JP2016009627A - Secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery that can prevent malfunction of a current cut-off unit and can more surely and stably cut off a current route when the inner pressure of a battery container increases.SOLUTION: A secondary battery has a current cut-off unit 50 in a current route between an electrode in a battery container 10 and an external terminal 20A provided to the battery container 10. The current cut-off unit 50 has a diaphragm 5 which is disposed in the battery container 10 and connected to the external terminal 20A, and a power collection plate 30A connected to an electrode. The diaphragm 5 has a joint portion joined to the power collection plate 30A, and a thin wall portion provided on the periphery of the joint portion.

Description

  The present invention relates to a secondary battery including a current interrupting unit that interrupts a current path between an external terminal and an electrode in a battery container.

  Conventionally, in the field of rechargeable secondary batteries, aqueous batteries such as lead batteries, nickel-cadmium batteries, and nickel-hydrogen batteries have been mainstream. However, as electric devices become smaller and lighter, lithium ion secondary batteries having a high energy density have attracted attention, and their research, development, and commercialization are rapidly progressing. In addition, electric vehicles (EV) and hybrid electric vehicles (HEV) that assist part of driving with electric motors have been developed by automobile manufacturers due to global warming and depleted fuel problems. Secondary batteries are being demanded.

  As a power source that meets such requirements, high-voltage non-aqueous lithium ion secondary batteries have attracted attention. In particular, a prismatic lithium ion secondary battery having a flat box type battery container is excellent in volumetric efficiency when packed into a pack, so that the demand as a power source mounted on HEV, EV, or other devices increases. ing. In a rectangular secondary battery including such a sealed battery container, the pressure inside the battery container may increase due to, for example, overcharge, excessive temperature rise, or damage due to external force.

  In such a case, a nonaqueous electrolyte secondary battery including a current interrupting unit that interrupts current is known (for example, see Patent Document 1 below). The non-aqueous electrolyte secondary battery described in Patent Document 1 is a pressure-sensitive deformation element that deforms in response to an increase in gas pressure inside a battery in the middle of a conductive path that electrically connects an external electrode terminal and an electrode body. Is provided. The external electrode terminal has a communication hole connecting the outside of the battery and a space in contact with the battery outer surface side of the pressure-sensitive deformation element. The pressure-sensitive deformation element deforms in response to an increase in the gas pressure inside the battery, and interrupts the electrical connection between the external electrode terminal and the electrode body.

JP 2008-66255 A

  In the nonaqueous electrolyte secondary battery described in Patent Document 1, the pressure-sensitive deformation element is constituted by a diaphragm and a shielding foil. The central part of the barrier foil is bonded to the central part of the inner surface of the battery of the diaphragm. A peripheral portion of the shielding foil is attached so as to cover a through hole provided in an insertion portion of a current collecting tab member located below the diaphragm. Therefore, when the current collecting tab member is warped or twisted, strain or stress acts on the barrier foil, causing contact failure between the barrier foil and the diaphragm, or damage or breakage of the barrier foil. There is a risk of malfunction of the current interrupter.

  The present invention has been made in view of the above-described problems, and the object of the present invention is to prevent malfunction of the current interrupting portion and more reliably and stably interrupt the current path when the internal pressure of the battery container increases. It is in providing the secondary battery which can do.

  In order to achieve the above object, the secondary battery of the present invention is a secondary battery including a current interrupting portion in a current path between an electrode in the battery container and an external terminal provided in the battery container. The current interrupting unit is disposed in the battery container, and includes a diaphragm connected to the external terminal and a current collecting plate connected to the electrode, and the diaphragm is joined to the current collecting plate. It has a junction part and the thin part provided in the circumference | surroundings of this junction part, It is characterized by the above-mentioned.

  In the secondary battery of the present invention, when the pressure in the battery container rises to the operating pressure of the current interrupting part, the thin part with relatively low strength is broken by the pressure acting on the diaphragm, and the connection between the current collector plate and the diaphragm is I will be refused. That is, the thin part which is broken when the current interrupting part is operated is provided in the diaphragm which is deformed by receiving the pressure in the battery container. Therefore, even if warping or twisting occurs during the production of the current collector plate, joining the diaphragm to the current collector plate after production of the current collector plate alleviates strain and stress acting on the thin wall of the diaphragm, Breakage or damage of the thin-walled portion can be prevented.

  Therefore, according to the secondary battery of the present invention, the malfunction of the current interrupting portion can be prevented, and the current path can be more reliably and stably interrupted when the internal pressure of the battery container increases. Problems, configurations, and effects other than those described above will become apparent from the following description of embodiments.

The perspective view which shows the external appearance of the secondary battery which concerns on embodiment of this invention. The disassembled perspective view of the secondary battery shown in FIG. The exploded perspective view of the winding body of the secondary battery shown in FIG. FIG. 2 is an enlarged cross-sectional view around a current interrupting portion of the secondary battery shown in FIG. 1. FIG. 2 is an exploded perspective view around a current interrupting unit of the secondary battery shown in FIG. 1. FIG. 6 is a plan view of the diaphragm shown in FIG. 5. Sectional drawing of the protrusion part vicinity of the diaphragm shown in FIG. Sectional drawing of the protrusion part vicinity which shows the modification of the diaphragm shown in FIG. The top view which shows the modification of the diaphragm shown in FIG. The expanded sectional view which shows the modification of the secondary battery shown in FIG.

  Hereinafter, embodiments of the secondary battery of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of a secondary battery 100 of the present embodiment. The secondary battery 100 of the present embodiment is, for example, a rectangular lithium ion secondary battery, and is a flat box-shaped battery container 10 constituted by a rectangular plate-shaped lid portion 11 and a bottomed rectangular tube-shaped battery can 12. It has. The battery container 10 is made of a metal material such as an aluminum alloy, for example. The battery container 10 is sealed by joining a lid 11 to the upper part of the battery can 12 by laser welding, for example.

  Positive and negative external terminals 20 </ b> A and 20 </ b> B are provided on the upper surface of the lid 11 outside the battery container 10 at both ends in the width direction of the battery container 10, that is, in the longitudinal direction of the lid 11. The insulating member 2 is disposed between the external terminals 20A and 20B and the lid portion 11, and the external terminals 20A and 20B are electrically insulated from the lid portion 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.

  Between the positive electrode and negative electrode external terminals 20A and 20B of the lid portion 11, a gas discharge valve 13 and a liquid injection port 14 are provided. The gas discharge valve 13 is provided, for example, by forming the groove portion 13a by thinning the lid portion 11, and cleaves to release the internal gas when the internal pressure of the battery container 10 rises above a predetermined value. Thus, the pressure inside 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. Positive and negative current collectors 30A and 30B are fixed to the lower surface of the lid 11 that is the inside of the battery case 10 at both ends in the longitudinal direction of the lid 11 via insulating members 3A and 3B. The positive current collector 30A is made of, for example, aluminum or an aluminum alloy, and the negative current collector 30B is made of, for example, copper or a copper alloy.

  The current collecting plates 30A and 30B are provided substantially parallel to the lower surface of the lid portion 11 and are bent at one side of the base portions 31A and 31B and the base portions 31A and 31B fixed to the lid portion 11 via the insulating members 3A and 3B. Terminal portions 32 </ b> A and 32 </ b> B extending toward the bottom surface 12 c of the battery can 12. The current collector plates 30A and 30B are formed with base portions 31A and 31B and terminal portions 32A and 32B by, for example, pressing and bending the plate material of the metal material.

  In the present embodiment, the base portion 31A of the positive electrode current collector plate 30A includes a first portion 31a having a small distance from the lid portion 11 and a second portion 31b having a large interval from the lid portion 11. The first portion 31a and the second portion 31b of the base portion 31A are plate-like portions provided substantially in parallel with the lid portion 11, and are fixed to the lid portion 11 via the insulating member 3A. Between the second portion 31b of the base portion 31A and the positive external terminal 20A, the diaphragm 5 connected thereto is disposed.

  The secondary battery 100 has a current path in a current path between the positive electrode 41 (see FIG. 3) provided in the wound body 40 in the battery container 10 and the external terminal 20 </ b> A provided on the lid portion 11 of the battery container 10. A blocking unit 50 is provided. The current interrupting unit 50 includes a diaphragm 5 disposed in the battery case 10 and connected to the external terminal 20A, and a current collecting plate 30A. More specifically, the current interrupting unit 50 is configured by the second portion 31b of the base 31A of the current collector plate 30A and the diaphragm 5. Although details will be described later, the current interrupting unit 50 interrupts the current path between the external terminal 20A and the positive electrode 41 when the internal pressure of the battery container 10 rises above a predetermined pressure.

  The terminal portions 32A and 32B of the positive and negative current collecting plates 30A and 30B are, for example, from one side of the base portions 31A and 31B in the thickness direction of the battery container 10 along the wide side surface 12b having the maximum area of the battery can 12. It is formed in a plate shape extending toward the bottom surface 12 c of the battery can 12. The terminal portions 32A and 32B are bent in the thickness direction of the battery case 10 in the middle of the extending direction, and are joined to the current collector plate joining portions 41d and 42d of the wound body 40 by, for example, ultrasonic welding.

  Thereby, the external terminals 20A and 20B are electrically connected to the current collector plate joint portions 41d and 42d of the wound body 40 via the current collector plates 30A and 30B. Further, the lid 11 is assembled with 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 unit 50, and the winding body 40. Has been.

  At the time of manufacturing the secondary battery 100, the lid assembly 60 includes an insulating sheet (not shown) disposed between the wound body 40 and the battery can 12 to electrically insulate them. The battery is inserted into the opening 12a of the battery can 12 from the lower curved portion 40b. In the wound body 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 battery can 12.

  Thereby, as for the winding body 40 in the battery container 10, one curved part 40b opposes the cover part 11, the other curved part 40b opposes the bottom face 12c of the battery can 12, and the plane part 40a is a wide side surface. The winding axis D direction is parallel to the width direction of the battery case 10, that is, the longitudinal direction of the lid 11. Then, with the lid portion 11 closing the opening portion 12a of the battery can 12, for example, by joining the entire circumference of the lid portion 11 to the upper opening portion 12a of the battery can 12 by laser welding, the lid portion 11 and The space between the battery can 12 is sealed to form the battery container 10.

Thereafter, a non-aqueous electrolyte is injected into the battery container 10 through the liquid injection port 14 of the lid 11, and the liquid injection plug 15 is joined and sealed to the liquid injection port 14 by laser welding, for example. 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 wound body 40 shown in FIG. 2 is developed. The wound body 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 wound body 40 has a semi-cylindrical shape that is disposed so as to be opposed to the pair of flat plane portions 40 a that are opposed to the wide side surface 12 b of the battery can 12 and the bottom surface 12 c of the lid portion 11 and the battery can 12. It has a pair of curved parts 40b.

  The wound body 40 is formed by winding a laminated body in which long belt-like electrodes 41 and 42 and long belt-like separators 43 and 44 are alternately laminated, for example, while applying a tensile load of about 10 N in the extending direction. It is made by doing. During winding of the laminated body, meandering control is performed so that the positions of the end portions of the respective members at the width direction of each of the long strip-shaped members, that is, both ends in the winding axis D direction of the wound body 40 are made constant. The separators 43 and 44 are electrically insulating sheets made of, for example, a microporous polyethylene material. The separators 43 and 44 insulate the positive electrode 41 and the negative electrode 42, and the negative electrode 42 wound around the outermost periphery. A separator 44 is also wound outside.

  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 in the width direction of the long belt-like positive electrode 41 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 foil exposed portion 42 c of the negative electrode 42 in the winding axis D direction.

  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 has 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 disposed on the opposite side of the foil exposed portion 41 c of the positive electrode 41 in the winding axis D direction.

  The negative electrode 42 is, for example, applied to the 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 one side in the width direction, dried, pressed, 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 axis 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 winding axis D direction of the wound body 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 wound body 40. Accordingly, 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 wound body 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 wound body 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 32A and 32B of the positive and negative current collector plates 30A and 30B, for example, by ultrasonic welding or the like. Accordingly, the positive and negative external terminals 20A and 20B are electrically connected to the electrodes 41 and 42 constituting the winding body 40 via the current collector plates 30A and 30B, respectively.

  In addition, in the winding axis D direction of the wound body 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 respectively The separators 43 and 44 protrude outward in the width direction from the end portions in the width direction. Therefore, the separators 43 and 44 do not hinder when the foil exposed portions 41c and 42c are bundled and welded.

  FIG. 4 is an enlarged cross-sectional view of the vicinity of the external terminal 20A along the IV-IV line of the secondary battery 100 shown in FIG. FIG. 5 is an exploded perspective view of each member shown in FIG. In addition, in FIG. 5, illustration of the winding body 40 is abbreviate | omitted.

  As described above, the current interrupting unit 50 includes the diaphragm 5 disposed in the battery case 10 and connected to the external terminal 20A, and the current collecting plate 30A connected to the electrode 41, and includes the electrode 41 and the external terminal 20A. Is provided in the current path between. In the present embodiment, the diaphragm 5 is connected to the external terminal 20 </ b> A via the conductive plate 6. Diaphragm 5 and conductive plate 6 are made of, for example, aluminum or aluminum alloy similar to external terminal 20A.

  The external terminal 20 </ b> A is provided at a plate-like portion 21 </ b> A extending along the width direction of the battery container 10, i.e., the longitudinal direction of the lid portion 11, and an end portion inside the plate-like portion 21 </ b> A in the width direction of the battery container 10. 11 and a columnar connection portion 22 </ b> A penetrating through 11. In addition, a through hole 23A that penetrates the plate-like portion 21A and the connecting portion 22A and communicates with the space between the diaphragm 5 and the conductive plate 6 can be arbitrarily formed in the external terminal 20A. Note that the through hole 23 </ b> A can be sealed so that it can be cleaved when the current interrupting unit 50 is operated.

  The plate-like portion 21A has a groove portion in the extending direction, that is, in the central portion in the longitudinal direction of the lid portion 11, along the direction intersecting the extending direction, for example, in the thickness direction of the battery case 10, that is, in the short direction of the lid portion 11. By forming 24A, the thickness is partially reduced. The connecting portion 22A has a stepped portion 22a provided in a stepped shape on the bottom surface of the plate-like portion 21A and a diameter-increased portion having an enlarged diameter from the plate-like portion 21A toward the tip in the axial direction penetrating the lid portion 11. 22b, a reduced diameter portion 22c having a reduced diameter, and a crimped portion 22d in which the diameter of the reduced diameter portion 22c is expanded by plastic deformation. The through hole 23A penetrates the external terminal 20A along the axial direction of the connecting portion 22A, and opens at the upper surface of the plate-like portion 21A and the center portion of the caulking portion 22d. The external terminal 20 </ b> A and the lid portion 11 are electrically insulated by the insulating member 2 and the gasket 4.

  The insulating member 2 is made of, for example, a resin material having insulating properties, and is disposed on the lid portion 11 outside the battery container 10, and an edge portion 2a that covers the peripheral side surface of the plate-like portion 21A of the external terminal 20A, and a plate-like portion And a bottom portion 2b that is in close contact with the bottom surface of 21A and the top surface of the lid portion 11. The edge portion 2a of the insulating member 2 covers the peripheral side surface of the plate-like portion 21A, thereby preventing a short circuit between the plate-like portion 21A and the lid portion 11 or other members. The bottom portion 2b of the insulating member 2 is disposed between the plate-like portion 21A of the external terminal 20A and the lid portion 11 to electrically insulate them. In the bottom 2b of the insulating member 2, a projection 2c (see FIG. 4) that engages with a recess 11a provided on the top surface of the lid 11 and an opening 2d (FIG. 5) through which the connection 22A of the external terminal 20A is inserted. For example).

  The gasket 4 is made of, for example, an insulating resin material, and is disposed between the lid portion 11 and the external terminal. The cylindrical portion 4a and the outer side of the battery container 10 in the axial direction of the cylindrical portion 4a. And a flange portion 4b provided at the end portion on the side. The cylindrical portion 4a of the gasket 4 is inserted into the through hole 11b of the lid portion 11 with the connection portion 22A of the external terminal 20A inserted inside, and the connection portion 22A of the external terminal 20A and the through hole of the lid portion 11 are inserted. It is arrange | positioned between the inner peripheral surfaces of 11b, and electrically insulates the connection part 22A and the cover part 11. FIG. The flange portion 4b of the gasket 4 is disposed in the opening 2d of the insulating member 2 and engages with a concave step portion 11c provided around the through hole 11b of the lid portion 11, and the step portion 11c and the external terminal It is compressed between the convex stepped portion 22a of 20A. As a result, the gasket 4 is in close contact with the concave step portion 11 c and the convex step portion 22 a and seals the through hole 11 b of the lid portion 11.

  The insulating member 3A is made of, for example, an insulating resin material, and is disposed on the lower surface side of the lid 11 inside the battery container 10 and extends in the width direction of the battery container 10, and the main body 3a. And a through hole 3b provided at the center in the extending direction. Further, the insulating member 3A protrudes from the main body 3a toward the inside of the battery case 10 to support the second portion 31b of the base 31A of the current collector plate 30A, and the first portion 31a and the first portion 31a of the base 31A. A cylindrical projection 3f that fixes the two portions 31b.

  The main body portion 3a includes a thick portion 3c disposed between the first portion 31a of the base portion 31A of the current collector plate 30A and the lid portion 11, and a thin portion 3d to which the diaphragm 5 is fixed via the conductive plate 6. have. That is, in the insulating member 3 </ b> A, the thickness of the portion between the conductive plate 6 and the lid portion 11 is thinner than the thickness of the portion between the first portion 31 a of the base portion 31 </ b> A and the lid portion 11. The thin portion 3d of the insulating member 3A is provided with a recess 3g with which the conductive plate 6 is engaged. The concave portion 3g of the thin portion 3d is formed in a planar shape corresponding to the planar shape of the conductive plate 6 in a plan view perpendicular to the lid portion 11.

  The protrusion 3f passes through the plurality of through holes 33 provided in the first portion 31a and the second portion of the base portion 31A of the current collector plate 30A, and the tip is melted and expanded by, for example, heat welding, and further solidified. Are fixed to the base 31A of the current collector plate 30A. Thereby, the protrusion 3f supports and fixes the first portion 31a and the second portion 31b of the base portion 31A of the current collector plate 30A to the thick portion 3c and the support portion 3e, respectively. The base 31A of the current collector plate 30A may be fixed to the insulating member 3A using screws, rivets, an adhesive, or the like.

  The negative-side insulating member 3B shown in FIG. 2 has a main body portion 3a and a through-hole 3b in the same manner as the positive-side insulating member 3A. However, the thick-walled portion 3c, the thin-walled portion 3d, the support portion 3e, and This is different from the positive-side insulating member 3A in that the protrusion 3f is not provided.

  The conductive plate 6 has a linear portion along the width direction of the battery case 10, that is, the longitudinal direction of the lid portion 11, and arc-shaped curved portions at both ends thereof, and has a field track shape in plan view perpendicular to the lid portion 11. It is a plate-shaped member having a planar shape. The planar shape of the conductive plate 6 may be formed in an oval shape or an elliptical shape with the width direction of the battery case 10 as the longitudinal direction corresponding to the planar shape of the diaphragm 5. The conductive plate 6 has a through hole 6a at a position corresponding to the through hole 3b of the insulating member 3A, and is fitted into the recess 3g of the thin portion 3d of the insulating member 3A having a corresponding planar shape.

  The conductive plate 6 extends from one end of the plate-like portion 21 </ b> A of the external terminal 20 </ b> A disposed on the upper surface side of the lid portion 11, and is connected to the lower surface side of the lid portion 11 by the connecting portion 22 </ b> A of the external terminal 20 </ b> A penetrating the lid portion 11. It is fixed by caulking through the insulating member 3A. Specifically, the tip of the connection portion 22A of the external terminal 20A inserted through the through hole 6a of the conductive plate 6 is plastically deformed and expanded on the surface 6c facing the second portion 31b of the base portion 31A of the current collector plate 30A. The conductive plate 6 is fixed to the lower surface side of the lid portion 11 via the insulating member 3A by forming the caulking portion 22d. As a result, the conductive plate 6 is held between the stepped portion between the enlarged diameter portion 22b and the reduced diameter portion 22c of the connection portion 22A and the caulking portion 22d, and is connected to the external terminal 20A via the connection portion 22A. Conductive connection.

  The conductive plate 6 is not arranged on the negative electrode side, and the external terminal 20B on the negative electrode side is caulked through the base 31B of the current collector plate 30B with the same connection part as the connection part 22A of the external terminal 20A on the positive electrode side. The part is formed. Further, the external terminal 20B on the negative electrode side does not have a through hole that penetrates the plate-like portion 21B and the connection portion.

  In this way, the insulating member 2, the gasket 4, the insulating member 3A, and the conductive plate 6 are integrally caulked and fixed to the lid portion 11 by the positive-side external terminal 20A, and the insulating member 2, The gasket 4, the insulating member 3 </ b> B, and the current collector plate 30 </ b> B are integrally caulked and fixed to the lid portion 11.

  The surface 6c of the conductive plate 6 facing the second portion 31b of the base portion 31A of the current collector plate 30A is preferably a flat surface having no ribs or convex portions. If the surface 6c of the conductive plate 6 facing the second portion 31b is flat, the caulking portion 22d is prevented from interfering with the ribs and the convex portions, so that the diameter of the caulking portion 22d is secured and the external terminal 20A is secured. This is because the strength of caulking and fixing by the connecting portion 22A can be ensured. Further, the conductive plate 6 has an annular groove 6b that engages the peripheral edge portion 5a of the diaphragm 5 with a surface 6c facing the second portion 31b. The annular groove 6 b is formed in a contour shape corresponding to the contour shape of the diaphragm 5 in a plan view perpendicular to the lid portion 11.

  FIG. 6 is a plan view of the diaphragm 5 when the diaphragm 5 is viewed from the base 31A side of the current collector plate 30A in a direction perpendicular to the lid 11. The diaphragm has a planar shape corresponding to the conductive plate 6 with a dimension along the longitudinal direction of the lid part 11 larger than a dimension along the short direction of the lid part 11 in a plan view perpendicular to the lid part 11. ing. That is, in the present embodiment, the diaphragm 5 has a linear portion along the longitudinal direction of the lid portion 11 and arcuate curved portions at both ends thereof, and a field track-shaped plane in a plan view perpendicular to the lid portion 11. It has a shape.

  Diaphragm 5 is formed in a bowl shape having a central portion at the bottom, and has a convex shape that bulges from lid portion 11 toward second portion 31b of base portion 31A of current collector plate 30A. The diaphragm 5 has a peripheral edge part 5a that engages with the annular groove 6b of the conductive plate 6 on the lid part 11 side, and the side wall part 5b and the bottom wall part 5c from the peripheral edge part 5a toward the second part 31b of the base part 31A. And a protrusion 5d.

  The peripheral edge portion 5a is bent along the bottom surface of the annular groove 6b of the conductive plate 6 shown in FIG. 4, engages with the annular groove 6b, abuts against the bottom of the annular groove 6b, and, for example, a conductive plate by laser welding. 6 is joined. Thereby, the diaphragm 5 is electrically connected to the conductive plate 6, and forms a space isolated from the internal space of the battery container 10 between the conductive plate 6. In the present embodiment, the space between the diaphragm 5 and the conductive plate 6 communicates with the external space of the battery case 10 through the through hole 23A of the external terminal 20A. The side wall portion 5b adjacent to the peripheral edge portion 5a extends from the peripheral edge portion 5a along the direction perpendicular to the lid portion 11 toward the second portion 31b of the base portion 31A of the current collector plate 30A, and is perpendicular to the lid portion 11 The angle with respect to is smaller than the angle with respect to the direction parallel to the lid portion 11.

  The bottom wall portion 5 c extends from the end of the side wall portion 5 b toward the center portion of the diaphragm 5 along a direction parallel to the lid portion 11, and an angle with respect to a direction perpendicular to the lid portion 11 is parallel to the lid portion 11. It is larger than the angle with respect to the direction. The bottom wall portion 5c is formed in a convex curved shape that bulges toward the second portion 31b. The protruding portion 5d of the diaphragm 5 is formed in a planar shape similar to the planar shape of the diaphragm 5 in a plan view perpendicular to the lid portion 11, and further protrudes one step from the convex top to the base portion 31A of the current collector plate 30A. It is formed as follows.

  FIG. 7 is an enlarged cross-sectional view of the vicinity of the protruding portion 5d of the diaphragm 5 shown in the cross-sectional view of FIG. The diaphragm 5 has a joint portion 5e joined to the current collector plate 30A and a thin portion 5f provided around the joint portion 5e. In the present embodiment, the joint 5e of the diaphragm 5 is joined to the second portion 31b of the base 31A of the current collector plate 30A. Moreover, the thin part 5f is formed by the recessed part 5g provided in the circumference | surroundings of the junction part 5e.

  In the secondary battery 100 of the present embodiment, the thin portion 5f and the joining portion 5e are formed on the protruding portion 5d that protrudes further from the convex top of the diaphragm 5 toward the current collecting plate 30A. The protruding portion 5d has a flat portion facing the current collecting plate 30A, and a surface facing the current collecting plate 30A abuts against the current collecting plate 30A. The thin portion 5f and the joining portion 5e are formed in a flat portion of the protruding portion 5d that contacts the current collector plate 30A. Further, the thin portion 5f is formed by a concave portion 5g provided on the bottom surface of a flat portion that contacts the current collector plate 30A of the protruding portion 5d.

  Here, as shown in FIG. 6, the recess 5g is preferably a circular annular groove 5h. In this case, it is preferable that the center of the recess 5g coincides with the center of the diaphragm 5. The center of the diaphragm 5 is the intersection of the center line L1 of the diaphragm 5 along the longitudinal direction of the lid portion 11 and the center line L2 of the diaphragm 5 along the short side direction of the lid portion 11. In addition, the recessed part 5g is not limited to the perfect circular cyclic | annular groove | channel 5h continuous in the circumferential direction like this embodiment, For example, the discontinuous several recessed part 5g arrange | positioned cyclically | annularly may be sufficient. Further, the depth of the recess 5g may be partially different.

  Furthermore, as shown in FIG. 8, the recesses 5g may be provided on both the surface of the diaphragm 5 that faces the current collector plate 30A and the surface opposite to the surface. In this case, the thin portion 5f is formed between a recess 5g provided on the inner surface 5i facing the current collector 30A of the diaphragm 5 and a recess 5g provided on the outer surface 5j opposite to the inner surface 5i. The The recess 5g may be provided only on the outer surface 5j of the diaphragm 5. In this case, in a plan view perpendicular to the lid portion 11, a circular or other planar concave portion 5g including the joint portion 5e can be formed inside the concave portion 5g. Thereby, the thin part 5f can be formed in the junction part 5e and its circumference | surroundings.

  As shown in FIG. 4, the diaphragm 5 is disposed between the base portion 31A of the current collector plate 30A and the lid portion 11, and the joint portion 5e is formed on the surface facing the lid portion 11 of the base portion 31A by, for example, laser welding. It is joined. As described above, the base portion 31 </ b> A has the first portion 31 a having a narrow interval with the lid portion 11 and the second portion 31 b having a wide interval with the lid portion 11. The diaphragm 5 is disposed between the second portion 31b and the lid portion 11, and the joint portion 5e is joined to the second portion 31b.

  As shown in FIG. 4, the base portion 31 </ b> A of the current collector plate 30 </ b> A extends in the direction from the first portion 31 a toward the second portion 31 b along the longitudinal direction of the lid portion 11, and includes the first portion 31 a and the second portion. It has the connection part 31c which connects 31b. The first portion 31a, the second portion 31b, and the connecting portion 31c are formed by, for example, pressing and bending the base portion 31A. The cross-sectional area along the short direction of the lid portion 11 perpendicular to the extending direction of the base portion 31A is smaller than the first portion 31a and the second portion 31b in the connecting portion 31c. In the present embodiment, the thickness of the connecting portion 31c is thinner than the first portion 31a and the second portion 31b.

  The connecting portion 31c has a smaller cross-sectional area than the first portion 31a and the second portion 31b, and has a plurality of bent portions, so that the connecting portion 31c is more flexible than the first portion 31a and the second portion 31b. ing. The connecting portion 31c connects the first portion 31a and the second portion 31b by forming a step in the direction perpendicular to the lid portion 11 between the first portion 31a and the second portion 31b. Thereby, the space | interval of the 2nd part 31b and the cover part 11 is wider than the space | interval of the 1st part 31a and the cover part 11. FIG.

  The base 31A of the current collector plate 30A is formed with a housing recess 34 for housing at least a part of the diaphragm 5 on the surface of the second portion 31b facing the diaphragm 5. In the present embodiment, a part of the diaphragm 5 is housed in the housing recess 34, but the shape and size of the diaphragm 5, the thickness of the base 31A of the current collector 30A, and the depth of the housing recess 34 are changed, The entire diaphragm 5 may be housed in the housing recess 34. The housing recess 34 can be formed by, for example, pressing or cutting the second portion 31b.

  The housing recess 34 is provided in a stepped shape that gradually becomes deeper from the peripheral edge 5 a of the diaphragm 5 toward the protrusion 5 d at the center. The housing recess 34 may be provided with an inclined surface or a concave curved surface so that the housing recess 34 gradually becomes deeper from the peripheral edge portion 5a of the diaphragm 5 toward the central projecting portion 5d. As described above, the accommodating recess 34 gradually becomes deeper toward the protruding portion 5d, so that the thickness of the second portion 31b of the base 31A of the current collector plate 30A facing the joint 5e of the diaphragm 5 is the thinnest. It has become. The joint 5e of the diaphragm 5 is joined to the thinnest part of the second part 31b by, for example, laser welding.

  The positive collector plate 30A has a cylindrical projection 3f of the insulating member 3A shown in FIG. 4 inserted through the through hole 33 of the base 31A shown in FIG. 5, and melts and expands the tip of the projection 3f. By being solidified, it is fixed to the insulating member 3A. Thereafter, in a state where the protruding portion 5d of the diaphragm 5 is in contact with the second portion 31b of the base portion 31A, for example, the lower surface side of the second portion 31b, that is, the surface opposite to the lid portion 11 is irradiated with laser. The joining portion 5e and the second portion 31b are welded and joined. As a result, the positive current collecting plate 30A is fixed to the lower surface side of the lid portion 11 via the insulating member 3A, and the current interrupting portion 50 is configured by the second portion 31b of the base portion 31A and the diaphragm 5.

  Thereafter, as shown in FIG. 2, the current collector plate joints 41d and 42d of the winding body 40 are connected to the terminal portions 32A and 32B of the current collector plates 30A and 30B on the positive electrode side and the negative electrode side, for example, by ultrasonic welding or resistance. The lid assembly 60 is formed by joining by welding. Then, the current collector plates 30A and 30B, the winding body 40, and the current interrupting portion 50 provided in the lid assembly 60 are inserted into the battery can 12 from the opening 12a at the top of the battery can 12, and the opening 12a is the lid portion. 11 is occluded. Thereafter, the lid portion 11 is welded to the upper opening portion 12a of the battery can 12 over the entire circumference by, for example, laser welding, and the electrolytic solution is injected from the liquid injection port. Then, for example, by laser welding, the liquid injection port 15 is welded to the liquid injection port 14 to seal the liquid injection port 14. The secondary battery 100 of this embodiment shown in FIG. 1 is configured as described above.

  Hereinafter, the operation of the secondary battery 100 of the present embodiment will be described. As described above, the secondary battery 100 includes the current interrupting unit 50 in the current path between the electrode 41 in the battery container 10 and the external terminal 20 </ b> A provided in the battery container 10. And the electric current interruption part 50 is arrange | positioned in the battery container 10, and is provided with the diaphragm 5 connected to the external terminal 20A, and the current collecting plate 30A connected to the electrode 41.

  Based on such a configuration, the secondary battery 100 according to the present embodiment is configured so that the power supplied via the external terminals 20A and 20B is wound by the current flowing through the current path including the current interrupting unit 50 in a normal state. Accumulate in 40. Further, the secondary battery 100 supplies the electric power stored in the wound body 40 to the external device via the external terminals 20A and 20B by the current flowing through the current path including the current interrupting unit 50.

  For example, when the internal pressure of the battery container 10 rises due to overcharge of the secondary battery 100, excessive temperature rise or damage due to external force, the pressure acting on the surface of the diaphragm 5 facing the base portion 31A of the current collector plate 30A is changed to the opposite side. It becomes larger than the pressure which acts on the surface which faces the cover part 11 of this. When the internal pressure of the battery container 10 reaches the set pressure, the thin portion 5f having relatively low strength is broken by the pressure acting on the diaphragm 5, and the connection between the current collector plate 30A and the diaphragm 5 is broken. Thereby, the current path between the external terminal 20A and the electrode 41 in the battery case 10 is interrupted.

  As described above, the current collecting plate 30A is formed with the base portion 31A and the terminal portion 32A, or the base portion 31A is formed with the first portion 31a, the second portion 31b, and the connecting portion 31c by pressing or bending each part. Sled or twisted. For this reason, when a current collector tab member is provided with a barrier foil that breaks when the current interrupter is operated, as in the conventional secondary battery described above, strain and stress are applied to the barrier foil, for example, the barrier foil and the diaphragm May cause a contact failure, or the barrier foil may be damaged or broken during steady state, resulting in malfunction of the current interrupter.

  On the other hand, the secondary battery 100 of this embodiment has the thin part 5f fractured | ruptured at the time of the action | operation of the electric current interruption part 50 in the diaphragm 5. FIG. Therefore, even if the current collector plate 30A is warped or twisted, for example, the base member 31A of the current collector plate 30A is fixed at a predetermined position by the insulating member 3A, and the joint portion 5e of the diaphragm 5 is joined to the base portion 31A. Can do. Thereby, the distortion and stress which act on the thin part 5f of the diaphragm 5 are relieved, and the fracture | rupture or damage of the thin part 5f at the time of steady state can be prevented.

  Further, in the secondary battery 100 of the present embodiment, the thin portion 5f is formed by the concave portion 5g provided around the joint portion 5e. In general, the diaphragm 5 has a simple shape as compared with the current collector plate 30A, and can be manufactured easily and accurately by, for example, pressing. Therefore, when the diaphragm 5 is manufactured, the concave portion 5g can be formed with high accuracy, the accuracy of the thickness of the thin portion 5f can be improved, and the diaphragm 5 can be accurately broken with a desired pressure.

  Further, as in the example shown in FIG. 7, by forming the thin portion 5f at a position away from the surface of the base portion 31A of the current collector plate 30A, the thin portion 5f is affected by heat during welding of the joint portion 5e. It is suppressed. Further, as in the example shown in FIG. 8, the thin wall portion 5f is provided on the concave portion 5g provided on the inner surface 5i facing the current collecting plate 30A of the diaphragm 5, and on the outer surface 5j opposite to the inner surface 5i. By forming it between the concave portions 5g, the thin portion 5f can be formed with high accuracy regardless of the thickness of the diaphragm 5, and the thin portion 5f can be made thinner and more easily broken.

  In the secondary battery 100 of the present embodiment, the recess 5g that forms the thin portion 5f in the diaphragm 5 is a circular annular groove 5h. The diaphragm 5 needs to be broken all around the joint 5e, but by forming the thin portion 5f with a circular annular groove 5h, the fracture length when breaking the joint 5e is minimized. Can be. Therefore, the stress required for breaking the diaphragm 5 is reduced, and when the internal pressure of the battery container 10 reaches a predetermined pressure, the diaphragm 5 is broken more accurately and the current interruption accuracy of the current interruption unit 50 is improved. be able to.

  When the thin wall portion 5f is formed in an annular shape around the joint portion 5e, the breakage occurs starting from one point of the thin wall portion 5f, and the breakage proceeds to a position away from the starting point. It is considered that the rupture finally proceeds over the entire circumference around the joint 5e, and the diaphragm 5 is ruptured. Here, as shown in FIG. 6, the dimension of the diaphragm 5 along the longitudinal direction of the lid 11 is larger than the dimension of the diaphragm 5 along the short direction of the lid 11 in a plan view perpendicular to the lid 11. . In this case, it is considered that the maximum stress acts on the diaphragm 5 along the center line L1 of the diaphragm 5 parallel to the longitudinal direction of the lid portion 11.

  As described above, in the secondary battery 100 according to the present embodiment, the shape of the diaphragm 5 viewed from the direction perpendicular to the lid portion 11 is, for example, a short side of the lid portion 11 such as a field track shape, an elliptical shape, or an oval shape. It is formed in a shape that is longer in the longitudinal direction of the lid portion 11 than in the direction. Further, the thin portion 5f of the diaphragm 5 is formed by an annular groove 5h provided around the joint portion 5e, and the center of the diaphragm 5 and the center of the annular groove 5h coincide with each other.

  Thereby, when the diaphragm 5 is broken, the thin portion 5f can be broken symmetrically with respect to the center line L2 perpendicular to the center line L1, starting from the point where the center line L1 and the annular groove 5h intersect. Therefore, the diaphragm 5 can be more easily broken as compared with the case where the starting point of breakage is not set or the case where the center of the annular groove 5h does not coincide with the center of the diaphragm 5. Therefore, the stress required for breaking the diaphragm 5 can be reduced, and when the internal pressure of the battery container 10 reaches a predetermined pressure, the diaphragm 5 can be broken more accurately, and the current interruption accuracy of the current interruption unit 50 can be reduced. Can be improved.

  In the secondary battery 100 of the present embodiment, the diaphragm 5 has a convex shape that bulges from the lid portion 11 toward the base portion 31A of the current collector plate 30A. Therefore, compared with the case where the diaphragm 5 is flat, the mechanical strength of the diaphragm 5 until the internal pressure of the battery container 10 reaches a predetermined pressure can be improved, and malfunction of the diaphragm 5 can be prevented. Moreover, when the internal pressure of the battery container 10 reaches a predetermined pressure, the diaphragm 5 is deformed so as to be reversed, whereby the responsiveness of deformation with respect to the pressure can be improved. Furthermore, the deformation amount of the diaphragm 5 can be increased, and conduction between the diaphragm 5 and the current collector plate 30A after being broken can be more reliably prevented.

  Further, the joint portion 5e and the thin portion 5f are formed in a portion that contacts the base portion 31A of the current collector plate 30A of the protruding portion 5d of the diaphragm 5. Thereby, the joining part 5e can be contact | abutted reliably to 31 A of bases, and the reliability of welding with the joining part 5e and 31 A of bases can be improved. In addition, the thin wall portion 5f is provided adjacent to the joint portion 5e, and the diaphragm 5 can be broken in the vicinity of the joint portion 5e, and the amount of deformation of the diaphragm 5 can be increased to more reliably cut off the current. Further, since the diaphragm 5 has the protruding portion 5d, the peripheral side wall of the protruding portion 5d acts as a rib, the strength of the diaphragm 5 is improved, and the diaphragm 5 can be prevented from being deformed due to malfunction.

  Further, the protruding portion 5 d is formed in a shape similar to the planar shape of the diaphragm 5 when viewed from a direction perpendicular to the lid portion 11. Thereby, when the internal pressure of the battery container 10 rises and the diaphragm 5 is broken, the surface area of the portion between the protruding portion 5d and the peripheral portion 5a is secured, and the convex diaphragm 5 is reversed to the lid portion 11 side. It can be made easy.

  Further, the secondary battery 100 of the present embodiment has a flat box shape in which the battery container 10 is sealed with a rectangular lid portion 11. The diaphragm 5 is formed in an oval shape, an oval shape, or a field track shape, for example, whose dimension along the longitudinal direction of the lid portion 11 is larger than the dimension along the short direction of the lid portion 11. Thereby, the surface area of the diaphragm 5 can be ensured in the flat battery container 10.

  Therefore, when the internal pressure of the battery container 10 reaches a predetermined pressure, the diaphragm 5 can be easily and reliably deformed, and the current path between the electrode 41 and the external terminal 20A can be more reliably interrupted. Become. In addition, by making the portion along the short direction of the diaphragm 5 into a curved shape, the diaphragm 5 can be easily and reliably deformed, and the current path between the electrode 41 and the external terminal 20A can be more reliably interrupted. It becomes possible.

  In the secondary battery 100 of the present embodiment, the current collector plates 30A and 30B are bent at one side of the base portions 31A and 31B and the base portions 31A and 31B fixed to the lid portion 11 via the insulating members 3A and 3B. Terminal portions 32 </ b> A and 32 </ b> B that extend toward the bottom surface 12 c of the battery case 10. The diaphragm 5 is disposed between the base portion 31A of the current collector plate 30A and the lid portion 11, and the joint portion 5e is joined to the surface of the base portion 31A facing the lid portion 11.

  When the current collector plates 30A and 30B are manufactured, warping or twisting may occur due to pressing or bending. However, after the current collector plate 30A is manufactured, the diaphragm 5 is disposed between the insulating member 3A fixed to the lid portion 11 and the base portion 31A of the current collector plate 30A, and the diaphragm 5 is disposed on the surface facing the lid portion 11 of the base portion 31A. By joining the joint 5e, the influence of the warp and twist of the current collector plate 30A on the thin part 5f of the diaphragm 5 can be minimized.

  Further, in the secondary battery 100 of the present embodiment, the base portion 31A of the current collector plate 30A has a first portion 31a having a narrow interval with the lid portion 11 and a second portion 31b having a wide interval with the lid portion 11. doing. And the diaphragm 5 is arrange | positioned between the 2nd part 31b and the cover part 11, and the junction part 5e is joined to the 2nd part 31b. Thereby, the space which arrange | positions the convex diaphragm 5 between the 2nd part 31b and the cover part 11 is securable.

  Furthermore, in the secondary battery 100 of the present embodiment, the base portion 31A of the current collector plate 30A extends along the lid portion 11 from the first portion 31a toward the second portion 31b, and the first portion 31a and the first portion It has the connection part 31c which connects 2 part 31b. And the cross-sectional area perpendicular | vertical to the extension direction of 31 A of base parts is smaller than the 1st part 31a and the 2nd part 31b in the connection part 31c.

  Therefore, for example, even if the wound body 40 in the secondary battery 100 swings due to vibration or inertial force, and stress or vibration acts on the first portion 31a of the base portion 31A from the terminal portion 32A of the current collector plate 30A, Stress and vibration transmitted from the first portion 31a to the second portion 31b can be relaxed by the connecting portion 31c. In particular, when the connecting portion 31c has a bent portion, the flexibility of the connecting portion 31c can be improved and the stress and vibration transmitted to the second portion 31b can be more effectively reduced. Thereby, the stress and vibration transmitted to the thin wall portion 5f of the diaphragm 5 can be relaxed, and malfunction of the current interrupting portion 50 can be prevented.

  Further, in the secondary battery 100 of the present embodiment, a housing recess 34 for housing a part of the diaphragm 5 is formed on the surface of the base portion 31A of the current collector plate 30A facing the diaphragm 5 of the second portion 31b.

  Therefore, the protrusion amount of the diaphragm 5 into the battery container 10 can be increased while suppressing an increase in the height dimension of the battery container 10 of the current interrupting part 50. Thereby, the deformation amount of the diaphragm 5 which deforms toward the outside of the battery container 10 is increased in a limited space between the wound body 40 and the lid portion 11 in the battery container 10, and the diaphragm 5 after the deformation The current path between the positive electrode 41 and the external terminal 20A can be more reliably interrupted by increasing the distance between the current collector plate 30A and the current collector plate 30A. Further, the thickness of the second portion 31b can be reduced to facilitate laser welding of the joint portion 5e of the diaphragm 5 and the second portion 31b. Such an effect can also be obtained by housing the entire diaphragm 5 in the housing recess 34.

  Further, in the secondary battery 100 of the present embodiment, the external terminal 20A is disposed on the upper surface side of the lid portion 11 and penetrates the lid portion 11 to the lower surface side of the lid portion 11 via the insulating member 3A. Has a connecting portion 22A. The diaphragm 5 has a peripheral edge 5 a bonded to the conductive plate 6, and forms a space isolated from the space in the battery container 10 with the conductive plate 6. Thereby, when the internal pressure of the battery case 10 rises, a differential pressure is generated between the space between the diaphragm 5 and the conductive plate 6 and the space in the battery case 10, and stress acts on the diaphragm 5, The diaphragm 5 is broken and deformed.

  Further, when the external terminal 20 </ b> A has a through hole 23 </ b> A that communicates the space between the diaphragm 5 and the conductive plate 6 and the external space of the battery container 10, the diaphragm 5 and the conductive plate 6 are An increase in pressure in the space between is prevented. Therefore, the diaphragm 5 can be more easily and reliably deformed, and the current path between the positive electrode 41 and the external terminal 20A can be interrupted more easily and reliably.

  Moreover, in the secondary battery 100 of the present embodiment, the diaphragm 5 is made of aluminum or an aluminum alloy. Therefore, compared with the case where a diaphragm made of copper or a copper alloy is disposed between the negative electrode external terminal 20B and the current collecting plate 30B, the mechanical strength of the material of the diaphragm 5 is reduced, and the deformation of the diaphragm 5 is reduced. Can be made easier. Therefore, the current path between the electrode 41 and the external terminal 20A can be interrupted more easily and reliably. In addition, the electric current interruption part 50 can also be provided in the negative electrode side.

  Further, after the diaphragm 5 is deformed and the current interrupting section 50 interrupts the current path between the positive electrode 41 and the external terminal 20A, when the gas pressure inside the battery container 10 further increases, the gas discharge valve 13 is opened. The gas inside the battery container 10 is released to the outside. Thereby, the safety of the secondary battery 100 can be ensured.

  As described above, according to the secondary battery 100 of the present embodiment, the malfunction of the current interrupting unit 50 can be prevented, and the current path can be more reliably and stably interrupted when the internal pressure of the battery container 10 increases. .

  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 diaphragm 5 in which the dimension along the longitudinal direction of the lid portion 11 is larger than the dimension along the short direction of the lid portion 11 has been described. However, in the diaphragm 5, the dimension along the longitudinal direction of the lid portion 11 may be equal to or smaller than the dimension along the short direction of the lid portion 11. Modification 1 of the diaphragm 5 is shown in FIG.

  FIG. 9 is a plan view of the diaphragm 5 </ b> A of the present modification corresponding to FIG. 6 as viewed from a direction perpendicular to the lid portion 11. The diaphragm 5A shown in FIG. 9 is different from the diaphragm 5 described in the above-described embodiment in that the planar shape viewed from the direction perpendicular to the lid portion 11 is circular. Since the other points of the diaphragm 5A of the present modification are the same as those of the diaphragm 5 described in the above-described embodiment, the same portions are denoted by the same reference numerals and description thereof is omitted.

  According to the secondary battery including the diaphragm 5A of the present modification, not only the same effect as the secondary battery 100 of the above-described embodiment is obtained, but also the distance from the joint portion 5e to the peripheral portion 5a becomes uniform. The diaphragm 5A can be deformed more uniformly, and the current interrupting unit 50 can be stably operated.

  In the above-described embodiment, the example in which the diaphragm 5 has a convex shape that bulges from the lid portion 11 toward the current collector plate 30A has been described. However, the secondary battery 100 of the present invention is not limited to this configuration. Modification 2 of the diaphragm 5 is shown in FIG.

  FIG. 10 is a cross-sectional view of a secondary battery 100B of the present modification corresponding to FIG. 4 described in the above embodiment. The secondary battery 100B shown in FIG. 10 has the above-described implementation in that the diaphragm 5B is formed in a flat plate shape from the peripheral edge 5a to the central protrusion 5d, and the conductive plate 6B includes the side wall 6d. This is different from the secondary battery 100 described in the embodiment. Since the other points of the secondary battery 100B of the present modification are the same as those of the secondary battery 100 described in the above embodiment, the same parts are denoted by the same reference numerals and the description thereof is omitted.

  The secondary battery 100B of this modification has a side wall portion 6d in which the conductive plate 6B is erected in a direction perpendicular to the lid portion 11, and the peripheral edge portion 5a of the diaphragm 5B is engaged with the stepped portion at the lower end of the side wall portion 6d. For example, it is joined by laser welding. The diaphragm 5B has a joint 5e joined to the current collector plate 30A and a thin part 5f provided around the joint 5e. Therefore, according to the secondary battery 100B of the present modification, as in the secondary battery 100 described in the above-described embodiment, the malfunction of the current interrupting unit 50 is prevented, and the current path is set when the internal pressure of the battery container 10 increases. It is possible to shut off more reliably and stably.

3A: Insulating member, 5, 5A, 5B ... Diaphragm, 5d ... Projection part, 5e ... Joint part, 5f ... Thin part, 5g ... Recessed part, 5h ... Circular groove, 5i ... Inner face, 5j ... Outer face, 6 ... Conductive Plate 10, Battery container 11, Lid (battery container) 12 Battery can (battery container) 20 A External terminal 22 A Connection unit 30 A Current collector 31 A Base 31 a First part , 31b ... second part, 31c ... connecting part, 32A ... terminal part, 41 ... positive electrode (electrode), 34 ... receiving recess, 50 ... current interrupting part, 100, 100B ... secondary battery

Claims (14)

A secondary battery comprising a current interrupting portion in a current path between an electrode in the battery container and an external terminal provided in the battery container,
The current interrupting unit is disposed in the battery container, and includes a diaphragm connected to the external terminal, and a current collector connected to the electrode,
The diaphragm has a joint part joined to the current collector plate and a thin part provided around the joint part.   The secondary battery according to claim 1, wherein the thin portion is formed by a concave portion provided around the joint portion.   3. The secondary according to claim 2, wherein the thin-walled portion is formed between the concave portions provided on both the surface of the diaphragm facing the current collector plate and the opposite surface thereof. battery.   The secondary battery according to claim 2, wherein the recess is a circular annular groove. The diaphragm is formed in a convex shape that bulges from the lid portion of the battery container provided with the external terminal toward the current collector plate, and further protrudes one step from the top portion of the convex shape toward the current collector plate. Having a protruding portion,
The secondary battery according to claim 1, wherein the joint portion is formed at a portion of the protruding portion that contacts the current collecting plate.   The secondary battery according to claim 5, wherein the projecting portion has a planar shape similar to a planar shape of the diaphragm as viewed from a direction perpendicular to the lid portion.   The secondary battery according to claim 6, wherein the diaphragm has a circular planar shape when viewed from a direction perpendicular to the lid portion. The battery container has a flat box shape sealed with the rectangular lid.
The secondary battery according to claim 6, wherein the diaphragm has a dimension along a longitudinal direction of the lid portion larger than a dimension along a short direction of the lid portion. The current collector plate includes a base portion fixed to the lid portion via an insulating member, and a terminal portion that is bent on one side of the base portion and extends toward the bottom surface of the battery container,
The diaphragm is disposed between the base and the lid,
The secondary battery according to claim 5, wherein the joining portion is joined to a surface of the base portion facing the lid portion. The base portion has a first portion having a narrow interval with the lid portion and a second portion having a wide interval with the lid portion,
The diaphragm is disposed between the second part and the lid part,
The secondary battery according to claim 9, wherein the joint portion is joined to the second portion. The base portion extends in a direction from the first portion toward the second portion along the lid portion, and has a connecting portion that connects the first portion and the second portion;
The secondary battery according to claim 10, wherein a cross-sectional area perpendicular to the extending direction of the base portion is smaller than that of the first portion and the second portion in the connecting portion.   11. The secondary battery according to claim 10, wherein an accommodation recess for accommodating at least a part of the diaphragm is formed on a surface of the second portion facing the diaphragm. The external terminal is disposed on the upper surface side of the lid portion that closes the upper portion of the battery container, and has a connection portion that penetrates the lid portion and fixes the conductive plate via an insulating member on the lower surface side of the lid portion. And
2. The secondary battery according to claim 1, wherein a peripheral portion of the diaphragm is joined to the conductive plate, and a space isolated from the space in the battery container is formed between the diaphragm and the conductive plate.   The secondary battery according to claim 1, wherein the diaphragm is made of aluminum or an aluminum alloy.

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