Battery monomer, battery and electric equipment

Abstract

The invention provides a battery monomer, a battery and electric equipment, and relates to the field of batteries. The battery monomer comprises an electrode assembly, a shell and a pressure relief mechanism, wherein the shell is used for accommodating the electrode assembly; the pressure relief mechanism is arranged on the lower portion of the shell and integrally formed with the shell. And when the single battery is normally used, the pressure relief mechanism is positioned at the lower part of the shell. Compared with the prior art that the pressure relief mechanism is welded to the end cover, the pressure relief mechanism and the shell are integrally formed, and liquid leakage caused by welding defects is avoided. In addition, the capacity of the pressure relief mechanism for resisting external impact can be improved. And meanwhile, the electrolyte in the shell can cause creep deformation or impact on the pressure relief mechanism, and the rigidity of the pressure relief mechanism can be improved by integrally forming the pressure relief mechanism and the shell, so that the resistance of the pressure relief mechanism to the creep deformation and impact of the electrolyte is relatively high, the service life of the pressure relief mechanism is favorably prolonged, and the risk of liquid leakage of the pressure relief mechanism is reduced.

Description

Battery cells, batteries and electrical equipment Technical Field

[0001] The present application relates to the field of batteries, and more specifically, to a battery cell, a battery, and an electrical device. Background Art

[0002] Batteries are widely used in new energy applications, such as electric vehicles and new energy vehicles, which have become a new trend in the automotive industry. Battery end caps are equipped with pressure relief mechanisms to release internal pressure when it reaches the detonation pressure. However, these pressure relief mechanisms are prone to leakage.

[0003] Summary of the Invention

[0004] The purpose of the embodiments of the present application is to provide a battery cell, a battery and an electrical device, which aims to improve the problem that the pressure relief mechanism in the related art is prone to leakage.

[0005] In a first aspect, an embodiment of the present application provides a battery cell, which includes an electrode assembly, a shell and a pressure relief mechanism. The shell is used to accommodate the electrode assembly, and the pressure relief mechanism is arranged at the lower part of the shell and is integrally formed with the shell.

[0006] In the above technical solution, when the battery cell is in normal use, the pressure relief mechanism is located at the lower part of the shell. Compared with the prior art in which the pressure relief mechanism is welded to the end cover, the present application integrates the pressure relief mechanism with the shell to avoid leakage caused by welding defects. In addition, the ability of the pressure relief mechanism to resist external impact can be improved. At the same time, since the electrolyte in the shell can cause creep or impact on the pressure relief mechanism, integrating the pressure relief mechanism with the shell can improve the rigidity of the pressure relief mechanism, so that the pressure relief mechanism has a stronger resistance to creep and impact of the electrolyte, which is beneficial to improving the life of the pressure relief mechanism and reducing the risk of leakage in the pressure relief mechanism.

[0007] As an optional technical solution of an embodiment of the present application, the pressure relief mechanism is arranged below the median vertical plane of the shell that is perpendicular to its height direction.

[0008] In the above technical solution, the electrolyte pressure is higher below the mid-vertical plane of the housing, making the pressure relief mechanism more susceptible to leakage. This application addresses the scenario where the pressure relief mechanism is disposed below the mid-vertical plane of the housing. By integrating the pressure relief mechanism with the housing, the pressure relief mechanism is enhanced in strength and rigidity, improving its impact and creep resistance, and reducing the risk of leakage.

[0009] As an optional technical solution of an embodiment of the present application, the shell has a wall portion that supports the electrode assembly in the direction of gravity, and the pressure relief mechanism is arranged on the wall portion and is integrally formed with the wall portion.

[0010] In the above technical solution, the wall supports the electrode assembly in the direction of gravity, and the electrolyte exerts the greatest pressure on the wall. If the pressure relief mechanism leaks, the electrolyte will flow out at a high speed and in large quantities. This application targets scenarios where the pressure relief mechanism is provided on the wall supporting the electrode assembly. By integrating the pressure relief mechanism with the wall, the pressure relief mechanism is formed integrally with the wall. This can enhance the strength and rigidity of the pressure relief mechanism, improve its impact resistance and creep resistance, and reduce the risk of leakage from the pressure relief mechanism.

[0011] As an optional technical solution of an embodiment of the present application, the shell includes a wall portion, the pressure relief mechanism is arranged on the wall portion, and the wall portion has an opening area; the wall portion has a first surface and a second surface arranged opposite to each other in its thickness direction; the pressure relief mechanism includes a notched groove, the notched groove is recessed along the direction from the first surface to the second surface, the notched groove is arranged along the edge of the opening area, and the opening area is configured to be able to open with the notched groove as the boundary.

[0012] In the above technical solution, the notched grooves can be formed by stamping or cold heading. This causes the groove walls to undergo cold work hardening (changing the grain arrangement, causing lattice distortion, reducing the metal's plasticity, and increasing the material's hardness). This enhances the metal's resistance to external impact and makes it less susceptible to damage from external impact. This helps reduce the risk of leakage from the pressure relief mechanism.

[0013] As an optional technical solution of an embodiment of the present application, the pressure relief mechanism includes at least one level of sink, and the at least one level of sink is arranged in sequence on the wall portion along the direction from the first surface to the second surface; the first bottom wall of the sink farthest from the first surface has the opening area.

[0014] In the above technical solution, at least one level of sinks and notches are sequentially arranged on the wall portion from the first surface to the second surface. During forming, the sinks and notches can be formed step by step, thereby reducing the forming force on the wall portion and the risk of cracks in the wall portion. The pressure relief mechanism is less likely to fail due to cracks in the location where the notches are set, thereby improving the long-term reliability of the pressure relief device. When forming at least one level of sinks and notches, stamping or cold heading can be used. In this way, the groove walls of the sinks and notches will undergo cold work hardening (the grain arrangement changes, resulting in lattice distortion, reducing the plasticity of the metal and increasing the hardness of the material), and their ability to resist external impact is enhanced, and they are not easily damaged by external impact. This helps to reduce the risk of leakage from the pressure relief mechanism.

[0015] As an optional technical solution of an embodiment of the present application, the pressure relief mechanism includes two levels of sinks, which are arranged in sequence along the direction from the first surface to the second surface. One level of sinks is arranged on the first surface, and the other level of sinks is arranged on the bottom surface of the first level of sinks, and the notched groove is arranged on the bottom surface of the other level of sinks.

[0016] In the above technical solution, a two-stage sinking groove is set, the forming steps are fewer, and the forming is relatively simple. At the same time, due to cold working hardening, the stiffness, strength and hardness of the wall of the notched groove can be more effectively improved, and the risk of leakage of the pressure relief mechanism can be effectively reduced, which is conducive to improving production efficiency and reducing production costs.

[0017] As an optional technical solution of an embodiment of the present application, the pressure relief mechanism includes multiple levels of scored grooves, which are arranged in sequence along the direction from the first surface to the second surface; in two adjacent levels of scored grooves, the first level scored groove away from the first surface is arranged on the bottom surface of the first level scored groove close to the first surface.

[0018] In the above technical solution, the multi-level scoring grooves are arranged sequentially from the first surface to the second surface, which can reduce the forming depth of each level of scoring grooves, thereby reducing the forming force applied to the wall during each level of scoring grooves and reducing the risk of cracks in the wall. As the multi-level scoring grooves are formed step by step from the first surface to the second surface, the hardness of the remaining portion of the wall where the scoring grooves are located increases with each level of scoring grooves. This improves the hardness of the remaining portion of the wall after the multi-level scoring grooves are formed, resulting in better long-term reliability and impact resistance, and reduces the probability of damage from external impact.

[0019] As an optional technical solution of the embodiment of the present application, along the thickness direction, the surface of the opening area away from the first surface is flush with the second surface.

[0020] In the above technical solution, the opening area does not protrude from the second surface along the thickness direction. In this way, the opening area occupies less internal space of the battery cell or the battery, which is beneficial to improving the energy density of the battery.

[0021] As an optional technical solution of the embodiment of the present application, the wall portion partially protrudes from the second surface in a direction away from the first surface to form a reinforcement portion; the reinforcement portion is arranged around the opening area.

[0022] In the above technical solution, a reinforcement portion is formed by partially protruding the wall portion from the second surface in a direction away from the first surface. When the wall portion is deformed, the reinforcement portion can reduce the effect of the deformation on the notched groove, thereby reducing the risk of leakage of the pressure relief mechanism.

[0023] As an optional technical solution of the embodiment of the present application, along the thickness direction, the surface of the opening area away from the first surface is flush with the surface of the reinforcement portion away from the first surface.

[0024] In the above technical solution, along the thickness direction, the opening area does not protrude from the surface of the reinforcement portion away from the first surface. In this way, the opening area occupies less internal space of the battery cell or the battery, which is beneficial to improving the energy density of the battery.

[0025] As an optional technical solution of the embodiment of the present application, along the thickness direction, the height of the reinforcement portion protruding from the second surface is A, satisfying: 05mm≤A≤4mm.

[0026] In the above technical solution, the height of the reinforcement portion protruding from the second surface along the thickness direction is limited to between 0.5 and 4 mm. This ensures that the reinforcement portion has a good reinforcing effect while not occupying too much space within the battery cell or battery, thereby effectively ensuring the battery's energy density. When A < 0.5 mm, the height of the reinforcement portion protruding from the second surface along the thickness direction is small, and the reinforcing effect is not significant. When A > 4 mm, the height of the reinforcement portion protruding from the second surface along the thickness direction is large, occupying a large amount of space and affecting the battery's energy density.

[0027] As an optional technical solution of the embodiment of the present application, 1mm≤A≤2.5mm.

[0028] In the above technical solution, the height of the reinforcing portion protruding from the second surface in the thickness direction is limited to between 1 and 2.5 mm, which can better improve the reinforcing effect of the reinforcing portion and occupy less internal space of the battery cell or battery.

[0029] As an optional technical solution of the embodiment of the present application, the opening area is bent along the thickness direction.

[0030] In the above technical solution, by bending the opening area along the thickness direction, when the wall is subjected to external impact, the wall can be deformed along the bending direction, thereby absorbing the energy of the external impact, thereby reducing the impact of the external impact on the location of the notched groove, and to a certain extent avoiding the location of the notched groove from being damaged by the external impact. In addition, the curved opening area is similar to a stress concentration area during pressure relief, making it easier for the bottom wall of the first groove to open at the location of the notched groove. Under the same blasting pressure, the depth of the notched groove can be shallower, and the thickness of the bottom wall of the first groove at the location of the notched groove can be greater, so that the bottom wall of the first groove is not easily opened by external interference at the location of the notched groove, thereby reducing the risk of leakage from the pressure relief mechanism.

[0031] As an optional technical solution of the embodiment of the present application, the opening area is bent in a direction from the second surface to the first surface.

[0032] In the above technical solution, when the opening area bends from the second surface to the first surface, the gas inside the battery cell, when acting on the opening area, will generate a pulling force on the bottom wall of the first slot at the location of the notch, making it easier for the bottom wall of the first slot to open at the notch. Under the same blasting pressure, the depth of the notch can be shallower, and the thickness of the bottom wall of the first slot at the location of the notch can be greater, making it less susceptible to external interference and opening at the notch, thereby reducing the risk of leakage from the pressure relief mechanism. When the electrolyte acts on the opening area, the force applied is relatively small. Although it will generate a pulling force on the bottom wall of the first slot at the location of the notch, it is not sufficient to cause the notch to open. Furthermore, the pulling force generated on the bottom wall of the first slot at the location of the notch disperses the force of the electrolyte, reducing the amplitude of the opening area and making it difficult for the pressure relief mechanism to open under the action of the electrolyte, thereby reducing the risk of leakage from the pressure relief mechanism.

[0033] As an optional technical solution of an embodiment of the present application, the pressure relief mechanism includes at least one level of sink, and the at least one level of sink is arranged in sequence on the wall portion along the direction from the first surface to the second surface, and the first groove bottom wall of the level of sink farthest from the first surface has the opening area; the first groove bottom wall includes a main body area, the main body area is arranged around the opening area, and the notched groove is arranged between the opening area and the main body area; along the thickness direction, the main body area has a third surface and a fourth surface, and the distance between the third surface and the fourth surface is B, and the opening area has a fifth surface away from the second surface, and the third surface and the fifth surface are located on the same side of the first groove bottom wall, and the maximum distance between the third surface and the fifth surface is C, satisfying: B / 10≤C≤B.

[0034] In the above technical solution, the distance between the third surface and the fourth surface along the thickness direction is 1 to 10 times the maximum distance between the third surface and the fifth surface along the thickness direction. This reflects the curvature of the opening area. When C>B, the curvature of the opening area is too large, making it susceptible to external impact and causing the bottom wall of the first groove to crack at the location of the scored groove. If C<B / 10, the curvature of the opening area is too small, affecting the stress release within the scored groove.

[0035] As an optional technical solution of an embodiment of the present application, the first surface is the outer surface of the wall.

[0036] In the above technical solution, when the first surface is the outer surface of the wall portion, the position of the bottom wall of the first groove is away from the first surface along the thickness direction. In this way, the notched groove arranged on the bottom wall of the first groove is not easily affected by external impact, and the pressure relief mechanism is not easily opened due to external impact, thereby reducing the risk of leakage of the pressure relief mechanism.

[0037] As an optional technical solution of an embodiment of the present application, the pressure relief mechanism includes at least one level of sink, and the at least one level of sink is arranged in sequence on the wall along the direction from the first surface to the second surface, and the first groove bottom wall of the first level of sink farthest from the first surface has the opening area; the strength of the wall is D1, the strength of the second groove bottom wall of the first level of sink closest to the first surface is D2, and the strength of the first groove bottom wall at the position of the notched groove is D3, satisfying: D3>D2≥D1; and / or the hardness of the wall is E1, the hardness of the second groove bottom wall is E2, and the hardness of the first groove bottom wall at the position of the notched groove is E3, satisfying: E3>E2≥E1; and / or the stiffness of the wall is F1, the stiffness of the second groove bottom wall is F2, and the stiffness of the first groove bottom wall at the position of the notched groove is F3, satisfying: F3>F2≥F1.

[0038] In the above technical solution, when the strength of the second groove bottom wall is greater than the strength of the wall portion, it is equivalent to providing a reinforcement around the scored groove, so that when the wall portion is subjected to external impact, the risk of damage to the first groove bottom wall at the scored groove position is reduced, and the pressure relief mechanism has better tolerance to external impact. In addition, although the strength of the first groove bottom wall at the scored groove position is higher, its hardness is also higher, and the material ductility decreases (the material becomes brittle), which makes it easy to open the valve under the action of internal gas. In this way, under the same detonation pressure, the thickness of the first groove bottom wall at the scored groove position can be thicker to enhance the resistance to external impact, so that the long-term reliability of the pressure relief mechanism is better. When forming the sink and scored groove, stamping or cold heading can be used, so that the groove walls of the sink and scored groove will undergo cold work hardening, so that the strength, rigidity and hardness of the second groove bottom wall and the first groove bottom wall at the scored groove position are correspondingly improved.

[0039] As an optional technical solution of the embodiment of the present application, 1.2E1≤E2≤2.5E1.

[0040] In the above technical solution, the hardness of the second groove bottom wall is 1.2 to 2.5 times the hardness of the wall portion, so that the second groove bottom wall can block external objects and reduce the risk of external objects acting on the scoring groove position.

[0041] As an optional technical solution of the embodiment of the present application, 2.5E1<E3≤5E1.

[0042] In the above technical solution, the hardness of the bottom wall of the first groove at the position of the notched groove is 2.5 to 5 (not including 2.5) times the hardness of the wall, making the bottom wall of the first groove at the position of the notched groove more brittle and easy to open under the action of internal air pressure.

[0043] As an optional technical solution of the embodiment of the present application, 5HBW≤E1≤150HBW.

[0044] In the above technical solution, when the strength of the wall portion is between 5 and 150 HBW, the wall portion has a strong impact resistance and good tolerance to external impact.

[0045] As an optional technical solution of the embodiment of the present application, 5HBW≤E3≤200HBW.

[0046] In the above technical solution, when the strength of the first groove bottom wall at the notched groove position is 5 to 2000 HBW, even if the wall is subjected to external impact, the first groove bottom wall is not easily damaged at the notched groove position, and the pressure relief mechanism has better tolerance to external impact.

[0047] As an optional technical solution of an embodiment of the present application, the minimum thickness of the bottom wall of the first groove at the position of the scoring groove is W1, satisfying: 5HBW / mm≤E3 / W1≤10000HBW / mm; preferably, 190HBW / mm≤E3 / W1≤4000HBW / mm.

[0048] In the above technical solution, not only the impact of the thickness of the first groove bottom wall at the notch location on the performance of the housing is taken into account, but also the impact of the hardness of the first groove bottom wall at the notch location on the performance of the housing is taken into account. 5HBW / mm≤E3 / W1≤10000HBW / mm ensures that the first groove bottom wall at the notch location has sufficient strength under normal battery cell use conditions, making it less susceptible to fatigue damage and thus increasing the battery cell service life. It also allows the housing to promptly release pressure through the opening area in the event of thermal runaway of the battery cell, reducing the risk of battery cell explosion and improving the safety of the battery cell. 190HBW / mm≤E3 / W1≤4000HBW / mm improves the overall performance of the housing, ensuring that the opening area can be opened promptly in the event of thermal runaway of the battery cell, while ensuring that the first groove bottom wall at the notch location has sufficient strength under normal battery cell use conditions. This improves the service life of the battery cell while ensuring the safety of the battery cell.

[0049] As an optional technical solution of the embodiment of the present application, the minimum thickness of the wall portion at the position of the notch groove is W1, and the minimum thickness of the wall portion W2 satisfies: 0.05≤W1 / W2≤0.95.

[0050] In the above technical solution, the notched groove is formed on the wall by stamping or cold heading, and W1 / W2 is controlled between 0.05 and 0.95, which can achieve the purpose of refining the grains of the wall at the notched groove position, improve the material mechanical properties of the wall at the notched groove position, improve the toughness and fatigue resistance of the wall at the notched groove position, reduce the risk of the wall at the notched groove position being damaged during normal use of the battery cell, improve the service life of the battery cell, and reduce the risk of the battery cell exploding during thermal runaway.

[0051] As an optional technical solution of an embodiment of the present application, 0.12≤W1 / W2≤0.8; preferably, 0.2≤W1 / W2≤0.5.

[0052] In the above technical solution, when 0.12≤W1 / W2≤0.8, the overall performance of the wall is improved. While ensuring that the wall at the scored groove location can be promptly destroyed in the event of thermal runaway of the battery cell, the wall is guaranteed to have sufficient strength at the scored groove location during normal use of the battery cell. When 0.2≤W1 / W2≤0.5, the risk of the wall at the scored groove location being destroyed under normal use conditions of the battery cell is further reduced, and the wall is guaranteed to be promptly destroyed in the event of thermal runaway of the battery cell, thereby improving the timeliness of pressure relief.

[0053] As an optional technical solution of an embodiment of the present application, 0.02mm≤W1≤1.6mm; preferably, 0.06mm≤W1≤0.4mm.

[0054] In the above technical solution, if W1 is too small, the scoring groove will be difficult to form, and the wall portion at the scoring groove position will be easily damaged during the forming process. If W1 is too large, the wall portion at the scoring groove position will be more difficult to destroy during thermal runaway of the battery cell, and pressure relief will be delayed. Therefore, when 0.02mm≤W1≤1.6mm, the timeliness of pressure relief of the battery cell during thermal runaway is improved while reducing the difficulty of forming the scoring groove. When 0.06mm≤W1≤0.4mm, the difficulty of forming the scoring groove is further reduced, and the timeliness of pressure relief of the battery cell during thermal runaway is improved.

[0055] As an optional technical solution of an embodiment of the present application, 1mm≤W2≤5mm; preferably, 1.2mm≤W2≤3.5mm; preferably, 2mm≤W2≤3mm.

[0056] In the above technical solution, if W2 is too large, the wall thickness is large, more material is used for the shell, the shell is heavy, and the cost-effectiveness is poor. If W2 is too small, the wall thickness is small, and the shell's deformation resistance is poor. Therefore, when 1mm ≤ W2 ≤ 5mm, the shell has better cost-effectiveness and good deformation resistance. When 1.2mm ≤ W2 ≤ 3.5mm, the shell has even better cost-effectiveness and deformation resistance.

[0057] As an optional technical solution of an embodiment of the present application, the pressure relief mechanism includes at least one level of sink, and the at least one level of sink is arranged in sequence on the wall portion along the direction from the first surface to the second surface, and the first groove bottom wall of the first level of the sink farthest from the first surface has the opening area; the average grain size of the wall portion is G1, the average grain size of the second groove bottom wall of the first level of the sink closest to the first surface is G2, and the average grain size of the first groove bottom wall at the notch groove position is G3, satisfying: G1>G2>G3.

[0058] In the above technical solution, when the sinking groove and the scoring groove are formed by stamping or cold heading, the grains of the material are broken and become finer. Therefore, the average grain size of the bottom wall of the first groove at the scoring groove position will be smaller than the average grain size of the bottom wall of the second groove, and the average grain size of the bottom wall of the second groove will be smaller than the average grain size of the wall.

[0059] As an optional technical solution of the embodiment of the present application, G3 / G1≤0.9.

[0060] In the above technical solution, the average grain size of the bottom wall of the first groove at the notch groove position is significantly different from the average grain size of the wall portion, which reduces the average grain size of the bottom wall of the first groove at the notch groove position, improves the mechanical properties of the material of the bottom wall of the first groove at the notch groove position, and further improves the toughness and fatigue resistance of the bottom wall of the first groove at the notch groove position.

[0061] As an optional technical solution of an embodiment of the present application, G3 / G1≥0.05; preferably, 0.1≤G3 / G1≤0.5.

[0062] In the above technical solution, G3 / G1 is too small, the difficulty of forming the sink and the notch groove increases, and the strength of the bottom wall of the first groove at the notch groove position is too great, and the difficulty of destroying the bottom wall of the first groove at the notch groove position when the battery cell thermal runaway occurs increases, and it is easy to cause untimely pressure relief. Therefore, G3 / G1≥0.05, which reduces the difficulty of forming the sink and the notch groove and improves the timeliness of pressure relief of the battery cell during thermal runaway. When 0.1≤G3 / G1≤0.5. The comprehensive performance of the wall is better, ensuring that the bottom wall of the first groove can be destroyed in time at the notch groove position when the battery cell thermal runaway occurs, and ensuring that the bottom wall of the first groove has sufficient strength at the notch groove position during normal use of the battery cell.

[0063] As an optional technical solution of an embodiment of the present application, 0.4μm≤G3≤75μm; preferably, 1μm≤G3≤10μm.

[0064] In the above technical solution, if G3 is too large, the toughness and fatigue resistance of the bottom wall of the first groove at the notch location will be poor; if G3 is too small, the formation of the sink and notch groove will be more difficult, and the strength of the bottom wall of the first groove at the notch location will be too great, making it more difficult for the bottom wall of the first groove at the notch location to be damaged during thermal runaway of the battery cell, which can easily lead to delayed pressure relief. Therefore, 0.4μm≤G3≤75μm, on the one hand, reduces the difficulty of forming the sink and notch groove, and improves the timeliness of pressure relief of the battery cell during thermal runaway; on the other hand, it improves the toughness and fatigue resistance of the bottom wall of the first groove at the notch location, reducing the risk of damage to the bottom wall of the first groove at the notch location under normal battery cell use conditions.

[0065] As an optional technical solution of an embodiment of the present application, 10μm≤G1≤150μm; preferably, 30μm≤G1≤100μm.

[0066] As an optional technical solution of an embodiment of the present application, the minimum thickness of the first groove bottom wall at the position of the notched groove is W1; the average grain size of the first groove bottom wall at the position of the notched groove is G3, satisfying: 1≤W1 / G3≤100; preferably, 5≤W1 / G3≤20.

[0067] In the above technical solution, if W1 / G3 is too small, the number of grain layers in the first groove bottom wall at the notch location in the thickness direction of the wall portion decreases, and the fatigue strength of the first groove bottom wall at the notch location is too low. If W1 / G3 is too large, the number of grain layers in the first groove bottom wall at the notch location in the thickness direction increases, and the strength of the first groove bottom wall at the notch location is too high, which may lead to the risk that the first groove bottom wall at the notch location may not be destroyed in time during thermal runaway of the battery cell. Therefore, when 1≤W1 / G3≤100, on the one hand, the number of grain layers in the first groove bottom wall at the notch location in the thickness direction is large, which improves the fatigue strength of the first groove bottom wall at the notch location and reduces the risk of the first groove bottom wall being destroyed at the notch location under normal use conditions of the battery cell. On the other hand, it allows the first groove bottom wall to be destroyed more promptly at the notch location during thermal runaway of the battery cell, thereby achieving the purpose of timely pressure relief. When 5≤W1 / G3≤20. This improves the overall performance of the wall, ensuring that the bottom wall of the first groove can be destroyed in time at the notched groove position when the battery cell experiences thermal runaway, and ensuring that the bottom wall of the first groove has sufficient fatigue strength at the notched groove position under normal use conditions of the battery cell, thereby improving the service life of the battery cell.

[0068] As an optional technical solution of an embodiment of the present application, the housing includes a shell and an end cover, the shell has an opening, the end cover is connected to the shell and closes the opening, and the pressure relief mechanism is arranged on the end cover.

[0069] In the above technical solution, the pressure relief mechanism is provided on the end cover, and the end cover is located at the lower part of the shell, corresponding to the scenario where the battery cell is inverted.

[0070] As an optional technical solution of an embodiment of the present application, the housing includes a shell and an end cover, the shell has an opening, the end cover is connected to the shell and closes the opening, and the pressure relief mechanism is arranged on the shell.

[0071] In the above technical solution, the pressure relief mechanism is provided on the shell, and the pressure relief mechanism is located at the lower part of the shell.

[0072] As an optional technical solution of an embodiment of the present application, along the first direction, both ends of the shell have openings, and the shell includes two end covers, and one end cover correspondingly closes one opening.

[0073] In a second aspect, an embodiment of the present application further provides a battery comprising the above-mentioned battery cell.

[0074] In a third aspect, an embodiment of the present application further provides an electrical device, comprising the above-mentioned battery, wherein the battery is used to provide electrical energy to the electrical device. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0076] FIG1 is a schematic structural diagram of a vehicle provided in some embodiments of the present application;

[0077] FIG2 is an exploded view of a battery provided in some embodiments of the present application;

[0078] FIG3 is a schematic structural diagram of a battery cell provided in some embodiments of the present application;

[0079] FIG4 is an exploded view of a battery cell provided in some embodiments of the present application;

[0080] FIG5 is a schematic structural diagram of a wall portion provided in some embodiments of the present application;

[0081] FIG6 is a schematic top view of a wall portion provided in some embodiments of the present application;

[0082] FIG7 is a cross-sectional view of position II in FIG6;

[0083] FIG8 is an enlarged view of position J in FIG7 ;

[0084] FIG9 is a schematic top view of a wall portion provided in some other embodiments of the present application;

[0085] FIG10 is a cross-sectional view of the LL position in FIG9;

[0086] FIG11 is an enlarged view of the position M in FIG10 ;

[0087] FIG12 is a schematic top view of a wall portion provided in some other embodiments of the present application;

[0088] FIG13 is a cross-sectional view taken along line NN in FIG12 ;

[0089] FIG14 is an enlarged view of position Q in FIG13 ;

[0090] FIG15 is a cross-sectional view of the PP position in FIG12;

[0091] FIG16 is an enlarged view of the R position in FIG15 .

[0092] Icons: 10-housing; 11-first part; 12-second part; 20-battery cell; 21-shell; 211-end cover; 212-shell; 213-wall; 2131-first surface; 2132-second surface; 2133-reinforcement; 22-electrode assembly; 23-pressure relief mechanism; 231-sink; 2311-bottom wall of the second groove; 2312-bottom wall of the first groove; 23121-opening area; 23121a-fifth surface; 23121b-flat area; 23121c-connecting area; 23122-body area; 23122a-third surface; 23122b-fourth surface; 232-notched groove; 24-mid-vertical plane; 100-battery; 200-controller; 300-motor; 1000-vehicle. DETAILED DESCRIPTION

[0093] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0094] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as commonly understood by those skilled in the art to which this application belongs. The terms used in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusions. The terms "first" and "second" in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order or a primary-secondary relationship.

[0095] References to "embodiments" in this application mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments.

[0096] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connected," and "attached" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to direct connections, indirect connections through an intermediate medium, or internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0097] The term "and / or" in this application simply describes an association between related objects, indicating that three possible relationships exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this application generally indicates that the related objects are in an "or" relationship.

[0098] In the embodiments of this application, the same reference numerals represent the same components, and for the sake of brevity, detailed descriptions of the same components in different embodiments are omitted. It should be understood that the thickness, length, width, and other dimensions of the various components in the embodiments of this application, as well as the overall thickness, length, width, and other dimensions of the integrated device shown in the drawings are merely illustrative and should not constitute any limitation on this application.

[0099] The term "plurality" used in this application refers to two or more (including two).

[0100] In this application, battery cells may include lithium-ion secondary batteries, lithium-ion primary batteries, lithium-sulfur batteries, sodium-lithium-ion batteries, sodium-ion batteries, or magnesium-ion batteries, etc., and the embodiments of this application do not limit this. Battery cells may be cylindrical, flat, rectangular, or other shapes, etc., and the embodiments of this application do not limit this. Battery cells are generally divided into three types based on the packaging method: cylindrical battery cells, prismatic battery cells, and soft-pack battery cells, and the embodiments of this application do not limit this.

[0101] The battery referred to in the embodiments of this application refers to a single physical module that includes one or more battery cells to provide higher voltage and capacity. For example, the battery referred to in this application may include a battery module or a battery pack. A battery generally includes a casing that encloses one or more battery cells. The casing prevents liquids or other foreign matter from affecting the charging or discharging of the battery cells.

[0102] A battery cell includes an electrode assembly and an electrolyte. The electrode assembly consists of a positive electrode sheet, a negative electrode sheet, and a separator. A battery cell primarily operates by the movement of metal ions between the positive and negative electrode sheets. The positive electrode sheet comprises a positive current collector and a positive active material layer. The positive active material layer is coated on the surface of the positive electrode collector. The portion of the positive electrode collector not coated with the positive active material layer protrudes from the portion coated with the positive active material layer. The portion of the positive electrode collector not coated with the positive active material layer serves as the positive electrode tab. For lithium-ion batteries, for example, the positive electrode current collector can be made of aluminum, and the positive active material can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide. The negative electrode sheet comprises a negative current collector and a negative active material layer. The negative active material layer is coated on the surface of the negative electrode collector. The portion of the negative electrode collector not coated with the negative active material layer protrudes from the portion coated with the negative active material layer. The portion of the negative electrode collector not coated with the negative active material layer serves as the negative electrode tab. The negative electrode current collector can be made of copper, and the negative active material can be carbon or silicon, among others. To ensure high current flow without melting, multiple positive tabs are stacked together, and multiple negative tabs are stacked together. The separator can be made of materials such as PP (polypropylene) or PE (polyethylene). Furthermore, the electrode assembly can be a wound or laminated structure, but the present invention is not limited thereto.

[0103] Currently, market developments indicate that batteries are increasingly being used. They are not only used in energy storage systems such as hydropower, thermal, wind, and solar power plants, but are also widely used in electric vehicles like electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. As battery applications continue to expand, market demand is also growing.

[0104] The development of battery technology must take into account multiple design factors at the same time, such as energy density, cycle life, discharge capacity, charge and discharge rate and other performance parameters. In addition, battery safety must also be considered.

[0105] For battery cells, in order to ensure the safety of the battery cells, the existing technology is to weld a pressure relief mechanism on the end cover of the battery cell. The pressure relief mechanism is provided with a notched groove, which defines a pressure relief portion. When the internal pressure of the battery cell reaches the detonation pressure, the pressure relief portion opens to release the pressure inside the battery cell, thereby reducing the risk of battery cell explosion or fire.

[0106] The inventors have discovered that welding the pressure relief mechanism to the end cover in the prior art is prone to welding defects, and the electrolyte in the battery cell is prone to leaking from the defective position. This is especially exacerbated when the battery cell is used upside down. In addition, when welding the pressure relief mechanism to the end cover, the high temperature generated by welding will affect the notched groove, and welding will cause the material to expand and contract, pulling the notched groove, resulting in a reduced lifespan of the pressure relief mechanism. This will also easily open the pressure relief mechanism under the action of the electrolyte, causing leakage. In addition, the pressure relief mechanism is easily opened by external impact, which can also cause leakage of the pressure relief mechanism. Furthermore, when the battery cell is used upside down, the electrolyte in the battery cell will have a creep effect on the pressure relief mechanism, which can also easily reduce the lifespan of the pressure relief mechanism and make the pressure relief mechanism prone to leakage.

[0107] In view of this, an embodiment of the present application provides a battery cell, which includes an electrode assembly, a shell and a pressure relief mechanism. The shell is used to accommodate the electrode assembly, and the pressure relief mechanism is arranged at the lower part of the shell and is integrally formed with the shell.

[0108] When the battery cell is in normal use, the pressure relief mechanism is located at the bottom of the shell. Compared with the prior art method of welding the pressure relief mechanism to the end cover, the present application integrates the pressure relief mechanism with the shell to avoid leakage caused by welding defects. In addition, it can also improve the ability of the pressure relief mechanism to resist external impact. At the same time, since the electrolyte in the shell will cause creep or impact on the pressure relief mechanism, integrating the pressure relief mechanism with the shell can improve the rigidity of the pressure relief mechanism, so that the pressure relief mechanism has a stronger resistance to creep and impact of the electrolyte, which is beneficial to improving the life of the pressure relief mechanism and reducing the risk of leakage in the pressure relief mechanism.

[0109] The technical solutions described in the embodiments of the present application are applicable to batteries and electrical devices using batteries.

[0110] Electrically powered devices may include vehicles, mobile phones, portable devices, laptop computers, ships, spacecraft, electric toys, and electric tools. Spacecraft include airplanes, rockets, space shuttles, and spacecraft. Electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys. Electric tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers. The embodiments of the present application do not impose any special restrictions on the above-mentioned electrical devices.

[0111] For the convenience of description, the following embodiments are described by taking the electric device as a vehicle 1000 as an example.

[0112] Please refer to Figure 1, which is a schematic structural diagram of a vehicle 1000 provided in some embodiments of the present application. The vehicle 1000 can be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A battery 100 is provided inside the vehicle 1000, and the battery 100 can be provided at the bottom, head or tail of the vehicle 1000. The battery 100 can be used to power the vehicle 1000. For example, the battery 100 can serve as an operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300. The controller 200 is used to control the battery 100 to power the motor 300, for example, for starting, navigating and driving the vehicle 1000.

[0113] In some embodiments of the present application, the battery 100 can serve not only as an operating power source for the vehicle 1000, but also as a driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0114] Please refer to Figure 2, which is an exploded view of a battery 100 provided in some embodiments of the present application. The battery 100 includes a housing 10 and a battery cell 20, with the battery cell 20 housed within the housing 10. The housing 10 provides a storage space for the battery cell 20 and can have various structures. In some embodiments, the housing 10 can include a first portion 11 and a second portion 12, which overlap each other and together define a storage space for the battery cell 20. The second portion 12 can be a hollow structure with one end open. The first portion 11 can be a plate-like structure, with the first portion 11 overlapping the open side of the second portion 12, so that the first portion 11 and the second portion 12 together define a storage space. Alternatively, the first portion 11 and the second portion 12 can each be a hollow structure with one end open, with the open side of the first portion 11 overlapping the open side of the second portion 12. Of course, the housing 10 formed by the first portion 11 and the second portion 12 can have various shapes, such as a cylinder, a rectangular parallelepiped, etc.

[0115] In the battery 100, there may be multiple battery cells 20, and the multiple battery cells 20 may be connected in series, in parallel, or in a hybrid connection. A hybrid connection refers to a combination of series and parallel connections among the multiple battery cells 20. The multiple battery cells 20 may be directly connected in series, in parallel, or in a hybrid connection, and then the entire battery cell 20 may be housed within the housing 10. Alternatively, the battery 100 may be constructed by first connecting multiple battery cells 20 in series, in parallel, or in a hybrid connection to form a battery module, which is then connected in series, in parallel, or in a hybrid connection to form a complete battery module, and then housed within the housing 10. The battery 100 may also include other structures, such as a busbar assembly for electrically connecting the multiple battery cells 20.

[0116] Each battery cell 20 may be a secondary battery cell or a primary battery cell; it may also be a lithium-sulfur battery cell, a sodium-ion battery cell, or a magnesium-ion battery cell, but is not limited thereto. The battery cell 20 may be cylindrical, flat, rectangular, or in other shapes.

[0117] Please refer to Figures 3, 4, 5, 6, 7 and 8. Figure 3 is a schematic structural diagram of a battery cell 20 provided in some embodiments of the present application. Figure 4 is an exploded view of a battery cell 20 provided in some embodiments of the present application. Figure 5 is a schematic structural diagram of a wall portion 213 provided in some embodiments of the present application. Figure 6 is a top schematic diagram of a wall portion 213 provided in some embodiments of the present application. Figure 7 is a cross-sectional view of position II in Figure 6. Figure 8 is an enlarged view of position J in Figure 7. An embodiment of the present application provides a battery cell 20, the battery cell 20 includes an electrode assembly 22, a shell 21 and a pressure relief mechanism 23, the shell 21 is used to accommodate the electrode assembly 22, and the pressure relief mechanism 23 is arranged at the lower part of the shell 21 and is integrally formed with the shell 21.

[0118] The battery cell 20 refers to the smallest unit constituting the battery 100 .

[0119] The housing 21 includes an end cap 211 and a shell 212. The shell 212 has an accommodation space with one end open for accommodating the electrode assembly 22. The end cap 211 is connected to the shell 212 and closes the opening.

[0120] The end cap 211 refers to a component that covers the opening of the shell 212 to isolate the internal environment of the battery cell 20 from the external environment. Without limitation, the shape of the end cap 211 can be adapted to the shape of the shell 212 to match the shell 212. Optionally, the end cap 211 can be made of a material with a certain hardness and strength (such as aluminum alloy), so that the end cap 211 is not easily deformed when squeezed or collided, so that the battery cell 20 can have a higher structural strength and the safety performance can also be improved. Functional components such as electrode terminals (not shown in the figure) can be provided on the end cap 211. The electrode terminal can be used to electrically connect to the electrode assembly 22 for outputting or inputting electrical energy of the battery cell 20. The material of the end cap 211 can also be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiments of the present application do not impose any special restrictions on this. In some embodiments, the battery cell 20 further includes an insulating member disposed inside the end cap 211 to isolate the electrical connection components within the housing 212 from the end cap 211 to reduce the risk of short circuits. For example, the insulating member may be made of plastic, rubber, or the like.

[0121] The housing 212 is a component that cooperates with the end cap 211 to form the internal environment of the battery cell 20. This internal environment can be used to accommodate the electrode assembly 22, electrolyte, and other components. The housing 212 and the end cap 211 can be separate components. An opening can be provided in the housing 212, and the end cap 211 is placed over the opening to form the internal environment of the battery cell 20. Alternatively, the end cap 211 and the housing 212 can be integrated. Specifically, the end cap 211 and the housing 212 can form a common joint surface before other components are inserted into the housing. When the interior of the housing 212 is to be enclosed, the end cap 211 is placed over the housing 212. The housing 212 can have a variety of shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, or a hexagonal prism. Specifically, the shape of the housing 212 can be determined based on the specific shape and size of the electrode assembly 22. The housing 212 can be made of a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and this embodiment of the present application does not impose any particular limitations on this.

[0122] The electrode assembly 22 is a component in the battery cell 20 where electrochemical reactions occur. One or more electrode assemblies 22 may be contained in the housing 21. The electrode assembly 22 is mainly formed by winding or stacking positive and negative electrode sheets, and a separator is usually provided between the positive and negative electrode sheets. The parts of the positive and negative electrode sheets with active materials constitute the main body of the electrode assembly 22, and the parts of the positive and negative electrode sheets without active materials each constitute a tab. The positive and negative electrode tabs may be located together at one end of the main body or respectively at both ends of the main body. During the charge and discharge process of the battery 100, the positive electrode active material and the negative electrode active material react with the electrolyte.

[0123] The pressure relief mechanism 23 is a component for opening when the internal pressure or temperature of the battery cell 20 reaches an explosion pressure to relieve the internal pressure of the battery cell 20 .

[0124] Assume that there is an imaginary plane perpendicular to the height direction of the housing 21. Along the height direction of the housing 21, the portion of the housing 21 above the imaginary plane accounts for 30% of the height of the housing 21, and the portion of the housing 21 below the imaginary plane accounts for 70% of the height of the housing 21. The lower portion refers to the portion of the housing 21 below the imaginary plane along the height direction.

[0125] Referring to FIG. 3 , the height direction of the housing 21 refers to the H direction shown in the figure.

[0126] Integrally formed means that the housing 21 and the pressure relief mechanism 23 are an integral structure when provided. For example, the pressure relief mechanism 23 can be formed on the housing 21 by stamping or cold heading.

[0127] When the battery cell 20 is in normal use, the pressure relief mechanism 23 is located at the lower part of the outer shell 21. Compared with the prior art in which the pressure relief mechanism 23 is welded to the end cover 211, the present application forms the pressure relief mechanism 23 and the outer shell 21 as one piece, thereby avoiding leakage caused by welding defects. In addition, since the pressure relief mechanism 23 and the outer shell 21 are formed as one piece, the strength of the pressure relief mechanism 23 is improved, and the ability of the pressure relief mechanism 23 to resist external impact is improved. At the same time, since the electrolyte in the outer shell 21 will cause creep or impact on the pressure relief mechanism 23, forming the pressure relief mechanism 23 and the outer shell 21 as one piece can improve the rigidity of the pressure relief mechanism 23, so that the pressure relief mechanism 23 has a stronger resistance to creep and impact of the electrolyte, which is beneficial to improving the life of the pressure relief mechanism 23 and reducing the risk of leakage of the pressure relief mechanism 23.

[0128] 3 , 4 , 5 , 6 , 7 and 8 , in some embodiments, the pressure relief mechanism 23 is disposed below a median vertical plane 24 of the housing 21 that is perpendicular to its height direction.

[0129] Please refer to Figure 3 , which shows a dotted line in the middle vertical plane 24. The middle vertical plane 24 is perpendicular to the height of the housing 21. Along the height of the housing 21, the portion of the housing 21 above the middle vertical plane 24 accounts for 50% of the height of the housing 21, and the portion of the housing 21 below the middle vertical plane 24 accounts for 50% of the height of the housing 21. The pressure relief mechanism 23 is located below the middle vertical plane 24.

[0130] Below the mid-vertical plane 24 in the height direction of the housing 21, the electrolyte pressure is higher, making the pressure relief mechanism 23 more susceptible to leakage. This application addresses the scenario where the pressure relief mechanism 23 is disposed below the mid-vertical plane 24 in the height direction of the housing 21. By integrally forming the pressure relief mechanism 23 with the housing 21, the strength and rigidity of the pressure relief mechanism 23 are enhanced, its impact resistance and creep resistance are improved, and the risk of leakage from the pressure relief mechanism 23 is reduced.

[0131] 3 , 4 , 5 , 6 , 7 and 8 , in some embodiments, the housing 21 has a wall 213 that supports the electrode assembly 22 in the direction of gravity, and the pressure relief mechanism 23 is disposed on the wall 213 and is integrally formed with the wall 213 .

[0132] Wall 213 is the portion of the outer shell 21 that supports the electrode assembly 22 in the direction of gravity. It can be understood that wall 213 is the bottom wall of the outer shell 21. Wall 213 can be a wall of the housing 212 or an end cap 211. When wall 213 is an end cap 211, the battery cell 20 is used in an inverted position.

[0133] The wall 213 supports the electrode assembly 22 in the direction of gravity, and the electrolyte exerts the greatest pressure on the wall 213. If the pressure relief mechanism 23 leaks, the electrolyte will flow out at a high rate and in large quantities. This application addresses scenarios where the pressure relief mechanism 23 is provided on the wall 213 supporting the electrode assembly 22. By integrally forming the pressure relief mechanism 23 with the wall 213, the strength and rigidity of the pressure relief mechanism 23 are enhanced, its impact resistance and creep resistance are improved, and the risk of leakage from the pressure relief mechanism 23 is reduced.

[0134] In other embodiments, the housing 21 has a wall portion 213 and a peripheral wall, wherein the wall portion 213 supports the electrode assembly 22 in the direction of gravity and the peripheral wall surrounds the periphery of the wall portion 213. The pressure relief mechanism 23 is disposed on the peripheral wall and is integrally formed with the peripheral wall.

[0135] Referring to Figures 3, 4, 5, 6, 7, and 8, in some embodiments, the housing 21 includes a wall portion 213, and the pressure relief mechanism 23 is disposed on the wall portion 213. The wall portion 213 has an opening area 23121. The wall portion 213 has a first surface 2131 and a second surface 2132 that are oppositely disposed in the thickness direction thereof. The pressure relief mechanism 23 includes a notched groove 232, which is recessed from the first surface 2131 to the second surface 2132. The notched groove 232 is disposed along the edge of the opening area 23121, and the opening area 23121 is configured to be openable with the notched groove 232 as the boundary.

[0136] Referring to FIG. 8 , the thickness direction may be the K direction shown in the figure.

[0137] The first surface 2131 and the second surface 2132 of the wall portion 213 are two opposing surfaces of the wall portion 213 in the thickness direction thereof, and the distance between the first surface 2131 and the second surface 2132 is the thickness of the wall portion 213. Taking the wall portion 213 as an end cap 211 as an example, the first surface 2131 may be the outer surface of the end cap 211, facing the outside of the battery cell 20, and the second surface 2132 may be the inner surface of the end cap 211, facing the inside of the battery cell 20.

[0138] The wall portion 213 is provided with a scored groove 232. The scored groove 232 can have various shapes, such as arc, H-shape, U-shape, or ring. The scored groove 232 on the wall portion 213 can be formed using various methods, such as stamping, cold heading, etc. For example, in the case of stamping, the scored groove 232 can be stamped into the wall portion 213 along the direction from the first surface 2131 to the second surface 2132.

[0139] The opening area 23121 is the pressure relief area of ​​the wall 213. When the internal pressure or temperature of the battery cell 20 reaches the detonation pressure, the opening area 23121 opens along the notch 232 to relieve pressure. The opening area 23121 can be opened by detaching or flipping. The notch 232 is located along the edge of the opening area 23121.

[0140] Furthermore, when forming the notched groove 232, stamping or cold heading can be used. This allows the groove wall of the notched groove 232 to undergo cold work hardening (changing the grain arrangement, causing lattice distortion, reducing the metal's plasticity, and increasing the material's hardness). This enhances its ability to resist external impacts and makes it less susceptible to damage from external impacts. This helps reduce the risk of leakage from the pressure relief mechanism 23.

[0141] 3, 4, 5, 6, 7, and 8, in some embodiments, the pressure relief mechanism 23 includes at least one primary recess 231, which is sequentially arranged on the wall portion 213 from the first surface 2131 to the second surface 2132. The first recess bottom wall 2312 of the primary recess 231, which is farthest from the first surface 2131, has an opening 23121.

[0142] The wall portion 213 may be provided with a single or multiple-stage recessed groove 231. If provided with multiple stages of recessed grooves 231, the recessed grooves 231 are sequentially arranged along the wall portion 213 from the first surface 2131 to the second surface 2132, with the bottom surface profile of each stage of recessed groove 231 decreasing gradually. The recessed grooves 231 may have various shapes, such as rectangular or circular. The recessed grooves 231 on the wall portion 213 may be formed using various methods, such as stamping or cold heading.

[0143] For example, as shown in Figure 8, a notched groove 232 and a two-stage sunken groove 231 are provided on the wall portion 213, and both the notched groove 232 and the sunken groove 231 are stamped. The first-stage sunken groove 231 can be stamped on the first surface 2131 first, and then the second-stage sunken groove 231 can be stamped on the bottom surface of the first-stage sunken groove 231. Finally, the notched groove 232 can be stamped on the bottom surface of the second-stage sunken groove 231.

[0144] At least one primary groove 231 and a scored groove 232 are sequentially arranged on the wall portion 213 along the direction from the first surface 2131 to the second surface 2132. During molding, all the grooves 231 can be formed on the wall portion 213 first, and then the scored groove 232 can be formed. The scored groove 232 is arranged on the bottom surface of the primary groove 231 farthest from the first surface 2131. If only a primary groove 231 is provided on the wall portion 213, this primary groove 231 is both the primary groove 231 closest to the first surface 2131 and the primary groove 231 farthest from the first surface 2131.

[0145] The first bottom wall 2312 of the primary trough 231 farthest from the first surface 2131 is the portion of the wall portion 213 below the bottom surface of the primary trough 231 farthest from the first surface 2131. After the wall portion 213 forms the primary trough 231 farthest from the first surface 2131, the remaining portion of the wall portion 213 where the primary trough 231 is located is the first bottom wall 2312 of the primary trough 231 farthest from the first surface 2131. As shown in FIG8 , taking the example of a wall portion 213 having two stages of troughs 231, the portion of the wall portion 213 below the bottom surface of the second stage trough 231 is the first bottom wall 2312 of the primary trough 231 farthest from the first surface 2131.

[0146] The opening area 23121 is formed on the first bottom wall 2312 of the primary sink 231 farthest from the first surface 2131 .

[0147] At least one level of recessed grooves 231 and notched grooves 232 are sequentially arranged on the wall portion 213 along the direction from the first surface 2131 to the second surface 2132. During molding, the recessed grooves 231 and notched grooves 232 can be formed step by step, thereby reducing the molding force on the wall portion 213 and the risk of cracks in the wall portion 213. The pressure relief mechanism 23 is less likely to fail due to cracks in the location where the notched grooves 232 are arranged, thereby improving the long-term reliability of the pressure relief device. When forming the at least one level of recessed grooves 231 and notched grooves 232, stamping or cold heading methods can be used. In this way, the groove walls of the recessed grooves 231 and notched grooves 232 undergo cold work hardening (changing the grain arrangement, resulting in lattice distortion, reducing the metal's plasticity, and increasing the material's hardness), thereby enhancing their ability to resist external impact and making them less susceptible to damage from external impact. This helps reduce the risk of leakage from the pressure relief mechanism 23.

[0148] Because the notched groove 232 is arranged along the edge of the opening area 23121 and the opening area 23121 can be opened with the notched groove 232 as the boundary, the pressure relief area of ​​the wall portion 213 is increased, thereby improving the pressure relief rate of the wall portion 213. Furthermore, because the first groove bottom wall 2312 of the primary groove 231, which is farthest from the first surface 2131, has the opening area 23121, the groove 231 provides a clearance space for the opening area 23121 during opening. Even if the first surface 2131 is blocked by an obstacle, the opening area 23121 can still be opened to relieve pressure.

[0149] Please refer to Figures 3, 4, 5, 6, 7 and 8. In some embodiments, the pressure relief mechanism 23 includes two-stage sink grooves 231, which are arranged in sequence from the first surface 2131 to the second surface 2132. The first-stage sink groove 231 is arranged on the first surface 2131, the other-stage sink groove 231 is arranged on the bottom surface of the first-stage sink groove 231, and the notched groove 232 is arranged on the bottom surface of the other-stage sink groove 231.

[0150] The two-stage sinking groove 231 has fewer molding steps and is relatively simple to form. At the same time, due to cold working hardening, the stiffness, strength and hardness of the wall of the notched groove 232 can be more effectively improved, and the risk of leakage of the pressure relief mechanism 23 is effectively reduced, which is conducive to improving production efficiency and reducing production costs.

[0151] In some embodiments, the pressure relief mechanism 23 includes multiple levels of scored grooves 232, which are sequentially arranged from the first surface 2131 to the second surface 2132. In two adjacent levels of scored grooves 232, the first level scored groove 232 farther from the first surface 2131 is arranged at the bottom surface of the first level scored groove 232 closer to the first surface 2131.

[0152] When the wall portion 213 is provided with the recessed groove 231 , the primary scoring groove 232 closest to the first surface 2131 is provided on the bottom surface of the primary recessed groove 231 farthest from the first surface 2131 .

[0153] In the case where the wall portion 213 is provided with a sink groove 231, the wall portion 213 may be provided with two, three, four, or five levels of scored grooves 232. Taking the case where the wall portion 213 is provided with two levels of scored grooves 232 and two levels of sink grooves 231 as an example, the first-level sink groove 231 (the outermost first-level sink groove 231) is provided on the first surface 2131, the second-level sink groove 231 (the first-level sink groove 231 farthest from the first surface 2131) is provided on the bottom surface of the first-level sink groove 231, the first-level scored groove 232 (the first-level scored groove 232 closest to the first surface 2131) is provided on the bottom surface of the second-level sink groove 231, and the second-level scored groove 232 (the first-level scored groove 232 farthest from the first surface 2131) is provided on the bottom surface of the first-level scored groove 232.

[0154] When multiple levels of notched grooves 232 are provided on the wall portion 213 , the shapes of the notched grooves 232 at each level are substantially the same and are all provided along the edge of the opening area 23121 .

[0155] The multi-stage scored grooves 232 are sequentially arranged from the first surface 2131 to the second surface 2132, which can reduce the forming depth of each stage of scored grooves 232, thereby reducing the forming force applied to the wall portion 213 during the formation of each stage of scored grooves 232, thereby reducing the risk of cracks in the wall portion 213. During the process of gradually forming the multi-stage scored grooves 232 from the first surface 2131 to the second surface 2132, the hardness of the remaining portion of the wall portion 213 in the area where the scored grooves 232 are located increases with each stage of scored grooves 232. This improves the hardness of the remaining portion of the wall portion 213 after the multi-stage scored grooves 232 are formed, resulting in improved long-term reliability and better impact resistance, and reduces the probability of damage from external impact.

[0156] 6 , 7 and 8 , in some embodiments, along the thickness direction, a surface of the opening area 23121 away from the first surface 2131 is flush with the second surface 2132 .

[0157] “Along the thickness direction, the surface of the opening area 23121 away from the first surface 2131 is flush with the second surface 2132 ” may also be understood as that along the thickness direction, the opening area 23121 does not protrude from the second surface 2132 .

[0158] By making the surface of the opening area 23121 away from the first surface 2131 in the thickness direction flush with the second surface 2132, the opening area 23121 reduces the internal space occupied by the battery cell 20 or the internal space occupied by the battery 100, which is beneficial to improving the energy density of the battery 100.

[0159] Please refer to Figures 9, 10, and 11. Figure 9 is a schematic top view of the wall portion 213 provided in other embodiments of the present application. Figure 10 is a cross-sectional view taken at position LL in Figure 9. Figure 11 is an enlarged view taken at position M in Figure 10. In other embodiments, the wall portion 213 partially protrudes from the second surface 2132 away from the first surface 2131 to form a reinforcement portion 2133. The reinforcement portion 2133 is disposed around the opening area 23121.

[0160] The reinforcement portion 2133 is an annular structure that protrudes from the second surface 2132. The reinforcement portion 2133 may be formed by partially protruding the wall portion 213 along the direction from the first surface 2131 to the second surface 2132 when the recessed groove 231 is stamped into the wall portion 213, forming a protrusion protruding from the second surface 2132. The primary recessed groove 231 farthest from the first surface 2131 is located within the reinforcement portion 2133. Specifically, the bottom surface of the primary recessed groove 231 farthest from the first surface 2131 is further from the first surface 2131 than the second surface 2132, resulting in the reinforcement portion 2133 surrounding the primary recessed groove 231 farthest from the first surface 2131.

[0161] By partially protruding the wall portion 213 from the second surface 2132 in a direction away from the first surface 2131 to form a reinforcement portion 2133, when the wall portion 213 is deformed, the reinforcement portion 2133 can reduce the impact of the deformation on the notched groove 232, thereby reducing the risk of leakage of the pressure relief mechanism 23.

[0162] In some embodiments, along the thickness direction, a surface of the opening area 23121 away from the first surface 2131 is flush with a surface of the reinforcement portion 2133 away from the first surface 2131 .

[0163] The phrase "along the thickness direction, the surface of the opening area 23121 away from the first surface 2131 is flush with the surface of the reinforcement portion 2133 away from the first surface 2131" means that, along the thickness direction, the distance between the surface of the opening area 23121 away from the first surface 2131 and the first surface 2131 is equal to the distance between the surface of the reinforcement portion 2133 away from the first surface 2131 and the first surface 2131. The opening area 23121 does not protrude beyond the surface of the reinforcement portion 2133 away from the first surface 2131.

[0164] Along the thickness direction, the opening area 23121 does not protrude from the surface of the reinforcement portion 2133 away from the first surface 2131. In this way, the opening area 23121 reduces the internal space occupied by the battery cell 20 or the internal space occupied by the battery 100, which is beneficial to improving the energy density of the battery 100.

[0165] 9 , 10 and 11 , in some embodiments, along the thickness direction, the height of the reinforcing portion 2133 protruding from the second surface 2132 is A, satisfying the following: 0.51 mm ≤ A ≤ 4 mm.

[0166] Along the thickness direction, the height of the reinforcement portion 2133 protruding from the second surface 2132 is the distance between the surface of the reinforcement portion 2133 facing away from the first surface 2131 and the second surface 2132 .

[0167] Along the thickness direction, the height of the reinforcement portion 2133 protruding from the second surface 2132 can be: A = 0.5mm, 0.8mm, 1mm, 1.2mm, 1.5mm, 1.8mm, 2mm, 2.2mm, 2.5mm, 2.8mm, 3mm, 3.2mm, 3.5mm, 3.8mm, 4mm, etc.

[0168] Limiting the height of the reinforcement portion 2133 protruding from the second surface 2132 along the thickness direction to between 0.5 and 4 mm ensures that the reinforcement portion 2133 provides a good reinforcement effect while not occupying too much space within the battery cell 20 or battery 100, thereby effectively ensuring the energy density of the battery 100. When A < 0.5 mm, the height of the reinforcement portion 2133 protruding from the second surface 2132 along the thickness direction is small, and the reinforcement effect is not significant. When A > 4 mm, the height of the reinforcement portion 2133 protruding from the second surface 2132 along the thickness direction is large, occupying a large space and affecting the energy density of the battery 100.

[0169] In some embodiments, 1 mm ≤ A ≤ 2.5 mm.

[0170] The height of the reinforcement portion 2133 protruding from the second surface 2132 along the thickness direction can be: A = 1mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm, 2mm, 2.1mm, 2.2mm, 2.3mm, 2.4mm, 2.5mm, etc.

[0171] Limiting the height of the reinforcing portion 2133 protruding from the second surface 2132 in the thickness direction to between 1 and 2.5 mm can effectively enhance the reinforcing effect of the reinforcing portion 2133 while occupying less internal space of the battery cell 20 or the battery 100 .

[0172] Please refer to Figures 12, 13, 14, 15, and 16. Figure 12 is a top view of the wall portion 213 provided in some other embodiments of the present application. Figure 13 is a cross-sectional view taken at position NN in Figure 12. Figure 14 is an enlarged view of position Q in Figure 13. Figure 15 is a cross-sectional view taken at position PP in Figure 12. Figure 16 is an enlarged view of position R in Figure 15. In some embodiments, the opening area 23121 is curved along the thickness direction.

[0173] In some embodiments, the opening region 23121 includes a straight region 23121b and a connecting region 23121c. Along the thickness direction, there is a height difference between the straight region 23121b and the open end of the scored groove 232. The connecting region 23121c connects the groove wall of the scored groove 232 and the straight region 23121b. Optionally, the straight region 23121b is located in the middle of the opening region 23121, and the connecting region 23121c is disposed around the straight region 23121b. The cross-section of the connecting region 23121c extends along an arc trajectory, causing the opening region 23121 to curve along the thickness direction.

[0174] In other embodiments, the opening area 23121 is an arched structure.

[0175] By bending the opening area 23121 along the thickness direction, when the wall portion 213 is subjected to an external impact, the wall portion 213 can deform along the bending direction, thereby absorbing the energy of the external impact, thereby reducing the impact of the external impact on the location of the notched groove 232, and to a certain extent preventing the location of the notched groove 232 from being damaged due to the external impact. In addition, the curved opening area 23121 is similar to a stress concentration area during pressure relief, making it easier for the first groove bottom wall 2312 to open at the notched groove 232 location. Under the same blasting pressure, the depth of the notched groove 232 can be shallower, and the thickness of the first groove bottom wall 2312 at the notched groove 232 location can be greater, so that the first groove bottom wall 2312 is not easily opened by external interference at the notched groove 232 location, thereby reducing the risk of leakage from the pressure relief mechanism 23.

[0176] 12 , 13 , 14 , 15 and 16 , in some embodiments, the opening area 23121 is bent in a direction from the second surface 2132 to the first surface 2131 .

[0177] The opening area 23121 is curved along the direction from the second surface 2132 to the first surface 2131, so that the opening area 23121 does not extend beyond the surface of the reinforcement portion 2133 facing away from the first surface 2131 in the thickness direction. In other words, the opening area 23121 is curved along the direction from the second surface 2132 to the first surface 2131, so that the bottom surface of the sink 231 is convex in the direction from the second surface 2132 to the first surface 2131.

[0178] In the embodiment where the opening area 23121 includes the straight area 23121 b and the connecting area 23121 c , the straight area 23121 b is located on one side of the scoring groove 232 along the direction from the second surface 2132 to the first surface 2131 .

[0179] In the embodiment where the opening area 23121 is an arched structure, the arch top of the opening area 23121 is located on one side of the notch groove 232 along the direction from the second surface 2132 to the first surface 2131 .

[0180] When the opening area 23121 curves from the second surface 2132 to the first surface 2131, the gas within the battery cell 20 acts on the opening area 23121, generating a pulling force on the first tank bottom wall 2312 at the location of the scored groove 232, making it easier for the first tank bottom wall 2312 to open at the location of the scored groove 232. Under the same burst pressure, the depth of the scored groove 232 can be shallower, and the thickness of the first tank bottom wall 2312 at the location of the scored groove 232 can be greater, making the first tank bottom wall 2312 less susceptible to external interference and opening at the location of the scored groove 232, thereby reducing the risk of leakage from the pressure relief mechanism 23. When the electrolyte acts on the opening area 23121, the force applied is relatively small. Although it will generate a pulling force on the first tank bottom wall 2312 at the location of the scored groove 232, it is not sufficient to cause the scored groove 232 to open. In addition, the pulling force generated on the bottom wall 2312 of the first groove at the position of the notched groove 232 disperses the force of the electrolyte, making the amplitude of the opening area 23121 smaller, and the pressure relief mechanism 23 is not easily opened under the action of the electrolyte, thereby reducing the risk of leakage of the pressure relief mechanism 23.

[0181] Referring to Figures 12, 13, 14, 15, and 16, in some embodiments, the pressure relief mechanism 23 includes at least one primary recess 231, which is sequentially arranged on the wall portion 213 from the first surface 2131 to the second surface 2132. The first recess bottom wall 2312 of the primary recess 231, which is furthest from the first surface 2131, has an opening 23121. The first recess bottom wall 2312 includes a body region 23122, which surrounds the opening 23121. The notched groove 232 is disposed between the opening 23121 and the body region 23122. Along the thickness direction, the body region 23122 has a third surface 23122a and a fourth surface 23122b, with a distance B between the third surface 23122a and the fourth surface 23122b. The opening area 23121 has a fifth surface 23121a away from the second surface 2132. The third surface 23122a and the fifth surface 23121a are located on the same side of the first groove bottom wall 2312. The maximum distance between the third surface 23122a and the fifth surface 23121a is C, satisfying: B / 10≤C≤B.

[0182] When the battery cell 20 releases pressure, the opening area 23121 on the first tank bottom wall 2312 opens, while the body area 23122 remains in place. The body area 23122 has a third surface 23122a and a fourth surface 23122b along the thickness direction. The third surface 23122a is closer to the first surface 2131 along the thickness direction, while the fourth surface 23122b is farther away from the first surface 2131 along the thickness direction.

[0183] B represents the distance between the third surface 23122 a and the fourth surface 23122 b along the thickness direction, that is, the thickness of the main region 23122 .

[0184] The opening area 23121 has a fifth surface 23121 a facing the first surface 2131 . The third surface 23122 a and the fifth surface 23121 a are located on the same side of the first groove bottom wall 2312 along the thickness direction.

[0185] C represents the maximum distance between the third surface 23122a and the fifth surface 23121a along the thickness direction.

[0186] The distance between the third surface 23122a and the fourth surface 23122b along the thickness direction is 1 to 10 times the maximum distance between the third surface 23122a and the fifth surface 23121a along the thickness direction. This reflects the curvature of the opening area 23121. When C>B, the curvature of the opening area 23121 is too great, making it susceptible to external impact and causing the first groove bottom wall 2312 to crack at the scored groove 232. If C<B / 10, the curvature of the opening area 23121 is too small, affecting the stress release within the scored groove 232.

[0187] In some embodiments, the first surface 2131 is the outer surface of the wall 213 .

[0188] The first surface 2131 is the outer surface of the wall portion 213 , which means that the first surface 2131 is the surface of the wall portion 213 facing away from the electrode assembly 22 . Correspondingly, the second surface 2132 is the inner surface of the wall portion 213 , and the second surface 2132 faces the electrode assembly 22 .

[0189] When the first surface 2131 is the outer surface of the wall portion 213, the position of the first groove bottom wall 2312 is away from the first surface 2131 along the thickness direction. In this way, the notched groove 232 arranged on the first groove bottom wall 2312 is not easily affected by external impact, and the pressure relief mechanism 23 is not easily opened due to external impact, thereby reducing the risk of liquid leakage from the pressure relief mechanism 23.

[0190] In some embodiments, the pressure relief mechanism 23 includes at least one primary recess 231, which is arranged sequentially along the wall portion 213 from the first surface 2131 to the second surface 2132. The first recess bottom wall 2312 of the primary recess 231, farthest from the first surface 2131, has an opening 23121. The wall portion 213 has a strength of D1, the second recess bottom wall 2311 of the primary recess 231 closest to the first surface 2131 has a strength of D2, and the first recess bottom wall 2312 has a strength of D3 at the location of the notched groove 232, satisfying the following conditions: D3 > D2 ≥ D1. Alternatively, the wall portion 213 has a hardness of E1, the second recess bottom wall 2311 has a hardness of E2, and the first recess bottom wall 2312 has a hardness of E3 at the location of the notched groove 232, satisfying the following conditions: E3 > E2 ≥ E1. And / or the stiffness of the wall portion 213 is F1, the stiffness of the second groove bottom wall 2311 is F2, and the stiffness of the first groove bottom wall 2312 at the position of the notched groove 232 is F3, satisfying: F3>F2≥F1.

[0191] When only one level of recessed grooves 231 is provided on the wall portion 213, the level of recessed grooves 231 closest to the first surface 2131 is also the level of recessed grooves 231 furthest from the first surface 2131. In other words, the first recessed groove bottom wall 2312 and the second recessed groove bottom wall 2311 are the same recessed groove bottom wall. When two or more levels of recessed grooves 231 are provided on the wall portion 213, the first recessed groove bottom wall 2312 and the second recessed groove bottom wall 2311 are different recessed groove bottom walls.

[0192] The strength, hardness, and / or rigidity of the first groove bottom wall 2312 at the location of the scored groove 232 is greater than the strength, hardness, and / or rigidity of the second groove bottom wall 2311. The strength, hardness, and / or rigidity of the second groove bottom wall 2311 is greater than or equal to the strength, hardness, and / or rigidity of the wall portion 213.

[0193] When the strength of the second groove bottom wall 2311 is greater than the strength of the wall portion 213, it is equivalent to providing a reinforcement around the notched groove 232. This reduces the risk of damage to the first groove bottom wall 2312 at the notched groove 232 when the wall portion 213 is subjected to an external impact, and the pressure relief mechanism 23 is more resistant to external impacts. In addition, although the strength of the first groove bottom wall 2312 at the notched groove 232 is higher, its hardness is also higher, and the material ductility decreases (the material becomes brittle), making it easier for the valve to open under the action of internal gas. In this way, under the same detonation pressure, the thickness of the first groove bottom wall 2312 at the notched groove 232 can be thicker to enhance resistance to external impacts, thereby improving the long-term reliability of the pressure relief mechanism 23. When forming the sink groove 231 and the notched groove 232, stamping or cold heading can be used, so that the groove walls of the sink groove 231 and the notched groove 232 will undergo cold work hardening, so that the strength, rigidity and hardness of the second groove bottom wall 2311 and the first groove bottom wall 2312 at the position of the notched groove 232 are correspondingly improved.

[0194] In some embodiments, 1.2E1≤E2≤2.5E1.

[0195] The ratio of the hardness of the second groove bottom wall 2311 to the hardness of the wall portion 213 can be: E2 / E1=1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, etc.

[0196] The hardness of the second groove bottom wall 2311 is 1.2 to 2.5 times that of the wall portion 213 , so that the second groove bottom wall 2311 can block external objects and reduce the risk of external objects acting on the position of the scoring groove 232 .

[0197] In some embodiments, 2.5E1<E3≤5E1.

[0198] The ratio of the hardness of the first groove bottom wall 2312 at the position of the scored groove 232 to the hardness of the wall portion 213 can be: E3 / E1=2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5, etc.

[0199] The hardness of the first groove bottom wall 2312 at the position of the scored groove 232 is 2.5 to 5 (excluding 2.5) times the hardness of the wall portion 213, making the first groove bottom wall 2312 relatively brittle at the position of the scored groove 232 and easily opened under the action of internal air pressure.

[0200] In some embodiments, 5HBW≤E1≤150HBW.

[0201] E1 can be any one of 5HBW, 8HBW, 9HBW, 9.5HBW, 10HBW, 12.HBW, 13HBW, 15HBW, 16HBW, 19HBW, 20HBW, 30HBW, 40HBW, 50HBW, 52HBW, 52.5HBW, 53HBW, 60HBW, 70HBW, 80HBW, 90HBW, 100HBW, 110HBW, 120HBW, 130HBW, 140HBW, and 150HBW, or a range between any two of them.

[0202] When the strength of the wall portion 213 is between 5 and 150 HBW, the wall portion 213 has a strong impact resistance and good tolerance to external impact.

[0203] In some embodiments, 5HBW≤E3≤200HBW.

[0204] E3 can be any one of 5HBW, 6HBW, 8HBW, 10HBW, 15HBW, 19HBW, 20HBW, 22.8HBW, 30HBW, 32HBW, 40HBW, 50HBW, 60HBW, 70HBW, 80HBW, 90HBW, 100HBW, 110HBW, 120HBW, 130HBW, 140HBW, 150HBW, 160HBW, 170HBW, 180HBW, 190HBW, and 200HBW, or a range between any two of them.

[0205] When the strength of the first groove bottom wall 2312 at the notched groove 232 is 5 to 2000 HBW, even if the wall portion 213 is subjected to external impact, the first groove bottom wall 2312 is not easily damaged at the notched groove 232, and the pressure relief mechanism 23 has better tolerance to external impact.

[0206] In some embodiments, the minimum thickness of the first groove bottom wall 2312 at the position of the scoring groove 232 is W1, which satisfies: 5HBW / mm≤E3 / W1≤10000HBW / mm; preferably, 190HBW / mm≤E3 / W1≤4000HBW / mm.

[0207] E3 / W1 can be 5HBW / mm, 6HBW / mm, 7HBW / mm, 20HBW / mm, 31HBW / mm, 32HBW / mm, 37.5HBW / mm, 42HBW / mm, 43HBW / mm, 50HBW / mm, 60HBW / mm, 61HBW / mm, 62HBW / mm, 63HBW / mm, 64HBW / mm, 75HBW / mm, 90HBW / mm, 100HBW / mm, Any one of 120HBW / mm, 150HBW / mm, 190HBW / mm, 500HBW / mm, 1000HBW / mm, 1200HBW / mm, 1750HBW / mm, 1800HBW / mm, 2100HBW / mm, 4000HBW / mm, 5000HBW / mm, 8000HBW / mm, 9000HBW / mm, and 10000HBW / mm, or the range between any two of them.

[0208] The hardness of the first groove bottom wall 2312 at the position of the notched groove 232 is the Brinell hardness, and the unit is HBW. The Brinell hardness measurement method can be implemented with reference to the measurement principle in GB / T 23.1-2018. In the actual measurement process, the hardness of the first groove bottom wall 2312 at the position of the notched groove 232 can be measured on two surfaces in the thickness direction. Taking the end cover 211 of the battery cell 20 as an example, the hardness of the first groove bottom wall 2312 at the position of the notched groove 232 can be measured on the surface of the first groove bottom wall 2312 at the position of the notched groove 232 away from the interior of the battery cell 20, and the hardness of the first groove bottom wall 2312 at the position of the notched groove 232 can also be measured on the surface of the first groove bottom wall 2312 at the position of the notched groove 232 facing the interior of the battery cell 20.

[0209] When E3 / W1 is greater than 10,000 HBW / mm, the first groove bottom wall 2312 is thinner and harder at the notch groove 232 location. This makes the first groove bottom wall 2312 very brittle at the notch groove 232 location, easily damaged under normal use conditions of the battery cell 20, shortening the service life of the battery cell 20. When E3 / W1 is less than 5 HBW / mm, the first groove bottom wall 2312 is thicker and less hard at the notch groove 232 location. In the event of thermal runaway of the battery cell 20, the first groove bottom wall 2312 at the notch groove 232 location will be stretched and extended, resulting in poor pressure relief.

[0210] Not only is the effect of the thickness of the first groove bottom wall 2312 at the position of the notched groove 232 on the performance of the shell 21 taken into consideration, but also the effect of the hardness of the first groove bottom wall 2312 at the position of the notched groove 232 on the performance of the shell 21 is taken into consideration, 5HBW / mm≤E3 / W1≤10000HBW / mm, which can ensure that the first groove bottom wall 2312 at the position of the notched groove 232 has sufficient strength under normal use conditions of the battery cell 20 and is not easily damaged by fatigue, thereby improving the service life of the battery cell 20; it can also ensure that the shell 21 releases pressure in time through the opening area 23121 when the battery cell 20 thermally runs away, thereby reducing the risk of explosion of the battery cell 20 and improving the safety of the battery cell 20.

[0211] In some embodiments, 190 HBW / mm≤E3 / W1≤4000 HBW / mm.

[0212] E3 / W1 can be any one of 190HBW / mm, 250HBW / mm, 280HBW / mm, 300HBW / mm, 350HBW / mm, 400HBW / mm, 450HBW / mm, 500HBW / mm, 600HBW / mm, 700HBW / mm, 875HBW / mm, 1000HBW / mm, 1200HBW / mm, 1500HBW / mm, 1750HBW / mm, 1800HBW / mm, 2000HBW / mm, 2100HBW / mm, 2500HBW / mm, 3000HBW / mm, 3500HBW / mm, and 4000HBW / mm, or a range between any two of them.

[0213] 190 HBW / mm ≤ E3 / W1 ≤ 4000 HBW / mm, resulting in better overall performance for the housing 21. This ensures that the opening area 23121 can be opened promptly in the event of thermal runaway of the battery cell 20, and that the first groove bottom wall 2312 has sufficient strength at the location of the notched groove 232 under normal use conditions of the battery cell 20. This improves the service life of the battery cell 20 while ensuring the safety of the battery cell 20.

[0214] 12 , 13 , 14 , 15 and 16 , in some embodiments, the minimum thickness of the wall portion 213 at the notch groove 232 is W1 , and the minimum thickness W2 of the wall portion 213 satisfies: 0.05≤W1 / W2≤0.95.

[0215] W1 / W2 can be any one of 0.05, 0.06, 0.07, 0.08, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.8, 0.85, 0.9, 0.95, or a range between any two of them.

[0216] The notched groove 232 is formed in the wall portion 213 by stamping or cold heading, and W1 / W2 is controlled between 0.05 and 0.95, which can achieve the purpose of refining the grains of the wall portion 213 at the notched groove 232 position, improve the material mechanical properties of the wall portion 213 at the notched groove 232 position, improve the toughness and fatigue resistance of the wall portion 213 at the notched groove 232 position, reduce the risk of the wall portion 213 at the notched groove 232 position being damaged during normal use of the battery cell 20, improve the service life of the battery cell 20, and reduce the risk of the battery cell 20 exploding during thermal runaway.

[0217] In some embodiments, 0.12≤W1 / W2≤0.8.

[0218] W1 / W2 can be any one of 0.12, 0.13, 0.14, 0.15, 0.17, 0.2, 0.22, 0.25, 0.27, 0.3, 0.32, 0.35, 0.37, 0.4, 0.42, 0.45, 0.47, 0.5, 0.52, 0.55, 0.57, 0.6, 0.62, 0.65, 0.66, 0.67, 0.7, 0.72, 0.75, 0.77, 0.8 or any range between two of them.

[0219] When 0.12≤W1 / W2≤0.8, the comprehensive performance of the wall portion 213 is better. While ensuring that the wall portion 213 at the position of the notch groove 232 can be destroyed in time when the battery cell 20 has thermal runaway, the wall portion 213 at the position of the notch groove 232 is ensured to have sufficient strength during normal use of the battery cell 20.

[0220] In some embodiments, 0.2≤W1 / W2≤0.5.

[0221] W1 / W2 can be any one of 0.2, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.3, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.4, 0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.5, or a range between any two of them.

[0222] When 0.2≤W1 / W2≤0.5, the risk of the wall portion 213 being damaged at the position of the notched groove 232 under normal use conditions of the battery cell 20 is further reduced, and the wall portion 213 is ensured to be damaged in time at the position of the notched groove 232 when the battery cell 20 thermally runs away, thereby improving the timeliness of pressure relief.

[0223] In some embodiments, 0.02 mm ≤ W1 ≤ 1.6 mm.

[0224] W1 can be any one of 0.02mm, 0.03mm, 0.04mm, 0.05mm, 0.06mm, 0.1mm, 0.15mm, 0.2mm, 0.25mm, 0.3mm, 0.35mm, 0.4mm, 0.45mm, 0.5mm, 0.55mm, 0.6mm, 0.7mm, 0.75mm, 0.8mm, 0.85mm, 0.9mm, 0.95mm, 1mm, 1.05mm, 1.1mm, 1.15mm, 1.2mm, 1.25mm, 1.3mm, 1.35mm, 1.4mm, 1.42mm, 1.43mm, 1.45mm, 1.47mm, 1.5mm, 1.55mm, 1.6mm, or any range between any two of them.

[0225] When W1 is less than 0.02 mm, the scoring groove 232 is difficult to form, and during the forming process, the wall portion 213 is easily damaged at the scoring groove 232. When W1 is greater than 1.6 mm, the wall portion 213 at the scoring groove 232 is more difficult to be damaged during thermal runaway of the battery cell 20, and pressure relief is likely to be delayed.

[0226] Therefore, 0.02 mm ≤ W1 ≤ 1.6 mm, while reducing the difficulty of forming the notch groove 232 , the timeliness of pressure relief of the battery cell 20 during thermal runaway is improved.

[0227] In some embodiments, 0.06 mm ≤ W1 ≤ 0.4 mm.

[0228] W1 can be any point value among 0.06mm, 0.07mm, 0.08mm, 0.1mm, 0.15mm, 0.18mm, 0.2mm, 0.24mm, 0.25mm, 0.3mm, 0.35mm, 0.4mm, or a range value between any two of them.

[0229] When 0.06 mm ≤ W1 ≤ 0.4 mm, the difficulty of forming the notched groove 232 is further reduced, and the timeliness of pressure relief of the battery cell 20 during thermal runaway is improved.

[0230] In some embodiments, 1 mm ≤ W2 ≤ 5 mm.

[0231] W2 can be any point value among 1mm, 2mm, 3mm, 4mm, 5mm, or a range of values ​​between any two of them.

[0232] When W2>5mm, the wall 213 is thicker, the shell 21 uses more material, the shell 21 is heavier, and the economy is poor. When W2<1mm, the wall 213 is thinner, and the shell 21 has poor anti-deformation ability.

[0233] Therefore, 1mm≤W2≤5mm, so that the shell 21 has better economy and better anti-deformation ability.

[0234] In some embodiments, 1.2 mm ≤ W2 ≤ 3.5 mm.

[0235] W2 can be any point value among 1.2mm, 1.25mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm, 2mm, 2.1mm, 2.2mm, 2.3mm, 2.4mm, 2.5mm, 2.6mm, 2.7mm, 2.8mm, 2.9mm, 3mm, 3.1mm, 3.2mm, 3.3mm, 3.4mm, 3.5mm, or a range value between any two of them.

[0236] When 1.2 mm ≤ W2 ≤ 3.5 mm, the housing 21 has better economy and deformation resistance.

[0237] Furthermore, 2mm≤W2≤3mm.

[0238] Referring to Figures 12, 13, 14, 15, and 16, in some embodiments, the pressure relief mechanism 23 includes at least one primary groove 231, which is sequentially arranged on the wall portion 213 from the first surface 2131 to the second surface 2132. The first groove bottom wall 2312 of the primary groove 231 farthest from the first surface 2131 has an open area 23121. The average grain size of the wall portion 213 is G1, the average grain size of the second groove bottom wall 2311 of the primary groove 231 closest to the first surface 2131 is G2, and the average grain size of the first groove bottom wall 2312 at the location of the notched groove 232 is G3, satisfying the following: G1>G2>G3.

[0239] The average grain size measurement method can be found in the intercept method in GB 6394-2017 and will not be further described here. When measuring the average grain size of the first groove bottom wall 2312 at the location of the scored groove 232, the measurement can be performed along the thickness direction of the first groove bottom wall 2312 at the location of the scored groove 232; when measuring the average grain size of the wall portion 213, the measurement can be performed along the thickness direction of the wall portion 213.

[0240] For ease of measurement, the number of grains per unit area can also be used for characterization. When characterizing by the number of grains per unit area, the number of grains per unit area of ​​the wall portion 213 is less than the number of grains per unit area of ​​the second groove bottom wall 2311 , and the number of grains per unit area of ​​the second groove bottom wall 2311 is less than the number of grains per unit area of ​​the first groove bottom wall 2312 at the location of the scored groove 232 .

[0241] When the sinking groove 231 and the scoring groove 232 are formed by stamping or cold heading, the grains of the material are broken and become finer. Therefore, the average grain size of the first groove bottom wall 2312 at the scoring groove 232 position will be smaller than the average grain size of the second groove bottom wall 2311, and the average grain size of the second groove bottom wall 2311 will be smaller than the average grain size of the wall portion 213.

[0242] In some embodiments, G3 / G1 ≤ 0.9.

[0243] G3 / G1 can be any one of 0.01, 0.03, 0.04, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, or a range between any two of them.

[0244] G3 / G1≤0.9, the average grain size of the first groove bottom wall 2312 at the position of the notched groove 232 is significantly different from the average grain size of the wall portion 213. Reducing the average grain size of the first groove bottom wall 2312 at the position of the notched groove 232 can refine the grains of the first groove bottom wall 2312 at the position of the notched groove 232, improve the mechanical properties of the material of the first groove bottom wall 2312 at the position of the notched groove 232, further improve the toughness and fatigue resistance of the first groove bottom wall 2312 at the position of the notched groove 232, reduce the risk of the first groove bottom wall 2312 at the position of the notched groove 232 being damaged under normal use conditions of the battery cell 20, and increase the service life of the battery cell 20.

[0245] In some embodiments, G3 / G1 ≥ 0.05.

[0246] The inventors noticed that when G3 / G1 is less than 0.05, the difficulty of forming the sink groove 231 and the notched groove 232 increases, and the strength of the first groove bottom wall 2312 at the notched groove 232 position is too great. The first groove bottom wall 2312 at the notched groove 232 position is more difficult to be destroyed when the battery cell 20 thermally runs away, and it is easy to cause untimely pressure relief.

[0247] Therefore, G3 / G1≥0.05, which reduces the difficulty of forming the sink groove 231 and the notched groove 232 and improves the timeliness of pressure relief of the battery cell 20 during thermal runaway.

[0248] In some embodiments, 0.1≤G3 / G1≤0.5.

[0249] G3 / G1 can be any one of 0.1, 0.12, 0.15, 0.17, 0.2, 0.22, 0.25, 0.27, 0.3, 0.32, 0.35, 0.37, 0.4, 0.42, 0.45, 0.47, 0.5, or a range between any two of them.

[0250] When 0.1≤G3 / G1≤0.5, the comprehensive performance of the wall portion 213 is improved, ensuring that the first groove bottom wall 2312 can be destroyed in time at the position of the notched groove 232 when the battery cell 20 experiences thermal runaway, and ensuring that the first groove bottom wall 2312 at the position of the notched groove 232 has sufficient strength during normal use of the battery cell 20.

[0251] In some embodiments, 0.4 μm ≤ G3 ≤ 75 μm.

[0252] G3 can be any point value among 0.4μm, 0.5μm, 1μm, 2μm, 3μm, 4μm, 5μm, 10μm, 15μm, 16μm, 20μm, 25μm, 28μm, 30μm, 35μm, 36μm, 40μm, 45μm, 47.5μm, 48μm, 49μm, 50μm, 55μm, 60μm, 65μm, 70μm, 72μm, 75μm, or any range value between any two of them.

[0253] If G3 is greater than 75 μm, the toughness and fatigue resistance of the first groove bottom wall 2312 at the scored groove 232 location are poor. If G3 is less than 0.4 μm, the formation of the sink groove 231 and the scored groove 232 is more difficult, and the strength of the first groove bottom wall 2312 at the scored groove 232 location is too great, making it more difficult for the first groove bottom wall 2312 at the scored groove 232 location to be damaged during thermal runaway of the battery cell 20, and thus prone to delayed pressure relief. Therefore, if 0.4 μm ≤ G3 ≤ 75 μm, on the one hand, the formation difficulty of the sink groove 231 and the scored groove 232 is reduced, and the timely pressure relief of the battery cell 20 during thermal runaway is improved; on the other hand, the toughness and fatigue resistance of the first groove bottom wall 2312 at the scored groove 232 location are improved, reducing the risk of damage to the first groove bottom wall 2312 at the scored groove 232 location during normal use of the battery cell 20.

[0254] In some embodiments, 1 μm ≤ G3 ≤ 10 μm.

[0255] G3 can be any point value among 1μm, 1.5μm, 1.6μm, 2μm, 2.5μm, 2.6μm, 3μm, 3.3μm, 3.5μm, 3.6μm, 4μm, 4.5μm, 4.6μm, 5μm, 5.5μm, 5.6μm, 6μm, 6.5μm, 6.6μm, 6.7μm, 7μm, 7.5μm, 7.6μm, 8μm, 8.5μm, 8.6μm, 9μm, 9.5μm, 9.6μm, 10μm, or any range value between any two of them.

[0256] 1μm≤G3≤10μm, so that the comprehensive performance of the wall portion 213 is better, ensuring that the first groove bottom wall 2312 can be destroyed in time at the position of the notched groove 232 when the battery cell 20 thermally runs away, and ensuring that the first groove bottom wall 2312 at the position of the notched groove 232 has sufficient strength under normal use conditions of the battery cell 20.

[0257] In some embodiments, 10 μm ≤ G1 ≤ 150 μm.

[0258] G1 can be any point value among 10μm, 13μm, 14μm, 15μm, 20μm, 25μm, 30μm, 32μm, 35μm, 40μm, 45μm, 50μm, 55μm, 60μm, 65μm, 70μm, 75μm, 80μm, 85μm, 90μm, 95μm, 100μm, 105μm, 110μm, 115μm, 120μm, 125μm, 130μm, 135μm, 140μm, 145μm, 150μm, or any range value between any two of them.

[0259] In some embodiments, 30 μm ≤ G1 ≤ 100 μm.

[0260] G1 can be any point value among 30μm, 32μm, 35μm, 37μm, 40μm, 42μm, 45μm, 47μm, 50μm, 52μm, 55μm, 57μm, 60μm, 62μm, 65μm, 67μm, 70μm, 72μm, 75μm, 77μm, 80μm, 82μm, 85μm, 87μm, 90μm, 92μm, 95μm, 97μm, 100μm or any range value between any two of them.

[0261] In some embodiments, the minimum thickness of the first groove bottom wall 2312 at the position of the scoring groove 232 is W1. The average grain size of the first groove bottom wall 2312 at the position of the scoring groove 232 is G3, which satisfies: 1≤W1 / G3≤100.

[0262] When W1 / G3 is less than 1, in the thickness direction of the wall portion 213, the fewer the number of grain layers of the first groove bottom wall 2312 at the position of the notched groove 232, the lower the fatigue strength of the first groove bottom wall 2312 at the position of the notched groove 232; when W1 / G3 is greater than 100, in the thickness direction, the number of grain layers of the first groove bottom wall 2312 at the position of the notched groove 232 is too large, the strength of the first groove bottom wall 2312 at the position of the notched groove 232 is too large, and there is a risk that the first groove bottom wall 2312 at the position of the notched groove 232 may not be destroyed in time when the battery cell 20 thermally runs away. Therefore, 1≤W1 / G3≤100. On the one hand, the first groove bottom wall 2312 has more grain layers in the thickness direction at the notch groove 232 position, thereby improving the fatigue strength of the first groove bottom wall 2312 at the notch groove 232 position and reducing the risk of the first groove bottom wall 2312 at the notch groove 232 position being damaged under normal use conditions of the battery cell 20; on the other hand, the first groove bottom wall 2312 at the notch groove 232 position can be destroyed more promptly when the battery cell 20 thermally runs away, thereby achieving the purpose of timely pressure relief.

[0263] In some embodiments, 5≤W1 / G3≤20.

[0264] W1 / G3 can be any one of 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.4, 8.5, 8.8, 8.9, 9, 9.5, 9.6, 10, 10.5, 11, 11.4, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5, 20 or any range between two of them.

[0265] 5≤W1 / G3≤20. This improves the overall performance of the wall portion 213, ensuring that the first groove bottom wall 2312 can be destroyed in time at the position of the notched groove 232 when the battery cell 20 experiences thermal runaway. This ensures that the first groove bottom wall 2312 at the position of the notched groove 232 has sufficient fatigue resistance under normal use conditions of the battery cell 20, thereby improving the service life of the battery cell 20.

[0266] In some embodiments, the housing 21 includes a shell 212 and an end cover 211 . The shell 212 has an opening. The end cover 211 is connected to the shell 212 and closes the opening. The pressure relief mechanism 23 is disposed on the end cover 211 .

[0267] The pressure relief mechanism 23 is provided on the end cover 211 , and the end cover 211 is located at the lower portion of the housing 212 , corresponding to the scenario where the battery cell 20 is inverted.

[0268] In some embodiments, the housing 21 includes a shell 212 and an end cover 211 . The shell 212 has an opening. The end cover 211 is connected to the shell 212 and closes the opening. The pressure relief mechanism 23 is disposed in the shell 212 .

[0269] The pressure relief mechanism 23 is disposed in the housing 212 , and the pressure relief mechanism 23 is located at the lower portion of the housing 212 .

[0270] In some embodiments, along the first direction, both ends of the shell 212 have openings, and the housing 21 includes two end covers 211 , with one end cover 211 correspondingly closing one opening.

[0271] The features and performance of the present application are further described in detail below with reference to the embodiments.

[0272] In each embodiment and comparative example, the battery cell 20 is a square battery cell 20 , the end cap 211 in the battery cell 20 serves as the wall portion 213 , the capacity of the battery cell 20 is 150 Ah, and the chemical system is NCM.

[0273] 1. Test Method

[0274] (1) Minimum thickness test of the first groove bottom wall 2312 at the position of the scored groove 232 and the wall portion 213.

[0275] The wall portion 213 was cut into three sections, and the middle section was used as a specimen. The cross-sections at both ends of the specimen were located at the first groove bottom wall 2312 at the notched groove 232 and at the wall portion 213 where the recessed groove 231 was not formed. The cutting direction was perpendicular to the length of the opening 23121. After the middle section was polished to remove burrs, the specimen was placed on a three-dimensional coordinate measuring machine, and the thickness of the first groove bottom wall 2312 at the notched groove 232 and the wall portion 213 were measured on the cross-section.

[0276] (2) Test of the average grain size of the first groove bottom wall 2312 at the position of the scored groove 232 and the wall portion 213 .

[0277] The average grain size of the first groove bottom wall 2312 at the position of the notched groove 232 and the wall portion 213 is tested using the electron backscatter diffraction (EBSD) method. The wall portion 213 is cut into sections, and the middle section is taken as a sample. The cross-sections at both ends of the sample are the position of the first groove bottom wall 2312 at the notched groove 232 and the position of the wall portion 213 where the sink groove 231 is not opened. The cutting direction is perpendicular to the length direction of the opening area 23121, and the cutting equipment does not change the grain structure. The sample is then electropolished and fixed on a sample stage tilted at 70°. A suitable magnification is selected and an EBSD scan is performed using a scanning electron microscope (SEM) equipped with an electron backscatter diffraction (EBSD) accessory. Based on the scanning results, the average grain size (i.e., the equal area circle diameter of the complete grains in the inspection surface) is finally calculated.

[0278] (3) Hardness test of the first groove bottom wall 2312 at the position of the notched groove 232 and the wall portion 213 .

[0279] Cut the wall portion 213 into sections, take the middle section as the sample, and the cross-sections at both ends of the sample are the position of the first groove bottom wall 2312 at the notch groove 232 and the position where the wall portion 213 is not provided with the recessed groove 231. The cutting direction is perpendicular to the length direction of the opening area 23121. After the test section is polished to fully remove burrs, the sample is placed horizontally (the direction of the sample cross-section is parallel to the extrusion direction of the hardness tester) on the Brinell hardness tester for hardness measurement. If the width of the first groove bottom wall 2312 at the notch groove 232 is less than 1mm or the indenter size of the Brinell hardness tester is much larger than the width of the first groove bottom wall 2312 at the notch groove 232, a non-standard indenter should be processed for hardness measurement according to the Brinell hardness measurement and conversion principle.

[0280] (4) The cracking rate of the first groove bottom wall 2312 at the position of the notched groove 232 under normal use conditions of the battery cell 20 .

[0281] The battery cells 20 were placed at 25±2°C and cycled between 5% and 97% SOC. The internal gas pressure of the battery cells 20 was monitored, and 500 tests were performed simultaneously. The test cutoff conditions were: the battery cell 20 lifespan decreased to 80% SOH, or any group of battery cells 20 exhibited cracking of the first tank bottom wall 2312 at the notched groove 232 during cycling. The criterion for cracking of the first tank bottom wall 2312 at the notched groove 232 was: a decrease in the internal gas pressure of the battery cell 20 greater than 10% of the maximum gas pressure. The crack rate of the first tank bottom wall 2312 at the notched groove 232 was calculated as follows: number of cracks / total number of cracks*100%.

[0282] (5) The explosion rate of the battery cell 20 during thermal runaway.

[0283] A small heating film was built into each battery cell 20. The heating film was energized to heat the battery cell 20 until thermal runaway occurred. The battery cell 20 was observed to see if it exploded. This test was repeated 500 times, and the explosion rate of the battery cells 20 was calculated: explosion rate = number of explosions / total number of explosions * 100%.

[0284] 2. Test Results

[0285] In each embodiment and comparative example, the test results of the minimum thickness W1 of the first groove bottom wall 2312 at the position of the scored groove 232, the minimum thickness W2 of the wall portion 213, the average grain size G3 of the first groove bottom wall 2312 at the position of the scored groove 232, the average grain size G1 of the wall portion 213, the hardness E3 of the first groove bottom wall 2312 at the position of the scored groove 232, and the hardness E1 of the wall portion 213 are shown in Table 1. In Table 1, the units of W1 and W2 are mm, the units of G3 and G1 are mm, and the units of E3 and E1 are HBW; the cracking rate Q1 of the first groove bottom wall 2312 at the position of the scored groove 232 under normal use conditions of the battery cell 20 and the explosion rate Q2 of the battery cell 20 during thermal runaway are shown in Table 2.

[0286] Table 1

[0287] Table 2

[0288] Combining Tables 1 and 2, a comparison of Examples 1-8 with Comparative Example 1 shows that when W1 / W2 > 0.95, the explosion rate of the battery cell 20 during thermal runaway is high, exceeding 12%. Comparing Examples 1-8 with Comparative Example 2 shows that when W1 / W2 < 0.05, the cracking rate of the first groove bottom wall 2312 at the scored groove 232 under normal battery cell 20 use conditions is high, exceeding 12%. A ratio of 0.05 ≤ W1 / W2 ≤ 0.95 reduces the risk of rupture of the first groove bottom wall 2312 at the scored groove 232 under normal battery cell 20 use conditions and allows for timely pressure relief through the first groove bottom wall 2312 at the scored groove 232 during thermal runaway, reducing the risk of battery cell 20 explosion. It can be seen from Examples 2 to 7 that when 0.12≤W1 / W2≤0.8, the overall performance of the battery cell 20 is better, the cracking rate of the first groove bottom wall 2312 at the notched groove 232 position under normal use conditions of the battery cell 20 and the explosion rate of the battery cell 20 during thermal runaway are both low, and 0.2≤W1 / W2≤0.5, the effect is better.

[0289] According to Examples 10 to 15, when G3 / G1 ≤ 0.9, the cracking rate of the first groove bottom wall 2312 at the scored groove 232 under normal use conditions of the battery cell 20 is low. In Example 9, when G3 / G1 > 0.9, the cracking rate of the first groove bottom wall 2312 at the scored groove 232 under normal use conditions of the battery cell 20 is significantly increased. Comparing Examples 10 to 15 with Example 9, it can be seen that controlling G3 / G1 to no more than 0.9 can effectively reduce the risk of damage to the first groove bottom wall 2312 at the scored groove 232 under normal use conditions of the battery cell 20, thereby increasing the service life of the battery cell 20.

[0290] According to Example 15, when G3 / G1 is less than 0.05, the first groove bottom wall 2312 becomes more difficult to destroy at the scored groove 232 location during thermal runaway of the battery cell 20. If pressure relief is not timely, the risk of battery cell 20 explosion is significantly increased. Comparing Examples 9 to 14 with Example 15, it can be seen that controlling G3 / G1 to no less than 0.5 can effectively reduce the explosion rate of the battery cell 20 during thermal runaway. When 0.1 ≤ G3 / G1 ≤ 0.5, the cracking rate of the first groove bottom wall 2312 at the scored groove 232 location under normal battery cell 20 use conditions and the explosion rate of the battery cell 20 during thermal runaway are both low. This ensures that the first groove bottom wall 2312 at the scored groove 232 location can be destroyed promptly during thermal runaway of the battery cell 20, ensuring that the first groove bottom wall 2312 at the scored groove 232 location has sufficient strength under normal battery cell 20 use conditions.

[0291] Comparing Examples 17-21 with Example 16, it can be seen that when 1 ≤ W1 / G3 ≤ 100, the battery cell 20 can promptly release pressure during thermal runaway, and the explosion rate of the battery cell 20 is low. When 5 ≤ W1 / G3 ≤ 20, the overall performance of the battery cell 20 is even better, with the cracking rate of the first groove bottom wall 2312 at the scored groove 232 under normal use conditions of the battery cell 20 and the explosion rate of the battery cell 20 during thermal runaway both being low.

[0292] Comparing Examples 23-27 with Example 22 shows that when E3 / W1>10,000 HBW / mm, the cracking rate of the first groove bottom wall 2312 at the scored groove 232 under normal use conditions of the battery cell 20 is high. Comparing Examples 23-27 with Example 28 shows that when E3 / W1<5 HBW / mm, the explosion rate of the battery cell 20 during thermal runaway is high. While 5 HBW / mm≤E3 / W1≤10,000 HBW / mm can reduce the risk of rupture of the first groove bottom wall 2312 at the scored groove 232 under normal use conditions of the battery cell 20, it can also provide timely pressure relief through the first groove bottom wall 2312 at the scored groove 232 during thermal runaway of the battery cell 20, reducing the risk of explosion of the battery cell 20. It can be seen from Examples 24 to 25 that when 190HBW / mm≤E3 / W1≤4000HBW / mm, the overall performance of the battery cell 20 is better, and the cracking rate of the first groove bottom wall 2312 at the position of the notched groove 232 under normal use conditions of the battery cell 20 and the explosion rate of the battery cell 20 during thermal runaway are both low.

[0293] Comparing Examples 29-30 with Examples 31-32, it can be seen that when E3 / E1 ≤ 1, the cracking rate of the first groove bottom wall 2312 at the location of the notched groove 232 under normal use conditions of the battery cell 20 is high. However, when E3 / E1 > 1, the cracking rate of the first groove bottom wall 2312 at the location of the notched groove 232 under normal use conditions of the battery cell 20 is effectively reduced. Comparing Example 30 with Example 29, it can be seen that when E3 / E1 > 5, the explosion rate of the battery cell 20 during thermal runaway is high. However, when E3 / E1 ≤ 5, the risk of explosion of the battery cell 20 is reduced.

[0294] The embodiment of the present application further provides a battery 100 , comprising the above-mentioned battery cell 20 .

[0295] An embodiment of the present application further provides an electrical device, comprising the above-mentioned battery 100, and the battery 100 is used to provide electrical energy to the electrical device.

[0296] According to some embodiments of the present application, please refer to Figures 3 to 14.

[0297] An embodiment of the present application provides a battery cell 20, which includes an electrode assembly 22, a shell 21 and a pressure relief mechanism 23. The shell 21 is used to accommodate the electrode assembly 22. The shell 21 has a wall portion 213 that supports the electrode assembly 22 in the direction of gravity. The pressure relief mechanism 23 is arranged on the wall portion 213 and is integrally formed with the wall portion 213. When the battery cell 20 is in normal use, the pressure relief mechanism 23 is located at the lower part of the shell 21. Compared with the prior art in which the pressure relief mechanism 23 is welded to the end cover 211, the present application integrally forms the pressure relief mechanism 23 with the wall portion 213, thereby avoiding leakage caused by welding defects. In addition, the ability of the pressure relief mechanism 23 to resist external impact can also be improved. At the same time, since the electrolyte in the shell 21 will cause creep or impact on the pressure relief mechanism 23, integrally forming the pressure relief mechanism 23 and the wall portion 213 can improve the rigidity of the pressure relief mechanism 23, so that the pressure relief mechanism 23 has a stronger resistance to the creep and impact of the electrolyte, which is beneficial to improving the life of the pressure relief mechanism 23 and reducing the risk of leakage of the pressure relief mechanism 23.

[0298] The wall portion 213 has a first surface 2131 and a second surface 2132 disposed opposite each other along its thickness. The pressure relief mechanism 23 includes a scored groove 232 and at least one primary recessed groove 231. The at least one primary recessed groove 231 and the scored groove 232 are sequentially arranged along the wall portion 213 from the first surface 2131 to the second surface 2132. The first groove bottom wall 2312 of the primary recessed groove 231, which is furthest from the first surface 2131, has an opening 23121. The scored groove 232 is disposed along the edge of the opening 23121, and the opening 23121 is configured to be openable with the scored groove 232 as the boundary. At least one level of recessed grooves 231 and scored grooves 232 are sequentially arranged on the wall portion 213 from the first surface 2131 to the second surface 2132. During molding, the recessed grooves 231 and scored grooves 232 can be formed step by step, thereby reducing the molding force on the wall portion 213 and the risk of cracks in the wall portion 213. The pressure relief mechanism 23 is less likely to fail due to cracks in the locations where the scored grooves 232 are arranged, thereby improving the long-term reliability of the pressure relief device. In addition, when forming the recessed grooves 231 and scored grooves 232, stamping or cold heading methods can be used. In this way, the groove walls of the recessed grooves 231 and scored grooves 232 undergo cold work hardening (changing the grain arrangement, resulting in lattice distortion, reducing the metal's plasticity, and increasing the material's hardness). This enhances their ability to resist external impact and makes them less susceptible to damage from external impact. This helps reduce the risk of leakage from the pressure relief mechanism 23.

[0299] The wall portion 213 partially protrudes from the second surface 2132 away from the first surface 2131 to form a reinforcement portion 2133. The reinforcement portion 2133 surrounds the first groove bottom wall 2312. By having the wall portion 213 partially protrude from the second surface 2132 away from the first surface 2131 to form the reinforcement portion 2133, when the wall portion 213 deforms, the reinforcement portion 2133 can reduce the impact of the deformation on the scored groove 232, thereby reducing the risk of leakage from the pressure relief mechanism 23.

[0300] The opening area 23121 curves from the second surface 2132 to the first surface 2131. When the opening area 23121 curves from the second surface 2132 to the first surface 2131, gas within the battery cell 20 acts on the opening area 23121, generating a pulling force on the first tank bottom wall 2312 at the location of the scored groove 232. This facilitates the opening of the first tank bottom wall 2312 at the location of the scored groove 232. Under the same burst pressure, the depth of the scored groove 232 can be shallower, and the thickness of the first tank bottom wall 2312 at the location of the scored groove 232 can be greater. This makes the first tank bottom wall 2312 less susceptible to external interference and thus reduces the risk of leakage from the pressure relief mechanism 23. However, when the electrolyte acts on the opening area 23121, the force exerted is relatively small. Although it generates a pulling force on the first tank bottom wall 2312 at the location of the scored groove 232, it is insufficient to cause the scored groove 232 to open. In addition, the pulling force generated on the bottom wall 2312 of the first groove at the position of the notched groove 232 disperses the force of the electrolyte, making the amplitude of the opening area 23121 smaller, and the pressure relief mechanism 23 is not easily opened under the action of the electrolyte, thereby reducing the risk of leakage of the pressure relief mechanism 23.

[0301] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A battery cell, in, include: Electrode assembly; A housing for accommodating the electrode assembly; The pressure relief mechanism is arranged at the lower part of the shell and is integrally formed with the shell.

2. The battery cell according to claim 1, in, The pressure relief mechanism is arranged below the mid-vertical plane of the shell which is perpendicular to the height direction thereof.

3. The battery cell according to claim 2, in, The shell has a wall portion supporting the electrode assembly in the direction of gravity, and the pressure relief mechanism is disposed on the wall portion and is integrally formed with the wall portion.

4. The battery cell according to any one of claims 1 to 3, in, The housing comprises a wall portion, the pressure relief mechanism is arranged on the wall portion, and the wall portion has an opening area; The wall portion has a first surface and a second surface arranged opposite to each other in the thickness direction thereof; The pressure relief mechanism comprises a notched groove, which is recessed from the first surface to the second surface, and is arranged along an edge of the opening area. The opening area is configured to be able to be opened with the notched groove as a boundary.

5. The battery cell according to claim 4, in, The pressure relief mechanism comprises at least one level of sink grooves, and the at least one level of sink grooves are sequentially arranged on the wall portion along a direction from the first surface to the second surface; The first bottom wall of the first sink at the level farthest from the first surface has the opening area.

6. The battery cell according to claim 5, in, The pressure relief mechanism includes two levels of sink grooves, which are arranged in sequence from the first surface to the second surface. The first level of sink grooves is arranged on the first surface, and the other level of sink grooves is arranged on the bottom surface of the first level of sink grooves. The notched grooves are arranged on the bottom surface of the other level of sink grooves.

7. The battery cell according to any one of claims 4 to 6, in, The pressure relief mechanism comprises a plurality of scored grooves, and the plurality of scored grooves are sequentially arranged along a direction from the first surface to the second surface; In two adjacent levels of the scoring grooves, the scoring groove of the first level away from the first surface is arranged on the bottom surface of the scoring groove of the first level close to the first surface.

8. The battery cell according to any one of claims 4 to 7, in, Along the thickness direction, a surface of the opening area away from the first surface is flush with the second surface.

9. The battery cell according to any one of claims 4 to 7, in, The wall portion partially protrudes from the second surface in a direction away from the first surface to form a reinforcement portion; The reinforcement portion is arranged around the opening area.

10. The battery cell according to claim 9, in, Along the thickness direction, a surface of the opening area away from the first surface is flush with a surface of the reinforcement portion away from the first surface.

11. The battery cell according to claim 9 or 10, in, Along the thickness direction, the height of the reinforcing portion protruding from the second surface is A, satisfying: 0.5 mm ≤ A ≤ 4 mm.

12. The battery cell according to claim 11, in, 1mm≤A≤2.5mm.

13. The battery cell according to any one of claims 4 to 12, in, The opening area is bent along the thickness direction.

14. The battery cell according to claim 13, in, The opening area is bent along a direction from the second surface to the first surface.

15. The battery cell according to claim 13 or 14, in, The pressure relief mechanism comprises at least one level of sink grooves, which are sequentially arranged on the wall portion along the direction from the first surface to the second surface, and the first groove bottom wall of the first level of the sink groove farthest from the first surface has the opening area; The first groove bottom wall comprises a body area, the body area is arranged around the opening area, and the notched groove is arranged between the opening area and the body area; Along the thickness direction, the main body area has a third surface and a fourth surface, the distance between the third surface and the fourth surface is B, the opening area has a fifth surface away from the second surface, the third surface and the fifth surface are located on the same side of the bottom wall of the first groove, the maximum distance between the third surface and the fifth surface is C, satisfying: B / 10≤C≤B.

16. The battery cell according to any one of claims 4 to 15, in, The first surface is an outer surface of the wall portion.

17. The battery cell according to any one of claims 4 to 16, in, The pressure relief mechanism comprises at least one level of sink grooves, which are sequentially arranged on the wall portion along the direction from the first surface to the second surface, and the first groove bottom wall of the first level of the sink groove farthest from the first surface has the opening area; The strength of the wall is D 1 The second bottom wall strength of the first level of the sink closest to the first surface is D 2 , the strength of the bottom wall of the first groove at the position of the notched groove is D 3 , satisfied: D 3 >D 2 ≥D 1 ; and / or The hardness of the wall is E 1 , the hardness of the bottom wall of the second groove is E 2 The hardness of the bottom wall of the first groove at the position of the notched groove is E 3 , satisfying: E 3 >E 2 ≥E 1 ; and / or The stiffness of the wall is F 1 , the stiffness of the bottom wall of the second groove is F 2 , the stiffness of the bottom wall of the first groove at the position of the notched groove is F 3 , satisfying: F 3 >F 2 ≥F 1 .

18. The battery cell according to claim 17, in, 1.2E 1 ≤E 2 ≤2.5E 1 。 19. The battery cell according to claim 17, in, 2.5E 1 <E 3 ≤5E 1 。 20. The battery cell according to any one of claims 17 to 19, in, 5HBW≤E 1 ≤150HBW。 21. The battery cell according to any one of claims 17 to 20, in, 5HBW≤E 3 ≤200HBW。 22. The battery cell according to any one of claims 17 to 21, in, The minimum thickness of the bottom wall of the first groove at the position of the notched groove is W 1 , meet: 5HBW / mm≤E 3 / W 1 ≤10000HBW / mm; preferably, 190HBW / mm≤E 3 / W 1 ≤4000HBW / mm.

23. The battery cell according to any one of claims 4 to 22, in, The minimum thickness of the wall at the position of the notch groove is W 1 , the minimum thickness W of the wall 2 , satisfying: 0.05≤W 1 / W 2 ≤0.

95.

24. The battery cell according to claim 23, in, 0.12≤W 1 / W 2 ≤0.8; preferably, 0.2≤W 1 / W 2 ≤0.

5.

25. The battery cell according to claim 23 or 24, in, 0.02mm≤W 1 ≤1.6mm; preferably, 0.06mm≤W 1 ≤0.4mm.

26. The battery cell according to any one of claims 23 to 25, in, 1mm≤W 2 ≤5mm; preferably, 1.2mm≤W 2 ≤3.5mm; preferably, 2mm≤W 2 ≤3mm.

27. The battery cell according to any one of claims 4 to 26, in, The pressure relief mechanism comprises at least one level of sink grooves, which are sequentially arranged on the wall portion along the direction from the first surface to the second surface, and the first groove bottom wall of the first level of the sink groove farthest from the first surface has the opening area; The average grain size of the wall is G 1 The average grain size of the second bottom wall of the first level of the sink closest to the first surface is G 2 The average grain size of the first groove bottom wall at the position of the notched groove is G 3 , satisfying: G 1 >G 2 >G 3 .

28. The battery cell according to claim 27, in, G 3 / G 1 ≤0.9。 29. The battery cell according to claim 28, in, G 3 / G 1 ≥0.05; preferably, 0.1≤G 3 / G 1 ≤0.

5.

30. The battery cell according to any one of claims 27 to 29, in, 0.4μm≤G 3 ≤75μm; preferably, 1μm≤G 3 ≤10μm.

31. The battery cell according to any one of claims 27 to 30, in, 10μm≤G 1 ≤150μm; preferably, 30μm≤G 1 ≤100μm.

32. The battery cell according to any one of claims 27 to 31, in, The minimum thickness of the bottom wall of the first groove at the position of the notched groove is W 1 ; The average grain size of the first groove bottom wall at the position of the notched groove is G 3 , satisfying: 1≤W 1 / G 3 ≤100; preferably, 5≤W 1 / G 3 ≤20.

33. The battery cell according to any one of claims 1 to 32, in, The housing comprises a shell and an end cover, the shell has an opening, the end cover is connected to the shell and closes the opening, and the pressure relief mechanism is arranged on the end cover.

34. The battery cell according to any one of claims 1 to 33, in, The housing comprises a shell and an end cover, the shell has an opening, the end cover is connected to the shell and closes the opening, and the pressure relief mechanism is arranged on the shell.

35. The battery cell according to claim 34, in, Along the first direction, both ends of the shell have openings, and the shell includes two end covers, and one end cover correspondingly closes one opening.

36. A battery, in, Comprising a battery cell according to any one of claims 1-35.

37. An electrical device, in, The battery according to claim 36 is used to provide electrical energy to the electrical device.

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