Battery monomer, battery device and electric device

Abstract

The utility model provides a battery monomer, a battery device and a power utilization device, and belongs to the technical field of batteries. The battery monomer comprises a shell, an electrode assembly and a pressure relief mechanism, the pressure relief mechanism is arranged on the wall part of the shell and comprises a connecting part, a weak part and a pressure relief part, the connecting part is connected with the wall part, the weak part is arranged around the pressure relief part, the weak part is connected with the connecting part and the pressure relief part, the pressure relief part is provided with at least one strip-shaped thinning area, and the minimum thickness of the thinning area is larger than that of the weak part. In a projection plane perpendicular to the thickness direction of the wall part, the position, closest to the geometric center of the orthographic projection of the pressure relief part, of the orthographic projection of the thinning area is a first position, and the position, farthest from the geometric center of the orthographic projection of the pressure relief part, of the orthographic projection of the thinning area is a second position; the minimum thickness of the thinning area at the first position is larger than the minimum thickness of the thinning area at the second position. The battery monomer can relieve the phenomenon that the detonation position of the pressure relief mechanism appears in a thinning area.

Description

Technical Field

[0001] This application relates to the field of battery technology, and more specifically, to a battery cell, a battery device, and an electrical device. Background Technology

[0002] In recent years, new energy vehicles have experienced rapid development. In the field of electric vehicles, power batteries, as the power source, play an irreplaceable and crucial role. With the vigorous promotion of new energy vehicles, the demand for power battery products is also increasing. Among them, battery devices, as core components of new energy vehicles, have high requirements in terms of reliability and service life.

[0003] In battery technology, to ensure the safety of individual battery cells, a pressure relief mechanism is typically installed on the casing of each cell to release internal pressure. This mechanism is activated to release the pressure when the internal pressure or temperature reaches a threshold. However, existing battery cells have a low pressure relief rate in the event of thermal runaway, which poses a risk of fire and explosion due to delayed pressure relief, resulting in low reliability of the battery cells. Utility Model Content

[0004] This application provides a battery cell, a battery device, and an electrical device, which can effectively improve the reliability of the battery cell.

[0005] In a first aspect, embodiments of this application provide a battery cell, including a housing, an electrode assembly, and a pressure relief mechanism; the housing has a wall portion; the electrode assembly is housed within the housing; the pressure relief mechanism is disposed on the wall portion, the pressure relief mechanism includes a connecting portion, a weak portion, and a pressure relief portion, the connecting portion being connected to the wall portion, the weak portion surrounding the pressure relief portion and connecting the connecting portion and the pressure relief portion, the weak portion being configured to be at least partially destroyed to release the pressure when the pressure inside the housing reaches a threshold, the pressure relief portion having at least one thinning region, the thinning region being strip-shaped, the minimum thickness of the thinning region being greater than the minimum thickness of the weak portion; wherein, in a projection plane perpendicular to the thickness direction of the wall portion, the position of the orthographic projection of the thinning region closest to the geometric center of the orthographic projection of the pressure relief portion is a first position, the position of the orthographic projection of the thinning region furthest from the geometric center of the orthographic projection of the pressure relief portion is a second position, the minimum thickness of the thinning region at the first position is greater than the minimum thickness of the thinning region at the second position.

[0006] In the above technical solution, a pressure relief mechanism is provided on the wall of the outer casing. The pressure relief mechanism has a weak part, which is configured to be at least partially destroyed to release pressure when the pressure inside the outer casing reaches a threshold. The pressure relief part located inside the weak part forms a strip-shaped weak area, thereby reducing the structural strength of the pressure relief part. This allows the pressure relief part to release stress through deformation during the cyclical changes in gas pressure inside the battery cell, enabling the pressure relief mechanism to "breathe." This helps mitigate the risk of fatigue cracking of the weak part of the pressure relief mechanism during use. Specifically, by setting the minimum thickness of the first position of the thinning zone closest to the center of the pressure relief part to be greater than the minimum thickness of the first position of the thinning zone furthest from the center of the pressure relief part... The minimum thickness structure at the two positions results in greater structural strength at the first position of the thinning zone closest to the center of the pressure relief section. This increases the structural strength of the area near the pressure relief section where the deformation is greatest during use. This allows the pressure relief section to release stress through deformation, reducing premature cracking of weak points. It also mitigates the phenomenon of cracking at the first position of the thinning zone near the center of the pressure relief section during thermal runaway of the battery cell. This reduces the likelihood of the pressure relief mechanism's explosion point occurring in the thinning zone, effectively alleviating the problem of insufficient pressure relief area during pressure relief. This helps reduce the risk of fire and explosion caused by untimely pressure relief, thus improving the reliability of the battery cell.

[0007] In some embodiments, the minimum thickness of the thinning region within the cross-section gradually increases from the second position to the first position along the extension direction of the thinning region.

[0008] In the above technical solution, by setting the minimum thickness of the thinning zone in the cross-section to gradually increase from the second position to the first position along the extension direction of the thinning zone, it is convenient to form thinning zones of different thicknesses, so that the thinning zone has a greater structural strength as it gets closer to the center of the pressure relief part. This also helps to reduce the molding difficulty of the thinning zone, thereby reducing the manufacturing difficulty of the pressure relief mechanism. On the other hand, it makes the thinning zone have a greater structural strength as it gets closer to the center of the pressure relief part, so that the thinning zone has a greater structural strength as it gets closer to the area of ​​the pressure relief part where the deformation is the greatest during use. This further alleviates the phenomenon that the area of ​​the thinning zone closer to the center of the pressure relief part is more prone to cracking when the battery cell experiences thermal runaway, thereby further reducing the risk that the explosion point of the pressure relief mechanism will occur in the thinning zone.

[0009] In some embodiments, the thinning region is connected to the weak portion at both ends in its extension direction.

[0010] In the above technical solution, by setting both ends of the thinning zone in its extension direction to be connected to the weak part, on the one hand, it is convenient to form the thinning zone and the weak part on the pressure relief mechanism, which helps to reduce the processing difficulty of the pressure relief mechanism. On the other hand, the thinning zone can divide the pressure relief part located inside the weak part into multiple areas, which helps to further improve the effect of the pressure relief part in releasing stress through deformation during the cyclic change of gas pressure inside the battery cell, so as to further alleviate the risk of fatigue cracking of the weak part of the pressure relief mechanism during use.

[0011] In some embodiments, the thinning region includes two interconnected first segments, the connection point of the two first segments is the first position, and the connection point of the first segment with the weak portion is the second position; wherein, along the extension direction of the thinning region, the lengths of the two first segments are equal.

[0012] In the above technical solution, by setting the two first segments formed by the first position as the boundary of the thinning area as a structure of equal length, and the other end of the two first segments are connected to the weak part, the shape regularity of the thinning area can be improved, which is conducive to reducing the processing difficulty of the thinning area. On the other hand, it can further improve the effect of the pressure relief part in releasing stress through deformation during the cyclic change of gas pressure inside the battery cell.

[0013] In some embodiments, the orthographic projection of the thinning region extends along an arc trajectory in a projection plane perpendicular to the thickness direction of the wall portion.

[0014] In the above technical solution, by setting the orthographic projection of the thinning area in the projection plane perpendicular to the thickness direction of the wall as a structure extending along an arc trajectory, the thinning area is a strip structure extending along an arc trajectory. With the structural strength of the pressure relief part, the pressure relief part can release stress through deformation during the cyclic change of gas pressure inside the battery cell, thereby mitigating the risk of fatigue cracking of the weak part of the pressure relief mechanism during use.

[0015] In some embodiments, the pressure relief portion is provided with two thinning regions, which are arranged opposite to each other along a first direction. In a projection plane perpendicular to the thickness direction of the wall portion, the geometric center of the orthographic projection of the pressure relief portion is located between the orthographic projections of the two thinning regions in the first direction, which is perpendicular to the thickness direction of the wall portion.

[0016] In the above technical solution, by setting two thinning zones that are arranged opposite each other along the first direction on the pressure relief part, and setting the geometric center of the pressure relief part to be located between the two thinning zones in the first direction, the pressure relief part can release stress through deformation during the cyclic change of gas pressure inside the battery cell. At the same time, it can also make the two thinning zones far away from the area of ​​the pressure relief part with the greatest degree of deformation during use. This helps to alleviate the fatigue phenomenon of the thinning zone. In the event of thermal runaway of the battery cell, it can reduce the phenomenon that the explosion point of the pressure relief mechanism is located in the thinning zone. This helps to reduce the risk of fire and explosion caused by untimely pressure relief of the pressure relief mechanism, thereby improving the reliability of the battery cell.

[0017] In some embodiments, the weak portion includes two straight segments and two curved segments. The two straight segments are arranged opposite each other along a first direction and extend along a second direction. The two curved segments are arranged opposite each other along the second direction and extend along a curved trajectory. One straight segment, one curved segment, another straight segment, and another curved segment are connected end to end in sequence. The first direction, the second direction, and the thickness direction of the wall are perpendicular to each other. The thinning region is connected to the two curved segments at both ends in its extension direction; or, the thinning region is connected to the same straight segment at both ends in its extension direction.

[0018] In the above technical solution, by connecting the two ends of the thinning region in its extension direction to the two arc segments of the weak part, the thinning region can divide the pressure relief part located inside the weak part into multiple regions and expand the length of the thinning region. This is beneficial to further improve the stress release effect of the pressure relief part through deformation during the cyclic change of gas pressure inside the battery cell, thereby further mitigating the risk of fatigue cracking of the weak part of the pressure relief mechanism during use. Similarly, by connecting the two ends of the thinning region in its extension direction to the same straight line segment, on the one hand, the thinning region can divide the pressure relief part located inside the weak part into multiple regions, which is beneficial to further improve the stress release effect of the pressure relief part through deformation during the cyclic change of gas pressure inside the battery cell, thereby further mitigating the risk of fatigue cracking of the weak part of the pressure relief mechanism during use. On the other hand, it is easier to form the thinning region and the weak part on the pressure relief mechanism, which helps to reduce the processing difficulty of the pressure relief mechanism.

[0019] In some embodiments, the thinning region includes a plurality of thinning segments connected in sequence; wherein, in a projection plane perpendicular to the thickness direction of the wall portion, the orthographic projection of at least one of the thinning segments extends along an arc trajectory, and the orthographic projection of at least one of the thinning segments extends along a straight trajectory.

[0020] In the above technical solution, by setting the thinning area as a structure including multiple thinning segments connected in sequence, and in the projection plane perpendicular to the thickness direction of the wall, the orthographic projection of at least one of the multiple thinning segments is set as a structure extending along an arc trajectory, and the orthographic projection of at least one thinning segment is set as a structure extending along a straight trajectory, so as to form a thinning area with strip structure of different shapes, which is beneficial to pressure relief mechanism applicable to different structures.

[0021] In some embodiments, the thinning region comprises three thinning segments; wherein, in a projection plane perpendicular to the thickness direction of the wall portion, the orthographic projection of the middle thinning segment extends along an arc trajectory, and the orthographic projection of the two end thinning segments extends along a straight trajectory.

[0022] In the above technical solution, by setting the thinning section of the thinning area to three, and in the projection plane perpendicular to the thickness direction of the wall, the orthographic projection of the middle thinning section is a structure extending along an arc trajectory, and the orthographic projection of the thinning sections at both ends is a structure extending along a straight trajectory, it is beneficial to improve the regularity of the shape of the thinning area and reduce the forming difficulty of thinning, thereby reducing the processing difficulty of the pressure relief mechanism.

[0023] In some embodiments, the thinning region includes a plurality of thinning segments connected in sequence; wherein, in a projection plane perpendicular to the thickness direction of the wall portion, the orthographic projection of the thinning segment extends along a straight trajectory, and the extension directions of the orthographic projections of two connected thinning segments intersect.

[0024] In the above technical solution, by setting the thinning zone as a structure including multiple thinning segments connected in sequence, in the projection plane perpendicular to the thickness direction of the wall, the thinning segments are structures that extend along a straight trajectory, and the extension directions of the orthographic projections of each two adjacent thinning segments are intersecting structures, so as to form a thinning zone with a broken line shape, which is beneficial for pressure relief mechanisms with different structures.

[0025] In some embodiments, the thinning region comprises two thinning segments.

[0026] In the above technical solution, by setting the thinning section of the thinning zone as two, the two thinning sections are connected and their extension directions intersect to form a thinning zone with a "V"-shaped structure. The structure is simple and easy to manufacture, which helps to reduce the manufacturing difficulty of the pressure relief mechanism.

[0027] In some embodiments, the orthographic projection of the thinning region extends along a straight trajectory in a projection plane perpendicular to the thickness direction of the wall portion.

[0028] In the above technical solution, by setting the extension direction of the orthogonal projection of the thinning area in the projection plane perpendicular to the thickness direction of the wall to extend along a straight trajectory, it is easier to form the thinning area on the pressure relief part, which helps to reduce the processing difficulty of the pressure relief mechanism.

[0029] In some embodiments, there are multiple thinning regions. In a projection plane perpendicular to the thickness direction of the wall portion, the orthographic projections of the multiple thinning regions intersect at the connecting region, and the geometric center of the orthographic projection of the pressure relief portion is located within the connecting region.

[0030] In the above technical solution, by setting the intersection of the orthographic projections of multiple thinning zones in the projection plane perpendicular to the thickness direction of the wall to coincide with the geometric center of the orthographic projection of the pressure relief part in the projection plane perpendicular to the thickness direction of the wall, the first positions of multiple thinning zones are all located at the same position, so that the positions with larger minimum thicknesses of multiple thinning zones are all located at the geometric center of the orthographic projection of the pressure relief part in the projection plane perpendicular to the thickness direction of the wall. This helps to reduce the forming difficulty of multiple thinning zones and reduce the processing difficulty of the pressure relief mechanism.

[0031] In some embodiments, in a projection plane perpendicular to the thickness direction of the wall portion, the orthographic projection of the thinning region passes through the geometric center of the orthographic projection of the pressure relief portion.

[0032] In the above technical solution, by setting the orthographic projection of the thinning area in the projection plane perpendicular to the thickness direction of the wall to pass through the geometric center of the orthographic projection of the pressure relief part, the geometric center of the orthographic projection of the pressure relief part is located within the orthographic projection of the thinning area in the projection plane perpendicular to the thickness direction of the wall. This enables the first position of the thinning area to coincide with the geometric center of the orthographic projection of the thinning area and the pressure relief part, which facilitates the processing and manufacturing of the thinning area and helps to reduce the manufacturing difficulty of the pressure relief mechanism.

[0033] In some embodiments, in a projection plane perpendicular to the thickness direction of the wall portion, the orthographic projection of the thinning region does not pass through the geometric center of the orthographic projection of the pressure relief portion.

[0034] In the above technical solution, in the projection plane perpendicular to the thickness direction of the wall, by setting the orthographic projection of the thinning area to the geometric center that does not pass through the orthographic projection of the pressure relief part, the thinning area can be far away from the area of ​​the pressure relief part with the greatest deformation during use. This helps to alleviate the fatigue phenomenon of the thinning area, thereby reducing the risk of further weakening of the structural strength of the thinning area. When the battery cell experiences thermal runaway, it can further alleviate the phenomenon that the explosion position of the pressure relief mechanism appears in the thinning area. In addition, it can further alleviate the phenomenon that the pressure relief mechanism has insufficient pressure relief area during pressure relief. This helps to further reduce the risk of fire and explosion caused by untimely pressure relief, thereby further improving the reliability of the battery cell.

[0035] In some embodiments, the minimum thickness of the weak portion is D1, the minimum thickness of the thinning zone is D2, and in a projection plane perpendicular to the thickness direction of the wall portion, the minimum distance between the geometric center of the orthographic projection of the pressure relief portion and the orthographic projection of the thinning zone is L1, and the maximum distance between the geometric center of the orthographic projection of the pressure relief portion and the orthographic projection of the weak portion is L2; ​​wherein, 0.06mm≤D1≤0.18mm and 0.26mm≤D2≤0.5mm, satisfying 0.1≤L1 / L2≤0.8; or 0.18mm<D1≤0.24mm and 0.35mm≤D2≤0.5mm, satisfying 0.1≤L1 / L2≤0.8; or 0.24mm<D1≤0.3mm and 0.45mm≤D2≤0.5mm, satisfying 0.1≤L1 / L2≤0.8.

[0036] In the above technical solution, when the pressure relief part is 0.06mm≤D1≤0.18mm and 0.26mm≤D2≤0.5mm, or 0.18mm<D1≤0.24mm and 0.35mm≤D2≤0.5mm, or 0.24mm<D1≤0.3mm and 0.45mm≤D2≤0.5mm, setting the ratio of L1 to L2 to 0.1 to 0.8 is beneficial to improve the stress release effect of the pressure relief part through deformation during the cyclic change of gas pressure inside the battery cell. At the same time, it can adjust the distance between the weak area and the area with the greatest deformation of the pressure relief part during use. This helps to alleviate the fatigue phenomenon in the thinned area, thereby reducing the risk of the structural strength of the thinned area being weakened. In the event of thermal runaway of the battery cell, it can alleviate the phenomenon that the explosion position of the pressure relief mechanism appears in the thinned area. In addition, it can alleviate the phenomenon of insufficient pressure relief area during pressure relief. This helps to reduce the risk of fire and explosion caused by untimely pressure relief, thereby improving the reliability of the battery cell.

[0037] In some embodiments, 0.2 ≤ L1 / L2 ≤ 0.8.

[0038] In the above technical solution, when 0.06mm≤D1≤0.18mm and 0.26mm≤D2≤0.5mm, or 0.18mm<D1≤0.24mm and 0.35mm≤D2≤0.5mm, or 0.24mm<D1≤0.3mm and 0.45mm≤D2≤0.5mm, by further setting the ratio of L1 to L2 to 0.2 to 0.8, it is beneficial to improve the effect of releasing stress through deformation during the cyclic change of gas pressure inside the battery cell in the pressure relief part. At the same time, it can further adjust the distance between the weak area and the area with the greatest deformation of the pressure relief part during use, which is beneficial to further alleviate the fatigue phenomenon in the thinned area. This can further reduce the risk of the structural strength of the thinned area being weakened, and further alleviate the phenomenon that the explosion position of the pressure relief mechanism appears in the thinned area when the battery cell experiences thermal runaway.

[0039] In some embodiments, the weak portion includes a first weak segment and a second weak segment connected end to end, wherein the minimum thickness of the second weak segment is greater than the minimum thickness of the first weak segment.

[0040] In the above technical solution, by setting the minimum thickness of the second weak segment of the weak part to be greater than the minimum thickness of the first weak segment of the weak part, the structural strength of the second weak segment is greater than that of the first weak segment. This allows the first weak segment to crack first compared to the second weak segment when the battery cell is depressurized, so that the depressurization part can be flipped around the second weak segment as an axis and open to depressurize. This is beneficial to improving the depressurization smoothness of the battery cell's depressurization mechanism and thus improving the timeliness of the battery cell's depressurization.

[0041] In some embodiments, the weak portion includes two straight segments and two curved segments. The two straight segments are arranged opposite each other along a first direction and extend along a second direction. The two curved segments are arranged opposite each other along the second direction and extend along a curved trajectory. One straight segment, one curved segment, another straight segment, and another curved segment are connected end to end in sequence. The first direction, the second direction, and the thickness direction of the wall are perpendicular to each other. The first weak portion includes two curved segments and one straight segment, and the second weak portion is the other straight segment.

[0042] In the above technical solution, the first weak segment includes two arc segments and one straight segment, and the second weak segment is another straight segment of the weak part. The arc segment, the straight segment, the arc segment, and the straight segment are connected end to end in sequence. By setting the two arc segments to extend along the arc trajectory and being arranged opposite each other in the second direction, and setting the two straight segments to extend along the second direction and being arranged opposite each other in the first direction, the battery cell with this structure can, on the one hand, facilitate the forming of the first and second weak segments with different thicknesses on the pressure relief mechanism, which helps to reduce the processing difficulty of the pressure relief mechanism. On the other hand, it can further improve the smoothness of the pressure relief part flipping around the second weak segment as the axis after the first weak segment cracks, and it can further expand the flipping angle of the pressure relief part located inside the weak part of the pressure relief mechanism, so as to further improve the pressure relief smoothness and pressure relief rate of the battery cell.

[0043] In some embodiments, the minimum thickness of the weak portion is D1, and the minimum thickness of the thinning region is D2, satisfying that 0.18≤D1 / D2≤0.62.

[0044] In the above technical solution, by setting the minimum thickness of the weak part to 0.18 to 0.62 times the minimum thickness of the thinning area, on the one hand, setting the minimum thickness of the weak part to be greater than or equal to 0.18 times the minimum thickness of the thinning area can alleviate the excessive processing difficulty caused by the minimum thickness of the weak part being too small, and can reduce the risk of premature cracking due to insufficient structural strength of the weak part, thereby improving the reliability of the battery cell. On the other hand, setting the minimum thickness of the weak part to be less than or equal to 0.62 times the minimum thickness of the thinning area can reduce the risk of the thinning area cracking before the weak part when the battery cell is depressurized. This can further alleviate the phenomenon that the explosion position of the depressurization mechanism occurs in the thinning area when the battery cell experiences thermal runaway, thereby further alleviating the phenomenon of insufficient depressurization area during depressurization. This is conducive to further reducing the risk of fire and explosion caused by untimely depressurization of the depressurization mechanism, and thus further improving the reliability of the battery cell.

[0045] In some embodiments, 0.02mm ≤ D1 ≤ 0.24mm; and / or, 0.22mm ≤ D2 ≤ 0.38mm.

[0046] In the above technical solution, by setting the minimum thickness of the weak part to 0.02mm to 0.24mm, on the one hand, setting the minimum thickness of the weak part to be greater than or equal to 0.02mm can alleviate the risk of premature cracking due to the minimum thickness of the weak part being too small, thereby improving the reliability of the battery cell. On the other hand, setting the minimum thickness of the weak part to be less than or equal to 0.24mm can reduce the burst pressure required by the pressure relief mechanism during pressure relief, thereby reducing the risk of the battery cell bursting or exploding during thermal runaway. Similarly, by setting the minimum thickness of the thinning zone to 0.22mm to 0.38mm, on the one hand, setting the minimum thickness of the thinning zone to be greater than or equal to 0.22mm can improve the structural strength of the thinning zone, so as to alleviate the phenomenon that the thinning zone cracks preferentially over the weak part when the battery cell is depressurized. This can further alleviate the phenomenon that the explosion position of the pressure relief mechanism appears in the thinning zone when the battery cell experiences thermal runaway. On the other hand, setting the minimum thickness of the thinning zone to be less than or equal to 0.38mm can improve the weakening effect of the structural strength of the pressure relief part, so that the pressure relief part can release stress through deformation during the cyclic change of gas pressure inside the battery cell, thereby further improving the "breathing" effect of the pressure relief mechanism during use.

[0047] In some embodiments, at least a portion of the pressure relief portion bulges towards or away from the electrode assembly along the thickness direction of the wall portion, forming a raised portion, and the weak portion surrounds the outside of the raised portion.

[0048] In the above technical solution, by setting a raised portion on the pressure relief portion inside the weak portion, which bulges towards or away from the electrode assembly, and the weak portion surrounds the outside of the raised portion, on the one hand, it can reduce the difficulty of forming the weak portion in the pressure relief mechanism and improve the material flow pattern of the weak portion during the processing, thereby improving the processing consistency of the weak portion. On the other hand, it makes the raised portion inside the weak portion form a pre-deformed structure, so that the weak portion of the pressure relief mechanism can crack and relieve pressure when the battery cell thermally runs away. Thus, under the same burst pressure, the thickness of the weak portion can be increased to alleviate fatigue cracking and other phenomena in the weak portion during use. This can effectively reduce the risk of premature valve opening of the pressure relief mechanism, thereby improving the service life and reliability of the battery cell.

[0049] In some embodiments, the raised portion includes at least a portion of the thinned region.

[0050] In the above technical solution, by setting the raised portion as a structure that includes at least a portion of the thinning area, so that the thinning area is also a structure that is at least partially raised, it is possible to further facilitate the pressure relief portion to release stress through deformation during the cyclic change of gas pressure inside the battery cell, thereby further improving the "breathing" effect of the pressure relief mechanism during use.

[0051] In some embodiments, along the thickness direction of the wall portion, the pressure relief mechanism has opposing first and second surfaces, the first surface is provided with a groove, the bottom wall of the groove includes the weak portion, and a portion of the bottom wall of the groove bulges along the direction from the second surface to the first surface to form the raised portion.

[0052] In the above technical solution, by setting a groove on the first surface of the pressure relief mechanism and setting the raised part to be a structure that bulges along the direction from the second surface to the first surface, the battery cell with this structure can achieve a structure in which the raised part bulges towards the side of the groove. On the one hand, the groove and the raised part can share part of the space in the thickness direction of the wall, which is beneficial to save the space occupied by the pressure relief mechanism and improve the space utilization of the battery cell. On the other hand, the groove can also play a certain protective role for the raised part, so as to reduce wear or bumps during use or assembly.

[0053] In some embodiments, the second surface is disposed facing the electrode assembly along the thickness direction of the wall portion.

[0054] In the above technical solution, by setting the second surface of the pressure relief mechanism to face the electrode assembly, the raised portion is a structure that protrudes away from the electrode assembly in the thickness direction of the wall portion. On the one hand, it can reduce the phenomenon of the raised portion occupying the internal space of the battery cell, thereby increasing the internal space of the battery cell for accommodating the electrode assembly, which is beneficial to improving the energy density of the battery cell. On the other hand, it can reduce the interference between the raised portion and other components inside the battery cell, which is beneficial to improving the reliability of the battery cell.

[0055] In some embodiments, the pressure relief mechanism is provided with a pressure relief groove and forms the weak part. In a projection plane perpendicular to the thickness direction of the wall, the orthographic projection of the weak part and the orthographic projection of the groove wall surface of the pressure relief groove overlap; wherein, the pressure relief groove is provided on the bottom surface of the groove.

[0056] In the above technical solution, a weak part is formed on the pressure relief mechanism by opening a pressure relief groove, which reduces the difficulty of forming the weak part on the pressure relief mechanism. In particular, by setting the pressure relief groove on the bottom surface of the groove, the pressure relief groove and the groove are located on the same side of the thickness direction of the wall of the pressure relief mechanism. This allows the pressure relief groove to be formed simultaneously with the groove, which helps to reduce the difficulty of forming the pressure relief groove on the pressure relief mechanism and optimizes the production cycle of the battery cell.

[0057] In some embodiments, the pressure relief mechanism is provided with a pressure relief groove and forms the weak part. In a projection plane perpendicular to the thickness direction of the wall, the orthographic projection of the weak part and the orthographic projection of the groove wall of the pressure relief groove overlap.

[0058] In the above technical solution, a weak part is formed on the pressure relief mechanism by opening a pressure relief groove, so that the pressure relief mechanism can crack along at least a part of the weak part when the battery cell is depressurized. This reduces the difficulty of forming the weak part on the pressure relief mechanism, and the structure is simple and easy to manufacture.

[0059] In some embodiments, the pressure relief portion is provided with a thinning groove and forms the thinning area. In a projection plane perpendicular to the thickness direction of the wall portion, the orthographic projection of the thinning area and the orthographic projection of the groove wall surface overlap.

[0060] In the above technical solution, a thinning area is formed on the pressure relief part by opening a thinning groove on the pressure relief part, thereby reducing the difficulty of forming a thinning area on the pressure relief part. The structure is simple and easy to manufacture.

[0061] In some embodiments, the pressure relief mechanism is separately disposed from the wall portion; or, the pressure relief mechanism is integrally formed with the wall portion.

[0062] In the above technical solutions, by setting the pressure relief mechanism and the wall as separate structures, the weak parts and thinning areas can be machined on the pressure relief mechanism first, and then the pressure relief mechanism can be assembled onto the wall of the outer casing. This reduces the molding difficulty of the pressure relief mechanism and optimizes the production cycle of the battery cell. Alternatively, by setting the pressure relief mechanism and the wall as an integral structure, the battery cell with this structure can improve the structural strength of the pressure relief mechanism connected to the wall, reducing the risk of the pressure relief mechanism detaching during use, thereby improving the stability and reliability of the battery cell.

[0063] In some embodiments, the housing includes a shell and an end cap; the shell includes an integrally formed sidewall and a bottom wall, the sidewall surrounding the bottom wall, one end of the sidewall being connected to the bottom wall along the thickness direction of the wall portion, and the other end forming an opening, the sidewall and the bottom wall together defining a receiving cavity, the electrode assembly being received within the receiving cavity; the end cap closes the opening; wherein, the end cap is the wall portion; or, the bottom wall is the wall portion.

[0064] In the above technical solution, by setting the wall of the outer casing as an end cap for sealing the opening, the battery cell with this structure facilitates the installation of a pressure relief mechanism on the end cap, thereby reducing the manufacturing difficulty of the battery cell and improving its production efficiency. By setting the wall of the outer casing as a bottom wall opposite the end cap in the thickness direction of the casing, the area where the pressure relief mechanism is located on the outer casing is far from the end cap. This effectively mitigates the stress generated by the connection between the end cap and the casing on the pressure relief mechanism, reducing its impact. This, in turn, reduces the risk of cracking or structural strength reduction in the weak points of the pressure relief mechanism under tensile stress, thus improving the service life and reliability of the battery cell.

[0065] Secondly, embodiments of this application also provide a battery device, including the aforementioned battery cell.

[0066] Thirdly, embodiments of this application also provide an electrical device, including the aforementioned battery cell, wherein the battery cell is used to provide electrical energy. Attached Figure Description

[0067] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0068] Figure 1 This application provides structural schematic diagrams of vehicles for some embodiments;

[0069] Figure 2 Exploded views of the structure of the battery device provided in some embodiments of this application;

[0070] Figure 3 This is a schematic diagram of the structure of a battery cell provided in some embodiments of this application;

[0071] Figure 4 Exploded views of the structure of a single battery cell provided in some embodiments of this application;

[0072] Figure 5 A front view of the pressure relief mechanism provided in some embodiments of this application in the thickness direction of the wall portion;

[0073] Figure 6 Cross-sectional views of pressure relief mechanisms provided in some embodiments of this application;

[0074] Figure 7 for Figure 6 A partial enlarged view of point A of the pressure relief mechanism shown;

[0075] Figure 8 for Figure 6 A partial enlarged view of point B of the pressure relief mechanism shown;

[0076] Figure 9 A front view of the pressure relief mechanism provided in some embodiments of this application in the thickness direction of the wall portion;

[0077] Figure 10 A front view of the pressure relief mechanism provided in some other embodiments of this application in the thickness direction of the wall portion;

[0078] Figure 11 A front view of the pressure relief mechanism provided in some embodiments of this application in the thickness direction of the wall portion;

[0079] Figure 12 A front view of the pressure relief mechanism provided in some further embodiments of this application in the thickness direction of the wall portion;

[0080] Figure 13 A cross-sectional view of a pressure relief mechanism provided in some further embodiments of this application;

[0081] Figure 14 for Figure 13 A partial enlarged view of point C of the pressure relief mechanism shown;

[0082] Figure 15 for Figure 13 A magnified view of part D of the pressure relief mechanism shown.

[0083] Icons: 1000 - Vehicle; 100 - Battery assembly; 10 - Housing; 11 - First housing body; 12 - Second housing body; 20 - Battery cell; 21 - Casing; 211 - Wall; 212 - Housing; 2121 - Opening; 213 - End cap; 22 - Electrode assembly; 221 - Tab; 23 - Pressure relief mechanism; 231 - Connection; 232 - Weak section; 232a - First weak section; 232b - Second weak section; 2321 - Straight section; 2322 - Arc segment; 233-Pressure relief section; 2331-Thinning area; 2331a-Thinning section; 2331b-First position; 2331c-Second position; 2331d-First segment; 2332-Thinning groove; 2333-Raised section; 234-Pressure relief groove; 235-First surface; 2351-Groove; 236-Second surface; 24-Electrode terminal; 200-Controller; 300-Motor; X-Thickness direction of the wall; Y-First direction; Z-Second direction. Detailed Implementation

[0084] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0085] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the description of this application is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms "comprising" and "having," and any variations thereof, in the description, claims, and accompanying drawings of this application are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the description, claims, or accompanying drawings of this application are used to distinguish different objects, not to describe a specific order or hierarchy.

[0086] In this application, the reference to "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments.

[0087] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "attachment" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0088] In this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, in this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0089] In the embodiments of this application, the same reference numerals denote the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width, and other dimensions of various components in the embodiments of this application shown in the accompanying drawings, as well as the overall thickness, length, width, and other dimensions of the integrated device, are merely illustrative and should not constitute any limitation on this application.

[0090] In this application, "multiple" means two or more (including two).

[0091] In this embodiment of the application, the battery cell can be a secondary battery, which refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

[0092] The battery cell can be a lithium-ion battery, sodium-ion battery, sodium-lithium-ion battery, lithium metal battery, sodium metal battery, lithium-sulfur battery, magnesium-ion battery, nickel-metal hydride battery, nickel-cadmium battery, lead-acid battery, etc., and the embodiments of this application are not limited to this.

[0093] A single battery cell typically includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator. During the charging and discharging process of a single battery cell, active ions (such as lithium ions) repeatedly insert and extract between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, helps prevent short circuits to some extent while allowing active ions to pass through.

[0094] In some embodiments, the positive electrode may be a positive electrode sheet, which may include a positive electrode current collector and a positive electrode active material disposed on at least one surface of the positive electrode current collector.

[0095] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material is disposed on either or both of the two opposite surfaces of the positive current collector.

[0096] As an example, the positive electrode current collector can be a metal foil or a composite current collector. For example, as a metal foil, it can be aluminum with a silver-plated surface, stainless steel with a silver-plated surface, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel, or titanium, etc. Composite current collectors can include a polymer material base layer and a metal layer. Composite current collectors can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0097] As an example, the positive electrode active material may include at least one of the following materials: lithium phosphate, lithium transition metal oxide, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium phosphate may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium iron manganese phosphate and carbon composites. Examples of lithium transition metal oxide may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds.

[0098] In some embodiments, the positive electrode can be a foamed metal. The foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloys, etc. When foamed metal is used as the positive electrode, the surface of the foamed metal may or may not contain a positive electrode active material. As an example, lithium source material, potassium metal, or sodium metal can also be filled and / or deposited within the foamed metal, where the lithium source material is lithium metal and / or a lithium-rich material.

[0099] In some embodiments, the negative electrode may be a negative electrode sheet, and the negative electrode sheet may include a negative electrode current collector.

[0100] As an example, the negative electrode current collector can be a metal foil, a foamed metal, or a composite current collector. For example, as a metal foil, it can be silver-treated aluminum or stainless steel, stainless steel, copper, aluminum, nickel, carbon electrode, nickel, or titanium, etc. Foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloy, etc. Composite current collectors can include a polymer material base layer and a metal layer. Composite current collectors can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0101] As an example, the negative electrode sheet may include a negative electrode current collector and a negative electrode active material disposed on at least one surface of the negative electrode current collector.

[0102] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active material is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0103] As an example, the negative electrode active material may be a negative electrode active material known in the art for use in battery cells. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as battery negative electrode active materials may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0104] In some embodiments, the positive current collector can be made of aluminum, and the negative current collector can be made of copper.

[0105] In some embodiments, the electrode assembly further includes an isolator disposed between the positive and negative electrodes.

[0106] In some embodiments, the separator is a separator membrane. The separator membrane can be of various types, and any known porous separator membrane with good chemical and mechanical stability can be selected.

[0107] As an example, the material of the separator may include at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer may be the same or different. The separator may be a separate component located between the positive and negative electrodes, or it may be attached to the surfaces of the positive and negative electrodes.

[0108] In some embodiments, the separator is a solid electrolyte. The solid electrolyte is disposed between the positive and negative electrodes, serving both to transport ions and to isolate the positive and negative electrodes.

[0109] In some embodiments, the battery cell also includes an electrolyte, which acts as a conductor of ions between the positive and negative electrodes. The electrolyte can be liquid, gel-like, or solid. Liquid electrolytes include electrolyte salts and solvents.

[0110] In some embodiments, the electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0111] In some embodiments, the solvent may include at least one selected from ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone. The solvent may also be an ether solvent. Ether solvents may include one or more selected from ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyl tetrahydrofuran, diphenyl ether, and crown ethers.

[0112] Among them, the gel electrolyte includes a polymer as the electrolyte backbone network, combined with an ionic liquid - lithium salt.

[0113] Solid electrolytes include polymer solid electrolytes, inorganic solid electrolytes, and composite solid electrolytes.

[0114] As an example, polymer solid electrolytes can be polyether (polyoxyethylene), polysiloxane, polycarbonate, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, monoionic polymers, polyionic liquids-lithium salts, cellulose, etc.

[0115] As an example, inorganic solid electrolytes may include one or more of the following: oxide solid electrolytes (crystalline perovskite, sodium superconducting ion conductor, garnet, amorphous LiPON thin film), sulfide solid electrolytes (crystalline lithium superconducting ion conductor (lithium germanium phosphate sulfide, silver sulfide germanium ore), amorphous sulfides), halide solid electrolytes, nitride solid electrolytes, and hydride solid electrolytes.

[0116] As an example, composite solid electrolytes are formed by adding inorganic solid electrolyte fillers to polymer solid electrolytes.

[0117] In some implementations, the electrode assembly has a wound structure. The positive and negative electrode sheets are wound into a wound structure.

[0118] In some implementations, the electrode assembly has a stacked structure.

[0119] As an example, multiple positive and negative electrodes can be set, and multiple positive and multiple negative electrodes can be stacked alternately.

[0120] As an example, multiple positive electrode plates can be provided, and negative electrode plates can be folded to form multiple stacked folded segments, with a positive electrode plate sandwiched between adjacent folded segments.

[0121] As an example, both the positive and negative electrode plates are folded to form multiple stacked folded segments.

[0122] As an example, multiple separators can be provided, each positioned between any adjacent positive or negative electrode plates.

[0123] As an example, the separators can be continuously arranged, either by folding or rolling between any adjacent positive or negative electrode plates.

[0124] In some embodiments, the electrode assembly can be cylindrical, flat, or polygonal, etc.

[0125] In some embodiments, the electrode assembly is provided with tabs that allow current to be drawn from the electrode assembly. The tabs include a positive tab and a negative tab.

[0126] In some embodiments, the battery cell may include a housing. The housing is used to encapsulate components such as electrode assemblies and electrolytes. The housing may be made of steel, aluminum, plastic (such as polypropylene), composite metal (such as copper-aluminum composite), or aluminum-plastic film, etc.

[0127] As an example, a battery cell can be a cylindrical battery cell, a prismatic battery cell, a pouch battery cell, or a battery cell of other shapes. Prismatic battery cells include, but are not limited to, square battery cells, blade-shaped battery cells, and multi-prismatic batteries, such as hexagonal prismatic batteries.

[0128] The battery device mentioned in the embodiments of this application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells, which are connected in series, parallel, or mixed connections via a busbar.

[0129] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells; as an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells into a single module. As an example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0130] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cell assemblies housed within the housing.

[0131] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module in the housing.

[0132] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0133] As an example, the enclosure may include a first enclosure body and a second enclosure body. The first enclosure body and the second enclosure body are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, which can be either sealed or unsealed. The first enclosure body may be a top cover or a bottom plate.

[0134] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0135] As an example, the housing can be part of the vehicle's chassis structure. For instance, the housing's roof can be at least part of the vehicle's floor, or the housing's frame can be at least part of the vehicle's crossbeams and longitudinal beams.

[0136] In some embodiments, the battery device refers to an energy storage device, which includes a housing with a door on at least one side. Energy storage devices include energy storage containers, energy storage cabinets, etc.

[0137] Battery devices possess outstanding advantages such as high energy density, low environmental pollution, high power density, long service life, wide applicability, and low self-discharge coefficient, making them an important component of today's new energy development. The development of battery technology must simultaneously consider multiple design factors, such as performance parameters like energy density, cycle life, discharge capacity, and charge / discharge rate. Furthermore, the reliability of the battery device must also be taken into account.

[0138] To ensure the safety of a typical battery cell, a pressure relief mechanism is usually installed on its casing. This mechanism releases internal pressure, effectively improving the cell's safety. The pressure relief mechanism is typically a flat plate structure. An annular pressure relief groove is punched into the mechanism, allowing it to crack along the groove when pressure is released from the battery cell. During the charging and discharging of a battery cell, the internal air pressure changes cyclically, causing the cell's casing to expand and contract—a phenomenon known as "breathing." Therefore, in related technologies, to enable the pressure relief mechanism to also "breathe" and mitigate fatigue cracking and premature valve opening caused by the cyclical changes in internal air pressure, a thinning groove is typically installed inside the pressure relief groove of the pressure relief mechanism. This thinning groove is connected to the pressure relief groove at both ends in its extension direction, reducing the structural strength of the area inside the pressure relief groove. This allows the area inside the pressure relief groove to release stress through deformation during the cyclical changes in internal air pressure, thus enabling the pressure relief mechanism to also "breathe" and effectively mitigating the stress caused by the pressure relief mechanism's design. The pressure groove area is prone to fatigue cracking during use. However, in the event of thermal runaway, the pressure relief mechanism of this type of battery cell is prone to cracking along the area where the thinning groove is located, rather than along the pressure relief groove itself. This is especially true in the part of the thinning groove near the center of the area where the pressure relief mechanism is located inside the pressure relief groove. Since the deformation of the pressure relief mechanism is greatest at the center of the area inside the pressure relief groove during use, it is more likely to crack along the area where the thinning groove is located, resulting in a smaller area for pressure relief. This leads to insufficient pressure relief area in the battery cell during thermal runaway, resulting in a low pressure relief rate. Consequently, the battery cell may be at risk of fire, explosion, or connection failure due to untimely pressure relief, which is detrimental to the reliability of the battery cell.

[0139] Based on the above considerations, in order to solve the problem of low reliability of battery cells, this application provides a battery cell including a casing, an electrode assembly, and a pressure relief mechanism. The casing has a wall. The electrode assembly is housed within the casing. The pressure relief mechanism is disposed in the wall and includes a connecting portion, a weak portion, and a pressure relief section. The connecting portion is connected to the wall, and the weak portion surrounds the pressure relief section and connects the connecting portion and the pressure relief section. The weak portion is configured to be at least partially destroyed to release pressure when the pressure inside the casing reaches a threshold. The pressure relief section has at least one thinning region, which is strip-shaped, and the minimum thickness of the thinning region is greater than the minimum thickness of the weak portion. In a projection plane perpendicular to the thickness direction of the wall, the position where the orthographic projection of the thinning region is closest to the geometric center of the orthographic projection of the pressure relief section is a first position, and the position where the orthographic projection of the thinning region is furthest from the geometric center of the orthographic projection of the pressure relief section is a second position. The minimum thickness of the thinning region at the first position is greater than the minimum thickness of the thinning region at the second position.

[0140] In this type of battery cell, a pressure relief mechanism is provided on the wall of the outer casing. This mechanism has a weak point, configured to at least partially break down when the internal pressure reaches a threshold, thus releasing pressure. The pressure relief section located inside the weak point forms a strip-shaped weak area, thereby reducing the structural strength of the pressure relief section. This allows the pressure relief section to release stress through deformation during the cyclical changes in internal gas pressure, enabling the pressure relief mechanism to "breathe." This helps mitigate the risk of fatigue cracking of the weak point during use. Specifically, the minimum thickness of the first position of the thinning zone closest to the center of the pressure relief section is set to be greater than that of the thinning zone furthest from the center of the pressure relief section. The minimum thickness structure at the second position makes the structural strength of the first position, which is closest to the center of the thinning zone and the pressure relief section, greater. This increases the structural strength of the area near the pressure relief section where the deformation is greatest during use. This allows the pressure relief section to release stress through deformation, reducing premature cracking of weak parts, while also mitigating cracking at the first position near the center of the thinning zone when the battery cell experiences thermal runaway. This also helps to prevent the explosion point of the pressure relief mechanism from appearing in the thinning zone, thus effectively mitigating the problem of insufficient pressure relief area during pressure relief. This reduces the risk of fire and explosion caused by untimely pressure relief, thereby improving the reliability of the battery cell.

[0141] The battery cells disclosed in this application can be used, but are not limited to, in electrical devices such as vehicles, ships, or aircraft. A power system for such an electrical device can be constructed using battery cells and battery devices disclosed in this application. This helps to mitigate the problem of fires and explosions caused by untimely pressure release of battery cells, thereby improving the reliability of battery cell use.

[0142] This application provides an electrical device that uses a single battery cell or battery assembly as a power source. The electrical device can be, but is not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0143] For ease of explanation, the following embodiments will be described using a vehicle as an example of an electrical device according to an embodiment of this application.

[0144] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the structure of a vehicle 1000 provided in some embodiments of this application. The vehicle 1000 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A battery device 100 is installed inside the vehicle 1000. The battery device 100 can be located at the bottom, front, or rear of the vehicle 1000. The battery device 100 can be used to supply power to the vehicle 1000; for example, the battery device 100 can serve as the operating power source or general power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300. The controller 200 controls the battery device 100 to supply power to the motor 300, for example, to meet the power needs of the vehicle 1000 during startup, navigation, and driving.

[0145] In some embodiments of this application, the battery device 100 can not only serve as the operating power or power source for the vehicle 1000, but also as the driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0146] Please refer to Figure 2 and Figure 3 , Figure 2 This is an exploded view of the structure of the battery device 100 provided in some embodiments of this application. Figure 3 This is a schematic diagram of the structure of a battery cell 20 provided in some embodiments of this application. The battery device 100 includes a housing 10 and battery cells 20, which are housed within the housing 10.

[0147] The housing 10 provides assembly space for the battery cell 20, and can adopt various structures. In some embodiments, the housing 10 may include a first housing body 11 and a second housing body 12, which overlap each other, and together define an assembly space for accommodating the battery cell 20. The second housing body 12 may be a hollow structure open at one end, and the first housing body 11 may be a plate-like structure, with the first housing body 11 covering the open side of the second housing body 12 so that the first housing body 11 and the second housing body 12 together define the assembly space; alternatively, the first housing body 11 and the second housing body 12 may both be hollow structures open on one side, with the open side of the first housing body 11 covering the open side of the second housing body 12.

[0148] Of course, the box 10 formed by the first box body 11 and the second box body 12 can be of various shapes, such as a cylinder, a cuboid, or a cube. For example, in... Figure 2 In the middle, the shape of box 10 is a cuboid.

[0149] In the battery device 100, there can be one or more battery cells 20 disposed within the housing 10. When there are multiple battery cells 20 disposed within the housing 10, they can be connected in series, in parallel, or in a mixed configuration. A mixed configuration means that multiple battery cells 20 are connected in both series and parallel configurations. Multiple battery cells 20 can be directly connected in series, in parallel, or in a mixed configuration, and then the entire assembly of the multiple battery cells 20 is housed within the housing 10. Alternatively, the battery device 100 can also consist of multiple battery cells 20 first connected in series, in parallel, or in a mixed configuration to form battery modules, and then multiple battery modules are connected in series, in parallel, or in a mixed configuration to form a whole, which is then housed within the housing 10.

[0150] In some embodiments, the battery device 100 may also include other structures. For example, the battery device 100 may also include a busbar for connecting multiple battery cells 20 to achieve electrical connection between the multiple battery cells 20.

[0151] Each battery cell 20 can be a secondary battery or a primary battery; it can also be a lithium-sulfur battery, a sodium-ion battery, or a magnesium-ion battery, but is not limited to these. The battery cell 20 can be in the form of a cuboid, cylinder, prism, or other shapes. For example, in... Figure 3 In the middle, the battery cell 20 has a cuboid structure.

[0152] According to some embodiments of this application, refer to Figure 3 Please refer to further details. Figure 4 , Figure 5 , Figure 6 , Figure 7 and Figure 8, Figure 4 This is an exploded view of the structure of a battery cell 20 provided in some embodiments of this application. Figure 5 This is a front view of the pressure relief mechanism 23 provided in some embodiments of this application in the thickness direction X of the wall portion. Figure 6 This is a cross-sectional view of the pressure relief mechanism 23 provided in some embodiments of this application. Figure 7 for Figure 6 A partial enlarged view of point A of the pressure relief mechanism 23 shown. Figure 8 for Figure 6 The diagram shows a partial enlarged view of the pressure relief mechanism 23 at point B. This application provides a battery cell 20, which includes a housing 21, an electrode assembly 22, and a pressure relief mechanism 23. The housing 21 has a wall portion 211. The electrode assembly 22 is housed within the housing 21. The pressure relief mechanism 23 is disposed on the wall portion 211 and includes a connecting portion 231, a weak portion 232, and a pressure relief portion 233. The connecting portion 231 is connected to the wall portion 211. The weak portion 232 surrounds the pressure relief portion 233 and connects the connecting portion 231 and the pressure relief portion 233. The weak portion 232 is configured to be at least partially destroyed to release pressure when the pressure inside the housing 21 reaches a threshold. The pressure relief portion 233 has at least one thinning region 2331, which is strip-shaped, and the minimum thickness of the thinning region 2331 is greater than the minimum thickness of the weak portion 232. In the projection plane perpendicular to the thickness direction X of the wall, the position of the orthographic projection of the thinning region 2331 closest to the geometric center of the orthographic projection of the pressure relief part 233 is the first position 2331b, and the position of the orthographic projection of the thinning region 2331 furthest from the geometric center of the orthographic projection of the pressure relief part 233 is the second position 2331c. The minimum thickness of the thinning region 2331 at the first position 2331b is greater than the minimum thickness of the thinning region 2331 at the second position 2331c.

[0153] The outer shell 21 can also be used to contain electrolytes, such as electrolyte solution. The outer shell 21 can have various structural forms, such as a cylinder, cuboid, or prism. Similarly, the outer shell 21 can be made of various materials, such as copper, iron, aluminum, steel, or aluminum alloy.

[0154] In some embodiments, the housing 21 may include a housing 212 and an end cap 213. The housing 212 has an internal cavity for accommodating the electrode assembly 22 and has an opening 2121. That is, the housing 212 is a hollow structure with an opening 2121 at one end. The end cap 213 covers the opening 2121 of the housing 212 and forms a sealed connection to form a closed space for accommodating the electrode assembly 22 and the electrolyte.

[0155] The housing 212 includes an integrally formed side wall and a bottom wall. The side wall surrounds the bottom wall, one end of the side wall is connected to the bottom wall, and the other end forms an opening 2121. The bottom wall and the end cap 213 are disposed opposite each other. The side wall and the bottom wall together define a receiving cavity, in which the electrode assembly 22 is received.

[0156] It should be noted that the wall portion 211 equipped with the pressure relief mechanism 23 can be the end cap 213 of the outer casing 21, or it can be one of the multiple walls of the bottom wall or side wall of the casing 212. For example, in... Figure 3 and Figure 4 In this embodiment, the wall portion 211 is the end cap 213 of the outer shell 21. Of course, in other embodiments, the wall portion 211 can also be the bottom wall of the shell 212. The pressure relief mechanism 23 is disposed on a wall of the shell 212 opposite to the end cap 213 in the thickness direction X of the wall portion. The wall portion 211 can also be the side wall of the shell 212.

[0157] When assembling the battery cell 20, the electrode assembly 22 can be placed into the housing 212 first, and the electrolyte can be filled into the housing 212. Then, the end cap 213 can be closed onto the opening 2121 of the housing 212 to complete the assembly of the battery cell 20.

[0158] The housing 212 can have various shapes, such as a cylinder, cuboid, or prism. The shape of the housing 212 can be determined according to the specific shape of the electrode assembly 22. For example, if the electrode assembly 22 is a cylindrical structure, a cylindrical housing 212 can be selected; if the electrode assembly 22 is a cuboid structure, a cuboid housing 212 can be selected. Of course, the end cap 213 can also have various structures, such as a plate-like structure or a hollow structure with one end open.

[0159] Of course, it is understandable that the outer casing 21 is not limited to the structure described above. The outer casing 21 can also be other structures. For example, the outer casing 21 can include a housing 212 and two end caps 213. The housing 212 is a hollow structure with openings 2121 on opposite sides. One end cap 213 is fitted onto one opening 2121 of the housing 212 and forms a sealed connection to form a closed space for accommodating the electrode assembly 22 and the electrolyte. That is, the housing 212 has openings 2121 on opposite sides, and the two end caps 213 are fitted onto the opposite sides of the housing 212 to close the corresponding openings 2121.

[0160] Optionally, the structure of the electrode assembly 22 can be various. For example, the electrode assembly 22 can be a wound structure formed by winding a positive electrode, an insulating element and a negative electrode, or a stacked structure formed by arranging a positive electrode, an insulating element and a negative electrode in layers.

[0161] For example, the separator is a separator membrane, and the main material of the separator membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.

[0162] Optionally, the electrode assembly 22 housed within the housing 21 can be one or more. For example, in... Figure 4 In this embodiment, only one electrode assembly 22 is provided inside the outer casing 21 of the battery cell 20. Of course, in other embodiments, there may be multiple electrode assemblies 22 provided inside the outer casing 21 of the battery cell 20. Multiple electrode assemblies 22 are stacked along their thickness direction. That is, multiple electrode assemblies 22 are stacked along the thickness direction of the battery cell 20. For example, there may be two, three, four, five, six, seven or eight electrode assemblies 22 housed in the outer casing 21.

[0163] In some embodiments, see Figure 3 and Figure 4 As shown, the battery cell 20 may also include an electrode terminal 24, which is insulated and mounted on the housing 21. One end of the electrode assembly 22 has a tab 221. The electrode terminal 24 is electrically connected to the tab 221 of the electrode assembly 22 to output or input electrical energy of the battery cell 20.

[0164] It should be noted that the electrode terminal 24 is insulated and mounted on the housing 21, meaning that there is no electrical connection between the electrode terminal 24 and the housing 21.

[0165] Among them, Figure 3 and Figure 4 In this battery cell 20, two electrode terminals 24 are spaced apart on the end cap 213. Correspondingly, each electrode assembly 22 has two tabs 221 with opposite polarities. The two tabs 221 are spaced apart and located at the end of the electrode assembly 22 facing the end cap 213. The two electrode terminals 24 are electrically connected to the two tabs 221 of the electrode assembly 22 to realize the input or output of electrical energy of the battery cell 20. It should be noted that the tabs 221 of the electrode assembly 22 are formed by stacking and connecting the regions of the positive electrode sheet that are not coated with a positive active material layer, or by stacking and connecting the regions of the negative electrode sheet that are not coated with a negative active material layer. If tab 221 is the positive tab of electrode assembly 22, then tab 221 is a component formed by stacking and connecting the regions on the positive electrode sheet that are not coated with the positive active material layer; if tab 221 is the negative tab of electrode assembly 22, then tab 221 is a component formed by stacking and connecting the regions on the negative electrode sheet that are not coated with the negative active material layer.

[0166] For example, the electrode terminal 24 can be made of various materials, such as copper, iron, aluminum, steel or aluminum alloy.

[0167] Optionally, the structure in which the electrode terminal 24 is mounted on the housing 21 can be varied; for example, in Figure 3 and Figure 4 In this embodiment, both electrode terminals 24 are mounted on the end cap 213 of the housing 21. Of course, the structure of the battery cell 20 is not limited to this. In other embodiments, the battery cell 20 can also have other structures. For example, both electrode terminals 24 can be mounted on the housing 212 of the housing 21. Similarly, one electrode terminal 24 can be mounted on the housing 212 of the housing 21, and the other electrode terminal 24 can be mounted on the end cap 213 of the housing 21.

[0168] In some embodiments, the battery cell 20 may also include two current collectors, both of which are disposed within the housing 21 and spaced apart. Each current collector is used to connect an electrode terminal 24 and a tab 221 of the same polarity in a plurality of electrode assemblies 22, so as to realize the electrical connection between the electrode terminal 24 and the electrode assembly 22, which helps to reduce the assembly difficulty between the tab 221 and the electrode terminal 24.

[0169] For example, the material of the current collector can be various, such as copper, iron, aluminum, steel or aluminum alloy.

[0170] In this embodiment, the pressure relief mechanism 23 plays a pressure relief role in the battery cell 20, and is used to release the internal pressure of the battery cell 20 when the internal pressure or temperature of the battery cell 20 reaches a predetermined value.

[0171] The pressure relief mechanism 23 is disposed on the wall portion 211. The pressure relief mechanism 23 and the wall portion 211 can be integrally formed or separately disposed. For example, in Figure 3 and Figure 4 In this embodiment, the pressure relief mechanism 23 and the wall portion 211 are separate structures. Correspondingly, the wall portion 211 is provided with a pressure relief hole. The pressure relief mechanism 23 is connected to the wall portion 211 and blocks the pressure relief hole. That is, the pressure relief mechanism 23 is assembled on the wall portion 211 and blocks and covers the pressure relief hole. The pressure relief hole penetrates the wall portion 211 and connects the inside and outside of the outer casing 21, so that when the pressure relief mechanism 23 is actuated and cracked, the inside and outside of the outer casing 21 can be interconnected to release the internal pressure of the battery cell 20. Similarly, in the embodiment where the pressure relief mechanism 23 and the wall portion 211 are separate but connected, the structure by which the pressure relief mechanism 23 is connected to the wall portion 211 can be various, such as welding, snap-fitting, or bonding.

[0172] See Figure 5 , Figure 6 and Figure 7 As shown, the pressure relief mechanism 23 may include a connecting portion 231, a weak portion 232, and a pressure relief portion 233. The weak portion 232 is a structure that connects the connecting portion 231 and the pressure relief portion 233. The weak portion 232 is configured to be at least partially destroyed to release pressure when the pressure inside the housing 21 reaches a threshold. That is, the pressure relief mechanism 23 is configured to be able to split at least part of the weak portion 232 when the battery cell 20 is depressurized, so as to release the internal pressure of the battery cell 20 after opening the pressure relief portion 233.

[0173] It should be noted that in the embodiment where the pressure relief mechanism 23 and the wall portion 211 are integrally formed, the connecting portion 231 is a part of the wall portion 211, and the connecting portion 231, the weak portion 232, and the pressure relief portion 233 are structures formed on the wall portion 211 by an integral forming process. In the embodiment where the pressure relief mechanism 23 and the wall portion 211 are separately arranged, the connecting portion 231 and the wall portion 211 are connected to each other, and the connection structure can be a welding connection, etc.

[0174] For example, see Figure 5 , Figure 6 and Figure 7 As shown, the pressure relief mechanism 23 has a pressure relief groove 234 on at least one side in the thickness direction X of the wall. The area of ​​the pressure relief mechanism 23 with the pressure relief groove 234 is the weak part 232. That is, in the projection plane perpendicular to the thickness direction X of the wall, the area of ​​the pressure relief mechanism 23 located in the orthographic projection of the groove wall surface of the pressure relief groove 234 is the weak part 232. The groove wall surface of the pressure relief groove 234 includes the groove side surface and the groove bottom surface of the pressure relief groove 234. Correspondingly, in the thickness direction X of the wall, the area of ​​the pressure relief mechanism 23 corresponding to the groove side surface and the groove bottom surface of the pressure relief groove 234 is the weak part 232.

[0175] For example, the pressure relief groove 234 is disposed on the side of the pressure relief mechanism 23 away from the electrode assembly 22 in the thickness direction X of the wall portion, and the pressure relief groove 234 on the pressure relief mechanism 23 is a groove structure formed by a stamping process.

[0176] The weak portion 232 is arranged around the pressure relief portion 233, and the weak portion 232 connects the connecting portion 231 and the pressure relief portion 233. That is, the weak portion 232 is a ring structure with the ends connected. Correspondingly, the pressure relief groove 234 is also a ring groove with the ends connected. The weak portion 232 is arranged around the pressure relief portion 233, so that the connecting portion 231 is also a structure that surrounds the outside of the weak portion 232, and the weak portion 232 is connected between the connecting portion 231 and the pressure relief portion 233. Correspondingly, the pressure relief portion 233 is the area enclosed by the weak portion 232. That is, the area enclosed by the weak portion 232 is the pressure relief portion 233 of the pressure relief mechanism 23. When the pressure inside the outer casing 21 reaches the threshold, at least a part of the weak portion 232 is destroyed, which can open the pressure relief portion 233 to release the internal pressure of the battery cell 20.

[0177] Optionally, the weak portion 232 includes two straight segments 2321 and two curved segments 2322. The two straight segments 2321 are arranged opposite each other along the first direction Y and extend along the second direction Z. The two curved segments 2322 are arranged opposite each other along the second direction Z and extend along the curved trajectory. One straight segment 2321, one curved segment 2322, another straight segment 2321, and another curved segment 2322 are connected end to end in sequence. The first direction Y, the second direction Z, and the thickness direction X of the wall are perpendicular to each other.

[0178] For example, both arc segments 2322 are arc-shaped structures extending along a circular arc trajectory.

[0179] For example, combined Figure 4 and Figure 5 As shown, the first direction Y is also the length direction of the battery cell 20. Correspondingly, the second direction Z is the thickness direction of the battery cell 20, and the thickness direction X of the wall is the height direction of the battery cell 20. That is to say, the arrangement direction of the two straight segments 2321 is consistent with the length direction of the battery cell 20, and the extension direction of the straight segments 2321 is consistent with the thickness direction of the battery cell 20. Correspondingly, the two arc segments 2322 are arranged opposite each other along the thickness direction of the battery cell 20. Of course, the structure of the battery cell 20 is not limited to this. In other embodiments, the first direction Y can also be the thickness direction of the battery cell 20, and the second direction Z can be the length direction of the battery cell 20. That is to say, the arrangement direction of the two straight segments 2321 is consistent with the thickness direction of the battery cell 20, and the extension direction of the straight segments 2321 is consistent with the length direction of the battery cell 20.

[0180] The pressure relief section 233 has at least one thinning region 2331, which is strip-shaped. That is, the pressure relief section 233 has at least one thinning region 2331 with weakened structural strength. The thinning region 2331 is a strip-shaped structure extending along a straight line trajectory, an arc trajectory, or a broken line trajectory.

[0181] For example, in Figure 5 In the process, the thinning region 2331 is connected to the weak part 232 at both ends in its extension direction. That is, both free ends of the thinning region 2331 are connected to the weak part 232, so that the thinning region 2331 divides the pressure relief part 233 into multiple regions, thereby reducing the structural strength of the pressure relief part 233. This makes it easier for the pressure relief part 233 to release the stress generated by the internal gas pressure through deformation during the cyclic charging and discharging process of the battery cell 20, so that the pressure relief part 233 has the function of "breathing".

[0182] For example, see Figure 5 , Figure 6 and Figure 8 As shown, the pressure relief part 233 has a thinning groove 2332 on at least one side in the thickness direction X of the wall. The area of ​​the pressure relief part 233 with the thinning groove 2332 is the thinning area 2331. That is, in the projection plane perpendicular to the thickness direction X of the wall, the area of ​​the pressure relief part 233 located within the orthographic projection of the groove wall surface of the thinning groove 2332 is the thinning area 2331. The groove wall surface of the thinning groove 2332 includes the groove side surface and the groove bottom surface of the pressure relief groove 234. Correspondingly, in the thickness direction X of the wall, the area of ​​the pressure relief part 233 corresponding to the groove side surface and the groove bottom surface of the thinning groove 2332 is the thinning area 2331. It should be noted that in the embodiment where the pressure relief mechanism 23 has a pressure relief groove 234, both ends of the thinning groove 2332 are connected to the pressure relief groove 234.

[0183] For example, the thinning groove 2332 is disposed on the side of the pressure relief part 233 away from the electrode assembly 22 in the thickness direction X of the wall, so that the thinning groove 2332 and the pressure relief groove 234 are both located on the same side of the pressure relief mechanism 23 in the thickness direction X of the wall, and the thinning groove 2332 on the pressure relief part 233 is a groove structure formed by a stamping process.

[0184] For example, in Figure 5 In this embodiment, the thinning region 2331 is a strip structure extending along an arc trajectory, and both ends of the thinning region 2331 are connected to the weak portion 232 in its extending direction. Correspondingly, the thinning groove 2332 is also an arc-shaped groove structure extending along an arc trajectory. Of course, in other embodiments, the thinning region 2331 may also be a strip structure extending along a straight line trajectory or a broken line trajectory, etc.

[0185] For example, in Figure 5In the pressure relief section 233, two thinning regions 2331 are provided, and the two thinning regions 2331 are arranged opposite to each other along the first direction Y. In the projection plane perpendicular to the thickness direction X of the wall, the orthographic projection of the two thinning regions 2331 is a structure that is centrally symmetrical about the geometric center of the orthographic projection of the pressure relief section 233. In the projection plane perpendicular to the thickness direction X of the wall, the orthographic projection of the two thinning regions 2331 intersects at the geometric center of the orthographic projection of the pressure relief section 233. Of course, in other embodiments, the number of thinning regions 2331 provided on the pressure relief section 233 can also be one, three or four, etc.

[0186] The minimum thickness of the thinning region 2331 is greater than the minimum thickness of the weak part 232. In other words, the minimum residual thickness of the pressure relief groove 234 is less than the minimum residual thickness of the thinning groove 2332, which makes the structural strength of the weak part 232 weaker than the structural strength of the thinning region 2331.

[0187] It should be noted that the minimum thickness of the weak part 232 in the thickness direction X of the wall is the thickness of the bottom wall of the pressure relief groove 234 corresponding to the area with the greatest groove depth in the wall in the thickness direction X of the wall, that is, the minimum thickness of the bottom wall of the pressure relief groove 234. If the bottom surface of the pressure relief groove 234 is a plane, then the minimum thickness of the weak part 232 in the thickness direction X of the wall is the thickness of the bottom wall of the pressure relief groove 234. If the bottom surface of the pressure relief groove 234 is an arc surface or a slope, then the minimum thickness of the weak part 232 in the thickness direction X of the wall is the thickness of the bottom wall of the pressure relief groove 234 at the lowest point of the bottom surface of the pressure relief groove 234. Similarly, the minimum thickness of the thinning region 2331 in the thickness direction X of the wall is the thickness of the bottom wall of the thinning groove 2332 corresponding to the area with the greatest groove depth in the wall in the thickness direction X, that is, the minimum thickness of the bottom wall of the thinning groove 2332. If the bottom surface of the thinning groove 2332 is a plane, then the minimum thickness of the thinning region 2331 in the thickness direction X of the wall is the thickness of the bottom wall of the thinning groove 2332. If the bottom surface of the thinning groove 2332 is an arc surface or a slope, then the minimum thickness of the thinning region 2331 in the thickness direction X of the wall is the thickness of the bottom wall of the thinning groove 2332 at the lowest point of the bottom surface of the thinning groove 2332.

[0188] In the projection plane perpendicular to the thickness direction X of the wall, the position where the orthographic projection of the thinning region 2331 is closest to the geometric center of the orthographic projection of the pressure relief part 233 is the first position 2331b. In other words, the first position 2331b is the position where the distance between the geometric center of the orthographic projection of the thinning region 2331 and the orthographic projection of the pressure relief part 233 is the smallest in the projection plane perpendicular to the thickness direction X of the wall.

[0189] The position where the orthographic projection of the thinning region 2331 is furthest from the geometric center of the orthographic projection of the pressure relief part 233 is the second position 2331c. In other words, the second position 2331c is the position where the distance between the geometric center of the orthographic projection of the thinning region 2331 and the orthographic projection of the pressure relief part 233 is the greatest in the projection plane perpendicular to the thickness direction X of the wall.

[0190] It should be noted that the geometric center of the orthographic projection of the pressure relief part 233 in the projection plane perpendicular to the thickness direction X of the wall is the geometric center of the plane defined by the outer contour of the orthographic projection of the pressure relief part 233 in the projection plane perpendicular to the thickness direction X of the wall.

[0191] For example, in Figure 5 In the middle, both ends of the thinning region 2331 are connected to the weak part 232. Correspondingly, the position where the thinning region 2331 is connected to the weak part 232 is the second position 2331c of the thinning region 2331.

[0192] The minimum thickness of the thinning region 2331 at the first position 2331b is greater than the minimum thickness of the thinning region 2331 at the second position 2331c. That is, in the cross section perpendicular to the extension direction of the thinning region 2331, the minimum thickness of the thinning region 2331 at the first position 2331b is greater than the minimum thickness of the thinning region 2331 at the second position 2331c.

[0193] In this embodiment, a pressure relief mechanism 23 is provided on the wall 211 of the outer casing 21. The pressure relief mechanism 23 has a weak portion 232, which is configured to be at least partially destroyed to release pressure when the pressure inside the outer casing 21 reaches a threshold. The pressure relief portion 233 located inside the weak portion 232 forms a strip-shaped weak area, thereby reducing the structural strength of the pressure relief portion 233. This allows the pressure relief portion 233 to release stress through deformation during the cyclical change of air pressure inside the battery cell 20, enabling the pressure relief mechanism 23 to "breathe". This helps to alleviate the risk of fatigue cracking of the weak portion 232 of the pressure relief mechanism 23 during use. The minimum thickness of the first position 2331b of the thinning area 2331 closest to the center of the pressure relief portion 233 is set to be greater than the second position of the thinning area 2331 furthest from the center of the pressure relief portion 233. The minimum thickness structure at position 2331c makes the first position 2331b of the thinning region 2331 closest to the center of the pressure relief part 233 greater in terms of structural strength. This increases the structural strength of the area of ​​the thinning region 2331 closest to the pressure relief part 233 during use, thereby reducing the premature cracking of the weak part 232 by releasing stress through deformation of the pressure relief part 233. It also mitigates the phenomenon of cracking at the first position 2331b of the thinning region 2331 closest to the center of the pressure relief part 233 during thermal runaway of the battery cell 20. This alleviates the phenomenon that the explosion point of the pressure relief mechanism 23 occurs in the thinning region 2331, and effectively mitigates the phenomenon of insufficient pressure relief area of ​​the pressure relief mechanism 23 during pressure relief. This helps to reduce the risk of fire and explosion caused by untimely pressure relief of the pressure relief mechanism 23, thereby improving the reliability of the battery cell 20.

[0194] According to some embodiments of this application, see Figure 5 As shown, the minimum thickness of the thinning region 2331 in the cross-section increases from the second position 2331c to the first position 2331b along the extension direction of the thinning region 2331, and the cross-section is perpendicular to the extension direction of the thinning region 2331. That is, the minimum thickness of the thinning region 2331 in the cross-section perpendicular to its extension direction is a structure that increases from the second position 2331c to the first position 2331b.

[0195] In one embodiment where a thinning groove 2332 is provided in the pressure relief section 233 and a thinning area 2331 is formed, the minimum thickness of the thinning area 2331 in the cross section perpendicular to its extension direction is the minimum residual thickness of the thinning groove 2332.

[0196] Optionally, the minimum thickness of the thinning region 2331 in the cross-section increases in a stepped manner from the second position 2331c to the first position 2331b along the extension direction of the thinning region 2331, or it can be a gradually increasing structure.

[0197] In this embodiment, by setting the minimum thickness of the thinning region 2331 in the cross-section to a structure that increases from the second position 2331c to the first position 2331b along the extension direction of the thinning region 2331, the structure of the thinning region 2331 becomes stronger as it gets closer to the center of the pressure relief section 233. This allows the structure of the thinning region 2331 to have greater structural strength as it gets closer to the area of ​​the pressure relief section 233 where the deformation is greatest during use. This further mitigates the phenomenon that the area of ​​the thinning region 2331 closer to the center of the pressure relief section 233 is more prone to cracking during thermal runaway of the battery cell 20, thereby further reducing the risk that the explosion point of the pressure relief mechanism 23 may occur in the thinning region 2331.

[0198] In some embodiments, please continue to see Figure 5 As shown, the minimum thickness of the thinning region 2331 in the cross-section gradually increases from the second position 2331c to the first position 2331b along the extension direction of the thinning region 2331. That is, the minimum thickness of the thinning region 2331 in the cross-section gradually and continuously increases from the second position 2331c to the first position 2331b along the extension direction of the thinning region 2331.

[0199] In this embodiment, by setting the minimum thickness of the thinning region 2331 in the cross-section to gradually increase from the second position 2331c to the first position 2331b along the extension direction of the thinning region 2331, it is convenient to form thinning regions 2331 with different thicknesses, so that the thinning region 2331 has a greater structural strength as it gets closer to the center of the pressure relief part 233, and it is also beneficial to reduce the molding difficulty of the thinning region 2331, thereby reducing the manufacturing difficulty of the pressure relief mechanism 23. On the other hand, it makes the thinning region 2331 have a greater structural strength as it gets closer to the center of the pressure relief part 233, so that the thinning region 2331 has a greater structural strength as it gets closer to the area of ​​the pressure relief part 233 where the deformation is the greatest during use, thereby further mitigating the phenomenon that the area of ​​the thinning region 2331 closer to the center of the pressure relief part 233 is more prone to cracking when the battery cell 20 experiences thermal runaway, thereby further reducing the risk that the explosion position of the pressure relief mechanism 23 will occur in the thinning region 2331.

[0200] According to some embodiments of this application, see Figure 5 As shown, the thinning region 2331 is connected to the weak portion 232 at both ends in its extension direction. That is, the pressure relief portion 233 is divided into multiple regions by the thinning region 2331, such that in the projection plane perpendicular to the thickness direction X of the wall, the orthographic projection of the thinning region 2331 is connected to the orthographic projection of the weak portion 232 at both ends in its extension direction.

[0201] In one embodiment where a pressure relief groove 234 is provided on the pressure relief mechanism 23 to form a weak part 232, and a thinning groove 2332 is provided on the pressure relief part 233 to form a thinning area 2331, the pressure relief groove 234 and the thinning groove 2332 are connected to each other and communicate with each other.

[0202] In this embodiment, by setting both ends of the thinning region 2331 in its extension direction to be connected to the weak part 232, it is convenient to form the thinning region 2331 and the weak part 232 on the pressure relief mechanism 23, which helps to reduce the processing difficulty of the pressure relief mechanism 23. On the other hand, the thinning region 2331 can divide the pressure relief part 233 located inside the weak part 232 into multiple regions, which helps to further improve the effect of the pressure relief part 233 in releasing stress through deformation during the cyclic change of gas pressure inside the battery cell 20, so as to further alleviate the risk of fatigue cracking of the weak part 232 of the pressure relief mechanism 23 during use.

[0203] In some embodiments, please continue to see Figure 5 As shown, the thinning region 2331 includes two interconnected first segments 2331d. The connection position of the two first segments 2331d is the first position 2331b, and the position where the first segment 2331d is connected to the weak part 232 is the second position 2331c. Along the extension direction of the thinning region 2331, the lengths of the two first segments 2331d are equal.

[0204] Among them, the first segment 2331d is the part of the thinning region 2331 extending from one end of the thinning region 2331 connected to the weak part 232 to the first position 2331b in its extension direction, so that the first position 2331b is also the connection position of the two first segments 2331d.

[0205] For example, in Figure 5 In the projection plane perpendicular to the thickness direction X of the wall, the orthographic projections of the two first segments 2331d are arranged in an axisymmetric manner with respect to the axis passing through the first position 2331b and extending along the first direction Y.

[0206] In this embodiment, by setting the two first segments 2331d formed by the first position 2331b as the boundary of the thinning region 2331 to be of equal length, and the other ends of the two first segments 2331d are connected to the weak part 232, the shape regularity of the thinning region 2331 can be improved, which is beneficial to reducing the processing difficulty of the thinning region 2331. On the other hand, the effect of the pressure relief part 233 in releasing stress by deformation during the cyclic change of gas pressure inside the battery cell 20 can be further improved.

[0207] According to some embodiments of this application, see Figure 5As shown, in the projection plane perpendicular to the thickness direction X of the wall, the orthographic projection of the thinning region 2331 extends along an arc trajectory.

[0208] For example, the orthographic projection of the thinning region 2331 in the projection plane perpendicular to the thickness direction X of the wall is a structure extending along an arc trajectory.

[0209] In this embodiment, by setting the orthographic projection of the thinning region 2331 in the projection plane perpendicular to the thickness direction X of the wall as a structure extending along an arc trajectory, the thinning region 2331 is a strip structure extending along an arc trajectory, thereby reducing the structural strength of the pressure relief part 233. This enables the pressure relief part 233 to release stress through deformation during the cyclic change of air pressure inside the battery cell 20, thereby mitigating the risk of fatigue cracking of the weak part 232 of the pressure relief mechanism 23 during use.

[0210] According to some embodiments of this application, please refer to Figure 5 As shown, the pressure relief section 233 is provided with two thinning areas 2331. The two thinning areas 2331 are arranged opposite each other along the first direction Y. In the projection plane perpendicular to the thickness direction X of the wall, the geometric center of the orthographic projection of the pressure relief section 233 is located between the orthographic projections of the two thinning areas 2331 in the first direction Y. The first direction Y is perpendicular to the thickness direction X of the wall.

[0211] The two thinning regions 2331 are arranged opposite each other along the first direction Y. That is, the bending directions of the orthographic projections of the two thinning regions 2331 in the projection plane perpendicular to the thickness direction X of the wall are opposite. In other words, in the projection plane perpendicular to the thickness direction X of the wall, the orthographic projection of one thinning region 2331 is a structure that bends towards the orthographic projection of the other thinning region 2331 in the first direction Y.

[0212] The geometric center of the orthographic projection of the pressure relief section 233 is located between the orthographic projections of the two thinning regions 2331 in the first direction Y. That is, in the projection plane perpendicular to the thickness direction X of the wall, the orthographic projections of the two thinning regions 2331 are located on both sides of the geometric center of the orthographic projection of the pressure relief section 233 in the first direction Y.

[0213] In this embodiment, by providing two thinning regions 2331 arranged opposite to each other along the first direction Y on the pressure relief section 233, and setting the geometric center of the pressure relief section 233 between the two thinning regions 2331 in the first direction Y, the pressure relief section 233 can release stress through deformation during the cyclic change of gas pressure inside the battery cell 20, while also ensuring that the two thinning regions 2331 are far away from the area of ​​the pressure relief section 233 with the greatest degree of deformation during use. This helps to alleviate the fatigue phenomenon of the thinning regions 2331, and thus reduces the phenomenon that the explosion position of the pressure relief mechanism 23 is located in the thinning region 2331 when thermal runaway occurs in the battery cell 20. This helps to reduce the risk of fire and explosion caused by untimely pressure relief of the pressure relief mechanism 23, thereby improving the reliability of the battery cell 20.

[0214] In some embodiments, please continue to see Figure 5 As shown, the weak portion 232 may include two straight segments 2321 and two curved segments 2322. The two straight segments 2321 are arranged opposite each other along the first direction Y and extend along the second direction Z. The two curved segments 2322 are arranged opposite each other along the second direction Z and extend along the curved trajectory. One straight segment 2321, one curved segment 2322, another straight segment 2321 and another curved segment 2322 are connected end to end in sequence. The first direction Y, the second direction Z and the thickness direction X of the wall are perpendicular to each other. The thinning region 2331 is connected to the two curved segments 2322 at both ends in its extension direction.

[0215] Among them, a straight line segment 2321, an arc segment 2322, another straight line segment 2321 and another arc segment 2322 are connected end to end in sequence. That is to say, the two straight line segments 2321 and the two arc segments 2322 of the weak part 232 are arranged alternately and connected to each other along the extension direction of the weak part 232.

[0216] It should be noted that the arc segment 2322 of the weak part 232 extends along an arc trajectory, and correspondingly, the straight segment 2321 of the weak part 232 extends along a straight trajectory. For example, in... Figure 5 In the structure, the arc segment 2322 is a structure that extends along a circular arc trajectory, and the straight segment 2321 is a structure that extends along the second direction Z. The arc segment 2322 is connected to two straight segments 2321 at both ends in its extension direction, and in the projection plane perpendicular to the thickness direction X of the wall, the orthographic projections of the two arc segments 2322 are axially symmetrical about the straight line extending along the first direction Y.

[0217] The thinning region 2331 is connected to two arc segments 2322 at both ends in its extension direction. That is, the thinning region 2331 extending along the arc trajectory is connected to one arc segment 2322 at one end in its extension direction and to another arc segment 2322 at the other end, so that a straight segment 2321, a part of an arc segment 2322, a part of another arc segment 2322 and the thinning region 2331 enclose a ring structure that is connected end to end.

[0218] In this embodiment, by connecting the two ends of the thinning region 2331 in its extension direction to the two arc segments 2322 of the weak portion 232 respectively, the thinning region 2331 can divide the pressure relief portion 233 located inside the weak portion 232 into multiple regions, and can expand the length dimension of the thinning region 2331. This is beneficial to further improve the effect of the pressure relief portion 233 in releasing stress through deformation during the cyclic change of gas pressure inside the battery cell 20, so as to further alleviate the risk of fatigue cracking of the weak portion 232 of the pressure relief mechanism 23 during use.

[0219] It should be noted that the structure of the battery cell 20 is not limited to this. In some embodiments, the battery cell 20 can also have other structures. For example, the weak part 232 may include two straight segments 2321 and two arc segments 2322. The two straight segments 2321 are arranged opposite each other along the first direction Y and extend along the second direction Z. The two arc segments 2322 are arranged opposite each other along the second direction Z and extend along an arc trajectory. One straight segment 2321, one arc segment 2322, another straight segment 2321 and another arc segment 2322 are connected end to end in sequence. The first direction Y, the second direction Z and the thickness direction X of the wall are perpendicular to each other. The thinning region 2331 is connected to the same straight segment 2321 at both ends in its extension direction.

[0220] In this process, the thinning region 2331 is connected to the same straight line segment 2321 at both ends in its extension direction. That is, the thinning region 2331 extending along the arc trajectory is connected to the same straight line segment 2321 at both ends in its extension direction, so that a part of the straight line segment 2321 and the thinning region 2331 enclose and form a closed ring structure.

[0221] In this embodiment, by connecting both ends of the thinning region 2331 in its extension direction to the same straight segment 2321, on the one hand, the pressure relief part 233 located inside the weak part 232 can be divided into multiple regions by the thinning region 2331, which is conducive to further improving the effect of the pressure relief part 233 in releasing stress through deformation during the cyclic change of gas pressure inside the battery cell 20, so as to further alleviate the risk of fatigue cracking of the weak part 232 of the pressure relief mechanism 23 during use. On the other hand, it is convenient to form the thinning region 2331 and the weak part 232 on the pressure relief mechanism 23, which is conducive to reducing the processing difficulty of the pressure relief mechanism 23.

[0222] According to some embodiments of this application, refer to Figure 9 As shown, Figure 9 This is a front view of the pressure relief mechanism 23 provided in some embodiments of this application in the thickness direction X of the wall. The thinning region 2331 includes a plurality of thinning segments 2331a connected in sequence. In the projection plane perpendicular to the thickness direction X of the wall, the orthographic projection of at least one thinning segment 2331a extends along an arc trajectory, and the orthographic projection of at least one thinning segment 2331a extends along a straight trajectory.

[0223] The thinning region 2331 includes multiple thinning segments 2331a connected in sequence, that is, the thinning region 2331 is composed of multiple thinning segments 2331a, and the multiple thinning segments 2331a are connected in sequence.

[0224] In the projection plane perpendicular to the thickness direction X of the wall, the orthographic projection of at least one thinning segment 2331a extends along an arc trajectory, and the orthographic projection of at least one thinning segment 2331a extends along a straight trajectory. That is, the extension trajectory of the orthographic projection of some thinning segments 2331a in the projection plane perpendicular to the thickness direction X of the wall is a straight line, and the extension trajectory of the orthographic projection of some thinning segments 2331a in the projection plane perpendicular to the thickness direction X of the wall is an arc.

[0225] For example, in Figure 9 In the thinning region 2331, there are three thinning segments 2331a. The extension trajectory of the orthographic projection of two of the three thinning segments 2331a in the projection plane perpendicular to the thickness direction X of the wall is a straight line, and the extension trajectory of the orthographic projection of the other thinning segment 2331a in the projection plane perpendicular to the thickness direction X of the wall is an arc.

[0226] In this embodiment, by setting the thinning region 2331 to include a plurality of thinning segments 2331a connected in sequence, and in the projection plane perpendicular to the thickness direction X of the wall, the orthographic projection of at least one of the plurality of thinning segments 2331a is set to extend along an arc trajectory, and the orthographic projection of at least one thinning segment 2331a is set to extend along a straight trajectory, so as to form a thinning region 2331 with different shapes of strip structure, which is beneficial to the pressure relief mechanism 23 applicable to different structures.

[0227] In some embodiments, please continue to see Figure 9 As shown, the thinning region 2331 has three thinning segments 2331a. In the projection plane perpendicular to the thickness direction X of the wall, the orthographic projection of the middle thinning segment 2331a extends along an arc trajectory, and the orthographic projection of the two ends of the thinning segment 2331a extends along a straight trajectory.

[0228] For example, one end of the thinning segment 2331a located at both ends of the three thinning segments 2331a is connected to the weak portion 232, and the other end is connected to one end of the thinning segment 2331a located in the middle of the three thinning segments 2331a.

[0229] For example, in the projection plane perpendicular to the thickness direction X of the wall, the extension direction of the orthographic projection of the thinning segment 2331a located at both ends of the three thinning segments 2331a is tangent to the extension direction of the orthographic projection of the thinning segment 2331a located in the middle of the three thinning segments 2331a.

[0230] In this embodiment, by setting three thinning segments 2331a of the thinning region 2331, and in the projection plane perpendicular to the thickness direction X of the wall, the orthographic projection of the middle thinning segment 2331a is a structure extending along an arc trajectory, and the orthographic projection of the thinning segments 2331a at both ends is a structure extending along a straight trajectory, it is beneficial to improve the regularity of the shape of the thinning region 2331 and reduce the difficulty of thinning molding, thereby reducing the processing difficulty of the pressure relief mechanism 23.

[0231] According to some embodiments of this application, refer to Figure 10 As shown, Figure 10 This is a front view of the pressure relief mechanism 23 provided in other embodiments of this application in the thickness direction X of the wall. The thinning region 2331 includes a plurality of thinning segments 2331a connected in sequence. In the projection plane perpendicular to the thickness direction X of the wall, the orthographic projection of the thinning segment 2331a extends along a straight trajectory, and the extension directions of the orthographic projections of two connected thinning segments 2331a intersect.

[0232] In the projection plane perpendicular to the thickness direction X of the wall, the orthographic projection of the thinning segment 2331a extends along a straight line trajectory, and the extension directions of the orthographic projections of two connected thinning segments 2331a intersect. That is to say, the orthographic projection of each thinning segment 2331a in the projection plane perpendicular to the thickness direction X of the wall is a strip structure extending along a straight line, and the orthographic projections of each two adjacent thinning segments 2331a are set at an acute angle, a right angle, or an obtuse angle, so that the thinning region 2331 is a strip structure extending in a broken line.

[0233] Optionally, the number of thinning segments 2331a in the thinning region 2331 of the strip structure extending in a zigzag pattern can be two, three, four, five, or six, etc.

[0234] For example, in Figure 10 In the middle, the thinning sections 2331a at both ends of the multiple thinning sections 2331a are connected to the weak part 232.

[0235] In this embodiment, by setting the thinning region 2331 as a structure including a plurality of thinning segments 2331a connected in sequence, in the projection plane perpendicular to the thickness direction X of the wall, the thinning segments 2331a are structures that extend along a straight trajectory, and the extension directions of the orthographic projections of each two adjacent thinning segments 2331a are intersecting structures, so as to form a thinning region 2331 with a broken line shape, which is beneficial for pressure relief mechanisms 23 with different structures.

[0236] In some embodiments, please continue to see Figure 10 As shown, the thinning section 2331a of the thinning region 2331 consists of two segments.

[0237] For example, one end of the two thinning segments 2331a is connected to each other, and the other end of each segment is connected to the weak portion 232.

[0238] In this embodiment, by setting two thinning segments 2331a of the thinning region 2331, the two thinning segments 2331a are connected and their extension directions intersect, so as to form a thinning region 2331 with a "V" shaped structure. The structure is simple and easy to manufacture, which helps to reduce the manufacturing difficulty of the pressure relief mechanism 23.

[0239] According to some embodiments of this application, refer to Figure 11 As shown, Figure 11 This is a front view of the pressure relief mechanism 23 provided in some embodiments of this application in the thickness direction X of the wall portion. In the projection plane perpendicular to the thickness direction X of the wall portion, the orthographic projection of the thinning region 2331 extends along a straight line trajectory.

[0240] For example, the thinning region 2331 is connected to the weak portion 232 at both ends opposite to each other in its extension direction. It should be noted that in the embodiment where the weak portion 232 includes two straight segments 2321 and two arc segments 2322, the thinning region 2331 at both ends opposite to each other in its extension direction can be a structure that is connected to the two straight segments 2321 respectively, or it can be a structure that is connected to the two arc segments 2322 respectively.

[0241] In this embodiment, by setting the extension direction of the orthogonal projection of the thinning region 2331 in the projection plane perpendicular to the thickness direction X of the wall to extend along a straight trajectory, it is easier to form the thinning region 2331 on the pressure relief part 233, which helps to reduce the processing difficulty of the pressure relief mechanism 23.

[0242] In some embodiments, please continue to see Figure 11 As shown, there are multiple thinning regions 2331. In the projection plane perpendicular to the thickness direction X of the wall, the orthographic projections of the multiple thinning regions 2331 intersect at the connecting region, and the geometric center of the orthographic projection of the pressure relief part 233 is located in the connecting region.

[0243] In the projection plane perpendicular to the thickness direction X of the wall, the orthographic projections of multiple thinning regions 2331 intersect at the connecting region. That is, the multiple thinning regions 2331 whose orthographic projections extend in a straight line are all located at the same position, namely the connecting region. Correspondingly, the geometric center of the orthographic projection of the pressure relief part 233 is located in the connecting region. In other words, in the projection plane perpendicular to the thickness direction X of the wall, the orthographic projections of multiple thinning regions 2331 all pass through the geometric center of the orthographic projection of the pressure relief part 233, and the geometric center of the orthographic projection of the pressure relief part 233 is also the intersection point of the orthographic projections of multiple thinning regions 2331.

[0244] In this embodiment, by setting the intersection of the orthographic projections of the multiple thinning regions 2331 in the projection plane perpendicular to the thickness direction X of the wall to coincide with the geometric center of the orthographic projection of the pressure relief part 233 in the projection plane perpendicular to the thickness direction X of the wall, the first position 2331b of the multiple thinning regions 2331 is located at the same position, so that the positions with larger minimum thicknesses of the multiple thinning regions 2331 are all located at the geometric center of the orthographic projection of the pressure relief part 233 in the projection plane perpendicular to the thickness direction X of the wall. This helps to reduce the molding difficulty of the multiple thinning regions 2331, thereby reducing the processing difficulty of the pressure relief mechanism 23.

[0245] According to some embodiments of this application, see Figure 5 , Figure 9 as well as Figure 11As shown, in the projection plane perpendicular to the thickness direction X of the wall, the orthographic projection of the thinning region 2331 passes through the geometric center of the orthographic projection of the pressure relief section 233. That is, in the projection plane perpendicular to the thickness direction X of the wall, the geometric center of the orthographic projection of the pressure relief section 233 is located within the orthographic projection of the thinning region 2331, such that the geometric centers of the orthographic projections of the thinning region 2331 and the pressure relief section 233 overlap.

[0246] In this embodiment, by setting the orthographic projection of the thinning region 2331 in the projection plane perpendicular to the thickness direction X of the wall portion to pass through the geometric center of the orthographic projection of the pressure relief part 233, the geometric center of the orthographic projection of the pressure relief part 233 is located within the orthographic projection of the thinning region 2331 in the projection plane perpendicular to the thickness direction X of the wall portion. This enables the first position 2331b of the thinning region 2331 to coincide with the geometric center of the orthographic projection of the thinning region 2331 and the pressure relief part 233, which facilitates the processing and manufacturing of the thinning region 2331 and helps to reduce the manufacturing difficulty of the pressure relief mechanism 23.

[0247] According to some embodiments of this application, please refer to Figure 12 , Figure 12 This is a front view of the pressure relief mechanism 23 provided in some embodiments of this application in the thickness direction X of the wall portion. In the projection plane perpendicular to the thickness direction X of the wall portion, the orthographic projection of the thinning region 2331 does not pass through the geometric center of the orthographic projection of the pressure relief part 233. That is, in the projection plane perpendicular to the thickness direction X of the wall portion, the geometric centers of the orthographic projections of the thinning region 2331 and the pressure relief part 233 do not overlap. Correspondingly, in the projection plane perpendicular to the thickness direction X of the wall portion, the minimum distance between the geometric center of the orthographic projection of the pressure relief part 2333 and the orthographic projection of the thinning region 2331 is L1, which is L1 > 0. In other words, in the projection plane perpendicular to the thickness direction X of the wall portion, the geometric center of the orthographic projection of the pressure relief part 233 and the orthographic projection of the pressure relief part 233 are spaced apart.

[0248] Wherein, L1 is: the minimum distance from the geometric center of the orthographic projection of the pressure relief section 233 to the orthographic projection of the thinning region 2331 in the projection plane perpendicular to the thickness direction X of the wall.

[0249] In this embodiment, in the projection plane perpendicular to the thickness direction X of the wall, by setting the orthographic projection of the thinning region 2331 to not pass through the geometric center of the orthographic projection of the pressure relief part 233, the thinning region 2331 can be far away from the area of ​​the pressure relief part 233 with the greatest deformation during use. This helps to alleviate the fatigue phenomenon of the thinning region 2331, thereby reducing the risk of further weakening of the structural strength of the thinning region 2331. This further alleviates the phenomenon that the explosion position of the pressure relief mechanism 23 appears in the thinning region 2331 when the battery cell 20 experiences thermal runaway. In addition, it further alleviates the phenomenon that the pressure relief mechanism 23 has insufficient pressure relief area during pressure relief, which helps to further reduce the risk of fire and explosion caused by untimely pressure relief of the pressure relief mechanism 23, thereby further improving the reliability of the battery cell 20.

[0250] According to some embodiments of this application, refer to Figure 12 Please refer to further details. Figure 13 , Figure 14 and Figure 15 As shown, Figure 13 A cross-sectional view of the pressure relief mechanism 23 provided in some further embodiments of this application. Figure 14 for Figure 13 A partial enlarged view of point C of the pressure relief mechanism 23 shown. Figure 15 for Figure 13 This is a partial enlarged view of point D on the pressure relief mechanism 23. The minimum thickness of the weak portion 232 is D1, and the minimum thickness of the thinning region 2331 is D2. In the projection plane perpendicular to the thickness direction X of the wall, the minimum distance between the geometric center of the orthographic projection of the pressure relief portion 233 and the orthographic projection of the thinning region 2331 is L1, and the maximum distance between the geometric center of the orthographic projection of the pressure relief portion 233 and the orthographic projection of the weak portion 232 is L2.

[0251] Where 0.06mm≤D1≤0.18mm and 0.26mm≤D2≤0.5mm, 0.1≤L1 / L2≤0.8 is satisfied; or 0.18mm<D1≤0.24mm and 0.35mm≤D2≤0.5mm, 0.1≤L1 / L2≤0.8 is satisfied; or 0.24mm<D1≤0.3mm and 0.45mm≤D2≤0.5mm, 0.1≤L1 / L2≤0.8 is satisfied.

[0252] In this embodiment, L2 is the maximum distance from the geometric center of the orthographic projection of the pressure relief portion 233 to the orthographic projection of the weak portion 232 in the projection plane perpendicular to the thickness direction X of the wall portion, along the direction from the geometric center of the orthographic projection of the pressure relief portion 233 to the outer contour of the orthographic projection of the pressure relief portion 233. For example, the size of the pressure relief portion 233 formed by the weak portion 232 in the second direction Z is larger than the size of the pressure relief portion 233 in the first direction Y. Correspondingly, L2 is the maximum distance between the geometric center of the orthographic projection of the pressure relief portion 233 and the orthographic projection of the weak portion 232 in the projection plane perpendicular to the thickness direction X of the wall portion, along the second direction Z.

[0253] If 0.06mm≤D1≤0.18mm and 0.26mm≤D2≤0.5mm, then 0.1≤L1 / L2≤0.8; or if 0.18mm<D1≤0.24mm and 0.35mm≤D2≤0.5mm, then 0.1≤L1 / L2≤0.8; or if 0.24mm<D1≤0.3mm and 0.45mm≤D2≤0.5mm, then 0.1≤L1 / L 2≤0.8, that is, when 0.06mm≤D1≤0.18mm and 0.26mm≤D2≤0.5mm are satisfied simultaneously, or when 0.18mm<D1≤0.24mm and 0.35mm≤D2≤0.5mm are satisfied simultaneously, or when 0.24mm<D1≤0.3mm and 0.45mm≤D2≤0.5mm are satisfied simultaneously, the ratio of L1 to L2 is 0.1 to 0.8.

[0254] For example, the ratio of L1 to L2 can be 0.1, 0.11, 0.12, 0.15, 0.18, 0.2, 0.22, 0.25, 0.28, 0.3, 0.32, 0.35, 0.38, 0.4, 0.42, 0.45, 0.48, 0.5, 0.52, 0.55, 0.58, 0.6, 0.62, 0.65, 0.68, 0.7, 0.72, 0.75, 0.78, or 0.8, etc.

[0255] To make the technical problems, technical solutions, and beneficial effects solved by the embodiments of this application clearer, the following will provide a more detailed description in conjunction with Comparative Examples 1-3 and Embodiments 1-12. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0256] Comparative Example 1

[0257] 1) Preparation of positive electrode sheet

[0258] LiNi, the positive electrode active material 0.7 Co 0.1 Mn 0.1 A positive electrode slurry is prepared in N-methylpyrrolidone (NMP) using O2, conductive agent Super P, and binder polyvinylidene fluoride (PVDF). The solid content of the positive electrode slurry is 50 wt%, and the solid component is LiNi. 0.7 Co 0.1 Mn 0.1 The mass ratio of O2, Super P, and PVDF is 8:1:1. The positive electrode slurry is coated on the upper and lower surfaces of the current collector aluminum foil and dried at 85°C. After cold pressing, the foil is trimmed, cut, and slit. Then it is dried under vacuum at 85°C for 4 hours to produce the positive electrode sheet.

[0259] 2) Preparation of negative electrode sheet

[0260] Graphite, conductive agent Super P, thickener carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) are mixed evenly in deionized water to prepare a negative electrode slurry. The solid content of the negative electrode slurry is 30 wt%, and the mass ratio of graphite, silicon suboxide, Super P, CMC, and binder styrene-butadiene rubber (SBR) in the solid components is 88:7:3:2. The negative electrode slurry is coated on the upper and lower surfaces of the current collector copper foil and dried at 85°C. Then, it is cold-pressed, trimmed, cut into sheets, and slit. Finally, it is dried under vacuum at 120°C for 12 hours to prepare the negative electrode sheet.

[0261] 3) Preparation of electrolytes

[0262] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), the thoroughly dried electrolyte salt LiPF6 was dissolved in a mixed solvent (the mixed solvent included ethylene carbonate (EC) and diethyl carbonate (DEC), and ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a mass ratio of 50:50) and mixed evenly to obtain a liquid electrolyte with a concentration of 1 mol / L.

[0263] 4) Isolation components

[0264] A 16μm polyethylene film was used as the separator.

[0265] 5) Preparation of battery cell 20

[0266] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to isolate them. The electrode assembly 22 is then wound and placed inside an aluminum casing 21. The electrolyte prepared above is injected into the dried casing 21. The process includes encapsulation, settling, formation, shaping, and capacity testing to complete the fabrication of the battery cell 20. The casing 21 of the battery cell 20 has a rectangular structure, and a pressure relief mechanism 23 is provided on the wall 211 of the casing 21. An annular pressure relief groove 234 is provided on one side of the pressure relief mechanism 23, and a thinning groove 2332 is provided within the area inside the pressure relief groove 234. The thinning groove 2332 extends along an arc trajectory, and both ends of the thinning groove 2332 are connected to the pressure relief groove 2334 in its extension direction. 4 are connected to form a weak part 232 of an annular structure in the area where the pressure relief groove 234 is provided in the pressure relief mechanism 23, and a thinning area 2331 is formed in the area where the thinning groove 2332 is provided in the pressure relief mechanism 23. In Comparative Example 1, the minimum thickness D1 of the weak part 232 of the pressure relief mechanism 23 in the thickness direction X of the wall is 0.08 mm, the minimum thickness D2 of the thinning area 2331 in the thickness direction X of the wall is 0.26 mm, and the minimum distance L1 between the geometric center of the orthographic projection of the pressure relief part 233 and the orthographic projection of the thinning area 2331 in the projection plane perpendicular to the thickness direction X of the wall is 0.525 mm, and the maximum distance L2 between the geometric center of the orthographic projection of the pressure relief part 233 and the orthographic projection of the weak part 232 is 10.5 mm.

[0267] The preparation methods of the battery cells 20 in Comparative Examples 2-3 and Examples 1-12 are the same as those in Comparative Example 1, except that D1, D2, L1 and L2 are different, as shown in Table 1.

[0268] The following comparative examples 1-3 and examples 1-12 demonstrate thermal runaway experiments on D1, D2, L1, and L2 under different conditions, showing the depressurization release mechanism 23 at the initiation point during thermal runaway depressurization of the battery cell 20. The specific experimental methods are as follows:

[0269] (1) A heating film is provided inside the casing 21 of the battery cell 20, and the battery cell 20 is thermally runaway by activating the heating film;

[0270] (2) Before testing, charge the battery cell 20 to 80%-100% SOC and ensure that the temperature of the battery cell 20 is 25±2℃.

[0271] (3) Sensor arrangement:

[0272] a. Temperature sensing wire arrangement: Apply a layer of Teflon to the two main surfaces, two sides, two poles of the top cover and the explosion-proof valve area of ​​the battery cell. Arrange the temperature sensing wire on top of the Teflon and then apply another layer of Teflon.

[0273] b. Voltage sampling line arrangement: A layer of Teflon is attached to the outer shell 21 and the two electrode terminals 24 of the battery cell 20. A voltage sampling line is arranged above the Teflon, and then another layer of Teflon is attached.

[0274] c. Air tube arrangement: Drill a hole in the wall 211 of the outer casing 21. The drilling position is located at the center of one side of the pressure relief mechanism 23 in the length direction of the wall 211, that is, the drilling position is located on one side of the pressure relief mechanism 23 in the length direction of the wall 211, and is located in the middle of the edge of the pressure relief mechanism 23 and the wall 211. Then, insert the air tube into the hole and seal it, and connect the air tube to the air pressure sensor; (a hole is also drilled at the center of the side of the battery cell to connect the air tube and the air pressure sensor).

[0275] d. Connect the temperature sensing wire, voltage sampling wire, and barometric pressure sensor to the data acquisition instrument to collect and analyze data in real time. The data acquisition frequency of the data acquisition instrument is ≤0.02 seconds.

[0276] (4) Assemble the fixture so that it completely covers the largest outer surface of the battery cell 20, with a clamping force of 3000N. (The arrangement order of the fixture, heating plate and battery cell 20 is: fixture + battery cell 20 + fixture).

[0277] (5) Test: Open the data acquisition instrument to collect temperature, voltage and air pressure data, and then trigger the heating of the battery cell 20 with a power of 100W-500W until the battery cell 20 thermally runs away and the pressure relief mechanism 23 bursts and opens the valve. During the experiment, the pressure relief mechanism 23 is recorded throughout the process to observe the detonation position of the pressure relief mechanism 23.

[0278] The criteria for determining thermal runaway of battery cell 20 are as follows: (a) a voltage drop occurs at the trigger point, and the voltage drops to more than 25% of the initial voltage; (b) the temperature at the detection point reaches the maximum operating temperature specified by the manufacturer; (c) the temperature rise rate at the detection point, dT / dt, is ≥1℃ / s and lasts for more than 3 seconds. When (a) and (c) or (b) and (c) are met, battery cell 20 is determined to have experienced thermal runaway, and the moment of thermal runaway of battery cell 20 is determined.

[0279] The opening criteria for the pressure relief mechanism 23 is as follows: when the air pressure drops by more than 25%, it can be determined that the pressure relief mechanism 23 has been opened.

[0280] The experimental results of Comparative Examples 1-3 and Examples 1-12 are shown in Table 1 below.

[0281] Table 1

[0282] Serial Number <![CDATA[D1(mm)]]> <![CDATA[D2(mm)]]> <![CDATA[L1(mm)]]> <![CDATA[L2(mm)]]> <![CDATA[L1 / L2]]> Experimental results (detonation location) Comparative Example 1 0.08 0.26 0.84 10.5 0.08 Thinning zone 2331 Example 1 0.08 0.26 1.05 10.5 0.1 Weak point 232 Example 2 0.08 0.26 2 10 0.2 Weak point 232 Example 3 0.1 0.3 3.4 8.5 0.4 Weak point 232 Example 4 0.18 0.35 6 7.5 0.8 Weak point 232 Comparative Example 2 0.2 0.38 0.84 10.5 0.08 Thinning zone 2331 Example 5 0.2 0.38 1.05 10.5 0.1 Weak point 232 Example 6 0.2 0.38 2 10 0.2 Weak point 232 Example 7 0.22 0.4 3.4 8.5 0.4 Weak point 232 Example 8 0.24 0.45 6 7.5 0.8 Weak point 232 Comparative Example 3 0.26 0.46 0.84 10.5 0.08 Thinning zone 2331 Example 9 0.26 0.46 1.05 10.5 0.1 Weak point 232 Example 10 0.26 0.46 2 10 0.2 Weak point 232 Example 11 0.28 0.48 3.4 8.5 0.4 Weak point 232 Example 12 0.3 0.5 6 7.5 0.8 Weak point 232

[0283] Referring to Table 1, the experimental results of Comparative Examples 1-3 and Examples 1-12 show that when conditions D1 and D2 are met, and the ratio of L1 to L2 is less than 0.1, the detonation location of the pressure relief mechanism 23 occurs in the thinned area 2331 of the pressure relief section 233. This results in insufficient pressure relief area of ​​the pressure relief mechanism 23, making the battery cell 20 prone to fire and explosion due to untimely pressure relief. However, when conditions D1 and D2 are met, and the ratio of L1 to L2 is greater than or equal to 0.1, the detonation location of the pressure relief mechanism 23 occurs in the weak section 232. This allows the pressure relief mechanism 23 to relieve pressure normally, which helps alleviate the risk of fire and explosion of the battery cell 20 due to untimely pressure relief, thereby improving the performance of the battery cell 20. For reliability, L1 / L2 is set to be greater than or equal to 0.1 when 0.06mm≤D1≤0.18mm and 0.26mm≤D2≤0.5mm, or 0.18mm<D1≤0.24mm and 0.35mm≤D2≤0.5mm, or 0.24mm<D1≤0.3mm and 0.45mm≤D2≤0.5mm. When L1 / L2 reaches 0.1 or above, the detonation position of the pressure relief mechanism 23 appears at the weak part 232. Therefore, in order to enable the pressure relief part 233 to release stress through deformation during the cyclic change of air pressure inside the battery cell 20, L1 / L2 is set to be less than or equal to 0.8.

[0284] In this embodiment, when 0.06mm≤D1≤0.18mm and 0.26mm≤D2≤0.5mm, or 0.18mm<D1≤0.24mm and 0.35mm≤D2≤0.5mm, or 0.24mm<D1≤0.3mm and 0.45mm≤D2≤0.5mm, by setting the ratio of L1 to L2 to 0.1 to 0.8, it is beneficial to improve the stress release effect of the pressure relief section 233 in the cyclic change of gas pressure inside the battery cell 20 through deformation, while also adjusting the thinness. The distance between the weak zone and the pressure relief section 233, which has the greatest deformation during use, helps to alleviate the fatigue phenomenon of the thinned zone 2331, thereby reducing the risk of the structural strength of the thinned zone 2331 being weakened. This also helps to mitigate the phenomenon that the explosion point of the pressure relief mechanism 23 occurs in the thinned zone 2331 when the battery cell 20 experiences thermal runaway. Furthermore, it helps to mitigate the phenomenon that the pressure relief mechanism 23 has insufficient pressure relief area during pressure relief, thereby reducing the risk of fire and explosion caused by untimely pressure relief and improving the reliability of the battery cell 20.

[0285] In some embodiments, see Figure 12 , Figure 13 , Figure 14 and Figure 15As shown in the figure, and in conjunction with Table 1, 0.2≤L1 / L2≤0.8.

[0286] In this embodiment, when the pressure relief part 233 is 0.06mm≤D1≤0.18mm and 0.26mm≤D2≤0.5mm, or 0.18mm<D1≤0.24mm and 0.35mm≤D2≤0.5mm, or 0.24mm<D1≤0.3mm and 0.45mm≤D2≤0.5mm, by further setting the ratio of L1 to L2 to 0.2 to 0.8, it is beneficial to improve the effect of stress release by deformation of the pressure relief part 233 during the cyclic change of gas pressure inside the battery cell 20, while also further adjusting the distance between the weak area and the area with the greatest deformation of the pressure relief part 233 during use. This is beneficial to further alleviate the fatigue phenomenon of the thinning area 2331, thereby further reducing the risk of the structural strength of the thinning area 2331 being weakened, and further mitigating the phenomenon that the explosion position of the pressure relief mechanism 23 appears in the thinning area 2331 when thermal runaway occurs in the battery cell 20.

[0287] According to some embodiments of this application, see Figure 5 As shown, the weak part 232 may include a first weak segment 232a and a second weak segment 232b connected end to end, and the minimum thickness of the second weak segment 232b is greater than the minimum thickness of the first weak segment 232a.

[0288] The weak portion 232 includes a first weak segment 232a and a second weak segment 232b connected end to end. That is, the annular weak portion 232 is divided into the first weak segment 232a and the second weak segment 232b, which are interconnected. The thickness of the second weak segment 232b is greater than the thickness of the first weak segment 232a. In other words, the minimum thickness of the portion of the weak portion 232 located in the second weak segment 232b along the thickness direction X of the wall is greater than the minimum thickness of the portion of the weak portion 232 located in the first weak segment 232a along the thickness direction X of the wall. Similarly, in an embodiment where the pressure relief mechanism 23 is provided with a pressure relief groove 234 and forms the weak portion 232, the minimum residual thickness of the region of the pressure relief groove 234 located in the second weak segment 232b is greater than the minimum residual thickness of the region of the pressure relief groove 234 located in the first weak segment 232a.

[0289] In this embodiment, by setting the minimum thickness of the second weak segment 232b of the weak portion 232 to be greater than the minimum thickness of the first weak segment 232a of the weak portion 232, the structural strength of the second weak segment 232b is greater than that of the first weak segment 232a. This allows the first weak segment 232a to crack first compared to the second weak segment 232b when the battery cell 20 is depressurized, so that the depressurization portion 233 can flip around the second weak segment 232b as an axis and open to depressurize. This helps to improve the depressurization smoothness of the depressurization mechanism 23 of the battery cell 20, thereby improving the timeliness of depressurization of the battery cell 20.

[0290] In some embodiments, please continue to see Figure 5 As shown, the weak section 232 includes two straight segments 2321 and two curved segments 2322. The two straight segments 2321 are arranged opposite each other along the first direction Y and extend along the second direction Z. The two curved segments 2322 are arranged opposite each other along the second direction Z and extend along a curved trajectory. One straight segment 2321, one curved segment 2322, another straight segment 2321, and another curved segment 2322 are connected end to end. The first direction Y, the second direction Z, and the thickness direction X of the wall are perpendicular to each other. The first weak section 232a includes two curved segments 2322 and one straight segment 2321, and the second weak section 232b is another straight segment 2321.

[0291] Among them, the two straight segments 2321 and the two arc segments 2322 of the weak part 232 are arranged alternately and connected to each other along the extension direction of the weak part 232, and the two arc segments 2322 and the one straight segment 2321 of the weak part 232 constitute the first weak segment 232a of the weak part 232. Correspondingly, the other straight segment 2321 of the weak part 232 is the second weak segment 232b of the weak part 232.

[0292] It should be noted that in the embodiment where the minimum thickness of the second weak segment 232b is greater than the minimum thickness of the first weak segment 232a, the minimum thickness of the straight segment 2321 of the second weak segment 232b in the thickness direction X of the wall is greater than the minimum thickness of the two curved segments 2322 and the other straight segment 2321 in the thickness direction X of the wall.

[0293] In this embodiment, the first weak segment 232a includes two arc segments 2322 and one straight segment 2321, and the second weak segment 232b is another straight segment 2321 of the weak part 232. The arc segments 2322, the straight segment 2321, the other arc segment 2322, and the other straight segment 2321 are connected end-to-end. This is achieved by configuring the two arc segments 2322 to extend along an arc trajectory and be positioned opposite each other along the second direction Z, and configuring the two straight segments 2321 to extend along the second direction Z and be positioned opposite each other along the first direction Y. With this configuration, the battery cell 20 is easier to form the first weak segment 232a and the second weak segment 232b with different thicknesses on the pressure relief mechanism 23, which helps to reduce the processing difficulty of the pressure relief mechanism 23. On the other hand, it can further improve the smoothness of the pressure relief part 233 flipping around the second weak segment 232b after the first weak segment 232a cracks. It also helps to further expand the flipping angle of the pressure relief part 233 located inside the weak segment 232 of the pressure relief mechanism 23, so as to further improve the pressure relief smoothness and pressure relief rate of the battery cell 20.

[0294] According to some embodiments of this application, see Figure 5 , Figure 7 and Figure 8 As shown, the minimum thickness of the weak part 232 is D1, and the minimum thickness of the thinning region 2331 is D2, which satisfies 0.18≤D1 / D2≤0.62.

[0295] In an embodiment where the pressure relief mechanism 23 is provided with a pressure relief groove 234 and forms a weak part 232, D1 is the minimum residual thickness of the pressure relief groove 234. Similarly, in an embodiment where the pressure relief part 233 is provided with a thinning groove 2332 and forms a thinning area 2331, D2 is the minimum residual thickness of the thinning groove 2332.

[0296] For example, the ratio of D1 to D2 can be 0.18, 0.19, 0.2, 0.21, 0.22, 0.25, 0.28, 0.3, 0.32, 0.35, 0.38, 0.4, 0.42, 0.45, 0.48, 0.5, 0.52, 0.55, 0.58, 0.6, 0.61, or 0.62, etc.

[0297] In this embodiment, by setting the minimum thickness of the weak portion 232 to 0.18 to 0.62 of the minimum thickness of the thinning region 2331, on the one hand, setting the minimum thickness of the weak portion 232 to be greater than or equal to 0.18 of the minimum thickness of the thinning region 2331 alleviates the excessive processing difficulty of the weak portion 232 caused by its excessively small minimum thickness, and reduces the risk of premature cracking due to insufficient structural strength of the weak portion 232, thereby improving the reliability of the battery cell 20. On the other hand, setting the minimum thickness of the weak portion 232 to be small... A thickness of 0.62 times or equal to the minimum thickness of the thinning region 2331 can reduce the risk of the thinning region 2331 cracking preferentially over the weak part 232 when the battery cell 20 is depressurized. This can further alleviate the phenomenon that the explosion position of the pressure relief mechanism 23 occurs in the thinning region 2331 when the battery cell 20 experiences thermal runaway. This can further alleviate the phenomenon that the pressure relief mechanism 23 has insufficient pressure relief area when depressurizing, which is conducive to further reducing the risk of fire and explosion caused by the pressure relief mechanism 23 due to untimely pressure relief. In this way, the reliability of the battery cell 20 can be further improved.

[0298] In some embodiments, see Figure 7 As shown, the minimum thickness of the weak part 232 is D1, which satisfies 0.02mm≤D1≤0.24mm.

[0299] For example, the minimum thickness D1 of the weak portion 232 can be 0.02mm, 0.03mm, 0.04mm, 0.05mm, 0.06mm, 0.07mm, 0.08mm, 0.09mm, 0.1mm, 0.11mm, 0.12mm, 0.13mm, 0.14mm, 0.15mm, 0.16mm, 0.17mm, 0.18mm, 0.19mm, 0.2mm, 0.21mm, 0.22mm, 0.23mm, or 0.24mm, etc.

[0300] In this embodiment, by setting the minimum thickness of the weak part 232 to 0.02mm to 0.24mm, on the one hand, setting the minimum thickness of the weak part 232 to be greater than or equal to 0.02mm can alleviate the risk of premature cracking due to the minimum thickness of the weak part 232 being too small, thereby improving the reliability of the battery cell 20. On the other hand, setting the minimum thickness of the weak part 232 to be less than or equal to 0.24mm can reduce the burst pressure required by the pressure relief mechanism 23 during pressure relief, thereby reducing the risk of the battery cell 20 bursting or exploding during thermal runaway.

[0301] In some embodiments, see Figure 8 As shown, the minimum thickness of the thinning region 2331 is D2, which satisfies 0.22mm≤D2≤0.38mm.

[0302] For example, the minimum thickness D2 of the thinning region 2331 can be 0.22mm, 0.23mm, 0.24mm, 0.25mm, 0.26mm, 0.27mm, 0.28mm, 0.29mm, 0.3mm, 0.31mm, 0.32mm, 0.33mm, 0.34mm, 0.35mm, 0.36mm, 0.37mm, or 0.38mm, etc.

[0303] In this embodiment, by setting the minimum thickness of the thinning region 2331 to 0.22mm to 0.38mm, on the one hand, setting the minimum thickness of the thinning region 2331 to be greater than or equal to 0.22mm can improve the structural strength of the thinning region 2331, so as to alleviate the phenomenon that the thinning region 2331 cracks preferentially over the weak part 232 when the battery cell 20 is depressurized. This further alleviates the phenomenon that the explosion position of the pressure relief mechanism 23 appears in the thinning region 2331 when the battery cell 20 experiences thermal runaway. On the other hand, setting the minimum thickness of the thinning region 2331 to be less than or equal to 0.38mm can improve the weakening effect of the structural strength of the pressure relief part 233, so that the pressure relief part 233 can release stress through deformation during the cyclic change of air pressure inside the battery cell 20, thereby further improving the "breathing" effect of the pressure relief mechanism 23 during use.

[0304] According to some embodiments of this application, see Figure 6 and Figure 7 as well as Figure 13 and Figure 14 As shown, along the thickness direction X of the wall portion, at least a portion of the pressure relief portion 233 protrudes towards or away from the electrode assembly 22 to form a raised portion 2333, and a weak portion 232 surrounds the outside of the raised portion 2333.

[0305] Wherein, the raised portion 2333 is a raised structure in which at least a portion of the pressure relief portion 233 protrudes in the thickness direction X of the wall portion toward or away from the electrode assembly 22. Optionally, the pressure relief portion 233 can be a structure in which the raised portion 2333 is partially raised, or it can be a structure in which the raised portion 2333 is entirely raised. For example, in Figure 7 and Figure 14 In this embodiment, the pressure relief part 233 is a partially raised structure. Of course, in other embodiments, the pressure relief part 233 can also be an overall raised structure. Correspondingly, the pressure relief part 233 is a raised part 2333.

[0306] The weak portion 232 surrounds the outside of the raised portion 2333, that is, the raised portion 2333 is located in the area enclosed by the weak portion 232.

[0307] Optionally, the raised portion 2333 can be a structure that protrudes in the thickness direction X of the wall towards the electrode assembly 22, or it can be a structure that protrudes in the direction away from the electrode assembly 22.

[0308] In this embodiment, by providing a raised portion 2333 on the pressure relief portion 233 inside the weak portion 232, which protrudes towards or away from the electrode assembly 22, and the weak portion 232 surrounds the outside of the raised portion 2333, on the one hand, the difficulty of forming the weak portion 232 on the pressure relief mechanism 23 can be reduced, and the material flow pattern of the weak portion 232 during the processing can be improved, thereby improving the processing consistency of the weak portion 232. On the other hand, the raised portion 2333 inside the weak portion 232 forms a pre-deformed structure, so that the weak portion 232 of the pressure relief mechanism 23 can crack and relieve pressure when the battery cell 20 thermally runs away. Thus, under the same burst pressure, the thickness of the weak portion 232 can be increased to alleviate fatigue cracking and other phenomena in the weak portion 232 during use. This can effectively reduce the risk of premature valve opening of the pressure relief mechanism 23, thereby improving the service life and reliability of the battery cell 20.

[0309] In some embodiments, combined with Figure 6 , Figure 7 and Figure 8 As shown, the raised portion 2333 includes at least a portion of the thinning region 2331, that is, a portion of the raised portion 2333 forms at least a portion of the thinning region 2331. In the embodiment where the pressure relief portion 233 is provided with a thinning groove 2332 and forms a thinning region 2331, at least a portion of the thinning groove 2332 is provided on the raised portion 2333.

[0310] In this embodiment, by setting the raised portion 2333 as a structure that includes at least a portion of the thinning region 2331, so that the thinning region 2331 is also at least partially raised, it is possible to further facilitate the pressure relief portion 233 to release stress through deformation during the cyclical change of air pressure inside the battery cell 20, thereby further improving the "breathing" effect of the pressure relief mechanism 23 during use.

[0311] According to some embodiments of this application, see Figure 6 and Figure 7 as well as Figure 13 and Figure 14 As shown, along the thickness direction X of the wall portion, the pressure relief mechanism 23 has a first surface 235 and a second surface 236 opposite to each other. The first surface 235 is provided with a groove 2351. The bottom wall of the groove 2351 includes a weak portion 232, and a portion of the bottom wall of the groove 2351 bulges along the direction from the second surface 236 to the first surface 235 to form a raised portion 2333.

[0312] The first surface 235 and the second surface 236 are respectively the two sides of the pressure relief mechanism 23 in the thickness direction X of the wall portion. For example, the first surface 235 and the second surface 236 are parallel to each other.

[0313] The first surface 235 is provided with a groove 2351, that is, the groove 2351 is a structure provided on the first surface 235 and recessed in the direction from the first surface 235 to the second surface 236.

[0314] The bottom wall of the groove 2351 includes a weak part 232. That is, the bottom wall of the groove 2351 forms a weak part 232. In the embodiment where the pressure relief mechanism 23 is provided with a pressure relief groove 234 and forms a weak part 232, the pressure relief groove 234 is a structure provided on the bottom wall of the groove 2351.

[0315] The bottom wall of the groove 2351 protrudes along the direction from the second surface 236 to the first surface 235 and forms a raised portion 2333. That is, the raised portion 2333 is a structure that protrudes in the thickness direction X of the wall towards the interior of the groove 2351.

[0316] In this embodiment, by providing a groove 2351 on the first surface 235 of the pressure relief mechanism 23 and setting the raised portion 2333 to a structure that protrudes along the direction from the second surface 236 to the first surface 235, the battery cell 20 with this structure can achieve a structure in which the raised portion 2333 protrudes towards the side of the groove 2351. On the one hand, the groove 2351 and the raised portion 2333 can share part of the space in the thickness direction X of the wall, which is beneficial to save the space occupied by the pressure relief mechanism 23 and improve the space utilization of the battery cell 20. On the other hand, the groove 2351 can also play a certain protective role for the raised portion 2333 to reduce wear or bumps during use or assembly.

[0317] In some embodiments, see Figure 4 , Figure 6 and Figure 7 As shown, the second surface 236 is disposed facing the electrode assembly 22 along the thickness direction X of the wall portion. That is, the protrusion 2333 is a structure that protrudes in the thickness direction X of the wall portion in a direction away from the electrode assembly 22.

[0318] In this embodiment, by setting the second surface 236 of the pressure relief mechanism 23 to face the electrode assembly 22, the raised portion 2333 is a structure that protrudes in the thickness direction X of the wall in a direction away from the electrode assembly 22. On the one hand, this can reduce the phenomenon that the raised portion 2333 occupies the internal space of the battery cell 20, thereby increasing the internal space of the battery cell 20 for accommodating the electrode assembly 22, which is beneficial to improving the energy density of the battery cell 20. On the other hand, it can reduce the interference between the raised portion 2333 and other components inside the battery cell 20, which is beneficial to improving the reliability of the battery cell 20.

[0319] In some embodiments, see Figure 6 and Figure 7 As shown, the pressure relief mechanism 23 is provided with a pressure relief groove 234 and forms a weak part 232. In the projection plane perpendicular to the thickness direction X of the wall, the orthographic projection of the weak part 232 and the orthographic projection of the groove wall of the pressure relief groove 234 overlap. The pressure relief groove 234 is provided on the bottom surface of the groove 2351.

[0320] In this embodiment, a weak part 232 is formed on the pressure relief mechanism 23 by opening a pressure relief groove 234 on the pressure relief mechanism 23, so as to reduce the difficulty of forming the weak part 232 on the pressure relief mechanism 23. In this embodiment, by setting the pressure relief groove 234 on the bottom surface of the groove 2351, the pressure relief groove 234 and the groove 2351 are both located on the same side of the thickness direction X of the wall of the pressure relief mechanism 23. This allows the pressure relief groove 234 to be formed simultaneously while processing the groove 2351, which helps to reduce the difficulty of forming the pressure relief groove 234 on the pressure relief mechanism 23 and optimizes the production cycle of the battery cell 20.

[0321] According to some embodiments of this application, see Figure 6 and Figure 7 As shown, the pressure relief mechanism 23 is provided with a pressure relief groove 234 and forms a weak part 232. In the projection plane perpendicular to the thickness direction X of the wall, the orthographic projection of the weak part 232 and the orthographic projection of the groove wall surface of the pressure relief groove 234 overlap.

[0322] In this embodiment, a weak part 232 is formed on the pressure relief mechanism 23 by opening a pressure relief groove 234 on the pressure relief mechanism 23, so that the pressure relief mechanism 23 can crack along at least a part of the weak part 232 when the battery cell 20 is depressurized. This reduces the difficulty of forming the weak part 232 on the pressure relief mechanism 23, and the structure is simple and easy to manufacture.

[0323] According to some embodiments of this application, see Figure 6 and Figure 8As shown, the pressure relief section 233 is provided with a thinning groove 2332 and forms a thinning area 2331. In the projection plane perpendicular to the thickness direction X of the wall, the orthographic projection of the thinning area 2331 and the orthographic projection of the groove wall surface of the thinning groove 2332 overlap.

[0324] In this embodiment, a thinning region 2331 is formed on the pressure relief part 233 by opening a thinning groove 2332 on the pressure relief part 233, thereby reducing the difficulty of forming the thinning region 2331 on the pressure relief part 233. The structure is simple and easy to manufacture.

[0325] According to some embodiments of this application, see Figure 3 and Figure 4 As shown, the pressure relief mechanism 23 and the wall portion 211 are separate components. That is, the pressure relief mechanism 23 and the wall portion 211 of the outer casing 21 are two independent parts. Correspondingly, the wall portion 211 is provided with a pressure relief hole, and the connecting part 231 of the pressure relief mechanism 23 is connected to the wall portion 211 and the pressure relief mechanism 23 blocks the pressure relief hole.

[0326] The connection structure of the connecting part 231 to the wall part 211 of the outer shell 21 can be various, such as welding connection, snap-fit ​​or adhesive connection.

[0327] In this embodiment, by setting the pressure relief mechanism 23 and the wall portion 211 as separate components, the weak portion 232 and the thinning area 2331 can be machined on the pressure relief mechanism 23 first, and then the pressure relief mechanism 23 can be assembled onto the wall portion 211 of the outer casing 21. This helps to reduce the molding difficulty of the pressure relief mechanism 23 and optimize the production cycle of the battery cell 20.

[0328] Of course, the structure of the battery cell 20 is not limited to this. In some embodiments, the battery cell 20 can also be other structures. For example, the pressure relief mechanism 23 is integrally formed with the wall portion 211. Correspondingly, the weak portion 232 and the weak area are structures formed on the wall portion 211 by an integral forming process, such as stamping, and the connecting portion 231 is a part of the wall portion 211.

[0329] In this embodiment, by setting the pressure relief mechanism 23 and the wall portion 211 as an integral structure, the battery cell 20 with this structure can improve the structural strength of the pressure relief mechanism 23 connected to the wall portion 211, thereby reducing the risk of the pressure relief mechanism 23 falling off during use, and thus improving the stability and reliability of the battery cell 20.

[0330] According to some embodiments of this application, see Figure 3 and Figure 4As shown, the outer casing 21 may include a housing 212 and an end cap 213. The housing 212 includes an integrally formed side wall and a bottom wall. The side wall surrounds the bottom wall. Along the thickness direction X of the wall, one end of the side wall is connected to the bottom wall, and the other end forms an opening 2121. The side wall and the bottom wall together define a receiving cavity. The electrode assembly 22 is received in the receiving cavity. The end cap 213 closes the opening 2121. The end cap 213 is a wall 211.

[0331] The end cap 213 is a wall portion 211, meaning that the pressure relief mechanism 23 is located on the end cap 213 of the outer casing 21.

[0332] In this embodiment, by setting the wall portion 211 of the outer casing 21 as an end cap 213 for closing the opening 2121, the battery cell 20 with this structure is convenient to set a pressure relief mechanism 23 on the end cap 213, which helps to reduce the manufacturing difficulty of the battery cell 20 and improve the production efficiency of the battery cell 20.

[0333] It should be noted that the structure of the battery cell 20 is not limited to this. In some embodiments, the battery cell 20 can also have other structures. For example, the outer casing 21 can include a housing 212 and an end cap 213. The housing 212 includes an integrally formed side wall and a bottom wall. The side wall surrounds the bottom wall. Along the thickness direction X of the wall portion, one end of the side wall is connected to the bottom wall, and the other end forms an opening 2121. The side wall and the bottom wall together define a receiving cavity, in which the electrode assembly 22 is received. The end cap 213 closes the opening 2121, and the bottom wall is a wall portion 211. That is, the wall portion 211 is the bottom wall of the housing 212 that is opposite to the end cap 213 in the thickness direction X of the wall portion, i.e., the pressure relief mechanism 23 is provided on the bottom wall of the housing 212.

[0334] The shell 212 includes an integrally formed side wall and bottom wall. In other words, the shell 212 is manufactured using an integral forming process, such as stamping, casting or extrusion molding. Thus, the side wall and bottom wall of the shell 212 are an integral structure.

[0335] In this embodiment, by setting the wall portion 211 of the outer casing 21 as the bottom wall of the casing 212 opposite to the end cap 213 in the thickness direction X of the wall portion, the battery cell 20 with this structure can ensure that the area of ​​the outer casing 21 where the pressure relief mechanism 23 is provided is far away from the end cap 213. This can effectively alleviate the phenomenon that the stress generated by the connection between the end cap 213 and the casing 212 acts on the pressure relief mechanism 23, thereby reducing the impact on the pressure relief mechanism 23. This helps to reduce the risk of cracking or structural strength reduction of the weak part 232 of the pressure relief mechanism 23 under the stress, thereby improving the service life and reliability of the battery cell 20.

[0336] According to some embodiments of this application, this application also provides a battery device 100, which includes a battery cell 20 of any of the above schemes.

[0337] Among them, see Figure 2 As shown, the battery device 100 may also include a housing 10, in which the battery cells 20 are housed.

[0338] In some embodiments, the housing 10 may include a first housing body 11 and a second housing body 12, the first housing body 11 and the second housing body 12 covering each other, the first housing body 11 and the second housing body 12 together defining an assembly space for accommodating the battery cell 20.

[0339] Optionally, the second box body 12 can be a hollow structure with one end open, and the first box body 11 can be a plate-like structure. The first box body 11 covers the open side of the second box body 12 so that the first box body 11 and the second box body 12 together define the assembly space; the first box body 11 and the second box body 12 can also be hollow structures with one side open, and the open side of the first box body 11 covers the open side of the second box body 12.

[0340] Of course, the box 10 formed by the first box body 11 and the second box body 12 can be of various shapes, such as a cylinder or a cuboid. For example, in... Figure 2 In the middle, box 10 has a rectangular structure.

[0341] Optionally, the battery cell 20 disposed within the housing 10 can be one or more. For example, in... Figure 2 In the battery device 100, multiple battery cells 20 are arranged inside the housing 10. The multiple battery cells 20 can be connected in series, parallel, or in a mixed manner. A mixed connection means that the multiple battery cells 20 are connected in both series and parallel. The multiple battery cells 20 can be directly connected in series, parallel, or in a mixed manner, and then the whole assembly of the multiple battery cells 20 is housed in the housing 10. Of course, the battery device 100 can also be formed by first connecting multiple battery cells 20 in series, parallel, or in a mixed manner to form a battery module, and then connecting multiple battery modules in series, parallel, or in a mixed manner to form a whole assembly, which is also housed in the housing 10.

[0342] The battery device 100 may also include other structures. For example, the battery device 100 may also include a busbar component that connects multiple battery cells 20 to achieve electrical connection between the multiple battery cells 20.

[0343] It should be noted that in some embodiments, the battery device 100 may not have a housing 10. The battery device 100 includes multiple battery cells 20, and the battery device 100 composed of multiple battery cells 20 can be directly mounted onto the electrical device to provide power to the electrical device through the multiple battery cells 20. That is, the housing 10 can be part of the electrical device. Taking a vehicle 1000 as an example, the housing 10 can be part of the chassis structure of the vehicle 1000. For example, a portion of the housing 10 can be at least a part of the floor of the vehicle 1000, or a portion of the housing 10 can be at least a part of the crossbeams and longitudinal beams of the vehicle 1000.

[0344] According to some embodiments of this application, this application also provides an electrical device, which includes a battery cell 20 of any of the above schemes, and the battery cell 20 is used to provide electrical energy to the electrical device.

[0345] The electrical device can be any of the aforementioned devices or systems that utilize battery cells 20.

[0346] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0347] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A battery cell, characterized by, The application relates to a pressure relief mechanism of an electrode assembly. The pressure relief mechanism comprises a connecting portion, a weakened portion and a pressure relief portion. The connecting portion is connected to the wall portion. The weakened portion is arranged around the pressure relief portion and connects the connecting portion and the pressure relief portion. The weakened portion is configured to be at least partially destroyed to release pressure when the pressure inside the shell reaches a threshold value. The pressure relief portion has at least one thinned area.

2. The battery cell of claim 1, wherein, The thinned area is strip-shaped.

3. The battery cell of claim 1, wherein, The minimum thickness of the thinned area is greater than the minimum thickness of the weakened portion.

4. The battery cell of claim 3, wherein, In a projection plane perpendicular to the thickness direction of the wall portion, the position of the closest projection of the thinned area to the geometric center of the closest projection of the pressure relief portion is a first position, and the position of the farthest projection of the thinned area to the geometric center of the closest projection of the pressure relief portion is a second position. The minimum thickness of the thinned area gradually increases from the second position to the first position along the extension direction of the thinned area.

5. The battery cell of claim 1, wherein, Both ends of the thinned area in the extension direction thereof are connected to the weakened portion.

6. The battery cell of claim 5, wherein, The thinned area comprises two first segments connected to each other.

7. The battery cell of claim 5, wherein, The connection position of the two first segments is the first position. The position where the first segment is connected to the weakened portion is the second position. In the extension direction of the thinned area, the lengths of the two first segments are equal.

8. The battery cell of claim 1, wherein, In the projection plane perpendicular to the thickness direction of the wall portion, the closest projection of the thinned area extends along an arc trajectory. The pressure relief portion is provided with two thinned areas.

9. The battery cell of claim 8, wherein, The two thinned areas are oppositely arranged along a first direction. In the projection plane perpendicular to the thickness direction of the wall portion, the geometric center of the closest projection of the pressure relief portion is located between the closest projections of the two thinned areas along the first direction. The first direction is perpendicular to the thickness direction of the wall portion. The weakened portion comprises two straight segments and two arc segments. The two straight segments are oppositely arranged along a first direction and extend along a second direction. The two arc segments are oppositely arranged along the second direction and extend along an arc trajectory. One straight segment, one arc segment, another straight segment and another arc segment are sequentially connected. The first direction, the second direction and the thickness direction of the wall portion are perpendicular to each other. The two ends of the thinned area in the extension direction thereof are respectively connected to the two arc segments. Or the two ends of the thinned area in the extension direction thereof are connected to the same straight segment. The thinned area comprises a plurality of thinned segments connected to each other. In the projection plane perpendicular to the thickness direction of the wall portion, the closest projection of at least one thinned segment extends along an arc trajectory, and the closest projection of at least one thinned segment extends along a straight line trajectory. The thinned segments of the thinned area are three. The central thinning section in the three thinning sections extends along an arc trajectory in the projection plane perpendicular to the thickness direction of the wall portion, and the two end thinning sections in the three thinning sections extend along a straight line trajectory.

10. The battery cell of claim 1, wherein, The thinning region comprises a plurality of thinning sections connected in sequence. The thinning section extends along a straight line trajectory in the projection plane perpendicular to the thickness direction of the wall portion, and the extension directions of the projections of the two connected thinning sections intersect.

11. The battery cell of claim 10, wherein, The thinning section of the thinning region is two.

12. The battery cell of claim 1, wherein, The projection of the thinning region extends along a straight line trajectory in the projection plane perpendicular to the thickness direction of the wall portion.

13. The battery cell of claim 12, wherein, The thinning region is a plurality of thinning regions, the projections of the plurality of thinning regions intersect at a connecting region in the projection plane perpendicular to the thickness direction of the wall portion, and the geometric center of the projection of the pressure relief portion is located in the connecting region.

14. The battery cell of any one of claims 1-13, wherein, The projection of the thinning region passes through the geometric center of the projection of the pressure relief portion in the projection plane perpendicular to the thickness direction of the wall portion.

15. The battery cell of any one of claims 1-13, wherein, The projection of the thinning region does not pass through the geometric center of the projection of the pressure relief portion in the projection plane perpendicular to the thickness direction of the wall portion.

16. The battery cell of claim 15, wherein, The minimum thickness of the weak portion is D1, the minimum thickness of the thinning region is D2, the minimum distance between the geometric center of the projection of the pressure relief portion and the projection of the thinning region is L1, and the maximum distance between the geometric center of the projection of the pressure relief portion and the projection of the weak portion is L2. 0.06mm≤D1≤0.18mm and 0.26mm≤D2≤0.5mm, and 0.1≤L1 / L2≤0.8; or 0.18mm<D1≤0.24mm and 0.35mm≤D2≤0.5mm, and 0.1≤L1 / L2≤0.8; or 0.24mm<D1≤0.3mm and 0.45mm≤D2≤0.5mm, and 0.1≤L1 / L2≤0.

8.

17. The battery cell of claim 16, wherein, 0.2≤L1 / L2≤0.

8.

18. The battery cell of claim 1, wherein, The weak portion comprises a first weak section and a second weak section connected in sequence, and the minimum thickness of the second weak section is greater than the minimum thickness of the first weak section.

19. The battery cell of claim 18, wherein, The weak portion comprises two straight line sections and two arc line sections, the two straight line sections are oppositely arranged along a first direction and extend along a second direction, the two arc line sections are oppositely arranged along the second direction and extend along an arc trajectory, and one straight line section, one arc line section, another straight line section and another arc line section are sequentially connected in sequence, the first direction, the second direction and the thickness direction of the wall portion are perpendicular to each other. The first weak section comprises two arc line sections and one straight line section, and the second weak section is another straight line section.

20. The battery cell of claim 1, wherein, The minimum thickness of the weak portion is D1, and the minimum thickness of the thinning region is D2, and 0.18≤D1 / D2≤0.

62.

21. The battery cell of claim 20, wherein, 0.02mm≤D1≤0.24mm; and / or 0.22mm≤D2≤0.38mm.

22. The battery cell of claim 1, wherein, At least part of the pressure relief portion is raised in a direction close to or away from the electrode assembly along a thickness direction of the wall portion and forms a raised portion, and the weakened portion is arranged outside the raised portion.

23. The battery cell of claim 22, wherein, The raised portion includes at least part of the thinned region.

24. The battery cell of claim 22, wherein, The pressure relief mechanism has opposite first and second surfaces along a thickness direction of the wall portion, the first surface is provided with a groove, a groove bottom wall of the groove includes the weakened portion, and part of the groove bottom wall is raised in a direction from the second surface to the first surface and forms the raised portion.

25. The battery cell of claim 24, wherein, The second surface is arranged to face the electrode assembly along the thickness direction of the wall portion.

26. The battery cell of claim 24, wherein, The pressure relief mechanism is provided with a pressure relief groove and forms the weakened portion, and in a projection plane perpendicular to the thickness direction of the wall portion, a normal projection of the weakened portion and a normal projection of a groove wall surface of the pressure relief groove overlap. The pressure relief groove is arranged on a groove bottom surface of the groove.

27. The battery cell of claim 1, wherein, The pressure relief mechanism is provided with a pressure relief groove and forms the weakened portion, and in a projection plane perpendicular to the thickness direction of the wall portion, a normal projection of the weakened portion and a normal projection of a groove wall surface of the pressure relief groove overlap.

28. The battery cell of claim 1, wherein, The pressure relief portion is provided with a thinned groove and forms the thinned region, and in a projection plane perpendicular to the thickness direction of the wall portion, a normal projection of the thinned region and a normal projection of a groove wall surface of the thinned groove overlap.

29. The battery cell of claim 1, wherein, The pressure relief mechanism is separately arranged from the wall portion; or The pressure relief mechanism is integrally formed with the wall portion.

30. The battery cell of claim 1, wherein, The housing includes: A housing including an integrally formed side wall and a bottom wall, the side wall being arranged around the bottom wall, one end of the side wall being connected to the bottom wall along a thickness direction of the wall portion, and the other end being closed to form an opening, the side wall and the bottom wall jointly defining a containing cavity, and the electrode assembly being contained in the containing cavity; An end cover closing the opening; The end cover is the wall portion; or The bottom wall is the wall portion.

31. A battery device, characterized by A battery cell as claimed in any one of claims 1 to 30.

32. An electrical device, comprising: A battery cell as claimed in any one of claims 1 to 30, the battery cell being used to provide electrical energy.

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