Battery case and battery cell

Abstract

The application discloses a battery shell and a battery monomer, and relates to the technical field of batteries. The battery shell comprises a shell and a cover plate. The shell has a containing cavity in communication with an opening. The shell comprises a side plate, and the containing cavity is surrounded by the side plate. The cover plate is arranged at the opening. A joint is formed between the cover plate and the side plate. A part of the side plate and a part of the cover plate are fused to form a welding mark structure to connect the side plate and the cover plate. The depth direction of the welding mark structure is parallel to the extension direction of the joint. In the depth direction of the welding mark structure, the lowest point of the welding mark structure is located on the cover plate. The battery shell can reduce the heat affected zone of the side plate of the shell, thereby improving the structural strength of the side plate of the shell, and further improving the welding strength and welding reliability of the battery shell.

Description

Technical Field

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

[0002] With the rapid development of the new energy industry, batteries, as energy storage and power sources, have been widely used in new energy vehicles, energy storage power stations, and other fields. The battery casing, as a crucial component of the battery, directly affects its safety and lifespan due to its structural stability and sealing performance. Among these factors, the welding quality between the casing and the cover plate is one of the key factors determining the overall performance of the battery casing. Laser welding technology, due to its high welding precision, is used in the battery production process to achieve sealing and structural fixation between the casing and the cover plate.

[0003] In existing technologies, welding processes primarily focus on the penetration depth and width of the weld mark, assuming that as long as these two parameters meet preset standards, welding quality can be guaranteed. However, in actual production, it has been found that even if the penetration depth and width meet the requirements, the welding strength of the battery casing can still fluctuate significantly, potentially leading to safety hazards such as battery leakage and short circuits. A heat-affected zone (HAZ) forms in the area corresponding to the weld mark. The material in the HAZ is affected by high temperatures, causing changes in its crystal structure and a decrease in strength after recrystallization. Since the structural strength of the side plates of the outer casing is lower than that of the cover plate, the HAZ has a significant impact on the structural strength of the side plates, thereby reducing the welding strength and reliability of the battery casing. Utility Model Content

[0004] This application provides a battery casing and a battery cell that can reduce the heat-affected zone of the side plate of the casing, thereby improving the structural strength of the side plate of the casing, and further improving the welding strength and welding reliability of the battery casing, so as to at least partially solve the above-mentioned technical problems.

[0005] To achieve the above objectives, according to a first aspect of this application, a battery casing is provided, comprising:

[0006] The housing has a receiving cavity communicating with an opening, the housing includes side plates, and the receiving cavity is surrounded by the side plates;

[0007] A cover plate is disposed at the opening, and a joint is formed between the cover plate and the side plate. A portion of the side plate and a portion of the cover plate are fused to form a weld structure to connect the side plate and the cover plate. The depth direction of the weld structure is parallel to the extension direction of the joint.

[0008] In the depth direction of the solder mark structure, the lowest point of the solder mark structure is located on the cover plate.

[0009] Optionally, the distance between the normal of the lowest point of the solder mark structure and the joint is an offset δ, and the offset δ satisfies: 0 < δ ≤ 1.0 mm.

[0010] Optionally, the offset δ satisfies: 0 < δ ≤ 0.5 mm.

[0011] Optionally, the side plate has opposing inner and outer walls and a top wall, and the joint is formed between the inner wall of the side plate and the cover plate.

[0012] Optionally, the outer surface of the solder mark structure covers the top wall of the side plate and extends to the outer wall of the side plate.

[0013] Optionally, the cover plate includes a body portion and a boss. The body portion has opposing top and bottom surfaces and side surfaces. The boss is disposed on the bottom surface of the body portion and extends toward the receiving cavity. The seam is formed between the bottom surface of the body portion and the top wall of the side plate.

[0014] Optionally, the outer surface of the solder mark structure covers the side of the body portion and extends to the top surface of the body portion.

[0015] Optionally, the body portion and the boss are separate structures; or, the body portion and the boss are integrally formed structures.

[0016] Optionally, the normal line of the lowest point of the solder pattern divides the solder pattern into a first part and a second part, the first part extending away from the outer shell and the second part extending toward the outer shell;

[0017] Wherein, the melt volume of the first part is less than or equal to the melt volume of the second part.

[0018] According to a second aspect of this application, a battery cell is provided, comprising an inner core and a battery housing as described in any of the preceding claims, wherein the inner core is mounted within a receiving cavity of the battery housing.

[0019] Beneficial Effects: Compared with the prior art, the battery casing and battery cell of the embodiments of this application include a battery casing and a cover plate, with the cover plate and the side plate of the casing connected by a welded structure. Since the structural strength of the side plate of the casing is less than that of the cover plate, the heat-affected zone has a greater impact on the structural strength of the side plate of the casing. In the depth direction of the welded structure, the lowest point of the welded structure is located on the cover plate, which can reduce the heat-affected zone of the side plate of the casing, thereby improving the structural strength of the side plate of the casing, and thus improving the welding strength and welding reliability of the battery casing.

[0020] Other features and advantages of this application will be described in detail in the following detailed description section. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] To gain a more complete understanding of this application and its beneficial effects, the following description will be provided in conjunction with the accompanying drawings, wherein the same reference numerals in the following description denote the same parts.

[0023] Figure 1 This is a schematic diagram of the structure of the battery casing with the lowest point located on the cover plate according to this application;

[0024] Figure 2 yes Figure 1 A magnified schematic diagram of the partial structure at point A in the middle;

[0025] Figure 3 This is a schematic diagram of the structure of the battery casing with the lowest point of the soldering structure located on the outer shell.

[0026] Figure 4 yes Figure 3 A magnified schematic diagram of the local structure at point B;

[0027] Figure 5 This is a schematic diagram of another type of battery casing soldering structure where the lowest point is located on the cover plate;

[0028] Figure 6 yes Figure 5 A magnified schematic diagram of the structure at point C.

[0029] Explanation of reference numerals in the attached figures:

[0030] 100. Battery casing; 1. Outer shell; 11. Side plate; 111. Inner wall; 112. Outer wall; 113. Top wall; 12. Receiving cavity; 13. Opening; 14. Bottom plate; 2. Cover plate; 21. Body part; 211. Top surface; 212. Bottom surface; 213. Side surface; 22. Boss; 3. Seam; 4. Welded structure; 41. Lowest point; 42. First part; 43. Second part; 200. Inner core; X1. Depth direction; X2. Extension direction. Detailed Implementation

[0031] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. In addition, it should be understood that the specific embodiments described herein are only for illustration and explanation of this application and are not intended to limit this application. In this application, unless otherwise stated, directional terms such as "up," "down," "left," and "right" generally refer to up, down, left, and right in the actual use or working state of the device, specifically the drawing directions in the accompanying drawings.

[0032] In this application, unless otherwise expressly specified and limited, the terms "connected," "linked," "stacked," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two elements or the interaction between two elements. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0033] This application provides a battery casing and a battery cell, which are described in detail below. It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of the embodiments of this application. Furthermore, the descriptions of each embodiment have their own emphasis; parts not described in detail in a certain embodiment can be referred to in the relevant descriptions of other embodiments.

[0034] Reference Figure 1 One embodiment of this application provides a battery cell, including a battery casing 100 and an inner core 200. The battery casing 100 has a receiving cavity 12, and the inner core 200 is installed within the receiving cavity 12 of the battery casing 100. The battery cell can have a square structure, a cylindrical structure, etc. Correspondingly, the battery casing 100 and the inner core 200 can have a square structure, a cylindrical structure, etc. In this application, a cylindrical structure of the battery cell is used as an example for description. The battery casing 100 may include an outer shell 1 and a cover plate 2. The cover plate 2 and the outer shell 1 are connected by welding, such as laser welding or resistance welding. In this application, the connection between the cover plate 2 and the outer shell 1 by laser welding is used as an example for description.

[0035] The outer shell 1 and cover plate 2 of the battery casing 100 can be made of metal, such as steel, aluminum, or aluminum alloy. The structural design of the battery casing 100 needs to be customized according to the battery type and installation space. Metal has good processing performance and can be processed into complex shapes through various processes such as stamping, stretching, bending, and welding, resulting in high production efficiency and ensuring dimensional accuracy. Metal has high tensile strength, yield strength, and hardness, providing a robust protective casing for the battery cells, effectively resisting external impacts, compression, and vibration, reducing the risk of deformation or breakage of the battery casing 100, preventing damage to the internal structure of the battery cells, and reducing the risk of short circuits or leakage. The metal battery casing 100 can withstand the pressure generated by the internal gas during the charging and discharging of the battery cells, preventing the battery casing 100 from expanding, deforming, or breaking. The metal battery casing 100 can quickly conduct the heat generated by the charging and discharging of the battery cells, and can also form an efficient heat dissipation path in conjunction with a heat dissipation system, helping to achieve a more uniform temperature distribution in all areas of the battery casing 100, avoiding localized overheating, and extending the service life of the battery cells. Metals have high melting points and good corrosion resistance, and can maintain structural stability even in extreme environments.

[0036] Specifically, refer to Figure 1 The outer shell 1 has a receiving cavity 12 communicating with the opening 13, that is, the outer shell 1 has an opening 13 and a receiving cavity 12, and the opening 13 communicates with the receiving cavity 12. The outer shell 1 may include a side plate 11, and the receiving cavity 12 may be formed by the side plate 11, and an opening 13 is formed at at least one of the two ends of the outer shell 1. In this embodiment, one end of the outer shell 1 forms an opening 13, and the other end of the outer shell 1 has a bottom plate 14, which together with the side plate 11 forms the receiving cavity 12. The side plate 11 and the bottom plate 14 may be separate structures and connected together by welding or other methods, such as laser welding. The side plate 11 and the bottom plate 14 may also be integrally formed structures. As a preferred embodiment, the side plate 11 and the bottom plate 14 are integrally formed. This not only improves the connection strength and sealing between the side plate 11 and the bottom plate 14, but also eliminates the need for welding or other methods to connect the side plate 11 and the bottom plate 14, reducing the production process of the outer shell 1, thereby reducing the production cost and improving the production efficiency of the outer shell 1. At the same time, it can also improve the dimensional accuracy of the outer shell 1, reduce assembly errors, and thus improve the fitting accuracy between the outer shell 1 and the cover plate 2.

[0037] Reference Figure 1A cover plate 2 is positioned at the opening 13, and its shape matches the shape of the opening 13 of the outer casing 1 to facilitate welding between the cover plate 2 and the outer casing 1, ensuring the strength and sealing of the weld. A seam 3 is formed between the cover plate 2 and the side plate 11, which is, for example, a fitting gap between the cover plate 2 and the side plate 11. The size of the seam 3 can be zero or greater than zero. A portion of the side plate 11 and a portion of the cover plate 2 are fused to form a weldment structure 4 to connect the side plate 11 and the cover plate 2. The weldment structure 4 also forms a sealed connection between the cover plate 2 and the side plate 11. The weldment structure 4 can be formed by laser welding. Laser welding melts a portion of the side plate 11 and a portion of the cover plate 2 on both sides of the seam 3 to form a molten pool. After the molten pool cools, the weldment structure 4 is formed. After laser welding, the weldment structure 4 can fill at least a portion of the seam 3 to form a sealed connection between the cover plate 2 and the side plate 11. The weld mark structure 4 extends from the surface of the battery casing 100 into its interior, with the depth direction X1 of the weld mark structure 4 parallel to the extension direction X2 of the joint 3. The depth direction X1 of the weld mark structure 4 refers to the direction perpendicular to the welding surface of the battery casing 100 and pointing towards the interior of the battery casing 100. The welding surface of the battery casing 100 includes portions of the outer shell 1 and the cover plate 2 located on both sides of the joint 3. During laser welding, a heat-affected zone (HAZ) is formed in the area corresponding to the weld mark structure 4, and the HAZ is adjacent to the weld mark structure 4. The HAZ refers to the area of ​​the base material that has been heated during welding but has not reached its melting point; its microstructure and mechanical properties change due to the high temperature. The material in the HAZ is affected by the high temperature, causing changes in its crystal structure, and its strength decreases after recrystallization.

[0038] In this application, the lowest point 41 of the solder joint structure 4 is located on the cover plate 2 along the depth direction X1. The distance between the normal of the lowest point 41 of the solder joint structure 4 and the joint 3 is an offset δ, which can be adjusted by adjusting the laser trajectory. The normal of the lowest point 41 of the solder joint structure 4 is parallel to the depth direction X1 of the solder joint structure 4, and the depth direction X1 of the solder joint structure 4 is parallel to the extension direction X2 of the joint 3. Therefore, the normal of the lowest point 41 of the solder joint structure 4, the depth direction X1 of the solder joint structure 4, and the extension direction X2 of the joint 3 are all parallel. (Refer to...) Figure 2 When the lowest point 41 of the solder mark structure 4 is located at the cover plate 2, the offset δ is a positive offset, and at this time δ>0. (Refer to...) Figure 3 and Figure 4 When the lowest point 41 of the solder mark structure 4 is located on the side plate 11, the offset δ is a negative offset, and at this time δ<0.

[0039] As an example, when the width and depth of the solder mark structure 4 remain unchanged, the lowest point 41 of the solder mark structure 4 located on the cover plate 2 can reduce the area formed by the solder mark structure 4 on the side plate 11 of the outer casing 1 compared to the solder mark structure 4 being located on the side plate 11. This reduces the heat-affected zone formed on the side plate 11, lowers the risk of the structural strength of the side plate 11 decreasing due to recrystallization, and thus improves the structural strength of the side plate 11. This makes the structural strength of the welded side plate 11 close to the structural strength of the base material, thereby improving the structural stability and reliability of the battery casing 100.

[0040] The shape of the solder mark structure 4 can be adjusted by changing the trajectory of the laser. The overall structure of the solder mark structure 4 can be roughly conical or approximately conical, and the cross-section of the solder mark structure 4 can be roughly triangular. The outer edge of the solder mark structure 4 can be regular or irregular in shape due to the welding process or the material of the battery casing 100. In this embodiment, for better illustration, the outer edge of the solder mark structure 4 will be described as having a regular shape.

[0041] As an example, the side plate 11 of the outer casing 1 and the cover plate 2 can be made of the same material. The thickness of the side plate 11 is thinner than that of the cover plate 2, so the structural strength of the side plate 11 is less than that of the cover plate 2.

[0042] In this application, since the structural strength of the side plate 11 of the outer casing 1 is less than that of the cover plate 2, the heat-affected zone has a greater impact on the structural strength of the side plate 11 of the outer casing 1. In the depth direction X1 of the solder pattern 4, the lowest point 41 of the solder pattern 4 is located on the cover plate 2. In this way, while ensuring the structural strength of the cover plate 2, the heat-affected zone of the side plate 11 of the outer casing 1 can be reduced, thereby improving the structural strength of the side plate 11 of the outer casing 1. This avoids the overall structural strength of the battery casing 100 being affected by the reduction in the structural strength of the outer casing 1, thereby improving the welding strength and welding reliability of the battery casing 100. This can prevent safety hazards such as battery cell leakage and short circuit, and improve the overall safety of the battery cell.

[0043] In one specific implementation, refer to Figure 2 When the lowest point 41 of the weldment structure 4 is located on the cover plate 2, the distance between the normal of the lowest point 41 of the weldment structure 4 and the joint 3 is the offset δ. The offset δ satisfies: 0 < δ ≤ 1.0 mm. For example, when the lowest point 41 of the weldment structure 4 is located on the cover plate 2, the offset δ can be any value among 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, etc., or any value between any two. As a preferred embodiment, the offset δ satisfies: 0 < δ ≤ 0.5 mm.

[0044] When the lowest point 41 of the weldment structure 4 is located on the cover plate 2, as the lowest point 41 of the weldment structure 4 shifts away from the joint 3, the heat-affected zone formed on the side plate 11 gradually decreases, thereby improving the structural strength of the side plate 11. However, as the lowest point 41 of the weldment structure 4 shifts away from the joint 3, the laser energy received on the side plate 11 also decreases, resulting in an excessively small volume of the weldment structure 4 on the side plate 11, i.e., a smaller molten volume on the side plate 11, which in turn reduces the connection strength between the side plate 11 and the cover plate 2. Therefore, by setting the lowest point 41 of the weldment structure 4 on the cover plate 2 and limiting the offset δ within a reasonable range, the heat-affected zone on the side plate 11 is effectively reduced, avoiding the problem of material strength decreasing due to recrystallization, making the welding strength close to the strength of the base material, and significantly improving the structural stability and reliability of the battery casing 100. At the same time, it ensures the full melting of the side plate 11, guaranteeing the weld appearance and sealing performance.

[0045] In one specific implementation, refer to Figure 1 and Figure 2 The side plate 11 has opposing inner walls 111 and outer walls 112, as well as a top wall 113. The inner wall 111 of the side plate 11 faces the receiving cavity 12, and the outer wall 112 of the side plate 11 faces away from the receiving cavity 12. A joint 3 is formed between the inner wall 111 of the side plate 11 and the cover plate 2. (Refer to...) Figure 5 and Figure 6 The outer diameter of cover plate 2 can be larger than the diameter of opening 13 in outer shell 1, see reference. Figure 1 and Figure 2 The outer diameter of the cover plate 2 can also be less than or equal to the diameter of the opening 13 of the outer shell 1.

[0046] Reference Figure 2 The extension direction X2 of the joint 3 is perpendicular to the top wall 113, and the depth direction X1 of the weldment structure 4 is perpendicular to the top wall 113.

[0047] Reference Figure 1 and Figure 2When the outer diameter of the cover plate 2 is less than or equal to the aperture of the opening 13 of the outer casing 1, at least a portion of the cover plate 2 is located within the receiving cavity 12, and the outer peripheral side of the cover plate 2 is disposed opposite to the inner wall 111 of the side plate 11. The cover plate 2 may include a body portion 21, that is, the outer diameter of the body portion 21 is less than or equal to the aperture of the opening 13 of the outer casing 1, at least a portion of the body portion 21 is located within the receiving cavity 12, and the outer peripheral side of the body portion 21 is disposed opposite to the inner wall 111 of the side plate 11. Specifically, when the outer diameter of the main body 21 is less than or equal to the aperture of the opening 13 of the outer casing 1, the main body 21 has a top surface 211, a bottom surface 212, and a side surface 213. The bottom surface 212 of the main body 21 faces the receiving cavity 12, the top surface 211 of the main body 21 faces away from the receiving cavity 12, and the side surface 213 of the main body 21 faces the inner wall 111 of the side plate 11. A seam 3 is formed between the side surface 213 of the main body 21 and the inner wall 111 of the side plate 11. At this time, laser welding can be performed from the top wall 113 of the side plate 11 and the top surface 211 of the main body 21 to weld the side plate 11 and the cover plate 2 together.

[0048] As a preferred embodiment, when a joint 3 is formed between the side surface 213 of the body portion 21 and the inner wall 111 of the side plate 11, and laser welding is performed from the top wall 113 of the side plate 11 and the top surface 211 of the body portion 21, the outer surface of the weld mark structure 4 covers a portion of the top surface 211 of the body portion 21, and simultaneously covers the top wall 113 of the side plate 11 and extends to the outer wall 112 of the side plate 11. This not only ensures sufficient melting of the side plate 11, thereby ensuring the stability of the connection between the side plate 11 and the cover plate 2, but also improves the sealing performance between the side plate 11 and the cover plate 2. Furthermore, the welding status of the side plate 11 can be visually inspected, thus achieving stability and consistency in welding quality and reducing the product defect rate.

[0049] Reference Figure 5 and Figure 6When the outer diameter of the cover plate 2 is larger than the aperture of the opening 13 of the outer shell 1, that is, when the outer diameter of the body portion 21 is larger than the aperture of the opening 13 of the outer shell 1, the cover plate 2 may include a boss 22, or the cover plate 2 may not include a boss 22. In this embodiment, when the outer diameter of the cover plate 2 is larger than the aperture of the opening 13 of the outer shell 1, the cover plate 2 includes a boss 22. The outer diameter of the boss 22 is smaller than or equal to the aperture of the opening 13 of the outer shell 1. The boss 22 is disposed on the bottom surface 212 of the body portion 21 and extends toward the receiving cavity 12. A seam 3 is formed between the bottom surface 212 of the body portion 21 and the top wall 113 of the side plate 11. At this time, laser welding can be performed from the outer wall 112 of the side plate 11 and the side surface 213 of the body portion 21 to weld the side plate 11 and the cover plate 2 together. The boss 22 not only improves the overall structural strength of the cover plate 2 and reduces the risk of deformation of the cover plate 2, but also has a guiding function. During the assembly process, the boss 2 can guide the cover plate 2 to fall into the preset position quickly, avoid the cover plate 2 tilting or getting stuck, and improve the assembly efficiency.

[0050] Reference Figure 6 The extension direction X2 of the joint 3 is perpendicular to the outer wall 112, and the depth direction X1 of the weldment structure 4 is perpendicular to the outer wall 112.

[0051] As a preferred embodiment, when a joint 3 is formed between the bottom surface 212 of the body portion 21 and the top wall 113 of the side plate 11, and laser welding is performed from the outer wall 112 of the side plate 11 and the side surface 213 of the body portion 21, the outer surface of the weld mark structure 4 covers a portion of the outer wall 112 of the side plate 11, and simultaneously covers the side surface 213 of the body portion 21 and extends to the top surface 211 of the body portion 21. This not only ensures sufficient melting of the body portion 21, thereby ensuring the stability of the connection between the side plate 11 and the cover plate 2, but also improves the sealing performance between the side plate 11 and the cover plate 2. Furthermore, the welding status of the body portion 21 can be visually inspected, thus achieving stability and consistency in welding quality and reducing the product defect rate.

[0052] The body portion 21 and the boss 22 can be separate structures, or they can be integrally formed. In this embodiment, the body portion 21 and the boss 22 are integrally formed. This achieves a seamless connection between the body portion 21 and the boss 22, fundamentally avoiding the reduction in structural strength of the cover plate 2 due to assembly process defects in a separate structure. The integrally formed structure can significantly shorten the production process and reduce process complexity. At the same time, the integrally formed structure allows for precise control of the dimensions of the cover plate 2 through the mold, resulting in high consistency of the cover plate 2, reducing quality fluctuations caused by assembly errors, and lowering the scrap rate.

[0053] A sealing ring (not shown) can be provided between the boss 22 and the inner wall 111 of the side plate 11. The sealing ring is, for example, an O-ring or an elastic gasket. The sealing ring can fill the assembly gap between the boss 22 and the side plate 11, forming an elastic sealing layer, blocking the electrolyte leakage path, thereby improving the sealing effect between the side plate 11 and the cover plate 2. The sealing ring can also fix the relative position between the side plate 11 and the cover plate 2, ensuring accurate alignment during laser welding and reducing the fluctuation of the offset δ. The sealing ring can also prevent welding spatter or oxide residue from entering the interior of the battery casing 100. At the same time, the battery cells are subjected to high-frequency vibration during vehicle operation, and the elasticity of the sealing ring can absorb some of the energy, preventing fatigue cracking of the weld joint.

[0054] Reference Figure 2 and Figure 6 The normal to the lowest point 41 of the solder joint structure 4 divides the solder joint structure 4 into a first part 42 and a second part 43. The first part 42 extends away from the outer shell 1, and the second part 43 extends towards the outer shell 1. In the depth direction X1 of the solder joint structure 4, when the lowest point 41 of the solder joint structure 4 is located on the cover plate 2, the first part 42 is located on the cover plate 2, and the second part 43 is located on both the side plate 11 and the cover plate 2. The molten volume of the first part 42 can be greater than the molten volume of the second part 43, or the molten volume of the first part 42 can be less than or equal to the molten volume of the second part 43. In this embodiment, the molten volume of the first part 42 is less than or equal to the molten volume of the second part 43. In this way, while reducing the heat-affected zone of the side plate 11 of the outer shell 1, it is also possible to ensure that the side plate 11 has a sufficient molten volume, thereby ensuring the connection strength and sealing performance between the side plate 11 and the cover plate 2.

[0055] The embodiments and comparative examples of this application will be described in detail below. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of protection of this application.

[0056] Unless otherwise specified, the outer shell 1 and cover plate 2 in the comparative examples and embodiments have the same structure and material, and the width and depth of the solder joint structure 4 are also the same. The outer diameter of the cover plate 2 is smaller than the aperture of the opening 13 of the outer shell 1. The outer periphery of the cover plate 2 is positioned opposite to the inner wall 111 of the side plate 11. Laser welding is performed from the top wall 113 of the side plate 11 and the top surface 211 of the body 21. The offset δ is adjusted by adjusting the trajectory of the laser.

[0057] The difference between the battery casing 100 in the comparative example and the embodiment is that the offset δ ≤ 0 in the comparative example and the offset δ > 0 in the embodiment.

[0058] Comparative tests of offset δ with the welding strength and welding appearance between side plate 11 and cover plate 2.

[0059] The test conditions are as follows: Tensile tests are performed on welded samples with different offsets δ using a universal testing machine. The weld appearance is visually inspected. When the outer surface of the weld mark structure 4 covers the top wall 113 of the side plate 11 and extends to the outer wall 112 of the side plate 11, the weld appearance is qualified; otherwise, the weld appearance is unqualified.

[0060] Test results: See Table 1.

[0061] Table 1

[0062] Comparative Example 1 0 106 qualified Comparative Example 2 -0.12 87 qualified Comparative Example 3 -0.21 79 qualified Comparative Example 4 -0.32 64 qualified Comparative Example 5 -0.39 47 qualified Example 1 0.11 112 qualified Example 2 0.19 115 qualified Example 3 0.31 120 qualified Example 4 0.42 118 qualified Example 5 0.48 116 qualified Example 6 0.59 121 Unqualified

[0063] As shown in Table 1, when the offset δ is negative (the lowest point 41 of the solder mark 4 is located on the side plate 11), the welding strength between the side plate 11 and the cover plate 2 decreases significantly with increasing absolute value of the offset δ. When the offset δ is positive (the lowest point 41 of the solder mark 4 is located on the cover plate 2), the welding strength between the side plate 11 and the cover plate 2 increases significantly with increasing absolute value of the offset δ. When the offset δ is positive and exceeds 0.5 mm, although the welding strength between the side plate 11 and the cover plate 2 is still relatively high, the appearance quality does not meet the requirements. Therefore, when the lowest point 41 of the solder mark 4 is located on the cover plate 2, the welding strength and welding reliability of the battery casing 100 can be improved.

[0064] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more features. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0065] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0066] The embodiments, implementation methods, and related technical features of this application can be combined and substituted for each other without conflict.

[0067] The above are merely preferred embodiments of this application and are not intended to limit this application in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of this application without departing from the technical solution of this application shall still fall within the scope of the technical solution of this application.

Claims

1. A battery casing, characterized in that, include: The outer shell (1) has a receiving cavity (12) communicating with an opening (13), the outer shell (1) includes a side plate (11), and the receiving cavity (12) is formed by the side plate (11); A cover plate (2) is provided at the opening (13). A joint (3) is formed between the cover plate (2) and the side plate (11). A portion of the side plate (11) and a portion of the cover plate (2) are fused to form a weld structure (4) to connect the side plate (11) and the cover plate (2). The depth direction (X1) of the weld structure (4) is parallel to the extension direction (X2) of the joint (3). In the depth direction (X1) of the soldering structure (4), the lowest point (41) of the soldering structure (4) is located on the cover plate (2).

2. The battery casing according to claim 1, characterized in that, The distance between the normal of the lowest point (41) of the soldering structure (4) and the joint (3) is the offset δ, and the offset δ satisfies: 0<δ≤1.0mm.

3. The battery casing according to claim 2, characterized in that, The offset δ satisfies: 0 < δ ≤ 0.5 mm.

4. The battery casing according to claim 1, characterized in that, The side plate (11) has opposing inner walls (111) and outer walls (112) and a top wall (113), and the joint (3) is formed between the inner wall (111) of the side plate (11) and the cover plate (2).

5. The battery casing according to claim 4, characterized in that, The outer surface of the solder mark structure (4) covers the top wall (113) of the side plate (11) and extends to the outer wall (112) of the side plate (11).

6. The battery casing according to claim 1, characterized in that, The cover plate (2) includes a body part (21) and a boss (22). The body part (21) has a top surface (211) and a bottom surface (212) and a side surface (213) facing each other. The boss (22) is disposed on the bottom surface (212) of the body part (21) and extends toward the receiving cavity (12). The seam (3) is formed between the bottom surface (212) of the body part (21) and the top wall (113) of the side plate (11).

7. The battery casing according to claim 6, characterized in that, The outer surface of the solder mark structure (4) covers the side surface (213) of the body part (21) and extends to the top surface (211) of the body part (21).

8. The battery casing according to claim 6, characterized in that, The body part (21) and the boss (22) are separate structures; or, the body part (21) and the boss (22) are integrally formed structures.

9. The battery casing according to claim 1, characterized in that, The normal of the lowest point (41) of the soldering structure (4) divides the soldering structure (4) into a first part (42) and a second part (43). The first part (42) extends away from the outer shell (1), and the second part (43) extends toward the outer shell (1). Wherein, the melt volume of the first part (42) is less than or equal to the melt volume of the second part (43).

10. A single battery cell, characterized in that, It includes an inner core (200) and a battery housing (100) as described in any one of claims 1 to 9, wherein the inner core (200) is installed in a receiving cavity (12) of the battery housing (100).

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