Welding printing structure and cylindrical lithium ion battery

Abstract

The utility model provides a weld print structure and cylindrical lithium ion battery, the weld print structure includes the welding weld print, the distance between the farthest point and the central point of the weld print line of the welding weld print is R1, the value range of R1 is 1-3mm, the width of the weld print line of the welding weld print is W1, the ratio range of W1 / R1 is 10%-30%, and the ratio range of W1 / R1 is 1%-30%. According to the welding printing structure, by setting the corresponding shell bottom welding printing welding line width proportion, it can be ensured that the welding printing area has enough effective over-current area, smooth passing of current is ensured, the temperature of the welding printing area is prevented from being too high, the welding reliability is improved, and then the safety performance of the battery is improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to battery technology field especially relates to a welding mark structure and cylindrical lithium ion battery. BACKGROUND

[0002] The welding mark of the shell bottom mostly adopts laser penetration welding process, specifically, welding from the outside of the shell bottom to the inside accurately, welding the negative current collector disc inside the shell bottom firmly together, realizing stable transmission of current, and guaranteeing normal operation of the battery device.

[0003] A battery negative electrode current collector welding structure with publication number CN207743316U includes a tab and a pole body, the pole body is a cylinder, the tab is placed on the outer cylindrical surface of the pole body, the outer surface of the tab is provided with a welding pressure ring, the pole material is copper, the tab material is copper, the welding pressure ring material is nickel, the pole body is placed at the center of the base, the lower surface of the pole body is in contact with the upper surface of the base, the center of the base is provided with a through hole, the pole body is provided with a cavity inside, and the cavity is communicated with the through hole.

[0004] The existing shell bottom welding mark welding line width ratio design is unreasonable, the welding mark welding line width ratio is too small, the effective flow area of the whole welding mark area is too small, the current passing is affected, the welding mark area temperature rises, the welding mark welding line width ratio is too large, the adjacent lines are directly close, the welding difficulty is increased, the local heat is concentrated, the welding line explosion point is prone to occur, the welding reliability is reduced, and the safety performance of the battery is reduced. UTILITY MODEL CONTENTS

[0005] Therefore, the utility model provides a welding mark structure and cylindrical lithium ion battery, through setting corresponding shell bottom welding mark welding line width ratio, enough effective flow area of welding mark area is ensured, current is smoothly passed, welding mark area temperature is avoided to be too high, meanwhile, the distance between adjacent lines is reasonable, welding difficulty is reduced, local heat concentration is prevented, welding line explosion point and other problems are reduced, welding reliability is improved, and the safety performance of the battery is improved.

[0006] The technical scheme of the utility model is as follows: in the first aspect, the utility model provides a welding mark structure, including fusion welding mark, the distance between the farthest point of the welding mark line of fusion welding mark and the center point is R1, and the value range of R1 is 1-3mm, the welding mark line width of fusion welding mark is W1, and the ratio range of W1 / R1 is 10%-30%.

[0007] On the basis of the above technical scheme, preferably, the shape of the fusion welding mark is arranged in equidistance spiral shape on the plane, and the welding mark line of the fusion welding mark extends along the setting direction of the spiral line.

[0008] On the basis of the above technical scheme, preferably, the distance between the innermost point of the welding line of the fusion welding and the center point is R2, wherein the ratio of R2 / R0 ranges from 1.5% to 8%.

[0009] On the basis of the above technical scheme, preferably, the ratio of the distance W2 between the adjacent two circles of welding lines and the width W1 of the fusion welding ranges from 52% to 72%.

[0010] On the basis of the above technical scheme, preferably, the distance W2 between the adjacent two circles of welding lines ranges from 0.15 to 0.35 mm.

[0011] On the basis of the above technical scheme, preferably, the width W1 of the welding line of the fusion welding ranges from 0.2 to 0.6 mm.

[0012] On the basis of the above technical scheme, preferably, the line segment L1 is between the innermost point of the welding line of the fusion welding and the center point, the line segment L2 is between the farthest point of the welding line of the fusion welding and the center point, an included angle A is formed between the line segments L1 and L2, and the value of the included angle A ranges from 145 to 225 degrees.

[0013] In a second aspect, the utility model provides a cylindrical lithium ion battery, including shell and welding mark structure, welding mark structure is used for fixing shell and negative pole current collector, the center point of fusion welding and the axis of shell coincide, the diameter of shell bottom is R0, wherein, the ratio of R1 / R0 ranges from 10% to 30%.

[0014] On the basis of the above technical scheme, preferably, the distance between the innermost point of the welding line of the fusion welding and the center point is R2, wherein the ratio of R2 / R0 ranges from 1.5% to 8%.

[0015] On the basis of the above technical scheme, preferably, the length of the welding line of the fusion welding is L, the circumference of the shell bottom is 2πR0, wherein the ratio of L / 2πR0 ranges from 20% to 40%.

[0016] The welding mark structure and the cylindrical lithium ion battery of the utility model have the following beneficial effects relative to the prior art:

[0017] (1) by setting the ratio between the width of the fusion welding and the distance between the farthest point and the center point, ensuring that the welding area has sufficient effective flow area, making the current flow uniformly and smoothly, reducing resistance loss and improving transmission efficiency, avoiding local heat concentration and improving battery safety performance, also reducing welding difficulty, ensuring welding quality, improving welding reliability and stability, ensuring electrical equipment performance and safety, and thus improving battery safety performance;

[0018] (2) Setting equidistant spiral welding stamps can increase the contact area between the welding stamp line and the current, making the current distribution more uniform, reducing resistance, reducing power loss, and improving charging and discharging efficiency; the counterclockwise spiral structure can evenly disperse thermal stress, avoid welding stamp deformation and cracking, improve mechanical strength and stability, and can also achieve a longer welding stamp line length in a limited space, improving space utilization.

[0019] (3) By keeping the R2 / R0 ratio within a reasonable range, the distance between the innermost point of the solder line and the center of the bottom of the shell can be moderate, which can reduce the difficulty of welding positioning and equipment debugging, and avoid the overall diameter of the solder line being too large; it can ensure accurate positioning of the welding equipment, improve welding efficiency and yield, and prevent soldering through and leakage, thereby improving battery safety performance and service life. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a plan view of the soldering structure of this utility model;

[0022] Figure 2 This is a schematic diagram of the included angle between line segments L1 and L2 of the soldering structure of this utility model;

[0023] Figure 3 This is a schematic diagram showing the connection between the casing and the soldering structure in the cylindrical lithium-ion battery of this utility model. Detailed Implementation

[0024] The technical solutions of this utility model will be clearly and completely described below with reference to the embodiments of this utility model. Obviously, the described embodiments are only a part of the embodiments of this utility model, and not all of them. Based on the embodiments of this utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this utility model.

[0025] Firstly, such as Figure 1 As shown, this utility model provides a solder mark structure, including a fusion solder mark 1. The distance between the farthest point of the solder mark 1 and its center point is R1, and the value of R1 ranges from 1 to 3 mm. The width of the solder mark 1 is W1, and the value of W1 ranges from 0.2 to 0.6 mm. The ratio of W1 to R1 ranges from 10% to 30%.

[0026] It should be noted that the welding structure is based on the comprehensive consideration of current transmission, heat distribution and welding process. In the welding of electrical equipment such as batteries, the fusion welding mark 1 plays a key role in current conduction. The distance R1 between the farthest point of the welding line and the center point and the welding line width W1 are closely related to the effective current transmission path and the heat effect in the welding process. A suitable R1 value can determine a relatively reasonable welding area range, ensure uniform distribution of current in the welding area, and avoid excessive concentration or dispersion of local current. When R1 is 1-3 mm, effective current conduction can be achieved in a smaller space, while the compactness of the overall structure of the equipment is taken into account.

[0027] In addition, the ratio of the welding line width W1 to R1 is set to 10%-30% to balance the current transmission capacity and the feasibility of the welding process. If the ratio of W1 / R1 is too small, it means that the welding line is relatively narrow, which can reduce the use of welding materials, but will result in a decrease in the effective current-carrying area, an increase in resistance when the current passes through, and the generation of more heat, which will affect the safety performance of the battery. On the contrary, if the ratio of W1 / R1 is too large, the welding line is too wide, and the distance between adjacent lines will decrease. In the welding process, due to the concentration of heat, interference between adjacent lines is easy to occur, increasing the difficulty of welding, and even problems such as welding wire explosion and abnormal welding wire color may occur, reducing the reliability of welding.

[0028] It can be understood that a reasonable R1 and W1 / R1 ratio range ensures that the welding area has sufficient effective current-carrying area, and the current can flow uniformly and smoothly in the welding line, reducing resistance loss in the current transmission process, improving current transmission efficiency, and avoiding local heat concentration. In the welding process, heat can be relatively uniformly distributed in the welding area to prevent problems such as welding wire explosion and welding wire deformation caused by local overheating. At the same time, when the equipment is running normally, it can also effectively dissipate the heat generated by the current passing through, maintain the temperature stability of the welding area, improve the safety performance of the battery, reduce the difficulty of welding, and ensure the welding quality. The welding gun can be more accurately operated to reduce welding defects caused by welding process problems, improve the reliability and stability of welding, and thus ensure the performance and safety of the entire electrical equipment.

[0029] Specifically, in the present embodiment, the distance between the farthest point of the welding line of the fusion welding mark 1 and the center point is R1=2 mm, and the welding line width of the fusion welding mark 1 is W1=0.4 mm. The ratio of W1 / R1 is 20%.

[0030] The shape of the fusion welding bead 1 in this embodiment is arranged in a plane as an equidistant spiral, and the welding bead line of the fusion welding bead 1 extends along the arrangement direction of the spiral line, and the rotation direction of the spiral line is counterclockwise.

[0031] It should be noted that the spiral welding bead line can increase the transmission path length of the current in the welding bead area. Compared with the linear welding bead, it can carry more current flow in the same space, effectively reduce the current density per unit length of the welding bead line, and reduce the resistance heat generated by current concentration, thereby ensuring the stability of current transmission. In the welding process, the welding heat source will generate thermal stress, and the counterclockwise spiral direction is beneficial to disperse the thermal stress and avoid excessive concentration of thermal stress in a certain local part, thereby reducing the risk of defects such as deformation and cracking of the welding bead area.

[0032] In this embodiment, the equidistant spiral fusion welding bead 1 increases the contact area of the welding bead line and the current, so that the current can be more evenly distributed on the welding bead line, effectively reducing the resistance in the current transmission process, reducing power loss, and improving the efficiency of the battery and other devices during charging and discharging. And the counterclockwise rotating spiral structure makes the thermal stress generated during welding evenly disperse along the spiral direction, avoiding problems such as welding bead deformation and cracking caused by excessive local thermal stress, improving the mechanical strength and stability of the welding bead structure, and enabling longer welding bead line length in a limited space, improving space utilization.

[0033] In this embodiment, the distance between the two adjacent welding bead lines is W2, and the ratio of W2 / R1 is in the range of 8%-18%.

[0034] It should be noted that if the W2 / R1 ratio is too small, it means that W2 decreases and R1 increases. At this time, the adjacent welding bead lines are very close, the welding operation space is limited, and the welding difficulty is significantly increased. Local heat concentration can easily cause problems such as welding line explosion, color abnormalities, and a significant decrease in welding reliability. At the same time, due to the dense lines and the welding offset, it is easy to exceed the weldable area, increasing the risk of welding and leakage. If the W2 / R1 ratio is too large, W2 becomes larger and R1 becomes smaller, the welding line width decreases, the effective flow area decreases, the current density at the welding site increases, the temperature rises, and the safety performance of the battery is affected. Moreover, a too large ratio can make the overall diameter of the welding bead line larger, combined with the welding offset, which can easily exceed the weldable area, causing welding and leakage safety hazards.

[0035] The reasonable setting of the ratio of the spacing W2 between the two adjacent welding lines and R1 in the embodiment can ensure that there is enough space between the welding lines for welding operation, avoiding the increase of welding difficulty due to the close distance between the lines. At the same time, the reasonable spacing helps to uniformly disperse the heat generated during welding, preventing local overheating from causing welding wire explosion, color abnormalities and other problems. In addition, the W2 / R1 ratio affects the effective flow area of the welding line. When the ratio is appropriate, it can ensure that the welding area has enough area for current to pass through, reduce current density, reduce resistance loss and temperature rise. Moreover, it can avoid the welding line from being too dense or the overall diameter being too large to exceed the weldable area, reducing the risk of welding through and liquid leakage, and ensuring the safety performance of the battery.

[0036] When the W2 / R1 ratio is within the reasonable range of 8%-18% in the embodiment, the appropriate distance is maintained between the adjacent welding lines, the welding operation space is sufficient, the welding difficulty is reduced, the welder can more accurately control the welding parameters, ensure the welding quality, reduce the defects such as welding wire explosion and color abnormalities caused by welding process problems, thereby improving the reliability of welding. The reasonable spacing makes the heat distribution more uniform during welding, avoiding the damage of local heat concentration to the welding line, further enhancing the stability and reliability of the welding structure. In addition, it ensures that the welding line has sufficient width and effective flow area, and the current can flow smoothly in the welding line, reducing the resistance in the current transmission process, reducing power loss and temperature rise, improving the efficiency of the battery during charging and discharging, and prolonging the service life of the battery. Moreover, even if there is a certain amount of offset during welding, the reasonable W2 / R1 ratio can to some extent buffer the impact of the offset, reducing the welding defects and safety risks caused by the offset.

[0037] Specifically, W2 / R1 = 12.5% in the embodiment.

[0038] In the embodiment, the ratio of the spacing W2 between the two adjacent welding lines and the width W1 of the fusion welding mark 1 is within the range of 52%-72%.

[0039] It should be noted that if the W2 / W1 ratio is too small, it means that W2 is small and W1 is large. In the case of welding offset, the adjacent welding lines will be very close, which not only affects the appearance of the product, but also significantly increases the welding difficulty. Local heat concentration can easily cause welding wire explosion, color abnormalities and other problems, reducing the welding quality, and even possibly leading to welding failure. If the W2 / W1 ratio is too large, W2 becomes large and W1 becomes small. The welding area of the welding line is reduced, and the effective flow area is also reduced, resulting in an increase in current density at the welding site and an increase in temperature rise, increasing the safety hazard of the battery.

[0040] It can be understood that when the W2 / W1 ratio is in a reasonable range of 52%-72%, the adjacent welding lines maintain a proper distance, the welding operation space is sufficient, the welder can more accurately control the welding parameters, ensure the stability of the welding process, reduce the generation of welding defects, thereby improving the welding quality, and ensure that the welding lines have sufficient welding area and effective flow area, the current can flow smoothly in the welding lines, reduce the resistance in the current transmission process, reduce the power loss and temperature rise, improve the efficiency of the battery in the charging and discharging process, prolong the service life of the battery, reduce the local overheating phenomenon caused by current concentration, reduce the probability of occurrence of safety hazards such as internal short circuit of the battery, and improve the safety performance of the battery. At the same time, the layout of the welding lines is more uniform and neat, the spacing between the lines is moderate, the appearance of the product is more beautiful, and the overall quality of the product is improved.

[0041] The spacing W2 between the two adjacent welding lines in the embodiment is 0.15-0.35 mm.

[0042] Specifically, in the embodiment, the ratio of the spacing between the two adjacent welding lines to the width of the fusion welding 1 is W2 / W1=62.5%; the value of the spacing between the two adjacent welding lines is W2=0.25 mm.

[0043] As shown in Figure 2 , in the embodiment, the line connecting the innermost point of the welding line of the fusion welding 1 to the center point is L1, the line connecting the farthest point of the welding line of the fusion welding 1 to the center point is L2, and the included angle A between the line segments L1 and L2 is formed. The value of the included angle A is 145-225°.

[0044] It should be noted that in the embodiment, the line L1 connecting the innermost point of the welding line of the fusion welding 1 to the center point, the line L2 connecting the farthest point to the center point, and the included angle A therebetween jointly determine the layout form of the welding line. The size of the included angle A directly affects the total length of the welding line; if the included angle is too small, the total length of the welding line will increase. In the case of meeting the flow capacity, the too long welding line will not have more beneficial effects on the flow, but will reduce the reliability of the welding, increase the risk of welding cracks, explosion points, and liquid leakage, etc. If the included angle is too large, the total length of the welding line will be reduced, and the effective welding flow area will be reduced, which will lead to a reduction in the flow area of the welding, an increase in the temperature rise of the welding, and a decrease in the safety performance of the battery.

[0045] It can be understood that when the included angle A is within a reasonable range of 145-225°, a good balance between the wire length, welding reliability and effective welding cross-sectional area can be achieved, at this time, the length of the welding wire is moderate, neither too long to increase the welding difficulty and reduce the reliability, nor too short to reduce the effective welding cross-sectional area, so that the welding process is more stable, the welding quality is improved, and at the same time, the current can smoothly pass through the welding area, the temperature rise at the welding position is reduced, and the safety performance of the battery is improved.

[0046] Specifically, the included angle A in the embodiment is 180°.

[0047] As shown in Figure 3 the second aspect, the utility model provides a cylindrical lithium ion battery, including shell 2 and welding mark structure, welding mark structure is used for fixed shell 2 and negative pole current collector, the center point of fusion welding mark 1 coincides with the axis of shell 2, the diameter of shell 2 bottom is R0, wherein, the ratio range of R1 / R0 is 10 %-30 %.

[0048] It should be noted that if the ratio range of R1 / R0 is too small, it means that the welding line is relatively compact relative to the bottom of the shell 2, and the interval between the welding lines is reduced as a whole. In the welding process, heat is generated when the current passes through the welding line. Since the welding line interval is small, heat is easily accumulated in these narrow areas, resulting in very concentrated local heat. Heat concentration can cause the local temperature of the welding line to rise too quickly. When the temperature exceeds the melting point of the welding material or causes a change in the internal stress of the material, it is easy to cause the phenomenon of explosion. At the same time, different local temperature differences can cause different degrees of oxidation on the welding surface, resulting in different colors. If the ratio of R1 / R0 is too large, the welding line will be relatively far from the center position of the shell bottom, causing the overall diameter of the welding line to increase. In actual welding operation, due to the existence of a certain welding offset, the welding line may exceed the pre-set weldable area. Once it exceeds the weldable area and continues to weld, the material and structure of the area may not be suitable for welding, which can easily lead to welding through, which can damage the integrity of the shell and cause the electrolyte inside the battery to leak out, thereby increasing the risk of leakage.

[0049] It can be understood that when the ratio of R1 / R0 is within a reasonable range of 10%-30%, the layout of the welding line on the bottom of the shell is reasonable, and the interval between the welding lines is moderate, which can ensure uniform distribution of heat during welding, avoid the problems of explosion and different colors caused by heat concentration, and ensure that the welding line will not exceed the weldable area due to the overall diameter being too large. This can improve the welding quality, ensure the reliability and stability of welding, reduce the risk of welding and leakage, and improve the safety performance and service life of the battery.

[0050] Specifically, in the embodiment, R1 / R0 = 19.05%, and the diameter R0 of the bottom of the shell 2 is 10.5 mm.

[0051] In the embodiment, the distance between the innermost point of the welding line of the fusion welding bead 1 and the center point is R2, and the ratio of R2 / R0 ranges from 1.5% to 8%.

[0052] It should be noted that when the ratio of R2 / R0 is small, the innermost point of the welding line is very close to the center position of the shell bottom. During welding, the positioning accuracy of the welding equipment is required to be extremely high due to the narrow space and close-to-center position. Any slight deviation may cause inaccurate welding position and affect the welding quality. At the same time, the position and angle of the welding head need to be accurately controlled during equipment debugging to adapt to such a close-to-center position, which increases the difficulty of equipment debugging, and the close-to-center welding position further increases the control difficulty because slight input changes may cause large output deviations, resulting in low welding efficiency and low yield. If the ratio of R2 / R0 is too large, the innermost point of the welding line will be far away from the center position of the shell bottom, resulting in an increase in the overall diameter of the welding line. In actual welding operation, due to the existence of a certain welding offset, the welding line is easy to exceed the pre-set weldable area. Once the welding continues beyond the weldable area, it is easy to cause welding through.

[0053] It can be understood that when the ratio of R2 / R0 is within the reasonable range of 1.5% to 8%, the distance between the innermost point of the welding line and the center position of the shell bottom is moderate, neither too close to the center to increase the difficulty of welding positioning and equipment debugging, nor too far from the center to make the overall diameter of the welding line too large. The accurate positioning of the welding equipment is ensured, the welding deviation is reduced, the welding efficiency and yield are improved, and the risk of welding through and leakage due to the welding line exceeding the weldable area is avoided, thereby improving the safety performance and service life of the battery.

[0054] Specifically, in the embodiment, R2 / R0 = 2.9%.

[0055] In the embodiment, the length of the welding line of the fusion welding bead 1 is L, and the circumference of the bottom of the shell 2 is 2πR0, wherein the ratio of L / 2πR0 ranges from 20% to 40%.

[0056] It should be noted that when the L / 2πR0 ratio is small, it means that the total length of the welding line is relatively short, and from the perspective of current transmission, the effective welding overcurrent area is closely related to the length and layout of the welding line; shorter welding line will lead to a decrease in the effective welding overcurrent area, because when the current passes through the welding area, the path available for the current to pass through is reduced; according to Joule's law, under the condition that the current I is constant, the resistance R is related to the cross-sectional area and length of the conductor, and the decrease in the effective overcurrent area will increase the resistance, and the heat generated by the current will increase, resulting in an increase in the temperature rise at the welding site, which will affect the performance and stability of the materials inside the battery and reduce the safety performance of the battery; when the L / 2πR0 ratio is too large, that is, the total length of the welding line is too long, in the case of meeting the overcurrent capacity, the excessively long welding line will not have more beneficial effects on overcurrent; on the contrary, the excessively long welding line will bring a series of problems in the welding process, first, the increase in the welding path will make the thermal stress distribution in the welding process more complex, the heat-affected zone will expand, and it is easy to cause welding cracks; second, local overheating may cause the welding line to explode, affecting the welding quality; in addition, the excessively long welding line is more susceptible to mechanical vibration, temperature changes and other factors during subsequent use, increasing the risk of leakage; thereby reducing the reliability of welding.

[0057] When the L / 2πR0 ratio in the embodiment is within a reasonable range of 20%-40%, the length of the welding line is moderate, which can not only ensure sufficient effective welding overcurrent area, reduce the temperature rise at the welding site, and improve the safety performance of the battery, but also will not increase the welding difficulty and risk due to the excessively long welding line, realize a stable welding process, improve the welding quality, and ensure the performance and safety of the battery during the charging and discharging process.

[0058] The welding line length L of the fusion welding mark 1 in the embodiment is in the range of 16mm-25mm; according to R0 being 10.5mm, the circumference of the bottom of the shell 2 is calculated to be 65.97mm.

[0059] Specifically, in the embodiment, the welding line length L of the fusion welding mark 1 is 20mm, and L / 2πR0 is 30.32%.

[0060] The above only describes the preferred embodiments of the present application, and is not intended to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A weld structure, characterized by, The fusion welding bead (1) has a distance between the farthest point of the welding line and the center point of the fusion welding bead (1) as R1, and R1 is 1-3 mm, and the welding line width of the fusion welding bead (1) is W1, wherein the ratio of W1 / R1 is 10%-30%.

2. The solder print structure of claim 1, wherein: The shape of the fusion welding bead (1) is equidistantly arranged in a spiral shape on a plane, and the welding line of the fusion welding bead (1) extends along the arrangement direction of the spiral line.

3. A weld structure according to any one of claims 1-2, characterized in that: The distance between the welding lines of the adjacent two turns is W2, wherein the ratio of W2 / R1 is 8%-18%.

4. A weld structure according to any one of claims 1-2, characterized in that: The ratio of the distance W2 between the welding lines of the adjacent two turns and the width W1 of the fusion welding bead (1) is 52%-72%.

5. The weld structure of any of claims 1-2, wherein: The distance W2 between the welding lines of the adjacent two turns is 0.15-0.35 mm.

6. The weld structure of any of claims 1-2, wherein: The welding line width W1 of the fusion welding bead (1) is 0.2-0.6 mm.

7. The weld structure of any of claims 1-2, wherein: The line between the innermost point of the welding line of the fusion welding bead (1) and the center point is L1, and the line between the farthest point of the welding line of the fusion welding bead (1) and the center point is L2, and the included angle A between the line segments L1 and L2 is 145-225°.

8. A cylindrical lithium-ion battery, characterized by: The welding bead structure is used for fixing the shell (2) and the negative current collector, the center point of the fusion welding bead (1) coincides with the axis of the shell (2), and the diameter of the bottom of the shell (2) is R0, wherein the ratio of R1 / R0 is 10%-30%.

9. The cylindrical lithium-ion battery of claim 8, wherein: The distance between the innermost point of the welding line of the fusion welding bead (1) and the center point is R2, wherein the ratio of R2 / R0 is 1.5%-8%.

10. The cylindrical lithium-ion battery of claim 8, wherein: The length of the welding line of the fusion welding bead (1) is L, and the circumference of the bottom of the shell (2) is 2πR0, wherein the ratio of L / 2πR0 is 20%-40%.

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