Battery cells and battery packs

Abstract

This invention relates to the field of battery technology and discloses a battery cell and a battery pack. The battery cell includes: a casing, one end of which is open along the Z-direction; a portion of the casing near the open end along the Z-direction is constructed as a first reinforcing section, the wall thickness of which is greater than the main wall thickness of the casing; and a length of A0 along the Z-direction for the first reinforcing section; a cover plate, which is placed over the open end of the casing and welded to the first reinforcing section to form a weld; the weld forms a heat-affected zone on the casing, the length of which along the Z-direction is A; wherein A0 and A satisfy the relationship: 0.75 ≤ A0 / A ≤ 3. By providing a thicker first reinforcing section at the open end of the casing, and limiting the ratio A0 / A between the length A0 of the first reinforcing section and the length A of the heat-affected zone to within the range of 0.75 to 3, the heat damage resistance and structural strength of the welded area are improved while simultaneously achieving structural lightweighting and reducing production costs.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to battery cells and battery packs. Background Technology

[0002] The battery cell casing and cover plate are welded together to form a sealed space to accommodate the electrode assembly, thus encapsulating the electrode assembly within the casing's inner cavity. The cover plate is placed over the open end of the casing. In existing technologies, the wall thickness of the area near the casing opening used for welding with the cover plate is generally less than or equal to the wall thickness of the main casing body. After welding the casing and cover plate, a heat-affected zone (HAZ) is formed on the casing. The strength of the HAZ is less than the strength of the casing material itself, making the casing prone to damage in the HAZ after welding. This seriously affects the battery cell production yield and the safety of the battery cell during use. Summary of the Invention

[0003] This invention provides a battery cell and battery pack to solve the problem that the casing is easily damaged in the heat-affected zone.

[0004] In a first aspect, the present invention provides a battery cell, comprising: a housing, one end of which is configured as an open end along the Z direction, a portion of the housing near the open end along the Z direction being constructed as a first reinforcing section, the wall thickness of the first reinforcing section being greater than the main wall thickness of the housing, and the length of the first reinforcing section along the Z direction being A0; a cover plate, which is disposed on the open end of the housing, the cover plate being welded to the first reinforcing section to form a weld, the weld forming a heat-affected zone on the housing, the length of the heat-affected zone along the Z direction being A; wherein, A0 and A satisfy the relationship: 0.75≤A0 / A≤3.

[0005] Beneficial effects: By setting a thicker first reinforcing section at the opening of the shell, the structural strength of the shell opening is effectively enhanced, thereby improving the strength of the welded joint after the shell cover is welded. At the same time, limiting the ratio A0 / A between the length of the first reinforcing section and the length A of the heat-affected zone to be within the range of 0.75 to 3, the first reinforcing section can fully cover the range of the heat-affected zone generated by welding, effectively strengthening the structural strength of the shell, preventing the heat-affected zone from extending too far beyond the area of ​​the first reinforcing section, and preventing the heat-affected zone from reaching the thinner main body of the shell due to the first reinforcing section being too short relative to the heat-affected zone. This avoids problems such as cracking and deformation of the shell in the heat-affected zone. It also avoids material waste, increased shell weight, and processing difficulties caused by an excessively long first reinforcing section. Thus, while improving the heat damage resistance and structural strength of the welded joint, it also takes into account structural lightweighting and production costs.

[0006] In one optional embodiment, the first reinforcing section includes at least a first stepped portion, the upper end of the first stepped portion along the Z direction is flush with the opening end of the housing, the cover plate is welded to the first stepped portion, the length of the first stepped portion along the Z direction is A1, and the weld penetration depth along the Z direction is A3. Among them, A3 and A1 satisfy the following relationship: A1≥1.2×A3; And / or, the length A1 of the first step portion along the Z direction is in the range of: 1 mm ≤ A1 ≤ 5 mm; And / or, the cover plate includes a mating section that abuts against the inner wall of the first step portion, the length of the mating section along the Z direction being A4, wherein A4 ≥ 1.2 × A3.

[0007] Beneficial effects: While limiting the ratio A0 / A between the length A0 of the first reinforcing section and the length A of the heat-affected zone to be within the range of 0.75 to 3, the length A1 of the first step is limited to not less than 1.2 times the weld penetration depth of the weld 3. This achieves the strength of the heat-affected zone on the reinforced shell 1, while preventing molten beads from falling into the shell during the welding process or causing welding defects such as pores or bursts. This avoids internal short circuits in the battery cell, ensures welding quality, and further improves the safety of the battery cell. And / or, by limiting A1 to a value within the range of 1 mm to 5 mm, the structural strength of the shell 1 can be effectively strengthened, preventing cracking and damage in the heat-affected zone, while also avoiding material waste and excessive processing difficulty, which is conducive to improving the molding yield of the shell 1; And / or, by limiting A4 to not less than 1.2 times A3, the mating section length of the cover plate has a reasonable value relative to the weld penetration depth, thereby ensuring welding quality and improving the production yield and product reliability of the battery cell.

[0008] In one optional embodiment, the main body of the housing is a shell body, and the first reinforcing section is connected to the shell body through a second reinforcing section. Along the direction from the first reinforcing section to the shell body, the wall thickness of the second reinforcing section gradually decreases in the XY plane.

[0009] Beneficial effects: The second reinforcing section with gradually varying wall thickness connects the first reinforcing section to the shell body, avoiding stress concentration caused by abrupt changes in wall thickness, making the force transmission smoother. The second reinforcing section can also serve as a buffer zone for the heat-affected zone. Even if the heat-affected zone extends beyond the first reinforcing section, the second reinforcing section can be used to strengthen the excess portion, further preventing cracking in the heat-affected zone.

[0010] In one optional embodiment, along the Z direction, the total length of the first reinforcing segment and the second reinforcing segment is A2, wherein 0.75≤A0 / A≤1 and A2 / A≥1.4; and / or, the second reinforcing segment forms a first inclined surface on the side facing the inner cavity of the shell, and the angle between the first inclined surface and the plane containing the inner wall of the shell body is B, wherein 5°≤B≤45°.

[0011] Beneficial effects: When the ratio of the length of the first reinforcing section to the length of the heat-affected zone is between 0.75 and 1, and the ratio of the total length of the first and second reinforcing sections to the length of the heat-affected zone, A2 / A, is limited to not less than 1.4, the portion of the heat-affected zone extending beyond the first reinforcing section in the X direction can fall onto the second reinforcing section, and the edge of the heat-affected zone is kept at a sufficient distance from the shell body. Since the wall thickness of the second reinforcing section is not less than the wall thickness of the shell body, the second reinforcing section can also play a certain role in structural reinforcement. This can prevent the heat-affected zone from extending directly onto the shell body with a smaller wall thickness and affecting the structural strength of the shell body, effectively solving the problem of heat-affected zone damage on the shell after the shell cover is welded, and improving the reliability of the shell. And / or, by limiting B to a value within the range of 5° to 45°, it is possible to avoid the second reinforcing section from extending too long along the Z direction due to an overly gentle transition slope, thereby saving materials and costs. It is also possible to prevent the wall thickness from changing abruptly and stress concentration due to an overly steep transition slope, thereby avoiding shell cracking and damage, reducing the molding difficulty of the shell, and improving the processing yield.

[0012] In one optional embodiment, the first reinforcing section is the first stepped portion, and in the XY plane, the wall thickness of the first stepped portion is C1, and the wall thickness of the shell body is C2. Among them, C1 and C2 satisfy the following relationship: 1.2≤C1 / C2≤2; and / or, the range of C2 is: 0.3 mm≤C2≤1 mm.

[0013] Beneficial effects: It can ensure that the first reinforcing section can effectively strengthen the structural strength of the shell opening, thereby avoiding the problem of damage to the welding heat-affected zone, reducing the processing difficulty, avoiding waste of material costs, and helping to achieve lightweight battery cells.

[0014] In one alternative embodiment, the first reinforcing section includes a first stepped portion and a second stepped portion, the second stepped portion being located along the Z direction on the side of the first stepped portion away from the opening end of the housing, and the wall thickness of the second stepped portion being less than the wall thickness of the first stepped portion, the second stepped portion and the first stepped portion being connected by a first transition section.

[0015] Beneficial effects: The wall thickness of the first step, the second step, and the shell body decreases sequentially. The first reinforcing section is arranged in a multi-layered, non-staggered step configuration, which makes the wall thickness of the first reinforcing section decrease in stages along the direction of welding heat transfer. This conforms to the law that the influence of welding heat on the shell gradually decreases from near to far. The second step further avoids the heat-affected zone from being too close to the shell body. This can both ensure the reinforcement of the welded area of ​​the shell by the first reinforcing section and reduce the material used in the first reinforcing section.

[0016] In one alternative embodiment, the first transition section forms a second inclined surface on the side facing the inner cavity of the shell, and the angle between the second inclined surface and the plane containing the inner wall of the shell body is 5° to 45°. And / or, the wall thickness of the first step portion is C1, the wall thickness of the second step portion is C11, and the wall thickness of the shell body is C2; wherein, 1.1≤C1 / C11≤2, 1.1≤C11 / C2≤2, and C1>C11>C2; and / or, the value range of C2 is: 0.3 mm≤C2≤1 mm.

[0017] Beneficial effects: By setting the first transition section to form a second inclined surface on the side facing the inner cavity of the shell, the wall thickness of the first transition section changes uniformly, avoiding stress concentration. Furthermore, the angle between the second inclined surface and the plane containing the inner wall of the shell body is limited to the range of 5° to 45°. This avoids the first transition section from extending too far along the Z direction due to an overly gentle transition slope, thus ensuring that the first and second steps have sufficient length. It also prevents the transition slope from being too steep, which could cause abrupt changes in wall thickness and stress concentration, thereby avoiding shell cracking and damage, reducing the molding difficulty of the shell, and improving the processing yield. And / or, by setting the wall thickness of the first step, the second step, and the shell body to decrease sequentially, and C1 / C11 taking values ​​in the range of 1.1 to 2 and C11 / C2 taking values ​​in the range of 1.1 to 2, it can be ensured that the first reinforcing section can effectively strengthen the structural strength of the shell opening end, thereby avoiding the problem of damage to the welding heat-affected zone. It can also ensure that the wall thickness changes uniformly from the shell opening end to the shell body, which can reduce the processing difficulty and avoid wasting material costs, and is conducive to achieving lightweight battery cells.

[0018] In one alternative embodiment, the first reinforcing section includes a first stepped portion and a second stepped portion, the second stepped portion being located at one end of the first stepped portion away from the opening end of the housing, and the wall thickness of the second stepped portion being greater than the wall thickness of the first stepped portion, the second stepped portion and the first stepped portion being connected by a second transition section.

[0019] Beneficial effects: The first reinforcing section is arranged in a multi-layered stepped staggered form. The second step further avoids the heat-affected zone from getting too close to the shell body, ensuring that the first reinforcing section strengthens the welded area of ​​the shell. In addition, the second step can also block molten beads during the welding process, preventing molten beads from falling into the inner cavity of the shell, further improving safety, and facilitating the assembly of the cover plate and the shell.

[0020] In one alternative embodiment, the second transition section forms a third inclined surface on the side facing the inner cavity of the housing, and the angle between the third inclined surface and the plane containing the inner wall of the housing body is 5° to 45°. And / or, the wall thickness of the first step portion is C1, the wall thickness of the second step portion is C11, and the wall thickness of the shell body is C2, wherein 1.1≤C11 / C1≤2, 1.1≤C1 / C2≤2, and C11>C1>C2; and / or, the value range of C2 is: 0.3 mm≤C2≤1 mm; And / or, along the Z direction, the length of the first step is A1, where 0 mm ≤ A1 - A4 ≤ 0.5 mm.

[0021] Beneficial effects: By limiting the values ​​of A1-A4 to between 0 mm and 0.5 mm, interference between the second transition section on the shell and the cover plate during the shell assembly process can be avoided, thus ensuring that the cover plate can be smoothly assembled onto the shell. It can also ensure the flatness between the surface of the cover plate and the end face of the shell opening after the shell is assembled, thus ensuring the yield of battery cell production.

[0022] Secondly, the present invention also provides a battery pack, comprising: a housing; and the aforementioned battery cell, wherein the battery cell is disposed within the housing. Since the battery pack includes the battery cell and has the same effects as the battery cell, further details are omitted here. Attached Figure Description

[0023] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the shell structure before the improvement. Figure 2 for Figure 1 The top view of the casing shown; Figure 3 for Figure 2 Cross-sectional view along the EE direction; Figure 4 for Figure 1 A cross-sectional view of the assembled structure after the shell and cover are assembled; Figure 5 for Figure 4 A magnified view of part of F; Figure 6 This is a partially enlarged cross-sectional view of the first shell and cover plate mating structure according to an embodiment of the present invention; Figure 7 for Figure 6 A magnified view of part of G and some of its dimensions; Figure 8 for Figure 6 A partially enlarged schematic diagram of G and another portion of its dimensions; Figure 9 This is a partially enlarged schematic diagram of a cross-sectional view of the second type of shell and cover plate mating structure according to an embodiment of the present invention, and some of its dimensions; Figure 10 for Figure 9 The enlarged partial view shown here, along with another portion of its dimensions; Figure 11 This is a partially enlarged schematic diagram of a cross-sectional view of the third type of shell and cover plate mating structure according to an embodiment of the present invention, and some of its dimensions; Figure 12 for Figure 11 The enlarged partial view shown here, along with another portion of its dimensions; Figure 13 for Figure 12 A magnified view of a portion of H.

[0025] Explanation of reference numerals in the attached figures: 1. Shell; 101. Edge of heat-affected zone; 11. First reinforcing section; 111. First step; 112. Second step; 113. First transition section; 1131. Second inclined surface; 114. Second transition section; 1141. Third inclined surface; 12. Shell body; 13. Second reinforcing section; 131. First inclined surface; 2. Cover plate; 3. Weld. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] The battery cell includes components such as a housing 1, a cover plate 2, and electrode groups. The cover plate 2 is positioned over the open end of the housing 1 and welded to it, thus encapsulating the electrode groups within the inner cavity of the housing 1. Figures 1 to 5 As shown, in the prior art, the wall thickness of the area where the housing 1 is welded to the cover plate 2 in a square battery cell is generally less than or equal to the wall thickness of the main body of the housing. The cover plate 2 is embedded inside the open end of the housing 1, and the outer peripheral wall of the cover plate 2 abuts against the inner peripheral wall of the housing 1. Welding is performed along the joint between the cover plate 2 and the housing 1 on the end face of the open end of the housing 1. The wall thickness of the welded part near the open end of the housing 1 is small. Due to the influence of welding heat, a heat-affected zone is formed on the housing during the welding of the cover plate. The heat-affected zone is usually larger than the weld penetration / width. The strength of the heat-affected zone is less than the strength of the housing material itself. It is easy to cause damage to the housing 1 in the heat-affected zone after the cover plate is welded. For example, it may be directly damaged after welding, which seriously affects the yield of battery cell production, or it may be damaged when the battery cell is subjected to force during use, which seriously affects the service life and safety of the battery cell.

[0028] The following is combined with Figures 6 to 13 The following describes embodiments of the present invention.

[0029] According to an embodiment of the present invention, in one aspect, a battery cell is provided, comprising: a housing 1 and a cover plate 2. One end of the housing 1 along the Z direction is configured as an open end, and a portion of the housing 1 along the Z direction near the open end is constructed as a first reinforcing section 11, the wall thickness of the first reinforcing section 11 being greater than the main wall thickness of the housing 1, and the length of the first reinforcing section 11 along the Z direction being A0; the cover plate 2 is disposed on the open end of the housing 1, and the cover plate 2 is welded to the first reinforcing section 11 to form a weld 3, the weld 3 forming a heat-affected zone on the housing 1, the length of the heat-affected zone along the Z direction being A; wherein, A0 and A satisfy the relationship: 0.75≤A0 / A≤3, and the units of A0 and A are both mm.

[0030] It should be noted that the battery cell has intersecting X, Y, and Z directions, where the X direction is the length direction of the housing 1, the Y direction is the width direction of the housing 1, and the Z direction is the height direction of the housing 1. The battery cell is a prismatic cell, and one end of the housing 1 along the Z direction is constructed as an open end. The housing 1 includes a bottom wall parallel to the XY plane and four side walls arranged circumferentially around the bottom wall, including two first and third side walls parallel to the XZ direction and arranged opposite each other, and two second and fourth side walls parallel to the YZ direction and arranged opposite each other. The first, second, third, and fourth side walls are connected end to end in sequence.

[0031] It should be noted that the cover plate 2 is embedded inside the housing 1, and the outer circumferential surface of the cover plate 2 abuts against the inner wall of the housing 1. The cover plate 2 is welded to the housing 1 from the outside of the battery cell along its circumference, forming a weld 3. The weld 3 extends downwards along the Z-direction from the end face of the opening end of the housing 1. The heat-affected zone (HAZ) refers to the area on the housing 1 that undergoes a change in hardness due to the welding heat. The HAZ extends along the Z-direction away from the opening end of the housing 1, and the extension length of the HAZ along the Z-direction is greater than the penetration depth of the weld 3 along the Z-direction. The HAZ has an edge 101 along the Z-direction away from the opening end of the housing, such as... Figures 6 to 12 As shown, the edge 101 of the heat-affected zone is an irregular curve. The edge 101 of the heat-affected zone has a position farthest from the end face of the shell opening (denoted as the farthest point). The length A of the heat-affected zone refers to the distance between the farthest point and the opening end of the shell along the Z direction.

[0032] It should be noted that the microhardness was measured using the heat-affected zone microhardness measurement method, and the specific measurement method is as follows: 1. Measurement conditions: Take a cross-section of the welded joint, grind it to a mirror finish, and do not corrode it; 2. Hardness tester: Vickers hardness HV0.5; 3. Measurement point layout: 1) Starting point: fusion line position (i.e., the end face of the shell opening); 2) Direction: continuous measurement points towards the base material in the Z direction; 3) Point spacing: 0.2 mm for ordinary argon arc welding and gas shielded welding, and 0.1 mm for thin plate laser welding. 4. Rules for determining the boundary of the heat-affected zone: 1) First, measure the hardness H0 of the original base material furthest from the weld; 2) As the hardness gradually increases along the Z-direction away from the end face of the shell opening, the hardness gradually increases. 3) When the hardness of three consecutive measuring points stabilizes at H0±3HV and no longer fluctuates, this point is the outer boundary of the heat-affected zone (i.e., the edge of the heat-affected zone 101). 4) The distance along the Z direction between the fusion line (the end face of the shell opening) and this point is the length A of the heat-affected zone.

[0033] The area near the opening end of the shell 1 is constructed as the first reinforcing section 11. The first reinforcing section 11 is used to increase the wall thickness of the area near the opening end of the shell 1 used for welding, thereby increasing the structural strength. The main wall thickness of the shell 1 refers to the wall thickness of the shell body 12. A0 is the length of the first reinforcing section 11, and A is the length of the heat-affected zone. If A0 / A is less than 0.75, the length of the first reinforcing section 11 is too small relative to the length of the heat-affected zone, and the heat-affected zone exceeds the size of the first reinforcing section 11 too much. The heat-affected zone reaches the shell body part with a smaller wall thickness, and this part cannot be strengthened by the first reinforcing section 11. The area of ​​the heat-affected zone on the shell body 12 has poor strength, and there is still a problem of cracking of the shell 1 in the heat-affected zone. It is easy to crack in the heat-affected zone during the cell breathing cycle test. If A0 / A is greater than 3, the length of the first reinforcing section 11 is too large relative to the length of the heat-affected zone, and the size of the first reinforcing section 11 exceeds the size of the heat-affected zone too much. The first reinforcing section 11 is too long, making the processing too difficult and affecting the molding yield of the shell 1.

[0034] By using the battery cell of this embodiment, a first reinforcing section 11 with a thicker wall is provided at the opening end of the housing 1, which effectively enhances the structural strength of the opening of the housing 1, thereby improving the strength of the welded joint of the housing 1 after the housing cover is welded. At the same time, the ratio A0 / A between the length A0 of the first reinforcing section 11 and the length A of the heat-affected zone is limited to a value between 0.75 and 3. This allows the first reinforcing section 11 to fully cover the range of the heat-affected zone generated by welding, effectively strengthening the structural strength of the housing 1, and preventing the heat-affected zone from extending too far beyond the area of ​​the first reinforcing section 11. This also prevents the heat-affected zone from reaching the main body of the housing 1 with a thinner wall due to the first reinforcing section 11 being too short relative to the heat-affected zone, thus avoiding cracking, deformation, and other damage to the housing 1 in the heat-affected zone. Furthermore, it avoids material waste, increased housing weight, and processing difficulties caused by the first reinforcing section 11 being too long. Thus, while improving the heat damage resistance and structural strength of the welded joint, it also takes into account structural lightweighting and production costs.

[0035] Optionally, A0 / A can take any value from 0.75, 1, 1.2, 1.5, 1.8, 2, 2.2, 2.5, 2.8, 3, or a value between any two values.

[0036] In one embodiment, the first reinforcing section 11 includes at least a first stepped portion 111, the upper end of the first stepped portion 111 along the Z direction being flush with the opening end of the housing 1, and the cover plate 2 being welded to the first stepped portion 111. It should be noted that the upper end mentioned refers to the upper end along the Z direction, that is, the end of the first stepped portion 111 that is away from the bottom surface of the housing along the Z direction.

[0037] In one embodiment, the length of the first step portion 111 along the Z direction is A1, and the penetration depth of the weld 3 along the Z direction is A3; wherein, A3 and A1 satisfy the relationship: A1≥1.2×A3, and the units of A1 and A3 are both mm. It should be noted that the weld 3 is formed on the first step portion 111, and A3 is equal to the vertical distance between the lowest point of the weld 3 along the Z direction and the end face of the shell opening; if A1 is less than 1.2 times A3, then the length of the first step portion 111 is too small relative to the penetration depth of the weld 3, which may result in weld defects such as molten beads falling into the shell during welding or the appearance of pores or bursts.

[0038] Therefore, while limiting the ratio A0 / A between the length A0 of the first reinforcing section 11 and the length A of the heat-affected zone to be within the range of 0.75 to 3, the length A1 of the first step portion 111 is limited to not less than 1.2 times the weld penetration depth of the weld 3. This achieves the strengthening of the heat-affected zone on the shell 1, while preventing molten beads from falling into the shell 1 during the welding process or causing welding defects such as pores or bursts, thereby avoiding internal short circuits in the battery cell, ensuring welding quality, and further improving the safety of the battery cell.

[0039] In one embodiment, the length A1 of the first step portion 111 along the Z direction ranges from 1 mm to 5 mm. If A1 is less than 1 mm, the length of the first step portion 111 is too short, which cannot effectively improve the structural strength of the shell 1; if A1 is greater than 5 mm, the length of the first step portion 111 is too long, making processing and manufacturing too difficult. Therefore, by limiting A1 to a value within the range of 1 mm to 5 mm, the structural strength of the shell 1 can be effectively strengthened, preventing cracking and damage in the heat-affected zone, while also avoiding material waste and excessive processing difficulty, which is beneficial to improving the molding yield of the shell 1.

[0040] Optionally, the value of A1 is any value among 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, and 5 mm, or a value between any two values.

[0041] In one embodiment, further combination Figure 7 , Figure 10 and Figure 13 As shown, the cover plate 2 includes a mating section that abuts against the inner wall of the first step portion 111. The length of the mating section along the Z direction is A4, where A4 ≥ 1.2 × A3. If A4 is less than 1.2 times A3, there is a risk of welding through the cover plate 2 during the welding process, resulting in welding defects such as porosity and blowholes. Therefore, by limiting A4 to not less than 1.2 times A3, the length of the mating section of the cover plate 2 is made to have a reasonable value relative to the weld penetration depth of the weld 3, thereby ensuring welding quality and improving the production yield and product reliability of the battery cells.

[0042] In one embodiment, the main body of the housing 1 is a shell body 12. The first reinforcing section 11 is connected to the shell body 12 via a second reinforcing section 13. Along the direction from the first reinforcing section 11 toward the main body of the housing 1, the wall thickness of the second reinforcing section 13 gradually decreases in the XY plane. It should be noted that the outer wall of the sidewall of the housing 1 is a flat surface. The second reinforcing section 13 connects the first reinforcing section 11 and the shell body 12. The wall thickness at the connection between the second reinforcing section 13 and the first reinforcing section 11 is equal to the wall thickness of the first reinforcing section 11, and the wall thickness at the connection between the second reinforcing section 13 and the shell body 12 is equal to the wall thickness of the shell body 12. The wall thickness at any point on the second reinforcing section 13 is between the wall thickness of the first reinforcing section 11 and the wall thickness of the shell body 12. The first reinforcing section 11 and the shell body 12 are connected by a second reinforcing section 13 with a gradually changing wall thickness, which avoids stress concentration caused by abrupt changes in wall thickness and makes the force transmission more gradual. The second reinforcing section 13 can also serve as a buffer zone for the heat-affected zone. Even if the heat-affected zone extends beyond the first reinforcing section 11, the second reinforcing section 13 can be used to strengthen the strength of the extended part, further preventing cracking of the heat-affected zone.

[0043] In one embodiment, the total length of the first reinforcing segment 11 and the second reinforcing segment 13 along the Z direction is A2, where 0.75 ≤ A0 / A ≤ 1 and A2 / A ≥ 1.4, and the units of A0, A, and A2 are all mm. It should be noted that A2 is the total length of the first reinforcing segment 11 and the second reinforcing segment 13. When the ratio A0 / A of the length of the first reinforcing segment 11 to the length of the heat-affected zone is between 0.75 and 1, the length of the first reinforcing segment 11 is not greater than the length of the heat-affected zone. If A2 is not limited, or if A2 / A is less than 1.4, the heat-affected zone may become too close to the shell body 12, or even extend along the Z direction to the shell body 12, causing damage to the structural strength of the shell body 12, and the shell still has a significant risk of damage. Therefore, when the ratio of the length of the first reinforcing section 11 to the length of the heat-affected zone is between 0.75 and 1, the ratio A2 / A of the total length of the first reinforcing section 11 and the second reinforcing section 13 to the length of the heat-affected zone is also limited to not less than 1.4. This ensures that the portion of the heat-affected zone extending beyond the first reinforcing section 11 in the X direction can fall onto the second reinforcing section 13, and that the edge 101 of the heat-affected zone is sufficiently far from the shell body 12. Since the wall thickness of the second reinforcing section 13 is not less than the wall thickness of the shell body 12, the second reinforcing section 13 can also play a certain structural reinforcing role. This can prevent the heat-affected zone from extending directly onto the shell body 12 with a smaller wall thickness and affecting the structural strength of the shell body 12, effectively solving the problem of heat-affected zone damage on the shell 1 after the shell cover is welded, and improving the reliability of the shell 1.

[0044] It is understood that in other embodiments, 1≤A0 / A≤3, the first reinforcing segment 11 has a sufficient length, and there is no need to further limit the relationship between the total length A2 of the first reinforcing segment 11 and the second reinforcing segment 13 and the length A of the heat-affected zone.

[0045] In one embodiment, the second reinforcing section 13 forms a first inclined surface 131 on the side facing the inner cavity of the shell 1. The angle between the first inclined surface 131 and the plane containing the inner wall of the shell body 12 is B, where 5°≤B≤45°. It should be noted that the outer wall surfaces of the shell body 12, the first reinforcing section 11, and the second reinforcing section 13 on the side facing away from the inner cavity of the shell are coplanar, facilitating the processing and forming of the shell 1. By forming the first inclined surface 131 on the side of the second reinforcing section 13 facing the inner cavity of the shell 1, the wall thickness of the second reinforcing section 13 varies uniformly, avoiding stress concentration caused by abrupt changes in wall thickness and further improving the strength of the shell 1.

[0046] It should be noted that if the wall thickness of the first reinforcing section 11 is greater than that of the shell body 12, then the dihedral angle between the first inclined surface 131 and the inner wall of the shell body 12 is an obtuse angle, and B refers to the acute angle complementary to this obtuse angle. If B is less than 5°, the first inclined surface 131 is close to being parallel to the inner wall of the shell body 12, and the extension distance of the second reinforcing section 13 along the Z direction is too long, wasting material costs and making it inconvenient to process; if B is greater than 45°, the transition of the first inclined surface 131 is too steep, the wall thickness changes drastically, and significant stress concentration is easily formed at the second reinforcing section 13, making the shell easily damaged and increasing the difficulty of shell molding.

[0047] Therefore, by limiting B to a value within the range of 5° to 45°, it is possible to avoid the second reinforcing section 13 from extending too far along the Z direction due to an overly gentle transition slope, thereby saving materials and costs. It is also possible to prevent the wall thickness from changing abruptly and stress concentration from an overly steep transition slope, thereby avoiding shell cracking and damage, reducing the molding difficulty of shell 1, and improving the processing yield.

[0048] Optionally, the value of B can be any value among 5°, 10°, 15°, 20°, 25°, 30°, 35°, 40°, and 45°, or a value between any two values.

[0049] In one embodiment, rounded transition connections are provided between the first inclined surface 131 and the shell body 12, and between the first inclined surface 131 and the first reinforcing section 11, which can prevent stress concentration from causing the shell 1 to crack, and further ensure the strength and reliability of the shell.

[0050] In one embodiment, such as Figures 6 to 8As shown, the first reinforcing segment 11 is the first step portion 111. The first reinforcing segment 11 only includes the first step portion 111. Therefore, the length A0 of the first reinforcing segment 11 along the Z direction is equal to the length A1 of the first step portion 111 along the Z direction, A0=A1; the total length of the first step portion 111 and the second reinforcing segment 13 along the Z direction is A20. Therefore, the total length of the first reinforcing segment 11 and the second reinforcing segment 13 is A2=A20.

[0051] In one embodiment, the first reinforcing segment 11 is a first stepped portion 111. In the XY plane, the wall thickness of the first stepped portion 111 is C1, and the wall thickness of the shell body 12 is C2. C1 and C2 satisfy the relationship: 1.2 ≤ C1 / C2 ≤ 2, where both C1 and C2 are in mm. If C1 / C2 is less than 1.2, the wall thickness of the first stepped portion 111 is too small relative to the wall thickness of the shell body 12, and the strengthening effect of the first stepped portion 111 on the structural strength of the shell 1 is limited. After the shell cover is welded, the heat-affected zone still has poor strength, leading to cracking and damage to the shell. If C1 / C2 is greater than 2, the wall thickness of the first stepped portion 111 is too large relative to the wall thickness of the shell body 12, making processing more difficult, wasting materials, and excessively increasing the weight of the shell 1, which is not conducive to achieving lightweight battery cells. Therefore, by limiting the values ​​of C1 / C2 to the range of 1.2 to 2, it is possible to ensure that the first reinforcing section 11 can effectively strengthen the structural strength of the shell opening end, thereby avoiding the problem of damage to the welding heat-affected zone, reducing the processing difficulty, avoiding waste of material costs, and facilitating the realization of lightweight battery cells.

[0052] Optionally, C1 / C2 can take any value from 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, or a value between any two values.

[0053] In one embodiment, the value of C2 is in the range of 0.3 mm ≤ C2 ≤ 1 mm. If C2 is less than 0.3 mm, the wall thickness of the shell body 12 is too small, the structural strength of the shell 1 itself is too poor, and the reliability is poor; if it is greater than 1 mm, the wall thickness of the shell body 12 is too large, the weight of the shell 1 is too large, and the cost is high. Therefore, by limiting the value of C2 to the range of 0.3 mm to 1 mm, it is possible to ensure that the shell 1 itself has sufficient structural strength and reliability, while avoiding excessive weight and cost of the shell 1, which is beneficial to achieving lightweight battery cells.

[0054] Optionally, C2 can be any value among 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, and 1 mm, or a value between any two of these values.

[0055] In addition, in other embodiments, further combined Figures 9 to 10 As shown, the first reinforcing section 11 includes a first step portion 111 and a second step portion 112. The second step portion 112 is located along the Z direction on the side of the first step portion 111 away from the opening end of the housing 1, and the wall thickness of the second step portion 112 is less than the wall thickness of the first step portion 111. The second step portion 112 and the first step portion 111 are connected by a first transition section 113.

[0056] It should be noted that the first reinforcing section 11 includes a first step portion 111 and a second step portion 112 with different wall thicknesses. The wall thicknesses of the first step portion 111, the second step portion 112, and the shell body 12 decrease sequentially. The first reinforcing section 11 is arranged in a multi-layered, non-staggered step configuration, which makes the wall thickness of the first reinforcing section 11 decrease in stages along the direction of welding heat transfer. This conforms to the law that the influence of welding heat on the shell gradually decreases from near to far. The second step portion 112 further avoids the heat-affected zone from being too close to the shell body 12. This can both ensure the reinforcement of the welding area of ​​the shell 1 by the first reinforcing section 11 and reduce the material used in the first reinforcing section 11.

[0057] Further integration Figure 9 As shown, along the Z direction, the length of the first step portion 111 is A1; the first reinforcing section 11 is composed of the first step portion 111, the second step portion 112, and the first transition section 113. The distance between the end of the first step portion 111 away from the second step portion 112 along the Z direction and the end of the second step portion 112 away from the first step portion 111 along the Z direction is A11, so the length of the first reinforcing section 11 is A0=A11; the total length of the first step portion 111, the first transition section 113, the second step portion 112, and the second reinforcing section 13 is A21, so the total length of the first reinforcing section 11 and the second reinforcing section 13 is A2=A21.

[0058] In one embodiment, a second inclined surface 1131 is formed on the side of the first transition section 113 facing the inner cavity of the shell 1, and the angle between the second inclined surface 1131 and the plane containing the inner wall of the shell body 12 is 5° to 45°. Similarly to the first inclined surface 131, by setting the second inclined surface 1131 on the side of the first transition section 113 facing the inner cavity of the shell 1, the wall thickness of the first transition section 113 changes uniformly, avoiding stress concentration. Furthermore, limiting the angle between the second inclined surface 1131 and the plane containing the inner wall of the shell body 12 to the range of 5° to 45° can both prevent the transition slope from being too gentle, causing the first transition section 113 to extend too long in the Z direction, thus ensuring that the first step portion 111 and the second step portion 112 have sufficient length, and prevent the transition slope from being too steep, causing abrupt changes in wall thickness and stress concentration, thereby avoiding shell cracking and damage, reducing the molding difficulty of the shell 1, and improving the processing yield.

[0059] In one embodiment, rounded corner transitions are provided between the inner wall of the second inclined surface 1131 and the first step portion 111, and between the second inclined surface 1131 and the second step portion 112, which can prevent stress concentration from causing the shell 1 to crack, and further ensure the strength and reliability of the shell.

[0060] In one embodiment, the wall thickness of the first step portion 111 is C1, the wall thickness of the second step portion 112 is C11, and the wall thickness of the shell body 12 is C2; wherein 1.1≤C1 / C11≤2, 1.1≤C11 / C2≤2, and C1>C11>C2, and the units of C1, C11, and C2 are all mm. It should be noted that by setting the wall thickness of the first step portion 111, the second step portion 112, and the shell body 12 to decrease sequentially, and C1 / C11 taking values ​​in the range of 1.1 to 2, and C11 / C2 taking values ​​in the range of 1.1 to 2, it can be ensured that the first reinforcing section 11 can effectively strengthen the structural strength of the shell opening end, thereby avoiding the problem of damage to the welding heat-affected zone, and it can also ensure that the wall thickness changes uniformly step by step from the opening end of the shell 1 to the shell body 12, which can reduce the processing difficulty and avoid wasting material costs, and is conducive to achieving lightweight battery cells.

[0061] Optionally, C1 / C11 can be any one of 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2 or a value between any two of them; C11 / C2 can be any one of 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2 or a value between any two of them.

[0062] In one embodiment, the value of C2 is in the range of 0.3 mm ≤ C2 ≤ 1 mm. This ensures that the housing 1 itself has sufficient structural strength and reliability, while avoiding excessive weight and cost of the housing 1, which is beneficial for achieving lightweight battery cells.

[0063] In addition, in other embodiments, further combined Figures 11 to 13 As shown, the first reinforcing section 11 includes a first step portion 111 and a second step portion 112. The second step portion 112 is located at the end of the first step portion 111 away from the opening end of the housing 1, and the wall thickness of the second step portion 112 is greater than the wall thickness of the first step portion 111. The second step portion 112 and the first step portion 111 are connected by a second transition section 114.

[0064] It should be noted that the first reinforcing section 11 includes a first step portion 111 and a second step portion 112 with different wall thicknesses. The second step portion 112, located between the first step portion 111 and the shell body 12, has the largest wall thickness. The first reinforcing section 11 is arranged in a multi-layered staggered step configuration. The second step portion 112 further prevents the heat-affected zone from getting too close to the shell body 12, ensuring that the first reinforcing section 11 strengthens the welding area of ​​the shell 1. In addition, the second step portion 112 can also block molten beads during the welding process, preventing molten beads from falling into the inner cavity of the shell, further improving safety, and facilitating the assembly of the cover plate 2 and the shell 1.

[0065] Further integration Figure 11 As shown, along the Z direction, the length of the first step portion 111 is A1; the first reinforcing section 11 is composed of the first step portion 111, the second step portion 112, and the second transition section 114. The distance between the end of the first step portion 111 away from the second step portion 112 along the Z direction and the end of the second step portion 112 away from the first step portion 111 along the Z direction is A12, so the length of the first reinforcing section 11 is A0=A12; the total length of the first step portion 111, the second transition section 114, the second step portion 112, and the second reinforcing section 13 is A22, so the total length of the first reinforcing section 11 and the second reinforcing section 13 is A2=A22.

[0066] In one embodiment, a third inclined surface 1141 is formed on the side of the second transition section 114 facing the inner cavity of the shell 1, and the angle between the third inclined surface 1141 and the plane containing the inner wall of the shell body 12 is 5° to 45°. This avoids the second transition section 114 from extending too far along the Z direction due to an overly gentle transition slope, thus ensuring that the first step portion 111 and the second step portion 112 have sufficient length. It also prevents the transition slope from being too steep, which could cause abrupt changes in wall thickness and stress concentration, thereby avoiding cracking and damage to the shell, reducing the molding difficulty of the shell 1, and improving the processing yield.

[0067] In one embodiment, rounded corner transitions are provided between the inner wall of the third inclined surface 1141 and the first step portion 111, and between the third inclined surface 1141 and the second step portion 112, which can prevent stress concentration from causing the shell 1 to crack, and further ensure the strength and reliability of the shell.

[0068] In one embodiment, the wall thickness of the first stepped portion 111 is C1, the wall thickness of the second stepped portion 112 is C11, and the wall thickness of the shell body 12 is C2, wherein 1.1≤C11 / C1≤2, 1.1≤C1 / C2≤2, and C11>C1>C2, and the units of C1, C11, and C2 are all mm. This design ensures that the first reinforcing section 11 can effectively strengthen the structural strength of the shell opening, thereby avoiding damage to the welding heat-affected zone, and also facilitates the processing and forming of the shell 1 and the assembly of the cover plate 2 with the shell 1.

[0069] In one embodiment, the value of C2 is in the range of 0.3 mm ≤ C2 ≤ 1 mm. This ensures that the housing 1 itself has sufficient structural strength and reliability, while avoiding excessive weight and cost of the housing 1, which is beneficial for achieving lightweight battery cells.

[0070] In one embodiment, further combination Figure 13 As shown, along the Z direction, the length of the first step portion 111 is A1, and the length of the mating section on the cover plate 2 along the Z direction is A4, where 0 mm ≤ A1 - A4 ≤ 0.5 mm. It should be noted that the circumferential edge of the cover plate 2 facing the inner cavity of the housing 1 along the Z direction is chamfered. Therefore, the mating section on the cover plate 2 that abuts against the inner wall of the first step portion 111 refers to the straight section of the cover plate 2 after removing the chamfer. If A1 - A4 is less than 0 mm, the length of the mating section is greater than the length of the first step portion 111. During the assembly of the cover plate 2 and the housing 1, the cover plate 2 interferes with the third inclined surface 1141, and the outer surface of the cover plate 2 protrudes beyond the end face of the opening end of the housing 1, which does not meet the requirements. If A1 - A4 is greater than 0.5 mm, the length of the first step portion 111 exceeding the mating section of the cover plate 2 is too large. After the housing and cover are assembled, the outer surface of the cover plate 2 is recessed below the end face of the opening end of the housing 1, which also fails to maintain the flatness of the outer surface of the battery cell.

[0071] Therefore, by limiting A1-A4 to values ​​between 0 mm and 0.5 mm, interference between the second transition section 114 on the housing 1 and the cover plate 2 can be avoided during the assembly process, thus ensuring that the cover plate 2 can be smoothly assembled onto the housing 1. Furthermore, the flatness between the surface of the cover plate 2 and the end face of the opening end of the housing 1 after the housing is assembled can be guaranteed, thus ensuring the yield of battery cell production.

[0072] According to an embodiment of the present invention, in another aspect, a battery pack is also provided, comprising: a housing and the aforementioned battery cells, wherein the battery cells are disposed within the housing. Optionally, the battery cells are lithium-ion battery cells.

[0073] The following examples and comparative models verify the impact of different parameter values ​​on the battery cell.

[0074] Table 1

[0075] As shown in Table 1, for the cells of Examples 1-1 to 1-3, A0 / A is in the range of 0.75 to 1, and A2 / A is greater than or equal to 1.4. The results show that after the shell and the cover plate are welded, the edge of the heat-affected zone falls on the slope reinforcement section of the shell (i.e., the second reinforcement section 13), which can improve the strength of the heat-affected zone. For the cells of Examples 1-4 to 1-13, the value of A0 / A is in the range of 1 to 3. After the shell and the cover plate are welded, the heat-affected zone falls on the first reinforcement section 11 at the opening of the shell, which can improve the shell strength of the heat-affected zone. For the battery cell of Comparative Example 1, the value of A0 / A is 0.5, which is less than the lower limit of A0 / A of 0.75 defined in this application. After the shell and the cover plate are welded, the edge of the heat-affected zone falls on the wall thickness of the shell body (i.e., the shell body 12), which reduces the shell strength and causes the shell to crack in the heat-affected zone. For the battery cells of Comparative Examples 1-2, the value of A0 / A is 5, which is greater than the upper limit of A0 / A of 3 defined in this application. The first reinforcing section is longer, which increases the manufacturing difficulty. It is not recommended to use it.

[0076] Table 2

[0077] Table 2 applies to shells with a single-layer stepped structure in which the first reinforcing section 11 only includes the first step portion 111, and shells with a multi-layer stepped non-misaligned arrangement in which the first reinforcing section 11 includes the first step portion 111 and the second step portion 112, and the wall thickness of the first step portion 111 is greater than the wall thickness of the second step portion 112.

[0078] As shown in Table 2, for the cells of Examples 2-1 to 2-12, the values ​​of A1 / A3 are all greater than or equal to 1.2. The results indicate that after the casing was welded, no molten beads fell into the battery after disassembly; and no air leakage occurred after the casing withstood a pressure of 1.2 MPa. However, for the cell of Comparative Example 2-1, the value of A1 / A3 is 1.04, which is less than 1.2 and outside the range defined in this application. After the casing was welded, molten beads fell into the battery after disassembly, damaging the electrode assembly (7 out of 10 cells tested failed). For the cell of Comparative Example 2-2, the value of A3 is 0.2 mm. After the casing was welded, no molten beads fell into the battery after disassembly; however, the weld depth was shallow, and air leakage occurred after the casing withstood a pressure of 1.2 MPa (3 out of 10 cells tested failed).

[0079] Table 3

[0080] Table 3 applies to shells with a multi-layered staggered arrangement, where the first reinforcing section 11 includes a first step portion 111 and a second step portion 112, and the wall thickness of the second step portion 112 is greater than the wall thickness of the first step portion 111.

[0081] As shown in Table 3, for the cells of Examples 3-1 to 3-12, the values ​​of A1 / A3 are all greater than or equal to 1.2. The results show that after the casing was welded, no welding defects such as burst holes or air holes were found when the battery was disassembled; and no air leakage occurred after the casing withstood a pressure of 1.2 MPa. However, for the cell of Comparative Example 3-1, the value of A1 / A3 is 1.04, which is less than 1.2 and is not within the range defined in this application. After the casing was welded, welding defects such as burst holes and air holes were prone to occur (7 out of 10 cells used for testing failed). For the cell of Comparative Example 3-2, the value of A3 is 0.2 mm. After the casing was welded, no welding defects such as burst holes or air holes were found when the battery was disassembled; however, the weld penetration was shallow, and air leakage occurred after the casing withstood a pressure of 1.2 MPa (3 out of 10 cells used for testing failed).

[0082] Unless otherwise stated, the values ​​of all parameters mentioned in this application can be determined using testing methods commonly used in the art. Unless otherwise stated, the test temperature for all parameters is 25°C.

[0083] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A battery cell, characterized in that, include: The shell has one end along the Z direction as an open end, and a portion of the shell along the Z direction near the open end is constructed as a first reinforcing section. The wall thickness of the first reinforcing section is greater than the wall thickness of the main body of the shell, and the length of the first reinforcing section along the Z direction is A0. A cover plate is provided on the open end of the housing. The cover plate is welded to the first reinforcing section to form a weld. The weld forms a heat-affected zone on the housing. The length of the heat-affected zone along the Z direction is A. Among them, A0 and A satisfy the relationship: 0.75≤A0 / A≤3.

2. The battery cell according to claim 1, characterized in that, The first reinforcing section includes at least a first stepped portion, the upper end of the first stepped portion along the Z direction is flush with the opening end of the shell, the cover plate is welded to the first stepped portion, the length of the first stepped portion along the Z direction is A1, and the penetration depth of the weld along the Z direction is A3. Among them, A3 and A1 satisfy the following relationship: A1≥1.2×A3; And / or, the length A1 of the first step portion along the Z direction is in the range of: 1 mm ≤ A1 ≤ 5 mm; And / or, the cover plate includes a mating section that abuts against the inner wall of the first step portion, the length of the mating section along the Z direction being A4, wherein A4 ≥ 1.2 × A3.

3. The battery cell according to claim 2, characterized in that, The main body of the shell is the shell body. The first reinforcing section is connected to the shell body through the second reinforcing section. Along the direction from the first reinforcing section to the shell body, the wall thickness of the second reinforcing section gradually decreases in the XY plane.

4. The battery cell according to claim 3, characterized in that, Along the Z direction, the total length of the first reinforcing segment and the second reinforcing segment is A2, where 0.75≤A0 / A≤1 and A2 / A≥1.4; and / or, the second reinforcing segment forms a first inclined surface on the side facing the inner cavity of the shell, and the angle between the first inclined surface and the plane containing the inner wall of the shell body is B, where 5°≤B≤45°.

5. The battery cell according to claim 3 or 4, characterized in that, The first reinforcing section is the first stepped portion. In the XY plane, the wall thickness of the first stepped portion is C1, and the wall thickness of the shell body is C2. Among them, C1 and C2 satisfy the following relationship: 1.2≤C1 / C2≤2; and / or, the range of C2 is: 0.3 mm≤C2≤1 mm.

6. The battery cell according to any one of claims 3 or 4, characterized in that, The first reinforcing section includes a first stepped portion and a second stepped portion. The second stepped portion is located along the Z direction on the side of the first stepped portion away from the opening end of the housing, and the wall thickness of the second stepped portion is less than the wall thickness of the first stepped portion. The second stepped portion and the first stepped portion are connected by a first transition section.

7. The battery cell according to claim 6, characterized in that, The first transition section forms a second inclined surface on the side facing the inner cavity of the shell, and the angle between the second inclined surface and the plane containing the inner wall of the shell body is 5°~45°. And / or, the wall thickness of the first step portion is C1, the wall thickness of the second step portion is C11, and the wall thickness of the shell body is C2; wherein, 1.1≤C1 / C11≤2, 1.1≤C11 / C2≤2, and C1>C11>C2; and / or, the value range of C2 is: 0.3 mm≤C2≤1 mm.

8. The battery cell according to any one of claims 3 or 4, characterized in that, The first reinforcing section includes a first stepped portion and a second stepped portion. The second stepped portion is located at the end of the first stepped portion away from the opening end of the housing, and the wall thickness of the second stepped portion is greater than the wall thickness of the first stepped portion. The second stepped portion and the first stepped portion are connected by a second transition section.

9. The battery cell according to claim 8, characterized in that, The second transition section forms a third inclined surface on the side facing the inner cavity of the shell, and the angle between the third inclined surface and the plane containing the inner wall of the shell body is 5°~45°; And / or, the wall thickness of the first step portion is C1, the wall thickness of the second step portion is C11, and the wall thickness of the shell body is C2, wherein 1.1≤C11 / C1≤2, 1.1≤C1 / C2≤2, and C11>C1>C2; and / or, the value range of C2 is: 0.3mm≤C2≤1 mm; And / or, along the Z direction, the length of the first step is A1, where 0 mm ≤ A1 - A4 ≤ 0.5 mm.

10. A battery pack, characterized in that, include: Box; The battery cell according to any one of claims 1 to 9, wherein the battery cell is disposed in the housing.

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