JP2015170395A - cylindrical secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery excellent in reliability and capable of preventing corrosion at the bottom of a battery can, even if welding is performed from the outside of the battery can.SOLUTION: In a lithium ion secondary battery having a power generation element formed by winding a positive electrode, a negative electrode and a separator around the axis, a battery can for housing the power generation element, and a connection lead plate for joining the power generation element and battery can, the connection lead plate and battery can are joined via a welding fusion zone. The welding fusion zone is formed to be exposed from a plating layer provided on the surface of the battery can, and covered with a protective layer in a cylindrical secondary battery. Corrosion of the welding fusion zone can be prevented, by covering the welding fusion zone exposed from the plating layer with the protective layer.

Description

  The present invention relates to a cylindrical secondary battery used for in-vehicle applications, for example.

  Due to the emergence of environmental problems such as global warming, the reduction of carbon dioxide emissions from automobiles has been demanded. The development of hybrid vehicles used as a part is rapidly progressing.

  In recent years, lithium ion secondary batteries with high energy density have been developed as power sources for electric vehicles and hybrid vehicles. As a secondary battery for in-vehicle use, there is a cylindrical secondary battery in which an electrode group is wound into a cylindrical shape and stored in a cylindrical can.

  In Patent Document 1, as a method of manufacturing a cylindrical battery, a lead is inserted into a cylindrical case having a bottom portion, and a rod-shaped jig is pressed against the lead from the inside of the battery can. A method for welding leads is described.

JP 2004-158318 A

  The surface of the battery can case is coated with Ni or the like to prevent corrosion. However, when the battery can and the lead are welded by laser welding from the outside of the battery can as disclosed in Patent Document 1, the coating applied to the surface of the battery can is melted and the material of the battery can partially covers the surface. It will be exposed. The material of the battery can is easily corroded, and if the corrosion progresses, a corrosion hole may be generated at the bottom of the battery can and cause leakage of the electrolyte inside.

  An object of the present invention is to provide a secondary battery with excellent reliability that prevents corrosion of the bottom of the battery can even if welding is performed from the outside of the battery can.

  The features of the present invention for solving the above-described problems are as follows.

  A lithium ion secondary battery having a power generation element formed by winding a positive electrode, a negative electrode, and a separator around an axis, a battery can that houses the power generation element, and a connection lead plate that joins the power generation element and the battery can In the above, the connecting lead plate and the battery can are joined through a welded melt part, and the welded melt part is formed by being exposed from a plating layer provided on the surface of the battery can, and the exposed part of the welded melt part Is a cylindrical secondary battery covered with a protective layer. By covering the welded molten part exposed from the plating layer with a protective layer, corrosion of the welded molten part can be prevented.

  Even if welding is performed from the outside of the battery can, it is possible to provide a secondary battery with excellent reliability that prevents corrosion at the bottom of the battery can.

Cross section of cylindrical secondary battery Exploded perspective view of cylindrical secondary battery Exploded sectional perspective view of power generation element Conceptual diagram of assembly process of cylindrical secondary battery Conceptual diagram of connecting lead plate holding jig insertion process Conceptual diagram showing the state of laser welding and the welding marks produced by welding Conceptual diagram of spray spray device and protective layer formation Schematic view of cylindrical secondary battery 1 as seen from the bottom side

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  Hereinafter, embodiments of a power storage device according to the present invention will be described with reference to the drawings.

  FIG. 1 is an enlarged cross-sectional view showing an embodiment of a cylindrical secondary battery.

  The cylindrical secondary battery 1 includes a battery case 4 including a cylindrical battery can 2 having a bottom and an upper opening, and a hat-type battery lid 3 that seals the top of the battery can 2. Inside the battery container 4, constituent members for power generation described below are accommodated, and a non-aqueous electrolyte 5 is injected.

  In the cylindrical battery can 2, a groove 2 a protruding to the inside of the battery can 2 is formed on the opening 2 b provided on the upper end side.

  A power generation element 10 is arranged inside the battery can 2. The power generation element 10 includes an elongated cylindrical shaft core 15 having a hollow portion along the axial direction, and a positive electrode and a negative electrode wound around the shaft core 15. The hollow portion of the cylindrical shaft core 15 has a different cross-sectional shape in a plane perpendicular to the axial direction in the axial direction (vertical direction in the drawing). The cross-sectional shape above the hollow portion is a track shape formed by parallel portions and curved portions. The cross-sectional shape below the hollow portion is a circle having a diameter smaller than the width of the upper parallel portion. A cylindrical positive current collecting ring 27 is press-fitted into the upper hollow portion 15a. The positive electrode current collecting ring 27 includes a disc-shaped base portion 27a, a lower cylindrical portion 27b that protrudes toward the shaft core 15 at the inner peripheral portion of the base portion 27a, and press-fitted into the inner surface of the shaft core 15, and a battery at the outer peripheral edge. And an upper cylindrical portion 27c protruding toward the lid 3 side. The positive electrode current collecting ring 27 is fixed and supported on the upper end portion of the shaft core 15 by the lower cylindrical portion 27b.

  The positive electrode tab 16 of the positive electrode is welded to the upper cylindrical portion 27 c of the positive electrode current collecting ring 27. The positive electrode current collecting ring 27 is made of, for example, an aluminum-based metal, and the positive electrode tab 16 and the pressing member 28 of the positive electrode are welded to the outer periphery of the upper cylindrical portion 27c. A number of the positive electrode tabs 16 are brought into close contact with the outer periphery of the upper cylindrical portion 27c of the positive electrode current collecting ring 27, and a pressing member 28 is wound around the outer periphery of the positive electrode tab 16 in a ring shape and temporarily fixed. In this state, ultrasonic welding is performed. Are joined together.

  A step portion 15b having a small outer diameter is formed on the outer periphery of the lower end portion of the shaft core 15, and a negative electrode current collecting ring 21 is press-fitted and fixed to the step portion 15b. The negative electrode current collector ring 21 is formed of, for example, a copper-based metal, and an opening 21b that is press-fitted into the step portion 15b of the shaft core 15 is formed in a disk-shaped base portion 21a. An outer peripheral cylindrical portion 21c that protrudes toward is formed. An opening 21 d (see FIG. 2) for allowing the nonaqueous electrolytic solution 5 injected into the hollow shaft of the shaft core 15 to penetrate into the power generation element 10 is formed in the base portion 21 a of the negative electrode current collecting ring 21.

The negative electrode tab 17 of the negative electrode is joined to the outer peripheral cylindrical portion 21 c of the negative electrode current collecting ring 21.
The negative electrode tab 17 and the pressing member 22 of the negative electrode are welded to the outer periphery of the outer peripheral cylindrical portion 21 c of the negative electrode current collecting ring 21. A number of negative electrode tabs 17 are brought into close contact with the outer periphery of the outer peripheral cylindrical portion 21c of the negative electrode current collector plate 21, and the holding member 22 is wound around the outer periphery of the negative electrode tab 17 in a ring shape and temporarily fixed, and is welded in this state. . A connection lead plate 50 is joined to the base portion 21a of the negative electrode current collecting ring 21 by resistance welding, laser welding, or the like.

  The multiple positive electrode tabs 16 are welded to the positive electrode current collecting ring 27, and the multiple negative electrode tabs 17 are welded to the negative electrode current collecting ring 21, whereby the positive electrode current collecting ring 27, the negative electrode current collecting ring 21, and the power generation element 10 are formed. The power generation unit 20 is formed as a unit. A predetermined amount of non-aqueous electrolyte 5 is injected into the battery can 2. As an example of the nonaqueous electrolytic solution 5, a solution in which a lithium salt is dissolved in a carbonate-based solvent is raised.

  FIG. 2 is an exploded perspective view of the cylindrical secondary battery.

  A cylindrical positive current collecting ring 27 is press-fitted above the hollow portion of the cylindrical shaft core 15. The positive electrode current collector ring 27 is made of, for example, an aluminum-based metal. An opening 27d for releasing gas generated inside the battery is formed in the base 27a of the positive electrode current collecting ring 27. The opening 27 e formed in the positive electrode current collection ring 27 is for inserting a connection lead plate pressing jig 80 (described later in FIG. 5) for welding the connection lead plate 50 to the battery can 2. The electrode rod is inserted into the hollow portion of the shaft core 15 from the opening portion 27e formed in the positive electrode current collecting ring 27, and the connection lead plate 50 is pressed against the inner surface of the bottom portion 2c of the battery can 2 at the front end thereof. Laser welding or resistance welding is performed. Thus, the power generation unit 20 is fixed to the bottom 2c of the battery can 2. Further, the bottom surface of the battery can 2 connected to the negative electrode current collecting ring 21 acts as one output terminal, and the electric power stored in the power generation element 10 can be taken out from the battery can 2. A flexible connecting member 33 formed by laminating a plurality of aluminum foils is joined to the upper surface of the base portion 27a of the positive electrode current collecting ring 27 by welding one end thereof.

  A battery lid unit 30 is disposed on the upper cylindrical portion 27 c of the positive electrode current collecting ring 27. The battery lid unit 30 includes a ring-shaped insulating plate 34, a connecting plate 35 fitted in an opening 34a provided in the insulating plate 34, a diaphragm 37 welded to the connecting plate 35, and a diaphragm 37 by caulking and welding. The battery cover 3 is fixed.

  The insulating plate 34 has a ring shape made of an insulating resin material having a circular opening 34 a, and is placed on the upper cylindrical portion 27 c of the positive electrode current collecting ring 27.

  The insulating plate 34 has an opening 34a and a side 34b protruding downward. A connecting plate 35 is fitted in the opening 34 a of the insulating plate 34. The other end of the connection member 33 is welded and joined to the lower surface of the connection plate 35.

  The connection plate 35 is made of an aluminum-based metal and has a substantially dish shape that is substantially uniform except for the central portion and is bent to a slightly lower position on the central side. A projection 35a that is thin and formed in a dome shape is formed at the center of the connection plate 35, and a plurality of openings 35b are formed around the projection 35a. The opening 35b has a function of releasing gas generated inside the battery. The protrusion 35 a of the connection plate 35 is joined to the bottom surface of the center portion of the diaphragm 37 by resistance welding or friction stir welding. The diaphragm 37 is formed of an aluminum-based metal, and has a circular cut 37 a centering on the center portion of the diaphragm 37. The cut 37a is formed by crushing the upper surface side into a V shape by pressing and thinning the remainder. The diaphragm 37 is provided for ensuring the safety of the battery, and has a function of cleaving at the cut 37a and releasing the internal gas when the internal pressure of the battery increases.

  The diaphragm 37 fixes the peripheral edge of the battery lid 3 at the peripheral edge. As shown in FIG. 2, the diaphragm 37 initially has a side wall 37 b erected vertically at the peripheral portion toward the battery lid 3 side. The battery lid 3 is accommodated in the side wall 37b, and the side wall 37b is bent and fixed to the upper surface side of the battery lid 3 by caulking.

  The battery lid 3 is made of iron such as carbon steel, nickel plated on both front and back surfaces, a disc-shaped peripheral edge 3a that contacts the diaphragm 37, and a cylindrical portion 3b that protrudes upward from the peripheral edge 3a. Having a hat shape. An opening 3c is formed in the cylindrical portion 3b. The opening 3c is for releasing gas to the outside of the battery when the diaphragm 37 is cleaved by the gas pressure generated inside the battery. The battery lid 3 acts as one power output end, and the stored electric power can be taken out from the battery lid 3.

  A gasket 43 made of an insulating member that covers the caulked portion between the diaphragm 37 and the battery lid 3 is provided. The gasket 43 is made of rubber, and is not intended to be limited, but one example of a preferable material is a fluorine-based resin.

  The gasket 43 has a shape having an outer peripheral wall portion 43b that is formed to rise substantially vertically toward the upper direction at the peripheral edge of the ring-shaped base portion 43a. Then, the outer peripheral wall 43b of the gasket 43 is bent together with the battery can 2 by pressing or the like, and the diaphragm 37 and the battery lid 3 are crimped by the base 43a and the outer peripheral wall 43b so as to be pressed in the axial direction. Thereby, the battery lid unit 30 in which the battery lid 3, the diaphragm 37, the insulating plate 34 and the connection plate 35 are integrally formed is fixed to the battery can 2 via the gasket 43, and the insulating plate 34 is attached to the power generation unit 20. The power generation unit 20 is pressed against the bottom side of the battery can 2 in contact with the positive electrode current collecting ring 27.

  FIG. 3 is an exploded cross-sectional perspective view showing details of the structure of the power generation element 10.

  The power generating element 10 has a structure in which a positive electrode 11, a negative electrode 12, and first and second separators 13 and 14 are wound around an axis 15.

  The shaft core 15 is formed of an insulating material such as PP (polypropylene) and has a hollow cylindrical shape. A first separator 13, a negative electrode 12, a second separator 14, and a positive electrode 11 are sequentially laminated and wound on the shaft core 15. Inside the innermost negative electrode 12, the first separator 13 and the second separator 14 are wound several times (one turn in FIG. 3). The first separator 13 and the second separator 14 are formed of an insulating porous body.

  In the innermost circumference (axial core side), the beginning of the negative electrode 12 extends in the circumferential direction from the beginning of the positive electrode 11. Further, at the outermost periphery (battery can side), the negative electrode 12 is wound more outward than the positive electrode 11, and the end of the negative electrode 12 is extended in the circumferential direction from the end of the positive electrode 11. Yes. A second separator 14 is wound around the outer periphery of the outermost negative electrode 12. The end of the second separator 14 on the outermost periphery is stopped with an adhesive tape 19. In some cases, the first separator 13 and the second separator 14 are wound several times on the outermost periphery and then stopped by the adhesive tape 19.

  The positive electrode 11 is formed of an aluminum foil, has a long shape, and includes a positive electrode metal foil 11a and a positive electrode mixture layer 11b in which a positive electrode mixture is applied to both surfaces of the positive electrode metal foil 11a. The upper side edge extending in the longitudinal direction of the positive electrode metal foil 11a is a positive electrode foil exposed portion 11c where the positive electrode mixture is not applied and the positive electrode metal foil 11a is exposed. A large number of positive electrode tabs 16 protruding upward along the axis of the shaft core 15 are integrally formed at equal intervals on the positive electrode foil exposed portion 11c.

  The positive electrode mixture includes a positive electrode active material, a positive electrode conductive material, and a positive electrode binder. Examples of the positive electrode active material include lithium oxides such as cobalt, manganese, and nickel.

  Examples of the positive electrode binder include polyvinylidene fluoride (PVDF) and fluororubber.

  Examples of the method for applying the positive electrode mixture to the positive electrode metal foil 11a include a roll coating method and a slit die coating method. A slurry obtained by kneading a dispersion solution in a positive electrode mixture is uniformly applied to both surfaces of an aluminum foil having a thickness of 20 μm, dried, pressed, and cut. An example of the coating thickness of the positive electrode mixture is about 40 μm on one side. When the positive electrode metal foil 11a is cut, the positive electrode tab 16 is integrally formed. All the positive electrode tabs 16 have substantially the same length.

  The negative electrode 12 includes a negative electrode metal foil 12a formed of copper foil and having a long shape, and a negative electrode mixture layer 12b in which a negative electrode mixture is applied to both surfaces of the negative electrode metal foil 12a. The side edge on the lower side extending in the longitudinal direction of the negative electrode metal foil 12a is a negative electrode foil exposed portion 12c where the negative electrode mixture is not applied and the copper foil is exposed. A large number of negative electrode tabs 17 extending in the direction opposite to the positive electrode tab 16 along the axis of the shaft core 15 are integrally formed at equal intervals on the negative electrode foil exposed portion 12c.

  The negative electrode mixture includes a negative electrode active material, a negative electrode binder, and a thickener. An example of the negative electrode active material is graphite carbon.

  Examples of the method for applying the negative electrode mixture to the negative electrode metal foil 12a include a roll coating method and a slit die coating method.

  A slurry obtained by kneading a dispersion solvent in a negative electrode mixture is uniformly applied to both sides of a rolled copper foil having a thickness of 10 μm, dried, and then cut. An example of the coating thickness of the negative electrode mixture is about 40 μm on one side. When the negative electrode metal foil 12a is cut by pressing, the negative electrode tab 17 is integrally formed. All the negative electrode tabs 17 have substantially the same length.

  The widths of the first and second separators 13 and 14 are larger than the width of the negative electrode mixture layer 12 b of the negative electrode 12. The width of the negative electrode mixture layer 12 b of the negative electrode 12 is larger than the width of the positive electrode mixture layer 11 b of the positive electrode 11. The width and length of the negative electrode mixture layer 12b are made larger than the width and length of the positive electrode mixture layer 11b, and the entire region of the positive electrode mixture layer 11b is covered with the negative electrode mixture layer 12b. In the case of a lithium ion secondary battery, lithium, which is a positive electrode active material, is ionized, penetrates the separator, and is occluded by the negative electrode active material. In this case, if the negative electrode active material is not formed on the negative electrode side and the negative electrode metal foil 12a is exposed, lithium is deposited on the negative electrode metal foil 12a, causing an internal short circuit. As described above, by covering the entire region of the positive electrode mixture layer 11b with the negative electrode mixture layer 12b, it is possible to prevent such an internal short circuit due to lithium deposition.

  The first separator 13 and the second separator 14 are each formed of, for example, a polyethylene porous film having a thickness of 40 μm.

  In FIG. 4, the conceptual diagram of the assembly process of the cylindrical secondary battery 1 is shown.

  First, the positive electrode 11, the negative electrode 12, and the first and second separators 13 and 14 are wound around the shaft core 15, and the negative electrode current collecting ring 21 and the positive electrode current collecting ring 27 for taking out electric power are attached. The winding group assembly 25 is assembled (winding group assembly assembling step 51).

  Next, the wound group assembly 25 is inserted into the battery can 2 (insertion step 52 of the wound group assembly into the battery can). The battery can 2 into which the wound group assembly 25 has been inserted is set on the welding set base 100 (setting step 53), and a connection lead holding jig for fixing the connection lead plate and the battery can bottom is inserted (connection lead). Plate pressing jig insertion step 54). The connection lead plate and the bottom of the battery can 2 are connected by laser welding or resistance welding (welding process 55). Further, a resin film is provided on the welded and melted portion by spray irradiation. By covering the weld melt with the protective layer, corrosion of the weld melt exposed from the plating layer can be prevented.

  Details of the connecting lead plate pressing jig insertion step 54 and subsequent steps will be described below.

  FIG. 5 is a conceptual diagram of the connecting lead plate pressing jig insertion step.

  The battery can 2 into which the wound group assembly 25 is inserted is set on the welding set base 100, and the connection lead plate 50 and the battery can 2 are connected by laser welding from the outside of the can bottom of the battery can 2. In welding the connection lead plate 50 and the battery can 2, the connection lead plate 50 and the battery can 2 are brought into contact with each other, and the connection lead plate 50 and the battery can 2 are melt-mixed and joined by laser welding. At the time of welding, the connection lead plate 50 is pressed from above the inside of the battery by the connection lead plate pressing jig 80 so that no space is generated between the connection lead plate 50 and the battery can 2. The connecting lead plate holding jig 80 is inserted into the battery can 25 of the wound group assembly 25 from the opening 27 e formed in the positive electrode current collecting ring 27, and reaches the connecting lead plate 50 through the shaft core 15. The connection lead plate 50 fixed by the connection lead plate holding jig 80 and the bottom surface of the battery can 2 are welded and joined by laser irradiation from the outside of the battery.

  FIG. 6 is a conceptual diagram showing a state of laser welding and welding marks generated by welding.

  The connection lead plate 50 and the bottom surface of the battery can 2 are welded by a laser oscillator 601 from the battery external bottom surface side. By laser welding, the bottom surface of the battery can 2 and a part of the connection lead 50 are melted to form a weld melting portion 70. The weld melting part 70 is formed so as to be constricted from the surface of the battery can 2 toward the inside of the battery, and the bottom surface of the battery can 2 and the connection lead 50 are joined via the weld melting part 70. The plating layer 60 provided on the surface of the battery can 2 is melted during laser welding and mixed with the connection lead plate 50 and the battery can 2 to form a weld melting portion 70. As described above, the weld melting portion 70 is formed to be exposed from the plating layer 60 through the connection lead plate 50 and the battery can 2.

  The battery can 2 is made of a material such as iron or aluminum, and is not highly resistant to corrosion. Therefore, corrosion of the battery can can be prevented by providing a plating layer 60 such as nickel or chromium in advance on the surface of the battery can 2. However, the plating layer 60 is melted by laser welding from the outside of the battery can 2, and the material of the battery can 2 is exposed on the surface of the battery. When the material of the battery can 2 that is not highly resistant to corrosion is exposed to the battery surface, corrosion occurs from the weld melt 70, and when the corrosion proceeds, corrosion holes are generated at the bottom of the battery can and the electrolyte leaks inside. May cause liquid.

  The welding device 600 includes a laser oscillator 601, a control device 602, and a condensing system lens 603. The laser oscillator 601 emits a pulse laser beam having a predetermined intensity at a predetermined timing based on a control signal obtained from the control device 602. As the laser oscillator 601, for example, a general laser beam such as a YAG laser or a CO2 laser can be used. The welding apparatus 600 has a plurality of lens optical systems, and shapes the laser beam emitted from the laser oscillator 601 into a predetermined shape by adjusting the position of the lens. The control device 602 controls the intensity and timing of laser beam irradiation by the laser oscillator 601.

  The exposure of the weld fusion part 70 can also occur in welding methods other than laser welding. In the case of resistance welding, since welding marks are generated on the inner surface of the battery can 2 and the surface of the connection lead plate 50, the welded melted portion 70 is difficult to be exposed from the plating layer 60. However, when welding is performed to such an extent that the welding marks are exposed from the plating layer 60, the plating layer 60 may be melted and a material having low corrosion resistance may be exposed to the battery surface.

  FIG. 7 is a conceptual diagram of the protective layer 90 formed on the weld-melting portion 70 and the formation of the protective layer 90 by the spray spraying device 700.

  By providing the protective layer 90 on the welded melted portion 70 exposed from the plating layer 60, corrosion due to exposure of the material of the battery can 2 can be prevented. When the battery is completed, an electrolytic solution is inserted above the plating layer 60, the battery can 2, and the connection lead plate 50. In a battery, a material that is easily corroded by welding may be exposed to the outside. However, if the weld melted portion 70 at the bottom of the can corrodes, cracks may reach the electrolyte and the electrolyte may leak. It is preferable to provide such a protective layer 90 at the bottom. Further, since the welded melted portion 70 has a large exposed area, the effect of the protective layer 90 is great. The thickness of the protective layer 90 is desirably 10 μm or more from the viewpoint of preventing corrosion, and is 200 μm or less when a bus bar is attached.

  The material of the protective layer 90 is a thermosetting resin such as epoxy resin, phenol, melamine, urea, alkyd, polyurethane, polyimide, or thermoplastic such as polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polystyrene, or polyvinyl acetate. What has water resistance, such as resin, can be used. From the viewpoint of corrosion resistance, polyimide is particularly preferable.

  As a method for forming the protective layer 90, for example, a method of spraying resin into droplets by a technique such as a spray method or an ink jet method can be used. 7 includes a control device 702 and a spray nozzle 701. The injection amount is controlled by the control device 702, and a predetermined amount of epoxy resin material can be injected from the injection nozzle 701 to form the protective layer 90.

  FIG. 8 is a conceptual diagram of the cylindrical secondary battery 1 as viewed from the bottom side.

  The protective layer 90 is formed so as to cover the welded melted portion 70 exposed from the plating layer 60. By covering the weld melting portion 70, corrosion of the weld melting portion 70 can be prevented.

  A cleavage valve 801 for injecting gas inside the battery can be provided on the bottom side of the cylindrical secondary battery 1 as a battery protection function when the pressure in the battery rises. In the case where the battery has such a cleavage valve 801, the protective layer 90 is preferably provided at a place away from the cleavage valve 801. When the protective layer 90 is formed on the cleavage valve 801, the cleavage valve 801 may be difficult to function. In particular, as shown in FIG. 8, the battery can 2 is preferably provided inside the cleavage valve 801 on the bottom surface.

  A bus bar 800 that connects the batteries to each other can be provided on the bottom surface of the cylindrical secondary battery 1 by welding. The bus bar 800 and the battery can 2 are joined, for example, by spot welding at a plurality of locations. Since the welding point 802 between the bus bar 800 and the battery can 2 is provided in a place where the protective layer 90 is not provided from the viewpoint of conductivity, the protective layer 90 needs to be provided avoiding the place where the welding point 802 is formed. . In particular, as shown in FIG. 8, it is preferable that the protective layer 90 is provided in a range on the inner side of the location that becomes the welding point 802 on the bottom surface of the battery can 2. For example, a protective layer 90 may be provided in a circular shape so as to cover the weld melt portion 70 at the center of the bottom surface of the battery can, and the bus bar and the battery can 2 can be welded at four locations outside the protective layer 90.

  In the case where the cylindrical secondary battery 1 has both the cleavage valve 801 and the welding point 802, the protective layer 90 is preferably provided in a range inside the cleavage valve on the bottom surface of the battery can 2 and inside the welding point. The protective layer 90 is provided inside the bottom surface of the battery can so as to cover the weld melting portion 70 and to the inner side of the battery can bottom from the welding point 802 of the cleavage valve 801 and the bus bar, thereby preventing corrosion of the weld melting portion 70 without impairing the function of the cleavage valve 801. You can also install bus bars.

  As a method of adjusting the formation range of the protective layer 90, in addition to adjusting the spraying range of the spray spraying device, for example, spraying is performed in a state in which masking is provided outside the range in which the protective layer 90 is provided. The formation range of the layer 90 can be limited. Moreover, the range in which the protective layer 90 is formed can be adjusted by applying the protective layer 90 by a method other than spraying, such as coating or stamping.

DESCRIPTION OF SYMBOLS 1 Cylindrical secondary battery 2 Battery can 2a Groove 2b Opening part 3 Battery cover 3a Peripheral part 3b Cylindrical part 3c Opening part 4 Battery container 5 Nonaqueous electrolyte 10 Power generation element 11 Positive electrode 11a Positive electrode metal foil 11b Positive electrode mixture layer 11c Positive foil exposed portion 12 Negative electrode 12a Negative metal foil 12b Negative electrode mixture layer 12c Negative foil exposed portion 13 First separator 14 Second separator 15 Axle core 15a Upper hollow portion 15b Step portion 16 Positive electrode tab 17 Negative electrode tab 19 Adhesive Tape 20 Power generation unit 21 Negative electrode current collector plate 21a Base portion 21b Opening portion 21c Outer peripheral tube portion 21d Opening portion 22 Holding member 25 Winding group assembly 27 Positive electrode current collecting ring 27a Base portion 27b Lower tube portion 27c Upper tube portion 27d Opening portion 27e Opening portion 28 Holding member 30 Battery cover unit 33 Connection member 34 Insulating plate 34a Opening 3 b Side portion 35 Connection plate 35a Projection portion 35b Opening portion 37 Diaphragm 37a Notch 37b Side wall 43 Gasket 43a Base portion 43b Outer peripheral wall portion 50 Connection lead plate 60 Plating layer 70 Weld melting portion 80 Connection lead plate pressing jig 90 Protection layer 100 Welding set Table 600 Welding device 601 Laser oscillator 602 Control device 603 Condensing lens 700 Spray injection device 701 Injection nozzle 702 Control device 800 Busbar 801 Cleavage valve 802 Welding point

Claims (12)

A power generation element formed by winding a positive electrode, a negative electrode, and a separator around an axis;
A battery can containing the power generation element;
In a lithium ion secondary battery having a connection lead plate for joining the power generation element and the battery can,
The connection lead plate and the battery can are joined via a welded melt part,
The weld fusion part is formed by being exposed from a plating layer provided on the surface of the battery can,
The exposed portion of the weld melt is a cylindrical secondary battery covered with a protective layer. In claim 1,
The weld-melting portion is a cylindrical secondary battery that is a mixture in which the lead plate, the battery can, and the plating layer are mixed. In claim 1 or claim 2,
The material of the protective material is a cylindrical secondary containing at least one of epoxy resin, phenol, melamine, urea, alkyd, polyurethane, polyimide, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polystyrene, and polyvinyl acetate. battery. In any one of Claims 1 thru | or 3,
The battery can includes iron;
The plating layer is a cylindrical secondary battery containing nickel or chromium. In any one of Claim 1 thru | or 4,
The weld melting part is provided on the bottom surface of the battery can;
A cleavage valve is provided on the bottom surface,
The protective layer is a cylindrical secondary battery formed so as to avoid the cleavage valve. In any one of Claim 1 thru | or 4,
The weld melting part is provided on the bottom surface of the battery can;
A bus bar is provided on the bottom surface via a welding point,
The welded fusion part is a cylindrical secondary battery formed so as to avoid the welding point. In any one of Claim 1 thru | or 4,
The weld melting part is provided on the bottom surface of the battery can;
The bottom surface is provided with a cleavage valve and a bus bar through a welding point,
The weld fusion part is a cylindrical secondary battery formed so as to avoid the cleavage valve and the welding point. In claim 5,
The said protective layer is a cylindrical secondary battery provided inside the said cleavage valve of the said bottom face. In claim 6,
The protective layer is a cylindrical secondary battery provided inside the welding point on the bottom surface. In claim 7,
The protective layer is a cylindrical secondary battery provided on the inner side of the cleavage valve on the bottom surface and on the inner side of the welding point. Storing the power generation element in the battery can;
Welding the battery can and the connection lead plate by laser welding from the outside of the battery can;
The method of manufacturing a cylindrical secondary battery according to claim 1, further comprising: spraying the welded melt portion to provide the protective layer. In claim 11,
12. The method of manufacturing a cylindrical secondary battery according to claim 1, wherein the step of providing the protective layer masks the portions other than the portion where the protective layer is provided in advance and sprays the spray.