Battery monomer, battery device and electric device

Abstract

The utility model provides a battery monomer, a battery device and a power utilization device. The battery monomer comprises a shell, an electrode assembly and a pressure relief mechanism, the shell is provided with a wall part, the base material of the wall part is iron, the electrode assembly is accommodated in the shell, and the pressure relief mechanism is arranged on the wall part. The base material of the pressure relief mechanism is iron. The pressure relief mechanism comprises a weak part, and the weak part is configured to be at least partially destroyed to release pressure when the pressure in the shell reaches a threshold value. Wherein the number of crystal grain layers of the weak part is N, and N is larger than or equal to 1 and smaller than or equal to 5. Under the condition that the thickness of the weak part is the same, the smaller the number of grain layers of the weak part is, the larger the average grain size of the weak part is, the smaller the interaction force between grain boundaries is, the tensile strength of the weak part can be reduced, and therefore the bursting pressure is reduced. Under the condition of the same bursting pressure, the thickness of the weak part can be set to be larger by enabling the number of the crystal grain layers of the weak part to be smaller than or equal to 5, the risk that the weak part is damaged in advance is reduced, and the service life of the battery monomer is prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of battery, in particular to a battery monomer, a battery device and a power utilization device. BACKGROUND

[0002] Batteries are widely used in the field of new energy, for example, electric vehicles, new energy vehicles, etc. New energy vehicles and electric vehicles have become a new trend in the development of the automobile industry. The development of battery technology needs to consider various design factors, such as energy density, discharge capacity, charge-discharge rate and other performance parameters. In addition, the cycle life of the battery also needs to be considered. However, the cycle life of the battery is currently relatively short. CONTENT OF THE INVENTION

[0003] The purpose of the embodiments of the present application is to provide a battery monomer, a battery device and a power utilization device, which aims to improve the problem of short cycle life of the battery in the related art.

[0004] In a first aspect, the embodiments of the present application provide a battery monomer, which comprises a shell, an electrode assembly and a pressure relief mechanism, the shell has a wall part, the base material of the wall part is iron; the electrode assembly is contained in the shell; the pressure relief mechanism is arranged on the wall part, the base material of the pressure relief mechanism is iron, the pressure relief mechanism comprises a weak part, the weak part is configured to be at least partially destroyed to release the pressure when the pressure inside the shell reaches a threshold value; wherein the number of grain layers of the weak part is N, which satisfies: 1≤N≤5.

[0005] In the technical solution, when the thickness of the weak portion is the same, the fewer the layers of the grains of the weak portion, the larger the average grain size of the weak portion, the smaller the grain boundary area, and the smaller the interaction force between the grain boundaries, thereby reducing the tensile strength of the weak portion and reducing the burst pressure. Therefore, under the same burst pressure, by setting the layers of the grains of the weak portion to be less than or equal to 5, the thickness of the weak portion can be set to be larger, so that when the battery cell is normally used, the weak portion is less likely to be cracked due to the change in the pressure inside the battery cell or external impact, thereby reducing the risk of the early destruction of the weak portion and improving the service life of the battery cell. The base material of the wall portion and the pressure relief mechanism is iron, which can reduce the thickness of the wall portion and the pressure relief mechanism, thereby improving the energy density of the battery cell. In addition, compared with the aluminum material explosion-proof valve in the prior art, the base material of the pressure relief mechanism is iron, and the thickness of the weak portion is smaller. When manufacturing, a slight change in the thickness of the weak portion will cause a large change in the burst pressure of the battery cell. By setting the layers of the grains of the weak portion to be less than or equal to 5, the thickness of the weak portion can be increased under the same burst pressure. The larger the thickness of the weak portion, the easier it is to manufacture, and the lower the precision requirement of the manufacturing equipment, thereby improving the consistency of the burst pressures of multiple battery cells.

[0006] As an optional technical solution of the embodiment, 1≤N≤3.

[0007] In the technical solution, under the same burst pressure, by setting the layers of the grains of the weak portion to be less than or equal to 3, the thickness of the weak portion can be set to be larger, so that when the battery cell is normally used, the weak portion is less likely to be cracked due to the change in the pressure inside the battery cell or external impact, thereby reducing the risk of the early destruction of the weak portion and improving the service life of the battery cell. In addition, the larger the thickness of the weak portion, the easier it is to manufacture, and the lower the precision requirement of the manufacturing equipment, thereby improving the consistency of the burst pressures of multiple battery cells.

[0008] As an optional technical solution of the embodiment, the grain size grade of the weak portion is 6-10.

[0009] In the technical scheme, when the grain size grade of the weak portion is less than or equal to 10, the grain size grade of the weak portion is small, the average grain size of the weak portion is large, the grain boundary area is small, and the interaction force between the grain boundaries is small, so that the tensile strength of the weak portion is reduced, and the burst pressure is reduced. Therefore, under the condition of the same burst pressure, the thickness of the weak portion can be set to be larger by setting the grain size grade of the weak portion to be less than or equal to 10, so that the weak portion is not easily cracked in advance due to the change of the pressure in the battery monomer or the impact from the outside when the battery monomer is normally used, and the risk of the weak portion being damaged in advance is reduced, and the service life of the battery monomer is improved. When the grain size grade of the weak portion is greater than or equal to 6, the grain size grade of the weak portion is not too small, the average grain size of the weak portion is not too large, and the weak portion is less likely to be brittle, so that the weak portion has good ductility and is convenient to process and manufacture. Therefore, when the grain size grade of the weak portion is 6 to 10, the weak portion can be conveniently processed and manufactured, and the service life of the battery monomer is improved.

[0010] As an optional technical scheme of the embodiment of the application, the grain size grade of the weak portion is 7 to 9.

[0011] In the technical scheme, when the grain size grade of the weak portion is less than or equal to 9, the grain size grade of the weak portion is small, the average grain size of the weak portion is large, the grain boundary area is small, and the interaction force between the grain boundaries is small, so that the tensile strength of the weak portion is reduced, and the burst pressure is reduced. Therefore, under the condition of the same burst pressure, the thickness of the weak portion can be set to be larger by setting the grain size grade of the weak portion to be less than or equal to 9, so that the weak portion is not easily cracked in advance due to the change of the pressure in the battery monomer or the impact from the outside when the battery monomer is normally used, and the risk of the weak portion being damaged in advance is reduced, and the service life of the battery monomer is improved. When the grain size grade of the weak portion is greater than or equal to 7, the grain size grade of the weak portion is not too small, the average grain size of the weak portion is not too large, and the weak portion is less likely to be brittle, so that the weak portion has good ductility and is convenient to process and manufacture. Therefore, when the grain size grade of the weak portion is 7 to 9, the weak portion can be conveniently processed and manufactured, and the service life of the battery monomer is improved.

[0012] As an optional technical scheme of the embodiment of the application, the pressure relief mechanism comprises a non-weak portion, the thickness of the non-weak portion is greater than the thickness of the weak portion, the non-weak portion comprises a pressure relief area, and the weak portion is arranged outside the pressure relief area.

[0013] In the technical solution, the thickness of the non-weak part is greater than the thickness of the weak part, and the strength of the weak part is lower than the strength of the non-weak part. When the pressure inside the battery cell reaches the threshold value, the pressure relief area can be opened along the weak part to form a larger opening, thereby relieving the pressure inside the battery cell, improving the timeliness of the pressure relief of the battery cell, and improving the reliability of the battery cell.

[0014] As an optional technical solution of the embodiment of the application, the difference between the grain size grade of the pressure relief area and the grain size grade of the weak part is less than or equal to 3 levels.

[0015] In the technical solution, when the difference between the grain size grade of the pressure relief area and the grain size grade of the weak part is less than or equal to 3 levels, the grain size grade of the pressure relief area and the grain size grade of the weak part are relatively close, the material consistency of the pressure relief mechanism is good, and the consistency of the burst pressure of the plurality of battery cells is improved.

[0016] As an optional technical solution of the embodiment of the application, the difference between the grain size grade of the pressure relief area and the grain size grade of the weak part is less than or equal to 2 levels.

[0017] In the technical solution, when the difference between the grain size grade of the pressure relief area and the grain size grade of the weak part is less than or equal to 2 levels, the grain size grade of the pressure relief area and the grain size grade of the weak part are more close, the material consistency of the pressure relief mechanism is better, and the consistency of the burst pressure of the plurality of battery cells is more improved.

[0018] As an optional technical solution of the embodiment of the application, the pressure relief mechanism further comprises a first transition part, the first transition part connects the weak part and the pressure relief area, the thickness of the first transition part increases along the direction from the weak part to the pressure relief area, and the difference between the grain size grade of the first transition part and the grain size grade of the weak part is less than or equal to 3 levels.

[0019] In the technical solution, by arranging the first transition part, the thickness of the first transition part increases along the direction from the weak part to the pressure relief area, the weak part can gradually transition to the pressure relief area, the grain size grade of the first transition part gradually changes from the weak part to the pressure relief area, the grain size does not easily change abruptly, the stress concentration is reduced, and the burst pressure of the plurality of battery cells manufactured is more consistent. In addition, when the difference between the grain size grade of the first transition part and the grain size grade of the weak part is less than or equal to 3 levels, the grain size grade of the first transition part and the grain size grade of the weak part are relatively close, the material consistency of the pressure relief mechanism is good, and the consistency of the burst pressure of the plurality of battery cells is improved.

[0020] As an optional technical solution of the embodiment of the application, the difference between the grain size grade of the first transition part and the grain size grade of the weak part is less than or equal to 2 levels.

[0021] In the technical solution, when the difference between the grain size grade of the first transition part and the grain size grade of the weak part is less than or equal to 2, the grain size grade of the first transition part and the grain size grade of the weak part are closer, the material consistency of the pressure relief mechanism is better, and the consistency of the burst pressures of the plurality of battery monomers is improved.

[0022] As an optional technical solution of the embodiment, the non-weak part further comprises a connecting area, the connecting area is arranged outside the weak part, the connecting area comprises a first part and a second part, the first part is welded with the wall part to form a welding mark, and the second part connects the weak part and the first part; the difference between the grain size grade of the second part and the grain size grade of the weak part is less than or equal to 3.

[0023] In the technical solution, the pressure relief mechanism is arranged separately from the wall part and is welded with the wall part, the welding connection with the wall part is facilitated by arranging the connecting area. When the difference between the grain size grade of the second part and the grain size grade of the weak part is less than or equal to 3, the grain size grade of the second part and the grain size grade of the weak part are closer, the material consistency of the pressure relief mechanism is better, and the consistency of the burst pressures of the plurality of battery monomers is improved.

[0024] As an optional technical solution of the embodiment, the difference between the grain size grade of the second part and the grain size grade of the weak part is less than or equal to 2.

[0025] In the technical solution, when the difference between the grain size grade of the second part and the grain size grade of the weak part is less than or equal to 2, the grain size grade of the second part and the grain size grade of the weak part are closer, the material consistency of the pressure relief mechanism is better, and the consistency of the burst pressures of the plurality of battery monomers is improved.

[0026] As an optional technical solution of the embodiment, the non-weak part further comprises a connecting area, the connecting area is arranged outside the weak part, the connecting area is integrally formed with the wall part; the difference between the grain size grade of the connecting area and the grain size grade of the weak part is less than or equal to 3.

[0027] In the technical solution, the connecting area is integrally formed with the wall part, and no additional welding or bonding process is needed, so that the risk of liquid leakage of the pressure relief mechanism is reduced. When the difference between the grain size grade of the connecting area and the grain size grade of the weak part is less than or equal to 3, the grain size grade of the connecting area and the grain size grade of the weak part are closer, the material consistency of the pressure relief mechanism is better, and the consistency of the burst pressures of the plurality of battery monomers is improved.

[0028] As an optional technical solution of the embodiment of the present application, the difference between the grain size grade of the connecting area and the grain size grade of the weak part is less than or equal to 2 levels.

[0029] In the above technical solution, when the difference between the grain size grade of the connecting area and the grain size grade of the weak part is less than or equal to 2 levels, the grain size grade of the connecting area and the grain size grade of the weak part are closer, the material consistency of the pressure relief mechanism is better, and it is more conducive to improving the consistency of the burst pressure of the plurality of battery monomers.

[0030] As an optional technical solution of the embodiment of the present application, the pressure relief mechanism further comprises a second transition part, the second transition part connects the weak part and the connecting area, the thickness of the second transition part increases along the direction from the weak part to the connecting area, and the difference between the grain size grade of the second transition part and the grain size grade of the weak part is less than or equal to 3 levels.

[0031] In the above technical solution, by setting the second transition part, the thickness of the second transition part increases along the direction from the weak part to the connecting area, the weak part can gradually transition to the connecting area, the grain size grade of the second transition part gradually changes from the direction of the weak part to the connecting area, the grain size is not easy to suddenly change, which is conducive to reducing stress concentration, so that the burst pressure of the plurality of battery monomers manufactured is more consistent. In addition, when the difference between the grain size grade of the second transition part and the grain size grade of the weak part is less than or equal to 3 levels, the grain size grade of the second transition part and the grain size grade of the weak part are closer, the material consistency of the pressure relief mechanism is better, and it is more conducive to improving the consistency of the burst pressure of the plurality of battery monomers.

[0032] As an optional technical solution of the embodiment of the present application, the difference between the grain size grade of the second transition part and the grain size grade of the weak part is less than or equal to 2 levels.

[0033] In the above technical solution, when the difference between the grain size grade of the second transition part and the grain size grade of the weak part is less than or equal to 2 levels, the grain size grade of the second transition part and the grain size grade of the weak part are closer, the material consistency of the pressure relief mechanism is better, and it is more conducive to improving the consistency of the burst pressure of the plurality of battery monomers.

[0034] As an optional technical solution of the embodiment of the present application, the hardness of the non-weak part is A, which satisfies: 145HV≤A≤185HV.

[0035] In the technical solution, when A≤185HV, the hardness of the non-weak part is small, so that the non-weak part is soft and is easy to deform under the action of the internal pressure of the battery cell, thereby facilitating the pulling of the weak part, so that the weak part is torn when the internal pressure of the battery cell reaches the threshold, which is beneficial to improve the consistency of the burst pressure of the plurality of battery cells. When A≥145HV, the hardness of the non-weak part is not too small, and accordingly, the strength of the non-weak part is not too low, so that the non-weak part is not easy to be damaged under the action of external force, which is beneficial to improve the life and reliability of the battery cell. Therefore, when 145HV≤A≤185HV, it is beneficial to improve the consistency of the burst pressure of the plurality of battery cells and the life and reliability of the battery cell.

[0036] As an optional technical solution of the embodiment of the application, 150HV≤A≤170HV.

[0037] In the technical solution, when A≤170HV, the hardness of the non-weak part is smaller, so that the non-weak part is softer and is easier to deform under the action of the internal pressure of the battery cell, thereby facilitating the pulling of the weak part, so that the weak part is torn when the internal pressure of the battery cell reaches the threshold, which is beneficial to improve the consistency of the burst pressure of the plurality of battery cells. When A≥150HV, the hardness of the non-weak part is not too small, and accordingly, the strength of the non-weak part is not too low, so that the non-weak part is not easy to be damaged under the action of external force, which is beneficial to improve the life and reliability of the battery cell. Therefore, when 150HV≤A≤170HV, it is beneficial to improve the consistency of the burst pressure of the plurality of battery cells and the life and reliability of the battery cell.

[0038] As an optional technical solution of the embodiment of the application, the pressure relief area is at least partially raised in a direction away from the electrode assembly.

[0039] In the technical solution, the existing pressure relief mechanism will gradually rise from a flat structure to a direction away from the electrode assembly under the action of the internal pressure of the battery cell when pressure relief, and after rising, the pressure relief mechanism will open under the action of the internal pressure of the battery cell. In the embodiment of the application, the pressure relief area of the pressure relief mechanism is at least partially raised in a direction away from the electrode assembly, and the pressure relief area forms a pre-deformation on the inner side of the weak part, thereby facilitating the cracking of the weak part to relieve pressure. In this way, under the same burst pressure, the thickness of the weak part can be larger, and the weak part is not easy to crack prematurely due to changes in the internal pressure of the battery cell or external impact when the battery cell is in normal use, which is beneficial to reduce the risk of damage to the weak part and improve the life of the battery cell.

[0040] As an optional technical solution of the embodiment of the present application, the non-weak portion further comprises a connecting area, the connecting area is arranged outside the weak portion, the connecting area is integrally formed with the wall portion or is separately arranged and connected with the wall portion, the connecting area is at least partially raised in a direction close to the electrode assembly, and the weak portion is connected to a part of the connecting area closest to the electrode assembly.

[0041] In the above technical solution, the connecting area is at least partially raised in a direction close to the electrode assembly, the pressure relief area is raised in a direction away from the electrode assembly, the raising direction of the connecting area is opposite to the raising direction of the pressure relief area, so that the pressure relief area can be raised by the raising height of the connecting area, thereby facilitating the reduction of the height of the pressure relief area beyond the surface of the part of the connecting area farthest away from the electrode assembly, reducing the occupation of the battery monomer or the internal space of the battery, and facilitating the improvement of the energy density of the battery monomer or the battery. In addition, since the weak portion is connected to the part of the connecting area closest to the electrode assembly, that is, the position of the weak portion is closer to the electrode assembly than the connecting position of the connecting area and the wall portion, and since one end of the connecting area is constrained by the wall portion, under the action of the gas pressure, the part of the connecting area raised in the direction close to the electrode assembly extrudes the weak portion, thereby inhibiting the cracking of the weak portion and preventing the creep failure of the weak portion during the normal operation of the battery monomer, effectively prolonging the service life of the battery monomer.

[0042] As an optional technical solution of the embodiment of the present application, the thickness of the weak portion is H, and 0.01mm≤H≤0.1mm is satisfied.

[0043] In the above technical solution, when H≥0.01mm, the thickness of the weak portion is relatively large, and the weak portion is not prone to be cracked in advance due to the pressure change inside the battery monomer or external impact, thereby facilitating the reduction of the risk of the weak portion being damaged in advance and facilitating the improvement of the service life of the battery monomer. When H≤0.1mm, the thickness of the weak portion is not too large, so that the pressure relief mechanism can be opened in time when the battery monomer is out of control, thereby facilitating the timeliness of the pressure relief of the pressure relief mechanism. Therefore, when 0.01mm≤H≤0.1mm, the service life of the battery monomer and the timeliness of the pressure relief can be considered.

[0044] As an optional technical solution of the embodiment of the present application, 0.015mm≤H≤0.06mm is satisfied.

[0045] In the technical solution, when H is greater than or equal to 0.015 mm, the thickness of the weak part is greater, and the weak part is less likely to be cracked in advance due to the pressure change inside the battery monomer or external impact, which is beneficial to reduce the risk of the weak part being damaged in advance and improve the service life of the battery monomer. When H is less than or equal to 0.06 mm, the thickness of the weak part is not too large, so that the pressure relief mechanism can be opened in time when the battery monomer is out of control, which is beneficial to improve the timeliness of the pressure relief mechanism. Therefore, when 0.015 mm≤H≤0.06 mm, the service life and the timeliness of the battery monomer can be considered.

[0046] As an optional technical solution of the embodiment of the application, the material of the pressure relief mechanism includes at least one of stainless steel and carbon steel.

[0047] In the technical solution, stainless steel and carbon steel have high strength, which can effectively improve the structural strength of the weak part, reduce the risk of the weak part being cracked due to external force, reduce the risk of the weak part being damaged in advance, and improve the service life and reliability of the battery monomer.

[0048] As an optional technical solution of the embodiment of the application, the material of the pressure relief mechanism includes at least one of SUS304 stainless steel, SUS305 stainless steel or SUS316L stainless steel.

[0049] In the technical solution, 304 stainless steel, 305 stainless steel and 316 stainless steel have the advantages of corrosion resistance, high temperature resistance and good processing performance. The pressure relief mechanism 24 made of 304 stainless steel, 305 stainless steel or 316 stainless steel has high strength, which can effectively improve the structural strength of the weak part, reduce the risk of the weak part being cracked due to external force, reduce the risk of the weak part being damaged in advance, improve the service life and reliability of the battery monomer, and improve the consistency of the burst pressure of the plurality of battery monomers 20.

[0050] As an optional technical solution of the embodiment of the application, the pressure relief mechanism is arranged separately from the wall part, the wall part is provided with a pressure relief hole, and the pressure relief mechanism is mounted on the wall part and covers the pressure relief hole.

[0051] In the technical solution, the pressure relief mechanism is arranged separately from the wall part and mounted on the wall part, so as to facilitate processing and manufacturing.

[0052] As an optional technical solution of the embodiment of the application, the pressure relief mechanism is integrally formed with the wall part.

[0053] In the technical solution, the pressure relief mechanism is integrally formed with the wall part, without the need for additional welding or bonding process, which is conducive to reducing the risk of liquid leakage of the pressure relief mechanism. In addition, the burst pressure of the processed battery cells is consistent during production.

[0054] As an optional technical solution of the embodiment, the shell comprises a housing and an end cover, one end of the housing has an opening, and the end cover seals the opening, and the end cover is the wall part.

[0055] In the technical solution, when the end cover is the wall part, the pressure relief mechanism is arranged on the end cover, which is simple and convenient to manufacture.

[0056] In a second aspect, the embodiment also provides a battery device, which comprises the battery cell.

[0057] In a third aspect, the embodiment also provides a power consumption device, which comprises the battery cell, and the battery cell is used to provide power for the power consumption device. BRIEF DESCRIPTION OF DRAWINGS

[0058] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor.

[0059] Figure 1 The structural schematic diagram of the vehicle is provided for some embodiments of the present application;

[0060] Figure 2 The explosion diagram of the battery is provided for some embodiments of the present application;

[0061] Figure 3 The structural schematic diagram of the battery cell is provided for some embodiments of the present application;

[0062] Figure 4 The explosion diagram of the battery cell is provided for some embodiments of the present application;

[0063] Figure 5 The top view schematic diagram of the wall part is provided for some embodiments of the present application;

[0064] Figure 6 The Figure 5 sectional view of position A-A;

[0065] Figure 7 The Figure 6 enlarged view of position B;

[0066] Figure 8 For Figure 7 A grain diagram (schematic view) of the pressure relief mechanism is shown.

[0067] Legend: 10 - case; 11 - first case body; 12 - second case body; 20 - battery cell; 21 - housing; 211 - case; 212 - end cap; 213 - wall portion; 2131 - pressure relief hole; 23 - electrode assembly; 231 - main body; 232 - tab; 24 - pressure relief mechanism; 241 - weak portion; 242 - non-weak portion; 2421 - pressure relief zone; 2422 - connection zone; 24221 - first portion; 24222 - second portion; 243 - first transition portion; 244 - second transition portion; 245 - pressure relief groove; 25 - electrode terminal; 26 - protection member; 27 - insulation member; 100 - battery device; 200 - controller; 300 - motor; 1000 - vehicle. DETAILED DESCRIPTION

[0068] In order to make the objects, 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 below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present application.

[0069] Unless otherwise defined, all technical and scientific terms used in the present application have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs; the terms used in the specification of the present application are only for the purpose of describing the specific embodiments and are not intended to limit the present application; the terms "include" and "have" and any variations thereof in the specification and claims of the present application and the above description of drawings are intended to cover non-exclusive inclusion. The terms "first", "second" and the like in the specification and claims of the present application and the above description of drawings are used to distinguish different objects, not to describe a particular order or primary and secondary relationship.

[0070] In the present application, the phrase "embodiment" means that the specific features, structures or characteristics described in connection with the embodiment can be included in at least one embodiment of the present application. The phrase appears at various places in the specification does not necessarily refer to the same embodiment, nor is it mutually exclusive or alternative to other embodiments.

[0071] In the description of the present application, it should be noted that unless specifically defined and limited otherwise, the terms "mount", "connected", "connection", "attach" should be broadly interpreted, for example, can be fixedly connected, can be detachably connected, or integrally connected; can be directly connected, or indirectly connected through an intermediate medium; can be internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0072] The term "and / or" in the present application is only to describe the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B can mean that A exists alone, A and B exist together, and B exists alone. In addition, the character " / " in the present application generally represents that the front and rear associated objects have an "or" relationship.

[0073] In the embodiments of the present application, the same reference signs represent the same parts, and for the sake of brevity, the detailed description of the same parts is omitted in different embodiments. It should be understood that the thickness, length, width and other dimensions of various components in the embodiments of the present application shown in the drawings, and the overall thickness, length, width and other dimensions of the integrated device are only exemplary and should not constitute any limitation on the present application.

[0074] "Multiple" appearing in the present application means two or more (including two).

[0075] In the embodiments of the present application, the battery cell can be a secondary battery, which refers to a battery cell that can be activated by charging after discharging.

[0076] The battery cell includes but is not limited to lithium ion battery, sodium ion battery, sodium lithium ion battery, lithium metal battery, sodium metal battery, lithium sulfur battery, magnesium ion battery, nickel hydrogen battery, nickel cadmium battery, lead-acid battery, etc.

[0077] The battery cell generally includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator. During the charging and discharging process of the battery cell, active ions (such as lithium ions) are embedded and extracted between the positive electrode and the negative electrode. The separator is arranged between the positive electrode and the negative electrode, which can reduce the risk of short circuit of the positive and negative electrodes, and at the same time allow the active ions to pass through.

[0078] In some embodiments, the positive electrode can be a positive electrode sheet, which can include a positive electrode current collector and a positive electrode active material arranged on at least one surface of the positive electrode current collector.

[0079] As an example, the positive electrode current collector has two opposite surfaces in its own thickness direction, and the positive electrode active material is arranged on any one or both of the two opposite surfaces of the positive electrode current collector.

[0080] As an example, the positive electrode current collector can employ a metal foil or a composite current collector. For example, as the metal foil, aluminum subjected to silver plating on the surface, stainless steel subjected to silver plating on the surface, stainless steel, copper, aluminum, nickel, a carbon electrode, carbon, nickel, or titanium, or the like can be employed. The composite current collector can include a high molecular material base layer and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, or the like) on a high molecular material base material (such as a base material of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, or the like).

[0081] As an example, the positive electrode active material can include at least one of a lithium-containing phosphate, a lithium transition metal oxide, and a modified compound of each thereof. However, the present application is not limited to these materials, and other conventional materials that can be used as a positive electrode active material of a battery cell can also be used. These positive electrode active materials can be used alone only one or two or more can be used in combination. Among them, examples of the lithium-containing phosphate can include, but are not limited to, at least one of lithium iron phosphate (such as LiFeP04 (which can also be referred to simply as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnP04), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon. Examples of the lithium transition metal oxide can include, but are not limited to, lithium cobalt oxide (such as LiCo02), lithium nickel oxide (such as LiNi02), lithium manganese oxide (such as LiMn02, LiMn204), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3Mn 1 / 3 O2 (which can also be referred to simply as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (which can also be referred to simply as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (which can also be referred to simply as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (which can also be referred to simply as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (which can also be referred to simply as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05O2) and modified compounds thereof, etc.

[0082] In some embodiments, the positive electrode can employ a foamed metal. The foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloy, etc. When the foamed metal is employed as the positive electrode, the foamed metal surface can be free of the positive electrode active material, or can be provided with the positive electrode active material. As an example, the foamed metal can be filled or / and deposited with a lithium source material, potassium metal, or sodium metal. The lithium source material can be lithium metal and / or a lithium-rich material.

[0083] In some embodiments, the negative electrode can be a negative electrode sheet, which can include a negative electrode current collector.

[0084] As an example, the negative electrode current collector can employ a metal foil, a foamed metal, or a composite current collector. For example, as the metal foil, aluminum with a silver-plated surface, stainless steel with a silver-plated surface, stainless steel, copper, aluminum, nickel, a carbon electrode, carbon, nickel, or titanium, etc. can be employed. The foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloy, etc. The composite current collector can include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material base material (such as a base material of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0085] As an example, the negative electrode sheet can include the negative electrode current collector and the negative electrode active material provided on at least one surface of the negative electrode current collector.

[0086] As an example, the negative electrode current collector has two surfaces opposite in the thickness direction thereof, and the negative electrode active material is provided on either one or both of the two opposite surfaces of the negative electrode current collector.

[0087] As an example, the negative electrode active material can employ a negative electrode active material known in the art for use in a battery cell. As an example, the negative electrode active material can include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, a silicon-based material, a tin-based material, and lithium titanate, etc. The silicon-based material can be selected from at least one of elemental silicon, a silicon oxide compound, a silicon-carbon composite, a silicon-nitrogen composite, and a silicon alloy. The tin-based material can be selected from at least one of elemental tin, a tin oxide compound, and a tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as a negative electrode active material for a battery cell can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0088] In some embodiments, the material of the positive electrode current collector can be aluminum, and the material of the negative electrode current collector can be copper.

[0089] In some embodiments, the separator is a separator film. The separator film can be any porous structure separator film known to have good chemical stability and mechanical stability.

[0090] As an example, the material of the separator film can include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator film can be a single layer film or a multi-layer composite film. When the separator film is a multi-layer composite film, the materials of the layers can be the same or different. The separator can be a separate component between the positive and negative electrodes or can be attached to the surface of the positive and negative electrodes.

[0091] In some embodiments, the battery cell further includes an electrolyte that functions to conduct ions between the positive and negative electrodes. The electrolyte can be in a liquid state, a gel state, or a solid state. Among them, the liquid electrolyte includes an electrolyte salt and a solvent.

[0092] In some embodiments, the electrolyte salt can include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorobisoxalate borate, lithium bisoxalate borate, lithium difluorobisoxalate phosphate, and lithium tetrafluorobisoxalate phosphate.

[0093] In some embodiments, the solvent can include at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, butyrosulfone, methyl ethyl sulfone, and diethyl sulfone. The solvent can also be an ether solvent. The ether solvent can include one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyl tetrahydrofuran, diphenyl ether, and crown ether.

[0094] Among them, the gel electrolyte includes a polymer as a skeleton network of the electrolyte, in combination with an ionic liquid-lithium salt.

[0095] In some embodiments, the electrode assembly is a wound structure. The positive electrode sheet and the negative electrode sheet are wound into a wound structure.

[0096] In some embodiments, the electrode assembly is a stacked structure.

[0097] As an example, a plurality of positive electrode sheets and a plurality of negative electrode sheets can be provided, respectively, and the plurality of positive electrode sheets and the plurality of negative electrode sheets can be alternately stacked.

[0098] As an example, the positive electrode sheet can be provided in a plurality of pieces, and the negative electrode sheet can be folded to form a plurality of folded sections arranged in layers.

[0099] As an example, the positive electrode sheet and the negative electrode sheet can each be folded to form a plurality of folded sections arranged in layers.

[0100] As an example, a plurality of separators can be provided, each provided between any adjacent positive electrode sheet or negative electrode sheet.

[0101] As an example, the separators can be provided continuously, and can be provided between any adjacent positive electrode sheet or negative electrode sheet by folding or winding.

[0102] In some embodiments, the electrode assembly can have a flat shape or a multi-prism shape, etc.

[0103] In some embodiments, the electrode assembly can be provided with tabs, which can guide current out of the electrode assembly. The tabs can include positive tabs and negative tabs.

[0104] In some embodiments, the battery cell can include a housing. The housing can be used to encapsulate components such as the electrode assembly and the electrolyte. The housing can be a steel housing, an aluminum housing, a composite metal housing (such as a copper-aluminum composite housing), etc.

[0105] In some embodiments, the housing can be a sealed structure or a non-sealed structure. As an example, when the housing is a sealed structure, the housing can protect the electrode assembly and prevent, to some extent, leakage of components such as the electrolyte. When the housing is a non-sealed structure, the housing can protect the electrode assembly, and a sealing bag can be further included between the housing and the electrode assembly. The sealing bag can be used to encapsulate components such as the electrode assembly and the electrolyte. Specifically, the sealing bag can be a bag-shaped insulating member or an aluminum-plastic film.

[0106] As an example, the battery cell can be a prismatic battery cell or a battery cell of another shape, such as a square battery cell, a blade battery cell, a multi-prismatic battery cell (e.g., a hexagonal battery cell), etc.

[0107] The battery device mentioned in the embodiments of the present application can include one or more battery cell assemblies for providing voltage and capacity. The battery cell assembly can include a plurality of battery cells connected in series, in parallel, or in a mixed connection through a busbar component.

[0108] In some embodiments, the battery cell assembly is generally formed by arranging a plurality of battery cells; as an example, the battery cell assembly can be a battery module, which is formed by arranging and fixing a plurality of battery cells into an independent module.

[0109] As an example, the battery module can be formed by bundling a plurality of battery cells with a cable tie.

[0110] In some embodiments, the battery device can be a battery pack, which can include a box and one or more battery cell assemblies housed in the box.

[0111] As an example, the battery cell assembly can be a battery module, which can be housed in the box by fixing the battery module in the box.

[0112] As an example, the battery cell assembly can also be housed in the box by fixing a plurality of battery cells directly in the box.

[0113] As an example, the box can include a first box body and a second box body. The first box body and the second box body are fastened so that an enclosed space is formed inside the box to accommodate the battery cell assembly. Here, enclosed means covered or closed, which can be sealed or unsealed. The first box body can be a top cover or a bottom plate.

[0114] As an example, the box can include a top cover, a frame, and a bottom plate. The top cover and the bottom plate are respectively connected with the frame so that an enclosed space is formed inside the box to accommodate the battery cell assembly.

[0115] As an example, the box can be part of a chassis structure of a vehicle. For example, the top cover of the box can be at least part of the floor of the vehicle, or the frame of the box can be at least part of the cross beam and the longitudinal beam of the vehicle.

[0116] In some embodiments, the battery device refers to an energy storage device, which includes a box, at least one side of which is provided with a door. The energy storage device includes an energy storage container, an energy storage cabinet, etc.

[0117] At present, from the development of market situation, the application of batteries is more and more extensive. Batteries are not only applied to energy storage power systems such as hydroelectric, thermal, wind and solar power stations, but also widely used in electric bicycles, electric motorcycles, electric vehicles and other electric vehicles, military equipment, aerospace and other fields. With the continuous expansion of the application field of batteries, the demand of the market is also increasing.

[0118] The development of battery technology needs to consider many design factors, such as energy density, discharge capacity, charge-discharge rate and other performance parameters. In addition, the cycle life of the battery also needs to be considered. However, the cycle life of the battery is currently short.

[0119] For the battery monomer, in order to improve the reliability of the battery monomer, the prior art is to provide a pressure relief mechanism on the battery monomer, and the pressure relief mechanism is provided with a weak part. When the internal pressure of the battery monomer reaches the burst pressure, the weak part is cracked to release the internal pressure of the battery monomer, thereby reducing the risk of explosion and fire of the battery monomer. However, in the prior art, the thickness of the weak part is small, and the weak part is easy to crack under the action of the change of the internal pressure of the battery monomer or the external impact, that is, the weak part is cracked before the internal pressure of the battery monomer reaches the expected burst pressure, resulting in early scrapping of the battery monomer and short service life of the battery monomer.

[0120] Therefore, the embodiments of the present application provide a battery monomer. The battery monomer comprises a shell, an electrode assembly and a pressure relief mechanism. The shell has a wall part, the base material of the wall part is iron, the electrode assembly is contained in the shell, and the pressure relief mechanism is arranged on the wall part. The base material of the pressure relief mechanism is iron. The pressure relief mechanism comprises a weak part configured to be at least partially destroyed to release pressure when the internal pressure of the shell reaches a threshold value. The number of grain layers of the weak part is N, and 1≤N≤5 is satisfied.

[0121] In the case of the same thickness of the weak part, the fewer the number of grain layers of the weak part, the larger the average grain size of the weak part, the smaller the grain boundary area, and the smaller the interaction force between the grain boundaries. Therefore, the tensile strength of the weak part can be reduced, thereby reducing the burst pressure. Therefore, under the condition of the same burst pressure, by setting the number of grain layers of the weak part to be less than or equal to 5 layers, the thickness of the weak part can be set to be larger. In this way, during normal use of the battery monomer, the weak part is not easy to crack due to the change of the internal pressure of the battery monomer or the external impact, which is beneficial to reduce the risk of early destruction of the weak part and improve the service life of the battery monomer. The base materials of the wall part and the pressure relief mechanism are both iron, which can reduce the thickness of the wall part and the pressure relief mechanism, thereby improving the energy density of the battery monomer. In addition, compared with the existing aluminum material explosion-proof valve, the base material of the pressure relief mechanism provided by the embodiments of the present application is iron, and the thickness of the weak part is small. When manufacturing, a little change in the thickness of the weak part will cause a great change in the burst pressure of the battery monomer. By setting the number of grain layers of the weak part to be less than or equal to 5 layers, the thickness of the weak part can be increased under the condition of the same burst pressure. The larger the thickness of the weak part, the easier it is to manufacture, and the precision requirement of the manufacturing equipment is lower, which is beneficial to improve the consistency of the burst pressures of multiple battery monomers.

[0122] The technical solutions described in the embodiments of the present application are applicable to various electric devices using battery monomers and battery devices, such as mobile phones, portable devices, notebook computers, electric vehicles, electric toys, electric tools, vehicles, ships and spacecraft, etc. For example, the spacecraft includes an airplane, a rocket, a space shuttle and a spaceship, etc.

[0123] The following embodiments are described by taking the electric device as a vehicle for example.

[0124] Please refer to Figure 1 , Figure 1 A structural schematic diagram of a vehicle 1000 is provided for some embodiments of the present application. The vehicle 1000 is internally provided with a battery device 100, which can be arranged at the bottom, head or tail of the vehicle 1000. The battery device 100 can be used for power supply of the vehicle 1000, for example, the battery device 100 can be used as the operating power supply of the vehicle 1000.

[0125] The vehicle 1000 can further include a controller 200 and a motor 300, the controller 200 being used to control the battery device 100 to supply power to the motor 300, for example, to meet the power demand of the vehicle 1000 during starting, navigation and driving.

[0126] In some embodiments of the present application, the battery device 100 can not only be used as the operating power supply of the vehicle 1000, but also be used as the driving power supply of the vehicle 1000, replacing or partially replacing the fuel or natural gas to provide driving power for the vehicle 1000.

[0127] Please refer to Figure 2 , Figure 2 An exploded view of the battery device 100 is provided for some embodiments of the present application. The battery device 100 can include a box body 10 and a battery cell 20, the box body 10 being used to accommodate the battery cell 20.

[0128] The box body 10 is internally formed with a closed space for accommodating the battery cell 20. The box body 10 can adopt various structures. In some embodiments, the box body 10 can include a first box body 11 and a second box body 12, the first box body 11 and the second box body 12 being mutually buckled. The first box body 11 and the second box body 12 can be various shapes, such as a cuboid, a cylinder, etc. The first box body 11 can be a hollow structure with one side open, and the second box body 12 can also be a hollow structure with one side open. The open side of the second box body 12 and the open side of the first box body 11 are buckled to each other, thereby forming the box body 10 with the closed space. Alternatively, the first box body 11 can be a hollow structure with one side open, and the second box body 12 can be a plate structure, the second box body 12 being buckled to the open side of the first box body 11, thereby forming the box body 10 with the accommodation cavity.

[0129] In the battery device 100, the battery cell 20 can be one or multiple. If the battery cell 20 is multiple, the multiple battery cells 20 can be connected in series, in parallel, or in a mixed connection. The mixed connection means that the multiple battery cells 20 are connected in series and in parallel. The multiple battery cells 20 can be connected in series, in parallel, or in a mixed connection to form a battery module, and the multiple battery modules are connected in series, in parallel, or in a mixed connection to form a whole, and are accommodated in the box 10. Alternatively, the multiple battery cells 20 can be directly connected in series, in parallel, or in a mixed connection, and the whole formed by the multiple battery cells 20 is accommodated in the box 10.

[0130] In some embodiments, the battery device 100 can further include a busbar component. The multiple battery cells 20 can be electrically connected through the busbar component to achieve the series connection, the parallel connection, or the mixed connection of the multiple battery cells 20. The busbar component can be a metal conductor, such as copper, iron, aluminum, stainless steel, aluminum alloy, etc.

[0131] Please refer to Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 and Figure 8 , Figure 3 for the structural schematic diagram of the battery cell 20 provided in some embodiments of the present application. Figure 4 for the exploded view of the battery cell 20 provided in some embodiments of the present application. Figure 5 for the top view of the wall portion 213 provided in some embodiments of the present application. Figure 6 for the sectional view of the position A-A in Figure 5 . Figure 7 for the enlarged view of the position B in Figure 6 . Figure 8 for the grain diagram (schematic diagram) of the pressure relief mechanism 24 shown in Figure 7 . The present application provides a battery cell 20, which includes a shell 21, an electrode assembly 23, and a pressure relief mechanism 24. The shell 21 has a wall portion 213, the base material of the wall portion 213 is iron, the electrode assembly 23 is accommodated in the shell 21, and the pressure relief mechanism 24 is arranged on the wall portion 213. The base material of the pressure relief mechanism 24 is iron. The pressure relief mechanism 24 includes a weak portion 241 configured to be at least partially destroyed to release pressure when the pressure inside the shell 21 reaches a threshold value. The number of grain layers of the weak portion 241 is N, which satisfies: 1≤N≤5.

[0132] The battery cell 20 refers to the smallest unit that constitutes the battery device 100.

[0133] The shell 21 includes a housing 211 and an end cover 212. The housing 211 has an open accommodating space for accommodating the electrode assembly 23. The end cover 212 is connected to the housing 211 and closes the opening.

[0134] The end cover 212 refers to a component that covers the opening of the shell 211 to isolate the internal environment of the battery cell 20 from the external environment. Without limitation, the shape of the end cover 212 can be adapted to the shape of the shell 211 to fit the shell 211. Optionally, the end cover 212 can be made of a material with certain hardness and strength, such as aluminum alloy, so that the end cover 212 is not easily deformed when subjected to extrusion collision, so that the battery cell 20 can have higher structural strength and reliability performance can also be improved. The material of the end cover 212 can include but is not limited to copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc. The end cover 212 is also provided with an electrode terminal 25, which is used to electrically connect with the tab 232 of the electrode assembly 23 to input or output the electrical energy of the battery cell 20. The electrode terminal 25 and the tab 232 can be directly connected, for example, the electrode terminal 25 and the tab 232 are directly welded. The electrode terminal 25 and the tab 232 can also be indirectly connected, for example, the electrode terminal 25 and the tab 232 are indirectly connected through a current collecting member. The battery cell 20 also includes an insulating member 27, which is arranged on the inner side of the end cover 212. The insulating member 27 can be used to isolate the electrical connection components in the shell 211 from the end cover 212 to reduce the risk of short circuit. Exemplarily, the insulating member 27 can be plastic, rubber, etc.

[0135] The shell 211 is a component for fitting the end cover 212 to form the internal environment of the battery cell 20, wherein the formed internal environment can be used to accommodate the electrode assembly 23, the electrolyte and other components. The shell 211 and the end cover 212 can be independent components, and an opening can be provided on the shell 211, and the end cover 212 is covered on the opening to form the internal environment of the battery cell 20. Without limitation, the end cover 212 and the shell 211 can also be integrated, specifically, the end cover 212 and the shell 211 can form a common joint surface before other components enter the shell, and when it is necessary to seal the inside of the shell 211, the end cover 212 is covered on the shell 211. The shell 211 can be various shapes and various sizes, such as rectangular parallelepiped, cylindrical, hexagonal prism, etc. Specifically, the shape of the shell 211 can be determined according to the specific shape and size of the electrode assembly 23. The material of the shell 211 can include but is not limited to copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc.

[0136] The electrode assembly 23 is a component in which electrochemical reactions occur in the battery cell 20. One or more electrode assemblies 23 can be contained within the case 211. The electrode assembly 23 is mainly formed by winding or stacking a positive electrode tab and a negative electrode tab, and an insulating film is generally provided between the positive electrode tab and the negative electrode tab. The positive electrode tab and the negative electrode tab have a portion with active material that constitutes a main body 231 of the electrode assembly 23, and a portion without active material that constitutes a tab 232 of each of the positive electrode tab and the negative electrode tab. The positive tab and the negative tab can be located together at one end of the main body 231 or at opposite ends of the main body 231. During charging and discharging of the battery device 100, the positive active material and the negative active material react with the electrolyte.

[0137] The wall portion 213 can be an end cover 212 of the housing 21 or a wall of the case 211 of the housing 21. Exemplarily, in the embodiments shown in FIGS. 1 to 3, the wall portion 213 is the end cover 212. In other embodiments, the wall portion 213 is a bottom wall of the case 211 opposite to the end cover 212. In yet other embodiments, the wall portion 213 can also be a side wall of the case 211 adjacent to the end cover 212 and connected to the end cover 212. Figure 3 and Figure 4 In the embodiments shown in FIGS. 1 to 3, the wall portion 213 is the end cover 212. In other embodiments, the wall portion 213 is a bottom wall of the case 211 opposite to the end cover 212. In yet other embodiments, the wall portion 213 can also be a side wall of the case 211 adjacent to the end cover 212 and connected to the end cover 212.

[0138] The “base material of the wall portion 213 is iron” means that the material with the largest mass percentage in the material of the wall portion 213 is iron. For example, the material of the wall portion 213 can be carbon steel or stainless steel. The carbon steel can be low-carbon steel, medium-carbon steel, or high-carbon steel.

[0139] It should be noted that the material of the wall portion 213 includes at least one of stainless steel and carbon steel, and if the wall portion 213 is the end cover 212 of the housing 21, the material of the end cover 212 includes at least one of stainless steel and carbon steel; if the wall portion 213 is a wall of the case 211, the material of the case 211 includes at least one of stainless steel and carbon steel.

[0140] In the present embodiment, by setting the material of the wall portion 213 to include at least one of stainless steel and carbon steel, the wall portion 213 made of steel has better strength due to the high strength of steel, so that the wall portion 213 can be made thinner under the condition that the burst pressure of the battery cell 20 is constant, which is beneficial to saving the space occupied by the wall portion 213.

[0141] Optionally, the material of the wall portion 213 includes at least one of SUS304 stainless steel, SUS305 stainless steel, or SUS316L stainless steel.

[0142] In some embodiments, the base material of the housing 21 is iron.

[0143] The pressure relief mechanism 24 is a component for opening when the internal pressure or temperature of the battery cell 20 reaches a predetermined value, to release the internal pressure of the battery cell 20. The pressure relief mechanism 24 can be a component mounted on the wall portion 213, in which case the pressure relief mechanism 24 is provided separately from the wall portion 213 and connected thereto. For example, the pressure relief mechanism 24 is a rupture disc mounted on the wall portion 213. The pressure relief mechanism 24 can also be a part of the wall portion 213, in which case the pressure relief mechanism 24 is integrally formed with the wall portion 213. The wall of the housing 21 that is the wall portion 213 can be determined by the position at which the pressure relief mechanism 24 is provided. For example, when the pressure relief mechanism 24 is provided at the end cover 212, the end cover 212 is the wall portion 213. When the pressure relief mechanism 24 is provided at the bottom wall of the housing 211, the bottom wall is the wall portion 213. When the pressure relief mechanism 24 is provided at the side wall of the housing 211, the side wall is the wall portion 213.

[0144] The "base material of the pressure relief mechanism 24 is iron" means that the material with the largest mass percentage in the material of the pressure relief mechanism 24 is iron. For example, the material of the pressure relief mechanism 24 can be carbon steel or stainless steel.

[0145] The weakened portion 241 functions as a pressure relief mechanism for enabling the pressure relief mechanism 24 to split along at least a part of the weakened portion 241 when the internal pressure or temperature of the battery cell 20 reaches a predetermined value, to release the internal pressure of the battery cell 20. The strength of the pressure relief mechanism 24 at the position of the weakened portion 241 is lower than the strength of the pressure relief mechanism 24 at other positions, so that the weakened portion 241 can split under the internal pressure when the internal pressure or temperature of the battery cell 20 reaches a predetermined value, to release the internal pressure of the battery cell 20. For example, when the internal pressure of the battery cell 20 reaches an initiation pressure, the weakened portion 241 ruptures under the action of the discharge (gas, electrolyte, etc.) inside the battery cell 20, enabling the discharge inside the battery cell 20 to be smoothly released. The weakened portion 241 can have various shapes, such as a rectangular shape, a circular shape, an elliptical shape, a ring shape, a circular arc shape, a U shape, an H shape, etc. The thickness of the weakened portion 241 can be uniform or non-uniform.

[0146] N represents the number of layers of grains of the weakened portion 241. Please refer to Figure 8 , a metallographic section is made perpendicular to the extension direction of the weakened portion 241, the grain morphology is etched out, an arbitrary vertical line is drawn along the thickness direction of the weakened portion 241, the number of grains that the vertical line passes through is counted, and the maximum value of the number of grains that the vertical line passes through is taken as the number of layers of grains of the weakened portion 241. Please refer to Figure 8 , the vertical line is shown by a dotted line in the figure, and the number of layers of grains of the weakened portion 241 is 5, i.e. N = 5.

[0147] The number of layers of grains of the weakened portion 241 can be: N = 1, 2, 3, 4, 5.

[0148] In the case of the same thickness of the weak portion 241, the fewer the layers of grains of the weak portion 241, the larger the average grain size of the weak portion 241, the smaller the grain boundary area, and the smaller the interaction force between the grain boundaries, thereby reducing the tensile strength of the weak portion 241 and reducing the burst pressure. Therefore, in the case of the same burst pressure, by making the layers of grains of the weak portion 241 less than or equal to 5 layers, the thickness of the weak portion 241 can be set larger, so that the weak portion 241 is less likely to be cracked prematurely due to changes in pressure inside the battery monomer 20 or external impact when the battery monomer 20 is normally used, which is conducive to reducing the risk of the weak portion 241 being damaged prematurely and improving the service life of the battery monomer 20. The base material of the wall portion 213 and the pressure relief mechanism 24 is iron, which can reduce the thickness of the wall portion 213 and the pressure relief mechanism 24, thereby improving the energy density of the battery monomer 20. In addition, compared with the aluminum material explosion-proof valve in the prior art, the base material of the pressure relief mechanism 24 provided by the embodiment of the application is iron, and the thickness of the weak portion 241 is smaller. When manufacturing, a slight change in the thickness of the weak portion 241 will cause a great change in the burst pressure of the battery monomer 20. By making the layers of grains of the weak portion 241 less than or equal to 5 layers, the thickness of the weak portion 241 can be increased under the same burst pressure. The larger the thickness of the weak portion 241, the easier it is to manufacture, and the lower the precision requirement for the manufacturing equipment, which is conducive to improving the consistency of the burst pressure of the plurality of battery monomers 20.

[0149] Optionally, 1≤N≤3.

[0150] The layers of grains of the weak portion 241 can be N=1, 2, or 3.

[0151] In the case of the same burst pressure, by making the layers of grains of the weak portion 241 less than or equal to 3 layers, the thickness of the weak portion 241 can be set larger, so that the weak portion 241 is less likely to be cracked prematurely due to changes in pressure inside the battery monomer 20 or external impact when the battery monomer 20 is normally used, which is conducive to reducing the risk of the weak portion 241 being damaged prematurely and improving the service life of the battery monomer 20. In addition, the larger the thickness of the weak portion 241, the easier it is to manufacture, and the lower the precision requirement for the manufacturing equipment, which is conducive to improving the consistency of the burst pressure of the plurality of battery monomers 20.

[0152] In order to make the technical problems, technical solutions and beneficial effects solved by the embodiments of the present application clearer, the following will be further described in detail in combination with Comparative Examples 1-2 and Embodiments 1-4. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and not intended to be limiting on the present application and its applications. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application.

[0153] Embodiment 1

[0154] 1) Preparation of positive electrode sheet

[0155] LiNi 0.8 Co 0.1 Mn 0.1 O2, conductive agent Super P, and binder polyvinylidene fluoride (PVDF) in N-methyl pyrrolidone (NMP) to prepare a positive electrode slurry, wherein the solid content in the positive electrode slurry is 50wt%, and the mass ratio of LiNi 0.7 Co 0.1 Mn 0.1 O2, Super P, and PVDF in the solid components is 8:1:1. The positive electrode slurry is coated on the upper and lower surfaces of the current collector aluminum foil, dried at 85°C, and then cold-pressed, followed by edge cutting, sheet cutting, and striping, and then dried at 85°C under vacuum conditions for 4h to prepare a positive electrode sheet.

[0156] 2) Preparation of negative electrode sheet

[0157] Graphite, conductive agent Super P, thickening agent carboxymethyl cellulose (CMC), and adhesive styrene butadiene rubber (SBR) are uniformly mixed in deionized water to prepare a negative electrode slurry, wherein the solid content in the negative electrode slurry is 30wt%, and the mass ratio of graphite, silicon monoxide, Super P, CMC, and adhesive styrene butadiene rubber (SBR) in the solid components is 88:7:3:2. The negative electrode slurry is coated on the upper and lower surfaces of the current collector copper foil and dried at 85°C, and then cold-pressed, edge cut, sheet cut, and striped, and then dried at 120°C under vacuum conditions for 12h to prepare a negative electrode sheet.

[0158] 3) Preparation of electrolyte

[0159] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), the fully dried electrolyte salt LiPF6 was dissolved in a mixed solvent (the mixed solvent included ethylene carbonate (EC) and diethyl carbonate (DEC), and the ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a mass ratio of 50:50), and a liquid electrolyte with a concentration of 1 mol / L was obtained after uniform mixing.

[0160] 4) separator

[0161] A 16 μm polyethylene film was used as the separator.

[0162] 5) Preparation of the battery monomer 20

[0163] The positive electrode sheet, the separator, and the negative electrode sheet were stacked in order, with the separator between the positive and negative electrode sheets to separate the positive and negative electrodes, and the electrode assembly 23 was obtained by winding. The electrode assembly 23 was placed in the outer shell 21 made of 304 stainless steel, the electrolyte prepared above was injected into the dried outer shell 21, and the battery monomer 20 was prepared after encapsulation, standing, formation, shaping, capacity testing, etc. The pressure relief mechanism 24 was welded on the end cover 212 of the battery monomer 20, wherein the outer shell 21 of the battery monomer 20 of Example 1 was a cuboid structure, the shell body 211 of the outer shell 21 was an open structure at one end, the end cover 212 was fitted on the opening, the pressure relief hole 2131 was provided on the end cover 212, the pressure relief mechanism 24 was made of 304 stainless steel, and the pressure relief mechanism 24 was welded on the end cover 212 and covered the pressure relief hole 2131. The pressure relief mechanism 24 was provided with a pressure relief groove 245, the groove bottom wall of the pressure relief groove 245 formed the above-mentioned weak part 241, and the weak part 241 was annular. The thickness of the battery monomer 20 was 39 mm, the width was 203 mm, the shoulder height (the size of the outer shell 21 in the height direction) was 122.7 mm, and the capacity was 185 Ah.

[0164] The thickness H of the weak part 241 was obtained by tomography and then measured by software. Or after the sample was placed in transparent epoxy resin glue and cured, the cross section was cut and ground, and then the thickness H of the weak part 241 was measured by a metallographic microscope.

[0165] The preparation methods of the battery monomers 20 of Comparative Examples 1-2 and Examples 2-4 were the same as those of Example 1, except that the number of layers of the crystal grains of the weak part 241 was different, and the specific conditions are shown in Table 1.

[0166] The battery monomer 20 needed to be pretreated before testing: ① drilling a hole at the injection hole of the battery monomer 20; ② inserting a hose into the battery monomer 20 by 10 mm from the injection hole; ③ stirring the AB glue evenly by extruding it on a hardboard; ④ applying the mixed AB glue around the interface between the hose and the battery monomer 20 (Note: the bonding surface cannot have bubbles or dirt), and standing for 30 minutes.

[0167] During the explosion experiment, the two large faces of the battery monomer 20 are clamped by a steel clamp (the large face is the wall with the largest surface area of the outer surface of the shell 21, the pre-tightening force is 3000N, simulating the constraint state of the battery monomer 20 in a real module or battery pack; at the same time, the pressure relief mechanism 24 is filmed throughout the experiment, and the initiation position and opening action are observed. Before the experiment, the explosion pressure test system is connected to the battery monomer 20 through a hose; during the experiment, the explosion pressure test system inflates the battery monomer 20 at a rate of 0.03MPa / s, and the inflation pressure of the battery monomer 20 is detected in real time. When the inflation pressure decreases by more than 0.02MPa, the inflation is stopped. Generally, the inflation pressure curve shows an increasing trend, and when the inflation pressure reaches the initiation pressure of the battery monomer 20, it will suddenly drop to 0, and the device will automatically record and display the initiation pressure value.

[0168] Repeat the above action to record the initiation pressure of multiple samples of one embodiment, and calculate the standard deviation of the explosion pressure, which is the initiation pressure standard deviation of the embodiment.

[0169] The experimental results of Comparative Examples 1-2 and Examples 1-4 are shown in Table 1 below:

[0170] Table 1

[0171]

[0172] Please refer to Table 1, as shown in Comparative Examples 1-2 and Examples 1-4, when the thickness of the weak part 241 is the same, the fewer the number of grain layers of the weak part 241, the smaller the explosion pressure. For the above-mentioned Comparative Examples 1-2 and Examples 1-4, when the battery monomer 20 is used in engineering, there is a requirement for the upper and lower limits of the initiation pressure (1.5±0.2MPa). Therefore, under the same explosion pressure, by making the number of grain layers of the weak part 241 less than or equal to 5 layers, the thickness of the weak part 241 can be set larger, so that when the battery monomer 20 is normally used, the weak part 241 is less likely to be cracked prematurely due to changes in pressure inside the battery monomer 20 or external impact, which helps to reduce the risk of premature damage to the weak part 241 and improve the service life of the battery monomer 20. In addition, the thicker the weak part 241, the easier it is to manufacture, and the precision requirement of the manufacturing equipment is lower, which helps to improve the consistency of the explosion pressure of multiple battery monomers 20.

[0173] In some embodiments, the grain size grade of the weak part 241 is 6-10.

[0174] The scale representing the grain size is called the grain size, which is usually represented by the number of grains in a unit volume (or unit area) or the average linear length (or diameter) of the grains. The grain size grade is used in industrial production to represent the grain size. The smaller the grain size grade, the larger the grain size, and the larger the grain size grade, the smaller the grain size.

[0175] The measurement method of the grain size grade can be implemented according to the measurement principle in GB / T 36165-2018 and GB / T 6394-2017.

[0176] The grain size grade of the weak portion 241 can be grade 6, grade 7, grade 8, grade 9, or grade 10.

[0177] When the grain size grade of the weak portion 241 is less than or equal to grade 10, the grain size grade of the weak portion 241 is small, the average grain size of the weak portion 241 is large, the grain boundary area is small, and the interaction force between the grain boundaries is small, which can reduce the tensile strength of the weak portion 241, thereby reducing the burst pressure. Therefore, under the same burst pressure, by setting the grain size grade of the weak portion 241 to be less than or equal to grade 10, the thickness of the weak portion 241 can be set to be larger, so that when the battery monomer 20 is normally used, the weak portion 241 is not easy to be cracked in advance due to the change of the pressure inside the battery monomer 20 or the external impact, which is beneficial to reduce the risk of the weak portion 241 being damaged in advance and improve the service life of the battery monomer 20. When the grain size grade of the weak portion 241 is greater than or equal to grade 6, the grain size grade of the weak portion 241 is not too small, the average grain size of the weak portion 241 is not too large, and the weak portion 241 is not easy to be brittle, so that the weak portion 241 has good ductility and is easy to process and manufacture. Therefore, when the grain size grade of the weak portion 241 is grade 6 to grade 10, the weak portion 241 can be easily processed and manufactured, and the service life of the battery monomer 20 can be improved.

[0178] Optionally, the grain size grade of the weak portion 241 is grade 7 to grade 9.

[0179] The grain size grade of the weak portion 241 can be grade 7, grade 8, or grade 9.

[0180] When the grain size grade of the weak portion 241 is less than or equal to 9, the grain size grade of the weak portion 241 is smaller, the average grain size of the weak portion 241 is larger, the grain boundary area is smaller, and the interaction force between the grain boundaries is smaller, which can reduce the tensile strength of the weak portion 241 and thus reduce the burst pressure. Therefore, under the same burst pressure, by setting the grain size grade of the weak portion 241 to be less than or equal to 9, the thickness of the weak portion 241 can be set to be larger, so that the weak portion 241 is less likely to be cracked in advance due to the pressure change inside the battery monomer 20 or external impact when the battery monomer 20 is normally used, which is beneficial to reduce the risk of the weak portion 241 being damaged in advance and improve the service life of the battery monomer 20. When the grain size grade of the weak portion 241 is greater than or equal to 7, the grain size grade of the weak portion 241 is not too small, the average grain size of the weak portion 241 is not too large, and the weak portion 241 is less likely to be brittle, so that the weak portion 241 has good ductility and is easy to process and manufacture. Therefore, when the grain size grade of the weak portion 241 is 7-9, the weak portion 241 can be easily processed and manufactured, and the service life of the battery monomer 20 can be improved.

[0181] Please refer to Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 and Figure 8 In some embodiments, the pressure relief mechanism 24 includes a non-weak portion 242, the thickness of the non-weak portion 242 is greater than the thickness of the weak portion 241, and the non-weak portion 242 includes a pressure relief area 2421, and the weak portion 241 is arranged outside the pressure relief area 2421.

[0182] The pressure relief mechanism 24 includes the weak portion 241 and the non-weak portion 242, the strength of the weak portion 241 is lower than the strength of the non-weak portion 242, and the weak portion 241 is more easily damaged than the non-weak portion 242.

[0183] Please refer to Figure 6 and Figure 7 The thickness of the non-weak portion 242 is greater than the thickness of the weak portion 241, that is, the minimum thickness of the non-weak portion 242 is greater than the maximum thickness of the weak portion 241. In some embodiments, the pressure relief mechanism 24 is provided with a pressure relief groove 245, the groove bottom wall of the pressure relief groove 245 forms the above-mentioned weak portion 241, and the part of the pressure relief mechanism 24 which is not thinned by the pressure relief groove 245 forms the above-mentioned non-weak portion 242.

[0184] The pressure relief groove 245 can be formed by various methods, such as stamping, milling, laser etching, etc., to achieve integral forming of the weak portion 241 and the non-weak portion 242. The pressure relief groove 245 can be a one-stage groove, and the groove side surface of the pressure relief groove 245 is continuous along the depth direction of the pressure relief groove 245, such as a rectangular prism, a columnar body, etc. The pressure relief groove 245 can also be a multi-stage groove, and the multi-stage groove is arranged along the depth direction of the pressure relief groove 245. In adjacent two-stage grooves, the inner side (deeper position) one-stage groove is arranged on the groove bottom surface of the outer side (shallower position) one-stage groove, such as a stepped groove. When forming, the multi-stage groove can be formed by stamping step by step along the depth direction of the pressure relief groove 245, and the weak portion 241 is formed on the groove bottom wall of the one-stage groove at the deepest position (innermost side) in the multi-stage groove.

[0185] The non-weak portion 242 includes a pressure relief area 2421, and the weak portion 241 is arranged outside the pressure relief area 2421. When the battery monomer 20 is relieved, the weak portion 241 cracks along the edge of the pressure relief area 2421, so that the pressure relief area 2421 can open to relieve pressure. The weak portion 241 can be an annular structure, for example, the weak portion 241 can be a circular ring, an elliptical ring, etc. The pressure relief area 2421 is the area where the weak portion 241 is opened after being damaged by the gas inside the shell 21. In the case of the weak portion 241 being an annular structure, the pressure relief area 2421 is the area inside the annular structure. In the case of the weak portion 241 being a non-annular structure, the pressure relief area 2421 is the annular area inside the weak portion 241 and the connecting line between the two ends of the weak portion 241. When the battery monomer 20 is relieved, the pressure relief area 2421 cracks along the weak portion 241, thereby opening a larger opening to relieve pressure.

[0186] The thickness of the non-weak portion 242 is greater than the thickness of the weak portion 241, and the strength of the weak portion 241 is lower than the strength of the non-weak portion 242. When the pressure inside the battery monomer 20 reaches a threshold value, the pressure relief area 2421 can open along the weak portion 241 to form a larger opening, thereby relieving the pressure inside the battery monomer 20, which is beneficial to improve the timeliness of the pressure relief of the battery monomer 20 and improve the reliability of the battery monomer 20.

[0187] In some embodiments, the difference between the grain size grade of the pressure relief area 2421 and the grain size grade of the weak portion 241 is less than or equal to 3 levels.

[0188] The grain size grade of the weak portion 241 can be greater than the grain size grade of the pressure relief area 2421, so that the average grain size of the weak portion 241 is smaller than the average grain size of the pressure relief area 2421. On the one hand, the average grain size of the weak portion 241 is smaller, which is conducive to improving the strength of the weak portion 241, so that the strength of the weak portion 241 is higher, which is conducive to reducing the risk of the weak portion 241 being damaged under normal use conditions of the battery monomer 20, and effectively improving the service life of the battery monomer 20. On the other hand, compared with the case where the average grain size of the pressure relief area 2421 and the average grain size of the weak portion 241 are the same and other conditions are unchanged, the strength of the pressure relief area 2421 is lower, and the pressure relief area 2421 is more likely to deform when subjected to external force. Thus, the external force is better buffered, the influence of the external force on the weak portion 241 is reduced, and the service life and reliability of the battery monomer 20 are improved.

[0189] The grain size grade of the weak portion 241 can be greater than the grain size grade of the pressure relief area 2421, so that the average grain size of the weak portion 241 is smaller than the average grain size of the pressure relief area 2421. On the one hand, the average grain size of the weak portion 241 is smaller, which is conducive to improving the strength of the weak portion 241, so that the strength of the weak portion 241 is higher, which is conducive to reducing the risk of the weak portion 241 being damaged under normal use conditions of the battery monomer 20, and effectively improving the service life of the battery monomer 20. On the other hand, compared with the case where the average grain size of the pressure relief area 2421 and the average grain size of the weak portion 241 are the same and other conditions are unchanged, the strength of the pressure relief area 2421 is lower, and the pressure relief area 2421 is more likely to deform when subjected to external force. Thus, the external force is better buffered, the influence of the external force on the weak portion 241 is reduced, and the service life and reliability of the battery monomer 20 are improved.

[0190] When the difference between the grain size grade of the pressure relief area 2421 and the grain size grade of the weak portion 241 is less than or equal to 3 levels, the grain size grade of the pressure relief area 2421 and the grain size grade of the weak portion 241 are relatively close, the material consistency of the pressure relief mechanism 24 is good, and the consistency of the burst pressure of the plurality of battery monomers 20 is improved.

[0191] Optionally, the difference between the grain size grade of the pressure relief area 2421 and the grain size grade of the weak portion 241 is less than or equal to 2 levels.

[0192] When the difference between the grain size grade of the pressure relief area 2421 and the grain size grade of the weak portion 241 is less than or equal to 2 levels, the grain size grade of the pressure relief area 2421 and the grain size grade of the weak portion 241 are more close, the material consistency of the pressure relief mechanism 24 is better, and the consistency of the burst pressure of the plurality of battery monomers 20 is more improved.

[0193] Please refer to Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 and Figure 8 In some embodiments, the pressure relief mechanism 24 further includes a first transition portion 243, the first transition portion 243 connects the weak portion 241 and the pressure relief area 2421, and the thickness of the first transition portion 243 increases in the direction of the weak portion 241 pointing to the pressure relief area 2421. The difference between the grain size grade of the first transition portion 243 and the grain size grade of the weak portion 241 is less than or equal to 3 levels.

[0194] The first transition portion 243 is located between the weak portion 241 and the pressure relief area 2421, and connects the weak portion 241 and the pressure relief area 2421.

[0195] The thickness of the first transition portion 243 can gradually increase in a direction from the weak portion 241 to the pressure relief area 2421, or the thickness of the first transition portion 243 can first gradually increase, then remain unchanged, and then gradually increase in a direction from the weak portion 241 to the pressure relief area 2421.

[0196] In some embodiments, the pressure relief mechanism 24 is provided with a pressure relief groove 245. When the pressure relief groove 245 is a single-stage groove, the groove bottom wall of the pressure relief groove 245 forms the weak portion 241, and the groove side wall of the pressure relief groove 245 located between the weak portion 241 and the pressure relief area 2421 forms the first transition portion 243. When the pressure relief mechanism 24 is a multi-stage groove, the weak portion 241 is formed on the groove bottom wall of the single-stage groove located at the deepest position (the innermost side) in the multi-stage groove, and the groove side wall of the single-stage groove located at the deepest position (the innermost side) and the groove bottom wall and the groove side wall of the other single-stage grooves together form the first transition portion 243.

[0197] The grain size grade of the weak portion 241 can be greater than or equal to the grain size grade of the first transition portion 243. In this way, the average grain size of the weak portion 241 is less than or equal to the average grain size of the first transition portion 243, and the average grain size of the weak portion 241 is small, which is beneficial to improve the strength of the weak portion 241, so that the strength of the weak portion 241 is high, which is beneficial to reduce the risk of damage of the weak portion 241 under normal use conditions of the battery monomer 20, and effectively improve the service life of the battery monomer 20.

[0198] The grain size grade of the weak portion 241 can be 0, 1, 2, or 3 greater than the grain size grade of the first transition portion.

[0199] By setting the first transition portion 243, the thickness of the first transition portion 243 gradually increases in a direction from the weak portion 241 to the pressure relief area 2421, the weak portion 241 can gradually transition to the pressure relief area 2421, the grain size grade of the first transition portion 243 gradually changes in a direction from the weak portion 241 to the pressure relief area 2421, the grain size does not easily change abruptly, which is beneficial to reduce stress concentration, so that the burst pressures of the plurality of battery monomers 20 manufactured are more consistent. In addition, when the difference between the grain size grade of the first transition portion 243 and the grain size grade of the weak portion 241 is less than or equal to 3, the grain size grade of the first transition portion 243 and the grain size grade of the weak portion 241 are relatively close, the material consistency of the pressure relief mechanism 24 is good, and the consistency of the burst pressures of the plurality of battery monomers 20 is improved.

[0200] Optionally, the difference between the grain size grade of the first transition portion 243 and the grain size grade of the weak portion 241 is less than or equal to 2 grades.

[0201] The grain size grade of the weak portion 241 can be 0, 1 or 2 grades larger than the grain size grade of the first transition zone.

[0202] When the difference between the grain size grade of the first transition portion 243 and the grain size grade of the weak portion 241 is less than or equal to 2 grades, the grain size grade of the first transition portion 243 and the grain size grade of the weak portion 241 are closer, and the material consistency of the pressure relief mechanism 24 is better, which is more conducive to improving the consistency of the burst pressure of the plurality of battery monomers 20.

[0203] Please refer to Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 and Figure 8 In some embodiments, the non-weak portion 242 further comprises a connecting zone 2422, the connecting zone 2422 is located outside the weak portion 241, the connecting zone 2422 comprises a first part 24221 and a second part 24222, the first part 24221 is welded with the wall portion 213 to form a weld mark, and the second part 24222 connects the weak portion 241 and the first part 24221. The difference between the grain size grade of the second part 24222 and the grain size grade of the weak portion 241 is less than or equal to 3 grades.

[0204] The connecting zone 2422 is located outside the weak portion 241, in the case that the weak portion 241 is a ring structure, the connecting zone 2422 is the part of the pressure relief mechanism 24 located outside the ring structure, and in the case that the weak portion 241 is a non-ring structure, the connecting zone 2422 is the part of the pressure relief mechanism 24 located outside the ring formed by the weak portion 241 itself and the line between the two ends of the weak portion 241.

[0205] The first part 24221 is the part of the connecting zone 2422 that is welded with the wall portion 213 and forms a weld mark, in other words, the first part 24221 is the weld mark part on the connecting zone 2422. The second part 24222 is located between the first part 24221 and the weak portion 241, and the second part 24222 connects the first part 24221 and the weak portion 241.

[0206] The grain size grade of the weak portion 241 can be greater than the grain size grade of the second portion 24222, so that the average grain size of the weak portion 241 is smaller than the average grain size of the second portion 24222. On the one hand, the average grain size of the weak portion 241 is smaller, which is conducive to improving the strength of the weak portion 241, so that the strength of the weak portion 241 is higher, which is conducive to reducing the risk of the weak portion 241 being damaged under normal use conditions of the battery monomer 20, and effectively improving the service life of the battery monomer 20. On the other hand, compared with the case where the average grain size of the second portion 24222 and the average grain size of the weak portion 241 are the same and other conditions are unchanged, the strength of the second portion 24222 is lower, and the second portion 24222 is more likely to deform when subjected to external force, thereby better buffering the external force and reducing the influence of the external force on the weak portion 241, which is conducive to improving the service life and reliability of the battery monomer 20.

[0207] The grain size grade of the weak portion 241 can be greater than the grain size grade of the second portion 24222, so that the average grain size of the weak portion 241 is smaller than the average grain size of the second portion 24222. On the one hand, the average grain size of the weak portion 241 is smaller, which is conducive to improving the strength of the weak portion 241, so that the strength of the weak portion 241 is higher, which is conducive to reducing the risk of the weak portion 241 being damaged under normal use conditions of the battery monomer 20, and effectively improving the service life of the battery monomer 20. On the other hand, compared with the case where the average grain size of the second portion 24222 and the average grain size of the weak portion 241 are the same and other conditions are unchanged, the strength of the second portion 24222 is lower, and the second portion 24222 is more likely to deform when subjected to external force, thereby better buffering the external force and reducing the influence of the external force on the weak portion 241, which is conducive to improving the service life and reliability of the battery monomer 20.

[0208] By providing the connecting area 2422, the connection with the wall portion 213 is facilitated. When the difference between the grain size grade of the second portion 24222 and the grain size grade of the weak portion 241 is less than or equal to 3 levels, the grain size grade of the second portion 24222 and the grain size grade of the weak portion 241 are relatively close, the material consistency of the pressure relief mechanism 24 is good, and the consistency of the burst pressure of the plurality of battery monomers 20 is improved.

[0209] Optionally, the difference between the grain size grade of the second portion 24222 and the grain size grade of the weak portion 241 is less than or equal to 2 levels.

[0210] When the difference between the grain size grade of the second portion 24222 and the grain size grade of the weak portion 241 is less than or equal to 2 levels, the grain size grade of the second portion 24222 and the grain size grade of the weak portion 241 are more close, the material consistency of the pressure relief mechanism 24 is better, and the consistency of the burst pressure of the plurality of battery monomers 20 is more improved.

[0211] In other embodiments, the non-weak portion 242 further includes a connecting area 2422, the connecting area 2422 is arranged outside the weak portion 241, and the connecting area 2422 is integrally formed with the wall portion 213. The difference between the grain size grade of the connecting area 2422 and the grain size grade of the weak portion 241 is less than or equal to 3 levels.

[0212] When the connecting area 2422 is integrally formed with the wall portion 213, the wall portion 213 is the pressure relief mechanism 24. For example, when the connecting area 2422 is integrally formed with the wall portion 213, and the end cover 212 is the wall portion 213, the end cover 212 is the pressure relief mechanism 24.

[0213] The grain size grade of the weak portion 241 can be greater than the grain size grade of the connecting region 2422, so that the average grain size of the weak portion 241 is smaller than the average grain size of the connecting region 2422. On the one hand, the average grain size of the weak portion 241 is smaller, which is conducive to improving the strength of the weak portion 241, so that the strength of the weak portion 241 is higher, which is conducive to reducing the risk of the weak portion 241 being damaged under normal use conditions of the battery monomer 20, and effectively improving the service life of the battery monomer 20. On the other hand, compared with the case where the average grain size of the connecting region 2422 and the average grain size of the weak portion 241 are the same and other conditions are unchanged, the strength of the connecting region 2422 is lower, and the connecting region 2422 is more likely to deform when subjected to external force, thereby better buffering the external force and reducing the influence of the external force on the weak portion 241, which is conducive to improving the service life and reliability of the battery monomer 20.

[0214] The grain size grade of the weak portion 241 can be greater than the grain size grade of the connecting region 2422, so that the average grain size of the weak portion 241 is smaller than the average grain size of the connecting region 2422. On the one hand, the average grain size of the weak portion 241 is smaller, which is conducive to improving the strength of the weak portion 241, so that the strength of the weak portion 241 is higher, which is conducive to reducing the risk of the weak portion 241 being damaged under normal use conditions of the battery monomer 20, and effectively improving the service life of the battery monomer 20. On the other hand, compared with the case where the average grain size of the connecting region 2422 and the average grain size of the weak portion 241 are the same and other conditions are unchanged, the strength of the connecting region 2422 is lower, and the connecting region 2422 is more likely to deform when subjected to external force, thereby better buffering the external force and reducing the influence of the external force on the weak portion 241, which is conducive to improving the service life and reliability of the battery monomer 20.

[0215] By arranging the connecting region 2422, the connection with the wall portion 213 is facilitated. When the difference between the grain size grade of the connecting region 2422 and the grain size grade of the weak portion 241 is less than or equal to 3 levels, the grain size grade of the connecting region 2422 and the grain size grade of the weak portion 241 are relatively close, the material consistency of the pressure relief mechanism 24 is good, and the consistency of the burst pressure of the plurality of battery monomers 20 is improved.

[0216] Optionally, the difference between the grain size grade of the connecting region 2422 and the grain size grade of the weak portion 241 is less than or equal to 2 levels.

[0217] When the difference between the grain size grade of the connecting region 2422 and the grain size grade of the weak portion 241 is less than or equal to 2 levels, the grain size grade of the connecting region 2422 and the grain size grade of the weak portion 241 are more close, the material consistency of the pressure relief mechanism 24 is better, and the consistency of the burst pressure of the plurality of battery monomers 20 is more improved.

[0218] Please refer to Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 and Figure 8 In some embodiments, the pressure relief mechanism 24 further comprises a second transition portion 244, the second transition portion 244 connects the weak portion 241 and the connecting region 2422, and the thickness of the second transition portion 244 increases in the direction of the weak portion 241 pointing to the connecting region 2422. The difference between the grain size grade of the second transition portion 244 and the grain size grade of the weak portion 241 is less than or equal to 3 levels.

[0219] The second transition portion 244 is located between the weak portion 241 and the connecting area 2422, and connects the weak portion 241 and the connecting area 2422.

[0220] The thickness of the second transition portion 244 can gradually increase in a direction from the weak portion 241 to the connecting area 2422, or the thickness of the second transition portion 244 can first gradually increase, then remain unchanged, and then gradually increase in a direction from the weak portion 241 to the connecting area 2422.

[0221] In some embodiments, the pressure relief mechanism 24 is provided with a pressure relief groove 245. When the pressure relief groove 245 is a single-stage groove, the groove bottom wall of the pressure relief groove 245 forms the weak portion 241, and the groove side wall of the pressure relief groove 245 located between the weak portion 241 and the connecting area 2422 forms the second transition portion 244. When the pressure relief mechanism 24 is a multi-stage groove, the weak portion 241 is formed on the groove bottom wall of the single-stage groove located at the deepest position (the innermost side) in the multi-stage groove, and the groove side wall of the single-stage groove located at the deepest position (the innermost side) and the groove bottom wall and the groove side wall of the other stages of the pressure relief groove 245 together form the second transition portion 244.

[0222] The grain size grade of the weak portion 241 can be greater than or equal to the grain size grade of the second transition portion 244. In this way, the average grain size of the weak portion 241 is less than or equal to the average grain size of the second transition portion 244, and the average grain size of the weak portion 241 is smaller, which is conducive to improving the strength of the weak portion 241, so that the strength of the weak portion 241 is higher, which is conducive to reducing the risk of damage to the weak portion 241 under normal use conditions of the battery monomer 20, and effectively improving the service life of the battery monomer 20.

[0223] The grain size grade of the weak portion 241 can be 0, 1, 2, or 3 greater than the grain size grade of the second transition area.

[0224] By providing the second transition portion 244, the thickness of the second transition portion 244 gradually increases in a direction from the weak portion 241 to the connecting area 2422, the weak portion 241 can gradually transition to the connecting area 2422, the grain size grade of the second transition portion 244 gradually changes in a direction from the weak portion 241 to the connecting area 2422, the grain size does not easily change abruptly, which is conducive to reducing stress concentration, so that the burst pressures of the plurality of battery monomers 20 manufactured are more consistent. In addition, when the difference between the grain size grade of the second transition portion 244 and the grain size grade of the weak portion 241 is less than or equal to 3, the grain size grade of the second transition portion 244 and the grain size grade of the weak portion 241 are relatively close, the material consistency of the pressure relief mechanism 24 is good, and the consistency of the burst pressures of the plurality of battery monomers 20 is improved.

[0225] Optionally, the difference between the grain size grade of the second transition portion 244 and the grain size grade of the weak portion 241 is less than or equal to 2 grades.

[0226] The grain size grade of the weak portion 241 can be 0, 1, or 2 grades larger than the grain size grade of the second transition zone.

[0227] When the difference between the grain size grade of the second transition portion 244 and the grain size grade of the weak portion 241 is less than or equal to 2 grades, the grain size grade of the second transition portion 244 and the grain size grade of the weak portion 241 are closer, the material consistency of the pressure relief mechanism 24 is better, and it is more conducive to improving the consistency of the burst pressure of the plurality of battery monomers 20.

[0228] In some embodiments, the hardness of the non-weak portion 242 is A, which satisfies: 145HV≤A≤185HV.

[0229] A represents the hardness of the non-weak portion 242. The hardness of the non-weak portion 242 is Vickers hardness. Vickers hardness refers to that a diamond right pyramid indenter with an included angle of 136 degrees between opposite faces is pressed into the surface of the test sample under a specified load, and after a certain time, the load is removed, the diagonal line length of the indentation is measured, and then the indentation surface area is calculated, and finally the average pressure on the indentation surface area is obtained, which is the Vickers hardness value of the metal, denoted by HV. In actual measurement, it is not necessary to calculate, but according to the measured indentation diagonal line length, the measured hardness value can be directly obtained by table lookup.

[0230] 145HV≤A≤185HV, that is, the Vickers hardness of the non-weak portion 242 is 145-185.

[0231] The hardness of the non-weak portion 242 can be: A=145HV, 150HV, 155HV, 160HV, 165HV, 170HV, 175HV, 180HV, 185HV, etc.

[0232] When A≤185HV, the hardness of the non-weak portion 242 is smaller, so that the non-weak portion 242 is softer and is easier to deform under the internal pressure of the battery cell 20, thereby facilitating the pulling of the weak portion 241, so that the weak portion 241 is torn when the internal pressure of the battery cell 20 reaches the threshold value, which is conducive to improving the consistency of the burst pressure of the plurality of battery cells 20. When A≥145HV, the hardness of the non-weak portion 242 is not too small, and accordingly, the strength of the non-weak portion 242 is not too low, so that the non-weak portion 242 is not easily damaged under external force, which is conducive to improving the service life and reliability of the battery cell 20. Therefore, when 145HV≤A≤185HV, both the consistency of the burst pressure of the plurality of battery cells 20 and the service life and reliability of the battery cell 20 are improved.

[0233] Optionally, 150HV≤A≤170HV.

[0234] The hardness of the non-weak portion 242 can be: A2=150HV, 152HV, 155HV, 158HV, 160HV, 162HV, 165HV, 168HV, 170HV, etc.

[0235] When A≤170HV, the hardness of the non-weak portion 242 is smaller, so that the non-weak portion 242 is softer and is easier to deform under the internal pressure of the battery cell 20, thereby facilitating the pulling of the weak portion 241, so that the weak portion 241 is torn when the internal pressure of the battery cell 20 reaches the threshold value, which is conducive to improving the consistency of the burst pressure of the plurality of battery cells 20. When A≥150HV, the hardness of the non-weak portion 242 is not too small, and accordingly, the strength of the non-weak portion 242 is not too low, so that the non-weak portion 242 is not easily damaged under external force, which is conducive to improving the service life and reliability of the battery cell 20. Therefore, when 150HV≤A≤170HV, both the consistency of the burst pressure of the plurality of battery cells 20 and the service life and reliability of the battery cell 20 are improved.

[0236] Please refer to Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 and Figure 8 In some embodiments, the pressure relief area 2421 is at least partially raised in a direction away from the electrode assembly 23.

[0237] The pressure relief area 2421 is partially or entirely raised in a direction away from the electrode assembly 23, forming a raised structure. The raised structure is a structure in which both the inner surface and the outer surface are arched in a direction away from the electrode assembly 23.

[0238] The existing pressure relief mechanism 24 is gradually bulged away from the electrode assembly 23 under the action of the internal pressure of the battery monomer 20 when the pressure relief, and then opens the pressure relief under the action of the internal pressure of the battery monomer 20. In the embodiment of the present application, the pressure relief area 2421 of the pressure relief mechanism 24 is at least partially bulged away from the electrode assembly 23, and the pressure relief area 2421 forms a pre-deformation on the inner side of the weak part 241, so as to facilitate the weak part 241 to crack and release pressure. In this way, under the same burst pressure, the thickness of the weak part 241 can be larger, and the weak part 241 is not easy to crack in advance due to the change of the internal pressure of the battery monomer 20 or external impact when the battery monomer 20 is normally used, which is beneficial to reduce the risk of the weak part 241 being damaged in advance and is beneficial to improve the service life of the battery monomer 20.

[0239] Please refer to Figure 3 、 Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 In some embodiments, the non-weak part 242 further comprises a connecting area 2422, the connecting area 2422 is surrounded on the outer side of the weak part 241, and the connecting area 2422 is integrally formed with the wall part 213 or is separately arranged and connected. The connecting area 2422 is at least partially bulged in the direction close to the electrode assembly 23, and the weak part 241 is connected to the part of the connecting area 2422 closest to the electrode assembly 23.

[0240] The connecting area 2422 can be partially bulged in the direction close to the electrode assembly 23, and the connecting area 2422 can be entirely bulged in the direction close to the electrode assembly 23. The weak part 241 is connected to the part of the connecting area 2422 closest to the electrode assembly 23.

[0241] The connection region 2422 is at least partially raised in a direction close to the electrode assembly 23, and the pressure relief region 2421 is raised in a direction away from the electrode assembly 23. The raising direction of the connection region 2422 is opposite to the raising direction of the pressure relief region 2421, so that the pressure relief region 2421 can be raised by the raising height of the connection region 2422, thereby facilitating reduction of the height of the pressure relief region 2421 beyond the surface of the connection region 2422 farthest away from the electrode assembly 23, reduction of the occupation of the battery cell 20 or the internal space of the battery, and improvement of the energy density of the battery cell 20 or the battery. In addition, since the weak portion 241 is connected to the part of the connection region 2422 closest to the electrode assembly 23, that is, the position of the weak portion 241 is closer to the electrode assembly 23 than the position of the connection of the connection region 2422 to the wall portion 213, and since one end of the connection region 2422 is constrained by the wall portion 213, the part of the connection region 2422 raised in the direction close to the electrode assembly 23 extrudes the weak portion 241 under the action of the gas pressure, thereby inhibiting the cracking of the weak portion 241 and preventing the creep failure of the weak portion 241 during the normal operation of the battery cell 20, effectively prolonging the service life of the battery cell 20.

[0242] Please refer to Figure 3 、 Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 In some embodiments, the thickness of the weak portion 241 is H, which satisfies: 0.01mm≤H≤0.1mm.

[0243] H represents the thickness of the weak portion 241. Along the extension direction of the weak portion 241, the thickness of the weak portion 241 at different positions can be uniform or variable. When the thickness of the weak portion 241 at different positions along the extension direction of the weak portion 241 is uniform, the thickness at different positions can be measured multiple times and the average value is taken as H. When the thickness of the weak portion 241 at different positions along the extension direction of the weak portion 241 is variable, the maximum thickness of the weak portion 241 is less than or equal to 0.1mm, and the minimum thickness of the weak portion 241 is greater than or equal to 0.1mm.

[0244] The thickness of the weak portion 241 can be: H=0.01mm, 0.02mm, 0.03mm, 0.04mm, 0.05mm, 0.06mm, 0.07mm, 0.08mm, 0.09mm, 0.1mm, etc.

[0245] When H is greater than or equal to 0.01 mm, the thickness of the weakened portion 241 is relatively large, and the weakened portion 241 is less likely to be cracked in advance due to changes in the internal pressure of the battery monomer 20 or external impact, which is conducive to reducing the risk of the weakened portion 241 being damaged in advance and improving the service life of the battery monomer 20. When H is less than or equal to 0.1 mm, the thickness of the weakened portion 241 is not too large, so that the pressure relief mechanism 24 can be opened in time when the battery monomer 20 is in thermal runaway, which is conducive to improving the timeliness of pressure relief of the pressure relief mechanism 24. Therefore, when 0.01 mm≤H≤0.1 mm, the service life and timeliness of pressure relief of the battery monomer 20 can be considered.

[0246] Optionally, 0.015 mm≤H≤0.06 mm.

[0247] The thickness of the weakened portion 241 can be: H=0.015 mm, 0.02 mm, 0.025 mm, 0.03 mm, 0.035 mm, 0.04 mm, 0.045 mm, 0.05 mm, 0.55 mm, 0.06 mm, etc.

[0248] When H is greater than or equal to 0.015 mm, the thickness of the weakened portion 241 is relatively large, and the weakened portion 241 is less likely to be cracked in advance due to changes in the internal pressure of the battery monomer 20 or external impact, which is conducive to reducing the risk of the weakened portion 241 being damaged in advance and improving the service life of the battery monomer 20. When H is less than or equal to 0.06 mm, the thickness of the weakened portion 241 is not too large, so that the pressure relief mechanism 24 can be opened in time when the battery monomer 20 is in thermal runaway, which is conducive to improving the timeliness of pressure relief of the pressure relief mechanism 24. Therefore, when 0.015 mm≤H≤0.06 mm, the service life and timeliness of pressure relief of the battery monomer 20 can be considered.

[0249] In some embodiments, the material of the pressure relief mechanism 24 includes at least one of stainless steel and carbon steel.

[0250] The material of the pressure relief mechanism 24 can be carbon steel or stainless steel, etc. The carbon steel can be low-carbon steel, medium-carbon steel or high-carbon steel. For example, the material of the pressure relief mechanism 24 can be: 304 stainless steel, 305 stainless steel, 316 stainless steel, etc.

[0251] Stainless steel and carbon steel have high strength, which can effectively improve the structural strength of the weakened portion 241, reduce the risk of the weakened portion 241 being cracked by external force, reduce the risk of the weakened portion 241 being damaged in advance, and improve the service life and reliability of the battery monomer 20.

[0252] Optionally, the material of the pressure relief mechanism 24 includes at least one of SUS304 stainless steel, SUS305 stainless steel or SUS316L stainless steel.

[0253] 304 stainless steel, 305 stainless steel and 316 stainless steel have the advantages of corrosion resistance, high temperature resistance and good processability. The pressure relief mechanism 24 made of 304 stainless steel, 305 stainless steel or 316 stainless steel has high strength, which can effectively improve the structural strength of the weak part 241, reduce the risk of the weak part 241 being cracked under external force, reduce the risk of the weak part 241 being damaged in advance, improve the service life and reliability of the battery monomer 20, and improve the consistency of the burst pressure of the plurality of battery monomers 20.

[0254] Please refer to Figure 3 、 Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 and Figure 8 In some embodiments, the pressure relief mechanism 24 is provided separately from the wall part 213, the wall part 213 is provided with a pressure relief hole 2131, and the pressure relief mechanism 24 is installed on the wall part 213 and covers the pressure relief hole 2131.

[0255] “the pressure relief mechanism 24 is provided separately from the wall part 213, the wall part 213 is provided with a pressure relief hole 2131, and the pressure relief mechanism 24 is installed on the wall part 213 and covers the pressure relief hole 2131” means that the pressure relief hole 2131 is formed on the wall part 213 during manufacturing, and the pressure relief mechanism 24 and the wall part 213 are provided separately and finally connected together. For example, the pressure relief mechanism 24 can be welded to the wall part 213. The pressure relief mechanism 24 can be a rupture disc installed on the wall part 213.

[0256] In some embodiments, the pressure relief mechanism 24 is arranged at one end of the pressure relief hole 2131 facing the electrode assembly 23. The battery monomer 20 comprises a protective member 26 arranged at one end of the pressure relief hole 2131 away from the electrode assembly 23 and covering the pressure relief hole 2131.

[0257] By providing the pressure relief mechanism 24 separately from the wall part 213 and installing it on the wall part 213, the manufacturing process is facilitated.

[0258] In some embodiments, the pressure relief mechanism 24 is welded to the wall part 213.

[0259] The base materials of the pressure relief mechanism 24 and the wall part 213 are both iron, and the pressure relief mechanism 24 and the wall part 213 are easier to weld, which helps to reduce the phenomenon of welding cracks in the pressure relief mechanism 24 and the wall part 213, thereby reducing the risk of liquid leakage of the battery monomer 20 and improving the reliability of the battery monomer 20.

[0260] In other embodiments, the pressure relief mechanism 24 is integrally formed with the wall part 213.

[0261] The integral molding refers to that the wall portion 213 and the pressure relief mechanism 24 are provided in an integral structure. For example, the pressure relief mechanism 24 can be formed on the wall portion 213 by punching or cold heading.

[0262] The integral molding of the pressure relief mechanism 24 and the wall portion 213 eliminates the need for additional welding or bonding processes, which is conducive to reducing the risk of liquid leakage of the pressure relief mechanism 24. Moreover, in production, it is easy to make the burst pressures of the processed plurality of battery monomers 20 consistent.

[0263] Please refer to Figures 3 to 8 、 ​ 、 ​ 、 ​ 、 ​ and ​ In some embodiments, the shell 21 includes a housing 211 and an end cover 212, one end of the housing 211 has an opening, and the end cover 212 closes the opening, and the end cover 212 is the wall portion 213.

[0264] The shell 21 can include a housing 211 and an end cover 212, the inside of the housing 211 forms an accommodation space with an opening, the accommodation space is used to accommodate the electrode assembly 23, and the end cover 212 closes the opening, and the end cover 212 is the wall portion 213.

[0265] It should be noted that the structure of the battery monomer 20 can also be various. In some embodiments, the shell 21 can include a housing 211 and two end covers 212, the inside of the housing 211 forms an accommodation space, the accommodation space is used to accommodate the electrode assembly 23, both ends of the housing 211 form openings, both openings communicate with the accommodation space, and the two end covers 212 respectively close the two openings, and one of the two end covers 212 is the wall portion 213.

[0266] Both ends of the housing 211 of the shell 21 are provided with openings, and the two end covers 212 respectively close the two openings, and the wall portion 213 is one of the two end covers 212. The battery monomer 20 with such a structure facilitates the assembly of the battery monomer 20 from both ends of the housing 211, which is conducive to reducing the manufacturing and assembly difficulty of the battery monomer 20.

[0267] When the end cover 212 is the wall portion 213, the pressure relief mechanism 24 is arranged on the end cover 212, which is simple and convenient to manufacture.

[0268] The embodiments of the present application also provide a battery device 100, which includes the above-mentioned battery monomer 20.

[0269] The embodiments of the present application also provide a power consumption device, which includes the above-mentioned battery monomer 20, and the battery monomer 20 is used to provide electric energy for the power consumption device.

[0270] According to some embodiments of the present application, please refer to ​ .

[0271] The battery cell 20 provided by the embodiments of the present application includes an outer shell 21, an electrode assembly 23 and a pressure relief mechanism 24. The outer shell 21 has a wall portion 213, the base material of the wall portion 213 is iron, the electrode assembly 23 is contained in the outer shell 21, and the pressure relief mechanism 24 is arranged on the wall portion 213. The base material of the pressure relief mechanism 24 is iron. The pressure relief mechanism 24 includes a weak portion 241 configured to be at least partially destroyed to release pressure when the pressure inside the outer shell 21 reaches a threshold value. The weak portion 241 has a number of grain layers N, and 1≤N≤5 is satisfied. In the case of the same thickness of the weak portion 241, the fewer the number of grain layers of the weak portion 241, the larger the average grain size of the weak portion 241, the smaller the grain boundary area, and the smaller the interaction force between the grain boundaries, thereby reducing the tensile strength of the weak portion 241 and reducing the burst pressure. Therefore, under the condition of the same burst pressure, by setting the number of grain layers of the weak portion 241 to be less than or equal to 5 layers, the thickness of the weak portion 241 can be set to be larger, so that the weak portion 241 is not easily cracked in advance due to the change of the pressure inside the battery cell 20 or the external impact when the battery cell 20 is normally used, which is beneficial to reduce the risk of the weak portion 241 being damaged in advance and improve the service life of the battery cell 20. The base materials of the wall portion 213 and the pressure relief mechanism 24 are both iron, which can reduce the thickness of the wall portion 213 and the pressure relief mechanism 24, thereby improving the energy density of the battery cell 20. In addition, compared with the aluminum material explosion-proof valve in the prior art, the base material of the pressure relief mechanism 24 provided by the embodiments of the present application is iron, and the thickness of the weak portion 241 is smaller. When manufacturing, a slight change in the thickness of the weak portion 241 will cause a great change in the burst pressure of the battery cell 20. By setting the number of grain layers of the weak portion 241 to be less than or equal to 5 layers, the thickness of the weak portion 241 can be increased under the condition of the same burst pressure. The larger the thickness of the weak portion 241, the easier it is to manufacture, and the lower the precision requirement of the manufacturing equipment, which is beneficial to improve the consistency of the burst pressures of a plurality of battery cells 20.

[0272] Optionally, 1≤N≤3. Under the condition of the same burst pressure, by setting the number of grain layers of the weak portion 241 to be less than or equal to 3 layers, the thickness of the weak portion 241 can be set to be larger, so that the weak portion 241 is not easily cracked in advance due to the change of the pressure inside the battery cell 20 or the external impact when the battery cell 20 is normally used, which is beneficial to reduce the risk of the weak portion 241 being damaged in advance and improve the service life of the battery cell 20. In addition, the larger the thickness of the weak portion 241, the easier it is to manufacture, and the lower the precision requirement of the manufacturing equipment, which is beneficial to improve the consistency of the burst pressures of a plurality of battery cells 20.

[0273] The grain size grade of the weak portion 241 is 7-9. When the grain size grade of the weak portion 241 is less than or equal to 9, the grain size grade of the weak portion 241 is smaller, the average grain size of the weak portion 241 is larger, the grain boundary area is smaller, and the interaction force between the grain boundaries is smaller, which can reduce the tensile strength of the weak portion 241 and thus reduce the burst pressure. Therefore, under the same burst pressure, by setting the grain size grade of the weak portion 241 to be less than or equal to 9, the thickness of the weak portion 241 can be set to be larger, so that the weak portion 241 is less likely to be cracked in advance due to the pressure change inside the battery monomer 20 or external impact when the battery monomer 20 is normally used, which is conducive to reducing the risk of the weak portion 241 being damaged in advance and improving the service life of the battery monomer 20. When the grain size grade of the weak portion 241 is greater than or equal to 7, the grain size grade of the weak portion 241 is not too small, the average grain size of the weak portion 241 is not too large, and the weak portion 241 is less likely to be brittle, so that the weak portion 241 has good ductility and is easy to process and manufacture. Therefore, when the grain size grade of the weak portion 241 is 7-9, the weak portion 241 can be easily processed and manufactured, and the service life of the battery monomer 20 can be improved.

[0274] The pressure relief mechanism 24 includes a non-weak portion 242, the thickness of the non-weak portion 242 is greater than the thickness of the weak portion 241, the non-weak portion 242 includes a pressure relief area 2421, and the weak portion 241 is arranged outside the pressure relief area 2421. The difference between the grain size grade of the pressure relief area 2421 and the grain size grade of the weak portion 241 is less than or equal to 2. When the difference between the grain size grade of the pressure relief area 2421 and the grain size grade of the weak portion 241 is less than or equal to 2, the grain size grade of the pressure relief area 2421 and the grain size grade of the weak portion 241 are closer, and the material consistency of the pressure relief mechanism 24 is better, which is more conducive to improving the consistency of the burst pressure of the plurality of battery monomers 20.

[0275] The pressure relief mechanism 24 further comprises a first transition portion 243 connecting the weak portion 241 and the pressure relief area 2421, the thickness of the first transition portion 243 has a trend of increasing in the direction from the weak portion 241 to the pressure relief area 2421, and the difference between the grain size grade of the first transition portion 243 and the grain size grade of the weak portion 241 is less than or equal to 2 levels. By arranging the first transition portion 243, the thickness of the first transition portion 243 has a trend of increasing in the direction from the weak portion 241 to the pressure relief area 2421, the weak portion 241 can gradually transition to the pressure relief area 2421, the grain size grade of the first transition portion 243 gradually changes in the direction from the weak portion 241 to the pressure relief area 2421, the grain size does not easily change abruptly, which is conducive to reducing stress concentration and making the burst pressures of the plurality of battery monomers 20 more consistent. In addition, when the difference between the grain size grade of the first transition portion 243 and the grain size grade of the weak portion 241 is less than or equal to 2 levels, the grain size grade of the first transition portion 243 and the grain size grade of the weak portion 241 are relatively close, the material consistency of the pressure relief mechanism 24 is good, and the consistency of the burst pressures of the plurality of battery monomers 20 is improved.

[0276] In some embodiments, the non-weak portion 242 further comprises a connecting area 2422 surrounding the outside of the weak portion 241, the connecting area 2422 comprises a first part 24221 and a second part 24222, the first part 24221 is welded with the wall portion 213 to form a welding mark, and the second part 24222 connects the weak portion 241 and the first part 24221. The difference between the grain size grade of the second part 24222 and the grain size grade of the weak portion 241 is less than or equal to 3 levels. By arranging the connecting area 2422, the connection with the wall portion 213 is facilitated. When the difference between the grain size grade of the second part 24222 and the grain size grade of the weak portion 241 is less than or equal to 3 levels, the grain size grade of the second part 24222 and the grain size grade of the weak portion 241 are relatively close, the material consistency of the pressure relief mechanism 24 is good, and the consistency of the burst pressures of the plurality of battery monomers 20 is improved.

[0277] In other embodiments, the non-weak portion 242 further comprises a connecting area 2422 surrounding the outside of the weak portion 241, the connecting area 2422 is integrally formed with the wall portion 213. The difference between the grain size grade of the connecting area 2422 and the grain size grade of the weak portion 241 is less than or equal to 3 levels. By arranging the connecting area 2422, the connection with the wall portion 213 is facilitated. When the difference between the grain size grade of the connecting area 2422 and the grain size grade of the weak portion 241 is less than or equal to 3 levels, the grain size grade of the connecting area 2422 and the grain size grade of the weak portion 241 are relatively close, the material consistency of the pressure relief mechanism 24 is good, and the consistency of the burst pressures of the plurality of battery monomers 20 is improved.

[0278] The pressure relief mechanism 24 further comprises a second transition portion 244 connecting the weak portion 241 and the connecting area 2422, the thickness of the second transition portion 244 has a trend of increasing in the direction from the weak portion 241 to the connecting area 2422, and the difference between the grain size grade of the second transition portion 244 and the grain size grade of the weak portion 241 is less than or equal to 2. By arranging the second transition portion 244, the thickness of the second transition portion 244 has a trend of increasing in the direction from the weak portion 241 to the connecting area 2422, the weak portion 241 can gradually transition to the connecting area 2422, the grain size grade of the second transition portion 244 gradually changes in the direction from the weak portion 241 to the connecting area 2422, the grain size does not easily change abruptly, which is conducive to reducing stress concentration and making the burst pressures of the plurality of battery monomers 20 more consistent. In addition, when the difference between the grain size grade of the second transition portion 244 and the grain size grade of the weak portion 241 is less than or equal to 2, the grain size grade of the second transition portion 244 and the grain size grade of the weak portion 241 are relatively close, the material consistency of the pressure relief mechanism 24 is good, which is conducive to improving the consistency of the burst pressures of the plurality of battery monomers 20.

[0279] The thickness of the weak portion 241 is H, and 0.01mm≤H≤0.1mm. When H≥0.01mm, the thickness of the weak portion 241 is large, and the weak portion 241 is not easy to crack prematurely due to changes in pressure inside the battery monomer 20 or external impact, which is conducive to reducing the risk of the weak portion 241 being damaged prematurely and improving the service life of the battery monomer 20. When H≤0.1mm, the thickness of the weak portion 241 is not too large, so that the pressure relief mechanism 24 can be opened in time when the battery monomer 20 is out of control, which is conducive to improving the timeliness of pressure relief of the pressure relief mechanism 24. Therefore, when 0.01mm≤H≤0.1mm, the service life of the battery monomer 20 and the timeliness of pressure relief can be considered.

[0280] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Those skilled in the art can make various modifications and changes to the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A battery cell, characterized by, The application relates to a battery, comprising: a shell having a wall, a base material of the wall being iron; an electrode assembly accommodated in the shell; a pressure relief mechanism arranged on the wall, a base material of the pressure relief mechanism being iron, the pressure relief mechanism comprising a weak portion configured to be at least partially destroyed to release pressure when the pressure inside the shell reaches a threshold value; wherein the weak portion has a grain layer number N satisfying 1<=N<=5.

2. The battery cell of claim 1, wherein, 1≤N≤3。 3. The battery cell of claim 1, wherein, The weak portion has a grain size grade of 6-10.

4. The battery cell of claim 3, wherein, The weak portion has a grain size grade of 7-9.

5. The battery cell of claim 1, wherein, The material of the pressure relief mechanism comprises at least one of stainless steel and carbon steel.

6. The battery cell of claim 5, wherein, The material of the pressure relief mechanism comprises at least one of SUS304 stainless steel, SUS305 stainless steel or SUS316L stainless steel.

7. The battery cell of claim 1, wherein, The pressure relief mechanism comprises a non-weak portion, the thickness of the non-weak portion being greater than that of the weak portion, the non-weak portion comprising a pressure relief area, and the weak portion being arranged outside the pressure relief area.

8. The battery cell of claim 7, wherein, The difference between the grain size grade of the pressure relief area and that of the weak portion is less than or equal to 3.

9. The battery cell of claim 8, wherein, The difference between the grain size grade of the pressure relief area and that of the weak portion is less than or equal to 2.

10. The battery cell of claim 7, wherein, The non-weak portion further comprises a connecting area, the connecting area being arranged outside the weak portion, the connecting area comprising a first portion and a second portion, the first portion being welded with the wall to form a weld mark, and the second portion connecting the weak portion and the first portion. The difference between the grain size grade of the second portion and that of the weak portion is less than or equal to 3.

11. The battery cell of claim 10, wherein, The difference between the grain size grade of the second portion and that of the weak portion is less than or equal to 2.

12. The battery cell of claim 7, wherein, The non-weak portion further comprises a connecting area, the connecting area being arranged outside the weak portion, the connecting area being integrally formed with the wall. The difference between the grain size grade of the connecting area and that of the weak portion is less than or equal to 3.

13. The battery cell of claim 12, wherein the cathode comprises a lithium metal oxide. The difference between the grain size grade of the connecting area and that of the weak portion is less than or equal to 2.

14. The battery cell of claim 10, wherein, The pressure relief mechanism further comprises a first transition portion, the first transition portion connecting the weak portion and the pressure relief area, the thickness of the first transition portion increasing in a direction from the weak portion to the pressure relief area, and the difference between the grain size grade of the first transition portion and that of the weak portion being less than or equal to 3. The pressure relief mechanism further comprises a second transition portion, the second transition portion connecting the weak portion and the connecting area, the thickness of the second transition portion increasing in a direction from the weak portion to the connecting area, and the difference between the grain size grade of the second transition portion and that of the weak portion being less than or equal to 3.

15. The battery cell of claim 14, wherein the cathode comprises a lithium metal oxide. The difference between the grain size grade of the first transition portion and that of the weak portion is less than or equal to 2; and / or The difference between the grain size grade of the second transition portion and that of the weak portion is less than or equal to 2.

16. The battery cell according to claim 7, characterized in that, The hardness of the non-weak portion is A, satisfying 145HV<=A<=185HV.

17. The battery cell of claim 16, wherein the cathode comprises a lithium metal oxide. 150HV<=A<=170HV.

18. The battery cell of claim 7, wherein, The pressure relief area is at least partially raised in a direction away from the electrode assembly.

19. The battery cell of claim 18, wherein the cathode comprises a lithium metal oxide. The non-weak portion further comprises a connecting area, the connecting area is arranged outside the weak portion, the connecting area is integrally formed with the wall portion or is separately arranged and connected, the connecting area is at least partially raised in a direction close to the electrode assembly, and the weak portion is connected to a part of the connecting area closest to the electrode assembly.

20. The battery cell of any one of claims 1-19, wherein, The thickness of the weak portion is H, and 0.01mm≤H≤0.1mm is satisfied.

21. The battery cell of claim 20, wherein, 0.015mm≤H≤0.06mm.

22. The battery cell of any one of claims 1-19, wherein, The pressure relief mechanism is separately arranged with the wall portion, the wall portion is provided with a pressure relief hole, and the pressure relief mechanism is mounted on the wall portion and covers the pressure relief hole.

23. The battery cell according to any one of claims 1-19, characterized in that, The pressure relief mechanism is integrally formed with the wall portion.

24. The battery cell of any one of claims 1-19, wherein, The shell comprises a shell body and an end cover, one end of the shell body is provided with an opening, the end cover closes the opening, and the end cover is the wall portion.

25. A battery device, characterized by The battery cell according to any one of claims 1-24.

26. An electrical device, comprising: The battery cell according to any one of claims 1-24 is used to provide electric energy for the electric device.

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