JP2002190283A - Manufacturing method of thin secondary battery and thin secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a thin secondary battery excellent in sealability, safety and productivity with a structure such that an electrode body is sealed within a closed body formed by an exterior material of an aluminum laminated film, and a thin secondary battery. SOLUTION: At least one of pairs of heater metal fittings 8a, 8b and 8c, 8d has a projection formed on a pressuring part corresponding to a sealed part of a peripheral part 5b of the external material 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a thin secondary battery in which an electrode body is housed and sealed by an exterior material having a protective layer and a heat-sealing layer formed on an aluminum or aluminum alloy sheet. And a thin secondary battery produced thereby.

[0002]

2. Description of the Related Art With the advance of electronic devices such as mobile phones and personal computers, secondary batteries used in these devices are required to be reduced in size, weight, thickness and capacity, and cost reduction is continually required. I have. Lithium-ion secondary batteries are examples of thin secondary batteries with high energy density, in which electrode materials such as positive electrode active material and negative electrode active material are changed to those with higher energy density, and the outer material is changed from iron to aluminum. And other improvements have been made.

Recently, a support is impregnated with a liquid electrolyte, a gel electrolyte, or a solid electrolyte as an electrode body.
In addition, a thin secondary battery has been proposed that is reduced in size, weight, and thickness by using a laminated film in which a protective layer and a sealant layer (heat sealing layer) are formed on the surface of an aluminum sheet as an exterior material. ing.

[0004] In these electrode bodies, a separator is interposed between a positive electrode and a negative electrode, and external leads are connected to the positive and negative electrodes, respectively. In addition, the electrolyte is stored in the exterior material,
The open peripheral portion of the exterior material is heated and pressed by a heater from both sides to seal and seal the sealant layers formed on the exterior material by heat fusion, and adhere to the external leads of the positive and negative electrodes. It is common to form a structure in which the tip of the external lead of the negative electrode extends outside the exterior material.

[0005] Since the metal material of the external lead and the sealant layer of the exterior material usually have poor adhesiveness and adhesiveness, a heat-adhesive film is interposed between the external lead and the sealant layer of the exterior material. A method of sealing by fusion is often used.

[0006]

However, in the above-described method for manufacturing a thin secondary battery, when the outer leads and the outer package are sealed by heat fusion with a heat adhesive film serving as a sealant layer interposed therebetween. As shown in FIG. 8, each of the external leads 33 and 34 of the positive electrode and the negative electrode is bent and opposed to a portion (Z) where the heat-adhesive film 37 is interposed between the external leads 31 sandwiching the external leads 33 and 34. Exterior materials 31, 31
(Y) where only the heat-adhesive film 37 is interposed, and further, the facing materials 31 and 31 which are bent and opposed to each other.
There are three fused portions having different thicknesses at a portion (X) where they are directly opposed to each other.

In order to simultaneously heat-bond these three places, if the amount of heat and pressure applied are insufficient, they will not adhere to each other, and the boundary where the thickness of the fused portion is different or the thickness of the fused portion is the thinnest. A gap is generated at a location, and the sealing performance is reduced. If the amount of heat and pressure to be applied are excessively increased in order to prevent the generation of a gap, the heat-adhesive film for improving the adhesion of the peripheral portion of the external lead becomes extremely thin, and the sealing performance is reduced. In addition, the insulation distance between the metal sheet part of the exterior material and the external lead becomes extremely short, and when the external leads of the positive and negative electrodes are simultaneously rectangularly connected to the metal sheet by applying impact, load, etc. to the fused part of the external lead, The battery is short-circuited and becomes extremely dangerous.

Therefore, when heat-sealing portions having different thicknesses of the fused portion, a heat-resistant rubber sheet is attached to the surface of at least one of the heater fittings to absorb the irregularities of the fused portion. The method is often used.

FIG. 9 is an explanatory view of a sealing method in which a heat-resistant rubber sheet is attached to the surface of a conventional heater fitting.
Heat-resistant rubber sheets 41 are attached to the surfaces on the opposite sides of the heater fittings 48a and 48b, respectively. In this state, the heat-resistant rubber sheet 4 is heated by the heater fittings 48a and 48b.
When the exterior material 31 is heated and pressurized from both sides through 1 and heat-sealed, the heat-resistant rubber sheet 41 is heated by the heater fittings 48a and 48b at the time of fusion because the heat-resistant rubber sheet 41 has poor thermal conductivity. The heat of the heat-resistant rubber sheet 41 is reduced while the heat of the heat-resistant rubber sheet 41 is reduced.
The heat from 8b is not sufficiently conducted, the fusing temperature is greatly reduced, and the time required for the heat-resistant rubber sheet 41 to recover to the original temperature is lengthened.

[0010] Therefore, if continuous heat fusion is performed, heat fusion is performed with the fusion temperature lowered, and near the boundary where the thicknesses of the fusion parts X, Y, Z shown in FIG. Gap 42
Occurs and sealing performance is not ensured.

[0011] Therefore, it is necessary to further raise the fusing temperature, lengthen the fusing time, or increase the fusing pressure. However, these methods lower the production efficiency and reduce the efficiency of production equipment including heat-resistant rubber sheets. Since the deterioration is accelerated, in particular, since the heat-resistant rubber sheet is always in a high temperature state, the deterioration of the rubber is large and attention must be paid to the management such as periodic replacement of the heat-resistant rubber sheet.

Furthermore, the insulation distance between the metal sheet layer such as aluminum or aluminum alloy of the exterior material and the external lead of the positive electrode or the negative electrode is not stable, which increases the risk of short-circuiting the battery, which is not preferable.

The present invention has been made in view of these circumstances, and a thin secondary battery having a structure in which an electrode body is sealed with an aluminum laminate film packaging material having improved sealing performance, safety, and productivity. It is an object of the present invention to provide a method of manufacturing the same and a thin secondary battery produced thereby.

[0014]

According to the means of the present invention, an external lead is connected to the inside of a sealed body formed of an aluminum sheet having a sealant layer formed on a bonding surface or an exterior material using an alloy sheet thereof. In a method for manufacturing a thin secondary battery in which a peripheral portion of the hermetic body is sealed by heating and pressing with a pair of heater fittings and a built-in electrode body, at least one of the heater fittings seals the peripheral portion. A method for manufacturing a thin secondary battery, wherein a pressurizing portion corresponding to a stop portion forms a convex portion.

Further, according to the means of the present invention, the sealing portion of the external lead is sealed with the exterior material in a state where the outer periphery of the external lead is covered with a heat-fusible film. This is a method for manufacturing a thin secondary battery.

Further, according to the means of the present invention, in the heater fitting, the volume of the region formed between the convex portions is equal to the volume of the external lead in the corresponding region and the volume of the heat-fusible film. A method for manufacturing a thin secondary battery, wherein the thickness is set to be smaller than the sum.

According to the present invention, there is provided a thin secondary battery manufactured by the method for manufacturing a thin secondary battery described above.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a thin secondary battery according to the present invention and a method for manufacturing the same will be described with reference to the drawings.

FIG. 1 is a perspective view of a thin secondary battery of the present invention.

In the thin secondary battery, a sealed structure is formed by an exterior material 1 having a laminated film structure having an aluminum or aluminum alloy sheet in an intermediate layer, and an electrode body 2 including a positive electrode, a negative electrode, and a separator is provided inside the sealed structure. A liquid electrolyte (not shown), a gel electrolyte (not shown), or a solid electrolyte (not shown) is stored. In addition, from the positive electrode and the negative electrode, a positive electrode external lead 3 and a negative electrode external lead 4 respectively extend outside the hermetically sealed structure.

The hermetically sealed structure of the exterior material 1 has three open peripheral portions 5a and 5b other than the bent portion 6 of the exterior material 1.
5c is sealed by heat fusion.

As shown in FIG. 2, the exterior material 1 uses a thin aluminum sheet 1b or aluminum alloy sheet having a small specific gravity as a barrier material, which can prevent permeation of moisture or gas. The sheet is formed by laminating resin films on both sides. That is, the exterior material 1 is 3
In a layer structure, a 25 μm nylon layer is formed as a protective layer 1a on one surface (front surface side) of a 40 μm aluminum sheet 1b, and a sealant layer 1c is formed on the other surface (back surface side).
30μm polyethylene layer (melting point about 120 ° C)
Are formed.

A film having mechanical strength is preferable on the surface side of the exterior material 1, and typically, polyethylene terephthalate (PET) or nylon is used. The innermost side (back side) of the exterior material 1 is a film having heat-fusibility (sealant layer 1c), and a polyolefin-based film such as polypropylene or polyethylene is used because of compatibility with the electrolyte and the contained solvent.

As the external lead, aluminum or aluminum alloy can be used for the positive external lead 3, and nickel or copper can be used for the negative external lead 4. In addition,
Since the metal material of the external leads 3 and 4 and the sealant layer 1c of the exterior material 1 usually have poor adhesion and adhesiveness, the heat between the external leads 3 and 4 and the sealant layer 1c of the exterior material 1 will be described later. A method of sealing by heat fusion using an adhesive film is used. Examples of the heat-adhesive film used at that time include acid-modified polyolefin films such as acid-modified polypropylene and acid-modified polyethylene.

Next, a method of manufacturing the thin secondary battery of the present invention will be described.

The method for manufacturing a thin secondary battery according to the present invention, which is basically the structure shown in FIG. 1 and in which the positive electrode external lead 3 and the negative electrode external lead 4 are connected at a predetermined position with respect to the package 1 After positioning the 2 and storing the electrolyte, the peripheral portions 5a, 5b, and 5c, which are sealing portions of the exterior material 1, are sealed by heating and pressing with a pair of heaters described below from the surface side of the exterior material 1 respectively. , Forming a closed structure. In this peripheral portion, 5a and 5c seal the sealant layers 1c and 1c with each other by heat fusion, and at least one of the pair of heater fittings corresponding to the peripheral portion 5b has a convex portion as described later. ing.

In this case, the heating temperature of the heater bracket is 160 ° C. to 200 ° C., and the pressing force is 1 kg.
/ Cm ^{2 to 5} kg / cm ² , and the required time is about 5 seconds.

Hereinafter, embodiments of the present invention will be described. The cross section of the battery used in each of the following examples is an AA cross section in FIG. (Embodiment 1) FIG. 3A is a completed view of a thin secondary battery, and FIG. 3B is an explanatory view of a heating and pressing process.

As shown in FIG. 3 (a), the thin secondary battery has an exterior material 1 in which a protective layer 1a of nylon is formed on the front side of an aluminum sheet 1b and a sealant layer 1c of polyethylene is formed on the back side. Between the positive external lead 3
The electrode body 2 in which the negative electrode external lead 4 is connected to the positive and negative electrodes, respectively, is tightly fixed. In addition, the positive electrode external lead 3 and the negative electrode external lead 4 are heat-welded to the sealant layer 1c while being encased in a heat-adhesive film 7 of acid-modified polyethylene.

The exterior material 1 has a positive electrode external lead 3 inside.
As compared with the portion where the negative external lead 4 is present, the portion where they are not present has a shorter distance between the opposing portions and is formed in an uneven shape.

As shown in FIG. 3B, these shapes are formed on the outer heater 1 and the positive external lead 3 and the negative external lead 4 positioned therein, on the lower heater fitting 8b. This is performed by placing the connected electrode body 2 and lowering and heating / pressing the upper heater fitting 8a. The opposite positions (seal surfaces) of the heater fittings 8a and 8b on the opposite side are similarly formed in the concave portion 9 and the convex portion 10. The portion corresponding to the portion where the positive electrode external lead 3 and the negative electrode external lead 4 exist is a concave portion 9.
The portion corresponding to the portion where the negative external lead 4 does not exist is the convex portion 10.

The sum of the volumes of the opposed concave portions 9 is
The total volume of the heat-adhesive film 7 enclosing the positive electrode external lead 3 or the negative electrode external lead 4 and the positive electrode external lead 3 or the negative electrode external lead 4 is smaller than the respective volumes. Accordingly, the upper and lower heaters 8a and 8b are operated to heat and press to form the exterior material 1 so that the heat-adhesive film 7 does not completely enter the convex portion 11 of the exterior material 1. Thereby, the inside of the convex portion 11 of the exterior material 1 can be filled with the thermal adhesive film 7 without any gap.

In this case, the portions where the heat-adhesive film 7 is interposed between the positive external lead 3 and the negative external lead 4 and the facing outer material 1 sandwiching the outer lead 1 and the outer material 1 are bent. There are three kinds of places, a place where the heat-adhesive film 7 is interposed between them, and a place where the exterior material 1 that is bent and facing directly faces.
Since the heater fittings 8a and 8b form the concave and convex portions 9 and 10 as described above, when performing the heat fusion, the heater fittings 8a and 8b are used.
By pressing and melting the peripheral portion 5b of the exterior material 1 with a and 8b, a hermetically sealed structure as shown in FIG. 3A can be formed.

As a result, there are no gaps at three places where the thickness of the heat-sealed portion is different, and the heat-adhesive film 7 as the insulating film around the external leads 3 and 4 does not become extremely thin. The sealing performance is ensured, and the insulation distance between the aluminum sheet 1b or the aluminum alloy sheet of the exterior material 1 and the positive electrode external lead 3 or the negative electrode external lead 4 is sufficiently ensured. A thin secondary battery can be manufactured. (Embodiment 2) FIG. 4 (a) is a completed view of a thin secondary battery, and FIG. 4 (b) is an explanatory view of a heating and pressing step. The same parts as those in FIGS. 3A and 3B are denoted by the same reference numerals, and the description thereof is omitted. Further, in order to avoid repetition of description, only portions different from the above (Example 1) will be described.

In this case, the shape of the thin secondary battery is as shown in FIG.
As shown in (a), one side has a concavo-convex shape as in (Example 1), but the other side has a flat shape without any concavity and convexity. Therefore, the heater fitting 8 facing this flat shape
The surface of c is also formed flat.

In this case, as in the first embodiment, the volume of the recess 9 of the heater fitting 8a (only one of the heater fittings 8a) is equal to that of the positive external lead 3 or the negative external lead 4.
Adhesive film 7 and positive electrode external lead 3
Alternatively, it is formed smaller than the respective volumes of the sum of the negative electrode external leads 4. (Embodiment 3) FIG. 5A is a completed view of a thin secondary battery, and FIG. 5B is an explanatory view of a heating and pressing step. The same parts as those in FIGS. 3A and 3B are denoted by the same reference numerals, and the description thereof is omitted. Further, in order to avoid repetition of description, only portions different from the above (Example 1) will be described.

In this case, the shape of the thin secondary battery is shown in FIG.
As shown in (a), the same as (Example 1),
Unlike (Example 1), the heat-adhesive film 7 is
Are separately provided at positions corresponding to the positive electrode external lead 3 or the negative electrode external lead 4. Both heater fittings 8a and 8b have the same shape as that of the first embodiment. The relationship between the volume of the recess 9 of the heater fittings 8a and 8b and the volume of the heat-adhesive film 7 is the same as that described in (Example 1). (Embodiment 4) FIG. 6 (a) is a completed view of a thin secondary battery, and FIG. 6 (b) is an explanatory view of a heating and pressing step. The same parts as those in FIGS. 3A and 3B are denoted by the same reference numerals, and the description thereof is omitted. Further, in order to avoid repetition of description, only portions different from the above (Example 1) will be described.

In this case, the shape of the thin secondary battery is shown in FIG.
As shown in (a), the same as (Example 1),
Unlike (Example 1), the heat-adhesive film 7 is
Are integrally provided on the respective sealant layers 1c including the position corresponding to the positive electrode external lead 3 or the negative electrode external lead 4. Both heater fittings 8a and 8b have the same shape as that of the first embodiment. The relationship between the volume of the recess 9 of the heater fittings 8a and 8b and the volume of the heat-adhesive film 7 is the same as that described in (Example 1). (Embodiment 5) FIG. 7 (a) is a completed view of a thin secondary battery, and FIG. 7 (b) is an explanatory view of a heating and pressing step. The same parts as those in FIGS. 3A and 3B are denoted by the same reference numerals, and the description thereof is omitted. Further, in order to avoid repetition of description, only portions different from the above (Example 1) will be described.

In this case, the shape of the thin secondary battery is shown in FIG.
As shown in (a), the outer shape is parallel and flat except for both ends. Accordingly, the heater fittings 8d and 8e also have correspondingly large recesses 9 except for both ends. Also in this case, the relationship between the volume of the concave portions 9 of the heater fittings 8d and 8e and the volume of the heat-adhesive film 7 is the same as that described in the first embodiment.

In each of the above embodiments, the heat-bonding film has a single-layer structure. However, the present invention is not limited to this, and a multi-layer structure may be used. In that case, at least, if the resin layer in contact with the positive electrode external lead and the negative electrode external lead is an acid-modified polyolefin-based film such as an acid-modified polypropylene or an acid-modified polyethylene having good adhesion to a metal, heat bonding of other portions is performed. The configuration of the conductive film 7 does not matter.

As described above, in the thin secondary battery and the method of manufacturing the same according to the present invention, the concave portion corresponding to the shape of the thin secondary battery is provided in the opposed portion of the heater fitting for heating and pressurizing the molten portion of the exterior material. Therefore, even if there are places where the thickness of the heat-sealed portion of the thin secondary battery is different, there is no gap between them, and the insulating film around the external leads does not become extremely thin. The sealing performance is ensured, and the insulation distance between the aluminum or aluminum alloy sheet of the exterior material and the positive electrode external lead or the negative electrode external lead is sufficiently ensured, so that a good thin secondary battery can be manufactured.

Further, the sealing surface of the two heater fittings facing each other has a gap formed by abutting the sealing surfaces, and the volume of the external lead, which exists at the same width as the gap before the heat fusion, is equal to the volume of the external lead. Since it is formed so as to be smaller than the sum of the volumes of the adhesive films, pressure can be easily applied at the time of heat fusion, and further, the sealing property is improved without generating a gap.

[0043]

According to the present invention, a thin secondary having excellent sealing properties, safety and productivity, in which an electrode body is sealed inside a closed body formed of an exterior material of a laminated film of aluminum or an alloy thereof. A method for manufacturing a battery and a thin secondary battery obtained therefrom are obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view of a thin secondary battery of the present invention.

FIG. 2 is a cross-sectional view of an exterior material.

3A is a cross-sectional view of a thin secondary battery showing an example of the present invention, and FIG.

4A is a cross-sectional view of a thin secondary battery showing an example of the present invention, and FIG. 4B is an explanatory view of a manufacturing method thereof.

5A is a cross-sectional view of a thin secondary battery showing an example of the present invention, and FIG.

6A is a cross-sectional view of a thin secondary battery showing an example of the present invention, and FIG. 6B is an explanatory view of a manufacturing method thereof.

7A is a cross-sectional view of a thin secondary battery showing an example of the present invention, and FIG. 7B is an explanatory view of a manufacturing method thereof.

FIG. 8 is a cross-sectional view of a conventional thin secondary battery.

FIG. 9 is an explanatory diagram of a conventional method for manufacturing a thin secondary battery.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Exterior material, 1a ... Protective layer, 1b ... Aluminum sheet, 1c ... Sealant layer, 2 ... Electrode body, 3 ... Positive external lead, 4 ... Negative external lead, 5a, 5b, 5c ... Peripheral part, 8a, 8b, 8c, 8d: heater bracket, 9: recess,
10 ... convex part

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[Procedure amendment]

[Submission date] January 19, 2001 (2001.1.1)
9)

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Fig. 4

[Correction method] Change

[Correction contents]

FIG. 4

[Procedure amendment 2]

[Document name to be amended] Drawing

[Correction target item name] Fig. 7

[Correction method] Change

[Correction contents]

FIG. 7

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Souichi Hanafusa 3-4-10 Minamishinagawa, Shinagawa-ku, Tokyo Inside AT Battery Inc. (72) Inventor Kei Shimoyamada 3-4-1 Minamishinagawa, Shinagawa-ku, Tokyo No. 10 Inside AT Battery Inc. (72) Inventor Masayoshi Nakajima 3-4-10 Minami Shinagawa, Shinagawa-ku, Tokyo Inside Inside AT Battery Inc. (72) Koichi Kawamura Isogo-ku, Yokohama-shi, Kanagawa 8 Shin-Sugita-cho Toshiba Electronic Engineering Corporation F-term (reference) 5H011 AA09 AA13 BB04 CC02 CC06 CC10 DD13 EE04 FF03 FF04 GG09 HH02 JJ25 JJ27 JJ29 KK02

Claims (4)

[Claims] 1. A pair of heater fittings in which an electrode body to which an external lead is connected is built inside a sealed body formed of an aluminum sheet having a sealant layer formed on a joint surface or an exterior material using an alloy sheet thereof. In the method for manufacturing a thin secondary battery for sealing by heating and pressurizing the peripheral portion of the hermetic body, at least one of the heater fittings has a pressing portion corresponding to a sealing portion of the peripheral portion having a convex portion. A method for manufacturing a thin secondary battery, comprising: 2. The thin type according to claim 1, wherein the sealing portion of the external lead is sealed by the exterior material in a state where the outer periphery of the external lead is covered with a heat-fusible film. A method for manufacturing a secondary battery. 3. The heater fitting is set such that the volume of a region formed between the protrusions is smaller than the sum of the volume of the external lead and the volume of the heat-fusible film in the corresponding region. The method for manufacturing a thin secondary battery according to claim 2, wherein: 4. A thin secondary battery manufactured by the method for manufacturing a thin secondary battery according to any one of claims 1 to 3.