Rechargeable batteries, battery packs, and electronic devices

Abstract

The present invention provides a secondary battery, battery pack, and electronic device that can solve the problem of relatively high requirements for suitable clearance of the weld gap when welding sealing pins to other components. [Solution] The present invention provides a secondary battery, a battery pack, and an electronic device, comprising an electrode assembly, a casing, a post, a sealing pin, and a weld mark, wherein the electrode assembly is housed inside the casing, one end of the casing has an opening, the end of the post away from the electrode assembly extends out of the casing through the opening, a groove is provided at the end of the post, a sealing pin is fitted into the groove, the outer end face of the sealing pin and the end face of the end of the post are welded to form a weld mark, the weld trajectory of the weld mark is configured such that the entire trajectory extends along a primary trajectory line and a portion rotates or reciprocates along a secondary trajectory line to expand the width of the primary trajectory line.

Description

Technical Field

[0001] The present invention relates to the field of batteries, specifically to secondary batteries, battery packs, and electronic devices.

Background Art

[0002] The sealing pin of a power battery is an important component used in battery packaging. It mainly ensures that the electrolyte inside the battery does not leak, and at the same time prevents external air and moisture from entering the battery. It is used to protect the service life and safety performance of the battery. Laser welding is a firm and commonly used assembly method for sealing pins. For example, in the prior art, continuous laser welding can be adopted to perform butt welding between the sealing pin and other components. However, the width of the molten pool formed by the conventional continuous laser welding is relatively narrow, and the requirements for the fitting clearance of the welding gap are relatively high.

Summary of the Invention

Problems to be Solved by the Invention

[0003] In some embodiments of the present invention, there is provided a secondary battery, a battery pack, and an electronic device that can solve the problem that the requirements for the fitting clearance of the welding gap are relatively high when welding the sealing pin and other components.

Means for Solving the Problems

[0004] The first aspect of the present invention provides a secondary battery including an electrode assembly, a casing, a post, a sealing pin, and a welding mark. The electrode assembly is housed inside the casing. One end of the casing has an opening. The end of the post away from the electrode assembly extends out of the casing through the opening. A concave groove is provided at the end of the post. The sealing pin fits and is inserted into the concave groove. The end face of the outer periphery of the sealing pin and the end face of the end of the post are welded to form a welding mark. The welding track of the welding mark is configured such that as a whole, it extends along a primary track line, and a part of it rotates or reciprocates along a secondary track line to expand the width of the primary track line.

[0005] Selectively, the shape and dimensions of the primary trajectory line and the outer circumference of the sealing pin correspond to each other.

[0006] Selectively, the quadratic trajectory line is a polyline, a dashed line, a helical line, a circular arc, or an elliptical arc.

[0007] Selectively, the quadratic trajectory is a circular arc, and the radius R of the arc is 0.3–1.0 mm.

[0008] Selectively, the parallel translation step length A of adjacent quadratic trajectories is 0.2–1.0 mm.

[0009] Selectively, the cross-section of the weld is rectangular or trapezoidal with a flat base.

[0010] Selectively, if S is the cross-sectional area of ​​the weld, W is the width of the weld, and D is the depth, then S / (W×D)>0.5.

[0011] Selectively, the outer surface of the weld is concave inward.

[0012] Selectively, the device further includes an injection hole and a sealing plug, the injection hole penetrating the bottom wall of the groove, and the sealing plug being inserted into the injection hole to seal it.

[0013] A sealing adhesive is selectively applied to the surface of the weld marks.

[0014] Selectively, the top of the sealing adhesive is lower than the end face of the sealing pin away from the electrode assembly.

[0015] Selectively, the sealing adhesive is an ultraviolet-curing adhesive.

[0016] A second aspect of the present invention provides a battery pack comprising a plurality of secondary batteries as provided in the first aspect of the present invention.

[0017] A third aspect of the present invention provides an electronic device including a battery pack provided in the second aspect of the present invention. [Effects of the Invention]

[0018] By utilizing a method in which the laser spot rotates or reciprocates along the secondary locus line, the overall width of the formed molten pool can be expanded, that is, by expanding the width of the weld mark, the problem that the requirement for the fitting clearance between the sealing pin and the positive post during welding is high can be overcome.

Brief Description of the Drawings

[0019] [Figure 1] It is a schematic diagram of the internal structure of a secondary battery provided in the first embodiment of the present invention. [Figure 2] It is a cross-sectional view of the positive terminal assembly of a secondary battery provided in the first embodiment of the present invention. [Figure 3] It is a schematic diagram of the welding locus of the positive post and the sealing pin of a secondary battery provided in the first embodiment of the present invention. [Figure 4] It is a partially enlarged view of the welding locus provided in the first embodiment of the present invention. [Figure 5] It is a cross-sectional metallographic photograph of the weld mark in the first embodiment of the present invention. [Figure 6] It is a cross-sectional view of the positive terminal assembly in the second embodiment of the present invention. [Figure 7] It is a schematic diagram of the structure of a battery pack provided in some embodiments of the present invention. [Figure 8] It is a schematic diagram of the structure of an electronic device provided in some embodiments of the present invention.

Modes for Carrying Out the Invention

[0020] Hereinafter, in conjunction with the drawings in the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. It is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those skilled in the art without creative labor belong to the protection scope of the present invention.

[0021] <First Embodiment>

[0022] FIG. 1 is a schematic internal structure diagram of a secondary battery 1 provided in the first embodiment of the present invention. FIG. 2 is a cross-sectional view of a positive terminal assembly 10 of the secondary battery 1 provided in the first embodiment of the present invention. Referring to FIGS. 1 and 2, in the present embodiment, the secondary battery 1 is a cylindrical secondary battery 1, that is, a single battery core packaged using a cylindrical casing 101.

[0023] The casing 101 can be made of steel, stainless steel or nickel-plated steel. The side wall portion 103 of the casing 101 has a hollow cylindrical shape, and the hollow portion is used to accommodate the electrode assembly 20. In FIG. 1, the upper end of the casing 101 is used to form the positive terminal assembly 10, and the lower end of the casing 101 is used to form the negative terminal assembly 11. The negative terminal assembly 11 electrically connects one electrode of the electrode assembly 20 and the casing 101, and the positive terminal assembly 10 electrically connects the other electrode of the electrode assembly 20 and the positive post 40, and electrically insulates the positive post 40 and the casing 101.

[0024] In FIG. 1, the structure of the upper end of the casing 101, that is, one end forming the positive terminal assembly 10, is as shown in FIG. 2. At this end portion, the side wall portion 103 integrally bends inward and extends to form an end plate 105 in a substantially flat form. An opening 107 is reserved at the center of the end plate 105, and thereby the positive terminal assembly 10 is formed at the location of the opening 107.

[0025] The thickness of the side wall portion 103 of the casing 101 can be approximately 0.2-0.6 mm, and the thickness of the end plate 105 can be approximately greater than the thickness of the side wall portion 103. For example, the end plate 105 can have a thickness of approximately 0.6-1.0 mm. By making the thickness of the side wall portion 103 thinner, the volume of the electrode assembly 20 that can be housed can be increased, and the energy density of the secondary battery 1 can be improved. At the same time, the thickness of the side wall portion 103 should not be excessively thin in order to increase the strength of the casing 101 and ensure the safety performance of the secondary battery 1. In some implementations, a nickel plating layer can be formed on the surface of the casing 101 to increase the strength of the casing 101.

[0026] The electrode assembly 20 of the secondary battery 1 is housed in a cavity formed by the cylindrical side wall portion 103 of the casing 101. The electrode assembly 20 includes a first electrode having a first polarity, a second electrode having a second polarity, and a separator placed between the first and second electrodes. The polarities of the first and second electrodes are opposite. The electrode assembly 20 has a winding core structure, specifically formed by sequentially stacking sheet-like first electrodes, separators, and second electrodes, and then winding a laminate in one direction. Any winding core structure known in the art can be applied to the secondary battery 1 provided by the present invention and will not be described in detail here.

[0027] For example, a positive electrode active material is applied to the surface of the first electrode, and a negative electrode active material is applied to the surface of the second electrode. The longitudinal ends of the electrode assembly 20 are not coated with the active material and are used for welding to the current collector 30, and are electrically connected to the positive post 40 or negative post of the secondary battery 1 via the current collector 30. The positive electrode active material can be, for example, lithium metal phosphate, the negative electrode active material can be, for example, carbon material, silicon, or silicon compound, and the separator can be, for example, a porous polymer thin film, such as polyethylene, polypropylene, or ethylene / butene copolymer.

[0028] The electrode assembly 20 can be immersed in an electrolyte (e.g., electrolyte solution), and the electrolyte can be injected into the hollow chamber of the casing 101 via an injection port (see, for example, the second embodiment, Figure 6), and the location of the injection port is not limited in this embodiment. The electrolyte can be a salt containing lithium ions, and the electrolyte can be used after being dissolved in an organic solvent.

[0029] As organic solvents, propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethyl methyl carbonate (EMC), γ-butyrolactone, or mixtures thereof can be selected.

[0030] Referring to Figure 2, in the positive electrode terminal assembly 10 of the secondary battery 1 provided in this embodiment, the positive post 40 is cylindrical overall, with an upper folded portion 401 formed by folding outward at the upper end (end 407), a lower folded portion 403 formed by folding outward at the lower end, and a flat bottom wall 405 in the center of the lower end. The shape and dimensions of the upper folded portion 401 and the lower folded portion 403 are mutually compatible with the shape and dimensions of the insulating portion 50, and the position of the positive post 40 is fixed using the insulating portion 50. The insulating portion 50 is installed between the positive post 40 and the casing 101, electrically insulating the positive post 40 from the casing 101. The insulating portion 50 includes a sealing ring 502, and both sides of the sealing ring 502 are sandwiched between the upper folded portion 401 and the end plate 105, respectively, to ensure the sealing effect at this location. The material of the sealing ring 502 may be, but is not limited to, EPDM (Ethylene Propylene Diene Monomer) rubber, fluorosilicone rubber, or fluororubber.

[0031] A groove 409 is provided in the middle of the upper end (i.e., end portion 407) of the standard post 40, and the groove 409 is the hollow portion of the end portion 407 of the cylindrical standard post 40. The sealing pin 411 is fitted into the groove 409, and the top surface of the outer circumference of the sealing pin 411 is flush with the top surface of the upper folded portion 401 of the standard post 40 and they are adjacent to each other. At the point where the top surface of the outer circumference of the sealing pin 411 and the top surface of the upper folded portion 401 meet, a butt welding method is adopted to weld and fix the sealing pin 411 and the upper folded portion 401 of the standard post 40. In this embodiment, the top surface of the outer circumference of the sealing pin 411 and the top surface of the upper folded portion 401 are described as being flush with each other. However, in other embodiments, the two do not need to be flush with each other. As long as the outer circumference of the sealing pin 411 and the inner edge of the top of the upper folded portion 401 are adjacent to each other and satisfy the compatibility relationship, butt welding can be achieved at this location, and the present invention does not exclude such methods.

[0032] Specifically, the butt welding process between the sealing pin 411 and the upper folded portion 401 is completed by a continuous laser welding process. Specifically, after completing the positioning and clamping of the secondary battery 1, the laser device is activated and the laser spot is irradiated onto the position where the sealing pin 411 and the upper folded portion 401 are in contact. For example, the laser can be irradiated onto the outer circumference of the sealing pin 411 and / or the inner edge of the upper folded portion 401 (i.e., near the position indicated by the weld mark 60 in the figure).

[0033] After continuously irradiating the metal to melt it and form a molten pool, the laser spot is moved along the welding trajectory 601. The welding trajectory 601 of continuous laser welding is as shown in Figure 3. By moving the laser spot along the welding trajectory 601 in Figure 3, the metal can be melted and a molten pool can be formed, and after the molten pool solidifies, a weld mark 60 is formed. Referring to Figure 3, the overall movement trajectory of the laser spot is the primary trajectory line 603 of the welding trajectory 601. Specifically, in this embodiment, since the outer circumference of the sealing pin 411 is circular, the primary trajectory line 603 corresponds to the shape and dimensions of the outer circumference of the sealing pin 411 and is also circular. The diameter of this circular primary trajectory line 603 and the outer diameter of the sealing pin 411 are basically equal, and their positions are basically where the sealing pin 411 and the upper folded portion 401 are in contact. In other embodiments, the primary trajectory line 603 can also be adjusted accordingly according to the shape and dimensions of the outer circumference of the sealing pin 411 and is not limited to the circular shape in this embodiment.

[0034] By enlarging a portion of the welding trajectory 601, excluding the primary trajectory 603 present as a whole, a portion of the secondary trajectory 605 can be revealed. Figure 4 is an enlarged view of a portion of the welding trajectory 601 provided in this embodiment. Referring to Figure 4, in this embodiment, the secondary trajectory 605 exhibits an arc shape with an inscribed angle greater than π and less than 2π. Specifically, multiple secondary trajectory 605s touch each other at their leading and trailing ends, connecting to form a circular welding trajectory 601 that extends along the primary trajectory 603 as a whole.

[0035] In this implementation method, compared to the conventional technique in which the laser spot moves directly along the primary trajectory 603, the rotation of the laser spot along the secondary trajectory 605 while moving along the primary trajectory 603 allows the width of the molten pool formed by the laser spot to be expanded, making the width of the molten pool wider than that formed by a single-point laser moving unidirectionally along the circumference.

[0036] In this implementation method, the arc radius R of the secondary trajectory line 605 is 0.3-1.0 mm. If the arc radius is too large, it is not possible to form a molten pool with a relatively flat bottom, and if the radius is too small, it is not possible to effectively increase the width of the molten pool. By setting the arc radius between 0.3 and 1.0 mm, it is possible to effectively form a rectangular or trapezoidal molten pool that is relatively wide and has a flat bottom, thereby overcoming the disadvantage that butt welding requires a relatively high clearance for the weld gap. In accordance with the arc radius R, the parallel movement step length A of adjacent secondary trajectory lines 605 is 0.2-1.0 mm. Setting an appropriate parallel movement step length A is beneficial for adjusting and controlling the depth of the molten pool. An excessively close parallel movement step length A easily leads to the laser spot irradiating the same or nearby positions repeatedly, which can result in an excessively deep molten pool and the appearance of an explosion point. On the other hand, an excessively long parallel movement step length A may lead to insufficient depth of the molten pool or the inability to form a continuous molten pool with a flat bottom.

[0037] In Figure 2, when viewed from top to bottom, the shape of the weld mark 60 formed by welding the sealing pin 411 and the positive post 40 is roughly circular, corresponding to the primary trajectory line 603. When viewed from the cross-sectional viewing direction adopted by Figure 2 itself, the cross-section of the weld mark 60 is rectangular or trapezoidal with a flat base.

[0038] Figure 5 is a metallographic cross-section of the weld mark 60. Referring to Figure 5, the cross-section of the weld mark 60 in this implementation is trapezoidal with a flat base. Specifically, the top surface of the cross-section of the weld mark 60 is relatively wide, the bottom surface is relatively narrow, and there is a constant circular arc transition step between the two side edges and the bottom surface. This cross-section is formed by the rotation of the laser spot along the secondary trajectory line 605. Specifically, since the laser spot itself can form a molten pool with a relatively narrow lower end and a relatively wide upper end, as the laser spot rotates along the secondary trajectory line 605, the laser spot forms a trapezoidal molten pool with a flat bottom and a relatively wide top. Furthermore, since the laser spot not only rotates along the secondary trajectory 605 but also moves in a circular motion along the primary trajectory 603, by rationally setting the dimensions and shape of the secondary trajectory 605 and the primary trajectory 603, it is possible to form a weld mark 60 with a trapezoidal shape in its cross-section (i.e., the normal plane perpendicular to the direction of laser spot movement) having a rounded corner transition at the bottom, as shown in Figure 5.

[0039] The heat generated during welding causes expansion of the molten pool, and further leads to the weld mark protruding from the weld surface. In some implementations, the contour of the formed weld mark can be adjusted by controlling the gap between the outer circumference of the sealing pin 411 and the inner edge of the top of the upper folded portion 401. A relatively good control method is to control the gap between the sealing pin 411 and the upper folded portion 401 to have a predetermined fit clearance, so that when the molten pool is formed by laser irradiation, the molten pool fills this fit clearance, and even if expansion occurs, the top of the entire molten pool remains lower than the top surface of the outer circumference of the sealing pin 411 (or the top surface of the upper folded portion 401). Furthermore, setting the fit clearance should also guarantee the weld strength. As shown in Figure 5, the outer surface of the weld mark 60 (i.e., the top surface of the weld mark 60 in Figure 5) is concave inward (i.e., downward in Figure 5).

[0040] Continuing to refer to Figure 5, let S be the cross-sectional area of ​​the weld mark 60, W be the width of the weld mark 60, and D be the depth, satisfying the condition S / (W×D)>0.5 between S, W, and D. Due to the characteristics of laser through-welding, the lower end width of the formed molten pool and the corresponding weld mark 60 is usually smaller than the upper end width. By rotating or reciprocating the laser spot along the secondary trajectory line 605, it is possible to improve the amount of metal melted, improve the degree of filling into the fitting clearance, increase the uniformity of the vertical width of the molten pool, and improve the weld strength and reliability.

[0041] In this implementation method, the example of the secondary trajectory line 605 being a circular arc is explained, but this does not limit its shape. In other implementation methods, the secondary trajectory line 605 may be a broken line, a dashed line, a spiral line, an elliptical arc, etc. Correspondingly, the method of movement of the laser spot along the secondary trajectory line 605 may be reciprocating movement along a broken line, dashed line, etc., or rotational movement along a spiral line, an elliptical arc, etc.

[0042] Butt welding using continuous laser welding generally employs infrared lasers, but smooth metal surfaces, such as the surface of an aluminum post 40, tend to exhibit high reflectivity to the laser during welding, leading to problems such as reduced photothermal conversion efficiency and large variations in welding quality. In this embodiment, the roughness of the top surface of the upper folded portion 401 of the post 40 and / or the top surface of the outer circumference of the sealing pin 411 can be controlled by polishing the surface of the post 40 or the sealing pin 411 or by selecting the material. Specifically, in this embodiment, the roughness R1 of the top surface of the outer circumference of the sealing pin 411 and the roughness R2 of the top surface of the upper folded portion 401 are both controlled to 0.5 mm or more, and by controlling the roughness at these locations, laser absorption can be increased, the heating rate can be improved, and the consistency of welding quality can be improved.

[0043] The secondary battery 1 provided by this implementation overcomes the problem in the prior art of requiring a high clearance between the sealing pin 411 and the positive post 40 when welding them together. This is achieved by limiting the welding method between the outer end face of the sealing pin 411 and the inner edge of the end 407 of the positive post 40, and by utilizing rotation or reciprocation along the secondary trajectory line 605 of the laser spot to expand the overall width of the formed molten pool.

[0044] <Second Implementation Method>

[0045] A second embodiment of the present invention provides a secondary battery 1, and Figure 6 is a cross-sectional view of the positive electrode terminal assembly 10 in the second embodiment. The main structural difference between the secondary battery 1 of the second embodiment and the first embodiment is that in the second embodiment, the secondary battery 1 further includes an electrolyte injection hole 70 and a sealing plug 71.

[0046] Referring to Figure 6, the current collector 30 is made of a conductive metallic material, such as aluminum or copper. The longitudinal end of the electrode assembly 20 is bent and then extended in a direction parallel to the current collector 30, and the bent portion connects with the current collector 30, completing the electrical connection between the current collector 30 and the electrode assembly 20. The side of the current collector 30 away from the electrode assembly 20 is connected to the positive post 40 or the negative post, thereby using the current collector 30 to collect and conduct current.

[0047] The positive post 40 is welded to the current collector 30 using the bottom wall 405. The groove 409 allows the bottom wall 405 to be exposed, and if a sealing pin 411 is not inserted into the groove 409, laser penetration welding can be used to complete the welded fixation between the bottom wall 405 and the current collector 30.

[0048] In this implementation, the electrolyte injection holes 70 are located in the center of the bottom wall 405 of the positive post 40 and in the central projection 302 of the current collector 30. Specifically, the electrolyte injection holes 70 penetrate both the bottom wall 405 and the projection 302, and the dimensions and positions of the electrolyte injection holes 70 on the bottom wall 405 and the electrolyte injection holes 70 on the projection 302 correspond to each other, allowing the manufacturer to inject electrolyte into the casing 101 of the secondary battery 1, particularly into the chamber housing the electrode assembly 20, via the electrolyte injection holes 70.

[0049] After the liquid injection is complete, a sealing plug 71 can be inserted into the injection hole 70 to seal it and improve the sealing performance of the secondary battery 1. The sealing plug 71 may be a rubber stopper. After sealing the injection hole 70 using the sealing plug 71, a sealing pin 411 can be inserted into the groove 409 to complete the welding of the sealing pin 411 to the positive post 40.

[0050] In this implementation, a stepped portion 413 is installed at the top of the groove 409, specifically on the inner edge of the upper folded portion 401, and the surface of the stepped portion 413 comes into contact with the sealing pin 411 and is used to receive the sealing pin 411, thereby initially limiting the position of the sealing pin 411 during the welding process.

[0051] In some embodiments of the present invention, a sealing adhesive 607 can be applied to the surface of the weld mark 60 to further improve the sealing effect of the sealing pin 411. The sealing adhesive 607 should not be too thick, for example, less than 0.5 mm thick. Specifically, the top of the sealing adhesive 607 is preferably lower than the end face of the sealing pin 411 away from the electrode assembly 2, that is, the top of the sealing adhesive 607 is lower than the upper end face of the sealing pin 411, so that the adhesive does not interfere with subsequent welding of the busbar and the upper end face of the sealing pin 411. The sealing adhesive 607 is preferably an ultraviolet curing adhesive. By using an ultraviolet curing adhesive as the sealing adhesive 607, there are advantages such as not absorbing heat during laser cleaning, having a fast curing speed, no volatilization, high transparency, and relatively low VOC emissions.

[0052] Referring to Figure 7, the present invention further provides a battery pack 8, which includes a secondary battery 1 provided in any of the above-described embodiments, and in an embodiment of the battery pack 8 of the present invention, the battery pack 8 includes a casing 81, a casing cover 82 and a plurality of secondary batteries 1, the plurality of secondary batteries 1 arranged inside the casing 81 and connected to each other in series, parallel, or a combination of series and parallel, and the casing cover 82 seals the casing 81 and provides protection for the plurality of secondary batteries 1. It should be noted that the battery pack 8 may include parts other than the secondary batteries 1 in an embodiment of the present invention, such as a battery pack thermal management system and a circuit board, and the battery pack 8 may be a battery module, a battery pack, or a power storage cabinet, etc., and these will not be explained in detail here.

[0053] Referring to Figure 8, the present invention further provides an electronic device 9, which includes the battery pack 8. A work unit 91 is electrically connected to the battery pack 8 to obtain power support. As an example, the electronic device 9 is a vehicle, which may be a gasoline car, a gas car, or a new energy car, and the new energy car may be, but is not limited to, a pure electric car, a hybrid car, or a range extender car. The work unit 91 is the vehicle body, and the battery pack 8 is installed at the bottom of the vehicle body to provide power support for the vehicle's movement or the operation of in-vehicle electrical components. However, in some other embodiments, the electronic device 9 may further be a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy, and a power tool. Spacecraft include airplanes, rockets, spacecraft, and spaceships. The work unit 91 may also be a unit component that receives power from the battery pack 8 to perform a corresponding task, such as a fan blade rotation unit or a vacuum cleaner suction work unit. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric boat toys, and electric airplane toys. Power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers. The embodiment of the present invention does not impose any special limitations on the electronic device 9 described above.

[0054] The foregoing are merely preferred embodiments of the present invention and do not limit it. Those skilled in the art will know that the present invention can be modified and altered in various ways. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection. [Industrial applicability]

[0055] The secondary battery, battery pack, and electronic device of the present invention can be applied in the field of battery technology. [Explanation of Symbols]

[0056] 1: Secondary battery 101: Casing 103: Side wall section 20: Electrode Assembly 10: Positive terminal assembly 11: Negative terminal assembly 105: End plate 107: Opening 30: Current collector 302:Protrusion 40: Regular Post 401: Upper folded section 403: Lower fold-over section 405: Bottom wall 407: End 409: Groove 411: Sealing pin 413: Stepped section 50: Insulation 502: Sealing ring 60: Weld marks 601: Welding trajectory 603: Primary trajectory line 605: Secondary trajectory line 607: Sealing Adhesive 70: Liquid injection hole 71: Sealing plug 8: Battery pack 81: Box body 82: Box cover 9:Electronic equipment 91: Work Unit

Claims

1. Electrode assembly and A casing that houses the electrode assembly and has an opening at one end, The end away from the electrode assembly extends out of the casing through the opening, and the end has a post with a groove provided therein. A sealing pin is fitted into the groove, and its outer end face and the end face of the post are welded together to form a weld mark. A secondary battery in which the welding trajectory of the weld mark is configured to extend entirely along a primary trajectory line, and a portion of it rotates or reciprocates along a secondary trajectory line to expand the width of the primary trajectory line.

2. The secondary battery according to claim 1, wherein the shape and dimensions of the outer circumference of the primary trajectory and the sealing pin correspond to each other.

3. The secondary battery according to claim 1, wherein the secondary trajectory line is a polyline, a wavy line, a helical line, a circular arc, or an elliptical arc.

4. The secondary battery according to claim 3, wherein the secondary trajectory line is an arc, and the radius R of the arc is 0.3-1.0 mm.

5. The secondary battery according to claim 3, wherein the parallel translation step length A of adjacent secondary trajectories is 0.2-1.0 mm.

6. The secondary battery according to claim 1, wherein the cross-section of the weld mark is rectangular or trapezoidal with a flat base.

7. The secondary battery according to claim 1, wherein S is the cross-sectional area of ​​the cross-section of the weld mark, W is the width of the weld mark, and D is the depth of the weld mark, and S / (W×D) > 0.

5.

8. The secondary battery according to claim 1, wherein the outer surface of the welded mark is recessed inward.

9. The liquid injection hole penetrates the bottom wall of the groove, The secondary battery according to claim 1, further comprising a sealing plug inserted into the liquid injection hole and blocking the liquid injection hole.

10. The secondary battery according to claim 9, wherein a sealing adhesive is applied to the surface of the welded area.

11. The secondary battery according to claim 10, wherein the top of the sealing adhesive is lower than the end face of the sealing pin away from the electrode assembly.

12. The secondary battery according to claim 10, wherein the sealing adhesive is an ultraviolet curing adhesive.

13. The secondary battery according to claim 1, wherein the primary trajectory is circular, and the diameter of the primary trajectory is equal to the outer diameter of the sealing pin.

14. A battery pack comprising a plurality of secondary batteries as described in any one of claims 1 to 13.

15. An electronic device comprising the battery pack described in claim 14.

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