Secondary battery and electronic device

Abstract

The utility model relates to the field of batteries, and particularly provides a secondary battery and electronic equipment, when an anti-explosion valve is opened, each petal of a collector plate is easy to open, and the mutually coplanar planeness between the petals is easier to maintain. The secondary battery comprises a shell, an electrode assembly and a collector plate, the shell comprises an end wall, and an anti-explosion valve is arranged on the end wall; the electrode assembly is accommodated in the shell, and a tab is led out from one end, facing the anti-explosion valve, of the electrode assembly; the current collecting plate is welded with the tab, the current collecting plate comprises a first opening and a plurality of second openings, the first opening penetrates through the center of the current collecting plate and extends in the radial direction of the current collecting plate, the second openings are distributed in the two sides of the first opening, and the parts, close to the ends of the first opening, of the second openings and the first opening form easy-to-tear parts of the current collecting plate; and when the internal pressure of the secondary battery is increased and is released through the anti-explosion valve, the current collecting disc is torn at the easy-to-tear part and is folded in the direction far away from the electrode assembly.

Description

TECHNICAL FIELD

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

[0002] Some secondary batteries are provided with explosion-proof valves on one end wall of the battery shell. The explosion-proof valve functions to release the internal pressure when the internal pressure of the battery abnormally rises, preventing the battery from exploding. In addition, in order to effectively collect and conduct current, some secondary batteries are also provided with current collecting plates. The current collecting plate is provided in correspondence with the explosion-proof valve, and under extreme conditions when the explosion-proof valve is opened, in order to improve the pressure relief effect, some current collecting plates can be torn and folded, avoiding the pressure relief airflow and the internally flying substances, so as to reduce the obstruction to the airflow and the internally flying substances. SUMMARY

[0003] In view of the above shortcomings of the prior art, the utility model provides a secondary battery and electronic equipment, when the explosion-proof valve is opened, each petal of the current collecting plate is easy to open, and the mutual coplanarity between the petals is easier to maintain.

[0004] The utility model discloses a secondary battery provided in the first aspect, including shell, electrode assembly and current collecting plate, the shell includes end wall, and the end wall is provided with explosion-proof valve, the electrode assembly is contained in the shell, and the electrode assembly is led to have the tab of one end to the explosion-proof valve, the current collecting plate is welded with the tab, and the current collecting plate includes first aperture and a plurality of second apertures, the first aperture passes through the center of the current collecting plate and extends along the radial direction of the current collecting plate, a plurality of second apertures are distributed on both sides of the first aperture, and the part between the end of the second aperture close to the first aperture and the first aperture constitutes the easy tearing part of the current collecting plate, when the internal pressure of the secondary battery increases and is relieved through the explosion-proof valve, the current collecting plate tears at the easy tearing part and is folded in the direction away from the electrode assembly.

[0005] According to the technical scheme, each petal of the current collecting plate only needs to tear one or two easy tearing parts to be freely folded, reducing the number of easy tearing parts needed to be torn for the free folding of one petal, so that each petal is more easy to open under the impact of the pressure relief airflow. In addition, because the petals of the current collecting plate are connected with each other in the middle part of the current collecting plate, the coplanarity between the petals can be maintained by the connection of the middle part during the processing and transportation, and when the current collecting plate and the tab are welded, the two can be firmly welded and fixed, avoiding the generation of the problem of false welding.

[0006] Optionally, the current collecting plate has two second apertures extending along the radial direction of the current collecting plate, and the first aperture and the second aperture divide the current collecting plate into four circumferential regions that can be independently folded. According to the technical scheme, only one easy tearing part needs to be torn, and the rapid folding of two petals of the current collecting plate, nearly half the area, can be completed, further improving the simplicity and response speed of tearing and folding each petal, and making the pressure relief airflow channel more unobstructed.

[0007] Optionally, the manifold has four second openings extending radially along its surface, dividing it into six independently foldable circumferential regions. In some designs, the folding capability of each segment of the manifold is limited by the opening size of the explosion-proof valve. As the manifold is divided into more segments circumferentially, the folding angle of each segment increases, thus better maintaining the unobstructed pressure relief channel. Simultaneously, the number of second openings should not be excessive. Too many openings increase the average number of tearable portions required to fold each segment, and also make the manifold difficult to manufacture. Therefore, evenly distributing four second openings is a preferred solution.

[0008] Optionally, the first opening has a central hole at a position corresponding to the center of the collector plate, and the central hole has multiple corners, which are respectively positioned towards the ends of multiple second openings near the first opening. According to this technical solution, the corners can increase stress concentration at these locations, making the tearable portion easier to tear, and the tearing pattern is more likely to follow the line direction connecting the central hole to the end of the second opening.

[0009] Optionally, the largest distance between the outer edges of the multiple corners of the central hole is the radial dimension d1 of the central hole, where d1 ≥ 8 mm. Specifically, the opening angle of the multiple corners of the central hole is θ, where 45° ≤ θ ≤ 90°. Due to the presence of sharp corners, the mold used to process this type of manifold is prone to edge wear and breakage during processing. According to this technical solution, when the radial dimension d1 of the central hole ≥ 8 mm and the opening angle θ of the corners satisfies 45° ≤ θ ≤ 90°, the service life of the mold used to process the manifold can be effectively improved, avoiding the increase of foreign matter caused by mold wear.

[0010] Optionally, the electrode assembly includes a central hole with a diameter of d2. The radial dimension of the central hole is d1, where d1 > d2, and the largest distance between the outer edges of the multiple corners is taken as the radial dimension of the central hole. According to this technical solution, the central hole of the electrode assembly typically serves as a channel for depressurized airflow, while substances such as electrolyte and particulate matter are mainly ejected from the outer periphery of the channel. By configuring d1 > d2, substances such as electrolyte and particulate matter can directly impact the corners, increasing the impact force on the corners and making the tear-resistant portion easier to tear from the corners.

[0011] Optionally, multiple weld marks are formed between the current collector and the tab, with each weld mark having a width W ≤ 1 mm. According to this technical solution, when tab peeling occurs, a single weld mark width W ≤ 1 mm can reduce the peeling force required in the initial stage of peeling. Furthermore, as the peeling process progresses, the increase in peeling force is more gradual due to the smaller width of the single weld mark, allowing the peeling process to proceed progressively.

[0012] Optionally, multiple weld marks, including multiple straight weld marks, are formed between the current collector and the tab. According to this technical solution, the straight weld marks reduce the peeling force required in the initial stage of folding and tab removal, requiring only the peeling of the end of the straight weld mark. Furthermore, the line width of the straight weld mark remains almost unchanged during the peeling process, and the magnitude of the peeling force also remains essentially constant. By combining multiple straight weld marks, while ensuring welding reliability, a gradual gradient of peeling force from small to large can be achieved during the peeling process, making it easier for the peeling process to proceed in the expected direction.

[0013] Optionally, the outline of the solder group is formed by the lines connecting the solder marks and their ends, and the outline has an angle close to and facing the center of the collector plate. Further, the first and second openings divide the collector plate into multiple circumferential regions along the circumferential direction. Multiple straight solder marks are divided into multiple solder group groups according to their respective circumferential regions. Each solder group includes a central solder mark and multiple side solder marks. The central solder mark is centrally located in the circumferential region, and the side solder marks are symmetrically distributed on both sides of the central solder mark. According to this technical solution, this symmetrically arranged solder group ensures that the peeling force required to resist the folding of each lobe (i.e., each circumferential region) of the collector plate is symmetrical, thereby guiding the folding direction of each lobe, causing each lobe of the collector plate to tend to fold along the extension direction of the central solder mark.

[0014] Optionally, in each solder joint, the end of the central solder joint is closest to the center hole of the manifold compared to the side solder joints, and the length d3 of the central solder joint is ≥10mm. According to this technical solution, by configuring the end of the central solder joint to be closest to the center hole of the manifold, since the folding process of each segment typically begins with peeling and folding near the center hole, when folding begins, only the welded fixation at the end of the central solder joint needs to be peeled off, resulting in a smaller initial peeling force required to initiate folding. Furthermore, configuring the length d3 of the central solder joint to d3≥10mm reduces internal resistance.

[0015] Optionally, each solder group includes multiple side solders spaced at different intervals from the central solder, with the side solders further away from the central solder being further from the central hole. According to this technical solution, during the folding and peeling of each tab, on the one hand, due to the guidance of the symmetrical structure, the folding and peeling process tends to proceed along the central axis; on the other hand, as the folding and peeling of the tab proceeds along the central axis, it will sequentially peel to the position where new side solders need to be peeled, thus making the peeling force required for the folding and peeling process gradually increase rather than abruptly increase, making the folding and peeling process easier to advance gradually.

[0016] Optionally, the capacity of the secondary battery is G Ah, and the total area of ​​the solder joint is S, where S ≥ G / 8 mm. 2 According to this technical solution, the larger the solder area, the larger the area of ​​the current-conducting portion between the current collector and the electrode, thereby reducing the contact resistance.

[0017] Optionally, the projection surface of the explosion-proof valve on the manifold along the height direction of the secondary battery is the projection range of the explosion-proof valve, and both the first opening and the second opening extend radially outward along the manifold to the outside of the projection range of the explosion-proof valve. According to this technical solution, configuring the first opening and the second opening to extend to the outside of the projection range of the explosion-proof valve can make full use of the area of ​​the explosion-proof valve as a pressure relief channel, thereby increasing the cross-sectional size of the pressure relief channel.

[0018] Optionally, the collector plate also has a positioning hole. Further, the positioning hole is located at the outer end of the second opening along the radial direction of the collector plate.

[0019] The second aspect of this invention provides an electronic device having a secondary battery as described in the first aspect of this invention. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the negative electrode current collector used in cylindrical batteries.

[0021] Figure 2 This is a schematic diagram of the structure of a secondary battery provided in some embodiments of this utility model.

[0022] Figure 3 The stacked structure of the electrode assembly provided in some embodiments of the present invention is shown.

[0023] Figure 4 This is a schematic diagram (front view) of the negative electrode current collector of the secondary battery provided in the first embodiment of this utility model.

[0024] Figure 5 This is a schematic diagram (front view) of the negative electrode current collector of the secondary battery provided in the second embodiment of this utility model.

[0025] Figure 6 This is a schematic diagram (front view) of the negative electrode current collector of the secondary battery provided in the third embodiment of this utility model.

[0026] Figure 7 This is a schematic diagram illustrating the physical quantity represented by the width W of the solder mark in some embodiments of this utility model.

[0027] Figure 8 This is a schematic diagram of the electronic device in an embodiment of this utility model.

[0028] Figure label:

[0029] 1002 - Petal; 1004 - Weight Reduction Hole; 1006 - Easy-Tear Section; 102 - First Opening; 104 - Second Opening; 106 - Petal; 108 - Easy-Tear Section; 110 - Circumferential Area; 112 - Welding Mark Group; 114 - Central Welding Mark; 116 - Side Welding Mark; 118 - First Side Welding Mark; 120 - Second Side Welding Mark; 122 - Center Hole; 124 - Corner; 126 - Positioning Hole; 128 - Explosion-proof Valve Projection Range; 130 - Shaded Area; 132 - Outline of Welding Mark Group; 200 - Working Section; 300 - Battery Pack; 400 - Electronic Equipment; 500 - Secondary Battery; 600 - Housing; 602 - Outer Can; 604 - Cover Plate; 6 06-Positive electrode post hole; 608-End plate; 610-Groove; 700-Electrode assembly; 702-Positive electrode sheet; 704-Negative electrode sheet; 706-Separator; 708-Coated area; 710-Uncoated area; 712-Center hole of electrode assembly; 714-Positive electrode tab; 716-Negative electrode tab; 800-Positive assembly; 802-Insulating seal; 804-Positive electrode post; 806-Positive current collector; 810-Electrode post body; 812-Upper flange; 814-Lower flange; 816-Upper insulating component; 818-Lower insulating component; 900-Negative assembly; 902 / 902A / 902B / 902C-Negative current collector; 904-Explosion-proof valve. Detailed Implementation

[0030] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0031] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in this invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention, as well as the prior art known to those skilled in the art and the description of this invention, may be implemented using any prior art methods, devices, and materials similar to or equivalent to those described, used, or made of materials in the embodiments of this invention.

[0032] <Terminology and its explanation>

[0033] The terms such as "upper", "lower", "left", "right", "middle" and "one" used in this specification are only for clarity of description and are not intended to limit the scope of implementation of this utility model. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered as within the scope of implementation of this utility model.

[0034] The term "tearable area" refers to a region that is relatively weaker than the surrounding area and is prone to stress concentration and tearing.

[0035] The terms "radial," "circumferential," etc., are relative to the axis of the object being described, and are not used to restrict the object to being circular. For example, for a slender object with an elliptical cross-section, the so-called "axis" is the line connecting the intersections of the major and minor axes of each elliptical cross-section; for a slender object with a rectangular cross-section, the so-called "axis" is the line connecting the intersections of the diagonals of each rectangular cross-section.

[0036] The term "petal" refers to an independently foldable and openable unit of the manifold, and in some implementations, it can be equated to a "circumferential region" of the manifold.

[0037] Figure 1 This is a schematic diagram of a collector plate. (Reference) Figure 1The collector plate includes four circumferentially distributed, foldable flaps 1002, connected by tearable sections 1006 that easily generate stress concentration. Weight-reducing holes 1004 are also present between the flaps. However, this structure requires tearing four tearable sections 1006 to allow one flap 1002 to fold, making it difficult to completely tear and fold all four flaps. Furthermore, the weight-reducing holes 1004 on the collector plate weaken the impact force that causes each flap 1002 to fold, making some flaps even more difficult to fold open. Moreover, due to the uncertainty of the accident location causing extreme conditions, the pressure relief airflow does not flow strictly along the central axis; correspondingly, the main stress-bearing parts of the collector plate may deviate to some extent from the central axis. In this situation, it is more likely that some of the valves 1002 will open, while others will fail to open due to insufficient force, thus obstructing the depressurization airflow.

[0038] Another type of manifold also exists, which also contains foldable lobes, but the lobes are not fixed to each other. Although each lobe of this type of manifold does not need to be torn before folding, it is difficult to maintain the flatness between the lobes during processing and transportation because the lobes are not fixed to each other, which is not conducive to processing, especially and can easily lead to the problem of incomplete welding during the welding process.

[0039] Secondary batteries

[0040] A schematic diagram of the structure of the secondary battery 500 provided in some embodiments of this utility model is shown below. Figure 2 As shown, the secondary battery 500 can be, for example, a cylindrical battery, mainly including a casing 600, an electrode assembly 700, a positive electrode assembly 800, and a negative electrode assembly 900. The electrode assembly 700 is disposed inside the casing 600. The positive electrode assembly 800 is disposed in the upper middle part of the casing 600 and is electrically isolated from the casing 600 by an insulating seal 802. The negative electrode assembly 900 is disposed at the lower end of the casing 600 and is electrically connected to the casing 600.

[0041] The following sections will introduce the structure, materials, and functional characteristics of each component of the secondary battery 500 in some embodiments of this utility model.

[0042] <Shell>

[0043] The housing 600 is shaped to effectively house the wound electrode assembly 700, for example, it is cylindrical. The housing 600 can be made of metal, such as steel or aluminum, which have good thermal conductivity. Steel is preferred because a steel housing 600 has good strength, can effectively suppress cell expansion, and is more suitable for high-energy systems such as silicon-carbon anode systems. Furthermore, the secondary battery 500 itself can serve as a structural support.

[0044] The casing 600 includes an outer can 602 and a cover plate 604. The outer can 602 is a cylindrical can with an integrally formed or connected end plate 608 at the top. A positive electrode post hole 606 is opened in the center of the end plate 608. The positive electrode assembly 800, including the positive electrode post 804, passes through the positive electrode post hole 606 and protrudes from the top of the cylindrical can. The bottom of the outer can 602 is sealed by the cover plate 604. Specifically, after the electrode assembly 700 is placed into the outer can 602, a negative electrode assembly 900 is provided at the other end of the outer can 602, electrolyte is injected, the cover plate 604 is installed and sealed, resulting in a secondary battery 500.

[0045] The specific dimensions of the outer can 602 can be determined based on the dimensions of the electrode assembly 700. For example, it can be an outer can 602 with a diameter of 46mm or more and a height of 80mm or more. The thickness of the outer can 602 can be 0.2-0.6mm, and the surface can be nickel-plated for corrosion and rust prevention.

[0046] After the electrode assembly 700 is placed into the outer can 602, a groove 610 can be made around the housing 600 near the opening of the outer can 602 using a hobbing cutter. The groove 610 is recessed into the side wall surface of the outer can 602, which can restrict the position of the electrode assembly 700 and prevent the electrode assembly 700 from moving in the height direction Z of the secondary battery 500.

[0047] <Electrode Assembly>

[0048] refer to Figure 3 The electrode assembly 700 of the cylindrical battery cell is manufactured by winding. Specifically, the positive electrode 702, the negative electrode 704, and the separator 706 are overlapped and wound to form a core. The separator 706 is disposed between the positive electrode 702 and the negative electrode 704 to prevent direct contact between them and thus a short circuit. Both the positive electrode 702 and the negative electrode 704 include a substrate formed of metal foil, a coated area 708 coated with active material, and an uncoated area 710 without active material. The substrate of the positive electrode 702 is aluminum foil, and the main body, i.e., the lower part of the substrate, is coated with positive active material. The substrate of the negative electrode 704 is copper foil, and the main body, i.e., the upper part of the substrate, is coated with negative active material. The uncoated areas 710 of the positive electrode 702 and the negative electrode 704 are located at opposite ends to prevent contact between them from causing a short circuit between the positive and negative electrodes. It should be noted that...Figure 3 As an example only, in other embodiments of the present invention, the uncoated area 710 of the positive electrode 702 may be disposed at the bottom of the electrode assembly 700, while the uncoated area 710 of the negative electrode 704 may be disposed at the top of the electrode assembly 700. The present invention does not limit this.

[0049] The top of the positive electrode 702 is not coated with active material and is used as a positive electrode tab 714 for electrical connection; the bottom of the negative electrode 704 is not coated with active material and is used as a negative electrode tab 716 for electrical connection. In some embodiments, the metal foil substrate of the uncoated area 710 can be cut into multiple flag electrodes (not shown in the figure), which are folded toward the center hole 712 of the electrode assembly 700 and then soldered to the current collector.

[0050] The core has a center hole 712 for the electrode assembly, which is the location of the center roller during the core manufacturing process. After the core is manufactured, the center roller is removed, leaving the center hole 712 for the electrode assembly. The center hole 712 allows the welding rod to pass through during the welding of the positive electrode post 804 and the positive electrode current collector 806, and also provides a channel for the depressurization of the generated gas in the event of thermal failure.

[0051] An electrolyte is also injected into the chamber of the housing 600 for accommodating the electrode assembly 700. The electrolyte is a non-aqueous electrolyte comprising a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. For the non-aqueous solvent, esters, ethers, nitriles, amides, and mixtures of two or more of these solvents can also be used. The non-aqueous solvent may also contain a halogen substitute obtained by replacing at least a portion of the hydrogen atoms of these solvents with halogen atoms such as fluorine. Furthermore, the non-aqueous electrolyte is not limited to a liquid electrolyte and can also be a solid electrolyte using a gel polymer, etc. For the electrolyte salt, lithium salts such as LiPF6 can be used. Examples of non-aqueous solvents include propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone, methyl ethyl carbonate, γ-butyrolactone, or mixtures thereof.

[0052] The positive electrode active material is mainly composed of lithium-containing metal composite oxides. Examples of metal elements contained in these lithium-containing metal composite oxides include Ni, Co, Mn, Al, B, Mg, Ti, V, Cr, Fe, Cu, Zn, Ga, Sr, Zr, Nb, In, Sn, Ta, and W. A preferred example of a lithium-containing metal composite oxide is one containing at least one of Ni, Co, Mn, and Al. The positive electrode active material can be, for example, lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide.

[0053] The positive electrode active material also includes conductive agents and binders. Conductive agents can be carbon materials such as carbon black, acetylene black, Ketjen black, and graphite. Binders can be fluoropolymers such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyimide, acrylic resin, and polyolefins. These resins can also be used in combination with cellulose derivatives such as carboxymethyl cellulose (CMC) or its salts, and polyethylene oxide (PEO).

[0054] The negative electrode active material uses a carbon material capable of reversibly absorbing and releasing lithium ions. Preferred carbon materials include natural graphite such as flake graphite, block graphite, and amorphous graphite, as well as artificial graphite such as block graphite and graphitized mesophase carbon microspheres. The negative electrode active material may also contain a Si-containing compound. Furthermore, the negative electrode active material may also use a lithium alloyed with a metal other than Si, an alloy containing that metal, or a compound containing that metal.

[0055] The binder used in the negative electrode active material can be the same as that used in the positive electrode active material, such as fluoropolymers, polyacrylonitrile, polyimide resins, acrylic resins, polyolefin resins, etc., with styrene-butadiene rubber (SBR) or its modifiers being preferred. In addition to SBR, the negative electrode active material may also contain carboxymethyl cellulose or its salts, polyacrylic acid (PAA) or its salts, polyvinyl alcohol, etc.

[0056] The diaphragm 706 uses a porous sheet material with ion permeability and insulation. The porous sheet material can be a porous film, woven fabric, non-woven fabric, etc. The preferred materials for the diaphragm 706 are polyethylene, polypropylene, or other olefin resins, cellulose, etc. The diaphragm 706 can be a single-layer structure or a laminated structure. A heat-resistant layer can also be formed on the surface of the diaphragm 706.

[0057] <Positive electrode assembly>

[0058] The positive electrode assembly 800 includes a positive electrode post 804, an insulating seal 802, and a positive electrode current collector 806.

[0059] The positive electrode post 804 is typically fixed to the positive electrode post hole 606 in the housing 600 by riveting. The riveting method can be that the post extends into the inside of the housing 600 and is riveted on the inside of the housing 600; or it can extend out of the inside of the housing 600 and be riveted on the outside of the housing 600. The positive electrode post 804 is generally made of aluminum.

[0060] The positive electrode post 804 includes a post body 810, an upper flange 812, and a lower flange 814. The upper flange 812 is located at one end of the post body 810, and the lower flange 814 is located at the other end of the post body 810. Both the upper flange 812 and the lower flange 814 protrude radially outward from the post body 810. In some embodiments, the housing 600 is electrically connected to the negative electrode of the electrode assembly 700. To electrically isolate the positive electrode post 804 from the housing 600, an insulating seal 802 is also provided. The insulating seal 802 includes an upper insulating member 816, a lower insulating member 818, and a sealing ring 820. The upper insulating member 816 is disposed between the upper flange 812 and the end plate 608 of the housing 600. The lower insulating member 818 is disposed between the end plate 608 of the housing 600 and the lower flange 814 or the positive electrode tab 714. The sealing ring 820 is disposed between the end plate 608 and the positive electrode post 804.

[0061] Each positive electrode tab 714 of the electrode assembly 700 is welded to the positive electrode current collector 806, and the positive electrode current collector 806 is welded and fixed to the positive electrode post 804, so that the current is transmitted to the positive electrode post 804 after being combined through the current collector.

[0062] <Negative electrode assembly>

[0063] The negative electrode assembly 900 includes at least a negative electrode current collector 902 and an explosion-proof valve 904 integrally formed on the cover plate 604. In some embodiments of this invention, the negative electrode tab 716 of the electrode assembly 700 is welded to the negative electrode current collector 902, and the negative electrode current collector 902 is welded and fixed to the groove 610 portion of the housing 600, thereby enabling the negative electrode of the electrode assembly 700 and the housing 600 to conduct electricity. In other embodiments of this invention, the negative electrode current collector 902 can also be directly welded and fixed to the cover plate 604.

[0064] The cover plate 604 can be designed with a weak point to function as an explosion-proof valve 904. In some embodiments of this invention, the explosion-proof valve 904 is located in the center of the cover plate 604 at the negative terminal. Specifically, the explosion-proof valve 904 can be obtained in a circular or other suitable shape by stamping or subtractive processing, such as by creating a groove or through hole in the circumferential direction of the cover plate 604. The explosion-proof valve 904 can open to release pressure when the internal pressure rises sharply, preventing the battery from exploding.

[0065] <First Implementation Method>

[0066] In the secondary battery provided in this embodiment, its negative electrode current collector 902A is configured as follows: Figure 4 The structure shown.

[0067] In the first embodiment of this utility model, the negative electrode current collector 902A is circular and includes a first opening 102 and two second openings 104.

[0068] The first opening 102 is a straight opening extending radially along the circular negative electrode current collector 902A. The length of the first opening 102 is slightly smaller than the diameter of the negative electrode current collector 902A. In other words, the two ends of the first opening 102 are adjacent to the outer edge of the negative electrode current collector 902A but still separated by a certain distance. The second opening 104 is also a straight opening. The two second openings 104 also extend radially along the negative electrode current collector 902A and are evenly distributed on both sides of the first opening 102. The extension direction of the second openings 104 is perpendicular to the first opening 102. One first opening 102 and two second openings 104 evenly divide the negative electrode current collector 902A circumferentially into four lobes 106, each with a circumferential angle of 90°. In the center of the negative electrode current collector 902A, the part of the second opening 104 near the end of the first opening 102 and between the second opening 104 and the first opening 102 constitutes the tear-off part 108 of the negative electrode current collector 902A, and the two petals 106 located on the same side of the first opening 102 are connected to each other by the tear-off part 108.

[0069] It should be noted that although the first opening 102 and the second opening 104 are straight openings in this embodiment, it is not limited to this. In other embodiments of this utility model, the first opening 102 and the second opening 104 can also be openings in the form of broken lines or curves, and correspondingly, their extension direction is the approximate extension direction of the broken line or curve.

[0070] When the internal pressure of the secondary battery 500 increases and is released through the explosion-proof valve 904, the negative electrode current collector 902A tears at the tear-resistant part 108 and folds away from the electrode assembly 700, i.e., towards... Figure 2 The lower part of the negative electrode current collector 902A is folded down. Each negative electrode current collector 902A provided in this embodiment has only two tear-resistant portions 108. Tearing either of the two tear-resistant portions 108 can fold down two petals 106 of the negative electrode current collector 902A (equivalent to opening nearly half the area of ​​the negative electrode current collector 902A). After both tear-resistant portions 108 are torn, all four petals 106 can be folded down. In other words, in this embodiment, the average number of tear-resistant portions 108 required to fold down each petal 106 is 0.5. Compared to the prior art, which requires tearing four tear-resistant portions to fold down one petal, the negative electrode current collector 902A provided in this embodiment effectively reduces the number of tear-resistant portions 108 required to fold down each petal 106, making each petal 106 easier to open under the impact of the depressurized airflow. Furthermore, since the segments 106 of the negative electrode current collector 902A are connected to each other in the middle of the negative electrode current collector 902A by the easy-tear portion 108, the flatness of the coplanarity between the segments 106 can still be maintained by the easy-tear portion 108 during processing and transportation. Thus, when welding the negative electrode current collector 902A and the negative electrode tab 716, the two can still be firmly welded and fixed, avoiding the problem of poor welding.

[0071] It should be noted that in this embodiment, the end of the second opening 104 near the first opening 102 has a neatly cut square corner. However, this invention is not limited to this. In other embodiments of this invention, the end of the second opening 104 near the first opening 102 can also have various other shapes to adapt to different battery design requirements and pressure relief requirements. For example, in some embodiments, the end of the second opening 104 near the first opening 102 can also be configured as a rounded corner or a sharp corner facing the center of the negative electrode current collector 902A.

[0072] Continue to refer to Figure 4 In this embodiment, the negative electrode current collector 902A is evenly divided into four petals 106 by the first opening 102 and the second opening 104, which are four circumferentially distributed regions 110. The negative electrode current collector 902A is fixed to the negative electrode tab 716 by at least a plurality of straight solder marks. The plurality of straight solder marks are also divided into four solder mark groups 112. Each solder mark group 112 includes a central solder mark 114 and a plurality of side solder marks 116. Among them, the central solder mark 114 is the longest in the solder mark group 112 and is centrally located in the center of each petal 106. The side solder marks 116 are symmetrically distributed on both sides of the central solder mark 114. Here, "centrally located" means located in the middle of the circumferential region 110 along the circumferential direction of the negative electrode current collector 902A. In other embodiments, in each solder mark group 112, there may be two or more central solder marks 114. Specifically, in this embodiment, each petal 106 is a fan-shaped area occupying a 90° circumferential angle. The central solder mark 114 is centrally located and extends radially, further dividing each petal 106 into two fan-shaped areas with 45° circumferential angles. Two side solder marks 116 are provided on each side of the central solder mark 114. Each side solder mark 116 is parallel to the central solder mark 114 and is substantially equidistant, thereby improving the uniformity of the welding distribution and enhancing the integrity and reliability of the negative electrode tab 716 welding. Moreover, during the folding process of each petal 106, this symmetrically arranged solder mark group 112 can provide a symmetrical peeling force distribution, which can guide the folding direction of each petal 106, causing each petal 106 to tend to fold along the extension direction of the central solder mark 114.

[0073] By making the central solder mark 114 the longest, specifically, by configuring the radially inner end of the central solder mark 114 to be closer to the center of the negative electrode current collector 902A than the inner end of the side solder marks 116, the magnitude of the initial peeling force required to initiate the folding of each petal 106 can be reduced. Specifically, since the folding process of each petal 106 usually begins with the tearing and folding of the easy-tear portion 108, that is, the folding usually begins at the center of the negative electrode current collector 902A, when the folding begins, because the distances of the central solder mark 114 and the side solder mark 116 from the center of the negative electrode current collector 902A are gradient, the initiation of the folding of each petal 106 does not need to resist the bonding force of multiple solder marks, but only needs to resist or break the bonding force of the radially inner end of the central solder mark 114, thereby greatly reducing the magnitude of the initial peeling force required to initiate the folding. More preferably, the length d3 of the middle solder mark 114 is configured to be d3≥10mm. This preferred length range of the middle solder mark 114 can also increase the number of turns of the negative electrode tab 716 welded to the negative electrode current collector 902A, and reduce the internal resistance of the secondary battery.

[0074] Similarly, continue to refer to Figure 4 The outline 132 of the solder group is formed by connecting the solder stamps (including the middle solder stamp 114 and the side solder stamp 116) and the ends of the solder stamps in the solder stamp group 112. The outline 132 has an angle close to and towards the center of the negative electrode current collector 902A, i.e. Figure 4 The upper right corner of the outline 132 of the solder joint. In this way, the bonding force required to initiate the folding of each petal 106 is smaller, thereby reducing the magnitude of the initial peeling force required to initiate the folding and making the increase of peeling force more gradual.

[0075] The side solder marks 116 include a first side solder mark 118 and a second side solder mark 120. Compared to the second side solder mark 120, the first side solder mark 118 is closer to the center solder mark 114. Compared to the second side solder mark 120, the radially inner end of the first side solder mark 118 is closer to the center of the negative electrode current collector 902A. In other words, among the multiple side solder marks 116, the side solder mark 116 further away from the center solder mark 114 is also farther from the center of the current collector 902A. Through the above methods, on the one hand, guided by the symmetrical structure of the solder stamp group 112, the folding and peeling process of the petal 106 tends to proceed along the direction of the central solder stamp 114. On the other hand, when being guided to peel along the direction of the central solder stamp 114, because the distances from different side solder stamps 116 to the center of the negative electrode current collector 902A have a gradient, the peeling edge will move sequentially to different positions where new side solder stamps 116 need to be peeled off. After the folding begins, the folded part of the negative electrode current collector 902A can obtain the kinetic energy to fold outward, which can overcome the gradually increasing peeling force.

[0076] In this embodiment, both the central weld mark 114 and the side weld mark 116 are straight weld marks, with a width W ≤ 1 mm for each straight weld mark. By using straight weld marks within this width range, the peeling force required in the initial stage of peeling is reduced. Furthermore, as the peeling process progresses, because the weld mark width is small, the increase in peeling force is also smaller each time the leading edge of the peeling area moves to a new weld mark, facilitating a gradual advancement of the peeling process. In addition, because the line width of the straight weld mark remains essentially constant, the magnitude of the peeling force contributed by a single weld mark during the peeling process remains essentially constant. Therefore, by using multiple straight weld marks in combination, while maintaining welding reliability, a smooth gradient of peeling force from small to large can be created during the peeling process, making it easier for the peeling process to proceed in the expected direction.

[0077] In accordance with the above methods, when the explosion-proof valve 904 is opened, the secondary battery 500 provided in this embodiment can fully open its four petals 106 by simply tearing two easy-tear sections 108. Furthermore, the process of tearing, folding, and peeling off the negative electrode tab 716 is smoother and more efficient, thereby reliably and efficiently releasing pressure when the secondary battery 500 faces extreme conditions.

[0078] <Second Implementation Method>

[0079] Figure 5 This is a schematic diagram of the negative electrode current collector 902B of the secondary battery 500 provided in the second embodiment of this utility model.

[0080] refer to Figure 5 The main difference between the structure of the negative electrode current collector 902B provided in the second embodiment and the structure of the negative electrode current collector 902A provided in the first embodiment is that, in the second embodiment, the first opening 102 has a central hole 122 at a position corresponding to the center of the negative electrode current collector 902B. The central hole 122 has two corner portions 124, which are respectively positioned towards the ends of the two second openings 104 near the first opening 102. By providing the corner portions 124, the stress concentration at the tear initiation end of the easy-tear portion 108 (i.e., the radially inner end of the easy-tear portion 108) can be increased, making the easy-tear portion 108 easier to tear. Furthermore, the corner portions 124 make the tearing pattern of the easy-tear portion 108 more inclined to follow the line direction connecting the central hole 122 to the end of the second opening 104.

[0081] The distance between the lines connecting the two corners 124 is the radial dimension d1 of the central hole 122. In this embodiment, the radial dimension d1 of the central hole 122 is ≥ 8 mm. Due to the presence of the sharp corners 124, the mold used to process this negative electrode current collector 902B is prone to edge wear and breakage during processing. By configuring the radial dimension d1 of the central hole 122 to ≥ 8 mm, the service life of the mold used to process the negative electrode current collector 902B can be effectively improved, and the increase of foreign matter caused by mold wear can be avoided.

[0082] In this embodiment, the opening angle θ of the corner 124 is 90°. In some embodiments of this invention, the opening angle θ of the corner 124 can also be other reasonable values ​​that satisfy the following condition: 45°≤θ≤90°. The opening angle of the corner 124 should not be too large or too small. If the corner 124 is too large, it is difficult to concentrate stress; if the corner 124 is too small, it is not convenient to process. The corner 124 within the above range can balance stress concentration and processing feasibility.

[0083] Furthermore, in this embodiment, a positioning hole 126 is also provided at the radially outer end of the second opening 104. Since the negative electrode current collector 902B provided in this embodiment has a relatively centrally symmetrical and axially symmetrical structure, by providing the positioning hole 126 at the radially outer end of the second opening 104, it can be integrally machined with the second opening 104, making processing more convenient. On the other hand, the positioning hole 126 can assist in positioning during welding, improving the positioning effect during the welding of the negative electrode tab 716 and the negative electrode current collector 902B. In some embodiments, the positioning hole 126 can also be a positioning hole 126 that facilitates pallet positioning of the negative electrode current collector 902B during transportation, or it can have both positioning functions during welding and transportation. Additionally, in this embodiment, the positioning hole 126 is described as being located at the outer end of the second opening 104 along the radial direction of the negative electrode current collector 902B. In other embodiments, the positioning hole 126 can also be located at other reasonable positions on the negative electrode current collector 902B, and this invention does not impose any limitations on this.

[0084] In this embodiment, corresponding to the corner 124, the end of the second opening 104 near the first opening 102 has a pointed angle opposite to the corner 124. The pointed angle can increase the stress concentration of the easy-tear portion 108, further guide the tearing direction of the easy-tear portion 108, and make the easy-tear portion 108 easier to tear.

[0085] In the above manner, the negative electrode current collector 902B provided in the second embodiment is provided with a central hole 122 having a corner 124. By utilizing the characteristic that the corner 124 can concentrate stress, the easy-tear portion 108 is made easier to tear and can guide the tearing direction.

[0086] <Third Implementation Method>

[0087] Figure 6 This is a schematic diagram (front view) of the negative electrode current collector 902C of the secondary battery provided in the third embodiment of this utility model.

[0088] refer to Figure 6 The main difference between the structure of the negative electrode current collector 902C provided in the third embodiment and the structures of the negative electrode current collector 902C provided in the first and second embodiments is that: in the third embodiment, the negative electrode current collector 902C has four second openings 104 extending in the radial direction of the negative electrode current collector 902C, the included angle between the second openings 104 is 60°, the included angle between the first opening 102 and the second opening 104 is also 60°, the first opening 102 and the second opening 104 together divide the negative electrode current collector 902C into 6 circumferential regions along the circumference, that is, 6 petals 106 that can be independently folded and separated from the negative electrode tab 716 after the easy-tear portion 108 is completely torn.

[0089] The explosion-proof valve 904 is obtained by making a circular notch or groove in the center of the cover plate 604 (or end wall). The projection surface of the explosion-proof valve 904 along the Z direction on the negative electrode manifold 902C is the explosion-proof valve projection range 128, i.e. Figure 6 The area is indicated by the dashed line. In this embodiment, the outer ends of the first opening 102 and the second opening 104 in the radial direction both extend beyond the projection range 128 of the explosion-proof valve. In other words, the first opening 102 and the second opening 104 both extend radially outward to the outside of the projection range 128 of the explosion-proof valve, thereby maximizing the use of the area of ​​the explosion-proof valve 904 as a pressure relief channel and increasing the cross-sectional size of the pressure relief channel.

[0090] On the other hand, because both the first opening 102 and the second opening 104 extend radially outward to the outside of the explosion-proof valve's projected area 128, the maximum opening angle / area when all six petals 106 are open is limited by the edge of the explosion-proof valve 904. Figure 6 Taking the left-side lobe 106 as an example, the maximum opening area of ​​each lobe 106 is actually... Figure 6The area shown in the shaded portion 130. Compared to the first and second embodiments where it is divided into 4 lobes 106, although the arc length of each lobe 106 decreases after being divided into 6 lobes 106, the proportion of the sum of the maximum opening areas of all lobes 106 to the area of ​​the explosion-proof valve projection range 128 is actually larger. Although in other embodiments the number of lobes 106 can be further greater than 6, as the number of lobes 106 increases, the processing difficulty of the manifold increases significantly, while the increase in the sum of the maximum opening areas is not very significant. Moreover, the average number of tearable portions 108 required to fold each lobe 106 will also increase accordingly. Therefore, it is more preferable that the number of lobes 106 is 4 or 6, and the corresponding number of second openings 104 is 2 or 4.

[0091] In this embodiment, the electrode assembly 700 has a central hole 712, the diameter of which is d2. Figure 6 In this embodiment, corresponding to the number of second openings 104, the number of corner portions 124 of the central hole 122 is also four. The distance between the outer edges of the two furthest corner portions 124 (i.e., two non-adjacent corner portions 124) is the radial dimension d1 of the central hole 122, where d1 > d2. Under extreme conditions, when the explosion-proof valve 904 is opened, the central hole 712 of the electrode assembly typically serves primarily as a channel for depressurized airflow, while the material flow containing electrolyte, particulate matter, and other substances is mainly ejected from the outer periphery of the airflow channel. The impact force of the material flow is typically greater than that of the airflow. By configuring d1 to be greater than d2, the material flow can directly impact the corner portions 124, increasing the impact force on the corner portions 124 and making the tear-resistant portion 108 easier to tear from the corner portions 124.

[0092] Furthermore, in this embodiment, in each solder group 112, a side solder group 116 is symmetrically arranged on both sides of the central solder group 114. The extension direction of the side solder group 116 is inclined to the central solder group 114 and parallel to the first opening 102 or the second opening 104 adjacent to the side solder group 116, thereby arranging the side solder groups 116 more evenly and improving the uniformity of solder distribution.

[0093] Through the above methods, the third embodiment of this utility model provides a negative electrode current collector 902C with a larger sum of maximum opening areas of each lobe 106, which can increase the area of ​​the pressure relief channel, thereby quickly relieving pressure, while also taking into account the ease of processing of the negative electrode current collector 902C.

[0094] In the above embodiments of this utility model, the capacity of the secondary battery 500 is GAh, and the total area of ​​the soldered area on the negative electrode current collector 902 is S, where S ≥ G / 8mm. 2The larger the solder area, the larger the area of ​​the current-conducting portion between the negative current collector 902 and the negative electrode tab 716, thereby reducing the contact resistance.

[0095] In the above embodiments of this utility model, the length d4 of the easy-tear portion 108 (reference) Figure 4 The distance between the end of the second opening 104 near the first opening 102 and the first opening 102 is limited to d4<2mm, so that the tearable part 108 becomes a relatively easy part to tear.

[0096] It should be noted that in the above embodiments of this utility model, the solder marks in the solder mark group 112 can be straight solder marks, or they can be broken line or curved solder marks, such as wavy solder marks. (Reference) Figure 7 For line or curve-shaped solder marks, the width W of the solder mark is Figure 7 The feature dimensions are indicated in the figure. By configuring the width of the solder mark to W≤1mm, excessive tension between the negative current collector 902 and the negative electrode tab 716 can be prevented from affecting the folding of the negative current collector 902.

[0097] <Electronic Devices>

[0098] Figure 8 A schematic diagram of the electronic device 400 in this embodiment is shown. For example... Figure 8 As shown, the electronic device 400 includes a battery pack 300 and a working unit 200 electrically connected to the battery pack 300. As an example, the electronic device 400 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 200 is the vehicle body, and the battery pack 300 is located at the bottom of the vehicle body, providing electrical power support for the vehicle's operation or the operation of its internal electrical components. However, in other embodiments, the electronic device 400 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 200 can be a unit component capable of obtaining electrical energy from the battery pack 300 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 400.

[0099] 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 in that, include: The housing includes an end wall on which an explosion-proof valve is disposed; An electrode assembly is housed within the housing, with a tab extending from the end of the electrode assembly facing the explosion-proof valve; A collector plate is disposed between the end wall and the electrode lug, and is welded to the electrode lug, wherein: The collector plate includes a first opening and a plurality of second openings. The first opening passes through the center of the collector plate and extends radially along the collector plate. The plurality of second openings are distributed on both sides of the first opening. The portion of the second opening near the end of the first opening and between the second opening and the first opening constitutes the tear-away portion of the current collector. The tear-away portion is configured such that when the internal pressure of the secondary battery increases and is released through the explosion-proof valve, the current collector tears at the tear-away portion and folds away from the electrode assembly.

2. The secondary battery as described in claim 1, characterized in that, The collector plate has two second openings extending radially along the collector plate, and the first and second openings divide the collector plate into four independently foldable circumferential regions.

3. The secondary battery as described in claim 1, characterized in that, The collector plate has four second openings extending radially along the collector plate, and the first and second openings divide the collector plate into six independently foldable circumferential regions.

4. The secondary battery according to any one of claims 1-3, characterized in that, The first opening has a central hole at a position corresponding to the center of the collector plate. The central hole has multiple corners, which are respectively positioned toward the ends of the multiple second openings near the first opening.

5. The secondary battery as described in claim 4, characterized in that, The radial dimension d1 of the central hole is the largest of the line distances connecting the outer edges of the plurality of corners, and the radial dimension d1 of the central hole is ≥ 8 mm.

6. The secondary battery as described in claim 5, characterized in that, The opening angle of the corner is θ, where 45°≤θ≤90°.

7. The secondary battery as described in claim 4, characterized in that, The electrode assembly includes a central hole with a diameter of d2. The radial dimension d1 of the central hole of the collector plate is the largest of the line distances between the outer edges of the plurality of corners, where d1 > d2.

8. The secondary battery as described in claim 1, characterized in that, Multiple weld marks are formed between the current collector and the electrode tab. The first opening and the second opening divide the current collector into multiple circumferential regions along the circumferential direction. The multiple weld marks located in each of the circumferential regions form a weld mark group. The width W of each weld mark is ≤1mm.

9. The secondary battery as described in claim 8, characterized in that, The solder marks include multiple straight solder marks.

10. The secondary battery as described in claim 9, characterized in that, The outline of the solder stamp group is formed by connecting the solder stamps in the group and the ends of the solder stamps, and the outline has an angle close to and towards the center of the manifold.

11. The secondary battery as described in claim 10, characterized in that, Each of the solder stamp groups includes a central solder stamp and multiple side solder stamps. The central solder stamp is centrally located in the circumferential region, and the side solder stamps are symmetrically distributed on both sides of the central solder stamp.

12. The secondary battery as described in claim 11, characterized in that, In each of the solder stamp groups, compared to the side solder stamps, the radially inner end of the middle solder stamp is closest to the center hole, and the length d3 of the middle solder stamp is ≥10mm.

13. The secondary battery as described in claim 12, characterized in that, The side solder mark includes a first side solder mark and a second side solder mark. Compared with the second side solder mark, the first side solder mark is closer to the middle solder mark, and the radial inner end of the first side solder mark is also closer to the center hole.

14. The secondary battery as described in claim 8, characterized in that, The capacity of the secondary battery is G Ah, and the total area of ​​the solder joint is S, where S ≥ G / 8 mm. 2 .

15. The secondary battery as described in claim 1, characterized in that, The projection surface of the explosion-proof valve on the collector plate along the height direction of the secondary battery is the projection range of the explosion-proof valve. Both the first opening and the second opening extend radially outward along the collector plate to the outside of the projection range of the explosion-proof valve.

16. The secondary battery as described in claim 1, characterized in that, The collector plate also has positioning holes.

17. The secondary battery as described in claim 16, characterized in that, The positioning hole is located at the outer end of the second opening along the radial direction of the collector plate.

18. The secondary battery as described in claim 1, characterized in that, The length d4 of the tear-off section is less than 2 mm.

19. An electronic device, characterized in that, The electronic device has a secondary battery as described in any one of claims 1-18.

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