Secondary battery, battery pack, and electronic device

Abstract

The utility model provides a secondary battery, battery pack and electronic equipment, including electrode subassembly, shell, pole, sealing nail and solder mark, electrode subassembly is accommodated in the shell, one end of shell has opening part; the end part, far away from the electrode assembly, of the pole extends out of the shell through the opening part, and a groove is formed in the end part of the pole; the sealing nail is embedded into the groove in a matched manner; the end surface of the periphery of the sealing nail is connected with the end surface of the end part of the post terminal; the sealing nail is welded and fixed to the pole through a welding mark, the welding mark is located at the connecting position of the end face of the periphery of the sealing nail and the end face of the end of the pole, and the welding track of the welding mark is constructed in the mode that the whole welding mark moves along the first-level track line, and the welding mark partially rotates or reciprocates along the second-level track line to expand the width of the first-level track line. According to the technical scheme, the problem that the requirement for the fit clearance between the sealing nail and the positive pole is high when the sealing nail and the positive pole are welded can be solved.

Description

Technical Field

[0001] The utility model relates to the field of batteries, in particular to a secondary battery, a battery pack and an electronic device. Background Art

[0002] The sealing pin of a power battery is a critical component used in battery packaging. It is primarily used to prevent electrolyte leakage within the battery and prevent air and moisture from entering the battery, thereby protecting the battery's service life and safety. Laser welding is a robust and commonly used method for assembling sealing pins. For example, continuous laser welding can be used to butt-weld the sealing pin to other components. However, the molten pool formed by existing continuous laser welding is relatively narrow, requiring a high clearance for the weld. Summary of the Invention

[0003] Some embodiments of the present application provide a secondary battery, a battery pack, and an electronic device that can solve the problem of high requirements for the fitting clearance of the weld when welding sealing pins and other components.

[0004] The first aspect of the present application provides a secondary battery, including an electrode assembly, a shell, a pole, a sealing pin and a weld mark, wherein the electrode assembly is accommodated inside the shell, and one end of the shell has an opening; the end of the pole away from the electrode assembly extends out of the shell through the opening, and the end of the pole is provided with a groove; the sealing pin is matched and embedded in the groove, and the end face of the outer periphery of the sealing pin is welded to the end face of the end of the pole to form a weld mark, and the welding track of the weld mark is constructed as follows: the whole extends along the primary track line, and the part rotates or reciprocates along the secondary track line to expand the width of the primary track line.

[0005] Optionally, the primary trajectory line corresponds to the shape and size of the outer circumference of the sealing pin.

[0006] Optionally, the secondary trajectory line is a broken line, a wavy line, a spiral line, a circular arc or an elliptical arc.

[0007] Optionally, the secondary trajectory line is an arc, and the radius R of the arc is 0.3-1.0 mm.

[0008] Optionally, the translation step length A of adjacent secondary trajectory lines is 0.2-1.0 mm.

[0009] Optionally, the cross section of the weld mark is a square or trapezoid with a flat bottom surface.

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

[0011] Optionally, the outer surface of the weld mark is recessed inwardly.

[0012] Optionally, it further includes a liquid injection hole and a sealing plug, the liquid injection hole passes through the bottom wall of the groove, and the sealing plug is inserted into and seals the liquid injection hole.

[0013] Optionally, the surface of the weld print is coated with a sealant.

[0014] Optionally, the top of the sealant is lower than the end surface of the sealing pin away from the electrode assembly.

[0015] Optionally, the sealant is a UV-curable adhesive.

[0016] A second aspect of the present application provides a battery pack including a plurality of secondary batteries provided by the first aspect of the present application.

[0017] A third aspect of the present application provides an electronic device, which includes the battery pack provided by the second aspect of the present application.

[0018] By rotating or reciprocating the laser spot along the secondary trajectory line, the overall width of the formed molten pool can be expanded, that is, the width of the weld mark can be expanded, thereby overcoming the problem of high requirements for the fitting gap between the sealing pin and the positive electrode when welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the internal structure of the secondary battery provided in the first embodiment of the present application.

[0020] Figure 2 This is a cross-sectional view of a positive electrode terminal assembly of a secondary battery provided in the first embodiment of the present application.

[0021] Figure 3 It is a schematic diagram of the welding trajectory of the positive electrode post and the sealing pin of the secondary battery provided by the first embodiment of the present application.

[0022] Figure 4 It is a partially enlarged view of the welding track provided in the first embodiment of the present application.

[0023] Figure 5 It is a cross-sectional view of a positive electrode terminal assembly in the second embodiment of the present application.

[0024] Figure 6 is a schematic structural diagram of a battery pack provided in some embodiments of the present application.

[0025] Figure 7 It is a schematic structural diagram of an electronic device provided in some embodiments of the present application.

[0026] Figure markings: 1-secondary battery; 101-shell; 103-side wall; 20-electrode assembly; 10-positive terminal assembly; 11-negative terminal assembly; 105-end plate; 107-opening; 30-current collector; 302-projection; 40-positive electrode column; 401-upper flange; 403-lower flange; 405-bottom wall; 407-end; 409-groove; 411-sealing pin; 413-step; 50-insulating portion; 502-sealing ring; 60-weld mark; 601-weld track; 603-primary track line; 605-secondary track line; 607-sealant; 70-liquid injection hole; 71-sealing plug; 8-battery pack; 81-box; 82-box cover; 9-electronic equipment; 91-working part. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0028] <First embodiment>

[0029] Figure 1 Schematic diagram of the internal structure of the secondary battery 1 provided in the first embodiment of the present application. Figure 2 1 is a cross-sectional view of the positive terminal assembly 10 of the secondary battery 1 provided in the first embodiment of the present application. Figure 1 and Figure 2 In this embodiment, the secondary battery 1 is a cylindrical secondary battery 1 , that is, a battery cell encapsulated in a cylindrical casing 101 .

[0030] The housing 101 can be made of steel, stainless steel or nickel-plated steel. The sidewall portion 103 of the housing 101 is in the shape of a hollow cylinder, and the hollow portion is used to accommodate the electrode assembly 20. Figure 1 The upper end of the middle 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 to the casing 101; the positive terminal assembly 10 electrically connects the other electrode of the electrode assembly 20 to the positive electrode post 40 and electrically isolates the positive electrode post 40 from the casing 101.

[0031] Figure 1 The upper end of the middle shell 101, which forms one end of the positive terminal assembly 10, is as follows Figure 2As shown, at this end, the side wall portion 103 is integrally bent inward and extended to form a substantially flat end plate 105 . An opening 107 is reserved in the center of the end plate 105 , thereby forming the positive terminal assembly 10 at the opening 107 .

[0032] The thickness of the sidewall 103 of the housing 101 can be approximately 0.2-0.6 mm, and the thickness of the end plate 105 can be slightly greater than the thickness of the sidewall 103. For example, the end plate 105 can have a thickness of approximately 0.6-1.0 mm. Making the sidewall 103 thinner can increase the volume of the electrode assembly 20 that can be accommodated, thereby improving the energy density of the secondary battery 1. At the same time, the thickness of the sidewall 103 should not be too thin to increase the strength of the housing 101 and ensure the safety performance of the secondary battery 1. In some embodiments, a nickel plating layer can be formed on the surface of the housing 101 to increase the strength of the housing 101.

[0033] The electrode assembly 20 of the secondary battery 1 is housed in a cavity enclosed by the cylindrical sidewall portion 103 of the housing 101. The electrode assembly 20 includes a first electrode having a first polarity, a second electrode having a second polarity, and a separator disposed between the first electrode and the second electrode. The polarities of the first polarity and the second polarity are opposite. The electrode assembly 20 is a winding core structure, specifically formed by winding a stack formed by stacking the sheet-like first electrode, the separator, and the second electrode in sequence in one direction. The winding core structures known in the art can be applied to the secondary battery 1 provided in this application and will not be described in detail here.

[0034] As an example, the surface of the first electrode is coated with a positive electrode active material, and the surface of the second electrode is coated with a negative electrode active material. The ends of the electrode assembly 20 in the longitudinal direction are not coated with active material and are used for welding to the current collector 30 to electrically connect the positive electrode post 40 or the negative electrode post of the secondary battery 1 through 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 a silicon compound, and the separator can be, for example, a porous polymer film such as polyethylene, polypropylene, or ethylene / butylene copolymer.

[0035] The electrode assembly 20 may be immersed in an electrolyte (eg, an electrolyte), and the electrolyte may be injected into the electrode assembly 20 via an injection hole (eg, see the second embodiment, Figure 5 ) is injected into the hollow chamber of the housing 101. The location of the injection hole is not limited in this embodiment. The electrolyte can be a salt containing lithium ions, and the electrolyte can be dissolved in an organic solvent for use.

[0036] As the organic solvent, propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide (dimethylsulfoxide), acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethyl methyl carbonate (EMC), γ-butyrolactone or a mixture thereof can be selected.

[0037] refer to Figure 2 In the positive terminal assembly 10 of the secondary battery 1 provided in this embodiment, the positive electrode post 40 is generally cylindrical in shape, with an upper flange portion 401 formed by an outward flange at the upper end (end 407), a lower flange portion 403 formed by an outward flange at the lower end, and a flat bottom wall 405 at the center of the lower end. The shape and size of the upper flange portion 401 and the lower flange portion 403 match the shape and size of the insulating portion 50, so that the position of the positive electrode post 40 is fixed by the insulating portion 50. The insulating portion 50 is arranged between the positive electrode post 40 and the housing 101 to electrically isolate the positive electrode post 40 from the housing 101. The insulating portion 50 includes a sealing ring 502, the two sides of which are respectively clamped between the upper flange portion 401 and the end plate 105 to ensure the sealing effect there. The material of the sealing ring 502 can be EPDM rubber, fluorosilicone rubber, or fluororubber, etc., but is not limited thereto.

[0038] A groove 409 is provided in the middle of the upper end (i.e., the end 407) of the positive electrode column 40. The groove 409 is the hollow portion of the end 407 of the cylindrical positive electrode column 40. The sealing pin 411 is matched and embedded in the groove 409. The top surface of the outer periphery of the sealing pin 411 is flush with the top surface of the upper flange portion 401 of the positive electrode column 40 and is adjacent to each other. At the place where the top surface of the outer periphery of the sealing pin 411 and the top surface of the upper flange portion 401 meet, the sealing pin 411 and the upper flange portion 401 of the positive electrode column 40 are welded and fixed by butt welding. In this embodiment, the top surface of the outer periphery of the sealing pin 411 is flush with the top surface of the upper flange portion 401 as an example for explanation. In other embodiments, the two may not be flush with each other. As long as the outer periphery of the sealing pin 411 and the top inner edge of the upper flange portion 401 are adjacent to each other and meet the matching relationship, butt welding can be achieved here. This application does not exclude such a solution.

[0039] Specifically, the butt welding process between the sealing pin 411 and the upper flange portion 401 is completed using a continuous laser welding process. Specifically, after the secondary battery 1 is positioned and clamped, the laser is activated and the laser spot is irradiated at the location where the sealing pin 411 and the upper flange portion 401 meet. For example, the laser spot can be irradiated at the outer periphery of the sealing pin 411 and / or the inner edge of the upper flange portion 401 (i.e., near the location indicated by the weld mark 60 in the figure).

[0040] After continuous irradiation to melt the metal to form a molten pool, the laser spot is moved along the welding track 601. The welding track 601 of continuous laser welding is as follows: Figure 3 As shown, by making the laser spot along Figure 3 The welding track 601 in the figure moves to melt the metal to form a molten pool, which solidifies to form a weld mark 60. 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 periphery of the sealing pin 411 is circular, the primary trajectory line 603 corresponds to the shape and size of the outer periphery of the sealing pin 411 and is also circular. The diameter of the circular primary trajectory line 603 is substantially equal to the outer diameter of the sealing pin 411, and the position is also substantially located at the junction of the sealing pin 411 and the upper flange portion 401. In other embodiments, the primary trajectory line 603 can also be adjusted according to the shape and size of the outer periphery of the sealing pin 411 and is not limited to the circular shape in this embodiment.

[0041] In addition to the overall primary trajectory line 603 , a local secondary trajectory line 605 can be presented by magnifying a portion of the welding trajectory 601 . Figure 4 This is a partial enlarged view of the welding track 601 provided in this embodiment, refer to Figure 4It can be seen that in this embodiment, the secondary trajectory line 605 is in the shape of an arc with a circumferential angle greater than π and less than 2π. Specifically, multiple secondary trajectory lines 605 are connected to each other end to end to form a circular welding trajectory 601 that extends along the primary trajectory line 603 as a whole.

[0042] In this embodiment, compared with the situation in the prior art where the laser spot moves directly along the primary trajectory line 603, by making the laser spot rotate along the secondary trajectory line 605 while moving along the primary trajectory line 603, the rotation of the laser spot along the secondary trajectory line 605 can expand the width of the molten pool formed by the laser spot, so that the width of the molten pool is wider than the width of the molten pool formed by the single-point laser moving in a unidirectional manner along a circle.

[0043] In this embodiment, the arc radius R of the secondary trajectory line 605 is 0.3-1.0mm. If the arc radius is too large, it will be impossible to form a molten pool with a relatively flat bottom. If the radius is too small, the width of the molten pool cannot be effectively increased. Setting the arc radius between 0.3-1.0mm can effectively form a square or trapezoidal molten pool with a wider width and a flat bottom, overcoming the disadvantage of high requirements for the fitting clearance of the seam welding. In conjunction with the arc radius R, the translation step A of adjacent secondary trajectory lines 605 is 0.2-1.0mm. Setting a suitable translation step A helps to control the depth of the molten pool. A translation step A that is too close can easily cause the laser spot to repeatedly irradiate the same or similar positions, making the molten pool too deep or even causing explosion points; while a translation step A that is too far may cause the molten pool to be insufficiently deep or unable to form a continuous molten pool with a flat bottom.

[0044] by Figure 2 From the top to the bottom, the shape of the weld mark 60 formed by the welding sealing nail 411 and the positive electrode 40 is roughly a circle corresponding to the primary track line 603. Figure 2 Viewed from the sectional direction used herein, the cross section of the weld mark 60 is a square or trapezoid with a flat bottom surface.

[0045] In this embodiment, the cross-section of the weld mark 60 is a trapezoid with a flat bottom. Specifically, the cross-section of the weld mark 60 is wider at the top and narrower at the bottom, with a circular arc transition between the two side edges and the bottom. This cross-section is formed by the laser spot rotating along the secondary trajectory 605. Specifically, because the laser spot itself can form a molten pool that is narrower at the bottom and wider at the top, as the laser spot rotates along the secondary trajectory 605, the laser spot will form a truncated cone-shaped molten pool with a flat bottom and a wider top. Because the laser spot not only rotates along the secondary trajectory 605 but also moves in a circle along the primary trajectory 603, by properly setting the size and shape of the secondary trajectory 605 and the primary trajectory 603, a weld mark 60 with a trapezoidal shape and a rounded corner transition at the bottom of the cross-section (i.e., the normal plane perpendicular to the direction of movement of the laser spot) can be formed.

[0046] The heat generated during welding will cause the molten pool to expand, which will cause the weld mark to protrude from the welding surface. In some embodiments, the morphology of the weld mark formed can be adjusted by controlling the gap between the outer periphery of the sealing pin 411 and the top inner edge of the upper flange portion 401. A more preferred control method is to control the sealing pin 411 and the upper flange portion 401 to have a specified fitting gap. When the molten pool is formed by laser irradiation, the molten pool will fill the fitting gap, so that even if expansion occurs, the top of the entire molten pool is still lower than the top surface of the outer periphery of the sealing pin 411 (or compared to the top surface of the upper flange portion 401). In addition, the setting of the fitting gap should also ensure the welding strength. The outer surface of the weld mark 60 is concave inward.

[0047] The cross-sectional area of weld mark 60 is S, the width of weld mark 60 is W, and the depth is D. The three factors S, W, and D satisfy S / (W×D)>0.5. Due to the characteristics of laser penetration welding, the lower width of the resulting molten pool and the corresponding weld mark 60 is typically smaller than the upper width. By rotating or reciprocating the laser spot along the secondary trajectory 605, not only can the amount of metal melted be increased and the degree of gap filling be improved, but the uniformity of the upper and lower widths of the molten pool can also be increased, thereby improving weld strength and reliability.

[0048] In this embodiment, the secondary trajectory line 605 is described as an arc, but this does not constitute a limitation on its shape. In other embodiments, the secondary trajectory line 605 can also be in the form of a broken line, a wavy line, a spiral line, an elliptical arc, etc. Correspondingly, the movement of the laser spot along the secondary trajectory line 605 can also be a reciprocating movement along a broken line, a wavy line, etc., or a rotational motion along a spiral line, an elliptical arc, etc.

[0049] Continuous laser welding generally uses infrared lasers for seam welding, and smooth metal surfaces, such as the surface of the positive electrode post 40 made of aluminum, are prone to high reflectivity to the laser during welding, which leads to a decrease in the light-to-heat conversion efficiency and a large difference in welding quality. In this embodiment, the roughness of the top surface of the upper flange portion 401 of the positive electrode post 40 can be controlled by polishing the surface of the positive electrode post 40 or the sealing pin 411 or by selecting the material, and / or the roughness of the top surface of the outer periphery of the sealing pin 411 can be controlled. Specifically, in this embodiment, the roughness R1 of the top surface of the outer periphery of the sealing pin 411 and the roughness R2 of the top surface of the upper flange portion 401 are both controlled to be above 0.5 mm. By controlling the roughness of the above-mentioned positions, the absorption of the laser can be increased, the heating rate can be increased, and the consistency of the welding quality can be improved.

[0050] The secondary battery 1 provided in this embodiment expands the overall width of the formed molten pool by limiting the welding method of the end face of the outer periphery of the sealing pin 411 and the inner edge of the end 407 of the positive electrode column 40, and utilizes the rotation or reciprocation of the laser spot along the secondary trajectory line 605, thereby overcoming the problem in the prior art of requiring a high fitting clearance between the sealing pin 411 and the positive electrode column 40 when welding the two.

[0051] <Second embodiment>

[0052] A second embodiment of the present application provides a secondary battery 1, Figure 5 1 is a cross-sectional view of the positive terminal assembly 10 in the second embodiment. The main structural difference between the secondary battery 1 in the second embodiment and the first embodiment is that the secondary battery 1 in the second embodiment further includes a liquid injection hole 70 and a sealing plug 71 .

[0053] refer to Figure 5 The current collector 30 is made of a conductive metal material, such as aluminum or copper. The ends of the electrode assembly 20 are bent in the longitudinal direction and extend in a direction parallel to the current collector 30. The bent portion is bonded to the current collector 30 to complete the electrical connection between the current collector 30 and the electrode assembly 20. The surface of the current collector 30 facing away from the electrode assembly 20 is bonded to the positive electrode post 40 or the negative electrode post, thereby utilizing the current collector 30 to collect and conduct current.

[0054] The positive electrode column 40 is welded to the current collector 30 using the bottom wall 405. The groove 409 can expose the bottom wall 405. When the sealing nail 411 is not filled in the groove 409, the bottom wall 405 and the current collector 30 can be welded together using laser penetration welding.

[0055] In this embodiment, the injection hole 70 is provided at the center of the bottom wall 405 of the positive electrode column 40 and at the protrusion 302 at the center of the current collector 30. Specifically, the injection hole 70 extends through the bottom wall 405 and the protrusion 302, and the sizes and positions of the injection hole 70 on the bottom wall 405 and the injection hole 70 on the protrusion 302 correspond to each other. The manufacturer can inject electrolyte into the housing 101 of the secondary battery 1, particularly into the chamber accommodating the electrode assembly 20, through the injection hole 70.

[0056] After the liquid injection is completed, a sealing plug 71 can be further inserted into the liquid injection hole 70 to seal the liquid injection hole 70 and improve the sealing performance of the secondary battery 1. The sealing plug 71 can be a rubber plug. After the sealing plug 71 is used to seal the liquid injection hole 70, a sealing nail 411 is inserted into the groove 409 and welded to the positive electrode post 40.

[0057] In this embodiment, a step portion 413 is provided at the top of the groove 409, specifically at the inner edge of the upper flange portion 401. The surface of the step portion 413 abuts against the sealing pin 411, and is used to receive the sealing pin 411 and preliminarily limit the position of the sealing pin 411 during the welding process.

[0058] In some embodiments of the present invention, the surface of the weld mark 60 can be coated with a sealant 607 to further improve the sealing effect of the sealing pin 411. The sealant 607 should not be too thick, for example, the thickness is less than 0.5 mm. Specifically, the top of the sealant 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 sealant 607 is lower than the upper end face of the sealing pin 411, which can avoid the glue from subsequently interfering with the welding of the bus and the upper end face of the sealing pin 411. The sealant 607 is preferably a UV-curing glue. Using UV-curing glue as the sealant 607 will not absorb heat during laser cleaning, and has the advantages of fast curing speed, no volatility, high transparency and low VOC emissions.

[0059] See also Figure 6 The present application also provides a battery pack 8, which includes the secondary battery 1 provided in any of the above-mentioned embodiments. In one embodiment of the battery pack 8 of the present application, the battery pack 8 includes a housing 81, a housing cover 82, and a plurality of secondary batteries 1. The plurality of secondary batteries 1 are placed in the housing 81 and are connected in series or in parallel, or in a combination of series and parallel. The housing cover 82 is sealed on the housing 81 to protect the plurality of secondary batteries 1. It should be noted that, in addition to the secondary batteries 1 in the embodiments of the present application, the battery pack 8 may also include a battery pack thermal management system, a circuit board, and other components. The battery pack 8 may be a battery module, a battery pack, an energy storage cabinet, etc.; these will not be described in detail here.

[0060] Please refer to Figure 7, the present application also provides an electronic device 9, which includes the above-mentioned battery pack 8. The working part 91 is electrically connected to the battery pack 8 to obtain power support. As an example, the electronic device 9 is a vehicle, and the vehicle can be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc., but is not limited to this. The working part 91 is the vehicle body, and the battery pack 8 is arranged at the bottom of the vehicle body and provides power support for the driving of the vehicle or the operation of electrical components in the vehicle. However, in some other embodiments, the electronic device 9 can also be a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy and an electric tool, etc. Spacecraft include airplanes, rockets, space shuttles and spacecraft, etc.; the working part 91 can be a unit component that can obtain power from the battery pack 8 and perform corresponding work, such as a fan blade rotation unit, a vacuum cleaner dust collection unit, etc. Electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric boat toys, and electric airplane toys; electric tools include metal cutting tools, grinding tools, assembly tools, and railway tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers. The present application does not impose any particular restrictions on the electronic device 9.

[0061] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A secondary battery, characterized in that: include: electrode assembly; a shell, wherein the electrode assembly is accommodated in the shell, and one end of the shell has an opening; an electrode post, an end of the electrode post away from the electrode assembly extending out of the shell through the opening, the end of the electrode post being provided with a groove; A sealing pin is matched and embedded in the groove, and the end face of the outer periphery of the sealing pin is welded to the end face of the end of the pole to form a weld mark, and the welding track of the weld mark is constructed as follows: the whole extends along the primary track line, and the part rotates or reciprocates along the secondary track line to expand the width of the primary track line.

2. The secondary battery according to claim 1, wherein The primary trajectory line corresponds to the shape and size of the outer periphery of the sealing pin.

3. The secondary battery according to claim 1, wherein The secondary trajectory line is a broken line, a wavy line, a spiral 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 translation step length A of adjacent secondary trajectory lines is 0.2-1.0 mm.

6. The secondary battery according to claim 1, wherein The cross section of the weld mark is a square or trapezoid with a flat bottom surface.

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

5.

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

9. The secondary battery according to claim 1, wherein Also includes: a liquid injection hole, passing through the bottom wall of the groove; A sealing plug is inserted into and blocks the liquid injection hole.

10. The secondary battery according to claim 9, wherein The surface of the weld mark is coated with sealant.

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

12. The secondary battery according to claim 10, wherein The sealant is ultraviolet light curing adhesive.

13. A battery pack, characterized in that: This battery pack includes a plurality of secondary batteries, and the secondary battery is the secondary battery according to any one of claims 1 to 12.

14. An electronic device, characterized in that: The electronic device comprises the battery pack according to claim 13.

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