Cylindrical lithium ion battery

Abstract

A first plate body of a positive collector plate of the cylindrical lithium ion battery is connected to a positive end of a roll core through laser welding, a tail body of the positive collector plate is connected to an end plate through laser welding, a first welding mark is formed, the first welding mark comprises a wavy first welding line extending in the width direction of the tail body, and a second welding line extending in the width direction of the tail body is formed. A second plate body of a negative current collecting plate is connected to the negative end of a roll core through laser welding, a plurality of second welding marks are formed, each second welding mark comprises at least two second welding lines which are arranged in parallel and extend in the radial direction of the plate face of the second plate body, and the first welding marks and the second welding marks formed through laser welding have good overcurrent capacity. The internal resistance of the battery can be reduced to a certain extent, and adverse effects of welding structures between the positive collector plate and the roll core as well as between the positive collector plate and the cap on the battery performance can be reduced, so that the battery performance can be fully exerted.

Description

Technical Field

[0001] The present application relates to the technical field of lithium-ion batteries, and in particular to a cylindrical lithium-ion battery. Background Art

[0002] Due to its significant advantages in high-rate charge and discharge performance, low internal resistance and temperature rise control, cylindrical lithium-ion batteries will adopt full-tab technology in some application scenarios.

[0003] In related technologies, the current collector is one of the core components of the internal structure of cylindrical lithium-ion batteries. It mainly connects the electrode sheets to the external circuit, collects and conducts current, and has a significant impact on the overall performance and reliability of the battery. The positive current collector is welded to the positive electrode and cap of the winding core, while the negative current collector is welded to the negative electrode of the winding core. Therefore, in a cylindrical lithium-ion battery, at least two weld structures are formed: between the positive current collector and the cap, and between the negative current collector and the winding core. However, if the welding scheme at these locations is unreasonable, it will lead to insufficient current flow capacity at the weld and increase the internal resistance of the battery, which will in turn affect the battery's performance, such as charge and discharge performance and output power. Summary of the Invention

[0004] An embodiment of the present application provides a cylindrical lithium-ion battery, which aims to reduce the adverse effects of the welding structure of the positive electrode current collecting disc and the negative electrode current collecting disc on the battery performance.

[0005] The present invention provides a cylindrical lithium-ion battery, comprising a housing, a cap, a positive electrode current collecting disc, a winding core, and a negative electrode current collecting disc, wherein the winding core comprises a positive terminal and a negative terminal, wherein:

[0006] The cap includes a circular end plate, and the positive current collector includes a square tail body. The tail body is connected to the end plate by laser welding to form a first weld mark. The first weld mark includes a wavy first weld line extending along the width direction of the tail body. The radius of the end plate is R0a, the width of the tail body is L1a, the width of the first weld line is W1a, and the length of the first weld line is L2a. The range of W1a / R0a is 15% to 32%, and the range of L2a / L1a is 56% to 76%.

[0007] The negative electrode current collector includes a second disk body, which is connected to the negative terminal by laser welding and forms a plurality of second weld marks. The plurality of second weld marks are spaced apart along the circumferential direction of the disk surface of the second disk body, and each second weld mark includes at least two second weld lines arranged in parallel and extending in the radial direction of the disk surface of the second disk body. The radius of the second disk body is R0b, the overall length of the second weld mark is L1b, and the overall width of the second weld mark is W1b. The range of L1b / R0b is 37% to 57%, and the range of W1b / R0b is 17% to 36%.

[0008] The cylindrical lithium-ion battery according to the embodiment of the present application has at least the following beneficial effects:

[0009] First, the first weld mark formed on the tail body by laser welding is set as a wavy first weld line, so that the first weld line has good current flow capacity and can reduce the internal resistance of the battery to a certain extent. Therefore, at the welding position of the end plate and the tail body, the temperature rise of the weld mark can be controlled within a reasonable range, thereby reducing the adverse effect of the first weld mark on the battery performance, which is beneficial to the performance of the battery.

[0010] Secondly, the second weld marks formed by laser welding between the negative electrode current collector and the negative end of the winding core are arranged at intervals along the circumferential direction of the second disk body, and each group of second weld marks contains at least two second welding lines, so that multiple areas in the circumferential direction of the disk surface of the second disk body provide multiple conductive paths, which can effectively shorten the average path length of electron transmission and increase the actual welding area, which helps to improve the current flow capacity of the positive electrode current collector, the negative electrode current collector and the winding core at the welding position and reduce the internal resistance of the battery, so that the performance of the battery can be fully utilized.

[0011] In addition, the first weld mark and the second weld mark can ensure the connection strength and realize redundant connection at the same time, so that the connection reliability of the overall structure can be maintained when the battery is vibrated or impacted.

[0012] In one possible embodiment, the second disk body includes a boss portion located in the center and a welding portion extending radially from the edge of the boss portion, the shell includes a shell bottom, the boss portion is connected to the inner surface of the shell bottom, the welding portion is laser welded to the negative terminal, and a plurality of second weld marks are formed on the welding portion, the minimum distance between the end of the second weld mark close to the boss portion and the boss portion is L0b, and the minimum distance between the end of the second weld mark away from the boss portion and the edge of the second disk body is L2b, the range of L0b / R0b is 5% to 16%, and the range of L2b / R0b is 5% to 16%.

[0013] In one possible embodiment, the projection area of ​​the second disk body along its thickness direction is S0, the projection area of ​​the boss portion along the thickness direction of the second disk body is S1, the range of S1 / S0 is 5% to 15%, the sum of the overall areas of each second weld mark is S2, the range of S2 / S0 is 10% to 20%, and the radius of the boss portion is R1b, and the range of R1b is 2 to 4 mm.

[0014] In a possible implementation, the range of L1b is 3.5 to 5.5 mm, the range of W1b is 1.6 to 3.4 mm, the range of L0b is 0.5 to 1.5 mm, the range of L2b is 0.5 to 1.5 mm, the range of W1a is 1 to 2 mm, the range of L2a is 3.5 to 4.5 mm, and the average line width of the first welding line is W4a, and the range of W4a is 0.2 to 0.4 mm.

[0015] In one possible embodiment, the tail body includes a fifth side and a sixth side extending along its length, and a fourth side located at the far end. In the portion of the tail body covering the end plate disk surface, the distance between the first welding line and the edge of the end plate on the side away from the fourth side is W2a, and the range of W2a / R0a is 40% to 51%.

[0016] In a possible implementation manner, a distance between a side of the first welding line close to the fourth side and the fourth side is W3a, and a range of W3a / R0a is 25% to 35%.

[0017] In a possible implementation, a distance between a side of the first welding line close to the fifth side and the fifth side is L3a, a distance between a side of the first welding line close to the sixth side and the sixth side is L4a, L3a / L1a ranges from 9% to 24%, and L4a / L1a ranges from 9% to 24%.

[0018] In one possible embodiment, the end plate is provided with a boss hole located in the center and a plurality of exhaust holes surrounding the boss hole, the plurality of exhaust holes are evenly spaced along the circumference of the end plate disk, the minimum distance between the first welding line and the edge of the end plate forming the exhaust hole is L5a, and the range of L5a / R0a is 24% to 38%.

[0019] In one possible embodiment, the end plate is provided with a boss hole located in the center and a plurality of exhaust holes surrounding the boss hole, and the plurality of exhaust holes are evenly spaced along the circumference of the end plate disk surface, and the exhaust hole is an arc-shaped waist-shaped hole, including an inner arc and an outer arc arranged radially from the inside to the outside and having the same center as the circle where the end plate is located, the width of the ring defined by the inner arc and the outer arc of the exhaust hole is H2a, the radius of the boss hole is R1a, the range of H2a / R0a is 12% to 26%, and the range of R1a / R0a is 17% to 25%.

[0020] In a possible embodiment, the end plate is provided with a boss hole located in the center and a plurality of exhaust holes surrounding the boss hole, and the plurality of exhaust holes are evenly spaced along the circumference of the disk surface of the end plate (210), and the exhaust holes are arc-shaped waist-shaped holes, including an inner arc and an outer arc arranged radially from the inside to the outside and having the same center as the circle where the end plate is located, the ring width of the ring defined by the boss hole and the inner arc is H1a, the ring width of the ring defined by the edge of the end plate and the outer arc is H3a, the range of H1a / R0a is 43% to 51%, and the range of H3a / R0a is 9% to 16%.

[0021] In a possible embodiment, the end plate is provided with a boss hole located in the center and a plurality of exhaust holes surrounding the boss hole, and the plurality of exhaust holes are evenly spaced along the circumference of the end plate disk surface, and the exhaust holes are arc-shaped waist-shaped holes, including an inner arc and an outer arc arranged radially from the inside to the outside and having the same center as the circle where the end plate is located, with the arc length of the center line arc of the exhaust hole being L6a, and the spacing between the center line arcs of two adjacent exhaust holes being L7a, the range of L6a / R0a is 71% to 88%, and the range of L7a / R0a is 12% to 20%.

[0022] In one possible embodiment, the second welding line includes a plurality of second crest portions, second connecting portions, and second trough portions that are alternately connected to each other, and the first welding line includes a plurality of first crest portions, first connecting portions, and first trough portions that are alternately connected to each other, the second connecting portion has a straight line segment in its extension direction, and the straight line segments of two adjacent second connecting portions have an angle Ab, and the angle Ab ranges from 70° to 120°, and the first connecting portion has a straight line segment in its extension direction, and the straight line segments of two adjacent first connecting portions have an angle Aa, and the angle Aa ranges from 25° to 65°. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0024] Figure 1 is an exploded schematic diagram of a cylindrical lithium-ion battery according to an embodiment of the present application;

[0025] Figure 2 Schematic diagram of the structure of the positive electrode current collecting disk in the cylindrical lithium-ion battery of the embodiment of the present application;

[0026] Figure 3 This is a schematic structural diagram of a middle end plate of a cylindrical lithium-ion battery according to an embodiment of the present application;

[0027] Figure 4 Schematic diagram of the connection between the middle end plate and the tail body of a cylindrical lithium battery according to an embodiment of the present application;

[0028] Figure 5 This is a front view schematic diagram of the connection between the middle end plate of the cylindrical lithium battery and the tail body of the positive electrode current collecting disk according to an embodiment of the present application;

[0029] Figure 6 yes Figure 5 Schematic diagram of the first bonding wire;

[0030] Figure 7 Schematic diagram of the structure of the negative electrode current collecting disk in the cylindrical lithium-ion battery of an embodiment of the present application;

[0031] Figure 8 1 is a top view of the negative electrode current collecting disk in the cylindrical lithium-ion battery of an embodiment of the present application;

[0032] Figure 9 yes Figure 7 Schematic diagram of a single second bond line in the second bond print.

[0033] Reference numerals:

[0034] 100 - shell, 110 - shell bottom, 120 - side wall, 121 - necking structure, 130 - inner cavity, 140 - opening;

[0035] 200-cap, 210-end plate, 211-boss hole, 212-exhaust hole, 2121-inner arc, 2122-outer arc, 2123-side arc, 220-top cover;

[0036] 300 - positive electrode current collecting disc, 310 - first disc body, 311 - first side, 312 - arc edge, 313 - second side, 314 - third side, 320 - tail body, 321 - fifth side, 322 - sixth side, 323 - fourth side;

[0037] 400-winding core, 410-positive terminal, 420-negative terminal;

[0038] 500-negative electrode current collecting disc, 510-second disc body, 511-boss portion, 512-welding portion;

[0039] 600a - first weld mark, 610a - first weld line, 611a - first crest portion, 612a - first connection portion, 613a - first trough portion, 600b - second weld mark, 610b - second weld line, 611b - second crest portion, 612b - second connection portion, 613b - second trough portion. DETAILED DESCRIPTION

[0040] The cylindrical lithium-ion batteries provided in the embodiments of the present application include batteries of various sizes manufactured by the rolling groove sealing process, such as the 21 series (cylindrical lithium-ion batteries with an outer diameter of 21 mm), which are not limited here. It is understandable that the cylindrical lithium-ion batteries manufactured by the rolling groove sealing process use a cylindrical shell to encapsulate the core, the shell is set to be closed at one end and open at the other end, and a necking structure formed by rolling grooves is set at the open port. The core can be placed in the shell through the open port, and then the cap is welded to the positive electrode current collecting disk located at the top of the core, and the electrolyte is injected into the shell. Finally, the cap is sealed in the necking structure and the open port of the shell is sealed through a sealing process, thereby isolating the core and the electrolyte from the external environment. The core and the electrolyte constitute a closed electrochemical system inside the shell.

[0041] like Figure 1 As shown, the cylindrical lithium-ion battery includes a housing 100 , a cap 200 , a positive electrode current collecting disc 300 , a winding core 400 and a negative electrode current collecting disc 500 .

[0042] The shell 100 is cylindrical as a whole and is configured to be closed on the negative electrode side (the bottom in the figure) and open on the positive electrode side (the top in the figure). Specifically, the shell 110 includes a shell bottom 110 and a side wall 120, wherein the shell bottom 110 is circular, and the side wall 120 extends upward along the edge of the shell bottom 110. The shell bottom 110 and the side wall 120 together define an inner cavity 130, and the top of the side wall 120 has an opening 140, which is connected to the inner cavity 130. It can be understood that the inner cavity 130 defined by the shell bottom 110 and the side wall 120 is also cylindrical and is used to accommodate the cap 200, the positive current collecting disc 300, the winding core 400 and the negative current collecting disc 500. In addition, by configuring the shell 110 to be open at the top, that is, the top of the shell 110 is provided with an opening 140, it is also convenient for the above-mentioned components to enter the shell 110 through the opening 140.

[0043] Furthermore, the side wall 120 is concave inward along the circumferential direction near the opening 140 to form a necking structure 121 for sealing the cap 200, which can be formed by a grooving process. During the sealing process of the cylindrical lithium-ion battery, the cap 200 completely closes the opening 140, sealing the positive electrode current collecting disc 300, the winding core 400, the negative electrode current collecting disc 500 and the electrolyte in the inner cavity 130, thereby forming a closed electrochemical system in the shell 100.

[0044] The positive electrode current collector disc 300 is located between the positive terminal 410 of the winding core 400 and the cap 200, and is connected to the cap 200 and the positive terminal 410, respectively, thereby electrically connecting the positive terminal 410 of the winding core 400 to the cap 200. The exposed top cover 220 of the cap 200 serves as the positive terminal of the cylindrical lithium-ion battery, which is used for conducting with an external circuit. The negative electrode current collector disc 500 is located between the negative terminal 420 of the winding core 400 and the inner surface of the shell bottom 110, and is connected to the shell bottom 110 and the negative terminal 420, respectively, thereby electrically connecting the negative terminal 420 of the winding core 400 to the shell 100, so that the shell 100 serves as the negative electrode of the cylindrical lithium-ion battery, which is used for conducting with an external circuit.

[0045] It is understood that the winding core 400 is an overall cylindrical structure formed by stacking and winding the positive electrode sheet, the separator, and the negative electrode sheet in sequence, with opposite positive terminals 410 and negative terminals 420 on both sides along the axial direction. The positive and negative electrode sheets can adopt a full-tab structure. In this case, after winding, the full-tab structure is flattened or cut and stacked to form a circular positive terminal 410 and a negative terminal 420 with a flat cross-section. This allows the positive terminal 410 and the negative terminal 420 to be bonded to the positive current collecting disc 300 and the negative current collecting disc 500, and the three can achieve good electrical and mechanical connection through laser welding.

[0046] It is understood that in the cylindrical lithium-ion battery described above, the positive electrode current collector disc 300 and the cap 200, as well as the negative electrode current collector disc 500 and the negative terminal 420, are both connected by welding. An unreasonable welding structure at any of these connection locations can lead to a bottleneck at that location, resulting in inadequate battery performance. The present embodiment also improves the welding structures between the positive electrode current collector disc 300 and the cap 200, and between the negative electrode current collector disc 500 and the negative terminal 420, to reduce the adverse effects of the welding structures in these locations on battery performance.

[0047] The welding structure between the positive electrode current collecting disc 300 and the cap 200 is described below.

[0048] like Figure 2 As shown, the positive electrode current collecting disc 300 includes a first disc body 310 and a tail body 320 connected to each other, wherein the first disc body 310 is used to connect to the positive terminal 410, and the tail body 320 is used to connect to the cap 200, thereby forming a passage between the positive terminal 410 and the cap 200. It should be noted that, for ease of observation, Figure 2 The tail body 320 is in the expanded state.

[0049] In order to match the geometric shapes of the housing 100 and the winding core 400 and optimize the path of electron flow, the first disk 310 is generally in the shape of a circular thin sheet. In some embodiments, the shape of the first disk 310 is a closed axisymmetric figure consisting of a first side 311, an arc edge 312, a second side 313, and a third side 314 connected end to end, and the tail body 320 includes a fifth side 321 and a sixth side 322 along its length, and a fourth side 323 away from the first disk 310. The two ends of the fifth side 321 are respectively connected to the fourth side 323 and the first side 311, and the two ends of the sixth side 322 are respectively connected to the fourth side 323 and the second side 313. Figure 2 From the perspective of the tail body 320, the tail body 320 is also a closed axisymmetric figure extending from one end of the first disk body 310. It should be noted that the third side 314 is a virtual side line proposed for the convenience of describing the first disk body 310. There is no such side in the actual product. Figure 2 Dotted lines are used to distinguish them.

[0050] In addition, combined Figure 1 When the positive electrode current collecting disc 300 is assembled to the cylindrical lithium-ion battery, the tail body 320 will be bent near the third side 314 , and its distal end will be located above the closed axisymmetric figure formed by the first disc body 310 .

[0051] like Figure 3 and Figure 4As shown, the cap 200 includes an end plate 210, which is located on the inner side of the cap 200 and is a circular disc-shaped component with a certain thickness for welding the positive electrode current collecting plate 300. Figure 1 In addition to the end plate 210 , the cap 200 further includes a top cover 220 located outside the cap 200 , which serves as a positive terminal of the battery and is connected to an external device.

[0052] It should be noted that the outside and inside described here refer to the relative positions of the various components of the cap 200 and the inner cavity 130 of the shell 100 after the cylindrical lithium-ion battery is assembled, that is, the end plate 210 is located at the top of the battery, and the top cover 220 is exposed to the outside of the battery. Correspondingly, for the end plate 210, it also has an outside and an inside, that is, the side facing the inner cavity 130 is the inside, and the side away from the inner cavity 130 is the outside.

[0053] Of course, in addition to the end plates 210 and the top cover 220, the cap 200 may also include other components. For example, in some embodiments, the cap 200 includes a bursting disc (not shown) located between the top cover 220 and the end plates 210. When the gas pressure inside the battery exceeds a preset value, the bursting disc opens to release the pressure, thereby preventing the battery from deforming, bulging, or even burning or exploding, thereby improving the safety of the battery.

[0054] In some embodiments, to facilitate welding with the burst-proof disk, a welding boss is formed in the center of the outer disk surface of the end plate 210, for example, by a stamping process. As a result, a boss hole 211 is formed on the inner disk surface. It will be understood that when the boss hole 211 is provided, the area where the boss hole 211 is located cannot be used for welding with the positive electrode current collecting disk 300, i.e., it is a non-weldable area.

[0055] In some embodiments, in order to facilitate auxiliary exhaust, the end plate 210 is further provided with an exhaust hole 212, preferably, as shown in FIG. Figure 3 As shown, there are five exhaust holes 212, which are evenly spaced along the circumference of the end plate 210 to improve exhaust efficiency. It is understood that when the exhaust holes 212 are provided, the area where the exhaust holes 212 are located cannot be used for welding with the positive electrode current collecting plate 300, that is, it is a non-weldable area.

[0056] It is understandable that the number of the exhaust holes 212 is not limited to 5, and it can be set to be less or more. For example, the number of the exhaust holes 212 can be 4, 6, etc.

[0057] Furthermore, in some embodiments, the vent holes 212 are arcuate waist-shaped holes (banana holes). That is, along the thickness direction of the end plate 210, the cross-section of the vent holes 212 is an arcuate waist-shaped hole. The vent holes 212 include an inner arc 2121, an outer arc 2122, and two side arcs 2123. Furthermore, the inner arc 2121 and the outer arc 2122 of the vent holes 212 are cocentric with the circle on which the end plate 210 is located. This minimizes the radial dimension occupied by the end plate 210 while maintaining exhaust efficiency, thereby increasing the weldable area and facilitating welding to the positive electrode current collector 300.

[0058] refer to Figure 4 and Figure 5 In the embodiment, the tail body 320 includes a fifth side 321 and a sixth side 322 along its length, and a fourth side 323 away from the first disc body 310, that is, the fourth side 323 is located at the far end, so that the two ends of the fourth side 323 are respectively connected to the fifth side 321 and the end of the sixth side 322 away from the first disc body 310. It should be noted that in Figure 4 and Figure 5 In the embodiment, the cap 200 is still in a vertically extended state. After the subsequent liquid injection and sealing processes, the tail body 320 will bend, so that the cap 200 is laid flat and the opening 140 of the shell 100 is closed.

[0059] It is understood that the distal end of the tail body 320 abuts the inner surface of the end plate 210, thereby forming a surface-to-surface connection between the two, facilitating laser welding. Furthermore, it is also understood that the length and width of the distal end of the tail body 320 are significantly smaller than the diameter of the end plate 210. Therefore, to facilitate laser welding, the tail body 320 extends generally along the radial direction of the end plate 210 and abuts against a semicircle of the inner surface of the end plate 210. Consequently, the fifth and sixth sides 321, 322 of the tail body 320 are parallel to the radial direction of the end plate 210, and the fourth side 323 passes exactly through the center of the end plate 210. This ensures that the tail body 320 covers at least the weldable area on the inner surface of the end plate 210, ensuring process feasibility.

[0060] In actual applications, due to assembly errors, it is not necessary to strictly ensure that the above conditions are met. For example, the fourth side 323 can be slightly higher or lower than the center of the end plate 210, and there is no limitation here.

[0061] It will be appreciated that after the tail body 320 is connected to the end plate 210 via laser welding, a first weld mark 600a left by the laser welding can be observed on the surface of the tail body 320. The first weld mark 600a comprises a first wavy weld line 610a extending along the width of the tail body 320. Specifically, the first weld line 610a comprises a plurality of alternating first wave crests 611a, first connecting portions 612a, and first wave troughs 613a, forming a periodically arranged, continuous undulating line, such as the image of a sine function.

[0062] As can be understood, during the laser welding process, the high-energy-density laser beam melts the metal material of the tail body 320 and the surface of the end plate 210. The melted metal material forms a specific weld mark upon solidification. In this embodiment, by controlling the welding path, a wavy first weld line 610a is formed on the tail body 320, extending along the width of the tail body 320. Given a constant width of the tail body 320, the total length of the wavy first weld line 610a is relatively long, effectively shortening the average path length of electron transmission and increasing the actual weld area. This not only improves the current flow capacity of the end plate 210 and tail body 320 at the weld location, but also reduces the internal resistance of the battery to a certain extent. This, in turn, improves heat generation during battery use, heat dissipation, and connection strength. Therefore, it can be understood that the cylindrical lithium-ion battery of this embodiment can fully utilize its battery performance, such as charge and discharge performance and output power.

[0063] It should be noted that although this article describes the welding mark formed on the tail body 320 as the first welding mark 600a, the first welding mark 600a will extend to the surface of the end plate 210 to achieve the connection between the end plate 210 and the tail body 320.

[0064] like Figure 5 As shown, combined with Figure 6 In some embodiments, with the radius of the end plate 210 as R0a, the width of the tail body 320 as L1a, and the width and length of the first weld line 610a as W1a and L2a, W1a / R0a ranges from 15% to 32%, and L2a / L1a ranges from 56% to 76%. It should be noted that the width W1a of the first weld line 610a is the height difference between its first crest 611a (highest point) and its first trough 613a (lowest point), while the length L2a of the first weld line 610a is the length of the orthographic projection of the first weld line 610a along the width of the tail body 320. For example, W1a / R0a can be 15%, 25%, 32%, etc., and L2a / L1a can be 56%, 65%, 76%, etc.

[0065] If W1a / R0a is too large, the first bond wire 610a is too wide. However, increasing the width of the first bond wire 610a has a marginal effect on improving the battery's internal resistance. In other words, a wider first bond wire 610a does not significantly reduce internal resistance. Instead, it increases welding time, reduces welding efficiency, and increases the risk of welding defects. Conversely, if W1a / R0a is too small, the effective welding area of ​​the first bond wire 610a is insufficient, resulting in insufficient current capacity and increased internal resistance. This, in turn, causes excessive temperature rise in the weld mark during battery use, affecting battery performance. Furthermore, the connection strength of the first bond mark 600a is insufficient.

[0066] If L2a / L1a is too large, the first bonding wire 610a will be too long. However, increasing the length of the first bonding wire 610a will have a marginal effect on improving the battery's internal resistance. That is, a longer first bonding wire 610a will not significantly improve internal resistance. Instead, it will increase welding time, reduce welding efficiency, and increase the risk of welding defects. Conversely, if L2a / L1a is too small, the effective bonding area of ​​the first bonding wire 610a will be insufficient, resulting in insufficient current capacity and increased internal resistance. This will in turn cause the weld mark temperature to rise excessively during battery use, affecting battery performance. Furthermore, the connection strength of the first bonding mark 600a will be insufficient.

[0067] In some embodiments, R0a ranges from 5.29 to 7.29 mm, and L1a ranges from 5 to 7 mm. For example, R0a may be 5.29 mm, 6.29 mm, or 7.29 mm, and L1a may be 5 mm, 6 mm, or 7 mm.

[0068] In some embodiments, W1a is in the range of 1 to 2 mm, and L2a is in the range of 3.5 to 4.5 mm. For example, W1a may be 1 mm, 1.5 mm, or 2 mm, and L2a may be 3.5 mm, 4 mm, or 4.5 mm.

[0069] If W1a is large, first bond wire 610a is too wide. However, increasing the width of first bond wire 610a has a marginal effect on improving the battery's internal resistance. In other words, a wider first bond wire 610a does not significantly reduce internal resistance. Instead, it increases welding time, reduces welding efficiency, and increases the risk of welding defects. Conversely, if W1a is too small, the effective welding area of ​​first bond wire 610a is insufficient, resulting in insufficient current capacity and increased internal resistance. This, in turn, causes excessive temperature rise in the weld mark during battery use, affecting battery performance. Furthermore, the connection strength of first bond mark 600a is insufficient.

[0070] If L2a is too large, the first bonding wire 610a is too long. However, increasing the length of the first bonding wire 610a has a marginal effect on improving the battery's internal resistance. In other words, a longer first bonding wire 610a does not significantly reduce internal resistance. Instead, it increases welding time, reduces welding efficiency, and increases the risk of welding defects. Conversely, if L2a is too small, the effective bonding area of ​​the first bonding wire 610a is insufficient, resulting in insufficient current capacity and increased internal resistance. This, in turn, causes excessive temperature rise in the weld mark during battery use, affecting battery performance. Furthermore, the connection strength of the first bonding mark 600a is insufficient.

[0071] In some embodiments, along the length direction of the tail body 320, at the portion of the tail body 320 covering the disk surface of the end plate 210, the first welding line 610a is away from the edge of the end plate 210 on the side away from the fourth side 323 ( Figure 5 The distance between the first welding line 610a and the fourth side 323 (shown by the dashed line) is W2a, the distance between the side of the first welding line 610a closest to the fourth side 323 and the fourth side 323 is W3a, W2a / R0a ranges from 40% to 51%, and W3a / R0a ranges from 25% to 35%. It is understood that when the fourth side 323 passes exactly through the center of the end plate 210, W1a+W2a+W3a=R0a. For example, W2a / R0a can be 40%, 45%, or 51%, and W3a / R0a can be 25%, 30%, or 35%.

[0072] If W2a / R0a is too large or W3a / R0a is too small, the first welding wire 610a is too close to the end of the tail body 320. Since the manufacturing process allows a certain offset tolerance for the tail body 320, when the first welding wire 610a is too close to the end of the tail body 320, there is a risk that the first welding wire 610a will deviate from the end of the tail body 320. As a result, the effective welding area will be insufficient, and the current carrying capacity of the first welding wire 610a will be insufficient. The internal resistance of the battery will increase, and the temperature rise of the welding mark will be too large when the battery is used, thereby affecting the battery performance. In addition, the connection strength of the first welding mark 600a will be insufficient. On the contrary, if W1a / R0a is too small or W3a / R0a is too large, the first weld line 610a is too close to the edge of the end plate 210, and there is a risk that the first weld line 610a will deviate from the tail body 320. As a result, the actual welding area will be insufficient, and the flow capacity of the first weld line 610a will be insufficient. The internal resistance of the battery will increase, and the temperature rise of the weld mark will be too large when the battery is used, thereby affecting the battery performance. In addition, it will also lead to insufficient connection strength of the first weld mark 600a.

[0073] In some embodiments, W2a ranges from 2.59 to 3.19 mm, and W3a ranges from 1.6 to 2.2 mm. For example, W2a may be 2.59 mm, 2.99 mm, or 3.19 mm, and W3a may be 1.6 mm, 1.8 mm, or 2.2 mm.

[0074] In some embodiments, along the width direction of the tail body 320, the distance between the side of the first welding line 610a closest to the fifth side 321 and the fifth side 321 is L3a, and the distance between the side of the first welding line 610a closest to the sixth side 322 and the sixth side 322 is L4a. L3a / L1a ranges from 9% to 24%, and L4a / L1a ranges from 9% to 24%. It is understood that L2a+L3a+L4a=L1a. For example, L3a / L1a can be 9%, 16%, or 24%, and W3a / R0a can be 9%, 16%, or 24%.

[0075] If L3a / L1a is too large or L4a / L1a is too small, the first welding line 610a is too close to the sixth side 322. Since the manufacturing process allows a certain offset tolerance for the tail body 320, when the first welding line 610a is too close to the sixth side 322, there is a risk that the first welding line 610a will deviate from the sixth side 323 of the tail body 320. As a result, the effective welding area will be insufficient, and the current carrying capacity of the first welding line 610a will be insufficient. The internal resistance of the battery will increase, and the temperature rise of the welding mark will be too large during battery use, thereby affecting battery performance. In addition, the connection strength of the first welding mark 600a will be insufficient. Conversely, if L3a / L1a is too small or L4a / L1a is too large, the first welding line 610a is too close to the fifth side 321. Since the manufacturing process allows a certain offset tolerance for the tail body 320, when the first welding line 610a is too close to the fifth side 321, there is a risk that the first welding line 610a will deviate from the fifth side 321 of the tail body 320. As a result, the effective welding area will be insufficient, and the current carrying capacity of the first welding line 610a will be insufficient. The internal resistance of the battery will increase, and the temperature rise of the welding mark will be too large when the battery is used, thereby affecting the battery performance. In addition, the connection strength of the first welding mark 600a will be insufficient.

[0076] In some embodiments, L3a is in the range of 0.6 to 1.4 mm, and L4a is in the range of 0.6 to 1.4 mm. For example, L3a may be 0.6 mm, 1 mm, or 1.4 mm, and L4a may be 0.6 mm, 1 mm, or 1.4 mm.

[0077] In some embodiments, the end plate 210 is provided with a boss hole 211 at the center, and is also provided with a plurality of exhaust holes 212 surrounding the boss hole 211. The plurality of exhaust holes 212 are evenly spaced along the circumference of the disk surface of the end plate 210. It can be understood that the boss hole 211 and the exhaust holes 212 are both non-weldable areas, and the first weld line 610a should be located in the area between the boss hole 211 and the exhaust holes 212. Figure 5 As shown, when there are multiple exhaust holes 212 , the first welding wire 610 a is only arranged between the exhaust holes 212 and the boss hole 211 in the area covered by the tail body 320 .

[0078] Furthermore, in some embodiments, the minimum distance between the first welding line 610a and the edge of the end plate 210 surrounding the exhaust hole 212 is L5a, and L5a / R0a ranges from 24% to 38%. For example, L5a / R0a can be 24%, 31%, or 38%.

[0079] If L5a / R0a is too large, the first welding wire 610a is too close to the boss hole 211. Since the process allows a certain offset tolerance for the tail body 320, when the first welding wire 610a is too close to the boss hole 211, there is a risk that the first welding wire 610a will be welded into the boss hole 211. As a result, the effective welding area will be insufficient, and the flow capacity of the first welding wire 610a will be insufficient. The internal resistance of the battery will increase, and the temperature rise of the weld mark will be too large when the battery is used, thereby affecting the battery performance. In addition, it will also lead to insufficient connection strength of the first weld mark 600a. On the other hand, if L5a / R0a is too small, the first welding wire 610a is too close to the exhaust hole 212. Since the process allows a certain offset tolerance for the tail body 320, when the first welding wire 610a is too close to the exhaust hole 212, there is a risk that the first welding wire 610a will be welded into the exhaust hole 212. As a result, the effective welding area will be insufficient, and the flow capacity of the first welding wire 610a will be insufficient. The internal resistance of the battery will increase, and the temperature rise of the welding mark will be too large when the battery is used, thereby affecting the battery performance. In addition, it will also lead to insufficient connection strength of the first welding mark 600a.

[0080] In some embodiments, L5a ranges from 1.57 mm to 2.37 mm. For example, L5a can be 1.57 mm, 1.97 mm, or 2.37 mm.

[0081] In some embodiments, as Figure 6 As shown, the first connection portion 612a of the first welding wire 610a has a straight line segment in its extension direction, and the straight line segments of two adjacent first connection portions 612a have an angle Aa, and the angle Aa ranges from 25° to 65°. For example, the angle Aa can be 25°, 41°, 65°, etc.

[0082] If angle Aa is too large, the actual length of first welding wire 610a will be shortened, while the length of first welding wire 610a in the extension direction remains constant. This will result in a smaller actual welding area, weakening the current flow capacity of the weld and causing excessively high overcurrent temperature rise, impacting battery performance. Furthermore, increasing the actual length of first welding wire 610a will inevitably require increasing its length in the extension direction, causing first welding wire 610a to extend beyond tail body 320, rendering part of first welding wire 610a inoperable and lacking current flow capacity. This weakens the current flow capacity of first welding wire 610a, increases the overcurrent temperature rise, and impacts battery performance and can also cause welding quality issues. Conversely, if angle Aa is too small, the first crest portion 611a, first connecting portion 612a, and first trough portion 613a of first welding wire 610a will be closely spaced, concentrating heat and resulting in poor heat dissipation. Heat concentration in first welding wire 610a can easily lead to welding quality issues, such as weld hot spots.

[0083] Continue to refer Figure 6 In some embodiments, the average width of the first welding wire 610a is W4a, and W4a ranges from 0.2 to 0.4 mm. For example, W4a may be 0.2 mm, 0.3 mm, or 0.4 mm.

[0084] If W4a is too large, heat will be concentrated at the bends of the first crest portion 611a and the first trough portion 612a during welding, which can easily lead to welding quality problems such as weld burnout. Conversely, if W4a is too small, the actual welding area of ​​the first welding wire 610a will be reduced, thereby weakening the current carrying capacity. During battery use, the overcurrent temperature rise will be too high, affecting battery performance.

[0085] In some embodiments, the end plate 210 is provided with a boss hole 211 at its center, and is further provided with a plurality of vent holes 212 in the form of arc-shaped waist-shaped holes surrounding the boss hole 211. The vent holes 212 include an inner arc 2121, an outer arc 2122, and two side arcs 2123. The plurality of vent holes 212 are evenly spaced along the circumference of the disk surface of the end plate 210, and the inner arc 2121 and outer arc 2122 of the vent holes 212 are cocentric with the circle in which the end plate 210 is located. It is understood that they are also necessarily cocentric with the boss hole 211. Therefore, the disk surface of the end plate 210 is radially arranged from the inside to the outside, namely, the innermost circular hole (boss hole 211), the circular ring formed by the boss hole 211 and the inner arc 2121 of the exhaust hole 212, the circular ring defined by the inner arc 2121 and the outer arc 2122 of the exhaust hole 212, and the circular ring defined by the edge of the end plate 210 and the outer arc 2122 of the exhaust hole 212.

[0086] Furthermore, in some embodiments, the radius of the boss hole 211 is R1a, and the ratio R1a / R0a is in the range of 17% to 25%. For example, R1a / R0a can be 17%, 21%, or 25%.

[0087] If R1a / R0a is too large, the boss hole 211 will occupy the weldable area on the end plate 210, resulting in insufficient effective welding area for the first weld line 610a. This, in turn, leads to insufficient current capacity, increased internal resistance of the battery, and excessive temperature rise in the weld mark during battery operation, thus affecting battery performance. Furthermore, this can lead to insufficient connection strength for the first weld mark 600a. Conversely, if R1a / R0a is too small, the corresponding structural dimensions of the boss hole 211 are insufficient to meet the CID power-off function and accommodate the wire for the burst-proof disk penetration weld. As the diameter of the wire bond between the burst-proof disk and the end plate 210 decreases, the wire bond's current capacity becomes insufficient, resulting in excessive temperature rise during battery operation. Furthermore, if the wire bond is too close to the CID power-off notch, the high welding temperature can affect the CID's power-off capability, compromising battery safety.

[0088] In some embodiments, R1a ranges from 1.15 to 1.55 mm. For example, R1a may be 1.15 mm, 1.35 mm, or 1.55 mm.

[0089] Furthermore, in some embodiments, the width of the ring defined by the inner arc 2121 and the outer arc 2122 of the exhaust hole 212 is H2a, and the ratio H2a / R0a is in the range of 12% to 26%. For example, H2a / R0a can be 12%, 19%, or 26%.

[0090] If H2a / R0a is too large, the vent holes 212 will occupy the weldable area on the end plate 210, resulting in insufficient effective welding area for the first weld line 610a. This, in turn, leads to insufficient current capacity, increased internal resistance of the battery, and excessive temperature rise of the weld mark during battery use, thus affecting battery performance. Furthermore, the connection strength of the first weld mark 600a will be insufficient. Conversely, if H2a / R0a is too small, the exhaust effect of the vent holes 212 will be affected, limiting their effectiveness in improving battery safety.

[0091] In some embodiments, H2a ranges from 0.8 to 1.6 mm. For example, H2a can be 0.8 mm, 1.2 mm, or 1.6 mm.

[0092] Furthermore, in some embodiments, the width of the ring defined by the boss hole 211 and the inner arc 2121 of the exhaust hole 212 is H1a, and H1a / R0a ranges from 43% to 51%. For example, H1a / R0a can be 43%, 47%, or 51%.

[0093] If H1a / R0a is too large, the area of ​​the vent hole 212 will be reduced, thereby affecting its venting effect. It may also be too close to the edge of the end plate 210 surface. When the end plate 210 is assembled to the cap 200, the vent hole 212 may be easily blocked by other components, further affecting its venting effect and limiting its effect on improving battery safety. Conversely, if H1a / R0a is too small, the weldable area on the end plate 210 surface is too small, resulting in insufficient effective welding area for the first weld line 610a. This in turn leads to insufficient current capacity, increased internal resistance of the battery, and excessive temperature rise of the weld mark during battery use, thus affecting battery performance. Furthermore, the connection strength of the first weld mark 600a may be insufficient.

[0094] In some embodiments, H1a ranges from 2.75 mm to 3.15 mm. For example, H1a may be 2.75 mm, 2.95 mm, or 3.15 mm.

[0095] Furthermore, in some embodiments, the width of the ring defined by the edge of the end plate 210 and the outer arc 2122 of the exhaust hole 212 is H3a, and H3a / R0a ranges from 9% to 16%. For example, H3a / R0a can be 9%, 12%, or 16%.

[0096] If H3a / R0a is too large, the vent hole 212 will shift toward the center of the end plate 210's surface, resulting in a reduced weldable area on the surface. This, in turn, results in insufficient effective welding area for the first weld line 610a, which in turn leads to insufficient current capacity, increased internal resistance of the battery, and excessive weld mark temperature rise during battery use, thus affecting battery performance. Furthermore, the connection strength of the first weld mark 600a will be insufficient. Conversely, if H3a / R0a is too small, the vent hole 212 will be too close to the edge of the end plate 210's surface. When the end plate 210 is assembled to the cap 200, the vent hole 212 will be easily blocked by other components, thereby affecting its exhaust efficiency and limiting its role in improving battery safety.

[0097] In some embodiments, H3a ranges from 0.59 to 0.99 mm. For example, H3a may be 0.59 mm, 0.79 mm, or 0.99 mm.

[0098] It can be understood that, in this embodiment, R1a+H1a+H2a+H3a=R0a.

[0099] Furthermore, in some embodiments, the length of the centerline arc of the vent hole 212 is L6a, the spacing between the centerline arcs of two adjacent vent holes 212 is L7a, L6a / R0a ranges from 71% to 88%, and L7a / R0a ranges from 12% to 20%. Here, the centerline arc refers to the arc connecting the vertices of the two side arcs 2123 of the vent hole 212, and this centerline arc is cocentric with the circle containing the end plate 210. It is understood that each point of this centerline arc passes through the midpoint of the circle defined by the inner arc 2121 and outer arc 2122 of the vent hole 212. For example, L6a / R0a can be 71%, 80%, or 88%, and L7a / R0a can be 12%, 16%, or 20%.

[0100] If L6a / R0a is too large or L7a / R0a is too small, the connection structure between two adjacent vent holes 212 will be insufficiently strong and prone to breakage. The resulting metal burrs or metal debris will adversely affect battery safety. Conversely, if L6a / R0a is too small or L7a / R0a is too large, the size of the vent holes 212 will be reduced, thereby affecting their exhaust efficiency and limiting their effectiveness in improving battery safety.

[0101] The effects of the present application are further described below with reference to specific examples and comparative examples.

[0102] It should be noted that the following embodiments and comparative examples of the present application are all designed and manufactured based on the 2170 cylindrical lithium-ion battery commonly used in the art. Therefore, in addition to manufacturing according to the aforementioned structure and welding the cap and the positive electrode current collector, other components and materials can be obtained with reference to the 2170 cylindrical lithium-ion battery.

[0103] Example 1:

[0104] Example 1 provides a cylindrical lithium-ion battery, which includes a cap 200 and a positive electrode current collecting disk 300. The innermost side of the cap 200 has an end plate 210. The tail body 320 is a square long strip structure, including a fifth side 321 and a sixth side 322 along its length, and a fourth side 323 away from the first disk body 310. The tail body 320 extends generally along the radial direction of the end plate 210 and abuts against the semicircle of the inner disk surface of the end plate 210. Its fifth side 321 and sixth side 322 are parallel to the radial direction of the end plate 210, and the fourth side 323 generally passes through the center of the end plate 210. The tail body 320 is connected to the end plate 210 by laser through-welding, and at the tail The body 320 forms a wavy first welding line 610a extending along the width direction of the tail body 320. In addition, the following parameters are met: R0a is 6.29 mm, W1a is 1.5 mm, W2a is 2.99 mm, W3a is 1.8 mm, L1a is 6 mm, L2a is 4 mm, L3a is 0.8 mm, and L4a is 1.2 mm. Therefore, in Example 1, W1a / R0a=23.85%, W2a / R0a=47.54%, W3a / R0a=28.62%, L2a / L1a=66.67%, L3a / L1a=13.33%, and L4a / L1a=20%.

[0105] Example 2:

[0106] Example 2 provides a cylindrical lithium-ion battery, which differs from Example 1 in that L3a is 0.6 mm, L4a is 1.4 mm, L3a / L1a=10%, and L4a / L1a=23.33%.

[0107] Comparative Example 1:

[0108] Comparative Example 1 provides a cylindrical lithium-ion battery, which differs from Example 1 in that L3a is 0.4 mm, L4a is 1.6 mm, L3a / L1a=6.67%, and L4a / L1a=26.67%.

[0109] Example 3:

[0110] Example 3 provides a cylindrical lithium-ion battery, which differs from Example 1 in that L2a is 3.6 mm, L3a is 1.2 mm, L2a / L1a=60%, and L3a / L1a=20%.

[0111] Comparative Example 2:

[0112] Comparative Example 2 provides a cylindrical lithium-ion battery, which differs from Example 1 in that L2a is 3.2 mm, L3a is 1.4 mm, L4a is 1.4 mm, L2a / L1a=53.33%, L3a / L1a=23.33%, and L4a / L1a=23.33%.

[0113] Example 4:

[0114] Example 4 provides a cylindrical lithium-ion battery, which differs from Example 1 in that: L2a is 4.4 mm, L3a is 0.8 mm, L4a is 0.8 mm, L2a / L1a=73.33%, L3a / L1a=13.33%, and L4a / L1a=13.33%.

[0115] Comparative Example 3:

[0116] Comparative Example 3 provides a cylindrical lithium-ion battery, which differs from Example 1 in that L2a is 4.8 mm, L3a is 0.6 mm, L4a is 0.6 mm, L2a / L1a=80%, L3a / L1a=10%, and L4a / L1a=10%.

[0117] Example 5:

[0118] Example 5 provides a cylindrical lithium-ion battery. Compared with Example 1, its R0a is 6.29 mm, W1a is 1.5 mm, W2a is 3.19 mm, W3a is 1.6 mm, L1a is 6 mm, L2a is 4 mm, L3a is 1 mm, and L4a is 1 mm. Therefore, in Example 5, W1a / R0a=23.85%, W2a / R0a=50.72%, W3a / R0a=25.44%, L2a / L1a=66.67%, L3a / L1a=16.67%, and L4a / L1a=16.67%.

[0119] Comparative Example 4:

[0120] Comparative Example 4 provides a cylindrical lithium-ion battery, which differs from Example 5 in that W2a is 3.39 mm, W3a is 1.4 mm, W2a / R0a=53.9%, and W3a / R0a=22.26%.

[0121] Example 6:

[0122] Example 6 provides a cylindrical lithium-ion battery, which differs from Example 5 in that W2a is 2.59 mm, W3a is 2.2 mm, W2a / R0a=41.18%, and W3a / R0a=34.98%.

[0123] Comparative Example 5:

[0124] Comparative Example 5 provides a cylindrical lithium-ion battery, which differs from Example 5 in that W2a is 2.19 mm, W3a is 2.6 mm, W2a / R0a=34.82%, and W3a / R0a=41.34%.

[0125] Example 7:

[0126] Example 7 provides a cylindrical lithium-ion battery, which differs from Example 5 in that W1a is 1.2 mm, W2a is 3.14 mm, W3a is 1.95 mm, W1a / R0a=19.08%, W2a / R0a=49.92%, and W3a / R0a=31%.

[0127] Example 8:

[0128] Example 8 provides a cylindrical lithium-ion battery, which differs from Example 5 in that W1a is 1 mm, W2a is 3.24 mm, W3a is 2.05 mm, W1a / R0a=15.9%, W2a / R0a=51.51%, and W3a / R0a=32.59%.

[0129] Comparative Example 6:

[0130] Comparative Example 6 provides a cylindrical lithium-ion battery, which differs from Example 5 in that W1a is 0.8 mm, W2a is 3.34 mm, W3a is 2.15 mm, W1a / R0a=12.72%, W2a / R0a=53.1%, and W3a / R0a=34.18%.

[0131] Example 9:

[0132] Example 9 provides a cylindrical lithium-ion battery, which differs from Example 5 in that W1a is 1.8 mm, W2a is 2.84 mm, W3a is 1.65 mm, W1a / R0a=28.62%, W2a / R0a=45.15%, and W3a / R0a=26.23%.

[0133] Example 10:

[0134] Example 10 provides a cylindrical lithium-ion battery, which differs from Example 5 in that W1a is 2 mm, W2a is 2.74 mm, W3a is 1.55 mm, W1a / R0a=31.8%, W2a / R0a=43.56%, and W3a / R0a=24.64%.

[0135] Comparative Example 7:

[0136] Comparative Example 7 provides a cylindrical lithium-ion battery, which differs from Example 5 in that W1a is 2.2 mm, W2a is 2.64 mm, W3a is 1.45 mm, W1a / R0a=34.98%, W2a / R0a=41.97%, and W3a / R0a=23.05%.

[0137] Table 1 evaluates the weld mark temperature rise, connection strength, and weld failure rate of the first weld mark 600a formed by laser welding between the middle end plate 210 and the tail body 320 of the cylindrical lithium-ion battery manufactured in the above-mentioned embodiment and comparative example.

[0138] The specific test method for the temperature rise of the weld mark is as follows: before the cylindrical lithium-ion batteries manufactured in the above embodiments and comparative examples are filled with liquid, a circular hole with a diameter of 2 mm is drilled on the cap 200, and a temperature control line is passed through the circular hole and attached to the first weld mark 600a formed on the surface of the tail body 320. After the liquid is filled according to the normal sample preparation process, the cap 200 is sealed, the circular hole is sealed with glue, and the battery is divided into different volumes to produce a qualified cylindrical lithium-ion battery. The battery is charged and discharged for 10 cycles at a high rate of 3C. After 10 cycles of charge and discharge, the temperature data of the first weld mark 600a collected by the temperature control line is obtained, and the maximum value Tmax within the temperature fluctuation range within the 10 cycles is taken and recorded.

[0139] The specific test method for the connection strength is as follows: in the process of manufacturing the cylindrical lithium-ion battery in the above-mentioned embodiments and comparative examples, after completing the welding of the end plate 210 and the tail body 320, use needle-nose pliers to start peeling from the tail end of the tail body 320 at the same position until the tail body 320 and the end plate 210 are completely separated, and the proportion of the residual area of ​​the first weld mark 600a remaining on the tail body 320 is calculated and recorded.

[0140] The specific testing method for welding quality is as follows: in the process of manufacturing cylindrical lithium-ion batteries in the above-mentioned embodiments and comparative examples, after completing the welding of the end plate 210 and the tail body 320, the CCD function of the equipment is used to perform an appearance inspection of the weld mark, and abnormal appearance conditions such as the explosion point and black color of the first weld mark 600a are detected and the defective rate is calculated.

[0141] Table 1

[0142]

[0143] As can be seen from Table 1, when the range of W1a / R0a is set at 15% to 32%, the range of L2a / R0a is set at 56% to 76%, the range of W1a is set at 1 to 2 mm, the range of L2a is set at 3.5 to 4.5 mm, the range of W2a / R0a is set at 40% to 51%, the range of W3a / R0a is set at 15% to 32%, and the ranges of L3a / L1a and L4a / L1a are set at 9% to 24%, the temperature rise Tmax of the first weld mark 600a is generally between 90° and 96°C, the residual area of ​​the first weld mark 600a after peeling is generally between 80% and 92%, and the welding defective rate of the first weld mark 600a is generally between 0.01% and 0.03%. It can be seen that within the above numerical range, the temperature rise, connection strength and welding quality of the first weld mark 600a of the tail body 320 can be well balanced, thereby balancing the charge and discharge performance, reliability and manufacturing cost of the cylindrical lithium-ion battery.

[0144] The welding structure between the negative electrode current collecting disc 500 and the negative terminal 420 is described below.

[0145] like Figure 7 and Figure 8 As shown, the negative electrode current collecting disc 500 includes a second disc body 510. In order to match the geometric shapes of the shell 100 and the winding core 400 and optimize the path through which electrons flow, the second disc body 510 is in the shape of a circular thin sheet, including a boss portion 511 located in the center and a welding portion 512 extending radially from the edge of the boss portion 511. After being assembled into a cylindrical lithium-ion battery, the boss portion 511 is connected to the inner surface of the shell bottom 110, and the welding portion 512 is connected to the negative terminal 420, thereby forming a passage between the three. That is, the negative electrode current collecting disc 500 indirectly connects the winding core 400 to the shell 100 to optimize the path through which current flows.

[0146] like Figure 7 and Figure 8 As shown, the boss portion 511 is circular and is arranged to protrude to one side along the thickness direction of the second disk body 510, so that in this direction, the surface of the boss portion 511 is higher than the surface of the welding portion 512. Furthermore, since the welding portion 512 is formed by extending radially outward from the edge of the boss portion 511, that is, the welding portion 512 is arranged around the circular boss portion 511, the overall shape is annular. During the assembly of the cylindrical lithium-ion battery, the surface of the boss portion 511 is connected to the inner surface of the shell bottom 110, and on the other side of the second disk body 510 in the thickness direction, the surface of the welding portion 512 is connected to the surface of the negative terminal 420. It is understandable that the boss portion 511 and the welding portion 512 can be formed from a metal sheet through a stamping process.

[0147] It can be further understood that since the boss portion 511 has a smaller area relative to the entire second disk body 510, it can ensure good surface flatness during the processing process, so that the surface of the boss portion 511 can better fit the inner surface of the shell bottom 110, and can effectively avoid welding quality problems such as cold welding between the two.

[0148] In this embodiment, the welding portion 512 of the second disk body 510 is connected to the negative terminal 420 of the winding core 400 by laser welding, and a plurality of second weld marks 600b are formed on the welding portion 512, that is, after the welding portion 512 of the disk body 510 is connected to the negative terminal 420 by laser welding, a plurality of second weld marks 600b are left on the welding portion 512, and these second weld marks 600b can be observed on the disk surface of the second disk body 510.

[0149] It is understood that during the laser welding process, the high-energy-density laser beam melts the metal material on the surface of the second plate 510 and the negative terminal 420. The melted metal material forms a specific weld mark after solidification. In the embodiment of the present application, by controlling the welding path, second weld marks 600b are formed in multiple circumferential regions of the second plate 510. Each set of second weld marks 600b includes multiple second weld lines 610b. These second weld lines 610b provide multiple conductive paths in a local area, which can reduce local current density. The total length of these second weld lines 610b is relatively long, effectively shortening the average path length of electron transport and increasing the actual weld area. This not only improves the current flow capacity of the winding core 400 and the negative current collecting plate 500 at the welding location and ensures uniform current flow, but also reduces the internal resistance of the cylindrical lithium-ion battery to a certain extent. This also effectively reduces the heat generation of the cylindrical lithium-ion battery during use. Therefore, it can be understood that the cylindrical lithium-ion battery of this embodiment can fully utilize battery performance, such as charge and discharge performance and output power. In addition, whether for multiple second weld marks 600b or for a single second weld mark 600b composed of multiple second weld lines 610b, multiple second weld marks 600b can achieve redundant connections and maintain the reliability of the overall structure when the battery is subjected to vibration or impact.

[0150] It should be noted that although this article describes the welding marks formed on the negative electrode current collecting disc 500 as the second weld marks 600b, these second weld marks 600b will all extend to the surface of the negative terminal 420, thereby physically connecting the negative electrode current collecting disc 500 and the winding core 400 together.

[0151] In some embodiments, four groups of second weld marks 600b are provided. These four groups of second weld marks 600b are spaced apart along the circumference of the second plate 510 on the welding portion 512 of the second plate 510. Furthermore, the four groups of second weld marks 600b are cross-symmetrically distributed, i.e., centrally symmetrically distributed around the boss portion 511. Each second weld mark 600b includes three second weld lines 610b. The second weld lines 610b in each group of second weld marks 600b are parallel to each other and spaced uniformly apart. Consequently, a total of twelve second weld lines 610b are distributed throughout the welding portion 512.

[0152] It is understood that the number of second weld marks 600b is not limited to four groups, and can be set to a greater number or more. For example, the number of second weld marks 600b can be three, five, etc. It is understood that the second weld marks 600b can also be unevenly distributed along the circumference of the second disk body 510. It is understood that the number of second weld lines 610b in the second weld mark 600b is not limited to three, and can be set to a lesser number or more. For example, the number of second weld lines 610b can be two, four, etc.

[0153] like Figure 9 As shown, in some embodiments, the second welding wire 610b is wavy, that is, the second welding wire 610b includes a plurality of second wave crests 611b, second connecting portions 612b, and second wave troughs 613b that are alternately connected, forming a periodically arranged, continuous undulating line, such as the image of a sine function. The multiple second welding wires 610b provide multiple conductive paths at the welding portion 512 of the second plate 510. Furthermore, given a constant diameter of the second plate 510, the wavy shape of the second welding wire 610b can effectively increase the length of the second welding wire 610b and the actual welding area, thereby improving battery performance and enhancing the reliability of the connection between the winding core 400 and the negative electrode current collecting plate 500.

[0154] It can be understood that the second welding line 610b extends along the radial direction of the disk surface of the second disk body 510, which does not mean that the second welding line 610b must strictly extend along the radial direction of the second disk body 510. There can also be a certain angle between the two. For example, the second welding line 610b is slightly inclined to the radial direction, that is, the extension direction of the second welding line 610b is at a certain angle to the radial direction.

[0155] refer to Figure 8In this embodiment, the radius of the second plate 510 is R0b. The minimum distance between the end of the second weld mark 600b on the side closest to the boss portion 511 and the boss portion 511 is L0b. The minimum distance between the end of the second weld mark 600b on the side away from the boss portion 511 and the edge of the second plate 510 is L2b. The range of L0b / R0b is 5% to 16%, and the range of L2b / R0b is 5% to 16%. For example, L0b / R0b can be 5%, 11%, 16%, etc., L0b can be 0.8 mm, 1.0 mm, 1.2 mm, etc., L2b / R0b can be 5%, 11%, 16%, etc., L2b can be 0.8 mm, 1.0 mm, 1.2 mm, etc., and R0b can be 9.5 mm.

[0156] First, if L0b / R0b is too large, the second weld line 610b may deviate from the second plate 510 during welding, reducing the effective area of ​​the second weld line 610b, reducing the current flow capacity at the second weld line 610b, and increasing the overcurrent temperature rise, thus affecting battery performance. Conversely, if L0b / R0b is too small, the second weld mark 600b is too close to the boss portion 511, making it easy for the laser weld to hit the boss portion 511. Since the boss portion 511 needs to be welded to the inner surface of the bottom of the shell 100, it will occupy the area where the boss portion 511 is originally welded to the shell 100, resulting in a reduction in the weldable area between the boss portion 511 and the shell 100. This will reduce the current flow capacity at the weld between the shell 100 and the boss portion 511, increase the overcurrent temperature rise, and affect battery performance. Secondly, if L2b / R0b is too large, the second weld mark 600b will be offset inward, too close to the boss portion 511, making it easy for the second weld line 610b to weld to the boss portion 511. Since the boss portion 511 is used for welding to the housing 100, welding to the boss portion 511 will reduce the weldable area between the boss portion 511 and the housing 100, reducing the current carrying capacity of the weld during through-welding of the housing 100 and increasing the overcurrent temperature rise, thus affecting battery performance. Conversely, if L2b / R0b is too small, the second weld mark 600b will be too close to the edge of the second plate 510, causing the second weld line 610b to deviate from the second plate 510 during welding. This reduces the effective area of ​​the second weld line 610b, reduces the current carrying capacity at the second weld line 610b, and increases the overcurrent temperature rise, thus affecting battery performance.

[0157] In some embodiments, the overall length of the second weld mark 600b is L1b, and L1b / R0b ranges from 37% to 57%. For example, L1b / R0b can be 37%, 42%, 47%, 52%, 57%, etc., and L1b can be 4.2 mm, 4.5 mm, 4.8 mm, etc. It should be noted that the overall length of the second weld mark 600b refers to the length of the second weld lines 610b that constitute the second weld mark 600b along the direction in which the second weld lines 610b extend.

[0158] If L1b / R0b is too large, the second bonding wire 610b will be too long, increasing the risk of poor welding and reducing welding reliability. Furthermore, after the second bonding wire 610b reaches a certain length, further lengthening the second bonding wire 610b will not further reduce the battery's internal resistance. Conversely, if L1b / R0b is too small, the current handling capacity of the second bonding wire 610b will decrease, and the battery's internal resistance will increase. This will lead to high localized heat generation during overcurrent, excessive weld temperature rise, and poor battery performance.

[0159] In some embodiments, the overall width of the second weld mark 600b is W1b, and W1b / R0b ranges from 17% to 36%. For example, W1b / R0b can be 17%, 22%, 26%, 30%, 36%, etc., and W1b can be 2.2 mm, 2.5 mm, 2.8 mm, etc. It should be noted that the overall width of the second weld mark 600b refers to the sum of the widths of all the second weld lines 610b that comprise the second weld mark 600b, as well as the spacing between the second weld lines 610b.

[0160] If W1b / R0b is too large, the distance between each second weld line 610b in the second weld mark 600b is large. During welding, the laser must weld each of the multiple second weld lines 610b one by one. Due to the large distance between adjacent second weld lines 610b, the laser travel becomes longer, reducing welding efficiency, affecting production capacity, and increasing manufacturing costs. Conversely, if W1b / R0b is too small, the second weld lines 610b in the second weld mark 600b are too concentrated, resulting in excessive heat accumulation during welding. This can easily lead to weld failures such as weld penetration and hot spots, resulting in an increased weld failure rate.

[0161] In some embodiments, L2b is in the range of 0.5-1.5 mm, and L0b is in the range of 0.5-1.5 mm. For example, L2b can be 0.5 mm, 0.7 mm, 1.0 mm, 1.2 mm, 1.5 mm, etc., and L0b can be 0.5 mm, 0.7 mm, 1.0 mm, 1.2 mm, 1.5 mm, etc.

[0162] If L2b is too long, the second weld line 610b will deviate inward, placing it too close to the boss 511. This will easily cause the second weld line 610b to weld to the boss 511, reducing the weldable area between the boss 511 and the housing 100. This will reduce the current carrying capacity of the weld through the housing 100 and increase the weld temperature, impacting battery performance. Conversely, if L2b is too short, the second weld line 610b will deviate outward, easily extending beyond the edge of the negative electrode current collecting disc 500. This will reduce the effective area of ​​the second weld line 610b, reduce the current carrying capacity at the second weld line 610b, and increase the overcurrent temperature, impacting battery performance.

[0163] In some embodiments, the overall length of the second weld mark 600b is L1b, the range of L1b / R0b is 37% to 57%, and the range of L1b is 3.5 to 5.5 mm. For example, L1b can be 3.5 mm, 4.0 mm, 4.5 mm, 5.0 mm, 5.5 mm, etc.; the overall width of the second weld mark 600b is W1b, the range of W1b / R0b is 17% to 36%, and the range of W1b is 1.6 to 3.4 mm. For example, W1b can be 1.6 mm, 2.0 mm, 2.5 mm, 3.0 mm, 3.4 mm, etc.

[0164] First, if L1b is too large, the second weld line 610b will be too long, increasing the risk of poor welding and reducing welding reliability. Furthermore, after the second weld line 610b reaches a certain length, further increasing its length will not further reduce the battery's internal resistance. Conversely, if L1b is too small, the second weld line 610b's current carrying capacity will decrease, leading to high localized heat generation during overcurrent, increasing the temperature of the second weld line 610b, and increasing the battery's internal resistance, thereby affecting battery performance. Second, if W1b is too large, the distance between each second weld line 610b in the second weld mark 600b will be large. During laser welding, the laser must weld each of the multiple second weld lines 610b one by one. Due to the large distance between adjacent second weld lines 610b, the laser's travel range increases, reducing welding efficiency, affecting production capacity, and increasing manufacturing costs. On the contrary, if W1b is too small, the second welding lines 610b in the second welding mark 600b are too concentrated, and heat accumulates more during welding, which easily causes welding defects such as welding through and cracking, resulting in an increase in the welding defect rate.

[0165] In some embodiments, the projection area of ​​the second plate 510 along its thickness direction is S0, the projection area of ​​the boss portion 511 along the thickness direction of the second plate 510 is S1, and the range of S1 / S0 is 5% to 15%. For example, the range of S1 / S0 can be 5%, 8%, 10%, 12%, 15%, etc., and S1 can be 28.3 mm 2 The total area of ​​each second weld mark 600b is S2, and the range of S2 / S0 is 10% to 20%. For example, the range of S2 / S0 can be 10%, 14%, 15.9%, 18%, 20%, etc., and S2 can be 45mm 2 The overall area of ​​the second weld mark 600b refers to the area enclosed by a single second weld mark 600b, such as Figure 8The area enclosed by the rectangular dotted frame, the sum of the overall areas of each second weld mark 600b refers to the sum of the overall areas of all the second weld marks 600b of the welding part 512. For example, in this embodiment, there are 4 groups of second weld marks 600b, and the area of ​​S2 is the sum of the overall areas of the 4 groups of second weld marks 600b.

[0166] First, if S1 / S0 is too large, the flatness of the surface of the boss portion 511 becomes difficult to control. If this flatness varies significantly, the boss portion 511 cannot be completely flush with the housing 100 during penetration welding, which can easily lead to weld defects and hot spots, impacting battery performance. Conversely, if S1 / S0 is too small, the effective weld area is insufficient during penetration welding of the boss portion 511 and the housing 100, resulting in a high temperature rise at the weld, impacting battery performance. Second, if S2 / S0 is too large, the area of ​​the second weld lines 610b increases, potentially reducing weld reliability. Furthermore, the distance between the second weld lines 610b is reduced, resulting in concentrated heat between the second weld lines 610b and making it difficult to dissipate heat quickly. Heat concentration within the second weld lines 610b can lead to weld quality issues, such as hot spots. Furthermore, a larger second weld mark 600b area does not improve the battery's internal resistance. On the contrary, if S2 / S0 is too small, the overall area of ​​the second weld mark 600 b is small, resulting in a decrease in the flow capacity, an increase in the temperature of the second weld mark 600 b, and an increase in the internal resistance of the battery, affecting the battery performance.

[0167] In some embodiments, the radius of the boss portion 511 is R1b, R1b / R0b ranges from 24% to 40%, and R1b ranges from 2.0mm to 4.0mm. For example, R1b / R0b can be 24%, 32%, 40%, etc., and R1b can be 2.0mm, 3.0mm, 4.0mm, etc.

[0168] If R1b / R0b is too large, the flatness of the boss portion 511 surface will be difficult to control. If the flatness varies significantly, the boss portion 511 cannot be completely flush with the housing 100 during through-welding. This can easily lead to cold welds and hot spots, affecting battery performance. Conversely, if R1b / R0b is too small, the effective welding area will be insufficient during through-welding of the boss portion 511 and the housing 100, resulting in a high temperature rise at the weld, affecting battery performance.

[0169] like Figure 9As shown, in some embodiments, the second connecting portion 612b has a straight line segment in its extension direction, and the straight line segments of two adjacent second connecting portions 612b have an angle Ab, and the angle Ab ranges from 70° to 120°. For example, the angle Ab can be 70°, 80°, 90°, 95°, 100°, 110°, 120°, etc.

[0170] Within a given length of second bonding wire 610b, if angle Ab is too large, the straight-line distance between the head and tail of second bonding wire 610b will become longer, causing second bonding wire 610b to protrude beyond the disk surface. This can render portions of second bonding wire 610b inoperable and lose their current-carrying capacity, weakening the current-carrying capacity at the second bonding wire 610b and increasing the overcurrent temperature rise, impacting battery performance. Conversely, if angle Ab is too small, the individual second bonding wires 610b are very close together, leading to concentrated heat and poor heat dissipation. This heat concentration can easily lead to welding quality issues, such as weld cracks, along the second bonding wire 610b.

[0171] The effects of the present application are further described below with reference to specific examples and comparative examples.

[0172] It should be noted that the following embodiments and comparative examples of the present application are designed and manufactured based on the 2170 cylindrical lithium-ion battery commonly used in the art. Therefore, in addition to manufacturing and welding the negative electrode current collecting plate 500 according to the aforementioned structure, other components and materials can be obtained by referring to the 2170 cylindrical lithium-ion battery.

[0173] Example 1:

[0174] Example 1 provides a cylindrical lithium-ion battery comprising a negative electrode current collector disc 500 and a winding core 400. The second disc body 510 of the negative electrode current collector disc 500 comprises a central boss portion 511 and a peripheral weld portion 512. The weld portion 512 is connected to the negative terminal 420 of the winding core 400 by laser welding. The laser welding forms a plurality of second weld marks 600b spaced apart along the circumferential direction of the disc surface of the second disc body 510. Each second weld mark 600b extends radially from an edge of the second disc body 510 toward the center of the disc. Each group of second weld marks 600b comprises three parallel wavy second weld lines 610b. Furthermore, the second weld marks 600b further meet the following parameters: R0b is 9.5 mm, S0 is 283.4 mm. 2 , R1b is 3mm, S1 is 28.3mm 2, L0b is 0.5 mm, L1b is 4.5 mm, L2b is 1.5 mm, and W1b is 2.5 mm. Therefore, in Example 1, L0b / R0b=5%, L2b / R0b=16%, L1b / R0b=47%, W1b / R0b=26%, S1 / S0=10%, and R1b / R0b=32%.

[0175] Example 2:

[0176] Example 2 provides a cylindrical lithium-ion battery, which differs from Example 1 in that L0b is 0.7 mm, L2b is 1.3 mm, L0b / R0b=7%, and L2b / R0b=14%.

[0177] Example 3:

[0178] Example 3 provides a cylindrical lithium-ion battery, which differs from Example 1 in that L0b is 1.3 mm, L2b is 0.7 mm, L0b / R0b=14%, and L2b / R0b=7%.

[0179] Example 4:

[0180] Example 4 provides a cylindrical lithium-ion battery, which differs from Example 1 in that L0b is 1.5 mm, L2b is 0.5 mm, L0b / R0b=16%, and L2b / R0b=5%.

[0181] Comparative Example 1:

[0182] Comparative Example 1 provides a cylindrical lithium-ion battery, which differs from Example 1 in that L0b is 1.8 mm, L2b is 0.2 mm, L0b / R0b=19%, and L2b / R0b=2%.

[0183] Comparative Example 2:

[0184] Comparative Example 2 provides a cylindrical lithium-ion battery, which differs from Example 1 in that L0b is 0.2 mm, L2b is 1.8 mm, L0b / R0b=2%, and L2b / R0b=19%.

[0185] Example 5:

[0186] Example 5 provides a cylindrical lithium-ion battery, which differs from Example 1 in that L0b is 1.2 mm, L1b is 4.1 mm, L2b is 1.2 mm, L0b / R0b=13%, L1b / R0b=43%, and L2b / R0b=13%.

[0187] Example 6:

[0188] Example 6 provides a cylindrical lithium-ion battery, which differs from Example 1 in that L0b is 1.4 mm, L1b is 3.7 mm, L2b is 1.4 mm, L0b / R0b=15%, L1b / R0b=39%, and L2b / R0b=15%.

[0189] Example 7:

[0190] Example 7 provides a cylindrical lithium-ion battery, which differs from Example 1 in that L0b is 0.8 mm, L1b is 4.9 mm, L2b is 0.8 mm, L0b / R0b=8%, L1b / R0b=52%, and L2b / R0b=8%.

[0191] Example 8:

[0192] Example 8 provides a cylindrical lithium-ion battery, which differs from Example 1 in that L0b is 0.6 mm, L1b is 5.3 mm, L2b is 0.6 mm, L0b / R0b=6%, L1b / R0b=56%, and L2b / R0b=6%.

[0193] Comparative Example 3:

[0194] Comparative Example 3 provides a cylindrical lithium-ion battery, which differs from Example 1 in that L0b is 1.9 mm, L1b is 2.7 mm, L2b is 1.9 mm, L0b / R0b=20%, L1b / R0b=28%, and L2b / R0b=20%.

[0195] Comparative Example 4:

[0196] Comparative Example 4 provides a cylindrical lithium-ion battery, which differs from Example 1 in that L0b is 0.2 mm, L1b is 6.1 mm, L2b is 0.2 mm, L0b / R0b=2%, L1b / R0b=64%, and L2b / R0b=2%.

[0197] Example 9:

[0198] Example 9 provides a cylindrical lithium-ion battery, which differs from Example 1 in that L0b is 1 mm, L2b is 1 mm, W1b is 2.3 mm, L0b / R0b=11%, L2b / R0b=11%, and W1b / R0b=24%.

[0199] Example 10:

[0200] Example 10 provides a cylindrical lithium-ion battery, which differs from Example 1 in that L0b is 1 mm, L2b is 1 mm, W1b is 2.0 mm, L0b / R0b=11%, L2b / R0b=11%, and W1b / R0b=21%.

[0201] Example 11:

[0202] Example 11 provides a cylindrical lithium-ion battery, which differs from Example 1 in that L0b is 1 mm, L2b is 1 mm, W1b is 1.6 mm, L0b / R0b=11%, L2b / R0b=11%, and W1b / R0b=17%.

[0203] Example 12:

[0204] Example 12 provides a cylindrical lithium-ion battery, which differs from Example 1 in that L0b is 1 mm, L2b is 1 mm, W1b is 2.7 mm, L0b / R0b=11%, L2b / R0b=11%, and W1b / R0b=28%.

[0205] Example 13:

[0206] Example 13 provides a cylindrical lithium-ion battery, which differs from Example 1 in that L0b is 1 mm, L2b is 1 mm, W1b is 3.0 mm, L0b / R0b=11%, L2b / R0b=11%, and W1b / R0b=32%.

[0207] Example 14:

[0208] Example 14 provides a cylindrical lithium-ion battery, which differs from Example 1 in that L0b is 1 mm, L2b is 1 mm, W1b is 3.4 mm, L0b / R0b=11%, L2b / R0b=11%, and W1b / R0b=36%.

[0209] Comparative Example 5:

[0210] Comparative Example 5 provides a cylindrical lithium-ion battery, which differs from Example 1 in that L0b is 1 mm, L2b is 1 mm, W1b is 1.2 mm, L0b / R0b=11%, L2b / R0b=11%, and W1b / R0b=13%.

[0211] Comparative Example 6:

[0212] Comparative Example 6 provides a cylindrical lithium-ion battery, which differs from Example 1 in that L0b is 1 mm, L2b is 1 mm, W1b is 3.8 mm, L0b / R0b=11%, L2b / R0b=11%, and W1b / R0b=40%.

[0213] Table 2 evaluates the second weld mark 600b formed by laser welding between the negative electrode current collecting disc 500 and the winding core 400 in the cylindrical lithium-ion batteries produced in the above-mentioned embodiments and comparative examples in terms of welding temperature rise, welding failure rate, connection strength, and welding time.

[0214] The welding temperature rise is measured at the second weld mark 600b. The specific test method is as follows: the winding core 400 and the negative electrode current collector 500 are welded according to the same equipment parameters. After welding, the temperature control probe is attached to the surface of the second weld line 610b of the negative electrode current collector 500. The winding core 400 and the negative electrode current collector 500 are placed into the shell. The other end of the temperature control line is passed through the 2mm diameter through-hole pre-drilled in the cap 200 from the inner surface to the outer surface. The through-hole is sealed with glue on the surface of the cap 200. The cap 200 is normally put into the shell and transferred to the next process. After the liquid is injected according to the normal battery production process, the cover is sealed and the battery is divided into different capacities to produce a qualified battery cell. The temperature control line at the outer end of the battery is connected to the temperature collection device, and 10 cycles of charge and discharge are performed at a large rate of 3C. After 10 cycles of charge and discharge, the temperature data of the welding part 512 area collected by the temperature control line is obtained, and the maximum value Tmax within the temperature fluctuation range within the 10 cycles is taken. The unit of measurement of Tmax is degrees Celsius (℃).

[0215] The testing method for the welding defect rate is as follows: the second disk body 510 of the negative electrode current collecting disk 500 is laser welded to the negative terminal 420 of the winding core 400 according to the normal process flow. After welding, the CCD function of the equipment in the next process in the equipment is used to detect the second welding line 610b, and the explosion point of the second welding line 610b and the abnormal conditions such as the second welding line 610b being abnormal, the color being black, etc. are detected, and the defect rate is calculated, and the defect rate is expressed as a percentage.

[0216] The specific test method for the connection strength is: place the negative electrode collector disc 500 at the same position as the winding core 400, use the same pressing force to completely fit the negative electrode collector disc 500 to the flattened layer of the negative terminal 420, use laser welding, weld the negative electrode collector disc 500 to the flattened layer of the negative terminal 420, and then use needle-nose pliers to start peeling from the tail end of the negative electrode collector disc 500 at the same position until the negative electrode collector disc 500 is completely separated from the negative terminal 420, and calculate the residual area remaining on the negative electrode collector disc 500, and the residual area is expressed as a percentage.

[0217] The specific test method for welding time is: on the welding station equipment, continuously weld 10 negative electrode current collecting plates 500 according to the same welding power and travel speed, and record the time required for welding 10 negative electrode current collecting plates 500. The welding time is measured in seconds (s).

[0218] Table 2

[0219]

[0220]

[0221] As shown in Table 2, when L0b / R0b is set within a range of 5% to 16% and L2b / R0b is set within a range of 5% to 16%, the temperature rise Tmax at the second weld mark 600b is typically between 102°C and 105°C, the weld failure rate is typically between 1.4% and 1.6%, the residual area ratio (connection strength) of the second weld mark 600b is between 83% and 87%, and the welding time is typically 4.7 seconds. It can be seen that within these values, the weld temperature rise, connection strength, weld failure rate, and welding time of the second weld mark 600b in the negative electrode current collector 500 are well balanced, thereby balancing the battery performance, reliability, and manufacturing cost of the cylindrical lithium-ion battery.

[0222] Although examples of the present embodiment have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and intent of the present embodiment, and the scope of the present embodiment is defined by the claims and their equivalents.

Claims

1. A cylindrical lithium-ion battery, characterized in that: The invention comprises a housing (100), a cap (200), a positive electrode current collecting disc (300), a winding core (400) and a negative electrode current collecting disc (500), wherein the winding core (400) comprises a positive terminal (410) and a negative terminal (420), wherein: The cap (200) includes a circular end plate (210), the positive electrode current collecting disc (300) includes a square tail body (320), the tail body (320) is connected to the end plate (210) by laser welding, and forms a first weld mark (600a), the first weld mark (600a) includes a wavy first weld line (610a) extending along the width direction of the tail body (320), the radius of the end plate (210) is R0a, the width of the tail body (320) is L1a, the width of the first weld line (610a) is W1a, the length of the first weld line (610a) is L2a, the range of W1a / R0a is 15% to 32%, and the range of L2a / L1a is 56% to 76%; The negative electrode current collecting disc (500) includes a second disc body (510), the second disc body (510) is connected to the negative terminal (420) by laser welding, and forms a plurality of second weld marks (600b), the plurality of second weld marks (600b) are spaced apart along the circumferential direction of the disc surface of the second disc body (510), and each second weld mark (600b) includes at least two second weld lines (610b) arranged in parallel and extending along the radial direction of the disc surface of the second disc body (510), the radius of the second disc body (510) is R0b, the overall length of the second weld mark (600b) is L1b, the overall width of the second weld mark (600b) is W1b, the range of L1b / R0b is 37% to 57%, and the range of W1b / R0b is 17% to 36%.

2. The cylindrical lithium-ion battery according to claim 1, characterized in that The second disk body (510) includes a boss portion (511) located in the center and a welding portion (512) extending radially from the edge of the boss portion (511); the shell (100) includes a shell bottom (110); the boss portion (511) is connected to the inner surface of the shell bottom (110); the welding portion (512) is laser welded to the negative terminal (410); a plurality of second weld marks (600b) are formed on the welding portion (512); the minimum distance between the end of the second weld mark (600b) close to the boss portion (511) and the boss portion (511) is L0b, and the minimum distance between the end of the second weld mark (600b) away from the boss portion (511) and the edge of the second disk body (510) is L2b; the range of L0b / R0b is 5% to 16%, and the range of L2b / R0b is 5% to 16%.

3. The cylindrical lithium-ion battery according to claim 2, characterized in that: The projection area of ​​the second disk body (510) along its thickness direction is S0, the projection area of ​​the boss portion (511) along the thickness direction of the second disk body (510) is S1, the range of S1 / S0 is 5% to 15%, the sum of the overall areas of each second weld mark (600b) is S2, the range of S2 / S0 is 10% to 20%, and the radius of the boss portion (511) is R1b, and the range of R1b is 2 to 4 mm.

4. The cylindrical lithium-ion battery according to claim 2, characterized in that: The range of L1b is 3.5-5.5 mm, the range of W1b is 1.6-3.4 mm, the range of L0b is 0.5-1.5 mm, the range of L2b is 0.5-1.5 mm, the range of W1a is 1-2 mm, the range of L2a is 3.5-4.5 mm, and the average line width of the first welding line (610a) is W4a, and the range of W4a is 0.2-0.4 mm.

5. The cylindrical lithium-ion battery according to any one of claims 1 to 4, characterized in that: The tail body (320) includes a fifth side (321) and a sixth side (322) extending along its length direction, and a fourth side (323) located at the far end. In the portion of the tail body (320) covering the disk surface of the end plate (210), the distance between the first welding line (610a) and the edge of the end plate (210) on the side away from the fourth side (323) is W2a, and the range of W2a / R0a is 40% to 51%.

6. The cylindrical lithium-ion battery according to claim 5, characterized in that: The distance between the side of the first welding line (610a) close to the fourth side (323) and the fourth side (323) is W3a, and the range of W3a / R0a is 25% to 35%.

7. The cylindrical lithium-ion battery according to claim 5, characterized in that: The distance between the side of the first welding line (610a) close to the fifth side (321) and the fifth side (321) is L3a, and the distance between the side of the first welding line (610a) close to the sixth side (322) and the sixth side (322) is L4a, and the range of L3a / L1a is 9% to 24%, and the range of L4a / L1a is 9% to 24%.

8. The cylindrical lithium-ion battery according to any one of claims 1 to 4, characterized in that: The end plate (210) is provided with a boss hole (211) located in the center and a plurality of exhaust holes (212) surrounding the boss hole (211); the plurality of exhaust holes (212) are evenly spaced along the circumference of the disk surface of the end plate (210); the minimum distance between the first welding line (610a) and the edge of the end plate (210) surrounding the exhaust holes (212) is L5a, and the range of L5a / R0a is 24% to 38%.

9. The cylindrical lithium-ion battery according to any one of claims 1 to 4, characterized in that: The end plate (210) is provided with a boss hole (211) located in the center and a plurality of exhaust holes (212) surrounding the boss hole (211). The plurality of exhaust holes (212) are evenly spaced along the circumference of the disk surface of the end plate (210). The exhaust holes (212) are arc-shaped waist-shaped holes, including an inner arc (2121) and an outer arc (2122) arranged radially from the inside to the outside and having the same center as the circle where the end plate (210) is located. The ring width of the ring defined by the inner arc (2121) and the outer arc (2122) of the exhaust hole (212) is H2a, the radius of the boss hole (211) is R1a, the range of H2a / R0a is 12% to 26%, and the range of R1a / R0a is 17% to 25%.

10. The cylindrical lithium-ion battery according to any one of claims 1 to 4, characterized in that: The end plate (210) is provided with a boss hole (211) located in the center and a plurality of exhaust holes (212) surrounding the boss hole (211). The plurality of exhaust holes (212) are evenly spaced along the circumference of the disk surface of the end plate (210). The exhaust holes (212) are arc-shaped waist-shaped holes, including an inner arc (2121) and an outer arc (2122) arranged radially from the inside to the outside and having the same center as the circle where the end plate (210) is located. The ring width of the ring defined by the boss hole (211) and the inner arc (2121) is H1a, and the ring width of the ring defined by the edge of the end plate (210) and the outer arc (2122) is H3a. The range of H1a / R0a is 43% to 51%, and the range of H3a / R0a is 9% to 16%.

11. The cylindrical lithium-ion battery according to any one of claims 1 to 4, characterized in that: The end plate (210) is provided with a boss hole (211) located in the center and a plurality of exhaust holes (212) surrounding the boss hole (211). The plurality of exhaust holes (212) are evenly spaced along the circumference of the disk surface of the end plate (210). The exhaust holes (212) are arc-shaped waist-shaped holes, including an inner arc (2121) and an outer arc (2122) arranged radially from the inside to the outside and having the same center as the circle where the end plate (210) is located. The arc length of the center line arc of the exhaust hole (212) is L6a, the spacing between the center line arcs of two adjacent exhaust holes (212) is L7a, the range of L6a / R0a is 71% to 88%, and the range of L7a / R0a is 12% to 20%.

12. The cylindrical lithium-ion battery according to any one of claims 1 to 4, characterized in that: The second welding line (610b) includes a plurality of second wave crest portions (611b), second connecting portions (612b) and second wave trough portions (613b) that are alternately connected to each other; the first welding line (610a) includes a plurality of first wave crest portions (611a), first connecting portions (612a) and first wave trough portions (613a) that are alternately connected to each other; the second connecting portion (612b) has a straight line segment in its extension direction; the straight line segments of two adjacent second connecting portions (612b) have an angle Ab, and the range of the angle Ab is 70° to 120°; the first connecting portion (612a) has a straight line segment in its extension direction; the straight line segments of two adjacent first connecting portions (612a) have an angle Aa, and the range of the angle Aa is 25° to 65°.

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