Battery, battery pack, electric device, and inspection method

Abstract

The present disclosure relates to the technical field of batteries, and relates to a battery, a battery pack, a power consumption device and a testing method. The battery has a shell and a battery cell arranged in the shell. The shell comprises a shell body and a cover plate. The shell body has an end wall and a side wall surrounding the end wall. The cover plate is opposite to the end wall. A welding area is formed between the side wall and the cover plate. In a cross section, a ratio of an overlapping area of the welding area and a triangular area to an area of the triangular area is greater than 0.05. The welding area has a first lowest point with a peripheral surface of the cover plate and a second lowest point with a second surface. The triangular area comprises a first side extending from the first lowest point to the second lowest point, a second side extending from the first lowest point in a perpendicular direction of the peripheral surface of the cover plate, and a third side extending from the second lowest point in a perpendicular direction of an outer surface of the side wall, and the first surface and the second surface are one and the other of the outer surface and the surface, respectively. The welding area reduces a risk of welding failure of the shell of the battery caused by being perpendicular to the second surface.

Description

Technical Field

[0001] This disclosure relates to the field of batteries, and in particular to a battery, a battery pack having the battery, an electrical device having the battery or the battery pack, and a testing method applicable to the battery. Background Technology

[0002] Batteries with a rectangular casing are known. Based on the cuboid shape of the casing, these batteries are also called prismatic batteries. Prismatic batteries are widely used in electrical devices such as those in passenger vehicles. Typically, multiple prismatic batteries are arranged in a battery pack along a direction perpendicular to their long sidewalls to form a battery array. The battery array is arranged in a battery pack with the short sidewalls of the prismatic batteries facing each other to supply power to the electrical device.

[0003] The welded area is formed between the cover plate and the side wall of the outer casing. The internal boundary of the welded area is the weak point of the welded area. During battery vibration, the risk of cracking in this welded area increases, leading to communication between the inside and outside of the battery and causing thermal runaway safety risks, which affects the safety of battery use. Summary of the Invention

[0004] In view of this, in a first aspect, the present disclosure provides a battery to at least solve the problem of weld failure at the weld joint between the casing and the cover plate, or at least reduce the risk of weld failure at the weld joint between the casing and the cover plate. The battery includes a casing and a cell disposed therein. The casing includes a housing and a cover plate. The housing includes an end wall and a side wall surrounding the end wall. The cover plate is perpendicular to the side wall, sealing the side of the housing away from the end wall, and is welded to the side wall to form a welded area. In a cross-section of the welded area perpendicular to the width direction of the cover plate, the area overlapping the welded area with a triangular region is S1, in mm. 2 The area of ​​the triangular region is S², in mm. 2 S1 / S2≥0.05, wherein the welding area has a first lowest point in the direction perpendicular to the first surface, the welding area and the outer surface of the sidewall have a second lowest point, the triangular region includes a first side extending from the first lowest point to the second lowest point, a second side extending from the first lowest point along the perpendicular direction of the first surface, and a third side extending from the second lowest point along the perpendicular direction of the second surface, the first surface is one of the outer surface and the surface, the second surface is the other of the outer surface and the surface, and the welding heat source points to the first surface.

[0005] The molten cover plate and the molten sidewalls flow and merge to form a molten pool. The weld zone is formed by the cooling and solidification of the molten pool. The internal interface of the weld zone is the boundary between the molten and unmolten cover plate, and also the boundary between the molten and unmolten sidewalls. The strength at the internal interface of the weld zone is usually lower than the strength at other locations in the weld zone. Therefore, it is necessary to ensure that the weld zone forms a continuous and uniform internal interface with respect to the sidewalls and cover plate, and to avoid the internal interface directly bearing large tensile or shear forces.

[0006] When the thermal conductivity of the cover plate and the sidewall differs significantly, the one with lower thermal conductivity melts rapidly, while the one with higher thermal conductivity melts slowly. This results in an uneven distribution of the molten pool, leading to an uneven distribution of the internal interface. Taking the sidewall's thermal conductivity as greater than that of the cover plate as an example, in the cross-section of the welding area 200 perpendicular to the width direction of the cover plate 106, the volume of the melted sidewall is smaller than the volume of the melted cover plate. The welding area is distributed closer to the cover plate, resulting in a smaller internal interface formed between the welding area and the sidewall. Therefore, the connection strength between the welding area and the sidewall is lower, and the battery is more prone to cracking at this location.

[0007] Furthermore, due to the slow melting of the sidewalls, the profile of the internal interface of the weld area adjacent to the sidewalls tends to extend along the top surface or edge of the sidewalls, thus making it easier to form straight edges perpendicular to the outer surface of the sidewalls. Additionally, because there is a gap between the cover plate and the sidewalls, the cover plate, which melts first, needs to flow across the gap to transfer heat to the sidewalls, further reducing the volume of sidewall melting. This makes it even easier for the profile of the internal interface to extend along the top surface or edge of the sidewalls, thus making it easier to form straight edges. Since the forces acting on the battery typically have a large component in the direction perpendicular to the outer surface of the sidewalls or the surface of the cover plate—for example, batteries typically experience shear forces perpendicular to the short sidewalls—the internal interface between the weld area and the sidewalls is prone to crack initiation at these straight edges. Furthermore, stress concentration is likely to occur near the straight edges at the internal interface of the weld area. This makes the internal interface between the weld area and the sidewalls more susceptible to cracking at the straight edges, increasing the risk of battery welding failure.

[0008] By specifying that the ratio of the area of ​​the weld zone overlapping with a triangular region conforming to the contour of an ideal internal interface to the area of ​​that triangular region is greater than 0.05, this disclosure ensures that both sides of the internal interface of the battery weld zone have sufficient dimensions, and also eliminates or at least avoids the presence of large straight edges in the internal interface. Therefore, the weld zone provided by this disclosure has improved strength and a more uniform stress distribution, thereby reducing the risk of weld failure in the battery.

[0009] In addition, since the triangular region conforms to the ideal contour of the internal interface of the welding zone, by controlling the difference in geometric shape between the internal interface of the welding zone and the triangular region, especially the first side of the triangular region, the heat input distribution, molten pool flow and molten pool cooling process during the welding process can be inferred simply and intuitively. This helps to find areas for improvement in the welding process and thus iterate the production process.

[0010] Secondly, this disclosure provides a battery pack including at least one battery according to the first aspect. Because of the aforementioned battery, the battery pack provided by this disclosure has similar beneficial effects to the battery of the first aspect, which will not be elaborated further here.

[0011] Thirdly, this disclosure provides an electrical device including at least one battery according to the first aspect and / or at least one battery pack according to the second aspect. The battery and / or the battery pack stores or provides electrical energy.

[0012] Fourthly, this disclosure provides an inspection method applicable to inspecting the battery described in the first aspect of this disclosure. The method includes: obtaining the battery; in a cross-section perpendicular to the welding movement direction of the welded area formed between the cover plate and the sidewall of the battery, when the ratio of the area of ​​the welded area overlapping with a triangular region to the area of ​​the triangular region is greater than 0.05, the battery is determined to be a good product. Otherwise, the battery is determined to be a bad product. The triangular region includes a first side extending from a first lowest point to a second lowest point, a second side extending from the first lowest point along a perpendicular direction to the plane of the cover plate away from the surface of the battery cell, and a third side extending from the second lowest point along a perpendicular direction to the plane of the outer surface of the sidewall. The welded area has a maximum penetration depth in a direction perpendicular to the first surface. The welded area has a first lowest point on the circumferential surface of the cover plate and a second lowest point on the second surface. Therefore, the method provided by this disclosure has a simpler operation compared to traditional inspection methods such as metallographic analysis and tensile testing, making product inspection more intuitive, faster, and more accurate. This greatly simplifies the battery quality control process and improves inspection efficiency, consistency, and traceability. With the help of technologies such as optical scanning and image analysis, the inspection method provided in this disclosure can also achieve non-destructive testing of the battery welding area. Attached Figure Description

[0013] It should be understood that the following figures only illustrate certain embodiments of this disclosure and should not be construed as limiting the scope.

[0014] It should be understood that the same or similar reference numerals are used in the accompanying drawings to denote the same or similar elements.

[0015] It should be understood that the accompanying drawings are only schematic, and the dimensions and scales of the elements in the drawings are not necessarily precise.

[0016] Figure 1 This is a schematic diagram of the battery structure provided in this disclosure.

[0017] Figure 2 This is a schematic diagram of the exploded structure of the battery provided in this disclosure.

[0018] Figure 3 for Figure 1 A cross-sectional view of the battery along line AA.

[0019] Figure 4 for Figure 3 A cross-sectional view of the middle battery along line BB.

[0020] Figure 5for Figure 3 An enlarged view of section C, showing that the welding zone is formed by top welding.

[0021] Figure 6 for Figure 5 A magnified view of a portion of the area, showing that the welding zone is formed using a top welding method.

[0022] Figure 7 for Figure 3 Another enlarged view of part C shows that the welding area is formed by side welding.

[0023] Figure 8 for Figure 7 A magnified view of a portion of the image, showing the welding zone formed using a side-welding method.

[0024] Figure 9 for Figure 3 Enlarged view of part D.

[0025] Figure 10 for Figure 1 A schematic diagram of the battery casing.

[0026] Figure 11 for Figure 1 A schematic diagram of the structure of the middle cover plate.

[0027] Figure 12 for Figure 11 A cross-sectional view of the middle cover plate along line EE.

[0028] Figure 13 This is a cross-sectional view of another battery along line AA provided in this disclosure.

[0029] Figure 14 for Figure 13 An enlarged view of part F, showing that the welding zone is formed by top welding.

[0030] Figure 15 for Figure 14 A magnified view of a portion of the area, showing that the welding zone is formed using a top welding method.

[0031] Figure 16 Another sectional view of the cover plate along the EE line provided in this disclosure.

[0032] Figure 17 This is a structural schematic diagram of another housing provided in this disclosure.

[0033] Figure 18 for Figure 16 middle cover plate and Figure 17 A cross-sectional view of the battery formed by assembling the inner casing along line AA.

[0034] Figure 19 for Figure 18 Enlarged view of the G part of the battery.

[0035] Figure 20 This is an exploded structural diagram of a battery pack provided in this disclosure.

[0036] Figure 21 for Figure 20 A top view of the battery pack.

[0037] Figure 22 for Figure 20 Side view of the battery pack.

[0038] Figure 23 A schematic diagram of the electrical equipment provided in this disclosure.

[0039] Figure 24 A flowchart of the testing method provided in this disclosure.

[0040] Figure 25 This is an industrial CT image of a weld bead on the short side of a battery casing.

[0041] Figure 26 An industrial CT image of the weld bead on the short side of another battery casing. Detailed Implementation

[0042] Numerous specific details are set forth below to provide an understanding of the structure, function, and use of the embodiments described and illustrated in the specification and figures. It is to be understood that the embodiments described and illustrated herein are non-limiting examples, and thus it will be appreciated that the particular structural and functional details disclosed herein are representative and exemplary. Variations and changes may be made to these embodiments without departing from the scope of the claims.

[0043] Specifically, refer to Figure 1 and Figure 2This disclosure provides a battery 100 capable of storing and providing electrical energy. The battery 100 may include a rectangular casing 102 and a cell 104 disposed within the casing 102. The cell 104 is the core component of the battery 100, capable of undergoing electrochemical reactions under charge and discharge conditions to achieve the interconversion between chemical energy and electrical energy. The casing 102 forms a sealed space to prevent moisture or dust from entering the casing 102 and interfering with the electrochemical reactions of the cell 104. The cell 104 is the basic unit in the battery 100, typically including a positive electrode, a negative electrode, and a separator. Lithium-ion cells primarily operate by the insertion and extraction of lithium ions between the positive and negative electrodes. In cylindrical cells, a three-layer thin-film structure is wound into a cylindrical electrode assembly, while in cuboid cells, the thin-film structure is wound or stacked into an electrode assembly with a generally cuboid shape. The cell 104 may also have other configurations. In the accompanying drawings provided in this disclosure, the battery 100 includes only one cell 104. However, battery 100 may also include multiple cells 104, and this disclosure does not make any particular limitation on this.

[0044] In this disclosure, battery 100 can be interpreted as a "secondary battery". The concept of "secondary battery" can include, but is not limited to, lithium-ion secondary batteries, sodium-ion secondary batteries, lead-acid batteries, and nickel-metal hydride batteries, etc.

[0045] refer to Figure 2 The housing 102 may include a housing 103 and a cover 106. The housing 103 may include an end wall 108 and side walls 110 arranged around the end wall 108. More specifically, refer to... Figure 8 The sidewall 110 may include a pair of short sidewalls 110a arranged opposite each other along the length direction of the battery 100 and a pair of long sidewalls 110b arranged opposite each other along the width direction of the battery 100, with the short sidewalls 110a and long sidewalls 110b connected end-to-end in sequence. An end wall 108 is connected to the bottom end of the sidewall 110 along the height direction of the battery 100. A cover plate 106 is supported by the top end of the sidewall 110 and is opposite to the end wall 108. (See reference) Figure 11 The cover plate 106 includes a cover plate peripheral surface 106a. The cover plate peripheral surface 106a is a surface surrounded by sidewalls 110. Specifically, refer to... Figure 9 At least a portion of the cover plate's peripheral surface 106a extends into the space of the housing 102 for accommodating the battery cell 104, and the sidewall 110 facing the inner surface 103a of the battery cell 104 is opposite to or in contact with the cover plate's peripheral surface 106a.

[0046] For ease of understanding, the following explanation is provided: In the figure, the X-axis represents the length direction of the battery 100 in this disclosure, that is, the direction in which the short sidewalls 110a are arranged relative to each other; the Y-axis represents the width direction of the battery 100 in this disclosure, that is, the direction in which the long sidewalls 110b are arranged relative to each other; and the Z-axis represents the height direction of the battery 100 in this disclosure, that is, the direction in which the cell 104 is installed into the housing 103 and the direction in which the sidewall 110 supports the cover plate 106. The positive direction of the Z-axis indicates the direction from the end wall 108 of the battery 100 to its cover plate 106, that is, the direction from the bottom side of the battery 100 to the top side of the battery 100. The terms "top," "upper," "bottom," or "lower" used in any element of this disclosure can be used as a reference here.

[0047] In this disclosure, the housing 103 is a component used to provide a receiving space to house the terminal post 107 and other components and isolate them from the outside environment. The housing 103 generally includes a body with an opening at at least one end and a receiving cavity. The opening of the housing 103 can be closed by a cover plate 106 to seal and isolate the internal environment of the battery 100 from the external environment. The materials of the housing 103 include, but are not limited to, copper, iron, aluminum, stainless steel, aluminum alloy, plastic, aluminum-plastic film, etc.

[0048] In this disclosure, cover 106 refers to a component that closes the opening of housing 103 to isolate the internal environment of battery 100, especially the cell 104 where electrochemical reactions occur, from the external environment. The material of cover 106 includes, but is not limited to, copper, iron, aluminum, stainless steel, aluminum alloy, plastic, and aluminum-plastic film.

[0049] refer to Figure 11 and Figure 12 The cover plate 106 may include a cover plate body 162 and a cover plate protrusion 164 disposed at the bottom of the cover plate body 162 along the height direction of the battery 100. Optionally, in a plane perpendicular to the height direction, the projection of the cover plate body 162 extends beyond the projection of the cover plate protrusion 164. The cover plate body 162 and the cover plate protrusion 164 together form a stepped structure that mates with the sidewall 110. Specifically, refer to... Figure 9 The bottom surface of the cover plate body 162 is supported on the top surface 116 of the side wall 110 to achieve positioning and assembly of the cover plate 160 and the housing 103. The cover plate protrusion 164 protrudes from the bottom surface of the cover plate body 162 toward the cell 104, extends into the cavity formed by the side wall 110, and is surrounded by the side wall 110. The cover plate peripheral surface 106a is provided on the cover plate protrusion 164 and faces the inner surface 103a of the side wall 110 along the height direction of the battery 100.

[0050] refer to Figure 3 and Figure 4 The welding area 200 is located between the sidewall 110 and the cover plate 106 and extends along the outer periphery of the cover plate 106, configured as a sealed battery cell 104. (Reference) Figure 25 and Figure 26 The figures show cross-sections of two types of welding zones 200 in actual production processes. The yellow dashed lines in the figures represent the internal interfaces of the welding zones 200. The red solid lines in the figures represent the triangular region S, which will be described in detail below. The inventors discovered that in practical use, Figure 25 The weld zone shown has a lower risk of cracking, while Figure 26 The weld zone shown in Figure 200 has a higher risk of cracking.

[0051] In the production process of battery 100, the cell 104 is first placed into the housing 103, and then the cover plate 106 is supported on the housing 103 and aligned with it. The welding heat source is arranged adjacent to the sidewall 110 or the cover plate 106, melting a portion of the sidewall 110 and a portion of the cover plate 106, and moving around the outer periphery of the cover plate 106. During the welding process, the molten sidewall 110 and the molten cover plate 106 (hereinafter referred to as the molten pool) solidify together after cooling to form the welding zone 200. (Reference) Figures 5 to 15 The welding area 200 and the cover plate 106 have a first lowest point P1. The first lowest point P1 can be located on the peripheral surface 106a of the cover plate or inside the cover plate 106 away from the side wall 110. Generally, the distance from the first lowest point P1 along a direction perpendicular to the first surface 120 to the plane containing the first surface 120 is equal to the dimension of the maximum weld depth H200.

[0052] In this disclosure, the surface of the battery 100 to which the welding heat source points during the aforementioned production process is defined as the first surface 120. The first surface 120 may be one of the outer surface 112 of the sidewall 110 and the surface 114 of the cover plate 106 facing away from the cell 104. The maximum penetration depth H200 of the welding zone 200 is typically perpendicular to the first surface 120, i.e., the welding heat source typically points towards the first surface 120. Correspondingly, the other of the outer surface 112 and surface 114 is defined as the second surface 130. Specifically, when top welding is used, the welding heat source is adjacent to the cover plate 106, the first surface is the surface 114 of the cover plate 106, and the second surface is the outer surface 112 of the sidewall 110. When side welding is used, the welding heat source is adjacent to the sidewall 110, the first surface is the outer surface 112 of the sidewall 110, and the second surface is the surface 114 of the cover plate 106. Figure 5 and Figure 6 The weld zone 200 formed when top welding is used is shown. Figure 7 and Figure 8 The weld zone 200 formed when side welding is used is shown.

[0053] It is understood that in this disclosure, the term "perpendicular" does not necessarily mean that the angle between the two objects described is exactly and absolutely equal to 90 degrees. The term "perpendicular" should be interpreted reasonably broadly. For example, two objects being "perpendicular" could mean that their angle is within a reasonably broad range of 85 to 95 degrees.

[0054] refer to Figures 5 to 15 The intersection line between the welding area 200 and the first surface 120 is called the first weld toe 120a. The intersection line between the welding area 200 and the second surface 130 is called the second weld toe 130a. The internal interface of the welding area 200 is formed between the first weld toe 120a and the second weld toe 130a and is close to the cell 104. Specifically, the internal interface is the boundary line between the molten cover plate 106 and the unmolten cover plate 106, and between the molten sidewall 110 and the unmolten sidewall 110. During the welding process, the molten cover plate 106 and the molten sidewall 110 flow and merge to form a molten pool, and the fluid in the molten pool is supported by the unmolten cover plate 106 (typically the cover plate protrusion 164) and the unmolten sidewall 110.

[0055] Existing battery packs 10 mostly adopt an arrangement direction along the large surface of the batteries 100, that is, an arrangement in which multiple batteries 100 are arranged perpendicular to the length direction of the batteries 100. When the battery pack 10 is subjected to vibration or impact, the short side of the cover plate 106 is subjected to greater vibration and impact, resulting in severe deformation. Cracks preferentially occur in the welded area 200 at the short side (i.e., the width direction) of the cover plate 106. For battery packs 10 suitable for commercial vehicles, especially those for long-distance transportation, the length-to-width ratio is large, and the short sides of the batteries 100 are subjected to greater stress, thus the risk of cracking is more serious.

[0056] The inventors discovered that the main reason for the cracking of the weld area 200 is that the contour of the weld area 200 is uneven during the welding process. In particular, stress concentration occurs in the straight edge area (i.e., the straight edge portion 300) formed by the contour of the portion near the cell 104 (hereinafter referred to as the internal interface). Furthermore, the internal boundary of the weld area 200 has defects such as uneven distribution relative to the cover plate 106 and the side wall 110, with straight edge portions 300 extending along the contact interface of the cover plate 106 or the side wall 110. Since the battery 100 and the battery array 105 are often subjected to shear forces perpendicular to the direction of the side wall 110 and forces perpendicular to the surface 114 of the cover plate 106, the straight edge portion 300 of the internal interface, especially the straight edge portion 300 of the weld area 200 formed between the short side wall 110a and the cover plate 106, is prone to cracking when facing vibration and impact. This poses a risk of welding failure to the battery 100, which will lead to safety risks such as thermal runaway and is detrimental to the safety of battery use.

[0057] The distribution and contour of the internal interface of the welding zone 200 are influenced by various factors. When the thermal conductivity of the cover plate 106 and the sidewall 110 differs significantly, the one with lower thermal conductivity melts rapidly, while the one with higher thermal conductivity melts slowly, resulting in an uneven distribution of the molten pool. For example, if the thermal conductivity of the sidewall 110 is greater than that of the cover plate 106, the thickness of the sidewall is less than that of the cover plate. In a cross-section perpendicular to the welding movement direction of the welding zone 200, the volume of the melted sidewall 110 is less than the volume of the melted cover plate 106, causing the distribution of the welding zone 200 to be biased towards the cover plate 106. This reduces the size of the internal interface of the welding zone 200 formed at the sidewall 110. Consequently, the connection strength between the welding zone 200 and the sidewall 110 decreases. When subjected to impacts or vibrations, the battery 100 is more prone to cracking at this location.

[0058] Furthermore, due to the slow melting of the sidewall 110, the contour of the internal interface of the weld area 200 adjacent to the sidewall 110 tends to extend along the surface or edge of the sidewall 110, thus making it easier to form a straight edge 300 perpendicular to the outer surface 112 of the sidewall 110 or the surface 114 of the cover plate 106. (See also, by way of example only.) Figure 7 and Figure 8 When the welding heat source is near surface 114, an internal interface is easily formed in the cross-section, extending along the top surface 116 of the sidewall 110 and perpendicular to the second surface 130. (Reference) Figure 5 and Figure 6 When the welding heat source is near the outer surface 112, an internal interface extending along the inner surface 103a of the sidewall 110 and the peripheral surface 106a of the cover plate is easily formed in the cross-section. Since the forces acting on the battery 100 typically have a large component in the direction perpendicular to the outer surface 112 of the sidewall 110 or the surface 114 of the cover plate 106, for example, the battery 100 experiences shear forces perpendicular to the outer surface 112, the internal interface between the welded area 200 and the sidewall 110 is prone to cracking at the straight edge 300, making the battery 100 susceptible to welding failure.

[0059] Furthermore, the inventors discovered that due to limitations in manufacturing precision, a gap inevitably exists between the cover plate 106 and the sidewall 110. Taking the welding heat source adjacent surface 114 as an example, the cover plate 106 melts first and must flow across the gap between the cover plate 106 and the sidewall 110 to transfer heat to the sidewall 110, melting the sidewall 110 from the top surface 116. Crossing the gap dissipates the heat of the molten pool, further reducing the amount of sidewall 110 that is melted. The contour of the internal interface is more likely to extend along the top surface 116 of the sidewall 110, thus making it easier to form a straight edge 300. The internal interface between the welding area 200 and the sidewall 110 is prone to cracking at the straight edge 300, which makes the battery 100 susceptible to welding failure.

[0060] To overcome the above defects, the inventors proposed a triangular region S. This is achieved by ensuring that the area S1 (in mm) of the overlap between the welded area 200 and the triangular region S in the cross-section is equal to the area of ​​the overlap. 2 ) and the area S2 of the triangular region (in mm) 2 A ratio greater than 0.05 ensures that the internal interface of the weld zone 200 has sufficient dimensions and that straight edges are eliminated or at least reduced. The weld zone 200 thus has improved structural strength and reduced welding defects. Specifically, refer to... Figures 5 to 15 The welding area 200 has a first lowest point P1 in a direction perpendicular to the first surface 120 and a second lowest point P2 with the outer surface 112. The triangular region S includes a first side E1 extending from the first lowest point P1 to the second lowest point P2, a second side E2 extending from the first lowest point P1 along the perpendicular direction of the surface 114 of the cover plate 106, and a third side E3 extending from the second lowest point P2 along the perpendicular direction of the outer surface 112 of the sidewall 110.

[0061] refer to Figure 5 and Figure 6 When the first surface 120 is surface 114 and the second surface 130 is outer surface 112, the maximum penetration depth H200 of the weld area 200 extends from the top side of the battery 100 to the bottom side. In some cross-sections, the maximum penetration depth H200 can be aligned with the circumferential surface 106a of the cover plate. In this case, the first side E1 indicates the ideal profile of the internal interface. When the internal interface between the sidewall 110 and the weld area 200 has a large straight edge 300, the straight edge 300 tends to extend along the direction of the third side E3. In this case, the area S1 of the triangular region S overlapping the weld area 200 is close to the area S2 of the triangular region S minus the product of the straight edge 300 and the second side E2. The larger S1 is, the smaller the value of the product of the straight edge 300 and the second side E2, the smaller the size of the straight edge 300 and the larger the size of the internal interface between the weld area 200 and the sidewall 110. The higher the connection strength between the sidewall 110 and the weld area 200. By constructing a triangular region S using the first side E1, the second side E2, and the third side E3, the quality of the weld zone 200 can be intuitively and quickly assessed and controlled while adhering to the thermodynamic laws of welding. Furthermore, compared to assessing and controlling the quality of the weld zone 200 by separately obtaining parameters such as the slope of the internal contour based on the geometric characteristics of the internal interface contour in various cross-sections perpendicular to the welding movement direction, the method provided in this disclosure is easier to implement and verify.

[0062] It should be noted that, in this disclosure, the term "maximum penetration depth" refers to the maximum distance from any point on the outer surface of the weld zone 200 to any point on the inner interface of the weld zone 200.

[0063] Similarly, refer to Figure 7 and Figure 8 When the first surface 120 is the outer surface 112 and the second surface 130 is the surface 114, the maximum penetration depth H200 of the weld zone 200 points from the outside to the inside of the sidewall 110. In some cross-sections, the maximum penetration depth H200 can be aligned with the top surface 116. In this case, the first side E1 indicates the ideal profile of the internal interface. When the internal interface between the sidewall 110 and the weld zone 200 has a large straight edge 300, the straight edge 300 tends to extend along the direction of the second side E2. In this case, the area S1 of the triangular region S overlapping the weld zone 200 is close to the area S2 of the triangular region S minus the product of the straight edge 300 and the third side E3. The larger S1 is, the smaller the value of the product of the straight edge 300 and the third side E3, the smaller the size of the straight edge 300 and the larger the size of the internal interface between the weld zone 200 and the sidewall 110. The higher the connection strength between the sidewall 110 and the weld zone 200. By constructing a triangular region S using the first side E1, the second side E2, and the third side E3, the quality of the weld zone 200 can be intuitively and quickly assessed and controlled while adhering to the thermodynamic laws of welding. Furthermore, compared to assessing and controlling the quality of the weld zone 200 by separately obtaining parameters such as the slope of the internal contour based on the geometric characteristics of the internal interface contour in various cross-sections perpendicular to the welding movement direction, the method provided in this disclosure is easier to implement and verify.

[0064] The internal interface of the welding area 200 conforming to the above standards can be achieved in various ways. For example, when using laser welding with inner and outer rings to connect the sidewall 110 and the cover plate 106, the contour of the internal interface of the welding area 200 can be adjusted by matching the power of the inner and outer ring lasers with the welding movement speed. When the sidewall 110 and the cover plate 106 are made of different materials, the contour of the internal interface of the welding area 200 can be adjusted by adjusting the position and angle of the laser. The following describes some configurations of the welding area 200 that contribute to achieving the above requirements. Those skilled in the art should understand that specific implementations of the welding area 200 include, but are not limited to, the configurations of components and structures in the battery 100 described below.

[0065] Return to reference Figure 10Each short sidewall 110a has a dimension L1 along the width direction of the battery 100, in mm. Each long sidewall 110b has a dimension L2 along the length direction of the battery 100, in mm. Here, L2 > L1, meaning that the long sidewall 110b is longer than the short sidewall 110a. For example, the ratio of L1 / L2 can satisfy: 0.02 ≤ L1 / L2 ≤ 0.58. For example, the values ​​of L1 / L2 can be: 0.02, 0.05, 0.08, 0.11, 0.14, 0.17, 0.20, 0.23, 0.26, 0.29, 0.32, 0.35, 0.38, 0.41, 0.44, 0.47, 0.50, 0.53, 0.56, or 0.58.

[0066] The inventors discovered that welding failures between the casing 103 and the cover plate 106 often occur at the weld area 200 formed between the short sidewall 110a and the cover plate 106. This may be attributed to the dimensional differences of the battery 100 in the length and width directions. This dimensional difference leads to more severe stress concentration at the weld area 200 formed at the short sidewall 110a. If the value of L1 / L2 is too large, for example, when L1 / L2 is greater than 0.58, the size of the short sidewall 110a is much smaller than the size of the long sidewall 110b, and the welding heat is concentrated in the molten pool at the short sidewall 110a, thus causing local overheating and making it difficult to achieve the contour of the internal interface of the weld area 200 as required by this disclosure by adjusting welding parameters. When L1 / L2 is less than 0.02, the properties of the weld areas 200 formed at the short sidewall 110a and the long sidewall 110b are similar, but this is not conducive to the spatial arrangement of multiple batteries 100. By setting L1 / L2 to satisfy 0.02≤L1 / L2≤0.58, it is possible to effectively take into account the arrangement of the battery 100 in different spaces while ensuring that the battery 100 of this disclosure can meet the contour requirements of the internal interface of the welding area 200, forming a welding area 200 that meets the connection strength, thereby reducing the risk of welding failure of the battery 100.

[0067] Optionally, refer to Figure 6 In the cross-section of the weld zone 200 formed between the cover plate 106 and the short sidewall 110a, S1 / S2 ≥ 0.05, that is, in the cross-section, the lower limit of the ratio of the area of ​​the weld zone 200 overlapping with the triangular region S to the area of ​​the triangular region S is increased. This further ensures that the internal interface of the weld zone 200 formed between the short sidewall 110a and the weld zone 200 has sufficient dimensions, while eliminating or reducing the straight edges 300.

[0068] Preferably, in the cross-section, S1 / S2 ≤ 0.95. In this case, the value of S1 / S2 can be: 0.05, 0.09, 0.13, 0.17, 0.21, 0.25, 0.29, 0.33, 0.37, 0.41, 0.45, 0.49, 0.53, 0.57, 0.61, 0.65, 0.69, 0.73, 0.77, 0.81, 0.85, 0.90, or 0.95. The value of S1 / S2 should not be too large or too small. When S1 / S2 is too small, the overlap area between the welding area 200 and the triangular region S is low. That is, in the cross-section, the internal interface between the welding area 200 and the sidewall 110 has a straight edge 300 extending along the sidewall 110 or a small internal interface, or the internal interface between the welding area 200 and the cover plate 106 has a straight edge 300 extending along the edge of the sidewall 110 or the cover plate 106 or a small internal interface. This results in insufficient connection strength between the welding area 200 and the sidewall 110 or the cover plate 106, or even incomplete welding or incomplete penetration. When the battery 100 is subjected to vibration or impact, this configuration of the internal interface of the welding area 200 may cause welding failure of the battery 100. When S1 / S2 is too large, the welding area 200 receives excessive welding heat at the sidewall 110 or the cover plate protrusion 164. This increases the area of ​​the heat-affected zone of the sidewall 110 or cover plate 106, thus reducing the material strength of the sidewall 110 or cover plate 106 itself, and even causing weld burn-through and damaging the cell 104, which is detrimental to the thermal safety of the battery 100. By controlling 0.05≤S1 / S2≤0.95, it is possible to ensure that the welding area 200 has sufficient connection strength while avoiding the risk of heat-affected zone expansion or weld burn-through due to excessive heat input, thereby ensuring the structural reliability and thermal safety of the battery 100.

[0069] Those skilled in the art will understand that, despite the aforementioned limitations, the aim is to limit the expansion of the size and reduction of the strength of the heat-affected zone outside the weld area 200 due to excessive heat received by the weld area 200. When the internal interface of the weld area 200 is located outside the first edge E1, the strength of the weld area 200 itself can still ensure a low risk of cracking deformation. That is, under suitable process conditions, the S1 / S2=1 solution is also included within the inventive concept of this disclosure.

[0070] Return to reference Figure 12The cover plate protrusion 164 has a thickness t1 of the same value along the height direction of the battery 100, in mm, where 0.3 ≤ t1 ≤ 2. The value of t1 can be: 0.30, 0.39, 0.48, 0.57, 0.66, 0.75, 0.84, 0.93, 1.02, 1.11, 1.20, 1.29, 1.38, 1.47, 1.56, 1.65, 1.74, 1.83, 1.92, or 2.00. When the welding heat source is adjacent to the outer surface 112 of the sidewall 110, the thickness t1 of the cover plate protrusion 164 will determine the difference in thermal conductivity between the sidewall 110 and the cover plate 106. The value of thickness t1 should not be too large or too small. When t1 is too large, the size of the cover plate protrusion 164 will cause the thermal conductivity of the cover plate 106 to significantly exceed that of the sidewall 110. The welding heat will be unevenly distributed between the sidewall 110 and the cover plate 106. The welding area 200, located near the sidewall 110, is prone to forming an internal interface with the cover plate protrusion 164 extending along the circumferential surface 106a of the cover plate. This internal interface makes it difficult for the overlap area between the welding area 200 and the triangular region S to meet the requirement of S1 / S2≥0.05. Therefore, the connection strength of the welding area 200 at the cover plate protrusion 164 is insufficient, and the battery 100 is prone to cracking along this internal interface when subjected to vibration or impact, which is detrimental to the thermal safety and structural reliability of the battery 100. When t1 is too small, the bottom surface of the cover plate protrusion 164 is too close to the molten pool. During welding, the fluid in the molten pool can easily weld through the cover plate protrusion 164 and splash onto the cell 104, causing an internal short circuit or thermal runaway in the battery 100, seriously threatening the thermal safety of the battery 100. By controlling 0.3≤t1≤2, it is possible to ensure that an internal interface with sufficient connection strength is formed between the welding area 200 and the cover plate protrusion 164, while avoiding the risk of weld burn-through due to the cover plate protrusion 164 being too thin.

[0071] Similarly, refer to Figures 5 to 15The sidewall 110 has a uniform thickness t2 along the height direction of the battery 100, in mm, where 0.45 ≤ t2 ≤ 1.5. The value of t2 can be: 0.45, 0.51, 0.56, 0.62, 0.67, 0.73, 0.78, 0.84, 0.89, 0.95, 1.00, 1.06, 1.11, 1.17, 1.22, 1.28, 1.33, 1.39, 1.44, or 1.50. When the welding heat source is adjacent to the surface 114 of the cover plate 106, the thickness t2 of the sidewall 110 will determine the difference in thermal conductivity between the sidewall 110 and the cover plate 106. The value of thickness t2 should not be too large or too small. When t2 is too large, the thermal conductivity of the sidewall 110 significantly exceeds that of the cover plate 106, resulting in uneven distribution of welding heat between the sidewall 110 and the cover plate 106. The welding area 200, located adjacent to the cover plate 106, easily forms an internal interface with the sidewall 110 extending along the top surface 116. This internal interface makes it difficult for the overlap area between the welding area 200 and the triangular region S to meet the requirement of S1 / S2≥0.05. Consequently, the connection strength of the welding area 200 at the sidewall 110 is insufficient, making the battery 100 prone to cracking along this internal interface when subjected to vibration or impact, which is detrimental to the thermal safety and structural reliability of the battery 100. When t2 is too small, the inner surface 103a of the sidewall 110 is too close to the molten pool. During the welding process, the fluid in the molten pool can easily penetrate the sidewall 110 and splash onto the cell 104, causing an internal short circuit or thermal runaway in the battery 100, seriously threatening the thermal safety of the battery 100. By controlling 0.45≤t2≤1.5, it is possible to ensure that an internal interface with sufficient connection strength is formed between the welding zone 200 and the sidewall 110 while avoiding the risk of burn-through due to the sidewall 110 being too thin.

[0072] In another possible implementation, refer to Figures 13 to 15 The sidewall 110 has a first recess 118 at one end near the cover plate 106, recessed from its inner surface 103a away from the cell 104. One end of the first recess 118 extends to the top surface 116 of the sidewall 110. The first recess 118 includes a first recess inner surface 118a that overlaps with at least a portion of the cover plate peripheral surface 106a along the height direction of the battery 100. At this time, the bottom surface of the cover plate body 162 is still supported by the top surface 116, and the welding area 200 is formed between the first recess 118 with a reduced thickness and the cover plate 106. Preferably, in the cross-section of the welding area 200 formed between the cover plate 106 and the short sidewall 110a, the thickness of the first recess 118 is t13 in mm. The thickness of the short sidewall 110a is t12 in mm, and 0.8 ≤ t13 / t12 ≤ 0.98.

[0073] The values ​​of t13 / t12 can be: 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, or 0.98. The values ​​of t13 / t12 should not be too large or too small. When t13 / t12 is too small, the first recess 118 is excessively recessed and far from the cell 104. This results in insufficient structural strength of the sidewall 110 at the first recess 118, making it difficult to stably support the cover plate 106, which is detrimental to the assembly and welding of the battery 100. Furthermore, when the first recess 118 is excessively recessed and far from the cell 104, it is difficult for the first recess 118 to support the flow of the molten pool caused by gravity. The fluid in the molten pool is prone to weld through the inner surface 103a and splash onto the cell 104, causing thermal runaway of the battery 100. The heat-affected zone formed at the first recess 118 is large, which further reduces the structural strength of the welded area 200. When t13 / t12 is too large, the excessively thick first recess 118 is unable to compensate for the significant difference in heat transfer performance between the side wall 110 and the cover plate 106. This will cause the internal interface of the welded area 200 to easily form a straight edge 300 extending along the top surface 116. This not only reduces the connection strength of the internal interface at the side wall 110, but also makes the battery 100 prone to cracking along the internal interface when subjected to vibration or impact, which is detrimental to the thermal safety and structural reliability of the battery 100. By controlling 0.8≤t13 / t12≤0.98, the first recess 118 can provide good support to the molten pool while balancing the heat exchange performance of the short sidewall 110a and the cover plate 106, thereby reducing the risk of cracking of the internal interface of the welding zone 200 due to its small size and straight edge extending along the top surface 116.

[0074] Optionally, along the height direction of the battery 100, the dimension of the overlapping portion between the inner surface 118a of the first recess and the peripheral surface 106a of the cover plate is d1, in mm. The dimension of the peripheral surface 106a of the cover plate is d2, in mm, where 0.8 ≤ d1 / d2 ≤ 1. The values ​​of d1 / d2 can be: 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, or 1.00.

[0075] The value of d1 / d2 should not be too large or too small. When d1 / d2 is too small, the overlap area between the inner surface 118a of the first recess and the peripheral surface 106a of the cover plate is too narrow, that is, the dimension of the first recess 118 along the height direction is too large, or the dimension of the cover plate protrusion 164 along the height direction is too small. At this time, the structural strength of the sidewall 110 is reduced, which is not conducive to supporting the cover plate 106. In addition, the thermal conductivity of the first recess 118 is significant. The molten first recess 118 may flow towards the bottom under the action of gravity and is difficult to be supported by the cover plate 106, especially the cover plate protrusion 164 with the peripheral surface 106a. The fluid from the molten pool splashes onto the cell 104, causing thermal runaway of the cell 104, and thus posing a safety hazard to the battery 100.

[0076] In another possible implementation, refer to Figures 16 to 19 The sidewall 110 has a guide portion 140 extending from its top surface 116 to its inner surface 103a. The cover plate 106 has a mating guide portion 150 extending from the bottom surface 117 of the cover plate body 162 to the peripheral surface 106a of the cover plate. In cross-section, the guide portion 140 and the top surface 116 have a first angle α. The guide portion 140 and the mating guide portion 150 face each other to support the mating guide portion 150 in the height direction.

[0077] By providing the guide portion 140 and the mating guide portion 150, on the one hand, they can form a mutually cooperating guiding and supporting structure in the height direction of the battery 100, so as to more stably support the cover plate 106 on the housing 103, improve the positional accuracy of the cover plate 106 relative to the side wall 110, and avoid uneven distribution of the welding area 200 caused by the displacement of the cover plate 106 during the welding process. On the other hand, during the welding process, regardless of whether the distribution of the welding area 200 is biased towards the side wall 110 or the cover plate protrusion 164, the molten pool tends to cool and solidify along the edge of the guide portion 140 or the mating guide portion 150 to form an internal interface extending along the edge of both. Since the internal interface has a first angle α with the outer surface 112 of the sidewall 110 and a second angle 90°-α with the surface 114 of the cover plate 106, when the battery 100 is subjected to shear forces such as those perpendicular to the outer surface 112, the inclined extension of the internal interface of the welding area 200 makes the direction of the shear force and the extension direction of the internal interface form an angle, thereby reducing the risk of cracks initiating or breaking at the internal interface, and significantly improving the shear resistance of the welding area 200 and the structural reliability of the battery 100.

[0078] At this point, optionally, refer to Figure 19In the cross-section, the value of the first angle α can satisfy: 30°≤α≤75°. The values ​​of the first angle α can be: 30.00°, 32.37°, 34.74°, 37.11°, 39.47°, 41.84°, 44.21°, 46.58°, 48.95°, 51.32°, 53.68°, 56.05°, 58.42°, 60.79°, 63.16°, 65.53°, 67.89°, 70.26°, 72.63°, or 75.00°. The dimension of the guide part 140 along the height direction is d3, in mm, and 0.1≤d3≤0.5. The value of d3 can be: 0.10, 0.12, 0.14, 0.16, 0.18, 0.20, 0.22, 0.24, 0.26, 0.28, 0.30, 0.32, 0.34, 0.36, 0.38, 0.40, 0.42, 0.44, 0.46, 0.48, or 0.50.

[0079] The value of d3 should not be too large or too small. When d3 is too large, the dimension of the guide portion 140 along the height direction is too large, which can easily guide the mating guide portion 150 to slide along its surface, reducing the assembly stability of the cover plate 106 before welding. The positional offset of the cover plate 106 may cause the welding area 200 to deviate from the actual molten pool position relative to the welding heat source, resulting in a reduction in the size of the internal interface of the welding area 200 formed at one of the side wall 110 or the cover plate 106. This, in turn, reduces the connection strength between the welding area 200 and the side wall 110 or the cover plate 106, increasing the risk of welding failure of the battery 100. When d3 is too small, the dimension of the guide portion 140 along the height direction is too small. This makes it difficult for the guide portion 140 and the mating guide portion 150 to effectively guide the contour of the internal interface during the cooling and solidification of the molten pool. Consequently, it is difficult to eliminate the straight edge portion 300 that may exist in the internal interface of the welding zone 200 extending along the edge of the sidewall 110 or the cover plate 106. This also reduces the structural strength of the welding zone 200 and is not conducive to reducing the risk of welding failure of the battery 100. By controlling 0.1≤d3≤0.5, it is possible to ensure that the guide portion 140 provides stable support to the mating guide portion 150 while ensuring that the guide portion 140 and the mating guide portion 150 can cooperate to eliminate or reduce the straight edge portion 300 in the internal interface of the welding zone 200. This significantly improves the connection strength of the welding zone 200 and the structural reliability of the battery 100.

[0080] Return to reference Figures 5 to 15In the cross-section, there is a gap between the circumferential surface 106a of the cover plate and the side wall 110, and the minimum distance between the circumferential surface 106a of the cover plate and the side wall 110 is i1, in mm, where 0.01 ≤ i1 ≤ 0.2. The value of i1 can be: 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19 or 0.20.

[0081] As described above, when there is a gap between the cover plate peripheral surface 106a and the side wall 110, the fluid in the molten pool formed by the side wall 110 or the cover plate body 162 needs to cross the gap to transfer heat to the cover plate protrusion 164 or the side wall 110. By limiting the minimum distance between the cover plate peripheral surface 106a and the side wall 110 to 0.01≤i1≤0.2, it is possible to eliminate or at least reduce the straight edge 300 in the internal interface profile of the welding area 200 under existing production conditions, thereby improving the connection strength of the welding area 200, increasing the structural reliability of the battery 100, and reducing its welding failure risk.

[0082] Return to reference Figures 5 to 15 In the cross-section, the weld zone 200 has a weld width W200 perpendicular to the second surface 130, in mm, where 0.2 ≤ W200 ≤ 1.3. The values ​​of W200 can be: 0.20, 0.26, 0.32, 0.38, 0.44, 0.50, 0.56, 0.62, 0.68, 0.74, 0.80, 0.86, 0.92, 0.98, 1.04, 1.10, 1.16, 1.22, 1.28, 1.30. In this disclosure, the "minimum weld width" affects the ability of the weld pool to allow gas to escape during cooling, rather than the minimum dimension of the weld zone 200 along the direction perpendicular to the second surface 130. Generally, the weld width W200 refers to the distance from the first weld toe 120a to the second weld toe 130a along the direction perpendicular to the second surface 130.

[0083] If a straight edge 300 exists at the second side E2 or the third side E3 of the welding area 200, then the welding area 200 has a weld width W200 in the direction of the second side E2 or the third side E3. During the cooling and solidification process of the molten pool, the welding area 200 has multiple clusters of columnar crystals growing towards each other from one side adjacent to the sidewall 110 and the other side adjacent to the cover plate protrusion 164. The crystals in the welding area 200 usually converge at the center of the weld width W200 to form a crystallization interface. Since the crystals at the crystallization interface usually contain impurities and bubbles, and the strength of the crystal interface formed by the mutual confinement of multiple crystals is lower than the strength of the grain boundary with dislocation and solid solution strengthening, the welding area 200 is prone to crack initiation at the weld width W200. By controlling 0.2≤W200≤1.3, it is possible to ensure that the welding area 200 has a sufficient weld width to have improved connection strength, reduce the risk of the welding area 200 cracking at the center of the weld width W200, and thus ensure the structural reliability and thermal safety of the battery 100.

[0084] Return to reference Figures 5 to 15 The internal interface of the welding area 200 includes a straight edge 300 that is substantially perpendicular to the first surface 120. The dimension of the straight edge 300 is a1, in mm, where 0.1 ≤ a1 ≤ 1.0. The value of a1 can be: 0.10, 0.15, 0.20, 0.24, 0.29, 0.34, 0.39, 0.44, 0.48, 0.53, 0.58, 0.63, 0.68, 0.72, 0.77, 0.82, 0.87, 0.92, 0.96, or 1.00.

[0085] It should be noted that, in this disclosure, the term "substantially perpendicular" means that the straight edge 300 and the first surface 120 can have an angle of 87° to 92°. The value of a1 should not be too large or too small. If a1 is too large, the shear force direction on the straight edge 300 and the short side of the battery 100 will be parallel or substantially parallel, making it prone to cracking or deformation at the straight edge 300. This increases the risk of failure such as cracking in the welded area 200, negatively impacting the reliability of the welded connection. If a1 is too small, to achieve the above-mentioned conditions for the welded area 200, the movement speed of the molten pool during welding needs to be increased, which reduces the volume of the molten pool, lowers the cross-section of the welded area 200, and reduces the structural strength. When the battery pack 10 is subjected to vibrations or impacts, the battery 100 is prone to cracking.

[0086] Optionally, the dimension a1 of the straight edge 300 is smaller than the dimension E11 of the first edge E1. In some possible implementations, 0.1 ≤ a1 / E11 ≤ 0.4. The value of a1 / E11 can be: 0.10, 0.12, 0.13, 0.15, 0.17, 0.18, 0.20, 0.22, 0.23, 0.25, 0.27, 0.28, 0.30, 0.32, 0.33, 0.35, 0.37, 0.38, or 0.40. The value of a1 / E1 should not be too large or too small. When a1 / E11 is too large, the proportion of the straight edge 300 in the internal interface of the welding area 200 increases, the risk of cracking of the internal interface of the welding area 200 increases, which is detrimental to the reliability of the welded connection. When a1 / E11 is too small, in order to obtain the required internal interface of the welding zone 200, the welding process may need to extend the welding time or increase the heat input, which is not conducive to improving welding efficiency. Therefore, controlling a1 / E11 within the range of 0.1 to 0.4 is beneficial to reduce the cracking risk of the welding zone 200 while taking into account welding efficiency, thereby improving welding consistency and product yield.

[0087] refer to Figures 20 to 22 This disclosure also provides a battery pack 10, including the aforementioned battery 100. Specifically, the battery pack 10 includes at least two battery rows 105. Each battery row 105 includes a plurality of batteries 100 arranged along the width direction of the battery 100, with the short sidewall 110a of each battery 100 in each battery row 105 facing the short sidewall 110a of the battery 100 in the adjacent battery row 105.

[0088] refer to Figure 21 Optionally, the dimension of the battery row 105 along the width direction of the battery 100 is L3, in mm. The dimension of the battery row 105 along the length direction of the battery 100 is L4, in mm. 2 ≤ L3 / L4. Since the battery 100 typically has a defined aspect ratio L1 / L2, the value of L4 / L3 is usually determined by the number of batteries 100 in the battery row 105. For electrical equipment 1000 or battery pack 10 suitable for long-haul commercial vehicles, passenger vehicles, etc., it is necessary to ensure that the battery pack 10 has improved energy density. Generally speaking, the energy density of the battery pack 10 can be achieved by increasing the number of batteries 100 arranged therein. For the battery row 105, this can be achieved by increasing the number of multiple batteries 100 arranged along the width direction of the battery 100. When L4 / L3 is too small, the battery row 105 includes only a few batteries 100. For electrical equipment 1000, such as passenger vehicles used for long-distance travel, the battery pack 10 arranged in this way has low space utilization and energy density, resulting in poor range. By ensuring that 2 ≤ L3 / L4, the shear stress condition of the battery 100 in the battery row 105 is improved. As a result, the risk of welding failure of the battery 100 can be reduced.

[0089] When 2 ≤ L3 / L4, preferably, in the cross-section formed between the cover plate 106 and the short sidewall 110a of the battery 100, S1 / S2 can be controlled to satisfy: 0.2 ≤ S1 / S2 ≤ 0.95. That is, the lower limit of S1 / S2 is increased. The cross-sectional size of the welding area 200 of the battery 100 that satisfies the above condition is increased, which can eliminate or at least reduce the straight edge portion 300 in the internal interface, and thus can overcome the increased shear force perpendicular to the short sidewall 110a caused by including more batteries 100 in the battery row 105, and reduce the risk of welding failure of the battery 100.

[0090] Optionally, the battery pack 10 includes N battery rows 105 arranged along the length of the battery 100. N > 2. Based on a similar principle, the lower limit of S1 / S2 can be increased relative to 0.05. The increased cross-sectional size of the welded area 200 of the battery 100, which satisfies the above conditions, can eliminate or at least reduce the straight edges 300 in the internal interface, and thus can overcome the increased shear force perpendicular to the short sidewall 110a caused by including more batteries 100 in the battery row 105, reducing the risk of welding failure of the battery 100.

[0091] refer to Figure 21 and Figure 22 Optionally, an adhesive 500 is provided between the short sidewalls 110a of adjacent battery rows 105 in the battery pack 10. The adhesive 500 connects adjacent battery rows 105. Along the height direction of the battery 100, the adhesive 500 is spaced from the surface 114 of the cover plate 106 of the battery 100 away from the cell 104. When the top surface of the adhesive 500 is spaced from the surface 114 along the height direction, the adhesive 500 does not directly contact the welding area 200, thereby preventing shear forces perpendicular to the short sidewalls 110a from being directly applied to the welding area 200, which reduces the risk of welding failure of the battery 100. In addition, the dimension of the adhesive 500 along the height direction can be appropriately increased. When the dimension of the adhesive 500 along the height direction increases, the area of ​​the adhesive 500 against the battery 100 increases, which can absorb the shear forces acting on the battery 100, support the battery 100 more stably, and thus reduce the risk of welding failure of the battery 100.

[0092] refer to Figure 23 This disclosure also provides an electrical device 1000, including a battery 100 as described above, or a battery pack 10 as described above. The electrical device 1000 can be a device such as a car or communication equipment that requires a continuous supply of voltage.

[0093] refer to Figure 24 This disclosure also provides a test method applicable to the above-described battery 100, comprising: Get battery 100; In a cross-section perpendicular to the welding movement direction of the welding area 200 formed between the cover plate 106 and the side wall 110 of the battery 100, the area of ​​the welding area 200 overlapping with a triangular region S is S1, in mm. 2 The area of ​​the triangular region S is S², in mm. 2 When S1 / S2≥0.05, battery 100 is determined to be a good product; otherwise, battery 100 is determined to be a bad product.

[0094] Because the aforementioned inspection methods are simpler to operate than traditional methods such as metallographic analysis and tensile testing, product inspection is more intuitive, faster, and more accurate. This greatly simplifies the quality control process for battery 100 and improves inspection efficiency, consistency, and traceability. Furthermore, with the help of technologies such as optical scanning and image analysis, these inspection methods can also achieve non-destructive testing of the weld area 200.

[0095] <Examples, Experimental Description, and Experimental Results> 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.

[0096] Size measurement methods Use measuring instruments such as micrometers or calipers to measure parameters such as length, width, depth, diameter, radius, distance, and thickness. The area is then calculated using these parameters.

[0097] Battery manufacturing (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).

[0098] (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).

[0099] (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.

[0100] (4) Preparation of the diaphragm: Polyethylene film is selected as the diaphragm.

[0101] (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.

[0102] 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.

[0103] 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.

[0104] The solvent can be deionized water, NMP (N-methylpyrrolidone), alcohol, ether, ketone or other types of pyrrolidone, etc.

[0105] 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.).

[0106] 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.).

[0107] In this test, the main active material of the positive electrode was selected from lithium iron phosphate, accounting for 98% of the mass of the positive active material, 0.5% of the conductive agent, and 1.5% of the binder; the active material of the negative electrode was selected from artificial graphite, accounting for 96.5% of the mass of the negative active material, 0.5% of the conductive agent, 0.5% of the thickener, and 2.5% of the binder.

[0108] The testing method is as follows: Test Method 1: Battery leakage rate under vibration conditions According to the above battery preparation method, for each embodiment and comparative example, 500 batteries will be prepared, 50 batteries will be grouped together, and two batteries will be arranged along the width direction of the battery to form a battery column. The battery columns will be arranged along the length direction of the battery to form a battery pack. The values ​​of S1 / S2 for each embodiment and comparative example are shown in Table 2 below. Other test conditions are kept consistent.

[0109] 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 Table 1 below.

[0110] Table 1 After the vibration ends, observe the junction between the short side of the battery cover and the battery casing to see if any leakage occurs. The leakage rate is calculated as (number of batteries leaking / 100). 100%.

[0111] If the battery leakage rate is less than or equal to 1%, the test result is considered good; if the battery leakage rate is greater than 1% but less than 3%, the test result is considered qualified; if the battery leakage rate is greater than 3%, it is considered unqualified.

[0112] Test Method 2: Solder Penetration Test of Insulating Film Following the battery fabrication method described above, 100 batteries were prepared for each embodiment and comparative example. First, the battery cell was placed into the casing, and the cover plate was welded to the casing using laser welding technology. During the welding process, the welding power was maintained at 2000W, and the welding speed was set to 50mm / s. After welding, the battery was disassembled to check for weld penetration of the insulating film. If weld penetration occurred, the structure was considered unqualified; otherwise, the result was acceptable. The examples are shown in the table below: Table 2 Referring to Table 2, in any of Examples 1 to 9, the value of S1 / S2 satisfies greater than or equal to 0.05 and less than or equal to 0.95, that is, the welded area 200 forms a continuous and uniform internal interface with respect to the sidewall 110 and the cover plate 106, and the probability of the internal interface having a straight edge 300 is low. In a sampling test of 500 batteries, the number of batteries with cracks at both the short side of the cover plate 106 and the short sidewall 110a is less than 15. In Example 1, the value of S1 / S2 is equal to 0.05, and it gives a satisfactory performance in performance 1. In Examples 2 to 9, the value of S1 / S2 is greater than 0.05, and it gives a good performance in performance 1. This verifies that as the value of S1 / S2 gradually increases from 0.05 to 0.95, the quality of the welded area 200 of the battery 100 gradually improves and the risk of cracking gradually decreases. The insulating film of all 100 batteries was not welded through. This verifies that when the welding area 200 does not completely overlap with the triangular area S, the risk of the insulating film between the batteries 100 being welded through and causing electrical connection is low.

[0113] In contrast, in Comparative Example 1, the value of S1 / S2 is less than 0.05. This means that although the welded area 200 overlaps with the triangular region S, the overlap is only in a small area, resulting in insufficient structural strength and an increased risk of straight edges 300 in the welded area 200. In this case, although the battery 100's performance 2 is acceptable, its performance 1 shows a failure. This indicates that when the risk of straight edges 300 in the welded area 200 is high, despite the battery 100's good insulation performance, the welded area 200 has a significant risk of cracking.

[0114] Meanwhile, in Comparative Example 2, the value of S1 / S2 is greater than 0.95. This means that although the welded area 200 overlaps with the triangular area S in a larger region, reducing the risk of a straight edge 300 in the welded area 200, the welded area 200 may receive more heat. This increases the heat-affected zone area of ​​the sidewall 110 or cover plate 106, thus reducing the material strength of the sidewall 110 or cover plate 106, and potentially causing weld burn-through and damage to the cell 104, which is detrimental to the thermal safety of the battery 100. In this case, although the battery 100's performance 1 is acceptable, its performance 2 shows a failure. This indicates that when the welded area 200 overlaps with the triangular area S in an excessively large region, although the risk of cracking in the welded area 200 is low, the risk of electrical interconnection between adjacent batteries 100 due to excessive welding heat increases significantly.

[0115] By controlling the area of ​​overlap between the welding area 200 and the triangular region S to satisfy 0.05≤S1 / S2≤0.95, this disclosure can ensure that the welding area 200 at the short side of the cover plate 106 has a low risk of cracking while avoiding the insulation film being welded through, thereby taking into account both the connection strength of the shell 103 and the electrical safety of the battery 100.

[0116] It should be understood that in this disclosure, multiple components and / or portions can be provided by a single integrated component or portion. Alternatively, a single integrated component or portion may be divided into multiple separate components and / or portions. The use of "a" or "an" to describe a component or portion in the disclosure does not imply the exclusion of other components or portions.

[0117] The basic principles of this disclosure have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this disclosure are merely examples and not limitations, and should not be considered as essential features of each embodiment of this disclosure. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the scope of this disclosure to the necessity of employing the aforementioned specific details for implementation.

[0118] The above are merely specific embodiments of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. A battery (100) characterized in that, include: The housing (102) and the battery cell (104) disposed therein, the housing (102) including a shell (103) and a cover plate (106), the shell (103) including an end wall (108) and a side wall (110) surrounding the end wall (108), the cover plate (106) being perpendicular to the side wall (110), sealing the side of the shell (103) away from the end wall (108), and being welded to the side wall (110) to form a welding area (200); In a cross section of the welding zone (200) in a width direction perpendicular to the cover plate (106), an area of the welding zone (200) overlapping with a triangular area (S) is S1, in mm2 2 , an area of the triangular area (S) is S2, in mm2 2 , S1 / S2≥0.05, wherein, The welding area (200) has a first lowest point (P1) in a direction perpendicular to the first surface (120), the welding area (200) and the outer surface (112) of the sidewall (110) have a second lowest point (P2), the triangular region (S) includes a first side (E1) extending from the first lowest point (P1) to the second lowest point (P2), a second side (E2) extending from the first lowest point (P1) along the perpendicular direction of the first surface (120) and a third side (E3) extending from the second lowest point (P2) along the perpendicular direction of the second surface (130), the first surface (120) is one of the outer surface (112) and the surface (114) of the cover plate (106) away from the cell (104), the second surface (130) is the other of the outer surface (112) and the surface (114), and the welding heat source is directed towards the first surface (120).

2. The battery (100) according to claim 1, characterized in that, In the cross-section, S1 / S2 ≤ 0.

95.

3. The battery (100) according to claim 1, characterized in that, The sidewall (110) includes a pair of short sidewalls (110a) arranged opposite each other along the length direction of the battery (100) and a pair of long sidewalls (110b) arranged opposite each other along the width direction of the battery (100). The short sidewalls (110a) and the long sidewalls (110b) are connected end to end in sequence. The dimension of each short sidewall (110a) along the width direction is L1, in mm; the dimension of each long sidewall (110b) along the length direction is L2, in mm. 0.02≤L1 / L2≤0.

58.

4. The battery (100) according to claim 3, characterized in that, In the cross section of the welded area (200) perpendicular to the width direction of the cover plate (106), S1 / S2≥0.

1.

5. The battery (100) according to claim 1, characterized in that, The cover plate (106) includes a cover plate body (162) and a cover plate protrusion (164) disposed at the bottom of the cover plate body (162) along the height direction of the battery (100). At least part of the cover plate body (162) is supported on the top surface (116) of the side wall (110). The cover plate peripheral surface (106a) is disposed on the cover plate protrusion (164) and faces the inner surface (103a) of the side wall (110) along the height direction.

6. The battery (100) according to claim 5, characterized in that, The thickness of the cover plate protrusion (164) is t1, in mm, and t1 is the same along the height direction, and 0.3≤t1≤2.

7. The battery (100) according to claim 5, characterized in that, The thickness of the sidewall (110) is t2 in mm, and t2 is the same along the height direction, and 0.45≤t2≤1.

5.

8. The battery (100) according to claim 5, characterized in that, The sidewall (110) near the end of the cover plate has a first recess (118) recessed from its inner surface (103a) away from the cell (104), one end of the first recess (118) extending to the top surface (116) of the sidewall (110), including the inner surface (118a) of the first recess that overlaps with at least a portion of the peripheral surface (106a) of the cover plate along the height direction.

9. The battery (100) according to claim 8, characterized in that, The sidewall (110) includes a pair of short sidewalls (110a) arranged opposite each other along the length direction of the battery (100) and a pair of long sidewalls (110b) arranged opposite each other along the width direction of the battery (100). The short sidewalls (110a) and the long sidewalls (110b) are connected end to end in sequence. The thickness of the first recess (118) at the short sidewall (110a) is t13 in mm, and the thickness of the short sidewall (110a) is t12 in mm, and 0.8≤t13 / t12≤0.

98.

10. The battery (100) according to claim 8, characterized in that, Along the height direction, the dimension of the overlapping portion of the inner surface (118a) of the first recess and the peripheral surface (106a) of the cover plate is d1 in mm, and the dimension of the peripheral surface (106a) of the cover plate is d2 in mm, where 0.8 ≤ d1 / d2 ≤ 1.

11. The battery (100) according to claim 5, characterized in that, The sidewall (110) is provided with a guide portion (140) extending from its top surface (116) to its inner surface (103a), and the cover plate (106) is provided with a mating guide portion (150) extending from the bottom surface (117) of the cover plate body (162) to the peripheral surface (106a) of the cover plate. In the cross-section, the guide portion (140) has a first angle (α) with the top surface (116) and faces the mating guide portion (150) to support the mating guide portion (150) along the height direction.

12. The battery (100) according to claim 11, characterized in that, In the cross-section, the first angle (α) is greater than or equal to 30 degrees and less than or equal to 75 degrees.

13. The battery (100) according to claim 11, characterized in that, In the cross-section, the dimension of the guide portion (140) along the height direction is d3, in mm, where 0.1 ≤ d3 ≤ 0.

5.

14. The battery (100) according to claim 1, characterized in that, In the cross section, the cover plate (106) includes a cover plate peripheral surface (106a) surrounded by the inner surface (103a) of the side wall (110), and the minimum distance between the cover plate peripheral surface (106a) and the inner surface (103a) of the side wall (110) is i1, in mm, 0.01≤i1≤0.

2.

15. The battery (100) according to claim 1, characterized in that, In the cross-section, the welded area (200) has a weld width W200 perpendicular to the second surface (130), in mm, where 0.2 ≤ W200 ≤ 1.

3.

16. The battery (100) according to claim 1, characterized in that, The cover plate (106) includes a cover plate peripheral surface (106a) surrounded by the inner surface (103a) of the sidewall (110), and the welding area (200) has a maximum penetration depth perpendicular to the first surface (120), which is aligned with the cover plate peripheral surface (106a) in the cross-section.

17. The battery (100) according to any one of claims 1 to 16, characterized in that, The internal interface of the welding area (200) includes a straight edge (300). In the cross-section, the dimension of the straight edge (300) is a1 in mm, 0.1≤a1≤1.

0. The included angle between the straight edge (300) and the first surface (120) is greater than or equal to 87 degrees and less than or equal to 92 degrees.

18. The battery (100) according to claim 17, characterized in that, The dimension of the straight edge (300) is a1 in mm, and the dimension of the first edge (E1) is E11 in mm, where a1 < E11.

19. The battery (100) according to claim 17, characterized in that, 0.1≤a1 / E11≤0.

4.

20. A battery pack (10), characterized in that, Includes the battery (100) according to any one of claims 1 to 19.

21. The battery pack (10) according to claim 20, characterized in that, The battery includes at least two battery rows (105), each battery (100) including a pair of short sidewalls (110a) arranged opposite each other along its length direction and a pair of long sidewalls (110b) arranged opposite each other along its width direction, the battery row (105) including a plurality of batteries (100) arranged along the width direction of the battery (100), the short sidewall (110a) of the battery (100) in each battery row (105) facing the short sidewall (110a) of the battery (100) in the adjacent battery row (105).

22. The battery pack (10) according to claim 21, characterized in that, The dimension of the battery array (105) along the width direction of the battery (100) is L3 in mm, and the dimension along the length direction of the battery (100) is L4 in mm, and 2 ≤ L3 / L4.

23. The battery pack (10) according to claim 22, characterized in that, In the cross section of the welded area (200) formed between the cover plate (106) and the short sidewall (110a) of the battery (100), 0.2 ≤ S1 / S2 ≤ 0.

95.

24. The battery pack (10) according to claim 22, characterized in that, An adhesive (500) is provided on the short sidewall (110a) of the adjacent battery column (105), the adhesive (500) connects the adjacent battery column (105), and the top surface of the adhesive (500) is spaced apart from the surface (114) along the height direction of the battery (100).

25. An electrical appliance (1000), characterized in that, Includes the battery (100) as claimed in any one of claims 1 to 19, and / or includes the battery pack (10) as claimed in any one of claims 20 to 24.

26. A testing method applicable to the battery (100) as described in any one of claims 1 to 19, comprising: Obtain the battery (100); In the section of the welding area (200) formed between the cover plate (106) of the battery (100) and the side wall (110) of the battery (100), the area of the welding area (200) overlapping with a triangular area (S) is S1, unit: mm 2 The area of the triangular area (S) is S2, unit: mm 2 When S1 / S2≥0.05, the battery (100) is determined to be a good product, otherwise, the battery (100) is determined to be a non-good product. The welding area (200) has a first lowest point (P1) in a direction perpendicular to the first surface (120), and the welding area (200) and the outer surface (112) of the sidewall (110) have a second lowest point (P2). The triangular region (S) includes a first side (E1) extending from the first lowest point (P1) to the second lowest point (P2), a second side (E2) extending from the first lowest point (P1) along the perpendicular direction of the first surface (120), and a third side (E3) extending from the second lowest point (P2) along the perpendicular direction of the second surface (130). The first surface (120) is one of the outer surface (112) and the surface (114), and the second surface (130) is the other of the outer surface (112) and the surface (114). The welding heat source is directed towards the first surface (120).

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