JP4781070B2 - Sealed battery and manufacturing method thereof - Google Patents

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 and thin battery using a film-like outer package made of a laminate film in which a metal layer such as aluminum and a resin layer are laminated has been developed. For example, as shown in FIG. 5, this laminate film has a structure in which a metal layer and a resin layer are laminated. For example, as shown in FIG. 6, a rectangular laminate film is formed into a cylindrical shape, The overlapping portion (4d) and the upper and lower end portions (4e, 4f) are sealed by thermocompression bonding or the like.

  In the battery of this configuration, the sealing layer 4e 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 4e 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.

  In order to solve this problem, Patent Document 1 proposes a technique of sealing by interposing a heat-sealable modified resin layer 5 between the current collecting tab 7 and the resin layer 102 on the inner surface of the exterior body ( (See FIG. 8 (a)).

Japanese Patent Laid-Open No. 10-289696

  According to the above technique, since the heat-sealable modified resin layer 5 is sufficiently bonded to the current collecting tab 7 and the resin layer 102 on the inner surface of the exterior body, the sealing performance of the sealing portion 4e from which the current collecting tab protrudes is dramatically improved. It is said that it can be increased.

However, in the above technique, when the current collecting tab is bent, as shown in FIG. 8 (b), the current collecting tab 7 and the metal layer 100 exposed on the end face of the laminate film are in contact with each other, and the metal layer having polarity is obtained. There was a problem that 100 corroded and the sealing performance deteriorated. In order to solve this problem, as shown in FIG. 7 and FIG. 8C, an insulating tab film (modified resin layer) 5 is heat-welded in a state of protruding from the end of the exterior body, A technique for preventing contact with the metal layer 100 has been proposed (see FIG. 8D).
As shown in FIGS. 7 and 8D, this insulating tab film ensures contact between the current collecting tab and the metal layer 100 on the end face of the laminated film even when the current collecting tabs 5 and 6 are bent. In order to prevent this, it protrudes to some extent from the end of the exterior body (the length indicated by L in FIG. 7).

  By the way, the thickness of the portion where the insulating tab films 5 and 6 are attached and the thickness of the tab protruding sealing portion 4a is thinner than the thickness of the portion where the electrode body is housed. A circuit or the like is arranged. In order to supply power to the protection circuit, the current collecting tabs 7 and 8 are bent and the wiring and terminals of the protection circuit are connected to the current collecting tab bodies 7 and 8 to which the insulating films 5 and 6 are not attached. To do. However, if the tab film protrusion length L is excessive, the current collecting tab is difficult to bend due to the elasticity of the tab film (substantially it can be bent only from the portion where the tab film is not attached) and protection is provided. It becomes difficult to attach circuit wiring and terminals to the current collecting tab body, and it becomes difficult to design a battery package incorporating a protection circuit or the like. However, the current manufacturing method has a problem that the variation in the projecting length L is large, and it is difficult to control the projecting length L.

  This invention solves the said subject, and it aims at providing the battery using the film-shaped exterior body which could control the protrusion length of a tab film.

  The present invention relating to a battery for solving the above problems includes a positive electrode including a positive electrode current collecting tab having an insulating tab film attached to the current collecting tab body, and a negative electrode having an insulating tab film attached to the current collecting tab body. 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 projecting sealing portion that is heat-sealed in a state in which the front end side of the current projecting portion protrudes to the outside, wherein the positive and negative current collecting tabs are at least the current collecting tabs in the tab projecting sealing portion. The main body and the tab film are bonded to each other, and the current collecting tab main body and the tab film are not bonded to each other on the tip side from the vicinity of the tab protruding sealing portion.

  The present invention will be described with reference to the drawings. As shown in FIG. 3, tab films 5 and 6 are attached to the current collecting tabs 7 and 8, respectively. The tab films 5 and 6 are arranged on the tab protruding sealing portion 4a side and the current collecting tab body and the tab. The film is adhered (5a, 6a), and the current collector tab body and the tab film are not adhered on the tip side from the vicinity of the tab protruding sealing portion (5b, 6b). In the battery having this configuration, the current collecting tabs 7 and 8 can be folded and the wiring and terminals of the protective circuit can be attached by folding or cutting the portions 5b and 6b that are not heat-welded to the sealing portion 4a side. It becomes easy.

  In addition, as shown to Fig.4 (a), when the tab film 5 whole is heat-welded, the excess tab film 5 cannot be return | folded or cut and removed. On the other hand, if the length of the tab film 5 is shortened from the beginning, the variation in the protruding length L of the tab film at the time of manufacture is large. There is a risk that insulation with the metal layer of the laminate film cannot be secured.

  In addition, the present invention relating to a battery manufacturing method for solving the above-described problems includes a positive electrode including a positive electrode current collecting tab in which an insulating tab film is attached to the current collecting tab body, and an insulating tab film on the current collecting tab body. A negative electrode including a negative electrode current collector tab with a mark, and a laminate film in which a metal layer and a resin layer are laminated, and an exterior body in which the electrode body is housed, And an exterior body having a tab protruding sealing portion that is heat-sealed in a state in which the leading end side of the positive and negative current collecting tabs protrudes to the outside, and the manufacturing method includes the tab protruding sealing The current collecting tab main body and the tab film at the planned site to be positioned in the part are bonded, and the current collecting tab main body and the tab film at the tip side portion excluding the predetermined site and the vicinity thereof are not bonded. Positive and negative Current collector tab attaching step to be attached to each of the electrodes, an electrode body producing step of producing the electrode body using positive and negative electrodes to which the positive and negative current collector tabs are attached, and the positive and negative current collecting tabs after the electrode body forming step. The electrode body is accommodated in the exterior body in a state of projecting out of the exterior body, and then a tab projecting sealing portion is formed by heat welding and sealing the exterior body opening portion from which the positive and negative current collecting tabs project. Tab projection cutting step that cuts and removes only the tab film at a portion that protrudes from the end of the exterior body and is not bonded to the current collector tab body after the tab protrusion formation step and the tab protrusion formation step. And a removing step.

  According to the said manufacturing method, as shown in FIG. 1, the tab film protrusion length L can be controlled to the minimum necessary by a cutting removal process. 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 cutting and removing step does not mean that the tab film is cut and removed at the boundary portion between the portion where the tab film is bonded to the current collecting tab and the portion where the tab film is not bonded. Means cutting to a length that can sufficiently prevent contact between the current collecting tab and the metal layer, and a portion that is not adhered to the tab film after cutting and removal may remain.

  In the said manufacturing method, in order to improve the adhesiveness of a metal and a tab film, it is preferable to adhere | attach a tab film by heat sealing | fusion.

  According to the present invention, since the protruding length of the tab film can be set to the minimum necessary, contact between the current collecting tab and the metal layer of the laminate film can be reliably prevented, and the current collecting tabs 7 and 8 can be bent, It is possible to realize a sealed battery in which the wiring and terminals of the protection circuit can be easily attached.

(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.
As shown in FIG. 3, the lithium ion secondary battery according to the present invention 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, and the current collecting tab main body and the tab film are bonded to the tab protruding sealing portion 4a side of the insulating tab film (5a 6a) The current collector tab body and the tab film are not bonded to each other on the tip side of the vicinity of the tab protruding sealing portion (5b, 6b).

  FIG. 1 shows another embodiment of the present invention. In this embodiment, the portions 5b and 6b where the current collector tab body and the tab film of the lithium ion secondary battery according to the present invention shown in FIG. 3 are not bonded are cut and removed.

  As shown in FIGS. 1 and 3, the aluminum laminate outer package 3 has a bottom portion formed by folding a film, and has a three-side sealing structure in which three flat shapes other than the bottom portion are sealed. . 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. 2), and the flat electrode body 1 is formed in the storage space 2. And a non-aqueous electrolyte is stored.

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 25 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.
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 was 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 made of an aluminum foil having a width (length in the short direction of the core) of 59 mm and a length (length in the longitudinal direction of the core) of 725 mm The positive electrode active material slurry was applied to both surfaces of the substrate with a uniform thickness. However, the slurry was not applied to the end portion of the positive electrode core body, and the core body was exposed.

This electrode plate was passed through a dryer to remove the organic solvent, and a dry electrode plate with a coating mass of 450 g / m ² was produced. This dry electrode plate was rolled using a roll press so that its thickness was 0.16 mm. Thereafter, a current collecting tab was attached to the exposed core portion, and a tab film made of polypropylene (PP) was attached over the tab projection sealing portion 4a and the periphery thereof. As shown in FIG. 4B, the tab film is attached by thermally welding the inner side of the battery (the lower side of the drawing) to the positive electrode current collecting tab 7 (5a). The upper side of the drawing) was not thermally welded (5b).

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.

<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 was prepared by mixing with an appropriate amount of water.

  Next, using a die coater or a doctor blade, a negative electrode core made of a copper foil having a width (length in the short direction of the core) of 61 mm and a length (length in the longitudinal direction of the core) of 715 mm The negative electrode active material slurry was applied to both surfaces of the substrate with a uniform thickness. However, the slurry was not applied to the end of the negative electrode core, and the core was exposed.

The electrode plate was passed through a dryer to remove moisture, and a dry electrode plate having a coating mass of 200 g / m ² was produced. Then, this dry electrode plate was rolled with a roll press so that the thickness became 0.14 mm. Thereafter, in the same manner as the positive electrode, the tab film 6 was attached to the negative electrode current collecting tab 8 so as to have a welded portion 6a and an unwelded portion 6b.

  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, 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 microporous membrane separator made of an olefin resin were wound by a winder, and an insulating anti-winding tape was 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 as a solution was dissolved at a rate of 1.0 M (mol / liter).

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 with high solubility of 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. The battery of the present invention shown in FIG. 3 was assembled by inserting into the storage space 2 and sealing the opening of the outer package. Thereafter, the unwelded portions 5b and 6b of the tab films 5 and 6 are cut and removed so that the projecting length L becomes 1.0 mm, and the lithium ion secondary battery according to the present embodiment shown in FIG. Completed.

Example 1
This example was manufactured in the same manner as the above embodiment.

(Comparative Example 1)
A battery according to Comparative Example 1 shown in FIG. 7 was produced in the same manner as in the above embodiment except that the entire tab film was thermally welded and the tab film was not cut after the battery was assembled.

[Measurement of tab film protrusion length]
Thirty batteries according to Example 1 and Comparative Example 1 were prepared, and the length (protrusion length) L of the portion where the tab film protruded from the end portion of the laminate film was measured. The results are shown in Table 1 below.

  From Table 1 above, Example 1 in which an unwelded portion was provided on the tab film, and this portion was cut after the battery was assembled, the average protrusion length was 1.0 mm, and the unwelded portion was not provided and the comparison was not performed. It can be seen that it can be smaller than 1.5 mm in Example 1. Further, it can be seen that the standard deviation σ of Example 1 was 0.15 mm, which was much smaller than that of Comparative Example 1 of 0.40 mm.

  This is considered as follows. When the tab film is cut after battery assembly as in Example 1, the protruding length L can be reduced, and the protruding length L of the tab film can be easily controlled in the cutting and removing process. On the other hand, in Comparative Example 1, since the cutting is not performed, the protruding length is increased, and the protruding length L cannot be controlled.

  Therefore, according to Example 1, since the protruding length of the tab film can be set to the minimum necessary, the contact between the current collecting tab and the metal layer of the laminate film can be reliably prevented, and the current collecting tab can be bent and protected. A sealed battery in which circuit wiring and terminals can be easily attached is obtained.

  In addition, although the said Example demonstrated using the structure which cut | disconnects all the unwelded parts 5b * 6b of a tab film, the unwelded part may remain in the tab film after a cutting | disconnection.

  As described above, according to the present invention, it is possible to provide a battery that can control the protruding length of the tab film from the outer package in the battery having the film-shaped outer package to the minimum necessary level. 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.

FIG. 1 is a front view of a battery having a film-like exterior body of the present invention. FIG. 2 is a cross-sectional view of the battery shown in FIG. FIG. 3 is a front view of a battery showing another embodiment of the present invention. 4A and 4B are diagrams showing a current collecting tab to which a tab film is attached. FIG. 4A shows the comparative example 1, and FIG. 4B shows the example 1. FIG. 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 a front view of a battery using the film-shaped exterior body according to Patent Document 1. FIG. FIG. 7 is a front view of a battery using the film-shaped exterior body according to Comparative Example 1. FIG. 8 is a diagram showing the contact between the current collecting tab and the metal layer of the laminate film in the tab protrusion sealing portion.

Explanation of symbols

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 7 Positive electrode current collection tab 8 Negative electrode current collection tab 100 Metal layer 101 Nylon layer 102 Polypropylene layer 103 Dry laminate adhesion Agent layer 104 Carboxylic acid-modified polypropylene layer

Claims (3)

An electrode body having a positive electrode having a positive electrode current collecting tab with an insulating tab film attached to the current collecting tab body, and a negative electrode having a negative electrode current collecting tab with an insulating tab film attached to the current collecting tab body;
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 positive and negative current collecting tabs are bonded to the current collecting tab body and the tab film at least in the tab protruding sealing portion, and the current collecting tab main body and the tab film are bonded closer to the tip side than the vicinity of the tab protruding sealing portion. It has not been,
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 the current collecting tab body, and a negative electrode having a negative electrode current collecting tab with an insulating tab film attached to the current collecting tab body;
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 current collector tab main body and the tab film are bonded to each other at the planned portion to be positioned in the tab protruding sealing portion, and the current collector tab main body and the tab film are not bonded to each other at the tip side excluding the predetermined portion and the vicinity thereof. A current collecting tab mounting step for attaching the current collecting tabs to the positive and negative electrodes, respectively;
An electrode body manufacturing step of manufacturing the electrode body using positive and negative electrodes to which the positive and negative current collecting tabs are attached;
After the electrode body forming step, the electrode body is housed in the exterior body with the positive and negative current collecting tabs protruding outside the exterior body, and then the exterior body opening portion where the positive and negative current collection tabs are projected is heat-welded. And tab protruding portion forming step for forming a tab protruding sealing portion formed by sealing,
After the tab protruding portion forming step, a tab film cutting and removing step for cutting and removing only the tab film at a portion protruding from the end of the exterior body and not bonded to the current collecting tab main body,
A method for manufacturing a sealed battery, comprising: The adhesion is thermal fusion;
The manufacturing method of the sealing battery of Claim 2 characterized by the above-mentioned.

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