JP2008251187A - Sealed battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sealed battery having excellent sealing properties and high safety by comprising a sealing body capable of preventing the clogging of the sealing body by contents and efficiently releasing gas even if a valve mechanism is operated due to an increase in gas pressure in the battery. <P>SOLUTION: The sealed battery has the sealing body having a pressure valve mechanism capable of exhausting gas to the outside when gas pressure in the battery reaches a prescribed value, arranged in an opening 41 of an outer can 40 to seal the opening. Abnormal heat generation opening forming parts 11c, 11d which open at the abnormal heat gereation of the battery and exhaust generated gas to the outside of the battery are formed in the sealing body 10 to enhance gas exhausting performance when abnormal heat is generated. More concretely, an opening 11c is formed at a top plate of a cap 11, and aluminum foil 11d joined to the opening 11c is cut out at the abnormal heat generation, and the opening is formed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a sealed battery having a sealing body at the opening of an outer can, and in particular, has a pressure valve mechanism that can discharge gas generated in the battery to the outside of the battery when the gas pressure exceeds a predetermined value. The present invention relates to a sealed battery in which a sealing body is disposed in an opening of an outer can and the opening is sealed.

  In general, in a sealed battery such as a lithium ion battery, when a device including a charger is broken, overcharged, or misused, a power generation element such as an electrolyte or an active material in the battery undergoes a chemical change. For example, the electrolyte solution or the active material is decomposed by an abnormal reaction due to overcharge or short circuit, and abnormally gas is generated inside the battery, so that the battery internal pressure becomes excessive. In such a case, there is a risk of the battery exploding or damaging the equipment used, so a pressure valve mechanism has been conventionally added to this type of battery. As a battery to which such a pressure valve mechanism is added, for example, Patent Document 1 (Japanese Patent Laid-Open No. 2000-36293) is known.

  As shown in FIG. 3, the sealed battery provided with the pressure valve mechanism proposed in Patent Document 1 includes a stainless steel first valve cap 31 formed in a cap shape, and a stainless steel formed in a dish shape. The sealing body 30 comprised from the made 2nd valve cap 32 is provided. The 1st valve cap 31 consists of the convex part 31a which bulges toward the battery exterior, and the flat flange part 31b which comprises the base part of this convex part 31a, and there are several in the corner | angular part of the convex part 31a. A gas vent hole 31c is provided. On the other hand, the 2nd valve cap 32 consists of the recessed part 32a which bulges toward the inside of a battery, and the flat flange part 32b which comprises the bottom part of this recessed part 32a. Degassing holes 32c are provided at the corners of the recesses 32a.

  Inside these first valve cap 31 and second valve cap 32, there is housed a conductive elastic deformation plate 33 that deforms when the gas pressure inside the battery rises and exceeds a predetermined pressure. The conductive elastic deformation plate 33 serves as a valve member, and includes a concave portion 33a and a flange portion 33b. The lowest portion of the recess 33a is fixedly disposed on the upper surface of the recess 32a of the second valve cap 32 by ultrasonic welding or laser welding, and the flange portion 33b is connected to the flange portion 31b of the first valve cap 31 and the second portion. The two valve caps 32 are sandwiched between the flange portions 32b.

A ring-shaped PTC (Positive Temperature Coefficient) thermistor element 34 is disposed at a part of the upper portion of the flange portion 32b. When an overcurrent flows in the battery and an abnormal heat generation phenomenon occurs, the PTC thermistor element 34 The resistance value increases to reduce the overcurrent. When the gas pressure inside the battery rises and exceeds a predetermined pressure, the concave portion 33a of the conductive elastic deformation plate 33 is deformed, so that the contact between the conductive elastic deformation plate 33 and the concave portion 32a of the second valve cap 32 is prevented. As a result, the overcurrent or short circuit current is cut off. Further, when the gas pressure inside the battery further rises after the overcurrent or the short-circuit current is cut off, the notch portion 33c formed in the conductive elastic deformation plate 33 is cleaved and the gas is released from the gas vent hole 31c. It has become so.
JP 2000-36293 A

  However, in the sealed battery proposed in Patent Document 1 described above, when the gas pressure inside the battery rises and the notch 33c formed in the conductive elastic deformation plate 33 is cleaved, the gas is vented. It is released from 31c. In this case, since the notch 33c is cleaved, a situation occurs in which the conductive elastic deformation plate 33 and a part of the contents of the battery block the gas vent hole 31c, and the gas is sufficiently discharged from the battery. In the worst case, there was a possibility that the battery would burst.

  Therefore, the present invention has been made to solve the above-described problems, and even when the gas pressure inside the battery rises and the valve mechanism is activated and the contents are scattered, the gas is effectively removed. It is an object of the present invention to provide a sealed battery having an excellent sealing property and improved safety by providing a sealing body that can be used.

  In the sealed battery of the present invention, a sealing body having a pressure valve mechanism capable of discharging the gas generated in the battery to the outside of the battery when the gas pressure becomes a predetermined value or more is disposed in the opening of the outer can. The opening is sealed. And in order to achieve the said objective, the opening formation part which can be opened to the sealing body at the time of the abnormal heat generation of the said battery, and can discharge | release the gas generated in the battery outside the battery is formed, and the abnormal heat generation of the said battery is formed. The gas discharge capacity is improved.

  Here, when the gas pressure in the battery rises and the valve mechanism operates, the contents in the battery scatter and the scattered contents close the gas vent hole. However, if an opening forming part is formed in the sealing body that can form an opening during abnormal heat generation and discharge the gas generated in the battery to the outside of the battery, the scattered contents block the gas vent hole Even if this occurs, a new opening is formed by the opening forming portion. For this reason, the gas is effectively discharged by the new opening. As a result, it is possible to prevent the battery from being ruptured and to provide a sealed battery with significantly improved safety.

  In this case, in consideration of manufacturability and safety, an opening forming portion is formed on the top plate portion or the side wall portion of the cap portion constituting the sealing body, and a part of these opening forming portions is lost during abnormal heat generation. It is desirable that an opening be formed. In order to form such an opening forming portion, a material having a lower melting point than the material forming the top plate portion or side wall portion of the cap portion, for example, a material having a melting point of 700 ° C. or less is disposed. You can do it.

  In the present invention, since the opening forming portion that can discharge the gas generated by forming a new opening during abnormal heat generation to the outside of the battery is formed in the sealing body, there is a situation that the battery may burst. This can be prevented and safety is greatly improved.

Hereinafter, a preferred embodiment when the sealed battery of the present invention is applied to a lithium ion battery will be described with reference to FIG. 1 and FIG. 2, but the present invention is not limited to this embodiment. The present invention can be implemented with appropriate modifications without changing the object of the present invention.
FIG. 1 is a diagram showing a sealed battery made of a lithium ion battery according to Example 1 of the present invention. FIG. 1 (a) shows a state in which a sealing body is attached to an opening of an outer can of the sealed battery. FIG. 1B is a cross-sectional view schematically showing the main part, and FIG. 1B is a top view schematically showing the upper surface of the main part of the cap part in FIG. FIG. 2 is a view showing a sealed battery made of a lithium ion battery according to Example 2 of the present invention. FIG. 2 (a) shows a state in which a sealing body is attached to an opening of an outer can of the sealed battery. It is sectional drawing which shows a principal part typically, FIG.2 (b) is a side view which shows typically the principal part side surface of the cap part of Fig.2 (a).

1. Sealing body (1) Example 1
The sealing body 10 of the present Example 1 is provided with the 1st valve cap 11 used as the positive electrode cap formed in the cap shape, and the 2nd valve cap 12 used as the bottom cover formed in the dish shape. Here, the first valve cap 11 is made of stainless steel and protrudes toward the outside of the battery (a top plate portion, for example, formed to have a diameter of 8.5 mm) 11a, It consists of a flat flange portion (for example, formed so as to have a diameter of 14.3 mm) 11b that constitutes the bottom portion of the convex portion (top plate portion) 11a.

A circular hole (for example, a diameter of 4 mm) 11c is formed at the center of the convex portion (top plate portion) 11a, and a low melting point metal foil (for example, a thickness of 0.3 mm) is formed on the circular hole 11c. 11d) is joined. In addition, a plurality of gas vent holes 11e are provided in the peripheral portion of the convex portion (top plate portion) 11a. In this case, an opening forming portion is formed by the circular hole 11c and the low melting point metal foil 11d. The low melting point metal foil 11d is preferably selected from aluminum foil (melting point: 660 ° C.), zinc foil (melting point: 420 ° C.), tin foil (melting point: 240 ° C.), or the like.
On the other hand, the second valve cap 12 is made of aluminum, and includes a concave portion 12a that bulges toward the inside of the battery, and a flat plate-like flange portion 12b that constitutes the bottom portion of the concave portion 12a. Gas vent holes 12c are provided at the corners of the recess 12a.

  Inside the first valve cap 11 and the second valve cap 12, an electrically conductive elastic deformation plate 13 made of aluminum that deforms when the gas pressure in the battery rises to a predetermined pressure or higher, and a PTC thermistor element 14 is housed. The conductive elastic deformation plate 13 serves as a valve member, and includes a concave portion 13a and a flange portion 13b. The lowest portion of the recess 13a is fixedly disposed on the upper surface of the recess 12a of the second valve cap 12 by ultrasonic welding or laser welding, and the flange portion 13b is connected to the flange portion 11b of the first valve cap 11 and the second portion. The two-valve cap 12 is sandwiched between the flange portion 12b.

  A ring-shaped PTC (Positive Temperature Coefficient) thermistor element 14 is disposed at a part of the upper portion of the flange portion 12b. When an overcurrent flows in the battery and an abnormal heat generation phenomenon occurs, the PTC thermistor element 14 The resistance value increases to reduce the overcurrent. Then, when the gas pressure inside the battery rises to a predetermined pressure or higher, the concave portion 13a of the conductive elastic deformation plate 13 is deformed, so that the contact between the conductive elastic deformation plate 13 and the concave portion 12a of the second valve cap 12 is prevented. As a result, the overcurrent or short circuit current is cut off. Further, when the gas pressure inside the battery further increases after the overcurrent or short circuit current is cut off, the notch portion 13c formed in the conductive elastic deformation plate 13 is cleaved, and the gas is released from the gas vent hole 11e. It has become so.

  Here, when the battery abnormally generates heat due to a short circuit or the like, the gas pressure in the battery suddenly increases, the notch portion 13c is cleaved, and a part of the conductive elastic deformation plate 13 is scattered, the temperature in the battery When the melting point of the low melting point metal foil 11d is equal to or higher than the melting point, the low melting point metal foil 11d is melted and missing. As a result, the inside and outside of the battery communicate with the opening forming portion 11c formed of a circular hole having a diameter of 4 mm, and the gas is effectively vented. As a result, a situation in which the battery is ruptured can be prevented, and the safety is significantly improved.

  In addition, the sealing body 10 which becomes the above structures is assembled | attached as follows. Specifically, first, a ring-shaped sealing body gasket 15 made of polypropylene (PP) having an L-shaped cross section and a thickness of 0.25 mm is placed on the flange portion 12 a of the second valve cap 12. The flange portion 13 b of the conductive elastic deformation plate 13 and the PTC thermistor element 14 are placed on the sealing gasket 15. Next, the contact portion between the lower surface of the sealing body insulating gasket 15 and the upper surface of the flange portion 12b of the second valve cap 12 is closely integrated with each other by heat welding or bonding with an adhesive. Thereafter, the first valve cap 11 is held by the flange portion 12b of the second valve cap 12 via the sealing body gasket 15 by crimping the end portion of the flange portion 12b of the second valve cap 12 inward. Thus, the sealing body 10 is formed.

(2) Example 2
The sealing body 20 of the present Example 2 is provided with the 1st valve cap 21 used as the positive electrode cap formed in the cap shape, and the 2nd valve cap 22 used as the bottom cover formed in the dish shape. Here, the first valve cap 21 is a disk-shaped top plate 21a, a flat plate constituting the bottom side of the top plate 21a, a ring-shaped flange portion 21b, and connecting the top plate 21a and the flange portion 21b. The connecting portion 21c and the side wall portion 21d. In this case, the top plate 21a, the flange portion 21b, and the connecting portion 21c are formed by integral molding. And between these, the side wall part 21d is arrange | positioned, the upper end part of the side wall part 21d and the outer peripheral part of the top plate 21a are joined by laser welding, the lower end part of the side wall part 21d, and the inner peripheral part of the flange part 21b, Further, both side end portions of the side wall portion 21d and the connecting portion 21c are joined to form a cylindrical peripheral side surface.

The side wall portion 21d is made of a low melting point metal (for example, aluminum (melting point is 660 ° C.), zinc (melting point is 420 ° C.), tin (melting point is 240 ° C.), etc.). A plurality of vent holes 21e are provided. An opening forming portion is formed by the side wall portion 21d made of the low melting point metal.
On the other hand, the second valve cap 22 is made of aluminum, and includes a recess 22a that bulges toward the inside of the battery, and a flat flange portion 22b that forms the bottom of the recess 22a.

  Inside the first valve cap 21 and the second valve cap 22, an aluminum conductive elastic deformation plate 23 that deforms when the gas pressure inside the battery rises and exceeds a predetermined pressure, and a PTC thermistor element 24 is housed. The conductive elastic deformation plate 23 serves as a valve member, and includes a concave portion 23a and a flange portion 23b. The lowest part of the recess 23a is fixedly disposed on the upper surface of the recess 22a of the second valve cap 22 by ultrasonic welding or laser welding, and the flange part 23b is connected to the flange part 21b of the first valve cap 21 and the second part. The two valve caps 22 are sandwiched between the flange portions 22b.

  A ring-shaped PTC (Positive Temperature Coefficient) thermistor element 24 is disposed at a part of the upper portion of the flange portion 22b. When an overcurrent flows in the battery and an abnormal heat generation phenomenon occurs, the PTC thermistor element 24 The resistance value increases to reduce the overcurrent. Then, when the gas pressure inside the battery rises to a predetermined pressure or higher, the concave portion 23a of the conductive elastic deformation plate 23 is deformed, so that the contact between the conductive elastic deformation plate 23 and the concave portion 22a of the second valve cap 22 is prevented. As a result, the overcurrent or short circuit current is cut off. Further, when the gas pressure inside the battery further rises after the overcurrent or short circuit current is cut off, the notch portion 23c formed in the conductive elastic deformation plate 23 is cleaved and the gas is released from the gas vent hole 21d. It has become so.

  Here, when the battery abnormally generates heat due to a short circuit or the like, the gas pressure in the battery suddenly rises, the notch portion 23c is cleaved, and the conductive elastic deformation plate 23 or a part of the contents of the battery is scattered. When the temperature in the battery reaches a temperature equal to or higher than the melting point of the low melting point metal (for example, 660 ° C. in the case of aluminum) constituting the side wall 21d, the side wall 21d is melted. As a result, the side wall portion 21d is lost as an opening forming portion, the inside and outside of the battery are communicated, and gas is effectively vented. As a result, a situation in which the battery is ruptured can be prevented, and the safety is significantly improved.

  In addition, the sealing body 20 which becomes the above structures is assembled | attached as follows. That is, first, on the flange portion 22a of the second valve cap 22, a ring-shaped sealing body gasket 25 made of polypropylene (PP) having an L-shaped cross section and a thickness of 0.25 mm is placed. The flange portion 23 b of the conductive elastic deformation plate 23 and the PTC thermistor element 24 are placed on the sealing body gasket 25. Next, the contact portion between the lower surface of the sealing body insulating gasket 25 and the upper surface of the flange portion 22b of the second valve cap 22 is closely integrated by thermal welding or bonding with an adhesive. Thereafter, the first valve cap 21 is held by the flange portion 22b of the second valve cap 22 through the sealing body gasket 25 by crimping the end portion of the flange portion 22b of the second valve cap 22 inward. Thus, the sealing body 20 is formed.

2. Next, a method for manufacturing lithium ion batteries A, B, and X that are sealed batteries using the sealing bodies 10, 20, and 30 that are configured as described above will be described below. 1 is the lithium ion battery A, the one using the sealing body 20 in FIG. 2 is the lithium ion battery B, and the one using the sealing body 30 in FIG. 3 is the lithium ion battery. Let X be.

  First, a negative electrode active material made of natural graphite and a binder made of polyvinylidene fluoride (PVDF) dissolved in an organic solvent made of N-methylpyrrolidone are mixed to obtain a slurry. The slurry is uniformly applied over the entire surface of both sides of a metal core (for example, copper foil) using a die coater, a doctor blade, or the like to form a negative electrode plate coated with an active material layer. Then, it is made to pass through a drier to remove the organic solvent necessary for slurry preparation and dry. The dried negative electrode plate is rolled by a roll press and then cut into a predetermined shape to obtain a negative electrode plate.

On the other hand, a positive electrode active material made of LiCoO ₂ , a carbon conductive agent such as acetylene black or graphite, and a binder made of polyvinylidene fluoride (PVDF) are dissolved in an organic solvent made of N-methylpyrrolidone. The mixture is mixed to make a slurry. This slurry is uniformly applied to both surfaces of a metal core (for example, aluminum foil) using a die coater, a doctor blade, or the like to form a positive electrode plate coated with an active material layer. After that, after passing through a dryer to remove the organic solvent necessary for slurry preparation and drying, the dried positive plate is rolled by a roll press and cut into a predetermined shape. And

  The negative electrode plate and the positive electrode plate produced as described above are overlapped with a separator made of a microporous film made of polyolefin resin in between, and wound by a winder. Thereafter, the outermost periphery is taped to form a spiral electrode group. Next, the insulating plates are respectively arranged above and below the spiral electrode group produced as described above from the opening 41 of the cylindrical outer can 40 having a bottom which also serves as a negative electrode terminal made of iron and nickel-plated on the surface. After that, the spiral electrode group is inserted into the outer can 40. At this time, the negative electrode conductive tab extending from the negative electrode plate of the spiral electrode group is welded to the outer can.

Thereafter, the upper portion of each outer can 40 is grooved to form an annular groove 40a, and then the outer can gasket 16 (26, 36) is mounted on the annular groove 40a. Then, the positive electrode conductive tab extended from the positive electrode plate of a spiral electrode body is welded to the lower surface of the recessed part 12a (22a, 32a) of the 2nd valve cap 12 (22, 32) of the sealing body 10 (20, 30). Then, a nonaqueous electrolyte (ethylene carbonate (EC) and diethyl carbonate (DEC) mixed in an equal volume ratio to the opening of the outer can 40 is mixed with 1 mol / liter of lithium hexafluorophosphate (LiPF ₆ ). Each dissolved solution is injected.

  Thereafter, the sealing body 10 (20, 30) is placed on the opening of the outer can 40 via the outer can gasket 16 (26, 36), and the upper end (caulking portion) 41 of the opening of the outer can 40 is placed. Is sealed on the sealing body 10 (20, 30) side in a liquid-tight manner. Thus, a lithium ion battery A of Example 1 as shown in FIG. 1, a lithium ion battery B of Example 2 as shown in FIG. 2, and a lithium ion battery X of Comparative Example 1 as shown in FIG. To do. Here, each of the lithium ion batteries A, B, and X is manufactured to have a diameter of 18 mm, a height of 65 mm, and a design capacity of 2500 mAh.

3. Combustion test after overcharging Next, 10 lithium ion batteries A, B, and X produced as described above were used, respectively, and charged at a charging current of 1 It until the battery voltage reached 4.4 V, and then The battery was charged at a constant voltage of 4.4 V for 3 hours to be fully charged. Overcharging was performed from the start of overcharging until the temperature of each battery reached 130 ° C. by supplying a charging current of 2 It between the positive and negative terminals of the lithium ion batteries A, B, and X that were fully charged in this way. . Thereafter, these overcharged lithium ion batteries A, B, and X were heated by a burner to confirm the presence or absence of rupture. The results are shown in Table 1 below. Here, the presence or absence of rupture is determined to be present when the electrode body is discharged from the outer can 40, and is determined to be absent when the electrode body is not discharged.

As is clear from the results in Table 1 above, the lithium ion battery A provided with the sealing body 10 formed with the opening forming portion composed of the circular hole 11c and the low melting point metal foil 11d, and the cylinder made of the low melting point metal In the lithium ion battery B provided with the sealing body 20 in which the opening forming portion formed of the side wall portion 21c is formed, it can be seen that no rupture occurred. On the other hand, in the lithium ion battery X provided with the sealing body 30 in which the opening forming portion is not formed, it can be seen that 60% of the batteries are ruptured.
From this, it is clear that the provision of the sealing body with the opening forming portion as in the present invention can prevent the battery from being ruptured, and the safety is greatly improved. It can be said that.

  In the above-described embodiment, an example in which natural graphite is used as the negative electrode active material has been described. However, in addition to natural graphite, silicon-based materials and carbon-based materials that can occlude and desorb lithium ions, such as artificial graphite and carbon Black, coke, glassy carbon, carbon fiber, or a fired body thereof is preferable. Further, an oxide capable of inserting and extracting lithium ions such as tin oxide and titanium oxide may be used.

In the above-described embodiment, an example in which LiCoO ₂ is used as the positive electrode active material has been described. However, in addition to LiCoO ₂ , lithium-containing transition metal compounds that can occlude and desorb lithium ions, such as LiNiO ₂ and LiCo _X Ni _(1-X) O ₂ , LiCrO ₂ , LiVO ₂ , LiMnO ₂ , αLiFeO ₂ , LiTiO ₂ , LiScO ₂ , LiYO ₂ , LiMn ₂ O ₄ , LiNi _X Mn _Y Co _Z O _{2 and the} like are preferred. You may mix and use a seed | species or more. Moreover, the transition metal element of these oxides may be substituted with another element or may be added. Further, a conductive polymer such as polyacetylene or polyaniline may be used.

Furthermore, the electrolyte is an ionic conductor in which a lithium salt is dissolved as a solute in an organic solvent, has high ionic conductivity, is chemically and electrochemically stable for both positive and negative electrodes, and is used. If the possible temperature range is wide, the safety is high, and the cost is low, it can be used. For example, as the organic solvent, in addition to the mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC), propylene carbonate (PC), sulfolane (SL), tetrahydrofuran (THF), γ-butyrolactone (GBL), dimethyl Carbonate (DMC), ethyl methyl carbonate (EMC), 1,2 dimethoxyethane (DME), vinylene carbonate (VC), or a mixed solvent thereof is preferable. Further, a lithium salt having a strong electron-withdrawing property is used as a solute. In addition to LiPF ₆ , for example, LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO _{3 and the} like are preferable.

  In the above-described embodiment, an example in which the present invention is applied to a lithium ion battery has been described. However, in addition to the lithium ion battery, the present invention is also applied to various sealed batteries such as a nickel-cadmium storage battery and a nickel-hydrogen storage battery. It is possible to apply.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the sealed battery of Example 1 of this invention, and Fig.1 (a) is sectional drawing which shows typically the principal part of the state which attached the sealing body to the opening part of the exterior can of a sealed battery. FIG. 1B is a top view schematically showing the upper surface of the main part of the cap portion of FIG. It is a figure which shows the sealed battery of Example 2 of this invention, and Fig.2 (a) is sectional drawing which shows typically the principal part of the state which attached the sealing body to the opening part of the exterior can of a sealed battery. FIG. 2 (b) is a side view schematically showing a main part side surface of the cap part of FIG. 2 (a). It is sectional drawing which shows typically the principal part of the state which attached the sealing body of the prior art example (comparative example) to the opening part of the exterior can of a sealed battery.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Sealing body, 11 ... 1st valve cap, 11a ... Convex part (top plate part), 11b ... Flange part, 11c ... Round hole, 11d ... Low melting metal foil, 11e ... Gas vent hole, 12 ... 2nd valve Cap, 12a ... concave portion, 12b ... flange portion, 13 ... conductive elastic deformation plate, 13a ... concave portion, 13b ... flange portion, 13c ... notch portion, 14 ... ring-shaped PTC thermistor element, 15 ... gasket for sealing body, 16 ... Gasket for exterior can, 20 ... Sealing body, 21 ... First valve cap, 21a ... Disk-shaped top plate, 21b ... Ring-shaped flange, 21c ... Connection part, 21d ... Side wall part, 21e ... Gas vent hole, 22 ... second valve cap, 22a ... concave, 22b ... flange, 23 ... conductive elastic deformation plate, 23a ... concave, 23b ... flange, 23c ... notch, 24 ... ring-shaped PTC thermistor element, 2 ... sealing-body gasket, 26 ... outer can gasket, 40 ... outer can, 40a ... annular groove, 41 ... upper end of the outer can (caulked portion)

Claims (4)

A sealed type in which a sealing body having a pressure valve mechanism capable of discharging the gas generated in the battery to the outside of the battery when the gas pressure exceeds a predetermined value is provided in the opening of the outer can, and the opening is sealed A battery,
An opening is formed in the sealing body when the battery is abnormally heated and an opening is formed to discharge gas generated in the battery to the outside of the battery. A sealed battery characterized by being enhanced.   The opening forming portion is formed on a top plate portion or a side wall portion of the cap portion constituting the sealing body, and an opening is formed when a part of the opening forming portion is lost during abnormal heat generation. The sealed battery according to claim 1, wherein:   A material having a lower melting point than the material forming the top plate or the side wall of the cap is disposed in the opening forming portion formed on the top or the side of the cap constituting the sealing body. The sealed battery according to claim 2.   5. The sealed battery according to claim 4, wherein a material having a lower melting point than a material forming the top plate portion or the side wall portion of the cap portion is made of a metal having a melting point of 700 ° C. or less.

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