Cylindrical lithium ion battery

Abstract

A first plate body of a positive collector plate of the cylindrical lithium ion battery is connected to the positive end of a roll core through laser welding, a plurality of first welding marks are formed, and each first welding mark comprises at least two first welding lines which are arranged in parallel and extend in the radial direction of the plate surface of the first plate body; a second plate body of the negative current collecting plate is connected to the negative end of the 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, a tail body of the positive current collecting plate is connected to the end plate through laser welding, and a third welding mark is formed. And the third welding mark comprises a wave-shaped third welding line extending along the width direction of the tail body, so that the adverse effect of the welding structure of the positive electrode current collecting plate and the negative electrode current collecting plate on the battery performance can be reduced, and 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, there are at least three welding structures: between the positive current collector and the winding core, 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 positive electrode current collector disk includes a first disk body, which is connected to the positive terminal by laser welding and forms a plurality of first weld marks. The plurality of first weld marks are spaced apart along the circumferential direction of the disk surface of the first disk body, and each first weld mark includes at least two first weld lines arranged in parallel and extending in the radial direction of the disk surface of the first disk body. The radius of the first disk body is R0a, the overall width of the first weld mark is W1a, the overall length of the first weld mark is W6a, the ratio of W1a / R0a is in the range of 20% to 30%, and the ratio of W6a / R0a is in the range of 48% to 62%.

[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 ratio L1b / R0b ranges from 37% to 57%, and the ratio W1b / R0b ranges from 17% to 36%.

[0008] The cap includes a circular end plate, and the positive current collector disc also includes a square tail body connected to the first disc body. The tail body is connected to the end plate by laser welding to form a third weld mark. The third weld mark includes a wavy third weld line extending along the width direction of the tail body. The radius of the end plate is R0c, the width of the tail body is L1c, the width of the third weld line is W1c, and the length of the third weld line is L2c. The range of W1c / R0c is 15% to 32%, and the range of L2c / L1c is 56% to 76%.

[0009] The cylindrical lithium-ion battery according to the embodiment of the present application has at least the following beneficial effects:

[0010] First, the first weld marks formed by laser welding between the positive electrode current collecting disc and the positive end of the winding core are arranged at intervals along the circumferential direction of the first disc body, and each group of first weld marks contains at least two first welding lines, thereby providing multiple conductive paths in multiple areas around the disc surface, thereby effectively shortening the average path length of electron transmission and increasing the actual welding area, which helps to improve the current flow capacity of the positive electrode current collecting disc 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] 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.

[0012] Furthermore, the third weld mark formed on the tail body by laser welding is set as a wavy third weld line, so that the third 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 third weld mark on the battery performance, which is beneficial to the performance of the battery.

[0013] In addition, the first weld print, the second weld print, and the third weld print can ensure the connection strength and realize redundant connection, so that the connection reliability of the overall structure can be maintained when the battery is vibrated or impacted.

[0014] 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%.

[0015] In one possible embodiment, a center hole is opened in the center of the disk surface of the first disk body, the radius of the first disk body is R0a, the minimum distance between the end of the first weld mark close to the center hole and the edge of the first disk body forming the center hole is W4a, the minimum distance between the end of the first weld mark away from the center hole and the edge of the first disk body is W5a, the range of W4a / R0a is 5% to 15%, and the range of W5a / R0a is 5% to 15%.

[0016] In one possible implementation, the overall width of the first weld mark is W1a, and the range of W1a is 2-3 mm. The width of each first weld line is W2a. The distance between two adjacent first weld lines is W3a. The range of W2a / W1a is 17%-27%, the range of W3a / W1a is 12%-22%, the range of W1c is 1-2 mm, the range of L2c is 3.5-4.5 mm, and the average line width of the third weld line is W4c, and the range of W4c is 0.2-0.4 mm.

[0017] In a possible implementation manner, 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, and the range of L2b is 0.5-1.5 mm.

[0018] In one possible embodiment, the disk surface of the first disk body is further provided with a plurality of peripheral holes surrounding the central hole, the minimum distance between the first weld mark and the edge of the first disk body forming the peripheral holes is W7a, the range of W7a / R0a is 7% to 17%, the distance between the peripheral holes and the central hole is L1a, the range of L1a / R0a is 5% to 12%, and the distance between the peripheral holes and the edge of the first disk body is L2a, and the range of L2a / R0a is 22% to 32%.

[0019] 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.

[0020] In a possible embodiment, the first welding line and the second welding line are both wavy, the first welding line includes a plurality of first wave crests, first connecting parts and first wave troughs alternately connected to each other, the second welding line includes a plurality of second wave crests, second connecting parts and second wave troughs alternately connected to each other, the third welding line includes a plurality of third wave crests, third connecting parts and third wave troughs alternately connected to each other, the first connecting part has a straight line segment in its extension direction, and the straight line segments of two adjacent first connecting parts have an angle Aa, and the angle Aa ranges from 50° to 75°, the second connecting part has a straight line segment in its extension direction, and the straight line segments of two adjacent second connecting parts have an angle Ab, and the angle Ab ranges from 70° to 120°, the third connecting part has a straight line segment in its extension direction, and the straight line segments of two adjacent third connecting parts have an angle Ac, and the angle Ac ranges from 25° to 65°.

[0021] In one possible embodiment, the tail body includes a fifth side and a sixth side extending along its length direction, 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 side of the third welding line away from the fourth side and the edge of the end plate is W2c, and the range of W2c / R0c is 40% to 51%.

[0022] In a possible implementation manner, a distance between a side of the third welding line close to the fourth side and the fourth side is W3c, and W3c / R0c is in a range of 25% to 35%.

[0023] In a possible implementation, a distance between a side of the third welding line close to the fifth side and the fifth side is L3c, a distance between a side of the third welding line close to the sixth side and the sixth side is L4c, and a range of L3c / L1c is 9% to 24%, and a range of L4c / L1c is 9% to 24%.

[0024] 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 third welding line and the edge of the end plate forming the exhaust holes is L5c, and the range of L5c / R0c is 24% to 38%.

[0025] 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 H2c, the radius of the boss hole is R1c, the range of H2c / R0c is 12% to 26%, and the range of R1c / R0c is 17% to 25%.

[0026] 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 H1c, the ring width of the ring defined by the edge of the end plate and the outer arc is H3c, the range of H1c / R0c is 43% to 51%, and the range of H3c / R0c is 9% to 16%.

[0027] 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 centerline arc of the exhaust hole being L6c, and the spacing between the centerline arcs of two adjacent exhaust holes being L7c, the range of L6c / R0c is 71% to 88%, and the range of L7c / R0c is 12% to 20%. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] 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.

[0029] Figure 1 1 is an exploded schematic diagram of a cylindrical lithium-ion battery according to an embodiment of the present application;

[0030] Figure 2 Schematic diagram of the structure of the positive electrode current collecting disk in the cylindrical lithium-ion battery of an embodiment of the present application;

[0031] Figure 3 yes Figure 2 Schematic diagram of the first weld print;

[0032] Figure 4 yes Figure 2 A partial schematic diagram of the first plate body of the middle positive electrode current collecting plate;

[0033] Figure 5 yes Figure 3 A schematic diagram of a single first welding line in a first welding print;

[0034] Figure 6 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;

[0035] Figure 7 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;

[0036] Figure 8 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 disc according to an embodiment of the present application;

[0037] Figure 9 yes Figure 8 Schematic diagram of the third welding line;

[0038] Figure 10 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;

[0039] Figure 11 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;

[0040] Figure 12 yes Figure 10 Schematic diagram of a single second bond line in the second bond print.

[0041] Reference numerals:

[0042] 100 - shell, 110 - shell bottom, 120 - side wall, 121 - necking structure, 130 - inner cavity, 140 - opening;

[0043] 200-cap, 210-end plate, 211-boss hole, 212-exhaust hole, 2121-inner arc, 2122-outer arc, 2123-side arc, 220-top cover;

[0044] 300 - positive electrode current collecting disc, 310 - first disc body, 311 - first side, 312 - arc edge, 313 - second side, 314 - third side, 315 - center hole, 316 - peripheral hole, 320 - tail body, 321 - fifth side, 322 - sixth side, 323 - fourth side;

[0045] 400-winding core, 410-positive terminal, 420-negative terminal;

[0046] 500-negative electrode current collecting disc, 510-second disc body, 511-boss portion, 512-welding portion;

[0047] 600a-first weld mark, 610a-first weld line, 611a-first wave crest, 612a-first connection, 613a-first wave valley, 600b-second weld mark, 610b-second weld line, 611b-second wave crest, 612b-second connection, 613b-second wave valley, 600c-third weld mark, 610c-third weld line, 611c-third wave crest, 612c-third connection, 613c-third wave valley. DETAILED DESCRIPTION

[0048] 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.

[0049] 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 .

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] It is understood that in the cylindrical lithium-ion battery described above, the positive electrode current collector disc 300 and the positive terminal 410, the negative electrode current collector disc 500 and the negative terminal 420, and the positive electrode current collector disc 300 and the cap 200 are all connected by welding. An unreasonable welding structure at any of these connection locations will lead to a bottleneck at that location, resulting in insufficient battery performance. The embodiments of the present application also improve the welding structures between the positive electrode current collector disc 300 and the positive terminal 410, between the negative electrode current collector disc 500 and the negative terminal 420, and between the positive electrode current collector disc 300 and the cap 200 to reduce the adverse effects of the welding structures in these locations on battery performance.

[0055] The welding structure between the positive electrode current collecting disc 300 and the positive terminal 410 is described below.

[0056] 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 deployed state.

[0057] 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.

[0058] 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 .

[0059] As previously described, the first plate 310 is shaped like a closed, axially symmetrical figure, consisting of a first side 311, an arcuate edge 312, a second side 313, and a third side 314 connected end-to-end. Therefore, while the first plate 310 is not a complete circle when viewed as a whole, it can be considered a circular member with respect to the arcuate edge 312. The diameter of the arcuate edge 312 is the diameter of the first plate 310. In this case, the diameter of the first plate 310 is the longest line segment between two points on the arcuate edge 312. Depending on practical needs, the diameter of the first plate 310 can be, for example, 17 to 19.2 mm, or a radius of 8.5 to 9.6 mm. Within this preferred diameter range, the first plate 310 ensures a larger contact area between the first plate 310 and the positive terminal 410, increasing the weldable area and broadening the adaptability of the first weld wire length and shape.

[0060] In some embodiments, a central hole 315 is provided at the center of the first plate 310, and a plurality of peripheral holes 316 are provided around the central hole 315. The central hole 315 is used to inject electrolyte into the battery, while the peripheral holes 316 are used to assist in electrolyte infiltration. Both the central hole 315 and the peripheral holes 316 can also function as exhaust. It should be noted that the center of the first plate 310 may be the center of the circle corresponding to the arc edge 114.

[0061] In this embodiment, the first disk body 310 and the positive terminal 410 are connected by laser welding, and a plurality of first weld marks 600a are formed on the first disk body 310. That is, after the first disk body 310 and the positive terminal 410 are connected by laser welding, a plurality of first weld marks 600a are left on the first disk body 310. These first weld marks 600a can be observed on the disk surface of the first disk body 310.

[0062] It is understood that during the laser welding process, the high-energy-density laser beam melts the metal material on the surface of the first plate 310 and the positive terminal 410. The melted metal material forms a specific weld mark after solidification. In the embodiment of the present application, by controlling the welding path, first weld marks 600a are formed in multiple circumferential regions of the first plate 310. Each set of first weld marks 600a includes multiple first weld lines 610a. These first weld lines 610a provide multiple conductive paths in a local area, which can reduce local current density. The total length of these first weld lines 610a 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 and uniformity of the positive current collecting plate 300 and the winding core 400 at the welding location, but also reduces the internal resistance of the cylindrical lithium-ion battery to a certain extent. In this case, the heat generation of the cylindrical lithium-ion battery during use can also be effectively improved. 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 first weld marks 600a or for a single first weld mark 600a composed of multiple first weld lines 610a, multiple first weld marks 600a can achieve redundant connections, and can still maintain the reliability of the overall structure when the battery is subjected to vibration or impact.

[0063] It should be noted that although this article describes the welding marks formed on the positive current collecting disc 300 as the first weld marks 600a, these first weld marks 600a will all extend to the surface of the positive terminal 410, thereby physically connecting the positive current collecting disc 300 and the winding core 400 together.

[0064] Specifically, if Figure 2 As shown, four groups of first weld marks 600a are provided. These four groups of first weld marks 600a are spaced circumferentially on the surface of the first disk body 310. Each first weld mark 600a includes three parallel first weld lines 610a extending radially along the surface of the first disk body 310. Thus, a total of twelve first weld lines 610a are provided on the entire surface of the first disk body 310. It is understood that the number of first weld marks 600a is not limited to four groups; fewer or more groups may be provided. For example, the number of first weld marks 600a may be three, five, or other groups.

[0065] It can also be understood that these first weld marks 600a can be evenly distributed along the circumferential direction of the disk surface of the first disk body 310. For example, four groups of first weld marks 600a are evenly distributed at a 90° angle between each other, but this is not limited to this. The first weld marks 600a can also be unevenly distributed along the circumferential direction of the disk surface of the first disk body 310. For example, Figure 2As shown, a central hole 315 is provided at the center of the first disk body 310, and three peripheral holes 316 are provided around the central hole 315. The first weld marks 600a are distributed between two adjacent peripheral holes 316, and in the weldable area defined by the first side 311, the second side 313 and the peripheral holes 316. Due to the limitations of the surrounding structure of the weldable area, the spacing distances, angles, etc. between the four groups of first weld marks 600a are not the same.

[0066] In addition, as mentioned above, the shape of the first plate 310 is a closed axisymmetric figure consisting of the first side 311, the arc edge 312, the second side 313 and the third side 314 connected end to end. Figure 2 As shown, the plurality of first weld marks 600a may also be distributed on the disk surface of the first disk body 310 in an axisymmetric manner along the symmetry axis of the above-mentioned figure.

[0067] like Figures 2 to 5 As shown, in some embodiments, the first bonding wire 610a is wavy, that is, the first bonding wire 610a includes a plurality of alternating first crest portions 611a, first connecting portions 612a, and first trough portions 613a, forming a periodically arranged, continuous undulating line, such as the image of a sine function. The multiple first bonding wires 610a provide multiple conductive paths in a localized area of ​​the first plate 310. Furthermore, compared to straight bonding wires, the wavy first bonding wires 610a can effectively increase the length of the first bonding wire 610a and the actual bonding area, while maintaining a constant diameter of the first plate 310. This effectively shortens the average path length of electron transmission, helps improve battery capacity, and reduces internal resistance, thereby enhancing battery performance, heat dissipation, and connection strength.

[0068] It is understandable that the first welding line 610a extends along the radial direction of the disk surface of the first disk body 310, which does not mean that the first welding line 610a must strictly extend along the radial direction of the disk surface of the first disk body 310. There may also be a certain angle between the two, for example, Figure 2 As shown, some of the first welding lines 610a extend slightly obliquely to the radial direction.

[0069] It is understandable that the number of the first welding lines 610a is not limited to 3, and may be less or more. For example, the number of the first welding marks 600a may be 2, 4, etc.

[0070] like Figure 3As shown, in this embodiment, the overall width of the first weld mark 600a is W1a, the width of each first weld line 610a is W2a, and the distance between two adjacent first weld lines 610a is W3a. The width W2a of the first weld line 610a is the height difference between the crest (highest point) and the trough (lowest point) thereof, and the distance W3a between two adjacent first weld lines 610a is the height difference between the crest and the trough that are close to each other. The overall width W1a of the first weld mark 600a is the sum of the widths W2a of all the first weld lines 610a constituting the first weld mark 600a and the distances W3a between the first weld lines 610a. For example, W1a can be 2mm, 2.3mm, 3mm, etc., that is, the range of W1a is 2~3mm; W2a can be 0.4mm, 0.5mm, 0.6mm, etc., that is, the range of W2a is 0.4~0.6mm; W3a can be 0.3mm, 0.4mm, 0.5mm, etc., that is, the range of W3a is 0.3~0.5mm.

[0071] Furthermore, in this embodiment, W2a / W1a ranges from 17% to 27%, and W3a / W1a ranges from 12% to 22%. For example, W2a / W1a can be 17%, 22%, 27%, etc., and W3a / W1a can be 12%, 17%, 22%, etc.

[0072] If W2a / W1a or W3a / W1a is too large, the first weld mark 600a may easily deviate from the weldable area, resulting in failure to meet process requirements. Conversely, if W2a / W1a or W3a / W1a is too small, welding quality issues such as weld cracking may occur. Furthermore, the electron flow path will be lengthened, the weld mark's current capacity will be insufficient, and the battery's internal resistance will increase. This will cause the weld mark to heat up excessively during use, thus affecting battery performance. Furthermore, the connection strength of the first weld mark 600a may be insufficient.

[0073] It is also understandable that if the overall width W1a of the first weld mark 600a is too large, the first weld mark 600a may easily deviate from the weldable area, resulting in failure to meet process requirements. Conversely, if W1a is too small, welding quality issues such as weld hot spots may easily occur. Furthermore, the electron flow path may be lengthened, the weld mark's current capacity may be insufficient, and the battery's internal resistance may increase, leading to excessive weld mark temperature rise during battery use, thus affecting battery performance. Furthermore, the connection strength of the first weld mark 600a may be insufficient.

[0074] like Figure 4As shown, in some embodiments, the radius of the first plate 310 is R0a, which ranges from 8.5 to 9.6 mm. For example, R0a can be 8.5 mm, 9.1 mm, 9.6 mm, etc. The minimum distance between the end of the first weld mark 600a near the center hole 315 and the edge of the first plate 310 surrounding the center hole 315 is W4a, which ranges from 0.6 to 1 mm. For example, W4a can be 0.6 mm, 0.8 mm, 1 mm, etc. The minimum distance between the end of the first weld mark 600a away from the center hole 315 and the edge of the first plate 310 is W5a, which ranges from 0.5 to 1.1 mm. For example, W5a can be 0.5 mm, 0.8 mm, 1.1 mm, etc.

[0075] Furthermore, in some embodiments, W4a / R0a ranges from 5% to 15%, and W5a / R0a ranges from 5% to 15%. For example, W4a / R0a can be 5%, 8%, 11%, 15%, and so on, and W5a / R0a can be 5%, 8%, 11%, 15%, and so on.

[0076] If W4a / R0a or W5a / R0a is too large, the electron flow path becomes longer, the weld mark's current capacity becomes insufficient, and the battery's internal resistance increases, causing the weld mark to heat up excessively during use, thus affecting battery performance. Furthermore, the connection strength of the first weld mark 600a may be insufficient. Conversely, if W4a / R0a or W5a / R0a is too small, the welding process becomes more difficult, and the first weld mark 600a may easily deviate from the weldable area, further increasing costs.

[0077] In some embodiments, the overall length of the first weld mark 600a is W6a, and W6a ranges from 4 to 6 mm. For example, W6a can be 4 mm, 5 mm, or 6 mm. Furthermore, in some embodiments, W6a / R0a ranges from 48% to 62%. For example, W6a / R0a can be 48%, 55%, or 62%. It should be noted that the overall length of the first weld mark 600a refers to the length of the first weld lines 610a that constitute the first weld mark 600a along the direction in which the first weld lines 610a extend.

[0078] If W6a / R0a is too large, the first weld mark 600a may easily deviate from the weldable area, increasing welding time and cost. Conversely, if W6a / R0a is too small, the electron flow path becomes longer, the weld mark's current capacity is insufficient, and the battery's internal resistance increases, leading to excessive weld mark temperature rise during battery use, thus affecting battery performance. Furthermore, the connection strength of the first weld mark 600a may be insufficient.

[0079] In some embodiments, W1a / R0a ranges from 20% to 30%. For example, W1a / R0a may be 20%, 25%, 30%, etc.

[0080] If W1a / R0a is too large, the first weld mark 600a may easily deviate from the weldable area, failing to meet process requirements. Conversely, if W1a / R0a is too small, the electron flow path becomes longer, the weld mark's current capacity is insufficient, and the battery's internal resistance increases, leading to excessive weld mark temperature rise during battery use, thus affecting battery performance. Furthermore, the connection strength of the first weld mark 600a may be insufficient.

[0081] In some embodiments, the minimum distance between the first weld mark 600a and the edge of the first plate 310 surrounding the peripheral hole 316 is W7a, and the range of W7a is 0.7-1.3 mm. For example, W7a can be 0.7 mm, 1 mm, 1.3 mm, etc. It should be noted that, if Figure 4 As shown, in the circumferential direction of the disk surface of the first disk body 310, when both sides of the first weld mark 600a have peripheral holes 316, W7a refers to the minimum distance between the first weld mark 600a and a peripheral hole 316 that is relatively closer to the first weld mark 600a.

[0082] Furthermore, in some embodiments, W7a / R0a ranges from 7% to 17%. For example, W7a / R0a may be 7%, 12%, 17%, etc.

[0083] If W7a / R0a is too large, the electron flow path becomes longer, the weld pad's current capacity becomes insufficient, and the battery's internal resistance increases, causing the weld pad's temperature to rise excessively during use, thus affecting battery performance. Furthermore, the connection strength of the first weld pad 600a may be insufficient. Conversely, if W7a / R0a is too small, the welding process becomes more difficult, and the first weld wire 610a may easily deviate from the weldable area. Furthermore, the connection strength of the first weld pad 600a may be insufficient.

[0084] In some embodiments, the distance between the outer hole 316 and the central hole 315 is L1a, and the range of L1a is 0.8~1.4mm. For example, L1a can be 0.8mm, 1.1mm, 1.4mm, etc. The distance between the outer hole 316 and the edge of the first disk body 310 is L2a, and the range of L2a is 1.5~3.5mm. For example, L2a can be 1.5mm, 2.5mm, 3.5mm, etc.

[0085] Further, in some embodiments, L1a / R0a ranges from 5% to 12%, for example, L1a / R0a can be 5%, 8.2%, 12%, 15%, etc., and L2a / R0a ranges from 22% to 32%, for example, L2a / R0a can be 22%, 27.5%, 32%, etc.

[0086] If L1a / R0a or L2a / R0a is too large or too small, the consistency of battery exhaust will be affected, as well as the opening speed of the explosion-proof valve in the cap 200 .

[0087] As previously described, the first welding line 610a includes a plurality of first wave crests 611a, first connecting portions 612a, and first wave troughs 613a that are alternately connected. It is understood that the first connecting portions 612a periodically rise and fall, i.e., one of two adjacent first connecting portions 612a rises while the other falls. It is understood that although the first welding line 610a is described herein as being separated into the first wave crests 611a, the first connecting portions 612a, and the first wave troughs 613a, it is understood that the first welding line 610a is a continuous linear structure. Furthermore, the first wave crests 611a and the first wave troughs 613a may be smoothly transitioned arcs.

[0088] like Figure 5 As shown, in some embodiments, the first connecting portion 612a has a straight line segment in its extension direction, and the straight line segments of two adjacent first connecting portions 612a have an angle Aa, and the angle Aa ranges from 50° to 75°. For example, the angle Aa can be 50°, 60°, 75°, etc.

[0089] If angle Aa is too large, the actual length of the first welding wire 610a will be shortened, while the length of the 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 excessive overcurrent temperature rise, impacting battery performance. Furthermore, increasing the actual length of the first welding wire 610a will inevitably require increasing its length in the extension direction, causing the first welding wire 610a to extend beyond the surface of the first plate 310. This will cause portions of the first welding wire 610a to become ineffective and lose their current flow capacity. This will weaken the current flow capacity of the first welding wire 610a, increase the overcurrent temperature rise, and affect battery performance and lead to welding quality issues. Conversely, if angle Aa is too small, the individual first welding wires 610a will be very close together, resulting in concentrated heat and poor heat dissipation. This heat concentration can easily lead to welding quality issues, such as weld hot spots.

[0090] like Figure 4 As shown, in some embodiments, an angle Ba is formed between two adjacent first weld marks 600a, and the angle Ba ranges from 75° to 105°. For example, the angle Ba can be 75°, 90°, 105°, etc. It should be noted that during actual measurement, the angle Ba is the angle between the lengthwise extensions of the first weld marks 600a or the first weld lines 610a.

[0091] If the angle Ba is too large, it will lead to uneven current distribution and increase the internal resistance of the battery. Conversely, if the angle Ba is too small, it will lead to excessive heat concentration on the first plate 310, resulting in excessive welding temperature rise when the battery is used.

[0092] The effects of the present application are further described below with reference to specific examples and comparative examples.

[0093] 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 positive electrode current collector according to the aforementioned structure, other components and materials can be obtained by referring to the 2170 cylindrical lithium-ion battery.

[0094] Example 1:

[0095] Example 1 provides a cylindrical lithium-ion battery, which includes a positive electrode current collector disc 300 and a winding core 400. The first disc body 310 of the positive electrode current collector disc 300 is connected to the positive terminal 410 of the winding core 400 by laser welding. A central hole 315 is provided at the center of the first disc body 310. Three peripheral holes 316 are also provided around the central hole 315. Four groups of first weld marks 600a are formed between the two by laser welding. The four groups of first weld marks 600a are arranged at intervals along the circumferential direction of the disc surface of the first disc body 310. These first weld marks 600a are located in a weldable area on the disc surface where the peripheral holes 316 are not provided, and extend radially from the edge of the first disc body 310 toward the center of the circle. Each group of first weld marks 600a includes three parallel wavy first weld lines. In addition, the first weld mark 600a also meets the following parameters: W1a is 2.3 mm, W2a is 0.5 mm, W3a is 0.4 mm, W4a is 0.8 mm, W5a is 0.8 mm, W6a is 5 mm, W7a is 1 mm, R0a is 9.1 mm, L1a is 1.1 mm, L2a is 2.5 mm, and the angle Aa is 60°. In addition, the radius R1 of the center hole 315 is 2.5 mm, and the radius R2 of the peripheral hole 316 is 1.5 mm. Therefore, in Example 1, W2a / W1a=22%, W3a / W1a=17%, W1a / R0a=25%, W4a / R0a=9%, W5a / R0a=9%, W6a / R0a=55%, and W7a / R0a=11%.

[0096] Example 2:

[0097] Example 2 provides a cylindrical lithium-ion battery, which differs from Example 1 in that W1a is 2.5 mm, W3a is 0.5 mm, W2a / W1a=20%, and W3a / W1a=20%.

[0098] Example 3:

[0099] Example 3 provides a cylindrical lithium-ion battery, which differs from Example 1 in that W1a is 2.1 mm, W3a is 0.3 mm, W2a / W1a=24%, and W3a / W1a=14%.

[0100] Example 4:

[0101] Example 4 provides a cylindrical lithium-ion battery, which differs from Example 1 in that W4a is 0.6 mm, W5a is 1 mm, W4a / R0a=7%, and W5a / R0a=11%.

[0102] Example 5:

[0103] Example 5 provides a cylindrical lithium-ion battery, which differs from Example 1 in that W4a is 1 mm, W5a is 0.6 mm, W4a / R0a=11%, and W5a / R0a=7%.

[0104] Comparative Example 1:

[0105] Comparative Example 1 provides a cylindrical lithium-ion battery, which differs from Example 1 in that W1a is 3.1 mm, W3a is 0.8 mm, W2a / W1a=16%, W3a / W1a=26%, and W1a / R0a=34%.

[0106] Comparative Example 2:

[0107] Comparative Example 2 provides a cylindrical lithium-ion battery, which differs from Example 1 in that W1a is 1.7 mm, W3a is 0.1 mm, W2a / W1a=29%, W3a / W1a=6%, and W1a / R0a=19%.

[0108] Comparative Example 3:

[0109] Comparative Example 3 provides a cylindrical lithium-ion battery, which differs from Example 1 in that W4a is 1.3 mm, W5a is 1.3 mm, W6a is 4 mm, W4a / R0a=14%, W5a / R0a=14%, and W6a / R0a=44%.

[0110] Comparative Example 4:

[0111] Comparative Example 4 provides a cylindrical lithium-ion battery, which differs from Example 1 in that W4a is 0.5 mm, W5a is 0.5 mm, W6a is 5.6 mm, W4a / R0a=5%, W5a / R0a=5%, and W6a / R0a=62%.

[0112] Comparative Example 5:

[0113] Comparative Example 5 provides a cylindrical lithium-ion battery, which differs from Example 1 in that W4a is 0.1 mm, W5a is 1.5 mm, W4a / R0a=1%, and W5a / R0a=16%.

[0114] Comparative Example 6:

[0115] Comparative Example 6 provides a cylindrical lithium-ion battery, which differs from Example 1 in that W4a is 1.5 mm, W5a is 0.1 mm, W4a / R0a=16%, and W5a / R0a=1%.

[0116] 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 positive electrode current collecting disc 300 and the winding core 400 in the cylindrical lithium-ion batteries manufactured in the above-mentioned embodiments and comparative examples.

[0117] 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 one of the first weld marks 600a on the surface of the first disk body 310 of the positive electrode current collecting disk 300. 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.

[0118] The specific test method for the connection strength 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 positive current collecting disc 300 and the winding core 400, use needle-nose pliers to start peeling from the tail end of the positive current collecting disc 300 at the same position until the first disc body 310 and the positive end 410 of the winding core 400 are completely separated, and calculate and record the proportion of the residual area of ​​the first weld mark 600a remaining on the first disc body 310.

[0119] 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 positive electrode current collecting disc 300 and the winding core 400, the CCD function of the equipment is used to perform weld mark appearance inspection, 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.

[0120] Table 1

[0121]

[0122]

[0123] As shown in Table 1, when W2a / W1a is set between 17% and 22% and W3a / W1a is set between 12% and 22%, the temperature rise Tmax at the first weld mark 600a is typically between 98°C and 102°C, the residual area of ​​the first weld mark 600a after peeling is typically between 76.4% and 78.1%, and the weld failure rate of the first weld mark 600a is typically between 1.5% and 1.54%. It can be seen that within these numerical ranges, the weld mark temperature rise, connection strength, and weld quality of the first weld mark 600a in the positive electrode current collector 300 are well balanced, thereby balancing the charge and discharge performance, reliability, and manufacturing cost of the cylindrical lithium-ion battery.

[0124] The welding structure between the positive electrode current collecting disc 300 and the cap 200 is described below.

[0125] like Figure 6 and Figure 7 As 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.

[0126] 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 inner side, and the side away from the inner cavity 130 is the outer side.

[0127] 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.

[0128] 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.

[0129] 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 6 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.

[0130] 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.

[0131] 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.

[0132] refer to Figure 7 and Figure 8 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 7 and Figure 8 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.

[0133] 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.

[0134] 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.

[0135] It will be appreciated that after the tail body 320 is connected to the end plate 210 via laser welding, a third weld mark 600c left by the laser welding can be observed on the surface of the tail body 320. The third weld mark 600c comprises a third wavy weld line 610c extending along the width of the tail body 320. Specifically, the third weld line 610c comprises a plurality of alternating third wave crests 611c, third connecting portions 612c, and third wave troughs 613c, forming a periodically arranged, continuous undulating line, such as the image of a sine function.

[0136] 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 forms a specific weld mark upon solidification. By controlling the welding path, this embodiment forms a wavy third weld line 610c extending along the width of the tail body 320. Given a constant width of the tail body 320, the total length of the wavy third weld line 610c 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 operation, 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.

[0137] It should be noted that although this article describes the welding mark formed on the tail body 320 as the third welding mark 600c, the third welding mark 600c will extend to the surface of the end plate 210, thereby achieving the connection between the end plate 210 and the tail body 320.

[0138] like Figure 8 As shown, combined with Figure 9 In some embodiments, with the radius of the end plate 210 as R0c, the width of the tail body 320 as L1c, and the width and length of the third weld line 610c as W1c and L2c, W1c / R0c ranges from 15% to 32%, and L2c / L1c ranges from 56% to 76%. It should be noted that the width W1c of the third weld line 610c is the height difference between its third crest 611c (highest point) and its third trough 613c (lowest point), while the length L2c of the third weld line 610c is the length of its orthographic projection along the width of the tail body 320. For example, W1c / R0c can be 15%, 25%, 32%, etc., and L2c / L1c can be 56%, 65%, 76%, etc.

[0139] If W1c / R0c is too large, the third bond wire 610c is too wide. However, increasing the width of the third bond wire 610c has a marginal effect on improving the battery's internal resistance. In other words, a wider third bond wire 610c does not significantly reduce internal resistance. Instead, it increases welding time, reduces welding efficiency, and increases the risk of welding defects. Conversely, if W1c / R0c is too small, the effective welding area of ​​the third bond wire 610c 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 third bond mark 600c is insufficient.

[0140] If L2c / L1c is too large, the third bonding wire 610c will be too long. However, increasing the length of the third bonding wire 610c will have a marginal effect on improving the battery's internal resistance. In other words, a longer third bonding wire 610c will not significantly reduce internal resistance. Instead, it will increase welding time, reduce welding efficiency, and increase the risk of welding defects. Conversely, if L2c / L1c is too small, the effective bonding area of ​​the third bonding wire 610c will be insufficient, resulting in insufficient current capacity and increased internal resistance. This will in turn cause the temperature of the bond pad to rise excessively during battery use, affecting battery performance. Furthermore, the connection strength of the third bonding pad 600c will be insufficient.

[0141] In some embodiments, R0c ranges from 5.29 to 7.29 mm, and L1c ranges from 5 to 7 mm. For example, R0c may be 5.29 mm, 6.29 mm, or 7.29 mm, and L1c may be 5 mm, 6 mm, or 7 mm.

[0142] In some embodiments, W1c is in the range of 1 to 2 mm, and L2c is in the range of 3.5 to 4.5 mm. For example, W1c can be 1 mm, 1.5 mm, or 2 mm, and L2c can be 3.5 mm, 4 mm, or 4.5 mm.

[0143] If W1c is large, the third weld line 610c is too wide. However, increasing the width of the third weld line 610c has a marginal effect on improving the battery's internal resistance. In other words, a wider third weld line 610c does not significantly reduce internal resistance. Instead, it increases welding time, reduces welding efficiency, and increases the risk of welding defects. Conversely, if W1c is too small, the effective welding area of ​​the third weld line 610c 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 third weld mark 600c is insufficient.

[0144] If L2c is too large, the third welding wire 610c will be too long. However, increasing the length of the third welding wire 610c will have a marginal effect on improving the battery's internal resistance. That is, a longer third welding wire 610c will not significantly improve internal resistance. Instead, it will increase welding time, reduce welding efficiency, and increase the risk of welding defects. Conversely, if L2c is too small, the effective welding area of ​​the third welding wire 610c will be insufficient, resulting in insufficient current capacity and increased internal resistance of the battery. This will in turn cause the weld mark temperature to rise excessively during battery use, affecting battery performance. Furthermore, the connection strength of the third welding mark 600c will be insufficient.

[0145] 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 side of the third welding line 610c away from the fourth side 323 is 100mm from the edge of the end plate 210 ( Figure 8 The distance between the third welding line 610c and the fourth edge 323 (shown by the dashed line) is W2c, and the distance between the side of the third welding line 610c closest to the fourth edge 323 and the fourth edge 323 is W3c. W2c / R0c ranges from 40% to 51%, and W3c / R0c ranges from 25% to 35%. It is understood that when the fourth edge 323 passes exactly through the center of the end plate 210, W1c+W2c+W3c=R0c. For example, W2c / R0c can be 40%, 45%, or 51%, and W3c / R0c can be 25%, 30%, or 35%.

[0146] If W2c / R0c is too large or W3c / R0c is too small, the third welding wire 610c 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 third welding wire 610c is too close to the end of the tail body 320, there is a risk that the third welding wire 610c 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 third welding wire 610c will be insufficient. The internal resistance of the battery will increase, and the temperature rise of the welding mark during battery use will be too large, thereby affecting the battery performance. In addition, the connection strength of the third welding mark 600c will be insufficient. On the other hand, if W1c / R0c is too small or W3c / R0c is too large, the third weld line 610c is too close to the edge of the end plate 210, and there is a risk that the third weld line 610c will deviate from the tail body 320. As a result, the actual welding area will be insufficient, which will lead to insufficient current carrying capacity of the third weld line 610c, increased internal resistance of the battery, and excessive temperature rise of the weld mark when the battery is used, thereby affecting battery performance. In addition, it will also lead to insufficient connection strength of the third weld mark 600c.

[0147] In some embodiments, W2c ranges from 2.59 to 3.19 mm, and W3c ranges from 1.6 to 2.2 mm. For example, W2c may be 2.59 mm, 2.99 mm, or 3.19 mm, and W3c may be 1.6 mm, 1.8 mm, or 2.2 mm.

[0148] In some embodiments, along the width direction of the tail body 320, the distance between the side of the third welding line 610c closest to the fifth side 321 and the fifth side 321 is L3c, and the distance between the side of the third welding line 610c closest to the sixth side 322 and the sixth side 322 is L4c. L3c / L1c ranges from 9% to 24%, and L4c / L1c ranges from 9% to 24%. It is understood that L2c+L3c+L4c=L1c. For example, L3c / L1c can be 9%, 16%, or 24%, and W3c / R0c can be 9%, 16%, or 24%.

[0149] If L3c / L1c is too large or L4c / L1c is too small, the third welding line 610c is too close to the sixth side 322. Since the manufacturing process allows a certain offset tolerance for the tail body 320, when the third welding line 610c is too close to the sixth side 322, there is a risk that the third welding line 610c 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 third welding line 610c will be insufficient. This will increase the internal resistance of the battery and cause the temperature rise of the welding mark to be too large during battery use, thereby affecting battery performance. In addition, the connection strength of the third welding mark 600c will be insufficient. Conversely, if L3c / L1c is too small or L4c / L1c is too large, the third weld line 610c is too close to the fifth side 321. Since the manufacturing process allows a certain offset tolerance for the tail body 320, when the third weld line 610c is too close to the fifth side 321, there is a risk that the third weld line 610c 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 third weld line 610c will be insufficient. This will increase the internal resistance of the battery and cause the weld mark temperature to rise too much during use, thereby affecting battery performance. In addition, the connection strength of the third weld mark 600c will be insufficient.

[0150] In some embodiments, L3c is in the range of 0.6 to 1.4 mm, and L4c is in the range of 0.6 to 1.4 mm. For example, L3c may be 0.6 mm, 1 mm, or 1.4 mm, and L4c may be 0.6 mm, 1 mm, or 1.4 mm.

[0151] 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 third weld line 610c should be located in the area between the boss hole 211 and the exhaust holes 212. Figure 8 As shown, when there are multiple exhaust holes 212 , the third welding wire 610 c is only arranged between the exhaust holes 212 and the boss hole 211 in the area covered by the tail body 320 .

[0152] Furthermore, in some embodiments, the minimum distance between the third welding line 610c and the edge of the end plate 210 surrounding the exhaust hole 212 is L5c, and L5c / R0c ranges from 24% to 38%. For example, L5c / R0c can be 24%, 31%, or 38%.

[0153] If L5c / R0c is too large, the third welding wire 610c is too close to the boss hole 211. Since the process allows a certain offset tolerance for the tail body 320, when the third welding wire 610c is too close to the boss hole 211, there is a risk that the third welding wire 610c will be welded into the boss hole 211. As a result, the effective welding area will be insufficient, and the current capacity of the third welding wire 610c 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, the connection strength of the third welding mark 600c will be insufficient. Conversely, if L5c / R0c is too small, the third welding wire 610c is too close to the exhaust hole 212. Since the process allows a certain offset tolerance for the tail body 320, when the third welding wire 610c is too close to the exhaust hole 212, there is a risk that the third welding wire 610c will be welded into the exhaust hole 212. As a result, the effective welding area will be insufficient, and the flow capacity of the third welding wire 610c 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 third welding mark 600c will be insufficient.

[0154] In some embodiments, L5c ranges from 1.57 mm to 2.37 mm. For example, L5c can be 1.57 mm, 1.97 mm, or 2.37 mm.

[0155] In some embodiments, as Figure 9 As shown, the third connection portion 612c of the third welding wire 610c has a straight line segment in its extension direction, and the straight line segments of two adjacent third connection portions 612c have an angle Ac, and the angle Ac ranges from 25° to 65°. For example, the angle Ac can be 25°, 41°, 65°, etc.

[0156] If the angle Ac is too large, the actual length of the third welding wire 610c will be shortened, while the length of the third welding wire 610c 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 the third welding wire 610c will inevitably require increasing its length in the extension direction, which will cause the third welding wire 610c to extend beyond the tail body 320, rendering part of the third welding wire 610c inoperable and lacking current flow capacity. This weakens the current flow capacity of the third welding wire 610c, increases the overcurrent temperature rise, and impacts battery performance and can also cause welding quality issues. Conversely, if the angle Ac is too small, the third crest portion 611c, third connecting portion 612c, and third trough portion 613c of the third welding wire 610c will be closely adjacent to each other, concentrating heat and resulting in poor heat dissipation. This heat concentration can easily lead to welding quality issues, such as weld hot spots, on the third welding wire 610c.

[0157] Continue to refer Figure 9 In some embodiments, the average width of the third welding wire 610c is W4c, and W4c ranges from 0.2 to 0.4 mm. For example, W4c can be 0.2 mm, 0.3 mm, or 0.4 mm.

[0158] If W4c is too large, heat will be concentrated at the bends of the third crest 611c and the third trough 612c during welding, which can easily lead to welding quality problems such as weld burnout. Conversely, if W4c is too small, the actual welding area of ​​the third welding wire 610c will be reduced, thereby weakening the current carrying capacity. During battery use, the overcurrent temperature rise will be too high, affecting battery performance.

[0159] 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.

[0160] Furthermore, in some embodiments, the radius of the boss hole 211 is R1c, and the ratio R1c / R0c is in the range of 17% to 25%. For example, R1c / R0c can be 17%, 21%, or 25%.

[0161] If R1c / R0c 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 third weld wire 610c. 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 of the third weld mark 600c. Conversely, if R1c / R0c 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-disc through-weld. As the diameter of the wire between the burst-disc and the end plate 210 decreases, the wire's current capacity becomes insufficient, resulting in excessive temperature rise during battery operation. Furthermore, the weld wire's proximity to the CID power-off notch can affect the CID's power-off capability, compromising battery safety.

[0162] In some embodiments, R1c ranges from 1.15 to 1.55 mm. For example, R1c may be 1.15 mm, 1.35 mm, or 1.55 mm.

[0163] 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 H2c, and the ratio H2c / R0c is in the range of 12% to 26%. For example, H2c / R0c can be 12%, 19%, or 26%.

[0164] If H2c / R0c 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 third weld line 610c. 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 third weld mark 600c will be insufficient. Conversely, if H2c / R0c is too small, the exhaust effect of the vent holes 212 will be affected, limiting their effectiveness in improving battery safety.

[0165] In some embodiments, H2c ranges from 0.8 to 1.6 mm. For example, H2c can be 0.8 mm, 1.2 mm, or 1.6 mm.

[0166] 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 H1c, and H1c / R0c ranges from 43% to 51%. For example, H1c / R0c can be 43%, 47%, or 51%.

[0167] If H1c / R0c is too large, the area of ​​the vent hole 212 will be reduced, thereby affecting its venting effect. It may also cause the vent hole 212 to 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 H1c / R0c is too small, the weldable area on the end plate 210 surface is too small, resulting in insufficient effective welding area for the third weld line 610c. 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 third weld mark 600c may be insufficient.

[0168] In some embodiments, H1c ranges from 2.75 mm to 3.15 mm. For example, H1c may be 2.75 mm, 2.95 mm, or 3.15 mm.

[0169] 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 H3c, and the ratio H3c / R0c ranges from 9% to 16%. For example, H3c / R0c can be 9%, 12%, or 16%.

[0170] If H3c / R0c 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 third weld line 610c, 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 third weld mark 600c will be insufficient. Conversely, if H3c / R0c 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.

[0171] In some embodiments, H3c ranges from 0.59 to 0.99 mm. For example, H3c may be 0.59 mm, 0.79 mm, or 0.99 mm.

[0172] It can be understood that, in this embodiment, R1c+H1c+H2c+H3c=R0c.

[0173] Furthermore, in some embodiments, the length of the centerline arc of the vent hole 212 is L6c, the spacing between the centerline arcs of two adjacent vent holes 212 is L7c, L6c / R0c ranges from 71% to 88%, and L7c / R0c 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, L6c / R0c can be 71%, 80%, or 88%, and L7c / R0c can be 12%, 16%, or 20%.

[0174] If L6c / R0c is too large or L7c / R0c is too small, the connection strength between two adjacent vent holes 212 is insufficient, making them prone to breakage. The resulting metal burrs or metal debris can adversely affect battery safety. Conversely, if L6c / R0c is too small or L7c / R0c is too large, the size of the vent holes 212 is reduced, further impacting their venting effectiveness and limiting their effectiveness in improving battery safety.

[0175] The effects of the present application are further described below with reference to specific examples and comparative examples.

[0176] 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.

[0177] Example 1:

[0178] 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 third welding line 610c extending along the width direction of the tail body 320. In addition, the following parameters are met: R0c is 6.29 mm, W1c is 1.5 mm, W2c is 2.99 mm, W3c is 1.8 mm, L1c is 6 mm, L2c is 4 mm, L3c is 0.8 mm, and L4c is 1.2 mm. Therefore, in Example 1, W1c / R0c = 23.85%, W2c / R0c = 47.54%, W3c / R0c = 28.62%, L2c / L1c = 66.67%, L3c / L1c = 13.33%, and L4c / L1c = 20%.

[0179] Example 2:

[0180] Example 2 provides a cylindrical lithium-ion battery, which differs from Example 1 in that L3c is 0.6 mm, L4c is 1.4 mm, L3c / L1c=10%, and L4c / L1c=23.33%.

[0181] Comparative Example 1:

[0182] Comparative Example 1 provides a cylindrical lithium-ion battery, which differs from Example 1 in that L3c is 0.4 mm, L4c is 1.6 mm, L3c / L1c=6.67%, and L4c / L1c=26.67%.

[0183] Example 3:

[0184] Example 3 provides a cylindrical lithium-ion battery, which differs from Example 1 in that L2c is 3.6 mm, L3c is 1.2 mm, L2c / L1c=60%, and L3c / L1c=20%.

[0185] Comparative Example 2:

[0186] Comparative Example 2 provides a cylindrical lithium-ion battery, which differs from Example 1 in that L2c is 3.2 mm, L3c is 1.4 mm, L4c is 1.4 mm, L2c / L1c=53.33%, L3c / L1c=23.33%, and L4c / L1c=23.33%.

[0187] Example 4:

[0188] Example 4 provides a cylindrical lithium-ion battery, which differs from Example 1 in that L2c is 4.4 mm, L3c is 0.8 mm, L4c is 0.8 mm, L2c / L1c=73.33%, L3c / L1c=13.33%, and L4c / L1c=13.33%.

[0189] Comparative Example 3:

[0190] Comparative Example 3 provides a cylindrical lithium-ion battery, which differs from Example 1 in that L2c is 4.8 mm, L3c is 0.6 mm, L4c is 0.6 mm, L2c / L1c=80%, L3c / L1c=10%, and L4c / L1c=10%.

[0191] Example 5:

[0192] Example 5 provides a cylindrical lithium-ion battery. Compared with Example 1, its R0c is 6.29 mm, W1c is 1.5 mm, W2c is 3.19 mm, W3c is 1.6 mm, L1c is 6 mm, L2c is 4 mm, L3c is 1 mm, and L4c is 1 mm. Therefore, in Example 5, W1c / R0c=23.85%, W2c / R0c=50.72%, W3c / R0c=25.44%, L2c / L1c=66.67%, L3c / L1c=16.67%, and L4c / L1c=16.67%.

[0193] Comparative Example 4:

[0194] Comparative Example 4 provides a cylindrical lithium-ion battery, which differs from Example 5 in that W2c is 3.39 mm, W3c is 1.4 mm, W2c / R0c=53.9%, and W3c / R0c=22.26%.

[0195] Example 6:

[0196] Example 6 provides a cylindrical lithium-ion battery, which differs from Example 5 in that W2c is 2.59 mm, W3c is 2.2 mm, W2c / R0c=41.18%, and W3c / R0c=34.98%.

[0197] Comparative Example 5:

[0198] Comparative Example 5 provides a cylindrical lithium-ion battery, which differs from Example 5 in that W2c is 2.19 mm, W3c is 2.6 mm, W2c / R0c=34.82%, and W3c / R0c=41.34%.

[0199] Example 7:

[0200] Example 7 provides a cylindrical lithium-ion battery, which differs from Example 5 in that W1c is 1.2 mm, W2c is 3.14 mm, W3c is 1.95 mm, W1c / R0c=19.08%, W2c / R0c=49.92%, and W3c / R0c=31%.

[0201] Example 8:

[0202] Example 8 provides a cylindrical lithium-ion battery, which differs from Example 5 in that W1c is 1 mm, W2c is 3.24 mm, W3c is 2.05 mm, W1c / R0c=15.9%, W2c / R0c=51.51%, and W3c / R0c=32.59%.

[0203] Comparative Example 6:

[0204] Comparative Example 6 provides a cylindrical lithium-ion battery, which differs from Example 5 in that W1c is 0.8 mm, W2c is 3.34 mm, W3c is 2.15 mm, W1c / R0c=12.72%, W2c / R0c=53.1%, and W3c / R0c=34.18%.

[0205] Example 9:

[0206] Example 9 provides a cylindrical lithium-ion battery, which differs from Example 5 in that W1c is 1.8 mm, W2c is 2.84 mm, W3c is 1.65 mm, W1c / R0c=28.62%, W2c / R0c=45.15%, and W3c / R0c=26.23%.

[0207] Example 10:

[0208] Example 10 provides a cylindrical lithium-ion battery, which differs from Example 5 in that W1c is 2 mm, W2c is 2.74 mm, W3c is 1.55 mm, W1c / R0c=31.8%, W2c / R0c=43.56%, and W3c / R0c=24.64%.

[0209] Comparative Example 7:

[0210] Comparative Example 7 provides a cylindrical lithium-ion battery, which differs from Example 5 in that W1c is 2.2 mm, W2c is 2.64 mm, W3c is 1.45 mm, W1c / R0c=34.98%, W2c / R0c=41.97%, and W3c / R0c=23.05%.

[0211] Table 2 evaluates the weld mark temperature rise, connection strength, and weld failure rate of the third weld mark 600c 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 embodiment and comparative example.

[0212] 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 third weld mark 600 c 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 third weld mark 600 c 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.

[0213] 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 calculate and record the proportion of the residual area of ​​the third weld mark 600c remaining on the tail body 320.

[0214] 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 weld mark appearance inspection, and abnormal appearance conditions such as the explosion point and black color of the third weld mark 600c are detected and the defective rate is calculated.

[0215] Table 2

[0216]

[0217]

[0218] As can be seen from Table 2, when the range of W1c / R0c is set at 15% to 32%, the range of L2c / R0c is set at 56% to 76%, the range of W1c is set at 1 to 2 mm, the range of L2c is set at 3.5 to 4.5 mm, the range of W2c / R0c is set at 40% to 51%, the range of W3c / R0c is set at 15% to 32%, and the ranges of L3c / L1c and L4c / L1c are set at 9% to 24%, the temperature rise Tmax of the third weld mark 600c is generally between 90° and 96°C, the residual area of ​​the third weld mark 600c after peeling is generally between 80% and 92%, and the welding defective rate of the third weld mark 600c 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 third weld mark 600c 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.

[0219] The welding structure between the negative electrode current collecting disc 500 and the negative terminal 420 is described below.

[0220] like Figure 10 and Figure 11 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.

[0221] like Figure 10 and Figure 11 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.

[0222] 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.

[0223] 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.

[0224] 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.

[0225] 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.

[0226] 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.

[0227] 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.

[0228] like Figure 12 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.

[0229] 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.

[0230] refer to Figure 11In 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.

[0231] 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.

[0232] 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.

[0233] 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.

[0234] 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.

[0235] 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.

[0236] 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.

[0237] 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.

[0238] 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.

[0239] 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.

[0240] 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 11The 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.

[0241] 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.

[0242] 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.

[0243] 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.

[0244] like Figure 12As 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.

[0245] 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.

[0246] The effects of the present application are further described below with reference to specific examples and comparative examples.

[0247] 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.

[0248] Example 1:

[0249] 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%.

[0250] Example 2:

[0251] 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%.

[0252] Example 3:

[0253] 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%.

[0254] Example 4:

[0255] 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%.

[0256] Comparative Example 1:

[0257] 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%.

[0258] Comparative Example 2:

[0259] 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%.

[0260] Example 5:

[0261] 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%.

[0262] Example 6:

[0263] 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%.

[0264] Example 7:

[0265] 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%.

[0266] Example 8:

[0267] 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%.

[0268] Comparative Example 3:

[0269] 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%.

[0270] Comparative Example 4:

[0271] 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%.

[0272] Example 9:

[0273] 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%.

[0274] Example 10:

[0275] 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%.

[0276] Example 11:

[0277] 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%.

[0278] Example 12:

[0279] 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%.

[0280] Example 13:

[0281] 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%.

[0282] Example 14:

[0283] 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%.

[0284] Comparative Example 5:

[0285] 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%.

[0286] Comparative Example 6:

[0287] 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%.

[0288] Table 3 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.

[0289] 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 (℃).

[0290] 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.

[0291] 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.

[0292] 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).

[0293] Table 3

[0294]

[0295]

[0296] As shown in Table 3, 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.

[0297] 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 positive electrode current collecting disc (300) includes a first disc body (310), the first disc body (310) is connected to the positive terminal (410) by laser welding, and forms a plurality of first weld marks (600a), the plurality of first weld marks (600a) are spaced apart along the circumferential direction of the disc surface of the first disc body (310), and each first weld mark (600a) includes at least two first weld lines (610a) arranged in parallel and extending along the radial direction of the disc surface of the first disc body (310), wherein the radius of the first disc body (310) is R0a, the overall width of the first weld mark (600a) is W1a, the overall length of the first weld mark (600a) is W6a, the range of W1a / R0a is 20% to 30%, and the range of W6a / R0a is 48% to 62%; 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%; The cap (200) includes a circular end plate (210), and the positive current collecting disc (300) also includes a square tail body (320) connected to the first disc body (310). The tail body (320) is connected to the end plate (210) by laser welding to form a third weld mark (600c). The third weld mark (600c) includes a wavy third weld line (610c) extending along the width direction of the tail body (320). The radius of the end plate (210) is R0c, the width of the tail body (320) is L1c, the width of the third weld line (610c) is W1c, and the length of the third weld line (610c) is L2c. The range of W1c / R0c is 15% to 32%, and the range of L2c / L1c is 56% to 76%.

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 1, characterized in that A center hole (315) is provided at the center of the disk surface of the first disk body (310), and the minimum distance between the end of the first weld mark (600a) close to the center hole (315) and the edge of the first disk body (310) surrounding the center hole (315) is W4a, and the minimum distance between the end of the first weld mark (600a) away from the center hole (315) and the edge of the first disk body (310) is W5a, and the range of W4a / R0a is 5% to 15%, and the range of W5a / R0a is 5% to 15%.

4. The cylindrical lithium-ion battery according to claim 1, characterized in that The overall width of the first weld mark (600a) is W1a, and the range of W1a is 2 to 3 mm. The width of each first weld line (610a) is W2a. The distance between two adjacent first weld lines (610a) is W3a. The range of W2a / W1a is 17% to 27%, the range of W3a / W1a is 12% to 22%, the range of W1c is 1 to 2 mm, the range of L2c is 3.5 to 4.5 mm, and the average line width of the third weld line (610c) is W4c, and the range of W4c is 0.2 to 0.4 mm.

5. 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, and the range of L2b is 0.5-1.5 mm.

6. The cylindrical lithium-ion battery according to claim 3, characterized in that: The disk surface of the first disk body (310) is further provided with a plurality of peripheral holes (316) surrounding the central hole (315); the minimum distance between the first weld mark (600a) and the edge of the first disk body (310) surrounding the peripheral holes (316) is W7a, and the range of W7a / R0a is 7% to 17%; the distance between the peripheral holes (316) and the central hole (315) is L1a, and the range of L1a / R0a is 5% to 12%; the distance between the peripheral holes (316) and the edge of the first disk body (310) is L2a, and the range of L2a / R0a is 22% to 32%.

7. 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.

8. The cylindrical lithium-ion battery according to claim 1, characterized in that The first welding line (610a) and the second welding line (610b) are both wavy. The first welding line (610a) includes a plurality of first wave crests (611a), first connecting parts (612a) and first wave troughs (613a) that are alternately connected to each other. The second welding line (610b) includes a plurality of second wave crests (611b), second connecting parts (612b) and second wave troughs (613b) that are alternately connected to each other. The third welding line (610c) includes a plurality of third wave crests (611c), third connecting parts (612c) and third wave troughs (613c) that are alternately connected to each other. The part (612a) has a straight line segment in its extension direction, and the straight line segments of two adjacent first connecting parts (612a) have an angle Aa, and the range of the angle Aa is 50° to 75°. The second connecting part (612b) has a straight line segment in its extension direction, and the straight line segments of two adjacent second connecting parts (612b) have an angle Ab, and the range of the angle Ab is 70° to 120°. The third connecting part (612c) has a straight line segment in its extension direction, and the straight line segments of two adjacent third connecting parts (612c) have an angle Ac, and the range of the angle Ac is 25° to 65°.

9. The cylindrical lithium-ion battery according to any one of claims 1 to 8, 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 side of the third welding line (610c) away from the fourth side (323) and the edge of the end plate (210) is W2c, and the range of W2c / R0c is 40% to 51%.

10. The cylindrical lithium-ion battery according to claim 9, characterized in that: The distance between the side of the third welding line (610c) close to the fourth side (323) and the fourth side (323) is W3c, and the range of W3c / R0c is 25% to 35%.

11. The cylindrical lithium-ion battery according to claim 9, characterized in that: The distance between the side of the third welding line (610c) close to the fifth side (321) and the fifth side (321) is L3c, and the distance between the side of the third welding line (610c) close to the sixth side (322) and the sixth side (322) is L4c, and the range of L3c / L1c is 9% to 24%, and the range of L4c / L1c is 9% to 24%.

12. The cylindrical lithium-ion battery according to any one of claims 1 to 8, 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 third welding line (610c) and the edge of the end plate (210) surrounding the exhaust holes (212) is L5c, and the range of L5c / R0c is 24% to 38%.

13. The cylindrical lithium-ion battery according to any one of claims 1 to 8, 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 a common center with 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 H2c, the radius of the boss hole (211) is R1c, the range of H2c / R0c is 12% to 26%, and the range of R1c / R0c is 17% to 25%.

14. The cylindrical lithium-ion battery according to any one of claims 1 to 8, 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 H1c, and the ring width of the ring defined by the edge of the end plate (210) and the outer arc (2122) is H3c. The range of H1c / R0c is 43% to 51%, and the range of H3c / R0c is 9% to 16%.

15. The cylindrical lithium-ion battery according to any one of claims 1 to 8, 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 L6c, and the spacing between the center line arcs of two adjacent exhaust holes (212) is L7c. The range of L6c / R0c is 71% to 88%, and the range of L7c / R0c is 12% to 20%.

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