Shell cover matching structure and battery cell

Abstract

This invention relates to the field of battery technology, and discloses a casing-cap mating structure and a battery cell. The casing-cap mating structure includes a casing and a cap assembly. By providing a thicker section with a larger wall thickness at the opening end of the casing, the structural strength at the casing opening is effectively enhanced, and the strength of the casing weld after the casing and cap are welded is improved. At the same time, the length of the thickened section is limited to 0.75 to 3 times the length of the heat-affected zone. This ensures that the thickened section fully covers the range of the heat-affected zone generated by welding, preventing the heat-affected zone from extending too far beyond the area of ​​the thickened section. It also prevents the heat-affected zone from reaching the main body section due to the thickened section being too short relative to the heat-affected zone, thus avoiding damage problems such as cracking and deformation of the main body section with a smaller wall thickness. Furthermore, it avoids material waste, increased casing weight, and processing difficulties caused by an excessively long thickened section. Thus, it achieves both improved heat damage resistance and structural strength at the welded part, while also considering structural lightweighting and economy.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to a casing-cap mating structure and a battery cell. Background Technology

[0002] The battery cell includes components such as a housing, a cover plate assembly, and electrode groups. The cover plate body of the cover plate assembly is placed on the opening end of the housing and welded to the housing to encapsulate the electrode groups in the inner cavity of the housing.

[0003] In the existing technology, the cover plate overlaps the end face of the opening end of the shell and is welded around the perimeter of the shell. The wall thickness of the shell is generally small, so the thickness of the welded part on the shell is small. Due to the influence of welding, a heat-affected zone is formed on the shell during the welding of the cover plate. The strength of the heat-affected zone is less than the strength of the shell material itself, which can easily cause damage to the shell in the heat-affected zone after the cover plate is welded, seriously affecting the yield of battery cell production. Summary of the Invention

[0004] This invention provides a shell-and-cover mating structure and a battery cell to solve the problem that the shell is prone to heat-affected zone damage after the shell and cover are welded.

[0005] In a first aspect, the present invention provides a shell-and-cover mating structure, comprising: a shell having an open end, the shell including a plurality of sidewalls, each sidewall including a main body segment, a thickened segment, and a first transition segment, the thickened segment being disposed on the side of the main body segment facing the open end in the X direction, and the first transition segment connecting the thickened segment and the main body segment; in the YZ plane, the wall thickness of the thickened segment is greater than the wall thickness of the main body segment, and the wall thickness of the first transition segment gradually decreases along the direction from the thickened segment to the main body segment; and a cover plate assembly disposed in... At the open end of the housing, the cover assembly includes a cover body, which includes a body portion and an overlapping ring portion. The overlapping ring portion is connected around the outer peripheral side of the body portion in the YZ plane. At least a portion of the body portion extends into the inner cavity of the housing. The overlapping ring portion overlaps the end face of the open end of the housing, forming a splice seam between them. The overlapping ring portion is adapted to be welded to the housing along the splice seam and form a heat-affected zone on the housing. Along the X direction, the length of the thickened section is 0.75 to 3 times the length of the heat-affected zone.

[0006] Beneficial effects: By setting a thicker section with a larger wall thickness at the opening end of the shell, the structural strength of the shell opening is effectively enhanced, thereby improving the strength of the shell weld after the shell cover is welded. The first transition section with a gradually changing wall thickness connects the thickened section and the main body section, avoiding stress concentration caused by abrupt changes in wall thickness, making the force transmission more gradual. The first transition section can also serve as a buffer zone for the heat-affected zone. Even if the heat-affected zone exceeds the thickened section, the first transition section can be used to strengthen the strength of the excess part. At the same time, the length of the thickened section is limited to 0.75 to 3 times the length of the heat-affected zone. This ensures that the thickened section fully covers the range of the heat-affected zone generated by welding, preventing the heat-affected zone from extending too far beyond the area of ​​the thickened section. It also prevents the heat-affected zone from reaching the main body section due to the thickened section being too short relative to the heat-affected zone, thus avoiding cracking, deformation, and other damage problems in the main body section with a smaller wall thickness. Furthermore, it avoids material waste, increased shell weight, and processing difficulties caused by an excessively long thickened section. Thus, it achieves the goal of improving the heat damage resistance and structural strength of the welded part while also considering structural lightweighting and economy.

[0007] In one alternative embodiment, the first transition section forms a first inclined surface on the side facing the inner cavity of the housing, and a rounded transition connection is provided between the first inclined surface and the main body section, and between the first inclined surface and the thickened section.

[0008] Beneficial effects: Prevents stress concentration from causing shell cracking, further improving the reliability of the shell.

[0009] In one optional embodiment, the angle between the first inclined plane and the plane containing the inner wall of the main body segment is B, wherein 5°≤B≤45°.

[0010] Beneficial effects: It can avoid the first transition section from being too long along the X direction due to an overly gentle transition slope, thus saving materials and costs. It can also prevent the wall thickness from changing abruptly and stress concentration due to an overly steep transition slope, thus avoiding shell cracking and damage, reducing the shell forming difficulty and improving the processing yield.

[0011] In one alternative embodiment, both ends of the housing along the X direction are configured as open ends.

[0012] In one alternative embodiment, the side of the body portion facing away from the housing along the X direction is flush with the side of the overlapping ring portion facing away from the housing along the X direction; and / or, in the YZ plane, the outer peripheral surface of the overlapping ring portion is flush with the outer wall surface of the housing.

[0013] Beneficial effects: The outer surface of the cover plate body is a flat plane, which is easy to process and has high reliability; and / or, the outer peripheral surface of the overlapping ring is flush with the outer wall surface of the shell, which facilitates the welding of the cover plate body and the shell, reduces the welding difficulty, helps to improve the welding quality, and makes the battery cell appearance flat, which is conducive to the subsequent covering of the battery cell with an insulating film.

[0014] In one optional embodiment, the thickened section includes a first section, one end of which, along the X direction, is flush with the end face of the opening end of the housing. The length of the first section along the X direction is A1. The housing and the cover plate body are welded together to form a weld mark. Along the X direction, the effective weld width of the weld mark on the housing is A3.

[0015] Beneficial effects: It facilitates the processing and forming of the thickened section on the shell, and ensures that the thickened section can effectively improve the strength of the weld position.

[0016] In one alternative implementation, along the X direction, the length of the thickened section is equal to the length of the first section, and the length of the heat-affected zone is A; Wherein, 0.75≤A1 / A≤3, and A1≥1.5×A3; or, along the X direction, the total length of the thickened segment and the first transition segment is A2, where 0.75≤A1 / A≤1, and A2 / A≥1.4; And / or, in the YZ plane, the wall thickness of the first segment is C1, and the wall thickness of the main segment is C2, wherein 1.2≤C1 / C2≤2.

[0017] Beneficial effects: By limiting the ratio A1 / A of the length of the thickened section to the length of the heat-affected zone to be between 0.75 and 3, and by limiting the length of the first section to be no less than 1.5 times the effective weld width, the strength of the heat-affected zone on the shell is enhanced, while preventing molten beads from falling into the shell during the welding process, thereby avoiding short circuits inside the shell and improving the safety of the battery cell. And / or, to prevent the heat-affected zone from extending directly to the main body section with a smaller wall thickness and affecting the structural strength of the main body section, effectively solve the problem of heat-affected zone damage on the shell after the shell cover is welded, and improve the reliability of the shell; And / or, by limiting C1 / C2 to values ​​within the range of 1.2 to 2, it can be ensured that the thickened 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 facilitating the lightweighting of the battery cell.

[0018] In one optional embodiment, the thickened section further includes a second section located between the first section and the main body section along the X direction. In the YZ plane, the wall thickness of the second section is less than the wall thickness of the first section. Along the X direction, the distance between the opening end of the shell and the end of the second section away from the first section is A11, the length of the thickened section is equal to A11, and the length of the heat-affected zone is A. Wherein, 0.75≤A11 / A≤3, and A1≥1.5×A3; or, along the X direction, the total length of the thickened segment and the first transition segment is A21, 0.75≤A11 / A≤1, and A21 / A≥1.4; And / or, in the YZ plane, the wall thickness of the first section is C1, the wall thickness of the second section is C11, the wall thickness of the main body section is C2, 1.1≤C1 / C11≤2, 1.1≤C11 / C2≤2, and C1>C11>C2; And / or, the first section and the second section are connected by a second transition section, the second transition section having an inclined surface on the side facing the inner cavity of the housing.

[0019] Beneficial effects: The thickened section is arranged in a multi-layered, non-staggered stepped form, which makes the thickness of the thickened 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 section further avoids the heat-affected zone from being too close to the main body section. This can both ensure the strengthening of the welded area of ​​the shell by the thickened section and reduce the amount of material used in the thickened section.

[0020] In one optional embodiment, the thickened section further includes a second section located between the first section and the main body section along the X direction. In the YZ plane, the wall thickness of the second section is greater than that of the first section. Along the X direction, the distance between the opening end of the shell and the end of the second section away from the first section is A12, the length of the thickened section is equal to A12, and the length of the heat-affected zone is A. Where 0.75≤A12 / A≤3, and A1≥1.5×A3; And / or, along the X direction, the mating length between the portion of the body extending into the inner cavity of the housing and the inner wall of the housing is D, where A1 ≥ 1.1 × D; And / or, in the YZ plane, the wall thickness of the first section is C1, the wall thickness of the second section is C11, the wall thickness of the main body section is C2, 1.1≤C11 / C1≤2, 1.1≤C1 / C2≤2, and C11>C1>C2; And / or, the first section and the second section are connected by a third transition section, the third transition section being inclined on the side facing the inner cavity of the housing.

[0021] Beneficial effects: The thickened section is arranged in a multi-layered stepped staggered form. The second section further avoids the heat-affected zone from being too close to the main body section, ensuring that the thickened section strengthens the welded area of ​​the shell. Moreover, the wall thickness of the first section does not need to be set too thick, which facilitates the processing and forming of the shell and the assembly of the cover plate body with the shell.

[0022] Secondly, the present invention also provides a battery cell, comprising: the aforementioned shell-and-cover mating structure; and an electrode assembly disposed within the inner cavity of the shell in the shell-and-cover mating structure. Since the battery cell includes the shell-and-cover mating structure and has the same effects as the shell-and-cover mating structure, it will not be described in detail 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 A sectional view of the shell-and-cover mating structure from the EE direction. Figure 4 for Figure 3 A magnified view of part of F; Figure 5 This is a partially enlarged cross-sectional view of the first shell-and-cover mating structure according to an embodiment of the present invention; Figure 6 for Figure 5 A magnified view of part of G and some of its dimensions; Figure 7 for Figure 5 A partially enlarged schematic diagram of G and another portion of its dimensions; Figure 8 This is a partially enlarged cross-sectional view of the second shell-cap mating structure according to an embodiment of the present invention; Figure 9 for Figure 8 A partially enlarged schematic diagram of J and some of its dimensions; Figure 10 for Figure 8 A partially enlarged schematic diagram of J and another portion of its dimensions; Figure 11 This is a partially enlarged schematic diagram of a cross-sectional view of the third shell-cap mating structure according to an embodiment of the present invention; Figure 12 for Figure 11 A magnified view of part of K and some of its dimensions; Figure 13 for Figure 11 A magnified view of part of K and another portion of its dimensions; Figure 14 for Figure 13 A magnified view of a portion of L.

[0025] Explanation of reference numerals in the attached figures: 1. Shell; 101. Edge of heat-affected zone; 11. Main body section; 12. Thickened section; 121. First section; 122. Second section; 123. Second transition section; 1231. Second inclined surface; 124. Third transition section; 1241. Third inclined surface; 13. First transition section; 131. First inclined surface; 2. Cover plate body; 21. Main body part; 22. Overlapping ring part; 3. Weld mark. 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 casing, a cover plate assembly, and electrode groups. The cover plate assembly consists of a cover plate body that covers the open end of the casing and is welded to the casing to encapsulate the electrode groups within the inner cavity of the casing. For example... Figures 1 to 4 As shown, in the prior art, the wall thickness of the area where the cover plate body is welded to the shell is generally less than or equal to the wall thickness of the shell body. The cover plate body of the blade cell overlaps the end face of the open end of the shell, and welding is performed around the perimeter of the shell at the joint between the two. Since the shell wall thickness is small, the thickness of the welded part on the shell is also small. Due to the influence of welding heat, a heat-affected zone is formed on the shell 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 shell material itself, which can easily cause damage to the shell 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 the cell production, or it may be damaged when the cell is subjected to stress during use, which seriously affects the service life and safety of the cell.

[0028] The following is combined with Figures 5 to 14 The following describes embodiments of the present invention.

[0029] According to an embodiment of the present invention, a shell-and-cover fitting structure is provided, comprising: a shell 1 and a cover assembly. The shell 1 has an open end and includes a plurality of sidewalls, each sidewall including a main body segment 11, a thickened segment 12, and a first transition segment 13. The thickened segment 12 is disposed on the side of the main body segment 11 facing the open end in the X direction, and the first transition segment 13 connects the thickened segment 12 and the main body segment 11. In the YZ plane, the wall thickness of the thickened segment 12 is greater than the wall thickness of the main body segment 11, and the wall thickness of the first transition segment 13 gradually decreases along the direction from the thickened segment 12 to the main body segment 11. The cover assembly is disposed at the open end of the shell 1, and the cover... The assembly includes a cover plate body 2, which includes a body portion 21 and an overlapping ring portion 22. The overlapping ring portion 22 surrounds the outer periphery of the body portion 21 in the YZ plane. At least a portion of the body portion 21 extends into the inner cavity of the housing 1. The overlapping ring portion 22 overlaps the end face of the open end of the housing 1, forming a splice seam between them. The overlapping ring portion 22 is adapted to be welded to the housing 1 along the splice seam and forms a heat-affected zone on the housing 1. Along the X direction, the length of the thickened section 12 is 0.75 to 3 times the length of the heat-affected zone. The shell-cover mating structure refers to the mating structure between the housing 1 and the cover plate assembly. The units for the length of the thickened section 12 and the length of the heat-affected zone are both mm.

[0030] like Figures 1 to 14 As shown, the shell 1 has intersecting X, Y, and Z directions, where the X direction is the length direction of the shell 1, the Y direction is the width direction of the shell 1, and the Z direction is the thickness direction of the shell 1. At least one end of the shell 1 along the X direction is configured as an open end. The shell 1 includes four sidewalls connected end to end, including two first sidewalls parallel to the XZ directions and arranged opposite each other, and two second sidewalls parallel to the XY directions and arranged opposite each other, with the area of ​​the first sidewalls being larger than the area of ​​the second sidewalls.

[0031] It should be noted that the battery cell is a blade battery cell, and the housing 1 is the housing of the blade battery cell; when the cover plate body 2 is welded to the housing 1, the welding is performed around the housing 1 along the splice seam between the overlapping ring 22 and the housing 1, forming a weld mark 3 after welding. Part of the weld mark 3 is located on the housing 1, and the other part is located on the cover plate body 2; the heat-affected zone refers to the area on the housing 1 that has undergone hardness changes due to the welding heat during the welding of the cover and the housing. The heat-affected zone on the housing 1 extends from the end face of the housing opening in the X direction away from the overlapping ring 22; along the X direction, the length of the heat-affected zone is greater than the length of the area occupied by the weld mark 3 on the housing 1, and the thickened section 12 increases the hardness of the housing 1. If the length of the thickened section 12 near the opening end used for welding is less than 0.75 times the length of the heat-affected zone, then the length of the thickened section 12 is too small relative to the length of the heat-affected zone. The heat-affected zone extends too far beyond the thickened section 12, and may even exceed the first transition section 13 and reach the main body section 11 with a smaller wall thickness. This makes it difficult to effectively strengthen the strength of the shell 1, and it is prone to cracking in the heat-affected zone during cell breathing cycle testing. If the length of the thickened section 12 is more than 3 times the length of the heat-affected zone, then the length of the thickened section 12 is too large relative to the length of the heat-affected zone. The thickened section 12 extends too far beyond the heat-affected zone, and the thickened section 12 is too long, making processing difficult and affecting the molding yield of the shell 1.

[0032] Among them, the microhardness of the heat-affected zone 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 HV 0.5 ; 3. Measurement point layout: 1) Starting point: fusion line position (i.e., the end face of the shell opening); 2) Direction: continuous measurement points perpendicular to weld 3 (i.e., X direction) toward the base material; 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) The hardness gradually increases from the weld seam outward (i.e., gradually away from the end face of the shell opening along the X direction); 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 from the fusion line to that point along the X direction is the length of the heat-affected zone.

[0033] By applying the shell-cover fitting structure of this embodiment, a thickened section 12 with a larger wall thickness is provided at the opening end of the shell 1, which effectively enhances the structural strength at the opening of the shell 1, thereby improving the strength of the welded joint of the shell 1 after the shell cover is welded. A first transition section 13 with a gradually changing wall thickness connects the thickened section 12 and the main body section 11, avoiding stress concentration caused by abrupt changes in wall thickness and making the force transmission smoother. The first transition section 13 can also serve as a buffer zone for the heat-affected zone. Even if the heat-affected zone extends beyond the thickened section 12, the first transition section 13 can be used to strengthen the strength of the extended portion, while simultaneously limiting the thickness of the thickened section 12. The length of the thickened section 12 is 0.75 to 3 times the length of the heat-affected zone. This ensures that the thickened section 12 can fully cover the area of ​​the heat-affected zone generated by welding, preventing the heat-affected zone from extending too far beyond the area of ​​the thickened section 12. It also prevents the heat-affected zone from reaching the main body section 11 due to the thickened section 12 being too short relative to the heat-affected zone, thus avoiding damage problems such as cracking and deformation of the main body section 11 with a smaller wall thickness. Furthermore, it avoids the waste of materials, increased shell weight, and processing difficulties caused by the thickened section 12 being too long. This achieves the goal of improving the heat damage resistance and structural strength of the welded parts while taking into account the lightweight structure and economy.

[0034] It should be noted that the wall thickness at any point on the first transition section 13 is between the wall thickness of the thickened section 12 and the wall thickness of the main section 11.

[0035] In one embodiment, further combination Figure 6 , Figure 9 and Figure 13 As shown, a first inclined surface 131 is formed on the side of the first transition section 13 facing the inner cavity of the shell 1. Rounded corner transition connections are provided between the first inclined surface 131 and the main body section 11, and between the first inclined surface 131 and the thickened section 12. It should be noted that the outer wall surface of the shell 1 on the side facing away from its inner cavity is a flat plane; that is, the outer wall surfaces of the main body section 11, the thickened section 12, and the first transition 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 a first inclined surface 131 on the side of the first transition section 13 facing the inner cavity of the shell 1, the thickness of the first transition section 13 varies uniformly. Furthermore, by providing rounded corner transition connections between the first inclined surface 131 and the thickened section 12 and the main body section 11, stress concentration that could lead to cracking of the shell 1 can be prevented, further improving the reliability of the shell 1.

[0036] In one embodiment, further combination Figure 7As shown, the angle between the first inclined surface 131 and the plane containing the inner wall of the main body segment 11 is B, where 5° ≤ B ≤ 45°. It should be noted that if the wall thickness of the thickened segment 12 is greater than that of the main body segment 11, then the dihedral angle between the first inclined surface 131 and the inner wall of the main body segment 11 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 nearly parallel to the inner wall of the main body segment 11, resulting in an excessively long extension distance of the first transition segment 13 along the X direction, wasting material costs and hindering processing. If B is greater than 45°, the transition of the first inclined surface 131 is too steep, with drastic changes in wall thickness, easily leading to significant stress concentration at the first transition segment 13, making the shell prone to damage and increasing the difficulty of shell molding. Therefore, by limiting B to a value within the range of 5° to 45°, it is possible to avoid the first transition segment 13 from extending too far along the X 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.

[0037] 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.

[0038] In one embodiment, both ends of the housing 1 along the X direction are configured as open ends. The housing 1 is the housing used for blade cells. The fact that both ends of the housing 1 along its length direction are configured as open ends facilitates the smooth insertion of the electrode assembly into the housing 1 along the length direction. At the same time, it facilitates the welding of both ends to the cover plate assembly to achieve encapsulation and lead-out of the electrode posts at both ends, thus adapting to the requirements of blade cells.

[0039] In one embodiment, the side of the body portion 21 facing away from the housing 1 along the X direction is flush with the side of the overlapping ring portion 22 facing away from the housing 1 along the X direction. It should be noted that the surfaces of the body portion 21 and the overlapping ring portion 22 facing away from the housing 1 along the X direction are flush, meaning the outer surface of the cover body 2 is a flat plane, facilitating processing and ensuring high reliability. The body portion 21 and the overlapping ring portion 22 are integrally formed, ensuring that the cover body 2 has high structural strength.

[0040] In one embodiment, in the YZ plane, the outer peripheral surface of the overlapping ring 22 is flush with the outer wall surface of the housing 1, which facilitates the welding of the cover plate body 2 and the housing 1, reduces the welding difficulty, improves the welding quality, and makes the battery cell appearance flat, which is beneficial for subsequent wrapping of the battery cell with an insulating film.

[0041] In one embodiment, the thickened section 12 includes a first section 121. The end of the first section 121 away from the main body section 11 along the X direction is flush with the end face of the opening end of the housing 1. The length of the first section 121 along the X direction is A1. The housing 1 and the cover plate body 2 are welded together to form a weld mark 3. The effective weld width of the weld mark 3 on the housing 1 is A3. It should be noted that the end of the thickened section 12 away from the main body section 11 along the X direction is flush with the end face of the opening end of the housing 1. The thickened section 12 includes at least the first section 121. During the welding of the housing and cover, the weld mark 3 is formed from the outside inwards, further bonding... Figure 6 As shown, the weld width of weld 3 along the X direction on the inner wall surface of the housing 1 is smaller than its weld width along the X direction on the outer wall surface of the housing 1. The effective weld width A3 of weld 3 refers to the weld width of weld 3 along the X direction on the inner wall surface of the housing 1. By setting the end of the first section 121 away from the main body section 11 along the X direction to be flush with the end face of the opening end of the housing 1, it is convenient for the thickened section 12 to be processed and formed on the housing 1, and it can be ensured that the thickened section 12 can effectively improve the strength of the weld position.

[0042] In one embodiment, such as Figures 5 to 7 As shown, along the X direction, the thickened section 12 only includes the first section 121. The thickened section 12 is in the shape of a single-layer step, and the length of the thickened section 12 is equal to the length A1 of the first section 121. The length of the heat-affected zone is A, where 0.75≤A1 / A≤3, and A1≥1.5×A3. The units of A1, A, and A3 are all mm. It should be noted that the heat-affected zone extends downward from the end face of the shell opening on the shell 1 along the X direction. The heat-affected zone has a heat-affected zone edge 101 along the X direction away from the shell opening, as shown... Figure 6 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 of the heat-affected zone refers to the distance between the farthest point and the opening end of the shell along the X direction. The solder mark 3 is formed on the first section 121. If A1 is less than 1.5 times A3, the length of the first section 121 is too small relative to the effective weld width of the solder mark 3. The molten beads are easy to fall into the shell and cause a short circuit.

[0043] Therefore, by limiting the ratio A1 / A of the length of the thickened section 12 to the length of the heat-affected zone to be between 0.75 and 3, and by limiting the length of the first section 121 (i.e. the thickened section 12) to be no less than 1.5 times the effective weld width of the solder mark 3, the strength of the heat-affected zone on the shell 1 is enhanced, while preventing molten beads from falling into the shell 1 during the welding process, thereby avoiding short circuits inside the shell 1 and improving the safety of the battery cell.

[0044] In other embodiments, along the X direction, the total length of the thickened segment 12 and the first transition segment 13 is A2, where 0.75 ≤ A1 / A ≤ 1, and A2 / A ≥ 1.4, and the units of A1, A, and A2 are all mm. Further combining... Figure 6 As shown, A2 refers to the distance along the X direction between the end face of the shell opening and the end of the first transition section 13 furthest from the shell opening. When the ratio A1 / A of the length of the thickened section 12 to the length of the heat-affected zone is between 0.75 and 1, the length of the thickened section 12 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 will be too close to the main body section 11, or even spread along the X direction to the main body section 11, causing damage to the structural strength of the main body section 11, and the shell will still have a large risk of damage. Therefore, when the ratio A1 / A of the length of the thickened section 12 to the length of the heat-affected zone is between 0.75 and 1, the ratio A2 / A of the total length of the thickened section 12 and the first transition 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 thickened section 12 in the X direction falls on the first transition section 13, and that the edge of the heat-affected zone has a sufficient distance from the main body section 11. Since the wall thickness of the first transition section 13 is not less than the wall thickness of the main body section 11, the first transition section 13 can also play a certain role in structural reinforcement. This can prevent the heat-affected zone from extending directly onto the main body section 11 with a smaller wall thickness and affecting the structural strength of the main body section 11, 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.

[0045] It is understood that in other embodiments, 1≤A1 / A≤3, the thickened segment 12 has sufficient length, and there is no need to further limit the relationship between the total length A2 of the thickened segment 12 and the first transition segment 13 and the length A of the heat-affected zone.

[0046] In one embodiment, further combination Figure 7As shown, in the YZ plane, the wall thickness of the first segment 121 is C1, and the wall thickness of the main segment 11 is C2, where 1.2 ≤ C1 / C2 ≤ 2, and the units of C1 and C2 are both mm. If C1 / C2 is less than 1.2, the wall thickness of the first segment 121 is too small relative to the wall thickness of the main segment 11, and the strengthening effect of the first segment 121 on the structural strength of the shell is limited. After the shell cover is welded, there is still the problem of poor strength of the weld heat-affected zone, and the shell cracking and damage. If C1 / C2 is greater than 2, the wall thickness of the first segment 121 is too large relative to the wall thickness of the main segment 11, which makes processing more difficult, wastes materials, and excessively increases the weight of the shell 1, which is not conducive to achieving lightweight battery cells. Therefore, by limiting the value of C1 / C2 to the range of 1.2 to 2, it can be ensured that the thickened segment 12 can effectively strengthen the structural strength of the shell opening end, thereby avoiding the problem of weld heat-affected zone damage, while also reducing processing difficulty and avoiding waste of material costs, which is conducive to achieving lightweight battery cells.

[0047] 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.

[0048] Additionally, in other embodiments, such as Figures 8 to 10 As shown, the thickened section 12 also includes a second section 122, which is located between the first section 121 and the main body section 11 along the X direction. In the YZ plane, the wall thickness of the second section 122 is less than the wall thickness of the first section 121. Along the X direction, the distance between the opening end of the shell 1 and the end of the second section 122 away from the first section 121 is A11, the length of the thickened section 12 is equal to A11, and the length of the heat-affected zone is A. Wherein, 0.75≤A11 / A≤3, and A1≥1.5×A3, and the units of A11, A, A1, and A3 are all mm.

[0049] It should be noted that the thickened section 12 includes a first section 121 and a second section 122 with different wall thicknesses. The wall thicknesses of the first section 121, the second section 122, and the main body section 11 decrease sequentially. The thickened section 12 is arranged in a multi-layered, non-staggered stepped manner, so that the thickness of the thickened section 12 decreases 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 section 122 further avoids the heat-affected zone from being too close to the main body section 1. This can both ensure the strengthening of the welding area of ​​the shell 1 by the thickened section 12 and reduce the material used for the thickened section 12. The length of the thickened section 12 is equal to the distance between the end of the first section 121 away from the second section 122 in the X direction and the end of the second section 122 away from the first section 121 in the X direction. The weld mark 3 is located on the first section 121 on the shell 1.

[0050] Wherein, A11 / A represents the ratio between the length of the thickened section 12 and the length of the heat-affected zone. By limiting the ratio A11 / A between the length of the thickened section 12 and the length of the heat-affected zone to a value between 0.75 and 3, and by limiting the length of the first section 121 to be no less than 1.5 times the effective weld width of the solder mark 3, the strength of the heat-affected zone on the shell 1 is enhanced, while preventing molten beads from falling into the shell 1 during the welding process, thereby avoiding short circuits inside the shell 1 and improving the safety of the battery cell.

[0051] In other embodiments, along the X direction, the total length of the thickened segment 12 and the first transition segment 13 is A21, 0.75≤A11 / A≤1, and A21 / A≥1.4, where the units of A11, A, and A21 are all mm. Further combining... Figure 9 As shown, A21 refers to the distance along the X direction between the end face of the shell opening and the end of the first transition section 13 furthest from the shell opening. The thickened section 12 and the first transition section 13 together constitute the reinforcing section. Similar to when the thickened section 12 only includes the first section 121, when the ratio A11 / A of the length of the thickened section 12 to the length of the heat-affected zone is between 0.75 and 1, the ratio A21 / A of the total length of the thickened section 12 and the first transition section 13 to the length of the heat-affected zone is also set to be not less than 1.4. This further prevents the heat-affected zone from directly extending onto the thinner main body section 11 or from the edge of the heat-affected zone being too close to the main body section 11, thereby further ensuring the structural strength of the welded area and effectively solving the problem of heat-affected zone damage on the shell 1 after the shell cover is welded, thus improving the reliability of the shell 1.

[0052] It is understood that in other embodiments, 1≤A11 / A≤3, the thickened segment 12 has a sufficient length, and there is no need to further limit the relationship between the total length A21 of the thickened segment 12 and the first transition segment 13 and the length A of the heat-affected zone.

[0053] In one embodiment, further combination Figure 10As shown, in the YZ plane, the wall thickness of the first segment 121 is C1, the wall thickness of the second segment 122 is C11, and the wall thickness of the main segment 11 is C2. 1.1 ≤ C1 / C11 ≤ 2, 1.1 ≤ C11 / C2 ≤ 2, and C1 > C11 > C2. The units of C1, C11, and C2 are all mm. It should be noted that by setting the wall thicknesses of the first segment 121, the second segment 122, and the main segment 11 to decrease sequentially, and with C1 / C11 and C11 / C2 both within the range of 1.2 to 2, it is possible to ensure that the thickened segment 12 effectively strengthens the structural strength of the shell opening, thus avoiding damage to the welding heat-affected zone. Furthermore, it ensures that the wall thickness changes uniformly from the opening of the shell 1 to the main segment 11, reducing processing difficulty and avoiding material waste, which is beneficial for achieving lightweight battery cells.

[0054] Optionally, C1 / C11 can be 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; C11 / C2 can be 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.

[0055] In one embodiment, further combination Figure 9 As shown, the first section 121 and the second section 122 are connected by a second transition section 123. The side of the second transition section 123 facing the inner cavity of the housing 1 is inclined, and is referred to as the second inclined surface 1231. By setting the second transition section 123 to connect the first section 121 and the second section 122, and the inner wall of the second transition section 123 is inclined, the wall thickness of the second transition section 123 gradually changes, avoiding stress concentration caused by abrupt changes in the wall thickness of the first section 121 and the second section 122, making the force transmission smoother, and facilitating processing and forming, which is beneficial to improving the production yield of the housing 1.

[0056] In one embodiment, the connection points between the second inclined surface 1231 and the inner wall surface of the first section 121 and the inner wall surface of the second section 122 are respectively connected by rounded corners, which can prevent stress concentration from causing the shell 1 to crack and further improve the reliability of the shell 1.

[0057] Additionally, in other embodiments, such as Figures 11 to 14As shown, the thickened section 12 also includes a second section 122, which is located between the first section 121 and the main body section 11 along the X direction. In the YZ plane, the wall thickness of the second section 122 is greater than the wall thickness of the first section 121. Along the X direction, the distance between the opening end of the shell 1 and the end of the second section 122 away from the first section 121 is A12. The length of the thickened section 12 is equal to A12, and the length of the heat-affected zone is A. Wherein, 0.75≤A12 / A≤3, and A1≥1.5×A3, and the units of A12, A, A1, and A3 are all mm.

[0058] It should be noted that the thickened section 12 includes a first section 121 and a second section 122 with different wall thicknesses. The second section 122, located between the first section 121 and the main body section 11, has the largest wall thickness. The thickened section 12 is arranged in a multi-layered stepped staggered form. The second section 122 further avoids the heat-affected zone from being too close to the main body section 11, ensuring that the thickened section 12 strengthens the welding area of ​​the shell 1. The wall thickness of the first section 121 does not need to be too thick, which facilitates the processing and forming of the shell 1 and the assembly of the cover plate body 2 with the shell 1. The length of the thickened section 12 is equal to the distance between the end of the first section 121 away from the second section 122 in the X direction and the end of the second section 122 away from the first section 121 in the X direction.

[0059] Wherein, A12 / A represents the ratio between the length of the thickened section 12 and the length of the heat-affected zone. By limiting the ratio A12 / A between the length of the thickened section 12 and the length of the heat-affected zone to a value between 0.75 and 3, and by limiting the length of the first section 121 to be no less than 1.5 times the effective weld width of the solder mark 3, the strength of the heat-affected zone on the shell 1 is enhanced, while preventing molten beads from falling into the shell 1 during the welding process, thereby avoiding short circuits inside the shell 1 and improving the safety of the battery cell.

[0060] At this time, the total length of the thickened section 12 and the first transition section 13 is A22, which satisfies 0.75≤A12 / A≤1 and A22 / A≥1.4. This avoids the heat-affected zone from extending directly to the main body section 11 with a smaller wall thickness and affecting the structural strength of the main body section 11. It effectively solves the problem of heat-affected zone damage on the shell 1 after the shell cover is welded, and improves the reliability of the shell 1.

[0061] In one embodiment, along the X direction, the portion of the body part 21 extending into the inner cavity of the housing 1 has a mating length D with the inner wall of the housing 1, where A1 ≥ 1.1 × D, and the units of A1 and D are both mm. Further combining... Figure 12 As shown, the body portion 21 includes a boss extending into the inner cavity of the housing 1. The edge of the boss away from the opening end of the housing along the X direction is chamfered. D refers to the length of the straight segment of the boss after removing the chamfer; this portion is parallel to the inner wall surface of the housing 1. Figure 14As shown, there is a height difference h between the length of the first section 121 and the length of the straight section of the boss, where h = A1 - D. By limiting the length of the first section 121 to be no less than 1.1 times the mating length D of the cover, the mating section between the cover body 2 and the inner wall of the shell 1 is kept at a certain distance from the end of the first section 121 (i.e., the end of the first section 121 away from the opening of the shell), which can avoid interference in the assembly of the cover and ensure the smooth progress of the assembly process.

[0062] Furthermore, 1.1≤A12 / A≤3, and A1≥1.1×D, while ensuring that the heat-affected zone falls on the thickened section 12, interference in the shell cover assembly is avoided, taking into account both the shell strength and the shell cover assembly effect.

[0063] In one embodiment, within the YZ plane, the wall thickness of the first segment 121 is C1, the wall thickness of the second segment 122 is C11, and the wall thickness of the main body segment 11 is C2, where 1.1 ≤ C11 / C1 ≤ 2, 1.1 ≤ C1 / C2 ≤ 2, and C11 > C1 > C2. The units of C1, C11, and C2 are all mm. This design ensures that the thickened segment 12 effectively strengthens the structural strength of the shell opening, thus 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 body 2 with the shell 1.

[0064] In one embodiment, the first segment 121 and the second segment 122 are connected by a third transition segment 124. The side of the third transition segment 124 facing the inner cavity of the housing 1 is inclined, denoted as the third inclined surface 1241. By setting the third transition segment 124 to connect the first segment 121 and the second segment 122, and the inner wall of the third transition segment 124 is inclined, the wall thickness of the third transition segment 124 gradually changes, avoiding stress concentration caused by abrupt changes in the wall thickness of the first segment 121 and the second segment 122, making the force transmission smoother, and facilitating processing and forming, which is beneficial to improving the production yield of the housing 1.

[0065] In one embodiment, the connection points between the third inclined surface 1241 and the inner wall surface of the first section 121 and the inner wall surface of the second section 122 are respectively connected by rounded corners, which can prevent stress concentration from causing the shell 1 to crack and further improve the reliability of the shell 1.

[0066] According to an embodiment of the present invention, another aspect provides a battery cell, comprising: the aforementioned shell-and-cover mating structure; and an electrode assembly disposed within the inner cavity of the shell 1 in the shell-and-cover mating structure. The cover plate assembly in the shell-and-cover mating structure further includes electrode posts integrated onto the cover plate body, and the electrode tabs of the electrode assembly are electrically connected to the electrode posts. Optionally, the battery cell is a lithium-ion battery cell.

[0067] The following examples and comparative models verify the impact of different parameter values ​​on the battery cell.

[0068] In Table 1, A1' represents the length of the thickened section 12 along the X direction, and A2' represents the total length of the thickened section 12 and the first transition section 13. Specifically, for a single-layer step structure in which the thickened section 12 only includes the first section 121, A1' is A1, and A2' is A2; for a multi-layer step structure in which the thickened section 12 includes the first section 121 and the second section 122, and the wall thickness of the second section 122 is less than the wall thickness of the first section 121, A1' is A11, and A2' is A21; for a multi-layer step structure in which the thickened section 12 includes the first section 121 and the second section 122, and the wall thickness of the second section 122 is greater than the wall thickness of the first section 121, A1' is A12, and A2' is A22.

[0069] Table 1

[0070] As shown in Table 1, for the cells of Examples 1-1 to 1-3, the ratio A1' / A of the length of the thickened section 12 to the length of the heat-affected zone 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 body are welded, the edge of the heat-affected zone falls on the shell slope reinforcement section (i.e., the first transition section 13), which improves the strength of the heat-affected zone. For the cells of Examples 1-4 to 1-13, the ratio of the length of the thickened section 12 to the length of the heat-affected zone is in the range of 1 to 3. After the shell and the cover plate body are welded, the heat-affected zone falls on the last reinforcement section (i.e., the thickened section 12) at the shell opening, which improves the shell strength of the heat-affected zone. For the battery cell of Comparative Example 1, the ratio of the length of the thickened section 12 to the length of the heat-affected zone is 0.45, which is less than the lower limit of 0.75 defined in this application. After the shell and the cover plate body are welded, the edge of the heat-affected zone falls on the wall thickness of the shell body (i.e., the main body section 11), which reduces the shell strength and makes the shell prone to cracking in the heat-affected zone. For the battery cells of Comparative Examples 1-2, the ratio of the length of the thickened section 12 to the length of the heat-affected zone is 4.5, which is greater than the upper limit of 3 defined in this application. The thickened section is longer, which increases the manufacturing difficulty and is not recommended.

[0071] Table 2

[0072] 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 1.5. The results indicate that after the casing was welded, no molten beads fell into the cell upon disassembly; and after the casing withstood a pressure of 1.2 MPa, there was no leakage. However, for the cell of Comparative Example 2-1, the value of A1 / A3 is 1.15, which is less than 1.5 and not within the range defined in this application. After the casing was welded, molten beads fell into the cell upon disassembly, damaging the electrode assembly (5 out of 10 cells tested failed). For the cell of Comparative Example 2-2, the value of A3 is 0.21 mm. After the casing was welded, no molten beads fell into the cell upon disassembly; however, the weld depth was shallow, and after the casing withstood a pressure of 1.2 MPa, leakage occurred (4 out of 10 cells tested failed).

[0073] 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.

[0074] 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 shell-and-cap mating structure, characterized in that, include: A housing having an open end, the housing including multiple sidewalls, each sidewall including a main body segment, a thickened segment, and a first transition segment, the thickened segment being disposed on the side of the main body segment facing the open end along the X direction, the first transition segment connecting the thickened segment and the main body segment; in the YZ plane, the wall thickness of the thickened segment is greater than the wall thickness of the main body segment, and the wall thickness of the first transition segment gradually decreases along the direction from the thickened segment to the main body segment; A cover plate assembly is disposed at the open end of the housing. The cover plate assembly includes a cover plate body, which includes a body portion and an overlapping ring portion. The overlapping ring portion is connected around the outer peripheral side of the body portion in the YZ plane. At least a portion of the body portion extends into the inner cavity of the housing. The overlapping ring portion overlaps the end face of the open end of the housing and forms a splice seam between them. The overlapping ring portion is adapted to be welded to the housing along the splice seam and form a heat-affected zone on the housing. Along the X direction, the length of the thickened section is 0.75 to 3 times the length of the heat-affected zone.

2. The shell-and-cap mating structure according to claim 1, characterized in that, The first transition section forms a first inclined surface on the side facing the inner cavity of the shell, and rounded corner transition connections are provided between the first inclined surface and the main body section, and between the first inclined surface and the thickened section.

3. The shell-and-cap mating structure according to claim 2, characterized in that, The angle between the first inclined plane and the plane containing the inner wall of the main body segment is B, where 5°≤B≤45°.

4. The shell-and-cap mating structure according to claim 1, characterized in that, Both ends of the housing along the X direction are constructed as open ends.

5. The shell-and-cap mating structure according to claim 1, characterized in that, The side of the main body portion facing away from the housing along the X direction is flush with the side of the overlapping ring portion facing away from the housing along the X direction. And / or, in the YZ plane, the outer peripheral surface of the overlapping ring is flush with the outer wall surface of the housing.

6. The shell-and-cap mating structure according to any one of claims 1 to 5, characterized in that, The thickened section includes a first section, one end of which, along the X direction, is flush with the end face of the opening end of the shell. The length of the first section along the X direction is A1. The shell and the cover plate body are welded to form a weld mark. Along the X direction, the effective weld width of the weld mark on the shell is A3.

7. The shell-and-cap mating structure according to claim 6, characterized in that, Along the X direction, the length of the thickened section is equal to the length of the first section, and the length of the heat-affected zone is A; Wherein, 0.75≤A1 / A≤3, and A1≥1.5×A3; or, along the X direction, the total length of the thickened segment and the first transition segment is A2, where 0.75≤A1 / A≤1, and A2 / A≥1.4; And / or, in the YZ plane, the wall thickness of the first segment is C1, and the wall thickness of the main segment is C2, wherein 1.2≤C1 / C2≤2.

8. The shell-and-cap mating structure according to claim 6, characterized in that, The thickened section further includes a second section, which is located between the first section and the main body section along the X direction. In the YZ plane, the wall thickness of the second section is less than the wall thickness of the first section. Along the X direction, the distance between the opening end of the shell and the end of the second section away from the first section is A11. The length of the thickened section is equal to A11, and the length of the heat-affected zone is A. Wherein, 0.75≤A11 / A≤3, and A1≥1.5×A3; or, along the X direction, the total length of the thickened segment and the first transition segment is A21, 0.75≤A11 / A≤1, and A21 / A≥1.4; And / or, in the YZ plane, the wall thickness of the first section is C1, the wall thickness of the second section is C11, the wall thickness of the main body section is C2, 1.1≤C1 / C11≤2, 1.1≤C11 / C2≤2, and C1>C11>C2; And / or, the first section and the second section are connected by a second transition section, the second transition section having an inclined surface on the side facing the inner cavity of the housing.

9. The shell-and-cap mating structure according to claim 6, characterized in that, The thickened section further includes a second section, which is located between the first section and the main body section along the X direction. In the YZ plane, the wall thickness of the second section is greater than that of the first section. Along the X direction, the distance between the opening end of the shell and the end of the second section away from the first section is A12. The length of the thickened section is equal to A12, and the length of the heat-affected zone is A. Where 0.75≤A12 / A≤3, and A1≥1.5×A3; And / or, along the X direction, the mating length between the portion of the body extending into the inner cavity of the housing and the inner wall of the housing is D, where A1 ≥ 1.1 × D; And / or, in the YZ plane, the wall thickness of the first section is C1, the wall thickness of the second section is C11, the wall thickness of the main body section is C2, 1.1≤C11 / C1≤2, 1.1≤C1 / C2≤2, and C11>C1>C2; And / or, the first section and the second section are connected by a third transition section, the third transition section being inclined on the side facing the inner cavity of the housing.

10. A battery cell, characterized in that, include: The shell-cap mating structure as described in any one of claims 1 to 9; The pole group is located in the inner cavity of the shell in the shell-cover mating structure.

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