JP2017224426A - Cylindrical battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent liquid leakage due to the oozing of an electrolyte from a sealing portion between an opening of an outer can and a sealing body, in a cylindrical battery.SOLUTION: A cylindrical battery according to an embodiment of the present invention includes: an electrode body; an electrolyte; a bottomed cylindrical outer can receiving the electrode body and the electrolyte; and a sealing body fixed by caulking through a gasket to an opening of the outer can. The distal end of the gasket is bent together with the opening of the outer can toward the center of the sealing body, and a part of the gasket including the distal end is exposed from between the outer can and the sealing body. In the gasket, a slit is formed from the distal end thereof toward an outer peripheral direction of the sealing body.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a cylindrical battery excellent in leakage resistance.

  Cylindrical batteries are suitable for processing a battery pack by connecting multiple batteries in series or in parallel, so that not only small electronic devices such as notebook computers but also electric tools, electric assist bicycles, electric cars, etc. It is also widely used as a drive power source. Therefore, the cylindrical battery is required to exhibit high reliability over a long period of time even under a severe use environment such as high temperature and high humidity.

  For cylindrical batteries, a bottomed cylindrical metal outer can is generally used as an outer body for accommodating an electrode body and an electrolytic solution. After the electrode body and the electrolytic solution are accommodated in the outer can, the inside of the battery is sealed by attaching the sealing body to the opening of the outer can.

  FIG. 5 is a top sectional view of the cylindrical battery disclosed in Patent Document 1. As shown in FIG. A groove 53a is formed on the side surface of the opening of the outer can 53, and a gasket 52 and a sealing body 51 are disposed on the groove 53a. The sealing body 51 is caulked and fixed to the opening of the outer can 53 via the gasket 52. When the sealing body 51 is caulked and fixed to the outer can 53, the gasket 52 is compressed by the outer can 53 and the sealing body 51. By adjusting the compression rate of the gasket 52 to an appropriate value, airtightness between the outer can 53 and the gasket 52 and between the sealing body 51 and the gasket 52 is ensured.

  Patent Document 1 discloses a technique for improving the sealing performance of a cylindrical battery by forming a resin layer made of a bron resin or an acrylic resin on the surface of a base resin layer of a gasket. Patent Documents 2 and 3 disclose that a sealant having a pitch as a main component is applied between the outer can and the gasket and between the sealing body and the gasket in order to improve the sealing performance of the cylindrical battery. .

JP 2008-204839 A JP-A-9-213288 JP 2003-151518 A

  As disclosed in Patent Documents 1 to 3, if the hermeticity of the sealing portion between the outer can and the sealing body is ensured, the electrolyte inside the battery is discharged to the outside unless there is a problem with the outer can and the sealing body. There seems to be no leaking path.

However, although the inside of the battery is sealed, the electrolyte leaks out from the sealing part between the opening of the outer can and the sealing body after the battery is manufactured, and the outer can has an appearance such as rust and dirt. Defects may occur. The cause is presumed as follows. When the sealing body is caulked and fixed to the outer can, the tip of the gasket is bent toward the center of the sealing body. At this time, since the tip of the gasket receives a large compressive stress, a wavy wrinkle may occur at the tip. When such wrinkles occur, the electrolytic solution adhering to the vicinity of the opening of the outer can in the electrolytic solution pouring process remains at the tip of the gasket. A part of the remaining electrolyte solution is not removed even by the battery cleaning process and oozes out of the battery after the battery is assembled, causing an appearance defect such as rust and dirt on the outer can.

  The present invention has been made in view of the above, and leakage due to leakage of electrolyte from the sealing portion between the outer can and the sealing body by preventing generation of wrinkles at the tip of the gasket The purpose is to prevent.

  In order to solve the above problems, a cylindrical battery according to one embodiment of the present invention includes an electrode body, an electrolytic solution, a bottomed tubular outer can that contains the electrode body and the electrolytic solution, and an opening of the outer can. And a sealing body fixed by caulking through a gasket. The front end of the gasket is bent toward the center of the sealing body together with the opening of the outer can, and a part of the gasket including the front end is exposed between the outer can and the sealing body. In the gasket, a slit is formed from the tip portion toward the outer periphery of the sealing body.

  According to one aspect of the present invention, when the sealing body is caulked and fixed to the opening of the outer can through the gasket, the sealing portion between the outer can and the sealing body is less likely to cause wrinkles at the tip of the gasket. Leakage due to leakage of electrolyte from is prevented.

1 is a cross-sectional perspective view of a nonaqueous electrolyte secondary battery according to an embodiment. The top view of the nonaqueous electrolyte secondary battery seen from the sealing body side. The enlarged view of the A section of FIG. The front view of a gasket. The upper cross-section part of the cylindrical battery disclosed by patent document 1. FIG.

  Hereinafter, the form for implementing this invention is demonstrated using a cylindrical nonaqueous electrolyte secondary battery. The present invention is not limited to the following embodiments, and various modifications can be made without departing from the gist of the present invention.

  FIG. 1 is a cross-sectional perspective view of a nonaqueous electrolyte secondary battery 10 according to an embodiment of the present invention. The outer can 21 contains the electrode body 16 and a non-aqueous electrolyte. An upper insulating plate 17 and a lower insulating plate 18 are disposed above and below the electrode body 16, respectively. A sealing body 19 is caulked and fixed to the opening of the outer can 21 via a gasket 20. The gasket 20 is compressed by the outer can 21 and the sealing body 19.

  An insulating resin having elasticity can be used for the gasket 20. Examples of such resins include polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), perfluoroalkoxy fluororesin (PFA), and nylon.

FIG. 2 is a plan view of the nonaqueous electrolyte secondary battery 10 as viewed from the sealing body 19 side. As shown in FIG. 2, a portion of the gasket 20 including the tip 20b is exposed from between the opening of the outer can 21 and the sealing body 19 to form an exposed portion 20a. A slit 20 c is formed in the gasket 20 from the front end 20 b toward the outer periphery of the sealing body 19. The slit 20 c is preferably formed along the radial direction of the sealing body 19. The slit 20c may be formed beyond the exposed portion 20a from the tip portion 20b. However, the slit 20c is formed so that the length L1 of the exposed portion 20a and the length L2 of the slit 20c shown in FIG. 3 satisfy 0.2 ≦ L2 / L1 <1 with the radial direction of the sealing body 19 as a reference. Is preferred. Thereby, the short circuit with the armored can 21 and the sealing body 19 is prevented effectively. Like this embodiment, it is preferable that the slit 20c is formed along the radial direction of the sealing body 19, and the length L2 of the slit 20c indicates the maximum length of the slit 20c in the radial direction of the sealing body 10. Is determined based on

  The gasket 20 before being attached to the nonaqueous electrolyte secondary battery 10 has a cylindrical portion 20d as shown in FIG. The gasket 20 is disposed on a grooving portion provided in the outer can 21, and the sealing body 19 is caulked and fixed to the outer can 21 in a state where the sealing body 19 is inserted into the cylindrical portion 20 d. When the sealing body 19 is caulked and fixed to the outer can 21, the front end 20 b of the gasket 20 is bent toward the center of the sealing body 19 together with the opening of the outer can 21. At this time, since the compressive stress received by the tip 20b of the gasket 20 is relaxed by the slit 20c, wrinkles are prevented from occurring at the tip 20b of the gasket 20.

  When the sealing body 19 is caulked and fixed to the outer can 21, the gasket 20 is subjected to a large compressive stress toward the tip 20 b side of the gasket 20, so that the gasket 20 is triangular so that the tip 20 b side is widened in advance as shown in FIG. It is preferable to form a slit 20c having a shape. Under the condition that the compressive stress received by the gasket 20 can be relaxed, the shape of the slit 20c can be arbitrarily changed to another shape such as a square shape. Although the width of the slit 20c after the battery is mounted is smaller than the width before the battery is mounted, the slit 20c can maintain a triangular shape in which the front end 20b side is wide before and after the battery is mounted. It is also possible to adjust the width of the slit 20c before mounting the battery to make the planar shape of the slit 20c after mounting the battery linear. In this case, the width of the slit 20c may be zero.

  The slits 20c are preferably formed at a plurality of positions of the gasket 20, and the total number of the slits 20c is preferably 4 or more and 12 or less. When the slits 20c are formed at a plurality of positions on the gasket 20, it is preferable that the positions at which the slits 20 are formed are arranged at equal intervals along the tip 20b of the gasket 20.

  W in FIG. 3 indicates the width of the slit 20 c at the tip 20 b of the gasket 20. The total width W of the slits 20c is preferably 20% or less of the length of the tip 20b of the gasket 20. The length of the tip 20b of the gasket 20 does not include the width W of the slit 20c.

  The electrode body 16 is produced by winding the positive electrode plate 11 and the negative electrode plate 12 with a separator 13 interposed therebetween. The positive electrode plate 11 and the negative electrode plate 12 are prepared by, for example, applying a mixture slurry containing an active material and a binder on a core made of a metal foil and drying to form a mixture layer on the core. Can do. A positive electrode lead 14 and a negative electrode lead 15 are connected to the positive electrode plate 11 and the negative electrode plate 12, respectively. Further, the positive electrode lead 14 is connected to the sealing body 19, and the negative electrode lead 15 is connected to the bottom of the outer can 21. Thereby, the sealing body 19 functions as a positive electrode external terminal, and the armored can 21 functions as a negative electrode external terminal.

As the positive electrode active material, a material that can reversibly occlude and release lithium ions can be appropriately selected and used. For example, a lithium transition metal composite oxide represented by LiMO ₂ (M is at least one of Co, Ni, and Mn), LiMn ₂ O ₄ , LiFePO ₄ , and the like can be used. These can be used alone or in combination of two or more. Moreover, these positive electrode active materials can also be used by adding at least one of zirconium, magnesium, aluminum, and titanium, or by replacing with a transition metal element.

As the negative electrode active material, a material that can reversibly occlude and release lithium ions can be appropriately selected and used. For example, carbon materials such as artificial graphite and natural graphite, and silicon materials such as silicon and silicon oxide can be used. These can be used alone or in combination of two or more.

As the separator, a microporous film mainly composed of polyolefin such as polyethylene (PE) or polypropylene (PP) can be used. The microporous membrane can be used singly or as a laminate of two or more layers. In a laminated separator having two or more layers, it is preferable to use a layer mainly composed of polyethylene (PE) having a low melting point as an intermediate layer and polypropylene (PP) excellent in oxidation resistance as a surface layer. Furthermore, inorganic particles such as aluminum oxide (Al ₂ O ₃ ), titanium oxide (TiO ₂ ), and silicon oxide (SiO ₂ ) can be added to the separator. Such inorganic particles can be carried in the separator and can be applied together with a binder on the separator surface.

  As the electrolytic solution, a nonaqueous electrolytic solution in which a lithium salt as an electrolyte salt is dissolved in a nonaqueous solvent can be used.

  As the non-aqueous solvent, a cyclic carbonate, a chain carbonate, a cyclic carboxylic acid ester and a chain carboxylic acid ester can be used, and it is preferable to use a mixture of two or more. Examples of the cyclic carbonate include ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC). In addition, a cyclic carbonate in which part of hydrogen is substituted with fluorine, such as fluoroethylene carbonate (FEC), can also be used. Examples of the chain carbonate include dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and methyl propyl carbonate (MPC). Examples of cyclic carboxylic acid esters include γ-butyrolactone (γ-BL) and γ-valerolactone (γ-VL). Examples of chain carboxylic acid esters include methyl pivalate, ethyl pivalate, methyl isobutyrate, and methyl Pionate is exemplified.

As lithium salts that can be used for the electrolyte salt, LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) ( C ₄ F ₉ SO ₂ ), LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) ₃ , LiAsF ₆ , LiClO ₄ , Li ₂ B ₁₀ Cl ₁₀ and Li ₂ B ₁₂ Cl ₁₂ are exemplified. The Among these, LiPF ₆ is particularly preferable, and the concentration in the nonaqueous electrolyte is preferably 0.5 to 2.0 mol / L. Other lithium salts such as LiBF ₄ may be mixed with LiPF ₆ .

  Hereinafter, specific examples of the cylindrical nonaqueous electrolyte secondary battery 10 according to an embodiment of the present invention will be described.

(Preparation of positive electrode plate)
As the positive electrode active material, a lithium nickel composite oxide represented by the formula LiNi _0.8 Co _0.15 Al _0.05 O ₂ was used. The positive electrode active material, acetylene black as a conductive agent, and polyvinylidene fluoride (PVdF) as a binder were mixed at a mass ratio of 100: 2.5: 1.7. The mixture was put into N-methyl-2-pyrrolidone as a dispersion medium and kneaded to prepare a positive electrode mixture slurry. The positive electrode mixture slurry was applied to both surfaces of a positive electrode core made of aluminum foil by a doctor blade method and dried to form a positive electrode mixture layer. At this time, an exposed portion of the positive electrode core in which the positive electrode mixture layer was not formed was provided on a part of the positive electrode core. Finally, the positive electrode mixture layer was compressed with a roller, and the compressed electrode plate was cut into a predetermined size to produce a positive electrode plate 11.

(Preparation of negative electrode plate)
Graphite as the negative electrode active material, styrene butadiene rubber (SBR) as the binder, and carboxymethyl cellulose (CMC) as the thickener were mixed at a mass ratio of 100: 0.6: 1. . The mixture was put into water as a dispersion medium and kneaded to prepare a negative electrode mixture slurry. The negative electrode mixture slurry was applied to both surfaces of a negative electrode core made of copper foil by a doctor blade method and dried to form a negative electrode mixture layer. At this time, the negative electrode core exposure part in which the negative mix layer was not formed in a part of negative electrode core was provided. Finally, the negative electrode mixture layer was compressed with a roller, and the compressed electrode plate was cut into a predetermined size to produce a negative electrode plate 12.

(Production of electrode body)
The positive electrode lead 14 was attached to the positive electrode core exposed portion of the positive electrode plate 11 by ultrasonic welding. Further, the negative electrode lead 15 was attached to the negative electrode core exposed portion of the negative electrode plate 12 by ultrasonic welding. And the positive electrode plate 11 and the negative electrode plate 12 were wound in the state which interposed the separator 13 which consists of a polyethylene microporous film, and the winding end part was fixed with the winding stop tape, and the electrode body 16 was produced.

(Preparation of non-aqueous electrolyte)
Ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) were mixed at a volume ratio of 2: 2: 6 (1 atm, 25 ° C.) to prepare a nonaqueous solvent. LiPF ₆ as an electrolyte salt was dissolved in the non-aqueous solvent so as to be 1 M (mol / liter) to prepare a non-aqueous electrolyte.

(Production of gasket)
The gasket 20 was produced by injection molding polypropylene (PP) resin into the shape shown in FIG. Six slits were formed in the tip 20b of the gasket 20. The planar shape of the slit 20c was a triangular shape in which the tip 20b side of the gasket 20 was wide.

(Preparation of non-aqueous electrolyte secondary battery)
The upper insulating plate 17 and the lower insulating plate 18 were respectively arranged above and below the electrode body 16, and the electrode body 16 was inserted into a bottomed cylindrical outer can 21. The negative electrode lead 15 was connected to the bottom of the outer can 21, and a grooving portion was formed in the vicinity of the opening of the outer can 21. Then, the positive electrode lead 14 was connected to the sealing body 19, and a nonaqueous electrolytic solution was injected into the outer can 21. Finally, the sealing body 19 was caulked and fixed to the outer can 21 via the gasket 20 to produce the nonaqueous electrolyte secondary battery 10.

(Visual inspection)
No wrinkles occurred at the tip of the gasket of the non-aqueous electrolyte secondary battery produced as described above. In addition, after washing the produced battery and leaving it for a certain period of time to visually check the appearance of the battery, there was no appearance failure such as rust or dirt on the outer can or sealing body, and the electrolyte leaked out. It was confirmed that leakage was prevented.

  As described above, the cylindrical non-aqueous electrolyte secondary battery is used as one embodiment of the present invention. However, the present invention is not limited to the non-aqueous electrolyte secondary battery, for example, a nickel cadmium battery or a nickel hydrogen battery using an alkaline aqueous solution. The present invention can also be widely applied to cylindrical batteries.

  The present invention can effectively prevent leakage due to leakage of electrolyte from the sealing portion between the opening of the outer can and the sealing body. Therefore, since the yield improving effect in mass production of cylindrical batteries is expected, the industrial applicability of the present invention is great.

DESCRIPTION OF SYMBOLS 10 Nonaqueous electrolyte secondary battery 11 Positive electrode plate 12 Negative electrode plate 13 Separator 16 Electrode body 19 Sealing body 20 Gasket 20a Exposed portion 20b End portion 20c Slit 21 Exterior can

Claims (6)

An electrode body, an electrolytic solution, a bottomed cylindrical outer can that contains the electrode body and the electrolytic solution, and a sealing body that is caulked and fixed to the opening of the outer can via a gasket,
The front end of the gasket is bent toward the center of the sealing body together with the opening of the outer can,
There is an exposed portion where a part of the gasket including the tip portion is exposed between the outer can and the sealing body,
A cylindrical battery in which a slit is formed in the gasket from the tip portion toward the outer periphery of the sealing body.   The cylindrical battery according to claim 1, wherein the slit is formed at a plurality of positions of the gasket.   The cylindrical battery according to claim 2, wherein positions where the slits are formed are arranged at equal intervals along the tip of the gasket.   The cylindrical battery according to any one of claims 1 to 3, wherein the slit has a planar shape in which a front end portion side of the gasket is wide.   The cylindrical battery according to any one of claims 1 to 4, wherein a total width of the slits at a front end portion of the gasket is 20% or less with respect to a length of the front end portion of the gasket.   6. The cylindrical shape according to claim 1, wherein a length L1 of the exposed portion and a length L2 of the slit satisfy 0.2 ≦ L2 / L1 <1 with respect to a radial direction of the sealing body. battery.

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