Battery and battery pack

Abstract

The present application relates to the technical field of batteries, and discloses a battery and a battery pack. The battery comprises a battery cell and a casing. The casing has a quadrangular prismatic structure, and comprises a casing main body and a cover plate. At least one end of the casing main body is open, and the cover plate is welded to the open end of the casing main body to form a welding zone. The tensile strength of the welding zone is F, a pressure relief structure is provided on a first surface of the casing, the projection area of the pressure relief structure on the first surface is S, and the area enclosed by the first surface is S0, satisfying 1≤F×(S / S0)≤500, where the unit of F is MPa, the unit of S is mm2, and the unit of S0 is mm2. In the present application, by means of comprehensively controlling the tensile strength F and the ratio S / S0 of the area occupied by the pressure relief structure on the first surface to the area enclosed by the first surface, blockage of the pressure relief structure by the battery cell during battery thermal runaway is avoided; such blockage would otherwise obstruct normal pressure relief, cause the cover plate to be blown open, and trigger more serious safety incidents such as battery fire. Thus, battery safety is ensured.

Description

Battery and battery pack

[0001] Cross Reference to Related Applications

[0002] The present application claims priority to the Chinese patent application No. 202411381131.9, filed on September 30, 2024, and entitled "Battery and battery pack", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0003] The present application relates to the technical field of battery, in particular to a battery and a battery pack. BACKGROUND

[0004] The battery generally comprises a battery cover plate, a shell and a battery cell, the battery cover plate and the shell are welded to form an accommodating space, and the battery cell is arranged in the accommodating space. In order to ensure the safety of the battery, a pressure relief structure such as an explosion-proof valve is usually arranged on the battery cover plate. When the battery encounters mechanical impact or internal abnormal short circuit, etc., it may cause thermal runaway of the battery, and high-temperature and high-pressure gas is generated inside the battery. When the gas pressure reaches a certain degree, the pressure relief structure will burst open to release the gas inside the battery. However, through experimental observation, it is found that when the battery experiences thermal runaway, the battery cover plate may be completely blown open, resulting in fire of the battery. SUMMARY

[0005] Therefore, the present application provides a battery and a battery pack to solve the problem that the battery cover plate is completely blown open when the battery in the prior art experiences thermal runaway, resulting in fire of the battery.

[0006] In a first aspect, the present application provides a battery, comprising: a battery cell and a shell; the shell is a quadrangular prism structure, the shell comprises a shell main body and a cover plate, at least one end of the shell main body is provided with an opening, the cover plate is welded with the opening end of the shell main body to form a welding area, the cover plate blocks the opening and forms an accommodating space with the shell main body, and 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, and 1≤F×(S / S0)≤500 is satisfied, wherein the unit of F is MPa, the unit of S is mm2, and the unit of S0 is mm2.

[0007] The application avoids the situation that the pressure relief structure is blocked by the battery cell when the battery is in thermal runaway, cannot normally release pressure, and causes the cover plate to be punched open, thereby causing more serious safety accidents such as fire of the battery, thereby ensuring the safety of the battery; when S / S0 is small, the area of the pressure relief structure is small, the release of gas is limited, the internal battery cell is lifted, the pressure relief structure is blocked, the pressure relief structure cannot normally exhaust, the internal gas still pulls the welding position of the cover plate and the shell main body, causing the welding position of the cover plate and the shell main body to be disconnected, the cover plate is punched open, and more serious safety accidents are caused; therefore, when the area of the pressure relief structure is small, the tensile strength of the cover plate and the shell main body needs to be adjusted to avoid separation of the cover plate and the shell main body; when S / S0 is 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 main body is reduced, but if the area of the pressure relief structure is too large, the pressure relief structure will be difficult to open, and the battery still has a high risk of fire and explosion.

[0008] In a second aspect, the application also provides a battery pack comprising the battery described above. BRIEF DESCRIPTION OF DRAWINGS

[0009] In order to more clearly illustrate the technical solutions in the specific embodiments or prior art of the application, the drawings needed in the following specific embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0010] Fig. 1 is a schematic diagram of the overall structure of a battery according to an embodiment of the application;

[0011] Fig. 2 is a top view of the battery shown in Fig. 1;

[0012] Fig. 3 is a schematic diagram of the cross-sectional structure of A-A in Fig. 2;

[0013] Fig. 4 is an enlarged view of B in Fig. 3;

[0014] Fig. 5 is a top view of another battery according to an embodiment of the application;

[0015] Fig. 6 is a schematic diagram of the cooperation structure of the shell main body and the cover plate according to an embodiment of the application;

[0016] Fig. 7 is an enlarged view of C in Fig. 6;

[0017] Fig. 8 is a schematic diagram of the cross-sectional structure of the battery when the pressure relief structure is arranged on the end wall according to an embodiment of the application;

[0018] Fig. 9 is a schematic diagram of the cross-sectional structure of the battery when the pressure relief structure is arranged on the side wall according to an embodiment of the application;

[0019] Fig. 10 is a structural schematic view of a first side wall, a second side wall and a transition portion according to an embodiment of the present application;

[0020] Fig. 11 is a structural schematic view of a weak portion of a pressure relief structure according to an embodiment of the present application;

[0021] Fig. 12 is a schematic view of another pressure relief structure according to an embodiment of the present application;

[0022] Fig. 13 is a schematic view of still another pressure relief structure according to an embodiment of the present application.

[0023] BRIEF DESCRIPTION OF DRAWINGS 1, shell body; 11, side wall; 111, first side wall; 112, second side wall; 113, transition portion; 12, end wall; 2, cover plate; 21, liquid injection hole; 3, pressure relief structure; 31, weak portion; 4, welding area; 5, pole column assembly; 51, pole column body; 6, second welding area; 10, battery cell; 101, battery cell body; 102, tab; 20, shell. DETAILED DESCRIPTION

[0024] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0025] The embodiments of the present application will be described below with reference to Figs. 1 to 13.

[0026] According to an embodiment of the present application, in one aspect, a battery is provided, comprising:

[0027] The battery cell 10 and the shell 20; the shell 20 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 provided with an opening, the cover plate 2 is welded with the opening end of the shell body 1 to form a welding area 4, the cover plate 2 blocks the opening and forms an accommodation space together with the shell body 1, and the battery cell 10 is located in the accommodation 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, the area enclosed by the first surface is S0, and 1≤F×(S / S0)≤500 is satisfied, wherein the unit of F is MPa, the unit of S is mm2, and the unit of S0 is mm2. 2 .

[0028] Specifically, the value of F x (S / S0) can be any 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 of the values.

[0029] The battery of the embodiment avoids the pressure relief structure 3 being blocked by the battery cell 10 and unable to normally release pressure, the cover plate 2 being broken open, and more serious safety accidents such as fire of the battery occurring when the battery is in thermal runaway, thereby ensuring the safety of the battery. When S / S0 is small, because the area of the pressure relief structure 3 is small, the release of gas is limited, the internal battery cell 10 is lifted up, the pressure relief structure 3 is blocked, the pressure relief structure 3 cannot normally release gas, and the internal gas still pulls the welding position of the cover plate 2 and the shell main body 1, causing the welding position of the cover plate 2 and the shell main body 1 to be disconnected, the cover plate 2 to be broken open, and more serious safety accidents to occur. Therefore, when the area of the pressure relief structure 3 is small, the tensile strength of the cover plate 2 and the shell main body 1 needs to be adjusted to avoid the cover plate 2 and the shell main body 1 from being separated. When S / S0 is large, the gas can be released from the position of the pressure relief structure 3, and the impact on the welding position of the cover plate 2 and the shell main body 1 is reduced, but if the area of the pressure relief structure 3 is too large, the pressure relief structure 3 will be difficult to open, and the battery still has a high risk of fire and explosion.

[0030] The welding tensile strength refers to the maximum bearing capacity of the welding area 4 under tensile load. Optionally, the welding tensile strength can be adjusted by adjusting welding parameters or welding processes. Specifically, the welding parameters include welding current, voltage, welding speed, etc., and the welding processes include 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 influence on the safety of the battery. For example, when short circuit, overcharge and other phenomena occur, it may cause thermal runaway in the battery, resulting in a sudden increase 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 overheats. For example, the pressure relief structure 3 can be a separate explosion-proof sheet, a through hole is provided on the shell 20, and the explosion-proof sheet is connected to the through hole. The explosion-proof sheet is provided with a weak part 31, which can be a local thinning area on the explosion-proof sheet, used to burst open when the battery overheats, and drive the explosion-proof sheet to open to release pressure. Alternatively, the weak part 31 can be a circumferential ring around the explosion-proof sheet, or it can be discontinuous, that is, some positions are not provided with a weak part 31. Alternatively, a weak part 31 can be directly stamped or formed on the shell 20 by laser etching as a pressure relief structure 3. The projected 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. Alternatively, referring to Figure 1, the pressure relief structure 3 is an explosion-proof sheet, and the projected area of the pressure relief structure 3 on the first surface is the area of the explosion-proof sheet. Referring to Figure 12, the H-shaped notch is used as the pressure relief structure 3, and the projected area of the pressure relief structure 3 on the first surface is the area of the region occupied by the H-shaped notch on the first surface (the area in the dashed line box in Figure 12). Referring to Figure 13, the weak part 31 stamped on the shell 20 is used as the pressure relief structure 3, and the projected area of the pressure relief structure 3 on the first surface is the area of the region occupied by the weak part 31 on the first surface, that is, the area enclosed by the weak part 31.

[0032] It should be noted that when the internal pressure of the battery is constant, the smaller the area of the pressure relief structure 3, the greater the stress acting on the pressure relief structure 3, which can make the pressure relief structure 3 easier to open.

[0033] Alternatively, it should be noted that when the tensile strength F of the welding area 4 is relatively small, although the connection strength of the cover plate 2 and the shell body 1 is relatively weak, it will still be greater than the strength at the weak part 31 of the pressure relief structure 3, that is, the battery will still burst at the pressure relief structure 3 to vent, so the pressure relief structure 3 is set to a larger area, which can have a larger venting area after the pressure relief structure 3 bursts, thereby enabling the battery internal gas to be quickly discharged, avoiding the battery internal gas continuously applying stress to the welding area 4 and the stress gradually increasing as the battery internal gas accumulates, thereby avoiding the cover plate 2 being blown open.

[0034] Therefore, in the embodiment, by limiting the value range of Fx(S / S0), the tensile strength of the welding area 4 and the area occupied by the pressure relief structure 3 on the shell 20 have reasonable values, so that when the battery overheats, the pressure relief structure 3 can be opened in time and quickly exhaust, and the cover plate 2 can be prevented from being punched open. Thus, the safety of the battery is ensured.

[0035] It should be noted that the battery of the embodiment is a four-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-cancelling, and the impact on the welding position of the cover plate 2 and the shell body 1 is relatively small. When the battery cell 10 of the four-prism battery expands, the internal unevenness of the battery cell 10 generates a relatively large impact on the welding position of the cover plate 2 and the shell body 1. During the thermal runaway test of the four-prism battery, the battery cell 10 is lifted to block the pressure relief structure 3, affecting the opening of the pressure relief structure 3, and the risk of separation of the cover plate 2 and the shell body 1 increases.

[0036] In addition, the tensile strength of the welding position of the cover plate 2 and the shell body 1 is smaller 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 and connected, the metal is melted during welding, the crystal structure changes, and the tensile strength of the welding area 4 of the cover plate 2 and the shell body 1 is weakened), and the welding position of the cover plate 2 and the shell body 1 is prone to cracking during the thermal runaway test of the battery, 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 arranged circumferentially around the edge of the cover plate 2 to weld the cover plate 2 and the shell body 1 along the circumference of the cover plate 2.

[0039] Alternatively, the value range of F is 60MPa≤F≤1300MPa, and the value range of S / S0 is 0.006≤S / S0≤0.6. In this way, the tensile strength is within an appropriate range, avoiding weak strength at the welding position of the cover plate 2 and the shell body 1, which leads to connection failure of the cover plate 2 and the shell body 1 when the battery overheats; and avoiding too large tensile strength, which requires high welding process and reduces the welding yield. The value of S / S0 is within an appropriate range, avoiding that the gas cannot be fully released through the pressure relief structure 3 when the battery overheats; and avoiding that the area of the pressure relief structure 3 is too large to affect the strength of the shell 20. Thus, the tensile strength of the welding area 4 and the area occupied by the pressure relief structure 3 on the shell 20 have reasonable values, and the safety of the battery is ensured.

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

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

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

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

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

[0045] Specifically, when the shell 20 is steel, the value of F×(S / S0) can be any one of 8, 40, 80, 120, 160, 200, 240, 280, 320, 360, 400, 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 punched open, so 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, while ensuring that the pressure relief structure 3 can be quickly opened when the battery is in thermal runaway, the connection strength of the cover plate 2 and the shell body 1 is ensured.

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

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

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

[0050] Optionally, 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 aluminum, the value of F can be any value in 80MPa, 90MPa, 100MPa, 110MPa, 120MPa, 130MPa, 140MPa, 150MPa, or a value between any two values; the value of S / S0 can be any value in 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, or a value between any two values.

[0052] For the setting position of the pressure relief structure 3, the pressure relief structure 3 can be set on the cover plate 2 or on the shell body 1.

[0053] As shown in FIGS. 1-5, the pressure relief structure 3 is arranged on the cover plate 2. When the shell 20 is steel, 600 MPa≤F≤1200 MPa. When the shell 20 is aluminum, 90 MPa≤F≤150 MPa. Arranging the pressure relief structure 3 on the cover plate 2 is simpler than arranging the pressure relief structure 3 on the shell body 1. In the present embodiment, when the pressure relief structure 3 is arranged on the cover plate 2, that is, the pressure relief structure 3 and the welding area 4 are arranged on the same side, the value range of the tensile strength of the welding area 4 is optionally limited, so as to avoid the battery internal gas concentrated impact on the side of the cover plate 2, excessive impact on the cover plate 2 and the welding area 4, and connection failure of the cover plate 2 and the shell body 1.

[0054] When the pressure relief structure 3 is arranged on the cover plate 2, as shown in FIG. 7, the penetration depth of the welding area 4 is d, and the penetration width of the welding area 4 is w. When the shell 20 is steel, 0.04≤d×w≤0.9. When the shell 20 is aluminum, 0.4≤d×w≤3. The unit of d is mm, and the unit of w is mm. In this way, the connection reliability between the cover plate 2 and the shell body 1 is ensured, the tensile strength of the welding area 4 of the cover plate 2 and the shell body 1 is improved, the connection failure of the welding area 4 of the cover plate 2 and the shell body 1 is avoided when the battery is in thermal runaway, and the cover plate 2 is prevented from being broken open or even the battery cell 10 is on fire, thereby avoiding more serious safety accidents.

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

[0056] Specifically, when the shell 20 is aluminum, the value of d×w can be any value in 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.5, 2, 2.5, 3, 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. 6, the thickness of the cover plate 2 is t1, and the wall thickness of the side wall 11 of the shell body 1 welded with the cover plate 2 is t2, and 1≤t1 / t2≤10. 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 can cause the welding penetration 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 wall thickness of the side wall 11 of the shell body 1 is too small, which can cause the welding penetration 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 in 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 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. 3, the cover plate 2 is provided with a pole assembly 5, the pole assembly 5 is electrically connected with the battery cell 10, the pole assembly 5 includes 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, 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, and 0≤│a-b│≤10 is satisfied, wherein the unit of a is mm and the unit of b is mm. By arranging the pressure relief structure 3 between the two pole bodies 51, the heat on both sides of the battery can be released from the pressure relief structure 3 in the length direction of the battery, so that the heat on one side of the battery is not too concentrated, thereby avoiding that the force on one side of the welding area 4 is too large, and thus avoiding that the connection between the cover plate 2 and the shell main body 1 on one side is invalid, and thus avoiding that the cover plate 2 is burst open.

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

[0061] It should be noted that in the embodiment, the "center" is the geometric center, for example, the center of a circle or the intersection point of the diagonals of a square.

[0062] Optionally, as shown in FIG. 2 and FIG. 5, 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. When the pole body 51 is provided with two, 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 thus further heat dissipation can be achieved by using the pole body 51, the influence of heat on the welding area 4 is reduced, and the welding quality of the welding area 4 is improved.

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

[0064] It should be noted that the two pole bodies 51 are positive and negative poles respectively.

[0065] Of course, as shown in FIG. 5, the cover plate 2 can also be provided with only one 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, 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, referring to FIG. 5, S0 = x1 * y1, wherein x1 is the length of the cover plate 2, y1 is the width of the cover plate 2, x1 is in mm, and y1 is in mm.

[0067] It should be noted that the battery cell 10 includes a battery cell body 101 and a tab 102 led out from the battery cell body 101, and the tab 102 can be directly electrically connected with the pole body 51; or the pole assembly 5 further includes a conversion sheet, the pole body 51 is electrically connected with the conversion sheet, and the conversion sheet is electrically connected with the tab 102.

[0068] When the pressure relief structure 3 is arranged on the cover plate 2, as shown in FIG. 2, the cover plate 2 is further 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 l3 is in mm. The liquid injection hole 21 is used for injecting electrolyte into the battery, and there is a possibility of electrolyte leakage during electrolyte injection. Therefore, by limiting the distance between the liquid injection hole 21 and the welding area 4, the contact between the electrolyte and the welding area 4 is avoided to cause corrosion of the welding area 4, and the strength of the welding area 4 is ensured.

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

[0070] It should be noted that the liquid injection hole 21 is usually arranged close to the positive electrode side, and therefore, the above l3 is usually the distance between the center of the projection of the liquid 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 400MPa≤F≤1100MPa is satisfied. When the shell 20 is made of aluminum, the pressure relief structure 3 can also be arranged on the shell body 1, and 80MPa≤F≤140MPa is satisfied. When the pressure relief structure 3 is arranged on the shell body 1, the pressure relief structure 3 and the cover plate 2 are not arranged on the same side, and the impact force of the gas in 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 relatively small, so as to avoid the decrease of the welding yield caused by the too large welding power and welding depth and width required for ensuring greater tensile strength. Specifically, the pressure relief structure 3 can be arranged on the end wall 12 of the shell body 1 or on the side wall 11 of the shell body 1.

[0072] As shown in FIG. 8, the pressure relief structure 3 is arranged on the shell body 1 and 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 arranged is h. When the shell 20 is made of steel, h≥80mm and 400MPa≤F≤1000MPa are satisfied. When the shell 20 is made of aluminum, h≥80mm and 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, so that the gas in the battery is 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, and thus the tensile strength of the welding area 4 can be appropriately reduced.

[0073] It should be noted that the shell body 1 includes an end wall 12 opposite to the cover plate 2, and the pressure relief structure 3 is arranged on the end wall 12. As shown in FIG. 8, h is the distance between the side surface of the cover plate 2 close to the battery cell 10 and the side surface of the end wall 12 close to the battery cell 10 along the height direction of the battery.

[0074] As shown in FIG. 8, the pressure relief structure 3 is arranged on the shell body 1 and opposite to the cover plate 2, and the battery cell 10 includes an opening surface, and the opening surface is opposite to the pressure relief structure 3. 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 opening surface of the battery cell 10 refers to the surface of the battery cell 10 which is not covered by the diaphragm. The opening surface can quickly release the gas, so that the opening surface of the battery cell 10 is arranged corresponding to the pressure relief structure 3, the gas released from the opening surface can be quickly discharged through the pressure relief structure 3, and the impact on the cover plate 2 is further reduced, 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; and 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 winding type battery cell 10, the diaphragm is wrapped along the winding direction, and the opening surface refers to the end surface of the battery cell 10 perpendicular to the winding direction. For the laminated battery cell 10, the positive electrode sheet, the diaphragm and the negative electrode sheet are arranged in layers, and the electrode sheets are arranged in layers to form the opening surface.

[0077] The pressure relief structure 3 is arranged on the shell body 1 and is arranged opposite to the cover plate 2, as shown in FIG. 8, the cover plate 2 is provided with the pole assembly 5, the electric core 10 includes the electric core body 101 and the tab 102 led out from the electric core body 101, the tab 102 and the pole assembly 5 are electrically connected, 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. The tab 102 and the pole assembly 5 can dissipate a part of heat, and the impact force of the battery internal gas on the cover plate 2 is further reduced, so that the distance between the cover plate 2 and the pressure relief structure 3 can be relatively reduced, and the heat on the side of the cover plate 2 can quickly reach the pressure relief structure 3 to be released.

[0078] As shown in FIG. 9, the shell body 1 includes the side wall 11, the side wall 11 is welded with the cover plate 2, and the pressure relief structure 3 is arranged on the side wall 11. When the shell 20 is steel, 500MPa≤F≤1100MPa is satisfied; when the shell 20 is aluminum, 90MPa≤F≤140MPa is satisfied. Arranging the pressure relief structure 3 on the side wall 11 of the shell body 1 reduces the impact on the welding position of the cover plate 2 and the shell body 1, so that the pulling force on the welding area 4 is reduced, and the tensile strength of the welding area 4 is further controlled, so that the connection strength of the cover plate 2 and the shell body 1 is ensured, and the high requirement on the welding process and the low 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, the pressure relief structure 3 is arranged on the side wall 11, the pressure relief structure 3 is more easily broken, the gas is more easily discharged from the pressure relief structure 3, and the pulling force on the welding area 4 is reduced.

[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] Optionally, as shown in FIG. 9, 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 further includes the end wall 12, the end wall 12 is connected with the side wall 11 and is 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, and h1>h2 is satisfied, 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, the connection strength of the end wall 12 and the side wall 11 is greater than the welding strength of the cover plate 2 and the side wall 11, so the impact resistance of the end wall 12 is higher than that of the cover plate 2, and the pressure relief structure 3 is arranged closer to the end wall 12, that is, farther away from the cover plate 2, so that the pulling of the welding position of the cover plate 2 and the shell body 1 by the battery internal gas released from the pressure relief structure 3 is further reduced.

[0082] Optionally, 1.1≤h1 / h2≤5 is satisfied. In this way, the position of the pressure relief structure 3 on the side wall 11 is more reasonable, while ensuring that neither the end wall 12 nor the cover plate 2 is burst open. Specifically, the value of h1 / h2 can be any one of 1.1, 2, 3, 4, 5, or a value between any two of them.

[0083] When the shell 20 is made of steel, the thickness of the cover plate 2 is t1, and 0.3mm≤t1≤1mm is satisfied. 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 large, so the thickness of the cover plate 2 can be set to be small, thereby improving the space utilization of the battery and improving the energy density of the battery.

[0084] Specifically, the shell 20 is made of steel, as shown in FIG. 10, the shell body 1 includes a first side wall 111 and a second side wall 112, both of which are welded with the cover plate 2, and a transition portion 113 is arranged between the first side wall 111 and the second side wall 112, and 0.01≤S / S0≤0.5 is satisfied.

[0085] It should be noted that, in the production process, the steel shell body 1 is not easy to process and form, and a square steel shell body 1 is usually first processed into a cylindrical barrel with both ends open, and then reshaped into a square shell body 1. Therefore, the square shell body 1 processing involves a round-to-square process, which results in a relatively weak position strength of 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 position is poor after the square shell body 1 is processed. Therefore, after the cover plate 2 and the shell body 1 are welded, the transition portion 113 position becomes a failure point, which increases the area occupied by the pressure relief structure 3, thereby reducing the impact of the gas inside the battery on the cover plate 2 and the welding area 4 of the shell body 1, and avoiding failure of the transition portion 113 position.

[0086] Optionally, as shown in FIG. 10, two first side walls 111 are arranged opposite to each other, and two second side walls 112 are arranged opposite to each other, and the adjacent first side wall 111 and second side wall 112 are connected through the transition portion 113, and the transition portion 113 is in a circular arc structure.

[0087] It should be noted that, referring to FIG. 6, both ends of the shell body 1 can be sealed by the cover plate 2; or, referring to FIGS. 8 and 9, one end of the shell body 1 is sealed by the cover plate 2, and the other end can be sealed by other structures (such as a flat plate structure).

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

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

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

[0091] Specifically, the shell 20 is aluminum, as shown in FIG. 10, the shell body 1 includes a first side wall 111 and a second side wall 112, both of which are welded with the cover plate 2, and a transition portion 113 is arranged between the first side wall 111 and the second side wall 112, and 0.015≤S / S0≤0.6 is satisfied. For the aluminum shell body 1, the transition portion 113 is also a failure point, so the area of the pressure relief structure 3 is increased, so that the impact of the gas in the battery on the welding area 4 of the cover plate 2 and the shell body 1 can be reduced, and the failure of the transition portion 113 can be avoided.

[0092] Optionally, as shown in FIG. 10, the first side wall 111 and the second side wall 112 are both provided with two, the two first side walls 111 are oppositely spaced, the two second side walls 112 are oppositely spaced, the adjacent first side wall 111 and the second side wall 112 are connected through the transition part 113, and the transition part 113 is in a circular arc 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 with the shell 20. When the shell 20 is steel, it satisfies 400MPa≤F≤1050MPa; when the shell 20 is aluminum, it satisfies 80MPa≤F≤135MPa. That is, the pressure relief structure 3 and the shell 20 are in a split structure, and an additional connection mode (such as bonding, welding, etc.) is used to fixedly connect the pressure relief structure 3 and the shell 20, at this time, the pressure relief structure 3 is more easily blown open to realize exhaust, and therefore the tensile strength of the welding area 4 can be appropriately reduced.

[0094] Specifically, as shown in FIG. 4, the pressure relief structure 3 is welded with the shell 20 to form a second welding area 6, and the tensile strength of the second welding area 6 is F0, which satisfies F0<F. In this way, when the battery is in thermal runaway, the pressure relief structure 3 and the shell body 1 can be separated first to realize exhaust, and the welding area 4 of the cover plate 2 and the shell body 1 is prevented from being broken.

[0095] It is worth noting that the through hole is first formed on the shell 20, and then the pressure relief structure 3 is arranged corresponding to the through hole, and the pressure relief structure 3 is welded with the shell 20.

[0096] Of course, in other alternative embodiments, the pressure relief structure 3 is integrally arranged with the shell 20, and satisfies 0.01≤S / S0≤0.5. Specifically, the pressure relief structure 3 can be formed on the shell 20 by stamping or laser etching, and therefore it is not necessary to separately arrange the pressure relief structure 3 on the shell 20 by using an additional connection mode, however, when the pressure relief structure 3 is formed on the shell 20, it will generate a large stress on other positions of the shell 20, causing the other positions of the shell 20 to be easily deformed or broken, and therefore if the area occupied by the pressure relief structure 3 is set too large, it will have a large impact on other positions of the shell 20. Therefore, the value of S / S0 is optionally limited, which can ensure that the pressure relief structure 3 can release gas, while avoiding the problems of deformation and breakage of the shell 20 when the pressure relief structure 3 is formed on the shell 20.

[0097] Optionally, when the pressure relief structure 3 is integrally arranged with the cover plate 2, it satisfies 550MPa≤F≤1200MPa for a steel shell 20, and satisfies 95MPa≤F≤135MPa for an aluminum shell 20. The pressure relief structure 3 and the shell 20 are integrally formed, and when the battery internal gas impacts the pressure relief structure 3, the impact force on other positions of the shell 20 is also large, which easily causes the cover plate 2 and the shell body 1 to separate, and therefore the tensile strength of the welding area 4 needs to be appropriately increased.

[0098] It is worth mentioning that the battery cell 10 is 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 formed into the battery cell 10 by winding or stacking. The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer, and the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer. The positive electrode current collector is not particularly limited as long as it has electrical conductivity without causing adverse chemical changes in the battery, and for example, stainless steel, aluminum, nickel, titanium, baked carbon, or aluminum or stainless steel treated on the surface with one of carbon, nickel, titanium, silver, etc. can be used; and the negative electrode current collector can be made of copper, stainless steel, nickel, titanium, etc. In specific embodiments, the positive electrode can be made of aluminum, and the negative electrode can be made of copper. The positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes nickel-cobalt-manganese ternary material, lithium iron phosphate material, lithium manganese iron phosphate material, etc.; and 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 material, etc.

[0099] The preparation process of the battery generally includes:

[0100] (1) Preparation of the positive electrode sheet.

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

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

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

[0104] (3) Preparation of the electrolyte.

[0105] Vinyl carbonate (EC), methyl ethyl carbonate (EMC) and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent, then the 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 the separator.

[0107] The separator is selected from a polyethylene film.

[0108] (5) Preparation of the lithium ion battery.

[0109] The positive electrode sheet, the separator, and the negative electrode sheet are stacked in sequence, the separator is positioned between the positive electrode sheet and the negative electrode sheet to play a role of isolation, and then the bare battery cell 10 is obtained by winding. The bare battery cell 10 is inserted into the shell from the opening of the shell main body 1, and the cover plate 2 and the shell main body 1 are laser sealed and welded. After drying, the electrolyte is injected, and the lithium ion battery is obtained after vacuum packaging, standing, formation, shaping, and other processes.

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

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

[0112] Table 1 Thermal runaway test results

[0113] In Table 1, the examples refer to batteries whose F and S / S0 values meet the requirements of the present embodiment, and the comparative examples refer to batteries whose F and / or S / S0 values do not meet the requirements of the present embodiment.

[0114] As can be seen from Table 1, in Examples 1 to 19, when the tensile strength of the welding area 4 and the area ratio of the pressure relief structure 3 satisfy 1≤F×(S / S0)≤500, the cover plate 2 and the shell main body 1 do not separate during the battery thermal runaway test, 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 area 4 and the area ratio of the pressure relief structure 3 do not satisfy 1≤F×(S / S0)≤500 and are lower than the lower limit value, the tensile strength of the welding area 4 is smaller, and the area ratio of the pressure relief structure 3 is small. During the battery thermal runaway test, the pressure relief structure 3 cannot fully release the internal heat, and the cover plate 2 and the shell main body 1 separate. 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 main body 1 do not separate, but the cover plate 2 at the position of the pressure relief structure 3 deforms. Due to the concentrated impact of the gas at the position of the pressure relief structure 3, the stress at the position of the pressure relief structure 3 is too large, and the cover plate 2 at the position of the pressure relief structure 3 deforms severely.

[0115] In summary, by comprehensively controlling the tensile strength of the welding area 4 and the area ratio of the pressure relief structure 3, the battery internal gas is smoothly released, and the welding reliability of the cover plate 2 and the shell body 1 is improved, thereby improving the safety performance of the battery.

[0116] It can be seen from Examples 1 to 5 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, 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, the cover plate 2 and the shell body 1 do not separate during the thermal runaway test of the steel shell 20 battery, and the cover plate 2 at the position of the pressure relief structure 3 does not deform, thereby achieving good safety performance.

[0117] In addition, in Example 6, for the steel shell 20 battery, when the tensile strength F of the welding area 4 is less than 400MPa, although the cover plate 2 and the shell body 1 do not separate, the welding position of the cover plate 2 and the shell body 1 slightly deforms. 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) is less than 8, although the cover plate 2 and the shell body 1 do not separate, the welding position of the cover plate 2 and the shell body 1 deforms severely.

[0118] It can be seen from Examples 11 to 15 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, 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, the cover plate 2 and the shell body 1 do not separate during the thermal runaway test of the aluminum shell 20 battery, and the cover plate 2 at the position of the pressure relief structure 3 does not deform, thereby achieving good safety performance.

[0119] In addition, in Example 16, for the aluminum shell 20 battery, when the tensile strength F of the welding area 4 is less than 80MPa, although the cover plate 2 and the shell body 1 do not separate, the welding position of the cover plate 2 and the shell body 1 slightly deforms. 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) is less than 1.5, although the cover plate 2 and the shell body 1 do not separate, the welding position of the cover plate 2 and the shell body 1 deforms severely.

[0120] It is worth noting that in Table 1, severe deformation refers to that the connection position of the shell body 1 and the cover plate 2 has an area of not less than 50% deformed; slight deformation refers to that the connection position of the shell body 1 and the cover plate 2 has an area of not more than 30% deformed.

[0121] It should be noted that the test process of the thermal runaway test refers to the national standard GB 38031-2020, and is generally as follows:

[0122] 1. Charge the battery. For specific charging strategies, the charging of nickel-cobalt-manganese ternary material, lithium iron phosphate positive material, lithium manganese iron phosphate positive material, lithium-rich manganese-based positive material, and lithium nickel-manganese acid positive material is as follows: nickel-cobalt-manganese ternary material is charged to 4.25V at a current of 1C, and constant voltage charging is performed until the current decreases to 0.05C; lithium iron phosphate is charged at 0.5C constant current to 3.65V, and constant voltage charging is performed until the current decreases to 0.05C; lithium manganese iron phosphate is charged to 4.25V at 0.5C, and constant voltage charging is performed until the current decreases to 0.05C; lithium-rich manganese-based is charged to 4.25V at 0.5C, and constant voltage charging is performed until the current decreases to 0.05C; and lithium nickel-manganese acid is charged to 4.85V at 1C, and constant voltage charging is performed until the current decreases to 0.05C.

[0123] 2. Place a heating sheet at the large surface of the battery to heat the triggering object at the maximum power of the device.

[0124] 3. When thermal runaway occurs or the temperature of the monitoring point reaches 300℃, stop triggering and turn off the heating device.

[0125] Optionally, the thermal runaway determination condition is that the triggering object generates a voltage drop, and the drop value exceeds 25% of the initial voltage, the temperature rise rate dT / dt of the monitoring point is ≥1℃ / s, and lasts for more than 3s, then it is determined that thermal runaway occurs.

[0126] It should be noted that the tensile strength test method is as follows:

[0127] 1. Cut the local position of the welding area 4 to obtain a sample with a width of 10mm and a length of 100mm;

[0128] 2. Test the tensile strength of the sample by a tensile testing machine;

[0129] 3. Finally, the fracture position is obtained and the tensile strength value is fed back.

[0130] According to the embodiments of the present application, on the other hand, a battery pack is also provided, comprising the above-mentioned battery.

[0131] Although the embodiments of the present application are described in conjunction with the drawings, various modifications and changes can be made by those skilled in the art without departing from the spirit and scope of the present application, and such modifications and changes fall within the scope defined by the appended claims.

Claims

1. A battery, characterized by, The F value range is 60MPa≤F≤1300MPa, and the S / S0 value range is 0.006≤S / S0≤0.

6. The battery cell (10) and the 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 provided with an opening, the cover plate (2) is welded with the opening end of the shell body (1) to form a welding area (4), the cover plate (2) blocks the opening and forms an accommodating space together with the shell body (1), and the battery cell (10) is located in the accommodating space; the tensile strength of the welding area (4) is F, a 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, the area enclosed by the first surface is S0, and 1<=F*(S / S0)<=500 is met, wherein the unit of F is MPa, the unit of S is mm 2 , and the unit of S0 is mm 2 .

2. The battery of claim 1, wherein, The shell (20) is steel, and satisfies 8≤F×(S / S0)≤400.

3. The battery according to claim 1 or 2, characterized in that, The shell (20) is aluminum, and satisfies 1.5≤F×(S / S0)≤45.

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

5.

5. The battery of claim 3, wherein, The F value range is 80MPa≤F≤150MPa, and the S / S0 value range is 0.01≤S / S0≤0.

6.

6. The battery of claim 4, wherein, The pressure relief structure (3) is arranged on the cover plate (2), and satisfies 600MPa≤F≤1200MPa.

7. The battery of claim 5, wherein, The pressure relief structure (3) is arranged on the cover plate (2), and satisfies 90MPa≤F≤150MPa.

8. The battery of claim 6, wherein, The penetration depth of the welding area (4) is d, and the penetration width of the welding area (4) is w, and satisfy 0.04≤d×w≤0.9, wherein the unit of d is mm, and the unit of w is mm.

9. The battery of claim 3, wherein, The penetration depth of the welding area (4) is d, and the penetration width of the welding area (4) is w, and satisfy 0.4≤d×w≤3, wherein the unit of d is mm, and the unit of w is mm.

10. The battery of claim 4, wherein, 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 with the cover plate (2) is t2, and satisfy 1≤t1 / t2≤10, wherein the unit of t1 is mm, and the unit of t2 is mm.

11. The battery of claim 5 or 6, wherein, The pressure relief structure (3) is arranged on the cover plate (2), and the cover plate (2) is provided with a pole assembly (5), the electric core (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 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 are a apart, and the center of the projection of the other pole body (51) on the first surface is b apart, and satisfy 0≤│a-b│≤10, wherein the unit of a is mm, and the unit of b is mm.

12. The battery of claim 5 or 6, wherein, The pressure relief structure (3) is arranged on the cover plate (2), and the cover plate (2) is provided with a pole assembly (5), the electric core (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, 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, and satisfy 0.07≤l1 / l2≤0.8, wherein the unit of l1 is mm, and the unit of l2 is mm.

13. The battery of claim 5 or 6, wherein, ​ 14. The battery of claim 5 or 6, wherein, The pressure relief structure (3) is arranged on the cover plate (2), and the cover plate (2) is further provided with a liquid injection hole (21), the minimum distance between the center of the projection of 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.

15. The battery of claim 5, wherein, The pressure relief structure (3) is arranged on the shell body (1), and 400MPa<=F<=1100MPa is satisfied.

16. The battery of claim 6, wherein, The pressure relief structure (3) is arranged on the shell body (1), and 80MPa<=F<=140MPa is satisfied.

17. The battery of claim 15, wherein, The pressure relief structure (3) is arranged on the shell body (1) and 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, and h>=80mm and 400MPa<=F<=1000MPa are satisfied.

18. The battery of claim 16, wherein, The pressure relief structure (3) is arranged on the shell body (1) and 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, and h>=80mm and 80MPa<=F<=130MPa are satisfied.

19. The battery of claim 15, wherein, The pressure relief structure (3) is arranged on the shell body (1) and opposite to the cover plate (2), the cell (10) comprises an opening surface, and the opening surface and the pressure relief structure (3) are opposite, and 15<=F*(S / S0)<=320 is satisfied.

20. The battery of claim 16, wherein, The pressure relief structure (3) is arranged on the shell body (1) and opposite to the cover plate (2), the cell (10) comprises an opening surface, and the opening surface and the pressure relief structure (3) are opposite, and 2.5<=F*(S / S0)<=36 is satisfied.

21. The battery of claim 15 or 16, wherein, The pressure relief structure (3) is arranged on the shell body (1) and opposite to the cover plate (2), the cover plate (2) is provided with a pole assembly (5), the cell (10) comprises a cell body (101) and a tab (102) led out from the cell body (101), the tab (102) and the pole assembly (5) are electrically connected, and the distance between the cover plate (2) and the shell body (1) where the pressure relief structure (3) is located is h, and h<=200mm is satisfied.

22. The battery of claim 15, wherein, The shell body (1) comprises a side wall (11), the side wall (11) is welded with the cover plate (2), and the pressure relief structure (3) is arranged on the side wall (11), and 500MPa<=F<=1100MPa is satisfied.

23. The battery of claim 16, wherein, The shell body (1) comprises a side wall (11), the side wall (11) is welded with the cover plate (2), and the pressure relief structure (3) is arranged on the side wall (11), and 90MPa<=F<=140MPa is satisfied.

24. The battery of claim 22 or 23, wherein, The shell body (1) comprises a side wall (11) welded with the cover plate (2), the pressure relief structure (3) is arranged on the side wall (11), the minimum distance between the center of the projection of the first surface and the welding area (4) is h1, the shell body (1) further comprises an end wall (12) connected with the side wall (11) and arranged opposite to the cover plate (2), the minimum distance between the center of the projection of 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 met.

25. The battery of claim 3, wherein, The shell (20) is made of steel, the thickness of the cover plate (2) is t1, and 0.3mm≤t1≤1mm is met.

26. The battery of claim 3, wherein, The shell (20) is made of steel, 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 with the cover plate (2), and a transition part (113) is arranged between the first side wall (111) and the second side wall (112), and 0.01≤S / S0≤0.5 is met.

27. The battery of claim 3, wherein, The shell (20) is made of steel, the pressure relief structure (3) comprises a weak part (31), the residual thickness of the weak part (31) is k, and 0.01mm≤k≤0.08mm is met.

28. The battery of claim 3, wherein, The material of the shell (20) comprises silicon element, the content of the silicon element is 0.1% to 0.3%, and 0.008≤S / S0≤0.45 is met.

29. The battery of claim 4, wherein, The material of the shell (20) comprises silicon element, the content of the silicon element is 3% to 25%, and 0.01≤S / S0≤0.5 is met.

30. The battery of claim 4, wherein, The shell (20) is made of aluminum, the thickness of the cover plate (2) is t1, and 1.2mm≤t1≤3.5mm is met.

31. The battery of claim 4, wherein, The shell (20) is made of aluminum, 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 with the cover plate (2), and a transition part (113) is arranged between the first side wall (111) and the second side wall (112), and 0.015≤S / S0≤0.6 is met.

32. The battery of claim 3, wherein, The shell (20) is provided with a through hole, the pressure relief structure (3) covers the through hole and is connected with the shell (20), and 400MPa≤F≤1050MPa is met.

33. The battery of claim 4, wherein, The shell (20) is provided with a through hole, the pressure relief structure (3) covers the through hole and is connected with the shell (20), and 80MPa≤F≤135MPa is met.

34. The battery of claim 32 or 33, wherein, The pressure relief structure (3) is welded with the shell (20) to form a second welding area (6), the tensile strength of the second welding area (6) is F0, and F0<F is met.

35. The battery of claim 1 or 2, wherein, The pressure relief structure (3) is integrally arranged with the shell (20), and 0.01≤S / S0≤0.5 is met.

36. The battery of claim 3, wherein, The pressure relief structure (3) is integrally arranged with the cover plate (2), and 550MPa≤F≤1200MPa is met.

37. The battery of claim 4, wherein, The pressure relief structure (3) is integrally arranged with the cover plate (2), and satisfies 95MPa≤F≤135MPa.

38. A battery pack, characterized by A battery comprising any one of claims 1 to 37.

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