JP2002245988A - Thin battery - Google Patents

Abstract

(57) [Problem] To provide a thin battery that prevents a short circuit between a positive electrode and a negative electrode and has excellent hermeticity. An exterior film material having at least a metal foil and a heat-fusible resin film, and a flat electrode group housed in the exterior film material and having a positive electrode, a negative electrode, and a separator interposed between the positive and negative electrodes, An external lead connected to the positive electrode and the negative electrode of the electrode group, respectively, and extending to the outside from the exterior film material. In a thin battery in which an electrode group is sealed by heat-sealing an insulating resin film on both surfaces of the thin film, the insulating resin film includes a first resin film in contact with an external lead and a second resin film not in contact with the external lead. The second resin film has a higher melting point than the first resin film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a thin battery.

[0002]

2. Description of the Related Art In recent years, with the development of electronic equipment, there has been a demand for the development of a secondary battery that is small, lightweight, has a high energy density, and can be repeatedly charged and discharged. As such a secondary battery, a negative electrode containing lithium or a lithium alloy as an active material and a suspension containing an active material containing an oxide, sulfide, or selenide of molybdenum, vanadium, titanium, or niobium were applied. A non-aqueous electrolyte secondary battery including a positive electrode made of a current collector and a non-aqueous electrolyte is known.

However, a secondary battery provided with a negative electrode using lithium or a lithium alloy as an active material has a problem that the charge / discharge cycle life is short because repetition of charge / discharge cycles generates lithium dendrites in the negative electrode. .

[0004] For this reason, a suspension containing a carbonaceous material that occludes and releases lithium ions, such as coke, graphite, carbon fiber, fired resin, and pyrolytic gas phase carbon, is applied to the negative electrode. A non-aqueous electrolyte secondary battery using a current collector has been proposed. In the secondary battery, the deterioration of the negative electrode characteristics due to dendrite deposition can be improved, so that the battery life and safety can be improved.

On the other hand, it has been attempted to use, as an exterior member, an exterior film material composed of a composite film having an aluminum foil and a heat-fusible resin film for the purpose of further reducing the thickness in place of a conventional metal can. Department has been put to practical use. As the nonaqueous electrolyte secondary battery having such an exterior film material, a rectangular concave portion (rectangular cup portion) produced by deep drawing, and edges extending horizontally in four sides of the cup portion And an outer film material having a flat plate portion connected to one of these edges, and a positive electrode, a negative electrode, and a positive electrode and a negative electrode, which are housed in a cup portion of the outer film material and capable of inserting and extracting lithium ions. Group provided with a separated separator or a lithium ion conductive solid electrolyte layer, and connected to the positive and negative electrodes of the electrode group, respectively, through one edge except for the edge connected to the flat plate portion of the exterior film material. And external leads of positive and negative electrodes extending to the
A thin battery has been developed in which the electrode group is air-tightly sealed in the cup by bending by 80 ° and heat-sealing the three edges except for the edge connected to the flat plate portion.

[0006]

The heat-fusible resin film constituting the exterior film material needs to be thin in order to make the battery thinner. However, when the thickness of the heat-fusible resin film is reduced, the electrode group is housed in the exterior film material, and when the periphery is thermally fused, the space between the exterior film materials other than the external lead portion is opposed. A gap is generated in the space, and it becomes impossible to perform hermetic sealing. Also,
When the heat-fusible resin film is softened by pressure during heat-sealing, the heat-fusible resin film is pushed away by the thickness of the external lead, such as aluminum of the external lead and the exterior film material. Contact between the metal foils causes a short circuit between the positive and negative electrodes.

For this reason, even if the heat-fusible resin film is displaced to some extent by the external leads during heat fusion, an insulating resin layer having a sufficient thickness is provided between the external leads and the metal foil of the exterior film material. In order to make the outer lead exist, an insulating resin film is arranged on the inner surface side of the exterior film material corresponding to the fused portion of the external lead, or an insulating resin film is arranged at a predetermined position of the external lead. . In particular, the former case is useful because there is no step in the alignment of the external leads or in the heat-sealed portion. As the insulating resin film, an acid-modified resin having good adhesion to metal is used.

In the case where the exterior film material is heat-sealed using the insulating resin film, an adhesive force between the heat-fusible resin film and the insulating resin film and between the insulating resin film and the external lead. Needs to be set to a sufficiently high value. In particular, the space between the insulating resin film and the external lead is located farthest from the heat source, and the external REIT is made of a metal having high thermal conductivity, so that the heat of fusion is easily radiated. Therefore, it is necessary to set the heat fusion temperature to a temperature considerably higher than the melting point of the insulating resin film.

However, when heat fusion is performed under the above-described conditions, the portion of the insulating resin film that contacts the external lead near the heat source tends to be softened at a high temperature. as a result,
Since the insulating resin film and the heat-fusible resin film continue to be deformed even after being displaced by the thickness of the external lead due to the pressure at the time of heat fusion, the external lead comes into contact with the metal foil of the exterior film. There is a possibility that short-circuit failure between the positive and negative electrodes may occur.

[0010] The present invention prevents short circuit failure between the positive and negative electrodes,
Another object of the present invention is to provide a thin battery having excellent sealing performance.

[0011]

A thin battery according to the present invention for achieving the above object is provided with an exterior film material having at least an aluminum foil and a heat-fusible resin film, and housed in the exterior film material. A positive electrode, a flat electrode group having a separator or a solid electrolyte layer interposed between a positive electrode and a negative electrode, and an external lead connected to the positive electrode and the negative electrode of this electrode group, respectively, and extending outside from the exterior film material. A thin battery in which the electrode group is sealed by heat-sealing the heat-fusible resin films of the exterior film material to each other and at both sides of the external leads at the extended portions of the external leads with an insulating resin film interposed therebetween. In the above, the insulating resin film may include a first resin film in contact with the external lead and a second resin film not in contact with the external lead. Consists of two or more layers of a multilayer structure including bets, the second resin film is characterized in that it has a higher melting point than the first resin film.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a thin battery (for example, a thin non-aqueous electrolyte secondary battery) according to the present invention will be described in detail with reference to FIGS.

FIG. 1 is a perspective view showing a thin battery, FIG. 2 is a cross-sectional view taken along the line II-II of the flat electrode group of FIG. 1, and FIG. 3 is a cross-section near a heat seal including external leads in the thin battery. FIG. The exterior film material 1 is composed of a main body 3 having a rectangular cup portion 2 and a lid 4 integrated with one end side wall of the main body 3 and heat-sealed to a peripheral edge of the cup portion 2. . As shown in FIG. 2, the main body 3 and the lid 4 of the exterior film material 1 include a heat-fusible resin film 5, a metal foil 6 such as an aluminum foil, and a rigid organic resin film 7, which are located at the innermost layer. It is composed of a composite film material laminated in this order.

The flat electrode group 8 is housed in the cup portion 2 of the main body 3 in the exterior film material 1. As shown in FIG. 2, the flat electrode group 8
A positive electrode 11 having a structure in which a current collector 10 is interposed therebetween, a separator 12, and a negative electrode 15 having a structure in which a current collector 14 is interposed between negative electrode layers 13 and 13 and a separator 12 are spirally wound into a substantially cylindrical shape. After that, for example, at room temperature, pressure 10-30
It is produced by pressure molding under the condition of kg / cm ² and flattening. The external leads 16 and 17 of the positive and negative electrodes
One end is connected to each of the positive and negative electrodes 11 and 15 of the electrode group 8, and the other end is an edge around the cup portion 2 of the main body 3 opposite to the integrated edge of the lid 4 in the exterior film material 1. Each part is extended outside.

The three edges around the cup portion 2 of the exterior film material 1 and the lid 4 are heat-sealed with the heat-fusible resin films 5 while extending the external leads 16 and 17. The external leads 16, 1
Strip insulating resin film 18a on both sides of 7, by thermally fusing across the 18b to form a thermal seal portion 19 _{1-19 3,} to seal the flat electrode group 8 in the exterior film material 1 I have. That is, the in the heat seal portion 19 ₂ of the external leads 16 and 17 are extended, the cup portion 2
The strip-shaped insulating resin films 18a and 18b are interposed between the main body 3 having the above, the external leads 16 and 17 and the lid 4 so as to cover both surfaces of the external leads 16 and 17, respectively, and are heat-sealed. These insulating resin films 18
a and 18b, as shown in FIGS. 2 and 3, a first resin film 20 which is in contact with the external leads 16 and 17 and which is melted at the time of thermal fusion and adheres to the external leads 16 and 17; 20, the first resin film 20
And a second resin film 21 having a higher melting point than that of the second resin film 21. The insulating resin film 1
In addition to the two-layer structure shown in FIGS. 2 and 3, the first and second leads 8 a and 18 b are melted at the time of thermal fusion as shown in FIG. A three-layer structure in which a second resin film 21 having a higher melting point than the first and third resin films 20 and 22 may be disposed between the third resin films 20 and 22 may be used. Of course, the insulating resin film is allowed to have a structure of four or more layers.

A non-aqueous electrolyte is accommodated in the cup portion 2 of the exterior film material 1 where the electrode group 8 is located.

[0017] Incidentally, the external leads 16 and 17 are two heat-sealed portion 19 except the heat-sealed portion 19 ₂ which is extended _1, 1
9 ₃ is bent 90 ° inwardly towards the cup portion 2 after heat fusion.

Next, the exterior film material 1, the positive electrode 1, the separator 2, the negative electrode 3, the exterior film material 7, and the non-aqueous electrolyte will be described.

1) Exterior Film Material The heat-fusible resin film constituting the exterior film material is, for example, a polyethylene (PE) film, a polypropylene (PP) film, a polypropylene-polyethylene copolymer film, an ionomer film, an ethylene A vinyl acetate (EVA) film or the like can be used.

As the metal foil constituting the exterior film material, for example, an aluminum foil can be used.

As the rigid organic resin film constituting the exterior film material, for example, a polyethylene terephthalate (PET) film, a nylon film or the like can be used.

2) Positive Electrode This positive electrode has a structure in which a positive electrode layer containing an active material and a binder is supported on both surfaces (or one surface) of a current collector.

Examples of the current collector include an aluminum, nickel, or stainless steel plate, and an aluminum, nickel, or stainless steel mesh.

As the active material, various oxides, for example,
Manganese dioxide, lithium manganese composite oxide, lithium
-Containing nickel oxide, lithium-containing cobalt oxide
Material, lithium-containing nickel-cobalt oxide, lithium-containing
Iron oxide, vanadium oxide containing lithium, disulfide
Chalcogen compounds such as titanium iodide and molybdenum disulfide
And so on. Among them, lithium cobalt acid
(LiCoO)_Two), Lithium nickel oxide (Li
NiO_Two), Lithium manganese oxide (LiMn) _TwoO_Four
Or LiMnO_Two) Can result in high voltage
Preferred for

Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), ethylene-propylene-diene copolymer (EPDM), and styrene-butadiene rubber (SBR). it can.

The positive electrode layer is allowed to contain a conductive agent such as acetylene black, carbon black and graphite.

It is preferable that the positive electrode layer has a thickness three to six times that of the current collector by one-sided coating (one-sided support).

3) Separator Examples of the separator include polyethylene, polypropylene, ethylene-propylene copolymer, and ethylene-propylene.
It is made of a microporous membrane made of a butene copolymer or a woven or nonwoven fabric having fibers of these materials.

4) Negative Electrode This negative electrode has a structure in which a negative electrode layer containing an active material and a binder is supported on both surfaces (or one surface) of a current collector.

Examples of the current collector include a copper plate and a copper mesh.

The active material is not particularly limited, but may be lithium metal, a lithium alloy, or reversibly occlude / release lithium ions during charge / discharge, or intercalate / intercalate lithium ions.
Deintercalating coke, carbon fiber, graphite,
Carbonaceous materials such as mesophase pitch-based carbon, pyrolytic gas-phase carbon material, and resin fired body can be exemplified.

Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), ethylene-propylene-diene copolymer (EPDM), styrene-butadiene rubber (SBR),
It is preferable to contain a binder such as carboxymethyl cellulose (CMC).

It is preferable that the negative electrode layer has a thickness three to six times that of the current collector by one-sided coating (one-sided support).

5) Nonaqueous Electrolyte This aqueous electrolyte has a composition in which an electrolyte is dissolved in a nonaqueous solvent.

As the electrolyte, for example, lithium perchlorate (LiClO ₄ ), lithium tetrafluoroborate (LiB
F ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium hexafluoroarsenate (LiAsF ₆ ), lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), LiN (CF
₃ SO ₂ ) ₂ or the like can be used.

Examples of the non-aqueous solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate and butylene carbonate; cyclic esters such as γ-butyrolactone; tetramethylsulfolane, dimethylsulfoxide, N-methylpyrrolidone, dimethylformamide and derivatives thereof. And other non-aqueous solvents; and the like. These non-aqueous solvents can be used in the form of one kind or a mixture of two or more kinds. In addition, dimethyl carbonate, methyl ethyl carbonate, chain carbonate such as diethyl carbonate and acetonitrile, ethyl acetate, methyl acetate, these non-aqueous solvents,
By mixing a solvent such as toluene and xylene, the viscosity of the non-aqueous electrolyte can be reduced.

The concentration of the electrolyte in the non-aqueous solvent is as follows:
It is preferable to set it to 0.5 mol / L or more.

In the thin battery according to the present invention, a solid electrolyte layer may be used instead of the separator.
However, in the thin battery having such a configuration, the nonaqueous electrolyte is held by the positive and negative electrodes and the solid electrolyte layer, respectively.

6) Insulating resin films 18a and 18b The insulating resin films 18a and 18b are different from the first resin film 20 in which the second resin film 21 not in contact with the external leads 16 and 17 is in contact with the external leads 16 and 17. It is preferred to have a low melt flow rate (MFR). In particular, the second resin film 21 not in contact with the external leads 16 and 17 preferably has a melt flow rate (MFR) of 2 g / 10 minutes.

The insulating resin film having a two-layer structure shown in FIGS. 2 and 3 comprises (a) an acid-modified polyethylene layer and a polyethylene layer, and an acid-modified polyethylene layer is disposed on the side in contact with the external lead. b) It is preferable that an acid-modified polypropylene layer is composed of an acid-modified polypropylene layer and a polypropylene layer, and the acid-modified polypropylene layer is disposed on the side in contact with the external lead.

In the three-layer insulating resin film shown in FIG. 4, (a) a polyethylene layer is disposed in the middle, and an acid-modified polyethylene layer is disposed on both sides of the polyethylene layer, or (b) a polyethylene layer is disposed in the middle. It is preferable to dispose a polypropylene layer, and dispose an acid-modified polypropylene layer on both sides of the polypropylene layer.

The acid-modified polyethylene is preferably, for example, an acid-modified low-density linear polyethylene or an acid-modified linear polyethylene.

It is preferable that the polythylene is, for example, a medium density or high density polyethylene.

The polypropylene is preferably, for example, a homopolymer-based polypropylene.

The acid-modified polypropylene is preferably, for example, a random copolymer-based polypropylene.

Next, one manufacturing method of the thin battery according to the present invention will be described below.

First, a rectangular cup portion 2 is formed by deep drawing a composite film material in which a heat-fusible resin film, a metal foil, and a rigid organic resin film are laminated in this order. Subsequently, the strip-shaped composite film material is cut so that one side of the opening of the rectangular cup portion 2 is located at the center, and the first narrow portion extends horizontally on four sides around the cup portion 2. to third edge 23 _{1-23 3} and breadth (the length and the width obtained by summing said cup portion 2 and a second edge 23 ₂₎
Making exterior film material 24 is cut out as the fourth edge 23 ₄ are formed. Subsequently, respectively thermally wearing strip of the insulating resin film 18a, 18b to the end portion of the second edge 23 ₂ and the fourth edge 23 ₄ of the outer film material 24. These insulating resin films 18a, 18b
As shown in FIGS. 2 and 3, for example, the first resin film 20 is in contact with the external leads 16 and 17 and is melted at the time of heat fusion and adheres to the external leads 16 and 17; 20 and a second resin film 21 having a higher melting point than the first resin film 20.

Next, a flat plate having external leads 16 and 17 is formed.
The flat electrode group 8 is connected to the cup portion 2 of the exterior film material 24.
The external leads 16 and 17 are inside the second edge 23._TwoOr
To extend to the outside. Next, the exterior
Wide fourth edge 23 of film material 24_FourFold 180 °
Bend the fourth edge 23_FourAnd the first to third edges 23 ₁
~ 23_ThreeAnd the third edge 23_ThreeTwo edges (excluding
1, the second edge 23₁, 23_Two) At the desired pressure.
It is heat-sealed. At this time, the external leads 16 and 17 are
Extended second edge 23_Two4th edge part 2 bent
3_FourIn the above, the insulating resin films 18a, 18b
When heat fusion is applied to both sides of the external leads 16 and 17,
Then, in the area excluding the external leads 16 and 17,
The memories 18a and 18b are thermally fused to each other. Also, the first edge
23₁And the fourth edge 23 bent_FourAnd in said outside
Heat-sealed resin films of the packaging film material 24 are heat-sealed
Is done. Thereafter, the non-aqueous electrolyte is applied to the third edge portion 23 of the unheated fusion.
_ThreeAnd the fourth edge 23 bent_FourThrough the gap with
The electrode group 8 injected into the cup part 2 and stored therein is
Impregnate with water electrolyte. Continue to remove the unheated part
After heat sealing to seal the flat electrode group 8 airtightly,
First and third edges 23₁, 23_Three4th edge bent
Part 23_FourThe heat-sealed portion is cut to a desired width, and these remaining edges are cut.
Part (heat seal part) is bent toward the cup part 2
Thus, the thin battery shown in FIGS.
You.

In the manufacture of the thin battery described above, the arrangement of the insulating resin film on the outer film material is not limited to the configuration shown in FIG. For example, as shown in FIG. 6, narrow _first to _third edges 231 to 233 extending horizontally on four sides around the cup portion 2 and wide portions (the cup portion 2 and the second edge portion). after producing a fourth exterior film material 24 edge 23 ₄ is formed of 23 ₂ and the length and same width obtained by summing), for accommodating a flat electrode group 8 with external leads 16 and 17 to the cup portion 2 insulating resin film on both surfaces portions corresponding to ₂ the second edge 23 thereof external leads 16 and 17 when (18
a, 18a), 18b, and 18b may be heat-sealed.

As described above, the thin battery according to the present invention has an exterior film material having at least a metal foil and a heat-fusible resin film, and is accommodated in the exterior film material, and has a positive electrode, a negative electrode, and a positive electrode and a negative electrode. A flat electrode group having an interposed separator or solid electrolyte layer, and an external lead connected to a positive electrode and a negative electrode of this electrode group, respectively, and extending outside from the external film material, In a thin battery in which the electrode group is sealed by heat-sealing the heat-fusible resin films to each other and both sides of the external leads at the extended portions of the external leads with the insulating resin film interposed therebetween, the insulating resin film includes: A multilayer structure of two or more layers including a first resin film in contact with the external lead and a second resin film not in contact with the external lead Rannahli, the second resin film has a higher melting point than the first resin film.

According to this structure, the second resin film not in contact with the external leads has a higher melting point than the first resin film in contact with the external leads. The second resin film having a high melting point acts as a protective layer at the time of heat fusion to prevent contact between a metal foil such as an aluminum foil of an exterior film material and an external lead, thereby preventing short-circuit between the positive and negative electrodes. Can be prevented.

That is, in order to make the outer leads and the insulating resin film adhere to each other, it is necessary to sufficiently soften the resin film around the outer leads to conform to the shape of the outer leads. For this purpose, the resin film (first resin film) in contact with the external leads is required to have a certain high flow characteristic, that is, MFR, at the time of fusion.

On the other hand, the resin film (the second resin film) not in contact with the external leads does not need the above-mentioned characteristics. Rather, the MFR of the second resin film close to the heat source is equivalent to the first resin film in contact with the external leads. Or if it is high, the layers of the resin film are mixed by the convection between the first and second resin films generated at the time of heat fusion,
The function as the protective layer is impaired, and a short circuit occurs due to contact between the metal foil of the exterior film material and the external leads.

Therefore, the insulating resin film interposed between the external lead and the exterior film material has a multilayer structure of at least two layers, and the second resin film not in contact with the external lead is replaced with the first resin film in contact with the external lead. By making the melting point relatively high, that is, a relatively low MFR, the second resin film having a low MFR acts as a protective layer at the time of heat fusion to prevent contact between the metal foil of the exterior film material and the external leads, The short-circuit failure between the positive and negative electrodes can be prevented.

In particular, as shown in FIG. 4, between the first and third resin films, one of which is in contact with the external lead, the second one having a higher melting point than the first and third resin films.
By using an insulating resin film having a three-layer structure in which a resin film is arranged, the first resin film is arranged on the external lead side as in the case of using an insulating resin film having a two-layer structure when setting the insulating resin film. Care should be taken that the desired resin film is disposed on the external lead side regardless of the complexity, regardless of whether the front and back resin films (first and third resin films) are disposed on the external lead side. Becomes possible. As a result, setting of the insulating resin film in the manufacturing process of the thin battery can be simplified.

[0056]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

Example 1 <Preparation of Exterior Film Material> Nylon having a thickness of 0.025 mm
Film / 0.04mm thick aluminum foil / thickness
Total thickness composed of 0.03mm polyethylene film
0.095mm composite film is subjected to deep drawing
Rectangular power 3.0mm deep, 54mm long, 34mm wide
A top portion 2 was formed. Next, this composite film material
By cutting, as shown in FIG.
A first 5 mm wide first part extending horizontally on four sides around the
~ Third edge 22₁~ 22_ThreeAnd a fourth edge 60 mm wide
22 _FourWith an outer dimension of 170 mm x 130 mm
A film material 23 was produced.

Next, the melting point is 120 ° C. and the MFR is 1.7.
g / min of an acid-modified linear low-density polyethylene (acid-modified LLDPE) having a thickness of 0.07 mm and a high-density polyethylene (HDPE) having a melting point of 120 ° C. and an MFR of 0.6 g / min. Become 0.05m thick
m 2nd resin film and total thickness 0.12mm
Was cut into dimensions of 5 mm in width and 30 mm in length to produce two strip-shaped insulating resin films. Subsequently, as shown in FIG. 5, the insulating resin films 18a and 18b are
Each end of the edge 22 _second and fourth edges 22 ₄ arranged such that their insulation resin film 18a, a second resin film comprising HDPE and 18b are abutted, and heat-sealed.

<Preparation of Electrode Group> First, L as an active material
A paste was prepared by mixing 89 parts by weight of iCoO ₃ powder, 8 parts by weight of graphite powder as a conductive filler and 3 parts by weight of polyvinylidene fluoride resin as a binder with 25 parts by weight of N-methylpyrrolidone. This paste is used as a current collector and has external dimensions of 50 mm × 370 mm and a thickness of 0.3 m.
50mm × 70mm on one side on both sides of aluminum foil
Was applied so that the edge portion of the non-coated portion remained as an uncoated portion, and was dried. Then, an aluminum external lead having a thickness of 0.1 mm and a width of 4 mm was welded to the uncoated portion to produce a positive electrode.

Next, after the mesophase pitch-based carbon fibers were pulverized, 100 parts by weight of the heat-treated carbon fiber powder were mixed with an aqueous solution containing carboxymethyl cellulose and 2 parts by weight of crosslinked rubber latex particles of styrene-butadiene to prepare a paste. This paste is used as a current collector and has an outer dimension of 51.5 mm × 380 mm and a thickness of 0.015 m.
m on both sides of the copper foil so that an edge of 51.5 mm x 60 mm is left as an uncoated part on one side, and dried,
A negative electrode was manufactured by welding a nickel external lead having a thickness of 0.1 mm and a width of 4 mm to the uncoated portion.

Next, 5 was placed between the positive and negative electrodes and the positive electrode side.
After arranging a 3 mm × 450 mm polyethylene microporous membrane, it was spirally wound by a winding machine so that the outermost peripheral surface was covered with the copper foil of the negative electrode, thereby producing 100 cylindrical objects. Subsequently, the cylindrical material is kept at room temperature under a pressure of 10 to 30.
By heating and pressing under the condition of kg / cm ² , 100 flat electrode groups having a thickness of about 3 mm and having the above-mentioned external leads 16 and 17 shown in FIG. 5 were produced.

<Preparation of Non-Aqueous Electrolyte> A non-aqueous solvent in which ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed at a volume ratio of 1: 1 was used as an electrolyte.
iPF ₆ was dissolved to a concentration of 1 mol / L to prepare a non-aqueous electrolyte.

<Production of Thin Lithium Ion Secondary Battery> As shown in FIG. 5 described above, the flat electrode group 8 having the external leads 16 and 17 is placed in the cup portion 2 of the exterior film material 24 by the external leads 16. , 17 are the second edges 2
From 3 ₂ it housed so as to extend to the outside. Subsequently, a fourth edge 23 ₄ wide of the outer film material 24 18
0 ° bent repeatedly and fourth edges 22 ₄ and the third edge 23 _{1-23 3} from the first, the two edges excluding the third edge 23 ₃ (first, second edge 23 _1, 4.0kgf to 23 ₂₎
While applying pressure at a pressure of / cm ³ , heat fusion was performed at a temperature of the melting point of the acid-modified LLDPE + 70 ° C. At this time, in the fourth edges 23 ₄ for the external leads 16 and 17 is bent and the second edge portion 23 ₂ is extended, the insulating resin film 18a, a first resin film made of acid-modified LLDPE and 18b The first resin films of the insulating resin films 18a and 18b were heat-sealed to each other except for the external leads 16 and 17 while being thermally fused to both surfaces of the external leads 16 and 17, respectively. Also, the outer film material 24 in the fourth edges 23 ₄ which is bent to the first edge 23 ₁
Of polyethylene films were heat-sealed. After this,
The said non-aqueous electrolyte solution of Minetsu fused 3 edge 23 ₃ the cup through the gap between the fourth edge 23 ₄ folded and section 2
The electrode group 8 housed therein was impregnated with a non-aqueous electrolyte. Subsequently, after the non-heat-sealed portion is heat-sealed to hermetically seal the flat electrode group 8, the first and third electrode groups 8 are sealed.
The heat-sealing portion of the edge 23 _1, 23 ₃ and the fourth edge 23 ₄ which is bent and cut so as to leave 2.5mm width, these remaining edges (heat seal portion) on the cup portion 2 of The external dimensions are 35 mm × 60 mm except for the external leads shown in FIGS.
100 thin lithium-ion secondary batteries of mAh were manufactured.

(Examples 2 to 6) Five kinds of thin lithium ion secondary batteries (each having a total number of 100) were prepared in the same manner as in Example 1 except that the belt-shaped insulating resin films having the structures shown in Table 1 below were used. Was manufactured.

(Examples 7 and 8) After the exterior film material 24 shown in FIG. 6 was produced in the same manner as in Example 1, the flat electrode group 8 having the external leads 16 and 17 was housed in the cup 2. structure of insulating resin films shown in table 2 on both portions corresponding to ₂ the second edge 23 thereof external leads 16 and 17 when (18a, 18a), 18b, 1
8b were heat-sealed. Thereafter, the external dimensions except for the external leads shown in FIGS. 1 to 3 are 35 mm × 60 mm and the capacity is 300 mA by the same method as in the first embodiment.
h two types of thin lithium ion secondary batteries (each 100
Was manufactured.

(Comparative Examples 1 to 5) Five kinds of thin lithium ion secondary batteries (each having a total number of 100) were manufactured in the same manner as in Example 1 except that the belt-shaped insulating resin films having the structures shown in Table 2 below were used. Was manufactured. FIG. 7 is a sectional view of the thin lithium ion secondary battery obtained in Comparative Example 1 near the heat seal of the external lead 16. 3 in FIG.
Reference numerals 1a and 31b denote insulating resin films made of only acid-modified LLDPE. 7, the same members as those in FIG. 3 described above are denoted by the same reference numerals.

The obtained Examples 1 to 8 and Comparative Examples 1 to 5
The number of short-circuits between the positive and negative electrodes after manufacture was examined for 100 secondary batteries. The results are shown in Tables 1 and 2 below.
In Tables 1 and 2, MDPE is an abbreviation for medium density polyethylene, and LDPE is an abbreviation for low density polyethylene.

[0068]

[Table 1]

[0069]

[Table 2] As is clear from Tables 1 and 2, the second resin film has a multilayer structure of two or more layers including a first resin film in contact with the external lead and a second resin film not in contact with the external lead. In the thin lithium ion secondary batteries of Examples 1 to 8 using the insulating resin film having a higher melting point than the resin film, the number of occurrences of positive and negative short circuits (100
Is zero, indicating high reliability.

On the other hand, in the thin lithium ion secondary battery of Comparative Example 1 using the insulating resin film made of the acid-modified LLDPE alone, the number of short-circuits (out of 100) of the positive and negative electrodes was 2
The number is extremely large at four, which indicates that there is a problem in reliability. Further, even if the second resin film has a multilayer structure of two or more layers including a first resin film in contact with the external lead and a second resin film not in contact with the external lead,
In the thin lithium ion secondary batteries of Comparative Examples 2 to 5 using an insulating resin film having a melting point equal to or lower than that of the resin film, the number of short circuit occurrences (out of 100) of the positive and negative electrodes was as large as 11 to 15, It turns out that there is a problem in terms of reliability.

[0071]

As described above in detail, according to the present invention, a short circuit between a positive electrode and a negative electrode is prevented and a cordless type such as an integrated video camera, a mobile communication device, a notebook type personal computer, etc., which is excellent in hermeticity. A highly reliable thin battery useful as a power source of a portable electronic device or the like can be provided.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one embodiment of a thin battery according to the present invention.

FIG. 2 is a cross-sectional view of the thin battery of FIG. 1 taken along the line II-II.

FIG. 3 is a cross-sectional view of the thin battery of FIG. 2 taken along the line III-III.

FIG. 4 is a perspective view showing another embodiment of the thin battery according to the present invention.

FIG. 5 is a perspective view for explaining a manufacturing process of the thin battery according to the present invention.

FIG. 6 is a plan view for explaining another manufacturing process of the thin battery according to the present invention.

FIG. 7 is a cross-sectional view of a conventional thin battery in the vicinity of a heat seal portion from which external leads extend.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Exterior film material, 2 ... Rectangular cup part, 5 ... Heat-fusible resin film, 6 ... Aluminum foil, 7 ... Rigid organic resin film, 8 ... Flat electrode group, 11 ... Positive electrode, 12 ... separator, 15 ... negative electrode, 16, 17 ... external leads, 18a, 18b ... insulating resin film, 19 _{1-19 3} ... heat seal portion, 20 ... first resin film, 21 ... second resin film, 22 ... third resin film, 23 _{1-23 4} ... edge, 24 ... exterior film material.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Kengo Kurata 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 Co., Ltd. (72) Inventor Masayoshi Nakajima 3-4-10 Minamishinagawa, Shinagawa-ku, Tokyo Inside 72 Co., Ltd. AT Battery Co., Ltd. (72) Koichi Kawamura Isogo-ku, Yokohama-shi, Kanagawa 8 Shinjukutacho Toshiba Electronic Engineering Corporation F-term (reference)

Claims (11)

[Claims] 1. A flat package having at least a metal foil and a heat-fusible resin film, and a separator or a solid electrolyte layer housed in the package film and interposed between a positive electrode, a negative electrode, and a positive electrode and a negative electrode. Electrode group, and external leads respectively connected to the positive electrode and the negative electrode of the electrode group and extending outside from the exterior film material, wherein the heat-fusible resin films of the exterior film material and the external leads are provided. A thin battery in which the electrode group is sealed by sandwiching an insulating resin film on both surfaces of the external lead at the extension portion of the thin battery, wherein the insulating resin film is in contact with the external lead.
A thin battery having a multilayer structure of two or more layers including a resin film and a second resin film not in contact with the external lead, wherein the second resin film has a higher melting point than the first resin film. . 2. The insulating resin film according to claim 1, wherein the second resin has a higher melting point between the two first and third resin films, one of which is in contact with the external lead, as compared with the first and third resin films. The thin battery according to claim 1, wherein the battery has a three-layer structure in which a resin film is disposed. 3. The thin battery according to claim 1, wherein the insulating resin film has a lower melt flow rate (MFR) in the second resin film than in the first resin film. 4. The thin battery according to claim 2, wherein the insulating resin film is such that the second resin film has a lower melt flow rate (MFR) than the first and third resin films. . 5. The thin battery according to claim 3, wherein the second resin film has a melt flow rate (MFR) of 2 g / 10 minutes. 6. The thin battery according to claim 1, wherein in the insulating resin film, the first resin film is made of acid-modified polyethylene, and the second resin film is made of polyethylene. 7. The thin battery according to claim 2, wherein in the insulating resin film, the first and third resin films are made of acid-modified polyethylene, and the second resin film is made of polyethylene. 8. The thin type according to claim 6, wherein the acid-modified polyethylene is made of an acid-modified low-density polyethylene or an acid-modified linear polyethylene, and the polythylene is made of a medium-density or high-density polyethylene. battery. 9. The thin battery according to claim 1, wherein in the insulating resin film, the first resin film is made of acid-modified polypropylene, and the second resin film is made of polypropylene. 10. The insulating resin film according to claim 1, wherein:
The third resin film is made of an acid-modified polypropylene,
The thin battery according to claim 2, wherein the second resin film is made of polypropylene. 11. The thin battery according to claim 9, wherein the acid-modified polypropylene is made of a random copolymer-based polypropylene, and the polypropylene is made of a homopolymer-based polypropylene.