Battery and battery pack

Abstract

The invention relates to the technical field of batteries, and discloses a battery and a battery pack. The shell is made of steel and is of a quadrangular prism structure, the shell comprises a shell body and a cover plate, at least one end of the shell body is open, and the cover plate is welded to the open end of the shell body to form a welding area; the tensile strength of the welding area is F, the first surface of the shell is provided with a pressure relief structure, the projection area of the pressure relief structure on the first surface is S, the area formed by enclosing of the first surface is S0, F * (S / S0) is larger than or equal to 8 and smaller than or equal to 400, the unit of F is MPa, the unit of S is mm < 2 >, and the unit of S0 is mm < 2 >. By comprehensively controlling the tensile strength F and the occupied area S / S0 of the pressure relief structure on the first surface, more serious safety accidents such as blockage of the pressure relief structure by the battery cell, incapability of normal pressure relief, burst-open of the cover plate and ignition of the battery when thermal runaway of the battery occurs are avoided, so that the safety of the battery is ensured.

Description

[0001] This application is a divisional application of the invention patent application with publication number CN202411381131.9. The application date of the original application is: 2024.09.30; the application number is: 202411381131.9; the name of the invention is: "Battery and Battery Pack". Technical Field

[0002] The present invention relates to the technical field of batteries, and in particular to batteries and battery packs. Background Art

[0003] The battery usually includes a battery cover, a shell and a battery cell. The battery cover and the shell are welded to enclose a storage space, and the battery cell is arranged in the storage space. In order to ensure the safety of the battery, a pressure relief structure, such as an explosion-proof valve, is usually provided on the battery cover. When the battery encounters mechanical impact or an abnormal internal short circuit, it may cause thermal runaway of the battery, and high-temperature and high-pressure gas will be generated inside the battery. When the gas pressure reaches a certain level, the pressure relief structure explodes and releases the gas inside the battery. However, through experimental observations, it was found that when the battery has thermal runaway, there is a situation where the battery cover is opened as a whole, causing the battery to catch fire. Summary of the invention

[0004] In view of this, the present invention provides a battery and a battery pack to solve the problem in the prior art that when thermal runaway occurs in the battery, the battery cover is completely opened, causing the battery to catch fire.

[0005] In a first aspect, the present invention provides a battery, comprising: a battery cell and a shell; the shell is made of steel, the shell is a quadrangular prism structure, the shell comprises a shell body and a cover plate, at least one end of the shell body is open, the cover plate is welded to the open end of the shell body to form a welding area, the cover plate blocks the opening and forms a accommodating space with the shell body, the battery cell is located in the accommodating space; the tensile strength of the welding area is F, the first surface of the shell is provided with a pressure relief structure, the projection area of ​​the pressure relief structure on the first surface is S, the area enclosed by the first surface is S0, satisfying 8≤F×(S / S0)≤400, wherein the unit of F is MPa, and the unit of S is mm 2 , the unit of S0 is mm 2 The shell is provided with a through hole, the pressure relief structure covers the through hole and is connected to the shell, or the pressure relief structure is integrally arranged with the shell.

[0006] The present application comprehensively controls the tensile strength F and the area S / S0 occupied by the pressure relief structure on the first surface to avoid the situation in which the pressure relief structure is blocked by the battery cell and cannot release pressure normally when thermal runaway occurs in the battery, the cover plate is broken open, and more serious safety accidents such as battery fire are caused, thereby ensuring the safety of the battery; when S / S0 is small, due to the small area of ​​the pressure relief structure, the released gas is limited, the internal battery cell is lifted up, the pressure relief structure is blocked, the pressure relief structure cannot be exhausted normally, and the internal gas will still pull the welding position of the cover plate and the shell body, causing the connection failure at the welding position of the cover plate and the shell body, the cover plate is broken open, and more serious safety accidents are caused; therefore, when the area of ​​the pressure relief structure is relatively small, it is necessary to adjust the tensile strength of the cover plate and the shell body to avoid separation of the cover plate and the shell body; when S / S0 is relatively large, the gas can be discharged from the position of the pressure relief structure, and the impact on the welding position of the cover plate and the shell body is reduced, but if the area of ​​the pressure relief structure is too large, it will make it difficult to open the pressure relief structure, and the battery still has a greater risk of fire and explosion.

[0007] In a second aspect, the present invention further provides a battery pack, comprising the above-mentioned battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0009] Figure 1 A schematic diagram of the overall structure of a battery according to an embodiment of the present invention;

[0010] Figure 2 for Figure 1 A top view of the battery shown;

[0011] Figure 3 for Figure 2 Schematic diagram of the cross-sectional structure of AA;

[0012] Figure 4 for Figure 3 The enlarged view of point B in the middle;

[0013] Figure 5 A top view of another battery according to an embodiment of the present invention;

[0014] Figure 6 It is a schematic diagram of the matching structure of the shell body and the cover plate according to an embodiment of the present invention;

[0015] Figure 7 for Figure 6 Enlarged view of point C in the middle;

[0016] Figure 8 It is a schematic cross-sectional structural diagram of a battery when the pressure relief structure according to an embodiment of the present invention is arranged on the end wall;

[0017] Fig. 9 It is a schematic cross-sectional structural diagram of a battery when the pressure relief structure according to an embodiment of the present invention is arranged on the side wall;

[0018] Fig.10 It is a schematic structural diagram of a first side wall, a second side wall and a transition portion according to an embodiment of the present invention;

[0019] Fig.11 A schematic diagram of the structure of the weak part of the pressure relief structure according to an embodiment of the present invention

[0020] Fig.12 A schematic diagram of another pressure relief structure according to an embodiment of the present invention;

[0021] Fig.13 Schematic diagram of another pressure relief structure according to an embodiment of the present invention.

[0022] Description of reference numerals:

[0023] 1. Shell body; 11. Side wall; 111. First side wall; 112. Second side wall; 113. Transition part; 12. End wall; 2. Cover plate; 21. Liquid injection hole; 3. Pressure relief structure; 31. Weak part; 4. Welding area; 5. Pole assembly; 51. Pole body; 6. Second welding area; 10. Battery cell; 101. Battery cell body; 102. Pole ear; 20. Shell. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0025] Combine the following Figures 1 to 13 , describing an embodiment of the present invention.

[0026] According to an embodiment of the present invention, on the one hand, a battery is provided, comprising:

[0027] A battery cell 10 and a shell 20; the shell 20 is a quadrangular prism structure, the shell 20 includes a shell body 1 and a cover plate 2, at least one end of the shell body 1 is open, the cover plate 2 is welded to the open end of the shell body 1 to form a welding area 4, the cover plate 2 blocks the opening and encloses the shell body 1 to form a receiving space, and the battery cell 10 is located in the receiving space; the tensile strength of the welding area 4 is F, the first surface of the shell 20 is provided with a pressure relief structure 3, the projection area of ​​the pressure relief structure 3 on the first surface is S, and the area enclosed by the first surface is S0, satisfying 1≤F×(S / S0)≤500, wherein the unit of F is MPa and the unit of S is mm 2 , the unit of S0 is mm 2 .

[0028] Specifically, the value of F×(S / S0) can be any value of 1, 25, 50, 75, 100, 125, 150, 175, 200, 225, 250, 275, 300, 325, 350, 375, 400, 425, 450, 475, 500, etc., or a value between any two values.

[0029] The battery of this embodiment comprehensively controls the tensile strength F and the area S / S0 occupied by the pressure relief structure 3 on the first surface to avoid that when the battery has thermal runaway, the pressure relief structure 3 is blocked by the battery cell 10, the pressure cannot be released normally, the cover plate 2 is opened, and more serious safety accidents such as battery fire are caused, thereby ensuring the safety of the battery; when S / S0 is small, since the area of ​​the pressure relief structure 3 is relatively small, the released gas is limited, the internal battery cell 10 is lifted up, the pressure relief structure 3 is blocked, the pressure relief structure 3 cannot be exhausted normally, and the internal gas will still cause the welding position of the cover plate 2 and the shell body 1. The pressure relief structure 3 is pulled at the position, causing the connection failure at the welding position of the cover plate 2 and the shell body 1, and the cover plate 2 is broken open, causing a more serious safety accident; therefore, when the area of ​​the pressure relief structure 3 is relatively small, it is necessary to adjust the tensile strength of the cover plate 2 and the shell body 1 to avoid separation of the cover plate 2 and the shell body 1; when S / S0 is relatively large, the gas can be discharged from the position of the pressure relief structure 3, and the impact on the welding position of the cover plate 2 and the shell body 1 is reduced. However, if the area of ​​the pressure relief structure 3 is too large, it will make it difficult to open the pressure relief structure 3, and the battery will still have a greater risk of fire, explosion, etc.

[0030] The welding tensile strength refers to the maximum bearing capacity of the welding zone 4 under tensile load. Further, the welding tensile strength can be adjusted by adjusting welding parameters or welding process. Specifically, welding parameters include welding current, voltage, welding speed, etc., and welding process includes welding sequence, number of layers, preheating and post-processing, etc.

[0031] It should be noted that the pressure relief structure 3 on the battery has an important impact on the safety of the battery. For example, when short circuit, overcharging and other phenomena occur, thermal runaway may occur inside the battery, resulting in a sudden rise in pressure or temperature. In this case, the internal pressure and temperature can be released outward through the pressure relief structure 3 to prevent the battery from exploding or catching fire. The specific form of the pressure relief structure 3 is not limited, and it is mainly used to release pressure in time when the battery has thermal runaway. For example, the pressure relief structure 3 can be a separate explosion-proof plate, a through hole is provided on the shell 20, the explosion-proof plate is connected to the through hole, and a weak portion 31 is provided on the explosion-proof plate. The weak portion 31 can be a local thinning area on the explosion-proof plate, which is used to explode when the battery has thermal runaway, and drive the explosion-proof plate to open and release pressure; further, the weak portion 31 can be arranged around the explosion-proof plate for a week, or it can be discontinuous, that is, the weak portion 31 is not provided at some positions; or, the weak portion 31 can be directly stamped on the shell 20 or formed by laser etching as the pressure relief structure 3. The projection area of ​​the pressure relief structure 3 on the first surface refers to the area enclosed by the projection of the pressure relief structure 3 on the first surface. Figure 1 , the pressure relief structure 3 is a bursting disc, and the projection area of ​​the pressure relief structure 3 on the first surface is the area of ​​the bursting disc; please refer to Fig.12 , the H-shaped notch serves as the pressure relief structure 3, and the projection area of ​​the pressure relief structure 3 on the first surface is the area occupied by the H-shaped notch on the first surface ( Fig.12 The area in the dashed box); see Fig.13 The weak portion 31 stamped on the shell 20 serves as the pressure relief structure 3 , and the projection area of ​​the pressure relief structure 3 on the first surface is the area occupied by the weak portion 31 on the first surface, that is, the area enclosed by the weak portion 31 .

[0032] It is worth noting that when the internal pressure of the battery is constant, the smaller the area of ​​the pressure relief structure 3 is, the greater the stress acting on the pressure relief structure 3 is, which makes the pressure relief structure 3 easier to open.

[0033] It should be further explained that when the tensile strength F of the welding zone 4 is relatively small, although the connection strength between the cover plate 2 and the shell body 1 is relatively weak, it is still greater than the strength at the weak portion 31 of the pressure relief structure 3, that is, the battery will still burst at the pressure relief structure 3 to exhaust gas. Therefore, the pressure relief structure 3 is set to a larger area, and when the pressure relief structure 3 bursts, it can have a larger exhaust area, so that the internal gas of the battery can be quickly discharged, avoiding the internal gas of the battery from continuously applying stress to the welding zone 4 and the stress will gradually increase with the accumulation of the internal gas of the battery, thereby avoiding the cover plate 2 from being blown open.

[0034] Therefore, in this embodiment, by limiting the value range of F×(S / S0), the tensile strength of the welding area 4 and the area occupied by the pressure relief structure 3 in the housing 20 have reasonable values, so that when the battery has thermal runaway, the pressure relief structure 3 can explode in time and exhaust quickly, and the cover plate 2 can be prevented from being opened. Thus, the safety of the battery is guaranteed.

[0035] It is worth noting that the battery of this embodiment is a quadrangular prism battery (i.e., a non-cylindrical battery), such as a square battery, a blade battery, etc. When the battery cell 10 of the cylindrical battery expands, the circumferential expansion of the battery cell 10 is self-offsetting, and the impact on the welding point between the cover plate 2 and the shell body 1 is relatively small; the battery cell 10 of the quadrangular prism battery expands, and the inside is uneven, which has a relatively large impact on the welding point between the cover plate 2 and the shell body 1. During the thermal runaway test of the quadrangular prism battery, the battery cell 10 is lifted up to cover the pressure relief structure 3, which affects the explosion of the pressure relief structure 3, and the risk of separation between the cover plate 2 and the shell body 1 increases.

[0036] In addition, since the tensile strength of the welding point between the cover plate 2 and the shell body 1 is lower than the tensile strength of other non-welding positions of the cover plate 2 (because the cover plate 2 and the shell body 1 are welded together, the metal melts during welding, and the grain structure changes, causing the tensile strength of the welding area 4 between the cover plate 2 and the shell body 1 to weaken), the welding position between the cover plate 2 and the shell body 1 is prone to cracking when the battery is subjected to a thermal runaway test, causing more serious safety accidents.

[0037] It should be noted that the area enclosed by the first surface is the area of ​​the surface enclosed by the outer contour of the first surface. The open end of the shell body 1 is the end of the shell body 1 provided with an opening.

[0038] It should be noted that the welding area 4 is circumferentially arranged corresponding to the edge of the cover plate 2 so as to weld the cover plate 2 and the shell body 1 along the circumference of the cover plate 2 .

[0039] Furthermore, the value range of F is 60MPa≤F≤1300MPa, and the value range of S / S0 is 0.006≤S / S0≤0.6. With such a setting, the value of tensile strength is within a suitable range, which avoids weak strength at the welding point between the cover plate 2 and the shell body 1, which may cause connection failure between the cover plate 2 and the shell body 1 when the battery has thermal runaway; it also avoids excessive tensile strength, high requirements for welding process, and reduced welding yield. The value of S / S0 is within a suitable range, which avoids the inability of gas to be fully released through the pressure relief structure 3 when the battery has thermal runaway; it also avoids the area of ​​the pressure relief structure 3 being too large, which affects the strength of the shell 20. Thereby, it is ensured that the tensile strength of the welding area 4 and the area occupied by the pressure relief structure 3 in the shell 20 have reasonable values, thereby ensuring the safety of the battery.

[0040] Specifically, the value of F can be any value among 60MPa, 100MPa, 200MPa, 300MPa, 400MPa, 500MPa, 600MPa, 700MPa, 800MPa, 900MPa, 1000MPa, 1100MPa, 1200MPa, 1300MPa, etc., or a value between any two values; the value of S / S0 can be any value among 0.006, 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, etc., or a value between any two values.

[0041] The material of the housing 20 can be steel or aluminum. That is, the cover plate 2 and the housing body 1 can both be made of steel, and the pressure relief structure 3 is also made of steel; the cover plate 2 and the housing body 1 can also be made of aluminum, and the pressure relief structure 3 is also made of aluminum.

[0042] Furthermore, the steel may be stainless steel, nickel-plated steel, etc., and the aluminum may be aluminum alloy, etc.

[0043] It should be noted that stainless steel is an alloy material, the main components of which include iron, chromium, nickel and a small amount of other elements. Chromium is the basic element that makes stainless steel corrosion-resistant, making it anti-oxidation and anti-corrosion, able to resist the erosion of most chemical media, and having a long service life. The corrosion resistance of stainless steel depends on the alloying elements contained in the steel, and it has good mechanical properties and wear resistance. Nickel-plated steel parts are metal products with a base material of ordinary steel, and a layer of nickel is plated on the surface through an electroplating process. Aluminum alloys usually use alloying elements such as copper, zinc, manganese, silicon, and magnesium.

[0044] When the shell 20 is made of steel, 8≤F×(S / S0)≤400 is satisfied. When the shell 20 is a steel shell, the tensile strength of the welding area 4 between the cover plate 2 and the shell body 1 is greater. Therefore, the area occupied by the pressure relief structure 3 can be appropriately reduced so that when the battery is thermally runaway, the pressure relief structure 3 with a smaller area can be opened quickly. Of course, the area occupied by the pressure relief structure 3 cannot be too small, otherwise the discharge speed of the gas inside the battery is too low, the gas inside the battery continues to apply stress to the welding area 4, and as the internal gas of the battery accumulates, the stress will gradually increase, and the cover plate 2 is at risk of being opened.

[0045] Specifically, when the shell 20 is made of steel, the value of F×(S / S0) can be any value among 8, 40, 80, 120, 160, 200, 240, 280, 320, 360, 400, etc., or a value between any two values.

[0046] For the steel shell 20, the melting point of steel is high, and the pressure relief structure 3 is difficult to be opened. Therefore, further, the value range of F is 400MPa≤F≤1200MPa, and the value range of S / S0 is 0.008≤S / S0≤0.5. In this way, the pressure relief structure 3 can be opened quickly when the battery is thermally runaway, while ensuring the connection strength between the cover plate 2 and the shell body 1.

[0047] Specifically, when the shell 20 is made of steel, the value of F can be any value among 400MPa, 500MPa, 600MPa, 700MPa, 800MPa, 900MPa, 1000MPa, 1100MPa, 1200MPa, etc., or a value between any two values; the value of S / S0 can be any value among 0.008, 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, etc., or a value between any two values.

[0048] When the shell 20 is made of aluminum, 1.5≤F×(S / S0)≤45 is satisfied. When the shell 20 is an aluminum shell, the tensile strength of the welding area 4 of the shell body 1 and the cover plate 2 is relatively weak. Therefore, the area occupied by the pressure relief structure 3 is set to be relatively large, so that the gas inside the battery can be quickly released, reducing the impact on the welding area 4 of the shell body 1 and the cover plate 2, and avoiding failure of the connection between the shell body 1 and the cover plate 2.

[0049] Specifically, when the shell 20 is made of aluminum, the value of F×(S / S0) can be any value of 1.5, 5, 10, 15, 20, 25, 30, 35, 40, 45, etc., or a value between any two values.

[0050] Furthermore, the value range of F is 80MPa≤F≤150MPa, and the value range of S / S0 is 0.01≤S / S0≤0.6.

[0051] Specifically, when the shell 20 is made of aluminum, the value of F can be any value among 80MPa, 90MPa, 100MPa, 110MPa, 120MPa, 130MPa, 140MPa, 150MPa, etc., or a value between any two values; the value of S / S0 can be any value among 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, etc., or a value between any two values.

[0052] Regarding the location of the pressure relief structure 3 , the pressure relief structure 3 can be disposed on the cover plate 2 or on the shell body 1 .

[0053] like Figures 1 to 5As shown, the pressure relief structure 3 is arranged on the cover plate 2. When the shell 20 is made of steel, at this time, 600MPa≤F≤1200MPa. When the shell 20 is made of aluminum, at this time, 90MPa≤F≤150MPa. Compared with setting the pressure relief structure 3 on the shell body 1, setting the pressure relief structure 3 on the cover plate 2 makes the processing technology simpler; in this embodiment, when the pressure relief structure 3 is set on the cover plate 2, that is, the pressure relief structure 3 and the welding area 4 are set on the same side, the range of values ​​of the tensile strength of the welding area 4 is further limited to avoid the internal gas of the battery from concentrating on the side of the cover plate 2, excessively impacting the cover plate 2 and the welding area 4, and causing the connection between the cover plate 2 and the shell body 1 to fail.

[0054] When the pressure relief structure 3 is arranged on the cover plate 2, as shown in FIG. Figure 7 As shown, the penetration depth of the welding zone 4 is d, the penetration width of the welding zone 4 is w, when the shell 20 is steel, it satisfies 0.04≤d×w≤0.9, when the shell 20 is aluminum, it satisfies 0.4≤d×w≤3, where d is in mm and w is in mm. Such a setting ensures the connection reliability between the cover plate 2 and the shell body 1, improves the tensile strength of the welding zone 4 of the cover plate 2 and the shell body 1, and avoids the connection failure of the welding point between the cover plate 2 and the shell body 1 when the battery has thermal runaway, thereby preventing the cover plate 2 from being broken open or even the battery cell 10 from catching fire, and avoiding more serious safety accidents.

[0055] Specifically, when the shell 20 is made of steel, the value of d×w can be any value among 0.04, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, etc., or a value between any two values.

[0056] Specifically, when the shell 20 is made of aluminum, the value of d×w can be any value among 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.5, 2, 2.5, 3, etc., or a value between any two values.

[0057] When the pressure relief structure 3 is arranged on the cover plate 2, as shown in FIG. Figure 6 As shown, the thickness of the cover plate 2 is t1, and the thickness of the side wall 11 of the shell body 1 welded to the cover plate 2 is t2, which satisfies 1≤t1 / t2≤10, where the unit of t1 is mm, and the unit of t2 is mm. If the value of t1 / t2 is too small, the thickness of the cover plate 2 is too small, which may cause the weld width of the cover plate 2 and the shell body 1 to fail to meet the requirements; if the value of t1 / t2 is too large, the thickness of the side wall 11 of the shell body 1 is too small, which may cause the weld depth of the cover plate 2 and the shell body 1 to fail to meet the requirements, and the risk of thermal deformation of the shell body 1 increases.

[0058] Specifically, the value of t1 / t2 can be any value of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, etc., or a value between any two values.

[0059] When the pressure relief structure 3 is arranged on the cover plate 2, as shown in FIG. Figure 3 As shown, a pole assembly 5 is arranged on the cover plate 2, and the battery cell 10 is electrically connected to the pole assembly 5. The pole assembly 5 includes two pole bodies 51, and the pressure relief structure 3 is arranged between the two pole bodies 51. The distance between the center of the projection of the pressure relief structure 3 on the first surface and the center of the projection of one of the pole bodies 51 on the first surface is a, and the distance between the center of the projection of the pressure relief structure 3 on the first surface and the center of the projection of the other pole body 51 on the first surface is b, which satisfies 0≤│ab│≤10, wherein the unit of a is mm, and the unit of b is mm. The pressure relief structure 3 is arranged between the two pole bodies 51, and in the length direction of the battery, the heat on both sides of the battery can be released from the pressure relief structure 3, so as to avoid excessive concentration of heat on one side of the battery and excessive force on one side of the welding area 4, thereby avoiding failure of the connection between the cover plate 2 and the shell body 1 on one side and causing the cover plate 2 to be flushed open.

[0060] Specifically, the value of |ab| can be any value of 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, etc., or a value between any two values.

[0061] It is worth noting that, in this embodiment, the “center” refers to the geometric center, such as the center of a circle or the intersection of the diagonals of a square.

[0062] Further, such as Figure 2 and Figure 5 As shown, the minimum distance between the center of the projection of the pole body 51 on the first surface and the welding area 4 is l1, and the distance between the center of the projection of the pole body 51 on the first surface and the center of the projection of the pressure relief structure 3 on the first surface is l2, satisfying 0.07≤l1 / l2≤0.8, wherein the unit of l1 is mm, and the unit of l2 is mm. When two pole bodies 51 are provided, l2=a or l2=b. In this way, the welding area 4 is arranged closer to the pole body 51 than the pressure relief structure 3, and therefore, the pole body 51 can be used to achieve further heat dissipation, reduce the influence of heat on the welding area 4, and improve the welding quality of the welding area 4.

[0063] Specifically, the value of l1 / l2 can be any value among 0.07, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, etc., or a value between any two values.

[0064] It is worth noting that the two pole bodies 51 are respectively a positive pole and a negative pole.

[0065] Of course, if Figure 5As shown, only one pole body 51 may be provided on the cover plate 2, and the minimum distance between the center of the projection of the pole body 51 on the first surface and the welding area 4 is l1, and the distance between the center of the pole body 51 and the center of the pressure relief structure 3 is l2.

[0066] At this time, the first surface is the end surface of the cover plate 2 provided with the pressure relief structure 3. Therefore, the area S0 enclosed by the first surface is the area of ​​the end surface of the cover plate 2; the projection area S of the pressure relief structure 3 on the first surface is the projection area of ​​the pressure relief structure 3 on the end surface of the cover plate 2. That is, please refer to Figure 5 , S0=x1×y1, wherein x1 is the length of the cover plate 2, y1 is the width of the cover plate 2, the unit of x1 is mm, and the unit of y1 is mm.

[0067] It is worth noting that the battery cell 10 includes a battery cell body 101 and a pole ear 102 extending from the battery cell body 101, and the pole ear 102 can be directly electrically connected to the pole body 51; or, the pole assembly 5 also includes a transition piece, the pole body 51 and the transition piece are electrically connected, and the transition piece and the pole ear 102 are electrically connected.

[0068] When the pressure relief structure 3 is arranged on the cover plate 2, as shown in FIG. Figure 2 As shown, the cover plate 2 is also provided with an injection hole 21, and the minimum distance between the center of the projection of the injection hole 21 on the first surface and the welding area 4 is l3, and the length of the battery is x1, which satisfies 0.1≤l3 / x1≤0.4, wherein the unit of l3 is mm. The injection hole 21 is used to inject electrolyte into the battery. When the electrolyte is injected, there is a possibility that the electrolyte will leak. Therefore, by limiting the distance between the injection hole 21 and the welding area 4, the electrolyte is prevented from contacting the welding area 4 to cause corrosion of the welding area 4, thereby ensuring the strength of the welding area 4.

[0069] Specifically, the value of l3 / x1 can be any value among 0.1, 0.2, 0.3, 0.4, etc., or a value between any two values.

[0070] It should be noted that the injection hole 21 is usually arranged close to the positive electrode side, so the above-mentioned l3 is usually the distance between the center of the projection of the injection hole 21 on the first surface and the welding area 4 corresponding to the positive electrode side.

[0071] When the shell 20 is made of steel, the pressure relief structure 3 can also be arranged on the shell body 1, and in this case 400MPa≤F≤1100MPa. When the shell 20 is made of aluminum, the pressure relief structure 3 can also be arranged on the shell body 1, and in this case 80MPa≤F≤140MPa. The pressure relief structure 3 is arranged on the shell body 1, and the pressure relief structure 3 and the cover plate 2 are not arranged on the same side. The impact force of the internal gas of the battery on the cover plate 2 is relatively small. Therefore, the tensile strength of the welding area 4 and / or the area occupied by the pressure relief structure 3 can be made relatively small, avoiding the welding power required to ensure greater tensile strength and the welding penetration depth and width being too large, resulting in a reduction in welding yield. Specifically, the pressure relief structure 3 can be arranged on the end wall 12 of the shell body 1, and can also be arranged on the side wall 11 of the shell body 1.

[0072] like Figure 8 As shown, the pressure relief structure 3 is arranged on the shell body 1, and is arranged opposite to the cover plate 2, and the distance between the cover plate 2 and the shell body 1 where the pressure relief structure 3 is located is h. When the shell 20 is made of steel, h≥80mm, 400MPa≤F≤1000MPa are satisfied. When the shell 20 is made of aluminum, h≥80mm, 80MPa≤F≤130MPa are satisfied. The pressure relief structure 3 and the cover plate 2 are arranged opposite to each other, and the distance between the pressure relief structure 3 and the cover plate 2 is large, the internal gas of the battery is concentratedly released from the pressure relief structure 3, and the impact force on the welding position of the cover plate 2 and the shell body 1 is small. Therefore, the tensile strength of the welding area 4 can be appropriately reduced.

[0073] It is worth noting that the shell body 1 includes an end wall 12 arranged opposite to the cover plate 2, and the pressure relief structure 3 is arranged on the end wall 12. Figure 8 The h mentioned above is the distance between the surface of the cover plate 2 close to the battery cell 10 and the surface of the end wall 12 close to the battery cell 10 along the height direction of the battery.

[0074] like Figure 8 As shown, the pressure relief structure 3 is arranged on the shell body 1 and is arranged opposite to the cover plate 2. The battery cell 10 includes an open surface, and the open surface and the pressure relief structure 3 are arranged opposite to each other. When the shell 20 is made of steel, 15≤F×(S / S0)≤320 is satisfied. When the shell 20 is made of aluminum, 2.5≤F×(S / S0)≤36 is satisfied. The outermost layer of the battery cell 10 is usually wrapped with a diaphragm, and the open surface of the battery cell 10 refers to the surface of the battery cell 10 that is not covered by the diaphragm. The open surface can quickly release gas, so that the open surface of the battery cell 10 is arranged corresponding to the pressure relief structure 3, and the gas released from the open surface can be quickly discharged through the pressure relief structure 3, further reducing the impact on the cover plate 2, so that the tensile strength of the welding area 4 can be further reduced.

[0075] At this time, the area S0 enclosed by the first surface is the area of ​​the end wall 12 of the shell body 1, that is, S0 is the product of the length of the end wall 12 and the width of the end wall 12; the projection area S of the pressure relief structure 3 on the first surface is the projection area of ​​the pressure relief structure 3 on the end wall 12 of the shell body 1.

[0076] It should be noted that for the wound cell 10, the separator is wrapped along the winding direction, and the open surface refers to the end surface of the cell 10 perpendicular to the winding direction. For the laminated cell 10, the positive electrode sheet, separator and negative electrode sheet are stacked, and in the stacking direction, the electrode sheets are arranged at intervals to form an open surface.

[0077] The pressure relief structure 3 is arranged on the shell body 1 and is arranged opposite to the cover plate 2. Figure 8 As shown, a pole assembly 5 is provided on the cover plate 2, and the battery cell 10 includes a battery cell body 101 and a pole ear 102 led out from the battery cell body 101, and the pole ear 102 is electrically connected to the pole assembly 5. The distance between the cover plate 2 and the shell body 112 where the pressure relief structure 3 is located is h, and h≤200mm is satisfied. A part of the heat can be dissipated through the pole ear 102 and the pole assembly 5, so that the impact force of the gas inside the battery on the cover plate 2 is further reduced. Therefore, the distance between the cover plate 2 and the pressure relief structure 3 can be relatively reduced, so that the heat on the side of the cover plate 2 can quickly reach the pressure relief structure 3 for release.

[0078] like Fig. 9 As shown, the shell body 1 includes a side wall 11, the side wall 11 is welded to the cover plate 2, and the pressure relief structure 3 is arranged on the side wall 11. When the shell 20 is made of steel, 500MPa≤F≤1100MPa is satisfied; when the shell 20 is made of aluminum, 90MPa≤F≤140MPa is satisfied. The pressure relief structure 3 is arranged on the side wall 11 of the shell body 1, and the impact on the welding position of the cover plate 2 and the shell body 1 is reduced, so the pulling force on the welding area 4 is reduced. By further controlling the tensile strength of the welding area 4, while ensuring the connection strength of the cover plate 2 and the shell body 1, high requirements on the welding process and reduced welding yield are avoided.

[0079] It should be noted that the thickness of the side wall 11 is usually smaller than the thickness of the cover plate 2 . By setting the pressure relief structure 3 on the side wall 11 , the pressure relief structure 3 is easier to explode, and the gas is easier to be discharged from the pressure relief structure 3 , thereby reducing the pulling force on the welding area 4 .

[0080] At this time, the area S0 enclosed by the first surface is the area of ​​the side wall 11 of the shell body 1, that is, S0 is the product of the width or length of the side wall 11 and the height of the side wall 11; the projection area S of the pressure relief structure 3 on the first surface is the projection area of ​​the pressure relief structure 3 on the side wall 11 of the shell body 1.

[0081] Further, such as Fig. 9As shown, the minimum distance between the center of the projection of the pressure relief structure 3 on the first surface and the welding area 4 is h1, and the shell body 1 also includes an end wall 12, which is connected to the side wall 11 and arranged opposite to the cover plate 2. The minimum distance between the center of the projection of the pressure relief structure 3 on the first surface and the end wall 12 is h2, satisfying h1>h2, wherein the unit of h1 is mm, and the unit of h2 is mm. At this time, the end wall 12 and the side wall 11 are integrally formed, and the connection strength between the end wall 12 and the side wall 11 is greater than the welding strength between the cover plate 2 and the side wall 11. Therefore, the impact resistance of the end wall 12 is higher than the impact resistance of the cover plate 2. The pressure relief structure 3 is arranged closer to the end wall 12, that is, farther away from the cover plate 2, so that when the internal gas of the battery is released by the pressure relief structure 3, the pulling of the welding position of the cover plate 2 and the shell body 1 is further reduced.

[0082] Furthermore, 1.1≤h1 / h2≤5. This arrangement makes the position of the pressure relief structure 3 on the side wall 11 more reasonable, while ensuring that the end wall 12 and the cover plate 2 are not opened. Specifically, the value of h1 / h2 can be any value among 1.1, 2, 3, 4, 5, etc., or a value between any two values.

[0083] When the shell 20 is made of steel, the thickness of the cover plate 2 is t1, which satisfies 0.3mm≤t1≤1mm. The strength of the steel cover plate 2 and the tensile strength of the welding area 4 between the cover plate 2 and the shell body 1 are both relatively large, so the thickness of the cover plate 2 can be set to be relatively small, thereby improving the space utilization of the battery and improving the battery energy density.

[0084] Specifically, the housing 20 is made of steel, such as Fig.10 As shown, the shell body 1 includes a first side wall 111 and a second side wall 112 , both of which are welded to the cover plate 2 , and a transition portion 113 is provided between the first side wall 111 and the second side wall 112 , satisfying 0.01≤S / S0≤0.5.

[0085] It should be noted that during the production process, the steel shell body 1 is not easy to process and shape. The square steel shell body 1 is usually first processed into a cylindrical barrel with openings at both ends, and then shaped into a square shell body 1. Therefore, the processing of the square shell body 1 involves a round-to-square process, resulting in relatively weak strength at the transition portion 113. Especially for the steel shell body 1, the plastic deformation of steel is poor, the round-to-square process is difficult, and the forming effect of the transition portion 113 is poor after the shell body 1 is processed into a square. Therefore, after the cover plate 2 and the shell body 1 are welded, the transition portion 113 becomes a failure point, and the area occupied by the pressure relief structure 3 is increased, so that the impact of the internal gas of the battery on the welding area 4 of the cover plate 2 and the shell body 1 can be reduced, and failure at the transition portion 113 is avoided.

[0086] Further, such as Fig.10As shown, two first side walls 111 and two second side walls 112 are provided, the two first side walls 111 are relatively spaced apart, the two second side walls 112 are relatively spaced apart, and the adjacent first side walls 111 and second side walls 112 are connected by a transition portion 113, and the transition portion 113 is an arc-shaped structure.

[0087] It is worth mentioning that please refer to Figure 6 , the openings at both ends of the shell body 1 can be blocked by the cover plate 2; or, please refer to Figure 8 and Fig. 9 One end opening of the shell body 1 is blocked by the cover plate 2, and the other end opening can be blocked by other structures (such as a flat plate structure).

[0088] When the housing 20 is made of steel, the pressure relief structure 3 is also made of steel, and the pressure relief structure 3 includes a weak portion 31, such as Fig.11 As shown, the residual thickness of the weak part 31 is k, which satisfies 0.01mm≤k≤0.08mm. When the battery has thermal runaway, the weak part 31 of the pressure relief structure 3 is opened first as a weak point, and then drives the entire pressure relief structure 3 to open and release gas. For the steel pressure relief structure 3, the strength and melting point of the weak part 31 are relatively high. Therefore, the residual thickness of the weak part 31 is set to be relatively small, so that the weak part 31 can be broken in time to release gas.

[0089] When the material of the steel shell 20 includes silicon, the content of silicon is between 0.1% and 0.3%, satisfying 0.008≤S / S0≤0.45. When the material of the aluminum shell 20 includes silicon, the content of silicon is between 3% and 25%, satisfying 0.01≤S / S0≤0.5. Silicon can significantly improve the elastic limit, yield point and tensile strength of the material. By increasing the silicon content, the tensile strength of the shell 20 can be increased, thereby improving the tensile strength of the welding area 4 of the cover plate 2 and the shell body 1. Therefore, the area occupied by the pressure relief structure 3 can be smaller, but if the area occupied by the pressure relief structure 3 is too small, it will cause the gas to increase the pulling force on the welding area 4; and if the silicon content is too high, it will cause the welding performance to deteriorate, which will in turn worsen the strength of the welding area 4 of the shell body 1 and the cover plate 2. Therefore, by comprehensively controlling the silicon content and the relationship between S / S0, the tensile strength of the welding area 4 between the cover plate 2 and the shell body 1 can be enhanced, while the area of ​​the pressure relief structure 3 can be appropriately reduced to improve the structural strength of the shell 20.

[0090] When the shell 20 is made of aluminum, the thickness of the cover plate 2 is t1, which satisfies 1.2 mm ≤ t1 ≤ 3.5 mm. The strength of the aluminum cover plate 2 and the tensile strength of the welding area 4 between the cover plate 2 and the shell body 1 are both relatively small, so the thickness of the cover plate 2 needs to be set larger to ensure the strength of the cover plate 2 itself and the connection strength between the cover plate 2 and the shell body 1.

[0091] Specifically, the housing 20 is made of aluminum. Fig.10 As shown, the shell body 1 includes a first side wall 111 and a second side wall 112, both of which are welded to the cover plate 2, and a transition portion 113 is provided between the first side wall 111 and the second side wall 112, satisfying 0.015≤S / S0≤0.6. For the aluminum shell body 1, the transition portion 113 is also a failure point, so the area occupied by the pressure relief structure 3 is increased, so that the impact of the internal gas of the battery on the cover plate 2 and the welding area 4 of the shell body 1 can be reduced, and failure at the transition portion 113 is avoided.

[0092] Further, such as Fig.10 As shown, two first side walls 111 and two second side walls 112 are provided, the two first side walls 111 are relatively spaced apart, the two second side walls 112 are relatively spaced apart, and the adjacent first side walls 111 and second side walls 112 are connected by a transition portion 113, and the transition portion 113 is an arc-shaped structure.

[0093] In one embodiment, the shell 20 is provided with a through hole, and the pressure relief structure 3 covers the through hole and is connected to the shell 20. When the shell 20 is made of steel, 400MPa≤F≤1050MPa is satisfied; when the shell 20 is made of aluminum, 80MPa≤F≤135MPa is satisfied. That is, the pressure relief structure 3 and the shell 20 are separate structures, and an additional connection method (such as bonding, welding, etc.) is used to fix the pressure relief structure 3 to the shell 20. At this time, the pressure relief structure 3 is more likely to explode to achieve exhaust, so the tensile strength of the welding area 4 can be appropriately reduced.

[0094] Specifically, Figure 4 As shown, the pressure relief structure 3 is welded to the shell 20 to form a second welding area 6, and the tensile strength of the second welding area 6 is F0, satisfying F0<F. In this way, when the battery is thermally runaway, the pressure relief structure 3 and the shell body 1 can be separated to achieve exhaust first, avoiding the welding area 4 of the cover plate 2 and the shell body 1 from being broken open.

[0095] It is worth noting that a through hole is firstly opened on the shell 20 , and then the pressure relief structure 3 is arranged corresponding to the through hole, and the pressure relief structure 3 and the shell 20 are welded.

[0096] Of course, in other alternative embodiments, the pressure relief structure 3 is integrally provided with the shell 20, satisfying 0.01≤S / S0≤0.5. Specifically, the pressure relief structure 3 can be formed on the shell 20 by stamping or laser etching, so there is no need to use an additional connection method to separately set the pressure relief structure 3 on the shell 20. However, when the pressure relief structure 3 is formed on the shell 20, it will generate greater stress on other positions of the shell 20, causing other positions of the shell 20 to be easily deformed or broken. Therefore, if the area occupied by the pressure relief structure 3 is set too large, it will have a greater impact on other positions of the shell 20. Therefore, the value of S / S0 is further limited, while ensuring that the pressure relief structure 3 can release gas, it avoids the occurrence of problems such as deformation and breakage of the shell 20 when the pressure relief structure 3 is formed on the shell 20.

[0097] Furthermore, when the pressure relief structure 3 is integrated with the cover plate 2, 550MPa≤F≤1200MPa is satisfied for the steel shell 20, and 95MPa≤F≤135MPa is satisfied for the aluminum shell 20. The pressure relief structure 3 and the shell 20 are integrally formed, and when the gas inside the battery impacts the pressure relief structure 3, the impact force on other positions of the shell 20 is also large, which can easily cause the cover plate 2 to separate from the shell body 1, so the tensile strength of the welding area 4 needs to be appropriately increased.

[0098] It is worth noting that the battery cell 10 includes a positive electrode sheet, a negative electrode sheet and a separator, the separator is arranged between the positive electrode sheet and the negative electrode sheet, and the positive electrode sheet, the negative electrode sheet and the separator are wound or laminated to form the battery cell 10. The positive electrode sheet includes a positive electrode collector and a positive electrode active material layer, and the negative electrode sheet includes a negative electrode collector and a negative electrode active material layer. There is no special restriction on the positive electrode collector, as long as it has conductivity and does not cause adverse chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, fired carbon, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc. can be used; the negative electrode collector can be copper, stainless steel, nickel, titanium, etc. In a specific embodiment, aluminum can be used for the positive electrode, and copper can be used for the negative electrode. The positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes a nickel-cobalt-manganese ternary material, a lithium iron phosphate material, a lithium iron manganese phosphate material, etc.; the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes artificial graphite, natural graphite, silicon-based materials, etc.

[0099] The battery preparation process usually includes:

[0100] (1) Preparation of positive electrode.

[0101] The prepared positive electrode active material, conductive agent acetylene black, and binder PVDF are mixed in a mass ratio of 96:2:2, and solvent NMP is added. The mixture is stirred under the action of a vacuum mixer until the system becomes uniform to obtain a positive electrode slurry. The positive electrode slurry is evenly coated on both surfaces of the positive electrode current collector aluminum foil, dried at room temperature, and then transferred to an oven for further drying, and then cold pressed and cut to obtain a positive electrode sheet.

[0102] (2) Preparation of negative electrode sheet.

[0103] The negative electrode active material graphite or a mixture of graphite and other active materials (such as silicon-based materials) in different mass ratios, the conductive agent acetylene black, the thickener CMC, and the binder SBR are mixed in a mass ratio of 96.4:1:1.2:1.4, and deionized water as a solvent is added. The mixture is stirred under the action of a vacuum stirrer until the system becomes uniform to obtain a negative electrode slurry; the negative electrode slurry is evenly coated on both surfaces of the negative electrode current collector copper foil, dried at room temperature, and then transferred to an oven for further drying, and then cold pressed and cut to obtain a negative electrode sheet.

[0104] (3) Preparation of electrolyte.

[0105] Ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent, and then fully dried lithium salt LiPF6 is dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0106] (4) Preparation of diaphragm.

[0107] A polyethylene film was selected as the separator.

[0108] (5) Preparation of lithium-ion batteries.

[0109] The positive electrode sheet, separator and negative electrode sheet are stacked in order, so that the separator is placed between the positive and negative electrode sheets to play an isolating role, and then wound to obtain a bare battery cell 10; the bare battery cell 10 is inserted into the shell from the opening of the shell body 1, and the cover plate 2 and the shell body 1 are laser sealed and welded; after drying, the electrolyte is injected, and after vacuum packaging, standing, forming, shaping and other processes, a lithium-ion battery is obtained.

[0110] It is worth noting that the tensile strength of the welding area 4 of the cover plate 2 and the shell body 1 can be adjusted by the laser welding power, welding rate, and defocus during welding. Among them, the power of welding the inner ring of the cover plate 2 and the shell body 1 is 700W-1550W, the power of welding the outer ring is 1370W-2000W, the welding rate is 200mm / s-250mm / s, and the defocus is 0-3mm.

[0111] Thermal runaway tests were conducted on the following batteries with different F and S / S0 values ​​to observe whether the cover plate 2 and the shell body 1 were separated and whether the cover plate 2 was deformed at the position of the pressure relief structure 3. The test results are shown in Table 1.

[0112] Table 1 Thermal runaway test results

[0113]

[0114] In Table 1, the example refers to a battery whose values ​​of F and S / S0 meet the requirements of the example, and the comparative example refers to a battery whose values ​​of F and / or S / S0 do not meet the requirements of the example.

[0115] It can be seen from Table 1 that in Examples 1 to 19, when the tensile strength of the welding zone 4 and the area ratio of the pressure relief structure 3 meet 1≤F×(S / S0)≤500, during the battery thermal runaway test, the cover plate 2 and the shell body 1 are not separated, and the shape of the cover plate 2 at the position of the pressure relief structure 3 is intact; in Comparative Example 1, the tensile strength of the welding zone 4 and the area ratio of the pressure relief structure 3 do not meet 1≤F×(S / S0)≤500 and are lower than the lower limit, the tensile strength of the welding zone 4 is small, and the area ratio of the pressure relief structure 3 is small, and the battery thermal runaway test is good. During the control test, the pressure relief structure 3 cannot fully release the internal heat, and the cover plate 2 and the shell body 1 are separated; in Comparative Example 2, the tensile strength of the welding area 4 and the area ratio of the pressure relief structure 3 do not satisfy 1≤F×(S / S0)≤500 and are higher than the upper limit value. During the battery thermal runaway test, the cover plate 2 and the shell body 1 are not separated, but the cover plate 2 at the position of the pressure relief structure 3 is deformed. Due to the concentrated impact of the gas on the position of the pressure relief structure 3, the pressure relief structure 3 is subjected to excessive force, and the cover plate 2 is severely deformed at the position corresponding to the pressure relief structure 3.

[0116] In summary, by comprehensively controlling the tensile strength of the welding area 4 and the area ratio of the pressure relief structure 3, the gas inside the battery is released smoothly, and the welding reliability of the cover plate 2 and the shell body 1 is improved, thereby improving the safety performance of the battery.

[0117] In combination with Examples 1 to 5, it can be seen that for the steel shell 20 battery, when the tensile strength of the welding area 4 and the area ratio of the pressure relief structure 3 satisfy the range of 8≤F×(S / S0)≤400 and the value of F satisfies the range of 400MPa≤F≤1200MPa, and the value of S / S0 satisfies the range of 0.008≤S / S0≤0.5, during the thermal runaway test of the steel shell 20 battery, the cover plate 2 and the shell body 1 did not separate, and the cover plate 2 at the position of the pressure relief structure 3 did not deform, thereby achieving better safety performance.

[0118] In addition, in Example 6, for the steel shell 20 battery, when the tensile strength F of the welding area 4 is less than 400 MPa, although the cover plate 2 and the shell body 1 are not separated, the welding position of the cover plate 2 and the shell body 1 is slightly deformed. In Example 10, for the steel shell 20 battery, when the tensile strength of the welding area 4 and the area ratio of the pressure relief structure 3 F×(S / S0) are less than 8, although the cover plate 2 and the shell body 1 are not separated, the welding position of the cover plate 2 and the shell body 1 is severely deformed.

[0119] In combination with Examples 11 to 15, it can be seen that for the aluminum shell 20 battery, when the tensile strength of the welding area 4 and the area ratio of the pressure relief structure 3 satisfy the range of 1.5≤F×(S / S0)≤45 and the value of F satisfies the range of 80MPa≤F≤150MPa, and the value of S / S0 satisfies the range of 0.01≤S / S0≤0.6, during the thermal runaway test of the aluminum shell 20 battery, the cover plate 2 and the shell body 1 did not separate, and the cover plate 2 at the position of the pressure relief structure 3 did not deform, achieving better safety performance.

[0120] In addition, in Example 16, for the aluminum shell 20 battery, when the tensile strength F of the welding area 4 is less than 80 MPa, although the cover plate 2 and the shell body 1 are not separated, the welding position of the cover plate 2 and the shell body 1 is slightly deformed. In Example 18, for the aluminum shell 20 battery, when the tensile strength of the welding area 4 and the area ratio of the pressure relief structure 3 F×(S / S0) are less than 1.5, although the cover plate 2 and the shell body 1 are not separated, the welding position of the cover plate 2 and the shell body 1 is severely deformed.

[0121] It is worth noting that in Table 1, severe deformation means that no less than 50% of the connection position of the shell body 1 and the cover plate 2 is deformed; slight deformation means that no more than 30% of the connection position of the shell body 1 and the cover plate 2 is deformed.

[0122] It should be noted that the test process of thermal runaway test refers to the national standard GB 38031-2020, which is generally:

[0123] 1. Charge the battery. For specific charging strategies, the charging of nickel-cobalt-manganese ternary materials, lithium iron phosphate positive electrode materials, lithium iron manganese phosphate positive electrode materials, lithium-rich manganese-based positive electrode materials, and lithium nickel manganese oxide positive electrode materials are as follows: nickel-cobalt-manganese ternary materials are charged to 4.25V at a current of 1C, and charged at a constant voltage until the current drops to 0.05C; lithium iron phosphate is charged to 3.65V at a constant current of 0.5C, and charged at a constant voltage until the current drops to 0.05C; lithium iron manganese phosphate is charged to 4.25V at 0.5C, and charged at a constant voltage until the current drops to 0.05C; lithium-rich manganese-based materials are charged to 4.25V at 0.5C, and charged at a constant voltage until the current drops to 0.05C; lithium nickel manganese oxide is charged to 4.85V at 1C, and charged at a constant voltage until the current drops to 0.05C.

[0124] 2. Place a heating sheet on the large surface of the battery to heat the trigger object with the maximum power of the heating device.

[0125] 3. When thermal runaway occurs or the temperature at the monitoring point reaches 300°C, stop triggering and turn off the heating device.

[0126] Furthermore, the thermal runaway determination conditions are as follows: the trigger object generates a voltage drop, and the drop value exceeds 25% of the initial voltage, and the temperature rise rate dT / dt of the monitoring point is ≥l℃ / s, and lasts for more than 3s, then it is determined that thermal runaway has occurred.

[0127] It is worth noting that the test method for tensile strength is:

[0128] 1. Cut the local position of welding area 4 to obtain a sample with a width of 10 mm and a length of 100 mm;

[0129] 2. Test the tensile strength of the sample using a tensile testing machine;

[0130] 3. Finally, the fracture position is obtained and the tensile strength value is fed back.

[0131] According to another aspect of an embodiment of the present invention, a battery pack is provided, comprising the above-mentioned battery.

[0132] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A battery, characterized in that: include: A battery cell (10) and a shell (20); the shell (20) is made of steel and is a quadrangular prism structure; the shell (20) comprises a shell body (1) and a cover plate (2); at least one end of the shell body (1) is open; the cover plate (2) is welded to the open end of the shell body (1) to form a welding area (4); the cover plate (2) blocks the opening and forms a housing space with the shell body (1); the battery cell (10) is located in the housing space; the tensile strength of the welding area (4) is F; a pressure relief structure (3) is provided on the first surface of the shell (20); the projection area of ​​the pressure relief structure (3) on the first surface is S; the area formed by the first surface is S0, and 8≤F×(S / S0)≤400 is satisfied, wherein the unit of F is MPa and the unit of S is mm 2 , the unit of S0 is mm 2 The shell (20) is provided with a through hole, the pressure relief structure (3) covers the through hole and is connected to the shell (20), or the pressure relief structure (3) is integrally arranged with the shell (20).

2. The battery according to claim 1, characterized in that The value range of F is 400MPa≤F≤1200MPa, and the value range of S / S0 is 0.008≤S / S0≤0.

5.

3. The battery according to claim 2, characterized in that The pressure relief structure (3) is arranged on the cover plate (2) and satisfies 600MPa≤F≤1200MPa.

4. The battery according to any one of claims 1 to 3, characterized in that The penetration depth of the welding zone (4) is d, and the penetration width of the welding zone (4) is w, which satisfies 0.04≤d×w≤0.9, wherein the unit of d is mm, and the unit of w is mm.

5. The battery according to claim 2 or 3, characterized in that: The pressure relief structure (3) is arranged on the cover plate (2), the thickness of the cover plate (2) is t1, and the wall thickness of the side wall (11) of the shell body (1) welded to the cover plate (2) is t2, satisfying 1≤t1 / t2≤10, wherein the unit of t1 is mm, and the unit of t2 is mm.

6. The battery according to claim 2 or 3, characterized in that: The pressure relief structure (3) is arranged on the cover plate (2), a pole assembly (5) is arranged on the cover plate (2), the battery cell (10) and the pole assembly (5) are electrically connected, the pole assembly (5) comprises two pole bodies (51), the pressure relief structure (3) is arranged between the two pole bodies (51), the distance between the center of the projection of the pressure relief structure (3) on the first surface and the center of the projection of one of the pole bodies (51) on the first surface is a, and the distance between the center of the projection of the pressure relief structure (3) on the first surface and the center of the projection of the other pole body (51) on the first surface is b, satisfying 0≤│ab│≤10, wherein the unit of a is mm, and the unit of b is mm.

7. The battery according to claim 2 or 3, characterized in that: The pressure relief structure (3) is arranged on the cover plate (2), a pole assembly (5) is arranged on the cover plate (2), the battery cell (10) and the pole assembly (5) are electrically connected, the pole assembly (5) comprises a pole body (51), the minimum distance between the center of the projection of the pole body (51) on the first surface and the welding area (4) is l1, the distance between the center of the projection of the pole body (51) on the first surface and the center of the projection of the pressure relief structure (3) on the first surface is l2, and 0.07≤l1 / l2≤0.8 is satisfied, wherein the unit of l1 is mm, and the unit of l2 is mm.

8. The battery according to claim 2 or 3, characterized in that: The pressure relief structure (3) is arranged on the cover plate (2), and the cover plate (2) is also provided with a liquid injection hole (21), the minimum distance between the center of the projection of the liquid injection hole (21) on the first surface and the welding area (4) is l3, the length of the battery is x1, and 0.1≤l3 / x1≤0.4 is satisfied, wherein the unit of l3 is mm, and the unit of x1 is mm.

9. The battery according to claim 2, characterized in that The pressure relief structure (3) is arranged on the shell body (1) and satisfies 400MPa≤F≤1100MPa.

10. The battery according to claim 9, characterized in that The pressure relief structure (3) is arranged on the shell body (1) and is arranged opposite to the cover plate (2); the distance between the cover plate (2) and the shell body (1) where the pressure relief structure (3) is located is h, satisfying h≥80mm and 400MPa≤F≤1000MPa.

11. The battery according to claim 9, characterized in that The pressure relief structure (3) is arranged on the shell body (1) and is arranged opposite to the cover plate (2); the battery cell (10) comprises an opening surface; the opening surface and the pressure relief structure (3) are arranged opposite to each other and satisfy 15≤F×(S / S0)≤320.

12. The battery according to claim 9, characterized in that The pressure relief structure (3) is arranged on the shell body (1) and is arranged opposite to the cover plate (2); a pole assembly (5) is arranged on the cover plate (2); the battery cell (10) comprises a battery cell body (101) and a pole ear (102) extending from the battery cell body (101); the pole ear (102) and the pole assembly (5) are electrically connected; the distance between the cover plate (2) and the shell body (1) where the pressure relief structure (3) is located is h, satisfying h≤200 mm.

13. The battery according to claim 9, characterized in that The shell body (1) comprises a side wall (11), the side wall (11) is welded to the cover plate (2), and the pressure relief structure (3) is arranged on the side wall (11), satisfying 500MPa≤F≤1100MPa.

14. The battery according to claim 13, characterized in that The shell body (1) comprises a side wall (11), the side wall (11) is welded to the cover plate (2), the pressure relief structure (3) is arranged on the side wall (11), and the minimum distance between the center of the projection of the pressure relief structure (3) on the first surface and the welding area (4) is h1. The shell body (1) also comprises an end wall (12), the end wall (12) is connected to the side wall (11) and is arranged opposite to the cover plate (2), and the minimum distance between the center of the projection of the pressure relief structure (3) on the first surface and the end wall (12) is h2, wherein the unit of h1 is mm, the unit of h2 is mm, and 1.1≤h1 / h2≤5 is satisfied.

15. The battery according to any one of claims 1 to 3, characterized in that The thickness of the cover plate (2) is t1, satisfying 0.3 mm ≤ t1 ≤ 1 mm.

16. The battery according to any one of claims 1 to 3, characterized in that The shell body (1) comprises a first side wall (111) and a second side wall (112); the first side wall (111) and the second side wall (112) are both welded to the cover plate (2); a transition portion (113) is provided between the first side wall (111) and the second side wall (112), and 0.01≤S / S0≤0.5 is satisfied.

17. The battery according to any one of claims 1 to 3, characterized in that The pressure relief structure (3) comprises a weak portion (31), the residual thickness of the weak portion (31) is k, and satisfies 0.01 mm≤k≤0.08 mm.

18. The battery according to any one of claims 1 to 3, characterized in that The material of the shell (20) includes silicon, the content of which is between 0.1% and 0.3%, satisfying 0.008≤S / S0≤0.

45.

19. The battery according to any one of claims 1 to 3, characterized in that The shell (20) is provided with a through hole, and the pressure relief structure (3) covers the through hole and is connected to the shell (20), satisfying 400MPa≤F≤1050MPa.

20. The battery according to claim 19, characterized in that The pressure relief structure (3) and the shell (20) are welded to form a second welding area (6), and the tensile strength of the second welding area (6) is F0, satisfying F0<F.

21. The battery according to any one of claims 1 to 3, characterized in that The pressure relief structure (3) and the housing (20) are integrally arranged, satisfying 0.01≤S / S0≤0.

5.

22. The battery according to any one of claims 1 to 3, characterized in that The pressure relief structure (3) is integrally arranged with the cover plate (2), satisfying 550MPa≤F≤1200MPa.

23. A battery pack, characterized in that: A battery comprising the battery according to any one of claims 1 to 22.

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