Cover plate and battery

Abstract

A cover plate and a battery. The cover plate comprises a cover plate body (1) and an explosion-proof valve, the explosion-proof valve is arranged on the cover plate body (1), and the explosion-proof valve is formed of an explosion-proof notch (2) formed in the cover plate body (1); the tensile strength of the cover plate body (1) is c, the yield strength of the cover plate body (1) is d, the burst pressure of the explosion-proof valve is e, and the proportion of the area of the explosion-proof valve to the surface area of the cover plate body (1) is f, wherein the following relational expressions are satisfied: (I) and (II). The strength of the cover plate is represented by the tensile strength c and the yield strength d, the safety performance of the cover plate is represented by the burst pressure e of the explosion-proof valve and the proportion f of the area of the explosion-proof valve to the surface area of the cover plate body (1), and the ratio of the strength performance to the safety performance is controlled, so that when thermal runaway occurs in a battery, it is ensured that the cover plate cannot break and the explosion-proof valve can be opened in time.

Description

Cover and battery

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application filed with the China Patent Office on December 7, 2023, with application number 202311670352.3 and invention name “Cover and Battery”, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present application relates to the field of battery technology, and in particular to a cover plate and a battery. Background Art

[0004] With the promotion and application of batteries, the requirements for battery safety performance are getting higher and higher. At present, in the field of power battery technology, battery shells are mostly made of aluminum. However, in the ternary system, the aluminum shell is prone to rupture due to insufficient pressure resistance, causing the battery to catch fire and explode. An explosion-proof valve is usually provided on the cover of the battery. The explosion-proof valve opens when the battery is under thermal runaway, and plays the role of exhausting and relieving pressure to prevent the battery from exploding due to excessive internal air pressure. The current aluminum explosion-proof valve is usually welded to the aluminum cover by laser welding. However, the welding method is prone to obvious explosion points, cold welding and other phenomena. It is difficult to ensure the strength and safety performance of the cover at the same time, resulting in low battery yield and is not conducive to ensuring battery safety.

[0005] Summary of the Invention

[0006] In view of this, the present application provides a cover plate and a battery to solve the problem in the prior art that it is difficult to simultaneously ensure structural strength and safety performance of the cover plate.

[0007] In a first aspect, the present application provides a cover plate, comprising: a cover plate body; an explosion-proof valve disposed on the cover plate body, the explosion-proof valve being formed by explosion-proof notches constructed on the cover plate body; the tensile strength of the cover plate body being c, the yield strength of the cover plate body being d, the bursting pressure of the explosion-proof valve being e, and the ratio of the area of ​​the explosion-proof valve to the surface area of ​​the cover plate body being f, satisfying: and

[0008] Beneficial effect: By directly processing explosion-proof notches on the cover body, the area enclosed by the explosion-proof notches forms an explosion-proof valve, and the explosion-proof notches break at a preset explosion pressure value to open the explosion-proof valve, discharge the high-pressure gas in the battery, and prevent the battery from exploding due to excessive internal air pressure. The explosion-proof valve is processed in the form of notches, which can reduce the traditional welding process. The process is simple and can avoid the explosion points, cold welds and other phenomena caused by welding the explosion-proof valve, thereby improving the reliability of the explosion-proof valve and the yield rate. In addition, the tensile strength c and yield strength d are used to characterize the strength of the cover, the explosion pressure e of the explosion-proof valve and the ratio f of the area of ​​the explosion-proof valve to the surface area of ​​the cover body are used to characterize the safety performance of the cover. By controlling the ratio between strength performance and safety performance, it is ensured that when thermal runaway occurs in the battery, the cover will not break and the explosion-proof valve can be opened in time, that is, while taking into account the structural strength of the cover, the safety performance of the cover is effectively guaranteed, thereby improving the reliability of the cover.

[0009] In an optional embodiment, the cover plate body is made of steel;

[0010] And / or, the explosion-proof notch is integrally formed with the cover body.

[0011] Beneficial Effects: Steel's high strength improves the structural strength of the cover plate, reduces the risk of cracking during thermal runaway, and enhances impact resistance. By designing the explosion-proof valve as an integrated notch—that is, a thinned area is machined directly into the cover plate itself—the valve is integrated into the cover plate, reducing the number of welding steps and addressing issues such as hot spots, cold welds, and low yields associated with welded steel explosion-proof valves. Furthermore, the integrated structure facilitates machining and offers high reliability.

[0012] In an optional embodiment, the tensile strength c of the cover plate body ranges from 400 MPa to 1000 MPa.

[0013] Beneficial effects: It can ensure the structural strength of the cover plate and prevent the cover plate from being deformed when squeezed by external force, and can also ensure the timeliness of the opening of the explosion-proof valve.

[0014] In an optional embodiment, the yield strength d of the cover plate body ranges from 200 MPa to 800 MPa.

[0015] Beneficial effect: It can avoid the problem that the cover plate is easily deformed when being squeezed by external force, ensure the structural strength of the cover plate, and ensure the timeliness of opening of the explosion-proof valve.

[0016] In an optional embodiment, the bursting pressure e of the explosion-proof valve ranges from 0.9 MPa to 1.8 MPa.

[0017] Beneficial effect: It can ensure that the explosion-proof valve will not open prematurely and can also avoid delayed opening of the explosion-proof valve, thereby ensuring the safety performance of the battery.

[0018] In an optional embodiment, the ratio f of the area of ​​the explosion-proof valve to the surface area of ​​the cover plate body is greater than or equal to 1 / 5.

[0019] Beneficial effect: By setting the area of ​​the explosion-proof valve to account for more than one-fifth of the entire cover surface area, it can be ensured that the gas in the battery can be discharged in time when the explosion-proof valve is opened, thereby ensuring the safety of the cover and the battery as a whole.

[0020] In an optional embodiment, the ratio f of the area of ​​the explosion-proof valve to the surface area of ​​the cover plate body ranges from 20% to 85%.

[0021] Beneficial effect: It can ensure that the gas in the battery can be discharged in time when the explosion-proof valve is opened, and can also ensure the structural strength of the cover itself, thereby taking into account both structural strength and safety performance.

[0022] In an optional embodiment, the thickness b of the cover plate body ranges from 0.2 mm to 1 mm;

[0023] And / or, the residual thickness h of the explosion-proof notch on the cover plate body is in the range of 0.03 mm to 0.1 mm.

[0024] Beneficial effect: By setting the thickness of the cover body within the range of 0.2mm to 1mm, it is possible to ensure that the cover has sufficient strength while avoiding excessive weight of the cover, thereby improving the energy density of the battery while ensuring the safety performance of the cover.

[0025] In an optional embodiment, a pole assembly and a liquid injection hole are further provided on the cover body, and the explosion-proof notch is spaced apart from the pole assembly and the liquid injection hole, or the explosion-proof notch surrounds the outside of the pole assembly and the liquid injection hole, or the explosion-proof notch is circumferentially arranged around the cover body.

[0026] Beneficial effects: The explosion-proof notch is set in the blank area on the cover body. The blank area on the cover body except for the pole assembly and the injection hole has enough space, which provides sufficient position for the setting of the explosion-proof notch, is easy to process, and has a high utilization rate of the cover body. The pole assembly and the injection hole are located in the area surrounded by the explosion-proof notch, which can avoid the situation where the blank area on the cover body is insufficient, thereby ensuring that the explosion-proof valve has sufficient area, and when the explosion-proof notch breaks and the explosion-proof valve opens, the pole assembly and the injection hole fly out with the explosion-proof valve, cutting off the electrical connection between the pole assembly and the pole group, avoiding aggravation of battery thermal runaway due to untimely circuit disconnection, and improving the safety performance of the battery. The explosion-proof notches are distributed around the entire cover, thereby ensuring that the explosion-proof valve has sufficient area, ensuring the smoothness of the exhaust process, and further preventing the battery from exploding.

[0027] In a second aspect, the present application further provides a battery, comprising: a shell having an open end; an electrode group disposed in the shell; and the above-mentioned cover plate, wherein the cover plate is disposed at the open end of the shell to close the shell.

[0028] Since the battery includes a cover plate, it has the same effect as the cover plate and will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the specific implementation methods or the description of the prior art. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0030] FIG1 is a schematic structural diagram of a cover plate according to an embodiment of the present application;

[0031] FIG2 is a cross-sectional view of the cover plate shown in FIG1 ;

[0032] FIG3 is a partial enlarged view of A in FIG2 ;

[0033] FIG4 is a schematic structural diagram of an explosion-proof valve on a cover plate according to an embodiment of the present application;

[0034] FIG5 is a schematic structural diagram of an explosion-proof valve on another cover plate according to an embodiment of the present application;

[0035] FIG6 is a schematic structural diagram of an explosion-proof valve on a cover plate according to another embodiment of the present application.

[0036] Explanation of the reference numerals: 1. Cover plate body; 2. Explosion-proof notch; 3. Pole assembly; 301. Pole; 302. Riveted block; 303. Upper plastic; 4. Liquid injection hole; 5. Lower plastic; 6. Sealing member. DETAILED DESCRIPTION

[0037] To make the purpose, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative efforts shall fall within the scope of protection of this application.

[0038] The following describes an embodiment of the present application in conjunction with FIG. 1 to FIG. 6 .

[0039] According to an embodiment of the present application, in one aspect, a cover plate is provided, as shown in Figures 1 to 6 , comprising: a cover plate body 1 and an explosion-proof valve. The explosion-proof valve is disposed on the cover plate body 1 and is formed by explosion-proof notches 2 constructed on the cover plate body 1. The tensile strength of the cover plate body 1 is c, the yield strength of the cover plate body 1 is d, the bursting pressure of the explosion-proof valve is e, and the ratio of the area of ​​the explosion-proof valve to the surface area of ​​the cover plate body 1 is f, satisfying the following conditions: and

[0040] The cover plate of this embodiment is directly processed with an explosion-proof notch 2 on the cover plate body 1. The area enclosed by the explosion-proof notch 2 forms an explosion-proof valve. The explosion-proof notch 2 breaks at a preset burst pressure value, allowing the explosion-proof valve to open and discharge the high-pressure gas in the battery to prevent the battery from exploding due to excessive internal pressure. The notch processing method of the explosion-proof valve can reduce the traditional welding process, simplify the process, and avoid the phenomenon of explosive spots and cold welds caused by welding the explosion-proof valve, thereby improving the reliability of the explosion-proof valve and the yield rate. In addition, the tensile strength c and yield strength d are used to characterize the strength of the cover plate, the burst pressure e of the explosion-proof valve, and the ratio f of the area of ​​the explosion-proof valve to the surface area of ​​the cover plate body 1 are used to characterize the safety performance of the cover plate. By controlling the ratio between strength performance and safety performance, it is ensured that the cover plate will not rupture and the explosion-proof valve can be opened in time when the battery experiences thermal runaway. That is, while taking into account the structural strength of the cover plate, the safety performance of the cover plate is effectively guaranteed, thereby improving the reliability of the cover plate.

[0041] It should be noted that for the formula and Among them, the tensile strength c and yield strength d are the properties of the cover material itself, c*10 -3 +d*10 -3 Characterizes the structural strength of the cover, c*10 -3 +d*10 -3 The larger the value of is, the greater the strength of the cover structure is. When the pressure inside the battery is high, the cover is less likely to break. If c*10 -3 +d*10-3 If the value of is too large, the material requirements for the cover plate will be too high, and the material required for the cover plate will be difficult to obtain and the cost will be high. However, if c*10 -3 +d*10 -3 If the value is too small, the cover plate is easy to rupture when the gas pressure in the battery is too high, resulting in a dangerous situation of battery explosion; the explosion-proof valve is at a critical pressure value for opening the explosion-proof valve at the bursting pressure e. The smaller the bursting pressure e of the explosion-proof valve, the easier it is to open the explosion-proof valve and the higher the safety performance of the cover plate. However, if the bursting pressure e of the explosion-proof valve is too small, the explosion-proof valve will open too early, affecting the service life of the battery. If the bursting pressure e of the explosion-proof valve is too large, the explosion-proof valve will be more difficult to open, and the explosion-proof valve will not be able to open in time, and the exhaust will not be timely, and the internal gas pressure of the battery will continue to increase, causing the cover plate to burst, and the safety performance of the cover plate is poor; the area of ​​the explosion-proof valve occupies 1% of the cover plate. The ratio f of the surface area of ​​the main body 1 reflects the size of the explosion-proof valve. If the ratio f is too small, the area of ​​the explosion-proof valve is too small, and there is a problem of untimely exhaust after the explosion-proof valve is opened. The battery is still in danger of explosion due to the continuous increase in internal air pressure. The larger the ratio f, the larger the area of ​​the explosion-proof valve, the larger the cross-sectional area of ​​the exhaust channel when the explosion-proof valve is opened, the smoother the exhaust, and the less likely the battery is to explode, that is, the better the safety performance of the cover. However, if the ratio f is too large, the area of ​​the entity part of the cover body 1 except the explosion-proof valve is too small, and the overall structural strength of the cover is too weak, making it difficult to provide effective support and protection for the pole group and other components inside the battery. Therefore, by setting The value is between 0.3 and 2, and The value is selected between 0.7 and 9. By correlating the tensile strength c, the yield strength d, the bursting pressure e of the explosion-proof valve and the ratio f of the area of ​​the explosion-proof valve to the surface area of ​​the cover body 1, and by restricting the value range, each parameter is reasonably selected, which can ensure the structural strength of the cover and the safety performance of the cover, thereby improving the reliability of the cover.

[0042] In one embodiment, the cover body 1 is made of steel. Steel has high strength, which is beneficial for improving the structural strength of the cover, reducing the risk of the cover rupture during battery thermal runaway, and improving anti-collision performance.

[0043] In one embodiment, the explosion-proof notch is integrally formed with the cover plate body 1. It should be noted that the steel cover plate improves the pressure resistance of the entire battery and improves the risk of thermal runaway. However, if the steel cover plate adopts the traditional welding method to weld the steel explosion-proof valve to the cover plate body 1, due to the influence of the material properties, obvious explosion points and cold welds are likely to occur, resulting in a low yield rate of the cover plate, affecting production efficiency and production capacity. By setting the explosion-proof valve as an integrated notch, that is, directly processing a thinning area on the cover plate body 1, and integrating the explosion-proof valve on the cover plate, the welding process can be reduced, and the problems of explosion points, cold welds, and low yield caused by welding the steel explosion-proof valve can be improved. In addition, the integrated structure is easy to process and has high reliability.

[0044] In one embodiment, the tensile strength c of the cover body 1 ranges from 400 MPa to 1000 MPa. Tensile strength characterizes the material's resistance to maximum uniform plastic deformation and is the maximum stress the material can withstand before breaking. It is a property of the cover material itself. If the tensile strength is less than 400 MPa, the maximum stress the cover can withstand is too small, the cover strength is low, the cover's own supporting strength is insufficient, the cover is prone to deformation or cracking, and the thinned area corresponding to the explosion-proof notch is extremely easy to break, which may cause the explosion-proof valve to open prematurely, affecting its service life. If the tensile strength is greater than 1000 MPa, the maximum stress the cover can withstand is too large, the thinned area corresponding to the explosion-proof notch is more difficult to break, and the pressure required to open the explosion-proof valve increases, which may cause the explosion-proof valve to fail to open in time, resulting in the battery exploding due to excessive internal pressure, which is very dangerous. Therefore, by controlling the tensile strength c to a value between 400 MPa and 1000 MPa, the structural strength of the cover can be guaranteed, preventing the cover from deforming when squeezed by external forces, and ensuring the timely opening of the explosion-proof valve.

[0045] In one embodiment, the yield strength d of the cover plate body 1 ranges from 200 MPa to 800 MPa. Yield strength is the yield limit of a material when yielding occurs. It is the stress at which a material begins to plastically deform under an external force and reflects the structural strength of the cover plate body 1. By controlling the yield strength d to be between 200 MPa and 800 MPa, deformation of the cover plate when subjected to external forces can be avoided, ensuring its structural strength, while also ensuring the timely opening of the explosion-proof valve.

[0046] In one embodiment, the bursting pressure e of the explosion-proof valve ranges from 0.9 MPa to 1.8 MPa. The bursting pressure e of the explosion-proof valve is the critical value for opening the explosion-proof valve. When the pressure inside the battery is less than the critical value, the explosion-proof valve does not open. When the pressure inside the battery is greater than or equal to the critical value, the explosion-proof valve opens to release pressure and prevent battery explosion, reflecting the safety performance of the cover plate. If the bursting pressure of the explosion-proof valve is less than 0.9 MPa, the opening pressure value is too low, and the explosion-proof valve opens prematurely, affecting the service life of the battery. If the bursting pressure of the explosion-proof valve is greater than 1.8 MPa, the opening pressure value is too high, making it more difficult to open the explosion-proof valve. The explosion-proof valve cannot open in time when the pressure inside the battery is too high, increasing the risk of battery explosion. Therefore, by controlling the bursting pressure of the explosion-proof valve to be within the range of 0.9 MPa to 1.8 MPa, it can be ensured that the explosion-proof valve does not open prematurely and can also avoid delayed opening of the explosion-proof valve, thereby ensuring the safety performance of the battery.

[0047] In one embodiment, the ratio f of the area of ​​the explosion-proof valve to the surface area of ​​the cover body 1 is greater than or equal to 1 / 5. It should be noted that the surface area of ​​the explosion-proof valve refers to the area enclosed by the explosion-proof notch 2, and the surface area of ​​the cover body 1 refers to the total area of ​​the area enclosed by the outer periphery of the cover body 1. If the area of ​​the explosion-proof valve is too small, the gas in the battery cannot be discharged in time after the explosion-proof valve is opened, and the gas pressure inside the battery continues to rise, thereby causing the battery to explode. The larger the ratio of the area of ​​the explosion-proof valve to the surface area of ​​the cover body 1, the larger the exhaust area after the explosion-proof valve is opened, the better the exhaust effect, and the gas pressure inside the battery can be reduced in time to prevent the battery from exploding due to excessive gas pressure. Therefore, by setting the area of ​​the explosion-proof valve to account for more than one-fifth of the entire surface area of ​​the cover, it can be ensured that the gas in the battery can be discharged in time when the explosion-proof valve is opened, thereby ensuring the safety of the cover and the battery as a whole.

[0048] In one embodiment, the ratio f of the area of ​​the explosion-proof valve to the surface area of ​​the cover body 1 ranges from 20% to 85%. If the ratio of the area of ​​the explosion-proof valve to the surface area of ​​the cover body 1 is greater than 85%, the area of ​​the explosion-proof valve is too large, and the area of ​​the solid portion of the cover body 1 other than the explosion-proof valve is too small, resulting in insufficient support force for the cover, insufficient structural strength of the cover as a whole, and easy deformation or rupture. Therefore, by setting the ratio of the area of ​​the explosion-proof valve to the total surface area of ​​the cover between 20% and 85%, it is possible to ensure that the gas in the battery can be discharged in a timely manner when the explosion-proof valve is opened, while also ensuring the structural strength of the cover itself, thereby achieving a balance between structural strength and safety performance.

[0049] In one embodiment, the thickness b of the cover plate body 1 ranges from 0.2 mm to 1 mm. The thickness b of the cover plate body 1 is shown in FIG3 . The greater the thickness of the cover plate body 1, the greater the structural strength of the cover plate. If the thickness of the cover plate body 1 is less than 0.2 mm, the thickness of the cover plate body 1 is too small, the cover plate support force is insufficient, and it is easy to deform. If the thickness of the cover plate body 1 is greater than 1 mm, the thickness of the cover plate body 1 is too large, the cover plate weight is too large, and it is not conducive to improving the energy density of the battery. Therefore, by setting the thickness of the cover plate body 1 to a value within the range of 0.2 mm to 1 mm, it is possible to ensure that the cover plate has sufficient strength and avoid excessive weight of the cover plate, thereby improving the energy density of the battery while ensuring the safety performance of the cover plate.

[0050] In one embodiment, the residual thickness h of the explosion-proof notch 2 on the cover body 1 ranges from 0.03 mm to 0.1 mm. 3 , the residual thickness h of the explosion-proof notch 2 is the difference between the thickness b of the cover body and the depth a of the explosion-proof notch 2, that is, the thickness of the remaining solid part (thinned area) corresponding to the explosion-proof notch 2 on the cover body 1. If the residual thickness of the explosion-proof notch 2 is less than 0.03 mm, the thickness of the thinned area is too small, the thinned area is very easy to break, the strength of the explosion-proof valve is insufficient, and the explosion-proof valve is easy to open prematurely, reducing the service life of the cover and the battery; if the residual thickness of the explosion-proof notch 2 is greater than 0.1 mm, the thickness of the thinned area is too large, the strength of the thinned area is too large, and it is not easy to break, the difficulty of opening the explosion-proof valve increases, the explosion-proof valve cannot be opened in time, and the risk of explosion of the battery due to excessive internal air pressure is increased. Therefore, by setting the residual thickness h of the explosion-proof notch 2 to a value within the range of 0.03 mm to 0.1 mm, it can be ensured that the explosion-proof valve has sufficient strength to avoid premature opening of the explosion-proof valve, and avoid the explosion-proof valve from being unable to open in time due to excessive strength, thereby ensuring that the explosion-proof valve can play its explosion-proof role in a timely and effective manner.

[0051] In one embodiment, as shown in FIG4 , the cover body 1 is further provided with a pole assembly 3 and a liquid injection hole 4, and the explosion-proof notch 2 is spaced apart from the pole assembly 3 and the liquid injection hole 4. That is, the explosion-proof notch 2 is provided in a blank area on the cover body 1. The blank area on the cover body other than the pole assembly 3 and the liquid injection hole 4 has sufficient space, providing sufficient space for the provision of the explosion-proof notch 2, and is easy to process, thereby increasing the utilization rate of the cover body 1. Optionally, the area enclosed by the explosion-proof notch 2 is rectangular, and the corners of the rectangle are rounded, which facilitates processing and avoids stress concentration at the corners.

[0052] In addition, in other embodiments, as shown in Figure 5, the explosion-proof notch 2 surrounds the outside of the pole assembly 3 and the liquid injection hole 4, that is, the pole assembly 3 and the liquid injection hole 4 are located in the area surrounded by the explosion-proof notch 2, which can avoid the situation where the blank area on the cover body 1 is insufficient, thereby ensuring that the explosion-proof valve has sufficient area, and when the explosion-proof notch 2 is broken and the explosion-proof valve is opened, the pole assembly 3 and the liquid injection hole 4 fly out with the explosion-proof valve, cutting off the electrical connection between the pole assembly 3 and the pole group, avoiding aggravation of battery thermal runaway due to untimely circuit cutting off, and improving the safety performance of the battery.

[0053] In addition, in other embodiments, as shown in FIG6 , the explosion-proof notches 2 are arranged circumferentially around the cover body 1 , that is, the explosion-proof notches 2 are distributed around the entire circumference of the cover, thereby ensuring that the explosion-proof valve has sufficient area, ensuring the smoothness of the exhaust process, and further preventing the battery from exploding.

[0054] In one embodiment, the pole assembly 3 includes a pole 301, a rivet block 302 and an upper plastic 303. The pole 301 is made of metal and is electrically connected to the pole group; the rivet block 302 is located between the pole 301 and the cover body 1 and is used to support the pole 301; the upper plastic 303 is located between the rivet block 302 and the cover body 1 to ensure that the rivet block 302 and the cover body 1 are insulated.

[0055] In one embodiment, the cover further includes a seal 6 and a lower plastic 5. The seal 6 is located between the pole 301 and the cover body 1 to ensure that the pole 301 is insulated from the cover body 1. The lower plastic 5 is arranged on the side of the cover body 1 facing the interior of the battery to provide insulating support between the pole group and the cover body 1.

[0056] In this embodiment, an integrated explosion-proof valve is provided on the steel cover plate, and the explosion-proof valve is arranged on the entire cover plate in the form of notches on the steel cover plate, so as to avoid the problems of low welding yield, explosion points, and cold welds caused by welding the steel explosion-proof valve. In addition, by controlling the relevant parameters of the integrated explosion-proof valve and the steel cover plate, the strength performance and safety performance of the cover plate structural parts are met at the same time.

[0057] According to another aspect of an embodiment of the present application, a battery is provided, comprising: a housing, an electrode group, and the aforementioned cover plate. The housing has an open end; the electrode group is disposed within the housing; and the cover plate is disposed at the open end of the housing to seal the housing. The battery may be a power battery.

[0058] The following describes the experimental results of thermal runaway tests on batteries using different parameter values ​​for experimental verification.

[0059] Table 1 Thermal runaway test results of the embodiment and comparative example

[0060] Among them, formula 1 refers to Formula 2 refers to As can be seen from Table 1, for the batteries of Examples 1 to 10, the tensile strength c of the cover body 1 is in the range of 400 MPa to 1000 MPa, the yield strength d of the cover body 1 is in the range of 200 MPa to 800 MPa, the bursting pressure e of the explosion-proof valve is in the range of 0.9 MPa to 1.8 MPa, and the ratio f of the area of ​​the explosion-proof valve to the surface area of ​​the cover body 1 is in the range of 20% to 85%. The calculation results of Formula 1 are in the range of 0.3 to 2, and the calculation results of Formula 2 are in the range of 0.7 to 9. The test results of the batteries of Examples 1 to 10 are that the explosion-proof valve opens normally and the cover and the shell are not broken, and they can pass the thermal runaway test.However, in Comparative Example 1, the tensile strength c of the cover body 1 is 330 MPa, and the yield strength d of the cover body 1 is 160 MPa. Correspondingly, the calculation result of Formula 1 is 0.28, that is, the tensile strength c of the cover body 1 is less than 400 MPa, and the yield strength d of the cover body 1 is less than 200 MPa. The calculation result of Formula 1 is less than 0.3, which is not within the range (0.3 to 2) specified in this application. The cover strength of the battery in Comparative Example 1 is insufficient. When the explosion pressure of the explosion-proof valve is not reached, the cover cracks as a whole, the explosion-proof valve does not open, and the pressure relief function is not achieved, and the thermal runaway test fails. In Comparative Example 2, the tensile strength c of the cover body 1 is 310 MPa, and the yield strength d of the cover body 1 is less than 200 MPa. The yield strength d of the plate body 1 is 145 MPa. Correspondingly, the calculation result of Formula 2 is 0.57, which is less than 0.7 and is not within the range (0.7 to 9) specified in this application. The cover plate strength of the battery in Comparative Example 2 is insufficient. When the bursting pressure of the explosion-proof valve is not reached, the cover plate cracks as a whole, the explosion-proof valve does not open, and the pressure relief function is not achieved. The thermal runaway test fails. In Comparative Example 3, the bursting pressure e of the explosion-proof valve is 2.5 MPa, which is greater than the maximum value of 1.8 MPa specified in this application. Correspondingly, the calculation result of Formula 1 is 0.25, which is less than 0.3 and is not within the range (0.3 to 2) specified in this application. The bursting pressure of the explosion-proof valve of the battery in Comparative Example 3 is too large, and the explosion-proof valve does not It can be opened in time, and cracks occur in the cover or shell. The thermal runaway test fails and the battery is unsafe. In Comparative Example 4, the bursting pressure e of the explosion-proof valve is 0.4 MPa, which is less than the minimum value of 0.9 MPa specified in this application. Correspondingly, the calculation result of Formula 1 is 2.59, which is greater than 2 and is not within the range (0.3 to 2) specified in this application. The bursting pressure of the explosion-proof valve of the battery in Comparative Example 4 is too small, the explosion-proof valve is scored and cracked, the battery cell fails, and the thermal runaway test fails. In Comparative Example 5, the ratio f of the area of ​​the explosion-proof valve to the surface area of ​​the cover body 1 is 12%, which is less than 20%. Correspondingly, the calculation result of Formula 2 is 10.81, which is greater than 9 and is not within the range specified in this application. 9), the explosion-proof valve of the battery in Comparative Example 5 accounts for too small an area. Although the explosion-proof valve opens in time, the gas in the battery cannot be discharged in time due to the small pressure relief area, resulting in the shell or cover being torn. The thermal runaway test fails and the battery is unsafe. In Comparative Example 6, the ratio f of the area of ​​the explosion-proof valve to the surface area of ​​the cover body 1 is 92%, which is greater than 85%. Correspondingly, the calculation result of Formula 2 is 0.67, which is less than 0.7 and is not within the range (0.7 to 9) specified in this application. The explosion-proof valve of the battery in Comparative Example 6 accounts for too large an area, and the score line is close to the edge. When the battery cell is slightly squeezed or vibrated, the cover score is prone to cracking, and the battery cell is unsafe.

[0061] In summary, the battery thermal runaway test can only be passed when the results of Formula 1 and Formula 2 fall within the range specified in this application, thereby achieving the goal of simultaneously ensuring structural strength and safety performance.

[0062] Although the embodiments of the present application have been described with reference to the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present application, and such modifications and variations shall fall within the scope defined by the appended claims.

Claims

1. A cover plate, characterized in that: include: Cover plate body; An explosion-proof valve is arranged on the cover body, and the explosion-proof valve is formed by an explosion-proof notch constructed on the cover body; The tensile strength of the cover body is c, the yield strength of the cover body is d, the bursting pressure of the explosion-proof valve is e, and the ratio of the area of ​​the explosion-proof valve to the surface area of ​​the cover body is f, satisfying: and 2. The cover plate according to claim 1, characterized in that: The cover plate body is made of steel; and / or the explosion-proof notch is integrally formed with the cover plate body.

3. The cover plate according to claim 1, characterized in that: The tensile strength c of the cover plate body ranges from 400 MPa to 1000 MPa.

4. The cover plate according to claim 1, characterized in that: The yield strength d of the cover plate body ranges from 200 MPa to 800 MPa.

5. The cover plate according to claim 1, characterized in that: The bursting pressure e of the explosion-proof valve ranges from 0.9 MPa to 1.8 MPa.

6. The cover plate according to claim 1, characterized in that: The ratio f of the area of ​​the explosion-proof valve to the surface area of ​​the cover plate body is greater than or equal to 1 / 5.

7. The cover plate according to claim 6, characterized in that: The ratio f of the area of ​​the explosion-proof valve to the surface area of ​​the cover plate body ranges from 20% to 85%.

8. The cover plate according to claim 1, characterized in that: The thickness b of the cover plate body ranges from 0.2 mm to 1 mm; And / or, the residual thickness h of the explosion-proof notch on the cover plate body ranges from 0.03 mm to 0.1 mm.

9. The cover plate according to any one of claims 1 to 8, characterized in that: The cover body is also provided with a pole assembly and a liquid injection hole, and the explosion-proof notch is spaced apart from the pole assembly and the liquid injection hole, or the explosion-proof notch surrounds the outside of the pole assembly and the liquid injection hole, or the explosion-proof notch is circumferentially arranged around the cover body.

10. A battery, characterized in that: include: a housing having an open end; A pole group, arranged in the shell; The cover plate according to any one of claims 1 to 9, wherein the cover plate is arranged at the open end of the shell to close the shell.

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