JP2016122581A - Hermetically sealed secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hermetically sealed secondary battery that has a high current interruption mechanism having heat resistance and can prevent deformation (creep) and fusion of a collector plate which are caused by Joule heat under high-rate charging/discharging.SOLUTION: A current interruption mechanism 80 of a hermetically sealed secondary battery 10 is configured so that when the inner pressure of a case 12 increases over a predetermined level, a current interruption valve 30 is deformed to be away from a plate-like collector plate 72 due to the inner pressure, and the collector plate is broken at a portion of an annular groove 79 of a center thin-wall portion 74 of the collector plate. Plural pores which are further concaved from the bottom surface of the annular groove 79 are formed along the bottom surface of the groove at the portion corresponding to the bottom surface of the annular groove 79 out of the center thin-wall portion 74 of the collector plate.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a sealed secondary battery (typically a sealed secondary battery whose overall shape is a square (cuboid shape)). Specifically, the present invention relates to a sealed secondary battery provided with a current interrupting mechanism that operates by increasing internal pressure.

  In recent years, secondary batteries such as lithium secondary batteries and nickel metal hydride batteries are preferably used as so-called portable power sources such as personal computers and portable terminals, and vehicle drive power sources. In particular, a lithium secondary battery that is lightweight and has a high energy density is expected to be preferably used as a high-output power source for driving vehicles such as electric vehicles and hybrid vehicles.

  As one of typical structures of such a secondary battery, there is a sealed battery (sealed battery) in which an electrode body including a positive electrode and a negative electrode is sealed in a battery case together with an electrolyte. When charging this type of battery, if there is a malfunction due to the presence of a defective battery or a failure of the charging device, it is assumed that a current exceeding the normal level is supplied to the battery, resulting in an overcharged state. During such overcharge, the battery reaction proceeds rapidly, gas is generated inside the sealed battery case, the internal pressure of the battery case rises, and the abnormal internal pressure (gas pressure) deforms the case. Etc. may occur. In order to cope with such abnormalities, as a conventional technology, current interruption is performed by deforming parts using the pressure (gas pressure) inside the case that accompanies abnormalities in the battery and physically breaking the energized part. A battery structure with a mechanism has been proposed.

  For example, Patent Document 1 is given as a conventional example related to a secondary battery having a current interruption mechanism having such a configuration. The current interrupting mechanism described in this document includes a plate-shaped current collector plate connected to an electrode body housed inside a case of a square-shaped sealed secondary battery, and energizing a part of the current collector plate. Inverted plate (current cutoff valve) welded as possible, and when the case internal pressure (gas pressure) rises, the gas plate reverses the reversing plate in the direction away from the electrode body and the current collector plate. The current collector plate is deformed and a part of the current collector plate including the welded portion is broken along with the deformation. In this way, current reversal is realized by reversing and deforming the reversing plate and separating from the main body of the current collecting plate.

JP 2010-212034 A

  In the current interruption mechanism configured as described in Patent Document 1 above, in order to realize that the current is correctly interrupted when reaching a preset case internal pressure (that is, a predetermined gas pressure), the case internal pressure In order to quickly break a part of the current collector plate including the welded portion together with the reversal / deformation of the reverse plate (current cutoff valve) when the current reaches the current plate, the welded portion of the current collector plate and its surroundings Measures are taken such as forming the wall relatively thinner than the other parts of the current collector plate and / or forming a groove (notch) in advance at a site to be broken.

  By the way, a sealed secondary battery used as a drive power source for a vehicle such as an electric vehicle or a hybrid vehicle (including a plug-in hybrid vehicle) has a high output and a large capacity (typical) for further enhancement of performance. Requires a battery having an hourly capacity of 3 Ah or more, for example, 5 to 20 Ah or 20 Ah or more (for example, 20 to 30 Ah). For this reason, charging / discharging at a high rate that is incomparable with a battery used as a power source for a personal computer or a portable terminal (that is, a consumer product) is required.

  However, when charging / discharging at a higher rate than that of a conventional secondary battery for vehicle driving power is required, in a sealed secondary battery having a current interruption mechanism having the above-described configuration, at the time of high-rate charging / discharging. However, it is necessary to construct a current interruption mechanism so that it is maintained normally and does not perform unexpected operations. For example, as described above, the thin wall formed on the current collector plate in order to quickly reverse and deform the current cutoff valve (reverse plate) at a predetermined case internal pressure (gas pressure) and to break a part of the current collector plate A portion or a portion where a groove (notch) is formed has a smaller cross-sectional area than that of a relatively thick portion around the portion. In particular, when a groove is further provided in the thin portion, the cross-sectional area of the groove forming portion is further reduced. When a large current flows through such a small cross-sectional area during high-rate charge / discharge, the part generates heat due to the generated Joule heat, and if the heat generation is excessive, the part deforms (creep) with overheating. ) And fusing. Such deformation (creep) and fusing are not preferable because they cause current interruption.

  The present invention has been made in view of such a point, and the object of the present invention is to prevent deformation (creep) and fusing of the current collector plate due to Joule heat even during high-rate charge / discharge associated with higher output of the battery. In addition, it is an object of the present invention to provide a sealed secondary battery including a highly reliable current interrupting mechanism that realizes current interrupting accurately when a predetermined case internal pressure (gas pressure) occurs.

In the case of adopting a plate-shaped current collector plate in which a breaking groove is formed in advance and a current interrupting mechanism using a current shut-off valve, the present inventor has predetermined conditions regarding the shape of the groove formed in the current collector plate. The present invention has been completed by finding that the above-mentioned object can be realized by designing the current collector plate to include
That is, a sealed secondary battery disclosed herein includes an electrode body including a positive electrode and a negative electrode, a battery case that houses the electrode body, and a positive electrode and a negative electrode of the electrode body that are provided on the outer surface of the battery case. A sealed secondary battery comprising a positive external terminal and a negative external terminal that are electrically connected to each other, and a current interrupt mechanism that interrupts current when the internal pressure in the case rises above a predetermined level.
The current interrupt mechanism is a current interrupt that is electrically connected to either the positive or negative terminal between the positive electrode of the electrode body and the positive external terminal or between the negative electrode of the electrode body and the negative external terminal. A valve, and a plate-shaped current collector electrically connected to either the positive or negative electrode of the electrode body.
Further, the current collector plate is composed of a central thin portion formed relatively thin and a thick portion formed relatively thick around the central thin portion, and A breaking groove is formed in an annular shape with a predetermined diameter inside the central thin portion.
The current cutoff valve is partly joined to the central thin portion of the current collector plate inside the annular groove so as to be energized, and when the internal pressure in the case rises above a predetermined level. The current cutoff valve is deformed in the direction away from the current collector plate by the internal pressure, and the central thin portion of the current collector plate is broken at the annular groove portion. The current cutoff valve with the part is separated and the current cutoff is realized.
In the sealed secondary battery disclosed here, a portion of the thin-walled portion corresponding to the bottom surface of the annular groove has pores recessed from the bottom surface of the annular groove along the surface of the groove. A plurality is formed.

  In the sealed secondary battery disclosed herein, when the internal pressure of the case of the battery reaches a predetermined pressure, the pores (typically, the pores formed in the bottom surface of the annular groove in the thin portion of the current collector plate). The stress concentrates on the end of the pore), and the current collector plate can be broken starting from the pore where the stress is concentrated (typically, the end of the pore). Therefore, the current interruption mechanism provided in the sealed secondary battery disclosed herein has a depth of the annular groove compared to the depth of the annular groove provided in the current collector plate provided in the conventional sealed secondary battery. Even if the thickness is shallow (that is, even if the thickness of the remaining portion of the thin portion of the current collector plate where the annular groove is formed), the pressure in the battery case (case internal pressure, gas pressure) When the pressure reaches a predetermined pressure, the current cutoff valve can be quickly deformed to break a part of the current collector plate. That is, according to the current interruption mechanism provided in the sealed secondary battery disclosed here, the current interruption effect at the predetermined case internal pressure (gas pressure) is highly exhibited, and the thin portion of the current collector plate The cross-sectional area of the annular groove forming portion can be increased. Thereby, the heat generation amount of Joule heat in the annular groove forming portion can be reduced, and the heat generation (overheating) in the thin wall portion (particularly, the annular groove forming portion) can be suppressed. That is, in the sealed secondary battery having such a configuration, the current collector plate is prevented from being deformed and blown at the time of high-rate charge / discharge accompanying the high output of the battery, and a current cutoff valve is provided at a predetermined case internal pressure (gas pressure). A part of the current collector plate can be broken by being quickly deformed. As described above, the reliability of the current interrupt mechanism is improved in response to the high rate charge / discharge required for high output of the battery, and a higher quality sealed secondary battery (for example, a sealed lithium secondary battery) is provided. Can do.

1 is a perspective view schematically showing an outer shape of a sealed lithium secondary battery (lithium ion battery) according to an embodiment. It is a figure which shows typically the structure of the current collecting plate in the sealed lithium secondary battery which concerns on one Embodiment. It is sectional drawing which shows typically the structure and state (before electric current interruption) of the electric current interruption mechanism provided in the positive electrode side of the sealed lithium secondary battery which concerns on one Embodiment. It is sectional drawing which shows typically the structure and state (after electric current interruption) of the electric current interruption mechanism provided in the positive electrode side of the sealed lithium secondary battery which concerns on one Embodiment. It is a perspective view which shows typically the shape of the annular groove and pore which are formed in the current collection board with which the electric current interruption mechanism of the sealed lithium secondary battery which concerns on one Embodiment is equipped. Such a perspective view is a cross section that passes through the center of the annular groove and cuts the current collector plate in the thickness direction, and shows a part of the current collector plate cut along a cross section that crosses one pore. It is a perspective view which shows typically the shape of the cyclic | annular groove | channel and pore of a current collecting plate (samples 1-5) evaluated in one test example. It is sectional drawing which shows typically the load condition at the time of performing the stress analysis of a current collecting plate in one test example. It is a schematic diagram which expands and shows the annular groove formation part about the result of having stress-analyzed the current collecting plate which concerns on the sample 3. FIG. Maximum when CAE (computer aided engineering) analysis is performed on the cross-sectional area of the annular groove forming portion of the current collector plate (samples 1 to 5) evaluated in one test example and the stress distribution generated in the current collector plate (samples 1 to 5) It is a graph which shows stress. The cross-sectional area of the annular groove forming portion according to each sample is shown as a relative ratio when the cross-sectional area of the annular groove forming portion in sample 1 is 100%, and the maximum stress related to each sample is the maximum stress generated in sample 1 Is shown as a relative ratio with respect to 100%.

  In the present specification, the “lithium secondary battery” refers to a secondary battery that uses lithium ions as electrolyte ions and is charged / discharged by movement of charges accompanying the lithium ions between the positive and negative electrodes. A secondary battery generally called a lithium ion battery (or a lithium ion secondary battery) is a typical example included in the lithium secondary battery in this specification. Further, in this specification, the “active material” refers to a substance (compound) involved in power storage on the positive electrode side or the negative electrode side. That is, it refers to a substance that is involved in the insertion and extraction of electrons during battery charge / discharge.

Hereinafter, a preferred embodiment relating to a lithium secondary battery (lithium ion battery) 10 as an example of a sealed secondary battery disclosed herein will be described with reference to the drawings. Although not intended to be particularly limited, hereinafter, a wound type electrode body (hereinafter referred to as a “wound electrode body”) and a non-aqueous electrolyte are accommodated in a rectangular (that is, a rectangular box shape) case. A lithium ion battery having the above-described form will be described as an example. The dimensional relationship (length, width, thickness, etc.) in each figure does not reflect the actual dimensional relationship. Further, members / parts having the same action are denoted by the same reference numerals, and redundant description is omitted or simplified.
Note that the present invention is not limited to a lithium secondary battery (typically a lithium ion battery having a nonaqueous electrolyte) as long as it has a current interruption mechanism having a configuration disclosed herein, The present invention can also be applied to nickel metal hydride batteries and other secondary batteries.

In the lithium ion battery 10 according to the present embodiment, a flat wound electrode body 50 as shown in FIG. 2 corresponds to the shape of the wound electrode body 50 together with a liquid electrolyte (electrolytic solution) not shown in FIG. The battery is configured to be accommodated in a flat rectangular battery case (that is, an exterior container) 12 as shown.
The battery case 12 has a box-shaped (that is, a bottomed rectangular parallelepiped) case body 14 having an opening at one end (corresponding to the upper end in a normal use state of the battery 10), and is attached to the opening. It is comprised from the sealing board (lid body) 16 which consists of a rectangular-shaped plate member which plugs up an opening part. The sealing plate (lid body) 16 is welded to the peripheral edge of the opening of the case body 14, so that a pair of case wide surfaces facing the wide surface of the flat wound electrode body 50 and the case wide surface are adjacent to each other. A battery case 12 having a hexahedron-shaped sealed structure with four rectangular case surfaces (that is, one of the rectangular case upper surfaces is constituted by the sealing plate 16) is formed.
Although it does not restrict | limit in particular, As a suitable size of the hexahedron shape case of this kind of square battery, the length of the long side of the case main body 14 and the sealing board 16: about 80-200 mm (for example, 100-150 mm), a case The length on the short side of the main body 14 and the sealing plate 16 (that is, the thickness of the case 12): about 8 to 25 mm (for example, 10 to 20 mm), and the height of the case 12: about 70 to 150 mm can be exemplified.

The material of case 12 should just be the same as what is used with the conventional sealed battery, and there is no restriction | limiting in particular. A case 12 mainly composed of a metal material that is lightweight and has good thermal conductivity is preferable. Examples of such a metal material include aluminum, stainless steel, nickel-plated steel, and the like. The case 12 (the case main body 14 and the sealing plate 16) according to the present embodiment is made of aluminum or an alloy mainly composed of aluminum.
Further, the thickness of the case 12 (the case main body 14 and the sealing plate 16) is not particularly limited, but in the case of constituting a sealed battery for a vehicle driving power source, about 0.3 mm to 2 mm is appropriate, and 0.5 mm to About 1 mm is preferable.

As shown in FIG. 1, a positive electrode external terminal 20 and a negative electrode external terminal 18 for external connection are formed on the sealing plate 16. These external terminals 18 and 20 can be equipped with a terminal plate or an external connection terminal having an appropriate shape according to the usage pattern of the lithium ion battery 10 according to the present embodiment.
Between the two terminals 18 and 20 of the sealing plate 16, the internal pressure is released when the internal pressure of the case 12 rises to a predetermined level (for example, a set valve opening pressure of about 0.3 to 1.0 MPa). A thin safety valve 40 and a liquid injection port 42 (FIG. 1 is a state in which the liquid injection port 42 is sealed and masked by a sealing material 43 after liquid injection) are formed.

  As shown in FIG. 2, the wound electrode body 50 has a long sheet-like positive electrode (positive electrode sheet) 52 and a long length (not shown) similar to the positive electrode sheet 52, similar to a wound electrode body of a normal lithium ion battery. A sheet-like negative electrode (negative electrode sheet) is laminated together with a total of two long sheet-like separators (separator sheets) 54 and wound in the longitudinal direction, and then the obtained wound body is crushed from the side direction and abducted. It is produced by. Specifically, the positive electrode sheet 52 and the negative electrode sheet are slightly shifted in the width direction so that one end in the width direction of either the positive or negative sheet protrudes from one end and the other end in the width direction of the separator sheet 54. It is wound in the state that was done. As a result, one end of the wound electrode body 50 in the winding axis direction and one end in the width direction of the positive electrode sheet 52 and the negative electrode sheet respectively are wound core portions 55 (that is, the positive electrode sheet and the negative electrode sheet). A portion protruding outward from a portion where the separator sheet is wound tightly is formed.

FIG. 2 shows a protruding portion 52 </ b> A of the positive electrode sheet 52, and the protruding portion 52 </ b> A of the positive electrode sheet 52 is interposed via a positive electrode current collecting tab 60 and a positive electrode internal terminal 70 disposed inside the case 12. Thus, the external connection positive electrode external terminal 20 is electrically connected. Similarly, the negative electrode side (not shown) is also electrically connected to the negative electrode external terminal 18 for external connection via a negative electrode current collector tab and a negative electrode current collector plate (not shown) arranged inside the case 12.
In the lithium ion battery 10 according to the present embodiment, the current cutoff mechanism 80 includes a part of the positive external terminal 20, a part of the positive internal terminal 70, and a current cutoff valve (reversing plate) 30. . The current interruption mechanism 80 will be described later.

The material and the member itself constituting the wound electrode body 50 may be the same as those of the electrode body provided in the conventional lithium ion battery, and are not particularly limited. For example, the positive electrode sheet 52 may have a configuration in which a positive electrode active material layer is formed on a long positive electrode current collector (for example, an aluminum foil). As the positive electrode active material used for forming this positive electrode active material layer, one or two or more materials conventionally used in lithium ion batteries can be used without particular limitation. As a preferred example, an oxide containing lithium and a transition metal element as constituent metal elements such as lithium nickel oxide (for example, LiNiO ₂ ), lithium cobalt oxide (for example, LiCoO ₂ ), and lithium manganese oxide (for example, LiMn ₂ O ₄ ). And a phosphate containing lithium and a transition metal element as constituent metal elements, such as lithium oxide (lithium transition metal oxide), lithium manganese phosphate (LiMnPO ₄ ), and lithium iron phosphate (LiFePO ₄ ).
The negative electrode sheet may have a configuration in which a negative electrode active material layer is formed on a long negative electrode current collector (for example, copper foil). As the negative electrode active material used for forming this negative electrode active material layer, one or two or more materials conventionally used in lithium ion batteries can be used without particular limitation. Preferable examples include carbon-based materials such as graphite carbon and amorphous carbon, lithium transition metal oxides, lithium transition metal nitrides, and the like. Moreover, as a suitable example of the said separator sheet, what was comprised with porous polyolefin resin is mentioned.

As the liquid electrolyte (electrolytic solution), the same non-aqueous electrolytic solution conventionally used in lithium ion batteries can be used without particular limitation. Such a non-aqueous electrolyte typically has a composition in which a supporting salt is contained in a suitable non-aqueous solvent. Examples of the non-aqueous solvent include ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 1,3-dioxolane, and the like. One kind or two or more kinds selected from the group can be used. Examples of the supporting salt include LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) _{3 and the} like. Lithium salts can be used. As an example, a nonaqueous electrolytic solution in which LiPF ₆ is contained in a mixed solvent of ethylene carbonate and diethyl carbonate (for example, a mass ratio of 1: 1) at a concentration of about 1 mol / L can be given. A solid or gel electrolyte may be used instead of the electrolytic solution.

Hereinafter, the current interrupting mechanism 80 will be described in detail with reference to the drawings. As shown in FIG. 2, the positive electrode protruding portion 52A protruding from one end portion in the winding axis direction of the wound electrode body 50 is electrically conductive. A positive electrode current collecting tab 60 made of metal (for example, made of aluminum or an alloy mainly composed of aluminum) is connected. A positive electrode internal terminal 70 made of metal (for example, made of aluminum or an aluminum-based alloy) having excellent electrical conductivity is formed so as to extend upward (that is, in the sealing plate direction) from the current collecting tab 60. The positive electrode internal terminal 70 has a plate-like current collector plate 72 (typically a rectangular plate shape, for example, a rectangular plate shape) that is disposed in proximity to the inner surface side of the sealing plate 16 and substantially parallel to the inner surface. The current collecting plate 72 and the positive current collecting tab 60 are configured by an arm-shaped connecting portion 71 that connects the current collecting plate 72 and the positive current collecting tab 60.
The current collecting plate 72 is composed of a central thin portion 74 to which a part (central recess 30A) of a current cutoff valve (reversing plate) 30 described later is welded and a relatively thick thick portion 78 around the central thin portion 74. . The central thin portion is typically formed in a circular shape or a rectangular shape. Further, as shown in FIG. 2, gas flow holes 74 </ b> A and 78 </ b> A are formed at a central portion of the central thin portion 74 and a plurality of locations (two locations in the present embodiment) of the thick portion 78. Further, as shown in FIG. 3, a breaking groove (notch) 79 is formed in a ring shape with a predetermined diameter inside the central thin portion 74. As shown in FIG. 3, the annular groove (notch) 79 for breakage is either a surface facing the electrode body 50 or a surface facing the insulating holder 32 among the surfaces of the thin portion 78 of the current collector plate 72. You may form in. Further, an appropriate cut may be provided at a position crossing the annular groove 79. By forming such a cut, it is possible to suppress deformation inhibition in the circumferential direction when the thin portion 74 of the current collector plate 72 is deformed, and to reduce stress (deformation stress) necessary for the current collector plate 72 to be deformed. Can do.

  As shown in FIG. 5, the bottom surface of the annular groove 79 has a plurality of (for example, 30 to 130, preferably 64 to 112) pores 76 that are recessed from the bottom surface of the annular groove 79. Are formed in an annular shape. Moreover, it is preferable that the center of the pore 76 and the center of the pore 76 are arrange | positioned at equal intervals for each pore. The pores 76 may be either through holes or non-through holes. The through hole is preferable because stress can be easily concentrated on the end portion of the pore, and the current collector plate can be suitably broken at the stress concentration portion. The shape of the pores 76 is not particularly limited, but the shape of the pores 76 when the surface of the current collector plate 72 on which the pores 76 are formed is viewed in plan view (typically circular), that is, It may be a cylindrical pore.

Although not particularly limited, in the case of a battery used as a drive power source for a vehicle, the length (short axis) of the short side of the current collecting plate 72 is typically about 6 mm to 15 mm. The length (major axis) on the long side of the plate 72 is typically defined to be about 2 to 5 times the minor axis.
The size of the central thin portion 74 is not particularly limited, but is a length corresponding to 40 to 70% of the length of the minor axis of the current collector plate 72 (for example, when the minor axis of the current collector plate 72 is 8 mm). It is appropriate to form a circular or square shape having a diameter of 3.2 mm to 5.6 mm.
The diameter of the annular groove 79 is preferably 2 mm or more (typically 3 mm or more and 6 mm or less). Moreover, although it is a formation position of the cyclic | annular groove | channel 79, from a viewpoint of the resistance (heat resistance) improvement with respect to the deformation | transformation and fusing of the current collecting plate 72, the distance of the thick part 78 and the cyclic | annular groove | channel 79 may be 1 mm or less. It is suitable, and 0.4 to 0.6 mm (for example, about 0.5 mm ± 0.05 mm) is preferable.

The thickness of the thick portion 78 is typically 2 mm or less (for example, 0.4 mm to 2 mm), and preferably 1 mm or less (for example, 0.5 mm to 1 mm). The thickness of the central thin portion 74 is typically 0.2 mm or less (for example, 0.05 mm to 0.2 mm), and preferably 0.15 mm or less (for example, 0.08 mm to 0.15 mm).
The depth (incision depth) of the annular groove 79 is suitably set so that the thickness of the thinnest portion of the remaining portion in the annular groove 79 forming portion is at least 0.03 mm or more. It is preferable to set it to be 0.05 mm or more, typically 0.08 mm or more. If the thickness of the remaining portion is too small, the heat generation in the annular groove 79 forming portion becomes too large, and the current collector plate (typically, the annular groove 79 forming portion in the thin wall portion of the current collector plate) is deformed (creep). ) And fusing. On the other hand, when the thickness of the remaining portion is too large, it is not preferable because it is difficult to break the current collector plate when a predetermined internal pressure is generated. For this reason, the depth (cut depth) of the annular groove 79 is such that the thickness of the thinnest portion of the remaining portion in the annular groove forming portion is, for example, 0.15 mm or less, typically 0.12 mm or less, Generally, it is preferable to set it to be 0.10 mm or less.

  Further, even if the cross-sectional area of the current collector plate in the annular groove 79 forming portion is increased by forming the above-mentioned pores on the bottom surface of the annular groove 79, it is accurate when a predetermined case internal pressure (gas pressure) occurs. A current interruption can be realized well. In other words, the cross-sectional area of the current collector plate where the annular groove 79 is formed is larger than the cross-sectional area of the current collector plate 72 where the pores 76 are not formed in the bottom of the annular groove 79. (For example, 1.1 times or more, typically 1.2 times or more, preferably 1.6 times or more). Here, in this specification, the cross-sectional area of the annular groove 79 forming portion of the current collector plate 72 is the annular groove 79 when the current collector plate 72 is cut in the thickness direction so as to pass through the center of the ring of the annular groove 79. The cross-sectional area of the current collector plate 72 (that is, the remaining portion of the current collector plate) at the formation portion, and the cross-section where the cross-sectional area is the smallest (typically cut so as to pass through the center of the pore 76) Section).

The size of the pores 76 is not particularly limited, but is preferably set so that the diameter of the pores 76 is smaller than the width of the annular groove 79. Typically, 0.02 mm to 0.1 mm (for example, 0.04 mm to 0.08 mm, preferably about 0.06 mm ± 0.01 mm) is appropriate. The interval between the pores 76 is suitably set such that the distance between the centers of the two pores 76 is about 1.8 to 4 times the diameter of the pores 76. By appropriately adjusting the diameter of the pores 76 and the interval between the pores 76, the pressure (reversing pressure) at which the current collector plate 72 breaks can be designed.
The formation method of such a pore 76 is not specifically limited, What is necessary is just to employ | adopt a well-known pore formation method. For example, it can be formed by a technique such as electric discharge machining or laser machining.

As shown in FIG. 3, the positive electrode external terminal 20 according to the present embodiment is mounted in a positive electrode mounting hole 16 </ b> A formed in advance on the sealing plate 16 on the outer surface side (upward direction in FIG. 3) of the sealing plate 16. A cylindrical connection terminal 22 and a gasket 24 sandwiched between the cylindrical connection terminal 22 and the sealing plate 16 (periphery of the mounting hole 16A) are provided. A rubber terminal plug 23 is sealed in the through hole 22B of the cylindrical connection terminal 22.
Furthermore, the positive electrode external terminal 20 according to the present embodiment is made of a cap-shaped synthetic resin in which insertion holes into which the cylindrical connection terminals 22 can be inserted are formed on the inner surface side (downward in FIG. 3) of the sealing plate 16. The insulating plate 26 and the metal sealing member tab 28 are provided.
More specifically, as shown in FIG. 3, the cylindrical connection terminals 22 electrically connected to the positive electrode internal terminal 70 are respectively formed on the gasket 24, the sealing plate 16, the insulating plate 26, and the sealing body tab 28. The members 22, 24, 16, 26, and 28 are integrally fixed by being inserted into the holes and caulking the tip 22 C as shown in the figure.

Further, the reversing plate 30 functioning as a plate-like current cutoff valve is welded to the edge of the cap-shaped sealing body tab 28, and the current collecting plate 72 and the peripheral portion of the reversing plate 30 are connected to the periphery of the reversing plate 30. An insulating holder 32 made of synthetic resin is disposed for the purpose of positioning the current collecting plate 72 and the reversing plate 30 and electrically insulating the peripheral portion.
Further, the central portion of the plate-like reversing plate 30 is recessed so as to contact the central thin portion 74 of the current collector plate 72 through a hole formed in the central portion of the corresponding insulating holder 32. The central recess 30A is joined to the inside of the annular groove 79 of the central thin portion 74 of the current collector plate 72 by laser welding or ultrasonic welding. In other words, in the central thin portion 74 of the current collector plate 72 of the positive electrode internal terminal 70, the fracture annular groove 79 exists around the joint portion of the central recess 30A of the reversing plate 30.
As a result of the above configuration, the positive electrode sheet 52 is electrically connected to the connection terminal 22 through the positive electrode protruding portion 52A, the current collecting tab 60, the positive electrode internal terminal 70, the reversing plate 30, and the sealing body tab 28.

  When the pressure (gas pressure) in the battery case 12 increases to a predetermined value or more, the reversing plate 30 is bent and deformed to the connection terminal 22 side (typically reversing and deforming to the connection terminal 22 side). Since the current collecting plate 72 is welded to the central recess 30A of the reversing plate 30 when the reversing plate 30 is deformed as described above when the pressure in the case 12 exceeds a predetermined value, Accordingly, the thin portion 74 of the current collector plate 72 is broken at the annular groove 79. Thereby, as shown in FIG. 4, the electrical connection between the reversing plate 30 and the current collecting plate 72 is interrupted. In addition, although the electric current interruption mechanism 80 which concerns on this embodiment is provided in the positive electrode external terminal 20 side, it is not restricted to this aspect, You may be provided in the negative electrode external terminal 18 side.

  Hereinafter, some specific test examples relating to the current collector provided by the present invention will be introduced, but the current collector provided by the present invention is intended to be limited to the form introduced below. is not.

A total of five types (samples 1, 2, 3, 4 and 5) of plate-shaped aluminum current collector plates 72 in which the annular groove 79 has the shape shown in FIG. 6 are designed, and CAE (computer aided engineering) analysis is performed for each sample. The stress analysis was performed. Samples 1 to 3 and 5 have an annular groove 79 formed on the surface facing the insulating holder 32 when the battery 10 is constructed using the current interrupting mechanism 80 provided with the current collector plate 72. An annular groove 79 was formed on the surface opposite to the annular groove forming surfaces 1 to 3 and 5 (that is, the surface facing the electrode body 50 when the battery was constructed). The current collecting plate 72 according to each sample is the same except for the depth of the annular groove 79 (the thickness of the remaining portion), the formation surface of the annular groove 79, the cross-sectional area of the annular groove forming portion, and the interval between the pores 76. Designed to be a parameter.
The annular groove 79 of the current collecting plate 72 according to the sample 1 has a predetermined internal pressure when the battery 10 having the current interrupting mechanism 80 including the current collecting plate 72 reaches a predetermined pressure when a predetermined stress is applied. The annular groove 79 having the same shape as the annular groove 79 formed in the conventional current collector plate 72, and the thickness of the thinnest portion of the remaining portion is reduced to 0. 075 mm. Further, the annular groove 79 of the current collector plate 72 according to the sample 2 has a smaller depth of cut than the annular groove 79 of the sample 1 (that is, the remaining portion is thicker), and is the thinnest of the remaining portions. The thickness of the part was 0.15 mm. In addition, a through-hole (pore 76) having a diameter of 0.06 mm is formed on the bottom surface of the annular groove 79 of the current collector plate 72 according to Samples 3 to 5, and Sample 3 and Sample 4 have the same pore spacing. Thus, Sample 5 was designed so that the pore spacing was wider than Samples 3 and 4. For samples 3 to 5, the thickness of the thinnest portion of the remaining portion was 0.15 mm as in sample 2. FIG. 9 shows a relative ratio of the cross-sectional area of the annular groove forming portion of the current collector plate 72 according to each sample when the cross-sectional area of the annular groove forming portion in Sample 1 is 100%.

With respect to the current collector plate 72 according to each example, as shown in FIG. 7, the surface facing the insulating holder 32 becomes the upper surface when the battery 10 including the current interruption mechanism 80 using the current collector plate 72 is constructed. The stress distribution was analyzed by CAE (computer aided engineering) analysis when the load was applied in the direction of fixing the end side surface of the thick portion 78 and pushing the end portion of the thin portion 74 upward. . FIG. 8 shows the result of the stress analysis of the current collector 72 according to the sample 3 (in FIG. 8, the portion where the stress is concentrated is shown in a dark color). As shown in FIG. 8, in the sample 3 in which the pores 76 are provided on the bottom surface of the annular groove 79, it was confirmed that stress was concentrated on the end portions of the pores 76. Further, although not shown here, it was confirmed that stress was concentrated on the ends of the pores 76 in the sample 4 and the sample 5 as in the case of the sample 3. FIG. 9 shows the relative ratio of the maximum stress generated in the current collector plate 72 according to each sample when the maximum stress generated in the current collector plate 72 according to sample 1 is 100%. The maximum stress generated in the current collector 72 according to the sample 2 is 0.6 times the maximum stress generated in the sample 1, and the breaking stress at which the annular groove 79 is broken even when a predetermined load (set load) is applied. It did not come. On the other hand, the maximum stress generated in the current collector plate according to Samples 3 to 5 provided with the pores 76 in the bottom surface of the annular groove 79 is 0.9 to 1.3 times the maximum stress generated in Sample 1. It was confirmed that by applying a predetermined load (set load), the annular groove 79 reached a breaking stress at which the annular groove 79 could break.
Further, as shown in FIG. 9, the cross-sectional area of the annular groove forming portion of the current collecting plate 72 according to Sample 3 and Sample 4 is 1.25 times the cross sectional area of the annular groove forming portion of the current collecting plate of Sample 1. The sectional area of the annular groove forming portion of the current collecting plate 72 according to Sample 5 was 1.6 times that of the annular groove forming portion of the current collecting plate 72 of Sample 1. That is, when comparing the Joule heat generated at the location where the cross-sectional area of the annular groove forming portion of the current collecting plate 72 relating to each sample is the smallest, Sample 3 and Sample 4 are 1 / 1.25 times as large as Sample 1 (approximately 80%), and Sample 5 was 1 / 1.6 times that of Sample 1 (approximately 62%). That is, it was confirmed that the generation of Joule heat at the annular groove forming portion can be suppressed by providing the pores 76 at the bottom of the annular groove 79.

  As described above, according to the present invention, a sealed secondary battery (typically a lithium secondary battery having a square outer shape or other sealed secondary battery having a current interruption mechanism using a current collector plate disclosed herein is used. Battery). Since such a current collector plate is a current collector plate in which deformation (creep) and fusing due to Joule heat that can occur in association with charge and discharge are suppressed, the current interrupting mechanism using the current collector plate is excellent in heat resistance and This is a highly reliable current interrupting mechanism that realizes current interrupting accurately when a predetermined case internal pressure (gas pressure) occurs. Therefore, a sealed secondary battery equipped with such a current interrupting mechanism is a vehicle (for example, a plug-in hybrid vehicle (PHV), a hybrid vehicle (HV), an electric vehicle (EV), etc.) that requires high-rate charging / discharging as the output increases. It is suitable as a driving power source.

  As mentioned above, although the specific example of this invention was demonstrated in detail, these are only illustrations and do not limit a claim. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

10 Secondary battery (lithium ion battery)
12 Battery case 14 Case body 16 Sealing plate (lid)
18 Negative External Terminal 20 Positive External Terminal 22 Connection Terminal 22B Through Hole 22C Tip 24 Gasket 26 Insulating Plate 28 Sealing Body Tab 30 Reverse Plate (Current Cutoff Valve)
30A Central recessed part 32 Insulation holder 50 Winding electrode body 52 Positive electrode sheet 54 Separator sheet 55 Winding core part 60 Positive electrode current collection tab 70 Positive electrode internal terminal 71 Connection part (arm part)
72 Current Collector Plate 74 Center Thin Wall 74A Gas Flow Hole 76 Fine Hole 78 Thick Wall 78A Gas Flow Hole 79 Annular Groove (Notch)
80 Current interrupt mechanism

Claims (1)

An electrode body comprising a positive electrode and a negative electrode;
A battery case that houses the electrode body;
A positive external terminal and a negative external terminal provided on the outer surface of the battery case and electrically connected to the positive electrode and the negative electrode of the electrode body, respectively;
A sealed secondary battery comprising a current interrupting mechanism that interrupts current when the internal pressure in the case rises above a predetermined level,
The current interruption mechanism is an electric current interruption electrically connected to either the positive or negative terminal between the positive electrode of the electrode body and the positive external terminal or between the negative electrode of the electrode body and the negative external terminal. A valve and a plate-shaped current collector electrically connected to either the positive or negative electrode of the electrode body,
The current collector plate is composed of a central thin portion formed relatively thin and a thick portion formed around the central thin portion and relatively thick, and the center A breaking groove is formed in an annular shape with a predetermined diameter inside the thin portion,
A part of the current cutoff valve is joined to the central thin part of the current collector plate inside the annular groove so as to be energized,
When the internal pressure in the case rises above a predetermined level, the current shut-off valve is deformed in a direction away from the current collector plate by the internal pressure, and the central thin portion of the current collector plate is at the annular groove portion. By breaking, the current cut-off valve with the broken central thin portion is separated from the current collector plate, and the current cut-off is configured to be realized.
A sealed secondary battery in which a plurality of pores recessed from the bottom surface of the annular groove are formed in a portion corresponding to the bottom surface of the annular groove in the thin portion, along the bottom surface of the groove.