Battery, battery pack, and electric device

Abstract

The application relates to the technical field of batteries, and discloses a battery, a battery pack and a power utilization device, which comprise: a shell comprising a shell body and a cover plate, at least one end of the shell body is formed with an opening part, the cover plate and the shell body are welded to form a welding area, the shell has a first surface, the first surface has two first edge parts which are oppositely arranged along the width direction of the first surface; an explosion-proof valve is arranged on the first surface, the explosion-proof valve has a thinning area; the penetration depth of the welding area is D1 mm, the fusion width of the welding area is D2 mm, the thickness of the battery along the width direction of the first surface is W mm, the distance between the thinning area and the first edge part is L1 mm, and the following conditions are met: W >= 35, 0.72 <= L1* D1* D2 <= 213. When the battery is in thermal runaway, the explosion-proof valve can be preferentially opened, the battery can be timely and directionally pressure released, meanwhile, the heat generated during the welding of the shell body and the cover plate is prevented from being too large to cause the melting of an insulating part, and the cover plate is prevented from being welded through to cause the damage of a battery cell.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to batteries, battery packs, and electrical devices. Background Technology

[0002] To ensure battery safety, batteries are typically equipped with explosion-proof valves to release high-temperature, high-pressure gases inside the battery in the event of thermal runaway, preventing more serious safety accidents such as battery explosions. With the continuous development of battery technology, the market demand for large-capacity batteries has gradually increased, leading to larger battery sizes. However, this has also resulted in more severe thermal runaway, causing weak points in the battery casing to rupture along with or even before the explosion-proof valve. This prevents the high-temperature, high-pressure gases inside the battery from being released through the explosion-proof valve, leading to the propagation of thermal runaway. Summary of the Invention

[0003] This invention provides a battery, a battery pack, and an electrical device to solve the problem in the prior art where high-temperature and high-pressure gases inside the battery cannot be discharged directionally through the explosion-proof valve, thus causing thermal runaway to spread.

[0004] In a first aspect, the present invention provides a battery comprising: An outer casing includes a housing and a cover plate, wherein at least one end of the housing has an opening, the cover plate is welded to the housing to form a welded area, the cover plate seals the opening and encloses the housing to form an accommodating space, and the outer casing has a first surface having two first edges spaced apart from each other along its width direction. An explosion-proof valve is disposed on the first surface. The explosion-proof valve has a thinning region and a main body region, wherein the thickness of the thinning region is less than the thickness of the main body region. The battery cell is disposed within the accommodating space; Wherein, the weld depth of the welding area is D1 mm, the weld width of the welding area is D2 mm, the thickness of the battery along the width direction of the first surface is W mm, and the distance between the thinning area and the first edge is L1 mm, satisfying W mm ≥ 35 mm and 0.72 ≤ L1 × D1 × D2 ≤ 213; The distance L1 mm between the thinning zone and the first edge satisfies 2.5 mm ≤ L1 mm ≤ 44 mm, the weld depth D1 mm and the weld width D2 mm of the welding zone satisfy 0.18 ≤ D1 × D2 ≤ 6; L1 and D1 × D2 are inversely correlated.

[0005] Beneficial effects: When the battery has a large thickness, the amount of gas generated during thermal runaway increases. By limiting the values ​​of the weld depth D1 mm, weld width D2 mm, and distance L1 mm between the thinned area and the first edge, the explosion-proof valve can be guaranteed to open first when the battery experiences thermal runaway. This allows the high-temperature and high-pressure gas inside the battery to be discharged in a directional manner, achieving timely and directional pressure relief of the battery and avoiding chain thermal runaway of adjacent batteries. At the same time, it avoids excessive heat generation during the welding of the casing and cover plate, which could cause the insulation to melt, and it also avoids damage to the battery cells caused by the cover plate being welded through, thus ensuring the quality of battery production. Specifically, if the values ​​of L1×D1×D2 are too small, it is easy for the welded area or the corner where the first edge is located to rupture during battery thermal runaway. This causes the high-temperature and high-pressure gas inside the battery to rush out from the rupture location, making it impossible to achieve directional discharge of the high-temperature and high-pressure gas, thus causing thermal propagation. This can lead to adjacent batteries also experiencing thermal runaway under the influence of high-temperature and high-pressure gas, resulting in a more serious safety accident. If the values ​​of L1×D1×D2 are too large, it is easy for the heat generated during the welding of the casing and cover plate to be too large, causing the insulation between the battery cover plate and the cell to melt. This can cause the cell to overlap with the casing or the positive and negative electrode plates inside the cell, resulting in a short circuit in the battery and affecting the battery's insulation performance. In addition, it is easy for the cover plate to be welded through during the welding of the casing and cover plate, causing the cell to be burned.

[0006] Secondly, the present invention also provides a battery pack comprising a plurality of the aforementioned batteries.

[0007] Thirdly, the present invention also provides an electrical device including the aforementioned battery pack. Attached Figure Description

[0008] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0009] Figure 1 This is a schematic cross-sectional view of a battery along its length and height directions according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the side welding structure of the shell and cover plate according to an embodiment of the present invention; Figure 3 for Figure 1 A schematic diagram of the structure when the battery welding area is not shown; Figure 4 for Figure 2 A schematic diagram of the structure when the battery welding area is not shown; Figure 5 This is a schematic diagram of the structure of a battery according to an embodiment of the present invention; Figure 6 for Figure 5 A top view of the battery shown; Figure 7 for Figure 6 A cross-sectional view along the AA direction; Figure 8 This is a schematic diagram of the structure of another battery according to an embodiment of the present invention; Figure 9 for Figure 8 A top view of the battery shown; Figure 10 for Figure 9 Cross-sectional view along the BB direction; Figure 11 for Figure 10 A magnified view of a section at point C; Figure 12 This is a schematic diagram of the structure of a shell according to an embodiment of the present invention; Figure 13 for Figure 12 The top view of the casing shown; Figure 14 for Figure 12 A magnified view of a section at point D; Figure 15 for Figure 13 A magnified view of a section at point E in the middle; Figure 16 This is a cross-sectional view of another battery along the length and height directions according to an embodiment of the present invention; Figure 17 This is a cross-sectional view of a housing along the width and height directions according to an embodiment of the present invention; Figure 18 This is a top view of the first surface and the thinning region according to an embodiment of the present invention; Figure 19 This is a cross-sectional view of another battery according to an embodiment of the present invention, along its length and height. Figure 20 This is a schematic diagram of the structure of a battery pack according to an embodiment of the present invention.

[0010] Explanation of reference numerals in the attached figures: 1. Outer shell; 11. Shell; 111. Shell opening; 112. Stepped section; 113. Second surface; 114. Third surface; 115. First corner; 116. Second corner; 12. Cover plate; 121. Body section; 122. Narrowing section; 13. Welding area; 131. Long side weld mark; 132. Short side weld mark; 14. First surface; 141. First side; 142. Second side; 2. Explosion-proof valve; 21. Thinning area; 211. Arc segment; 212. Straight segment; 22. Opening section; 221. First side; 222. Second side; 3. Battery cell; 4. Insulating component; 10. Battery; 100. Battery pack. Detailed Implementation

[0011] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0012] In battery manufacturing, the casing is typically made by stamping metal sheets, forming a square cylindrical structure with five sides enclosed and one side open, or a structure with four sides enclosed and two sides open. Due to bending deformation at the connection points between adjacent sides, and a certain degree of stretching during casing processing, the connection points (i.e., corners) are relatively thin, resulting in lower structural strength. Furthermore, after the battery cell is inserted into the casing, a cover plate is used to seal the opening, and the cover plate and casing are fixed together by welding. During the welding process, the cover plate and casing undergo high-temperature recrystallization, making the strength of the weld wire generally lower than that of the cover plate and casing. Moreover, the structural strength of the weld wire is further reduced by high temperatures. Therefore, the corners of the casing or the weld lines between the casing and the cover plate are prone to becoming weak points in the outer shell. If the battery is poorly manufactured, there is a risk that it may rupture along with or even before the explosion-proof valve in the event of thermal runaway, making it difficult for the explosion-proof valve to release pressure in a directional manner and increasing the pressure relief area. Therefore, this application provides a battery in which, in the event of thermal runaway, the explosion-proof valve opens before the weak point of the outer casing, thereby achieving directional pressure relief of the battery.

[0013] The following is combined Figures 1 to 20 The following describes embodiments of the present invention.

[0014] According to an embodiment of the present invention, in one aspect, a battery 10 is provided, comprising: The outer casing 1 includes a housing 11 and a cover plate 12. At least one end of the housing 11 is formed with an opening. The cover plate 12 and the housing 11 are welded to form a welding area 13. The cover plate 12 seals the opening and encloses the housing 11 to form an accommodating space. The outer casing 1 has a first surface 14. The first surface 14 has two first edges 141 that are spaced apart from each other along its width direction. An explosion-proof valve 2 is disposed on the first surface 14. The explosion-proof valve 2 has a thinning region 21 and a main body region. The thickness of the thinning region is less than the thickness of the main body region. Battery cell 3 is housed within the receiving space; The welding depth of the welding area 13 is D1 mm, the welding width of the welding area 13 is D2 mm, the thickness of the battery 10 along the width direction of the first surface 14 is W mm, and the distance between the thinning area 21 and the first edge 141 is L1 mm, satisfying W mm≥35 mm and 0.72≤L1×D1×D2≤213.

[0015] When the battery 10 of this embodiment has a large thickness, the amount of gas generated during thermal runaway increases. By limiting the values ​​of the weld depth D1 mm, weld width D2 mm, and distance L1 mm between the thinning area 21 and the first edge 141 in the welded area 13, the explosion-proof valve 2 can be opened first when thermal runaway occurs in the battery 10. This allows the high-temperature and high-pressure gas inside the battery 10 to be discharged in a directional manner, achieving timely and directional depressurization of the battery 10 and avoiding chain thermal runaway of adjacent batteries 10. At the same time, it avoids excessive heat generation during welding of the casing 11 and the cover plate 12, which could cause the insulation to melt, and it also avoids the cover plate 12 being welded through, which could damage the cell 3, thus ensuring the production quality of the battery 10.

[0016] It is worth noting that as the value of L1 gradually increases, the tensile force on the first edge gradually decreases when the thinning zone opens; and as the value of D1×D2 gradually increases, the welding strength of the welding zone gradually increases. When the value of L1 relatively increases, the value of D1×D2 relatively decreases, and when the value of L1 relatively decreases, the value of D1×D2 relatively increases. That is, L1 and D1×D2 are inversely correlated.

[0017] Specifically, if the values ​​of L1×D1×D2 are too small, it is easy for the welding area 13 or the corner where the first side 141 is located to rupture when the battery 10 experiences thermal runaway. This causes the high-temperature and high-pressure gas inside the battery 10 to rush out from the rupture location, making it impossible to achieve directional discharge of the high-temperature and high-pressure gas, thus causing thermal propagation. This can lead to the adjacent battery 10 also experiencing thermal runaway under the influence of the high-temperature and high-pressure gas, resulting in a more serious safety accident. If the values ​​of L1×D1×D2 are too large, it is easy for the heat generated during the welding of the casing 11 and the cover plate 12 to be too large, causing the insulation 4 between the battery cover plate and the cell to melt. This can cause the cell to overlap with the casing or the positive and negative electrode plates inside the cell to overlap, resulting in a short circuit in the battery and affecting the insulation performance of the battery 10. In addition, it is easy for the cover plate 12 to be welded through during the welding of the casing 11 and the cover plate 12, causing the cell 3 to be burned.

[0018] Optionally, L1×D1×D2 can be any value from 0.72, 1.5, 3.6, 5, 10, 30, 50, 80, 100, 103.5, 120, 150, 180, 200, 213 or a value between any two values.

[0019] Preferably, the value of L1×D1×D2 satisfies 3.6≤L1×D1×D2≤103.5.

[0020] Optionally, W can be any value from 35, 35.5, 36, 40, 50, 60, 80, 100, or a value between any two values. Of course, it can also be a value greater than 100.

[0021] It is worth noting that when the battery 10 experiences a short circuit, thermal runaway, or other safety issues, high-temperature and high-pressure gas will be generated inside the battery 10. By setting up the explosion-proof valve 2, when the pressure inside the battery 10 reaches a certain value (that is, the opening pressure of the explosion-proof valve 2), the high-temperature and high-pressure gas will break through the thinned area 21, causing the explosion-proof valve 2 to open and achieve directional pressure relief of the battery 10 at the explosion-proof valve 2.

[0022] However, research has found that for batteries 10 with a larger thickness, especially those ≥35mm, the capacity of the battery 10 is larger, and the amount of gas generated during thermal runaway is also greater. The pressure inside the outer casing 1 will be greater than that of batteries 10 with a normal thickness. At this time, the risk of cracking of the casing or the welding line is greater. Areas with lower structural strength, such as welding lines and corners of the casing 11, are at risk of cracking before or simultaneously with the thinning area 21, causing safety hazards.

[0023] In particular, the large surface of the battery 10 where the first edge 141 (extending along the length of the first surface 14, i.e., the long side of the first surface 14) is located is severely bulging, which further increases the risk of cracking at the weld at the first edge 141 or at the corner where the first edge 141 is located.

[0024] Therefore, in this embodiment, by controlling the distance L1 mm between the thinning area 21 and the first edge 141, the tensile force applied to the first edge 141 when the thinning area 21 is opened is limited. By controlling the weld depth D1 mm and / or weld width D2 mm of the welding area 13, the welding strength of the welding area 13 is ensured, thereby effectively reducing the risk of cracking at the weak point of the outer shell 1. At the same time, it ensures that the explosion-proof valve 2 can release pressure smoothly, reducing the safety risks of using the battery 10.

[0025] It is worth noting that the width direction of the first surface 14 is the thickness of the battery 10, which is also the stacking direction of the positive and negative electrode sheets in the cell 3.

[0026] It should be noted that the aforementioned insulating components can be one or more of the following: a lower plastic film, a cell insulating film (Mylar film), and a separator. The lower plastic film is typically fixed to the surface of the cover plate facing the cell, used to insulate the cell from the cover plate to reduce the risk of short circuits. The thickness of the lower plastic film is typically 0.5mm-2mm. The lower plastic film can be plastic, rubber, or other insulating materials. Plastics can be any of the following: polyethylene terephthalate (PET), polypropylene (PP), polycarbonate (PC), and polyvinyl chloride (PVC). Rubber can be any of the following: fluororubber, nitrile rubber, or isobutyl rubber. The cell insulating film (Mylar film) covers the surface of the cell, used to insulate the cell from the battery's metal casing and prevent the cell from being scratched when installed in the battery casing. The side of the Mylar film closest to the cover plate is heat-fused or bonded to the side of the lower plastic film. Mylar films are commonly made of polyester polymers, such as PP, HDPE, and PRTP, and have good surface smoothness, transparency, and mechanical flexibility. In actual production, the Mylar membrane is a semi-transparent, flexible thin film (e.g., with a thickness of approximately 0.1 mm). A separator is placed between the positive and negative electrodes to separate them and prevent short circuits. The separator's dimensions extend beyond the positive and negative electrodes. The separator can be at least one of glass fiber, non-woven fabric, polyethylene (PE), polypropylene (PP), and polyvinylidene fluoride (PVDF). A coating can also be applied to the separator surface. This coating can be inorganic and / or organic, wherein the inorganic coating material includes at least one of alumina, silicon dioxide, titanium dioxide, magnesium oxide, zirconium oxide, and boehmite; and the organic coating includes at least one of aramid coating and polyvinylidene fluoride (PVDF) coating.

[0027] It is understandable that when the heat generated during the welding of the shell and cover plate is too large, the diaphragm shrinks due to heat, causing the positive and negative electrode plates to come into contact and triggering a short circuit.

[0028] It is worth noting that the welding method for the cover plate and the shell can be laser welding, resistance welding, brazing, etc., with laser welding being preferred. Preferably, along the weld depth direction and / or weld width direction, the dimension of the welded area on the cover plate is larger than the dimension on the shell, in order to ensure the weld strength between the shell and the cover plate.

[0029] It should be further explained that the penetration direction is parallel to the welding direction, while the weld width direction is perpendicular to the penetration direction. Along the penetration direction, the weld width of the weld zone generally narrows gradually, or it may narrow in a step-like manner.

[0030] Regarding the placement of the explosion-proof valve 2 on the housing 1, it can be placed on the cover plate 12, in which case the first surface 14 is formed on the cover plate 12; alternatively, it can be placed on the housing 11, in which case the first surface 14 is formed on the housing 11. The specific implementation methods of placing the explosion-proof valve 2 on the cover plate 12 and on the housing 11 are described below.

[0031] In the first implementation, such as Figure 1 , Figure 5 , Figure 8 As shown, the explosion-proof valve 2 is mounted on the cover plate 12, and the thickness of the cover plate 12 is greater than the wall thickness of the housing 11. The cover plate 12 is thicker than the housing 11, and mounting the explosion-proof valve 2 on the cover plate 12 increases the strength of the explosion-proof valve 2, further ensuring its reliability.

[0032] It is worth noting that the cover plate 12 is made thicker than the shell 11 to ensure the strength of the cover plate itself. Specifically, the cover plate is generally provided with functional components such as liquid injection holes, terminal post assemblies or explosion-proof valves, which need to be strong enough to resist deformation. In addition, in order to ensure the utilization rate of the internal space of the battery, the thickness of the shell is set to be less than the thickness of the cover plate.

[0033] In the first implementation, such as Figure 1 As shown, the weld penetration direction of the welding area 13 is parallel to the thickness direction of the cover plate 12, that is, the shell 11 and the cover plate 12 are welded together by top welding. At this time, the weld penetration direction of the welding area 13 is parallel to the main vibration direction of the battery 10, and the shear force on the welding area 13 is greater, which increases the risk of cracking of the welding area 13. Therefore, the distance L1 mm between the thinning area 21 and the first edge 141 is made to satisfy 4mm≤L1 mm≤40mm. By further limiting the value of L1 mm, the tensile force on the weld line at the first edge 141 when the thinning area 21 is opened is further reduced, the risk of cracking of the welding area 13 is reduced, and the directional pressure relief of the battery 10 is ensured.

[0034] It is worth noting that the direction of the weld depth in the welding zone 13 is parallel to the thickness direction of the cover plate 12, which can also be understood as the direction of the weld depth in the welding zone 13 being perpendicular to the side of the cover plate 12 away from the accommodating space.

[0035] Of course, as alternative implementation methods, such as Figure 2 As shown, the weld penetration direction of the welding area 13 can also be perpendicular to the thickness direction of the cover plate 12. That is, the shell 11 and the cover plate 12 can be welded together using side welding. In this case, the weld penetration direction of the welding area 13 is perpendicular to the main vibration direction of the battery 10, which reduces the shear force on the welding area 13 and makes it easier to ensure the structural strength of the welding area 13.

[0036] In the first implementation, such as Figures 1 to 4 As shown, along the thickness direction of the cover plate 12, the dimension of the portion of the welding area 13 within the cover plate 12 is D3 mm. At least a portion of the cover plate 12 along its thickness direction is inserted into the opening, and the thickness of the portion of the cover plate 12 inserted into the opening along its thickness direction is a mm, satisfying D3 < a. This arrangement further ensures that the welding area 13 will not weld through the cover plate 12, guarantees the welding quality of the welding area 13, ensures the insulation performance of the insulating component, and avoids damage to the battery cell 3.

[0037] It is worth noting that, such as Figure 1 and Figure 3 As shown, the cover plate 12 can be inserted entirely into the opening along its thickness direction. In this case, the thickness of the portion of the cover plate 12 inserted into the opening is the entire thickness of the cover plate 12. Furthermore, the housing 11 and the cover plate 12 are typically welded together using a top-welding method. Figure 2 and Figure 4 As shown, the cover plate 12 can also be partially inserted into the opening along the thickness direction. In this case, the thickness of the part of the cover plate 12 inserted into the opening is the partial thickness of the cover plate 12. In addition, the housing 11 and the cover plate 12 are usually welded by side welding.

[0038] Of course, as an alternative implementation, D3 ≥ a can also be made. In this case, it is only necessary to ensure that the part of the welding area 13 inside the cover plate 12 does not penetrate the cover plate, or to weld the welding area beyond the cover plate into the housing.

[0039] Furthermore, in the first embodiment, the dimension D3 mm of the portion of the welding area 13 within the cover plate 12 and the thickness a mm of the portion of the cover plate 12 inserted into the opening satisfy 0.2 ≤ a - D3 ≤ 2.7. This arrangement ensures the welding strength of the welding area 13 while reducing the impact of the heat generated during welding on the insulating components and the battery cell 3.

[0040] It is worth noting that if the value of a-D3 is too large, the welding size of the welding area 13 may be too small, reducing the welding strength of the welding area 13 and increasing the risk that high-temperature and high-pressure gas will break through the welding area 13 during thermal runaway of the battery 10, thus affecting the directional pressure relief of the battery 10. If the value of a-D3 is too small, the heat generated during the welding of the casing 11 and the cover plate 12 may be too large, causing the insulating components to melt and affecting the insulation performance of the battery 10. In addition, it may cause the cover plate 12 to be welded through during the welding of the casing 11 and the cover plate 12, resulting in the cell 3 being burned.

[0041] Optionally, the value of a-D3 can be any one of 0.2, 0.5, 0.8, 1, 1.2, 1.5, 1.8, 2, 2.2, 2.5, 2.7 or a value between any two values.

[0042] Specifically, in the first implementation, such as Figure 6 As shown, the distance L1mm between the thinning zone 21 and the first edge 141 satisfies 2.5mm ≤ L1mm ≤ 40mm. By placing the explosion-proof valve 2 on the cover plate 12, which has a greater thickness and higher structural strength, the impact force transmitted from the thinning zone 21 to the first edge 141 is reduced when the thinning zone 21 opens under the action of high-temperature and high-pressure gas, thus lowering the risk of breakage of the welded area 13. Therefore, by further limiting the value of L1mm, the setting range of the thinning zone 21 can be further increased, improving the gas flow area after the explosion-proof valve 2 opens and achieving rapid pressure relief.

[0043] Optionally, L1 can be any value from 2.5, 4, 5, 6, 8, 10, 12, 15, 18, 20, 22, 25, 28, 30, 32, 35, 38, 40, or a value between any two values.

[0044] Furthermore, in the first embodiment, such as Figure 6 As shown, the first surface 14 has two second sides 142 spaced apart along its length. The distance between the thinned area 21 and the second side 142 along the length of the first surface 14 is L2 mm, satisfying 50 mm ≤ L2 mm ≤ 200 mm. This arrangement reduces the pulling effect on the welding area 13 when the explosion-proof valve 2 is opened, preventing the welding area 13 from tearing, ensuring directional pressure relief of the battery 10, and ensuring the gas flow area after the explosion-proof valve 2 is opened.

[0045] It is worth noting that if the value of L2 mm is too small, when the high-temperature and high-pressure gas inside the battery 10 breaks through the explosion-proof valve 2 in the thinning zone 21, the force of the high-temperature and high-pressure gas on the explosion-proof valve 2 will be quickly transmitted to the welding zone 13 at the second side 142, increasing the risk of tearing of the welding zone 13. This would cause the high-temperature and high-pressure gas inside the battery 10 to rush out from the rupture point of the welding zone 13, making it impossible to achieve directional discharge of the high-temperature and high-pressure gas, thus causing thermal propagation. Consequently, adjacent batteries 10 may also experience thermal runaway under the influence of the high-temperature and high-pressure gas, leading to a more serious safety accident. If the value of L2 mm is too large, it may reduce the setting range of the thinning zone 21, resulting in a smaller gas flow area after the explosion-proof valve 2 is opened. This would not be able to guarantee the rapid depressurization of the battery 10, increasing the risk of explosion of the battery 10.

[0046] Optionally, L2 can be any value from 50, 80, 100, 120, 150, 180, 200 or a value between any two values.

[0047] It should be noted that, as Figure 6 As shown, the second side 142 extends along the width direction of the first surface 14, which is the short side of the first surface 14.

[0048] It needs to be further explained that, such as Figure 7 and Figure 19 As shown, the welding area 13 includes a long-side weld mark 131 extending along the length direction of the cover plate 12 and a short-side weld mark 132 extending along the width direction of the cover plate 12. That is, the long-side weld mark 131 is provided along the first side 141, and the short-side weld mark 132 is provided along the second side 142.

[0049] It is worth noting that the shell may have an opening at only one end, which is then sealed with a cover plate. Alternatively, the shell may have openings at both opposite ends, with two cover plates sealing each opening respectively.

[0050] In the second implementation, such as Figure 16 As shown, the first surface 14 is located on the housing 11 and is positioned opposite to the cover plate 12. At this time, the explosion-proof valve 2 and the welding area 13 are located at opposite ends in the height direction of the battery 10 (that is, the thickness direction of the cover plate 12). When the explosion-proof valve 2 is opened, the welding area 13 is subjected to less pulling force, which reduces the risk of tearing of the welding area 13.

[0051] It is worth noting that the first surface can be either the bottom or top surface of the battery. Preferably, the first surface is the bottom surface of the battery, which can better achieve thermal and electrical separation and ensure the safety of battery use.

[0052] Furthermore, in the second embodiment, the value of L1 mm is set to satisfy 2.5 mm ≤ L1 mm ≤ 35 mm, so as to increase the pressure relief area of ​​the battery after the explosion-proof valve is opened and improve the exhaust rate.

[0053] In the second implementation, such as Figure 17 As shown, the housing 11 includes a third surface 114 perpendicular to the first surface 14, and the third surface 114 is parallel to the length direction of the first surface 14. The area of ​​the first surface 14 is smaller than the area of ​​the third surface 114. That is, the first surface 14 where the explosion-proof valve 2 is located is not the large surface of the battery 10, thus avoiding the risk of abnormal opening of the explosion-proof valve 2 due to the large deformation of the large surface of the battery 10.

[0054] Furthermore, in the second embodiment, such as Figure 17 As shown, a second corner portion 116 is formed at the junction of the first surface 14 and the third surface 114. The wall thickness of the housing 11 at the second corner portion 116 is i mm, satisfying 0.25 mm ≤ i mm ≤ 1.4 mm. This configuration ensures both the structural strength of the second corner portion 116 and the volumetric energy density of the battery 10.

[0055] It is worth noting that if the value of i mm is too small, the casing 11 will be too thin at the second corner 116, resulting in insufficient structural strength of the second corner 116. Under the action of high-temperature and high-pressure gas inside the battery 10, it is prone to rupture, causing the high-temperature and high-pressure gas inside the battery 10 to rush out from the rupture location of the second corner 116. This prevents the directional discharge of the high-temperature and high-pressure gas, causing heat propagation and resulting in thermal runaway of adjacent batteries 10 under the influence of high-temperature and high-pressure gas, leading to a more serious safety accident. If the value of i mm is too large, it is easy to make the wall thickness of the casing 11 too large, occupying the arrangement space of the cell 3 and affecting the volumetric energy density of the battery 10.

[0056] Optionally, the value of i can be any one of 0.25, 0.3, 0.4, 0.5, 0.8, 1, 1.2, 1.3, 1.4 or a value between any two values.

[0057] Furthermore, in the second embodiment, such as Figure 16 and Figure 17 As shown, a second corner 116 is formed at the junction of the first surface 14 and the third surface 114. The wall thickness of the shell 11 at the second corner 116 is i mm, and the thickness of the thinning region 21 is j mm, satisfying ij≤0.5. This configuration ensures that the structural strength at the second corner 116 is higher than that at the thinning region 21, guaranteeing that the explosion-proof valve 2 opens preferentially in the event of thermal runaway of the battery 10, thereby achieving directional pressure relief of the battery 10.

[0058] Optionally, ij can take any value from 0, 0.1, 0.2, 0.3, 0.4, 0.5 or a value between any two values.

[0059] Furthermore, in the second embodiment, the weld penetration depth D1 mm of the welded area 13 and the wall thickness i mm of the shell 11 at the second corner 116 satisfy D1 > i. This configuration can further improve the welding strength of the welded area 13, prevent the welded area 13 from rupturing under the action of high temperature and high pressure gas, and further ensure that the explosion-proof valve 2 opens preferentially in the event of thermal runaway of the battery 10, thereby achieving directional pressure relief of the battery 10.

[0060] Specifically, in the second implementation, such as Figure 16 As shown, along the thickness direction of the cover plate 12, the height of the battery 10 is H mm, satisfying H mm ≤ 120 mm. This setting avoids the side where the welding area 13 is located being too far from the side where the explosion-proof valve 2 is located, which would cause high-temperature and high-pressure gas to accumulate on the side where the welding area 13 is located, reducing the impact of high-temperature and high-pressure gas on the welding area 13, and preventing the welding area 13 from rupturing and affecting the directional pressure relief of the battery 10.

[0061] Furthermore, the value of L1×D1×D2 satisfies 0.72≤L1×D1×D2≤103.5.

[0062] Optionally, H can be any value from 120, 115, 110, 105, 90, 80, 60, 50, 20, or any value between two values. Of course, it can also be a value less than 20.

[0063] It is worth noting that the thickness direction of the cover plate 12 is the same as the thickness direction of the first surface 14, which is also the height direction of the battery 10.

[0064] Of course, as an alternative implementation, the height H mm of the battery 10 along the thickness direction of the cover plate 12 can also be greater than 120 mm.

[0065] It is worth noting that in other alternative embodiments, when the first surface 14 is located on the housing 11, the first surface can also be the surface of the housing used to connect with the cover plate (i.e., the side of the housing). Preferably, the first surface is the surface of the housing connected to the short side of the cover plate.

[0066] In one embodiment, such as Figure 11As shown, the cover plate 12 includes a body portion 121 and a narrowing portion 122 connected along its thickness direction. The narrowing portion 122 is disposed on the side of the body portion 121 facing the battery cell 3. Along the length and width directions of the cover plate 12, the size of the narrowing portion 122 is smaller than the size of the body portion 121, and the narrowing width of the end of the narrowing portion 122 away from the body portion 121 is b mm, satisfying 0.2 mm ≤ b mm ≤ 1 mm. By providing the narrowing portion 122, a guiding effect is provided for the cover plate 12 to be inserted into the opening of the housing 11. Furthermore, by limiting the value of b mm, the guiding effect of the narrowing portion 122 is ensured while the welding quality of the welding area 13 is guaranteed.

[0067] It is worth noting that if the value of b mm is too small, the narrowing degree of the narrowing portion 122 is relatively low compared to the main body portion 121, and there is still a risk that the cover plate 12 is not easy to be inserted into the shell, affecting the assembly efficiency and fit effect of the cover plate 12 and the shell 11. If the value of b mm is too large, the narrowing degree of the narrowing portion 122 is relatively large compared to the main body portion 121, affecting the setting range of the welding area 13, which can easily lead to poor welding. In addition, it can easily cause cracks in the welding area 13 along the outer peripheral surface of the narrowing portion 122 and the outer peripheral surface of the main body portion 121, affecting the welding strength of the welding area 13. Under the action of high temperature and high pressure gas inside the battery 10, the welding area 13 is prone to rupture, causing the high temperature and high pressure gas inside the battery 10 to rush out from the rupture position of the welding area 13, making it impossible to achieve directional discharge of high temperature and high pressure gas, causing heat propagation phenomenon, thereby causing adjacent batteries 10 to also experience thermal runaway under the influence of high temperature and high pressure gas, leading to a more serious safety accident.

[0068] Optionally, b can take any value from 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, or a value between any two values.

[0069] It is worth noting that a chamfer is formed on the outer periphery (full or partial) of the portion of the cover plate substrate near the cell along the thickness direction to create a narrowed section. Furthermore, the chamfer can be provided on one side along the length and / or width direction of the cover plate for narrowing, or it can be narrowed on both sides along the length and / or width direction of the cover plate; the aforementioned narrowing width b mm refers to the narrowing dimension on one side.

[0070] In one embodiment, such as Figures 12 to 15As shown, the housing 11 includes a housing opening 111 surrounding the opening, and a stepped portion 112. The stepped portion 112 is located on the side of the housing opening 111 away from the opening, and protrudes towards the battery cell 3 compared to the housing opening 111. The cover plate 12 abuts against the side of the stepped portion 112 facing the opening. The wall thickness of the housing 11 at the housing opening 111 is c mm, and the wall thickness of the housing 11 at the stepped portion 112 is e mm, satisfying e > c. By providing the stepped portion 112, the abutment limit of the cover plate 12 during assembly is used to ensure the positional accuracy of the cover plate 12 and the fit between the cover plate 12 and the housing 11, thereby facilitating welding of the cover plate and the housing and improving the welding yield. In addition, by providing the stepped portion, the laser can also be prevented from hitting the receiving space during laser welding of the cover plate and the housing, avoiding problems such as shrinkage of insulating components such as the diaphragm. In addition, by setting a stepped section, the part of the shell used for welding with the cover plate has a greater thickness, which improves the welding strength of the welding area inside the shell and ensures the connection strength between the shell and the cover plate.

[0071] Furthermore, in one embodiment, such as Figures 12 to 15 As shown, the housing 11 includes two second surfaces 113 that are spaced apart from each other along the length of the cover plate 12 and two third surfaces 114 that are spaced apart from each other along the width of the cover plate 12. The second surfaces 113 and the third surfaces 114 are connected to form a first corner portion 115, and a step portion 112 is formed at at least one first corner portion 115.

[0072] It is worth noting that there are four first corner portions 115, and at least one of the first corner portions 115 is provided with a step portion 112. Preferably, the two first corner portions 115 that are diagonally arranged are provided with step portions 112, or all four first corner portions 115 are provided with step portions 112.

[0073] As an alternative implementation, the step portion 112 may also be provided on the second surface 113 and / or the third surface 114.

[0074] Specifically, in one embodiment, such as Figure 11 As shown, the thickness of the cover plate 12 is f mm, which satisfies 1.5 mm ≤ f mm ≤ 3.5 mm. This setting ensures the structural strength of the cover plate 12 and the welding strength of the welding area 13, while also guaranteeing the volumetric energy density of the battery 10.

[0075] It is worth noting that if the value of f mm is too small, the structural strength of the cover plate 12 may be insufficient, affecting the welding range of the welding area 13 and causing insufficient welding strength. Under the influence of high-temperature and high-pressure gas inside the battery 10, the welding area 13 is prone to rupture, allowing the high-temperature and high-pressure gas inside the battery 10 to escape through the rupture point. This prevents the directional discharge of the high-temperature and high-pressure gas, leading to heat propagation and causing adjacent batteries 10 to also experience thermal runaway under the influence of the high-temperature and high-pressure gas, resulting in a more serious safety accident. If the value of f mm is too large, the cover plate 12 may occupy too much space in the battery 10, affecting the placement range of the cell 3 and the volumetric energy density of the battery 10.

[0076] Optionally, f can take any value from 1.5, 1.8, 2, 2.2, 2.5, 2.8, 3, 3.2, 3.5, or a value between any two values.

[0077] Specifically, in one embodiment, such as Figure 11 As shown, the wall thickness of the casing 11 is g mm, satisfying 0.45 mm ≤ g mm ≤ 1.5 mm. This configuration ensures both the structural strength of the casing 11 and the volumetric energy density of the battery 10.

[0078] It is worth noting that if the value of g mm is too small, the structural strength of the casing 11 may be insufficient. The corners of the casing 11 are prone to rupture under the influence of the high-temperature, high-pressure gas inside the battery 10. This allows the high-temperature, high-pressure gas inside the battery 10 to escape through the ruptured corner, preventing directional discharge and causing heat propagation. Consequently, adjacent batteries 10 may also experience thermal runaway under the influence of the high-temperature, high-pressure gas, leading to a more serious safety accident. If the value of g mm is too large, the casing 11 may occupy too much space in the battery 10, affecting the placement range of the cell 3 and the volumetric energy density of the battery 10.

[0079] Optionally, g can take any value from 0.45, 0.5, 0.6, 0.8, 1, 1.2, 1.4, 1.5 or a value between any two values.

[0080] Furthermore, in one embodiment, the thickness f mm of the cover plate 12 and the wall thickness g mm of the housing 11 satisfy 0.5 ≤ fg ≤ 3.05.

[0081] Optionally, fg can be any value from 0.5, 0.6, 0.8, 1, 1.2, 1.5, 1.8, 2, 2.2, 2.5, 2.8, 3.05, or a value between any two values.

[0082] In one embodiment, such as Figure 5 and Figure 18 As shown, the length direction of the thinning region 21 is parallel to the length direction of the first surface 14, and the distance L1 mm between the thinning region 21 and the first edge 141 satisfies 5 mm ≤ L1 mm ≤ 40 mm. This arrangement provides sufficient layout space along the length direction of the first surface 14, increasing the installation range of the thinning region 21 and improving the gas flow area after the explosion-proof valve 2 is opened, thus achieving rapid pressure relief. Therefore, the distance between the thinning region 21 and the first edge 141 can be further increased, further reducing the tensile force on the first edge 141 when the thinning region 21 is opened, reducing the risk of cracking at the welding area 13 or corners, and ensuring directional pressure relief of the battery 10.

[0083] It is worth noting that, such as Figure 18 As shown, the area enclosed by the thinning region 21 is typically oblong. Specifically, the thinning region 21 includes two arc segments 211 and at least one straight segment 212. The two arc segments 211 are spaced apart relative to each other along the length of the cover plate 12, and the straight segment 212 extends along the length of the cover plate 12 and connects the two ends of the two arc segments 211 that are positioned opposite each other along the length of the cover plate 12. Therefore, the extending direction of the straight segment 212 is the length direction of the thinning region 21.

[0084] In another embodiment, such as Figure 8 As shown, the length direction of the thinning region 21 is parallel to the width direction of the first surface 14. In this case, the space in the width direction of the first surface 14 is limited, which easily leads to the thinning region 21 being too close to the first edge 141. The impact force when the thinning region 21 is opened has a significant impact on the welding region 13, easily causing the welding region 13 to crack and affecting the directional pressure relief of the battery 10. Therefore, the weld depth D1 mm and weld width D2 mm of the welding region 13 are made to satisfy 0.4≤D1×D2≤6, thereby further increasing the welding strength of the welding region 13, reducing the cracking risk of the welding region 13, and ensuring the directional pressure relief of the battery 10.

[0085] In one embodiment, such as Figure 1 and Figure 19 As shown, the explosion-proof valve 2 includes an opening portion 22 formed by a thinning region 21. The opening portion 22 has a first side 221 facing away from the battery cell 3 and a second side 222 facing the battery cell 3. Along the thickness direction of the first surface 14, the thinning region 21 is positioned close to the first side 221 or close to the second side 222. The thickness of the thinning region 21 is j mm, satisfying 0.04 mm ≤ j mm ≤ 0.3 mm. This configuration ensures that the explosion-proof valve 2 opens preferentially, allowing the high-temperature and high-pressure gas inside the battery 10 to be directionally discharged, achieving timely and directional pressure relief of the battery 10. At the same time, it ensures the predetermined opening pressure of the explosion-proof valve 2, preventing premature or accidental opening of the explosion-proof valve 2 and ensuring its reliability.

[0086] Specifically, if the value of j mm is too small, the structural strength of the explosion-proof valve 2 may be insufficient, resulting in a decrease in the opening pressure of the explosion-proof valve 2. This could cause the explosion-proof valve 2 to open prematurely, and the explosion-proof valve 2 may open unexpectedly when the battery 10 is subjected to collisions or impacts. If the value of j mm is too large, the opening pressure of the explosion-proof valve 2 may be too large. When the battery 10 experiences thermal runaway, the corner of the welding area 13 and the shell 11 may be subjected to excessive pressure and rupture. This could cause the high-temperature and high-pressure gas inside the battery 10 to rush out from the rupture location, making it impossible to achieve directional discharge of the high-temperature and high-pressure gas. This could lead to thermal propagation, causing adjacent batteries 10 to also experience thermal runaway under the influence of the high-temperature and high-pressure gas, resulting in a more serious safety accident.

[0087] Optionally, j can take any value from 0.04, 0.06, 0.08, 0.1, 0.15, 0.2, 0.22, 0.25, 0.28, 0.3, or a value between any two values.

[0088] Specifically, in one embodiment, the penetration depth D1 mm of the welding zone 13 satisfies 0.3 mm ≤ D1 mm ≤ 2 mm.

[0089] Optionally, D1 can be any value from 0.3, 0.5, 0.8, 1, 1.2, 1.5, 1.8, 2, or a value between any two values.

[0090] Specifically, in one embodiment, the weld width D2 mm of the weld zone 13 satisfies 0.6 mm ≤ D2 mm ≤ 3 mm.

[0091] Optionally, D2 can be any value from 0.6, 0.8, 1, 1.5, 2, 2.2, 2.5, 2.8, 3, or a value between any two values.

[0092] Specifically, in one embodiment, the weld depth D1 mm and the weld width D2 mm of the weld zone 13 satisfy 0.18≤D1×D2≤6.

[0093] Optionally, the value of D1×D2 can be any one of 0.18, 0.4, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6 or a value between any two values.

[0094] This configuration ensures the welding strength of the welding zone 13 while reducing the impact of the heat generated during welding on the insulating components and the battery cell 3.

[0095] It is worth noting that if the values ​​of D1 mm and D2 mm are too small, the welding strength of the welding area 13 may be insufficient, increasing the risk that high-temperature and high-pressure gas will break through the welding area 13 during thermal runaway of the battery 10, thus affecting the directional pressure relief of the battery 10. If the values ​​of D1 mm and D2 mm are too large, the heat generated during the welding of the casing 11 and the cover plate 12 may be too large, causing the insulating components to melt and affecting the insulation performance of the battery 10. In addition, it may cause the cover plate 12 to be welded through during the welding of the casing 11 and the cover plate 12, resulting in the cell 3 being burned.

[0096] Specifically, in one embodiment, the distance L1 mm between the thinning region 21 and the first edge 141 satisfies 2.5 mm ≤ L1 mm ≤ 44 mm. This setting reduces the tensile force on the weld wire at the first edge 141 when the thinning region 21 is opened, reduces the risk of cracking in the welded area 13, ensures directional pressure relief of the battery 10, and ensures the gas flow area after the explosion-proof valve 2 is opened, thus achieving rapid pressure relief.

[0097] It is worth noting that if the value of L1mm is too small, the distance between the thinning area and the first edge may be too close. When the high-temperature and high-pressure gas inside the battery 10 breaks the explosion-proof valve 2 in the thinning area 21, the force of the high-temperature and high-pressure gas on the explosion-proof valve 2 will be quickly transmitted to the welding area 13 at the first edge, increasing the risk of tearing of the welding area 13. This will cause the high-temperature and high-pressure gas inside the battery 10 to rush out from the rupture point of the welding area 13, making it impossible to achieve directional discharge of the high-temperature and high-pressure gas, causing thermal propagation. Consequently, adjacent batteries 10 may also experience thermal runaway under the influence of the high-temperature and high-pressure gas, leading to a more serious safety accident. If the value of L1mm is too large, the setting range of the thinning area 21 may be reduced, resulting in a smaller gas flow area after the explosion-proof valve 2 is opened. This will not be able to guarantee the rapid depressurization of the battery 10, increasing the risk of explosion of the battery 10.

[0098] Optionally, L1 can take any value from 2.5, 5, 7.5, 10, 12.5, 15, 17.5, 20, 22.5, 25, 27.5, 30, 32.5, 35, 37.5, 40, 42, 44, or a value between any two values.

[0099] In one embodiment, the battery cell 3 is disposed on the upper part of the first surface 14, which supports the battery cell 3. The distance L1 mm between the thinned area 21 and the first edge 141 satisfies 6 mm ≤ L1 mm ≤ 40 mm. That is, the first surface 14 serves as the bottom surface of the battery 10. At this time, the explosion-proof valve 2 is exposed at the bottom. When the explosion-proof valve 2 opens to release pressure, the high-temperature and high-pressure gas will not be ejected towards the passenger compartment, thus improving the pressure release safety of the battery 10. However, the battery cell 3 is prone to clogging the explosion-proof valve 2 due to gravity. Therefore, by further limiting the value of L1 mm, the stress on the explosion-proof valve 2 under the action of high-temperature and high-pressure gas is increased, ensuring that the explosion-proof valve 2 can open quickly to release pressure.

[0100] According to an embodiment of the present invention, in another aspect, a battery pack 100 is also provided, such as... Figure 20 As shown, it includes several of the aforementioned batteries 10.

[0101] Furthermore, in one embodiment, a plurality of batteries 10 are provided, and the plurality of batteries 10 are arranged sequentially along a direction perpendicular to the first side 141. In this arrangement, in adjacent batteries 10, the sides of the casing 11 connected to the first side 141 are in close contact with each other, that is, the large sides of the batteries 10 are in close contact with each other, which reduces the degree of expansion of the large sides of the batteries 10 and further reduces the risk of cracking in the welding area 13.

[0102] According to an embodiment of the present invention, in another aspect, an electrical device is also provided, including the battery pack 100 described above.

[0103] 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.

[0104] The preparation of the example battery and the comparative battery includes the following steps: (1) Preparation of the positive electrode: The prepared positive electrode active material, conductive agent (e.g., acetylene black), and binder (e.g., 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 foil, dried at room temperature, and then transferred to an oven for further drying. The positive electrode sheet is then obtained by rolling and slitting.

[0105] Specifically, the mass ratio of positive electrode active material: conductive agent: binder satisfies (92~98):(4~1):(4~1).

[0106] (2) Preparation of negative electrode: The negative electrode active material, conductive agent (e.g., acetylene black), thickener (e.g., carboxymethyl cellulose (CMC)), and binder (e.g., styrene-butadiene rubber (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 foil, air-dried at room temperature, and then transferred to an oven for further drying. Finally, the negative electrode sheet is obtained by rolling and slitting.

[0107] Specifically, the ratio of negative electrode active material: conductive agent: thickener: binder satisfies (90~96): (4~2): (2~1): (4~1).

[0108] (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.

[0109] (4) Preparation of the diaphragm: Polyethylene film is selected as the diaphragm.

[0110] (5) Preparation of lithium-ion batteries: The positive electrode, separator, and negative electrode are stacked in sequence and formed into a bare cell by winding or stacking. The bare cell is then placed in a battery casing, which is a prismatic casing. The battery is dried, injected with electrolyte, and then packaged, allowed to stand, formed, and calibrated to obtain a lithium-ion battery.

[0111] In the selection of materials for the battery, this application may also select other materials, not limited to the materials limited by the above preparation method. The positive electrode active material may 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 may be selected from one or more negative electrode active main materials, such as artificial graphite, natural graphite, silicon carbide, silicon oxide, and lithium titanate.

[0112] The conductive agent includes, but is not limited to, one or more combinations of graphite, superconducting carbon, carbon black (such as acetylene black, Ketjen black, Super P, etc.), carbon nanotubes, graphene, and carbon nanofibers.

[0113] 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.

[0114] The solvent can be deionized water, NMP (N-methylpyrrolidone), alcohol, ether, ketone or other types of pyrrolidone, etc.

[0115] 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.).

[0116] 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.).

[0117] The difference between the batteries in each embodiment and the comparative battery lies in the values ​​of W, L1, D1, and D2. Apart from these, all other characteristics of the batteries are the same, as shown in Table 1.

[0118] For the measurement of weld penetration and weld width, metallographic analysis was used. Weld cross-sectional specimens were prepared, and the penetration and width were directly observed and quantified under an optical microscope. The measurement method and implementation procedure are as follows: (a) Sampling: From the welded battery casing, along the direction perpendicular to the weld, use a cutting machine (e.g., Beta-300Pro) with a silicon carbide (SiC) cutting disc to cut a sample containing the complete weld in a low-speed pulse mode (6A, 0.6mm / s, 2200rpm) to avoid deformation of the heat-affected zone.

[0119] (ii) Embedding: TJ2210 acrylic resin or TJ2568 epoxy resin are preferred. Apply 0.3MPa pressure for 15 minutes in a pressure cold embedding machine (e.g., Theta Mount pressure cold embedding machine) to avoid thermal stress damaging the microstructure of the weld.

[0120] (III) Grinding and polishing: Use a grinding and polishing machine (such as GP-2000A) to grind step by step in the order of gradient sandpaper (P400 grit → 800 grit → 1200 grit → 2500 grit), and finally use 0.05μm alumina polishing liquid to obtain a mirror surface, ensuring that the weld interface is clearly visible.

[0121] (iv) Corrosion: Soak in 0.01mol / L-0.5mol / L NaOH solution for 30 minutes, or chemically corrode with 10% ammonium persulfate aqueous solution to make the welded area and the heat-affected zone clearly contrast.

[0122] (v) Observation and measurement: Use a stereomicroscope or metallographic microscope to observe the cross-section, and use professional image analysis software to measure the melt depth and melt width.

[0123] Among them, the penetration depth refers to the vertical distance from the surface of the base material to the deepest melting point of the weld; the weld width refers to the horizontal width of the melting boundary of the base material on both sides of the weld.

[0124] Furthermore, the methods for controlling the weld penetration depth (D1) and weld width (D2) in the welding zone can be achieved by adjusting the welding process, the materials of the shell and cover plate, and the thickness of the weld joint. For example, when using laser welding, the welding process can be controlled by adjusting the laser power (range: 1000W to 6000W), welding speed (range: 200–400mm / s), defocusing amount (positive defocusing range: +0.5mm to +4mm, negative defocusing range: -0.5mm to -3mm), pulse waveform (sharp wave or double peak wave), and laser oscillation mode (using a "figure-eight" or "elliptical" trajectory). When the shell is made of steel, aluminum, titanium, etc., the proportion of trace doping elements in the shell material, such as Mg, Cu, Cr, Fe, Mn, Zn, C, Si, and N, can be adjusted. For example, in a steel shell, the carbon content is 0.008%–0.02% (low-carbon design improves ductility and stamping performance, avoids embrittlement in the welded area, and reduces the risk of fracture), the manganese content is 0.1%–0.5%, the silicon content is ≤0.03%, the phosphorus content is 0.015%–0.03%, the sulfur content is 0.0020%–0.03%, and the aluminum content is 0.050%–0.10%; in an aluminum shell, the manganese content is 1.0%–1.5%, the iron content is ≤0.7%, the silicon content is ≤0.6%, the magnesium content is 2.2%–4.9%, the copper content is ≤0.10%, the zinc content is 0.10%, and the titanium content is ≤0.15%; in a titanium shell, the aluminum content is 5.5%–6.5%, and the vanadium content is 3.5%–4.5%.

[0125] For measurement methods such as dimensions and area, measuring instruments such as micrometers or calipers are used to measure parameters such as length, width, distance, and thickness. The area is calculated from the measured parameters such as length, width, distance, and thickness.

[0126] The relevant performance of the batteries in the above embodiments and comparative examples was tested, and the test results are recorded in Table 1. The test methods are as follows: Performance 1: Cover plate weld line cracking ratio Following the battery fabrication method described above, 50 batteries were prepared for each embodiment and comparative example, with all other test conditions remaining consistent. The batteries were charged at a constant current rate of 1 / 3C to the upper limit voltage at room temperature (20°C), then switched to constant voltage charging until the current was less than 0.05C, and allowed to stand for 30 minutes. Heating wires were then evenly wrapped around the surface of each battery, and the batteries were placed in an adiabatic accelerated calorimeter (ARC) for adiabatic thermal stability testing until thermal runaway occurred.

[0127] After the battery thermal runaway ends, observe the weld lines of the battery casing and cover plate. If a break occurs at the weld line, exposing the inside of the casing, it is judged as a crack in the cover plate weld line. The cracking rate of the cover plate weld line is calculated as (number of batteries with cracked cover plate weld lines / 50) × 100%. If the cracking rate of the cover plate weld line is less than or equal to 4%, it is considered good; if the cracking rate is greater than 4% but less than or equal to 8%, it is considered acceptable; if the cracking rate is greater than 8%, it is considered unacceptable.

[0128] For different battery systems, the upper and lower voltage limits for a single cell need to be adjusted accordingly: Lithium iron phosphate (LFP) - upper limit 3.65V, lower limit 2.5V; Nickel-cobalt-manganese ternary NCM - upper limit 4.25V, lower limit 2.5V; Lithium manganese iron phosphate (LFMP) - upper limit 4.25V, lower limit 2.5V; Lithium nickel manganese oxide - upper limit 4.8V, lower limit 3.5V. In this test, the positive electrode active material was selected from LiNi... 0.6 Co 0.2 Mn 0.2 Taking O2 as an example, other positive electrode materials all meet the above test requirements, and the mass ratio of positive electrode active material: conductive agent: binder meets 96:2:2; the negative electrode active material is selected from artificial graphite, and the ratio of negative electrode active material: conductive agent: thickener: binder meets 95:2:1:2.

[0129] Performance 2: The proportion of the lower insulating component (lower plastic) that melts Following the battery preparation method described above, 100 batteries were prepared for each embodiment and comparative example. After the cover plate and casing were welded together, the batteries were left to stand at room temperature (20°C) for 30 minutes. The cover plate and casing were then separated, and the edges of the lower insulating component were observed to check for localized melting. In this test, polyethylene terephthalate (PET) was selected as the material for the lower insulating component; other materials for the lower insulating component met the above test requirements.

[0130] The percentage of the lower insulation component that melts = (number of batteries with partial melting of the lower insulation component / 100) × 100%. If the percentage of the lower insulation component that melts is less than or equal to 3%, it is considered good; if the percentage of the lower insulation component that melts is greater than 3% but less than or equal to 5%, it is considered acceptable; if the percentage of the lower insulation component that melts is greater than 5%, it is considered unacceptable.

[0131] Table 1:

[0132] As can be seen from Table 1, in Examples 1 to 17, the values ​​of L1×D1×D2 are all within the range of 0.72 to 213. Therefore, in Examples 1 to 17, there are no unqualified cases in the test of the proportion of cracked cover plate welding wires, and there are no unqualified cases in the test of the proportion of melting of the lower insulating component (lower plastic).

[0133] As can be seen from Table 1, in Comparative Example 1 and Comparative Example 2, the values ​​of L1×D1×D2 are not within the range of 0.72 to 213 and are less than 0.72, which leads to the failure of the battery cover weld line cracking ratio test in Comparative Example 1 and Comparative Example 2.

[0134] In addition, as can be seen from Table 1, in Comparative Example 4, the thickness of the battery is relatively small (W mm is less than 35 mm). Therefore, even though the values ​​of L1×D1×D2 are not in the range of 0.72 to 213 and are less than 0.72, the test of the cracking ratio of the battery cover weld line in Comparative Example 4 is still relatively good.

[0135] As can be seen from Table 1, in Comparative Example 3, the values ​​of L1×D1×D2 are not within the range of 0.72 to 213 and are greater than 213, which causes the proportion test of melting of the lower insulating part (lower plastic) of the battery in Comparative Example 3 to fail.

[0136] Furthermore, as can be seen from Table 1, in Examples 1 to 4, the above-mentioned test of the cracking ratio of the cover plate weld line and the test of the melting ratio of the lower insulating component (lower plastic) both meet the test requirements. However, the values ​​of some parameters have some impact on the relevant performance. Specifically, the values ​​of L1×D1×D2 are too small (less than 3.6), which increases the risk of the weld line of the shell and the cover plate being broken, and the cracking ratio of the cover plate weld line is relatively large.

[0137] Furthermore, as can be seen from Table 1, in Examples 13 to 16, the above-mentioned test results for the cracking ratio of the cover plate weld line and the melting ratio of the lower insulating component (lower plastic) both meet the test requirements. However, the values ​​of some parameters have some impact on the relevant performance. Specifically, the values ​​of L1×D1×D2 are too large (greater than 103.5), which increases the risk of melting the lower insulating component (lower plastic) during the welding of the cover plate and the shell, and the melting ratio of the lower insulating component (lower plastic) is relatively large.

[0138] The following is an explanation of the terms used in this application.

[0139] Battery packs can serve as the operating power source for electrical devices, or as the driving power source for electrical devices, replacing or partially replacing fuel or natural gas to provide driving power for vehicles. Electrical devices include: energy storage devices, electric ships, aircraft, laptops, power tools, electric bicycles, electric motorcycles, electric cars, military equipment, aerospace, and many other technological fields.

[0140] A battery pack consists of multiple batteries, which can be connected in series, parallel, or a combination thereof. A combination thereof means that multiple batteries are connected in both series and parallel.

[0141] The battery pack is a cluster-level battery structure formed by multiple batteries connected in series, where the number of batteries in each cluster is strictly configured according to voltage and capacity requirements. Specifically, the battery cells of the battery pack include multiple batteries with similar capacity and internal resistance. Some of the batteries are connected in series to form a cluster that meets the preset power supply voltage requirements, and at least one spare battery among the multiple batteries is bypassed.

[0142] The battery pack may include battery cells and a switching control unit.

[0143] A battery can store chemical energy and controllably convert it into electrical energy. In recyclable batteries, the active materials can be reactivated by charging after discharge, allowing for continued use. A battery consists of a casing and battery cells housed within the casing.

[0144] A housing is a component used to provide a space to house and isolate electrode assemblies (cells) and other parts from the external environment. A housing generally includes a body with an opening at at least one end and a receiving cavity. The opening of the housing can be closed by a cover plate, sealing and isolating the internal environment of the battery cell from the external environment. Housing materials include, but are not limited to, copper, iron, aluminum, stainless steel, and aluminum alloys.

[0145] A cover is a component that seals the opening of the battery cell to isolate the internal environment of the battery cell from the external environment. Cover materials include, but are not limited to, copper, iron, aluminum, stainless steel, aluminum alloy, plastic, and aluminum-plastic film.

[0146] A battery cell is the component in a battery where electrochemical reactions occur; it is the smallest unit in a battery capable of performing electrochemical reactions such as charging and discharging. A battery cell is the basic unit of a battery and typically includes a positive electrode, a negative electrode, and a separator. Lithium-ion battery cells primarily function by the movement 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 (wound cell), while in cuboid cells, the thin-film structure is wound or stacked (laminated cell) into an electrode assembly with a roughly cuboid shape. Laminated cells are manufactured by using a lamination process to stack the positive electrode, negative electrode, and separator. The positive and negative electrodes are separated by a separator, and adjacent positive and / or negative electrode layers within the cell are discontinuous. Lamination processes include layering or Z-folding.

[0147] Terminals are used to electrically connect the battery cell located inside the casing to external devices (adjacent batteries or other electrical equipment) located outside the casing. The battery can discharge to external devices through the cell output terminals (tabs) and the external device output terminals (terminals), and an external power source can charge the battery through the terminals and tabs. Terminals can be directly electrically connected to the cell tabs, or they can be electrically connected to the tabs through metal adapters.

[0148] The electrode post is made of metal materials including but not limited to copper, aluminum, aluminum alloy, and copper-aluminum alloy.

[0149] An explosion-proof valve is a component or part that can be actuated to release internal pressure or temperature when the internal pressure or temperature of a battery cell reaches a predetermined threshold.

[0150] During battery use, explosion-proof valves are mainly used to prevent excessive pressure buildup inside the battery, which could cause deformation or explosion, by allowing gas to escape and reducing the internal pressure of the battery in the event of thermal runaway or other situations.

[0151] The materials used for explosion-proof valves are not limited, including but not limited to aluminum, steel, and alloys. The shapes of explosion-proof valves are not limited, such as square, oblong, elliptical, racetrack-shaped, etc. The types of explosion-proof valves are not limited, such as scored explosion-proof valves, which can be formed by stamping or laser etching.

[0152] The explosion-proof valve and the housing can be separate structures, that is, the housing and the explosion-proof valve plate are manufactured separately and then fixed (welded) together; or an integrated explosion-proof valve can be used, that is, a thinning zone is made on the first surface of the housing, which can be formed by mechanical cutting, laser etching or other methods.

[0153] The explosion-proof valve (pressure relief mechanism) achieves pressure relief by reducing the thickness of the explosion-proof valve plate (pressure relief plate) to form a weak part. The thinned weak part forms a groove. The groove can be formed on the side close to the battery cell, on the side away from the battery cell, or on both sides. The groove can form a V-shaped groove, a U-shaped groove, or a trapezoidal groove, etc.

[0154] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A battery, characterized in that, include: The outer shell (1) includes a shell (11) and a cover plate (12). At least one end of the shell (11) is formed with an opening. The cover plate (12) and the shell (11) are welded to form a welded area (13). The cover plate (12) seals the opening and encloses the shell (11) to form an accommodating space. The outer shell (1) has a first surface (14). The first surface (14) has two first edges (141) that are spaced apart from each other along its width direction. An explosion-proof valve (2) is disposed on the first surface (14). The explosion-proof valve (2) has a thinning area (21) and a main body area. The thickness of the thinning area is less than the thickness of the main body area. The battery cell (3) is disposed within the accommodating space; Wherein, the weld depth of the welding area (13) is D1 mm, the weld width of the welding area (13) is D2 mm, the thickness of the battery (10) along the width direction of the first surface (14) is W mm, and the distance between the thinning area (21) and the first edge (141) is L1 mm, satisfying W mm≥35 mm, 0.72≤L1×D1×D2≤213; The distance L1 mm between the thinning area (21) and the first edge (141) satisfies 2.5 mm ≤ L1 mm ≤ 44 mm, the weld depth D1 mm of the welding area (13) and the weld width D2 mm of the welding area (13) satisfy 0.18 ≤ D1 × D2 ≤ 6; L1 and D1 × D2 are inversely correlated.

2. The battery according to claim 1, characterized in that, The explosion-proof valve (2) is disposed on the cover plate (12), and the thickness of the cover plate (12) is greater than the wall thickness of the housing (11).

3. The battery according to claim 2, characterized in that, The direction of the weld depth of the welding area (13) is parallel to the thickness direction of the cover plate (12), and the distance L1 mm between the thinning area (21) and the first edge (141) satisfies 4mm≤L1 mm≤40mm.

4. The battery according to claim 2, characterized in that, Along the thickness direction of the cover plate (12), the size of the portion of the welding area (13) within the cover plate (12) is D3 mm, at least a portion of the cover plate (12) is inserted into the opening along its thickness direction, and the thickness of the portion of the cover plate (12) inserted into the opening along the thickness direction of the cover plate (12) is a mm, satisfying D3 < a.

5. The battery according to claim 4, characterized in that, The dimension D3 mm of the portion of the welding area (13) inside the cover plate (12) and the thickness a mm of the portion of the cover plate (12) inserted into the opening satisfy 0.2≤a-D3≤2.

7.

6. The battery according to claim 2, characterized in that, The direction of the weld depth of the welding zone (13) is perpendicular to the thickness direction of the cover plate (12).

7. The battery according to claim 2, characterized in that, The distance L1 mm between the thinning zone (21) and the first edge (141) satisfies 2.5 mm ≤ L1 mm ≤ 40 mm; and / or, The first surface (14) has two second sides (142) that are spaced apart from each other along its length direction. The distance between the thinning area (21) and the second side (142) along the length direction of the first surface (14) is L2 mm, which satisfies 50 mm ≤ L2 mm ≤ 200 mm.

8. The battery according to claim 1, characterized in that, The cover plate (12) includes a body portion (121) and a narrowing portion (122) connected along its thickness direction. The narrowing portion (122) is disposed on the side of the body portion (121) facing the battery cell (3). Along the length direction and the width direction of the cover plate (12), the size of the narrowing portion (122) is smaller than the size of the body portion (121), and the narrowing width of the end of the narrowing portion (122) away from the body portion (121) is b mm, satisfying 0.2 mm ≤ b mm ≤ 1 mm.

9. The battery according to claim 1, characterized in that, The housing (11) includes a shell opening (111) surrounding the opening, and the housing (11) also includes a stepped portion (112). The stepped portion (112) is located on the side of the shell opening (111) away from the opening. The stepped portion (112) protrudes towards the battery cell (3) relative to the shell opening (111). The cover plate (12) abuts against the side of the stepped portion (112) facing the opening. The wall thickness of the housing (11) at the shell opening (111) is c mm, and the wall thickness of the housing (11) at the stepped portion (112) is e mm, satisfying e mm > c mm.

10. The battery according to claim 9, characterized in that, The housing (11) includes two second surfaces (113) spaced apart from each other along the length of the cover plate (12) and two third surfaces (114) spaced apart from each other along the width of the cover plate (12). The second surfaces (113) and the third surfaces (114) are connected to form a first corner (115). The step (112) is formed at at least one of the first corners (115).

11. The battery according to claim 1, characterized in that, The thickness of the cover plate (12) is f mm, satisfying 1.5 mm ≤ f mm ≤ 3.5 mm; and / or, The wall thickness of the shell (11) is g mm, which satisfies 0.45 mm ≤ g mm ≤ 1.5 mm.

12. The battery according to claim 1, characterized in that, The first surface (14) is located on the housing (11) and is disposed opposite to the cover plate (12).

13. The battery according to claim 12, characterized in that, The housing (11) includes a third surface (114) arranged perpendicular to the first surface (14), the third surface (114) being arranged parallel to the length direction of the first surface (14), and the area of ​​the first surface (14) being smaller than the area of ​​the third surface (114).

14. The battery according to claim 13, characterized in that, A second corner (116) is formed at the junction of the first surface (14) and the third surface (114). The wall thickness of the shell (11) at the second corner (116) is imm, which satisfies 0.25mm≤i mm≤1.4mm.

15. The battery according to claim 13, characterized in that, A second corner (116) is formed at the junction of the first surface (14) and the third surface (114). The wall thickness of the shell (11) at the second corner (116) is imm, and the thickness of the thinning area (21) is j mm, satisfying ij≤0.

5.

16. The battery according to claim 15, characterized in that, The weld depth D1 mm of the welding zone (13) and the wall thickness i mm of the shell (11) at the second corner (116) satisfy D1 > i.

17. The battery according to claim 15, characterized in that, Along the thickness direction of the cover plate (12), the height of the battery (10) is H mm, which satisfies H mm ≤ 120 mm.

18. The battery according to any one of claims 1 to 17, characterized in that, The length direction of the thinning area (21) is parallel to the length direction of the first surface (14), and the distance L1 mm between the thinning area (21) and the first edge (141) satisfies 5mm≤L1 mm≤40mm.

19. The battery according to any one of claims 1 to 17, characterized in that, The length direction of the thinning zone (21) is parallel to the width direction of the first surface (14), and the weld depth D1 mm and the weld width D2 mm of the welding zone (13) satisfy 0.4≤D1×D2≤6.

20. The battery according to any one of claims 1 to 17, characterized in that, The explosion-proof valve (2) includes an opening portion (22) formed by the thinning area (21). The opening portion (22) has a first side (221) facing away from the battery cell (3) and a second side (222) facing the battery cell (3). Along the thickness direction of the first surface (14), the thinning area (21) is located close to the first side (221) or close to the second side (222). The thickness of the thinning area (21) is j mm, which satisfies 0.04 mm ≤ j mm ≤ 0.3 mm.

21. The battery according to any one of claims 1 to 17, characterized in that, The penetration depth D1mm of the welded area (13) satisfies 0.3mm≤D1mm≤2mm; and / or, The weld width D2 mm of the welded area (13) satisfies 0.6 mm ≤ D2 mm ≤ 3 mm.

22. The battery according to any one of claims 1 to 17, characterized in that, The battery cell is disposed on the upper part of the first surface, and the first surface is used to support the battery cell. The distance L1 mm between the thinning area (21) and the first edge (141) satisfies 6mm≤L1 mm≤40mm.

23. A battery pack, characterized in that, Includes the battery (10) according to any one of claims 1 to 22.

24. The battery pack according to claim 23, characterized in that, The battery (10) is provided in a plurality of units, and the plurality of batteries are arranged sequentially along a direction perpendicular to the first side.

25. An electrical appliance, characterized in that, Includes the battery pack (100) as described in claim 23 or 24.

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