Battery cells and battery packs

Abstract

The utility model relates to battery technical field discloses a kind of battery monomer and battery pack.The battery monomer includes: shell, the one end of shell is provided with opening, the outer periphery of shell is formed with the rolling groove recessed towards shell;Cover plate, cover plate is installed in the side of rolling groove close to opening and closes opening, cover plate from its edge towards the center axis direction including installation part, the explosion-proof part of center axis area and the stress buffer portion between installation part and explosion-proof part, explosion-proof part is provided with controllable rupture structure, controllable rupture structure is configured to at least partially rupture to release internal pressure of battery monomer when the pressure inside battery monomer exceeds threshold value;Wherein, stress buffer portion includes first transition wall, second transition wall and the buffer wall connected between first transition wall and second transition wall, first transition wall is connected with installation part, second transition wall is connected with explosion-proof part, at least partial buffer wall thickness along the center axis direction of cover plate is less than the material thickness of cover plate.

Description

Technical Field

[0001] This utility model relates to the field of battery technology, and in particular to a battery cell and a battery pack. Background Technology

[0002] Currently, the main assembly technologies for battery covers and casings are laser welding and sealing. Laser welding suffers from low efficiency and the generation of metal shavings, while sealing technology, which combines the cover with sealing materials for mechanical sealing, remains the preferred choice for new national standard safety batteries. In actual manufacturing processes, since the cover not only provides a seal but also often integrates an explosion-proof valve, the mechanical seal places high demands on the rationality of the cover design.

[0003] In related technologies, when designing cover plates, designers often focus more on optimizing the axial stress deformation caused by gas production during the cover plate's life cycle, often neglecting the stress concentration and damage to the cover plate during the sealing process, which affects the function of the explosion-proof valve. Utility Model Content

[0004] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a battery cell in which, during the sealing process or extrusion process, the buffer wall in the stress buffer section of the cover plate preferentially undergoes controllable deformation, thereby absorbing the mechanical stress transmitted from the edge of the cover plate and effectively suppressing the transmission of the mechanical stress to the explosion-proof section.

[0005] This utility model further proposes a battery pack.

[0006] A battery cell according to a first aspect of the present invention includes: a housing, one end of which has an opening, and a groove formed on the outer periphery of the housing that is recessed toward the interior of the housing; a cover plate, which is mounted on the side of the groove near the opening and closes the opening, the cover plate including a mounting portion, an explosion-proof portion near the central axis, and a stress buffer portion located between the mounting portion and the explosion-proof portion from its edge toward its central axis, the explosion-proof portion being provided with a controllable rupture structure, the controllable rupture structure being configured to at least partially rupture to release the internal pressure of the battery cell when the pressure inside the battery cell exceeds a threshold; wherein the stress buffer portion includes a first transition wall, a second transition wall, and a buffer wall connected between the first transition wall and the second transition wall, the first transition wall being connected to the mounting portion, the second transition wall being connected to the explosion-proof portion, and the wall thickness of at least a portion of the buffer wall along the central axis of the cover plate being less than the material thickness of the cover plate.

[0007] Therefore, by thinning the wall thickness of at least a portion of the buffer wall, the stiffness of this portion of the buffer wall is lower than that of the first transition wall and the second transition wall. During the sealing process or the extrusion process, the at least a portion of the buffer wall preferentially undergoes controllable deformation. Through local deformation, energy is dissipated, effectively absorbing the mechanical stress transmitted from the mounting part, significantly suppressing the transmission of the mechanical stress to the explosion-proof part, and preventing the controllable fracture structure from prematurely rupturing due to assembly residual stress.

[0008] According to some embodiments of the present invention, the controllable fracture structure is constructed as explosion-proof markings, the explosion-proof markings are distributed continuously or discontinuously along the circumference of the cover plate, the stress buffer portion is distributed continuously or discontinuously along the circumference of the cover plate, the stress buffer portion is arranged around the explosion-proof portion, and the stress buffer portion and the explosion-proof markings are arranged correspondingly in the circumference.

[0009] According to some embodiments of this utility model, along the radial direction perpendicular to the circumference of the cover plate, the distance from the edge of the buffer wall near the central axis to the central axis is R1, the distance from the edge of the explosion-proof groove away from the central axis to the central axis is R2, the wall thickness of at least a portion of the buffer wall along the central axis direction is d, the material thickness of the cover plate is D, and the minimum remaining material thickness of the cover plate at the explosion-proof groove is v. The d satisfies the relationship: k×v×(R2 / R1)<d<D; where k is a constant, and 1<k<2.

[0010] According to some embodiments of the present invention, along the radial direction, the width of the explosion-proof groove at its own opening end is L1, and the width of the buffer wall is L2. The L2 satisfies the following relationship: L2≥3L1, 0.4mm≤L1≤0.8mm.

[0011] According to some embodiments of this utility model, along the radial direction, the distance from the edge of the cover plate to the central axis is R; the distance from the edge of the explosion-proof groove away from the central axis to the central axis is R2; the distance from the edge of the stress buffer part near the central axis to the edge of the cover plate is C1; the mounting part is an annular platform arranged along the circumferential direction and its thickness along the central axis direction is equal to the material thickness of the cover plate; the width of the mounting part along the radial direction is C2; the width of the buffer wall along the radial direction is L2; ​​the widths of the first transition wall and the second transition wall along the radial direction are both L3; L2 is (C1-C2-2L3), where 0.4mm≤L3≤0.8mm, 3mm≤C2≤6mm, and C1<(R-R2), where 0.5R≤R2≤0.7R.

[0012] According to some embodiments of the present invention, the cover plate further includes: a first reinforcing rib, the first reinforcing rib being located between the stress buffer portion and the explosion-proof portion, along the central axis direction, the first reinforcing rib protruding relative to the mounting portion, and the first reinforcing rib being distributed continuously or discontinuously along the circumference of the cover plate and surrounding the explosion-proof portion.

[0013] According to some embodiments of this utility model, along the radial direction, the distance from the edge of the cover plate to the side of the first reinforcing rib closest to the central axis is C3; the width of the bottom wall of the first reinforcing rib along the radial direction is L4; the width of the two side walls of the first reinforcing rib along the radial direction is the same and both are L5; the width of the explosion-proof groove at its own opening end along the radial direction is L1; the distance between the edge of the first reinforcing rib away from the central axis and the edge of the stress buffer part closest to the central axis is C4; L2 is [C3-C2-C4-(L4+2L5)-2L3], where C3<(R-R2), C4≥0.5mm, 0.4mm≤L5≤0.8mm, L4>L1.

[0014] According to some embodiments of the present invention, along the radial direction, the distance between the edge of the first reinforcing rib near the central axis and the edge of the explosion-proof groove away from the central axis is C5; L2 is [(R-R2)-C2-C4-(L4+2L5)-2L3-C5], where 0.5mm≤C5≤5mm.

[0015] According to some embodiments of the present invention, the explosion-proof part is provided with a second reinforcing rib. The second reinforcing rib is distributed continuously or discontinuously along the circumference of the cover plate and is located radially inside the explosion-proof groove. Along the central axis, the second reinforcing rib protrudes relative to the mounting part, and the protrusion direction of the second reinforcing rib is opposite to the protrusion direction of the first reinforcing rib.

[0016] According to some embodiments of this utility model, along the central axis direction, the protrusion height of the first reinforcing rib is h1, the protrusion height of the second reinforcing rib is h2, the material thickness of the cover plate is D, and h1 and h2 both satisfy the following relationships: 0.5D≤h1≤3D, 0.5D≤h2≤3D; and / or along the central axis direction, if the first reinforcing rib protrudes toward the opening side of the housing, then the height difference between the side of the first reinforcing rib away from the surface of the cover plate and the end face of the housing on the opening side is greater than 0, and the height difference between the side of the second reinforcing rib away from the surface of the cover plate and the side of the groove away from the cover plate is greater than 0; or along the central axis direction, if the first reinforcing rib protrudes toward the groove side, the height difference between the side of the first reinforcing rib away from the surface of the cover plate and the side of the groove away from the cover plate is greater than 0, and the height difference between the side of the second reinforcing rib away from the surface of the cover plate and the end face of the housing on the opening side is greater than 0.

[0017] According to some embodiments of the present invention, along the central axis direction, the first reinforcing rib protrudes relative to the mounting portion to form a first groove with the surface of the cover plate, and the groove opening direction of the first groove is the same as the opening direction of the explosion-proof marking; and / or the first transition wall, the buffer wall and the second transition wall form a second groove, and the groove opening direction of the second groove is the same as the opening direction of the explosion-proof marking.

[0018] According to some embodiments of the present invention, along the central axis direction, the stress buffer portion is recessed relative to the cover plate surface on the side near the groove, so as to form a boss on the other side relative to the cover plate surface. The height difference between the side of the boss away from the cover plate surface and the cover plate surface is greater than or equal to 0, and the height difference between the side of the boss away from the cover plate surface and the end face of the housing on its opening side is greater than 0; or along the central axis direction, the stress buffer portion is recessed relative to the cover plate surface on the side near the opening of the housing, so as to form a boss on the other side relative to the cover plate surface. The height difference between the side of the boss away from the cover plate surface and the cover plate surface is greater than or equal to 0, and the height difference between the side of the boss away from the cover plate surface and the side of the groove away from the cover plate is greater than 0.

[0019] The battery pack according to a second aspect of the present invention includes the aforementioned battery cells.

[0020] Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0021] The above and / or additional aspects and advantages of this utility model will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a schematic diagram of the appearance of a battery cell according to an embodiment of the present utility model; Figure 2 This is a cross-sectional schematic diagram of a battery cell according to an embodiment of the present utility model; Figure 3 This is a cross-sectional schematic diagram of the assembly of the shell and the cover plate according to an embodiment of the present utility model; Figure 4 This is a schematic diagram of the cover plate according to an embodiment of the present utility model; Figure 5 This is a cross-sectional schematic diagram of the cover plate according to an embodiment of the present utility model; Figure 6 This is a schematic diagram of the dimensions of the cover plate according to an embodiment of the present utility model.

[0022] Figure label: 100. Battery cell; 1. Housing; 11. Opening; 12. Groove; 2. Cover plate; 21. Mounting part; 22. Explosion-proof part; 2201. Explosion-proof groove; 23. Stress buffer part; 2301. First transition wall; 2302. Second transition wall; 2303. Buffer wall; 24. First reinforcing rib; 25. Second reinforcing rib; 26. First groove; 27. Second groove; 28. Boss; 3. Seal. Detailed Implementation

[0023] The embodiments of the present invention are described in detail below. The embodiments described with reference to the accompanying drawings are exemplary. The embodiments of the present invention are described in detail below.

[0024] The following is for reference. Figures 1-6 This invention describes a battery cell 100 and a battery pack including the battery cell 100 according to embodiments of the present invention.

[0025] like Figures 1-3 As shown, the battery cell 100 according to an embodiment of the present invention includes: a housing 1 and a cover plate 2. One end of the housing 1 has an opening 11, and a groove 12 recessed towards the inside of the housing 1 is formed on the outer periphery of the housing 1. The cover plate 2 is installed on the side of the groove 12 near the opening 11 and closes the opening 11. A receiving cavity is formed inside the housing 1 for accommodating the battery cell, electrolyte, and other necessary components of the battery cell 100. One end of the housing 1 has an opening 11, and the shape of the cover plate 2 is adapted to the shape of the opening 11.

[0026] Specifically, the housing 1 has a groove 12 that is radially recessed towards the housing 1 on the outer periphery of the side near the opening 11. The cover plate 2 is installed on the step on the side of the groove 12 away from the battery cell through the opening 11. When the housing 1 is sealed, the opening 11 area of ​​the housing 1 is deformed by mechanical extrusion so as to press the cover plate 2 and the sealing element 3 tightly in the opening 11 area of ​​the housing 1, thereby achieving a mechanical seal of the housing 1 at the opening 11 end.

[0027] During the sealing process or extrusion process, the opening 11 end of the shell 1 is deformed by external force, and radial and / or axial extrusion force is applied to the edge of the cover plate 2. The stress generated by this extrusion force will be transmitted to the explosion-proof valve area through the cover plate 2, resulting in additional residual stress at the score, thereby reducing its actual burst pressure threshold. This causes the score to open unexpectedly when the internal pressure of the battery cell 100 does not reach the preset safety value, affecting the safety and reliability of the battery cell 100.

[0028] Therefore, in combination Figures 3-5 As shown, an embodiment of the present invention provides a cover plate 2. The cover plate 2 includes a mounting portion 21, an explosion-proof portion 22 near the central axis, and a stress buffer portion 23 located between the mounting portion 21 and the explosion-proof portion 22 from its edge toward its central axis. The explosion-proof portion 22 is provided with a controllable rupture structure, which is configured to at least partially rupture to release the internal pressure of the battery cell 100 when the pressure inside the battery cell 100 exceeds a threshold.

[0029] The mounting part 21 provides a sealing mating surface for placing the sealing element 3. During the sealing process, the opening 11 end of the housing 1 is deformed by pressure, pressing the sealing element 3 tightly between the mounting part 21 and the inner wall of the housing 1, thereby achieving a mechanical seal of the housing 1 at the opening 11 end.

[0030] The controllable rupture structure of the explosion-proof part 22 forms a pressure-weak part, and the pressure borne at the controllable rupture structure is the explosion-proof pressure threshold of the battery cell 100. When the pressure inside the battery cell 100 exceeds the threshold, the controllable rupture structure ruptures at least partially to release the internal pressure of the battery cell 100, thereby achieving axial directional explosion of the battery cell 100 due to thermal runaway.

[0031] This invention provides a stress buffer 23 between the mounting part 21 and the explosion-proof part 22. During the sealing process or extrusion process, the stress buffer 23 absorbs the radial and / or axial stress transmitted from the mounting part 21, thereby blocking or attenuating the mechanical stress transmitted from the mounting part 21 to the explosion-proof part 22 and preventing the mechanical stress from being transmitted to the explosion-proof part 22. This ensures that the controllable rupture structure is only triggered to rupture when the internal pressure of the battery cell 100 reaches a set threshold.

[0032] Further, the stress buffer section 23 includes a first transition wall 2301, a second transition wall 2302, and a buffer wall 2303 connected between the first transition wall 2301 and the second transition wall 2302. The first transition wall 2301 is connected to the mounting section 21, and the second transition wall 2302 is connected to the explosion-proof section 22. At least a portion of the buffer wall 2303 has a wall thickness along the central axis of the cover plate 2 that is less than the material thickness of the cover plate 2. Figure 5 and Figure 6 As shown, the central axis of cover plate 2 is a straight line m, and the direction along straight line m is the direction of the central axis of cover plate 2.

[0033] Specifically, at least a portion of the buffer wall 2303 has a wall thickness less than the material thickness of the cover plate 2 along the central axis direction, which makes the stiffness of this portion of the buffer wall 2303 lower than that of the first transition wall 2301 and the second transition wall 2302. During the sealing process or extrusion process, this portion of the buffer wall 2303 preferentially undergoes controllable deformation due to its lower stiffness. Through local deformation, it dissipates energy and effectively absorbs the mechanical stress transmitted by the mounting part 21, significantly suppressing the transmission of the mechanical stress to the explosion-proof part 22, and preventing the controllable fracture structure from prematurely breaking due to assembly residual stress.

[0034] The first transition wall 2301 connects the mounting portion 21 and the buffer wall 2303. Its wall thickness gradually changes from the thickness of the mounting portion 21 along the central axis of the cover plate 2 to the thinner thickness of the buffer wall 2303, thus mitigating the stiffness difference between the two and preventing stress concentration. The second transition wall 2302 connects the buffer wall 2303 and the explosion-proof portion 22, further smoothing the stress transmission path and ensuring that mechanical loads are preferentially absorbed by the buffer wall 2303 rather than directly acting on the controllable fracture structure of the explosion-proof portion 22. The connection between the second transition wall 2302 and the explosion-proof portion 22 is not limited to a direct connection.

[0035] It should be noted that the material thickness of cover plate 2 refers to the thickness of the non-thinning and non-functional areas of cover plate 2. The non-thinning area refers to the area of ​​the cover plate 2 substrate that has not undergone thinning processing, i.e., its thickness remains the original rolled thickness of the substrate, as opposed to the thinning areas (such as the stress buffer part 23, which needs to be thinned to a thinner size through processes such as stamping and etching). The non-thinning area may include some functional areas (such as the mounting part 21, which does not require thinning and is also considered a non-thinning area) and non-functional areas. Non-functional areas refer to areas on cover plate 2 that do not directly undertake the core functions of sealing, buffering, and explosion protection, but only serve a structural connection function, as opposed to functional areas (such as the stress buffer part 23). Among these, non-functional areas typically belong to the non-thinning areas (which do not require thinning).

[0036] Therefore, by thinning the wall thickness of at least a portion of the buffer wall 2303, the stiffness of this portion of the buffer wall 2303 is lower than that of the first transition wall 2301 and the second transition wall 2302. During the sealing process or the extrusion process, the at least a portion of the buffer wall 2303 preferentially undergoes controllable deformation. Through local deformation, energy is dissipated, effectively absorbing the mechanical stress transmitted by the mounting part 21, significantly suppressing the transmission of the mechanical stress to the explosion-proof part 22, and preventing the controllable fracture structure from prematurely fractured due to assembly residual stress.

[0037] In some embodiments of this utility model, the controllable fracture structure is constructed as an explosion-proof notch 2201. The explosion-proof notch 2201 is distributed continuously or discontinuously along the circumference of the cover plate 2. The stress buffer part 23 is distributed continuously or discontinuously along the circumference of the cover plate 2. The stress buffer part 23 is arranged around the explosion-proof part 22. The stress buffer part 23 and the explosion-proof notch 2201 are arranged correspondingly in the circumference of the cover plate 2.

[0038] Specifically, the explosion-proof grooves 2201 are distributed continuously or discontinuously along the circumference of the cover plate 2, while the stress buffer section 23 adopts a distribution pattern corresponding to the explosion-proof grooves 2201 and surrounds the explosion-proof section 22, forming a circumferentially continuous or discontinuous stress barrier. Regardless of the radial direction of the stress transmitted from the cover plate 2, it must first pass through the stress buffer section 23 to absorb energy through deformation, thereby suppressing the transmission of mechanical stress to the explosion-proof section 22. This achieves all-round stress shielding and effectively prevents the explosion-proof grooves 2201 from cracking prematurely. If the stress buffer section 23 is only partially provided (such as on one side), the stress may "bypass" into the explosion-proof section 22 from places without the stress buffer section 23. However, the surrounding arrangement ensures that the stress flow must pass through the stress buffer section 23, forcibly guiding the energy dissipation path. Even if the stress buffer section 23 is discontinuous, as long as each segment covers the key outer peripheral area of ​​the explosion-proof grooves 2201, it can still effectively suppress the transmission of stress to the explosion-proof section 22. For ease of description below, the central axis of cover plate 2 is simply referred to as the central axis, the circumferential direction of cover plate 2 is simply referred to as the circumferential direction, and the radial direction of cover plate 2 is simply referred to as the radial direction.

[0039] In some embodiments of this utility model, such as Figure 6 As shown, along the radial direction perpendicular to the circumference of the cover plate 2, the distance from the edge of the buffer wall 2303 near the central axis to the central axis is R1, the distance from the edge of the explosion-proof notch 2201 away from the central axis to the central axis is R2, the wall thickness of at least part of the buffer wall 2303 along the central axis direction is d, the material thickness of the cover plate 2 is D, and at the explosion-proof notch 2201, the minimum remaining material thickness of the cover plate 2 is v. d satisfies the relationship: k×v×(R2 / R1)<d<D; where k is a constant, and 1<k<2.

[0040] Since at least a portion of the buffer wall 2303 has a wall thickness along the central axis that is less than the material thickness of the cover plate 2, in order to prevent the strength of this portion of the buffer wall 2303 from being too low and breaking before the explosion-proof notch 2201, this embodiment needs to limit the wall thickness of this portion of the buffer wall 2303 along the central axis.

[0041] First, the strength of the buffer wall 2303 and the strength of the explosion-proof notch 2201 are calculated separately. The strength of the buffer wall 2303 is calculated as: perimeter of the buffer wall 2303 × wall thickness × material strength = 2π × R1 × d × T; the strength of the explosion-proof notch 2201 is calculated as: perimeter of the explosion-proof notch 2201 × remaining thickness of the cover plate 2 × material strength = 2π × R2 × v × T. It should be noted that, to avoid the buffer wall 2303 breaking before the explosion-proof notch 2201 due to insufficient strength, the strength of the explosion-proof notch 2201 at its deepest point is compared with the strength of the stress-relief part 23.

[0042] Therefore, the strength ratio of the buffer wall 2303 to the explosion-proof notch 2201 is k = (R1×d) / (R2×v). To prevent the buffer wall 2303 from breaking before the explosion-proof notch 2201 due to its low strength, and considering that the buffer wall 2303 is too close to the edge of the cover plate 2 and is affected by the tensile strength, d > k×v×(R2 / R1) and 1 < k < 2 are limited. This ensures that the stiffness of the buffer wall 2303 is between the stiffness of the mounting part 21 and the stiffness of the explosion-proof notch 2201, forming an orderly stress attenuation gradient and significantly reducing the risk of unexpected breakage of the explosion-proof part 22.

[0043] Preferably, k is 1.5, so that the strength of the buffer wall 2303 is greater than 1.5 times the strength of the explosion-proof groove 2201, ensuring that the actual crack resistance of the buffer wall 2303 is higher than the crack resistance of the explosion-proof groove 2201, and avoiding the buffer wall 2303 from breaking first and losing its buffer function when the pressure does not reach the internal pressure threshold of the battery cell 100, and the pressure directly impacts the casing 1.

[0044] In some embodiments of this utility model, such as Figure 6 As shown, along the radial direction, the width of the explosion-proof groove 2201 at its own opening 11 end is L1, and the width of the buffer wall 2303 is L2. L2 satisfies the following relationship: L2≥3L1, 0.4mm≤L1≤0.8mm.

[0045] To ensure the machinability of the buffer wall 2303, this part needs to be thinned and then stretched. The mold needs to have a certain width. Therefore, the width of the buffer wall 2303 is designed proportionally to the width of the explosion-proof notch 2201 to facilitate processing and forming.

[0046] Furthermore, if the L2 value is too small (e.g., equal to L1), the buffering capacity of the buffer wall 2303 is limited, which may cause the pressure to be directly transmitted to the explosion-proof notch 2201 and cause the valve to open accidentally. When L2 ≥ 3L1, the width of the buffer wall 2303 is much larger than the width of the explosion-proof notch 2201, which can provide sufficient deformation redundancy and ensure that the buffer wall 2303 has sufficient buffering capacity.

[0047] In some embodiments of this utility model, such as Figure 6 As shown, the distance from the edge of the cover plate 2 to the central axis is R along the radial direction, the distance from the edge of the explosion-proof groove 2201 away from the central axis is R2, the distance from the edge of the stress buffer part 23 near the central axis to the edge of the cover plate 2 is C1, the mounting part 21 is an annular platform arranged circumferentially and its thickness along the central axis direction is equal to the material thickness of the cover plate 2, the width of the mounting part 21 along the radial direction is C2, the width of the buffer wall 2303 along the radial direction is L2, and the width of the first transition wall 2301 and the second transition wall 2302 along the radial direction is L3; L2 is (C1-C2-2L3), where 0.4mm≤L3≤0.8mm, 3mm≤C2≤6mm, and C1<(R-R2), where 0.5R≤R2≤0.7R.

[0048] The mounting section 21 is constructed as a ring platform, which provides a flat and high-rigidity sealing mating surface, ensuring that the sealing element 3 is subjected to uniform pressure during the upsetting process and achieving reliable airtightness. At the same time, the thickness of the mounting section 21 is equal to the material thickness of the cover plate 2, ensuring the structural strength of the edge of the cover plate 2 and providing sufficient impact and deformation resistance.

[0049] In designing the appropriate dimensions for L2, the radial position of the explosion-proof notch 2201 along the cover plate 2 needs to be determined first. Considering that the diameter of the cover plate 2 commonly used in the market is 43.6 mm, and the diameter of the explosion-proof notch 2201 is 24 mm to 32 mm (based on thermal runaway tests, experimental results ensuring the function of the explosion-proof valve), if the diameter of the explosion-proof notch 2201 is too small, the residual thickness will be very low, making manufacturing difficult; if the diameter of the explosion-proof notch 2201 is too large, the lateral extrusion effect of the groove 12 sealing will increase, worsening the stability of the finished product. Therefore, by designing 0.5R≤R2≤0.7R, the explosion-proof notch 2201 is located in the central annular region of the cover plate 2, ensuring the stability of the explosion-proof notch 2201.

[0050] After determining the value of R2, a stress buffer portion 23 can be provided on the portion of the cover plate 2 between the edge of the explosion-proof notch 2201 away from the central axis and the edge of the cover plate 2. Moreover, considering that the stress buffer portion 23 and the explosion-proof notch 2201 cannot overlap, and to avoid instability in the overlapping area, the distance C1 from the edge of the stress buffer portion 23 near the central axis to the edge of the cover plate 2 is < (R-R2).

[0051] After determining C1, the radial widths of the mounting portion 21 and the first transition wall 2301 and the second transition wall 2302 also need to be considered. To ensure sealing quality and functional requirements, the radial width C2 of the mounting portion 21 is ≥ 3mm, and considering the existing cover plate 2 specifications, C2 ≤ 6mm. Furthermore, the radial widths of the first transition wall 2301 and the second transition wall 2302 are the same, and both range from 0.4mm to 0.8mm. This width range is the same as the material thickness range of the cover plate 2, meeting the processing requirements for the stress buffer portion 23 of the cover plate 2.

[0052] Therefore, L2 = C1 - C2 - 2L3, and the value of L2 is determined based on the size range of each part of the cover plate 2 mentioned above.

[0053] In some embodiments of this utility model, such as Figures 3-5 As shown, the cover plate 2 also includes: a first reinforcing rib 24, which is located between the stress buffer part 23 and the explosion-proof part 22. Along the central axis, the first reinforcing rib 24 protrudes relative to the mounting part 21. The first reinforcing rib 24 is distributed continuously or discontinuously along the circumference of the cover plate 2 and is arranged around the explosion-proof part 22.

[0054] By surrounding the explosion-proof part 22 with the first reinforcing rib 24 protruding relative to the mounting part 21, the rigidity of the outer periphery of the explosion-proof part 22 can be improved. When the battery cell 100 is in a non-operating state (such as during assembly or transportation), the impact resistance around the explosion-proof part 22 can be enhanced, and lateral compressive stress can be absorbed, thereby preventing mechanical damage to the explosion-proof notch 2201. When the battery cell 100 is in an operating state, if the explosion-proof notch 2201 ruptures due to internal overpressure, the first reinforcing rib 24 acts as a rigid stop, limiting the expansion of the crack to an unintended area on the outer periphery. Furthermore, during the high-temperature and high-pressure gas injection process, the first reinforcing rib 24 provides support, keeping the pressure relief port in a stable open state and maintaining an effective pressure relief channel.

[0055] In some embodiments of this utility model, such as Figure 6 As shown, along the radial direction, the distance from the edge of the first reinforcing rib 24 near the central axis to the edge of the cover plate 2 is C3; the radial width of the bottom wall of the first reinforcing rib 24 is L4; the radial width of the two side walls of the first reinforcing rib 24 is the same and both are L5; the radial width of the explosion-proof groove 2201 at its own opening 11 end is L1; the distance between the edge of the first reinforcing rib 24 away from the central axis and the edge of the stress buffer part 23 near the central axis is C4; L2 is [C3-C2-C4-(L4+2L5)-2L3], where C3<(R-R2), C4≥0.5mm, 0.4mm≤L5≤0.8mm, L4>L1.

[0056] Since the cover plate 2 has an added first reinforcing rib 24, the design of the dimensions of L2 also needs to consider the design dimensions of the first reinforcing rib 24. First, determine the radial position of the explosion-proof notch 2201 along the cover plate 2, i.e., 0.5R≤R2≤0.7R.

[0057] After determining the value of R2, a stress buffer portion 23 and a first reinforcing rib 24 can be provided on the portion of the cover plate 2 between the edge of the explosion-proof notch 2201 away from the central axis and the edge of the cover plate 2. Moreover, considering that the first reinforcing rib 24 and the explosion-proof notch 2201 cannot overlap, and to avoid instability in the overlapping area, the distance C3 from the edge of the first reinforcing rib 24 near the central axis to the edge of the cover plate 2 is < (R-R2).

[0058] After determining C3, in addition to considering the radial width of the mounting part 21 and the radial width of the first transition wall 2301 and the second transition wall 2302, it is also necessary to consider the radial width of the bottom wall of the first reinforcing rib 24 and the radial width of the two side walls of the first reinforcing rib 24, as well as the distance between the first reinforcing rib 24 and the stress buffer wall 2303.

[0059] Since the first reinforcing rib 24 needs to be stretched during processing, the amount of material processed is greater than that of the explosion-proof notch 2201. Therefore, the width of the mold needs to be greater than the width of the explosion-proof notch 2201 at its opening 11 to ensure the strength of the stretching mold. Thus, the radial width of the bottom wall of the first reinforcing rib 24 is greater than the radial width of the explosion-proof notch 2201 at its opening 11, i.e., L4 > L1. Furthermore, the radial widths of the two side walls of the first reinforcing rib 24 are the same, and both range from 0.4mm to 0.8mm. This width range is the same as the material thickness range of the cover plate 2, which meets the processing requirements for the first reinforcing rib 24 of the cover plate 2.

[0060] Furthermore, considering that the stress buffer portion 23 and the first reinforcing rib 24 cannot overlap, to avoid instability in the overlapping area, the distance C4 between the edge of the first reinforcing rib 24 away from the central axis and the edge of the stress buffer portion 23 near the central axis is ≥0.5mm.

[0061] Therefore, L2 = [C3 - C2 - C4 - (L4 + 2L5) - 2L3], and the value of L2 is determined based on the size range of each part of the cover plate 2 mentioned above.

[0062] In some embodiments of this utility model, such as Figure 6As shown, along the radial direction, the distance between the edge of the first reinforcing rib 24 near the central axis and the edge of the explosion-proof notch 2201 away from the central axis is C5; L2 is [(R-R2)-C2-C4-(L4+2L5)-2L3-C5], where 0.5mm≤C5≤5mm.

[0063] Specifically, in designing the dimensions of L2, it is also necessary to consider that a machining precision gap of 0.5mm needs to be reserved between the first reinforcing rib 24 and the explosion-proof groove 2201, and also to consider that if the distance between the two is too large, it will not be able to absorb the lateral compressive stress. Therefore, the value of C5 between the edge of the first reinforcing rib 24 near the central axis and the edge of the explosion-proof groove 2201 away from the central axis is within the range of 0.5mm to 5mm.

[0064] Therefore, L2 = [(R-R2)-C2-C4-(L4+2L5)-2L3-C5], and the value of L2 is determined based on the size range of each part of the cover plate 2 mentioned above.

[0065] In some embodiments of this utility model, such as Figures 3-5 As shown, the explosion-proof part 22 is provided with a second reinforcing rib 25. The second reinforcing rib 25 is distributed continuously or discontinuously along the circumference of the cover plate 2 and is located on the radial inner side of the explosion-proof groove 2201. Along the central axis direction, the second reinforcing rib 25 protrudes relative to the mounting part 21, and the protrusion direction of the second reinforcing rib 25 is opposite to the protrusion direction of the first reinforcing rib 24.

[0066] Thus, the first reinforcing rib 24 is located radially outside the explosion-proof notch 2201, and the second reinforcing rib 25 is located radially inside the explosion-proof notch 2201, with their protrusion directions opposite. This symmetrically arranged reinforcing structure significantly improves the overall structural rigidity of the explosion-proof part 22, thereby enhancing its resistance to deformation under non-overpressure conditions, ensuring the integrity of the explosion-proof notch 2201, and improving its stability against internal pressure fluctuations. During normal charging and discharging or temperature cycling of the battery cell 100, there are small pressure fluctuations inside the casing 1, which may cause low-frequency vibration or fatigue in the explosion-proof notch 2201. The placement of the first reinforcing rib 24 and the second reinforcing rib 25 effectively reduces the risk of fatigue cracking. In addition, it can maintain the long-term stability of the explosion-proof part 22 structure, preventing the explosion-proof part 22 from collapsing or warping due to material creep or residual stress release, and ensuring that the explosion-proof notch 2201 is always in the preset position and tension state.

[0067] Preferably, the distance between the edge of the second reinforcing rib 25 away from the central axis and the central axis is R4, where R4≤0.8R2. This prevents the distance between the explosion-proof notch 2201 and the second reinforcing rib 25 from being too small, which would cause the material to flow unevenly during the processing of the explosion-proof notch 2201 and result in unstable burst values, thus ensuring the stability of the explosion-proof notch 2201.

[0068] In some embodiments of this utility model, along the central axis direction, the protrusion height of the first reinforcing rib 24 is h1, the protrusion height of the second reinforcing rib 25 is h2, the material thickness of the cover plate 2 is D, and h1 and h2 both satisfy the relationship: 0.5D≤h1≤3D, 0.5D≤h2≤3D.

[0069] Specifically, the protrusion height of the first reinforcing rib 24 needs to comprehensively consider the manufacturing capabilities of the cover plate 2 and the reinforcement effect. The first reinforcing rib 24 can improve the rigidity of the outer periphery of the explosion-proof part 22. However, since the first reinforcing rib 24 is stretched during processing, if the protrusion height is too large, the wall thickness of the first reinforcing rib 24 will be reduced too much, resulting in insufficient structural strength. If the protrusion height is too small, the reinforcement effect will be minimal. Therefore, based on experience, the protrusion height h1 of the first reinforcing rib 24 is limited to within 0.5D to 3D. The protrusion height of the second reinforcing rib 25 is within the same range as that of the first reinforcing rib 24.

[0070] In addition, the radial width of the bottom wall of the first reinforcing rib 24 is L4 = 0.5D × h1. In the formula, 0.5D is a proportional coefficient based on the material thickness constraint of the cover plate 2. The correlation of "0.5D × h1" is introduced: when D is small, the coefficient 0.5D decreases synchronously to avoid L4 being too wide; when h1 increases, L3 increases synchronously to ensure that the width and height ratio is appropriate.

[0071] In one embodiment of this utility model, along the central axis direction, the first reinforcing rib 24 protrudes toward the opening 11 side of the housing 1. The height difference between the side of the first reinforcing rib 24 away from the surface of the cover plate 2 and the end face of the housing 1 on the side of its opening 11 is greater than 0, and the height difference between the side of the second reinforcing rib 25 away from the surface of the cover plate 2 and the side of the groove 12 away from the cover plate 2 is greater than 0.

[0072] like Figures 3-5In the illustrated embodiment, along the central axis, the first reinforcing rib 24 protrudes towards the opening 11 of the housing 1, while the second reinforcing rib 25 protrudes towards the groove 12 of the housing 1. To ensure that the first reinforcing rib 24 does not exceed the maximum outer envelope size of the battery cell 100 and to avoid affecting the energy density of the battery cell 100, the height difference between the side of the first reinforcing rib 24 away from the surface of the cover plate 2 and the end face of the housing 1 on the side of its opening 11 is greater than 0. Similarly, to ensure that the second reinforcing rib 25 does not affect the reserved distance between the internal space of the housing 1 and the end face of the cell, the height difference between the side of the second reinforcing rib 25 away from the surface of the cover plate 2 and the side of the groove 12 away from the cover plate 2 is greater than 0.

[0073] In another embodiment of this utility model, along the central axis, the first reinforcing rib 24 protrudes towards the side of the groove 12, and the height difference between the side of the first reinforcing rib 24 away from the surface of the cover plate 2 and the side of the groove 12 away from the cover plate 2 is greater than 0, and the height difference between the side of the second reinforcing rib 25 away from the surface of the cover plate 2 and the end face of the housing 1 on the side of its opening 11 is greater than 0. Similarly to the above embodiment, it is ensured that the second reinforcing rib 25 does not exceed the maximum outer envelope size of the battery cell 100, and that the first reinforcing rib 24 does not affect the reserved distance between the internal space of the housing 1 and the end face of the battery cell.

[0074] In some embodiments of this utility model, along the central axis direction, the first reinforcing rib 24 protrudes relative to the mounting portion 21 to form a first groove 26 with the surface of the cover plate 2. The groove direction of the first groove 26 is the same as the opening direction of the explosion-proof groove 2201.

[0075] like Figures 3-5 In the embodiment shown, the first reinforcing rib 24 protrudes towards the opening 11 of the housing 1. The first reinforcing rib 24 and the surface of the cover plate 2 opposite to the opening 11 form a first groove 26, such that the groove opening of the first groove 26 and the opening 11 of the explosion-proof groove 2201 are both towards the rolling groove 12 inside the housing 1.

[0076] With this configuration, the groove direction of the first groove 26 is the same as the opening direction of the explosion-proof notch 2201. When the edge of the cover plate 2 is subjected to radial and / or axial pressure, energy will be absorbed preferentially through the first groove 26 to the radially inward compression deformation. When the deformation of the first groove 26 is at its maximum, the remaining stress will continue to be transmitted to the explosion-proof notch 2201, thereby effectively suppressing the transmission of stress to the explosion-proof notch 2201. If the groove direction of the first groove 26 is opposite to the opening direction of the explosion-proof notch 2201, and there is a "peak and trough shape", it will cause the "peak and trough" to compress and deform synchronously. That is, when the first groove 26 compresses and deforms radially inward, some stress will be transmitted to the explosion-proof notch 2201 simultaneously, resulting in additional residual stress at the explosion-proof notch 2201, thereby reducing its actual burst pressure threshold. Therefore, the groove direction of the first groove 26 is the same as the opening direction of the explosion-proof groove 2201, which effectively ensures that the first groove 26 fully absorbs the lateral extrusion stress and avoids the stress being transmitted to the explosion-proof groove 2201, achieving the effect of "1+1>2".

[0077] In some embodiments of this utility model, the first transition wall 2301, the buffer wall 2303, and the second transition wall 2302 together form a second groove 27, and the groove opening direction of the second groove 27 is the same as the opening 11 direction of the explosion-proof notch 2201. Similarly to the above embodiments, the groove opening direction of the second groove 27 is the same as the opening 11 direction of the explosion-proof notch 2201, which effectively ensures that the second groove 27 absorbs the lateral compressive stress more fully and avoids the stress being transmitted to the explosion-proof notch 2201, thus achieving the same "1+1>2" effect.

[0078] In one embodiment of the present invention, along the central axis direction, the stress buffer portion 23 is recessed on the side near the groove 12 relative to the surface of the cover plate 2, so as to form a boss 28 on the other side relative to the surface of the cover plate 2. The height difference between the side of the boss 28 away from the surface of the cover plate 2 and the surface of the cover plate 2 is greater than or equal to 0, and the height difference between the side of the boss 28 away from the surface of the cover plate 2 and the end face of the housing 1 on the side of its opening 11 is greater than 0.

[0079] like Figures 3-5In the illustrated embodiment, along the central axis, the stress buffer portion 23 is recessed relative to the surface of the cover plate 2 on the side near the groove 12, forming a boss 28 on the other side relative to the surface of the cover plate 2. The height difference between the side of the boss 28 away from the surface of the cover plate 2 and the surface of the cover plate 2 is greater than or equal to 0. When the height difference between the side of the boss 28 away from the surface of the cover plate 2 and the surface of the cover plate 2 is equal to 0, the side of the stress buffer portion 23 away from the groove 12 is flush with the surface of the cover plate 2. When the height difference between the side of the boss 28 away from the surface of the cover plate 2 and the surface of the cover plate 2 is greater than 0, a directional deformation path can be constructed for the stress buffer portion 23, guiding the deformation of the stress buffer portion 23 along a preset direction. For example, in this embodiment, during the sealing process or extrusion process, the cover plate 2 is subjected to radial and / or axial pressure, and the boss 28 will preferentially deform towards the opening 11 of the housing 1. This directional deformation can avoid lateral displacement and will not deform towards the explosion-proof portion 22, protecting the integrity of the explosion-proof portion 22 and ensuring the function of the explosion-proof valve. Furthermore, in order to ensure that the boss 28 does not exceed the maximum outer envelope size of the battery cell 100 and to avoid affecting the energy density of the battery cell 100, the height difference between the side of the boss 28 away from the surface of the cover plate 2 and the end face of the housing 1 on the side of its opening 11 is greater than 0.

[0080] In another embodiment of this utility model, along the central axis direction, the stress buffer portion 23 is recessed on the side near the opening 11 of the housing 1 relative to the surface of the cover plate 2, so as to form a boss 28 on the other side relative to the surface of the cover plate 2. The height difference between the side of the boss 28 away from the surface of the cover plate 2 and the surface of the cover plate 2 is greater than or equal to 0, and the height difference between the side of the boss 28 away from the surface of the cover plate 2 and the side of the groove 12 away from the cover plate 2 is greater than 0. The same principle applies as in the above embodiments, and will not be repeated.

[0081] The battery pack according to a second aspect of the present invention includes a battery cell 100.

[0082] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0083] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example.

[0084] Although embodiments of the present invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A battery cell, characterized in that, include: A housing, one end of which is provided with an opening, and a groove is formed on the outer periphery of the housing that is recessed toward the inside of the housing; A cover plate is installed on the side of the groove near the opening and closes the opening. The cover plate includes a mounting portion, an explosion-proof portion near the central axis, and a stress buffer portion located between the mounting portion and the explosion-proof portion from its edge toward its central axis. The explosion-proof portion is provided with a controllable rupture structure, which is configured to at least partially rupture when the pressure inside the battery cell exceeds a threshold to release the internal pressure of the battery cell. The stress buffer includes a first transition wall, a second transition wall, and a buffer wall connected between the first transition wall and the second transition wall. The first transition wall is connected to the mounting part, and the second transition wall is connected to the explosion-proof part. The wall thickness of at least a portion of the buffer wall along the central axis of the cover plate is less than the material thickness of the cover plate.

2. The battery cell according to claim 1, characterized in that, The controllable fracture structure is constructed as explosion-proof markings, which are distributed continuously or discontinuously along the circumference of the cover plate. The stress buffer is distributed continuously or discontinuously along the circumference and is arranged around the explosion-proof part. The stress buffer and the explosion-proof markings are arranged correspondingly in the circumference.

3. The battery cell according to claim 2, characterized in that, Along the radial direction perpendicular to the circumference of the cover plate, the distance from the central axis to the edge of the buffer wall near the central axis is R1, the distance from the central axis to the edge of the explosion-proof groove away from the central axis is R2, the wall thickness of at least a portion of the buffer wall along the central axis direction is d, the material thickness of the cover plate is D, and the minimum remaining material thickness of the cover plate at the explosion-proof groove is v. The d satisfies the relationship: k×v×(R2 / R1)<d<D; where k is a constant, and 1<k<2.

4. The battery cell according to claim 2, characterized in that, Along the radial direction, the width of the explosion-proof groove at its own opening end is L1, and the width of the buffer wall is L2. The L2 satisfies the following relationship: L2≥3L1, 0.4mm≤L1≤0.8mm.

5. The battery cell according to claim 2, characterized in that, Along the radial direction, the distance from the edge of the cover plate to the central axis is R; the distance from the edge of the explosion-proof groove away from the central axis to the central axis is R2; the distance from the edge of the stress buffer part near the central axis to the edge of the cover plate is C1; the mounting part is an annular platform arranged circumferentially and its thickness along the central axis direction is equal to the material thickness of the cover plate; the width of the mounting part along the radial direction is C2; the width of the buffer wall along the radial direction is L2; ​​the widths of the first transition wall and the second transition wall along the radial direction are both L3; L2 is (C1-C2-2L3), where 0.4mm≤L3≤0.8mm, 3mm≤C2≤6mm, and C1<(R-R2), where 0.5R≤R2≤0.7R.

6. The battery cell according to claim 5, characterized in that, The cover plate further includes: a first reinforcing rib, which is located between the stress buffer portion and the explosion-proof portion, along the central axis direction, the first reinforcing rib protrudes relative to the mounting portion, and the first reinforcing rib is distributed continuously or discontinuously along the circumferential direction and is arranged around the explosion-proof portion.

7. The battery cell according to claim 6, characterized in that, Along the radial direction, the distance from the edge of the cover plate to the side of the first reinforcing rib closest to the central axis is C3; the width of the bottom wall of the first reinforcing rib along the radial direction is L4; the width of the two side walls of the first reinforcing rib along the radial direction is the same and both are L5; the width of the explosion-proof groove at its own opening end along the radial direction is L1; the distance between the edge of the first reinforcing rib away from the central axis and the edge of the stress buffer part closest to the central axis is C4; L2 is [C3-C2-C4-(L4+2L5)-2L3], where C3<(R-R2), C4≥0.5mm, 0.4mm≤L5≤0.8mm, L4>L1.

8. The battery cell according to claim 7, characterized in that, Along the radial direction, the distance between the edge of the first reinforcing rib near the central axis and the edge of the explosion-proof groove away from the central axis is C5; L2 is [(R-R2)-C2-C4-(L4+2L5)-2L3-C5], where 0.5mm≤C5≤5mm.

9. The battery cell according to claim 6, characterized in that, The explosion-proof part is provided with a second reinforcing rib. The second reinforcing rib is distributed continuously or discontinuously along the circumference and is located radially inside the explosion-proof groove. Along the central axis, the second reinforcing rib protrudes relative to the mounting part, and the protrusion direction of the second reinforcing rib is opposite to the protrusion direction of the first reinforcing rib.

10. The battery cell according to claim 9, characterized in that, Along the central axis, the protrusion height of the first reinforcing rib is h1, the protrusion height of the second reinforcing rib is h2, the material thickness of the cover plate is D, and h1 and h2 both satisfy the following relationships: 0.5D≤h1≤3D, 0.5D≤h2≤3D; and / or Along the central axis, if the first reinforcing rib protrudes towards the opening side of the housing, then the height difference between the side of the first reinforcing rib away from the cover plate surface and the end face of the housing on the opening side is greater than 0, and the height difference between the side of the second reinforcing rib away from the cover plate surface and the side of the groove away from the cover plate is greater than 0; or Along the central axis, the first reinforcing rib protrudes toward the side of the groove, the height difference between the side of the first reinforcing rib away from the cover plate surface and the side of the groove away from the cover plate is greater than 0, and the height difference between the side of the second reinforcing rib away from the cover plate surface and the end face of the housing on the side of its opening is greater than 0.

11. The battery cell according to claim 6, characterized in that, Along the central axis, the first reinforcing rib protrudes relative to the mounting portion to form a first groove with the surface of the cover plate, the groove opening direction being the same as the opening direction of the explosion-proof markings; and / or The first transition wall, the buffer wall, and the second transition wall together form a second groove, and the groove opening direction of the second groove is the same as the opening direction of the explosion-proof marking.

12. The battery cell according to claim 1, characterized in that, Along the central axis, the stress buffer portion is recessed relative to the cover plate surface on the side near the groove, forming a boss on the other side relative to the cover plate surface. The height difference between the side of the boss away from the cover plate surface and the cover plate surface is greater than or equal to 0, and the height difference between the side of the boss away from the cover plate surface and the end face of the housing on its opening side is greater than 0; or Along the central axis, the stress buffer portion is recessed on the side of the opening near the housing relative to the cover plate surface to form a boss on the other side relative to the cover plate surface. The height difference between the side of the boss away from the cover plate surface and the cover plate surface is greater than or equal to 0, and the height difference between the side of the boss away from the cover plate surface and the side of the groove away from the cover plate is greater than 0.

13. A battery pack, characterized in that, Includes the battery cell according to any one of claims 1 to 12.

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