Battery cell

Abstract

The utility model discloses a single battery and relates to the technical field of batteries, the single battery comprises a shell and a cover plate assembly, the end part of the shell is provided with an opening, the outer side wall of the shell at the opening is shrunk inwards, the cover plate assembly is welded at the opening of the shell, and a welding bulge is formed between the cover plate assembly and the shell, the thickness of the welding protrusion is smaller than or equal to the maximum distance that the outer side wall, at the opening, of the shell shrinks inwards. In the technical scheme provided by the embodiment of the invention, the welding bulge formed by welding the cover plate assembly and the shell is arranged at the sunken position of the shell, and the welding bulge does not exceed the outer surface of the shell, so that the situation that the battery cannot be flatly placed due to the convex position of the welding bulge when the battery is laterally placed is avoided; and the outer coating film at the welding bulges is abraded due to overlarge local stress, so that the problem that the outer coating film is seriously abraded due to large contact local stress of the welding bulges between the adjacent battery monomers when a plurality of battery monomers form a module is solved.

Description

battery cell Technical Field

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

[0002] The battery casing is a crucial structural component of a single battery cell. Its primary function is to protect the internal cells from external environmental influences such as dust, moisture, and mechanical impact, while also providing structural support and electrical insulation. Casings are typically made of metal (such as aluminum or steel) or plastic, with the specific choice depending on the battery type, application, and performance requirements. Furthermore, the shape and size of the casing also affect battery installation and integration; common structures include cylindrical, prismatic, and pouch cells.

[0003] For square batteries, the outer casing typically consists of two parts: a cover assembly and a housing. The cover assembly and the housing are welded together using laser welding. Laser welding uses a high-energy-density laser beam as a heat source to generate high-energy heat in a short time, melting the material and forming a strong weld. The weld protrudes from the surface of the housing. When the battery is laid flat, the local protrusion of the weld can cause stress concentration at that location, making it easy to wear through the outer film of the battery. Summary of the Invention

[0004] Several embodiments in this application propose a battery cell designed to provide a battery cell whose insulating film is not easily damaged.

[0005] One embodiment of this application proposes a battery cell comprising:

[0006] A housing, wherein the ends of the housing have openings, and the outer sidewalls of the housing at the openings taper inwards; and

[0007] A cover plate assembly, which is welded to the opening of the housing and forms a weld protrusion between the cover plate assembly and the housing;

[0008] Wherein, the thickness of the welded protrusion is less than or equal to the maximum distance by which the outer wall of the shell contracts inward at the opening.

[0009] In one embodiment, the housing includes a first straight section, a bent section, and a second straight section connected in sequence, the opening being located in the second straight section and at least a portion of the structure of the second straight section being welded to the cover plate assembly.

[0010] In one embodiment, the first straight segment and the second straight segment are offset in a first direction, which is perpendicular to the sidewall of the housing.

[0011] In one embodiment, the distance between the side of the first straight segment facing away from the receiving cavity and the side of the second straight segment facing away from the receiving cavity along the first direction is greater than or equal to 0.2 mm and less than or equal to 0.8 mm.

[0012] In one embodiment, the length of the second straight segment along the direction perpendicular to the cover plate assembly is greater than or equal to 3 mm and less than or equal to 5 mm.

[0013] In one embodiment, the housing includes four side plates connected end to end, each side plate having an inner wall facing the receiving cavity and an outer wall facing away from the receiving cavity;

[0014] The outer side wall includes a first outer side wall and a second outer side wall, the second outer side wall being disposed at one end near the cover plate assembly, and the distance between the first outer side wall and the inner side wall being greater than the distance between the second outer side wall and the inner side wall.

[0015] In one embodiment, the distance between the two first outer sidewalls of the two oppositely arranged side plates is greater than the distance between the two second outer sidewalls.

[0016] In one embodiment, the outer sidewall further includes a third outer sidewall connecting the first outer sidewall and the second outer sidewall;

[0017] The third outer sidewall is configured as an arc surface, a straight surface, or an inclined surface.

[0018] In one embodiment, the housing has a contraction portion at one end near the cover assembly, and the contraction portion gradually contracts toward one end of the cover assembly.

[0019] In one embodiment, the cover plate assembly includes a cover plate assembly body and a pole post disposed on the cover plate assembly body;

[0020] The battery cell also includes an insulating film, which covers the casing.

[0021] In several embodiments provided in this application, the open cross-sectional area of ​​the housing is reduced by contracting inward at the end of the housing near the cover assembly. This prevents the welding protrusion from protruding from the outer surface of the housing during welding. Specifically, the cover assembly is welded to the open part of the housing, and the housing and cover assembly together form a receiving cavity for the inner core. The contraction at the end of the housing near the cover assembly is structurally manifested as a recess inward into the receiving cavity, thereby ensuring that the welding protrusion is located at the recessed position of the housing, that is, at the maximum distance of the inward contraction of the housing. This ensures that the welding protrusion does not exceed the outer surface of the housing, thus avoiding the problem that the battery cannot be laid flat when placed on its side due to the protruding position of the welding protrusion, and the outer film at the welding protrusion position is subjected to excessive local stress and wear. It also avoids the problem that when multiple battery cells are assembled into a module, the contact position of the welding protrusion between adjacent battery cells is subjected to large local stress, resulting in severe wear of the outer film. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments or prior art of this application, the drawings used in the description of the embodiments or prior art 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 the structures shown in these drawings without creative effort.

[0023] Figure 1 is a schematic diagram of the structure of a conventional battery cell;

[0024] Figure 2 is a magnified view of part A in Figure 1;

[0025] Figure 3 is a cross-sectional structural diagram of an embodiment of the battery cell provided in this application;

[0026] Figure 4 is a partial enlarged view of the first embodiment at point B in Figure 3;

[0027] Figure 5 is a partial enlarged view of the second embodiment at point B in Figure 3;

[0028] Figure 6 is a partial enlarged view of the third embodiment at point B in Figure 3;

[0029] Figure 7 is a partial enlarged view of the fourth embodiment at point B in Figure 3;

[0030] Figure 8 is a structural schematic diagram of three embodiments of the third outer sidewall in Figure 5;

[0031] Figure 9 is a schematic diagram of the structure in Figure 4;

[0032] Figure 10 is a schematic diagram of the cover plate assembly;

[0033] Figure 11 is a schematic diagram of the exploded structure of the battery cell provided in this application.

[0034] Explanation of icon numbers:

[0035] 100. Battery cell; 1. Cover plate assembly; 11. Cover plate assembly body; 12. Terminal post; 121. Positive terminal post; 122. Negative terminal post; 1a. Step opening; 2. Shell; 21. First straight section; 22. Second straight section; 23. Third straight section; 24. Side plate; 241. Inner side wall; 242. Outer side wall; 242a. First outer side wall; 242b. Second outer side wall; 242c. Third outer side wall; 25. Contraction section; 251. First end; 252. Second end; 25a. Welding surface; 3. Welding protrusion; X. First direction; 4. Inner core; 5. Insulating film. Detailed Implementation

[0036] The technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings of several embodiments. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0037] It should be noted that if directional indications (such as up, down, left, right, front, back, etc.) are involved in multiple embodiments of this application, the directional indications are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0038] Furthermore, if multiple embodiments of this application involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text implies three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed in this application.

[0039] For square batteries, their outer casing typically consists of two parts: a cover assembly 1 and a housing 2. The cover assembly 1 and the housing 2 are welded together using laser welding. Laser welding uses a high-energy-density laser beam as a heat source to generate a high-energy heat source in a short time, causing the material to melt and form a strong weld protrusion 3. The weld protrusion 3 protrudes from the surface of the outer casing. When the battery is laid flat, the local protrusion of the weld protrusion 3 will cause the stress to be concentrated at that location, which can easily wear through the outer film of the battery.

[0040] To address the aforementioned problems, this application proposes a battery cell 100 to solve the technical issues mentioned above.

[0041] Please refer to Figures 1 to 11. In one embodiment of this application, the battery cell 100 includes a cover assembly 1 and a housing 2. The end of the housing 2 has an opening. The outer wall of the housing 2 at the opening is recessed inward. The cover assembly is welded to the opening of the housing 2, and a welding protrusion 3 is formed between the cover assembly and the housing 2. The thickness of the welding protrusion 3 is less than or equal to the maximum distance of the outer wall of the housing 2 at the opening that is recessed inward.

[0042] Understandably, the shell 2 contracts towards the receiving cavity at the opening. Specifically, please refer to Figure 4. The partially inwardly contracted outer wall of the shell 2 can be achieved by thinning the side wall of the shell 2, or by pressing the shell 2 inward near the opening through methods such as stamping or bending. By forming a contraction at the opening of the shell 2, it can be ensured that the welding protrusion 3 is welded through the contracted outer wall when welding the shell 2 to the cover assembly, thereby ensuring that the welding protrusion 3 does not protrude beyond the uncontracted outer wall of the shell 2.

[0043] It should be noted that the battery cell 100 can also be assembled and welded from two cover plate assemblies 1 and a middle section. The two cover plate assemblies 1 are a top cover plate assembly 1 and a bottom cover plate assembly 1. The middle section is composed of four side plates 24 connected end to end, with each adjacent side plate 24 perpendicular to each other. The middle section presents a flat, U-shaped structure with openings at both ends. The top cover plate assembly 1 and the bottom cover plate assembly 1 are respectively placed over the two openings, and the top cover plate assembly 1 and the bottom cover plate assembly 1 are welded along the edges of the openings. The laser welding process uses a high-temperature laser to melt the surface material of the shell 2 and the cover plate assembly 1, melting part of the structure of the cover plate assembly 1 and the shell 2 into one piece, and forming a strong weld protrusion 3 after cooling. To ensure that the weld protrusion 3 does not protrude from the outer surface of the shell 2, in this embodiment, the shell 2 adopts a tapering design at both ends near the top cover plate assembly 1 and the bottom cover plate assembly 1, respectively, so that the end part of the shell 2 shrinks towards the receiving cavity.

[0044] The aforementioned welding protrusion 3 is an outward protrusion formed by the melting of material at high temperature during the welding of the housing 2 and the cover plate assembly. It is used to connect the housing 2 and the cover plate assembly. Therefore, the welding protrusion 3 is not a completely uniform outward protrusion ring structure. There may be a high point and a low point of the welding protrusion 3, which is the distance from the end of the welding protrusion 3 away from the housing 2 to the outer wall of the housing 2. The thickness of the welding protrusion 3 refers to the maximum distance from the end of the welding protrusion 3 away from the housing 2 to the outer wall of the housing 2. This ensures that the thickness of the non-uniform area of ​​the welding protrusion 3 does not exceed the distance from the non-constricted area to the constricted area of ​​the housing 2, thereby avoiding local stress on the welding protrusion 3 and causing wear.

[0045] Furthermore, the thickness of the weld protrusion 3 should be less than or equal to the maximum inward contraction distance of the outer wall of the shell 2 at the opening. The maximum inward contraction distance of the outer wall of the shell 2 at the opening refers to the distance from the lowest point of the contraction portion 25 of the shell 2 to the outer wall of the shell 2 in the non-contraction area. Taking cross-sectional contraction as an example, the maximum inward contraction distance refers to the distance between the first outer wall 242a and the second outer wall 242b. Specifically, please refer to Figures 5 and 9. b in the figures is the aforementioned maximum distance. For the gradually contracting shell 2 structure, since the contraction portion 25 is inclined as a whole, the maximum distance is the distance between the lowest point of the contraction portion 25, the end near the cover plate assembly, and the non-contraction area.

[0046] It is understandable that, in terms of the cross-sectional shape of the battery cell 100, stepped surfaces are formed at both ends of the casing 2 near the opening, thereby compensating for the thickness of the welding protrusion 3 and preventing the welding protrusion 3 from protruding beyond the outer surface of the casing 2. This prevents the outer casing of the battery cell 100 from being easily worn through due to the stress concentration caused by the local protrusion of the welding protrusion 3 after the outer film is applied. The contraction portion 25 has a welding surface 25a near the opening and facing away from the receiving cavity. The welding surface 25a is the outer wall surface of the side plate 24 of the welding portion 25 away from the casing 2. Specifically, please refer to Figure 4. Part of the structure of the welding protrusion 3 overlaps the edge of the cover plate assembly body 11, and another part of the structure overlaps the welding surface 25a of the welding portion 25, thereby realizing the connection between the casing 2 and the cover plate assembly 1.

[0047] In the technical solution of this application, the end of the housing 2 near the cover plate assembly 1 adopts an inwardly tapering design. This can be a sectional tapering or a gradual, uniform tapering at a certain slope; this application does not limit this. A sectional tapering means that the housing 2 is bent inward at a certain position near the end to form a layered cross-section, similar to the connecting vertical surface between two consecutive steps. A gradual, uniform tapering involves tilting the housing 2 near the end, close to the receiving cavity. The tilted surface has a first position connecting to the main body of the housing 2 and a second position abutting against the cover plate assembly 1. The first and second positions are a certain distance apart along a direction perpendicular to the side wall of the housing 2. Since the cover plate assembly 1 is welded to the second position of the housing 2 during welding, the welding protrusion 3 will not protrude beyond the outer wall of the housing 2, i.e., it will be flush with the first position. The choice between a sectional tapering or a gradual tapering design should be made adaptively based on the actual needs of the product and the installation location. Specifically, the section shrinkage is easier to process. By pressing the end area of ​​the housing 2 before welding the housing 2 and the cover plate assembly 1 with a stamping equipment, the shrinkage can be achieved. The overall consistency of the housing 2 with the tapered design is better and the visual effect is more beautiful. The tapered design avoids the appearance of the stepped surface, thereby avoiding the step surface from directly hitting the battery pack shell or adjacent battery cells 100 and causing damage when the battery cells 100 are assembled into modules.

[0048] In several embodiments provided in this application, the opening cross-sectional area of ​​the housing 2 is reduced by contracting inward at the end of the housing 2 near the cover plate assembly 1. This prevents the protruding welding protrusion 3 from protruding beyond the outer surface of the housing 2 when the housing 2 is welded to the cover plate assembly 1. Specifically, the cover plate assembly 1 is welded to the opening of the housing 2, and the housing 2 and the cover plate assembly 1 together form a receiving cavity for the inner core 4. The contraction at the end of the housing 2 near the cover plate assembly 1 is structurally manifested as a recess inward into the receiving cavity, thereby ensuring that the welding protrusion 3 is located in the recessed position of the housing 2 and does not protrude beyond the outer surface of the housing 2. This avoids the problem that when the battery is placed on its side, the battery cannot be laid flat due to the protruding position of the welding protrusion 3, and the outer film at the welding protrusion 3 is subjected to excessive local stress and wears through. It also avoids the problem that when multiple battery cells 100 are assembled into a module, the contact position of the welding protrusion 3 between adjacent battery cells 100 is subjected to large local stress, resulting in severe wear of the outer film.

[0049] This application provides several structures that cause the ends of the housing 2 to contract towards the receiving cavity. These structures mainly fall into three categories: First, a secondary extrusion molding operation is performed on the ends of the formed housing 2 using a stamping device. The metal housing 2 has a certain degree of ductility and will deform inward when subjected to inward extrusion, thus forming two misaligned surfaces. Second, the side plate 24 of the housing 2 is thinned near the end, thereby forming two misaligned surfaces on the outer wall of the housing 2. Third, a tapered opening is formed near the end of the housing 2 using an integral molding process. The product can select a more practical structural type according to actual design requirements.

[0050] In the first embodiment of this application, the housing 2 includes a first straight section 21, a bent section, and a second straight section 22 connected sequentially from the bottom cover to the top cover. Specifically, please refer to Figures 3 and 4. Since the structures of the four sides of the housing 2 are identical, taking one side as an example, when the battery cell 100 is placed on a horizontal plane, the first straight section 21 and the second straight section 22 are both planes perpendicular to the horizontal plane, and the first straight section 21 and the second straight section 22 are connected by the bent section. In this embodiment, the housing 2 is manufactured by a process of molding followed by extrusion, so that the housing 2 can be produced using traditional molds without the need for new mold making. The extrusion molding process at the ends of the housing 2 is also very simple, with low overall processing difficulty, and can ensure that the first straight section 21, the bent section, and the second straight section 22 are all integrally formed structures, thus giving the housing 2 excellent sealing performance. When assembling the housing 2 and the cover assembly 1, the outer periphery of the opening of the housing 2 is a straight surface, namely the second straight section 22, which ensures good fit between the housing 2 and the cover assembly 1. During welding, the welding head is perpendicular to the second straight section 22. When the laser is perpendicular to the surface of the second straight section 22, the laser energy can be absorbed by the weld joint to the maximum extent because the reflection loss is relatively small when the incident light is perpendicular. In addition, when irradiated perpendicularly, the laser energy is relatively uniformly distributed in the weld joint area. This uniform energy distribution helps to form regular and full weld joints. The laser energy can be concentrated on the part that needs to be welded, so that the material can melt uniformly at a suitable temperature and energy, thereby ensuring good fusion of the metal on the surfaces of the cover assembly 1 and the housing 2.

[0051] In the second embodiment of this application, the housing 2 includes four side plates 24 connected end to end. Each side plate 24 has an inner sidewall 241 facing the receiving cavity and an outer sidewall facing away from the receiving cavity. The outer sidewall includes a first outer sidewall 242a and a second outer sidewall 242b that are offset along the direction perpendicular to the outer sidewall. Specifically, please refer to Figure 5. In this embodiment, the inner sidewall 241 is a flat straight surface without a step surface, while the outer sidewall has two parts: a first outer sidewall 242a and a second outer sidewall 242b. The first outer sidewall 242a and the second outer sidewall 242b are connected by a step surface. The distance between the first outer sidewall 242a and the inner sidewall 241 is greater than the distance between the second outer sidewall 242b and the inner sidewall 241, so that the connection end between the housing 2 and the cover plate assembly 1 is contracted inward. This ensures that the welding protrusion 3 is located on the second outer sidewall 242b and the cover plate assembly 1, and is not higher than the height of the first outer sidewall 242a.

[0052] It should be noted that the side plate 24 structure proposed in this embodiment can be obtained by integral molding or by stamping followed by extrusion. This application does not limit this. In one embodiment of this application, after the side plate 24 is formed, it is extruded near the open end of the side plate 24. During this process, a support member is provided in the receiving cavity. The support member abuts against the inner sidewall 241 of the side plate 24 so that when the outer sidewall of the side plate 24 is extruded, the overall structure of the product will not deform. That is, only the outer sidewall of the side plate 24 is concave inward, while the inner sidewall 241 of the side plate 24 remains straight and does not bend. In this way, when the inner core 4 is subsequently installed, the inner sidewall 241 of the side plate 24 is flat and has no extra protrusions, thus ensuring that the installation of the inner core 4 is not obstructed and avoiding the safety hazards caused by the inner core 4 being extruded by the inner convex surface. The side plate 24 structure proposed in the second embodiment can optimize the installation of the inner core 4 and simplify the installation process.

[0053] In this second embodiment, several different implementation methods are proposed. A third outer wall 242c is provided between the first outer wall 242a and the second outer wall 242b. The two ends of the third outer wall 242c are respectively connected to the first outer wall 242a and the second outer wall 242b. Specifically, please refer to Figure 8. In the first embodiment, the third outer wall 242c is an arc surface, which smoothly connects the first outer wall 242a and the second outer wall 242b. The arc surface can reduce stress concentration at the step and make the appearance more aesthetically pleasing. In the second embodiment, the third outer wall 242c is a slope. During the assembly process, the slope transition can reduce wear between components and extend the service life of the product. In the third embodiment, the third outer wall 242c is a straight surface and is perpendicular to the first outer wall 242a and the second outer wall 242b. This embodiment is generally suitable for smaller battery cells 100. Since the height of the casing 2 is small, the distance of the third outer wall 242c is limited. Setting the third outer wall 242c as a vertical surface can make more effective use of the limited space.

[0054] The three implementation methods mentioned above can also be combined with the first embodiment mentioned above. Taking the second implementation method as an example, the bending section in the first embodiment can also be configured as a straight section with an inclination. The inner sidewall 241 and the outer sidewall of the housing 2 are both inclined to the same side near the end opening.

[0055] In the third embodiment of this application, the portion of the shell 2 near the end opening gradually tapers inward toward the opening. Specifically, referring further to FIG6, the tapering portion 25 has a first end 251 connecting to the main body of the shell 2 and a second end 252 connecting to the cover plate assembly 1. The first end 251 and the second end 252 are offset along the first direction X, and the vertical distance between the first end 251 and the cover plate assembly 1 along the first direction X is greater than the vertical distance between the second end 252 and the cover plate assembly 1. The tapering portion 25 is inclined upward. The gradually tapering design helps to reduce stress concentration because the slope can smoothly transition materials of different thicknesses, thereby reducing stress peaks caused by abrupt changes. Secondly, the gradually inclined slope can improve the stability and durability of the structure because it can distribute the load and reduce the stress in a single area. In addition, the gradually inclined slope also helps to simplify the manufacturing process, reduce the need for precision machining, and thus reduce production costs. The gradually shrinking contraction section 25 has a small shrinkage angle, so there is no obvious step surface in terms of the product's appearance, which reduces the risk of bumping or hitting the step surface. In addition, it also avoids the problem of stress concentration and improves the stability of the structure.

[0056] In the fourth embodiment of this application, the cross-section of the contraction portion 25 adopts a continuous arc surface structure. Specifically, please refer to Figure 7. The continuous arc surface structure allows the second end 252 of the contraction portion 25 to be better assembled with the step opening 1a of the cover plate assembly 1. It also allows the outer wall of the second end 252 to be set perpendicular to the first direction X, thereby ensuring that it forms a perpendicular angle with the welding head during welding and avoiding laser energy loss. The continuous arc surface that contracts inward also avoids corners and step surfaces, thereby avoiding stress concentration and improving the overall structural strength of the shell 2.

[0057] Since the height of the weld protrusion 3 resulting from the welding of the cover assembly 1 to the housing 2 is generally 0.2 to 0.3 mm, to ensure that the weld protrusion 3 does not protrude beyond the outer surface of the housing 2 after welding, taking the first embodiment as an example, the distance along the first direction X between the side of the first straight segment 21 facing away from the receiving cavity and the side of the second straight segment 22 facing away from the receiving cavity is greater than or equal to 0.2 mm. Specifically, please refer to Figure 9, which is the distance b shown in the figure. In addition, if the value of b is too large, that is, the difference in height between the first straight segment 21 and the second straight segment 22 is large, it will cause the thickness of the second straight segment 22 to be insufficient to support the overall structural strength, and will cause the cover assembly 1 to be suspended, which is not conducive to the placement stability of the battery cell 100. Therefore, the value of b should be less than or equal to 0.8 mm, that is, 0.2 mm ≤ b ≤ 0.8 mm. In one embodiment of this application, the thickness of b is 0.35 mm to match the height of the welding protrusion 3, so that the welding protrusion 3 is flush with the outer surface of the housing 2. This avoids the situation where the battery cell 100 is suspended near the cover plate assembly 1, which would cause the structure to be unstable. It also avoids the welding protrusion 3 protruding from the outer surface of the housing 2 and being subjected to concentrated force, which could easily lead to wear of the insulating film 5 or deformation of the housing 2.

[0058] To prevent the battery cell 100 from being unstable when placed on its side, the length of the second straight section 22 along the direction perpendicular to the cover assembly 1 is greater than or equal to 3 mm and less than or equal to 5 mm. Specifically, please refer to Figure 9, i.e., the distance 'a' shown in the figure. 'a' being less than or equal to 5 mm ensures that the contraction portion 25 near the end opening of the housing 2 will not affect the stability of the battery cell 100 when placed on its side. 'a' being greater than or equal to 3 mm ensures that the welding protrusion 3 has sufficient length for welding and is easy to process. In one embodiment of this application, the length 'a' of the second straight section 22 along the direction perpendicular to the cover assembly 1 is 4 mm, which satisfies the stability requirements of the battery side-placed structure while also reducing the molding difficulty.

[0059] It should be noted that the material of the casing 2 can be aluminum, plastic, composite materials, or steel, etc., and this application does not impose any restrictions. In one embodiment of this application, the casing 2 is made of aluminum. Aluminum has a low mass density, which can effectively reduce the overall weight of the battery cell 100 and help achieve battery lightweighting. Although aluminum has a low density, it has good mechanical strength and can withstand a certain amount of external pressure and impact, protecting the internal structure of the battery from damage. In addition, aluminum has excellent thermal conductivity, which can effectively conduct the heat generated inside the battery, maintain the stability of the battery temperature, and prevent overheating. Aluminum easily forms a dense oxide film in the air, protecting the aluminum casing from corrosion and extending the battery's service life.

[0060] In the technical solution of this application, using an aluminum shell makes it easier to process the structure of the shell 2 near the open end. Aluminum has good ductility and plasticity, which allows the aluminum shell to be shaped into complex shapes through various processing methods such as stamping, extrusion, and casting. At the same time, aluminum has a small work hardening effect and is not prone to cracking even during cold working, which further reduces the processing difficulty. Therefore, in this embodiment, aluminum is selected as the preferred material for the shell 2. The thickness of the aluminum shell, i.e., the distance c shown in Figure 9, is between 0.3mm and 0.6mm. The specific thickness should be adjusted according to the actual design requirements. For example, if the energy storage capacity of the battery cell 100 is small and the battery needs to be lightweight, a 0.3mm thick aluminum shell should be selected to reduce the overall weight of the shell while ensuring a certain level of structural strength. If the battery has high requirements for safety and rigidity, a 0.6mm thick aluminum shell should be selected to improve the battery's impact resistance and deformation resistance.

[0061] In one embodiment of this application, the outer side of the battery cell 100 is covered with an insulating film 5. The cover assembly 1 includes a cover assembly body 11 and a terminal post 12. The terminal post 12 passes through the cover assembly body 11 and includes a positive terminal post 121 and a negative terminal post 122. The positive terminal post 121 and the negative terminal post 122 pass through the cover assembly 1 and are electrically connected to the inner core 4 inside the receiving cavity. In this embodiment, since the welding protrusion 3 is positioned significantly lower than the outer surface of the housing 2, it can be ensured that even when the insulating film 5 is attached to the outside of the welding protrusion 3, the welding protrusion 3 will not be worn or damaged due to the small local stress or no local stress.

[0062] The above description is merely an exemplary embodiment of this application and does not limit the patent scope of this application. Any equivalent structural transformations made based on the technical concept of this application and the contents of the specification and drawings of this application, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this application.

Claims

1. A battery cell, characterized in that, include: A housing (2) having an opening at one end, the outer wall of the housing (2) being recessed inward at the opening; and a cover assembly (1) welded to the opening of the housing (2) and forming a weld protrusion (3) between the cover assembly (1) and the housing (2); wherein the thickness of the weld protrusion (3) is less than or equal to the maximum distance by which the outer wall of the housing (2) is recessed inward at the opening.

2. The battery cell as described in claim 1, characterized in that, The housing (2) includes a first straight section (21), a bent section and a second straight section (22) connected in sequence, the opening is located in the second straight section (22) and at least a portion of the structure of the second straight section (22) is welded to the cover plate assembly (1).

3. The battery cell as described in claim 2, characterized in that, The first straight segment (21) and the second straight segment (22) are offset in a first direction, which is perpendicular to the side wall of the housing (2).

4. The battery cell as described in claim 3, characterized in that, The housing (2) has a receiving cavity, and the distance between the side of the first straight segment (21) facing away from the receiving cavity and the side of the second straight segment (22) facing away from the receiving cavity along the first direction is greater than or equal to 0.2 mm and less than or equal to 0.8 mm.

5. The battery cell as described in claim 2, characterized in that, The second straight segment (22) has a length of greater than or equal to 3 mm and less than or equal to 5 mm in the direction perpendicular to the cover plate assembly (1).

6. The battery cell as described in claim 1, characterized in that, The housing (2) includes four side plates (24) connected end to end. Each side plate (24) has an inner side wall (241) and an outer side wall (242). The outer side wall (242) includes a first outer side wall (242a) and a second outer side wall (242b). The second outer side wall (242b) is located at one end near the cover plate assembly (1). The distance between the first outer side wall (242a) and the inner side wall (241) is greater than the distance between the second outer side wall (242b) and the inner side wall (241).

7. The battery cell as described in claim 6, characterized in that, The distance between the two first outer sidewalls (242a) of the two oppositely arranged side plates (24) is greater than the distance between the two second outer sidewalls (242b).

8. The battery cell as described in claim 6, characterized in that, The outer side wall also includes a third outer side wall (242c) connecting the first outer side wall (242a) and the second outer side wall (242b); the third outer side wall (242c) is configured as an arc surface, a straight surface, or an inclined surface.

9. The battery cell as described in claim 1, characterized in that, The housing (2) has a contraction portion (25) at one end near the cover plate assembly (1), and the contraction portion (25) gradually contracts toward one end of the cover plate assembly (1).

10. The battery cell according to any one of claims 1 to 8, characterized in that, The cover plate assembly (1) includes a cover plate assembly body (11) and an electrode post (12) disposed on the cover plate assembly body (11); the battery cell also includes an insulating film (5), which covers the housing (2).

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