Secondary battery

Abstract

A secondary battery, comprising a battery cell, a casing internally provided with a chamber, and a cover plate for sealing the casing. The battery cell is accommodated in the chamber, and an explosion-proof apparatus is provided on the casing and / or the cover plate. The explosion-proof apparatus is inserted into the chamber, and the explosion-proof apparatus comprises an explosion-proof valve and a flame arrester, there being a certain distance between the explosion-proof valve and the flame arrester. One end of the flame arrester faces the explosion-proof valve, and the opposite end thereof faces the outside. The explosion-proof apparatus is arranged in the chamber, and thus does not occupy the external space of the secondary battery. After the explosion-proof valve bursts because of the overhigh internal gas pressure of the secondary battery, the flame arrester opposite to the explosion-proof valve can quickly treat high-heat gas rushing out of the explosion-proof valve and, by means of rapid flame retardance, prevents the spread of the high-heat gas outside the secondary battery from affecting an adjacent secondary battery in a battery module or battery pack.

Description

secondary batteries Technical Field

[0001] The present application relates to the technical field of energy storage devices, and in particular to a secondary battery. Background Art

[0002] Secondary batteries are new, environmentally friendly energy storage components and are currently widely used in energy storage, hybrid vehicles, communications, home appliances, military, aerospace, and other technical fields. However, as electric vehicle technology continues to improve and electric and hybrid vehicles become increasingly commonplace in people's daily lives, the industry is placing higher demands on the safety performance of the secondary batteries that power electric vehicles.

[0003] The battery cells of secondary batteries can usually be of a wound structure or a stacked structure. For the wound structure, a certain amount of space is usually left in the middle after winding to buffer the expansion of the electrode during subsequent battery charging and discharging, alleviate the stress on the wound structure battery cell, and thus improve safety.

[0004] Additionally, secondary batteries generate heat during charging, especially under extreme conditions such as high voltage, overcharging, and fast charging. The growth of lithium dendrites on the graphite negative electrode can cause perforation of the polymer separator. Once the separator loses its blocking function, the direct contact between the positive and negative electrodes causes a short circuit within the battery, generating even more heat, further increasing the internal temperature and triggering a series of unwanted, violent chemical reactions, producing large amounts of flammable gases and potentially causing a fire. Similarly, the electrolyte may also decompose and produce gas due to impurities such as water and metal impurities. Alternatively, the electrolyte may have a low electrochemical window or come into contact with the active surfaces of the positive or negative electrode materials, decomposing to produce low-boiling-point hydrocarbons, esters, ethers, or carbon dioxide.

[0005] Since the cover and shell of secondary batteries are usually characterized by high temperature resistance, high sealing and high safety, if the gas inside the battery cannot be released, it may cause more serious safety accidents such as explosions. At present, most of the industry will install explosion-proof valves on the cover. When the internal pressure of the battery is too high and exceeds the preset value, the explosion-proof valve opens to release the pressure, thereby preventing explosion accidents. However, if the high-calorie gas discharged from the explosion-proof valve is not handled, it will affect the outside world, such as other secondary batteries in the battery pack or battery module, and will also affect management systems such as BMS. At present, the industry also uses coolants or fire retardants in secondary batteries or battery packs to treat the high-calorie gas discharged from the explosion-proof valve, but usually the coolant or fire retardant is set independently from the explosion-proof valve. It is set on the outside of the secondary battery and not only has a slow reaction, but is also easily affected by external forces and fails when the battery module or battery pack is assembled. It also occupies external space.

[0006] Application Contents

[0007] In response to the above-mentioned problems, the present application aims to provide a secondary battery. The explosion-proof device of the secondary battery of the present application is disposed in the cavity of the housing, taking up no additional space in the battery module or battery pack. Furthermore, the flame arrester and explosion-proof valve are disposed in correspondence with each other, so that the flame arrester can quickly initiate a flame retardant reaction on the high-heat gas discharged from the explosion-proof valve, thereby preventing it from affecting adjacent secondary batteries in the battery module or battery pack.

[0008] To achieve the above-mentioned purpose, the present application provides a secondary battery, comprising a battery cell, a shell having a cavity inside, and a cover plate sealing the shell, wherein the battery cell is accommodated in the cavity, and an explosion-proof device is provided on the shell and / or the cover plate, and the explosion-proof device is inserted into the cavity. The explosion-proof device includes an explosion-proof valve and a flame arrester, and a certain distance is provided between the explosion-proof valve and the flame arrester, and one end of the flame arrester faces the explosion-proof valve, and the other end faces the outside world.

[0009] In the secondary battery of the present application, the explosion-proof device, including the explosion-proof valve and the flame arrester, is located in the cavity, without occupying the external space of the secondary battery. One end of the flame arrester faces the explosion-proof valve, while the other end faces the outside world. Therefore, if the internal pressure of the secondary battery is too high and the explosion-proof valve explodes, the flame arrester opposite the explosion valve can quickly treat the high-heat gas rushing out of the explosion valve. By quickly igniting it, it prevents the high-heat gas from spreading outside the secondary battery and affecting adjacent secondary batteries in the battery module or battery pack.

[0010] As a technical solution of the present application, the cover plate protrudes toward the direction of the battery cell to form an explosion-proof cavity, the explosion-proof device is arranged in the explosion-proof cavity, the explosion-proof cavity includes a top wall away from the cover plate and a peripheral wall connected to the top wall, the explosion-proof valve is arranged on the top wall, and the flame arrester is fixed in the explosion-proof cavity.

[0011] As a technical solution of the present application, the bottom of the shell bulges outward toward the cover plate to form an explosion-proof cavity, and the explosion-proof device is arranged in the explosion-proof cavity. The explosion-proof cavity includes a top wall close to the cover plate and a peripheral wall connected to the top wall. The explosion-proof valve is arranged on the top wall, and the flame arrester is fixed in the explosion-proof cavity.

[0012] As a technical solution of the present application, a through hole is provided inside the battery core in the vertical direction, and the explosion-proof device is inserted into the through hole.

[0013] As a technical solution of the present application, a gap is provided between the battery core and the shell, and the explosion-proof device is inserted into the gap.

[0014] As a technical solution of the present application, there are multiple battery cells, two adjacent battery cells and the shell form a cavity, and the explosion-proof device is inserted into the cavity.

[0015] As a technical solution of the present application, the battery cell has a flat structure, comprising two opposite flat portions and two curved portions between the two flat portions. A through hole is provided in the middle of the battery cell. There are multiple explosion-proof devices, one of which is inserted into the through hole and close to one of the curved portions, and the second of the explosion-proof devices is inserted into the through hole and close to the other curved portion.

[0016] As a technical solution of the present application, the explosion-proof valve and the top wall are integrally formed.

[0017] As a technical solution of the present application, an explosion-proof hole is opened on the top wall, and the explosion-proof valve is sealed and welded to the explosion-proof hole.

[0018] As a technical solution of the present application, in the vertical direction, the size of the peripheral wall is less than half the size of the shell.

[0019] As a technical solution of the present application, in the horizontal direction, the area of ​​the top wall is less than one quarter of the area of ​​the cover plate.

[0020] As a technical solution of the present application, the flame arrester is made of metal sheet, and the flame arrester divides the explosion-proof cavity into multiple gas channels. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG1 is a perspective view of a secondary battery according to a first embodiment of the present application.

[0022] FIG. 2 is a top view of a secondary battery according to the first embodiment of the present application.

[0023] FIG3 is a bottom view of the secondary battery according to the first embodiment of the present application.

[0024] FIG4 is a cross-sectional view of the secondary battery according to the first embodiment of the present application along the central axis.

[0025] FIG5 is a top view of a secondary battery according to a second embodiment of the present application.

[0026] FIG6 is a front view of a secondary battery according to a second embodiment of the present application.

[0027] FIG7 is a vertical cross-sectional view of a secondary battery according to a second embodiment of the present application.

[0028] FIG8 is a variation of FIG6 .

[0029] FIG9 is a cross-sectional view of the secondary battery of FIG8 along the horizontal direction.

[0030] FIG. 10 is a top view of a secondary battery according to a third embodiment of the present application.

[0031] FIG11 is a horizontal cross-sectional view of a secondary battery according to a third embodiment of the present application.

[0032] FIG12 is a vertical cross-sectional view of a secondary battery according to a third embodiment of the present application.

[0033] FIG. 13 is a first variation diagram of FIG. 10 .

[0034] FIG. 14 is a first variation diagram of FIG. 11 .

[0035] FIG. 15 is a first variation diagram of FIG. 12 .

[0036] FIG. 16 is a second variation diagram of FIG. 10 .

[0037] FIG. 17 is a second variation diagram of FIG. 11 .

[0038] FIG. 18 is a second variation diagram of FIG. 12 .

[0039] FIG19 is a cross-sectional view of the explosion-proof device of the secondary battery of the present application.

[0040] FIG20 is a partial top view of the explosion-proof device of the secondary battery of the present application.

[0041] FIG21 is a perspective view of a flame arrester in an explosion-proof device for a secondary battery of the present application.

[0042] FIG. 22 is a variation of FIG. 21 .

[0043] FIG23 is a three-dimensional view of the flame arrester in the explosion-proof device of the secondary battery of the present application before being formed.

[0044] FIG. 24 is a variation of FIG. 23 .

[0045] FIG. 25 is another variation of FIG. 23 .

[0046] Explanation of Component Symbols 100 - secondary battery; 10 - housing; 30 - cover; 31 - first electrode; 33 - second electrode; 50 - battery cell; 51a / 51b - flat portion; 53a / 53b - curved portion; 70 - explosion-proof device; 71 - explosion-proof chamber; 711 - top wall; 713 - peripheral wall; 73 - explosion-proof valve; 75 - flame arrester; 751 - first metal sheet; 753 - second metal sheet; 755 - third metal sheet; 77 - fixing plate; X - horizontal direction; Y - vertical direction; d - spacing DETAILED DESCRIPTION

[0047] To better illustrate the purpose, technical solutions and beneficial effects of this application, the following will further illustrate this application with reference to specific drawings and implementation methods. It should be noted that the following implementation methods are further explanations of this application and should not be regarded as limitations on this application.

[0048] As shown in FIGS. 1 to 18 , a secondary battery 100 includes a battery cell 50 , a housing 10 having a cavity therein, and a cover plate 30 that seals the housing 10 .

[0049] The battery cell 50 can be wound or laminated. If wound, the battery cell 50 comprises a wound body formed by stacking a first electrode sheet, a separator, and a second electrode sheet in sequence. If laminated, the battery cell 50 comprises a plurality of laminated bodies formed by stacking a first electrode sheet, a separator, and a second electrode sheet in sequence.

[0050] The housing 10 has a cavity (not shown) within it, which houses the battery cell 50. The housing 10 and cover 30 can be welded, bonded, or interlocked. The housing 10 can be made of stainless steel, aluminum, carbon steel, magnesium alloy, or insulating materials such as ceramic.

[0051] The cover plate 30 is provided with a first terminal 31 electrically connected to one of the electrodes in the battery cell 50. The first terminal 31 can be integrally formed with the cover plate 30 or insulated and fixed to the cover plate 30. The housing 10 can serve as a second terminal for output, electrically connected to the other electrode in the battery cell 50. Alternatively, a second terminal 33 can be protruding from the cover plate 30, electrically connected to the other electrode. At least one of the first terminal 31 and the second terminal 33 is electrically insulated from the cover plate 30. The cover plate 30 can be single, with the housing 10 having an opening, which the cover plate 30 seals. Alternatively, the cover plate 30 can be dual, with the housing 10 having two opposing openings, each of which seals the other openings.

[0052] The housing 10 of the secondary battery 100 of the present application can be a cylindrical structure or a square structure. For ease of description, the cylindrical structure is first used as an example for detailed description.

[0053] As shown in Figures 1 to 4 , the cylindrical secondary battery 100 further includes an explosion-proof device 70 , which is inserted into the cavity and can be disposed on the housing 10 .

[0054] When the explosion-proof device 70 is provided in the housing 10, the explosion-proof device 70 includes an explosion-proof valve 73 and a flame arrester 75. A certain distance d is provided between the explosion-proof valve 73 and the flame arrester 75, and one end of the flame arrester 75 faces the explosion-proof valve 73, and the other end faces the outside. Therefore, when the internal air pressure of the secondary battery 100 is too high, after the explosion-proof valve 73 explodes, the flame arrester 75 opposite to the explosion-proof valve 73 can quickly process the high-calorie gas rushing out of the explosion-proof valve 73, and quickly prevent the high-calorie gas from spreading outside the secondary battery 100 and affecting the adjacent secondary batteries 100 in the battery module or battery pack through flame retardancy. A certain distance d is provided between the flame arrester 75 and the explosion-proof valve 73 to reserve a buffer space for the high-calorie gas rushing out of the explosion-proof valve 73.

[0055] Furthermore, as shown in Figures 4 and 19, the bottom of the housing 10 bulges outward toward the cover plate 30 to form an explosion-proof chamber 71, and an explosion-proof device 70 is disposed within the explosion-proof chamber 71. The explosion-proof chamber 71 includes a top wall 711 adjacent to the cover plate 30 and a peripheral wall 713 connected to the top wall 711. An explosion-proof valve 73 is disposed on the top wall 711, and a flame arrester 75 is fixed within the explosion-proof chamber 71. The bottom of the housing 10 bulges outward toward the cover plate 30 to form the explosion-proof chamber 71. The explosion-proof valve 73 is disposed on the top wall 711 adjacent to the cover plate 30. This design can gather gas generated within the secondary battery 100 near the explosion-proof chamber 71, thereby enabling the explosion-proof valve 73 to perform a directional explosion, thereby improving the timeliness of the explosion. The explosion-proof valve 73 and the top wall 711 can be integrally formed, or an explosion-proof hole (not shown) can be provided in the top wall 711, and the explosion-proof valve 73 is sealed and welded to the explosion-proof hole.

[0056] In addition, as shown in FIG4 , a through hole is provided inside the battery cell 50, and the explosion-proof device 70 is inserted into the through hole. Before the battery cell 50 is wound through the pole piece, a large winding needle can be used so that a through hole can be formed inside the battery cell 50 after winding. Alternatively, before the battery cell 50 is wound through the pole piece, part of the pole piece at the starting end of the winding is cut off, and a winding needle with a small top and a large bottom is used for winding, so that a through hole with a small top and a large bottom can be formed inside the battery cell after winding, and the explosion-proof device 70 is inserted into the through hole. Based on the cylindrical structure of the battery cell 50, since it is a winding structure, a certain amount of space will usually be left in the middle after winding. The explosion-proof device 70 is arranged in the middle, which will not take up too much space and has a very low impact on the volume energy density of the battery cell 50. Furthermore, in the vertical direction Y, the size of the peripheral wall 713 is less than half the size of the shell 10. In the horizontal direction X, the area of ​​the top wall 711 is less than one quarter of the area of ​​the cover plate 30 , thereby controlling the volume occupied by the explosion-proof device 90 in the housing 10 and maintaining sufficient volume energy density of the secondary battery 100 .

[0057] Next, a detailed description will be given using the square-shaped secondary battery 100 shown in Figures 5 to 17 as an example. The square-shaped secondary battery 100 also includes an explosion-proof device 70, which is inserted into the cavity. The explosion-proof device 70 can be installed on the housing 10 (as shown in Figures 6 to 9) or the cover 30 (as shown in Figures 10 to 18).

[0058] When the explosion-proof device 70 is provided in the housing 10, the explosion-proof device 70 includes an explosion-proof valve 73 and a flame arrester 75. A certain distance d is provided between the explosion-proof valve 73 and the flame arrester 75, and one end of the flame arrester 75 faces the explosion-proof valve 73, and the other end faces the outside. Therefore, when the internal air pressure of the secondary battery 100 is too high, after the explosion-proof valve 73 explodes, the flame arrester 75 opposite to the explosion-proof valve 73 can quickly process the high-calorie gas rushing out of the explosion-proof valve 73, and quickly prevent the high-calorie gas from spreading outside the secondary battery 100 and affecting the adjacent secondary batteries 100 in the battery module or battery pack through flame retardancy. A certain distance d is provided between the flame arrester 75 and the explosion-proof valve 73 to reserve a buffer space for the high-calorie gas rushing out of the explosion-proof valve 73.

[0059] Furthermore, as shown in Figures 6 to 9 and 19, the bottom of the housing 10 bulges outward toward the cover plate 30 to form an explosion-proof chamber 71, within which an explosion-proof device 70 is located. The explosion-proof chamber 71 includes a top wall 711 adjacent to the cover plate 30 and a peripheral wall 713 connected to the top wall 711. An explosion-proof valve 73 is located on the top wall 711, and a flame arrester 75 is fixed within the explosion-proof chamber 71. The bottom of the housing 10 bulges outward toward the cover plate 30 to form the explosion-proof chamber 71. The explosion-proof valve 73 is located on the top wall 711 adjacent to the cover plate 30. This design can direct the gas generated within the secondary battery 100 toward the explosion-proof chamber 71, thereby enabling the explosion-proof valve 73 to be directionally detonated, thereby improving the timeliness of the explosion. Similarly, the explosion-proof valve 73 and the top wall 711 can be integrally formed, or an explosion-proof hole (not shown) can be provided in the top wall 711, with the explosion-proof valve 73 sealed and welded to the explosion-proof hole. In addition, a gap is provided between the battery cell 50 and the housing 10, into which an explosion-proof device 70 is inserted. This gap is formed by removing a portion of the electrode sheet at the end of the winding. There can be one or more explosion-proof devices 70. If there are multiple explosion-proof devices 70, preferably an even number, they are evenly distributed and close to the peripheral wall of the housing 10. If there is only one explosion-proof device 70, it is preferably located in the middle of the battery cell 50 and closely adjacent to the innermost circle of the battery cell 50. The outer contour of the explosion-proof device 70 is consistent with the shape of the innermost circle of the battery cell 50. As shown in Figure 9, the outer contour of the explosion-proof device 70 is also flat. Typically, after winding, a certain amount of space is left in the middle of the battery cell 50 to buffer the expansion of the electrode sheets. Therefore, placing the explosion-proof device 70 close to the innermost circle of the battery cell 50 helps fully utilize the internal space and has a minimal impact on the volumetric energy density of the battery cell 50. Similarly, further, in the vertical direction Y, the size of the peripheral wall 713 is less than half the size of the housing 10. In the horizontal direction X, the area of ​​the top wall 711 is less than one-quarter the area of ​​the cover plate 30. This limits the volume occupied by the explosion-proof device 90 within the housing 10 and maintains a sufficient volumetric energy density for the secondary battery 100. A certain distance is provided between the flame arrester 75 and the explosion-proof valve 73 to provide a buffer space for the high-temperature gases escaping from the explosion-proof valve 73.

[0060] As shown in Figures 10 to 18, when the explosion-proof device 70 is provided on the cover body 30, the explosion-proof device 70 includes an explosion-proof valve 73 and a flame arrester 75. A certain distance d is provided between the explosion-proof valve 73 and the flame arrester 75. One end of the flame arrester 75 faces the explosion-proof valve 73, and the other end faces the outside. The cover plate 30 is protruded toward the battery cell 50 to form an explosion-proof cavity 71, and the explosion-proof device 70 is provided in the explosion-proof cavity 71. The explosion-proof cavity 71 includes a top wall 711 away from the cover plate 30 and a peripheral wall 713 connected to the top wall 711. The explosion-proof valve 73 is provided on the top wall 711, and the flame arrester 75 is fixed in the explosion-proof cavity 71. The explosion-proof device is integrated into the cover body 30, with a high degree of integration and easy assembly. The cover plate 30 is convexly formed toward the battery cell 50 to form an explosion-proof cavity 71. An explosion-proof valve 73 is provided on the top wall 711 of the explosion-proof cavity 71, which is away from the cover plate 30. This design allows the gas generated within the secondary battery 100 to be concentrated near the explosion-proof cavity 71, thereby enabling the explosion-proof valve 73 to perform a directional explosion, thereby improving the timeliness of the explosion. The explosion-proof valve 73 and the top wall 711 can be integrally formed, or an explosion-proof hole (not shown) can be provided in the top wall 711, and the explosion-proof valve 73 is sealed and welded to the explosion-proof hole. As shown in Figures 13 to 15, when the explosion-proof device 70 is installed on the cover body 30, a gap is provided between the battery cell 50 and the housing 10, and the explosion-proof device 70 is inserted into the gap.

[0061] Furthermore, the battery cells 50 may be one or more. If there are multiple battery cells 50, as shown in Figures 13-15, two adjacent battery cells 50 and the housing 10 enclose a cavity, and the explosion-proof device 70 is inserted into the cavity. In this manner, the explosion-proof device 70 only utilizes the gaps between the battery cells 50 and does not affect the volume occupied by the battery cells 50 in the cavity of the housing 10, thereby maximizing volume utilization. Alternatively, as shown in Figures 10-12 and 16-18, the battery cell 50 may be a flat structure, including two opposing flat portions 51a / 51b and two curved portions 53a / 53b between the two flat portions 51a / 51b. A through hole is provided in the center of the battery cell 50, and there are multiple explosion-proof devices 70. One explosion-proof device 70 is inserted into the through hole near one of the curved portions 53a, and the second explosion-proof device 70 is inserted into the through hole near the other curved portion 53b. Typically, the space in the innermost circle of the flat-shaped battery cell 50 at the curved portion 53a / 53b is larger than that in the flat portion 51a / 51b. Providing an explosion-proof device 70 near the curved portion 53a / 53b can maximize space utilization. In a flat-shaped battery cell, there are preferably multiple explosion-proof devices 70, and preferably an even number, evenly distributed in the through-holes. Similarly, further, in the vertical direction Y, the size of the peripheral wall 713 is less than half the size of the shell 10. In the horizontal direction X, the area of ​​the top wall 711 is less than one-quarter the area of ​​the cover plate 30, thereby controlling the volume occupied by the explosion-proof device 90 in the shell 10 to maintain sufficient volume energy density of the secondary battery 100.

[0062] The flame arrester 75 of the secondary battery 100 of the present application is made of metal sheet. As shown in Figures 19 and 20, the flame arrester 75 divides the explosion-proof chamber 71 into multiple gas channels. By dividing into multiple gas channels, heat can be dispersed to reduce the temperature to play a flame retardant role. In addition, combustion and explosion are stimulated by external energy (heat energy, radiation energy, electrical energy, chemical reaction energy, etc.), which causes molecules to split into very active free radicals. The explosion-proof chamber 71 is divided into multiple gas channels, and the probability of collision between free radicals and reactive molecules is reduced, while the probability of collision between free radicals and channel walls is increased, until the free radical reaction is reduced, and thus the flame is prevented. The flame arrester 75 is made of metal sheet, so it has a certain heat dissipation effect, which is conducive to the dissipation of heat concentrated in the middle of the battery cell 50, thereby preventing thermal runaway. The interior of the flame arrester 75 is a honeycomb structure with multiple isolated holes. The outer contour of the flame arrester 75 can be a corrugated structure as shown in Figure 21, or a mesh structure as shown in Figure 22. Of course, the flame arrester 75 is not limited to the above two structures. Other structures that can separate the explosion-proof chamber 71 into multiple gas channels and have a hole structure are also acceptable. During assembly, the flame arrester 75 can be inserted into the explosion-proof chamber 71 and then fixed by a fixing plate 77. To facilitate subsequent replacement, the fixing plate 77 and the explosion-proof chamber 71 are detachably connected. The flame arrester 75 can be formed by winding a first metal sheet 751 as shown in Figure 23. Of course, the shape of the flame arrester 75 can also be replaced by winding a second metal sheet 753 as shown in Figure 24. Alternatively, the flame arrester 75 can also be formed by stacking multiple grid-shaped third metal sheets 753 as shown in Figure 25, and the stacked structure can be shown in Figure 22.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit the scope of protection of the present application. Although the present application has been described in detail with reference to the preferred embodiments, it is not limited to those listed in the embodiments. Those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A secondary battery, characterized in that: The invention comprises a battery cell, a shell having a cavity inside and a cover plate sealing the shell, wherein the battery cell is accommodated in the cavity, an explosion-proof device is arranged on the shell and / or the cover plate, the explosion-proof device is inserted in the cavity, the explosion-proof device comprises an explosion-proof valve and a flame arrester, a certain distance is arranged between the explosion-proof valve and the flame arrester, one end of the flame arrester faces the explosion-proof valve, and the other end faces the outside.

2. The secondary battery according to claim 1, characterized in that: The cover plate is protruded toward the battery core to form an explosion-proof cavity, the explosion-proof device is arranged in the explosion-proof cavity, the explosion-proof cavity includes a top wall away from the cover plate and a peripheral wall connected to the top wall, the explosion-proof valve is arranged on the top wall, and the flame arrester is fixed in the explosion-proof cavity.

3. The secondary battery according to claim 1, characterized in that: The bottom of the shell body bulges outward toward the cover plate to form an explosion-proof cavity, in which the explosion-proof device is arranged, and the explosion-proof cavity includes a top wall close to the cover plate and a peripheral wall connected to the top wall, the explosion-proof valve is arranged on the top wall, and the flame arrester is fixed in the explosion-proof cavity.

4. The secondary battery according to claim 2 or 3, characterized in that: In the vertical direction, a through hole is provided inside the battery core, and the explosion-proof device is inserted into the through hole.

5. The secondary battery according to claim 2 or 3, characterized in that: A gap is provided between the battery core and the shell, and the explosion-proof device is inserted in the gap.

6. The secondary battery according to claim 2 or 3, characterized in that: There are multiple battery cells, and two adjacent battery cells and the shell are surrounded to form a cavity, and the explosion-proof device is inserted in the cavity.

7. The secondary battery according to claim 2 or 3, characterized in that: The battery core is a flat structure, comprising two opposite flat portions and two curved portions between the two flat portions. A through hole is provided in the middle of the battery core. There are multiple explosion-proof devices, one of which is inserted into the through hole and close to one of the curved portions, and the second of which is inserted into the through hole and close to the other curved portion.

8. The secondary battery according to claim 2 or 3, characterized in that: The explosion-proof valve and the top wall are integrally formed.

9. The secondary battery according to claim 2 or 3, characterized in that: An explosion-proof hole is provided on the top wall, and the explosion-proof valve is sealed and welded to the explosion-proof hole.

10. The secondary battery according to claim 2 or 3, characterized in that: In the vertical direction, the size of the peripheral wall is less than half of the size of the shell.

11. The secondary battery according to claim 2 or 3, characterized in that: In the horizontal direction, the area of ​​the top wall is less than one quarter of the area of ​​the cover plate.

12. The secondary battery according to claim 2 or 3, characterized in that: The flame arrester is made of metal sheets and divides the explosion-proof cavity into a plurality of gas channels.

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