JP2010182542A - Sealed battery, and method for manufacturing the same - Google Patents

Abstract

Provided is a sealed battery that can suppress springback and has high safety.
A positive electrode having a positive electrode current collecting tab with an insulating tab film attached to both surfaces of the current collecting tab and a negative electrode having a negative electrode current collecting tab with an insulating tab film attached to both surfaces of the current collecting tab. It is an exterior body that includes an electrode body, a laminate film in which a metal layer and a resin layer are laminated, and the electrode body is accommodated therein, and a state in which the tip side of the positive and negative current collecting tabs protrudes to the outside A sealing battery including a tab projecting sealing portion heat-sealed at the front end side projecting to the outside of the positive current collecting tab and the negative current collecting tab The insulating tab film that is bent on the same surface of the bent portion and covers the outer surface of the bent portion has a portion that is thinner than the insulating tab film that covers the inner surface.
[Selection] Figure 4

Description

  The present invention relates to a battery using a film-shaped outer package such as a laminate film as a battery case.

  With the demand for miniaturization of mobile electronic devices such as mobile phones and PDAs, batteries used for the power supply are required to be further thinner and lighter.

  In order to meet this demand, a lightweight thin battery using a film-like exterior body made of a laminate film in which a metal layer such as aluminum and a resin layer are laminated as a battery case has been developed. For example, as shown in FIG. 5, the laminate film has a structure in which a metal layer and a resin layer are laminated. For example, as shown in FIG. 9, a rectangular laminate film is folded to form a bottom portion and left and right end portions. (4b, 4c) and the upper end 4a are sealed by thermocompression bonding or the like.

  In the battery of this configuration, the sealing layer 4a from which the tabs 7 and 8 protrude has a structure in which the resin layer on the inner surface of the laminate film and the current collecting tab are bonded, but the adhesive force between the resin layer and the metal is poor. For this reason, the adhesion of the sealing portion 4a becomes insufficient, and there is a problem that moisture or the like enters the inside of the battery from this portion and deteriorates the battery performance.

  Further, when the current is taken out, the current collecting tab is usually bent and used. In this case, as shown in FIG. 10B, the current collecting tab 7 and the metal layer 100 exposed on the end face of the laminate film There is a problem that the metal layer 100 having polarity is corroded and the sealing performance is deteriorated.

  In order to solve these problems, a technique has been proposed in which a resin insulating tab film is thermally welded in the vicinity of the tab protruding sealing portion of the current collecting tab (see Patent Documents 1 to 3).

JP 2007-95467 A JP 2004-200144 A JP 2001-93489 A

  A battery with a tab film attached is shown in FIG. As shown in FIG. 11, the insulating tab film 5 is interposed between the current collecting tab 7 and the resin layer 102 of the laminate film, whereby the adhesion between the resin layer 102 and the current collecting tab 7 is improved. Rise. Further, the insulating tab film 5 protrudes to some extent from the end face of the laminate film in order to reliably prevent contact between the current collector tab 7 and the metal layer 100 of the end face of the laminate film even when the current collector tab 7 is bent. I am letting.

  In such a battery, the thickness of the tab protruding sealing portion is thinner than the thickness of the portion in which the electrode body is accommodated, and a protective circuit or the like is disposed in order to effectively use this space. In order to supply a current to the protection circuit or the like, it is necessary to bend the current collecting tab toward the tab protruding sealing portion. At this time, in order to prevent the contact between the current collecting tab and the metal layer exposed on the end face of the laminate film, the portion to which the tab film is attached must be bent, but this portion is the portion to which the tab film is not attached. It is harder to bend than it, and spring back is easy to occur. For this reason, the space utilization efficiency cannot be improved sufficiently.

  The present invention solves the above-mentioned problems, and reliably prevents contact between the current collecting tab and the metal layer exposed on the end face of the laminate film, and does not cause spring back even if the current collecting tab is bent. It aims at providing the battery using this.

  A first aspect of the present invention for solving the above problems includes a positive electrode including a positive electrode current collecting tab having an insulating tab film attached to both sides of the current collecting tab, and a negative electrode having an insulating tab film attached to both sides of the current collecting tab. A negative electrode including a current collecting tab, and an outer package body comprising an electrode body having a laminate film formed by laminating a metal layer and a resin layer, and the electrode body is housed therein, the positive and negative current collectors A sealing battery having a tab protruding sealing portion that is heat-sealed in a state in which a tip end side of the tab protrudes to the outside, and a tip protruding to the outside of the positive electrode current collecting tab and the negative electrode current collecting tab Both sides are bent on the same surface of the tab protruding sealing portion, and the insulating tab film covering the outer surface of the bent portion has a thinner portion than the insulating tab film covering the inner surface. Characterized by the presence of To.

  The present invention will be described with reference to the drawings. As shown in FIG. 6, an insulating tab film 5 is attached to the current collecting tab 7, and the thickness of the insulating tab film 5 is on the lower side in FIG. A thin portion 5a is present. When the current collecting tab 7 is folded to the protruding sealing portion 4a side at the portion where the insulating tab film 5 is attached, if the current collecting tab 7 is folded at the thin portion 5a, it is easier to bend than the other portions, and the spring back Is less likely to occur. For this reason, a sealed battery with high space utilization efficiency can be obtained.

  Here, the bent part means all the bent parts of the current collecting tab as shown in FIG.

  In the above configuration, the insulating tab film has a laminated structure in which low melting point resin layers are disposed on both sides of a high melting point resin layer, and the thin portion is only the low melting point resin layer on the current collecting tab side. It can be set as the structure comprised by these.

  As the insulating tab film, when using a laminated structure in which low melting point resin layers are arranged on both sides of the high melting point resin layer, the high melting point resin layer is difficult to melt when sealing the tab protruding sealing part 4a. Contact between the current collecting tab and the metal layer of the laminate film can be reliably suppressed during sealing. In addition, the high melting point resin is usually more difficult to bend than the low melting point resin, and the spring back is likely to occur. However, the presence of the thin portion as described above can suppress this.

  By the way, when the battery falls into an abnormal state such as overcharge, a large amount of gas is generated in the battery. If the internal pressure of the battery is increased by the gas, there is a risk that the battery may burst. Here, when the internal pressure of the battery is increased by the gas, the gas peels off the weakest part of the sealing strength from the inside of the battery, and the opening is formed continuously from the external space through which the gas is discharged from the battery. To be released. In the above configuration, the weakest part of the sealing strength is the interface between the high melting point resin layer and the low melting point resin layer of the insulating tab film. When peeling progresses at this interface, the position continuous with the external space is insulated. It becomes a thin part of the property tab film. For this reason, since the distance from the tab protrusion sealing part 4a can be shortened rather than the current collection tab with a normal tab film, when battery internal pressure rises abnormally, opening is formed rapidly. Therefore, safety is increased.

  Here, the high melting point resin means a resin having a melting point of 200 ° C. or higher, and the low melting point resin means a resin having a melting point of less than 200 ° C.

  A second aspect of the present invention for solving the above problems is a positive electrode including a positive electrode current collecting tab having an insulating tab film attached to both sides of the current collecting tab, and a negative electrode having an insulating tab film attached to both sides of the current collecting tab. A negative electrode having a current collecting tab, an electrode body having a laminate film in which a metal layer and a resin layer are laminated, and an electrode body in which the electrode body is housed, wherein the positive and negative current collecting tabs A sealing battery having a tab protruding sealing portion that is heat-sealed in a state in which the tip end side protrudes to the outside, and a tip end side protruding outside the positive electrode current collecting tab and the negative electrode current collecting tab Are both folded on the same surface of the tab protruding sealing portion, the inner surface of the bent portion is completely covered with the insulating tab film, and the outer surface of the bent portion is the insulating property. Covered with tab film Characterized in that had moiety is present.

  The second aspect of the present invention is the same as that of the first aspect of the present invention except that the tab film of the portion is removed instead of partially reducing the thickness of the outer surface of the tab film. For this reason, as in the first aspect of the present invention, it is possible to obtain a sealed battery in which the current collecting tab can be easily bent and spring back hardly occurs. For this reason, a sealed battery with high space utilization efficiency can be realized.

  In the above configuration, the portion with the weakest sealing strength is the interface between the tab film and the current collecting tab when a single layer is used as the tab film, and the high melting point resin layer when a laminated layer is used. In any case, the internal pressure of the battery is abnormal because the distance from the tab protruding sealing part 4a to the position where the opening can be made can be made shorter than the current collecting tab with a tab film. When the height increases, an opening is quickly formed. Therefore, safety is increased.

  Here, the thin part and the part which is not covered with the tab film may exist in a part of the bending part, or may be all. Further, a portion having a small thickness or a portion not covered with the tab film may be formed on the front end side of the current collecting tab with respect to the bent portion.

  The said structure WHEREIN: The outer side surface of the area | region where the said positive / negative current collection tab bend | folds can be said not to be covered with the said insulating tab film.

  With this configuration, since there is a portion that is not covered with the insulating tab film in the portion where the bending starts, the bending becomes easier and the distance from the tab protruding sealing portion 4a to the position where the opening can be made can be shortened.

  Here, as shown in FIG. 8, the folding start region means a region having a length of 50% on the tab protruding sealing portion side in the bent portion (bending portion) of the current collecting tab.

A third aspect of the present invention for solving the above problems includes a positive electrode including a positive electrode current collecting tab having an insulating tab film attached to both surfaces of the current collecting tab, and a negative electrode having an insulating tab film attached to both surfaces of the current collecting tab. A negative electrode having a current collecting tab, an electrode body having a laminate film in which a metal layer and a resin layer are laminated, and an electrode body in which the electrode body is housed, wherein the positive and negative current collecting tabs A sealing battery having a tab protruding sealing portion that is heat-sealed in a state in which the front end side of the battery is protruded to the outside, wherein the manufacturing method is positive or negative with the insulating tab film attached thereto. A tab protruding seal formed by housing the electrode body in the exterior body with the current collecting tab projecting outside the exterior body, and then heat-sealing and sealing the exterior body opening portion from which the positive and negative current collection tabs project. Tab protrusion formation to form stop And extent, after the tab projection formation process is irradiated with CO ₂ laser on one surface of the insulating tab film, and tab film removing step of removing a part or all of said insulating tab film of the portion, said tab And a tab folding step of folding the positive and negative current collecting tabs so that the surface from which the insulating tab film is removed is located outside after the film removing step.

  The removal of the tab film may be performed before sealing, but this method makes it difficult to control the removal position of the tab film. In the said manufacturing method, since removal of a tab film is performed after sealing, the removal position of a tab film is easy to control. Therefore, it is possible to provide a sealed battery in which the current collecting tabs 7 and 8 can be bent and the wiring and terminals of the protection circuit can be easily attached.

  Here, the tab film can be wider than the current collecting tab. If this structure is employ | adopted, the contact with the metal layer of a laminate film and a current collection tab can be prevented more reliably.

In addition, when adopting a configuration in which the tab film is wider than the current collecting tab, the tab film located outside the current collecting tab is simultaneously removed in the step of removing part or all of the tab film. May be. If this structure is employ | adopted, the springback resulting from the tab film located outside a current collection tab can be suppressed. In order to achieve this configuration, a method of removing the tab film by irradiating the CO ₂ laser as described above is suitable. In this case, in order to ensure reliability, only the portion covering both end faces of the current collecting tab may be left without removing the tab film.

  According to the present invention, since the spring back can be effectively suppressed, it is possible to realize a sealed battery with high space utilization efficiency in which the current collecting tab can be bent and the wiring and terminals of the protection circuit can be easily attached.

FIG. 1 is a front view of a battery having a film-shaped exterior body according to the present invention. FIG. 2 is a back view of a battery having a film-shaped outer casing according to the present invention. 3 is a cross-sectional view taken along line AA in FIG. FIG. 4 is an enlarged view showing a folded state of the battery having the film-shaped outer casing according to the present invention. FIG. 5 is a diagram showing a cross-sectional structure of an aluminum laminate film that is a constituent material of the film outer package. FIG. 6 is an enlarged view showing a modification of the present invention. FIG. 7 is a diagram for explaining the springback angle. FIG. 8 is a diagram for explaining a folding portion and a folding start region. FIG. 9 is a front view of a battery having a conventional film-shaped outer package. FIG. 10 is a diagram illustrating the contact between the current collecting tab and the metal layer. FIG. 11 is a diagram illustrating a state in which contact between the current collecting tab and the metal layer is prevented by the tab film.

(Embodiment)
The case where the battery of the present invention is applied to a lithium ion secondary battery will be described below with reference to the drawings. FIG. 1 is a front view of a lithium ion secondary battery according to the present embodiment, FIG. 2 is a back view of the lithium ion secondary battery according to the present embodiment, and FIG. FIG.

  As shown in FIG. 1, the lithium ion secondary battery according to the present embodiment has an aluminum laminate outer package 3 using an aluminum laminate material which is an example of a film-shaped outer package. Insulating tab films 5 and 6 are attached to the current collecting tabs 7 and 8, respectively.

  As shown in FIG. 1 and FIG. 2, the aluminum laminate outer package 3 has a bottom portion formed by folding a laminate film, and has a three-side sealing structure in which three flat shapes other than the bottom portion are sealed. is there. A storage space 2 is formed inside the main body surrounded by the bottom and the three sealing portions 4a, 4b, and 4c (see FIG. 3), and the flat electrode body 1 is formed in the storage space 2. And a non-aqueous electrolyte.

  One side of the aluminum laminate outer package 3 is provided with a recess for accommodating the electrode body, and the other is substantially flat (see FIG. 3). The insulating tab films 5 and 6 are wider than the current collecting tabs 7 and 8, and are therefore attached in a state extending outward from the current collecting tabs 7 and 8. Here, the current collecting tabs 7 and 8 have portions that are not covered with the insulating tab films 5 and 6 on the flat surface side (the back surface of the lithium ion secondary battery) of the aluminum laminate outer package 3. ing. Further, the insulating tab films 5 and 6 extending outward from the current collecting tabs 7 and 8 are removed only in the vicinity of the portions of the current collecting tabs 7 and 8 that are not covered with the insulating tab films 5 and 6. ing. (See FIGS. 1 and 2).

  FIG. 4 shows a lithium ion secondary battery in which the current collecting tabs 7 and 8 are bent. As shown in FIG. 4, the current collecting tabs 7 and 8 are folded back so that the surface with the portion 5 a where the tab film does not exist is on the outside. Further, the bending start position is a portion 5a where the tab film does not exist.

  As shown in FIGS. 1, 2, and 4, the tab protruding sealing portion 4 a that is sealed in a state where the current collecting tab 7 protrudes is not sealed to the tab protruding end portion 3 a of the exterior body. This is because during the thermocompression bonding at the time of sealing, a strong pressure is easily applied to the tab protruding end 3a of the outer package, the thickness of the resin layer 102 is reduced, and the metal layer 100 and the current collecting tab 7 are in contact with each other. This is to prevent the metal layer 100 from being polar and thereby corroding the metal layer 100 and reducing the sealing performance.

  Here, the allowance L1 (see FIG. 1) of the tab films 5 and 6 is preferably 1.0 to 5.0 mm, and more preferably 1.0 to 2.5 mm. Moreover, it is preferable that the distance L2 (refer FIG. 2) from the tab protrusion edge part 3a to a tab film removal part is 0.1-0.5 mm. Moreover, it is preferable that the length L3 (refer FIG. 2) of the tab film removal part is 0.05-0.5 mm.

Next, an aluminum laminate material that is a constituent material of the exterior body 3 will be described. As shown in the cross-sectional view of FIG. 5, the aluminum laminate material has a 15 μm thick nylon layer 101 (a layer present outside the battery) disposed on one surface of a 35 μm thick metal layer 100 made of aluminum. The metal layer 100 has a structure in which a polypropylene layer 102 (a layer existing inside the battery) having a thickness of 30 μm is disposed on the other surface of the metal layer 100. The metal layer 100 and the nylon layer 101 are bonded by a dry laminate adhesive layer 103 having a thickness of 5 μm, while the metal layer 100 and the polypropylene layer 102 have a thickness of 5 μm in which a carboxyl group is added to polypropylene. The structure is bonded by the carboxylic acid-modified polypropylene layer 104. In FIG. 4, the dry laminate adhesive layer is omitted.
Needless to say, the application of the present invention is not limited to the exterior body using the aluminum laminate material having this structure.

  A method for manufacturing the lithium ion secondary battery having the above structure will be described.

<Preparation of positive electrode>
A ratio of 90: 5: 5 mass ratio of a positive electrode active material made of lithium cobaltate (LiCoO ₂ ), a carbon-based conductive agent such as acetylene black or graphite, and a binder made of polyvinylidene fluoride (PVDF). The sample is dissolved in an organic solvent composed of N-methyl-2-pyrrolidone and then mixed to prepare a positive electrode active material slurry.

  Next, using a die coater or a doctor blade, a positive electrode core body made of an aluminum foil having a width (length in the short direction of the core body) of 43 mm and a length (length in the longitudinal direction of the core body) of 470 mm The positive electrode active material slurry is applied to both surfaces of the substrate with a uniform thickness. However, the slurry is not applied to the end portion of the positive electrode core body, and the core body is exposed.

This electrode plate is passed through a dryer to remove the organic solvent, and a dry electrode plate is produced. This dry electrode plate is rolled using a roll press so that its thickness is 0.12 mm. Thereafter, a plate-shaped aluminum current collecting tab having a thickness of 0.1 mm is attached to the exposed portion of the core, and modified propylene (thickness 30 μm) / polyethylene naphthalate (thickness 15 μm) / modified propylene (thickness 30 μm). ) Is attached. At this time, the allowance L1 (refer FIG. 2) from the tab protrusion edge part 3a of a tab film shall be 2.0 mm.
Here, the melting point of modified propylene is 150 ° C., and the melting point of polyethylene naphthalate is 270 ° C.

As the positive electrode active material used in the lithium ion secondary battery according to the present embodiment, for example, lithium nickelate (LiNiO ₂ ), lithium manganate (LiMn ₂ O ₄ ), lithium ferrate ( LiFeO ₂ ) or a lithium-containing transition metal composite oxide such as an oxide obtained by substituting a part of the transition metal contained in these oxides with other elements may be used alone or in combination of two or more. it can.

Here, as a material used for the innermost layer which is in direct contact with the current collecting tab, acid-modified polyolefin resins such as acid-modified polypropylene and acid-modified polyethylene are preferable.
In addition to the acid-modified polyolefin resin, the material used for the outermost layer that is welded to the inner resin of the aluminum laminate is a propylene resin (polypropylene, ethylene / propylene copolymer, ethylene / propylene / butene copolymer, etc.) ), Ethylene resin (low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, ethylene / butene copolymer, copolymer of ethylene and acrylic acid or methacrylic acid derivative, ethylene and vinyl acetate A copolymer, polyethylene or polypropylene grafted with metal ion-containing polyethylene and unsaturated carboxylic acid, or a blend thereof), or those obtained by acid modification thereof can be used.
Moreover, as a material used for the high melting point layer (intermediate layer), polyethylene naphthalate, polymethylpentene, polyethylene terephthalate and the like are preferable.
Here, the reason why the resin material suitable for the innermost layer is less than the resin material suitable for the outermost layer is that the innermost layer is welded to a current collecting tab that is a metal, and thus there are large material restrictions.

<Production of negative electrode>
A negative electrode active material made of artificial graphite having a volume average particle diameter of 20 μm, a binder made of styrene butadiene rubber, and a thickener made of carboxymethyl cellulose were weighed in a mass ratio of 98: 1: 1, and these were measured. A negative electrode active material slurry is prepared by mixing with an appropriate amount of water.

  Next, using a die coater or a doctor blade, this negative electrode active material slurry is applied to both surfaces of the negative electrode core made of copper foil with a uniform thickness. However, the slurry is not applied to the end of the negative electrode core, and the core is exposed.

  The electrode plate is passed through a dryer to remove moisture, and a dried electrode plate is produced. Then, this dry electrode plate is rolled by a roll press so that the thickness becomes 0.12 mm. Thereafter, in the same manner as the above positive electrode, a plate-shaped nickel-made negative electrode current collecting tab 8 having a thickness of 0.1 mm to which the tab film 6 is attached is attached. At this time, the allowance L1 (refer FIG. 2) from the tab protrusion edge part 3a of a tab film shall be 2.0 mm.

  Here, as a negative electrode material used in the lithium ion secondary battery according to the present embodiment, for example, natural graphite, carbon black, coke, glassy carbon, carbon fiber, or a carbonaceous material such as a fired body thereof, or the carbon A mixture of the material and one or more selected from the group consisting of lithium metal, a lithium alloy, and a metal oxide capable of occluding and releasing lithium can be used.

<Production of electrode body>
The positive electrode, the negative electrode, and a separator of a microporous film made of an olefin resin are wound by a winder, and an insulating anti-winding tape is provided to complete the flat electrode body 1. The material for the tab protection tape and the separator is not particularly limited to the above materials.

<Preparation of electrolyte>
An electrolyte salt is added to a nonaqueous solvent in which ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) are mixed at a volume ratio of 1: 1: 8 (when converted to 1 atm and 25 ° C.). As an electrolytic solution, LiPF ₆ dissolved at a rate of 1.0 M (mol / liter) is used.

Here, the non-aqueous solvent used in the lithium ion secondary battery according to the present embodiment is not limited to the above combinations, and for example, lithium salts such as ethylene carbonate, propylene carbonate, butylene carbonate, and γ-butyrolactone. A high-dielectric-constant solvent having high solubility in water, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, 1,2-dimethoxyethane, tetrahydrofuran, anisole, 1,4-dioxane, 4-methyl-2-pentanone, cyclohexanone, acetonitrile, pro It can be used by mixing with a low viscosity solvent such as pionitrile, dimethylformamide, sulfolane, methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, ethyl propionate. Furthermore, the high dielectric constant solvent and the low viscosity solvent can be used as a mixed solvent of two or more. In addition to the LiPF ₆ described above, for example, LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ , LiClO _4, or LiBF ₄ may be used alone or in combination of two or more. Can be used.

<Production of battery>
An aluminum laminate outer package 3 having a three-sided sealing structure in which the flat electrode body 1 and the electrolyte solution have a bottom portion formed by folding a film and three flat shapes other than the bottom portion are sealed. It inserts in the storage space 2, and the opening part of this exterior body is sealed. After that, the CO ₂ laser is irradiated to a region (0.3 mm) having a width L2 at a position 0.1 mm (L3) away from the protruding end of the tab film, and this portion (collected) The tab film (including the part protruding from the electric tab) is removed, and the battery shown in FIGS. 1 and 2 is assembled.

  Thereafter, the current collecting tabs 7 and 8 are bent so that the tab film removal side is on the outside, and the lithium ion secondary battery according to the present embodiment shown in FIG. 4 is completed. The bending condition is a condition that a 2 kgf load is applied and the tab is bent 180 ° and held for 3 seconds.

Example 1
A battery according to Example 1 was fabricated in the same manner as in the above embodiment. In addition, the bending of the tab was based on the tab film removal part.

(Example 2)
A battery according to Example 2 was fabricated in the same manner as in the above embodiment, except that modified propylene (thickness 75 μm, single-layer tab film) was used as the current collecting tab. In addition, the bending of the tab was based on the tab film removal part.

(Comparative Example 1)
On both sides of the current collecting tab, the CO ₂ laser is irradiated to a region having a width L2 at a position 0.1 mm (L3) away from the protruding end of the tab, and this portion (including a portion protruding from the current collecting tab) A battery according to Comparative Example 1 was fabricated in the same manner as in the above embodiment except that the tab film was removed. In addition, the bending of the tab was based on the tab film removal part.

(Comparative Example 2)
A battery according to Comparative Example 2 was produced in the same manner as Comparative Example 1 except that modified propylene (thickness 75 μm, single-layer tab film) was used as the current collecting tab. In addition, the bending of the tab was based on the tab film removal part.

(Comparative Example 3)
The Projection L1 of insulating tab film and 0.1 mm, except that was not performed CO ₂ laser irradiation, in the same manner as in Comparative Example 1 A battery was produced according to Comparative Example 3. It should be noted that the tab film allowance was changed when it was attached to the tab (using a short tab film), and the tab was bent with the tip of the tab film as a base point.

(Comparative Example 4)
A battery according to Comparative Example 4 was produced in the same manner as Comparative Example 1 except that the allowance L1 of the insulating tab film was 0.5 mm and the CO ₂ laser irradiation was not performed. It should be noted that the tab film allowance was changed when it was attached to the tab (using a short tab film), and the tab was bent with the tip of the tab film as a base point.

(Comparative Example 5)
A battery according to Comparative Example 5 was fabricated in the same manner as Comparative Example 1 except that the allowance L1 of the insulating tab film was 1.0 mm and the CO ₂ laser irradiation was not performed. In addition, the tab film protrusion was changed when it was attached to the tab (a short tab film was used), and the bending of the tab was based on the boundary between the sealing portion 4a and the tab film.

(Comparative Example 6)
A battery according to Comparative Example 6 was produced in the same manner as Comparative Example 1 except that the allowance L1 of the insulating tab film was 2.0 mm and the CO ₂ laser irradiation was not performed. The bending of the tab was based on the boundary between the sealing portion 4a and the tab film.

(Comparative Example 7)
A battery according to Comparative Example 7 was fabricated in the same manner as Comparative Example 2 except that the allowance L1 of the insulating tab film was 0.1 mm and the CO ₂ laser irradiation was not performed. It should be noted that the tab film allowance was changed when it was attached to the tab (using a short tab film), and the tab was bent with the tip of the tab film as a base point.

(Comparative Example 8)
The Projection L1 of insulating tab film and 0.5 mm, except that was not performed CO ₂ laser irradiation, in the same manner as in Comparative Example 2 A battery was produced according to Comparative Example 8. It should be noted that the tab film allowance was changed when it was attached to the tab (using a short tab film), and the tab was bent with the tip of the tab film as a base point.

(Comparative Example 9)
A battery according to Comparative Example 9 was fabricated in the same manner as Comparative Example 2 except that the allowance L1 of the insulating tab film was 1.0 mm and the CO ₂ laser irradiation was not performed. In addition, the tab film protrusion was changed when it was attached to the tab (a short tab film was used), and the bending of the tab was based on the boundary between the sealing portion 4a and the tab film.

(Comparative Example 10)
A battery according to Comparative Example 10 was fabricated in the same manner as Comparative Example 2 except that the allowance L1 of the insulating tab film was 2.0 mm and the CO ₂ laser irradiation was not performed. The bending of the tab was based on the boundary between the sealing portion 4a and the tab film.

[Short-circuit measurement of tab protruding sealing part (Short-circuit A)]
20 batteries (before bending) were produced under the same conditions as in Examples 1 and 2 and Comparative Examples 1 to 10, respectively, and left in an environment at 25 ° C. for 10 days. Thereafter, the laminate film was observed for corrosion. The results are shown in Table 1 below.

[Springback angle measurement]
Twenty batteries were produced respectively under the same conditions as in Examples 1 and 2 and Comparative Examples 1 to 10, and left for 6 hours after bending the tab, and the spring back angle (see FIG. 7) was examined. The results (average value) are shown in Table 1 below.

[Short-circuit measurement of tab protruding sealing part (bending) (short circuit B)]
The tab portion of the battery after the spring back test was bent again under the above conditions, fixed with a clip so as to maintain the bent state, and left in an environment of 25 ° C. for 10 days. Thereafter, the laminate film was observed for corrosion. The results are shown in Table 1 below.

  From Table 1 above, it can be seen that in Examples 1 and 2 and Comparative Examples 1 to 10 to which the tab film was attached, the short circuit A was 0. Therefore, it turns out that a tab film can prevent reliably the current collection tab in a sealing part, and the aluminum layer of an aluminum laminate film.

  Further, from Table 1 above, in Examples 1 and 2 and Comparative Examples 1 to 4, 7 and 8 in which the allowance (distance from the tab protruding end portion to the removal portion or the tip) is 0.5 mm or less on the bent outer surface, The comparative examples 5, 6, 9, and 10 in which the spring allowance is 1.0 mm or more on the bent outer surface, while the spring back angle is 10 to 18 °, the spring back angle is 108 to 127 ° in the positive electrode. It can be seen that it is 59 to 67 ° at the negative electrode.

  This is considered as follows. In Comparative Examples 5, 6, 9, and 10, the folding position is the boundary between the sealing portion 4a and the tab film, and the tab film is bent at the part attached to both sides. Enlarge. On the other hand, in Examples 1 and 2 and Comparative Examples 1 and 2, since the tab film is bent at the outer surface, the above problem does not occur and spring back is suppressed. In Comparative Examples 5, 6, 9, and 10, it is considered that the springback angle greatly differs between the positive electrode and the negative electrode due to the difference in the material of the current collecting tab (positive electrode: aluminum, negative electrode: nickel).

  Moreover, it turns out that the spring back angle is slightly larger in Example 1 and Comparative Examples 1 and 3-6 using the tab film A than in Example 2 and Comparative Examples 2 and 7-10 using the tab film B. . This is presumably because polyethylene naphthalate used in the laminated tab film is harder than the modified propylene, thereby increasing the springback angle.

  From Table 1 above, in Examples 1 and 2, and Comparative Examples 5, 6, 9, and 10 where the allowance (distance from the tab protruding end to the removed portion or the tip) is 1.0 mm or more on the inner side surface of the bent, a short circuit occurs. Comparative Examples 1 to 4, 7, and 8 in which the allowance (distance from the tab protruding end portion to the removed portion or the tip end) is 0.5 mm or less on the inner side surface of the bending while B was no corrosion was 20 It turns out that 7-11 pieces are corroded.

  This is considered as follows. In Comparative Examples 1-4, 7, and 8, on the bent inner surface, the tab is exposed at a distance close to the tab protruding end, and in this part, the negative electrode tab and the aluminum layer on the laminate end surface are in contact with each other, The aluminum layer corrodes. On the other hand, in Examples 1 and 2 and Comparative Examples 5, 6, 9, and 10, the tab sheet protrusion allowance on the bent inner surface is sufficiently secured to be 1.0 to 2.0 mm, so the negative electrode tab and the aluminum layer No contact occurs and the aluminum layer does not corrode.

  Next, in order to evaluate the safety of each battery, the following tests were performed.

[Safety test]
A plurality of batteries were produced under the same conditions as in Examples 1 and 2 and Comparative Examples 1 to 10, and the batteries were continuously charged with a constant current, and the presence / absence of rupture / smoke / ignition was confirmed. For those that did not, the same test was performed with increasing current values by 0.1 It for new batteries. The maximum current value (It) at which no rupture / smoke / ignition is confirmed is defined as the limiting current rate. Note that 1 It is 750 mA.

[Sealing reliability test]
Batteries were produced under the same conditions as in Examples 1 and 2 and Comparative Examples 1 to 10, and charged for 24 minutes at a constant current of 1 It (40% charge). Saved the day. Then, the presence or absence of the opening of a sealing part and the presence or absence of a leak were confirmed, and this result is shown in Table 2 below.

  From Table 2 above, it can be seen that Examples 1 and 2 and Comparative Examples 1 to 10 to which the tab film was attached had no leak or opening in the sealing reliability test.

  That is, even if a part of the tab film is removed, it can be seen that there is sealing reliability equivalent to that which is not removed.

  In addition, from Table 2 above, Examples 1 and 2 and Comparative Examples 1 to 4 and 7 in which the allowance (distance from the tab protruding end to the removed portion or the tip) is 0.1 to 0.5 mm on the bent outer surface. , 8 are comparative examples 5, 6, and 9 in which the limiting current is 1.1 to 1.2 It and the state is a complete opening, while the allowance is 1.0 to 2.0 mm on the bent outer surface. , 10 has a limit current of 0.8 to 1.0 It, and the state is in the middle of opening, and Examples 1, 2, and Comparative Examples 1-4, 7, 7, and 8 have better safety during overcharging. I understand that.

  This is considered as follows. When the electrolyte is decomposed due to overcharge and gas is generated to increase the internal pressure of the battery, the portion of the sealed portion that is weak (the interface between the tab and the tab film or the high melting point resin layer and the low melting point resin layer of the tab film) Will start to peel from the inside of the battery, but if the distance to the tab exposed part is short (progress is short), the time for this peeling to reach the tab exposed part is short, and the gas release opening is quickly It is formed. This increases the safety of the battery and increases the limiting current rate.

  As described above, according to the present invention, the springback of the sealed battery using the laminate outer package can be suppressed, and the safety can be improved. When this battery is used, it is easy to make a battery package with a protection circuit or the like attached thereto, which is of great industrial significance.

DESCRIPTION OF SYMBOLS 1 Electrode body 2 Storage space 3 Film-shaped exterior body 4a, 4b, 4c Sealing part 5 Positive electrode tab film 6 Negative electrode tab film 5a, 6a Tab film removal part 7 Positive electrode current collection tab 8 Negative electrode current collection tab 100 Metal layer 101 Nylon layer 102 Polypropylene layer 103 Dry laminate adhesive layer 104 Carboxylic acid modified polypropylene layer

Claims (5)

An electrode body having a positive electrode having a positive electrode current collecting tab with an insulating tab film attached to both sides of the current collecting tab and a negative electrode having a negative electrode current collecting tab having an insulating tab film attached to both surfaces of the current collecting tab;
It is an exterior body made of a laminate film in which a metal layer and a resin layer are laminated, and the electrode body is housed therein, and is heat-sealed with the positive and negative current collecting tabs protruding to the outside. An exterior body having a tab protruding sealing portion,
In a sealed battery comprising:
The leading end side protruding outside of the positive electrode current collecting tab and the negative electrode current collecting tab is both bent to the same surface of the tab protruding sealing portion, and the insulating tab film covering the outer surface of the bent portion is included in the insulating tab film. , Compared to the insulating tab film covering the inner surface, there is a thin portion,
A sealed battery characterized by that. The sealed battery according to claim 1,
The insulating tab film has a laminated structure in which a low melting point resin layer is laminated on both sides of a high melting point resin layer,
The thin portion of the insulating tab film is composed only of the low melting point resin layer on the current collecting tab side,
A sealed battery characterized by that. An electrode body having a positive electrode having a positive electrode current collecting tab with an insulating tab film attached to both sides of the current collecting tab and a negative electrode having a negative electrode current collecting tab having an insulating tab film attached to both surfaces of the current collecting tab;
It is an exterior body made of a laminate film in which a metal layer and a resin layer are laminated, and the electrode body is housed therein, and is heat-sealed with the positive and negative current collecting tabs protruding to the outside. An exterior body having a tab protruding sealing portion;
In a sealed battery comprising:
Both the positive electrode current collecting tab and the negative electrode current collecting tab are protruded from the front end side to the same surface of the tab protruding sealing portion, and the inner side surface of the bent portion is completely formed on the insulating tab film. And the outer surface of the bent portion has a portion not covered with the insulating tab film,
A sealed battery characterized by that. The sealed battery according to claim 3.
The outer surface of the region where the positive and negative current collecting tabs start to be bent is not covered with the insulating tab film,
A sealed battery characterized by that. An electrode body having a positive electrode having a positive electrode current collecting tab with an insulating tab film attached to both sides of the current collecting tab and a negative electrode having a negative electrode current collecting tab having an insulating tab film attached to both surfaces of the current collecting tab;
It is an exterior body made of a laminate film in which a metal layer and a resin layer are laminated, and the electrode body is housed therein, and is heat-sealed with the positive and negative current collecting tabs protruding to the outside. An exterior body having a tab protruding sealing portion;
In a manufacturing method of a sealed battery comprising:
The manufacturing method includes:
The electrode body is housed in the exterior body with the positive and negative current collecting tabs to which the insulating tab film is attached protruded outside the exterior body, and then the exterior body opening portion from which the positive and negative current collection tabs are projected is heated. A tab protrusion forming step for forming a tab protrusion sealing portion formed by welding and sealing; and
After the tab protrusion forming step, a tab film removing step of irradiating one surface of the insulating tab film with CO ₂ laser to remove part or all of the insulating tab film of the portion;
After the tab film removal step, a tab bending step of bending the positive and negative current collecting tabs so that the surface from which the insulating tab film has been removed becomes the outside,
A method for manufacturing a sealed battery, comprising:

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