Battery cells and electrical devices

Abstract

This invention relates to the field of new energy technology and discloses a battery cell and an electrical device. The battery cell includes: a shell having an opening along a first direction; a top surface of the shell formed at the end face of the opening along the first direction; a cover plate disposed at the opening of the shell, the cover plate including a body portion and an overlapping portion, the overlapping portion abutting against the top surface of the shell along the first direction; and a welding portion adapted to weld the shell and the cover plate together, the welding portion forming a molten first end and a molten second end, the direction from the molten first end to the molten second end being the welding direction; in a plane perpendicular to the welding direction, the projected area of ​​the molten first end is larger than the projected area of ​​the molten second end; along the welding direction, the molten second end is located within the body portion area. The battery cell provided by this invention allows the heat-affected zone during welding to penetrate deep into the interior of the cover plate along a direction perpendicular to the first direction, reducing the impact of the heat-affected zone on the thickness direction of the shell and improving the strength of the shell.

Description

Technical Field

[0001] This invention relates to the field of new energy technology, specifically to a battery cell and an electrical device. Background Technology

[0002] The battery includes a casing and a cover plate. The casing has an opening, and the cover plate is disposed in the opening and sealed to the casing. The casing and the cover plate together enclose a sealed chamber for accommodating the electrode assembly.

[0003] In related technologies, the housing and cover plate are often sealed together by laser welding. However, the housing becomes thinner at the weld line, which reduces the strength of the housing. Summary of the Invention

[0004] In view of this, the present invention provides a battery cell and an electrical device to solve the problem that the casing becomes thinner at the welding line position, resulting in a decrease in casing strength.

[0005] In a first aspect, the present invention provides a battery cell, comprising: The shell has an opening, the opening direction of which is a first direction; the shell forms a top surface at the end face of the opening along the first direction. A cover plate is provided at the opening of the housing. The cover plate includes a body portion and an overlapping portion extending from the body portion in a direction perpendicular to a first direction. The overlapping portion abuts against the top surface of the housing in the first direction. The welding section is suitable for welding the shell and the cover plate together. The welding section forms a first molten end and a second molten end. The direction from the first molten end to the second molten end is the welding direction. In the plane perpendicular to the welding direction, the orthographic projection area of ​​the first molten end is larger than the orthographic projection area of ​​the second molten end. Along the orthographic projection plane perpendicular to the welding direction, the orthographic projection of the welding section is located within the orthographic projection range of the main body. Along the welding direction, the molten second end is located within the body region.

[0006] Beneficial effects: The formation of the welded part will melt the shell material and the cover plate material, resulting in a reduction in the structural strength of the part of the shell where the welded part is formed. In this embodiment, along the welding direction, the molten second end is located in the body part area, ensuring that the end of the welded part is constricted inside the body part of the cover plate, thereby preventing the molten second end from extending towards the inside of the shell along the first direction; the welded part's penetration direction corresponds to the welding direction. By reasonably controlling the welding direction, only a small part of the welded part extends into the shell; this allows the heat-affected zone during welding to penetrate deep into the inside of the cover plate perpendicular to the first direction, reducing the influence of the heat-affected zone on the shell thickness direction and improving the shell's strength.

[0007] Secondly, the present invention also provides an electrical device, comprising: The main body of the electrical device, and the battery cells as described above that are electrically connected to the main body of the electrical device.

[0008] Since the electrical device includes individual battery cells and has the same effect as individual battery cells, it will not be elaborated further here. Attached Figure Description

[0009] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0010] Figure 1 A scanned image of the welding between the shell and the cover plate before the improvement; Figure 2 This is a cross-sectional schematic diagram of a single battery cell of the present invention; Figure 3 for Figure 2 Enlarged view of point A in the middle; Figure 4 for Figure 3 A schematic diagram of the welding section is shown on the basis; Figure 5 for Figure 3 A schematic diagram showing the welded section and heat-affected zone is provided. Figure 6 for Figure 3 A schematic diagram showing the area of ​​the welded section; Figure 7 This is a partially enlarged view of the disassembled shell and cover plate of the present invention; Figure 8 This is a schematic diagram illustrating another possible combination of the housing and the cover plate according to the present invention.

[0011] Explanation of reference numerals in the attached figures: 1. Shell; 11. Opening; 12. Top surface of shell; 13. First wall thickness portion; 14. Second wall thickness portion; 2. Cover plate; 21. Body part; 22. Overlapping part; 3. Welded section; 31. First molten end; 32. Second molten end; 4. Battery cells. Detailed Implementation

[0012] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0013] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0014] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0015] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0016] The battery includes a casing and a cover plate. The casing has an opening, and the cover plate is disposed in the opening and sealed to the casing. The casing and the cover plate together enclose a sealed chamber for accommodating the electrode assembly.

[0017] In related technologies, the shell and cover plate are often sealed together by laser welding. During the welding process, laser energy locally heats the material to a molten state, and after cooling, a weld mark is formed, thereby achieving a sealed fixation between the shell and the cover plate. In the welding stage, the heat of the welding arc melts the base material in the welding area. The molten metal area formed is usually pool-shaped, called the molten pool, and a weld mark is formed after the liquid metal solidifies.

[0018] Research has found that when butt welding is performed between the inner wall of the shell and the outer wall of the cover plate, i.e., using top welding, the welding direction is downward, for example... Figure 1 As shown, a molten pool is formed at the weld between the shell and the cover plate. The direction of the molten pool's depth corresponds to the welding direction. The molten pool extends to the shell throughout the entire depth direction. The formation of the molten pool melts the shell material, resulting in a reduction in the structural strength of the part of the shell where the molten pool is formed.

[0019] Furthermore, the rapid heating and cooling process of laser welding creates a heat-affected zone (HAZ) around the weld. The material in this HAZ may undergo the following changes: grain coarsening (metal grains grow at high temperatures, leading to decreased toughness); transformation hardening (some alloys, such as aluminum alloys, may form a hard and brittle phase after welding, reducing fatigue resistance); and residual stress (uneven thermal expansion and contraction generate tensile stress, becoming a potential starting point for crack initiation). The presence of the HAZ further weakens the mechanical properties of the corresponding area of ​​the shell, resulting in reduced shell strength.

[0020] To address the aforementioned technical problems, the battery cell proposed in this invention optimizes the welding structure design, avoiding the direct impact of welding penetration on the thickness of the main body of the casing, thereby effectively improving the structural integrity of the casing in the weld area and enhancing the casing strength.

[0021] The following is combined with Figures 2 to 8 The following describes embodiments of the present invention.

[0022] According to an embodiment of the present invention, in one aspect, a battery cell is provided, comprising: The housing 1 has an opening 11, the opening direction of which is a first direction; the housing 1 forms a top surface 12 at the end face of the opening 11 along the first direction. Cover plate 2 is provided at the opening 11 of the housing 1. Cover plate 2 includes a body part 21 and an overlapping part 22 extending from the body part 21 in a direction perpendicular to the first direction. Along the first direction, the overlapping part 22 abuts against the top surface 12 of the housing. The welding part 3 is suitable for welding the shell 1 to the cover plate 2. The welding part 3 forms a molten first end 31 and a molten second end 32. The direction from the molten first end 31 to the molten second end 32 is the welding direction. In the plane perpendicular to the welding direction, the orthographic projection area of ​​the molten first end 31 is larger than the orthographic projection area of ​​the molten second end 32. Along the orthographic projection plane perpendicular to the welding direction, the orthographic projection of the welding part 3 is located within the orthographic projection range of the body part 21. Along the welding direction, the molten second end 32 is located within the body portion 21.

[0023] In this embodiment, the housing 1 is a component used to provide a receiving space to house the electrode assembly and other components and isolate them from the outside environment. The housing 1 generally includes a body with an opening at at least one end and a receiving cavity. The opening of the housing 1 can be closed by a cover plate 2, sealing and isolating the internal environment of the battery cell from the external environment. The materials of the housing 1 include, but are not limited to, copper, iron, aluminum, stainless steel, aluminum alloy, and aluminum-plastic film.

[0024] In this embodiment, the cover plate 2 is a component that closes the opening of the casing to isolate the internal environment of the battery cell from the external environment. The material of the cover plate 2 includes, but is not limited to, copper, iron, aluminum, stainless steel, aluminum alloy, aluminum-plastic film, etc.

[0025] In this embodiment, the housing 1 has a receiving cavity, and one end of the housing 1 has an opening 11. The cover plate 2 is disposed at the opening 11 to close the receiving cavity, thereby achieving sealed housing of the internal components of the battery. The receiving cavity can accommodate the battery cell 5 and electrolyte, ensuring that the battery cell has complete electrochemical function.

[0026] The cover plate 2 includes a body portion 21 and an overlapping portion 22 extending from the body portion 21 in a direction perpendicular to the first direction. The overlapping portion 22 and the body portion 21 form an integrated structure.

[0027] The overlapping portion 22 forms a surface contact with the top surface 12 of the shell in the first direction, and a welded portion 3 is formed in the contact area between the overlapping portion 22 and the top surface 12 of the shell by laser welding.

[0028] The welding part 3 is formed by melting and cooling the contact area between the shell 1 and the cover plate 2 along the welding direction using a laser welding device. The welding direction refers to the direction in which the laser beam of the laser welding device is emitted.

[0029] During the welding process, the laser energy locally melts the contact area between the cover plate 2 and the shell 1, forming a gradually changing molten pool extending from the first molten end 31 to the second molten end 32, and forming the welded part 3 after cooling. It should be noted that in this embodiment, the first molten end 31 can specifically be the large molten end, and the second molten end 32 can be the small molten end; because the first molten end 31 is affected by the area with higher laser energy input, it has a larger amount of molten metal, forming a welded structure with a larger cross-section after cooling, while the second molten end 32 forms a gradually narrowing end due to energy attenuation and a smaller molten range.

[0030] The formation of the weld joint melts the shell material and the cover plate material, resulting in a decrease in the structural strength of the welded portion of the shell. Figure 5 As shown, in this embodiment, along the welding direction, the molten second end 32 is located within the body portion 21 area, ensuring that the end of the welded portion 3 is constricted within the body portion 21 of the cover plate 2, thereby preventing the molten second end 32 from extending towards the interior of the shell 1 along the first direction; the weld depth direction of the welded portion 3 corresponds to the welding direction, and by reasonably controlling the welding direction, only a small portion of the welded portion 3 extends into the shell; this allows the heat-affected zone during welding to penetrate deep into the interior of the cover plate 2 perpendicular to the first direction, reducing the influence of the heat-affected zone on the thickness direction of the shell 1 and improving the strength of the shell 1.

[0031] The welding process generates a heat-affected zone (HAZ), which is the area in the base material where the microstructure and properties change due to the heat of welding. Since the distribution and orientation of the HAZ can affect the properties of the surrounding materials, in this embodiment, by controlling the molten second end 32 within the body portion 21, the area of ​​the HAZ on the shell 1 can be reduced, effectively suppressing the expansion of the HAZ into the interior of the shell 1, thereby avoiding the problem of reduced strength of the shell 1 due to heat.

[0032] In some embodiments, combined with Figure 6 As shown, in one of the cross sections perpendicular to the extension direction of the welded part 3, the area of ​​the region where the welded part 3 overlaps with the shell 1 is S1mm², the total area of ​​the welded part 3 is S2mm², and satisfies 0.1≤S1 / S2≤0.45.

[0033] It should be noted that since the welding part 3 is arranged in a closed ring along the circumference of the opening 11, and the extension direction of the welding part 3 is consistent with the peripheral extension direction of the cover plate 2, "one section perpendicular to the extension direction of the welding part 3" refers to the section obtained by cutting perpendicular to the extension direction of the welding part 3. Specifically, the section of the welding part 3 at multiple positions can be obtained by scanning with CT scan, and one section can be selected as the target section.

[0034] It should be noted that the area where the welded part 3 overlaps with the shell 1 refers to the area within the shell 1 formed by the welded part 3 along its extension direction. Specifically, it can be the area where the outline of the welded part 3 overlaps with that of the shell 1 after the target cross-section is determined.

[0035] Similarly, the total area of ​​welded part 3 refers to the total area of ​​welded part 3 within the target cross section after the target cross section is determined.

[0036] The specific method for measuring areas S1 and S2 is as follows: select a target section, cut the combined structure of shell 1 and cover plate 2, grind the cut surface and etch out the metallographic structure, then use a metallographic microscope or a two-dimensional image analysis system to obtain the metallographic image, perform outlining and calibration through image processing software, and calculate areas S1 and S2 based on the calibration area.

[0037] By limiting the upper limit of S1 / S2, the proportion of the welded part 3 in the shell 1 area can be effectively restricted, preventing excessive heat input from being concentrated in the shell 1, effectively suppressing the expansion of the heat-affected zone, reducing the impact of the heat-affected zone on the shell 1, and improving the strength of the shell 1. At the same time, by limiting the lower limit of S1 / S2, it can be ensured that the welded part 3 has sufficient connection area in the shell 1, ensuring the reliability of the connection between the shell 1 and the cover plate 2, avoiding structural loosening due to insufficient connection area, and improving the structural load-bearing capacity of the shell 1.

[0038] For example, in this embodiment, the value of S1 / S2 can be 0.1 or 0.15 or 0.2 or 0.22 or 0.25 or 0.28 or 0.3 or 0.32 or 0.35 or 0.38 or 0.4 or 0.42 or 0.45, or it can be any range formed by any two of the above values.

[0039] For example, in this embodiment, the value of S1 can be 0.1 or 0.2 or 0.3 or 0.4 or 0.5 or 0.6 or 0.7 or 0.8 or 0.9 or 1.0, or it can be a range formed by any two of the above values.

[0040] For example, in this embodiment, the value of S2 can be 1.0, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.3, 2.4, or 2.5, or it can be a range formed by any two of the above values.

[0041] Regarding the measurement of dimensions, thickness, distance, and area involved in this application, a micrometer, caliper, or scanning electron microscope can be used to measure dimensions, thickness, distance, etc., and the area can be calculated from the dimensions.

[0042] The battery cells of this application can be prepared using the following methods: (1) Preparation of the positive electrode: The positive electrode active material, conductive agent acetylene black, and binder PVDF are mixed, and solvent NMP is added. The mixture is stirred under vacuum until the system is homogeneous to obtain a positive electrode slurry. The positive electrode slurry is uniformly coated on both surfaces of the positive electrode current collector aluminum foil, air-dried at room temperature, and then transferred to an oven for further drying. Finally, it is cold-pressed and slit to obtain the positive electrode sheet. Specifically, the mass ratio of positive electrode active material: conductive agent: binder satisfies (92~98):(4~1):(4~1).

[0043] (2) Preparation of negative electrode: The negative electrode active material, conductive agent acetylene black, thickener CMC, and binder SBR are mixed, and deionized water is added as a solvent. The mixture is stirred under vacuum until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on both surfaces of the negative electrode current collector copper foil, air-dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the negative electrode sheet is obtained. The ratio of negative electrode active material: conductive agent: thickener: binder satisfies (90~96): (4~2): (2~1): (4~1).

[0044] (3) Preparation of electrolyte: Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0045] (4) Preparation of the diaphragm: Polyethylene film is selected as the diaphragm.

[0046] (5) Battery fabrication: The positive electrode, separator, and negative electrode are stacked in sequence and wound to form a bare battery cell, which is then placed in a prismatic battery casing. The battery is dried, injected with electrolyte, sealed with a sealing device, and then subjected to settling, formation, and volume adjustment to obtain the battery.

[0047] The positive electrode active material can be selected from one or more lithium-containing positive electrode active materials, including lithium iron phosphate, ternary materials containing nickel, cobalt, and manganese, and lithium manganese iron phosphate; the negative electrode active material can be selected from one or more negative electrode active main materials, such as artificial graphite, natural graphite, silicon carbide, silicon oxide, and lithium titanate.

[0048] The adhesive includes, but is not limited to, one or more combinations of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium alginate, polymethacrylic acid, carboxymethyl chitosan, etc.

[0049] The solvent can be deionized water, NMP (N-methylpyrrolidone), alcohol, ether, ketone or other types of pyrrolidone, etc.

[0050] The positive electrode current collector foil can be a metal foil or a composite current collector. For example, as a metal foil, it can be made of stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel, or titanium with a silver-plated surface. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0051] The negative electrode current collector foil can be made of stainless steel, copper, aluminum, nickel, carbon electrodes, or titanium, and can be surface-plated with silver. Composite current collectors may include a polymer base layer and a metal layer. Composite current collectors can be formed by forming metal materials (aluminum, aluminum alloys, copper, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on a polymer base material (such as polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0052] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0053] Referring to Table 1 below, through several embodiments and comparative tests, the leakage rate of the battery cell provided in this application after 1000 battery cycles and the leakage rate under vibration conditions were tested to verify its qualification.

[0054] Performance 1: Leakage rate test after 1000 battery cycles, the method is as follows: According to the above-described battery cell preparation method, for each embodiment and comparative example, corresponding battery cells were prepared. The values ​​of S1 and S2 for each embodiment and comparative example are shown in Table 1 below, and other test conditions are kept consistent.

[0055] The battery was charged at room temperature (25℃) with a constant current of 0.33C to the upper limit voltage of 4.25V, and then discharged with a constant voltage until the current dropped to 0.05C. After resting for 5 minutes, the battery was discharged with a constant current of 0.33C to the lower limit voltage of 2.5V. This constitutes one cycle. After performing 1000 charge-discharge cycles on the lithium-ion battery, the junction between the battery casing and the seal was observed for leakage. The leakage rate was calculated as (number of leaking batteries / 100) × 100%.

[0056] If the battery leakage rate is less than or equal to 2%, the test result is considered good; if the battery leakage rate is less than or equal to 4% but greater than 2%, the test result is considered qualified; if the battery leakage rate is greater than 4%, it is considered unqualified.

[0057] Different systems require corresponding adjustments to the upper and lower voltage limits: Lithium iron phosphate (LFP) - upper limit voltage 3.65V, lower limit voltage 2.5V; Nickel cobalt manganese ternary NCM - upper limit voltage 4.25V, lower limit voltage 2.5V; Lithium manganese iron phosphate (LFMP) - upper limit voltage 4.25V, lower limit voltage 2.5V; Lithium nickel manganese oxide - upper limit voltage 4.8V, lower limit voltage 3.5V.

[0058] In this test, the active material for the positive electrode of the battery was selected from a nickel-cobalt-manganese ternary LiNi alloy. 0.6 Co 0.2Mn 0.2 Taking O2 as an example, all other positive electrode materials meet the above test requirements, and the mass ratio of positive electrode active material: conductive agent: binder meets 96:2:2; the negative electrode active material is selected from artificial graphite, and the ratio of negative electrode active material: conductive agent: thickener: binder meets 95:2:1:2.

[0059] Performance 2: Battery leakage rate test under vibration conditions, the method is as follows: According to the above-described battery cell preparation method, for each embodiment and comparative example, corresponding battery cells were prepared. The values ​​of S1 and S2 for each embodiment and comparative example are shown in Table 1 below, and other test conditions are kept consistent.

[0060] The battery was mounted on a vibration table according to GB / T2423.43. The testing procedure was carried out according to GB / T2423.56. Random and fixed-frequency vibration loads were applied in each direction, and the loading sequence should preferably be random z-axis, fixed-frequency z-axis, random y-axis, fixed-frequency y-axis, random x-axis, fixed-frequency x-axis (the direction of the line connecting the front and rear of the battery is the x-axis direction, and the other horizontal direction perpendicular to the x-axis direction is the y-axis direction). The vibration frequency, power spectral density (PSD), vibration time, etc., are shown in the table below.

[0061]

[0062] After the vibration ends, observe the junction between the battery casing and the seal to see if there is any leakage. The percentage of batteries that leak is calculated as (number of batteries that leak / 100) × 100%.

[0063] If the battery leakage rate is less than or equal to 2%, the test result is considered good; if the battery leakage rate is less than or equal to 4% but greater than 2%, the test result is considered qualified; if the battery leakage rate is greater than 4%, it is considered unqualified.

[0064] Table 1

[0065] Regarding the test results, referring to Table 1 above, the explanation is as follows: As can be seen from Examples 1-9, when the value of the formula S1 / S2 meets the above range, the leakage ratio test after 1000 battery cycles all show qualified results, with no unqualified results; the battery leakage ratio test under vibration conditions also shows qualified results; and the performance requirements are met.

[0066] In Comparative Example 1, the value of S1 / S2 exceeded the upper limit, resulting in a failed battery leakage ratio test under vibration conditions, failing to meet performance requirements. In Comparative Example 2, the value of S1 / S2 was below the lower limit, leading to a failed leakage ratio test after 1000 battery cycles, also failing to meet performance requirements.

[0067] In some embodiments, the thickness of the overlap portion 22 along the first direction is C mm, satisfying: 0.3 mm ≤ C mm ≤ 1.0 mm; And / or, along the direction perpendicular to the first direction, the length of the overlap 22 is Dmm, satisfying: 0.3mm≤Dmm≤1.2mm.

[0068] By limiting the lower limit of the thickness Cmm of the overlapping part 22, it can be ensured that the overlapping part 22 has sufficient structural strength to withstand the mechanical stress during overlapping assembly and the thermal stress during welding, avoiding welding deformation or breakage due to excessive thinness and ensuring welding effect; at the same time, by limiting the upper limit of the thickness Cmm of the overlapping part 22, material waste and increased assembly difficulty can be avoided.

[0069] By limiting the lower limit of the length Dmm of the overlapping part 22, sufficient contact area can be ensured between the overlapping part 22 and the top surface 12 of the shell, ensuring the continuity and sealing reliability of the welding part 3 and guaranteeing the welding effect; by limiting the upper limit of the length Dmm of the overlapping part 22, the overlapping part 22 can be prevented from extending excessively and encroaching on the internal space of the shell 1, affecting the cell assembly accuracy, and ensuring the overall compactness of the battery cell structure.

[0070] For example, in this embodiment, the value of Cmm can be 0.3mm or 0.35mm or 0.4mm or 0.45mm or 0.5mm or 0.55mm or 0.6mm or 0.65mm or 0.7mm or 0.75mm or 0.8mm or 0.85mm or 0.9mm or 0.95mm or 1.0mm, or it can be a range formed by any two of the above values.

[0071] For example, in this embodiment, the value of Dmm can be 0.3mm or 0.35mm or 0.4mm or 0.45mm or 0.5mm or 0.55mm or 0.6mm or 0.65mm or 0.7mm or 0.75mm or 0.8mm or 0.85mm or 0.9mm or 0.95mm or 1.0mm or 1.1mm or 1.2mm, etc., or it can be a range formed by any two of the above values.

[0072] In some embodiments, the thickness of the body portion 21 along the first direction is Emm, satisfying: 0.6mm≤Emm≤4.0mm.

[0073] By limiting the lower limit of the thickness Emm of the body portion 21, it is possible to ensure that the body portion 21 has sufficient thickness to increase the contact area between the body portion 21 and the inner wall of the casing 1 along the direction perpendicular to the first direction. This prevents high-temperature slag from entering the battery casing during welding, which could cause the separator to shrink and thus trigger a short circuit between the positive and negative electrodes. At the same time, by limiting the upper limit of Emm, the overall weight and space ratio of the cover plate 2 can be controlled, thereby improving the energy density of the battery cells.

[0074] For example, in this embodiment, the value of Emm can be 0.6mm or 0.8mm or 1.0mm or 1.2mm or 1.5mm or 1.8mm or 2.0mm or 2.2mm or 2.5mm or 2.8mm or 3.0mm or 3.2mm or 3.5mm or 3.8mm or 4.0mm, or it can be any range formed by any two of the above values.

[0075] In some embodiments, the wall thickness of the housing 1 is F mm along the direction perpendicular to the first direction, satisfying: 0.2 mm ≤ F mm ≤ 1.19 mm.

[0076] By limiting the lower limit of the wall thickness Fmm of the casing 1, sufficient structural rigidity of the casing 1 can be ensured, while ensuring the area of ​​the casing 1 involved in welding, thus ensuring the welding effect and avoiding insufficient weld penetration due to excessively thin wall thickness, which would affect the welding strength and sealing performance. At the same time, by limiting the upper limit of Fmm, the overall weight of the casing can be reduced, material redundancy can be avoided, and the energy density and space utilization of the battery cells can be improved.

[0077] For example, in this embodiment, the value of Fmm can be 0.2mm or 0.25mm or 0.3mm or 0.35mm or 0.4mm or 0.45mm or 0.5mm or 0.55mm or 0.6mm or 0.65mm or 0.7mm or 0.75mm or 0.8mm or 0.85mm or 0.9mm or 0.95mm or 1.0mm or 1.05mm or 1.1mm or 1.15mm or 1.19mm, or it can be any range formed by any two of the above values.

[0078] In some embodiments, the thickness of the body portion 21 is greater than the wall thickness of the housing 1. That is, Emm > Fmm.

[0079] By making the thickness of the body part 21 greater than the wall thickness of the shell 1, sufficient weld penetration margin is reserved for the body part 21, so that the weld penetration is located as close as possible to the area of ​​the cover plate 2, thereby avoiding a reduction in the strength of the shell 1.

[0080] In other embodiments, combined with Figure 8As shown, along the first direction, the housing 1 includes a first wall thickness portion 13 and a second wall thickness portion 14, with the first wall thickness portion 13 disposed along the first direction on the side of the second wall thickness portion 14 near the overlapping portion 22. Along the direction perpendicular to the first direction, the wall thickness of the first wall thickness portion 13 is greater than the wall thickness of the second wall thickness portion 14.

[0081] By changing the wall thickness distribution of the casing 1, the first wall thickness portion 13 has greater structural strength, which facilitates butt welding with the overlapping portion 22 to improve the connection reliability of the welding area. At the same time, the second wall thickness portion 14 is relatively thin, which helps to reduce the overall weight of the casing and optimize the energy density of the battery cell.

[0082] In some embodiments, the wall thickness of the first wall thickness portion 13 is G mm along the direction perpendicular to the first direction, satisfying: 0.2 mm ≤ G mm ≤ 1.19 mm; And / or, the wall thickness of the second wall thickness portion 14 is H mm, satisfying: 0.15 mm ≤ H mm ≤ 1.1 mm.

[0083] By limiting the lower limit of Gmm, it can be ensured that the first wall thickness 13 has sufficient space for welding molten pool and structural support; and by limiting the upper limit of Gmm, material waste caused by excessive local thickness can be avoided.

[0084] By limiting the upper limit of Hmm, the amount of material used in the second wall thickness 14 can be effectively reduced, thus reducing the overall weight of the shell. At the same time, by limiting the lower limit of Hmm, the basic structural integrity can be ensured, and the deformation or insufficient strength caused by excessive thinness can be avoided.

[0085] For example, in this embodiment, the value of Gmm can be 0.2mm or 0.25mm or 0.3mm or 0.35mm or 0.4mm or 0.45mm or 0.5mm or 0.55mm or 0.6mm or 0.65mm or 0.7mm or 0.75mm or 0.8mm or 0.85mm or 0.9mm or 0.95mm or 1.0mm or 1.05mm or 1.1mm or 1.15mm or 1.19mm, or it can be any range formed by any two of the above values.

[0086] For example, in this embodiment, the value of Hmm can be 0.15mm or 0.2mm or 0.25mm or 0.3mm or 0.35mm or 0.4mm or 0.45mm or 0.5mm or 0.55mm or 0.6mm or 0.65mm or 0.7mm or 0.75mm or 0.8mm or 0.85mm or 0.9mm or 0.95mm or 1.0mm or 1.05mm or 1.1mm, or it can be a range formed by any two of the above values.

[0087] In some embodiments, the wall thickness of the first wall thickness portion 13 is G mm along the first direction perpendicular to the first direction; the thickness of the body portion 21 is E mm along the first direction, satisfying: 0.05≤G / E≤1.6.

[0088] By controlling the ratio of G to E within the above range, it is possible to ensure that the first wall thickness 13 has sufficient structural strength to achieve stable welding, while avoiding material waste and increased shell weight due to excessive thickness.

[0089] For example, in this embodiment, the value of G / E can be 0.05 or 0.1 or 0.2 or 0.3 or 0.4 or 0.5 or 0.6 or 0.8 or 1.0 or 1.2 or 1.4 or 1.6, or it can be a range formed by any two of the above values.

[0090] In some embodiments, the weld depth length of the welded portion 3 is a mm along the welding direction; and the weld depth width of the welded portion 3 is b mm along the direction perpendicular to the welding direction; wherein a mm > b mm.

[0091] By increasing the penetration length amm of the welded part 3 along the welding direction, the penetration depth is ensured to fully penetrate the lap joint in the welding direction, thus guaranteeing the weld's reliability and improving the weld's tensile and shear strength. This allows the heat-affected zone during welding to penetrate deep into the cover plate 2 along a direction perpendicular to the first direction.

[0092] By making the weld width bmm along the weld direction perpendicular to the weld direction smaller, the expansion of the heat-affected zone is effectively suppressed, the influence of the heat-affected zone on the shell 1 is reduced, and the strength of the shell 1 is improved.

[0093] In some embodiments, combined with Figure 4 As shown, the minimum distance between the welded part 3 and the edge of the cover plate 2 on the side away from the housing 1 along the first direction is J mm, which satisfies: 0 mm ≤ J mm ≤ 0.5 mm.

[0094] By limiting the lower limit of the minimum distance Jmm between the welded part 3 and the edge of the cover plate 2 along the first direction, the heat-affected zone of the weld can be prevented from being too close to the edge of the cover plate 2, which could lead to material melting or structural weakening. At the same time, by limiting the upper limit of Jmm, the welded part 3 can be ensured to have reasonable layout space, avoiding the weakening of the connection rigidity between the cover plate 2 and the shell 1 due to excessive spacing, thus ensuring sealing reliability.

[0095] For example, in this embodiment, the value of Jmm can be 0mm or 0.05mm or 0.1mm or 0.15mm or 0.2mm or 0.25mm or 0.3mm or 0.35mm or 0.4mm or 0.45mm or 0.5mm, or it can be a range formed by any two of the above values.

[0096] In some embodiments, the weld depth of the welded portion 3 is a mm along the welding direction; the wall thickness of the housing 1 is F mm along the direction perpendicular to the first direction; satisfying: a mm > F mm.

[0097] By controlling the weld depth length amm of the welded part 3 to be greater than the wall thickness Fmm of the shell 1, it is ensured that the weld depth completely penetrates the wall thickness of the shell 1 and extends into the interior of the cover plate 2 to form a metallurgical bond, thereby improving the overall load-bearing capacity of the welded part 3.

[0098] In some embodiments, the weld depth width of the welded portion 3 is bmm along the direction perpendicular to the welding direction; the thickness of the body portion 21 is Emm along the first direction; satisfying: bmm < Emm.

[0099] By controlling the weld penetration width bmm of the welded part 3 to be less than the thickness Emm of the body part 21, the expansion range of the heat-affected zone is effectively limited, and the body part of the cover plate 2 is prevented from deteriorating or deforming due to excessive heating, thereby maintaining the structural integrity of the cover plate 2.

[0100] In some embodiments, the welding direction is perpendicular to the first direction.

[0101] Ensure that the melt depth extends along the optimal path within the interface between shell 1 and cover plate 2, reducing the risk of warping and improving overall dimensional stability.

[0102] In some embodiments, the welded portion 3 forms a closed-loop structure around the cover plate 2 in the circumferential direction. That is, by continuous circumferential welding, a closed annular weld is formed, which effectively improves the connection strength and sealing performance; ensures the continuity and uniformity of the welded area, and prevents the generation of leakage paths.

[0103] According to an embodiment of the present invention, in another aspect, an electrical device is also provided, comprising: The main body of the electrical device, and the battery cells as described above that are electrically connected to the main body of the electrical device.

[0104] In this embodiment, the electrical device can be a battery pack, electric vehicle, electric ship, aircraft, electric device, energy storage device, laptop, aerospace equipment, etc.

[0105] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Although embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and all such modifications and variations fall within the scope defined by the present invention.

Claims

1. A battery cell, characterized in that, include: The shell (1) has an opening (11) with the opening direction of the opening (11) being a first direction; the shell (1) forms a shell top surface (12) at the end face of the opening (11) along the first direction. A cover plate (2) is provided in the opening (11) of the housing (1). The cover plate (2) includes a body part (21) and an overlapping part (22) extending from the body part (21) in a direction perpendicular to the first direction. The overlapping part (22) abuts against the top surface (12) of the housing in the first direction. The welding part (3) is adapted to weld the shell (1) to the cover plate (2). The welding part (3) forms a molten first end (31) and a molten second end (32). The direction from the molten first end (31) to the molten second end (32) is the welding direction. On the plane perpendicular to the welding direction, the orthographic projection area of ​​the molten first end (31) is greater than the orthographic projection area of ​​the molten second end (32). Along the orthographic projection plane perpendicular to the welding direction, the orthographic projection of the welding part (3) is located within the orthographic projection range of the body part (21). Along the welding direction, the molten second end (32) is located within the area of ​​the body portion (21).

2. The battery cell according to claim 1, characterized in that, In one of the cross sections perpendicular to the extension direction of the welded part (3), the area of ​​the region where the welded part (3) overlaps with the shell (1) is S1 mm², the total area of ​​the welded part (3) is S2 mm², and satisfies 0.1 ≤ S1 / S2 ≤ 0.

45.

3. The battery cell according to claim 1, characterized in that, Along the first direction, the thickness of the overlapping portion (22) is C mm, satisfying: 0.3 mm ≤ C mm ≤ 1.0 mm; And / or, along the direction perpendicular to the first direction, the length of the overlapping portion (22) is Dmm, satisfying: 0.3mm≤Dmm≤1.2mm.

4. The battery cell according to claim 1, characterized in that, Along the first direction, the thickness of the body part (21) is Emm, which satisfies: 0.6mm≤Emm≤4.0mm.

5. The battery cell according to claim 1, characterized in that, Along the direction perpendicular to the first direction, the wall thickness of the shell (1) is F mm, which satisfies: 0.2 mm ≤ F mm ≤ 1.19 mm.

6. The battery cell according to any one of claims 1 to 5, characterized in that, The thickness of the body part (21) is greater than the wall thickness of the shell (1).

7. The battery cell according to any one of claims 1 to 5, characterized in that, Along the first direction, the housing (1) includes a first wall thickness portion (13) and a second wall thickness portion (14), wherein the first wall thickness portion (13) is disposed along the first direction on the side of the second wall thickness portion (14) near the overlapping portion (22); Along the direction perpendicular to the first direction, the wall thickness of the first wall thickness portion (13) is greater than the wall thickness of the second wall thickness portion (14).

8. The battery cell according to claim 7, characterized in that, Along the direction perpendicular to the first direction, the wall thickness of the first wall thickness portion (13) is G mm, which satisfies: 0.2 mm ≤ G mm ≤ 1.19 mm; And / or, the wall thickness of the second wall thickness portion (14) is Hmm, satisfying: 0.15mm≤Hmm≤1.1mm.

9. The battery cell according to claim 7, characterized in that, Along the first direction, the wall thickness of the first wall thickness portion (13) is G mm; along the first direction, the thickness of the body portion (21) is E mm, satisfying: 0.05≤G / E≤1.

6.

10. The battery cell according to any one of claims 1 to 5, characterized in that, Along the welding direction, the weld depth length of the weld (3) is amm; along the direction perpendicular to the welding direction, the weld depth width of the weld (3) is bmm; wherein, amm > bmm.

11. The battery cell according to any one of claims 1 to 5, characterized in that, The minimum distance between the welded part (3) and the edge of the cover plate (2) on the side away from the shell (1) along the first direction is J mm, which satisfies: 0 mm ≤ J mm ≤ 0.5 mm.

12. The battery cell according to any one of claims 1 to 5, characterized in that, Along the welding direction, the weld depth of the weld (3) is amm; along the direction perpendicular to the first direction, the wall thickness of the shell (1) is Fmm; satisfying: amm>Fmm.

13. The battery cell according to any one of claims 1 to 5, characterized in that, Along the welding direction perpendicular to the welding direction, the weld depth width of the welded part (3) is bmm; along the first direction, the thickness of the body part (21) is Emm; satisfying: bmm < Emm.

14. The battery cell according to any one of claims 1 to 5, characterized in that, The welding direction is perpendicular to the first direction.

15. The battery cell according to any one of claims 1 to 5, characterized in that, The welded part (3) forms a closed-loop structure around the cover plate (2) in the circumference.

16. An electrical appliance, characterized in that, include: The electrical device body and the battery cell as described in any one of claims 1 to 15, which is electrically connected to the electrical device body.

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