JP2016096014A - Secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery with a higher quality in welding between a member which constitutes a current path and a diaphragm which is disposed in the current path between an outside terminal and a wound electrode group in the battery container for shutting-off the current path by deforming due to an increase of internal pressure in a battery container.SOLUTION: A diaphragm 5 is disposed in a current path between an outside terminal 20A and an electrode group 40 in a battery container 10. The diaphragm 5 is deformed to shut-off the current path when the internal pressure increases in the battery container 10. The thickness in a part (peripheral part 5a, central part 5d) which is welded to a member constituting a current path (conductive plate 6, collector plate 30A) is thicker than the thickness in a deformation part (side wall part 5b, bottom wall part 5c) which is deformed by the internal pressure increases.SELECTED DRAWING: Figure 4A

Description

  The present invention relates to a secondary battery used for in-vehicle use.

  Conventionally, for example, a secondary battery has been used as an in-vehicle power source for supplying electric power to an electric motor or the like mounted on a vehicle such as an electric vehicle or a hybrid electric vehicle, or a power source for other devices. As such a secondary battery, a lithium ion secondary battery having a high energy density has attracted attention, and its research, development, and commercialization are rapidly progressing. In a sealed lithium ion secondary battery, for example, when gas is generated inside the battery due to overcharging or overheating, the internal pressure of the battery may increase.

  As described above, there is known a nonaqueous electrolyte secondary battery including a current interrupting mechanism that interrupts electrical connection between the external terminal and the electrode body inside the exterior body when the pressure inside the battery exterior body increases. (See Patent Document 1 below). In the non-aqueous electrolyte secondary battery described in Patent Document 1, as described in FIGS. 2, 4, 5 and paragraph 0050, etc., in the central part of the positive electrode current collector (16), a connection part is formed. A hole (16c) is formed.

  In the nonaqueous electrolyte secondary battery described in Patent Document 1, the inner wall portion of the convex portion (16p) formed in an annular shape at the edge of the connection portion forming hole of the positive electrode current collector and the reversing plate (33) The gap is laser welded at a plurality of locations to form a connection portion (16q). In patent document 1, it becomes easy to weld the side part of the hole for connection part formation, and the boundary part of an inversion board by forming a convex part in the edge of the hole for connection part formation, and the quality of a connection part is stabilized. , And.

JP 2013-157137 A

  In the nonaqueous electrolyte secondary battery described in Patent Document 1, a convex portion provided at an edge of a hole for forming a connection portion of a positive electrode current collector connected by laser welding and an inversion plate are provided as a positive electrode current collector. Are adjacent to each other in the thickness direction. When forming the connection portion by welding the inner wall portion of the convex portion of the positive electrode current collector to the reversal plate by laser welding, the laser light is usually irradiated from a direction substantially perpendicular to the positive electrode current collector.

  The inner wall part of the convex part of the positive electrode current collector irradiated with the laser beam melts and spreads like an avalanche on the reversing plate, thereby melting a part of the reversing plate and melting the inner wall part of the convex part The positive electrode current collector and the reversal plate are welded by being mixed with metal and integrated. However, in this case, since the reversal plate melts only a small part, the molten metal of the positive electrode current collector and the molten metal of the reversal plate are mixed and integrated with the entire weld metal part formed by welding. There are very few parts. Therefore, there is a risk that poor welding is likely to occur, such as a decrease in welding strength and a weld crack due to shrinkage when the molten metal solidifies.

  The present invention has been made in view of the above problems, and is arranged in a current path between an external terminal and a wound electrode group in a battery container, and is deformed by an increase in the internal pressure of the battery container to block the current path. It aims at providing the secondary battery which can improve the welding quality between a diaphragm and the member which comprises the electric current path.

  In order to achieve the above object, the secondary battery according to the present invention is disposed in a current path between the external terminal and the wound electrode group in the battery container, and is deformed by an increase in the internal pressure of the battery container to change the current path. A secondary battery having a diaphragm for blocking, wherein the diaphragm is thicker at a portion welded to a member constituting the current path than a deformed portion deformed by the increase in internal pressure. Features.

  According to the secondary battery of the present invention, the amount of molten metal that is melted and mixed at the time of welding the member constituting the current path between the external terminal and the wound electrode group in the battery container and the diaphragm is increased. The welding quality can be improved.

1 is a perspective view of a secondary battery according to Embodiment 1 of the present invention. The disassembled perspective view of the secondary battery shown in FIG. FIG. 3 is an exploded perspective view of the wound electrode group shown in FIG. 2. The expanded sectional view of the electric current interruption part shown in FIG. The expanded sectional view before welding of the center part of the diaphragm shown to FIG. 4A. The expanded sectional view after the welding of the center part of the diaphragm shown to FIG. 4A. The expanded sectional view before welding of the peripheral part of the diaphragm shown to FIG. 4A. The expanded sectional view after the welding of the peripheral part of the diaphragm shown to FIG. 4A. FIG. 4B is an exploded perspective view of the diaphragm shown in FIG. 4A and its peripheral members. The expanded sectional view equivalent to FIG. 4A of the secondary battery which concerns on Embodiment 2 of this invention. FIG. 6B is an enlarged cross-sectional view of the central portion of the diaphragm shown in FIG. 6A before welding. FIG. 6B is an enlarged cross-sectional view after welding of the central portion of the diaphragm shown in FIG. 6A.

  Hereinafter, embodiments of the secondary battery of the present invention will be described in detail with reference to the drawings.

[Embodiment 1]
FIG. 1 is a perspective view of a secondary battery 100 according to Embodiment 1 of the present invention. The secondary battery 100 of the present embodiment is, for example, a rectangular secondary battery including a flat box-shaped battery container 10. The battery container 10 includes a flat rectangular battery can 12 that houses a flat wound electrode group, and a rectangular battery lid 11 that seals the battery can 12. The battery container 10 is made of a metal material such as an aluminum alloy, for example.

  Positive and negative external terminals 20 </ b> A and 20 </ b> B are provided on both sides of the battery container 10 in the width direction, that is, in the longitudinal direction of the battery cover 11, on the upper surface of the battery cover 11 outside the battery container 10. The insulating member 2 is disposed between the external terminals 20A and 20B and the battery cover 11, and the external terminals 20A and 20B are electrically insulated from the battery cover 11. The positive external terminal 20A is made of, for example, aluminum or an aluminum alloy, and the negative external terminal 20B is made of, for example, copper or a copper alloy.

  The battery lid 11 is provided with a gas discharge valve 13 and a liquid injection port 14 between the positive and negative external terminals 20A and 20B. The gas discharge valve 13 is provided, for example, by thinning the battery lid 11 to form a groove 13a, and is cleaved to release the internal gas when the internal pressure of the battery container 10 exceeds a predetermined value. Thus, the internal pressure of the battery container 10 is reduced. The liquid injection port 14 is used for injecting an electrolytic solution into the battery container 10, and the liquid injection plug 15 is welded and sealed by laser welding, for example.

  FIG. 2 is an exploded perspective view of the secondary battery 100 shown in FIG. On both ends of the battery lid 11 in the longitudinal direction, positive and negative current collecting plates 30A and 30B are fixed to the lower surface of the battery lid 11 inside the battery container 10 via insulating members 3A and 3B. The current collecting plates 30A and 30B are respectively opposed to the lower surface of the battery lid 11 with the insulating members 3A and 3B interposed therebetween, and a base 31 disposed substantially in parallel with the battery lid 11, and a bottom surface 12c of the battery can 12 from the base 31. Terminal portion 32 extending toward the top. The positive current collecting plate 30A is made of, for example, aluminum or an aluminum alloy, and the negative current collecting plate 30B is made of, for example, copper or a copper alloy.

  The terminal portions 32 of the positive and negative current collecting plates 30 </ b> A and 30 </ b> B extend from the both sides of the base portion 31 in the thickness direction of the battery case 10 along the wide side surface 12 b of the maximum area of the battery can 12. It is formed in a plate shape extending toward 12c. The respective terminal portions 32 of the current collector plates 30A and 30B extend from the outer end portions of the respective base portions 31 in the longitudinal direction of the battery lid 11, that is, the width direction of the battery container 10, and are, for example, ultrasonic pressure welding or resistance welding. Are joined to current collector plate joints 41d and 42d at the ends of the electrode group 40, respectively.

  Thus, the positive current collecting plate 30A is disposed at one end of the electrode group 40 in the winding axis D direction, and is electrically connected to the positive electrode 41 (see FIG. 3) of the electrode group 40. The negative current collector 30B is disposed at the other end in the winding axis D direction and is electrically connected to the negative electrode 42 (see FIG. 3) of the electrode group. Further, the electrode group 40 has the current collector plate joints 41d and 42d joined to the respective terminal portions 32 of the current collector plates 30A and 30B, so that the current collector plates 30A and 30B and the insulating members 3A and 3B are interposed. It is fixed to the battery lid 11.

  The secondary battery 100 includes a current blocking unit 50 that blocks a current path between the positive external terminal 20 </ b> A and the electrode group 40 in the battery container 10. The electric current interruption part 50 has the diaphragm 5 as a main component. In the secondary battery 100 of the present embodiment, the current interrupting unit 50 is not provided between the negative external terminal 20B and the current collector plate 30B.

  The diaphragm 5 is disposed in a current path between the positive external terminal 20A and the electrode group 40 in the battery container 10, and electrically connects the positive external terminal 20A and the base of the positive current collecting plate 30A. Yes. As will be described in detail later, the diaphragm 5 is deformed by an increase in the internal pressure of the battery container 10 and blocks the current path between the positive external terminal 20 </ b> A and the electrode group 40.

  The external terminals 20A and 20B, the insulating member 2, the insulating members 3A and 3B, the current collecting plates 30A and 30B, the current interrupting portion 50, and the electrode group 40 are assembled to the battery lid 11 to constitute a lid assembly 60. The lid assembly 60 includes an insulating sheet (not shown) disposed between the electrode group 40 and the battery can 12 when the secondary battery 100 is manufactured, and the electrode assembly 40 is electrically insulated from each other. The battery is inserted into the opening 12a of the battery can 12 from the lower curved portion 40b. In the electrode group 40, the narrow side surfaces 12d and 12d of the battery can 12 are located on both sides in the winding axis D direction, and the winding axis D direction is substantially parallel to the bottom surface 12c and the wide side surface 12b of the battery can 12. Housed in a can 12.

  Thus, in the electrode group 40, one curved portion 40b faces the battery lid 11, the other curved portion 40b faces the bottom surface 12c of the battery can 12, and the flat portion 40a faces the wide side surface 12b. Become. Then, with the battery lid 11 closed by the battery lid 11, the battery lid 11 and the battery can can be joined by joining the entire circumference of the battery lid 11 to the opening 12 a of the battery can 12, for example, by laser welding. A battery container 10 composed of 12 is formed.

Thereafter, a non-aqueous electrolyte is injected into the battery container 10 through the liquid injection port 14 of the battery lid 11, and the liquid injection plug 15 is joined to the liquid injection port 14 by laser welding, for example, and sealed. The battery container 10 is sealed. Examples of the non-aqueous electrolyte injected into the battery container 10 include lithium hexafluorophosphate (LiPF ₆ ) in a mixed solution in which ethylene carbonate and dimethyl carbonate are mixed at a volume ratio of 1: 2. Can be used at a concentration of 1 mol / liter.

  FIG. 3 is an exploded perspective view in which a part of the electrode group 40 shown in FIG. 2 is developed. The electrode group 40 is a wound electrode group in which positive and negative electrodes 41 and 42 stacked with separators 43 and 44 interposed therebetween are wound around an axis parallel to the winding axis D and formed into a flat shape. The electrode group 40 includes a pair of flat flat portions 40 a disposed to face the wide side surface 12 b of the battery can 12, and a pair of semi-cylindrical shapes disposed to face the battery lid 11 and the bottom surface 12 c of the battery can 12. The curved portion 40b is provided. The separators 43 and 44 insulate the positive electrode 41 and the negative electrode 42, and the separator 44 is wound outside the negative electrode 42 wound around the outermost periphery. The separators 43 and 44 are made of, for example, a porous polyethylene resin.

  The positive electrode 41 includes a positive electrode foil 41a that is a positive electrode current collector, and a positive electrode mixture layer 41b made of a positive electrode active material mixture applied to both surfaces of the positive electrode foil 41a. One side of the positive electrode 41 in the width direction is a foil exposed portion 41c where the positive electrode mixture layer 41b is not formed and the positive foil 41a is exposed. The positive electrode 41 is wound around the winding axis D such that the foil exposed portion 41 c is disposed on the opposite side of the winding axis D direction of the foil exposed portion 42 c of the negative electrode 42.

  The positive electrode 41, for example, a positive electrode active material mixture kneaded by adding a conductive material, a binder and a dispersion solvent to the positive electrode active material, is applied to both surfaces of the positive electrode foil 41a except for one side in the width direction, It can be produced by drying, pressing and cutting. As the positive electrode foil 41a, for example, an aluminum foil with a thickness of about 20 μm can be used. The thickness of the positive electrode mixture layer 41b not including the thickness of the positive electrode foil 41a is, for example, about 90 μm.

As a material of the positive electrode active material mixture, for example, 100 parts by weight of lithium manganate (chemical formula LiMn ₂ O ₄ ) is used as the positive electrode active material, 10 parts by weight of flaky graphite as the conductive material, and 10% by weight as the binder. Part of polyvinylidene fluoride (hereinafter referred to as PVDF) and N-methylpyrrolidone (hereinafter referred to as NMP) can be used as a dispersion solvent. The positive electrode active material is not limited to the above-described lithium manganate. For example, another lithium manganate having a spinel crystal structure, or a lithium manganese composite oxide partially substituted or doped with a metal element may be used. Further, as the positive electrode active material, lithium cobaltate or lithium titanate having a layered crystal structure, and a lithium-metal composite oxide obtained by substituting or doping a part thereof with a metal element may be used.

  The negative electrode 42 includes a negative electrode foil 42a that is a negative electrode current collector, and a negative electrode mixture layer 42b made of a negative electrode active material mixture applied to both surfaces of the negative electrode foil 42a. One side in the width direction of the negative electrode 42 is a foil exposed portion 42c where the negative electrode mixture layer 42b is not formed and the negative foil 42a is exposed. The negative electrode 42 is wound around the winding axis D such that the foil exposed portion 42 c is arranged on the opposite side of the foil exposed portion 41 c of the positive electrode 41 in the winding axis D direction.

  For example, the negative electrode 42 is prepared by applying a negative electrode active material mixture kneaded by adding a binder and a dispersion solvent to the negative electrode active material on both sides of the negative electrode foil 42a except for one side in the width direction, drying, pressing, It can be produced by cutting. As the negative electrode foil 42a, for example, a copper foil having a thickness of about 10 μm can be used. The thickness of the negative electrode mixture layer 42b not including the thickness of the negative electrode foil 42a is, for example, about 70 μm.

As a material for the negative electrode active material mixture, for example, 100 parts by weight of amorphous carbon powder as the negative electrode active material, 10 parts by weight of PVDF as the binder, and NMP as the dispersion solvent can be used. The negative electrode active material is not limited to the above-mentioned amorphous carbon, and natural graphite capable of inserting and removing lithium ions, various artificial graphite materials, carbonaceous materials such as coke, and compounds such as Si and Sn (for example, , SiO, TiSi ₂ or the like), or a composite material thereof. The particle shape of the negative electrode active material is not particularly limited, and a particle shape such as a scale shape, a spherical shape, a fiber shape, or a lump shape can be appropriately selected.

  The binder used for the positive electrode and negative electrode mixture layers 41b and 42b is not limited to PVDF. Examples of the binder include polytetrafluoroethylene (PTFE), polyethylene, polystyrene, polybutadiene, butyl rubber, nitrile rubber, styrene butadiene rubber, polysulfide rubber, nitrocellulose, cyanoethyl cellulose, various latexes, acrylonitrile, and vinyl fluoride. Polymers such as vinylidene fluoride, propylene fluoride, chloroprene fluoride, and acrylic resins, and mixtures thereof may be used.

  In addition, the axial core when winding the positive electrode 41 and the negative electrode 42 with the separators 43 and 44 interposed therebetween is, for example, more flexible than the positive foil 41a, the negative foil 42a, and the separators 43 and 44. A roll of a high resin sheet can be used.

  In the direction of the winding axis D of the electrode group 40, the width of the negative electrode mixture layer 42 b of the negative electrode 42 is wider than the width of the positive electrode mixture layer 41 b of the positive electrode 41. A negative electrode 42 is wound around the innermost and outermost circumferences of the electrode group 40. Thus, the positive electrode mixture layer 41b is sandwiched between the negative electrode mixture layer 42b from the innermost periphery to the outermost periphery of the electrode group 40.

  The foil exposed portions 41c and 42c of the positive electrode 41 and the negative electrode 42 are respectively bundled by the flat surface portion 40a of the electrode group 40 to form the current collector plate joint portions 41d and 42d (see FIG. 2). The current collector plate joints 41d and 42d of the positive electrode 41 and the negative electrode 42 are joined to the terminal portions 32 of the positive and negative current collectors 30A and 30B, for example, by ultrasonic welding, resistance welding, or the like. . Accordingly, on the positive electrode side and the negative electrode side, the external terminals 20A and 20B are electrically connected to the positive and negative electrodes 41 and 42 constituting the electrode group 40 via the current collector plates 30A and 30B, respectively.

  In addition, in the winding axis D direction of the electrode group 40, the width of the separators 43 and 44 is wider than the width of the negative electrode mixture layer 42b, but the foil exposed portions 41c and 42c of the positive electrode 41 and the negative electrode 42 are separators, respectively. It protrudes outward in the width direction from the ends in the width direction of 43 and 44. Therefore, the separators 43 and 44 do not hinder when the foil exposed portions 41c and 42c are bundled and welded.

  4A is an enlarged cross-sectional view of the current interrupting unit 50 shown in FIG. FIG. 5 is an exploded perspective view of members around the current interrupting unit 50 shown in FIG. 4A. In FIG. 5, illustration of the electrode group 40 is omitted, and a state before the engaging portion 3f is formed on the protruding portion 3d of the insulating member 3A is shown.

  The external terminal 20A of the positive electrode includes a plate-like portion 21 that extends along the longitudinal direction of the battery lid 11 on the battery lid 11, a columnar connection portion 22 that passes through the battery lid 11 and is connected to the diaphragm 5, and a plate A through hole 23 that penetrates the shape portion 21 and the connection portion 22 and a bolt 24 are provided. Note that the through hole 23 may not be provided in the positive external terminal 20A.

  The plate-like portion 21 is provided with a through hole 21 a at the end in the longitudinal direction of the battery lid 11, that is, the inner side in the width direction of the battery container 10. Bolts 24 are inserted through the through holes 21a from the lower surface side of the plate-like portion 21 toward the upper surface side. The plate-like portion 21 is partially thickened by forming a groove portion 21b in the central portion in the width direction of the battery case 10 along the short side direction of the battery lid 11, that is, the thickness direction of the battery case 10. It is thinned.

  The connecting portion 22 is provided at an end portion of the plate-like portion 21 positioned on the outer side in the width direction of the battery container 10, and has a diameter-enlarged portion 22 a having an enlarged diameter toward the direction penetrating the battery lid 11. It has a reduced diameter portion 22b that has been reduced, and a caulking portion 22c that has been expanded by plastically deforming the tip of the reduced diameter portion 22b. The through hole 23 of the external terminal 20A passes through the external terminal 20A along the axial direction of the connecting portion 22 and opens at the upper surface of the plate-like portion 21 and the center portion of the caulking portion 22c.

  The insulating member 2 outside the battery case 10 is made of, for example, an insulating resin material, and includes an edge 2a that covers the peripheral side surface of the plate-like portion 21 of the external terminal 20A, the bottom surface of the plate-like portion 21, and the battery lid 11. And a bottom portion 2b that is in close contact with the upper surface. The edge 2a of the insulating member 2 covers the peripheral side surface of the plate-like portion 21, thereby preventing a short circuit between the plate-like portion 21 and the battery lid 11 or other member. The bottom portion 2b of the insulating member 2 is disposed between the plate-like portion 21 of the external terminal 20A and the battery lid 11, and electrically insulates them. The bottom portion 2b of the insulating member 2 is provided with a convex portion 2c that engages with a concave portion 11a provided on the upper surface of the battery lid 11, and an opening portion 2d through which the connecting portion 22 of the external terminal 20A is inserted. The head of the bolt 24 is accommodated inside the convex portion 2c.

  The gasket 4 is made of, for example, an insulating resin material, and includes a cylindrical tubular portion 4a and a flange portion 4b provided at an end portion on the outer side of the battery container 10 in the axial direction of the tubular portion 4a. Have. The cylindrical portion 4a of the gasket 4 is inserted into the through hole 11b of the battery lid 11 with the connection portion 22 of the external terminal 20A inserted inside, and the connection portion 22 of the external terminal 20A and the through hole of the battery lid 11 are inserted. It arrange | positions between the inner peripheral surfaces of 11b, and electrically insulates the connection part 22 and the battery cover 11. FIG. The flange portion 4b of the gasket 4 is disposed in the opening 2d of the insulating member 2, engages with a step portion 11c provided around the through hole 11b of the battery lid 11, and the step portion 11c and the external terminal 20A are engaged with each other. It is compressed between the bottom surface of the plate-like portion 21. Thereby, the gasket 4 is in close contact with the concave stepped portion 11 c and the bottom surface of the plate-like portion 21, and seals the through hole 11 b of the battery lid 11.

  The insulating member 3A inside the battery container 10 is made of, for example, an insulating resin material, and extends in the width direction of the battery container 10, that is, the winding axis D direction of the electrode group 40, and the main body part 3a. And a through hole 3b provided at the center in the extending direction. The main body 3a of the insulating member 3A has a recess 3c for disposing the conductive plate 6 and the diaphragm 5, and a plurality of protrusions 3d for fixing the base 31 of the current collector plate 30A. An engaging recess 3e that is formed in a planar shape corresponding to the planar shape of the conductive plate 6 and engages the conductive plate 6 is provided on the surface of the concave portion 3c of the insulating member 3A that faces the inside of the battery case 10. .

  The plurality of protrusions 3d of the insulating member 3A protrude in the direction penetrating the base 31 of the current collector plate 30A, that is, in the thickness direction of the base 31 and are passed through the fixing holes 33 provided in the base 31 of the current collector 30A. ing. The insulating member 3A including the protruding portion 3d is formed of a thermoplastic resin material. The tip of the protrusion 3d penetrates the fixing hole 33 of the base 31 of the current collector plate 30A, and is thermally welded to the base 31, for example. Thereby, the tip of the protrusion 3d is expanded in diameter to form the engaging portion 3f, and the base 31 of the current collector plate 30A is fixed to the insulating member 3A. In addition, the fixing method of the base 31 of the current collector plate 30A to the insulating member 3A is not limited to the thermal welding of the protrusion 3d. If further strong bonding is required, bonding with screws or rivets or bonding with an adhesive can be employed.

  The electric current interruption part 50 accommodated in the battery container 10 is provided with the diaphragm 5 as a main component. Further, the current interrupting part 50 of the present embodiment includes a conductive plate 6 welded to the peripheral edge part 5 a of the diaphragm 5. Diaphragm 5 and conductive plate 6 are made of a conductive metal material, for example, aluminum or aluminum alloy similar to positive electrode external terminal 20A and current collector plate 30A.

  The diaphragm 5 is disposed between the battery lid 11 of the battery container 10 and the base 31 of the current collecting plate 30A and between the conductive plate 6 and the base 31 of the current collecting plate 30A. The diaphragm 5 of the present embodiment has a circular planar shape in a plan view perpendicular to the battery lid 11, and has a convex shape that bulges toward the base portion 31 of the current collector plate 30 </ b> A, and is perpendicular to the battery lid 11. It is formed in a bowl shape having a depth in the direction. The shape of the diaphragm 5 is not limited to the circular planar shape and the convex shape as in the present embodiment. For example, the diaphragm 5 may have a planar shape such as an elliptical shape or a racetrack shape, in which the dimension in the longitudinal direction of the battery lid 11 is larger than the dimension in the short direction of the battery lid 11. May be.

  The conductive plate 6 is a plate-like member having a planar shape corresponding to the diaphragm 5, and includes a through hole 6 a through which the connecting portion 22 of the external terminal 20 </ b> A is inserted, and an annular groove 6 b that engages the peripheral portion 5 a of the diaphragm 5. ,have.

  The tip of the connection portion 22 of the external terminal 20A is expanded in diameter on the lower surface 6c side of the conductive plate 6 facing the base portion 31 of the current collector plate 30A and is plastically deformed, and a caulking portion 22c is formed at the tip of the connection portion 22. Yes. As a result, the caulking portion 22c and the conductive plate 6 are brought into contact to electrically connect the external terminal 20A and the conductive plate 6, and the external terminal 20A, the insulating member 2, the gasket 4, the insulating member 3A, and the conductive plate. 6 is fixed to the battery lid 11. In this state, the external terminal 20A and the conductive plate 6 are electrically insulated from the battery lid 11 by the insulating member 2, the gasket 4, and the insulating member 3A.

  The peripheral edge 5a of the diaphragm 5 is bent along a direction parallel to the battery lid 11, and engages with an annular groove 6b formed on the surface of the conductive plate 6 facing the inside of the battery container 10 to engage with the annular groove 6b. It contacts the bottom and is welded to the conductive plate 6 over the entire circumference, for example, by laser welding. Thereby, the space between the diaphragm 5 and the conductive plate 6 is isolated from the internal space of the battery case 10 and communicates with the external space of the battery case 10 through the through hole 23 of the external terminal 20A. The diaphragm 5 has a peripheral edge portion 5 a connected to the connection portion 22 of the external terminal 20 </ b> A via the conductive plate 6.

  The side wall 5b adjacent to the inside of the peripheral edge 5a of the diaphragm 5 extends from the peripheral edge 5a along the direction perpendicular to the battery lid 11 toward the bottom surface 12c of the battery can 12 and is perpendicular to the battery lid 11. The angle is smaller than the angle with respect to the direction parallel to the battery lid 11. The bottom wall 5c adjacent to the inside of the side wall 5b of the diaphragm 5 extends toward the center of the diaphragm 5 along a direction parallel to the battery lid 11, and an angle with respect to the direction perpendicular to the battery lid 11 is the battery lid. 11 is larger than an angle with respect to a direction parallel to 11. The bottom wall 5c has a convex curved surface facing the base 31 of the current collector plate 30A. In the present embodiment, the side wall 5b and the bottom wall 5c are deformed portions of the diaphragm 5 that are deformed by receiving the internal pressure when the internal pressure of the battery case 10 is increased. In this embodiment, the thickness of the side wall part 5b and the bottom wall part 5c of the diaphragm 5 is thinner than the thickness of the peripheral part 5a.

  The central portion 5d of the diaphragm 5 is a flat portion that is provided at the bottom of the bottom wall portion 5c and contacts the base 31 of the current collector plate 30A. The thickness of the central portion 5d of the diaphragm 5 is thicker than the thickness of the side wall portion 5b and the bottom wall portion 5c which are deformed portions. The center part 5d of the diaphragm 5 has a surface opposite to the base part 31 of the current collector plate 30A that is continuous with the bottom wall part 5c, which is a deformed part, without a step, and a surface that faces the base part 31 of the current collector plate 30A has a bottom surface. There is a step between the wall portion 5c and it protrudes toward the base portion 31 of the current collector plate 30A. The central portion 5d of the diaphragm 5 has a surface facing the base portion 31 of the current collecting plate 30A that is continuous with the bottom wall portion 5c without a step, and a surface opposite to the base portion 31 of the current collecting plate 30A is the bottom wall portion 5c. You may have a level | step difference between. Further, the center portion 5d of the diaphragm 5 may have a step between the surface facing the base portion 31 of the current collector plate 30A and the surface opposite to the base portion 31 between the bottom wall portion 5c.

  The base 31 of the current collector plate 30 </ b> A has a recess 31 d formed on the upper surface facing the diaphragm 5 and facing outward from the battery container 10. Although the formation method of the recessed part 31d is not specifically limited, For example, it can form by press work. The concave portion 31d has an inclined surface that follows the convex shape of the bottom wall portion 5c of the diaphragm 5, and a flat bottom portion 31e that comes into contact with the central portion 5d of the diaphragm 5. The bottom 31 e of the recess 31 d is in contact with the bottom surface of the central portion 5 d of the diaphragm 5.

  As shown in FIG. 5, an annular groove 31f is formed at the center of the bottom 31e of the recess 31d provided on the surface of the base 31 of the current collector 30A that faces the diaphragm 5, thereby forming the base of the current collector 30A. An annular thin portion 31h is provided. The annular thin portion 31h has an arbitrary annular shape such as a circle, an ellipse, or a field track. The annular thin portion 31 h is a portion that is thinner than the other portions of the base 31 of the current collector plate 30 </ b> A and breaks when the diaphragm 5 is deformed by an increase in the internal pressure of the battery container 10.

  As described above, the secondary battery 100 of the present embodiment includes the conductive plate 6, the diaphragm 5, and the current collector plate 30 </ b> A in the current path between the positive external terminal 20 </ b> A and the electrode group 40 in the battery container 10. The current interrupting section 50 that is arranged and mainly interrupts the current path is constituted by the diaphragm 5 and the current collecting plate 30A.

  4B and 4C are enlarged sectional views before and after welding of the central portion 5d of the diaphragm 5 shown in FIG. 4A.

  The center portion 5d of the diaphragm 5 can be welded to the inside of the annular thin portion 31h provided on the base portion 31 of the current collector plate 30A, for example, by the following procedure. First, the central portion 5d of the diaphragm 5 protruding toward the base portion 31 of the current collector plate 30A is brought into contact with the inside and the outside of the annular thin portion 31h of the current collector plate 30A, so that the thickness of the base portion 31 and the thickness of the current collector plate 30A is increased. Overlapping in the direction.

  Next, a high energy beam such as a laser or an electron beam is applied to the inside of the annular thin portion 31h of the current collecting plate 30A from the surface opposite to the surface of the base 31 of the current collecting plate 30A where the diaphragm 5 contacts. Irradiate. Thereby, the base 31 of the current collecting plate 30A and a part of the central portion 5d of the diaphragm 5 are melted, and the inside of the annular thin portion 31h of the current collecting plate 30A and the central portion 5d of the diaphragm 5 are overlap-welded. It should be noted that the number of locations where the current collector plate 30A and the diaphragm 5 are overlap-welded may be one or a plurality of locations.

  As described above, the central portion 5d of the diaphragm 5 is overlapped and welded inside the annular thin portion 31h of the current collecting plate 30A, and a welded portion W1 is formed between the diaphragm 5 and the current collecting plate 30A. The outer side of the annular thin portion 31h of the current collector plate 30A and the central portion 5d of the diaphragm 5 are in contact with each other, but are not welded.

  Here, the thickness of the central portion 5d of the diaphragm 5 is thicker than the thickness of the side wall portion 5b and the bottom wall portion 5c which are deformed portions. Therefore, compared to the case where the thickness of the central portion 5d is equal to or less than the thickness of the side wall portion 5b and the bottom wall portion 5c, the weld depth of the welded portion W1 is increased and the amount of molten metal during welding is increased. Can be increased. Thereby, the part which the molten metal of the diaphragm 5 and the molten metal of the current collector plate 30A are mixed and integrated is increased, and the weld quality of the welded portion W1 between the diaphragm 5 and the current collector plate 30A is improved. Can do.

  More specifically, the weld depth of the welded portion W1 is increased, and the molten metal of the diaphragm 5 and the molten metal of the current collecting plate 30A are mixed and integrated to increase the welded portion W1. It is possible to prevent the occurrence of poor welding and improve the strength of the welded portion W1. Further, by increasing the welding depth of the welded portion W1, the cross-sectional area of the welded portion W1 along the interface between the current collector plate 30A and the diaphragm 5 can be increased, and the strength of each welded portion W1 can be improved. .

  On the other hand, when the thickness of the central portion 5d of the diaphragm 5 is equal to or less than the thickness of the side wall portion 5b and the bottom wall portion 5c which are deformed portions, high energy beam welding such as laser welding or electron beam welding is used. In order to prevent the diaphragm 5 from opening a hole, the welded portion W1 having a sufficient welding depth cannot be formed, and the molten metal of the diaphragm 5 and the molten metal of the current collector plate 30A are mixed in the welded portion W1. As a result, the number of integrated parts decreases, and the weld quality and weld strength of the weld W1 may be reduced.

  4D and 4E are enlarged sectional views before and after welding of the peripheral edge portion 5a of the diaphragm 5 shown in FIG. 4A.

  The peripheral edge 5a of the diaphragm 5 can be welded to the conductive plate 6 by the following procedure, for example. First, the peripheral portion 5a of the diaphragm 5 is engaged with an annular groove 6b formed on the surface of the conductive plate 6 facing the base portion 31 of the current collecting plate 30A, and the outer peripheral end surface of the peripheral portion 5a and the inner wall of the annular groove 6b. And face each other.

  Next, for example, by irradiating a high energy beam such as a laser or an electron beam, the outer peripheral end surface of the peripheral portion 5 a of the diaphragm 5 and the inner wall of the annular groove 6 b of the conductive plate 6 are opposed to each other. Then, it is melted over the entire circumference of the annular groove 6b. Thereby, the peripheral edge 5a of the diaphragm 5 and the inner wall of the annular groove 6b of the conductive plate 6 are butt welded. As described above, the outer peripheral end surface of the peripheral edge portion 5 a of the diaphragm 5 and the inner wall of the annular groove 6 b of the conductive plate 6 are butt welded, and a welded portion W <b> 2 is formed between the diaphragm 5 and the conductive plate 6.

  Here, the thickness of the peripheral portion 5a of the diaphragm 5 is thicker than the thickness of the side wall portion 5b and the bottom wall portion 5c, which are deformed portions. Therefore, compared with the case where the thickness of the peripheral part 5a of the diaphragm 5 is equal to or less than the thickness of the side wall part 5b and the bottom wall part 5c, the amount of molten metal at the time of welding can be increased. Thereby, the part which the molten metal of the diaphragm 5 and the molten metal of the electrically conductive plate 6 mixed and integrated can be increased, and the welding quality of the welding part W2 between the diaphragm 5 and the electrically conductive plate 6 can be improved. .

  In addition, since the amount of molten metal during welding increases, there is a gap between the outer peripheral end surface of the peripheral portion 5a of the diaphragm 5 and the inner wall of the annular groove 6b of the conductive plate 6 between them. Even if it occurs, the gap can be sufficiently filled with molten metal. Therefore, it is possible to prevent the occurrence of poor welding such as weld cracking due to shrinkage when the molten metal solidifies, and to improve the weld quality and weld strength of the welded portion W2 between the diaphragm 5 and the conductive plate 6.

  On the other hand, when the thickness of the peripheral portion 5a of the diaphragm 5 is equal to or less than the thickness of the side wall portion 5b and the bottom wall portion 5c, which are deformed portions, for example, the outer peripheral end surface of the peripheral portion 5a of the diaphragm 5; When a gap is formed between the inner wall of the annular groove 6b of the conductive plate 6, it is conceivable that the amount of molten metal for filling the gap is insufficient. In this case, welding defects such as weld cracks due to shrinkage when the molten metal solidifies may occur, and the weld quality and weld strength of the welded portion W2 between the diaphragm 5 and the conductive plate 6 may be reduced.

  As shown in FIGS. 1 and 2, the secondary battery 100 of the present embodiment does not include the current interrupting unit 50 between the negative external terminal 20 </ b> B and the current collector plate 30 </ b> B. The negative external terminal 20B has the same connecting portion 22 as the positive external terminal 20A shown in FIG. 4A, but does not have the through hole 23. The connecting portion 22 of the negative external terminal 20B penetrates the through hole of the base 31 of the current collector plate 30B instead of the conductive plate 6, and a caulking portion 22c similar to the positive external terminal 20A is formed at the tip.

  Thereby, the negative external terminal 20B is electrically connected to the base 31 of the current collector plate 30B, and the external terminal 20B and the current collector plate 30B are connected to the battery lid 11 via the insulating members 2 and 3B and the gasket 4. It is fixed. In this state, similarly to the positive electrode side shown in FIG. 4A, the negative external terminal 20 </ b> B and the current collector plate 30 </ b> B are electrically insulated from the battery lid 11 by the insulating members 2 and 3 </ b> B and the gasket 4.

  With such a configuration, the secondary battery 100 supplies the power supplied from a power supply source such as a generator to the positive and negative external terminals 20A and 20B, the current interrupting unit 50, and the positive and negative current collecting plates 30A, in a steady state. It accumulates in the electrode group 40 accommodated inside the battery container 10 via 30B. Further, the electric power stored in the electrode group 40 is supplied to an external device such as an electric motor via the positive and negative current collecting plates 30A and 30B, the current interrupting unit 50, and the positive and negative external terminals 20A and 20B.

  In addition, in the secondary battery 100, for example, when an abnormality such as overcharge or overheating occurs, gas may be generated inside the battery container 10 and the internal pressure may increase. In such a case, when the internal pressure of the battery container 10 rises to a predetermined pressure, the current interrupting unit 50 disposed in the current path between the positive external terminal 20A and the electrode group 40 interrupts the current path.

  Specifically, in the diaphragm 5 constituting the current interrupting part 50, the side wall part 5 b and the bottom wall part 5 c which are deformation parts are deformed toward the battery lid 11 by the pressure of the gas in the battery container 10. Since the central portion 5d of the diaphragm 5 is welded to the inside of the annular thin portion 31h provided on the current collector plate 30A, the annular portion provided around the welded portion W1 between the diaphragm 5 and the current collector plate 30A. Stress acts on the thin portion 31h. Thereby, the annular thin portion 31h is broken, the connection between the diaphragm 5 and the current collector plate 30A is cut, and the current path between the positive external terminal 20A and the electrode group 40 is cut off. Thereafter, when the pressure inside the battery container 10 further increases and exceeds a predetermined value, the gas discharge valve 13 is cleaved to release the gas inside the battery container 10 to the outside, thereby reducing the internal pressure of the battery container 10.

  Thus, when an abnormality occurs in the secondary battery 100 and the internal pressure of the battery container 10 rises, the current path between the positive external terminal 20A and the electrode group 40 is reliably interrupted with the set pressure. For this purpose, the welding quality and welding strength of the welded portions W1 and W2 between the diaphragm 5 and the members constituting the current path, such as the conductive plate 6 and the current collecting plate 30A, are important.

  For example, in the conventional non-aqueous electrolyte secondary battery described in Patent Document 1, a convex portion provided at the edge of a hole for forming a connection portion of a positive electrode current collector and an inversion plate are provided as a positive electrode current collector. Are adjacent to each other in the thickness direction, but do not face each other in the direction along the positive electrode current collector. Therefore, for example, when performing laser welding, the reverse plate is difficult to melt during welding at the portion covered with the convex portion of the positive electrode current collector, and the convex portion melts and flows like an avalanche on the reverse plate. Only the expanded part and a part of the reversing plate melted in contact with the part are mixed and integrated and welded.

  In this case, the parts welded by melting and integrating both members to be welded are less than the total melted meat, resulting in poor quality such as weld strength insufficiency and weld cracking due to shrinkage after solidification of the melted part. Is likely to occur. That is, there is a risk that the connection portion formed by welding may have insufficient strength, cracks, or the like, and the quality of the connection portion may be reduced. In this case, the connection portion may be broken by vibrations or inertial forces acting on the nonaqueous electrolyte secondary battery in a steady state. In addition, when an abnormality occurs, the strength of the connecting portion is not sufficient, and the current interrupt mechanism may not operate correctly with a preset pressure.

  On the other hand, in the diaphragm 5 of the secondary battery 100 of the present embodiment, the thickness of the portion welded to the member constituting the current path between the external terminal 20A and the electrode group 40 is increased in the internal pressure of the battery container 10. It is thicker than the wall thickness of the deformed part deformed by. More specifically, in the diaphragm 5, the thickness of the peripheral portion 5a and the central portion 5d welded to the conductive plate 6 and the current collecting plate 30A constituting the current path between the external terminal 20A and the electrode group 40 is as follows. It is thicker than the wall thickness of the side wall part 5b and the bottom wall part 5c which deform | transform with the internal pressure rise of the battery container 10. FIG.

  Thereby, as above-mentioned, the quantity of the molten metal at the time of welding can be increased, and the welding quality and welding strength of welding part W1, W2 can be improved. As a result, the welded portions W1, W2 are prevented from being broken by vibrations and inertial forces acting on the secondary battery 100 during a steady state, and the strength of the welded portions W1, W2 is secured, and an abnormality occurs in the secondary battery 100. Sometimes the current interrupter 50 can be accurately operated at a preset pressure.

  The diaphragm 5 is formed in a convex shape that bulges toward the base 31 of the current collector plate 30A. Therefore, compared to the case where the diaphragm 5 has a flat plate shape, when the surface area of the diaphragm 5 is increased and the internal pressure of the battery container 10 increases due to an abnormality of the secondary battery 100, the diaphragm 5 is easily deformed. Thus, current interruption can be reliably performed at a lower pressure. Moreover, compared with the case where the diaphragm 5 is flat, the mechanical strength until the gas pressure inside the battery container 10 reaches a predetermined pressure can be improved, and malfunction of the diaphragm 5 can be prevented.

  Moreover, the diaphragm 5, the current collecting plate 30A, and the conductive plate 6 are made of aluminum or an aluminum alloy. Therefore, compared with the case where the diaphragm comprised with copper or the copper alloy is arrange | positioned between the external terminal 20B of negative electrode, and the current collecting plate 30B, the intensity | strength of the diaphragm 5 is reduced and the deformation | transformation of the diaphragm 5 is made easy. be able to. Therefore, it is possible to more easily and reliably interrupt the current path between the current collector plate 30A and the external terminal 20A. In addition, the electric current interruption part 50 can also be provided in the negative electrode side. Moreover, by manufacturing the diaphragm 5, the current collecting plate 30A, and the conductive plate 6 with the same kind of metal, the weldability can be improved and the welding quality of the welded portions W1, W2 can be improved.

  Further, the central portion 5d of the diaphragm 5 has a surface opposite to the base portion 31 of the current collecting plate 30A that is continuous with the bottom wall portion 5c, which is a deformed portion, without a step, and a surface facing the base portion 31 of the current collecting plate 30A. And has a step between the bottom wall portion 5c and protrudes toward the base portion 31 of the current collector plate 30A. Thereby, the bottom wall part 5c which is a deformation | transformation part of the diaphragm 5 can be kept away from the welding part W1, and the heat at the time of welding can be made difficult to be transmitted to the bottom wall part 5c, and the influence of the heat with respect to the bottom wall part 5c is minimized. Can be.

  As described above, according to the secondary battery 100 of the present embodiment, the conductive plate 6 and the current collecting plate 30A constituting the current path between the external terminal 20A and the electrode group 40 in the battery container 10, and the diaphragm 5, the amount of molten metal that is melted and mixed can be increased, and the welding quality of the welds W1 and W2 can be improved.

[Embodiment 2]
Hereinafter, a secondary battery according to Embodiment 2 of the present invention will be described with reference to FIGS. 1 to 3 and 5 and FIGS. 6A to 6C. FIG. 6A is an enlarged cross-sectional view corresponding to FIG. 4A of the secondary battery according to the present embodiment. 6B and 6C are enlarged cross-sectional views of the central portion of the diaphragm shown in FIG. 6A before and after welding.

  The secondary battery of the present embodiment has a convex portion 5f that is thicker than the side wall portion 5b and the bottom wall portion 5c, which are deformed portions, at the center portion 5d of the diaphragm 5, and the current collector plate 30A is an annular thin portion. It has the through-hole 31g into which the convex part 5f is inserted inside 31h, the outer peripheral surface of the convex part 5f and the inner peripheral surface of the through-hole 31g are butt-welded to form the welded part W3. This is different from the secondary battery 100 described in the first embodiment. Since the other points of the secondary battery of the present embodiment are the same as those of the secondary battery 100 described in the first embodiment, the same portions are denoted by the same reference numerals and description thereof is omitted.

  The center portion 5d of the diaphragm 5 can be welded to the inside of the annular thin portion 31h provided on the base portion 31 of the current collector plate 30A, for example, by the following procedure. First, the convex portion 5f of the central portion 5d of the diaphragm 5 protruding toward the base portion 31 of the current collecting plate 30A is inserted into the through hole 31g inside the annular thin portion 31h of the current collecting plate 30A. Thereby, the outer peripheral surface of the convex part 5f and the inner peripheral surface of the through-hole 31g are made to oppose and face each other.

  Next, for example, a high energy beam such as a laser or an electron beam is applied along the circumferential direction of the through hole 31g to a portion where the outer peripheral surface of the convex portion 5f of the diaphragm 5 and the inner peripheral surface of the through hole 31g are opposed to each other. Irradiation is performed over a plurality of locations or the entire circumference, and the outer peripheral surface of the convex portion 5f of the diaphragm 5 and the inner peripheral surface of the through hole 31g are butt welded. By the above, the outer peripheral surface of the convex part 5f of the diaphragm 5 and the inner peripheral surface of the through-hole 31g are butt-welded, and the welding part W3 is formed between the diaphragm 5 and the current collecting plate 30A.

  According to the present embodiment, the thickness of the central portion 5d of the diaphragm 5 is thicker than the thickness of the side wall portion 5b and the bottom wall portion 5c, which are deformed portions, and therefore, the same effect as the secondary battery of the first embodiment can be obtained. can get. In addition, the convex portion 5f of the central portion 5d of the diaphragm 5 is inserted into the through hole 31g of the current collector plate 30A, and the outer peripheral surface of the convex portion 5f of the diaphragm 5 and the inner peripheral surface of the through hole 31g are butt welded. Yes. Therefore, the outer peripheral surface of the convex portion 5f of the diaphragm 5 facing each other and the inner peripheral surface of the through-hole 31g are melted and mixed evenly in a state where they are accumulated between each other without causing both molten metals to flow and spread. The diaphragm 5 and the current collector plate 30A can be welded by solidifying and integrating.

  As a result, when the current collector plate 30A and the diaphragm 5 are welded, a portion where both are melted, mixed, and solidified and welded occupies substantially the entire molten meat, that is, the welded portion W3. Therefore, in high energy beam welding such as laser welding in which the volume of the welded portion W3 formed between the diaphragm 5 and the current collector plate 30A is relatively small, weld cracking is prevented and high welding strength is stably provided. Can be obtained. Therefore, according to the secondary battery of this embodiment, the welding quality between the diaphragm 5 and the current collector plate 30A can be improved as compared with the conventional case.

  Further, it is possible to weld the diaphragm 5 and the current collector plate 30A with less welding energy as compared with the first embodiment in which the central portion 5d of the diaphragm 5 is melted via the current collector plate 30A. Further, even when the welding depth increases, the thickness of the central portion 5d of the diaphragm 5 is thicker than the thickness of the side wall portion 5b and the bottom wall portion 5c, thereby preventing the diaphragm from being opened and stabilizing. The range of conditions under which welding can be performed can be widened.

  The embodiment of the present invention has been described in detail with reference to the drawings, but the specific configuration is not limited to this embodiment, and there are design changes and the like without departing from the gist of the present invention. They are also included in the present invention.

  For example, in the above-described embodiment, the current collector plate and the conductive plate are illustrated as an example of the member to which the diaphragm is welded. However, the member to which the diaphragm is welded is not limited to the current collector plate and the conductive plate. For example, when the diaphragm is welded to another member that forms a current path between the external terminal and the wound electrode group in the battery container, the diaphragm is a portion of the wall welded to the member that forms the current path. It is sufficient that the thickness is thicker than the thickness of the deformed portion that is deformed by an increase in internal pressure. Thereby, similarly to the above-mentioned embodiment, the welding quality between a diaphragm and the member which comprises the electric current path can be improved.

  In the above-described embodiment, the case where the thickness of both the central portion and the peripheral portion of the diaphragm is thicker than the thickness of the side wall portion and the bottom wall portion, which are deformed portions, has been described. If the thickness of at least one of the peripheral portion is thicker than the thickness of the deformed portion, the weld quality can be improved at that portion. Further, the shape of the diaphragm is not limited to a bowl-shaped convex shape that bulges toward the current collector plate, and may be a flat plate shape.

5 Diaphragm, 5a Peripheral part, 5b Side wall part (deformed part), 5c Bottom wall part (deformed part),
5d center part, 5f convex part, 6 conductive plate (current path), 6b annular groove, 10 battery container,
20A external terminal, 40 electrode group (winding electrode group), 100 secondary battery, 30A current collector plate (current path), 31g through-hole, 31h annular thin part

Claims (8)

A secondary battery provided with a diaphragm that is arranged in a current path between an external terminal and a wound electrode group in the battery container, and that is deformed by an increase in internal pressure of the battery container and blocks the current path,
The secondary battery is characterized in that a thickness of a portion welded to a member constituting the current path of the diaphragm is thicker than a thickness of a deformed portion deformed by the increase in the internal pressure. A current collector connected to the wound electrode group;
2. The secondary battery according to claim 1, wherein a central portion of the diaphragm is welded to an inner side of an annular thin portion provided on the current collector plate. Comprising a conductive plate connected to the external terminal;
The peripheral edge of the diaphragm is welded to the conductive plate,
The secondary battery according to claim 2, wherein the diaphragm has a thickness of at least one of the central portion and the peripheral portion that is larger than a thickness of the deformed portion. The thickness of the central part is thicker than the thickness of the deformed part,
The secondary battery according to claim 3, wherein the central portion is lap welded to the inside of the annular thin portion of the current collector plate. The wall thickness of the peripheral portion is thicker than the thickness of the deformed portion,
The secondary battery according to claim 3, wherein the peripheral edge engages with an annular groove provided in the conductive plate and is butt welded to an inner wall of the annular groove. The diaphragm has a convex part thicker than the deformed part at the central part,
The current collector plate has a through hole into which the convex portion is inserted inside the annular thin portion,
The secondary battery according to claim 3, wherein an outer peripheral surface of the convex portion and an inner peripheral surface of the through hole are butt welded.   7. The diaphragm according to claim 3, wherein the diaphragm has a convex shape that is disposed between the conductive plate and the current collector plate and bulges toward the current collector plate. 8. Secondary battery described in 1.   The secondary battery according to claim 3, wherein the diaphragm, the current collector plate, and the conductive plate are made of aluminum or an aluminum alloy.

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