Welding structure of lower end plate and collector plate and cylindrical lithium ion battery

Abstract

The utility model relates to the technical field of cylindrical batteries, and provides a lower end plate and collector plate welding structure and a cylindrical lithium ion battery, the lower end plate and collector plate welding structure comprises a lower end plate and a positive collector plate, the middle of the lower end plate is provided with a boss groove, and the periphery of the lower end plate is provided with air holes; the positive collector plate comprises a plate body and a tail body, one end of the tail body is integrally formed on the plate body, and the other end of the tail body is welded and fixed on the lower end plate; the area of the lower end plate is S1, the sum of the area of the boss groove and the area of the air hole is S11, the projection area of the tail body on the lower end plate is S2, and 35% (S1-S11) < = S2 < = 45% (S1-S11). According to the utility model, the projection area of the tail body on the lower end plate is limited, so that the welding reliability and the overflowing capability of the lower end plate and the positive collector plate can be ensured, and the exhaust effect of the air holes can be ensured, thereby effectively improving the overall performance of the battery.

Description

Technical Field

[0001] This utility model relates to the field of cylindrical battery technology, and in particular to a welding structure of a lower end plate and a current collector, and a cylindrical lithium-ion battery. Background Technology

[0002] With the continuous development of new energy technologies, batteries, as high-efficiency energy storage devices, are widely used in various portable electronic products, electric vehicles, and large-scale energy storage systems. Among them, cylindrical lithium-ion batteries have gradually become one of the mainstream products in the market due to their excellent performance and high energy density.

[0003] The lower end plate is an important component in the cap assembly of a cylindrical lithium-ion battery. It is electrically connected to the top cover plate. The positive current collector is the core component of the positive electrode assembly of a cylindrical lithium-ion battery. It is responsible for collecting the current generated by the positive electrode active material. By welding the lower end plate to the positive current collector, the top cover plate and the core positive electrode can be connected to ensure the normal use of the cylindrical lithium-ion battery.

[0004] For example, the steel-cased battery cell structure disclosed in utility model with announcement number CN217134502U has a positive electrode connecting piece set on one side of the edge of the positive electrode current collector, which is then welded and fixed to the orifice plate. However, if the projected area of ​​the positive electrode connecting piece on the orifice plate is too large, it will not only block the vents on the orifice plate and affect its exhaust effect, but also increase the weight and production cost of the battery. If the projected area of ​​the positive electrode connecting piece on the orifice plate is too small, it will weaken the current carrying capacity of both and affect the overall performance of the battery. Utility Model Content

[0005] In view of this, this utility model proposes a welding structure of the lower end plate and the current collector and a cylindrical lithium-ion battery. By reasonably setting the projected area of ​​the tail body on the lower end plate, the explosion-proof performance and overcurrent capacity of the battery can be taken into account, thereby effectively improving the overall performance of the battery.

[0006] The technical solution of this utility model is implemented as follows: On the one hand, this utility model provides a welding structure between a lower end plate and a current collector, including a lower end plate and a positive current collector, wherein,

[0007] The lower end plate has a boss groove in the middle and air holes on the outer periphery of the lower end plate.

[0008] The positive current collector includes a disc body and a tail body. The disc body is used for electrical connection with the positive electrode tab of the winding core. One end of the tail body is integrally formed on the disc body, and the other end is welded and fixed to the lower end plate.

[0009] The area of ​​the lower end plate is S1, and the sum of the areas of the boss groove and the air hole is S. 11 The projected area of ​​the tail body on the lower end plate is S2, wherein 35% (S1-S2)11 )≤S2≤45%(S1-S 11 ).

[0010] Based on the above technical solutions, preferably, the tail body is provided with a welding surface area and a weld mark, the weld mark being the welding trajectory between the tail body and the lower end plate, which is located within the welding surface area;

[0011] The welding area is rectangular, the span of the weld mark along the length direction of the welding area is equal to the length of the welding area, and the span of the weld mark along the width direction of the welding area is equal to the width of the welding area.

[0012] The area of ​​the welded surface region is S3, of which 4.5% (S1-S2) 11 )≤S3≤8.5%(S1-S 11 ).

[0013] Based on the above technical solutions, preferably, the air pores are arc-shaped or waist-shaped;

[0014] The radius of the lower end plate is R0, and the average width of the air hole is W1, wherein 12%R0≤W1≤26%R0.

[0015] More preferably, the straight-line distance between the two ends of the vent is L1, wherein 71%R0≤L1≤88%R0.

[0016] More preferably, the vent is provided in a plurality of vents, and the plurality of vents are arranged in a circumferential array around the axis of the boss groove;

[0017] The minimum distance between two adjacent pores is D1, where 12%R0≤D1≤20%R0.

[0018] More preferably, the air hole is an arc-shaped hole, the center of which coincides with the center point of the boss groove;

[0019] The minimum distance between the air hole and the boss groove is D2, where 43%R0≤D2≤51%R0.

[0020] More preferably, the minimum distance between the vent and the periphery of the lower end plate is D3, wherein 9%R0≤D3≤16%R0.

[0021] Based on the above technical solutions, preferably, the radius of the boss groove is R1, wherein 17%R0≤R1≤25%R0.

[0022] Further preferred dimensions are L1 = 4.5mm-5.5mm and D1 = 0.8mm-1.2mm.

[0023] Secondly, this utility model provides a cylindrical lithium-ion battery, including the aforementioned welded structure of the lower end plate and the current collector.

[0024] The welding structure of the lower end plate and the current collector plate of this utility model, and the cylindrical lithium-ion battery therein, have the following advantages over the prior art:

[0025] (1) By integrally forming the tail body on the disk and welding it to the lower end plate, and limiting the projected area of ​​the tail body on the lower end plate, not only can the welding reliability and current carrying capacity of the lower end plate and the positive current collector be guaranteed, but also the exhaust effect of the vent can be guaranteed, thereby effectively improving the overall performance of the battery.

[0026] (2) By limiting the area of ​​the welding surface, the welding reliability and current carrying capacity of the lower end plate and the positive current collector can be further improved, and the welding defect rate of the lower end plate and the positive current collector can be reduced, thereby improving the processing efficiency of the battery.

[0027] (3) By restricting the specifications of the vents and boss grooves, not only can the structural strength of the lower end plate be guaranteed, but the venting effect of the vents can also be further improved, thereby enhancing the explosion-proof performance of the battery. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a front view of a welding structure between a lower end plate and a collector plate according to this utility model;

[0030] Figure 2 This is a partial front view of the welding surface area in a welding structure between a lower end plate and a collector plate according to this utility model;

[0031] Figure 3 This is a front view of the lower end plate in a welding structure between the lower end plate and the collector plate according to this utility model;

[0032] Figure 4 This is a front view of a cylindrical lithium-ion battery according to the present invention.

[0033] Among them: 1. Lower end plate; 101. Boss groove; 102. Air hole; 2. Positive current collector; 21. Disc body; 22. Tail body; 201. Welding surface area; 202. Welding mark. Detailed Implementation

[0034] The technical solutions of this utility model will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this utility model, and not all of them. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0035] Cylindrical lithium-ion batteries, also known as cylindrical lithium batteries, have advantages such as high safety, high energy density, and good charge and discharge performance, and are widely used in electric vehicles, electric two-wheelers, power tools and other fields.

[0036] This utility model discloses a cylindrical lithium-ion battery comprising a casing, a core, a positive electrode current collector 2, a cap assembly, and a welded structure between a lower end plate and the current collector. The cap assembly is fixedly disposed at the sealing point of the casing. The core and the positive electrode current collector 2 are both disposed within the casing, and the positive electrode current collector 2 is electrically connected to the positive electrode of the core. The cap assembly includes a top cover plate, an explosion-proof sheet, and a lower end plate 1. The top cover plate and the lower end plate 1 are electrically connected, and the explosion-proof sheet is disposed between the top cover plate and the lower end plate 1. Figure 4 As shown, by using the welding structure between the lower end plate and the current collector to fix and connect the lower end plate 1 and the positive current collector 2, the connection between the top cover plate and the core positive electrode can be realized, thereby ensuring the normal operation of the battery positive electrode system.

[0037] like Figure 3 As shown, a boss groove 101 is provided in the middle of the lower end plate 1. The boss groove 101 is formed by extrusion molding of the lower end plate 1. By extruding the middle position of the lower end plate 1, a boss groove 101 is formed in the middle position of the lower end plate 1 on the side away from the top cover plate, and a boss is formed in the middle position of the lower end plate 1 on the side close to the top cover plate. By using the boss to weld with the top cover plate, the flatness of the welding position can be guaranteed, and the welding firmness between the lower end plate 1 and the top cover plate can be improved.

[0038] like Figure 3 As shown, the lower end plate 1 has vents 102 on its outer periphery. When thermal runaway occurs inside the cylindrical lithium-ion battery and a large amount of gas is generated, the gas inside the casing can pass through the vents 102 and impact the explosion-proof sheet. When the gas pressure inside the casing is high enough, it will break through the explosion-proof sheet to achieve the pressure relief and explosion-proof effect of the battery. At the same time, the gas inside the casing will also break the connection between the lower end plate 1 and the top cover plate, thereby disconnecting the battery from power and preventing the gas generation problem from continuing to occur. This improves the safety of cylindrical lithium-ion batteries and reduces the risk of using cylindrical lithium-ion batteries.

[0039] like Figure 1As shown, the positive current collector 2 includes a disk body 21 and a tail body 22. The disk body 21 is used for electrical connection with the positive electrode tab of the winding core. One end of the tail body 22 is integrally formed on the disk body 21, and the other end of the tail body 22 is welded and fixed to the lower end plate 1. The tail body 22 can be bent in order to realize the assembly of the cylindrical lithium-ion battery.

[0040] The radius of the lower end plate 1 is R0, and the area of ​​the lower end plate 1 is S1, where S1 = π·R0 2 The sum of the areas of the boss groove 101 and the vent 102 is S. 11 Then the effective solid area on the lower end plate 1 is S1-S 11 The projected area of ​​the tail body 22 on the lower end plate 1 is S2, that is, the area covered by the tail body 22 on the lower end plate 1 is S2.

[0041] In some embodiments, 35% (S1-S 11 )≤S2≤45%(S1-S 11 That is, the projected area of ​​the tail body 22 on the lower end plate 1 is 35%, 40%, or 45% of the effective solid area on the lower end plate 1, etc. If S2 < 35% (S1 - S2), then... 11 If the positive current collector 2 does not adhere sufficiently to the lower end plate 1, the weldable area between the positive current collector 2 and the lower end plate 1 will be reduced, resulting in a smaller weldable area and weakened current-carrying capacity at the weld location. This will cause the battery temperature to rise, affecting battery performance. If S2 > 45% (S1 - S2), the positive current collector 2 will not adhere sufficiently to the lower end plate 1, resulting in a smaller weldable area and weakened current-carrying capacity at the weld location. This will cause the battery temperature to rise, affecting battery performance. 11 If the positive current collector 2 has too large an area attached to the lower end plate 1, the length of the positive current collector 2 needs to be increased, which increases the material cost of the positive current collector 2 and the weight of the battery, resulting in a decrease in the energy density of the battery.

[0042] like Figure 2 As shown, the tail body 22 is provided with a welding surface area 201 and a weld mark 202. The weld mark 202 is the welding trajectory between the tail body 22 and the lower end plate 1. That is, when welding the tail body 22 and the lower end plate 1, the welding gun head of the welding equipment moves along the path of the weld mark 202. The area where the weld mark 202 is located is the welding surface area 201, and the weld mark 202 is located within the welding surface area 201.

[0043] The weld mark 202 is preferably a continuous S-shape, which not only reduces the travel distance of the welding torch head but also increases the weld length, improving the welding reliability between the tail body 22 and the lower end plate 1. Correspondingly, as... Figure 2 As shown, the welding area 201 is rectangular, the span of the weld mark 202 along the length direction of the welding area 201 is equal to the length of the welding area 201, and the span of the weld mark 202 along the width direction of the welding area 201 is equal to the width of the welding area 201.

[0044] The area of ​​welding surface region 201 is S3.

[0045] In some embodiments, 4.5% (S1-S 11 )≤S3≤8.5%(S1-S 11 That is, the area of ​​the welding surface 201 is 4.5%, 6.5%, or 8.5% of the effective solid area on the lower end plate 1, etc. If S3 < 4.5% (S1 - S2), then... 11 If the positive electrode current collector 2 and the lower end plate 1 are welded together, the internal resistance of the battery will increase, the overcurrent capacity at the welded position will weaken, and the temperature of the battery will rise, which will affect the performance of the battery; if S3 > 8.5% (S1 - S 11 If the welding area between the positive electrode current collector 2 and the lower end plate 1 is too large, the effect of optimizing the internal resistance of the battery will not be obvious, but it will increase the risk of defects in the welding position, leading to an increase in welding failure rate and battery manufacturing cost, and reducing battery manufacturing efficiency.

[0046] To improve the explosion-proof performance of the battery, it is preferable to set the vent 102 to be flat and elongated, such as an arc-shaped vent or an oblong vent; similarly, multiple vents 102 can be set, and multiple vents 102 can be arranged in a circular array around the axis of the boss groove 101.

[0047] Preferably, the air hole 102 is set in an arc shape, and the center of the arc of the air hole 102 coincides with the center point of the boss groove 101, so that the air hole 102 and the lower end plate 1 are evenly spaced, which helps to improve the structural stability and balance of the lower end plate 1 and ensure the uniformity of air exhaust of the air hole 102.

[0048] like Figure 3 As shown, the straight-line distance between the two ends of the air hole 102 is L1, the average width of the air hole 102 is W1, the minimum distance between two adjacent air holes 102 is D1, the minimum distance between the air hole 102 and the boss groove 101 is D2, the minimum distance between the air hole 102 and the periphery of the lower end plate 1 is D3, and the radius of the boss groove 101 is R1, i.e., R0=R1+D2+W1+D3.

[0049] In some embodiments, 71%R0≤L1≤88%R0, that is, the straight-line distance between the two ends of the vent 102 is 71%, 80%, or 88% of the radius of the lower end plate 1, etc. If L1<71%R0, the area of ​​the vent 102 is reduced accordingly. When thermal runaway occurs inside the battery and a large amount of gas is generated, the gas inside the casing cannot be discharged through the vent 102 in time, which will affect the explosion-proof performance of the battery. If L1>88%R0, the span of the vent 102 is larger, the distance between two adjacent vents 102 is smaller, and the structural strength between two adjacent vents 102 is lower. When the vent 102 is stamped, it is easy to cause the risk of breakage between two adjacent vents 102, which will affect the safety performance of the battery.

[0050] In some embodiments, 12%R0≤W1≤26%R0, meaning the average width of the vent 102 is 12%, 19%, or 26% of the radius of the lower end plate 1, etc. If W1<12%R0, the area of ​​the vent 102 decreases accordingly. When thermal runaway occurs inside the battery and a large amount of gas is generated, the gas inside the casing cannot be discharged through the vent 102 in time, which will affect the explosion-proof performance of the battery. If W1>26%R0, the area of ​​the vent 102 increases accordingly, which will occupy the weldable area of ​​the positive current collector 2 and the lower end plate 1, resulting in a smaller weldable area between the positive current collector 2 and the lower end plate 1, an increase in the internal resistance of the battery, and a weakening of the overcurrent capacity at the welding position, thereby causing the battery temperature to rise and affecting the battery performance.

[0051] In some embodiments, 12%R0≤D1≤20%R0, meaning the minimum distance between two adjacent vents 102 is 12%, 16%, or 20% of the radius of the lower end plate 1. If D1<12%R0, the two vents 102 are too close together, resulting in lower structural strength between adjacent vents 102. During stamping of the vents 102, there is a risk of breakage between adjacent vents 102, affecting the safety performance of the battery. If D1>20%R0, the area of ​​the vents 102 is correspondingly reduced. When thermal runaway occurs inside the battery and a large amount of gas is generated, the gas inside the casing cannot be discharged through the vents 102 in time, affecting the explosion-proof performance of the battery.

[0052] In some embodiments, 43%R0≤D2≤51%R0, that is, the minimum distance between the vent 102 and the boss groove 101 is 43%, 47%, or 51% of the radius of the lower end plate 1. If D2<43%R0, the vent 102 is too close to the boss groove 101, which reduces the weldable area between the positive electrode current collector 2 and the lower end plate 1, increases the internal resistance of the battery, weakens the current carrying capacity at the welding position, and thus raises the temperature of the battery, affecting its performance. If D2>51%R0, the vent 102 is too far from the boss groove 101, which affects the venting area of ​​the vent 102. When thermal runaway occurs inside the battery and a large amount of gas is generated, the gas inside the casing cannot be discharged through the vent 102 in time, which will affect the explosion-proof performance of the battery.

[0053] In some embodiments, 9%R0≤D3≤16%R0, that is, the minimum distance between the vent 102 and the periphery of the lower end plate 1 is 9%, 13%, or 16% of the radius of the lower end plate 1, etc. If D3<9%R0, the vent 102 is too close to the edge of the lower end plate 1, which will cause the position of the vent 102 to be misaligned with the position of the vent of the inner rubber ring between the lower end plate 1 and the explosion-proof sheet, resulting in the gas not being able to be discharged smoothly. When thermal runaway occurs inside the battery and a large amount of gas is generated, the gas inside the casing cannot be discharged in time, which will affect the explosion-proof performance of the battery. If D3>16%R0, the vent 102 is too close to the boss groove 101, which will occupy the welding area between the positive electrode current collector 2 and the lower end plate 1, resulting in a smaller weldable area between the positive electrode current collector 2 and the lower end plate 1, an increase in the internal resistance of the battery, a weakening of the current carrying capacity at the welding position, and thus an increase in the temperature of the battery, which will affect the performance of the battery.

[0054] In some embodiments, 17%R0≤R1≤25%R0, meaning the radius of the boss groove 101 is 17%, 21%, or 25% of the radius of the lower end plate 1, etc. If R1<17%R0, the area of ​​the boss groove 101 is too small, the welding area between the lower end plate 1 and the top cover plate is too small, and the current carrying capacity at the welding position between the lower end plate 1 and the top cover plate is weakened, thereby causing the battery temperature to rise and affecting the battery performance. If R1>25%R0, the area of ​​the boss groove 101 is too large, which will occupy the welding area between the positive electrode current collector 2 and the lower end plate 1, resulting in a smaller weldable area between the positive electrode current collector 2 and the lower end plate 1, an increase in the battery's internal resistance, and a weakening of the current carrying capacity at the welding position, thereby causing the battery temperature to rise and affecting the battery performance.

[0055] In some embodiments, R0 = 6.29 mm, L1 = 4.5 mm - 5.5 mm, and D1 = 0.8 mm - 1.2 mm to ensure the overall performance of the battery and the venting capacity of the vent 102.

[0056] In some embodiments, R0 = 6.29 mm, S1-S 11 =89.25mm 2 S2 = 36.15 mm 2 S3 = 6mm 2 L1 = 5mm, W1 = 1.2mm, D1 = 1mm, D2 = 2.95mm, D3 = 0.79mm, R1 = 1.35mm; at this time, the welding reliability and current carrying capacity of the positive electrode current collector 2 and the lower end plate 1 are reasonably balanced with the exhaust performance of the vent 102, thereby effectively improving the overall performance of the battery.

[0057] The welding structure of the lower end plate and the current collector plate of this utility model, and the working principle of the cylindrical lithium-ion battery are as follows:

[0058] The current generated by the positive electrode active material of the core is transmitted to the top cover plate through the disk 21, tail 22 and lower end plate 1 in sequence, so that the electrical equipment or other electrodes connected to the top cover plate can be powered. When thermal runaway occurs inside the battery and a large amount of gas is generated, the gas inside the casing is discharged through the vent 102 and breaks through the explosion-proof sheet to ensure the explosion-proof performance of the battery.

[0059] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A welding structure between a lower end plate and a collector plate, characterized in that: Includes a lower end plate (1) and a positive current collector (2), wherein, The lower end plate (1) has a boss groove (101) in the middle and air holes (102) on the outer periphery of the lower end plate (1). The positive current collector (2) includes a plate body (21) and a tail body (22). The plate body (21) is used to electrically connect with the positive electrode of the winding core. One end of the tail body (22) is integrally formed on the plate body (21), and the other end is welded and fixed on the lower end plate (1). The area of ​​the lower end plate (1) is S1, and the sum of the areas of the boss groove (101) and the air hole (102) is S. 11 The projected area of ​​the tail body (22) on the lower end plate (1) is S2, wherein 35% (S1-S2) 11 )≤S2≤45%(S1-S 11 ).

2. The welding structure of the lower end plate and the collector plate as described in claim 1, characterized in that: The tail body (22) is provided with a welding surface area (201) and a weld mark (202). The weld mark (202) is the welding trajectory between the tail body (22) and the lower end plate (1), and it is located within the welding surface area (201). The welding area (201) is rectangular, the span of the weld mark (202) along the length direction of the welding area (201) is equal to the length of the welding area (201), and the span of the weld mark (202) along the width direction of the welding area (201) is equal to the width of the welding area (201). The area of ​​the welding surface region (201) is S3, of which 4.5% (S1-S2) 11 )≤S3≤8.5%(S1-S 11 ).

3. The welding structure of the lower end plate and the collector plate as described in claim 1, characterized in that: The vent (102) is an arc-shaped vent or an oblong vent; The radius of the lower end plate (1) is R0, and the average width of the air hole (102) is W1, wherein 12%R0≤W1≤26%R0.

4. The welding structure of the lower end plate and the collector plate as described in claim 3, characterized in that: The straight-line distance between the two ends of the vent (102) is L1, where 71%R0≤L1≤88%R0.

5. The welding structure of the lower end plate and the collector plate as described in claim 4, characterized in that: The air holes (102) are provided in a plurality of them, and the plurality of air holes (102) are arranged in a circumferential array around the axis of the boss groove (101); The minimum distance between two adjacent pores (102) is D1, where 12%R0≤D1≤20%R0.

6. The welding structure of the lower end plate and the collector plate as described in claim 3, characterized in that: The air hole (102) is an arc-shaped hole, and its center coincides with the center point of the boss groove (101); The minimum distance between the air hole (102) and the boss groove (101) is D2, where 43%R0≤D2≤51%R0.

7. The welding structure of the lower end plate and the collector plate as described in claim 6, characterized in that: The minimum distance between the vent (102) and the periphery of the lower end plate (1) is D3, where 9%R0≤D3≤16%R0.

8. The welding structure of the lower end plate and the collector plate as described in any one of claims 1-7, characterized in that: The radius of the boss groove (101) is R1, where 17%R0≤R1≤25%R0.

9. The welding structure of the lower end plate and the collector plate as described in claim 5, characterized in that: L1=4.5mm-5.5mm, D1=0.8mm-1.2mm.

10. A cylindrical lithium-ion battery, characterized in that: Includes the welded structure of the lower end plate and the manifold as described in any one of claims 1-9.

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