is formed with an outer edge face which, when projected in the electrode assembly 2 height direction, onto the plane in which the outer-ring tab 201 lies (this plane is substantially perpendicular to the Z direction), forms an outer edge face projection 9032 which overlaps at least part of each outer-ring tab 201 between two adjacent first extensions 31. Specifically, the outer edge face can be constituted by the plane in which the groove fixing portion 321 lies, or by the plane in which the groove fixing portion 321 and its circumferential extension portion lie.

[0071] By contacting the outer-ring tab 201 via the first extension 31, the first extension 31 can effectively press the corresponding outer-ring tab 201 to prevent it from turning outward during insertion into the case. At the same time, the contact between the first extension 31 and the outer-ring tab 201 also helps to reduce internal resistance. For the second extension 32, since its outer edge face projection 9032 overlaps at least part of the outer-ring tab 201, when the electrode assembly 2 is inserted into the case 1 after the first current collector 3 has been welded, the degree of turning outward (i.e. the degree of deviation from the Z direction in the direction away from the central hole 21) of the corresponding outer-ring tab 201 can be limited to avoid the outer-ring tab 201 turning outward to the outside of the electrode assembly 2. Moreover, since the second extension 32 does not apply pressure to the outer-ring tab 201, it will be beneficial for the electrode assembly 2 to be able to vent smoothly when thermal runaway occurs, especially for cylindrical batteries 100 in which the venting is to the negative electrode. In addition, the at least partial overlap of the outer edge face projection 9032 of the second extension 32 with each outer-ring tab 201 between two adjacent first extensions 31 ensures that each outer-ring tab 201 is either directly contacted by the first extension 31 or limited in its degree of turning outward by the second extension 32 during insertion into the case, so that the diameter of the electrode assembly 2 does not increase. By providing a plurality of first extensions 31 and a plurality of second extensions 32, not only can the above-mentioned effect of preventing turning outward be achieved, but the overall weight of the first current collector 3 can also be reduced while ensuring functionality. It should be noted here that the outer-ring tab 201 corresponding to the second extension 32 can have a certain degree of turning outward, but when the degree of turning outward is too large, it will be limited by the second extension 32, thereby preventing it from turning outward further to the outside of the electrode assembly 2 and affecting the diameter of the electrode assembly 2. Here, turning outward of the outer-ring tab 201 to the outside of the electrode assembly 2 means that the projection of the end of the outer-ring tab 201 away from the electrode assembly 2 onto a plane perpendicular to the Z direction exceeds the range of the end face of the electrode assembly 2.

[0072] In some embodiments, reference is made to Figure 11The second extension 32 comprises a groove fixing portion 321 and a bridging portion 322, the two ends of the bridging portion 322 are connected to the outer edge of the main body portion 30 and the groove fixing portion 321 respectively, and the groove fixing portion 321 is welded and fixed to the side of the groove 101 away from the electrode assembly 2. Since the groove fixing portion 321 is welded and fixed to the side of the groove 101 away from the electrode assembly 2, the stress of the bridging portion 322 connected to the groove fixing portion 321 towards the groove 101 is appropriate, so that the groove fixing portion 321 is better fitted with the groove 101, which is conducive to improving the operability of welding and improving the welding quality. Preferably, the bridging portion 322 is spaced apart from the first extension 31 on both adjacent sides, which is conducive to reducing the overall weight of the first current collector 3 and facilitating smooth pressure relief during thermal runaway. Although in the illustrated embodiment, the bridging portion 322 has a uniform width, in other embodiments, the bridging portion 322 can have curved side portions.

[0073] In some embodiments, the bridging portion 322 is bent in a manner that has stress deformation towards the groove 101. The stress deformation is an elastic deformation, and when the fixation of the second extension 32 to the groove 101 is released, the end of the bridging portion 322 close to the groove 101 elastically recovers in a manner of deforming away from the electrode assembly 2. In combination with the description of the assembly process above. Figure 6 When the electrode assembly 2 with the welded first current collector 3 is placed into the shell 1, the free end of the bridging portion 322 is higher than the position on the side wall 10 for forming the groove 101 in the Z direction, so that interference between the jig (such as the hob 500) for machining the groove 101 and the first current collector 3 can be avoided. Therefore, when the bridging portion 322 is not subjected to external force, the free end thereof is staggered with the groove 101 in the Z direction, and the conductive connection between the groove fixing portion 321 connected to the free end of the bridging portion 322 and the groove 101 can be achieved only by bending through external force. That is, the bridging portion 322 is bent in a manner that has stress deformation towards the groove 101, so that the groove fixing portion 321 connected to the free end of the bridging portion 322 is conductively connected to the groove 101. Since the bridging portion 322 is bent in a manner that has stress deformation towards the groove 101, when the fixation of the second extension 32 to the groove 101 is released, for example, after the bridging portion 322 conductively connected to the groove 101 is cut off, the bridging portion 322 elastically recovers in the Z direction away from the electrode assembly 2.

[0074] In some embodiments, the height of the outer ring tab 201 in the free stretching state is H1, which can be defined as the distance from the edge of the negative current collector in the electrode assembly 2 to the edge of the active material layer. As shown in Figure 10As shown, the distance between the first extension 31 and the second extension 32 in the assembled state is H2, and the value of H1 / H2 is in the range of 1.1-2. The height H1 of the outer ring tab 201 is slightly greater than H2, which can effectively prevent the outer ring tab 201 from turning outward and enable the second extension 32 to not exert pressure on the outer ring tab 201 when the assembly is completed, thereby facilitating smooth pressure relief during thermal runaway.

[0075] In some embodiments, as shown in Figure 10 As shown, the diameter d of the cylindrical battery form secondary battery 100 and the depth D of the rolling groove 101 satisfy the following numerical formula relationship: 12≤d / D≤23. The diameter d of the cylindrical battery form secondary battery 100 refers to the maximum diameter of the cross section of the cylindrical battery, which in some cases is the outer diameter of the shell 1. The depth D of the rolling groove 101 includes the thickness of the shell 1. In some embodiments, the depth D of the rolling groove 101 is less than or equal to 4 mm.

[0076] As shown in Figure 11 Each rolling groove fixing portion 321 is welded and fixed to the rolling groove 101 by a plurality of spaced-apart welding marks 4, which are straight-line welding marks 4 extending in the circumferential direction. In combination with the foregoing description of the assembly process, each rolling groove fixing portion 321 is welded and fixed to the rolling groove 101 by a plurality of spaced-apart welding marks 4, which can effectively guarantee the flow area and avoid the problem of poor welding caused by the middle point of a longer welding mark. Specifically, when a single welding mark is used, the welding mark needs to have a certain length in order to ensure the flow area. However, due to the following two reasons, the longer welding mark is prone to have a middle point that causes poor contact: on the one hand, as described above, the second extension 32 is pressed on the rolling groove 101 due to stress and has a certain elastic stress; on the other hand, the surface of the rolling groove 101 is not a complete plane and is difficult to completely match the rolling groove fixing portion 321. The plurality of shorter spaced-apart welding marks 4 provided in this embodiment can effectively avoid the problems that can be caused by a longer welding mark. Figure 8 In addition, due to the small depth D of the rolling groove 101, the main continuous contact surface between the second extension 32 and the rolling groove 101 is located in the circumferential direction. Therefore, the straight-line welding mark 4 extending in the circumferential direction helps to improve the stability of the welding. At the same time, using the straight-line welding mark 4 also helps to simplify the welding process. Specifically, if arc welding is required, the electrode assembly 2 must be rotated in coordination with the welding speed, which is difficult to operate. The straight-line welding mark 4 in this embodiment can avoid the problem of complex arc welding operation.

[0077] In summary, by using a plurality of straight-line welding marks 4, not only the welding quality is guaranteed, but also the production efficiency is significantly improved.

[0078] In some embodiments, as shown in

[0079] Figure 12 ​Each of the groove fixing portions 321 is welded and fixed to the groove 101 by a plurality of welding spots 4 spaced apart from each other, and the length L of each of the welding spots 4 satisfies 2mm≤L≤(W-(n+1)) / n mm. Wherein, W is the maximum length of each of the groove fixing portions 321 in the circumferential direction, i.e. the distance between the two end points farthest apart in the circumferential direction of the groove fixing portion 321. n is the number of welding spots 4 on each of the groove fixing portions 321. When the length L of the welding spot 4 satisfies the above formula relationship, the length L of the welding spot 4 is not too short, so that the flow area can be guaranteed, and the length L of the welding spot 4 is not too long, so that it is beneficial to avoid the occurrence of the explosion point and improve the welding quality.

[0080] Preferably, n=2, and the value range of W is 14mm-18mm. When the number of welding spots 4 on each of the groove fixing portions 321 is 2, the welding quality is better. When the number of welding spots 4 on each of the groove fixing portions 321 exceeds 2, the welding efficiency may be reduced, and the problem of unstable laser caused by too short welding length may occur. When the value range of the maximum length W of each of the groove fixing portions 321 is 14mm-18mm, it is easier to operate when welding a plurality of welding spots 4.

[0081] In the secondary battery of the optional technical scheme of the utility model, the maximum circumference of the secondary battery is C, and the value range of C / W is 7 to 11. In combination with the convenience of welding, the welding area and the shielding effect on the negative tab 20, C / W preferably adopts a value within 7 to 11. For example, when the diameter of the shell 1 of the secondary battery 100 is 46mm, C is 144.44mm, according to the preferred range of C / W, W is preferably, for example, 14mm, 15mm, 16mm, 17mm and the like.

[0082] In some embodiments, reference is made to Figure 11Each groove fixing part 321 is welded and fixed to the groove 101 using multiple spaced weld marks 4. The current collector has four first extensions 31 evenly distributed in the circumferential direction and four second extensions 32 evenly distributed in the circumferential direction. The first extensions 31 and the second extensions 32 are arranged alternately, and a gap 33 is reserved at the outer peripheral edge of each first extension 31 and each second extension 32. With the above arrangement, the current of the first extension 31 can be effectively transmitted through the second extension 32, forming a stable current path. In addition, by setting four first extensions 31 and four second extensions 32 evenly distributed in the circumferential direction, the angle between two adjacent first extensions 31 and two adjacent second extensions 32 can be 90°. This symmetry is advantageous in production. For example, since the angles of the second extensions 32 are equidistantly distributed, the secondary battery 100 can achieve precise angle control when rotating to weld another second extension 32. This simplifies the welding process and improves the consistency and stability of the welding. In addition, the reserved gap 33 can release the elastic stress of the second extension 32, avoid tearing and damage to the first collector plate 3, and avoid interference with the welding of the first extension 31 and the negative electrode tab 20.

[0083] Through the above methods, the solutions in some embodiments of this utility model can be effectively applied to cylindrical secondary batteries 100. Cylindrical batteries pursue maximum energy density and have a large group margin (the group margin is the ratio of the maximum diameter of the electrode assembly 2 to the maximum inner diameter of the housing 1; the group margin of cylindrical batteries is generally 94%-99%), resulting in a very low process window for assembling the electrode assembly 2 into the housing 1. However, by setting the first current collector 3 provided in some embodiments of this utility model, the assembly efficiency can be effectively improved, avoiding the assembly defects caused by the excessively large diameter of the electrode assembly 2.

[0084] <Battery Pack 700>

[0085] Figure 13 A schematic diagram of the battery pack 700 in this embodiment is shown. (As shown) Figure 13 As shown, the battery pack 700 includes a housing 710, a cover 720, and multiple secondary batteries 100. The multiple secondary batteries 100 are placed in the housing 710 and are connected in series, parallel, or a combination of both. The cover 720 seals the housing 710 to protect the multiple secondary batteries 100. It should be noted that the battery pack 700 may also include a thermal management system, circuit boards, etc., in addition to the secondary batteries 100. The battery pack 700 can be a battery module, a battery pack, an energy storage cabinet, etc., which will not be described in detail here.

[0086] <Electronic Devices 800>

[0087] Figure 14 A schematic diagram of the electronic device 800 in this embodiment is shown. (As shown) Figure 14 As shown, the electronic device 800 includes the aforementioned battery pack 700 and a working unit 600 electrically connected to the battery pack 700. As an example, the electronic device 800 is a vehicle, which can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, but are not limited thereto. The working unit 600 is the vehicle body, and the battery pack 700 is located at the bottom of the vehicle body, providing electrical power support for the vehicle's movement or the operation of its internal electrical components. However, in other embodiments, the electronic device 800 can also be a mobile phone, portable device, laptop computer, ship, spacecraft, electric toy, and power tool, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. The working unit 600 can be a unit component capable of obtaining electrical energy from the battery pack 700 and performing corresponding tasks, such as a fan blade rotation unit or a vacuum cleaner suction unit. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric boat toys, and electric airplane toys, etc.; power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. This application does not impose any special limitations on the aforementioned electronic device 800.

[0088] The above are merely preferred embodiments of the present utility model and are not intended to limit the present utility model. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A secondary battery characterized by comprising: The application relates to a secondary battery, comprising: a shell, which comprises a cylindrical side wall, one end of the side wall comprising an opening, the side wall being formed with a groove recessed to the inside of the shell near the opening; an electrode assembly accommodated in the shell, the groove limiting the movement of the electrode assembly in the height direction of the secondary battery in the shell, one end of the electrode assembly near the groove in the height direction having a tab, the tab being bent towards the center hole of the electrode assembly, and the tab closest to the outer edge of the electrode assembly being an outer ring tab of the electrode assembly; and a current collecting plate, which comprises a main body, a plurality of first extending parts and a plurality of second extending parts, the main body being arranged between the groove and the electrode assembly, one side surface of the main body being in conductive connection with the tab, the first extending parts being in the same plane as the main body, the first extending parts extending radially outward from the outer edge of the main body to contact the outer ring tab, one end of the second extending part being connected to the main body between two adjacent first extending parts, and the other end being in conductive connection with the groove, the outer edge of the second extending part being formed with an outer edge surface in the circumferential direction, the outer edge surface being orthogonally projected on the plane perpendicular to the height direction of the electrode assembly to form an outer edge surface projection, the outer edge surface projection overlapping at least part of each outer ring tab between two adjacent first extending parts.

2. The secondary battery according to claim 1, wherein the second extending part comprising a groove fixing part and a bridging part, the bridging part having two ends connected to the outer edge of the main body and the groove fixing part respectively, the groove fixing part being welded to the side of the groove away from the electrode assembly, and the bridging part being bent in a manner that it has stress deformation towards the groove, or the tab being a cut-and-fold tab.

3. The secondary battery according to claim 2, wherein the stress deformation being elastic deformation, when the second extending part is released from the groove, the end of the bridging part near the groove deforms in a manner that it is deformed away from the electrode assembly and elastically recovers.

4. The secondary battery according to claim 2, wherein the second extending part being in conductive connection with the groove in a welded manner, and each groove fixing part being welded to the groove by a plurality of spaced-apart welds.

5. The secondary battery according to claim 4, wherein the welds being straight-line welds extending in the circumferential direction, or the length L of each weld satisfying 2mm<=L<=(W-(n+1)) / n mm, wherein W is the maximum circumferential length of each groove fixing part, and n is the number of welds on each groove fixing part.

6. The secondary battery according to claim 5, wherein n=2, or the maximum circumference of the secondary battery being C, and the value range of C / W being 7-11.

7. The secondary battery according to claim 1, wherein the current collecting plate having four first extending parts and four second extending parts which are uniformly distributed in the circumferential direction, and the first extending parts and the second extending parts being arranged in turn and at intervals, each first extending part and each second extending part being provided with a gap at the outer peripheral edge of the main body.

8. The secondary battery according to claim 1, wherein Further comprising a cover plate for sealing the opening of the shell, the other end of the side wall comprises an end wall, the end wall is provided with a mounting hole for mounting a pole, an insulating piece is further provided between the pole and the end wall for electrically insulating the end wall and the pole, The secondary battery is a cylindrical battery, a diameter d of the cylindrical battery and a depth D of the rolling groove satisfy a numerical formula relationship: 12≤d / D≤23. The cover plate comprises an explosion-proof valve, the explosion-proof valve is an annular notch on the cover plate, or, A height of the outer ring tab is H1, a distance from the first extension to the second extension is H2, and a value range of H1 / H2 is 1.1-2.

9. A battery pack characterized by comprising: The secondary battery as claimed in any one of claims 1-8.

10. An electronic device, comprising: The battery pack as claimed in claim 9.

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