Welding method, battery cell, battery pack and electric equipment

Abstract

The invention discloses a welding method, a battery cell, a battery pack and electric equipment. The welding method is used for controlling welding equipment to perform welding operation on a welding battery cell. The battery cell comprises a shell, a first cover plate and a second cover plate, and the first cover plate and the second cover plate are located at the two ends of the shell respectively; the welding method comprises the steps that a first welding track for welding the first cover plate and the shell and a second welding track for welding the second cover plate and the shell are determined; the first welding track is divided into M first welding sub-sections, and the second welding track is divided into M welding sub-sections with the number equal to that of the second welding sub-sections; m > = 1; and the welding equipment is controlled to sequentially and alternately weld the first welding sub-section and the second welding sub-section until the first welding track and the second welding track are welded. According to the welding method provided by the embodiment of the invention, the flatness of the battery cell welding area can be reduced.

Description

Technical Field

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

[0002] Welding is a common processing technique in battery production and assembly. It is required in the preparation of electrode components, the encapsulation of battery cells, and the assembly of battery packs. During the encapsulation of battery cells, welding is used to seal the positive and negative electrode covers to the casing.

[0003] In related technologies, some battery cells have uneven welding areas. Summary of the Invention

[0004] This application provides a welding method, a battery cell, a battery pack, and an electrical device to at least partially solve the above-mentioned technical problems.

[0005] In a first aspect, embodiments of this application provide a welding method for controlling welding equipment to perform welding operations on a battery cell; the battery cell includes a housing, a first cover plate, and a second cover plate, the first cover plate and the second cover plate being located at opposite ends of the housing; the welding method includes: Determine the first welding trajectory between the first cover plate and the housing, and the second welding trajectory between the second cover plate and the housing; The first welding trajectory is divided into M first sub-welding segments, and the second welding trajectory is divided into M second sub-welding segments; M≥1; The welding equipment is controlled to alternately weld the first sub-welding segment and the second sub-welding segment in sequence until the welding of the first welding trajectory and the second welding trajectory is completed.

[0006] By adopting the above scheme, the welding heat of the first cover plate and the second cover plate can be dissipated alternately through alternating welding, avoiding excessive local temperature caused by prolonged welding on one side. This can reduce unevenness of the cell shell opening caused by uneven thermal expansion and contraction, reduce the flatness deviation of the battery after welding, thereby reducing the mechanical assembly difficulty in the cell assembly process, reducing uneven contact, stacking deviation or decreased module rigidity, and improving assembly quality.

[0007] In one embodiment, before dividing the first welding trajectory into M first sub-welding segments and the second welding trajectory into M second sub-welding segments, the method further includes: The value of M is determined based on the ratio W / H of the width W of the battery cell to the length H of the battery cell.

[0008] By adopting the above scheme, the number of segments can be determined based on the length-to-width ratio of the battery cell, which can improve the control effect of the battery cell flatness.

[0009] In one embodiment, determining the value of M based on the ratio W / H of the width W of the battery cell to the length H of the battery cell includes: In the case of 0.15 ≤ W / H < 0.27, determine M ≥ 2; or, In the case of 0.27 ≤ W / H < 0.42, determine M ≥ 3; or, Given that 0.42 ≤ W / H, we determine that M ≥ 4.

[0010] By adopting the above scheme, the number of welding segments is determined according to the W / H range, so that the welding process can be matched with the structural characteristics of the battery cell. When welding battery cells with different length-to-width ratios, the reasonable number of segments can promote uniform heat dissipation and stress release, thereby stably controlling the flatness of the battery cell.

[0011] In one embodiment, the method further includes: Adjust the clamping force applied to the first cover plate and the second cover plate according to the current sub-welding segment to be welded.

[0012] By adopting the above scheme, the force during the welding process can be more balanced through dynamic adjustment of the clamping force, which further optimizes the control effect of the cell flatness and avoids damage to the cell caused by improper clamping force, thereby improving the stability of the welding process and the reliability of the welding quality.

[0013] In one embodiment, adjusting the clamping force applied to the first cover plate and the second cover plate according to the current sub-welding segment to be welded includes: When the current sub-welding segment is the first sub-welding segment, increase the clamping force applied to the first region of the first cover plate and decrease the clamping force applied to the second region of the second cover plate; or, When the current sub-welding segment is the second sub-welding segment, the clamping force applied to the first region of the first cover plate is reduced, and the clamping force applied to the second region of the second cover plate is increased; The first region and the second region are symmetrically arranged with respect to the geometric center of the shell.

[0014] By adopting the above scheme and adjusting the clamping force in the opposite direction for symmetrical areas, the uniformity of stress distribution during welding can be improved, local thermal deformation can be suppressed, the flatness of the battery cell can be better controlled, and potential damage to the internal structure of the battery cell caused by excessive clamping can be avoided.

[0015] In one embodiment, during the alternating welding of the first sub-welding segment and the second sub-welding segment, the welding power of the latter sub-welding segment is less than or equal to the welding power of the former sub-welding segment.

[0016] By adopting the above scheme, the welding power can be dynamically adjusted according to the welding process, which can adapt to the temperature changes of the battery cell and avoid thermal deformation caused by excessive heat input. This can reduce the flatness deviation of the battery cell and improve the welding quality.

[0017] In one embodiment, the welding equipment includes a laser; Wherein, the laser power of the laser ranges from 1KW to 3.5KW; and / or, The welding speed ranges from 0 mm / s to 300 mm / s; and / or, The pulse frequency ranges from 1 to 1000 Hz; and / or, The pulse width ranges from 1 to 10 ms; and / or, The defocusing amount ranges from -1.5 to 1 mm; and / or, The flow rate of the protective gas ranges from 0 to 50 L / min.

[0018] By adopting the above scheme and controlling the range of values ​​of various key parameters of the welding equipment, the stability and consistency of welding quality can be ensured.

[0019] Secondly, embodiments of this application provide a battery cell, including a housing, a first cover plate, and a second cover plate, wherein the first cover plate, the second cover plate, and the housing are welded together by any one of the welding methods described in the embodiments of the first aspect.

[0020] By adopting the above scheme and welding method for cell welding and assembly, the flatness and structural stability of the cells can be improved, the assembly difficulty in the cell assembly process can be reduced, and the overall performance of the battery pack can be improved.

[0021] Thirdly, embodiments of this application provide a battery pack including the battery cells as described in any one of the embodiments of the second aspect.

[0022] Fourthly, embodiments of this application provide an electrical device including a battery cell as described in any one of the embodiments of the second aspect, or a battery pack as described in any one of the embodiments of the third aspect. Attached Figure Description

[0023] 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.

[0024] 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.

[0025] Figure 1 This is a flowchart of a welding method provided in an embodiment of this application; Figure 2 This is another flowchart of the welding method provided in an embodiment of this application; Figure 3 This is a schematic diagram of the battery cell structure provided in an embodiment of this application; Figure 4 This is a schematic diagram of the clamping device used in the welding method provided in the embodiments of this application; Figure 5 This is a schematic diagram showing the relative positions of the cell welding area and the clamping device provided in an embodiment of this application.

[0026] Explanation of reference numerals in the attached figures: 300, Battery cell; 400, Housing pressure plate; 500, Top cover pressure plate; 600, Welding area. Detailed Implementation

[0027] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. Furthermore, it should be understood that the specific embodiments described herein are only for illustration and explanation of this application and are not intended to limit this application.

[0028] In this application, unless otherwise stated, directional terms such as "upper" and "lower" generally refer to the upper and lower positions of the device in its actual use or operating state, specifically the drawing directions in the accompanying drawings; while "inner" and "outer" refer to the outline of the device. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". The terms first, second, third, etc., are used merely as illustrative purposes and do not impose numerical requirements or establish a numerical order.

[0029] References such as “one embodiment” or “some embodiments” as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the terms “comprising,” “including,” “having,” and variations thereof, as used in this specification, mean “including, but not limited to,” unless otherwise specifically emphasized.

[0030] In this application, "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural.

[0031] Blade batteries are a type of battery with a flat, elongated cell structure, typically long, narrow, and thin. Blade battery cells usually employ a dual-sided tab structure, meaning the tabs extend from opposite ends of the cell (usually along its length) outwards. Correspondingly, the positive and negative electrode sides of the cell casing have openings, and the positive and negative electrode covers need to be fully welded to the casing's circumference to achieve a seal. In related technologies, the entire weld seam is usually formed in one step. However, because the welding sequence of the positive and negative electrodes is difficult to synchronize perfectly, there is a significant temperature gradient between the welded and unwelded areas. The cooling and contraction after welding at one end can exert a tensile force on the unwelded area at the other end, causing an imbalance in the stress on the casing opening. This leads to unevenness in the welded area, increasing flatness deviation, and consequently causing problems such as uneven contact and stacking deviations during cell assembly, even posing safety risks.

[0032] In view of this, embodiments of this application provide a welding method, a battery cell 300, a battery pack, and an electrical device to at least partially solve the above-mentioned technical problems.

[0033] refer to Figure 1 and Figure 3 In a first aspect, embodiments of this application provide a welding method for controlling welding equipment to perform welding operations on a battery cell 300; the battery cell 300 includes a housing, a first cover plate, and a second cover plate, the first cover plate and the second cover plate being located at opposite ends of the housing; the welding method includes: S102. Determine the first welding trajectory between the first cover plate and the housing, and the second welding trajectory between the second cover plate and the housing.

[0034] S104. Divide the first welding trajectory into M segments (first sub-welding segments) and the second welding trajectory into M segments (second sub-welding segments); M ≥ 1.

[0035] S106. Control the welding equipment to alternately weld the first sub-welding segment and the second sub-welding segment in sequence until the welding of the first welding trajectory and the second welding trajectory are completed.

[0036] The first cover plate and the second cover plate can be the positive electrode cover plate and the negative electrode cover plate, respectively. The first welding trajectory refers to the path through which the first cover plate and the shell need to be welded together, and its shape and length are adapted to the connection edge between the first cover plate and the shell; similarly, the second welding trajectory is the welding path between the second cover plate and the shell. The first sub-welding segment is a single welding unit after segmenting the first welding trajectory, and the second sub-welding segment is a single welding unit after segmenting the second welding trajectory, where M is the number of segments. The lengths of the M sub-welding segments can be equal or unequal. The lengths of the symmetrical first and second sub-welding segments can be equal or unequal. Alternating welding of the first and second sub-welding segments allows the heat from the welding process to be alternately distributed and input from the first and second cover plate sides, reducing excessive expansion caused by local high temperatures and reducing deformation caused by residual stress after cooling.

[0037] For example, alternatingly welding the first sub-welding segment and the second sub-welding segment can be done by first welding a section of the first sub-welding segment, then welding a section of the second sub-welding segment, and so on, to complete the first welding trajectory and the second welding trajectory. The first sub-welding segment welded in this process can be either the first sub-welding segment or the second sub-welding segment. Welding can begin from either the positive electrode side cover plate or the negative electrode side cover plate. The specific location of the cover plate forming the first sub-welding segment and the location of the first sub-welding segment are not limited in this application.

[0038] For example, the positions of the first sub-welded segment and the second sub-welded segment can be symmetrical about the geometric center of the shell. That is, after the first sub-welded segment is welded, the second sub-welded segment, which is diagonally opposite to the first sub-welded segment, is then welded. Since the weld will generate a pulling force towards the inside of the cell 300 due to thermal shrinkage during welding, the sub-welded segments are welded in a diagonal relationship in sequence. This can make the shrinkage force of the first sub-welded segment opposite to the shrinkage force of the second sub-welded segment during each alternating welding process, thereby suppressing the unevenness of the welding area 600 caused by the shrinkage force.

[0039] By adopting the above scheme, the welding heat of the first cover plate and the second cover plate can be dissipated alternately through alternating welding, avoiding excessive local temperature caused by prolonged welding on one side. This can reduce the unevenness of the cell 300 shell opening caused by uneven thermal expansion and contraction, reduce the flatness deviation of the battery after welding, thereby reducing the mechanical assembly difficulty in the cell 300 assembly process, reducing uneven contact, stacking deviation or decrease in module rigidity, and improving the assembly quality.

[0040] In one embodiment, reference Figure 2 Before dividing the first welding trajectory into M first sub-welding segments and the second welding trajectory into M second sub-welding segments, the method further includes: S101. Determine the value of M based on the ratio W / H of the width W of the battery cell 300 to the length H of the battery cell 300.

[0041] The length H of the battery cell 300 refers to the vertical distance between the positive and negative terminals of the battery cell 300. The W / H ratio reflects the length-to-width ratio of the battery cell 300. Different proportions of the battery cell 300 result in different heat distribution and stress conditions during the welding process. Therefore, different number of segments M can be set according to the length-to-width ratio of the battery cell 300.

[0042] It is understandable that the W / H of the battery cell 300 affects the degree of thermal deformation during the welding process. When the length of the battery cell 300 is equal, the larger its width, the longer the length of the first welding trajectory and the second welding trajectory, the easier it is for heat to concentrate during continuous welding, and the more obvious the thermal deformation. Therefore, in this embodiment, more segments are set for the battery cell 300 with a larger W / H to disperse heat and stress.

[0043] By adopting the above scheme, the number of segments is determined based on the length-to-width ratio of the battery cell 300, which can improve the control effect of the flatness of the battery cell 300.

[0044] In one embodiment, the value of M is determined based on the ratio W / H of the width W of the cell 300 to the length H of the cell 300, including: In the case of 0.15 ≤ W / H < 0.27, determine M ≥ 2; or, In the case of 0.27 ≤ W / H < 0.42, determine M ≥ 3; or, Given that 0.42 ≤ W / H, we determine that M ≥ 4.

[0045] Specifically, when 0.15≤W / H<0.27, the width of cell 300 is relatively small, and two-segment welding can meet the heat dissipation requirements; when 0.27≤W / H<0.42, the width of cell 300 increases, and at least three-segment welding is required to effectively control thermal deformation; when W / H≥0.42, cell 300 is relatively wide, and heat concentration and stress problems are more prominent, so at least four-segment welding is required.

[0046] By adopting the above scheme, the number of welding segments is determined according to the W / H range, so that the welding process can be matched with the structural characteristics of the battery cell 300. When welding battery cells 300 with different length-to-width ratios, the reasonable number of segments can promote uniform heat dissipation and stress release, thereby stably controlling the flatness of the battery cell 300.

[0047] In one embodiment, the method further includes: Adjust the clamping force applied to the first and second cover plates according to the current sub-welding segment to be welded.

[0048] The clamping force refers to the pressure applied to the cover plate during welding. Its function is to suppress warping caused by welding shrinkage, ensure the fit between the cover plate and the shell, and thus guarantee welding quality. The clamping force can be applied through components such as a contour plate. The current sub-welding section refers to the sub-welding section where the welding equipment is currently welding or about to weld. By dynamically adjusting the clamping force, it can adapt to the stress requirements of different welding areas.

[0049] It is understandable that during the welding of different sub-sections, the corresponding cover plate area will experience localized thermal deformation due to the welding heat. Adjusting the clamping force can specifically suppress warping in that area, while simultaneously reserving sufficient stress release space for other areas. This avoids cover plate deformation or internal structural damage caused by excessive clamping, and also prevents insufficient clamping force from failing to suppress warping. During the adjustment of the clamping force, the clamping force applied to the entire cover plate can be adjusted, or only the clamping force can be adjusted in the vicinity of the current sub-section area and in areas on another cover plate that are symmetrical to the current sub-section area.

[0050] refer to Figure 4 and Figure 5 For example, a housing pressure plate 400 and a top cover pressure plate 500 can be respectively provided on the outer surfaces of the housing and top cover of the battery cell 300 to form a four-sided or six-sided constraint on the battery cell 300. The area of ​​the housing pressure plate 400 and the top cover pressure plate 500 corresponds to the housing and top cover, respectively. There is a gap between the pressure plates, thereby reserving clearance space for the laser path and weld seam tracking sensor, and preventing the pressure plates from obstructing the welding. When the welding equipment is about to weld the first sub-welding segment of the first section, the clamping force applied to the corresponding area of ​​the first cover plate can be adjusted to 500N, and the clamping force applied to the corresponding area of ​​the second cover plate can be adjusted to 400N; when switching to welding the second sub-welding segment of the first section, the clamping force in the corresponding area of ​​the first cover plate can be adjusted to 400N, and the clamping force in the corresponding area of ​​the second cover plate can be adjusted to 500N.

[0051] By adopting the above scheme, the force during the welding process can be more balanced through dynamic adjustment of the clamping force, which further optimizes the control effect of the flatness of the battery cell 300, while avoiding damage to the battery cell 300 caused by improper clamping force, and improving the stability of the welding process and the reliability of the welding quality.

[0052] In one embodiment, adjusting the clamping force applied to the first and second cover plates according to the current sub-welding segment to be welded includes: When the current sub-welding segment is the first sub-welding segment, increase the clamping force applied to the first region of the first cover plate and decrease the clamping force applied to the second region of the second cover plate; or, When the current sub-welding segment is the second sub-welding segment, reduce the clamping force applied to the first region on the first cover plate and increase the clamping force applied to the second region on the second cover plate; The first and second regions are symmetrically arranged with respect to the geometric center of the shell.

[0053] The first region is the area on the first cover plate corresponding to the first sub-welded segment currently being welded, and the second region is the area on the second cover plate that is symmetrical to the first region relative to the geometric center of the shell. The symmetrically arranged first and second regions experience symmetrical stress and thermal deformation during welding, and stress balance and cancellation can be achieved by adjusting the clamping forces of the two regions in opposite directions.

[0054] It is understandable that when the current sub-welding segment is welded, the corresponding area will expand and contract due to heat input. Increasing the clamping force in this area can effectively suppress warping. Meanwhile, the symmetrical area is not being welded at this time. Reducing its clamping force can reserve a certain amount of stress release space for the overall structure, avoid excessive constraint on the symmetrical area leading to increased deformation of the current welding area 600, and thus achieve overall stress balance.

[0055] By adopting the above scheme and adjusting the clamping force in the opposite direction for the symmetrical area, the uniformity of stress distribution during welding can be improved, local thermal deformation can be suppressed, the flatness of the battery cell 300 can be better controlled, and potential damage to the internal structure of the battery cell 300 caused by excessive clamping can be avoided.

[0056] In one embodiment, during the alternating welding of the first sub-welding segment and the second sub-welding segment, the welding power of the latter sub-welding segment is less than or equal to the welding power of the former sub-welding segment.

[0057] Welding power refers to the energy output of the welding equipment. For example, in laser welding, the welding power is the energy output of the laser in the welding equipment. Its magnitude directly affects the heat input during the welding process. As the welding process progresses, the overall temperature of the battery cell 300 gradually increases. If the same welding power is maintained, the heat input of the subsequent welding area 600 will be relatively excessive due to the accumulation of heat in the early stage, leading to aggravated thermal deformation. Therefore, in this embodiment, the welding power of each sub-welding segment is gradually reduced, or the welding power of sub-welding segments located on different welding trajectories is made equal, which can control the total heat input during the welding process, thereby controlling the thermal deformation of the shell and cover plate.

[0058] For example, in a three-stage welding process, the welding power of the first sub-welding segment of the first stage can be set to 2.8kW, the welding power of the second sub-welding segment of the first stage can be set to 2.7kW, the welding power of the first sub-welding segment of the second stage can be set to 2.6kW, the welding power of the second sub-welding segment of the second stage can be set to 2.5kW, the welding power of the first sub-welding segment of the third stage can be set to 2.4kW, and the welding power of the second sub-welding segment of the third stage can be set to 2.3kW. If the initial temperature of the 300 cell is low, the power of the first two sub-welding segments can be kept consistent, and the power of the third stage can be appropriately reduced, such as the first and second stages being 2.8kW and the third stage being 2.6kW.

[0059] Understandably, since the temperature of the battery cell 300 will continuously rise during the welding process, the battery cell 300 already has a certain preheating foundation when welding subsequent sub-sections. Therefore, the required welding power can be appropriately reduced compared to the initial stage to avoid problems such as excessive heat input leading to excessive penetration and aggravated deformation. The power of the subsequent sub-section is less than or equal to that of the previous sub-section, which can ensure the balance of heat input throughout the welding process and achieve stable welding.

[0060] By adopting the above scheme, the welding power can be dynamically adjusted according to the welding process to adapt to the temperature changes of the battery cell 300, avoid the problem of thermal deformation caused by excessive heat input, thereby reducing the flatness deviation of the battery cell 300 and improving the welding quality.

[0061] In one embodiment, the welding equipment includes a laser; The laser power of the laser ranges from 1 kW to 3.5 kW; and / or, The welding speed ranges from 0 mm / s to 300 mm / s; and / or, The pulse frequency ranges from 1 to 1000 Hz; and / or, The pulse width ranges from 1 to 10 ms; and / or, The defocusing amount ranges from -1.5 to 1 mm; and / or, The flow rate of the protective gas ranges from 0 to 50 L / min.

[0062] The laser is the core component of laser welding equipment, used to output the laser energy required for welding. Laser power determines the heat input intensity of the weld, while welding speed refers to the speed at which the welding torch moves along the welding trajectory. Both laser power and welding speed jointly affect the weld penetration and width. A pulsed mode can be used during welding, which outputs laser energy in high-frequency pulses. Heat dissipates during the pulse intervals, thus reducing overall thermal deformation. Pulse frequency refers to the number of pulses output by the laser per unit time, pulse width refers to the duration of a single pulse, and defocus refers to the distance between the laser focus and the welding surface, affecting the concentration of laser energy. Shielding gas is used to prevent oxidation of the welding area and ensure weld quality; commonly used shielding gases include inert gases such as argon.

[0063] For example, for cell 300 with W / H=0.35, a three-stage welding method can be used, with a laser power of 2.8kW, a welding speed of 100mm / s, a pulse frequency of 500HZ, a pulse width of 5ms, a defocusing amount of -0.5mm, and a shielding gas flow rate of 30L / min. For cell 300 with a smaller size and the same aspect ratio, a three-stage welding method can also be used, with a laser power of 1.5kW, a welding speed of 200mm / s, a pulse frequency of 800HZ, a pulse width of 3ms, a defocusing amount of 0.3mm, and a shielding gas flow rate of 15L / min.

[0064] It is understandable that the above parameter range is determined based on the process requirements and equipment performance for welding the battery cell 300 casing. In practical applications, the parameters can be adjusted within this range according to the specific dimensions, material properties, and welding quality requirements of the battery cell 300 to achieve the best welding results. For example, when welding a thicker casing, a higher laser power and a slower welding speed can be selected; when welding a thinner cover plate, the laser power can be appropriately reduced and the welding speed increased to improve production efficiency.

[0065] By adopting the above scheme and controlling the range of values ​​of various key parameters of the welding equipment, the stability and consistency of welding quality can be ensured.

[0066] The embodiments of this application are further illustrated below with reference to specific examples. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of this application.

[0067] Example 1 The battery cell 300 provided in Example 1 satisfies the following conditions: 0.15≤W / H<0.27. The positive terminal cap and the shell are welded together by a single-stage welding process, and the negative terminal cap and the shell are welded together, with M=1.

[0068] Example 2 The battery cell 300 provided in Example 2 has the same structure as in Example 1, and adopts two-stage welding to form the weld between the positive terminal cap and the shell and the weld between the negative terminal cap and the shell, M=2.

[0069] Example 3 The battery cell 300 provided in Example 3 has the same structure as in Example 1, and uses three-section welding to form the weld between the positive terminal cap and the shell and the weld between the negative terminal cap and the shell, M=3.

[0070] After welding, the flatness deviation of cell 300 was measured by a coordinate measuring machine. The test data are shown in Table 1.

[0071] Table 1

[0072] Example 4 The battery cell 300 provided in Example 4 satisfies the following conditions: 0.27≤W / H<0.42. The positive terminal cap and the shell are welded together by a single-stage welding process, and the negative terminal cap and the shell are welded together, with M=1.

[0073] Example 5 The battery cell 300 provided in Example 5 has the same structure as in Example 4, and adopts two-stage welding to form the weld between the positive terminal cap and the shell and the weld between the negative terminal cap and the shell, M=2.

[0074] Example 6 The battery cell 300 provided in Example 6 has the same structure as in Example 4, and uses three-section welding to form the weld between the positive terminal cap and the shell and the weld between the negative terminal cap and the shell, M=3.

[0075] Example 7 The battery cell 300 provided in Example 7 has the same structure as in Example 4, and uses three-section welding to form the weld between the positive terminal cap and the shell and the weld between the negative terminal cap and the shell, M=4.

[0076] After welding, the flatness deviation of cell 300 was measured by a coordinate measuring machine. The test data are shown in Table 2.

[0077] Table 2

[0078] Example 8 The battery cell 300 provided in Example 8 satisfies the following conditions: W / H≥0.42, and the weld between the positive terminal cap and the shell and the weld between the negative terminal cap and the shell are formed by one-stage welding, with M=1.

[0079] Example 9 The battery cell 300 provided in Example 9 has the same structure as in Example 8, and adopts two-stage welding to form the weld between the positive terminal cap and the shell and the weld between the negative terminal cap and the shell, M=2.

[0080] Example 10 The battery cell 300 provided in Example 10 has the same structure as in Example 8, and uses three-section welding to form the weld between the positive terminal cap and the shell and the weld between the negative terminal cap and the shell, M=3.

[0081] Example 11 The battery cell 300 provided in Example 11 has the same structure as in Example 8, and uses four-segment welding to form the weld between the positive terminal cap and the shell and the weld between the negative terminal cap and the shell, M=4.

[0082] Example 12 The battery cell 300 provided in Example 12 has the same structure as in Example 8, and uses five-segment welding to form the weld between the positive terminal cap and the shell and the weld between the negative terminal cap and the shell, M=5.

[0083] After welding, the flatness deviation of cell 300 was measured by a coordinate measuring machine. The test data are shown in Table 3.

[0084] In the above embodiments, the flatness deviation refers to the maximum difference between the highest and lowest points of the end faces of the positive and negative electrode cover plates connected to the shell after welding, relative to the designed plane. The specific testing process is as follows: the welded battery cell is placed on the worktable of a coordinate measuring machine and fixed with a fixture. The end faces of the positive and negative electrode cover plates of the battery cell are used as the measurement surfaces. A measurement point is set every 30 mm, and a measurement point is set every 15 mm at the weld. The probe is controlled to collect three-dimensional coordinate data point by point according to the planned path, and the Z-axis height value of each measurement point is recorded. The software built into the measuring machine is used to fit all Z-axis data to an ideal plane (to minimize the sum of the squares of the deviations of all measurement points from the plane). The vertical distance from each measurement point to the ideal plane is calculated, and the maximum absolute value among all deviations is taken as the flatness deviation of the battery cell.

[0085] Table 3

[0086] According to the test data in Tables 1 to 3, when the weld between the end cap and the shell is formed in one step, the flatness deviation of cell 300 is relatively large, and the larger the W / H ratio, the greater the flatness deviation. When welding in sections, increasing the number of welding sections can reduce the flatness deviation. While ensuring the flatness deviation meets requirements, the number of welding sections can be minimized to improve production efficiency.

[0087] Secondly, embodiments of this application provide a battery cell 300, including a housing, a first cover plate, and a second cover plate, wherein the first cover plate, the second cover plate, and the housing are welded together by any one of the welding methods described in the embodiments of the first aspect.

[0088] Among them, the 300 cell can be used to form a blade battery.

[0089] By adopting the above scheme and welding method for welding and assembling the battery cell 300, the flatness and structural stability of the battery cell 300 can be improved, the assembly difficulty of the battery cell 300 in the assembly process can be reduced, and the overall performance of the battery pack can be improved.

[0090] Thirdly, embodiments of this application provide a battery pack including a cell 300 as described in any one of the embodiments of the second aspect.

[0091] The battery pack has all the beneficial effects of the aforementioned cell 300, which will not be repeated here.

[0092] Fourthly, embodiments of this application provide an electrical device including a battery cell 300 as described in any one of the embodiments of the second aspect, or a battery pack as described in any one of the embodiments of the third aspect.

[0093] In some embodiments of this application, the electrical equipment can be one of the following: smart wearable devices, mobile communication devices, transportation equipment, and power tools.

[0094] The electrical device has all the beneficial effects of the aforementioned battery pack, which will not be elaborated further in this application.

[0095] 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.

[0096] 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.

[0097] The embodiments, implementation methods, and related technical features of this application can be combined and substituted for each other without conflict.

[0098] 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 welding method, characterized in that, The device is used to control welding equipment to perform welding operations on a battery cell (300); the battery cell (300) includes a housing, a first cover plate, and a second cover plate, the first cover plate and the second cover plate being located at opposite ends of the housing; the welding method includes: Determine the first welding trajectory between the first cover plate and the housing, and the second welding trajectory between the second cover plate and the housing; The first welding trajectory is divided into M first sub-welding segments, and the second welding trajectory is divided into M second sub-welding segments; M≥1; The welding equipment is controlled to alternately weld the first sub-welding segment and the second sub-welding segment in sequence until the welding of the first welding trajectory and the second welding trajectory is completed.

2. The welding method according to claim 1, characterized in that, Before dividing the first welding trajectory into M first sub-welding segments and the second welding trajectory into M second sub-welding segments, the method further includes: The value of M is determined based on the ratio W / H of the width W of the battery cell (300) to the length H of the battery cell (300).

3. The welding method according to claim 2, characterized in that, The step of determining the value of M based on the ratio W / H of the width W of the battery cell (300) to the length H of the battery cell (300) includes: In the case of 0.15 ≤ W / H < 0.27, determine M ≥ 2; or, In the case of 0.27 ≤ W / H < 0.42, determine M ≥ 3; or, Given that 0.42 ≤ W / H, we determine that M ≥ 4.

4. The welding method according to claim 1, characterized in that, The method further includes: Adjust the clamping force applied to the first cover plate and the second cover plate according to the current sub-welding segment to be welded.

5. The welding method according to claim 4, characterized in that, The adjustment of the clamping force applied to the first cover plate and the second cover plate according to the current sub-welding segment to be welded includes: When the current sub-welding segment is the first sub-welding segment, increase the clamping force applied to the first region of the first cover plate and decrease the clamping force applied to the second region of the second cover plate; or, When the current sub-welding segment is the second sub-welding segment, the clamping force applied to the first region of the first cover plate is reduced, and the clamping force applied to the second region of the second cover plate is increased; The first region and the second region are symmetrically arranged with respect to the geometric center of the shell.

6. The welding method according to any one of claims 1 to 5, characterized in that, During the alternating welding of the first sub-welding segment and the second sub-welding segment, the welding power of the latter sub-welding segment is less than or equal to the welding power of the former sub-welding segment.

7. The welding method according to any one of claims 1 to 5, characterized in that, The welding equipment includes a laser; Wherein, the laser power of the laser ranges from 1KW to 3.5KW; and / or, The welding speed ranges from 0 mm / s to 300 mm / s; and / or, The pulse frequency ranges from 1 to 1000 Hz; and / or, The pulse width ranges from 1 to 10 ms; and / or, The defocusing amount ranges from -1.5 to 1 mm; and / or, The flow rate of the protective gas ranges from 0 to 50 L / min.

8. A battery cell (300), characterized in that, It includes a housing, a first cover plate, and a second cover plate, wherein the first cover plate, the second cover plate, and the housing are welded together by the welding method as described in any one of claims 1 to 7.

9. A battery pack, characterized in that, Includes the battery cell (300) as described in claim 8.

10. An electrical appliance, characterized in that, It includes the cell (300) as described in claim 8, or the battery pack as described in claim 9.

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