Battery case, battery cell, battery pack, and electric device

Abstract

The application discloses a battery shell, a battery monomer, a battery pack and a power utilization equipment, and belongs to the technical field of batteries. The battery shell is provided with a score part and a sink part on a bottom wall. The score part is arranged at least partially around the sink part. Compared with the related art in which only the score part is arranged on the bottom wall, the material thinning rate of the score part of the embodiment is lower, and the forming is more stable, which is beneficial to improving the compressive strength of the bottom wall of the battery shell and ensuring the stability and safety of the bottom wall of the battery shell when the bottom wall is subjected to mechanical external force.

Description

Technical Field

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

[0002] A cylindrical battery cell includes a battery casing and electrode assemblies disposed inside the casing. Cylindrical battery cells must meet the new national standard requirements: the battery cell must not catch fire or explode after thermal runaway. When a battery cell experiences thermal runaway, the separator of the electrode assembly contracts, short-circuiting the positive and negative electrodes. The internal temperature of the battery cell rises sharply, accompanied by gas release and pressure increase. If the high-pressure gas inside the battery casing is not released to relieve pressure, the internal pressure of the battery cell will reach the maximum pressure limit of the battery casing, resulting in an explosion.

[0003] In related technologies, battery casings are typically designed as single-channel casings, meaning the casing has an opening at the top and a bottom wall. A cover plate is welded to the top opening, with the cover plate serving as the negative electrode of the battery cell and the casing as the positive electrode. The cover plate has grooves. However, if grooves are placed at the bottom of the casing, it weakens the structural strength of the bottom wall at that location, resulting in lower compressive strength. Furthermore, since the current collector is welded to the bottom wall, if the bottom wall is thick, the high energy of the laser during penetration welding can burn the separator, causing internal short circuits in the battery cells. Summary of the Invention

[0004] This application provides a battery casing, a battery cell, a battery pack, and an electrical device 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 housing is provided, comprising: a bottom wall and a side wall connected to each other, the bottom wall having a recessed portion and a grooved portion, wherein the thickness of the recessed portion is less than the thickness of the bottom wall, the recessed portion is adapted to be welded to the current collector of a battery cell, and the grooved portion is configured to partially surround the recessed portion.

[0006] By simultaneously providing a notched portion and a recessed portion on the bottom wall of the battery casing, the recessed portion is suitable for welding with the current collector of the battery cell. Since the thickness of the recessed portion is less than the thickness of the bottom wall, the energy of the laser for penetration welding can be reduced when the recessed portion is welded to the current collector, thereby avoiding diaphragm burn when the recessed portion is welded to the current collector. Furthermore, the notched portion is constructed to at least partially surround the recessed portion. Compared to related technologies where only a notched portion is provided on the bottom wall, the material thinning rate is lower and the forming is more stable during the notched portion processing of the bottom wall of the battery cell provided in this application embodiment. This is beneficial to improving the compressive strength of the bottom wall of the battery casing, while ensuring the stability and safety of the bottom wall of the battery casing under mechanical external force.

[0007] Optionally, the residual wall thickness of the grooved portion is τ1, and the thickness of the recessed portion is t1; wherein τ1 < t1, so that the structural strength of the grooved portion is lower than that of the recessed portion, so that the grooved portion will fracture preferentially when high-pressure gas acts on the bottom wall.

[0008] Optionally, the residual wall thickness of the grooved portion is τ1, and the thickness of the recessed portion is t1; η is set to τ1 / t1, where η satisfies: 0.2≤η≤0.5. When η satisfies: 0.2≤η≤0.5, the grooved portion remains the weakest point of the bottom wall of the battery casing, ensuring preferential fracture at the grooved portion, avoiding unpredictable tearing at the recessed portion, and guaranteeing the consistency of the residual wall thickness of the grooved portion and the stability of the valve opening pressure.

[0009] Optionally, t1 satisfies: 0.3mm ≤ t1 ≤ 1.0mm. This means that if the thickness t1 of the recessed portion is set to less than 0.3mm, the recessed portion will be relatively thin, which is not conducive to the recessed portion bearing the stress of the bottom wall, and the "mechanical adjustment" effect of the recessed portion protecting the scored area will be weakened. If the thickness t1 of the recessed portion is set to greater than 1.0mm, it is not conducive to reducing the laser power during the penetration welding process between the manifold and the recessed portion, which may lead to burns to the diaphragm and cause a short circuit in the core package.

[0010] Optionally, τ1 satisfies: 0.05mm ≤ τ1 ≤ 0.25mm. This means that if the residual wall thickness τ1 of the scored portion is less than 0.05mm, the structural strength at the scored portion will be weak, making it prone to breakage when the bottom wall of the battery casing is subjected to mechanical forces. If the residual wall thickness τ1 of the scored portion is greater than 0.25mm, the actual valve opening pressure at the scored portion will be higher, leading to unpredictable tearing of the bottom wall's recessed area and other regions.

[0011] Optionally, the thickness of the bottom wall is t3, and the thickness of the recessed portion is t1; wherein 0.4≤t1 / t3≤0.8, it can ensure that no microcracks or fractures occur in the area where the recessed portion is located during the stamping process, thereby ensuring the airtightness and structural integrity of the battery casing. The recessed portion is formed by locally stamping and stretching the bottom wall. The battery casing is made of metal material, which thins during stretching. When the thinning rate of the metal material (1-t1 / t3) is too large, the metal material may neck or even crack due to excessive stretching.

[0012] Optionally, in a top-view orientation, the notched portion is arc-shaped, and the recessed platform is circular. The recessed platform and the notched portion are concentrically connected. The radial distance between the notched portion and the recessed platform is d, where d satisfies 3.0mm ≤ d ≤ 8.0mm. This effectively isolates the residual stress generated during the forming of the recessed platform and the welding of the recessed platform to the current collector, thereby ensuring that the opening state of the notched portion depends on the internal high-pressure airflow of the battery cell. This results in a more precise and stable opening pressure for the notched portion. Simultaneously, it ensures a safe welding distance, providing a safe threshold for the heat-affected zone of laser penetration welding and preventing high temperatures from affecting the material properties of the notched portion.

[0013] Optionally, the first end and the second end of the etched portion are spaced apart to form a etched angle α, and the central angle formed by the center of the etched portion and the first end and the second end is defined as α, where α satisfies: 5°≤α≤180°.

[0014] When the scribe line angle α is set to less than 5°, the fragments are prone to flying out when the scribe line opens, potentially leading to a short circuit. When the scribe line angle α is set to greater than 180°, the shear stress of the material is greater, and the scribe line can only open a small opening when it opens, resulting in a smaller pressure relief area. The pressure relief rate of the scribe line is less than the internal gas generation rate of the battery cell, leading to untimely pressure relief and increasing the risk of explosion.

[0015] Optionally, the thickness of the bottom wall is greater than the thickness of the side wall; and / or, the thickness of the bottom wall is set to t3, and the thickness of the side wall is set to t4, where 0.5mm ≤ t3 ≤ 2.0mm, and 0.2mm ≤ t4 ≤ 0.5*t3. It is understood that when the wall thickness t3 of the bottom wall of the battery casing is set to less than 0.5mm, the corresponding wall thickness t4 of the side wall will further decrease, resulting in a weaker overall structural strength of the battery casing. Conversely, when the wall thickness t3 of the bottom wall of the battery casing is set to greater than 2.0mm, the difficulty of cold extrusion or stretch forming of the battery casing increases significantly, which is detrimental to the lightweight design of the battery cells. Furthermore, under the premise that the external dimensions of the battery cells remain unchanged, when the wall thickness t3 of the bottom wall of the battery casing is set to greater than 2.0mm, the internal volume of the battery casing will be significantly reduced, thereby affecting the energy density of the battery cells.

[0016] Optionally, the recessed portion is configured to be formed by an indentation through the outer surface of the bottom wall, and / or the recessed portion is configured to be formed by an indentation through the inner surface of the bottom wall.

[0017] According to a second aspect of this application, a battery cell is provided, comprising a battery housing as described above, the battery housing including a bottom wall having a recessed portion; an electrode assembly disposed within the battery housing; and a current collector welded to the recessed portion of the bottom wall and electrically connected to the battery housing and the electrode assembly.

[0018] Optionally, the collector plate includes a boss portion, which is welded to the recessed portion; wherein the thickness of the recessed portion is t1, the thickness of the boss portion is t2, and 0.5≤t1 / t2≤2.

[0019] Optionally, t1 satisfies: 0.3mm≤t1≤1.0mm; and / or t2 satisfies: 0.15mm≤t2≤2.0mm.

[0020] According to a third aspect of this application, a battery pack is also provided, comprising a plurality of battery cells as described above; and a housing in which the plurality of battery cells are mounted.

[0021] According to a fourth aspect of this application, an electrical device is also provided, including the battery pack described above.

[0022] In the battery casing of this application embodiment, by simultaneously providing a grooved portion and a recessed portion on the bottom wall of the battery casing, firstly, the recessed portion is suitable for welding with the current collector of the battery cell. Since the thickness of the recessed portion is less than the thickness of the bottom wall, the energy of the laser for penetration welding can be reduced when the recessed portion is welded to the current collector, thereby preventing the separator from being burned when the recessed portion is welded to the current collector. Secondly, the grooved portion is constructed to at least partially surround the recessed portion, so that the recessed portion can change the stress distribution at the location of the grooved portion. Compared with the related technology where only a grooved portion is provided on the bottom wall, the bottom wall of the battery casing provided in this application embodiment has a lower material thinning rate at the location of the grooved portion during the processing of the grooved portion around the recessed portion, and the forming is more stable. This is beneficial to improving the compressive strength of the bottom wall of the battery casing, while ensuring the stability and safety of the bottom wall of the battery casing under mechanical external force.

[0023] Other features and advantages of this application will be described in detail in the following detailed description section. Attached Figure Description

[0024] 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.

[0025] 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.

[0026] Figure 1 This is a three-dimensional structural diagram of a battery cell provided in an exemplary embodiment of this disclosure; Figure 2 This is an internal cross-sectional view of a battery cell provided in an exemplary embodiment of this disclosure; Figure 3 yes Figure 2 A magnified view of a portion of the image; Figure 4 This is a bottom view of the battery casing of a battery cell provided in an exemplary embodiment of this disclosure; Figure 5a This is a schematic diagram of the stress analysis of the grooved part on the bottom wall of a battery cell without a set-top platform, provided in proportion. Figure 5b This is a schematic diagram of the stress analysis of the grooved portion on the bottom wall of a battery cell that is provided with both a recessed portion and a grooved portion in an exemplary embodiment of this disclosure; Figure 6This is an internal cross-sectional view of the battery casing of a battery cell provided in an exemplary embodiment of this disclosure; Figure 7 yes Figure 6 Enlarged view of point A; Figure 8 yes Figure 6 Enlarged view of point B.

[0027] Explanation of reference numerals in the attached figures: 100. Battery cell; 1. Battery casing; 11. Opening; 12. Bottom wall; 13. Side wall; 14. Recessed platform; 2. Scratched area; 3. Electrode assembly; 4. Collector plate; 41. Bossed section. Detailed Implementation

[0028] 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 a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the protection scope of this application.

[0029] A cylindrical battery cell includes a battery casing and an electrode assembly 3 disposed inside the battery casing. Cylindrical battery cells must meet the new national standard requirements: the battery cell must not catch fire or explode after thermal runaway. When thermal runaway occurs in a battery cell, the separator of the electrode assembly 3 contracts, short-circuiting the positive and negative electrodes. The internal temperature of the battery cell rises sharply, accompanied by gas release and pressure increase. If the high-pressure gas inside the battery casing is not released to relieve pressure, the internal pressure of the battery cell will reach the maximum pressure limit of the battery casing, resulting in an explosion.

[0030] In related technologies, battery casings are typically designed as single-channel casings, meaning the casing has an opening at the top and a bottom wall. A cover plate is welded to the top opening, with the cover plate serving as the negative electrode of the battery cell and the casing as the positive electrode. The cover plate has grooves. However, if grooves are placed at the bottom of the casing, it weakens the structural strength of the bottom wall at that location, resulting in lower compressive strength. Furthermore, since the current collector is welded to the bottom wall, if the bottom wall is thick, the high energy of the laser during penetration welding can burn the separator, causing internal short circuits in the battery cells.

[0031] In view of this, this application provides a battery pack that can be used in electrical devices that use the battery pack as a power source or in various energy storage systems that use the battery pack as an energy storage element.

[0032] Electrical devices that use battery packs as a power source can include, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc. Taking vehicles as an example, the vehicles can be gasoline-powered cars, natural gas-powered cars, or new energy vehicles. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc.

[0033] The battery pack includes a housing and an assembly of one or more battery cells disposed within the housing. The housing may be part of the chassis structure of the electric vehicle. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0034] A battery cell assembly is typically formed by arranging multiple battery cells. As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form an independent module.

[0035] As an example, a battery cell may include a lithium-ion secondary battery cell, a lithium-ion primary battery cell, a lithium-sulfur battery cell, a sodium-lithium-ion battery cell, a sodium-ion battery cell, or a magnesium-ion battery cell, etc.

[0036] like Figure 1 and Figure 2 As shown, the battery cell 100 includes a battery casing 1, a core pack, and a current collector 4.

[0037] The battery casing 1 is a single-pass battery casing, meaning it has an opening 11 at the top. The battery casing 1 includes a bottom wall 12 and a side wall 13 connected together. The bottom wall 12 is connected to the bottom end of the side wall 13. A cover plate is welded to the top opening of the battery casing. One of the cover plate and the battery casing serves as the negative electrode of the battery cell, and the other serves as the positive electrode. The battery casing 1 has a receiving cavity, and the core pack is installed in the receiving cavity inside the battery casing 1. The battery casing 1 is a hollow cylinder, and suitable materials for manufacturing the battery casing 1 include aluminum, aluminum alloy, nickel-plated steel sheet, and stainless steel.

[0038] The core package includes an electrode assembly 3 and an electrolyte. The electrode assembly 3 comprises multiple positive electrode sheets, multiple separators, and multiple negative electrode sheets formed by winding, or multiple positive electrode sheets, multiple separators, and multiple negative electrode sheets formed by stacking. Each separator is disposed between each positive electrode sheet and each negative electrode sheet to provide electrical isolation. The electrolyte is filled within the electrode assembly 3. The electrode assembly 3 can be a wound assembly or a stacked assembly.

[0039] The current collector 4 is configured to connect the electrode assembly 3 and the battery housing 1. As an example, the battery housing 1 serves as the positive electrode of the battery cell 100, and the tabs of each positive electrode of the electrode assembly 3 are welded to the current collector 4, which is welded to the battery housing 1.

[0040] Among them, such as Figure 2 and Figure 3 As shown, the bottom wall 12 of the battery casing 1 is provided with a recessed portion 14. During the electrolyte injection process of the battery cell 100, the recessed portion 14 contacts and is fixed to the electrolyte injection tray, and the recessed portion 14 is also configured to be welded to the current collector 4. Since the gravity of the electrode assembly 3 and the injected electrolyte both act on the bottom wall 12, the bottom wall 12 of the battery casing 1 needs to be thickened to prevent deformation. Therefore, in the embodiment of this application, the thickness of the bottom wall 12 is greater than the thickness of the side wall 13. The current collector 4 needs to be welded to the bottom wall 12 of the battery casing 1 to achieve electrical connection. It is understandable that if the thickness of the bottom wall 12 is too large, the laser power required during the welding process will increase, resulting in a higher temperature of the current collector 4, which may cause the current collector 4 to burn the diaphragm of the electrode assembly 3, thereby causing an internal short circuit in the electrode assembly 3. In this application, by providing a recessed portion 14 on the bottom wall 12, the thickness of the recessed portion 14 is significantly smaller than the thickness of the bottom wall 12, thereby reducing the laser power of the penetration welding and avoiding burns to the diaphragm.

[0041] In the embodiments of this application, reference continues to be made to... Figures 2 to 4 The bottom wall 12 is also provided with a notched portion 2, which is configured to partially surround the recessed portion 14. This allows the battery cell 100 to release pressure at the bottom through the notched portion 2 in the event of thermal runaway, thereby improving the safety performance of the battery cell 100. Furthermore, when the internal pressure of the battery cell 100 increases, the recessed portion 14 can absorb some energy through its own deformation, making the force exerted by the high-pressure gas on the notched portion 2 more gradual and controllable, thus helping to widen the process window for the valve opening pressure of the notched portion 2. The recessed portion 14 can be formed by stamping, and it has sufficient thickness to allow for significant plastic deformation.

[0042] It should be noted that, in order to improve the pressure relief capability of the battery cell 100, a serrated structure can be provided on both the bottom wall 12 of the battery casing 1 and the cover plate at the top opening of the battery casing 1. The serrated structures provided on the bottom wall 12 and the cover plate can be the same or different, thereby enabling the battery cell 100 to simultaneously relieve pressure from the top and bottom, thus significantly improving the safety performance of the battery cell 100.

[0043] Furthermore, the applicant discovered through research that when both the notched portion 2 and the recessed portion 14 are provided on the bottom wall 12, compared to only providing the notched portion 2 on the bottom wall 12, the material thinning rate of the bottom wall 12 is lower and the forming is more stable during the processing of the notched portion 2. This is beneficial to improving the compressive strength of the bottom wall 12 of the battery casing 1, while ensuring the stability and safety of the bottom wall 12 of the battery casing 1 when subjected to mechanical external forces.

[0044] This application is verified by setting up embodiments and comparative examples. The bottom wall 12 of the battery casing 1 provided in the embodiment is provided with both a grooved part 2 and a recessed part 14, wherein the residual wall thickness of the grooved part 2 is τ1. The bottom wall of the battery casing provided in the comparative example is only provided with a grooved part 2, and the residual wall thickness of the grooved part 2 is τ2.

[0045] like Figure 4 , Figure 5a and Figure 5b As shown, where, Figure 5a This is a force analysis diagram provided to the scale, showing only the notched portion 2 on the bottom wall 12. Figure 5b This is a force analysis diagram provided in an embodiment of the present application, showing that a recessed platform 14 and a notched section 2 are provided on the bottom wall 12.

[0046] F0 is defined as the ultimate stress value of the material resisting fracture of the notched portion 2 of the bottom wall 12 of the battery casing 1. F1 is the effective resultant force acting directly on the notched portion 2 and causing it to open under internal pressure in the battery cell provided in the comparative example. F4 is the effective resultant force acting directly on the notched portion 2 and causing it to open under internal pressure in the battery cell provided in the embodiment. F2 is the constraint reaction force provided by the unnotched area of ​​the side wall 13 or bottom wall 12 of the battery casing 1 to the notched portion 2. β is the angle between the direction of action of F2 and the normal direction of the cross-section of the notched portion 2, reflecting the directional characteristics of the constraint reaction force of the battery casing 1. θ is the angle between the cross-section of the notched portion 2 and the normal of the bottom wall 12 of the battery casing 1, used to project each force onto the effective direction of the cross-section of the notched portion 2.

[0047] In the battery casing 1 provided in the embodiment, the recessed portion 14 acts as a localized plastic deformation zone. Under internal pressure, the recessed portion 14 generates an additional deformation resistance F3. This deformation resistance F3 is transmitted to the notched portion 2 through the material of the bottom wall 12, thereby changing the stress state at the notched portion 2. α is set as the angle between the direction of action of F3 and the normal direction of the cross-section of the notched portion 2, reflecting the directional characteristics of the additional force generated by the recessed portion 14.

[0048] Based on force balance analysis, in the embodiments provided in this application, F4 = (F2 × cosβ + F3 × cosα - F0) / cosθ. In the comparative example provided in this application, F1 = (F2 × cosβ - F0) / cosθ. When the notched portion 2 opens, the battery cell 100 provided in the embodiment needs to satisfy: F2 × cosβ + F3 × cosα - F4cosθ = F0, and the battery cell 100 provided in the comparative example needs to satisfy: F2 × cosβ - F1cosθ = F0. Under the condition that the opening value F0 of the notched portion 2 is the same, F4 > F1, that is, the residual wall thickness τ1 of the notched portion 2 of the bottom wall 12 of the battery casing 1 of the battery cell 100 provided in the embodiment is greater than the residual wall thickness τ2 of the notched portion 2 of the bottom wall 12 of the battery casing 1 of the battery cell 100 provided in the comparative example. Therefore, in the process of processing the grooved portion 2, the bottom wall 12 of the battery housing 1 provided in the embodiment has a lower material thinning rate, more stable forming, and can effectively improve the compressive strength of the bottom wall 12 of the battery housing 1, ensuring the stability and safety of the bottom wall 12 of the battery housing 1 when subjected to mechanical external force.

[0049] The target opening pressure of the battery cell 100 is set at 1.2 MPa. In this embodiment, a notched portion 2 and a recessed portion 14 are provided on the bottom wall 12 of the battery casing 1. The residual wall thickness τ1 of the notched portion 2 is preset to 0.12 mm with a standard deviation of 0.05 mm. Testing of the opening pressure of the battery cell 100 provided in this embodiment revealed that the opening pressure of all battery cells 100 provided in this embodiment is between 1.13 MPa and 1.28 MPa, which is within the target opening pressure range for the battery cell 100. Furthermore, upon opening, the notched lines of the notched portion 2 are neatly torn open, and plastic tensile deformation occurs in the area where the recessed portion 14 is located, without any fragmentation. When a compressive force is applied to the bottom wall 12 of the battery casing 1 until the battery casing 1 is permanently deformed, the average bearing pressure is 620 N. In the embodiment, a notched portion 2 and a recessed portion 14 are simultaneously provided on the bottom wall 12 of the battery casing 1. The recessed portion 14 changes the stress distribution of the bottom wall 12, making the stress distribution of the notched portion 2 more concentrated. Therefore, the residual wall thickness τ1 of the notched portion 2 can be thicker and easier to process, achieving the same precise and stable valve opening pressure. At the same time, because the residual wall thickness τ1 of the notched portion 2 is thicker, it, together with the recessed portion 14, improves the rigidity of the bottom wall 12 of the battery casing 1.

[0050] The battery casing 1 provided in the comparative example has only a notched portion 2 on its bottom wall 12, and the target opening valve value for the comparative battery cell 100 is set at 1.2 MPa. According to empirical formulas, the residual wall thickness of the notched portion 2 of the battery casing 1 provided in the comparative example must be 0.07 mm to meet the target opening valve value requirement. Testing the opening valve pressure of the battery cell 100 provided in the comparative example revealed that some of the battery cells 100 opened prematurely before reaching 1.02 MPa, while others did not open even after exceeding 1.35 MPa. This means the standard deviation of the opening valve pressure of the battery cell 100 provided in the comparative example is as high as 0.15 MPa. Furthermore, during valve opening, the notched portion 2 on the bottom wall 12 of the battery casing 1 of some battery cells 100 is incompletely torn, and there is a risk of small fragments peeling off. When a compressive force is applied to the bottom wall 12 of the battery casing 1 until the battery casing 1 is permanently deformed, the average bearing pressure is only 320N, which is far lower than the average bearing pressure of the bottom wall 12 of the battery casing 1 of the battery cell 100 provided in the embodiment. Specific data can be found in Table 1 below.

[0051] Table 1. Experimental data of the examples and comparative examples.

[0052] In some embodiments, such as Figure 3 , Figure 6 and Figure 7 As shown, the residual wall thickness of the etched portion 2 is τ1, and the thickness of the recessed portion 14 is t1, where τ1 < t1. This results in the structural strength of the etched portion 2 being lower than that of the recessed portion 14, causing the etched portion 2 to fracture preferentially when high-pressure gas acts on the bottom wall 12.

[0053] In some embodiments, η is set to τ1 / t1, where η satisfies: 0.2 ≤ η ≤ 0.5. If η is less than 0.2, with the thickness t1 of the recessed portion 14 remaining constant, the residual wall thickness τ1 of the grooved portion 2 is thinner, resulting in lower structural strength of the grooved portion 2, which in turn leads to a smaller actual pressure relief threshold of the grooved portion 2, thereby weakening the functional clarity of the grooved portion 2 as a preset weak point. If η is greater than 0.5, with the thickness τ1 of the grooved portion 2 remaining constant, the thickness t1 of the recessed portion 14 is thinner, or with the thickness t1 of the recessed portion 14 remaining constant, the thickness τ1 of the grooved portion 2 is thicker, which weakens the stress-sharing function of the recessed portion 14 and the "mechanical adjustment" effect of protecting the grooved portion 2. Understandably, when η satisfies 0.2 ≤ η ≤ 0.5, the notched portion 2 remains the weakest point of the bottom wall 12 of the battery casing 1. This ensures that fracture occurs preferentially at the notched portion 2, preventing unpredictable tearing at the recessed portion 14, and guaranteeing the consistency of the residual wall thickness of the notched portion 2 and the stability of the valve opening pressure. As examples, the ratio η between the residual wall thickness τ1 of the notched portion 2 and the thickness t1 of the recessed portion 14 can be 0.2, 0.3, 0.4, 0.5, or any two of the above values, or a range between any two of the above values.

[0054] In some embodiments, the residual wall thickness τ1 of the notched portion 2 satisfies: 0.05mm ≤ τ1 ≤ 0.25mm. It should be noted that the residual wall thickness τ1 of the notched portion 2 defined here is the average of the residual wall thicknesses of each region of the notched portion 2. It can be understood that if the residual wall thickness τ1 of the notched portion 2 is set to less than 0.05mm, the structural strength at the notched portion 2 will be weak, making it prone to breakage when the bottom wall 12 of the battery casing 1 is subjected to mechanical external force. If the residual wall thickness τ1 of the notched portion 2 is set to greater than 0.25mm, the actual valve opening pressure value at the notched portion 2 will be large, leading to unpredictable tearing of the recessed portion 14 of the bottom wall 12 and other areas. As examples, the residual wall thickness τ1 of the notched portion 2 can be 0.05 mm, 0.09 mm, 0.10 mm, 0.12 mm, 0.15 mm, 0.18 mm, 0.20 mm, 0.23 mm, 0.25 mm, or any value between any two of the above values, or a range between any two of the above values.

[0055] In some embodiments, the thickness t1 of the recessed portion 14 satisfies: 0.3mm ≤ t1 ≤ 1.0mm. It should be noted that the thickness t1 of the recessed portion 14 defined here is the average thickness of each region of the recessed portion 14. It is understood that if the thickness t1 of the recessed portion 14 is set to less than 0.3mm, the recessed portion 14 will be relatively thin, which is not conducive to the recessed portion 14 sharing the stress of the bottom wall 12, and the "mechanical adjustment" effect of the recessed portion 14 protecting the scored portion 2 will be weakened. If the thickness t1 of the recessed portion 14 is set to greater than 1.0mm, it is not conducive to reducing the laser power during the through-welding process between the collector plate 4 and the recessed portion 14, thereby causing burns to the diaphragm and leading to a short circuit in the core package. As some examples, the thickness t1 of the recessed portion 14 can be 0.3mm, 0.5mm, 0.8mm, 1.0mm, or any value between any two of the above, or a range between any two of the above values.

[0056] In some embodiments, such as Figure 3 and Figure 8 As shown, the thickness of the bottom wall 12 is t3, and the thickness of the recessed portion 14 is t1; where 0.4 ≤ t1 / t3 ≤ 0.8. When the ratio of the thickness t1 of the recessed portion 14 to the thickness t3 of the bottom wall 12 satisfies 0.4 ≤ t1 / t3 ≤ 0.8, it can be ensured that no microcracks or fractures will occur in the area where the recessed portion 14 is located during the stamping process, thereby ensuring the airtightness and structural integrity of the battery casing 1. The recessed portion 14 is formed by locally stamping and stretching the bottom wall 12. The battery casing 1 is made of metal material. The metal material will become thinner during the stretching process. When the thinning rate of the metal material (1-t1 / t3) is too large, the metal material will necking or even crack due to excessive stretching. Furthermore, if t1 / t3 > 0.8 mm, meaning the thickness of the recessed portion 14 is too thick, higher laser energy will be required to penetrate it during welding with the current collector 4, narrowing the welding process window and imposing stringent requirements on the stability of the welding equipment. Moreover, penetrating the thicker recessed portion 14 necessitates increased laser heat input, leading to an expansion of the heat-affected zone and an increased risk of damaging the separator, thus contradicting the design intent of the recessed portion 14. Conversely, if t1 / t3 < 0.4 mm, meaning the thickness of the recessed portion 14 is too thin, visible microcracks will appear in the recessed portion 14 during the stamping process, resulting in a yield rate of less than 60% for the battery casing 1 and posing a risk of leakage. As examples, the ratio of the thickness t1 of the recessed platform 14 to the thickness t3 of the bottom wall 12 can be 0.4, 0.43, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, or any value between any two of the above values, or a range between any two of the above values.

[0057] In some embodiments, the recessed portion 14 is configured to be formed by a recess in the outer surface of the bottom wall 12, or the recessed portion 14 is configured to be formed by a recess in the inner surface of the bottom wall 12. Alternatively, the recessed portion 14 is configured to be formed by a recess in both the outer and inner surfaces of the bottom wall 12.

[0058] In some embodiments, such as Figure 3 and Figure 4 As shown, the notched portion 2 is configured as a C-shaped valve, meaning that in the top view, the notched portion 2 is arc-shaped, and the recessed portion 14 is circular. The notched portion 2 and the recessed portion 14 are concentrically arranged, and the radial distance between the notched portion 2 and the recessed portion 14 is d, which satisfies: 3.0mm ≤ d ≤ 8.0mm. It should be noted that the radial distance d between the notched portion 2 and the recessed portion 14 defined here is the average value of the radial distance between the notched portion 2 and the recessed portion 14 in each region. When the radial distance d between the notched portion 2 and the recessed portion 14 is less than 3.0mm, the recessed portion 14 will rely solely on the notched portion 2, causing the recessed portion 14 to undergo severe plastic deformation during the stamping process, leading to material flow. This can easily cause stress concentration in the notched portion 2 during the forming process, resulting in accidental tearing or micro-cracks in the notched portion 2, thereby compromising the sealing performance and preset pressure value of the notched portion 2. When the radial distance d between the notched portion 2 and the recessed portion 14 is greater than 8.0 mm, assuming the area of ​​the recessed portion 14 remains unchanged, the edge of the notched portion 2 will approach the side wall 13 of the battery casing 1, thus weakening the stress concentration effect of the notched portion 2 and causing the valve opening pressure of the notched portion 2 to increase or become unstable. However, when the radial distance d between the notched portion 2 and the recessed portion 14 satisfies 3.0 mm ≤ d ≤ 8.0 mm, it effectively isolates the residual stress generated during the forming of the recessed portion 14 and the welding of the recessed portion 14 to the current collector 4. This ensures that the valve opening state of the notched portion 2 depends on the internal high-pressure airflow of the battery cell 100, resulting in a more precise and stable valve opening pressure. Simultaneously, it ensures a safe welding distance, providing a safe threshold for the heat-affected zone of laser penetration welding and preventing high temperatures from affecting the material properties of the notched portion 2. As examples, the radial distance d between the notched portion 2 and the recessed portion 14 can be 3.0 mm, 3.5 mm, 4.0 mm, 4.5 mm, 5.0 mm, 5.5 mm, 6.0 mm, 6.5 mm, 7.0 mm, 7.5 mm, 8.0 mm, or any value between any two of the above, or a range between any two of the above values.

[0059] In some embodiments, such as Figure 4As shown, the notched section 2 is configured as a C-shaped valve, meaning that the first and second ends of the notched section 2 are spaced apart, forming a notch angle α. The central angle formed by the center of the notched section 2 and the first and second ends of the notched section 21 is defined as the notch angle α, which satisfies the following condition: 5° ≤ α ≤ 180°. When the notch angle α is less than 5°, when the notched section 2 opens, the fragment is easily ejected, potentially leading to a short circuit. When the notch angle α is greater than 180°, the shear stress of the material is greater, and when the notched section 2 opens, it can only open a small opening, resulting in a smaller pressure relief area. The pressure relief rate of the notched section 2 is less than the internal gas generation rate of the battery cell 100, leading to untimely pressure relief and increasing the risk of explosion. As examples, the scribe angle α of the scribe portion 2 can be 5°, 10°, 20°, 40°, 80°, 90°, 100°, 120°, 130°, 140°, 150°, 160°, 170°, 180°, or any two of the above degrees, or a range between any two of the above degrees.

[0060] In some embodiments, the thickness of the bottom wall 12 of the battery housing 1 is greater than the thickness of the side wall 13, so as to enhance the deformation resistance of the bottom wall 12 of the battery housing 1.

[0061] As some examples, such as Figure 8 As shown, the thickness of the bottom wall 12 of the battery casing 1 is set to t3, and the thickness of the side wall 13 is set to t4, where 0.5mm ≤ t3 ≤ 2.0mm, and 0.2mm ≤ t4 ≤ 0.5*t3. It should be noted that the wall thickness t3 of the bottom wall 12 defined here is the average thickness of all regions of the bottom wall 12 except for the notched portion 21 and the recessed portion 14, and the thickness t4 of the side wall 13 defined here is the average thickness of all regions of the side wall 13. It is understandable that when the wall thickness t3 of the bottom wall 12 of the battery casing 1 is set to less than 0.5mm, the corresponding wall thickness t4 of the side wall 13 will further decrease, thus making the overall structural strength of the battery casing 1 weaker. When the wall thickness t3 of the bottom wall 12 of the battery casing 1 is set to be greater than 2.0 mm, the difficulty of cold extrusion or stretch forming of the battery casing 1 increases significantly, which is not conducive to the lightweight design of the battery cell 100. Furthermore, with the external dimensions of the battery cell 100 remaining unchanged, a wall thickness t3 of the bottom wall 12 of the battery casing 1 being greater than 2.0 mm will result in a significant reduction in the internal volume of the battery casing 1, thereby affecting the energy density of the battery cell 100. As some examples, the wall thickness t3 of the bottom wall 12 of the battery casing 1 can be 0.5 mm, 0.6 mm, 0.8 mm, 1.0 mm, 1.2 mm, 1.4 mm, 1.6 mm, 1.8 mm, 2.0 mm, or any value between any two of the above, or a range between any two of the above values.

[0062] If the wall thickness t4 of the side wall 13 is less than 0.2 mm, the overall structural strength of the battery casing 1 will be significantly insufficient, making the side wall 13 of the battery casing 1 easily damaged during the chemical reaction and gas generation process inside the battery cell 100. If the wall thickness t3 of the bottom wall 12 of the battery casing 1 remains unchanged, and the wall thickness t4 of the side wall 13 is greater than 0.5 * t3, the reduction in wall thickness t4 of the side wall 13 relative to the wall thickness t3 of the bottom wall 12 will be small. This will significantly increase the processing difficulty of the battery casing 1 during cold extrusion or stretching, and will also cause greater stress at the connection between the side wall 13 and the bottom wall 12. As examples, the ratio of the wall thickness t4 of the side wall 13 to the wall thickness t3 of the bottom wall 12 can be 0.4, 0.45, 0.5, or any value between any two of the above ratios, or a range between any two of the above ratios.

[0063] In some embodiments, such as Figure 3 As shown, the collector plate 4 includes a boss portion 41 located at the center, which is welded to the recessed portion 14. The thickness of the recessed portion 14 is set to t1, and the thickness of the boss portion 41 of the collector plate 4 is set to t2, where 0.5 ≤ t1 / t2 ≤ 2. Through research, the applicant discovered that when t1 / t2 < 2, the laser energy completely melts through the recessed portion 14, forming a stable weld nugget of approximately 0.7 mm with the boss portion 41 of the collector plate 4. The weld is full, without spatter, and the diaphragm directly below the weld is intact without any thermal damage. When t1 / t2 = 2, the recessed portion 14 and the boss portion 41 can achieve penetration welding, with a weld nugget depth of approximately 0.8 mm, and the diaphragm remains undamaged. When t1 / t2 > 2, the same laser power cannot penetrate the thick boss portion 41, requiring a significant increase in laser energy or welding time. This results in a noticeable yellowish-brown heat-aging area on the separator below the weld point, with slight melting visible under a microscope. When t1 / t2 < 0.5, the thickness of the recessed portion 14 is relatively thin, while the thickness of the boss portion 41 of the current collector 4 is relatively thick. In this case, there is no burn on the separator, and the recessed portion 14 of the bottom wall 12 of the battery casing 1 can be easily penetrated by welding. However, the thickness of the boss portion 41 of the current collector 4 is relatively thick, making it difficult for the laser heat to fully melt it, resulting in shallow weld points, weak bonding strength, or even "false welds." As examples, t1 / t2 can be 0.5, 0.8, 1.0, 1.3, 1.5, 1.8, 2.0, or any two of the above values, or a range between any two of the above values.

[0064] In some embodiments, continue to refer to Figure 3The thickness of the recessed portion 14 is t1, which satisfies the condition: 0.3mm ≤ t1 ≤ 1.0mm. It should be noted that the thickness t1 of the recessed portion 14 defined here is the average thickness of all regions of the recessed portion 14. The thickness t1 of the recessed portion 14 is set to be no less than 0.3mm to ensure that the recessed portion 14 has sufficient structural strength and rigidity to withstand the pressure of the electrolyte inside the battery casing 1, the stress during cycling, and to maintain good sealing performance, preventing deformation or cracking of the recessed portion 14 of the bottom wall 12 of the battery casing 1 during welding or use. The thickness t1 of the recessed portion 14 is set to be no greater than 1.0mm, mainly based on the lightweight design and weldability considerations of the battery casing 1. It is understandable that when the thickness of the recessed portion 14 is greater than 1.0mm, the corresponding wall thickness of the battery casing 1 is greater, meaning the battery casing 1 has a larger weight, which is not conducive to increasing the energy density of the battery cell 100 and will increase the material cost of the battery casing 1. Meanwhile, from a welding perspective, a wall thickness of 1.0 mm is a practical upper limit for single-pulse laser penetration welding. Exceeding this welding thickness requires special welding processes, such as oscillating welding or multi-pass welding, which significantly increases process complexity and manufacturing costs. As examples, the thickness t1 of the recessed portion 14 can be 0.3 mm, 0.4 mm, 0.5 mm, 0.8 mm, 1.0 mm, or any value between any two of these values, or a range between any two of these values.

[0065] In some embodiments, continue to refer to Figure 3The thickness of the boss portion 41 of the current collector 4 is t2, which satisfies the condition: 0.15mm ≤ t2 ≤ 2.0mm. This is beneficial for laser penetration welding, with low heat input, effectively preventing burns to the separator, and avoiding excessive occupation of the internal height space of the battery cell 100 by the boss portion 41 of the current collector 4. It should be noted that the thickness t2 of the boss portion 41 defined here is the average thickness of the various regions of the boss portion 41. Understandably, when the thickness t2 of the boss portion 41 of the current collector 4 is set to less than 0.15mm, the thickness of the boss portion 41 of the current collector 4 is too thin, which leads to easy instantaneous melting or ablation during laser welding, making it difficult to form an effective weld, and the mechanical strength of the boss portion 41 of the current collector 4 is too low, making it prone to breakage under vibration conditions. When the thickness t2 of the boss portion 41 of the current collector 4 is set to greater than 2.0mm, a higher power laser is required, the welding heat input increases significantly, and it is easy to damage the core package. Meanwhile, the protrusion 41 of the current collector 4 occupies a significant portion of the internal height space of the battery casing 1, thereby affecting the energy density of the battery cell 100 and significantly increasing the manufacturing cost of the battery cell 100. As examples, the thickness t2 of the protrusion 41 of the current collector 4 can be 0.15mm, 0.20mm, 0.3mm, 0.5mm, 0.8mm, 1.0mm, 1.3mm, 1.5mm, 1.8mm, 2.0mm, or any value between any two of the above, or a range between any two of the above values.

[0066] 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.

[0067] 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.

[0068] The embodiments, implementation methods, and related technical features of this application can be combined and substituted for each other without conflict.

[0069] 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 scope of the technical solution of this application shall still fall within the scope of the technical solution of this application.

Claims

1. A battery casing (1), suitable for a single battery cell (100), characterized in that, include: A bottom wall (12) and a side wall (13) are connected. The bottom wall (12) is provided with a recessed portion (14) and a grooved portion (2). The thickness of the recessed portion (14) is less than the thickness of the bottom wall (12). The recessed portion (14) is adapted to be welded to the current collector (4) of the battery cell (100). The grooved portion (2) is configured to partially surround the recessed portion (14).

2. The battery casing (1) according to claim 1, characterized in that, The residual wall thickness of the etched portion (2) is τ1, and the thickness of the recessed portion (14) is t1; Where τ1 < t1; And / or, where η is set to τ1 / t1, and η satisfies: 0.2≤η≤0.

5.

3. The battery casing (1) according to claim 2, characterized in that, t1 satisfies: 0.3mm ≤ t1 ≤ 1.0mm; And / or, τ1 satisfies: 0.05mm≤τ1≤0.25mm.

4. The battery casing (1) according to any one of claims 1 to 3, characterized in that, The thickness of the bottom wall (12) is t3, and the thickness of the platform (14) is t1; Where 0.4≤t1 / t3≤0.

8.

5. The battery casing (1) according to any one of claims 1 to 3, characterized in that, Along the top view direction, the etched part (2) is set in an arc shape, the recessed part (14) is set in a circle, the recessed part (14) and the etched part (2) are set concentrically, and the radial distance between the etched part (2) and the recessed part (14) is d, which satisfies: 3.0mm≤d≤8.0mm.

6. The battery casing (1) according to any one of claims 1 to 3, characterized in that, The first end and the second end of the etched portion (2) are spaced apart and form a etched angle α. The central angle formed by the center of the etched portion (2) and the first end and the second end is defined as the etched angle α, and α satisfies: 5°≤α≤180°.

7. The battery casing (1) according to any one of claims 1 to 3, characterized in that, The thickness of the bottom wall (12) is greater than the thickness of the side wall (13); And / or, the thickness of the bottom wall (12) is set to t3 and the thickness of the side wall (13) is set to t4, wherein 0.5mm≤t3≤2.0mm and 0.2mm≤t4≤0.5*t3.

8. The battery casing (1) according to any one of claims 1 to 3, characterized in that, The recessed portion (14) is configured to be formed by recessing through the outer surface of the bottom wall (12), and / or the recessed portion (14) is configured to be formed by recessing through the inner surface of the bottom wall (12).

9. A battery cell (100), characterized in that, include: The battery casing (1) as described in any one of claims 1 to 8; An electrode assembly (3) is disposed inside the battery casing (1); The collector plate (4) is welded to the recessed portion (14) of the bottom wall (12) and electrically connected to the battery housing (1) and the electrode assembly (3).

10. The battery cell (100) according to claim 9, characterized in that, The collector plate (4) includes a boss (41), which is welded to the recessed plate (14). The thickness of the recessed portion (14) is t1, the thickness of the protruding portion (41) is t2, and 0.5≤t1 / t2≤2.

11. The battery cell (100) according to claim 10, characterized in that, t1 satisfies: 0.3mm ≤ t1 ≤ 1.0mm; And / or, t2 satisfies: 0.15mm≤t2≤2.0mm.

12. A battery pack, characterized in that, include: Multiple battery cells (100) as described in any one of claims 9 to 11. The housing contains multiple battery cells (100) mounted therein.

13. An electrical appliance, characterized in that, Includes the battery pack as described in claim 12.

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