JP2001093483A - Bag for thin battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bag for a thin battery which can prevent a burst of the bag without deteriorating productivity and generating inferior goods. SOLUTION: A circumferential area of a bag 1 is formed on a heat seal part 2. A part of the heat seal part 2 is notched from an inner edge 2a toward an outer edge 2b such that a width of the part is narrower than that of other parts of the heat seal part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin battery bag for housing a power generating element for a thin battery such as a lithium ion secondary battery (LIB).

[0002]

2. Description of the Related Art With the recent development of various electronic devices, there is an increasing need for miniaturization and space saving of electronic devices. Flexibility is required. In order to meet such needs, a lithium ion secondary battery using a gel polymer electrolyte is entering a stage of practical use.

FIGS. 4 and 5 show examples of the structure of a lithium ion secondary battery using this type of gel polymer electrolyte. In these figures, 31 is a positive electrode current collector made of an aluminum foil, 32 is a positive electrode made of a lithium-containing composite oxide such as lithium cobalt oxide, 33 is a separator made of a polymer electrolyte polymerized with a solvent, and 34 is a charcoal. A negative electrode 35 made of a material is a negative electrode current collector made of copper foil, and these constitute a power generating element. The power generation element is housed in a bag 36 made of an aluminum laminate sheet, and the periphery of the bag 36 is heat-sealed to form a heat-sealed portion 36c, thereby forming a battery. In addition, reference numeral 37 denotes an electrode.

Usually, a three-layer laminate sheet of a polyethylene layer, an aluminum foil layer and a polyethylene layer is used as the above-mentioned aluminum laminate sheet (Japanese Patent Application Laid-Open No. 9-7636).

[0005] In the above-mentioned lithium ion secondary battery, since the power generating element generates Joule heat during use (during charge / discharge), the temperature inside the bag rises to about 60 ° C. When a short circuit or abnormal charge / discharge occurs, the internal temperature may exceed 100 ° C. Due to this increase in temperature, the organic solvent contained in the gel constituting the power generation element is vaporized, and the vaporized product swells the thin battery bag made of the laminate sheet to stop charging and discharging. As the temperature drops, the vaporized organic solvent returns to the gel.

However, the internal pressure of the bag body abnormally increases,
If the strength of the bag cannot withstand the internal pressure, there is a risk that the bag may burst. Such a rupture, even when the battery is housed in a hard case,
There is a risk of breaking this, and at the same time, the electrolyte and the like in the bag body scatter and contaminate the surroundings. To avoid this,
For example, as shown in FIG. 6, when heat sealing the periphery of the aluminum laminate sheet to form a bag,
It has been proposed and practiced to partially dispose the hardly-adhesive resin 38 in a part of the peripheral edge opening and heat seal in that state. The bag obtained in this manner has a small adhesive force due to heat sealing at the portion where the hardly-adhesive resin 38 is provided, so that the portion where the hard-adhesive resin 38 is provided before the internal pressure reaches a dangerous level. Peel off and open. Therefore, the vapor is released to the outside. In this case, since the peeled portion is only a part of the bag body, the scattering of the electrolytic solution or the like does not occur. As shown in FIG. 6, the portion where the hardly-adhesive resin 38 is provided usually has a positive electrode lead wire and a negative electrode lead wire (electrode 37) drawn out from a power generating element housed in the bag body. ).

[0007]

[Problems to be solved by the invention]

[0008] However, as shown in FIG.
Heat sealing in a state where the above-mentioned hardly-adhesive resin 38 is disposed in the portion between 7 is time-consuming, resulting in poor productivity. Also, during the heat sealing, the resin 38 is displaced, This causes problems such as the occurrence of defective products.

The present invention has been made in view of such circumstances, and provides a thin battery bag which can prevent the bag from being ruptured without causing a problem of reduced productivity and occurrence of defective products. For that purpose.

[0010]

In order to achieve the above object, a thin battery bag according to the present invention is a bag for accommodating a power generating element for a thin battery, wherein the periphery of the bag is heated. The heat seal portion is formed in the seal portion, and a part of the heat seal portion is formed in a cutout shape from the inner edge to the outer edge so as to be narrower than the seal width of the other heat seal portions.

That is, in the thin battery bag of the present invention, a part of the heat seal portion is formed in a notch from the inner edge to the outer edge so as to be narrower than the seal width of the other heat seal portions. Therefore, when the internal pressure of the bag body rises abnormally due to overcharging or heat generation due to an abnormally large current, the pressure concentrates on the notch-formed portion. Since the seal width at this portion is narrow, the seal at that portion peels off due to the above pressure, and the vaporized material in the bag is released to the outside. As a result, the rupture of the bag is avoided, and the scattering of the electrolyte or the like due to the rupture of the bag is also prevented. The sealing width of the heat sealing portion can be easily reduced by partially narrowing the pressing surface of the heat sealing portion forming die. Therefore, according to the present invention, the production process can be simplified, and it is not necessary to provide another component such as a hardly-adhesive resin, so that the number of components can be reduced.

In particular, the notch-shaped portion of the heat seal portion is formed between the positive electrode lead and the negative electrode lead of the power generating element for a thin battery housed in the bag. As a result, the release of the vapor in the bag becomes smooth.
For example, when the battery is mounted inside the electronic device, the heat seal portions 2 ′ (see FIG. 1) on both left and right edges of the bag are bent inward (in the direction of arrow A) from the inner edge 2 ″.
Mounting is performed in a compact shape. At this time, if a part of the heat seal portion on both side edges of the bag body is formed in a notch shape, the bent portion blocks the notched portion with the bent edge of the inner edge 2 ″. In some cases, the release of vapors in the bag does not proceed smoothly. However, as described above, when the cutout portion is formed between the positive electrode lead wire and the negative electrode lead wire, since this portion is not bent, the release of the vaporized material in the bag is performed smoothly. Become like

Next, the present invention will be described in detail.

[0014] The thin battery bag of the present invention is, for example, a single substantially square laminate sheet is folded from substantially half to two, and both side edges are heat-sealed to form a cylinder. A power generation element is housed inside the battery and the opening is heat-sealed to form a battery.

The thin battery bag is formed of a substantially square laminate sheet comprising a metal layer and a sealant layer. The metal layer may be made of aluminum, aluminum, or the like obtained by rolling, electrolysis, or the like. Metal foils made of alloys, copper, copper alloys, iron, stainless steel, titanium, titanium alloys and the like are used. And the thickness is 5-10
It is preferable that the distance is set in the range of 0 μm. When the thickness is less than 5 μm, pinholes and the like are easily generated in the metal foil, and the gas barrier property and the water shielding property of the laminate material are reduced,
If the thickness exceeds 100 μm, it is disadvantageous for thinning and flexibility of the thin battery bag.

The material of the sealant layer is as follows:
Polypropylene (PP), polyethylene (PE), polyester, polyacrylonitrile, ethylene vinyl acetate copolymer (EVA), polyvinyl alcohol (PV
A), modified polypropylene, modified polyethylene, polyvinyl acetate, polyvinyl acetate, or a composite product thereof. Particularly, polypropylene and polyethylene are preferable from the viewpoint of gas barrier properties and chemical resistance. The thickness is preferably set in the range of 5 to 1000 μm. When the thickness is less than 5 μm, the airtightness (embedding property of the sealant) of the electrode seal portion and the insulation between the electrode and the metal layer are reduced, and when the thickness is more than 1000 μm, it is disadvantageous for thinning the thin battery bag. Because.

The above-mentioned laminate is not particularly limited as long as it is a laminate of a metal layer and a sealant layer. Also,
Other layers may be formed in addition to the metal layer and the sealant layer. For example, if a layer made of a polyimide film is formed between the metal layer and the sealant layer, the polyimide layer having excellent heat resistance and acid resistance allows the metal layer to contact the current collecting terminal even when the sealant layer is dissolved. And the danger of short-circuiting can be avoided. Also,
If a gas barrier film is used for the layer, it is possible to effectively prevent moisture and oxygen from entering the bag. Furthermore, a polyethylene terephthalate (P)
When a layer composed of an ET) film is formed, a PET film can form a bag having excellent thermal stability and chemical resistance and high physical strength.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is an enlarged view of a main part showing an embodiment of a thin battery bag according to the present invention. This thin battery bag 1 is formed from one elongated aluminum laminate sheet. The sheet is formed by laminating a PP film, an aluminum foil, a polyamide film, and a PET film in this order. Then, the sheet is folded in half from about half so that the PP film side of the sheet is on the inside, the portion is set as the bottom, and the right and left side edges are heat-sealed to make the whole cylindrical, and the opening of the cylindrical body is opened. From inside the power generating element [for example, 40 mm ×
80 mm × 2 mm (thickness)], and the opening of the cylindrical body is heat-sealed to form a battery. The opening of the tubular body is heat-sealed while sandwiching two electrodes 3 fed from a power generating element housed in the bag 1. It should be noted that, as shown in FIG. 1, at a part of the heat seal portion 2 between the two electrodes 3, the seal width d is smaller than the seal width e of the other heat seal portions. From the outside toward the outer edge 2b. The remaining configuration of the thin battery bag of the present invention is the same as that of the conventional example shown in FIGS. 4 and 5, and therefore illustration and description are omitted.

In the heat seal section 2, the seal width on the left and right side edges is usually formed to be 10 mm wide, and the upper seal width e is formed to be 4 mm wide. With respect to this width, the seal width d at the location formed in the notch shape is 1 to 2 mm.
(25 to 50% of the seal width e) (see FIG. 1). This is the same for the other embodiments shown in FIGS. That is, if the seal width e is less than 1 mm (25%), there is a tendency for peeling to occur even when the internal pressure rises within an appropriate range.
If it exceeds mm (50%), it may not be peeled off at the time of abnormal internal pressure.

FIGS. 2 and 3 are enlarged views of a main part showing another embodiment of the thin battery bag. This embodiment differs from the embodiment shown in FIG. 1 in that the notched shapes are quadrangular and semicircular, respectively. Otherwise, the embodiment is the same as the above embodiment, and the operation and effect are also the same.

In the above-described embodiment, the bag is formed only by heat-sealing the sheet, but an adhesive may be used in combination to improve the sealing property. In this case, the adhesive includes modified polyolefin, urethane,
Epoxy, EEA, silane coupling agents and the like are used. Further, when the electrode fed from the power generating element is made of, for example, copper, copper and PP are hard to adhere to each other even when heated and pressed, and therefore, it is preferable to use an adhesive or the like in combination.

The thin battery bag of the present invention is manufactured, for example, as follows. First, the above-described sheet cut into a substantially square shape is prepared, and the sheet is vertically moved from approximately half to the top and bottom.
Fold it up. Then, both sides of the folded part are heat-sealed to form a cylindrical bag. At this time, a long plate-shaped mold is used as a pair of upper and lower molds for heat sealing both side edges. Next, a thin battery power generating element is accommodated from the opening in the tubular bag body, and the positive electrode lead and the negative electrode lead fed from the thin battery power generating element are made to go out of the opening of the bag. Then, the opening is heat-sealed. Thereby, a thin battery is formed. At this time, a pair of upper and lower molds for heat-sealing the opening are long plate-shaped molds, which are partially cut away. As a result, a part of the heat seal portion that covers the opening is formed in a notch shape as described above.

In the thus obtained product, the notched portion of the heat seal portion did not peel off if the inside of the bag was within an appropriate pressure range, but the power generating element generated abnormal heat and the internal pressure became abnormally large. When this occurred, the notch-like portion was peeled off to release the pressure, thereby avoiding breakage of the bag.

[0025]

As described above, according to the thin battery bag of the present invention, the notch is formed from the inner edge to the outer edge so that a part of the heat seal portion becomes narrower than the seal width of the other heat seal portions. When the internal pressure of the bag body rises abnormally due to heat generated by overcharging or overdischarging, the pressure concentrates on the cutout portion. Since the seal width at this portion is narrow, the seal at that portion peels off due to the above pressure, and the vaporized material in the bag is released to the outside.
As a result, the rupture of the bag is avoided, and the scattering of the electrolytic solution or the like due to the rupture of the bag is also prevented. And, to partially narrow the seal width of the heat seal portion, by partially narrowing the pressing surface of the heat seal portion forming mold or the like,
Since it can be formed easily, a conventionally difficult-to-adhesive resin is not required, and productivity can be improved and the number of parts can be reduced.

[Brief description of the drawings]

FIG. 1 is an enlarged view of a main part showing a thin battery bag according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a main part showing a thin battery bag according to another embodiment of the present invention.

FIG. 3 is an enlarged view of a main part showing a thin battery bag according to another embodiment of the present invention.

FIG. 4 is a perspective view showing a conventional lithium ion secondary battery.

FIG. 5 is a sectional view taken along line A-A ′ of FIG. 4;

FIG. 6 is an enlarged view of a main part showing a conventional lithium ion secondary battery.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Thin battery bag 2 Heat seal part 2a Inner edge 2b Outer edge

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 5H011 AA09 AA13 CC02 CC06 CC10 DD07 DD13 EE04 KK01 5H029 AJ12 AJ14 AK03 AL06 AM00 AM16 BJ04 CJ04 CJ05 DJ02 DJ03 DJ05 EJ12 HJ04 HJ12

Claims (2)

[Claims] 1. A bag for accommodating a power generating element for a thin battery, wherein a peripheral edge of the bag is formed in a heat seal portion, and a part of the heat seal portion is sealed with another heat seal portion. A thin battery bag body formed in a notch shape from an inner edge to an outer edge so as to be narrower than a width. 2. The notch-shaped portion is formed between a positive electrode lead and a negative electrode lead fed from a power generating element for a thin battery housed in the bag. 2. The bag for a thin battery according to 1.